Wavevector-Frequency Spectra of Nonhomogeneous Fields
1987-01-22
TITLE (Indud* Security Qasafication) WAVEVECTOR-FREQUENCY SPECTRA OF NONHOMOGENEOUS FIELDS 12. PERSONAL AUTHOR(S) Dr . Wayne A. Strawderman...SAME AS RPT. D DTIC USERS 22a. NAME OF RESPONSIBLE INDIVIDUAL Dr . Wayne A. Strawderman 21. ABSTRACT SECURITY CLASSIFICATION UNCLASSIFIED 22b.T...Program Element 62314N. The NUSC Project No. is B60010. Principal Investigator Dr . H. P. Bakewell, Jr., Code 2141. The Sponsoring Activity was the Office
Identification of trapped electron modes in frequency fluctuation spectra
NASA Astrophysics Data System (ADS)
Arnichand, H.; Citrin, J.; Hacquin, S.; Sabot, R.; Krämer-Flecken, A.; Garbet, X.; Bourdelle, C.; Bottereau, C.; Clairet, F.; Giacalone, J. C.; Guimarães-Filho, Z. O.; Guirlet, R.; Hornung, G.; Lebschy, A.; Lotte, P.; Maget, P.; Medvedeva, A.; Molina, D.; Nikolaeva, V.; Prisiazhniuk, D.; Tore Supra, the; the ASDEX Upgrade Teams
2016-01-01
Ion temperature gradient (ITG) and trapped electron modes (TEM) are two important micro-instabilities in the plasma core region of fusion devices (r/a≤slant 0.9 ). They usually coexist in the same range of spatial scale (around 0.1<{{k}\\bot}{ρi}<1 ), which makes their discrimination difficult. To investigate them, one can perform gyrokinetic simulations, transport analysis and phase velocity estimations. In Tore Supra, the identification of trapped electron modes (TEM) is made possible due to measured frequency fluctuation spectra. Indeed, turbulent spectra generally expected to be broad-band, can become narrow in case of TEM turbulence, inducing ‘quasi-coherent’ (QC) modes named QC-TEM. Therefore the analysis of frequency fluctuation spectra becomes a possible tool to differentiate TEM from ITG. We have found indications that the TEM can have a QC signature by comparing frequency fluctuation spectra from reflectometry measurements, gyrokinetic simulations and synthetic diagnostic results. Then the scope of the analysis of QC-TEM are discussed and an application is shown, namely transitions between TEM turbulence and MHD fluctuations.
GENERAL RELATIVISTIC EFFECTS ON NONLINEAR POWER SPECTRA
Jeong, Donghui; Gong, Jinn-Ouk; Noh, Hyerim; Hwang, Jai-chan E-mail: jgong@lorentz.leidenuniv.nl E-mail: jchan@knu.ac.kr
2011-01-20
The nonlinear nature of Einstein's equation introduces genuine relativistic higher order corrections to the usual Newtonian fluid equations describing the evolution of cosmological perturbations. We study the effect of such novel nonlinearities on the next-to-leading order matter and velocity power spectra for the case of a pressureless, irrotational fluid in a flat Friedmann background. We find that pure general relativistic corrections are negligibly small over all scales. Our result guarantees that, in the current paradigm of standard cosmology, one can safely use Newtonian cosmology even in nonlinear regimes.
Frequency Spectra of Magnetoacoustic Emission in Meteorites
NASA Astrophysics Data System (ADS)
Ivanchenko, S. V.; Grokhovsky, V. I.; Kolchanov, N. N.
2016-08-01
We analyzed the magnetoacoustic emission spectra of iron meteorites and their industrial analogs. The revealed differences in signal amplitude, position and width of the peaks are associated with the features of structure and the magnetic texture.
Signal Frequency Spectra with Audacity®
ERIC Educational Resources Information Center
Gailey, Alycia
2015-01-01
The primary objective of the activity presented here is to allow students to explore the frequency components of various simple signals, with the ultimate goal of teaching them how to remove unwanted noise from a voice signal. Analysis of the frequency components of a signal allows students to design filters that remove unwanted components of a…
Frequency spectra of short-period variations of cosmic ray
NASA Technical Reports Server (NTRS)
Antonova, V. P.; Zusmanovich, A. G.
1985-01-01
Frequency spectra for different periods of solar activity were calculated by 5-minutes data of a neutron super-monitor, (altitude 3340 m, cutoff rigidity is 6, 7 GV, counting rate is about 4.5.10 per hour). It was shown that shifting of the spectrum power from low-frequency range to high-frequency range takes place from minimum to maximum of the solar activity. It was reliably distinguished the peak with 160-minutes period coincided with the period of the Sun's atmosphere oscillation and some types of geomagnetic pulsation by the method of accumulation of the frequency spectra. It was conducted the comparison of cosmic ray spectra with spectra of geomagnetic field for the same point of the registration and at the same period.
Frequency spectra of laminated piezoelectric cylinders
NASA Astrophysics Data System (ADS)
Siao, J. C.-T.; Dong, S. B.; Song, J.
1994-07-01
A finite-element method is presented for determining the vibrational characteristics of a circular cylinder composed of bonded piezoelectric layers. Finite-element modeling occurs in the radial direction only using quadratic polynomials and the variationally derived partial differential equations are functions of the hoop and axial coordinates (theta, z) and time t. Using solution form Q exp (i(xi(z) + n(theta) + (omega)t)), with Q as the nodal amplitudes, leads to an algebraic eigensystem where any one of the three parameters (n, xi, omega), the circumferential or axial wave number or natural frequency, can act as the eigenvalue. Integer values always are assigned to n, leaving two possible eigenvalue problems. With omega as the eigenvalue and real values assigned to xi, the solutions represent propagating waves or harmonic standing vibrations in an infinite cylinder. When xi is the eigenvalue and real values assigned to omega, this eigensystem admits both real and complex eigendata. Real xi's represent propagating waves or harmonic standing vibrations as noted before. Complex conjugate pairs of xi 's describe end vibrations, which arise when an incident wave impinges upon a free end of a cylindrical bar. They are standing waves whose amplitudes decay sinusoidally or exponentially from the free end into the interior. Two examples are given to illustrate the method of analysis, viz., a solid piezoelectric cylinder of PZT-4 ceramic material and a two-layer cylinder of PZT-4 covering an isotropic material.
Power spectra at radio frequency of lightning return stroke waveforms
NASA Technical Reports Server (NTRS)
Lanzerotti, L. J.; Thomson, D. J.; Maclennan, C. G.; Rinnert, K.; Krider, E. P.
1989-01-01
The power spectra of the wideband (10 Hz to 100 kHz) magnetic field signals in a number of lightning return strokes (primarily first return strokes) measured during a lightning storm which occurred in Lindau, West Germany in August, 1984 have been calculated. The RF magnetic field data were obtained with the engineering unit of the Galileo Jupiter Probe lightning experiment. The spectra of the magnetic field data definitely show fine structure, with two or three distinct peaks appearing in the spectra of many of the waveforms. An enhancement of power at frequencies of about 60-70 kHz is often seen in the spectra of the waveform time segments preceding and following the rise-to-peak amplitude of the return stroke.
Measuring Complex Sum Frequency Spectra with a Nonlinear Interferometer.
Wang, Jing; Bisson, Patrick J; Marmolejos, Joam M; Shultz, Mary Jane
2016-06-02
Currently, the only techniques capable of delivering molecular-level data on buried or soft interfaces are the nonlinear spectroscopic methods: sum frequency generation (SFG) and second harmonic generation (SHG). Deducing molecular information from spectra requires measuring the complex components-the amplitude and the phase-of the surface response. A new interferometer has been developed to determine these components with orders-of-magnitude improvement in uncertainty compared with current methods. Both the sample and reference spectra are generated within the interferometer, hence the label nonlinear interferometer. The interferometer configuration provides experimenters with wide latitude for both the sample enclosure and reference material choice and is thus widely applicable. The instrument is described and applied to the well-studied octadecyltrichlorosilane (OTS) film. The OTS spectra support the interpretation that variation in fabrication solvent water content and substrate preparation account for differences in OTS spectra reported in the literature.
Retrieving sea-wave spectra using satellite-imagery spectra in a wide range of frequencies
NASA Astrophysics Data System (ADS)
Bondur, V. G.; Dulov, V. A.; Murynin, A. B.; Ignatiev, V. Yu.
2016-11-01
A method to register sea-wave spectra using optical aerospace imagery has been developed. The method is based on the use of retrieval operators both in areas of high and low spatial frequencies, including the areas of spectral maximum. The approach to adjust and validate the method developed using sea truth data obtained by string wave recorders has been suggested. This paper presents the results of using the suggested method to study sea-wave spectra using high-resolution satellite imagery for various water areas under different conditions of wave generation.
Cascadia Tremor Spectra from Beamforming Fall Off as Frequency Squared
NASA Astrophysics Data System (ADS)
Gerstoft, P.; Zhang, J.; Shearer, P. M.; Yao, H.; Vidale, J. E.; Ghosh, A.
2010-12-01
The spectral decay of non-volcanic tremor (NVT) contains important information about the physical processes involved in Episodic Tremor and Slip (ETS). Using a small-aperture seismic array deployed on Big Skidder Hill, WA, we employ frequency-domain beamforming to obtain spatiotemporal spectral estimates of NVT activity in Cascadia on May 6-19, 2008. By shooting rays up from the plate boundary, potential tremor source locations are found where they best match the beamformer output. While energy from 2.5 Hz up to 25 Hz can radiate simultaneously from different patches, they often tend to come from the same region and migrate from the south to the north. An advantage of using beamforming for spectral analysis is that we can suppress noise and focus on the tremor phase by deriving the cross-power spectrum. This enables extracting tremor spectra for higher frequencies. We then compute the tremor source spectrum by using nearby small earthquakes to estimate empirical path and attenuation corrections. Our results show that displacement spectral amplitudes of the Cascadia tremor fall off roughly as the inverse of frequency squared over 5-20 Hz, agreeing with standard frequency-squared spectral models for earthquakes, but disagreeing with prior tremor analyses that have indicated a falloff proportional to frequency rather than frequency squared.
Non-Equilibrium Allele Frequency Spectra Via Spectral Methods
Hey, Jody; Chen, Kevin
2011-01-01
A major challenge in the analysis of population genomics data consists of isolating signatures of natural selection from background noise caused by random drift and gene flow. Analyses of massive amounts of data from many related populations require high-performance algorithms to determine the likelihood of different demographic scenarios that could have shaped the observed neutral single nucleotide polymorphism (SNP) allele frequency spectrum. In many areas of applied mathematics, Fourier Transforms and Spectral Methods are firmly established tools to analyze spectra of signals and model their dynamics as solutions of certain Partial Differential Equations (PDEs). When spectral methods are applicable, they have excellent error properties and are the fastest possible in high dimension; see [15]. In this paper we present an explicit numerical solution, using spectral methods, to the forward Kolmogorov equations for a Wright-Fisher process with migration of K populations, influx of mutations, and multiple population splitting events. PMID:21376069
A generalized modal shock spectra method for spacecraft loads analysis
NASA Technical Reports Server (NTRS)
Trubert, M.; Salama, M.
1979-01-01
Unlike the traditional shock spectra approach, the generalization presented in this paper permits elastic interaction between the spacecraft and launch vehicle in order to obtain accurate bounds on the spacecraft response and structural loads. In addition, the modal response from a previous launch vehicle transient analysis - with or without a dummy spacecraft - is exploited in order to define a modal impulse as a simple idealization of the actual forcing function. The idealized modal forcing function is then used to derive explicit expressions for an estimate of the bound on the spacecraft structural response and forces.
Excitation spectra of generalized antiferromagnetic Heisenberg spin chains (abstract)
NASA Astrophysics Data System (ADS)
Parkinson, J. B.; Bonner, J. C.
1988-04-01
We compare the excitation spectra in the presence of a magnetic field of a number of integrable (exactly solvable) and nonintegrable quantum spin chains of various spin value s. The archetypal Bethe-ansatz integrable model is the s= 1/2 Heisenberg antiferromagnet (HB AFM). The excitation spectra are characterized by a soft mode which tracks across the Brillouin zone as the field increases to its saturation value. A class of Bethe-ansatz integrable models with SU(2) symmetry and the general spin s display excitation spectra qualitatively similar to the spin- 1/2 model above, for all s. A second class of Bethe-ansatz integrable models has SU(n) symmetry, where n=2s+1. Like the SU(2) integrable chains, these models have gapless excitation spectra, but the basic Brillouin zone changes from k=±2π/(2s+1)a. Studies show that periodicity of the SU(3) member of the class changes (increases) as the field increases to saturation. For both classes of integrable models, there is a single type of excitation pattern which is generically similar for all s. In the case of the other models, on the other hand, numerical studies show that the excitations divide into at least two distinct classes. In the case of the s=1 HB AFM, at high fields (corresponding to SzT=N,N-1, . . .,N/2) the excitations map approximately onto the complete set of excitations for s= 1/2 , whereas at low fields (SzT=N/2,N/2-1,. . .,0) the excitations have notable classical character. In the case of the s=1 model with pure biquadratic exchange, one set of excitations, corresponding to SzT even (SzT=N,N-2,. . .,2,0), again shows an approximate mapping to the complete excitation set for s= 1/2 . The second class of excitations, corresponding to SzT odd, are very different. They are symmetric about k=±π/2a for all SzT, i.e., correspond to a basic Brillouin zone of ±π/2a.
High-frequency Broadband Modulations of Electroencephalographic Spectra
Onton, Julie; Makeig, Scott
2009-01-01
High-frequency cortical potentials in electroencephalographic (EEG) scalp recordings have low amplitudes and may be confounded with scalp muscle activities. EEG data from an eyes-closed emotion imagination task were linearly decomposed using independent component analysis (ICA) into maximally independent component (IC) processes. Joint decomposition of IC log spectrograms into source- and frequency-independent modulator (IM) processes revealed three distinct classes of IMs that separately modulated broadband high-frequency (∼15–200 Hz) power of brain, scalp muscle, and likely ocular motor IC processes. Multi-dimensional scaling revealed significant but spatially complex relationships between mean broadband brain IM effects and the valence of the imagined emotions. Thus, contrary to prevalent assumption, unitary modes of spectral modulation of frequencies encompassing the beta, gamma, and high gamma frequency ranges can be isolated from scalp-recorded EEG data and may be differentially associated with brain sources and cognitive activities. PMID:20076775
Frequency spectra of nonlinear elastic pulse-mode waves
Kadish, A.; TenCate, J.A.; Johnson, P.A.
1996-09-01
The frequency spectrum of simple waves is used to derive a closed form analytical representation for the frequency spectrum of damped nonlinear pulses in elastic materials. The damping modification of simple wave theory provides an efficient numerical method for calculating propagating wave forms. The spectral representation, which is neither pulse length nor amplitude limited, is used to obtain estimates for parameters of the nonlinear state relation for a sandstone sample from published experimental data, and the results are compared with those of other theories. The method should have broad application to many solids.
NASA Astrophysics Data System (ADS)
Maggs, J. E.; Morales, G. J.
2011-10-01
The dynamics of transport at the edge of magnetized plasmas is deterministic chaos. The connection is made by a previous survey [M. A. Pedrosa , Phys. Rev. Lett. 82, 3621 (1999)PRLTAO0031-900710.1103/PhysRevLett.82.3621] of measurements of fluctuations that is shown to exhibit power spectra with exponential frequency dependence over a broad range, which is the signature of deterministic chaos. The exponential character arises from Lorentzian pulses. The results suggest that the generalization to complex times used in studies of deterministic chaos is a representation of Lorentzian pulses emerging from the chaotic dynamics.
Frequency variations of solar radio zebras and their power-law spectra
NASA Astrophysics Data System (ADS)
Karlický, M.
2014-01-01
Context. During solar flares several types of radio bursts are observed. The fine striped structures of the type IV solar radio bursts are called zebras. Analyzing them provides important information about the plasma parameters of their radio sources. We present a new analysis of zebras. Aims: Power spectra of the frequency variations of zebras are computed to estimate the spectra of the plasma density variations in radio zebra sources. Methods: Frequency variations of zebra lines and the high-frequency boundary of the whole radio burst were determined with and without the frequency fitting. The computed time dependencies of these variations were analyzed with the Fourier method. Results: First, we computed the variation spectrum of the high-frequency boundary of the whole radio burst, which is composed of several zebra patterns. This power spectrum has a power-law form with a power-law index -1.65. Then, we selected three well-defined zebra-lines in three different zebra patterns and computed the spectra of their frequency variations. The power-law indices in these cases are found to be in the interval between -1.61 and -1.75. Finally, assuming that the zebra-line frequency is generated on the upper-hybrid frequency and that the plasma frequency ωpe is much higher than the electron-cyclotron frequency ωce, the Fourier power spectra are interpreted to be those of the electron plasma density in zebra radio sources.
NASA Astrophysics Data System (ADS)
Wan, Quan; Galli, Giulia
2015-12-01
We present a first-principles framework to compute sum-frequency generation (SFG) vibrational spectra of semiconductors and insulators. The method is based on density functional theory and the use of maximally localized Wannier functions to compute the response to electric fields, and it includes the effect of electric field gradients at surfaces. In addition, it includes quadrupole contributions to SFG spectra, thus enabling the verification of the dipole approximation, whose validity determines the surface specificity of SFG spectroscopy. We compute the SFG spectra of ice Ih basal surfaces and identify which spectra components are affected by bulk contributions. Our results are in good agreement with experiments at low temperature.
Theoretical aspects and the experience of studying spectra of low-frequency microseisms
NASA Astrophysics Data System (ADS)
Birialtsev, E.; Vildanov, A.; Eronina, E.; Rizhov, D.; Rizhov, V.; Sharapov, I.
2009-04-01
The appearance of low-frequency spectral anomalies in natural microseismic noise over oil and gas deposits is observed since 1989 in different oil and gas regions (S. Arutunov, S. Dangel, G. Goloshubin). Several methods of prospecting and exploration of oil and gas deposits based on this effect (NTK ANCHAR, Spectraseis AG). There are several points of view (S. Arutunov, E. Birialtsev, Y. Podladchikov) about the physical model of effect which are based on fundamentally different geophysical mechanisms. One of them is based on the hypothesis of generation of the microseismic noise in to an oil and gas reservoir. Another point of view is based on the mechanism of the filtering microseismic noise in the geological medium where oil and gas reservoir is the contrast layer. For the first hypothesis an adequate quantity physical-mathematical model is absent. Second hypothesis has a discrepancy of distribution energy on theoretical calculated frequencies of waveguides «ground surface - oil deposit» eigenmodes. The fundamental frequency (less than 1 Hz for most cases) should have a highest amplitude as opposed to the regular observation range is 1-10 Hz. During 2005-2008 years by specialists of «Gradient» JSC were processed microsesmic signals from more 50 geological objects. The parameters of low-frequency anomalies were compared with medium properties (porosity, saturation and viscosity) defined according to drilling, allowed to carry out a statistical analysis and to establish some correlation. This paper presents results of theoretical calculation of spectra of microseisms in the zone of oil and gas deposits by mathematical modeling of propagation of seismic waves and comparing spectra of model microseisms with actually observed. Mathematical modeling of microseismic vibrations spectra showed good correlation of theoretical spectra and observed in practice. This is proof the applicability of microseismic methods of exploration for oil and gas. Correlation between
Generalized Linear Multi-Frequency Imaging in VLBI
NASA Astrophysics Data System (ADS)
Likhachev, S.; Ladygin, V.; Guirin, I.
2004-07-01
In VLBI, generalized Linear Multi-Frequency Imaging (MFI) consists of multi-frequency synthesis (MFS) and multi-frequency analysis (MFA) of the VLBI data obtained from observations on various frequencies. A set of linear deconvolution MFI algorithms is described. The algorithms make it possible to obtain high quality images interpolated on any given frequency inside any given bandwidth, and to derive reliable estimates of spectral indexes for radio sources with continuum spectrum.
Adams, M L; Sinars, D B; Scott, H A
2005-01-10
We describe a general computational spectroscopic framework for interpreting observed spectra. The framework compares synthetic spectra with measured spectra, then optimizes the agreement using the Dakota toolkit to minimize a merit function that incorporates established spectroscopic techniques. We generate synthetic spectra using the self-consistent nonlocal thermodynamic equilibrium atomic kinetics and radiative transfer code Cretin, relativistic atomic structure and cross section data from Hullac, and detailed spectral line shapes from Totalb. We test the capabilities of both our synthetic spectra model and general spectroscopic framework by analyzing a K-shell argon spectrum from a Z-pinch dynamic hohlraum inertial confinement fusion capsule implosion experiment. The framework obtains close agreement between an experimental spectrum measured by a time integrated focusing spectrometer and the optimal synthetic spectrum. The synthetic spectra show that considering the spatial extent of the capsule and including the effects of optically thick resonance lines significantly affects the interpretation of measured spectra.
NASA Astrophysics Data System (ADS)
Reppert, Mike; Tokmakoff, Andrei
2013-04-01
The interpretation of protein amide I infrared spectra has been greatly assisted by the observation that the vibrational frequency of a peptide unit reports on its local electrostatic environment. However, the interpretation of spectra remains largely qualitative due to a lack of direct quantitative connections between computational models and experimental data. Here, we present an empirical parameterization of an electrostatic amide I frequency map derived from the infrared absorption spectra of 28 dipeptides. The observed frequency shifts are analyzed in terms of the local electrostatic potential, field, and field gradient, evaluated at sites near the amide bond in molecular dynamics simulations. We find that the frequency shifts observed in experiment correlate very well with the electric field in the direction of the C=O bond evaluated at the position of the amide oxygen atom. A linear best-fit mapping between observed frequencies and electric field yield sample standard deviations of 2.8 and 3.7 cm-1 for the CHARMM27 and OPLS-AA force fields, respectively, and maximum deviations (within our data set) of 9 cm-1. These results are discussed in the broader context of amide I vibrational models and the effort to produce quantitative agreement between simulated and experimental absorption spectra.
Reppert, Mike; Tokmakoff, Andrei
2013-01-01
The interpretation of protein amide I infrared spectra has been greatly assisted by the observation that the vibrational frequency of a peptide unit reports on its local electrostatic environment. However, the interpretation of spectra remains largely qualitative due to a lack of direct quantitative connections between computational models and experimental data. Here, we present an empirical parameterization of an electrostatic amide I frequency map derived from the infrared absorption spectra of 28 dipeptides. The observed frequency shifts are analyzed in terms of the local electrostatic potential, field, and field gradient, evaluated at sites near the amide bond in molecular dynamics simulations. We find that the frequency shifts observed in experiment correlate very well with the electric field in the direction of the C=O bond evaluated at the position of the amide oxygen atom. A linear best-fit mapping between observed frequencies and electric field yield sample standard deviations of 2.8 and 3.7 cm−1 for the CHARMM27 and OPLS-AA force fields, respectively, and maximum deviations (within our data set) of 9 cm−1. These results are discussed in the broader context of amide I vibrational models and the effort to produce quantitative agreement between simulated and experimental absorption spectra. PMID:23574217
Determination of the Brunt-Vaisala frequency from vertical velocity spectra
NASA Technical Reports Server (NTRS)
Rottger, J.
1986-01-01
Recent work on the spectra of vertical velocity oscillations due to gravity waves in the troposphere, stratosphere and the mesosphere has revealed a typical feature which we call the Brunt-Vaisala cutoff. Several observers noticed a spectral peak near the Brunt-Vaisala frequency. This peak often is characterized by a very steep slope at the high frequency part, but a fairly shallow slope towards lower frequencies. Some example spectra of stratosphere observations are given. This distinct spectral shape (most clear at the upper height 22.5 km) can be explained by the fact that the vertical velocity amplitudes of atmospheric gravity waves increase with frequency up to their natural cutoff at the Brunt-Vaisala frequency. The measurement of the frequency of the peak in a vertical velocity spectrum was found to yield most directly the Brunt-Vaisala-frequency profile. Knowing the Brunt-Vaisala frequency profile, one can deduce the potential temperature profile, if one has a calibration temperature at one height. However, even the uncalibrated profile will be quite useful, e.g., to determine fronts (defined by temperature inversions) and the tropopause height. This method fails for superadiabatic lapse rates when the Brunt-Viasala frequency is imaginary. The application of this method will also be difficult when the wind velocity is too high, causing the Doppler effect to smear out the total spectrum and blur the Brunt-Vaisala cutoff. A similar deficiency will also appear if the gravity-wave distribution has a maximum in wind direction.
Influence of sex, smoking and age on human hprt mutation frequencies and spectra.
Curry, J; Karnaoukhova, L; Guenette, G C; Glickman, B W
1999-01-01
Examination of the literature for hprt mutant frequencies from peripheral T cells yielded data from 1194 human subjects. Relationships between mutant frequency, age, sex, and smoking were examined, and the kinetics were described. Mutant frequency increases rapidly with age until about age 15. Afterward, the rate of increase falls such that after age 53, the hprt mutant frequency is largely stabilized. Sex had no effect on mutant frequency. Cigarette smoking increased mean mutant frequency compared to nonsmokers, but did not alter age vs. mutant frequency relationships. An hprt in vivo mutant database containing 795 human hprt mutants from 342 individuals was prepared. No difference in mutational spectra was observed comparing smokers to nonsmokers, confirming previous reports. Sex affected the frequency of deletions (>1 bp) that are recovered more than twice as frequently in females (P = 0. 008) compared to males. There is no indication of a significant shift in mutational spectra with age for individuals older than 19 yr, with the exception of A:T --> C:G transversions. These events are recovered more frequently in older individuals. PMID:10388825
Frequency response characteristics and response spectra of base-isolated and un-isolated structures
Mok, G.C.; Namba, H.
1995-07-06
The transmissibility of seismic loads through a linear base-isolation system is analyzed using an impedance method. The results show that the system acts like a {open_quotes}low-pass{close_quotes} filter. It attenuates high-frequency loads but passes through low-frequency ones. The filtering effect depends on the vibration frequencies and damping of the isolated structure and the isolation system. This paper demonstrates the benefits and design principles of base isolation by comparing the transmissibilities and response spectra of isolated and un-isolated structures. Parameters of typical isolated buildings and ground motions of the 1994 Northridge earthquake are used for the demonstration.
Simulation of multi-frequency EPR spectra for a distribution of the zero-field splitting.
Azarkh, Mykhailo; Groenen, Edgar J J
2015-06-01
We present a numerical procedure called 'grid-of-errors' to extract the distribution of magnetic interactions from continuous-wave electron-paramagnetic-resonance (EPR) spectra at multiple microwave frequencies. The approach is based on the analysis of the lineshape of the spectra and explicitly worked out for high-spin systems for which the lineshape is determined by a distribution of the zero-field splitting. Initial principal values of the zero-field splitting tensor are obtained from the EPR spectrum at a microwave frequency in the high-field limit, and the initial distribution is taken Gaussian. Subsequently, the grid-of-errors procedure optimizes this distribution, without any restriction to its shape, taking into account spectra at various microwave frequencies. The numerical procedure is illustrated for the Fe(III)-EDTA complex. An optimized distribution of the zero-field splitting is obtained, which provides a proper description of the EPR spectra at 9.5, 34, 94, and 275 GHz. The proposed approach can be used as well for distributions of magnetic interactions other than the zero-field splitting.
High-frequency ESR spectra of the type Ib synthetic diamond and nanodiamond at low temperatures
NASA Astrophysics Data System (ADS)
Khatsko, E.; Kobets, M.; Dergachev, K.; Kulbickas, A.; Rasteniene, L.; Vaisnoras, R.
2013-12-01
The ESR absorption spectra on paramagnetic centers in the type Ib bulk diamond and nanodiamond powder were studied before and after irradiation with high energy electrons (2 MeV) for a wide range of frequencies (70-120 GHz) and temperatures (4.2-90 K). The absorption lines related to the nickel-ion growth catalyst Ni1+ and single nitrogen paramagnetic center N0 were observed in the ESR spectrum of bulk diamond. In the nanodiamond, the absorption lines of the paramagnetic centers with dangling bonds on the surface of the nanodiamond crystallites (surface defects) and the sidelines related to the hyperfine interaction were observed in the ESR spectra.
Buch, V; Tarbuck, T; Richmond, G L; Groenzin, H; Li, I; Shultz, M J
2007-11-28
A new computational scheme is presented for calculation of sum frequency generation (SFG) spectra, based on the exciton model for OH bonds. The scheme is applied to unified analysis of the SFG spectra in the OH-stretch region of the surfaces of ice, liquid water, and acid solution. A significant role of intermolecularly coupled collective modes is pointed out. SFG intensity amplification observed for acid solutions in the H-bonded OH-stretch region is reproduced qualitatively and accounted for by enhanced orientational preference "into the surface" of the H(2)O bisectors within the hydronium solvation shell.
Spatial-frequency spectra of printed characters and human visual perception.
Põder, Endel
2003-06-01
It is well known that certain spatial frequency (SF) bands are more important than others for character recognition. Solomon and Pelli [Nature 369 (1994) 395-397] have concluded that human pattern recognition mechanism is able to use only a narrow band from available SF spectrum of letters. However, the SF spectra of letters themselves have not been studied carefully. Here I report the results of an analysis of SF spectra of printed characters and discuss their relationship to the observed band-pass nature of letter recognition.
Costa, C H O; Vasconcelos, M S
2013-07-17
We employ a microscopic theory to investigate spin wave (magnon) propagation through their dispersion and transmission spectra in magnonic crystals arranged to display deterministic disorder. In this work the quasiperiodic arrangement investigated is the well-known generalized Fibonacci sequence, which is characterized by the σ(p,q) parameter, where p and q are non-zero integers. In order to determine the bulk modes and transmission spectra of the spin waves, the calculations are carried out for the exchange dominated regime within the framework of the Heisenberg model and taking into account the random phase approximation. We have considered magnetic materials that have a ferromagnetic order, and the transfer-matrix treatment is applied to simplify the algebra. The results reveal that spin wave spectra display a rich and interesting magnonic pass- and stop-bands structures, including an almost symmetric band gap distribution around of a mid-gap frequency, which depends on the Fibonacci sequence type.
NASA Astrophysics Data System (ADS)
Costa, C. H. O.; Vasconcelos, M. S.
2013-07-01
We employ a microscopic theory to investigate spin wave (magnon) propagation through their dispersion and transmission spectra in magnonic crystals arranged to display deterministic disorder. In this work the quasiperiodic arrangement investigated is the well-known generalized Fibonacci sequence, which is characterized by the σ(p,q) parameter, where p and q are non-zero integers. In order to determine the bulk modes and transmission spectra of the spin waves, the calculations are carried out for the exchange dominated regime within the framework of the Heisenberg model and taking into account the random phase approximation. We have considered magnetic materials that have a ferromagnetic order, and the transfer-matrix treatment is applied to simplify the algebra. The results reveal that spin wave spectra display a rich and interesting magnonic pass- and stop-bands structures, including an almost symmetric band gap distribution around of a mid-gap frequency, which depends on the Fibonacci sequence type.
Radial evolution of the high/low frequency breakpoint in magnetic field spectra
NASA Technical Reports Server (NTRS)
Feynman, J.; Ruzmaikin, A.; Smith, E. J.
1995-01-01
The spectra of magnetic field variations in the solar wind show different behavior in two frequency regions; a high frequency region in which the spectral exponent is about -5/3 and a low frequency region in which it is typically -1. The two types of variations must arise from different processes and a clue to the relationship between the spectral regions lies in understanding the behavior of the breakpoint between the spectral regions. Studies of the average behavior of spectra have shown that the break point occurs at about 3.5 hours at 1 AU. It is also known that, on average, the breakpoint occurs at lower frequencies with larger heliocentric distances. Ideally however, instead of the average properties of the spectra, we would like to know how the breakpoint evolves in particular samples of the solar wind as they propagate to larger heliocentric distances. In the study reported here we take advantage of the fact that, in 1974, Pioneer 10 (4.4 AU) and Pioneer 11 (5.6 AU) were close to being co-aligned and being aligned with the Earth. Solar wind observed at Earth can be closely matched with solar wind later observed at P10 and P11. We here compare the breakpoint observed at Earth with that observed at Pioneers 10 and 11 for matched samples of the wind.
Cao, Shu-Min; Qi, Li-Jian; Guo, Qing-Hong; Zhong, Zeng-Qiu; Qiu, Zhi-Li; Li, Zhi-Gang
2008-04-01
The object of the present study is the synthetic jadeite jade produced by American General Electric Corporation. Fourier transform infrared spectroscopy (FTIR) and Laser Raman spectroscopy were used to test its spectral properties in order to examine the feature of this kind of synthetic jadeite jade by vibrational spectroscopy and to figure out the mark for discriminate synthetic jadeite jade from natural jadeite jade. The study shows that GE synthetic jadeite jade is identical with natural jadeite jade in the main on fingerprint region in FTIR; There are clearly differences in the 2 000 -4 000 cm(-1) functional region in FTIR: a group of frequencies at 3 375, 3 471 and 3 614 cm(-1) indicate vibration absorption of O-H. GE synthetic jadeite jade has proven consistent with natural jadeite jade in the laser Raman spectra by a group of sharp scattering peaks at 376, 700, 989 and 1 039 cm(-1). In addition these scattering peaks show an intact crystal shape. The FTIR peaks and Raman spectral peaks shift to higher frequencies showing GE synthetic jadeite jade lacking isomorphism of heavy positive ions.
NASA Astrophysics Data System (ADS)
Szmacineki, Henryk; Lakowicz, Joseph R.; Johnson, Michael L.
1988-06-01
We report measurements of time-resolved emission spectra of N-acetyl-L-tryptophanamide (NATA), adrenocorticotropic hormone (ACTH, residues 1-24), and of S. Nuclease. These spectra were calculated from the frequency-response of the emission, measured at several wavelengths across the emission spectra. Measurements were performed on samples not quenched and quenched by acrylamide, the latter providing additional information on the short time events. The time-resolved center-of-gravity does not decay as a single exponential. At least two spectral relaxation times are needed to account for the present data. NATA and ACTH each display relaxation times near 50 and 800 ps, which may be characteristic of exposed tryptophan residues. S. nuclease displayed slower relaxation times near 0.5 and 10 ns, which probably reflect the dynamic protein matrix which surrounds the residue.
Investigating the frequency dependence of mantle Q by stacking P and PP spectra
NASA Astrophysics Data System (ADS)
Warren, Linda M.; Shearer, Peter M.
2000-11-01
Using seismograms from globally distributed, shallow earthquakes between 1988 and 1998, we compute spectra for P arrivals from epicentral distances of 40° to 80° and PP arrivals from 80° to 160°. Selecting records with estimated signal-to-noise ratios greater than 2, we find 17,836 P and 14,721 PP spectra. We correct each spectrum for the known instrument response and for an ω-2 source model that accounts for varying event sizes. Next, we stack the logarithms of the P and PP spectra in bins of similar source-receiver range. The stacked log spectra, denoted as log(DP') and log(DPP'), appear stable between about 0.16 and 0.86 Hz, with noise and/or bias affecting the results at higher frequencies. Assuming that source spectral differences are randomly distributed, then for shallow events, when the PP range is twice the P range, the average residual source spectrum may be estimated as 2 log(DP')-log(DPP'), and the average P wave attenuation spectrum may be estimated as log(DPP') - log(DP'). The residual source spectral estimates exhibit a smooth additional falloff as ω-0.15±0.05 between 0.16 and 0.86 Hz, indicating that ω-2.15±0.05 is an appropriate average source model for shallow events. The attenuation spectra show little distance dependence over this band and have a P wave t¯* value of ˜0.5 s. We use t¯* measurements from individual P and PP spectra to invert for a frequency-independent Q model and find that the upper mantle is nearly 5 times as attenuating as the lower mantle. Frequency dependence in Qα is difficult to resolve directly in these data but, as previous researchers have noted, is required to reconcile these values with long-period Q estimates. Using Q model QL6 [Durek and Ekström, 1996] as a long-period constraint, we experiment with fitting our stacked log spectra with an absorption band model. We find that the upper corner frequency f2 in the absorption band must be depth-dependent to account for the lack of a strong distance
Temperature effects in low-frequency Raman spectra of corticosteroid hormones
NASA Astrophysics Data System (ADS)
Minaeva, V. A.; Minaev, B. F.; Baryshnikov, G. V.; Surovtsev, N. V.; Cherkasova, O. P.; Tkachenko, L. I.; Karaush, N. N.; Stromylo, E. V.
2015-02-01
Experimental Raman spectra of the corticosteroid hormones corticosterone and desoxycorticosterone are recorded at different temperatures (in the range of 30-310 K) in the region of low-frequency (15-120 cm-1) vibrations using a solid-state laser at 532.1 nm. The intramolecular vibrations of both hormones are interpreted on the basis of Raman spectra calculated by the B3LYP/6-31G(d) density functional theory method. The intermolecular bonds in tetramers of hormones are studied with the help of the topological theory of Bader using data of X-ray structural analysis for crystalline samples of hormones. The total energy of intermolecular interactions in the tetramer of desoxycorticosterone (-49.1 kJ/mol) is higher than in the tetramer of corticosterone (-36.9 kJ/mol). A strong intramolecular hydrogen bond O21-H⋯O=C20 with an energy of -42.4 kJ/mol was revealed in the corticosterone molecule, which is absent in the desoxycorticosterone molecule. This fact makes the Raman spectra of both hormones somewhat different. It is shown that the low-frequency lines in the Raman spectra are associated with skeletal vibrations of molecules and bending vibrations of the substituent at the C17 atom. The calculated Raman spectrum of the desoxycorticosterone dimer allows one to explain the splitting and shift of some lines and to interpret new strong lines observed in the spectra at low temperatures, which are caused by the intermolecular interaction and mixing of normal vibrations in a crystal cell. On the whole the calculated frequencies are in a good agreement with the experimental results.
NASA Astrophysics Data System (ADS)
Pivac, Ivan; Barbir, Frano
2016-09-01
The results of electrochemical impedance spectroscopy of proton exchange membrane (PEM) fuel cells may exhibit inductive phenomena at low frequencies. The occurrence of inductive features at high frequencies is explained by the cables and wires of the test system. However, explanation of inductive loop at low frequencies requires a more detailed study. This review paper discusses several possible causes of such inductive behavior in PEM fuel cells, such as side reactions with intermediate species, carbon monoxide poisoning, and water transport, also as their equivalent circuit representations. It may be concluded that interpretation of impedance spectra at low frequencies is still ambiguous, and that better equivalent circuit models are needed with clearly defined physical meaning of each of the circuit elements.
First Measurements of High Frequency Cross-Spectra from a Pair of Large Michelson Interferometers
NASA Astrophysics Data System (ADS)
Chou, Aaron S.; Gustafson, Richard; Hogan, Craig; Kamai, Brittany; Kwon, Ohkyung; Lanza, Robert; McCuller, Lee; Meyer, Stephan S.; Richardson, Jonathan; Stoughton, Chris; Tomlin, Raymond; Waldman, Samuel; Weiss, Rainer; Holometer Collaboration
2016-09-01
Measurements are reported of the cross-correlation of spectra of differential position signals from the Fermilab Holometer, a pair of colocated 39 m long, high power Michelson interferometers with flat broadband frequency response in the MHz range. The instrument obtains sensitivity to high frequency correlated signals far exceeding any previous measurement in a broad frequency band extending beyond the 3.8 MHz inverse light-crossing time of the apparatus. The dominant but uncorrelated shot noise is averaged down over 2 ×1 08 independent spectral measurements with 381 Hz frequency resolution to obtain 2.1 ×10-20m /√{Hz } sensitivity to stationary signals. For signal bandwidths Δ f >11 kHz , the sensitivity to strain h or shear power spectral density of classical or exotic origin surpasses a milestone PSDδ h
NASA Astrophysics Data System (ADS)
Lakowicz, Joseph R.; Gryczynski, Ignazy; Cherek, Henryh; Laczko, Gabor; Joshi, Nanda
1987-01-01
Measurements of time-resolved fluorescence are often used for studies of biological macromolecules. Such measurements are usually performed in the time-domain, by measurement of the time-dependent emission following pulsed excitation. It has recently become possible to measure the frequency-response of the emission to intensity modulated light, over a wide range of modulation frequencies. We used frequency-domain fluorometers which operates from 1 to 220 MHz, and more recently to 2000 MHz. The frequency-domain data provide excellent resolution of time-dependent spectral parameters. It is now possible to resolve closely spaced fluorescence lifetimes, to determine multi-exponential decays of anisotropy and to determine time-resolved emission spectra of samples which display time-dependent spectral shifts. In this article we show representative results on tryptophan fluorescence from proteins and for protein-bound fluorophores.
First Measurements of High Frequency Cross-Spectra from a Pair of Large Michelson Interferometers
Chou, Aaron S.; Gustafson, Richard; Hogan, Craig; Kamai, Brittany; Kwon, Ohkyung; Lanza, Robert; McCuller, Lee; Meyer, Stephan S.; Richardson, Jonathan; Stoughton, Chris; Tomlin, Raymond; Waldman, Samuel; Weiss, Rainer
2016-09-01
Measurements are reported of high frequency cross-spectra of signals from the Fermilab Holometer, a pair of co-located 39 m, high power Michelson interferometers. The instrument obtains differential position sensitivity to cross-correlated signals far exceeding any previous measurement in a broad frequency band extending to the 3.8 MHz inverse light crossing time of the apparatus. A model of universal exotic spatial shear correlations that matches the Planck scale holographic information bound of space-time position states is excluded to 4.6{\\sigma} significance.
Tong, Yujin; Zhao, Yanbao; Li, Na; Osawa, Masatoshi; Davies, Paul B; Ye, Shen
2010-07-21
A general theoretical calculation is described for predicting the interference effect in the sum frequency generation (SFG) spectra from a model thin-film system as a function of film thickness. The calculations were carried out for a three-layer thin film consisting of an organic monolayer, a dielectric thin film of variable thickness, and a gold substrate. This system comprises two sources of SFG, namely, a resonant contribution from the monolayer/dielectric film interface and a nonresonant contribution from the dielectric film/gold interface. The calculation shows that both the spectral intensity and the shape of the SFG spectra vary significantly with the thickness of the dielectric layer due to interference effects in the thin film. The intensity changes at a particular frequency were explained in terms of the changes in the local field factors (L factors) as a function of the dielectric film thickness. The L factor for each beam changes periodically with the thickness of the dielectric film. However, the combined L factor for the three beams shows complicated thickness dependent features and no clear periodicity was found. On the other hand, if the susceptibilities of both the resonant and nonresonant terms are fixed, changes in the spectral shape will be mainly due to changes in the phase differences between the two terms with the film thickness. The interference behavior also depends strongly on the polarization combinations of the sum frequency, visible, and infrared beams. A general method is provided for predicting changes in the spectral shapes at different film thicknesses by taking into account the relative intensities and phases of the SFG signals from the two interfaces. The model calculation provides important insights for understanding the nonlinear optical responses from any thin-film system and is an essential tool for quantitatively revealing the nonlinear susceptibilities, which are directly related to the actual structure of the interfacial
Brunner, Patricia; Merwa, Robert; Missner, Andreas; Rosell, Javier; Hollaus, Karl; Scharfetter, Hermann
2006-05-01
Magnetic induction tomography (MIT) of biological tissue is used for the reconstruction of the complex conductivity distribution kappa inside the object under investigation. It is based on the perturbation of an alternating magnetic field caused by the object and can be used in all applications of electrical impedance tomography (EIT) such as functional lung monitoring and assessment of tissue fluids. In contrast to EIT, MIT does not require electrodes and magnetic fields can also penetrate non-conducting barriers such as the skull. As in EIT, the reconstruction of absolute conductivity values is very difficult because of the method's sensitivity to numerical errors and noise. To overcome this problem, image reconstruction in EIT is often done differentially. Analogously, this concept has been adopted for MIT. Two different methods for differential imaging are applicable. The first one is state-differential, for example when the conductivity change between inspiration and expiration in the lung regions is being detected. The second one is frequency-differential, which is of high interest in motionless organs like the brain, where a state-differential method cannot be applied. An equation for frequency-differential MIT was derived taking into consideration the frequency dependence of the sensitivity matrix. This formula is valid if we can assume that only small conductivity changes occur. In this way, the non-linear inverse problem of MIT can be approximated by a linear one (depending only on the frequency), similar to in EIT. Keeping this limitation in mind, the conductivity changes between one or more reference frequencies and several measurement frequencies were reconstructed, yielding normalized conductivity spectra. Due to the differential character of the method, these spectra do not provide absolute conductivities but preserve the shape of the spectrum. The validity of the method was tested with artificial data generated with a spherical perturbation within a
Two-frequency /Delta k/ microwave scatterometer measurements of ocean wave spectra from an aircraft
NASA Technical Reports Server (NTRS)
Johnson, J. W.; Jones, W. L.; Weissman, D. E.
1981-01-01
A technique for remotely sensing the large-scale gravity wave spectrum on the ocean surface using a two frequency (Delta k) microwave scatterometer has been demonstrated from stationary platforms and proposed from moving platforms. This measurement takes advantage of Bragg type resonance matching between the electromagnetic wavelength at the difference frequency and the length of the large-scale surface waves. A prominent resonance appears in the cross product power spectral density (PSD) of the two backscattered signals. Ku-Band aircraft scatterometer measurements were conducted by NASA in the North Sea during the 1979 Maritime Remote Sensing (MARSEN) experiment. Typical examples of cross product PSD's computed from the MARSEN data are presented. They demonstrate strong resonances whose frequency and bandwidth agree with the surface characteristics and the theory. Directional modulation spectra of the surface reflectivity are compared to the gravity wave spectrum derived from surface truth measurements.
NASA Astrophysics Data System (ADS)
Laß, K.; Friedrichs, G.
2011-08-01
Natural nanolayers originating from sea surface and subsurface water samples collected in the Baltic Sea have been investigated using surface-sensitive vibrational sum frequency generation (VSFG) spectroscopy. Distinct spectral signatures of CH and OH bond stretch vibrations have been detected at wavenumbers ranging from 2700 to 3900 cm-1. Measured water-air interface spectra as well as observed signal intensity trends are discussed in terms of composition and structure of the natural organic nanolayer. Reasoning was based on the comparison with reference spectra, spectral trends inferred from previous VSFG studies, reported average composition of dissolved organic matter in seawater, and simplified assumption that surfactants can be classified as soluble (wet) and insoluble (dry) surfactants. Wet surfactants have been found to be dominant, and often lipid-like compounds form a very dense surfactant nanolayer. Supported by comparison spectra of xanthan gum solutions, the observed VSFG spectral signatures were tentatively assigned to lipopolysaccharides or other lipid-like compounds embedded in colloidal matrices of polymeric material. In addition, VSFG spectra of a polluted harbor water sample and a water sample covered with diesel oil are reported.
NASA Astrophysics Data System (ADS)
Rosa, Reinaldo; Veronese, Thalita; José Alves Bolzan, Maurício; Fernandes, Francisco; Cecatto, José; Karlicky, Marian; Sawant, Hanumant
The search for turbulent-like patterns and extreme dynamics from time series of solar radio burts has recently advanced due to high-resolution and high-sensitivity observations. Such so-lar radio emissions in the decimetric frequency range (above 1 GHz) are very rich in temporal and spectral fine structures due to nonlinear processes occurring in the magnetic structures on the corresponding active regions. In this paper we analize the decimetric fine structures of 8 X-Class Flares events observed from Brazilian Solar Spectroscope (1-2.5 GHz) and On-drejov radiospectrograph (3 GHz). The Singularity Spectra [1] and Generalized Extreme Value (GEV) distribution [2] are obtained and we interpret our findings as evidence of inhomogeneous lagrangian-like MHD turbulence driving the underlying non-gaussian plasma emission process. Once GEV statistical behavior was found for 75% of the events, the flare ocurrence is discussed into the context of solar extreme events. [1] Bolzan et al., Ann. Geophys., 27, 569-576, 2009. [2] S. Coles, An Introduction to Statistical Modeling of Extreme Values, Springer Series in Statistics, (2001) 228 pp., Springer-Verlag, Berlin, Germany.
NASA Astrophysics Data System (ADS)
Vats, H. O.; Booker, H. G.; Majidiahi, G.
1981-12-01
Strong intensity spectra were observed simultaneously by Vats (1981) on transmissions through the ionospheric F-region at 40, 140, and 360 MHz from a stationary satellite. These spectra are explained quantitatively in terms of refractive scattering, using the approach of Booker and MajidiAhi (1981). The outer and inner scales are 50 km and 5 m, respectively, and the integrated mean square fluctuation of ionization density is 10 to the 28th/m. The spectral index of three produces the correct spectral behavior at high fluctuation frequencies, and the correct ratios of the upper roll-off frequencies at three wave frequencies. The rms fluctuation of phase is about 130 rad at 360 MHz, 340 rad at 140 MHz, and 1200 rad at 40 MHz. At 40 MHz, the scale of the intensity fluctuation at ground level is about 10 m; removal of almost all fluctuations in the ionosphere at scales below the Fresnel scale leaves the fine structure of the intensity spectrum at ground level virtually unaffected.
Kwon, Dohyeon; Jeon, Chan-Gi; Shin, Junho; Heo, Myoung-Sun; Park, Sang Eon; Song, Youjian; Kim, Jungwon
2017-01-01
Timing jitter is one of the most important properties of femtosecond mode-locked lasers and optical frequency combs. Accurate measurement of timing jitter power spectral density (PSD) is a critical prerequisite for optimizing overall noise performance and further advancing comb applications both in the time and frequency domains. Commonly used jitter measurement methods require a reference mode-locked laser with timing jitter similar to or lower than that of the laser-under-test, which is a demanding requirement for many laser laboratories, and/or have limited measurement resolution. Here we show a high-resolution and reference-source-free measurement method of timing jitter spectra of optical frequency combs using an optical fibre delay line and optical carrier interference. The demonstrated method works well for both mode-locked oscillators and supercontinua, with 2 × 10−9 fs2/Hz (equivalent to −174 dBc/Hz at 10-GHz carrier frequency) measurement noise floor. The demonstrated method can serve as a simple and powerful characterization tool for timing jitter PSDs of various comb sources including mode-locked oscillators, supercontinua and recently emerging Kerr-frequency combs; the jitter measurement results enabled by our method will provide new insights for understanding and optimizing timing noise in such comb sources. PMID:28102352
NASA Astrophysics Data System (ADS)
Kwon, Dohyeon; Jeon, Chan-Gi; Shin, Junho; Heo, Myoung-Sun; Park, Sang Eon; Song, Youjian; Kim, Jungwon
2017-01-01
Timing jitter is one of the most important properties of femtosecond mode-locked lasers and optical frequency combs. Accurate measurement of timing jitter power spectral density (PSD) is a critical prerequisite for optimizing overall noise performance and further advancing comb applications both in the time and frequency domains. Commonly used jitter measurement methods require a reference mode-locked laser with timing jitter similar to or lower than that of the laser-under-test, which is a demanding requirement for many laser laboratories, and/or have limited measurement resolution. Here we show a high-resolution and reference-source-free measurement method of timing jitter spectra of optical frequency combs using an optical fibre delay line and optical carrier interference. The demonstrated method works well for both mode-locked oscillators and supercontinua, with 2 × 10‑9 fs2/Hz (equivalent to ‑174 dBc/Hz at 10-GHz carrier frequency) measurement noise floor. The demonstrated method can serve as a simple and powerful characterization tool for timing jitter PSDs of various comb sources including mode-locked oscillators, supercontinua and recently emerging Kerr-frequency combs; the jitter measurement results enabled by our method will provide new insights for understanding and optimizing timing noise in such comb sources.
The effect of sampling rate and anti-aliasing filters on high-frequency response spectra
Boore, David M.; Goulet, Christine
2013-01-01
The most commonly used intensity measure in ground-motion prediction equations is the pseudo-absolute response spectral acceleration (PSA), for response periods from 0.01 to 10 s (or frequencies from 0.1 to 100 Hz). PSAs are often derived from recorded ground motions, and these motions are usually filtered to remove high and low frequencies before the PSAs are computed. In this article we are only concerned with the removal of high frequencies. In modern digital recordings, this filtering corresponds at least to an anti-aliasing filter applied before conversion to digital values. Additional high-cut filtering is sometimes applied both to digital and to analog records to reduce high-frequency noise. Potential errors on the short-period (high-frequency) response spectral values are expected if the true ground motion has significant energy at frequencies above that of the anti-aliasing filter. This is especially important for areas where the instrumental sample rate and the associated anti-aliasing filter corner frequency (above which significant energy in the time series is removed) are low relative to the frequencies contained in the true ground motions. A ground-motion simulation study was conducted to investigate these effects and to develop guidance for defining the usable bandwidth for high-frequency PSA. The primary conclusion is that if the ratio of the maximum Fourier acceleration spectrum (FAS) to the FAS at a frequency fsaa corresponding to the start of the anti-aliasing filter is more than about 10, then PSA for frequencies above fsaa should be little affected by the recording process, because the ground-motion frequencies that control the response spectra will be less than fsaa . A second topic of this article concerns the resampling of the digital acceleration time series to a higher sample rate often used in the computation of short-period PSA. We confirm previous findings that sinc-function interpolation is preferred to the standard practice of using
[On peculiarities of temperature dependences of water spectra in the terahertz frequency domain].
Penkov, N V; Yashin, V A; Shvirst, N E; Fesenko, E E; Fesenko, E E
2014-01-01
We analyzed spectra of light and heavy water at temperatures from 4 up to 50 degrees C in a frequency range of 0.15 to 6.5 THz. It was shown that the amplitude of high-frequency relaxation absorption band with its maximum at 0.5 THz extends with increasing, temperature and this temperature dependence for light water has a marked feature at 35-40 degrees C as a sharp growth. This fact is noteworthy because this range corresponds to physiological values of a body temperature of the warm-blooded organisms. At the same time, the analogous temperature dependence for heavy water in the considered temperature range lacks this particular feature. Thus, the water with its properties differs significantly not only from other fluids, but also from its own isotopologues.
Role of geometry on the frequency spectra of U-shaped atomic force microscope probes
NASA Astrophysics Data System (ADS)
Rezaei, E.; Turner, J. A.
2017-02-01
Contact resonance atomic force microscopy (CR-AFM) is a specific technique that is used to determine elastic or viscoelastic properties of materials. The success of this technique is highly dependent on the accuracy of frequency spectra that must be measured for both noncontact and the case in which the tip is in contact with the sample of interest. Thus, choosing the right probe is crucial for accurate experiments. U-shaped probes also offer new opportunities for CR-AFM measurements because of certain specific modes that have tip motion parallel to the sample surface such that these resonances can access in-plane sample properties. However, analysis of the spectra from U-shaped probes is much more challenging due to these modes. The geometry of these probes is the main driver for the spectral response. Here, this influence on the resonance frequencies of the commercially fabricated U-shaped probe AN2-300 is evaluated with respect to geometry in terms of leg width, crossbeam width, and crossbeam length. Both noncontact and contact cases are examined with respect to variations of the nominal geometry. An energy distribution approach is also presented to assist with the identification of modes that have close resonances. Finally, this analysis allows recommendations to be made in order to minimize the convergence of multiple resonances for a specific range of measurement parameters.
First Measurements of High Frequency Cross-Spectra from a Pair of Large Michelson Interferometers.
Chou, Aaron S; Gustafson, Richard; Hogan, Craig; Kamai, Brittany; Kwon, Ohkyung; Lanza, Robert; McCuller, Lee; Meyer, Stephan S; Richardson, Jonathan; Stoughton, Chris; Tomlin, Raymond; Waldman, Samuel; Weiss, Rainer
2016-09-09
Measurements are reported of the cross-correlation of spectra of differential position signals from the Fermilab Holometer, a pair of colocated 39 m long, high power Michelson interferometers with flat broadband frequency response in the MHz range. The instrument obtains sensitivity to high frequency correlated signals far exceeding any previous measurement in a broad frequency band extending beyond the 3.8 MHz inverse light-crossing time of the apparatus. The dominant but uncorrelated shot noise is averaged down over 2×10^{8} independent spectral measurements with 381 Hz frequency resolution to obtain 2.1×10^{-20}m/sqrt[Hz] sensitivity to stationary signals. For signal bandwidths Δf>11 kHz, the sensitivity to strain h or shear power spectral density of classical or exotic origin surpasses a milestone PSD_{δh}
First measurements of high frequency cross-spectra from a pair of large Michelson interferometers
Chou, Aaron S.; Gustafson, Richard; Hogan, Craig; Kamai, Brittany; Kwon, Ohkyung; Lanza, Robert; McCuller, Lee; Meyer, Stephan S.; Richardson, Jonathan; Stoughton, Chris; Tomlin, Raymond; Waldman, Samuel; Weiss, Rainer
2016-09-09
Here, measurements are reported of the cross-correlation of spectra of differential position signals from the Fermilab Holometer, a pair of colocated 39 m long, high power Michelson interferometers with flat broadband frequency response in the MHz range. The instrument obtains sensitivity to high frequency correlated signals far exceeding any previous measurement in a broad frequency band extending beyond the 3.8 MHz inverse light-crossing time of the apparatus. The dominant but uncorrelated shot noise is averaged down over 2 × 10^{8} independent spectral measurements with 381 Hz frequency resolution to obtain 2.1 × 10^{-20}m/ √Hz sensitivity to stationary signals. For signal bandwidths Δf > 11 kHz, the sensitivity to strain h or shear power spectral density of classical or exotic origin surpasses a milestone PSD_{δh} < t_{p} where t_{p} = 5.39 × 10^{-44}/ Hz is the Planck time.
First measurements of high frequency cross-spectra from a pair of large Michelson interferometers
Chou, Aaron S.; Gustafson, Richard; Hogan, Craig; ...
2016-09-09
Here, measurements are reported of the cross-correlation of spectra of differential position signals from the Fermilab Holometer, a pair of colocated 39 m long, high power Michelson interferometers with flat broadband frequency response in the MHz range. The instrument obtains sensitivity to high frequency correlated signals far exceeding any previous measurement in a broad frequency band extending beyond the 3.8 MHz inverse light-crossing time of the apparatus. The dominant but uncorrelated shot noise is averaged down over 2 × 108 independent spectral measurements with 381 Hz frequency resolution to obtain 2.1 × 10-20m/ √Hz sensitivity to stationary signals. For signal bandwidths Δf >more » 11 kHz, the sensitivity to strain h or shear power spectral density of classical or exotic origin surpasses a milestone PSDδh < tp where tp = 5.39 × 10-44/ Hz is the Planck time.« less
NASA Astrophysics Data System (ADS)
Zhang, Yu; Xu, Yixian; Xia, Jianghai
2012-12-01
A better understanding of the influences of different surface fluid drainage conditions on the propagation and attenuation of surface waves as the stipulated frequency is varied is a key issue to apply surface wave method to detect subsurface hydrological properties. Our study develops three-dimensional dynamical Green's functions in poroelastic media for Rayleigh waves of possible free surface conditions: permeable - "open pore," impermeable - "closed pore," and partially permeable boundaries. The full transient response of wave fields and spectra due to a stress impulse wavelet on the surface are investigated in the exploration seismic frequency band for typical surface drainage conditions, viscous coupling-damping, solid frame properties and porous fluid flowing configuration. Our numerical results show that, due to the slow dilatational wave - P2 wave, two types of Rayleigh waves, designated as R1 and R2 waves, exist along the surface. R1 wave possesses high energy as classic Rayleigh waves in pure elastic media for each porous materials. A surface fluid drainage condition is a significant factor to influence dispersion and attenuation, especially attenuation of R1 waves. R2 wave for closed pore and partially permeable surfaces is only observed for a low coupling-damping coefficient. The non-physical wave for partially surface conditions causes the R1 wave radiates into the R2 wave in the negative attenuation frequency range. It makes weaker R1 wave and stronger R2 wave to closed pore surface. Moreover, it is observed that wave fields and spectra of R1 wave are sensitive to frame elastic moduli change for an open pore surface, and to pore fluid flow condition change for closed pore and partially permeable surface.
Menin, O H; Martinez, A S; Costa, A M
2016-05-01
A generalized simulated annealing algorithm, combined with a suitable smoothing regularization function is used to solve the inverse problem of X-ray spectrum reconstruction from attenuation data. The approach is to set the initial acceptance and visitation temperatures and to standardize the terms of objective function to automate the algorithm to accommodate different spectra ranges. Experiments with both numerical and measured attenuation data are presented. Results show that the algorithm reconstructs spectra shapes accurately. It should be noted that in this algorithm, the regularization function was formulated to guarantee a smooth spectrum, thus, the presented technique does not apply to X-ray spectrum where characteristic radiation are present.
Unexpected, high-Q, low-frequency peaks in seismic spectra
NASA Astrophysics Data System (ADS)
Thomson, David J.; Vernon, Frank L.
2015-09-01
It was established over a decade ago that the normal modes of the Earth are continuously excited at times without large earthquakes, but the sources of the `seismic hum' have remained unresolved. In addition to the normal modes of the Earth, we show spectral lines in seismic data with frequencies which correspond closely to normal modes of the Sun. Moreover, the widths of the low-frequency lines in the seismic spectra are similar to those of solar modes and much narrower than those of the Earth's normal mode peaks. These seismic lines are highly coherent with magnetic fields measured on both the Geostationary Operations Environmental Satellite (GOES)-10 satellite and the Advanced Composition Explorer (ACE) spacecraft located at L1, 1.5 million km sunward of Earth suggesting that the solar modes are transmitted to the Earth by the interplanetary magnetic field and solar wind. The solar modes are split by multiples of a cycle/day and, surprisingly, by the `quasi two-day' mode and other frequencies. Both the phase of the coherences and slight frequency offsets between seismic and geomagnetic data at observatories exclude the possibility that these effects are simply spurious responses of the seismometers to the geomagnetic field. We emphasize data from low-noise seismic observatories: Black Forest (BFO), Piñon Flat (PFO), Eskdalemuir (ESK) and Obninsk (OBN). Horizontal components of seismic velocity show higher coherences with the external (ACE) magnetic field than do the vertical components. This effect appears to be larger near the seismic torsional, or T-mode, frequencies.
NASA Astrophysics Data System (ADS)
O. Vats, Hari; Booker, Henry G.; Majidiahi, Gholamreza
Under evening equatorial conditions, strong intensity spectra observed simultaneously on transmissions through the ionospheric F-region at 40, 140 and 360 MHz from a stationary satellite are explained quantitatively in terms of refractive scattering using the approach of BOOKER and MAJIDIAHI (1981). Use is made of an outer scale (wavelength/2gp) of 50 km, an inner scale of 5 m and an integrated mean square fluctuation of ionization density [ ∝ overline(ΔN) 2dz] of 10 28 m -5. The spectral index required to fit the observations is 3, and no major departure from this value is permissible either way. This produces the correct spectral behavior at high fluctuation frequencies and the correct ratios of the upper roll-off frequencies at the three wave frequencies. The RMS fluctuation of phase is about 130 rad at 360 MHz, 340 rad at 140 MHz and 1200 rad at 40 MHz. At 40MHz the scale of the intensity fluctuation at ground level is about 10m, and this is caused by refractive scattering in the ionosphere at scales of the order of the outer scale; removal of practically all fluctuations in the ionosphere at scales below the Fresnel scale leaves the fine structure of the intensity spectrum at ground level virtually unaffected.
Doppler frequency in interplanetary radar and general relativity
NASA Technical Reports Server (NTRS)
Mcvittie, G. C.
1972-01-01
The change of frequency of an interplanetary radar signal sent from the earth to another planet or to a space probe is worked out according to general relativity. The Schwarzschild spacetime is employed and its null geodesics control the motion of the signals. Exact Doppler frequency formulas are derived for one-way and two-way radar in terms of an arbitrary Schwarzschild radial coordinate. A reduction to the special relativity case is used to interpret the formulas in terms of the relative radial velocity of emitter and target. The general relativity corrections are worked out approximately for each of three possible Schwarzschild radial coordinates, and a numerical example is given. The amount of the correction is different according as one or the other of the Schwarzschild coordinates is identified with the radius vector deduced from classical celestial mechanics. The identification problem is discussed.
NASA Astrophysics Data System (ADS)
Gelman, L.; Petrunin, I.; Komoda, J.
2010-02-01
The new chirp-Wigner higher order spectra (CWHOS) are proposed for transient signals with any known nonlinear polynomial variation of instantaneous frequency. The proposed technique is effective for nonlinearity detection for transient signals with nonlinear polynomial time variation of the instantaneous frequency.
Implementation of the Frequency Separation Technique in general lineshape codes
NASA Astrophysics Data System (ADS)
Alexiou, S.
2013-06-01
The Frequency Separation Technique (FST) has been proposed and theoretically documented. It is a technique capable of unifying and improving lineshape calculations, for both accuracy and speed. In this work, we briefly recall its key features and advantages and present a practical way of implementing it in lineshape codes. We note that the FST is a general technique, capable of working with practically any modern lineshape framework that can either employ or go beyond the standard framework.
Ishiyama, Tatsuya; Morita, Akihiro; Tahara, Tahei
2015-06-07
Two-dimensional heterodyne-detected vibrational sum frequency generation (2D HD-VSFG) spectra at vapor/water interface were studied by molecular dynamics (MD) simulation with a classical flexible and nonpolarizable model. The present model well describes the spectral diffusion of 2D infrared spectrum of bulk water as well as 2D HD-VSFG at the interface. The effect of isotopic dilution on the 2D HD-VSFG was elucidated by comparing the normal (H{sub 2}O) water and HOD water. We further performed decomposition analysis of 2D HD-VSFG into the hydrogen-bonding and the dangling (or free) OH vibrations, and thereby disentangled the different spectral responses and spectral diffusion in the 2D HD-VSFG. The present MD simulation demonstrated the role of anharmonic coupling between these modes on the cross peak in the 2D HD-VSFG spectrum.
Broadband cavity-enhanced molecular spectra from Vernier filtering of a complete frequency comb.
Rutkowski, Lucile; Morville, Jérôme
2014-12-01
We present a new approach to cavity enhanced-direct frequency comb spectroscopy where the full emission bandwidth of a titanium:sapphire laser is exploited, currently at gigahertz resolution. The technique is based on low-resolution Vernier filtering obtained with an appreciable actively stabilized mismatch between the cavity-free spectral range and the laser repetition rate, using a diffraction grating and a split-photodiode. Spectra covering 1300 cm⁻¹ (40 THz) are acquired in less than 100 ms, and a baseline noise of 1.7×10⁻⁸ cm⁻¹ is reached with a cavity finesse of only 300, providing an absorption figure of merit M=6×10⁻¹¹ cm⁻¹·Hz(-1/2).
Dynamics of phase oscillators with generalized frequency-weighted coupling
NASA Astrophysics Data System (ADS)
Xu, Can; Gao, Jian; Xiang, Hairong; Jia, Wenjing; Guan, Shuguang; Zheng, Zhigang
2016-12-01
Heterogeneous coupling patterns among interacting elements are ubiquitous in real systems ranging from physics, chemistry to biology communities, which have attracted much attention during recent years. In this paper, we extend the Kuramoto model by considering a particular heterogeneous coupling scheme in an ensemble of phase oscillators, where each oscillator pair interacts with different coupling strength that is weighted by a general function of the natural frequency. The Kuramoto theory for the transition to synchronization can be explicitly generalized, such as the expression for the critical coupling strength. Also, a self-consistency approach is developed to predict the stationary states in the thermodynamic limit. Moreover, Landau damping effects are further revealed by means of linear stability analysis and resonance poles theory below the critical threshold, which turns to be far more generic. Our theoretical analysis and numerical results are consistent with each other, which can help us understand the synchronization transition in general networks with heterogenous couplings.
NASA Astrophysics Data System (ADS)
Wu, Yue-Chao; Zhao, Bin; Lee, Soo-Y.
2016-02-01
Femtosecond stimulated Raman spectroscopy (FSRS) on the Stokes side arises from a third order polarization, P(3)(t), which is given by an overlap of a first order wave packet, |" separators=" Ψ2 ( 1 ) ( p u , t ) > , prepared by a narrow band (ps) Raman pump pulse, Epu(t), on the upper electronic e2 potential energy surface (PES), with a second order wave packet, <" separators=" Ψ1 ( 2 ) ( p r ∗ , p u , t ) | , that is prepared on the lower electronic e1 PES by a broadband (fs) probe pulse, Epr(t), acting on the first-order wave packet. In off-resonant FSRS, |" separators=" Ψ2 ( 1 ) ( p u , t ) > resembles the zeroth order wave packet |" separators=" Ψ1 ( 0 ) ( t ) > on the lower PES spatially, but with a force on |" separators=" Ψ2 ( 1 ) ( p u , t ) > along the coordinates of the reporter modes due to displacements in the equilibrium position, so that <" separators=" Ψ1 ( 2 ) ( p r ∗ , p u , t ) | will oscillate along those coordinates thus giving rise to similar oscillations in P(3)(t) with the frequencies of the reporter modes. So, by recovering P(3)(t) from the FSRS spectrum, we are able to deduce information on the time-dependent quantum-mechanical wave packet averaged frequencies, ω ¯ j ( t ) , of the reporter modes j along the trajectory of |" separators=" Ψ1 ( 0 ) ( t ) > . The observable FSRS Raman gain is related to the imaginary part of P(3)(ω). The imaginary and real parts of P(3)(ω) are related by the Kramers-Kronig relation. Hence, from the FSRS Raman gain, we can obtain the complex P(3)(ω), whose Fourier transform then gives us the complex P(3)(t) to analyze for ω ¯ j ( t ) . We apply the theory, first, to a two-dimensional model system with one conformational mode of low frequency and one reporter vibrational mode of higher frequency with good results, and then we apply it to the time-resolved FSRS spectra of the cis-trans isomerization of retinal in rhodopsin [P. Kukura et al., Science 310, 1006 (2005)]. We obtain the vibrational
Wu, Yue-Chao; Zhao, Bin; Lee, Soo-Y
2016-02-07
Femtosecond stimulated Raman spectroscopy (FSRS) on the Stokes side arises from a third order polarization, P(3)(t), which is given by an overlap of a first order wave packet, |Ψ2(1)(pu,t)>, prepared by a narrow band (ps) Raman pump pulse, Epu(t), on the upper electronic e2 potential energy surface (PES), with a second order wave packet, <Ψ1(2)(pr(∗),pu,t)|, that is prepared on the lower electronic e1 PES by a broadband (fs) probe pulse, Epr(t), acting on the first-order wave packet. In off-resonant |FSRS, Ψ2(1)(pu,t)> resembles the zeroth order wave packet |Ψ1(0)(t)> on the lower PES spatially, but with a force on |Ψ2(1)(pu,t)> along the coordinates of the reporter modes due to displacements in the equilibrium position, so that <Ψ1(2)(pr(∗),pu,t)| will oscillate along those coordinates thus giving rise to similar oscillations in P(3)(t) with the frequencies of the reporter modes. So, by recovering P(3)(t) from the FSRS spectrum, we are able to deduce information on the time-dependent quantum-mechanical wave packet averaged frequencies, ω̄j(t), of the reporter modes j along the trajectory of |Ψ1 (0)(t)>. The observable FSRS Raman gain is related to the imaginary part of P(3)(ω). The imaginary and real parts of P(3)(ω) are related by the Kramers-Kronig relation. Hence, from the FSRS Raman gain, we can obtain the complex P(3)(ω), whose Fourier transform then gives us the complex P(3)(t) to analyze for ω̄j(t). We apply the theory, first, to a two-dimensional model system with one conformational mode of low frequency and one reporter vibrational mode of higher frequency with good results, and then we apply it to the time-resolved FSRS spectra of the cis-trans isomerization of retinal in rhodopsin [P. Kukura et al., Science 310, 1006 (2005)]. We obtain the vibrational frequency up-shift time constants for the C12-H wagging mode at 216 fs and for the C10-H wagging mode at 161 fs which are larger than for the C11-H wagging mode at 127 fs, i.e., the C11-H
Sun, Tao; Song, Yi-Zhong
2013-11-01
The mutual evolving processes of signals' waveforms and their spectra were numerically analyzed in time and frequency domains. The purpose was to research the essential relation between the signals' waveforms and their spectra. Then, the mutual transform principle was applied to analyze moiré pattern spectra, acquiring phase distribution information of the pattern. The rectangular window function was used to simulate the mutual transform between the impulse signal and direct-current waveform. Many rectangular window signals with deferent widths were obtained by changing the window width The unit impulse signal was obtained by changing the width down to zero, and the direct-current waveform obtained by changing the width up to +infinity. For smart, quick, and easy implementation of discrete Fourier transforms to rectangular pulses and obtain signals' spectra, a simple FFT system was worked out. With its calculating, the mutual evolving processes of signals' waveforms and their spectra were tracked deeply. All signals here were transformed with it. As the result, first, the spectra of rectangular window signals were in the form of sampling function [Sa(x) = sin(x)/x]. Second, with the change in the window's width, the waveform of Sa(x) changed. Third, when the width decreased, the waveform of Sa(x) extended, and vibrated more slowly. It changed into direct-current waveform when the width decreased to zero. Last, when the width increased, the waveform of Sa(x) shranked, and vibrated faster. It changed into impulse waveform when the width increased to +infinity. Signals' waveforms were in mutual transforms between the time and frequency domain. The transforming essence was considered as that the frequency component principle in Fourier series theory is reflected in the frequency domain. According to the principle of mutual transforms between signals' waveforms and their spectra, the first order spectrum of the moiré pattern was extracted out and normalized to a
NASA Technical Reports Server (NTRS)
Panda, J.; Roozeboom, N. H.; Ross, J. C.
2016-01-01
The recent advancement in fast-response Pressure-Sensitive Paint (PSP) allows time-resolved measurements of unsteady pressure fluctuations from a dense grid of spatial points on a wind tunnel model. This capability allows for direct calculations of the wavenumber-frequency (k-?) spectrum of pressure fluctuations. Such data, useful for the vibro-acoustics analysis of aerospace vehicles, are difficult to obtain otherwise. For the present work, time histories of pressure fluctuations on a flat plate subjected to vortex shedding from a rectangular bluff-body were measured using PSP. The light intensity levels in the photographic images were then converted to instantaneous pressure histories by applying calibration constants, which were calculated from a few dynamic pressure sensors placed at selective points on the plate. Fourier transform of the time-histories from a large number of spatial points provided k-? spectra for pressure fluctuations. The data provides first glimpse into the possibility of creating detailed forcing functions for vibro-acoustics analysis of aerospace vehicles, albeit for a limited frequency range.
NASA Astrophysics Data System (ADS)
Van Huffel, Sabine; Wang, Yu; Vanhamme, Leentje; Van Hecke, Paul
2002-09-01
Several algorithms for automatic frequency alignment and quantitation of single resonances in multiple magnetic resonance (MR) spectra are investigated. First, a careful comparison between the complex principal component analysis (PCA) and the Hankel total least squares-based methods for quantifying the resonances in the spectral sets of magnetic resonance spectroscopy imaging (MRSI) spectra is presented. Afterward, we discuss a method based on complex PCA plus linear regression and a method based on cross correlation of the magnitude spectra for correcting frequency shifts of resonances in sets of MR spectra. Their advantages and limitations are demonstrated on simulated MR data sets as well as on an in vivo MRSI data set of the human brain.
General Applicable Frequency Map for the Amide-I Mode in β-Peptides.
Cai, Kaicong; Du, Fenfen; Zheng, Xuan; Liu, Jia; Zheng, Renhui; Zhao, Juan; Wang, Jianping
2016-02-18
In this work, a general applicable amide-I vibrational frequency map (GA map) for β-peptides in a number of common solvents was constructed, based on a peptide derivative, N-ethylpropionamide (NEPA). The map utilizes force fields at the ab initio computational level to accurately describe molecular structure and solute-solvent interactions, and also force fields at the molecular mechanics level to take into account long-range solute-solvent interactions. The results indicate that the GA map works reasonably for mapping the vibrational frequencies of the amide-I local-modes for β-peptides, holding promises for understanding the complicated infrared spectra of the amide-I mode in β-polypeptides.
Generalized regular singular-point description of low-frequency dielectric responses
NASA Astrophysics Data System (ADS)
Frenning, Göran; Nilsson, Martin; Strømme, Maria
2004-07-01
This paper presents a generalized regular singular-point (GRSP) model developed to account for dielectric spectra of the wide range of materials having a frequency response containing more than two power-law regions. In fact, the model is valid for an unlimited number of such regions, and is shown to provide a good description of the entire dielectric spectrum of tablets made of microcrystalline cellulose, including two relaxation peaks and power-law responses at low and high frequencies. This finding puts the GRSP model in a unique position, since no model existing in the literature is able to describe the totality of features present in the spectrum, without resorting to a superposition of more elementary responses.
Filter Design for Generalized Frequency-Division Multiplexing
NASA Astrophysics Data System (ADS)
Han, Seungyul; Sung, Youngchul; Lee, Yong H.
2017-04-01
In this paper, optimal filter design for generalized frequency-division multiplexing (GFDM) is considered under two design criteria: rate maximization and out-of-band (OOB) emission minimization. First, the problem of GFDM filter optimization for rate maximization is formulated by expressing the transmission rate of GFDM as a function of GFDM filter coefficients. It is shown that Dirichlet filters are rate-optimal in additive white Gaussian noise (AWGN) channels with no carrier frequency offset (CFO) under linear zero-forcing (ZF) or minimum mean-square error (MMSE) receivers, but in general channels perturbed by CFO a properly designed nontrivial GFDM filter can yield better performance than Dirichlet filters by adjusting the subcarrier waveform to cope with the channel-induced CFO. Next, the problem of GFDM filter design for OOB emission minimization is formulated by expressing the power spectral density (PSD) of the GFDM transmit signal as a function of GFDM filter coefficients, and it is shown that the OOB emission can be reduced significantly by designing the GFDM filter properly. Finally, joint design of GFDM filter and window for the two design criteria is considered.
NASA Astrophysics Data System (ADS)
Nigmatullin, Raoul R.
2009-02-01
Based on the reduction property of dielectric spectra associated with the power-law function [∼( jωτ) ± ν] that appears in the frequency domain, one can develop an effective procedure for detection of different reduced motions (described by the corresponding power-law exponents) in temperature domain. If the power-law exponent ν is related to characteristic relaxation time τ by the relationship ν= ν0 ln( τ/ τ s)/ln( τ/ τ0) (here τ s, τ0 are the characteristic times characterizing a movement over fractal cluster that is defined in Ref. [Ya.E. Ryabov, Yu. Feldman, J. Chem. Phys. 116 (2002) 8610]) and the simple temperature dependence of τ( T)= τ A exp( E/ T) obeys the traditional Arrhenius relationship, then one can prove that any extreme point figuring in the complex permittivity ε( jω) spectra (characterized by the values [ ω m, y( ω m)]) obeys the generalized Vogel-Fulcher-Tamman (VFT) equation. This important statement confirms the existence of the ‘universal’ response (UR) (discovered and classified by Jonscher in frequency domain) and opens new possibilities in the detection of the ‘hidden’ collective motions in temperature region for self-similar (heterogeneous) systems. It gives also the extended interpretation of the VFT equation and allows one to differentiate collective motions passing through an extreme point. This differentiation, in turn, allows one to select the proper fitting function containing one or two (at least) relaxation times for the fitting of the complex permittivity function ε( jω) in the limited frequency domain. This conclusion can allow for the classification of dielectric spectroscopy as the spectroscopy of the reduced ( collective) motions, which are described by different power-law exponents on the mesoscale region. The verification of this approach on available DS data (poly(ethylene glycol)-based-single-ion conductors) completely confirms the basic statements of this theory and opens new possibilities
Cametti, C
2010-03-01
We have investigated the dielectric properties of water-in-oil microemulsions composed of sodium bis(2-ethyl-hexyl)sulfosuccinate, water, and decane, using radiofrequency impedance spectroscopy, below the percolation threshold, where the system behaves as surfactant-coated individual water droplets dispersed in a continuous oil phase. The analysis of the dielectric spectra has evidenced that the whole dielectric response below percolation is due to two different contributions, which give rise to two partially overlapping dielectric relaxations, approximately in the frequency range from 10 to 500 MHz. The first of these mechanisms is originated by the bulk polarization of counterions distributed in the electrical double layer of the droplet interior. The second mechanism is associated with a correlated motion of the anionic head groups SO3- at the surfactant-water interface. The introduction of this latter contribution allows us to justify the experimentally observed increase in the low-frequency permittivity as a function of temperature up to temperatures very close to percolation. The present study shows that deviations from the expected values on the basis of dielectric theories of heterogeneous systems (Maxwell-Wagner effect) observed when percolation is approaching can be accounted for, in a reasonable way, by the introduction of a further polarization mechanism, which involves the anionic surfactant groups. Only very close to percolation, when microemulsions undergo a scaling behavior, deviations of the permittivity (and electrical conductivity as well) are a print of the structural rearrangement of the whole system and models based on colloidal particle suspension theories fail. Even if the whole picture of the dielectric properties of microemulsion systems does not change in deep, nevertheless, the refinement introduced in this paper demonstrates how different polarization mechanisms could be simultaneously present in these rather complex systems and, above
The widest frequency radio relic spectra: observations from 150 MHz to 30 GHz
NASA Astrophysics Data System (ADS)
Stroe, Andra; Shimwell, Timothy; Rumsey, Clare; van Weeren, Reinout; Kierdorf, Maja; Donnert, Julius; Jones, Thomas W.; Röttgering, Huub J. A.; Hoeft, Matthias; Rodríguez-Gonzálvez, Carmen; Harwood, Jeremy J.; Saunders, Richard D. E.
2016-01-01
Radio relics are patches of diffuse synchrotron radio emission that trace shock waves. Relics are thought to form when intracluster medium electrons are accelerated by cluster merger-induced shock waves through the diffusive shock acceleration mechanism. In this paper, we present observations spanning 150 MHz to 30 GHz of the `Sausage' and `Toothbrush' relics from the Giant Metrewave and Westerbork telescopes, the Karl G. Jansky Very Large Array, the Effelsberg telescope, the Arcminute Microkelvin Imager and Combined Array for Research in Millimeter-wave Astronomy. We detect both relics at 30 GHz, where the previous highest frequency detection was at 16 GHz. The integrated radio spectra of both sources clearly steepen above 2 GHz, at the ≳6σ significance level, supporting the spectral steepening previously found in the `Sausage' and the Abell 2256 relic. Our results challenge the widely adopted simple formation mechanism of radio relics and suggest more complicated models have to be developed that, for example, involve re-acceleration of aged seed electrons.
Hieu, Hoang Chi; Li, Hongyan; Miyauchi, Yoshihiro; Mizutani, Goro; Fujita, Naoko; Nakamura, Yasunori
2015-03-05
We report a sum frequency generation (SFG) spectroscopy study of d-glucose, d-fructose and sucrose in the CH stretching vibration regime. Wetting effect on the SFG spectra was investigated. The SFG spectrum of d-glucose changed from that of α-d-glucose into those of α-d-glucose monohydrate by wetting. The SFG spectra showed evidence of a small change of β-d-fructopyranose into other anomers by wetting. SFG spectra of sucrose did not change by wetting. Assignments of the vibrational peaks in the SFG spectra of the three sugars in the dry and wet states were performed in the CH stretching vibration region near 3000cm(-1).
Diaper dermatitis: frequency and severity among a general infant population.
Jordan, W E; Lawson, K D; Berg, R W; Franxman, J J; Marrer, A M
1986-06-01
The frequency and severity of diaper dermatitis was measured among a midwestern suburban population of 1089 infants ranging in age from 1 to 20 months. No diagnosis of specific etiology was made. Fecal samples were collected and analyzed for Candida albicans, and information on family characteristics, infant diet, general health, history of rash, and diapering habits and practices was collected by questionnaire. The distribution of the severity of observed diaper rash can be described as a logarithmic-normal function, implying several multiplicative causative factors. Within the total severity range, there appear to be three subcategories of diaper rash, differing in some manner, perhaps reflecting different etiologies. The frequency of observed diaper rash was a function of the maturity of the infant, reaching a maximum around 9 to 12 months of age. The prevalence of severe rash correlated with the presence and level of fecal C. albicans. Infants diapered exclusively in disposable diapers showed less rash (P less than 0.001) than those diapered exclusively or sometimes in cloth diapers.
Multivariate cross-frequency coupling via generalized eigendecomposition
Cohen, Michael X
2017-01-01
This paper presents a new framework for analyzing cross-frequency coupling in multichannel electrophysiological recordings. The generalized eigendecomposition-based cross-frequency coupling framework (gedCFC) is inspired by source-separation algorithms combined with dynamics of mesoscopic neurophysiological processes. It is unaffected by factors that confound traditional CFC methods—such as non-stationarities, non-sinusoidality, and non-uniform phase angle distributions—attractive properties considering that brain activity is neither stationary nor perfectly sinusoidal. The gedCFC framework opens new opportunities for conceptualizing CFC as network interactions with diverse spatial/topographical distributions. Five specific methods within the gedCFC framework are detailed, these are validated in simulated data and applied in several empirical datasets. gedCFC accurately recovers physiologically plausible CFC patterns embedded in noise that causes traditional CFC methods to perform poorly. The paper also demonstrates that spike-field coherence in multichannel local field potential data can be analyzed using the gedCFC framework, which provides significant advantages over traditional spike-field coherence analyses. Null-hypothesis testing is also discussed. DOI: http://dx.doi.org/10.7554/eLife.21792.001 PMID:28117662
A development of a generalized frequency - domain transient program - FTP
Nagaoka, N.; Ametani, A. )
1988-10-01
A generalized frequency-domain transient program (FTP) is developed in the paper. The FTP is based on a frequency-time transform method adopting nodal analysis, admittance parameter and modal theories. Discontinuous and nonlinear elements are solved as initial condition problems using a piece-wise linear approximation of the nonlinear characteristics. The FTP is used to solve the transient and steady states of a network composed of an arbitrary interconnection of basic circuit elements. The FTP is structured to be compatible with the EMTP so that the same input data and output formats are those of the EMTP can be used. The present version of the FTP can deal with a network with over a hundred of nodes and branches. Comparisons of calculated results by the FTP with field test results and calculated results by the EMTP confirm a high accuracy and a satisfactory efficiency of the FTP. The FTP is of great advantage to offer the most accurate or theoretically exact solutions of transients on distributed-parameter lines.
NASA Astrophysics Data System (ADS)
Gusev, A. A.; Guseva, E. M.
2016-05-01
We describe a procedure for mass determination of the "source-controlled f max"—an important though not conventional parameter of earthquake source spectrum, relabeled here as "the third corner frequency," f c3, and discuss the results of its application. f max is the upper cutoff frequency of Fourier acceleration spectrum of a record of a local earthquake; both source and path attenuation contribute to f max. Most researchers believe the role of attenuation (" κ" parameter) to be dominating or exclusive. Still, source effect on f max is sometimes revealed. If real, it may be important for source physics. To understand better the f max phenomena, the constituents of f max must be accurately separated. With this goal, we process seismograms of moderate earthquakes from Kamchatka subduction zone. First, we need reliable estimates of attenuation to recover source spectra. To this goal, an iterative processing procedure is constructed, that adjusts the attenuation model until the recovered source acceleration spectra become, on the average, flat up either to f c3, or up to the high-frequency limit of the frequency range analyzed. The latter case occurs when f c3 is non-existent or unobservable. Below f c3, the double-corner source spectral model is thought to be valid, and the lower bound of acceleration spectral plateau is considered as the second corner frequency of earthquake source spectrum, fc2. The common corner frequency, f c1, is also estimated. Following this approach, more than 500 S-wave spectra of M = 4-6.5 Kamchatka earthquakes with hypocentral distances 80-220 km were analyzed. In about 80 % of the cases, f c3 is clearly manifested; the remaining cases show, at high frequency, flat source acceleration spectra. In addition, in about 2/3 of cases, f c2 is clearly above f c1, showing that double-corner spectra may dominate even at moderate magnitudes. Scaling behavior was examined for each of the corners. The f c1 vs. M 0 trend is common and close to
NASA Astrophysics Data System (ADS)
Tsutaoka, Takanori; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi
2013-05-01
We have studied the relative complex permittivity (ɛr = ɛr'- iɛr″) of copper granular composite materials containing coagulated Cu particles in the microwave range as well as the electrical conductivity. The insulator to metal transition was observed at the percolation threshold φc = 16.0 vol. %. The enhancement of permittivity in the insulating state can be described by the Effective Cluster Model. Above the percolation threshold φc, it was found that the Cu granular composites show negative permittivity spectra below a characteristic frequency f0 indicating the low frequency plasmonic state. Characteristic frequency tends to increase with particle content.
Lyakin, D V; Ryabukho, V P
2013-10-31
The results of theoretical and experimental studies of the longitudinal correlation properties of an optical field with broad angular and frequency spectra and manifestations of these properties in interference microscopy are presented. The joint and competitive influence of the angular and frequency spectra of the object-probing field on the longitudinal resolution and on the amplitude of the interference microscope signals from the interfaces between the media inside a multilayer object is demonstrated. The method of compensating the so-called defocusing effect that arises in the interference microscopy using objectives with a large numerical aperture is experimentally demonstrated, which consists in using as a light source in the interference microscope an illuminating interferometer with a frequency-broadband light source. This method of compensation may be used as the basis of simultaneous determination of geometric thickness and refractive index of media forming a multilayer object. (optical fields)
Generalized Exponential Distribution in Flood Frequency Analysis for Polish Rivers.
Markiewicz, Iwona; Strupczewski, Witold G; Bogdanowicz, Ewa; Kochanek, Krzysztof
2015-01-01
Many distributions have been used in flood frequency analysis (FFA) for fitting the flood extremes data. However, as shown in the paper, the scatter of Polish data plotted on the moment ratio diagram shows that there is still room for a new model. In the paper, we study the usefulness of the generalized exponential (GE) distribution in flood frequency analysis for Polish Rivers. We investigate the fit of GE distribution to the Polish data of the maximum flows in comparison with the inverse Gaussian (IG) distribution, which in our previous studies showed the best fitting among several models commonly used in FFA. Since the use of a discrimination procedure without the knowledge of its performance for the considered probability density functions may lead to erroneous conclusions, we compare the probability of correct selection for the GE and IG distributions along with the analysis of the asymptotic model error in respect to the upper quantile values. As an application, both GE and IG distributions are alternatively assumed for describing the annual peak flows for several gauging stations of Polish Rivers. To find the best fitting model, four discrimination procedures are used. In turn, they are based on the maximized logarithm of the likelihood function (K procedure), on the density function of the scale transformation maximal invariant (QK procedure), on the Kolmogorov-Smirnov statistics (KS procedure) and the fourth procedure based on the differences between the ML estimate of 1% quantile and its value assessed by the method of moments and linear moments, in sequence (R procedure). Due to the uncertainty of choosing the best model, the method of aggregation is applied to estimate of the maximum flow quantiles.
Tsutaoka, Takanori Fukuyama, Koki; Kinoshita, Hideaki; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi
2013-12-23
The relative complex permittivity and permeability spectra of the coagulated copper and yttrium iron garnet (Cu/YIG) hybrid granular composite materials have been studied in the microwave range. The insulator to metal transition was observed at the percolation threshold of Cu particle content (φ{sub Cu} = 16.0 vol. %) in the electrical conductivity. In the percolation threshold, the low frequency plasmonic state caused by the metallic Cu particle networks was observed. The percolated Cu/YIG granular composites show simultaneous negative permittivity and permeability spectra under external magnetic fields.
X-ray Spectra and Pulse Frequency Changes in SAX J2103.5+4545
NASA Technical Reports Server (NTRS)
Baykal, A.; Stark, M. J.; Swank, J. H.; White, Nicholas E. (Technical Monitor)
2002-01-01
The November 1999 outburst of the transient pulsar SAX J2103.5+4545 was monitored with the large area detectors of the Rossi X-Ray Timing Explorer until the pulsar faded after a year. The 358 s pulsar was spun up for 150 days, at which point the flux dropped quickly by a factor of approximately 7, the frequency saturated and, as the flux continued to decline, a weak spin-down began. The pulses remained strong during the decay and the spin-up/flux correlation can be fit to the Ghosh and Lamb derivations for the spin-up caused by accretion from a thin, pressure-dominated disk, for a distance approximately 3.2 kpc and a surface magnetic field approximately 1.2 x 10(exp 13) Gauss. During the bright spin-up part of the outburst, the flux was subject to strong orbital modulation, peaking approximately 3 days after periastron of the eccentric 12.68 day orbit, while during the faint part, there was little orbital modulation. The X-ray spectra were typical of accreting pulsars, describable by a cut-off power-law, with an emission line near the 6.4 keV of Kappa(sub alpha) fluorescence from cool iron. The equivalent width of this emission did not share the orbital modulation, but nearly doubled during the faint phase, despite little change in the column density. The outburst could have been caused by an episode of increased wind from a Be star, such that a small accretion disk is formed during each periastron passage. A change in the wind and disk structure apparently occurred after 5 months such that the accretion rate was no longer modulated or the diffusion time was longer. The distance estimate implies the X-ray luminosity observed was between 1 X 10(exp 36) ergs s(exp -1) and 6 x 10(exp 34) ergs s(exp -1), with a small but definite correlation of the intrinsic power-law spectral index.
NASA Astrophysics Data System (ADS)
Rimskaya-Korsakova, L. K.; Lalayants, M. R.; Supin, A. Ya.; Tavartkiladze, G. A.
2011-01-01
A psychoacoustic method for measuring masking thresholds based on the application of single-type stimuli and maskers intended for revealing compressive nonlinearity of displacements of the cochlea basila membrane and evaluation of the frequency resolution of hearing in a narrow frequency range near the central frequency of the stimulus is considered. High-frequency pulses with an envelope in the form of a Gaussian function with a sinusoidal filling with the frequency band corresponding to the width of the critical hearing band have been used as stimuli (referred to as compact). Noises with a spike structure of the amplitude spectrum with a limited frequency band width served as maskers. With the central frequencies of stimuli and maskers being equal, a band noise with the central frequency corresponding with a spike of an indented spectrum was called an on(rip)-frequency masker, while that with the central frequency corresponding to a dip in an indented spectrum was called an off(rip)-frequency masker. The central frequencies and frequency bands of the stimuli and maskers were 4 kHz and 1000 Hz, respectively. The spike (dip) frequencies of an indented amplitude spectrum of a masker were 1000 Hz. In the case of successive and simultaneous masking, the dependences of the thresholds of off(rip)-frequency masking of compact stimuli on the masker level revealed compressive nonlinearity of basila membrane displacements. However, threshold on(rip)/off(rip)-frequency masking differences visualized it much better. The estimates of the frequency resolution obtained under conditions of simultaneous masking of compact stimuli during variations in the frequency of spikes of indented masker spectra of low and medium levels corresponded to the width of the critical hearing band measured using a classical method of tone masking by a pair of narrow-band noise maskers. Within the spike frequency range of 500-2000 Hz, the steepness of the dependence of off(rip)-masking of compact
NASA Astrophysics Data System (ADS)
Feng, Zhipeng; Chen, Xiaowang; Liang, Ming; Ma, Fei
2015-10-01
The vibration signal of planetary gearboxes exhibits the characteristics of both amplitude modulation (AM) and frequency modulation (FM), and thus has a complex sideband structure. Time-varying speed and/or load will result in time variant characteristic frequency components. Since the modulating frequency is related to the gear fault characteristic frequency, the AM and FM parts each alone contains the information of the gear fault. We propose a time-frequency amplitude and frequency demodulation analysis metbhod to avoid the complex time-variant sideband analysis, and thereby identify the time-variant gear fault characteristic frequency. We enhance the time-frequency analysis via iterative generalized demodulation (IGD). The time-varying amplitude and frequency demodulated spectra have fine time-frequency resolution and are free of cross term interferences. They do not involve complex time-variant sidebands, thus considerably facilitating fault diagnosis of planetary gearboxes under nonstationary conditions. The method is validated using both numerically simulated data and experimental signals.
A high-frequency Doppler feature in the power spectra of simulated GRMHD black hole accretion disks
Wellons, Sarah; Zhu, Yucong; Narayan, Ramesh; McClintock, Jeffrey E.; Psaltis, Dimitrios
2014-04-20
Black hole binaries exhibit a wide range of variability phenomena, from large-scale state changes to broadband noise and quasi-periodic oscillations, but the physical nature of much of this variability is poorly understood. We examine the variability properties of three GRMHD simulations of thin accretion disks around black holes of varying spin, producing light curves and power spectra as would be seen by observers. We find that the simulated power spectra show a broad feature at high frequency, which increases in amplitude with the inclination of the observer. We show that this high-frequency feature is a product of the Doppler effect and that its location is a function of the mass and spin of the black hole. This Doppler feature demonstrates that power spectral properties of the accretion disk can be tied to, and potentially used to determine, physical properties of the black hole.
1994-05-01
Index and Bulk Parameters for Frequency- Direction Spectra Measured at CERC Field Research Facility, September 1991 to August 1992 Accion For by...Prepared for U.S. Army Corps of Engineers Washington, DC 20314-1000 Under Civil Works Research Work Unit 32484 M US Army Corps of Engineers Waterways...that affect coastal engineering pro- jects. This effort was authorized by Headquarters, U.S. Army Corps o.’ Engi- neers (HQUSACE), under Civil Works
NASA Astrophysics Data System (ADS)
Fredi, André; Nolis, Pau; Cobas, Carlos; Martin, Gary E.; Parella, Teodor
2016-05-01
The current Pros and Cons of a processing protocol to generate pure chemical shift NMR spectra using Generalized Indirect Covariance are presented and discussed. The transformation of any standard 2D homonuclear and heteronuclear spectrum to its pure shift counterpart by using a reference DIAG spectrum is described. Reconstructed pure shift NMR spectra of NOESY, HSQC, HSQC-TOCSY and HSQMBC experiments are reported for the target molecule strychnine.
Fredi, André; Nolis, Pau; Cobas, Carlos; Martin, Gary E; Parella, Teodor
2016-05-01
The current Pros and Cons of a processing protocol to generate pure chemical shift NMR spectra using Generalized Indirect Covariance are presented and discussed. The transformation of any standard 2D homonuclear and heteronuclear spectrum to its pure shift counterpart by using a reference DIAG spectrum is described. Reconstructed pure shift NMR spectra of NOESY, HSQC, HSQC-TOCSY and HSQMBC experiments are reported for the target molecule strychnine.
Samet, M; Levchenko, V; Boiteux, G; Seytre, G; Kallel, A; Serghei, A
2015-05-21
The characteristic frequencies of electrode polarization and of interfacial polarization effects in dielectric spectra of ionic liquids and of polymer bi-layers are determined and systematically analyzed, based on dielectric measurements by means of broadband dielectric spectroscopy, numerical simulations, and analytical calculations. It is shown that, to a large extent, identical scaling laws can be derived for these two dielectric phenomena taking place at external and internal interfaces. Surprisingly, a fundamentally different behavior concerning the interrelation between the characteristic frequencies is found. This brings direct evidence that different manifestations of the phenomenon of electrical polarization can be discriminated by examining the inter-relation governing their characteristic frequencies, which can be of significant importance in disseminating the nature of different contributions appearing in the dielectric spectra of complex materials. Based on our analysis, we derive a new formula, valid for both electrode polarization and interfacial polarization effects, that allows one to determine the conductivity value from the frequency position of the Maxwell-Wagner-Sillars peak. An excellent agreement between experiment and calculations is obtained. The formula can be used, furthermore, to estimate the thickness of the interfacial layers formed due to electrode polarization effects. Values in the order of several nanometers, increasing with decreasing temperature, are reported.
Pseudo-real-time low-pass filter in ECG, self-adjustable to the frequency spectra of the waves.
Christov, Ivaylo; Neycheva, Tatyana; Schmid, Ramun; Stoyanov, Todor; Abächerli, Roger
2017-02-04
The electrocardiogram (ECG) acquisition is often accompanied by high-frequency electromyographic (EMG) noise. The noise is difficult to be filtered, due to considerable overlapping of its frequency spectrum to the frequency spectrum of the ECG. Today, filters must conform to the new guidelines (2007) for low-pass filtering in ECG with cutoffs of 150 Hz for adolescents and adults, and to 250 Hz for children. We are suggesting a pseudo-real-time low-pass filter, self-adjustable to the frequency spectra of the ECG waves. The filter is based on the approximation procedure of Savitzky-Golay with dynamic change in the cutoff frequency. The filter is implemented pseudo-real-time (real-time with a certain delay). An additional option is the automatic on/off triggering, depending on the presence/absence of EMG noise. The analysis of the proposed filter shows that the low-frequency components of the ECG (low-power P- and T-waves, PQ-, ST- and TP-segments) are filtered with a cutoff of 14 Hz, the high-power P- and T-waves are filtered with a cutoff frequency in the range of 20-30 Hz, and the high-frequency QRS complexes are filtered with cutoff frequency of higher than 100 Hz. The suggested dynamic filter satisfies the conflicting requirements for a strong suppression of EMG noise and at the same time a maximal preservation of the ECG high-frequency components.
Energy Spectra and High Frequency Oscillations in 4U 0614+091
NASA Technical Reports Server (NTRS)
Ford, E. C.; Kaaret, P.; Chen, K.; Tavani, M.; Barret, D.; Bloser, P.; Grindlay, J.; Harmon, B. A.; Paciesas, W. S.; Zhang, S. N.
1997-01-01
We investigate the behavior of the high frequency quasi-periodic oscillations (QPOs) in 4U 0614+091, combining timing and spectral analysis of RXTE (Rossi X-ray Timing Explorer) observations. The energy spectrum of the source can be described by a power law plus a blackbody component. The blackbody has a variable temperature (kT approximately 0.8 to 1.4 keV) and accounts for 10 to 25% of the total energy flux. The power law flux and photon index also vary (F approximately 0.8 to 1.6 x 10(exp -9) erg/sq cm.s and alpha approximately 2.0 to 2.8 respectively). We find a robust correlation of the frequency of the higher frequency QPO with the flux of the blackbody. The source follows the same relation even in observations separated by several months. The QPO frequency does not have a similarly unique correlation with the total flux or the flux of the power law component. The RMS amplitudes of the higher frequency QPO rise with energy but are consistent with a constant for the lower frequency QPO. These results may be interpreted in terms of a beat frequency model for the production of the high frequency QPOs.
NASA Technical Reports Server (NTRS)
Jackson, F. C.
1980-01-01
Scanning beam microwave radars were used to measure ocean wave directional spectra from satellites. In principle, surface wave spectral resolution in wave number can be obtained using either short pulse (SP) or dual frequency (DF) techniques; in either case, directional resolution obtains naturally as a consequence of a Bragg-like wave front matching. A four frequency moment characterization of backscatter from the near vertical using physical optics in the high frequency limit was applied to an analysis of the SP and DF measurement techniques. The intrinsic electromagnetic modulation spectrum was to the first order in wave steepness proportional to the large wave directional slope spectrum. Harmonic distortion was small and was a minimum near 10 deg incidence. NonGaussian wave statistics can have an effect comparable to that in the second order of scattering from a normally distributed sea surface. The SP technique is superior to the DF technique in terms of measurement signal to noise ratio and contrast ratio.
Comparison of the RF frequency spectra of HEMP and lightning. Technical report, 22 Sep 87-10 Jul 90
Uman, M.A.
1991-03-01
Cloud pulses are much more common than these earlier studies indicate. Our spectra of the largest overhead cloud pulses are nearly parallel to but significantly below the HEMP spectrum from 1 MHz to 50 MHz, while obtained from lighting tens of kilometer offshore over salt water show faster relative decay with increasing frequency, are significantly below ours between 10 and 50 MHz, and are about equal to ours between 3 and 10 MHz. The shortest rise time to initial peak value of overhead lighting pulses are of the order of 0.3 micro sec. A broader bandwidth system than that used would allow measurement of the rapid field variation occurring throughout the cloud pulses associated with frequencies above abut 50 MHz but would observe essentially the same risetime to initial peak. That is, the higher frequency content of the cloud pulses is contained in the rapid field variation throughout the overall waveforms and not in the initial rise to peak value.
Boore, David M.; Di Alessandro, Carola; Abrahamson, Norman A.
2014-01-01
The stochastic method of simulating ground motions requires the specification of the shape and scaling with magnitude of the source spectrum. The spectral models commonly used are either single-corner-frequency or double-corner-frequency models, but the latter have no flexibility to vary the high-frequency spectral levels for a specified seismic moment. Two generalized double-corner-frequency ω2 source spectral models are introduced, one in which two spectra are multiplied together, and another where they are added. Both models have a low-frequency dependence controlled by the seismic moment, and a high-frequency spectral level controlled by the seismic moment and a stress parameter. A wide range of spectral shapes can be obtained from these generalized spectral models, which makes them suitable for inversions of data to obtain spectral models that can be used in ground-motion simulations in situations where adequate data are not available for purely empirical determinations of ground motions, as in stable continental regions. As an example of the use of the generalized source spectral models, data from up to 40 stations from seven events, plus response spectra at two distances and two magnitudes from recent ground-motion prediction equations, were inverted to obtain the parameters controlling the spectral shapes, as well as a finite-fault factor that is used in point-source, stochastic-method simulations of ground motion. The fits to the data are comparable to or even better than those from finite-fault simulations, even for sites close to large earthquakes.
Stability and noise spectra of relative Loran-C frequency comparisons
NASA Technical Reports Server (NTRS)
Proverbio, E.; Quesada, V.; Simoncini, A.
1973-01-01
Relative comparisons of Loran-C frequency transmissions between the master station of Catanzaro (Simeri Crichi) and the X, Z slave stations of Estartit (Spain) and Lampedusa (Italy) are carrying out by the GG LORSTA monitor station of the Mediterranean Sea Loran-C chain. These comparisons are able to emphasize the relative and, under certain conditions, the absolute rate of the emitting standard frequencies of the slave stations and some relevant statistical properties of the Loran-C Method for frequency transmission and time synchronization. The stability of each Loran-C frequency standard transmission is subject to perturbations, more or less known, due to the propagation medium and other causes. Following the Allan (1966) method for data processing, the performance of the relative rate of frequency of the transmissions of the X, Z slave stations are described calculating the standard deviation of a set of N frequency measurements from its mean averaged during sampling times. This standard deviation is designated as the measure of the stability of the Loran-C frequency transmission.
Low-frequency Raman spectra and fragility of imidazolium ionic liquids
Ribeiro, Mauro C. C.
2010-07-14
Raman spectra within the 5-200 cm{sup -1} range have been recorded as a function of temperature for different ionic liquids based on imidazolium cations. A correlation has been found between fragility and the temperature dependence of the strength of fast relaxational motions. Understanding quasielastic scattering as the relaxational contribution to ionic mean-squared displacement elucidates some effects on ionic liquids' fragility resulting from modifications in the chemical structure.
NASA Technical Reports Server (NTRS)
Weissman, D. E.; Johnson, J. W.
1984-01-01
The directional spectrum and the microwave modulation transfer function of ocean waves can be measured with the airborne two frequency scatterometer technique. Similar to tower based observations, the aircraft measurements of the Modulation Transfer Function (MTF) show that it is strongly affected by both wind speed and sea state. Also detected are small differences in the magnitudes of the MTF between downwind and upwind radar look directions, and variations with ocean wavenumber. The MTF inferred from the two frequency radar is larger than that measured using single frequency, wave orbital velocity techniques such as tower based radars or ROWS measurements from low altitude aircraft. Possible reasons for this are discussed. The ability to measure the ocean directional spectrum with the two frequency scatterometer, with supporting MTF data, is demonstrated.
Fine structure of the low-frequency spectra of heart rate and blood pressure
Kuusela, Tom A; Kaila, Timo J; Kähönen, Mika
2003-01-01
Background The aim of this study was to explore the principal frequency components of the heart rate and blood pressure variability in the low frequency (LF) and very low frequency (VLF) band. The spectral composition of the R–R interval (RRI) and systolic arterial blood pressure (SAP) in the frequency range below 0.15 Hz were carefully analyzed using three different spectral methods: Fast Fourier transform (FFT), Wigner-Ville distribution (WVD), and autoregression (AR). All spectral methods were used to create time–frequency plots to uncover the principal spectral components that are least dependent on time. The accurate frequencies of these components were calculated from the pole decomposition of the AR spectral density after determining the optimal model order – the most crucial factor when using this method – with the help of FFT and WVD methods. Results Spectral analysis of the RRI and SAP of 12 healthy subjects revealed that there are always at least three spectral components below 0.15 Hz. The three principal frequency components are 0.026 ± 0.003 (mean ± SD) Hz, 0.076 ± 0.012 Hz, and 0.117 ± 0.016 Hz. These principal components vary only slightly over time. FFT-based coherence and phase-function analysis suggests that the second and third components are related to the baroreflex control of blood pressure, since the phase difference between SAP and RRI was negative and almost constant, whereas the origin of the first component is different since no clear SAP–RRI phase relationship was found. Conclusion The above data indicate that spontaneous fluctuations in heart rate and blood pressure within the standard low-frequency range of 0.04–0.15 Hz typically occur at two frequency components rather than only at one as widely believed, and these components are not harmonically related. This new observation in humans can help explain divergent results in the literature concerning spontaneous low-frequency oscillations. It also raises methodological
NASA Astrophysics Data System (ADS)
Rouge, C.; Lhémery, A.; Aristégui, C.
2014-04-01
Magnetostriction arises in ferromagnetic materials subjected to magnetization, e.g., when an EMAT (Electro-Magnetic Acoustic Transducer) is used to generate ultrasonic waves. In such a case, the magnetostriction force must be taken into account as a transduction process that adds up to the Lorentz force. When the static magnetic field is high compared to the dynamic field, both forces are driven by the excitation frequency. For lower static relative values of the magnetic fields, the Lorentz force comprises both the excitation frequency and its first harmonic. In this work, a model is derived to predict the frequency content of the magnetostrictive force that comprises several harmonics. The discrete frequency spectrum strongly depends on both the static field and the relative amplitude of the dynamic field. The only material input data needed to predict it is the curve of macroscopic magnetostrictive strain that can be measured in the direction of an imposed magnetic field. Then, the various frequency-dependent distributions of Lorentz and magnetostriction body forces can be transformed into equivalent surface stresses. Examples of computation are given for different static and dynamic magnetic fields to study their influence on the frequency content of waves generated in ferromagnetic materials.
Shi, L.; Ni, Y.; Drews, S. E. P.; Skinner, J. L.
2014-08-28
Two intrinsic difficulties in modeling condensed-phase water with conventional rigid non-polarizable water models are: reproducing the static dielectric constants for liquid water and ice Ih, and generating the peak at about 200 cm{sup −1} in the low-frequency infrared spectrum for liquid water. The primary physical reason for these failures is believed to be the missing polarization effect in these models, and consequently various sophisticated polarizable water models have been developed. However, in this work we pursue a different strategy and propose a simple empirical scheme to include the polarization effect only on the dipole surface (without modifying a model's intermolecular interaction potential). We implement this strategy for our explicit three-body (E3B) model. Our calculated static dielectric constants and low-frequency infrared spectra are in good agreement with experiment for both liquid water and ice Ih over wide temperature ranges, albeit with one fitting parameter for each phase. The success of our modeling also suggests that thermal fluctuations about local minima and the energy differences between different proton-disordered configurations play minor roles in the static dielectric constant of ice Ih. Our analysis shows that the polarization effect is important in resolving the two difficulties mentioned above and sheds some light on the origin of several features in the low-frequency infrared spectra for liquid water and ice Ih.
Tong, Yujin; Zhao, Yanbao; Li, Na; Ma, Yunsheng; Osawa, Masatoshi; Davies, Paul B; Ye, Shen
2010-07-21
In this paper, the results of the modeling calculations carried out for predicting the interference effects expected in the sum frequency generation (SFG) spectra of a specific thin-layer system, described in the accompanying paper, are tested by comparing them with the experimental spectra obtained for a real thin-layer film comprising an organic monolayer/variable thickness dielectric layer/gold substrate. In this system, two contributions to the SFG spectra arise, a resonant contribution from the organic film and a nonresonant contribution from the gold substrate. The modeling calculations are in excellent agreement with the experimental spectra over a wide range of thicknesses and for different polarization combinations. The introduction of another resonant monolayer adjacent to the gold substrate and with the molecules having a reverse orientation has a significant affect on the spectral shapes which is predicted. If a dielectric substrate such as CaF(2) is used instead of a gold substrate, only the spectral intensities vary with the film thickness but not the spectral shapes. The counterpropagating beam geometry will change both the thickness dependent spectral shapes and the intensity of different vibrational modes in comparison with a copropagating geometry. The influences of these experimental factors, i.e., the molecular orientational structure in the thin film, the nature of the substrate, and the selected incident beam geometry, on the experimental SFG spectra are quantitatively predicted by the calculations. The thickness effects on the signals from a SFG active monolayer contained in a thin liquid-layer cell of the type frequently used for in situ electrochemical measurements is also discussed. The modeling calculation is also valid for application to other thin-film systems comprising more than two resonant SFG active interfaces by appropriate choice of optical geometries and relevant optical properties.
NASA Astrophysics Data System (ADS)
Dykeman, Eric C.; Sankey, Otto F.
2010-02-01
We describe a technique for calculating the low-frequency mechanical modes and frequencies of a large symmetric biological molecule where the eigenvectors of the Hessian matrix are determined with full atomic detail. The method, which follows order N methods used in electronic structure theory, determines the subset of lowest-frequency modes while using group theory to reduce the complexity of the problem. We apply the method to three icosahedral viruses of various T numbers and sizes; the human viruses polio and hepatitis B, and the cowpea chlorotic mottle virus, a plant virus. From the normal-mode eigenvectors, we use a bond polarizability model to predict a low-frequency Raman scattering profile for the viruses. The full atomic detail in the displacement patterns combined with an empirical potential-energy model allows a comparison of the fully atomic normal modes with elastic network models and normal-mode analysis with only dihedral degrees of freedom. We find that coarse-graining normal-mode analysis (particularly the elastic network model) can predict the displacement patterns for the first few (˜10) low-frequency modes that are global and cooperative.
NASA Astrophysics Data System (ADS)
Litvinenko, G. V.; Lecacheux, A.; Rucker, H. O.; Konovalenko, A. A.; Ryabov, B. P.; Taubenschuss, U.; Vinogradov, V. V.; Shaposhnikov, V. E.
2009-01-01
Aims: The wide-band dynamic spectra of Jovian decameter emission obtained over the last decade with high-frequency and high time resolution equipment on the largest decameter band antenna array, the Ukrainian T-shape Radio telescope (UTR-2), are presented. Methods: We analyzed the data obtained with the Digital SpectroPolarimiter (DSP) and WaveForm Reciever (WFR) installed at UTR-2. The combination of the large antenna and high performance equipment gives the best sensitivity and widest band of analysis, dynamic range, time and frequency resolutions. The wavelet transform method and the Fourier technique was used for further data processing. Results: The main characteristics of already known and newly detected modulation events were investigated and specified. The new receiving-recording facilities, methodology and program of observations are described in detail.
Ycas, Gabriel G; Quinlan, Franklyn; Diddams, Scott A; Osterman, Steve; Mahadevan, Suvrath; Redman, Stephen; Terrien, Ryan; Ramsey, Lawrence; Bender, Chad F; Botzer, Brandon; Sigurdsson, Steinn
2012-03-12
We describe and characterize a 25 GHz laser frequency comb based on a cavity-filtered erbium fiber mode-locked laser. The comb provides a uniform array of optical frequencies spanning 1450 nm to 1700 nm, and is stabilized by use of a global positioning system referenced atomic clock. This comb was deployed at the 9.2 m Hobby-Eberly telescope at the McDonald Observatory where it was used as a radial velocity calibration source for the fiber-fed Pathfinder near-infrared spectrograph. Stellar targets were observed in three echelle orders over four nights, and radial velocity precision of ∼10 m/s (∼6 MHz) was achieved from the comb-calibrated spectra.
NASA Astrophysics Data System (ADS)
Feng, Jun; Wu, Dan; Wen, Jia; Liu, Shi-lin; Wang, Hong-fei
2008-08-01
The C-H stretch vibrational spectra of the trisiloxane superspreading surfactant Silwet L-77 ((CH3)3Si-O-Si(CH3)(C3H6)(OCH2CH2)7-8OCH3)-O-Si(CH3)3) at the air/water interface are measured with the surface Sum Frequency Generation Vibrational Spectroscopy (SFG-VS). The spectra are dominated with the features from the -Si-CH3 groups around 2905 cm-1 (symmetric stretch or SS mode) and 2957 cm-1 (mostly the asymmetric stretch or AS mode), and with the weak but apparent contribution from the -O-CH2- groups around 2880 cm-1 (symmetric stretch or SS mode). Comparison of the polarization dependent SFG spectra below and above the critical aggregate or micelle concentration (CAC) indicates that the molecular orientation of the C-H related molecular groups remained unchanged at different surface densities of the Silwet L-77 surfactant. The SFG-VS adsorption isotherm suggested that there was no sign of Silwet L-77 bilayer structure formation at the air/water interface. The Gibbs adsorption free energy of the Silwet surfactant to the air/water interface is -42.2±0.8kcal/mol, indicating the unusually strong adsorption ability of the Silwet L-77 superspreading surfactant.
Low-frequency dynamics of DNA in Brillouin light scattering spectra
NASA Astrophysics Data System (ADS)
Lushnikov, S. G.; Dmitriev, A. V.; Fedoseev, A. I.; Zakharov, G. A.; Zhuravlev, A. V.; Medvedeva, A. V.; Schegolev, B. F.; Savvateeva-Popova, E. V.
2014-02-01
Brillouin light scattering studies of deoxyribonucleic acid (DNA) in the temperature interval 297-375 K are presented. The DNA fragment (119 bp) from the first intron of D melanogaster limk1 gene with AT-rich insertion (28 bp, mutant agn ts3) was used as an experimental sample. The temperature dependence of the hypersonic velocity was found to exhibit anomalies in the vicinity of 347 and 335 K. Computer modeling of possible conformational states which might be attained by the DNA fragment under study has shown the existence of local structures that evolve with varying temperature. Combined analysis of experimental data and results of the modeling reveals a close relation between the anomalous behavior of Brillouin light scattering spectra and conformational DNA dynamics. The results are discussed in the framework of modern models of conformational DNA transformations.
Schmidt, R; Jonas, I; Schulte-Mönting, J; Kappert, H F; Rakosi, T
1991-12-01
With the aid of bipolar surface electrodes, the electromyographic activity of the anterior temporal and the superficial masseter muscles were recorded bilaterally and evaluated by counting the integrated potentials and mean power frequency using Fourier's analysis. A comparison between 17 patients with myofacial pain dysfunction (average age 21.3 years) and a group of 20 controls (average age 20.5 years) revealed a significantly greater activity in patients with pain syndrome, while no significant inter-group difference in mean power frequency was seen. The differences in the level of activity between the right and left sides in the control group were significantly smaller than in patients with pain dysfunction. An investigation of measures aimed at reducing the right/left asymmetry in a further 14 patients with pain dysfunction revealed the practice of "maximum occlusion with feedback" to be the most effective measure.
Frequency Width in Predictions of Windsea Spectra and the Role of the Nonlinear Solver
2012-12-20
which many readers will be familiar with.2 JON - SWAP y - 1 corresponds to fully developed seas, which tend to be relatively broad in frequency space...Phys. Oceanogr. 15. 1369-1377. Hasselmann. S.. Hasselmann. K.. Allender. J.H.. Barnett . T.P.. 1985. Computations and parameterizations of the...Oceanogr. 15. 1378-1391. Hasselmann. K., Barnett , T.P., Bouws, E.. Carlson. H.. Cartwright. D.E.. Enke, K.. Ewing. J.A., Cienapp, H., Hasselman, D.E
Frequency tuning of hearing in the beluga whale: discrimination of rippled spectra.
Sysueva, Evgenia V; Nechaev, Dmitry I; Popov, Vladimir V; Supin, Alexander Ya
2014-02-01
Frequency tuning was measured in the beluga whale (Delphinapterus leucas) using rippled-noise test stimuli in conjunction with an auditory evoked potential (AEP) technique. The test stimulus was a 2-octave-wide rippled noise with frequency-proportional ripple spacing. The rippled-noise signal contained either a single reversal or rhythmic (1-kHz rate) reversals of the ripple phase. Single or rhythmic phase reversals evoked, respectively, a single auditory brainstem response (ABR) or a rhythmic AEP sequence-the envelope following response (EFR). The response was considered as an indication of resolvability of the ripple pattern. The rhythmic phase-reversal test with EFR recording revealed higher resolution than the single phase-reversal test with single ABR recording. The limit of ripple-pattern resolution with the single phase-reversal test ranged from 17 ripples per octave (rpo) at 32 kHz to 24 rpo at 45 to 64 kHz; for the rhythmic phase-reversal test, the limit ranged from 20 to 32 rpo. An interaction model of a ripple spectrum with frequency-tuned filters suggests that the ripple-pattern resolution limit of 20 to 32 rpo requires a filter quality Q of 29 to 46. Possible causes of disagreement of these estimates with several previously published data are discussed.
Energy spectra of 2D gravity and capillary waves with narrow frequency band excitation
NASA Astrophysics Data System (ADS)
Kartashova, E.
2012-02-01
In this letter we present a new method, called increment chain equation method (ICEM), for computing a cascade of distinct modes in a two-dimensional weakly nonlinear wave system generated by narrow frequency band excitation. The ICEM is a means for computing the quantized energy spectrum as an explicit function of frequency ω0 and stationary amplitude A0 of excitation. The physical mechanism behind the generation of the quantized cascade is modulation instability. The ICEM can be used in numerous 2D weakly nonlinear wave systems with narrow frequency band excitation appearing in hydrodynamics, nonlinear optics, electrodynamics, convection theory etc. In this letter the ICEM is demonstrated with examples of gravity and capillary waves with dispersion functions ω(k)~k1/2 and ω(k)~k3/2, respectively, and for two different levels of nonlinearity ɛ=A0k0: small (ɛ~0.1 to 0.25) and moderate (ɛ~0.25 to 0.4).
Frequency Width in Predictions of Windsea Spectra and the Role of the Nonlinear Solver
2013-01-01
parameter c, which many readers will be familiar with.2 JON - SWAP c = 1 corresponds to fully developed seas, which tend to be relatively broad in frequency...nonlinear transfer integral. J. Phys. Oceanogr. 15, 1369–1377. Hasselmann, S., Hasselmann, K., Allender, J.H., Barnett , T.P., 1985. Computations and...wave models. J. Phys. Oceanogr. 15, 1378–1391. Hasselmann, K., Barnett , T.P., Bouws, E., Carlson, H., Cartwright, D.E., Enke, K., Ewing, J.A., Gienapp
DFT calculation of vibrational frequencies of clusters in GaAs and the Raman spectra
NASA Astrophysics Data System (ADS)
Radhika Devi, V.; Shrivastava, Keshav N.
2012-09-01
We have calculated the vibrational frequencies of clusters of Ga and As atoms from the first principles using the density-functional theory (DFT) method and the local-density approximation (LDA). We find that the calculated value of 286.2 cm-1 for a linear cluster of Ga2As2 is very near the experimental value of 292 ± 4 cm-1. The calculated value of 289.4 cm-1 for Ga2As6 (dumb bell) cluster is indeed very near the experimental value. There are strong phonon correlations so that the cluster frequency is within the dispersion relation of the crystal LO value. There is a weak line in the experimental Raman spectrum at 268 cm-1 which is very near the value of 267.3 cm-1 calculated for the Ga2As (triangular) cluster. The weak lines corresponding to the linear bonds provide the strength to the amorphous samples. There are clusters of atoms in the glassy state of GaAs.
Representation of high frequency Space Shuttle data by ARMA algorithms and random response spectra
NASA Technical Reports Server (NTRS)
Spanos, P. D.; Mushung, L. J.
1990-01-01
High frequency Space Shuttle lift-off data are treated by autoregressive (AR) and autoregressive-moving-average (ARMA) digital algorithms. These algorithms provide useful information on the spectral densities of the data. Further, they yield spectral models which lend themselves to incorporation to the concept of the random response spectrum. This concept yields a reasonably smooth power spectrum for the design of structural and mechanical systems when the available data bank is limited. Due to the non-stationarity of the lift-off event, the pertinent data are split into three slices. Each of the slices is associated with a rather distinguishable phase of the lift-off event, where stationarity can be expected. The presented results are rather preliminary in nature; it is aimed to call attention to the availability of the discussed digital algorithms and to the need to augment the Space Shuttle data bank as more flights are completed.
Mixed Polarization Vibrational Sum Frequency Generation Spectra of Organic Semiconducting Thin Films
NASA Astrophysics Data System (ADS)
Kearns, Patrick; Sohrabpour, Zahara; Massari, Aaron M.
2014-06-01
The buried interface of an organic semiconductor at the dielectric has a large on influence on the function of organic field effect transistors (OFETs). The use of vibrational sum frequency generation (VSFG) to obtain structural and orientational information on the buried interfaces of organic thin films has historically been complicated by the signals from other interfaces in the system. A thin film of N,N'-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) was deposited on a SiO2 dielectric to simulate the interfaces found in OFETs. We will show how probing the sample with a varying mixture of linear polarizations in the experimental setup can deconvolute contributions to the overall signal from multiple interfaces.
Radiation transfer with partial frequency redistribution and generalized redistribution functions.
NASA Astrophysics Data System (ADS)
Hubeny, I.
The author attempted to analyse the available astrophysical partial redistribution studies. He introduced the term quasi-Markovian, classical view, where the basic physical concepts of the current astrophysical approach are summarized. Its physical uncertainties, and even inconsistencies, are discussed in detail. The quasi-Markovian, classical treatment has been used to generalize the Oxenius (1965) approach. The reformulation of the Oxenius' approach, in the two-level-atom case, to a form similar to that of Milkey and Mihalas (1973) and Heasley and Kneer (1976) showed, that both formulations yield almost identical results. Using the same approach as in reformulating the two-level-atom case, the author derived a suitable form of the emission coefficient in the case of the multilevel atom. Comparing its form to that following from a heuristic derivation, two points appeared to be different.
A general low frequency acoustic radiation capability for NASTRAN
NASA Technical Reports Server (NTRS)
Everstine, G. C.; Henderson, F. M.; Schroeder, E. A.; Lipman, R. R.
1986-01-01
A new capability called NASHUA is described for calculating the radiated acoustic sound pressure field exterior to a harmonically-excited arbitrary submerged 3-D elastic structure. The surface fluid pressures and velocities are first calculated by coupling a NASTRAN finite element model of the structure with a discretized form of the Helmholtz surface integral equation for the exterior fluid. After the fluid impedance is calculated, most of the required matrix operations are performed using the general matrix manipulation package (DMAP) available in NASTRAN. Far field radiated pressures are then calculated from the surface solution using the Helmholtz exterior integral equation. Other output quantities include the maximum sound pressure levels in each of the three coordinate planes, the rms and average surface pressures and normal velocities, the total radiated power and the radiation efficiency. The overall approach is illustrated and validated using known analytic solutions for submerged spherical shells subjected to both uniform and nonuniform applied loads.
NASA Technical Reports Server (NTRS)
Schoeberl, Mark R.; Douglass, Anne R.; Zhu, Zhengxin; Pawson, Steven
2002-01-01
We use kinematic and diabatic back trajectory calculations, driven by winds from a general circulation model (GCM) and two different data assimilation systems (DAS), to compute the age spectrum at three latitudes in the lower stratosphere. The age-spectra are compared to chemical transport model (CTM) calculations, and the mean ages from all of these studies are compared to observations. The age spectra computed using the GCM winds show a reasonably isolated tropics in good agreement with observations; however, the age spectra determined from the DAS differ from the GCM spectra. For the DAS diabatic trajectory calculations there is too much exchange between the tropics and mid-latitudes. The age spectrum is thus too broad and the tropical mean age is too old as a result of mixing older mid latitude air with tropical air. Likewise the mid latitude mean age is too young due to the in mixing of tropical air. The DAS kinematic trajectory calculations show excessive vertical dispersion of parcels in addition to excessive exchange between the tropics and mid latitudes. Because air is moved rapidly to the troposphere from the vertical dispersion, the age spectrum is shifted toward the young side. The excessive vertical and meridional dispersion compensate in the kinematic case giving a reasonable tropical mean age. The CTM calculation of the age spectrum using the DAS winds shows the same vertical and meridional dispersive characteristics of the kinematic trajectory calculation. These results suggest that the current DAS products will not give realistic trace gas distributions for long integrations; they also help explain why the extra tropical mean ages determined in a number of previous DAS driven CTM s are too young compared with observations. Finally, we note trajectory-generated age spectra . show significant age anomalies correlated with the seasonal cycles. These anomalies can be linked to year-to-year variations in the tropical heating rate. The anomalies are
NASA Astrophysics Data System (ADS)
Chen, Xiaowang; Feng, Zhipeng
2016-12-01
Planetary gearboxes are widely used in many sorts of machinery, for its large transmission ratio and high load bearing capacity in a compact structure. Their fault diagnosis relies on effective identification of fault characteristic frequencies. However, in addition to the vibration complexity caused by intricate mechanical kinematics, volatile external conditions result in time-varying running speed and/or load, and therefore nonstationary vibration signals. This usually leads to time-varying complex fault characteristics, and adds difficulty to planetary gearbox fault diagnosis. Time-frequency analysis is an effective approach to extracting the frequency components and their time variation of nonstationary signals. Nevertheless, the commonly used time-frequency analysis methods suffer from poor time-frequency resolution as well as outer and inner interferences, which hinder accurate identification of time-varying fault characteristic frequencies. Although time-frequency reassignment improves the time-frequency readability, it is essentially subject to the constraints of mono-component and symmetric time-frequency distribution about true instantaneous frequency. Hence, it is still susceptible to erroneous energy reallocation or even generates pseudo interferences, particularly for multi-component signals of highly nonlinear instantaneous frequency. In this paper, to overcome the limitations of time-frequency reassignment, we propose an improvement with fine time-frequency resolution and free from interferences for highly nonstationary multi-component signals, by exploiting the merits of iterative generalized demodulation. The signal is firstly decomposed into mono-components of constant frequency by iterative generalized demodulation. Time-frequency reassignment is then applied to each generalized demodulated mono-component, obtaining a fine time-frequency distribution. Finally, the time-frequency distribution of each signal component is restored and superposed to
Shirota, Hideaki; Kakinuma, Shohei
2015-07-30
In this study, the temperature dependence of the low-frequency spectra of liquid bis(trifluoromethylsulfonyl)amide salts of the monocations 1-methyl-3-propylimidazolium and 1-hexyl-3-methylimidazolium and the dications 1,6-bis(3-methylimidazolium-1-yl)hexane and 1,12-bis(3-methylimidazolium-1-yl)dodecane has been investigated by means of femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy. The intensity in the low-frequency region below 20 cm(-1) in the spectra of the four ionic liquids increases with rising temperature. From a line-shape analysis of the broadened low-frequency spectra of the ionic liquids, it is clear that the lowest-frequency component, which peaks at approximately 5 cm(-1), contributes to the temperature dependence of the spectra. This implies that the activity of the intermolecular translational vibrational motion is increasing with rising temperature. It is also possible that decoupling in the crossover process between intermolecular vibrational motion and structural relaxation occurs as a result of a deterioration of the non-Markovian feature or the loss of memory caused by the higher temperature. The peak of the highest-frequency component, which is due mainly to the imidazolium ring libration, shifts to lower frequency with increasing temperature. This is attributed to weaker interactions of the ionic liquids at higher temperatures. Temperature-dependent viscosities from 293 to 353 K of the four ionic liquids have also been characterized.
Chiang, Yun-Wei; Freed, Jack H.
2011-01-01
The Lanczos algorithm (LA) is a useful iterative method for the reduction of a large matrix to tridiagonal form. It is a storage efficient procedure requiring only the preceding two Lanczos vectors to compute the next. The quasi-minimal residual (QMR) method is a powerful method for the solution of linear equation systems, Ax = b. In this report we provide another application of the QMR method: we incorporate QMR into the LA to monitor the convergence of the Lanczos projections in the reduction of large sparse matrices. We demonstrate that the combined approach of the LA and QMR can be utilized efficiently for the orthogonal transformation of large, but sparse, complex, symmetric matrices, such as are encountered in the simulation of slow-motional 1D- and 2D-electron spin resonance (ESR) spectra. Especially in the 2D-ESR simulations, it is essential that we store all of the Lanczos vectors obtained in the course of the LA recursions and maintain their orthogonality. In the LA-QMR application, the QMR weight matrix mitigates the problem that the Lanczos vectors lose orthogonality after many LA projections. This enables substantially more Lanczos projections, as required to achieve convergence for the more challenging ESR simulations. It, therefore, provides better accuracy for the eigenvectors and the eigenvalues of the large sparse matrices originating in 2D-ESR simulations than does the previously employed method, which is a combined approach of the LA and the conjugate-gradient (CG) methods, as evidenced by the quality and convergence of the 2D-ESR simulations. Our results show that very slow-motional 2D-ESR spectra at W-band (95 GHz) can be reliably simulated using the LA-QMR method, whereas the LA-CG consistently fails. The improvements due to the LA-QMR are of critical importance in enabling the simulation of high-frequency 2D-ESR spectra, which are characterized by their very high resolution to molecular orientation. PMID:21261335
Chiang, Yun-Wei; Freed, Jack H
2011-01-21
The Lanczos algorithm (LA) is a useful iterative method for the reduction of a large matrix to tridiagonal form. It is a storage efficient procedure requiring only the preceding two Lanczos vectors to compute the next. The quasi-minimal residual (QMR) method is a powerful method for the solution of linear equation systems, Ax = b. In this report we provide another application of the QMR method: we incorporate QMR into the LA to monitor the convergence of the Lanczos projections in the reduction of large sparse matrices. We demonstrate that the combined approach of the LA and QMR can be utilized efficiently for the orthogonal transformation of large, but sparse, complex, symmetric matrices, such as are encountered in the simulation of slow-motional 1D- and 2D-electron spin resonance (ESR) spectra. Especially in the 2D-ESR simulations, it is essential that we store all of the Lanczos vectors obtained in the course of the LA recursions and maintain their orthogonality. In the LA-QMR application, the QMR weight matrix mitigates the problem that the Lanczos vectors lose orthogonality after many LA projections. This enables substantially more Lanczos projections, as required to achieve convergence for the more challenging ESR simulations. It, therefore, provides better accuracy for the eigenvectors and the eigenvalues of the large sparse matrices originating in 2D-ESR simulations than does the previously employed method, which is a combined approach of the LA and the conjugate-gradient (CG) methods, as evidenced by the quality and convergence of the 2D-ESR simulations. Our results show that very slow-motional 2D-ESR spectra at W-band (95 GHz) can be reliably simulated using the LA-QMR method, whereas the LA-CG consistently fails. The improvements due to the LA-QMR are of critical importance in enabling the simulation of high-frequency 2D-ESR spectra, which are characterized by their very high resolution to molecular orientation.
NASA Astrophysics Data System (ADS)
Chiang, Yun-Wei; Freed, Jack H.
2011-01-01
The Lanczos algorithm (LA) is a useful iterative method for the reduction of a large matrix to tridiagonal form. It is a storage efficient procedure requiring only the preceding two Lanczos vectors to compute the next. The quasi-minimal residual (QMR) method is a powerful method for the solution of linear equation systems, Ax = b. In this report we provide another application of the QMR method: we incorporate QMR into the LA to monitor the convergence of the Lanczos projections in the reduction of large sparse matrices. We demonstrate that the combined approach of the LA and QMR can be utilized efficiently for the orthogonal transformation of large, but sparse, complex, symmetric matrices, such as are encountered in the simulation of slow-motional 1D- and 2D-electron spin resonance (ESR) spectra. Especially in the 2D-ESR simulations, it is essential that we store all of the Lanczos vectors obtained in the course of the LA recursions and maintain their orthogonality. In the LA-QMR application, the QMR weight matrix mitigates the problem that the Lanczos vectors lose orthogonality after many LA projections. This enables substantially more Lanczos projections, as required to achieve convergence for the more challenging ESR simulations. It, therefore, provides better accuracy for the eigenvectors and the eigenvalues of the large sparse matrices originating in 2D-ESR simulations than does the previously employed method, which is a combined approach of the LA and the conjugate-gradient (CG) methods, as evidenced by the quality and convergence of the 2D-ESR simulations. Our results show that very slow-motional 2D-ESR spectra at W-band (95 GHz) can be reliably simulated using the LA-QMR method, whereas the LA-CG consistently fails. The improvements due to the LA-QMR are of critical importance in enabling the simulation of high-frequency 2D-ESR spectra, which are characterized by their very high resolution to molecular orientation.
Triola, Christopher; Badiane, Driss M; Balatsky, Alexander V; Rossi, E
2016-06-24
We obtain the general conditions for the emergence of odd-frequency superconducting pairing in a two-dimensional (2D) electronic system proximity coupled to a superconductor, making minimal assumptions about both the 2D system and the superconductor. Using our general results we show that a simple heterostructure formed by a monolayer of a group VI transition metal dichalcogenide, such as molybdenum disulfide, and an s-wave superconductor with Rashba spin-orbit coupling exhibits odd-frequency superconducting pairing. Our results allow the identification of a new class of systems among van der Waals heterostructures in which odd-frequency superconductivity should be present.
NASA Technical Reports Server (NTRS)
Fritts, David C.; Wang, Ding-Yi
1991-01-01
Results are presented of radar observations of horizontal and vertical velocities near the summer mesopause at Poker Flat (Alaska), showing that the observed vertical velocity spectra were influenced strongly by Doppler-shifting effects. The horizontal velocity spectra, however, were relatively insensitive to horizontal wind speed. The observed spectra are compared with predicted spectra for various models of the intrinsic motion spectrum and degrees of Doppler shifting.
NASA Astrophysics Data System (ADS)
Iomdina, Elena N.; Goltsman, Gregory N.; Seliverstov, Sergey V.; Sianosyan, Alisa A.; Teplyakova, Kseniya O.; Rusova, Anastasia A.
2016-09-01
An adequate water balance (hydration extent) is one of the basic factors of normal eye function, including its external shells: the cornea and the sclera. Adequate control of corneal and scleral hydration is very important for early diagnosis of a variety of eye diseases, stating indications for and contraindications against keratorefractive surgeries and the choice of contact lens correction solutions. THz systems of creating images in reflected beams are likely to become ideal instruments of noninvasive control of corneal and scleral hydration degrees. This paper reports on the results of a study involving transmittance and reflectance spectra for the cornea and the sclera of rabbit and human eyes, as well as those of the rabbit eye, in the frequency range of 0.13 to 0.32 THz. The dependence of the reflectance coefficient of these tissues on water mass percentage content was determined. The experiments were performed on three corneas, three rabbit scleras, two rabbit eyes, and three human scleras. The preliminary results demonstrate that the proposed technique, based on the use of a continuous THz radiation, may be utilized to create a device for noninvasive control of corneal and scleral hydration, which has clear potential of broad practical application.
Precessional frequency of a gyroscope in the quaterionic formulation of general relativity
Sachs, M.
1989-01-01
The precessional frequency of a gyroscope in a reference frame that orbits about a gravitational body is compared between Einstein's tensor formulation of general relativity and the author's quaternion generalization - obtained from a factorization of the tensor form. The difference in predictions then suggests an experiment that could choose which of these formulations of general relativity is more valid in the analysis of gyroscopic motion.
Caballero, O. L.; McLaughlin, G. C.; Surman, R. E-mail: olcaball@ncsu.edu E-mail: surmanr@union.edu
2012-02-01
Black hole (BH) accretion disks have been proposed as good candidates for a range of interesting nucleosynthesis, including the r-process. The presence of the BH influences the neutrino fluxes and affects the nucleosynthesis resulting from the interaction of the emitted neutrinos and hot outflowing material ejected from the disk. We study the impact of general relativistic effects on the neutrinos emitted from BH accretion disks. We present abundances obtained by considering null geodesics and energy shifts for two different disk models. We find that both the bending of the neutrino trajectories and the energy shifts have important consequences for the nucleosynthetic outcome.
NASA Technical Reports Server (NTRS)
Groner, P.; Durig, J. R.
1977-01-01
The torsional far infrared and Raman spectra of gaseous CH3OCH3, CD3OCH3, and CD3OCD3 are presented. They are analyzed using a computer program which is based on the results of an extensive investigation of the isometric groups and of the symmetry groups of the rotation-internal rotation Hamiltonians of a series of semirigid two-top models. Four or more Fourier coefficients of the potential functions in two variables could be determined for each isotope. Strong evidence was found for Fermi-resonance-type interactions with the COC bending mode.
A Generalized Fast Frequency Sweep Algorithm for Coupled Circuit-EM Simulations
Rockway, J D; Champagne, N J; Sharpe, R M; Fasenfest, B
2004-01-14
Frequency domain techniques are popular for analyzing electromagnetics (EM) and coupled circuit-EM problems. These techniques, such as the method of moments (MoM) and the finite element method (FEM), are used to determine the response of the EM portion of the problem at a single frequency. Since only one frequency is solved at a time, it may take a long time to calculate the parameters for wideband devices. In this paper, a fast frequency sweep based on the Asymptotic Wave Expansion (AWE) method is developed and applied to generalized mixed circuit-EM problems. The AWE method, which was originally developed for lumped-load circuit simulations, has recently been shown to be effective at quasi-static and low frequency full-wave simulations. Here it is applied to a full-wave MoM solver, capable of solving for metals, dielectrics, and coupled circuit-EM problems.
NASA Astrophysics Data System (ADS)
Rossi, Enrico; Triola, Christopher; Badiane, Driss; Balatsky, Alexander V.
We obtain the general conditions for the emergence of odd-frequency superconducting pairing in a two-dimensional (2D) electronic system proximity-coupled to a superconductor, making minimal assumptions about both the 2D system and the superconductor. Using our general results we show that a simple heterostructure formed by a monolayer of a group VI transition metal dichalcogenide, such as molybdenum disulfide, and an s-wave superconductor with Rashba spin-orbit coupling will exhibit odd-frequency superconducting pairing. Work supported by US DOE BES E304, KAW, ACS-PRF-53581-DNI5, and NSF-DMR-1455233.
Frequency-Specific Alterations of Local Synchronization in Idiopathic Generalized Epilepsy
Wang, Jue; Zhang, Zhiqiang; Ji, Gong-Jun; Xu, Qiang; Huang, Yubin; Wang, Zhengge; Jiao, Qing; Yang, Fang; Zang, Yu-Feng; Liao, Wei; Lu, Guangming
2015-01-01
Abstract Recurrently and abnormally hypersynchronous discharge is a striking feature of idiopathic generalized epilepsy (IGE). Resting-state functional magnetic resonance imaging has revealed aberrant spontaneous brain synchronization, predominately in low-frequency range (<0.1 Hz), in individuals with IGE. Little is known, however, about these changes in local synchronization across different frequency bands. We examined alterations to frequency-specific local synchronization in terms of spontaneous blood oxygen level-dependent (BOLD) fluctuations across 5 bands, spanning 0 to 0.25 Hz. Specifically, we compared brain activity in a large cohort of IGE patients (n = 86) to age- and sex-matched normal controls (n = 86). IGE patients showed decreased local synchronization in low frequency (<0.073 Hz), primarily in the default mode network (DMN). IGE patients also exhibited increased local synchronization in high-frequency (>0.073 Hz) in a “conscious perception network,” which is anchored by the pregenual and dorsal anterior cingulate cortex, as well as the bilateral insular cortices, possibly contributing to impaired consciousness. Furthermore, we found frequency-specific alternating local synchronization in the posterior portion of the DMN relative to the anterior part, suggesting an interaction between the disease and frequency bands. Importantly, the aberrant high-frequency local synchronization in the middle cingulate cortex was associated with disease duration, thus linking BOLD frequency changes to disease severity. These findings provide an overview of frequency-specific local synchronization of BOLD fluctuations, and may be helpful in uncovering abnormal synchronous neuronal activity in patients with IGE at specific frequency bands. PMID:26266394
Yamamoto, Shigeki; Morisawa, Yusuke; Sato, Harumi; Hoshina, Hiromichi; Ozaki, Yukihiro
2013-02-21
Low-frequency vibrational bands observed in the Raman and terahertz (THz) spectra in the region of 50-150 cm(-1) of crystalline powder poly-(R)-3-hydroxybutyrate (PHB) were assigned based on comparisons of the Raman and THz spectra, polarization directions of THz absorption spectra, and their congruities to quantum mechanically (QM) calculated spectra. This combination, Raman and THz spectroscopies and the QM simulations, has been rarely adopted in spite of its potential of reliable assignments of the vibrational bands. The QM simulation of a spectrum has already been popular in vibrational spectroscopies, but for low-frequency bands of polymers it is still a difficult task due to its large scales of systems and a fact that interactions among polymer chains should be considered in the calculation. In this study, the spectral calculations with the aid of the Cartesian-coordinate tensor transfer (CCT) method were applied successfully to the crystalline PHB, which include the explicit consideration of an intermolecular interaction among helical polymer chains. The agreements between the calculations and the experiments are good in both the Raman and THz spectra in terms of spectral shapes, frequencies, and intensities. A Raman active band at 79 cm(-1) was assigned to the intermolecular vibrational mode of the out-of-plane C═O + CH(3) vibration. A polarization state of the corresponding far-infrared absorption band at ∼82 cm(-1), perpendicular to the helix-elongation direction of PHB, was reproduced only under the explicit correction, which indicates that this polarized band originates from the interaction among the polymer chains. The calculation explored that the polarization direction of this band was along the a axis, which is consistent with the direction in which weak intermolecular hydrogen bonds are suggested between the C═O and CH(3) groups of two parallel polymer chains. The results obtained here have confirmed sensitivity of the low-frequency
NASA Astrophysics Data System (ADS)
Offringa, A. R.; Trott, C. M.; Hurley-Walker, N.; Johnston-Hollitt, M.; McKinley, B.; Barry, N.; Beardsley, A. P.; Bowman, J. D.; Briggs, F.; Carroll, P.; Dillon, J. S.; Ewall-Wice, A.; Feng, L.; Gaensler, B. M.; Greenhill, L. J.; Hazelton, B. J.; Hewitt, J. N.; Jacobs, D. C.; Kim, H.-S.; Kittiwisit, P.; Lenc, E.; Line, J.; Loeb, A.; Mitchell, D. A.; Morales, M. F.; Neben, A. R.; Paul, S.; Pindor, B.; Pober, J. C.; Procopio, P.; Riding, J.; Sethi, S. K.; Shankar, N. U.; Subrahmanyan, R.; Sullivan, I. S.; Tegmark, M.; Thyagarajan, N.; Tingay, S. J.; Wayth, R. B.; Webster, R. L.; Wyithe, J. S. B.
2016-05-01
Experiments that pursue detection of signals from the Epoch of Reionization (EoR) are relying on spectral smoothness of source spectra at low frequencies. This article empirically explores the effect of foreground spectra on EoR experiments by measuring high-resolution full-polarization spectra for the 586 brightest unresolved sources in one of the Murchison Widefield Array (MWA) EoR fields using 45 h of observation. A novel peeling scheme is used to subtract 2500 sources from the visibilities with ionospheric and beam corrections, resulting in the deepest, confusion-limited MWA image so far. The resulting spectra are found to be affected by instrumental effects, which limit the constraints that can be set on source-intrinsic spectral structure. The sensitivity and power-spectrum of the spectra are analysed, and it is found that the spectra of residuals are dominated by point spread function sidelobes from nearby undeconvolved sources. We release a catalogue describing the spectral parameters for each measured source.
Magosso, Elisa; Cona, Filippo; Ursino, Mauro
2013-01-01
Exposure to synchronous but spatially disparate auditory and visual stimuli produces a perceptual shift of sound location towards the visual stimulus (ventriloquism effect). After adaptation to a ventriloquism situation, enduring sound shift is observed in the absence of the visual stimulus (ventriloquism aftereffect). Experimental studies report opposing results as to aftereffect generalization across sound frequencies varying from aftereffect being confined to the frequency used during adaptation to aftereffect generalizing across some octaves. Here, we present an extension of a model of visual-auditory interaction we previously developed. The new model is able to simulate the ventriloquism effect and, via Hebbian learning rules, the ventriloquism aftereffect and can be used to investigate aftereffect generalization across frequencies. The model includes auditory neurons coding both for the spatial and spectral features of the auditory stimuli and mimicking properties of biological auditory neurons. The model suggests that different extent of aftereffect generalization across frequencies can be obtained by changing the intensity of the auditory stimulus that induces different amounts of activation in the auditory layer. The model provides a coherent theoretical framework to explain the apparently contradictory results found in the literature. Model mechanisms and hypotheses are discussed in relation to neurophysiological and psychophysical data.
2013-01-01
Exposure to synchronous but spatially disparate auditory and visual stimuli produces a perceptual shift of sound location towards the visual stimulus (ventriloquism effect). After adaptation to a ventriloquism situation, enduring sound shift is observed in the absence of the visual stimulus (ventriloquism aftereffect). Experimental studies report opposing results as to aftereffect generalization across sound frequencies varying from aftereffect being confined to the frequency used during adaptation to aftereffect generalizing across some octaves. Here, we present an extension of a model of visual-auditory interaction we previously developed. The new model is able to simulate the ventriloquism effect and, via Hebbian learning rules, the ventriloquism aftereffect and can be used to investigate aftereffect generalization across frequencies. The model includes auditory neurons coding both for the spatial and spectral features of the auditory stimuli and mimicking properties of biological auditory neurons. The model suggests that different extent of aftereffect generalization across frequencies can be obtained by changing the intensity of the auditory stimulus that induces different amounts of activation in the auditory layer. The model provides a coherent theoretical framework to explain the apparently contradictory results found in the literature. Model mechanisms and hypotheses are discussed in relation to neurophysiological and psychophysical data. PMID:24228250
A simple and general strategy for generating frequency-anticorrelated photon pairs
Zhang, Xin; Xu, Chang; Ren, Zhongzhou
2016-01-01
Currently, two-photon excitation microscopy is the method of choice for imaging living cells within thick specimen. A remaining problem for this technique is the damage caused by the high photon flux in the excitation region. To reduce the required flux, a promising solution is to use highly frequency-anticorrelated photon pairs, which are known to induce two-photon transitions much more efficiently. It is still an open question what the best scheme is for generating such photon pairs. Here we propose one simple general strategy for this task. As an example, we show explicitly that this general strategy can be realized faithfully within the widely applicable coherently pumped Jaynes-Cummings model. It is shown quantitatively that this strategy can generate highly frequency-anticorrelated photon pairs which can dramatically enhance two-photon excitation efficiency. We believe the proposed strategy can guide new designs for generating frequency-anticorrelated photon pairs. PMID:27087255
Frequencies of Nonaxisymmetric F-Modes in Rapidly Rotating Polytropes in Full General Relativity
NASA Astrophysics Data System (ADS)
Zink, Burkhard; Stergioulas, Nikolaos; Korobkin, Oleg; Schnetter, Erik; Diener, Peter; Tiglio, Manuel
The computation of frequencies of nonaxisymmetric f-modes in rapidly rotating stars in full general relativity is a long-standing problem that has not been solved, to date, without resorting to some approximation, such as the slow-rotation approximation or the Cowling approximation. We present the first computation of such frequencies in full general relativity and rapid rotation, without any such approximation. We achieve this by using long-term simulations of oscillating polytropic models with a nonlinear numerical code, where spacetime is evolved in the harmonic formulation. We compare our results to previous results for zero-frequency (neutral modes) that were obtained with a perturbative method, and comment on the relevance of our work to the gravitational-radiation-driven (CFS) secular instability of nonaxisymmetric f-modes.
NASA Astrophysics Data System (ADS)
Li, Chuan; Liang, Ming
2012-01-01
The vibration data, especially those collected during the system run-up and run-down periods, contain rich information for gearbox condition monitoring. Time-frequency (TF) signal analysis is an effective tool to detect gearbox faults under varying shaft speed. However, the feature of the amplitude modulated-frequency modulated (AM-FM) gearbox fault signal usually cannot be directly extracted from the blurred time-frequency representation (TFR) caused by the time-varying frequency and noisy multicomponent measurement. As such, we propose to use a generalized synchrosqueezing transform (GST)-based TF method to detect and diagnose gearbox faults. With this method, the original vibration signal is first mapped into another analytical signal to facilitate synchrosqueezing of the TF picture. A time-scale domain restoration process is then applied to recover the instantaneous frequency profile with concentrated TFR. The gearbox fault, if any, can then be detected by observing the presence of the meshing frequency and sideband components in the TFR. The faulty gear can be identified via frequency relation analysis of AM-FM components. The proposed method is evaluated using both simulated and experimental gearbox vibration signals. The results show that the proposed approach is effective for gearbox condition monitoring.
Philipp, M; Vergnat, C; Müller, U; Sanctuary, R; Baller, J; Possart, W; Alnot, P; Krüger, J K
2009-01-21
The non-equilibrium process of polymerization of reactive polymers can be accompanied by transition phenomena like gelation or the chemical glass transition. The sensitivity of the mechanical properties at hypersonic frequencies-including the generalized Cauchy relation-to these transition phenomena is studied for three different polyurethanes using Brillouin spectroscopy. As for epoxies, the generalized Cauchy relation surprisingly holds true for the non-equilibrium polymerization process and for the temperature dependence of polyurethanes. Neither the sol-gel transition nor the chemical and thermal glass transitions are visible in the representation of the generalized Cauchy relation. Taking into account the new results and combining them with general considerations about the elastic properties of the isotropic state, an improved physical foundation of the generalized Cauchy relation is proposed.
General-form 3-3-3 interpolation kernel and its simplified frequency-response derivation
NASA Astrophysics Data System (ADS)
Deng, Tian-Bo
2016-11-01
An interpolation kernel is required in a wide variety of signal processing applications such as image interpolation and timing adjustment in digital communications. This article presents a general-form interpolation kernel called 3-3-3 interpolation kernel and derives its frequency response in a closed-form by using a simple derivation method. This closed-form formula is preliminary to designing various 3-3-3 interpolation kernels subject to a set of design constraints. The 3-3-3 interpolation kernel is formed through utilising the third-degree piecewise polynomials, and it is an even-symmetric function. Thus, it will suffice to consider only its right-hand side when deriving its frequency response. Since the right-hand side of the interpolation kernel contains three piecewise polynomials of the third degree, i.e. the degrees of the three piecewise polynomials are (3,3,3), we call it the 3-3-3 interpolation kernel. Once the general-form frequency-response formula is derived, we can systematically formulate the design of various 3-3-3 interpolation kernels subject to a set of design constraints, which are targeted for different interpolation applications. Therefore, the closed-form frequency-response expression is preliminary to the optimal design of various 3-3-3 interpolation kernels. We will use an example to show the optimal design of a 3-3-3 interpolation kernel based on the closed-form frequency-response expression.
NASA Astrophysics Data System (ADS)
Eliazar, Iddo
2017-03-01
Inequality indices are widely applied in economics and in the social sciences as quantitative measures of the socioeconomic inequality of human societies. The application of inequality indices extends to size-distributions at large, where these indices can be used as general gauges of statistical heterogeneity. Moreover, as inequality indices are plentiful, arrays of such indices facilitate high-detail quantification of statistical heterogeneity. In this paper we elevate from arrays of inequality indices to inequality spectra: continuums of inequality indices that are parameterized by a single control parameter. We present a general methodology of constructing Lorenz-based inequality spectra, apply the general methodology to establish four sets of inequality spectra, investigate the properties of these sets, and show how these sets generalize known inequality gauges such as: the Gini index, the extended Gini index, the Rényi index, and hill curves.
Rodrigues, G. Mal, Kedar; Kumar, Narender; Lakshmy, P. S.; Mathur, Y.; Kumar, P.; Kanjilal, D.; Roy, A.; Baskaran, R.
2014-02-15
Studies on the effect of the frequency tuning on the bremsstrahlung spectra, beam intensities, and beam shape of various ions have been carried out in the 10 GHz NANOGAN ECR ion source. The warm and cold components of the electrons were found to be directly correlated with beam intensity enhancement in case of Ar{sup 9+} but not so for O{sup 5+}. The warm electron component was, however, much smaller compared to the cold component. The effect of the fine tuning of the frequency on the bremsstrahlung spectrum, beam intensities and beam shape is presented.
Kwac, Kijeong; Lee, Hochan; Cho, Minhaeng
2004-01-15
By carrying out molecular dynamics simulations of an N-methylacetamide (NMA) in methanol solution, the amide I mode frequency fluctuation and hydrogen bonding dynamics were theoretically investigated. Combining an extrapolation formula developed from systematic ab initio calculation studies of NMA-(CH3OH)n clusters with a classical molecular dynamics simulation method, we were able to quantitatively describe the solvatochromic vibrational frequency shift induced by the hydrogen-bonding interaction between NMA and solvent methanol. It was found that the fluctuating amide I mode frequency distribution is notably non-Gaussian and it can be decomposed into two Gaussian peaks that are associated with two distinctively different solvation structures. The ensemble-average-calculated linear response function associated with the IR absorption is found to be oscillating, which is in turn related to the doublet amide I band shape. Numerically calculated infrared absorption spectra are directly compared with experiment and the agreement was found to be excellent. By using the Onsager's regression hypothesis, the rate constants of the interconversion process between the two solvation structures were obtained. Then, the nonlinear response functions associated with two-dimensional infrared pump-probe spectroscopy were simulated. The physics behind the two-dimensional line shape and origin of the cross peaks in the time-resolved pump-probe spectra is explained and the result is compared with 2D spectra experimentally measured recently by Woutersen et al.
Computing frequency by using generalized zero-crossing applied to intrinsic mode functions
NASA Technical Reports Server (NTRS)
Huang, Norden E. (Inventor)
2006-01-01
This invention presents a method for computing Instantaneous Frequency by applying Empirical Mode Decomposition to a signal and using Generalized Zero-Crossing (GZC) and Extrema Sifting. The GZC approach is the most direct, local, and also the most accurate in the mean. Furthermore, this approach will also give a statistical measure of the scattering of the frequency value. For most practical applications, this mean frequency localized down to quarter of a wave period is already a well-accepted result. As this method physically measures the period, or part of it, the values obtained can serve as the best local mean over the period to which it applies. Through Extrema Sifting, instead of the cubic spline fitting, this invention constructs the upper envelope and the lower envelope by connecting local maxima points and local minima points of the signal with straight lines, respectively, when extracting a collection of Intrinsic Mode Functions (IMFs) from a signal under consideration.
Nonlinear gyrokinetic equations for low-frequency electromagnetic waves in general plasma equilibria
Frieman, E.A.; Chen, L.
1981-10-01
A nonlinear gyrokinetic formalism for low-frequency (less than the cyclotron frequency) microscopic electromagnetic perturbations in general magnetic field configurations is developed. The nonlinear equations thus derived are valid in the strong-turbulence regime and contain effects due to finite Larmor radius, plasma inhomogeneities, and magentic field geometries. The specific case of axisymmetric tokamaks is then considered, and a model nonlinear equation is derived for electrostatic drift waves. Also, applying the formalism to the shear Alfven wave heating sceme, it is found that nonlinear ion Landau damping of kinetic shear-Alfven waves is modified, both qualitatively and quantitatively, by the diamagnetic drift effects. In particular, wave energy is found to cascade in wavenumber instead of frequency.
NASA Astrophysics Data System (ADS)
Kirienko, T. P.; Poplavnoy, A. S.
2010-09-01
Phonon spectra and state densities of MeF2 (Me = Ca, Sr, Cd, Ba, or Pb) crystals are calculated in the basis of sublattice state vectors using the Born-Mayer model. The phonon spectra and the sublattice state densities are calculated in the field of the second frozen sublattice. It is demonstrated that optical crystal branches are mainly due to oscillations of fluorine ions; moreover, the topology of optical branches in the spectrum and the crystal state densities are close to the topology of the spectra and state densities of the fluorine sublattice in the frozen metal sublattice. Exception is CaF2 whose ion and cation masses are close in values.
Application of generalized Snoek's law over a finite frequency range: A case study
NASA Astrophysics Data System (ADS)
Rozanov, Konstantin N.; Koledintseva, Marina Y.
2016-02-01
Generalized Snoek's law proposed in an integral form by Acher and coauthors is a useful tool for investigation of high-frequency properties of magnetic materials. This integral law referred to as Acher's law allows for evaluating the ultimate performance of RF and microwave devices which employ magnetic materials. It may also be helpful in obtaining useful information on the structure and morphology of the materials. The key factor in practical application of Acher's law is an opportunity to employ either measured or calculated data available over a finite frequency range. The paper uses simple calculations to check the applicability of Acher's law in cases when the frequency range is limited and the magnetic loss peak is comparatively wide and has a distorted shape. The cases of large magnetic damping, pronounced skin effect, and inhomogeneity of the material are considered. It is shown that in most cases calculation of the integral through fitting of actual magnetic frequency dispersion by the Lorentzian dispersion law results in accurate estimations of the ultimate high-frequency performance of magnetic materials.
Qin, Kaihuai; Yang, Chun; Sun, Feng
2014-01-01
In ultrasonic nondestructive testing (NDT), the phase shift migration (PSM) technique, as a frequency-domain implementation of the synthetic aperture focusing technique (SAFT), can be adopted for imaging of regularly layered objects that are inhomogeneous only in depth but isotropic and homogeneous in the lateral direction. To deal with irregularly layered objects that are anisotropic and inhomogeneous in both the depth and lateral directions, a generalized frequency- domain SAFT, called generalized phase shift migration (GPSM), is proposed in this paper. Compared with PSM, the most significant innovation of GPSM is that the phase shift factor is generalized to handle anisotropic media with lateral velocity variations. The generalization is accomplished by computer programming techniques without modifying the PSM model. In addition, SRFFT (split-radix fast Fourier transform) input/output pruning algorithms are developed and employed in the GPSM algorithm to speed up the image reconstructions. The experiments show that the proposed imaging techniques are capable of reconstructing accurate shapes and interfaces of irregularly layered objects. The computing time of the GPSM algorithm is much less than the time-domain SAFT combined with the ray-tracing technique, which is, at present, the common method used in ultrasonic NDT industry for imaging layered objects. Furthermore, imaging regularly layered objects can be regarded as a special case of the presented technique.
Yamamoto, Kohji; Kabir, Md Humayun; Hayashi, Michitoshi; Tominaga, Keisuke
2005-05-07
We have measured the frequency dependent extinction coefficients and refractive indices of electron donor-acceptor (EDA) complexes consisting of hexamethylbenzene (HMB; electron donor) and tetracyanoethylene (TCNE; electron acceptor) in the low-frequency region by terahertz time-domain spectroscopy (THz-TDS). A mixture of the 1:1 (DA) and 2:1 (D2A) EDA complexes exist in carbon tetrachloride solution, and we successfully obtained the spectral components of the 1:1 and 2:1 EDA complexes separately by analyzing the concentration dependence of the THz spectra. The 1:1 and 2:1 complexes show quite different THz spectra of the extinction coefficient, reflecting unique features of dynamics, fluctuations and intermolecular interactions of these complexes. Polarization-selective THz-TDS on the crystalline DA complex shows two peaks at 53 and 70 cm(-1) in the spectral component perpendicular to the crystal axis. On the other hand, the crystalline D2A complex exhibits peaks at 42 and 50 cm(-1) in the perpendicular spectral component. We compare the obtained spectra of the crystalline complex and the results of molecular orbital calculations at the HF/6-31G(d) level of theory to discuss the intermolecular vibrational modes of the complexes.
Yang, Xiaoning
2016-08-01
In this study, I used seismic waveforms recorded within 2 km from the epicenter of the first four Source Physics Experiments (SPE) explosions to invert for the moment-tensor spectra of these explosions. I employed a one-dimensional (1D) Earth model for Green's function calculations. The model was developed from P- and R_{g}-wave travel times and amplitudes. I selected data for the inversion based on the criterion that they had consistent travel times and amplitude behavior as those predicted by the 1D model. Due to limited azimuthal coverage of the sources and the mostly vertical-component-only nature of the dataset, only long-period, volumetric components of the moment-tensor spectra were well constrained.
Yang, Xiaoning
2016-08-01
In this study, I used seismic waveforms recorded within 2 km from the epicenter of the first four Source Physics Experiments (SPE) explosions to invert for the moment-tensor spectra of these explosions. I employed a one-dimensional (1D) Earth model for Green's function calculations. The model was developed from P- and Rg-wave travel times and amplitudes. I selected data for the inversion based on the criterion that they had consistent travel times and amplitude behavior as those predicted by the 1D model. Due to limited azimuthal coverage of the sources and the mostly vertical-component-only nature of the dataset, only long-period, volumetricmore » components of the moment-tensor spectra were well constrained.« less
Testing General Relativity with Low-Frequency, Space-Based Gravitational-Wave Detectors.
Gair, Jonathan R; Vallisneri, Michele; Larson, Shane L; Baker, John G
2013-01-01
We review the tests of general relativity that will become possible with space-based gravitational-wave detectors operating in the ∼ 10(-5) - 1 Hz low-frequency band. The fundamental aspects of gravitation that can be tested include the presence of additional gravitational fields other than the metric; the number and tensorial nature of gravitational-wave polarization states; the velocity of propagation of gravitational waves; the binding energy and gravitational-wave radiation of binaries, and therefore the time evolution of binary inspirals; the strength and shape of the waves emitted from binary mergers and ringdowns; the true nature of astrophysical black holes; and much more. The strength of this science alone calls for the swift implementation of a space-based detector; the remarkable richness of astrophysics, astronomy, and cosmology in the low-frequency gravitational-wave band make the case even stronger.
NASA Astrophysics Data System (ADS)
Shi, Juanjuan; Liang, Ming; Necsulescu, Dan-Sorin; Guan, Yunpeng
2016-04-01
The energy concentration level is an important indicator for time-frequency analysis (TFA). Weak energy concentration would result in time-frequency representation (TFR) diffusion and thus leading to ambiguous results or even misleading signal analysis results, particularly for nonstationary multicomponent signals. To improve the energy concentration level, this paper proposes a generalized stepwise demodulation transform (GSDT). The rationale of the proposed method is that (1) the generalized demodulation (GD) can map the original signal into an analytic signal with constant instantaneous frequency (IF) and improve the energy concentration level on time-frequency plane, and (2) focusing on a short window around the time instant of interest, a backward demodulation operation can recover the original frequency at the time instant without affecting the improved energy concentration level. By repeating the backward demodulation at every time instant of interest, the TFR of the entire signal can be attained with enhanced energy concentration level. With the GSDT, an iterative GSDT (IGSDT) is developed to analyze multicomponent signal that is subjected to different modulating sources for their constituent components. The IGSDT iteratively demodulates each constituent component to attain its TFR and the TFR of the whole signal is derived from superposing all the resulting TFRs of constituent components. The cross-term free and more energy concentrated TFR of the signal is, therefore, obtained, and the diffusion in the TFR can be reduced. The GSDT-based synchrosqueezing transform is also elaborated to further enhance the GSDT(IGSDT) yielded TFR. The effectiveness of the proposed method in TFA is tested using both simulated monocomponent and multicomponent signals. The application of the proposed method to bearing fault detection is explored. Bearing condition and fault pattern can be revealed by the proposed method resulting TFR. The main advantages of the proposed method
Pulse retrieval in frequency-resolved optical gating based on the method of generalized projections
DeLong, K.W.; Fittinghoff, D.N.; Trebino, R. ); Kohler, B.; Wilson, K. )
1994-12-15
We use the algorithmic method of generalized projections (GP's) to retrieve the intensity and phase of an ultrashort laser pulse from the experimental trace in frequency-resolved optical gating (FROG). Using simulations, we show that the use of GP's improves significantly the convergence properties of the algorithm over the basic FROG algorithm. In experimental measurements, the GP-based algorithm achieves significantly lower errors than previous algorithms. The use of GP's also permits the inclusion of an arbitrary material response function in the FROG problem.
Note: Direct sensor resistance-to-frequency conversion with generalized impedance converter.
Ramírez Muñoz, D; Sánchez Moreno, J; Casans Berga, S; Navarro Antón, A E
2010-12-01
In this note a squared output signal is generated from an astable circuit. Its frequency has a linear dependence on the resistance value of a resistive temperature sensor. The main circuit to obtain this direct relationship is the generalized impedance converter configured as a capacitor controlled by a sensor resistance. The proposed measurement method allows a direct analog-to-digital interface of information involved in resistive sensors. The converter finds applications in portable low voltage and low power design of instrumentation electronic systems.
Brunner, Daniel; Porte, Xavier; Soriano, Miguel C.; Fischer, Ingo
2012-01-01
The unstable emission of semiconductor lasers due to delayed optical feedback is characterized by combined intensity and frequency dynamics. Nevertheless, real-time experimental investigations have so far been restricted to measurements of intensity dynamics only. Detailed analysis and comparison with numerical models, therefore, have suffered from limited experimental information. Here, we report the simultaneous determination of the lasers optical emission intensity and emission frequency with high temporal resolution. The frequency dynamics is made accessible using a heterodyne detection scheme, in which a beat signal between the delayed feedback laser and a reference laser is generated. Our experiment provides insight into the overall spectral drift on nanosecond timescales, the spectral distribution of the unstable pulsations and the role of the individual external cavity modes. This opens new perspectives for the analysis, understanding and functional utilization of delayed feedback semiconductor lasers. PMID:23066501
NASA Technical Reports Server (NTRS)
Barcilon, V.
1978-01-01
The problem of inferring the speed of sound in a contained spherically symmetric fluid solely from its natural frequencies of vibration is considered. An investigation of the case in which the data consist of the two spectra associated with the angular numbers 0 and 1, suggests the possibility that a one-parameter family of slowness profiles can be constructed. These profiles are compatible with the data, up to first order in the non-uniformity of the fluid. It is conjectured that for other angular numbers, the loss of information increases as the difference between them increases.
A Horn-fed Frequency Scanning Holographic Antenna Based on Generalized Law of Reflection
Liu, Dawei; Cheng, Bo; Pan, Xiaotian; Qiao, Lifang
2016-01-01
A new method of designing horn-fed frequency scanning holographic antenna is proposed. The artificial surface design of holographic antenna is based on generalized law of reflection. The input admittance is utilized to construct the interference pattern of the surface which is intervened by the excitation wave and the required radiation wave. The scalar admittance unit cell which is composed of sub-wavelength metallic patch on grounded dielectric substrate is implemented to design artificial surface, and the simulation results are just as expected that the antenna can scan the beam as the frequency changes. Furthermore, a cross shaped patch printed on grounded dielectric unit cells is used to reduce the designing complexity of tensor admittance surface. At last, a frequency scanning holographic antenna with tensor admittance surface with ability of changing linear polarization excitation wave to left-hand circular polarization (LCP) radiation wave is designed and fabricated. The full-wave simulation and experimental results show well agreement and confirm the method proposed. PMID:27515782
Villanea, Fernando A; Safi, Kristin N; Busch, Jeremiah W
2015-01-01
The ABO locus in humans is characterized by elevated heterozygosity and very similar allele frequencies among populations scattered across the globe. Using knowledge of ABO protein function, we generated a simple model of asymmetric negative frequency dependent selection and genetic drift to explain the maintenance of ABO polymorphism and its loss in human populations. In our models, regardless of the strength of selection, models with large effective population sizes result in ABO allele frequencies that closely match those observed in most continental populations. Populations must be moderately small to fall out of equilibrium and lose either the A or B allele (N(e) ≤ 50) and much smaller (N(e) ≤ 25) for the complete loss of diversity, which nearly always involved the fixation of the O allele. A pattern of low heterozygosity at the ABO locus where loss of polymorphism occurs in our model is consistent with small populations, such as Native American populations. This study provides a general evolutionary model to explain the observed global patterns of polymorphism at the ABO locus and the pattern of allele loss in small populations. Moreover, these results inform the range of population sizes associated with the recent human colonization of the Americas.
NASA Astrophysics Data System (ADS)
Tan, Pingheng; Hu, Chengyong; Dong, Jian; Shen, Wanci; Zhang, Baofa
2001-12-01
The Raman spectra of a new type of graphite whiskers have been measured in the range of 150-7800 cm-1. The intensity of the overtone (2D) located at ~2700 cm-1 is found to be about 10 times stronger than that of the C-C stretching mode (G) at 1582 cm-1. Because of the peculiar enhancement of the 2D mode, high-order Raman bands up to fifth order at ~7500 cm-1 have been observed. Polarized micro-Raman spectroscopy has been performed on an individual graphite whisker, and angular-dependent intensity measurements of all Raman modes in the VV and HV geometries are in agreement with the theoretical calculated results. Laser-energy-dependent dispersion effects and the frequency discrepancy of Raman modes between their Stokes and anti-Stokes lines in graphite whiskers are also carefully investigated. The energy dispersion of the D mode and G mode is very similar to that of highly oriented pyrolytic graphite (HOPG). In contrast to the Raman spectra of HOPG and other graphite materials, two laser-energy-dependent Raman lines are revealed in the low-frequency region of the Raman spectra of graphite whiskers, which are believed to be the resonantly enhanced phonons in the transverse-acoustic and longitudinal-acoustic phonon branches. Moreover, the obvious energy dispersion of the D' mode at ~1620 cm-1 is observed in graphite whiskers. The results clearly reveal how strongly the peak parameters of Raman modes of graphite materials are dependent on their structural geometry. The Stokes and anti-Stokes scattering experiments show that the frequency discrepancy between the Stokes and anti-Stokes sides of a Raman mode in graphite materials is equal to the frequency value covered by the one-phonon energy of this Raman mode in its frequency versus laser energy curve, which is the product of the one-phonon energy of this mode (Eωs) and the value of its laser-energy dispersions (∂Eωs/∂ɛL).
NASA Technical Reports Server (NTRS)
Trubert, M.; Salama, M.
1979-01-01
Unlike an earlier shock spectra approach, generalization permits an accurate elastic interaction between the spacecraft and launch vehicle to obtain accurate bounds on the spacecraft response and structural loads. In addition, the modal response from a previous launch vehicle transient analysis with or without a dummy spacecraft - is exploited to define a modal impulse as a simple idealization of the actual forcing function. The idealized modal forcing function is then used to derive explicit expressions for an estimate of the bound on the spacecraft structural response and forces. Greater accuracy is achieved with the present method over the earlier shock spectra, while saving much computational effort over the transient analysis.
NASA Astrophysics Data System (ADS)
Litvinenko, G.; Konovalenko, A.; Zakharenko, V.; Vinogradov, V.; Shaposhnikov, V.; Zarka, Ph.
2012-09-01
One of the promising approaches to investigating features of the Jovian decameter radio emission (DAM) is application of novel experimental techniques with a further detailed analysis of the obtained data using both well-known and modern mathematical methods. Several observational campaigns were performed in November 2009 with the use of the UTR-2 radio telescope (Kharkov, Ukraine) and efficient registration systems with high frequency and temporal resolutions (the antenna effective area is about 105 m2, the frequency resolution is 4 kHz, the temporal resolution is 0.25 ms, and the dynamic range is 70 dB) [1]. The main goal of these campaigns was to experimentally investigate new properties of the Jovian DAM emission which could be detected using the above mentioned equipment. Also an original software package was developed for control the digital receiver and for off-line data analysis at the postprocessing stage.
NASA Astrophysics Data System (ADS)
Varga, Gábor; Csendes, Zita; Peintler, Gábor; Berkesi, Ottó; Sipos, Pál; Pálinkó, István
2014-03-01
One of the aims of our long-term research is the identification of metal ion-ligand coordination sites in bioinspired metal ion-C- or N-protected amino acid (histidine, tyrosine, cysteine or cystine) complexes immobilised on the surface of chloropropylated silica gel or Merrifield resin. In an attempt to reach this goal, structurally related, but much simpler complexes have been prepared and their metal ion-ligand vibrations were determined from their low-frequency IR spectra. The central ions were Mn(II), Co(II), Ni(II) or Cu(II) and the ligands (imidazole, isopropylamine, monosodium malonate) were chosen to possess only one-type of potential donor group. The low-frequency IR spectra were taken of the complexes for each ion-ligand combination and the typical metal ion-functional group vibration bands were selected and identified. The usefulness of the obtained assignments is demonstrated on exemplary immobilised metal ion-protected amino acid complexes.
NASA Astrophysics Data System (ADS)
Ataeva, G.; Gitterman, Y.; Shapira, A.
2017-01-01
This study analyzes and compares the P- and S-wave displacement spectra from local earthquakes and explosions of similar magnitudes. We propose a new approach to discrimination between low-magnitude shallow earthquakes and explosions by using ratios of P- to S-wave corner frequencies as a criterion. We have explored 2430 digital records of the Israeli Seismic Network (ISN) from 456 local events (226 earthquakes, 230 quarry blasts, and a few underwater explosions) of magnitudes Md = 1.4-3.4, which occurred at distances up to 250 km during 2001-2013 years. P-wave and S-wave displacement spectra were computed for all events following Brune's source model of earthquakes (1970, 1971) and applying the distance correction coefficients (Shapira and Hofstetter, Teconophysics 217:217-226, 1993; Ataeva G, Shapira A, Hofstetter A, J Seismol 19:389-401, 2015), The corner frequencies and moment magnitudes were determined using multiple stations for each event, and then the comparative analysis was performed.
Matsuki, Yoh; Eddy, Matthew T.; Herzfeld, Judith
2009-01-01
A simple and effective method, SIFT (Spectroscopy by Integrating Frequency and Time domain information) is introduced for processing non-uniformly sampled multidimensional NMR data. Applying the computationally efficient Gerchberg-Papoulis (G-P) algorithm, used previously in picture processing and medical imaging, SIFT supplements data at non-uniform points in the time domain with the information carried by known “dark” points (i.e. empty regions) in the frequency domain. We demonstrate that this rapid integration not only removes the severe pseudo-noise characteristic of the Fourier transforms of non-uniformly sampled data, but also provides a robust procedure for using frequency information to replace time measurements. The latter can be used to avoid unnecessary sampling in sampling-limited experiments and the former can be used to take advantage of the ability of non-uniformly sampled data to minimize trade-offs between the signal-to-noise ratio and the resolution in sensitivity-limited experiments. Processing 2D and 3D datasets takes about 0.1 and 2 min, respectively, on a personal computer. With these several attractive features, SIFT offers a novel, model-independent, flexible, and user-friendly tool for efficient and accurate processing of multidimensional NMR data. PMID:19284727
Matsuki, Yoh; Eddy, Matthew T; Herzfeld, Judith
2009-04-08
A simple and effective method, SIFT (spectroscopy by integration of frequency and time domain information), is introduced for processing nonuniformly sampled multidimensional NMR data. Applying the computationally efficient Gerchberg-Papoulis (G-P) algorithm, used previously in picture processing and medical imaging, SIFT supplements data at nonuniform points in the time domain with the information carried by known "dark" points (i.e., empty regions) in the frequency domain. We demonstrate that this rapid integration not only removes the severe pseudonoise characteristic of the Fourier transforms of nonuniformly sampled data, but also provides a robust procedure for using frequency information to replace time measurements. The latter can be used to avoid unnecessary sampling in sampling-limited experiments, and the former can be used to take advantage of the ability of nonuniformly sampled data to minimize trade-offs between the signal-to-noise ratio and the resolution in sensitivity-limited experiments. Processing 2D and 3D data sets takes about 0.1 and 2 min, respectively, on a personal computer. With these several attractive features, SIFT offers a novel, model-independent, flexible, and user-friendly tool for efficient and accurate processing of multidimensional NMR data.
Dykeman, Eric C; Sankey, Otto F
2009-01-21
We present a theoretical study of the low frequency vibrational modes of the M13 bacteriophage using a fully atomistic model. Using ideas from electronic structure theory, the few lowest vibrational modes of the M13 bacteriophage are determined using classical harmonic analysis. The relative Raman intensity is estimated for each of the mechanical modes using a bond polarizability model. Comparison of the atomic mechanical modes calculated here with modes derived from elastic continuum theory shows that a much richer spectrum emerges from an atomistic picture.
NASA Astrophysics Data System (ADS)
Kashuri, Klaida; Kashuri, Hektor; Iannacchione, Germano
2011-03-01
It is well known that the folding / unfolding of proteins is related directly to their structure and functionality. Calorimetry (both AC and MDSC) studies as well as low-frequency (1Hz to 100 kHz) dielectric measurements have been performed on hen egg white lysozyme dissolved in PBS (pH 7.4) from 20 to 100& circ; C. From the heat capacity profile, the temperatures and related an enthalpy change of the protein denaturing is probed. The heat capacity peak broadens and new features are reveled as the temperature scan rate is lowered to +0.017 K/min for the AC calorimetric method. Significant differences are observed using the (M)DSC technique at scan rates of from 1 to 5 K/min. The temperature dependence of the permittivity, ɛ ' , and the loss factor, ɛ , at 100 kHz of the diluted protein show features associated with those seen in the heat capacity (AC and MDSC). All results are interpreted in terms of protein denaturing then subsequent gelation that depend on protein sample concentration, which is supported by the frequency dependence of the permittivity at room temperature after thermally cycling Worcester Polytechnic Institute (WPI).
NASA Astrophysics Data System (ADS)
Millon, M. A.; Goertz, C. K.
1988-01-01
Magnetospheric radio frequency emission power has been shown to vary as a function of both solar wind and planetary values such as magnetic field by Kaiser and Desch. Planetary magnetic fields have been shown to scale with planetary variables such as density and angular momentum by numerous researchers. This paper combines two magnetic scaling laws (Busse's and Curtis Ness') with the radiometric law to yield "Bode's"-type laws governing planetary radio emission. Further analysis allows the reduction of variables to planetary mass and orbital distance. These generalized laws are then used to predict the power output of Neptune to be about 1.6×107W; with the intensity peaking at about 3 MHz.
Ab Initio Calculation Of Vibrational Frequencies In AsxS1-x Glass And The Raman Spectra
NASA Astrophysics Data System (ADS)
Rosli, Ahmad Nazrul; Kassim, Hasan Abu; Shrivastava, Keshav N.
2009-06-01
We have made many different models for the understanding of the structure of AsS glass. In particular, we made the models of AsS3 (triangular), AsS3 (pyramid), AsS4 (3S on one side, one on the other side of As, S3-As-S), AsS4 (pyramid), AsS4 (tetrahedral), AsS7, As2S6 (dumb bell), As2S3 (bipyramid), As2S3 (zig-zag), As3S2 (bipyramid), As3S2 (linear), As4S4 (cubic), As4S4 (ring), As4S (tetrahedral), As4S (pyramid), As4S3 (linear) and As6S2 (dumb bell) by using the density functional theory which solves the Schrödinger equation for the given number of atoms in a cluster in the local density approximation. The models are optimized for the minimum energy which determines the structures, bond lengths and angles. For the optimized clusters, we calculated the vibrational frequencies in each case by calculating the gradients of the first principles potential. We compare the experimentally observed Raman frequencies with those calculated so that we can identify whether the cluster is present in the glass. In this way we find that AsS4 (S3-As-S), As4S4 (ring), As2S3 (bipyramid), As4S4 (cubic), As4S3 (linear), As2S3 (zig-zag), AsS4 (Td), As2S6 (dumb bell), AsS3 (triangle) and AsS3 (pyramid) structures are present in the actual glass.
Chen, Yu-Wen; Chen, Chien-Chih; Huang, Po-Jung; Tseng, Sheng-Hao
2016-04-01
Diffuse reflectance spectroscopy (DRS) based on the frequency-domain (FD) technique has been employed to investigate the optical properties of deep tissues such as breast and brain using source to detector separation up to 40 mm. Due to the modeling and system limitations, efficient and precise determination of turbid sample optical properties from the FD diffuse reflectance acquired at a source-detector separation (SDS) of around 1 mm has not been demonstrated. In this study, we revealed that at SDS of 1 mm, acquiring FD diffuse reflectance at multiple frequencies is necessary for alleviating the influence of inevitable measurement uncertainty on the optical property recovery accuracy. Furthermore, we developed artificial neural networks (ANNs) trained by Monte Carlo simulation generated databases that were capable of efficiently determining FD reflectance at multiple frequencies. The ANNs could work in conjunction with a least-square optimization algorithm to rapidly (within 1 second), accurately (within 10%) quantify the sample optical properties from FD reflectance measured at SDS of 1 mm. In addition, we demonstrated that incorporating the steady-state apparatus into the FD DRS system with 1 mm SDS would enable obtaining broadband absorption and reduced scattering spectra of turbid samples in the wavelength range from 650 to 1000 nm.
Chen, Yu-Wen; Chen, Chien-Chih; Huang, Po-Jung; Tseng, Sheng-Hao
2016-01-01
Diffuse reflectance spectroscopy (DRS) based on the frequency-domain (FD) technique has been employed to investigate the optical properties of deep tissues such as breast and brain using source to detector separation up to 40 mm. Due to the modeling and system limitations, efficient and precise determination of turbid sample optical properties from the FD diffuse reflectance acquired at a source-detector separation (SDS) of around 1 mm has not been demonstrated. In this study, we revealed that at SDS of 1 mm, acquiring FD diffuse reflectance at multiple frequencies is necessary for alleviating the influence of inevitable measurement uncertainty on the optical property recovery accuracy. Furthermore, we developed artificial neural networks (ANNs) trained by Monte Carlo simulation generated databases that were capable of efficiently determining FD reflectance at multiple frequencies. The ANNs could work in conjunction with a least-square optimization algorithm to rapidly (within 1 second), accurately (within 10%) quantify the sample optical properties from FD reflectance measured at SDS of 1 mm. In addition, we demonstrated that incorporating the steady-state apparatus into the FD DRS system with 1 mm SDS would enable obtaining broadband absorption and reduced scattering spectra of turbid samples in the wavelength range from 650 to 1000 nm. PMID:27446671
Sert, Yusuf; Sreenivasa, S; Doğan, Hatice; Mohan, N R; Suchetan, P A; Ucun, Fatih
2014-09-15
The experimental FT-IR (4000-400 cm(-1)) and Laser-Raman spectra (4000-100 cm(-1)) of ethyl (2E)-2-cyano-3-(4-methoxyphenyl)-acrylate in solid phase have been recorded. Its theoretical vibrational frequencies, IR intensities, Raman activities and optimized geometric parameters (bond lengths and bond angles) have been calculated using density functional theory (DFT/B3LYP: Becke, 3-parameter, Lee-Yang-Parr and DFT/M06-2X: the highly parameterized empirical exchange correlation function) with 6-311++G(d, p) basis set by Gaussian 03 software, for the first time. The assignments of the vibrational frequencies have been done by potential energy distribution (PED) analysis using VEDA4 software. The optimized geometric parameters and vibrational frequencies have been seen to be in good agreement with the corresponding experimental data and results in the literature. In addition, the highest occupied molecular orbital (HOMO) energy, the lowest unoccupied molecular orbital (LUMO) energy and the other related molecular energy values of the compound have been investigated by using the same theoretical calculations.
NASA Astrophysics Data System (ADS)
Alobaidi, Mohammad H.; Marpu, Prashanth R.; Ouarda, Taha B. M. J.; Chebana, Fateh
2015-10-01
Regional frequency analysis (RFA) deals with the estimation of hydrological characteristics at sites where little or no data is available. Recently, machine learning applications to RFA have received considerable attention in terms of their flexibility in modeling as well as superior generalization ability compared to conventional approaches. The proper application of machine learning techniques, however, requires good understanding of the available information about system's dynamics, i.e. system variables. This paper presents two contributions to the literature. First, novel ensemble architecture, using a unique two-stage resampling approach, is proposed. The objective of the proposed ensemble model is to promote diversity within the individual learners and reduce over fitting. Second, the application of the proposed model is demonstrated in RFA case study to obtain improved regional flood quantile estimates at ungauged sites. A jackknife validation procedure is used for the evaluation of the model's performance. The method is applied to data from the province of Quebec, Canada. The model showed similar performance and generalization compared to major ensemble models in the literature, which were investigated in previous studies using the same data set. The proposed model confirmed the diversity requirement in ensemble modeling and, in the same time, validated the proposed model adherence to ensemble learning theory.
NASA Technical Reports Server (NTRS)
Jackson, F. C.
1979-01-01
Two simple microwave radar techniques that are potentially capable of providing routine satellite measurements of the directional spectrum of ocean waves were developed. One technique, the short pulse technique, makes use of very short pulses to resolve ocean surface wave contrast features in the range direction; the other technique, the two frequency correlation technique makes use of coherency in the transmitted waveform to detect the large ocean wave contrast modulation as a beat or mixing frequency in the power backscattered at two closely separated microwave frequencies. A frequency domain analysis of the short pulse and two frequency systems shows that the two measurement systems are essentially duals; they each operate on the generalized (three frequency) fourth-order statistical moment of the surface transfer function in different, but symmetrical ways, and they both measure the same directional contrast modulation spectrum. A three dimensional physical optics solution for the fourth-order moment was obtained for backscatter in the near vertical, specular regime, assuming Gaussian surface statistics.
High frequency permeability and permittivity spectra of BiFeO{sub 3}/(CoTi)-BaM ferrite composites
Peng, Yun; Wu, Xiaohan; Li, Qifan; Yu, Ting; Feng, Zekun; Chen, Zhongyan; Su, Zhijuan; Chen, Yajie; Harris, Vincent G.
2015-05-07
Low magnetic loss ferrite composites consisting of Ba(CoTi){sub 1.2}Fe{sub 9.6}O{sub 19} and BiFeO{sub 3} (BFO) ferrite were investigated for permeability, permittivity, and high frequency losses at 10 MHz–1 GHz. The phase fraction of BiFeO{sub 3} was quantitatively analyzed by X-ray diffraction measurements. An effective medium approach was employed to predict the effective permeability and permittivity for the ferrite composites, which was found to be in good agreement with experimental data. The experiment demonstrated low magnetic losses (<0.128), modified by BFO phase fraction, while retaining high permeability (∼10.86) at 300 MHz. More importantly, the BFO phase resulted in a reduction of magnetic loss by 32%, as BFO phase increased from 2.7 vol. % to 12.6 vol. %. The effect of BFO phase on magnetic and dielectric properties revealed great potential for use in the miniaturization of high efficiency antennas.
Baer, Marcel; Mundy, Christopher J.; Chang, Tsun-Mei; Tao, Fu-Ming; Dang, Liem X.
2010-06-01
We investigated the solvation and spectroscopic properties of SO2 at the air/water interface using molecular simulation techniques. Molecular interactions from both Kohn-Sham (KS) density functional theory (DFT) and classical polarizable models were utilized to understand the properties of SO2:(H2O)x complexes in the vicinity of the air/water interface. The KS-DFT was included to allow comparisons with sum-frequency generation spectroscopy through the identification of surface SO2:(H2O)x complexes. Using our simulation results, we were able to develop a much more detailed picture for the surface structure of SO2 that is consistent with the spectroscopic data obtained Richmond and coworkers (J. Am. Chem. Soc. 127, 16806 (2005)). We also found many similarities and differences between to the two interaction potentials, including a noticeable weakness of the classical potential model in reproducing the asymmetric hydrogen bonding of water with SO2 due to its inability to account for SO2 resonance structures. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.
Barbiellini, Bernardo; Kuriplach, Jan
2015-04-10
Positron annihilation spectroscopy is often used to analyze the local electronic structure of materials of technological interest. Reliable theoretical tools are crucial to interpret the measured spectra. Here, we propose a parameter-free gradient correction scheme for a local-density approximation obtained from high-quality quantum Monte Carlo data. The results of our calculations compare favorably with positron affinity and lifetime measurements, opening new avenues for highly precise and advanced positron characterization of materials.
2004-09-01
seismology and earthquake seismology . The generalized screen propagator (GSP) is based on the one-way wave equation and the one-return approximation. The...High-Frequency (1-25 HZ) Regional Phases at Large Distances O (>1000 KM) Using Generalized Screen Propagators (GSP) SApproved for public release...DTRA 01-97-1-0004 Synthesizing High-Freguency (1-25 HZ) Regional Phases at Large Distances (1 > 1000 KM) Using Generalized Screen Propagators (GSP) 5b
Zhang, Xu; Sander, Stanley P
2011-09-08
Infrared absorption spectra have been measured for the mixture of CO(2) and H(2)O in a cryogenic nitrogen matrix. The 1:1 CO(2)/H(2)O complex has been observed. Each structure of this complex should have two bending frequencies corresponding to the CO(2) fundamental bending mode (ν(2)). In this work, three bending frequencies corresponding to the CO(2) fundamental bending mode (ν(2)) have been detected; one of them at 660.3 cm(-1) is reported here for the first time. This finding helps confirm the existence of two structures for this complex. A new feature attributed to a CO(2) and H(2)O complex is observed at 3604.4 cm(-1) and is tentatively assigned to the CO(2)/H(2)O complex band corresponding to the CO(2) combination mode (ν(3) + 2ν(2)). In addition, a band that belongs to a CO(2) and H(2)O complex is detected at 3623.8 cm(-1) for the first time and is tentatively assigned to the (CO(2))(2)/H(2)O complex band corresponding to the symmetric stretching mode (ν(1)) of H(2)O.
NASA Astrophysics Data System (ADS)
Yamamoto, Kenneth K.; Reznicek, Nathan J.; Wilson, D. Keith
2013-05-01
The Environmental Awareness for Sensor and Emitter Employment (EASEE) software, being developed by the U. S. Army Engineer Research and Development Center (ERDC), provides a general platform for predicting sensor performance and optimizing sensor selection and placement in complex terrain and weather conditions. It incorporates an extensive library of target signatures, signal propagation models, and sensor systems. A flexible object-oriented design supports efficient integration and simulation of diverse signal modalities. This paper describes the integration of modeling capabilities for radio-frequency (RF) transmission and radar systems from the U. S. Navy Electromagnetic Propagation Integrated Resource Environment (EMPIRE), which contains nearly twenty different realistic RF propagation models. The integration utilizes an XML-based interface between EASEE and EMPIRE to set inputs for and run propagation models. To accommodate radars, fundamental improvements to the EASEE software architecture were made to support active-sensing scenarios with forward and backward propagation of the RF signals between the radar and target. Models for reflecting targets were defined to apply a target-specific, directionally dependent reflection coefficient (i.e., scattering cross section) to the incident wavefields.
Asad, Munazza; Ahmed, Farah; Zafar, Humaira; Farman, Sabir
2015-01-01
Background and Objective: Both Hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are rapidly spreading in the developing countries. Both of them are blood borne and are transmitted through un-screened blood transfusion, inadequately sterilized needles and equipment. According to WHO’s criteria of endemicity, Pakistan has high disease burden of Hepatitis B and C. The present study was planned to determine the frequency and to identify the risk factors of hepatitis B and C virus in the general community of Farash town. Methods: This descriptive study was carried out in Al Nafees Medical Hospital Lab, from January 2013 to December 2013. Both the genders and all age groups were included in the study. All the patients who fulfilled the inclusion criteria had given a written consent. Data was collected through questionnaire and was analyzed on Statistical Package for Social Sciences (SPSS) version 21. Results: Three-hundred and forty five patients were studied. Among these 92 (27%) were males and 253(73%) were female, 33% of them had hepatitis C, 9% had hepatitis B. History of injections was reported in all of the patients. Visit to community barbers was present in 58.6% and 41% cases of hepatitis B and C. History of dental procedures was obtained in 7(24%) and 15(13%) patients of hepatitis B and C. Conclusion: Major contributors for Hepatitis B and C in Farash town are use of unsterilized therapeutic injections and visit to community barbers. Education of the barbers regarding sterilization may help in reducing the burden of infection in this community. PMID:26870103
NASA Astrophysics Data System (ADS)
Gebresellasie, K.; Shirokoff, J.; Lewis, J. C.
2012-12-01
X-ray line spectra profile fitting using Pearson VII, pseudo-Voigt and generalized Fermi functions was performed on asphalt binders prior to the calculation of aromaticity and crystallite size parameters. The effects of these functions on the results are presented and discussed in terms of the peak profile fit parameters, the uncertainties in calculated values that can arise owing to peak shape, peak features in the pattern and crystallite size according to the asphalt models (Yen, modified Yen or Yen-Mullins) and theories. Interpretation of these results is important in terms of evaluating the performance of asphalt binders widely used in the application of transportation systems (roads, highways, airports).
Wu, Tiapin; Childers, David; Gomez, Carolina; Karim, Ayman M.; Schweitzer, Neil; Kropf, Arthur; Wang, Hui; Bolin, Trudy B.; Hu, Yongfeng; Kovarik, Libor; Meyer, Randall; Miller, Jeffrey T.
2012-10-08
Bimetallic PtPd on silica nano-particle catalysts have been synthesized and their average structure determined by Pt L3 and Pd K-edge extended X-ray absorption finestructure (EXAFS) spectroscopy. The bimetallic structure is confirmed from elemental line scans by STEM for the individual 1-2 nm sized particles. A general method is described to determine the surface composition in bimetallic nanoparticles even when both metals adsorb, for example, CO. By measuring the change in the L3 X-ray absorption near-edge structure (XANES) spectra with and without CO in bimetallic particles and comparing these changes to those in monometallic particles of known size the fraction of surface atoms can be determined. The turnover rates (TOR) and neopentane hydrogenolysis and isomerization selectivities based on the surface composition suggest that the catalytic and spectroscopic properties are different from those in monometallic nano-particle catalysts. At the same neo-pentane conversion, the isomerization selectivity is higher for the PtPd catalyst while the TOR is lower than that of both Pt and Pd. As with the catalytic performance, the infrared spectra of adsorbed CO are not a linear combination of the spectra on monometallic catalysts. Density functional theory calculations indicate that the Pt-CO adsorption enthalpy increases while the Pd-CO bond energy decreases. The ability to determine the surface composition allows for a better understanding of the spectroscopic and catalytic properties of bimetallic nanoparticle catalysts.
NASA Astrophysics Data System (ADS)
Cheng, Junsheng; Yang, Yu; Yu, Dejie
2010-02-01
The generalized demodulation time-frequency analysis is a novel signal processing method, which is particularly suitable for the processing of multi-component amplitude-modulated and frequency-modulated (AM-FM) signals as it can decompose a multi-component signal into a set of single-component signals whose instantaneous frequencies own physical meaning. While fault occurs in gear, the vibration signals measured from gearbox would exactly display AM-FM characteristics. Therefore, targeting the modulation feature of gear vibration signal in run-ups and run-downs, a fault diagnosis method in which generalized demodulation time-frequency analysis and envelope order spectrum technique are combined is put forward and applied to the transient analysis of gear vibration signal. Firstly the multi-component vibration signal of gear is decomposed into some mono-component signals using the generalized demodulation time-frequency analysis approach; secondly the envelope analysis is performed to each single-component signal; thirdly each envelope signal is re-sampled in angle domain; finally the spectrum analysis is applied to each re-sampled signal and the corresponding envelope order spectrum can be obtained. Furthermore, the gear working condition can be identified according to the envelope order spectrum. The analysis results from the simulation and experimental signals show that the proposed algorithm was effective in gear fault diagnosis.
Busuttil, Rita A.; Muñoz, Denise P.; Garcia, Ana Maria; Rodier, Francis; Kim, Woo Ho; Suh, Yousin; Hasty, Paul; Campisi, Judith; Vijg, Jan
2008-01-01
Non-homologous end joining (NHEJ) is thought to be an important mechanism for preventing the adverse effects of DNA double strand breaks (DSBs) and its absence has been associated with premature aging. To investigate the effect of inactivated NHEJ on spontaneous mutation frequencies and spectra in vivo and in cultured cells, we crossed a Ku80-deficient mouse with mice harboring a lacZ-plasmid-based mutation reporter. We analyzed various organs and tissues, as well as cultured embryonic fibroblasts, for mutations at the lacZ locus. When comparing mutant with wild-type mice, we observed a significantly higher number of genome rearrangements in liver and spleen and a significantly lower number of point mutations in liver and brain. The reduced point mutation frequency was not due to a decrease in small deletion mutations thought to be a hallmark of NHEJ, but could be a consequence of increased cellular responses to unrepaired DSBs. Indeed, we found a substantial increase in persistent 53BP1 and γH2AX DNA damage foci in Ku80−/− as compared to wild-type liver. Treatment of cultured Ku80-deficient or wild-type embryonic fibroblasts, either proliferating or quiescent, with hydrogen peroxide or bleomycin showed no differences in the number or type of induced genome rearrangements. However, after such treatment, Ku80-deficient cells did show an increased number of persistent DNA damage foci. These results indicate that Ku80-dependent repair of DNA damage is predominantly error-free with the effect of alternative more error-prone pathways creating genome rearrangements only detectable after extended periods of time, i.e., in young adult animals. The observed premature aging likely results from a combination of increased cellular senescence and an increased load of stable, genome rearrangements. PMID:18941635
Nadorff, Michael R.; Porter, Ben; Rhoades, Howard M.; Greisinger, Anthony J.; Kunik, Mark E.; Stanley, Melinda A.
2012-01-01
This study investigated the relation between generalized anxiety disorder (GAD) and frequency of bad dreams in older adults. A secondary analysis from a randomized clinical trial comparing cognitive behavioral therapy for anxiety (CBT) to enhanced usual care (EUC), it assessed bad dream frequency at baseline, post-treatment (3 months), and 6, 9, 12 and 15 months. Of 227 participants (mean age = 67.4), 134 met GAD diagnostic criteria (CBT = 70, EUC = 64), with the remaining 93 serving as a comparison group. Patients with GAD had significantly more bad dreams than those without, and bad dream frequency was significantly associated with depression, anxiety, worry, and poor quality of life. CBT for anxiety significantly reduced bad dream frequency at post-treatment and throughout follow-up compared to EUC. PMID:23470116
Nadorff, Michael R; Porter, Ben; Rhoades, Howard M; Greisinger, Anthony J; Kunik, Mark E; Stanley, Melinda A
2014-01-01
This study investigated the relation between generalized anxiety disorder (GAD) and frequency of bad dreams in older adults. A secondary analysis from a randomized clinical trial comparing cognitive behavioral therapy (CBT) for anxiety to enhanced usual care (EUC) assessed bad dream frequency at baseline, post treatment (3 months), and at 6, 9, 12, and 15 months. Of 227 participants (mean age = 67.4), 134 met GAD diagnostic criteria (CBT = 70, EUC = 64), with the remaining 93 serving as a comparison group. Patients with GAD had significantly more bad dreams than those without, and bad dream frequency was significantly associated with depression, anxiety, worry, and poor quality of life. CBT for anxiety significantly reduced bad dream frequency at post treatment and throughout follow up compared to EUC.
Goedbloed, J. P.
2012-06-15
It is shown that some of the main results of the recent paper by Lakhin and Ilgisonis [Phys. Plasmas 18, 092103 (2011)], viz. the derivation of the equations for the continuous spectra of poloidally and toroidally rotating plasmas and their special solution for large aspect ratio tokamaks with large parallel flows were obtained before by Goedbloed, Belieen, van der Holst, and Keppens [Phys. Plasmas 11, 28 (2004)]. A further rearrangement of the system of equations for the coupled Alfven and slow continuous spectra clearly exhibits: (a) coupling through a single tangential derivative, which is a generalization of the geodesic curvature; (b) the 'transonic' transitions of the equilibrium, which need to be carefully examined in order to avoid entering hyperbolic flow regimes where the stability formalism breaks down. A critical discussion is devoted to the implications of this failure, which is generally missed in the tokamak literature, possibly as a result of the wide-spread use of the sonic Mach number of gas dynamics, which is an irrelevant and misleading parameter in 'transonic' magnetohydrodynamics. Once this obstacle in understanding is removed, further application of the theory of trans-slow Alfven continuum instabilities to both tokamaks, with possible implications for the L-H transition, and astrophysical objects like 'fat' accretion disks, with a possible new route to magnetohydrodynamic turbulence, becomes feasible.
A generalized equation for the resonance frequencies of a fluid-filled crack
NASA Astrophysics Data System (ADS)
Maeda, Yuta; Kumagai, Hiroyuki
2017-01-01
Although a model of the resonance of a rectangular fluid-filled crack (crack model) is one of the most frequently used source models of long-period seismic events at volcanoes, there has been no analytical solution for the resonance frequencies. We previously proposed an empirical expression for the resonance frequencies as a mathematical function of the crack length, aperture, and properties of the fluid and the surrounding elastic medium. However, the expression contained an empirical constant that had to be investigated numerically for each crack aspect ratio and oscillation mode, a requirement that prevented widespread use of the expression. In the present study, we examined the theoretical basis for the expression. We assumed that the ratio of the crack wall displacement to the fluid pressure near each crack edge varied as the square root of the distance from the edge. Using this assumption, we showed theoretically that the previously proposed empirical analytical expression was a good approximation (difference ≤ 2%) to another more complete expression. This theoretical expression is a closed form of a mathematical function of the crack model parameters and oscillation mode number; there are no empirical constants to be determined numerically. The expression thus enabled us to analytically compute the resonance frequencies for arbitrary rectangular cracks, and the results were in good agreement (difference ≤ 5%) with numerical solutions. Resonance frequencies of cracks can be very easily predicted using this expression. This predictive ability may enhance our quantitative understanding of the processes that generate long-period events at volcanoes.
Liu, Yushun; Zhou, Wenjun; Li, Pengfei; Yang, Shuai; Tian, Yan
2016-01-01
Due to electromagnetic interference in power substations, the partial discharge (PD) signals detected by ultrahigh frequency (UHF) antenna sensors often contain various background noises, which may hamper high voltage apparatus fault diagnosis and localization. This paper proposes a novel de-noising method based on the generalized S-transform and module time-frequency matrix to suppress noise in UHF PD signals. The sub-matrix maximum module value method is employed to calculate the frequencies and amplitudes of periodic narrowband noise, and suppress noise through the reverse phase cancellation technique. In addition, a singular value decomposition de-noising method is employed to suppress Gaussian white noise in UHF PD signals. Effective singular values are selected by employing the fuzzy c-means clustering method to recover the PD signals. De-noising results of simulated and field detected UHF PD signals prove the feasibility of the proposed method. Compared with four conventional de-noising methods, the results show that the proposed method can suppress background noise in the UHF PD signal effectively, with higher signal-to-noise ratio and less waveform distortion. PMID:27338409
NASA Astrophysics Data System (ADS)
Murdachaew, Garold; Szalewicz, Krzysztof; Jiang, Hao; Bačić, Zlatko
2004-12-01
rationalized in terms of the physical components of the intermolecular forces and related to monomer properties. The accuracy of the SAPT PES was tested by performing calculations of rovibrational levels. The transition frequencies obtained were found to be in excellent agreement (to within 0.02 cm-1) with the measurements of Lovejoy and Nesbitt [J. Chem. Phys. 93, 5387 (1990)]. The SAPT PES predicts a dissociation energy for the complex of 7.74 cm-1 which is probably more accurate than the experimental value of 10.1±1.2 cm-1. Our analysis of the ground-state rovibrational wave function shows that the He-HCl configuration is favored over the He-ClH configuration despite the ordering of minima. This is due to the greater volume of the well in the former case. We have also determined positions and widths of three low-lying resonance states through scattering calculations. These predictions are expected to be more accurate than values derived from experiment.
NASA Technical Reports Server (NTRS)
Sivapalan, Murugesu; Wood, Eric F.; Beven, Keith J.
1993-01-01
One of the shortcomings of the original theory of the geomorphologic unit hydrograph (GUH) is that it assumes that runoff is generated uniformly from the entire catchment area. It is now recognized that in many catchments much of the runoff during storm events is produced on partial areas which usually form on narrow bands along the stream network. A storm response model that includes runoff generation on partial areas by both Hortonian and Dunne mechanisms was recently developed by the authors. In this paper a methodology for integrating this partial area runoff generation model with the GUH-based runoff routing model is presented; this leads to a generalized GUH. The generalized GUH and the storm response model are then used to estimate physically based flood frequency distributions. In most previous work the initial moisture state of the catchment had been assumed to be constant for all the storms. In this paper we relax this assumption and allow the initial moisture conditions to vary between storms. The resulting flood frequency distributions are cast in a scaled dimensionless framework where issues such as catchment scale and similarity can be conveniently addressed. A number of experiments are performed to study the sensitivity of the flood frequency response to some of the 'similarity' parameters identified in this formulation. The results indicate that one of the most important components of the derived flood frequency model relates to the specification of processes within the runoff generation model; specifically the inclusion of both saturation excess and Horton infiltration excess runoff production mechanisms. The dominance of these mechanisms over different return periods of the flood frequency distribution can significantly affect the distributional shape and confidence limits about the distribution. Comparisons with observed flood distributions seem to indicate that such mixed runoff production mechanisms influence flood distribution shape. The
NASA Astrophysics Data System (ADS)
Feng, Zhipeng; Chen, Xiaowang; Liang, Ming
2016-08-01
Planetary gearbox vibration signals under nonstationary conditions are characterized by time-varying nature and complex multi-components, making it very difficult to extract features for fault diagnosis. Order spectrum analysis is one of the effective approaches for nonstationary signal analysis of rotating machinery. The main idea of order analysis is to map the time-varying frequency components into constant ones. Inspired by this idea, we propose a new order spectrum analysis method to exploit the unique property of iterative generalized demodulation in converting arbitrary instantaneous frequency trajectories of multi-component signals into constant frequency lines on the time-frequency plane. This new method is completely algorithm-based and tachometer/encoder-free, thus easy to implement. It does not involve equi-angular resampling commonly required by most order tracking methods and is hence free from the decimation and/or interpolation error. The proposed order analysis method can eliminate the time-variation effect of frequency and thus can effectively reveal the harmonic order constituents of nonstationary multi-component signals. However, the planetary gearbox vibration signals also lead to complex sideband orders. As such, we further propose to analyze the order spectrum of amplitude envelope. This will eliminate the complex sideband orders in the order spectrum of original signals, leading to a substantially simplified and more reliable gear characteristic frequency identification process. Nevertheless, the gear and/or planet carrier rotating frequency orders, which are irrelevant to gear fault, may still exist. To avoid possible misleading results due to such frequency orders, we also propose to analyze the order spectrum of instantaneous frequency. Theoretically, the peaks present in frequency order spectrum directly correspond to the gear characteristic frequency orders, which can be used to extract gear fault signature more explicitly. The proposed
Coen, Stéphane; Randle, Hamish G; Sylvestre, Thibaut; Erkintalo, Miro
2013-01-01
A generalized Lugiato-Lefever equation is numerically solved with a Newton-Raphson method to model Kerr frequency combs. We obtain excellent agreement with past experiments, even for an octave-spanning comb. Simulations are much faster than with any other technique despite including more modes than ever before. Our study reveals that Kerr combs are associated with temporal cavity solitons and dispersive waves, and opens up new avenues for the understanding of Kerr-comb formation.
Liu, Chang; Dodin, Ilya Y.
2015-08-15
The nonlinear frequency shift is derived in a transparent asymptotic form for intense Langmuir waves in general collisionless plasma. The formula describes both fluid and kinetic effects simultaneously. The fluid nonlinearity is expressed, for the first time, through the plasma dielectric function, and the kinetic nonlinearity accounts for both smooth distributions and trapped-particle beams. Various known limiting scalings are reproduced as special cases. The calculation avoids differential equations and can be extended straightforwardly to other nonlinear plasma waves.
A garden of orchids: a generalized Harper equation at quadratic irrational frequencies
NASA Astrophysics Data System (ADS)
Mestel, B. D.; Osbaldestin, A. H.
2004-10-01
We consider a generalized Harper equation at quadratic irrational flux, showing, in the strong coupling limit, the fluctuations of the exponentially decaying eigenfunctions are governed by the dynamics of a renormalization operator on a renormalization strange set. This work generalizes previous analyses which have considered only the golden mean case. Projections of the renormalization strange sets are illustrated analogous to the 'orchid' present in the golden mean case.
NASA Astrophysics Data System (ADS)
Suh, Kyoung Whoan
2007-02-01
This paper proposes an efficient and comprehensive algorithm for computing the protection ratio and illustrates some results applicable to the initial planning of frequency coordination for fixed wireless networks. A net filter discrimination depending upon transmitter spectrum mask and overall receiver filter characteristic is also examined to see the effect of adjacent channel interferences. Numerical simulations for cochannel and adjacent channel protection ratios are performed for the 6.2 GHz frequency band, including transmitter spectrum mask and receiver filter response. According to results for 64-QAM (quadrature amplitude modulation) and 60 km at bit error ratio 10-6, fade margin and cochannel protection ratio are 41.1 and 74.9 dB, respectively. In addition, it is shown that the net filter discrimination for 30 MHz channel bandwidth provides 26.5 dB at the first adjacent channel, which yields adjacent channel protection ratio of 48.4 dB. The proposed method gives an easy and systematic method to compute the protection ratio and can be applied to frequency coordination in fixed wireless networks up to the millimeter wave band.
NASA Astrophysics Data System (ADS)
Frazier, Michael J.; Hussein, Mahmoud I.
2016-05-01
It is common for dispersion curves of damped periodic materials to be based on real frequencies as a function of complex wavenumbers or, conversely, real wavenumbers as a function of complex frequencies. The former condition corresponds to harmonic wave motion where a driving frequency is prescribed and where attenuation due to dissipation takes place only in space alongside spatial attenuation due to Bragg scattering. The latter condition, on the other hand, relates to free wave motion admitting attenuation due to energy loss only in time while spatial attenuation due to Bragg scattering also takes place. Here, we develop an algorithm for 1D systems that provides dispersion curves for damped free wave motion based on frequencies and wavenumbers that are permitted to be simultaneously complex. This represents a generalized application of Bloch's theorem and produces a dispersion band structure that fully describes all attenuation mechanisms, in space and in time. The algorithm is applied to a viscously damped mass-in-mass metamaterial exhibiting local resonance. A frequency-dependent effective mass for this damped infinite chain is also obtained.
Asquith, William H.; Slade, R.M.
1999-01-01
The U.S. Geological Survey, in cooperation with the Texas Department of Transportation, has developed a computer program to estimate peak-streamflow frequency for ungaged sites in natural basins in Texas. Peak-streamflow frequency refers to the peak streamflows for recurrence intervals of 2, 5, 10, 25, 50, and 100 years. Peak-streamflow frequency estimates are needed by planners, managers, and design engineers for flood-plain management; for objective assessment of flood risk; for cost-effective design of roads and bridges; and also for the desin of culverts, dams, levees, and other flood-control structures. The program estimates peak-streamflow frequency using a site-specific approach and a multivariate generalized least-squares linear regression. A site-specific approach differs from a traditional regional regression approach by developing unique equations to estimate peak-streamflow frequency specifically for the ungaged site. The stations included in the regression are selected using an informal cluster analysis that compares the basin characteristics of the ungaged site to the basin characteristics of all the stations in the data base. The program provides several choices for selecting the stations. Selecting the stations using cluster analysis ensures that the stations included in the regression will have the most pertinent information about flooding characteristics of the ungaged site and therefore provide the basis for potentially improved peak-streamflow frequency estimation. An evaluation of the site-specific approach in estimating peak-streamflow frequency for gaged sites indicates that the site-specific approach is at least as accurate as a traditional regional regression approach.
Frequency-dependent magneto-optical conductivity in the generalized α -T3 model
NASA Astrophysics Data System (ADS)
Kovács, Áron Dániel; Dávid, Gyula; Dóra, Balázs; Cserti, József
2017-01-01
We have studied a generalized three-band crossing model in 2D, the generalized α -T3 lattice, ranging from the pseudospin-1 Dirac equation through a quadratic+flat band touching to the pseudospin-1/2 Dirac equation. A general method is presented to determine the operator form of the Green's function, being gauge and representation independent. This yields the Landau level structure in a quantizing magnetic field and the longitudinal and transversal magneto-optical conductivities of the underlying system. Although the magneto-optical selection rules allow for many transitions between Landau levels, the dominant one stems from exciting a particle from/to the flat band to/from a propagating band. The Hall conductivity from each valley is rational (not quantized at all), in agreement with Berry phase considerations, though their sum is always integer quantized.
Wu, Chi-Hsun; Chang, Hsiang-Chih; Lee, Po-Lei; Li, Kuen-Shing; Sie, Jyun-Jie; Sun, Chia-Wei; Yang, Chia-Yen; Li, Po-Hung; Deng, Hua-Ting; Shyu, Kuo-Kai
2011-03-15
This paper presents an empirical mode decomposition (EMD) and refined generalized zero crossing (rGZC) approach to achieve frequency recognition in steady-stated visual evoked potential (SSVEP)-based brain computer interfaces (BCIs). Six light emitting diode (LED) flickers with high flickering rates (30, 31, 32, 33, 34, and 35 Hz) functioned as visual stimulators to induce the subjects' SSVEPs. EEG signals recorded in the Oz channel were segmented into data epochs (0.75 s). Each epoch was then decomposed into a series of oscillation components, representing fine-to-coarse information of the signal, called intrinsic mode functions (IMFs). The instantaneous frequencies in each IMF were calculated by refined generalized zero-crossing (rGZC). IMFs with mean instantaneous frequencies (f(GZC)) within 29.5 Hz and 35.5 Hz (i.e., 29.5≤f(GZC)≤35.5 Hz) were designated as SSVEP-related IMFs. Due to the time-locked and phase-locked characteristics of SSVEP, the induced SSVEPs had the same frequency as the gazing visual stimulator. The LED flicker that contributed the majority of the frequency content in SSVEP-related IMFs was chosen as the gaze target. This study tests the proposed system in five male subjects (mean age=25.4±2.07 y/o). Each subject attempted to activate four virtual commands by inputting a sequence of cursor commands on an LCD screen. The average information transfer rate (ITR) and accuracy were 36.99 bits/min and 84.63%. This study demonstrates that EMD is capable of extracting SSVEP data in SSVEP-based BCI system.
NASA Technical Reports Server (NTRS)
Silva, Walter A.
1993-01-01
A methodology for modeling nonlinear unsteady aerodynamic responses, for subsequent use in aeroservoelastic analysis and design, using the Volterra-Wiener theory of nonlinear systems is presented. The methodology is extended to predict nonlinear unsteady aerodynamic responses of arbitrary frequency. The Volterra-Wiener theory uses multidimensional convolution integrals to predict the response of nonlinear systems to arbitrary inputs. The CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) code is used to generate linear and nonlinear unit impulse responses that correspond to each of the integrals for a rectangular wing with a NACA 0012 section with pitch and plunge degrees of freedom. The computed kernels then are used to predict linear and nonlinear unsteady aerodynamic responses via convolution and compared to responses obtained using the CAP-TSD code directly. The results indicate that the approach can be used to predict linear unsteady aerodynamic responses exactly for any input amplitude or frequency at a significant cost savings. Convolution of the nonlinear terms results in nonlinear unsteady aerodynamic responses that compare reasonably well with those computed using the CAP-TSD code directly but at significant computational cost savings.
NASA Astrophysics Data System (ADS)
Ermakova, E. N.; Yahnin, A. G.; Yahnina, T. A.; Demekhov, A. G.; Kotik, D. S.
2016-01-01
We study the dynamics of the geomagnetic-pulsation spectra at unusually high frequencies (including the frequencies exceeding the Schumann resonance frequency 8 Hz), which were detected for the first time at the Novaya Zhizn' midlatitude station (the McIlwain parameter L = 2.6) at the time of a strong magnetic storm on November 07-14, 2004. To interpret the observed pulsation frequencies, we used the data from the NOAA low-orbit satellites which recorded localized precipitations of energetic protons (with energies of 30 to 80 keV) and calculations of the singlepass cyclotron amplification of electromagnetic ion-cyclotron waves. Amplitude and polarization characteristics of the radiation spectra at frequencies of up to 15 Hz at the Novaya Zhizn' and Lovozero stations (L = 5.2) are compared. It is shown that the magnetic field oscillations in the frequency range 7-15 Hz correlate with proton precipitations and proton auroras at geomagnetic latitudes 50°-57° (L = 2.42-3.37). It is also shown that for a high anisotropy of the pitch-angle distribution of the ring-current protons at such low geomagnetic latitudes, the frequency spectrum of observed high-frequency radiation agrees well with the calculated location of the maximum of the single-pass cyclotron amplification of electromagnetic ion-cyclotron waves. Analysis of the data and calculation results has led to the conclusion that inherently the recorded signals are a high-frequency counterpart of the Pc1 pulsations and are due to the generation of ion-cyclotron waves in the magnetosphere at unusually low latitudes, which are probably stipulated by the shift of the plasma pause to these latitudes during a strong magnetic storm.
General theory of frequency modulated selective reflection. Influence of atom surface interactions
NASA Astrophysics Data System (ADS)
Ducloy, M.; Fichet, M.
1991-12-01
We calculate the modulation of the reflection coefficient for a frequency-modulated (FM) light beam incident on the interface between a dielectric and an atomic vapor. The vapor is described as a gas of resonant, Doppler-broadened, two-level systems, with transition frequency and linewidth arbitrarily depending on the atom-dielectric distance. The atoms are supposed to get deexcited at collisions with the surface. The transient atomic response is calculated to first order in the incident field, for both incoming and desorbed atoms. The reflection coefficient, evaluated to first order in the vapor dipole polarization, leads to a formal expression of the reflectivity modulation, valid for arbitrary atom-surface interaction potentials. One first discusses the reflection signal in absence of wall interactions, for arbitrary modulation frequencies. At large frequencies, it allows one to monitor both vapor absorption and dispersion. Second, the formal theory is applied to the case of a Van der Waals-London surface attraction exerted on the atomic vapor. Both normal and oblique beam incidences are considered. One shows how the vapor dispersion signal is red-shifted and strongly distorted by the appearance of vapor-surface long-range interactions, and how it can be used to monitor these interactions. At non-normal incidences, the lineshapes get Doppler-broadened. On calcule le coefficient de réflexion d'un faisceau lumineux, modulé en fréquence, incident sur une interface entre un milieu diélectrique et une vapeur atomique. Cette vapeur est décrite comme un ensemble de systèmes à deux niveaux, présentant un élargissement Doppler, et dont la fréquence de transition et la largeur de raie sont supposées dépendre de la distance au milieu diélectrique. On suppose par ailleurs que les atomes sont déexcités sur la paroi. La réponse transitoire des atomes est analysée au premier ordre en fonction du champ électromagnétique incident. Du coefficient de r
The effects of sampling frequency on the climate statistics of the ECMWF general circulation model
Phillips, T.J.; Gates, W.L.; Arpe, K.
1992-09-01
The effects of sampling frequency on the first- and second-moment statistics of selected EC model variables are investigated in a simulation of ``perpetual July`` with a diurnal cycle included and with surface and atmospheric fields saved at hourly intervals. The shortest characteristic time scales (as determined by the enfolding time of lagged autocorrelation functions) are those of ground heat fluxes and temperatures, precipitation and run-off, convective processes, cloud properties, and atmospheric vertical motion, while the longest time scales are exhibited by soil temperature and moisture, surface pressure, and atmospheric specific humidity, temperature and wind. The time scales of surface heat and momentum fluxes and of convective processes are substantially shorter over land than over the oceans.
The effects of sampling frequency on the climate statistics of the ECMWF general circulation model
Phillips, T.J.; Gates, W.L. ); Arpe, K. )
1992-09-01
The effects of sampling frequency on the first- and second-moment statistics of selected EC model variables are investigated in a simulation of perpetual July'' with a diurnal cycle included and with surface and atmospheric fields saved at hourly intervals. The shortest characteristic time scales (as determined by the enfolding time of lagged autocorrelation functions) are those of ground heat fluxes and temperatures, precipitation and run-off, convective processes, cloud properties, and atmospheric vertical motion, while the longest time scales are exhibited by soil temperature and moisture, surface pressure, and atmospheric specific humidity, temperature and wind. The time scales of surface heat and momentum fluxes and of convective processes are substantially shorter over land than over the oceans.
Bachmann, Talis; Luiga, Iiris; Põder, Endel
2004-12-01
The forward masking of faces by spatially quantized masking images was studied. Masks were used in order to exert different types of degrading effects on the early representations in facial information processing. Three types of source images for masks were used: Same-face images (with regard to targets), different-face images, and random Gaussian noise that was spectrally similar to facial images. They were all spatially quantized over the same range of quantization values. Same-face masks had virtually no masking effect at any of the quantization values. Different-face masks had strong masking effects only with fine-scale quantization, but led to the same efficiency of recognition as in the same-face mask condition with the coarsest quantization. Moreover, compared with the noise-mask condition, coarsely quantized different-face masks led to a relatively facilitated level of recognition efficiency. The masking effect of the noise mask did not vary significantly with the coarseness of quantization. The results supported neither a local feature processing account, nor a generalized spatial-frequency processing account, but were consistent with the microgenetic configuration-processing theory of face recognition. Also, the suitability of a spatial quantization technique for image configuration processing research has been demonstrated.
Weisman, R; Njegovan, M; Sturdy, C; Phillmore, L; Coyle, J; Mewhort, D
1998-09-01
The acoustic frequency ranges in birdsongs and human speech can provide important pitch cues for recognition. Zebra finches and humans were trained to sort contiguous frequencies into 3 or 8 ranges, based on associations between the ranges and reward. The 3-range task was conducted separately in 3 spectral regions. Zebra finches discriminated 3 ranges in the medium and high spectral regions faster than in the low region and discriminated 8 ranges with precision. Humans discriminated 3 ranges in all 3 spectral regions to the same modest standard and acquired only a crude discrimination of the lowest and highest of 8 ranges. The results indicate that songbirds have a special sensitivity to the pitches in conspecific songs and, relative to humans, have a remarkable general ability to sort pitches into ranges.
NASA Technical Reports Server (NTRS)
Durbin, P. A.
1983-01-01
It is shown how a high frequency analysis can be made for general problems involving flow-generated noise. In the parallel shear flow problem treated by Balsa (1976) and Goldstein (1982), the equation governing sound propagation in the moving medium could be transformed into a wave equation for a stationary medium with an inhomogeneous index of refraction. It is noted that the procedure of Avila and Keller (1963) was then used to construct a high frequency Green function. This procedure involves matching a solution valid in an inner region around the point source to an outer, ray-acoustics solution. This same procedure is used here to construct the Green function for a source in an arbitrary mean flow. In view of the fact that there is no restriction to parallel flow, the governing equations cannot be transformed into a wave equation; the analysis therefore proceeds from the equations of motion themselves.
NASA Astrophysics Data System (ADS)
Alvarez-Martinez, R.; Martinez-Mekler, G.; Cocho, G.
2011-01-01
The behavior of rank-ordered distributions of phenomena present in a variety of fields such as biology, sociology, linguistics, finance and geophysics has been a matter of intense research. Often power laws have been encountered; however, their validity tends to hold mainly for an intermediate range of rank values. In a recent publication (Martínez-Mekler et al., 2009 [7]), a generalization of the functional form of the beta distribution has been shown to give excellent fits for many systems of very diverse nature, valid for the whole range of rank values, regardless of whether or not a power law behavior has been previously suggested. Here we give some insight on the significance of the two free parameters which appear as exponents in the functional form, by looking into discrete probabilistic branching processes with conflicting dynamics. We analyze a variety of realizations of these so-called expansion-modification models first introduced by Wentian Li (1989) [10]. We focus our attention on an order-disorder transition we encounter as we vary the modification probability p. We characterize this transition by means of the fitting parameters. Our numerical studies show that one of the fitting exponents is related to the presence of long-range correlations exhibited by power spectrum scale invariance, while the other registers the effect of disordering elements leading to a breakdown of these properties. In the absence of long-range correlations, this parameter is sensitive to the occurrence of unlikely events. We also introduce an approximate calculation scheme that relates this dynamics to multinomial multiplicative processes. A better understanding through these models of the meaning of the generalized beta-fitting exponents may contribute to their potential for identifying and characterizing universality classes.
Control-oriented high-frequency turbomachinery modeling: General one-dimensional model development
Badmus, O.O.; Eveker, K.M.; Nett, C.N.
1995-07-01
In this paper, an approach for control-oriented high-frequency turbomachinery modeling previously developed by the authors is applied to develop one-dimensional unsteady compressible viscous flow models for a generic turbojet engine and a generic compression system. The authors begin by developing models for various components commonly fund in turbomachinery systems. These components include: ducting without combustion, blading, ducting with combustion, heat soak, blading with heat soak, inlet, nozzle, abrupt area change with incurred total pressure lose, flow splitting, bleed, mixing, and the spool. Once the component models have been developed, they are combined to form system models for a generic turbojet engine and a generic compression system. These models are developed so that they can be easily modified and used with appropriate maps to form a model for a specific rig. It is shown that these system models are explicit (i.e., can be solved with any standard ODE solver without iteration) due to the approach used in their development. Furthermore, since the nonlinear models are explicit, explicit analytical linear models can be derived from the nonlinear models. The procedure for developing these analytical linear models is discussed. An interesting feature of the models developed here is the use of effective lengths within the models, as functions of axial Mach number and nondimensional rotational speed, for rotating components. These effective lengths account for the helical path of the flow as it moves through a rotating component. Use of these effective lengths in the unsteady conservation equations introduces a nonlinear dynamic lag consistent with experimentally observed compressor lag and replaces less accurate linear first-order empirical lags proposed to account for this phenomenon. Models of the type developed here are expected to prove useful in the design and simulation of (integrated) surge control and rotating stall avoidance schemes.
NASA Astrophysics Data System (ADS)
Shibuya, Makiko; Hiraoki, Toshifumi; Kimura, Kunie; Fukushima, Kazuaki; Suzuki, Kuniaki
2012-12-01
We investigated the effects of general anesthetics on liposome containing spin labels, 5-doxyl stearic acid (5-DSA) and 16-doxyl stearic acid (16-DSA), and purified Na,K-ATPase or membrane protein of microsome using an electron spin resonance (ESR) spectroscopy. The spectra of 16-DSA in liposomes with both proteins showed three sharp signals compared with 5-DSA. The difference in the order parameter S value of 5-DSA and 16-DSA suggested that the nitroxide radical location of 5-DSA and 16-DSA were different in the membrane bilayer. The results were almost the same as those obtained in liposomes without proteins. The addition of sevoflurane, isoflurane, halothane, ether, ethanol and propofol increased the intensity of the signals, but the clinical concentrations of anesthetics did not significantly alter the S and τ values, which are indices of the fluidity of the membrane. These results suggest that anesthetics remain on the surface of the lipid bilayer and do not act on both the inside hydrophobic area and the relatively hydrophilic area near the surface. These results and others also suggest that the existence of Na,K-ATPase and microsomal proteins did not affect the environment around the spin labels in the liposome and the effects of anesthetics on liposome as a model membrane.
Scott; Paul; Kaler
2000-10-15
Electrode polarization effects have long aggravated the efforts of low frequency analysis, particularly those investigations carried out on biological material or in highly conductive media. Beginning from elementary equations of electrostatics and hydrodynamics, a comprehensive model is devised to account for the screening of a general planar electrode by an ionic double layer. The surface geometry of the planar electrode is left unspecified to include any type of micromachined array. Building on the previous work by DeLacey and White (1982, J. Chem. Soc. Faraday Trans. 2 78, 457) using a variational theorem, we extend their numerical results with compact analytic solutions, analogous to the Debye-Hückel potential for dc systems, but applicable now to dynamic ac experiments. The variational approach generates functions that are not restricted by perturbation expansions or numerical convergence, representing optimal approximations to the exact solutions. Copyright 2000 Academic Press.
Gao, Feng; Keinan, Alon
2016-01-01
The site frequency spectrum (SFS) and other genetic summary statistics are at the heart of many population genetic studies. Previous studies have shown that human populations have undergone a recent epoch of fast growth in effective population size. These studies assumed that growth is exponential, and the ensuing models leave an excess amount of extremely rare variants. This suggests that human populations might have experienced a recent growth with speed faster than exponential. Recent studies have introduced a generalized growth model where the growth speed can be faster or slower than exponential. However, only simulation approaches were available for obtaining summary statistics under such generalized models. In this study, we provide expressions to accurately and efficiently evaluate the SFS and other summary statistics under generalized models, which we further implement in a publicly available software. Investigating the power to infer deviation of growth from being exponential, we observed that adequate sample sizes facilitate accurate inference; e.g., a sample of 3000 individuals with the amount of data expected from exome sequencing allows observing and accurately estimating growth with speed deviating by ≥10% from that of exponential. Applying our inference framework to data from the NHLBI Exome Sequencing Project, we found that a model with a generalized growth epoch fits the observed SFS significantly better than the equivalent model with exponential growth (P-value [Formula: see text]). The estimated growth speed significantly deviates from exponential (P-value [Formula: see text]), with the best-fit estimate being of growth speed 12% faster than exponential.
NASA Astrophysics Data System (ADS)
Palit, Sourav; Chakrabarti, Sandip Kumar; Ray, Suman
2016-07-01
The hard and soft X-ray regions of a solar flare spectrum are the manifestation of interaction, namely of bremsstrahlung radiation of the non-thermal electrons moving inward in the denser part of the solar atmosphere with the plasma heated by those energetic electrons. The continuous and uninterrupted knowledge of X-ray photon spectra of flares are of great importance to derive information on the electron acceleration and hence time-evolution of energy transport and physics during solar flares. Satellite observations of solar X-ray spectrum are often limited by the restricted windows in each duty cycle to avoid the interaction of detectors and instruments with harmful energetic charge particles. In this work we have tried to tackle the problem by examining the possibility of using Earth's ionosphere and atmosphere as the detector of such transient events. Earth's lower ionosphere and upper atmosphere are the places where the X-rays and gamma-rays from such astronomical sources are absorbed. The electron-ion production rates due to the ionization of such energetic photons at different heights depend on the intensity and wavelength of the injected spectra and hence vary from one source to another. Obviously the electron and ion density vs. altitude profile has the imprint of the incident photon spectrum. As a preliminary exercise we developed a novel deconvolution method to extract the soft X-ray part of spectra of some solar flares of different classes from the electron density profiles obtained from Very Low Frequency (VLF) observation of lower ionosphere during those events. The method presented here is useful to carry out a similar exercise to infer the higher energy part of solar flare spectra and spectra of more energetic events such as the GRBs, SGRs etc. with the possibilities of probing even lower parts of the atmosphere.
NASA Astrophysics Data System (ADS)
Frances, Felix; Salas, Jose D.; Boes, Duane C.
1994-06-01
Historical and paleoflood data have become an important source of information for flood frequency analysis. A number of studies have been proposed in the literature regarding the value of historical and paleoflood information for estimating flood quantiles. These studies have been generally based on computer simulation experiments. In this paper the value of using systematic and historical/paleoflood data relative to using systematic records alone is examined analytically by comparing the asymptotic variances of flood quantiles assuming a two-parameter general extreme value marginal distribution, type 1 and type 2 censored data, and maximum likelihood estimation method. The results of this study indicate that the value of historical and paleoflood data for estimating flood quantiles can be small or large depending on only three factors: the relative magnitudes of the length of the systematic record (N) and the length of the historical period (M); the return period (T) of the flood quantile of interest; and the return period (H) of the threshold level of perception. For instance, for N = 50, M = 50 and T = 500, the statistical gain for type 2 censoring becomes significantly larger than for type 1 censoring as H becomes greater than 100 years. In addition, computer experiments have shown that the results regarding the statistical gain based on asymptotic considerations are valid for the usual sample sizes.
NASA Technical Reports Server (NTRS)
Fomin, V. V.
1979-01-01
The generalization spectral line contour concept and formulas for a two component mixture, as well as consequences of the general formula are discussed. The calculation procedure, initial information, calculation results and comparison of calculations with available experimental data, for radiation absorption in three CO2 bands are presented.
2014-01-01
Background Advances in science and technology of electrical equipment, despite increasing human welfare in everyday life, have increased the number of people exposed to Electro-Magnetic Fields (EMFs). Because of possible adverse effects on the health of exposed individuals, the EMFs have being the center of attention. This study was performed to determine possible correlation between Extremely Low Frequency Electro-Magnetic Fields (ELF EMFs) and sleep quality and public health of those working in substation units of a petrochemical complex in southern Iran. Materials and method To begin with, magnetic flux density was measured at different parts of a Control Building and two substations in accordance with IEEE std 644–1994. Subsequently, the questionnaires “Pittsburgh Sleep Quality Index” (PSQI) and “General Health Quality (GHQ)” were used to investigate relationship between ELF exposure level and sleep quality and public health, respectively. Both questionnaires were placed at disposal of a total number of 40 workers at the complex. The filled out questionnaires were analyzed by T-test, Duncan and the Chi-square tests. Results The obtained results revealed that 28% of those in case group suffered from poor health status and 61% were diagnosed with a sleep disorder. However, all members in control group were in good health condition and only 4.5% of them had undesirable sleep quality. Conclusion In spite of a significant difference between the case and control groups in terms of sleep quality and general health, no significant relationship was found between the exposure level and sleep quality and general health. It is worth noting that the measured EMF values were lower than the standard limits recommended by American Conference of Industrial Hygienists (ACGIH). However, given the uncertainties about the pathogenic effects caused by exposure to ELF EMFs, further epidemiological studies and periodic testing of personnel working in high voltage substations
NASA Astrophysics Data System (ADS)
Stangarone, C.; Helbert, J.; Tribaudino, M.; Maturilli, A.; D'Amore, M.; Ferrari, S.; Prencipe, M.
2015-12-01
Spectral signatures of minerals are intimately related to the crystal structure; therefore they may represent a remote sensing model to determine surface composition of planetary bodies, by analysing their spectral reflectance and emission. However, one of the most critical point is data interpretation considering planetary surfaces, as Mercury, where the changes in spectral characteristics are induced by the high temperatures conditions (Helbert et al., 2013). The aim of this work is to interpret the experimental thermal emissivity spectra with an innovative approach: simulating IR spectra of the main mineral families that compose the surface of Mercury, focusing on pyroxenes (Sprague et al., 2002), both at room and high temperature, exploiting the accuracy of ab initio quantum mechanical calculations, by means of CRYSTAL14 code (Dovesi et al., 2014). The simulations will be compared with experimental emissivity measurements of planetary analogue samples at temperature up to 1000K, performed at Planetary Emissivity Laboratory (PEL) by Institute of Planetary Research (DLR, Berlin). Results will be useful to create a theoretical background to interpret HT-IR emissivity spectra that will be collected by the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS), a spectrometer developed by DLR that will be on board of the ESA BepiColombo Mercury Planetary Orbiter (MPO) scheduled for 2017. The goal is to point out the most interesting spectral features for a geological mapping of Mercury and other rocky bodies, simulating the environmental conditions of the inner planets of Solar System. Dovesi R., Saunders V. R., Roetti C., Orlando R., Zicovich-Wilson C. M., Pascale F., Civalleri B., Doll K., Harrison N. M., Bush I. J., D'Arco P., Llunell M., Causà M. & Noël Y. 2014. CRYSTAL14 User's Manual, University of Torino. Sprague, A. L., Emery, J. P., Donaldson, K. L., Russell, R. W., Lynch, D. K., & Mazuk, A. L. (2002). Mercury: Mid-infrared (3-13.5
NASA Astrophysics Data System (ADS)
Tai, C.
2007-12-01
These two-dimensional spectra show the prevalence of free baroclinic Rossby waves from the equatorial region to the mid-latitudes. An innovation based on segregating the Fourier components into standing and propagating modes has helped reveal the Rossby waves more clearly where they have been obscured previously by the seal- level signatures of the seasonal heating and cooling cycle. It is found that the linear theory of Rossby waves applies well for most of the ocean (i.e., ignoring zonal and meridional density variations associated with the mean flow) with the possible exception in regions closer to the western boundary currents. That is, the Rossby wave speed is more or less uniform zonally across the North Pacific except closer to the western end in mid- latitudes. From the zonal and meridional distribution of the power of these Rossby waves, the source of these waves can be deciphered.
NASA Astrophysics Data System (ADS)
Hou, Dan; Ma, Yong-Tao; Zhang, Xiao-Long; Zhai, Yu; Li, Hui
2016-06-01
Direct infrared spectra predictions for van der Waals (vdW) complexes rely on accurate intra-molecular vibrationally excited inter-molecular potential. Due to computational cost increasing with number of freedom, constructing an effective reduced-dimension potential energy surface, which only includes direct relevant intra- molecular modes, is the most feasible way and widely used in the recent potential studies. However, because of strong intra-molecular vibrational coupling, some indirect relevant modes are also play important roles in simulating infrared spectra of vdW complexes. The questions are how many intra-molecular modes are needed, and which modes are most important in determining the effective potential and direct infrared spectra simulations. Here, we explore these issues using a simple, flexible and efficient vibration-averaged approach, and apply the method to vdW complex C_2H_2-H_2. With initial examination of the intra-molecular vibrational coupling, an effective seven-dimensional ab initio potential energy surface(PES) for C_2H_2-H_2, which explicitly takes into account the Q_1,Q_2 symmetric-stretch and Q_3 asymmetric-stretch normal modes of the C_2H_2 monomer, has been generated. Analytic four-dimensional PESs are obtained by least-squares fitting vibrationally averaged interaction energies for νb{3}(C_2H_2)=0 and 1 to the Morse/long-range(MLR) potential function form. We provide the first prediction of the infrared spectra and band origin shifts for C_2H_2-H_2 dimer. We particularly examine the dependence of the symmetric-stretch normal mode on asymmetric-stretch frequency shift for the complex.
Analytic calculations of anharmonic infrared and Raman vibrational spectra.
Cornaton, Yann; Ringholm, Magnus; Louant, Orian; Ruud, Kenneth
2016-02-07
Using a recently developed recursive scheme for the calculation of high-order geometric derivatives of frequency-dependent molecular properties [Ringholm et al., J. Comp. Chem., 2014, 35, 622], we present the first analytic calculations of anharmonic infrared (IR) and Raman spectra including anharmonicity both in the vibrational frequencies and in the IR and Raman intensities. In the case of anharmonic corrections to the Raman intensities, this involves the calculation of fifth-order energy derivatives-that is, the third-order geometric derivatives of the frequency-dependent polarizability. The approach is applicable to both Hartree-Fock and Kohn-Sham density functional theory. Using generalized vibrational perturbation theory to second order, we have calculated the anharmonic infrared and Raman spectra of the non- and partially deuterated isotopomers of nitromethane, where the inclusion of anharmonic effects introduces combination and overtone bands that are observed in the experimental spectra. For the major features of the spectra, the inclusion of anharmonicities in the calculation of the vibrational frequencies is more important than anharmonic effects in the calculated infrared and Raman intensities. Using methanimine as a trial system, we demonstrate that the analytic approach avoids errors in the calculated spectra that may arise if numerical differentiation schemes are used.
Analytic calculations of anharmonic infrared and Raman vibrational spectra
Louant, Orian; Ruud, Kenneth
2016-01-01
Using a recently developed recursive scheme for the calculation of high-order geometric derivatives of frequency-dependent molecular properties [Ringholm et al., J. Comp. Chem., 2014, 35, 622], we present the first analytic calculations of anharmonic infrared (IR) and Raman spectra including anharmonicity both in the vibrational frequencies and in the IR and Raman intensities. In the case of anharmonic corrections to the Raman intensities, this involves the calculation of fifth-order energy derivatives—that is, the third-order geometric derivatives of the frequency-dependent polarizability. The approach is applicable to both Hartree–Fock and Kohn–Sham density functional theory. Using generalized vibrational perturbation theory to second order, we have calculated the anharmonic infrared and Raman spectra of the non- and partially deuterated isotopomers of nitromethane, where the inclusion of anharmonic effects introduces combination and overtone bands that are observed in the experimental spectra. For the major features of the spectra, the inclusion of anharmonicities in the calculation of the vibrational frequencies is more important than anharmonic effects in the calculated infrared and Raman intensities. Using methanimine as a trial system, we demonstrate that the analytic approach avoids errors in the calculated spectra that may arise if numerical differentiation schemes are used. PMID:26784673
Line Coupling in Atmospheric Spectra
NASA Technical Reports Server (NTRS)
Tipping, R. H.
1996-01-01
The theoretical modeling of atmospheric spectra is important for a number of different applications: for instance, in the determination of minor atmospheric constituents such as ozone, carbon dioxide, CFC's etc.; in monitoring the temperature profile for climate studies; and in measuring the incoming and outgoing radiation to input into global climate models. In order to accomplish the above mentioned goal, one needs to know the spectral parameters characterizing the individual spectral lines (frequency, width, strength, and shape) as well as the physical parameters of the atmosphere (temperature, abundances, and pressure). When all these parameters are known, it is usually assumed that the resultant spectra and concomitant absorption coefficient can then be calculated by a superposition of individual profiles of appropriate frequency, strength and shape. However, this is not true if the lines are 'coupled'. Line coupling is a subtle effect that takes place when lines of a particular molecule overlap in frequency. In this case when the initial states and the final states of two transitions are connected by collisions, there is a quantum interference resulting in perturbed shapes. In general, this results in the narrowing of Q-branches (those in which the rotational quantum number does not change), and vibration-rotational R- and P branches (those in which the rotational quantum number changes by +/- 1), and in the spectral region beyond band heads (regions where the spectral lines pile up due to centrifugal distortion). Because these features and spectral regions are often those of interest in the determination of the abundances and pressure-temperature profiles, one must take this effect into account in atmospheric models.
NASA Astrophysics Data System (ADS)
Banerjee, Pradipta K.; Datta, Asit K.
2013-02-01
The paper proposes an improved strategy for face recognition using correlation filter under varying lighting conditions and occlusion where spatial domain preprocessing is carried out by two convolution kernels. The first convolution kernel is a contour kernel for emphasizing high frequency components of face image and the other kernel is a smoothing kernel used for minimization of noise those may arise due to preprocessing. The convolution kernels are obtained by training a generalized regression neural network using enhanced face features. Face features are enhanced by conventional principal component analysis. The proposed method reduces the false acceptance rate and false rejection rate in comparison to other standard correlation filtering techniques. Moreover, the processing is fast when compared to the existing illumination normalization techniques. A scheme of hardware implementation of all optical correlation technique is also suggested based on single spatial light modulator in a beam folding architecture. Two benchmark databases YaleB and PIE are used for performance verification of the proposed scheme and the improved results are obtained for both illumination variations and occlusions in test face images.
Cansiz, Mustafa; Abbasov, Teymuraz; Kurt, M Bahattin; Celik, A Recai
2016-11-02
In this study, radio frequency electromagnetic field exposure levels were measured on the main streets in the city center of Diyarbakır, Turkey. Measured electric field levels were plotted on satellite imagery of Diyarbakır and were compared with exposure guidelines published by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). Exposure measurements were performed in dense urban, urban and suburban areas each day for 7 consecutive days. The measurement system consisted of high precision and portable spectrum analyzer, three-axis electric field antenna, connection cable and a laptop which was used to record the measurement samples as a data logger. The highest exposure levels were detected for two places, which are called Diclekent and Batıkent. It was observed that the highest instantaneous electric field strength value for Batıkent was 7.18 V/m and for Diclekent was 5.81 V/m. It was statistically determined that the main contributor band to the total exposure levels was Universal Mobile Telecommunications System band. Finally, it was concluded that all measured exposure levels were lower than the reference levels recommended by ICNIRP for general public health.Journal of Exposure Science and Environmental Epidemiology advance online publication, 2 November 2016; doi:10.1038/jes.2016.64.
NASA Astrophysics Data System (ADS)
Ausloos, M.
2012-09-01
A nonlinear dynamics approach can be used in order to quantify complexity in written texts. As a first step, a one-dimensional system is examined: two written texts by one author (Lewis Carroll) are considered, together with one translation into an artificial language (i.e., Esperanto) are mapped into time series. Their corresponding shuffled versions are used for obtaining a baseline. Two different one-dimensional time series are used here: one based on word lengths (LTS), the other on word frequencies (FTS). It is shown that the generalized Hurst exponent h(q) and the derived f(α) curves of the original and translated texts show marked differences. The original texts are far from giving a parabolic f(α) function, in contrast to the shuffled texts. Moreover, the Esperanto text has more extreme values. This suggests cascade model-like, with multiscale time-asymmetric features as finally written texts. A discussion of the difference and complementarity of mapping into a LTS or FTS is presented. The FTS f(α) curves are more opened than the LTS ones.
Ausloos, M
2012-09-01
A nonlinear dynamics approach can be used in order to quantify complexity in written texts. As a first step, a one-dimensional system is examined: two written texts by one author (Lewis Carroll) are considered, together with one translation into an artificial language (i.e., Esperanto) are mapped into time series. Their corresponding shuffled versions are used for obtaining a baseline. Two different one-dimensional time series are used here: one based on word lengths (LTS), the other on word frequencies (FTS). It is shown that the generalized Hurst exponent h(q) and the derived f(α) curves of the original and translated texts show marked differences. The original texts are far from giving a parabolic f(α) function, in contrast to the shuffled texts. Moreover, the Esperanto text has more extreme values. This suggests cascade model-like, with multiscale time-asymmetric features as finally written texts. A discussion of the difference and complementarity of mapping into a LTS or FTS is presented. The FTS f(α) curves are more opened than the LTS ones.
NASA Astrophysics Data System (ADS)
Bera, Partha P.; Head-Gordon, Martin; Lee, Timothy J.
2013-11-01
We have studied relative energies, structures, rotational, vibrational, and electronic spectra of the pyrylium cation, an oxygen-containing six-membered carbocyclic ring, and its six isomers, using ab initio quantum chemical methods. Isoelectronic with benzene, the pyrylium cation has a benzenoid structure and is the global minimum on the singlet potential energy surface of C5H5O+. The second lowest energy isomer, the furfuryl cation, has a five membered backbone akin to a sugar, and is only 16 kcal mol-1 above the global minimum computed using coupled cluster theory with singles, doubles, and perturbative triple excitations (CCSD(T)) with the correlation consistent cc-pVTZ basis set. Other isomers are 25, 26, 37, 60, and 65 kcal mol-1 above the global minimum, respectively, at the same level of theory. Lower level methods such as density functional theory (B3LYP) and second order Møller-Plesset perturbation theory performed well when tested against the CCSD(T) results. The pyrylium and furfuryl cations, although separated by only 16 kcal mol-1, are not easily interconverted, as multiple bonds must be broken and formed, and the existence of more than one transition state is likely. Additionally, we have also investigated the asymptotes for the barrierless ion-molecule association of molecules known to exist in the interstellar medium that may lead to formation of the pyrylium cation.
NASA Astrophysics Data System (ADS)
Pankratov, Oleg; Kuvshinov, Alexei
2010-04-01
Electromagnetic (EM) studies of the Earth have advanced significantly over the past few years. This progress was driven, in particular, by new developments in the methods of 3-D inversion of EM data. Due to the large scale of the 3-D EM inverse problems, iterative gradient-type methods have mostly been employed. In these methods one has to calculate multiple times the gradient of the penalty function-a sum of misfit and regularization terms-with respect to the model parameters. However, even with modern computational capabilities the straightforward calculation of the misfit gradients based on numerical differentiation is extremely time consuming. Much more efficient and elegant way to calculate the gradient of the misfit is provided by the so-called `adjoint' approach. This is now widely used in many 3-D numerical schemes for inverting EM data of different types and origin. It allows the calculation of the misfit gradient for the price of only a few additional forward calculations. In spite of its popularity we did not find in the literature any general description of the approach, which would allow researchers to apply this methodology in a straightforward manner to their scenario of interest. In the paper, we present formalism for the efficient calculation of the derivatives of EM frequency-domain responses and the derivatives of the misfit with respect to variations of 3-D isotropic/anisotropic conductivity. The approach is rather general; it works with single-site responses, multisite responses and responses that include spatial derivatives of EM field. The formalism also allows for various types of parametrization of the 3-D conductivity distribution. Using this methodology one can readily obtain appropriate formulae for the specific sounding methods. To illustrate the concept we provide such formulae for a number of EM techniques: geomagnetic depth sounding (GDS), conventional and generalized magnetotellurics, the magnetovariational method, horizontal
NASA Astrophysics Data System (ADS)
Fletcher, S. T.; Broomhall, A.-M.; Chaplin, W. J.; Elsworth, Y.; New, R.
2011-08-01
We present a new and highly efficient algorithm for computing a power spectrum made from evenly spaced data which combines the noise-reducing advantages of the weighted fit with the computational advantages of the fast Fourier transform. We apply this method to a 10-yr data set of the solar p-mode oscillations obtained by the Birmingham Solar Oscillations Network (BiSON) and thereby uncover three new low-frequency modes. These are the ℓ= 2, n= 5 and n= 7 modes and the ℓ= 3, n=7 mode. In the case of the ℓ= 2, n= 5 mode, this is believed to be the first such identification of this mode in the literature. The statistical weights needed for the method are derived from a combination of the real data and a sophisticated simulation of the instrument performance. Variations in the weights are due mainly to the differences in the noise characteristics of the various BiSON instruments, the change in those characteristics over time and the changing line-of-sight velocity between the stations and the Sun. It should be noted that a weighted data set will have a more time-dependent signal than an unweighted set and that, consequently, its frequency spectrum will be more susceptible to aliasing.
Bégué, Didier; Baraille, Isabelle; Andersen, Heidi Gade; Wentrup, Curt
2013-10-28
Methyliminopropadienone MeN=C=C=C=O 1a was generated by flash vacuum thermolysis from four different precursors and isolated in solid argon. The matrix-isolation infrared spectrum is dominated by unusually strong anharmonic effects resulting in complex fine structure of the absorptions due to the NCCCO moiety in the 2200 cm(-1) region. Doubling and tripling of the corresponding absorption bands are observed for phenyliminopropadienone PhN=C=C=C=O 1b and bis(phenylimino)propadiene PhN=C=C=C=NPh 9, respectively. Anharmonic vibrational frequency calculations allow the identification of a number of overtones and combination bands as the cause of the splittings for each molecule. This method constitutes an important tool for the characterization of reactive intermediates and unusual molecules by matrix-isolation infrared spectroscopy.
Continuum Fitting HST QSO Spectra
NASA Technical Reports Server (NTRS)
Tytler, David; Oliversen, Ronald J. (Technical Monitor)
2002-01-01
The Principal Component Analysis (PCA) method which we are using to fit and describe QSO spectra relies upon the fact that QSO continuum are generally very smooth and simple except for emission and absorption lines. To see this we need high signal-to-noise (S/N) spectra of QSOs at low redshift which have relatively few absorption lines in the Lyman-a forest. We need a large number of such spectra to use as the basis set for the PCA analysis which will find the set of principal component spectra which describe the QSO family as a whole. We have found that too few HST spectra have the required S/N and hence we need to supplement them with ground based spectra of QSOs at higher redshift. We have many such spectra and we have been working to make them suitable for this analysis. We have concentrated on this topic since 12/15/01.
NASA Astrophysics Data System (ADS)
Al-Share, Mohammad Abdel Karim
1990-01-01
The rotational microwave spectra of the three isotopes (^{13}CH _3^{12}C^ {15}N, ^{12} CH_3^{13}C ^{15}N, and ^ {13}CH_3^{13 }C^{15}N) of the methyl cyanide molecule in the nu _8 = 3, nu_8 = 2, nu_7 = 1 and nu_4 = 1 vibrational energy levels for the rotational components 1 <=q J <=q 5 (for a range of frequency 17-95 GHz.) were experimentally and theoretically examined. Rotational components in each vibration were measured to determine the mutual interactions in each vibration between any of the vibrational levels investigated. The method of isotopic substitution was employed for internal tuning of each vibrational level by single and double substitution of ^{13} C in the two sites of the molecule. It was found that relative frequencies within each vibration with respect to another vibration were shifted in a systematic way. The results given in this work were interpreted on the basis of these energy shifts. Large departure between experimentally measured and theoretically predicted frequency for the quantum sets (J, K = +/-1, l = +/-1), K l = 1 in the nu_8 = 3 vibrational states for the ^{13 }C and ^{15}N tagged isotopes of CH_3CN showed anomalous behavior which was explained as being due to Fermi resonance. Accidentally strong resonances (ASR) were introduced to account for some departures were not explained by Fermi resonance.
NASA Technical Reports Server (NTRS)
Seidel, D. A.
1994-01-01
The Program for Solving the General-Frequency Unsteady Two-Dimensional Transonic Small-Disturbance Equation, XTRAN2L, is used to calculate time-accurate, finite-difference solutions of the nonlinear, small-disturbance potential equation for two- dimensional transonic flow about airfoils. The code can treat forced harmonic, pulse, or aeroelastic transient type motions. XTRAN2L uses a transonic small-disturbance equation that incorporates a time accurate finite-difference scheme. Airfoil flow tangency boundary conditions are defined to include airfoil contour, chord deformation, nondimensional plunge displacement, pitch, and trailing edge control surface deflection. Forced harmonic motion can be based on: 1) coefficients of harmonics based on information from each quarter period of the last cycle of harmonic motion; or 2) Fourier analyses of the last cycle of motion. Pulse motion (an alternate to forced harmonic motion) in which the airfoil is given a small prescribed pulse in a given mode of motion, and the aerodynamic transients are calculated. An aeroelastic transient capability is available within XTRAN2L, wherein the structural equations of motion are coupled with the aerodynamic solution procedure for simultaneous time-integration. The wake is represented as a slit downstream of the airfoil trailing edge. XTRAN2L includes nonreflecting farfield boundary conditions. XTRAN2L was developed on a CDC CYBER mainframe running under NOS 2.4. It is written in FORTRAN 5 and uses overlays to minimize storage requirements. The program requires 120K of memory in overlayed form. XTRAN2L was developed in 1987.
Xu Feng; Zhang Xiaoyu; Nguyen Nguyen Phuoc; Ma Yungui; Ong, C. K.
2009-02-15
In this work, we investigate the high-frequency permeability spectra of as-sputtered FeCoSiN/Al{sub 2}O{sub 3} laminated films, and discuss their dependence on the thickness of each FeCoSiN layer, based on the phenomenological Landau-Lifshitz-Gilbert equation. The damping factor and coercivity show their minima with lamination, deviating from the expectation based on the grain size confinement effect. Such dependences on the layer thickness indicate the influence of magnetic coupling. The decreases in the damping factor and the coercivities with lamination can be partially attributed to the decrease in the magnetostatic coupling induced by ripple structures. The enhanced damping and enlarged coercivity values obtained with further lamination are ascribed to the enhanced Neel couplings. The dependences show that the lamination can be effective in tuning the magnetization dynamics by changing the magnetic couplings.
Lee, Christopher M; Chen, Xing; Weiss, Philip A; Jensen, Lasse; Kim, Seong H
2017-01-05
Vibrational sum-frequency-generation (SFG) spectroscopy is capable of selectively detecting crystalline biopolymers interspersed in amorphous polymer matrices. However, the spectral interpretation is difficult due to the lack of knowledge on how spatial arrangements of crystalline segments influence SFG spectra features. Here we report time-dependent density functional theory (TD-DFT) calculations of cellulose crystallites in intimate contact with two different polarities: parallel versus antiparallel. TD-DFT calculations reveal that the CH/OH intensity ratio is very sensitive to the polarity of the crystallite packing. Theoretical calculations of hyperpolarizability tensors (βabc) clearly show the dependence of SFG intensities on the polarity of crystallite packing within the SFG coherence length, which provides the basis for interpretation of the empirically observed SFG features of native cellulose in biological systems.
Terahertz-sideband spectra involving Kapteyn series
NASA Astrophysics Data System (ADS)
Lerche, Ian; Tautz, Robert C.; Citrin, D. S.
2009-09-01
Kapteyn series of the second kind appear in models of even- and odd-order sideband spectra in the optical regime of a quantum system modulated by a high-frequency (e.g., terahertz) electromagnetic field (Citrin D S 1999 Phys. Rev. B 60 5659) and in certain time-periodic transport problems in superlattices (Ignatov A A and Romanov Y A 1976 Phys. Status Solidi b 73 327; Feise M W and Citrin D S 1999 Appl. Phys. Lett. 75 3536). This paper shows that both the even- and the odd-order Kapteyn series that appear can be summed in closed form, thereby allowing more transparent insight into the structural dependence of the sideband spectra and also providing an analytic control for the accuracy of numerical procedures designed to evaluate the series. The general method of analysis may also be of interest for other Kapteyn series.
Fu, Li; Chen, Shunli; Wang, Hongfei
2016-03-03
Reliably determination of the spectral features and their phases in sum-frequency generation vibrational spectroscopy (SFG-VS) for surfaces with closely overlapping peaks has been a standing issue. Here we present two approaches towards resolving such issue. The first utilizes the high resolution and accurate lineshape from the recently developed sub-wavenumber high resolution broadband SFG-VS (HR-BB-SFG-VS), from which the detail spectral parameters, including relative spectral phases, of overlapping peaks can be determined through reliable spectral fitting. These results are further validated by using the second method that utilizes the azimuthal angle phase dependence of the z-cut α-quartz crystal, a common phase standard, through the spectral interference between the SFG fields of the quartz surface, as the internal phase reference, and the adsorbed molecular layer. Even though this approach is limited to molecular layers that can be transferred or deposited onto the quartz surface, it is simple and straightforward, as it requires only an internal phase standard with a single measurement that is free of phase drifts. More importantly, it provides unambiguous SFG spectral phase information of such surfaces. Using this method, the absolute phase of the molecular susceptibility tensors of the CH3, CH2 and chiral C-H groups in different Langmuir-Blodgett (LB) molecular monolayers and drop-cast peptide films are determined. These two approaches are fully consistent with and complement to each other, making both easily applicable tools in SFG-VS studies. More importantly, as the HR-BB-SFG-VS technique can be easily applied to various surfaces and interfaces, such validation of the spectral and phase information from HR-BB-SFG-VS measurement demonstrates it as one most promising tool for interrogating the detailed structure and interactions of complex molecular interfaces.
NASA Technical Reports Server (NTRS)
Devenport, William J.; Glegg, Stewart A. L.
1993-01-01
spectrum especially for the spectral peak at low frequencies, which previously was poorly predicted.
ERIC Educational Resources Information Center
Douglas, Scott Roy
2015-01-01
Independent confirmation that vocabulary in use unfolds across levels of performance as expected can contribute to a more complete understanding of validity in standardized English language tests. This study examined the relationship between Lexical Frequency Profiling (LFP) measures and rater judgements of test-takers' overall levels of…
NASA Astrophysics Data System (ADS)
Duclut, Charlie; Delamotte, Bertrand
2017-01-01
We derive the necessary conditions for implementing a regulator that depends on both momentum and frequency in the nonperturbative renormalization-group flow equations of out-of-equilibrium statistical systems. We consider model A as a benchmark and compute its dynamical critical exponent z . This allows us to show that frequency regulators compatible with causality and the fluctuation-dissipation theorem can be devised. We show that when the principle of minimal sensitivity (PMS) is employed to optimize the critical exponents η , ν , and z , the use of frequency regulators becomes necessary to make the PMS a self-consistent criterion.
Infrared spectra of substituted polycylic aromatic hydrocarbons
NASA Technical Reports Server (NTRS)
Langhoff, S. R.; Bauschlicher, C. W. Jr; Hudgins, D. M.; Sandford, S. A.; Allamandola, L. J.
1998-01-01
Calculations are carried out using density functional theory (DFT) to determine the harmonic frequencies and intensities of 1-methylanthracene, 9-methylanthracene, 9-cyanoanthracene, 2-aminoanthracene, acridine, and their positive ions. The theoretical data are compared with matrix-isolation spectra for these species also reported in this work. The theoretical and experimental frequencies and relative intensities for the neutral species are in generally good agreement, whereas the positive ion spectra are only in qualitative agreement. Relative to anthracene, we find that substitution of a methyl or CN for a hydrogen does not significantly affect the spectrum other than to add the characteristic methyl C-H and C triple bond N stretches near 2900 and 2200 cm-1, respectively. However, addition of NH2 dramatically affects the spectrum of the neutral. Not only are the NH2 modes themselves strong, but this electron-withdrawing group induces sufficient partial charge on the ring to give the neutral molecule spectra characteristics of the anthracene cation. The sum of the absolute intensities is about four times larger for 2-aminoanthracene than those for 9-cyanoanthracene. Substituting nitrogen in the ring at the nine position (acridine) does not greatly alter the spectrum compared with anthracene.
Rossinol, Antoni; Molina, Irene; Rossinol, Tomeu; Garcia-Mas, Alexandre
2013-07-01
INTRODUCTION. The perceived quality of life (QoL) in persons with epilepsy has demonstrated to be a relevant factor for the continuity of treatment and for the patients' own general health perception. Currently, the positive concept of QoL is used to assess the psychosocial factors of the epilepsy, replacing the concept of stigma. AIM. To analyze the relationship between QoL and general health perception, with several relevant clinical parameters in a sample of persons with epilepsy, in order to draw conclusions that help to suggest a more global approach to the disease. PATIENTS AND METHODS. We applied the Spanish versions of the QOLIE-10, the GHQ-12, and MMSE, and registered the clinical parameters (diagnostic, years of illness, electroencephalographic patterns, seizure type and frequency, response to medication, and side effects) in a sample of 29 persons with epilepsy. RESULTS. QoL and perceived general health are two unrelated factors respect to the clinical features. QoL is closely related to the frequency and type of crisis, whilst the years of illness and the level of neurocognitive impairment are not related with QoL. CONCLUSIONS. From the clinical point of view, it must be taken into account the relationship between the persons with epilepsy perceived QoL with factors such as the seizure frequency, side effects of the medication, and the general health perception, in order to obtain the best response and treatment adherence.
Herath, J.W.; Grimshaw, R.W.
1971-01-01
Clay mineral analyses were made of several alluvial clay materials from Ceylon. These studies show that the soil materials can be divided into 3 clay mineral provinces on the basis of the frequency distribution of clay and associated minerals. The provinces closely follow the climatic divisions. The characteristic feature of this classification is the progressive development of gibbsite from Dry to Wet Zone areas. Gibbsite has been used as a reliable indicator mineral. ?? 1971.
NASA Technical Reports Server (NTRS)
2007-01-01
portion is defined by the day/night boundary (known as the terminator).
These two images illustrate only a small fraction of the information contained in a single LEISA scan, highlighting just one aspect of the power of infrared spectra for atmospheric studies.
Díaz, F J; Vega, J A; Patiño, P J; Bedoya, G; Nagles, J; Villegas, C; Vesga, R; Rugeles, M T
2000-01-01
Repeated exposure to human immunodeficiency virus (HIV) does not always result in seroconversion. Modifications in coreceptors for HIV entrance to target cells are one of the factors that block the infection. We studied the frequency of Delta-32 mutation in ccr5 gene in Medellin, Colombia. Two hundred and eighteen individuals distributed in three different groups were analyzed for Delta-32 mutation in ccr5 gene by polymerase chain reaction (PCR): 29 HIV seropositive (SP), 39 exposed seronegative (ESN) and 150 individuals as a general population sample (GPS). The frequency of the Delta-32 mutant allele was 3.8% for ESN, 2.7% for GPS and 1.7% for SP. Only one homozygous mutant genotype (Delta-32/Delta-32) was found among the ESN (2.6%). The heterozygous genotype (ccr5/Delta-32) was found in eight GPS (5.3%), in one SP (3.4%) and in one ESN (2.6%). The differences in the allelic and genotypic frequencies among the three groups were not statistically significant. A comparison between the expected and the observed genotypic frequencies showed that these frequencies were significantly different for the ESN group, which indirectly suggests a protective effect of the mutant genotype (Delta-32/Delta-32). Since this mutant genotype explained the resistance of infection in only one of our ESN persons, different mechanisms of protection must be playing a more important role in this population.
NASA Astrophysics Data System (ADS)
Kurpaska, L.; Lesniak, M.; Jadach, R.; Sitarz, M.; Jasinski, J. J.; Grosseau-Poussard, J.-L.
2016-12-01
In this study displacement of monoclinic bands of zirconia were investigated in the function of oxidation time using the Raman spectroscopy technique. Oxidations were performed on pure zirconium and zirconium alloy in-situ at 600 °C for 6 h. Analysis of the absolute intensities as well as the positions of the characteristic for monoclinic and tetragonal phase Raman bands were performed. Reported results has highlighted that monoclinic phase of zirconia undergoes a continuous band displacement, individual for each Raman mode. Recorded shift of low frequency vibrational spectra of monoclinic phase was employed to study stress developed in zirconia during high temperature oxidation - herein called as growing stress. In addition, based on the Raman band intensity we discuss observed transition of the metastable tetragonal phase to stable monoclinic phase. Reported results, for the first time showed that studied metals (pure zirconium and its alloy) behave similarly in terms of band shift. However the resulting value of growing stress associated to the band displacement is slightly different in regards of individual band and studied sample.
Powell, Marta K.; Benková, Kamila; Selinger, Pavel; Dogoši, Marek; Kinkorová Luňáčková, Iva; Koutníková, Hana; Laštíková, Jarmila; Roubíčková, Alena; Špůrková, Zuzana; Laclová, Lucie; Eis, Václav; Šach, Josef
2016-01-01
Objective AIDS-related mortality has changed dramatically with the onset of highly active antiretroviral therapy (HAART), which has even allowed compensated HIV-infected patients to withdraw from secondary therapy directed against opportunistic pathogens. However, in recently autopsied HIV-infected patients, we observed that associations with a broad spectrum of pathogens remain, although detailed analyses are lacking. Therefore, we focused on the possible frequency and spectrum shifts in pathogens associated with autopsied HIV-infected patients. Design We hypothesized that the pathogens frequency and spectrum changes found in HIV-infected patients examined postmortem did not recapitulate the changes found previously in HIV-infected patients examined antemortem in both the pre- and post-HAART eras. Because this is the first comprehensive study originating from Central and Eastern Europe, we also compared our data with those obtained in the West and Southwest Europe, USA and Latin America. Methods We performed autopsies on 124 HIV-infected patients who died from AIDS or other co-morbidities in the Czech Republic between 1985 and 2014. The pathological findings were retrieved from the full postmortem examinations and autopsy records. Results We collected a total of 502 host-pathogen records covering 82 pathogen species, a spectrum that did not change according to patients’ therapy or since the onset of the epidemics, which can probably be explained by the fact that even recently deceased patients were usually decompensated (in 95% of the cases, the last available CD4+ cell count was falling below 200 cells*μl-1) regardless of the treatment they received. The newly identified pathogen taxa in HIV-infected patients included Acinetobacter calcoaceticus, Aerococcus viridans and Escherichia hermannii. We observed a very limited overlap in both the spectra and frequencies of the pathogen species found postmortem in HIV-infected patients in Europe, the USA and Latin
Hamilton, W T; Hall, G H; Round, A P
2001-01-01
BACKGROUND: Chronic fatigue syndrome (CFS) research has concentrated on infective, immunological, and psychological causes. Illness behaviour has received less attention, with most research studying CFS patients after diagnosis. Our previous study on the records of an insurance company showed a highly significant increase in illness reporting before development of CFS. AIM: To investigate the number and type of general practitioner (GP) consultations by patients with CFS for 15 years before they develop their condition. DESIGN OF STUDY: Case-control study in 11 general practices in Devon. SETTING: Forty-nine patients with CFS (satisfying the Centers for Disease Control criteria), 49 age, sex, and general practice matched controls, and 37 patients with multiple sclerosis (MS) were identified from the general practices' computerised databases. METHOD: The number of general practice consultations and symptoms recorded in three five-year periods (quinquennia) were counted before development of the patients' condition. RESULTS: The median number of consultations was significantly higher for CFS patients than that of matched controls in each of the quinquennia: ratios for first quinquennium = 1.88, P = 0.01; second quinquennium = 1.70, P = 0.005; last quinquennium = 2.25, P < 0.001. More CFS patients than controls attended for 13 of the 18 symptoms studied. Significant increases were found for upper respiratory tract infection (P < 0.001), lethargy (P < 0.001), and vertigo (P = 0.02). Similar results were found for CFS patients when compared with MS. CONCLUSIONS: CFS patients consulted their GP more frequently in the 15 years before development of their condition, for a wide variety of complaints. Several possibilities may explain these findings. The results support the hypothesis that behavioural factors have a role in the aetiology of CFS. PMID:11462315
Calculation of IR-spectra of structural fragments of lignins
NASA Astrophysics Data System (ADS)
Derkacheva, O. Yu.; Ishankhodzhaeva, M. M.
2016-12-01
To study structure of softwood lignins the experimental and theoretical IR-spectra in middle IR-diapason were analyzed. To interpret these data the quantum chemical calculations of IR-spectra of general dimmer fragments of softwood lignins by method of density functional theory (DFT/B3LYP) with 6-31G(d,p) as basis set were carried out. These calculations showed that frequencies of normal vibrations of fragment with β-alkyl-aryl linkage are close to the experimental values of the IR absorption bands of lignin, and infrared spectrum of this structure is similar to the experimental spectrum of lignin. The calculations with accounting for the solvent showed a strong increase in the intensity of the majority of the bands and the solvent effect on the frequencies of vibrations.
Shao, Yu; Chang, Chip-Hong
2007-08-01
We present a new speech enhancement scheme for a single-microphone system to meet the demand for quality noise reduction algorithms capable of operating at a very low signal-to-noise ratio. A psychoacoustic model is incorporated into the generalized perceptual wavelet denoising method to reduce the residual noise and improve the intelligibility of speech. The proposed method is a generalized time-frequency subtraction algorithm, which advantageously exploits the wavelet multirate signal representation to preserve the critical transient information. Simultaneous masking and temporal masking of the human auditory system are modeled by the perceptual wavelet packet transform via the frequency and temporal localization of speech components. The wavelet coefficients are used to calculate the Bark spreading energy and temporal spreading energy, from which a time-frequency masking threshold is deduced to adaptively adjust the subtraction parameters of the proposed method. An unvoiced speech enhancement algorithm is also integrated into the system to improve the intelligibility of speech. Through rigorous objective and subjective evaluations, it is shown that the proposed speech enhancement system is capable of reducing noise with little speech degradation in adverse noise environments and the overall performance is superior to several competitive methods.
Infrared Spectra of Substituted Polycyclic Aromatic Hydrocarbons
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Hudgins, Douglas M.; Sandford, Scott A.; Allamandola, Louis J.; Arnold, James O. (Technical Monitor)
1997-01-01
Calculations are carried out using density functional theory (DFT) to determine the harmonic frequencies and intensities of 1-methylanthracene, 9-methylanthracene, 9-cyanoanthracene, 2-aminoanthracene, acridine, and their positive ions. The theoretical data are compared with matrix-isolation spectra for these species also reported in this work. The theoretical and experimental frequencies and relative intensities for the neutral species are in generally good agreement, whereas the positive ion spectra are only in qualitative agreement. Relative to anthracene, we find that substitution of amethyl or CN for a hydrogen does not significantly affect the spectrum other than to add the characteristic methyl C-H stretch and C-N stretch (near 2200/cm), respectively. However, addition of NH2 dramatically affects the spectrum of the neutral. Not only are the NH2 modes themselves strong, but this electron withdrawing group induces sufficient partial charge on the ring to give the neutral molecule characteristics of the anthracene cation spectrum. The sum of the absolute intensities is about four times larger for 2-aminoanthracene than for 9-cyanoanthracene. Substituting nitrogen in the ring at the nine position (acridine) does not greatly alter the spectrum compared with anthracene.
Generalized spectra model for 1-100 keV X-ray emission from Cygnus X-3 based on EXOSAT data
NASA Astrophysics Data System (ADS)
Rajeev, M. R.; Chitnis, V. R.; Rao, A. R.; Singh, K. P.
1994-03-01
The X-ray spectrum of the highly variable X-ray source, Cyg X-3, has so far defied a consistent explanation based on simple emission models. We have extracted two of the best data sets from the EXOSAT archives and performed a detailed spectral analysis for its 'high' and 'low' states. The analysis of the less frequently occurring 'low' state is presented for the first time for the EXOSAT data. Combining data from the medium-energy argon and xenon detectors and the gas scintillation proportional counter, with a better energy resolution, and carrying out a simultaneous fit, we find that the X-ray continuum in both the 'high' and 'low' state can be explained as a sum of a blackbody emission and emission from a Comptonized plasma cloud with a common absorption. The Comptonization model is sufficient as well as preferable to many other models, in explaining the observed X-ray emission up to 100 keV. In addition, we find an emission-line feature due to ionized iron (Fe XX-Fe XXVI) and absorption features due to cold iron (Fe I) as well as highly ionized iron (Fe XXV-Fe XXXVI). The presence of absorption due to Fe I has been shown for the first time here. This is the simplest and the most generalized spectral model for the 1-100 keV X-ray emission from Cyg X-3, to date. We find that the blackbody temperature derived in the 'high ' state (1.47 keV) is much lower than that derived for the 'low' state (2.40 keV) and is associated with an increase in the blackbodly radius in the 'high' state. The ratio of blackbody flux to the total flux is approximately 0.61 in the 'high' state and approximately 0.44 in the 'low' state. The Fe line energy is significantly higher in the 'high' state (approximately 6.95 keV) compared to the 'low' state (approximately 6.56 keV). The Comptonization parameter changes from 2 to approximately 15 in going from the 'high' to the 'low' state implying a highly saturated Comptonization in the 'low' state. The Comptonized region has high electron
NASA Astrophysics Data System (ADS)
Alsina Ballester, E.; Belluzzi, L.; Trujillo Bueno, J.
2017-02-01
The spectral line polarization encodes a wealth of information about the thermal and magnetic properties of the solar atmosphere. Modeling the Stokes profiles of strong resonance lines is, however, a complex problem both from a theoretical and computational point of view, especially when partial frequency redistribution (PRD) effects need to be taken into account. In this work, we consider a two-level atom in the presence of magnetic fields of arbitrary intensity (Hanle–Zeeman regime) and orientation, both deterministic and micro-structured. Working within the framework of a rigorous PRD theoretical approach, we have developed a numerical code that solves the full non-LTE radiative transfer problem for polarized radiation, in one-dimensional models of the solar atmosphere, accounting for the combined action of the Hanle and Zeeman effects, as well as for PRD phenomena. After briefly discussing the relevant equations, we describe the iterative method of solution of the problem and the numerical tools that we have developed and implemented. We finally present some illustrative applications to two resonance lines that form at different heights in the solar atmosphere, and provide a detailed physical interpretation of the calculated Stokes profiles. We find that magneto-optical effects have a strong impact on the linear polarization signals that PRD effects produce in the wings of strong resonance lines. We also show that the weak-field approximation has to be used with caution when PRD effects are considered.
Spectra: Time series power spectrum calculator
NASA Astrophysics Data System (ADS)
Gallardo, Tabaré
2017-01-01
Spectra calculates the power spectrum of a time series equally spaced or not based on the Spectral Correlation Coefficient (Ferraz-Mello 1981, Astron. Journal 86 (4), 619). It is very efficient for detection of low frequencies.
Microwave spectra of some volatile organic compounds
NASA Technical Reports Server (NTRS)
White, W. F.
1975-01-01
A computer-controlled microwave (MRR) spectrometer was used to catalog reference spectra for chemical analysis. Tables of absorption frequency, peak absorption intensity, and integrated intensity are included for 26 volatile organic compounds, all but one of which contain oxygen.
Mackie, Cameron J. Candian, Alessandra; Tielens, Alexander G. G. M.; Huang, Xinchuan; Maltseva, Elena; Buma, Wybren Jan; Petrignani, Annemieke; Oomens, Jos; Lee, Timothy J.
2015-12-14
Current efforts to characterize and study interstellar polycyclic aromatic hydrocarbons (PAHs) rely heavily on theoretically predicted infrared (IR) spectra. Generally, such studies use the scaled harmonic frequencies for band positions and double harmonic approximation for intensities of species, and then compare these calculated spectra with experimental spectra obtained under matrix isolation conditions. High-resolution gas-phase experimental spectroscopic studies have recently revealed that the double harmonic approximation is not sufficient for reliable spectra prediction. In this paper, we present the anharmonic theoretical spectra of three PAHs: naphthalene, anthracene, and tetracene, computed with a locally modified version of the SPECTRO program using Cartesian derivatives transformed from Gaussian 09 normal coordinate force constants. Proper treatments of Fermi resonances lead to an impressive improvement on the agreement between the observed and theoretical spectra, especially in the C–H stretching region. All major IR absorption features in the full-scale matrix-isolated spectra, the high-temperature gas-phase spectra, and the most recent high-resolution gas-phase spectra obtained under supersonically cooled molecular beam conditions in the CH-stretching region are assigned.
Holden, J.J.A. |; Chalifoux, M.; Wing, M.
1994-09-01
The fragile X (FRAXA) syndrome is the most common inherited form of developmental disability and was the first genetic disorder in which the mechanism of mutation is triplet repeat expansion. The normal fragile X mental retardation-1 gene has 6-52 copies of the CGG-repeat; affected males have extensive amplification, coupled with methylation and gene inactivation; and carriers have between about 55 and 200 copies. There is some overlap in the 45-55 repeat range, with some alleles showing stable and othres unstable transmission. There have been several estimates of the incidence of the FRAXA syndrome, based on testing of special populations using chromosome analysis and the range is 1/750-1/2000. Because of the high burden associated with this syndrome, and in the face of discussions about population screening, it is important to know the actual incidence of mutations in this gene, as well as the distribution of unstable repeats above 45 copes. We have initiated a general population screening to examine 50,000 newborn samples using PCR, and have developed a rapid, inexpensive and reliable method for amplifying the CGG-repeat from Guthrie spots. In the first 1600 samples examined, we found 15 alleles with greater than 45 CGG-repeats, with the highest being 61 repeats.
Institóris, László; Tóth, Anita Réka; Molnár, Attila; Arok, Zsófia; Kereszty, Eva; Varga, Tibor
2013-01-10
In the framework of the DRUID (Driving under the Influence of Drugs, Alcohol, and Medicines) EU-6 project, a roadside survey was performed in South-East Hungary to determine the incidence of alcohol and the most frequent illicit and licit drug consumption (amphetamines, THC, illicit and medical opiates, cocaine, ketamine, benzodiazepines, zopiclone and zolpidem) in the general driving population. All 3110 drivers stopped between 01 January 2008 and 31 December 2009 were checked for alcohol, and among them 2738 persons (87.7%) participated in the further examinations, on a voluntary basis. Licit and illicit drugs were determined from their oral fluid samples by GC-MS analysis. Illicit drugs were detected in 27 cases (0.99%), licit drugs in 85 cases (3.14%), and alcohol (cut off: 0.1g/l) was found in 4 (0.13%) cases. Illicit drug consumption was the highest among men of the ages 18-34, during the spring, and on the week-end nights. With respect to licit drugs, the highest incidence was found among women over the age of 50, during the summer, and on the week-days. All alcohol positive cases were men over the age of 35. In comparison to international European averages, the alcohol and illicit drug consumption was low, but the licit drug consumption was over the European average.
Measurement of high frequency waves using a wave follower
NASA Technical Reports Server (NTRS)
Tang, S.; Shemdin, O. H.
1983-01-01
High frequency waves were measured using a laser-optical sensor mounted on a wave follower. Measured down-wind wave slope spectra are shown to be wind speed dependent; the mean square wave-slopes are generally larger than those measured by Cox and Munk (1954) using the sun glitter method.
NASA Astrophysics Data System (ADS)
Ramalingam, S.; Jayaprakash, A.; Mohan, S.; Karabacak, M.
2011-11-01
FT-IR and FT-Raman (4000-100 cm -1) spectral measurements of 3-methyl-1,2-butadiene (3M12B) have been attempted in the present work. Ab-initio HF and DFT (LSDA/B3LYP/B3PW91) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, IR intensities and Raman activities. Complete vibrational assignments on the observed spectra are made with vibrational frequencies obtained by HF and DFT (LSDA/B3LYP/B3PW91) at 6-31G(d,p) and 6-311G(d,p) basis sets. The results of the calculations have been used to simulate IR and Raman spectra for the molecule that showed good agreement with the observed spectra. The potential energy distribution (PED) corresponding to each of the observed frequencies are calculated which confirms the reliability and precision of the assignment and analysis of the vibrational fundamentals modes. The oscillation of vibrational frequencies of butadiene due to the couple of methyl group is also discussed. A study on the electronic properties such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The thermodynamic properties of the title compound at different temperatures reveal the correlations between standard heat capacities ( C) standard entropies ( S), and standard enthalpy changes ( H).
DesRoches, Caro-Lyne; Patel, Jaina; Wang, Peixiang; Minassian, Berge; Salomons, Gajja S; Marshall, Christian R; Mercimek-Mahmutoglu, Saadet
2015-07-10
Creatine transporter deficiency (CRTR-D) is an X-linked inherited disorder of creatine transport. All males and about 50% of females have intellectual disability or cognitive dysfunction. Creatine deficiency on brain proton magnetic resonance spectroscopy and elevated urinary creatine to creatinine ratio are important biomarkers. Mutations in the SLC6A8 gene occur de novo in 30% of males. Despite reports of high prevalence of CRTR-D in males with intellectual disability, there are no true prevalence studies in the general population. To determine carrier frequency of CRTR-D in the general population we studied the variants in the SLC6A8 gene reported in the Exome Variant Server database and performed functional characterization of missense variants. We also analyzed synonymous and intronic variants for their predicted pathogenicity using in silico analysis tools. Nine missense variants were functionally analyzed using transient transfection by site-directed mutagenesis with In-Fusion HD Cloning in HeLa cells. Creatine uptake was measured by liquid chromatography tandem mass spectrometry for creatine measurement. The c.1654G>T (p.Val552Leu) variant showed low residual creatine uptake activity of 35% of wild type transfected HeLa cells and was classified as pathogenic. Three variants (c.808G>A; p.Val270Met, c.942C>G; p.Phe314Leu and c.952G>A; p.Ala318Thr) were predicted to be pathogenic based on in silico analysis, but proved to be non-pathogenic by our functional analysis. The estimated carrier frequency of CRTR-D was 0.024% in females in the general population. We recommend functional studies for all novel missense variants by transient transfection followed by creatine uptake measurement by liquid chromatography tandem mass spectrometry as fast and cost effective method for the functional analysis of missense variants in the SLC6A8 gene.
Computer Simulation of NMR Spectra.
ERIC Educational Resources Information Center
Ellison, A.
1983-01-01
Describes a PASCAL computer program which provides interactive analysis and display of high-resolution nuclear magnetic resonance (NMR) spectra from spin one-half nuclei using a hard-copy or monitor. Includes general and theoretical program descriptions, program capability, and examples of its use. (Source for program/documentation is included.)…
Infrared Spectra of Perdeuterated Naphthalene, Phenanthrene, Chrysene, and Pyrene
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Sandford, Scott A.; Hudgins, Douglas M.; Arnold, James O. (Technical Monitor)
1996-01-01
Calculations are carried out using density functional theory (DFT) to determine the harmonic frequencies and intensities of perdeuterated naphthalene, phenanthrene, pyrene, and chrysene. We also report matrix- isolation spectra for these four species. The theoretical and experimental frequencies and relative intensities for the perdeuterated species are in generally good agreement. The effect of perdeuteration is to reduce the sum of the integrated intensities by a factor of about 1.75. This reduction occurs for all vibrational motions, except for the weak low frequency ring deformation modes. There is also a significant redistribution of the relative intensities between the out-of-plane C-D bands relative to those found for the out-of-plane C-H bands. The theoretical isotopic ratios provide an excellent diagnostic of the degree of C-H(C-D) involvement in the vibrational bands, allowing in most cases a clear distinction of the type of motion.
Low-frequency scaling applied to stochastic finite-fault modeling
NASA Astrophysics Data System (ADS)
Crane, Stephen; Motazedian, Dariush
2014-01-01
Stochastic finite-fault modeling is an important tool for simulating moderate to large earthquakes. It has proven to be useful in applications that require a reliable estimation of ground motions, mostly in the spectral frequency range of 1 to 10 Hz, which is the range of most interest to engineers. However, since there can be little resemblance between the low-frequency spectra of large and small earthquakes, this portion can be difficult to simulate using stochastic finite-fault techniques. This paper introduces two different methods to scale low-frequency spectra for stochastic finite-fault modeling. One method multiplies the subfault source spectrum by an empirical function. This function has three parameters to scale the low-frequency spectra: the level of scaling and the start and end frequencies of the taper. This empirical function adjusts the earthquake spectra only between the desired frequencies, conserving seismic moment in the simulated spectra. The other method is an empirical low-frequency coefficient that is added to the subfault corner frequency. This new parameter changes the ratio between high and low frequencies. For each simulation, the entire earthquake spectra is adjusted, which may result in the seismic moment not being conserved for a simulated earthquake. These low-frequency scaling methods were used to reproduce recorded earthquake spectra from several earthquakes recorded in the Pacific Earthquake Engineering Research Center (PEER) Next Generation Attenuation Models (NGA) database. There were two methods of determining the stochastic parameters of best fit for each earthquake: a general residual analysis and an earthquake-specific residual analysis. Both methods resulted in comparable values for stress drop and the low-frequency scaling parameters; however, the earthquake-specific residual analysis obtained a more accurate distribution of the averaged residuals.
El Dib, Regina P; Silva, Edina MK; Morais, José F; Trevisani, Virgínia FM
2008-01-01
Background Music is ever present in our daily lives, establishing a link between humans and the arts through the senses and pleasure. Sound technicians are the link between musicians and audiences or consumers. Recently, general concern has arisen regarding occurrences of hearing loss induced by noise from excessively amplified sound-producing activities within leisure and professional environments. Sound technicians' activities expose them to the risk of hearing loss, and consequently put at risk their quality of life, the quality of the musical product and consumers' hearing. The aim of this study was to measure the prevalence of high frequency hearing loss consistent with noise exposure among sound technicians in Brazil and compare this with a control group without occupational noise exposure. Methods This was a cross-sectional study comparing 177 participants in two groups: 82 sound technicians and 95 controls (non-sound technicians). A questionnaire on music listening habits and associated complaints was applied, and data were gathered regarding the professionals' numbers of working hours per day and both groups' hearing complaint and presence of tinnitus. The participants' ear canals were visually inspected using an otoscope. Hearing assessments were performed (tonal and speech audiometry) using a portable digital AD 229 E audiometer funded by FAPESP. Results There was no statistically significant difference between the sound technicians and controls regarding age and gender. Thus, the study sample was homogenous and would be unlikely to lead to bias in the results. A statistically significant difference in hearing loss was observed between the groups: 50% among the sound technicians and 10.5% among the controls. The difference could be addressed to high sound levels. Conclusion The sound technicians presented a higher prevalence of high frequency hearing loss consistent with noise exposure than did the general population, although the possibility of residual
Sun, Hong-Liu; Zhu, Wei; Zhang, Yu-Rong; Pan, Xiao-Hong; Zhang, Jun-Ru; Chen, Xiang-Ming; Liu, Yu-Xia; Li, Shu-Cui; Wang, Qiao-Yun; Deng, Da-Ping
2017-03-01
As a promising method for treating intractable epilepsy, the inhibitory effect of low-frequency stimulation (LFS) is well known, although its mechanisms remain unclear. Excessive levels of cerebral glutamate are considered a crucial factor for epilepsy. Therefore, we designed experiments to investigate the crucial parts of the glutamate cycle. We evaluated glutamine synthetase (GS, metabolizes glutamate), glutaminase (synthesizes glutamate), and glutamic acid decarboxylase (GAD, a γ-aminobutyric acid [GABA] synthetase) in different regions of the brain, including the dentate gyrus (DG), CA3, and CA1 subregions of the hippocampus, and the cortex, using western blots, immunohistochemistry, and enzyme activity assays. Additionally, the concentrations of glutamate, GABA, and glutamine (a product of GS) were measured using high-performance liquid chromatography (HPLC) in the same subregions. The results indicated that a transiently promoted glutamate cycle was closely involved in the progression from focal to generalized seizure. Low-frequency stimulation (LFS) delivered to the ventral hippocampus had an antiepileptogenic effect in rats exposed to amygdaloid-kindling stimulation. Simultaneously, LFS could partly reverse the effects of the promoted glutamate cycle, including increased GS function, accelerated glutamate-glutamine cycling, and an unbalanced glutamate/GABA ratio, all of which were induced by amygdaloid kindling in the DG when seizures progressed to stage 4. Moreover, glutamine treatment reversed the antiepileptic effect of LFS with regard to both epileptic severity and susceptibility. Our results suggest that the effects of LFS on the glutamate cycle may contribute to the antiepileptogenic role of LFS in the progression from focal to generalized seizure.
NASA Astrophysics Data System (ADS)
Hayes, Anna C.; Vogel, Petr
2016-10-01
We present a review of the antineutrino spectra emitted from reactors. Knowledge of these spectra and their associated uncertainties is crucial for neutrino oscillation studies. The spectra used to date have been determined either by converting measured electron spectra to antineutrino spectra or by summing over all of the thousands of transitions that make up the spectra, using modern databases as input. The uncertainties in the subdominant corrections to β-decay plague both methods, and we provide estimates of these uncertainties. Improving on current knowledge of the antineutrino spectra from reactors will require new experiments. Such experiments would also address the so-called reactor neutrino anomaly and the possible origin of the shoulder observed in the antineutrino spectra measured in recent high-statistics reactor neutrino experiments.
NASA Astrophysics Data System (ADS)
Scoccimarro, Enrico; Gualdi, Silvio; Navarra, Antonio
2010-05-01
This study investigates the possible changes that the greenhouse global warming might generate in the characteristics of the tropical cyclones (TCs). The analysis has been performed using climate scenario simulations carried out with a fully coupled high-resolution global general circulation model (INGV-SXG) with a T106 atmospheric resolution. The capability of the model to reproduce a reasonably realistic TC climatology has been assessed by comparing the model results from a simulation of the XX Century with observations. The model appears to be able to simulate tropical cyclone-like vortices with many features similar to the observed TCs. The simulated TC activity exhibits realistic geographical distribution, seasonal modulation and interannual variability, suggesting that the model is able to reproduce the major basic mechanisms that link the TC occurrence with the large scale circulation. The results from the climate scenarios reveal a substantial general reduction of the TC frequency when the atmospheric CO2 concentration is doubled and quadrupled. The reduction appears particularly evident for the tropical north west Pacific (NWP) and north Atlantic (ATL). In the NWP the weaker TC activity seems to be associated with a reduced amount of convective instabilities. In the ATL region the weaker TC activity seems to be due to both the increased stability of the atmosphere and a stronger vertical wind shear. Despite the generally reduced TC activity, there is evidence of increased rainfall associated with the simulated cyclones. Using the new fully coupled CMCC model (CMCC_MED), with a T159 atmospheric resolution, we found a significant modulation of the Ocean Heat Transport (OHT) induced by the TC activity. Thus the possible changes that greenhouse induced global warming during 21st century might generate in the characteristics of the TC-induced OHT have been analyzed.
NASA Astrophysics Data System (ADS)
Biri, Stavroula; Serra, Nuno; Scharffenberg, Martin G.; Stammer, Detlef
2016-06-01
Frequency and wavenumber spectra of sea surface height (SSH) and surface geostrophic velocity are presented, as they result for the Atlantic Ocean from a 23 year long altimeter data set and from a hierarchy of ocean model simulations with spatial resolutions of 16, 8, and 4 km. SSH frequency spectra follow a spectral decay of roughly f-1 on long periods; toward higher frequencies a spectral decay close to f-2 is found. For geostrophic velocity spectra, a somewhat similar picture emerges, albeit with flatter spectral relations. In terms of geostrophic velocity wavenumber spectra, we find a general relation close to k-3 in the high-resolution model results. Outside low-energy regions all model spectra come close to observed spectra at low frequencies and wavenumbers in terms of shape and amplitude. However, the highest model resolution appears essential for reproducing the observed spectra at high frequencies and wavenumbers. This holds especially for velocity spectra in mid and high latitudes, suggesting that eddy resolving ocean models need to be run at a resolution of 1/24° or better if one were to fully resolve the observed mesoscale eddy field. Causes for remaining discrepancies between observed and simulated results can be manifold. At least partially, they can be rationalized by taking into account an aliasing effect of unresolved temporal variability in the altimetric observations occurring on periods smaller than the 20 days Nyquist period of the altimetric data, thereby leading to an overestimate of variability in the altimetric estimates, roughly on periods below 100 days.
NASA Astrophysics Data System (ADS)
Gukov, Sergei; Nawata, Satoshi; Saberi, Ingmar; Stošić, Marko; Sułkowski, Piotr
2016-03-01
This paper provides both a detailed study of color-dependence of link homologies, as realized in physics as certain spaces of BPS states, and a broad study of the behavior of BPS states in general. We consider how the spectrum of BPS states varies as continuous parameters of a theory are perturbed. This question can be posed in a wide variety of physical contexts, and we answer it by proposing that the relationship between unperturbed and perturbed BPS spectra is described by a spectral sequence. These general considerations unify previous applications of spectral sequence techniques to physics, and explain from a physical standpoint the appearance of many spectral sequences relating various link homology theories to one another. We also study structural properties of colored HOMFLY homology for links and evaluate Poincaré polynomials in numerous examples. Among these structural properties is a novel "sliding" property, which can be explained by using (refined) modular S-matrix. This leads to the identification of modular transformations in Chern-Simons theory and 3d {N}=2 theory via the 3d/3d correspondence. Lastly, we introduce the notion of associated varieties as classical limits of recursion relations of colored superpolynomials of links, and study their properties.
Gukov, Sergei; Nawata, Satoshi; Saberi, Ingmar; Stošić, Marko; Sułkowski, Piotr
2016-03-02
In this article, we provide both a detailed study of color-dependence of link homologies, as realized in physics as certain spaces of BPS states, and a broad study of the behavior of BPS states in general. We consider how the spectrum of BPS states varies as continuous parameters of a theory are perturbed. This question can be posed in a wide variety of physical contexts, and we answer it by proposing that the relationship between unperturbed and perturbed BPS spectra is described by a spectral sequence. These general considerations unify previous applications of spectral sequence techniques to physics, and explain from a physical standpoint the appearance of many spectral sequences relating various link homology theories to one another. We also study structural properties of colored HOMFLY homology for links and evaluate Poincar e polynomials in numerous examples. Among these structural properties is a novel "sliding" property, which can be explained by using (re fined) modular S-matrix. This leads to the identi fication of modular transformations in Chern-Simons theory and 3d N = 2 theory via the 3d/3d correspondence. In conclusion, we introduce the notion of associated varieties as classical limits of recursion relations of colored superpolynomials of links, and study their properties.
Gukov, Sergei; Nawata, Satoshi; Saberi, Ingmar; ...
2016-03-02
In this article, we provide both a detailed study of color-dependence of link homologies, as realized in physics as certain spaces of BPS states, and a broad study of the behavior of BPS states in general. We consider how the spectrum of BPS states varies as continuous parameters of a theory are perturbed. This question can be posed in a wide variety of physical contexts, and we answer it by proposing that the relationship between unperturbed and perturbed BPS spectra is described by a spectral sequence. These general considerations unify previous applications of spectral sequence techniques to physics, and explainmore » from a physical standpoint the appearance of many spectral sequences relating various link homology theories to one another. We also study structural properties of colored HOMFLY homology for links and evaluate Poincar e polynomials in numerous examples. Among these structural properties is a novel "sliding" property, which can be explained by using (re fined) modular S-matrix. This leads to the identi fication of modular transformations in Chern-Simons theory and 3d N = 2 theory via the 3d/3d correspondence. In conclusion, we introduce the notion of associated varieties as classical limits of recursion relations of colored superpolynomials of links, and study their properties.« less
Trigonometric Polynomials For Estimation Of Spectra
NASA Technical Reports Server (NTRS)
Greenhall, Charles A.
1990-01-01
Orthogonal sets of trigonometric polynomials used as suboptimal substitutes for discrete prolate-spheroidal "windows" of Thomson method of estimation of spectra. As used here, "windows" denotes weighting functions used in sampling time series to obtain their power spectra within specified frequency bands. Simplified windows designed to require less computation than do discrete prolate-spheroidal windows, albeit at price of some loss of accuracy.
Isotope shifts in spectra of molecular liquids
NASA Astrophysics Data System (ADS)
Dubrovskaya, E. V.; Kolomiitsova, T. D.; Shurukhina, A. V.; Shchepkin, D. N.
2016-02-01
In the IR absorption spectra of low-temperature molecular liquids, we have observed anomalously large isotope shifts of frequencies of vibrational bands that are strong in the dipole absorption. The same effect has also been observed in their Raman spectra. At the same time, in the spectra of cryosolutions, the isotope shifts of the same bands coincide with a high accuracy (±(0.1-0.5) cm-1) with the shifts that are observed in the spectra of the gas phase. The difference between the spectra of examined low-temperature systems is caused by the occurrence of resonant dipole-dipole interactions between spectrally active identical molecules. The calculation of the band contour in the spectrum of liquid freon that we have performed in this work taking into account the resonant interaction between states of simultaneous transitions in isotopically substituted molecules can explain this effect.
NASA Astrophysics Data System (ADS)
Mohd Ariff, Noratiqah; Jemain, Abdul Aziz; Wan Zin, Wan Zawiah
2013-04-01
Rainfall characteristics can be analyzed by using storm events with storms representing actual rainfall events instead of rainfall amounts in fixed time frames. One of the most commonly used methods in rainfall analysis is the construction of intensity-duration-frequency (IDF) curves. IDF curves help in designing hydraulic structures by providing a mathematical relationship between storm intensity, duration and return period. In Peninsular Malaysia, these curves are often built using the generalized extreme value (GEV) distribution to represent annual maximum storm intensity. The mathematical formula for the curves is usually taken from either known empirical equations or from quantile functions of probability distributions. However, there is no research which compares and analyzes the differences between the curves obtained for storms in Peninsular Malaysia based on the empirical and quantile functions. Thus, the aim of this study is to build IDF curves for storms in Peninsular Malaysia using typical empirical equations and the quantile function of the GEV distribution. Then, the analysis of differences is performed on the curves obtained from both approaches. The analysis consists of the coefficient of variation of root mean square error mean percentage difference and the coefficient of determination, R2. The analysis shows small differences between the curves based on the empirical equations and those obtained using the quantile function of GEV distribution. According to these results, it can be concluded that the simple empirical equations are sufficient in constructing IDF curves based on GEV distribution for storms in Peninsular Malaysia.
QUALITATIVE INTERPRETATION OF GALAXY SPECTRA
Sanchez Almeida, J.; Morales-Luis, A. B.; Terlevich, R.; Terlevich, E.; Cid Fernandes, R. E-mail: abml@iac.es E-mail: eterlevi@inaoep.mx
2012-09-10
We describe a simple step-by-step guide to qualitative interpretation of galaxy spectra. Rather than an alternative to existing automated tools, it is put forward as an instrument for quick-look analysis and for gaining physical insight when interpreting the outputs provided by automated tools. Though the recipe is for general application, it was developed for understanding the nature of the Automatic Spectroscopic K-means-based (ASK) template spectra. They resulted from the classification of all the galaxy spectra in the Sloan Digital Sky Survey data release 7, thus being a comprehensive representation of the galaxy spectra in the local universe. Using the recipe, we give a description of the properties of the gas and the stars that characterize the ASK classes, from those corresponding to passively evolving galaxies, to H II galaxies undergoing a galaxy-wide starburst. The qualitative analysis is found to be in excellent agreement with quantitative analyses of the same spectra. We compare the mean ages of the stellar populations with those inferred using the code STARLIGHT. We also examine the estimated gas-phase metallicity with the metallicities obtained using electron-temperature-based methods. A number of byproducts follow from the analysis. There is a tight correlation between the age of the stellar population and the metallicity of the gas, which is stronger than the correlations between galaxy mass and stellar age, and galaxy mass and gas metallicity. The galaxy spectra are known to follow a one-dimensional sequence, and we identify the luminosity-weighted mean stellar age as the affine parameter that describes the sequence. All ASK classes happen to have a significant fraction of old stars, although spectrum-wise they are outshined by the youngest populations. Old stars are metal-rich or metal-poor depending on whether they reside in passive galaxies or in star-forming galaxies.
Vibrational spectra study on quinolones antibiotics
NASA Astrophysics Data System (ADS)
Wang, Yu; Yu, Ke; Wang, Sihuan
2006-09-01
In order to be able to fully understand and easily identify the quilonoles, we collected IR and Raman spectra of six quinolones, and attempted to assign the attribution of the observed frequencies and their association with specific modes of vibration. According to the structure, the compounds were divided into the groups, and the similarities and differences were further studied by comparing. The result of the study shows that the frequency and intensity are comparable to the corresponding structure. The spectra not only have the commonness but also the individualities.
Action spectra for photosynthetic inhibition
NASA Technical Reports Server (NTRS)
Caldwell, M. M.; Flint, S.; Camp, L. B.
1981-01-01
The ultraviolet action spectrum for photosynthesis inhibition was determined to fall between that of the general DNA action spectrum and the generalized plant action spectrum. The characteristics of this action spectrum suggest that a combination of pronounced increase in effectiveness with decreasing wavelength, substantial specificity for the UV-B waveband, and very diminished response in the UV-A waveband result in large radiation amplification factors when the action spectra are used as weighting functions. Attempted determination of dose/response relationships for leaf disc inhibition provided inconclusive data from which to deconvolute an action spectrum.
Tiernan, M.
1980-09-01
Crack spectra derived from velocity data have been shown to exhibit systematics which reflect microstructural and textural differences between samples (Warren and Tiernan, 1980). Further research into both properties and information content of crack spectra have yielded the following: Spectral features are reproducible even at low pressures; certain observed spectral features may correspond to non-in-situ crack populations created during sample retrieval; the functional form of a crack spectra may be diagnostic of the sample's grain texture; hysteresis is observed in crack spectra between up and down pressure runs - it may be due to friction between the faces of closed crack populations.
Photographic spectra of fireballs
NASA Astrophysics Data System (ADS)
Borovička, J.
2016-01-01
Two methods of spectroscopy of meteors using image intensified video cameras and classical photographic film cameras are compared. Video cameras provide large number of low resolution spectra of meteors of normal brightness, which can be used for statistical studies. Large format film cameras have been used through the history and provide high resolution spectra, which can be used to derive temperature, density and absolute abundances of various elements in the radiating plasma. The sensitivity of films is, however, low and only spectra of bright meteors (fireballs) can be studied. Examples of photographic fireball spectra are provided.
Estimation of Sea Surface Wave Spectra Using Acoustic Tomography.
1987-09-01
develops a new technique for estimating quasi- homogeneous and quasi-stationary sea surface wave frequency-direction spectra using acoustic tomog...problems for the homogeneous and quasi- homogeneous frequency-direction spectrum are introduced. The theory is ap- plied tosynthetic data which simulate...thesis introduces a technique that estimates the quasi-stationary and quasi- homogeneous sea surface wave frequency-direction spectrum from the spectra of
Vibrational spectra of 3,5-dimethylpyrazole and deuterated derivatives.
Orza, J M; García, M V; Alkorta, I; Elguero, J
2000-07-01
The infrared (IR) and Raman spectra of 3,5-dimethylpyrazole have been recorded in the vapor, liquid (melt and solution) and solid states. Two deuterated derivatives, C5H7N-ND and C5D7N-NH, were also studied in solid state and in solutions. Instrumental resolution was relatively low, 2.0 cm(-1) in the IR and approximately 2.7 cm(-1) in the Raman spectra. The solids are made of cyclic hydrogen-bonded trimers. These trimers, present also in chloroform and acetone solutions, give rise to characteristic high absorption IR spectra in the 3200-2500 cm(-1) region, related to Fermi resonance involving nu(NH) vibrations. Bands from trimers are not present in water solutions but these solutions show spectral features similar in several ways to those of the trimer, attributable to solvent-bonded complexes. Evidence of H-bonding interactions with the other solvents is also visible in the high-frequency region. The two very intense bands in the Raman spectra of the solids appearing at 115 and 82 cm(-1) in the parent compound are also connected with a trimer formation. To interpret the experimental data, ab initio computations of the harmonic vibrational frequencies and IR and Raman intensities were carried out using the Gaussian 94 program package after full optimization at the RHF/6-31G* level for the three monomeric compounds as well as for three models of the trimer, with C3h, C3 and C1 symmetry. The combined use of experiments and computations allow a firm assignment of most of the observed bands for all the systems. In general, the agreement between theory and experiment is very good, with the exception of the IR and Raman intensities of some transitions. Particularly noticeable is the failure of the theoretical calculation in accounting for the high intensity of the Raman bands of the solid about 115 and 82 cm(-1).
Infrared Spectra of Polycyclic Aromatic Hydrocarbons: Nitrogen Substitution
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W.; Arnold, James O. (Technical Monitor)
1998-01-01
The B3LYP/4-31G approach is used to compute the harmonic frequencies of substituted naphthalene, anthracene, and their cations. The substitutions include cyano (CN), aminio (NH2), imino (NH), and replacement of a CH group by a nitrogen atom. All unique sites are considered, namely 1 and 2 for naphthalene and 1, 2, and 9 for an'tracene, except for the imino, where only 2-iminonaphthalene is studied. The IR spectra of these substituted species are compared with those of the unsubstituted molecules. The addition of a CN group does not significantly affect the spectra except to add the CN stretching frequency. Replacing a CH group by N has only a small effect on the IR spectra. The addition of the NH2 group dramatically affects the neutral spectra, giving it much of the character of the cation spectra. However, the neutral 2-irrinonaphthalene spectra looks more like that of naphthalene than like the 2-aminonaphthalene spectra.
Characteristics of magnetospheric radio noise spectra
NASA Technical Reports Server (NTRS)
Herman, J. R.
1976-01-01
Magnetospheric radio noise spectra (30 kHz to 10 MHz) taken by IMP-6 and RAE-2 exhibit time-varying characteristics which are related to spacecraft position and magnetospheric processes. In the mid-frequency range (100-1,000 kHz) intense noise peaks rise by a factor of 100 or more above background; 80% of the peak frequencies are within the band 125 kHz to 600 kHz, and the peak occurs most often (18% of the time) at 280 kHz. This intense mid-frequency noise has been detected at radial distances from 1.3 Re to 60 Re on all sides of the Earth during magnetically quiet as well as disturbed periods. Maximum occurrence of the mid-frequency noise is in the evening to midnight hours where splash-type energetic particle precipitation takes place. ""Magnetospheric lightning'' can be invoked to explain the spectral shape of the observed spectra.
Eigenvectors of optimal color spectra.
Flinkman, Mika; Laamanen, Hannu; Tuomela, Jukka; Vahimaa, Pasi; Hauta-Kasari, Markku
2013-09-01
Principal component analysis (PCA) and weighted PCA were applied to spectra of optimal colors belonging to the outer surface of the object-color solid or to so-called MacAdam limits. The correlation matrix formed from this data is a circulant matrix whose biggest eigenvalue is simple and the corresponding eigenvector is constant. All other eigenvalues are double, and the eigenvectors can be expressed with trigonometric functions. Found trigonometric functions can be used as a general basis to reconstruct all possible smooth reflectance spectra. When the spectral data are weighted with an appropriate weight function, the essential part of the color information is compressed to the first three components and the shapes of the first three eigenvectors correspond to one achromatic response function and to two chromatic response functions, the latter corresponding approximately to Munsell opponent-hue directions 9YR-9B and 2BG-2R.
Terahertz spectra of DNA nucleobase crystals: A joint experimental and computational study.
Wang, Fang; Zhao, Dongbo; Dong, Hao; Jiang, Ling; Liu, Yunfei; Li, Shuhua
2017-02-21
Terahertz (THz) spectra of DNA nucleobase crystals were experimentally studied by terahertz time domain spectroscopy (THz-TDS), Fourier transform infrared spectroscopy (FTIR), and computationally studied by the generalized energy-based fragmentation approach under periodic boundary conditions (denoted as PBC-GEBF). We analyzed the vibrational spectra of solid-state DNA nucleobases and assigned the corresponding vibrational modes to the main peaks in the experimental spectra with the PBC-GEBF results. The computational results were verified to be in good accordance with the experimental data. Harmonic vibrational frequency results revealed that all the vibrational modes belong to collective vibrational modes, which involve complicated mixtures of inter- and intramolecular displacements, somewhere in the vicinity of 0.5-9THz.
Fourier smoothing of digital photographic spectra
NASA Astrophysics Data System (ADS)
Anupama, G. C.
1990-03-01
Fourier methods of smoothing one-dimensional data are discussed with particular reference to digital photographic spectra. Data smoothed using lowpass filters with different cut-off frequencies are intercompared. A method to scale densities in order to remove the dependence of grain noise on density is described. Optimal filtering technique which models signal and noise in Fourier domain is also explained.
NASA Technical Reports Server (NTRS)
2004-01-01
The color image on the lower left from the panoramic camera on the Mars Exploration Rover Opportunity shows the 'Lily Pad' bounce-mark area at Meridiani Planum, Mars. This image was acquired on the 3rd sol, or martian day, of Opportunity's mission (Jan.26, 2004). The upper left image is a monochrome (single filter) image from the rover's panoramic camera, showing regions from which spectra were extracted from the 'Lily Pad' area. As noted by the line graph on the right, the green spectra is from the undisturbed surface and the red spectra is from the airbag bounce mark.
Stretched-exponential Doppler spectra in underwater acoustic communication channels.
van Walree, P A; Jenserud, T; Otnes, R
2010-11-01
The theory of underwater sound interacting with the sea surface predicts a Gaussian-spread frequency spectrum in the case of a large Rayleigh parameter. However, recent channel soundings reveal more sharply peaked spectra with heavier tails. The measured Doppler spread increases with the frequency and differs between multipath arrivals. The overall Doppler spectrum of a broadband waveform is the sum of the spectra of all constituent paths and frequencies, and is phenomenologically described by a stretched or compressed exponential. The stretched exponential also fits well to the broadband spectrum of a single propagation path, and narrowband spectra summed over all paths.
Effects of axion-photon mixing on gamma-ray spectra from magnetized astrophysical sources
Hochmuth, Kathrin A.; Sigl, Guenter
2007-12-15
Astrophysical {gamma}-ray sources come in a variety of sizes and magnetizations. We deduce general conditions under which {gamma}-ray spectra from such sources would be significantly affected by axion-photon mixing. We show that, depending on strength and coherence of the magnetic field, axion couplings down to {approx}(10{sup 13}GeV){sup -1} can give rise to significant axion-photon conversions in the environment of accreting massive black holes. Resonances can occur between the axion mass term and the plasma frequency term as well as between the plasma frequency term and the vacuum Cotton-Mouton shift. Both resonances and nonresonant transitions could induce detectable features or even strong suppressions in finite energy intervals of {gamma}-ray spectra from active galactic nuclei. Such effects can occur at keV to TeV energies for couplings that are currently allowed by all experimental constraints.
Prediction of electroencephalographic spectra from neurophysiology
NASA Astrophysics Data System (ADS)
Robinson, P. A.; Rennie, C. J.; Wright, J. J.; Bahramali, H.; Gordon, E.; Rowe, D. L.
2001-02-01
A recent neurophysical model of propagation of electrical waves in the cortex is extended to include a physiologically motivated subcortical feedback loop via the thalamus. The electroencephalographic spectrum when the system is driven by white noise is then calculated analytically in terms of physiological parameters, including the effects of filtering of signals by the cerebrospinal fluid, skull, and scalp. The spectral power at low frequencies is found to vary as f-1 when awake and f-3 when asleep, with a breakpoint to a steeper power-law tail at frequencies above about 20 Hz in both cases; the f-1 range concurs with recent magnetoencephalographic observations of such a regime. Parameter sensitivities are explored, enabling a model with fewer free parameters to be proposed, and showing that spectra predicted for physiologically reasonable parameter values strongly resemble those observed in the laboratory. Alpha and beta peaks seen near 10 Hz and twice that frequency, respectively, in the relaxed wakeful state are generated via subcortical feedback in this model, thereby leading to predictions of their frequencies in terms of physiological parameters, and of correlations in their occurrence. Subcortical feedback is also predicted to be responsible for production of anticorrelated peaks in deep sleep states that correspond to the occurrence of theta rhythm at around half the alpha frequency and sleep spindles at 3/2 times the alpha frequency. An additional positively correlated waking peak near three times the alpha frequency is also predicted and tentatively observed, as are two new types of sleep spindle near 5/2 and 7/2 times the alpha frequency, and anticorrelated with alpha. These results provide a theoretical basis for the conventional division of EEG spectra into frequency bands, but imply that the exact bounds of these bands depend on the individual. Three types of potential instability are found: one at zero frequency, another in the theta band at around
On the analysis of photo-electron spectra
Gao, C.-Z.; Dinh, P.M.; Reinhard, P.-G.; Suraud, E.
2015-09-15
We analyze Photo-Electron Spectra (PES) for a variety of excitation mechanisms from a simple mono-frequency laser pulse to involved combination of pulses as used, e.g., in attosecond experiments. In the case of simple pulses, the peaks in PES reflect the occupied single-particle levels in combination with the given laser frequency. This usual, simple rule may badly fail in the case of excitation pulses with mixed frequencies and if resonant modes of the system are significantly excited. We thus develop an extension of the usual rule to cover all possible excitation scenarios, including mixed frequencies in the attosecond regime. We find that the spectral distributions of dipole, monopole and quadrupole power for the given excitation taken together and properly shifted by the single-particle energies provide a pertinent picture of the PES in all situations. This leads to the derivation of a generalized relation allowing to understand photo-electron yields even in complex experimental setups.
Modeling the Infrared Emission Spectra of Specific PAH Molecules in Interstellar Space
NASA Astrophysics Data System (ADS)
Li, Aigen
2007-05-01
The 3.3, 6.2, 7.7, 8.6 and 11.3 micron emission features ubiquitously seen in a wide variety of Galactic and extragalactic objects, are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. Although the PAH hypothesis is quite successful in explaining the general pattern of the observed emission spectra, so far there is no actual precise identification of a single specific PAH molecule in interstellar space. Therefore, when modeling the observed PAH emission spectra, astronomers usually take an empirical approach by constructing 'astro-PAHs' which do not represent any specific material, but approximate the actual absorption properties of the PAH mixture in astrophysical regions. We propose a Spitzer Theory Program to study the photoexcitation of specific PAH molecules and their ions in interstellar space, taking a statistical-mechanical (instead of thermal) approach. For most of the specific PAH molecules selected for this research (with a small number of vibrational degrees of freedom), thermal approximation is not valid. Using available laboratory and quantum-chemical data (e.g. vibrational frequencies, UV/visible/IR absorption cross sections), we will calculate the emission spectra of 21 representative specific PAH molecules and their ions, ranging from naphthalene to circumcoronene, illuminated by interstellar radiation fields of a wide range of intensities. This program will create a web-based 'library' of the emission spectra of 21 specific PAH molecules and their ions as a function of starlight intensities. This 'library' will be made publicly available by October 2008 on the internet at http://www.missouri.edu/~lia/. By comparing observed PAH spectra with model spectra produced by co-adding the emission spectra of different PAH molecules available in this 'library' (with different weights for different species), one will be able to estimate the total PAH mass and relative abundances of each PAH species, using real PAH properties.
Cleaning HI Spectra Contaminated by GPS RFI
NASA Astrophysics Data System (ADS)
Sylvia, Kamin; Hallenbeck, Gregory L.; Undergraduate ALFALFA Team
2016-01-01
The NUDET systems aboard GPS satellites utilize radio waves to communicate information regarding surface nuclear events. The system tests appear in spectra as RFI (radio frequency interference) at 1381MHz, which contaminates observations of extragalactic HI (atomic hydrogen) signals at 50-150 Mpc. Test durations last roughly 20-120 seconds and can occur upwards of 30 times during a single night of observing. The disruption essentially renders the corresponding HI spectra useless.We present a method that automatically removes RFI in HI spectra caused by these tests. By capitalizing on the GPS system's short test durations and predictable frequency appearance we are able to devise a method of identifying times containing compromised data records. By reevaluating the remaining data, we are able to recover clean spectra while sacrificing little in terms of sensitivity to extragalactic signals. This method has been tested on 500+ spectra taken by the Undergraduate ALFALFA Team (UAT), in which it successfully identified and removed all sources of GPS RFI. It will also be used to eliminate RFI in the upcoming Arecibo Pisces-Perseus Supercluster Survey (APPSS).This work has been supported by NSF grant AST-1211005.
Microwave spectra of some chlorine and fluorine compounds. [spectroscopic analysis
NASA Technical Reports Server (NTRS)
White, W. F.
1975-01-01
A computer-controlled microwave spectrometer was used to catalog reference spectra for chemical analysis. Tables of absorption frequencies, peak absorption intensities, and integrated intensities are shown for 21 organic compounds which contain chlorine, fluorine, or both.
1989-03-22
with a wave follower during Marsen. J. Gophysical Res. 88, 9844-9849. 11. Hughes, B.A., 1978. The effects on internal waves on surface waves : 2...Spectra of Surface Waves K. Watson March 1989 JSR-88-130 Approved for public release; distribution unlimited. DTIC SELECTE JUN0 11989 0 JASONE The...Arlington, VA 22209 8503Z 11. TITLE (hlde Secvfty Cof.kaftn) SPECTRA OF SURFACE WAVES (U) 12. PERSONAL AUTHOfRS) K. Watson 13a. TYPE OF REPORT 13b. TIME
Spatial evolution of ocean wave spectra
NASA Technical Reports Server (NTRS)
Beal, R. C.
1981-01-01
The spatially evolving deep water synthetic aperture radar (SAR) directional spectra of a mixed ocean wave system are compared with a comprehensive set of surface and aircraft measurements. The evolution of the SAR spectra, at least for ocean wavelengths greater than 80 m, is seen as generally consistent with the auxiliary data set in both time and space. From the spatial evolution of the angular component of the spectra, it is possible to project back to an apparent remote storm source that is also consistent with the storm location via GOES satellite imagery. The data provide compelling evidence that the spatial evolution of SAR ocean wave spectra can be a useful tool in global ocean wave monitoring and forecasting.
Contribution to the study of turbulence spectra
NASA Technical Reports Server (NTRS)
Dumas, R.
1979-01-01
An apparatus suitable for turbulence measurement between ranges of 1 to 5000 cps and from 6 to 16,000 cps was developed and is described. Turbulence spectra downstream of the grills were examined with reference to their general characteristics, their LF qualities, and the effects of periodic turbulence. Medium and HF are discussed. Turbulence spectra in the boundary layers are similarly examined, with reference to their fluctuations at right angles to the wall, and to lateral fluctuations. Turbulence spectra in a boundary layer with suction to the wall is discussed. Induced turbulence, and turbulence spectra at high Reynolds numbers. Calculations are presented relating to the effect of filtering on the value of the correlations in time and space.
NASA Astrophysics Data System (ADS)
Casas-Castillo, M. Carmen; Rodríguez-Solà, Raúl; Navarro, Xavier; Russo, Beniamino; Lastra, Antonio; González, Paula; Redaño, Angel
2016-11-01
The fractal behavior of extreme rainfall intensities registered between 1940 and 2012 by the Retiro Observatory of Madrid (Spain) has been examined, and a simple scaling regime ranging from 25 min to 3 days of duration has been identified. Thus, an intensity-duration-frequency (IDF) master equation of the location has been constructed in terms of the simple scaling formulation. The scaling behavior of probable maximum precipitation (PMP) for durations between 5 min and 24 h has also been verified. For the statistical estimation of the PMP, an envelope curve of the frequency factor (k m ) based on a total of 10,194 station-years of annual maximum rainfall from 258 stations in Spain has been developed. This curve could be useful to estimate suitable values of PMP at any point of the Iberian Peninsula from basic statistical parameters (mean and standard deviation) of its rainfall series.
NASA Astrophysics Data System (ADS)
Arce, Julio Cesar
This work focuses on time-dependent quantum theory and methods for the study of the spectra and dynamics of atomic and molecular systems. Specifically, we have addressed the following two problems: (1) Development of a time-dependent spectral method for the construction of spectra of simple quantum systems. This includes the calculation of eigenenergies, the construction of bound and continuum eigenfunctions, and the calculation of photo cross-sections. Computational applications include the quadrupole photoabsorption spectra and dissociation cross-sections of molecular hydrogen from various vibrational states in its ground electronic potential-energy curve. This method is seen to provide an advantageous alternative, both from the computational and conceptual point of view, to existing standard methods. (2) Explicit time-dependent formulation of photoabsorption processes -- Analytical solutions of the time-dependent Schrodinger equation are constructed and employed for the calculation of probability densities, momentum distributions, fluxes, transition rates, expectation values and correlation functions. These quantities are seen to establish the link between the dynamics and the calculated, or measured, spectra and cross-sections, and to clarify the dynamical nature of the excitation, transition and ejection processes. Numerical calculations on atomic and molecular hydrogen corroborate and complement the previous results, allowing the identification of different regimes during the photoabsorption process.
NASA Astrophysics Data System (ADS)
Arce, Julio Cesar
1992-01-01
This work focuses on time-dependent quantum theory and methods for the study of the spectra and dynamics of atomic and molecular systems. Specifically, we have addressed the following two problems: (i) Development of a time-dependent spectral method for the construction of spectra of simple quantum systems--This includes the calculation of eigenenergies, the construction of bound and continuum eigenfunctions, and the calculation of photo cross-sections. Computational applications include the quadrupole photoabsorption spectra and dissociation cross-sections of molecular hydrogen from various vibrational states in its ground electronic potential -energy curve. This method is seen to provide an advantageous alternative, both from the computational and conceptual point of view, to existing standard methods. (ii) Explicit time-dependent formulation of photoabsorption processes --Analytical solutions of the time-dependent Schrodinger equation are constructed and employed for the calculation of probability densities, momentum distributions, fluxes, transition rates, expectation values and correlation functions. These quantities are seen to establish the link between the dynamics and the calculated, or measured, spectra and cross-sections, and to clarify the dynamical nature of the excitation, transition and ejection processes. Numerical calculations on atomic and molecular hydrogen corroborate and complement the previous results, allowing the identification of different regimes during the photoabsorption process.
National Institute of Standards and Technology Data Gateway
SRD 78 NIST Atomic Spectra Database (ASD) (Web, free access) This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The NIST Atomic Spectroscopy Data Center has carried out these critical compilations.
NASA Astrophysics Data System (ADS)
Cecchet, F.; Lis, D.; Caudano, Y.; Mani, A. A.; Peremans, A.; Champagne, B.; Guthmuller, J.
2012-03-01
The knowledge of the first hyperpolarizability tensor elements of molecular groups is crucial for a quantitative interpretation of the sum frequency generation (SFG) activity of thin organic films at interfaces. Here, the SFG response of the terminal methyl group of a dodecanethiol (DDT) monolayer has been interpreted on the basis of calculations performed at the density functional theory (DFT) level of approximation. In particular, DFT calculations have been carried out on three classes of models for the aliphatic chains. The first class of models consists of aliphatic chains, containing from 3 to 12 carbon atoms, in which only one methyl group can freely vibrate, while the rest of the chain is frozen by a strong overweight of its C and H atoms. This enables us to localize the probed vibrational modes on the methyl group. In the second class, only one methyl group is frozen, while the entire remaining chain is allowed to vibrate. This enables us to analyse the influence of the aliphatic chain on the methyl stretching vibrations. Finally, the dodecanethiol (DDT) molecule is considered, for which the effects of two dielectrics, i.e. n-hexane and n-dodecane, are investigated. Moreover, DDT calculations are also carried out by using different exchange-correlation (XC) functionals in order to assess the DFT approximations. Using the DFT IR vectors and Raman tensors, the SFG spectrum of DDT has been simulated and the orientation of the methyl group has then been deduced and compared with that obtained using an analytical approach based on a bond additivity model. This analysis shows that when using DFT molecular properties, the predicted orientation of the terminal methyl group tends to converge as a function of the alkyl chain length and that the effects of the chain as well as of the dielectric environment are small. Instead, a more significant difference is observed when comparing the DFT-based results with those obtained from the analytical approach, thus indicating
IR SPECTRA BY DFT FOR GLUCOSE AND ITS EPIMERS: A COMPARISON BETWEEN VACUUM AND SOLVATED SPECTRA
Technology Transfer Automated Retrieval System (TEKTRAN)
Infrared spectra were calculated for the low energy geometry optimized structures of glucose and all of its epimers, at B3LYP/6-311++G** level of theory. Calculations were performed both in vacuo and using the COSMO solvation method. Frequencies, zero point energies, enthalpies, entropies, and rel...
GAMMA-RAY BURST SPECTRA AND SPECTRAL CORRELATIONS FROM SUB-PHOTOSPHERIC COMPTONIZATION
Chhotray, Atul; Lazzati, Davide
2015-04-01
One of the most important unresolved issues in gamma-ray burst (GRB) physics is the origin of the prompt gamma-ray spectrum. Its general non-thermal character and the softness in the X-ray band remain unexplained. We tackle these issues by performing Monte Carlo simulations of radiation–matter interactions in a scattering dominated photon–lepton plasma. The plasma—initially in equilibrium—is driven to non-equilibrium conditions by a sudden energy injection in the lepton population, mimicking the effect of a shock wave or the dissipation of magnetic energy. Equilibrium restoration occurs due to an energy exchange between the photons and leptons. While the initial and final equilibrium spectra are thermal, the transitional photon spectra are characterized by non-thermal features such as power-law tails, high energy bumps, and multiple components. Such non-thermal features are observed at infinity if the dissipation occurs at small to moderate optical depths, and the spectrum is released before thermalization is complete. We model the synthetic spectra with a Band function and show that the resulting spectral parameters are similar to observations for a frequency range of 2–3 orders of magnitude around the peak. In addition, our model predicts correlations between the low-frequency photon index and the peak frequency as well as between the low- and high-frequency indices. We explore baryon and pair-dominated fireballs and reach the conclusion that baryonic fireballs are a better model for explaining the observed features of GRB spectra.
Interpretation of Nitroindolinospirobenzothiopyran Vibrational Spectra
NASA Astrophysics Data System (ADS)
Gladkov, L. L.; Khamchukov, Yu. D.; Lyubimov, A. V.
2016-05-01
The structures of four possible stereoisomers of the closed form of photochromic nitroindolinospirobenzothiopyran (NISTP) {1',3'-dihydro-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzothiopyran-2,2'-(2H)-indoline]} were determined by the DFT method. The geometry of the most stable isomer was defined. Nitro-substitution changes mainly the lengths of bonds formed by S and N with spiro-atom Cs. According to the calculations, the CsS bond changes most and lengthens by 0.019 Å. It is shown that the S atom has large displacement amplitudes in normal modes assigned to Raman lines at 230, 285, 360, and 575 cm-1 and weak IR bands at 467 and 577 cm-1. Oscillations involving the nitro group are very active in Raman and IR spectra. Their frequencies are slightly lower than similar frequencies of nitrobenzene and nitroindolinospirobenzopyran, indicating a higher degree of vibrational coupling of the NO2 group with the NISTP molecular skeleton.
Quadrupolar Echo Spectra of the Tunneling CD 3Group
NASA Astrophysics Data System (ADS)
Olejniczak, Z.; Detken, A.; Manz, B.; Haeberlen, U.
Deuteron NMR spectra of both single crystal and powder samples of acetylsalicylic acid-CD 3were measured using the quadrupolar-echo technique. The experiments were done in the temperature range 17-100 K, with a special emphasis on the range 20- 30 K, in which the observable tunneling frequency decreases rapidly from its low-temperature value of 2.7 down to 1.2 MHz. In the tunneling regime, modulations of the line intensities and phases as a function of the echo time τ are observed in the single-crystal spectra. The modulation frequency is equal to the orientation-dependent displacement of the inner satellite pairs (α lines) from the Larmor frequency. These effects were confirmed in numerical simulations and fully explain the phase-modulation effects observed previously in quadrupolar-echo spectra of methyl-deuterated methanol and para-xylene guest molecules in some inclusion compounds. By measuring the temperature and orientation dependence of the quadrupolar lineshapes, it was found that the echo spectra are more sensitive to the value of the tunneling frequency than the spectra obtained from the free induction decay. It is pointed out that, because of the modulation effects, special care must be taken when structural parameters are to be extracted from quadrupolar-echo spectra, in particular from spectra of powder samples.
Evolution of Fourier spectra through interplanetary shocks
NASA Astrophysics Data System (ADS)
Pitna, Alexander; Safrankova, Jana; Nemecek, Zdenek; Nemec, Frantisek; Goncharov, Oleksandr
2014-05-01
Well established nearly isothermic solar wind expansion requires an additional heating. A dissipation of large scale variations of the solar wind kinetic energy into the thermal energy via turbulence cascades is thought to be an important source of this heating, although the exact mechanism is yet to be found. For this reason, the turbulence in the solar wind is a subject of extensive theoretical and experimental studies on different time scales ranging from years to minutes. The frequency spectrum of magnetic field fluctuations can be divided into several domains differing by spectral indices - the lowest frequencies are controlled by the solar activity, MHD activity shapes the spectrum at higher (up to 0.1 Hz) frequencies, whereas the ion and electron kinetic effects dominate at the high frequency end of the spectra. Interplanetary shocks of various origins are a part of solar wind turbulence naturally occurring in the solar wind and the BMSW instrument onboard the Spektr-R spacecraft has detected tens of them in course of the 2011-2013 years. Based on its high-time resolution of the ion flux, density and velocity measurements reaching 31 ms, we study an evolution of the frequency spectra on MHD and kinetic scales across fast forward low Mach number shocks. We have found that the power of downstream fluctuations rises by an order of magnitude in a broad range of frequencies independently of its upstream value but the slope of the spectrum on the kinetic scale (≡3-8 Hz) has been found to be statistically steeper downstream than upstream of the shock. The time needed to a full relaxation to the pre-shock spectral shape is as long as several hours. A combination of the ion flux power spectra obtained by BMSW with fast magnetic field observations of other spacecraft enhances our understanding of dissipation mechanisms.
Terahertz absorption spectra of highly energetic chemicals
NASA Astrophysics Data System (ADS)
Slingerland, E. J.; Vallon, M. K.; Jahngen, E. G. E.; Giles, R. H.; Goyette, T. M.
2010-04-01
Research into absorption spectra is useful for detecting chemicals in the field. Each molecule absorbs a set of specific frequencies, which are dependent on the molecule's structure. While theoretical models are available for predicting the absorption frequencies of a particular molecule, experimental measurements are a more reliable method of determining a molecule's actual absorption behavior. The goal of this research is to explore chemical markers (absorption frequencies) that can be used to identify highly energetic molecules of interest to the remote sensing community. Particular attention was paid to the frequency ranges located within the terahertz transmission windows of the atmosphere. In addition, theoretical derivations, with the purpose of calculating the detection limits of such chemicals, will also be presented.
Natural broadening in the quantum emission spectra of higher-dimensional Schwarzschild black holes
NASA Astrophysics Data System (ADS)
Hod, Shahar
2017-01-01
Following an intriguing heuristic argument of Bekenstein, many researches have suggested during the last four decades that quantized black holes may be characterized by discrete radiation spectra. Bekenstein and Mukhanov (BM) have further argued that the emission spectra of quantized (3 +1 )-dimensional Schwarzschild black holes are expected to be sharp in the sense that the characteristic natural broadening δ ω of the black-hole radiation lines, as deduced from the quantum time-energy uncertainty principle, is expected to be much smaller than the characteristic frequency spacing Δ ω =O (TBH/ℏ) between adjacent black-hole quantum emission lines. It is of considerable physical interest to test the general validity of the interesting conclusion reached by BM regarding the sharpness of the Schwarzschild black-hole quantum radiation spectra. To this end, in the present paper we explore the physical properties of the expected radiation spectra of quantized (D +1 )-dimensional Schwarzschild black holes. In particular, we analyze the functional dependence of the characteristic dimensionless ratio ζ (D )≡δ ω /Δ ω on the number D +1 of spacetime dimensions. Interestingly, it is proved that the dimensionless physical parameter ζ (D ), which characterizes the sharpness of the black-hole quantum emission spectra, is an increasing function of D . In particular, we prove that the quantum emission lines of (D +1 )-dimensional Schwarzschild black holes in the regime D ≳10 are characterized by the dimensionless ratio ζ (D )≳1 and are therefore effectively blended together. The results presented in this paper thus suggest that, even if the underlying energy spectra of quantized (D +1 )-dimensional Schwarzschild black holes are fundamentally discrete, as argued by many authors, the quantum phenomenon of natural broadening is expected to smear the characteristic emission spectra of these higher-dimensional black holes into a continuum.
Jet Signatures in the Spectra of Accreting Black Holes
NASA Astrophysics Data System (ADS)
O' Riordan, Michael; Pe'er, Asaf; McKinney, Jonathan C.
2016-03-01
Jets are observed as radio emission in active galactic nuclei and during the low/hard state in X-ray binaries (XRBs), but their contribution at higher frequencies has been uncertain. We study the dynamics of jets in XRBs using the general-relativistic magnetohydrodynamic code HARM. We calculate the high-energy spectra and variability properties using a general-relativistic radiative transport code based on grmonty. We find the following signatures of jet emission: (i) a significant γ-ray peak above ˜1022 Hz, (ii) a break in the optical/UV spectrum, with a change from ν {L}ν ˜ {ν }0 to ν {L}ν ˜ ν , followed by another break at higher frequencies where the spectrum roughly returns to ν {L}ν ˜ {ν }0, and (iii) a pronounced synchrotron peak near or below ˜1014 Hz indicates that a significant fraction of any observed X-ray emission originates in the jet. We investigate the variability during a large-scale magnetic field inversion in which the Blandford-Znajek (BZ) jet is quenched and a new transient hot reconnecting plasmoid is launched by the reconnecting field. The ratio of the γ-rays to X-rays changes from {L}γ /{L}{{X}}\\gt 1 in the BZ jet to {L}γ /{L}{{X}}\\lt 1 during the launching of the transient plasmoid.
Predicting Infrared Spectra of Nerve Agents Using Density Functional Theory
NASA Astrophysics Data System (ADS)
Zhang, Y.-P.; Wang, H.-T.; Zheng, W.-P.; Sun, C.; Bai, Y.; Guo, X.-D.; Sun, H.
2016-09-01
Vibration frequencies of four nerve agents and two simulators are calculated using B3LYP coupled with ten basis sets. To evaluate the accuracy of calculated spectra, root mean square error (RMSE) and weighted cross-correlation average (WCCA) are considered. The evaluation shows that B3LYP/6-311+g(d,p) performs best in predicting infrared spectra, and polarization functions are found to be more important than diffusion functions in spectra simulation. Moreover, B3LYP calculation underestimates frequencies related to the P atom. The WCCA metric derives 1.008 as a unique scaling factor for calculated frequencies. The results indicate that the WCCA metric can identify six agents based on calculated spectra.
Observation of exponential spectra and Lorentzian pulses in the TJ-K stellarator
NASA Astrophysics Data System (ADS)
Hornung, G.; Nold, B.; Maggs, J. E.; Morales, G. J.; Ramisch, M.; Stroth, U.
2011-08-01
An experimental investigation of the low-frequency density fluctuations in the plasma edge region of the TJ-K stellarator [N. Krause et al., Rev. Sci. Inst. 73, 3474 (2002)] finds that the ensemble-averaged frequency spectra exhibit a near exponential frequency dependence whose origin can be traced to individual pulses having a Lorentzian temporal shape. Similar features have been previously observed [D. C. Pace et al., Phys. Plasmas 15, 122304 (2008)] in a linear magnetized device under conditions in which cross-field pressure gradients are present. The reported observation of such features within the turbulent environment of a toroidal confinement device provides support for the conjecture that the underlying processes are a general feature of pressure gradients. Also presented is the magnetic field strength dependence of the pulse widths and the waiting time distribution between pulses.
NASA Technical Reports Server (NTRS)
2004-01-01
The color image on the lower left shows a rock outcrop at Meridiani Planum, Mars. This image was taken by the panoramic camera on the Mars Exploration Rover Opportunity, looking north, and was acquired on the 4th sol, or martian day, of the rover's mission (Jan. 27, 2004). The yellow box outlines an area detailed in the top left image, which is a monochrome (single filter) image from the rover's panoramic camera. The top image uses solid colors to show several regions on or near the rock outcrop from which spectra were extracted: the dark soil above the outcrop (yellow), the distant horizon surface (aqua), a bright rock in the outcrop (green), a darker rock in the outcrop (red), and a small dark cobblestone (blue). Spectra from these regions are shown in the plot to the right.
On optimization of absorption-dispersion spectra
NASA Astrophysics Data System (ADS)
Hawranek, J. P.; Grabska, J.; Beć, K. B.
2016-12-01
A modified approach to the analysis of spectra of the complex electric permittivity of liquids in the Infrared region is presented. These spectra are derived from experimental spectra of the complex refractive index. Subsequently they are used to determine important secondary quantities, e.g. spectra of complex molecular polarizabilities and an integral property - the molar vibrational polarization. The accuracy of these quantities depends essentially on the accuracy of both components of the complex electric permittivity spectrum. In the proposed procedure, the spectra of the complex electric permittivity are approximated using the Classical Damped Harmonic Oscillator (CDHO) model for the description of individual bandshapes. The CDHO model defines both the real and imaginary part of the complex permittivity. The fitting procedure includes a simultaneous optimization of both the real and imaginary parts of the complex permittivity spectrum. A comparison of absorption-only curve fitting and the novel absorption-dispersion double curve fitting is presented; advantages of the new approach in accuracy, reliability and convergence time are pointed out. Due to the complexity of the problem, the choice was restricted to non-gradient methods of optimization. The performance of several gradientless algorithms was tested. Among numerous procedures the Powell General Least Squares Method Without Derivatives was found to be the most efficient. The reliability of obtained results of the band separatiovn process was tested on several simulated spectra of increasing complexity. The applicability of the developed approach to the analysis of exemplary experimental data was evaluated and discussed.
NASA Technical Reports Server (NTRS)
1997-01-01
These IMP spectra show the characteristics of the rock surface measured by the Alpha Proton X-Ray Spectrometer (blue), the soil trapped in pits on the rock surface (red), and the deposit of bright drift on the top of the rock. The area measured by the APXS has the properties expected for nearly unweathered igneous rock, and the soil trapped in the pits is intermediate to the unweathered rock and the highly weathered drift material.
A nonlinear generalization of spectral Granger causality.
He, Fei; Wei, Hua-Liang; Billings, Stephen A; Sarrigiannis, Ptolemaios G
2014-06-01
Spectral measures of linear Granger causality have been widely applied to study the causal connectivity between time series data in neuroscience, biology, and economics. Traditional Granger causality measures are based on linear autoregressive with exogenous (ARX) inputs models of time series data, which cannot truly reveal nonlinear effects in the data especially in the frequency domain. In this study, it is shown that the classical Geweke's spectral causality measure can be explicitly linked with the output spectra of corresponding restricted and unrestricted time-domain models. The latter representation is then generalized to nonlinear bivariate signals and for the first time nonlinear causality analysis in the frequency domain. This is achieved by using the nonlinear ARX (NARX) modeling of signals, and decomposition of the recently defined output frequency response function which is related to the NARX model.
Beat frequency interference pattern characteristics study
NASA Technical Reports Server (NTRS)
Ott, J. H.; Rice, J. S.
1981-01-01
The frequency spectra and corresponding beat frequencies created by the relative motions between multiple Solar Power Satellites due to solar wind, lunar gravity, etc. were analyzed. The results were derived mathematically and verified through computer simulation. Frequency spectra plots were computer generated. Detailed computations were made for the seven following locations in the continental US: Houston, Tx.; Seattle, Wa.; Miami, Fl.; Chicago, Il.; New York, NY; Los Angeles, Ca.; and Barberton, Oh.
Pulsars: observations of spectra.
Goldstein, R M
1968-07-05
Dynamic spectrograms of two of the recently discovered pulsating radio sources have been obtained. The data provide the instantaneous spectrum and the time-frequency history of the signals over a bandwidth of 3 megahertz.
THE SPITZER ATLAS OF STELLAR SPECTRA (SASS)
Ardila, David R.; Van Dyk, Schuyler D.; Makowiecki, Wojciech; Stauffer, John; Rho, Jeonghee; Fajardo-Acosta, Sergio; Hoard, D. W.; Wachter, Stefanie; Song, Inseok
2010-12-15
We present the Spitzer Atlas of Stellar Spectra, which includes 159 stellar spectra (5-32 {mu}m; R {approx} 100) taken with the Infrared Spectrograph on the Spitzer Space Telescope. This Atlas gathers representative spectra of a broad section of the Hertzsprung-Russell diagram, intended to serve as a general stellar spectral reference in the mid-infrared. It includes stars from all luminosity classes, as well as Wolf-Rayet (WR) objects. Furthermore, it includes some objects of intrinsic interest, such as blue stragglers and certain pulsating variables. All of the spectra have been uniformly reduced, and all are available online. For dwarfs and giants, the spectra of early-type objects are relatively featureless, characterized by the presence of hydrogen lines in A spectral types. Besides these, the most noticeable photospheric features correspond to water vapor and silicon monoxide in late-type objects and methane and ammonia features at the latest spectral types. Most supergiant spectra in the Atlas present evidence of circumstellar gas and/or dust. The sample includes five M supergiant spectra, which show strong dust excesses and in some cases polycyclic aromatic hydrocarbon features. Sequences of WR stars present the well-known pattern of lines of He I and He II, as well as forbidden lines of ionized metals. The characteristic flat-top shape of the [Ne III] line is evident even at these low spectral resolutions. Several Luminous Blue Variables and other transition stars are present in the Atlas and show very diverse spectra, dominated by circumstellar gas and dust features. We show that the [8]-[24] Spitzer colors (IRAC and MIPS) are poor predictors of spectral type for most luminosity classes.
Electrical spectra of undisturbed soil from a crop rotation study
Technology Transfer Automated Retrieval System (TEKTRAN)
Soil permittivity can be determined across a range of frequencies, but little is known about how the factors derived from the frequency spectra are related to soil pore structure or crop management. The purpose of this study was to test the use of a 12-wire, quasi-coaxial probe for determining soil ...
Radial Distribution of Electron Spectra from High-Energy Ions
NASA Technical Reports Server (NTRS)
Cucinotta, Francis A.; Katz, Robert; Wilson, John W.
1998-01-01
The average track model describes the response of physical and biological systems using radial dose distribution as the key physical descriptor. We report on an extension of this model to describe the average distribution of electron spectra as a function of radial distance from an ion. We present calculations of these spectra for ions of identical linear energy transfer (LET), but dissimilar charge and velocity to evaluate the differences in electron spectra from these ions. To illustrate the usefulness of the radial electron spectra for describing effects that are not described by electron dose, we consider the evaluation of the indirect events in microdosimetric distributions for ions. We show that folding our average electron spectra model with experimentally determined frequency distributions for photons or electrons provides a good representation of radial event spectra from high-energy ions in 0.5-2 micrometer sites.
Simulation of dielectric spectra of erythrocytes with various shapes
NASA Astrophysics Data System (ADS)
Asami, Koji
2009-07-01
Dielectric spectra of erythrocyte suspensions were numerically simulated over a frequency range from 1 kHz to 100 MHz to study the effects of erythrocyte shape on the dielectric spectra. First, a biconcave-discoid model for normal erythrocytes or discocytes was compared with an equivalent oblate spheroid model. The two models showed similar dielectric spectra to each other, suggesting that the oblate spheroid model can be approximately used for discocytes. Second, dielectric spectra were simulated for discocytes deformed by osmotic cell swelling. The deformation resulted in the increase in relaxation intensity and the sharpening of spectrum shape. Finally, dielectric spectra were simulated for echinocytes, stomatocytes and sickle cells that are induced by chemical agents and diseases. The dielectric spectra of echinocytes and stomatocytes were similar to each other, being distinguishable from that of discocytes and quite different from that of sickle cells.
A novel computational method for comparing vibrational circular dichroism spectra.
Shen, Jian; Zhu, Chengyue; Reiling, Stephan; Vaz, Roy
2010-08-01
A novel method, SimIR/VCD, for comparing experimental and calculated VCD (vibrational circular dichroism) spectra is developed, based on newly defined spectra similarities. With computationally optimized frequency scaling and shifting, a calculated spectrum can be easily identified to match an observed spectrum, which leads to an unbiased molecular chirality assignment. The time-consuming manual band-fitting work is greatly reduced. With (1S)-(-)-alpha-pinene as an example, it demonstrates that the calculated VCD similarity is correlated with VCD spectra matching quality and has enough sensitivity to identify variations in the spectra. The study also compares spectra calculated using different DFT methods and basis sets. Using this method should facilitate the spectra matching, reduce human error and provide a confidence measure in the chiral assignment using VCD spectroscopy.
Verma, Bhupesh; Mishra, Tarun Kumar; Balasubramaniam, Krishnan; Rajagopal, Prabhu
2014-03-01
The use of ultrasonic guided waves for the inspection of pipes with elbow and U-type bends has received much attention in recent years, but studies for more general bend angles which may also occur commonly, for example in cross-country pipes, are limited. Here, we address this topic considering a general bend angle φ, a more general mean bend radius R in terms of the wavelength of the mode studied and pipe thickness b. We use 3D Finite Element (FE) simulation to understand the propagation of fundamental axisymmetric L(0,2) mode across bends of different angles φ. The effect of the ratio of the mean bend radius to the wavelength of the mode studied, on the transmission and reflection of incident wave is also considered. The studies show that as the bend angle is reduced, a progressively larger extent of mode-conversion affects the transmission and velocity characteristics of the L(0,2) mode. However the overall message on the potential of guided waves for inspection and monitoring of bent pipes remains positive, as bends seem to impact mode transmission only to the extent of 20% even at low bend angles. The conclusions seem to be valid for different typical pipe thicknesses b and bend radii. The modeling approach is validated by experiments and discussed in light of physics of guided waves.
Sader, John E.; Yousefi, Morteza; Friend, James R.
2014-02-15
Thermal noise spectra of nanomechanical resonators are used widely to characterize their physical properties. These spectra typically exhibit a Lorentzian response, with additional white noise due to extraneous processes. Least-squares fits of these measurements enable extraction of key parameters of the resonator, including its resonant frequency, quality factor, and stiffness. Here, we present general formulas for the uncertainties in these fit parameters due to sampling noise inherent in all thermal noise spectra. Good agreement with Monte Carlo simulation of synthetic data and measurements of an Atomic Force Microscope (AFM) cantilever is demonstrated. These formulas enable robust interpretation of thermal noise spectra measurements commonly performed in the AFM and adaptive control of fitting procedures with specified tolerances.
Separating Peaks in X-Ray Spectra
NASA Technical Reports Server (NTRS)
Nicolas, David; Taylor, Clayborne; Wade, Thomas
1987-01-01
Deconvolution algorithm assists in analysis of x-ray spectra from scanning electron microscopes, electron microprobe analyzers, x-ray fluorescence spectrometers, and like. New algorithm automatically deconvolves x-ray spectrum, identifies locations of spectral peaks, and selects chemical elements most likely producing peaks. Technique based on similarities between zero- and second-order terms of Taylor-series expansions of Gaussian distribution and of damped sinusoid. Principal advantage of algorithm: no requirement to adjust weighting factors or other parameters when analyzing general x-ray spectra.
Hadron rapidity spectra within a hybrid model
NASA Astrophysics Data System (ADS)
Khvorostukhin, A. S.; Toneev, V. D.
2017-01-01
A 2-stage hybrid model is proposed that joins the fast initial state of interaction, described by the hadron string dynamics (HSD) model, to subsequent evolution of the expanding system at the second stage, treated within ideal hydrodynamics. The developed hybrid model is assigned to describe heavy-ion collisions in the energy range of the NICA collider under construction in Dubna. Generally, the model is in reasonable agreement with the available data on proton rapidity spectra. However, reproducing proton rapidity spectra, our hybrid model cannot describe the rapidity distributions of pions. The model should be improved by taking into consideration viscosity effects at the hydrodynamical stage of system evolution.
Four years of meteor spectra patrol
NASA Technical Reports Server (NTRS)
Harvey, G. A.
1974-01-01
The development of the NASA-Langley Research Center meteor spectra patrol is described in general terms. The recording of very faint meteors was made possible by three great strides in optical and photographic technology in the 1960's: (1) the availability of optical-grade fused silica at modest cost, (2) the development of large transmission gratings with high blaze efficiency, and (3) the development of a method for avoiding plate fogging due to background skylight, which consisted of using a photoelectric meteor detector which actuates the spectrograph shutter when a meteor occurs in the field. The classification scheme for meteor spectra developed by Peter M. Millman is described.
Adaptive filtering of Echelle spectra of distant Quasars
NASA Technical Reports Server (NTRS)
Priebe, A.; Liebscher, D.-E.; Lorenz, H.; Richter, G.-M.
1992-01-01
The study of the Ly alpha - forest of distant (approximately greater than 3) Quasars is an important tool in obtaining a more detailed picture of the distribution of matter along the line of sight and thus of the general distribution of matter in the Universe and is therefore of important cosmological significance. Obviously, this is one of the tasks where spectral resolution plays an important role. The spectra used were obtained with the EFOSC at the ESO 3.6m telescope. Applying for the data reduction the standard Echelle procedure, as it is implemented for instance in the MIDAS-package, one uses stationary filters (e.g. median) for noise and cosmic particle event reduction in the 2-dimensional Echelle image. These filters are useful if the spatial spectrum of the noise reaches essentially higher frequencies then the highest resolution features in the image. Otherwise the resolution in the data will be degraded and the spectral lines smoothed. However, in the Echelle spectra the highest resolution is already in the range of one or a few pixels and therefore stationary filtering means always a loss of resolution. An Echelle reduction procedure on the basis of a space variable filter described which recognizes the local resolution in the presence of noise and adapts to it is developed. It was shown that this technique leads to an improvement in resolution by a factor of 2 with respect to standard procedures.
FLUXEN portable equipment for direct X-ray spectra measurements
NASA Astrophysics Data System (ADS)
Aiello, S.; Bottigli, U.; Fauci, F.; Golosio, B.; Lo Presti, D.; Masala, G. L.; Oliva, P.; Raso, G.; Stumbo, S.; Tangaro, S.
2004-02-01
The proper use of imaging equipment in radiological units is based on an appropriate knowledge of the physical characteristics of the X-ray beam used. The FLUXEN PROJECT is working on a portable apparatus which, together with dedicated software, is able to perform an exact spectral reconstruction of the radiation produced in diagnostic X-ray tubes. The apparatus characterizes the energy spectrum of radiological tubes and also provides a measurement of the emitted flux. The acquisition system is based on a commercial CZT detector (3×3×2 mm 3), produced by AMPTEK, cooled by a Peltier cell, with a high efficiency in the diagnostic X-ray energy range and modified in the shaping electronics so as to obtain a faster response. The acquiring section lies on a NuDAQ I/O card with a sampling frequency of up to 20 MHz. The signal produced by the X-ray tube is wholly acquired and an off-line analysis is made so as to make possible an accurate recognition of pile-up events and a reconstruction of the emitted spectra. The reconstructed spectra of a General Electric Senographe DMR mammographic X-ray tube are shown.
Planck intermediate results. XLV. Radio spectra of northern extragalactic radio sources
NASA Astrophysics Data System (ADS)
Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Aller, H. D.; Aller, M. F.; Arnaud, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Burigana, C.; Calabrese, E.; Catalano, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombo, L. P. L.; Couchot, F.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gruppuso, A.; Gurwell, M. A.; Hansen, F. K.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Hildebrandt, S. R.; Hobson, M.; Hornstrup, A.; Hovatta, T.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Järvelä, E.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Max-Moerbeck, W.; Meinhold, P. R.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Mingaliev, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Nati, F.; Natoli, P.; Nieppola, E.; Noviello, F.; Novikov, D.; Novikov, I.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Ramakrishnan, V.; Rastorgueva-Foi, E. A.; S Readhead, A. C.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Richards, J. L.; Ristorcelli, I.; Rocha, G.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Savelainen, M.; Savini, G.; Scott, D.; Sotnikova, Y.; Stolyarov, V.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tammi, J.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tornikoski, M.; Tristram, M.; Tucci, M.; Türler, M.; Valenziano, L.; Valiviita, J.; Valtaoja, E.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wehrle, A. E.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.
2016-12-01
Continuum spectra covering centimetre to submillimetre wavelengths are presented for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37 GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at high frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.
2011-09-01
Transportation Services program with the Dragon capsule. (Credit: SpaceX /Chris Thompson) S p a c e c r a f t e n g in e e r in g spectra NRL...secondary payloads on board a Space Exploration Technologies ( SpaceX ), Inc., Falcon 9 launch vehicle. NRL’s nanosatellites are part of the CubeSat...Maryland. The primary payload launched aboard the SpaceX Falcon 9 was the Dragon capsule. Developed by SpaceX and sponsored by NASA’s Commercial Orbital
Determinations of Photon Spectra
1989-01-01
COVERED O14. DATE OF REPORT (Year, Month, Day) 115. PAGE COUNT THESIS/ftFROW*W FROM TO 1989 1 54 16. SUPPLEMENTARY NOTATION A ?RQVk;U kOR 3UB LIC RELEASE...IAW AFR 190- 1 ERNEST A. HAYGOOD, 1st Lt, USAF Executive Officer, Civilian Institution ProQrams 17. COSATI CODES 18. SUBJECT TERMS (Continue on...spectra from measurements obtained with a sodium iodide counting system. A response matrix is computed by combining photon cross sections with
Theoretical infrared spectra of some model polycyclic aromatic hydrocarbons - Effect of ionization
NASA Technical Reports Server (NTRS)
De Frees, D. J.; Miller, M. D.; Talbi, D.; Pauzat, F.; Ellinger, Y.
1993-01-01
In order to test the hypothesis of ionized PAHs as possible carriers of the UIR bands, we realized a computational exploration on selected PAHs of small dimension in order to identify which changes ionization would induce on their IR spectra. In this study we performed ab initio calculations of the spectra of neutral and positively ionized naphthalene, anthracene, and pyrene. The results are significantly important. The frequencies in the cations are slightly shifted with respect to the neutral species, but no general conclusion can be reached from the three molecules considered. By contrast, the relative intensities of most vibrations are strongly affected by ionization, leading to a much better agreement between the calculated CH/CC vibration intensity ratios and those deduced from observations.
NASA Astrophysics Data System (ADS)
Aguiar, Roberto; Rivas-Medina, Alicia; Caiza, Pablo; Quizanga, Diego
2017-03-01
The Metropolitan District of Quito is located on or very close to segments of reverse blind faults, Puengasí, Ilumbisí-La Bota, Carcelen-El Inca, Bellavista-Catequilla and Tangahuilla, making it one of the most seismically dangerous cities in the world. The city is divided into five areas: south, south-central, central, north-central and north. For each of the urban areas, elastic response spectra are presented in this paper, which are determined by utilizing some of the new models of the Pacific Earthquake Engineering Research Center (PEER) NGA-West2 program. These spectra are calculated considering the maximum magnitude that could be generated by the rupture of each fault segment, and taking into account the soil type that exists at different points of the city according to the Norma Ecuatoriana de la Construcción (2015). Subsequently, the recurrence period of earthquakes of high magnitude in each fault segment is determined from the physical parameters of the fault segments (size of the fault plane and slip rate) and the pattern of recurrence of type Gutenberg-Richter earthquakes with double truncation magnitude (Mmin and Mmax) is used.
Theoretical Studies of Molecular Spectra
NASA Technical Reports Server (NTRS)
McKay, Christopher (Technical Monitor); Freedman, Richard S.
2002-01-01
This summary describes the research activities of the principal investigator during the reporting period. The research includes spectroscopy, management of molecular databases, and generation of spectral line profiles and opacity data. The spectroscopy research includes oxygen broadening of nitric oxide (NO), analysis of CO2 spectra, analysis of HNO3 spectra, and analysis of CO spectra.
Distances in spaces of physical models: partition functions versus spectra
NASA Astrophysics Data System (ADS)
Cornelissen, Gunther; Kontogeorgis, Aristides
2017-01-01
We study the relation between convergence of partition functions (seen as general Dirichlet series) and convergence of spectra and their multiplicities. We describe applications to convergence in physical models, e.g., related to topology change and averaging in cosmology.
Andrews, Lester; Thanthiriwatte, K Sahan; Wang, Xuefeng; Dixon, David A
2013-07-15
Reactions of laser-ablated Th atoms with F2 produce ThF4 as the major product based on agreement with matrix spectra recorded of the vapor from the solid at 800-850 °C. Weaker higher-frequency bands at (567.2, 564.8), (575.9, 575.1), and (531.0, 528.4) cm(-1) in argon are assigned to ThF, ThF2 and ThF3, ThF3(F2) on the basis of their chemical behavior upon increasing reagent concentrations, annealing, and irradiation, the use of NF3, OF2, and HF as F-atom sources, and a comparison with frequencies calculated at the DFT/B3LYP and CCSD(T) levels with a large segmented + ECP basis set on Th and the aug-cc-pVTZ basis set on F. An additional broader band at 460 cm(-1) is assigned to the ThF5(-) anion. The trigonal-bipyramidal ThF5(-) anion (calculated electron detachment energy of 7.17 eV) increases at the expense of ThF3(F2) and F3(-) on full mercury arc irradiation. [ThF3(+)][F2(-)] is shown by calculations to be an ionic complex with a side-bound F2(-) subunit. This paper reports the first evidence for novel pentacoordinated thorium species including the unique [ThF3(+)][F2(-)] ionic radical-ion pair molecule and its electron-capture product, the very stable ThF5(-) anion.
NASA Astrophysics Data System (ADS)
Elliott, Ben M.; Sung, Keeyoon; Miller, Charles E.
2015-06-01
In this report, we extend our Fourier transform infrared (FT-IR) spectroscopy measurements of CO2 in the ν3 region (2200-2450 cm-1, 65-75 THz) to the 18O-, and 13C-substituted isotopologues, using the JPL Bruker IFS-125HR Fourier Transform Spectrometer (JPL-FTS). High quality (S/N ∼ 2000) spectra were obtained separately for each of the 18O-, and 13C-isotopically enriched samples. The absolute wavenumber accuracies were better than 3 × 10-6 cm-1 (∼100 kHz) for strong, isolated transitions, calibrated against the highest accuracy reported CO and 16O12C16O (626) frequency measurements. The JPL-FTS performance and calibration procedure is shown to be reliable and consistent, achievable through vigorous maintenance of the optical alignment and regular monitoring of its instrumental line shape function. Effective spectroscopic constant fits of the 00011 ← 00001 fundamental bands for 16O12C18O (628), 18O12C18O (828), and 16O13C16O (636) were obtained with RMS residuals of 2.9 × 10-6 cm-1, 2.8 × 10-6 cm-1, and 2.9 × 10-6 cm-1, respectively. The observed bands encompassed 79 lines over the Jmax range of P67/R67, 47 lines over P70/R62, and 60 lines over P70/R70 for 628, 828, and 636, respectively. These results complement our recent work on the 17O-enriched isotopologues (Elliott et al., 2014), providing additional high-quality frequency measurements for atmospheric remote sensing applications.
Solvent effect on the vibrational spectra of Carvedilol
NASA Astrophysics Data System (ADS)
Billes, Ferenc; Pataki, Hajnalka; Unsalan, Ozan; Mikosch, Hans; Vajna, Balázs; Marosi, György
2012-09-01
Carvedilol (CRV) is an important medicament for heart arrhythmia. The aim of this work was the interpretation of its vibrational spectra with consideration on the solvent effect. Infrared and Raman spectra were recorded in solid state as well in solution. The experimental spectra were evaluated using DFT quantum chemical calculations computing the optimized structure, atomic net charges, vibrational frequencies and force constants. The same calculations were done for the molecule in DMSO and aqueous solutions applying the PCM method. The calculated force constants were scaled to the experimentally observed solid state frequencies. The characters of the vibrational modes were determined by their potential energy distributions. Solvent effects on the molecular properties were interpreted. Based on these results vibrational spectra were simulated.
Solvent effect on the vibrational spectra of Carvedilol.
Billes, Ferenc; Pataki, Hajnalka; Unsalan, Ozan; Mikosch, Hans; Vajna, Balázs; Marosi, György
2012-09-01
Carvedilol (CRV) is an important medicament for heart arrhythmia. The aim of this work was the interpretation of its vibrational spectra with consideration on the solvent effect. Infrared and Raman spectra were recorded in solid state as well in solution. The experimental spectra were evaluated using DFT quantum chemical calculations computing the optimized structure, atomic net charges, vibrational frequencies and force constants. The same calculations were done for the molecule in DMSO and aqueous solutions applying the PCM method. The calculated force constants were scaled to the experimentally observed solid state frequencies. The characters of the vibrational modes were determined by their potential energy distributions. Solvent effects on the molecular properties were interpreted. Based on these results vibrational spectra were simulated.
Probability and Relative Frequency
NASA Astrophysics Data System (ADS)
Drieschner, Michael
2016-01-01
The concept of probability seems to have been inexplicable since its invention in the seventeenth century. In its use in science, probability is closely related with relative frequency. So the task seems to be interpreting that relation. In this paper, we start with predicted relative frequency and show that its structure is the same as that of probability. I propose to call that the `prediction interpretation' of probability. The consequences of that definition are discussed. The "ladder"-structure of the probability calculus is analyzed. The expectation of the relative frequency is shown to be equal to the predicted relative frequency. Probability is shown to be the most general empirically testable prediction.
NASA Astrophysics Data System (ADS)
Shorb, Justin Matthew
The first portion of this thesis describes an extension of work done in the Skinner group to develop an empirical frequency map for N-methylacetamide (NMA) in water. NMA is a peptide bond capped on either side by a methyl group and is therefore a common prototypical molecule used when studying complicated polypeptides and proteins. This amide bond is present along the backbone of every protein as it connects individual component amino acids. This amide bond also has a strong observable frequency in the IR due to the Amide-I mode (predominantly carbon-oxygen stretching motion). This project describes the simplification of the prior model for mapping the frequency of the Amide-I mode from the electric field due to the environment and develops a parallel implementation of this algorithm for use in larger biological systems, such as the trans-membrane portion of the tetrameric polypeptide bundle protein CD3zeta. The second portion of this thesis describes the development, implementation and evaluation of an online textbook within the context of a cohesive theoretical framework. The project begins by describing what is meant when discussing a digital textbook, including a survey of various types of digital media being used to deliver textbook-like content. This leads into the development of a theoretical framework based on constructivist pedagogical theory, hypertext learning theory, and chemistry visualization and representation frameworks. The implementation and design of ChemPaths, the general chemistry online text developed within the Chemistry Education Digital Library (ChemEd DL) is then described. The effectiveness of ChemPaths being used as a textbook replacement in an advanced general chemistry course is evaluated within the developed theoretical framework both qualitatively and quantitatively.
Radio frequency noise from clinical linear accelerators.
Burke, B; Lamey, M; Rathee, S; Murray, B; Fallone, B G
2009-04-21
There is a great deal of interest in image-guided radiotherapy (IGRT), and to advance the state of IGRT, an integrated linear accelerator-magnetic resonance (linac-MR) system has been proposed. Knowledge of the radiofrequency (RF) emissions near a linac is important for the design of appropriate RF shielding to facilitate the successful integration of these two devices. The frequency spectra of both electric and magnetic fields of RF emission are measured using commercially available measurement probes near the treatment couch in three clinical linac vaults with distinct physical layouts. The magnitude spectrum of the RF power emitted from these three linacs is then estimated. The electric field spectrum was also measured at several distances from the linac modulator in order to assess the effects of variations in spatial location in the treatment vault. A large fraction of RF power is emitted at frequencies below 5 MHz. However, the measured RF power at the Larmor frequency (8.5 MHz) of the proposed 0.2 T MR in the linac-MR (0.4-14.6 microW m(-2)) is still large enough to cause artifacts in MR images. Magnetron-based linacs generally emit much larger RF power than klystron-based linacs. In the frequency range of 1-50 MHz, only slight variation in the measured electric field is observed as a function of measurement position. This study suggests that the RF emissions are strong enough to cause image artifacts in MRI systems.
Laboratory spectra of C60 and related molecular structures
NASA Technical Reports Server (NTRS)
Janca, J.; Solc, M.; Vetesnik, M.
1994-01-01
The electronic spectra of fullerene structures in high frequency discharge are studied in the plasma chemistry laboratory of the Faculty of Science of Masaryk University in Brno. The ultraviolet and visual spectra are investigated in order to be compared with the diffuse interstellar bands and interpreted within the theory of quantum mechanics. The preliminary results of the study are presented here in the form of a poster.
Infrared spectra of lunar soils. [using a Michelson interferometer
NASA Technical Reports Server (NTRS)
Aronson, J. R.; Emslie, A. G.; Smith, E. M.
1979-01-01
Measured data obtained by Michelson interferometer spectrometer were stored in a computer file and smoothed by being passed forward and backward through a digital four-pole low pass filter. Infrared spectra of the 10 lunar samples are presented in the format of brightness temperature versus frequency. The mol % of feldspar, pyroxene, olivine, ilmenite and ferromagnetic silicate in each sample is presented in tables. The reflectance spectra of ilmenite and enstatite are shown in graphs.
NASA Technical Reports Server (NTRS)
Poole, L. R.
1976-01-01
An initial attempt was made to verify the Langley Research Center and Virginia Institute of Marine Science mid-Atlantic continental-shelf wave refraction model. The model was used to simulate refraction occurring during a continental-shelf remote sensing experiment conducted on August 17, 1973. Simulated wave spectra compared favorably, in a qualitative sense, with the experimental spectra. However, it was observed that most of the wave energy resided at frequencies higher than those for which refraction and shoaling effects were predicted, In addition, variations among the experimental spectra were so small that they were not considered statistically significant. In order to verify the refraction model, simulation must be performed in conjunction with a set of significantly varying spectra in which a considerable portion of the total energy resides at frequencies for which refraction and shoaling effects are likely.
Specific heat of multifractal energy spectra
NASA Astrophysics Data System (ADS)
da Silva, L. R.; Vallejos, R. O.; Tsallis, C.; Mendes, R. S.; Roux, S.
2001-07-01
Motivated by the self-similar character of energy spectra demonstrated for quasicrystals, we investigate the case of multifractal energy spectra, and compute the specific heat associated with simple archetypal forms of multifractal sets as generated by iterated maps. We considered the logistic map and the circle map at their threshold to chaos. Both examples show nontrivial structures associated with the scaling properties of their respective chaotic attractors. The specific heat displays generically log-periodic oscillations around a value that characterizes a single exponent, the ``fractal dimension,'' of the distribution of energy levels close to the minimum value set to 0. It is shown that when the fractal dimension and the frequency of log oscillations of the density of states are large, the amplitude of the resulting log oscillation in the specific heat becomes much smaller than the log-periodic oscillation measured on the density of states.
A simple model for strong ground motions and response spectra
Safak, Erdal; Mueller, Charles; Boatwright, John
1988-01-01
A simple model for the description of strong ground motions is introduced. The model shows that response spectra can be estimated by using only four parameters of the ground motion, the RMS acceleration, effective duration and two corner frequencies that characterize the effective frequency band of the motion. The model is windowed band-limited white noise, and is developed by studying the properties of two functions, cumulative squared acceleration in the time domain, and cumulative squared amplitude spectrum in the frequency domain. Applying the methods of random vibration theory, the model leads to a simple analytical expression for the response spectra. The accuracy of the model is checked by using the ground motion recordings from the aftershock sequences of two different earthquakes and simulated accelerograms. The results show that the model gives a satisfactory estimate of the response spectra.
Yang, Meng-li; Fu, Wei; Wang, Bao-hua; Zhang, Ya-qian; Huang, Xiao-rong; Niu, Hu-jie
2015-03-01
The silicate nickel ores developed in the lateritic nickel deposit, from Kolonodale, Sulawesi Island, Indonesia, and Yuanjiang, Yunnan province, China, were selected for the present study. The X-ray diffraction and Fourier infrared spectra were used to analyze the mineralogical attribute of laterite nickel ores from two different places. The results show that these two different silicate nickel ores have unique infrared spectra characteristics individually, which contributes to the ore classification. The silicate nickel ores from Kolonodale deposit, Indonesia, can be classified as the serpentine type, the montmorillonite + serpentine type, and the garnierite type. While, the silicate nickel ores from Yuanjiang deposit, China, can be classified as the serpentine type and the talc + serpentine type. Moreover, the mineral crystallinity of Yuanjiang nickel ores is generally better than Kolonodale nickel ores. According to the advantage of infrared absorption spectra in distinguishing mineral polytypes, it can be determined that lizardite is the main mineral type in the silicate nickel ores of the two deposits, and there is no obvious evidence of chrysotile and antigorite's existence. The characteristic of infrared absorption spectra also shows that frequency change of OH libration indicates Ni (Fe) replacing Mg in the serpentine type nickel-bearing mineral, that is, OH libration of serpentine moves to higher frequency, with the proportion of Ni (Fe) replacing Mg increasing.
Discriminating Dysarthria Type From Envelope Modulation Spectra
Liss, Julie M.; LeGendre, Sue; Lotto, Andrew J.
2013-01-01
Purpose Previous research demonstrated the ability of temporally based rhythm metrics to distinguish among dysarthrias with different prosodic deficit profiles (J. M. Liss et al., 2009). The authors examined whether comparable results could be obtained by an automated analysis of speech envelope modulation spectra (EMS), which quantifies the rhythmicity of speech within specified frequency bands. Method EMS was conducted on sentences produced by 43 speakers with 1 of 4 types of dysarthria and healthy controls. The EMS consisted of the spectra of the slow-rate (up to 10 Hz) amplitude modulations of the full signal and 7 octave bands ranging in center frequency from 125 to 8000 Hz. Six variables were calculated for each band relating to peak frequency and amplitude and relative energy above, below, and in the region of 4 Hz. Discriminant function analyses (DFA) determined which sets of predictor variables best discriminated between and among groups. Results Each of 6 DFAs identified 2–6 of the 48 predictor variables. These variables achieved 84%–100% classification accuracy for group membership. Conclusions Dysarthrias can be characterized by quantifiable temporal patterns in acoustic output. Because EMS analysis is automated and requires no editing or linguistic assumptions, it shows promise as a clinical and research tool. PMID:20643800
Interpreting Chromosome Aberration Spectra
NASA Technical Reports Server (NTRS)
Levy, Dan; Reeder, Christopher; Loucas, Bradford; Hlatky, Lynn; Chen, Allen; Cornforth, Michael; Sachs, Rainer
2007-01-01
Ionizing radiation can damage cells by breaking both strands of DNA in multiple locations, essentially cutting chromosomes into pieces. The cell has enzymatic mechanisms to repair such breaks; however, these mechanisms are imperfect and, in an exchange process, may produce a large-scale rearrangement of the genome, called a chromosome aberration. Chromosome aberrations are important in killing cells, during carcinogenesis, in characterizing repair/misrepair pathways, in retrospective radiation biodosimetry, and in a number of other ways. DNA staining techniques such as mFISH ( multicolor fluorescent in situ hybridization) provide a means for analyzing aberration spectra by examining observed final patterns. Unfortunately, an mFISH observed final pattern often does not uniquely determine the underlying exchange process. Further, resolution limitations in the painting protocol sometimes lead to apparently incomplete final patterns. We here describe an algorithm for systematically finding exchange processes consistent with any observed final pattern. This algorithm uses aberration multigraphs, a mathematical formalism that links the various aspects of aberration formation. By applying a measure to the space of consistent multigraphs, we will show how to generate model-specific distributions of aberration processes from mFISH experimental data. The approach is implemented by software freely available over the internet. As a sample application, we apply these algorithms to an aberration data set, obtaining a distribution of exchange cycle sizes, which serves to measure aberration complexity. Estimating complexity, in turn, helps indicate how damaging the aberrations are and may facilitate identification of radiation type in retrospective biodosimetry.
Database-Driven Analyses of Astronomical Spectra
NASA Astrophysics Data System (ADS)
Cami, Jan
2012-03-01
Spectroscopy is one of the most powerful tools to study the physical properties and chemical composition of very diverse astrophysical environments. In principle, each nuclide has a unique set of spectral features; thus, establishing the presence of a specific material at astronomical distances requires no more than finding a laboratory spectrum of the right material that perfectly matches the astronomical observations. Once the presence of a substance is established, a careful analysis of the observational characteristics (wavelengths or frequencies, intensities, and line profiles) allows one to determine many physical parameters of the environment in which the substance resides, such as temperature, density, velocity, and so on. Because of this great diagnostic potential, ground-based and space-borne astronomical observatories often include instruments to carry out spectroscopic analyses of various celestial objects and events. Of particular interest is molecular spectroscopy at infrared wavelengths. From the spectroscopic point of view, molecules differ from atoms in their ability to vibrate and rotate, and quantum physics inevitably causes those motions to be quantized. The energies required to excite vibrations or rotations are such that vibrational transitions generally occur at infrared wavelengths, whereas pure rotational transitions typically occur at sub-mm wavelengths. Molecular vibration and rotation are coupled though, and thus at infrared wavelengths, one commonly observes a multitude of ro-vibrational transitions (see Figure 13.1). At lower spectral resolution, all transitions blend into one broad ro-vibrational molecular band. The isotope. Molecular spectroscopy thus allows us to see a difference of one neutron in an atomic nucleus that is located at astronomical distances! Since the detection of the first interstellar molecules (the CH [21] and CN [14] radicals), more than 150 species have been detected in space, ranging in size from diatomic
Submillimeter Spectra of Low Temperature Gases and Mixtures
Wishnow, E H; Gush, H P; Halpern M; Ozier, I
2002-09-19
Submillimeter absorption spectra of nitrogen, nitrogen-argon mixtures, and methane have been measured using temperatures and pressures near to those found in the atmospheres of Titan and Saturn. The experiments show the spectral signature of dimers which will likely appear in far-infrared spectra of Titan that will be obtained by the Composite Infrared Spectrometer (CIRS) onboard the Cassini spacecraft. The recent CIRS spectrum of Jupiter shows far-infrared spectral lines of methane and the corresponding lines are observed in the laboratory. We are extending this work to lower frequencies using a new differential Michelson interferometer that operates over the frequency region 3-30 cm{sup -1}.
Submillimeter Spectra of Low Temperature Gases and Mixtures
NASA Technical Reports Server (NTRS)
Wishnow, E. H.; Gush, H. P.; Halpern, M.; Ozier, I.
2002-01-01
Submillimeter absorption spectra of nitrogen, nitrogen-argon mixtures, and methane have been measured using temperatures and pressures near to those found in the atmospheres of Titan and Saturn. The experiments show the spectral signature of dimers which will likely appear in far-infrared spectra of Titan that will be obtained by the Composite Infrared Spectrometer (CIS) onboard the Cassini spacecraft. The recent CIRS spectrum of Jupiter shows far-infrared spectral lines of methane and the corresponding lines are observed in the laboratory. We are extending this work to lower frequencies using a new differential Michelson interferometer that operates over the frequency region 3-30 1/cm..
Terahertz absorption spectra and potential energy distribution of liquid crystals.
Chen, Zezhang; Jiang, Yurong; Jiang, Lulu; Ma, Heng
2016-01-15
In this work, the terahertz (THz) absorption spectra of a set of nematic liquid crystals were studied using the density functional theories (DFT). An accurate assignment of the vibrational modes corresponding to absorption frequencies were performed using potential energy distribution (PED) in a frequency range of 0-3 THz. The impacts of different core structures on THz absorption spectra were discussed. The results indicate that scope of application must be considered in the LC-based THz device designing. This proposed work may give a useful suggestion on the design of novel liquid crystal material in THz wave.
Terahertz absorption spectra and potential energy distribution of liquid crystals
NASA Astrophysics Data System (ADS)
Chen, Zezhang; Jiang, Yurong; Jiang, Lulu; Ma, Heng
2016-01-01
In this work, the terahertz (THz) absorption spectra of a set of nematic liquid crystals were studied using the density functional theories (DFT). An accurate assignment of the vibrational modes corresponding to absorption frequencies were performed using potential energy distribution (PED) in a frequency range of 0-3 THz. The impacts of different core structures on THz absorption spectra were discussed. The results indicate that scope of application must be considered in the LC-based THz device designing. This proposed work may give a useful suggestion on the design of novel liquid crystal material in THz wave.
1989-12-15
New long-wavelength observations of Galactic supernova remnants ( SNRs ) at 30.9 and 57.5 MHz are used to derive detailed low-frequency radio spectra...for 32 SNRs . Of these, approximately two-thirds show turnovers at low frequencies, implying the presence of a widespread, but inhomogeneous, ionized... SNRs and to constrain the physical properties of the ionized gas responsible for the absorption. Three generally accepted ionized components of the
NASA Astrophysics Data System (ADS)
Hänsch, Theodor W.; Picqué, Nathalie
Much of modern research in the field of atomic, molecular, and optical science relies on lasers, which were invented some 50 years ago and perfected in five decades of intense research and development. Today, lasers and photonic technologies impact most fields of science and they have become indispensible in our daily lives. Laser frequency combs were conceived a decade ago as tools for the precision spectroscopy of atomic hydrogen. Through the development of optical frequency comb techniques,
Laboratory simulation of dust spectra
NASA Technical Reports Server (NTRS)
Allamandola, L. J.; Sandford, S. A.
1988-01-01
Laboratory studies of the IR spectra of interstellar dust are reviewed. Studies of the absorption spectra of dense molecular clouds are discussed, including methods to produce interstellar ice analogues, simulations of astronomical spectra, and IR absorption features caused by ices. Comparisons are made between observational and experimental results of interstellar dust studies. Also, the interstellar emission features associated with dusty regions exposed to UV radiation are examined, including bands related to PAHs and PAH-related materials. It is shown that interstellar spectra are more consistant with emission from free PAHs than with emission from particles.
NASA Astrophysics Data System (ADS)
Gayen, Saurabh; Behera, Surjyo; Bose, Shyamalendu
2006-03-01
The Raman spectra of a single-wall carbon nanotube (SWNT) consist of three types of modes; (i) the high frequency G-mode arising out of tangential oscillations of carbon atoms, (ii) D-mode due to the defects in the nanotube and (iii) the low frequency radial breathing mode (RBM) resulting out of radial oscillations of the carbon atoms. In this paper we theoretically investigate the effects of collective oscillations of electrons (plasmons) on the G and RBM modes in the Raman spectra of a filled and unfilled metallic SWNT. Inclusion of plasmon and the filling (rattler) atom produces four peaks in the Raman spectra in general. The positions and relative strengths of the Raman peaks [1] depend upon phonon frequencies of the nanotube and that of the filling atoms, the plasmon frequency, the strength of the electron-phonon interaction, strength of the interactions between the nanotube phonons and rattler phonon and radius of the nanotube [2]. Usually the intensity of the G-mode is higher than that of RBM. For heavier filling atoms the frequency of the rattler phonon is lower in value, which may broaden the peak to such an extent that it may disappear in the background spectrum altogether. 1.S.M. Bose et al., Physica B 351, 129 (2004) 2. S.M. Bose, S.Gayen and S. Behera, Phys. Rev. B 72, 153402 (2005).
Far-infrared spectra of acetanilide revisited
NASA Astrophysics Data System (ADS)
Spire, A.; Barthes, M.; Kellouai, H.; De Nunzio, G.
2000-03-01
A new investigation of the temperature dependence of the far-infrared spectra of acetanilide and some isotopomers is presented. Four absorption bands are considered at 31, 42, 64, and 80 cm-1, and no significant change of their integrated intensity is observed when reducing the temperature. The temperature induced frequency shift values and other properties of these bands are consistent with an assignment as anharmonic lattice phonons. These results rule out the assignment of the 64, 80, and 106 cm-1 bands as normal modes of the polaronic excitation, as previously suggested.
General interference law for nonstationary, separable optical fields.
Manea, Vladimir
2009-09-01
An approach to the theory of partial coherence for nonstationary optical fields is presented. Starting with a spectral representation, a favorable decomposition of the optical signals is discussed that supports a natural extension of the mathematical formalism. The coherence functions are redefined, but still as temporal correlation functions, allowing the obtaining of a more general form of the interference law for partially coherent optical signals. The general theory is applied in some relevant particular cases of nonstationary interference, namely, with quasi-monochromatic beams of different frequencies and with phase-modulated quasi-monochromatic beams of similar frequency spectra. All the results of the general treatment are reducible to the ones given in the literature for the case of stationary interference.
First dynamic spectra of stellar microwave flares
NASA Technical Reports Server (NTRS)
Bastian, T. S.; Bookbinder, J. A.
1987-01-01
The VLA has been used in the spectral-line mode at 1.4 GHz to obtain the first dynamic spectra of stellar sources other than the sun. Two very intense, highly circularly polarized, microwave outbursts were observed on the dMe flare star UV Cet, in addition to a slowly varying, unpolarized component. One outburst was purely left circularly polarized and showed no variations as a function of frequency across the 41 MHz band, whereas the other was as much as 70 percent right-circularly polarized and showed distinct variations with frequency. Although the slowly varying emission is probably due to incoherent gyrosynchrotron emission, the two flaring events are the result of coherent mechanisms. The coherent emission is interpreted in terms of plasma radiation and the cyclotron maser instability.
Catalogue of representative meteor spectra
NASA Astrophysics Data System (ADS)
Vojáček, V.; Borovička, J.; Koten, P.; Spurný, P.; Štork, R.
2016-01-01
We present a library of low-resolution meteor spectra that includes sporadic meteors, members of minor meteor showers, and major meteor showers. These meteors are in the magnitude range from +2 to -3, corresponding to meteoroid sizes from 1 mm to10 mm. This catalogue is available online at the CDS for those interested in video meteor spectra.
Projecting Spectra for Classroom Investigations.
ERIC Educational Resources Information Center
Sadler, Philip
1991-01-01
Describes an inexpensive spectrum projector that makes high-dispersion, high-efficiency diffraction gratings using a holographic process. Discusses classroom applications such as transmission spectra, absorption spectra, reflection characteristics of materials, color mixing, florescence and phosphorescence, and break up spectral colors. (MDH)
How to avoid misinterpretation of heart rate variability power spectra?
Cammann, Henning; Michel, Josef
2002-04-01
Spectral analysis of R-R Interval time series is increasingly used to determine periodic components of heart rate variability (HRV). Particular diagnostic relevance is assigned to a low-frequency (LF) component, associated with blood pressure regulation, and a high-frequency (HF) component, also referred to as respiratory sinus arrhythmia (RSA) in the HRV power spectra. Frequency ranges for parametrisation of power spectra have been defined for either component in numerous publications.Results obtained from examinations with standardised psychic load in which ECG and respiratory signal are continuously recorded and adequately processed have shown that the true individual frequency range of the HF component can be reliably determined only by means of characteristics of respiration (respiratory rate (RR), range and median value of RR, tidal depth). Respiratory rhythms are interindividually extremely differentiated and of individual-specific nature. In many cases LF and HF components may be totally superimposed on each other and, consequently, cannot be diagnostically evaluated.
Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores
Burris, Paul C.; Laage, Damien; Thompson, Ward H.
2016-05-20
Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this Paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D_{2}O is considered. An empirical mapping approach is used to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. Lastly, the simulated spectra indicate that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra.
Burris, Paul C; Laage, Damien; Thompson, Ward H
2016-05-21
Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D2O is considered. An empirical mapping approach is used to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. The simulated spectra indicates that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra.
Simulations of the infrared, Raman, and 2D-IR photon echo spectra of water in nanoscale silica pores
Burris, Paul C.; Laage, Damien; Thompson, Ward H.
2016-05-20
Vibrational spectroscopy is frequently used to characterize nanoconfined liquids and probe the effect of the confining framework on the liquid structure and dynamics relative to the corresponding bulk fluid. However, it is still unclear what molecular-level information can be obtained from such measurements. In this Paper, we address this question by using molecular dynamics (MD) simulations to reproduce the linear infrared (IR), Raman, and two-dimensional IR (2D-IR) photon echo spectra for water confined within hydrophilic (hydroxyl-terminated) silica mesopores. To simplify the spectra the OH stretching region of isotopically dilute HOD in D2O is considered. An empirical mapping approach is usedmore » to obtain the OH vibrational frequencies, transition dipoles, and transition polarizabilities from the MD simulations. The simulated linear IR and Raman spectra are in good general agreement with measured spectra of water in mesoporous silica reported in the literature. The key effect of confinement on the water spectrum is a vibrational blueshift for OH groups that are closest to the pore interface. The blueshift can be attributed to the weaker hydrogen bonds (H-bonds) formed between the OH groups and silica oxygen acceptors. Non-Condon effects greatly diminish the contribution of these OH moieties to the linear IR spectrum, but these weaker H-bonds are readily apparent in the Raman spectrum. The 2D-IR spectra have not yet been measured and thus the present results represent a prediction. Lastly, the simulated spectra indicate that it should be possible to probe the slower spectral diffusion of confined water compared to the bulk liquid by analysis of the 2D-IR spectra.« less
Analytic studies of dispersive properties of shear Alfvén and acoustic wave spectra in tokamaks
Chavdarovski, Ilija; Zonca, Fulvio
2014-05-15
The properties of the low frequency shear Alfvén and acoustic wave spectra in toroidal geometry are examined analytically and numerically considering wave particle interactions with magnetically trapped and circulating particles, using the theoretical model described in [I. Chavdarovski and F. Zonca, Plasma Phys. Controlled Fusion 51, 115001 (2009)] and following the framework of the generalized fishbone-like dispersion relation. Effects of trapped particles as well as diamagnetic effects on the frequencies and damping rates of the beta-induced Alfvén eigenmodes, kinetic ballooning modes and beta-induced Alfvén-acoustic eigenmodes are discussed and shown to be crucial to give a proper assessment of mode structure and stability conditions. Present results also demonstrate the mutual coupling of these various branches and suggest that frequency as well as mode polarization are crucial for their identification on the basis of experimental evidence.
Analytic studies of dispersive properties of shear Alfvén and acoustic wave spectra in tokamaks
NASA Astrophysics Data System (ADS)
Chavdarovski, Ilija; Zonca, Fulvio
2014-05-01
The properties of the low frequency shear Alfvén and acoustic wave spectra in toroidal geometry are examined analytically and numerically considering wave particle interactions with magnetically trapped and circulating particles, using the theoretical model described in [I. Chavdarovski and F. Zonca, Plasma Phys. Controlled Fusion 51, 115001 (2009)] and following the framework of the generalized fishbone-like dispersion relation. Effects of trapped particles as well as diamagnetic effects on the frequencies and damping rates of the beta-induced Alfvén eigenmodes, kinetic ballooning modes and beta-induced Alfvén-acoustic eigenmodes are discussed and shown to be crucial to give a proper assessment of mode structure and stability conditions. Present results also demonstrate the mutual coupling of these various branches and suggest that frequency as well as mode polarization are crucial for their identification on the basis of experimental evidence.
A New Approach for Resolution of Complex Tissue Impedance Spectra in Hearts
Barr, Roger C.
2014-01-01
This study was designed to test the feasibility of using sinusoidal approximation in combination with a new instrumentation approach to resolve complex impedance (uCI) spectra from heart preparations. To assess that feasibility, we applied stimuli in the 10–4000 Hz range and recorded potential differences (uPDs) in a four-electrode configuration that allowed identification of probe constants (Kp) during calibration that were in turn used to measure total tissue resistivity ρt from rabbit ventricular epicardium. Simultaneous acquisition of a signal proportional to the supplied current (Vstim) with uPD allowed identification of the V –I ratio needed for ρt measurement, as well as the phase shift from Vstim to uPD needed for uCI spectra resolution. Performance with components integrated to reduce noise in cardiac electrophysiologic experiments, in particular, and provide accurate electrometer-based measurements, in general, was first characterized in tests using passive loads. Load tests showed accurate uCI recovery with mean uPD SNRs between 101 and 103 measured with supplied currents as low as 10 nA. Comparable performance characteristics were identified during calibration of nine arrays built with 250 µm Ag/AgCl electrodes, with uCIs that matched analytic predictions and no apparent effect of frequency (F = 0.12, P = 0.99). The potential ability of parasitic capacitance in the presence of the electrode–electrolyte interface associated with the small sensors to influence the uCI spectra was therefore limited by the instrumentation. Resolution of uCI spectra in rabbit ventricle allowed measurement of ρt = 134 ± 53 Ω·cm. The rapid identification available with this strategy provides an opportunity for new interpretations of the uCI spectra to improve quantification of disease-, region-, tissue-, and species-dependent intercellular uncoupling in hearts. PMID:23625349
IR Spectra and Bond Energies Computed Using DFT
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles; Andrews, Lester; Arnold, James (Technical Monitor)
2000-01-01
The combination of density functional theory (DFT) frequencies and infrared (IR) intensities and experimental spectra is a very powerful tool in the identification of molecules and ions. The computed and measured isotopic ratios make the identification much more secure than frequencies and intensities alone. This will be illustrated using several examples, such as Mn(CO)n and Mn(CO)n-. The accuracy of DFT metal-ligand bond energies will also be discussed.
Development of site-specific earthquake response spectra for eastern US sites
Beavers, J.E.; Brock, W.R.; Hunt, R.J.; Shaffer, K.E.
1993-08-01
Site-specific earthquake, uniform-hazard response spectra have been defined for the Department of Energy Oak Ridge, Tennessee, and Portsmouth, Ohio, sites for use in evaluating existing facilities and designing new facilities. The site-specific response spectra were defined from probabilistic and deterministic seismic hazard studies following the requirements in DOE-STD-1024-92, ``Guidelines for Probabilistic Seismic Hazard Curves at DOE Sites.` For these two sites, the results show that site-specific uniform-hazard response spectra are slightly higher in the high-frequency range and considerably lower in the low-frequency range compared with response spectra defined for these sites in the past.
Millimeter wave absorption spectra of biological samples
Gandhi, O.P.; Hagmann, M.J.; Hill, D.W.; Partlow, L.M.; Bush, L.
1980-01-01
A solid-state computer-controlled system has been used to make swept-frequency measurements of absorption of biological specimens from 26.5 to 90.0 GHz. A wide range of samples was used, including solutions of DNA and RNA, and suspensions of BHK-21/C13 cells, Candida albicans, C krusei, and Escherichia coli. Sharp spectra reported by other workers were not observed. The strong absorbance of water (10--30 dB/mm) caused the absorbance of all aqueous preparations that we examined to have a water-like dependence on frequency. Reduction of incident power (to below 1.0 microW), elimination of modulation, and control of temperature to assure cell viability were not found to significantly alter the water-dominated absorbance. Frozen samples of BHK-21/C13 cells tested at dry ice and liquid nitrogen temperatures were found to have average insertion loss reduced to 0.2 dB/cm but still showed no reproducible peaks that could be attributed to absorption spectra. It is concluded that the special resonances reported by others are likely to be in error.
Rotary spectra analysis applied to static stabilometry.
Chiaramello, E; Knaflitz, M; Agostini, V
2011-01-01
Static stabilometry is a technique aimed at quantifying postural sway during quiet standing in the upright position. Many different models and many different techniques to analyze the trajectories of the Centre of Pressure (CoP) have been proposed. Most of the parameters calculated according to these different approaches are affected by a relevant intra- and inter-subject variability or do not have a clear physiological interpretation. In this study we hypothesize that CoP trajectories have rotational characteristics, therefore we decompose them in clockwise and counter-clockwise components, using the rotary spectra analysis. Rotary spectra obtained studying a population of healthy subjects are described through the group average of spectral parameters, i.e., 95% spectral bandwidth, mean frequency, median frequency, and skewness. Results are reported for the clockwise and the counter-clockwise components and refer to the upright position maintained with eyes open or closed. This study demonstrates that the approach is feasible and that some of the spectral parameters are statistically different between the open and closed eyes conditions. More research is needed to demonstrate the clinical applicability of this approach, but results so far obtained are promising.
Understanding Vibration Spectra of Planetary Gear Systems for Fault Detection
NASA Technical Reports Server (NTRS)
Mosher, Marianne
2003-01-01
An understanding of the vibration spectra is very useful for any gear fault detection scheme based upon vibration measurements. The vibration measured from planetary gears is complicated. Sternfeld noted the presence of sidebands about the gear mesh harmonics spaced at the planet passage frequency in spectra measured near the ring gear of a CH-47 helicopter. McFadden proposes a simple model of the vibration transmission that predicts high spectral amplitudes at multiples of the planet passage frequency, for planetary gears with evenly spaced planets. This model correctly predicts no strong signal at the meshing frequency when the number of teeth on the ring gear is not an integer multiple of the number of planets. This paper will describe a model for planetary gear vibration spectra developed from the ideas started in reference. This model predicts vibration to occur only at frequencies that are multiples of the planet repetition passage frequency and clustered around gear mesh harmonics. Vibration measurements will be shown from tri-axial accelerometers mounted on three different planetary gear systems and compared with the model. The model correctly predicts the frequencies with large components around the first several gear mesh harmonics in measurements for systems with uniformly and nonuniformly spaced planet gears. Measurements do not confirm some of the more detailed features predicted by the model. Discrepancies of the ideal model to the measurements are believed due to simplifications in the model and will be discussed. Fault detection will be discussed applying the understanding will be discussed.
Frequency Correction for MIRO Chirp Transformation Spectroscopy Spectrum
NASA Technical Reports Server (NTRS)
Lee, Seungwon
2012-01-01
This software processes the flyby spectra of the Chirp Transform Spectrometer (CTS) of the Microwave Instrument for Rosetta Orbiter (MIRO). The tool corrects the effect of Doppler shift and local-oscillator (LO) frequency shift during the flyby mode of MIRO operations. The frequency correction for CTS flyby spectra is performed and is integrated with multiple spectra into a high signal-to-noise averaged spectrum at the rest-frame RF frequency. This innovation also generates the 8 molecular line spectra by dividing continuous 4,096-channel CTS spectra. The 8 line spectra can then be readily used for scientific investigations. A spectral line that is at its rest frequency in the frame of the Earth or an asteroid will be observed with a time-varying Doppler shift as seen by MIRO. The frequency shift is toward the higher RF frequencies on approach, and toward lower RF frequencies on departure. The magnitude of the shift depends on the flyby velocity. The result of time-varying Doppler shift is that of an observed spectral line will be seen to move from channel to channel in the CTS spectrometer. The direction (higher or lower frequency) in the spectrometer depends on the spectral line frequency under consideration. In order to analyze the flyby spectra, two steps are required. First, individual spectra must be corrected for the Doppler shift so that individual spectra can be superimposed at the same rest frequency for integration purposes. Second, a correction needs to be applied to the CTS spectra to account for the LO frequency shifts that are applied to asteroid mode.
Candidates for Pulsars with Gigahertz-Peaked Spectra
NASA Astrophysics Data System (ADS)
Tarczewski, L.; Kijak, J.; Lewandowski, W.
2012-12-01
Kijak et al. (2011) provided a definite evidence for a new type of pulsar radio spectra. These spectra show the maximum flux above 1 GHz and their energy decreases below 1 GHz, producing a positive spectral index at lower frequencies. They called these objects the gigahertz-peaked spectra (GPS) pulsars. We study a spectrum of radio pulsars and try to find pulsars with the turn-over effect at high frequencies. We created a database of candidates for pulsars with GPS effect using Maron et al. (2000) and ATNF database (Manchester et al. 2005), and also using recent papers where flux measurements were published (for example Bates et al. 2011). As a result a set of 22 candidates for pulsars with GPS was found.
Raman intensity and spectra predictions for cylindrical viruses
NASA Astrophysics Data System (ADS)
Dykeman, Eric C.; Sankey, Otto F.; Tsen, Kong-Thon
2007-07-01
A theoretical framework for predicting low frequency Raman vibrational spectra of viral capsids is presented and applied to the M13 bacteriophage. The method uses a continuum elastic theory for the vibrational modes and a bond-charge polarizability model of an amorphous material to roughly predict the Raman intensities. Comparison is made to experimental results for the M13 bacteriophage virus.
Infrared spectra of molecules and materials of astrophysical interest
NASA Technical Reports Server (NTRS)
Durig, J. R.
1972-01-01
Vibrational spectra were studied from 400 to 33/cm for molecules which may be present in the atmosphere of Jovian planets. The microwave spectrum of cis glyoxal was studied. Sources of color variation in the Jovian atmosphere were analyzed in relation to molecular crystals. The low frequency modes of acetaldehyde and acetaldehyde-d sub 4 are discussed.
Phonon spectra of alkali metals
NASA Astrophysics Data System (ADS)
Zeković, S.; Vukajlović, F.; Veljković, V.
1982-10-01
In this work we used a simple local model pseudopotential which includes screening for the phonon spectra calculations of alkali metals. The results obtained are in very good agreement with experimental data. In some branches of phonon spectra the differences between theoretical and experimental results are within 1-2%, while the maximum error is about 6%. The suggested form of the pseudopotential allows us to describe the phonon spectra of Na, K and Rb with only one, and, at the same time, a unique, parameter. In this case, the maximum disagreements from experiment are 9% for Na, 8% for K and 7% for Rb.
Detection of Ordered and Chaotic Motion using the Dynamical Spectra
NASA Astrophysics Data System (ADS)
Voglis, N.; Contopoulos, G.; Efthymiopoulos, C.
The dynamical spectra of stretching numbers, helicity, twist, and rotation angles can be used in developing efficient methods for distinguishing between ordered and chaotic motion in dynamical systems. A fast and detailed investigation of phase-space in 2 or 3 degrees of freedom can be obtained by the above methods. In 2 degrees of freedom a combined use of moments of angular dynamical spectra (of the twist and the rotation angles) can determine the main frequencies of an orbit, and detect rotational tori, thin chaotic layers, islands and cantori. In 3 degrees of freedom dynamical spectra can detect chaotic orbits with even extremely small Lyapunov Characteristic Numbers (e.g. 10^(-7)). The method is based on the fact that the dynamical spectra are invariant with respect to the initial orientation of the deviation vector for chaotic orbits, while they are not invariant for ordered orbits.
Infrared spectra of jennite and tobermorite from first-principles
Vidmer, Alexandre Sclauzero, Gabriele; Pasquarello, Alfredo
2014-06-01
The infrared absorption spectra of jennite, tobermorite 14 Å, anomalous tobermorite 11 Å, and normal tobermorite 11 Å are simulated within a density-functional-theory scheme. The atomic coordinates and the cell parameters are optimized resulting in structures which agree with previous studies. The vibrational frequencies and modes are obtained for each mineral. The vibrational density of states is analyzed through extensive projections on silicon tetrahedra, oxygen atoms, OH groups, and water molecules. The coupling with the electric field is achieved through the use of density functional perturbation theory, which yields Born effective charges and dielectric constants. The simulated absorption spectra reproduce well the experimental spectra, thereby allowing for a detailed interpretation of the spectral features in terms of the underlying vibrational modes. In the far-infrared part of the absorption spectra, the interplay between Ca and Si related vibrations leads to differences which are sensitive to the calcium/silicon ratio of the mineral.
Plasmon-polariton fractal spectra in quasiperiodic multilayers
NASA Astrophysics Data System (ADS)
Vasconcelos, M. S.; Albuquerque, E. L.
1998-02-01
We carry out a theoretical analysis for the spectra of plasmon polaritons in multiple semiconductor layers arranged in a quasiperiodical fashion. This quasiperiodicity can be of the type of so-called substitutional sequences. They are characterized by the nature of their Fourier spectrum, which can be dense pure point (Fibonacci sequences) or singular continuous (Thue-Morse and double-period sequences). These substitutional sequences are described in terms of a series of generations that obey peculiar recursion relations. In order to study the plasmon-polariton spectra, we use a convenient theoretical model based on a transfer-matrix treatment, with the layers characterized by a frequency-dependent dielectric function, including the effect of retardation. We present numerical results to discuss the fractal aspect of the spectra, and compare it with the nonfractal spectra presented in the periodic case.
[Study on THz spectra of nicotinic acid, nicotinamide and nicotine].
Yu, Bin; Huang, Zhen; Wang, Xiao-yan; Zhao, Guo-zhong
2009-09-01
The terahertz (THz) spectra of nicotinic acid, nicotinamide and nicotine were studied at room temperature. The time-domain THz spectra were measured. The frequency-domain spectra were obtained by fast Fourier transform (FFT). The spectral response and the dispersive relationship of refractive index in THz spectral range were obtained. The results show that the samples have obvious spectral response in THz spectral range except nicotine. The corresponding stimulated spectra were given by using density functional theory (DFT) method for both nicotinamide and nicotinic acid. The origin of the absorption peaks of nicotinic acid and nicotinamide was explored. It is thought that the absorption peak of nicotinic acid is caused by the torsion and wagging of the molecule, but the absorption peaks of nicotinamide (except 1.93 THz) are caused by intermolecular or phonon mode. It was shown that the molecule structure and vibrational modes of nicotinic acid and nicotinamide can be analyzed by the combination of simulation and experimental results.
Pulsar gamma-rays: Spectra luminosities and efficiencies
NASA Technical Reports Server (NTRS)
Harding, A. K.
1980-01-01
The general characteristics of pulsar gamma ray spectra are presented for a model where the gamma rays are produced by curvature radiation from energetic particles above the polar cap and attenuated by pair production. The shape of the spectrum is found to depend on pulsar period, magnetic field strength, and primary particle energy. By a comparison of numerically calculated spectra with the observed spectra of the Crab and Vela pulsars, it is determined that primary particles must be accelerated to energies of about 3 x 10 to the 7th power mc sq. A genaral formula for pulsar gamma ray luminosity is determined and is found to depend on period and field strength.
Computer Processing Of Tunable-Diode-Laser Spectra
NASA Technical Reports Server (NTRS)
May, Randy D.
1991-01-01
Tunable-diode-laser spectrometer measuring transmission spectrum of gas operates under control of computer, which also processes measurement data. Measurements in three channels processed into spectra. Computer controls current supplied to tunable diode laser, stepping it through small increments of wavelength while processing spectral measurements at each step. Program includes library of routines for general manipulation and plotting of spectra, least-squares fitting of direct-transmission and harmonic-absorption spectra, and deconvolution for determination of laser linewidth and for removal of instrumental broadening of spectral lines.
Formation of cyclotron lines in gamma-ray burst spectra
NASA Technical Reports Server (NTRS)
Alexander, S. G.; Meszaros, P.
1989-01-01
A transmission model of gamma-ray burst sources is studied using the relativistic QED magnetic-resonant opacities including multiple photon scattering, incorporated into a discrete-ordinate radiative-transport scheme. The physics of the cyclotron line-producing region is discussed in general, and the expected line profiles, relative harmonic strengths, and polarizations are indicated under various conditions. The calculated spectra for these models show good agreement with the spectra reported from Ginga for GB 880205 and GB 870303.
NASA Technical Reports Server (NTRS)
Dennison, Brian; Weiler, K. W.; Johnston, K. J.; Simon, R. S.; Spencer, J. H.; Hammarstrom, L. M.; Wilhelm, P. G.; Kaiser, M. L.; Desch, M. D.; Fainberg, J.
1987-01-01
The Low Frequency Space Array (LFSA) is a conceptual mission to survey the entire sky and to image individual sources at frequencies between 1.5 and 26 MHz, a frequency range over which the earth's ionosphere transmits poorly or not at all. With high resolution, high sensitivity observations, a new window will be opened in the electromagnetic spectrum for astronomical investigation. Also, extending observations down to such low frequencies will bring astronomy to the fundamental limit below which the galaxy becomes optically thick due to free-free absorption. A number of major scientific goals can be pursued with such a mission, including mapping galactic emission and absorption, studies of individual source spectra in a frequency range where a number of important processes may play a role, high resolution imaging of extended sources, localization of the impulsive emission from Jupiter, and a search for coherent emission processes.
Mid-infrared spectra of comet nuclei
NASA Astrophysics Data System (ADS)
Kelley, Michael S. P.; Woodward, Charles E.; Gehrz, Robert D.; Reach, William T.; Harker, David E.
2017-03-01
Comet nuclei and D-type asteroids have several similarities at optical and near-IR wavelengths, including near-featureless red reflectance spectra, and low albedos. Mineral identifications based on these characteristics are fraught with degeneracies, although some general trends can be identified. In contrast, spectral emissivity features in the mid-infrared provide important compositional information that might not otherwise be achievable. Jovian Trojan D-type asteroids have emissivity features strikingly similar to comet comae, suggesting that they have the same compositions and that the surfaces of the Trojans are highly porous. However, a direct comparison between a comet and asteroid surface has not been possible due to the paucity of spectra of comet nuclei at mid-infrared wavelengths. We present 5-35 μm thermal emission spectra of comets 10P/Tempel 2, and 49P/Arend-Rigaux observed with the Infrared Spectrograph on the Spitzer Space Telescope. Our analysis reveals no evidence for a coma or tail at the time of observation, suggesting the spectra are dominated by the comet nucleus. We fit each spectrum with the near-Earth asteroid thermal model (NEATM) and find sizes in agreement with previous values. However, the NEATM beaming parameters of the nuclei, 0.74-0.83, are systematically lower than the Jupiter-family comet population mean of 1.03 ± 0.11, derived from 16- and 22-μm photometry. We suggest this may be either an artifact of the spectral reduction, or the consequence of an emissivity low near 16 μm. When the spectra are normalized by the NEATM model, a weak 10-μm silicate plateau is evident, with a shape similar to those seen in mid-infrared spectra of D-type asteroids. A silicate plateau is also evident in previously published Spitzer spectra of the nucleus of comet 9P/Tempel 1. We compare, in detail, these comet nucleus emission features to those seen in spectra of the Jovian Trojan D-types (624) Hektor, (911) Agamemnon, and (1172) Aneas, as well
NASA Astrophysics Data System (ADS)
Challis, Peter
2013-12-01
P. Challis, Harvard-Smithsonian Center for Astrophysics (CfA), on behalf of the CfA Supernova Group, report spectra (range 320-860 nm) of various SN obtained during Dec. 24-27 UT by P. Challis, S. Gottilla (MMTO.org), and E. Marin (MMTO.org) with the MMT 6.5-m telescope (+ Blue Channel). Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J.
Inversion of generalized relaxation time distributions with optimized damping parameter
NASA Astrophysics Data System (ADS)
Florsch, Nicolas; Revil, André; Camerlynck, Christian
2014-10-01
Retrieving the Relaxation Time Distribution (RDT), the Grains Size Distribution (GSD) or the Pore Size Distribution (PSD) from low-frequency impedance spectra is a major goal in geophysics. The “Generalized RTD” generalizes parametric models like Cole-Cole and many others, but remains tricky to invert since this inverse problem is ill-posed. We propose to use generalized relaxation basis function (for instance by decomposing the spectra on basis of generalized Cole-Cole relaxation elements instead of the classical Debye basis) and to use the L-curve approach to optimize the damping parameter required to get smooth and realistic inverse solutions. We apply our algorithm to three examples, one synthetic and two real data sets, and the program includes the possibility of converting the RTD into GSD or PSD by choosing the value of the constant connecting the relaxation time to the characteristic polarization size of interest. A high frequencies (typically above 1 kHz), a dielectric term in taken into account in the model. The code is provided as an open Matlab source as a supplementary file associated with this paper.
Can We Infer Ocean Dynamics from Altimeter Wavenumber Spectra?
NASA Technical Reports Server (NTRS)
Richman, James; Shriver, Jay; Arbic, Brian
2012-01-01
The wavenumber spectra of sea surface height (SSH) and kinetic energy (KE) have been used to infer the dynamics of the ocean. When quasi-geostrophic dynamics (QG) or surface quasi-geostrophic (SQG) turbulence dominate and an inertial subrange exists, a steep SSH wavenumber spectrum is expected with k-5 for QG turbulence and a flatter k-11/3 for SQG turbulence. However, inspection of the spectral slopes in the mesoscale band of 70 to 250 km shows that the altimeter wavenumber slopes typically are much flatter than the QG or SQG predictions over most of the ocean. Comparison of the altimeter wavenumber spectra with the spectra estimated from the output of an eddy resolving global ocean circulation model (the Hybrid Coordinate Ocean Model, HYCOM, at 1/25 resolution), which is forced by high frequency winds and includes the astronomical forcing of the sun and the moon, suggests that the flatter slopes of the altimeter may arise from three possible sources, the presence of internal waves, the lack of an inertial subrange in the 70 to 250 km band and noise or submesoscales at small scales. When the wavenumber spectra of SSH and KE are estimated near the internal tide generating regions, the resulting spectra are much flatter than the expectations of QG or SQG theory. If the height and velocity variability are separated into low frequency (periods greater than 2 days) and high frequency (periods less than a day), then a different pattern emerges with a relatively flat wavenumber spectrum at high frequency and a steeper wavenumber spectrum at low frequency. The stationary internal tides can be removed from the altimeter spectrum, which steepens the spectral slopes in the energetic internal wave regions. Away from generating regions where the internal waves
Near Infrared Spectra of Mixtures Relevant to Icy Satellites
NASA Technical Reports Server (NTRS)
Mastrapa, Rachel M. E.; Bernstein, Max P.; Sanford, Scott A.
2005-01-01
We will present near IR spectra of ice mixtures and review the differences between spectra of mixtures and those of pure solids: the creation of new features, weakening and shifting of bands, dependence on concentration, and changes with temperature. The forbidden CO2 (2nu3) overtone at 2.134 microns (4685/cm) is absent from the spectrum of pure CO2, but present in all of the following mixtures: H2O/CO2 = 5 and = 25, H2O:CH3OH:CO2 = 100:2.5:1, and CH3OH:CO2 = 5. Also, in mixtures of H2O and any other material, we see a feature at 1.89 microns (5290/cm) that is possibly related to the "dangling OH" feature at 2.73 microns (3360/cm). The features of a material in H2O are generally weaker and shifted to longer wavelength in comparison to the pure substance. For example, the largest near-IR absorption of pure solid CH4 is located at 2.324 microns (4303/cm) but is broader and at slightly longer wavelength in samples mixed with H2O. The degree of shifting and weakening depends on the ratio of the mixture. The mixture mentioned above was at a ratio of H2O/ CH4 = 3. When the ratio rises to H2O/ CH4 = 87, the CH4 feature at 2.324 microns is shifted to shorter wavelength and is much broader and weaker. In CH4/ H2O mixtures the peaks shift to higher frequency and become increasingly broad, but this trend is reversible on re-cooling, even though the phase transitions of H2O are irreversible. In short, mixtures created in the lab produce spectra that are very different from modeled combinations of end member species. Recent Cassini VIMS observations show the CO2 fundamental at 4.255 microns (2350/cm) on Iapetus [l] and at 4.26 microns (2347/cm) on Phoebe [2], while Galileo NIMS observed it at 4.25 microns (2353/cm) on Ganymede [3]. Since pure CO2 is located at 4.266 (2344/cm), the CO2 must be mixed with something else to produce the shift. A mixture of CH3OH:CO2 = 5 at 90 K shifts the fundamental to 4.262 microns (2346/cm). The shifts in the feature between satellites could
Covariance Analysis of Gamma Ray Spectra
Trainham, R.; Tinsley, J.
2013-01-01
The covariance method exploits fluctuations in signals to recover information encoded in correlations which are usually lost when signal averaging occurs. In nuclear spectroscopy it can be regarded as a generalization of the coincidence technique. The method can be used to extract signal from uncorrelated noise, to separate overlapping spectral peaks, to identify escape peaks, to reconstruct spectra from Compton continua, and to generate secondary spectral fingerprints. We discuss a few statistical considerations of the covariance method and present experimental examples of its use in gamma spectroscopy.
Covariance analysis of gamma ray spectra
Trainham, R.; Tinsley, J.
2013-01-15
The covariance method exploits fluctuations in signals to recover information encoded in correlations which are usually lost when signal averaging occurs. In nuclear spectroscopy it can be regarded as a generalization of the coincidence technique. The method can be used to extract signal from uncorrelated noise, to separate overlapping spectral peaks, to identify escape peaks, to reconstruct spectra from Compton continua, and to generate secondary spectral fingerprints. We discuss a few statistical considerations of the covariance method and present experimental examples of its use in gamma spectroscopy.
Palafox, M Alcolea; Rastogi, V K; Tanwar, R P; Mittal, Lalit
2003-09-01
Vibrational study of the biomolecule 2-thiouracil was carried out. Ab initio and density functional calculations were performed to assign the experimental spectra. A comparison with the uracil molecule was made, and specific scale factors were deduced and employed in the predicted frequencies of 2-thiouracil. Several scaling procedures were used. The geometry structure of the molecule was determined. The effect of sulfur substitution at C2 position in the uracil molecule, on the N1-H and N3-H frequencies and intensities reflects changes in proton donor abilities of these groups. Calculations with the 6-31 G** basis set with HF and DFT methods appear in general to be useful for interpretation of the general features of the IR and Raman spectra of the molecule. Using specific scale factors a very small error was obtained. The use of these specific scale factors resolve and correct some of the controversial assignments in the literature.
Multiband frequency selective surface
NASA Astrophysics Data System (ADS)
Wu, Te-Kao
1998-10-01
This paper addresses the similarity of microwave/millimeter wave frequency selective surfaces (FSS) to optical filters. Specifically, the design approaches of the 4-band FSSs developed for NASA's CASSINI high gain antenna are described in detail. Representative RF test results are given to demonstrate the validity of these designs. These design approaches are very general and can be applied to multiband optical filters.
Analysis of positron lifetime spectra in polymers
NASA Technical Reports Server (NTRS)
Singh, Jag J.; Mall, Gerald H.; Sprinkle, Danny R.
1988-01-01
A new procedure for analyzing multicomponent positron lifetime spectra in polymers was developed. It requires initial estimates of the lifetimes and the intensities of various components, which are readily obtainable by a standard spectrum stripping process. These initial estimates, after convolution with the timing system resolution function, are then used as the inputs for a nonlinear least squares analysis to compute the estimates that conform to a global error minimization criterion. The convolution integral uses the full experimental resolution function, in contrast to the previous studies where analytical approximations of it were utilized. These concepts were incorporated into a generalized Computer Program for Analyzing Positron Lifetime Spectra (PAPLS) in polymers. Its validity was tested using several artificially generated data sets. These data sets were also analyzed using the widely used POSITRONFIT program. In almost all cases, the PAPLS program gives closer fit to the input values. The new procedure was applied to the analysis of several lifetime spectra measured in metal ion containing Epon-828 samples. The results are described.
IRAS Low Resolution Spectra of Asteroids
NASA Technical Reports Server (NTRS)
Cohen, Martin; Walker, Russell G.
2002-01-01
Optical/near-infrared studies of asteroids are based on reflected sunlight and surface albedo variations create broad spectral features, suggestive of families of materials. There is a significant literature on these features, but there is very little work in the thermal infrared that directly probes the materials emitting on the surfaces of asteroids. We have searched for and extracted 534 thermal spectra of 245 asteroids from the original Dutch (Groningen) archive of spectra observed by the IRAS Low Resolution Spectrometer (LRS). We find that, in general, the observed shapes of the spectral continua are inconsistent with that predicted by the standard thermal model used by IRAS. Thermal models such as proposed by Harris (1998) and Harris et al.(1998) for the near-earth asteroids with the "beaming parameter" in the range of 1.0 to 1.2 best represent the observed spectral shapes. This implies that the IRAS Minor Planet Survey (IMPS, Tedesco, 1992) and the Supplementary IMPS (SIMPS, Tedesco, et al., 2002) derived asteroid diameters are systematically underestimated, and the albedos are overestimated. We have tentatively identified several spectral features that appear to be diagnostic of at least families of materials. The variation of spectral features with taxonomic class hints that thermal infrared spectra can be a valuable tool for taxonomic classification of asteroids.
Characteristics of magnetospheric radio noise spectra
NASA Technical Reports Server (NTRS)
Herman, J. R.
1976-01-01
Magnetospheric radio noise spectra (30 kHz to 10 MHz) taken by IMP-6 and RAE-2 exhibit time varying characteristics which are related to spacecraft position and magnetospheric processes. In the midfrequency range (100-1000 kHz) intense noise peaks rise a factor of 100 or more above background; 80% of the peak frequencies are within the band 125 kHz to 600 kHz, and the peak occurs most often (18% of the time) at 280 kHz. Bandwidths of the peaks range from about 100 kHz to more than 500 kHz; most often the lower cutoff is at about 100 kHz and the upper at 380 kHz for a total bandwidth of 280 kHz. This intense mid-frequency noise was detected at radial distances from 1.3 Re to 60 Re on all sides of the earth (i.e., all local times) during magnetically quiet as well as disturbed periods. Maximum occurrence of the mid-frequency noise is in the evening to midnight hours where splash-type energetic particle precipitation takes place.
Similarity spectra analysis of high-performance jet aircraft noise.
Neilsen, Tracianne B; Gee, Kent L; Wall, Alan T; James, Michael M
2013-04-01
Noise measured in the vicinity of an F-22A Raptor has been compared to similarity spectra found previously to represent mixing noise from large-scale and fine-scale turbulent structures in laboratory-scale jet plumes. Comparisons have been made for three engine conditions using ground-based sideline microphones, which covered a large angular aperture. Even though the nozzle geometry is complex and the jet is nonideally expanded, the similarity spectra do agree with large portions of the measured spectra. Toward the sideline, the fine-scale similarity spectrum is used, while the large-scale similarity spectrum provides a good fit to the area of maximum radiation. Combinations of the two similarity spectra are shown to match the data in between those regions. Surprisingly, a combination of the two is also shown to match the data at the farthest aft angle. However, at high frequencies the degree of congruity between the similarity and the measured spectra changes with engine condition and angle. At the higher engine conditions, there is a systematically shallower measured high-frequency slope, with the largest discrepancy occurring in the regions of maximum radiation.
Axisymmetric toroidal modes of general relativistic magnetized neutron star models
Asai, Hidetaka; Lee, Umin E-mail: lee@astr.tohoku.ac.jp
2014-07-20
We calculate axisymmetric toroidal modes of magnetized neutron stars with a solid crust in the general relativistic Cowling approximation. We assume that the interior of the star is threaded by a poloidal magnetic field, which is continuous at the surface with an outside dipole field. We examine the cases of the field strength B{sub S} ∼ 10{sup 16} G at the surface. Since separation of variables is not possible for the oscillations of magnetized stars, we employ finite series expansions for the perturbations using spherical harmonic functions. We find discrete normal toroidal modes of odd parity, but no toroidal modes of even parity are found. The frequencies of the toroidal modes form distinct mode sequences and the frequency in a given mode sequence gradually decreases as the number of radial nodes of the eigenfunction increases. From the frequency spectra computed for neutron stars of different masses, we find that the frequency is almost exactly proportional to B{sub S} and is well represented by a linear function of R/M for a given B{sub S}, where M and R are the mass and radius of the star. The toroidal mode frequencies for B{sub S} ∼ 10{sup 15} G are in the frequency range of the quasi-periodic oscillations (QPOs) detected in the soft-gamma-ray repeaters, but we find that the toroidal normal modes cannot explain all the detected QPO frequencies.
Interactions between tides and other frequencies in the Indonesian seas
NASA Astrophysics Data System (ADS)
Robertson, Robin
2011-01-01
Interactions of tidal constituents and the transfer of energy from the tidal frequencies to other frequencies are investigated using 3-D tidal simulations for the Indonesian seas, focusing on an area of active internal tides. Semidiurnal tides strongly affect diurnal tides; however, semidiurnal tides are essentially unaffected by diurnal tides. The semidiurnal and diurnal constituents interact with each other through non-linear interference, both destructive and constructive. Semidiurnal tides generate harmonics at nearly the diurnal frequency and higher vertical wavenumbers. In Ombai Strait, these harmonics are out of phase with the diurnal tides and interact destructively with the diurnal tides, effectively negating the diurnal response in some locations. However, this is not a general response, and interactions differ between locations. Energy is also transferred from both semidiurnal and diurnal tides to other frequencies across the spectrum, with more energy originating from semidiurnal tides. These energy transfers are not homogeneous, and the spectral responses differ between the Makassar and Ombai Straits, with the region east of Ombai showing a more active surface response compared to a more intense benthic response in Makassar. In deep water away from topography, velocity spectra generally follow the Garrett-Munk (GM) relation. However, in areas of internal tide generation, spectral density levels exceed GM levels, particularly between 4 and 8 cycles per day (cpd), indicating increased non-linear interactions and energy transfer through resonant interactions. The model indicates strong surface trapping of internal tides, with surface velocity spectra having significantly higher energy between 4 and 8 cpd even 100 km away from the prominent sill generating the internal tides.
Magnetoabsorption spectra of bilayer graphene ribbons with Bernal stacking
NASA Astrophysics Data System (ADS)
Huang, Y. C.; Chang, C. P.; Lin, M. F.
2008-09-01
Magnetoabsorption spectra of bilayer graphene ribbons with Bernal stacking are studied by the Peierls-coupling tight-binding method. When the magnetic confinement prevails over the quantum confinement, low-energy spectra chiefly exhibit many Landau peaks, which are strongly modified by the inter-ribbon interactions and the magnetic-field magnitude (B) . The spectra show denser Landau peaks in bilayer graphene ribbon than in a monolayer ribbon with the same ribbon width. The absorption frequencies of Landau peaks of a wide monolayer ribbon show the B dependence, while those of a bilayer ribbon exhibit a varying B -field dependence. In the spectra region ω≤100meV , the absorption frequencies of Landau peaks are linearly dependent on the magnetic-field magnitude. At ω≥100meV , they evolve from the B dependence to the B dependence with the increase in the field strength. The absorption frequencies of Landau peaks exhibit B dependence at B≥20T . The relationship between the magneto-optical properties and electronic structures (the state energies and wave functions) are explored. The Landau wave functions are illustrated and used to identify the optical selection rule.
Maturation of EEG Power Spectra in Early Adolescence: A Longitudinal Study
ERIC Educational Resources Information Center
Cragg, Lucy; Kovacevic, Natasa; McIntosh, Anthony Randal; Poulsen, Catherine; Martinu, Kristina; Leonard, Gabriel; Paus, Tomas
2011-01-01
This study investigated the fine-grained development of the EEG power spectra in early adolescence, and the extent to which it is reflected in changes in peak frequency. It also sought to determine whether sex differences in the EEG power spectra reflect differential patterns of maturation. A group of 56 adolescents were tested at age 10 years and…
Vibrational Spectra of Selected Monohalogenated Monocarboxylic Acids.
HALOGENATED HYDROCARBONS, INFRARED SPECTRA), (*CARBOXYLIC ACIDS, *INFRARED SPECTRA), IODINE COMPOUNDS, CHLORINE COMPOUNDS, BROMINE COMPOUNDS, ACETIC ACID , ACETATES, MOLECULAR STRUCTURE, MOLECULAR ASSOCIATION
Raman spectra of solid benzene under high pressure
NASA Technical Reports Server (NTRS)
Thiery, M.-M.; Kobashi, K.; Spain, I. L.
1985-01-01
Raman spectra of solid benzene have been measured at room temperature up to about 140 kbar, using the diamond anvil cell. Effort has been focused upon the lattice vibration spectra at pressures above that of phase II. It is found that a change in slopes occurs in the frequency-pressure curves at about 40 kbar. Furthermore, a new band appears above 90 kbar. These features probably correspond respectively to the II-III phase transition, which has been reported previously, and a III-IV phase transition, reported here for the first time.
LSD-based analysis of high-resolution stellar spectra
NASA Astrophysics Data System (ADS)
Tsymbal, V.; Tkachenko, A.; Van, Reeth T.
2014-11-01
We present a generalization of the method of least-squares deconvolution (LSD), a powerful tool for extracting high S/N average line profiles from stellar spectra. The generalization of the method is effected by extending it towards the multiprofile LSD and by introducing the possibility to correct the line strengths from the initial mask. We illustrate the new approach by two examples: (a) the detection of astroseismic signatures from low S/N spectra of single stars, and (b) disentangling spectra of multiple stellar objects. The analysis is applied to spectra obtained with 2-m class telescopes in the course of spectroscopic ground-based support for space missions such as CoRoT and Kepler. Usually, rather high S/N is required, so smaller telescopes can only compete successfully with more advanced ones when one can apply a technique that enables a remarkable increase in the S/N of the spectra which they observe. Since the LSD profiles have a potential for reconstruction what is common in all the spectral profiles, it should have a particular practical application to faint stars observed with 2-m class telescopes and whose spectra show remarkable LPVs.
Photon spectra from WIMP annihilation
Cembranos, J. A. R.; Cruz-Dombriz, A. de la; Dobado, A.; Maroto, A. L.; Lineros, R. A.
2011-04-15
If the present dark matter in the Universe annihilates into standard model particles, it must contribute to the fluxes of cosmic rays that are detected on the Earth and, in particular, to the observed gamma-ray fluxes. The magnitude of such a contribution depends on the particular dark matter candidate, but certain features of the produced photon spectra may be analyzed in a rather model-independent fashion. In this work we provide the complete photon spectra coming from WIMP annihilation into standard model particle-antiparticle pairs obtained by extensive Monte Carlo simulations. We present results for each individual annihilation channel and provide analytical fitting formulas for the different spectra for a wide range of WIMP masses.
47 CFR 2.1507 - Test frequencies.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 47 Telecommunication 1 2011-10-01 2011-10-01 false Test frequencies. 2.1507 Section 2.1507 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL... Radiobeacons (EPIRBs) Environmental and Operational Test Procedures § 2.1507 Test frequencies. Testing of...
47 CFR 2.1507 - Test frequencies.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 47 Telecommunication 1 2010-10-01 2010-10-01 false Test frequencies. 2.1507 Section 2.1507 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL... Radiobeacons (EPIRBs) Environmental and Operational Test Procedures § 2.1507 Test frequencies. Testing of...
NASA Astrophysics Data System (ADS)
Pan, A.; Ghosh, A.
2002-06-01
Relaxation dynamics of Ag+ ions and scaling of the conductivity spectra in lead bismuthate glasses of different compositions have been investigated in the frequency range from 10 Hz to 2 MHz and in the temperature range from 83 K to just below glass transition temperature. We have observed that relaxation dynamics and the frequency exponent depend on the cation constriction. We have also observed that the scaling of the conductivity spectra obeys time-temperature superposition principle, but it is dependent on composition.
Inflation in general covariant theory of gravity
NASA Astrophysics Data System (ADS)
Huang, Yongqing; Wang, Anzhong; Wu, Qiang
2012-10-01
In this paper, we study inflation in the framework of the nonrelativistic general covariant theory of the Hořava-Lifshitz gravity with the projectability condition and an arbitrary coupling constant λ. We find that the Friedmann-Robterson-Walker (FRW) universe is necessarily flat in such a setup. We work out explicitly the linear perturbations of the flat FRW universe without specifying to a particular gauge, and find that the perturbations are different from those obtained in general relativity, because of the presence of the high-order spatial derivative terms. Applying the general formulas to a single scalar field, we show that in the sub-horizon regions, the metric and scalar field are tightly coupled and have the same oscillating frequencies. In the super-horizon regions, the perturbations become adiabatic, and the comoving curvature perturbation is constant. We also calculate the power spectra and indices of both the scalar and tensor perturbations, and express them explicitly in terms of the slow roll parameters and the coupling constants of the high-order spatial derivative terms. In particular, we find that the perturbations, of both scalar and tensor, are almost scale-invariant, and, with some reasonable assumptions on the coupling coefficients, the spectrum index of the tensor perturbation is the same as that given in the minimum scenario in general relativity (GR), whereas the index for scalar perturbation in general depends on λ and is different from the standard GR value. The ratio of the scalar and tensor power spectra depends on the high-order spatial derivative terms, and can be different from that of GR significantly.
NASA Astrophysics Data System (ADS)
Longhi, Pietro
In this thesis we develop and apply novel techniques for analyzing BPS spectra of supersymmetric quantum field theories of class S. By a combination of wall-crossing, spectral networks and quiver methods we explore the BPS spectra of higher rank four-dimensional N = 2 super Yang-Mills, uncovering surprising new phenomena. Focusing on the SU(3) case, we prove the existence of wild BPS spectra in field theory, featuring BPS states of higher spin whose degeneracies grow exponentially with the energy. The occurrence of wild BPS states is surprising because it appears to be in tension with physical expectations on the behavior of the entropy as a function of the energy scale. The solution to this puzzle comes from realizing that the size of wild BPS states grows rapidly with their mass, and carefully analyzing the volume-dependence of the entropy of BPS states. We also find some interesting structures underlying wild BPS spectra, such as a Regge-like relation between the maximal spin of a BPS multiplet and the square of its mass, and the existence of a universal asymptotic distribution of spin-j irreps within a multiplet of given charge. We also extend the spectral networks construction by introducing a refinement in the topological classification of 2d-4d BPS states, and identifying their spin with a topological invariant known as the "writhe of soliton paths". A careful analysis of the 2d-4d wall-crossing behavior of this refined data reveals that it is described by motivic Kontsevich-Soibelman transformations, controlled by the Protected Spin Character, a protected deformation of the BPS index encoding the spin of BPS states. Our construction opens the way for the systematic study of refined BPS spectra in class S theories. We apply it to several examples, including ones featuring wild BPS spectra, where we find an interesting relation between spectral networks and certain functional equations. For class S theories of A 1 type, we derive an alternative technique for
Atomic frequency standards for ultra-high-frequency stability
NASA Technical Reports Server (NTRS)
Maleki, L.; Prestage, J. D.; Dick, G. J.
1987-01-01
The general features of the Hg-199(+) trapped-ion frequency standard are outlined and compared to other atomic frequency standards, especially the hydrogen maser. The points discussed are those which make the trapped Hg-199(+) standard attractive: high line Q, reduced sensitivity to external magnetic fields, and simplicity of state selection, among others.
MEASUREMENT OF THE HIGH ENERGY COMPONENT OF THE X-RAY SPECTRA INTHE VENUS ECR ION SOURCE
Leitner, Daniela; Benitez, Janilee Y.; Lyneis, Claude M.; Todd,Damon S.; Ropponen,Tommi; Ropponen,Janne; Koivisto, Hannu; Gammino, Santo
2007-11-15
High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for Nuclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental set-up to measure bremsstrahlung spectra from ECR ion sources is somewhat different than for the traditional nuclear physics measurements these detectors are generally used for. In particular the collimation and background shielding can be problematic. In this paper we will discuss the experimental set-up for such a measurement, the energy calibration and background reduction, the correction for detector efficiency, the shielding of the detector and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates in dependence of various ion source parameters such as confinement fields, minimum B-field, rf power and heating frequency.
Leitner, D.; Benitez, J. Y.; Lyneis, C. M.; Todd, D. S.; Ropponen, T.; Ropponen, J.; Koivisto, H.; Gammino, S.
2008-03-15
High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for NUclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet, adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different from that for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper, we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates depending on various ion source parameters, such as confinement fields, minimum B-field, rf power, and heating frequency.
On the calibration of the IRAS low-resolution spectra
NASA Technical Reports Server (NTRS)
Volk, Kevin; Cohen, Martin
1989-01-01
The need for corrections to the LRS spectra based on a study of a number of normal stars observed by IRAS is discussed. The spectra of bright stars, such as alpha CMa, were found to be inconsistent with blackbody sources, this effect being generally observed in sources earlier than about K3. An attempt is made to correct the LRS spectra by changing the blackbody calibration temperature for Alpha Tau, assumed to be a 10,000-K blackbody source for the original LRS flux calibration. It is found that an anomalously low color temperature must be assumed for alpha Tau to produce reasonable results for earlier-type stars. Corrections based on a set of stars with well-determined effective temperatures are examined, as are the resulting color temperatures for 72 stars with Atlas spectra.
47 CFR 95.1113 - Frequency coordinator.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequency coordinator. 95.1113 Section 95.1113... SERVICES Wireless Medical Telemetry Service (WMTS) General Provisions § 95.1113 Frequency coordinator. (a) The Commission will designate a frequency coordinator(s) to manage the usage of the frequency...
47 CFR 74.503 - Frequency selection.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency selection. 74.503 Section 74.503... § 74.503 Frequency selection. (a) Each application for a new station or change in an existing station shall be specific with regard to frequency. In general, the lowest suitable frequency will be...
47 CFR 95.1113 - Frequency coordinator.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequency coordinator. 95.1113 Section 95.1113... SERVICES Wireless Medical Telemetry Service (WMTS) General Provisions § 95.1113 Frequency coordinator. (a) The Commission will designate a frequency coordinator(s) to manage the usage of the frequency...
47 CFR 74.503 - Frequency selection.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency selection. 74.503 Section 74.503... § 74.503 Frequency selection. (a) Each application for a new station or change in an existing station shall be specific with regard to frequency. In general, the lowest suitable frequency will be...
47 CFR 74.503 - Frequency selection.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 47 Telecommunication 4 2014-10-01 2014-10-01 false Frequency selection. 74.503 Section 74.503... § 74.503 Frequency selection. (a) Each application for a new station or change in an existing station shall be specific with regard to frequency. In general, the lowest suitable frequency will be...
47 CFR 95.1113 - Frequency coordinator.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequency coordinator. 95.1113 Section 95.1113... SERVICES Wireless Medical Telemetry Service (WMTS) General Provisions § 95.1113 Frequency coordinator. (a) The Commission will designate a frequency coordinator(s) to manage the usage of the frequency...
47 CFR 74.503 - Frequency selection.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 47 Telecommunication 4 2013-10-01 2013-10-01 false Frequency selection. 74.503 Section 74.503... § 74.503 Frequency selection. (a) Each application for a new station or change in an existing station shall be specific with regard to frequency. In general, the lowest suitable frequency will be...
47 CFR 95.1113 - Frequency coordinator.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequency coordinator. 95.1113 Section 95.1113... SERVICES Wireless Medical Telemetry Service (WMTS) General Provisions § 95.1113 Frequency coordinator. (a) The Commission will designate a frequency coordinator(s) to manage the usage of the frequency...
47 CFR 74.503 - Frequency selection.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency selection. 74.503 Section 74.503... § 74.503 Frequency selection. (a) Each application for a new station or change in an existing station shall be specific with regard to frequency. In general, the lowest suitable frequency will be...
47 CFR 95.1113 - Frequency coordinator.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequency coordinator. 95.1113 Section 95.1113... SERVICES Wireless Medical Telemetry Service (WMTS) General Provisions § 95.1113 Frequency coordinator. (a) The Commission will designate a frequency coordinator(s) to manage the usage of the frequency...
Terahertz spectra and normal mode analysis of the crystalline VA class dipeptide nanotubes.
Zhang, Hailiang; Siegrist, Karen; Plusquellic, David F; Gregurick, Susan K
2008-12-31
Terahertz (THz) vibrational modes are characterized by nonlocal, collective molecular motions which are relevant to conformational changes and molecular functions in biological systems. We have investigated the THz spectra of a set of small bionanotubes which can serve as very simple models of membrane pores, and have examined the character of the THz modes which can impact transport processes. In this work, THz spectra of the crystalline VA class dipeptide nanotubes were calculated at both the harmonic and vibrational self-consistent field (VSCF) level using the CHARMM22 force field with periodic boundary conditions. Comparison of the calculated THz spectra against the experimental spectra revealed that the VSCF corrections generally improved the predictions in the low-frequency region. The improvements were especially manifested in the overall blue-shifts of the VSCF frequencies relative to the harmonic values, and blue shifts were attributed to the overall positive coupling strengths in all systems. Closer examination of the motions in the most significantly coupled normal mode pairs leads us to propose that, when two similar side-chain squeezing modes are coupled, the rapidly increased van der Waals interactions can lead to a stiffening of the effective potential, which in turn leads to the observed blue-shifts. However, we also noted that when the side-chain atoms become unphysically proximate and the van der Waals repulsion becomes too large, the VSCF calculations tend to deviate in the high frequency region and for the system of l-isoleucyl-l-valine. In addition, normal-mode analysis revealed a series of channel-breathing motions in all systems except l-valyl-l-alanine. We show that the inner products of the backbone vibrations between these channel-breathing motions divided the remaining VA class dipeptide systems into two subgroups. It is suggested that these modes may facilitate a pathway for the guest molecule absorption, substitution and removal in the
NASA Astrophysics Data System (ADS)
Subramanian, N.; Sundaraganesan, N.; Dereli, Ö.; Türkkan, E.
2011-12-01
The purpose of finding conformer among six different possible conformers of 2,5-di-tert-butyl-hydroquinone (DTBHQ), its equilibrium geometry and harmonic wavenumbers were calculated by the B3LYP/6-31G(d,p) method. The infrared and Raman spectra of DTBHQ were recorded in the region 400-4000 cm -1 and 50-3500 cm -1, respectively. In addition, the IR spectra in CCl 4 at various concentrations of DTBHQ are also recorded. The computed vibrational wavenumbers were compared with the IR and Raman experimental data. Computational calculations at B3LYP level with two different basis sets 6-31G(d,p) and 6-311++G(d,p) are also employed in the study of the possible conformer of DTBHQ. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated using VEDA 4 program. The general agreement between the observed and calculated frequencies was established.
NASA Astrophysics Data System (ADS)
Aschaffenburg, Daniel J.; Williams, Michael R. C.; Schmuttenmaer, Charles A.
2016-05-01
Terahertz time-domain spectroscopic polarimetry has been used to measure the polarization state of all spectral components in a broadband THz pulse upon transmission through generalized anisotropic media consisting of two-dimensional arrays of lithographically defined Archimedean spirals. The technique allows a full determination of the frequency-dependent, complex-valued transmission matrix and eigenpolarizations of the spiral arrays. Measurements were made on a series of spiral array orientations. The frequency-dependent transmission matrix elements as well as the eigenpolarizations were determined, and the eigenpolarizations were found be to elliptically corotating, as expected from their symmetry. Numerical simulations are in quantitative agreement with measured spectra.
Parameterization of directional spectra, part 2, volume 1
NASA Astrophysics Data System (ADS)
Juszko, Barbara-Ann
1989-12-01
The description of complex directional wave spectra using a limited number of parameters would reduce data storage requirements and facilitate the theoretical and practical use of spectral characteristics. The present work assessed the ability of a 10 parameter model developed in the WAVEC study and the existing OGDP hindcast model to represent hindcast directional wave spectra observed at a single location near Hibernia. The parametric model acceptably reproduced the hindcast spectra over 90 percent of the time. There was little loss of information as indicated by the behavior of the spectral statistics. A significant correlation was observed between energy levels, peak wave direction and vector mean direction between hindcast and observed behavior. No definite conclusions could be formed on specific frequency direction features due to intrinsic limitations in directional spectral techniques. A coherence analysis between hindcast and measured winds indicated that the man machine mix of hindcast input wind did provide an improvement over a purely geostrophic estimate. The coherence squared dropped below acceptable levels at frequencies above 0.75 cycles per day (cpd). This behavior was reflected in the coherence of the vector mean wave field. Limiting the analysis to selected wave frequency bands, indicated that the hindcast model did not reproduce the observed swell signature with any statistical confidence while the set showed acceptable coherence to frequencies between 0.75 and 1.0 cpd.
Tuning vibrational mode localization with frequency windowing
NASA Astrophysics Data System (ADS)
Cheng, Xiaolu; Talbot, Justin J.; Steele, Ryan P.
2016-09-01
Local-mode coordinates have previously been shown to be an effective starting point for anharmonic vibrational spectroscopy calculations. This general approach borrows techniques from localized-orbital machinery in electronic structure theory and generates a new set of spatially localized vibrational modes. These modes exhibit a well-behaved spatial decay of anharmonic mode couplings, which, in turn, allows for a systematic, a priori truncation of couplings and increased computational efficiency. Fully localized modes, however, have been found to lead to unintuitive mixtures of characteristic motions, such as stretches and bends, and accordingly large bilinear couplings. In this work, a very simple, tunable localization frequency window is introduced, in order to realize the transition from normal modes to fully localized modes. Partial localization can be achieved by localizing only pairs of modes within this traveling frequency window, which allows for intuitive interpretation of modes. The optimal window size is suggested to be a few hundreds of wave numbers, based on small- to medium-sized test systems, including water clusters and polypeptides. The new sets of partially localized coordinates retain their spatial coupling decay behavior while providing a reduced number of potential energy evaluations for convergence of anharmonic spectra.
Pechousek, J.
2010-07-13
This paper is focused on a quality characterizing the Moessbauer spectra measured for various frequencies of the velocity signal. Standard electromechanical double-loudspeaker drive and digital PID velocity controller were used for calibration spectra measurement in the frequency interval from 4 up to 100 Hz. Several parameters were evaluated for recommendation of the suitable velocity signal frequency.
Koch, Michael; Denzler, Joachim; Redies, Christoph
2010-08-19
Art images and natural scenes have in common that their radially averaged (1D) Fourier spectral power falls according to a power-law with increasing spatial frequency (1/f(2) characteristics), which implies that the power spectra have scale-invariant properties. In the present study, we show that other categories of man-made images, cartoons and graphic novels (comics and mangas), have similar properties. Further on, we extend our investigations to 2D power spectra. In order to determine whether the Fourier power spectra of man-made images differed from those of other categories of images (photographs of natural scenes, objects, faces and plants and scientific illustrations), we analyzed their 2D power spectra by principal component analysis. Results indicated that the first fifteen principal components allowed a partial separation of the different image categories. The differences between the image categories were studied in more detail by analyzing whether the mean power and the slope of the power gradients from low to high spatial frequencies varied across orientations in the power spectra. Mean power was generally higher in cardinal orientations both in real-world photographs and artworks, with no systematic difference between the two types of images. However, the slope of the power gradients showed a lower degree of mean variability across spectral orientations (i.e., more isotropy) in art images, cartoons and graphic novels than in photographs of comparable subject matters. Taken together, these results indicate that art images, cartoons and graphic novels possess relatively uniform 1/f(2) characteristics across all orientations. In conclusion, the man-made stimuli studied, which were presumably produced to evoke pleasant and/or enjoyable visual perception in human observers, form a subset of all images and share statistical properties in their Fourier power spectra. Whether these properties are necessary or sufficient to induce aesthetic perception remains
Classical Trajectories and Quantum Spectra
NASA Technical Reports Server (NTRS)
Mielnik, Bogdan; Reyes, Marco A.
1996-01-01
A classical model of the Schrodinger's wave packet is considered. The problem of finding the energy levels corresponds to a classical manipulation game. It leads to an approximate but non-perturbative method of finding the eigenvalues, exploring the bifurcations of classical trajectories. The role of squeezing turns out decisive in the generation of the discrete spectra.
Discrimination of petroleum fluorescence spectra.
Stelmaszewski, Adam
2007-01-01
This paper presents studies of the total spectra (fluorescence-excitation matrix) of petroleum with regard to the utilization of fluorescence for determining petroleum pollutants. Thorough testing of one group, comprising almost forty lubricating oils in the form of their hexane solutions, points out their discrimination.
Shape effects on asteroid spectra
NASA Astrophysics Data System (ADS)
Davalos, J.; Carvano, J.
2014-07-01
The objective of this work is to probe how the shape of a body like an asteroid could be modifying its observed spectra and the derived mineralogical interfaces based on spectral modeling. To model this effect, we construct an oblate ellipsoid with triangular facets, where each facet contributes to the overall reflectance. The synthetic spectra is generated by the isotropic multiple-scattering approximation (IMSA) reflectance model of Hapke (1993). First, we obtained optical constants by inverting the spectra of meteorites, obtained from the RELAB spectral database. These optical constants were found inverting the reflectance bidirectional equation of Hapke; this is made in two steps: (i) The first inversion is to find the single-scattering albedo π (ii) in the model of Hapke, this albedo is found under the regime of the geometric optics, where the particle size is much larger than the wavelength of the incident radiation. Here we assumed a constant value for the real part of the optical constant n=1.5. With these optical constants, we can construct synthetic spectra for any particle size. The phase function used is the double Henyey-Greenstein phase function and an accurate expression for the H-functions. We started with the ellipsoidal shape a=1.0, b=c=0.5 for two particle size 50 and 250 μ m, in this part, we found good differences in the BAR parameter between the two geometric models, this was done for 100 Eucrite meteorites spectra. In this first study, we found that the BAR parameter between the two models is bigger when the particle size increases. In the second part, we started with different ellipsoidal shapes and produced synthetic spectra for material with eucrite and diogenite composition with a phase angle of 20 degrees, incidence and emission angles of 10 degrees, and particle size at 250 μ m. All spectra was generated for four parameters of phase angle b=[0.2,0.4,0.6,0.8] taking the empirical relation between the phase constants of Hapke (2012
NASA Astrophysics Data System (ADS)
Vollmer, Bernd; Derriere, Sebastian; Krichbaum, Thomas P.; Boch, Thomas; Gassmann, Brice; Davoust, Emmanuel; Dubois, Pascal; Genova, Françoise; Ochsenbein, François; van Driel, Wim
2007-08-01
We have used the 20 largest radio continuum catalogues contained in VizieR (CDS) to determine radio continuum spectra between wavelengths of 2cm and 1m. For 67,000 out of the 3.5 million catalogued sources we could extract radio spectra with measurements at at least three independent frequencies (Vollmer et al. 2005, A&A, 431, 1177). These have been validated by comparison with existing spectral indices from the literature. This work allowed us to investigated the compatibility between the 20 radio continuum catalogues (Vollmer et al. 2005, A&A, 436, 757). Our radio spectra data base was searched for Gigahertz peaked source candidates, which we then observed quasi-simultaneously with the Effelsberg 100-m radio telescope at 6cm (4.85GHz), 2.8cm (10.45GHz), and 9mm (32GHz). This represents an efficient procedure to discover new Gigahertz peaked sources, which are believed to be AGNs at the beginning of their radio evolution. In our sample of more than 200 sources we find more than 50% bona fide GPS sources. In addition, we can estimate the percentage of variable sources in our multi-epoch sample of radio sources which show an inverted spectrum. We are generalizing the method by using VO capabilities to: (i) identify pertinent radio catalogues in the VO registry using Uniform Content Descriptions (UCDs); all catalogues containing a user defined set of UCDs (e.g., PHOT_FLUX_RADIO* for a radio flux, POS_EQ_RA and POS_EQ_DEC for the position) are located in the VO registry and listed for further queries; (ii) extract relevant data, the user can easily assign a row of a given catalogue to a row of a previously defined output catalogue; and (iii) normalize these for the determination of radio spectra; units can be converted, aconymes can be created, flags can be created, etc. This procedure allows to homogenize the information retrieved from a heterogenuous set of catalogues. For this purpose software allowing semi-automated information retrieval is being developed at the
Infrared Spectra of Polycyclic Aromatic Hydrocarbons: Methyl Substitution and Loss of H
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W.; Langhoff, Stephen R.; Arnold, James O. (Technical Monitor)
1998-01-01
The B3LYP approach, in conjunction with the 4-31G basis set, is used to compute the harmonic frequencies of 1- and 2-methylnaphthalene, 1-, 2-, and 9-methylanthracene, and their cations. The IR spectra of the methyl substituted species are very similar to the parent spectra, except for the addition of the methyl C-H stretch at lower frequency than the aromatic C-H stretch. The loss of a single hydrogen from naphthalene, anthracene, and their cations is shown to have a very small effect on the IR spectra. Loss of a methyl hydrogen from 1- or 2-methylnaphthalene, or their cations, is shown to shift the side group C-H frequencies from below aromatic hydrogen stretching frequencies to above them. The loss of IT from 2-methylenenaphthalene shows only a small shift in the side group C-H stretching frequency.
Butkus, Vytautas; Valkunas, Leonas; Abramavicius, Darius
2014-01-21
A general theory of electronic excitations in aggregates of molecules coupled to intramolecular vibrations and the harmonic environment is developed for simulation of the third-order nonlinear spectroscopy signals. It is applied in studies of the time-resolved two-dimensional coherent spectra of four characteristic model systems: weakly/strongly vibronically coupled molecular dimers interacting with high/low frequency intramolecular vibrations. The results allow us to (i) classify and define the typical spectroscopic features of vibronically coupled molecules, (ii) separate the cases, when the long-lived quantum coherences due to vibrational lifetime borrowing should be expected, (iii) define when the complete exciton–vibrational mixing occurs, and (iv) when separation of excitonic and vibrational coherences is possible.
Hyper Raman spectra calculated in a time-dependent Hartree-Fock method
NASA Astrophysics Data System (ADS)
Mohammed, Abdelsalam; Ågren, Hans; Ringholm, Magnus; Thorvaldsen, Andreas J.; Ruud, Kenneth
2012-10-01
Hyper Raman scattering (HRS) of the benzonitrile (BN) and 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) molecules is studied by means of ab initio calculations. The computational procedure employs a recently developed methodology for the analytic calculations of frequency-dependent polarizability gradients of arbitrary order, including perturbation dependent basis sets. The result are compared to normal Raman scattering (NRS) and coherent anti-Stokes Raman scattering (CARS) that previously have been studied using the same technology. It is found that some suppressed or silent modes in CARS and NRS spectra are clearly seen in HRS, and that although under general excitation conditions the HRS intensities are much lower than for CARS and NRS, HRS provides complementary information useful for target identification.
Optical transmission spectra in quasiperiodic multilayered photonic structure
NASA Astrophysics Data System (ADS)
de Medeiros, F. F.; Albuquerque, E. L.; Vasconcelos, M. S.
2006-10-01
Optical transmission spectra in quasiperiodic multilayered photonic structures, composed of both positive (SiO2) and negative refractive index materials, are calculated by using a theoretical model based on the transfer matrix approach for normal incidence geometry. The quasiperiodic structures are substitutional sequences, characterized by the nature of their Fourier spectrum, which can be dense pure point (e.g. Fibonacci sequence) or singular continuous (e.g. Thue-Morse and double-period sequences). The transmission spectra for the case where both refractive indices can be approximated by a different constant show a unique mirror symmetrical profile, with no counterpart for the positive refractive index case, as well as a striking self-similar behaviour related to the Fibonacci sequence. For a more realistic frequency-dependent refractive index, the transmission spectra are characterized by a rich transmission profile of Bragg peaks with no more self-similarity or mirror symmetry.
Matanovic, Ivana; Atanassov, Plamen; Kiefer, Boris; Garzon, Fernando; Henson, Neil J.
2014-10-05
The structural equilibrium parameters, the adsorption energies, and the vibrational frequencies of the nitrogen molecule and the hydrogen atom adsorbed on the (111) surface of rhodium have been investigated using different generalized-gradient approximation (GGA), nonlocal correlation, meta-GGA, and hybrid functionals, namely, Perdew, Burke, and Ernzerhof (PBE), Revised-RPBE, vdW-DF, Tao, Perdew, Staroverov, and Scuseria functional (TPSS), and Heyd, Scuseria, and Ernzerhof (HSE06) functional in the plane wave formalism. Among the five tested functionals, nonlocal vdW-DF and meta-GGA TPSS functionals are most successful in describing energetics of dinitrogen physisorption to the Rh(111) surface, while the PBE functional provides the correct chemisorption energy for the hydrogen atom. It was also found that TPSS functional produces the best vibrational spectra of the nitrogen molecule and the hydrogen atom on rhodium within the harmonic formalism with the error of 22.62 and 21.1% for the NAN stretching and RhAH stretching frequency. Thus, TPSS functional was proposed as a method of choice for obtaining vibrational spectra of low weight adsorbates on metallic surfaces within the harmonic approximation. At the anharmonic level, by decoupling the RhAH and NAN stretching modes from the bulk phonons and by solving one- and two-dimensional Schr€odinger equation associated with the RhAH, RhAN, and NAN potential energy we calculated the anharmonic correction for NAN and RhAH stretching modes as 231 cm21 and 277 cm21 at PBE level. Anharmonic vibrational frequencies calculated with the use of the hybrid HSE06 function are in best agreement with available experiments.
Higher-order spectra for identification of nonlinear modal coupling
NASA Astrophysics Data System (ADS)
Hickey, Daryl; Worden, Keith; Platten, Michael F.; Wright, Jan R.; Cooper, Jonathan E.
2009-05-01
Over the past four decades considerable work has been done in the area of power spectrum estimation. The information contained within the power spectrum relates to a signal's autocorrelation or 'second-order statistics'. The power spectrum provides a complete statistical description of a Gaussian process; however, a problem with this information is that it is phase blind. This problem is addressed if one turns to a system's frequency response function (FRF). The FRF graphs the magnitude and phase of the frequency response of a system; in order to do this it requires information regarding the frequency content of the input and output signals. Situations arise in science and engineering whereby signal analysts are required to look beyond second-order statistics and analyse a signal's higher-order statistics (HOS). HOS or spectra give information on a signal's deviation from Gaussianity and consequently are a good indicator function for the presence of nonlinearity within a system. One of the main problems in nonlinear system identification is that of high modal density. Many modelling schemes involve making some expansion of the nonlinear restoring force in terms of polynomial or other basis terms. If more than one degree-of-freedom is involved this becomes a multivariate problem and the number of candidate terms in the expansion grows explosively with the order of nonlinearity and the number of degrees-of-freedom. This paper attempts to use HOS to detect and qualify nonlinear behaviour for a number of symmetrical and asymmetrical systems over a range of degrees-of-freedom. In doing so the paper also attempts to show that HOS are a more sensitive tool than the FRF in detecting nonlinearity. Furthermore, the object of this paper is to try and identify which modes couple in a nonlinear manner in order to reduce the number of candidate coupling terms, for a model, as much as possible. The bispectrum method has previously been applied to simple low-DOF systems with high
Phobos surface spectra mineralogical modeling
NASA Astrophysics Data System (ADS)
Pajola, M.; Lazzarin, M.; Dalle Ore, C. M.; Cruikshank, D. P.; Roush, T. L.; Pendleton, Y.; Bertini, I.; Magrin, S.; Carli, C.; La Forgia, F.; Barbieri, C.
2014-04-01
A mineralogical model composed of a mixture of Tagish Lake meteorite (TL) and Pyroxene Glass (PM80) was presented in [1] to explain the surface reflectance of Phobos from 0.25 to 4.0 μm. The positive results we obtained, when comparing the OSIRIS data [2] extended in wavelength to include the [3,4] spectra, forced us to perform a wider comparison between our TL-PM80 model and the CRISM and OMEGA Phobos spectra presented in [5]. Such spectra cover three different regions of interest (ROIs) situated in the Phobos sub-Mars hemisphere: the interior of the Stickney crater, its eastern rim, and its proximity terrain southeast of the Reldresal crater. We decided to vary the percentage mixture of the components of our model (80% TL, 20% PM80), between pure TL and pure PM80, by means of the radiative transfer code based on the [6] formulation of the slab approximation. Once this spectral range was derived, see Fig. 1, we attempted to compare it with the [5] spectra between 0.4 and 2.6 μm, i.e. below the thermal emitted radiation, to see if any spectral match was possible. We observed that CRISM scaled spectra above 1.10 μm fall within pure Tagish Lake composition and the [1] model. The CRISM data below 1.10 μm present more discrepancies with our models, in particular for the Stickney's rim spectrum. Nevertheless the TL and PM80 components seem to be good mineralogical candidates on Phobos. We performed the same analysis with the OMEGA data and, again, we found out that the Stickney's rim spectrum lies out of our model range, while the two remaining spectra still lie between pure TL and 80% TL - 20% PM80, but indicating that a different, more complicated mixture is expected in order to explain properly both the spectral trend and the possible absorption bands located above 2.0 μm. Within this analysis, we point out that a big fraction of TL material (modeled pure or present with a minimum percentage of 80% mixed together with 20% PM80) seems to explain Phobos spectral
Model investigation of the Raman spectra of amorphous silicon
NASA Astrophysics Data System (ADS)
Marinov, M.; Zotov, N.
1997-02-01
A model for calculating the first-order Raman spectra of amorphous silicon (a-Si) without adjustable parameters is proposed. Calculations on the original 216-atom model of a-Si, generated by the algorithm of Wooten, Winer, and Weaire (WWW) are in very good agreement with experimental spectra and give further indication that the WWW cluster is a realistic model of moderately disordered a-Si. The TA-TO assignment of the low and high frequency bands is supported by direct numerical calculations of the phase quotient and the stretching character of the vibrational modes. The calculated participation ratios and correlation lengths of the vibrational modes indicate that the high-frequency TO-like modes are strongly localized on defects. The relative intensities of the TA-, LA-, and LO-like bands depend on the intermediate-range order, while that of the TO-like band mainly on the short-range order.
NASA Astrophysics Data System (ADS)
Fan, Yalin; Rogers, W. Erick
2016-06-01
In this study, Donelan, M.A., Babanin, A.V., Young, I.R., Banner, M.L., 2006. J. Phys. Oceanogr. 36, 1672-1688 source function is used to calculate drag coefficients from both the scanning radar altimeter (SRA) measured two dimensional wave spectra obtained during hurricane Ivan in 2004 and the WAVEWATCH III simulated wave spectra. The drag coefficients disagree between the SRA and model spectra mainly in the right/left rear quadrant of the hurricane where the observed spectra appear to be bimodal while the model spectra are single peaked with more energy in the swell frequencies and less energy in the wind sea frequencies. These results suggest that WAVEWATCH III is currently not capable of providing sensible stress calculations in the rear quadrants of the hurricane.
Simulation of transient infrared spectra of a photoswitchable peptide.
Kobus, Maja; Lieder, Martin; Nguyen, Phuong H; Stock, Gerhard
2011-12-14
In transient infrared (IR) experiments, a molecular system may be photoexcited in a nonstationary conformational state, whose time evolution is monitored via IR spectroscopy with high temporal and structural resolution. As a theoretical formulation of these experiments, this work derives explicit expressions for transient one- and two-dimensional IR spectra and discusses various levels of approximation and sampling strategies. Adopting a photoswitchable octapeptide in water as a representative example, nonequilibrium molecular dynamics simulations are performed and the photoinduced conformational dynamics and associated IR spectra are discussed in detail. Interestingly, it is found that the time scales of dynamics and spectra may differ from residue to residue by up to an order of magnitude. Considering merely the cumulative spectrum of all residues, the contributions of the individual residues largely compensate each other, which may explain the surprisingly small frequency shifts and short photoproduct rise times found in experiment. Even when a localized amide I mode is probed (e.g., via isotope labeling), the vibrational frequency shift is shown to depend in a complicated way on the conformation of the entire peptide as well as on the interaction with the solvent. In this context, various issues concerning the interpretation of transient IR spectra and conformational dynamics in terms of a few exponential time scales are discussed.
[Raman, FTIR spectra and normal mode analysis of acetanilide].
Liang, Hui-Qin; Tao, Ya-Ping; Han, Li-Gang; Han, Yun-Xia; Mo, Yu-Jun
2012-10-01
The Raman and FTIR spectra of acetanilide (ACN) were measured experimentally in the regions of 3 500-50 and 3 500-600 cm(-1) respectively. The equilibrium geometry and vibration frequencies of ACN were calculated based on density functional theory (DFT) method (B3LYP/6-311G(d, p)). The results showed that the theoretical calculation of molecular structure parameters are in good agreement with previous report and better than the ones calculated based on 6-31G(d), and the calculated frequencies agree well with the experimental ones. Potential energy distribution of each frequency was worked out by normal mode analysis, and based on this, a detailed and accurate vibration frequency assignment of ACN was obtained.
Zhou, Tao; Wu, Yidong; Cao, Juncheng; Zou, Liangliang; Yuan, Jie; Yao, Zhenwei; Xu, Gongjie
2017-02-01
Terahertz time-domain spectroscopy (THz-TDS) is used to investigate the absorption spectra of polycrystalline L- and DL-histidine in the frequency range of 10-100 cm(-1). The spectra exhibit distinct differences in peak frequencies between the enantiomer (L-histidine) and racemic compound (DL-histidine). The observed spectral differences are attributed to the intermolecular interactions. With the density function theory (DFT) method, the frequencies of vibrational modes of L-histidine and DL-histidine in the THz range are calculated and well assigned according to the measured spectra. The origin of the observed vibrational modes is found to be non-localized and of a collective (phonon-like) nature, which points to the lattice and skeleton vibrations mediated by the hydrogen bond. Furthermore, we propose and demonstrate a method for determining the composition ratio of histidine mixtures based on the THz absorption spectra.
Hierarchical analysis of molecular spectra
Davis, M.J.
1996-03-01
A novel representation of molecular spectra in terms of hierarchical trees has proven to be an important aid for the study of many significant problems in gas-phase chemical dynamics. Trees are generated from molecular spectra by monitoring the changes that occur in a spectrum as resolution is changed in a continuous manner. A tree defines a genealogy among all lines of a spectrum. This allows for a detailed understanding of the assignment of features of a spectrum that may be difficult to obtain any other way as well as an understanding of intramolecular energy transfer time scales, mechanisms, and pathways. The methodology has been applied to several problems: transition state spectroscopy, intramolecular energy transfer in highly excited molecules, high-resolution overtone spectroscopy, and the nature of the classical-quantum correspondence when there is classical chaos (``quantum chaos``).
Accelerated Fitting of Stellar Spectra
NASA Astrophysics Data System (ADS)
Ting, Yuan-Sen; Conroy, Charlie; Rix, Hans-Walter
2016-07-01
Stellar spectra are often modeled and fitted by interpolating within a rectilinear grid of synthetic spectra to derive the stars’ labels: stellar parameters and elemental abundances. However, the number of synthetic spectra needed for a rectilinear grid grows exponentially with the label space dimensions, precluding the simultaneous and self-consistent fitting of more than a few elemental abundances. Shortcuts such as fitting subsets of labels separately can introduce unknown systematics and do not produce correct error covariances in the derived labels. In this paper we present a new approach—Convex Hull Adaptive Tessellation (chat)—which includes several new ideas for inexpensively generating a sufficient stellar synthetic library, using linear algebra and the concept of an adaptive, data-driven grid. A convex hull approximates the region where the data lie in the label space. A variety of tests with mock data sets demonstrate that chat can reduce the number of required synthetic model calculations by three orders of magnitude in an eight-dimensional label space. The reduction will be even larger for higher dimensional label spaces. In chat the computational effort increases only linearly with the number of labels that are fit simultaneously. Around each of these grid points in the label space an approximate synthetic spectrum can be generated through linear expansion using a set of “gradient spectra” that represent flux derivatives at every wavelength point with respect to all labels. These techniques provide new opportunities to fit the full stellar spectra from large surveys with 15-30 labels simultaneously.
Odor Impression Prediction from Mass Spectra.
Nozaki, Yuji; Nakamoto, Takamichi
2016-01-01
The sense of smell arises from the perception of odors from chemicals. However, the relationship between the impression of odor and the numerous physicochemical parameters has yet to be understood owing to its complexity. As such, there is no established general method for predicting the impression of odor of a chemical only from its physicochemical properties. In this study, we designed a novel predictive model based on an artificial neural network with a deep structure for predicting odor impression utilizing the mass spectra of chemicals, and we conducted a series of computational analyses to evaluate its performance. Feature vectors extracted from the original high-dimensional space using two autoencoders equipped with both input and output layers in the model are used to build a mapping function from the feature space of mass spectra to the feature space of sensory data. The results of predictions obtained by the proposed new method have notable accuracy (R≅0.76) in comparison with a conventional method (R≅0.61).
An atlas of selected calibrated stellar spectra
NASA Technical Reports Server (NTRS)
Walker, Russell G.; Cohen, Martin
1992-01-01
Five hundred and fifty six stars in the IRAS PSC-2 that are suitable for stellar radiometric standards and are brighter than 1 Jy at 25 microns were identified. In addition, 123 stars that meet all of our criteria for calibration standards, but which lack a luminosity class were identified. An approach to absolute stellar calibration of broadband infrared filters based upon new models of Vega and Sirius due to Kurucz (1992) is presented. A general technique used to assemble continuous wide-band calibrated infrared spectra is described and an absolutely calibrated 1-35 micron spectrum of alpha(Tau) is constructed and the method using new and carefully designed observations is independently validated. The absolute calibration of the IRAS Low Resolution Spectrometer (LRS) database is investigated by comparing the observed spectrum of alpha(Tau) with that assumed in the original LRS calibration scheme. Neglect of the SiO fundamental band in alpha(Tau) has led to the presence of a specious 'emission' feature in all LRS spectra near 8.5 microns, and to an incorrect spectral slope between 8 and 12 microns. Finally, some of the properties of asteroids that effect their utility as calibration objects for the middle and far infrared region are examined. A technique to determine, from IRAS multiwaveband observations, the basic physical parameters needed by various asteroid thermal models that minimize the number of assumptions required is developed.
Odor Impression Prediction from Mass Spectra
Nakamoto, Takamichi
2016-01-01
The sense of smell arises from the perception of odors from chemicals. However, the relationship between the impression of odor and the numerous physicochemical parameters has yet to be understood owing to its complexity. As such, there is no established general method for predicting the impression of odor of a chemical only from its physicochemical properties. In this study, we designed a novel predictive model based on an artificial neural network with a deep structure for predicting odor impression utilizing the mass spectra of chemicals, and we conducted a series of computational analyses to evaluate its performance. Feature vectors extracted from the original high-dimensional space using two autoencoders equipped with both input and output layers in the model are used to build a mapping function from the feature space of mass spectra to the feature space of sensory data. The results of predictions obtained by the proposed new method have notable accuracy (R≅0.76) in comparison with a conventional method (R≅0.61). PMID:27326765
Frequency Adaptability and Waveform Design for OFDM Radar Space-Time Adaptive Processing
Sen, Satyabrata; Glover, Charles Wayne
2012-01-01
We propose an adaptive waveform design technique for an orthogonal frequency division multiplexing (OFDM) radar signal employing a space-time adaptive processing (STAP) technique. We observe that there are inherent variabilities of the target and interference responses in the frequency domain. Therefore, the use of an OFDM signal can not only increase the frequency diversity of our system, but also improve the target detectability by adaptively modifying the OFDM coefficients in order to exploit the frequency-variabilities of the scenario. First, we formulate a realistic OFDM-STAP measurement model considering the sparse nature of the target and interference spectra in the spatio-temporal domain. Then, we show that the optimal STAP-filter weight-vector is equal to the generalized eigenvector corresponding to the minimum generalized eigenvalue of the interference and target covariance matrices. With numerical examples we demonstrate that the resultant OFDM-STAP filter-weights are adaptable to the frequency-variabilities of the target and interference responses, in addition to the spatio-temporal variabilities. Hence, by better utilizing the frequency variabilities, we propose an adaptive OFDM-waveform design technique, and consequently gain a significant amount of STAP-performance improvement.
Optical Spectra of Triggered Lightning
NASA Astrophysics Data System (ADS)
Walker, T. D.; Biagi, C. J.; Hill, J. D.; Jordan, D. M.; Uman, M. A.; Christian, H. J., Jr.
2009-12-01
In August 2009, the first optical spectra of triggered lightning flashes were acquired. Data from two triggered lightning flashes were obtained at the International Center for Lightning Research and Testing in north-central Florida. The spectrometer that was used has an average dispersion of 260 Å/mm resulting in an average resolution of 5 Å when mated to a Photron (SA1.1) high-speed camera. The spectra captured with this system had a free spectral range of 3800-8000 Å. The spectra were captured at 300,000 frames per second. The spectrometer's vertical field of view was 3 m at an altitude 50 m above the launch tower, intended to view the middle of the triggering wire. Preliminary results show that the copper spectrum dominated the earliest part of the flash and copper lines persisted during the total lifetime of the detectable spectrum. Animations over the lifetime of the stroke from the initial wire illumination to multiple return strokes show the evolution of the spectrum. In addition, coordinated high speed channel base current, electric field and imagery measurements of the exploding wire, downward leaders, and return strokes were recorded. Quantitative analysis of the spectral evolution will be discussed in the context of the overall flash development.
Ultraviolet Spectra of Uranian Satellites
NASA Astrophysics Data System (ADS)
Roush, Ted
1996-07-01
The ultraviolet reflectance spectra of the icy satellites ofUranus are largely unknown. We propose to use the HubbleSpace Telescope Faint Object Spectrograph in order to obtainthe first high S/N UV spectra of Ariel, Titania, and Oberon.Because of our innovative targeting approach, we have alsobeen able to include Umbriel in our observational plans.These satellites sample almost the full range of UV albedosand UV/VIS colors exhibited by the large Uranian satellites.The spectral resolution and range will overlap with earth-based telescopic and spacecraft observations of these objectsallowing for comparisons of the UV data with existing visualand near-infrared spectra of these objects. These comparisonswill ultimately provide greater constraints on the relativelylow albedo spectrally neutral non-ice component on the Uraniansatellites. The existance of UV spectral features due tospecies such as O_3, H_2O_2 or carbon-rich macromolecules(e.g. polycyclic aromatic hydrocarbons) can provide evidencefor modification of the surfaces via plasma or meteoriticbombardment, alteration by high-energy ultraviolet radiation,or accretion of particles from nearby sources such asplanetary rings or dust bands.
Assessment of multiple frequency ELF electric and magnetic field exposure
NASA Astrophysics Data System (ADS)
Leitgeb, N.
2008-01-01
Electromagnetic fields both in daily life and at workplaces exhibit increasingly complex frequency spectra. Present spectral assessment rules proved to be too conservative for health risk assessment. This is because they are based on the assumption that cells would react like linear systems in terms of responding to a sum of frequencies by a sum of independent responses to each individual frequency. Based on numerical investigations with the Hodgkin-Huxley and the Frankenhaeuser-Huxley nerve cell models, it could be shown that accounting for the nonlinear behaviour of cellular excitation processes avoids considerable overestimation of simultaneous exposures to multiple frequency ELF electric and magnetic fields. Besides this, it could be shown that the role of phase relationships is less important than that assumed so far. The present assessment rules lead to non-compliances of marketed electric appliances. For general application, a nonlinear biology-based assessment (NBBA) rule has been proposed, validated and proven advantageous compared with ICNIRP's rule. While staying conservative it avoids unnecessary overestimation and demonstrates compliance even in cases of suspected non-conformities. It is up to responsible bodies to decide upon the adoption of this proposal and the potential need for implementing additional or reducing the already incorporated safety factors.
Assessment of multiple frequency ELF electric and magnetic field exposure.
Leitgeb, N
2008-01-21
Electromagnetic fields both in daily life and at workplaces exhibit increasingly complex frequency spectra. Present spectral assessment rules proved to be too conservative for health risk assessment. This is because they are based on the assumption that cells would react like linear systems in terms of responding to a sum of frequencies by a sum of independent responses to each individual frequency. Based on numerical investigations with the Hodgkin-Huxley and the Frankenhaeuser-Huxley nerve cell models, it could be shown that accounting for the nonlinear behaviour of cellular excitation processes avoids considerable overestimation of simultaneous exposures to multiple frequency ELF electric and magnetic fields. Besides this, it could be shown that the role of phase relationships is less important than that assumed so far. The present assessment rules lead to non-compliances of marketed electric appliances. For general application, a nonlinear biology-based assessment (NBBA) rule has been proposed, validated and proven advantageous compared with ICNIRP's rule. While staying conservative it avoids unnecessary overestimation and demonstrates compliance even in cases of suspected non-conformities. It is up to responsible bodies to decide upon the adoption of this proposal and the potential need for implementing additional or reducing the already incorporated safety factors.
Precision spectral peak frequency measurement using a window leakage ratio function
NASA Astrophysics Data System (ADS)
Swanson, David C.
2015-03-01
For power spectra of signals consisting of stationary sinusoids mixed with random noise, the frequency and amplitude of a spectral peak can be estimated with greater accuracy than the nearest frequency bin of the Fourier transform by exploiting the spectral leakage characteristics for the particular data window used. Techniques such as linear interpolation or an amplitude weighted average have inadequate precision due to the nonlinear leakage into adjacent bins and the dependence on data window type. This paper offers a new general algorithm presented using the Fourier coefficients ck of the input data window to produce a function which is the ratio of the side-bin amplitudes of the window in the frequency domain. The ratio function allows one to use the amplitudes of the adjacent bins of a spectral peak to precisely estimate the peak frequency and amplitude when the frequency does not lie exactly on a frequency bin (in between the discrete bins of a Fourier transform). Examples are provided for a number of popular data windows. The ratio function can be most easily implemented using a simplified log-ratio function for the window side bin magnitudes. A statistical analysis provides a useful frequency estimation error estimate given the signal-to-noise ratio of the spectral peak based on an approximation of the ratio of non-zero mean Gaussian variables. The benefits of this technique are not just improved estimation accuracy for amplitude and frequency, but also allow large spectral data files to be accurately reduced in size for remote monitoring of vibration spectra. An example is given of a methodology for reduction of spectral data file size without the loss of important signals for analysis where the file size is reduced by 88% with only a few percent error, which is mostly confined to the background noise in the reconstructed spectrum.
Preliminary investigation on the relation between maximum wave height and wave spectra
NASA Astrophysics Data System (ADS)
Tao, Aifeng; Wen, Cheng; Wu, Yuqing; Wu, Haoran; Li, Shuo; Cao, Guangsui
2016-04-01
The maximum wave height is important not only for the determination of design wave parameters but also for the marine disaster defense. While it cannot be predicted straightforwardly at present, since the general numerical models for wave forecasting are all based on phase averaged spectra model. Then it becomes very useful to make clear the relationship between the maximum wave height and wave spectra parameters, such as average wave steepness, spectra width and spectra type, such as one single peak spectra or multi peaks spectra. In order to perform this research procedure, plenty of observed wave data are required. We collected ten years wave data measured from a ship in North Sea, one year wave pressure data from nine points around Korea, four years buoy data from three points along Chinese coast. The preliminary investigation results on the relations between maximum waves and spectra via the mention observed data will be present here.
X ray spectra of cataclysmic variables
NASA Technical Reports Server (NTRS)
Patterson, Joseph; Halpern, Jules
1990-01-01
X ray spectral parameters of cataclysmic variables observed with the 'Einstein' imaging proportional counter were determined by fitting an optically thin, thermal bremsstrahlung spectrum to the raw data. Most of the sources show temperatures of order a few keV, while a few sources exhibit harder spectra with temperatures in excess of 10 keV. Estimated 0.1 to 3.5 keV luminosities are generally in the range from 10(exp 30) to 10(exp 32) erg/sec. The results are consistent with the x rays originating in a disk/white dwarf boundary layer of non-magnetic systems, or in a hot, post-shock region in the accretion column of DQ Her stars, with a negligible contribution from the corona of the companion. In a few objects column densities were found that are unusually high for interstellar material. It was suggested that the absorption occurs in the system itself.
Relationship between harmonic spectra and coercive field of immobilized magnetic nanoparticles
NASA Astrophysics Data System (ADS)
Sasayama, Teruyoshi; Yoshida, Takashi; Enpuku, Keiji
2017-02-01
We studied the AC hysteresis loop and the harmonic spectra of samples containing immobilized magnetic nanoparticles (MNPs) at different values of the excitation field frequency f and amplitude H 0. First, we measured the dependences of the coercive field
Spectra of volcanic rocks glasses as analogues of Mercury surface spectra
NASA Astrophysics Data System (ADS)
Carli, C.; Capaccioni, F.; de Sanctis, M.; Filacchione, G.; Sgavetti, M.; di Genova, D.; Vona, A.; Visonà, D.; Ammannito, E.
2010-12-01
Remote-sensing studies have revealed that most of the inner planets surfaces are composed by magmatic effusive rocks as lava flows or pyroclastic deposits, that are the natural products of magma-rock dynamic systems controlled by T, P, oxygen fugacity and time. These materials generally contain a fair amount of volcanic glass, due to the magma rapid cooling once effused on the surface. The VNIR reflectance spectroscopy is one of the most relevant tools for remote-sensing studies and in the last decades gave important results identifying the presence of different Fe-Mg silicates, such as olivine and pyroxenes, on the planets surfaces. However, the mineralogical interpretation of the observed spectral features of several volcanic areas on the inner Solar System bodies is still matter of debate. In particular the presence of dark volcanic glass, which can dominate or not the rock texture, influences the spectra signatures. In fact samples with a glass-bearing groundmass have lower albedo and reduced band intensity of the spectra of samples with comparable mineral composition and intergranular texture. As a consequence, an important goal for studying the planetary crusts is to understand the spectral behavior of volcanic material, where chemical or physical parameters are different depending on geologic context and effusive processes. We present here preliminary laboratory activity to investigate VNIR reflectance spectra of several volcanic glasses. Reflectance spectra, in the wavelength range between 0.35- 2.50 μm, are measured on powders of magmatic rocks, having different composition and textures, at fine (<60 μm in diameter) and very fine (<10 μm) grain sizes. For each rock sample a corresponding “thermal shocked-sample” is produced by heating at 1300°C and P=1 atm and a glass-sample was produced by melting at 1500°C and P=1 atm, than quenching it in air. Reflectance spectra of powders of shocked and glass-samples were acquired at the same grain size, and
Polarization effects in cutaneous autofluorescent spectra
NASA Astrophysics Data System (ADS)
Borisova, E.; Angelova, L.; Jeliazkova, Al.; Genova, Ts.; Pavlova, E.; Troyanova, P.; Avramov, L.
2014-05-01
Used polarized light for fluorescence excitation one could obtain response related to the anisotropy features of extracellular matrix. The fluorophore anisotropy is attenuated during lesions' growth and level of such decrease could be correlated with the stage of tumor development. Our preliminary investigations are based on in vivo point-by-point measurements of excitation-emission matrices (EEM) from healthy volunteers skin on different ages and from different anatomical places using linear polarizer and analyzer for excitation and emission light detected. Measurements were made using spectrofluorimeter FluoroLog 3 (HORIBA Jobin Yvon, France) with fiber-optic probe in steady-state regime using excitation in the region of 280-440 nm. Three different situations were evaluated and corresponding excitation-emission matrices were developed - with parallel and perpendicular positions for linear polarizer and analyzer, and without polarization of excitation and fluorescence light detected from a forearm skin surface. The fluorescence spectra obtained reveal differences in spectral intensity, related to general attenuation, due to filtering effects of used polarizer/analyzer couple. Significant spectral shape changes were observed for the complex autofluorescence signal detected, which correlated with collagen and protein cross-links fluorescence, that could be addressed to the tissue extracellular matrix and general condition of the skin investigated, due to morphological destruction during lesions' growth. A correlation between volunteers' age and the fluorescence spectra detected was observed during our measurements. Our next step is to increase developed initial database and to evaluate all sources of intrinsic fluorescent polarization effects and found if they are significantly altered from normal skin to cancerous state of the tissue, this way to develop a non-invasive diagnostic tool for dermatological practice.
Universality of vibrational spectra of globular proteins
NASA Astrophysics Data System (ADS)
Na, Hyuntae; Song, Guang; ben-Avraham, Daniel
2016-02-01
It is shown that the density of modes of the vibrational spectrum of globular proteins is universal, i.e. regardless of the protein in question, it closely follows one universal curve. The present study, including 135 proteins analyzed with a full atomic empirical potential (CHARMM22) and using the full complement of all atoms Cartesian degrees of freedom, goes far beyond previous claims of universality, confirming that universality holds even in the frequency range that is well above 100 cm-1 (300-4000 cm-1), where peaks and turns in the density of states are faithfully reproduced from one protein to the next. We also characterize fluctuations of the spectral density from the average, paving the way to a meaningful discussion of rare, unusual spectra and the structural reasons for the deviations in such ‘outlier’ proteins. Since the method used for the derivation of the vibrational modes (potential energy formulation, set of degrees of freedom employed, etc) has a dramatic effect on the spectral density, another significant implication of our findings is that the universality can provide an exquisite tool for assessing and improving the quality of potential functions and the quality of various models used for NMA computations. Finally, we show that the input configuration also affects the density of modes, thus emphasizing the importance of simplified potential energy formulations that are minimized at the outset. In summary, our findings call for a serious two-way dialogue between theory and experiment: experimental spectra of proteins could now guide the fine tuning of theoretical empirical potentials, and the various features and peaks observed in theoretical studies—being universal, and hence now rising in importance—would hopefully spur experimental confirmation.
Curved Radio Spectra of Weak Cluster Shocks
NASA Astrophysics Data System (ADS)
Kang, Hyesung; Ryu, Dongsu
2015-08-01
In order to understand certain observed features of arc-like giant radio relics such as the rareness, uniform surface brightness, and curved integrated spectra, we explore a diffusive shock acceleration (DSA) model for radio relics in which a spherical shock impinges on a magnetized cloud containing fossil relativistic electrons. Toward this end, we perform DSA simulations of spherical shocks with the parameters relevant for the Sausage radio relic in cluster CIZA J2242.8+5301, and calculate the ensuing radio synchrotron emission from re-accelerated electrons. Three types of fossil electron populations are considered: a delta-function like population with the shock injection momentum, a power-law distribution, and a power law with an exponential cutoff. The surface brightness profile of the radio-emitting postshock region and the volume-integrated radio spectrum are calculated and compared with observations. We find that the observed width of the Sausage relic can be explained reasonably well by shocks with speed {u}{{s}}˜ 3× {10}3 {km} {{{s}}}-1 and sonic Mach number {M}{{s}}˜ 3. These shocks produce curved radio spectra that steepen gradually over (0.1-10){ν }{br} with a break frequency {ν }{br}˜ 1 GHz if the duration of electron acceleration is ˜60-80 Myr. However, the abrupt increase in the spectral index above ˜1.5 GHz observed in the Sausage relic seems to indicate that additional physical processes, other than radiative losses, operate for electrons with {γ }{{e}}≳ {10}4.
Generalized Fourier analysis for phase retrieval of fringe pattern.
Zhong, Jingang; Weng, Jiawen
2010-12-20
A generalized Fourier analysis, by use of an adaptive multiscale windowed Fourier transform (AWFT), has been presented for the phase retrieval of fringe patterns. The Fourier transform method can be considered as a special case of AWFT method with a maximum window. The instantaneous frequency of the local signal is introduced to estimate whether the condition for separating the first spectrum component is satisfied for the phase retrieval of fringe patterns. The adaptive window width for this algorithm is determined by the length of the local stationary fringe pattern in order to balance the frequency and space resolution. The local stationary length of fringe pattern is defined as the signal satisfying the condition that whose first spectrum component is separated from all the other spectra within the local spatial area. In comparison with Fourier transform, fixed windowed Fourier transform and wavelet transform in numerical simulation and experiment, the adaptive multiscale windowed Fourier transform can present more accurate results of phase retrieval.
Dead-Time Modifications to Fast Fourier Transform Power Spectra
NASA Astrophysics Data System (ADS)
Zhang, W.; Jahoda, K.; Swank, J. H.; Morgan, E. H.; Giles, A. B.
1995-08-01
Time series analysis in X-ray astronomy is complicated by the effects of detector dead time which can cause significant departures of power spectra from those expected from simple Poisson statistics. In this paper we study the effects of both the paralyzable and nonparalyzable dead times on the underlying time series which obeys Poisson counting statistics. We present analytical formulae for the autocorrelation function, auto-covariances, and power spectra, for both kinds of dead time. These formulae, taken as a whole, offer a general qualitative and quantitative framework to further understand the effects of dead time in an X-ray detection and data processing system.
Turner, David R; Kubelka, Jan
2007-02-22
Theoretical simulations are used to investigate the effects of aqueous solvent on the vibrational spectra of model alpha-helices, which are only partly exposed to solvent to mimic alpha-helices in proteins. Infrared absorption (IR) and vibrational circular dichroism (VCD) amide I' spectra for 15-amide alanine alpha-helices are simulated using density functional theory (DFT) calculations combined with the property transfer method. The solvent is modeled by explicit water molecules hydrogen bonded to the solvated amide groups. Simulated spectra for two partially solvated model alpha-helices, one corresponding to a more exposed and the other to a more buried structure, are compared to the fully solvated and unsolvated (gas phase) simulations. The dependence of the amide I spectra on the orientation of the partially solvated helix with respect to the solvent and effects of solvation on the amide I' of 13C isotopically substituted alpha-helices are also investigated. The partial exposure to solvent causes significant broadening of the amide I' bands due to differences in the vibrational frequencies of the explicitly solvated and unsolvated amide groups. The different degree of partial solvation is reflected primarily in the frequency shifts of the unsolvated (buried) amide group vibrations. Depending on which side of the alpha-helix is exposed to solvent, the simulated IR band-shapes exhibit significant changes, from broad and relatively featureless to distinctly split into two maxima. The simulated amide I' VCD band-shapes for the partially solvated alpha-helices parallel the broadening of the IR and exhibit more sign variation, but generally preserve the sign pattern characteristic of the alpha-helical structures and are much less dependent on the alpha-helix orientation with respect to the solvent. The simulated amide I' IR spectra for the model peptides with explicitly hydrogen-bonded water are consistent with the experimental data for small alpha-helical proteins
Theoretical IR spectra of ionized naphthalene
NASA Technical Reports Server (NTRS)
Pauzat, F.; Talbi, D.; Miller, M. D.; DeFrees, D. J.; Ellinger, Y.
1992-01-01
We report the results of a theoretical study of the effect of ionization on the IR spectrum of naphthalene, using ab initio molecular orbital theory. For that purpose we determined the structures, band frequencies, and intensities of neutral and positively ionized naphthalene. The calculated frequencies and intensities allowed an assignment of the most important bands appearing in the newly reported experimental spectrum of the positive ion. Agreement with the experimental spectrum is satisfactory enough to take into consideration the unexpected and important result that ionization significantly affects the intensities of most vibrations. A possible consequence on the interpretation of the IR interstellar emission, generally supposed to originate from polycyclic aromatic hydrocarbons (PAHs), is briefly presented.
Frequency domain nonlinear optics
NASA Astrophysics Data System (ADS)
Legare, Francois
2016-05-01
The universal dilemma of gain narrowing occurring in fs amplifiers prevents ultra-high power lasers from delivering few-cycle pulses. This problem is overcome by a new amplification concept: Frequency domain Optical Parametric Amplification - FOPA. It enables simultaneous up-scaling of peak power and amplified spectral bandwidth and can be performed at any wavelength range of conventional amplification schemes, however, with the capability to amplify single cycles of light. The key idea for amplification of octave-spanning spectra without loss of spectral bandwidth is to amplify the broad spectrum ``slice by slice'' in the frequency domain, i.e. in the Fourier plane of a 4f-setup. The striking advantages of this scheme, are its capability to amplify (more than) one octave of bandwidth without shorting the corresponding pulse duration. This is because ultrabroadband phase matching is not defined by the properties of the nonlinear crystal employed but the number of crystals employed. In the same manner, to increase the output energy one simply has to increase the spectral extension in the Fourier plane and to add one more crystal. Thus, increasing pulse energy and shortening its duration accompany each other. A proof of principle experiment was carried out at ALLS on the sub-two cycle IR beam line and yielded record breaking performance in the field of few-cycle IR lasers. 100 μJ two-cycle pulses from a hollow core fibre compression setup were amplified to 1.43mJ without distorting spatial or temporal properties. Pulse duration at the input of FOPA and after FOPA remains the same. Recently, we have started upgrading this system to be pumped by 250 mJ to reach 40 mJ two-cycle IR few-cycle pulses and latest results will be presented at the conference. Furthermore, the extension of the concept of FOPA to other nonlinear optical processes will be discussed. Frequency domain nonlinear optics.
NASA Astrophysics Data System (ADS)
Dubs, Martin; Sposetti, Stefano; Spinner, Roger; Booz, Beat
2017-01-01
On January 2, 2017 two peculiar meteors (M20170102_001216 and M20170102_015202) were observed by several stations in Switzerland. Both had a long duration, slow velocity, similar brightness and a very similar radiant. As they appeared in a time interval of 100 minutes, a satellite was suspected as a possible origin of these two observations. A closer inspection however showed that this interpretation was incorrect. The two objects were slow meteors. Spectra were taken from both objects, which were nearly identical. Together this points to a common origin of the two meteors.
The Optical Spectra of Aerosols.
1983-10-01
espressione dell’ampiezza di diffusione in * avanti vengono fattorizzati. In questo modo la somma delle am- piezze di diftusione di "cluster" con...F1D-Ali35 687 THE OPTICAL SPECTRA OF REROSOLSOU) MESSINA UNIV (ITALY) i/i 1ST DI STRIJTTURA DELLA IIATERIA F BORIIHESE OCT 83 UNCLASSIFIED DRR78--85F...ELEMENT PROJECT, TASK AREA & WORK UNIT NUMBERS * Istituto di Struttura della Materia 61102A-1T161102-BH57-01 Un iversita di Messina V~nina. Ttalv St
Method of processing positron lifetime spectra
Valuev, N.P.; Klimov, A.B.; Zhikharev, A.N.
1985-05-01
This paper describes a method for the processing of spectra of positron annihilation which permits a much more relaible determination of the lifetime during numerical processing of spectra by computer.
Infrared Spectra of Polycyclic Aromatic Hydrocarbons (PAHs)
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W., Jr.; Bakes, E. L. O.
2000-01-01
We have computed the synthetic infrared spectra of some polycyclic aromatic hydrocarbons containing up to 54 carbon atoms. The species studied include ovalene, circumcoronene, dicoronylene, and hexabenzocoronene. We report spectra for anions, neutrals, cations, and multiply charged cations.
Terahertz spectra of 1-cyanoadamantane in the orientationally ordered and disordered phases
NASA Astrophysics Data System (ADS)
Tanno, Takenori; Umeno, Kyoko; Ide, Erino; Katsumata, Ikumi; Fujiwara, Kazuhiko; Ogawa, Nobuaki
2014-01-01
We report the characteristic terahertz spectra of a plastic crystal and the alterations caused by phase transitions. The low-frequency vibrational modes of 1-cyanoadamantane in orientationally ordered and disordered (plastic) phases were investigated with a terahertz spectrometer. The frequencies of the intramolecular vibrational modes were in good agreement with theoretical calculations. The librational mode, which was directly observed for the first time, appeared at a lower frequency for the plastic phase.
Noise correction of turbulent spectra obtained from Acoustic Doppler Velocimeters
Durgesh, Vibhav; Thomson, Jim; Richmond, Marshall C.; Polagye, Brian
2014-03-02
Accurately estimated auto-spectral density functions are essential for characterization of turbulent flows, and they also have applications in computational fluid dynamics modeling, site and inflow characterization for hydrokinetic turbines, and inflow turbulence generation. The Acoustic Doppler Velocimeter (ADV) provides single-point temporally resolved data, that are used to characterize turbulent flows in rivers, seas, and oceans. However, ADV data are susceptible to contamination from various sources, including instrument noise, which is the intrinsic limit to the accuracy of acoustic velocity measurements. Due to the presence of instrument noise, the spectra obtained are altered at high frequencies. The focus of this study is to develop a robust and effective method for accurately estimating auto-spectral density functions from ADV data by reducing or removing the spectral contribution derived from instrument noise. For this purpose, the “Noise Auto-Correlation” (NAC) approach was developed, which exploits the correlation properties of instrument noise to identify and remove its contribution from spectra. The spectra estimated using the NAC approach exhibit increased fidelity and a slope of -5/3 in the inertial range, which is typically observed for turbulent flows. Finally, this study also compares the effectiveness of low-pass Gaussian filters in removing instrument noise with that of the NAC approach. For the data used in this study, both the NAC and Gaussian filter approaches are observed to be capable of removing instrument noise at higher frequencies from the spectra. However, the NAC results are closer to the expected frequency power of -5/3 in the inertial sub-range.
Definition of energy-calibrated spectra for national reachback
Kunz, Christopher L.; Hertz, Kristin L.
2014-01-01
Accurate energy calibration is critical for the timeliness and accuracy of analysis results of spectra submitted to National Reachback, particularly for the detection of threat items. Many spectra submitted for analysis include either a calibration spectrum using ^{137}Cs or no calibration spectrum at all. The single line provided by ^{137}Cs is insufficient to adequately calibrate nonlinear spectra. A calibration source that provides several lines that are well-spaced, from the low energy cutoff to the full energy range of the detector, is needed for a satisfactory energy calibration. This paper defines the requirements of an energy calibration for the purposes of National Reachback, outlines a method to validate whether a given spectrum meets that definition, discusses general source considerations, and provides a specific operating procedure for calibrating the GR-135.
Gamma-ray Output Spectra from 239 Pu Fission
Ullmann, John
2015-05-25
Gamma-ray multiplicities, individual gamma-ray energy spectra, and total gamma energy spectra following neutron-induced fission of 239Pu were measured using the DANCE detector at Los Alamos. Corrections for detector response were made using a forward-modeling technique based on propagating sets of gamma rays generated from a paramaterized model through a GEANT model of the DANCE array and adjusting the parameters for best fit to the measured spectra. The results for the gamma-ray spectrum and multiplicity are in general agreement with previous results, but the measured total gamma-ray energy is about 10% higher. A dependence of the gamma-ray spectrum on the gamma-raymore » multplicity was also observed. Global model calculations of the multiplicity and gamma energy distributions are in good agreement with the data, but predict a slightly softer total-energy distribution.« less
Systematic view of optical absorption spectra in the actinide series
Carnall, W.T.
1985-01-01
In recent years sufficient new spectra of actinides in their numerous valence states have been measured to encourage a broader scale analysis effort than was attempted in the past. Theoretical modelling in terms of effective operators has also undergone development. Well established electronic structure parameters for the trivalent actinides are being used as a basis for estimating parameters in other valence states and relationships to atomic spectra are being extended. Recent contributions to our understanding of the spectra of 4+ actinides have been particularly revealing and supportive of a developing general effort to progress beyond a preoccupation with modelling structure to consideration of the much broader area of structure-bonding relationships. We summarize here both the developments in modelling electronic structure and the interpretation of apparent trends in bonding. 60 refs., 9 figs., 1 tab.
47 CFR 2.1055 - Measurements required: Frequency stability.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 47 Telecommunication 1 2013-10-01 2013-10-01 false Measurements required: Frequency stability. 2.1055 Section 2.1055 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES AND REGULATIONS Equipment Authorization...
47 CFR 2.1055 - Measurements required: Frequency stability.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 47 Telecommunication 1 2014-10-01 2014-10-01 false Measurements required: Frequency stability. 2.1055 Section 2.1055 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES AND REGULATIONS Equipment Authorization...
47 CFR 2.1055 - Measurements required: Frequency stability.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 47 Telecommunication 1 2010-10-01 2010-10-01 false Measurements required: Frequency stability. 2.1055 Section 2.1055 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES AND REGULATIONS Equipment Authorization...
47 CFR 2.1055 - Measurements required: Frequency stability.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 47 Telecommunication 1 2012-10-01 2012-10-01 false Measurements required: Frequency stability. 2.1055 Section 2.1055 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES AND REGULATIONS Equipment Authorization...
47 CFR 2.1055 - Measurements required: Frequency stability.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 47 Telecommunication 1 2011-10-01 2011-10-01 false Measurements required: Frequency stability. 2.1055 Section 2.1055 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES AND REGULATIONS Equipment Authorization...