Connecting physical resonant amplitudes and lattice QCD
NASA Astrophysics Data System (ADS)
Bolton, Daniel R.; Briceño, Raúl A.; Wilson, David J.
2016-06-01
We present a determination of the isovector, P-wave ππ scattering phase shift obtained by extrapolating recent lattice QCD results from the Hadron Spectrum Collaboration using mπ = 236 MeV. The finite volume spectra are described using extensions of Lüscher's method to determine the infinite volume Unitarized Chiral Perturbation Theory scattering amplitude. We exploit the pion mass dependence of this effective theory to obtain the scattering amplitude at mπ = 140 MeV. The scattering phase shift is found to agree with experiment up to center of mass energies of 1.2 GeV. The analytic continuation of the scattering amplitude to the complex plane yields a ρ-resonance pole at Eρ = [ 755 (2) (1) (02) -i/2 129 (3) (1) (7 1) ] MeV. The techniques presented illustrate a possible pathway towards connecting lattice QCD observables of few-body, strongly interacting systems to experimentally accessible quantities.
Connecting physical resonant amplitudes and lattice QCD
NASA Astrophysics Data System (ADS)
Bolton, Daniel R.; Briceño, Raúl A.; Wilson, David J.
2016-06-01
We present a determination of the isovector, P-wave ππ scattering phase shift obtained by extrapolating recent lattice QCD results from the Hadron Spectrum Collaboration using mπ = 236 MeV. The finite volume spectra are described using extensions of Lüscher's method to determine the infinite volume Unitarized Chiral Perturbation Theory scattering amplitude. We exploit the pion mass dependence of this effective theory to obtain the scattering amplitude at mπ = 140 MeV. The scattering phase shift is found to agree with experiment up to center of mass energies of 1.2 GeV. The analytic continuation of the scattering amplitude to the complex plane yields a ρ-resonance pole at Eρ = [ 755 (2) (1) (20 02) -i/2 129 (3) (1) (7 1) ] MeV. The techniques presented illustrate a possible pathway towards connecting lattice QCD observables of few-body, strongly interacting systems to experimentally accessible quantities.
A proposed physical analog for a quantum probability amplitude
NASA Astrophysics Data System (ADS)
Boyd, Jeffrey
What is the physical analog of a probability amplitude? All quantum mathematics, including quantum information, is built on amplitudes. Every other science uses probabilities; QM alone uses their square root. Why? This question has been asked for a century, but no one previously has proposed an answer. We will present cylindrical helices moving toward a particle source, which particles follow backwards. Consider Feynman's book QED. He speaks of amplitudes moving through space like the hand of a spinning clock. His hand is a complex vector. It traces a cylindrical helix in Cartesian space. The Theory of Elementary Waves changes direction so Feynman's clock faces move toward the particle source. Particles follow amplitudes (quantum waves) backwards. This contradicts wave particle duality. We will present empirical evidence that wave particle duality is wrong about the direction of particles versus waves. This involves a paradigm shift; which are always controversial. We believe that our model is the ONLY proposal ever made for the physical foundations of probability amplitudes. We will show that our ``probability amplitudes'' in physical nature form a Hilbert vector space with adjoints, an inner product and support both linear algebra and Dirac notation.
NASA Astrophysics Data System (ADS)
Dutta, Tanima
This dissertation focuses on the link between seismic amplitudes and reservoir properties. Prediction of reservoir properties, such as sorting, sand/shale ratio, and cement-volume from seismic amplitudes improves by integrating knowledge from multiple disciplines. The key contribution of this dissertation is to improve the prediction of reservoir properties by integrating sequence stratigraphy and rock physics. Sequence stratigraphy has been successfully used for qualitative interpretation of seismic amplitudes to predict reservoir properties. Rock physics modeling allows quantitative interpretation of seismic amplitudes. However, often there is uncertainty about selecting geologically appropriate rock physics model and its input parameters, away from the wells. In the present dissertation, we exploit the predictive power of sequence stratigraphy to extract the spatial trends of sedimentological parameters that control seismic amplitudes. These spatial trends of sedimentological parameters can serve as valuable constraints in rock physics modeling, especially away from the wells. Consequently, rock physics modeling, integrated with the trends from sequence stratigraphy, become useful for interpreting observed seismic amplitudes away from the wells in terms of underlying sedimentological parameters. We illustrate this methodology using a comprehensive dataset from channelized turbidite systems, deposited in minibasin settings in the offshore Equatorial Guinea, West Africa. First, we present a practical recipe for using closed-form expressions of effective medium models to predict seismic velocities in unconsolidated sandstones. We use an effective medium model that combines perfectly rough and smooth grains (the extended Walton model), and use that model to derive coordination number, porosity, and pressure relations for P and S wave velocities from experimental data. Our recipe provides reasonable fits to other experimental and borehole data, and specifically
Application of converted-wave amplitude for fracture strike delineation - a physical model study
NASA Astrophysics Data System (ADS)
Chang, Chih-Hsiung; Chang, Young-Fo Chang; Tseng, Po-Yen; Lin, Chao-Ming
2013-04-01
The objective of this study is aiming on directing the fracture strike in a vertically aligned fracture reservoir using the seismic signature of the azimuthal dependence of C-wave amplitude (ADCA). A fractured reservoir has made itself as one of the most important productive zones in petroleum exploration. The existence of fractures not just provides the space for the residence of oils and gases but creates pathways for migration. In terms of seismic anisotropy, reservoirs that possess vertical fractures system (VFS) has its physical properties vary in azimuth and is often grouped as a horizontally transversely isotropy (HTI). Since fracture strike is the priori information in drilling engineering that has to be known to maximize production or to enhance oil recovery (EOR) from a VFS reservoir. Therefore, characterizing a fractured reservoir and orienting the fracture strike has attracted much attention by exploration geophysicists and drilling engineers. To validate our objective, a HTI model was designed to simulate a VFS reservoir. A spherical dome was caved at one side of the HTI model. In laboratory, a pair of S-type transducer was used to carry out our reflection experiments. And constant offset reflections were acquired along principal symmetry directions and diagonal direction of the HTI model at two different offset intervals. In all, two constant offset reflection data sets were obtained and each data set consists of three observations collected at different azimuths. In the acquired seismic profile, a mixture of P-wave, S-wave and C-wave events were recognized. In analyzing the variation of C-wave amplitude in azimuth in the HTI model, reflections that were originated from apex of the dome structure were sorted and displayed as a common-reflection-point (CRP) gather. Our laboratory data show C-wave amplitude decrease with azimuth varying from a strike direction toward a direction transverse to the strike in the HTI model. The phenomenon of ADCA that was
ATOMIC AND MOLECULAR PHYSICS: Integral Reduction Arising in Double Transfer and Excitation Amplitude
NASA Astrophysics Data System (ADS)
Zerarka, A.; Soukeur, A.; Bensalah, N.
2010-03-01
The purpose of this article is to develop an integral derived from the double transfer and excitation theory. The reduced form of this integral, so obtained, can serve in the computation of the transition amplitude which is from numerical point of view difficult to implement. This amplitude is of great interest in the resonant and non resonant transfer and excitation (RTE and NTE) processes.
Coleman, A J; Saunders, J E
1993-01-01
Extracorporeal shockwave lithotripsy (ESWL) has now been used for more than a decade in the treatment of urinary stone disease. During this period there has been a wide range of studies on the physical properties of the high-amplitude focussed fields used in ESWL and the biological effects of exposure to such fields, including their ability to fragment hard concretions. These studies form a distinct body of knowledge whose relevance to the broader literature on biological effects from lower amplitude exposures has yet to be fully evaluated. This review attempts to present the main results of biological-effects studies in ESWL along with what is known of the physical properties of lithotripsy fields with the aim of assisting this evaluation. In general, the reported biological effects of lithotripsy fields are compatible with those that have been observed at those lower amplitudes of focussed pulsed ultrasound in which transient cavitation is the dominant mechanism of interaction. The relatively large amplitudes and low frequencies in ESWL, however, make it a more potent generator of transient cavitation than most other forms of medical ultrasound. Biological-effects studies with lithotripsy fields may, therefore, be expected to extend our understanding of the nature of transient cavitation and, in particular, its effects in mammalian tissue.
NASA Astrophysics Data System (ADS)
Chang, C.; Sun, L.; Lin, C.; Chang, Y.; Tseng, P.
2013-12-01
The existence of fractures not only provides spaces for the residence of oils and gases reside, but it also creates pathways for migration. Characterizing a fractured reservoir thus becomes an important subject and has been widely studied by exploration geophysicists and drilling engineers. In seismic anisotropy, a reservoir of systematically aligned vertical fractures (SAVF) is often treated as a transversely isotropic medium (TIM) with a horizontal axis of symmetry (HTI). Subjecting to HTI, physical properties vary in azimuth. P-wave reflection amplitude, which is susceptible to vary in azimuth, is one of the most popular seismic attributes which is widely used to delineate the fracture strike of an SAVF reservoir. Instead of going further on analyzing P-wave signatures, in this study, we focused on evaluating the feasibility of orienting the fracture strike of an SAVF reservoir using converted (C-) wave amplitude. For a C-wave is initiated by a downward traveling P-wave that is converted on reflection to an upcoming S-wave; the behaviors of both P- and S-waves should be theoretically woven in a C-wave. In our laboratory work, finite offset reflection experiments were carried out on the azimuthal plane of a HTI model at two different offset intervals. To demonstrate the azimuthal variation of C-wave amplitude in a HTI model, reflections were acquired along the principal symmetry directions and the diagonal direction of the HTI model. Inheriting from phenomenon of S-wave splitting in a transversely isotropic medium (TIM), P-waves get converted into both the fast (S1) and slow (S2) shear modes at all azimuths outside the vertical symmetry planes, thus producing split PS-waves (PS1 and PS2). In our laboratory data, the converted PS1- (C1-) wave were observed and identified. As the azimuth varies from the strike direction to the strike normal, C1-wave amplitude exhibits itself in a way of weakening and can be view from the common-reflection-point (CRP) gathers
NASA Astrophysics Data System (ADS)
Marciniak, A.; Pilcher, F.; Santana-Ros, T.; Oszkiewicz, D.; Kankiewicz, P.
2014-07-01
Introduction: Spin and shape parameters of a large sample of asteroids are an important reference point for theories describing Solar System formation and evolution, with, e.g., thermal forces influencing orbital and physical properties of minor bodies. However, the available sample of well-studied asteroids is burdened with substantial selection effects. There exists a strong observational bias against small and/or low-albedo, and/or distant objects due to the limitations of instruments that are commonly used for photometric studies. But there are also other strong selection effects working against asteroids with long period of rotation (here: P>12h) and low lightcurve amplitude (here: a_{max}<0.25 mag). Each of these groups corresponds to almost half of the whole population of bright (H<11 mag) main-belt asteroids, while spin and shape models have been determined for only 20 % of them (source: LCDB; Warner et al. 2009). On the other hand, the remaining populations (short-period and large-amplitude objects) have been each modeled with nearly 40 % completeness. Thus, asteroids modelled today are in majority quickly rotating and elongated in shape. This inevitably skews our knowledge, e.g., on their internal structure and density, on the frequency versus size distribution, and possibly also on the distribution of asteroid spin axes in space. Observing campaign: We have recently started a large, long-term campaign aimed at reducing the observational bias that exist against long-period and low-amplitude asteroids, to obtain their spin and shape models. To do this we coordinated a few telescopes in Poland, Spain and in the US for efficient photometric observations of those asteroids that were usually avoided by the majority of previous studies. We designed a novel observing strategy that makes use of a robotic telescope ability to quickly switch between different targets. Since May 2013, we have been gathering data using, among others, the robotic 80-cm TJO telescope
Vähä-Ypyä, Henri; Vasankari, Tommi; Mänttäri, Ari; Vuorimaa, Timo
2015-01-01
Purpose Our recent study of three accelerometer brands in various ambulatory activities showed that the mean amplitude deviation (MAD) of the resultant acceleration signal performed best in separating different intensity levels and provided excellent agreement between the three devices. The objective of this study was to derive a regression model that estimates oxygen consumption (VO2) from MAD values and validate the MAD-based cut-points for light, moderate and vigorous locomotion against VO2 within a wide range of speeds. Methods 29 participants performed a pace-conducted non-stop test on a 200 m long indoor track. The initial speed was 0.6 m/s and it was increased by 0.4 m/s every 2.5 minutes until volitional exhaustion. The participants could freely decide whether they preferred to walk or run. During the test they carried a hip-mounted tri-axial accelerometer and mobile metabolic analyzer. The MAD was calculated from the raw acceleration data and compared to directly measured incident VO2. Cut-point between light and moderate activity was set to 3.0 metabolic equivalent (MET, 1 MET = 3.5 ml · kg-1 · min-1) and between moderate and vigorous activity to 6.0 MET as per standard use. Results The MAD and VO2 showed a very strong association. Within individuals, the range of r values was from 0.927 to 0.991 providing the mean r = 0.969. The optimal MAD cut-point for 3.0 MET was 91 mg (milligravity) and 414 mg for 6.0 MET. Conclusion The present study showed that the MAD is a valid method in terms of the VO2 within a wide range of ambulatory activities from slow walking to fast running. Being a device-independent trait, the MAD facilitates directly comparable, accurate results on the intensity of physical activity with all accelerometers providing tri-axial raw data. PMID:26292225
Field, J.H. . E-mail: john.field@cern.ch
2006-03-15
Feynman's laws of quantum dynamics are concisely stated, discussed in comparison with other formulations of quantum mechanics and applied to selected problems in the physical optics of photons and massive particles as well as flavour oscillations. The classical wave theory of light is derived from these laws for the case in which temporal variation of path amplitudes may be neglected, whereas specific experiments, sensitive to the temporal properties of path amplitudes, are suggested. The reflection coefficient of light from the surface of a transparent medium is found to be markedly different to that predicted by the classical Fresnel formula. Except for neutrino oscillations, good agreement is otherwise found with previous calculations of spatially dependent quantum interference effects.
NASA Astrophysics Data System (ADS)
Tang, Shawn; Crocker, N. A.; Carter, T. A.; Fredrickson, E. D.; Guttenfelder, W.; Gorelenkov, N. N.; NSTX-U Team
2015-11-01
Electron thermal confinement in NSTX was observed to deteriorate with increasing toroidal field and beam power, which potentially has significant implications for NSTX-U. The leading candidates for this anomalous electron transport are high-frequency Alfvén eigenmodes excited through Doppler-shifted cyclotron resonance with beam ions. These modes were identified as compressional (CAE) and global (GAE) Alfvén eigenmodes. The potential impact of these modes motivates the investigation of the physics controlling their spectra, structure, and amplitude. A database of neutral beam heated NSTX shots spanning a broad range of plasma parameters has been compiled to investigate fast-ion driven mode activity. This database is extended to include measures of CAE/GAE activity in order to statistically investigate the physics parameters controlling the characteristics of these modes and how they contribute to anomalous electron transport. We show preliminary results of this investigation. Supported by US DOE Contracts DE-SC0011810 & DE-AC02-09CH11466.
NASA Astrophysics Data System (ADS)
Walter, W. R.; Ford, S. R.; Xu, H.; Pasyanos, M. E.; Pyle, M. L.; Matzel, E.; Mellors, R. J.; Hauk, T. F.
2012-12-01
It is well established empirically that regional distance (200-1600 km) amplitude ratios of seismic P-to-S waves at sufficiently high frequencies (~>2 Hz) can identify explosions among a background of natural earthquakes. However the physical basis for the generation of explosion S-waves, and therefore the predictability of this P/S technique as a function of event properties such as size, depth, geology and path, remains incompletely understood. A goal of the Source Physics Experiments (SPE) at the Nevada National Security Site (NNSS, formerly the Nevada Test Site (NTS)) is to improve our physical understanding of the mechanisms of explosion S-wave generation and advance our ability to numerically model and predict them. Current models of explosion P/S values suggest they are frequency dependent with poor performance below the source corner frequencies and good performance above. This leads to expectations that small magnitude explosions might require much higher frequencies (>10 Hz) to identify them. Interestingly the 1-ton chemical source physics explosions SPE2 and SPE3 appear to discriminate well from background earthquakes in the frequency band 6-8 Hz, where P and S signals are visible at the NVAR array located near Mina, NV about 200 km away. NVAR is a primary seismic station in the International Monitoring System (IMS), part of the Comprehensive nuclear-Test-Ban Treaty (CTBT). The NVAR broadband element NV31 is co-located with the LLNL station MNV that recorded many NTS nuclear tests, allowing the comparison. We find the small SPE explosions in granite have similar Pn/Lg values at 6-8 Hz as the past nuclear tests mainly in softer rocks. We are currently examining a number of other stations in addition to NVAR, including the dedicated SPE stations that recorded the SPE explosions at much closer distances with very high sample rates, in order to better understand the observed frequency dependence as compared with the model predictions. We plan to use these
Schulz, André; Strelzyk, Florian; Ferreira de Sá, Diana S; Naumann, Ewald; Vögele, Claus; Schächinger, Hartmut
2013-11-01
Little is known about the impact of stress and stress hormones on the processing of visceral-afferent signals. Clinical data suggest that cortisol may lower the threshold for interoceptive stimuli, while a pharmacological administration of cortisol decreases the sensitivity for physical symptoms. To clarify the role of cortisol for the processing of interoceptive signals, we investigated 16 healthy men on two occasions, once during the infusion of 4 mg of cortisol and once during the infusion of a placebo substance. Heartbeat-evoked potentials (HEP; derived from resting EEG and ECG, during open and closed eyes), which are psychophysiological indicators for the cortical processing of cardioceptive signals, were measured over 6-min periods once before, and four times after the infusion (1-7, 11-17, 21-27 and 31-37 min). We found that HEP amplitudes were higher during open than during closed eyes between 1 and 17 min after cortisol infusion. There was no effect of cortisol on heart rate. We conclude that cortisol may rapidly modulate the cortical processing of cardioceptive neural signals. These results may have relevance for the effects of stress on the development and maintenance of psychosomatic symptoms.
Tempo and amplitude in growth.
Hermanussen, Michael
2011-01-01
Growth is defined as an increase of size over time with time usually defined as physical time. Yet, the rigid metric of physical time is not directly relevant to the internal dynamics of growth. Growth is linked to maturation. Children and adolescents differ in the tempo at which they mature. One calendar year differs in its meaning in a fast maturing, and in a slow maturing child. The slow child needs more calendar years for completing the same stage of maturity. Many characteristics in the human growth curve are tempo characteristics. Tempo - being fast or slow maturing - has to be carefully separated from amplitude - being tall or short. Several characteristic phenomena such as catch-up growth after periods of illness and starvation are largely tempo phenomena, and do usually not affect the amplitude component of growth. Applying Functional Data Analysis and Principal Component Analysis, the two main sources of height variance: tempo and amplitude can statistically be separate and quantified. Tempo appears to be more sensitive than amplitude to nutrition, health and environmental stress. An appropriate analysis of growth requires disentangling its two major components: amplitude and tempo. The assessment of the developmental tempo thus is an integral part of assessing child and adolescent growth. Though an Internet portal is currently available to process small amounts of height data (www.willi-will-wachsen.com) for separately determining amplitude and tempo in growth, there is urgent need of better and practical solutions for analyzing individual growth.
Model selection for amplitude analysis
NASA Astrophysics Data System (ADS)
Guegan, B.; Hardin, J.; Stevens, J.; Williams, M.
2015-09-01
Model complexity in amplitude analyses is often a priori under-constrained since the underlying theory permits a large number of possible amplitudes to contribute to most physical processes. The use of an overly complex model results in reduced predictive power and worse resolution on unknown parameters of interest. Therefore, it is common to reduce the complexity by removing from consideration some subset of the allowed amplitudes. This paper studies a method for limiting model complexity from the data sample itself through regularization during regression in the context of a multivariate (Dalitz-plot) analysis. The regularization technique applied greatly improves the performance. An outline of how to obtain the significance of a resonance in a multivariate amplitude analysis is also provided.
Calculating scattering amplitudes efficiently
Dixon, L.
1996-01-01
We review techniques for more efficient computation of perturbative scattering amplitudes in gauge theory, in particular tree and one- loop multi-parton amplitudes in QCD. We emphasize the advantages of (1) using color and helicity information to decompose amplitudes into smaller gauge-invariant pieces, and (2) exploiting the analytic properties of these pieces, namely their cuts and poles. Other useful tools include recursion relations, special gauges and supersymmetric rearrangements. 46 refs., 11 figs.
Greenblatt, M.H.
1958-03-25
This patent pertains to pulse amplitude analyzers for sorting and counting a serles of pulses, and specifically discloses an analyzer which ls simple in construction and presents the puise height distribution visually on an oscilloscope screen. According to the invention, the pulses are applied to the vertical deflection plates of an oscilloscope and trigger the horizontal sweep. Each pulse starts at the same point on the screen and has a maximum amplitude substantially along the same vertical line. A mask is placed over the screen except for a slot running along the line where the maximum amplitudes of the pulses appear. After the slot has been scanned by a photocell in combination with a slotted rotating disk, the photocell signal is displayed on an auxiliary oscilloscope as vertical deflection along a horizontal time base to portray the pulse amplitude distribution.
Lewis, I.A.D.
1956-05-15
This patent pentains to an electrical pulse amplitude analyzer, capable of accepting input pulses having a separation between adjacent pulses in the order of one microsecond while providing a large number of channels of classification. In its broad aspect the described pulse amplitude analyzer utilizes a storage cathode ray tube und control circuitry whereby the amplitude of the analyzed pulses controls both the intensity and vertical defiection of the beam to charge particular spots in horizontal sectors of the tube face as the beam is moved horizontally across the tube face. As soon as the beam has swept the length of the tube the information stored therein is read out by scanning individually each horizontal sector corresponding to a certain range of pulse amplitudes and applying the output signal from each scan to separate indicating means.
Reinforcing Saccadic Amplitude Variability
ERIC Educational Resources Information Center
Paeye, Celine; Madelain, Laurent
2011-01-01
Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we…
Syzygies probing scattering amplitudes
NASA Astrophysics Data System (ADS)
Chen, Gang; Liu, Junyu; Xie, Ruofei; Zhang, Hao; Zhou, Yehao
2016-09-01
We propose a new efficient algorithm to obtain the locally minimal generating set of the syzygies for an ideal, i.e. a generating set whose proper subsets cannot be generating sets. Syzygy is a concept widely used in the current study of scattering amplitudes. This new algorithm can deal with more syzygies effectively because a new generation of syzygies is obtained in each step and the irreducibility of this generation is also verified in the process. This efficient algorithm can also be applied in getting the syzygies for the modules. We also show a typical example to illustrate the potential application of this method in scattering amplitudes, especially the Integral-By-Part(IBP) relations of the characteristic two-loop diagrams in the Yang-Mills theory.
Erbert, G
2009-09-01
The Amplitude Modulator Chassis (AMC) is the final component in the MOR system and connects directly to the PAM input through a 100-meter fiber. The 48 AMCs temporally shape the 48 outputs of the MOR using an arbitrary waveform generator coupled to an amplitude modulator. The amplitude modulation element is a two stage, Lithium Niobate waveguide device, where the intensity of the light passing through the device is a function of the electrical drive applied. The first stage of the modulator is connected to a programmable high performance Arbitrary Waveform Generator (AWG) consisting of 140 impulse generators space 250 ps apart. An arbitrary waveform is generated by independently varying the amplitude of each impulse generator and then summing the impulses together. In addition to the AWG a short pulse generator is also connected to the first stage of the modulator to provide a sub 100-ps pulse used for timing experiments. The second stage of the modulator is connect to a square pulse generator used to further attenuate any pre or post pulse light passing through the first stage of the modulator. The fast rise and fall time of the square pulse generator is also used to produce fast rise and fall times of the AWG by clipping the AWG pulse. For maximum extinction, a pulse bias voltage is applied to each stage of the modulator. A pulse voltage is applied as opposed to a DC voltage to prevent charge buildup on the modulator. Each bias voltage is adjustable to provide a minimum of 50-dB extinction. The AMC is controlled through ICCS to generate the desired temporal pulse shape. This process involves a closed-loop control algorithm, which compares the desired temporal waveform to the produced optical pulse, and iterates the programming of the AWG until the two waveforms agree within an allowable tolerance.
Tello, M; San Paulo, A; Rodríguez, T R; Blanco, M C; García, R
2003-01-01
In many situations of interest amplitude modulation AFM is characterized by the coexistence of two solutions with different physical properties. Here, we compare the performance of those solutions in the imaging of cobalt nanoparticles. We show that imaging with the high amplitude solution implies an irreversible deformation of the nanoparticles while repeated imaging with the low solution does not produce noticeable changes in the nanoparticles. Theoretical simulations show that the maximum tip-surface force in the high amplitude solution is about 14nN while in the low amplitude solution is about -4nN. We attribute the differences in the high and low amplitude images to the differences in the exerted forces on the sample. PMID:12801669
Tello, M; San Paulo, A; Rodríguez, T R; Blanco, M C; García, R
2003-01-01
In many situations of interest amplitude modulation AFM is characterized by the coexistence of two solutions with different physical properties. Here, we compare the performance of those solutions in the imaging of cobalt nanoparticles. We show that imaging with the high amplitude solution implies an irreversible deformation of the nanoparticles while repeated imaging with the low solution does not produce noticeable changes in the nanoparticles. Theoretical simulations show that the maximum tip-surface force in the high amplitude solution is about 14nN while in the low amplitude solution is about -4nN. We attribute the differences in the high and low amplitude images to the differences in the exerted forces on the sample.
Closed string amplitudes as single-valued open string amplitudes
NASA Astrophysics Data System (ADS)
Stieberger, Stephan; Taylor, Tomasz R.
2014-04-01
We show that the single trace heterotic N-point tree-level gauge amplitude ANHET can be obtained from the corresponding type I amplitude ANI by the single-valued (sv) projection: ANHET=sv(ANI). This projection maps multiple zeta values to single-valued multiple zeta values. The latter represent a subclass of multiple zeta values originating from single-valued multiple polylogarithms at unity. Similar relations between open and closed string amplitudes or amplitudes of different string vacua can be established. As a consequence the α‧-expansion of a closed string amplitude is dictated by that of the corresponding open string amplitude. The combination of single-valued projections, Kawai-Lewellen-Tye relations and Mellin correspondence reveal a unity of all tree-level open and closed superstring amplitudes together with the maximally supersymmetric Yang-Mills and supergravity theories.
PULSE AMPLITUDE DISTRIBUTION RECORDER
Cowper, G.
1958-08-12
A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.
Full one-loop amplitudes from tree amplitudes
Giele, Walter T.; Kunszt, Zoltan; Melnikov, Kirill; /Hawaii U.
2008-01-01
We establish an efficient polynomial-complexity algorithm for one-loop calculations, based on generalized D-dimensional unitarity. It allows automated computations of both cut-constructible and rational parts of one-loop scattering amplitudes from on-shell tree amplitudes. We illustrate the method by (re)-computing all four-, five- and six-gluon scattering amplitudes in QCD at one-loop.
Feynman amplitudes with confinement included
NASA Astrophysics Data System (ADS)
Simonov, Yu. A.
2009-07-01
Amplitudes for any multipoint Feynman diagram are written taking into account vacuum background confining field. Higher order gluon exchanges are treated within background perturbation theory. For amplitudes with hadrons in initial or final states vertices are shown to be expressed by the corresponding wave function with the renormalized z factors. Examples of two-point functions, three-point functions (form factors), and decay amplitudes are explicitly considered.
On the Period-Amplitude and Amplitude-Period Relationships
NASA Technical Reports Server (NTRS)
Wilson, Robert M.; Hathaway, David H.
2008-01-01
Examined are Period-Amplitude and Amplitude-Period relationships based on the cyclic behavior of the 12-month moving averages of monthly mean sunspot numbers for cycles 0.23, both in terms of Fisher's exact tests for 2x2 contingency tables and linear regression analyses. Concerning the Period-Amplitude relationship (same cycle), because cycle 23's maximum amplitude is known to be 120.8, the inferred regressions (90-percent prediction intervals) suggest that its period will be 131 +/- 24 months (using all cycles) or 131 +/- 18 months (ignoring cycles 2 and 4, which have the extremes of period, 108 and 164 months, respectively). Because cycle 23 has already persisted for 142 months (May 1996 through February 2008), based on the latter prediction, it should end before September 2008. Concerning the Amplitude-Period relationship (following cycle maximum amplitude versus preceding cycle period), because cycle 23's period is known to be at least 142 months, the inferred regressions (90-percent prediction intervals) suggest that cycle 24's maximum amplitude will be about less than or equal to 96.1 +/- 55.0 (using all cycle pairs) or less than or equal to 91.0 +/- 36.7 (ignoring statistical outlier cycle pairs). Hence, cycle 24's maximum amplitude is expected to be less than 151, perhaps even less than 128, unless cycle pair 23/24 proves to be a statistical outlier.
Chiral extrapolation of SU(3) amplitudes
Ecker, Gerhard
2011-05-23
Approximations of chiral SU(3) amplitudes at NNLO are proposed to facilitate the extrapolation of lattice data to the physical meson masses. Inclusion of NNLO terms is essential for investigating convergence properties of chiral SU(3) and for determining low-energy constants in a controllable fashion. The approximations are tested with recent lattice data for the ratio of decay constants F{sub K}/F{sub {pi}}.
Ooguri, H.
1995-08-01
In physics, solvable models have played very important roles. Understanding a simple model in detail teaches us a lot about more complicated models in generic situations. Five years ago, C. Vafa and I found that the closed N = 2 string theory, that is a string theory with the N = 2 local supersymmetry on the worldsheet, is classically equivalent to the self-dual Einstein gravity in four spacetime dimensions. Thus this string theory is solvable at the classical level. More recently, we have examined the N = 2 string partition function for spacial compactifications, and computed it to all order in the string perturbation expansion. The fact that such computation is possible at all suggests that the N = 2 string theory is solvable even quantum mechanically.
Integrable spin chains and scattering amplitudes
NASA Astrophysics Data System (ADS)
Bartels, J.; Lipatov, L. N.; Prygarin, A.
2011-11-01
In this review, we show that the multi-particle scattering amplitudes in {N}=4 SYM at large Nc and in the multi-Regge kinematics for some physical regions have the high energy behavior appearing from the contribution of the Mandelstam cuts in the complex angular momentum plane of the corresponding t-channel partial waves. These Mandelstam cuts or Regge cuts result from gluon composite states in the adjoint representation of the gauge group SU(Nc). In the leading logarithmic approximation (LLA), their contribution to the six-point amplitude is in full agreement with the known two-loop result. The Hamiltonian for the Mandelstam states constructed from n gluons in LLA coincides with the local Hamiltonian of an integrable open spin chain. We construct the corresponding wavefunctions using the integrals of motion and the Baxter-Sklyanin approach.
Small amplitude quasibreathers and oscillons
Fodor, Gyula; Lukacs, Arpad; Forgacs, Peter; Horvath, Zalan
2008-07-15
Quasibreathers (QB) are time-periodic solutions with weak spatial localization introduced in G. Fodor et al. in [Phys. Rev. D 74, 124003 (2006)]. QB's provide a simple description of oscillons (very long-living spatially localized time dependent solutions). The small amplitude limit of QB's is worked out in a large class of scalar theories with a general self-interaction potential, in D spatial dimensions. It is shown that the problem of small amplitude QB's is reduced to a universal elliptic partial differential equation. It is also found that there is the critical dimension, D{sub crit}=4, above which no small amplitude QB's exist. The QB's obtained this way are shown to provide very good initial data for oscillons. Thus these QB's provide the solution of the complicated, nonlinear time dependent problem of small amplitude oscillons in scalar theories.
Positive amplitudes in the amplituhedron
NASA Astrophysics Data System (ADS)
Arkani-Hamed, Nima; Hodges, Andrew; Trnka, Jaroslav
2015-08-01
The all-loop integrand for scattering amplitudes in planar SYM is determined by an "amplitude form" with logarithmic singularities on the boundary of the amplituhedron. In this note we provide strong evidence for a new striking property of the superamplitude, which we conjecture to be true to all loop orders: the amplitude form is positive when evaluated inside the amplituhedron. The statement is sensibly formulated thanks to the natural "bosonization" of the superamplitude associated with the amplituhedron geometry. However this positivity is not manifest in any of the current approaches to scattering amplitudes, and in particular not in the cellulations of the amplituhedron related to on-shell diagrams and the positive grassmannian. The surprising positivity of the form suggests the existence of a "dual amplituhedron" formulation where this feature would be made obvious. We also suggest that the positivity is associated with an extended picture of amplituhedron geometry, with the amplituhedron sitting inside a co-dimension one surface separating "legal" and "illegal" local singularities of the amplitude. We illustrate this in several simple examples, obtaining new expressions for amplitudes not associated with any triangulations, but following in a more invariant manner from a global view of the positive geometry.
Feshbach Correlations and Closed Channel Amplitudes
NASA Astrophysics Data System (ADS)
Lopez, Nicolas; Tsai, Shan-Wen; Timmermans, Eddy
2012-02-01
The magnetically controlled Feshbach resonance is a prominent member of the cold atom toolkit. The ability to tune binary particle interactions in a quantum many body system has given access to collapsing BEC-physics in bosenovas, to BEC-BCS crossover physics, to the unitarity regime, and to quantum phase transitions. The resonance is accessed by tuning the energy of a quasi-bound spin-rearranged molecular state near the vaccuum of the interacting particles. Does the amplitude of the spin-rearranged or ``closed channel'' state play a significant role in the many body physics? We present a microscopic derivation of the Feshbach resonance interactions and obtain the parameters of the two-channel model in a optical lattice. We study two atoms interacting in a harmonic oscillator potential near a Feshbach resonance to derive the closed channel probabibilty and to uncover the validity-range of the two channel lattice model.
Search for a relationship between solar cycle amplitude and length
NASA Astrophysics Data System (ADS)
Solanki, S. K.; Krivova, N. A.; Schüssler, M.; Fligge, M.
2002-12-01
The cross-correlation between time series of solar cycle length and amplitude suggests that the length precedes the amplitude. The relationship between the two is found to be more complex than a simple lag or phase shift, however. A simple empirical model is constructed which allows the amplitude of a given cycle to be predicted with relatively high accuracy from the lengths of earlier cycles. This result not only adds to the means at our disposal for predicting the amplitudes of future cycles, but also implies that the solar dynamo carries a memory of the length of one cycle over into the next. It may also have a bearing on why solar cycle length correlates better with the Earth's temperature record than cycle amplitude (Friis-Christensen & Lassen \\cite{Friis-Christensen:Lassen:1991}). Thoughts on possible physical causes are presented.
Amplitude transitions of swimmers and flexors in viscoelastic fluids
NASA Astrophysics Data System (ADS)
Guy, Robert; Thomases, Becca
2015-11-01
In both theoretical and experimental studies of the effect of fluid elasticity on micro-organism swimming, very different behavior has been observed for small and large amplitude strokes. We present simulations of an undulatory swimmer in an Oldroyd-B fluid and show that the resulting viscoelastic stresses are a nonlinear function of the amplitude. Specifically, there appears to be an amplitude dependent transition that is key to obtaining a speed-up over the Newtonian swimming speed. To understand the physical mechanism of the transition, we examine the stresses in a time-symmetric oscillatory bending beam, or flexor. We compare the flow in a neighborhood of the flexor tips with a large-amplitude oscillatory extensional flow, and we see similar amplitude dependent transitions. We relate these transitions to observed speed-ups in viscoelastic swimmers.
ERIC Educational Resources Information Center
Bromley, D. Allan
1980-01-01
The author presents the argument that the past few years, in terms of new discoveries, insights, and questions raised, have been among the most productive in the history of physics. Selected for discussion are some of the most important new developments in physics research. (Author/SA)
Factorization of chiral string amplitudes
NASA Astrophysics Data System (ADS)
Huang, Yu-tin; Siegel, Warren; Yuan, Ellis Ye
2016-09-01
We re-examine a closed-string model defined by altering the boundary conditions for one handedness of two-dimensional propagators in otherwise-standard string theory. We evaluate the amplitudes using Kawai-Lewellen-Tye factorization into open-string amplitudes. The only modification to standard string theory is effectively that the spacetime Minkowski metric changes overall sign in one open-string factor. This cancels all but a finite number of states: as found in earlier approaches, with enough supersymmetry (e.g., type II) the tree amplitudes reproduce those of the massless truncation of ordinary string theory. However, we now find for the other cases that additional fields, formerly thought to be auxiliary, describe new spin-2 states at the two adjacent mass levels (tachyonic and tardyonic). The tachyon is always a ghost, but can be avoided in the heterotic case.
Shape of Pion Distribution Amplitude
Radyushkin, Anatoly
2009-11-01
A scenario is investigated in which the leading-twist pion distribution amplitude $\\varphi_\\pi (x)$ is approximated by the pion decay constant $f_\\pi$ for all essential values of the light-cone fraction $x$. A model for the light-front wave function $\\Psi (x, k_\\perp)$ is proposed that produces such a distribution amplitude and has a rapidly decreasing (exponential for definiteness) dependence on the light-front energy combination $ k_\\perp^2/x(1-x)$. It is shown that this model easily reproduces the fit of recent large-$Q^2$ BaBar data on the photon-pion transition form factor. Some aspects of scenario with flat pion distribution amplitude are discussed.
Scattering Amplitudes: The Most Perfect Microscopic Structures in the Universe
Dixon, Lance J.; /CERN /SLAC
2011-11-04
This article gives an overview of many of the recent developments in understanding the structure of relativistic scattering amplitudes in gauge theories ranging from QCD to N = 4 super-Yang-Mills theory, as well as (super)gravity. I also provide a pedagogical introduction to some of the basic tools used to organize and illuminate the color and kinematic structure of amplitudes. This article is an invited review introducing a special issue of Journal of Physics A devoted to 'Scattering Amplitudes in Gauge Theories'.
Automated force controller for amplitude modulation atomic force microscopy.
Miyagi, Atsushi; Scheuring, Simon
2016-05-01
Atomic Force Microscopy (AFM) is widely used in physics, chemistry, and biology to analyze the topography of a sample at nanometer resolution. Controlling precisely the force applied by the AFM tip to the sample is a prerequisite for faithful and reproducible imaging. In amplitude modulation (oscillating) mode AFM, the applied force depends on the free and the setpoint amplitudes of the cantilever oscillation. Therefore, for keeping the applied force constant, not only the setpoint amplitude but also the free amplitude must be kept constant. While the AFM user defines the setpoint amplitude, the free amplitude is typically subject to uncontrollable drift, and hence, unfortunately, the real applied force is permanently drifting during an experiment. This is particularly harmful in biological sciences where increased force destroys the soft biological matter. Here, we have developed a strategy and an electronic circuit that analyzes permanently the free amplitude of oscillation and readjusts the excitation to maintain the free amplitude constant. As a consequence, the real applied force is permanently and automatically controlled with picoNewton precision. With this circuit associated to a high-speed AFM, we illustrate the power of the development through imaging over long-duration and at various forces. The development is applicable for all AFMs and will widen the applicability of AFM to a larger range of samples and to a larger range of (non-specialist) users. Furthermore, from controlled force imaging experiments, the interaction strength between biomolecules can be analyzed. PMID:27250433
Employing helicity amplitudes for resummation
NASA Astrophysics Data System (ADS)
Moult, Ian; Stewart, Iain W.; Tackmann, Frank J.; Waalewijn, Wouter J.
2016-05-01
Many state-of-the-art QCD calculations for multileg processes use helicity amplitudes as their fundamental ingredients. We construct a simple and easy-to-use helicity operator basis in soft-collinear effective theory (SCET), for which the hard Wilson coefficients from matching QCD onto SCET are directly given in terms of color-ordered helicity amplitudes. Using this basis allows one to seamlessly combine fixed-order helicity amplitudes at any order they are known with a resummation of higher-order logarithmic corrections. In particular, the virtual loop amplitudes can be employed in factorization theorems to make predictions for exclusive jet cross sections without the use of numerical subtraction schemes to handle real-virtual infrared cancellations. We also discuss matching onto SCET in renormalization schemes with helicities in 4- and d -dimensions. To demonstrate that our helicity operator basis is easy to use, we provide an explicit construction of the operator basis, as well as results for the hard matching coefficients, for p p →H +0 , 1, 2 jets, p p →W /Z /γ +0 , 1, 2 jets, and p p →2 , 3 jets. These operator bases are completely crossing symmetric, so the results can easily be applied to processes with e+e- and e-p collisions.
Small amplitude quasibreathers and oscillons
NASA Astrophysics Data System (ADS)
Fodor, Gyula; Forgács, Péter; Horváth, Zalán; Lukács, Árpád
2008-07-01
Quasibreathers (QB) are time-periodic solutions with weak spatial localization introduced in G. Fodor et al. in [Phys. Rev. D 74, 124003 (2006)PRVDAQ0556-282110.1103/PhysRevD.74.124003]. QB’s provide a simple description of oscillons (very long-living spatially localized time dependent solutions). The small amplitude limit of QB’s is worked out in a large class of scalar theories with a general self-interaction potential, in D spatial dimensions. It is shown that the problem of small amplitude QB’s is reduced to a universal elliptic partial differential equation. It is also found that there is the critical dimension, Dcrit=4, above which no small amplitude QB’s exist. The QB’s obtained this way are shown to provide very good initial data for oscillons. Thus these QB’s provide the solution of the complicated, nonlinear time dependent problem of small amplitude oscillons in scalar theories.
Toward complete pion nucleon amplitudes
Mathieu, Vincent; Danilkin, Igor V.; Fernández-Ramírez, Cesar; Pennington, Michael R.; Schott, Diane M.; Szczepaniak, Adam P.; Fox, G.
2015-10-05
We compare the low-energy partial wave analyses πN scattering with a high-energy data via finite energy sum rules. We also construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy, Regge parametrization and then reconstruct the real parts using dispersion relations.
Extracting amplitudes from photoproduction data
NASA Astrophysics Data System (ADS)
Workman, R. L.
2011-09-01
We consider the problems associated with amplitude extraction, from meson photoproduction data, over the first resonance regions. The notion of a complete experiment has motivated the FROST program at Jefferson Lab. Exercises applied to pion photoproduction data illustrate the problems to be confronted in any attempt to extract underlying resonance signals from these data (without introducing a model for the resonant process).
The pion distribution amplitude from SDE-BSE
NASA Astrophysics Data System (ADS)
Cobos-Martínez, J. J.
2015-11-01
A brief exposition of the Schwinger-Dyson-Bethe-Salpeter equations of Quantum Chromodynamics and their application to hadron physics is given. Results for the rainbow- ladder trucantion scheme are presented. The Pion distribution amplitude is calculated in the SDE-BSE approach to hadron physics employing a novel method of computation [28]. The SDE-BSE is a well founded continuum approach to nonperturbative hadron physics that unifies a range of hadron observables.
Pion-pion scattering amplitude
Pelaez, J.R.; Yndurain, F.J.
2005-04-01
We obtain reliable {pi}{pi} scattering amplitudes consistent with experimental data, both at low and high energies, and fulfilling appropriate analyticity properties. We do this by first fitting experimental low energy (s{sup 1/2}{<=}1.42 GeV) phase shifts and inelasticities with expressions that incorporate analyticity and unitarity. In particular, for the S wave with isospin 0, we discuss in detail several sets of experimental data. This provides low energy partial wave amplitudes that summarize the known experimental information. Then, we impose Regge behavior as follows from factorization and experimental data for the imaginary parts of the scattering amplitudes at higher energy, and check fulfillment of dispersion relations up to 0.925 GeV. This allows us to improve our fits. The ensuing {pi}{pi} scattering amplitudes are then shown to verify dispersion relations up to 1.42 GeV, as well as s-t-u crossing sum rules and other consistency conditions. The improved parametrizations therefore provide a reliable representation of pion-pion amplitudes with which one can test chiral perturbation theory calculations, pionium decays, or use as input for CP-violating K decays. In this respect, we find [a{sub 0}{sup (0)}-a{sub 0}{sup (2)}]{sup 2}=(0.077{+-}0.008)M{sub {pi}}{sup -2} and {delta}{sub 0}{sup (0)}(m{sub K}{sup 2})-{delta}{sub 0}{sup (2)}(m{sub K}{sup 2})=52.9{+-}1.6{sup o}.
Constructing QCD one-loop amplitudes
Forde, Darren; /SLAC /UCLA
2008-02-22
In the context of constructing one-loop amplitudes using a unitarity bootstrap approach we discuss a general systematic procedure for obtaining the coefficients of the scalar bubble and triangle integral functions of one-loop amplitudes. Coefficients are extracted after examining the behavior of the cut integrand as the unconstrained parameters of a specifically chosen parameterization of the cut loop momentum approach infinity. Measurements of new physics at the forthcoming experimental program at CERN's Large Hadron Collider (LHC) will require a precise understanding of processes at next-to-leading order (NLO). This places increased demands for the computation of new one-loop amplitudes. This in turn has spurred recent developments towards improved calculational techniques. Direct calculations using Feynman diagrams are in general inefficient. Developments of more efficient techniques have usually centered around unitarity techniques [1], where tree amplitudes are effectively 'glued' together to form loops. The most straightforward application of this method, in which the cut loop momentum is in D = 4, allows for the computation of 'cut-constructible' terms only, i.e. (poly)logarithmic containing terms and any related constants. QCD amplitudes contain, in addition to such terms, rational pieces which cannot be derived using such cuts. These 'missing' rational parts can be extracted using cut loop momenta in D = 4-2 {var_epsilon}. The greater difficulty of such calculations has restricted the application of this approach, although recent developments [3, 4] have provided new promise for this technique. Recently the application of on-shell recursion relations [5] to obtaining the 'missing' rational parts of one-loop processes [6] has provided an alternative very promising solution to this problem. In combination with unitarity methods an 'on-shell bootstrap' approach provides an efficient technique for computing complete one-loop QCD amplitudes [7]. Additionally
NASA Astrophysics Data System (ADS)
Campbell, Norman Robert
2013-03-01
Preface; Introduction; Part I. The Propositions of Science: 1. The subject matter of science; 2. The nature of laws; 3. The nature of laws (contd); 4. The discovery and proof of laws; 5. The explanation of laws; 6. Theories; 7. Chance and probability; 8. The meaning of science; 9. Science and philosophy; Part II. Measurement: 10. Fundamental measurement; 11. Physical number; 12. Fractional and negative magnitudes; 13. Numerical laws and derived magnitudes; 14. Units and dimensions; 15. The uses of dimensions; 16. Errors of measurement; methodical errors; 17. Errors of measurement; errors of consistency and the adjustment of observations; 18. Mathematical physics; Appendix; Index.
Genus dependence of superstring amplitudes
Davis, Simon
2006-11-15
The problem of the consistency of the finiteness of the supermoduli space integral in the limit of vanishing super-fixed point distance and the genus-dependence of the integral over the super-Schottky coordinates in the fundamental region containing a neighborhood of |K{sub n}|=0 is resolved. Given a choice of the categories of isometric circles representing the integration region, the exponential form of bounds for superstring amplitudes is derived.
Pulse amplitude modulated chlorophyll fluorometer
Greenbaum, Elias; Wu, Jie
2015-12-29
Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.
Variable-amplitude oscillatory shear response of amorphous materials
NASA Astrophysics Data System (ADS)
Perchikov, Nathan; Bouchbinder, Eran
2014-06-01
Variable-amplitude oscillatory shear tests are emerging as powerful tools to investigate and quantify the nonlinear rheology of amorphous solids, complex fluids, and biological materials. Quite a few recent experimental and atomistic simulation studies demonstrated that at low shear amplitudes, an amorphous solid settles into an amplitude- and initial-conditions-dependent dissipative limit cycle, in which back-and-forth localized particle rearrangements periodically bring the system to the same state. At sufficiently large shear amplitudes, the amorphous system loses memory of the initial conditions, exhibits chaotic particle motions accompanied by diffusive behavior, and settles into a stochastic steady state. The two regimes are separated by a transition amplitude, possibly characterized by some critical-like features. Here we argue that these observations support some of the physical assumptions embodied in the nonequilibrium thermodynamic, internal-variables based, shear-transformation-zone model of amorphous viscoplasticity; most notably that "flow defects" in amorphous solids are characterized by internal states between which they can make transitions, and that structural evolution is driven by dissipation associated with plastic deformation. We present a rather extensive theoretical analysis of the thermodynamic shear-transformation-zone model for a variable-amplitude oscillatory shear protocol, highlighting its success in accounting for various experimental and simulational observations, as well as its limitations. Our results offer a continuum-level theoretical framework for interpreting the variable-amplitude oscillatory shear response of amorphous solids and may promote additional developments.
Remarks on the identities of gluon tree amplitudes
NASA Astrophysics Data System (ADS)
Tye, S.-H. Henry; Zhang, Yang
2010-10-01
Recently, Bjerrum-Bohr, Damgaard, Feng, and Sondergaard derived a set of new interesting quadratic identities of the Yang-Mills (YM) tree scattering amplitudes, besides Bern-Carrasco-Johansson (BCJ) identities. Here we comment that these quadratic identities of YM amplitudes actually follow directly from the KLT (Kawai-Lewellen-Tye) relation for graviton-dilaton-axion scattering amplitudes (in four-dimensional spacetime). This clarifies their physical origin and also provides a simpler version of the new identities. We also comment that the recently discovered BCJ identities of YM helicity amplitudes, at least for the maximal helicity-violating case, can be verified by using (repeatedly) the Schouten identity. We also point out additional quadratic identities that can be written down from the KLT relations.
Moments of pseudoscalar meson distribution amplitudes from the lattice
Braun, V. M.; Goeckeler, M.; Horsley, R.; Zanotti, J. M.; Perlt, H.; Schiller, A.; Pleiter, D.; Schroers, W.; Schierholz, G.; Stueben, H.
2006-10-01
Based on lattice simulations with two flavors of dynamical, O(a)-improved Wilson fermions we present results for the first two moments of the distribution amplitudes of pseudoscalar mesons at several values of the valence quark masses. By extrapolating our results to the physical masses of up/down and strange quarks, we find the first two moments of the K{sup +} distribution amplitude and the second moment of the {pi}{sup +} distribution amplitude. We use nonperturbatively determined renormalization coefficients to obtain results in the MS scheme. At a scale of 4 GeV{sup 2} we find a{sub 2}{sup {pi}}=0.201(114) for the second Gegenbauer moment of the pion's distribution amplitude, while for the kaon, a{sub 1}{sup K}=0.0453(9)(29) and a{sub 2}{sup K}=0.175(18)(47)
Remarks on the identities of gluon tree amplitudes
Tye, S.-H. Henry; Zhang Yang
2010-10-15
Recently, Bjerrum-Bohr, Damgaard, Feng, and Sondergaard derived a set of new interesting quadratic identities of the Yang-Mills (YM) tree scattering amplitudes, besides Bern-Carrasco-Johansson (BCJ) identities. Here we comment that these quadratic identities of YM amplitudes actually follow directly from the KLT (Kawai-Lewellen-Tye) relation for graviton-dilaton-axion scattering amplitudes (in four-dimensional spacetime). This clarifies their physical origin and also provides a simpler version of the new identities. We also comment that the recently discovered BCJ identities of YM helicity amplitudes, at least for the maximal helicity-violating case, can be verified by using (repeatedly) the Schouten identity. We also point out additional quadratic identities that can be written down from the KLT relations.
Amplitude Scaling of Active Separation Control
NASA Technical Reports Server (NTRS)
Stalnov, Oksana; Seifert, Avraham
2010-01-01
Three existing and two new excitation magnitude scaling options for active separation control at Reynolds numbers below one Million. The physical background for the scaling options was discussed and their relevance was evaluated using two different sets of experimental data. For F+ approx. 1, 2D excitation: a) The traditional VR and C(mu) - do not scale the data. b) Only the Re*C(mu) is valid. This conclusion is also limited for positive lift increment.. For F+ > 10, 3D excitation, the Re corrected C(mu), the St corrected velocity ratio and the vorticity flux coefficient, all scale the amplitudes equally well. Therefore, the Reynolds weighted C(mu) is the preferred choice, relevant to both excitation modes. Incidence also considered, using Ue from local Cp.
Oscillations of a Simple Pendulum with Extremely Large Amplitudes
ERIC Educational Resources Information Center
Butikov, Eugene I.
2012-01-01
Large oscillations of a simple rigid pendulum with amplitudes close to 180[degrees] are treated on the basis of a physically justified approach in which the cycle of oscillation is divided into several stages. The major part of the almost closed circular path of the pendulum is approximated by the limiting motion, while the motion in the vicinity…
Bromley, D A
1980-07-01
From massive quarks deep in the hearts of atomic nuclei to the catastrophic collapse of giant stars in the farthest reaches of the universe, from the partial realization of Einstein's dream of a unified theory of the forces of nature to the most practical applications in technology, medicine, and throughout contemporary society, physics continues to have a profound impact on man's view of the universe and on the quality of life. The author argues that the past few years, in terms of new discoveries, new insight-and the new questions-have been among the most productive in the history of the field and puts into context his selection of some of the most important new developments in this fundamental science.
An Analysis of Fundamental Mode Surface Wave Amplitude Measurements
NASA Astrophysics Data System (ADS)
Schardong, L.; Ferreira, A. M.; van Heijst, H. J.; Ritsema, J.
2014-12-01
Seismic tomography is a powerful tool to decipher the Earth's interior structure at various scales. Traveltimes of seismic waves are widely used to build velocity models, whereas amplitudes are still only seldomly accounted for. This mainly results from our limited ability to separate the various physical effects responsible for observed amplitude variations, such as focussing/defocussing, scattering and source effects. We present new measurements from 50 global earthquakes of fundamental-mode Rayleigh and Love wave amplitude anomalies measured in the period range 35-275 seconds using two different schemes: (i) a standard time-domain amplitude power ratio technique; and (ii) a mode-branch stripping scheme. For minor-arc data, we observe amplitude anomalies with respect to PREM in the range of 0-4, for which the two measurement techniques show a very good overall agreement. We present here a statistical analysis and comparison of these datasets, as well as comparisons with theoretical calculations for a variety of 3-D Earth models. We assess the geographical coherency of the measurements, and investigate the impact of source, path and receiver effects on surface wave amplitudes, as well as their variations with frequency in a wider range than previously studied.
Constructing Amplitudes from Their Soft Limits
Boucher-Veronneau, Camille; Larkoski, Andrew J.; /SLAC
2011-12-09
The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an (n-1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which 'soft' particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedure and relate it to Britto-Cachazo-Feng-Witten recursion. We show that all tree-level amplitudes in gauge theory and gravity up through seven points can be constructed in this way, as well as certain classes of NMHV gauge-theory amplitudes with any number of external legs. This provides us with a systematic procedure for constructing amplitudes solely from their soft limits.
Large Amplitude Oscillations in Prominences
NASA Astrophysics Data System (ADS)
Luna, Manuel
2016-07-01
Large-amplitude Oscillations in prominences are spectacular manifestations of the solar activity. In such events nearby energetic disturbances induce periodic motions on filaments with displacements comparable to the size of the filaments themselves and with velocities larger than 20 km/s. Recent studies have shown that such oscillations open a new window on coronal connectivity, as well as novel diagnostics for hard-to-measure prominence properties such as magnetic field strength and geometry. In addition, this oscillation could be related with activation of filaments prior to eruptions. In this talk I will show past and current research on this subject in order to understand the nature of the solar prominences. Additionally, a large catalogue of such events will be presented.
Non-perturbative QCD amplitudes in quenched and eikonal approximations
NASA Astrophysics Data System (ADS)
Fried, H. M.; Grandou, T.; Sheu, Y.-M.
2014-05-01
Even though approximated, strong coupling non-perturbative QCD amplitudes remain very difficult to obtain. In this article, in eikonal and quenched approximations at least, physical insights are presented that rely on the newly-discovered property of effective locality. The present article also provides a more rigorous mathematical basis for the crude approximations used in the previous derivation of the binding potential of quarks and nucleons. Furthermore, the techniques of Random Matrix calculus along with Meijer G-functions are applied to analyze the generic structure of fermionic amplitudes in QCD.
Light-Front Holography and Hadronization at the Amplitude Level
Brodsky, Stanley J.; Teramond, Guy F. de; Shrock, Robert
2008-10-13
The correspondence between theories in anti-de Sitter space and conformal field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD which has scale invariance at short distances and color confinement at large distances. Light-front holography is a remarkable feature of AdS/CFT: it allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates and the behavior of the QCD coupling in the infrared. We suggest that the spatial support of QCD condensates is restricted to the interior of hadrons, since they arise due to the interactions of confined quarks and gluons. Chiral symmetry is thus broken in a limited domain of size 1/m{sub {pi}}, in analogy to the limited physical extent of superconductor phases. A new method for computing the hadronization of quark and gluon jets at the amplitude level, an event amplitude generator, is outlined.
Veneziano amplitudes, spin chains and Abelian reduction of QCD
NASA Astrophysics Data System (ADS)
Kholodenko, Arkady
2009-05-01
Although QCD can be treated perturbatively in the high energy limit, lower energies require uses of nonperturbative methods such as ADS/CFT and/or Abelian reduction. These methods are not equivalent. While the first is restricted to supersymmetric Yang-Mills model with number of colors going to infinity, the second is not restricted by requirements of supersymmetry and is designed to work in the physically realistic limit of a finite number of colors. In this paper we provide arguments in favor of the Abelian reduction methods. This is achieved by further developing results of our recent works re-analyzing Veneziano and Veneziano-like amplitudes and the models associated with these amplitudes. It is shown, that the obtained new partition function for these amplitudes can be mapped exactly into that for the Polychronakos-Frahm (P-F) spin chain model recoverable from the Richardon-Gaudin (R-G) XXX spin chain model originally designed for treatments of the BCS-type superconductivity. Because of this, it is demonstrated that the obtained mapping is compatible with the method of Abelian reduction. The R-G model is recovered from the asymptotic (WKB-type) solutions of the rational Knizhnik-Zamolodchikov (K-Z) equation. Linear independence of these solutions is controlled by determinants whose explicit form (up to a constant) coincides with Veneziano (or Veneziano-like) amplitudes. In the simplest case, the determinantal conditions coincide with those discovered by Kummer in the 19th century. Kummer's results admit physical interpretation by relating determinantal formula(s) to Veneziano-like amplitudes. Furthermore, these amplitudes can be interpreted as Poisson-Dirichlet distributions playing a central role in the stochastic theory of random coagulation-fragmentation processes. Such an interpretation is complementary to that known for the Lund model widely used for the description of coagulation-fragmentation processes in QCD.
Coupling of Large Amplitude Inversion with Other States
NASA Astrophysics Data System (ADS)
Pearson, John; Yu, Shanshan
2016-06-01
The coupling of a large amplitude motion with a small amplitude vibration remains one of the least well characterized problems in molecular physics. Molecular inversion poses a few unique and not intuitively obvious challenges to the large amplitude motion problem. In spite of several decades of theoretical work numerous challenges in calculation of transition frequencies and more importantly intensities persist. The most challenging aspect of this problem is that the inversion coordinate is a unique function of the overall vibrational state including both the large and small amplitude modes. As a result, the r-axis system and the meaning of the K-quantum number in the rotational basis set are unique to each vibrational state of large or small amplitude motion. This unfortunate reality has profound consequences to calculation of intensities and the coupling of nearly degenerate vibrational states. The case of NH3 inversion and inversion through a plane of symmetry in alcohols will be examined to find a general path forward.
Lorentz constraints on massive three-point amplitudes
NASA Astrophysics Data System (ADS)
Conde, Eduardo; Marzolla, Andrea
2016-09-01
Using the helicity-spinor language we explore the non-perturbative constraints that Lorentz symmetry imposes on three-point amplitudes where the asymptotic states can be massive. As it is well known, in the case of only massless states the three-point amplitude is fixed up to a coupling constant by these constraints plus some physical requirements. We find that a similar statement can be made when some of the particles have mass. We derive the generic functional form of the three-point amplitude by virtue of Lorentz symmetry, which displays several functional structures accompanied by arbitrary constants. These constants can be related to the coupling constants of the theory, but in an unambiguous fashion only in the case of one massive particle. Constraints on these constants are obtained by imposing that in the UV limit the massive amplitude matches the massless one. In particular, there is a certain Lorentz frame, which corresponds to projecting all the massive momenta along the same null momentum, where the three-point massive amplitude is fully fixed, and has a universal form.
Amplitude-dependent station magnitude
NASA Astrophysics Data System (ADS)
Radzyner, Yael; Ben Horin, Yochai; Steinberg, David M.
2016-04-01
Magnitude, a concept first presented by Gutenberg and Richter, adjusts measurements of ground motion for epicentral distance and source depth. Following this principle, the IDC defines the j'th station body wave magnitude for event i as mb(stai,j) = log 10(Aj,i/Tj,i) + V C(Δj,i,hi) , where VC is the Veith-Clawson (VC) correction to compensate for the epicentral distance of the station and the depth of the source. The network magnitude is calculated as the average of station magnitudes. The IDC magnitude estimation is used for event characterization and discrimination and it should be as accurate as possible. Ideally, the network magnitude should be close in value to the station magnitudes. In reality, it is observed that the residuals range between -1 and 1 mu or ±25% of a given mb(neti) value. We show that the residual, mb(neti) -mb(staj,i), depends linearly on log 10(Aj,i/Tj,i), and we correct for this dependence using the following procedure: Calculate a "jackknifed" network magnitude, mbj,n(neti), i.e. an average over all participating stations except station n. Using all measurements at station n, calculate the parameters an, bn of the linear fit of the residual mbj,n(neti) - mb(stan,i to log 10(An,i/Tn,i). For each event i at station n calculate the new station magnitude mbnew(stan,i) = (an + 1)log(An,i/Tn,i) + V C(Δn,i,hi) + bn Calculate the new network magnitude: mbnew(neti) = 1N- ∑ n=1nmbnew(stan,i) The procedure was used on more than two million station-event pairs. Correcting for the station-specific dependence on log amplitude reduces the residuals by roughly a third. We have calculated the spread of the distributions, and compared the original values and those for the corrected magnitudes. The spread is the ratio between the variance of the network magnitudes, and the variance of the residual. Calculations show an increase in the ratio of the variance, meaning that the correction process presented in this document did not lead to loss of variance
Gravity and Yang-Mills amplitude relations
Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Soendergaard, Thomas; FengBo
2010-11-15
Using only general features of the S matrix and quantum field theory, we prove by induction the Kawai-Lewellen-Tye relations that link products of gauge theory amplitudes to gravity amplitudes at tree level. As a bonus of our analysis, we provide a novel and more symmetric form of these relations. We also establish an infinite tower of new identities between amplitudes in gauge theories.
Minimal Basis for Gauge Theory Amplitudes
Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Vanhove, Pierre
2009-10-16
Identities based on monodromy for integrations in string theory are used to derive relations between different color-ordered tree-level amplitudes in both bosonic and supersymmetric string theory. These relations imply that the color-ordered tree-level n-point gauge theory amplitudes can be expanded in a minimal basis of (n-3)exclamation amplitudes. This result holds for any choice of polarizations of the external states and in any number of dimensions.
Discontinuities of multi-Regge amplitudes
NASA Astrophysics Data System (ADS)
Fadin, V. S.
2015-04-01
In the BFKL approach, discontinuities of multiple production amplitudes in invariant masses of produced particles are discussed. It turns out that they are in evident contradiction with the BDS ansatz for n-gluon amplitudes in the planar N = 4 SYM at n ≥ 6. An explicit expression for the NLO discontinuity of the two-to-four amplitude in the invariant mass of two produced gluons is is presented.
Radiation Belt Electron Dynamics Driven by Large-Amplitude Whistlers
NASA Technical Reports Server (NTRS)
Khazanov, G. V.; Tel'nikhin, A. A.; Kronberg, T. K.
2013-01-01
Acceleration of radiation belt electrons driven by oblique large-amplitude whistler waves is studied. We show analytically and numerically that this is a stochastic process; the intensity of which depends on the wave power modified by Bessel functions. The type of this dependence is determined by the character of the nonlinear interaction due to coupling between action and phase. The results show that physically significant quantities have a relatively weak dependence on the wave power.
Classical gluon production amplitude in heavy-ion collisions
NASA Astrophysics Data System (ADS)
Chirilli, Giovanni Antonio
2016-03-01
The distribution of quarks and gluons produced in the initial stages of nuclear collisions, known as the initial condition of the Quark-Gluon Plasma formation, is the fundamental building block of heavy-ion theory. I will present the scattering amplitude, beyond the leading order, of the classical gluon produced in heavy-ion collisions. The result is obtained in the framework of saturation physics and Wilson lines formalism.
Comment on [open quotes]Validity of certain soft photon amplitudes[close quotes
Liou, M.K.; Li, Y. ); Timmermans, R. ); Gibson, B.F. )
1999-09-01
The criteria suggested by Welsh and Fearing to judge the validity of certain soft-photon amplitudes are examined. Some aspects of their analysis lead to incorrect conclusions. [copyright] [ital 1999] [ital The American Physical Society
Interlimb coupling strength scales with movement amplitude.
Peper, C Lieke E; de Boer, Betteco J; de Poel, Harjo J; Beek, Peter J
2008-05-23
The relation between movement amplitude and the strength of interlimb interactions was examined by comparing bimanual performance at different amplitude ratios (1:2, 1:1, and 2:1). For conditions with unequal amplitudes, the arm moving at the smaller amplitude was predicted to be more strongly affected by the contralateral arm than vice versa. This prediction was based on neurophysiological considerations and the HKB model of coupled oscillators. Participants performed rhythmic bimanual forearm movements at prescribed amplitude relations. After a brief mechanical perturbation of one arm, the relaxation process back to the initial coordination pattern was examined. This analysis focused on phase adaptations in the unperturbed arm, as these reflect the degree to which the movements of this arm were affected by the coupling influences stemming from the contralateral (perturbed) arm. The thus obtained index of coupling (IC) reflected the relative contribution of the unperturbed arm to the relaxation process. As predicted IC was larger when the perturbed arm moved at a larger amplitude than did the unperturbed arm, indicating that coupling strength scaled with movement amplitude. This result was discussed in relation to previous research regarding sources of asymmetry in coupling strength and the effects of amplitude disparity on interlimb coordination.
New relations for gauge-theory amplitudes
Bern, Z.; Carrasco, J. J. M.; Johansson, H.
2008-10-15
We present an identity satisfied by the kinematic factors of diagrams describing the tree amplitudes of massless gauge theories. This identity is a kinematic analog of the Jacobi identity for color factors. Using this we find new relations between color-ordered partial amplitudes. We discuss applications to multiloop calculations via the unitarity method. In particular, we illustrate the relations between different contributions to a two-loop four-point QCD amplitude. We also use this identity to reorganize gravity tree amplitudes diagram by diagram, offering new insight into the structure of the Kawai-Lewellen-Tye (KLT) relations between gauge and gravity tree amplitudes. This insight leads to similar but novel relations. We expect this to be helpful in higher-loop studies of the ultraviolet properties of gravity theories.
Thermal cracking and amplitude dependent attenuation
Johnston, D.H.; Toksoez, M.N.
1980-02-10
The role of crack and grain boundary contacts in determining seismic wave attenuation in rock is investigated by examining Q as a function of thermal cycling (cracking) and wave strain amplitude. Q values are obtained using a longitudinal resonant bar technique in the 10- to 20-kHz range for maximum strain amplitudes varying from roughly 10/sup -8/ to 10/sup -5/. The samples studied include the Berea and Navajo sandstones, Plexiglas, Westerly granite, Solenhofen limestone, and Frederick diabase, the latter two relatively crack free in their virgin state. Measurements were made at room temperature and pressure in air. Q values for both sandstones are constant at low strains (<10/sup -6/) but decrease rapidly with amplitude at higher strains. There is no hysteresis of Q with amplitude. Q values for Plexiglas show no indication of amplitude dependent behavior. The granite, limestone, and diabase are thermally cycled at both fast and slow heating rates in order to induce cracking. Samples slowly cycled at 400/sup 0/C show a marked increase in Q that cannot be entirely explained by outgassing of volatiles. Cycling may also widen thin cracks and grain boundaries, reducing contact areas. Samples heated beyond 400/sup 0/C, or rapidly heated, result in generally decreasing Q values. The amplitude dependence of Q is found to be coupled to the effects of thermal cycling. For rock slowly cycled 400)C or less, the transition from low-amplitude contant Q to high-amplitude variable Q behavior decreases to lower amplitudes as a function of maximum temperature. Above 400/sup 0/C, and possibly in th rapidly heated samples also, the transition moves to higher amplitudes.
NASA Astrophysics Data System (ADS)
Roiban, Radu; Spradlin, Marcus; Volovich, Anastasia
2011-11-01
This issue aims to serve as an introduction to our current understanding of the structure of scattering amplitudes in gauge theory, an area which has seen particularly rapid advances in recent years following decades of steady progress. The articles contained herein provide a snapshot of the latest developments which we hope will serve as a valuable resource for graduate students and other scientists wishing to learn about the current state of the field, even if our continually evolving understanding of the subject might soon render this compilation incomplete. Why the fascination with scattering amplitudes, which have attracted the imagination and dedicated effort of so many physicists? Part of it stems from the belief, supported now by numerous examples, that unexpected simplifications of otherwise apparently complicated calculations do not happen by accident. Instead they provide a strong motivation to seek out an underlying explanation. The insight thereby gained can subsequently be used to make the next class of seemingly impossible calculations not only possible, but in some cases even trivial. This two-pronged strategy of exploring and exploiting the structure of gauge theory amplitudes appeals to a wide audience from formal theorists interested in mathematical structure for the sake of its own beauty to more phenomenologically-minded physicists eager to speed up the next generation of analysis software. Understandably it is the maximally supersymmetric 𝒩 = 4 Yang-Mills theory (SYM) which has the simplest structure and has correspondingly received the most attention. Rarely in theoretical physics are we fortunate enough to encounter a toy model which is simple enough to be solved completely yet rich enough to possess interesting non-trivial structure while simultaneously, and most importantly, being applicable (even if only as a good approximation) to a wide range of 'real' systems. The canonical example in quantum mechanics is of course the harmonic
Computation of the radiation amplitude of oscillons
NASA Astrophysics Data System (ADS)
Fodor, Gyula; Forgács, Péter; Horváth, Zalán; Mezei, Márk
2009-03-01
The radiation loss of small-amplitude oscillons (very long-living, spatially localized, time-dependent solutions) in one-dimensional scalar field theories is computed in the small-amplitude expansion analytically using matched asymptotic series expansions and Borel summation. The amplitude of the radiation is beyond all orders in perturbation theory and the method used has been developed by Segur and Kruskal in Phys. Rev. Lett. 58, 747 (1987)PRLTAO0031-900710.1103/PhysRevLett.58.747. Our results are in good agreement with those of long-time numerical simulations of oscillons.
Form factor and boundary contribution of amplitude
NASA Astrophysics Data System (ADS)
Huang, Rijun; Jin, Qingjun; Feng, Bo
2016-06-01
The boundary contribution of an amplitude in the BCFW recursion relation can be considered as a form factor involving boundary operator and unshifted particles. At the tree-level, we show that by suitable construction of Lagrangian, one can relate the leading order term of boundary operators to some composite operators of mathcal{N} = 4 superYang-Mills theory, then the computation of form factors is translated to the computation of amplitudes. We compute the form factors of these composite operators through the computation of corresponding double trace amplitudes.
Amplitude- and rise-time-compensated filters
Nowlin, Charles H.
1984-01-01
An amplitude-compensated rise-time-compensated filter for a pulse time-of-occurrence (TOOC) measurement system is disclosed. The filter converts an input pulse, having the characteristics of random amplitudes and random, non-zero rise times, to a bipolar output pulse wherein the output pulse has a zero-crossing time that is independent of the rise time and amplitude of the input pulse. The filter differentiates the input pulse, along the linear leading edge of the input pulse, and subtracts therefrom a pulse fractionally proportional to the input pulse. The filter of the present invention can use discrete circuit components and avoids the use of delay lines.
A link representation for gravity amplitudes
NASA Astrophysics Data System (ADS)
He, Song
2013-10-01
We derive a link representation for all tree amplitudes in supergravity, from a recent conjecture by Cachazo and Skinner. The new formula explicitly writes amplitudes as contour integrals over constrained link variables, with an integrand naturally expressed in terms of determinants, or equivalently tree diagrams. Important symmetries of the amplitude, such as supersymmetry, parity and (partial) permutation invariance, are kept manifest in the formulation. We also comment on rewriting the formula in a GL( k)-invariant manner, which may serve as a starting point for the generalization to possible Grassmannian contour integrals.
Photoinduced Enhancement of the Charge Density Wave Amplitude.
Singer, A; Patel, S K K; Kukreja, R; Uhlíř, V; Wingert, J; Festersen, S; Zhu, D; Glownia, J M; Lemke, H T; Nelson, S; Kozina, M; Rossnagel, K; Bauer, M; Murphy, B M; Magnussen, O M; Fullerton, E E; Shpyrko, O G
2016-07-29
Symmetry breaking and the emergence of order is one of the most fascinating phenomena in condensed matter physics. It leads to a plethora of intriguing ground states found in antiferromagnets, Mott insulators, superconductors, and density-wave systems. Exploiting states of matter far from equilibrium can provide even more striking routes to symmetry-lowered, ordered states. Here, we demonstrate for the case of elemental chromium that moderate ultrafast photoexcitation can transiently enhance the charge-density-wave (CDW) amplitude by up to 30% above its equilibrium value, while strong excitations lead to an oscillating, large-amplitude CDW state that persists above the equilibrium transition temperature. Both effects result from dynamic electron-phonon interactions, providing an efficient mechanism to selectively transform a broad excitation of the electronic order into a well-defined, long-lived coherent lattice vibration. This mechanism may be exploited to transiently enhance order parameters in other systems with coupled degrees of freedom. PMID:27517781
Photoinduced Enhancement of the Charge Density Wave Amplitude
NASA Astrophysics Data System (ADS)
Singer, A.; Patel, S. K. K.; Kukreja, R.; Uhlíř, V.; Wingert, J.; Festersen, S.; Zhu, D.; Glownia, J. M.; Lemke, H. T.; Nelson, S.; Kozina, M.; Rossnagel, K.; Bauer, M.; Murphy, B. M.; Magnussen, O. M.; Fullerton, E. E.; Shpyrko, O. G.
2016-07-01
Symmetry breaking and the emergence of order is one of the most fascinating phenomena in condensed matter physics. It leads to a plethora of intriguing ground states found in antiferromagnets, Mott insulators, superconductors, and density-wave systems. Exploiting states of matter far from equilibrium can provide even more striking routes to symmetry-lowered, ordered states. Here, we demonstrate for the case of elemental chromium that moderate ultrafast photoexcitation can transiently enhance the charge-density-wave (CDW) amplitude by up to 30% above its equilibrium value, while strong excitations lead to an oscillating, large-amplitude CDW state that persists above the equilibrium transition temperature. Both effects result from dynamic electron-phonon interactions, providing an efficient mechanism to selectively transform a broad excitation of the electronic order into a well-defined, long-lived coherent lattice vibration. This mechanism may be exploited to transiently enhance order parameters in other systems with coupled degrees of freedom.
Amplitude dynamics favors synchronization in complex networks
NASA Astrophysics Data System (ADS)
Gambuzza, Lucia Valentina; Gómez-Gardeñes, Jesus; Frasca, Mattia
2016-04-01
In this paper we study phase synchronization in random complex networks of coupled periodic oscillators. In particular, we show that, when amplitude dynamics is not negligible, phase synchronization may be enhanced. To illustrate this, we compare the behavior of heterogeneous units with both amplitude and phase dynamics and pure (Kuramoto) phase oscillators. We find that in small network motifs the behavior crucially depends on the topology and on the node frequency distribution. Surprisingly, the microscopic structures for which the amplitude dynamics improves synchronization are those that are statistically more abundant in random complex networks. Thus, amplitude dynamics leads to a general lowering of the synchronization threshold in arbitrary random topologies. Finally, we show that this synchronization enhancement is generic of oscillators close to Hopf bifurcations. To this aim we consider coupled FitzHugh-Nagumo units modeling neuron dynamics.
Amplitude dynamics favors synchronization in complex networks
Gambuzza, Lucia Valentina; Gómez-Gardeñes, Jesus; Frasca, Mattia
2016-01-01
In this paper we study phase synchronization in random complex networks of coupled periodic oscillators. In particular, we show that, when amplitude dynamics is not negligible, phase synchronization may be enhanced. To illustrate this, we compare the behavior of heterogeneous units with both amplitude and phase dynamics and pure (Kuramoto) phase oscillators. We find that in small network motifs the behavior crucially depends on the topology and on the node frequency distribution. Surprisingly, the microscopic structures for which the amplitude dynamics improves synchronization are those that are statistically more abundant in random complex networks. Thus, amplitude dynamics leads to a general lowering of the synchronization threshold in arbitrary random topologies. Finally, we show that this synchronization enhancement is generic of oscillators close to Hopf bifurcations. To this aim we consider coupled FitzHugh-Nagumo units modeling neuron dynamics. PMID:27108847
GENERAL Holomorphic Factorization of Superstring Scattering Amplitudes
NASA Astrophysics Data System (ADS)
Simon, Davis
2011-01-01
The holomorphic factorization of the superstring partition function is verified at arbitrary genus. The evaluation of scattering amplitudes and the implications of genus-dependent estimates on the string coupling are given.
Motivic multiple zeta values and superstring amplitudes
NASA Astrophysics Data System (ADS)
Schlotterer, O.; Stieberger, S.
2013-11-01
The structure of tree-level open and closed superstring amplitudes is analyzed. For the open superstring amplitude we find a striking and elegant form, which allows one to disentangle its α‧-expansion into several contributions accounting for different classes of multiple zeta values. This form is bolstered by the decomposition of motivic multiple zeta values, i.e. the latter encapsulate the α‧-expansion of the superstring amplitude. Moreover, a morphism induced by the coproduct maps the α‧-expansion onto a non-commutative Hopf algebra. This map represents a generalization of the symbol of a transcendental function. In terms of elements of this Hopf algebra the α‧-expansion assumes a very simple and symmetric form, which carries all the relevant information. Equipped with these results we can also cast the closed superstring amplitude into a very elegant form.
The amplitude of quantum field theory
Medvedev, B.V. ); Pavlov, V.P.; Polivanov, M.K. ); Sukhanov, A.D. )
1989-05-01
General properties of the transition amplitude in axiomatic quantum field theory are discussed. Bogolyubov's axiomatic method is chosen as the variant of the theory. The axioms of this method are analyzed. In particular, the significance of the off-shell extension and of the various forms of the causality condition are examined. A complete proof is given of the existence of a single analytic function whose boundary values are the amplitudes of all channels of a process with given particle number.
Amplitude metrics for cellular circadian bioluminescence reporters.
St John, Peter C; Taylor, Stephanie R; Abel, John H; Doyle, Francis J
2014-12-01
Bioluminescence rhythms from cellular reporters have become the most common method used to quantify oscillations in circadian gene expression. These experimental systems can reveal phase and amplitude change resulting from circadian disturbances, and can be used in conjunction with mathematical models to lend further insight into the mechanistic basis of clock amplitude regulation. However, bioluminescence experiments track the mean output from thousands of noisy, uncoupled oscillators, obscuring the direct effect of a given stimulus on the genetic regulatory network. In many cases, it is unclear whether changes in amplitude are due to individual changes in gene expression level or to a change in coherence of the population. Although such systems can be modeled using explicit stochastic simulations, these models are computationally cumbersome and limit analytical insight into the mechanisms of amplitude change. We therefore develop theoretical and computational tools to approximate the mean expression level in large populations of noninteracting oscillators, and further define computationally efficient amplitude response calculations to describe phase-dependent amplitude change. At the single-cell level, a mechanistic nonlinear ordinary differential equation model is used to calculate the transient response of each cell to a perturbation, whereas population-level dynamics are captured by coupling this detailed model to a phase density function. Our analysis reveals that amplitude changes mediated at either the individual-cell or the population level can be distinguished in tissue-level bioluminescence data without the need for single-cell measurements. We demonstrate the effectiveness of the method by modeling experimental bioluminescence profiles of light-sensitive fibroblasts, reconciling the conclusions of two seemingly contradictory studies. This modeling framework allows a direct comparison between in vitro bioluminescence experiments and in silico ordinary
Amplitude-temporal method of speech coding
NASA Astrophysics Data System (ADS)
Ababii, Victor; Sudacevschi, Viorica
2005-02-01
A method of speech coding and decoding is proposed. The speech coding algorithm is based on first derivate calculation of input speech signal, identification of critical points and input signal amplitude in these points, time period measurement between critical points. The result of codification represents a sequence of amplitudes and time periods. The decoding algorithm utilizes values of COS or SIN functions for reconstruction on the input speech. The codec structure that consists from encoder and decoder units is proposed.
Twistor-strings and gravity tree amplitudes
NASA Astrophysics Data System (ADS)
Adamo, Tim; Mason, Lionel
2013-04-01
Recently we discussed how Einstein supergravity tree amplitudes might be obtained from the original Witten and Berkovits twistor-string theory when external conformal gravitons are restricted to be Einstein gravitons. Here we obtain a more systematic understanding of the relationship between conformal and Einstein gravity amplitudes in that twistor-string theory. We show that although it does not in general yield Einstein amplitudes, we can nevertheless obtain some partial twistor-string interpretation of the remarkable formulae recently been found by Hodges and generalized to all tree amplitudes by Cachazo and Skinner. The Hodges matrix and its higher degree generalizations encode the world sheet correlators of the twistor string. These matrices control both Einstein amplitudes and those of the conformal gravity arising from the Witten and Berkovits twistor-string. Amplitudes in the latter case arise from products of the diagonal elements of the generalized Hodges matrices and reduced determinants give the former. The reduced determinants arise if the contractions in the worldsheet correlator are restricted to form connected trees at MHV. The (generalized) Hodges matrices arise as weighted Laplacian matrices for the graph of possible contractions in the correlators and the reduced determinants of these weighted Laplacian matrices give the sum of the connected tree contributions by an extension of the matrix-tree theorem.
Amplitude Modulations of Acoustic Communication Signals
NASA Astrophysics Data System (ADS)
Turesson, Hjalmar K.
2011-12-01
In human speech, amplitude modulations at 3 -- 8 Hz are important for discrimination and detection. Two different neurophysiological theories have been proposed to explain this effect. The first theory proposes that, as a consequence of neocortical synaptic dynamics, signals that are amplitude modulated at 3 -- 8 Hz are propagated better than un-modulated signals, or signals modulated above 8 Hz. This suggests that neural activity elicited by vocalizations modulated at 3 -- 8 Hz is optimally transmitted, and the vocalizations better discriminated and detected. The second theory proposes that 3 -- 8 Hz amplitude modulations interact with spontaneous neocortical oscillations. Specifically, vocalizations modulated at 3 -- 8 Hz entrain local populations of neurons, which in turn, modulate the amplitude of high frequency gamma oscillations. This suggests that vocalizations modulated at 3 -- 8 Hz should induce stronger cross-frequency coupling. Similar to human speech, we found that macaque monkey vocalizations also are amplitude modulated between 3 and 8 Hz. Humans and macaque monkeys share similarities in vocal production, implying that the auditory systems subserving perception of acoustic communication signals also share similarities. Based on the similarities between human speech and macaque monkey vocalizations, we addressed how amplitude modulated vocalizations are processed in the auditory cortex of macaque monkeys, and what behavioral relevance modulations may have. Recording single neuron activity, as well as, the activity of local populations of neurons allowed us to test both of the neurophysiological theories presented above. We found that single neuron responses to vocalizations amplitude modulated at 3 -- 8 Hz resulted in better stimulus discrimination than vocalizations lacking 3 -- 8 Hz modulations, and that the effect most likely was mediated by synaptic dynamics. In contrast, we failed to find support for the oscillation-based model proposing a
Amplitude-dependent orbital period in alternating gradient accelerators
NASA Astrophysics Data System (ADS)
Machida, S.; Kelliher, D. J.; Edmonds, C. S.; Kirkman, I. W.; Berg, J. S.; Jones, J. K.; Muratori, B. D.; Garland, J. M.
2016-03-01
Orbital period in a ring accelerator and time of flight in a linear accelerator depend on the amplitude of betatron oscillations. The variation is negligible in ordinary particle accelerators with relatively small beam emittance. In an accelerator for large emittance beams like muons and unstable nuclei, however, this effect cannot be ignored. We measured orbital period in a linear non-scaling fixed-field alternating-gradient accelerator, which is a candidate for muon acceleration, and compared it with the theoretical prediction. The good agreement between them gives important ground for the design of particle accelerators for a new generation of particle and nuclear physics experiments.
Elementary amplitudes in the multiple diffraction theory reexamined
Martini, A.F.; Menon, M.J.; Thober, D.S.
1996-08-01
We show that, in the context of Glauber{close_quote}s multiple diffraction theory, the square of the correction factor introduced by Bourrely, Soffer, and Wu in a double-pole form factor parametrization, may be interpreted as an elementary (parton-parton) amplitude. The condition concerning the existence of a well-defined Fourier transform is demonstrated, and it is shown that the corresponding profile function comes from an ordinary transform (Bessel function) plus a generalized transform ({delta} distribution). Comparisons with a modified parametrization and results from a model-independent analysis are also presented and discussed. {copyright} {ital 1996 The American Physical Society.}
Dependence of seismoelectric amplitudes on water content - a field study
NASA Astrophysics Data System (ADS)
Strahser, M. H. P.; Matthey, P.-D.; Jouniaux, L.; Sailhac, P.
2009-04-01
In porous saturated media, seismic compressional waves can cause seismoelectric and seismoelectromagnetic signals through electrokinetic coupling. It has been observed that these measureable signals also occur in partially saturated media, but the theory is largely unknown for these circumstances. Seismoelectromagnetic tomography is expected to combine the sensitivity of electrical properties to water-content and permeability, to the high spatial resolution of seismic surveys. A better understanding of the physical processes and a reliable quantification of the conversion between seismic and electric energy are necessary and need to take into account the effect of water-content, especially for shallow subsurface investigations. In order to quantify seismoelectric signals with changing water content, we repeated seismoelectric and seismic measurements on the same profile in the Vosges Mountains during several months. The electrical resistivity was also monitored to take into account the water-content variations. We show that an exponential relation can be established between the seismoelectric amplitudes normalized with the seismic amplitudes and the resistivity which in turn is related to the saturation: Increasing resistivity (decreasing water content) leads to decreasing normalized seismoelectric amplitudes. These results imply that the electrokinetic coefficient should increase with water-saturation, as measured in laboratory, but not predicted by theory. This work was funded by CNRS and Université Louis Pasteur de Strasbourg.
Amplitude spectroscopy of a solid-state artificial atom.
Berns, David M; Rudner, Mark S; Valenzuela, Sergio O; Berggren, Karl K; Oliver, William D; Levitov, Leonid S; Orlando, Terry P
2008-09-01
The energy-level structure of a quantum system, which has a fundamental role in its behaviour, can be observed as discrete lines and features in absorption and emission spectra. Conventionally, spectra are measured using frequency spectroscopy, whereby the frequency of a harmonic electromagnetic driving field is tuned into resonance with a particular separation between energy levels. Although this technique has been successfully employed in a variety of physical systems, including natural and artificial atoms and molecules, its application is not universally straightforward and becomes extremely challenging for frequencies in the range of tens to hundreds of gigahertz. Here we introduce a complementary approach, amplitude spectroscopy, whereby a harmonic driving field sweeps an artificial atom through the avoided crossings between energy levels at a fixed frequency. Spectroscopic information is obtained from the amplitude dependence of the system's response, thereby overcoming many of the limitations of a broadband-frequency-based approach. The resulting 'spectroscopy diamonds', the regions in parameter space where transitions between specific pairs of levels can occur, exhibit interference patterns and population inversion that serve to distinguish the atom's spectrum. Amplitude spectroscopy provides a means of manipulating and characterizing systems over an extremely broad bandwidth, using only a single driving frequency that may be orders of magnitude smaller than the energy scales being probed.
Periodic amplitude variations in Jovian continuum radiation
NASA Technical Reports Server (NTRS)
Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.
1986-01-01
An analysis of periodic variations in the amplitude of continuum radiation near 3 kHz trapped in the Jovian magnetosphere shows structure with periods near both five and ten hours. Contrary to a plausible initial idea, the continuum amplitudes are not organized by position of the observer relative to the dense plasma sheet. Instead, there seem to be preferred orientations of system III longitude with respect to the direction to the sun which account for the peaks. This implies a clock-like modulation of the continuum radiation intensity as opposed to a searchlight effect. The importance of the dipole longitude-solar wind alignment to the amplitude of the continuum radiation implies the source region of the radiation is near the magnetopause and may indirectly tie the generation of the radio waves to the clocklike modulation of energetic electron fluxes from Jupiter.
A description of seismic amplitude techniques
NASA Astrophysics Data System (ADS)
Shadlow, James
2014-02-01
The acquisition of seismic data is a non-invasive technique used for determining the sub surface geology. Changes in lithology and fluid fill affect the seismic wavelet. Analysing seismic data for direct hydrocarbon indicators (DHIs), such as full stack amplitude anomalies, or amplitude variation with offset (AVO), can help a seismic interpreter relate the geophysical response to real geology and, more importantly, to distinguish the presence of hydrocarbons. Inversion is another commonly used technique that attempts to tie the seismic data back to the geology. Much has been written about these techniques, and attempting to gain an understanding on the theory and application of them by reading through various journals can be quite daunting. The purpose of this paper is to briefly outline DHI analysis, including full stack amplitude anomalies, AVO and inversion and show the relationship between all three. The equations presented have been included for completeness, but the reader can pass over the mathematical detail.
Cut-constructible part of QCD amplitudes
Britto, Ruth; Feng Bo; Mastrolia, Pierpaolo
2006-05-15
Unitarity cuts are widely used in analytic computation of loop amplitudes in gauge theories such as QCD. We expand upon the technique introduced in hep-ph/0503132 to carry out any finite unitarity cut integral. This technique naturally separates the contributions of bubble, triangle and box integrals in one-loop amplitudes and is not constrained to any particular helicity configurations. Loop momentum integration is reduced to a sequence of algebraic operations. We discuss the extraction of the residues at higher-order poles. Additionally, we offer concise algebraic formulas for expressing coefficients of three-mass triangle integrals. As an application, we compute all remaining coefficients of bubble and triangle integrals for nonsupersymmetric six-gluon amplitudes.
Method to repair localized amplitude defects in a EUV lithography mask blank
Stearns, Daniel G.; Sweeney, Donald W.; Mirkarimi, Paul B.; Chapman, Henry N.
2005-11-22
A method and apparatus are provided for the repair of an amplitude defect in a multilayer coating. A significant number of layers underneath the amplitude defect are undamaged. The repair technique restores the local reflectivity of the coating by physically removing the defect and leaving a wide, shallow crater that exposes the underlying intact layers. The particle, pit or scratch is first removed the remaining damaged region is etched away without disturbing the intact underlying layers.
Quantum discord protection from amplitude damping decoherence.
Yune, Jiwon; Hong, Kang-Hee; Lim, Hyang-Tag; Lee, Jong-Chan; Kwon, Osung; Han, Sang-Wook; Kim, Yong-Su; Moon, Sung; Kim, Yoon-Ho
2015-10-01
Entanglement is known to be an essential resource for many quantum information processes. However, it is now known that some quantum features may be acheived with quantum discord, a generalized measure of quantum correlation. In this paper, we study how quantum discord, or more specifically, the measures of entropic discord and geometric discord are affected by the influence of amplitude damping decoherence. We also show that a protocol deploying weak measurement and quantum measurement reversal can effectively protect quantum discord from amplitude damping decoherence, enabling to distribute quantum correlation between two remote parties in a noisy environment. PMID:26480116
Topographic quantitative EEG amplitude in recovered alcoholics.
Pollock, V E; Schneider, L S; Zemansky, M F; Gleason, R P; Pawluczyk, S
1992-05-01
Topographic measures of electroencephalographic (EEG) amplitude were used to compare recovered alcoholics (n = 14) with sex- and age-matched control subjects. Delta, alpha, and beta activity did not distinguish the groups, but regional differences in theta distribution did. Recovered alcoholics showed more uniform distributions of theta amplitudes in bilateral anterior and posterior regions compared with controls. Because a minimum of 5 years had elapsed since the recovered alcoholic subjects fulfilled DSM-III-R criteria for alcohol abuse or dependence, it is unlikely these EEG theta differences reflect the effects of withdrawal.
Dual amplitude pulse generator for radiation detectors
Hoggan, Jerry M.; Kynaston, Ronnie L.; Johnson, Larry O.
2001-01-01
A pulsing circuit for producing an output signal having a high amplitude pulse and a low amplitude pulse may comprise a current source for providing a high current signal and a low current signal. A gate circuit connected to the current source includes a trigger signal input that is responsive to a first trigger signal and a second trigger signal. The first trigger signal causes the gate circuit to connect the high current signal to a pulse output terminal whereas the second trigger signal causes the gate circuit to connect the low current signal to the pulse output terminal.
Towards NMHV amplitudes at strong coupling
NASA Astrophysics Data System (ADS)
Belitsky, A. V.
2016-10-01
Pentagon Operator Product Expansion provides a non-perturbative framework for analysis of scattering amplitudes in planar maximally supersymmetric gauge theory building up on their duality to null polygonal superWilson loop and integrability. In this paper, we construct a systematic expansion for the main ingredients of the formalism, i.e., pentagons, at large 't Hooft coupling as a power series in its inverse value. The calculations are tested against relations provided by the so-called Descent Equation which mixes transitions at different perturbative orders. We use leading order results to have a first glimpse into the structure of scattering amplitude at NMHV level at strong coupling.
Explosion Amplitude Reduction due to Fractures in Water-Saturated and Dry Granite
NASA Astrophysics Data System (ADS)
Stroujkova, A. F.; Leidig, M.; Bonner, J. L.
2013-12-01
Empirical observations made at the Semipalatinsk Test Site suggest that nuclear tests in the fracture zones left by previous explosions ('repeat shots') show reduced seismic amplitudes compared to the nuclear tests in virgin rocks. Likely mechanisms for the amplitude reduction in the repeat shots include increased porosity and reduced strength and elastic moduli, leading to pore closing and frictional sliding. Presence of pore water significantly decreases rock compressibility and strength, thus affecting seismic amplitudes. A series of explosion experiments were conducted in order to define the physical mechanism responsible for the amplitude reduction and to quantify the degree of the amplitude reduction in fracture zones of previously detonated explosions. Explosions in water-saturated granite were conducted in central New Hampshire in 2011 and 2012. Additional explosions in dry granite were detonated in Barre, VT in 2013. The amplitude reduction is different between dry and water-saturated crystalline rocks. Significant reduction in seismic amplitudes (by a factor of 2-3) in water-saturated rocks was achieved only when the repeat shot was detonated in the extensive damage zone created by a significantly larger (by a factor of 5) explosion. In case where the first and the second explosions were similar in yield, the amplitude reduction was relatively modest (5-20%). In dry rocks the amplitude reduction reached a factor of 2 even in less extensive damage zones. In addition there are differences in frequency dependence of the spectral amplitude ratios between explosions in dry and water-saturated rocks. Thus the amplitude reduction is sensitive to the extent of the damage zone as well as the pore water content.
The Finite Amplitude Method for the Qrpa
NASA Astrophysics Data System (ADS)
Avogadro, Paolo; Nakatsukasa, Takashi
We present the finite amplitude method (FAM) for the Quasi Particle Random Phase Approximation (QRPA). This method allows to extract a QRPA code starting from a Hartree-Fock-Bogoliubov (HFB) code. The code obtained is fully self consistent, moreover since the FAM is not restricted to spherical symmetry it can be used to obtain deformed QRPA codes.
Cardiac phase: Amplitude analysis using macro programming
Logan, K.W.; Hickey, K.A.
1981-11-01
The analysis of EKG gated radionuclide cardiac imaging data with Fourier amplitude and phase images is becoming a valuable clinical technique, demonstrating location, size, and severity of regional ventricular abnormalities. Not all commercially available nuclear medicine computer systems offer software for phase and amplitude analysis; however, many systems do have the capability of linear image arithmetic using simple macro commands which can easily be sequenced into stored macro-strings or programs. Using simple but accurate series approximations for the Fourier operations, macro programs have been written for a Digital Equipment Corporation Gamma-11 system to obtain phase and amplitude images from routine gated cardiac studies. In addition, dynamic cine-mode presentation of the onset of mechanical systole is generated from the phase data, using only a second set of macro programs. This approach is easily adapted to different data acquisition protocols, and can be used on any system with macro commands for image arithmetic. Key words: Fourier analysis, cardiac cycle, gated blood pool imaging, amplitude image, phase image
Particle Distribution Modification by Low Amplitude Modes
White, R. B.; Gorelenkov, N.; Heidbrink, W. W.; Van Zeeland, M. A.
2009-08-28
Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.
Kaon decay amplitudes using staggered fermions
Sharpe, S.R.
1986-12-01
A status report is given of an attempt, using staggered fermions to calculate the real and imaginary parts of the amplitudes for K ..-->.. ..pi pi..,. Semi-quantitative results are found for the imaginary parts, and these suggest that epsilon' might be smaller than previously expected in the standard model.
Amplitude Frequency Response Measurement: A Simple Technique
ERIC Educational Resources Information Center
Satish, L.; Vora, S. C.
2010-01-01
A simple method is described to combine a modern function generator and a digital oscilloscope to configure a setup that can directly measure the amplitude frequency response of a system. This is achieved by synchronously triggering both instruments, with the function generator operated in the "Linear-Sweep" frequency mode, while the oscilloscope…
Representation of the contextual statistical model by hyperbolic amplitudes
Khrennikov, Andrei
2005-06-01
We continue the development of a so-called contextual statistical model (here context has the meaning of a complex of physical conditions). It is shown that, besides contexts producing the conventional trigonometric cos-interference, there exist contexts producing the hyperbolic cos-interference. Starting with the corresponding interference formula of total probability we represent such contexts by hyperbolic probabilistic amplitudes or in the abstract formalism by normalized vectors of a hyperbolic analogue of the Hilbert space. There is obtained a hyperbolic Born's rule. Incompatible observables are represented by noncommutative operators. This paper can be considered as the first step towards hyperbolic quantum probability. We also discuss possibilities of experimental verification of hyperbolic quantum mechanics: in physics of elementary particles, string theory as well as in experiments with nonphysical systems, e.g., in psychology, cognitive sciences, and economy.
Stochastic Closures for Finite Amplitude Internal Waves
NASA Astrophysics Data System (ADS)
Polzin, K. L.; Lvov, Y.
2012-12-01
The theoretical paradigm of a self-consistent theory for the interaction of finite amplitude oceanic internal waves and its evolution from the resonant, infinitesimal amplitude limit are considered. The two limits are investigated using ray tracing techniques, analytic approximations to kinetic equations, and solutions for moments of a diffusive approximation to the resonant kinetic equation. We focus here on high frequency internal waves interacting with larger vertical and horizontal scale waves having inertial frequency. Tracing high frequency waves in one and two inertial wave backgrounds demonstrates that the infinitesimal amplitude and finite amplitude limits are phenomenologically distinct: the finite amplitude state is characterized by the coalescing of the two small scale members of the triad and a transition to a bound wave phenomena. This coalescence marks the transition to a strongly nonlinear parameter regime. Tracing high frequency waves in a stochastic background of inertial oscillations provides estimates of the evolution of the time mean and variance of wavenumber and intrinsic frequency. These estimates are compared to the evolution of the first and second moments of a diffusive approximation of the kinetic equation. In the finite but weakly nonlinear regime we find a diffusive characterization. In the strongly nonlinear limit we find an advective characterization. We next turn to the Finescale Paramterization of Polzin (2004, J. Phys. Oceanogr.), which has been used to successfully predict observations of turbulent dissipation. The Finescale Parameterization is an advective closure, and we demonstrate how it can be derived from resonant formula, which is a diffusive characterization. We conclude by considering application to the atmospheric internal wavefield.
Flutter of articulated pipes at finite amplitude
NASA Technical Reports Server (NTRS)
Rousselet, J.; Herrmann, G.
1975-01-01
Previous studies of the behavior of pipes conveying fluid have assumed that the fluid velocity relative to the pipe is a known quantity and is unaffected by the motion of the pipe. This approach eliminates the need to find the flow equations of motion, and is adequate for infinitesimal transverse amplitudes of motion of the pipe system, but is incapable of predicting what will be the effect of larger amplitudes. This last shortcoming may be of importance when flow velocities are near critical velocities, that is, velocities at which the system begins to flutter. It is the purpose of the present study to investigate in greater detail the dynamic behavior of pipes in the vicinity of critical velocities.
Amplitudes of MHD Waves in Sunspots
NASA Astrophysics Data System (ADS)
Norton, Aimee Ann; Cally, Paul; Baldner, Charles; Kleint, Lucia; Tarbell, Theodore D.; De Pontieu, Bart; Scherrer, Philip H.; Rajaguru, Paul
2016-05-01
The conversion of p-modes into MHD waves by strong magnetic fields occurs mainly in the sub-photospheric layers. The photospheric signatures of MHD waves are weak due to low amplitudes at the beta=1 equipartion level where mode-conversion occurs. We report on small amplitude oscillations observed in the photosphere with Hinode SOT/SP in which we analyze time series for sunspots ARs 12186 (11.10.2014) and 12434 (17.10.2015). No significant magnetic field oscillations are recovered in the umbra or penumbra in the ME inversion. However, periodicities in the inclination angle are found at the umbral/penumbral boundary with 5 minute periods. Upward propagating waves are indicated in the intensity signals correlated between HMI and AIA at different heights. We compare SP results with the oscillations observed in HMI data. Simultaneous IRIS data shows transition region brightening above the umbral core.
Differential equations, associators, and recurrences for amplitudes
NASA Astrophysics Data System (ADS)
Puhlfürst, Georg; Stieberger, Stephan
2016-01-01
We provide new methods to straightforwardly obtain compact and analytic expressions for ɛ-expansions of functions appearing in both field and string theory amplitudes. An algebraic method is presented to explicitly solve for recurrence relations connecting different ɛ-orders of a power series solution in ɛ of a differential equation. This strategy generalizes the usual iteration by Picard's method. Our tools are demonstrated for generalized hypergeometric functions. Furthermore, we match the ɛ-expansion of specific generalized hypergeometric functions with the underlying Drinfeld associator with proper Lie algebra and monodromy representations. We also apply our tools for computing ɛ-expansions for solutions to generic first-order Fuchsian equations (Schlesinger system). Finally, we set up our methods to systematically get compact and explicit α‧-expansions of tree-level superstring amplitudes to any order in α‧.
Multilayered models for electromagnetic reflection amplitudes
NASA Technical Reports Server (NTRS)
Linlor, W. I.
1976-01-01
The remote sensing of snowpack characteristics with surface installations or with an airborne system could have important applications in water resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multilayer snow models is analyzed. Normally incident plane waves are assumed at frequencies ranging from 10 to the 6th power to 10 to the 10th power Hz, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice sheets. Layers are defined by a thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients, versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the reflection coefficient variations as a function of frequency.
Automatic generation of tree level helicity amplitudes
NASA Astrophysics Data System (ADS)
Stelzer, T.; Long, W. F.
1994-11-01
The program MadGraph is presented which automatically generates postscript Feynman diagrams and Fortran code to calculate arbitrary tree level helicity amplitudes by calling HELAS[1] subroutines. The program is written in Fortran and is available in Unix and VMS versions. MadGraph currently includes standard model interactions of QCD and QFD, but is easily modified to include additional models such as supersymmetry.
Automatic generation of tree level helicity amplitudes
NASA Astrophysics Data System (ADS)
Stelzer, T.; Long, W. F.
1994-07-01
The program MadGraph is presented which automatically generates postscript Feynman diagrams and Fortran code to calculate arbitrary tree level helicity amplitudes by calling HELAS[1] subroutines. The program is written in Fortran and is available in Unix and VMS versions. MadGraph currently includes standard model interactions of QCD and QFD, but is easily modified to include additional models such as supersymmetry.
Phase analysis of amplitude binary mask structures
NASA Astrophysics Data System (ADS)
Puthankovilakam, Krishnaparvathy; Scharf, Toralf; Herzig, Hans Peter; Vogler, Uwe; Bramati, Arianna; Voelkel, Reinhard
2016-03-01
Shaping of light behind masks using different techniques is the milestone of the printing industry. The aerial image distribution or the intensity distribution at the printing distances defines the resolution of the structure after printing. Contrast and phase are the two parameters that play a major role in shaping of light to get the desired intensity pattern. Here, in contrast to many other contributions that focus on intensity, we discuss the phase evolution for different structures. The amplitude or intensity characteristics of the structures in a binary mask at different proximity gaps have been analyzed extensively for many industrial applications. But the phase evolution from the binary mask having OPC structures is not considered so far. The mask we consider here is the normal amplitude binary mask but having high resolution Optical Proximity Correction (OPC) structures for corners. The corner structures represent a two dimensional problem which is difficult to handle with simple rules of phase masks design and therefore of particular interest. The evolution of light from small amplitude structures might lead to high contrast by creating sharp phase changes or phase singularities which are points of zero intensity. We show the phase modulation at different proximity gaps and can visualize the shaping of light according to the phase changes. The analysis is done with an instrument called High Resolution Interference Microscopy (HRIM), a Mach-Zehnder interferometer that gives access to three-dimensional phase and amplitude images. The current paper emphasizes on the phase measurement of different optical proximity correction structures, and especially on corners of a binary mask.
A Brief Introduction to Modern Amplitude Methods
NASA Astrophysics Data System (ADS)
Dixon, Lance J.
I provide a basic introduction to modern helicity amplitude methods, including color organization, the spinor helicity formalism, and factorization properties. I also describe the BCFW (on-shell) recursion relation at tree level, and explain how similar ideas -- unitarity and on-shell methods -- work at the loop level. These notes are based on lectures delivered at the 2012 CERN Summer School and at TASI 2013, and are close to the material Zvi Bern lectured on at TASI 2014.
Understanding the amplitudes of noise correlation measurements
Tsai, Victor C.
2011-01-01
Cross correlation of ambient seismic noise is known to result in time series from which station-station travel-time measurements can be made. Part of the reason that these cross-correlation travel-time measurements are reliable is that there exists a theoretical framework that quantifies how these travel times depend on the features of the ambient noise. However, corresponding theoretical results do not currently exist to describe how the amplitudes of the cross correlation depend on such features. For example, currently it is not possible to take a given distribution of noise sources and calculate the cross correlation amplitudes one would expect from such a distribution. Here, we provide a ray-theoretical framework for calculating cross correlations. This framework differs from previous work in that it explicitly accounts for attenuation as well as the spatial distribution of sources and therefore can address the issue of quantifying amplitudes in noise correlation measurements. After introducing the general framework, we apply it to two specific problems. First, we show that we can quantify the amplitudes of coherency measurements, and find that the decay of coherency with station-station spacing depends crucially on the distribution of noise sources. We suggest that researchers interested in performing attenuation measurements from noise coherency should first determine how the dominant sources of noise are distributed. Second, we show that we can quantify the signal-to-noise ratio of noise correlations more precisely than previous work, and that these signal-to-noise ratios can be estimated for given situations prior to the deployment of seismometers. It is expected that there are applications of the theoretical framework beyond the two specific cases considered, but these applications await future work.
Meson distribution amplitudes in holographic models
NASA Astrophysics Data System (ADS)
Hwang, Chien-Wen
2012-07-01
We study the wave functions of light and heavy mesons in both hard-wall (HW) and soft-wall (SW) holographic models which use AdS/CFT correspondence. In the case of massless constituents, the asymptotic behaviors of the electromagnetic form factor, the distribution amplitudes, and the decay constants for the two models are the same, if the relation between the dilaton scale parameter and the size of meson is an inverse proportion. On the other hand, by introducing a quark mass dependence in the wave function, the differences of the distribution amplitudes between the two models are obvious. In addition, for the SW model, the dependences of the decay constants of meson on the dilaton scale parameter κ differ; especially fQq˜κ3/mQ2 is consistent with the prediction of the heavy quark effective theory if κ˜mQ1/2. Thus the parameters of the two models are fit by the decay constants of the distinct mesons; the distribution amplitudes and the ξ-moments are calculated and compared.
Amplitude-integrated electroencephalography in neonates.
El-Dib, Mohamed; Chang, Taeun; Tsuchida, Tammy N; Clancy, Robert R
2009-11-01
Conventional electroencephalography (EEG) has been used for decades in the neonatal intensive care unit for formulating neurologic prognoses, demonstrating brain functional state and degree of maturation, revealing cerebral lesions, and identifying the presence and number of electrographic seizures. However, both the immediate availability of conventional EEG and the expertise with which it is interpreted are variable. Amplitude-integrated EEG provides simplified monitoring of cerebral function, and is rapidly gaining popularity among neonatologists, with growing use in bedside decision making and inclusion criteria for randomized clinical studies. Nonetheless, child neurologists and neurophysiologists remain cautious about relying solely on this tool and prefer interpreting conventional EEG. The present review examines the technical aspects of generating, recording, and interpreting amplitude-integrated EEG and contrasts this approach with conventional EEG. Finally, several proposed amplitude-integrated EEG classification schemes are reviewed. A clear understanding of this emerging technology of measuring brain health in the premature or sick neonate is critical in modern care of the newborn infant. PMID:19818932
Continuous phase and amplitude holographic elements
NASA Technical Reports Server (NTRS)
Maker, Paul D. (Inventor); Muller, Richard E. (Inventor)
1995-01-01
A method for producing a phase hologram using e-beam lithography provides n-ary levels of phase and amplitude by first producing an amplitude hologram on a transparent substrate by e-beam exposure of a resist over a film of metal by exposing n is less than or equal to m x m spots of an array of spots for each pixel, where the spots are randomly selected in proportion to the amplitude assigned to each pixel, and then after developing and etching the metal film producing a phase hologram by e-beam lithography using a low contrast resist, such as PMMA, and n-ary levels of low doses less than approximately 200 micro-C/sq cm and preferably in the range of 20-200 micro-C/sq cm, and aggressive development using pure acetone for an empirically determined time (about 6 s) controlled to within 1/10 s to produce partial development of each pixel in proportion to the n-ary level of dose assigned to it.
Zeroing in on Supersymmetric Radiation Amplitude Zeros
Hewett, JoAnne L.; Ismail, Ahmed; Rizzo, Thomas G.; /SLAC
2012-02-15
Radiation amplitude zeros have long been used to test the Standard Model. Here, we consider the supersymmetric radiation amplitude zero in chargino-neutralino associated production, which can be observed at the luminosity upgraded LHC. Such an amplitude zero only occurs if the neutralino has a large wino fraction and hence this observable can be used to determine the neutralino eigenstate content. We find that this observable can be measured by comparing the p{sub T} spectrum of the softest lepton in the trilepton {tilde {chi}}{sub 1}{sup {+-}} {tilde {chi}}{sub 2}{sup 0} decay channel to that of a control process such as {tilde {chi}}{sub 1}{sup +} {tilde {chi}}{sub 1}{sup -} or {tilde {chi}}{sub 2}{sup 0} {tilde {chi}}{sub 2}{sup 0}. We test this technique on a previously generated model sample of the 19 dimensional parameter space of the phenomenological MSSM, and find that it is effective in determining the wino content of the neutralino.
Is amplitude loss of sonic waveforms due to intrinsic attenuation or source coupling to the medium?
Lee, Myung W.
2006-01-01
Sonic waveforms acquired in gas-hydrate-bearing sediments indicate strong amplitude loss associated with an increase in sonic velocity. Because the gas hydrate increases sonic velocities, the amplitude loss has been interpreted as due to intrinsic attenuation caused by the gas hydrate in the pore space, which apparently contradicts conventional wave propagation theory. For a sonic source in a fluid-filled borehole, the signal amplitude transmitted into the formation depends on the physical properties of the formation, including any pore contents, in the immediate vicinity of the source. A signal in acoustically fast material, such as gas-hydrate-bearing sediments, has a smaller amplitude than a signal in acoustically slower material. Therefore, it is reasonable to interpret the amplitude loss in the gas-hydrate-bearing sediments in terms of source coupling to the surrounding medium as well as intrinsic attenuation. An analysis of sonic waveforms measured at the Mallik 5L-38 well, Northwest Territories, Canada, indicates that a significant part of the sonic waveform's amplitude loss is due to a source-coupling effect. All amplitude analyses of sonic waveforms should include the effect of source coupling in order to accurately characterize the formation's intrinsic attenuation.
NASA Astrophysics Data System (ADS)
Fredette, Luke; Dreyer, Jason T.; Rook, Todd E.; Singh, Rajendra
2016-06-01
The dynamic stiffness properties of automotive hydraulic bushings exhibit significant amplitude sensitivity which cannot be captured by linear time-invariant models. Quasi-linear and nonlinear models are therefore proposed with focus on the amplitude sensitivity in magnitude and loss angle spectra (up to 50 Hz). Since production bushing model parameters are unknown, dynamic stiffness tests and laboratory experiments are utilized to extract model parameters. Nonlinear compliance and resistance elements are incorporated, including their interactions in order to improve amplitude sensitive predictions. New solution approximations for the new nonlinear system equations refine the multi-term harmonic balance term method. Quasi-linear models yield excellent accuracy but cannot predict trends in amplitude sensitivity since they rely on available dynamic stiffness measurements. Nonlinear models containing both nonlinear resistance and compliance elements yield superior predictions to those of prior models (with a single nonlinearity) while also providing more physical insight. Suggestion for further work is briefly mentioned.
Nonlinear rocket motor stability prediction: Limit amplitude, triggering, and mean pressure shifta)
NASA Astrophysics Data System (ADS)
Flandro, Gary A.; Fischbach, Sean R.; Majdalani, Joseph
2007-09-01
High-amplitude pressure oscillations in solid propellant rocket motor combustion chambers display nonlinear effects including: (1) limit cycle behavior in which the fluctuations may dwell for a considerable period of time near their peak amplitude, (2) elevated mean chamber pressure (DC shift), and (3) a triggering amplitude above which pulsing will cause an apparently stable system to transition to violent oscillations. Along with the obvious undesirable vibrations, these features constitute the most damaging impact of combustion instability on system reliability and structural integrity. The physical mechanisms behind these phenomena and their relationship to motor geometry and physical parameters must, therefore, be fully understood if instability is to be avoided in the design process, or if effective corrective measures must be devised during system development. Predictive algorithms now in use have limited ability to characterize the actual time evolution of the oscillations, and they do not supply the motor designer with information regarding peak amplitudes or the associated critical triggering amplitudes. A pivotal missing element is the ability to predict the mean pressure shift; clearly, the designer requires information regarding the maximum chamber pressure that might be experienced during motor operation. In this paper, a comprehensive nonlinear combustion instability model is described that supplies vital information. The central role played by steep-fronted waves is emphasized. The resulting algorithm provides both detailed physical models of nonlinear instability phenomena and the critically needed predictive capability. In particular, the origin of the DC shift is revealed.
ComPWA: A common amplitude analysis framework for PANDA
NASA Astrophysics Data System (ADS)
Michel, M.; Feldbauer, F.; Götzen, K.; Jasinski, P.; Karavdina, A.; Peters, K.; Fritsch, M.
2014-06-01
A large part of the physics program of the PANDA experiment at FAIR deals with the search for new conventional and exotic hadronic states like e.g. hybrids and glueballs. For many analyses PANDA will need an amplitude analysis, e.g. a partial wave analysis (PWA), to identify possible candidates and for the classification of known states. Therefore, a new, agile and efficient amplitude analysis framework ComPWA is under development. It is modularized to provide easy extension with models and formalisms as well as fitting of multiple datasets, even from different experiments. Experience from existing PWA programs was used to fix the requirements of the framework and to prevent it from restrictions. It will provide the standard estimation and optimization routines like Minuit2 and the Geneva library and be open to insert additional ones. The challenges involve parallelization, fitting with a high number of free parameters, managing complex meta-fits and quality assurance / comparability of fits. To test and develop the software, it will be used with data from running experiments like BaBar or BESIII. These proceedings show the status of the framework implementation as well as first test results.
Fatigue damage analysis under variable amplitude cycling
NASA Technical Reports Server (NTRS)
Leis, B. N.; Forte, T. P.
1983-01-01
This paper explores the suitability of a recently proposed mean stress parameter and introduces a nonlinear damage accumulation procedure. Data covering a range of positive and negative stress ratios from +0.6 to -2.66, for several aluminum alloys and steels, are assembled and shown to be well correlated by a simple damage parameter. A nonlinear damage accumulation postulate is advanced to replace the usual linear procedure. Results of critical experiments performed to assess the suitability of the postulate are introduced and shown to support a non-linear criterion. The implications of this work related to variable amplitude life prediction are discussed.
Information transfer for small-amplitude signals
NASA Astrophysics Data System (ADS)
Kostal, Lubomir; Lansky, Petr
2010-05-01
We study the optimality conditions of information transfer in systems with memory in the low signal-to-noise ratio regime of vanishing input amplitude. We find that the optimal mutual information is represented by a maximum variance of the signal time course, with correlation structure determined by the Fisher information matrix. We provide illustration of the method on a simple biologically inspired model of electrosensory neuron. Our general results apply also to the study of information transfer in single neurons subject to weak stimulation, with implications to the problem of coding efficiency in biological systems.
Approximate formulas for moderately small eikonal amplitudes
NASA Astrophysics Data System (ADS)
Kisselev, A. V.
2016-08-01
We consider the eikonal approximation for moderately small scattering amplitudes. To find numerical estimates of these approximations, we derive formulas that contain no Bessel functions and consequently no rapidly oscillating integrands. To obtain these formulas, we study improper integrals of the first kind containing products of the Bessel functions J0(z). We generalize the expression with four functions J0(z) and also find expressions for the integrals with the product of five and six Bessel functions. We generalize a known formula for the improper integral with two functions Jυ (az) to the case with noninteger υ and complex a.
Loop-quantum-gravity vertex amplitude.
Engle, Jonathan; Pereira, Roberto; Rovelli, Carlo
2007-10-19
Spin foam models are hoped to provide the dynamics of loop-quantum gravity. However, the most popular of these, the Barrett-Crane model, does not have the good boundary state space and there are indications that it fails to yield good low-energy n-point functions. We present an alternative dynamics that can be derived as a quantization of a Regge discretization of Euclidean general relativity, where second class constraints are imposed weakly. Its state space matches the SO(3) loop gravity one and it yields an SO(4)-covariant vertex amplitude for Euclidean loop gravity.
Fatigue crack growth under variable amplitude loading
NASA Technical Reports Server (NTRS)
Sidawi, Jihad A.
1994-01-01
Fatigue crack growth tests were conducted on an Fe 510 E C-Mn steel and a submerged arc welded joint from the same material under constant, variable, and random loading amplitudes. Paris-Erdogan's crack growth rate law was tested for the evaluation of m and C using the stress intensity factor K, the J-integral, the effective stress intensity factor K(sub eff), and the root mean square stress intensity factor K(sub rms) fracture mechanics concepts. The effect of retardation and residual stresses resulting from welding was also considered. It was found that all concepts gave good life predictions in all cases.
Measuring amplitudes of harmonics and combination frequencies in variable stars
NASA Astrophysics Data System (ADS)
Bellinger, E. P.; Wysocki, D.; Kanbur, S. M.
2016-05-01
Discoveries of RR Lyrae and Cepheid variable stars with multiple modes of pulsation have increased tremendously in recent years. The Fourier spectra of these stars can be quite complicated due to the large number of combination frequencies that can exist between their modes. As a result, light- curve fits to these stars often suffer from undesirable ringing effects that arise from noisy observations and poor phase coverage. These non-physical overfitting artifacts also occur when fitting the harmonics of single-mode stars. Here we present a new method for fitting light curves that is much more robust against these effects. We prove that the amplitude measurement problem is very difficult (NP-hard) and provide a heuristic algorithm for solving it quickly and accurately.
Arbitrary amplitude quantum dust ion-acoustic solitary waves
Tribeche, Mouloud; Ghebache, Siham; Aoutou, Kamel; Zerguini, Taha Houssine
2008-03-15
The one-dimensional quantum hydrodynamic model for a three-species quantum plasma is used to study the quantum counterpart of the well known dust ion-acoustic (DIA) wave. Two cases of physical interest are investigated, namely positive and negative dust charge. It is shown that only rarefactive solitary potentials associated with nonlinear quantum DIA (QDIA) waves involving electron density deeps can exist. The QDIA soliton experiences a spreading and the quantum effects tend to make it wider. Under certain conditions, the soliton enlarges and its pulse shape evolves into a broad central flat-bottomed (or table-bottomed) soliton as a limiting-amplitude member of the QDIA soliton family. Linear stability analysis as well as quasineutral solutions are succinctly outlined. The investigation could be of relevance to astrophysical quantum dusty plasmas.
Arbitrary amplitude quantum dust ion-acoustic solitary waves
NASA Astrophysics Data System (ADS)
Tribeche, Mouloud; Ghebache, Siham; Aoutou, Kamel; Zerguini, Taha Houssine
2008-03-01
The one-dimensional quantum hydrodynamic model for a three-species quantum plasma is used to study the quantum counterpart of the well known dust ion-acoustic (DIA) wave. Two cases of physical interest are investigated, namely positive and negative dust charge. It is shown that only rarefactive solitary potentials associated with nonlinear quantum DIA (QDIA) waves involving electron density deeps can exist. The QDIA soliton experiences a spreading and the quantum effects tend to make it wider. Under certain conditions, the soliton enlarges and its pulse shape evolves into a broad central flat-bottomed (or table-bottomed) soliton as a limiting-amplitude member of the QDIA soliton family. Linear stability analysis as well as quasineutral solutions are succinctly outlined. The investigation could be of relevance to astrophysical quantum dusty plasmas.
Wrist Proprioception: Amplitude or Position Coding?
Marini, Francesca; Squeri, Valentina; Morasso, Pietro; Masia, Lorenzo
2016-01-01
This work examines physiological mechanisms underlying the position sense of the wrist, namely, the codification of proprioceptive information related to pointing movements of the wrist toward kinesthetic targets. Twenty-four healthy subjects participated to a robot-aided assessment of their wrist proprioceptive acuity to investigate if the sensorimotor transformation involved in matching targets located by proprioceptive receptors relies on amplitude or positional cues. A joint position matching test was performed in order to explore such dichotomy. In this test, the wrist of a blindfolded participant is passively moved by a robotic device to a preset target position and, after a removal movement from this position, the participant has to actively replicate and match it as accurately as possible. The test involved two separate conditions: in the first, the matching movements started from the same initial location; in the second one, the initial location was randomly assigned. Target matching accuracy, precision, and bias in the two conditions were then compared. Overall results showed a consistent higher performance in the former condition than in the latter, thus supporting the hypothesis that the joint position sense is based on vectorial or amplitude coding rather than positional. PMID:27807417
Modeling the amplitude statistics of ultrasonic images.
Eltoft, Torbørn
2006-02-01
In this paper, a new statistical model for representing the amplitude statistics of ultrasonic images is presented. The model is called the Rician inverse Gaussian (RiIG) distribution, due to the fact that it is constructed as a mixture of the Rice distribution and the Inverse Gaussian distribution. The probability density function (pdf) of the RiIG model is given in closed form as a function of three parameters. Some theoretical background on this new model is discussed, and an iterative algorithm for estimating its parameters from data is given. Then, the appropriateness of the RiIG distribution as a model for the amplitude statistics of medical ultrasound images is experimentally studied. It is shown that the new distribution can fit to the various shapes of local histograms of linearly scaled ultrasound data better than existing models. A log-likelihood cross-validation comparison of the predictive performance of the RiIG, the K, and the generalized Nakagami models turns out in favor of the new model. Furthermore, a maximum a posteriori (MAP) filter is developed based on the RiIG distribution. Experimental studies show that the RiIG MAP filter has excellent filtering performance in the sense that it smooths homogeneous regions, and at the same time preserves details.
Spurious cross-frequency amplitude-amplitude coupling in nonstationary, nonlinear signals
NASA Astrophysics Data System (ADS)
Yeh, Chien-Hung; Lo, Men-Tzung; Hu, Kun
2016-07-01
Recent studies of brain activities show that cross-frequency coupling (CFC) plays an important role in memory and learning. Many measures have been proposed to investigate the CFC phenomenon, including the correlation between the amplitude envelopes of two brain waves at different frequencies - cross-frequency amplitude-amplitude coupling (AAC). In this short communication, we describe how nonstationary, nonlinear oscillatory signals may produce spurious cross-frequency AAC. Utilizing the empirical mode decomposition, we also propose a new method for assessment of AAC that can potentially reduce the effects of nonlinearity and nonstationarity and, thus, help to avoid the detection of artificial AACs. We compare the performances of this new method and the traditional Fourier-based AAC method. We also discuss the strategies to identify potential spurious AACs.
Topics in Nonsupersymmetric Scattering Amplitudes in Gauge and Gravity Theories
NASA Astrophysics Data System (ADS)
Nohle, Joshua David
vanishing perturbative matrix elements in exactly D = 4 dimensions. Similarly, evanescent fields do not propagate in D = 4; a three-form field is in this class, since it is dual to a cosmological-constant contribution. In this chapter, we show that evanescent operators and fields modify the leading ultraviolet divergence in pure gravity. To analyze the divergence, we compute the two-loop identical-helicity four-graviton amplitude and determine the coefficient of the associated (non-evanescent) R3 counterterm studied long ago by Goroff and Sagnotti. We compare two pairs of theories that are dual in D = 4: gravity coupled to nothing or to three-form matter, and gravity coupled to zero-form or to two-form matter. Duff and van Nieuwenhuizen showed that, curiously, the one-loop conformal anomaly---the coefficient of the Gauss-Bonnet operator---changes under p-form duality transformations. We concur, and also find that the leading R3 divergence changes under duality transformations. Nevertheless, in both cases the physical renormalized two-loop identical-helicity four-graviton amplitude can be chosen to respect duality. Its renormalization-scale dependence is unaltered. (Abstract shortened by UMI.).
Flutter of articulated pipes at finite amplitude
NASA Technical Reports Server (NTRS)
Rousselet, J.; Herrmann, G.
1977-01-01
The plane motion of an articulated pipe made of two segments is examined and the flow velocity at which flutter manifests itself is sought. The pressure in the reservoir feeding the pipe is kept constant. In contrast to previous works, the flow velocity is not taken as a prescribed parameter of the system but is left to follow the laws of motion. This approach requires a nonlinear formulation of the problem and the equations of motion are solved using Krylov-Bogoliubov's method. A graph of the amplitude of the limit cycles, as a function of the fluid-system mass ratio, is presented and conclusions are drawn as to the necessity of considering nonlinearities in the analysis.
On the pion distribution amplitude shape
NASA Astrophysics Data System (ADS)
Polyakov, M. V.
2009-10-01
We argue that the recent BaBar data on γ → π e.m. transition form factor at large photon virtuality supports the idea that pion distribution amplitude (DA) is close to unity with ϕ{π/'}(0)/6 ≫ 1 at a normalization point of μ = 0.6-0.8 GeV. Such pion DA can be obtained in the effective chiral quark model. The possible flat shape of the pion DA implies that the standard expansion of the DA in Gegenbauer polynomials can be divergent. On basis of chiral models we predict that the two-pion DA should exhibit anomalous endpoint behaviour for pions in the S-wave and that such feature is absent for higher partial waves. The latter implies that the ρ, f 2, etc. meson DAs have no anomalous endpoint behaviour. Possible implications of such pion DA for other hard exclusive processes are shortly discussed.
Speech recognition with amplitude and frequency modulations
NASA Astrophysics Data System (ADS)
Zeng, Fan-Gang; Nie, Kaibao; Stickney, Ginger S.; Kong, Ying-Yee; Vongphoe, Michael; Bhargave, Ashish; Wei, Chaogang; Cao, Keli
2005-02-01
Amplitude modulation (AM) and frequency modulation (FM) are commonly used in communication, but their relative contributions to speech recognition have not been fully explored. To bridge this gap, we derived slowly varying AM and FM from speech sounds and conducted listening tests using stimuli with different modulations in normal-hearing and cochlear-implant subjects. We found that although AM from a limited number of spectral bands may be sufficient for speech recognition in quiet, FM significantly enhances speech recognition in noise, as well as speaker and tone recognition. Additional speech reception threshold measures revealed that FM is particularly critical for speech recognition with a competing voice and is independent of spectral resolution and similarity. These results suggest that AM and FM provide independent yet complementary contributions to support robust speech recognition under realistic listening situations. Encoding FM may improve auditory scene analysis, cochlear-implant, and audiocoding performance. auditory analysis | cochlear implant | neural code | phase | scene analysis
Experimental generation of amplitude squeezed vector beams.
Chille, Vanessa; Berg-Johansen, Stefan; Semmler, Marion; Banzer, Peter; Aiello, Andrea; Leuchs, Gerd; Marquardt, Christoph
2016-05-30
We present an experimental method for the generation of amplitude squeezed high-order vector beams. The light is modified twice by a spatial light modulator such that the vector beam is created by means of a collinear interferometric technique. A major advantage of this approach is that it avoids systematic losses, which are detrimental as they cause decoherence in continuous-variable quantum systems. The utilisation of a spatial light modulator (SLM) gives the flexibility to switch between arbitrary mode orders. The conversion efficiency with our setup is only limited by the efficiency of the SLM. We show the experimental generation of Laguerre-Gauss (LG) modes with radial indices 0 or 1 and azimuthal indices up to 3 with complex polarization structures and a quantum noise reduction up to -0.9dB±0.1dB. The corresponding polarization structures are studied in detail by measuring the spatial distribution of the Stokes parameters. PMID:27410153
A damped simple pendulum of constant amplitude
NASA Astrophysics Data System (ADS)
Abdelkader, Mostafa A.
1984-03-01
A simple pendulum acted on by gravity and subjected to a resistance proportional to the velocity of the bob is considered. If the length of the string and the mass of the bob are held constant, the amplitude of the bob decreases gradually because of the damping. We want to keep the maximum swing of the bob constant for all time; this we achieve by varying the length of the string, the mass of the bob or both. The key to the solution of our problem is a second-order nonlinear differential equation having arbitrary nonlinearity and an arbitrary coefficient function, for which we give the exact integral. We also give an application of this differential equation to a boundary-value problem for a nonlinear generalization of a hypergeometric equation.
Amplitude and phase modulation with waveguide optics
Burkhart, S.C.; Wilcox, R.B.; Browning, D.; Penko, F.A.
1996-12-17
We have developed amplitude and phase modulation systems for glass lasers using integrated electro-optic modulators and solid state high- speed electronics. The present and future generation of lasers for Inertial Confinement Fusion require laser beams with complex temporal and phase shaping to compensate for laser gain saturation, mitigate parametric processes such as transverse stimulated Brillouin scattering in optics, and to provide specialized drive to the fusion targets. These functions can be performed using bulk optoelectronic modulators, however using high-speed electronics to drive low voltage integrated optical modulators has many practical advantages. In particular, we utilize microwave GaAs transistors to perform precision, 250 ps resolution temporal shaping. Optical bandwidth is generated using a microwave oscillator at 3 GHz amplified by a solid state amplifier. This drives an integrated electrooptic modulator to achieve laser bandwidths exceeding 30 GHz.
Localized finite-amplitude disturbances and selection of solitary waves
Kliakhandler; Porubov; Velarde
2000-10-01
It turns out that evolution of localized finite-amplitude disturbances in perturbed KdV equation is qualitatively different compared with conventional small-amplitude initial conditions. Namely, relatively fast solitary waves, with one and the same amplitude and velocity, are formed ahead of conventional chaotic-like irregular structures. The amplitude and velocity of the waves, obtained from the asymptotic theory, are in excellent agreement with numerics. PMID:11089043
NASA Astrophysics Data System (ADS)
Araki, Tohru; Shinbori, Atsuki
2016-05-01
The local time variation of geomagnetic sudden commencements (SCs) has not been taken into account in the Siscoe's linear relationship which connects the SC amplitude with the corresponding dynamic pressure variation of the solar wind. By considering the physical background of SC, we studied which local time is best to extract the information of the solar wind dynamic pressure and concluded that the SC amplitude at 4-5 h local time of middle- and low-latitude stations most directly reflects the dynamic pressure effect. This result is used to re-check the order of magnitude of the largest 3 SCs observed since 1868.
New coordinates for the amplitude parameter space of continuous gravitational waves
NASA Astrophysics Data System (ADS)
Whelan, John T.; Prix, Reinhard; Cutler, Curt J.; Willis, Joshua L.
2014-03-01
The parameter space for continuous gravitational waves (GWs) can be divided into amplitude parameters (signal amplitude, inclination and polarization angles describing the orientation of the source, and an initial phase) and phase-evolution parameters (signal frequency and frequency derivatives, and parameters such as sky position which determine the Doppler modulation of the signal). The division is useful in part because of the existence of a set of functions known as the Jaranowski-Królak-Schutz (JKS) coordinates, which are a set of four coordinates on the amplitude parameter space such that the GW signal can be written as a linear combination of four template waveforms (which depend on the phase-evolution parameters) with the JKS coordinates as coefficients. We define a new set of coordinates on the amplitude parameter space, with the same properties, which can be more closely connected to the physical amplitude parameters. These naturally divide into two pairs of Cartesian-like coordinates on two-dimensional subspaces, one corresponding to left- and the other to right-circular polarization. We thus refer to these as circular polarization factored (CPF) coordinates. The corresponding two sets of polar coordinates (known as CPF-polar) can be related in a simple way to the physical parameters. A further coordinate transformation can be made, within each subspace, between CPF and so-called root-radius coordinates, whose radial coordinate is the fourth root of the radial coordinate in CPF-polar coordinates. We illustrate some simplifying applications for these various coordinate systems, such as a calculation of the Jacobian for the transformation between JKS or CPF coordinates and the physical amplitude parameters (amplitude, inclination, polarization and initial phase); a demonstration that the Jacobian between root-radius coordinates and the physical parameters is a constant; an illustration of the signal coordinate singularities associated with left- and right
Amplitude blanking in seismic profiles from Lake Baikal
Lee, M.W.; Agena, W.F.; Hutchinson, D.R.
1996-01-01
Imaging of the deepest sedimentary section in Lake Baikal using multichannel seismic profiling was hampered by amplitude blanking that is regionally extensive, is associated with water depths greater than about 900 m and occurs at sub-bottom depths of 1-2 km in association with the first water-bottom multiple. Application of a powerful multiple suppression technique improved the quality of occasional discontinuous, dipping primary reflections, but failed to substantially alter the non-reflective character of the blanking zone. Detailed analysis of amplitudes from original data and synthetic models show that the threshold for detecting primary energy in deep water of Lake Baikal occurs when the primary is about 14-20 dB less than the multiple energy. The blanking occurs because of anomalously low reflectivities of the deep sediments coupled with this 20 dB limitation in real data processing. The blanking cuts across seismic stratal boundaries, and is therefore probably unrelated to depositional lithologies. The deepest, early rift deposits, inferred to come from a mixed fluvial and lacustrine setting, do not easily explain the widespread and uniform character of the blanked deposits. More likely, blanking occurs because of processes or phenomena that physically alter the deposits, causing them to be non-reflective and/or highly attenuating. No single process explains all the observations, but a combination of diagenesis, overpressure, and the presence of dispersed free gas at sub-bottom depths of 1-2 km, offer plausible and possible conditions that contribute to blanking. Copyright ?? 1996 Published by Elsevier Science Ltd.
Charge amplitude distribution of the Gossip gaseous pixel detector
NASA Astrophysics Data System (ADS)
Blanco Carballo, V. M.; Chefdeville, M.; Colas, P.; Giomataris, Y.; van der Graaf, H.; Gromov, V.; Hartjes, F.; Kluit, R.; Koffeman, E.; Salm, C.; Schmitz, J.; Smits, S. M.; Timmermans, J.; Visschers, J. L.
2007-12-01
The Gossip gaseous pixel detector is being developed for the detection of charged particles in extreme high radiation environments as foreseen close to the interaction point of the proposed super LHC. The detecting medium is a thin layer of gas. Because of the low density of this medium, only a few primary electron/ion pairs are created by the traversing particle. To get a detectable signal, the electrons drift towards a perforated metal foil (Micromegas) whereafter they are multiplied in a gas avalanche to provide a detectable signal. The gas avalanche occurs in the high field between the Micromegas and the pixel readout chip (ROC). Compared to a silicon pixel detector, Gossip features a low material budget and a low cooling power. An experiment using X-rays has indicated a possible high radiation tolerance exceeding 10 16 hadrons/cm 2. The amplified charge signal has a broad amplitude distribution due to the limited statistics of the primary ionization and the statistical variation of the gas amplification. Therefore, some degree of inefficiency is inevitable. This study presents experimental results on the charge amplitude distribution for CO 2/DME (dimethyl-ether) and Ar/iC 4H 10 mixtures. The measured curves were fitted with the outcome of a theoretical model. In the model, the physical Landau distribution is approximated by a Poisson distribution that is convoluted with the variation of the gas gain and the electronic noise. The value for the fraction of pedestal events is used for a direct calculation of the cluster density. For some gases, the measured cluster density is considerably lower than given in literature.
Feed-forward digital phase and amplitude correction system
Yu, David U. L.; Conway, Patrick H.
1994-01-01
Phase and amplitude modifications in repeatable RF pulses at the output of a high power pulsed microwave amplifier are made utilizing a digital feed-forward correction system. A controlled amount of the output power is coupled to a correction system for processing of phase and amplitude information. The correction system comprises circuitry to compare the detected phase and amplitude with the desired phase and amplitude, respectively, and a digitally programmable phase shifter and attenuator and digital logic circuitry to control the phase shifter and attenuator. The Phase and amplitude of subsequent are modified by output signals from the correction system.
Feed-forward digital phase and amplitude correction system
Yu, D.U.L.; Conway, P.H.
1994-11-15
Phase and amplitude modifications in repeatable RF pulses at the output of a high power pulsed microwave amplifier are made utilizing a digital feed-forward correction system. A controlled amount of the output power is coupled to a correction system for processing of phase and amplitude information. The correction system comprises circuitry to compare the detected phase and amplitude with the desired phase and amplitude, respectively, and a digitally programmable phase shifter and attenuator and digital logic circuitry to control the phase shifter and attenuator. The phase and amplitude of subsequent are modified by output signals from the correction system. 11 figs.
Leading Wave Amplitude of a Tsunami
NASA Astrophysics Data System (ADS)
Kanoglu, U.
2015-12-01
Okal and Synolakis (EGU General Assembly 2015, Geophysical Research Abstracts-Vol. 17-7622) recently discussed that why the maximum amplitude of a tsunami might not occur for the first wave. Okal and Synolakis list observations from 2011 Japan tsunami, which reached to Papeete, Tahiti with a fourth wave being largest and 72 min later after the first wave; 1960 Chilean tsunami reached Hilo, Hawaii with a maximum wave arriving 1 hour later with a height of 5m, first wave being only 1.2m. Largest later waves is a problem not only for local authorities both in terms of warning to the public and rescue efforts but also mislead the public thinking that it is safe to return shoreline or evacuated site after arrival of the first wave. Okal and Synolakis considered Hammack's (1972, Ph.D. Dissertation, Calif. Inst. Tech., 261 pp., Pasadena) linear dispersive analytical solution with a tsunami generation through an uplifting of a circular plug on the ocean floor. They performed parametric study for the radius of the plug and the depth of the ocean since these are the independent scaling lengths in the problem. They identified transition distance, as the second wave being larger, regarding the parameters of the problem. Here, we extend their analysis to an initial wave field with a finite crest length and, in addition, to a most common tsunami initial wave form of N-wave as presented by Tadepalli and Synolakis (1994, Proc. R. Soc. A: Math. Phys. Eng. Sci., 445, 99-112). We compare our results with non-dispersive linear shallow water wave results as presented by Kanoglu et al. (2013, Proc. R. Soc. A: Math. Phys. Eng. Sci., 469, 20130015), investigating focusing feature. We discuss the results both in terms of leading wave amplitude and tsunami focusing. Acknowledgment: The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no 603839 (Project ASTARTE - Assessment, Strategy and Risk
Amplitude interpretation and visualization of three-dimensional reflection data
Enachescu, M.E. )
1994-07-01
Digital recording and processing of modern three-dimensional surveys allow for relative good preservation and correct spatial positioning of seismic reflection amplitude. A four-dimensional seismic reflection field matrix R (x,y,t,A), which can be computer visualized (i.e., real-time interactively rendered, edited, and animated), is now available to the interpreter. The amplitude contains encoded geological information indirectly related to lithologies and reservoir properties. The magnitude of the amplitude depends not only on the acoustic impedance contrast across a boundary, but is also strongly affected by the shape of the reflective boundary. This allows the interpreter to image subtle tectonic and structural elements not obvious on time-structure maps. The use of modern workstations allows for appropriate color coding of the total available amplitude range, routine on-screen time/amplitude extraction, and late display of horizon amplitude maps (horizon slices) or complex amplitude-structure spatial visualization. Stratigraphic, structural, tectonic, fluid distribution, and paleogeographic information are commonly obtained by displaying the amplitude variation A = A(x,y,t) associated with a particular reflective surface or seismic interval. As illustrated with several case histories, traditional structural and stratigraphic interpretation combined with a detailed amplitude study generally greatly enhance extraction of subsurface geological information from a reflection data volume. In the context of three-dimensional seismic surveys, the horizon amplitude map (horizon slice), amplitude attachment to structure and [open quotes]bright clouds[close quotes] displays are very powerful tools available to the interpreter.
A Shock-Refracted Acoustic Wave Model for Screech Amplitude in Supersonic Jets
NASA Technical Reports Server (NTRS)
Kandula, Max
2007-01-01
A physical model is proposed for the estimation of the screech amplitude in underexpanded supersonic jets. The model is based on the hypothesis that the interaction of a plane acoustic wave with stationary shock waves provides amplification of the transmitted acoustic wave upon traversing the shock. Powell's discrete source model for screech incorporating a stationary array of acoustic monopoles is extended to accommodate variable source strength. The proposed model reveals that the acoustic sources are of increasing strength with downstream distance. It is shown that the screech amplitude increases with the fully expanded jet Mach number. Comparisons of predicted screech amplitude with available test data show satisfactory agreement. The effect of variable source strength on the directivity of the fundamental (first harmonic, lowest frequency mode) and the second harmonic (overtone) is found to be unimportant with regard to the principal lobe (main or major lobe) of considerable relative strength, and is appreciable only in the secondary or minor lobes (of relatively weaker strength).
Non-Perturbative, Unitary Quantum-Particle Scattering Amplitudes from Three-Particle Equations
Lindesay, James V
2002-03-19
We here use our non-perturbative, cluster decomposable relativistic scattering formalism to calculate photon-spinor scattering, including the related particle-antiparticle annihilation amplitude. We start from a three-body system in which the unitary pair interactions contain the kinematic possibility of single quantum exchange and the symmetry properties needed to identify and substitute antiparticles for particles. We extract from it unitary two-particle amplitude for quantum-particle scattering. We verify that we have done this correctly by showing that our calculated photon-spinor amplitude reduces in the weak coupling limit to the usual lowest order, manifestly covariant (QED) result with the correct normalization. That we are able to successfully do this directly demonstrates that renormalizability need not be a fundamental requirement for all physically viable models.
Light-Front Holography and QCD Hadronization at the Amplitude Level
Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.
2009-01-09
Light-front holography allows hadronic amplitudes in the AdS/QCD fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. The AdS coordinate z is identified with an invariant light-front coordinate {zeta} which separates the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single-variable light-front Schroedinger equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. A new method for computing the hadronization of quark and gluon jets at the amplitude level using AdS/QCD light-front wavefunctions is outlined.
A Shock-Refracted Acoustic Wave Model for the Prediction of Screech Amplitude in Supersonic Jets
NASA Technical Reports Server (NTRS)
Kandula, Max
2007-01-01
A physical model is proposed for the estimation of the screech amplitude in underexpanded supersonic jets. The model is based on the hypothesis that the interaction of a plane acoustic wave with stationary shock waves provides amplification of the transmitted acoustic wave upon traversing the shock. Powell's discrete source model for screech incorporating a stationary array of acoustic monopoles is extended to accommodate variable source strength. The proposed model reveals that the acoustic sources are of increasing strength with downstream distance. It is shown that the screech amplitude increases with the fuiiy expanded jet Mach number. Comparisons of predicted screech amplitude with available test data show satisfactory agreement. The effect of variable source strength on directivity of the fundamental (first harmonic, lowest frequency mode) and the second harmonic (overtone) is found to be unimportant with regard to the principal lobe (main or major lobe) of considerable relative strength, and is appreciable only in the secondary or minor lobes (of relatively weaker strength
A new polarization amplitude bias reduction method
NASA Astrophysics Data System (ADS)
Vidal, Matias; Leahy, J. P.; Dickinson, C.
2016-09-01
Polarization amplitude estimation is affected by a positive noise bias, particularly important in regions with low signal-to-noise ratio (SNR). We present a new approach to correct for this bias in the case there is additional information about the polarization angle. We develop the `known-angle estimator' that works in the special case when there is an independent and high SNR (≳ 2σ) measurement of the polarization angle. It is derived for the general case where the uncertainties in the Q, U Stokes parameters are not symmetric. This estimator completely corrects for the polarization bias if the polarization angle is perfectly known. In the realistic case, where the angle template has uncertainties, a small residual bias remains, but that is shown to be much smaller that the one left by other classical estimators. We also test our method with more realistic data, using the noise properties of the three lower frequency maps of Wilkinson Microwave Anisotropy Probe. In this case, the known-angle estimator also produces better results than methods that do not include the angle information. This estimator is therefore useful in the case where the polarization angle is expected to be constant over different data sets with different SNR.
A generalized fidelity amplitude for open systems.
Gorin, T; Moreno, H J; Seligman, T H
2016-06-13
We consider a central system which is coupled via dephasing to an open system, i.e. an intermediate system which in turn is coupled to another environment. Considering the intermediate and far environment as one composite system, the coherences in the central system are given in the form of fidelity amplitudes for a certain perturbed echo dynamics in the composite environment. On the basis of the Born-Markov approximation, we derive a master equation for the reduction of that dynamics to the intermediate system alone. In distinction to an earlier paper (Moreno et al 2015 Phys. Rev. A 92, 030104. (doi:10.1103/PhysRevA.92.030104)), where we discussed the stabilizing effect of the far environment on the decoherence in the central system, we focus here on the possibility of using the measurable coherences in the central system for probing the open quantum dynamics in the intermediate system. We illustrate our results for the case of chaotic dynamics in the near environment, where we compare random matrix simulations with our analytical result.
Kaon distribution amplitude from QCD sum rules
Khodjamirian, A.; Mannel, Th.; Melcher, M.
2004-11-01
We present a new calculation of the first Gegenbauer moment a{sub 1}{sup K} of the kaon light cone distribution amplitude. This moment is determined by the difference between the average momenta of strange and nonstrange valence quarks in the kaon. To calculate a{sub 1}{sup K}, QCD sum rule for the diagonal correlation function of local and nonlocal axial-vector currents is used. Contributions of condensates up to dimension six are taken into account, including O({alpha}{sub s})-corrections to the quark-condensate term. We obtain a{sub 1}{sup K}=0.05{+-}0.02, differing by the sign and magnitude from the recent sum rule estimate from the nondiagonal correlation function of pseudoscalar and axial-vector currents. We argue that the nondiagonal sum rule is numerically not reliable. Furthermore, an independent indication for a positive a{sub 1}{sup K} is given, based on the matching of two different light cone sum rules for the K{yields}{pi} form factor. With the new interval of a{sub 1}{sup K}, we update our previous numerical predictions for SU(3)-violating effects in B{sub (s)}{yields}K form factors and charmless B decays.
New Fermionic Soft Theorems for Supergravity Amplitudes.
Chen, Wei-Ming; Huang, Yu-Tin; Wen, Congkao
2015-07-10
Soft limits of a massless S matrix are known to reflect the symmetries of the theory. In particular, for theories with Goldstone bosons, the double-soft limit of scalars reveals the coset structure of the vacuum manifold. In this Letter, we propose that such universal double-soft behavior is not only true for scalars, but also for spin-1/2 particles in four dimensions and fermions in three dimensions. We first consider the Akulov-Volkov theory and demonstrate that the double-soft limit of Goldstinos yields the supersymmetry algebra. More surprisingly, we also find that amplitudes in 4≤N≤8 supergravity theories in four dimensions as well as N=16 supergravity in three dimensions behave universally in the double-soft-fermion limit, analogous to the scalar ones. The validity of the new soft theorems at loop level is also studied. The results for supergravity are beyond what is implied by supersymmetry Ward identities and may impose nontrivial constraints on the possible counterterms for supergravity theories.
The pulsed amplitude unit for the SLC
Rolfe, J.; Browne, M.J.; Jobe, R.K.
1987-02-01
There is a recurring requirement in the SLC for the control of devices such as magnets, phase shifters, and attenuators on a beam-by-beam basis. The Pulsed Amplitude Unit (PAU) is a single width CAMAC module developed for this purpose. It provides digitally programmed analog output voltages on a beam-by-beam basis. Up to 32 preprogrammed values of output voltage are available from the single analog output of the module, and any of these values can be associated with any of the 256 possible SLC beam definitions. A 12-bit Analog-to-Digital Converter (ADC) digitizes an analog input signal at the appropriate beam time and stores it in a buffer memory. This feature is normally used to monitor the response of the device being controlled by the PAU at each beam time. Initial application of the PAU is a part of the system that controls the output of Klystrons in the SLC. The PAU combines several different functions in a single module. In order to accommodate these functions in a single width CAMAC module, field programmed logic is used extensively. Field Programmable Logic Arrays, Programmed Array Logic, and a Field Programmable Logic Sequencer are employed.
Geoacoustic inversion by mode amplitude perturbation
NASA Astrophysics Data System (ADS)
Poole, Travis L.; Lynch, James F.; Pierce, Allan D.; Frisk, George V.
2005-09-01
In a shallow-water waveguide the geoacoustic properties of the seafloor have a significant effect on the way sound propagates through the water. Because of this, measurements of the pressure field in the water can be used to estimate bottom properties. In this talk a perturbative method is presented which allows one to use measurements of the modal amplitudes to estimate a set of bottom parameters. A key component of the method is an expression for the derivative of the mode functions with respect to some bottom parameter. Following from the work of Thode and Kim [J. Acoust. Soc. Am. 116, 3370-2283 (2004)], the derivative is expressed as a weighted sum over all modes (both propagating and leaky). It is thought that this method can be used alongside eigenvalue perturbation [Rajan et al., J. Acoust. Soc. Am. 82, 998-1017 (1987)] to provide an inversion scheme more robust to measurement noise. To demonstrate its feasibility, the method is applied to synthetic and real data. [Work supported by the WHOI education office.
Sensitivity to changes in amplitude envelope
NASA Astrophysics Data System (ADS)
Gallun, Erick; Hafter, Ervin R.; Bonnel, Anne-Marie
2002-05-01
Detection of a brief increment in a tonal pedestal is less well predicted by energy-detection (e.g., Macmillan, 1973; Bonnel and Hafter, 1997) than by sensitivity to changes in the stimulus envelope. As this implies a mechanism similar to an envelope extractor (Viemeister, 1979), sinusoidal amplitude modulation was used to mask a single ramped increment (10, 45, or 70 ms) added to a 1000-ms pedestal with carrier frequency (cf)=477 Hz. As in informational masking (Neff, 1994) and ``modulation-detection interference'' (Yost and Sheft, 1989), interference occurred with masker cfs of 477 and 2013 Hz. While slight masking was found with modulation frequencies (mfs) from 16 to 96 Hz, masking grew inversely with still lower mfs, being greatest for mf=4 Hz. This division is reminiscent of that said to separate sensations of ``roughness'' and ``beats,'' respectively (Terhardt, 1974), with the latter also being related to durations associated with auditory groupings in music and speech. Importantly, this result held for all of the signal durations and onset-offset ramps tested, suggesting that an increment on a pedestal is treated as a single auditory object whose detection is most difficult in the presence of other objects (in this case, ``beats'').
Laryngeal-level amplitude modulation in vibrato.
Dromey, Christopher; Reese, Lorie; Hopkin, J Arden
2009-03-01
The goal of this investigation was to test a new methodology for measuring amplitude modulation (AM) at the level of the vocal folds during vibrato in trained singers, because previous research has suggested that AM arises in large part as an acoustic epiphenomenon through an interaction of the harmonics in the laryngeal source with the resonances of the vocal tract as the fundamental frequency oscillates. A within-subjects model was used to compare vocal activity across three pitch and three loudness conditions. Seventeen female singers with a range of training and experience were recorded with a microphone and an electroglottograph (EGG). Fluctuations in the ratio of closing to opening peaks in the first derivative of the EGG signal were used as an index of laryngeal-level AM. Evidence of laryngeal AM was found to a greater or lesser extent in all the singers, and its extent was not related to the degree of training. Across singers and pitch conditions, it was more prominent at lower intensities. The differentiated EGG signal lends itself to the measurement of AM at the level of the larynx, and the extent of the modulation appears more related to the level of vocal effort than to individual singer characteristics. PMID:17658720
Precise measurement of the matter power spectrum amplitude and the background radiation amplitude
NASA Astrophysics Data System (ADS)
Jena, Tridivesh
2004-09-01
We investigate the one dimensional flux power spectrum of the Lymanα forest and compare it with Lymanα forest simulations using state of the art hydrodynamical simulations. We investigate how properties of the forest, such as the mean flux
Amplitude growth due to random, correlated kicks
Michelotti, L.; Mills, F.
1989-03-01
Historically, stochastic processes, such as gas scattering or stochastic cooling, have been treated by the Fokker-Planck equation. In this approach, usually considered for one dimension only, the equation can be considered as a continuity equation for a variable which would be a constant of the motion in the absence of the stochastic process, for example, the action variable, I = epsilon/2..pi.. for betatron oscillations, where epsilon is the area of the Courant-Snyder ellipse, or energy in the case of unbunched beams, or the action variable for phase oscillations in case the beam is bunched. A flux, /Phi/, including diffusive terms can be defined, usually to second order. /Phi/ = M/sub 1/F(I) + M/sub 2/par. deltaF/par. deltaI + /hor ellipsis/. M/sub 1/ and M/sub 2/ are the expectation values of deltaI and (deltaI)/sup 2/ due to the individual stochastic kicks over some period of time, long enough that the variance of these quantities is sufficiently small. Then the Fokker-Planck equation is just par. deltaF/par. deltaI + par. delta/Phi//par. deltaI = 0. In many cases those where the beam distribution has already achieved its final shape, it is sufficient to find the rate of increase of by taking simple averages over the Fokker-Planck equation. At the time this work was begun, there was good knowledge of the second moment for general stochastic processes due to stochastic cooling theory, but the form of the first moment was known only for extremely wideband processes. The purposes of this note are to derive an expression relating the expected single particle amplitude growth to the noise autocorrelation function and to obtain, thereby, the form of M/sub 1/ for narrow band processes. 4 refs.
Virtual color-kinematics duality: 6-pt 1-loop MHV amplitudes
NASA Astrophysics Data System (ADS)
Yuan, Ellis Ye
2013-05-01
We study 1-loop MHV amplitudes in {N} = 4 super Yang-Mills theory and in {N} = 8 supergravity. For Yang-Mills we find that the simple form for the full amplitude presented by Del Duca, Dixon and Maltoni naturally leads to one that has physical residues on all compact contours. After expanding the simple form in terms of standard scalar integrals, we introduce redundancies under certain symmetry considerations to impose the color-kinematics duality of Bern, Carrasco and Johansson (BCJ). For five particles we directly find the results of Carrasco and Johansson as well as a new compact form for the supergravity amplitude. For six particles we find that all kinematic dual Jacobi identities are encapsulated in a single functional equation relating the expansion coefficients. By the BCJ double-copy construction we obtain a formula for the corresponding {N} = 8 super-gravity amplitude. Quite surprisingly, all physical information becomes independent of the expansion coefficients modulo the functional equation. In other words, there is no need to solve the functional equation at all. This is quite welcome as the functional equation we find, using our restricted set of redundancies, actually has no solutions. For this reason we call these results virtual color-kinematics duality. We end with speculations about the meaning of an interesting global vs. local feature of the functional equation and the situation at higher points.
Amplitude and Frequency Modulations of Spontaneous Otoacoustic Emissions
NASA Astrophysics Data System (ADS)
Bian, Lin
2009-02-01
It has been speculated that the spontaneous otoacoustic emissions (SOAEs) are associated with the mechanical feedback from the cochlear outer hair cells. In humans, the amplitudes and frequencies of SOAEs could be modulated by a low-frequency bias tone. The effects on the SOAE magnitudes were an amplitude modulation and a suppression. In the spectral domain, there was an upward shift of the SOAE frequencies with the bias tone level. In the time domain, variations of the SOAE amplitudes and frequencies followed the bias tone phase. Increasing the biasing pressure in either direction reduced the SOAE amplitudes and elevated the frequencies. The amplitude modulation pattern was consistent with the first derivative of a sigmoid-shaped nonlinear function representing hair cell transduction. Both amplitude and frequency modulations of SOAEs indicate that the nonlinear transducer characteristics and mechanical properties of the cochlear hair cells can influence the SOAE generation.
N >= 4 Supergravity Amplitudes from Gauge Theory at One Loop
Bern, Z.; Boucher-Veronneau, C.; Johansson, H.; /Saclay
2011-08-19
We expose simple and practical relations between the integrated four- and five-point one-loop amplitudes of N {ge} 4 supergravity and the corresponding (super-)Yang-Mills amplitudes. The link between the amplitudes is simply understood using the recently uncovered duality between color and kinematics that leads to a double-copy structure for gravity. These examples provide additional direct confirmations of the duality and double-copy properties at loop level for a sample of different theories.
Amplitudes and Ultraviolet Behavior of N = 8 Supergravity
Bern, Zvi; Carrasco, John Joseph; Dixon, Lance J.; Johansson, Henrik; Roiban, Radu; /Penn State U.
2011-05-20
In this contribution we describe computational tools that permit the evaluation of multi-loop scattering amplitudes in N = 8 supergravity, in terms of amplitudes in N = 4 super-Yang-Mills theory. We also discuss the remarkable ultraviolet behavior of N = 8 supergravity, which follows from these amplitudes, and is as good as that of N = 4 super-Yang-Mills theory through at least four loops.
Finite amplitude vibrations of cantilevers of rectangular cross sections in viscous fluids
NASA Astrophysics Data System (ADS)
Phan, Catherine N.; Aureli, Matteo; Porfiri, Maurizio
2013-07-01
In this paper, we study finite amplitude vibrations of a cantilever beam of rectangular cross section immersed in a viscous fluid under harmonic base excitation. Fluid-structure interactions are modeled through a complex hydrodynamic function that describes added mass and damping effects in response to moderately large oscillation amplitudes. The hydrodynamic function is identified from the analysis of the two-dimensional flow physics generated by a rigid rectangle undergoing harmonic oscillations in a quiescent fluid. Computational fluid dynamics is used to investigate the effects of three salient non-dimensional parameters on the flow physics and inform the formulation of a tractable expression for the hydrodynamic function. Theoretical results are validated against experimental findings on underwater vibration of compliant beams of varying cross sections.
Linking Spe Body-Wave Amplitudes and Site Characterization
NASA Astrophysics Data System (ADS)
Mellors, R. J.; Walter, W. R.; Ford, S. R.; Pitarka, A.; Wagoner, J. L.; Matzel, E.; Hauk, T. F.
2013-12-01
The purpose of the Source Physics Experiments is to investigate the generation and propagation of seismic waves from buried underground chemical explosions. Here we present results from an analysis of the tests up to date with emphasis on implications for discrimination and yield estimation using seismic data at very local (<20 km) distances. For example, previous work indicates that local (< 100 km) distance recordings of the SPE series do not appear to discriminate well using P/S ratios at some stations. We attempt to correlate variations in body wave amplitudes as a function of azimuth observed at very local ranges (< 20 km) with differences in 1) site effects; 2) path effects; 3) path topography; and 4) near-source (< 200 m) effects using both observations and modeling as a guide. Possible path effects are evaluated using a combination of existing geologic models combined with seismic velocity/attenuation models constructed using ambient noise tomography. Modeling is conducted with a finite-difference code capable of handling topographic effects. Near-source effects will rely on measurements of near-source geology, velocity models, and near-field observations (including spall) with focus on azimuthal variations.
Determining the sign of the Z-penguin amplitude
Haisch, Ulrich; Weiler, Andreas
2007-10-01
We point out that the precision measurements of the pseudo observables R{sub b}{sup 0}, A{sub b}, and A{sub FB}{sup 0,b} performed at the CERN LEP and the Stanford Linear Collider suggest that in models with minimal-flavor violation the sign of the Z-penguin amplitude is identical to the one present in the standard model. We determine the allowed range for the nonstandard contribution to the Inami-Lim function C and show, by analyzing possible scenarios with positive and negative interference of standard model and new physics contributions, that the derived bound holds in each given case. Finally, we derive lower and upper limits for the branching ratios of K{sup +}{yields}{pi}{sup +}{nu}{nu}, K{sub L}{yields}{pi}{sup 0}{nu}{nu}, K{sub L}{yields}{mu}{sup +}{mu}{sup -}, B{yields}X{sub d,s}{nu}{nu}, and B{sub d,s}{yields}{mu}{sup +}{mu}{sup -} within constrained minimal-flavor violation, making use of the wealth of available data collected at the Z pole.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2007-07-03
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2008-10-21
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2007-07-17
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2007-10-02
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Method of differential-phase/absolute-amplitude QAM
Dimsdle, Jeffrey William
2009-09-01
A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.
Resonance behavior of atomic and molecular photoionization amplitudes
Cherepkov, N. A.; Kuznetsov, V. V.; Semenov, S. K.
2007-07-15
The behavior of the partial photoionization amplitudes with a given orbital angular momentum l in the complex plane in resonances is studied. In the autoionization resonances the trajectory of the amplitude in the complex plane corresponds to a circle. With increasing photoelectron energy the amplitude moves about a circle in the counterclockwise direction. The new expressions for the partial amplitudes in the resonance are proposed which are similar to the Fano form but contain the 'partial' profile parameters which are connected with the Fano parameter q by a simple relation. In the giant dipole resonances the amplitudes in the complex plane also move about a circle in the counterclockwise direction provided the Coulomb phase is excluded from the amplitude. In the correlational resonances created by channel interactions with the giant dipole resonance the trajectories of the amplitudes acquire a loop about which the amplitudes move in the counterclockwise direction. Very similar behavior of partial photoionization amplitudes in the complex plane is demonstrated also for the dipole transitions from the K shells of the N{sub 2} molecule in the {sigma}* shape resonance.
[Potential reversal/amplitude analysis: problems of normal value determination].
Finsterer, J; Mamoli, B
1991-09-01
Turn/amplitude-analysis was applied to the right m. biceps brachii and the right m. rectus femoris of 30 healthy women aged 19 to 39 years. Interference patterns were recorded at 20, 40 and 60% of the individual maximum force of both muscles. We evaluated the turns/s, the amplitude/turn and the ratios amplitude/turns:turns/s and turns/s:amplitude/turn. Normal values of the turn/amplitude-parameter were calculated as means +/- 2 SD at defined levels of force (table 1 and fig. 2) and in form of clouds (fig. 3). Our clouds were clearly different from those of Stalberg. Since normal values of our and other studies were inconsistent we believe that every laboratory has to elaborate its own normal values. Turns/s, amplitude/turn and the ratio turns/s:amplitude/turn increased and the ratio amplitude/turns/s decreased with increasing force (fig. 6 and 7). Turn/amplitude-parameters were partly significantly higher or lower in the m. biceps brachii than in the m. rectus femoris (fig. 8.).
Phase and amplitude control system for Stanford Linear Accelerator
Yoo, S.J.
1983-09-26
The computer controlled phase and amplitude detection system measures the instantaneous phase and amplitude of a 1 micro-second 2856 MHz rf pulse at a 180 Hz rate. This will be used for phase feedback control, and also for phase and amplitude jitter measurement. The program, which was originally written by John Fox and Keith Jobe, has been modified to improve the function of the system. The software algorithms used in the measurement are described, as is the performance of the prototype phase and amplitude detector system.
A Regge Model for Nucleon-Nucleon Spin Dependent Amplitudes
William P. Ford, Jay Van Orden
2013-01-01
There are currently no models readily available that provide nucleon-nucleon spin dependent scattering amplitudes at high energies (s {ge} 6 GeV{sup 2}). This work aims to provide a model for calculating these high energy scattering amplitudes. The foundation of the model is Regge theory since it allows for a relativistic description and full spin dependence. We present our parameterization of the amplitudes, and show comparisons of our solutions to the data set we have collected. Overall the model works as intended, and provides an adequate description of the scattering amplitudes.
Recurrence relations of Kummer functions and Regge string scattering amplitudes
NASA Astrophysics Data System (ADS)
Lee, Jen-Chi; Mitsuka, Yoshihiro
2013-04-01
We discover an infinite number of recurrence relations among Regge string scattering amplitudes [11, 30] of different string states at arbitrary mass levels in the open bosonic string theory. As a result, all Regge string scattering amplitudes can be algebraically solved up to multiplicative factors. Instead of decoupling zero-norm states in the fixed angle regime, the calculation is based on recurrence relations and addition theorem of Kummer functions of the second kind. These recurrence relations among Regge string scattering amplitudes are dual to linear relations or symmetries among high-energy fixed angle string scattering amplitudes discovered previously.
Optimization of single-step tapering amplitude and energy detuning for high-gain FELs
NASA Astrophysics Data System (ADS)
Li, He-Ting; Jia, Qi-Ka
2015-01-01
We put forward a method to optimize the single-step tapering amplitude of undulator strength and initial energy tuning of electron beam to maximize the saturation power of high gain free-electron lasers (FELs), based on the physics of longitudinal electron beam phase space. Using the FEL simulation code GENESIS, we numerically demonstrate the accuracy of the estimations for parameters corresponding to the linac coherent light source and the Tesla test facility.
Drechsel, D.; Knoechlein, G.; Metz, A.; Scherer, S.
1997-01-01
We discuss the low-energy behavior of the spin-averaged amplitude of virtual Compton scattering off a nucleon. Based on gauge invariance, Lorentz invariance, and the discrete symmetries, it is shown that to first order in the frequency of the final real photon only two generalized polarizabilities appear. Different low-energy expansion schemes are discussed and put into perspective. {copyright} {ital 1997} {ital The American Physical Society}
Source-Space Cross-Frequency Amplitude-Amplitude Coupling in Tinnitus
Zobay, Oliver; Adjamian, Peyman
2015-01-01
The thalamocortical dysrhythmia (TCD) model has been influential in the development of theoretical explanations for the neurological mechanisms of tinnitus. It asserts that thalamocortical oscillations lock a region in the auditory cortex into an ectopic slow-wave theta rhythm (4–8 Hz). The cortical area surrounding this region is hypothesized to generate abnormal gamma (>30 Hz) oscillations (“edge effect”) giving rise to the tinnitus percept. Consequently, the model predicts enhanced cross-frequency coherence in a broad range between theta and gamma. In this magnetoencephalography study involving tinnitus and control cohorts, we investigated this prediction. Using beamforming, cross-frequency amplitude-amplitude coupling (AAC) was computed within the auditory cortices for frequencies (f1, f2) between 2 and 80 Hz. We find the AAC signal to decompose into two distinct components at low (f1, f2 < 30 Hz) and high (f1, f2 > 30 Hz) frequencies, respectively. Studying the correlation of AAC with several key covariates (age, hearing level (HL), tinnitus handicap and duration, and HL at tinnitus frequency), we observe a statistically significant association between age and low-frequency AAC. Contrary to the TCD predictions, however, we do not find any indication of statistical differences in AAC between tinnitus and controls and thus no evidence for the predicted enhancement of cross-frequency coupling in tinnitus. PMID:26665004
Amplitude equation approach to spatiotemporal dynamics of cardiac alternans
NASA Astrophysics Data System (ADS)
Echebarria, Blas; Karma, Alain
2007-11-01
Amplitude equations are derived that describe the spatiotemporal dynamics of cardiac alternans during periodic pacing of one- [B. Echebarria and A. Karma, Phys. Rev. Lett. 88, 208101 (2002)] and two-dimensional homogeneous tissue and one-dimensional anatomical reentry in a ring of homogeneous tissue. These equations provide a simple physical understanding of arrhythmogenic patterns of period-doubling oscillations of action potential duration with a spatially varying phase and amplitude, as well as explicit quantitative predictions that can be compared to ionic model simulations or experiments. The form of the equations is expected to be valid for a large class of ionic models but the coefficients are derived analytically only for a two-variable ionic model and calculated numerically for the original Noble model of Purkinje fiber action potential. In paced tissue, this theory explains the formation of “spatially discordant alternans” by a linear instability mechanism that produces a periodic pattern of out-of-phase domains of alternans. The wavelength of this pattern, equal to twice the spacing between nodes separating out-of-phase domains, is shown to depend on three fundamental length scales that are determined by the strength of cell-to-cell coupling and conduction velocity (CV) restitution. Moreover, the patterns of alternans can be either stationary, with fixed nodes, or traveling, with moving nodes and hence quasiperiodic oscillations of action potential duration, depending on the relative strength of the destabilizing effect of CV restitution and the stabilizing effect of diffusive coupling. For the ring geometry, we recover the results of Courtemanche, Glass, and Keener [Phys. Rev. Lett. 70, 2182 (1993)] with two important modifications due to cell-to-cell diffusive coupling. First, this coupling breaks the degeneracy of an infinite-dimensional Hopf bifurcation such that the most unstable mode of alternans corresponds to the longest quantized wavelength
Amplitude equation approach to spatiotemporal dynamics of cardiac alternans.
Echebarria, Blas; Karma, Alain
2007-11-01
Amplitude equations are derived that describe the spatiotemporal dynamics of cardiac alternans during periodic pacing of one- [B. Echebarria and A. Karma, Phys. Rev. Lett. 88, 208101 (2002)] and two-dimensional homogeneous tissue and one-dimensional anatomical reentry in a ring of homogeneous tissue. These equations provide a simple physical understanding of arrhythmogenic patterns of period-doubling oscillations of action potential duration with a spatially varying phase and amplitude, as well as explicit quantitative predictions that can be compared to ionic model simulations or experiments. The form of the equations is expected to be valid for a large class of ionic models but the coefficients are derived analytically only for a two-variable ionic model and calculated numerically for the original Noble model of Purkinje fiber action potential. In paced tissue, this theory explains the formation of "spatially discordant alternans" by a linear instability mechanism that produces a periodic pattern of out-of-phase domains of alternans. The wavelength of this pattern, equal to twice the spacing between nodes separating out-of-phase domains, is shown to depend on three fundamental length scales that are determined by the strength of cell-to-cell coupling and conduction velocity (CV) restitution. Moreover, the patterns of alternans can be either stationary, with fixed nodes, or traveling, with moving nodes and hence quasiperiodic oscillations of action potential duration, depending on the relative strength of the destabilizing effect of CV restitution and the stabilizing effect of diffusive coupling. For the ring geometry, we recover the results of Courtemanche, Glass, and Keener [Phys. Rev. Lett. 70, 2182 (1993)] with two important modifications due to cell-to-cell diffusive coupling. First, this coupling breaks the degeneracy of an infinite-dimensional Hopf bifurcation such that the most unstable mode of alternans corresponds to the longest quantized wavelength of
Abnormal Selective Attention Normalizes P3 Amplitudes in PDD
ERIC Educational Resources Information Center
Hoeksma, Marco R.; Kemner, Chantal; Kenemans, J. Leon; van Engeland, Herman
2006-01-01
This paper studied whether abnormal P3 amplitudes in PDD are a corollary of abnormalities in ERP components related to selective attention in visual and auditory tasks. Furthermore, this study sought to clarify possible age differences in such abnormalities. Children with PDD showed smaller P3 amplitudes than controls, but no abnormalities in…
Proof of a new colour decomposition for QCD amplitudes
NASA Astrophysics Data System (ADS)
Melia, Tom
2015-12-01
Recently, Johansson and Ochirov conjectured the form of a new colour decom-position for QCD tree-level amplitudes. This note provides a proof of that conjecture. The proof is based on `Mario World' Feynman diagrams, which exhibit the hierarchical Dyck structure previously found to be very useful when dealing with multi-quark amplitudes.
P wave {pi}{pi} amplitude from dispersion relations
Szczepaniak, Adam P.; Guo, Peng; Battaglieri, M.; De Vita, R.
2010-08-01
We solve the dispersion relation for the P-wave {pi}{pi} amplitude. We discuss the role of the left-hand cut vs the Castillejo-Dalitz-Dyson pole contribution and compare the solution with a generic quark model description. We review the generic properties of analytical partial wave scattering and production amplitudes and discuss their applicability and fits of experimental data.
On the Pion Distribution Amplitude: Derivation, Properties, Predictions
NASA Astrophysics Data System (ADS)
Stefanis, N. G.; Mikhailov, S. V.; Pimikov, A. V.
2015-09-01
We provide an in-depth analysis of the π distribution amplitude in terms of two different Gegenbauer representations. Detailed predictions for the transition form factor are presented, obtained with light-cone sum rules. Various π distribution amplitudes are tested and the crucial role of their endpoint behavior in the form-factor analysis is discussed. Comparison with the data is given.
Amplitudes in N = 4 Super-Yang-Mills Theory
NASA Astrophysics Data System (ADS)
Spradlin, Marcus
These lecture notes provide a lightning introduction to some aspects of scattering amplitudes in maximally supersymmetric theory, aimed at the audience of students attending the 2014 TASI summer school "Journeys Through the Precision Frontier: Amplitudes for Colliders". Emphasis is placed on explaining modern terminology so that students needing to delve further may more easily access the available literature.
Broadband metasurfaces with simultaneous control of phase and amplitude.
Liu, Lixiang; Zhang, Xueqian; Kenney, Mitchell; Su, Xiaoqiang; Xu, Ningning; Ouyang, Chunmei; Shi, Yunlong; Han, Jiaguang; Zhang, Weili; Zhang, Shuang
2014-08-01
By combining the freedom of both the structural design and the orientation of split ring resonator antennas, we demonstrate terahertz metasurfaces that are capable of controlling both the phase and amplitude profiles over a very broad bandwidth. As an example, we show that the phase-amplitude metasurfaces can be engineered to control the diffraction orders arbitrarily. PMID:24863731
All one-loop NMHV gluon amplitudes in = 1 SYM
NASA Astrophysics Data System (ADS)
Ochirov, Alexander
2013-12-01
We compute the next-to-maximally-helicity-violating one-loop n-gluon amplitudes in = 1 super-Yang-Mills theory. These amplitudes contain three negative-helicity gluons and an arbitrary number of positive-helicity gluons, and constitute the first infinite series of amplitudes beyond the simplest, MHV, amplitudes. We assemble ingredients from the = 4 NMHV tree super-amplitude into previously unwritten double cuts and use the spinor integration technique to calculate all bubble coefficients. We also derive the missing box coefficients from quadruple cuts. Together with the known formula for three-mass triangles, this completes the set of NMHV one-loop master integral coefficients in = 1 SYM. To facilitate further use of our results, we provide their Mathematica implementation.
Renormalization of massless Feynman amplitudes in configuration space
NASA Astrophysics Data System (ADS)
Nikolov, Nikolay M.; Stora, Raymond; Todorov, Ivan
2014-05-01
A systematic study of recursive renormalization of Feynman amplitudes is carried out both in Euclidean and in Minkowski configuration spaces. For a massless quantum field theory (QFT), we use the technique of extending associate homogeneous distributions to complete the renormalization recursion. A homogeneous (Poincaré covariant) amplitude is said to be convergent if it admits a (unique covariant) extension as a homogeneous distribution. For any amplitude without subdivergences — i.e. for a Feynman distribution that is homogeneous off the full (small) diagonal — we define a renormalization invariant residue. Its vanishing is a necessary and sufficient condition for the convergence of such an amplitude. It extends to arbitrary — not necessarily primitively divergent — Feynman amplitudes. This notion of convergence is finer than the usual power counting criterion and includes cancellation of divergences.
High Frequency Amplitude Detector for GMI Magnetic Sensors
Asfour, Aktham; Zidi, Manel; Yonnet, Jean-Paul
2014-01-01
A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI) sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted. PMID:25536003
Discontinuities of BFKL amplitudes and the BDS ansatz
NASA Astrophysics Data System (ADS)
Fadin, V. S.; Fiore, R.
2015-12-01
We perform an examination of discontinuities of multiple production amplitudes, which are required for further development of the BFKL approach. It turns out that the discontinuities of 2 → 2 + n amplitudes obtained in the BFKL approach contradict to the BDS ansatz for amplitudes with maximal helicity violation in N = 4 supersymmetric Yang-Mills theory with large number of colors starting with n = 2. Explicit expressions for the discontinuities of the 2 → 3 and 2 → 4 amplitudes in the invariant mass of pairs of produced gluons are obtained in the planar N = 4 SYM in the next-to-leading logarithmic approximation. These expressions can be used for checking the conjectured duality between the light-like Wilson loops and the MHV amplitudes.
Amplitude death in networks of delay-coupled delay oscillators.
Höfener, Johannes M; Sethia, Gautam C; Gross, Thilo
2013-09-28
Amplitude death is a dynamical phenomenon in which a network of oscillators settles to a stable state as a result of coupling. Here, we study amplitude death in a generalized model of delay-coupled delay oscillators. We derive analytical results for degree homogeneous networks which show that amplitude death is governed by certain eigenvalues of the network's adjacency matrix. In particular, these results demonstrate that in delay-coupled delay oscillators amplitude death can occur for arbitrarily large coupling strength k. In this limit, we find a region of amplitude death which already occurs at small coupling delays that scale with 1/k. We show numerically that these results remain valid in random networks with heterogeneous degree distribution.
Reinforcing saccadic amplitude variability in a visual search task.
Paeye, Céline; Madelain, Laurent
2014-11-20
Human observers often adopt rigid scanning strategies in visual search tasks, even though this may lead to suboptimal performance. Here we ask whether specific levels of saccadic amplitude variability may be induced in a visual search task using reinforcement learning. We designed a new gaze-contingent visual foraging task in which finding a target among distractors was made contingent upon specific saccadic amplitudes. When saccades of rare amplitudes led to displaying the target, the U values (measuring uncertainty) increased by 54.89% on average. They decreased by 41.21% when reinforcing frequent amplitudes. In a noncontingent control group no consistent change in variability occurred. A second experiment revealed that this learning transferred to conventional visual search trials. These results provide experimental support for the importance of reinforcement learning for saccadic amplitude variability in visual search.
Kaminski, R.; Pelaez, J. R.; Yndurain, F. J.
2008-03-01
We complete and improve the fits to experimental {pi}{pi} scattering amplitudes, both at low and high energies, that we performed in the previous papers of this series. We then verify that the corresponding amplitudes satisfy analyticity requirements, in the form of partial wave analyticity at low energies, forward dispersion relations (FDR) at all energies, and Roy equations belowKK threshold; the first by construction, the last two, inside experimental errors. Then we repeat the fits including as constraints FDR and Roy equations. The ensuing central values of the various scattering amplitudes verify very accurately FDR and, especially, Roy equations, and change very little from what we found by just fitting data, with the exception of the D2 wave phase shift, for which one parameter moves by 1.5{sigma}. These improved parametrizations therefore provide a reliable representation of pion-pion amplitudes with which one can test various physical relations. We also present a list of low energy parameters and other observables. In particular, we find a{sub 0}{sup (0)}=0.223{+-}0.009M{sub {pi}}{sup -1}, a{sub 0}{sup (2)}=-0.0444{+-}0.0045M{sub {pi}}{sup -1}, and {delta}{sub 0}{sup (0)}(m{sub K}{sup 2})-{delta}{sub 0}{sup (2)}(m{sub K}{sup 2})=50.9{+-}1.2{sup o}.
Nonlinear reflection of high-amplitude laser pulses from relativistic electron mirrors
NASA Astrophysics Data System (ADS)
Kulagin, V. V.; Kornienko, V. N.; Cherepenin, V. A.
2016-04-01
A coherent X-ray pulse of attosecond duration can be formed in the reflection of a counterpropagating laser pulse from a relativistic electron mirror. The reflection of a high-amplitude laser pulse from the relativistic electron mirror located in the field of an accelerating laser pulse is investigated by means of two-dimensional (2D) numerical simulation. It is shown that provided the amplitude of the counterpropagating laser pulse is several times greater than the amplitude of the accelerating laser pulse, the reflection process is highly nonlinear, which causes a significant change in the X-ray pulse shape and its shortening up to generation of quasi-unipolar pulses and single-cycle pulses. A physical mechanism responsible for this nonlinearity of the reflection process is explained, and the parameters of the reflected X-ray pulses are determined. It is shown that the duration of these pulses may constitute 50 - 60 as, while their amplitude may be sub-relativistic.
Lindesay, James V
2002-03-12
Starting from a unitary, Lorentz invariant two-particle scattering amplitude, we show how to use an identification and replacement process to construct a unique, unitary particle-antiparticle amplitude. This process differs from conventional on-shell Mandelstam s,t,u crossing in that the input and constructed amplitudes can be off-diagonal and off-energy shell. Further, amplitudes are constructed using the invariant parameters which are appropriate to use as driving terms in the multi-particle, multichannel nonperturbative, cluster decomposable, relativistic scattering equations of the Faddeev-type integral equations recently presented by Alfred, Kwizera, Lindesay and Noyes. It is therefore anticipated that when so employed, the resulting multi-channel solutions will also be unitary. The process preserves the usual particle-antiparticle symmetries. To illustrate this process, we construct a J=0 scattering length model chosen for simplicity. We also exhibit a class of physical models which contain a finite quantum mass parameter and are Lorentz invariant. These are constructed to reduce in the appropriate limits, and with the proper choice of value and sign of the interaction parameter, to the asymptotic solution of the nonrelativistic Coulomb problem, including the forward scattering singularity , the essential singularity in the phase, and the Bohr bound-state spectrum.
Frequency adaptation for enhanced radiation force amplitude in dynamic elastography.
Ouared, Abderrahmane; Montagnon, Emmanuel; Kazemirad, Siavash; Gaboury, Louis; Robidoux, André; Cloutier, Guy
2015-08-01
In remote dynamic elastography, the amplitude of the generated displacement field is directly related to the amplitude of the radiation force. Therefore, displacement improvement for better tissue characterization requires the optimization of the radiation force amplitude by increasing the push duration and/or the excitation amplitude applied on the transducer. The main problem of these approaches is that the Food and Drug Administration (FDA) thresholds for medical applications and transducer limitations may be easily exceeded. In the present study, the effect of the frequency used for the generation of the radiation force on the amplitude of the displacement field was investigated. We found that amplitudes of displacements generated by adapted radiation force sequences were greater than those generated by standard nonadapted ones (i.e., single push acoustic radiation force impulse and supersonic shear imaging). Gains in magnitude were between 20 to 158% for in vitro measurements on agar-gelatin phantoms, and 170 to 336% for ex vivo measurements on a human breast sample, depending on focus depths and attenuations of tested samples. The signal-to-noise ratio was also improved more than 4-fold with adapted sequences. We conclude that frequency adaptation is a complementary technique that is efficient for the optimization of displacement amplitudes. This technique can be used safely to optimize the deposited local acoustic energy without increasing the risk of damaging tissues and transducer elements.
Bootstrapping Multi-Parton Loop Amplitudes in QCD
Bern, Zvi; Dixon, Lance J.; Kosower, David A.; /Saclay, SPhT
2005-07-06
The authors present a new method for computing complete one-loop amplitudes, including their rational parts, in non-supersymmetric gauge theory. This method merges the unitarity method with on-shell recursion relations. It systematizes a unitarity-factorization bootstrap approach previously applied by the authors to the one-loop amplitudes required for next-to-leading order QCD corrections to the processes e{sup +}e{sup -} {yields} Z, {gamma}* {yields} 4 jets and pp {yields} W + 2 jets. We illustrate the method by reproducing the one-loop color-ordered five-gluon helicity amplitudes in QCD that interfere with the tree amplitude, namely A{sub 5;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}) and A{sub 5;1}(1{sup -}, 2{sup +}, 3{sup -}, 4{sup +}, 5{sup +}). Then we describe the construction of the six- and seven-gluon amplitudes with two adjacent negative-helicity gluons, A{sub 6;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}, 6{sup +}) and A{sub 7;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}, 6{sup +}, 7{sup +}), which uses the previously-computed logarithmic parts of the amplitudes as input. They present a compact expression for the six-gluon amplitude. No loop integrals are required to obtain the rational parts.
Broadband metasurface holograms: toward complete phase and amplitude engineering
NASA Astrophysics Data System (ADS)
Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili
2016-09-01
As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography.
Broadband metasurface holograms: toward complete phase and amplitude engineering.
Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili
2016-01-01
As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography.
Broadband metasurface holograms: toward complete phase and amplitude engineering.
Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili
2016-01-01
As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography. PMID:27615519
Broadband metasurface holograms: toward complete phase and amplitude engineering
Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili
2016-01-01
As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography. PMID:27615519
Amplitude path corrections for regional phases in China
Phillips, W.S.; Velasco, A.A.; Taylor, S.R.; Randall, G.E.
1998-12-31
The authors investigate the effectiveness of amplitude path corrections for regional phases on seismic event discrimination and magnitude estimation. Waveform data from digital stations in China for regional, shallow (< 50 km) events were obtained from the IRIS Data Management Center (DMC) for years 1986 to 1996 using the USGS Preliminary Determination of Epicenters (PDE) and the Chinese State Seismological Bureau (SSB) catalogs. For each event, the amplitudes for each regional phase (P{sub n}, P{sub g}, S{sub n}, L{sub g}) were measured, as well as the P{sub g} and L{sub g} coda. Measured amplitudes were corrected for source scaling using estimates of m{sub b} and for distance using a power law that accounts for attenuation and spreading. The amplitude residuals were interpolated and mapped as 2-D amplitude correction surfaces. The authors employ several methods to create the amplitude correction surfaces: a waveguide method, and two interpolation methods (Baysian kriging and a circular moving window mean smoother). They explore the sensitivities of the surfaces to the method and to regional propagation, and apply these surfaces to correct amplitude data to reduce scatter in discrimination ratios and magnitude estimates.
Large amplitude ion-acoustic solitons in dusty plasmas
NASA Astrophysics Data System (ADS)
Tiwari, R. S.; Jain, S. L.; Mishra, M. K.
2011-08-01
Characteristics of ion-acoustic soliton in dusty plasma, including the dynamics of heavily charged massive dust grains, are investigated following the Sagdeev Potential formalism. Retaining fourth order nonlinearities of electric potential in the expansion of the Sagdeev Potential in the energy equation for a pseudo particle and integrating the resulting energy equation, large amplitude soliton solution is determined. Variation of amplitude (A), half width (W) at half maxima and the product P = AW2 of the Korteweg-deVries (KdV), dressed and large amplitude soliton as a function of wide range of dust concentration are numerically studied for recently observed parameters of dusty plasmas. We have also presented the region of existence of large amplitude ion-acoustic soliton in the dusty plasma by analyzing the structure of the pseudo potential. It is found that in the presence of positively charged dust grains, system supports only compressive solitons, on the other hand, in the presence of negatively charged dust grains, the system supports compressive solitons up to certain critical concentration of dust grains and above this critical concentration, the system can support rarefactive solitons also. The effects of dust concentration, charge, and mass of the dust grains, on the characteristics of KdV, dressed and large amplitude the soliton, i.e., amplitude (A), half width at half maxima (W), and product of amplitude (A) and half width at half maxima (P = AW2), are discussed in detail
Large amplitude ion-acoustic solitons in dusty plasmas
Tiwari, R. S.; Jain, S. L.; Mishra, M. K.
2011-08-15
Characteristics of ion-acoustic soliton in dusty plasma, including the dynamics of heavily charged massive dust grains, are investigated following the Sagdeev Potential formalism. Retaining fourth order nonlinearities of electric potential in the expansion of the Sagdeev Potential in the energy equation for a pseudo particle and integrating the resulting energy equation, large amplitude soliton solution is determined. Variation of amplitude (A), half width (W) at half maxima and the product P = AW{sup 2} of the Korteweg-deVries (KdV), dressed and large amplitude soliton as a function of wide range of dust concentration are numerically studied for recently observed parameters of dusty plasmas. We have also presented the region of existence of large amplitude ion-acoustic soliton in the dusty plasma by analyzing the structure of the pseudo potential. It is found that in the presence of positively charged dust grains, system supports only compressive solitons, on the other hand, in the presence of negatively charged dust grains, the system supports compressive solitons up to certain critical concentration of dust grains and above this critical concentration, the system can support rarefactive solitons also. The effects of dust concentration, charge, and mass of the dust grains, on the characteristics of KdV, dressed and large amplitude the soliton, i.e., amplitude (A), half width at half maxima (W), and product of amplitude (A) and half width at half maxima (P = AW{sup 2}), are discussed in detail.
Discriminating Simulated Vocal Tremor Source Using Amplitude Modulation Spectra
Carbonell, Kathy M.; Lester, Rosemary A.; Story, Brad H.; Lotto, Andrew J.
2014-01-01
Objectives/Hypothesis Sources of vocal tremor are difficult to categorize perceptually and acoustically. This paper describes a preliminary attempt to discriminate vocal tremor sources through the use of spectral measures of the amplitude envelope. The hypothesis is that different vocal tremor sources are associated with distinct patterns of acoustic amplitude modulations. Study Design Statistical categorization methods (discriminant function analysis) were used to discriminate signals from simulated vocal tremor with different sources using only acoustic measures derived from the amplitude envelopes. Methods Simulations of vocal tremor were created by modulating parameters of a vocal fold model corresponding to oscillations of respiratory driving pressure (respiratory tremor), degree of vocal fold adduction (adductory tremor) and fundamental frequency of vocal fold vibration (F0 tremor). The acoustic measures were based on spectral analyses of the amplitude envelope computed across the entire signal and within select frequency bands. Results The signals could be categorized (with accuracy well above chance) in terms of the simulated tremor source using only measures of the amplitude envelope spectrum even when multiple sources of tremor were included. Conclusions These results supply initial support for an amplitude-envelope based approach to identify the source of vocal tremor and provide further evidence for the rich information about talker characteristics present in the temporal structure of the amplitude envelope. PMID:25532813
Glauber exchange amplitudes. [electron scattering from H atoms
NASA Technical Reports Server (NTRS)
Madan, R. N.
1975-01-01
The extrapolation method of Ochkur, valid for intermediate energies (about 50 eV), is applied to the exchange form of the Glauber amplitudes. In the case of elastic scattering of electrons from hydrogen atoms at 54.4 Ev the 'post' and 'prior' forms of the exchange amplitude are equivalent, whereas for the case of inelastic scattering there is a minute discrepancy between the two forms of the amplitude. The results are compared with the close-coupling calculation. The investigation is expected to be useful for optically forbidden exchange-allowed transitions due to electron impact at intermediate energies.
NASA Astrophysics Data System (ADS)
Leonardi, Sabrina; Gresta, Stefano; Mulargia, Francesco
2000-06-01
A strong correlation between the amplitude of volcanic tremor and the flux of SO2 has been found at Mount Etna volcano, Sicily, corresponding to enhanced volcanic activity in the period 1987-1995. We therefore suggest that tremors and SO2 emissions have a common physical origin linked to the magma dynamics of the volcano.
Movement amplitude and tempo change in piano performance
NASA Astrophysics Data System (ADS)
Palmer, Caroline
2001-05-01
Music performance places stringent temporal and cognitive demands on individuals that should yield large speed/accuracy tradeoffs. Skilled piano performance, however, shows consistently high accuracy across a wide variety of rates. Movement amplitude may affect the speed/accuracy tradeoff, so that high accuracy can be obtained even at very fast tempi. The contribution of movement amplitude changes in rate (tempo) is investigated with motion capture. Cameras recorded pianists with passive markers on hands and fingers, who performed on an electronic (MIDI) keyboard. Pianists performed short melodies at faster and faster tempi until they made errors (altering the speed/accuracy function). Variability of finger movements in the three motion planes indicated most change in the plane perpendicular to the keyboard across tempi. Surprisingly, peak amplitudes of motion before striking the keys increased as tempo increased. Increased movement amplitudes at faster rates may reduce or compensate for speed/accuracy tradeoffs. [Work supported by Canada Research Chairs program, HIMH R01 45764.
Effect of vibration amplitude on vapor cavitation in journal bearings
NASA Technical Reports Server (NTRS)
Brewe, D. E.; Jacobson, B. O.
1986-01-01
Computational movies were used to analyze the formation and collapse of vapor cavitation bubbles in a submerged journal bearing. The effect of vibration amplitude on vapor cavitation was studied for a journal undergoing circular whirl. The boundary conditions were implemented using Elrod's algorithm, which conserves mass flow through the cavitation bubble as well as through the oil-film region of the bearing. The vibration amplitudes for the different cases studied resulted in maximum eccentricity ratios ranging from 0.4 to 0.9. The minimum eccentricity ratio reached in each case was 0.1. For the least vibration amplitude studied in which the eccentricity ratio varied between 0.1 and 0.4, no vapor cavitation occurred. The largest vibration amplitude (i.e., eccentricity ratios of 0.1 to 0.9) resulted in vapor cavitation present 76 percent of one complete orbit.
Amplitude sorting of oscillatory burst signals by sampling
Davis, Thomas J.
1977-01-01
A method and apparatus for amplitude sorting of oscillatory burst signals is described in which the burst signal is detected to produce a burst envelope signal and an intermediate or midportion of such envelope signal is sampled to provide a sample pulse output. The height of the sample pulse is proportional to the amplitude of the envelope signal and to the maximum burst signal amplitude. The sample pulses are fed to a pulse height analyzer for sorting. The present invention is used in an acoustic emission testing system to convert the amplitude of the acoustic emission burst signals into sample pulse heights which are measured by a pulse height analyzer for sorting the pulses in groups according to their height in order to identify the material anomalies in the test material which emit the acoustic signals.
N >= 4 Supergravity Amplitudes from Gauge Theory at Two Loops
Boucher-Veronneau, C.; Dixon, L.J.; /SLAC
2012-02-15
We present the full two-loop four-graviton amplitudes in N = 4, 5, 6 supergravity. These results were obtained using the double-copy structure of gravity, which follows from the recently conjectured color-kinematics duality in gauge theory. The two-loop four-gluon scattering amplitudes in N = 0, 1, 2 supersymmetric gauge theory are a second essential ingredient. The gravity amplitudes have the expected infrared behavior: the two-loop divergences are given in terms of the squares of the corresponding one-loop amplitudes. The finite remainders are presented in a compact form. The finite remainder for N = 8 supergravity is also presented, in a form that utilizes a pure function with a very simple symbol.
Normalized amplitude quotient for parametrization of the glottal flow.
Alku, Paavo; Bäckström, Tom; Vilkman, Erkki
2002-08-01
Normalized amplitude quotient (NAQ) is presented as a method to parametrize the glottal closing phase using two amplitude-domain measurements from waveforms estimated by inverse filtering. In this technique, the ratio between the amplitude of the ac flow and the negative peak amplitude of the flow derivative is first computed using the concept of equivalent rectangular pulse, a hypothetical signal located at the instant of the main excitation of the vocal tract. This ratio is then normalized with respect to the length of the fundamental period. Comparison between NAQ and its counterpart among the conventional time-domain parameters, the closing quotient, shows that the proposed parameter is more robust against distortion such as measurement noise that make the extraction of conventional time-based parameters of the glottal flow problematic. Experiments with breathy, normal, and pressed vowels indicate that NAQ is also able to separate the type of phonation effectively. PMID:12186049
Amplitude chimeras and chimera death in dynamical networks
NASA Astrophysics Data System (ADS)
Zakharova, Anna; Kapeller, Marie; Schöll, Eckehard
2016-06-01
We find chimera states with respect to amplitude dynamics in a network of Stuart- Landau oscillators. These partially coherent and partially incoherent spatio-temporal patterns appear due to the interplay of nonlocal network topology and symmetry-breaking coupling. As the coupling range is increased, the oscillations are quenched, amplitude chimeras disappear and the network enters a symmetry-breaking stationary state. This particular regime is a novel pattern which we call chimera death. It is characterized by the coexistence of spatially coherent and incoherent inhomogeneous steady states and therefore combines the features of chimera state and oscillation death. Additionally, we show two different transition scenarios from amplitude chimera to chimera death. Moreover, for amplitude chimeras we uncover the mechanism of transition towards in-phase synchronized regime and discuss the role of initial conditions.
Amplitude and phase chimeras in an ensemble of chaotic oscillators
NASA Astrophysics Data System (ADS)
Bogomolov, S. A.; Strelkova, G. I.; Schöll, E.; Anishchenko, V. S.
2016-07-01
The transition from coherence to incoherence in an ensemble of nonlocally coupled logistic maps is considered. Chimera states of two types (amplitude and phase) are found. The mechanism and conditions of their appearance are determined.
Amplitude Equation for Instabilities Driven at Deformable Surfaces - Rosensweig Instability
NASA Astrophysics Data System (ADS)
Pleiner, Harald; Bohlius, Stefan; Brand, Helmut R.
2008-11-01
The derivation of amplitude equations from basic hydro-, magneto-, or electrodynamic equations requires the knowledge of the set of adjoint linear eigenvectors. This poses a particular problem for the case of a free and deformable surface, where the adjoint boundary conditions are generally non-trivial. In addition, when the driving force acts on the system via the deformable surface, not only Fredholm's alternative in the bulk, but also the proper boundary conditions are required to get amplitude equations. This is explained and demonstrated for the normal field (or Rosensweig) instability in ferrofluids as well as in ferrogels. An important aspect of the problem is its intrinsic dynamic nature, although at the end the instability is stationary. The resulting amplitude equation contains cubic and quadratic nonlinearities as well as first and (in the gel case) second order time derivatives. Spatial variations of the amplitudes cannot be obtained by using simply Newell's method in the bulk.
Optical vector network analyzer based on amplitude-phase modulation
NASA Astrophysics Data System (ADS)
Morozov, Oleg G.; Morozov, Gennady A.; Nureev, Ilnur I.; Kasimova, Dilyara I.; Zastela, Mikhail Y.; Gavrilov, Pavel V.; Makarov, Igor A.; Purtov, Vadim A.
2016-03-01
The article describes the principles of optical vector network analyzer (OVNA) design for fiber Bragg gratings (FBG) characterization based on amplitude-phase modulation of optical carrier that allow us to improve the measurement accuracy of amplitude and phase parameters of the elements under test. Unlike existing OVNA based on a single-sideband and unbalanced double sideband amplitude modulation, the ratio of the two side components of the probing radiation is used for analysis of amplitude and phase parameters of the tested elements, and the radiation of the optical carrier is suppressed, or the latter is used as a local oscillator. The suggested OVNA is designed for the narrow band-stop elements (π-phaseshift FBG) and wide band-pass elements (linear chirped FBG) research.
Scattering amplitudes for multi-indexed extensions of solvable potentials
Ho, C.-L.; Lee, J.-C.; Sasaki, R.
2014-04-15
New solvable one-dimensional quantum mechanical scattering problems are presented. They are obtained from known solvable potentials by multiple Darboux transformations in terms of virtual and pseudo virtual wavefunctions. The same method applied to confining potentials, e.g. Pöschl–Teller and the radial oscillator potentials, has generated the multi-indexed Jacobi and Laguerre polynomials. Simple multi-indexed formulas are derived for the transmission and reflection amplitudes of several solvable potentials. -- Highlights: •Scattering amplitudes calculated for infinitely many new solvable potentials. •New scattering potentials obtained by deforming six known solvable potentials. •Multiple Darboux transformations in terms of (pseudo) virtual states employed. •Scattering amplitudes checked to obey the shape invariance relation. •Errors in scattering amplitudes of some undeformed potentials in the literature corrected.
Laser beam complex amplitude measurement by phase diversity.
Védrenne, Nicolas; Mugnier, Laurent M; Michau, Vincent; Velluet, Marie-Thérèse; Bierent, Rudolph
2014-02-24
The control of the optical quality of a laser beam requires a complex amplitude measurement able to deal with strong modulus variations and potentially highly perturbed wavefronts. The method proposed here consists in an extension of phase diversity to complex amplitude measurements that is effective for highly perturbed beams. Named camelot for Complex Amplitude MEasurement by a Likelihood Optimization Tool, it relies on the acquisition and processing of few images of the beam section taken along the optical path. The complex amplitude of the beam is retrieved from the images by the minimization of a Maximum a Posteriori error metric between the images and a model of the beam propagation. The analytical formalism of the method and its experimental validation are presented. The modulus of the beam is compared to a measurement of the beam profile, the phase of the beam is compared to a conventional phase diversity estimate. The precision of the experimental measurements is investigated by numerical simulations.
Beyond Planck-Einstein quanta: Amplitude-driven quantum excitation
NASA Astrophysics Data System (ADS)
Shen, Wen; Devereaux, T. P.; Freericks, J. K.
2014-11-01
Linear-response quantum excitation is proportional to the amplitude of the field, with the energy of the excitation given by the driving frequency. As the amplitude is increased, there is a crossover, where the excitation energy is governed by the amplitude of the driving field, not its frequency. As the amplitude is increased even further, then complex quantum oscillations develop. We illustrate this phenomena with the exact solution of the simplest model of a charge-density-wave insulator driven by a spatially uniform time-dependent electric field. The driving by the field can be mapped onto a series of Landau-Zener problems, but with a complex, nonmonochromatic drive that varies for each momentum point in the reduced Brillouin zone.
Amplitude death of identical oscillators in networks with direct coupling.
Illing, Lucas
2016-08-01
It is known that amplitude death can occur in networks of coupled identical oscillators if they interact via diffusive time-delayed coupling links. Here we consider networks of oscillators that interact via direct time-delayed coupling links. It is shown analytically that amplitude death is impossible for directly coupled Stuart-Landau oscillators, in contradistinction to the case of diffusive coupling. We demonstrate that amplitude death in the strict sense does become possible in directly coupled networks if the node dynamics is governed by second-order delay differential equations. Finally, we analyze in detail directly coupled nodes whose dynamics are described by first-order delay differential equations and find that, while amplitude death in the strict sense is impossible, other interesting oscillation quenching scenarios exist. PMID:27627306
Interdecadal Modulation of ENSO Amplitude During the Last Millennium
NASA Astrophysics Data System (ADS)
Li, J.; Xie, S.; Cook, E.; Huang, G.; D'Arrigo, R.; Liu, F.; Ma, J.; Zheng, X.
2010-12-01
El Niño/Southern Oscillation (ENSO) is the dominant mode of interannual variability, and affects climate around the globe. ENSO amplitude displays considerable variations on the instrumental record, and its future change is highly uncertain. Here we analyze a newly updated version of the tree-ring derived North American Drought Atlas (NADA) for the past 1100 years, and show that ENSO variance displays a quasi-regular cycle of 50-90 years. Interannual variability and its low-frequency amplitude modulation in NADA are in broad agreement with independent proxy records in the Pacific and surrounding regions. Large volcanic eruptions tend to trigger El Niño, but for the past millennium solar variations seem to drive amplitude modulation of ENSO. Simulating the quasi-periodic ENSO amplitude modulation may hold the key to improving models and their prediction of ENSO behavior in global warming.
High Amplitude (delta)-Scutis in the Large Magellanic Cloud
Garg, A; Cook, K H; Nikolaev, S; Huber, M E; Rest, A; Becker, A C; Challis, P; Clocchiatti, A; Miknaitis, G; Minniti, D; Morelli, L; Olsen, K; Prieto, J L; Suntzeff, N B; Welch, D L; Wood-Vasey, W M
2010-01-25
The authors present 2323 High-Amplitude {delta}-Scutis (HADS) candidates discovered in the Large Magellanic Cloud (LMC) by the SuperMACHO survey (Rest et al. 2005). Frequency analyses of these candidates reveal that several are multimode pulsators, including 119 whose largest amplitude of pulsation is in the fundamental (F) mode and 19 whose largest amplitude of pulsation is in the first overtone (FO) mode. Using Fourier decomposition of the HADS light curves, they find that the period-luminosity (PL) relation defined by the FO pulsators does not show a clear separation from the PL-relation defined by the F pulsators. This differs from other instability strip pulsators such as type c RR Lyrae. They also present evidence for a larger amplitude, subluminous population of HADS similar to that observed in Fornax (Poretti et al. 2008).
Amplitude death of identical oscillators in networks with direct coupling
NASA Astrophysics Data System (ADS)
Illing, Lucas
2016-08-01
It is known that amplitude death can occur in networks of coupled identical oscillators if they interact via diffusive time-delayed coupling links. Here we consider networks of oscillators that interact via direct time-delayed coupling links. It is shown analytically that amplitude death is impossible for directly coupled Stuart-Landau oscillators, in contradistinction to the case of diffusive coupling. We demonstrate that amplitude death in the strict sense does become possible in directly coupled networks if the node dynamics is governed by second-order delay differential equations. Finally, we analyze in detail directly coupled nodes whose dynamics are described by first-order delay differential equations and find that, while amplitude death in the strict sense is impossible, other interesting oscillation quenching scenarios exist.
Direct inversion methods for spectral amplitude modulation of femtosecond pulses.
Delgado-Aguillón, Jesús; Garduño-Mejía, Jesús; López-Téllez, Juan Manuel; Bruce, Neil C; Rosete-Aguilar, Martha; Román-Moreno, Carlos Jesús; Ortega-Martínez, Roberto
2014-04-01
In the present work, we applied an amplitude-spatial light modulator to shape the spectral amplitude of femtosecond pulses in a single step, without an iterative algorithm, by using an inversion method defined as the generalized retardance function. Additionally, we also present a single step method to shape the intensity profile defined as the influence matrix. Numerical and experimental results are presented for both methods.
Weak measurements measure probability amplitudes (and very little else)
NASA Astrophysics Data System (ADS)
Sokolovski, D.
2016-04-01
Conventional quantum mechanics describes a pre- and post-selected system in terms of virtual (Feynman) paths via which the final state can be reached. In the absence of probabilities, a weak measurement (WM) determines the probability amplitudes for the paths involved. The weak values (WV) can be identified with these amplitudes, or their linear combinations. This allows us to explain the "unusual" properties of the WV, and avoid the "paradoxes" often associated with the WM.
Three-point disc amplitudes in the RNS formalism
NASA Astrophysics Data System (ADS)
Becker, Katrin; Becker, Melanie; Robbins, Daniel; Su, Ning
2016-06-01
We calculate all tree level string theory vacuum to Dp-brane disc amplitudes involving an arbitrary RR-state and two NS-NS vertex operators. This computation was earlier performed by K. Becker, Guo, and Robbins for the simplest case of a RR-state of type C (p - 3). Here we use the aid of a computer to calculate all possible three-point amplitudes involving a RR-vertex operator of type C (p + 1 + 2 k).
Leading Twist Parton Distribution Amplitudes in Heavy Vector Mesons
NASA Astrophysics Data System (ADS)
Gao, Fei; Ding, Minghui; Chang, Lei; Liu, Yu-Xin; Roberts, Craig D.
2016-03-01
We employed QCD's Dyson-Schwinger equations (DSEs) for heavy quarks and obtained the leading twist parton distribution amplitudes (PDAs) in heavy vector mesons J/Ψ and ϒ. We found that all of the amplitudes are narrower than the asymptotic form, while they deviate from δ function. This indicates that the interaction between the two continent quarks are still important in the mesons consisted of charm and bottom quarks.
Real part of scattering amplitude at ultrahigh energies
NASA Astrophysics Data System (ADS)
Anisovich, V. V.; Nikonov, V. A.; Nyiri, J.
2015-10-01
On the basis of requirements of unitarity and analyticity we analyze the real and imaginary parts of the scattering amplitude at recent ultrahigh energies, 1-100TeV. The predictions for the region s > 100TeV and q2 < 0.4GeV2 are given supposing the black disk asymptotic regime. It turns out that the real part of the amplitude is concentrated in the impact parameter space at the border of the black disk.
Theory of the amplitude-phase retrieval in any linear-transform system and its applications
NASA Astrophysics Data System (ADS)
Yang, Guozhen; Gu, Ben-Yuan; Dong, Bi-Zhen
1992-12-01
This paper is a summary of the theory of the amplitude-phase retrieval problem in any linear transform system and its applications based on our previous works in the past decade. We describe the general statement on the amplitude-phase retrieval problem in an imaging system and derive a set of equations governing the amplitude-phase distribution in terms of the rigorous mathematical derivation. We then show that, by using these equations and an iterative algorithm, a variety of amplitude-phase problems can be successfully handled. We carry out the systematic investigations and comprehensive numerical calculations to demonstrate the utilization of this new algorithm in various transform systems. For instance, we have achieved the phase retrieval from two intensity measurements in an imaging system with diffraction loss (non-unitary transform), both theoretically and experimentally, and the recovery of model real image from its Hartley-transform modulus only in one and two dimensional cases. We discuss the achievement of the phase retrieval problem from a single intensity only based on the sampling theorem and our algorithm. We also apply this algorithm to provide an optimal design of the phase-adjusted plate for a phase-adjustment focusing laser accelerator and a design approach of single phase-only element for implementing optical interconnect. In order to closely simulate the really measured data, we examine the reconstruction of image from its spectral modulus corrupted by a random noise in detail. The results show that the convergent solution can always be obtained and the quality of the recovered image is satisfactory. We also indicated the relationship and distinction between our algorithm and the original Gerchberg- Saxton algorithm. From these studies, we conclude that our algorithm shows great capability to deal with the comprehensive phase-retrieval problems in the imaging system and the inverse problem in solid state physics. It may open a new way to
Light Diffraction by Large Amplitude Ultrasonic Waves in Liquids
NASA Technical Reports Server (NTRS)
Adler, Laszlo; Cantrell, John H.; Yost, William T.
2016-01-01
Light diffraction from ultrasound, which can be used to investigate nonlinear acoustic phenomena in liquids, is reported for wave amplitudes larger than that typically reported in the literature. Large amplitude waves result in waveform distortion due to the nonlinearity of the medium that generates harmonics and produces asymmetries in the light diffraction pattern. For standing waves with amplitudes above a threshold value, subharmonics are generated in addition to the harmonics and produce additional diffraction orders of the incident light. With increasing drive amplitude above the threshold a cascade of period-doubling subharmonics are generated, terminating in a region characterized by a random, incoherent (chaotic) diffraction pattern. To explain the experimental results a toy model is introduced, which is derived from traveling wave solutions of the nonlinear wave equation corresponding to the fundamental and second harmonic standing waves. The toy model reduces the nonlinear partial differential equation to a mathematically more tractable nonlinear ordinary differential equation. The model predicts the experimentally observed cascade of period-doubling subharmonics terminating in chaos that occurs with increasing drive amplitudes above the threshold value. The calculated threshold amplitude is consistent with the value estimated from the experimental data.
Ball bearing vibrations amplitude modeling and test comparisons
NASA Technical Reports Server (NTRS)
Hightower, Richard A., III; Bailey, Dave
1995-01-01
Bearings generate disturbances that, when combined with structural gains of a momentum wheel, contribute to induced vibration in the wheel. The frequencies generated by a ball bearing are defined by the bearing's geometry and defects. The amplitudes at these frequencies are dependent upon the actual geometry variations from perfection; therefore, a geometrically perfect bearing will produce no amplitudes at the kinematic frequencies that the design generates. Because perfect geometry can only be approached, emitted vibrations do occur. The most significant vibration is at the spin frequency and can be balanced out in the build process. Other frequencies' amplitudes, however, cannot be balanced out. Momentum wheels are usually the single largest source of vibrations in a spacecraft and can contribute to pointing inaccuracies if emitted vibrations ring the structure or are in the high-gain bandwidth of a sensitive pointing control loop. It is therefore important to be able to provide an a priori knowledge of possible amplitudes that are singular in source or are a result of interacting defects that do not reveal themselves in normal frequency prediction equations. This paper will describe the computer model that provides for the incorporation of bearing geometry errors and then develops an estimation of actual amplitudes and frequencies. Test results were correlated with the model. A momentum wheel was producing an unacceptable 74 Hz amplitude. The model was used to simulate geometry errors and proved successful in identifying a cause that was verified when the parts were inspected.
Wilson loops and QCD/string scattering amplitudes
Makeenko, Yuri; Olesen, Poul
2009-07-15
We generalize modern ideas about the duality between Wilson loops and scattering amplitudes in N=4 super Yang-Mills theory to large N QCD by deriving a general relation between QCD meson scattering amplitudes and Wilson loops. We then investigate properties of the open-string disk amplitude integrated over reparametrizations. When the Wilson-loop is approximated by the area behavior, we find that the QCD scattering amplitude is a convolution of the standard Koba-Nielsen integrand and a kernel. As usual poles originate from the first factor, whereas no (momentum-dependent) poles can arise from the kernel. We show that the kernel becomes a constant when the number of external particles becomes large. The usual Veneziano amplitude then emerges in the kinematical regime, where the Wilson loop can be reliably approximated by the area behavior. In this case, we obtain a direct duality between Wilson loops and scattering amplitudes when spatial variables and momenta are interchanged, in analogy with the N=4 super Yang-Mills theory case.
Amplitude relations in non-linear sigma model
NASA Astrophysics Data System (ADS)
Chen, Gang; Du, Yi-Jian
2014-01-01
In this paper, we investigate tree-level scattering amplitude relations in U( N) non-linear sigma model. We use Cayley parametrization. As was shown in the recent works [23,24], both on-shell amplitudes and off-shell currents with odd points have to vanish under Cayley parametrization. We prove the off-shell U(1) identity and fundamental BCJ relation for even-point currents. By taking the on-shell limits of the off-shell relations, we show that the color-ordered tree amplitudes with even points satisfy U(1)-decoupling identity and fundamental BCJ relation, which have the same formations within Yang-Mills theory. We further state that all the on-shell general KK, BCJ relations as well as the minimal-basis expansion are also satisfied by color-ordered tree amplitudes. As a consequence of the relations among color-ordered amplitudes, the total 2 m-point tree amplitudes satisfy DDM form of color decomposition as well as KLT relation.
Dependence of kink oscillation damping on the amplitude
NASA Astrophysics Data System (ADS)
Goddard, C. R.; Nakariakov, V. M.
2016-05-01
Context. Kink oscillations of coronal loops are one of the most intensively studied oscillatory phenomena in the solar corona. In the large-amplitude rapidly damped regime, these oscillations are observed to have a low quality factor with only a few cycles of oscillation detected before they are damped. The specific mechanism responsible for rapid damping is commonly accepted to be associated with the linear coupling between collective kink oscillations and localised torsional oscillations, the phenomenon of resonant absorption of the kink mode. The role of finite amplitude effects, however, is still not clear. Aims: We investigated the empirical dependence of the kink oscillation damping time and its quality factor, which is defined as the ratio of damping time to oscillation period, on the oscillation amplitude. Methods: We analysed decaying kink oscillation events detected previously with TRACE, SDO/AIA and and STEREO/EUVI in the extreme ultraviolet (EUV) 171 Å band. Results: We found that the ratio of the kink oscillation damping time to the oscillation period systematically decreases with the oscillation amplitude. We approximated the quality factor dependence on the oscillation displacement amplitude via the power-law dependence with the exponent of -1/2, however we stress that this is a by-eye estimate, and a more rigorous estimation of the scaling law requires more accurate measurements and increased statistics. We conclude that damping of kink oscillations of coronal loops depends on the oscillation amplitude, indicating the possible role of non-linear mechanisms for damping.
Mapping Pn amplitude spreading and attenuation in Asia
Yang, Xiaoning; Phillips, William S; Stead, Richard J
2010-12-06
Pn travels most of its path in the mantle lid. Mapping the lateral variation of Pn amplitude attenuation sheds light on material properties and dynamics of the uppermost region of the mantle. Pn amplitude variation depends on the wavefront geometric spreading as well as material attenuation. We investigated Pn geometric spreading, which is much more complex than a traditionally assumed power-law spreading model, using both synthetic and observed amplitude data collected in Asia. We derived a new Pn spreading model based on the formulation that was proposed previously to account for the spherical shape of the Earth (Yang et. al., BSSA, 2007). New parameters derived for the spreading model provide much better correction for Pn amplitudes in terms of residual behavior. Because we used observed Pn amplitudes to construct the model, the model incorporates not only the effect of the Earth's spherical shape, but also the effect of potential upper-mantle velocity gradients in the region. Using the new spreading model, we corrected Pn amplitudes measured at 1, 2, 4 and 6 Hz and conducted attenuation tomography. The resulting Pn attenuation model correlates well with the regional geology. We see high attenuation in regions such as northern Tibetan Plateau and the western Pacific subduction zone, and low attenuation for stable blocks such as Sichuan and Tarim basins.
Separation of musical instruments based on amplitude and frequency comodulation
NASA Astrophysics Data System (ADS)
Jacobson, Barry D.; Cauwenberghs, Gert; Quatieri, Thomas F.
2002-05-01
In previous work, amplitude comodulation was investigated as a basis for monaural source separation. Amplitude comodulation refers to similarities in amplitude envelopes of individual spectral components emitted by particular types of sources. In many types of musical instruments, amplitudes of all resonant modes rise/fall, and start/stop together during the course of normal playing. We found that under certain well-defined conditions, a mixture of constant frequency, amplitude comodulated sources can unambiguously be decomposed into its constituents on the basis of these similarities. In this work, system performance was improved by relaxing the constant frequency requirement. String instruments, for example, which are normally played with vibrato, are both amplitude and frequency comodulated sources, and could not be properly tracked under the constant frequency assumption upon which our original algorithm was based. Frequency comodulation refers to similarities in frequency variations of individual harmonics emitted by these types of sources. The analytical difficulty is in defining a representation of the source which properly tracks frequency varying components. A simple, fixed filter bank can only track an individual spectral component for the duration in which it is within the passband of one of the filters. Alternatives are therefore explored which are amenable to real-time implementation.
Quantitative phase-amplitude microscopy I: optical microscopy.
Barone-Nugent, E D; Barty, A; Nugent, K A
2002-06-01
In this paper, the application of a new optical microscopy method (quantitative phase-amplitude microscopy) to biological imaging is explored, and the issue of resolution and image quality is examined. The paper begins by presenting a theoretical analysis of the method using the optical transfer function formalism of Streibl (1985). The effect of coherence on the formation of the phase image is explored, and it is shown that the resolution of the method is not compromised over that of a conventional bright-field image. It is shown that the signal-to-noise ratio of the phase recovery, however, does depend on the degree of coherence in the illumination. Streibl (1985) notes that partially coherent image formation is a non-linear process because of the intermingling of amplitude and phase information. The work presented here shows that the quantitative phase-amplitude microscopy method acts to linearize the image formation process, and that the phase and amplitude information is properly described using a transfer function analysis. The theoretical conclusions are tested experimentally using an optical microscope and the theoretical deductions are confirmed. Samples for microscopy influence both the phase and amplitude of the light wave and it is demonstrated that the new phase recovery method can separate the amplitude and phase information, something not possible using traditional phase microscopy. In the case of a coherent wave, knowledge of the phase and amplitude constitutes complete information that can be used to emulate other forms of microscopy. This capacity is demonstrated by recovering the phase of a sample and using the data to emulate a differential interference contrast image.
Peng, Jiegang
2015-12-01
Weakly electric fish sense their surroundings in complete darkness by their active electrolocation system. For biologists, the active electrolocation system has been investigated for near 60 years. And for engineers, bio-inspired active electrolocation sensor has been investigated for about 20 years. But how the amplitude information response will be affected by frequencies of detecting electric fields in the active electrolocation system was rarely investigated. In this paper, an electrolocation experiment system has been built. The amplitude information-frequency characteristics (AIFC) of the electrolocation system for sinusoidal electric fields of varying frequencies have been investigated. We find that AIFC of the electrolocation system have relevance to the material properties and geometric features of the probed object and conductivity of surrounding water. Detect frequency dead zone (DFDZ) and frequency inflection point (FIP) of AIFC for the electrolocation system were found. The analysis model of the electrolocation system has been investigated for many years, but DFDZ and FIP of AIFC can be difficult to explain by those models. In order to explain those AIFC phenomena for the electrolocation system, a simple relaxation model based on Cole-Cole model which is not only a mathematical explanation but it is a physical one for the electrolocation system was advanced. We also advance a hypothesis for physical mechanism of weakly electrical fish electrolocation system. It may have reference value for physical mechanism of weakly electrical fish active electrolocation system. PMID:26531142
Peng, Jiegang
2015-11-04
Weakly electric fish sense their surroundings in complete darkness by their active electrolocation system. For biologists, the active electrolocation system has been investigated for near 60 years. And for engineers, bio-inspired active electrolocation sensor has been investigated for about 20 years. But how the amplitude information response will be affected by frequencies of detecting electric fields in the active electrolocation system was rarely investigated. In this paper, an electrolocation experiment system has been built. The amplitude information-frequency characteristics (AIFC) of the electrolocation system for sinusoidal electric fields of varying frequencies have been investigated. We find that AIFC of the electrolocation system have relevance to the material properties and geometric features of the probed object and conductivity of surrounding water. Detect frequency dead zone (DFDZ) and frequency inflection point (FIP) of AIFC for the electrolocation system were found. The analysis model of the electrolocation system has been investigated for many years, but DFDZ and FIP of AIFC can be difficult to explain by those models. In order to explain those AIFC phenomena for the electrolocation system, a simple relaxation model based on Cole-Cole model which is not only a mathematical explanation but it is a physical one for the electrolocation system was advanced. We also advance a hypothesis for physical mechanism of weakly electrical fish electrolocation system. It may have reference value for physical mechanism of weakly electrical fish active electrolocation system.
All Tree-level Amplitudes in Massless QCD
Dixon, Lance J.; Henn, Johannes M.; Plefka, Jan; Schuster, Theodor; /Humboldt U., Berlin
2010-10-25
We derive compact analytical formulae for all tree-level color-ordered gauge theory amplitudes involving any number of external gluons and up to three massless quark-anti-quark pairs. A general formula is presented based on the combinatorics of paths along a rooted tree and associated determinants. Explicit expressions are displayed for the next-to-maximally helicity violating (NMHV) and next-to-next-to-maximally helicity violating (NNMHV) gauge theory amplitudes. Our results are obtained by projecting the previously-found expressions for the super-amplitudes of the maximally supersymmetric Yang-Mills theory (N = 4 SYM) onto the relevant components yielding all gluon-gluino tree amplitudes in N = 4 SYM. We show how these results carry over to the corresponding QCD amplitudes, including massless quarks of different flavors as well as a single electroweak vector boson. The public Mathematica package GGT is described, which encodes the results of this work and yields analytical formulae for all N = 4 SYM gluon-gluino trees. These in turn yield all QCD trees with up to four external arbitrary-flavored massless quark-anti-quark-pairs.
An overlooked effect of systemic anticholinergics: alteration on accommodation amplitude
Sekeroglu, Mehmet Ali; Hekimoglu, Emre; Anayol, Mustafa Alpaslan; Tasci, Yasemin; Dolen, Ismail
2016-01-01
AIM To investigate the effect of oral solifenacin succinate, tolterodine-L-tartarate and oxybutinin hydrochloride (HCl) on accommodation amplitude. METHODS Female overactive bladder syndrome (OAB) patients who were planned to use oral anticholinergics, patients that uses solifenacin succinate 5 mg (Group I, n=25), tolterodine-L-tartarate 4 mg (Group II, n=25), and oxybutinin HCl 5 mg b.i.d (Group III, n=25) and age matched healthy female subjects (Group IV, n=25) were recruited and complete ophthalmological examination and accommodation amplitude assessment were done at baseline and 4wk after initiation of treatment. RESULTS The mean age of 100 consecutive female subjects was 51.6±5.7 (40-60)y and there were no statistically significant difference with regard to the mean age (P=0.107) and baseline accommodation amplitude (P=0.148) between study groups. All treatment groups showed a significant decrease in accommodation amplitude following a 4-week course of anticholinergic treatment (P=0.008 in Group I, P=0.002 in Group II, P=0.001 in Group III), but there was no statistically significant difference in Group IV (P=0.065). CONCLUSION A 4-week course of oral anticholinergic treatment have statistically significant effect on accommodation amplitude. Clinicians should avoid both overestimating this result, as this would unnecessarily restrict therapeutic possibilities, and also underestimating it which may lead to drug intolerance. PMID:27275433
Forecasting Wave Amplitudes after the Arrival of a Tsunami
NASA Astrophysics Data System (ADS)
Nyland, David; Huang, Paul
2014-12-01
The destructive Pacific Ocean tsunami generated off the east coast of Honshu, Japan, on 11 March 2011 prompted the West Coast and Alaska Tsunami Warning Center (WCATWC) to issue a tsunami warning and advisory for the coastal regions of Alaska, British Columbia, Washington, Oregon, and California. Estimating the length of time the warning or advisory would remain in effect proved difficult. To address this problem, the WCATWC developed a technique to estimate the amplitude decay of a tsunami recorded at tide stations within the Warning Center's Area of Responsibly (AOR). At many sites along the West Coast of North America, the tsunami wave amplitudes will decay exponentially following the arrival of the maximum wave ( Mofjeld et al., Nat Hazards 22:71-89, 2000). To estimate the time it will take before wave amplitudes drop to safe levels, the real-time tide gauge data are filtered to remove the effects of tidal variations. The analytic envelope is computed and a 2 h sequence of amplitude values following the tsunami peak is used to obtain a least squares fit to an exponential function. This yields a decay curve which is then combined with an average West Coast decay function to provide an initial tsunami amplitude-duration forecast. This information may then be provided to emergency managers to assist with response planning.
Amplitude death of coupled hair bundles with stochastic channel noise
NASA Astrophysics Data System (ADS)
Kim, Kyung-Joong; Ahn, Kang-Hun
2014-04-01
Hair cells conduct auditory transduction in vertebrates. In lower vertebrates such as frogs and turtles, due to the active mechanism in hair cells, hair bundles (stereocilia) can be spontaneously oscillating or quiescent. Recently an amplitude death phenomenon has been proposed [K.-H. Ahn, J. R. Soc. Interface, 10, 20130525 (2013)] as a mechanism for auditory transduction in frog hair-cell bundles, where sudden cessation of the oscillations arises due to the coupling between nonidentical hair bundles. The gating of the ion channel is intrinsically stochastic due to the stochastic nature of the configuration change of the channel. The strength of the noise due to the channel gating can be comparable to the thermal Brownian noise of hair bundles. Thus, we perform stochastic simulations of the elastically coupled hair bundles. In spite of stray noisy fluctuations due to its stochastic dynamics, our simulation shows the transition from collective oscillation to amplitude death as interbundle coupling strength increases. In its stochastic dynamics, the formation of the amplitude death state of coupled hair bundles can be seen as a sudden suppression of the displacement fluctuation of the hair bundles as the coupling strength increases. The enhancement of the signal-to-noise ratio through the amplitude death phenomenon is clearly seen in the stochastic dynamics. Our numerical results demonstrate that the multiple number of transduction channels per hair bundle is an important factor to the amplitude death phenomenon, because the phenomenon may disappear for a small number of transduction channels due to strong gating noise.
The amplitude mode at the superfluid-mott insulator transition
NASA Astrophysics Data System (ADS)
Pekker, David
2012-02-01
We study a two dimensional gas of repulsively interacting bosons in the presence of both an optical lattice and a trap using optical lattice modulation spectroscopy. The strongly interacting superfluid supports two types of low energy modes associated with the symmetry breaking at the phase transition: gapless phase (Goldstone) modes and gapped amplitude (Anderson-Higgs) modes. Both experimentally and in theoretical simulations lattice modulation spectroscopy shows an onset of absorption at a frequency associated with the amplitude mode gap, followed by a broad absorption peak at higher frequencies. From the simulations, we learn that energy is being absorbed by various amplitude modes, which inside a trap resemble the modes of a (gapped) drum. Our main results are: (1) despite coupling to the phase modes, modulation spectroscopy shows a sharp absorption onset at the frequency associated with the amplitude mode gap; (2) as we approach the Mott transition the gap softens and finally disappears at the transition point; (3) in the weak coupling regime, deep in the superfluid phase, the amplitude mode disappears.
Phase and amplitude phase restoration in synthetic aperture radar imaging.
Soumekh, M; Choi, J H
1992-01-01
Methods for addressing two types of multiplicative noise in synthetic aperture radar (SAR) imaging are presented. The authors consider a multiplicative noise with a real phase (i.e. the SAR signal's phase is contaminated but its amplitude is uncorrupted) that possesses unknown functional characteristics with respect to the radar signal's temporal frequencies. A perturbation solution for phase reconstruction from amplitude is developed from a wave equation governing the SAR signal and a Riccati equation that relates the amplitude and phase functions of the SAR signal. This solution is converted into a noniterative analytical solution in terms of the moments and powers of the log amplitude function. Next, the authors consider a multiplicative noise with a complex phase (i.e. both the amplitude and phase of the SAR signal are contaminated) that varies linearly with respect to the radar signal's temporal frequencies. The two wave equations governing the SAR signal at two temporal frequencies of the radar signal are combined to derive a method to reconstruct the complex phase error function.
Simulation of absolute amplitudes of ultrasound signals using equivalent circuits.
Johansson, Jonny; Martinsson, Pär-Erik; Delsing, Jerker
2007-10-01
Equivalent circuits for piezoelectric devices and ultrasonic transmission media can be used to cosimulate electronics and ultrasound parts in simulators originally intended for electronics. To achieve efficient system-level optimization, it is important to simulate correct, absolute amplitude of the ultrasound signal in the system, as this determines the requirements on the electronics regarding dynamic range, circuit noise, and power consumption. This paper presents methods to achieve correct, absolute amplitude of an ultrasound signal in a simulation of a pulse-echo system using equivalent circuits. This is achieved by taking into consideration loss due to diffraction and the effect of the cable that connects the electronics and the piezoelectric transducer. The conductive loss in the transmission line that models the propagation media of the ultrasound pulse is used to model the loss due to diffraction. Results show that the simulated amplitude of the echo follows measured values well in both near and far fields, with an offset of about 10%. The use of a coaxial cable introduces inductance and capacitance that affect the amplitude of a received echo. Amplitude variations of 60% were observed when the cable length was varied between 0.07 m and 2.3 m, with simulations predicting similar variations. The high precision in the achieved results show that electronic design and system optimization can rely on system simulations alone. This will simplify the development of integrated electronics aimed at ultrasound systems. PMID:18019234
On the field theory expansion of superstring five point amplitudes
NASA Astrophysics Data System (ADS)
Boels, Rutger H.
2013-11-01
A simple recursive expansion algorithm for the integrals of tree level superstring five point amplitudes in a flat background is given which reduces the expansion to simple symbol(ic) manipulations. This approach can be used for instance to prove the expansion is maximally transcendental to all orders and to verify several conjectures made in recent literature to high order. Closed string amplitudes follow from these open string results by the KLT relations. To obtain insight into these results in particular the maximal R-symmetry violating amplitudes (MRV) in type IIB superstring theory are studied. The obtained expansion of the open string amplitudes reduces the analysis for MRV amplitudes to the classification of completely symmetric polynomials of the external legs, up to momentum conservation. Using Molien's theorem as a counting tool this problem is solved by constructing an explicit nine element basis for this class. This theorem may be of wider interest: as is illustrated at higher points it can be used to calculate dimensions of polynomials of external momenta invariant under any finite group for in principle any number of legs, up to momentum conservation. In the closed (or mixed) case this follows after application of the Kawai-Lewellen-Tye [1] relations (or their analogons [2,3]).
Turaev-Viro amplitudes from 2+1 loop quantum gravity
NASA Astrophysics Data System (ADS)
Pranzetti, Daniele
2014-04-01
The Turaev-Viro state sum model provides a covariant spin foam quantization of three-dimensional Riemannian gravity with a positive cosmological constant Λ. We complete the program to canonically quantize the theory in the BF formulation using the formalism of loop quantum gravity. In particular, we show first how quantum group structures arise from the requirement of the constraint algebra to be anomaly free. This allows us to generalize the construction of the physical scalar product, from the Λ=0 case, in the presence of a positive Λ. We prove the equivalence between the covariant and canonical quantizations by recovering the spin foam amplitudes.
Gauge amplitude identities by on-shell recursion relation in S-matrix program
NASA Astrophysics Data System (ADS)
Feng, Bo; Huang, Rijun; Jia, Yin
2011-01-01
Using only the Britto-Cachazo-Feng-Witten (BCFW) on-shell recursion relation we prove color-order reversed relation, U(1)-decoupling relation, Kleiss-Kuijf (KK) relation and Bern-Carrasco-Johansson (BCJ) relation for color-ordered gauge amplitude in the framework of S-matrix program without relying on Lagrangian description. Our derivation is the first pure field theory proof of the new discovered BCJ identity, which substantially reduces the color-ordered basis from (n-2)! to (n-3)!. Our proof gives also its physical interpretation as the mysterious bonus relation with 1/z behavior under suitable on-shell deformation for no adjacent pair.
Large amplitude solitary waves in a warm magnetoplasma with kappa distributed electrons
El-Tantawy, S. A.; El-Bedwehy, N. A.; Abd El-Razek, H. N.; Mahmood, S.
2013-02-15
The large amplitude nonlinear ion acoustic solitary wave propagating obliquely to an external magnetic field in a magnetized plasma with kappa distributed electrons and warm ions is investigated through deriving energy-balance-like expression involving a Sagdeev potential. Analytical and numerical calculations of the values of Mach number reveal that both of subsonic and supersonic electrostatic solitary structures can exist in this system. The influence on the soliton characteristics of relevant physical parameters such as the Mach number, the superthermal parameter, the directional cosine, the ratio of ion-to-electron temperature, and the ion gyrofrequency has been investigated.
Exclusive two-photon processes: Tests of QCD at the amplitude level
Brodsky, S.J.
1992-07-01
Exclusive two-photon processes at large momentum transfer, particularly Compton scattering {gamma}p{yields}{gamma}p and its crossed-channel reactions {gamma}{gamma}{yields}{bar p}p and {bar p}p{yields}{gamma}{gamma}, can provide definitive information on the bound-state distributions of quarks in hadrons at the amplitude level. Recent theoretical work has shown that QCD predictions based on the factorization of long and short distance physics are already applicable at momentum transfers of order of a few GeV.
A high-stability non-contact dilatometer for low-amplitude temperature-modulated measurements.
Luckabauer, Martin; Sprengel, Wolfgang; Würschum, Roland
2016-07-01
Temperature modulated thermophysical measurements can deliver valuable insights into the phase transformation behavior of many different materials. While especially for non-metallic systems at low temperatures numerous powerful methods exist, no high-temperature device suitable for modulated measurements of bulk metallic alloy samples is available for routine use. In this work a dilatometer for temperature modulated isothermal and non-isothermal measurements in the temperature range from room temperature to 1300 K is presented. The length measuring system is based on a two-beam Michelson laser interferometer with an incremental resolution of 20 pm. The non-contact measurement principle allows for resolving sinusoidal length change signals with amplitudes in the sub-500 nm range and physically decouples the length measuring system from the temperature modulation and heating control. To demonstrate the low-amplitude capabilities, results for the thermal expansion of nickel for two different modulation frequencies are presented. These results prove that the novel method can be used to routinely resolve length-change signals of metallic samples with temperature amplitudes well below 1 K. This high resolution in combination with the non-contact measurement principle significantly extends the application range of modulated dilatometry towards high-stability phase transformation measurements on complex alloys.
Hoang, Thai M; Bharath, Hebbe M; Boguslawski, Matthew J; Anquez, Martin; Robbins, Bryce A; Chapman, Michael S
2016-08-23
Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. This mechanism gives rise to massless Nambu-Goldstone modes and massive Anderson-Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase or amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal nonequilibrium dynamics in the Kibble-Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure the energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite-size effects lead to a nonzero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition. PMID:27503886
A high-stability non-contact dilatometer for low-amplitude temperature-modulated measurements.
Luckabauer, Martin; Sprengel, Wolfgang; Würschum, Roland
2016-07-01
Temperature modulated thermophysical measurements can deliver valuable insights into the phase transformation behavior of many different materials. While especially for non-metallic systems at low temperatures numerous powerful methods exist, no high-temperature device suitable for modulated measurements of bulk metallic alloy samples is available for routine use. In this work a dilatometer for temperature modulated isothermal and non-isothermal measurements in the temperature range from room temperature to 1300 K is presented. The length measuring system is based on a two-beam Michelson laser interferometer with an incremental resolution of 20 pm. The non-contact measurement principle allows for resolving sinusoidal length change signals with amplitudes in the sub-500 nm range and physically decouples the length measuring system from the temperature modulation and heating control. To demonstrate the low-amplitude capabilities, results for the thermal expansion of nickel for two different modulation frequencies are presented. These results prove that the novel method can be used to routinely resolve length-change signals of metallic samples with temperature amplitudes well below 1 K. This high resolution in combination with the non-contact measurement principle significantly extends the application range of modulated dilatometry towards high-stability phase transformation measurements on complex alloys. PMID:27475604
Amplitude various angles (AVA) phenomena in thin layer reservoir: Case study of various reservoirs
Nurhandoko, Bagus Endar B. E-mail: bagusnur@rock-fluid.com; Susilowati E-mail: bagusnur@rock-fluid.com
2015-04-16
Amplitude various offset is widely used in petroleum exploration as well as in petroleum development field. Generally, phenomenon of amplitude in various angles assumes reservoir’s layer is quite thick. It also means that the wave is assumed as a very high frequency. But, in natural condition, the seismic wave is band limited and has quite low frequency. Therefore, topic about amplitude various angles in thin layer reservoir as well as low frequency assumption is important to be considered. Thin layer reservoir means the thickness of reservoir is about or less than quarter of wavelength. In this paper, I studied about the reflection phenomena in elastic wave which considering interference from thin layer reservoir and transmission wave. I applied Zoeppritz equation for modeling reflected wave of top reservoir, reflected wave of bottom reservoir, and also transmission elastic wave of reservoir. Results show that the phenomena of AVA in thin layer reservoir are frequency dependent. Thin layer reservoir causes interference between reflected wave of top reservoir and reflected wave of bottom reservoir. These phenomena are frequently neglected, however, in real practices. Even though, the impact of inattention in interference phenomena caused by thin layer in AVA may cause inaccurate reservoir characterization. The relation between classes of AVA reservoir and reservoir’s character are different when effect of ones in thin reservoir and ones in thick reservoir are compared. In this paper, I present some AVA phenomena including its cross plot in various thin reservoir types based on some rock physics data of Indonesia.
A high-stability non-contact dilatometer for low-amplitude temperature-modulated measurements
NASA Astrophysics Data System (ADS)
Luckabauer, Martin; Sprengel, Wolfgang; Würschum, Roland
2016-07-01
Temperature modulated thermophysical measurements can deliver valuable insights into the phase transformation behavior of many different materials. While especially for non-metallic systems at low temperatures numerous powerful methods exist, no high-temperature device suitable for modulated measurements of bulk metallic alloy samples is available for routine use. In this work a dilatometer for temperature modulated isothermal and non-isothermal measurements in the temperature range from room temperature to 1300 K is presented. The length measuring system is based on a two-beam Michelson laser interferometer with an incremental resolution of 20 pm. The non-contact measurement principle allows for resolving sinusoidal length change signals with amplitudes in the sub-500 nm range and physically decouples the length measuring system from the temperature modulation and heating control. To demonstrate the low-amplitude capabilities, results for the thermal expansion of nickel for two different modulation frequencies are presented. These results prove that the novel method can be used to routinely resolve length-change signals of metallic samples with temperature amplitudes well below 1 K. This high resolution in combination with the non-contact measurement principle significantly extends the application range of modulated dilatometry towards high-stability phase transformation measurements on complex alloys.
Stello, Dennis; Huber, Daniel; Bedding, Timothy R.; Benomar, Othman; Kallinger, Thomas; Basu, Sarbani; Mosser, BenoIt; Hekker, Saskia; Mathur, Savita; GarcIa, Rafael A.; Gilliland, Ronald L.; Verner, Graham A.; Chaplin, William J.; Elsworth, Yvonne P.; Meibom, Soeren; Molenda-Zakowicz, Joanna; Szabo, Robert
2011-08-10
Scaling relations that link asteroseismic quantities to global stellar properties are important for gaining understanding of the intricate physics that underpins stellar pulsations. The common notion that all stars in an open cluster have essentially the same distance, age, and initial composition implies that the stellar parameters can be measured to much higher precision than what is usually achievable for single stars. This makes clusters ideal for exploring the relation between the mode amplitude of solar-like oscillations and the global stellar properties. We have analyzed data obtained with NASA's Kepler space telescope to study solar-like oscillations in 100 red giant stars located in either of the three open clusters, NGC 6791, NGC 6819, and NGC 6811. By fitting the measured amplitudes to predictions from simple scaling relations that depend on luminosity, mass, and effective temperature, we find that the data cannot be described by any power of the luminosity-to-mass ratio as previously assumed. As a result we provide a new improved empirical relation which treats luminosity and mass separately. This relation turns out to also work remarkably well for main-sequence and subgiant stars. In addition, the measured amplitudes reveal the potential presence of a number of previously unknown unresolved binaries in the red clump in NGC 6791 and NGC 6819, pointing to an interesting new application for asteroseismology as a probe into the formation history of open clusters.
J. J. Sakurai Prize: Scattering Amplitudes - the Story of Loops and Legs
NASA Astrophysics Data System (ADS)
Dixon, Lance
2014-03-01
Scattering amplitudes are at the interface between quantum field theory and particle experiment. Precise predictions for reactions at energy frontier machines such as the Large Hadron Collider (LHC) rely on quantum corrections to scattering amplitudes involving multiple quarks and gluons, as well as other particles. For decades, theorists used Feynman diagrams for this job. However, Feynman diagrams are just too slow, even on fast computers, to allow adequate precision for complicated events with many jets of hadrons in the final state. Such events are produced copiously at the LHC, and constitute formidable backgrounds to many searches for new physics. Over the past two decades, alternative methods to Feynman diagrams have come to fruition. The new ``on-shell'' methods are based on the old principle of unitarity. They can be much more efficient because they exploit the underlying simplicity of scattering amplitudes, and recycle lower-loop information. The same methods have also enabled new insight into the structure of gauge theory and gravity at the quantum level, especially in highly supersymmetric theories where they maintain all of the symmetries. I'll give a brief motivation for and introduction to the new methods, which will be followed by descriptions of their phenomenological and formal applications by David Kosower and Zvi Bern.
Investigations of amplitude and phase excitation profiles in femtosecond coherence spectroscopy
NASA Astrophysics Data System (ADS)
Kumar, Anand T. N.; Rosca, Florin; Widom, Allan; Champion, Paul M.
2001-01-01
We present an effective linear response approach to pump-probe femtosecond coherence spectroscopy in the well-separated pulse limit. The treatment presented here is based on a displaced and squeezed state representation for the nonstationary states induced by an ultrashort pump laser pulse or a chemical reaction. The subsequent response of the system to a delayed probe pulse is modeled using closed form nonstationary linear response functions, valid for a multimode vibronically coupled system at arbitrary temperature. When pump-probe signals are simulated using the linear response functions, with the mean nuclear positions and momenta obtained from a rigorous moment analysis of the pump induced (doorway) state, the signals are found to be in excellent agreement with the conventional third-order response approach. The key advantages offered by the moment analysis-based linear response approach include a clear physical interpretation of the amplitude and phase of oscillatory pump-probe signals, a dramatic improvement in computation times, a direct connection between pump-probe signals and equilibrium absorption and dispersion lineshapes, and the ability to incorporate coherence associated with rapid nonradiative surface crossing. We demonstrate these aspects using numerical simulations, and also apply the present approach to the interpretation of experimental amplitude and phase measurements on reactive and nonreactive samples of the heme protein myoglobin. The role played by inhomogeneous broadening in the observed amplitude and phase profiles is discussed in detail. We also investigate overtone signals in the context of reaction driven coherent motion.
An analytical solution of finite-amplitude solitary kinetic Alfven waves
Wu, D.; Wang, D.; Faelthammar, C.
1995-12-01
An analytical solution of finite-amplitude solitary kinetic Alfven waves (SKAWs) in a low-{beta} ({beta}{much_lt}{ital m}{sub {ital e}}/{ital m}{sub {ital i}}{much_lt}1) plasma is presented. This solution has been compared with the solution of the Korteweg--de Vries (KdV) equation in the small-amplitude limit. It is found that the KdV soliton solution is valid only for the maximum relative density perturbation {ital N}{sub {ital m}}{lt}0.1. For the larger {ital N}{sub {ital m}}, the exact analytical solution shows that the SKAWs have a much wider structure and much stronger perturbed fields than the KdV solitons with the same {ital N}{sub {ital m}}. Moreover, the relations between the width and the amplitude of SKAWs are also considerably different from that of the KdV solitons. In addition, the possibility for applying these results to some events observed from the Freja scientific satellite is discussed. (The Freja is a Swedish--German scientific project for the investigation of ionospheric and magnetospheric plasmas, and the Freja satellite was launched on a Long-March II rocket of China on October 6, 1992.) {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Hoang, Thai M.; Bharath, Hebbe M.; Boguslawski, Matthew J.; Anquez, Martin; Robbins, Bryce A.; Chapman, Michael S.
2016-01-01
Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. This mechanism gives rise to massless Nambu–Goldstone modes and massive Anderson–Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase or amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal nonequilibrium dynamics in the Kibble–Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure the energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite-size effects lead to a nonzero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition. PMID:27503886
NASA Technical Reports Server (NTRS)
Shertzer, Janine; Temkin, Aaron
2007-01-01
In the first two papers in this series, we developed a method for studying electron-hydrogen scattering that does not use partial wave analysis. We constructed an ansatz for the wave function in both the static and static exchange approximations and calculated the full scattering amplitude. Here we go beyond the static exchange approximation, and include correlation in the wave function via a modified polarized orbital. This correlation function provides a significant improvement over the static exchange approximation: the resultant elastic scattering amplitudes are in very good agreement with fully converged partial wave calculations for electron-hydrogen scattering. A fully variational modification of this approach is discussed in the conclusion of the article Popular summary of Direct calculation of the scattering amplitude without partial wave expansion. III ....." by J. Shertzer and A. Temkin. In this paper we continue the development of In this paper we continue the development of a new approach to the way in which researchers have traditionally used to calculate the scattering cross section of (low-energy) electrons from atoms. The basic mathematical problem is to solve the Schroedinger Equation (SE) corresponding the above physical process. Traditionally it was always the case that the SE was reduced to a sequence of one-dimensional (ordinary) differential equations - called partial waves which were solved and from the solutions "phase shifts" were extracted, from which the scattering cross section was calculated.
NASA Astrophysics Data System (ADS)
Hoang, Thai M.; Bharath, Hebbe M.; Boguslawski, Matthew J.; Anquez, Martin; Robbins, Bryce A.; Chapman, Michael S.
2016-08-01
Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. This mechanism gives rise to massless Nambu-Goldstone modes and massive Anderson-Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase or amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal nonequilibrium dynamics in the Kibble-Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure the energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite-size effects lead to a nonzero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition.
Hoang, Thai M; Bharath, Hebbe M; Boguslawski, Matthew J; Anquez, Martin; Robbins, Bryce A; Chapman, Michael S
2016-08-23
Spontaneous symmetry breaking occurs in a physical system whenever the ground state does not share the symmetry of the underlying theory, e.g., the Hamiltonian. This mechanism gives rise to massless Nambu-Goldstone modes and massive Anderson-Higgs modes. These modes provide a fundamental understanding of matter in the Universe and appear as collective phase or amplitude excitations of an order parameter in a many-body system. The amplitude excitation plays a crucial role in determining the critical exponents governing universal nonequilibrium dynamics in the Kibble-Zurek mechanism (KZM). Here, we characterize the amplitude excitations in a spin-1 condensate and measure the energy gap for different phases of the quantum phase transition. At the quantum critical point of the transition, finite-size effects lead to a nonzero gap. Our measurements are consistent with this prediction, and furthermore, we demonstrate an adiabatic quench through the phase transition, which is forbidden at the mean field level. This work paves the way toward generating entanglement through an adiabatic phase transition.
Amplitude-dependent Lamb wave dispersion in nonlinear plates.
Packo, Pawel; Uhl, Tadeusz; Staszewski, Wieslaw J; Leamy, Michael J
2016-08-01
The paper presents a perturbation approach for calculating amplitude-dependent Lamb wave dispersion in nonlinear plates. Nonlinear dispersion relationships are derived in closed form using a hyperelastic stress-strain constitutive relationship, the Green-Lagrange strain measure, and the partial wave technique integrated with a Lindstedt-Poincaré perturbation approach. Solvability conditions are derived using an operator formalism with inner product projections applied against solutions to the adjoint problem. When applied to the first- and second-order problems, these solvability conditions lead to amplitude-dependent, nonlinear dispersion corrections for frequency as a function of wavenumber. Numerical simulations verify the predicted dispersion shifts for an example nonlinear plate. The analysis and identification of amplitude-dependent, nonlinear Lamb wave dispersion complements recent research focusing on higher harmonic generation and internally resonant waves, which require precise dispersion relationships for frequency-wavenumber matching. PMID:27586758
Optimization of phase contrast in bimodal amplitude modulation AFM.
Damircheli, Mehrnoosh; Payam, Amir F; Garcia, Ricardo
2015-01-01
Bimodal force microscopy has expanded the capabilities of atomic force microscopy (AFM) by providing high spatial resolution images, compositional contrast and quantitative mapping of material properties without compromising the data acquisition speed. In the first bimodal AFM configuration, an amplitude feedback loop keeps constant the amplitude of the first mode while the observables of the second mode have not feedback restrictions (bimodal AM). Here we study the conditions to enhance the compositional contrast in bimodal AM while imaging heterogeneous materials. The contrast has a maximum by decreasing the amplitude of the second mode. We demonstrate that the roles of the excited modes are asymmetric. The operational range of bimodal AM is maximized when the second mode is free to follow changes in the force. We also study the contrast in trimodal AFM by analyzing the kinetic energy ratios. The phase contrast improves by decreasing the energy of second mode relative to those of the first and third modes.
Collinear limit of scattering amplitudes at strong coupling.
Basso, Benjamin; Sever, Amit; Vieira, Pedro
2014-12-31
In this Letter, we consider the collinear limit of gluon scattering amplitudes in planar N=4 super-Yang-Mills theory at strong coupling. We argue that in this limit scattering amplitudes map into correlators of twist fields in the two dimensional nonlinear O(6) sigma model, similar to those appearing in recent studies of entanglement entropy. We provide evidence for this assertion by combining the intuition springing from the string world-sheet picture and the predictions coming from the operator product expansion series. One of the main implications of these considerations is that scattering amplitudes receive equally important contributions at strong coupling from both the minimal string area and its fluctuations in the sphere. PMID:25615305
Statistical amplitude scale estimation for quantization-based watermarking
NASA Astrophysics Data System (ADS)
Shterev, Ivo D.; Lagendijk, Reginald L.; Heusdens, Richard
2004-06-01
Quantization-based watermarking schemes are vulnerable to amplitude scaling. Therefore the scaling factor has to be accounted for either at the encoder, or at the decoder, prior to watermark decoding. In this paper we derive the marginal probability density model for the watermarked and attacked data, when the attack channel consists of amplitude scaling followed by additive noise. The encoder is Quantization Index Modulation with Distortion Compensation. Based on this model we obtain two estimation procedures for the scale parameter. The first approach is based on Fourier Analysis of the probability density function. The estimation of the scaling parameter relies on the structure of the received data. The second approach that we obtain is the Maximum Likelihood estimator of the scaling factor. We study the performance of the estimation procedures theoretically and experimentally with real audio signals, and compare them to other well known approaches for amplitude scale estimation in the literature.
Berends-Giele recursion for double-color-ordered amplitudes
NASA Astrophysics Data System (ADS)
Mafra, Carlos R.
2016-07-01
Tree-level double-color-ordered amplitudes are computed using Berends-Giele recursion relations applied to the bi-adjoint cubic scalar theory. The standard notion of Berends-Giele currents is generalized to double-currents and their recursions are derived from a perturbiner expansion of linearized fields that solve the non-linear field equations. Two applications are given. Firstly, we prove that the entries of the inverse KLT matrix are equal to Berends-Giele double-currents (and are therefore easy to compute). And secondly, a simple formula to generate tree-level BCJ-satisfying numerators for arbitrary multiplicity is proposed by evaluating the field-theory limit of tree-level string amplitudes for various color orderings using double-color-ordered amplitudes.
Mammalian cycles: internally defined periods and interaction-driven amplitudes.
Ginzburg, L R; Krebs, C J
2015-01-01
The cause of mammalian cycles-the rise and fall of populations over a predictable period of time-has remained controversial since these patterns were first observed over a century ago. In spite of extensive work on observable mammalian cycles, the field has remained divided upon what the true cause is, with a majority of opinions attributing it to either predation or to intra-species mechanisms. Here we unite the eigenperiod hypothesis, which describes an internal, maternal effect-based mechanism to explain the cycles' periods with a recent generalization explaining the amplitude of snowshoe hare cycles in northwestern North America based on initial predator abundance. By explaining the period and the amplitude of the cycle with separate mechanisms, a unified and consistent view of the causation of cycles is reached. Based on our suggested theory, we forecast the next snowshoe hare cycle (predicted peak in 2016) to be of extraordinarily low amplitude.
Loop Integrands for Scattering Amplitudes from the Riemann Sphere
NASA Astrophysics Data System (ADS)
Geyer, Yvonne; Mason, Lionel; Monteiro, Ricardo; Tourkine, Piotr
2015-09-01
The scattering equations on the Riemann sphere give rise to remarkable formulas for tree-level gauge theory and gravity amplitudes. Adamo, Casali, and Skinner conjectured a one-loop formula for supergravity amplitudes based on scattering equations on a torus. We use a residue theorem to transform this into a formula on the Riemann sphere. What emerges is a framework for loop integrands on the Riemann sphere that promises to have a wide application, based on off-shell scattering equations that depend on the loop momentum. We present new formulas, checked explicitly at low points, for supergravity and super-Yang-Mills amplitudes and for n -gon integrands at one loop. Finally, we show that the off-shell scattering equations naturally extend to arbitrary loop order, and we give a proposal for the all-loop integrands for supergravity and planar super-Yang-Mills theory.
Amplitude variations on the Extreme Adaptive Optics testbed
Evans, J; Thomas, S; Dillon, D; Gavel, D; Phillion, D; Macintosh, B
2007-08-14
High-contrast adaptive optics systems, such as those needed to image extrasolar planets, are known to require excellent wavefront control and diffraction suppression. At the Laboratory for Adaptive Optics on the Extreme Adaptive Optics testbed, we have already demonstrated wavefront control of better than 1 nm rms within controllable spatial frequencies. Corresponding contrast measurements, however, are limited by amplitude variations, including those introduced by the micro-electrical-mechanical-systems (MEMS) deformable mirror. Results from experimental measurements and wave optic simulations of amplitude variations on the ExAO testbed are presented. We find systematic intensity variations of about 2% rms, and intensity variations with the MEMS to be 6%. Some errors are introduced by phase and amplitude mixing because the MEMS is not conjugate to the pupil, but independent measurements of MEMS reflectivity suggest that some error is introduced by small non-uniformities in the reflectivity.
Air-segmented amplitude-modulated multiplexed flow analysis.
Inui, Koji; Uemura, Takeshi; Ogusu, Takeshi; Takeuchi, Masaki; Tanaka, Hideji
2011-01-01
Air-segmentation is applied to amplitude-modulated multiplexed flow analysis, which we proposed recently. Sample solutions, the flow rates of which are varied periodically, are merged with reagent and/or diluent solution. The merged stream is segmented by air-bubbles and, downstream, its absorbance is measured after deaeration. The analytes in the samples are quantified from the amplitudes of the respective wave components in the absorbance. The proposed method is applied to the determinations of a food dye, phosphate ions and nitrite ions. The air-segmentation is effective for limiting amplitude damping through the axial dispersion, resulting in an improvement in sensitivity. This effect is more pronounced at shorter control periods and longer flow path lengths.
General mechanism for amplitude death in coupled systems.
Resmi, V; Ambika, G; Amritkar, R E
2011-10-01
We introduce a general mechanism for amplitude death in coupled synchronizable dynamical systems. It is known that when two systems are coupled directly, they can synchronize under suitable conditions. When an indirect feedback coupling through an environment or an external system is introduced in them, it is found to induce a tendency for antisynchronization. We show that, for sufficient strengths, these two competing effects can lead to amplitude death. We provide a general stability analysis that gives the threshold values for onset of amplitude death. We study in detail the nature of the transition to death in several specific cases and find that the transitions can be of two types--continuous and discontinuous. By choosing a variety of dynamics, for example, periodic, chaotic, hyperchaotic, and time-delay systems, we illustrate that this mechanism is quite general and works for different types of direct coupling, such as diffusive, replacement, and synaptic couplings, and for different damped dynamics of the environment.
Chronotaxic systems with separable amplitude and phase dynamics.
Suprunenko, Yevhen F; Clemson, Philip T; Stefanovska, Aneta
2014-01-01
Until recently, deterministic nonautonomous oscillatory systems with stable amplitudes and time-varying frequencies were not recognized as such and have often been mistreated as stochastic. These systems, named chronotaxic, were introduced in Phys. Rev. Lett. 111, 024101 (2013). In contrast to conventional limit cycle models of self-sustained oscillators, these systems posses a time-dependent point attractor or steady state. This allows oscillations with time-varying frequencies to resist perturbations, a phenomenon which is ubiquitous in living systems. In this work a detailed theory of chronotaxic systems is presented, specifically in the case of separable amplitude and phase dynamics. The theory is extended by the introduction of chronotaxic amplitude dynamics. The wide applicability of chronotaxic systems to a range of fields from biological and condensed matter systems to robotics and control theory is discussed.
Amplitude analysis of the B+/--->phiK*(892)+/- decay.
Aubert, B; Bona, M; Boutigny, D; Karyotakis, Y; Lees, J P; Poireau, V; Prudent, X; Tisserand, V; Zghiche, A; Garra Tico, J; Grauges, E; Lopez, L; Palano, A; Eigen, G; Stugu, B; Sun, L; Abrams, G S; Battaglia, M; Brown, D N; Button-Shafer, J; Cahn, R N; Groysman, Y; Jacobsen, R G; Kadyk, J A; Kerth, L T; Kolomensky, Yu G; Kukartsev, G; Lopes Pegna, D; Lynch, G; Mir, L M; Orimoto, T J; Ronan, M T; Tackmann, K; Wenzel, W A; del Amo Sanchez, P; Hawkes, C M; Watson, A T; Held, T; Koch, H; Lewandowski, B; Pelizaeus, M; Schroeder, T; Steinke, M; Walker, D; Asgeirsson, D J; Cuhadar-Donszelmann, T; Fulsom, B G; Hearty, C; Mattison, T S; McKenna, J A; Khan, A; Saleem, M; Teodorescu, L; Blinov, V E; Bukin, A D; Druzhinin, V P; Golubev, V B; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Todyshev, K Yu; Bondioli, M; Curry, S; Eschrich, I; Kirkby, D; Lankford, A J; Lund, P; Mandelkern, M; Martin, E C; Stoker, D P; Abachi, S; Buchanan, C; Foulkes, S D; Gary, J W; Liu, F; Long, O; Shen, B C; Zhang, L; Paar, H P; Rahatlou, S; Sharma, V; Berryhill, J W; Campagnari, C; Cunha, A; Dahmes, B; Hong, T M; Kovalskyi, D; Richman, J D; Beck, T W; Eisner, A M; Flacco, C J; Heusch, C A; Kroseberg, J; Lockman, W S; Schalk, T; Schumm, B A; Seiden, A; Williams, D C; Wilson, M G; Winstrom, L O; Chen, E; Cheng, C H; Fang, F; Hitlin, D G; Narsky, I; Piatenko, T; Porter, F C; Andreassen, R; Mancinelli, G; Meadows, B T; Mishra, K; Sokoloff, M D; Blanc, F; Bloom, P C; Chen, S; Ford, W T; Hirschauer, J F; Kreisel, A; Nagel, M; Nauenberg, U; Olivas, A; Smith, J G; Ulmer, K A; Wagner, S R; Zhang, J; Gabareen, A M; Soffer, A; Toki, W H; Wilson, R J; Winklmeier, F; Zeng, Q; Altenburg, D D; Feltresi, E; Hauke, A; Jasper, H; Merkel, J; Petzold, A; Spaan, B; Wacker, K; Brandt, T; Klose, V; Kobel, M J; Lacker, H M; Mader, W F; Nogowski, R; Schubert, J; Schubert, K R; Schwierz, R; Sundermann, J E; Volk, A; Bernard, D; Bonneaud, G R; Latour, E; Lombardo, V; Thiebaux, Ch; Verderi, M; Clark, P J; Gradl, W; Muheim, F; Playfer, S; Robertson, A I; Xie, Y; Andreotti, M; Bettoni, D; Bozzi, C; Calabrese, R; Cecchi, A; Cibinetto, G; Franchini, P; Luppi, E; Negrini, M; Petrella, A; Piemontese, L; Prencipe, E; Santoro, V; Anulli, F; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Pacetti, S; Patteri, P; Peruzzi, I M; Piccolo, M; Rama, M; Zallo, A; Buzzo, A; Contri, R; Lo Vetere, M; Macri, M M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Chaisanguanthum, K S; Morii, M; Wu, J; Dubitzky, R S; Marks, J; Schenk, S; Uwer, U; Bard, D J; Dauncey, P D; Flack, R L; Nash, J A; Nikolich, M B; Panduro Vazquez, W; Tibbetts, M; Behera, P K; Chai, X; Charles, M J; Mallik, U; Meyer, N T; Ziegler, V; Cochran, J; Crawley, H B; Dong, L; Eyges, V; Meyer, W T; Prell, S; Rosenberg, E I; Rubin, A E; Gao, Y Y; Gritsan, A V; Guo, Z J; Lae, C K; Denig, A G; Fritsch, M; Schott, G; Arnaud, N; Béquilleux, J; Davier, M; Grosdidier, G; Höcker, A; Lepeltier, V; Le Diberder, F; Lutz, A M; Pruvot, S; Rodier, S; Roudeau, P; Schune, M H; Serrano, J; Sordini, V; Stocchi, A; Wang, W F; Wormser, G; Lange, D J; Wright, D M; Bingham, I; Chavez, C A; Forster, I J; Fry, J R; Gabathuler, E; Gamet, R; Hutchcroft, D E; Payne, D J; Schofield, K C; Touramanis, C; Bevan, A J; George, K A; Di Lodovico, F; Menges, W; Sacco, R; Cowan, G; Flaecher, H U; Hopkins, D A; Paramesvaran, S; Salvatore, F; Wren, A C; Brown, D N; Davis, C L; Allison, J; Barlow, N R; Barlow, R J; Chia, Y M; Edgar, C L; Lafferty, G D; West, T J; Yi, J I; Anderson, J; Chen, C; Jawahery, A; Roberts, D A; Simi, G; Tuggle, J M; Blaylock, G; Dallapiccola, C; Hertzbach, S S; Li, X; Moore, T B; Salvati, E; Saremi, S; Cowan, R; Dujmic, D; Fisher, P H; Koeneke, K; Sciolla, G; Sekula, S J; Spitznagel, M; Taylor, F; Yamamoto, R K; Zhao, M; Zheng, Y; Mclachlin, S E; Patel, P M; Robertson, S H; Lazzaro, A; Palombo, F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Côté, D; Simard, M; Taras, P; Viaud, F B; Nicholson, H; De Nardo, G; Fabozzi, F; Lista, L; Monorchio, D; Sciacca, C; Baak, M A; Raven, G; Snoek, H L; Jessop, C P; LoSecco, J M; Benelli, G; Corwin, L A; Honscheid, K; Kagan, H; Kass, R; Morris, J P; Rahimi, A M; Regensburger, J J; Wong, Q K; Blount, N L; Brau, J; Frey, R; Igonkina, O; Kolb, J A; Lu, M; Rahmat, R; Sinev, N B; Strom, D; Strube, J; Torrence, E; Gagliardi, N; Gaz, A; Margoni, M; Morandin, M; Pompili, A; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Voci, C; Ben-Haim, E; Briand, H; Calderini, G; Chauveau, J; David, P; Del Buono, L; de la Vaissière, Ch; Hamon, O; Leruste, Ph; Malclès, J; Ocariz, J; Perez, A; Gladney, L; Biasini, M; Covarelli, R; Manoni, E; Angelini, C; Batignani, G; Bettarini, S; Carpinelli, M; Cenci, R; Cervelli, A; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Mazur, M A; Morganti, M; Neri, N; Paoloni, E; Rizzo, G; Walsh, J J; Haire, M; Biesiada, J; Elmer, P; Lau, Y P; Lu, C; Olsen, J; Smith, A J S; Telnov, A V; Baracchini, E; Bellini, F; Cavoto, G; D'Orazio, A; del Re, D; Di Marco, E; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Jackson, P D; Li Gioi, L; Mazzoni, M A; Morganti, S; Piredda, G; Polci, F; Renga, F; Voena, C; Ebert, M; Hartmann, T; Schröder, H; Waldi, R; Adye, T; Castelli, G; Franek, B; Olaiya, E O; Ricciardi, S; Roethel, W; Wilson, F F; Aleksan, R; Emery, S; Escalier, M; Gaidot, A; Ganzhur, S F; Hamel de Monchenault, G; Kozanecki, W; Vasseur, G; Yèche, Ch; Zito, M; Chen, X R; Liu, H; Park, W; Purohit, M V; Wilson, J R; Allen, M T; Aston, D; Bartoldus, R; Bechtle, P; Berger, N; Claus, R; Coleman, J P; Convery, M R; Dingfelder, J C; Dorfan, J; Dubois-Felsmann, G P; Dunwoodie, W; Field, R C; Glanzman, T; Gowdy, S J; Graham, M T; Grenier, P; Hast, C; Hryn'ova, T; Innes, W R; Kaminski, J; Kelsey, M H; Kim, H; Kim, P; Kocian, M L; Leith, D W G S; Li, S; Luitz, S; Luth, V; Lynch, H L; MacFarlane, D B; Marsiske, H; Messner, R; Muller, D R; O'Grady, C P; Ofte, I; Perazzo, A; Perl, M; Pulliam, T; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Snyder, A; Stelzer, J; Su, D; Sullivan, M K; Suzuki, K; Swain, S K; Thompson, J M; Va'vra, J; van Bakel, N; Wagner, A P; Weaver, M; Wisniewski, W J; Wittgen, M; Wright, D H; Yarritu, A K; Yi, K; Young, C C; Burchat, P R; Edwards, A J; Majewski, S A; Petersen, B A; Wilden, L; Ahmed, S; Alam, M S; Bula, R; Ernst, J A; Jain, V; Pan, B; Saeed, M A; Wappler, F R; Zain, S B; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Ritchie, J L; Ruland, A M; Schilling, C J; Schwitters, R F; Izen, J M; Lou, X C; Ye, S; Bianchi, F; Gallo, F; Gamba, D; Pelliccioni, M; Bomben, M; Bosisio, L; Cartaro, C; Cossutti, F; Della Ricca, G; Lanceri, L; Vitale, L; Azzolini, V; Lopez-March, N; Martinez-Vidal, F; Milanes, D A; Oyanguren, A; Albert, J; Banerjee, Sw; Bhuyan, B; Hamano, K; Kowalewski, R; Nugent, I M; Roney, J M; Sobie, R J; Back, J J; Harrison, P F; Ilic, J; Latham, T E; Mohanty, G B; Pappagallo, M; Band, H R; Chen, X; Dasu, S; Flood, K T; Hollar, J J; Kutter, P E; Pan, Y; Pierini, M; Prepost, R; Wu, S L; Neal, H
2007-11-16
We perform an amplitude analysis of B+/--->phi(1020)K*(892)+/- decay with a sample of about 384 x 10(6) BB[over ] pairs recorded with the BABAR detector. Overall, twelve parameters are measured, including the fractions of longitudinal fL and parity-odd transverse f perpendicular amplitudes, branching fraction, strong phases, and six parameters sensitive to CP violation. We use the dependence on the Kpi invariant mass of the interference between the JP=1(-) and 0+ Kpi components to resolve the discrete ambiguity in the determination of the strong and weak phases. Our measurements of fL=0.49+/-0.05+/-0.03, f perpendicular=0.21+/-0.05+/-0.02, and the strong phases point to the presence of a substantial helicity-plus amplitude from a presently unknown source. PMID:18233133
Mammalian cycles: internally defined periods and interaction-driven amplitudes.
Ginzburg, L R; Krebs, C J
2015-01-01
The cause of mammalian cycles-the rise and fall of populations over a predictable period of time-has remained controversial since these patterns were first observed over a century ago. In spite of extensive work on observable mammalian cycles, the field has remained divided upon what the true cause is, with a majority of opinions attributing it to either predation or to intra-species mechanisms. Here we unite the eigenperiod hypothesis, which describes an internal, maternal effect-based mechanism to explain the cycles' periods with a recent generalization explaining the amplitude of snowshoe hare cycles in northwestern North America based on initial predator abundance. By explaining the period and the amplitude of the cycle with separate mechanisms, a unified and consistent view of the causation of cycles is reached. Based on our suggested theory, we forecast the next snowshoe hare cycle (predicted peak in 2016) to be of extraordinarily low amplitude. PMID:26339557
Mammalian cycles: internally defined periods and interaction-driven amplitudes
Krebs, CJ
2015-01-01
The cause of mammalian cycles—the rise and fall of populations over a predictable period of time—has remained controversial since these patterns were first observed over a century ago. In spite of extensive work on observable mammalian cycles, the field has remained divided upon what the true cause is, with a majority of opinions attributing it to either predation or to intra-species mechanisms. Here we unite the eigenperiod hypothesis, which describes an internal, maternal effect-based mechanism to explain the cycles’ periods with a recent generalization explaining the amplitude of snowshoe hare cycles in northwestern North America based on initial predator abundance. By explaining the period and the amplitude of the cycle with separate mechanisms, a unified and consistent view of the causation of cycles is reached. Based on our suggested theory, we forecast the next snowshoe hare cycle (predicted peak in 2016) to be of extraordinarily low amplitude. PMID:26339557
Extracting forward strong amplitudes from elastic differential cross sections
C.M. Chen; D.J. Ernst; Mikkel B. Johnson
2001-07-01
The feasibility of a model-independent extraction of the forward strong amplitude from elastic nuclear cross section data in the Coulomb-nuclear interference region is assessed for {pi} and K{sup +} scattering at intermediate energies. Theoretically-generated ''data'' are analyzed to provide criteria for optimally designing experiments to measure these amplitudes, whose energy dependence (particularly that of the real parts) is needed for disentangling various sources of medium modifications of the projectile-nucleon interaction. The issues considered include determining the angular region over which to make the measurements, the role of the most forward angles measured, and the effects of statistical and systematic errors. We find that there is a region near the forward direction where Coulomb-nuclear interference allows reliable extraction of the strong forward amplitude for both pions and the K{sup +} from .3 to 1 GeV/c.
Kernel Phase and Kernel Amplitude in Fizeau Imaging
NASA Astrophysics Data System (ADS)
Pope, Benjamin J. S.
2016-09-01
Kernel phase interferometry is an approach to high angular resolution imaging which enhances the performance of speckle imaging with adaptive optics. Kernel phases are self-calibrating observables that generalize the idea of closure phases from non-redundant arrays to telescopes with arbitrarily shaped pupils, by considering a matrix-based approximation to the diffraction problem. In this paper I discuss the recent fhistory of kernel phase, in particular in the matrix-based study of sparse arrays, and propose an analogous generalization of the closure amplitude to kernel amplitudes. This new approach can self-calibrate throughput and scintillation errors in optical imaging, which extends the power of kernel phase-like methods to symmetric targets where amplitude and not phase calibration can be a significant limitation, and will enable further developments in high angular resolution astronomy.
Top Quark Amplitudes with an Anomolous Magnetic Moment
Larkoski, Andrew J.; Peskin, Michael E.; /SLAC
2011-06-23
The anomalous magnetic moment of the top quark may be measured during the first run of the LHC at 7 TeV. For these measurements, it will be useful to have available tree amplitudes with t{bar t} and arbitrarily many photons and gluons, including both QED and color anomalous magnetic moments. In this paper, we present a method for computing these amplitudes using the Britto-Cachazo-Feng-Witten recursion formula. Because we deal with an effective theory with higher-dimension couplings, there are roadblocks to a direct computation with the Britto-Cachazo-Feng-Witten method. We evade these by using an auxiliary scalar theory to compute a subset of the amplitudes.
Optimization of phase contrast in bimodal amplitude modulation AFM
Damircheli, Mehrnoosh; Payam, Amir F
2015-01-01
Summary Bimodal force microscopy has expanded the capabilities of atomic force microscopy (AFM) by providing high spatial resolution images, compositional contrast and quantitative mapping of material properties without compromising the data acquisition speed. In the first bimodal AFM configuration, an amplitude feedback loop keeps constant the amplitude of the first mode while the observables of the second mode have not feedback restrictions (bimodal AM). Here we study the conditions to enhance the compositional contrast in bimodal AM while imaging heterogeneous materials. The contrast has a maximum by decreasing the amplitude of the second mode. We demonstrate that the roles of the excited modes are asymmetric. The operational range of bimodal AM is maximized when the second mode is free to follow changes in the force. We also study the contrast in trimodal AFM by analyzing the kinetic energy ratios. The phase contrast improves by decreasing the energy of second mode relative to those of the first and third modes. PMID:26114079
Determining pseudoscalar meson photoproduction amplitudes from complete experiments
A. M. Sandorfi, S. Hoblit, H. Kamano, T.-S. H. Lee
2011-05-01
In preparation for a new generation of complete experiments with the goal of performing a high precision extraction of pseudoscalar meson photo-production amplitudes, we present expressions that allow the direct numerical calculation of matrix elements with arbitrary spin projections from Chew-Goldberger-Low-Nambu (CGLN) amplitudes. We use this numerical tool to verify the most general analytic form of the cross section, dependent upon the three polarization vectors of the beam, target and recoil baryon, including all single, double and triple-polarization terms involving 16 spin-dependent observables. Analytic expressions that determine the recoil baryon polarization are presented, together with examples of their potential use with quasi-4? detectors to deduce observables. We assemble the analytic equations relating the 16 experimental observables and the CGLN amplitudes and use our independent method of numerical evaluation to resolve sign differences that exist in the literature.
Calculating phases between B{yields}K*{pi} amplitudes
Gronau, Michael; Pirjol, Dan; Rosner, Jonathan L.
2010-05-01
A phase {Delta}{Phi} between amplitudes for B{sup 0{yields}}K*{sup 0{pi}0} and B{sup 0{yields}}K*{sup +{pi}-} plays a crucial role in a method for constraining Cabibbo-Kobayashi-Maskawa parameters. We present a general argument for destructive interference between amplitudes for B{sup 0{yields}}K*{sup +{pi}-} and B{sup 0{yields}}K*{sup 0{pi}0} forming together a smaller I(K*{pi})=3/2 amplitude. Applying flavor SU(3) and allowing for conservative theoretical uncertainties, we obtain lower limits on |{Delta}{Phi}| and its charge conjugate. Values of these two phases favored by the BABAR collaboration are in good agreement with our bounds.
Gauge dependence in QED amplitudes in expanding de Sitter space
NASA Astrophysics Data System (ADS)
Nicolaevici, Nistor
2016-04-01
We consider first-order transition amplitudes in external fields in QED in the expanding de Sitter space and point out that they are gauge dependent quantities. We examine the gauge variations of the amplitudes assuming a decoupling of the interaction at large times, which allows to conclude that the source of the problem lies in the fact that the frequencies of the modes in the infinite future become independent of the comoving momenta. We show that a possibility to assure the gauge invariance of the external field amplitudes is to restrict to potentials which vanish sufficiently fast at infinite times, and briefly discuss a number of options in the face of the possible gauge invariance violation in the full interacting theory.
Amplitude and polarization asymmetries in a ring laser
NASA Technical Reports Server (NTRS)
Campbell, L. L.; Buholz, N. E.
1971-01-01
Asymmetric amplitude effects between the oppositely directed traveling waves in a He-Ne ring laser are analyzed both theoretically and experimentally. These effects make it possible to detect angular orientations of an inner-cavity bar with respect to the plane of the ring cavity. The amplitude asymmetries occur when a birefringent bar is placed in the three-mirror ring cavity, and an axial magnetic field is applied to the active medium. A simplified theoretical analysis is performed by using a first order perturbation theory to derive an expression for the polarization of the active medium, and a set of self-consistent equations are derived to predict threshold conditions. Polarization asymmetries between the oppositely directed waves are also predicted. Amplitude asymmetries similar in nature to those predicted at threshold occur when the laser is operating in 12-15 free-running modes, and polarization asymmetry occurs simultaneously.
Amplitude Noise Reduction of Ion Lasers with Optical Feedback
NASA Technical Reports Server (NTRS)
Herring, Gregory C.
2011-01-01
A reduction in amplitude noise on the output of a multi-mode continuous-wave Ar-ion laser was previously demonstrated when a fraction of the output power was retroreflected back into the laser cavity. This result was reproduced in the present work and a Fabry-Perot etalon was used to monitor the longitudinal mode structure of the laser. A decrease in the number of operating longitudinal cavity modes was observed simultaneously with the introduction of the optical feedback and the onset of the amplitude noise reduction. The noise reduction is a result of a reduced number of lasing modes, resulting in less mode beating and amplitude fluctuations of the laser output power.
Choi, M J; Coleman, A J; Saunders, J E
1993-11-01
This study concerns the radial dynamics of a bubble driven by pulsed ultrasound of the type generated during extracorporeal shock wave lithotripsy. In particular, a numerical model has been used to examine the sensitivity of the bubble oscillations to changes in both the amplitude of the driving field and the physical conditions of the fluid surrounding the bubble: viscosity, surface tension, temperature and gas content. It is shown that, at high negative pressures (p- = 10 MPa) as in lithotripsy, the timing and amplitude of bubble collapses have a considerably reduced sensitivity to the initial bubble size and all fluid parameters, except gas content, compared with those expected in lower-amplitude fields (p- = 0.2 MPa). This study indicates that, in the lithotripsy fields, the differences in the viscosity, surface tension and temperature of body fluids and the initial bubble size will have little effect on bubble dynamics compared with those expected in water.
Quasi-steady, marginally unstable electron cyclotron harmonic wave amplitudes
NASA Astrophysics Data System (ADS)
Zhang, Xiaojia; Angelopoulos, Vassilis; Ni, Binbin; Thorne, Richard M.; Horne, Richard B.
2013-06-01
Electron cyclotron harmonic (ECH) waves have long been considered a potential driver of diffuse aurora in Earth's magnetotail. However, the scarcity of intense ECH emissions in the outer magnetotail suggests that our understanding of the amplification and the relative importance of these waves for electron scattering is lacking. We conduct a comprehensive study of wave growth and quasi-linear diffusion to estimate the amplitude of loss-cone-driven ECH waves once diffusion and growth balance but before convection or losses alter the background hot plasma sheet population. We expect this to be the most common state of the plasma sheet between episodes of fast convection. For any given wave amplitude, we model electron diffusion caused by interaction with ECH waves using a 2-D bounce-averaged Fokker-Planck equation. After fitting the resultant electron distributions as a superposition of multicomponent subtracted bi-Maxwellians, we estimate the maximum path-integrated gain using the HOTRAY ray-tracing code. We argue that the wave amplitude during quasi-steady state is the inflection point on a gain-amplitude curve. During quasi-steady state, ECH wave amplitudes can be significant (~1 mV/m) at L ~ 8 but drop to very low values (<~0.1 mV/m) in the outer magnetotail (L ~ 16) and likely fall below the sensitivity of typical instrumentation relatively close to Earth mainly because of the smallness of the loss cone. Our result reinforces the potentially important role of ECH waves in driving diffuse aurora and suggests that careful comparison of theoretical wave amplitude estimates and observations is required for resolving the equatorial scattering mechanism of diffuse auroral precipitation.
Six open string disk amplitude in pure spinor superspace
NASA Astrophysics Data System (ADS)
Mafra, Carlos R.; Schlotterer, Oliver; Stieberger, Stephan; Tsimpis, Dimitrios
2011-05-01
The tree-level amplitude of six massless open strings is computed using the pure spinor formalism. The OPE poles among integrated and unintegrated vertices can be efficiently organized according to the cohomology of pure spinor superspace. The identification and use of these BRST structures and their interplay with the system of equations fulfilled by the generalized Euler integrals allow the full supersymmetric six-point amplitude to be written in compact form. Furthermore, the complete set of extended Bern-Carrasco-Johansson relations are derived from the monodromy properties of the disk world-sheet and explicitly verified for the supersymmetric numerator factors.
Modulated Source Interferometry with Combined Amplitude and Frequency Modulation
NASA Technical Reports Server (NTRS)
Gutierrez, Roman C. (Inventor)
1998-01-01
An improved interferometer is produced by modifying a conventional interferometer to include amplitude and/or frequency modulation of a coherent light source at radio or higher frequencies. The phase of the modulation signal can be detected in an interfering beam from an interferometer and can be used to determine the actual optical phase of the beam. As such, this improvement can be adapted to virtually any two-beam interferometer, including: Michelson, Mach-Zehnder, and Sagnac interferometers. The use of an amplitude modulated coherent tight source results in an interferometer that combines the wide range advantages of coherent interferometry with the precise distance measurement advantages of white light interferometry.
Closed-form decomposition of one-loop massive amplitudes
Britto, Ruth; Feng Bo; Mastrolia, Pierpaolo
2008-07-15
We present formulas for the coefficients of 2-, 3-, 4-, and 5-point master integrals for one-loop massive amplitudes. The coefficients are derived from unitarity cuts in D dimensions. The input parameters can be read off from any unitarity-cut integrand, as assembled from tree-level expressions, after simple algebraic manipulations. The formulas presented here are suitable for analytical as well as numerical evaluation. Their validity is confirmed in two known cases of helicity amplitudes contributing to gg{yields}gg and gg{yields}gH, where the masses of the Higgs and the fermion circulating in the loop are kept as free parameters.
Scattering amplitudes for the rationally extended PT symmetric complex potentials
NASA Astrophysics Data System (ADS)
Kumari, Nisha; Yadav, Rajesh Kumar; Khare, Avinash; Bagchi, Bijan; Mandal, Bhabani Prasad
2016-10-01
In this paper, we consider the rational extensions of two different classes of PT symmetric complex potentials namely the asymptotically vanishing Scarf II and asymptotically non-vanishing Rosen-Morse II [ RM-II] and obtain the accompanying bound state eigenfunctions in terms of the exceptional Xm Jacobi polynomials and a certain class of orthogonal polynomials. By considering the asymptotic behavior of the exceptional polynomials, we also derive the reflection and transmission amplitudes for them and discuss the various novel properties of the corresponding amplitudes.
Enhanced Electroweak Penguin Amplitude in B{yields}VV Decays
Beneke, M.; Rohrer, J.; Yang, D.
2006-04-14
We discuss a novel electromagnetic penguin contribution to the transverse helicity amplitudes in B decays to two vector mesons, which is enhanced by two powers of m{sub B}/{lambda} relative to the standard penguin amplitudes. This leads to unique polarization signatures in penguin-dominated decay modes such as B{yields}{rho}K* similar to polarization effects in the radiative decay B{yields}K*{gamma} and offers new opportunities to probe the magnitude and chirality of flavor-changing neutral current couplings to photons.
Calculation of the Scattering Amplitude Without Partial Wave Expansion
NASA Technical Reports Server (NTRS)
Shertzer, J.; Temkin, Aaron; Fisher, Richard R. (Technical Monitor)
2001-01-01
Two developments in the direct calculation of the angular differential scattering amplitude have been implemented: (a) The integral expansion of the scattering amplitude is simplified by analytically integration over the azimuthal angle. (b) The resulting integral as a function of scattering angle is calculated by using the numerically generated wave function from a finite element method calculation. Results for electron-hydrogen scattering in the static approximation will be shown to be as accurate as a partial wave expansion with as many l's as is necessary for convergence at the incident energy being calculated.
Mukherjee, Arunava; Bhattacharyya, Sudip E-mail: sudip@tifr.res.in
2012-09-01
A kilohertz quasi-periodic oscillation (kHz QPO) is an observationally robust high-frequency timing feature detected from neutron star low-mass X-ray binaries (LMXBs). This feature can be very useful to probe the superdense core matter of neutron stars and the strong gravity regime. Although many models exist in the literature, the physical origin of kHz QPO is not known, and hence this feature cannot be used as a tool yet. The energy dependence of kHz QPO fractional rms amplitude is an important piece of the jigsaw puzzle to understand the physical origin of this timing feature. It is known that the fractional rms amplitude increases with energy at lower energies. At higher energies, the amplitude is usually believed to saturate, although this is not established. We combine tens of lower kHz QPOs from a neutron star LMXB 4U 1728-34 in order to improve the signal-to-noise ratio. Consequently, we, for the first time to the best of our knowledge, find a significant and systematic decrease of the fractional rms amplitude with energy at higher photon energies. Assuming an energy spectrum model, blackbody+powerlaw, we explore if the sinusoidal variation of a single spectral parameter can reproduce the above-mentioned fractional rms amplitude behavior. Our analysis suggests that the oscillation of any single blackbody parameter is favored over the oscillation of any single power-law parameter, in order to explain the measured amplitude behavior. We also find that the quality factor of a lower kHz QPO does not plausibly depend on photon energy.
Mortola, Jacopo P; Lanthier, Clement
2004-09-01
We questioned whether the amplitudes of the circadian pattern of body temperature (T(b)), oxygen consumption (V (O(2))) and heart rate (HR) changed systematically among species of different body weight (W). Because bodies of large mass have a greater heat capacitance than those of smaller mass, if the relative amplitude (i.e., amplitude/mean value) of metabolic rate was constant, one would expect the T(b) oscillation to decrease with the increase in the species W. We compiled data of T(b), V (O(2)) and HR from a literature survey of over 200 studies that investigated the circadian pattern of these parameters. Monotremata, Marsupials and Chiroptera, were excluded because of their characteristically low metabolic rate and T(b). The peak-trough ratios of V (O(2)) (42 species) and HR (35 species) averaged, respectively, 1.57+/-0.08, and 1.35+/-0.07, and were independent of W. The daily high values of T(b) did not change, while the daily low T(b) values slightly increased, with the species W; hence, the high-low T(b) difference (57 species) decreased with W (3.3 degrees C.W(-0.13)). However, the decrease in T(b) amplitude with W was much less than expected from physical principles, and the high-low T(b) ratio remained significantly above unity even in the largest mammals. Thus, it appears that in mammals, despite the huge differences in physical characteristics, the amplitude of the circadian pattern is a fixed (for V (O(2)) and HR), or almost fixed (for T(b)), fraction of the 24-h mean value. Presumably, the amplitudes of the oscillations are controlled parameters of physiological significance.
Kim, Juntae; Helgeson, Matthew E.; Merger, Dimitri; Wilhelm, Manfred
2014-09-01
We investigate yielding in a colloidal gel that forms a heterogeneous structure, consisting of a two-phase bicontinuous network of colloid-rich domains of fractal clusters and colloid-poor domains. Combining large amplitude oscillatory shear measurements with simultaneous small and ultra-small angle neutron scattering (rheo-SANS/USANS), we characterize both the nonlinear mechanical processes and strain amplitude-dependent microstructure underlying yielding. We observe a broad, three-stage yielding process that evolves over an order of magnitude in strain amplitude between the onset of nonlinearity and flow. Analyzing the intracycle response as a sequence of physical processes reveals a transition from elastic straining to elastoplastic thinning (which dominates in region I) and eventually yielding (which evolves through region II) and flow (which saturates in region III), and allows quantification of instantaneous nonlinear parameters associated with yielding. These measures exhibit significant strain rate amplitude dependence above a characteristic frequency, which we argue is governed by poroelastic effects. Correlating these results with time-averaged rheo-USANS measurements reveals that the material passes through a cascade of structural breakdown from large to progressively smaller length scales. In region I, compression of the fractal domains leads to the formation of large voids. In regions II and III, cluster-cluster correlations become increasingly homogeneous, suggesting breakage and eventually depercolation of intercluster bonds at the yield point. All significant structural changes occur on the micron-scale, suggesting that large-scale rearrangements of hundreds or thousands of particles, rather than the homogeneous rearrangement of particle-particle bonds, dominate the initial yielding of heterogeneous colloidal gels.
Fisk, Mark D.; Pasyanos, Michael E.
2016-05-03
Characterizing regional seismic signals continues to be a difficult problem due to their variability. Calibration of these signals is very important to many aspects of monitoring underground nuclear explosions, including detecting seismic signals, discriminating explosions from earthquakes, and reliably estimating magnitude and yield. Amplitude tomography, which simultaneously inverts for source, propagation, and site effects, is a leading method of calibrating these signals. A major issue in amplitude tomography is the data quality of the input amplitude measurements. Pre-event and prephase signal-to-noise ratio (SNR) tests are typically used but can frequently include bad signals and exclude good signals. The deficiencies ofmore » SNR criteria, which are demonstrated here, lead to large calibration errors. To ameliorate these issues, we introduce a semi-automated approach to assess the bandwidth of a spectrum where it behaves physically. We determine the maximum frequency (denoted as Fmax) where it deviates from this behavior due to inflections at which noise or spurious signals start to bias the spectra away from the expected decay. We compare two amplitude tomography runs using the SNR and new Fmax criteria and show significant improvements to the stability and accuracy of the tomography output for frequency bands higher than 2 Hz by using our assessments of valid S-wave bandwidth. We compare Q estimates, P/S residuals, and some detailed results to explain the improvements. Lastly, for frequency bands higher than 4 Hz, needed for effective P/S discrimination of explosions from earthquakes, the new bandwidth criteria sufficiently fix the instabilities and errors so that the residuals and calibration terms are useful for application.« less
NASA Astrophysics Data System (ADS)
Ito, Kazuhito; Nakagawa, Seiji
2015-07-01
A novel hearing aid system utilizing amplitude-modulated bone-conducted ultrasound (AM-BCU) is being developed for use by profoundly deaf people. However, there is a lack of research on the acoustic aspects of AM-BCU hearing. In this study, acoustic fields in the ear canal under AM-BCU stimulation were examined with respect to the self-demodulation effect of amplitude-modulated signal components generated in the ear canal. We found self-demodulated signals with an audible sound pressure level related to the amplitude-modulated signal components of bone-conducted ultrasonic stimulation. In addition, the increases in the self-demodulated signal levels at low frequencies in the ear canal after occluding the ear canal opening, i.e., the positive occlusion effect, indicate the existence of a pathway by which the self-demodulated signals pass through the aural cartilage and soft tissue, and radiate into the ear canal.
One-loop corrections from higher dimensional tree amplitudes
NASA Astrophysics Data System (ADS)
Cachazo, Freddy; He, Song; Yuan, Ellis Ye
2016-08-01
We show how one-loop corrections to scattering amplitudes of scalars and gauge bosons can be obtained from tree amplitudes in one higher dimension. Starting with a complete tree-level scattering amplitude of n + 2 particles in five dimensions, one assumes that two of them cannot be "detected" and therefore an integration over their LIPS is carried out. The resulting object, function of the remaining n particles, is taken to be four-dimensional by restricting the corresponding momenta. We perform this procedure in the context of the tree-level CHY formulation of amplitudes. The scattering equations obtained in the procedure coincide with those derived by Geyer et al. from ambitwistor constructions and recently studied by two of the authors for bi-adjoint scalars. They have two sectors of solutions: regular and singular. We prove that the contribution from regular solutions generically gives rise to unphysical poles. However, using a BCFW argument we prove that the unphysical contributions are always homogeneous functions of the loop momentum and can be discarded. We also show that the contribution from singular solutions turns out to be homogeneous as well.
Reconnaissance amplitude versus offset techniques in the Niger Delta
Barton, J.; Gullette, K.
1996-08-01
Reconnaissance AVO (amplitude vs. offset) techniques have been invaluable in allowing the analyses and mapping of AVO on large-volume data sets in the Nigerian Niger Delta. Forward modelling of rock properties derived from well data on the shelf and regional ties of common depth point gathers to well control show that a shale on hydrocarbon bearing sand typically generates increasing amplitude with offset [Class 2 and Class 3 type anomalies of the Rutherford and Williams (1989) classification]. Consequently, processing and display techniques have been developed that distinguish the increasing amplitude with offset response associated with hydrocarbon bearing sands from the flatter AVO response of background water wet sands and shales. Attributes are created from angle stacks rather than by analyses of individual common depth point gathers over an entire data set. We show examples of a new AVO attribute which we call the Enhanced Restricted Gradient that highlights Class 2 and Class 3 type AVO anomalies more clearly than some of the standard AVO attributes used in the industry. The techniques described here provide a cost-effective and practical way of evaluating AVO character on large volume 2D and 3D data sets and should also be useful in other areas worldwide where hydrocarbon bearing reservoirs generate increasing amplitude with offset.
Note on permutation sum of color-ordered gluon amplitudes
NASA Astrophysics Data System (ADS)
Du, Yi-Jian; Feng, Bo; Fu, Chih-Hao
2012-01-01
In this Letter we show that under BCFW-deformation the large-z behavior of permutation sum of color-ordered gluon amplitudes found by Boels and Isermann in arxiv:arxiv:1109.5888 can be simply understood from the well known Kleiss-Kuijf relation and Bern-Carrasco-Johansson relation.
Nonlinear Saturation Amplitude in Classical Planar Richtmyer-Meshkov Instability
NASA Astrophysics Data System (ADS)
Liu, Wan-Hai; Wang, Xiang; Jiang, Hong-Bin; Ma, Wen-Fang
2016-04-01
The classical planar Richtmyer-Meshkov instability (RMI) at a fluid interface supported by a constant pressure is investigated by a formal perturbation expansion up to the third order, and then according to definition of nonlinear saturation amplitude (NSA) in Rayleigh-Taylor instability (RTI), the NSA in planar RMI is obtained explicitly. It is found that the NSA in planar RMI is affected by the initial perturbation wavelength and the initial amplitude of the interface, while the effect of the initial amplitude of the interface on the NSA is less than that of the initial perturbation wavelength. Without marginal influence of the initial amplitude, the NSA increases linearly with wavelength. The NSA normalized by the wavelength in planar RMI is about 0.11, larger than that corresponding to RTI. Supported by the National Natural Science Foundation of China under Grant Nos. 11472278 and 11372330, the Scientific Research Foundation of Education Department of Sichuan Province under Grant No. 15ZA0296, the Scientific Research Foundation of Mianyang Normal University under Grant Nos. QD2014A009 and 2014A02, and the National High-Tech ICF Committee
Adaptive whitening of the electromyogram to improve amplitude estimation.
Clancy, E A; Farry, K A
2000-06-01
Previous research showed that whitening the surface electromyogram (EMG) can improve EMG amplitude estimation (where EMG amplitude is defined as the time-varying standard deviation of the EMG). However, conventional whitening via a linear filter seems to fail at low EMG amplitude levels, perhaps due to additive background noise in the measured EMG. This paper describes an adaptive whitening technique that overcomes this problem by cascading a nonadaptive whitening filter, an adaptive Wiener filter, and an adaptive gain correction. These stages can be calibrated from two, five second duration, constant-angle, constant-force contractions, one at a reference level [e.g., 50% maximum voluntary contraction (MVC)] and one at 0% MVC. In experimental studies, subjects used real-time EMG amplitude estimates to track a uniform-density, band-limited random target. With a 0.25-Hz bandwidth target, either adaptive whitening or multiple-channel processing reduced the tracking error roughly half-way to the error achieved using the dynamometer signal as the feedback. At the 1.00-Hz bandwidth, all of the EMG processors had errors equivalent to that of the dynamometer signal, reflecting that errors in this task were dominated by subjects' inability to track targets at this bandwidth. Increases in the additive noise level, smoothing window length, and tracking bandwidth diminish the advantages of whitening. PMID:10833845
Amplitude Correction Factors of Korean VLBI Network Observations
NASA Astrophysics Data System (ADS)
Lee, Sang-Sung; Byun, Do-Young; Oh, Chung Sik; Kim, Hyo Ryoung; Kim, Jongsoo; Jung, Taehyun; Oh, Se-Jin; Roh, Duk-Gyoo; Jung, Dong-Kyu; Yeom, Jae-Hwan
2015-10-01
We report results of investigation of amplitude calibration for very long baseline interferometry (VLBI) observations with Korean VLBI Network (KVN). Amplitude correction factors are estimated based on comparison of KVN observations at 22~GHz correlated by Daejeon hardware correlator and DiFX software correlator in Korea Astronomy and Space Science Institute (KASI) with Very Long Baseline Array (VLBA) observations at 22~GHz by DiFX software correlator in National Radio Astronomy Observatory (NRAO). We used the observations for compact radio sources, 3C~454.3, NRAO~512, OJ 287, BL Lac, 3C 279, 1633+382, and 1510-089, which are almost unresolved for baselines in a range of 350-477~km. Visibility data of the sources obtained with similar baselines at KVN and VLBA are selected, fringe-fitted, calibrated, and compared for their amplitudes. We find that visibility amplitudes of KVN observations should be corrected by factors of 1.10 and 1.35 when correlated by DiFX and Daejeon correlators, respectively. These correction factors are attributed to the combination of two steps of 2-bit quantization in KVN observing systems and characteristics of Daejeon correlator.
Large-amplitude inviscid fluid motion in an accelerating container
NASA Technical Reports Server (NTRS)
Perko, L. M.
1968-01-01
Study of dynamic behavior of the liquid-vapor interface of an inviscid fluid in an accelerating cylindrical container includes an analytical-numerical method for determining large amplitude motion. The method is based on the expansion of the velocity potential in a series of harmonic functions with time dependent coefficients.
Production amplitudes in N = 4 SUSY and integrability
Lipatov, L. N.
2009-03-23
Due to the AdS/CFT correspondence in N = 4 SUSY the BFKL Pomeron is equivalent to the reggeized graviton. The BDS ansatz for production amplitudes is not valid beyond one loop due to the presence of the Mandelstam cuts. The hamiltonian for the corresponding reggeon states coincides with the hamiltonian of an integrable open Heisenberg spin chain.
Path integral approach to the quantum fidelity amplitude
2016-01-01
The Loschmidt echo is a measure of quantum irreversibility and is determined by the fidelity amplitude of an imperfect time-reversal protocol. Fidelity amplitude plays an important role both in the foundations of quantum mechanics and in its applications, such as time-resolved electronic spectroscopy. We derive an exact path integral formula for the fidelity amplitude and use it to obtain a series of increasingly accurate semiclassical approximations by truncating an exact expansion of the path integral exponent. While the zeroth-order expansion results in a remarkably simple, yet non-trivial approximation for the fidelity amplitude, the first-order expansion yields an alternative derivation of the so-called ‘dephasing representation,’ circumventing the use of a semiclassical propagator as in the original derivation. We also obtain an approximate expression for fidelity based on the second-order expansion, which resolves several shortcomings of the dephasing representation. The rigorous derivation from the path integral permits the identification of sufficient conditions under which various approximations obtained become exact. PMID:27140973
Saturation amplitude of the f-mode instability
NASA Astrophysics Data System (ADS)
Kastaun, Wolfgang; Willburger, Beatrix; Kokkotas, Kostas D.
2010-11-01
We investigate strong nonlinear damping effects which occur during high amplitude oscillations of neutron stars, and the gravitational waves they produce. For this, we use a general relativistic nonlinear hydrodynamics code in conjunction with a fixed spacetime (Cowling approximation) and a polytropic equation of state (EOS). Gravitational waves are estimated using the quadrupole formula. Our main interest are l=m=2 f modes subject to the CFS (Chandrasekhar, Friedman, Schutz) instability, but we also investigate axisymmetric and quasiradial modes. We study various models to determine the influence of rotation rate and EOS. We find that axisymmetric oscillations at high amplitudes are predominantly damped by shock formation, while the nonaxisymmetric f modes are mainly damped by wave breaking and, for rapidly rotating models, coupling to nonaxisymmetric inertial modes. From the observed nonlinear damping, we derive upper limits for the saturation amplitude of CFS-unstable f modes. Finally, we estimate that the corresponding gravitational waves for an oscillation amplitude at the upper limit should be detectable with the advanced LIGO (Laser Interferometer Gravitational Wave Observatory) and VIRGO interferometers at distances above 10 Mpc. This strongly depends on the stellar model, in particular, on the mode frequency.
A Precise Annotation of Phase-Amplitude Coupling Intensity
Xu, Xiaxia; Zhang, Tao
2016-01-01
Neuronal information can be coded in different temporal and spatial scales. Cross-frequency coupling of neuronal oscillations, especially phase-amplitude coupling (PAC), plays a critical functional role in neuronal communication and large scale neuronal encoding. Several approaches have been developed to assess PAC intensity. It is generally agreed that the PAC intensity relates to the uneven distribution of the fast oscillation amplitude conditioned on the slow oscillation phase. However, it is still not clear what the PAC intensity exactly means. In the present study, it was found that there were three types of interferential signals taking part in PAC phenomenon. Based on the classification of interferential signals, the conception of PAC intensity is theoretically annotated as the proportion of slow or fast oscillation that is involved in a related PAC phenomenon. In order to make sure that the annotation is proper to some content, simulation data are constructed and then analyzed by three PAC approaches. These approaches are the mean vector length (MVL), the modulation index (MI), and a new permutation mutual information (PMI) method in which the permutation entropy and the information theory are applied. Results show positive correlations between PAC values derived from all three methods and the suggested intensity. Finally, the amplitude distributions, i.e. the phase-amplitude plots, obtained from different PAC intensities show that the annotation proposed in the study is in line with the previous understandings. PMID:27701458
Contextual Modulation of N400 Amplitude to Lexically Ambiguous Words
ERIC Educational Resources Information Center
Titone, Debra A.; Salisbury, Dean F.
2004-01-01
Through much is known about the N400 component, an event-related EEG potential that is sensitive to semantic manipulations, it is unclear whether modulations of N400 amplitude reflect automatic processing, controlled processing, or both. We examined this issue using a semantic judgment task that manipulated local and global contextual cues. Word…
Path integral approach to the quantum fidelity amplitude.
Vaníček, Jiří; Cohen, Doron
2016-06-13
The Loschmidt echo is a measure of quantum irreversibility and is determined by the fidelity amplitude of an imperfect time-reversal protocol. Fidelity amplitude plays an important role both in the foundations of quantum mechanics and in its applications, such as time-resolved electronic spectroscopy. We derive an exact path integral formula for the fidelity amplitude and use it to obtain a series of increasingly accurate semiclassical approximations by truncating an exact expansion of the path integral exponent. While the zeroth-order expansion results in a remarkably simple, yet non-trivial approximation for the fidelity amplitude, the first-order expansion yields an alternative derivation of the so-called 'dephasing representation,' circumventing the use of a semiclassical propagator as in the original derivation. We also obtain an approximate expression for fidelity based on the second-order expansion, which resolves several shortcomings of the dephasing representation. The rigorous derivation from the path integral permits the identification of sufficient conditions under which various approximations obtained become exact.
Maximally supersymmetric planar Yang-Mills amplitudes at five loops
Bern, Z.; Carrasco, J. J. M.; Johansson, H.; Kosower, D. A.
2007-12-15
We present an Ansatz for the planar five-loop four-point amplitude in maximally supersymmetric Yang-Mills theory in terms of loop integrals. This Ansatz exploits the recently observed correspondence between integrals with simple conformal properties and those found in the four-point amplitudes of the theory through four loops. We explain how to identify all such integrals systematically. We make use of generalized unitarity in both four and D dimensions to determine the coefficients of each of these integrals in the amplitude. Maximal cuts, in which we cut all propagators of a given integral, are an especially effective means for determining these coefficients. The set of integrals and coefficients determined here will be useful for computing the five-loop cusp anomalous dimension of the theory which is of interest for nontrivial checks of the AdS/CFT duality conjecture. It will also be useful for checking a conjecture that the amplitudes have an iterative structure allowing for their all-loop resummation, whose link to a recent string-side computation by Alday and Maldacena opens a new venue for quantitative AdS/CFT comparisons.
The Determination of Pseudoscalar Meson Photoproduction Amplitudes from Complete Experiments
A. M. Sandorfi, S. Hoblit, H. Kamano, and T-S. H. Lee
2011-10-01
A new generation of complete experiments is currently underway with the goal of performing a high precision extraction of pseudoscalar meson photo-production amplitudes. Here we review the most general analytic form of the cross section, dependent upon the three polarization vectors of the beam, target and recoil baryon, including all single, double and triple-polarization terms involving 16 spin-dependent observables. Analytic expressions that determine the recoil baryon polarization are also presented. Different conventions are in use in the literature and we have used a numerical calculation of cross sections from Chew-Goldberger-Low-Nambu amplitudes with arbitrary spin projections to clarify apparent sign differences. As an illustration of the use of this machinery, we carry out a multipole analysis of the gammap --> K+Lambda reaction and examine the impact of recently published polarization measurements. In fitting multipoles, we use a combined Monte Carlo sampling of the amplitude space, with gradient minimization, and find a shallow chi2 valley pitted with a very large number of local minima, despite the inclusion of recent data on 8 different observables. We conclude that, while a mathematical solution to the problem of determining an amplitude free of ambiguities may require 8 observables, as has been pointed out in the literature, experiments with realistically achievable uncertainties will require a significantly larger number.
End point behaviour of the pion distribution amplitude
NASA Astrophysics Data System (ADS)
Szcepaniak, Adam; Mankiewicz, Lech
1991-08-01
We study the end point structure of the pion distribution amplitude and reexamine the perturbative analysis of the high-Q2 pion form factor in the factorization approach. Permanent address: Nicolaus Copernicus Astronomical Centre, Bartycka 18, PL-00-716 Warsaw, Poland.
Quantitative phase-amplitude microscopy. III. The effects of noise.
Paganin, D; Barty, A; McMahon, P J; Nugent, K A
2004-04-01
We explore the effect of noise on images obtained using quantitative phase-amplitude microscopy - a new microscopy technique based on the determination of phase from the intensity evolution of propagating radiation. We compare the predictions with experimental results and also propose an approach that allows good-quality quantitative phase retrieval to be obtained even for very noisy data.
Path integral approach to the quantum fidelity amplitude.
Vaníček, Jiří; Cohen, Doron
2016-06-13
The Loschmidt echo is a measure of quantum irreversibility and is determined by the fidelity amplitude of an imperfect time-reversal protocol. Fidelity amplitude plays an important role both in the foundations of quantum mechanics and in its applications, such as time-resolved electronic spectroscopy. We derive an exact path integral formula for the fidelity amplitude and use it to obtain a series of increasingly accurate semiclassical approximations by truncating an exact expansion of the path integral exponent. While the zeroth-order expansion results in a remarkably simple, yet non-trivial approximation for the fidelity amplitude, the first-order expansion yields an alternative derivation of the so-called 'dephasing representation,' circumventing the use of a semiclassical propagator as in the original derivation. We also obtain an approximate expression for fidelity based on the second-order expansion, which resolves several shortcomings of the dephasing representation. The rigorous derivation from the path integral permits the identification of sufficient conditions under which various approximations obtained become exact. PMID:27140973
Cross-Channel Amplitude Sweeps Are Crucial to Speech Intelligibility
ERIC Educational Resources Information Center
Prendergast, Garreth; Green, Gary G. R.
2012-01-01
Classical views of speech perception argue that the static and dynamic characteristics of spectral energy peaks (formants) are the acoustic features that underpin phoneme recognition. Here we use representations where the amplitude modulations of sub-band filtered speech are described, precisely, in terms of co-sinusoidal pulses. These pulses are…
Saturation amplitude of the f-mode instability
Kastaun, Wolfgang; Willburger, Beatrix; Kokkotas, Kostas D.
2010-11-15
We investigate strong nonlinear damping effects which occur during high amplitude oscillations of neutron stars, and the gravitational waves they produce. For this, we use a general relativistic nonlinear hydrodynamics code in conjunction with a fixed spacetime (Cowling approximation) and a polytropic equation of state (EOS). Gravitational waves are estimated using the quadrupole formula. Our main interest are l=m=2 f modes subject to the CFS (Chandrasekhar, Friedman, Schutz) instability, but we also investigate axisymmetric and quasiradial modes. We study various models to determine the influence of rotation rate and EOS. We find that axisymmetric oscillations at high amplitudes are predominantly damped by shock formation, while the nonaxisymmetric f modes are mainly damped by wave breaking and, for rapidly rotating models, coupling to nonaxisymmetric inertial modes. From the observed nonlinear damping, we derive upper limits for the saturation amplitude of CFS-unstable f modes. Finally, we estimate that the corresponding gravitational waves for an oscillation amplitude at the upper limit should be detectable with the advanced LIGO (Laser Interferometer Gravitational Wave Observatory) and VIRGO interferometers at distances above 10 Mpc. This strongly depends on the stellar model, in particular, on the mode frequency.
Large-amplitude motion in polymer crystals and mesophases
Wunderlich, B. |
1994-12-31
Large-amplitude motion of macromolecules involves mainly rotation about bonds (conformational motion). In the liquid phases, the large- amplitude motion is coupled with disorder and accounts for the flow and viscoelastic behavior. Perfectly ordered crystals, in contrast, permit only little large-amplitude motion. The mesophases are intermediate in order and mobility. In crystals, large-amplitude motion leads initially to gauche defects and kinks (conformational defects), and ultimately may produce conformationally disordered crystals (conis crystals). Molecular dynamics simulations of crystals with up to 30,000 atoms have been carried out and show the mechanism of defect formation, permit the study of the distribution of defects, and the visualization of hexagonal crystals. Distinction between main-chain liquid-crystalline macromolecules and condis crystals, the two mesophases of polymers, can be done on basis of analysis of phase separation (partial crystallinity), present in condis crystals and not in liquid crystals. Solid state NMR is the tool of choice for detecting mobile and rigid phases. In highly drawn fibers one can find four different states of order and mobility. Besides the (defect) crystalline phase and the isotropic amorphous phase, an intermediate oriented phase and a rigid amorphous phase exists.
Structure of the Small Amplitude Motion on Transversely Sheared Mean Flows
NASA Technical Reports Server (NTRS)
Goldstein, Marvin E.; Afsar, Mohamed Z.; Leib, Stewart J.
2013-01-01
This paper considers the small amplitude unsteady motion of an inviscid non-heat conducting compressible fluid on a transversely sheared mean flow. It extends a previous result given in Goldstein (1978(b) and 1979(a)) which shows that the hydrodynamic component of the motion is determined by two arbitrary convected quantities in the absence of solid surfaces or other external sources. The result is important because it can be used to specify appropriate boundary conditions for unsteady surface interaction problems on transversely sheared mean flows in the same way that the vortical component of the Kovasznay (1953) decomposition is used to specify these conditions for surface interaction problems on uniform mean flows. But unlike the Kovasznay (1953) case the arbitrary convected quantities no longer bear a simple relation to the physical variables. One purpose of this paper is to derive a formula that relates these quantities to the (physically measurable) vorticity and pressure fluctuations in the flow.
Joint inversion of surface and borehole magnetic amplitude data
NASA Astrophysics Data System (ADS)
Li, Zelin; Yao, Changli; Zheng, Yuanman; Yuan, Xiaoyu
2016-04-01
3D magnetic inversion for susceptibility distribution is a powerful tool in quantitative interpretation of magnetic data in mineral exploration. However, the inversion and interpretation of such data are faced with two problems. One problem is the poor imaging results of deep sources when only surface data are inverted. The other is the unknown total magnetization directions of sources when strong remanence exists. To deal with these problems simultaneously, we propose a method through the joint inversion of surface and borehole magnetic amplitude data. In this method, we first transform both surface and borehole magnetic data to magnetic amplitude data that are less sensitive to the directions of total magnetization, and then preform a joint inversion of the whole amplitude data to generate a 3D susceptibility distribution. The amplitude inversion algorithm uses Tikhonov regularization and imposes a positivity constraint on the effective susceptibility defined as the ratio of magnetization magnitude over the geomagnetic field strength. In addition, a distance-based weighting function is used to make the algorithm applicable to joint data sets. To solve this positivity-constraint inversion problem efficiently, an appropriate optimization method must be chosen. We first use an interior-point method to incorporate the positivity constraint into the total objective function, and then minimize the objective function via a Gauss-Newton method due to the nonlinearity introduced by the positivity constraint and the amplitude data. To further improve the efficiency of the inversion algorithm, we use a conjugate gradient method to carry out the fast matrix-vector multiplication during the minimization. To verify the utility of the proposed method, we invert the synthetic and field data using three inversion methods, including the joint inversion of surface and borehole three-component magnetic data, the inversion of surface magnetic amplitude data, and the proposed joint
Nonlinear amplitude frequency characteristics of attenuation in rock under pressure
NASA Astrophysics Data System (ADS)
Mashinskii, E. I.
2006-12-01
Laboratory experiments have been carried out to investigate the influence of change in strain amplitude on the frequency dependence of attenuation in samples of sandstone, smoky quartz and duralumin. The measurements were performed using the reflection method on pulse frequency of 1 MHz in the strain range ~(0.3-2.0) × 10-6 under a confining pressure of 20 MPa. The attenuation in rocks is nonlinearly dependent on frequency and strain amplitude. In sandstone for P-waves and in smoky quartz for P- and S-waves, the dependences Q-1p(f) and Q-1s(f) have the attenuation peak. With increasing amplitude, the peak frequency can shift towards both the lower and the higher frequencies. It depends on the location of the frequency of an incident (input) pulse with respect to the peak frequency on the frequency axis. For sandstone the peak frequency of P-waves shifts towards the higher frequencies. For smoky quartz the shift of peak frequency is absent in P-waves, and S-waves shift towards the lower frequencies. The attenuation at the incident frequency always monotonically decreases with amplitude, and the other frequency components have complex or monotonic characters depending on the location of the incident frequency in the relaxation spectrum. Q-1p(f) in duralumin has monotonic character, i.e. a relaxation peak in the measurement frequency band is absent. Attenuation strongly decreases with increasing frequency and weakly depends on strain amplitude. The curve Q-1s(f) has an attenuation peak, and its character essentially depends on strain amplitude. With increasing amplitude, the peak frequency shifts towards the lower frequencies. The unusual increase of peak frequency of the P-wave spectrum in the bottom reflection in comparison with peak frequency in spectrum of the initial reflection is detected. The unusual behaviour of attenuation is explained by features of the joint action of viscoelastic and microplastic mechanisms. These results can be used for improving methods
Analytical parameters for amplitude-modulated multiplexed flow analysis.
Kurokawa, Yohei; Takeuchi, Masaki; Tanaka, Hideji
2010-01-01
Analytical conditions of amplitude-modulated multiplexed flow analysis, the basic concept of which was recently proposed by our group, are investigated for higher sample throughput rate. The performance of the improved system is evaluated by applying it to the determination of chloride ions. The flow rates of two sample solutions are independently varied in accordance with sinusoidal voltage signals, each having different frequency. The solutions are merged with a reagent solution and/or a diluent, while the total flow rate is held constant. Downstream, the analytical signal V(d) is monitored with a spectrophotometer. The V(d) shows a complicated profile resulting from amplitude modulated and multiplexed information on the two samples. The V(d) can, however, be deconvoluted to the contribution of each sample through fast Fourier transform (FFT). The amplitudes of the separated wave components are closely related to the concentrations of the analytes in the samples. By moving the window for FFT analysis with time, a temporal profile of the amplitudes can be obtained in real-time. Analytical conditions such as modulation period and system configuration have been optimized using aqueous solutions of Malachite Green (MG). Adequate amplitudes are obtained at the period of as low as 5 s. At this period, the calibration curve for the MG concentration of 0-30 micromol dm(-3) has enough linearity (r(2) = 0.999) and the limit of detection (3.3sigma) is 1.3 micromol dm(-3); the relative standard deviation of repeated measurements (C(MG) = 15 micromol dm(-3), n = 10) is 2.4%. The developed system has been applied to the determination of chloride ions by a mercury(II) thiocyanate method. The system can adequately follow the changes in analyte concentration. The recoveries of chloride ion spiked in real water samples (river and tap water) are satisfactory, around 100%. PMID:20631441
Observing rapid quasi-wave ionospheric disturbance using amplitude charts
NASA Astrophysics Data System (ADS)
Kurkin, Vladimir; Laryunin, Oleg; Podlesnyi, Alexey
Data from vertical (quasi-vertical) sounding are traditionally used for determining a number of ionospheric parameters such as critical frequencies of E and F layers, peaks of these layers, and for reconstructing electron density profiles. In this respect, radio sounding is not used to its full capacity. Modern ionosondes provide additional information encoded in ionospheric echoes, including information on reflected-signal amplitude. The time dependence of the amplitude-frequency characteristic of reflected signal has been named "amplitude chart" (A-chart). Ionosondes used by the ISTP SB RAS Geophysical Observatory for constructing A-charts employ the frequency-modulated continuous-wave (FMCW) signal in a range 1.3-15 MHz. One-minute sounding interval allows a more detailed study of dynamic processes in the ionosphere. The ionosonde has a direct digital synthesizer and direct sampling receiver without automatic gain control (AGC). The absence of AGC and the high dynamic range enable determination of the relative field strength at a receiving point and registration of relative long-term variations in reflected-signal amplitude over the entire range of operating frequencies of the ionosonde. We have revealed that the passage of travelling ionospheric disturbances (TID) along with height-frequency distortion modulates amplitude characteristics of signal. The characteristic depth of the modulation reaches 40 dB. The pronounced alternate vertical stripes typical for A-charts are likely to be associated with focusing properties of TID. In order to examine the space-time structure of TID able to induce such a focusing of the radio waves, we performed ray tracing simulations. We used geometrical-optics approximation, took magneto-ionic effects into account and prescribed electron density to be a stratified electron density profile on which an undulating disturbance was superimposed. This work was supported by the RFBR grant №14-05-00259-а.
Volumetric imaging with an amplitude-steered array.
Frazier, Catherine H; Hughes, W Jack; O'Brien, William D
2002-12-01
Volumetric acoustic imaging is desirable for the visualization of underwater objects and structures; however, the implementation of a volumetric imaging system is difficult due to the high channel count of a fully populated two-dimensional array. Recently, a linear amplitude-steered array with a reduced electronics requirement was presented, which is capable of collecting a two-dimensional set of data with a single transmit pulse. In this study, we demonstrate the use of the linear amplitude-steered array and associated image formation algorithms for collecting and displaying volumetric data; that is, proof of principle of the amplitude-steering concept and the associated image formation algorithms is demonstrated. Range and vertical position are obtained by taking advantage of the frequency separation of a vertical linear amplitude-steered array. The third dimension of data is obtained by rotating the array such that the mainlobe is mechanically steered in azimuth. Data are collected in a water tank at the Pennsylvania State University Applied Research Laboratory for two targets: a ladder and three pipes. These data are the first experimental data collected with an amplitude-steered array for the purposes of imaging. The array is 10 cm in diameter and is operated in the frequency range of 80 to 304 kHz. Although the array is small for high-resolution imaging at these frequencies, the rungs of the ladder are recognizable in the images. The three pipes are difficult to discern in two of the projection images; however, the pipes separated in range are clear in the image showing vertical position versus range. The imaging concept is demonstrated on measured data, and the simulations agree well with the experimental results. PMID:12508995
[Methods for quantifying phasic skin conductance amplitudes: threats to validity?].
Zimmer, H; Vossel, G
1993-01-01
Two methods of determining the event-related skin conductance response (SCR) amplitude are in common use. In one of these, the difference in conductance between the point of onset and the peak level of a single wave is measured (method 1). The second approach is to determine the difference between two measures, one characterizing the prestimulus level, the other the highest conductance point of the SCR reached within a fixed period following the stimulus (method 2). A problem with quantifying the SCR amplitude occurs when a SCR is elicited before an immediately preceding response has had time to recover, because in this case the two methods lead to quite different values. If the amplitude of each response is measured from its own individual deflection point, the measurable amplitude of the second response will be smaller when it occurs immediately after or in the ascending limb of the first response. The problem is most evident in situations with a high probability of response superimposition, such as when a large number of nonspecific responses occur at the same time as the SCRs. This is found in individuals with a high degree of electrodermal lability. Electrodermal lability refers to a psychophysiological construct that is operationally defined by the frequency of spontaneous electrodermal fluctuations. In the present study, we therefore systematically investigated the effects of the two score methods on SCR amplitude in relation to lability by analyzing electrodermal data from two habituation studies. As expected, several method-specific effects which were related to lability emerged. Results and questions concerning the relevance of the findings are discussed, with special emphasis on the validity of psychophysiological investigations.
Physical Development: Thinking Physically
ERIC Educational Resources Information Center
Strickland, Erik
2005-01-01
Children grow and develop physically according to their own experiences, characteristics, and abilities. Physical development is so important and the environment should allow each child to find her space in the sunshine. This can be done by: (1) creating the right outdoor environment; (2) allowing children time to use it; (3) encouraging movement…
Human Neuromagnetic Steady-State Responses to Amplitude-Modulated Tones, Speech, and Music
Parkkonen, Lauri; Hari, Riitta
2014-01-01
Objectives: Auditory steady-state responses that can be elicited by various periodic sounds inform about subcortical and early cortical auditory processing. Steady-state responses to amplitude-modulated pure tones have been used to scrutinize binaural interaction by frequency-tagging the two ears’ inputs at different frequencies. Unlike pure tones, speech and music are physically very complex, as they include many frequency components, pauses, and large temporal variations. To examine the utility of magnetoencephalographic (MEG) steady-state fields (SSFs) in the study of early cortical processing of complex natural sounds, the authors tested the extent to which amplitude-modulated speech and music can elicit reliable SSFs. Design: MEG responses were recorded to 90-s-long binaural tones, speech, and music, amplitude-modulated at 41.1 Hz at four different depths (25, 50, 75, and 100%). The subjects were 11 healthy, normal-hearing adults. MEG signals were averaged in phase with the modulation frequency, and the sources of the resulting SSFs were modeled by current dipoles. After the MEG recording, intelligibility of the speech, musical quality of the music stimuli, naturalness of music and speech stimuli, and the perceived deterioration caused by the modulation were evaluated on visual analog scales. Results: The perceived quality of the stimuli decreased as a function of increasing modulation depth, more strongly for music than speech; yet, all subjects considered the speech intelligible even at the 100% modulation. SSFs were the strongest to tones and the weakest to speech stimuli; the amplitudes increased with increasing modulation depth for all stimuli. SSFs to tones were reliably detectable at all modulation depths (in all subjects in the right hemisphere, in 9 subjects in the left hemisphere) and to music stimuli at 50 to 100% depths, whereas speech usually elicited clear SSFs only at 100% depth. The hemispheric balance of SSFs was toward the right hemisphere
Detailed analysis of amplitude and recurrence times of LP activity at Mt. Etna Volcano, Italy.
NASA Astrophysics Data System (ADS)
Cauchie, L.; Saccorotti, G.; Bean, C.; de Barros, L.
2012-04-01
streams, in order to discriminate small-amplitude events previously undetected by the STA/LTA triggering method. This procedure allowed for a significant enrichment of the catalogues, from which we retrieved amplitudes and inter-event times associated with individual families. The retrieved amplitude distributions differ significantly from the GR law, and there is no clear relationship between events amplitude and recurrence times. Comparison with data from both lab experiments and numerical simulations of (i) brittle-fracturing of high-viscosity materials, and (ii) fluid flow under different regimes, are needed in order to better understand the physics governing the observed distributions. Hopefully, these steps will lead to an improved understanding of LP activity, in turn clarifying their significance in terms of eruption forecasting.
Evidence that Stress Amplitude Does Not Affect the Temporal Distribution of Aftershocks
NASA Astrophysics Data System (ADS)
Felzer, K. R.
2005-12-01
Most physical aftershock triggering models, including the rate and state friction model of Dieterich (1994), the stress corrosion model (see discussion in Gomberg, 2001) and other accelerating failure models predict that larger stress changes on a fault will lead to an aftershocks that happens more quickly (larger clock advance), all else equal. Thus as stress change amplitude decreases with distance from the mainshock, there is an expected shift in the aftershock distribution toward longer time delays. This effect was formalized by Dieterich (1994) as an increase of the modified Omori Law c value (N(t) = A/(t+c)p where t = time, N(t) = aftershock rate, and A, p, and c are constants). Jones and Hauksson (1998), however, found no change in c value with distance after the 1992 MW 7.3 Landers earthquake. The assumption that the aftershock temporal distribution is independent of distance is also made in ETAS (Epidemic Triggering Aftershock Sequence) aftershock simulations (Ogata, 1998; Helmstetter, 2002) without adverse affect on fitting real data. Here we verify the independence of stress change and aftershock temporal distribution using a data set of 33 M 5-6 mainshocks from throughout California. These mainshocks are large enough to produce a significant number of aftershocks in the near and far field, but small enough to be frequent and thus provide good statistical sampling. Our data verifies that the temporal distribution of aftershocks is independent of stress change amplitude. We suggest that the most likely explanation for this observation is that the timing of each fault that participates in an aftershock sequence is independent of the amplitude of the stress that triggers it. In this case aftershock decay with distance from the mainshock cannot be caused by smaller clock advances on lesser-stressed faults, as in the Dieterich (1994) model, but rather by a stress amplitude dependent probability that a fault will be clock advanced at all. In future work we
Hepta-cuts of two-loop scattering amplitudes
NASA Astrophysics Data System (ADS)
Badger, Simon; Frellesvig, Hjalte; Zhang, Yang
2012-04-01
We present a method for the computation of hepta-cuts of two loop scattering amplitudes. Four dimensional unitarity cuts are used to factorise the integrand onto the product of six tree-level amplitudes evaluated at complex momentum values. Using Gram matrix constraints we derive a general parameterisation of the integrand which can be computed using polynomial fitting techniques. The resulting expression is further reduced to master integrals using conventional integration by parts methods. We consider both planar and non-planar topologies for 2 → 2 scattering processes and apply the method to compute hepta-cut contributions to gluon-gluon scattering in Yang-Mills theory with adjoint fermions and scalars.
Nonrelativistic Dynamics of the Amplitude (Higgs) Mode in Superconductors.
Cea, T; Castellani, C; Seibold, G; Benfatto, L
2015-10-01
Despite the formal analogy with the Higgs particle, the amplitude fluctuations of the order parameter in weakly coupled superconductors do not identify a real mode with a Lorentz-invariant dynamics. Indeed, its resonance occurs at 2Δ_{0}, which coincides with the threshold 2E_{gap} for quasiparticle excitations that spoil any relativistic dynamics. Here we investigate the fate of the Higgs mode in the unconventional case where 2E_{gap} becomes larger than 2Δ_{0}, as due to strong coupling or strong disorder. We show that also in this situation, the amplitude fluctuations never identify a real mode at 2Δ_{0}, since such a "bosonic" limit is always reached via strong mixing with the phase fluctuations, which dominate the low-energy part of the spectrum. Our results have direct implications for the interpretation of the subgap optical absorption in disordered superconductors.
Pump pulse duration dependence of coherent phonon amplitudes in antimony
NASA Astrophysics Data System (ADS)
Misochko, O. V.
2016-08-01
Coherent optical phonons of A 1 k and E k symmetry in antimony have been studied using the femtosecond pump-probe technique. By varying the pump-pulse duration and keeping the probe duration constant, it was shown that the amplitude of coherent phonons of both symmetries exponentially decreases with increasing pulse width. It was found that the amplitude decay rate for the fully symmetric phonons with larger frequency is greater than that of the doubly degenerate phonons, whereas the frequency and lifetime for coherent phonons of both symmetries do not depend on the pump-pulse duration. Based on this data, the possibility of separation between dynamic and kinematic contributions to the generation mechanism of coherent phonons is discussed.
Nonrelativistic Dynamics of the Amplitude (Higgs) Mode in Superconductors.
Cea, T; Castellani, C; Seibold, G; Benfatto, L
2015-10-01
Despite the formal analogy with the Higgs particle, the amplitude fluctuations of the order parameter in weakly coupled superconductors do not identify a real mode with a Lorentz-invariant dynamics. Indeed, its resonance occurs at 2Δ_{0}, which coincides with the threshold 2E_{gap} for quasiparticle excitations that spoil any relativistic dynamics. Here we investigate the fate of the Higgs mode in the unconventional case where 2E_{gap} becomes larger than 2Δ_{0}, as due to strong coupling or strong disorder. We show that also in this situation, the amplitude fluctuations never identify a real mode at 2Δ_{0}, since such a "bosonic" limit is always reached via strong mixing with the phase fluctuations, which dominate the low-energy part of the spectrum. Our results have direct implications for the interpretation of the subgap optical absorption in disordered superconductors. PMID:26550746
Finite-amplitude solutions in rotating Hagen-Poiseuille flow
NASA Astrophysics Data System (ADS)
Pier, Benoît; Kumar, Abhishek; Govindarajan, Rama
2015-11-01
While the pipe Poiseuille base flow is linearly stable at all Reynolds numbers, a small amount of rotation of the pipe around its axis induces linear instability beyond a low critical Reynolds number Rc ~= 83 [Pedley, J. Fluid Mech. 1969]. More recently [Fernandez-Feria and del Pino, Phys. Fluids 2002], this configuration has been shown to become absolutely unstable at Reynolds numbers of the same order of magnitude. Using direct numerical simulations, we investigate here finite-amplitude solutions resulting from saturation of exponentially growing small-amplitude initial perturbations. The base flow depends on two dynamical parameters (axial Reynolds number and rotation rate) and the initial perturbation is characterized by its axial wavenumber and its azimuthal mode number. The range of nonlinear waves prevailing in this configuration, the associated nonlinear dispersion relation and the spatial structure of these solutions are systematically obtained by exploring the parameter space. Funding from CEFIPRA is gratefully acknowledged.
Fidelity amplitude of the scattering matrix in microwave cavities
NASA Astrophysics Data System (ADS)
Schäfer, R.; Gorin, T.; Seligman, T. H.; Stöckmann, H.-J.
2005-06-01
The concept of fidelity decay is discussed from the point of view of the scattering matrix, and the 'scattering fidelity' is introduced as the parametric cross-correlation of a given S-matrix element, taken in the time domain, normalized by the corresponding autocorrelation function. We show that for chaotic systems, this quantity represents the usual fidelity amplitude, if appropriate ensemble and/or energy averages are taken. We present a microwave experiment where the scattering fidelity is measured for an ensemble of chaotic systems. The results are in excellent agreement with random matrix theory for the standard fidelity amplitude. The only parameter, namely the perturbation strength, could be determined independently from level dynamics of the system, thus providing agreement between theory and experiment without any free fit parameter.
Analytic evolution of singular distribution amplitudes in QCD
NASA Astrophysics Data System (ADS)
Radyushkin, A. V.; Tandogan, A.
2014-04-01
We describe a method of analytic evolution of distribution amplitudes (DAs) that have singularities, such as nonzero values at the end points of the support region, jumps at some points inside the support region and cusps. We illustrate the method by applying it to the evolution of a flat (constant) DA and antisymmetric flat DA, and then use the method for evolution of the two-photon generalized distribution amplitude. Our approach has advantages over the standard method of expansion in Gegenbauer polynomials, which requires an infinite number of terms in order to accurately reproduce functions in the vicinity of singular points, and over a straightforward iteration of an initial distribution with evolution kernel. The latter produces logarithmically divergent terms at each iteration, while in our method the logarithmic singularities are summed from the start, which immediately produces a continuous curve, with only one or two iterations needed afterwards in order to get rather precise results.
Symbol rate identification for auxiliary amplitude modulation optical signal
NASA Astrophysics Data System (ADS)
Wei, Junyu; Dong, Zhi; Huang, Zhiping; Zhang, Yimeng
2016-09-01
In this paper, we creatively propose and demonstrate a method for symbol rate identification (SRI) of auxiliary amplitude modulation (AAM) optical signal based on asynchronous delay-tap sampling (ADTS) and average magnitude difference function (AMDF). The method can accurately estimate symbol rate and has large transmission impairments tolerance. Furthermore, it can be realized in the digital signal processor (DSP) with low logical resources because of multiplication-free. In order to improve the accuracy of SRI, the peak to valley ratio (PTVR) of AMDF is introduced into our method for blind chromatic dispersion (CD) compensation. The results of the numerical simulations show that the overall maximum SRI error is smaller 0.079% for return-to-zero (RZ) on-off keying (OOK), RZ differential phase-shift keying (DPSK), RZ differential quadrature phase-shift keying (DQPSK) and RZ 16-ary quadrature amplitude modulation (QAM) with 50% duty cycles.
Towards an amplitude analysis of exclusive. gamma gamma. processes
Pennington, M.R.
1988-06-01
The potential of two photon processes to shed light on the parton content of resonances, we maintain, can only be realized in practice by moving towards an Amplitude Analysis of experimental data. By using the process ..gamma gamma.. ..-->.. ..pi pi.. as an example, the way to do this is discussed. Presently claimed uncertainties in the ..gamma gamma.. width of even the well-known f/sub 2/ (1270) are shown to be over-optimistic and the fitted couplings of the overlapping scalar states in the 1 GeV region meaningless. Only the use of Amplitude Analysis techniques on the new higher statistics data from SLAC and DESY can resolve these uncertainties and lead to definite and significant results. 37 refs., 18 figs.
Infrared singularities of scattering amplitudes in perturbative QCD
Becher, Thomas; Neubert, Matthias
2013-11-01
An exact formula is derived for the infrared singularities of dimensionally regularized scattering amplitudes in massless QCD with an arbitrary number of legs, valid at any number of loops. It is based on the conjecture that the anomalous-dimension matrix of n-jet operators in soft-collinear effective theory contains only a single non-trivial color structure, whose coefficient is the cusp anomalous dimension of Wilson loops with light-like segments. Its color-diagonal part is characterized by two anomalous dimensions, which are extracted to three-loop order from known perturbative results for the quark and gluon form factors. This allows us to predict the three-loop coefficients of all 1/epsilon^k poles for an arbitrary n-parton scattering amplitudes, generalizing existing two-loop results.
Hexagonal multiple phase-and-amplitude-shift-keyed signal sets
NASA Technical Reports Server (NTRS)
Simon, M. K.; Smith, J. G.
1973-01-01
Selection of a particular signal set array for a bandwidth-constrained multiple phase-and-amplitude-shift-keyed (MPASK) communication system for a linear additive Gaussian noise channel requires consideration of factors such as average and/or peak power vs symbol error probability, signal amplitude dynamic range, simplicity of generation and detection, and number of bit errors per symbol error (Gray code properties). A simple technique is presented for generating and optimally detecting the honeycomb (hexagonal) signal set, i.e., the signal set that has the tightest sphere-packing properties. The symbol and bit error probability performance of this set is compared to other two-dimensional signal sets that have been investigated in the literature, and is shown to be slightly superior from an average power standpoint. The paper concludes with a comparison of all of these signal sets from the standpoint of the factors listed above.
Light-induced suppression of endogenous circadian amplitude in humans
NASA Technical Reports Server (NTRS)
Jewett, Megan; Czeisler, Charles A.; Kronauer, Richard E.
1991-01-01
A recent demonstration that the phase of the human circadian pacemaker could be inverted using an unconventional three-cycle stimulus has led to an investigation of whether critically timed exposure to a more moderate stimulus could drive that oscillator toward its singularity, a phaseless position at which the amplitude of circadian oscillation is zero. It is reported here that exposure of humans to fewer cycles of bright light, centered around the time at which the human circadian pacemaker is most sensitive to light-induced phase shifts, can markedly attenuate endogenous cicadian amplitude. In some cases this results in an apparent loss of rhythmicity, as expected to occur in the region of singularity.
Molecular dynamics simulation of amplitude modulation atomic force microscopy.
Hu, Xiaoli; Egberts, Philip; Dong, Yalin; Martini, Ashlie
2015-06-12
Molecular dynamics (MD) simulations were used to model amplitude modulation atomic force microscopy (AM-AFM). In this novel simulation, the model AFM tip responds to both tip-substrate interactions and to a sinusoidal excitation signal. The amplitude and phase shift of the tip oscillation observed in the simulation and their variation with tip-sample distance were found to be consistent with previously reported trends from experiments and theory. These simulation results were also fit to an expression enabling estimation of the energy dissipation, which was found to be smaller than that in a corresponding experiment. The difference was analyzed in terms of the effects of tip size and substrate thickness. Development of this model is the first step toward using MD to gain insight into the atomic-scale phenomena that occur during an AM-AFM measurement.
Analytical {pi}{pi} scattering amplitude and the light scalars
Achasov, N. N.; Kiselev, A. V.
2011-03-01
In this work we construct the {pi}{pi} scattering amplitude T{sub 0}{sup 0} with regular analytical properties in the s complex plane, which describes simultaneously the data on the {pi}{pi} scattering, {phi}{yields}{pi}{sup 0}{pi}0{gamma} decay, and {pi}{pi}{yields}KK reaction. The chiral shielding of the {sigma}(600) meson and its mixing with the f{sub 0}(980) meson are also taken into account. The data agrees with the four-quark nature of the {sigma}(600) and f{sub 0}(980) mesons. The amplitude in the range -5m{sub {pi}}{sup 2}
Amplitude Modulation in the ZZ Ceti Star GD 244
NASA Astrophysics Data System (ADS)
Bognár, Zs.; Paparó, M.; Molnár, L.; Plachy, E.; Sódor, Á.
2015-06-01
Previous studies of GD 244 revealed seven pulsation frequencies (two doublets and three single periods) in the light variations of the star. The data obtained at McDonald Observatory between 2003 and 2006, and our additional measurements in 2006 and 2007 at Konkoly Observatory, allow the investigation of the long-term pulsational behaviour of GD 244. We found that the 307.1 s period component of one of the doublets show long-term, periodic amplitude modulation with a time scale of ˜ 740 days. Possible explanations are that nonlinear resonant mode coupling is operating among the rotationally split frequency components, or two modes, unresolved in the yearly data are excited at ˜ 307.1 s. This is the first time that such long-term periodic amplitude modulation is published on a ZZ Ceti star.
Evaluation of the Cachazo-He-Yuan gauge amplitude
NASA Astrophysics Data System (ADS)
Lam, C. S.; Yao, York-Peng
2016-05-01
The Cachazo-He-Yuan (CHY) formula for n -gluon scattering is known to give the same amplitude as the one obtained from Feynman diagrams, though the former contains neither vertices nor propagators explicitly. The equivalence was shown by indirect means, not by a direct evaluation of the (n -3 )-dimensional integral in the CHY formula. The purpose of this paper is to discuss how such a direct evaluation can be carried out. There are two basic difficulties in the calculation: how to handle the large number of terms in the reduced Pfaffian, and how to carry out the integrations in the presence of a σ dependence much more complicated than the Parke-Taylor form found in a CHY double-color scalar amplitude. We have solved both of these problems, and have formulated a method that can be applied to any n . Many examples are provided to illustrate these calculations.
Thermal lens spectrometry: Optimizing amplitude and shortening the transient time
NASA Astrophysics Data System (ADS)
Silva, Rubens; de Araújo, Marcos A. C.; Jali, Pedro; Moreira, Sanclayton G. C.; Alcantara, Petrus; de Oliveira, Paulo C.
2011-06-01
Based on a model introduced by Shen et al. for cw laser induced mode-mismatched dual-beam thermal lens spectrometry (TLS), we explore the parameters related with the geometry of the laser beams and the experimental apparatus that influence the amplitude and time evolution of the transient thermal lens (TL) signal. By keeping the sample cell at the minimum waist of the excitation beam, our results show that high amplitude TL signals, very close to the optimized value, combined with short transient times may be obtained by reducing the curvature radius of the probe beam and the distance between the sample cell and the detector. We also derive an expression for the thermal diffusivity which is independent of the excitation laser beam waist, considerably improving the accuracy of the measurements. The sample used in the experiments was oleic acid, which is present in most of the vegetable oils and is very transparent in the visible spectral range.
Analytic Evolution of Singular Distribution Amplitudes in QCD
Radyushkin, Anatoly V.; Tandogan Kunkel, Asli
2014-03-01
We describe a method of analytic evolution of distribution amplitudes (DA) that have singularities, such as non-zero values at the end-points of the support region, jumps at some points inside the support region and cusps. We illustrate the method by applying it to the evolution of a flat (constant) DA, anti-symmetric at DA and then use it for evolution of the two-photon generalized distribution amplitude. Our approach has advantages over the standard method of expansion in Gegenbauer polynomials, which requires infinite number of terms in order to accurately reproduce functions in the vicinity of singular points, and over a straightforward iteration of an initial distribution with evolution kernel. The latter produces logarithmically divergent terms at each iteration, while in our method the logarithmic singularities are summed from the start, which immediately produces a continuous curve, with only one or two iterations needed afterwards in order to get rather precise results.
Nonlinear finite amplitude torsional vibrations of cantilevers in viscous fluids
NASA Astrophysics Data System (ADS)
Aureli, Matteo; Pagano, Christopher; Porfiri, Maurizio
2012-06-01
In this paper, we study torsional vibrations of cantilever beams undergoing moderately large oscillations within a quiescent viscous fluid. The structure is modeled as an Euler-Bernoulli beam, with thin rectangular cross section, under base excitation. The distributed hydrodynamic loading experienced by the vibrating structure is described through a complex-valued hydrodynamic function which incorporates added mass and fluid damping elicited by moderately large rotations. We conduct a parametric study on the two dimensional computational fluid dynamics of a pitching rigid lamina, representative of a generic beam cross section, to investigate the dependence of the hydrodynamic function on the governing flow parameters. As the frequency and amplitude of the oscillation increase, vortex shedding and convection phenomena increase, thus resulting into nonlinear hydrodynamic damping. We derive a handleable nonlinear correction to the classical hydrodynamic function developed for small amplitude torsional vibrations for use in a reduced order nonlinear modal model and we validate theoretical results against experimental findings.
Finite-amplitude waves in inviscid shear flows
NASA Astrophysics Data System (ADS)
Moore, D. W.; Saffman, P. G.
1982-08-01
This paper examines the existence and properties of steady finite-amplitude waves of cats-eye form superposed on a unidirectional inviscid, incompressible shear flow. The problem is formulated as the solution of nonlinear Poisson equations for the stream function with boundary conditions on the unknown edges of the cats-eyes. The dependence of vorticity on stream function is assumed outside the cats-eyes to be as in the undisturbed flow, and uniform unknown vorticity is assumed inside. It is argued on the basis of a finite difference discretization that the problem is determinate, and numerical solutions are obtained for Couette-Poiseuille channel flow. These are compared with the predictions of a weakly nonlinear theory based on the approach of Benney and Bergeron (1969) and Davis (1969). The phase speed of the waves is found to be linear in the wave amplitude.
Large amplitude electromagnetic solitons in intense laser plasma interaction
NASA Astrophysics Data System (ADS)
Li, Bai-Wen; S, Ishiguro; M, Skoric M.
2006-09-01
This paper shows that the standing, backward- and forward-accelerated large amplitude relativistic electromagnetic solitons induced by intense laser pulse in long underdense collisionless homogeneous plasmas can be observed by particle simulations. In addition to the inhomogeneity of the plasma density, the acceleration of the solitons also depends upon not only the laser amplitude but also the plasma length. The electromagnetic frequency of the solitons is between about half and one of the unperturbed electron plasma frequency. The electrostatic field inside the soliton has a one-cycle structure in space, while the transverse electric and magnetic fields have half-cycle and one-cycle structure respectively. Analytical estimates for the existence of the solitons and their electromagnetic frequencies qualitatively coincide with our simulation results.
Excitation of nearly steady finite-amplitude barotropic waves
NASA Technical Reports Server (NTRS)
Hou, A. Y.; Farrell, B. F.
1986-01-01
An exact nonlinear stationary solution is obtained for barotropic waves in a beta-plane channel and it is shown that it can be excited under a range of initial conditions. Results show that a finite-amplitude wave in a constant shear flow, given an initial phase tilt against the shear and a sufficient initial amplitude, interacts with the mean flow to produce a nearly steady state close to the exact stationary solution. This equilibration process involves nonlinear transients; in particular, as the flow equilibrates, the emergence of critical levels is accompanied by the neutralization of local mean vorticity gradients at these levels, thus allowing the solution to attain a nonsingular modal structure.
K+-nucleus potentials from K+-nucleon amplitudes
NASA Astrophysics Data System (ADS)
Friedman, E.
2016-10-01
Optical potentials for K+-nucleus interactions are constructed from K+-nucleon amplitudes using recently developed algorithm based on K+-N kinematics in the nuclear medium. With the deep penetration of K+ mesons into the nucleus at momenta below 800 MeV / c it is possible to test this approach with greater sensitivity than hitherto done with K- and pions. The energy-dependence of experimental reaction and total cross sections on nuclei is better reproduced with this approach compared to fixed-energy amplitudes. The inclusion of Pauli correlations in the medium also improves the agreement between calculation and experiment. The absolute scale of the cross sections is reproduced very well for 6Li but for C, Si and Ca calculated cross sections are (23 ± 4)% smaller than experiment, in agreement with earlier analyses. Two phenomenological models that produce such missing strength suggest that the imaginary part of the potential needs about 40% enhancement.
Vertex amplitudes in spin foam loop quantum cosmology
NASA Astrophysics Data System (ADS)
Craig, David
2016-03-01
We discuss properties of the vertex expansion for homogeneous, isotropic loop quantum cosmological models sourced by a massless, minimally coupled scalar field, which in this model plays the role of an internal matter ``clock''. We show that the vertex expansion, first written down by Ashtekar, Campiglia and Henderson, must be thought of as a short-time expansion in the sense that the amplitude for volume transitions is constrained both by the order of the expansion and by the elapsed scalar field. To calculate the amplitude for significant volume changes or between large differences in the value of the scalar field requires the expansion be evaluated to very high order. This contribution describes work in collaboration with P. Singh.
TASI 2014: Lectures on Gauge and Gravity Amplitude Relations
NASA Astrophysics Data System (ADS)
Carrasco, John Joseph M.
In these lectures I talk about simplifications and universalities found in scattering amplitudes for gauge and gravity theories. In contrast to Ward identities, which are understood to arise from familiar symmetries of the classical action, these structures are currently only understood in terms of graphical organizational principles, such as the gauge-theoretic color-kinematics duality and the gravitational double-copy structure, for local representations of multi-loop S-matrix elements. These graphical principles make manifest new relationships in and between gauge and gravity scattering amplitudes. My lectures will focus on arriving at such graphical organizations for generic theories with examples presented from maximal supersymmetry, and their use in unitarity-based multiloop integrand construction.
BPS amplitudes, helicity supertraces and membranes in M-theory
NASA Astrophysics Data System (ADS)
Wit, B. d.; Lüst, D.
2000-03-01
We study BPS dominated loop amplitudes in M-theory on T2. For this purpose we generalize the concept of helicity supertraces to nine spacetime dimensions. These traces distinguish between various massive supermultiplets and appear as coefficients in their one-loop contributions to n-graviton scattering amplitudes. This can be used to show that only ultrashort BPS multiplets contribute to the R4 term in the effective action, which was first computed by Green, Gutperle and Vanhove. There are two inequivalent ultrashort BPS multiplets which describe the Kaluza-Klein states and the wrapped membranes that cover the torus a number of times. From the perspective of the type-II strings they correspond to momentum and winding states and D0 or D1 branes.
Amplitude-squeezed fiber-Bragg-grating solitons
Lee, R.-K.; Lai Yinchieh
2004-02-01
Quantum fluctuations of optical fiber-Bragg-grating solitons are investigated numerically by the back-propagation method. It is found that the band-gap effects of the grating act as a nonlinear filter and cause the soliton to be amplitude squeezed. The squeezing ratio saturates after a certain grating length and the optimal squeezing ratio occurs when the pulse energy is slightly above the fundamental soliton energy.
Amplitude and Width Correlations in COBALT-57 and VANADIUM-49.
NASA Astrophysics Data System (ADS)
Ramakrishnan, Prabha K.
Angular distributions of the inelastically scattered protons and of the deexcitation (gamma)-rays in the ('56)Fe(p,p'(gamma)) reaction were measured for d-wave resonances in the proton energy range 3.10 to 4.01 MeV. The experiment was performed with an overall energy resolution of 350 to 400 eV (FWHM) at the Triangle Universities Nuclear Laboratory KN Van de Graaff accelerator and associated high resolution system. Results were obtained for 141 resonances; 83 resonances were assigned J('(pi)) = 5/2('+), while 58 resonances were assigned J('(pi)) = 3/2('+). Mixing parameters for the inelastic decay amplitudes were uniquely determined for the 5/2('+) resonances. For the 3/2('+) resonances sufficient information is not available from this experiment to extract a unique solution for the mixing parameters. Magnitudes and relative signs of three inelastic decay amplitudes were determined for the 5/2('+) resonances in ('57)Co. The angular distributions for the deexcitation (gamma)-rays were measured in coincidence with the inelastically scattered protons for 30 3/2('+) resonances in ('49)V in the proton energy region 2.2 to 3.1 MeV. The singles measurements from a previous experiment were combined with these coincidence measurements to eliminate the ambiguity in the solutions for the mixing parameters. Amplitude and width measurements were determined for the three decay channels for 30 3/2('+) resonances. Statistical analyses were performed on the set of 83 5/2('+) resonances in ('57)Co and on the set of 30 3/2('+) resonances in ('49)V. In both cases, large amplitude and width correlations are observed. These results are interpreted as evidence for direct reactions between the inelastic channels.
Tailoring quantum superpositions with linearly polarized amplitude-modulated light
Pustelny, S.; Koczwara, M.; Cincio, L.; Gawlik, W.
2011-04-15
Amplitude-modulated nonlinear magneto-optical rotation is a powerful technique that offers a possibility of controllable generation of given quantum states. In this paper, we demonstrate creation and detection of specific ground-state magnetic-sublevel superpositions in {sup 87}Rb. By appropriate tuning of the modulation frequency and magnetic-field induction the efficiency of a given coherence generation is controlled. The processes are analyzed versus different experimental parameters.
Binarity and multiperiodicity in high-amplitude delta Scuti stars .
NASA Astrophysics Data System (ADS)
Derekas, A.; Kiss, L. L.; Csák, B.; Griffin, J.; Lindström, C.; Mészáros, Sz.; Székely, P.; Ashley, M. C. B.; Bedding, T. R.
We present our first results for a sample of southern high-amplitude delta Scuti stars (HADS), based on a spectrophotometric survey started in 2003. For CY Aqr and AD CMi, we found very stable light and radial velocity (RV) curves; we confirmed the double-mode nature of ZZ Mic, BQ Ind and RY Lep. Finally, we detected gamma -velocity changes in RS Gru and RY Lep.
Asteroid 4962 Vecherka: A High-Amplitude Slow Rotator
NASA Astrophysics Data System (ADS)
Tomov, Dimitar; Kurtenkov, Alexander; Enimanev, Mihail; Teneva, Deana
2016-10-01
We present nine nights of photometric observations of the main-belt asteroid 4962 Vecherka. Its amplitude during our observations was not less than 1.08 ± 0.02 mag. We estimated its synodic rotation period at 14 ± 2 d (336 ± 48 h), meaning that 4962 Vecherka is probably among a rare class of slowly rotating, highamplitude asteroids. A much longer observational campaign is required to calculate the period of rotation with a satisfactory accuracy.
A BiCMOS integrated charge to amplitude converter
Gallin-Martel, L.; Pouxe, J.; Rossetto, O.
1996-12-31
This paper describes a fast two channel gated charge to amplitude converter (QAC) which has been designed with the 1.2 {mu}m BiCMOS technology from AMS (Austria Mikro Systeme). It can integrate fast negative impulse currents up to 100 mA. Associated with an audio 18 bit low cost ADC, it can easily be used to make a 12 to 13 bit QDC. The problems of current to current conversion, pedestal and offset stability are discussed.
Phase and amplitude binning for 4D-CT imaging
NASA Astrophysics Data System (ADS)
Abdelnour, A. F.; Nehmeh, S. A.; Pan, T.; Humm, J. L.; Vernon, P.; Schöder, H.; Rosenzweig, K. E.; Mageras, G. S.; Yorke, E.; Larson, S. M.; Erdi, Y. E.
2007-07-01
We compare the consistency and accuracy of two image binning approaches used in 4D-CT imaging. One approach, phase binning (PB), assigns each breathing cycle 2π rad, within which the images are grouped. In amplitude binning (AB), the images are assigned bins according to the breathing signal's full amplitude. To quantitate both approaches we used a NEMA NU2-2001 IEC phantom oscillating in the axial direction and at random frequencies and amplitudes, approximately simulating a patient's breathing. 4D-CT images were obtained using a four-slice GE Lightspeed CT scanner operating in cine mode. We define consistency error as a measure of ability to correctly bin over repeated cycles in the same field of view. Average consistency error μe ± σe in PB ranged from 18% ± 20% to 30% ± 35%, while in AB the error ranged from 11% ± 14% to 20% ± 24%. In PB nearly all bins contained sphere slices. AB was more accurate, revealing empty bins where no sphere slices existed. As a proof of principle, we present examples of two non-small cell lung carcinoma patients' 4D-CT lung images binned by both approaches. While AB can lead to gaps in the coronal images, depending on the patient's breathing pattern, PB exhibits no gaps but suffers visible artifacts due to misbinning, yielding images that cover a relatively large amplitude range. AB was more consistent, though often resulted in gaps when no data existed due to patients' breathing pattern. We conclude AB is more accurate than PB. This has important consequences to treatment planning and diagnosis.
Coherent diffractive imaging: a new statistically regularized amplitude constraint
NASA Astrophysics Data System (ADS)
Dilanian, R. A.; Williams, G. J.; Whitehead, L. W.; Vine, D. J.; Peele, A. G.; Balaur, E.; McNulty, I.; Quiney, H. M.; Nugent, K. A.
2010-09-01
Statistical information about measurement errors is incorporated in an algorithm that reconstructs the image of an object from x-ray diffraction data. The distribution function of measurement errors is included directly into reconstruction processes using a statistically based amplitude constraint. The algorithm is tested using simulated and experimental data and is shown to yield high-quality reconstructions in the presence of noise. This approach can be generalized to incorporate experimentally determined measurement error functions into image reconstruction algorithms.
Dynamical Selection of the Primordial Density Fluctuation Amplitude
Lehners, Jean-Luc; Steinhardt, Paul J.
2011-02-25
In inflationary models, the predicted amplitude of primordial density perturbations Q is much larger than the observed value ({approx}10{sup -5}) for natural choices of parameters. To explain the requisite exponential fine-tuning, anthropic selection is often invoked, especially in cases where microphysics is expected to produce a complex energy landscape. By contrast, we find examples of ekpyrotic models based on heterotic M theory for which dynamical selection naturally favors the observed value of Q.
Small-amplitude oscillatory shear magnetorheology of inverse ferrofluids.
Ramos, Jose; de Vicente, Juan; Hidalgo-Alvarez, Roque
2010-06-15
A comprehensive investigation is performed on highly monodisperse silica-based inverse ferrofluids under small-amplitude oscillatory shear in the presence of external magnetic fields up to 1 T. The effect of particle volume fraction and continuous medium Newtonian viscosity is thoroughly investigated. Experimental results for storage modulus are used to validate existing micromechanical magnetorheological models assuming different particle-level field-induced structures. PMID:20345105
Measurement of RT amplitudes and wavelengths of laser driven plates
Frank, A.M.; Gillespie, C.H.
1997-10-16
A laser drive plate, that is a dense solid plate drive by a laser heated, lower density plasma, is inherently Raleigh-Taylor (R-T) unstable, We have previously indicated that observed surface perturbation on the plate are probably R-T instabilities, initiated by the mode structure of the driving laser beam. Using a semi- transparent impact target viewed with a polarized Epi-Illuminated Confocal Streak Microscope, has allowed us to measure the amplitude and growth of the instability.
Dynamical selection of the primordial density fluctuation amplitude.
Lehners, Jean-Luc; Steinhardt, Paul J
2011-02-25
In inflationary models, the predicted amplitude of primordial density perturbations Q is much larger than the observed value (∼10(-5)) for natural choices of parameters. To explain the requisite exponential fine-tuning, anthropic selection is often invoked, especially in cases where microphysics is expected to produce a complex energy landscape. By contrast, we find examples of ekpyrotic models based on heterotic M theory for which dynamical selection naturally favors the observed value of Q. PMID:21405562
Respiratory Amplitude Guided 4-Dimensional Magnetic Resonance Imaging
Hu, Yanle; Caruthers, Shelton D.; Low, Daniel A.; Parikh, Parag J.; Mutic, Sasa
2013-05-01
Purpose: To evaluate the feasibility of prospectively guiding 4-dimensional (4D) magnetic resonance imaging (MRI) image acquisition using triggers at preselected respiratory amplitudes to achieve T{sub 2} weighting for abdominal motion tracking. Methods and Materials: A respiratory amplitude-based triggering system was developed and integrated into a commercial turbo spin echo MRI sequence. Initial feasibility tests were performed on healthy human study participants. Four respiratory states, the middle and the end of inhalation and exhalation, were used to trigger 4D MRI image acquisition of the liver. To achieve T{sub 2} weighting, the echo time and repetition time were set to 75 milliseconds and 4108 milliseconds, respectively. Single-shot acquisition, together with parallel imaging and partial k-space imaging techniques, was used to improve image acquisition efficiency. 4D MRI image sets composed of axial or sagittal slices were acquired. Results: Respiratory data measured and logged by the MRI scanner showed that the triggers occurred at the appropriate respiratory levels. Liver motion could be easily observed on both 4D MRI image datasets by sensing either the change of liver in size and shape (axial) or diaphragm motion (sagittal). Both 4D MRI image datasets were T{sub 2}-weighted as expected. Conclusions: This study demonstrated the feasibility of achieving T{sub 2}-weighted 4D MRI images using amplitude-based respiratory triggers. With the aid of the respiratory amplitude-based triggering system, the proposed method is compatible with most MRI sequences and therefore has the potential to improve tumor-tissue contrast in abdominal tumor motion imaging.
Compensating temperature-induced ultrasonic phase and amplitude changes
NASA Astrophysics Data System (ADS)
Gong, Peng; Hay, Thomas R.; Greve, David W.; Junker, Warren R.; Oppenheim, Irving J.
2016-04-01
In ultrasonic structural health monitoring (SHM), environmental and operational conditions, especially temperature, can significantly affect the propagation of ultrasonic waves and thus degrade damage detection. Typically, temperature effects are compensated using optimal baseline selection (OBS) or optimal signal stretch (OSS). The OSS method achieves compensation by adjusting phase shifts caused by temperature, but it does not fully compensate phase shifts and it does not compensate for accompanying signal amplitude changes. In this paper, we develop a new temperature compensation strategy to address both phase shifts and amplitude changes. In this strategy, OSS is first used to compensate some of the phase shifts and to quantify the temperature effects by stretching factors. Based on stretching factors, empirical adjusting factors for a damage indicator are then applied to compensate for the temperature induced remaining phase shifts and amplitude changes. The empirical adjusting factors can be trained from baseline data with temperature variations in the absence of incremental damage. We applied this temperature compensation approach to detect volume loss in a thick wall aluminum tube with multiple damage levels and temperature variations. Our specimen is a thick-walled short tube, with dimensions closely comparable to the outlet region of a frac iron elbow where flow-induced erosion produces the volume loss that governs the service life of that component, and our experimental sequence simulates the erosion process by removing material in small damage steps. Our results show that damage detection is greatly improved when this new temperature compensation strategy, termed modified-OSS, is implemented.
A Generic Receiver Tracking Model for GPS Ionospheric Amplitude Scintillation
NASA Astrophysics Data System (ADS)
Paula, E. R.; Moraes, A. D.; Perrella, W. J.; Galera Monico, J. F.
2012-12-01
Ionospheric scintillations result in rapid variations in phase and amplitude of the radio signal, which propagates through the ionosphere. Depending on the temporal and spatial situation, the scintillation can represent a problem in the availability and precision of the Global Navigation Satellite Systems (GNSS). Scintillations affect the receiver performance, specially the tracking loop level. Depending on the scintillation level, the receiver might increase the measurement errors or even can lead to a loss of lock of the carrier and code loops. In extreme cases, the scintillation can result in full disrupting of the receiver. In this work we introduce a generic model to evaluate the effects of ionospheric amplitude scintillation on GPS receiver tracking loops. This model is based on α-μ distribution, which can be seen as a generalized fading model, that includes a variety of distributions such as Gamma, Nakagami-m, Exponential, Weibull, one-sided Gaussian and Rayleigh. Differently from the model based only on Nakagami-m, this one is not limited to S4< 0,71 which allows using it to predict amplitude scintillation effects for stronger scenarios. The estimation of α-μ coefficients, the empirical parameterization based on field measurements and the typical values estimated based on observations made during the last solar maximum are presented and discussed.
AMPLITUDE AND TIME MEASUREMENT ASIC WITH ANALOG DERANDOMIZATION.
O CONNOR,P.; DE GERONIMO,G.; KANDASAMY,A.
2002-11-10
We describe a new ASIC for accurate and efficient processing of high-rate pulse signals from highly segmented detectors. In contrast to conventional approaches, this circuit affords a dramatic reduction in data volume through the use of analog techniques (precision peak detectors and time-to-amplitude converters) together with fast arbitration and sequencing logic to concentrate the data before digitization. In operation the circuit functions like a data-driven analog first-in, first-out (FIFO) memory between the preamplifiers and the ADC. Peak amplitudes of pulses arriving at any one of the 32 inputs are sampled, stored, and queued for readout and digitization through a single output port. Hit timing, pulse risetime, and channel address are also available at the output. Prototype chips have been fabricated in 0.35 micron CMOS and tested. First results indicate proper functionality for pulses down to 30 ns peaking time and input rates up to 1.6 MHz/channel. Amplitude accuracy of the peak detect and hold circuit is 0.3% (absolute). TAC accuracy is within 0.3% of full scale. Power consumption is less than 2 mW/channel. Compared with conventional techniques such as track-and-hold and analog memory, this new ASIC will enable efficient pulse height measurement at 20 to 300 times higher rates.
Large-amplitude hydromagnetic waves. [in solar wind
NASA Technical Reports Server (NTRS)
Barnes, A.; Hollweg, J. V.
1974-01-01
Several aspects of the theory of large-amplitude hydromagnetic waves and their behavior in the interplanetary medium are examined. The characteristic modes of the full (i.e., nonlinearized) MHD equations and their modification by collisionless and finite-frequency effects are considered. Special attention is paid to the transverse Alfven mode, which is undamped and characterized by strictly constant pressure, density, and B; this seems to be the predominant propagating fluctuation at 1 AU. It is shown that its propagation in the small-wavelength (WKB) approximation is essentially identical to that of the small-amplitude Alfven wave of linearized theory. It is also suggested that its presence at 1 AU may provide a natural explanation of the observed power anisotropy of the fluctuations. A second-order analysis is used to study fluctuations that are not characteristic modes. It is found that for a small range of propagation directions, and subject to third-order effects, a finite-amplitude wave can exist that is linearly polarized with delta B perpendicular to both B sub zero and k; such a wave can damp nonlinearly.
Magnitude of luminance modulation specifies amplitude of perceived movement.
Allik, J; Pulver, A
1995-01-01
A compelling impression of movement, which is perceptually indistinguishable from a real displacement, can be elicited by patterns containing no spatially displaced elements. An apparent oscillation, w-movement, was generated by a stationary pattern containing a large number of horizontal pairs of spatially adjacent dots modulated in brightness. The observer's task was to adjust the perceived amplitude of the w-motion to match the amplitude of a real oscillation. All of the data can be accounted for by a simple rule: If the relative change in the luminance, W = delta L/L, between two adjacent stationary dots is kept constant, the distance over which these dots appeared to travel in space comprises a fixed fraction of the total distance by which they are separated. The apparent amplitude of the w-motion increases strictly in proportion with luminance contrast, provided that the contrast is represented in the motion-encoding system by a rapidly saturating compressive Weibull transformation. These findings can be explained in terms of bilocal motion encoders comparing two luminance modulations occurring at two different locations.
Spectral saliency via automatic adaptive amplitude spectrum analysis
NASA Astrophysics Data System (ADS)
Wang, Xiaodong; Dai, Jialun; Zhu, Yafei; Zheng, Haiyong; Qiao, Xiaoyan
2016-03-01
Suppressing nonsalient patterns by smoothing the amplitude spectrum at an appropriate scale has been shown to effectively detect the visual saliency in the frequency domain. Different filter scales are required for different types of salient objects. We observe that the optimal scale for smoothing amplitude spectrum shares a specific relation with the size of the salient region. Based on this observation and the bottom-up saliency detection characterized by spectrum scale-space analysis for natural images, we propose to detect visual saliency, especially with salient objects of different sizes and locations via automatic adaptive amplitude spectrum analysis. We not only provide a new criterion for automatic optimal scale selection but also reserve the saliency maps corresponding to different salient objects with meaningful saliency information by adaptive weighted combination. The performance of quantitative and qualitative comparisons is evaluated by three different kinds of metrics on the four most widely used datasets and one up-to-date large-scale dataset. The experimental results validate that our method outperforms the existing state-of-the-art saliency models for predicting human eye fixations in terms of accuracy and robustness.
Wigner function and transition amplitude of three mutually coupled oscillators
NASA Astrophysics Data System (ADS)
Nassar, M. M.; Sebawe Abdalla, M.
2007-04-01
A full quantum mechanical treatment of three electromagnetic fields is considered. The proposed model consists of three different coupling parameters for which the rotating and counter-rotating terms are retained. An exact solution of the wave function in the Schrödinger picture is obtained and the connection with the coherent states wave function is given. The symmetrical ordered quasi-probability distribution function ( W-Wigner function) is calculated via the wave function in the coherent states representation. The squeezing phenomenon is also examined for both single mode and squared-amplitude, where the collapse and revival phenomena are observed. For the case in which λ3=0 and ω1=ω2=ω3 (exact resonances) we find that the late phenomenon is apparent but only after long period of the time considered. The transition amplitude between two different coherent states (a state in which all the coupling parameters are involved and a state when the coupling parameter λ3=0) is calculated. It is shown that the probability amplitude is sensitive to the variation of the mean photon numbers, and the coupling parameters as well as to the field frequencies.
Three applications of a bonus relation for gravity amplitudes
NASA Astrophysics Data System (ADS)
Spradlin, Marcus; Volovich, Anastasia; Wen, Congkao
2009-04-01
Arkani-Hamed et al. have recently shown that all tree-level scattering amplitudes in maximal supergravity exhibit exceptionally soft behavior when two supermomenta are taken to infinity in a particular complex direction, and that this behavior implies new non-trivial relations amongst amplitudes in addition to the well-known on-shell recursion relations. We consider the application of these new 'bonus relations' to MHV amplitudes, showing that they can be used quite generally to relate (n - 2) !-term formulas typically obtained from recursion relations to (n - 3) !-term formulas related to the original BGK conjecture. Specifically we provide (1) a direct proof of a formula presented by Elvang and Freedman, (2) a new formula based on one due to Bedford et al., and (3) an alternate proof of a formula recently obtained by Mason and Skinner. Our results also provide the first direct proof that the conjectured BGK formula, only very recently proven via completely different methods, satisfies the on-shell recursion.
Mechanical annealing under low-amplitude cyclic loading in micropillars
NASA Astrophysics Data System (ADS)
Cui, Yi-nan; Liu, Zhan-li; Wang, Zhang-jie; Zhuang, Zhuo
2016-04-01
Mechanical annealing has been demonstrated to be an effective method for decreasing the overall dislocation density in submicron single crystal. However, simultaneously significant shape change always unexpectedly happens under extremely high monotonic loading to drive the pre-existing dislocations out of the free surfaces. In the present work, through in situ TEM experiments it is found that cyclic loading with low stress amplitude can drive most dislocations out of the submicron sample with virtually little change of the shape. The underlying dislocation mechanism is revealed by carrying out discrete dislocation dynamic (DDD) simulations. The simulation results indicate that the dislocation density decreases within cycles, while the accumulated plastic strain is small. By comparing the evolution of dislocation junction under monotonic, cyclic and relaxation deformation, the cumulative irreversible slip is found to be the key factor of promoting junction destruction and dislocation annihilation at free surface under low-amplitude cyclic loading condition. By introducing this mechanics into dislocation density evolution equations, the critical conditions for mechanical annealing under cyclic and monotonic loadings are discussed. Low-amplitude cyclic loading which strengthens the single crystal without seriously disturbing the structure has the potential applications in the manufacture of defect-free nano-devices.
Radial convection of finite ion temperature, high amplitude plasma blobs
Wiesenberger, M. Kendl, A.; Madsen, J.
2014-09-15
We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width, and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very well described by the ratio of the ion gyroradius to the characteristic gradient scale length of the blob. We compare the global gyrofluid model with a partly linearized local model. For low ion temperatures, we find that simulations of the global model show more coherent blobs with an increased cross-field transport compared to blobs simulated with the local model. The maximal blob amplitude is significantly higher in the global simulations than in the local ones. When the ion temperature is comparable to the electron temperature, global blob simulations show a reduced blob coherence and a decreased cross-field transport in comparison with local blob simulations.
Thread amplitudes and frequencies in a fluid mechanical `sewing machine'
NASA Astrophysics Data System (ADS)
Morris, Stephen W.; Dawes, J. H. P.; Lister, John; Dalziel, Stuart
2006-11-01
A viscous thread falling on a surface exhibits the famous rope- coiling effect, in which the thread buckles to form loops. If the surface is replaced by a belt moving at speed U, the rotational symmetry of the buckling instability is broken and a wealth of interesting states are observed (1). We experimentally studied this fluid mechanical `sewing machine' in a new, more precise apparatus. As U is reduced, the stretched thread bifurcates into a meandering state in which the thread displacements are only transverse to the motion of the belt. We measured the amplitudes A and frequency φ of the meandering close to the bifurcation. For small U, single- frequency meandering bifurcates to a two-frequency `figure 8' state, which contains a significant 2φ component and parallel as well as transverse displacements. This eventually reverts to single-frequency coiling at smaller U. More complex, highly hysteretic states with additional harmonics are observed for larger nozzle heights. We propose to understand this zoology in terms of the generic amplitude equations appropriate for resonant interactions between three oscillatory modes with frequencies φ, 2φ and 3φ. The form of the amplitude equations captures both the axisymmetry of the U=0 coiling state and the symmetry-breaking effects induced by the moving belt.(1) Chiu-Webster and Lister, J. Fluid Mech., in press.
Mapping High Latitude Gravity Wave Amplitudes over Antarctica during Summer
NASA Astrophysics Data System (ADS)
Badenhausen, P.; Millan, R. M.; Gerrard, A. J.
2015-12-01
Appropriate inclusion of gravity wave amplitudes into general circulation models is required to get accurate atmospheric circulation characteristics. However, high latitude gravity wave amplitudes are particularly difficult to obtain due to the challenging experimental and logistical constraints in these regions. In this study, we present gravity wave climatology of high latitudes during austral summer conditions over the Antarctic continent. These data were obtained using high-resolution GPS measurements aboard long duration high altitude balloon flights that were flown as part of the NASA Balloon Array for Radiation-belt Relativistic Electron Losses (BARREL) mission in December 2013-February 2014 and December 2012-February 2013. The results show increased gravity wave activity along the coast of the Antarctic continent, particularly over the Peninsula and Halley Bay, whereas at higher latitudes, particularly over regions near the South Pole, gravity wave amplitudes decrease substantially. Through use of horizontal winds data, we obtained measurements of the vertical transport of horizontal momentum fluxes, which were unusually high for the summer high latitude lower stratosphere. Such unique measurements as these are immediately applicable to understanding of upwelling in the summer middle atmosphere as well as to the formation of overlaying mesospheric clouds formation.
NASA Astrophysics Data System (ADS)
Santosa, H.; Hobara, Y.; Balikhin, M. A.
2015-12-01
Very Low Frequency (VLF) waves have been proposed as an approach to study and monitor the lower ionospheric conditions. The ionospheric perturbations are identified in relation with thunderstorm activity, geomagnetic storm and other factors. The temporal dependence of VLF amplitude has a complicated and large daily variabilities in general due to combinations of both effects from above (space weather effect) and below (atmospheric and crustal processes) of the ionosphere. Quantitative contributions from different external sources are not known well yet. Thus the modelling and prediction of VLF wave amplitude are important issues to study the lower ionospheric responses from various external parameters and to also detect the anomalies of the ionosphere. The purpose of the study is to model and predict nighttime average amplitude of VLF wave propagation from the VLF transmitter in Hawaii (NPM) to receiver in Chofu (CHO) Tokyo, Japan path using NARX neural network. The constructed model was trained for the target parameter of nighttime average amplitude of NPM-CHO path. The NARX model, which was built based on daily input variables of various physical parameters such as stratosphere temperature, cosmic rays and total column ozone, possessed good accuracies. As a result, the constructed models are capable of performing accurate multistep ahead predictions, while maintaining acceptable one step ahead prediction accuracy. The results of the predicted daily VLF amplitude are in good agreement with observed (true) value for one step ahead prediction (r = 0.92, RMSE = 1.99), multi-step ahead 5 days prediction (r = 0.91, RMSE = 1.14) and multi-step ahead 10 days prediction (r = 0.75, RMSE = 1.74). The developed model indicates the feasibility and reliability of predicting lower ionospheric properties by the NARX neural network approach, and provides physical insights on the responses of lower ionosphere due to various external forcing.
Phase and Pupil Amplitude Recovery for JWST Space-Optics Control
NASA Technical Reports Server (NTRS)
Dean, B. H.; Zielinski, T. P.; Smith, J. S.; Bolcar, M. R.; Aronstein, D. L.; Fienup, J. R.
2010-01-01
This slide presentation reviews the phase and pupil amplitude recovery for the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam). It includes views of the Integrated Science Instrument Module (ISIM), the NIRCam, examples of Phase Retrieval Data, Ghost Irradiance, Pupil Amplitude Estimation, Amplitude Retrieval, Initial Plate Scale Estimation using the Modulation Transfer Function (MTF), Pupil Amplitude Estimation vs lambda, Pupil Amplitude Estimation vs. number of Images, Pupil Amplitude Estimation vs Rotation (clocking), and Typical Phase Retrieval Results Also included is information about the phase retrieval approach, Non-Linear Optimization (NLO) Optimized Diversity Functions, and Least Square Error vs. Starting Pupil Amplitude.
Estimation and application of EMG amplitude during dynamic contractions.
Clancy, E A; Bouchard, S; Rancourt, D
2001-01-01
The sections above have described an EMG amplitude estimator and an initial application of this estimator to the EMG-torque problem. The amplitude estimator consists of six stages. In the first stage, motion artifact and power-line interference are attenuated. Motion artifact is typically removed with a highpass filter. Elimination of power-line noise is more difficult. Commercial systems tend to use notch filters, accepting the concomitant loss of "true" signal power in exchange for simplicity and robustness. Adaptive methods may be preferable, however, to preserve more "true" signal power. In stage two, the signal is whitened. One fixed whitening technique and two adaptive whitening methods were described. For low-amplitude levels, the adaptive whitening technique that includes adaptive noise cancellation may be necessary. In stage three, multiple EMG channels (all overlying the same muscle) are combined. For most applications, simple gain normalization is all that is required. Stage four rectifies the signal and then applies the power law required to demodulate the signal. In stage six, the inverse of the power law is applied to relinearize the signal. Direct comparison of MAV (first power) to RMS (second power) processing demonstrates little difference between the two. Therefore, unless there is reason to believe that the EMG density departs strongly from that found in the existing studies, RMS and MAV processing are essentially identical. In stage five, the demodulated samples are averaged across all channels and then smoothed (time averaged) to reduce the variance of the amplitude estimate, but at the expense of increasing the bias. For best performance, the window length that best trades off variance and bias error is selected. The advanced EMG processing was next applied to dynamic EMG-torque estimation about the elbow joint. Results showed that improved EMG amplitude estimates led to improved EMG-torque estimates. An initial comparison of different system
Determining pseudoscalar meson photoproduction amplitudes from complete experiments
NASA Astrophysics Data System (ADS)
Sandorfi, A. M.; Hoblit, S.; Kamano, H.; Lee, T.-S. H.
2011-05-01
A new generation of complete experiments is focused on a high precision extraction of pseudoscalar meson photoproduction amplitudes. Here, we review the development of the most general analytic form of the cross section, dependent upon the three polarization vectors of the beam, target and recoil baryon, including all single-, double- and triple-polarization terms involving 16 spin-dependent observables. We examine the different conventions that have been used by different authors, and we present expressions that allow the direct numerical calculation of any pseudoscalar meson photoproduction observables with arbitrary spin projections from the Chew-Goldberger-Low-Nambu amplitudes. We use this numerical tool to clarify apparent sign differences that exist in the literature, in particular with the definitions of six double-polarization observables. We also present analytic expressions that determine the recoil baryon polarization, together with examples of their potential use with quasi-4π detectors to deduce observables. As an illustration of the use of the consistent machinery presented in this review, we carry out a multipole analysis of the γp → K+Λ reaction and examine the impact of recently published polarization measurements. When combining data from different experiments, we utilize the Fierz identities to fit a consistent set of scales. In fitting multipoles, we use a combined Monte Carlo sampling of the amplitude space, with gradient minimization, and find a shallow χ2 valley pitted with a very large number of local minima. This results in broad bands of multipole solutions that are experimentally indistinguishable. While these bands have been noticeably narrowed by the inclusion of new polarization measurements, many of the multipoles remain very poorly determined, even in sign, despite the inclusion of data on eight different observables. We have compared multipoles from recent PWA codes with our model-independent solution bands and found that such
High Amplitude Events in relation to Interplanetary disturbances
NASA Astrophysics Data System (ADS)
Mishra, Rajesh Kumar; Agarwal Mishra, Rekha
2012-07-01
The Sun emits the variable solar wind which interacts with the very local interstellar medium to form the heliosphere. Hence variations in solar activity strongly influence interplanetary space, from the Sun's surface out to the edge of the heliosphere. Superimposed on the solar wind are mass ejections from the Sun and/or its corona which, disturb the interplanetary medium - hence the name "interplanetary disturbances". Interplanetary disturbances are the sources of large-scale particle acceleration, of disturbances in the Earth's magnetosphere, of modulations of galactic cosmic rays in short, they are the prime focus for space weather studies. The investigation deals with the study of cosmic ray intensity, solar wind plasma and interplanetary magnetic field parameters variation due to interplanetary disturbances (magnetic clouds) during an unusual class of days i.e. high amplitude anisotropic wave train events. The high amplitude anisotropic wave train events in cosmic ray intensity has been identified using the data of ground based Goose Bay neutron monitor and studied during the period 1981-94. Even though, the occurrence of high amplitude anisotropic wave trains does not depend on the onset of interplanetary magnetic clouds. But the possibility of occurrence of these events cannot be overlooked during the periods of interplanetary magnetic cloud events. It is observed that solar wind velocity remains higher (> 300) than normal and interplanetary magnetic field B remains lower than normal on the onset of interplanetary magnetic cloud during the passage of these events. It is also noted from the superposed epoch analysis of cosmic ray intensity and geomagnetic activity for high amplitude anisotropic wave train events during the onset of interplanetary magnetic clouds that the increase in cosmic ray intensity and decrease in geomagnetic activity start not at the onset of magnetic clouds but after few days. The north south component of IMF (Bz), IMF (B), proton
Determining pseudoscalar meson photoproduction amplitudes from complete experiments
Sandorfi, A.M.; Hoblit, S.; Sandorfi,A.M.; Hoblit,S.; Kamano,H.; Lee,T-S.H.
2011-04-06
A new generation of complete experiments is focused on a high precision extraction of pseudoscalar meson photoproduction amplitudes. Here, we review the development of the most general analytic form of the cross section, dependent upon the three polarization vectors of the beam, target and recoil baryon, including all single-, double- and triple-polarization terms involving 16 spin-dependent observables. We examine the different conventions that have been used by different authors, and we present expressions that allow the direct numerical calculation of any pseudoscalar meson photoproduction observables with arbitrary spin projections from the Chew-Goldberger-Low-Nambu amplitudes. We use this numerical tool to clarify apparent sign differences that exist in the literature, in particular with the definitions of six double-polarization observables. We also present analytic expressions that determine the recoil baryon polarization, together with examples of their potential use with quasi-4{pi} detectors to deduce observables. As an illustration of the use of the consistent machinery presented in this review, we carry out a multipole analysis of the {gamma}p {yields} K{sup +}{Lambda} reaction and examine the impact of recently published polarization measurements. When combining data from different experiments, we utilize the Fierz identities to fit a consistent set of scales. In fitting multipoles, we use a combined Monte Carlo sampling of the amplitude space, with gradient minimization, and find a shallow {chi}{sup 2} valley pitted with a very large number of local minima. This results in broad bands of multipole solutions that are experimentally indistinguishable. While these bands have been noticeably narrowed by the inclusion of new polarization measurements, many of the multipoles remain very poorly determined, even in sign, despite the inclusion of data on eight different observables. We have compared multipoles from recent PWA codes with our model
Berger, Carola F.; Del Duca, Vittorio; Dixon, Lance J.
2006-08-18
We consider a scalar field, such as the Higgs boson H, coupled to gluons via the effective operator H tr G{sub {mu}{nu}} G{sup {mu}{nu}} induced by a heavy-quark loop. We treat H as the real part of a complex field {phi} which couples to the self-dual part of the gluon field-strength, via the operator {phi} tr G{sub SD {mu}{nu}} G{sub SD}{sup {mu}{nu}}, whereas the conjugate field {phi} couples to the anti-self-dual part. There are three infinite sequences of amplitudes coupling {phi} to quarks and gluons that vanish at tree level, and hence are finite at one loop, in the QCD coupling. Using on-shell recursion relations, we find compact expressions for these three sequences of amplitudes and discuss their analytic properties.
NASA Technical Reports Server (NTRS)
Cattell, Cynthia; Breneman, A.; Goetz, K.; Kellogg, P.; Kersten, K.; Wygant, J.; Wilson, L. B., III; Looper, Mark D.; Blake, J. Bernard; Roth, I.
2012-01-01
One of the critical problems for understanding the dynamics of Earth's radiation belts is determining the physical processes that energize and scatter relativistic electrons. We review measurements from the Wind/Waves and STEREO S/Waves waveform capture instruments of large amplitude whistler-mode waves. These observations have provided strong evidence that large amplitude (100s mV/m) whistler-mode waves are common during magnetically active periods. The large amplitude whistlers have characteristics that are different from typical chorus. They are usually nondispersive and obliquely propagating, with a large longitudinal electric field and significant parallel electric field. We will also review comparisons of STEREO and Wind wave observations with SAMPEX observations of electron microbursts. Simulations show that the waves can result in energization by many MeV and/or scattering by large angles during a single wave packet encounter due to coherent, nonlinear processes including trapping. The experimental observations combined with simulations suggest that quasilinear theoretical models of electron energization and scattering via small-amplitude waves, with timescales of hours to days, may be inadequate for understanding radiation belt dynamics.
Observations and Implications of Large-amplitude Longitudinal Oscillations in a Solar Filament
NASA Astrophysics Data System (ADS)
Luna, M.; Knizhnik, K.; Muglach, K.; Karpen, J.; Gilbert, H.; Kucera, T. A.; Uritsky, V.
2014-04-01
On 2010 August 20, an energetic disturbance triggered large-amplitude longitudinal oscillations in a nearby filament. The triggering mechanism appears to be episodic jets connecting the energetic event with the filament threads. In the present work, we analyze this periodic motion in a large fraction of the filament to characterize the underlying physics of the oscillation as well as the filament properties. The results support our previous theoretical conclusions that the restoring force of large-amplitude longitudinal oscillations is solar gravity, and the damping mechanism is the ongoing accumulation of mass onto the oscillating threads. Based on our previous work, we used the fitted parameters to determine the magnitude and radius of curvature of the dipped magnetic field along the filament, as well as the mass accretion rate onto the filament threads. These derived properties are nearly uniform along the filament, indicating a remarkable degree of cohesiveness throughout the filament channel. Moreover, the estimated mass accretion rate implies that the footpoint heating responsible for the thread formation, according to the thermal nonequilibrium model, agrees with previous coronal heating estimates. We estimate the magnitude of the energy released in the nearby event by studying the dynamic response of the filament threads, and discuss the implications of our study for filament structure and heating.
Observations and Implications of Large-Amplitude LongitudinalOscillations in a Solar Filament
NASA Astrophysics Data System (ADS)
Karpen, Judith T.; Luna, Manuel; Knizhnik, Kalman J.; Muglach, Karin; Gilbert, Holly; Kucera, Therese A.; Uritsky, Vadim
2014-06-01
On 20 August 2010 an energetic disturbance triggered large-amplitude longitudinal oscillations in a large fraction of a nearby filament. The triggering mechanism appears to be episodic jets connecting the energetic event with the filament threads. We analyzed this periodic motion to characterize the underlying physics of the oscillation as well as the filament properties. The results support our previous theoretical conclusions that the restoring force of large-amplitude longitudinal oscillations is solar gravity, and the damping mechanism is the ongoing accumulation of mass onto the oscillating threads. Based on our previous work, we used the fitted parameters to determine the magnitude and radius of curvature of the dipped magnetic field along the filament, as well as the mass accretion rate onto the filament threads. These derived properties are nearly uniform along the filament, indicating a remarkable degree of homogeneity throughout the filament channel. Moreover, the estimated mass accretion rate implies that the footpoint heating responsible for the thread formation, according to the thermal nonequilibrium model, agrees with previous coronal heating estimates. We also estimated the magnitude of the energy released in the nearby event by studying the dynamic response of the filament threads, and concluded that the initiating event is likely to be a microflare. We will present the results of this investigation and discuss their implications for filament structure and heating. This work was supported by NASA’s H-SR program.
NASA Astrophysics Data System (ADS)
Geroux, Christopher M.; Deupree, Robert G.
2015-02-01
Three-dimensional hydrodynamic simulations of full amplitude RR Lyrae stars have been computed for several models across the instability strip. The three-dimensional nature of the calculations allows convection to be treated without reference to a phenomenological approach such as the local mixing length theory. Specifically, the time-dependent interaction of large-scale eddies and radial pulsation is controlled by conservation laws, while the effects of smaller convective eddies are simulated by an eddy viscosity model. The light amplitudes for these calculations are quite similar to those of our previous two-dimensional calculations in the middle of the instability strip, but somewhat lower near the red edge, the fundamental blue edge, and for the one first overtone model we computed. The time-dependent interaction between the radial pulsation and the convective energy transport is essentially the same in three dimensions as it is in two dimensions. There are some differences between the light curves of the two- and three-dimensional simulations, particularly during decreasing light. Reasons for the differences, both numerical and physical, are explored.
Zhao, Xiaoyan; Qin, Renjia
2015-04-01
This paper makes persuasive demonstrations on some problems about the human ear sound transmission principle in existing physiological textbooks and reference books, and puts forward the authors' view to make up for its literature. Exerting the knowledge of lever in physics and the acoustics theory, we come up with an equivalent simplified model of manubrium mallei which is to meet the requirements as the long arm of the lever. We also set up an equivalent simplified model of ossicular chain--a combination of levers of ossicular chain. We disassemble the model into two simple levers, and make full analysis and demonstration on them. Through the calculation and comparison of displacement amplitudes in both external auditory canal air and internal ear lymph, we may draw a conclusion that the key reason, which the sound displacement amplitude is to be decreased to adapt to the endurance limit of the basement membrane, is that the density and sound speed in lymph is much higher than those in the air.
Observations and implications of large-amplitude longitudinal oscillations in a solar filament
Luna, M.; Knizhnik, K.; Muglach, K.; Karpen, J.; Gilbert, H.; Kucera, T. A.; Uritsky, V.
2014-04-10
On 2010 August 20, an energetic disturbance triggered large-amplitude longitudinal oscillations in a nearby filament. The triggering mechanism appears to be episodic jets connecting the energetic event with the filament threads. In the present work, we analyze this periodic motion in a large fraction of the filament to characterize the underlying physics of the oscillation as well as the filament properties. The results support our previous theoretical conclusions that the restoring force of large-amplitude longitudinal oscillations is solar gravity, and the damping mechanism is the ongoing accumulation of mass onto the oscillating threads. Based on our previous work, we used the fitted parameters to determine the magnitude and radius of curvature of the dipped magnetic field along the filament, as well as the mass accretion rate onto the filament threads. These derived properties are nearly uniform along the filament, indicating a remarkable degree of cohesiveness throughout the filament channel. Moreover, the estimated mass accretion rate implies that the footpoint heating responsible for the thread formation, according to the thermal nonequilibrium model, agrees with previous coronal heating estimates. We estimate the magnitude of the energy released in the nearby event by studying the dynamic response of the filament threads, and discuss the implications of our study for filament structure and heating.
Geroux, Christopher M.; Deupree, Robert G.
2015-02-10
Three-dimensional hydrodynamic simulations of full amplitude RR Lyrae stars have been computed for several models across the instability strip. The three-dimensional nature of the calculations allows convection to be treated without reference to a phenomenological approach such as the local mixing length theory. Specifically, the time-dependent interaction of large-scale eddies and radial pulsation is controlled by conservation laws, while the effects of smaller convective eddies are simulated by an eddy viscosity model. The light amplitudes for these calculations are quite similar to those of our previous two-dimensional calculations in the middle of the instability strip, but somewhat lower near the red edge, the fundamental blue edge, and for the one first overtone model we computed. The time-dependent interaction between the radial pulsation and the convective energy transport is essentially the same in three dimensions as it is in two dimensions. There are some differences between the light curves of the two- and three-dimensional simulations, particularly during decreasing light. Reasons for the differences, both numerical and physical, are explored.
Tribeche, Mouloud; Mayout, Saliha; Amour, Rabia
2009-04-15
Arbitrary amplitude dust acoustic waves in a high energy-tail ion distribution are investigated. The effects of charge variation and ion suprathermality on the large amplitude dust acoustic (DA) soliton are then considered. The correct suprathermal ion charging current is rederived based on the orbit motion limited approach. In the adiabatic case, the variable dust charge is expressed in terms of the Lambert function and we take advantage of this transcendental function to show the existence of rarefactive variable charge DA solitons involving cusped density humps. The dust charge variation leads to an additional enlargement of the DA soliton, which is less pronounced as the ions evolve far away from Maxwell-Boltzmann distribution. In the nonadiabatic case, the dust charge fluctuation may provide an alternate physical mechanism causing anomalous dissipation the strength of which becomes important and may prevail over that of dispersion as the ion spectral index {kappa} increases. Our results may provide an explanation for the strong spiky waveforms observed in auroral electric field measurements by Ergun et al.[Geophys. Res. Lett. 25, 2025 (1998)].
Proposed proper Engle-Pereira-Rovelli-Livine vertex amplitude
NASA Astrophysics Data System (ADS)
Engle, Jonathan
2013-04-01
As established in a prior work of the author, the linear simplicity constraints used in the construction of the so-called “new” spin-foam models mix three of the five sectors of Plebanski theory as well as two dynamical orientations, and this is the reason for multiple terms in the asymptotics of the Engle-Pereira-Rovelli-Livine vertex amplitude as calculated by Barrett et al. Specifically, the term equal to the usual exponential of i times the Regge action corresponds to configurations either in sector (II+) with positive orientation or sector (II-) with negative orientation. The presence of the other terms beyond this cause problems in the semiclassical limit of the spin-foam model when considering multiple 4-simplices due to the fact that the different terms for different 4-simplices mix in the semiclassical limit, leading in general to a non-Regge action and hence non-Regge and nongravitational configurations persisting in the semiclassical limit. To correct this problem, we propose to modify the vertex so its asymptotics include only the one term of the form eiSRegge. To do this, an explicit classical discrete condition is derived that isolates the desired gravitational sector corresponding to this one term. This condition is quantized and used to modify the vertex amplitude, yielding what we call the “proper Engle-Pereira-Rovelli-Livine vertex amplitude.” This vertex still depends only on standard SU(2) spin-network data on the boundary, is SU(2) gauge-invariant, and is linear in the boundary state, as required. In addition, the asymptotics now consist in the single desired term of the form eiSRegge, and all degenerate configurations are exponentially suppressed. A natural generalization to the Lorentzian signature is also presented.
Finite amplitude method for the quasiparticle random-phase approximation
NASA Astrophysics Data System (ADS)
Avogadro, Paolo; Nakatsukasa, Takashi
2011-07-01
We present the finite amplitude method (FAM), originally proposed in Ref. , for superfluid systems. A Hartree-Fock-Bogoliubov code may be transformed into a code of the quasiparticle-random-phase approximation (QRPA) with simple modifications. This technique has advantages over the conventional QRPA calculations, such as coding feasibility and computational cost. We perform the fully self-consistent linear-response calculation for the spherical neutron-rich nucleus 174Sn, modifying the hfbrad code, to demonstrate the accuracy, feasibility, and usefulness of the FAM.
A two-dimensional white-light amplitude interferometer
NASA Technical Reports Server (NTRS)
Breckinridge, J. B.
1979-01-01
A review of the applications of a point-symmetric, 180-degree, rotational shearing interferometer is given. Material includes, photographs of the Michelson stellar interferometer fringes from Alpha-Lyr, measures of amplitude of phase excursions in the atmosphere, and a measure of the order of interference of speckle patterns. New material includes unpublished double star speckle patterns to illustrate the isoplanatic patch, a measure of the time fluctuations in the earth's atmosphere, and measurements of the properties of a 256 channel linear reticon.
Electroglottographic Quasi-open quotient and amplitude in crescendo phonation.
Hacki, T
1996-12-01
Crescendo phonation (swelltone) was used to evaluate the laryngeal tensioning behavior of seven normal speakers and of 12 dysphonic patients. EGG quasi-open quotient (qOq), stroboscopic open quotient, and vocal sound pressure level (SPL) were measured, and EGG amplitude and the mucosal wave were assessed qualitatively. For normal speakers, the qOq decreased greatly as vocal intensity increased. The same tendency was observed, but to a lesser extent, among hyperfunctional dysphonics. In contrast, qOq increased with vocal intensity among the hypofunctional dysphonics. The crescendo task combined with EGG assessment appears to offer a valid approach to the classification of laryngeal dysfunctions.
Transition Distribution Amplitudes for γ⋆γ collisions
NASA Astrophysics Data System (ADS)
Lansberg, J. P.; Pire, B.; Szymanowski, L.
2008-11-01
We study the exclusive production of ππ and ρπ in hard γ⋆γ scattering in the forward kinematical region where the virtuality of one photon provides us with a hard scale in the process. The newly introduced concept of Transition Distribution Amplitudes (TDA) is used to perform a QCD calculation of these reactions thanks to two simple models for TDAs. The sizable cross sections for ρπ and ππ production may be tested at intense electron-positron colliders such as CLEO and B factories (Belle and BABAR).
Attenuation of ground-motion spectral amplitudes in southeastern Australia
Allen, T.I.; Cummins, P.R.; Dhu, T.; Schneider, J.F.
2007-01-01
A dataset comprising some 1200 weak- and strong-motion records from 84 earthquakes is compiled to develop a regional ground-motion model for southeastern Australia (SEA). Events were recorded from 1993 to 2004 and range in size from moment magnitude 2.0 ??? M ??? 4.7. The decay of vertical-component Fourier spectral amplitudes is modeled by trilinear geometrical spreading. The decay of low-frequency spectral amplitudes can be approximated by the coefficient of R-1.3 (where R is hypocentral distance) within 90 km of the seismic source. From approximately 90 to 160 km, we observe a transition zone in which the seismic coda are affected by postcritical reflections from midcrustal and Moho discontinuities. In this hypocentral distance range, geometrical spreading is approximately R+0.1. Beyond 160 km, low-frequency seismic energy attenuates rapidly with source-receiver distance, having a geometrical spreading coefficient of R-1.6. The associated regional seismic-quality factor can be expressed by the polynomial: log Q(f) = 3.66 - 1.44 log f + 0.768 (log f)2 + 0.058 (log f)3 for frequencies 0.78 ??? f ??? 19.9 Hz. Fourier spectral amplitudes, corrected for geometrical spreading and anelastic attenuation, are regressed with M to obtain quadratic source scaling coefficients. Modeled vertical-component displacement spectra fit the observed data well. Amplitude residuals are, on average, relatively small and do not vary with hypocentral distance. Predicted source spectra (i.e., at R = 1 km) are consistent with eastern North American (ENA) Models at low frequencies (f less than approximately 2 Hz) indicating that moment magnitudes calculated for SEA earthquakes are consistent with moment magnitude scales used in ENA over the observed magnitude range. The models presented represent the first spectral ground-motion prediction equations develooed for the southeastern Australian region. This work provides a useful framework for the development of regional ground-motion relations
Superposed pulse amplitude modulation for visible light communication.
Li, J F; Huang, Z T; Zhang, R Q; Zeng, F X; Jiang, M; Ji, Y F
2013-12-16
We propose and experimentally demonstrate a novel modulation scheme called superposed pulse amplitude modulation (SPAM) which is low-cost, insensitive to non-linearity of light emitting diode (LED). Multiple optical pulses transmit parallelly from different spatial position in the LED array and overlap linearly in free space to realize SPAM. With LED arrangement, the experimental results show that using the modulation we proposed the data rate of 120 Mbit/s with BER 1 × 10(-3) can be achieved with an optical blue filter and RC post-equalization. PMID:24514674
Lattice results for low moments of light meson distribution amplitudes
Arthur, R.; Boyle, P. A.; Broemmel, D.; Flynn, J. M.; Rae, T. D.; Sachrajda, C. T. C.; Donnellan, M. A.
2011-04-01
As part of the UKQCD and RBC collaborations'N{sub f}=2+1 domain-wall fermion phenomenology programme, we calculate the first two moments of the light-cone distribution amplitudes of the pseudoscalar mesons {pi} and K and the (longitudinally polarized) vector mesons {rho}, K{sup *}, and {phi}. We obtain the desired quantities with good precision and are able to discern the expected quark-mass dependence of SU(3)-flavor breaking effects. An important ingredient of the calculation is the nonperturbative renormalization of lattice operators using a regularization-independent momentum scheme.
Phase coherence and pairing amplitude in photo-excited superconductors
NASA Astrophysics Data System (ADS)
Perfetti, Luca; Piovera, Christian; Zhang, Zailan
2016-05-01
New data on Bi2Sr2CaCu2O8+δ (Bi2212) reveal interesting aspects of photoexcited superconductors. The electrons dynamics show that inelastic scattering by nodal quasiparticles decreases when the temperature is lowered below the critical value of the superconducting phase transition. This drop of electronic dissipation is astonishingly robust and survives to photoexcitation densities much larger than the value sustained by long-range superconductivity. The unconventional behavior of quasiparticle scattering is ascribed to superconducting correlations extending on a length scale comparable to the inelastic mean-free path. Our measurements indicate that strongly driven superconductors enter in a regime without phase coherence but finite pairing amplitude.
Calculation of inclusive probabilities from single-particle amplitudes
NASA Astrophysics Data System (ADS)
Kürpick, Peter; Lüdde, Hans Jürgen
1993-04-01
On the basis of the independent particle model, used to describe collisions between ions and atoms involving many electrons, the formalism of inclusive probabilities allows the computation of many-electron transition probabilities from single-particle amplitudes. The method presented can answer practically any experimental question formulated in terms of a certain number of vacancies and occupancies as can be measured in a typical ion-atom collision experiment. It is specialised to calculate many-particle probabilities with respect to a minimum number of vacancies or occupancies in one or more subshells as obtained e.g. in KLL- or KLM-Auger spectra.
Statistical modeling of in situ hiss amplitudes using ground measurements
NASA Astrophysics Data System (ADS)
Golden, D. I.; Spasojevic, M.; Li, W.; Nishimura, Y.
2012-05-01
Plasmaspheric hiss is a naturally occurring extremely low frequency electromagnetic emission that is often observed within the Earth's plasmasphere. Plasmaspheric hiss plays a major role in the scattering and loss of electrons from the Earth's radiation belts, thereby contributing to the maintenance of the slot region between the inner and outer electron belt. Traditionally, in situ satellite observations have been the measurement modality of choice for studies of plasmaspheric hiss due to their ability to directly measure the hiss source region. However, satellite studies are relatively short-lived and very few satellite receivers remain operational for an entire 11-year solar cycle. Ground stations, in contrast, may collect multiple solar cycles' worth of data during their lifetime, yet they cannot directly measure the hiss source region. This study aims to determine the extent to which measurements of hiss at midlatitude ground stations may be used to predict the mean amplitude of in situ measurements of plasmaspheric hiss. We use coincident measurements between Palmer Station, Antarctica (L = 2.4, 50°S invariant latitude) and the THEMIS spacecraft from June 2008 through May 2010, during solar minimum. Using an autoregressive multiple regression model, we show that in the local time sector from 00 < MLT < 12, when the ionosphere above Palmer Station is in darkness and hiss is observed at Palmer, the amplitude of plasmaspheric hiss observed by the THEMIS spacecraft is 1.4 times higher than when hiss is not observed at Palmer. In the same local time sector when the ground station is in daylight and hiss is observed, the THEMIS observed amplitudes are not significantly different from those when hiss is not observed on the ground. A stronger relationship is found in the local time sector from 12 < MLT < 24 where, when Palmer is in daylight and hiss is observed, THEMIS plasmaspheric hiss amplitudes are 2 times higher compared to when hiss is not observed at Palmer
Higher-order multipole amplitudes in charmonium radiative transitions
NASA Astrophysics Data System (ADS)
Artuso, M.; Blusk, S.; Khalil, S.; Mountain, R.; Randrianarivony, K.; Skwarnicki, T.; Stone, S.; Wang, J. C.; Zhang, L. M.; Bonvicini, G.; Cinabro, D.; Lincoln, A.; Smith, M. J.; Zhou, P.; Zhu, J.; Naik, P.; Rademacker, J.; Asner, D. M.; Edwards, K. W.; Reed, J.; Robichaud, A. N.; Tatishvili, G.; White, E. J.; Briere, R. A.; Vogel, H.; Onyisi, P. U. E.; Rosner, J. L.; Alexander, J. P.; Cassel, D. G.; Ehrlich, R.; Fields, L.; Galik, R. S.; Gibbons, L.; Gray, S. W.; Hartill, D. L.; Heltsley, B. K.; Hunt, J. M.; Kreinick, D. L.; Kuznetsov, V. E.; Ledoux, J.; Mahlke-Krüger, H.; Patterson, J. R.; Peterson, D.; Riley, D.; Ryd, A.; Sadoff, A. J.; Shi, X.; Stroiney, S.; Sun, W. M.; Yelton, J.; Rubin, P.; Lowrey, N.; Mehrabyan, S.; Selen, M.; Wiss, J.; Kornicer, M.; Mitchell, R. E.; Shepherd, M. R.; Tarbert, C. M.; Besson, D.; Pedlar, T. K.; Xavier, J.; Cronin-Hennessy, D.; Gao, K. Y.; Hietala, J.; Poling, R.; Zweber, P.; Dobbs, S.; Metreveli, Z.; Seth, K. K.; Tan, B. J. Y.; Tomaradze, A.; Brisbane, S.; Libby, J.; Martin, L.; Powell, A.; Spradlin, P.; Thomas, C.; Wilkinson, G.; Mendez, H.; Ge, J. Y.; Miller, D. H.; Shipsey, I. P. J.; Xin, B.; Adams, G. S.; Hu, D.; Moziak, B.; Napolitano, J.; Ecklund, K. M.; Insler, J.; Muramatsu, H.; Park, C. S.; Thorndike, E. H.; Yang, F.
2009-12-01
Using 24×106 ψ'≡ψ(2S) decays in CLEO-c, we have searched for higher multipole admixtures in electric-dipole-dominated radiative transitions in charmonia. We find good agreement between our data and theoretical predictions for magnetic quadrupole (M2) amplitudes in the transitions ψ'→γχc1,c2 and χc1,c2→γJ/ψ, in striking contrast to some previous measurements. Let b2J and a2J denote the normalized M2 amplitudes in the respective aforementioned decays, where the superscript J refers to the angular momentum of the χcJ. By performing unbinned maximum likelihood fits to full five-parameter angular distributions, we found the following values of M2 admixtures for Jχ=1: a2J=1=(-6.26±0.63±0.24)×10-2 and b2J=1=(2.76±0.73±0.23)×10-2, which agree well with theoretical expectations for a vanishing anomalous magnetic moment of the charm quark. For Jχ=2, if we fix the electric octupole (E3) amplitudes to zero as theory predicts for transitions between charmonium S states and P states, we find a2J=2=(-9.3±1.6±0.3)×10-2 and b2J=2=(1.0±1.3±0.3)×10-2. If we allow for E3 amplitudes we find, with a four-parameter fit, a2J=2=(-7.9±1.9±0.3)×10-2, b2J=2=(0.2±1.4±0.4)×10-2, a3J=2=(1.7±1.4±0.3)×10-2, and b3J=2=(-0.8±1.2±0.2)×10-2. We determine the ratios a2J=1/a2J=2=0.67-0.13+0.19 and a2J=1/b2J=1=-2.27-0.99+0.57, where the theoretical predictions are independent of the charmed quark magnetic moment and are a2J=1/a2J=2=0.676±0.071 and a2J=1/b2J=1=-2.27±0.16.
Non-gauge phase transformations in quantum transition amplitudes
NASA Technical Reports Server (NTRS)
Reiss, H. R.
1993-01-01
The prescription for introducing a gauge transformation into a quantum transition amplitude, nominally well known, contains an ambiguous feature. It is presumed by some authors that an appropriate transformation of the phase of a wave function will generate the associated gauge transformation. It is shown that this is a necessary but not sufficient step. Examples from the literature are cited to show the consequences of the failure of this procedure. One must distinguish between true gauge transformations and unitary transformations within a fixed gauge.
SPECTRAL AMPLITUDE AND PHASE EVOLUTION IN PETAWATT LASER PULSES
Filip, C V
2010-11-22
The influence of the active gain medium on the spectral amplitude and phase of amplified pulses in a CPA system is studied. Results from a 10-PW example based on Nd-doped mixed glasses are presented. In conclusion, this study shows that, by using spectral shaping and gain saturation in a mixed-glass amplifier, it is possible to produce 124 fs, 1.4 kJ laser pulses. One detrimental effect, the pulse distortion due to resonant amplification medium, has been investigated and its magnitude as well as its compensation calculated.
Fluidic Oscillator Having Decoupled Frequency and Amplitude Control
NASA Technical Reports Server (NTRS)
Koklu, Mehti (Inventor)
2016-01-01
A fluidic oscillator having independent frequency and amplitude control includes a fluidic-oscillator main flow channel having a main flow inlet, a main flow outlet, and first and second control ports disposed at opposing sides thereof. A fluidic-oscillator controller has an inlet and outlet. A volume defined by the main flow channel is greater than the volume defined by the controller. A flow diverter coupled to the outlet of the controller defines a first fluid flow path from the controller's outlet to the first control port and defines a second fluid flow path from the controller's outlet to the second control port.
Demodulation techniques for the amplitude modulated laser imager
NASA Astrophysics Data System (ADS)
Mullen, Linda; Laux, Alan; Cochenour, Brandon; Zege, Eleonora P.; Katsev, Iosif L.; Prikhach, Alexander S.
2007-10-01
A new technique has been found that uses in-phase and quadrature phase (I/Q) demodulation to optimize the images produced with an amplitude-modulated laser imaging system. An I/Q demodulator was used to collect the I/Q components of the received modulation envelope. It was discovered that by adjusting the local oscillator phase and the modulation frequency, the backscatter and target signals can be analyzed separately via the I/Q components. This new approach enhances image contrast beyond what was achieved with a previous design that processed only the composite magnitude information.
Optimal beam splitters for the division-of-amplitude photopolarimeter
NASA Astrophysics Data System (ADS)
Azzam, R. M. A.; de, A.
2003-05-01
Optimal optical parameters of the beam splitter that is used in the division-of-amplitude photopolarimeter are determined. These are (1) 50%-50% split ratio of the all-dielectric beam splitter, (2) differential phase shifts in reflection and transmission Δr and Δt that differ by +/-π/2, and (3) ellipsometric parameters (ψr, ψt)= (27.368°, 62.632°) or (62.632°, 27.368°). It is also shown that for any nonabsorbing beam splitter that splits incident unpolarized light equally, the relationship ψr+ψt=π/2 is always satisfied.
Terahertz holography for imaging amplitude and phase objects.
Hack, Erwin; Zolliker, Peter
2014-06-30
A non-monochromatic THz Quantum Cascade Laser and an uncooled micro-bolometer array detector with VGA resolution are used in a beam-splitter free holographic set-up to measure amplitude and phase objects in transmission. Phase maps of the diffraction pattern are retrieved using the Fourier transform carrier fringe method; while a Fresnel-Kirchhoff back propagation algorithm is used to reconstruct the complex object image. A lateral resolution of 280 µm and a relative phase sensitivity of about 0.5 rad are estimated from reconstructed images of a metallic Siemens star and a polypropylene test structure, respectively. Simulations corroborate the experimental results.
Short Large-Amplitude Magnetic Structures (SLAMS) at Venus
NASA Technical Reports Server (NTRS)
Collinson, G. A.; Wilson, L. B.; Sibeck, D. G.; Shane, N.; Zhang, T. L.; Moore, T. E.; Coates, A. J.; Barabash, S.
2012-01-01
We present the first observation of magnetic fluctuations consistent with Short Large-Amplitude Magnetic Structures (SLAMS) in the foreshock of the planet Venus. Three monolithic magnetic field spikes were observed by the Venus Express on the 11th of April 2009. The structures were approx.1.5->11s in duration, had magnetic compression ratios between approx.3->6, and exhibited elliptical polarization. These characteristics are consistent with the SLAMS observed at Earth, Jupiter, and Comet Giacobini-Zinner, and thus we hypothesize that it is possible SLAMS may be found at any celestial body with a foreshock.
Elliptic multiple zeta values and one-loop superstring amplitudes
NASA Astrophysics Data System (ADS)
Broedel, Johannes; Mafra, Carlos R.; Matthes, Nils; Schlotterer, Oliver
2015-07-01
We investigate iterated integrals on an elliptic curve, which are a natural genus-one generalization of multiple polylogarithms. These iterated integrals coincide with the multiple elliptic polylogarithms introduced by Brown and Levin when constrained to the real line. At unit argument they reduce to an elliptic analogue of multiple zeta values, whose network of relations we start to explore. A simple and natural application of this framework are one-loop scattering amplitudes in open superstring theory. In particular, elliptic multiple zeta values are a suitable language to express their low energy limit. Similar to the techniques available at tree-level, our formalism allows to completely automatize the calculation.
NASA Astrophysics Data System (ADS)
Timofeev, Vladislav
2016-07-01
As part of the Yakut complex systems by measuring the intensity of cosmic rays has a unique device spherical - ionization chamber ASK-1 with a lead screen thickness of 12 cm. The camera allows you to explore the physical characteristics of the so-called "ionization jerks " - sharp increases ionization current caused by the passage through the device much ionizing particles of cosmic origin. Due to a large increase in current nuclear cascade "showers", formed mainly by particles of cosmic rays in the camera screen. Over the entire period of observation (50 years old) camera ASK-1 was registered 59125 aftershocks. Their nature and properties still does not sufficiently studied, especially in medium and large amplitudes.
Relativistic, model-independent, multichannel 2→2 transition amplitudes in a finite volume
Briceno, Raul A.; Hansen, Maxwell T.
2016-07-13
We derive formalism for determining 2 + J → 2 infinite-volume transition amplitudes from finite-volume matrix elements. Specifically, we present a relativistic, model-independent relation between finite-volume matrix elements of external currents and the physically observable infinite-volume matrix elements involving two-particle asymptotic states. The result presented holds for states composed of two scalar bosons. These can be identical or non-identical and, in the latter case, can be either degenerate or non-degenerate. We further accommodate any number of strongly-coupled two-scalar channels. This formalism will, for example, allow future lattice QCD calculations of themore » $$\\rho$$-meson form factor, in which the unstable nature of the $$\\rho$$ is rigorously accommodated. In conclusion, we also discuss how this work will impact future extractions of nuclear parity and hadronic long-range matrix elements from lattice QCD.« less
The effects of dual-channel coupling on the transition from amplitude death to oscillation death
NASA Astrophysics Data System (ADS)
Chen, Jiangnan; Liu, Weiqing; Zhu, Yun; Xiao, Jinghua
2016-07-01
Oscillation quenching including amplitude death (AD) and oscillation death (OD) in addition to the transition processes between them have been hot topics in aspect of chaos control, physical and biological applications. The effects of dual-channel coupling on the AD and OD dynamics regimes, and their transition processes in coupled nonidentical oscillators are explored numerically and theoretically. Our results indicate that an additional repulsive coupling tends to shrink the AD domain while it enlarges the OD domain, however, an additional attractive coupling acts inversely. As a result, the transitions from AD to OD are replaced by transitions from oscillation state (OS) to AD or from OS to OD in the dual-channel coupled oscillators with different frequency mismatches. Our results are helpful to better understand the control of AD and OD and their transition processes.
Generalizing the transition from amplitude to oscillation death in coupled oscillators.
Zou, Wei; Senthilkumar, D V; Koseska, Aneta; Kurths, Jürgen
2013-11-01
Amplitude death (AD) and oscillation death (OD) are two structurally different oscillation quenching types in coupled nonlinear oscillators. The transition from AD to OD has been recently realized due to the interplay between heterogeneity and coupling strength [A. Koseska et al., Phys. Rev. Lett. 111, 024103 (2013)]. We identify here the transition from AD to OD in nonlinear oscillators with couplings of distinct natures. It is demonstrated that the presence of time delay in the coupling cannot induce such a transition in identical oscillators, but it can indeed facilitate its occurrence with a low degree of heterogeneity. Moreover, it is further shown that the AD to OD transition is reliably observed in identical oscillators with dynamic and conjugate couplings. The coexistence of AD and OD and rich stable OD configurations after the transition are revealed, which are of great significance for potential applications in physics, biology, and control studies.
NASA Astrophysics Data System (ADS)
Minář, Jiří; Grémaud, Benoît
2015-04-01
In this paper we show that a Dirac Hamiltonian in a curved background spacetime can be interpreted, when discretized, as a tight-binding Hamiltonian with non-unitary tunneling amplitudes. We find the form of the non-unitary tunneling matrices in terms of the metric tensor. The main motivation behind this exercise is the feasibility of such Hamiltonians by means of laser-assisted tunnelings in cold atomic experiments. The mapping thus provides a physical interpretation of such Hamiltonians. We demonstrate the use of the mapping on the example of a time-dependent metric in 2+1 dimensions. Studying the spin dynamics, we find qualitative agreement with known theoretical predictions, namely particle pair creation in an expanding Universe.
Amplitude and frequency content analysis of optoacoustic signals in laser heated ex-vivo tissues
NASA Astrophysics Data System (ADS)
Laderoute, Annie
Laser thermal therapy involves heating tissue using light to temperatures between 55 °C and 95 °C for several minutes resulting in coagulation and cell death. This treatment method has been under investigation for use as a minimally invasive method for eradicating solid tumors and cancer cells. Optoacoustic imaging involves exposing optically absorbing media to nanosecond pulsed laser light causing rapid localized heating and inducing acoustic waves to be detected by wideband transducers. It has been proposed as a real-time, noninvasive method for monitoring laser thermal therapy. This thesis investigates the use of optoacoustics to discriminate between native and coagulated ex-vivo tissues (porcine tenderloin muscle, bovine liver and bovine kidney). Tissues were heated using a 1000 mum core optical fibre coupled to an 810 nm diode laser to generate lesions. Samples were scanned at 1064 nm using a prototype reverse-mode optoacoustic system consisting of a pulsed laser coupled to a bifurcated fibre bundle, and an 8 element annular array wideband ultrasound transducer with a central frequency of ˜5 MHz. Thermal coagulation effects were analyzed using optoacoustic signal amplitude-based and frequency-based analysis. Significant differences (p<0.05) in optoacoustic signals, between native and coagulated porcine muscle, were observed with both amplitude-based and frequency-based analysis methods. Inconsistencies in the amplitude-based analysis were observed in the bovine liver and bovine kidney. Significant differences between native and coagulated bovine liver tissues were observed in two of the three frequency parameters of interest (slope and midband fit, p<0.05). No significant differences between native and coagulated bovine kidney tissues using frequency-based analysis. Amplitude-based analysis methods take advantage of the optical and thermo-mechanical properties of the tissues, while the frequency-based method extracts metrics related physical parameters of
Large amplitude nonlinear structures in the nighttime polar mesosphere
NASA Astrophysics Data System (ADS)
Maharaj, Shimul K.; Bharuthram, Ramashwar; Singh Lakhina, Gurbax; Muralikrishna, Polinaya; Singh, Satyavir
2016-07-01
The existence of large amplitude potential structures will be investigated for a plasma composed of negative ions, positive ions, electrons and an additional fourth component of charged (usually positive) nano-sized ions in an attempt to model the plasma composition in the nighttime polar mesosphere (˜80 - 90 km altitude) [1]. The fourth ionic component becomes positively charged if there is a high enough concentration of negative ions which are sufficiently heavy. The positive charge on the fourth component can be explained by the capture of currents, and is not a result of photo-emission and secondary electron emission processes. Consequently, if the negative ions are much lighter, then the fourth ion component will become negatively charged. The charged ion species will be treated as inertial species which are cold or adiabatic, whilst the electrons will be considered to be Boltzmann-distributed (isothermal). Taking into consideration not only the dynamics of the heaviest species (dust-acoustic) but also the lighter ions (ion-acoustic), the theoretical study will use the Sagdeev pseudo-potential formalism to explore the existence of arbitrary amplitude solitons and double layer potential structures. [1] Observations of positively charged nanoparticles in the nighttime polar mesosphere, M. Rapp, J. Hedin, I. Strelnikova, M. Friederich, J. Gumbel, and F.˜J. Lübken, Geophys. Res. Letters. 32, L23821, doi:10.1029/2005GL024676 (2005).
Excitation and evolution of finite-amplitude plasma wave
Hou, Y. W.; Wu, Y. C.; Chen, M. X.; Yu, M. Y.; Wu, B.
2015-12-15
The evolution of a small spatially periodic perturbation in the electron velocity distribution function in collisionless plasma is reconsidered by numerically solving the Vlasov and Poisson equations. The short as well as long time behaviors of the excited oscillations and damping/modulation are followed. In the small but finite-amplitude excited plasma wave, resonant electrons become trapped in the wave potential wells and their motion affects the low-velocity electrons participating in the plasma oscillations, leading to modulation of the latter at an effective trapping frequency. It is found that the phase space of the resonant and low-velocity electrons becomes chaotic, but then self-organization takes place but remains fine-scale chaotic. It is also found that as long as particles are trapped, there is only modulation and no monotonic damping of the excited plasma wave. The modulation period/amplitude increases/decreases as the magnitude of the initial disturbance is reduced. For the initial and boundary conditions used here, linear Landau damping corresponds to the asymptotic limit of the modulation period becoming infinite, or no trapping of the resonant electrons.
Virtuality and transverse momentum dependence of the pion distribution amplitude
NASA Astrophysics Data System (ADS)
Radyushkin, A. V.
2016-03-01
We describe basics of a new approach to transverse momentum dependence in hard exclusive processes. We develop it in application to the transition process γ*γ →π0 at the handbag level. Our starting point is coordinate representation for matrix elements of operators [in the simplest case, bilocal O (0 ,z ) ] describing a hadron with momentum p . Treated as functions of (p z ) and z2, they are parametrized through virtuality distribution amplitudes (VDA) Φ (x ,σ ) , with x being Fourier conjugate to (p z ) and σ Laplace conjugate to z2. For intervals with z+=0 , we introduce the transverse momentum distribution amplitude (TMDA) Ψ (x ,k⊥), and write it in terms of VDA Φ (x ,σ ). The results of covariant calculations, written in terms of Φ (x ,σ ), are converted into expressions involving Ψ (x ,k⊥). Starting with scalar toy models, we extend the analysis onto the case of spin-1 /2 quarks and QCD. We propose simple models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BABAR and BELLE) data on the pion transition form factor. We also discuss how one can generate high-k⊥ tails from primordial soft distributions.
Nighttime ionospheric D region parameters from VLF phase and amplitude
NASA Astrophysics Data System (ADS)
Thomson, Neil R.; Clilverd, Mark A.; McRae, Wayne M.
2007-07-01
Nighttime ionospheric D region heights and electron densities are determined from an extensive set of VLF radio phase and amplitude observations. The D region parameters are characterized by the traditional H' (height in kilometers) and β (sharpness in km-1) as used by Wait and by the U. S. Navy in their Earth-ionosphere waveguide programs. The VLF measurements were made with several frequencies in the range 10 kHz to 41 kHz on long, mainly all-sea paths, including Omega La Reunion and Omega Argentina to Dunedin, New Zealand, NAU (Puerto Rico) and NAA (Maine, USA) to Cambridge, UK, and NPM (Hawaii) to San Francisco. Because daytime VLF propagation on such paths is readily measured and predicted, the differences between night and day amplitudes and phases were measured and compared with calculations for a range of nighttime ionospheric parameters. This avoided the problem of uncertainties in the transmitter powers. In this way the height, H', and the sharpness, β, when averaged over periods of several days, at least for the midlatitude D region near solar minimum, were found to be 85.1 ± 0.4 km and 0.63 ± 0.04 km-1, respectively.
Quantifying phase-amplitude coupling in neuronal network oscillations.
Onslow, Angela C E; Bogacz, Rafal; Jones, Matthew W
2011-03-01
Neuroscience time series data from a range of techniques and species reveal complex, non-linear interactions between different frequencies of neuronal network oscillations within and across brain regions. Here, we briefly review the evidence that these nested, cross-frequency interactions act in concert with linearly covariant (within-frequency) activity to dynamically coordinate functionally related neuronal ensembles during behaviour. Such studies depend upon reliable quantification of cross-frequency coordination, and we compare the properties of three techniques used to measure phase-amplitude coupling (PAC)--Envelope-to-Signal Correlation (ESC), the Modulation Index (MI) and Cross-Frequency Coherence (CFC)--by standardizing their filtering algorithms and systematically assessing their robustness to noise and signal amplitude using artificial signals. Importantly, we also introduce a freely-downloadable method for estimating statistical significance of PAC, a step overlooked in the majority of published studies. We find that varying data length and noise levels leads to the three measures differentially detecting false positives or correctly identifying frequency bands of interaction; these conditions should therefore be taken into careful consideration when selecting PAC analyses. Finally, we demonstrate the utility of the three measures in quantifying PAC in local field potential data simultaneously recorded from rat hippocampus and prefrontal cortex, revealing a novel finding of prefrontal cortical theta phase modulating hippocampal gamma power. Future adaptations that allow detection of time-variant PAC should prove essential in deciphering the roles of cross-frequency coupling in mediating or reflecting nervous system function.
Large-Amplitude Longitudinal Oscillations in a Solar Filament
NASA Technical Reports Server (NTRS)
Luna, M.; Karpen, J.
2012-01-01
We have developed the first self-consistent model for the observed large-amplitude oscillations along filament axes that explains the restoring force and damping mechanism. We have investigated the oscillations of multiple threads formed in long, dipped flux tubes through the thermal nonequilibrium process, and found that the oscillation properties predicted by our simulations agree with the observed behavior. We then constructed a model for the large-amplitude longitudinal oscillations that demonstrates that the restoring force is the projected gravity in the tube where the threads oscillate. Although the period is independent of the tube length and the constantly growing mass, the motions are strongly damped by the steady accretion of mass onto the threads by thermal nonequilibrium. The observations and our model suggest that a nearby impulsive event drives the existing prominence threads along their supporting tubes, away from the heating deposition site, without destroying them. The subsequent oscillations occur because the displaced threads reside in magnetic concavities with large radii of curvature. Our model yields a powerful seismological method for constraining the coronal magnetic field and radius of curvature of dips. Furthermore, these results indicate that the magnetic structure is most consistent with the sheared-arcade model for filament channels.
Virtuality and transverse momentum dependence of the pion distribution amplitude
Radyushkin, Anatoly V.
2016-03-08
We describe basics of a new approach to transverse momentum dependence in hard exclusive processes. We develop it in application to the transition process γ*γ → π0 at the handbag level. Our starting point is coordinate representation for matrix elements of operators (in the simplest case, bilocal O (0,z)) describing a hadron with momentum p. Treated as functions of (pz) and z2, they are parametrized through virtuality distribution amplitudes (VDA) Φ(x,σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z2. For intervals with z+ = 0, we introduce the transverse momentum distribution amplitude (TMDA) ψ(x, k), and writemore » it in terms of VDA Φ(x,σ). The results of covariant calculations, written in terms of Φ(x, σ) are converted into expressions involving ψ(x, k). Starting with scalar toy models, we extend the analysis onto the case of spin-1/2 quarks and QCD. We propose simple models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BaBar and BELLE) data on the pion transition form factor. Furthermore, we discuss how one can generate high-k tails from primordial soft distributions.« less
Amplitude-Stabilized Oscillator for a Capacitance-Probe Electrometer
NASA Technical Reports Server (NTRS)
Blaes, Brent R.; Schaefer, Rembrandt T.
2012-01-01
A multichannel electrometer voltmeter that employs a mechanical resonator maintained in sustained amplitude-stabilized oscillation has been developed for the space-based measurement of an Internal Electrostatic Discharge Monitor (IESDM) sensor. The IESDM is new sensor technology targeted for integration into a Space Environmental Monitor (SEM) subsystem used for the characterization and monitoring of deep dielectric charging on spacecraft. Creating a stable oscillator from the mechanical resonator was achieved by employing magnetic induction for sensing the resonator s velocity, and forcing a current through a coil embedded in the resonator to produce a Lorentz actuation force that overcomes the resonator s dissipative losses. Control electronics employing an AGC loop provide conditions for stabilized, constant amplitude harmonic oscillation. The prototype resonator was composed of insulating FR4 printed-wireboard (PWB) material containing a flat, embedded, rectangular coil connected through flexure springs to a base PWB, and immersed in a magnetic field having two regions of opposite field direction generated by four neodymium block magnets. In addition to maintaining the mechanical movement needed for the electrometer s capacitor-probe transducer, this oscillator provides a reference signal for synchronous detection of the capacitor probe s output signal current so drift of oscillation frequency due to environmental effects is inconsequential.
Structure of ionospheric irregularities from amplitude and phase scintillation observations
Bhattacharyya, A.; Rastogi, R.G. )
1991-04-01
The mutual coherence function Gamma 2, or the second moment of the complex amplitude of a radio wave which traverses through equatorial F region irregularities, is computed from amplitude and phase scintillation data. Theoretically, the equation satisfied by the coherence function has an analytic solution over the whole range of scintillation strength. This solution is directly related to the structure function for the phase fluctuations produced by the irregularities. Hence, the shape of the correlation function for variations in the total electron content along the signal path can be derived from the computed values of Gamma 2. With a suitable power-law model for the irregularities, an 'intermediate break scale', this scale, as well as the rms density fluctuation are deduced from a comparison of computed values for short-time lags with those expected from theory. During a postsunset scintillation event, this scale is found to increase with local time. In the context of the generalized Rayleigh-Taylor instability, which is the likely source of the irregularities, this increase may be attributed to a decline in the effective electric field prevailing in the region of the irregularities. 26 refs.
Data dependence for the amplitude equation of surface waves
NASA Astrophysics Data System (ADS)
Secchi, Paolo
2016-04-01
We consider the amplitude equation for nonlinear surface wave solutions of hyperbolic conservation laws. This is an asymptotic nonlocal, Hamiltonian evolution equation with quadratic nonlinearity. For example, this equation describes the propagation of nonlinear Rayleigh waves (Hamilton et al. in J Acoust Soc Am 97:891-897, 1995), surface waves on current-vortex sheets in incompressible MHD (Alì and Hunter in Q Appl Math 61(3):451-474, 2003; Alì et al. in Stud Appl Math 108(3):305-321, 2002) and on the incompressible plasma-vacuum interface (Secchi in Q Appl Math 73(4):711-737, 2015). The local-in-time existence of smooth solutions to the Cauchy problem for the amplitude equation in noncanonical variables was shown in Hunter (J Hyperbolic Differ Equ 3(2):247-267, 2006), Secchi (Q Appl Math 73(4):711-737, 2015). In the present paper we prove the continuous dependence in strong norm of solutions on the initial data. This completes the proof of the well-posedness of the problem in the classical sense of Hadamard.
Large-amplitude ULF waves at high latitudes
NASA Astrophysics Data System (ADS)
Guido, T.; Tulegenov, B.; Streltsov, A. V.
2014-11-01
We present results from the statistical study of ULF waves detected by the fluxgate magnetometer in Gakona, Alaska during several experimental campaigns conducted at the High Frequency Active Auroral Research Program (HAARP) facility in years 2011-2013. We analyzed frequencies of ULF waves recorded during 26 strongly disturbed geomagnetic events (substorms) and compared them with frequencies of ULF waves detected during magnetically quiet times. Our analysis demonstrates that the frequency of the waves carrying most of the power in almost all these events is less than 1 mHz. We also analyzed data from the ACE satellite, measuring parameters of the solar wind in the L1 Lagrangian point between Earth and Sun, and found that in several occasions there is a strong correlation between oscillations of the magnetic field in the solar wind and oscillations detected on the ground. We also found several cases when there is no correlation between signals detected on ACE and on the ground. This finding suggests that these frequencies correspond to the fundamental eigenfrequency of the coupled magnetosphere-ionosphere system, and the amplitude of these waves can reach significant magnitude when the system is driven by the external driver (for example, the solar wind) with this particular frequency. When the frequency of the driver does not match the frequency of the system, the waves still are observed, but their amplitudes are much smaller.
A canonical circuit for generating phase-amplitude coupling.
Onslow, Angela C E; Jones, Matthew W; Bogacz, Rafal
2014-01-01
'Phase amplitude coupling' (PAC) in oscillatory neural activity describes a phenomenon whereby the amplitude of higher frequency activity is modulated by the phase of lower frequency activity. Such coupled oscillatory activity--also referred to as 'cross-frequency coupling' or 'nested rhythms'--has been shown to occur in a number of brain regions and at behaviorally relevant time points during cognitive tasks; this suggests functional relevance, but the circuit mechanisms of PAC generation remain unclear. In this paper we present a model of a canonical circuit for generating PAC activity, showing how interconnected excitatory and inhibitory neural populations can be periodically shifted in to and out of oscillatory firing patterns by afferent drive, hence generating higher frequency oscillations phase-locked to a lower frequency, oscillating input signal. Since many brain regions contain mutually connected excitatory-inhibitory populations receiving oscillatory input, the simplicity of the mechanism generating PAC in such networks may explain the ubiquity of PAC across diverse neural systems and behaviors. Analytic treatment of this circuit as a nonlinear dynamical system demonstrates how connection strengths and inputs to the populations can be varied in order to change the extent and nature of PAC activity, importantly which phase of the lower frequency rhythm the higher frequency activity is locked to. Consequently, this model can inform attempts to associate distinct types of PAC with different network topologies and physiologies in real data. PMID:25136855
Analytic evolution of singular distribution amplitudes in QCD
NASA Astrophysics Data System (ADS)
Tandogan, Asli
Distribution amplitudes (DAs) are the basic functions that contain information about the quark momentum. DAs are necessary to describe hard exclusive processes in quantum chromodynamics. We describe a method of analytic evolution of DAs that have singularities such as nonzero values at the end points of the support region, jumps at some points inside the support region and cusps. We illustrate the method by applying it to the evolution of a flat (constant) DA, antisymmetric flat DA, and then use the method for evolution of the two-photon generalized distribution amplitude. Our approach to DA evolution has advantages over the standard method of expansion in Gegenbauer polynomials [1, 2] and over a straightforward iteration of an initial distribution with evolution kernel. Expansion in Gegenbauer polynomials requires an infinite number of terms in order to accurately reproduce functions in the vicinity of singular points. Straightforward iteration of an initial distribution produces logarithmically divergent terms at each iteration. In our method the logarithmic singularities are summed from the start, which immediately produces a continuous curve. Afterwards, in order to get precise results, only one or two iterations are needed.
Turns-amplitude analysis in normal and myopathic facial muscles.
Karandreas, Nikos; Kararizou, Evangelia; Papagianni, Aikaterini; Zambelis, Thomas; Kokotis, Panagiotis
2011-03-01
The purpose of this study was to assess turns/amplitude analysis (TAA) as an objective alternative to conventional qualitative electromyography (EMG) for detection of myopathy in facial muscles. Normal values of TAA parameters were calculated in the frontalis and mentalis muscles of 26 control subjects. We estimated the slope of the regression line of mean amplitude/turn values (MA) plotted against the number of turns/second (NT) and the resulting clouds. The 95% confidence limits of the cloud data were drawn as an ellipse. The sensitivity of TAA was determined from a group of 35 myopathic patients and specificity from a second group of 25 control subjects. Significant differences for every TAA parameter were found between frontalis and mentalis. Cumulative sensitivity and specificity of TAA for frontalis and mentalis were 74.6%, 56.5%, and 73.3%, 70.8%, respectively. With at least two of the aforementioned criteria abnormal, the sensitivity and specificity for frontalis and mentalis were 61.3%, 82.6%, and 56.7%, 100.0%, respectively.
Limiting amplitudes of fully nonlinear interfacial tides and solitons
NASA Astrophysics Data System (ADS)
Aguiar-González, Borja; Gerkema, Theo
2016-08-01
A new two-fluid layer model consisting of forced rotation-modified Boussinesq equations is derived for studying tidally generated fully nonlinear, weakly nonhydrostatic dispersive interfacial waves. This set is a generalization of the Choi-Camassa equations, extended here with forcing terms and Coriolis effects. The forcing is represented by a horizontally oscillating sill, mimicking a barotropic tidal flow over topography. Solitons are generated by a disintegration of the interfacial tide. Because of strong nonlinearity, solitons may attain a limiting table-shaped form, in accordance with soliton theory. In addition, we use a quasi-linear version of the model (i.e. including barotropic advection but linear in the baroclinic fields) to investigate the role of the initial stages of the internal tide prior to its nonlinear disintegration. Numerical solutions reveal that the internal tide then reaches a limiting amplitude under increasing barotropic forcing. In the fully nonlinear regime, numerical experiments suggest that this limiting amplitude in the underlying internal tide extends to the nonlinear case in that internal solitons formed by a disintegration of the internal tide may not reach their table-shaped form with increased forcing, but appear limited well below that state.
Amplitude equations for the electrohydrodynamic instability in nematic liquid crystals
NASA Astrophysics Data System (ADS)
Kaiser, M.; Pesch, W.
1993-12-01
We study the near-threshold behavior of electrohydrodynamic convection (EHC) in planarly aligned nematic liquid crystals in the (low-frequency) conduction regime. The investigations are based on a rigorous and systematic weakly nonlinear analysis of the standard hydrodynamic equations leading to a reduced description in terms of order-parameter equations. The typical experimental stability regimes in control parameter and wave-number space are identified for normal rolls near threshold. In particular, the decisive role of mean-flow effects in triggering the typical secondary zigzag instability leading to oblique rolls is emphasized. Subsequently, a set of coupled amplitude equations is derived directly from the basic equations that includes the mean-flow effects and higher-order gradient terms important at least in EHC. Simulations of the amplitude equations point to the possible existence of more than one attractor beyond the zigzag destabilization line, which might explain the sometimes conflicting experimental results. The scenario of ``weak turbulence'' (sometimes called ``defect turbulence'') is well accounted for by the theory.
Spatial horizons in amplitude and frequency modulation atomic force microscopy.
Font, Josep; Santos, Sergio; Barcons, Victor; Thomson, Neil H; Verdaguer, Albert; Chiesa, Matteo
2012-04-01
In dynamic atomic force microscopy (AFM) the cantilever is vibrated and its dynamics are monitored to probe the sample with nanoscale and atomic resolution. Amplitude and frequency modulation atomic force microscopy (AM-AFM and FM-AFM) have established themselves as the most powerful methods in the field. Nevertheless, it is still debatable whether one or the other technique is preferred in a given medium or experiment. Here, we quantitatively establish and compare the limitations in resolution of both techniques by introducing the concept of spatial horizon (SH) and quantifying it. The SH is the limiting spatial boundary beyond which collective atomic interactions do not affect the detection parameters of a given feedback system. We show that while an FM-AFM feedback can resolve a single atom or atomic defect where an AM feedback might fail, relative contrast is in fact equivalent for both feedback systems. That is, if the AM feedback could detect sufficiently small amplitude shifts and there was no noise, the detection of single atoms or atomic defects would be equivalent in AM-AFM and FM-AFM.
One-loop amplitudes on the Riemann sphere
NASA Astrophysics Data System (ADS)
Geyer, Yvonne; Mason, Lionel; Monteiro, Ricardo; Tourkine, Piotr
2016-03-01
The scattering equations provide a powerful framework for the study of scattering amplitudes in a variety of theories. Their derivation from ambitwistor string theory led to proposals for formulae at one loop on a torus for 10 dimensional supergravity, and we recently showed how these can be reduced to the Riemann sphere and checked in simple cases. We also proposed analogous formulae for other theories including maximal super-Yang-Mills theory and supergravity in other dimensions at one loop. We give further details of these results and extend them in two directions. Firstly, we propose new formulae for the one-loop integrands of Yang-Mills theory and gravity in the absence of supersymmetry. These follow from the identification of the states running in the loop as expressed in the ambitwistor-string correlator. Secondly, we give a systematic proof of the non-supersymmetric formulae using the worldsheet factorisation properties of the nodal Riemann sphere underlying the scattering equations at one loop. Our formulae have the same decomposition under the recently introduced Q-cuts as one-loop integrands and hence give the correct amplitudes.
Electromyographic amplitude variability of chewing cycles in deaf individuals.
de Oliveira, A Siriani; Vitti, M; Chaves, T C; Bevilaqua-Grossi, D; Zuccolotto, M C C; Regalo, S C H
2006-09-01
This study had the goal of determining if the amplitude of the surface electromyograph signals changes in terms of time of analysis and subjects, deaf or normal listeners, when estimated in a 250 ms of length window, visually determined, considering the most stable signal period from the center of the chewing cycle. In order to do this, groups with control subjects, listeners and deaf individuals, who made use of the Brazilian sign language (LIBRAS), were studied. All participants performed continuous 5 s of chewing for the electromyographic recording of the temporalis and masseter muscles. The normalized RMS values of three chewing cycles were compared between and among groups. The results from the Kruskall-Wallis test did not show any statistically significant differences (p > 0.05) between the normalized RMS values obtained in the three individual chewing cycles, for each of the two completed and evaluated cycles, in both groups studied. The Mann-Whitney test showed that the mean normalized RMS values obtained in the first chewing cycle were higher for the control group when compared to the mean amplitude values of the first chewing cycle of the group of deaf volunteers. It can be concluded that, in these experimental conditions, the RMS values obtained from the select windows of 250 ms length duration, in relatively stable periods of the electromyographic signal of chewing cycles did not suffer any changes in terms of EMG register duration, in both studied groups, but does give evidence of the differences among the groups.
Wavefront construction Kirchhoff migration with ray-amplitude corrections
Fehler, Michael C.; Hildebrand, S. T.; Huang, L.; Alde, D. M.
2002-01-01
Kirchhoff migration using ray tracing travel times has been a popular imaging method for many years. There are significant limitations in the ability of Kirchhoff migration using only first arrivals to reliably image regions of complex structure. Thus, new methods for imaging have been sought. One approach for improving imaging capability is to use ray tracing methods that allow the calculation of multiple-valued travel time tables to be used in migration. Additional improvements in ray-based imaging methods may be obtained by including amplitudes and phases of rays calculated using some ray tracing approach. One approach for calculating multiple-valued travel time tables along with estimates of amplitudes and phases is the use of wavefront construction ray tracing. We introduce our wavefront construction-based migration algorithm and present some example images obtained using the method. We compare the images obtained with those obtained using a dual-domain wave-equation migration method that we call Extended Local Rytov Fourier migration method.
Seizure Prediction and Detection via Phase and Amplitude Lock Values
Myers, Mark H.; Padmanabha, Akshay; Hossain, Gahangir; de Jongh Curry, Amy L.; Blaha, Charles D.
2016-01-01
A robust seizure prediction methodology would enable a “closed-loop” system that would only activate as impending seizure activity is detected. Such a system would eliminate ongoing stimulation to the brain, thereby eliminating such side effects as coughing, hoarseness, voice alteration, and paresthesias (Murphy et al., 1998; Ben-Menachem, 2001), while preserving overall battery life of the system. The seizure prediction and detection algorithm uses Phase/Amplitude Lock Values (PLV/ALV) which calculate the difference of phase and amplitude between electroencephalogram (EEG) electrodes local and remote to the epileptic event. PLV is used as the seizure prediction marker and signifies the emergence of abnormal neuronal activations through local neuron populations. PLV/ALVs are used as seizure detection markers to demarcate the seizure event, or when the local seizure event has propagated throughout the brain turning into a grand-mal event. We verify the performance of this methodology against the “CHB-MIT Scalp EEG Database” which features seizure attributes for testing. Through this testing, we can demonstrate a high degree of sensivity and precision of our methodology between pre-ictal and ictal events. PMID:27014017
LARGE-AMPLITUDE LONGITUDINAL OSCILLATIONS IN A SOLAR FILAMENT
Luna, M.
2012-05-01
We have developed the first self-consistent model for the observed large-amplitude oscillations along filament axes that explains the restoring force and damping mechanism. We have investigated the oscillations of multiple threads formed in long, dipped flux tubes through the thermal nonequilibrium process, and found that the oscillation properties predicted by our simulations agree with the observed behavior. We then constructed a model for the large-amplitude longitudinal oscillations that demonstrates that the restoring force is the projected gravity in the tube where the threads oscillate. Although the period is independent of the tube length and the constantly growing mass, the motions are strongly damped by the steady accretion of mass onto the threads by thermal nonequilibrium. The observations and our model suggest that a nearby impulsive event drives the existing prominence threads along their supporting tubes, away from the heating deposition site, without destroying them. The subsequent oscillations occur because the displaced threads reside in magnetic concavities with large radii of curvature. Our model yields a powerful seismological method for constraining the coronal magnetic field and radius of curvature of dips. Furthermore, these results indicate that the magnetic structure is most consistent with the sheared-arcade model for filament channels.
Multichannel 1 → 2 transition amplitudes in a finite volume
Briceno, Raul A.; Hansen, Maxwell T.; Walker-Loud, Andre
2015-02-03
We perform a model-independent, non-perturbative investigation of two-point and three-point finite-volume correlation functions in the energy regime where two-particle states can go on-shell. We study three-point functions involving a single incoming particle and an outgoing two-particle state, relevant, for example, for studies of meson decays (e.g., B⁰ → K*l⁺l⁻) or meson photo production (e.g., πγ* → ππ). We observe that, while the spectrum solely depends upon the on-shell scattering amplitude, the correlation functions also depend upon off-shell amplitudes. The main result of this work is a non-perturbative generalization of the Lellouch-Luscher formula relating matrix elements of currents in finite and infinite spatial volumes. We extend that work by considering a theory with multiple, strongly-coupled channels and by accommodating external currents which inject arbitrary four-momentum as well as arbitrary angular-momentum. The result is exact up to exponentially suppressed corrections governed by the pion mass times the box size. We also apply our master equation to various examples, including two processes mentioned above as well as examples where the final state is an admixture of two open channels.
Suprathreshold effects of adaptation produced by amplitude modulation
NASA Astrophysics Data System (ADS)
Wojtczak, Magdalena; Viemeister, Neal F.
2003-08-01
This work extends the study of adaptation to amplitude modulation (AM) to the perception of highly detectable modulation. A fixed-level matching procedure was used to find perceptually equivalent modulation depths for 16-Hz modulation imposed on a 1-kHz standard and a 4-kHz comparison. The modulation depths in the two stimuli were compared before and after a 10-min exposure to a 1-kHz tone (adaptor) 100% modulated in amplitude at different rates. For modulation depths of 63% (20 log m=-4) and smaller, the perceived modulation depth was reduced after exposure to the adaptor that was modulated at the same rate as the standard. The size of this reduction expressed as a difference between the post- and pre-exposure AM depths was similar to the increase in AM-detection threshold observed after adaptation. Postexposure suprathreshold modulation depth was not appreciably reduced when the modulation depth of the standard was large (approached 100%). A much smaller or no reduction in the perceived modulation depth was also observed when the modulation rates of the adaptor and the standard tone were different. The tuning of the observed effect of the adaptor appears to be much sharper than the tuning shown by modulation-masking results.
Large-amplitude solitons in gravitationally balanced quantum plasmas
Akbari-Moghanjoughi, M.
2014-08-15
Using the quantum fluid model for self-gravitating quantum plasmas with the Bernoulli pseudopotential method and taking into account the relativistic degeneracy effect, it is shown that gravity-induced large-amplitude density rarefaction solitons can exist in gravitationally balanced quantum plasmas. These nonlinear solitons are generated due to the force imbalance between the gravity and the quantum fluid pressure via local density perturbations, similar to that on shallow waters. It is found that both the fluid mass-density and the atomic-number of the constituent ions have significant effect on the amplitude and width of these solitonic profiles. Existence of a large-scale gravity-induced solitonic activities on neutron-star surface, for instance, can be a possible explanation for the recently proposed resonant shattering mechanism [D. Tsang et al., Phys. Rev. Lett. 108, 011102 (2012)] causing the intense short gamma ray burst phenomenon, in which release of ≃10{sup 46}–10{sup 47} ergs would be possible from the surface. The resonant shattering of the crust in a neutron star has been previously attributed to the crust-core interface mode and the tidal surface tensions. We believe that current model can be a more natural explanation for the energy liberation by solitonic activities on the neutron star surfaces, without a requirement for external mergers like other neutron stars or black holes for the crustal shatter.
On the distribution of seismic reflection coefficients and seismic amplitudes
Painter, S.; Paterson, L.; Beresford, G.
1995-07-01
Reflection coefficient sequences from 14 wells in Australia have a statistical character consistent with a non-Gaussian scaling noise model based on the Levy-stable family of probability distributions. Experimental histograms of reflection coefficients are accurately approximated by symmetric Levy-stable probability density functions with Levy index between 0.99 and 1.43. These distributions have the same canonical role in mathematical statistics as the Gaussian distribution, but they have slowly decaying tails and infinite moments. The distribution of reflection coefficients is independent of the spatial scale (statistically self-similar), and the reflection coefficient sequences have long-range dependence. These results suggest that the logarithm of seismic impedance can be modeled accurately using fractional Levy motion, which is a generalization of fractional Brownian motion. Synthetic seismograms produced from the authors` model for the reflection coefficients also have Levy-stable distributions. These isolations include transmission losses, the effects of reverberations, and the loss of resolution caused by band-limited wavelets, and suggest that actual seismic amplitudes with sufficient signal-to-noise ratio should also have a Levy-stable distribution. This prediction is verified using post-stack seismic data acquired in the Timor Sea and in the continental USA. However, prestack seismic amplitudes from the Timor Sea are nearly Gaussian. They attribute the difference between prestack and poststack data to the high level of measurement noise in the prestack data.
A Stringent Limit on the Amplitude of Alfvénic Perturbations in High-beta Low-collisionality Plasmas
NASA Astrophysics Data System (ADS)
Squire, J.; Quataert, E.; Schekochihin, A. A.
2016-10-01
It is shown that low-collisionality plasmas cannot support linearly polarized shear-Alfvén fluctuations above a critical amplitude δ {B}\\perp /{B}0∼ {β }-1/2, where β is the ratio of thermal to magnetic pressure. Above this cutoff, a developing fluctuation will generate a pressure anisotropy that is sufficient to destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, interrupting the fluctuation before any oscillation. The magnetic field lines rapidly relax into a sequence of angular zig-zag structures. Such a restrictive bound on shear-Alfvén-wave amplitudes has far-reaching implications for the physics of magnetized turbulence in the high-β conditions prevalent in many astrophysical plasmas, as well as for the solar wind at ∼1 au where β ≳ 1.
NASA Astrophysics Data System (ADS)
Chen, Wei; de Swart, Huib E.
2016-03-01
Several field studies in bays and estuaries have revealed pronounced subsurface maxima in the vertical profiles of the current amplitude of the principal tidal harmonic, or of its vertical shear, over the water column. To gain fundamental understanding about these phenomena, a semi-analytical model is designed and analysed, with focus on the sensitivity of the vertical structure of the tidal current amplitude to formulations of the vertical shape of the eddy viscosity. The new analytical solutions for the tidal current amplitude are used to explore their dependence on the degree of surface mixing, the vertical shape of eddy viscosity in the upper part of the water column and the density stratification. Sources of surface mixing are wind and whitecapping. Results show three types of current amplitude profiles of tidal harmonics, characterised by monotonically decreasing shear towards the surface, "surface jumps" (vertical shear of tidal current amplitude has a subsurface maximum) and "subsurface jets" (maximum tidal current amplitude below the surface), respectively. The "surface jumps" and "subsurface jets" both occur for low turbulence near the surface, whilst additionally the surface jumps only occur if the eddy viscosity in the upper part of the water column decreases faster than linearly to the surface. Furthermore, "surface jumps" take place for low density stratification, while and "subsurface jets" occur for high density stratification. The physics causing the presence of surface jumps and subsurface jets is also discussed.
2013-01-01
Background The aim of the present pilot study was to determine if pulse photoplethysmography amplitude (PPGA) could be used as an indicator of critical illness and as a predictor of higher need of care in emergency department patients. Methods This was a prospective observational study. We collected vital signs and one minute of pulse photoplethysmograph signal from 251 consecutive patients admitted to a university hospital emergency department. The patients were divided in two groups regarding to the modified Early Warning Score (mEWS): > 3 (critically ill) and ≤ 3 (non-critically ill). Photoplethysmography characteristics were compared between the groups. Results Sufficient data for analysis was acquired from 212 patients (84.5%). Patients in critically ill group more frequently required intubation and invasive hemodynamic monitoring in the ED and received more intravenous fluids. Mean pulse photoplethysmography amplitude (PPGA) was significantly lower in critically ill patients (median 1.105 [95% CI of mean 0.9946-2.302] vs. 2.476 [95% CI of mean 2.239-2.714], P = 0.0257). Higher variability of PPGA significantly correlated with higher amount of fluids received in the ED (r = 0.1501, p = 0.0296). Conclusions This pilot study revealed differences in PPGA characteristics between critically ill and non-critically ill patients. Further studies are needed to determine if these easily available parameters could help increase accuracy in triage when used in addition to routine monitoring of vital signs. PMID:23799988
NASA Technical Reports Server (NTRS)
Bonacuse, Peter J.; Kalluri, Sreeramesh
2001-01-01
The experiments described herein were performed to determine whether damage imposed by axial loading interacts with damage imposed by torsional loading. This paper is a follow on to a study that investigated effects of load-type sequencing on the cumulative fatigue behavior of a cobalt base superalloy, Haynes 188 at 538 C Both the current and the previous study were used to test the applicability of cumulative fatigue damage models to conditions where damage is imposed by different loading modes. In the previous study, axial and torsional two load level cumulative fatigue experiments were conducted, in varied combinations, with the low-cycle fatigue (high amplitude loading) applied first. In present study, the high-cycle fatigue (low amplitude loading) is applied initially. As in the previous study, four sequences (axial/axial, torsion/torsion, axial/torsion, and torsion/axial) of two load level cumulative fatigue experiments were performed. The amount of fatigue damage contributed by each of the imposed loads was estimated by both the Palmgren-Miner linear damage rule (LDR) and the non-linear damage curve approach (DCA). Life predictions for the various cumulative loading combinations are compared with experimental results.
NASA Technical Reports Server (NTRS)
Krasnov, V. M.; Yakovets, A. F.
1972-01-01
Equipment for studying the amplitude frequency response of the ionospheric scattering channel is described, having multipath signal propagation. Experimental results are reported, including nonuniformity in the channel's amplitude frequency response.
Large-amplitude circularly polarized electromagnetic waves in magnetized plasma
Vasko, I. Y. Artemyev, A. V.; Zelenyi, L. M.
2014-05-15
We consider large-amplitude circularly polarized (LACP) waves propagating in a magnetized plasma. It is well-known that the dispersion relation for such waves coincides with the dispersion relation given by the linear theory. We develop the model of LACP wave containing a finite population of Cerenkov resonant particles. We find that the current of resonant particles modifies the linear dispersion relation. Dispersion curves of low-frequency (i.e., whistler and magnetosonic) waves are shifted toward larger values of the wave vector, i.e., waves with arbitrarily large wavelengths do not exist in this case. Dispersion curves of high-frequency waves are modified so that the wave phase velocity becomes smaller than the speed of light.
Amplitude equations for reaction-diffusion systems with cross diffusion
NASA Astrophysics Data System (ADS)
Zemskov, Evgeny P.; Vanag, Vladimir K.; Epstein, Irving R.
2011-09-01
Using Taylor series expansion, multiscaling, and further expansion in powers of a small parameter, we develop general amplitude equations for two-variable reaction-diffusion systems with cross-diffusion terms in the cases of Hopf and Turing instabilities. We apply this analysis to the Oregonator and Brusselator models and find that inhibitor cross diffusion induced by the activator and activator cross diffusion induced by the inhibitor have opposite effects in the two models as a result of the different structure of their community matrices. Our analysis facilitates finding regions of supercritical and subcritical bifurcations, as well as wave and antiwave domains and domains of turbulent waves in the case of Hopf instability.
Amplitude equations for reaction-diffusion systems with cross diffusion.
Zemskov, Evgeny P; Vanag, Vladimir K; Epstein, Irving R
2011-09-01
Using Taylor series expansion, multiscaling, and further expansion in powers of a small parameter, we develop general amplitude equations for two-variable reaction-diffusion systems with cross-diffusion terms in the cases of Hopf and Turing instabilities. We apply this analysis to the Oregonator and Brusselator models and find that inhibitor cross diffusion induced by the activator and activator cross diffusion induced by the inhibitor have opposite effects in the two models as a result of the different structure of their community matrices. Our analysis facilitates finding regions of supercritical and subcritical bifurcations, as well as wave and antiwave domains and domains of turbulent waves in the case of Hopf instability. PMID:22060484
Neural processing of amplitude and formant rise time in dyslexia.
Peter, Varghese; Kalashnikova, Marina; Burnham, Denis
2016-06-01
This study aimed to investigate how children with dyslexia weight amplitude rise time (ART) and formant rise time (FRT) cues in phonetic discrimination. Passive mismatch responses (MMR) were recorded for a/ba/-/wa/contrast in a multiple deviant odd-ball paradigm to identify the neural response to cue weighting in 17 children with dyslexia and 17 age-matched control children. The deviant stimuli had either partial or full ART or FRT cues. The results showed that ART did not generate an MMR in either group, whereas both partial and full FRT cues generated MMR in control children while only full FRT cues generated MMR in children with dyslexia. These findings suggest that children, both controls and those with dyslexia, discriminate speech based on FRT cues and not ART cues. However, control children have greater sensitivity to FRT cues in speech compared to children with dyslexia.
Nonlinear saturation amplitude of cylindrical Rayleigh—Taylor instability
NASA Astrophysics Data System (ADS)
Liu, Wan-Hai; Yu, Chang-Ping; Ye, Wen-Hua; Wang, Li-Feng
2014-09-01
The nonlinear saturation amplitude (NSA) of the fundamental mode in the classical Rayleigh—Taylor instability with a cylindrical geometry for an arbitrary Atwood number is analytically investigated by considering the nonlinear corrections up to the third order. The analytic results indicate that the effects of the initial radius of the interface (r0) and the Atwood number (A) play an important role in the NSA of the fundamental mode. The NSA of the fundamental mode first increases gently and then decreases quickly with increasing A. For a given A, the smaller the r0/λ (λ is the perturbation wavelength), the larger the NSA of the fundamental mode. When r0/λ is large enough (r0 ≫ λ), the NSA of the fundamental mode is reduced to the prediction in the previous literatures within the framework of the third-order perturbation theory.
Method of Analytic Evolution of Flat Distribution Amplitudes in QCD
NASA Astrophysics Data System (ADS)
Tandogan, Asli; Radyushkin, Anatoly V.
A new analytical method of performing ERBL evolution is described. The main goal is to develop an approach that works for distribution amplitudes that do not vanish at the end points, for which the standard method of expansion in Gegenbauer polynomials is inefficient. Two cases of the initial DA are considered: a purely flat DA, given by the same constant for all x, and an antisymmetric DA given by opposite constants for x > 1/2. For a purely flat DA, the evolution is governed by an overall (x\\bar {x})t dependence on the evolution parameter t times a factor that was calculated as an expansion in t. For an antisymmetric flat DA, an extra overall factor |1 - 2x|2t appears due to a jump at x = 1/2. A good convergence was observed in the t ≲ 1/2 region. For larger t, one can use the standard method of the Gegenbauer expansion.
De Wijk gas field: Reservoir mapping with amplitude anomalies
Bruijn, B. )
1993-09-01
De Wijk field, discovered in 1949, is located in the northeastern part of Netherlands. The main gas accumulation is contained in cretaceous and Triassic sandstone reservoirs trapped in a broad salt-induced structure of around 80 km[sup 2] areal extent. The field contains gas in the tertiary, Chalk, Zechstein 2 Carbonate, and Carboniferous reservoirs as well. De Wijk field is unique in the Netherlands as most gas-producing reservoirs in the Cretaceous/Triassic are of no commercial interest. Post-depositional leaching has positively affected the reservoir properties of the Triassic formations subcropping below the Cretaceous unconformity. Optimum, interpretation of 3-D seismic data acquired in 1989 resulted in spectacular displays highlighting the uniqueness of the field. Most gas-bearing reservoirs are expressed on seismic by amplitude anomalies. Various attribute-measurement techniques show the effect of gas fill, leaching, and sand distribution in the various reservoirs.
Image recovery from double amplitudes in fractional Fourier domain
NASA Astrophysics Data System (ADS)
Liao, Tian-He; Gao, Qiong
2006-02-01
The classical Gerchberg-Saxton algorithm is introduced into the image recovery in fractional Fourier domain after adaptation. When this algorithm is applied directly, its performance is good for smoothed image, but bad for unsmoothed image. Based on the diversity of fractional Fourier transform on its orders, this paper suggests a novel iterative algorithm, which extracts the information of the original image from amplitudes of its fractional Fourier transform at two orders. This new algorithm consists of two independent Gerchberg-Saxton procedures and an averaging operation in each circle. Numerical simulations are carried out to show its validity for both smoothed and unsmoothed images with most pairs of orders in the interval [0, 1].
Shoaling Large Amplitude Internal Solitary Waves in a Laboratory Tank
NASA Astrophysics Data System (ADS)
Allshouse, Michael; Larue, Conner; Swinney, Harry
2014-11-01
The shoaling of internal solitary waves onto the continental shelf can change both the wave dynamics and the state of the environment. Previous observations have demonstrated that these waves can trap fluid and transport it over long distances. Through the use of a camshaft-based wavemaker, we produce large amplitude shoaling waves in a stratified fluid in a laboratory tank. Simulations of solitary waves are used to guide the tuning of the wave generator to approximate solitary waves; thus nonlinear waves can be produced within the 4m long tank. PIV and synthetic schlieren measurements are made to study the transport of fluid by the wave as it moves up a sloping boundary. The results are then compared to numerical simulations and analyzed using finite time Lyapunov exponent calculations. This Lagrangian analysis provides an objective measure of barriers surrounding trapped regions in the flow. Supported by ONR MURI Grant N000141110701 (WHOI).
Filamentation instability of large-amplitude Alfven waves
NASA Technical Reports Server (NTRS)
Kuo, S. P.; Whang, M. H.; Lee, M. C.
1988-01-01
An instability that leads to the filamentation of large-amplitude Alfven waves and gives rise to purely growing density and magnetic field fluctuations is studied. The dispersion relation of the instability is derived, from which the threshold conditions and the growth rates of the instability are analyzed quantitatively for applications to the solar wind plasma. Their dependence on the filamentation spectrum, the plasma beta, and the pump frequency and intensity was examined for both right-hand and left-hand circularly polarized Alfven waves. The excitation of filamentation instability for certain cases of interest is discussed and compared with that of the parametric decay and modulation instability. The relevance of the proposed instability to some observations is discussed.
Transient elasticity and polymeric fluids: Small-amplitude deformations.
Müller, Oliver; Liu, Mario; Pleiner, Harald; Brand, Helmut R
2016-02-01
Transient elasticity (TE) is a concept useful for a systematic generalization of viscoelasticity. Due to its thermodynamic consistency, it naturally leads to a simple description of non-Newtonian effects displayed by polymeric fluids, granular media, and other soft matter. We employ a continuum-mechanical theory that is derived from TE and tailored to polymeric fluids, showing how it captures a surprisingly large number of phenomena in shear and elongational flows, including stationary, oscillatory, and transient ones, as well as the flow down an inclined channel. Even the Weissenberg effect is well accounted for. This theory is applicable for small- as well as large-amplitude deformations. We concentrate on the former in the present article, leaving the latter to a companion article. PMID:26986419
Modeling and Analysis of Large Amplitude Flight Maneuvers
NASA Technical Reports Server (NTRS)
Anderson, Mark R.
2004-01-01
Analytical methods for stability analysis of large amplitude aircraft motion have been slow to develop because many nonlinear system stability assessment methods are restricted to a state-space dimension of less than three. The proffered approach is to create regional cell-to-cell maps for strategically located two-dimensional subspaces within the higher-dimensional model statespace. These regional solutions capture nonlinear behavior better than linearized point solutions. They also avoid the computational difficulties that emerge when attempting to create a cell map for the entire state-space. Example stability results are presented for a general aviation aircraft and a micro-aerial vehicle configuration. The analytical results are consistent with characteristics that were discovered during previous flight-testing.
Small-amplitude acoustics in bulk granular media.
Henann, David L; Valenza, John J; Johnson, David L; Kamrin, Ken
2013-10-01
We propose and validate a three-dimensional continuum modeling approach that predicts small-amplitude acoustic behavior of dense-packed granular media. The model is obtained through a joint experimental and finite-element study focused on the benchmark example of a vibrated container of grains. Using a three-parameter linear viscoelastic constitutive relation, our continuum model is shown to quantitatively predict the effective mass spectra in this geometry, even as geometric parameters for the environment are varied. Further, the model's predictions for the surface displacement field are validated mode-by-mode against experiment. A primary observation is the importance of the boundary condition between grains and the quasirigid walls.
Frequency domain optoacoustic tomography using amplitude and phase
Mohajerani, Pouyan; Kellnberger, Stephan; Ntziachristos, Vasilis
2014-01-01
We introduce optoacoustic tomographic imaging using intensity modulated light sources and collecting amplitude and phase information in the frequency domain. Imaging is performed at multiple modulation frequencies. The forward modeling uses the Green's function solution to the pressure wave equation in frequency domain and the resulting inverse problem is solved using regularized least squares minimization. We study the effect of the number of frequencies and of the bandwidth employed on the image quality achieved. The possibility of employing an all-frequency domain optoacoustic imaging for experimental measurements is studied as a function of noise. We conclude that frequency domain optoacoustic tomography may evolve to a practical experimental method using light intensity modulated sources, with advantages over time-domain optoacoustics. PMID:25431755
Phase and amplitude inversion of crosswell radar data
Ellefsen, Karl J.; Mazzella, Aldo T.; Horton, Robert J.; McKenna, Jason R.
2011-01-01
Phase and amplitude inversion of crosswell radar data estimates the logarithm of complex slowness for a 2.5D heterogeneous model. The inversion is formulated in the frequency domain using the vector Helmholtz equation. The objective function is minimized using a back-propagation method that is suitable for a 2.5D model and that accounts for the near-, intermediate-, and far-field regions of the antennas. The inversion is tested with crosswell radar data collected in a laboratory tank. The model anomalies are consistent with the known heterogeneity in the tank; the model’s relative dielectric permittivity, which is calculated from the real part of the estimated complex slowness, is consistent with independent laboratory measurements. The methodologies developed for this inversion can be adapted readily to inversions of seismic data (e.g., crosswell seismic and vertical seismic profiling data).
BFKL Pomeron and production amplitudes in N = 4 SUSY
Lipatov, L. N.
2009-05-14
Theoretical approaches to the problem of the high energy hadron-hadron scattering in the Regge kinematics are reviewed. It is shown, that the gluon in QCD is reggeized and the Pomeron is a two gluon composite state. Further, the equation for the multi-gluon composite states is integrable at N{sub c}{yields}{infinity}. Due to the AdS/CFT correspondence in N = 4 SUSY the BFKL Pomeron is equivalent to the reggeized graviton. The important properties of the maximal transcendentality and integrability are realized in this model. Multi-gluon scattering amplitudes are investigated in the Regge limit. The BDS ansatz for them is not valid beyond one loop due to the presence of the Mandelstam cuts. The hamiltonian for the corresonding reggeon states coincides with the hamiltonian of an integrable open Heisenberg spin chain.
Dispersion interferometer using modulation amplitudes on LHD (invited)
Akiyama, T. Yasuhara, R.; Kawahata, K.; Okajima, S.; Nakayama, K.
2014-11-15
Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO{sub 2} laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 10{sup 17} m{sup −3} is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 10{sup 20} m{sup −3} can be overcome by a sufficient sampling rate of about 100 kHz.
Active Phase and Amplitude Fluctuations of Flagellar Beating
NASA Astrophysics Data System (ADS)
Ma, Rui; Klindt, Gary S.; Riedel-Kruse, Ingmar H.; Jülicher, Frank; Friedrich, Benjamin M.
2014-07-01
The eukaryotic flagellum beats periodically, driven by the oscillatory dynamics of molecular motors, to propel cells and pump fluids. Small but perceivable fluctuations in the beat of individual flagella have physiological implications for synchronization in collections of flagella as well as for hydrodynamic interactions between flagellated swimmers. Here, we characterize phase and amplitude fluctuations of flagellar bending waves using shape mode analysis and limit-cycle reconstruction. We report a quality factor of flagellar oscillations Q =38.0±16.7 (mean±s.e.). Our analysis shows that flagellar fluctuations are dominantly of active origin. Using a minimal model of collective motor oscillations, we demonstrate how the stochastic dynamics of individual motors can give rise to active small-number fluctuations in motor-cytoskeleton systems.
Active phase and amplitude fluctuations of flagellar beating.
Ma, Rui; Klindt, Gary S; Riedel-Kruse, Ingmar H; Jülicher, Frank; Friedrich, Benjamin M
2014-07-25
The eukaryotic flagellum beats periodically, driven by the oscillatory dynamics of molecular motors, to propel cells and pump fluids. Small but perceivable fluctuations in the beat of individual flagella have physiological implications for synchronization in collections of flagella as well as for hydrodynamic interactions between flagellated swimmers. Here, we characterize phase and amplitude fluctuations of flagellar bending waves using shape mode analysis and limit-cycle reconstruction. We report a quality factor of flagellar oscillations Q = 38.0 ± 16.7 (mean ± s.e.). Our analysis shows that flagellar fluctuations are dominantly of active origin. Using a minimal model of collective motor oscillations, we demonstrate how the stochastic dynamics of individual motors can give rise to active small-number fluctuations in motor-cytoskeleton systems.
Ultrasound transmission attenuation tomography using energy-scaled amplitude ratios
NASA Astrophysics Data System (ADS)
Chen, Ting; Shin, Junseob; Huang, Lianjie
2016-04-01
Ultrasound attenuation of breast tumors is related to their types and pathological states, and can be used to detect and characterize breast cancer. Particularly, ultrasound scattering attenuation can infer the margin properties of breast tumors. Ultrasound attenuation tomography quantitatively reconstructs the attenuation properties of the breast. Our synthetic-aperture breast ultrasound tomography system with two parallel transducer arrays records both ultrasound reflection and transmission signals. We develop an ultrasound attenuation tomography method using ultrasound energy-scaled amplitude decays of ultrasound transmission signals and conduct ultrasound attenuation tomography using a known sound-speed model. We apply our ultrasound transmission attenuation tomography method to a breast phantom dataset, and compare the ultrasound attenuation tomography results with conventional beamforming ultrasound images obtained using reflection signals. We show that ultrasound transmission attenuation tomography complements beamforming images in identifying breast lesions.
N =2⋆ from topological amplitudes in string theory
NASA Astrophysics Data System (ADS)
Florakis, Ioannis; Zein Assi, Ahmad
2016-08-01
In this paper, we explicitly construct string theory backgrounds that realise the so-called N =2⋆ gauge theory. We prove the consistency of our models by calculating their partition function and obtaining the correct gauge theory spectrum. We further provide arguments in favour of the universality of our construction which covers a wide class of models all of which engineer the same gauge theory. We reproduce the corresponding Nekrasov partition function once the Ω-deformation is included and the appropriate field theory limit taken. This is achieved by calculating the topological amplitudes Fg in the string models. In addition to heterotic and type II constructions, we also realise the mass deformation in type I theory, thus leading to a natural way of uplifting the result to the instanton sector.
Symmetry breaking of nematic umbilical defects through an amplitude equation.
Clerc, Marcel G; Vidal-Henriquez, Estefania; Davila, Juan Diego; Kowalczyk, Michał
2014-07-01
The existence, stability properties, and bifurcation diagram of the nematic umbilical defects is studied. Close to the Fréedericksz transition of nematic liquid crystals with negative anisotropic dielectric constant and homeotropic anchoring, an anisotropic Ginzburg-Landau equation for the amplitude of the tilt of the director away from the vertical axis is derived by taking the three-dimensional (3D) to 2D limit of the Frank-Oseen model. The anisotropic Ginzburg-Landau equation allows us to reveal the mechanism of symmetry breaking of nematic umbilical defects. The positive defect is fully characterized as a function of the anisotropy, while the negative defect is characterized perturbatively. Numerical simulations show quite good agreement with the analytical results. PMID:25122324
Exact results for amplitude spectra of fitness landscapes.
Neidhart, Johannes; Szendro, Ivan G; Krug, Joachim
2013-09-01
Starting from fitness correlation functions, we calculate exact expressions for the amplitude spectra of fitness landscapes as defined by Stadler [1996. Landscapes and their correlation functions. J. Math. Chem. 20, 1] for common landscape models, including Kauffman's NK-model, rough Mount Fuji landscapes and general linear superpositions of such landscapes. We further show that correlations decaying exponentially with the Hamming distance yield exponentially decaying spectra similar to those reported recently for a model of molecular signal transduction. Finally, we compare our results for the model systems to the spectra of various experimentally measured fitness landscapes. We claim that our analytical results should be helpful when trying to interpret empirical data and guide the search for improved fitness landscape models.
Transient elasticity and polymeric fluids: Small-amplitude deformations
NASA Astrophysics Data System (ADS)
Müller, Oliver; Liu, Mario; Pleiner, Harald; Brand, Helmut R.
2016-02-01
Transient elasticity (TE) is a concept useful for a systematic generalization of viscoelasticity. Due to its thermodynamic consistency, it naturally leads to a simple description of non-Newtonian effects displayed by polymeric fluids, granular media, and other soft matter. We employ a continuum-mechanical theory that is derived from TE and tailored to polymeric fluids, showing how it captures a surprisingly large number of phenomena in shear and elongational flows, including stationary, oscillatory, and transient ones, as well as the flow down an inclined channel. Even the Weissenberg effect is well accounted for. This theory is applicable for small- as well as large-amplitude deformations. We concentrate on the former in the present article, leaving the latter to a companion article.
Dirichlet series as interfering probability amplitudes for quantum measurements
NASA Astrophysics Data System (ADS)
Feiler, C.; Schleich, W. P.
2015-06-01
We show that all Dirichlet series, linear combinations of them and their analytical continuations represent probability amplitudes for measurements on time-dependent quantum systems. In particular, we connect an arbitrary Dirichlet series to the time evolution of an appropriately prepared quantum state in a non-linear oscillator with logarithmic energy spectrum. However, the realization of a superposition of two Dirichlet sums and its analytical continuation requires two quantum systems which are entangled, and a joint measurement. We illustrate our approach of implementing arbitrary Dirichlet series in quantum systems using the example of the Riemann zeta function and relate its non-trivial zeros to the interference of two quantum states reminiscent of a Schrödinger cat.
Amplitude-dependent neutral modes in compressible boundary layer flows
NASA Technical Reports Server (NTRS)
Gajjar, J. S. B.
1990-01-01
The ideas of Benney and Bergeron (1969) and Davies (1970) on nonlinear critical layers are extended, and some new nonlinear neutral modes are computed for compressible boundary layer flow. A special case of the work is when the generalized inflexion point criterion holds. Neutral modes are found for a range of phase-speeds, dependent on the Mach number, and the properties of these are discussed. As in the linear case when the flow is relatively supersonic, multiple neutral modes exist. The behavior of the neutral amplitude in some limiting cases is also considered, and it is found that the results are significantly different from that in incompressible flow when the flow is locally supersonic.
High amplitude waves in the expanding solar wind plasma
NASA Technical Reports Server (NTRS)
Schmidt, J. M.; Velli, M.; Grappin, R.
1995-01-01
We simulated the 1-D nonlinear time-evolution of high-amplitude Alfven, slow and fast magnetoacoustic waves in the solar wind propagating outward at different angles to the mean magnetic (spiral) field, using the expanding box model. The simulation results for Alfven waves and fast magnetoacustic waves fit the observational constraints in the solar wind best, showing decreasing trends for energies and other rms-quantities due to expansion and the appearance of inward propagating waves as minor species in the wind. Inward propagating waves are generated by reflection of Alfven waves propagating at large angles to the magnetic field or they coincide with the occurrence of compressible fluctuations. In our simulations, fast and slow magnetoacoustic waves seem to have a level in the density-fluctuations which is too high when we compare with the observations. Furthermore, the evolution of energies for slow magnetoacoustic waves differs strongly from the evolution of fluctuation energies in situ.
Single Polymer Dynamics under Large Amplitude Oscillatory Extensional (LAOE) Flow
NASA Astrophysics Data System (ADS)
Zhou, Yuecheng; Schroeder, Charles M.
Over the past two decades, advances in fluorescence imaging and particle manipulation have enabled the direct observation of single polymer dynamics in model flows such as shear flow and planar extensional flow. The vast majority of single polymer studies, however, has focused on chain dynamics using simple transient step forcing functions. In order to study single polymer dynamics in non-idealized model flows, there is a clear need to implement more complicated transient flow forcing functions. In bulk rheology, large amplitude oscillatory shear (LAOS) was widely used to study the linear and nonlinear viscoelasticity of materials, but not yet been applied to molecular rheology. In this work, we directly probe single polymer dynamics using oscillatory extensional flow in precisely controlled microfluidic devices. We are able to generate large and small amplitude sinusoidal oscillatory extensional flow in a cross-slot microfluidic device while imaging the conformational dynamics of a single polymer trapped at the stagnation point. In this flow, polymer chains are stretched, squeezed, and rotated between extensional/compressional axes in a highly dynamic and transient manner. Using this technique, we studied the dynamics and coil-stretch transition of a single λ-DNA as a function of the Weissenberg number (Wi) and Deborah number (De). Moreover, we use Brownian dynamics simulation to map a wide range of Pipkin space for polymers from linear steady-state conditions to non-linear unsteady-states. Our results reveal a critical Wi at the coil-stretch transition that is function of the De in LAOE flow. Department of Materials Science and Engineering.
Effient Supply-Modulated Transmitters for Variable Amplitude Radar
NASA Astrophysics Data System (ADS)
Zai, Andrew H.
This thesis introduces an efficient radar transmitter with improved spectral confinement, enabled by a pulse waveform that contains both amplitude and frequency modulation. The theoretical behavior of the Class-B power amplifier (PA) under Gaussian envelope is compared to that of a Class-A PA. Experimental validation is performed on a 4-W 10-GHz GaN MMIC PA, biased in Class B with a power added efficiency (PAE) of 50%. When driven with a Gaussian-like pulse envelope with a 5 MHz linear frequency modulation (LFM), the PA demonstrates a 31% average efficiency over the pulse duration. To improve the efficiency, a simple resonant supply modulator with a peak efficiency of 92% is used for the pulse Gaussian amplitude modulation, while the LFM is provided only through the PA input. This case results in a 5-point improvement in system efficiency, with an average PAE=40% over the pulse duration for the PA alone, and with simultaneous 40-dB reduction in spectral emissions relative to a rectangular pulse with the same energy. A measurement bench, which was internally developed, and supply-modulation simulations with Applied Wave Research (AWR) Microwave Office and VSS are also presented. Supply modulation simulation is helpful for predicting the performance of a supply-modulated system while a well calibrated bench is essential for verification. Both tools are used to demonstrate resonant supply-modulated GaN MMIC PAs. Lastly, the design of an X-Band GaN Doherty MMIC PA for use in a variable power radar is presented. Simulations and preliminary measurement demonstrate power added efficiency of greater that 40% from 30 to 35 dBm of output power.
The Evolution of Finite Amplitude Wavetrains in Plane Channel Flow
NASA Technical Reports Server (NTRS)
Hewitt, R. E.; Hall, P.
1996-01-01
We consider a viscous incompressible fluid flow driven between two parallel plates by a constant pressure gradient. The flow is at a finite Reynolds number, with an 0(l) disturbance in the form of a traveling wave. A phase equation approach is used to discuss the evolution of slowly varying fully nonlinear two dimensional wavetrains. We consider uniform wavetrains in detail, showing that the development of a wavenumber perturbation is governed by Burgers equation in most cases. The wavenumber perturbation theory, constructed using the phase equation approach for a uniform wavetrain, is shown to be distinct from an amplitude perturbation expansion about the periodic flow. In fact we show that the amplitude equation contains only linear terms and is simply the heat equation. We review, briefly, the well known dynamics of Burgers equation, which imply that both shock structures and finite time singularities of the wavenumber perturbation can occur with respect to the slow scales. Numerical computations have been performed to identify areas of the (wavenumber, Reynolds number, energy) neutral surface for which each of these possibilities can occur. We note that the evolution equations will breakdown under certain circumstances, in particular for a weakly nonlinear secondary flow. Finally we extend the theory to three dimensions and discuss the limit of a weak spanwise dependence for uniform wavetrains, showing that two functions are required to describe the evolution. These unknowns are a phase and a pressure function which satisfy a pair of linearly coupled partial differential equations. The results obtained from applying the same analysis to the fully three dimensional problem are included as an appendix.
Spectroscopy and dynamics of small molecules with large amplitude motion
NASA Astrophysics Data System (ADS)
Dawadi, Mahesh B.
This dissertation addresses the effect of large amplitude vibrations (LAV or LAVs) on the other small amplitude vibrations (SAVs) for investigating the vibrational dynamics on the molecular systems ranging from G6 to G12 symmetry, including methanol, methylamine, nitromethane, 2-methylmalonaldehyde (2-MMA) and 5-methyltropolone (5-MT). The study of the high-resolution infrared spectrum of methylamine (CH 3NH2) in the nu11 asymmetric CH stretch region (2965-3005 cm1) under sub-Doppler slit-jet conditions reveals that the torsion-inversion tunneling patterns are heavily impacted by perturbations and hence different both from the ground state and from the theoretical predictions. Two torsion-inversion tunneling models are reported for studying the high-barrier tunneling behavior in the methyl CH stretch vibrationally excited states of the molecules with G12 symmetry. These models predict the inverted tunneling pattern of the four tunneling states (A, B, E 1 and E2 symmetries) in the asymmetric CH stretch excited states relative to the ground state. The trends in the patterns relative to tunneling rates and coupling parameters are presented and comparisons are made to the available experimental data. Additionally, a remarkable result that follows from the approximate adiabatic separation of the fast and slow vibrations in methanol is the existence of vibrational conical intersections (CIs) where the surfaces representing the two asymmetric CH stretches meet like the points of two cones touching point-to-point. The CIs occur in the slow coordinates space consisting of the torsion and the COH bend. Finally, the analysis of the high-resolution synchrotron based Fourier transform infrared (FTIR) spectrum for NO2 in-plane rock, nu 7, band of nitromethane reveals that the rotational energy pattern in the lowest torsional state (m' = 0) of the upper vibrational state is similar relative to the vibrational ground state.
NASA Astrophysics Data System (ADS)
Gluck, Paul
2004-04-01
It makes good sense to extend the range of usefulness of a piece of equipment beyond that intended originally. A commonly available "variable g" physical pendulum allows one to vary the angle α of its plane of oscillation to the vertical, so that in the expression for its period, g cos α replaces g. As shown in Fig. 1, the physical pendulum consists of a heavy cylindrical steel bob that can slide up and down a light aluminum rod whose top is attached to a cylindrical pivot resting on ball bearings. The aim of this paper is to describe a sequence of activities in rigid-body dynamics based on a triply modified version of this pendulum, extending over two lab sessions, carried out toward the end of a calculus-based mechanics course. However, the experiment can be analyzed at various levels, whether calculus based or by more elementary means. Figure 1 shows how we bolted a protractor to the top front of the instrument, so that one can measure the initial amplitude θ0 from which the bob is released. This enables one to study the amplitude dependence of the period between 0-90°. In addition, we have turned on the lathe an aluminum bob of identical shape and size. For this much lighter bob, the aluminum rod contributes a significant fraction to the total moment of inertia of the pendulum. Finally, we have improved the pivot's ball bearings, so that when released from 90° the pendulum continues swinging for 20 minutes or more, enabling one to observe the decay of its amplitude over a long time.