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Harmonic
Kinds of Harmonic Terms modified by Harmonic Selected AbstractsBody Position and Cardiac Dynamic and Chronotropic Responses to Steady-State Isocapnic Hypoxaemia in HumansEXPERIMENTAL PHYSIOLOGY, Issue 2 2000S. Deborah Lucy Neural mediation of the human cardiac response to isocapnic (IC) steady-state hypoxaemia was investigated using coarse-graining spectral analysis of heart rate variability (HRV). Six young adults were exposed in random order to a hypoxia or control protocol, in supine and sitting postures, while end-tidal PCO2 (PET,CO2) was clamped at resting eucapnic levels. An initial 11 min period of euoxia (PET,O2 100 mmHg; 13.3 kPa) was followed by a 22 min exposure to hypoxia (PET,O2 55 mmHg; 7.3 kPa), or continued euoxia (control). Harmonic and fractal powers of HRV were determined for the terminal 400 heart beats in each time period. Ventilation was stimulated (P < 0.05) and cardiac dynamics altered only by exposure to hypoxia. The cardiac interpulse interval was shortened (P < 0.001) similarly during hypoxia in both body positions. Vagally mediated high-frequency harmonic power (Ph) of HRV was decreased by hypoxia only in the supine position, while the fractal dimension, also linked to cardiac vagal control, was decreased in the sitting position (P < 0.05). However, low-frequency harmonic power (Pl) and the HRV indicator of sympathetic activity (Pl/Ph) were not altered by hypoxia in either position. These results suggest that, in humans, tachycardia induced by moderate IC hypoxaemia (arterial O2 saturation Sa,O2, 85%) was mediated by vagal withdrawal, irrespective of body position and resting autonomic balance, while associated changes in HRV were positionally dependent. [source] Harmonic suppressed and size-reduced bandstop and bandpass filtersMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2009Majeed A. S. Alkanhal Abstract New bandstop/bandpass microstrip structures with harmonic suppression are presented in this article. By replacing the series quarter-wavelength connecting lines of conventional open-stub bandpass/bandstop filters with the equivalent ,-shaped line section, compact open-stub bandstop/bandpass filters with second harmonic suppression are achieved. Transmission-line theory is used to derive the design equations of the equivalent ,-shaped lines. Simulation and experiments have also been done to validate the proposed design concept. When compared with the conventional open-stub Bandpass/Bandstop filters, the second harmonic is suppressed and size reduction is achieved in both the Bandstop/bandpass structures. Moreover, results confirm that the proposed shaped bandpass filter achieves a further third harmonic rejection. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2109,2114, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24580 [source] Harmonic and refined Rayleigh,Ritz for the polynomial eigenvalue problemNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 1 2008Michiel E. Hochstenbach Abstract After reviewing the harmonic Rayleigh,Ritz approach for the standard and generalized eigenvalue problem, we discuss several extraction processes for subspace methods for the polynomial eigenvalue problem. We generalize the harmonic and refined Rayleigh,Ritz approaches which lead to new approaches to extract promising approximate eigenpairs from a search space. We give theoretical as well as numerical results of the methods. In addition, we study the convergence of the Jacobi,Davidson method for polynomial eigenvalue problems with exact and inexact linear solves and discuss several algorithmic details. Copyright © 2008 John Wiley & Sons, Ltd. [source] Solvothermal production of CdS nanorods using polyvinylpyrrolidone as a templateCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2009Titipun Thongtem Abstract CdS nanorods were solvothermally produced using Cd(NO3)2 and S powder in ethylenediamine containing different amounts of polyvinylpyrrolidone (PVP). The phase with hexagonal structure was detected using X-ray diffraction (XRD) and selected area electron diffraction (SAED). Their SAED patterns were in accordance with those of the simulations. Scanning and transmission electron microscopies (SEM and TEM) revealed the presence of CdS nanorods with their lengths influenced by different amounts of PVP. The nanorods were also characterized using high resolution TEM (HRTEM). They grew in the [001] direction normal to the (002) parallel crystallographic planes composing the nanorods. Raman spectra showed the 1LO (first harmonic) and 2LO (second harmonic) modes at the same wavenumbers although the products were produced under different conditions. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Seismic isolation of buildings with sliding concave foundation (SCF)EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2003M. Hamidi Abstract In this paper, a new base isolation system, namely the sliding concave foundation (SCF), is introduced and the behaviour of the buildings using such a system is theoretically investigated. A building supported on the new system behaves like a compound pendulum during seismic excitation. The pendulum behaviour accompanied by the large radius of foundation curvature shifts the fundamental period of the system to a high value (e.g. more than 8sec), in a frequency range where none of the previously recorded earthquakes had considerable energy. This results in a large decrease in the structural responses. Since small friction forces are essential on the contact surfaces, PTFE sheets can be used as sliding surfaces. Although the pure frictional sliding systems have the same efficiency as the SCF, in reducing the responses of the superstructure, the main advantage of the new system is a significant decrease in sliding displacement. The performance of the SCF subjected to a number of harmonic and non-harmonic base excitations is studied and its ability to reduce the structural responses is examined. Some numerical examples are solved for a single-degree-of-freedom (SDOF) structure and the responses are compared with the responses of the same SDOF structure on a fixed base or a pure frictional sliding support system. The comparisons confirm the effectiveness of the new system. Copyright © 2002 John Wiley & Sons, Ltd. [source] A Versatile System for Arbitrary Function Large-Amplitude Fourier Transformed VoltammetryELECTROANALYSIS, Issue 13 2007Lishi Wang Abstract A novel low-cost instrument for arbitrary function large-amplitude Fourier transformed voltammetry was developed. Description of both hardware and software was given in detail in this paper. A micro-control-unit (MCU) in combination with a field programmable gate array (FPGA) was designed to act as the controller of the instrument. Profiting from the built-in USB2.0 standard interface of the MCU, vast amount of data to/from the high resolution digital-to-analog converter (DAC)/analog-to-digital converter (ADC) then could be exchanged with computer in real-time, instead of being temporarily stored at the capacity limited memory of the instrument which always restricted the length of sampling time and the size of the collected data set. In the [Fe(CN)6]4+/3+ system, by superimposing a sinusoidal waveform with an amplitude of 120,mV onto a triangular potential and then applying to a macro electrode through the instrument, voltammograms up to the eighth harmonic could be well resolved by FT-IFT method. Excellent agreement was attained with Bond's similar experiment [Anal. Chem. 76 (2004) 3619] in respect of the shape and relative peak height of each harmonic. With the simply structured instrument, stable performance, flexible and versatile function was achieved. Arbitrary forms of AC perturbation which may not necessarily be sinusoidal or square-wave or other regular formed periodic signal could be synthesized and superimposed onto a DC potential as the excitation signal with this instrument. Some more useful electrode process information was expected to unveil by utilizing the FT-IFT algorithm to dissect the response signal. [source] Tonotopic representation of missing fundamental complex sounds in the human auditory cortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2003Takako Fujioka Abstract The N1m component of the auditory evoked magnetic field in response to tones and complex sounds was examined in order to clarify whether the tonotopic representation in the human secondary auditory cortex is based on perceived pitch or the physical frequency spectrum of the sound. The investigated stimulus parameters were the fundamental frequencies (F0 = 250, 500 and 1000 Hz), the spectral composition of the higher harmonics of the missing fundamental sounds (2nd to 5th, 6th to 9th and 10th to 13th harmonic) and the frequencies of pure tones corresponding to F0 and to the lowest component of each complex sound. Tonotopic gradients showed that high frequencies were more medially located than low frequencies for the pure tones and for the centre frequency of the complex tones. Furthermore, in the superior,inferior direction, the tonotopic gradients were different between pure tones and complex sounds. The results were interpreted as reflecting different processing in the auditory cortex for pure tones and complex sounds. This hypothesis was supported by the result of evoked responses to complex sounds having longer latencies. A more pronounced tonotopic representation in the right hemisphere gave evidence for right hemispheric dominance in spectral processing. [source] Systematic unbalanced interharmonic interaction analysis with power constraintsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 1 2005Jesús C. Contreras Sampayo Abstract This paper presents a systematic technique to solve for the harmonic and interharmonic interaction between a power system and several harmonic sources. The technique can potentially analyze any power electronic source that can be modeled as a piece-wise linear circuit. Harmonic source data is input to the procedure using a standard lumped parameter description. Two test cases are presented. The first test case shows the interaction between a static var compensator (SVC) and an HVDC in unbalanced operating conditions. The second test case analyzes a complete current source variable speed drive connected to a distribution network. Both test cases include power constraints. Copyright © 2005 John Wiley & Sons, Ltd. [source] New passive filter design for neutral current cancellation in balanced 3-phase 4-wire non-linear distribution systemsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2003E. F. El-Saadany Different types of non-linear loads are expected to proliferate into the distribution system, causing the harmonic distortion levels on these systems to increase. Third harmonic and all other triplen harmonic currents have little diversity among different loads and add in the neutral. The neutral current in a low voltage three-phase four-wire distribution system is expected to increase resulting in significant problems. The factors that affect the neutral current magnitude as well as the phase currents distortion are investigated. A new technique, namely, reactance one-port compensator is presented in order to cancel the neutral current and improve the overall system distortion levels. The attenuation and diversity effects are considered during performing this study. The analysis uses the electromagnetic transient program (EMTP) to model the loads as well as the overall system. The proposed filter drastically improves the system performance and substantially reduces the neutral current. [source] About the role of the park imaginary power on the three-phase line voltage dropEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2000A. Ferrero In this paper the line voltage drop concept is investigated and extended to non-sinusoidal conditions. The results are applied to the three-phase configuration. In this approach the presence of harmonic and sequence components is taken into account. The formal invariance of the obtained results with respect to the original single-phase relationships is ensured by means of the three-phase rms concept. The Park transformation is used as well, so that the three-phase relationships are reduced to a simpler formal single-phase approach: the simultaneous contributions of harmonic and sequence components are unified in a single formulation. Therefore the Park imaginary power role results as a natural extension of the usual single-phase reactive power concept. [source] Dependence of s -waves on continuous dimension: The quantum oscillator and free systemsFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 12 2006K.B. Wolf Abstract Wavefunctions with rotational symmetry (i.e., zero angular momentum) in D dimensions, are called s -waves. In quantum quadratic systems (free particle, harmonic and repulsive oscillators), their radial parts obey Schrödinger equations with a fictitious centrifugal (for integer D , 4) or centripetal (for D = 2) potential. These Hamiltonians close into the three-dimensional Lorentz algebra so(2,1), whose exceptional interval corresponds to the critical range of continuous dimensions 0 < D < 4, where they exhibit a one-parameter family of self-adjoint extensions in ,2(,+). We study the characterization of these extensions in the harmonic oscillator through their spectra which , except for the Friedrichs extension , are not equally spaced, and we build their time evolution Green function. The oscillator is then contracted to the free particle in continuous- D dimensions, where the extension structure is mantained in the limit of continuous spectra. Finally, we compute the free time evolution of the expectation values of the Hamiltonian, dilatation generator, and square radius between three distinct sets of ,heat'-diffused localized eigenstates. This provides a simple group-theoretic description of the purported contraction/expansion of Gaussian-ring s -waves in D > 0 dimensions. [source] Effects of mode coupling and location of rotational axis on glacial induced rotational deformation in a laterally heterogeneous viscoelastic earthGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2006Patrick Wu SUMMARY Lateral viscosity variations introduce two problems in the study of glacial induced rotational deformation. One of them is mode coupling. The other arises because centrifugal deformations are dependent on the location of the rotational axis relative to the lateral heterogeneities in the earth. The effects of mode coupling and displacement of the rotational axis on centrifugal induced potential perturbations are studied on a layered earth with lateral viscosity variations inferred from seismic tomography. The modified coupled Laplace-finite-element method is used to calculate the centrifugal deformations. It is found that mode coupling is weak because the lateral viscosity variation in the deep mantle is relatively small. The effect of displacing the rotational axis is to shift the spectral amplitude from degree 2 and order 0 harmonic to other orders within degree 2 as is required for changing the orientation of the applied centrifugal potential, but again the leakage of spectral amplitude to other harmonics are small. This implies that rotational motion in an earth with lateral viscosity variations can be approximated by the calculation of the corresponding laterally homogeneous earth. [source] Simulated geomagnetic reversals and preferred virtual geomagnetic pole pathsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2004C. Kutzner SUMMARY The question of whether virtual geomagnetic poles (VGPs) recorded during reversals and excursions show a longitudinal preference is a controversial one amongst palaeomagnetists. One possible mechanism for such VGP clustering is the heterogeneity of heat flux at the core,mantle boundary (CMB). We use 3-D convection-driven numerical dynamo models with imposed non-uniform CMB heat flow that show stochastic reversals of the dipole field. We calculate transitional VGPs for a large number of token sites at the Earth's surface. In a model with a simple heat flux variation given by a Y22 harmonic, the VGP density maps for individual reversals differ substantially from each other, but the VGPs have a tendency to fall around a longitude of high heat flow. The mean VGP density for many reversals and excursions shows a statistically significant correlation with the heat flow. In a model with an imposed heat flux pattern derived from seismic tomography we find maxima of the mean VGP density at American and East Asian longitudes, roughly consistent with the VGP paths seen in several palaeomagnetic studies. We find that low-latitude regions of high heat flow are centres of magnetic activity where intense magnetic flux bundles are generated. They contribute to the equatorial dipole component and bias its orientation in longitude. During reversals the equatorial dipole part is not necessarily dominant at the Earth's surface, but is strong enough to explain the longitudinal preference of VGPs as seen from different sites. [source] Calibration of the pass-through magnetometer,II.GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2002Application Summary We describe the experimental procedure we use to calibrate a cryogenic pass-through magnetometer. The procedure is designed to characterize the magnetometer sensitivity as a function of position within the sensing region. Then we extend a theory developed in an earlier paper to cover inexact observations and apply it to the data set. The theory allows the calculation of a smooth, harmonic, internally consistent interpolating function for each of the nine components of the response tensor of the magnetometer. With these functions we can calculate the response to a dipole source in any orientation and position, and predict the magnetometer signal from any kind of specimen. The magnetometer in the paleomagnetic laboratory onboard the research vessel Joides Resolution is the subject of one such experiment and we present the results. The variation with position of sensitivity is displayed in a series of plane slices through the magnetometer. We discover from the calibration model that the X and Z coils are misaligned so that the magnetic centre of the coils is displaced from the geometric centre by approximately 0.7 cm. We synthesize the signal expected from the magnetometer when a variety of simple cores are measured. We find that, unless appropriate corrections are made, changes in magnetization direction can appear as variations in magnetic intensity, and conversely, fluctuations in the magnetization strength can produce apparent swings in declination and inclination. The magnitude of these effects is not small and is certainly worth taking into account in the interpretation of records from this kind of instrument. In a pilot study on data from a core measured with the shipboard magnetometer, we observe some large distortions, particularly in declination, that are attributable to uncorrected instrumental effects. [source] Upper mantle stratification by P and S receiver functionsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2000Véronique Farra Summary Seismic stratification of the upper mantle is investigated by applying two complementary techniques to the records of the Graefenberg array in southern Germany. The anisotropic P receiver function technique (Kosarev et al. 1984; Vinnik & Montagner 1996) is modified by using summary seismic events instead of individual events and different weighting functions instead of the same function for the harmonic angular analysis of the SV and T components of the Pds phases. The summary events provide better separation of the second azimuthal harmonic than the individual events. The parameters of the second harmonics of SV and T thus evaluated should be similar if they reflect the effects of azimuthal anisotropy. This can be used as a criterion to identify the anisotropy. To detect the Sdp phases and their azimuthal variations caused by azimuthal anisotropy we have developed a stacking technique, which can be termed the S receiver function technique It includes axis rotation to separate interfering P and S arrivals, determination of the principal (M) component of the S -wave motion, deconvolution of the P components of many recordings by their respective M components and stacking of the deconvolved P components with weights depending on the level of noise and the angle between the M direction and the backazimuth of the event. Both techniques yield consistent results for the Graefenberg array. As indicated by the P receiver functions, the upper layer of the mantle between the Moho and 80 km depth is anisotropic with dVs/Vs around 0.03 and the fast direction close to 20° clockwise from north. The fast direction of anisotropy below this layer is around 110°, The boundary between the upper and the lower anisotropic layers is manifested by the detectable Pds and Sdp converted phases. Shear wave splitting in SKS is strongly dominated by azimuthal anisotropy in the lower layer (asthenosphere). [source] 24-Hour Distribution of Migraine AttacksHEADACHE, Issue 1 2008Karl Alstadhaug MD Background., It is a widespread opinion that migraine attacks arise more frequently in the morning and that circadian rhythms may be responsible for the temporal pattern in migraine. However, only one small prospective study has previously been published on this topic. Objective., To investigate circadian variation in migraine. Method., Eighty-nine females in fertile age who had participated in a previous questionnaire-based study volunteered to prospectively record in detail every migraine attack for 12 consecutive months. We reviewed all diary entries covering the period from March 2004 through April 2005, and did time-series analysis. Results., Fifty-eight patients had complete recordings over the 12 months and 26 completed the diaries for 1,11 months. Three patients were excluded due to missing data and 2 patients were excluded due to chronic migraine or medication-overuse headache. A total of 2314 attacks were experienced, in average 27.5 per patient (range 1,75). By fitting a sine curve to the data there was a harmonic trend with a peak around 13.40 and the peak/low ratio was 25.6 (95% CI: 8.3,78.6). Conclusion., The main finding in our study is that migraine attacks tend to recur in a harmonic 24-hour cyclic manner with a peak around the middle of the day and that there is no difference between migraine with aura and migraine without aura regarding this. [source] Fourier methods for quasi-periodic oscillationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2006Frank Schilder Abstract Quasi-periodic oscillations and invariant tori play an important role in the study of forced or coupled oscillators. This paper presents two new numerical methods for the investigation of quasi-periodic oscillations. Both algorithms can be regarded as generalizations of the averaging and the harmonic (spectral) balance methods. The algorithms are easy to implement and require only minimal a priori knowledge of the system. Most importantly, the methods do not depend on an a priori co-ordinate transformation. The methods are applied to a number of illustrative examples from non-linear electrical engineering and the results show that the methods are efficient and reliable. In addition, these examples show that the presented algorithms can also continue through regions of sub-harmonic (phase-locked) resonance even though they are designed only for the quasi-periodic case. Copyright © 2006 John Wiley & Sons, Ltd. [source] CFD analysis of an oscillating wing at various reduced frequenciesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2009Farooq Umar Abstract The effect of various reduced frequencies has been examined for an oscillating aspect ratio 10 NACA 0015 wing. An unsteady, compressible three-dimensional (3D) Navier,Stokes code based on Beam and Warming algorithm with the Baldwin,Lomax turbulence model has been used. The code is validated for the study against published experimental data. The 3D unsteady flow field is simulated for reduced frequency values of 0.1, 0.2 and 0.3 for a fixed mean angle of attack position and fixed amplitude. The type of motion is sinusoidal harmonic. The force coefficients, pressure distributions and flow visualization show that at the given conditions the flow remains attached to the wing surface even at high angles of attack with no clear separation or typical light-to-deep category of dynamic stall. Increased magnitude of hysteresis and higher gradients are seen at higher reduced frequencies. The 3D effects are even found at midspan locations. In addition, the rate of decrease in lift near the wing tips compared with the wing root is not much like in the static cases. Copyright © 2008 John Wiley & Sons, Ltd. [source] Periodic noise analysis of electric circuits: Artifacts, singularities and a numerical methodINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 7 2010Angelo Brambilla Abstract In this paper it is shown that a numerical method largely adopted for the simulation of noise in autonomous circuits is affected by singularities that manifest when the frequency at which the noise analysis is carried out approaches a harmonic of the autonomous circuit. The resulting noise power spectral density (PSD) is thus characterized by spurious spikes. The presence of these singularities is for the first time justified from an analytical standpoint and their effects are shown by simulating some oscillators, employed as benchmarks. Furthermore, the presented approach justifies the 1/(fs,f)2 shape of the PSD of noise at the output when the fs frequency approaches the f fundamental of a stable oscillator and the 1/|fs,f|3 shape when the effects of flicker noise are manifest. Copyright © 2009 John Wiley & Sons, Ltd. [source] A method for analysing the transient and the steady-state oscillations in third-order oscillators with shifting biasINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 5 2001A. Buonomo Abstract We provide an asymptotic method for systematically analysing the transient and the steady-state oscillations in third-order oscillators with shifting bias. The method allows us to construct the general solution of the weakly non-linear differential equation describing these oscillators through an iteration procedure of successive approximations typical of perturbation methods. The approximation to first order is obtained solving a system of two first-order non-linear differential equations in the leading terms of solution (dc component and fundamental harmonic), whereby the dominant dynamics, the stationary states and their stability can be easily analysed. Unlike existing approaches, our method also enables us to determine the higher harmonics as well as the frequency shift from the system's natural frequency in the exact solution through analytical formulae. In addition, formulae for higher-order approximations of the above quantities are determined. The proposed method is applied to a practical circuit to show its usefulness in both analysis and design problems. Copyright © 2001 John Wiley & Sons, Ltd. [source] The annual cycle and interannual variability of atmospheric pressure in the vicinity of the North PoleINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2003Richard I. Cullather Abstract A comparison of National Centers for Environmental Prediction,National Center for Atmospheric Research reanalysis six-hourly sea-level pressure data with former Soviet drifting station observations over the central Arctic Basin reveals high monthly correlations throughout the period 1950,91, but also a preferred winter season negative bias of about 1.4 hPa. Using the reanalysis, supplemented by Arctic Ocean Buoy Program fields and in situ observations, a generalized depiction of the annual cycle of pressure fields over the Arctic may be constructed. Above the Canada Basin,Laptev Sea side of the Arctic, the annual cycle of surface pressure is dominated by the first harmonic, which has an amplitude of about 5 hPa and maximum pressure occurring in March. Along the periphery of northern Greenland and extending to the North Pole, a weak semiannual cycle is found in surface pressure with maxima in May and November. The presence of the semiannual variation over time is highly variable. Dynamically, this progression of the annual cycle may be attributed to the transfer of atmospheric mass from Eurasia and into the Canadian Archipelago in spring and the reverse condition in autumn. Over the central Arctic Basin, springtime pressure increases result from an enhanced poleward mass transport from Eurasia. An increase of equatorward transport over the Canadian Archipelago in May and June results in central Arctic pressure decreases into summer. A less distinct temporal separation between the poleward Canadian transport and the equatorward Eurasian transport results in the weaker second pressure maximum in autumn. On interannual time-scales, atmospheric mass over the central Arctic is exchanged with the storm track centres of action in the North Atlantic and North Pacific. In particular, the large decrease in central Arctic Basin sea-level pressure during the late 1980s is due to a large transfer of atmospheric mass into the North Pacific. Copyright © 2003 Royal Meteorological Society [source] Quantum dynamics of a discontinuously kicked charged particle in harmonic, symmetric double, or triple wellsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2009S. Ghosh Abstract The quantum dynamics of a charged particle in a harmonic trap in the presence of discontinuous reversals of a homogeneous or an inhomogeneous electric field is studied. The dynamics reveals classically expected patterns in harmonic wells. In a symmetric double-well potential, the discontinuously switched low intensity homogeneous electric field does not appear to assist tunneling, whereas an inhomogeneous electric field is found to assist the process. Resonance like enhancement is noticed at a critical reversal frequency. Dynamics in a triple well is also analyzed under similar conditions. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] A time-domain large-signal measurement setupINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 1 2005H. Arthaber Abstract An active harmonic load-pull setup with the possibility to measure the inner voltages and currents is presented. To overcome stability issues, the realized setup uses open loops with synchronized generators for the 2nd and 3rd harmonic. Application examples show transistor-model verification and influences between harmonic matches. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [source] Mode-selective stereomutation tunneling as compared to parity violation in hydrogen diselenide isotopomers 1,2,3H280Se2ISRAEL JOURNAL OF CHEMISTRY, Issue 3-4 2003Michael Gottselig We present quantitative calculations of the mode-selective stereomutation tunneling in the chiral hydrogen diselenide isotopomers X2Se2 with X = H, D, and T. The torsional tunneling stereomutation dynamics were investigated with a quasi-adiabatic channel quasi-harmonic reaction path Hamiltonian approach, which treats the torsional motion anharmonically in detail and all remaining coordinates as harmonic (but anharmonically coupled to the reaction coordinate). We also investigated the influence of the excitation of fundamental modes on the stereomutation dynamics and predict which modes should be promoting or inhibiting. Our stereomutation dynamics results and the influence of parity violation on these are discussed in relation to our recent investigations for the analogous molecules H2O2, HSOH, H2S2, and Cl2S2. The electronic potential energy barrier heights for the torsional motion of hydrogen diselenide are similar to those of HSOH, whereas the torsional tunneling splittings are similar to the corresponding values of HSSH. The ground-state torsional tunneling splittings calculated here for D2Se2 are of the same order as the parity-violating energy difference reported by Laerdahl and Schwerdtfeger (Phys. Rev. A 1999, 60, 4439), whereas for T2Se2 the corresponding tunneling splitting is about three orders of magnitude smaller. [source] Stretching single DNA molecules to demonstrate high-force capabilities of holographic optical tweezersJOURNAL OF BIOPHOTONICS, Issue 4 2010Arnau Farré Abstract The well calibrated force-extension behaviour of single double-stranded DNA molecules was used as a standard to investigate the performance of phase-only holographic optical tweezers at high forces. Specifically, the characteristic overstretch transition at 65 pN was found to appear where expected, demonstrating (1) that holographic optical trap calibration using thermal fluctuation methods is valid to high forces; (2) that the holographic optical traps are harmonic out to >250 nm of 2.1 ,m particle displacement; and (3) that temporal modulations in traps induced by the spatial light modulator (SLM) do not affect the ability of optical traps to hold and steer particles against high forces. These studies demonstrate a new high-force capability for holographic optical traps achievable by SLM technologies. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fourier transformation of arterial Doppler waveforms of the lower extremityJOURNAL OF CLINICAL ULTRASOUND, Issue 6 2004Hong Gi Lee MD Abstract Purpose Although it is well known that the normal, triphasic pulsatile arterial Doppler waveform changes in shape as flow is impaired, interpretation of the waveform has largely been subjective. We aimed to describe the Doppler waveforms of the lower extremity objectively using Fourier transformation. Methods Sixty-eight zero-crossing detector arterial recordings from 25 lower extremities were grouped as follows: group 1, no ischemic symptoms with an ankle-brachial index (ABI) > 0.9 (n = 17, 8 limbs); group 2, no ischemic symptoms with ABI < 0.9 (n = 18, 5 limbs); group 3, symptoms of claudication (n = 19, 7 limbs); group 4, rest pain or tissue loss (n = 14, 5 limbs). The waveforms were Fourier transformed and their amplitudes and phases were compared up to the third harmonic (H3). Results Amplitudes of both the fundamental (H1) and second harmonic (H2) were predominant in group 1. In contrast, amplitudes of the H2 and H3 decreased with altered flow (p < 0.0001 for group 1 versus others). The phases of the H1 and H2 were delayed with altered flow (p < 0.05 for group 1 versus others). Phases of the H1 were different between group 2 and 4 (p < 0.05). The difference of phase between the H3 and H1 was shortened with altered flow (p < 0.05 for group 1 or 2 versus group 4). Multivariate analysis revealed that the relative amplitudes of the H2 and H3, the phases of the H1 and H2, and the relative phase of the H3 were significant discriminators among the groups. Conclusion Abnormal waveforms could be characterized by the predominant amplitude of the H1, phase delay of the H1 and H2, and shortening of the relative phase of the H3. These parameters may be useful in the evaluation of Doppler waveforms in patients with peripheral arterial disease. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:277,285, 2004 [source] Quantitative assessment of fetal bowel echogenicity: Comparison of harmonic, compound, and fundamental sonographic imagesJOURNAL OF CLINICAL ULTRASOUND, Issue 6 2003Hak Jong Lee MD Abstract Purpose The aims of this study were to assess normal fetal bowel echogenicity quantitatively and to compare the levels of bowel echogenicity observed with the use of 3 different sonographic image-processing techniques,harmonic plus compound imaging, harmonic imaging alone, and fundamental imaging,and 2 different broadband transducers. Methods Women with normal singleton second-trimester fetuses underwent sonographic scanning with both a 2,5-MHz and a 4,7-MHz transducer. The use of the 3 imaging techniques and the 2 transducers resulted in 6 types of images: 2,5-HC (harmonic plus compound images), 2,5-H (harmonic images), and 2,5-F (fundamental images), and 4,7-HC, 4,7-H, and 4,7-F images. The relative echogenicities (brightness) of the fetal bowel and iliac bone were measured, and bowel echogenicity ratios (bowel echogenicity/iliac bone echogenicity × 100) were calculated using graphics software. The resulting data were analyzed to evaluate differences in echogenicity ratios between the 6 types of images. Results We examined 37 fetuses during the study period. The bowel echogenicity ratios were highest on the images obtained with harmonic and compound,imaging techniques (2,5-HC, 84.7 ± 23.4%; 4,7-HC, 98.5 ± 36.4%). The bowel echogenicity ratio for the 2,5-HC images was significantly higher than those for the 2,5-H and the 2,5-F images (p < 0.01 and p < 0.001, respectively), and those for the 4,7-HC and 4,7-H images were higher than that for the 4,7-F images (p < 0.01 for both comparisons). Conclusions A sonographic finding of echogenic fetal bowel should be interpreted cautiously because the use of special image-processing techniques can artificially enhance the apparent level of echogenicity of the bowel. We recommend rescanning without the use of those techniques if the fetal bowel appears to have an increased level of echogenicity. © 2003 Wiley Periodicals, Inc. J Clin Ultrasound 31:302,307, 2003 [source] Coarse-grained force field for the nucleosome from self-consistent multiscalingJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2008Karine Voltz Abstract A coarse-grained simulation model for the nucleosome is developed, using a methodology modified from previous work on the ribosome. Protein residues and DNA nucleotides are represented as beads, interacting through harmonic (for neighboring) or Morse (for nonbonded) potentials. Force-field parameters were estimated by Boltzmann inversion of the corresponding radial distribution functions obtained from a 5-ns all-atom molecular dynamics (MD) simulation, and were refined to produce agreement with the all-atom MD simulation. This self-consistent multiscale approach yields a coarse-grained model that is capable of reproducing equilibrium structural properties calculated from a 50-ns all-atom MD simulation. This coarse-grained model speeds up nucleosome simulations by a factor of 103 and is expected to be useful in examining biologically relevant dynamical nucleosome phenomena on the microsecond timescale and beyond. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Fundamental vibrational frequencies and dominant resonances in methylamine isotopologues by ab initio and density functional theory methods,JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 8 2008Chen Levi Abstract Ab initio and density functional theory (DFT) calculations were performed for obtaining fundamental vibrational frequencies of methylamine, CH3NH2, and its deuterated variants CH3ND2, CD3NH2, and CD3ND2. The calculations were carried out using the CCSD(T) coupled cluster approximation with cc-pVTZ and cc-pVQZ basis sets, and by the DFT method with the semiempirical hybrid functional B97-1 with polarization consistent pc-2 and pc-3 basis sets. Reasonable performance of the DFT harmonic and ab initio harmonic calculations was found, which improved considerably upon combination of the harmonic fundamental frequencies with anharmonic corrections from the smaller, pc-2, basis. The computed anharmonic fundamental frequencies of methylamine isotopologues agree very well with the experimental values and represent a useful tool for assignment and analysis of the dominant resonances. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Variational treatment of the vibrational Hamiltonian for NH3 and H2NOJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2002Philippe Marsal Abstract The full vibrational Hamiltonian for the inversion of NH3 and H2NO has been diagonalized in a basis set that is the direct product of functions of the inversion coordinate and of harmonic vibrational functions independent of this inversion coordinate. The kinetic part of the Hamiltonian matrix is constructed with the use of the closure relation for these vibrational functions. The method is tested with the potential function which is supposed to be harmonic for the vibrations orthogonal to the inversion coordinate: the first computed levels are in good agreement with experimental levels for NH3. For higher levels, anharmonic terms should be included. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 541,547, 2002; DOI 10.1002/jcc.10033 [source] | |||||||||||||||||||||||||||||||||||||||||||