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Phase Difference (phase + difference)
Selected AbstractsDistinguishing Linear from Star-Branched Polystyrene Solutions with Fourier-Transform RheologyMACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004Thorsten Neidhöfer Abstract Summary: Fourier-Transform rheology (FT rheology) was used to study the influence of the degree of branching on the nonlinear relaxation behaviour of polystyrene solutions. The results were compared with those obtained under oscillatory shear and step-shear conditions. The different topologies could be distinguished using FT rheology where the other rheological measurements failed. Significant differences occurred under large amplitude oscillatory shear (LAOS) conditions as particularly reflected in the phase difference of the third harmonic, ,3, which could be related to strain-softening and strain-hardening behaviour. Currently, this work is extended towards different topologies in polyolefins (e.g. long chain branched). Phase difference ,3 as a function of the Deborah number De at ,0,=,2 for the polystyrene solutions measured at temperatures from 295 to 350.5 K. [source] Noncontact Operational Modal Analysis of Structural Members by Laser Doppler VibrometerCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2009Dionysius M. Siringoringo The system employs natural excitation technique (NExT) to generate the cross-correlation functions from laser signals, and the eigensystem realization algorithm (ERA) to identify modal parameters of structural members. To facilitate simultaneous modal identification, time-synchronization technique and construction of cross-correlation functions from ambient response of laser signals are proposed. Performance of the proposed system is verified experimentally by evaluating the consistency and accuracy of identification results in different measurement conditions. The work presented here is an extension of the previous study, where a modal-based damage detection method using LDV was formulated. In the present study, application of LDV for structural parameters identification of a combined dynamical system is proposed. A model that represents the connection properties in terms of additional stiffness and damping is developed, and its importance for structural damage detection is discussed. The study shows that the presence of simulated damage in a steel connection can be detected by tracking the modal phase difference and by quantifying the additional stiffness and damping. [source] Metabolic Heat Production, Heat Loss and the Circadian Rhythm of Body Temperature in the RatEXPERIMENTAL PHYSIOLOGY, Issue 3 2003Roberto Refinetti Metabolic heat production (calculated from oxygen consumption), dry heat loss (measured in a calorimeter) and body temperature (measured by telemetry) were recorded simultaneously at 6 min intervals over five consecutive days in rats maintained in constant darkness. Robust circadian rhythmicity (confirmed by chi square periodogram analysis) was observed in all three variables. The rhythm of heat production was phase-advanced by about half an hour in relation to the body temperature rhythm, whereas the rhythm of heat loss was phase-delayed by about half an hour. The balance of heat production and heat loss exhibited a daily oscillation 180 deg out of phase with the oscillation in body temperature. Computations indicated that the amount of heat associated with the generation of the body temperature rhythm (1.6 kJ) corresponds to less than 1% of the total daily energy budget (172 kJ) in this species. Because of the small magnitude of the fraction of heat balance associated with the body temperature rhythm, it is likely that the daily oscillation in heat balance has a very slow effect on body temperature, thus accounting for the 180 deg phase difference between the rhythms of heat balance and body temperature. [source] Heat transportation by oscillatory flow with steady flow componentHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2006Akira Inukai Abstract This paper deals with heat transportation by an oscillatory flow composed of a sinusoidal oscillatory flow superimposed with a steady flow. Velocity and temperature fields, heat transportation rate, work rate, and heat transportation efficiency were investigated through numerical analysis. Results obtained elucidated that (1) the phase difference between velocity and temperature variation remained the same as that of the sinusoidal reciprocal flow without the use of a steady flow component. (2) In the upstream direction heat was mainly transported by the steady flow component and in the downstream direction transportation was mainly performed by the oscillatory flow component. (3) The heat transportation rate of the present oscillatory flow composed of both steady and oscillatory flow components was less than the arithmetic sum of the rates produced by the steady flow and the sinusoidal oscillatory flow. (4) The heat transportation rate was increased immensely by superimposing the steady flow on the sinusoidal oscillatory flow. (5) Conversely, work done by the present oscillatory flow increased only slightly. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(7): 482,500, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20130 [source] Measurement of atmospheric water vapour on the ground's surface by radio wavesHYDROLOGICAL PROCESSES, Issue 11 2001Tokuo Kishii Abstract Water vapour in the atmosphere and various meteorological phenomena are essential to the understanding of the mechanism of the water cycle. However, it is very difficult to observe water vapour in the atmosphere because the quantities are usually observed at a single point not over long intervals or in a specific plane or volume. Accordingly, the use of radio waves is considered to be necessary to observe water vapour. Radio waves can be transmitted over long intervals and across large areas, and generally speaking, the characteristics of radio waves change due to material in the atmosphere, especially water vapour. Usually absorption is used to observe the quantity of water vapour. But the relationship between absorption and the quantity of water vapour is not linear, so we try to utilize the phase difference between two radio waves as an alternative method. First, the relationship between the phase delay and the water vapour was induced by a physical equation and the resulting phase delay was found to be proportional to the quantity of water vapour. Furthermore, the phase difference between two separate points was observed by use of two radio waves in the field, specifically 84 GHz and 245 GHz. For reference and comparison, water vapour density in the atmosphere was simultaneously observed by meteorological observation. As a result, the density of the water vapour was found to be proportional to the phase difference between the two radio waves. The result also shows that this method is able to measure the diurnal changes in water vapour density in each season. Copyright © 2001 John Wiley & Sons, Ltd. [source] Influence on mass-selective ion ejection of the phase difference between the drive r.f. and the axial modulation potentialsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2005G. Dobson Abstract The phase difference between the drive r.f. and the axial modulation potential is known to influence significantly the mass shift, and all commercial ion trap mass spectrometers use a fixed value for this difference. However, although this important parameter is partly responsible for the good precision achievable today in most commercial ion traps, little discussion on the variation of the phase difference between the drive r.f. and the axial modulation potential has appeared in the literature. We present here an examination of the influence of a low-level axial modulation potential superimposed by capacitive coupling between the electrodes. Low-level axial modulation potentials are used for certain analytical scans such as reverse scan or slow scan speeds. Such low-level potentials help to prevent deterioration of mass resolution due to, for example, the dissociation of the ions during their resonant ejection from the ion trap. Reverse and forward scans are used to illustrate the mass shift and change in resolution, caused by a change in the phase difference between the drive r.f. potential applied to the ring electrode and the axial modulation potential applied on an end-cap electrode, in electrospray ionization mass spectra. Copyright © 2005 John Wiley & Sons, Ltd. [source] Distinguishing Linear from Star-Branched Polystyrene Solutions with Fourier-Transform RheologyMACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004Thorsten Neidhöfer Abstract Summary: Fourier-Transform rheology (FT rheology) was used to study the influence of the degree of branching on the nonlinear relaxation behaviour of polystyrene solutions. The results were compared with those obtained under oscillatory shear and step-shear conditions. The different topologies could be distinguished using FT rheology where the other rheological measurements failed. Significant differences occurred under large amplitude oscillatory shear (LAOS) conditions as particularly reflected in the phase difference of the third harmonic, ,3, which could be related to strain-softening and strain-hardening behaviour. Currently, this work is extended towards different topologies in polyolefins (e.g. long chain branched). Phase difference ,3 as a function of the Deborah number De at ,0,=,2 for the polystyrene solutions measured at temperatures from 295 to 350.5 K. [source] Shaping and timing gradient pulses to reduce MRI acoustic noise,MAGNETIC RESONANCE IN MEDICINE, Issue 2 2010Marcel Segbers MSc Abstract A method to reduce the acoustic noise generated by gradient systems in MRI has been recently proposed; such a method is based on the linear response theory. Since the physical cause of MRI acoustic noise is the time derivative of the gradient current, a common trapezoid current shape produces an acoustic gradient coil response mainly during the rising and falling edge. In the falling edge, the coil acoustic response presents a 180° phase difference compared to the rising edge. Therefore, by varying the width of the trapezoid and keeping the ramps constant, it is possible to suppress one selected frequency and its higher harmonics. This value is matched to one of the prominent resonance frequencies of the gradient coil system. The idea of cancelling a single frequency is extended to a second frequency, using two successive trapezoid-shaped pulses presented at a selected interval. Overall sound pressure level reduction of 6 and 10 dB is found for the two trapezoid shapes and a single pulse shape, respectively. The acoustically optimized pulse shape proposed is additionally tested in a simulated echo planar imaging readout train, obtaining a sound pressure level reduction of 12 dB for the best case. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source] Theoretical and experimental study of polarization characteristics of polarization maintaining fiber based on wavelength-sweeping modulationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2010Zuo-Liang Duan Abstract We analyze theoretically the polarization characteristics of polarization maintaining fiber and study the basic measurement principles of beat length and polarization extinction ratio of this kind of optical fiber. According to the dependence of the phase difference between two orthogonally polarized modes (denoted as HE and HE) transmitted in the polarization maintaining fiber on the light wavelength, we propose the wavelength-sweeping modulation method to measure the beat length and the model birefringence. Based on this technique, the beat length and polarization extinction ratio of the PANDA polarization maintaining fibers (PMFs) (provided by Yangtze Optical Fiber and Cable Company, Wuhan, China) were investigated in detail. Experimental results show good consistent with the theoretical ones. We find that this method shows high measurement precision with the advantages of clear measurement principle and easy to operate. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1466,1469, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25244 [source] Broadband Wilkinson balun using pure left-handed transmission lineMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2010Young-Ho Ryu Abstract Utilizing the opposite phase shift property of a microstrip line (MSL) and a pure left-handed transmission line (PLH TL), the broadband Wilkinson balun is designed. The PLH TL without a right-handed (RH) branch is designed using effectively negative elements obtained by a cross connection of vias to ground. The PLH TL gives inherently phase-advanced response properties because of negative phase velocity, whereas a conventional MSL has a phase-lag response. The property of a broadband left-handed branch of a PLH TL applies to the implementation of broadband balun. The proposed balun has a good return loss, a good isolation between output ports, an equal-power division, and a 180° ± 10° phase difference in a wide fractional bandwidth of ,71%. Furthermore, the wideband balun that has the fractional bandwidth of 107.8% is theoretically designed with the modified PLH TL having four unit cells. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1665,1668, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25242 [source] A symmetric log-periodic balun for ultra-wideband applicationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2008Chu-Yu Chen Abstract Compared with the conventional log-periodic balun, the design of a symmetric log-periodic balun can provide better performance over the entire designed band. A novel ultra-wideband (UWB) balun with 3,6 GHz passband is demonstrated for UWB applications. The problems of fabrication and measurement of the conventional log-periodic balun operated at higher frequency problems can be further improved. The magnitude and phase difference between two output ports are kept balancing at higher band edge portion. The measured amplitude imbalance is about ±1.1 dB with a corresponding phase difference about ±4°. The bandwidth of the balun is around 70%. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 947,948, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23264 [source] A novel internal antenna with high gain for wireless phoneMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2007Ying Liu Abstract A novel internal antenna for synchronous code division multiple access band wireless phone is presented. Traditional internal antenna is monopole or Planar Inverted-F Antenna, which have no gain high enough in the limited space in phone. The proposed antenna is composed of two antenna elements with equal magnitude and 180° phase difference, to assure voice quality with high gain. The measured maximum gain is 2.69 dBi and maximum efficiency is 70.1% in the frequency band 450,470 MHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2112,2114, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22708 [source] Polarization-dependent electromagnetic band gap (PDEBG) structures: Designs and applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2004Fan Yang Abstract EBG structures exhibit an in-phase reflection coefficient, which makes them desirable for low-profile antenna designs. However, a conventional EBG structure has an identical reflection phase for a normally incident plane wave in spite of its polarization state. This paper presents novel polarization-dependent EBG (PDEBG) structures whose reflection phases are different, depending upon the polarization state of the incident plane wave. This polarization-dependent reflection-phase feature is realized by changing the unit geometries, for example, by using a rectangular patch to replace the square patch, by cutting slots into the patch, or by offsetting the vias. By properly tailoring the phase difference between different polarizations, a useful EBG reflector is introduced, which can control the polarization state of the reflected wave. One attractive application of this reflector is that the reflected wave of a circularly polarized incident plane wave can maintain its polarization sense. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 439,444, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20164 [source] Return mapping of phases and the analysis of the gravitational clustering hierarchyMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002Lung-Yih Chiang ABSTRACT In the standard paradigm for cosmological structure formation, clustering develops from initially random-phase (Gaussian) density fluctuations in the early Universe by a process of gravitational instability. The later, non-linear stages of this process involve Fourier mode,mode interactions that result in a complex pattern of non-random phases. We present a novel mapping technique that reveals mode coupling induced by this form of non-linear interaction and allows it to be quantified statistically. The phase mapping technique circumvents the difficulty of the circular characteristic of ,k and illustrates the statistical significance of phase difference at the same time. This generalized phase method allows us to detect weak coupling of phases on any ,k scales. [source] Stationary models for fast and slow logarithmic spiral patterns in disc galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2002Yu-Qing Lou A recent wavelet analysis on multiwavelength image data of the nearby spiral galaxy NGC 6946 revealed a multi-arm spiral structure that persists well into the outer differentially rotating disc region. The extended spiral arms in polarized radio-continuum emission and in red light appear interlaced with each other, while the spiral arms in emissions of total radio continuum, of H, from H ii regions, and of neutral hydrogen all trace the red-light spiral arms, although to a somewhat lesser extent. The key issue now becomes how to sustain extended slow magnetohydrodynamic (MHD) density wave features in a thin magnetized disc with a flat rotation curve. We describe here a theoretical model to examine stationary non-axisymmetric logarithmic spiral configurations constructed from a background equilibrium of a magnetized singular isothermal disc (MSID) with a flat rotation curve and with a non-force-free azimuthal magnetic field. It is found analytically that two types of stationary spiral MSID configurations may exist, physically corresponding to the two possibilities of fast and slow spiral MHD density waves. Such stationary MHD density waves are possible only at proper MSID rotation speeds. For the fast MSID configuration, logarithmic spiral enhancements of magnetic field and gas density are either in phase in the tight-winding regime or shifted with a spatial phase difference ,,/2 for open spiral structures. For the slow MSID configuration, logarithmic spiral enhancements of magnetic field and gas density are either out of phase in the tight-winding regime or shifted with a spatial phase difference for open spiral structures and persist in a flat rotation curve. For NGC 6946, several pertinent aspects of the slow MSID scenario with stationary logarithmic spiral arms are discussed. The two exact solutions can be also utilized to test relevant numerical MHD codes. [source] Lateralization During the Weber Test: Animal ExperimentsTHE LARYNGOSCOPE, Issue 3 2002Jean-Yves Sichel MD Abstract Objectives/Hypothesis The objective of this study were to present an assessment of a new theory to explain lateralization during the Weber test using an animal model. This theory is based on the discovery that a major pathway in bone conduction stimulation to the inner ear is through the skull contents (probably the cerebrospinal fluid [CSF]). The placement of a bone vibrator or tuning fork on the skull excites the inner ear by the classic osseous pathway and by the suggested CSF pathway. We assume that there is a phase difference between the stimulation mediated by the ossicular chain (inertial and occlusion mechanisms) and the one mediated by the CSF. The presence of a conductive pathology will decrease the magnitude of the sound energy mediated by the ossicular chain. Thus, the out-of-phase signal arriving through the bony pathways will be decreased, hence increasing the resultant sound intensity stimulating the cochlea. Study Design Prospective animal study. Methods The experiment was performed on 10 fat sand rats, which had undergone unilateral cochleostomy and a small craniotomy. The auditory nerve brainstem response (ABR) thresholds were measured to air-conducted stimulation, to stimulation with the bone vibrator applied to the skull, and to stimulation with the bone vibrator applied directly to the brain through the craniotomy. The ossicular chain of the second ear was then fixed to the middle ear walls with cyanoacrylate glue to induce a conductive hearing loss. The ABR thresholds to the same three stimuli were then measured again. Results After ossicular chain fixation, the ABR threshold to air-conducted stimulation increased, to bone vibrator stimulation on the bone decreased (hearing improvement), and to bone vibrator stimulation directly on the brain remained unchanged. Conclusions This experiment confirms the proposed theory. During clinical bone conduction stimulation, there is a phase difference between sound energy reaching the inner ear through the middle ear ossicles and from the CSF. A middle ear conductive pathology removes one of these components, thus increasing the effective sound intensity in the affected ear. On the other hand, when the bone vibrator is applied on the brain, the inner ear is stimulated only through the CSF, so ossicular chain fixation does not change the ABR threshold. Moreover, this study proves that lateralization during the Weber phenomenon is the result, at least in part, of an intensity difference between sound energy reaching the two cochleae. [source] Secular variation of hemispheric phase differences in the solar cycleASTRONOMISCHE NACHRICHTEN, Issue 8 2010N.V. Zolotova Abstract We investigate the phase difference of the sunspot cycles in the two hemispheres and compare it with the latitudinal sunspot distribution. If the north-south phase difference exhibits a long-term tendency, it should not be regarded as a stochastic phenomenon. We use datasets of historical sunspot records and drawings made by Staudacher, Hamilton, Gimingham, Carrington, Spörer, and Greenwich observers, as well as the sunspot activity during the Maunder minimum reconstructed by Ribes and Nesme-Ribes. We employ cross-recurrence plots to analyse north-south phase differences. We show that during the last 300 years, the persistence of phase-leading in one of the hemispheres exhibits a secular variation. Changes from one hemisphere to the other leading in phase were registered near 1928 and 1968 as well as two historical ones near 1783 and 1875. A long-term anticorrelation between the hemispheric phase differences in the sunspot cycles and the latitudinal distribution of sunspots was traced since 1750 (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Generating Consistent Motion Transition via Decoupled Framespace InterpolationCOMPUTER GRAPHICS FORUM, Issue 3 2000G. Ashraf The framespace interpolation algorithm abstracts motion sequences as 1D signals, and interpolates between them to create higher dimension signals, with weights drawn from a user specified curve in a bounded region. We reformulate the algorithm to achieve motion-state based transition via dynamic warping of framespaces and automatic transition timing via framespace frequency interpolation. Basis motions displaying diverse coordination configurations between upper and lower body-halves, cannot be consistently corresponded at a macro level. We address this problem here, through decoupled blending of these halves to achieve true consistency, and eliminate accumulated phase differences via cosine phase warp functions. This generalization enables interpolation of motions with diverse coordinations between the upper and lower bodies. [source] Thinking about flagellar oscillationCYTOSKELETON, Issue 8 2009Charles J. Brokaw Abstract Bending of cilia and flagella results from sliding between the microtubular outer doublets, driven by dynein motor enzymes. This review reminds us that many questions remain to be answered before we can understand how dynein-driven sliding causes the oscillatory bending of cilia and flagella. Does oscillation require switching between two distinct, persistent modes of dynein activity? Only one mode, an active forward mode, has been characterized, but an alternative mode, either inactive or reverse, appears to be required. Does switching between modes use information from curvature, sliding direction, or both? Is there a mechanism for reciprocal inhibition? Can a localized capability for oscillatory sliding become self-organized to produce the metachronal phase differences required for bend propagation? Are interactions between adjacent dyneins important for regulation of oscillation and bend propagation? Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] Analysis of an Unconfined Aquifer Subject to Asynchronous Dual-Tide PropagationGROUND WATER, Issue 2 2008Kolja Rotzoll Most published solutions for aquifer responses to ocean tides focus on the one-sided attenuation of the signal as it propagates inland. However, island aquifers experience periodic forcing from the entire coast, which can lead to integrated effects of different tidal signals, especially on narrow high-permeability islands. In general, studies disregard a potential time lag as the tidal wave sweeps around the island. We present a one-dimensional analytical solution to the ground water flow equation subject to asynchronous and asymmetric oscillating head conditions on opposite boundaries and test it on data from an unconfined volcanic aquifer in Maui. The solution considers sediment-damping effects at the coastline. The response of Maui Aquifers indicate that water table elevations near the center of the aquifer are influenced by a combination of tides from opposite coasts. A better match between the observed ground water head and the theoretical response can be obtained with the proposed dual-tide solution than with single-sided solutions. Hydraulic diffusivity was estimated to be 2.3 × 107 m2/d. This translates into a hydraulic conductivity of 500 m/d, assuming a specific yield of 0.04 and an aquifer thickness of 1.8 km. A numerical experiment confirmed the hydraulic diffusivity value and showed that the y -intercepts of the modal attenuation and phase differences estimated by regression can approximate damping factors caused by low-permeability units at the boundary. [source] Wave propagation velocity under a vertically vibrated surface foundationINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2009Jaehun Ahn Abstract The ultimate objective of the research conducted by the authors is to explore the feasibility of determining reliable in situ values of soil modulus as a function of strain. In field experiments, an excitation is applied on the ground surface using large-scale shakers, and the response of the soil deposit is recorded through receivers embedded in the soil. The focus of this paper is on the simulation and observation of signals that would be recorded at the receiver locations under idealized conditions to provide guidelines on the interpretation of the field measurements. Discrete models are used to reproduce one-dimensional and three-dimensional geometries. When the first times of arrival are detected by receivers under the vertical impulse, they coincide with the arrival of the P wave; therefore related to the constrained modulus of the material. If one considers, on the other hand, phase differences between the motions at two receivers, the picture is far more complicated and one would obtain propagation velocities, function of frequency and measuring location, which do not correspond to either the constrained modulus or Young's modulus. It is necessary then to conduct more rigorous and complicated analyses in order to interpret the data. This paper discusses and illustrates these points. Copyright © 2008 John Wiley & Sons, Ltd. [source] Dynamics of human neocortex that optimizes its stability and flexibilityINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 9 2006Walter J. Freeman The electroencephalogram (EEG) in states of awake, sleep, and seizure in a patient with intractable partial complex seizures was recorded through a 1- × 1-cm microgrid of 64 electrodes on the right inferior temporal gyrus during a week-long neurosurgical evaluation. Comparisons with a normal intracranial EEG were perforce from animals. Analytic phase and amplitude from the Hilbert transform gave the temporal resolution needed to resolve EEG spatiotemporal structure. The rest state revealed multiple overlapping patterns of high-frequency coherent oscillations resembling bubbles in boiling water. Bubble diameters gave estimates of the distances across the cortex over which the cortical oscillations were synchronized. Superimposed on these bubbles were large-sized epochs of phase locking with briefly constant frequency and high amplitude. These coordinated analytic phase differences occurred between short periods of high phase variance. The variance gave evidence for state transitions between transiently stable states with constant phase gradients. In sleep these phase patterns persisted with reduced amplitude, occasionally interrupted by long-lasting (,1 s) epochs with no spatial textures in phase and amplitude despite a large increase in amplitude. Seizures had high amplitude 3/s spikes with steep spatial gradients. Onset occurred after pre-ictal reduction in bubble diameters as evidence for large-scale cortical disintegration preceding loss of stability. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 881,901, 2006. [source] Circadian phase entrainment via nonlinear model predictive controlINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 17 2007N. Bagheri Abstract A nonlinear model predictive control algorithm is developed to investigate the phase-resetting properties of robust nonlinear biological oscillators; in particular, those of the circadian rhythm. This pacemaker is an autonomous biochemical oscillator with a free-running period close to 24 h. Research in chronobiology indicates that light stimuli may delay or advance the phase of the oscillator, allowing it to synchronize physiological processes and entrain to the environment. In this paper, a closed-loop optimal phase tracking control algorithm is developed and applied to a mammalian circadian model. The integration of MPC-based light pulses, coupled with environmental light:dark cycles, allows the circadian system to recover phase differences within 1.5 days,a fraction of the natural open-loop simulated mammalian recovery time. Accelerated phase entrainment may alleviate disorders caused by circadian rhythms that are out of phase with the environment, and improve performance. Copyright © 2007 John Wiley & Sons, Ltd. [source] IS THERE AN ECOPHYSIOLOGICAL EXPLANATION FOR THE GAMETOPHYTE,TETRASPOROPHYTE RATIO IN GELIDIUM SESQUIPEDALE (RHODOPHYTA)?,JOURNAL OF PHYCOLOGY, Issue 2 2006Raquel Carmona In the fall, when 61% of the fronds of the Gelidium sesquipedale (Clem.) Born. et Thur. population located in Albufeira (southern Portugal) were reproductive, about 90% of these fronds were tetrasporophytes, whereas an equal percentage of female and male gametophytes was found (5%). The comparison of physiological performances of the reproductive phases (males, females and tetrasporophytes) did not reveal a physiological advantage of tetrasporic fronds. There were no significant differences either in the photosynthesis, nitrogen uptake, nitrate reductase activity, or biochemical composition of adult fronds. On the other hand, vegetative recruitment and spore production in the laboratory were significantly different. The re-attachment to calcareous substrate and the subsequent rhizoidal growth were faster in tetrasporophytes. Particular levels of temperature, rather than irradiance, had an important effect on the phase differences in the spore release, attachment, and germination rates. Significant results were the higher release of carpospores at all irradiances at 17°C, and the higher attachment percentage of carpospores at 13°C versus tetraspores. Under higher temperatures (21°C), tetraspores showed higher attachment rates while carpospores germinated more. G. sesquipedale cystocarps released carpospores for 2 months, while tetrasporangia stopped shedding tetraspores after 1 month, resulting in a 3-fold higher production of carpospores than tetraspores. Results showed that vegetative and spore recruitment may explain the low gametophyte,tetrasporophyte ratio of the studied population of G. sesquipedale as opposed to the physiological performance of phases. [source] Multiple-beam X-ray interferometry for phase-contrast microtomographyJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2001Ulrich Bonse The first successful operation of an X-ray interferometer under conditions of non-planar three-beam diffraction for phase-contrast X-ray microtomography is reported. Intrinsic phase differences of the reflections used cancel from the three-dimensional phase image of the specimen. With simultaneous hkl and reflections of a synchrotron radiation beam in a side-by-side geometry, the size of the usable field of view is doubled and the investigated specimen volume is increased by a factor of four. As an example, the reconstructed slice of a mouse kidney is shown in phase contrast at 71,keV. Optimized choices of three-beam reflections and matching interferometer geometries useful for applications are presented. [source] A penalized likelihood approach to image warpingJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 3 2001C. A. Glasbey A warping is a function that deforms images by mapping between image domains. The choice of function is formulated statistically as maximum penalized likelihood, where the likelihood measures the similarity between images after warping and the penalty is a measure of distortion of a warping. The paper addresses two issues simultaneously, of how to choose the warping function and how to assess the alignment. A new, Fourier,von Mises image model is identified, with phase differences between Fourier-transformed images having von Mises distributions. Also, new, null set distortion criteria are proposed, with each criterion uniquely minimized by a particular set of polynomial functions. A conjugate gradient algorithm is used to estimate the warping function, which is numerically approximated by a piecewise bilinear function. The method is motivated by, and used to solve, three applied problems: to register a remotely sensed image with a map, to align microscope images obtained by using different optics and to discriminate between species of fish from photographic images. [source] The impact of menstrual cycle phase on cardiac autonomic regulationPSYCHOPHYSIOLOGY, Issue 4 2009Paula S. Mckinley Abstract This study investigated menstrual cycle phase differences in heart rate (HR) and RR interval variability (RRV) in 49 healthy, premenopausal, eumenorrheic women (age 30.2±6.2 years). HR and RRV were computed from ambulatory 24-h electrocardiogram, collected for up to 6 days, with at least 1 day each during early to midfollicular and midluteal menstrual phases. Phase effects on HR and RRV were assessed using linear mixed effects models with a random intercept to account for the correlation of observations within each subject as well as intrasubject variation. During follicular phase monitoring, women had significantly lower average HR (,2.33 bpm), and higher standard deviation, the root mean squared successive difference, and high frequency (0.04,0.15 Hz) and low frequency (0.15,0.40 Hz) RRV than during the luteal phase. These results provide strong support for the influence of menstrual phase on cardiac autonomic regulation in premenopausal women. [source] Comparative Histology and Vibration of the Vocal Folds: Implications for Experimental Studies in Microlaryngeal Surgery ,THE LARYNGOSCOPE, Issue 5 2000C. Gaelyn Garrett MD Abstract Objectives/Hypothesis To determine the most suitable animal model for experimental studies on vocal fold surgery and function by a histological comparison of the microflap surgical plane and laryngeal videostroboscopy (LVS) in different species of animals. A second goal was to determine how the layered vocal fold structure in humans and three different animal species affects surgical dissection within the lamina propria. Study Design Prospective laboratory. Methods Three larynges each from dogs, monkeys, and pigs were compared with three ex vivo human larynges. Microflap surgery was performed on one vocal fold from each larynx. Both the operated and nonoperated vocal folds were examined histologically using stains specific for elastin, mature collagen, and ground substance. Based on the histological results, LVS was performed on two dogs and two pigs after first performing a tracheotomy for ventilation and airflow through the glottis. Arytenoid adduction sutures were placed to facilitate vocal fold adduction. Results The distributions of the collagen and elastin fibers were found to differ among the species with concentrations varying within species. Unlike the human vocal fold, which has a higher elastin concentration in the deeper layers of the lamina propria, both the pig and the dog had a thin band of elastin concentrated just deep to the basement membrane zone in the superficial layer. Just deep to this thin band, the collagen and the elastin were less concentrated. The monkey vocal fold had a very thin mucosal layer with less elastin throughout the mucosa. The microflap dissections in each of the dog, pig, and human vocal folds were similar, being located within that portion of the superficial lamina propria where the elastin and mature collagen are less concentrated. The microflap plane in the monkey vocal fold was more deeply located near the vocalis fibers. Despite the differences in elastin concentration, the microflap plane in both the dog and the pig was found to be similar to that in humans. The dog anatomy was much more suitable for microsuspension laryngoscopy and stroboscopic examination. The dog vocal folds vibrated in a similar fashion to human vocal folds with mucosal waves and vertical phase differences, features not seen in the pig vocal folds. Conclusions Based on both the histological and stroboscopic results, the dog was believed to be a more suitable animal model for studies on vocal fold surgery, acknowledging that no animal's laryngeal anatomy is identical to that of the human. The dog LVS model presented allows for longitudinal laryngeal studies requiring repeated examinations at multiple time periods with histological correlation applied at sacrifice. [source] Secular variation of hemispheric phase differences in the solar cycleASTRONOMISCHE NACHRICHTEN, Issue 8 2010N.V. Zolotova Abstract We investigate the phase difference of the sunspot cycles in the two hemispheres and compare it with the latitudinal sunspot distribution. If the north-south phase difference exhibits a long-term tendency, it should not be regarded as a stochastic phenomenon. We use datasets of historical sunspot records and drawings made by Staudacher, Hamilton, Gimingham, Carrington, Spörer, and Greenwich observers, as well as the sunspot activity during the Maunder minimum reconstructed by Ribes and Nesme-Ribes. We employ cross-recurrence plots to analyse north-south phase differences. We show that during the last 300 years, the persistence of phase-leading in one of the hemispheres exhibits a secular variation. Changes from one hemisphere to the other leading in phase were registered near 1928 and 1968 as well as two historical ones near 1783 and 1875. A long-term anticorrelation between the hemispheric phase differences in the sunspot cycles and the latitudinal distribution of sunspots was traced since 1750 (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||||||||||||||