Signal Propagation Time Research Articles

Semi-mechanistic modelling of the tumour growth inhibitory effects of LY2157299, a new type I receptor TGF-β kinase antagonist, in mice

Human xenografts Calu6 (non-small cell lung cancer) and MX1 (breast cancer) were implanted subcutaneously in nude mice and LY2157299, a new type I receptor TGF-β kinase antagonist, was administered orally. Plasma levels of LY2157299, percentage of phosphorylated Smad2,3 (pSmad) in tumour, and tumour size were used to establish a semi-mechanistic pharmacokinetic/pharmacodynamic model. An indirect response model was used to relate plasma concentrations with pSmad. The model predicts complete inhibition of pSmad and rapid turnover rates [ t 1/2 (min) = 18.6 (Calu6) and 32.0 (MX1)]. Tumour growth inhibition was linked to pSmad using two signal transduction compartments characterised by a mean signal propagation time with estimated values of 6.17 and 28.7 days for Calu6 and MX1, respectively. The model provides a tool to generate experimental hypothesis to gain insights into the mechanisms of signal transduction associated to the TGF-β membrane receptor type I.

Rosetta Radio Science Investigations (RSI)

The Rosetta spacecraft has been successfully launched on 2nd March 2004 to its new target comet 67 P/Churyumov-Gerasimenko. The science objectives of the Rosetta Radio Science Investigations (RSI) experiment address fundamental aspects of cometary physics such as the mass and bulk density of the nucleus, its gravity field, its interplanetary orbit perturbed by nongravitational forces, its size and shape, its internal structure, the composition and roughness of the nucleus surface, the abundance of large dust grains, the plasma content in the coma and the combined dust and gas mass flux. The masses of two asteroids, Steins and Lutetia, shall be determined during flybys in 2008 and 2010, respectively. Secondary objectives are the radio sounding of the solar corona during the superior conjunctions of the spacecraft with the Sun during the cruise phase. The radio carrier links of the spacecraft Telemetry, Tracking and Command (TT&C) subsystem between the orbiter and the Earth will be used for these investigations. An Ultrastable oscillator (USO) connected to both transponders of the radio subsystem serves as a stable frequency reference source for both radio downlinks at X-band (8.4 GHz) and S-band (2.3 GHz) in the one-way mode. The simultaneous and coherent dual-frequency downlinks via the High Gain Antenna (HGA) permit separation of contributions from the classical Doppler shift and the dispersive media effects caused by the motion of the spacecraft with respect to the Earth and the propagation of the signals through the dispersive media, respectively. The investigation relies on the observation of the phase, amplitude, polarization and propagation times of radio signals transmitted from the spacecraft and received with ground station antennas on Earth. The radio signals are affected by the medium through which the signals propagate (atmospheres, ionospheres, interplanetary medium, solar corona), by the gravitational influence of the planet on the spacecraft and finally by the performance of the various systems involved both on the spacecraft and on ground.

Comparison of measured signal coherence time in shallow and deep water

Temporal coherence of acoustic signals determines the processing of a sonar system for various applications. This paper studies the frequency and range dependence of the temporal coherence time of signal propagation in deep water versus that in shallow water. The signal coherence time has been measured in deep water since the 1970s, in terms of a parameter called the phase rate (the rate of phase change of the signal). Signal coherence time in shallow water has received little attention until only recently. We compare measurement data from more than a dozen of experiments covering a wide range of frequencies at different source‐receiver ranges in deep and shallow water. We find that the signal coherence time in both shallow and deep water can be fitted with a universal equation, which exhibits a 3/2 power frequency dependence and 1/2 power range dependence. The signal coherence time in shallow water is two to five times longer than the signal coherence time in deep water at the same frequency and range. The signal coherence times are comparable between shallow and deep water if measured in terms of the range‐to‐depth ratio. [This work is supported by the U.S. Office of Naval Research.]

Variational calculation of the limit cycle and its frequency in a two-neuron model with delay

We consider a model system of two coupled Hopfield neurons, which is described by delay differential equations taking into account the finite signal propagation and processing times. When the delay exceeds a critical value, a limit cycle emerges via a supercritical Hopf bifurcation. First, we calculate its frequency and trajectory perturbatively by applying the Poincaré-Lindstedt method. Then, the perturbation series are resummed by means of the Shohat expansion in good agreement with numerical values. However, with increasing delay, the accuracy of the results from the Shohat expansion worsens. We thus apply variational perturbation theory (VPT) to the perturbation expansions to obtain more accurate results, which moreover hold even in the limit of large delays.

A new approach for target motion analysis with signal time delay

A new approach is proposed in this paper for the problem of the target motion analysis (TMA) with signal propagation time delay. This problem is an unobservable tracking problem in which the acoustic signal transmits with time delay. We present an intelligent range parameterized unscented Kalman filter (IRPUKF) algorithm to estimate the state of the nonlinear unobservable tracking system and propose a recursive model parameter online adjustment method to deal with the time delay in signal propagation. In a simulation of tracking target using a maneuvering acoustic sensor with signal time delay case study, the effectiveness and efficiency of the proposed algorithm is testified to perform better, compared with the range parameterized extended Kalman filter (RPEKF) algorithm.

Measurement of the parameters of a pulse propagation path in a medium with noise, dispersion, and selective absorption

A method of signal processing is proposed that allows one to determine the propagation time of pulsed signals, the dispersion, and the selective absorption in the medium when the shape of the pulses is substantially distorted under the effect of the two aforementioned factors and noise. The method is based on measuring the complex frequency response of the propagation path for a narrow frequency band within which the frequency response is governed by the desired parameters of the medium. To determine the parameters of the path from the data of acoustic measurements, both cepstral analysis and numerical differentiation are used. The data of numerical experiments are presented.

Delayed‐Mutual Coupling Dynamics of Lasers: Scaling Laws and Resonances

We consider a model for two lasers that are mutually coupled optoelectronically by modulating the pump of one laser with the intensity deviations of the other. Signal propagation time in the optoelectronic loop causes a significant delay leading to the onset of oscillatory output. Multiscale perturbation methods are used to describe the amplitude and period of oscillations as a function of the coupling strength and delay time. For weak coupling the oscillations have the laser’s relaxation period, and the amplitude varies as the one‐fourth power of the parameter deviations from the bifurcation point. For order‐one coupling strength the period is determined as multiples of the delay time, and the amplitude varies with a square‐root power law. Because we allow for independent control of the individual coupling constants, for certain parameter values there is an atypical amplitude‐resonance phenomena. Finally, our theoretical results are consistent with recent experimental observations when the inclusion of a low‐pass filter in the coupling loop is taken into account.

Ground-penetrating radar measurement of crop and surface water content dynamics

Ground-penetrating radar (GPR) with a suspended 1 GHz horn antenna was deployed for measurement of soil water contents and crop canopy properties over bare and electrically terminating surfaces. Surface reflection (SR) and signal propagation times (PT) were used to independently determine dielectric permittivity and water content of soil and canopy. Measured surface reflection coefficients progressively decreased with increasing canopy biomass according to Beer-Lambert type relationships. In contrast, PT measurements remained unaffected by canopy, and hence provided an accurate account of soil water content dynamics. Immediately after canopy removal, SR-based soil water content measurements were in close agreement with PT values. Canopy dielectric properties were inferred from canopy water contents ( ɛ c-CWC ) and canopy propagation times ( ɛ c-CPT ). Distinct canopy reflections were correlated with key canopy biophysical parameters. The study demonstrates the usefulness of a horn antenna GPR for characterization of vegetation canopy scattering, and for subcanopy water content measurements within a well-defined footprint, thereby offering a potential for calibration and verification of radar data collected from air- and spaceborne platforms.

Collective dynamics of delay-coupled limit cycle oscillators

Coupled limit cycle oscillators with instantaneous mutual coupling offer a useful but idealized mathematical paradigm for the study of collective behavior in a wide variety of biological, physical and chemical systems. In most real-life systems however the interaction is not instantaneous but is delayed due to finite propagation times of signals, reaction times of chemicals, individual neuron firing periods in neural networks etc. We present a brief overview of the effect of time-delayed coupling on the collective dynamics of such coupled systems. Simple model equations describing two oscillators with a discrete time-delayed coupling as well as those describing linear arrays of a large number of oscillators with time-delayed global or local couplings are studied. Analytic and numerical results pertaining to time delay induced changes in the onset and stability of amplitude death and phase-locked states are discussed. A number of recent experimental and theoretical studies reveal interesting new directions of research in this field and suggest exciting future areas of exploration and applications.

Low-cost laser rangefinder with crystal-controlled accuracy

We present a novel laser ranging system that offers improved accuracy and low-cost implementations for short to medium range target distance and velocity measurement. This is accomplished through the emission of an eye-safe amplitude modulated laser beam, whose echo return is processed with a phase-computing discrete Fourier transform (DFT). The data for the DFT are collected directly from the received signal through equivalent time sampling, and the automatic gain control (AGC) function is moved to that part of the system where its varying signal propagation time will not impact measurement accuracy. All emission and data collection signals are derived directly from a single crystal oscillator, which establishes the system's accuracy. The system is also capable of resolving the distance/velocity ambiguity problem inherent in conventional hetero/homodyne laser ranging systems, and, lastly, digital data can be transmitted and received concurrently with the distance measurement process.

Structural and dynamical analyses of the kinase network derived from the transpath database.

We analyze the structural design and the dynamical properties of a protein kinase network derived from the Transpath database. We consider structural properties, such as feedback cycles, pathway lengths, fraction of shortest pathways and crosstalk. Dynamic characteristics of the network are analyzed by using nonlinear differential equations with a special focus on kinase amplitudes and signal propagation times. Comparison with random networks shows that the cellular kinase network exhibits special features which might be a result of natural selection. In particular, the Transpath network contains no cycles, and input kinases and output kinases are generally connected by shortest signalling routes. Moreover, it displays a characteristic spectrum of cross-talk between different pathways.

Figures Of Merit For CMOS Switching Speed

A Figure of Merit for CMOS switching speed has been investigated using variations of device parameters of CMOS transistors for several technology generations. A modification of the Figure of Merit to predict the signal propagation time of a CMOS circuit is suggested. The modified Figure of Merit permits a prediction of the signal propagation time in CMOS circuits with a significantly improved accuracy, because it accounts for several dynamic effects. Due to the improved accuracy, the modified Figure of Merit can be used as a tool to evaluate the impact of different technological options on the CMOS circuit performance.

Systematic distortions of signal propagation times in random inhomogeneous media

Systematic distortions of signal propagation times in random inhomogeneous media

Nonlinear electrodynamic lag of electromagnetic signals in a magnetic dipole field

We investigate the propagation of electromagnetic waves in the magnetic dipole and gravitational fields of a neutron star, which follows the laws of nonlinear electrodynamics in a vacuum. Electromagnetic signals in these fields are shown to propagate along different rays and at different velocities, depending on their polarization. We found the law of motion for these signals along rays. We calculate the difference between the propagation times of electromagnetic signals with different polarizations from the same source to the detector. This difference is shown to reach a measurable value of 1 μs in some cases.

Non-local microscopic view of signal propagation times in BJTs biased up to high currents

This paper presents a microscopic analysis of signal propagation delay in bipolar transistors featuring relevant non-equilibrium transport effects. First, the physical mechanisms responsible of signal delay are reviewed. A novel technique to extract signal delays from self-consistent Monte Carlo device simulations is presented. These results are then used for a physically based comparison between compact quasi-static delay formulas and more accurate particle simulations carried out over a broad range of collector currents.

Potentialities of cepstral analysis in refining the reciprocal delays and amplitudes of signals

It is demonstrated that the determination of the relative positions of two signals on the time axis with the help of cepstral analysis is characterized by higher immunity to signal fluctuations than a direct measurement of their positions. The theory of the cepstral approach and the results of numerical calculations that demonstrate its potentialities are presented. The cepstral analysis is applied to the processing of signals obtained in a full-scale tomographic experiment in the Mediterranean Sea in 1994. Refined values of the time intervals between the arrivals of signals transmitted through a 200-km-long propagation path are determined. It is demonstrated that the method used for the determination of the signal propagation times is immune to noise associated with the distortions of the signal wave form.

Synchronization and Clustering in a Network of Three Globally Coupled Neural Oscillators

Collective dynamics of three globally coupled Hodgkin–Huxley neurons with a symmetric synaptic coupling has been studied as a paradigm of one of the simplest but nontrivial example of physiology-based coupled oscillator networks capable of displaying synchrony and clustering. Rich phase dynamics have been observed and the phase diagram for various phase states, in particular the synchronized state and clustered states, have been constructed by direct numerical simulations of the full system. We find that the computed phase diagram in the synaptic parameter space of the reversal potential and the signal propagation time delay reveals a rich bifurcation structure and agrees with one from bifurcation analysis of the reduced phase model. Implication of our findings in connection with two-coupled neurons and larger neural networks is discussed.

Low dielectric constant materials and methods for interlayer dielectric films in ultralarge-scale integrated circuit multilevel interconnections

This paper reviews low dielectric constant materials for interlayer dielectric films in ultralarge-scale integrated circuit (ULSI) multilevel interconnections. The trends of ULSIs in the last decade were briefly described first. Then, the requirements for interlayer dielectric film properties and their formation techniques were explained. They are: (1) a low dielectric constant, (2) a surface planarity, (3) a gap-filling capability, and (4) a low residual stress. In contrast with the requirements, the interlayer dielectric films and related technologies developed in the last decade were reviewed. In the requirements, the low dielectric constant materials are strongly required because the device performance has been limited by signal propagation time and cross-talk in the multilevel interconnections. Furthermore, the low dielectric constant is also required for reduction of power consumption in ULSI operation. Finally, the low dielectric constant materials were summarized, and future trends of the low dielectric constant interlayer dielectric film technologies are discussed.

Large Scale Teleoperation on the Lunar Surface

AbstractThe popular success of the Mars Pathfinder mission, especially in terms of individual access to “live”pictures over the internet, demonstrates substantial mass appeal of space exploration on a personal level. Teleoperation provides an inexpensive approach to remote presence, but is distance-limited due to finite signal propagation times. The proximity of the Lunar surface permits near real-time teleoperation, and through a Virtual Reality approach, presents a sense of “being there” without the difficulty of getting there (and back).While limited single user teleoperated Lunar Rovers concepts have been proposed (Luna Corp., Inc.), an on-going and economically self supporting venture would require simultaneous teleoperation of many vehicles on a large scale. In addition, each vehicle would carry several simultaneous stereoscopic remote viewing television camera heads, whose position is controlled by the head movements of Earth bound viewers. The overall concept is similar to a small fleet of touring busses, although some smaller scout vehicles may be included, as well as a tow truck. An access fee structure for Earth bound teleoperators provides for return on investment.Technical issues for an on-going operation in the Lunar environment include temperature extremes, high vacuum, solar radiation, micrometeorites, abrasive nature of Lunar dust and its capacity to electrostatically attach to surfaces are discussed, as are their impact on vehicle design and operation. Optical data links are considered to handle bandwidth requirements of 500 simultaneous users. The economics of scale, on multiple levels, demonstrates the feasibility of large scale teleoperation. Various base-line studies are presented.

磁気信号伝送方式の伝播時間

Magnetic signal transmission (MST) is an effective method for transmitting information underground by radio to allow efficient drilling work. This paper shows that the transmission media of MST are an electromagnetic wave and a domain wall. Experiments showed that the propagation time for MST signals becomes longer as the distance between the transmitting and receiving coils increases. The propagation time for magnetic signals is also affected by the rod material, the frequency, and the current. MST signals have a velocity of 2653.4 [m/s] when ƒ=200 [Hz], It=0.25 [A], χ= 1 [m] and the rod material is SPCC. The cause of the variance of the propagation time of MST signals was confirmed by impulse response.