scholarly journals Acquiring the large phase jumping beyond pi with phase unwrapping assisted by auxiliary light in PHI-OTDR

2020 ◽  
Author(s):  
Zhen Zhong ◽  
Xiangchuan Wang ◽  
Feng Wang ◽  
Xuping Zhang
Keyword(s):  
Quantitative Measurement ◽  
Pulse Sequence ◽  
Phase Unwrapping ◽  
Absolute Difference ◽  
Maximum Phase ◽  
Probe Light ◽  
Light Pulses ◽  
New Process ◽  
Phase Signal ◽  
Large Phase

The absolute difference (phase jumping) between two adjacent phases should be less than pi in order to accurately recover the phase signal with traditional phase unwrapping algorithm, which limits the capability of quantitative measurement for traditional PHI-OTDR. In this article, a new process of phase unwrapping with an auxiliary light in coherent PHI-OTDR is proposed, so the resolvable phase jumping is extended to a larger value beyond pi and the capability of phase unwrapping is improved. In this PHI-OTDR system, wrapped differential phases between a reference position and the subsequent positions of fiber are firstly acquired for all probe light pulses. And wrapped differential phases of interleaving pulse sequence are unwrapped using the traditional phase unwrapping algorithm. Then, positions where the differential phases are correctly unwrapped are obtained from the discontinuously linear profile of the phase change curves of the original probe light. Based on these positions, the information of perturbation can be correctly retrieved. In experiment, the new process of phase unwrapping with the auxiliary for PHI-OTDR is executed and a perturbation signal which induces a maximum phase jumping of 3.7154 rad is well reconstructed. More experimental results all demonstrate the validity of the proposed method.

scholarly journals Acquiring the large phase jumping beyond pi with phase unwrapping assisted by auxiliary light in PHI-OTDR

2020 ◽  
Author(s):  
Zhen Zhong ◽  
Xiangchuan Wang ◽  
Feng Wang ◽  
Xuping Zhang
Keyword(s):  
Quantitative Measurement ◽  
Pulse Sequence ◽  
Phase Unwrapping ◽  
Absolute Difference ◽  
Maximum Phase ◽  
Probe Light ◽  
Light Pulses ◽  
New Process ◽  
Phase Signal ◽  
Large Phase

The absolute difference (phase jumping) between two adjacent phases should be less than pi in order to accurately recover the phase signal with traditional phase unwrapping algorithm, which limits the capability of quantitative measurement for traditional PHI-OTDR. In this article, a new process of phase unwrapping with an auxiliary light in coherent PHI-OTDR is proposed, so the resolvable phase jumping is extended to a larger value beyond pi and the capability of phase unwrapping is improved. In this PHI-OTDR system, wrapped differential phases between a reference position and the subsequent positions of fiber are firstly acquired for all probe light pulses. And wrapped differential phases of interleaving pulse sequence are unwrapped using the traditional phase unwrapping algorithm. Then, positions where the differential phases are correctly unwrapped are obtained from the discontinuously linear profile of the phase change curves of the original probe light. Based on these positions, the information of perturbation can be correctly retrieved. In experiment, the new process of phase unwrapping with the auxiliary for PHI-OTDR is executed and a perturbation signal which induces a maximum phase jumping of 3.7154 rad is well reconstructed. More experimental results all demonstrate the validity of the proposed method.

Differential effects of bright light and social cues on reentrainment of human circadian rhythms

1995 ◽  
Vol 268 (2) ◽  
pp. R528-R535 ◽  
Author(s):  
K. Honma ◽  
S. Honma ◽  
K. Nakamura ◽  
M. Sasaki ◽  
T. Endo ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Phase Shift ◽  
Light Pulse ◽  
Bright Light ◽  
Maximum Phase ◽  
Differential Effects ◽  
Light Pulses ◽  
Human Circadian Rhythm ◽  
The Social ◽  
Temperature Rhythms

Reentrainment of human circadian rhythm to an 8-h advanced schedule of sleep and social contacts was assessed under two different conditions: with and without bright light (4,000-6,000 lx). Subjects spent 15 days without knowing the natural day-night alternation. On the fourth day, the social schedule was phase-advanced by 8 h. In one experiment, a bright light pulse of 3-h duration was given in every subjective morning, and in the other no light pulse was applied. Plasma melatonin and rectal temperature rhythms were measured. Seven of nine subjects showed an orthodromic phase shift, the rate of which was significantly larger with bright light pulses than without them. The maximum phase-advance shift by three consecutive light pulses was observed when the first pulse was applied approximately 4 h after the onset of melatonin rise. By contrast, the maximum phase shift of a similar extent was detected at 1 h after the onset of melatonin rise, when ordinary room light (300-500 lx) at the time corresponding to bright light was regarded as a dim light pulse. It is concluded that bright light accelerates the reentrainment of human circadian rhythm, and bright light and social schedule have differential effects on the reentrainment.

scholarly journals Subpulse drifting and periodic nulling in single pulse emission of PSR B2000+40

2020 ◽  
Vol 499 (1) ◽  
pp. 906-913 ◽  
Author(s):  
Rahul Basu ◽  
Wojciech Lewandowski ◽  
Jarosław Kijak
Keyword(s):  
Pulse Sequence ◽  
Single Pulse ◽  
Central Component ◽  
Core Component ◽  
Pulse Emission ◽  
Select Group ◽  
Large Phase ◽  
Pulse Behaviour ◽  
Phase Variations ◽  
Evolution With Time

ABSTRACT We have carried out a detailed study of single pulse emission from the pulsar B2000+40 (J2002+4050), observed at 1.6-GHz frequencies using the Effelsberg radio telescope. The pulsar has three components, which are not well separated, with the central component resembling core emission. We have investigated modulations in single pulse behaviour using the fluctuation spectral analysis, which showed the presence of two prominent periodicities, around 2.5P and 40P, respectively. The shorter periodicity was associated with the phenomenon of subpulse drifting and was seen to be absent in the central core component. Drifting showed large phase variations in conal components. Additionally, the periodic modulations had significant evolution with time, varying between very sharp and highly diffuse features. In addition to drifting the pulsar also had the presence of nulling in the single pulse sequence. The longer periodic feature in the fluctuation spectra was associated with nulling behaviour. The pulsar joins a select group, which shows the presence of the phase-modulated drifting as well as periodic nulling in the presence of core emission. This provides further evidence for the two phenomena to be distinct from each other with different physical origins.

scholarly journals Circadian Rhythm of Output from Neurones in the Eye of Aplysia: IV. A Model of the Clock: Differential Sensitivity to Light and Low Temperature Pulses

1977 ◽  
Vol 70 (1) ◽  
pp. 195-211
Author(s):  
JACK A. BENSON ◽  
JON W. JACKLET
Keyword(s):  
Phase Response Curve ◽  
Relaxation Oscillator ◽  
Differential Sensitivity ◽  
Synthesis Process ◽  
Reference Level ◽  
Phase Point ◽  
Potential Oscillations ◽  
Light Pulses ◽  
Large Phase ◽  
Experimental Findings

1. A relaxation oscillator, feed-back model for the circadian clock in the eye of Aplysia is proposed to account for the experimental findings described earlier. Further data on the effects of light pulses and temperature pulses are reported here to test the hypothesis that light and temperature perturb the clock oscillation at different points in the feed-back loop. 2. The rising phase of the CAP frequency rhythm is postulated to be due to an energy-requiring, synthesis process, and the falling phase to a passive, diffusional process. Synthesis produces a substance, C, which controls CAP frequency, and the level of which oscillates about a reference level, R. 3. The synthesis phase of the oscillation is suggested to be temperature compensated from about 9 °C to at least 22.5 °C. Cooling the eye to 6 °C for long periods therefore inhibits synthesis so that the clock eventually stops at its lowest phase point. 4. 12 h cold pulses of 4 °C applied during the rising phase of the rhythm (i.e. during synthesis) cause large phase delays (9 h), while similar cold pulses applied during the falling phase (i.e. during diffusion} cause only small phase delays (2 h). 5. The action of light is to lower the value of the reference level, R, so that the constant illumination damps the oscillation until the clock is stopped at its lowest phase point. 6. The model predicts that light pulses applied during the rising phase will effectively accelerate the increase in level of C, thus causing phase advances, while phase delays will result from light pulses applied during the falling phase. A phase response curve for 2 h, 1100 lux light pulses confirms this. A rhythm splitting effect due to an appropriately timed light pulse is predicted and tested. 7. Possibilities of clock control of the CAP generating mechanism are discussed with reference to recent findings on the regulation of membrane potential oscillations in molluscan bursting pacemaker neurones. Note: Laboratory of Sensory Sciences, University of Hawaii at Manoa, 1993 East-West Road, Honolulu, Hawaii 96822, U.S.A.

Mice lacking the PACAP type I receptor have impaired photic entrainment and negative masking

2008 ◽  
Vol 295 (6) ◽  
pp. R2050-R2058 ◽  
Author(s):  
Jens Hannibal ◽  
Philippe Brabet ◽  
Jan Fahrenkrug
Keyword(s):  
Phase Response Curve ◽  
Phase Response ◽  
Type I ◽  
Receptor Signaling ◽  
Pac1 Receptor ◽  
Low Light ◽  
Late Night ◽  
Light Pulses ◽  
Light Intensities ◽  
Large Phase

The retinohypothalamic tract (RHT) is a retinofugal neuronal pathway which, in mammals, mediates nonimage-forming vision to various areas in the brain involved in circadian timing, masking behavior, and regulation of the pupillary light reflex. The RHT costores the two neurotransmitters glutamate and pituitary adenylate cyclase activating peptide (PACAP), which in a rather complex interplay are mediators of photic adjustment of the circadian system. To further characterize the role of PACAP/PACAP receptor type 1 (PAC1) receptor signaling in light entrainment of the clock and in negative masking behavior, we extended previous studies in mice lacking the PAC1 receptor (PAC1 KO) by examining their phase response to single light pulses using Aschoff type II regime, their ability to entrain to non-24-h light-dark (LD) cycles and large phase shifts of the LD cycle (jet lag), as well as their negative masking response during different light intensities. A prominent finding in PAC1 KO mice was a significantly decreased phase delay of the endogenous rhythm at early night. In accordance, PAC1 KO mice had a reduced ability to entrain to T cycles longer than 26 h and needed more time to reentrain to large phase delays, which was prominent at low light intensities. The data obtained at late night indicated that PACAP/PAC1 receptor signaling is less important during the phase-advancing part of the phase-response curve. Finally, the PAC1 KO mice showed impaired negative masking behavior at low light intensities. Our findings substantiate a role for PACAP/PAC1 receptor signaling in nonimage-forming vision and indicate that the system is particularly important at lower light intensities.

scholarly journals Mode changing, subpulse drifting, and nulling in four component conal pulsar PSR J2321+6024

2020 ◽  
Vol 500 (3) ◽  
pp. 4139-4152
Author(s):  
S k Minhajur Rahaman ◽  
Rahul Basu ◽  
Dipanjan Mitra ◽  
George I Melikidze
Keyword(s):  
Radio Emission ◽  
Pulse Sequence ◽  
Average Duration ◽  
Single Pulse ◽  
Orthogonal Polarization ◽  
Gap Model ◽  
Large Phase ◽  
Polarization Behaviour ◽  
Phase Variations ◽  
Different Characteristics

ABSTRACT In this study, we report on a detailed single pulse polarimetric analysis of the radio emission from the pulsar J2321+6024 (B2319+60) observed with the Giant Metrewave Radio Telescope, over wide frequencies ranging between 300 to 500 MHz and widely separated observing sessions. The pulsar profile shows the presence of four distinct conal components and belongs to a small group of pulsars classified as a conal quadrupole profile type. The single pulse sequence reveals the presence of three distinct emission modes, A, B, and ABN showing subpulse drifting. Besides, there were sequences when the pulsar did not show any drifting behaviour suggesting the possibility of a new emission state, which we have termed as mode C. The evolution of the mode changing behaviour was seen during the different observing sessions with different abundance as well as the average duration of the modes seen on each date. The drifting periodicities were 7.8 ± 0.3 P, 4.3 ± 0.4 P, and 3.1 ± 0.2 P in the modes A, B, and ABN, respectively, and showed large phase variations within the mode profile. The pulsar also showed the presence of orthogonal polarization modes, particularly in the leading and trailing components, which has different characteristics for the stronger and weaker pulses. However, no correlation was found between the emission modes and their polarization behaviour, with the estimated emission heights remaining roughly constant throughout. We have used the Partially Screened Gap model to understand the connection between drifting, mode changing, and nulling.

Circadian system of mice integrates brief light stimuli

1998 ◽  
Vol 275 (2) ◽  
pp. R654-R657 ◽  
Author(s):  
Anthony N. Van Den Pol ◽  
Vinh Cao ◽  
H. Craig Heller
Keyword(s):  
Phase Shift ◽  
Sensory Information ◽  
Phase Shifts ◽  
Circadian System ◽  
Suprachiasmatic Nuclei ◽  
Light Pulses ◽  
Light Duration ◽  
Total Light ◽  
Large Phase ◽  
Light Stimuli

Light is the primary sensory stimulus that synchronizes or entrains the internal circadian rhythms of animals to the solar day. In mammals photic entrainment of the circadian pacemaker residing in the suprachiasmatic nuclei is due to the fact that light at certain times of day can phase shift the pacemaker. In this study we show that the circadian system of mice can integrate extremely brief, repeated photic stimuli to produce large phase shifts. A train of 2-ms light pulses delivered as one pulse every 5 or 60 s, with a total light duration of 120 ms, can cause phase shifts of several hours that endure for weeks. Single 2-ms pulses of light were ineffective. Thus these data reveal a property of the mammalian circadian clock: it can integrate and store latent sensory information in such a way that a series of extremely brief photic stimuli, each too small to cause a phase shift individually, together can cause a large and long-lasting change in behavior.

The High Resolution Appearance of Biological Substrates

1969 ◽  
Vol 27 ◽  
pp. 416-417
Author(s):  
Glen B. Haydon
Keyword(s):  
High Resolution ◽  
Phase Image ◽  
Biological Structure ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Resolution Electron ◽  
Discrete Structures ◽  
Large Phase ◽  
Biological Substrates ◽  
High Resolution Electron Micrographs

High resolution electron microscopic study of negatively stained macromolecules and thin sections of tissue embedded in a variety of media are difficult to interpret because of the superimposed phase image granularity. Although all of the information concerning the biological structure of interest may be present in a defocused electron micrograph, the high contrast of large phase image granules produced by the substrate makes it impossible to distinguish the phase ‘points’ from discrete structures of the same dimensions. Theory predicts the findings; however, it does not allow an appreciation of the actual appearance of the image under various conditions. Therefore, though perhaps trivial, training of the cheapest computer produced by mass labor has been undertaken in order to learn to appreciate the factors which affect the appearance of the background in high resolution electron micrographs.

A quantitative image analysis method for the determination of cocontinuity in polymer blends

1993 ◽  
Vol 51 ◽  
pp. 894-895
Author(s):  
William A. Heeschen
Keyword(s):  
Image Analysis ◽  
Polymer Blends ◽  
Quantitative Measurement ◽  
Morphological Evolution ◽  
Phase Ratio ◽  
Irregular Shapes ◽  
Quantitative Image ◽  
Discrete Domains ◽  
A Domains

Two new morphological measurements based on digital image analysis, CoContinuity and CoContinuity Balance, have been developed and implemented for quantitative measurement of morphology in polymer blends. The morphology of polymer blends varies with phase ratio, composition and processing. A typical morphological evolution for increasing phase ratio of polymer A to polymer B starts with discrete domains of A in a matrix of B (A/B < 1), moves through a cocontinuous distribution of A and B (A/B ≈ 1) and finishes with discrete domains of B in a matrix of A (A/B > 1). For low phase ratios, A is often seen as solid convex particles embedded in the continuous B phase. As the ratio increases, A domains begin to evolve into irregular shapes, though still recognizable as separate domains. Further increase in the phase ratio leads to A domains which extend into and surround the B phase while the B phase simultaneously extends into and surrounds the A phase.

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