Solitons in a 
	    
	    PT
	    
	  -symmetric grating-assisted co-directional coupler

Abstract We explore a co-directional coupling arrangement between two waveguides mediated by a PT-symmetric sinusoidal grating characterized by an index-modulation parameter κ and a gain/loss parameter g. We show that the device supports soliton-like solutions for both the PT -conserving regime g < κ and the PT -broken regime g > κ. In the first case the coupler exhibits a gap in wave-number k and the solitons can be regarded as an extension of a previous solution found for pure index modulation. In the second case the coupler exhibits a gap in frequency ω and the solutions are entirely new.

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Investigation of X-band backscattering from wave breaking in a laboratory experiment

10.5194/egusphere-egu21-9084 ◽

2021 ◽

Author(s):

Nikita Rusakov ◽

Georgy Baidakov ◽

Evgeny Poplavsky ◽

Yuliya Troitskaya ◽

Maksim Vdovin

Keyword(s):

Cross Section ◽

Wave Breaking ◽

Spectral Characteristics ◽

Wave Number ◽

Scattered Signal ◽

Channel Cross Section ◽

Frequency Wave ◽

First Case ◽

X Band ◽

Working Section

The work is concerned with the study of the breaking surface wave effect on the intensity and spectral characteristics of a scattered radar signal in laboratory conditions.The experiments were carried out on the reconstructed TSWiWaT wind wave flume of the IAP RAS. The channel is 12 m long, the channel cross-section varies from 0.7 x 0.7 m at the entrance to 0.7 x 0.9 m in the working section at a distance of 9 m. The airflow speed on the axis is 3-35 m/s, which corresponds to the values of the wind speed U10 of 11-50 m/s.The wave characteristics in the flume were measured by an array of three wave gauges positioned in the corners of an equal-side triangle with 2.5 cm side, the data sampling rate was 200 Hz. Such a system gives the opportunity to retrieve 3D frequency-wave number spectra of surface waves.The airflow parameters were measured using the profiling method. The velocity profiles were measured in the working section using an S-shaped Pitot tube. Microwave measurements were carried out using an X-band coherent Doppler scatterometer with a wavelength of 3.2 cm with sequential reception of linear polarizations.&#160; The absolute value of the radar cross-section (RCS) on the wavy water surface was determined by comparing the scattered signal with the signal reflected from the calibrator with a known value of the RCS - a metal ball with a diameter of 6 cm. The dimensions of the observation cross-section were 40 cm x 40 cm, the incidence angles were 30&#176;, 40&#176;, 50&#176; for the upwind direction, the distance to the target was 3.15 m.Two series of experiments were carried out. In the first case, wind waves on the surface of pure deep water, developing under the action of a fan generated wind, were studied. In the second case, a train of three waves was generated at the beginning of the channel, with the fan turned on, in order to simulate shallow water an inclined plate was placed under water in front of the measurement area. As a result, the breaking waves occurred at a fixed point and at weaker winds compared to the first case.As a result, an increase in the scattered signal intensity during artificial wave breaking in the case of weak winds was noted. For strong winds, the effect turned out to be insignificant, despite the increased amplitude of the waves under study. The Doppler spectra analysis is also presented.This work was supported by the RFBR projects No. 19-05-00249, 19-05-00366. &#160;

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Matter-wave solitons of Bose–Einstein condensates with time-dependent complex potentials

International Journal of Modern Physics B ◽

10.1142/s0217979218501849 ◽

2018 ◽

Vol 32 (15) ◽

pp. 1850184 ◽

Cited By ~ 1

Author(s):

Emmanuel Kengne ◽

Ahmed Lakhssassi

Keyword(s):

Modulational Instability ◽

Time Dependent ◽

Matter Wave ◽

Linear Potential ◽

Dissipative Term ◽

Loss Parameter ◽

Gain Loss ◽

Three Body ◽

External Trapping Potential ◽

Bose Einstein

To analytically investigate the matter-wave solitons of Bose–Einstein condensates (BECs) in time-dependent complex potential, we consider a cubic-quintic Gross–Pitaevskii (GP) equation with distributed coefficients and a dissipative term. By introducing a suitable ansatz, we establish the criterion of the modulational instability (MI) of the system and present an explicit expression for the growth rate of a purely growing MI. Effects of the parabolic background potential, as well as of the linear potential, the gain/loss parameter, and the two- and three-body interatomic interactions on the MI are investigated. We show how the feeding/loss parameter can be well used to control the instability of the system. The analytical resolution of the considered GP equation leads to exact bright, dark and kink solitary wave solutions which are used to investigate analytically the dynamics of matter-wave solitons in BECs under consideration. These analytical investigations show that the amplitude and the motion of bright, dark and kink solitary waves depend on the strengths of the two- and three-body interatomic interactions, as well as on the strengths of the external trapping potential and the parameter of the gain/loss of atoms in the condensate.

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A Study of False Alarms of a Major Sudden Stratospheric Warming by Real-Time Subseasonal-to-Seasonal Forecasts for the 2017/2018 Northern Winter

Atmosphere ◽

10.3390/atmos11080875 ◽

2020 ◽

Vol 11 (8) ◽

pp. 875

Author(s):

Masakazu Taguchi

Keyword(s):

False Alarm ◽

Real Time ◽

Winter Season ◽

Wave Activity ◽

Wave Number ◽

False Alarms ◽

Stratospheric Warming ◽

Seasonal Forecasts ◽

Sudden Stratospheric Warming ◽

First Case

This study investigates false alarms of a major sudden stratospheric warming (MSSW) by real-time subseasonal-to-seasonal forecast data of the European Centre for Medium-Range Weather Forecasts system for the 2017/2018 Northern Hemisphere winter season. The analysis reveals two false alarm cases in the season, one in early December and the other in early February. Each case is characterized by ensembles of which a considerable part of the members (MSSW members) show an MSSW, that is, reversal of the zonal mean zonal wind in the extratropical stratosphere on similar calendar dates. Ensemble forecasts that are initialized earlier or later basically lack an MSSW, demonstrating clear intraseasonal variability in the frequency of forecasted MSSWs. For each false alarm case, the MSSW member mean field shows equatorward displacement of the polar vortex around the onset date. For both cases, the MSSW members accompany stronger wave activity in the lower stratosphere than other non-MSSW members and reanalysis data. They are further associated with higher geopotential height than the non-MSSW members, in the upper troposphere over northeastern Canada and Greenland before the first case, and lower height over northeastern Eurasia before the second case. These are located over the ridge and trough, respectively, of the climatological planetary wave of zonal wave number one, and are consistent with the increased wave activity.

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Sound waves in hadronic matter

EPJ Web of Conferences ◽

10.1051/epjconf/201817201002 ◽

2018 ◽

Vol 172 ◽

pp. 01002

Author(s):

Grzegorz Wilk ◽

Zbigniew Włodarczyk

Keyword(s):

Scale Parameter ◽

High Energy ◽

Hadronic Matter ◽

Wave Number ◽

Sound Waves ◽

Periodic Oscillations ◽

First Case ◽

Self Similar Solution ◽

Self Similar ◽

Two Parameters

We argue that recent high energy CERN LHC experiments on transverse momenta distributions of produced particles provide us new, so far unnoticed and not fully appreciated, information on the underlying production processes. To this end we concentrate on the small (but persistent) log-periodic oscillations decorating the observed pT spectra and visible in the measured ratios R = σdata(pT) / σfit (pT). Because such spectra are described by quasi-power-like formulas characterised by two parameters: the power index n and scale parameter T (usually identified with temperature T), the observed logperiodic behaviour of the ratios R can originate either from suitable modifications of n or T (or both, but such a possibility is not discussed). In the first case n becomes a complex number and this can be related to scale invariance in the system, in the second the scale parameter T exhibits itself log-periodic oscillations which can be interpreted as the presence of some kind of sound waves forming in the collision system during the collision process, the wave number of which has a so-called self similar solution of the second kind. Because the first case was already widely discussed we concentrate on the second one and on its possible experimental consequences.

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Explicit Solutions to Single Scattering of SH Waves with a Radially Gradient Interphase Layer

Shock and Vibration ◽

10.1155/2019/6978305 ◽

2019 ◽

Vol 2019 ◽

pp. 1-7

Author(s):

Jiading Bao ◽

Jun Zhang ◽

Longhai Zeng

Keyword(s):

Linear Function ◽

Cross Sections ◽

Aluminum Matrix ◽

Single Scattering ◽

Current Approach ◽

Wave Number ◽

Sh Waves ◽

Sic Fiber ◽

First Case ◽

Scattering Cross Sections

In this work, analytical solutions to the single scattering of horizontally polarized shear waves (SH) by cylindrical fibers with two specific radially gradient interphase layers are presented. In the first case, the shear modulus μr=e2βr and the square of wave number k2 is a linear function of 1/r; in the second case μr=e−βr2 and k2 is a linear function of r2. As an example, we solve the single scattering of SH waves by a SiC fiber with the two interphase layers in an aluminum matrix. The calculated scattering cross sections are compared to values obtained by an approximate method (dividing the continuous varying layer into multiple homogeneous sublayers). The results indicate the current approach gives excellent performance.

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Non-Hermitian Electronics Multipods of Electromagnetically Induced Transparency (EIT) and Absorption (EIA)

10.21203/rs.3.rs-772656/v1 ◽

2021 ◽

Author(s):

Senghor TAGOUEGNI ◽

Fernande FOTSA-NGAFFO ◽

Aurélien KENFACK-JIOTSA

Keyword(s):

Electromagnetically Induced Transparency ◽

Exceptional Point ◽

Coupling Mechanism ◽

Probe Field ◽

Physical Mechanisms ◽

Complex Modes ◽

Weak Regime ◽

Loss Parameter ◽

Gain Loss ◽

Induced Transparency

Abstract We study a non-Hermitian electronic dimers system based on an imaginary resistor (Z) in a (N+2) level atomic multi-pod configuration. Non-Hermitian systems depend on a gain/loss parameter and are specifically marked by a degeneracy exhibited at an exceptional point (EP) separating different phases of complex modes dynamics. Interestingly, the structural characterization and the dispersive properties reveal a broad range of strong coupling where the interplay between the control and the probe field induce a simultaneous EIT, EIA and ATS. Here, by identifying the underlying physical mechanisms, we show that multiple windows of transparency can be strongly enhanced by the incorporation of several dimers in the multipod network. On the other hand, if the pumping field is resonant in the weak regime, multiple EIT and EIA windows result in the number of dimers. Remarkably, the proposed system embedded a multiple coupling mechanism whose modulation induces a couplingless point whereby the energy cross. At this point EIT and related phenomena vanish.

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The Fractional Nonlinear PT Dimer

10.21203/rs.3.rs-199590/v1 ◽

2021 ◽

Author(s):

Mario I. Molina

Keyword(s):

Order Derivative ◽

Marked Contrast ◽

Standard Case ◽

First Order ◽

Damped Oscillations ◽

Main Effect ◽

Loss Parameter ◽

Small Gain ◽

Gain Loss ◽

Parameter Values

Abstract We examine a fractional Discrete Nonlinear Schrodinger dimer, where the usual first-order derivative of the time evolution is replaced by a non integer-order derivative. The dimer is nonlinear (Kerr) and PT-symmetric, and we examine the exchange dynamics between both sites. By means of the Laplace transformation technique, the linear PT dimer is solved in closed form in terms of Mittag-Leffler functions, while for the nonlinear regime, we resort to numerical computations using the direct explicit Grunwald algorithm. In general, the main effect of the fractional derivative is the onset of a monotonically decreasing time envelope for the amplitude of the oscillatory exchange. In the presence of PT symmetry, the dynamics shows damped oscillations for small gain/loss in both sites, while at higher gain/loss parameter values, the amplitudes of both sites grows unbounded. In the presence of nonlinearity, selftrapping is still possible although the trapped fraction decreases as the nonlinearity is increased past threshold, in marked contrast with the standard case.

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Cascaded PT-Symmetric Artificial Sheets: Multimodal Manipulation of Self-Dual Emitter-Absorber Singularities, and Unidirectional and Bidirectional Reflectionless Transparencies

Journal of Physics D Applied Physics ◽

10.1088/1361-6463/ac3300 ◽

2021 ◽

Author(s):

Minye Yang ◽

Zhilu Ye ◽

Mohamed Farhat ◽

Pai-Yen Chen

Keyword(s):

Light Propagation ◽

Propagation Direction ◽

The Self ◽

Exceptional Point ◽

Frequency Selective Surfaces ◽

Transmission Resonance ◽

Loss Parameter ◽

Transmission Resonances ◽

Gain Loss ◽

Dual Laser

Abstract We herein introduce cascaded parity-time (PT)-symmetric artificial sheets (e.g., metasurfaces or frequency selective surfaces) that may exhibit multiple higher-order laser-absorber modes and bidirectional reflectionless transmission resonances within the PT-broken phase, as well as a unidirectional reflectionless transmission resonance associated with the exceptional point (EP). We derive the explicit expressions of the gain-loss parameter required for obtaining these modes and their intriguing physical properties. By exploiting the cascaded PT structures, the gain-loss threshold for the self-dual laser-absorber operation can be remarkably lowered, while the EP remains unaltered. We further study interferometric sensing based on such a multimodal laser-absorber and demonstrate that its sensitivity could be unprecedentedly high and proportional to the number of metasurfaces along the light propagation direction.

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Independent Spatial-Frequency-Tuned Channels in Binocular Fusion and Rivalry

Perception ◽

10.1068/p040125 ◽

1975 ◽

Vol 4 (2) ◽

pp. 125-143 ◽

Cited By ~ 184

Author(s):

Bela Julesz ◽

Joan E Miller

Keyword(s):

Spatial Frequency ◽

Binocular Rivalry ◽

Sinusoidal Grating ◽

Two Dimensional ◽

Binocular Fusion ◽

One Dimensional ◽

First Case ◽

Noise Energy ◽

Random Dot Stereograms ◽

Masking Noise

Monocular masking studies show that the visibility of a one-dimensional sinusoidal grating remains unchanged in the presence of masking noise filtered so as to contain spectral components that are at least two octaves away from the spatial frequency of the grating (Stromeyer and Julesz 1972). In the present study, random-dot stereograms were bandpass filtered in the two-dimensional Fourier domain, and masking noise of various spatial frequency bands was added to the filtered stereograms. Masking noise bands containing equally effective noise energy were selected such that their bands were either overlapping with the stereoscopic image spectrum or were two octaves distant. The first case resulted in binocular rivalry; however, in the second case stereoscopic fusion could be maintained in the presence of strong binocular rivalry owing to the masking noise. This finding indicates that spatial-frequency-tuned channels are not restricted to one-dimensional gratings but operate on two-dimensional patterns as well. Furthermore, these frequency channels are utilized in stereopsis and work independently from each other, since some of these channels can be in binocular rivalry while at the same time other channels yield fusion. The main binocular experiments are demonstrated.

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Hemoglobin crystals of the red blood cells in the human renal cortex: electron microscopic observations of the renal lithiasis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100083266 ◽

1978 ◽

Vol 36 (2) ◽

pp. 480-481

Author(s):

Kosuke Ueda ◽

Hiroto Washida ◽

Nakazo Watari

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Renal Cortex ◽

Uranyl Acetate ◽

Osmic Acid ◽

Renal Lithiasis ◽

Electron Microscopic ◽

Hemoglobin C ◽

First Case ◽

Ultrathin Sections

IntroductionHemoglobin crystals in the red blood cells were electronmicroscopically reported by Fawcett in the cat myocardium. In the human, Lessin revealed crystal-containing cells in the periphral blood of hemoglobin C disease patients. We found the hemoglobin crystals and its agglutination in the erythrocytes in the renal cortex of the human renal lithiasis, and these patients had no hematological abnormalities or other diseases out of the renal lithiasis. Hemoglobin crystals in the human erythrocytes were confirmed to be the first case in the kidney.Material and MethodsTen cases of the human renal biopsies were performed on the operations of the seven pyelolithotomies and three ureterolithotomies. The each specimens were primarily fixed in cacodylate buffered 3. 0% glutaraldehyde and post fixed in osmic acid, dehydrated in graded concentrations of ethanol, and then embedded in Epon 812. Ultrathin sections, cut on LKB microtome, were doubly stained with uranyl acetate and lead citrate.

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