phase singularity
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2021 ◽  
Vol 127 (27) ◽  
Author(s):  
Yulong Liu ◽  
Qichun Liu ◽  
Shuaipeng Wang ◽  
Zhen Chen ◽  
Mika A. Sillanpää ◽  
...  

2021 ◽  
Vol 127 (26) ◽  
Author(s):  
Mengqi Liu ◽  
Chen Zhao ◽  
Yixuan Zeng ◽  
Yang Chen ◽  
Changying Zhao ◽  
...  

2021 ◽  
Author(s):  
Desmond Albert Kabus ◽  
Louise Arno ◽  
Lore Leenknegt ◽  
Alexander V. Panfilov ◽  
Hans Dierckx

Electrical waves that rotate in the heart organize dangerous cardiac arrhythmias. Finding the region around which such rotation occurs is one of the most important practical questions for arrhythmia management. For many years, the main method for finding such regions was so-called phase mapping, in which a continuous phase was assigned to points in the heart based on their excitation status and defining the rotation region as a point of phase singularity. Recent analysis, however, showed that in many rotation regimes there exist phase discontinuities and the region of rotation must be defined not as a point of phase singularity, but as a phase defect line. In this paper we use this novel methodology and perform comparative study of three different phase definitions applied to in-silico data and to experimental data obtained from optical voltage mapping experiments on monolayers of human atrial myocytes. We introduce new phase defect detection algorithms and compare them with those that appeared in literature already. We find that the phase definition is more important than the algorithm to identify sudden spatial phase variations. Sharp phase defect lines can be obtained from a phase derived from local activation times observed during  one cycle of arrhythmia. Alternatively,  similar quality can be obtained from a reparameterization of the classical phase obtained from observation of a single timeframe of transmembrane potential. We found that the phase defect line length was 35.9(62)mm in the Fenton-Karma model and 4.01(55)mm in cardiac human atrial myocyte monolayers. As local activation times are obtained during standard clinical cardiac mapping, the methods are also suitable to be applied to clinical datasets. All studied methods are publicly available and can be downloaded from an institutional web-server.


2021 ◽  
Author(s):  
Sekip Dalgac ◽  
Kholoud Elmabruk

Vortex beams acquire increasing attention due to their unique properties. These beams have an annular spatial profile with a dark spot at the center, the so-called phase singularity. This singularity defines the helical phase structure which is related to the topological charge value. Topological charge value allows vortex beams to carry orbital angular momentum. The existence of orbital angular momentum offers a large capacity and high dimensional information processing which make vortex beams very attractive for free-space optical communications. Besides that, these beams are well capable of reducing turbulence-induced scintillation which leads to better system performance. This chapter introduces the research conducted up to date either theoretically or experimentally regarding vortex beam irradiance, scintillation, and other properties while propagating in turbulent mediums.


2021 ◽  
Author(s):  
Klaus Mantel ◽  
Irina Harder ◽  
Vanusch Nercissian ◽  
Ismail Barakat ◽  
Sergej Rothau

Photonics ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 259
Author(s):  
Svetlana N. Khonina ◽  
Sergey I. Kharitonov ◽  
Sergey G. Volotovskiy ◽  
Viktor A. Soifer

In this paper, we consider the comparative formation of perfect optical vortices in the non-paraxial mode using various optical elements: non-paraxial and parabolic toroidal vortex lenses, as well as a vortex axicon in combination with a parabolic lens. The theoretical analysis of the action of these optical elements, as well as the calculation of caustic surfaces, is carried out using a hybrid geometrical-optical and wave approach. Numerical analysis performed on the basis of the expansion in conical waves qualitatively confirms the results obtained and makes it possible to reveal more details associated with diffraction effects. Equations of 3D-caustic surfaces are obtained and the conditions of the ring radius dependence on the order of the vortex phase singularity are analyzed. In the non-paraxial mode, when small light rings (several tens of wavelengths) are formed, a linear dependence of the ring radius on the vortex order is shown. The revealed features should be taken into account when using the considered optical elements forming the POV in various applications.


2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Yuye Wang ◽  
Shuwen Zeng ◽  
Aurelian Crunteanu ◽  
Zhenming Xie ◽  
Georges Humbert ◽  
...  

Highlights A zero-reflection-induced phase singularity is achieved through precisely controlling the resonance characteristics using two-dimensional nanomaterials. An atomically thin nano-layer having a high absorption coefficient is exploited to enhance the zero-reflection dip, which has led to the subsequent phase singularity and thus a giant lateral position shift. We have improved the detection limit of low molecular weight molecules by more than three orders of magnitude compared to current state-of-art nanomaterial-enhanced plasmonic sensors. Abstract Detection of small cancer biomarkers with low molecular weight and a low concentration range has always been challenging yet urgent in many clinical applications such as diagnosing early-stage cancer, monitoring treatment and detecting relapse. Here, a highly enhanced plasmonic biosensor that can overcome this challenge is developed using atomically thin two-dimensional phase change nanomaterial. By precisely engineering the configuration with atomically thin materials, the phase singularity has been successfully achieved with a significantly enhanced lateral position shift effect. Based on our knowledge, it is the first experimental demonstration of a lateral position signal change > 340 μm at a sensing interface from all optical techniques. With this enhanced plasmonic effect, the detection limit has been experimentally demonstrated to be 10–15 mol L−1 for TNF-α cancer marker, which has been found in various human diseases including inflammatory diseases and different kinds of cancer. The as-reported novel integration of atomically thin Ge2Sb2Te5 with plasmonic substrate, which results in a phase singularity and thus a giant lateral position shift, enables the detection of cancer markers with low molecular weight at femtomolar level. These results will definitely hold promising potential in biomedical application and clinical diagnostics.


APL Photonics ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 016101
Author(s):  
F. Ghasemzadeh ◽  
A. R. Rashed ◽  
H. Caglayan

Optica ◽  
2020 ◽  
Vol 7 (12) ◽  
pp. 1721
Author(s):  
Zhengli Han ◽  
Seigo Ohno ◽  
Hiroaki Minamide

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