Search

Pure shift techniques, as one of the rapidly developing frontiers in nuclear magnetic resonance (NMR) fields, can significantly enhance the resolution of NMR spectrum with a removal of splittings induced by scalar couplings. However, periodic artifacts due to residual scalar couplings during acquisition arise on all direct pure shift spectra, causing severe problems in analysis of complicated samples. Herein, we construct a signal model for the pure shift data and discuss the mechanism of periodic artifacts. Then, based on constraints on the low-rank property of pure shift NMR data, a subsequent artifact-suppression method is proposed to reconstruct a clean pure shift spectrum. With the proposed method, clean $^{\mathbf {1}}\text{H}$ pure shift spectrum can be obtained from only one experiment, greatly accelerating the experiment time while remaining the accuracy of the quantitative measurement. Experiments on a synthesis NMR signal, a complex sample of quinine with pseudo 2-D acquisition, and a medicine sample of azithromycin with 1-D acquisition are carried out to evaluate the feasibility and universality of the proposed method for different experimental techniques. Both the theoretical analysis and experimental results demonstrate the effectiveness of the proposed method for periodic artifacts suppression on complex samples and its potential for practical applications. [ABSTRACT FROM AUTHOR]

Fano-like lineshapes in whispering-gallery modes (WGMs) microresonators are of critical for many actual applications, such as high-sensitivity sensors, slow light, and optical switches. In this paper, we theoretically and experimentally demonstrate dynamic transmission lineshapes, including Lorentzian lineshapes, Fano-like lineshapes and gain-like lineshapes, with a simple system, where a surface nanoscale axial photonic (SNAP) microbottle is coupled to the transition of a tapered fiber by carefully choosing tapered fiber diameters. Controlled and robust coupling with a clean and almost equidistant spectrum for different axial modes is achieved while maintaining contact between the resonator and the taper. Our device offers five similar dynamic transmission lineshapes arranged in order simultaneously, demonstrating stable tuning and a high number of potential degrees of freedom in contrast to other coupling systems for single- or double-coupled microresonators. By using coupled-mode theory, these transmission lineshapes are fitted to explain these experiment observations. We also explore a tunable transmission spectra obtained by increasing the powers of the input laser. Our approach hold unique potential in sensitivity-enhanced sensing, quantum information processing, and all-optical switching. [ABSTRACT FROM AUTHOR]

This paper presents the design of dual circularly polarized (CP) series-fed arrays based on the sequential rotation (SR) technique with uniform radiation elements. The radiation elements and feeding network used in the array are uniform, which leads to the possibility of dual-CP radiation by series-fed SR arrays. Meanwhile, the elements radiate unequal powers due to this arrangement. The relationship between the axial ratio and four key parameters of the array is derived and thoroughly discussed. Good polarization purity and port isolation can be realized by optimizing these parameters. A dual-CP array working at 10 GHz is designed with the help of the analysis. The experimental results show that the proposed antenna has good properties. [ABSTRACT FROM AUTHOR]

In this paper, the relationship between the magnetic properties and microstructures of nanocomposite isotropic exchange-coupled systems with the structure of \alpha -Fe crystalline grains embedded in Nd2Fe14B matrices has been estimated by micromagnetic finite-element method. And then, the results have been analyzed by means of the effectiveness of exchange coupling between the magnetically hard Nd2Fe14B and soft \alpha -Fe phase of the exchange-coupled Nd2Fe 14\text{B}/\alpha -Fe magnetic systems. The effectiveness of interphase exchange coupling has been estimated by the volume fractions of exchange coupling area near phase boundaries between \alpha -Fe grains and Nd2Fe14B matrix. The results have shown the micromagnetic mechanism of the advanced magnetic properties of the exchange coupled magnetic systems with the structure of $\alpha $ -Fe grains embedded in Nd2Fe14B matrix. In addition, the optimal magnetic properties can be expected in the case of comparatively the large grain sizes of $\alpha $ -Fe and Nd2Fe14B phase due to the characteristic structure of those magnetic systems. [ABSTRACT FROM AUTHOR]