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Wang Z.-Q.,Anhui University of Science and Technology | Zhou J.-H.,Anhui University of Science and Technology | Zhong M.-C.,Anhui University of Science and Technology | Li D.,Anhui University of Science and Technology | And 2 more authors.
Optics Express

The power spectrum density (PSD) has long been explored for calibrating optical tweezers stiffness. Fast Fourier transform (FFT) based spectral estimator is typically used. This approach requires a relatively longer data acquisition time to achieve adequate spectral resolution. In this paper, an autoregressive (AR) model is proposed to obtain the spectrum density using a limited number of samples. According to our method, the arithmetic model has been established with burg arithmetic, and the final prediction error criterion has been used to select the most appropriate order of the AR model, the power spectrum density has been estimated based the AR model. Then, the optical tweezers stiffness has been determined with the simple calculation from the power spectrum. Since only a small number of samples are used, the data acquisition time is significantly reduced and real-time stiffness calibration becomes feasible. To test this calibration method, we study the variation of the trap stiffness as a function of the parameters of the data length and the trapping depth. Both of the simulation and experiment results have showed that the presented method returns precise results and outperforms the conventional FFT method when using a limited number of samples. © 2014 Optical Society of America. Source

Sojka D.K.,University of Washington | Plougastel-Douglas B.,University of Washington | Yang L.,University of Washington | Pak-Wittel M.A.,University of Washington | And 12 more authors.

Natural killer (NK) cells belong to the innate immune system; they can control virus infections and developing tumors by cytotoxicity and producing inflammatory cytokines. Most studies of mouse NK cells, however, have focused on conventional NK (cNK) cells in the spleen. Recently, we described two populations of liver NK cells, tissue-resident NK (trNK) cells and those resembling splenic cNK cells. However, their lineage relationship was unclear; trNK cells could be developing cNK cells, related to thymic NK cells, or a lineage distinct from both cNK and thymic NK cells. Herein we used detailed transcriptomic, flow cytometric, and functional analysis and transcription factor-deficient mice to determine that liver trNK cells form a distinct lineage from cNK and thymic NK cells. Taken together with analysis of trNK cells in other tissues, there are at least four distinct lineages of NK cells: cNK, thymic, liver (and skin) trNK, and uterine trNK cells. Source

Lou Y.,Hefei University of Technology | Cong S.,Hefei University of Technology | Cong S.,Hefei National Laboratory for Physical science at the Microscale | Yang J.,Hefei University of Technology | Kuang S.,Hefei University of Technology
IET Control Theory and Applications

The state transfer of closed quantum systems in the interaction picture is studied. The convergent problem encountered in designing control laws based on the Lyapunov method is solved by the well constructed observable operator and a path programming control strategy. It is proved that the condition for the target state being a stable point in the Lyapunov's sense is the coherent vectors of the observable operator and the target state must be in opposite directions. For the local optimisation limitation of the Lyapunov-based method, the path programming control strategy is proposed, which is used to change the distribution of stationary points or choose a transition path by appropriately selecting intermediate target states. Comparative numerical system simulation experiments are implemented on a four-level quantum system and the experimental results are analysed. © 2011 The Institution of Engineering and Technology. Source

Mao X.,Yangzhou University | Sun H.,Yangzhou University | Sun H.,Nanjing University | Wang W.,Yangzhou University | And 4 more authors.
Applied Physics Letters

Multiferroic properties of four-layered Bi4.25La 0.75Fe0.5Co0.5Ti3O15 ceramics were carefully investigated. X-ray diffraction and high resolution transmission electron microscopy analyses indicate that the as-prepared sample is almost free from secondary phases, and magnetization measurements confirm a ferromagnetic transition ∼483 K. At room temperature (RT), the sample shows a typical ferromagnetism with a remnant magnetization (2Mr) of ∼51.2 m emu/g, and a good ferroelectric hysteresis with a remnant polarization (2Pr) of ∼15.4 μC/cm2. More importantly, an obvious magneto-dielectric (MD) effect has been found under a low magnetic field of 1 T at RT with a maximum of magneto-dielectric constant of ∼10.5%. © 2013 American Institute of Physics. Source

Kuang S.,Hefei University of Technology | Cong S.,Hefei University of Technology | Cong S.,Hefei National Laboratory for Physical science at the Microscale
Zidonghua Xuebao/Acta Automatica Sinica

This paper studies the population control problem associated with the equilibrium states of mixed-state quantum systems by using a Lyapunov function with degrees of freedom. The control laws are designed by ensuring the monotonicity of the Lyapunov function; main results on the largest invariant set in the sense of LaSalle are given; and the strict expression of any state in the largest invariant set is normally deduced in the framework of Bloch vectors. By analyzing the obtained largest invariant set and the Lyapunov function itself, this paper also discusses the determination problem of the degrees of freedom. Numerical simulation experiments on a three-level system show the validity of research results. Copyright © 2010 Acta Automatica Sinica. All rights reserved. Source

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