Widefield multifrequency fluorescence lifetime imaging using a two-tap complementary metal-oxide semiconductor camera with lateral electric field charge modulators.

Widefield frequency-domain fluorescence lifetime imaging microscopy (FD-FLIM) measures the fluorescence lifetime of entire images in a fast and efficient manner. We report a widefield FD-FLIM system based on a complementary metal-oxide semiconductor camera equipped with two-tap true correlated double sampling lock-in pixels and lateral electric field charge modulators. Owing to the fast intrinsic response and modulation of the camera, our system allows parallel multifrequency FLIM in one measurement via fast Fourier transform. We demonstrate that at a fundamental frequency of 20 MHz, 31-harmonics can be measured with 64 phase images per laser repetition period. As a proof of principle, we analyzed cells transfected with Cerulean and with a construct of Cerulean-Venus that shows Förster Resonance Energy Transfer at different modulation frequencies. We also tracked the temperature change of living cells via the fluorescence lifetime of Rhodamine B at different frequencies. These results indicate that our widefield multifrequency FD-FLIM system is a valuable tool in the biomedical field

Finite element exterior calculus for parabolic problems

In this paper, we consider the extension of the finite element exterior calculus from elliptic problems, in which the Hodge Laplacian is an appropriate model problem, to parabolic problems, for which we take the Hodge heat equation as our model problem. The numerical method we study is a Galerkin method based on a mixed variational formulation and using as subspaces the same spaces of finite element differential forms which are used for elliptic problems. We analyze both the semidiscrete and a fully-discrete numerical scheme.Comment: 17 page

Security-based resilient event-triggered control of networked control systems under denial of service attacks

This paper is concerned with the security control problem of the networked control system (NCSs) subjected to denial of service (DoS) attacks. In order to guarantee the security performance, this paper treats the influence of packet dropouts due to DoS attacks as a uncertainty of triggering condition. Firstly, a novel resilient triggering strategy by considering the uncertainty of triggering condition caused by DoS attacks is proposed. Secondly, the event-based security controller under the resilient triggering strategy is designed while the DoS-based security performance is preserved. At last, the simulation results show that the proposed resilient triggering strategy is resilient to DoS attacks while guaranteing the security performance

Resilient control of networked control systems with stochastic denial of service attacks

This paper focuses on resilient control of networked control systems (NCSs) under the denial of service (DoS) attacks characterized by a Markov process. Firstly, based on the game between attack strategies and defense strategies, the packet dropouts induced by DoS attacks are modeled as a Markov process. Secondly, an NCS under DoS attacks is modeled as a Markovian jump linear system. Then, by use of the Lyapunov theory and the derived NCS model, four theorems are given for the system stability analysis and controller design. Finally, a numerical example is used to illustrative the effectiveness of proposed method