Detecting Slow Wave Sleep Using a Single EEG Signal Channel

Background: In addition to the cost and complexity of processing multiple signal channels, manual sleep staging is also tedious, time consuming, and error-prone. The aim of this paper is to propose an automatic slow wave sleep (SWS) detection method that uses only one channel of the electroencephalography (EEG) signal. New Method: The proposed approach distinguishes itself from previous automatic sleep staging methods by using three specially designed feature groups. The first feature group characterizes the waveform pattern of the EEG signal. The remaining two feature groups are developed to resolve the difficulties caused by interpersonal EEG signal differences. Results and comparison with existing methods: The proposed approach was tested with 1,003 subjects, and the SWS detection results show kappa coefficient at 0.66, an accuracy level of 0.973, a sensitivity score of 0.644 and a positive predictive value of 0.709. By excluding sleep apnea patients and persons whose age is older than 55, the SWS detection results improved to kappa coefficient, 0.76; accuracy, 0.963; sensitivity, 0.758; and positive predictive value, 0.812. Conclusions: With newly developed signal features, this study proposed and tested a single-channel EEG-based SWS detection method. The effectiveness of the proposed approach was demonstrated by applying it to detect the SWS of 1003 subjects. Our test results show that a low SWS ratio and sleep apnea can degrade the performance of SWS detection. The results also show that a large and accurately staged sleep dataset is of great importance when developing automatic sleep staging methods

Design and fabrication of robust broadband extreme ultraviolet multilayers

The random layer thickness variations can induce a great deformation of the experimental reflection of broadband extreme ultraviolet multilayer. In order to reduce this influence of random layer thickness fluctuations, the multiobjective genetic algorithm has been improved and used in the robust design of multilayer with a broad angular bandpass. The robust multilayer with a lower sensitivity to random thickness errors have been obtained and the corresponding multilayer mirrors were fabricated. The experimental results of robust Mo/Si multilayer with a wide angular band were presented and analyzed, and the advantage of robust multilayer design was demonstrated

Why do firms adopt stock options and who benefits? A natural experiment in China

A regulatory change in 2006, permitting equity compensations in China, offers a natural experiment to investigate drivers and outcomes of stock options. There are two unique features. First, adoption of stock options occurred rapidly compared to the US, where stock options have been around for more than 100 years with periods of high (1990s) and low (before 1950s) adoption. Second, stock options have been issued by state-owned enterprises (SOEs), an unusual aspect. This study analyzes all listed companies in China from 2004 to 2014, testing two competing theories: optimal contracting and managerial power. If managers own more equity, if the CEO also serves as board chairman and if compensation committees exist, managers are more likely to receive stock options. Ownership type and firm characteristics are also essential factors in granting stock options. In non-SOEs, evidence suggests that controlling shareholders award stock options less frequently but if they do they seem to induce managers to collude in tunneling. Applying a propensity score matching approach to account for an alleged self-selection bias, we do not observe any improvements in firm performance or shareholder value after stock options have been issued. Accordingly, managerial power seems to be the predominant driver for the introduction of stock options. Hence, managerial accountability and better disclosure are essential to ensure that stock options do contribute to value creation