Measurement of the linewidth of a home-built vacuum ultraviolet comb by frequency comb spectroscopy on NO.

Optical frequency comb in the vacuum ultraviolet (VUV)/extreme ultraviolet (XUV) region has attracted a great deal of attention, as it provides coherent VUV/XUV radiation source with a rather narrow bandwidth, facilitating precise spectroscopic measurements in the short wavelength regime. In this study, we report on the linewidth measurement of a home-built VUV comb centered at 148 nm using direct frequency comb spectroscopy with NO. The measurement reveals that the upper bound of our comb linewidth is less than 28 MHz.

[Macrostructure of sleep in patients with vascular cognitive impairment-no dementia].

Objective: To investigate the sleep structure in patients with vascular cognitive impairment-no dementia (VCI-ND) and its differences from that of normal individuals.

Methods: The whole night sleep record of 20 patients with VCI-ND were monitored by 32-head video-taped polysomnographic system, and the results were compared with the data of 20 normal subjects.

Results: Compared with normal subjects, patients with VCI-ND showed significantly reduced total sleep duration, increased waking times, increased stage 1 sleep, decreased stage 2 sleep, decreased stage 3 sleep, decreased rapid eye movement stage (REM) and reduced sleep efficiency.