Simultaneous detection of the Ca and Ca+ layers by a dual-wavelength tunable lidar system.

A dual-wavelength tunable lidar system that simultaneously detects the Ca and Ca+ layers has been established in Yanqing Station (40.41°N, 116.01°E). The lidar system implements a pulsed Nd:YAG laser that simultaneously pumps two dye lasers, which reduces the hardware configuration of the lidar system. The two dye lasers use infrared laser dyes with high conversion efficiency suitable for long-term observation. The resonance wavelengths of Ca and Ca+ are generated by frequency doubling of the two infrared laser beams. We compared the dual-wavelength tunable lidar system to previous dye-based systems and performed experiments to determine resonance frequencies to within 0.4 pm and to test the dual optical fiber receiving system and found it does not cause cross talk. Three nights of preliminary simultaneous observations of Ca and Ca+ layers are reported; the diversity of these observations begs for more systematic observations and challenging interpretations in terms of Ca processes in the ionosphere and illustrates the effectiveness of this system for aeronomy and space physics studies.

Sodium lidar observation over full diurnal cycles in Beijing, China.

Due to the severe interference from strong solar background light on the received signal, daytime ground-based lidar observation of the sodium (Na) layer is challenging. In this paper, a Na lidar permitting full-diurnal-cycle observation of the metal Na layer over Beijing, China (40.5°N, 116°E) was reported. In order to suppress the skylight background during daytime effectively with less signal losses, a dual-channel Faraday filtering unit was implemented in the lidar receiver. Based on the diurnal Na lidar system, a good number of continuous observational results that lasted more than 120 h with good signal-to-noise ratio were obtained, demonstrating its reliability. Considerable variations within the Na layer during the day were revealed, especially on the layer top and bottom side. In particular, strong sporadic Na layer (Nas) events that occurred during the daytime of 3 consecutive days were also captured with complete evolution process. These observational results showed the advantages of the diurnal Na lidar for investigating the metal layer photochemistry and dynamics in the mesosphere and lower thermosphere region. Na layer observations over the whole diurnal cycle not only benefit the improvements of current theoretical models, but also can allow for a specialized analysis of Nas that occur in the daytime and provide valuable observational support for investigating the rapid production and disappearance mechanisms of Na atoms.

Development of a solid-state sodium Doppler lidar using an all-fiber-coupled injection seeding unit for simultaneous temperature and wind measurements in the mesopause region.

A solid-state sodium (Na) Doppler lidar developed at YanQing Station, Beijing, China (40°N, 116°E) aiming to simultaneous wind and temperature measurement of mesopause region was reported. The 589 nm pulse laser was produced by two injection seeded 1064 nm and 1319 nm Nd:YAG pulse lasers using the sum-frequency generation (SFG) technique. A fiber amplifier is implemented to boost the seed power at 1064 nm, enabling a robust, all-fiber-coupled design for seeding laser unit, absolute laser frequency locking, and cyclic three-frequency switching necessary for simultaneous temperature and wind measurements. The all-fiber-coupled injection seeding configuration together with the solid-state Nd:YAG lasers make the Na Doppler lidar more compact and greatly reduce the system maintenance, which is conducive to transportable and unattended operation. A preliminary observational result obtained with this solid-state sodium Doppler lidar was also reported in this paper.

Superparamagnetic Iron Oxide Nanoparticles as Magnetic Resonance Imaging Contrast Agents and Induced Autophagy Response in Endothelial Progenitor Cells.

Endothelial progenitor cells (EPCs) have been used in clinical trials for the treatment of patients with ischemic diseases, such as myocardial infarction and limb ischemia, as they could secrete angiogenic growth factors and promote neovascularization. However, the clinical employment of EPC therapy relies on the establishment of a noninvasive, timely, effective, and safe assessment system. In this study, we recruited superparamagnetic iron oxide nanoparticles (SPION) enhanced magnetic resonance imaging (MRI) to track EPCs in vitro. We evaluated the labeling efficiency of SPION in EPCs without cationic transfection reagents and determined the threshold value of the labeled cell quantity for MRI. Our data suggested that 1×105 EPCs incubated with SPION at a concentration of 100 µg Fe/mL for 24 h could be detected with a clinical 3T MRI T2 scan. SPION were not cytotoxic for EPCs; however, SPION induced autophagy and impaired neovascularization. We then examined if the impairment could be alleviated through the inhibition of autophagy. The observed autophagy response and its function in EPCs may provide a strategy to improve the safety of SPION labeling. It may also verify that the assessment of autophagy may be a more sensitive detection method to evaluate the biocompatibility of tracking reagents.