Search

Bark beetles Tomicus yunnanensis and T. minor are two important pests of Pinus yunnanensis and can cause massive death of pine trees. In this study, we examined several traits related to photosynthesis in P. yunnanensis and their relationship with antibiotic defense responses after joint attack by the two bark beetles at the shoot and the trunk stages. When shoots were attacked by the beetles, the abundance of chlorophylls, carotenoids, and the rates of net photosynthesis (Pn) and transpiration (E) decreased in needles, while the levels of superoxide dismutase and malondialdehyde remained unchanged in both needles and phloem. The activity of peroxidases also remained unchanged in needles, but increased in phloem. The activity of catalases increased in both needles and phloem. When trunks were attacked by the bark beetles, chlorophyll abundance, Pn, E, and antioxidative enzyme activities all declined, and the declines were more pronounced than in the attacked shoots. A decrease in protein concentrations was also observed in needles and phloem from the attacked pines. Attack on shoots by the bark beetles suppressed host defense and provided a favorable environment for larval growth and development, resulting in long-term decline of pine growth potential. The results suggest that attacks on trunks by beetles caused more severe damage to host trees than attacks on shoots.

We demonstrate a compact all-fiber polarization-independent up-conversion single-photon detector based on integrated reverse proton exchanged periodically poled lithium niobate waveguides. The horizontally and vertically polarized components of randomly polarized signals are separated with a fiber-coupled polarization beam splitter, launched into two orthogonally polarized polarization maintaining fibers and fetched into two adjacent independent waveguides on the same device. The up-converted outputs from both waveguide channels are then combined with a multi-mode fiber combiner and detected by a silicon detector. With this configuration, the polarization-independent single-photon counting at 1.55 um is achieved with a system detection efficiency of 29.3%, a dark count rate of 1600 counts per second, and a polarization dependent loss of 0.1dB. This compact all-fiber system is robust and has great application potential in practical quantum key distribution systems., Comment: 17pages, 4 figures

The dynamic strain and vibration acceleration are two key parameters in the monitoring of vibrations that can damage track and affect the safety of railway traffic. This paper presents a remote measurement system for the online monitoring of train-induced vibration responses in rail tracks. A precision data acquisition node is designed for the conditioning and monitoring of the vibration signals generated by trains traveling at full speed. The monitored data is remotely acquired using a wireless sensor network. Furthermore, the use of solar power significantly increases the long-term service life of the system. The system is validated using both laboratory tests and a field deployment over a period of several months on an in-service high-speed railway. The obtained results indicate that the remote measurement system can accurately collect dynamic strain and vibration acceleration signals in a rail; these signals can be processed and analyzed to allow timely maintenance actions.