Research on Acquisition and Tracing Algorithm of GPS Receiver

An acquisition and tracing algorithm of GPS receiver is introduced. The shortage of time domain acquisition algorithm is pointed out by analyzing the composition of GPS signal and C/A code’s correlation property. Then the frequency domain acquisition algorithm is discussed. The carrier wave track loop and C/A code track loop are designed and the algorithms of them are determined. Using these two loops can get the navigation message, etc that used for positioning and navigation. The GPS raw intermediate data is processed and the satellites signals are acquired and traced in MATLAB, then obtain the navigation message verified the feasibility and availability of the acquisition and tracing algorithm.

Fibronectin tetrapeptide is target for syphilis spirochete cytadherence.

The syphilis bacterium, Treponema pallidum, parasitizes host cells through recognition of fibronectin (Fn) on cell surfaces. The active site of the Fn molecule has been identified as a four-amino acid sequence, arg-gly-asp-ser (RGDS), located on each monomer of the cell-binding domain. The synthetic heptapeptide gly-arg-gly-asp-ser-pro-cys (GRGDSPC), with the active site sequence RGDS, specifically competed with 125I-labeled cell-binding domain acquisition by T. pallidum. Additionally, the same heptapeptide with the RGDS sequence diminished treponemal attachment to HEp-2 and HT1080 cell monolayers. Related heptapeptides altered in one key amino acid within the RGDS sequence failed to inhibit Fn cell-binding domain acquisition or parasitism of host cells by T. pallidum. The data support the view that T. pallidum cytadherence of host cells is through recognition of the RGDS sequence also important for eukaryotic cell-Fn binding.