Accurate and fast-convergent time synchronization is very important for wireless sensor networks. The flooding time synchronization converges fast, but its transmission delay and by-hop error accumulation seriously reduce the synchronization accuracy. In this paper, a rapid-flooding multiple oneway broadcast time-synchronization (RMTS) protocol for largescale wireless sensor networks is proposed. To minimize the byhop error accumulation, the RMTS uses maximum likelihood estimations for clock skew estimation and clock offset estimation, and quickly shares the estimations among the networks. As a result, the synchronization error resulting from delays is greatly reduced, while faster convergence and higher-accuracy synchronization is achieved. Extensive experimental results demonstrate that, even over 24-hops networks, the RMTS is able to build accurate synchronization at the third synchronization period, and moreover, the by-hop error accumulation is slower when the network diameter increases.

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BACKGROUND Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. Surgical resection and tyrosine kinase inhibitors are defined as the main treatments but cannot cure patients with advanced GIST, which eventually develops into recurrence and acquired drug resistance. Therefore, it is necessary to identify prognostic biomarkers and new therapeutic targets for GISTs. CC chemokine receptor type 8 (CCR8) protein participates in regulation of immune responses. Recent studies on CCR8 in non-small cell lung cancer and colorectal cancer showed that it was highly expressed in tumor-infiltrating regulatory T cells and correlated with a poor prognosis. AIM To detect CCR8 expression in GIST tissues and analyze its relationships with clinicopathological features and prognosis in patients with GISTs. METHODS Tissue samples were used for the tissue microarrays construction. The microarrays were then subjected to immunohistochemical analyses to detect CCR8 expression. Next, Kaplan–Meier analysis was utilized to calculate the survival rate of patients with complete follow-up data, and the potential prognostic value of CCR8 was evaluated by Cox regression analysis. Finally, a Gene Ontology/Kyoto Encyclopedia of Genes and Genomes single-gene enrichment chart of CCR8 was constructed using the STRING database. RESULTS CCR8-positive signals were detected as brown or brown-yellow particles by immunohistochemistry located in the cytoplasm. Among 125 tissue samples, 74 had CCR8 high expression and 51 had low or negative expression. Statistical analyses suggested CCR8 was significantly correlated with tumor size, mitotic index, AFIP-Miettinen risk classification and tumor location. Kaplan–Meier and multivariate analyses showed that patients with low or negative CCR8 expression, mitotic index < 5/high-power fields (HPF) and tumor diameter < 5 cm had a better prognosis. Based on the STRING database, CCR8 was significantly enriched in biological processes such as tumor immunity, T lymphocyte chemotaxis, migration and pathways like the nuclear factor-κB and tumor necrosis factor pathways as well as intestinal immune regulation networks. CONCLUSION CCR8 is a prognostic biomarker for malignant potential of GISTs, with high expression correlated with malignancy and poor prognosis.

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