A Joint Energy Replenishment and Data Collection Strategy in Heterogeneous Wireless Rechargeable Sensor Networks.

In wireless rechargeable sensor networks, mobile vehicles (MVs) combining energy replenishment and data collection are studied extensively. To reduce data overflow, most recent work has utilized more vehicles to assist the MV to collect buffered data. However, the practical network environment and the limitations of the vehicle in the data collection are not considered. UAV-enabled data collection is immune to complex road environments in remote areas and has higher speed and less traveling cost, which can overcome the lack of the vehicle in data collection. In this paper, a novel framework joining the MV and UAV is proposed to prolong the network lifetime and reduce data overflow. The network lifetime is correlated with the charging order; therefore, we first propose a charging algorithm to find the optimal charging order. During the charging period of the MV, the charging time may be longer than the collecting time. An optimal selection strategy of neighboring clusters, which could send data to the MV, was found to reduce data overflow. Then, to further reduce data overflow, an algorithm is also proposed to schedule the UAV to assist the MV to collect buffered data. Finally, simulation results verified that the proposed algorithms can maximize network lifetime and minimize the data loss simultaneously.

Individualized elective irradiation of the clinically node-negative neck in definitive radiotherapy for head and neck squamous cell carcinoma.

BACKGROUND: Oral cavity (OC), oropharyngeal (OP), hypopharyngeal (HP), and laryngeal (LA) squamous cell carcinoma (SCC) have a high incidence of regional lymph node metastasis (LNM). Elective irradiation for clinically node-negative neck is routinely administered to treat lymph nodes harboring occult metastasis. However, the optimal elective irradiation schemes are still inconclusive. In this study, we aimed to establish individualized elective irradiation schemes for the ipsilateral and contralateral node-negative neck of these four types of cancer. METHODS: From July 2005 to December 2018, 793 patients with OC-SCC, 464 with OP-SCC, 413 with HP-SCC, and 645 with LA-SCC were recruited retrospectively. Based on the actual incidence of LNM and the tumor characteristics, risk factors for contralateral LNM, as well as node level coverage schemes for elective irradiation, were determined using logistic regression analysis. Additionally, we developed a publicly available online tool to facilitate the widespread clinical use of these schemes. RESULTS: For the ipsilateral node-negative neck, elective irradiation at levels I-III for OC-SCC and levels II-IVa for OP-, HP- and LA-SCC are generally recommended. In addition, level VIIa should be included in patients with OP-SCC. Multivariate analyses revealed that posterior hypopharyngeal wall and post-cricoid region involvement were independently associated with level VIIa metastasis in HP-SCC (all P < 0.05). For the contralateral node-negative neck, multivariate analyses revealed that ipsilateral N2b2-N3, tumors with body midline involvement, and degree of tumor invasion were the independent factors for contralateral LNM (all P < 0.05). In patients who require contralateral neck irradiation, levels I-II are recommended for OC-SCC, and additional level III is recommended for patients with ipsilateral N3 disease. Levels II-III are recommended for OP-, HP-, and LA-SCC, and additional level IVa is recommended for patients with advanced T or ipsilateral N classifications. Furthermore, additional level VIIa is recommended only for OP-SCC with T4 and ipsilateral N3 disease. CONCLUSION: Based on our findings, we suggest that individualized and computer-aided elective irradiation schemes could reduce irradiation volumes in OC-, OP- and HP-SCC patients, as compared to current guidelines, and could thus positively impact the patients' quality of life after radiotherapy.

Energy-Efficient Connected-Coverage Scheme in Wireless Sensor Networks.

In the wireless sensor network, the lifetime of the network can be prolonged by improving the efficiency of limited energy. Existing works achieve better energy utilization, either through node scheduling or routing optimization. In this paper, an efficient solution combining node scheduling with routing protocol optimization is proposed in order to improve the network lifetime. Firstly, to avoid the redundant coverage, a node scheduling scheme that is based on a genetic algorithm is proposed to find the minimum number of sensor nodes to monitor all target points. Subsequently, the algorithm prolongs the lifetime of the network through choosing redundant sleep nodes to replace the dead node. Based on the obtained minimum coverage set, a new routing protocol, named Improved-Distributed Energy-Efficient Clustering (I-DEEC), is proposed. When considering the energy and the distance of the sensor node to the sink, a new policy choosing the cluster head is proposed. To make the energy load more balanced, uneven clusters are constructed. Meanwhile, the data communication way of sensor nodes around the sink is also optimized. The simulation results show that the proposed sensor node scheduling algorithm can reduce the number of redundant sensor nodes, while the I-DEEC routing protocol can improve the energy efficiency of data transmission. The lifetime of the network is greatly extended.

A Charging Algorithm for the Wireless Rechargeable Sensor Network with Imperfect Charging Channel and Finite Energy Storage.

Recently, wireless energy transfer technology becomes a popular way to address energy shortage in wireless sensor networks. The capacity of the mobile wireless charging car (WCV) and the wireless channel between the WCV and the sensor are two important factors influencing the energy efficiency of the wireless sensor network, which has not been well considered. In this paper, we study the energy efficiency of a wireless rechargeable sensor network charged by a finite capacity WCV through an imperfect wireless channel. To estimate the energy efficiency, we first propose a new metric named waste rate, which is defined as a function of the charging channel quality. Then, energy efficiency optimization is modeled as minimizing the waste rate. Through optimizing the distance between the WCV and sensor nodes, the set of optimal charging sensor nodes is obtained. By using the Hamiltonian circle, the nearest neighbor algorithm is proposed to find the traveling path of the WCV. Furthermore, to avoid the untimely death of sensor nodes and the coverage hole, an extended node dynamic replacement strategy is proposed. The simulation results show that the proposed method can reduce the waste rate and the total charging time; i.e., the sum of traveling time and charging delay can be significantly reduced, which indicates that the proposed algorithm can improve the energy efficiency of the network.

[Tumor suppressive effect and relative mechanisms of tea polyphenol on nasopharyngeal carcinoma cells].

OBJECTIVE: To investigate the effect and mechanism of tea polyphenol (TP) on the proliferation, apoptosis, migration and invasion of nasopharyngeal carcinoma(NPC) cell line HONEl. METHOD: After treated with different concentration of tea polyphenol, CCK-8 assay, fluorescent staining, cell scratching assay and transwell assay were applied to detect the effect of tea polyphenol on the HONE1 cells. Furthermore, the expression of protein VEGF was investigated by flow cytometry assay. RESULT: It was found that tea polyphenol could inhibit NPC cell proliferation significantly in a dose-dependent manner, however, little impact was observed in normal nasopharyngeal epithelial cell line NP69. Furthermore, it was demonstrated by fluorescent staining assay that tea polyphenol could induce NPC cell apoptosis, and cell scratching assay and transwell assay showed that tea polyphenol could inhibit cell migration and invasion. CONCLUSION: Tea polyphenol can significantly inhibit cell proliferation, induce cell apoptosis and decreased the migration and invasion ability of NPC cells in vitro. Tea polyphenol might be a tumor suppressor of NPC cells.

The effect of RAD51 135 G>C and XRCC2 G>A (rs3218536) polymorphisms on ovarian cancer risk among Caucasians: a meta-analysis.

Genetic polymorphisms of RAD51 135 G>C and XRCC2 G>A (rs3218536) have been reported to change the risk of ovarian cancer, but the results are controversial. To get a more precise result, a meta-analysis was performed. A comprehensive literature search in PubMed, Excerpta Medica Database, and China National Knowledge Infrastructure was carried out to get case-control studies published up to November 2013. The pooled odds ratio (OR) and its corresponding 95 % confidence interval (CI) were conducted to estimate the effect of RAD51 135 G>C and XRCC2 G>A (rs3218536) polymorphisms on ovarian cancer risk. A total of 13 independent case-control studies with 5,927 cases and 10,303 controls were included in this meta-analysis. There was no significant association between RAD51 135 G>C polymorphism and risk of ovarian cancer. However, the result of total studies indicated the XRCC2 G>A (rs3218536) polymorphism could reduce the risk of ovarian cancer (heterozygote model AG vs. GG: OR=0.877, 95 % CI=0.770-0.999, P=0.048; dominant model AA/AG vs. GG: OR=0.864, 95 % CI=0.763-0.979, P=0.022). The result was still significant after Hardy-Weinberg equilibrium-violating studies were excluded (allele contrast A vs. G: OR=0.836, 95 % CI=0.74-0.943, P=0.004; homozygote model AA vs. GG: OR=0.562, 95 % CI=0.317-0.994, P=0.048; heterozygote model AG vs. GG: OR=0.859, 95 % CI=0.753-0.98, P=0.023; dominant model AA/AG vs. GG: OR=0.842, 95 % CI=0.74-0.958, P=0.009). In the stratified analysis by ethnicity, significantly reduced risk was observed among Caucasians in dominant model (AA/AG vs. GG: OR=0.867, 95 % CI=0.764-0.984, P=0.027). No significant association was found between the RAD51 135G>C polymorphism and the risk of ovarian cancer. Interestingly, XRCC2 G>A (rs3218536) polymorphism might reduce the risk of ovarian cancer. Larger-scale and well-designed studies are needed to further clarify the association.