Determining Sensor Locations in Wireless Sensor Networks

Network lifetime plays an important role in the design of wireless sensor networks. This paper studies the problem of prolonging the wireless sensor network's lifetime, through introducing additional sensors at proper locations to achieve the goal of minimizing the length of the longest edge in the network. The problem is in fact the bottleneck Steiner tree problem, trying to find a Steiner tree minimizing the length of the longest edges for the given n terminals in the Euclidean plane by introducing at most k Steiner points. A restricted bottleneck Steiner tree problem is studied in this paper, which requires that only degree ≥3 Steiner points are not allowed to be adjacent in the optimal solution. We show that the restricted problem is MAX-SNP hard and cannot be approximated within performance ratio 2 in polynomial time unless P = NP; we first propose a polynomial time 3 -approximation algorithm and then improve the ratio to 2 + ε for any given ε > 0 , by presenting a polynomial time randomized approximation algorithm, which is almost optimal to the restricted problem

Efficient Deployment of Base Stations in Wireless Communication Networks

In the design of wireless communication networks, we may have to interconnect n stations locating at given points in the plane such that the distance among each stations is as small as possible by introducing at most k extra stations subjective to a budget limit. In this paper, our goal is to determine the locations of the extra k stations interconnecting the existing n stations to minimize the longest distance among stations. This is so-called bottleneck Steiner tree problem, which also has applications in VLSI routing, WDM optical networks design and phylogenetic tree reconstruction. The problem has been proved to be NP-hard and cannot be approximated in the performance ratio 2 in polynomial time in both Euclidean and rectilinear plane and approximation algorithms in the best possible performance ratios presented for the problem in both planes. In this paper, we improve the time complexity of the approximation algorithms and conduct simulations to demonstrate the validness of our improvements.Published versio

Evaluation of Antioxidant Activity and Drug Delivery Potential of Cell-Derived Extracellular Vesicles from <i>Citrus reticulata</i> Blanco cv. ‘Dahongpao’

Plant extracellular vesicles (PEVs) have attracted increasing attention due to their rich composition, good antioxidant and anti-inflammatory activity, and ability to transport drugs. As a common fruit, citrus is an ideal material for extracting PEVs because of the diversity and abundance of bioactive substances in it. In our study, citrus-derived extracellular vesicles (CEVs) were extracted from red mandarin (Citrus reticulata Blanco cv. ‘Dahongpao’) and it was found that they contain high levels of lipids, proteins, and carbohydrates. The high levels of total phenols and total flavonoids suggest that CEVs have good chemical antioxidant properties. We also demonstrated through cell experiments that CEVs have significant antioxidant and anti-inflammatory effects. Furthermore, we found that CEVs have an encapsulation rate of 71.5 ± 0.19% and a high drug-carrying capacity of 4.96 ± 0.22% and can enhance antioxidant and anti-inflammatory activity when loaded with tangeretin. Our results show that CEVs contain abundant bioactive components, have low toxicity, exhibit good antioxidant and anti-inflammatory properties, and can serve as drug delivery agents. This study has important implications for utilizing citrus materials and developing natural anti-oxidative and anti-inflammatory biomaterials