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In multihop wireless sensor networks that are often characterized by many-to-one (convergecast) traffic patterns, problems related to energy imbalance among sensors often appear. Sensors closer to a data sink are usually required to forward a large amount of traffic for sensors farther from the data sink. Therefore, these sensors tend to die early, leaving(More)
In this paper, we address a fundamental problem concerning the best flooding strategy to minimize cost and latency for target discovery in wireless networks. Should we flood the network only once to search for the target, or should we apply a so-called “expansion ring” mechanism to reduce the cost? If the “expansion ring” mechanism is better in terms of the(More)
In multi-hop wireless sensor networks that are characterized by many-to-one traffic patterns, problems related to energy imbalance among sensors often appear. When each node has a fixed transmission range, the amount of traffic that sensor nodes are required to forward increases dramatically as the distance to the data sink becomes smaller. Thus, sensors(More)
In mobile ad hoc networks, node mobility causes frequent link failures, thus invalidating the routes containing those links. Once a link is detected broken, an alternate route has to be discovered, incurring extra route discovery overhead and packet latency. The traffic is also interrupted at the transport layer, and proper traffic recovery schemes have to(More)
In this paper, we address a fundamental problem concerning the optimal searching strategy in terms of searching cost for the target discovery problem in wireless networks. In order to find the nearest k targets from a total of m members using the minimum cost, should we search the network only once, or should we apply a so-called “expansion ring scheme?”(More)
If induced pluripotent stem (iPS) cells are to be used to treat damaged tissues or repair organs in elderly patients, it will be necessary to establish iPS cells from their tissues. To determine the feasibility of using this technology with elderly patients, we asked if it was indeed possible to establish iPS cells from the bone marrow (BM) of aged mice. BM(More)
BACKGROUND Although pathological involvements of diabetic polyneuropathy (DPN) have been reported, no dependable treatment of DPN has been achieved. Recent studies have shown that mesenchymal stem cells (MSCs) ameliorate DPN. Here we demonstrate a differentiation of induced pluripotent stem cells (iPSCs) into MSC-like cells and investigate the therapeutic(More)
Human histocompatibility antigens are quite heterogeneous and promote the rejection of transplanted tissue. Recent advances in stem cell research that enable the use of a patient's own stem cells for transplantation are very important because rejection could be avoided. In particular, Yamanaka’s group in Japan gave new hope to patients with incurable(More)