Piwi-interacting RNA (piRNA) are small RNA abundant in the germline across animal species. In fruit flies and mice, piRNA have been implicated in maintenance of genomic integrity by transposable elements silencing. Outside of the germline, piRNA have only been found in fruit fly ovarian follicle cells. Previous studies have further reported presence of multiple piRNA-like small RNA (pilRNA) in fly heads and a small number of pilRNA have been reported in mouse tissues and in human NK cells. Here, we analyze high-throughput small RNA sequencing data in more than 130 fruit fly, mouse and rhesus macaque samples. The results show widespread presence of pilRNA, displaying all known characteristics of piRNA in multiple somatic tissues of these three species. In mouse pancreas and macaque epididymis, pilRNA abundance was compatible with piRNA abundance in the germline. Using in situ hybridizations, we further demonstrate pilRNA co-localization with mRNA expression of Piwi-family genes in all macaque tissues. Further, using western blot, we have shown the expression of Miwi protein in mouse pancreas. These findings indicate that piRNA-like molecules might play important roles outside of the germline.

Dynamic nature of vehicular ad hoc networks (VANETs) creates great challenges for message dissemination. To satisfy the high reliability and low delivery latency requirements for safety applications in VANETs, a dynamic epidemic broadcasting model is presented in this paper. On the basis of the ordinary differential equations, the proposed optimal control scheme is analyzed to understand the epidemic broadcasting properties, which include the message delivery probability, the expected delivery latency, and the number of copies. The correctness of the theoretical analyses is confirmed by simulations, and the experiment results prove the efficiency of the optimal epidemic broadcasting model. subclass of the WAVE technologies for vehicle-to-vehicle and vehicle-to-infrastructure interactions, which aims at accelerating the deployment of VANETs as well as improving traffic safety [2][3][4][5]. However, because the IEEE 1609 family provides only the overall protocol that is suitably used in VANETs, the actual model for information dissemination and the efficient algorithm to be implemented under this protocol are left to the designers.On the other hand, VANETs face great challenges including dynamic network topology, lack of centralized control, and unattended potential failures in wireless link [6]. High mobility of vehicles leads to more uncertainty of opportunistic transmission between two vehicles. Additionally, sparse node density and opportunistic inter-meeting between any two vehicles make absence of end-to-end paths from communication sources to their destinations in VANETs in most time [7]. VANETs are also characterized by intermittent connection in many traffic situations and process message propagation in the delay-tolerant manner as delay tolerant networks. So, many traditional routing protocols and message dissemination models are no longer suitable or fail to work for VANETs, and a novel-efficient broadcasting mechanism for message dissemination is necessary [8].In the past few years, a novel routing paradigm, so called 'the store-carry-and-forward', has been developed and studied at full length to support opportunistic communication in VANETs [9]. In this routing paradigm, a mobile node is able to store the message in its buffer with limited capacity after receiving that message and then carries the message as it moves unless the next hop for routing the message is available. This node will forward the stored message to other new mobile nodes when those nodes that it encounters move into its communication coverage. The process is named as 'communication contact' or 'inter-meeting' between two vehicles and can be analogous to the spread of infectious diseases [10]. Some improved variations of the epidemic-based routing have recently received a large amount of attentions in current research literatures [11][12][13][14][15]. For example, Ren et al. adopt an approach of adaptive compression of vectors to reduce some redundant overhead when nodes exchange summary vectors (SVs) and request vectors and store th...

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