Cloud Compute-and-Forward with Relay Cooperation

We study a cloud network with M distributed receiving antennas and L users, which transmit their messages towards a centralized decoder (CD), where M>=L. We consider that the cloud network applies the Compute-and-Forward (C&F) protocol, where L antennas/relays are selected to decode integer equations of the transmitted messages. In this work, we focus on the best relay selection and the optimization of the Physical-Layer Network Coding (PNC) at the relays, aiming at the throughput maximization of the network. Existing literature optimizes PNC with respect to the maximization of the minimum rate among users. The proposed strategy maximizes the sum rate of the users allowing nonsymmetric rates, while the optimal solution is explored with the aid of the Pareto frontier. The problem of relay selection is matched to a coalition formation game, where the relays and the CD cooperate in order to maximize their profit. Efficient coalition formation algorithms are proposed, which perform joint relay selection and PNC optimization. Simulation results show that a considerable improvement is achieved compared to existing results, both in terms of the network sum rate and the players' profits.Comment: Submitted to IEEE Transactions on Wireless Communication

Root colonization and spore population by VA-mycorrhizal fungi in four grapevine rootstocks

The occurrence of vesicular arbuscular (VA) mycorrhizae was investigated in an experimental vineyard at the Thessaloniki prefecture, in a soil which was poor in available P. The soil had not received any phosphorus fertilization for several years, nevertheless the leaves had an adequate P content (0.17 - 0.31 % of d.w.). The vineyard was planted with 4 introduced (Cinsaut, Syrah, Grenache, Carignan) and 4 local cultivars (Athiri, Roditis, Assyrtiko, Malagouzia), grafted to the rootstocks 110 R, 41 B, 140 Ru and 1103 P. Microscopic examination showed that all 4 rootstocks were colonized by VA-mycorrhizal fungi at frequencies ranging from 45 to 75 %. The number of vesicles varied between 16 and 47 and the number of arbuscules between 5 and 26 per cm of infected root. Spore number produced by the mycorrhizal fungi in the rhizosphere ranged from 196 to 280 per 100 g of soil. Spores of the genus Glomus were more commonly encountered, in particular those of G. mosseae and G. macrocarpum. The roots of 1103 P, followed by 41 B, 140 Ru and 110 R were most heavily colonized. The same pattern was observed with regard to the number of spores in the rhizosphere of these rootstocks. Grafted cultivars were found to have some influence on the degree of colonization of these rootstocks and on the population of spores, but had no effect on the formation of vesicles and arbuscules. The degree of colonization of roots by endomycorrhizal fungi was inversely related to the available P content of the soil. At the time of root sampling the P content of leaves was not directly related neither to the degree of root colonization nor to the P content of the soil. However, leaves were found to be adequately supplied with P in all cases. Therefore, the differences observed among the 8 cultivars can be attributed primarily to a variety-specific demand for P

Simplicity - the key to fruitful medical research

Medical research is here divided -into two broad categories. The great majority of research is "complex" and includes all studies of intricate body mechanisms. A minority of research is "simple" and deals mainly with direct relationships between human environmental or lifestyle factors and disease incidence (or with analogous studies on animals). In addition, it includes studies of simple body mechanisms. Examples are provided to demonstrate that most of our medical knowledge of practical benefit derives from simple research. This is particularly the case in the area of prevention

Opportunistic Access Point Selection for Mobile Edge Computing Networks

In this paper, we investigate a mobile edge computing (MEC) network with two computational access points (CAPs), where the source is equipped with multiple antennas and it has some computational tasks to be accomplished by the CAPs through Nakagami-m distributed wireless links. Since the MEC network involves both communication and computation, we first define the outage probability by taking into account the joint impact of latency and energy consumption. From this new definition, we then employ receiver antenna selection (RAS) or maximal ratio combining (MRC) at the receiver, and apply selection combining (SC) or switch-and-stay combining (SSC) protocol to choose a CAP to accomplish the computational task from the source. For both protocols along with the RAS and MRC, we further analyze the network performance by deriving new and easy-to-use analytical expressions for the outage probability over Nakagami-m fading channels, and study the impact of the network parameters on the outage performance. Furthermore, we provide the asymptotic outage probability in the low regime of noise power, from which we obtain some important insights on the system design. Finally, simulations and numerical results are demonstrated to verify the effectiveness of the proposed approach. It is shown that the number of transmit antenna and Nakagami parameter can help reduce the latency and energy consumption effectively, and the SSC protocol can achieve the same performance as the SC protocol with proper switching thresholds of latency and energy consumption

GATA3-driven Th2 responses inhibit TGF-beta1-induced FOXP3 expression and the formation of regulatory T cells.

Transcription factors act in concert to induce lineage commitment towards Th1, Th2, or T regulatory (Treg) cells, and their counter-regulatory mechanisms were shown to be critical for polarization between Th1 and Th2 phenotypes. FOXP3 is an essential transcription factor for natural, thymus-derived (nTreg) and inducible Treg (iTreg) commitment; however, the mechanisms regulating its expression are as yet unknown. We describe a mechanism controlling iTreg polarization, which is overruled by the Th2 differentiation pathway. We demonstrated that interleukin 4 (IL-4) present at the time of T cell priming inhibits FOXP3. This inhibitory mechanism was also confirmed in Th2 cells and in T cells of transgenic mice overexpressing GATA-3 in T cells, which are shown to be deficient in transforming growth factor (TGF)-beta-mediated FOXP3 induction. This inhibition is mediated by direct binding of GATA3 to the FOXP3 promoter, which represses its transactivation process. Therefore, this study provides a new understanding of tolerance development, controlled by a type 2 immune response. IL-4 treatment in mice reduces iTreg cell frequency, highlighting that therapeutic approaches that target IL-4 or GATA3 might provide new preventive strategies facilitating tolerance induction particularly in Th2-mediated diseases, such as allergy