Rank-Two Beamforming and Power Allocation in Multicasting Relay Networks

In this paper, we propose a novel single-group multicasting relay beamforming scheme. We assume a source that transmits common messages via multiple amplify-and-forward relays to multiple destinations. To increase the number of degrees of freedom in the beamforming design, the relays process two received signals jointly and transmit the Alamouti space-time block code over two different beams. Furthermore, in contrast to the existing relay multicasting scheme of the literature, we take into account the direct links from the source to the destinations. We aim to maximize the lowest received quality-of-service by choosing the proper relay weights and the ideal distribution of the power resources in the network. To solve the corresponding optimization problem, we propose an iterative algorithm which solves sequences of convex approximations of the original non-convex optimization problem. Simulation results demonstrate significant performance improvements of the proposed methods as compared with the existing relay multicasting scheme of the literature and an algorithm based on the popular semidefinite relaxation technique

Macroecology of methane-oxidizing bacteria: the β-diversity of pmoA genotypes in tropical and subtropical rice paddies

Studies addressing microbial biogeography have increased during the past decade, but research on microbial distribution patterns is still in its infancies, and many aspects are only poorly understood. Here, we compared the methanotroph community in paddy soils sampled in Indonesia, Vietnam, China and Italy, focusing on the distance-decay relationship. We used the pmoA gene as marker for methanotroph diversity in terminal restriction fragment length polymorphism, microarray and pyrosequencing approaches. We could observe a significant increase of -diversity with geographical distance across continents (12000km). Measured environmental parameters explained only a small amount of data variation, and we found no evidence for dispersal limitation. Thus, we propose historical contingencies being responsible for the observed patterns. Furthermore, we performed an in-depth analysis of type II methanotroph pmoA distribution at the sequence level. We used ordination analysis to project sequence dissimilarities into a three-dimensional space (multidimensional scaling). The ordination suggests that type II methanotrophs in paddy fields can be divided into five major groups. However, these groups were found to be distributed in all soils independent of the geographic origin. By including tropical field sites (Indonesia and Vietnam) into the analysis, we further observed the first paddy fields harbouring a methanotroph community depleted in type II methanotrophs

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Advanced Relaying Methods for One-Way and Two-Way Communication

In wireless communication, relays are devices that receive and forward radio signals. Relays are attractive as they can increase the coverage of cellular networks. Moreover, relays improve the robustness of the wireless radio communication as they create additional signal paths. In this thesis, we propose novel schemes for one- and two-way communication in wireless relay networks. We aim to select the optimum relaying parameters by meeting two different design goals. The first goal is to minimize the transmit power where we assume constraints on the signal quality at the receivers. The second goal is to maximize the signal quality where we assume that the transmit power is limited. For one-directional communication, we propose schemes for communication over frequency selective radio channels that lead to inter-symbol-interference (ISI). First, we consider a multi-antenna source that transmits individual data streams to multiple destinations via multi-antenna relays. The proposed relaying scheme mitigates ISI as well as multi-user interference by using linear filters at the relays. Moreover, we demonstrate that linear precoding at the source efficiently improves the signal quality at the destinations. Then, we show that the latter scheme with a single source and multiple destinations includes the multi-user peer-to-peer (p2p) relaying scheme as a special case. In the p2p scheme, multiple source terminals transmit messages to multiple destination terminals via a network of relays. The simulation results demonstrate that increasing the relay filter length substantially improves the signal quality at the destinations. For relay networks with frequency-flat channels, we propose a novel multicasting scheme where a single source transmits common information to multiple destinations. The relays use the amplify-and-forward (AF) protocol to scale and adjust the phases of their received signals by using weight coefficients. To increase the number of degrees of freedom in the system, a rank-two beamforming method is used to create two communication links from the source to each destination. We propose an iterative algorithm that computes the relay weights and the optimal transmit power of the source and the relays. For bi-directional two-way AF relay communication, we first consider a single user pair. We analytically compare three different bi-directional schemes by their maximum rate. Then, we generalize the bi-directional communication of a single user pair to multiple pairs using an AF relay network. To limit the multi-user interference in the network, we propose to use novel multiple access schemes. For the bi-directional communication of a single user pair via a multi-antenna relay, a new differential scheme is proposed that allows to compute the relay weights without explicit knowledge of the communication channels. The proposed scheme is easy to implement and can be adapted to other relaying protocols