Cellular connectivity for UAVs: Network modeling, performance analysis, and design guidelines

The growing use of aerial user equipments (UEs) in various applications requires ubiquitous and reliable connectivity for safe control and data exchange between these devices and ground stations. Key questions that need to be addressed when planning the deployment of aerial UEs are whether the cellular network is a suitable candidate for enabling such connectivity and how the inclusion of aerial UEs might impact the overall network efficiency. This paper provides an in-depth analysis of user and network-level performance of a cellular network that serves both unmanned aerial vehicles (UAVs) and ground users in the downlink. Our results show that the favorable propagation conditions that UAVs enjoy due to their height often backfire on them, as the increased load-dependent co-channel interference received from neighboring ground base stations (BSs) is not compensated by the improved signal strength. When compared with a ground user in an urban area, our analysis shows that a UAV flying at 100 m can experience a throughput decrease of a factor 10 and a coverage drop from 76% to 30%. Motivated by these findings, we develop UAV and network-based solutions to enable an adequate integration of UAVs into cellular networks. In particular, we show that an optimal tilting of the UAV antenna can increase the coverage from 23% to 89% and throughput from 3.5 to 5.8 b/s/Hz, outperforming ground UEs. Furthermore, our findings reveal that depending on the UAV altitude and its antenna configuration, the aerial user performance can scale with respect to the network density better than that of a ground user. Finally, our results show that network densification and the use of microcells limit the UAV performance. Although UAV usage has the potential to increase the area spectral efficiency (ASE) of cellular networks with a moderate number of cells, they might hamper the development of future ultradense networks

Establishment and characterization of two human breast carcinoma cell lines by spontaneous immortalization: Discordance between Estrogen, Progesterone and HER2/neu receptors of breast carcinoma tissues with derived cell lines

Background: Breast cancer is one of the most common cancers among women throughout the world. Therefore, established cell lines are widely used as in vitro experimental models in cancer research.Methods: Two continuous human breast cell lines, designated MBC1 and MBC2, were successfully established and characterized from invasive ductal breast carcinoma tissues of Malaysian patients. MBC1 and MBC2 have been characterized in terms of morphology analysis, population doubling time, clonogenic formation, wound healing assay, invasion assay, cell cycle, DNA profiling, fluorescence immunocytochemistry, Western blotting and karyotyping.Results: MBC1 and MBC2 exhibited adherent monolayer epithelial morphology at a passage number of 150. Receptor status of MBC1 and MBC2 show (ER+, PR+, HER2+) and (ER+, PR-, HER2+), respectively. These results are in discordance with histopathological studies of the tumoral tissues, which were triple negative and (ER-, PR-, HER2+) for MBC1 and MBC2, respectively. Both cell lines were capable of growing in soft agar culture, which suggests their metastatic potential. The MBC1 and MBC2 metaphase spreads showed an abnormal karyotype, including hyperdiploidy and complex rearrangements with modes of 52-58 chromosomes per cell.Conclusions: Loss or gain in secondary properties, deregulation and specific genetic changes possibly conferred receptor changes during the culturing of tumoral cells. Thus, we hypothesize that, among heterogenous tumoral cells, only a small minority of ER+/PR+/HER2+ and ER+/PR-/HER2+ cells with lower energy metabolism might survive and adjust easily to in vitro conditions. These cell lines will pave the way for new perspectives in genetic and biological investigations, drug resistance and chemotherapy studies, and would serve as prototype models in Malaysian breast carcinogenesis investigations. © 2012 Kamalidehghan et al.; licensee BioMed Central Ltd

A mesh free numerical method for the solution of an inverse heat problem

summary:We combine the theory of radial basis functions with the finite difference method to solve the inverse heat problem, and use five standard radial basis functions in the method of the collocation. In addition, using the newly proposed numerical procedure, we also discuss some experimental numerical results

The growth, survival rate and reproductive characteristics of Artemia urmiana fed by Dunaliella tertiolecta, Tetraselmis suecica, Nannochloropsis oculata, Chaetoceros sp., Chlorella sp. and Spirolina sp. as feeding microalgae

This study was performed to compare the efficiency of six microalgae namely Dunaliella tertiolecta, Tetraselmis suecica, Nannochloropsis oculata, Chaetoceros sp., Chlorella sp. and Spirolina sp. on the growth, survival rate and reproduction efficacy in Artemia urmiana in laboratory conditions. Artemia cysts were harvested from Urmia Lake and hatched according to the standard method. Live microalgae were cultured using the f/2 culture medium. Artemia survival was determined in treatments on days 8, 11, 14, 17 and 20. A highly significant difference (p<0.01) were found among three microalgae in terms of length growth, survival rates and reproduction characteristics in A. urmiana. In spite of higher length growth of A.urmiana fed on N. oculata than A. urmiana fed by T. suecica but survival and reproduction in the latter was better than the first treatment. In general, D. tertiolecta was more efficient than other microalgae examined in the present study on A. urmiana concerning not only to growth and survival but also to reproduction mode. So, it is preferred to feed A. urmiana

Coverage maximization for a poisson field of drone cells

The use of drone base stations to provide wireless connectivity for ground terminals is becoming a promising part of future technologies. The design of such aerial networks is however different compared to cellular 2D networks, as antennas from the drones are looking down, and the channel model becomes height-dependent. In this paper, we study the effect of antenna patterns and height-dependent shadowing. We consider a random network topology to capture the effect of dynamic changes of the flying base stations. First we characterize the aggregate interference imposed by the co-channel neighboring drones. Then we derive the link coverage probability between a ground user and its associated drone base station. The result is used to obtain the optimum system parameters in terms of drones antenna beamwidth, density and altitude. We also derive the average LoS probability of the associated drone and show that it is a good approximation and simplification of the coverage probability in low altitudes up to 500 m according to the required signal-to-interference-plus-noise ratio (SINR)

Mesenchymal Stem Cells for Treatment of CNS Injury

Brain and spinal cord injuries present significant therapeutic challenges. The treatments available for these conditions are largely ineffective, partly due to limitations in directly targeting the therapeutic agents to sites of pathology within the central nervous system (CNS). The use of stem cells to treat these conditions presents a novel therapeutic strategy. A variety of stem cell treatments have been examined in animal models of CNS trauma. Many of these studies have used stem cells as a cell-replacement strategy. These investigations have also highlighted the significant limitations of this approach. Another potential strategy for stem cell therapy utilises stem cells as a delivery mechanism for therapeutic molecules. This review surveys the literature relevant to the potential of mesenchymal stem cells for delivery of therapeutic agents in CNS trauma in humans

The effects of Pediococcus acidilactici as a probiotic on growth performance and survival rate of great sturgeon, Huso huso (Linnaeus, 1758)

This study was accomplished to investigate the effect of Artemia urmiana nauplii enriched with Pediococcus acidilactici as probiotic on growth performance and survival rate of great sturgeon, Huso huso. Artemia nauplii were enriched with P. acidilactici at a final concentration of 10^10 CFU mL^-1 in three time dependent treatments as 3 h (T3), 6 h (T6), 9 h (T9), and one non-enriched Artemia as the control treatment. All treatments were considered in triplicates. Since the nauplii enriched for 9 hours (T9) had the most significant CFU/g compared to other treatments (p0.05). On the other hand, a decreasing trend was recorded in food conversion ratio (FCR) and final biomass changed significantly for T9 in comparison with that recorded in the control group (p<0.05). The results indicated that P. acidilactici had a positive effect on growth and survival of beluga larvae, and a different time of enrichment had a significant effect on LAB effect. The best time of enrichment for beluga larvae was found to be 9 hours