For the development of new 5G systems to operate in bands up to 100 GHz, there is a need for accurate radio propagation models at these bands that currently are not addressed by existing channel models developed for bands below 6 GHz. This document presents a preliminary overview of 5G channel models for bands up to 100 GHz. These have been derived based on extensive measurement and ray tracing results across a multitude of frequencies from 6 GHz to 100 GHz, and this document describes an initial 3D channel model which includes: 1) typical deployment scenarios for urban microcells (UMi) and urban macrocells (UMa), and 2) a baseline model for incorporating path loss, shadow fading, line of sight probability, penetration and blockage models for the typical scenarios. Various processing methodologies such as clustering and antenna decoupling algorithms are also presented.
MicroRNAs (miRNAs) are 20- to 24-nucleotide small noncoding RNAs that regulate gene expression in eukaryotic organisms. Several plant miRNAs, such as miR166, have vital roles in plant growth, development and responses to environmental stresses. One such environmental stress encountered by crop plants is exposure to cadmium (Cd), an element highly toxic to most organisms, including humans and plants. In this study, we analyzed the role of miR166 in Cd accumulation and tolerance in rice (). The expression levels of miR166 in both root and leaf tissues were significantly higher in the reproductive stage than in the seedling stage in rice. The expression of miR166 in the roots of rice seedlings was reduced after Cd treatment. Overexpression of miR166 in rice improved Cd tolerance, a result associated with the reduction of Cd-induced oxidative stress in transgenic rice plants. Furthermore, overexpression of miR166 reduced both Cd translocation from roots to shoots and Cd accumulation in the grains. miR166 targets genes encoding the class-III homeodomain-Leu zipper (HD-Zip) family proteins in plants. In rice, () gene (Os03g43930), which encodes an HD-Zip protein, was up-regulated by Cd treatment but down-regulated by overexpression of miR166 in transgenic rice plants. Overexpression of increased Cd sensitivity and Cd accumulation in the leaves and grains of transgenic rice plants. By contrast, silencing by RNA interference enhanced Cd tolerance in transgenic rice plants. These results indicate a critical role for miR166 in Cd accumulation and tolerance through regulation of its target gene, , in rice.
The IEEE 802.11p Wireless Access in Vehicular Environment (WAVE) protocol providing for vehicle-toinfrastructure and vehicle-to-vehicle radio communication is currently under standardization. We provide an NS-2 simulation study of the proposed IEEE 802.11p MAC protocol focusing on vehicle-to-infrastructure communication. We show that the specified MAC parameters for this protocol can lead to undesired throughput performance because the backoff window sizes are not adaptive to dynamics in the numbers of vehicles attempting to communicate. We propose two solutions to this problem. One is a centralized approach where exact information about the number of concurrent transmitting vehicles is used to calculate the optimal window size, and the other is a distributed approach in which vehicles use local observations to adapt the window size. We show that these schemes can provide significant improvements over the standard MAC protocol under dense and dynamic conditions.
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