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Abstract-This paper proposes a multi-channel token ring media access control (MAC) protocol (MCTRP) for inter-vehicle communications (IVC). Through adaptive ring coordination and channel scheduling, vehicles are autonomously organized into multiple rings operating on different service channels. Based on the multi-channel ring structure, emergency messages can be disseminated with a low delay. With the token based data exchange protocol, the network throughput is further improved for non-safety multimedia applications. An analytical model is developed to evaluate the performance of MCTRP in terms of the average full ring delay, emergency message delay, and ring throughput. Extensive simulations with ns-2 are conducted to validate the analytical model and demonstrate the efficiency and effectiveness of the proposed MCTRP.

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The piling up storage and compute stacks in cloud data center are expected to accommodate the majority of internet traffic in the future. However, as the number of mobile devices significantly increases, getting massive data into and out of the cloud wirelessly inflicts high pressure on the bandwidth, and meanwhile induces unpredictable latency. Fog computing, which advocates extending clouds to network edge, guarantees low latency and location-aware service provisioning. In this article, we consider fog computing as an ideal complement rather than a substitute of cloud computing, and we propose a software defined networking (SDN) enabled framework for cloud-fog interoperation, aiming at improving quality of experience and optimizing network resource usage. Two case studies are provided to illuminate the feasibility and advantage of the proposed framework. At last, potential research issues are presented for further investigation.

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In order to obtain a pH-sensitive delivery carrier for doxorubicin (DOX), DOX-loaded polyurethane (PU·DOX) nanoparticles were readily prepared in water by electrostatic interactions between amphiphilic polyurethane with carboxyl pendent groups (PU-COOH) and doxorubicin hydrochloride (DOX·HCl). The structures of the products obtained were characterized by Fourier transform infrared spectroscopy, 1 H NMR spectroscopy, gel permeation chromatography, UV-visible spectroscopy, dynamic light scattering and transmission electron microscopy. The average hydrodynamic size of the PU·DOX nanoparticles was around 182 nm with negative surface charge (−1.1 mV) and a spherical or rodlike shape. PU·DOX nanoparticles had a higher drug-loading content of 14.1 wt%. The in vitro drug release properties of PU·DOX nanoparticles were investigated at pH 4.0, 5.0 and 7.4, respectively. PU·DOX nanoparticles exhibited a good pH-sensitive drug release property, but there was almost no release of DOX from PU·DOX nanoparticles at pH 7.4. The in vitro cellular uptake assay and the Cell Counting Kit-8 assay demonstrated that PU·DOX nanoparticles had a higher level of cellular internalization and higher inhibitory effects on the proliferation of human breast cancer (MCF-7) cells than pure DOX. The enhancement of the inhibition effects resulted from increasing apoptosis-inducing effects on MCF-7 cells, which was related to the enhancement of Bax expression and the reduction of Bcl-2 expression confirmed by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay, real-time polymerase chain reaction (PCR) assay and western blot assay.