Rate of convergence in the Smoluchowski-Kramers approximation for mean-field stochastic differential equations

In this paper we study a second-order mean-field stochastic differential systems describing the movement of a particle under the influence of a time-dependent force, a friction, a mean-field interaction and a space and time-dependent stochastic noise. Using techniques from Malliavin calculus, we establish explicit rates of convergence in the zero-mass limit (Smoluchowski-Kramers approximation) in the $L^p$-distances and in the total variation distance for the position process, the velocity process and a re-scaled velocity process to their corresponding limiting processes

Effect of Cavβ Subunits on Structural Organization of Cav1.2 Calcium Channels

BACKGROUND:Voltage-gated Ca(v)1.2 calcium channels play a crucial role in Ca(2+) signaling. The pore-forming alpha(1C) subunit is regulated by accessory Ca(v)beta subunits, cytoplasmic proteins of various size encoded by four different genes (Ca(v)beta(1)-beta(4)) and expressed in a tissue-specific manner. METHODS AND RESULTS:Here we investigated the effect of three major Ca(v)beta types, beta(1b), beta(2d) and beta(3), on the structure of Ca(v)1.2 in the plasma membrane of live cells. Total internal reflection fluorescence microscopy showed that the tendency of Ca(v)1.2 to form clusters depends on the type of the Ca(v)beta subunit present. The highest density of Ca(v)1.2 clusters in the plasma membrane and the smallest cluster size were observed with neuronal/cardiac beta(1b) present. Ca(v)1.2 channels containing beta(3), the predominant Ca(v)beta subunit of vascular smooth muscle cells, were organized in a significantly smaller number of larger clusters. The inter- and intramolecular distances between alpha(1C) and Ca(v)beta in the plasma membrane of live cells were measured by three-color FRET microscopy. The results confirm that the proximity of Ca(v)1.2 channels in the plasma membrane depends on the Ca(v)beta type. The presence of different Ca(v)beta subunits does not result in significant differences in the intramolecular distance between the termini of alpha(1C), but significantly affects the distance between the termini of neighbor alpha(1C) subunits, which varies from 67 A with beta(1b) to 79 A with beta(3). CONCLUSIONS:Thus, our results show that the structural organization of Ca(v)1.2 channels in the plasma membrane depends on the type of Ca(v)beta subunits present

QoE-oriented resource efficiency for 5G two-tier cellular networks: A femtocaching framework

Video streaming applications and services (VASs) consume an enormous amount of scarce resources in mobile devices and cellular wireless networks due to the demand for high data rates of video streaming. The limited resource of wireless media and unreliable nature of wireless channels in cellular networks make VASs challenging to deliver videos at high quality of experience (QoE). Therefore, in this paper, we propose a femtocaching framework of QoE-oriented resource efficiency optimization for high performance of cooperative VASs over 5G two-tier cellular networks, where the collaboration between macro base stations (BSs) and femtocells are exploited to efficiently deliver videos to mobile users (MUs). Our proposed framework aims at solving two problems. The first problem is how to cache the videos in femtocells to minimize the bandwidth resource consumed at the BSs and wasted at femtocells while guaranteeing high hit rate and utilizing the available storage resource of femtocells. The second one is how to encode the videos into descriptions and assign them to each femtocell for transmission, so as to minimize the reconstructed distortion of received videos for high playback quality at the MUs. The simulation results are further provided to demonstrate the benefits of the proposed framework.Scopu

Quality of sustainability optimization design for mobile ad hoc networks in disaster areas

During a disaster, communication systems are partially (or completely) interrupted with very limited resources due to infrastructures destruction and hence the lack of essential services. Meanwhile, the demand for communication reaches its highest peak ever since users need to contact loved ones and make sure they are safe, inform first responders and local governments about surrounding conditions, and receive urgent instructions for safety and resilience. Rather than only high quality of service (QoS), the affected users now require high quality of sustainability (QoSus) of communications that are characterized by high response, interoperable and robust connections, high hit rate and delivery capacity of contents, and resource savings. In this paper, we therefore design a QoSuS model for Mobile Ad Hoc Networks (MANET) to reduce as much harm as possible when a disaster strikes. To this end, we propose optimization problems that we solve for high QoSus of MANET in three-tier cellular networks (i.e., macrocells, femtocells, and mobile devices). Our optimal results include a number of replicas of each cached content, a set of femtocells to cache the replicas, a set of cellular users to share their sub-channels with other mobile devices, and a set of relay nodes for mobile device-to-device communications. We further take into account the constraints of co-channel interference due to many simultaneous channel accesses, storage resource of femtocells, and energy resource of mobile devices, to efficiently gain high performance of solution. Simulation results demonstrate that our proposed solutions provide the best possible QoSus under such severe conditions. 2015 IEEE.Scopus2-s2.0-8496482087