ECRP: an energy-aware cluster-based routing protocol for wireless sensor networks

Energy conservation is the main issue in wireless sensor networks. Many existing clustering protocols have been proposed to balance the energy consumption and maximize the battery lifetime of sensor nodes. However, these protocols suffer from the excessive overhead due to repetitive clustering resulting in high-energy consumption. In this paper, we propose energy-aware cluster-based routing protocol (ECRP) in which not only the cluster head (CH) role rotates based on energy around all cluster members until the end of network functioning to avoid frequent re-clustering, but also it can adapt the network topology change. Further, ECRP introduces a multi-hop routing algorithm so that the energy consumption is minimized and balanced. As well, a fault-tolerant mechanism is proposed to cope up with the failure of CHs and relay nodes. We perform extensive simulations on the proposed protocol using different network scenarios. The simulation results demonstrate the superiority of ECRP compared with recent and relevant existing protocols in terms of main performance metrics.

     

Electronic and Magnetic Properties of Os-Doped Rhodium Clusters: a Theoretical Study

The stability and electronic and magnetic properties of Rh_nOs (n=?2–12) clusters in their most stable configurations were systematically studied by using density functional theory (DFT) at M06L/aug-cc-pVDZ level. Calculation of the second-order difference of energies and fragmentation energies exhibited that Rh₃Os, Rh₅Os, Rh₇Os, and Rh₉Os clusters are more stable than any other clusters. The calculated HOMO-LUMO energy gaps of the Rh_nOs clusters are found to be in the range of 0.018 to 0.299 eV, implying that the metallic behavior can appear in these clusters. Accordingly, the Rh_nOs clusters can be employed as heterogeneous nanocatalysts in many chemical reactions. The local Fukui function (\(f_{k}^{-} )\) has also been calculated, and the obtained results reveal that the highest \(f_{k}^{-} \) values are predicted for the Rh atoms. Therefore, the Rh atoms in the clusters are considered the most reactive sites that undergo reactions with electrophilic reagents. The analysis of the magnetic properties of the Rh_nOs clusters shows that the total magnetic moment per atom of these clusters varies from 0.67 to 1.75 µ_B/atom. And, the PDOS analysis reveals that the d orbitals play a crucial role for the magnetism of the Rh_nOs clusters, and the contribution of the s and p orbitals is small.     

IARP: An Intelligent ACO-Based Routing Protocol with Multiple Mobile Sinks Support for Wireless Sensor Networks

Wireless Personal Communications - Using a single fixed sink in wireless sensor networks (WSNs) creates the hotspot problem. Recently, the mobile sink technique is considered as a good solution to...     

Static Ferromagnetic Modulation Revealed by Neutron Scattering in La1−xCaxMnO3

Mn perovskites La_1?x Ca _x MnO₃ (0≤x0.1) have been studied by small angle neutron scattering (SANS) and “elastic” neutron scattering (ESANS). At low temperature, both experiments reveal a broad modulation centered at the same q _m whatever the q direction. This scattering pattern is typical of a liquid-like distribution of similar magnetic droplets, or large magnetic polarons.     

Lysophosphatic acid modulates prostaglandin secretion in the bovine uterus

Lysophosphatidic acid (LPA) modulates prostaglandin (PG) synthesis via LPA receptor 3 (LPAR3) in the murine endometrium. The lack of functional LPAR3 in mice may lead to embryo mortality. In the present study, we examined the role of LPA in the bovine uterus. We confirmed that LPA is locally produced and released from the bovine endometrium. Moreover, there are enzymes involved in LPA synthesis (phospholipase (PL) D(2) and PLA2G1B) in the bovine endometrium during estrous cycle and early pregnancy. Expression of the receptor for LPA (LPAR1) was positively correlated with the expression of PGE(2) synthase (PGES) and negatively correlated with the expression of PGF(2alpha) synthase (aldose reductase with 20 alpha-hydroxysteroid dehydrogenase activity - PGFS) during early pregnancy. In vivo LPA induced P4 and PGE(2) secretion was inhibited by LPAR1 antagonist (Ki16425). The overall results indicate that LPA is locally produced and released from the bovine endometrium. Moreover, LPAR1 gene expression in the endometrium during the estrous cycle and early pregnancy indicates that LPA may play autocrine and/or paracrine roles in the bovine uterus. LPAR1 gene expression is positively correlated with the expression of the enzyme responsible for luteotropic PGE(2) production (PGES) in endometrium. In cow, LPA stimulates P4 and PGE(2) secretion. Thus, LPA in the bovine reproductive tract may indirectly (via endometrium) or directly support corpus luteum action via the increase of P4 synthesis and the increase of PGE(2)/PGF(2)(alpha) ratio. It suggests that LPA may serve as an important factor in the maintenance of early pregnancy in cow.     

Highly efficient electron field emission from graphene oxide sheets supported by nickel nanotip arrays

Electron field emission is a quantum tunneling phenomenon whereby electrons are emitted from a solid surface due to a strong electric field. Graphene and its derivatives are expected to be efficient field emitters due to their unique geometry and electrical properties. So far, electron field emission has only been achieved from the edges of graphene and graphene oxide sheets. We have supported graphene oxide sheets on nickel nanotip arrays to produce a high density of sharp protrusions within the sheets and then applied electric fields perpendicular to the sheets. Highly efficient and stable field emission with low turn-on fields was observed for these graphene oxide sheets, because the protrusions appear to locally enhance the electric field and dramatically increase field emission. Our simple and robust approach provides prospects for the development of practical electron sources and advanced devices based on graphene and graphene oxide field emitters.     

Reconstructing the flight kinematics of swarming and mating in wild mosquitoes

We describe a novel tracking system for reconstructing three-dimensional tracks of individual mosquitoes in wild swarms and present the results of validating the system by filming swarms and mating events of the malaria mosquito Anopheles gambiae in Mali. The tracking system is designed to address noisy, low frame-rate (25 frames per second) video streams from a stereo camera system. Because flying A. gambiae move at 1–4 m s⁻¹, they appear as faded streaks in the images or sometimes do not appear at all. We provide an adaptive algorithm to search for missing streaks and a likelihood function that uses streak endpoints to extract velocity information. A modified multi-hypothesis tracker probabilistically addresses occlusions and a particle filter estimates the trajectories. The output of the tracking algorithm is a set of track segments with an average length of 0.6–1 s. The segments are verified and combined under human supervision to create individual tracks up to the duration of the video (90 s). We evaluate tracking performance using an established metric for multi-target tracking and validate the accuracy using independent stereo measurements of a single swarm. Three-dimensional reconstructions of A. gambiae swarming and mating events are presented.     

Properties of InAs grown on misoriented GaAs substrates by atmospheric pressure metal–organic vapor phase epitaxy

InAs epilayers were grown by atmospheric pressure metal–organic vapor phase epitaxy on GaAs (1 0 0) exactly oriented substrates and misoriented by 2° and 10° toward [1 1 1]A. The layers had varying thicknesses and were deposited under the same growth conditions. Atomic force microscopy analysis show that surface morphology depends on surface misorientation and presents a low root mean square. High resolution X-ray diffraction analysis and Hall effect measurements were preformed to check the substrate misorientation effect on the crystalline quality and electrical properties respectively.