Stress integration procedures for a biaxial isotropic material model of biological membranes and for hysteretic models of muscle fibres and surfactant

Stress calculation for a biaxial isotropic material model of a biological membrane and for hysteretic models of muscle fibres and surfactant is presented in the paper. The non‐linear elastic membrane model is defined by uniaxial and biaxial stress–stretch relations, while the hysteretic models of tissue fibres and surfactant are described by the stress–stretch and surface tension–surfactant area ratio constitutive relationships, respectively. The conditions when tissue is or is not covered by surfactant are considered. It is assumed that the material is subjected to cyclic loading. Quasi‐static and steady conditions are considered. The models are implemented in large strain finite element incremented‐iterative analysis of shell deformations. Numerical examples demonstrate characteristics of the computational procedures and structural response of biological membranes when subjected to cyclic loading. Hysteretic response of biological membranes subjected to cyclic loading is caused by hysteresis of fibres and hysteresis of surfactant. The hysteretic effects may play an important role in the physiology of human body. Copyright © 2006 John Wiley & Sons, Ltd.     

Urinary volatile profiles of pine vole,Microtus pinetorum,and their endocrine dependency

The volatile compounds identified by combined gas chromatography-mass spectrometry inMicrotus pinetorum urine include alcohols, aldehydes, hydrocarbons, ketones, nitriles, and pyrazines. Several lactone derivatives were found to be characteristic urinary substances of this species. Ovariectomy depressed concentrations of only five out of a great number of profile constituents. Elevating estrogen levels (by exposing females to male-soiled bedding or treating them with estradiol) tends to depress the urinary concentration of a number of selected volatiles. Estrogen implantation provoked a periodic increase in the level of three compounds (nonanal, benzal-dehyde, and an unidentified substance). The volatile profile of castrate male urine was similar to that of intact male urine. Female urine contained -octanoic lactone and two pyrazine derivatives in higher concentrations andp-methyI-propenylbenzene in a lower concentration, when compared to male urine. No qualitative differences between the urinary profiles of males and females were observed.     

Sunlight-proof optical distance measurements with a dual-line lock-in time-of-flight sensor

This work describes time-of-flight distance measurements with a line sensor based on the correlation principle. It is capable of suppressing maximum bright sunlight and even more electronically in each pixel autonomously without using any optical filters. The optical fill factor of a pixel is 58% embodying a 100 × 100 μm2 photodiode. Working principle of the pixel circuit and the mechanism for suppression of ambient illumination as well as physical limitation of accuracy are discussed. Characterizations of the single-pixel performance with 650 nm laser and 850 nm LED sources with optical output powers of 1 mW and 900 mW, respectively, are presented. Finally, measured characteristics of the line sensor for distances up to 3.2 m are shown. The standard deviation is below 2 cm up to 1.2 m at a measurement time of 50 ms per distance point and the near-infrared LED illumination.     

Performance analysis of LoRa in the 2.4 GHz ISM band: coexistence issues with Wi-Fi

Telecommunication Systems - Within realization of the visions of the Internet-of-Things (IoT), Low Power Wide Area Networks (LPWANs) are undoubtedly one of the fields that attract high interest...     

Ambient Protection of Few‐Layer Black Phosphorus via Sequestration of Reactive Oxygen Species

Few‐layer black phosphorous (BP) has emerged as a promising candidate for next‐generation nanophotonic and nanoelectronic devices. However, rapid ambient degradation of mechanically exfoliated BP poses challenges in its practical deployment in scalable devices. To date, the strategies employed to protect BP have relied upon preventing its exposure to atmospheric conditions. Here, an approach that allows this sensitive material to remain stable without requiring its isolation from the ambient environment is reported. The method draws inspiration from the unique ability of biological systems to avoid photo‐oxidative damage caused by reactive oxygen species. Since BP undergoes similar photo‐oxidative degradation, imidazolium‐based ionic liquids are employed as quenchers of these damaging species on the BP surface. This chemical sequestration strategy allows BP to remain stable for over 13 weeks, while retaining its key electronic characteristics. This study opens opportunities to practically implement BP and other environmentally sensitive 2D materials for electronic applications.     

Hop count optimal position-based packet routing algorithms for ad hoc wireless networks with a realistic physical Layer

Existing routing and broadcasting protocols for ad hoc networks assume an ideal physical layer model. We apply the log-normal shadow fading model to represent a realistic physical layer and use the probability p(x) for receiving a packet successfully as a function of distance x between two nodes. We define the transmission radius R as the distance at which p(R)=0.5. We propose a medium access control layer protocol, where receiver node acknowledges packet to sender node u times, where u*p(x)/spl ap/1. We derived an approximation for p(x) to reduce computation time. It can be used as the weight in the optimal shortest hop count routing scheme. We then study the optimal packet forwarding distance to minimize the hop count, and show that it is approximately 0.73R (for power attenuation degree 2). A hop count optimal, greedy, localized routing algorithm [referred as ideal hop count routing (IHCR)] for ad hoc wireless networks is then presented. We present another algorithm called expected progress routing with acknowledgment (referred as aEPR) for ad hoc wireless networks. Two variants of aEPR algorithm, namely, aEPR-1 and aEPR-u are also presented. Next, we propose projection progress scheme, and its two variants, 1-Projection and u-Projection. Iterative versions of aEPR and projection progress attempt to improve their performance. We then propose tR-greedy routing scheme, where packet is forwarded to neighbor closest to destination, among neighbors that are within distance tR. All described schemes are implemented, and their performances are evaluated and compared.     

Sparse structures for searching and broadcasting algorithms over internet graphs and peer-to-peer computing systems

In a broadcasting problem, a message is sent from a source to all the other nodes in the network. Blind flooding is a classical mechanism for broadcasting, where each node retransmits received message to all its neighbors. Despite its important advantages, an increase in the number of requests or the network size or density produces communication overheads that limit the scalability of blind flooding, especially in networks with dynamic topologies. Theoretically optimal solution is based on minimal spanning trees (MST), but its construction is expensive. We discuss here protocols based on local knowledge and newly proposed sparse structures. In weighted RNG (Relative Neighborhood Graph), messages are forwarded only on links which are not the ‘longest’ in any triangle. In weighted RNGQ, messages are forwarded to links which are not the longest in any triangle or quadrangle. Each node constructs weighted MST based on its 2-hop knowledge. Weighted LMST (Localized LMST) preserves only edges that are selected by both endpoints, and messages are forwarded on these links. Any available metric, such as delay, reliability, reputation etc. can be used as weight. Analysis and simulation show that weighted RNG performs better than existing Flooding and Rumor Mongering (or Gossip) schemes. The parameterless weighted LMST, MST, RNG and RNGQ (RNG over Quadrangle) based broadcasting schemes are compared, showing overall advantage for LMST. We also hint that a number of existing protocols can be simplified by applying concept from this article.