Evaluating a cross-layer approach for routing in Wireless Mesh Networks

Routing in Wireless Mesh Networks is challenging due to the unreliable characteristics of the wireless medium. Traditional routing paradigms are not able to propose an efficient solution to this problem. Further, Gupta et al. demonstrated that the average throughput capacity per node of a wireless multi-hop network decreases as 1/n, where n is the number of nodes in the network. Recent studies have shown that a cross-layer approach is a promising solution to get closer to the theoretic throughput capacity bound. Cross-layer solutions have been already proposed either for specific TDMA/CDMA networks or for power-efficient routing protocols. These proposals are strongly MAC dependent, or suffer from targeting a steady state offering the best trade-off performance. In this paper, the problem we tackle in a more general context, disregarding the specific MAC and Physical layers technologies, can be formulated as follows: How to design a routing algorithm able to increase the average throughput capacity experienced by Wireless Mesh Networks? Starting from a theoretic result, we analyze the gain that a cross-layer approach can deliver, the metrics suitable to improve throughput capacity, and the power control policy that reduces interference. We take a MAC independent approach, focusing on the general characteristics of wireless links, targeting the improvement of throughput capacity in Wireless Mesh Networks. Our proposal performs path selection and power optimization based on three metrics, namely physical transmission rate, interference, and packet error rate. Performances are thoroughly analyzed and evaluated by extensive simulations, with both TCP and UDP traffic, and compared to other multi-hop routing protocols. For both kind of traffic, the simple heuristic we propose here allows to double the average throughput the network is able to route.     

Coupling of Carbon Dioxide with Epoxides Efficiently Catalyzed by Thioether‐Triphenolate Bimetallic Iron(III) Complexes: Catalyst Structure–Reactivity Relationship and Mechanistic DFT Study

A series of dinuclear iron(III)^I complexes supported by thioether‐triphenolate ligands have been prepared to attain highly Lewis acidic catalysts. In combination with tetrabutylammonium bromide (TBAB) they are highly active catalysts in the synthesis of cyclic organic carbonates through the coupling of carbon dioxide to epoxides with the highest initial turnover frequencies reported to date for the conversion of propylene oxide to propylene carbonate for iron‐based catalysts (5200 h⁻¹; 120 °C, 2 MPa, 1 h). In particular, these complexes are shown to be highly selective catalysts for the coupling of carbon dioxide to internal oxiranes affording the corresponding cyclic carbonates in good yield and with retention of the initial stereochemical configuration. A density functional theory (DFT) investigation provides a rational for the relative high activity found for these Fe(III) complexes, showing the fundamental role of the hemilabile sulfur atom in the ligand skeleton to promote reactivity. Notably, in spite of the dinuclear nature of the catalyst precursor only one metal center is involved in the catalytic cycle.

     

A distributed and multi‐tiered software architecture for assessing e‐Commerce recommendations

Recently, an ever increasing number of e‐Commerce tools has been made available that are able to help customers by generating purposed recommendations. Many of them are centralized so that they have to face problems related to efficiency and scalability. A few of them are distributed, but in this case, the complexity of the e‐Commerce process implies computation overhead on the client side, which is often unsuitable if mobile devices are used by customers. In this paper, we study how the software distribution in recommender systems affects their performances, depending on the characteristics of the e‐Commerce population. To this end, we present a distributed testbed architecture for e‐Commerce recommender systems using a multi‐tiered agent‐based approach to generate effective recommendations without requiring such an onerous amount of computation per single client. We use such a testbed to study the main advantages and limitations associated with the problem of distributing the computation of recommendations. Copyright © 2016 John Wiley & Sons, Ltd.     

Powder Injection Molding – An innovative manufacturing method for He-cooled DEMO divertor components

At Karlsruhe Institute of Technology (KIT), a He-cooled divertor design for future fusion power plants has been developed. This concept is based on the use of modular cooling fingers made from tungsten and tungsten alloy, which are presently considered the most promising divertor materials to withstand the specific heat load of 10 MW/m². Since a large number of the finger modules (n > 250,000) are needed for the whole reactor, developing a mass-oriented manufacturing method is indispensable. In this regard, an innovative manufacturing technology, Powder Injection Molding (PIM), has been adapted to W processing at KIT since a couple of years. This production method is deemed promising in view of large-scale production of tungsten parts with high near-net-shape precision, hence, offering an advantage of cost-saving process compared to conventional machining.The complete technological PIM process for tungsten materials and its application on manufacturing of real divertor components, including the design of a new PIM tool is outlined and, results of the examination of the finished product after heat-treatment are discussed. A binary tungsten powder feedstock with a solid load of 50 vol.% was developed and successfully tested in molding experiments. After design, simulation and manufacturing of a new PIM tool, real divertor parts are produced. After heat-treatment (pre-sintering and HIP) the successful finished samples showed a sintered density of approximately 99%, a hardness of 457 HV0.1, a grain size of approximately 5 μm and a microstructure without cracks and porosity.     

Advantage of redundancy in the controllability of remote handling manipulator

To carry out a variety of remote handling operations inside the ITER divertor a Water Hydraulic MANipulator (WHMAN) and its control system have been designed and developed at Tampere University of Technology. The manipulator is installed on top of Cassette Multifunctional Mover (CMM) to assist during the cassette removal and installation operations. While CMM is designed to carry heavy components such as cassettes through the service ducts relying on positioning accuracy and repeatability, WHMAN is designed to execute a mix of remote handling operations using position trajectories and master-slave telemanipulation. WHMAN is composed of eight joints: six rotational and two translational. Since a manipulator requires only six joints to acquire the desired position and orientation in operational-space, the two additional joints of WHMAN provide the redundant degrees of mobility. This paper presents how this redundancy of WHMAN can be an advantage to optimize the execution of remote handling tasks. The paper also discusses an effective way to practically exploit the redundancy. The results show that the additional degrees of freedom can be utilized to improve the dynamic behavior of the manipulator.     

New insights on the interaction mechanism between tau protein and oleocanthal, an extra-virgin olive-oil bioactive component

Oleocanthal (OLC) is a phenolic component of extra-virgin olive oil, recently supposed to be involved in the modulation of some human diseases, such as inflammation and Alzheimer. In particular, OLC has been shown to abrogate fibrillization of tau protein, one of the main causes of Alzheimer neurodegeneration. A recent interpretation of this mechanism has been attempted on the basis of OLC reactivity with the fibrillogenic tau hexapeptide VQIVYK and SDS-PAGE of OLC/tau incubation mixtures, suggesting that covalent modification events modulate tau fibrillization. In this paper we report a detailed mass spectrometric investigation of the OLC reactive profile with both tau protein fibrillogenic fragment K18 and propylamine in biomimetic conditions. We show that K18 is prone to be covalently modified by OLC through Schiff base formation between the ε-amino group of lysine residues and OLC aldehyde carbonyls. Moreover, as expected from its de-structured conformation, K18 shows a non-selective modification profile, reacting with several lysine residues to give cyclic pyridinium-like stable adducts. These data give new insights on the mechanism of inhibition of tau fibrillization mediated by OLC.     

Expression of Clementine Asp-Rich Proteins (CcASP-RICH) in Tobacco Plants Interferes with the Mechanism of Pollen Tube Growth

Low-molecular-weight, aspartic-acid-rich proteins (ASP-RICH) have been assumed to be involved in the self-incompatibility process of clementine. The role of ASP-RICH is not known, but hypothetically they could sequester calcium ions (Ca²⁺) and affect Ca²⁺-dependent mechanisms. In this article, we analyzed the effects induced by clementine ASP-RICH proteins (CcASP-RICH) when expressed in the tobacco heterologous system, focusing on the male gametophyte. The aim was to gain insight into the mechanism of action of ASP-RICH in a well-known cellular system, i.e., the pollen tube. Pollen tubes of tobacco transgenic lines expressing CcASP-RICH were analyzed for Ca²⁺ distribution, ROS, proton gradient, as well as cytoskeleton and cell wall. CcASP-RICH modulated Ca²⁺ content and consequently affected cytoskeleton organization and the deposition of cell wall components. In turn, this affected the growth pattern of pollen tubes. Although the expression of CcASP-RICH did not exert a remarkable effect on the growth rate of pollen tubes, effects at the level of growth pattern suggest that the expression of ASP-RICH may exert a regulatory action on the mechanism of plant cell growth.     

Carotenoid-Enriched Nanoemulsions and γ-Rays Synergistically Induce Cell Death in a Novel Radioresistant Osteosarcoma Cell Line

We previously demonstrated that SAOS human osteosarcoma cells, incubated with carotenoid-enriched nanoemulsions (CEN), activated a nonprotective form of autophagy and delayed cell proliferation. The present work focuses on the biological effects of CEN on a derivative of SAOS cells named SAOS400, recently described for their radiation resistance and higher expression of therapy-induced senescence (TIS) markers. SAOS400 cells, incubated with CEN, activated a “cytostatic” form of autophagy confirmed by cell cycle arrest in the G2/M phase and increased expression of autophagic proteins. Treatment of SAOS400 cells with CEN also resulted in decreased expression of the senescence marker p16^INK4. However, when SAOS400 cells were γ-irradiated in combination with CEN, the threshold for cell death was reached (>60% after 96 h). We showed that this type of cell death corresponded to ‘cytotoxic’ or ‘lethal’ autophagy and that the combined treatment of CEN plus γ-rays was synergistic, with the combination index < 1. Since CEN contained β-carotene, the pure compound was used in SAOS400 cells at the same concentration present in CEN and up to 10 times higher. However, no radio-sensitizing effect of β-carotene was observed, suggesting that the biological effect of CEN was due to less abundant but more bioactive molecules, or to the synergistic activity of multiple components present in the extracts, confirming the functional pleiotropy of natural extracts enriched in bioactive molecules.