Solving multi-metric network problems: An interplay between idempotent semiring rules

We motivate computations in a multifunctional networked system as instances of algebraic path problems on labeled graphs. We illustrate, using examples, that composition operators used in many function computations in a networked system follow semiring axioms. We present an abstract framework, using a special idempotent semiring algebraic path problem, to handle multiple metrics for composition. We show that using different vector order relations in this abstract framework, we can obtain different rules of compositions such as Pareto, lexicographic and max-order efficiency. Under this framework, we identify a class of tractable composition rules that can be solved in different multi-criteria settings at affordable computational cost. We demonstrate using an example of trusted routing in which logical security rules of admission control can be combined with delay performance metrics in the multi-criteria optimization framework.     

Aza-Nazarov cyclization cascades

Benzamides with tethered acetal groups undergo reactions in CF₃SO₃H to give ring-fused isoindolinones by a cyclization cascade. The reaction initially forms an N-acyliminium ion which then gives the isoindolinone by the aza-Nazarov reaction. An unusual variant also cyclizes at the allylic position.     

Synthesis,spectroscopic studies and biological screening of 18-membered octaazamacrocyclic complexes derived from acetonylacetone and thiocarbohydrazide

A series of the macrocyclic complexes is synthesized by condensation of acetonylacetone and thiocarbohydrazide in the presence of divalent metal salts in the methanolic medium. The complexes are of the type: [M(TML)X₂] where, M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); X = Cl⁻ CH₃COO⁻ and TML is a tetradentate macrocyclic ligand. The complexes have been characterized with the help of various physicochemical techniques like elemental analyses, conductance measurements, magnetic measurements, NMR, infrared and electronic spectral studies. The low value of molar conductance indicates them to be non-electrolyte. On the basis of various studies a distorted octahedral geometry may be proposed for all the complexes. All the synthesized metal complexes were also tested for their in vitro antibacterial activities against some bacterial strains. The results obtained were compared with standard antibiotic: Ciprofloxacin. Some of the tested complexes shows good antibacterial activities against some bacterial strains.     

New Molybdaborane Clusters with a Bridged Phosphido Ligand

Abstract  

Treatment of [Cp*MoCl₄], 1 (Cp* = η⁵-C₅Me₅), with [LiBH₄.thf] in toluene at −40 °C, followed by thermolysis with [(thf)Li{CH(PPh₂–BH₃)₂}] results in the formation of a new class of phosphido bridged molybdaborane [(Cp*Mo)₂B₄H₇(μ-PPh₂)], 2 which has been characterized crystallographically. In addition, the above reaction also produces known [(Cp*Mo)₂B₅H₉], 3 and an unusual molybdaborane [(Cp*Mo)₂B₅H₈(O ⁱ Pr)], 4 ( ⁱ Pr = –CH(CH₃)₂). All the new compounds have been characterized in solution by ¹H, ¹¹B, ¹³C, ³¹P NMR spectroscopy and the structural types were unambiguously established by X-ray crystallographic analysis of compounds 2 and 4.     

Polymeric stabilization of hybrid nanocomposites: a comparison between in situ and ex situ-grown CuInS2 in poly(3-hexylthiophene) polymer

CuInS₂ (CIS) particles were directly synthesized in P3HT matrix with different concentrations ratio of P3HT and CIS (1:2, 1:4, and 1:8) by decomposition of copper indium xanthate (CIX). Here, copper indium xanthate and P3HT were mixed homogeneously in o-dichlorobenzene (DCB), which induced the formation of the CIS nanoparticles by the thermal decomposition of the precursor compound in situ at temperatures as low as 110 °C. The effects of the precursor concentration on the size of the CIS nanoparticles was studied by microstructure investigations (TEM, AFM, XRD) and UV–vis measurements show that these CIS composites possess a direct bandgap energy higher than 1.45 eV depending on the concentration of P3HT. PL quenching of P3HT polymer (i.e., higher accessible fraction of fluorophores) was found to be more for in situ rather than ex situ conditions for comparable CIX concentrations or particle size. This can be attributed to the fact that in in situ synthesis, P3HT act as surface directing template for CIS nanoparticles which is not so in the case of ex situ synthesis. Due to this, the polymeric stabilization of the CIS nanocomposites is better realized for in situ synthesis as compared to ex situ synthesis.     

Synthesis and Characterization of Functionalized Polyaniline Having Methyl Violet as Pendant Groups

Methyl violet–substituted polyaniline is prepared by oxidative polymerization of aniline in an aqueous acidic media using tosic acid as dopant and ammonium persulphate as oxidant. Substitution of methyl violet (dye moieties) on polyaniline backbone takes place in the presence of butyl lithium. The structures of methyl violet–substituted polyanilinewas elucidated by Fourier transform infrared (FT-IR), fluorescence spectra, XRD and differential scanning calorimetery (DSC). Molecular weight is determined by gel permeation chromatography (GPC) and viscosity method. Conductivity and band gap of methyl violet–substituted polyaniline was computed by a two-probe conductometer.     

New 1,8-naphthyridine-based probes for the selective fluorescence signalling of toxic cadmium: synthesis,photophysical studies and molecular modelling

Newly synthesised 1,8-naphthyridine-based molecular probes, NAP-1 and NAP-2, exhibit highly selective fluorescence responses towards the toxic cadmium over coordinatively competing Zn²⁺ and several other metal ions examined. On the one hand, NAP-1 (MeOH:H₂O, v/v 80:20, pH 7.4) exhibits ca. 1.5 order of magnitude higher stability constant for Cd²⁺ over Zn²⁺; on the other hand, NAP-2 in MeOH offers unique selectivity only towards Cd²⁺, exhibiting both absorbance and emission red shifts as well as fluorescence enhancement. By ¹H NMR analysis, the tetra-coordinated binding is indicated at least for the NAP-1+Cd²⁺ complex and theoretical calculations reveal relatively stronger binding of Cd²⁺ over Zn²⁺.

     

Spectral,Antimicrobial, and Thermal Studies of Some Transition Metal Complexes Derived from Bidentate Ligands Containing N and S Donor Atoms

Abstract

Bidentate ligands have been synthesized by the reaction of 2,4-dichlorobenzaldehyde with 4-amino-5-mercapto-1,2,4-triazole and 4-amino-5-mercapto-3-propyl-1,2,4-triazole. The ligands react with acetates of Co(II), Ni(II), Cu(II), and Zn(II) to yield 1:2 [metal:ligand] complexes. The newly synthesized compounds were characterized by elemental analyses, spectral (UV-Vis, IR, ¹H NMR, fluorescence, ESR) studies, thermal techniques, and magnetic measurements. Thermal studies of the complexes showed a multistep decomposition pattern. A square planar geometry for Cu(II) and octahedral geometry for Co(II), Ni(II), and Zn(II) complexes have been proposed. The synthesized complexes exhibit enhanced antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Aspergillus niger, and A. flavus compared to parent ligands. However, tested compounds did not exhibit any activity against Escherichia coli and Pseudomonas aeruginosa.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Particle swarm optimization based network selection in heterogeneous wireless environment

Deployment of heterogeneous wireless networks is spreading throughout the world as users want to be connected anytime, anywhere, and anyhow. Meanwhile, users are increasingly interested in multimedia applications such as audio, video streaming and Voice over IP (VoIP), which require strict Quality of Service (QoS) support. Provisioning of Always Best Connected (ABC) network with such constraints is a challenging task. Considering the availability of various access technologies, it is difficult for a network operator to find reliable criteria to select the best network that ensures user satisfaction while reducing multiple network selection. Designing an efficient Network selection algorithm, in this type of environment, is an important research problem. In this paper, we propose a novel network selection algorithm utilizing signal strength, available bit rate, signal to noise ratio, achievable throughput, bit error rate and outage probability metrics as criteria for network selection. The selection metrics are combined with PSO for relative dynamic weight optimization. The proposed algorithm is implemented in a typical heterogeneous environment of EDGE (2.5G) and UMTS (3G). Switching rate of the user between available networks has been used as the performance metric. Moreover, a utility function is used to maintain desired QoS during transition between networks, which is measured in terms of the throughput. It is shown here that PSO based approach yields optimal network selection in heterogeneous wireless environment.     

Network selection algorithm based on link quality parameters for heterogeneous wireless networks

Next generation wireless networks consist of heterogeneous access technologies. In order to provide global ubiquitous communication, it is required to provide a framework in which user can move across multiple access interfaces while maintaining its ongoing communication at perceived quality of service. Given the scenario of multiple access networks, it is further required to select the optimum network out of multiple candidate networks to meet the requirements of the ongoing session. The selection of optimum network in such heterogeneous environment is generally based on network conditions and user preference. In this paper, we propose an algorithm for network selection based on averaged received signal strength, outage probability and distance. The proposed algorithm comprises of two stages. Assuming that network conditions are dominant in network selection, in first stage, overlapping region is identified through distance estimation. Network selection algorithm based on averaged received signal strength plus outage is invoked in second stage to select the optimum network. Numerical results are obtained through a simulation model of two disparate networks – GSM and UMTS. It has been shown that the proposed algorithm offers 68% improved performance in terms of network selection rate.