Finding hypernetworks in directed hypergraphs

The term “hypernetwork” (more precisely, s-hypernetwork and (s, d)-hypernetwork) has been recently adopted to denote some logical structures contained in a directed hypergraph. A hypernetwork identifies the core of a hypergraph model, obtained by filtering off redundant components. Therefore, finding hypernetworks has a notable relevance both from a theoretical and from a computational point of view.     

The Well-Posedness Issue in Sobolev Spaces for Hyperbolic Systems with Zygmund-Type Coefficients

In this paper we study the well-posedness of the Cauchy problem for first order hyperbolic systems with constant multiplicities and with low regularity coefficients depending just on the time variable. We consider Zygmund and log-Zygmund type assumptions, and we prove well-posedness in H^∞ respectively without loss and with finite loss of derivatives. The key to obtain the results is the construction of a suitable symmetrizer for our system, which allows us to recover energy estimates (with or without loss) for the hyperbolic operator under consideration. This can be achievied, in contrast with the classical case of systems with smooth (say Lipschitz) coefficients, by adding one step in the diagonalization process, and building the symmetrizer up to the second order.     

Free and forced linear dynamics of a homogeneous model for beam-like structures

A homogeneous shear beam model is used here to address the free and forced dynamic behavior of a multi-story building. After a brief recall of the model, which is taken from the literature, and the hypotheses on which it is grounded, discussion on the free dynamics is carried out, highlighting the intriguing organization of the natural frequencies and modes in triplets, as functions of the wave-number. Then, the properties of the undamped and proportionally damped forced response to external loads is evaluated, and a discussion on the effects of the tip mass related to the top story is addressed. A case-study is analyzed to show the reliability of the homogeneous model, after comparing the outcomes with those provided by F.E.M. procedures applied to the corresponding multi-d.o.f. structure.

     

Toward scale‐free like behavior under increasing cognitive load

To understand how cognition and response selection processes might emerge from dynamic brain systems, we analyzed reaction times during the performance of both a working memory task and a choice reaction time task at different levels of “cognitive load.” Our findings suggest a continuous transition—tuned by load—from random behavior toward scale‐free like behavior as an expanding connectivity process in a network poised near a critical point. © 2012 Wiley Periodicals, Inc. Complexity, 2012     

Analytical application of carbon nanotubes,fullerenes and nanodiamonds in nanomaterials-based chromatographic stationary phases: A review

An overview of the most significative results so far attained in the application of carbon nanotubes, fullerenes and nanodiamonds as chromatographic separation media is presented. In particular, the authors focus on their use in capillary and packed-column gas chromatography, in high performance liquid chromatography and capillary electrochromatography, paying also attention to recently developed stationary phases for fast chromatography and nanochromatography. The performance of the nanomaterials is compared to that of planar and amorphous carbon sorbents and critically discussed in regard to retentive capability and selectivity. A wide part of this review is devoted to the most recent improvements achieved in terms of selectivity by use of functionalized nanotubes and by combination of carbon nanotubes with ionic liquids. Practical aspects of synthetic procedures in preparing novel stationary phases in relationship with their chromatographic behaviour are also commented.     

Part mass and shrinkage in micro injection moulding: Statistical based optimisation using multiple quality criteria

Purpose

The aim of this paper is to optimise process conditions in micro injection moulding (μ−IM) to minimise shrinkage whilst maximising part mass.

Method

A Design of Experiment (DoE) approach was implemented for studying the effect of five processing parameters on shrinkage and part mass. A multiple quality criteria based analysis was used to optimise the process.

Results

Significant factors were found for shrinkage and part mass.

Conclusions

The multiple quality criteria could be optimized, and this optimization validated experimentally.     

VO2+ complexation by bioligands showing keto-enol tautomerism: a potentiometric, spectroscopic, and computational study

The interaction of VO(2+) ion with ligands of biological interest that are present in important metabolic pathways--2-oxopropanoic acid (pyruvic acid, pyrH), 3-hydroxy-2-oxopropanoic acid (3-hydroxypyruvic acid, hydpyrH), oxobutanedioic acid (oxalacetic acid, oxalH(2)), (S)-hydroxybutanedioic acid (l-malic acid, malH(2)), and 2,3-dihydroxy-(E)-butanedioic acid (dihydroxyfumaric acid, dhfH(2))--was described. Their complexing capability was compared with that of similar ligands: 3-hydroxy-2-butanone (hydbut) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (squaric acid, squarH(2)). All of these ligands (except l-malic acid) exhibit keto-enol tautomerism, and the presence of a metal ion can influence such an equilibrium. The different systems were studied with electron paramagnetic resonance (EPR) and UV-vis spectroscopies and with pH potentiometry. Density functional theory (DFT) methods provide valuable information on the relative energy of the enol and keto forms of the ligands both in the gas phase and in aqueous solution, on the geometry of the complexes, and on EPR and electronic absorption parameters. The results show that most of the ligands behave like α-hydroxycarboxylates, forming mono- and bis-chelated species with (COO(-), O(-)) coordination, demonstrating that the metal ion is able to stabilize the enolate form of some ligands. With dihydroxyfumaric acid, the formation of a non-oxidovanadium(IV) complex, because of rearrangement of dihydroxyfumaric to dihydroxymaleic acid (dhmH(2)), can be observed. With 3-hydroxy-2-butanone and 3,4-dihydroxy-3-cyclobutene-1,2-dione, complexation of VO(2+) does not take place and the reason for this behavior is explained by chemical considerations and computational calculations.