Free poset algebras and combinatorics of cones

In Free poset Boolean algebra F(P ), uniqueness of normal form of non-zero elements is proved and the notion of support of a non-zero element is, therefore, well defined. An Inclusion–Exclusion-like formula is given by defining, for each non-zero element x, using support of x ∈F(P ) in a very natural way.      

On the transformation of nonlinear dynamical systems into the extended nonlinear observable canonical form

This article deals with the transformation of a class of nonlinear systems into an extended nonlinear observable canonical form (ENOCF) by dynamic extension. The dynamic extension is obtained by adding auxiliary dynamics and virtual outputs to the original system, thus giving rise to a higher dimensional system in an extended state space. Sufficient geometrical conditions to guarantee the existence of a local diffeomorphism which allow the transformation of the extended system into the ENOCF are given. In particular, an algorithm that permits us to compute such a diffeomorphism is derived.     

Anisotropie des proprietes electriques de l'oxyde de fer Fe2O3α

The electrical conductivity and the thermoelectric power of trivalent iron oxide α-Fe₂O₃, studied in the crystallographic plane (001) and along the [001] axis, have shown typical anisotropic behaviour.In the same material, the existence of two electronic transitions at 2.14 and 2.50 eV respectively has been found after optical absorption measurements.At high temperature (T > 1020 K) the electrical conductivity has an essentially intrinsic origin, and is practically independent of the oxygen pressure, while the extrinsic contribution predominates below 720 K.According to the model developped for the interpretation of the above experimental results, the peculiar behaviour of the electrical conductivity results from variations in the mobility of the carriers, depending on the electronic levels they are likely to occupy. These levels were identified as the results of a split in the t_2g orbitals of iron under the influence of the rhombohedral. distortion of the crystal field.Furthermore, the anisotropy of mobility is strongly dependent on the magnetic order below Néel temperature.

Résumé

L'étude de la conductivité électrique et du pouvoir thermoélectrique de l'oxyde de fer Fe₂O₃α, effectuée selon la direction cristallographique [001] et dans le plan (001), a révélé une grande anisotropie de comportement. Sur le même matériau des mesures d'absorption optique ont montré l'existence de deux transitions électroniques, à 2,14 et 2,50 eV respectivement.Prenant en compte l'ensemble de ces résultats un modèle a été proposé pour expliquer les propriétés du matériau à diverses températures et sous différentes pressions partielles d'oxygène.A température élevée (T > 1020 K) la conductivité électrique, pratiquement indépendante de la pression d'oxygène, est à forte dominante intrinsèque. En revanche, à basse température (T < 720 K), la conductivité est d'origine extrinsèque.La diversité des mécanismes de conduction observés peut s'expliquer par l'existence de porteurs dont la mobilité varie suivant les niveaux d'énergie qu'ils occupent. Ces niveaux résultent de l'éclatement des orbitales t_2g du fer dû à la distorsion rhomboédrique du champ cristallin.Les mobilités anisotropes sont fortement affectées par l'ordre magnétique au-dessous de la température de Néel.     

Removal of metal ions in aqueous solutions by organic polymers: use of a polydiphenylamine resin

Adsorption of Ni(II), Cu(II), Zn(II), Pb(II) and Cd(II) ions on a polydiphenylamine resin prepared at a strongly oxidizing controlled potential of 3.2 V (vs. ECS) was studied in aqueous solutions. The optimum sorption conditions were determined. The optimum pH for the removal of metal ions was between 4 and 6 for Ni(II), 6 for Cu(II) and Pb(II) and 5 for Zn(II) and Cd(II). The total sorption capacity of the resin was 57.3 mg g⁻¹ for Ni(II), 23 mg g⁻¹ for Cu(II), 36.9 mg g⁻¹ for Zn(II), 19 mg g⁻¹ for Pb(II) and 24.5 mg g⁻¹ for Cd(II). The sorption capacity was compared with other conventional chelating polymers. The sorption kinetics was fairly rapid, as apparent from the loading half time (t_1/2) values, indicating a better accessibility of the chelating sites. The study of the selectivity of the metal ions in the binary solutions shows that the resin presents a higher affinity for the ions of nickel (II).     

Fluorescence spectroscopy of the longwave chlorophylls in trimeric and monomeric photosystem I core complexes from the cyanobacterium Spirulina platensis

The organization and interaction of chlorophylls (Chl) and the kinetics of the energy transfer in the core antenna of photosystem I (PSI) trimeric and monomeric complexes, isolated from Spirulina platensis with Triton X-100 have been studied by stationary and time-resolved fluorescence. At 295 K both complexes show an unusually intense long-wavelength emission band with prominent peaks at 730 nm (trimers) or 715 nm (monomers), whose intensity is independent of the redox state of P700. A broad band extending from 710 to 740 nm in the absorption and fluorescence excitation spectra of trimers also indicates the existence of the longwave Chls at 295 K. The 77 K fluorescence emission of PSI trimers frozen after addition of dithionite under illumination (P700 and the PSI acceptor side reduced) shows an intense band at 760 (F760) and a smaller one at 725 nm (F725); when P700 is oxidized, the intensity of F760 decreases about 15 times. In the 77 K spectrum of monomers only F725 is present in the longwave region, and its intensity does not depend on the redox state of P700. Bands of Chls with maxima near 680, 710, and 738 nm were found in the 77 K excitation spectrum of trimers, and bands near 680 and 710 nm were seen in the spectrum of monomers. Five spectrally different red Chl forms in PSI trimers and three red Chl in monomers have been resolved by deconvolution of their 77 K absorption spectra. The difference absorption spectrum, trimers-minus-monomers, shows that the appearance of the 735 nm band in trimers is accompanied by a decrease of 708, 698, and 688 nm bands present in monomers. The reversible changes of F760 intensity of Spirulina membranes as a result of their salt treatment confirm the idea that the most longwave Chl form originates from an interaction of Chls bound to different monomeric PSI subunits forming the trimer. The time-resolved fluorescence spectra of PSI trimers and monomers, measured at 287 K in the region 680-770 nm, are substantially different, although a set of similar lifetimes (9, approximately 30, approximately 66, and 1400-2200 ps) was necessary for a good fit. No effect of P700 redox state was observed on the fluorescence kinetics of both complexes at 287 K.     

Incidence structures and Stone–Priestley duality

We observe that if R: = (I,ρ, J) is an incidence structure, viewed as a matrix, then the topological closure of the set of columns is the Stone space of the Boolean algebra generated by the rows. As a consequence, we obtain that the topological closure of the collection of principal initial segments of a poset P is the Stone space of the Boolean algebra Tailalg (P) generated by the collection of principal final segments of P, the so-called tail-algebra of P. Similar results concerning Priestley spaces and distributive lattices are given. A generalization to incidence structures valued by abstract algebras is considered.      

A DNA microarray for fission yeast: minimal changes in global gene expression after temperature shift

Completion of the fission yeast genome sequence has opened up possibilities for post-genomic approaches. We have constructed a DNA microarray for genome-wide gene expression analysis in fission yeast. The microarray contains DNA fragments, PCR-amplified from a genomic DNA template, that represent > 99% of the 5000 or so annotated fission yeast genes, as well as a number of control sequences. The GenomePRIDE software used attempts to design similarly sized DNA fragments corresponding to gene regions within single exons, near the 3'-end of genes that lack homology to other fission yeast genes. To validate the design and utility of the array, we studied expression changes after a 2 h temperature shift from 25 degrees C to 36 degrees C, conditions widely used when studying temperature-sensitive mutants. Obligingly, the vast majority of genes do not change more than two-fold, supporting the widely held view that temperature-shift experiments specifically reveal phenotypes associated with temperature-sensitive mutants. However, we did identify a small group of genes that showed a reproducible change in expression. Importantly, most of these corresponded to previously characterized heat-shock genes, whose expression has been reported to change after more extreme temperature shifts than those used here. We conclude that the DNA microarray represents a useful resource for fission yeast researchers as well as the broader yeast community, since it will facilitate comparison with the distantly related budding yeast, Saccharomyces cerevisiae. To maximize the utility of this resource, the array and its component parts are fully described in On-line Supplementary Information and are also available commercially.     

Energy-efficient joint video encoding and transmission framework for WVSN

Multimedia Tools and Applications - In this paper, we propose an energy-efficient joint video encoding and transmission framework for network lifetime extension, under an end-to-end video quality...     

Carrier sense aware multipath geographic routing protocol

Over the last few years, wireless sensor networks have become a great field of interest for the scientific community. This novel kind of network provides an array of applications for different aspects of human life. To give a satisfying performance to the final user, the wireless sensor networks must ensure the quality of service. The use of multipath technique was widely applied in the literature. Nevertheless, there might be a problem if the interference issues are not taken into account by the multipath routing design. In this paper, we propose a novel multipath routing protocol called Carrier Sense Aware Multipath Geographic Routing protocol (CSA‐MGR). This protocol creates multiple paths while avoiding any shared carrier sense range by using a distributed and dynamic process. In addition, the CSA‐MGR employs a new metrics named the Number of Common Neighbors to guarantee a faster and an efficient path construction. Simulations conducted over the NS‐2 simulator show promising results in terms of delay, Packet Delivery Ratio and routing overhead. The performance gain of CSA‐MGR in terms of delay is up to 275% compared with the Two‐Phase geographical Greedy Forwarding and up to 565% compared with the ad hoc on‐demand multipath distance vector. For the Packet Delivery Ratio, the performance gain of CSA‐MGR is up to 16% compared with the Two‐Phase geographic Greedy Forwarding and up to 28% compared with the ad hoc on‐demand multipath distance vector. Copyright © 2015 John Wiley & Sons, Ltd.     

Iron(III) and Cobalt(III) Complexes with Oxalate and Phenanthroline: Synthesis,Crystal Structure,Spectroscopy Properties and Magnetic Properties

We report herein the synthesis and physicochemical characterization of two mixed-ligand complexes of the following stoichiometric formulae: [Fe(phen)₂(ox)](NO₃)?2H₂O (1) and [Co(phen)₂(ox)](NO₃)?4H₂O (2) (as phen: 1,10-orthophenanthroline; ox: oxalate dianion). Both compounds have been prepared by slow evaporation at room temperature and characterized by single-crystal X-ray diffraction. They have been characterized by IR and UV–Vis spectra and thermoanalysis (TG and DTA) The structures of these compounds are highly symmetric. Indeed, the two compounds are isomorphous and crystallize in the orthorhombic space group Ibca. In each material, the M^III ion has a slightly distorted square bipyramidal environment, coordinated by one oxalate ion and two 1,10-orthophenanthroline ligands. Structural cohesion is established essentially by π–π interactions between the rings of phen groups and intermolecular O–H…O hydrogen bonds connecting the ionic entities and uncoordinated water molecules. Magnetic susceptibility measurements of (1) in the range 5–300 K exhibit paramagnetic behavior at high temperature. However, at low temperature, the magnetic data show the occurrence of weak antiferromagnetic intermolecular interactions between the local spins.