Neighbor discovery in wireless networks: A multiuser-detection approach

The problem of determining which sensors are neighbors of a given one in a wireless network operating on a frequency-flat Gaussian channel is considered. While recent neighbor discovery (ND) algorithms operate at protocol level, the developed schemes exploit signal processing techniques to perform ND at physical layer. Similarly to the existing approaches, it is assumed that sensors transmit at random instants copy of the signature waveform associated to their identities. Borrowing techniques from multiuser detection, it turns out that the developed ND algorithms can handle multi-sensor interference environments where protocol level algorithms entail waste of energy due to packet collisions. A number of neighbor discovery algorithms based on different optimization criteria are introduced and analyzed. Numerical results show that reduced complexity algorithms can achieve a satisfactory performance.     

Light-induced transformation of alkylurea derivatives in aqueous TiO2 dispersion

The light-induced degradation of alkylurea derivatives under simulated solar irradiation has been investigated in aqueous solutions containing TiO(2) as a photocatalyst. Herein, we will focus on how the presence of one or more methyl (or ethyl) groups on urea modifies the kinetics of disappearance and influences both the ratio and the extent of the inorganic nitrogen formation caused by different degradation pathways. In the present work, we have elucidated a mechanism for the formation of transformation products of the alkyl derivatives by combining several analytical and spectroscopic procedures and the theoretical simulation of ab initio calculations. In all cases, N-demethylation represents only a secondary pathway, while the main transformation proceeds through an unexpected cyclization, involving (m)ethyl- and di(m)ethylureas with the formation of (methyl)amino-2,3-dihydro-1,2,4-oxadiazol-3-one as the principal intermediate of the reaction (with a yield of 60 %). This behaviour is rather unexpected and in contrast with the typical photocatalyzed transformation pathways, which proceed through the formation of more simple structures.     

On the nuclearity of certain Cuntz‐Pimsner algebras

In the present paper, we give a short proof of the nuclearity property of a class of Cuntz‐Pimsner algebras associated with a Hilbert ??‐bimodule ??, where ?? is a separable and nuclear C *‐algebra. We assume that the left ??‐action on the bimodule ?? is given in terms of compact module operators and that ?? is direct summand of the standard Hilbert module over ?? (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and properties of new potentially nonthrombogenic polymeric materials

A new family of block copolymers have been synthesized and characterized. These copolymers have a central block deriving from the polyaddition of N,N′-dimethylethylenediamine to 1,4-bis-acryloylpiperazine, and lateral blocks of polystyrene. Preliminary biocompatibility tests have demonstrated that these new products show promise as long-acting nonthrombogenic materials.     

About (k,n) stochastic matrices

We study extremals for multidimensional stochastic matrices. Some related results are also considered.     

Visible Light Induced Generation of Hydrogen from H2S in CdS-Dispersions,Hole Transfer Catalysis by RuO2

Illumination of US-dispersions by visible light in solutions containing H₂S or sulfide ions leads to efficient generation of hydrogen and sulfur. Very small quantities of RuO₂ deposited on the CdS-particles improve markedly the quantum yield of H₂-formation for which the optimum value obtained so far is ? = 0.35 ± 0.1. The effect of RuO₂ is attributed to catalysis of hole transfer from the valence band of CdS to H₂S or sulfide in solution.     

(E) and (Z)-α-hydroxy and α-methoxyimino-4-nitro-1H-imidazole-1-acetic acids and esters. Spectral properties,conformations and photoisomerization of the new compounds

Detailed experimental procedures are given for the preparation of the stereoisomeric (E)- and (Z)-methyl-α-hydroxy and α-methoxyimino-4-nitro-1H-imidazole-1-acetates and of the related acids. (Z)-Isomers have been prepared by synthesis. (E)-Isomers have been obtained only by photoisomerization. Decarboxylation of the acids left the corresponding aldehydes which are ideal compounds for structural studies and configurational assignments.     

Simultaneous kinetic determination of uric acid ascorbic acid mixtures

A kinetic stopped-flow method is described for the simultaneous determination of uric acid and ascorbic acid with tris (2,2'-bipyridine)iron(III). For the least favourable ratios of uric to ascorbic acid, in a total concentration of 10^-5 M, the error in the determination of uric acid is estimated at ±10%.     

Titrations of sulphonamides in cationic micellar systems

A titrimetric determination of some sulphonamides with 0.1 M sodium hydroxide in the presence of hexadecylpyridinium chloride is described. Potentiometric titrations are slow; visual titrations are satisfactory. The pK_a shift can be interpreted in the light of general micellar behaviour.