On the sum of two N0-matrices

In this paper, we study the Fan product of two N₀-matrices and inequalities for two N₀-matrices A,B with A ≤ B. Necessary and sufficient conditions are given for the sum of two symmetric N₀-matrices to be an N₀-matrix.     

Exact analysis of asymmetric random polling systems with single buffers and correlated input process

We introduce a simple approach for modeling and analyzing asymmetric random polling systems with single buffers and correlated input process. We consider two variations of single buffers system: the conventional system and the buffer relaxation system. In the conventional system, at most one customer may be resided in any queue at any time. In the buffer relaxation system, a buffer becomes available to new customers as soon as the current customer is being served. Previous studies concentrate on conventional single buffer system with independent Poisson process input process. It has been shown that the asymmetric system requires the solution ofm 2 ^m –1) linear equations; and the symmetric system requires the solution of 2 ^m–1–1 linear equations, wherem is the number of stations in the system. For both the conventional system and the buffer relaxation system, we give the exact solution to the more general case and show that our analysis requires the solution of 2 ^m –1 linear equations. For the symmetric case, we obtain explicit expressions for several performance measures of the system. These performance measures include the mean and second moment of the cycle time, loss probability, throughput, and the expected delay observed by a customer.     

Crystallographic report: Bis(N,N‐diethyldithiocarbamato)(2,9‐dimethyl‐1, 10‐phenanthroline)cadmium(II)

The mononuclear structure of Cd(S₂CNEt₂)₂(2,9‐Me₂‐1,10‐phenanthroline) shows symmetric coordination of the dithiocarbamate ligands and a distorted octahedral geometry for cadmium, defined by an N₂S₄ donor set, results. Copyright © 2002 John Wiley & Sons, Ltd.     

Geometry of the common dynamics of flipped Pisot substitutions

In this article we study the common dynamics of two different Pisot substitutions σ ₁ and σ ₂ having the same incidence matrix. This common dynamics arises in the study of the adic systems associated with the substitutions σ ₁ and σ ₂. Since the adic systems considered here have geometric realizations given by solutions to graph-directed iterated function systems, we actually study topological and measure-theoretic properties of the solution of those iterated function systems which describe the common dynamics. We also consider generalizations of these results to the nonunimodular case, the case of more than two substitutions and the case of two substitutions with different incidence matrices.     

Synthesis and light-emitting properties of disubstituted polyacetylenes carrying chromophoric naphthylethynylphenyl pendants

Poly(1-phenyl-1-alkyne)s bearing chromophoric pendants and containing alkyl spacers (-{(C 6H 5)CC[(CH 2) m OCOC 6H 4CCNp]} n - [P 1( m) ( m = 3, 4, 9); Np = 1-naphthyl]) were synthesized, and the effects of structural variations on the optical properties, especially electroluminescence, of the polymers were investigated. The monomers were prepared in high yields by esterification and coupling reactions of n-phenyl-( n - 1)-alkyn-1-ols. Selective polymerizations of the 1-phenyl-1-alkyne unit of the monomers were effected by WCl 6-Ph 4Sn catalyst, affording polymers with high molecular weights ( M w up to 63 000) in high yields (up to 83%). Structures and properties of the polymers were characterized and evaluated by IR, NMR, TGA, UV, PL, and EL analyses. All the polymers are thermally very stable, losing almost no weight when heated up to 400 degrees C. Photoexcitation of the polymer solutions induces strong blue light emission at 460 nm, with quantum yields up to 98%. No aggregation quenching was observed when the polymers were fabricated into solid films. Multilayer EL devices with the configuration of ITO/P 1( m):PVK/BCP/Alq 3/LiF/Al were fabricated, which emitted blue light with luminance up to 498 cd/m (2). The device performance varied with the spacer length ( m), with P 1(4) giving the highest external quantum efficiency of 0.47%. The value was further enhanced to 0.86% by optimizing the layer thickness and inserting a hole-injection layer.     

Conventional spark versus nanosecond repetitively pulsed discharge for a turbulence facilitated ignition phenomenon

This work applies both conventional-single-spark-discharge (CSSD) at 500-µs pulse duration time and nanosecond-repetitively-pulsed-discharge (NRPD) at various pulsed-repetitive-frequency PRF = 5–70 kHz to explore a turbulence facilitated ignition (TFI) phenomenon using a pair of pin-to-pin electrodes at an inter-electrode gap of 0.8 mm in randomly-stirred lean n-butane/air mixture with Lewis number ? 1. For CSSD, measured laminar and turbulent minimum ignition energies (MIE_L and MIE_T) at 50% ignitability show that MIE_L≈ 23 mJ > the smallest MIE_T≈ 19.7 mJ at u′ = 0.9 m/s (TFI) and then MIE_T≈ 28.6/30.8/36.8 mJ at u′ = 1.4/2.1/2.8 m/s (no TFI), where u′ is the r.m.s turbulent fluctuating velocity. For comparison, all NRPD experiments apply the same total ignition energy E_tot≈ 23 mJ via a fixed train of 11 pulses, each pulse with 2.2 mJ except for the first pulse with 1 mJ. NRPD results show a cumulatively synergistic effect depending on the coherence between PRF and an inward reactant flow recirculation frequency (f_RC) inside the torus-like kernel induced by the discharge that could enhance ignition. When PRF is approximately synchronizing with f_RC, the synergistic effect is most profound at PRF = 20-kHz/40-kHz with very high ignition probability P_ig = 90%/85% > 50% in quiescence, whereas lower values of P_ig = 42%/34% are found at PRF = 10-kHz/60-kHz. Further, P_ig = 0 at PRF = 5-kHz even when 5000 pulses (E_tot≈ 10 J) are applied. We discover that P_ig decreases significantly with increasing u′ for most PRFs (no TFI) except at higher PRF ≥ 60 kHz showing possible TFI. These results are attributed to the interactions between turbulent dissipation, differential diffusion, and synergistic influence, which are substantiated by Schlieren images of initial kernel development and the ignition time determined at one half of the flame critical radius that leads to a self-sustained spherical flame propagation.     

Deterioration of edible oils during food processing by ultrasound

During food emulsification and processing of sunflower oil (most used edible oil), a metallic and rancid odour has been detected only for insonated oil and foods. Some off-flavour compounds (hexanal and hept-2-enal) resulting from the sono-degradation of sunflower oil have been identified. A wide variety of analytical techniques (GC determination of fatty acids, UV spectroscopy, free fatty acids and GC/MS) were used to follow the quality of insonated sunflower oil and emulsion. Different edible oils (olive, sunflower, soybean, em leader ) show significant changes in their composition (chemical and flavour) due to ultrasound treatment.     

Optical excitations in carbon nanoscrolls

The optical properties of carbon nanoscrolls in the presence of uniform electric fields are investigated by using gradient approximation. Absorption spectra exhibit rich prominent peaks structures, which is caused by one-dimensional sub-bands. The numbers, spectral intensities, and energies of the absorption peaks are strongly dependent on the geometry and the electric field strength. There exists an optical selection rule originating from the two equivalent sublattices in graphene. The two-fold degeneracy of the absorption peaks can be lifted by the inter-wall interactions or the electric field. The variations of the absorption peak energies with the geometry and field strength are also explored. These theoretical predictions can be validated by optical absorption measurements.     

Synthesis and biological profiling of tellimagrandin I and analogues reveals that the medium ring can significantly modulate biological activity

A novel synthesis of the ellagitannin natural product tellimagrandin I and a series of medium ring analogues is described. These compounds were all subsequently screened for redox activity, ability to precipitate protein and cellular phenotype in HeLa cells. From this we have shown that all properties can be modulated independently by varying ring size and by moving the ester out of conjugation with the biaryl ring system. Increasing ring size increased redox activity and cytotoxicity, leading to the identification of a compound (10) which was significantly more cytotoxic. In addition compounds identified with a redox active scaffold and low cytotoxicity may be employed as a new class of redox probes.     

Biomimicking polysaccharide nanofibers promote vascular phenotypes: a potential application for vascular tissue engineering

The potential of electrospun pullulan/dextran (P/D) nanofibers (average diameter = 323 nm) for vascular tissue engineering applications is explored. The mechanical properties of the nanofibers are of the same order of magnitude as that of human arteries (Young's modulus ≈0.88 MPa; tensile strength ≈0.35 MPa). It is demonstrated that the nanofiber topography enables cell adhesion and that the endothelial phenotype is maintained on the nanofibers. Moreover, P/D nanofibers support a stable confluent monolayer of endothelial cells over 14 d. SMCs seeded on nanofibers display similar levels of alpha smooth muscle actin and a lower proliferation rate than cells on 2D cultures. The observations suggest that nanofibers promote a shift to a quiescent contractile phenotype in SMCs.