Separation and determination of tocopherols in vegetable oils by solid phase extraction on porous polymers SPE cartridges and capillary gas chromatography analysis

In this study we present the solid phase extraction selectivity of tocopherols from vegetable oils using four porous polymers (Porapak P, Porapak Q, Porapak QS, Porapak N). The tocopherols elution from SPE cartridges was performed using several hexanes:ethyl acetate mixtures (100:0, 95:5, 90:10, 85:15, v/v). Tocopherols (α, γ and δ-tocopherol) were analyzed by gas chromatography without any derivation steep. The amount of NaOH used for triglyceride removal was optimized. Particularly liquid-liquid and solid phase extraction methods for the extraction of tocopherols from vegetable oils were compared. The results confirmed that porous polymers represent promising SPE alternatives for the extraction of tocopherols from oils.     

On uniform exponential stability for skew-evolution semiflows on Banach spaces

The aim of this paper is to give several characterizations for the property of stability for skew-evolution semiflows on Banach spaces. Thus, we obtain generalizations of some well known results due to Barbashin, Datko and Rolewicz in the case of evolution equations in Banach spaces. A unified treatment in the uniform setting is provided.     

Ligand Mediated Metal Cations Exchanges within Metallo-Dynameric Solid Films

Dynameric solid films may be generated via the adequate imine-bond connection between bis(pyridine-2,6-diimine) core centres, coordinated with different metal cations and diaminoPEG connectors. The adequate selection of metal cations leads to cross-linked metallo-dynameric films, allowing the fine modulation of their colour and mechanical property. The coordination of the metal cations and bis(pyridine-2,6-diimine), results in the formation of interlocked structures, leading to the most probably formation of interweaved structures with better mechanical properties than those formed in the absence of the metallic cations. Removal and addition of metal cations from solid films can be achieved via tris(2-aminoethyl)amine (TREN) complexing agent, which strongly binds the metal cations, followed by subsequent insertion of other metallic cations. It allows a ligand-modulated dynamic release of the metal cations from the solid films, together with colour transfer and change of mechanical strength at the interfaces between various solid films.     

The Journal of Nanoparticle Research at 10 years

Fundamental physical considerations indicate that the scaling of devices that use electron charge as the information carrier will limit within the next one to two decades. The Nanoelectronics Research Initiative (NRI), a joint industry-government program, has been developed to fund university research seeking devices that utilize alternative physical information carriers or non-equilibrium switching mechanisms to continue the historical cost and performance trends of information technology. Three research centers have been established to pursue five research vectors that have been identified as critical to the effort to replace the electronic switch. A brief history and rationale for NRI is given and the projects currently underway are described in the context of the five research vectors.     

On nonuniform exponential dichotomy of evolution operators in Banach spaces

The problem of nonuniform exponential dichotomy of evolution operators in Banach spaces is considered. Connections between this concept and admissibility of the pair (C ₀,C ₀) are established. Generalizations to the nonuniform case of some results of Van Min, Räbiger and Schnaubelt ([MRS]) are obtained. It is shown that an implication from the uniform case is not true for nonuniform exponential dichotomy. The results are applicable for general time-varying linear equations with unbounded coefficients in Banach spaces.     

Pseudocompact Whyburn spaces need not be Fréchet

We prove in ZFC that there exists a Tychonoff pseudocompact scattered AP-space of uncountable tightness. We give some sufficient and necessary conditions for a -space to be AP as well as a characterization of AP-property in linearly ordered topological spaces.

     

On a problem of Turán about positive definite functions

We study the following question posed by Turán. Suppose is a convex body in Euclidean space which is symmetric in and with value at the origin; which one has the largest integral? It is probably the case that the extremal function is the indicator of the half-body convolved with itself and properly scaled, but this has been proved only for a small class of domains so far. We add to this class of known Turán domains the class of all spectral convex domains. These are all convex domains which have an orthogonal basis of exponentials , . As a corollary we obtain that all convex domains which tile space by translation are Turán domains.

We also give a new proof that the Euclidean ball is a Turán domain.