Deddens Algebras and Shift

We consider Deddens algebras associated to operators of the form S−λI, where S is the unilateral shift and λ is a complex number. We show that such an algebra properly contains the commutant of S and that it is always weakly dense in L(H){{\mathcal L}({\mathcal H})}. Yet, it contains no rank one operators, unless λ = 0, in which case it equals L(H){{\mathcal L}({\mathcal H})}.     

Benefits of environmental conditions for growing coriander in Banat Region, Serbia

As one of the oldest multi-purpose plants (spice, aromatic, honey and medicinal), coriander is widespread across Europe. Although in Serbia there are favorable conditions for its growth and development, it is grown on relatively small areas. During both investigated years it took more than 1200 degrees C for transfer from vegetative to generative phase of development and over 2000 degrees C for it to be ready for harvesting. Coriander is a photophilic plant, which requires around 1000 hours of light from sowing to ripening.. As for humidity, coriander grows well, if there are more than 200 mm of rainfall during growing season. In 2009 and 2010, the experiment carried out at the experimental field in Ostoji?evo (Banat, Vojvodina province, Serbia) monitored the effect of parameters mentioned above on development of coriander plants, seed yield and essential oil content. The average yields of 1866 kg ha(-1) (2009) and 2470 kg ha(-1) (2010), and relatively high content of essential oil (1.06% in both years) indicate a great potential of this plant species in Serbia, which is, however, greatly dependent on environmental conditions during year.     

Magnon–magnon interactions in O(3) ferromagnets and equations of motion for spin operators

The method of equations of motion for spin operators in the case of O(3) Heisenberg ferromagnet is systematically analyzed starting from the effective Lagrangian. It is shown that the random phase approximation and the Callen approximation can be understood in terms of perturbation theory for type B magnons. Also, the second order approximation of Kondo and Yamaji for one dimensional ferromagnet is reduced to the perturbation theory for type A magnons. An emphasis is put on the physical picture, i.e. on magnon–magnon interactions and symmetries of the Heisenberg model. Calculations demonstrate that all three approximations differ in manner in which the magnon–magnon interactions arising from the Wess–Zumino term are treated, from where specific features and limitations of each of them can be deduced.     

Photoluminescence spectroscopy of CdSe nanoparticles embedded in transparent glass

In this paper we present photoluminescence measurements of CdSe nanoparticles embedded in transparent glass. Sample is prepared using an original technique, which combines both heat treatment and ultraviolet laser irradiation. Photoluminescence spectra displayed one main emission band at 2.14 eV. We identify this bands energy as basic interband transition in CdSe nanoparticle. We calculated energy of basic (1s_h–1s_e) transition in spherical CdSe quantum dot (QD), within infinite potential barrier, in effective-mass approximation. On the basis of this model, average radius of synthesized CdSe QDs is about 3 nm, which is in consistence with AFM measurements and UV–VIS absorption measurements.     

Multiphase‐Separated Polyurethanes Studied by Micro‐Raman Spectroscopy

Micro‐Raman spectroscopy has been used to investigate the chemical micro‐heterogeneity of multiphase‐separated poly(ether urethanes) (PETU). Analysis of PETU cross‐sections by means of micro‐Raman spectroscopy revealed the nearly complete absence of soft segments in AI aggregates (called globules). These aggregates are in the order of a few micrometers in size. The composition of the matrix and the AII aggregates (spherulites) was comparable.

Example of an AFM image (sample 706, scan size 25 μm, converted to monochromatic image).     

Self-modeling curve resolution analysis of on-line vibrational spectra of polymerisation and transesterification

This article discusses the potential of self-modeling curve resolution analysis (SMCR) for the evolution of on-line vibrational spectral data of polymerisation and transesterification. After the general introduction of the SMCR approach, representative SMCR techniques like orthogonal projection analysis (OPA) and simple-to-use interactive self-modeling mixture analysis (SIMPLISMA) are briefly outlined. As examples the SMCR analysis of the Raman spectra of the block copolymerisation of styrene and 1,3-butadiene and that of the near-infrared (NIR) spectra of the melt-extrusion transesterification of ethylene-vinylacetate copolymer will be illustrated. In the last part of this review paper, a new powerful SMCR method that we have recently proposed is demonstrated.     

Fourier‐Transform Raman Spectroscopic On‐Line Monitoring of the Anionic Dispersion Block Copolymerization of Styrene and 1,3‐Butadiene

The anionic dispersion block copolymerization of styrene and 1,3‐butadiene has proved a suitable technique to synthesize block copolymers of tailor‐made blocklength under technically relevant conditions. For this purpose, however, an efficient analytical on‐line technique is required to control the concentrations of individual reactants and product. The present communication shortly outlines the potential of non‐invasive light‐fiber Fourier‐transform Raman spectroscopy in combination with a self‐modeling curve‐resolution analysis to monitor the polymerization progress and to derive concentration profiles of the two monomers and polybutadiene without prior calibration of the investigated system.