Minimal Blocking Sets in PG(2, 8) and Maximal Partial Spreads in PG(3, 8)

We prove that PG(2, 8) does not contain minimal blocking sets of size 14. Using this result we prove that 58 is the largest size for a maximal partial spread of PG(3, 8). This supports the conjecture that q ²–q+ 2 is the largest size for a maximal partial spread of PG(3, q), q>7.     

Magnetization reversal in submicron disks: exchange biased vortices

Submicron, circular, ferromagnetic-antiferromagnetic dots exhibit different magnetization reversal mechanisms depending on the direction of the magnetic applied field. Shifted, constricted hysteresis loops, typical for vortex formation, are observed for fields along the exchange bias direction. However, for fields applied close to perpendicular to the exchange bias direction, magnetization reversal occurs via coherent rotation. Magnetic force microscopy imaging together with micromagnetic simulations are used to further clarify the different magnetic switching behaviors.     

Mössbauer studies of magnetic Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/SiO<Subscript>2</Subscript> nanocomposites

A large variety of glass and glass ceramics may be obtained by sol-gel process from hydrolysis of tetraethoxysilane. The transformation involves hydrolysis and polycondensation reactions leading to the growth of clusters that eventually collide together to form a gel. The structure and properties of the final product have been found to be strongly dependent on the initial conditions of preparation. Silica nanocomposites based on Fe₂O₃/SiO₂ were prepared with the help of ultrasonic activation and subsequent annealing in nitrogen atmosphere or air with concentrations of iron oxide of about 20 to 30wt.%.     

Photodissociation of t-butyl nitrite by UV and blue photons

The photodissociation of t-butyl nitrite at 266, 355, 454, 474 and 494 nm has been studied by probing the NO(X²Π) fragment. Either two lasers at different wavelengths were used for dissociating and probing or a single laser was used for both. The results show strong dependence of the vibrational and rotational excitation of the NO on the photodissociation wavelength.     

Computationally tractable pairwise complexity profile

Quantifying the complexity of systems consisting of many interacting parts has been an important challenge in the field of complex systems in both abstract and applied contexts. One approach, the complexity profile, is a measure of the information to describe a system as a function of the scale at which it is observed. We present a new formulation of the complexity profile, which expands its possible application to high‐dimensional real‐world and mathematically defined systems. The new method is constructed from the pairwise dependencies between components of the system. The pairwise approach may serve as both a formulation in its own right and a computationally feasible approximation to the original complexity profile. We compare it to the original complexity profile by giving cases where they are equivalent, proving properties common to both methods, and demonstrating where they differ. Both formulations satisfy linear superposition for unrelated systems and conservation of total degrees of freedom (sum rule). The new pairwise formulation is also a monotonically nonincreasing function of scale. Furthermore, we show that the new formulation defines a class of related complexity profile functions for a given system, demonstrating the generality of the formalism. © 2013 Wiley Periodicals, Inc. Complexity 18:20–27, 2013     

Near IR-emitting DNA-probes exploiting stepwise energy transfer processes

The synthesis and characterisation of two new cyclen-based near IR-emitting lanthanide complexes is reported; the lanthanides are sensitised by rhodamine, which in turn is excited by energy transfer from a coumarin 2 moiety. The three lumophores function as an energy transfer cascade spanning the UV-visible-near IR region of the spectrum, resulting in large Stokes shifts. Double stranded DNA selectively switches one of the two energy transfer processes off, enabling luminescent DNA-sensing in the near IR region. The regioselective di-alkylation of the cyclen scaffold is explained with the help of DFT calculations.     

Generation of pH-oscillations in closed chemical systems: method and applications

All pH-oscillators reported to date function only under open (flow reactor) conditions. We describe an approach to generating pH-oscillations in a closed system by starting from an open system pH-oscillator, finding semibatch conditions under which it oscillates with an inflow of a single reactant to an otherwise closed reactor containing the remaining components, and replacing this inflow with a layer of silica gel impregnated with the key reactant. We present data showing the successful application of this technique to the BrO(3)(-)-Mn(2+)-SO(3)(2-), IO(3)(-)-Fe(CN)(6)(4-)-SO(3)(2-), and BrO(3)(-)-Fe(CN)(6)(4-)-SO(3)(2-) systems. In all three cases, sulfite ion is the species that is replenished via dissolution from the gel layer.     

Identification strategy for unknown pollutants using high-resolution mass spectrometry: Androgen-disrupting compounds identified through effect-directed analysis

Effect-directed analysis has been applied to a river sediment sample of concern to identify the compounds responsible for the observed effects in an in vitro (anti-)androgenicity assay. For identification after non-target analysis performed on a high-resolution LTQ-Orbitrap, we developed a de novo identification strategy including physico-chemical parameters derived from the effect-directed analysis approach. With this identification strategy, we were able to handle the immense amount of data produced by non-target accurate mass analysis. The effect-directed analysis approach, together with the identification strategy, led to the successful identification of eight androgen-disrupting compounds belonging to very diverse compound classes: an oxygenated polyaromatic hydrocarbon, organophosphates, musks, and steroids. This is one of the first studies in the field of environmental analysis dealing with the difficult task of handling the large amount of data produced from non-target analysis. The combination of bioassay activity assessment, accurate mass measurement, and the identification and confirmation strategy is a promising approach for future identification of environmental key toxicants that are not included as priority pollutants in monitoring programs.     

Ionization-loss stimulated Raman spectroscopy for conformational probing of flexible molecules

The approach of studying structural and dynamical properties of flexible molecules is of substantial interest, as it allows decoding the shapes and intrinsic properties of isolated molecular constituents, which have an influence on the selectivity and functionality in biological processes. Combining quantum computation methods with double resonance or infrared hole burning techniques, mainly covering hydride stretch vibrations, recently led to great progress in understanding the structure of a variety of biological building blocks. Measurements of spectra in the lower frequency range, with relatively compact and convenient laser sources, still pose major challenges. For this reason, the method of ionization-loss stimulated Raman spectroscopy (ILSRS) has been developed and applied for monitoring the spectral features of the 2-phenylethanol prototype. The bands observed in the Raman spectra of its two conformers uniquely identify their structures and are in accord with anharmonic results obtained by density functional theory calculations. These findings point to future opportunities for ILSRS as a powerful conformational probe and set new standards for detailed interrogation of structure and intra- and inter-molecular interactions.