Electronic spectrum of UO2(2+) and [UO2Cl4]2- calculated with time-dependent density functional theory

The electronic spectra of UO(2) (2+) and [UO(2)Cl(4)](2-) are calculated with a recently proposed relativistic time-dependent density functional theory method based on the two-component zeroth-order regular approximation for the inclusion of spin-orbit coupling and a noncollinear exchange-correlation functional. All excitations out of the bonding sigma(u) (+) orbital into the nonbonding delta(u) or phi(u) orbitals for UO(2) (2+) and the corresponding excitations for [UO(2)Cl(4)](2-) are considered. Scalar relativistic vertical excitation energies are compared to values from previous calculations with the CASPT2 method. Two-component adiabatic excitation energies, U-O equilibrium distances, and symmetric stretching frequencies are compared to CASPT2 and combined configuration-interaction and spin-orbit coupling results, as well as to experimental data. The composition of the excited states in terms of the spin-orbit free states is analyzed. The results point to a significant effect of the chlorine ligands on the electronic spectrum, thereby confirming the CASPT2 results: The excitation energies are shifted and a different luminescent state is found.     

The magid-ryan conjecture for 4-dimensional affine spheres

In this paper we prove the Magid-Ryan conjecture for 4-dimensional affine hyperspheres in R⁵. This conjecture states that every affine hypersphere with non-zero Pick invariant and constant sectional curvature is affinely equivalent with either (x ₁ ² ±x ₂ ² )(x ₃ ² ±x ₄ ² ...(x _2m−1 ² ±x _2m ² ) = 1 or (x ₁ ² ±x ₂ ² (x ₃ ² ±x ₄ ² )...(x _2m−1 ² ±x _2m ² )x _2m+1 = 1 where the dimensionn satisfiesn = 2m orn =2m + 1. This conjecture was proved in [11] in case the metric is positive definite and in [2] in case the metric is Lorentzian.     

Identification of substances migrating from plastic baby bottles using a combination of low‐resolution and high‐resolution mass spectrometric analysers coupled to gas and liquid chromatography

This work presents a strategy for elucidation of unknown migrants from plastic food contact materials (baby bottles) using a combination of analytical techniques in an untargeted approach. First, gas chromatography (GC) coupled to mass spectrometry (MS) in electron ionisation mode was used to identify migrants through spectral library matching. When no acceptable match was obtained, a second analysis by GC‐(electron ionisation) high resolution mass spectrometry time of flight (TOF) was applied to obtain accurate mass fragmentation spectra and isotopic patterns. Databases were then searched to find a possible elemental composition for the unknown compounds. Finally, a GC hybrid quadrupole‐TOF‐MS with an atmospheric pressure chemical ionisation source was used to obtain the molecular ion or the protonated molecule. Accurate mass data also provided additional information on the fragmentation behaviour as two acquisition functions with different collision energies were available (MS^E approach). In the low‐energy function, limited fragmentation took place, whereas for the high‐energy function, fragmentation was enhanced. For less volatile unknowns, ultra‐high pressure liquid chromatography‐quadrupole‐TOF‐MS was additionally applied. Using a home‐made database containing common migrating compounds and plastic additives, tentative identification was made for several positive findings based on accurate mass of the (de)protonated molecule, product ion fragments and characteristic isotopic ions. Six illustrative examples are shown to demonstrate the modus operandi and the difficulties encountered during identification. The combination of these techniques was proven to be a powerful tool for the elucidation of unknown migrating compounds from plastic baby bottles. Copyright © 2015 John Wiley & Sons, Ltd.     

An Edge-Isoperimetric Problem for Powers of the Petersen Graph

In this paper we introduce a new order on the set of n-dimensional tuples and prove that this order preserves nestedness in the edge isoperimetric problem for the graph Pⁿ, defined as the nth cartesian power of the well-known Petersen graph. The cutwidth and wirelength of Pⁿ are also derived. These results are then generalized for the cartesian product of Pⁿ and the m-dimensional binary hypercube.     

Determination of the distance between the two neutral flavin radicals in augmenter of liver regeneration by pulsed ELDOR

Pulsed electron-electron double resonance (ELDOR) has been used to obtain structural information from a FAD-dependent sulfhydryl oxidase, Augmenter of Liver Regeneration (ALR). ALR is a homodimer with each subunit containing a noncovalently bound FAD cofactor. Both FADs may be converted into the blue neutral radical form by aerobic treatment with DTT. From three-pulse and four-pulse ELDOR experiments, a distance of 26.1 +/- 0.8 A could be determined between the FAD cofactors in human ALR. Taking into account the electron spin density distribution in a neutral flavin radical obtained from density functional theory calculations, a distance of 26.9 A could be estimated for the separation of the spin centers in the X-ray structure of rat ALR. The good agreement confirms that rat ALR may be used as a model for mechanistic discussions of human ALR. The experiments also demonstrate that neutral flavin radicals have the appropriate properties to be used as intrinsic spin labels for distance determinations in proteins.     

Please or Squeeze? Brand performance implications of constrained and unconstrained multi-item promotions

Existing research on price promotions typically investigates the effects of single-product promotions. However, brand managers often promote multiple items simultaneously to bolster the performance of a complete brand line. This paper investigates the brand performance implications of such multi-item promotions. We distinguish between two types of multi-item promotions: traditional, unconstrained multi-item promotions that grant a discount irrespective of the size or composition of the purchase set, and constrained multi-item promotions that require consumers to purchase specific quantities (self-bundling) or even predetermined combinations (fixed bundling) of promoted items. Using a normative consumer decision model, the authors analyze the relative effectiveness of these promotions in terms of unit sales and revenue impact and show that promotion performance is moderated by consumers’ preference for variety. The authors find that unconstrained multi-item promotions outperform single-item promotions, especially in markets without variety-seeking. In markets with variety seeking, unconstrained multi-item promotions are not as effective in stealing extra sales from competition because consumers prefer to spread their purchases across all items, including competitive ones. However, in those markets, self-bundling promotions are particularly effective because they force consumers to adopt larger amounts of the promoted items at the expense of competitors. Finally, in neither type of market does fixed bundling substantially improve promotion performance.     

Improvements to a surface plasmon resonance-based immunoassay for the steroid hormone progesterone

The effects of modifications to an existing protocol for a surface plasmon resonance biosensor-based inhibition immunoassay for progesterone in cow's milk with a sensitivity of 3.5 ng/mL were examined to establish if the detection limit could be further reduced to broaden the potential applications of the assay. The mean relative standard deviation of duplicate measurements was 0.62% and the high precision resulted in very low values for the lower detection limits. Hence, the standard concentrations giving 95% maximum binding [effective dose (ED 95)] were compared instead. The ED 95 was not affected within a running temperature range of 20-37 degrees C, or at a flow rate and a contact time above 20 microL/min and 90 s, respectively. Increasing both the absolute sample volume and the antibody dilution improved sensitivity. However, there was a simultaneous reduction in the working range when the assay was applied to milk due to nonspecific binding. Less antibody was associated with large decreases in the maximum binding, but because the high precision extended over a broad analytical range, an ED 95 of 0.4-0.6 ng/mL in milk and 35-60 pg/mL in HBS-EP buffer were achieved. Thus, simple procedural modifications with the same sensor chip can alter performance characteristics of the assay as required for different applications.     

Measurements of the alpha factor of a distributed-feedback quantum cascade laser by an optical feedback self-mixing technique

We demonstrate measurements of the alpha factor of a distributed-feedback quantum cascade laser (QCL) by using a newly modified self-mixing interferometric technique exploring the laser itself as the detector. We find a strong dependence of the alpha factor on the injection current, ranging from -0.44 at 120 mA to 2.29 at 180 mA, which can be attributed to the inherent physics of QCLs.     

Multiscale modeling for ferroelectric materials: a transition from the atomic level to phase-field modeling

To link the atomic level and the mesoscale within a knowledge-based multiscale modeling approach for ferroelectric materials, a method is suggested to transfer results from first-principles calculations into a phase-field model. DFT calculations and atomistic simulations are applied and provide a set of intrinsic and extrinsic material properties for PbTiO₃ and tetragonal Pb(Zr_0.5Ti_0.5)O₃. The Helmholtz free energy of the phase-field model that contains all crystallographic and domain wall information is discussed in detail, and a sensitivity analysis is performed to identify the coefficients of the energy function. Then, a method is developed to adjust the coefficients of the Helmholtz free energy solely based on results from first-principles calculations. Full sets of adjusted energy coefficients for PbTiO₃ and Pb(Zr_0.5Ti_0.5)O₃ are presented and discussed, as well the limits of the suggested adjustment method.