Closed-form solution for horizontal and vertical shiftings of viscoelastic material functions in frequency domain

The closed-form shifting (CFS) algorithm is a simple mathematical methodology which determines the unique solution in the process of constructing master curves at selected reference temperature and pressure conditions. In a previous paper, the CFS algorithm has been fully described for monotonically increasing or monotonically decreasing functions only. This paper presents detailed steps of the generalized CFS methodology for non-monotonic functions, like the loss tangent. Performing shifting on the loss tangent, which does not require vertical shifting, is particularly important for materials which require vertical adjustment of dynamic viscoelastic functions, i.e., loss and storage moduli. Thus, based on horizontal shifting of the loss tangent, the CFS-based procedure of consecutive horizontal-vertical superposition for the storage modulus is proposed and analyzed. The analysis is done on the example of two synthetically generated non-monotonic tan delta segments and corresponding storage modulus segments in respect to different experimental parameters. It has been shown that the error brought by the shifting method into non-monotonic loss tangent and storage modulus master curves is twice smaller than the corresponding experimental noise level.     

Raman spectroscopic characterization of the copper,cobalt, and nickel selenites: Synthetic analogs of chalcomenite,cobaltomenite, and ahlfeldite

Raman spectroscopy has been used to study synthetic analogs of the minerals chalcomenite, cobaltomenite, and ahlfeldite occurring in nature. The results obtained are compared with the spectra of these minerals. In general, the majority of vibrational bands of synthetic species are in good agreement with natural chalcomenite, cobaltomenite, and ahlfeldite. The noticeable discrepancies are found for the bands assigned to the deformation mode of selenite groups. A better signal-to-noise ratio realized with synthetic species aids in comprehensive analysis of the spectra, especially in the region of water bands.     

Miller–Urey Spark-Discharge Experiments in the Deuterium World

We designed and conducted a series of primordial-soup Miller-Urey style experiments with deuterated gases and reagents to compare the spark-discharge products of a “deuterated world” with the standard reaction in the “hydrogenated world”. While the deuteration of the system has little effect on the distribution of amino acid products, significant differences are seen in other regions of the product-space. Not only do we observe about 120 new species, we also see significant differences in their distribution if the two hydrogen isotope worlds are compared. Several isotopologue matches can be identified in both, but a large proportion of products have no equivalent in the corresponding isotope world with ca. 43 new species in the D world and ca. 39 new species in the H world. This shows that isotopic exchange (the addition of only one neutron) may lead to significant additional complexity in chemical space under otherwise identical reaction conditions.     

Self-Assembly of an Amino Acid Derivative into an Antimicrobial Hydrogel Biomaterial

N-(4-Nitrobenzoyl)-Phe self-assembled into a transparent supramolecular hydrogel, which displayed high fibroblast and keratinocyte cell viability. The compound showed a mild antimicrobial activity against E. coli both as a hydrogel and in solution. Single-crystal XRD data revealed packing details, including protonation of the C-terminus due to an apparent pK_a shift, as confirmed by pH titrations. MicroRaman analysis revealed almost identical features between the gel and crystal states, although more disorder in the former. The hydrogel is thermoreversible and disassembles within a range of temperatures that can be fine-tuned by experimental conditions, such as gelator concentration. At the minimum gelling concentration of 0.63 wt %, the hydrogel disassembles in a physiological temperature range of 39–42 °C, thus opening the way to its potential use as a biomaterial.     

Scintillation properties of Ce3+-doped YCl3 and YBr3

The dependence of the scintillation properties of Ce³⁺-doped YCl₃ and YBr₃ on activator concentration (0.5, 1 and 2 mol%) has been studied. The radioluminescence spectra of both materials contain asymmetric bands with maxima located at 3.13 eV (383 nm) for YCl₃:Ce³⁺ and 2.84 eV (422 nm) for YBr₃:Ce³⁺. The scintillation pulse decay curves for both materials are described by two components with decay constants of 37 and 640 ns for YCl₃:Ce³⁺ and 36 and 450 ns for YBr₃:Ce³⁺, the fractions of the faster component being 86 and 79 per cent, respectively. The dependences of the light yield of the studied materials on Ce³⁺ concentration pass through a maximum near 1 mol% of the activator, and the maximum light yields (relative to NaI:Tl) are 8700 photons per MeV for YCl₃:Ce³⁺ and 20,600 photons per MeV for YBr₃:Ce³⁺.     

An Exact Class of Bulk Field Potentials onto the 5D-Warp of de Sitter Spacetime

In the five-dimensionally warped FRW Universe, we integrate the corresponding Einstein equations for a scalar source depending only on the extra-dimension. It yields a de Sitter brane and a specific warp factor for which we derive the effective bulk field potentials. These are generalizing some of the previously proposed forms in the literature.     

Dual wavelength asymmetric photochemical synthesis with circularly polarized light

Asymmetric photochemical synthesis using circularly polarized (CP) light is theoretically attractive as a means of absolute asymmetric synthesis and postulated as an explanation for homochirality on Earth. Using an asymmetric photochemical synthesis of a dihydrohelicene as an example, we demonstrate the principle that two wavelengths of CP light can be used to control separate reactions. In doing so, a photostationary state (PSS) is set up in such a way that the enantiomeric induction intrinsic to each step can combine additively, significantly increasing the asymmetric induction possible in these reactions. Moreover, we show that the effects of this dual wavelength approach can be accurately determined by kinetic modelling of the PSS. Finally, by coupling a PSS to a thermal reaction to trap the photoproduct, we demonstrate that higher enantioselectivity can be achieved than that obtainable with single wavelength irradiation, without compromising the yield of the final product.