High resolution 31P NMR study of octacalcium phosphate

We have assigned the (31)P high-resolution spectrum of octacalcium phosphate by (31)P double quantum and HETCOR spectroscopy. The (31)P peaks at -0.2, 2.0, 3.3 and 3.7 ppm are assigned to P5/P6, P3, P2/P4 and P1, respectively. Our data reveal that substantial amount of the PO(4)(3-) groups at the P2 and P4 sites have been transformed to HPO(4)(2-) in our octacalcium phosphate sample.     

Operator ultra-amenability

Extending M. Daws’ definition of ultra-amenable Banach algebras, we introduce the notion of operator ultra-amenability for completely contractive Banach algebras. For a locally compact group G, we show that the operator ultra-amenability of A(G) imposes severe restrictions on G. In particular, it forces G to be a discrete, amenable group with no infinite abelian subgroups. For various classes of such groups, this means that G is finite.     

A study of the effect of locust bean gum on the rheological behaviour and microstructure of a β-lactoglobulin gel at pH 7

The effect of locust bean gum (LBG), a non-gelling polysaccharide, on the thermal gelation of -lactoglobulin, at 80 °C, and on the gel properties after quenching to 20 °C was studied by small deformation rheology and by confocal laser scanning microscopy (CLSM). The concentration of -lactoglobulin was kept constant at 10 wt% and that of LBG varied from 0 to 0.78 wt%. For all the concentrations studied, the presence of LBG enhanced the aggregation rate and the strength of the protein gel, but the magnitude of these effects depended on the -lactoglobulin/LBG ratio: 0.35 wt% LBG resulted only in a very slight increase of G, whereas 0.45 wt% LBG caused a ~fivefold jump; for higher LBG concentrations, the differences between the systems were quite small. The linear viscoelastic behaviour, at 20 °C, was characterized over the 10^–5 to 100 rad/s frequency range by combining the dynamic and retardation tests. Compliance data were converted from the time to the frequency domain. The viscoelastic plateau was seen to extend down in the 0.001–0.0001 rad/s range and its lower limit seemed not to vary much with LBG concentration. Its upper limit was visibly beyond 100 rad/s. The observed microstructure of the gels showed that they were two-phase and that the state of aggregation of -lactoglobulin was influenced by the -lactoglobulin/LBG ratio.This paper was presented at the first Annual European Rheology Conference (AERC) held in Guimarães, Portugal on September 11–13, 2003     

Turbulence Filter and POD Analysis for Velocity Fields in Lifted CH4-Air Diffusion Flames

The turbulence filter and the proper orthogonal decomposition (POD)methods are applied to PIV measurements of lifted CH₄-air diffusionflames at three different Reynolds numbers. Properties such as vorticityand strain rate distributions of the decomposed fields are analyzed inorder to assess the physical behavior. The turbulence filter can userelatively less data than the POD method while still providingsignificant insight about the flow field. The energy activation ratesshow the first modes (mean flow) account for 85% of the total energy.Reconstruction of the POD modes reveals that the combination of modesyields a complex fluctuating behavior. The averaged Reynolds stress ofthe mean flow removed parts shows interesting correlation with the meanflow vorticity and strain rate distributions. Selected turbulentproperties are calculated and discussed.     

Thermal characterization and compounds identification of commercial Stevia rebaudiana Bertoni sweeteners and thermal degradation products at high temperatures by TG–DSC,IR and LC–MS/MS

Journal of Thermal Analysis and Calorimetry - The thermal behavior of two commercially available sweeteners based on Stevia rebaudiana Bertoni was studied by TG–DSC and EGA. The composition...     

Pressure-Induced Perovskite-to-non-Perovskite Phase Transition in CsPbBr3

The expanding range of optoelectronic applications of lead-halide perovskites requires their production in diverse forms (single crystals, thin- and thick-films or even nanocrystals), motivating the development of diverse materials processing and deposition routes that are specifically suited for these structurally soft, low-melting semiconductors. Pressure-assisted deposition of compact pellets or thick-films are gaining popularity, necessitating studies on the pressure effects on the atomic structure and properties of the resulting material. Herein we report the phase transformation in bulk polycrystalline cesium lead bromide from its three-dimensional perovskite phase (γ-CsPbBr₃) into the one-dimensional polymorph (δ-CsPbBr₃) upon application of hydrostatic pressure (0.35 GPa). δ-CsPbBr₃ is characterized by a wide bandgap of 2.9 eV and broadband yellow luminescence at 585 nm (2.1 eV) originating from self-trapped excitons. The formation of δ-CsPbBr₃ was confirmed and characterized by Raman spectroscopy, ²⁰⁷Pb and ¹³³Cs solid-state nuclear magnetic resonance, X-ray diffraction, absorption spectroscopy, and temperature-dependent and time-resolved photoluminescence spectroscopy. No such phase transition was observed in colloidal CsPbBr₃ nanocrystals.     

An Accurate Molecular Structure of Phenyl,the Simplest Aryl Radical

The phenyl radical (C₆H₅^.) is the prototypical σ‐type aryl radical and one of the most common aromatic building blocks for larger ring molecules. Using a combination of rotational spectroscopy of singly substituted isotopic species and vibrational corrections calculated theoretically, an extremely accurate molecular structure has been determined. Relative to benzene, the phenyl radical has a substantially larger C‐C_ipso‐C bond angle [125.8(3)° vs. 120°], and a shorter distance [2.713(3) Å vs. 2.783(2) Å] between the ipso and para carbon atoms.     

The relationship between the antimicrobial activity of eugenol and the LPETG peptide structure and associated analysis for docking purposes

Sortase A is responsible for the virulence of Gram-positive pathogens, including staphylococci and streptococci. The LPETG is the peptide surface anchor signal for Sortase A. The inhibitors of this enzyme shared similar binding pattern with substrate LPETG. Eugenol and its derivatives may act as sortase A inhibitor. The antimicrobial activity of eugenol and its derivatives was tested in vitro against bacterial strains: Staphylococcus aureus, Streptococcus mutans and Escherichia coli. All the tested derivatives demonstrated antimicrobial activity. Differences between derivatives in terms of in vitro activity and interactions between the amino acid residues were correlated in the docking analysis for the same derivatives. According to the relationship observed in this study between the antimicrobial activity of eugenol and the LPETG peptide structure, some of the eugenol derivatives proved to be more active inhibiting sortase A than eugenol against microorganisms when tested at the same concentrations.     

Sulfamic acid: An efficient and recyclable catalyst for the regioselective hydrothiolation of terminal alkenes and alkynes with thiols

Herein, we described a new method for the preparation of thioethers through hydrothiolation of alkenes and alkynes, using sulfamic acid as a reusable catalyst. Generally, this new methodology afforded the desired products in very good yields, under metal and solvent-free conditions. Furthermore, the catalyst was easily recovered and reused for further catalytic reactions without loss of activity.