Determination of nitric acid concentration by using europium ion fluorescence

A method is presented for the determination of 2-10M nitric acid based on the fact that the presence of high nitric acid concentration causes an enhancement of the intensity of some bands in the fluorescence spectra of rare earth ions in solution. The 616-nm band of Eu(3+) shows the most dramatic intensity enhancement with increasing nitric acid concentration. The present method, based on the measurement of the ratio of Eu(3+) fluorescent band intensities is shown to be independent of Eu(3+) concentration and relatively free of interference. This robust method allows the presence of an interferent to be determined from the experimental data.     

A precise uranium assay using solvent extraction and spectrophotometry

The uranium spectrophotometric measurement using the uranylnitrate-quaternaryamine solvent extraction method is investigated to identify factors that affect precision and accuracy of the uranium determination. The inherent spectrophotometric precision was measured with neutral density filters in the sample light path and was found to be <0.1% relative standard deviation (RSD). Under selected experimental conditions, temperature instability has a –0.02% effect on the extraction, and a –0.4% effect on the absorbance of the uranium extract in 2-nitropropane (2-NP) or methyl isobutyl ketone (MIBK) solvents. Under optimum conditions at the 10 mg uranium level, RSDs of 0.1% resulted.     

Properties and separation method of enantiomers of the mono- and bis-substituted derivatives of 3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene: structural analysis using X-ray diffraction and circular dichroism

This work expands on the recent separation of the enantiomers of the C₂-symmetrical bis-substituted derivatives of 1,1′-diphosphaferrocene. The effective separation of mono-substituted 1,1′-diphosphaferrocenes by the proposed method is demonstrated. The absolute configuration of the three separated components was established using X-ray diffraction. Circular dichroism spectra were collected for all of the separated compounds. The spectrum of each compound shows a characteristic curve, and the curves for the enantiomers are symmetrical. We also show that the correct absolute configuration for similar species can be assigned on the basis of the obtained data. We propose an explanation for the abnormal ¹H NMR spectra of phospholyl protons in some derivatives of 1,1′-diphosphaferrocene. A density functional theory (DFT) study of the conformation, as well as circular dichroism and NMR spectra of the chosen species, is also presented.     

Thermo-mechanical behavior of electrospun thermoplastic polyurethane nanofibers

Analysis of the thermo-mechanical behavior of electrospun thermoplastic polyurethane (TPU) block co-polymer nanofibers (glass transition temperature ∼−50 °C) is presented. Upon heating, nanofibers began to massively contract, at ∼70 °C, whereas TPU cast films started to expand. Radial wide-angle X-ray scattering (WAXS) profiles of the nanofibers and the films showed no diffraction peaks related to crystals, whereas their amorphous halo had an asymmetric shape, which can be approximated by two components, associated with hard and soft segments. During heating, noticeable changes in the contribution of these components were only observed in nanofibers. These changes, which were accompanied with an endothermic DSC peak, coinciding with the start of the nanofibers contraction, can be attributed to relaxation of an oriented stretched amorphous phase created during electrospinning. Such structure relaxation becomes possible when a portion of the hard segment clusters, forming an effective physical network, is destroyed upon heating.     

Influence of Plant Extract Addition to Marinades on Polycyclic Aromatic Hydrocarbon Formation in Grilled Pork Meat

Marinating is one of the most common methods of pre-processing meat. Appropriate selection of marinade ingredients can influence the physicochemical properties of the meat and can reduce the level of polycyclic aromatic hydrocarbons (PAHs) in the final product. The effects of the inclusion of natural plant extracts such as bay leaf (BL), black pepper (BP), turmeric (TU), jalapeno pepper (JP) and tamarind paste (TA) in marinades on the physicochemical properties of grilled pork neck were studied. The addition of spice extracts to marinades increased the proportion of colour components L* and b*. The use of TU, TA, JP, MX and C marinades lowered the hardness and pH of the meat. The highest phenolic compound levels were observed in the case of the mixture of all extracts (MX) and JP marinades, and the highest total antioxidant capacity was exhibited by the BL and MX marinades. The highest PAH content was recorded in the CON marinade (Σ12PAH 98.48 ± 0.81 µg/kg) and the lowest in the JP marinade (4.76 ± 0.08 µg/kg), which had the strongest, statistically significant reducing effect (95% reduction) on PAH levels. Analysis of correlation coefficients showed a relationship between the total antioxidant capacity of the marinades and the PAH content in grilled pork.     

Parametrix for the localization of the Bergman metric on strictly pseudoconvex domains

We give the parameter version of a localization theorem for the Bergman metric near the boundary points of strictly pseudoconvex domains. The approximation theorem for square integrable holomorphic functions on such domains in the spirit of Graham-Kerzman is proved in the hereby paper, as well.