PHOTOOXIDATION OF A REFINED PETROLEUM OIL: INHIBITION BY β-CAROTENE AND ROLE OF SINGLET OXYGEN

Abstract— β-Carotene, at concentrations 0.1 m M , inhibits the formation of hydroperoxides and other oxidation products in a refined petroleum oil exposed to Pyrex-filtered UV. The effect appears to be due to ¹O₂ quenching. A mechanism incorporating ¹O₂ and radical processes is proposed as a model for environmental photooxidation of petroleum.     

Study of polymerizing styrene through depolarized light scattering

The thermal polymerization of clean styrene has been studied through Rayleigh-Brillouin light scattering. The frequency shifts, Rayleigh to Brillouin intensity ratios, Rayleigh depolarization ratios, and depolarized intensities were measured as the polymerization proceeded to completion at 90°C. The depolarized intensities decreased and the frequency shifts increased smoothly from the monomer to the polymer values. The Vv intensities and Rayleigh to Brillouin intensity ratios increase dramatically during the first stages of polymerization then decrease systematically to their final values. There is a large increase in the Rayleigh to Brillouin intensity ratio from the monomer to the final polymer value. The vertical depolarization ratio pv and the horizontal depolarization ratio pV were found to be respectively 0.4 and 1 for the polymer. Our observations are explained in terms of light being scattered from concentration fluctuations in the early stages of polymerization and from spherically symmetric strain fields in the polymer. We believe that the background, which we observed to embrace a wide range of frequencies, was due to rotational Raman transitions.     

On data-guided optimal control simulation of human motion

This work investigates the combination of optical motion capturing data with optimal control simulations of human motion, which can be important in a wide range of applications in the professional as well as the private sector, ranging from health and ergonomics over human-machine-interaction to sports and games [1–3]. There are methodically very different approaches to include optical measurement data in the simulation of human motion, see e.g. [4–6]. Two different approaches to combine data and simulation are investigated in this work. Either we use a soft constraints approach, where the difference of simulated and measured marker positions is part of the objective function (1), or we formulate an hard constraints approach with nonlinear constraints that set an upper bound on this difference (2), while the objective function is purely physiologically motivated. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Transverse dipole association and negative dielectric anisotropy of nematic liquid crystals

Measurements are reported of the dielectric properties of three laterally substituted dicyano compounds with large molecular dipole moments perpendicular to the long molecular axis. Results are given for the materials in solution, in the isotropic liquid state, and for one compound in the nematic state. There is evidence of a high degree of local ferroelectric order in all phases, and dipole correlation factors in excess of 3 were obtained. The significance of these observations for macroscopic ferroelectrically ordered and biaxial liquid-crystalline phases is considered.     

Investigating sorption-driven dissolved organic matter fractionation by multidimensional fluorescence spectroscopy and PARAFAC

Soil organic matter is involved in many ecosystem processes, such as nutrient supply, metal solubilization, and carbon sequestration. This study examined the ability of multidimensional fluorescence spectroscopy and parallel factor analysis (PARAFAC) to provide detailed chemical information on the preferential sorption of higher-molecular-weight components of natural organic matter onto mineral surfaces. Dissolved organic matter (DOM) from soil organic horizons and tree leaf tissues was obtained using water extracts. The suite of fluorescence spectra was modeled with PARAFAC and it was revealed that the DOM extracts contained five fluorescing components: tryptophan-like (peak location at excitation <255 nm:emission 342 nm), tyrosine-like (276 nm:312 nm), and three humic-substance-like components (<255 nm:456 nm, 309 nm:426 nm, <255 nm:401 nm). In general, adsorption onto goethite and gibbsite increased with increasing DOM molecular weight and humification. PARAFAC analysis of the pre- and post-sorption DOM indicated that the ordering of sorption extent was humic-like components (average 91% sorption) > tryptophan-like components (52% sorption) > tyrosine-like components (29% sorption). This differential sorption of the modeled DOM components in both the soil organic horizon and leaf tissue extracts led to the fractionation of DOM. The results of this study demonstrate that multidimensional fluorescence spectroscopy combined with PARAFAC can quantitatively describe the chemical fractionation process due to the interaction of DOM with mineral surfaces.     

Comparison of visual immunoassay and chromogenic culture medium for the presence of Listeria spp. in foods

Two rapid screening methods [the TECRA Listeria Visual Immunoassay (LIS-VIS) kit, an AOAC-approved 48 h visual test, which detects Listeria through colorimetry, and BCM Listeria isolation and differentiation plating agar] were used to screen U.S. Food and Drug Administration-regulated commodities for the presence of Listeria spp. Seventy-four different food samples were screened for the presence of Listeria spp. by using both protocols. Test results for the TECRA LIS-VIA showed 66 negative samples and 1 false positive, with 4 confirmed as L. monocytogenes and 3 as L. innocua. With the BCM agar, 67 samples were negative, 4 were confirmed as L. monocytogenes, and 3 were confirmed as L. innocua. Both methods showed similar results and were effective screening tools for Listeria spp. in foods. The BCM agar method proved to be a rapid, sensitive, and excellent tool for early screening and differentiation of Listeria spp. present in foods.     

Search for the scalar top quark in pp collisions at square root[s] = 1.8 TeV

We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of pp events corresponding to 108.3 pb(-1) of data collected with the D0 detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, t-->b chi+1 and t-->blnu, no evidence for signal is found. We derive cross-section limits as a function of stop ( t ), chargino ( chi+1), and sneutrino ( nu) masses.