Raman spectrum modification in the presence of solvated electrons. Observation by polarization CARS

The multiple-scattering series for depolarized light scattering from simple liquids is investigated. It is found that the leading term in the series, due to double—double scattering, is probably not large compared to double—triple (DT) scattering contributions. Existing theories, which neglect DT scattering, have concluded that the experimental data cannot be explained using the dipole—induced dipole (DID) model for the pair polarizability. It is suggested that a theory which includes DT scattering will not lead to rejection of the DID model.     

Synthesis and structure of μ-oxo-bis [(acetylacetonato)(thioacetylacetonato)] dioxodimolybdenum(V) and υ-oxo-[tris(acetylacetonato)(thioacetylacetonato)]dioxodimolybdenum(V)

In the reaction of Mo₂O₃ (acac)₄ and Mo₂O₃ (OAc)₄ with thioacetylacetone two new complexes of molybdenum(V), Mo₂O₃ (acac)₂(Sacac)₂ (complexI) and Mo₂O₃(acac)₃(Sacac) (complexII), respectively, have been prepared. Their crystal structures have been determined from single crystal diffractometer data and refined to the finalR values of 0.068 and 0.044, respectively. Both complexes crystallize in the tetragonal space groupI4₁/a with cell dimensions, (I):a=21.646(3),c=11.627(2) Å,D _calc=1.630 g cm^–3,Z=8 and (II):a=21.240(3),c=11.688(2) Å,D _clac=1.644 g cm^3–,Z=8 and have essentially the same structure. In the structure of (II) half of thioacetylacetone of (I) is statistically replaced by acetylacetone causing thus an occupational disorder in this region of the structure. Both complex molecules are dinuclear and have crystallographically imposed ¯1 symmetry with the bridging oxygen atom in the center of symmetry. Molybdenum atoms exhibit distorted octahedral coordinations. Sulfur atom of the Sacac ligand in (I) shows a considerably largertrans influence than the oxo-oxygen atom.     

Removal of Pb(II) ions from aqueous systems using thiol-functionalized cobalt-ferrite magnetic nanoparticles

We have investigated the removal of Pb²⁺ ions from water using thiol-functionalized, cobalt-ferrite, magnetic nanoparticles. These magnetic nanoparticles were prepared using the co-precipitation method and their surfaces were modified with tetraethoxy silane and 3-mercaptopropyl trimethoxysilane in order to provide a sufficient surface concentration of the thiol (–SH) functional groups. The adsorption of the Pb²⁺ ions from the aqueous solutions onto the thiol-functionalized, cobalt-ferrite, magnetic nanoparticles was studied. The investigated parameters include the pH value of the model water, the concentration of the adsorbent, the contact time and the temperature of adsorption. The removal of the Pb²⁺ was found to be greater at the higher pH values and increasing the temperature was also found to increase the removal of Pb²⁺ ions.     

Recent trends in image evaluation of HPTLC chromatograms

Abstract

In the current article, an overview of recent applications and opportunities of image evaluation of high-performance thin-layer chromatograms (HPTLC) in food analysis and natural product research is presented. The article shortly covers the aspects of specialized software packages for image analysis, image post-correction, signal acquisition, and preprocessing. Contemporary aspects of image-based HPTLC fingerprinting, quantification of target compounds, and advanced chemometric modeling were reviewed. Special attention was dedicated to freely available software packages. Advantages and disadvantages of each one were discussed in terms of abilities to obtain chromatographic profiles and perform crucial steps in signal manipulation, such as background subtraction, denoising, and background detrending. The most frequently applied techniques for signal manipulation have been discussed and recommendation provided. In that sense, the article aims to provide a valuable guideline for readers dealing with the application of HPTLC image analysis in food and natural products research, especially in connection with the most frequently used chemometric techniques, in domains of pattern recognition, classification, and regression.     

Preparation and characterization of PLA composites with modified magnesium hydroxide obtained from seawater

Journal of Thermal Analysis and Calorimetry - Modification of poly(lactic acid) (PLA) was performed with the surface modified magnesium hydroxide (mMH) obtained from seawater. Surface modification...     

Effect and Modeling of Glucose Inhibition and In Situ Glucose Removal During Enzymatic Hydrolysis of Pretreated Wheat Straw

The enzymatic hydrolysis of lignocellulosic biomass is known to be product-inhibited by glucose. In this study, the effects on cellulolytic glucose yields of glucose inhibition and in situ glucose removal were examined and modeled during extended treatment of heat-pretreated wheat straw with the cellulolytic enzyme system, Celluclast? 1.5 L, from Trichoderma reesei, supplemented with a β-glucosidase, Novozym? 188, from Aspergillus niger. Addition of glucose (0–40 g/L) significantly decreased the enzyme-catalyzed glucose formation rates and final glucose yields, in a dose-dependent manner, during 96 h of reaction. When glucose was removed by dialysis during the enzymatic hydrolysis, the cellulose conversion rates and glucose yields increased. In fact, with dialytic in situ glucose removal, the rate of enzyme-catalyzed glucose release during 48–72 h of reaction recovered from 20–40% to become ≈70% of the rate recorded during 6–24 h of reaction. Although Michaelis–Menten kinetics do not suffice to model the kinetics of the complex multi-enzymatic degradation of cellulose, the data for the glucose inhibition were surprisingly well described by simple Michaelis–Menten inhibition models without great significance of the inhibition mechanism. Moreover, the experimental in situ removal of glucose could be simulated by a Michaelis–Menten inhibition model. The data provide an important base for design of novel reactors and operating regimes which include continuous product removal during enzymatic hydrolysis of lignocellulose.     

Structural Changes in a Protein Fragment from Abalone Shell during the Precipitation of Calcium Carbonate

Mineralized tissues grow through biologically controlled processes in which specific macromolecules are involved. Some of these molecules, which are present in very low concentrations and are difficult to localize and characterize, become entrapped inside the mineralized tissue. Herein, a protein fragment, GP, which was obtained by the alkaline digestion of the green sheet of the abalone shell, is used as a probe to study the changes in molecular structure that occur during the precipitation of calcium carbonate. This important goal was achieved by exploiting a fluorescent tag in GP. The experimental results that were obtained by using spectroscopic‐, chromatographic‐, and microscopic techniques indicate that GP controls the precipitation kinetics and morphology of calcium carbonate crystals, and that it only undergoes structural reorganization when entrapped inside calcium carbonate crystals. To the best of our knowledge, this report represents one of the first studies on the conformational changes of a protein fragment that is involved in biomineralization processes on moving from the solution phase into the mineral phase.     

Structure and stability of common sesquiterpenes

We present data on the electronic structure, polarity and relative stability of 14 common sesquiterpenes. The data were obtained by a combination of spectroscopic and high-level theoretical analysis. The discussion also includes comments on possible implication of molecular properties for physiological behaviour.     

Photochemistry via photoelectron spectroscopy: N-substituted phthalimides

The electronic structures of several N-substituted phthalimides have been investigated by UV photoelectron spectroscopy and outer valence Greens function calculations. Some spectra reveal the presence of photofragmentation and photoelimination processes related to the decay of the aminium radical cation. We compared the fragmentation mechanisms in the gas phase and in the solution.