DISTRIBUTION OF PRIORITY POLYCYCLIC AROMATIC HYDROCARBONS IN THE SEDIMENT OF LAKE BALATON,HUNGARY

The determination of 13 PAH pollutants was carried out on sediment samples collected at 27 sites at the Lake Balaton, Hungary. The aim was to investigate the distribution patterns of PAHs and the correlation of source-sink relationship. Sediment samples were collected from the upper 10 cm and from 20 to 70 cm depth. The dry mass ratio of the fine grain-size fraction (<0.063 mm) and the coarse sand sediments (0.063–500 mm) were analyzed. Principal component analysis (PCA) was performed on the PAH compositional data for 110 samples to estimate the distribution of PAHs in different compartments. The average concentration of PAHs was found as 132 μg/kg dry weight (11–1734 μg/kg) for all sites and depth. Considering the harbors, at some sites, 930–950 μg/kg of total PAHs were obtained. The ratio of phenantrene/anthracene (PHE/AN) and fluoranthene/pyrene (FA/PY) indicated that most of the samples showed pyrogenic origin. It can be established that the upper 10 cm of the sediment is significantly more polluted than the deeper layers. The interim sediment quality guideline (ISQG) values and the probable effect level (PEL) were used to compare our findings with other data. No concentrations of PAHs were found higher than either ISQG and PEL values of samples collected inside of the lake, so the sediment has not been associated with adverse biological effects. However, the maximum concentrations of 7 out of 9 PAH compounds found in samples of harbors were higher than ISOG values but lower than PELs. Analysis of the harbor sediments revealed an elevated amount of contamination probably derived from the fuel of ships.     

Performance Evaluation of an Improved Particle Size Magnifier (PSM) for Single Nanoparticle Detection

Several modifications of the particle size magnifier (PSM) developed by Okuyama et al. have been introduced recently for detection of particles at diameters of 1 nm and below. However, their evaluation has been incomplete. Here we provide the first direct measurements of counting efficiencies near unity below 2 nm. We use the modified PSM described by Sgro and Fernández de la Mora, which separates thermally the PSM's original vapor generator from the water-cooled growth chamber by means of a narrow and short T where turbulent mixing with the aerosol takes place. The counting efficiency is seen to depend greatly on the aerosol flow, the amount of vapor, and temperature. With ethylene glycol vapor, under optimal conditions, the counting efficiency is 100% down to 1.6 nm (actual diameter of 1.2 nm), and negative particles are more easily activated than positive particles. The improved PSM is applied to the measurement of gold nanoparticle size distributions, and the results show it is a powerful aerosol detector for nanoparticles.     

Solid Fat Content Estimation by Differential Scanning Calorimetry: Prior Treatment and Proposed Correction

The objective of this work was to develop a corrected method for solid fat content estimation by differential scanning calorimetry (DSC), as important differences are usually observed between the results given by DSC and pulsed nuclear magnetic resonance (NMR). Cold storage after full melting of fats was necessary to avoid the appearance of exothermic peaks in the modulated temperature DSC thermograms, in order to make an appropriate estimation of melting energy. Different fats were analyzed by NMR and DSC, obtaining considerably higher solid fat content values with the latter, uncorrected method. These differences were attributed to the fact that consumed energy per unit of melted mass tends to increase with the increase of the melting temperature of each fraction of the fats. A linear correlation between melting enthalpy and melting point of different triglycerides was used to estimate the energy per unit of mass consumed at each temperature. From these data, an estimated transformation of melting energy into melted mass was performed and new solid fat content values were calculated. The results obtained from this correction were much closer to the measurements made by NMR, in comparison to the uncorrected DSC method.     

Thermodegradative study of HDPE–HA nanocomposites: IKP and E 2 function

IKP and E ₂ function methods were used to study thermal stability of HDPE–HA nanocomposites synthesized by in situ ethylene polymerization at different volumes of solvent and temperatures. Thermal analysis was carried out at five different heating rates, β = 3, 5, 7, 10, and 13 °C/min, under N₂ atmosphere. Kinetics parameters calculated by IKP method presented a slight increase on activation energy when HA was incorporated in HDPE. A similar tendency was observed in the results obtained from the E ₂ function method, where the activation energy of the nanocomposites increased 100 kJ/mol with respect to unfilled polymer (420–460 kJ/mol). These results implied higher stability of HDPE due to HA incorporation. HDPE and HDPE–HA degradation mechanisms are represented by a set of functions, those with the highest probability were: nucleation and nucleus growth (S3) 23 %, reaction order (S5) 16 %, reaction in the interface (S6. S7, S8) 11–14 %, and potential law (S14, S17) 3 %.     

Copolymers of long-side-chain di-n-alkyl itaconates or methyl n-alkyl itaconates with styrene: synthesis, characterization, and thermal properties

Two series of copolymers of styrene with di-n-alkyl itaconates or methyl n-alkyl itaconates with n-alkyl side chains of 12, 14, 16, 18, and 22, using different compositions in the feed have been prepared in bulk via radical at 60 °C with AIBN as initiator. In most of the cases the copolymers were obtained in goods yields, their composition being close to the feed composition and their physical states depending on the composition and the itaconate structure. The copolymers were characterized by FTIR and NMR spectroscopy. The ¹H NMR studies indicate that the copolymers have a mainly random distribution of the monomeric units. The thermal degradation process occurs in one step with decomposition temperatures intermediate between those of polyitaconate and polystyrene. Finally, the alkyl side chains of the itaconate moieties are able to crystallize in a paraffinic phase where the melting temperature and enthalpy increase as the itaconate content and the side chain length rise.     

Electrical,rheological and electromagnetic interference shielding properties of thermoplastic polyurethane/carbon nanotube composites

Electrically conducting rubbery composites based on thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs) were prepared through melt blending using a torque rheometer equipped with a mixing chamber. The electrical conductivity, morphology, rheological properties and electromagnetic interference shielding effectiveness (EMI SE) of the TPU/CNT composites were evaluated and also compared with those of carbon black (CB)‐filled TPU composites prepared under the same processing conditions. For both polymer systems, the insulator–conductor transition was very sharp and the electrical percolation threshold at room temperature was at CNT and CB contents of about 1.0 and 1.7 wt%, respectively. The EMI SE over the X‐band frequency range (8–12 GHz) for TPU/CNT and TPU/CB composites was investigated as a function of filler content. EMI SE and electrical conductivity increased with increasing amount of conductive filler, due to the formation of conductive pathways in the TPU matrix. TPU/CNT composites displayed higher electrical conductivity and EMI SE than TPU/CB composites with similar conductive filler content. EMI SE values found for TPU/CNT and TPU/CB composites containing 10 and 15 wt% conductive fillers, respectively, were in the range ?22 to ?20 dB, indicating that these composites are promising candidates for shielding applications. © 2013 Society of Chemical Industry     

Review of quantitative structure‐activity/property relationship studies of dyes: recent advances and perspectives

Dyes have been applied and are playing an increasingly important role in many industries, including the textile, printing, medical and energy industries. Their wide applications imply that specific dyes possessing given properties need to be effectively designed. The present review aims to survey information related to activity/property research of dyes that has been published in the past two decades. Emphasis is laid particularly on studies based on quantitative structure–activity/property relationships that have contributed to the theoretical design and application of dyes. Finally, the perspectives of quantitative structure‐activity/property relationship studies are set out in order to show how this method may be used to design new dyes and to evaluate their different properties. The challenges facing these studies are also outlined.     

Effect of Temperature on C3S and C3S + Nanosilica Hydration and C–S–H Structure

This study aimed to monitor the effect of temperature and the addition of nanosilica on the nanostructure of the C–S–H gel forming during tricalcium silicate (C₃S) hydration. Two types of paste were prepared from a synthesized T₁ C₃S. The first consisted of a blend of deionized water and C₃S at a water/solid ratio of 0.425. In the second, a 90 wt% C₃S + 10 wt% of nanosilica blend was mixed with water at a water/solid ratio of 0.7. The pastes were stored in closed containers at 100% RH and 25°C, 40°C, or 65°C. The hydration reaction was detained after 1, 14, 28, or 62 d with acetone, and then pastes were studied by ²⁹Si magic angle spinning nuclear magnetic resonance (²⁹Si MAS NMR).The main conclusion was that adding nSA expedites C₃S hydration at any age or temperature and modifies the structure of the C–S–H gel formed, two types of C–S–H gel appear. At 25°C and 40°C, more orderly, longer chain gels are initially (1 d) obtained as a result of the pozzolanic reaction between nSA and portlandite (CH) (C–S–H_II gel formation). Subsequently, ongoing C₃S hydration and the concomitant flow of dimers shorten the mean chain length in the gel.     

Effects of Tm3+ Additions on the Crystallization of LaF3 Nanocrystals in Oxyfluoride Glasses: Optical Characterization and Up‐Conversion

The influence of the addition of 1 mol% Tm₂O₃ on the nanocrystallization of LaF₃ in a glass of composition 55SiO₂–20Al₂O₃–15Na₂O–10LaF₃ (mol%) has been studied. Tm₂O₃ affects the phase separation in the glass and delays the onset of crystallization with respect to the undoped glass. Additionally, the maximum LaF₃ crystal size is slightly greater than that in the undoped glass–ceramics. The microstructural and compositional changes in the glass matrix have been studied using several techniques, including viscosity, dilatometry, X‐ray and neutron diffraction (XRD, ND), quantitative Rietveld refinement, transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and Raman spectroscopy. Photoluminescence measurements indicate that the Tm³⁺ ions are distributed between the glassy matrix and LaF₃ crystals. Eu₂O₃ has been used as structure probe and part of the Eu³⁺ ions are reduced to Eu²⁺ when incorporated in the LaF₃ nano‐crystals. Up‐conversion spectra under IR‐excitation show a higher intensity of the blue emission in the Tm‐doped glass–ceramic compared with that in the glass.