Effects and modelling of ultrasonic waste‐activated sludge disintegration

Sonication is a well‐known sludge pretreatment technique with the advantages of simple operation and high efficiency. However, it is an energy‐intensive process. Hence, it is very important to predetermine its sludge disintegration efficiency at varying pretreatment conditions in order to minimize the ultrasonic energy consumption. In this study, it was found that the ultrasonic sludge disintegration occurred in two stages: rapid and subsequent slow disintegration stages. For this reason, it was aimed to develop a simple and accurate mathematical model to describe the two‐stage sludge disintegration as a function of pretreatment conditions. Sludge concentration and ultrasonic density along with sonication period were involved in this model as independent variables. It was determined that the mathematical model can predict accurately the degree of sludge disintegration. Thus, the proposed model was seen to be very useful for evaluating the disintegration efficiency and/or for process design using the operating parameters under different conditions.     

Seasonality in Estonian Traditional Landscape: The Example of Large Village Swings

Like every nation, Estonians have their own indigenous customs and habits. Village swings and the place of these swings in the landscape are focused upon as an example of such Estonian customs, and changes in landscape as related to seasonality and liminality are discussed. The word ‘swing’ is used to denote a large construction (traditionally made of wood) that is able to carry and swing at least two people. Village swings (for public use) are usually located in the middle of a village and the site is commonly used by young people as a place to meet and have a good time. Swinging takes place mostly in the spring and summer, forming one of the many seasonal activities that make up the Estonian traditional calendar. The seasonal break in swinging activity contributes to the eagerness with which swinging is resumed when spring returns, so seasonality creates frames, with the most valued time being the spring. With swinging, the spring has been celebrated as a very valuable and long-awaited season. Although the religious background for swinging has been forgotten, the place is still special and is visited mostly on certain festive occasions. As there is no comparable alternative to swing sites as a socializing place in the village, they have persisted through the centuries. The importance of preserving such unique seasonal places in Estonia's social landscape is demonstrated.     

Novel colloidal nanofiber electrolytes from PVA‐organoclay/poly(MA‐alt‐MVE), and their NaOH and Ag‐carrying polymer complexes

Novel multifunctional polymer nanofiber electrolytes with covalence crosslinked structures from various solution blends of reactive intercalated poly(vinyl alcohol)/octadecylamine montmorillonite (as a matrix polymer), poly(maleic anhydride‐alt‐methyl vinyl ether) (as a partner polymer) and their NaOH‐absorbing and Ag‐carrying polymer complexes were fabricated via electrospinning. Chemical, physical, morphological, and electrical properties of nanofiber structures were investigated by FTIR, XRD, SEM, and electrical analysis methods. Ag precursors in fiber composites significantly improved phase separation processing, fiber morphologies, diameter distributions, and electrical properties of the fibers. In situ generation of Ag nanoparticles and their distribution on nanofiber surfaces during fiber formation occurred via complex formation between silver cations and electronegative functional groups from both matrix and partner polymers as stabilizing/reducing agents. Electrical resistance and conductivity strongly depended on matrix/partner polymer ratios and absorption time of NaOH solution on nanofibers. Addition of NaOH changed the electrical properties of fiber structures from almost dielectric state to excellent conductivity form. The fabricated unique nanofiber electrolytes are promising candidates for applications in power and fuel cell nanotechnology, electrochemical, and bioengineering processes as reactive semiconductive platforms. POLYM. ENG. SCI., 56:204–213, 2016. © 2015 Society of Plastics Engineers     

Dielectric study of side-chain liquid crystalline polyazomethine/fullerene C<Subscript>60</Subscript> nanocomposite

For side-chain liquid crystalline polyazomethine/fullerene C₆₀ nanocomposite (C₆₀ loading is 0.25 wt%), both real and imaginary components of the dielectric permittivity were investigated in wide regions of temperature and frequency. Analysis of frequency dependent permittivity allowed finding three relaxations (α, β ₁ and β ₂) in the nanocomposite. They were attributed to specific modes of molecular mobility. β-relaxations were described with the Arrhenius equation, whereas α-relaxation was described with the Vogel-Fulcher-Tammann equation. Anti-plasticization effect of the C₆₀ doping was shown to be manifested as an increase of the glass transition temperature of the nanocomposite as compared with that of the neat polymer.     

Pt nanoparticles synthesized with new surfactants: improvement in C1–C3 alcohol oxidation catalytic activity

Platinum electrocatalysts were prepared using PtCl₄ as a starting material and 1-decylamine, N,N-dimethyldecylamine, 1-dodecylamine, N,N-dimethyldodecylamine, 1-hexadecylamine, and 1-octadecylamine as surfactants. These surfactants were used for the first time in this synthesis to determine whether the primary and/or tertiary structure and/or chain length of the surfactants, affects the size and/or activity of the catalysts in C₁–C₃ alcohol electro-oxidation reactions. Electrochemical measurements (cyclic voltammetry and chronoamperometry) indicated that the highest electrocatalytic performance was observed for the Pt nanocatalysts that were stabilized by N,N-dimethyldecylamine, and this has a tertiary amine structure with a short chain length (R = C₁₀H₂₁). The high performance may be due to the high electrochemical surface area, Pt(0)/Pt(IV) ratio, %Pt utility, and roughness factor (R _f). X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy were used to determine the parameters that affect the catalytic activities.     

Hybrid dual-curable cyanate ester/boron phosphate composites via sequential thiol-ene photopolymerization and thermal polymerization

The aim of this study was to improve hybrid dual-curable cyanate ester/boron phosphate composites via sequential thiol-ene photopolymerization and thermal polymerization for high performance applications such as aerospace and electronic devices. A novel 2,2′-diallylbisphenol A dicyanate ester (DA-BADCy) which is the allyl group containing cyanate ester was synthesized and characterized. DA-BADCy, silicon containing monofunctional thiol compound, trifunctional thiol compound and boron phosphate were cured using both ultraviolet (UV) and thermal methods. Using thiol-ene system, cyanate ester formulations, which are normally prepared at high temperatures, were prepared at room temperature. This study maintains ease of application for cyanate esters. Thermal stability, flammability and thermal conductivity of the samples were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), limiting oxygen index (LOI) and laser flash method, respectively. The samples were characterized with the following analysis; gel content, water absorption capacity and stress–strain test. Hydrophobicity of the samples was determined by the contact angle measurements. Moreover, the surface morphology of the samples was investigated by a scanning electron microscopy (SEM–EDS). The obtained results prove that the composites have good thermal and mechanical properties and with the help of easier preparation techniques, they can be used in many applications such as aerospace, electronic devices, materials engineering.     

Synthesis of Invar 36 type alloys from elemental and prealloyed powders by mechanical alloying

Invar 36 (Fe₆₄Ni₃₆) nanocrystalline powders were successfully obtained by the mechanical alloying process. The mechanically alloyed Invar 36 powders were obtained from both, Fe–Ni elemental and Fe–Ni₃Fe prealloyed powders. XRD, DSC and magnetic measurements were used to characterise the Invar 36 powders. The lattice parameter evolution versus temperature of Invar 36 powders was investigated by in-situ high-temperature X-ray diffraction (HT-XRD). For both, Invar 36 (Fe, Ni) and Invar 36 (Fe, Ni₃Fe) powders, the lattice parameter values are constant up to about 350°C. The magnetic measurement also indicated that the Invar 36-type alloys are formed after 16?h of milling.     

pH- and heat-induced structural changes of bovine α-lactalbumin in response to oleic acid binding

Bovine α-lactalbumin (α-LA) is able to interact with fatty acids, resulting in structural changes that are potentially responsible for the HAMLET/BAMLET role. Different states of α-LA induced by pH, temperature and fatty acid binding have been examined. Evidences of the structural changes of α-LA in molten globule and native states in correlation with oleic acid (OA) binding are shown using fluorescence spectroscopy and in silico approach. In addition, the α-LA was subjected to automated docking analysis, to better understand the interaction with oleic acid, using the PatchDock algorithm. The experimental results demonstrate a more flexible conformation of the protein at pH 2.5 when compared to neutral pH, thus facilitating the oleic acid binding to α-LA. The quenching experiments indicate the remarkable increase in the content of molten globule state at pH 2.5 and a more compact and rigid structure for α-LA–OA complexes at pH 7.0. The docking results are consistent with the experimental data concerning the thermal stability of the α-LA–OA complex. α-LA in different conformations/complexes was sensitive to pH and temperature. Several different molecular species induced by pH, heat treatment and oleic acid binding were suggested. The structure of the protein was more flexible at acidic pH, therefore favoring the hydrophobic exposure.     

Electrical characterization of the boron trifluoride doped poly(3‐aminoacetophenone)/p‐Si junction

Electrical and interface state properties of the borontrifluoride doped poly(3‐aminoacetophenone)/p‐Si junction have been investigated by current‐voltage and impedance spectroscopy methods. Al/p‐Si/P₃APBF₃/Aldiode indicates a nonideal behavior with electrical parameters (n = 3.53, ?_B = 0.82 eV, and R_s = 1.48 kΩ), which result from the interfacial layer, series resistance, and resistance of the organic semiconductor. The obtained barrier height value of the Al/p‐Si/P₃APBF₃/Aldiode is higher than that of the conventional Al/p‐Si (?_B = 0.58 eV) Schottky diode. The interface state density of the diode was of the order of 1.05× 10¹² eV^?1 cm^?2. It is evaluated that the barrier height and interface state density values of the diode are modified using the boron trifluoride doped poly (3‐aminoacetophenone) organic semiconductor. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers