A new Schiff base epoxy oligomer resin: Synthesis,characterization, and thermal decomposition kinetics

Oligo{2,2′‐{1,4‐phenylenebis[nitrilomethylylidene]}bis(6‐methoxyphenol)} (OPNMMP) was synthesized from o‐vanillin and p‐phenylene diamine by oxidative polycondensation with NaOCl in an aqueous alkaline. Then, a new Schiff Base epoxy oligomer resin, OPNMMP–epichlorohydrine (EPC), was produced with EPC. The structures of the resulting compounds were confirmed by Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, ¹H‐NMR, and ¹³C‐NMR. Further characterization processes were preformed by thermogravimetry (TG)–differential thermal analysis, gel permeation chromatography, and solubility testing. Also, the kinetics of the thermal decomposition of OPNMMP–EPC were investigated by thermogravimetric analysis. The TG curves showed that the thermal decomposition of OPNMMP–EPC occurred in one stage. The kinetic parameters related to the decomposition kinetics of OPNMMP–EPC were obtained from TG curves with the following methods: Friedman, Flynn–Wall–Ozawa, Kissinger, invariant kinetic parameter, and Coats–Redfern (CR), under an N₂ dynamic atmosphere and different heating rates (5, 10, 15, and 20°C/min). The mechanism function and pre‐exponential factor were also determined by a master plots method. The apparent activation energies of the thermal decomposition were calculated from these methods for OPNMMP–EPC. The analysis of the results obtained by the CR and master plots methods showed that the decomposition mechanism of OPNMMP–EPC in N₂ was a deceleration‐type mechanism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

From Metalloligand to Extended 3D Network: Synthesis, Crystal Structure and Magnetic Property of {[Cu(en)2][Cu(μ3-pydc)2]·6H2O}n

A novel 2D coordination polymer, {[Cu(en)₂][Cu(μ₃-pydc)₂]·6H₂O} _n (1) pyridine-2,3-dicarboxylic acid (pydcH₂); ethylenediamine (en), based on the metalloligand [Cu(μ-pydcH)₂] _n , has been prepared and characterized by IR, UV–Vis and ESR spectroscopy, thermal analysis, differential scanning calorimetry and single crystal X-ray diffraction techniques. The temperature dependent magnetic properties have also been studied. The pydc ligand exhibits tetradentate-μ₃ bridging mode, being coordinated through three carboxylate oxygens and one nitrogen atom. The complex contains two copper(II) ions that exhibit two different coordination environment with two en and two pydc ligands. The single crystal structure shows that the complex forms a 3D framework with 2D layers along the c-axis. Van der Waals interactions are responsible for the self-assembly of the layer into a 3D network.     

Synthesis of tetrahedral quasi-type-II CdSe-CdS core-shell quantum dots

Synthesis of colloidal nanocrystals of II-VI semiconductor materials has been refined in recent decades and their size dependent optoelectronic properties have been well established. Here we report a facile synthesis of CdSe-CdS core-shell heterostructures using a two-step hot injection process. Red-shifts in absorption and photoluminescence spectra show that the obtained quantum dots have quasi-type-II alignment of energy levels. The obtained nanocrystals have a heterostructure with a large and highly faceted tetrahedral CdS shell grown epitaxially over a spherical CdSe core. The obtained morphology as well as high resolution electron microscopy confirms that the tetrahedral shell have a zinc blende crystal structure. A phenomenological mechanism for the growth and morphology of the nanocrystals is discussed.     

Effect of Ni and Al doping on structural,optical, and CO2 gas sensing properties of 1D ZnO nanorods produced by hydrothermal method

In the present study, the one-dimensional ZnO nanorod structures are produced within the different nickel and aluminum molecular weight ratios of 0–7% using the hydrothermal method. It is found that the aluminum (Al) and nickel (Ni) impurities with different ionic radius, chemical valence, and electron configurations of outer shell cause to vary the fundamental characteristic features including the crystallinity quality, crystallite size, surface morphology, nanorod diameter, optical absorbance, energy band gap, resistance, gas response, and gas sensing properties. The structural analyses performed by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the samples are found to crystallize in the hexagonal wurtzite structure. The presence of optimum nickel and aluminum in the crystal system improves considerably the crystallinity quality and surface morphology. Additionally, the combination of electron dispersive X-ray (EDX) and XRD results declare that the Ni and Al impurities incorporate successfully into the ZnO crystal structure. Moreover, the diameters of nanorod structures in 1D orientation are determined to be 80 nm or below. The hexagonal wurtzite-type ZnO nanorod structure prepared by 5% Ni has more space between the nanorods and thus presents higher response to the CO₂ detection. Further, the optical absorbance spectra display that the band gap value is observed to decrease regularly with the increment in the doping level as a result of band shrinkage effect depending on the enhancement of mobile hole carrier concentrations in the crystal structure. In other words, the doping mechanism leads to vary the homogeneities in the interfacial charges, nanorod diameters, ZnO oxide layer composition and thickness. The last test conducted in this study is responsible for the determination of CO₂ gas sensing levels. The obtained gas sensing results are further compared with each other and literature findings. It is observed that 5% Ni-doped sample provides more successful results than other samples in the sensing CO₂ gas at the different concentrations. All in all, the paper establishing a strong methodology between doping mechanism and change in the fundamental characteristic features of hexagonal wurtzite-type ZnO with the aid of advanced microscopy techniques will become pioneering research to answer key questions in materials sciences and electronic research.     

Cold plasma for the preservation of aquatic food products: An overview

Cold plasma (CP) is an upcoming technology implemented for the preservation of highly perishable foods, especially aquatic food products (AFPs). The high moisture content, high-quality protein with all essential amino acids and unsaturated fatty acids makes AFP more susceptible to microbial spoilage and oxidation of lipids and proteins. Spoilage lowers the nutritive value and could generate toxic components, making it unsafe for consumption. In recent times, the rising demand for food products of aquatic origin with preserved quality and extended shelf-life has been recorded. In addition, minimally or nonthermally processed and preserved foods are gaining great attention. CP technology has demonstrated an excellent ability to inactivate microorganisms without promoting their resistance and triggering some deteriorative enzymes, which are typical factors responsible for the spoilage of AFP. Consequently, CP could be recommended as a minimal processing intervention for preserving the quality of AFP. This review focuses on different mechanisms of fish spoilage, that is, by microorganisms and oxidation, their inhibition via the application of CP, and the retention of quality and shelf-life extension of AFP.     

Effects of an intense,high-frequency laser field on bound states in Ga1 ? xInxNyAs1 ? y/GaAs double quantum well

Within the envelope function approach and the effective-mass approximation, we have investigated theoretically the effect of an intense, high-frequency laser field on the bound states in a Ga_xIn_{1 − x}N_yAs_{1 − y}/GaAs double quantum well for different nitrogen and indium mole concentrations. The laser-dressed potential, bound states, and squared wave functions related to these bound states in Ga_{1 − x}In_xN_yAs_{1 − y}/GaAs double quantum well are investigated as a function of the position and laser-dressing parameter. Our numerical results show that both intense laser field and nitrogen (indium) incorporation into the GaInNAs have strong influences on carrier localization.     

The effect of welding parameters on fracture toughness of resistance spot-welded galvanized DP600 automotive steel sheets

The aim of this study was to evaluate the fracture toughness of resistance spot welded (RSW) lap joints of galvanized DP600 steels. RSW lap joints galvanized DP600 steel sheets were performed on spot welded in a pneumatic, phase-shift-controlled, and 0–9?kA effective weld current capable AC spot welding machine. Defect-free RSW lap joints were produced on galvanized DP600 steel sheets. Fracture toughness of RSW lap joints were calculated from the results of shearing tensile tests: the dependence of fracture toughness to welding current, welding time, and hardness of welding zone for galvanized DP600 steel sheets. According to the experimental data, the fracture toughness increases as welding current and welding time increase up to a certain value, then the fracture toughness starts to decrease. Also, it was seen that the fracture toughness varies with the hardness of the welding zone. This variation is related to welding current.     

Treatment of leachate by electrocoagulation using aluminum and iron electrodes

In this paper, treatment of leachate by electrocoagulation (EC) has been investigated in a batch process. The sample of leachate was supplied from Odayeri Landfill Site in Istanbul. Firstly, EC was compared with classical chemical coagulation (CC) process via COD removal. The first comparison results with 348 A/m2 current density showed that EC process has higher treatment performance than CC process. Secondly, effects of process variables such as electrode material, current density (from 348 to 631 A/m2), pH, treatment cost, and operating time for EC process are investigated on COD and NH4-N removal efficiencies. The appropriate electrode type search for EC provided that aluminum supplies more COD removal (56%) than iron electrode (35%) at the end of the 30 min operating time. Finally, EC experiments were also continued to determine the efficiency of ammonia removal, and the effects of current density, mixing, and aeration. All the findings of the study revealed that treatment of leachate by EC can be used as a step of a joint treatment.     

The importance of lactic acid bacteria for the prevention of bacterial growth and their biogenic amines formation: A review

Foodborne pathogens (FBP) represent an important threat to the consumers' health as they are able to cause different foodborne diseases. In order to eliminate the potential risk of those pathogens, lactic acid bacteria (LAB) have received a great attention in the food biotechnology sector since they play an essential function to prevent bacterial growth and reduce the biogenic amines (BAs) formation. The foodborne illnesses (diarrhea, vomiting, and abdominal pain, etc.) caused by those microbial pathogens is due to various reasons, one of them is related to the decarboxylation of available amino acids that lead to BAs production. The formation of BAs by pathogens in foods can cause the deterioration of their nutritional and sensory qualities. BAs formation can also have toxicological impacts and lead to different types of intoxications. The growth of FBP and their BAs production should be monitored and prevented to avoid such problems. LAB is capable of improving food safety by preventing foods spoilage and extending their shelf-life. LAB are utilized by the food industries to produce fermented products with their antibacterial effects as bio-preservative agents to extent their storage period and preserve their nutritive and gustative characteristics. Besides their contribution to the flavor for fermented foods, LAB secretes various antimicrobial substances including organic acids, hydrogen peroxide, and bacteriocins. Consequently, in this paper, the impact of LAB on the growth of FBP and their BAs formation in food has been reviewed extensively.     

Sour Cherry By-products: Compositions,Functional Properties and Recovery Potentials – A Review

Abstract

Sour (tart) cherry is an industrial fruit where a considerable amount of by-products remain after processing. Sour cherry by-products consist of pomace (skin and flesh) and seeds (pit, stone) which remain after the fruit juice and IQF processes. Sour cherry pomace is characterized with a high content of phenolic compounds and the seed constitutes a high oil yield with beneficial effects on human health because of their antioxidant, antimicrobial, and anti-inflammatory properties. There has been a great interest in sour cherry by-products due to the increasing production rate of sour cherry worldwide and the increasing efforts on seeking bioactive compounds from natural sources as functional food. Thus, there have been a number of studies regarding the sour cherry pomace and sour cherry seed, especially in the last five years. The present review summarizes the chemical, biological, functional, and technological properties of the sour cherry pomace and sour cherry seed with their current and potential applications.