Morphology and magnetic characterisation of aluminium substituted yttrium-iron garnet nanoparticles prepared using sol gel technique

Aluminum substituted yttrium iron garnet nano particles with compositional variation of Y(3.0-x) A1(x)Fe5O12, where x = 0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 were prepared using sol gel technique. The X-ray diffraction results showed that the best garnet phase appeared when the sintering temperature was 800 degrees C. Nano-crystalline particles with high purity and sizes ranging from 20 to 100 nm were obtained. It was found that the aluminum substitution had resulted in a sharp fall of the d-spacing when x = 2, which we speculated is due to the preference of the aluminum atoms to the smaller tetrahedron and octahedron sites instead of the much larger dodecahedron site. High resolution transmission electron microscope (HRTEM) and electron diffraction (ED) patterns showed single crystal nanoparticles were obtained from this method. The magnetic measurement gave moderate values of initial permeability; the highest value of 5.3 was shown by sample Y3Fe5O12 at more than 100 MHz which was attributed to the morphology of the microstructure which appeared to be homogeneous. This had resulted in an easy movement of domain walls. The substitution of aluminum for yttrium is speculated to cause a cubic to rhombodedral structural change and had weakened the super-exchange interactions thus a fall of real permeability was observed. This might have created a strain in the sub-lattices and had subsequently caused a shift of resonance frequencies to more than 1.8 GHz when x > 0.5.     

Impact of industrial discharges on the zooplankton community in the Messaieed industrial area,Qatar (Persian Gulf)

Zooplankton samples were collected from the Messaieed Marine Area that is subject to industrial and sewage discharge, thermal pollution, as well as oil loading and unloading activities. Copepods formed 74% of the zooplankton community followed by bivalves (7.6%) and Gastropod veligers (5.5%), Ostracods (4.7%) and Cladocera (3.4%). Industrial discharge not only impacted the total number of zooplankton but also species diversity. Diversity indices were higher for inner coastal waters. Pollution levels more than reduction in food source impacted the distribution of main zooplankton groups. The pollution stress changed the structure of zooplankton community rather than impacting the total population. Copepods showed resistance to oil pollution but were reduced in numbers at areas affected by oxygen demanding wastes. Polychaete larvae and Chaetognatha withstand elevated temperature, ammonia and pH levels.     

The role of partnerships in water‐related research in Palestine

This study analyses the good effect of science and engineering inputs from partnerships and applied research in promoting sustainable management of water and environmental resources in Palestine. The capacity building achieved during the past 10 years at the Institute of Environmental and Water Studies (IEWS) is reviewed. Palestine faces major constraints, and these affect everyone and everything. A problem‐solving approach can be beneficial.     

Predicting the risk of contractor default in Saudi Arabia utilizing artificial neural network (ANN) and genetic algorithm (GA) techniques

The construction project is subject to several risks, one of the most important of which is contractor default because contractor default may increase the final project cost considerably. In the US construction industry, owners commonly shield themselves from the risk of contractor default by transferring this risk to the contractor, who in turn transfers this risk to a surety company. On the other hand, the General Directorate of Military Works (GDMW) of the Kingdom of Saudi Arabia retains the risk of contractor default rather than transferring it to a third party. An artificial neural network (ANN) and a genetic algorithm (GA) are used in this study to predict the risk of contractor default in construction projects undertaken for the Saudi armed forces. Based on this prediction, the Saudi GDMW can make a decision to engage or not to engage the services of a contractor. In case the models are not able to generate reliable predictions (or generate contradictory outcomes), the GDMW will have to augment its budget with contingency funds to be used in the event of contractor default. The outcome of this study is of particular relevance to construction owners because it proposes an approach that can allow them to replace an indiscriminate blanket policy by a policy that is rational, effective, prudent and economical.     

Geochemical reactions resulting from in situ oxidation of PCE-DNAPL by KMnO4 in a sandy aquifer

Although the potential for KMnO4 to destroy chlorinated ethenes in situ was first recognized more than a decade ago, the geochemical processes that accompany the oxidation have not previously been examined. In this study, aqueous KMnO4 solutions (10-30 g/L) were injected into an unconfined sand aquifer contaminated by the dense non-aqueous-phase liquid (DNAPL) tetrachloroethylene (PCE). The effects of the injections were monitored using depth-specific, multilevel groundwater samplers, and continuous cores. Two distinct geochemical zones evolved within several days after injection. In one zone where DNAPL is present, reactions between KMnO4 and dissolved PCE resulted in the release of abundant chloride and hydrogen ions to the water. Calcite and dolomite dissolved, buffering the pH in the range of 5.8-6.5, releasing Ca, Mg, and CO2 to the pore water. In this zone, the aqueous Ca/Cl concentration ratio is close to 5:12, consistent with the following reaction for the oxidation of PCE in a carbonate-rich aquifer: 3C2Cl4 + 5CaCO3(s) + 4KMnO4 + 2H+ --> 11CO2 + 4MnO2(s) + H2O + 12Cl- + 5Ca2+ + 4K+. In addition to Mg from dolomite dissolution, increases in the concentration of Mg as well as Na may result from exchange with K at cation-exchange sites. In the second zone, where lesser amounts of PCE were present, KMnO4 persisted in the aquifer for more than 14 months, and the porewater pH increased graduallyto between 9 and 10 as a resultof reaction between KMnO4 and H2O. A small increase in SO4 concentrations in the zones invaded by KMnO4 suggests that KMnO4 injections caused oxidation of sulfide minerals. There are important benefits of carbonate mineral buffering during DNAPL remediation by in situ oxidation. In a carbonate-buffered system, Mn(VII) is reduced to Mn(IV) and is immobilized in the groundwater by precipitating as insoluble manganese oxide. Energy-dispersive X-ray spectroscopy analyses of the manganese oxide coatings on aquifer mineral grains have detected the impurities Al, Ca, Cl, Cu, Pb, P, K, Si, S, Ti, U, and Zn indicating that, similar to natural systems, precipitation of manganese oxide is accompanied by coprecipitation of other elements. In addition, the consumption of excess KMnO4 by reaction with reduced minerals such as magnetite will be minimized because the rates of these reactions increase with decreasing pH. Aquifer cores collected after the KMnO4 injections exhibit dark brown to black bands of manganese oxide reaction products in sand layers where DNAPL was originally present. Mineralogical investigations indicate that the manganese oxide coatings are uniformly distributed over the mineral grains. Observations of the coatings using transmission electron microscopy indicate that they are on the order of 1 microm thick, and consequently, the decrease in porosity through the formation of the coatings is negligible.     

The effect of gamma irradiation on the microbial load,mineral concentration and sensory characteristics of liquorice (Glycyrrhiza glabra L)

Ground liquorice roots were exposed to various doses (0, 5, 10, 15 and 20 kGy) of gamma radiation from a ⁶⁰Co source. Irradiated and non‐irradiated samples were stored at room temperature. Microbial population, viscosity, concentrations of some minerals and the sensory properties of the extracts were evaluated after 0 and 12 months of storage. Tests carried out immediately after irradiation showed that the microbial count had been reduced and that the dose required to reduce the count by 1 log cycle (D₁₀) was about 2 kGy. No effect was observed on the total dissolved solids in extracts of liquorice roots. Glycyrrhizinic acid concentration in the extracts and the viscosities of suspensions produced from irradiated roots were lower than those from non‐irradiated ones. Sensory evaluation indicated that there were no significant differences (P < 0.05) in colour, taste or flavour between extracts produced from irradiated and non‐irradiated roots. However, after 12 months of storage, some mineral ion (Na⁺, Ca²⁺ and K⁺) concentrations in extracts produced from irradiated roots were lower than in those from non‐irradiated ones; no significant differences (P < 0.05) in viscosity were found between suspensions of irradiated and non‐irradiated roots. © 2002 Society of Chemical Industry     

Oscillatory Rheology and Creep Behavior of Barley β‐d‐glucan Concentrate Dough: Effect of Particle Size,Temperature, and Water Content

Small amplitude oscillatory rheology and creep behavior of β‐glucan concentrate (BGC) dough were studied as function of particle size (74, 105, 149, 297, and 595 μm), BGC particle‐to‐water ratio (1:4, 1:5, and 1:6), and temperature (25, 40, 55, 70, and 85 °C). The color intensity and protein content increased with decreasing particle size by creating more surface areas. The water holding capacity (WHC) and sediment volume fraction increased with increasing particle size from 74 to 595 μm, which directly influences the mechanical rigidity and viscoelasticity of the dough. The dough exhibited predominating solid‐like behavior (elastic modulus, G′ > viscous modulus, G″). A discrete retardation spectrum is employed to the creep data to obtain retardation time and compliance parameters, which varied significantly with particle size and the process temperature. Creep tests exhibited more pronounced effect on dough behavior compared to oscillatory measurement. The protein denaturation temperature was insignificantly increased with particle fractions from 107 to 110 °C. All those information could be helpful to identify the particle size range and WHC of BGC that could be useful to produce a β‐d ‐glucan enriched designed food.     

The pH‐responsive cycloterpolymers of diallyldimethylammonium chloride, 3‐(N,N‐diallylammonio)propanesulfonate,and sulfur dioxide

The cycloterpolymerizations of diallyldimethylammonium chloride, 3‐(N,N‐diallylammonio)propanesulfonate, and sulfur dioxide afforded a series of pH‐responsive cycloterpolymers in excellent yields. The solution properties of these ionic polymers were controlled by the composition of the monomeric units; exhibiting dominance either in polyzwitterionic or cationic character. The unquenched valency of nitrogen in the monomeric units of the sulfobetaine zwitterions has permitted these cationic/zwitterionic polymers to be converted into a series of polyampholytes with a charge asymmetry arising out of excess of either the cationic or anionic centers. The water‐solubility of these polymers, upon low‐ and high‐salt (NaCl) additions has been investigated to provide critical solution concentrations to promote water‐insolubility and ‐solubility. A series of associating polymers of the above two monomers and SO₂ with a hydrophobic incorporation of 3–7 mol % of diallyloctadecylammonium chloride has also been synthesized. The solubility and viscosity of the hydrophobically modified polymers in the polyampholytic form were increased considerably in the presence of anionic surfactant sodium dodecyl sulfate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Dielectric dispersion and AC conductivity of acrylonitrile butadiene rubber‐poly(vinyl chloride)/graphite composite

Dielectric properties and ac electrical conductivity of Acrylonitrile Butadiene Rubber‐poly(vinyl chloride)/Graphite Composite were studied at different frequencies (10²?10⁶ Hz) in the temperature range (298–423 K). The results show that the dielectric constant (ε′), dielectric loss (ε″), ac electrical conductivity (σ_ac) and, the electric modulus are strongly dependent on the frequency and temperature. The dielectric constant ε′ increases with temperature and decreases with frequency, whereas the dielectric loss ε″ displays a broad maximum peak whose position shifts with temperature to a higher frequency region. Cole–Cole diagrams have been used to investigate the frequency dependence of the complex impedance at different temperature and graphite loading. Interfacial or Maxwell‐Wagner‐Sillars relaxation process was revealed in the frequency range and temperature interval of the measurements, which was found to follow the Havriliak–Negami approach for the distribution of relaxation times. At constant temperature, the frequency dependence of ac conductivity was found to fit with the established equation σ_ac(ω) = Aω^s quite well. The values of S for the investigated samples lie between 0.88 and 0.11. The conduction mechanism of ac conduction was discussed by comparing the behavior of the frequency exponent S(T) with different theoretical models. It was found that the correlated barrier hopping (C.B.H.) is the dominant conduction mechanism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

壳聚糖的改性及其应用进展

介绍了壳聚糖的结构;重点论述了壳聚糖的一些主要的改性方法,包括醚化、氧化、酰化、交联、烷基化、接枝共聚、季铵化及和其他材料复合等方法;并综述了壳聚糖及其衍生物在水处理、医药、食品加工及其他领域的应用现状。