Various amounts of dicyandiamide (Dicy), two grades of epoxy resins, i.e. Epiran 06 and Epikote 828, and three different accelerators including benzyl dimethyl amine (BDMA), 3-(4-chlorophenyl)-1, 1-dimethyl urea (Monuron) and 2-methyl imidazole (Im) were used in curing of Dicy/epoxy resin system. Both of the used epoxy resins were based on diglycidyl ether of bisphenol A (DGEBA). The effects of type and concentration of accelerators on curing behavior were studied by differential scanning calorimetry (DSC) method in dynamic or non-isothermal mode. The optimum concentration of Dicy for curing of epoxy resins was obtained based on the glass transition temperature of the cured epoxy/Dicy formulations. The maximum glass transition temperature of 139oC was obtained at the stoichiometric ratio of Dicy to epoxy of 0.65. The results showed that BDMA has a broader curing peak in DSC and starts the cure reaction earlier than the others. However, Monuron has a narrow curing reaction peak with good cure latency. The tensile properties of Dicy-cured Epiran 06 and Epikote 828 epoxy resins reinforced with chopped strand mat showed that these two epoxy resins have similar mechanical properties. For composites based on the Epiran 06 and Epikote 828 reinforced with 40 wt % glass chopped strand mat, tensile strength and modulus were 156 and 153.4 MPa and 11.6 and 12.4 GPa, respectively.

The oil-impregnated dielectric papers are the main components of distribution transformer which govern its service time. Therefore, durability enhancement of this grade of paper will cause to extend transformers life. In this research, long fiber unbleached Kraft pulp and its mixture with bagasse soda pulp at the ratios of 20% to 80% were used to make oil-impregnated dielectric papers with the grammage of 60 g/m2. The effect of dicyandiamide impregnation and its content in the paper structure and thermal aging were then assessed on dielectric properties and tensile strength of the insulation papers. The results showed that with increasing dicyandiamide content, the capacitance and tensile strength index decreased in comparison with untreated samples, but dielectric loss, insulation resistance, and breakdown voltage were improved. However, slight changes were observed in most dielectric properties during aging, but dicyandiamide caused to prevent loss of the tensile strength of insulated papers. Generally it could be concluded that dicyandiamide acts efficiently in thermal stabilization of insulation paper exposed to aggressive conditions inside the oil-filled transformer.

Toughening of a diglycidyl ether of bisphenol-A (DGEBA)-based epoxy resin with liquid carboxyl-terminated butadiene acrylonitrile (CTBN) copolymer has been investigated. For this purpose six blend samples were prepared by mixing DGEBA with different concentrations of CTBN from 0 to 25 phr with an increment of 5 phr. The samples were cured with dicyandiamide curing agent accelerated by Monuron. The reactions between oxirane groups of DGEBA and carboxyl groups of CTBN were followed by Fourier-transform infrared (FTIR) spectroscopy. Tensile, impact, fracture toughness and dynamic mechanical analysis of neat as well as the modified epoxies have been studied to observe the effect of CTBN modification. The tensile strength of the blend systems increased by 26 % when 5 phr CTBN was added, and it remained almost unchanged up to 15 phr of CTBN. The elongation-at-break and Izod notched impact strength increased significantly, whereas tensile modulus decreased gradually upon the addition of CTBN. The maximum toughness of the prepared samples was achieved at optimum concentration of 15 phr of CTBN, whereas the fracture toughness (K IC) remained stable for all blend compositions of more than 10 phr of CTBN. The glass transition temperature (T g) of the epoxy resin significantly increased (11.3oC) upon the inclusion of 25 phr of CTBN. Fractured surfaces of tensile test samples have been studied by scanning electron microscopic analysis. This latter test showed a two-phase morphology where the rubber particles were distributed in the epoxy resin with a tendency towards co-continuous phase upon the inclusion of 25 phr of CTBN.

Soil and water pollution and waste of resources have occurred due to the excessive use of nitrogen fertilizers in paddy fields. Considering that the biofilm of periphyton formed in paddy fields is mainly responsible for the exchange of nutrients, the present research was designed to investigate the effect of periphyton in the nitrification process in paddy fields and performed with 12 treatments. The treatments included powerful and weak nitrifiers isolated from periphyton, periphyton, periphyton enriched with nitrifiers, and their combination with a dicyandiamide chemical inhibitor. The research was carried out in a rice greenhouse cultivation for 30 days. The results showed that the simultaneous application of periphyton enriched with low-power nitrifier and dicyandiamide can increase the amount of total soil nitrogen, soil phosphorus, soil ammonium, total plant nitrogen, plant phosphorus, plant potassium, shoot length, and dry weight of rice plants. While this treatment reduced the conversion of ammonium to nitrate and subsequently reduced the potential of nitrate formation in the soil, with the increase of ammonium accumulation, it increased the utilization of rice plants. Periphyton can be considered a source for the isolation of nitrifiers. Also, the use of periphyton in paddy fields as a biological and healthy solution to inhibit the nitrification process in front of the use of inhibiting chemicals is placed in the path of future research.

Hypothesis: The effects of four accelerators 2, 4, 6-tris(dimethyl aminomethyl) phenol (DMP30), 2-methylimidazole (2MI), 2-phenylimidazole (2PhI) and carbonyldiimidazole (CDI) at 0. 6 and 1 phr contents on the curing behavior of a diglycidyl ether of bisphenol A epoxy resin and dicyandiamide (dicy), a solid curing agent, was investigated. Obviously, by changing the type and amount of accelerator, the reactivity and curing behavior of the epoxy/dicy system can be controlled. Methods: Measuring the viscosity build-up versus time, gelation time measurement at 110, 120 and 130° C, tack, non-isothermal differential scanning calorimetry (DSC) and glass transition temperature (Tg) characterization were used to study the reactivity and curing behavior of epoxy/dicy system. Findings: The CDI accelerator at 0. 6 phr content showed the highest pot-life. The pot-life of formulations decreased by increasing the amount of accelerator particularly when CDI was used. This difference in pot-life was lower for 2PhI and was not changed for 2MI. Gel-time data showed that the reactivity of different accelerators at high temperature was in order: 2MI > DMP30 > CDI > 2PhI. DSC test results showed that by increasing the amount of accelerator the heat of reaction increased, curing profile became sharp and glass transition temperature remarkably decreased. The broadest curing profile of 14° C also was seen for CDI. The DSC results showed that the reactivity of different accelerators was in order: 2MI > CDI > DMP30 > 2PhI. In other words, 2PhI showed the lowest activity and the sharpest curing profile and 2MI showed the highest activity with the wide curing behavior. It seems that the CDI accelerator at 0. 6 phr content would be the best accelerator regarding the highest potlife at room temperature, high curing rate and maximum glass transition temperature (Tg).

Dicyandiamide (DCD) is a nitrogenous compound which is generally used as a fertilizer, antimicrobial and nitrogen enrichment agent in soil. Grass and drinking water contamination with DCD may lead to presence of the chemical residues in milk and infant formula. The aim of this study was to investigate a rapid, simple and accurate method for quantitation of DCD in infant formula using electromemebrane extraction with reinforced hallow fiber by graphene oxide (GO-EME). The extraction method was optimized by solvent, graphene oxide concentration, voltage, stirring speed, pH and time parameters. After extraction, DCD was analyzed by HPLC coupled with UV/Vis detector. The analytical method validation parameters including accuracy, precision, LOD and LOQ were determined to ensure the method's validity. The calibration curve with a correlation ratio of 0. 999 was obtained. The recoveries were from 78. 0% to 80. 0%. The LOD and LOQ were 0. 04 mg L-1 and 0. 1 mg L-1. This study indicates that the graphen oxide-electromembrane extraction is a simple, accurate and rapid method for determination of DCD in infant formula.

Introduction: Nitrification inhibitors are compounds that slow biological oxidation of ammonium to nitrite by reducing the activity of Nitrosomonas bacteria, without affecting the subsequent oxidation of nitrite to nitrate, either by inhibiting or interfering with the metabolism of nitrifying bacteria. The first step of nitrification is inhibited (i. e., the activity of Nitrosomonas bacteria) by the nitrification inhibitors, while the second step for oxidation of nitrite (NO2-) to nitrate (NO3-) is normally not influenced. In recent years, numerous compounds have been identified and used as nitrification inhibitors, particularly in agricultural soils. They are chemical compounds that slow the nitrification of ammonia, ammonium-containing, or urea-containing fertilizers, which are applied to soil as fertilizers, such as thiourea, carbon Sulfide, thioethers, ethylene, 3-amino-1, 2, 4-triazole, dicyandiamide (DCD), 2-amino-4-chloro-6-methyl pyrimidine, ammonium thiosulphate and 3, 4-dimethylpyrazole phosphate (DMPP). These inhibitors reduce the losses of nitrogen in soil. Some nitrification inhibitors are very effective in the efficiency of the nitrogen fertilizers. Recently, a lot of attention has been paid to nitrification inhibitors from an environmental point of view. Some nitrification inhibitors are very expensive and not economically suitable for land application. Nonetheless, many farmers and researchers apply these compounds for many purposes in some specific places. On the other hand, there are many inexpensive natural nitrification inhibitors such as Artemisia powder, Karanj (Pongamia glabra), neem (Azadrachta indica) and tea (Camellia sinensis) waste which can compete with the artificial nitrification inhibitors such as 3, 4-dimethylpyrazole phosphate (DMPP), dicyandiamide (DCD) which are very common nitrification inhibitors. Applying 1. 5 kg ha-1 of DMPP is sufficient to achieve optimal nitrification inhibition. 4-dimethylpyrazole phosphate (DMPP) can significantly shrink nitrate (NO3) leaching. 4-dimethylpyrazole phosphate (DMPP) may also decrease N2O emission and the use of DMPP-containing fertilizers can improve yield. The aim of this study was to compare the effect of 3, 4-dimethylpyrazole phosphate (DMPP), Dicyandiamide (DCD) and powder Artemisia (ART) at the presence of Urea, cow manure and Vermicompost. Material and Methods: Effects of three nitrification inhibitors, (3, 4-dimethylpyrazole phosphate (DMPP), Dicyandiamide (DCD) and powder Artemisia (ART)) at the presence of three nitrogen sources (Urea, cow manure and Vermicompost) were investigated in a calcareous soil under lettuce cultivation in a greenhouse condition. The changes in the soil mineral nitrogen (nitrate and ammonium), plant nitrogen, nitrate accumulation in leaves and some of growth characteristics such as lettuce chlorophyll content, leaf area index, leaf dry weight and root dry weight were determined. The experiment was carried out in a completely randomized factorial design with three replications. Soil ammonium and nitrate concentration were measured during the experiment. The growth characteristics of lettuce were also measured at the end of experiment. Nitrogen and nitrate contents were also determined in lettuce leaves. Results and Discussion: The results of the experiment showed that soil nitrate decreased at the presence of three nitrification inhibitors but the soil nitrogen ammonium increased significantly. Application of nitrification inhibitors also reduced the concentration of nitrate in the lettuce leaves during two harvesting times. Moreover, the nitrogen concentration in the plant increased at the presence of nitrification inhibitors. The application of nitrification inhibitors influenced the plant growth characteristics and changed the lettuce growth characteristics. Chlorophyll content increased significantly in lettuce leaves. Leaf area index, leaf and root dry weight of lettuce increased notably when 3, 4-dimethylpyrazole phosphate (DMPP) and powder Artemisia (ART) nitrification inhibitors were applied to the soil samples. These growth characteristics, however, reduced significantly when dicyandiamide nitrification inhibitors was applied to the soil samples. In addition, the symptoms of toxicity were observed in lettuce plant when dicyandiamide nitrification inhibitors were applied to the soil samples. In general, the highest efficiency of nitrification inhibitors was recorded at the presence of urea fertilizer source and the greatest efficiency was observed initially for powder Artemisia (ART) and then for 3, 4-dimethylpyrazole phosphate (DMPP) and dicyandiamide, respectively, when urea fertilizer was applied to the soil samples. There was a positive correlation between soil nitrogen content and plant nitrate in the first and second harvest. The correlation between soil ammonium and plant nitrate (in the first and second harvest) and soil nitrate was negative.

Copper (II) complexes of [Cu (II) (1-amidino-O-2-methoxyethylurea)2] CI2 (1) and [Cu (II) (1-amidino-O-2-ethoxyethylurea)2] CL2 (2) have been synthesized and characterized by elemental analysis, magnetic moment, conductance, thermal analysis, IR, UV, powdered XRD and EPR spectral studies. The trend in g values g||>g^>2.0023 in the EPR spectra of the complexes suggest that the unpaired electron on copper (II) ion has dx2-y2 character and the complexes have square planar structure which is also supported by electronic absorption spectral studies. The bonding parameters of these complexes in DMF have been calculated based on the EPR and electronic spectral data. The complexes (1) and (2) exhibit K||>K^which indicates the presence of significant out-of plane p bonding. Powdered XRD spectral patterns show that complexes crystallize in a monoclinic system. The binding of the complexes with calf thymus DNA was investigated by absorption and emission spectroscopy, viscosity measurements, DNA melting and cyclic voltam metric studies. DNA interaction studies show that the complexes bind to calf thymus DNA in a non-intercalative mode. The two complexes exhibit growth inhibitory activity against pathogenic bacteria, viz., Escherichia coli, Klebsiella pneumonia sub sp. Pneumoniae, Proteus mirabilis.