Simultaneous quantification of N‐butylthiophosphoric triamide and dicyandiamide in urea formulation by liquid chromatography with tandem mass spectrometry

A new liquid chromatography with tandem mass spectrometry method employing a mixed‐mode zwitterionic stationary phase was developed for simultaneous determination of urease inhibitor (N‐butylthiophosphoric triamide) and nitrification inhibitor (dicyandiamide) in urea fertilizer. Molecular modeling based on density functional theory calculations was employed to provide an insight into the interaction mechanism of urea, dicyandiamide, and N‐butylthiophosphoric triamide with zwitterionic stationary phase in chromatographic separation system. The detection of analytes was performed on a triple quadrupole tandem mass spectrometer in multiple reaction monitoring mode using positive electrospray ionization. The ion transitions monitored were m/z 85→68 for dicyandiamide and m/z 168.2→74 for N‐butylthiophosphoric triamide, respectively. The standard calibration curves of dicyandiamide and N‐butylthiophosphoric triamide were linear over the range of 1.0 ? 15 ppm (coefficient of determination = 0.9984), 0.05 ? 1 ppm (coefficient of determination = 0.9995), with limit of detection of 25 and 5 ppb, respectively. The recoveries of low, middle, and high concentrations were from 96.7 to 105.8% for N‐butylthiophosphoric triamide and 94.4 to 105.8% for dicyandiamide with accuracy (relative error %) of ≤5.8% and ≤5.8%, the precision (coefficients of variation) was ≤2.0% and ≤2.9%, respectively. The validated method was successfully applied on real urea samples to determine N‐butylthiophosphoric triamide and dicyandiamide simultaneously.     

Convergence and an Explicit Formula for the Joint Moments of the Circular Jacobi $$\beta $$ β -Ensemble Characteristic Polynomial

Mathematical Physics, Analysis and Geometry - Thanks to the Birman-Schwinger principle, Weyl’s laws for Birman-Schwinger operators yields semiclassical Weyl’s laws for the corresponding...     

Oxidative bromination of ketones using ammonium bromide and oxone®

A highly efficient, environmentally safe and economic method for selective α-monobromination of aralkyl, cyclic, acyclic, 1,3-diketones and β-keto esters and α,α-dibromination of 1,3-diketones and β-keto esters without catalyst is reported using ammonium bromide as a bromine source and oxone® as an oxidant. The reaction proceeds at ambient temperature and yields range from moderate to excellent. Bromination of unsymmetrical ketones takes place at the less substituted α-position predominantly. Aromatisation of tetralones is also carried out with this reagent system.     

Laser Heated Emissive Probes Design and Development under National Fusion Program and Potential Measurement

Emissive probes are the tools for the direct deter- mination of the plasma potential ~PL and they deliver a more reliable measure of φPL compared to the indi- rect measurements with cold Langmuir probes. The emissive probe works on the principle of compensating the well-known asymmetry of the I-V characteristic of a single cold Langmuir probe by an electron emission current from the probe into the plasma. In an ideal case, the saturated value of floating potential V（А,em） of a highly emissive probe should equal the plasma potential. A conventional emissive probe usu- ally consists of a loop of tungsten wire heated by an electric current passing through it. These conven- tional emissive probes containing an electric current- heated metal wire loop suffer a huge drawback when it comes to their lifetime. The metal wire used in these probes evaporates and subsequently breaks when heated with high current, leading to frequent replacements of these wires. When used in ultra high vacuum （UHV） plasma systems, frequent replacement of these wires requires frequent vacuum breaks in the plasma systems. In many plasma systems espe- cially in magnetized toroidal hot plasmas like toka- maks, where determination of the electric fields leads to a great deal of useful information, frequent breaking of the vacuum is impossible for changing the filament of the emissive probes. Hence, along with the other drawbacks of the conventional emissive probes such as limited emission current, bending in a magnetic field makes their use impractical in these plasma systems. The most suitable alternative is the emissive probes heated by a focused infra-red laser. Due to them having several advantages over the conventional emis- sive probes, laser heated emissive probes （LHEPs） are found to have more and more uses in plasma systems. The advantages of the LHEP are： longer lifetime （no filament breaking issues）, attainment of higher tem- perature without melting or evaporation and thus higher emissivity, no deformation of the pr     

Control of flow in forced jets: a comparison of round and square cross sections

Abstract  

Direct numerical simulation of incompressible, spatially developing round and square jets at a Reynolds number of 1,000 is performed. The effect of two types of inlet perturbation on the flow structures is analyzed. First, dual-mode excitation, which is a combination of axisymmetric perturbation at preferred mode frequency and helical perturbation at sub-harmonic frequency is used, having a disturbance frequency ratio equal to R _f  = 2. It is observed that the circular and square jets bifurcate and spread on one of the orthogonal planes forming a Y-shape jet in the downstream while no spreading is visible on the other plane. The second type of perturbation is a flapping excitation at a sub-harmonic frequency, St _F = 0.2. It leads to a Y-shape bifurcation for both square and circular jets. On the other hand, for flapping excitation at the preferred mode frequency, namely, St _F = 0.4, a circular jet bifurcates into a Ψ-shape whereas the square jet reveals simple spreading.