Unexpected products from the reaction of chalcones with cyanoguanidine

A new series of unexpected dihydrochalcones DHCs attached with cyanoiminopyrimidine moiety in addition to expected cyanoaminopyrimidines CAMPs were synthesized by efficient and facile method via reaction of cyanoguanidine with chalcone derivatives in the presence of EtONa.     

An off-line NMPC strategy for continuous-time nonlinear systems using an extended modal series method

This paper presents a new off-line nonlinear model predictive control (NMPC) approach for continuous-time affine-input nonlinear systems. In this approach, the NMPC-related nonlinear two-point boundary value problem derived from the Pontryagin’s maximum principle is solved by the extended modal series method. The resulting suboptimal control law explicitly depends on the initial conditions and is updated by replacing the initial conditions with the new state measurements in future sampling instants. Therefore, there is no need to repeat the recursive online optimization process in each sampling instant. Since the applicability of NMPC is generally restricted by computational burden of the online optimization, we propose an NMPC scheme, which not only reduces the online computational burden significantly, but also can be applied to fast dynamic systems with short prediction horizons. An efficient algorithm is presented which approximates the order of the modal series such that feasibility of the optimization problem is guaranteed. Closed-loop stability of the proposed NMPC approach is shown using the off-line terminal region calculations suggested in quasi-infinite horizon NMPC scheme. The applicability and effectiveness of the proposed approach are illustrated by two numerical examples.     

Homotopy simulation of nanofluid dynamics from a non-linearly stretching isothermal permeable sheet with transpiration

In this article we derive semi-analytical/numerical solutions for transport phenomena (momentum, heat and mass transfer) in a nanofluid regime adjacent to a nonlinearly porous stretching sheet by means of the Homotopy analysis method (HAM). The governing equations are reduced to a nonlinear, coupled, non-similar, ordinary differential equation system via appropriate similarity transformations. This system is solved under physically realistic boundary conditions to compute stream function, velocity, temperature and concentration function distributions. The results of the present study are compared with numerical quadrature solutions employing a shooting technique with excellent correlation. Furthermore the current HAM solutions demonstrate very good correlation with the non-transpiring finite element solutions of Rana and Bhargava (Commun. Nonlinear Sci. Numer. Simul. 17:212–226, 2012). The influence of stretching parameter, transpiration (wall suction/injection) Prandtl number, Brownian motion parameter, thermophoresis parameter and Lewis number on velocity, temperature and concentration functions is illustrated graphically. Transpiration is shown to exert a substantial influence on flow characteristics. Applications of the study include industrial nanotechnological fabrication processes.     

Influence of rotational barrier of single-molecule electric revolving door on energies,aromaticity and quadrupole moment

We studied the response of rotation of spindle ring on energies, aromaticity and quadrupole moment in single-molecule revolving door (S-MERD) by using M05-2X/6-311++G^** level of theory. The rotational barrier was considered about the spindle ring from 0° to 180° by 10° intervals. Energies, aromaticity and quadrupole moment values are dependent on the rotation of spindle ring of S-MERD and were plotted as functions of rotation of spindle ring. Rotational barrier of energies, aromaticity and quadrupole moment for all substituents produces a cos²θ function. The nucleus-independent chemical shifts (NICS) of spindle ring increase as the spindle ring gradually rotates out of planarity and reach the highest NICS in the perpendicular conformation. For all substituents, the values of quadrupole moment of spindle ring decrease from 0° to 90° and then increase from 90° to 180°.     

Some CNDO Calculations and Structural Spectroscopic Studies of Paracetamol Complexes

Through complete neglect of differential overlap (CNDO) calculations of the electronic energy among different possible structures of paracetamol (PA) molecule, it has been concluded that its structure has C_s point group symmetry of the cis‐form in which the methyl group has a restricted free rotation around its bond with the carbon atom of the amide group. The electronic spectra of PA compound were studied in different polar and nonpolar solvents. The temperature effect on the electronic spectra confirms the presence of one conformer only. The hydrogen bonding and the orientation energies of the polar solvents were determined from the studies of mixed solvents. Complexes of PA with metal ions M(II) (Cu⁺⁺, Zn⁺⁺, or Fe⁺⁺) of ratio 2:1, respectively, were prepared, and their structure has been confirmed by elemental analysis, atomic absorption spectra, IR spectra, and ¹H‐NMR spectra. It has been concluded that the structure of the complexes has C_2h point group symmetry in which two PA molecules are chelated to any one of the metal ions Cu⁺⁺, Zn⁺⁺, and Fe⁺⁺.     

Structural and dielectric properties of polyvinyl alcohol/barium zirconium titanate polymer–ceramic composite

The polyvinyl alcohol (PVA)/barium zirconium titanate Ba[Zr_0.1Ti_0.9]O₃ (BZT) polymer–ceramic composites with different volume percentage are obtained from solution mixing and hot-pressing method. Their structural and electrical properties are characterized by X-ray diffraction (XRD), Rietveld refinement, cluster modeling, scanning electron microscope and dielectric study. XRD patterns of PVA/BZT polymer–ceramics composite (with 50% volume fractions) indicate no obvious differences than the XRD patterns of pure BZT which shows that the crystal structure is still stable in the composite. The scanning electron micrograph indicates that the BZT ceramic is dispersed homogeneously in the polymer matrix without agglomeration. The dielectric permittivity (ε_r) and the dielectric loss (tan δ) of the composites increase with the increase of the volume fraction of BZT ceramic. Theoretical models are employed to rationalize the dielectric behavior of the polymer composites. The dielectric properties of the composites display good stability within a wide range of temperature and frequency. The excellent dielectric properties of these polymer–ceramic composites indicate that the BZT/PVA composites can be a candidate for embedded capacitors.     

Synthesis,characterization and study of antibacterial activity of enaminone complexes of zinc and iron

Complexes of enaminones; 4-N,N-diethylamine-pent-3-ene-2-one [HL¹], 4-N,N-di n-propylamine-pent-3-ene-2-one [HL²] and 4-N,N-dicyclohexylamine-pent-3-ene-2-one [HL³] with Fe(II) and Zn(II) ions were prepared by reacting the equimolar ethanolic solutions of the ligands (HL¹, HL² and HL³) with ethanolic metal solutions. The complexes formed, were characterized by infrared, ultraviolet and atomic absorption spectroscopy. Ligands and their metal complexes were tested against Escherichia coli and Staphylococcus aureus bacteria to assess their antibacterial action using disc diffusion method. Ligands were completely inactive against bacteria whereas the complex Zn (HL¹) has significant action on both bacteria, indicating that it has a good potential as bactericide. Other complexes have normal antiseptic character.     

Efficient Synthesis of Urea Derivatives via a Sequential One-Pot Nucleophilic Addition/Ugi Five-Component Reaction Under Solvent-Free Conditions

Urea polyfunctional derivatives were successfully synthesized via a one-pot, five-component nucleophilic addition/Ugi reaction sequence. Simplicity, solvent-free conditions, and good yields of products are advantages of this method.     

Central composite design with the help of multivariate curve resolution in loadability optimization of RP‐HPLC to scale‐up a binary mixture

Chromatographic method development for preparative targets is a time‐consuming and subjective process. This can be particularly problematic because of the use of valuable samples for isolation and the large consumption of solvents in preparative scale. These processes could be improved by using statistical computations to save time, solvent and experimental efforts. Thus, contributed by ESI‐MS, after applying DryLab software to gain an overview of the most effective parameters in separation of synthesized celecoxib and its co‐eluted compounds, design of experiment software that relies on multivariate modeling as a chemometric approach was used to predict the optimized touching‐band overloading conditions by objective functions according to the relationship between selectivity and stationary phase properties. The loadability of the method was investigated on the analytical and semi‐preparative scales, and the performance of this chemometric approach was approved by peak shapes beside recovery and purity of products.     

Elemental analysis of limestone by instrumental neutron activation analysis

Limestone samples from Assuit Governrate in Upper Egypt were subjected to elemental analysis by instrumental neutron activation analysis and X-ray fluorescence techniques. The samples were properly prepared together with their standards and simultaneously irradiated in a neutron flux of the order 7 × 1011 n/cm² s using TRIGA research reactor at Mainz. After activation the samples were subjected to γ-ray spectrometry using a high purity germanium detection system and computerized multichannel analyzer. Nineteen elements: Na, Ca, Mn, Fe, Sc, Cr, Co, Zn, Sn, La, Ce, Nd, Eu, Sm, Yb, Lu, Hf, Th and U were analyzed. X-ray fluorescence spectrometry have been also used. The presence of any elements in higher or lower levels in certain limestone samples is contingent on the occurrence of its bearing minerals, nature of parent sediments and depositional environments of these sediments. The major elements in the samples were also observed to be among the elements that had high enrichment factors in the study of suspended dust particulate within and around cement industries. This confirms cement as the major contributor to the airborne particulate matter in the environs.