E-Z Isomerization in ethyl cyano(hydrazono)acetate, a push-pull imine

Transformation of the E form of Et cyanoglyoxalate phenylhydrazone (E-I) into Z-I is catalyzed by proton-acceptor-type H-bonding solvents (H-bonding bases). Kinetic and allied data gathered on the approach of E-I towards equil. with Z-I in acetone have been utilized to delimit possible processes by which acetone may catalyze the transformation, under the basic premise that a consequence of H-bonding by the base solvent is enhancement of electron d. at amino N

Correlation of 13C^{13}C Shifts with Substituent Parameters in 3,4-Diphenyl-1,2,5-oxadiazole 2-Oxides Substituted at the Para-Positions of Either or Both Phenyl Rings

C-1′, C-1″, C-3, and C-4 $^{13}C$ shifts in 3,4-di(4′-or/and 4″-X)phenyl-1,2,5-oxadiazole 2-oxides (3,4-diarylfurazan 2-oxides; three series: X=NMe2, OMe, Me, Cl, H, and $NO_2)$ were correlated vs. seven different divided substituent parameter sets. Results have implied that i) the C-3–C-4 bond does not transmit mesomeric effects efficiently; ii) no effects can be specifically attributed to the possibility that the C-3 aryl maintains a higher dihedral angle with respect to the furoxan ring than the C-4 aryl; iii) there appears to be a directionality to the propagation of localized π-polarization due to lesser ability of C=N(O)→O to convey effects compared with C=N(O); and, iv) the furazan N-oxide ring, being generally an electron acceptor, transmits substituent effects nonlinearly

SLL REDUCTION IN APERIODIC LINEAR ARRAY ANTENNA SYSTEM WITH SCAN ANGLES

ABSTRACT: In modern wireless communication system one of the criteria is control over the antenna beam pattern. Antenna array provides better control over the beam pattern and provides flexibility of scanning in the required direction. The important parameter for consideration in array is spacing between elements. As the spacing between elements is increased beyond half wavelength, the steerability from broadside will significantly reduce due to appearance of grating lobe. In this paper a model of thinned aperiodic linear phased arrays is presented. Differential Evolution algorithm is used for synthesizing the performance of peak side lobe levels Keywords: Antenna arrays, Differential Evolution algorithm, Driving point impedance, Scan angle, thinned aperiodic arrays. I.INTRODUCTION The traditional way of creating linear thinned array is by exciting a number of elements in a uniform spaced linear array. The first thinned array was created by removing elements randomly or by trial and error Ошибка! Источник ссылки не найден., Ошибка! Источник ссылки не найден. . The problem with this arbitrary technique was poor side lobe suppression. This is due to the non-optimal locations of radiating elements. The recent work in thinned arrays made use of different optimization algorithms to remove elements in such a way to have minimum peak side lobe level. Most work on thinning arrays is concentrated only in optimizing an array with low side lobe levels at broadside. As these arrays are scanned a small angle away from broadside, grating lobe appears Ошибка! Источник ссылки не найден., Ошибка! Источник ссылки не найден.. This paper presents a model of thinned aperiodic linear phased arrays for various scan angles. DE algorithm is used for synthesizing the performance of peak side lobe levels. The optimization process causes the perturbation added to each element in periodic array to create an aperiodic array. II. ANTENNA ARRAY CONFIGURATION For a single element antenna the dimension of element gives the aperture. For linear array, the aperture is decided by the distance between two farthest elements. With the help of antenna arrays pattern control and beam scanning are possible. A basic array geometry and coordinate system is shown i

The structures of ethyl 1,4,5-exo-trimethyl-7-oxo-2,3-diphenylbicyclo[2.2.1]hept-2-ene-5-endo-carboxylate (A) and ethyl 1,4-dimethyl-7-oxo-2,3-diphenylbicyclo[2.2.1]hept-2-ene-5-endo-carboxylate (B)

Crystals of C<SUB>25</SUB>H<SUB>26</SUB>O<SUB>3</SUB> are triclinic, space group Pï, with a=9.197(2), b=10.357 (2), c=11.086 (3) Å, α=94.07 (2), β=98.21 (3), γ=90.82(2) °, V=1042.2 Å<SUP>3</SUP>, Z=2, D<SUB>obs</SUB>=1.19, , D<SUB>calc</SUB>=1.198 Mg m<SUP>-3</SUP> and μ (Cu Kα)=0.661 mm<SUP>-1</SUP>; R=6.2% for 2525 significant reflections. Crystals of C<SUB>24</SUB>H<SUB>24</SUB>O<SUB>3</SUB> (B) are monoclinic, space group P21/a, with a=11.584 (2), b=11.315 (2), c=15.900 (4) Å, β=104.02 (2)°, V=2022.4 Å<SUP>3</SUP>, Z=4, D<SUB>obs</SUB>=1.199, D<SUB>calc</SUB>=1.185 Mg m<SUP>-3</SUP>and μ (Cu Kα=0.081 mm<SUP>-1</SUP>; R=4.2% for 1990 significant reflections. The steric strain introduced by the bulky sbstituents on the norbornenone system is discussd. In addition, a possible relationshp between the orienation of the ester function and the anisochrony of O-methylene protons is brought out

A comparison of the DNMR behaviour of methyl 5,6-bis(2-methoxyphenyl)-1,4-dimethyl-7-oxobicyclo[2.2.1]hept-5-en-2-<i style="mso-bidi-font-style:normal">endo</i>-carboxylate and its 7-oxa analogue

735-741Methyl 5,6-Bis(2-methoxyphenyl)-1,4-dimethyl-7-oxobicyclo[2.2.1] hept-5-en-2-endo-carboxylate, a moderately crowded norbornenone ester, exhibits complex VT-DNMR behav iour. A similar behaviour is not seen in its 7-oxa analogue, showing that conformational transmission from position 7 has a crucial influence on the distance parameters that govern the dynamic processes involving the substituents on the bicycloheptene framework

Selectivities in the formation of pyridines and pyrimidines by ammonia-induced cyclocondensations of vinamidiniums

Arylvinamidines (2-, 3- or 4-aryl-4-(N,N-dimethyl)amino-1-azabuta-1,3-dienes), generated from 1,1,5,5-tetramethyl-2- or -3-phenyl-1,5-diazapentadienium salts, cyclocondense orientation-specifically under two regioselections forming 1-4' + 4-3' and 1-2' + 4-1' bonds on exposure to ammonia. The initial cyclates aromatise eliminatively to give mixtures of diarylpyridines and arylpyrimidines. The 2-arylvinamidines do not participate as 2-centre reactants and their 4-aryl isomers not as 4-centre reactants in the cyclocondensations which appear to be stepwise and not concerted. Reasons for the selective participation appear to be that the required eliminations from the initial cyclates are disfavoured in the first case and that a geometric factor prevents cyclate-formation in the second

Enhancement of the leaching rate of uranium in the presence of ultrasound

In the present work, experiments have been performed for leaching (recovery) of uranium from MgF2 (byproduct from the uranium ore recovery process) under various conditions of leach acid concentration with and without the presence of ultrasound, under different energy dissipation rates (different rotational speeds of conventional stirring by impeller), and on different MgF2 particle size distributions. The enhancement of the leaching rate due to ultrasound is found to occur in two steps: (1) MgF2 particle fragmentation leading to high specific solid-liquid interfacial area and by increase in the surface diffusional rate of the reactive species; (2) enhancement in the convective diffusivity of the leach acid solvent through micropores of the MgF2 agglomerate structure due to convective motion created by the cavitation phenomena (shock wave propagation, microjet formation) at the solid-liquid interface. Thus, the overall recovery has been increased by the application of ultrasound with several additional advantages such as low leach acid concentration and decrease in the leaching operation time. The energy dissipation rate with the use of ultrasound was very high, yet, at an equivalent energy dissipation rate in the form of conventional stirring, leaching rates or the final extent of the leaching could not be matched. This indicated that the scale (time and spatial) of energy dissipation has important effect on the overall leaching rate. Kinetics shows that the leaching operation can be explained as a classical shrinking core kinetics phenomenon with pore diffusion resistance as the rate-limiting step