Study of surface roughness with MHD and couple stress fluid on porous curved annular plates

The purpose of this article is to examine the effect of surface roughness on porous curved annular plates lubricated with couple stress fluid in the presence of magnetic field. The MHD-Stochastic Reynolds equation is derived using Christensen’s stochastic model and applied to predict the squeeze film characteristics of porous curved annular plates. The expressions for squeeze film pressure, load-carrying capacity, and squeeze film time are obtained analytically, the results are discussed for various values of operating parameters, and are plotted graphically. It is found that the squeeze film characteristics of porous curved annular plates are improved using a non-Newtonian fluid in the presence of an external magnetic field. The effect of roughness parameter is to increase (decrease) the squeeze film attributes for azimuthal (radial) roughness configuration as compared to the smooth case. Furthermore, the effect of permeability parameter is to decrease the pressure, load-carrying capacity, and squeeze-film time as compared to the non-porous case

Designed β-hairpin peptides with defined tight turn stereochemistry

The conformational analysis of two synthetic octapeptides, Boc-Leu-Val-Val-D-Pro-L-Ala-Leu-Val-Val-OMe (1) and Boc-Leu-Val-Val-D-Pro-D-Ala-Leu-Val-Val-OMe (2) has been carried out in order to investigate the effect of β-turn stereochemistry on designed β-hairpin structures. Five hundred megahertz 1H NMR studies establish that both peptides 1 and 2 adopt predominantly β-hairpin conformations in methanol solution. Specific nuclear Overhauser effects provide evidence for a type II′ β-turn conformation for the D-Pro-L-Ala segment in 1, while the NMR data suggest that the type I D-Pro-D-Ala β-turn conformation predominates in peptide 2. Evidence for a minor conformation in peptide 2, in slow exchange on the NMR time scale, is also presented. Interstrand registry is demonstrated in both peptides 1 and 2. The crystal structure of 1 reveals two independent molecules in the crystallographic asymmetric unit, both of which adopt β-hairpin conformations nucleated by D-Pro-L-Ala type II′ β-turns and are stabilized by three cross-strand hydrogen bonds. CD spectra for peptides 1 and 2 show marked differences, presumably as a consequence of the superposition of spectral bands arising from both β-turn and β-strand conformations

Study of surface roughness with MHD and couple stress fluid on porous curved annular plates

The purpose of this article is to examine the effect of surface roughness on porous curved annular plates lubricated with couple stress fluid in the presence of magnetic field. The MHD-Stochastic Reynolds equation is derived using Christensen’s stochastic model and applied to predict the squeeze film characteristics of porous curved annular plates. The expressions for squeeze film pressure, load-carrying capacity, and squeeze film time are obtained analytically, the results are discussed for various values of operating parameters, and are plotted graphically. It is found that the squeeze film characteristics of porous curved annular plates are improved using a non-Newtonian fluid in the presence of an external magnetic field. The effect of roughness parameter is to increase (decrease) the squeeze film attributes for azimuthal (radial) roughness configuration as compared to the smooth case. Furthermore, the effect of permeability parameter is to decrease the pressure, load-carrying capacity, and squeeze-film time as compared to the non-porous case

Synthesis, crystal structure and spectral studies of silver(I) cyclohexyldiphenylphosphine complexes : towards the biological evaluation on malignant and non-malignant cells

Please read abstract in the article.The University Research Council of the University of Johannesburg, SASOL, and TESP.https://www.tandfonline.com/loi/gcoo202023-02-22hj2023Chemistr

Spectral Simplification and "Pseudo Decoupling" in One-Dimensional Proton NMR Spectra Using Pulsed-Field Gradients

High-resolution proton NMR spectra of complex molecules are generally crowded due to the homonuclear spin–spin couplings. Knowledge of chemical-shift frequencies from such crowded spectra are of utmost importance in identifying the spin system. These shifts would have been easily measurable had it been possible to achieve proton decoupling. Since the pioneering work of Aue et al. (1) , two- dimensional J-resolved spectroscopy seems to have offered the best route to ‘‘broadband-decoupled’’ proton spectra. Subsequently, various attempts have been made to improve upon the technique (2–9) , of which the most promising solution seems to be ‘‘purged J spectroscopy’’ ( 8, 9) . Recently, a new proton ‘‘decoupling’’ method has been proposed (10) which uses the classic spin-echo sequence without any purging pulse. A new era has started in the field of NMR with the use of pulsed-field gradients, which in turn, is a result of technological progress in the design of high- doublequality shielded gradients. We have reported the use of these gradients for editing one-dimensional proton NMR spectra (11) , where the gradients are used for suppressing artifacts arising from $180^o$ pulse imperfections and for z filtering. It was shown that the experiment can be used to identify unambiguously singlets and triplets overlapping with other multiplets. This was done by suppressing the signals arising from doublets and quartets by matching the interval between the two $90^o_x$ pulses with \tau= 1/2J and with the use of gradient pulses (Fig. 1a) . This process leaves the coherences of the singlets unaffected. For triplets, the central line is unaffected and the outer lines are inverted (Fig. 2a) . We report here the extensions of this pulse sequence to filter singlets and triplets without any distortions (Fig. 1b) and to achieve ‘‘pseudo-decoupling’’ of the triplets in the proton NMR spectra (Figs. 1c and 1d)

4-Amino-N-(2-hydroxy-4-pentadecylbenzylidene)benzenesulfonamide

4-Amino-N-(2-hydroxy-4-pentadecylbenzylidene)benzenesulfonamide has been synthesized by reaction of 2-hydroxy-4-pentadecylbenzaldehyde with 4-aminobenzenesulfonamide in the presence of acetic acid in ethanol. The structure of this new compound was confirmed by elemental analysis, IR, 1H-NMR, 13C-NMR and mass spectral analysis

4-[(2-Hydroxy-4-pentadecylbenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one

Novel 4-[(2-hydroxy-4-pentadecylbenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one was prepared via condensation of 2-hydroxy-4-pentadecylbenzaldehyde (1) with 4-amino-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (2) in ethanol/acetic acid under reflux. The structure of the synthesized compound was assigned on the basis of elemental analysis and spectral data