Anomalous flow behavior in closed and open thin walled nanochannels

Molecular dynamics simulations have been carried out to examine water flow in symmetric and asymmetric open and closed ends nanochannels with hydrophilic surfaces. The results are counterintuitive and the opposite of what is observed in macro-systems-closed channels fill faster with fluid than do their open counterparts. In addition, hybrid closed-open asymmetric channels fill up even faster. These results can be explained on the basis of the fluid-structure interaction that arises through the different vibrational behaviors of the surface molecules that are part of the wall forming these channels. Such effects are not expected to be of significance in macro-channels, and point to an important case where macro and nanochannels exhibit contrary behavior. Since these effects results from strong interactions between the fluid molecules and solid surface, one would not expect them with hydrophobic walls, and our simulations confirm such behavior.     

Thin Film Flow of a Second Grade Fluid over a Stretching/Shrinking Sheet with Variable Temperature-Dependent Viscosity

Effects of variable viscosity on the flow and heat transfer in a thin film on a horizontal porous stretching sheet are analyzed. The steady boundary layer equations for momentum and thermal energy are simplified by using similarity transformations. The resulted and coupled nonlinear differential equations are solved by Homotopy analysis method. The results are presented graphically to interpret various physical parameters appearing in the problem.     

Unsteady hydromagnetic rotating flow of a conducting second grade fluid

The purpose of this work is to investigate the hydromagnetic oscillatory flow of a fluid bounded by a porous plate, when the entire system rotates about an axis normal to the plate. The fluid is assumed to be non-Newtonian (second grade), incompressible and electrically conducting. The magnetic field is applied transversely to the direction of the flow. Such a flow model has great significance not only of its theoretical interest, but also for applications to geophysics and engineering. The resulting initial value problem has been solved analytically for steady and unsteady cases. The analysis of the obtained results showed that the flow field is appreciably influenced by the material parameter of the second grade fluid, the applied magnetic field, the imposed frequency, rotation and suction and blowing parameters. It is observed in a second grade fluid that a steady asymptotic hydromagnetic solution exists for blowing and resonance which is different from the hydrodynamic situation.     

A semi-classical approach to two-frequency solitons in a three-level cascade atomic system

A semi-classical theory of two intense optical fields interacting with a third-order non-linear medium composed of a three-level cascade atomic system is presented. It is predicted that non-linear atom-field interactions allow the formation of two-frequency bright, dark and grey spatial solitons. We demonstrate through numerical simulations and analytic stability analysis that the bright and grey solitons are stable.     

Lie ideals and (\alpha ,\beta )-derivations of *-prime rings

Let \((R,*)\) be a \(2\)-torsion free \(*\)-prime ring with involution \(*\), \(L\ne \{0\}\) be a \(*\)-Lie ideal of \(R\). An additive mapping \(d:R\rightarrow R\) is called an \((\alpha ,\beta )\)-derivation of \(R\) such that \(d(xy)=d(x)\alpha (y)+\beta (x)d(y)\). In the present paper, we shall show that when \(L\) satisfies any of several identities involving \(d\), then \(L\) is central.     

Disposable highly ordered pyrolytic graphite-like electrodes: Tailoring the electrochemical reactivity of screen printed electrodes

We demonstrate that the electron transfer properties of disposable screen printed electrodes can be readily tailored via the introduction of a polymeric formulation into the ink used to fabricate these electrochemical platforms. This approach allows the role of the binder on the underpinning electrochemical properties to be explored and allows the electrochemical reactivity of the screen printed electrodes to be tailored from that of edge plane to basal plane of highly ordered pyrolytic graphite.     

Sulfur-mediated C(sp2)–H imidation and 1,2-imidofluorination of vinyl sulfides

A new strategy for the C(sp²)–H imidation and 1,2-imidofluorination of vinylsulfides has been established through simple treatment with N-fluorobis(benzenesulfonyl)imide, which acts as both oxidant and nitrogen source. For alkyl and electron-rich aryl vinylsulfides, alkyl/arylthioenamines are produced in up to 92% total yields. However, for steric and electron-deficient aryl vinylsulfides, 1,2-imidofluorination products are prepared in up to 73% yields. The chemoselectivity is controlled by the steric and electronic effects of aryl substituents. Thionium ions are proposed as key intermediates in the two reactions.     

Efficient copper-catalyzed Sonogashira coupling reactions and simulation studies

A practical copper-catalyzed I-substitutions of alkyl-2-iodobenzoates with alkynes have been developed using Cu powder as a catalyst under solvent, cocatalyst, and base-free conditions. This reaction system is new, facile, efficient, and economical that gives Sonogashira coupling products in excellent yields (up to 97%). The coupled products (A–J) were characterized by CHNS, ¹H NMR, and ¹³C NMR and are found soluble in ethyl acetate and dichloromethane. In addition, simulation studies of A–J were performed with aspulvinone dimethylallyltransferase enzyme and observe good binding affinity. The reported compounds may act as anti-cizmatics, anti-fobic in future and also have the inhibition of aspulvinone dimethylallyltransferase properties to control Alzheimer’s, Schizophrenia, etc. diseases.     

Prediction of hydrogen solubility in heavy hydrocarbons over a range of temperatures and pressures using molecular dynamics simulations

Using the method of molecular dynamics (MD), we have estimated the solubility of hydrogen in heavy hydrocarbons for a range of temperatures and pressures. Heavy hydrocarbon systems are known to be challenging not only for experimental measurements but also for reliable estimations using traditional equations of state (EOS). The simulation system used was designed with semi-permeable membranes to mimic actual experimental studies of gas solubility. Binary interaction parameters between the solute gas and the solvent (heavy hydrocarbons) components were adjusted when necessary to improve agreement with experimental results and then used in subsequent multi-component studies. Temperature and pressure ranges studied included higher temperatures and pressures which are especially difficult to investigate experimentally. Simulation results were finally used to adjust the binary interaction parameters (BIP) in simulation packages (e.g. Aspen) to enable quick and reliable predictions.     

Cosmetic Electrochemistry II: Rapid and Facile Production of Metallic Electrocatalytic Ensembles

We demonstrate a facile methodology for the production of metallic electrocatalytic microdomain ensembles for a range of analytical sensing challenges. A commercially available off‐the‐shelf cosmetic product can change the voltammetric characteristics of a metallic macro‐electrode created electrolytically into that of a random ensemble of metallic microelectrode domains. Proof‐of‐concept is shown for three examples: a palladium ensemble for hydrazine sensing, a gold ensemble for arsenic(III) detection via anodic stripping voltammetry and platinum ensembles for the direct oxidation of arsenic(III). Last we demonstrate that the fabrication of metallic microdomains can be simplified by sputter coating screen printed electrochemical sensing platforms which are beneficially constructed using this cosmetic methodology. Given the facile fabrication and low cost of the underlying electrode substrate and the cosmetic modifier, the widespread implementation of this novel fabrication methodology is expected.