Scaling Transformations for Boundary Layer Flow near the Stagnation-Point on a Heated Permeable Stretching Surface in a Porous Medium Saturated with a Nanofluid and Heat Generation/Absorption Effects

In this article, a similarity solution of the steady boundary layer flow near the stagnation-point flow on a permeable stretching sheet in a porous medium saturated with a nanofluid and in the presence of internal heat generation/absorption is theoretically studied. The governing partial differential equations with the corresponding boundary conditions are reduced to a set of ordinary differential equations with the appropriate boundary conditions via Lie-group analysis. Copper (Cu) with water as its base fluid has been considered and representative results have been obtained for the nanoparticle volume fraction parameter f{\phi} in the range 0 ￡ f ￡ 0.2{0\leq \phi \leq 0.2} with the Prandtl number of Pr = 6.8 for the water working fluid. Velocity and temperature profiles as well as the skin friction coefficient and the local Nusselt number are determined numerically. The influence of pertinent parameters such as nanofluid volume fraction parameter, the ratio of free stream velocity and stretching velocity parameter, the permeability parameter, suction/blowing parameter, and heat source/sink parameter on the flow and heat transfer characteristics is discussed. Comparisons with published results are also presented. It is shown that the inclusion of a nanoparticle into the base fluid of this problem is capable to change the flow pattern.     

Micellar effects on the alkaline hydrolysis of isatin and its derivatives

Herein we have investigated the hydrolysis of 1H-indol-2,3-dione (isatin, I) and its derivatives of different hydrophobicities, viz. N-dimethylaminomethyl indol-2,3-dione (II), N-morpholinomethyl indol-2,3-dione (III), N-pipridinomethyl indol-2,3-dione (IV), N-heptylaminomethyl indol-2,3-dione (V), N-dodecylaminomethyl indol-2,3-dione (VI), N-hexylanilinomethyl indol-2,3-dione (VII), N-decylanilinomethyl indol-2,3-dione (VIII), and N-hexadecylanilinomethyl indol-2,3-dione (IX), in the presence of an excess amount of sodium hydroxide. All the isatin derivatives were synthesized in the laboratory. The progress of the reactions was studied by exploiting UV-visible spectrophotometry. The observed rate constant, k(w), increases linearly on increasing the hydroxide ion concentration, indicating first-order dependence on [OH(-)]. The effects of surfactants, cationic (cetyltrimethylammonium chloride, CTACl), and anionic (sodium dodecyl sulfate, SDS) were also investigated. The rate of reaction increased on increasing the concentration of CTACl and, after reaching a maximum, it started decreasing. Conversely, anionic micelles of SDS inhibited the rate of hydrolysis of isatin and its derivatives. The results of the effect of CTACl were analyzed using a pseudophase ion-exchange model while the inhibition by SDS was analyzed using a simple Menger-Portnoy model. The effects of added salts, such as NaBr, NaCl, and (CH(3))(4)NBr, were also seen on the isatin hydrolysis. It was found that the addition of salts decreased the rate enhancement efficiency of the CTACl.     

Flexo-Ionic Effect of Ionic Liquid Crystal Elastomers

The first study of the flexo-ionic effect, i.e., mechanical deformation-induced electric signal, of the recently discovered ionic liquid crystal elastomers (iLCEs) is reported. The measured flexo-ionic coefficients were found to strongly depend on the director alignment of the iLCE films and can be over 200 µC/m. This value is orders of magnitude higher than the flexo-electric coefficient found in insulating liquid crystals and is comparable to the well-developed ionic polymers (iEAPs). The shortest response times, i.e., the largest bandwidth of the flexo-ionic responses, is achieved in planar alignment, when the director is uniformly parallel to the substrates. These results render high potential for iLCE-based devices for applications in sensors and wearable micropower generators.     

Similarity solution of boundary layer stagnation-point flow towards a heated porous stretching sheet saturated with a nanofluid with heat absorption/generation and suction/blowing: A Lie group analysis

In this paper, heat and mass transfer analysis for boundary layer stagnation-point flow over a stretching sheet in a porous medium saturated by a nanofluid with internal heat generation/absorption and suction/blowing is investigated. The governing partial differential equation and auxiliary conditions are converted to ordinary differential equations with the corresponding auxiliary conditions via Lie group analysis. The boundary layer temperature, concentration and nanoparticle volume fraction profiles are then determined numerically. The influences of various relevant parameters, namely, thermophoresis parameter Nt, Brownian motion parameter Nb, Lewis number Le, suction/injection parameter S, permeability parameter k₁, source/sink parameter λ and Prandtl parameter Pr on temperature and concentration as well as wall heat flux and wall mass flux are discussed. Comparison with published results is presented.     

Influence of degree of sulfation on the rheology of cellulose nanocrystal suspensions

The rheology and microstructure of two different cellulose nanocrystals (CNC) samples possessing different degrees of sulfation are studied over a broad concentration range of 1 to 15 wt%. CNC suspensions are isotropic at low concentration and experience two different transitions as concentration increases. First, they form chiral nematic liquid crystals above a first critical concentration where the samples exhibit a fingerprint texture and the viscosity profile shows a three-region behavior, typical of liquid crystals. By further increasing the concentration, CNC suspensions form gels above a second critical concentration, where the viscosity profile shows a single shear-thinning behavior over the whole range of shear rates investigated. It has been found that the degree of sulfation of CNC particles has a significant effect on the critical concentrations at which transitions from isotropic to liquid crystal and liquid crystal to gel occur. Rheological properties and microstructure of these suspensions have been studied using polarized optical microscopy combined with rheometry.     

The structure and magnetism of Fe/Mo(0 0 1) surface: A pseudopotential calculation

The effect of structure on the magnetism of iron monolayers (MLs) on molybdenum is investigated using the density functional theory (DFT) with norm conserving pseudopotentials and a plane wave basis, under the local spin density approximation (LSDA). Relaxation of 5 and 7 ML of Mo resulted in a contraction of 11.3% and 11.7%, respectively, for the top Mo–Mo interlayer spacing in close agreement with experimental results. In the case of one Fe overlayer, the top Fe–Mo interlayer spacing contracted by 15.8% for a ferromagnetic (FM) p(1×1) and 20.6% for an antiferromagnetic (AF) c(2×2) configuration. The magnetic moment of the surface (Fe) layer is enhanced from its theoretically calculated bulk value. Total energy calculations show that the AF c(2×2) is the stable state with a magnetic moment of 2.53 μ_B. The surface Fe atoms are AF coupled with each other and with the Mo layers below, showing layered AF coupling. The present study demonstrates the reliability of the pseudopotential approach under LSDA with core corrections included to the calculation of magnetic properties of combined transition metal systems.     

A rapid magnetizable solid phase radioimmunoassay kit for human placental lactogen

The radioimmunoessay of human placental lactogen (HPL) with separation of antibody bound and free hormone was achieved by the magnetizable solid phase coupled to antibody. The precision, accuracy, sensitivity and specificity of the method has been carefully checked in this study and the procedure of the assay was performed at room temperature. The above parameters were evaluated by recovery test (99%); within assays (4%), between assays (5%), sensitivity (0.04 g/ml) and there was no obvious cross reactivity with human growth hormone (hGH) and human chorionic gonadotropin (hCG).     

Investigation of the microstructure of micelles formed by hard-sphere chains interacting via size nonadditivity by discontinuous molecular dynamics simulation

Micelle formation by short nonadditive hard surfactant chains was investigated at different size ratios, reduced densities, and nonadditivity parameters using molecular dynamics simulation. It was found that spherical, cylindrical, lamellar, and reverse micelles can form in systems with different head, tail, and solvent characteristics. Hard-core surfactant chains composed of a head segment and three tail segments were simulated in a solvent of hard spheres. The formation of micelles was found to be a strong function of the packing fraction and nonadditivity parameter. Micelles were more stable at higher densities and larger nonadditivity parameters. At lower densities, micelles tended to break into small, dynamic globules.     

Characterizing Laser-induced Plasma Generated from MgO/PVA Solid Targets

Optics and Spectroscopy - This contribution reports on the characterization of laser-induced plasma generated from the surface of magnesium oxide dispersed in Poly (vinyl alcohol) (MgO/PVA) pellet...     

Mathematics for chromatography. Part I: Concentration distributions and their moments

Several distributions of interest in chromatography were studied. In each case, the moments up to 4th moment were evaluated and the skew and the excess were deduced. The distributions studied in this article are the normal, continuous Poisson, discrete Poisson, exponentially modified normal, and exponentially modified Poisson distributions.