Complex dynamical invariant for a PT- symmetric Hamiltonian system in higher dimensions

With a view to get further insight into the integrability of a dynamical system, we investigate the complex invariant for a three-dimensional Hamiltonian system using the extended complex phase space approach (ECPSA) characterized by $x=x_1+i{p}_4,y=x_2+i{p}_5,z=x_3+i{p}_6,p_x=p_1+i{x}_4,p_y=p_2+i{x}_5$ and $p_z=p_3+i{x}_6$. For this purpose the rationalization method is utilized and the invariant obtained is expected to play an important role in the study of the complex trajectories for the system of concern.     

A novel technique for active vibration control,based on optimal tracking control

Determination of concentration of major elements such as Ca, Si, Al, and Fe in cement is very important for quality control during its production, correct classification according to the existing standards, and thus for appropriate use in the construction industry. For this purpose, neutron activation analysis is very suitable. In this preliminary theoretical work, the irradiation and consecutive measurement of the percentage of the constituent elements in different cement samples were done using MCNPX with γ-ray spectra as the output. Specific peaks of Ca, Si, Al, and Fe obtained from these spectra were used as input for artificial neural network (18 of them for training and 8 for testing) resulting in the determination of each element in the given sample. The mean absolute errors of the results are less than 0.4%, which is very promising for the future experimental work where the uncertainties are usually one order higher.     

Instability of binary nanofluids with magnetic field

The present paper investigates the effects of a vertical magnetic field on the double diffusive nanofluid convection. The effects of the Brownian motion and thermophoresis due to the presence of nanoparticles and the effects of the Dufour and Soret parameters due to the presence of solute are included in the investigated model. The normal mode technique is used to solve the conservation equations. For the analytical study, valid approximations are made in the complex expression for the Rayleigh number to get useful and interesting results. The bottom heavy binary nanofluids are more stable than the regular binary fluids, while the top heavy binary nanofluids are less stable than the regular binary fluids. The critical wave number and the critical Rayleigh number increase whereas the frequency of oscillation (for the bottom heavy configuration) decreases when the Chandrasekhar number increases. The numerical results for the alumina-water nanofluid are studied by use of the MATHEMATICA software.     

Two-dimensional analytical subthreshold model of graded channel DG FD SOI n-MOSFET with gate misalignment effect

A two-dimensional (2-D) analytical subthreshold model is developed for a graded channel double gate (DG) fully depleted SOI n-MOSFET incorporating a gate misalignment effect. The conformal mapping transformation (CMT) approach has been used to provide an accurate prediction of the surface potential, electric field, threshold voltage and subthreshold behavior of the device, considering the gate misalignment effect to be on both source and drain side. The model is applied to both uniformly doped (UD) and graded channel (GC) DG MOSFETs. The results of an analytical model agree well with 3-D simulated data obtained by ATLAS-3D device simulation software.     

Effect of composition modulation on the structural and optical properties of Si/Ge bilayers

We report structural as well as optical studies on Si/Ge bilayer structures having different individual layer thicknesses. The Raman spectrum of [Ge (5 nm)/Si (5 nm)] bilayer structure shows amorphous nature, while the [Si (5 nm)/Ge (5 nm)] bilayer structure shows a mixed nanocrystalline/amorphous behaviour of the layers. As the thickness of the individual layers increases to 10 nm, the introduction of large number of Si atoms at the interface results in reduction of Ge crystallization as well as higher intensity of interfacial SiGe alloy formation. This may be regarded as a consequence of the island growth induced surface roughening in the later case (i.e. in [Si (10 nm)/Ge (10 nm)] bilayer) as also revealed by corresponding atomic force microscopy (AFM) images. These results are also supported by Photoluminescence (PL) spectra recorded using two different photon energies of 300 and 488 nm along with the optical absorption measurements giving higher values of band gap as compared to their corresponding bulks, revealing the effect of quantum confinement in the deposited layers.     

Kinetics and mechanism of oxidation of β-Alanine by <Emphasis Type="Italic">N</Emphasis>-bromophthalimide in the presence of Ru(III) chloride as homogenous catalyst in acidic medium

The kinetics of Ru(III) chloride-catalyzed oxidation of β-Alanine (NH₃ ⁺CH₂CH₂COOH, β-Ala) by N–bromophthalimide (NBP) in aqueous perchloric acid medium was studied at 35 °C. The rate law followed a first-order and zero-order dependence with respect to [NBP] and [β-Ala], respectively. The reaction followed first-order kinetics with respect to [Ru(III)] chloride at a range of low concentrations while the order changed from first- to zero-order at high concentration of [Ru(III)] chloride; demonstrating the catalytic effect for the oxidation of β-Ala by NBP. The rate decreased with increase in acidity. Chloride ions positively influenced the rate of the reaction. Neither phthalimide (NHP) nor Hg(II) influenced the reaction rate. Ionic strength (I) and dielectric constant (D) of the medium had no significant effect on the rate. Activation parameters of the reactions were determined by studying the reaction at different temperatures (30–50 °C). The colorimetric, FTIR, and GC-MS techniques were used to identify methyl cyanide (CH₃CN) and CO₂ as products of the reaction. In the reaction, approximately 2.3 moles of NBP oxidized one mole of β-Ala. A reaction scheme of the oxidation of β-Ala by NBP in the presence of Ru(III) chloride was found to be in consistent with the rate law and the reaction stoichiometry.     

Concentration-dependent energy transfer studies in ternary dye mixture of Stilbene-420, Coumarin-540 and Nile Blue

The energy transfer studies in the case of ternary dye mixture [Stilbene-420 (donor)+Coumarin-540 (intermediator)+Nile Blue (acceptor)] have been done and discussed through optical gain characteristics at various acceptor concentrations under nitrogen laser excitation. The concentration of the other two dyes were kept constant. It is observed that the concentration of the acceptor dye plays a very critical role in energy transfer dye laser (ETDL) as small change in its concentration varies the intensity of the laser output in the red region by large amount. Also, the highest laser output in the red region is obtained when the concentration of the acceptor dye is slightly higher than that of the intermediator dye. The present studies are helpful in deciding the optimum concentration of the acceptor dye to be used in ternary dye mixture for maximum gain and tuning range. The ternary dye mixture under study provides an ETDL tuning range up to 700 nm.     

Epimerization‐Free Block Synthesis of Peptides from Thioacids and Amines with the Sanger and Mukaiyama Reagents

Highly activated thioesters formed by the rapid reaction of C‐terminal thioacids derived from protected amino acids and peptides with the Sanger reagent and other electron‐deficient aryl halides in the presence of a free amine immediately form a peptide bond with the amine. This essentially epimerization‐free method was used for the 4+4 block synthesis of a hindered octapeptide (see scheme; Boc, Pbf, and Trt are protecting groups).