Micellar Aggregates of Gemini Surfactants: Monte Carlo Simulation of a Microscopic Model

We propose a "microscopic" model of gemini surfactants in aqueous solution. Carrying out extensive Monte Carlo simulations, we study the variation of the critical micellar concentration (CMC) of these model gemini surfactants with the variation of the (a) length of the spacer connecting the two hydrophilic heads, (b) length of the hydrophobic tail and (c) the bending rigidity of the hydrocarbon chains forming the spacer and the tail; some of the trends of variation are counter-intuitive but are in excellent agreement with the available experimental results. Our simulations also elucidate the dependence of the shapes of the micellar aggregates and the magnitude of the CMC on the geometrical shape and size of the surfactant molecules and the electrical charge on the hydrophilic heads

Metal-insulator transition in an aperiodic ladder network: an exact result

We show, in a completely analytical way, that a tight binding ladder network composed of atomic sites with on-site potentials distributed according to the quasiperiodic Aubry model can exhibit a metal-insulator transition at multiple values of the Fermi energy. For specific values of the first and second neighbor electron hopping, the result is obtained exactly. With a more general model, we calculate the two-terminal conductance numerically. The numerical results corroborate the analytical findings and yield a richer variety of spectrum showing multiple mobility edges.Comment: 4 pages, 3 figure

Chemical reactivity of the compressed noble gas atoms and their reactivity dynamics during collisions with protons

Attempts are made to gain insights into the effect of confinement of noble gas atoms on their various reactivity indices. Systems become harder, less polarizable and difficult to excite as the compression increases. Ionization also causes similar effects. A quantum fluid density functional technique is adopted in order to study the dynamics of reactivity parameters during a collision between protons and He atoms in different electronic states for various projectile velocities and impact parameters. Dynamical variants of the principles of maximum hardness, minimum polarizability and maximum entropy are found to be operative

Experimental investigation on possible dependence of plastic zone size on specimen geometry

In this investigation the extent of the plastic zone size ahead of a crack-tip in single edge notched tension (SENT), compact tension (CT) specimens has been examined experimentally by micro-hardness technique and by elastic-plastic finite element analyses at different applied load levels. The magnitudes of the plastic zone size (PZS), rp ahead of crack-tip in the investigated specimens have been compared using normalized J-integral (J/a?y, where, a-crack length and ?y-yield stress of the material). The results show the dependence of PZS on specimen geometry due to varied in-plane crack-tip constraint. The results also demonstrate that the existing analytical models do not explain the experimental results of PZS satisfactorily

Electron transport through multilevel quantum dot

Quantum transport properties through some multilevel quantum dots sandwiched between two metallic contacts are investigated by the use of Green's function technique. Here we do parametric calculations, based on the tight-binding model, to study the transport properties through such bridge systems. The electron transport properties are significantly influenced by (a) number of quantized energy levels in the dots, (b) dot-to-electrode coupling strength, (c) location of the equilibrium Fermi energy $E_F$ and (d) surface disorder. In the limit of weak-coupling, the conductance ($g$) shows sharp resonant peaks associated with the quantized energy levels in the dots, while, they get substantial broadening in the strong-coupling limit. The behavior of the electron transfer through these systems becomes much more clearly visible from our study of current-voltage ($I$-$V$) characteristics. In this context we also describe the noise power of current fluctuations ($S$) and determine the Fano factor ($F$) which provides an important information about the electron correlation among the charge carriers. Finally, we explore a novel transport phenomenon by studying the surface disorder effect in which the current amplitude increases with the increase of the surface disorder strength in the strong disorder regime, while, the amplitude decreases in the limit of weak disorder. Such an anomalous behavior is completely opposite to that of bulk disordered system where the current amplitude always decreases with the disorder strength. It is also observed that the current amplitude strongly depends on the system size which reveals the finite quantum size effect.Comment: 12 pages, 7 figure

pSiM24 is a Novel Versatile Gene Expression Vector for Transient Assays as Well as Stable Expression of Foreign Genes in Plants

We have constructed a small and highly efficient binary Ti vector pSiM24 for plant transformation with maximum efficacy. In the pSiM24 vector, the size of the backbone of the early binary vector pKYLXM24 (GenBank Accession No. HM036220; a derivative of pKYLX71) was reduced from 12.8 kb to 7.1 kb. The binary vector pSiM24 is composed of the following genetic elements: left and right T-DNA borders, a modified full-length transcript promoter (M24) of Mirabilis mosaic virus with duplicated enhancer domains, three multiple cloning sites, a 3\u27rbcsE9 terminator, replication functions for Escherichia coli (ColE1) and Agrobacterium tumefaciens (pRK2-OriV) and the replicase trfA gene, selectable marker genes for kanamycin resistance (nptII) and ampicillin resistance (bla). The pSiM24 plasmid offers a wide selection of cloning sites, high copy numbers in E. coli and a high cloning capacity for easily manipulating different genetic elements. It has been fully tested in transferring transgenes such as green fluorescent protein (GFP) and β-glucuronidase (GUS) both transiently (agro-infiltration, protoplast electroporation and biolistic) and stably in plant systems (Arabidopsis and tobacco) using both agrobacterium-mediated transformation and biolistic procedures. Not only reporter genes, several other introduced genes were also effectively expressed using pSiM24 expression vector. Hence, the pSiM24 vector would be useful for various plant biotechnological applications. In addition, the pSiM24 plasmid can act as a platform for other applications, such as gene expression studies and different promoter expressional analyses

Quantum analogue of the Kolmogorov-Arnold-Moser transition in the field induced barrier penetration in a quartic potential

Quantum signatures of the Kolmogorov-Arnold-Moser (KAM) transition from the regular to chaotic classical dynamics of a double-well oscillator in the presence of an external monochromatic field of different amplitudes are analysed in terms of the corresponding Bohmian trajectories. It is observed that the classical chaos generally enhances the quantum fluctuations, while the quantum nonclassical effects try to suppress classical stochasticity

Josephson effect in graphene SBS junctions

We study Josephson effect in graphene superconductor- barrier- superconductor junctions with short and wide barriers of thickness $d$ and width $L$, which can be created by applying a gate voltage $V_0$ across the barrier region. We show that Josephson current in such graphene junctions, in complete contrast to their conventional counterparts, is an oscillatory function of both the barrier width $d$ and the applied gate voltage $V_0$. We also demonstrate that in the thin barrier limit, where $V_0 \to \infty$ and $d \to 0$ keeping $V_0 d$ finite, such an oscillatory behavior can be understood in terms of transmission resonance of Dirac-Bogoliubov-de Gennes quasiparticles in superconducting graphene. We discuss experimental relevance of our work.Comment: 7 Pg., 6 Figs, extended version submitted to PR

Nb(III) Trisoxinate & Niobyl Phosphoniobate

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