Structure–property relationship studies in amine functionalized multiwall carbon nanotubes filled polypropylene composite fiber

Amine functionalized multiwalled carbon nanotubes (a‐MWNT) based polypropylene (PP) composite fibers were prepared in the presence of polypropylene‐g‐maleic anhydride (PP‐g‐MA) by melt‐mixing followed by melt‐spinning with subsequent post‐drawing of the as‐spun fibers of varying draw ratio (DR). In order to enhance the interfacial interaction, a‐MWNT were utilized in combination with PP‐g‐MA during melt‐mixing. Fourier transform infrared spectroscopic analysis revealed the formation of imide bonds between MA functionality of PP‐g‐MA and amine functional group of a‐MWNT. Higher tensile properties of PP/a‐MWNT/PP‐g‐MA composite fibers were registered with varying DR of the as‐spun fiber. Orientation factors of a‐MWNT and PP chains along the fiber axis were correlated with the higher tensile modulus and tensile strength of PP/a‐MWNT/PP‐g‐MA composite fiber of varying DR. Crystallization studies indicated the role of hetero‐nucleating action of a‐MWNT in PP/a‐MWNT/PP‐g‐MA composite fiber. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Identification of influential vertices in complex networks: A hitting time-based approach

Unravelling the dynamics of network vertices is pivotal, and traditional centrality measures have limitations in adapting to structural changes, directed and weighted networks, and temporal analyses. This paper introduces a ground breaking approach - hitting time-based centrality. Utilizing network matrix notations and a random walk model on a connected network , we establish a Markov chain to quantify the hitting time, hitting distance, and hitting centrality, providing a nuanced measure prioritizing central vertices. Through extensive experiments using Kendall's tau coefficient, the paper evaluates the method's correlation with actual influence in the Susceptible-Infectious (SI) model, showcasing superior performance across diverse network sizes and structures. The hitting centrality method exhibits sensitivity to connectivity dynamics, effective incorporation of temporal dynamics, and robust handling of weighted and directed networks. Positive Kendall's tau coefficients underline the method's proficiency in prioritizing influential vertices by correlating hitting centrality values with actual infection ability. The demonstrated robustness to structural changes enhances its utility for dynamic network analysis. In conclusion, our hitting time-based centrality approach emerges as a promising method, mitigating the shortcomings of traditional measures. By integrating information propagation speed, accommodating network dynamics, and enabling time-dependent analyses, it offers a comprehensive tool for evaluating vertex importance and influence in complex networks.     

DNA binding and unwinding by self-assembled supramolecular hetero-bimetallacycles

Two new tetracationic hetero-bimetallacycles were prepared from a bis-pyridine amide ligand and metal (Pd and Pt) acceptors. We found that both self-assembled hetero-bimetallacycles bind and unwind supercoiled DNA as established by photophysical and gel electrophoresis analyses, respectively.     

Component Inventory Costs in an Assembly Problem with Uncertain Supplier Lead-Times

We present a generic study of inventory costs in a factory stockroom that supplies component parts to an assembly line. Specifically, we are concerned with the increase in component inventories due to uncertainty in supplier lead-times, and the fact that several different components must be present before assembly can begin. It is assumed that the suppliers of the various components are independent, that the suppliers' operations are in statistical equilibrium, and that the same amount of each type of component is demanded by the assembly line each time a new assembly cycle is scheduled to begin. We use, as a measure of inventory cost, the expected time for which an order of components must be held in the stockroom from the time it is delivered until the time it is consumed by the assembly line. Our work reveals the effects of supplier lead-time variability, the number of different types of components, and their desired service levels, on the inventory cost. In addition, under the assumptions that inventory holding costs and the cost of delaying assembly are linear in time, we study optimal ordering policies and present an interesting characterization that is independent of the supplier lead-time distributions.     

Numerical computation of the linear convective and absolute stability of free-shear flows

The linear stability of free-shear flows is governed by their dispersion characteristics. The dispersion relation can be obtained by integrating the Rayleigh equation. The integration process can be hampered by the presence of singularities within the domain of integration. A complex-domain contour integration procedure is presented that enables this integration to be performed in a modular and robust fashion. This is accomplished by deforming the original integration contour into piecewise-continuous line-segments in the complex domain to avoid all the singularities. This integration technique can then be used to find absolute and convective instabilities of the medium by a simple procedure. However when the velocity profile for a shear layer is obtained from experiments or numerical simulations, it is available only along the real-axis. Thus the complex-domain integration procedure cannot be applied unless a functional fit is obtained for the velocity profile. For convectively unstable systems, the integration can be carried out along the real-axis only for self-excited systems. However, for a certain class of free-shear flows, it is shown that an absolute instability can still be calculated by integrating the Rayleigh equation along the real-axis. This leads to the development of a fully automatic absolute-instability solver and a semi-automatic convective-instability solver.     

Pressure induced phase transformation and electronic properties of AlAs

We have performed the first-principle study to analyze the structural and electronic properties of aluminum arsenide under the application of pressure. The computations have been carried out using the ground state total energy calculation approach of the system. The first-principle approach has been used to compute the stability of various phases of AlAs, like original zinc blende (B3), intermediate NiAs (B8), NaCl (B1) and CsCl (B2) type as a function of pressure. The study observes a B3–B8, B3–B1 and B3–B2 transitions at 6.99 GPa, 8.18 GPa and 73.43 GPa. The computed phase transition pressures, lattice parameters, bulk modulus, and energy gaps are in good agreement with their experimental as well as theoretical counterparts. Band structure and density of states analysis have also been performed and results have been discussed in detail.     

Analysis of F-shape microstrip line fed dualband antenna for WLAN applications

An analysis of microstrip line fed antennas has been presented theoretically using circuit theory concept. The theoretical investigations of F-shape antenna parameters such as return loss, VSWR, gain and efficiency have been calculated. It is found that antenna resonate at 2.4 and 5.2 GHz for lower and upper resonance frequencies respectively. The bandwidth of the F-shape antenna at lower resonance frequency is 20.08 % (simulated) and 17.05 % (theoretical) whereas at upper resonance frequency, it is 5.93 % (simulated) and 5.78 % (theoretical). The characteristics of the F-shape antenna is compared with other microstrip line fed antennas. It is found that F-shape antenna is linearly polarised along the X direction. The theoretical results are compared with IE3D simulation results as well as reported experimental results and they are in close agreement.     

Allosteric Binding Sites of Aβ Peptides on the Acetylcholine Synthesizing Enzyme ChAT as Deduced by In Silico Molecular Modeling

The native function of amyloid-β (Aβ) peptides is still unexplored. However, several recent reports suggest a prominent role of Aβ peptides in acetylcholine homeostasis. To clarify this role of Aβ, we have reported that Aβ peptides at physiological concentrations can directly enhance the catalytic efficiency of the key cholinergic enzyme, choline acetyltransferase (ChAT), via an allosteric interaction. In the current study, we further aimed to elucidate the underlying ChAT-Aβ interaction mechanism using in silico molecular docking and dynamics analysis. Docking analysis suggested two most probable binding clusters on ChAT for Aβ₄₀ and three for Aβ₄₂. Most importantly, the docking results were challenged with molecular dynamic studies of 100 ns long simulation in triplicates (100 ns × 3 = 300 ns) and were analyzed for RMSD, RMSF, RoG, H-bond number and distance, SASA, and secondary structure assessment performed together with principal component analysis and the free-energy landscape diagram, which indicated that the ChAT-Aβ complex system was stable throughout the simulation time period with no abrupt motion during the evolution of the simulation across the triplicates, which also validated the robustness of the simulation study. Finally, the free-energy landscape analysis confirmed the docking results and demonstrated that the ChAT-Aβ complexes were energetically stable despite the unstructured nature of C- and N-terminals in Aβ peptides. Overall, this study supports the reported in vitro findings that Aβ peptides, particularly Aβ₄₂, act as endogenous ChAT-Potentiating-Ligand (CPL), and thereby supports the hypothesis that one of the native biological functions of Aβ peptides is the regulation of acetylcholine homeostasis.