Electrostatic assembly of nanoparticles and biomacromolecules

The controlled assembly of nanoparticles in thin film form on solid supports, both as monolayers and as superlattice structures, is a problem of considerable topical interest. Among the many interactions used to program the assembly of nanoparticles, electrostatic forces are particularly interesting for many reasons. This Account deals with assembling surface-modified nanoparticles in thin film form using electrostatic interactions at the air-water interface and in thermally evaporated lipid films. The generality of the electrostatic assembly protocol is demonstrated in the immobilization of DNA and proteins in lipid films.     

Thermomechanical Framework for the Constitutive Modeling of Asphalt Concrete

This study is concerned with the constitutive modeling of asphalt concrete. Unlike most constitutive models for asphalt concrete that do not take into account the evolution of the microstructure of the material, this study incorporates the evolution of the microstructure by using a framework that recognizes that a body’s natural configurations can evolve as the microstructure changes. The general framework, on which this study is based, is cast within a full thermomechanical setting. In this paper, we develop models within the context of a mechanical framework that stems from the general framework for models based on the full thermodynamic framework and the resulting equations represent a nonlinear rate type viscoelastic model. The creep and stress relaxation experiments of Monismith and Secor are used for validating the efficacy of the model, and it is found that the predictions of the theory agree very well with the available experimental results. The advantages of using such a framework are many, especially when one wants to model the diverse mechanical and thermodynamic response characteristics of asphalt and asphalt concrete.     

Impulse differential inclusions: a viability approach to hybridsystems

Impulse differential inclusions are introduced as a framework for modeling hybrid phenomena. Connections to standard problems in the area of hybrid systems are discussed. Conditions are derived that allow one to determine whether a set of states is viable or invariant under the action of an impulse differential inclusion. For sets that violate these conditions, methods are developed for approximating their viability and invariance kernels, that is the largest subset that is viable or invariant under the action of the impulse differential inclusion. The results are demonstrated on examples     

Daily intake of manganese by the adult population of Mumbai

The daily intake of manganese (Mn) estimated through air, water and duplicate dietary analysis is found to range from 0.67 to 4.99 mg with a mean value of 2.21 mg. Ingestion through food contributed to the predominant fraction of the intake. The turnover rate of Mn through blood is approximately 2 h, based on the mean concentration of Mn in blood of 1.54 microg l(-1). The average concentrations of Mn in water and air were approximately 1.42 microg l(-1) and 37 ng m(-3), respectively. The daily intake of Mn by the adult population of Mumbai is closer to the lower bound of the recommended limit of 2-5 mg. Electro Thermal Atomic Absorption Spectrophotometry (ET-AAS), has been used for the determination of Mn in a variety of environmental and human biological fluids. The detection limit of Mn for a volume injection of 20 microl is 2 pg absolute. The precision of the method is established by analyzing a synthetic mixture containing various elements in different quantities (0.5-10 ppm) and is found to be within +/- 8%. The reliability of estimation is further assessed through the analysis of Standard Reference Materials (SRMs) of soil, hay, milk powder and fish tissue obtained from IAEA.     

Switching through singularities

Asymptotic tracking is studied for systems which are not regular, that is, the relative degree is not well defined. For these systems, the input–output linearizing control law has singularities. We propose a tracking control law which switches between an approximate tracking law (Hauser et al., IEEE Trans. Automat. Control 37 (3) (1992) 392–398) close to the singularities, and an exact tracking law away from the singularities, and we study the applicability of this law based on the behavior of the system’s zero dynamics at the switching boundary. As in Hauser et al. (IEEE Trans. Automat. Control 37 (3) (1992) 392–398), the ball and beam example is used to motivate the study.     

Numerical solution of Fredholm integral equations with a logarithmic singularity

Generalized quadrature is used for the numerical solution of two Fredholm integral equations which occur in electrostatics and aerodynamics.     

Connectivity, clusters, and transport: use of percolation concepts and atomistic simulation to track intracellular ion migration

The cytoskeleton is an intracellular highway system, teaming with signalling ions that zip from site to site along filaments. These tiny particles alternately embrace and slip free of protein receptors with wide-ranging affinities, as they propagate in a blur of motion along cytoskeletal corridors at transport rates far exceeding ordinary diffusive motion. Recent experimental breakthroughs have enabled optical tracking of these single ion-binding events in the physiological and diseased states. However, traditional continuum modelling methods have proven ineffective for modelling migration of biometals such as copper and zinc, whose cytosolic concentrations are putatively vanishingly small, or very tightly controlled. Rather, the key modelling problem that must be solved for biometals is determination of the optimal placement of biosensors that bind and detect the metal ions within the heterogeneous environment of the cell. We discuss herein how percolation concepts, in combination with atomistic simulation and sensor delivery models, have been used to gain insights on this problem, and a roadmap for future breakthroughs.     

Tailoring the curvature, bowl rigidity and stability of heterobuckybowls: theoretical design of synthetic strategies towards heterosumanenes

Quantum mechanical calculations predict that larger heteroatom substituents on the periphery increase the feasibility of the crucial third ring closure in sumanene and are responsible for the accompanying modulations in the curvature, rigidity, stability and some of the physicochemical properties of the resulting heterosumanenes. Systematic application of semiempirical, ab initio, and DFT methods reveal that the qualitative trends obtained and our principal conclusions are independent of level of theory, albeit with minor quantitative differences.