WorldCat Identities


Works: 8 works in 8 publications in 1 language and 8 library holdings
Publication Timeline
Intermolecular Slip Mechanism in Tropocollagen Nanofibrils( )

1 edition published in 2009 in English and held by 0 WorldCat member libraries worldwide

Collagen is the most important structural protein in the animal kingdom and is responsible for the strength and integrity of many tissues like bone, teeth, cartilage and tendons. The mechanical properties of these tissues are determined by their hierarchical structure. However, how each level contributes to the overall properties of collagenous tissues, and how individual hierarchical levels interact, remains poorly understood. Furthermore, despite extensive experimental and computational studies including both the single molecule and macro-scale levels, few studies have focused on the level of collagen fibrils. Here we report a detailed study of the shear interaction between two tropocollagen molecules, a major mechanism that contributes to the fibril mechanical behavior. Using steered molecular dynamics (SMD) simulations in explicit solvent, we model the slip of two tropocollagen molecules at varying pulling rates. We find that the adhesion strength is highly sensitive to the pulling rate, and that it converges to a value of 10.12 pN/Angstrom for vanishing loading rates. We find that intermolecular H-bonds play a key role in determining the resistance against slip. Our results provide quantitative details on this mechanism of load transmission inside collagen fibrils and fibers, which is crucial for the development of constitutive models of collagenous tissues at larger hierarchical levels. Such constitutive models of collagenous tissue mechanics have many applications, ranging from development of bio-inspired materials to studies in tissue engineering. By incorporating pathological collagen mutations, these studies could advance our knowledge of mechanisms underlying important collagen-related diseases like Osteogenesis Imperfecta or Ehlers-Danlos Syndrome
The Use of Dipolar Coupled Nuclear Spins for Quantum Information Processing and Quantum Computation( )

1 edition published in 2004 in English and held by 0 WorldCat member libraries worldwide

The goal of this project is to improve our control over nuclear spins in the solid state. We have: 1. Characterized the growth of multi-spin coherences in 1D and 3D spin systems under the dipolar interaction. Measured the decay rates of correlated spin states and characterized the resulting scaling behavior. 2. Studied the transport of polarization in 1D spin chains, both experimentally and in simulations. We have experimentally created states in which polarization is localized to the ends of the chain and studied the ensuing dynamics. 3. Demonstrated the role of nuclear spin dipolar diffusion in dynamic nuclear polarization (DNP) experiments, in dielectric samples with abundant nuclear spins. Achieved a 29Si polarization of 8.3% at 66 GHz and 1.1 K in single-crystal P-doped, the highest ever reported, using DNP. Took delivery of a He-3 cryostat that will allow these experiments to be extended to 94 GHz electron spin frequencies and 300 mK temperatures allowing us to achieve close to unit polarization
Electron-Nuclear Quantum Information Processing( )

1 edition published in 2008 in English and held by 0 WorldCat member libraries worldwide

We devised a novel scheme for electron-nuclear quantum information processing that exploits the anisotropic hyperfine coupling. This scheme enables universal control over a 1-electron, N-nuclear spin system, addressing only a single electron spin transition. Not having to address the nuclear spins directly significantly speeds up the control. We designed and fabricated a pulsed electron spin resonance spectrometer, along with a cryogenic probe which we used to experimentally implement this scheme on a single crystal sample of irradiated malonic acid
Using Nuclear Magnetic Resonance to Assess and Optimize the Precision of Methods for Controlling Quantum Dynamics( )

1 edition published in 2005 in English and held by 0 WorldCat member libraries worldwide

The most significant achievements of this project were: (1) Development and validation of the hardware and software needed to implement "strongly modulating pulses", by which high precision quantum gates can be obtain in realistic systems of up to 12 qubits; (2) A detailed analysis and evaluation of a 3-qubit quantum Fourier transform via full quantum process tomography; (3) An extensive set of mathematical and computational techniques to accomplish these goals, including Hadamard products, the real density matrix, and methods of fitting superoperators to experimental data; (4) Creation of a 3-qubit "noiseless subsystem", of a Bell state on two 2-qubit decoherence-free subspaces (DFS), and the invention of "partial" pseudopure states which will enable us to demonstrate robust methods for controlling multi-DFS-qubit systems by NMR; (5) Implementation of several quantum chaotic maps, and the discovery that these provide a scalable approach to determining the magnitude and kind of errors present in complex quantum computations; (6) The invention of a "spin amplifier", by which entanglement can be used to enable single spin measurement, and a small-scale demonstration by NMR; (7) Experiments demonstrating that the foregoing advances enable implementation of complex entangling unitary and decoherent operations, culminating in creation of a 12-qubit CAT state
Quantum Information Technology: Entanglement, Teleportation, and Memory( )

1 edition published in 2005 in English and held by 0 WorldCat member libraries worldwide

A team of researchers from the Massachusetts Institute of Technology and Northwestern University worked to develop the technology elements needed to perform long-distance, high-fidelity qubit teleportation. In particular: this team developed novel sources of polarization-entangled photons based on chi-2 and chi-3 materials; it developed devices for high-efficiency quantum state frequency conversion and demonstrated long-distance entanglement distribution via optical fiber; and it worked toward realizing quantum memory elements in both trapped-atom and atomic-ensemble systems. The experimental work was supported by a variety of theoretical studies. Other theoretical work addressed more general issues in quantum communication and entanglement applications
Alpha-Helical Protein Domains Unify Strength and Robustness through Hierarchical Nanostructures( )

1 edition published in 2009 in English and held by 0 WorldCat member libraries worldwide

Hierarchical nanostructures, ranging through atomistic, molecular and macroscopic scales, represent universal features of biological protein materials. Here we show for the case of alpha-helical (AH) protein domains that this use of molecular hierarchies within the structural arrangement leads to an extended physical dimension in the material design space that resolves the conflict between disparate material properties such as strength and robustness, a limitation faced by many synthetic materials. An optimal combination of redundancies at different hierarchical levels enables superior mechanical performance without additional material use. Our analysis is facilitated by the application of a Hierarchical Bell model (HBM), which explicitly considers the hierarchical architecture of H-bonds within the protein structure, providing a structure?property relationship of strength properties of AH protein nanostructures. The HBM is validated by large-scale molecular dynamics simulations of several model protein structures. Our findings may enable the development of self-assembled de novo bioinspired nanomaterials based on peptide and protein building blocks, and could help in elucidating the mechanistic role of AHs in cell signaling and mechanotransduction
Artificial muscle technology : physical principles and naval prospects by Ian W Hunter( )

1 edition published in 2003 in English and held by 0 WorldCat member libraries worldwide

Understanding of the advantages of unsteady flow and locomotion in fish and insects is creating a demand for biomimetic actuator technologies. New actuator materials that employ voltage, field, or temperature driven dimensional changes to produce forces and displacements are suggesting new approaches to propulsion and maneuverability. The fundamental properties of these new materials are presented, and examples of potential undersea applications are examined to assist those involved in hydrodynamic design and actuator research evaluate the current status and the developing potential of these artificial muscle technologies. The technologies described are based on newly explored materials developed over the past decade, and also on older materials whose properties are not widely known. The materials are dielectric elastomers, ferroelectric polymers, liquid crystal elastomers, molecular actuators, giant magnetostrictive materials, thermal and ferromagnetic shape memory alloys, ionic polymer/metal composites, conducting polymers, and carbon nanotubes. All the technologies involve materials that change dimensions in response to input electrical, thermal, or optical power. A table of the mechanical properties of mammalian skeletal muscle is presented for comparison with the properties of each of the materials described. The properties are maximum strain, maximum stress, work density, density, peak strain rate, power to mass, bandwidth, life cycle, coupling, efficiency, modulus of elasticity, speed of sound, coefficient of thermal expansion, strength, voltage, charge, and maximum field. Fundamental mechanisms, basic properties, synthesis, fabrication, and applications are presented. The paper concludes with two case studies presenting the best artificial muscle technologies for a variable camber propeller and for increasing thrust by generating unsteady flow conditions when used with a REMUS autonomous underwater vehicle (AUV) propeller. (13 tables, 3 figures, 125 refs7
A Comprehensive Approach to Fusion for Microsensor Networks: Distributed and Hierarchical Inference, Communication, and Adaption( )

1 edition published in 2000 in English and held by 0 WorldCat member libraries worldwide

This final report summarizes the research and activities under the ODDR & E MURI on Data Fusion in Large Arrays of Microsensors. The report reviews the intellectual themes and research concentration areas of this program provides a listing of all personnel involved in the program and the infrastructure and website created; summarizes highlights of the impact our work has already had; lists many of the awards and recognition we have received; describes interactions with and transitions to DoD activities as well as the infrastructure we have put in place (including the program website which will continue into the future); and briefly summarizes the major research accomplishments we have had. The report closes with a complete listing of the very substantial list of publications that have resulted from research supported by this project