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2004

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Articles 1 - 9 of 9

Full-Text Articles in Engineering

Biomimetic Actuators: Where Technology And Cell Biology Merge [Review Article], Michael Knoblauch, Winfried Peters Nov 2004

Biomimetic Actuators: Where Technology And Cell Biology Merge [Review Article], Michael Knoblauch, Winfried Peters

Winfried S. Peters

The structural and functional analysis of biological macromolecules has reached a level of resolution that allows mechanistic interpretations of molecular action, giving rise to the view of enzymes as molecular machines. This machine analogy is not merely metaphorical, as bio-analogous molecular machines actually are being used as motors in the fields of nanotechnology and robotics. As the borderline between molecular cell biology and technology blurs, developments in the engineering and material sciences become increasingly instructive sources of models and concepts for biologists. In this review, we provide a – necessarily selective – summary of recent progress in the usage of …

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White Light Electrophosphorescence From Polyfluorene-Based Light-Emitting Diodes:€‰ Utilization Of Fluorenone Defects†, Xiong Gong Sep 2004

White Light Electrophosphorescence From Polyfluorene-Based Light-Emitting Diodes:€‰ Utilization Of Fluorenone Defects†, Xiong Gong

Xiong Gong

Poly(9,9-dioctylfluorene-co-fluorenone) with 1% fluorenone, (PFO−F(1%)), was synthesized as a model compound to investigate the optical and electrical effects of fluorenone defects in poly(9,9-dioctylfluoren-2,7-diyl), PFO. Photoluminescence (PL) and electroluminescence (EL) measurements demonstrate that PFO−F(1%) emits stable green light. PL and EL studies indicate that Förster energy transfer to and charge carrier trapping on fluorenone defects (with subsequent fluorenone emission) are responsible for the color degradation typically observed with the polyfluorenes. By utilization of “fluorenone defects” in PFO−fluorenone copolymers (PFO−F), white electrophosphorescent light-emitting diodes were fabricated. Polymer blends were spin-cast from solution containing PFO, PFO−F (1%), and tris[2,5-bis(9,9-dihexylfluoren-2-yl)pyridine-κ2NC3]iridium(III), Ir(HFP)3. The white emission …

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Growth Dynamics Of Isotactic Polypropylene Single Crystals During Isothermal Crystallization From A Miscible Polymeric Solvent, Thein Kyu Sep 2004

Growth Dynamics Of Isotactic Polypropylene Single Crystals During Isothermal Crystallization From A Miscible Polymeric Solvent, Thein Kyu

Thein Kyu

The present article presents a spatiotemporal growth of isotactic polypropylene (iPP) single crystals, melt crystallized from a polymeric solvent, i.e., poly (ethylene octene) copolymer that is known to be miscible with iPP. Optical and atomic force microscopic investigations reveal that the melt grown single crystals of iPP develop in the form of two parallel rows of crystal lamellae, but these crystals merge at the tips. To elucidate the mechanism of these emerging parallel rows of iPP crystals, a phase field model pertaining to solidification phenomena has been employed that involves a nonconserved crystal order parameter and a chain-tilting angle. This …

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Knowledge Discovery From Multispectral Satellite Images, Arun D. Kulkarni Sep 2004

Knowledge Discovery From Multispectral Satellite Images, Arun D. Kulkarni

Arun Kulkarni

A new approach to extract knowledge from multispectral images is suggested. We describe a method to extract and optimize classification rules using fuzzy neural networks (FNNs). The FNNs consist of two stages. The first stage represents a fuzzifier block, and the second stage represents the inference engine. After training, classification rules are extracted by backtracking along the weighted paths through the FNN. The extracted rules are then optimized by use of a fuzzy associate memory bank. We use the algorithm to extract classification rules from a multispectral image obtained with a Landsat Thematic Mapper sensor. The scene represents the Mississippi …

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Planning Evaluation Of Radiotherapy For Complex Lung Cancer Cases Using Helical Tomotherapy, Tomas Kron, Grigor Grigorov, Edward Yu, Slav Yartsev, Jeff Chen, Eugene Wong, George Rodrigues, Kris Trenka, Terry Coad, Glenn Bauman, Jake Van Dyk Aug 2004

Planning Evaluation Of Radiotherapy For Complex Lung Cancer Cases Using Helical Tomotherapy, Tomas Kron, Grigor Grigorov, Edward Yu, Slav Yartsev, Jeff Chen, Eugene Wong, George Rodrigues, Kris Trenka, Terry Coad, Glenn Bauman, Jake Van Dyk

Edward Yu

Lung cancer treatment is one of the most challenging fields in radiotherapy. The aim of the present study was to investigate what role helical tomotherapy (HT), a novel approach to the delivery of highly conformal dose distributions using intensity-modulated radiation fan beams, can play in difficult cases with large target volumes typical for many of these patients. Tomotherapy plans were developed for 15 patients with stage III inoperable non-small-cell lung cancer. While not necessarily clinically indicated, elective nodal irradiation was included for all cases to create the most challenging scenarios with large target volumes. A 2 cm margin was used …

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Does Active Learning Work? A Review Of The Research, Michael Prince Jun 2004

Does Active Learning Work? A Review Of The Research, Michael Prince

Michael J. Prince

No abstract provided.

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Standard-Deviation Minimization For Calibrating The Radii Of Spheres Attached To Atomic Force Microscope Cantilevers, Nancy Burnham, E Thoreson Apr 2004

Standard-Deviation Minimization For Calibrating The Radii Of Spheres Attached To Atomic Force Microscope Cantilevers, Nancy Burnham, E Thoreson

Nancy A. Burnham

We describe an efficient method for determining the radii of spheres attached to atomic force microscope(AFM) cantilevers by minimizing the square root of the square error for a segment of circular arc cross-sectional data. The approach we present has benefits: (1) The method fits a function, with two fitting parameters, to a number of data points, rather than calculating the radius based on two points of cross-sectional data, (2) a fit is performed in a common spreadsheet application, using a solving feature, and (3) spheres of diameters 2 to 60 μm were measured to an accuracy of 9% and a …

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Forisomes, A Novel Type Of Ca2+-Dependent Contractile Protein Motor [Review Article], Michael Knoblauch, Winfried Peters Apr 2004

Forisomes, A Novel Type Of Ca2+-Dependent Contractile Protein Motor [Review Article], Michael Knoblauch, Winfried Peters

Winfried S. Peters

This paper has no abstract; this is the first paragraph. Motility of cell components in both animal and plant cells is mostly based on the movement of motor proteins along actin filaments or microtubules [Boal, 2002]. The dominance of ATP hydrolysis as the energy source for such movements is so complete, that modern textbooks define “motor proteins” as nucleoside triphosphate-dependent actuators [e.g., Alberts et al., 2002]. In only one known case, a reversible mechanism of cell motility is driven by the interaction of Ca2+ and the responsive protein(s). Some sessile ciliates control the effective length of their stalk by means …

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Kinetics Of Silicon Film Growth And The Deposition Phase Diagram, G. Ferreira, A. Ferlauto, Chi Chen, Joshua Pearce, R. Koval, C. Ross, C. Wronski, Robert Collins Mar 2004

Kinetics Of Silicon Film Growth And The Deposition Phase Diagram, G. Ferreira, A. Ferlauto, Chi Chen, Joshua Pearce, R. Koval, C. Ross, C. Wronski, Robert Collins

Joshua M. Pearce

Three different surface microstructural transitions have been identified versus accumulated bulk layer thickness db during the growth of hydrogenated silicon (Si:H) films by plasma enhanced chemical vapor deposition (PECVD): (i) an amorphous growth regime roughening transition, (ii) an amorphous-to-(mixed-phase amorphous + microcrystalline) roughening transition, and (iii) a (mixed-phase)-to-(single-phase) microcrystalline smoothening transition. These transitions are observed using real time spectroscopic ellipsometry, and the results can be summarized succinctly using deposition phase diagrams wherein the transition thicknesses of interest are plotted versus the H2-dilution ratio R=[H2]/[SiH4]. For Si:H p–i–n solar cells, a greater understanding of processing-property relations and optimization procedures is possible …

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