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Mechanical Engineering

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Iowa State University

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Probing The Enzymatic Activity Of Alkaline Phosphatase Within Quantum Dot Bioconjugates, Jonathan C. Claussen, Anthony Malanoski, Joyce C. Breger, Eunkeu Oh, Scott A. Walper, Kimihiro Susumu, Ramasis Goswami, Jeffrey R. Deschamps, Igor L. Medintz Jan 2015

Probing The Enzymatic Activity Of Alkaline Phosphatase Within Quantum Dot Bioconjugates, Jonathan C. Claussen, Anthony Malanoski, Joyce C. Breger, Eunkeu Oh, Scott A. Walper, Kimihiro Susumu, Ramasis Goswami, Jeffrey R. Deschamps, Igor L. Medintz

Jonathan C. Claussen

Enzymes provide the critical means by which to catalyze almost all biological reactions in a controlled manner. Methods to harness and exploit their properties are of strong current interest to the growing field of biotechnology. In contrast to depending upon recombinant genetic approaches, a growing body of evidence suggests that apparent enzymatic activity can be enhanced when located at a nanoparticle interface. We use semiconductor quantum dots (QDs) as a well-defined and easily bioconjugated nanoparticle along with Escherichia coli-derived alkaline phosphatase (AP) as a prototypical enzyme to seek evidence for this process in a de novo model system. We began ...


Complex Logic Functions Implemented With Quantum Dot Bionanophotonic Circuits, Jonathan C. Claussen, Niko Hildebrandt, Kimihiro Susumu, Mario G. Ancona, Igor L. Medintz Jan 2014

Complex Logic Functions Implemented With Quantum Dot Bionanophotonic Circuits, Jonathan C. Claussen, Niko Hildebrandt, Kimihiro Susumu, Mario G. Ancona, Igor L. Medintz

Jonathan C. Claussen

We combine quantum dots (QDs) with long-lifetime terbium complexes (Tb), a near-IR Alexa Fluor dye (A647), and self-assembling peptides to demonstrate combinatorial and sequential bionanophotonic logic devices that function by time-gated Förster resonance energy transfer (FRET). Upon excitation, the Tb-QD-A647 FRET-complex produces time-dependent photoluminescent signatures from multi-FRET pathways enabled by the capacitor-like behavior of the Tb. The unique photoluminescent signatures are manipulated by ratiometrically varying dye/Tb inputs and collection time. Fluorescent output is converted into Boolean logic states to create complex arithmetic circuits including the half-adder/half-subtractor, 2:1 multiplexer/1:2 demultiplexer, and a 3-digit, 16-combination keypad ...


Nanomaterial-Mediated Biosensors For Monitoring Glucose, Eric S. Mclamore, Masashige Taguchi, Andre Ptitsyn, Jonathan C. Claussen Jan 2014

Nanomaterial-Mediated Biosensors For Monitoring Glucose, Eric S. Mclamore, Masashige Taguchi, Andre Ptitsyn, Jonathan C. Claussen

Jonathan C. Claussen

Real-time monitoring of physiological glucose transport is crucial for gaining new understanding of diabetes. Many techniques and equipment currently exist for measuring glucose, but these techniques are limited by complexity of the measurement, requirement of bulky equipment, and low temporal/spatial resolution. The development of various types of biosensors (eg, electrochemical, optical sensors) for laboratory and/or clinical applications will provide new insights into the cause(s) and possible treatments of diabetes. State-of-the-art biosensors are improved by incorporating catalytic nanomaterials such as carbon nanotubes, graphene, electrospun nanofibers, and quantum dots. These nanomaterials greatly enhance biosensor performance, namely sensitivity, response time ...


A Microfluidic Paper-Based Electrochemical Biosensor Array For Multiplexed Detection Of Metabolic Biomarkers, Chen Zhao, Martin M. Thuo, Xinyu Liu Oct 2013

A Microfluidic Paper-Based Electrochemical Biosensor Array For Multiplexed Detection Of Metabolic Biomarkers, Chen Zhao, Martin M. Thuo, Xinyu Liu

Martin M. Thuo

Paper-based microfluidic devices have emerged as simple yet powerful platforms for performing low-cost analytical tests. This paper reports a microfluidic paper-based electrochemical biosensor array for multiplexed detection of physiologically relevant metabolic biomarkers. Different from existing paper-based electrochemical devices, our device includes an array of eight electrochemical sensors and utilizes a handheld custom-made electrochemical reader (potentiostat) for signal readout. The biosensor array can detect several analytes in a sample solution and produce multiple measurements for each analyte from a single run. Using the device, we demonstrate simultaneous detection of glucose, lactate and uric acid in urine, with analytical performance comparable to ...


Aerodynamic Simulation Of Vertical-Axis Wind Turbines, A. Korobenko, Ming-Chen Hsu, I. Akkerman, Y. Bazilevs Sep 2013

Aerodynamic Simulation Of Vertical-Axis Wind Turbines, A. Korobenko, Ming-Chen Hsu, I. Akkerman, Y. Bazilevs

Ming-Chen Hsu

Full-scale, 3D, time-dependent aerodynamics modeling and simulation of a Darrieus-type vertical-axis wind turbine (VAWT) is presented. The simulations are performed using a moving-domain finite-element-based ALE-VMS technique augmented with a sliding-interface formulation to handle the rotor-stator interactions present. We simulate a single VAWT using a sequence of meshes with increased resolution to assess the computational requirements for this class of problems. The computational results are in good agreement with experimental data. We also perform a computation of two side-by-side counterrotating VAWTs to illustrate how the ALE-VMS technique may be used for the simulation of multiple turbines placed in arrays.


Finite Element Simulation Of Wind Turbine Aerodynamics: Validation Study Using Nrel Phase Vi Experiment, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs Mar 2013

Finite Element Simulation Of Wind Turbine Aerodynamics: Validation Study Using Nrel Phase Vi Experiment, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs

Ming-Chen Hsu

A validation study using the National Renewable Energy Laboratory (NREL) Phase VI wind turbine is presented. The aerodynamics simulations are performed using the finite element arbitrary Lagrangian–Eulerian–variational multiscale formulation augmented with weakly enforced essential boundary conditions. In all cases, the rotor is assumed to be rigid and its rotation is prescribed. The rotor-only simulations are performed for a wide range of wind conditions, and the computational results compare favorably with the experimental findings in all cases. The sliding-interface method is adopted for the simulation of the full wind turbine configuration. The full-wind-turbine simulations capture the blade–tower interaction ...


Blended Isogeometric Shells, D. J. Benson, S. Hartmann, Y. Bazilevs, Ming-Chen Hsu, T.J.R. Hughes Mar 2013

Blended Isogeometric Shells, D. J. Benson, S. Hartmann, Y. Bazilevs, Ming-Chen Hsu, T.J.R. Hughes

Ming-Chen Hsu

We propose a new isogeometric shell formulation that blends Kirchhoff–Love theory with Reissner–Mindlin theory. This enables us to reduce the size of equation systems by eliminating rotational degrees of freedom while simultaneously providing a general and effective treatment of kinematic constraints engendered by shell intersections, folds, boundary conditions, the merging of NURBS patches, etc. We illustrate the blended theory’s performance on a series of test problems.


Biophotonic Logic Devices Based On Quantum Dots And Temporally-Staggered Forster Energy Transfer Relays, Jonathan C. Claussen, W. Russ Algar, Niko Hildebrandt, Kimihiro Susumu, Mario G. Ancona, Igor L. Medintz Jan 2013

Biophotonic Logic Devices Based On Quantum Dots And Temporally-Staggered Forster Energy Transfer Relays, Jonathan C. Claussen, W. Russ Algar, Niko Hildebrandt, Kimihiro Susumu, Mario G. Ancona, Igor L. Medintz

Jonathan C. Claussen

Integrating photonic inputs/outputs into unimolecular logic devices can provide significantly increased functional complexity and the ability to expand the repertoire of available operations. Here, we build upon a system previously utilized for biosensing to assemble and prototype several increasingly sophisticated biophotonic logic devices that function based upon multistep Förster resonance energy transfer (FRET) relays. The core system combines a central semiconductor quantum dot (QD) nanoplatform with a long-lifetime Tb complex FRET donor and a near-IR organic fluorophore acceptor; the latter acts as two unique inputs for the QD-based device. The Tb complex allows for a form of temporal ...


Emerging Technologies For Non-Invasive Quantification Of Physiological Oxygen Transport In Plants, P. Chaturvedi, M. Taguchi, S. L. Burrs, B. A. Hauser, W.W. A.W. Salim, Jonathan C. Claussen, E. S. Mclamore Jan 2013

Emerging Technologies For Non-Invasive Quantification Of Physiological Oxygen Transport In Plants, P. Chaturvedi, M. Taguchi, S. L. Burrs, B. A. Hauser, W.W. A.W. Salim, Jonathan C. Claussen, E. S. Mclamore

Jonathan C. Claussen

Oxygen plays a critical role in plant metabolism, stress response/signaling, and adaptation to environmental changes (Lambers and Colmer, Plant Soil 274:7-15, 2005; Pitzschke et al., Antioxid Redox Signal 8:1757-1764, 2006; Van Breusegem et al., Plant Sci 161:405-414, 2001). Reactive oxygen species (ROS), by-products of various metabolic pathways in which oxygen is a key molecule, are produced during adaptation responses to environmental stress. While much is known about plant adaptation to stress (e.g., detoxifying enzymes, antioxidant production), the link between ROS metabolism, O2 transport, and stress response mechanisms is unknown. Thus, non-invasive technologies for measuring O2 ...


Fluid–Structure Interaction Modeling Of Wind Turbines: Simulating The Full Machine, Ming-Chen Hsu, Yuri Bazilevs Dec 2012

Fluid–Structure Interaction Modeling Of Wind Turbines: Simulating The Full Machine, Ming-Chen Hsu, Yuri Bazilevs

Ming-Chen Hsu

In this paper we present our aerodynamics and fluid–structure interaction (FSI) computational techniques that enable dynamic, fully coupled, 3D FSI simulation of wind turbines at full scale, and in the presence of the nacelle and tower (i.e., simulation of the “full machine”). For the interaction of wind and flexible blades we employ a nonmatching interface discretization approach, where the aerodynamics is computed using a low-order finite-element-based ALE-VMS technique, while the rotor blades are modeled as thin composite shells discretized using NURBS-based isogeometric analysis (IGA). We find that coupling FEM and IGA in this manner gives a good combination ...


Isogeometric Fluid–Structure Interaction Analysis With Emphasis On Non-Matching Discretizations, And With Application To Wind Turbines, Y. Bazilevs, Ming-Chen Hsu, M. A. Scott Dec 2012

Isogeometric Fluid–Structure Interaction Analysis With Emphasis On Non-Matching Discretizations, And With Application To Wind Turbines, Y. Bazilevs, Ming-Chen Hsu, M. A. Scott

Ming-Chen Hsu

In this paper we develop a framework for fluid–structure interaction (FSI) modeling and simulation with emphasis on isogeometric analysis (IGA) and non-matching fluid–structure interface discretizations. We take the augmented Lagrangian approach to FSI as a point of departure. Here the Lagrange multiplier field is defined on the fluid–structure interface and is responsible for coupling of the two subsystems. Thus the FSI formulation does not rely on the continuity of the underlying function spaces across the fluid–structure interface in order to produce the correct coupling conditions between the fluid and structural subdomains. However, in deriving the final ...


Wind Turbine Aerodynamics Using Ale–Vms: Validation And The Role Of Weakly Enforced Boundary Conditions, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs Oct 2012

Wind Turbine Aerodynamics Using Ale–Vms: Validation And The Role Of Weakly Enforced Boundary Conditions, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs

Ming-Chen Hsu

In this article we present a validation study involving the full-scale NREL Phase VI two-bladed wind turbine rotor. The ALE–VMS formulation of aerodynamics, based on the Navier–Stokes equations of incompressible flows, is employed in conjunction with weakly enforced essential boundary conditions. We find that the ALE–VMS formulation using linear tetrahedral finite elements is able to reproduce experimental data for the aerodynamic (low-speed shaft) torque and cross-section pressure distribution of the NREL Phase VI rotor. We also find that weak enforcement of essential boundary conditions is critical for obtaining accurate aerodynamics results on relatively coarse boundary layer meshes ...


Ale-Vms And St-Vms Methods For Computer Modeling Of Wind-Turbine Rotor Aerodynamics And Fluid–Structure Interaction, Yuri Bazilevs, Ming-Chen Hsu, Kenji Takizawa, Tayfun E. Tezduyar Jul 2012

Ale-Vms And St-Vms Methods For Computer Modeling Of Wind-Turbine Rotor Aerodynamics And Fluid–Structure Interaction, Yuri Bazilevs, Ming-Chen Hsu, Kenji Takizawa, Tayfun E. Tezduyar

Ming-Chen Hsu

We provide an overview of the Arbitrary Lagrangian–Eulerian Variational Multiscale (ALE-VMS) and Space–Time Variational Multiscale (ST-VMS) methods we have developed for computer modeling of wind-turbine rotor aerodynamics and fluid–structure interaction (FSI). The related techniques described include weak enforcement of the essential boundary conditions, Kirchhoff–Love shell modeling of the rotor-blade structure, NURBS-based isogeometric analysis, and full FSI coupling. We present results from application of these methods to computer modeling of NREL 5MW and NREL Phase VI wind-turbine rotors at full scale, including comparison with experimental data.


Bacterial Isolation By Lectin-Modified Microengines, Susana Campuzano, Jahir Orozco, Daniel Kagan, Maria Guix, Wei Gao, Sirilak Sattayasamitsathit, Jonathan C. Claussen, Arben Merkoci, Joseph Wang Jan 2012

Bacterial Isolation By Lectin-Modified Microengines, Susana Campuzano, Jahir Orozco, Daniel Kagan, Maria Guix, Wei Gao, Sirilak Sattayasamitsathit, Jonathan C. Claussen, Arben Merkoci, Joseph Wang

Jonathan C. Claussen

New template-based self-propelled gold/nickel/polyaniline/platinum (Au/Ni/PANI/Pt) microtubular engines, functionalized with the Concanavalin A (ConA) lectin bioreceptor, are shown to be extremely useful for the rapid, real-time isolation of Escherichia coli (E. coli) bacteria from fuel-enhanced environmental, food, and clinical samples. These multifunctional microtube engines combine the selective capture of E. coli with the uptake of polymeric drug-carrier particles to provide an attractive motion-based theranostics strategy. Triggered release of the captured bacteria is demonstrated by movement through a low-pH glycine-based dissociation solution. The smaller size of the new polymer-metal microengines offers convenient, direct, and label-free optical ...


Melting Point Suppression In New Lanthanoid(Iii) Ionic Liquids By Trapping Of Kinetic Polymorphs: An In Situsynchrotron Powder Diffraction Study, Anthony S.R. Chesman, Mei Yang, Bert Mallick, Tamsyn M. Ross, Ian A. Gass, Glen B. Deacon, Stuart R. Batten, Anja V. Mudring Jan 2012

Melting Point Suppression In New Lanthanoid(Iii) Ionic Liquids By Trapping Of Kinetic Polymorphs: An In Situsynchrotron Powder Diffraction Study, Anthony S.R. Chesman, Mei Yang, Bert Mallick, Tamsyn M. Ross, Ian A. Gass, Glen B. Deacon, Stuart R. Batten, Anja V. Mudring

Anja V. Mudring

he inclusion of lanthanoids in ionic liquids (ILs) offers an ideal route to incorporate their unique luminescent and magnetic properties into a bulk solution.1,2 However, lanthanoid compounds often exhibit a poor solubility in commonly used ILs because the IL anions are typically very weakly coordinating, prohibiting the simple dissolution of a lanthanoid salt by complexation to any beneficial extent.2 One strategy used to achieve high lanthanoid concentrations is to incorporate the lanthanoid cation directly into an anion that will form ILs.3 This is best accomplished by employing a ligand which readily coordinates to a lanthanoid atom ...


Considering Etiquette In The Design Of An Adaptive System, Michael C. Dorneich, Patricia May Ververs, Santosh Mathan, Stephen Whitlow, Caroline C. Hayes Jan 2012

Considering Etiquette In The Design Of An Adaptive System, Michael C. Dorneich, Patricia May Ververs, Santosh Mathan, Stephen Whitlow, Caroline C. Hayes

Michael C. Dorneich

In this article, the authors empirically assess the costs and benefits of designing an adaptive system to follow social conventions regarding the appropriateness of interruptions. Interruption management is one area within the larger topic of automation etiquette. The authors tested these concepts in an outdoor environment using the Communications Scheduler, a wearable adaptive system that classifies users' cognitive state via brain and heart sensors and adapts its interactions. Designed to help dismounted soldiers, it manages communications in much the same way as a good administrative assistant. Depending on a combination of message priority, user workload, and system state, it decides ...


Ultrasound-Assisted Synthesis Of Mesoporous Β-Ni(Oh)2 And Nio Nano-Sheets Using Ionic Liquids, Tarek Alammar, Osama Shekhah, Jonas Wohlgemuth, Anja V. Mudring Jan 2012

Ultrasound-Assisted Synthesis Of Mesoporous Β-Ni(Oh)2 And Nio Nano-Sheets Using Ionic Liquids, Tarek Alammar, Osama Shekhah, Jonas Wohlgemuth, Anja V. Mudring

Anja V. Mudring

Via a facile ultrasound synthesis from nickel acetate and sodium hydroxide with ionic liquids as the solvent and template it is possible to obtain nano-β-Ni(OH)2 of various dimensionalities depending on the reaction conditions with the ionic liquid (IL) being the most important factor. Scanning electron microscopy (SEM) imaging showed β-Ni(OH)2 to form as nanosheets, nanorods and nanospheres depending on the IL. ILs with strong to moderate hydrogen bonding capability like [C3mimOH][Tf2N] (1-(3-hydroxypropyl)-3-methylimidazolium bis(trifluoromethanesulfonylamide)), [C4mim][Tf2N] (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonylamide)) and [Edimim][Tf2N] (1-ethyl-2,3-diemethylimidazolium bis(trifluoromethanesulfonylamide)) lead to the formation of nanosheets whilst ...


Mercuric Ionic Liquids: [Cnmim][Hgx3], Where N = 3, 4 And X = Cl, Br, Bert Mallick, Andreas Metlen, Mark Nieuwenhuyzen, Robin D. Rogers, Anja V. Mudring Jan 2012

Mercuric Ionic Liquids: [Cnmim][Hgx3], Where N = 3, 4 And X = Cl, Br, Bert Mallick, Andreas Metlen, Mark Nieuwenhuyzen, Robin D. Rogers, Anja V. Mudring

Anja V. Mudring

A series of mercury(II) ionic liquids, [Cnmim][HgX3], where [Cnmim] = n-alkyl-3-methylimidazolium with n = 3, 4 and X = Cl, Br, have been synthesized following two different synthetic approaches, and structurally characterized by means of single-crystal X-ray structure analysis ([C3mim][HgCl3] (1), Cc (No. 9), Z = 4, a = 16.831(4) Å, b = 10.7496(15) Å, c = 7.4661(14) Å, β = 105.97(2)°, V = 1298.7(4) Å3 at 298 K; [C4mim][HgCl3] (2), Cc (No. 9), Z = 4, a = 17.3178(28) Å, b = 10.7410(15) Å, c = 7.4706(14) Å, β = 105.590(13 ...


3d Simulation Of Wind Turbine Rotors At Full Scale. Part Ii: Fluid–Structure Interaction Modeling With Composite Blades, Y. Bazilevs, Ming-Chen Hsu, J. Kiendel, R. Wuchner, K. U. Bletzigner Oct 2011

3d Simulation Of Wind Turbine Rotors At Full Scale. Part Ii: Fluid–Structure Interaction Modeling With Composite Blades, Y. Bazilevs, Ming-Chen Hsu, J. Kiendel, R. Wuchner, K. U. Bletzigner

Ming-Chen Hsu

In this two-part paper, we present a collection of numerical methods combined into a single framework, which has the potential for a successful application to wind turbine rotor modeling and simulation. In Part 1 of this paper we focus on: 1. The basics of geometry modeling and analysis-suitable geometry construction for wind turbine rotors; 2. The fluid mechanics formulation and its suitability and accuracy for rotating turbulent flows; 3. The coupling of air flow and a rotating rigid body. In Part 2, we focus on the structural discretization for wind turbine blades and the details of the fluid–structure interaction ...


High-Performance Computing Of Wind Turbine Aerodynamics Using Isogeometric Analysis, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs Oct 2011

High-Performance Computing Of Wind Turbine Aerodynamics Using Isogeometric Analysis, Ming-Chen Hsu, Ido Akkerman, Yuri Bazilevs

Ming-Chen Hsu

In this article we present a high-performance computing framework for advanced flow simulation and its application to wind energy based on the residual-based variational multiscale (RBVMS) method and isogeometric analysis. The RBVMS formulation and its suitability and accuracy for turbulent flow in a moving domain are presented. Particular emphasis is placed on the parallel implementation of the methodology and its scalability. Two challenging flow cases were considered: the turbulent Taylor–Couette flow and the NREL 5 MW offshore baseline wind turbine rotor at full scale. In both cases, flow quantities of interest from the simulation results compare favorably with the ...


Thermal Conductivity Reduction Through Isotope Substitution In Nanomaterials: Predictions From An Analytical Classical Model And Nonequilibrium Molecular Dynamics Simulations, Ganesh Balasubramanian, Ishwar K. Puri, Michael C. Bohm, Frederic Leroy Jul 2011

Thermal Conductivity Reduction Through Isotope Substitution In Nanomaterials: Predictions From An Analytical Classical Model And Nonequilibrium Molecular Dynamics Simulations, Ganesh Balasubramanian, Ishwar K. Puri, Michael C. Bohm, Frederic Leroy

Ganesh Balasubramanian

We introduce an analytical model to rapidly determine the thermal conductivity reduction due to mass disorder in nanomaterials. Although this simplified classical model depends only on the masses of the different atoms, it adequately describes the changes in thermal transport as the concentrations of these atoms vary. Its predictions compare satisfactorily with nonequilibrium molecular dynamics simulations of the thermal conductivity of 14C–12C carbon nanotubes as well as with previous simulations of other materials. We present it as a simple tool to quantitatively estimate the thermal conductivity decrease that is induced by isotope substitution in various materials.


Heat Conduction Across A Solid-Solid Interface: Understanding Nanoscale Interfacial Effects On Thermal Resistance, Ganesh Balasubramanian, Ishwar K. Puri Jul 2011

Heat Conduction Across A Solid-Solid Interface: Understanding Nanoscale Interfacial Effects On Thermal Resistance, Ganesh Balasubramanian, Ishwar K. Puri

Ganesh Balasubramanian

Phonons scatter and travel ballistically in systems smaller than the phonon mean free path. At larger lengths, the transport is instead predominantly diffusive. We employ molecular dynamics simulations to describe the length dependence of the thermal conductivity. The simulations show that the interfacial thermal resistance Rk for a Si-Ge superlattice is inversely proportional to its length, but reaches a constant value as the system dimension becomes larger than the phonon mean free path. This nanoscale effect is incorporated into an accurate continuum model by treating the interface as a distinct material with an effective thermal resistance equal to Rk .


Manufacturing Self-Assembled Coatings Of Micro- And Nano-Particles By Controlled Evaporation Of Drops And Thin Films, Junfeng Xiao, Rajneesh Bhardwaj, Daniel Attinger Apr 2011

Manufacturing Self-Assembled Coatings Of Micro- And Nano-Particles By Controlled Evaporation Of Drops And Thin Films, Junfeng Xiao, Rajneesh Bhardwaj, Daniel Attinger

Daniel Attinger

The engineered deposition of self-assembled coatings of micro- and nano-particles on solid surfaces has applications in photonic crystals, optoelectronic devices, sensors, waveguides and antireflective coatings. Besides lithographic, etching or vapor deposition methods, these coatings can be self-assembled on small (


A Large Deformation, Rotation-Free, Isogeometric Shell, D. J. Benson, Y. Bazilevs, Ming-Chen Hsu, T. J. R. Hughes Mar 2011

A Large Deformation, Rotation-Free, Isogeometric Shell, D. J. Benson, Y. Bazilevs, Ming-Chen Hsu, T. J. R. Hughes

Ming-Chen Hsu

Conventional finite shell element formulations use rotational degrees of freedom to describe the motion of the fiber in the Reissner–Mindlin shear deformable shell theory, resulting in an element with five or six degrees of freedom per node. These additional degrees of freedom are frequently the source of convergence difficulties in implicit structural analyses, and, unless the rotational inertias are scaled, control the time step size in explicit analyses. Structural formulations that are based on only the translational degrees of freedom are therefore attractive. Although rotation-free formulations using C0 basis functions are possible, they are complicated in comparison to their ...


Experimental And Molecular Dynamics Investigation Into The Amphiphilic Nature Of Sulforhodamine B, Baris E. Polat, Shangchao Lin, Jonathan D. Mendenhall, Brett Vanveller, Robert Langer, Daniel Blankschtein Jan 2011

Experimental And Molecular Dynamics Investigation Into The Amphiphilic Nature Of Sulforhodamine B, Baris E. Polat, Shangchao Lin, Jonathan D. Mendenhall, Brett Vanveller, Robert Langer, Daniel Blankschtein

Brett VanVeller

Sulforhodamine B (SRB), a common fluorescent dye, is often considered to be a purely hydrophilic molecule, having no impact on bulk or interfacial properties of aqueous solutions. This assumption is due to the high water solubility of SRB relative to most fluorescent probes. However, in the present study, we demonstrate that SRB is in fact an amphiphile, with the ability to adsorb at an air/water interface and to incorporate into sodium dodecyl sulfate (SDS) micelles. In fact, SRB reduces the surface tension of water by up to 23 mN/m, and the addition of SRB to an aqueous SDS ...


Microbiosensors Based On Dna Modified Single-Walled Carbon Nanotube And Pt Black Nanocomposites, Jin Shi, Tae-Gon Cha, Jonathan C. Claussen, Alfred R. Diggs, Jong Hyun Choi, D. Marshall Porterfield Jan 2011

Microbiosensors Based On Dna Modified Single-Walled Carbon Nanotube And Pt Black Nanocomposites, Jin Shi, Tae-Gon Cha, Jonathan C. Claussen, Alfred R. Diggs, Jong Hyun Choi, D. Marshall Porterfield

Jonathan C. Claussen

Glucose and ATP biosensors have important applications in diagnostics and research. Biosensors based on conventional materials suffer from low sensitivity and low spatial resolution. Our previous work has shown that combining single-walled carbon nanotubes (SWCNTs) with Pt nanoparticles can significantly enhance the performance of electrochemical biosensors. The immobilization of SWCNTs on biosensors remains challenging due to the aqueous insolubility originating from van der Waals forces. In this study, we used single-stranded DNA (ssDNA) to modify SWCNTs to increase solubility in water. This allowed us to explore new schemes of combining ssDNA-SWCNT and Pt black in aqueous media systems. The result ...


Electrochemical Glutamate Biosensing With Nanocube And Nanosphere Augmented Single-Walled Carbon Nanotube Networks: A Comparative Study, Jonathan C. Claussen, Mayra S. Artiles, Eric S. Mclamore, Subhashree Mohanty, Jin Shi, Jenna L. Rickus, Timothy S. Fisher, D. Marshall Porterfield Jan 2011

Electrochemical Glutamate Biosensing With Nanocube And Nanosphere Augmented Single-Walled Carbon Nanotube Networks: A Comparative Study, Jonathan C. Claussen, Mayra S. Artiles, Eric S. Mclamore, Subhashree Mohanty, Jin Shi, Jenna L. Rickus, Timothy S. Fisher, D. Marshall Porterfield

Jonathan C. Claussen

We describe two hybrid nanomaterial biosensor platforms, based on networks of single-walled carbon nanotubes (SWCNTs) enhanced with Pd nanocubes and Pt nanospheres and grown in situ from a porous anodic alumina (PAA) template. These nanocube and nanosphere SWCNT networks are converted into glutamate biosensors by immobilizing the enzyme glutamate oxidase (cross-linked with gluteraldehyde) onto the electrode surface. The Pt nanosphere/SWCNT biosensor outperformed the Pd nanocube/SWCNT biosensor and previously reported similar nanomaterial-based biosensors by amperometrically monitoring glutamate concentrations with a wide linear sensing range (50 nM to 1.6 mM) and a small detection limit (4.6 nM, 3s ...


3d Simulation Of Wind Turbine Rotors At Full Scale. Part I: Geometry Modeling And Aerodynamics, Y. Bazilevs, Ming-Chen Hsu, I. Akkerman, S. Wright, K. Takizawa, B. Henicke, T. Spielman, T. E. Tezduyar Jan 2011

3d Simulation Of Wind Turbine Rotors At Full Scale. Part I: Geometry Modeling And Aerodynamics, Y. Bazilevs, Ming-Chen Hsu, I. Akkerman, S. Wright, K. Takizawa, B. Henicke, T. Spielman, T. E. Tezduyar

Ming-Chen Hsu

In this two-part paper we present a collection of numerical methods combined into a single framework, which has the potential for a successful application to wind turbine rotor modeling and simulation. In Part 1 of this paper we focus on: 1. The basics of geometry modeling and analysis-suitable geometry construction for wind turbine rotors; 2. The fluid mechanics formulation and its suitability and accuracy for rotating turbulent flows; 3. The coupling of air flow and a rotating rigid body. In Part 2 we focus on the structural discretization for wind turbine blades and the details of the fluid–structure interaction ...


Effects Of Carbon Nanotube-Tethered Nanosphere Density On Amperometric Biosensing: Simulation And Experiment, Jonathan C. Claussen, James B. Hengenius, Monique M. Wickner, Timothy S. Fisher, David M. Umulis, D. Marshall Porterfield Jan 2011

Effects Of Carbon Nanotube-Tethered Nanosphere Density On Amperometric Biosensing: Simulation And Experiment, Jonathan C. Claussen, James B. Hengenius, Monique M. Wickner, Timothy S. Fisher, David M. Umulis, D. Marshall Porterfield

Jonathan C. Claussen

Nascent nanofabrication approaches are being applied to reduce electrode feature dimensions from the microscale to the nanoscale, creating biosensors that are capable of working more efficiently at the biomolecular level. The development of nanoscale biosensors has been driven largely by experimental empiricism to date. Consequently, the precise positioning of nanoscale electrode elements is typically neglected, and its impact on biosensor performance is subsequently overlooked. Herein, we present a bottom-up nanoelectrode array fabrication approach that utilizes low-density and horizontally oriented single-walled carbon nanotubes (SWCNTs) as a template for the growth and precise positioning of Pt nanospheres. We further develop a computational ...


Do Surfaces With Mixed Hydrophilic And Hydrophobic Areas Enhance Pool Boiling?, Amy Rachel Betz, Jie Xu, Huihe Qiu, Daniel Attinger Oct 2010

Do Surfaces With Mixed Hydrophilic And Hydrophobic Areas Enhance Pool Boiling?, Amy Rachel Betz, Jie Xu, Huihe Qiu, Daniel Attinger

Daniel Attinger

We demonstrate that smooth and flat surfaces combining hydrophilic and hydrophobicpatterns improve pool boiling performance. Compared to a hydrophilicsurface with 7° wetting angle, the measured critical heat flux and heat transfer coefficients of the enhanced surfaces are, up to respectively, 65% and 100% higher. Different networks combining hydrophilic and hydrophobic regions are characterized. While all tested networks enhance the heat transfer coefficient, large enhancements of critical heat flux are typically found for hydrophilic networks featuring hydrophobic islands. Hydrophilic networks indeed are shown to prevent the formation of an insulating vapor layer.