Engineering Commons^™

Tob1 Is A Constitutively Expressed Repressor Of Liver Regeneration, Karen J. Ho, Nhue L. Do, Hasan H. Otu, Martin J. Dib, Xianghui Ren, Keiichi Enjyoji, Simon C. Robson, Ernest F. Terwilliger, Seth J. Karp

Department of Electrical and Computer Engineering: Faculty Publications

How proliferative and inhibitory signals integrate to control liver regeneration remains poorly understood. A screen for antiproliferative factors repressed after liver injury identified transducer of ErbB2.1 (Tob1), a member of the PC3/BTG1 family of mito-inhibitory molecules as a target for further evaluation. Tob1 protein decreases after 2/3 hepatectomy in mice secondary to posttranscriptional mechanisms. Deletion of Tob1 increases hepatocyte proliferation and accelerates restoration of liver mass after hepatectomy. Down-regulation of Tob1 is required for normal liver regeneration, and Tob1 controls hepatocyte proliferation in a dose-dependent fashion. Tob1 associates directly with both Caf1 and cyclindependent kinase (Cdk) 1 and …

Iterative Signal Processing In Communications, Christian Schlegel, Peter Hoeher, Owe Axelsson, Lance C. Pérez

Department of Electrical and Computer Engineering: Faculty Publications

Iterative signal processing in communications has experienced an explosive rise in popularity in recent years. The catalytic origins of this paradigm-shifting new philosophy among communications experts can be traced to the invention of turbo coding, and the subsequent rediscovery of low-density parity check (LDPC) coding, both in the field of error control coding. Both systems rely on iterative decoding algorithms to achieve their astounding performance. However, iterative signal processing is not confined to the decoding of error control codes and rather quickly spread to many other possible applications. The purpose of this special issue is to examine the concept of …

The Manifestation Of Stopping Sets And Absorbing Sets As Deviations On The Computation Trees Of Ldpc Codes, Eric T. Psota, Lance C. Perez

Department of Electrical and Computer Engineering: Faculty Publications

The error mechanisms of iterative message-passing decoders for low-density parity-check codes are studied. A tutorial review is given of the various graphical structures, including trapping sets, stopping sets, and absorbing sets that are frequently used to characterize the errors observed in simulations of iterative decoding of low-density parity-check codes. The connections between trapping sets and deviations on computation trees are explored in depth using the notion of problematic trapping sets in order to bridge the experimental and analytic approaches to these error mechanisms. A new iterative algorithm for finding low-weight problematic trapping sets is presented and shown to be capable …

Mimo Self-Encoded Spread Spectrum With Iterative Detection Over Rayleigh Fading Channels, Shichuan Ma, Lim Nguyen, Won Mee Jang, Yaoqing (Lamar) Yang

Department of Electrical and Computer Engineering: Faculty Publications

Self-encoded spread spectrum (SESS) is a novel communication technique that derives its spreading code from the randomness of the source stream rather than using conventional pseudorandom noise (PN) code. In this paper, we propose to incorporate SESS in multiple-input multiple-output (MIMO) systems as a means to combat against fading effects in wireless channels. Orthogonal space-time block-coded MIMO technique is employed to achieve spatial diversity, and the inherent temporal diversity in SESS modulation is exploited with iterative detection. Simulation results demonstrate that MIMO-SESS can effectively mitigate the channel fading effect such that the system can achieve a bit error rate of …

Non-Destructiveapproachto Ellipsometric Monitoring Of A Film Coating On The Inner Surface Of A Tube Shaped Sample, Gregory K. Prilbil, John A. Woollam, Martin M. Liphardt, James D. Welch

Department of Electrical and Computer Engineering: Faculty Publications

Disclosed is the use of a focused electromagnetic beam which is caused to impinge on the top surface of a tube shaped sample, to investigate a film coating on inner surface during fabrication thereof and/or thereafter.

A Non-Vacuum Process For Preparing Nanocrystalline Cuin1−XGaXSe2 Materials Involving An Open-Air Solvothermal Reaction, J. Olejníček, Chad A. Kamler, A. Mirasano, A. L. Martinez-Skinner, M. A. Ingersoll, C. L. Exstrom, S. A. Darveau, J. L. Huguenin-Love, M. Diaz, Natale J. Ianno, Rodney J. Soukup

Department of Electrical and Computer Engineering: Faculty Publications

A non-vacuum, two-step process has been used to prepare a series of nanocrystalline CuIn_1−xGa_xSe₂ (x = 0, 0.25, 0.5, 0.75, 1) materials. An open-air solvothermal preparation in triethylenetetramine solvent was followed by annealing at 500 °C in a nitrogen atmosphere for 20 min. All materials have mixed clustered plate, spherical particle, and nanorod morphologies with the smallest particle diameters ranging between 20 and 40 nm. Raman spectroscopy and X-ray diffraction (XRD) confirm that indium/gallium ratio control is possible over a wide range. The solvothermal reaction step yields a mixture of chalcopyrite and Cu …

Magneto-Optical Properties Of Cobalt Slanted Columnar Thin Films, Daniel Schmidt, Tino Hofmann, Craig M. Herzinger, Eva Schubert, Mathias Schubert

Department of Electrical and Computer Engineering: Faculty Publications

Magneto-optical properties of ferromagnetic slanted columnar thin films from cobalt made by electron-beam glancing angle deposition are reported. Magneto-optic ellipsometry in the polar Kerr effect configuration was employed to determine the field- and wavelength-dependent complex magneto-optic polarizability parameter within the spectral range from 0.74 to 3.0 eV. Kerr effect measurements and calculations reveal a strong azimuthal dependence for the incident linear polarization with peak Kerr rotation one order of magnitude larger than what has been reported for solid Co thin films.

Interface Polarization Coupling In Piezoelectric-Semiconductor Ferroelectric Heterostructures, Venkata M. Voora, Tino Hofmann, M. Brandt, M. Lorenz, M. Grundmann, N. Ashkenov, H. Schmidt, Natale J. Ianno, Mathias Schubert

Department of Electrical and Computer Engineering: Faculty Publications

We present a dielectric continuum model approach for studying the electrical polarization properties of interface polarization coupled BaTiO₃, BaTiO₃-ZnO, and ZnO-BaTiO₃-ZnO thin-film structures consisting of several hundred nanometer thick layers. Our model augments the effects of electric field driven switchable polarization and depletion layer formation with spontaneous interface polarization coupling. Wurtzite-structure (piezoelectric) n-type ZnO and perovskite-structure (ferroelectric) highly insulating BaTiO₃ layers were prepared and investigated. The coupling between the nonswitchable spontaneous polarization of ZnO and the electrically switchable spontaneous polarization of BaTiO₃ causes strong asymmetric polarization hysteresis behavior. The n-type ZnO reveals …

Variable-Wavelength Frequency-Domain Terahertz Ellipsometry, Tino Hofmann, C. M. Herzinger, A. Boosalis, T. E. Tiwald, John A. Woollam, Mathias Schubert

Department of Electrical and Computer Engineering: Faculty Publications

We report an experimental setup for wavelength-tunable frequency-domain ellipsometric measurements in the terahertz spectral range from 0.2 to 1.5 THz employing a desktop-based backward wave oscillator source. The instrument allows for variable angles of incidence between 30° and 90° and operates in a polarizer-sample-rotating analyzer scheme. The backward wave oscillator source has a tunable base frequency of 107–177 GHz and is augmented with a set of Schottky diode frequency multipliers in order to extend the spectral range to 1.5 THz. We use an odd-bounce image rotation system in combination with a wire grid polarizer to prepare the input polarization state. …

Hydrogen In Inn: A Ubiquitous Phenomenon In Molecular Beam Epitaxy Grown Material, V. Darakchieva, K. Lorenz, N. P. Barradas, E. Alves, B. Monemar, Mathias Schubert, N. Franco, C. L. Hsiao, L. C. Chen, W. J. Schaff, L. W. Tu, T. Yamaguchi, Y. Nanishi

Department of Electrical and Computer Engineering: Faculty Publications

We study the unintentional H impurities in relation to the free electron properties of state-of-the-art InN films grown by molecular beam epitaxy (MBE). Enhanced concentrations of H are revealed in the near surface regions of the films, indicating postgrowth surface contamination by H. The near surface hydrogen could not be removed upon thermal annealing and may have significant implications for the surface and bulk free electron properties of InN. The bulk free electron concentrations were found to scale with the bulk H concentrations while no distinct correlation with dislocation density could be inferred, indicating a major role of hydrogen for …

Secure Communication Over Fading Channels With Statistical Qos Constraints, Deli Qiao, M. Cenk Gursoy, Senem Velipasalar

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, secure transmission of information over an ergodic fading channel is studied in the presence of statistical quality of service (QoS) constraints.We employ effective capacity to measure the secure throughput of the system, i.e., effective secure throughput. We assume that the channel side information (CSI) of the main and the eavesdropper channels is available at the transmitter side. Under this assumption, we investigate the optimal power control policies that maximize the effective secure throughput. In particular, it is noted that opportunistic transmission is no longer optimal and the transmitter should not wait to send the data at …

A Noncooperative Power Control Game In Multiple-Access Fading Channels With Qos Constraints, Deli Qiao, M. Cenk Gursoy, Senem Velipasalar

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, a game-theoretic analysis for the resource allocation policies in fading multiple-access channels (MAC) in the presence of quality of service (QoS) constraints is performed. Effective capacity, which provides the maximum constant arrival rate, or throughput, that a given service process can support while satisfying statistical delay constraints, is considered in a multiuser scenario. We assume that the channel side information (CSI) is available at both the receiver and transmitters, and the transmitters are selfish, rational with certain QoS constraints and average power limitations. Without the aid of the receiver, we prove that there is always a unique …

A Grammar-Based Distance Metric Enables Fast And Accurate Clustering Of Large Sets Of 16s Sequences, David J. Russell, Samuel F. Way, Andrew K. Benson, Khalid Sayood

Department of Electrical and Computer Engineering: Faculty Publications

Background: We propose a sequence clustering algorithm and compare the partition quality and execution time of the proposed algorithm with those of a popular existing algorithm. The proposed clustering algorithm uses a grammar-based distance metric to determine partitioning for a set of biological sequences. The algorithm performs clustering in which new sequences are compared with cluster-representative sequences to determine membership. If comparison fails to identify a suitable cluster, a new cluster is created.

Results: The performance of the proposed algorithm is validated via comparison to the popular DNA/RNA sequence clustering approach, CD-HIT-EST, and to the recently developed algorithm, …

Crack Nucleation In A Peridynamic Solid, S. A. Silling, O. Weckner, E. Askari, Florin Bobaru Ph.D.

Department of Engineering Mechanics: Faculty Publications

A condition for the emergence of a discontinuity in an elastic peridynamic body is proposed, resulting in a material stability condition for crack nucleation. The condition is derived by determining whether a small discontinuity in displacement, superposed on a possibly large deformation, grows over time. Stability is shown to be determined by the sign of the eigenvalues of a tensor field that depends only on the linearized material properties. This condition for nucleation of a discontinuity in displacement can be interpreted in terms of the dynamic stability of plane waves with very short wavelength. A numerical example illustrates that cracks …

Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.

Department of Engineering Mechanics: Faculty Publications

In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as well …

Evaluation Of Biological Cell Properties Using Dynamic Indentation Measurement, Guoxin Cao, Namas Chandra

Department of Engineering Mechanics: Faculty Publications

Viscoelastic mechanical properties of biological cells are commonly measured using atomic force microscope (AFM) dynamic indentation with spherical tips. A semiempirical analysis based on numerical simulation is built to determine the cell mechanical properties. It is shown that the existing analysis cannot reflect the accurate values of cell elastic/dynamic modulus due to the effects of substrate, indenter tip size, and cell size. Among these factors, substrate not only increases the true contact radius but also interferes the indentation stress field, which can cause the overestimation of cell moduli. Typically, the substrate effect is much stronger than the other two influences …

Dynamics Of Fibrillar Precursors Of Shishes As A Function Of Stress, Luigi Balzano, Dario Cavallo, Tim B. Van Erp, Zhe Ma, Jan-Willem Housmans, Lucia Fernandez-Ballester, Gerrit W. M. Peters

Department of Engineering Mechanics: Faculty Publications

Shishes are fibrillar crystallites that can be created by deforming a polymer melt. The formation of shishes takes place when flow is strong enough to stretch molecules. In the early stages, bundles of stretched molecules with pre-crystalline order form metastable precursors whose stability depends on their size and, hence, on the stress level. We find that for a specific isotactic polypropylene, close to the nominal melting point, a stress larger than 0.10 MPa leads to stable fibrillar precursors that are partially crystalline immediately after flow. On the other hand, below 0.10 MPa, the aspect ratio of precursors tends to unity …

Effects Of The Antimicrobial Tylosin On The Microbial Community Structure Of An Anaerobic Sequencing Batch Reactor, Toshio Shimada, Xu Li, Julie L. Zilles, Eberhard Morgenroth, Lutgarde Raskin

Civil and Environmental Engineering: Faculty Publications

The effects of the antimicrobial tylosin on a methanogenic microbial community were studied in a glucosefed laboratory-scale anaerobic sequencing batch reactor (ASBR) exposed to stepwise increases of tylosin (0, 1.67, and 167 mg/L). The microbial community structure was determined using quantitative fluorescence in situ hybridization (FISH) and phylogenetic analyses of bacterial 16S ribosomal RNA (rRNA) gene clone libraries of biomass samples. During the periods without tylosin addition and with an influent tylosin concentration of 1.67 mg/L, 16S rRNA gene sequences related to Syntrophobacter were detected and the relative abundance of Methanosaeta species was high. During the highest tylosin dose of …

Aviation History, Southwest Minnesota State University

Aeronautics

Bibliography and photograph of a display of government documents from Southwest Minnesota State University.

On Coalgebras Over Algebras, Adriana Balan, Alexander Kurz

Engineering Faculty Articles and Research

We extend Barr’s well-known characterization of the final coalgebra of a Set-endofunctor as the completion of its initial algebra to the Eilenberg-Moore category of algebras for a Set-monad M for functors arising as liftings. As an application we introduce the notion of commuting pair of endofunctors with respect to the monad M and show that under reasonable assumptions, the final coalgebra of one of the endofunctors involved can be obtained as the free algebra generated by the initial algebra of the other endofunctor.