Digital Commons Network^™

A Third-Order Sliding-Mode Controller For Dcmc Converters With Constant Power Loads, Yue Zhao, Wei Qiao

Department of Electrical and Computer Engineering: Faculty Publications

Incorporating a medium-voltage DC (MVDC) integrated power system is a goal for future surface combatants and submarines. In a MVDC shipboard power system, DCIDC converters are commonly employed to supply constant power to electric loads. These constant-power loads have a characteristic of negative incremental impedance, which may cause system instability during disturbances if the system is not properly controlled. This paper proposes a third-order sliding-mode controller (SMC) for DCIDC buck converters with constant power loads. The SMC is able to stabilize the DC power systems over the entire operating range in the presence of significant variations in the load power …

Secure Relay Beamforming Over Cognitive Radio Channels, Junwei Zhang, Mustafa Cenk Gursoy

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, a cognitive relay channel is considered, and amplify-and-forward (AF) relay beam forming designs in the presence of an eavesdropper and a primary user are studied. Our objective is to optimize the performance of the cognitive relay beamforming system while limiting the interference in the direction of the primary receiver and keeping the transmitted signal secret from the eavesdropper. We show that under both total and individual power constraints, the problem becomes a quasiconvex optimization problem which can be solved by interior point methods. We also propose two sub-optimal null space beamforming schemes which are obtained in a …

Formation Of Graphene Sheets Through Laser Exfoliation Of Highly Ordered Pyrolytic Graphite, Min Qian, Yun-Shen Zhou, Yang Gao, Jong Bok Park, Tao Feng, Su Mei Huang, Zhuo Sun, Lan Jiang, Yongfeng Lu

Department of Electrical and Computer Engineering: Faculty Publications

Freestanding two-dimensional (2D) few-layer graphene was formed through laser exfoliation of highly ordered pyrolytic graphite, using a pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. Graphene sheets of several nanometers in thickness and micrometers in size were obtained. The laser exfoliation process was investigated at different laser fluences and distances between target and substrate. Three different phases, amorphous carbon, few-layer graphene sheets, and thin graphite films, were obtained as the laser fluence increased. This study reveals an existing route of forming freestanding 2D nanostructures through laser exfoliation.

Terahertz Optical-Hall Effect Characterization Of Two-Dimensional Electron Gas Properties In Algan/Gan High Electron Mobility Transistor Structures, S. Schöche, Junxia Shi, A. Boosalis, P. Kühne, C. M. Herzinger, John A. Woollam, W. J. Schaff, L. F. Eastman, M. Schubert, Tino Hofmann

Department of Electrical and Computer Engineering: Faculty Publications

The free-charge carrier mobility, sheet density, and effective mass of a two-dimensional electron gas are exemplarily determined in the spectral range from 640 GHz to 1 THz in a AlGaN/GaN heterostructure using the optical-Hall effect at room temperature. Complementary midinfrared spectroscopic ellipsometry measurements are performed for analysis of heterostructure constituents layer thickness, phonon mode, and free-charge carrier parameters. The electron effective mass is determined to be (0.22 ± 0.04)m₀. The high-frequency sheet density and carrier mobility parameters are in good agreement with results from dc electrical Hall effect measurements, indicative for frequency-independent carrier scattering mechanisms of the …

Small Molecule Inhibitors Of Staphylococcus Aureus Rnpa Alter Cellular Mrna Turnover, Exhibit Antimicrobial Activity, And Attenuate Pathogenesis, Patrick D. Olson, Lisa J. Kuechenmeister, Kelsi L. Anderson, Sonja Daily, Karen E. Beenken, Christelle M. Roux, Michelle L. Reniere, Tami L. Lewis, William J, Weiss, Mark Pulse, Phung Nguyen, Jerry W. Simecka, John M. Morrison, Khalid Sayood, Oluwatoyin A. Asojo, Mark S. Smeltzer, Eric P. Skaar, Paul M. Dunman

Department of Electrical and Computer Engineering: Faculty Publications

Methicillin-resistant Staphylococcus aureus is estimated to cause more U.S. deaths annually than HIV/AIDS. The emergence of hypervirulent and multidrug-resistant strains has further amplified public health concern and accentuated the need for new classes of antibiotics. RNA degradation is a required cellular process that could be exploited for novel antimicrobial drug development. However, such discovery efforts have been hindered because components of the Gram-positive RNA turnover machinery are incompletely defined. In the current study we found that the essential S. aureus protein, RnpA, catalyzes rRNA and mRNA digestion in vitro. Exploiting this activity, high through-put and secondary screening assays identified …

A Coaching-Based Framework For Individual Consultations, Deandra Little, Michael S. Palmer

To Improve the Academy: A Journal of Educational Development

Educational developers committed to promoting effective teaching and learning practices often make the same mistake we advise instructors to avoid: privileging content over process in individual consultations. We describe a process-oriented consultation model based on effective practices from the literature on individual consultations, coaching, learning, and motivation. Using this three-step model, educational developers can systematically create a collaborative environment that is nonjudgmental and nonprescriptive and draws on the client’s capabilities, experiences, aspirations, and resourcefulness.

Using Students To Support Faculty Development, Teresa M. Redd, Carl E. Brown Jr.

To Improve the Academy: A Journal of Educational Development

Howard University’s Center for Excellence in Teaching, Learning, and Assessment (CETLA) provides faculty development for more than fifteen hundred facuity. Yet it is CETLA’s students who make the difference. They are both the motivation for improving teaching and the means to that end. Students have contributed to everything from the design of CETLA’s infrastructure, to the implementation of instructional technologies, to the assessment of student learning. Meanwhile, supporting faculty development has contributed to the students’ own development. A cost-benefit analysis as well as survey data confirms that working with students at CETLA is a win-win opportunity for the university, faculty, …

Distribution And Penetration Of Teaching-Learning Development Units In Higher Education: Implications For Strategic Planning And Research, Sally Kuhlenschmidt

To Improve the Academy: A Journal of Educational Development

This chapter presents descriptive information about 1,267 U.S. teaching­learning development units (TLDUs). It provides strategic planning and research tools previously unavailable. Results indicate that TLDUs occur in at least 21.2 percent of U.S. higher education institutions, and their presence is correlated at a higher level with student enrollment than with number of faculty. The study provides normative data on the nature of higher education in the United States and on TLDUs by Carnegie classification, location, and type of institution. Additional information is provided about the presence of centers at special-focus institutions such as Hispanic-serving institutions.

Writing Groups For Work-Life Balance: Faculty Writing Group Leaders Share Their Stories, Dannielle Joy Davis, Kara Provost, Amanda E. Major

To Improve the Academy: A Journal of Educational Development

Faculty writing groups can promote both the work-life balance and productivity of members of the professoriate. The benefits of such development initiatives expand beyond productivity to include retention, promotion, and improved teaching. Through the development of writing groups, faculty developers can empower faculty to meet research obligations, establish equilibrium in their work practices, and maintain work-life balance.

The Citizenship Imperative And The Role Of Faculty Development, Jeffrey L. Bernstein, Rebecca S. Nowacek, Michael B. Smith

To Improve the Academy: A Journal of Educational Development

By teaching the capacity for citizenship across the curriculum, colleges and universities can better serve their role as socially responsive institutions. We argue that citizenship themes can be more central to a wide variety of classes, including some in disciplines not considered traditional homes for civic education. Faculty development centers can play a critical role in helping facuity integrate citizenship into the curriculum and evaluate the learning that occurs in their citizenship-oriented classes. We offer guidelines for how learning communities can best serve these purposes.

Review Of Fuel Treatment Effectiveness In Forests And Rangelands And A Case Study From The 2007 Megafires In Central Idaho Usa, Andrew T. Hudak, Ian Rickert, Penelope Morgan, Eva Strand, Sarah A. Lewis, Pete Robichaud, Chad Hoffman, Zachary A. Holden

United States Department of Agriculture, Forest Service / University of Nebraska-Lincoln: Faculty Publications

This report provides managers with the current state of knowledge regarding the effectiveness of fuel treatments for mitigating severe wildfire effects. A literature review examines the effectiveness of fuel treatments that had been previously applied and were subsequently burned through by wildfire in forests and rangelands. A case study focuses on WUI fuel treatments that were burned in the 2007 East Zone and Cascade megafires in central Idaho. Both the literature review and case study results support a manager consensus that forest thinning followed by some form of slash removal is most effective for reducing subsequent wildfire severity.

Flight Instructors Model Code Of Conduct, Aviators Code Initiative

Flight Instructors Model Code of Conduct

The Flight Instructors Model Code of Conduct (Code of Conduct) offers recommendations to advance safety and professionalism in both ground and flight instruction. The Code of Conduct presents a vision of excellence for flight and ground instructors. Its principles complement and underscore legal requirements.

National Board Of Professional Teaching Standards Certification Portfolio Option, Tracy Lynn Bell Maxted

Graduate Research Papers

The National Board of Professional Teaching Standards (NBPTS) is an independent organization that encourages teachers to voluntarily examine and reflect on their teaching. Twelve teaching standards are used for the evaluation. For Adolescence and Young Adulthood Science the standards are to show teachers:

■ Understand Students;

■ Understand Science;

■ Understand Science Teaching;

■ Engage the Science Learner;

■ Sustain a Learning Environment;

■ Promote Diversity, Equity & Fairness;

■ Foster Science Inquiry;

■ Make connections in Science;

■ Assess for Results;

■ Reflect on Teaching and Learning;

■ Develop Collegiality & Leadership; and

■ Connect with Families & Community.

Advanced Underwater Vehicle Navigation, M. Jordan Stanway

Link Foundation Ocean Engineering and Instrumentation Fellowship Reports

Underwater vehicles–both manned and unmanned–are critical in our efforts to explore and study the depths of the ocean. Most underwater sensors possess a relatively small field of view; this means they must be carried over large distances to achieve high spatial coverage and resolution. The vast amount of data these sensors collect is much more valuable if the location of the vehicle is precisely known at the time the data is collected. This gives rise to the maxim: The data is only as good as the navigation. Navigation remains a challenging problem for underwater vehicles. Fundamental limitations of sensing technology …

Process Development And Cgmp Manufacturing Of A Recombinant Ricin Vaccine: An Effective And Stable Recombinant Ricin A-Chain Vaccine—RveCTm, Michael M. Meagher, Javier G. Seravalli, S. Todd Swanson, Roger G. Ladd, Yogender P. Khasa, Mehmet Inan, Jay C. Harner, Scott K. Johnson, Kevin E. Van Cott, Changhong Lindsey, Robert Wannemacher, Leonard A. Smith

Papers in Biomolecular Engineering

Ricin is a potent toxin and a potential bioterrorism weapon with no specific countermeasures or vaccines available. The holotoxin is composed of two polypeptide chains linked by a single disulfide bond: the A-chain (RTA), which is an N-glycosidase enzyme, and the B-chain (RTB), a lectin polypeptide that binds galactosyl moieties on the surface of the mammalian target cells. Previously (McHugh et al.), a recombinant truncated form of RTA (rRTA1-33/ 44-198 protein, herein denoted RVEa^TM) expressed in Escherichia coli using a codon-optimized gene was shown to be non-toxic, stable, and protective against a ricin challenge in mice. Here, we …

The Spreading, Migration And Proliferation Of Mouse Mesenchymal Stem Cells Cultured Inside Hyaluronic Acid Hydrogels, Yuguo Lei, Shiva Gojgini, Jonathan Lam, Tatiana Segura

Department of Chemical and Biomolecular Engineering: Faculty Publications

Synthetic hydrogel scaffolds that can be used as culture systems that mimic the natural stem cell niche are of increased importance for stem cell biology and regenerative medicine. These artificial niches can be utilized to control the stem cell fate and will have potential applications for expanding/differentiating stem cells in vitro, delivering stem cells in vivo, as well as making tissue constructs. In this study, we synthesized hyaluronic acid (HA) hydrogels that could be degraded through a combination of cell-released enzymes and used them to culture mouse mesenchymal stem cells (mMSC). To form the hydrogels, HA was modified to contain …

Community College Student Engagement Patterns: A Typology Revealed Through Exploratory Cluster Analysis, Victor B. Sáenz, Deryl K. Hatch, Beth E. Bukoski, Suyun Kim, Kye-Hyoung Lee, Patrick Valdez

Department of Educational Administration: Faculty Publications

This study employs survey data from the Center for Community College Student Engagement to examine the similarities and differences that exist across student-level domains in terms of student engagement in community colleges. In total, the sample used in the analysis pools data from 663 community colleges and includes more than 320,000 students. Using data-mining techniques to discover a parsimonious number of natural clusters and, in turn, a k-means cluster analysis as a means of revealing a naturally occurring typology of engagement patterns, our findings reveal that support service utilization is the most distinguishing feature of the similarities and dissimilarities across …

Hyaluronic Acid And Fibrin Hydrogels With Concentrated Dna/ Pei Polyplexes For Local Gene Delivery, Yuguo Lei, Maha Rahim, Quinn Ng, Tatiana Segura

Department of Chemical and Biomolecular Engineering: Faculty Publications

Local delivery of DNA through a hydrogel scaffold would increase the applicability of gene therapy in tissue regeneration and cancer therapy. However, the delivery of DNA/cationic polymer nanoparticles (polyplexes) using hydrogels is challenging due to the aggregation and inactivation of polyplexes during their incorporation into hydrogel scaffolds. We developed a novel process (termed Caged Nanoparticle Encapsulation or CnE) to load concentrated and unaggregated nonviral gene delivery nanoparticles into various hydrogels. Previously, we showed that PEG hydrogels loaded with DNA/PEI polyplexes through this process were able to deliver genes both in vitro and in vivo. In this study, we found that …

Experimental Validation Of A Fundamental Model For Pcr Efficiency, Tobias M. Louw, Christine S. Booth, Elsje Pienaar, Joel R. Termaat, Scott E. Whitney, Hendrik J. Viljoen

Department of Chemical and Biomolecular Engineering: Faculty Publications

Recently a theoretical analysis of PCR efficiency has been published by Booth et al., (2010). The PCR yield is the product of three efficiencies: (i) the annealing efficiency is the fraction of templates that form binary complexes with primers during annealing, (ii)the polymerase binding efficiency is the fraction of binary complexes that bind to polymerase to form ternary complexes and (iii)the elongation efficiency is the fraction of ternary complexes that extend fully. Yield is controlled by the smallest of the three efficiencies and control could shift from one type of efficiency to another over the course of a PCR experiment. …

Could Metabolic Syndrome, Lipodystrophy, And Aging Be Mesenchymal Stem Cell Exhaustion Syndromes?, Eduardo Mansilla, Vanina Díaz Aquino, Daniel Zambón, Gustavo Horacio Marin, Karina Mártire, Gustavo Roque, Thomas Ichim, Neil H. Riordan, Amit Patel, Flavio Sturla, Gustavo F. Larsen, Rubén Spretz, Luis Núñez, Carlos Soratti, Ricardo Ibar, Michiel Van Leeuwen, José María Tau, Hugo Drago, Alberto Maceira

Department of Chemical and Biomolecular Engineering: Faculty Publications

One of the most important and complex diseases ofmodern society is metabolic syndrome. This syndrome has not been completely understood, and therefore an effective treatment is not available yet. We propose a possible stem cell mechanism involved in the development ofmetabolic syndrome. This way of thinking lets us consider also other significant pathologies that could have similar etiopathogenic pathways, like lipodystrophic syndromes, progeria, and aging. All these clinical situations could be the consequence of a progressive and persistent stemcell exhaustion syndrome (SCES). Themain outcome of this SCES would be an irreversible loss of the effective regenerative mesenchymal stem cells (MSCs) …

Improved Cellular Infiltration Into Nanofibrous Electrospun Crosslinked Gelatin Scaffolds Templated With Micrometer Sized Polyethylene Glycol Fibers, Maciej Skotak, Jorge Ragusa, Daniela Gonzalez, Anuradha Subramanian

Department of Chemical and Biomolecular Engineering: Faculty Publications

Gelatin-based nanofibrous scaffolds with a mean fiber diameter of 300 nm were prepared with and without micrometer-sized polyethylene glycol (PEG) fibers that served as sacrificial templates. Upon fabrication of the scaffolds via electrospinning, the gelatin fibers were crosslinked with glutaraldehyde, and the PEG templates were removed using tert-butanol to yield nanofibrous scaffolds with pore diameters ranging from 10 to 100 μm, as estimated with mercury intrusion porosimetry. Non-templated gelatin-based nanofibrous matrices had an average pore size of 1 μm. Fibroblasts were seeded onto both types of the gelatin-based nanfibrous surfaces and cultured for 14 days. For comparative purposes, chitosan-based and …

Functional Factor Viii Made With Von Willebrand Factor At High Levels In Transgenic Milk, Steven W. Pipe, Hongzhi Miao, Stephen P. Butler, Jennifer Calcaterra, William H. Velander

Department of Chemical and Biomolecular Engineering: Faculty Publications

Background—Current manufacturing methods for recombinant human Factor VIII (rFVIII) within mammalian cell cultures are inefficient which limit the abundance needed for affordable, worldwide treatment of hemophilia A. However, rFVIII has been expressed at very high levels by the transgenic mammary gland of mice, rabbits, sheep and pigs. Unfortunately, it is secreted into milk with low specific activity due in part to the labile, heterodimeric structure that results from furin processing of its B domain.

Objectives—To express biologically active rFVIII in the milk of transgenic mice through targeted bioengineering.

Methods—Transgenic mice were made with a mammary specific FVIII gene (226/N6) bioengineered …

Corrosion Rate Trajectories Of Concreted Iron And Steel Shipwrecks And Structures In Seawater— The Weins Number, Donald L. Johnson, D. J. Medlin, L. E. Murphy, J. D. Carr, D. L. Conlin

Department of Chemistry: Faculty Publications

The Weins number (Wn) concept is proposed to predict the long-term corrosion rate of wrought iron and steel in seawater for variable marine environments. Plotted as a function of reciprocal absolute temperature, Weins numbers generate a linear plot from which the corrosion rates are calculated when temperature, oxygen concentration, and concretion thickness are known. Application of the theory of absolute reaction rates is described.

Bacterial Protein Structures Reveal Phylum Dependent Divergence, Matthew D. Shortridge, Thomas Triplet, Peter Revesz, Mark A. Griep, Robert Powers

Robert Powers Publications

Protein sequence space is vast compared to protein fold space. This raises important questions about how structures adapt to evolutionary changes in protein sequences. A growing trend is to regard protein fold space as a continuum rather than a series of discrete structures. From this perspective, homologous protein structures within the same functional classification should reveal a constant rate of structural drift relative to sequence changes. The clusters of orthologous groups (COG) classification system was used to annotate homologous bacterial protein structures in the Protein Data Bank (PDB). The structures and sequences of proteins within each COG were compared against …

Engineering A Future For Amphibians Under Climate Change, Luke P. Shoo, Deanna H. Olson, Sarah K. Mcmenamin, Kris A. Murray, Monique Van Sluys, Maureen A. Donnelly, Danial Stratford, Juhani Terhivuo, Andres Merino-Viteri, Sarah M. Herbert, Phillip J. Bishop, Paul Stephen Corn, Liz Dovey, Richard A. Griffiths, Katrin Lowe, Michael Mahony, Hamish Mccallum, Jonathan D. Shuker, Clay Simpkins, Lee F. Skerrat, Stephen E. Williams, Jean-Marc Hero

United States Department of Agriculture, Forest Service / University of Nebraska-Lincoln: Faculty Publications

1. Altered global climates in the 21st century pose serious threats for biological systems and practical actions are needed to mount a response for species at risk.

2. We identify management actions from across the world and from diverse disciplines that are applicable to minimizing loss of amphibian biodiversity under climate change. Actions were grouped under three thematic areas of intervention: (i) installation of microclimate and microhabitat refuges; (ii) enhancement and restoration of breeding sites; and (iii) manipulation of hydroperiod or water levels at breeding sites.

3. Synthesis and applications. There are currently few meaningful management actions that will …

Robust Rnai-Based Resistance To Mixed Infection Of Three Viruses In Soybean Plants Expressing Separate Short Hairpins From A Single Transgene, Xiuchun Zhang, Shirley Sato, Xiaohong Ye, Anne E. Dorrance, Thomas Jack Morris, Thomas E. Clemente, Feng Qu

Nebraska Center for Virology: Faculty Publications

Transgenic plants expressing double-stranded RNA (dsRNA) of virus

origin have been previously shown to confer resistance to virus infections

through the highly conserved RNA-targeting process termed RNA silencing

or RNA interference (RNAi). In this study we applied this strategy to

soybean plants and achieved robust resistance to multiple viruses with a

single dsRNA-expressing transgene. Unlike previous reports that relied

on the expression of one long inverted repeat (IR) combining sequences

of several viruses, our improved strategy utilized a transgene designed to

express several shorter IRs. Each of these short IRs contains highly conserved

sequences of one virus, forming dsRNA of …

A Shock Tube Technique For Blast Wave Simulation And Studies Of Flow Structure Interactions In Shock Tube Blast Experiments, Nicholas N. Kleinschmit

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Improvised explosive devices (IED’s) are widely used against US and allied forces fighting in Iraq and Afghanistan. Exposure to IED blast may cause blast-induced traumatic brain injury (bTBI). The injury mechanisms are however not well understood. A critical need in bTBI-related research is the ability to replicate the loading conditions of IED blast waves in a laboratory environment. In this work, experimental studies have been carried out to explore the use of the shock tube technique for generating air shock waves that mimic the temporal and spatial characteristics of free-field blast waves and to investigate the blast wave-test sample interactions …

Susceptibility Of Selected Potato Varieties To Zebra Chip Potato Disease, Joseph E. Munyaneza, Jeremy L. Buchman, Venkatesan G. Sengoda, Tonja W. Fisher, Cole C. Pearson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Zebra chip (ZC), an emerging and serious disease of potato has caused millions of dollars in losses to the potato industry in the United States, Mexico, Central America, and New Zealand. The disease has recently been associated with a previously undescribed species of liberibacter tentatively named “Candidatus Liberibacter solanacearum” transmitted to potato by the potato psyllid, Bactericera cockerelli (Šulc). At present, applications of insecticides targeted against the potato psyllid are the only means to manage ZC. Given the low psyllid density and short inoculation access period required to induce the disease, insecticides may not act fast enough to prevent …

What Do We Know About Metal Recycling Rates?, T. E. Graedel, Julian Allwood, Jean-Pierre Birat, Matthias Buchert, Christian Hagelűken, Barbara K. Reck, Scott F. Sibley, Guido Sonnemann

United States Geological Survey: Staff Publications

The recycling of metals is widely viewed as a fruitful sustainability strategy, but little information is available on the degree to which recycling is actually taking place. This article provides an overview on the current knowledge of recycling rates for 60 metals. We propose various recycling metrics, discuss relevant aspects of recycling processes, and present current estimates on global end-of-life recycling rates (EOL-RR; i.e., the percentage of a metal in discards that is actually recycled), recycled content (RC), and old scrap ratios (OSRs; i.e., the share of old scrap in the total scrap flow). Because of increases in metal use …

Evaluation Of Single And Two-Stage Adaptive Sampling Designs For Estimation Of Density And Abundance Of Freshwater Mussels In A Large River, D. R. Smith, J. T. Rogala, B. R. Gray, Steven J. Zigler, Teresa J. Newton

United States Geological Survey: Staff Publications

Reliable estimates of abundance are needed to assess consequences of proposed habitat restoration and enhancement projects on freshwater mussels in the Upper Mississippi River (UMR). Although there is general guidance on sampling techniques for population assessment of freshwater mussels, the actual performance of sampling designs can depend critically on the population density and spatial distribution at the project site. To evaluate various sampling designs, we simulated sampling of populations, which varied in density and degree of spatial clustering. Because of logistics and costs of large river sampling and spatial clustering of freshwater mussels, we focused on adaptive and non-adaptive versions …