Physical Sciences and Mathematics Commons^™

Systems And Methods For Actuating Soft Robotic Actuators, Robert F. Shepherd, Adam Stokes, Stephen A. Morin, Ludovico Cademartiri, Jacob Freake, Rui Nunes, Xin Chen, George M. Whitesides

Department of Chemistry: Faculty Publications

Systems and methods for providing a soft robot is provided. In one system , a robotic device includes a flexible body having a fluid chamber, where a portion of the flexible body includes an elastically extensible material and a portion of the flexible body is strain limiting relative to the elastically extensible material. The robotic device can further include a pressurizing inlet in fluid communication with the fluid chamber, and a pressurizing device in fluid communication with the pressurizing inlet, the pressurizing device including a reaction chamber configured to accommodate a gas producing chemical reaction for providing pressurized gas to …

Tin Nanoparticles Encapsulated Carbon Nanoboxes As High-Performance Anode For Lithium-Ion Batteries, Ziming Yang, Hong-Hui Wu, Zhiming Zheng, Yong Cheng, Pei Li, Qiaobao Zhang, Ming-Sheng Wang

Department of Chemistry: Faculty Publications

One of the crucial challenges for applying Sn as an anode of lithium-ion batteries (LIBs) is the dramatic volume change during lithiation/delithiation process, which causes a rapid capacity fading and then deteriorated battery performance. To address this issue, herein, we report the design and fabrication of Sn encapsulated carbon nanoboxes (denoted as Sn@C) with yolk@shell architectures. In this design, the carbon shell can facilitate the good transport kinetics whereas the hollow space between Sn and carbon shell can accommodate the volume variation during repeated charge/discharge process. Accordingly, this composite electrode exhibits a high reversible capacity of 675 mAh g^{−1 …}

Anatomy Of Stem Teaching In American Universities: A Snapshot From A Large-Scale Observation Study, Marilyne Stains, Jordan Harshman, Megan K. Barker, Stephanie V. Chasteen, Renee Cole, Sue Ellen Dechenne-Peters, M. Kevin Eagan Jr., Joan M. Esson, Jennifer K. Knight, Frank A. Laski, Marc Levis-Fitzgerald, Christopher J. Lee, Stanley M. Lo, Lisa M. Mcdonnell, Timothy A. Mckay, Nicole Michelotti, Michael S. Palmer, Kathryn M. Plank, Tamara M. Rodela, Erin R. Sanders, Natalie G. Schimpf, Patricia M. Schulte, Michelle Smith, Mackenzie Stetzer, Jackie Stewart, Blaire Van Valkenburgh, Erin Vinson, Laura K. Weir, Paul J. Wendel, Lindsay B. Wheeler, Anna M. Young

Department of Chemistry: Faculty Publications

National and local initiatives focused on the transformation of STEM teaching in higher education have multiplied over the last decade. These initiatives often focus on measuring change in instructional practices, but it is difficult to monitor such change without a national picture of STEM educational practices, especially as characterized by common observational instruments. We characterized a snapshot of this landscape by conducting the first large scale observation-based study. We found that lecturing was prominent throughout the undergraduate STEM curriculum, even in classrooms with infrastructure designed to support active learning, indicating that further work is required to reform STEM education. Additionally, …

Honeycomb Lattice Na2iro3 At High Pressures: A Robust Spin-Orbit Mott Insulator, Xiaoxiang Xi, Xiangyan Bo, X. S. Xu, P. P. Kong, Z. Liu, X. G. Hong, C. Q. Jin, G. Cao, Xiangang Wan, G. L. Carr

Xiaoshan Xu Papers

The honeycomb iridate Na₂IrO₃ has received much attention as a candidate to realize a quantum spin liquid state, but the nature of its insulating state remains controversial. We found that the material exhibits structural transitions at 3 and 10 GPa. The former is accompanied by 166-meV suppression of the activation gap, but the energies for the low-lying interband transitions change by less than 10 meV. This can be reconciled in a picture in which the application of high pressure barely shifts the electronic bands, but rather merely broadens them. First-principles calculations uncover a strong correlation between the …

Tuning The Neel Temperature Of Hexagonal Ferrites By Structural Distortion, Kishan Sinha, Haohan Wang, Xiao Wang, Liying Zhou, Yuewei Yin, Wenbin Wang, Xuemei Cheng, David J. Keavney, Huibo Cao, Yaohua Liu, Xifan Wu, Xiaoshan Xu

Xiaoshan Xu Papers

To tune the magnetic properties of hexagonal ferrites, a family of magnetoelectric multiferroic materials, by atomic-scale structural engineering, we studied the effect of structural distortion on the magnetic ordering temperature (T_N) in these materials. Using the symmetry analysis, we show that unlike most antiferromagnetic rare-earth transition-metal perovskites, a larger structural distortion leads to a higher T_N in hexagonal ferrites and manganites, because the K₃ structural distortion induces the three-dimensional magnetic ordering, which is forbidden in the undistorted structure by symmetry. We also revealed a nearlinear relation between T_N and the tolerance factor and a …

Stabilization And Control Of Majorana Bound States With Elongated Skyrmions, Utkan Güngördü, Shane Sandhoefner, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

We show that elongated magnetic skyrmions can host Majorana bound states in a proximity-coupled two-dimensional electron gas sandwiched between a chiral magnet and an s-wave superconductor. Our proposal requires stable skyrmions with unit topological charge, which can be realized in a wide range of multilayer magnets, and it allows quantum information transfer by using standard methods in spintronics via skyrmion motion. We also show how braiding operations can be realized in our proposal.

Indications Of Magnetic Coupling Effects In Spin Cross-Over Molecular Thin Films, Xin Zhang, Alpha T. N'Diaye, Xuanyuan Jiang, Xiaozhe Zhang, Yuewei Yin, Xuegang Chen, Xia Hong, Xiaoshan Xu, Peter Dowben

Xia Hong Publications

Room temperature isothermal reversible spin crossover switching of [Fe(H₂B(pz)₂)₂(bipy)] thin films is demonstrated. The magnetic oxide substrate locks the [Fe{H₂B(pz)₂}₂(bipy)] largely in a low spin state. With an X-ray fluence, excitation to a high spin state occurs, while relaxation back to low spin state is aided by alternating the substrate magnetization.

Includes supplementary materials.

Spin-Polarized Electron Transmission Through Chiral Halocamphor Molecules, J. M. Dreiling, F. W. Lewis, Timothy J. Gay

Timothy J. Gay Publications

We have measured electron-circularly-dichroic asymmetries when longitudinally-polarized (chiral) electrons are scattered quasi-elastically by chiral halocamphor molecules: 3-bromocamphor (C₁₀H₁₅BrO), 3-iodocamphor (C₁₀H₁₅IO), and 10-iodocamphor. The proposed dynamic origins of these asymmetries are considered in terms of three classical models related to Mott scattering, target electron helicity density, and spin-other-orbit interactions. The asymmetries observed for 3-bromocamphor and 3-iodocamphor scale roughly as Z², where Z is the nuclear charge of the heaviest atom in the target molecule, but the scaling is violated by 10- iodocamphor, which has a smaller asymmetry than that for 3-iodocamphor. …

Cybersecurity And The New Era Of Space Activities, David P. Fidler

Articles by Maurer Faculty

No abstract provided.

The New Writs Of Assistance, Ian Samuel

Articles by Maurer Faculty

The providers of network services (and the makers of network devices) know an enormous amount about our lives. Because they do, these network intermediaries are being asked with increasing frequency to assist the government in solving crimes or gathering intelligence. Given how much they know about us, if the government can secure the assistance of these intermediaries, it will enjoy a huge increase in its theoretical capacity for surveillance—the ability to learn, in principle, almost anything about anyone. That has the potential to create serious social harm, even assuming that the government continues to adhere to ordinary democratic norms and …

Climate Change Challenges For Land Conservation: Rethinking Conservation Easements, Strategies, And Tools, W. William Weeks, Jessica Owley, Federico Cheever, Adena R. Rissman, M. Rebecca Shaw, Barton H. Thompson

Articles by Maurer Faculty

Climate change has significant consequences for land conservation. Government agencies and nonprofit land trusts heavily rely on perpetual conservation easements. However, climate change and other dynamic landscape changes raise questions about the effectiveness and adaptability of permanent conservation instruments like conservation easements. Building upon a study of 269 conservation easements and interviews with seventy conservation-easement professionals in six different states, we examine the adaptability of conservation easements to climate change. We outline four potential approaches to enhance conservation outcomes under climate change: (1) shift land-acquisition priorities to account for potential climate-change impacts; (2) consider conservation tools other than perpetual conservation …

Expanding The Artificial Intelligence-Data Protection Debate, Fred H. Cate, Christopher Kuner, Orla Lynskey, Christopher Millard, Nora Ni Loideain, Dan Jerker B. Svantesson

Articles by Maurer Faculty

No abstract provided.

Reductive Cleavage Of Organic Peroxides By Iron Salts And Thiols, Anderw Olson, Abigail J. Jameson, Shiva K. Kyasa, Boone W. Evans, Patrick H. Dussault

Department of Chemistry: Faculty Publications

Despite the low bond strength of the oxygen− oxygen bond, organic peroxides are often surprisingly resistant to cleavage by nucleophiles and reductants. As a result, achieving decomposition under mild conditions can be challenging. Herein, we explore the reactivity of a selection of peroxides toward thiolates, phenyl selenide, Fe(II) salts, and iron thiolates. Peroxides activated by conjugation, strain, or stereoelectronics are rapidly cleaved at room temperature by thiolate anions, phenylselenide, or Fe(II) salts. Under the same conditions, unhindered dialkyl peroxides are only marginally reactive; hindered peroxides, including triacetone triperoxide and diacetone diperoxide (DADP), are inert. In contrast, all but the most …

The Secant Rate Of Corrosion: Correlating Observations Of The Uss Arizona Submerged In Pearl Harbor, Donald L. Johnson, Robert J. Deangelis, Dana J. Medlin, Jon E. Johnson, James D. Carr, David L. Conlin

Department of Chemistry: Faculty Publications

Contrary to previous linear projections of steel corrosion in seawater, analysis of an inert marker embedded in USS Arizona concretion since the 7 December 1941 attack on Pearl Harbor reveals evidence that the effective corrosion rate decreases with time. The secant rate of corrosion, or SRC correlation, derived from this discovery could have a significant impact on failure analysis investigations for concreted shipwrecks or underwater structures. The correlation yields a lower rate of metal thinning than predicted. Development of the correlation is described.

Study Of The Oxidation Kinetics Of Nitrite Ions By Potassium Ferrate(Vi), J. Carr, I. Goncharova, D. Golovko, C. Mclaughlin, I. Golovko, J. Erickson

Department of Chemistry: Faculty Publications

Вивчено кiнетику окиснення нiтрит до нiтрат йонiв калiй фератом(VI) в широкому дiапазонi рН, вiд нейтрального до лужного сере- довища. Проведено двi серiї кiнетичних експе- риментiв, заснованих на рiзних технологiях одержання калiй ферату(VI). В першiй серiї експериментiв кристалiчний калiй ферат(VI) отримували хiмiчним синтезом. В дiапазонi рН 6.5–11 твердий K₂FeO₄ додавали до роз- чинiв нiтрит йонiв при вiдомiй концентрацiї та рН. Експерименти проводили пiд контролем рН та йонної сили. Кiнетичнi дослiдження коливалися вiд мiлiсекунд до декiлькох хви- лин. В другiй серiї експериментiв розчини K₂FeO₄ було отримано електрохiмiчним син- тезом. Лужнi розчини калiй ферату(VI) в 8.0 М …

Structure And Mechanism Of A Bacterial T6a Biosynthesis System, Amit Luthra, William Swinehart, Susan Bayooz, Phuc Phan, Boguslaw Stec, Dirk Iwata-Reuyl, Manal A. Swairjo

Chemistry Faculty Publications and Presentations

The universal N(6)-threonylcarbamoyladenosine (t⁶A) modification at position 37 of ANN-decoding tRNAs is central to translational fidelity. In bacteria, t⁶A biosynthesis is catalyzed by the proteins TsaB, TsaC/TsaC2, TsaD and TsaE. Despite intense research, the molecular mechanisms underlying t⁶A biosynthesis are poorly understood. Here, we report biochemical and biophysical studies of the t⁶A biosynthesis system from Thermotoga maritima. Small angle X-ray scattering analysis reveals a symmetric 2:2 stoichiometric complex of TsaB and TsaD (TsaB₂D₂), as well as 2:2:2 complex (TsaB₂D₂E₂), in …

Facile Synthesis Of Ligand-Free Iridium Nanoparticles And Their In Vitro Biocompatibility, Anna L. Brown, Hayden Winter, Andrea M. Goforth, Gaurav Sahay, Conroy Sun

Chemistry Faculty Publications and Presentations

High-density inorganic nanoparticles have shown promise in medical applications that utilize radiation including X-ray imaging and as radiation dose enhancers for radiotherapy. We have developed an aqueous synthetic method to produce small (~ 2 nm) iridium nanoparticles (IrNPs) by reduction of iridium(III) chloride using a borohydride reducing agent. Unlike other solution-based synthesis methods, uniform and monodispersed IrNPs are produced without the use of surfactants or other solubilizing ligands. These nanoparticles are highly crystalline as observed by X-ray diffraction and high-resolution transmission electron microscopy (TEM). In vitro metabolic toxicity assays using hepatocyte and macrophage cells demonstrate that both IrNPs and iridium(III) …

Evaluation Of The Influence Of Wording Changes And Course Type On Motivation Instrument Functioning In Chemistry, Regis Komperda, Kathryn N. Hosbein, Jack Barbera

Chemistry Faculty Publications and Presentations

Increased understanding of the importance of the affective domain in chemistry education research has led to the development and adaptation of instruments to measure chemistry-specific affective traits, including motivation. Many of these instruments are adapted from other fields by using the word ‘chemistry’ in place of other disciplines or more general ‘science’ wording. Psychometric evidence is then provided for the functioning of the new adapted instrument. When an instrument is adapted from general language to specific (e.g. replacing ‘science’ with ‘chemistry’), an opportunity exists to compare the functioning of the original instrument in the same context as the adapted instrument. …

Long-Term Changes In Extreme Air Pollution Meteorology And Implications For Air Quality, Pei Hou

Dissertations, Master's Theses and Master's Reports

Extreme air pollution meteorology, such as heat waves, temperature inversions, and atmospheric stagnation episodes, can significantly affect air quality. In this study, we analyze their long-term trends and the potential impacts on air quality. The significant increasing trends for the occurrences of extreme meteorological events in 1951-2010 are identified with the reanalysis data, especially over the continental regions. A statistical analysis combining air quality data and meteorological data indicates strong sensitivities of air quality, including both average air pollutant concentrations and high pollution episodes, to extreme meteorological events. Results also show significant seasonal and spatial variations in the sensitivity of …

Direct Measurement Of Rupture Force Of Single Triazole Molecule By Atomic Force Microscope And Solid Phase Synthesis Of Monodisperse Polyethylene Glycols, Ashok Khanal

Dissertations, Master's Theses and Master's Reports

This dissertation includes two topics, which are related to each other: (1) Rupture force measurement of single triazole molecule by atomic force microscope (AFM) and (2) Solid phase stepwise synthesis of polyethylene glycols (PEGs).

The reaction of an alkyne and an azide to form a 1,2,3- triazole has found wide applications. However, the stability of triazole under mechanical stress is unclear. We investigated the cycloreversion at the single molecular level using atomic force microscopy. A mica surface functionalized with a molecule containing a 1,2,3-triazole moiety in the middle and an activated ester at the end was prepared. An AFM tip …

Joint Analysis For Multiple Traits, Zhenchuan Wang

Dissertations, Master's Theses and Master's Reports

This dissertation includes three papers with each distributed in one chapter.

In chapter 1, we proposed an Adaptive Weighting Reverse Regression (AWRR) method to test association between multiple traits and rare variants in a genomic region. AWRR is robust to the directions of effects of causal variants and is also robust to the directions of association of traits. Using extensive simulation studies, we compared the performance of AWRR with canonical correlation analysis (CCA), Single-TOW, and the Weighted Sum Reverse Regression (WSRR). Our results showed that, in all of the simulation scenarios, AWRR is consistently more powerful than CCA. In most …

Agroforestry Standards For Regenerative Agriculture [Review], Craig R. Elevitch, D. Niki Mazaroli, Diane Ragone

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

Agroforestry is increasingly being recognized as a holistic food production system that can have numerous significant environmental, economic, and social benefits. This growing recognition is paralleled in the USA by the budding interest in regenerative agriculture and motivation to certify regenerative practices. Current efforts to develop a regenerative agriculture certification offer an opportunity to consider agroforestry’s role in furthering regenerative goals. To understand this opportunity, we first examine how agroforestry practices can advance regenerative agriculture’s five core environmental concerns: soil fertility and health, water quality, biodiversity, ecosystem health, and carbon sequestration. Next, we review a subset of certification programs, standards, …

Vegetation Responses To Sagebrush-Reduction Treatments Measured By Satellites, Aaron N. Johnston, Erik A. Beever, Jerod A. Merkle, Geneva Chong

United States Geological Survey: Staff Publications

Time series of vegetative indices derived from satellite imagery constitute tools to measure ecological effects of natural and management-induced disturbances to ecosystems. Over the past century, sagebrush-reduction treatments have been applied widely throughout western North America to increase herbaceous vegetation for livestock and wildlife. We used indices from satellite imagery to 1) quantify effects of prescribed-fire, herbicide, and mechanical treatments on vegetative cover, productivity, and phenology, and 2) describe how vegetation changed over time following these treatments. We hypothesized that treatments would increase herbaceous cover and accordingly shift phenologies towards those typical of grass-dominated systems. We expected prescribed burns would …

Evaluating Restored Tidal Freshwater Wetlands, Andrew H. Baldwin1,, Richard S. Hammerschlag, Donald R. Cahoon

United States Geological Survey: Staff Publications

Tidal freshwater wetlands are recognized as highly productive coastal wetlands that support diverse assemblages of plants and animals and complex biogeochemical cycles (in this book, see Chapter 18 by Whigham et al. and Chapter 19 by Megonigal and Neubauer). Many tidal freshwater wetlands and their associated ecosystem services have been damaged or destroyed by urbanization, agriculture, and other human activities (Baldwin, 2004; Barendregt et al., 2006). Increasing recognition of the value of remaining wetlands and environmental regulations requiring wetland mitigation (i.e., enhancement, creation, or restoration of wetlands to compensate for wetland losses; Kentula, 2000) has driven the restoration of all …

The Global Food-Energy-Water Nexus, Paolo D’Odorico, Kyle Frankel Davis, Lorenzo Rosa, Joel A. Carr, Davide Chiarelli, Jampel Dell’Angelo, Jessica Gephart, Graham K. Macdonald, David A. Seekell, Samir Suweis, Maria Cristina Rulli

United States Geological Survey: Staff Publications

Water availability is a major factor constraining humanity’s ability to meet the future food and energy needs of a growing and increasingly affluent human population. Water plays an important role in the production of energy, including renewable energy sources and the extraction of unconventional fossil fuels that are expected to become important players in future energy security. The emergent competition for water between the food and energy systems is increasingly recognized in the concept of the “food-energy-water nexus.” The nexus between food and water is made even more complex by the globalization of agriculture and rapid growth in food trade, …

Evaluating The Waterfowl Breeding Population And Habitat Survey For Scaup, Michael L. Schummer, Alan D. Afton, Shannon S. Badzinski, Scott A. Petrie, Glenn H. Olsen, Mark A. Mitchell

United States Geological Survey: Staff Publications

Potential bias in breeding population estimates of certain duck species from the Waterfowl Breeding Population and Habitat Survey (WBPHS) has been a concern for decades. The WBPHS does not differentiate between lesser (Aythya affinis) and greater (A. marila) scaup, but lesser scaup comprise 89% of the combined scaup population and their population estimates are suspected to be biased. We marked female lesser scaup (i.e., marked scaup) in the Mississippi and Atlantic Flyways, Canada and United States, with implantable satellite transmitters to track their spring migration through the traditional and eastern survey areas of the WBPHS, 2005–2010. Our goal was to …

Is Sensitivity To Anticoagulant Rodenticides Affected By Repeated Exposure In Hawks?, Barnett A. Rattner, Rebecca S. Lazarus, Thomas G. Bean, Katherine E. Horak,, Steven F. Volker, Julia Lankton

United States Geological Survey: Staff Publications

A seminal question in wildlife toxicology is whether exposure to an environmental contaminant, in particular a secondgeneration anticoagulant rodenticide, can evoke subtle long lasting effects on body condition, physiological function and survival. Many reports indicate that non-target predators often carry residues of several rodenticides, which is indicative of multiple exposures. An often-cited study in laboratory rats demonstrated that exposure to the second-generation anticoagulant rodenticide brodifacoum prolongs blood clotting time for a few days, but weeks later when rats were re-exposed to the first-generation anticoagulant rodenticide warfarin, coagulopathy was more pronounced in brodifacoum-treated rats than naïve rats exposed to warfarin. To …

Focused Electron-Beam-Induced Deposition For Fabrication Of Highly Durable And Sensitive Metallic Afm-Ir Probes, Wen Qian, Shuo Sun, Jingfeng Song, Charles Nguyen, Stephen Ducharme, Joesph A. Turner

Stephen Ducharme Publications

We report on the fabrication of metallic, ultra-sharp atomic force microscope tips for localized nanoscale infrared (IR) spectrum measurements by using focused electron-beam-induced deposition of platinum or tungsten. The tip length can be controlled by changing the duration time of the electron beam. Probes of 12.0 ± 5.0 nm radius-of-curvature can be routinely produced with high repeatability and near-100% yield. The near-field-enhancement appears stronger at the extremity of the metallic tip, compared with commercial pristine silicon-nitride probe tip. Finally, the performance of the modified metallic tips is demonstrated by imaging PVDF and PMMA thin films, which shows that spatial resolution …

Investigation Of Toppling Ball Flight In American Football With A Mechanical Field-Goal Kicker, Chase M Pfeifer, Timothy J. Gay, Jeff A. Hawks, Shane Farritor, Judith M. Burnfield

Department of Mechanical and Materials Engineering: Faculty Publications

A mechanical field-goal kicking machine was used to investigate toppling ball flight in American football place-kicking, eliminating a number of uncontrollable impact variables present with a human kicker. Ball flight trajectories were recorded using a triangulation-based projectile tracking system to account for the football’s 3-dimensional position during flight as well as initial launch conditions. The football flights were described using kinematic equations relating to projectile motion including stagnant air drag and were compared to measured trajectories as well as projectile motion equations that exclude stagnant air drag. Measured football flight range deviations from the non-drag equations of projectile motion corresponded …

Recent Ecological Change In Ancient Lakes, Stephanie E. Hampton, Suzanne Mcgowan, Ted Ozersky, Salvatore G. P. Virdis, Tuong Thuy Vu, Trisha L. Spanbauer, Benjamin M. Kraemer, George Swann, Anson W. Mackay, Stephen M. Powers, Michael F. Meyer, Stephanie G. Labou, Catherine M. O'Reilly, Morgan Dicarlo, Aaron W. E. Galloway, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

Ancient lakes are among the best archivists of past environmental change, having experienced more than one full glacial cycle, a wide range of climatic conditions, tectonic events, and long association with human settlements. These lakes not only record long histories of environmental variation and human activity in their sediments, but also harbor very high levels of biodiversity and endemism. Yet, ancient lakes are faced with a familiar suite of anthropogenic threats, which may degrade the unusual properties that make them especially valuable to science and society. In all ancient lakes for which data exist, significant warming of surface waters has …