Digital Commons Network^™

Effect Of Flow Gradient, Roi Size And Random Scatterer Movement During Speckle Size Estimation Based Blood Flow Measurement, Tiantian Xu, Greg Bashford

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Conventional blood flow velocity measurement using ultrasound is capable of resolving the axial component (i.e., that aligned with the ultrasound propagation direction) of the blood flow velocity vector. However, these Doppler-based methods are incapable of detecting blood flow in the direction normal to the ultrasound beam. An algorithm which measures the lateral blood flow velocity using speckle size change with scan velocity was developed in our previous studies. This method uses the apparent speckle size change that occurs when scatterers are moving relative to the spatial rate of A-line acquisition. Our previous results showed that the estimation error of this …

Evaluation Of Select Sensors For Real-Time Monitoring Of Escherichia Coli In Water Distribution Systems, Syreeta L. Miles, Ryan G. Sinclair, Mark R. Riley, Ian L. Pepper

Department of Agricultural and Biological Systems Engineering: Faculty Publications

This study evaluated real-time sensing of Escherichia coli as a microbial contaminant in water distribution systems. Most sensors responded to increased E. coli concentrations, showing that select sensors can detect microbial water quality changes and be utilized as part of a contaminant warning system.

Improved Soil Mixing And Delivery System For A Storm Runoff Simulator, William C. Alms, Thomas G. Franti, David P. Shelton

Department of Agricultural and Biological Systems Engineering: Faculty Publications

An earlier version of a storm runoff simulator to test conservation buffers reproduced target hydrographs and sedigraphs using uniform, fine sand; however, it was unable to uniformly mix and deliver native sediment. The objectives of this work reported were to create a method to process native agricultural sediment, mix a uniform sediment slurry at a target concentration, and create a control system that will deliver the slurry in varying flow rates corresponding to a target sedigraph. Eroded silty clay (14% sand) was scraped, dried, and processed with a hammer mill. A sand (93% sand) and loam (44% sand) were dried …

Irrigation Efficiency And Uniformity, And Crop Water Use Efficiency, Suat Irmak, Lameck O. Odhiambo, William L. Kranz, Dean E. Eisenhauer

Department of Agricultural and Biological Systems Engineering: Faculty Publications

This Extension Circular describes various irrigation efficiency, crop water use efficiency, and irrigation uniformity evaluation terms that are relevant to irrigation systems and management practices currently used in Nebraska, in other states, and around the world. The definitions and equations described can be used by crop consultants, irrigation district personnel, and university, state, and federal agency personnel to evaluate how efficiently irrigation water is applied and/or used by the crop, and can help to promote better or improved use of water resources in agriculture.

As available water resources become scarcer, more emphasis is given to efficient use of irrigation water …

A Case Study Concerning The Effects Of Controller Response And Turning Movements On Application Rate Uniformity With A Self-Propelled Sprayer, Joe D. Luck, A. Sharda, Santosh Pitla, J. P. Fulton, S. A. Shearer

Department of Agricultural and Biological Systems Engineering: Faculty Publications

The use of precision agriculture technologies such as automatic boom section control allows producers to reduce off-target application when applying herbicides. While automatic boom section control provides benefits, pressure differences across the spray boom resulting from boom section actuation may lead to off-rate application errors. Off-rate errors may also result from spray rate controller compensation for ground speed changes or velocity variation across the spray boom during turning movements. This project focused on characterizing application rate variation for three fields located in central Kentucky. GPS coordinates, boom control status, and nozzle pressure data (at 15 nozzle locations) were recorded as …

Systems-Scale Analysis Reveals Pathways Involved In Cellular Response To Methamphetamine, Lijie Sun, Hong-Mei Li, Manfredo J. Seufferheld, Kent R. Walters Jr., Venu M. Margam, Amber Jannasch, Naomi Diaz, Catherine P. Riley, Weilin Sun, Yueh-Feng Li, William M. Muir, Jun Xie, Jing Wu, Fan Zhang, Jake Y. Chen, Eric L. Barker, Jiri Adamec, Barry R. Pittendrigh

Department of Biochemistry: Faculty Publications

Background: Methamphetamine (METH), an abused illicit drug, disrupts many cellular processes, including energy metabolism, spermatogenesis, and maintenance of oxidative status. However, many components of the molecular underpinnings of METH toxicity have yet to be established. Network analyses of integrated proteomic, transcriptomic and metabolomic data are particularly well suited for identifying cellular responses to toxins, such as METH, which might otherwise be obscured by the numerous and dynamic changes that are induced.

Methodology/Results: We used network analyses of proteomic and transcriptomic data to evaluate pathways in Drosophila melanogaster that are affected by acute METH toxicity. METH exposure caused changes in the …

Phot1 Inhibition Of Abcb19 Primes Lateral Auxin Fluxes In The Shoot Apex Required For Phototropism, John M. Christie, Haibing Yang, Gregory L. Ritcher, Stuart Sullivan, Catriona E. Thomson, Jinshan Lin, Boosaree Titapiwatanakun, Margaret Ennis, Eirini Kaiserli, Ok Ran Lee, Jiri Adamec, Wendy A. Peer, Angus S. Murphy

Department of Biochemistry: Faculty Publications

It is well accepted that lateral redistribution of the phytohormone auxin underlies the bending of plant organs towards light. In monocots, photoreception occurs at the shoot tip above the region of differential growth. Despite more than a century of research, it is still unresolved how light regulates auxin distribution and where this occurs in dicots. Here, we establish a system in Arabidopsis thaliana to study hypocotyl phototropism in the absence of developmental events associated with seedling photomorphogenesis. We show that auxin redistribution to the epidermal sites of action occurs at and above the hypocotyl apex, not at the elongation zone. …

A 4-Selenocysteine, 2-Selenocysteine Insertion Sequence (Secis) Element Methionine Sulfoxide Reductase From Metridium Senile Reveals A Non-Catalytic Function Of Selenocysteines, Byung Cheon Lee, Alexey V. Lobanov, Stefano M. Marino, Alaattin Kaya, Javier Seravalli, Dolph L. Hatfield, Vadim N. Gladyshev

Department of Biochemistry: Faculty Publications

Selenocysteine (Sec) residues occur in thiol oxidoreductase families, and functionally characterized selenoenzymes typically have a single Sec residue used directly for redox catalysis. However, how new Sec residues evolve and whether non-catalytic Sec residues exist in proteins is not known. Here, we computationally identified several genes with multiple Sec insertion sequence (SECIS) elements, one of which was a methionine-Rsulfoxide reductase (MsrB) homolog from Metridium senile that has four in-frame UGA codons and two nearly identical SECIS elements. One of the UGA codons corresponded to the conserved catalytic Sec or Cys in MsrBs, whereas the three other UGA codons evolved recently …

Escherichia Coli Thioredoxin-Like Protein Ybbn Contains An Atypical Tetratricopeptide Repeat Motif And Is A Negative Regulator Of Groel, Jiusheng Lin, Mark A. Wilson

Department of Biochemistry: Faculty Publications

Many proteins contain a thioredoxin (Trx)-like domain fused with one or more partner domains that diversify protein function by the modular construction of new molecules. The Escherichia coli protein YbbN is a Trx-like protein that contains a C-terminal domain with low homology to tetratricopeptide repeat motifs. YbbN has been proposed to act as a chaperone or co-chaperone that aids in heat stress response andDNAsynthesis. We report the crystal structure of YbbN, which is an elongated molecule with a mobile Trx domain and four atypical tetratricopeptide repeat motifs. The Trx domain lacks a canonical CXXC active site architecture and is not …

Functional Diversification Of Thylakoidal Processing Peptidases In Arabidopsis Thaliana, Shih-Chi Hsu, Joshua K. Endow, Nicholas J. Ruppel, Rebecca Roston, Amy J. Baldwin, Kentaro Inoue

Department of Biochemistry: Faculty Publications

Thylakoidal processing peptidase (TPP) is responsible for removing amino-terminal thylakoid-transfer signals from several proteins in the thylakoid lumen. Three TPP isoforms are encoded by the nuclear genome of Arabidopsis thaliana. Previous studies showed that one of them termed plastidic type I signal peptidase 1 (Plsp1) was necessary for processing three thylakoidal proteins and one protein in the chloroplast envelope in vivo. The lack of Plsp1 resulted in seedling lethality, apparently due to disruption of proper thylakoid development. The physiological roles of the other two TPP homologs remain unknown. Here we show that the three A. thaliana TPP isoforms …

The Lyr Protein Mzm1 Functions In The Insertion Of The Rieske Fe/S Protein In Yeast Mitochondria, Aaron Atkinson, Pamela Smith, Jennifer L. Fox, Tie-Shong Cui, Oleh Khalimonchuk, Dennis R. Winge

Department of Biochemistry: Faculty Publications

The assembly of the cytochrome bc1 complex in Saccharomyces cerevisiae is shown to be conditionally dependent on a novel factor, Mzm1. Cells lacking Mzm1 exhibit a modest bc₁ defect at 30°C, but the defect is exacerbated at elevated temperatures. Formation of bc₁ is stalled in mzm1 Δ cells at a late assembly intermediate lacking the Rieske iron-sulfur protein Rip1. Rip1 levels are markedly attenuated in mzm1 Δ cells at elevated temperatures. Respiratory growth can be restored in the mutant cells by the overexpression of the Rip1 subunit. Elevated levels of Mzm1 enhance the stabilization of Rip1 through …

Increased Transsulfuration Mediates Longevity And Dietary Restriction In Drosophila, Hadise Kabil, Omer Kabil, Ruma Banerjee, Lawrence G. Harshman, Scott D. Pletcher

School of Biological Sciences: Faculty Publications

The mechanisms through which dietary restriction enhances health and longevity in diverse species are unclear. The transsulfuration pathway (TSP) is a highly conserved mechanism for metabolizing the sulfur-containing amino acids, methionine and cysteine. Here we show that Drosophila cystathionine β-synthase (dCBS), which catalyzes the rate-determining step in the TSP, is a positive regulator of lifespan in Drosophila and that the pathway is required for the effects of diet restriction on animal physiology and lifespan. dCBS activity was up-regulated in flies exposed to reduced nutrient conditions, and ubiquitous or neuron-specific transgenic overexpression of dCBS enhanced longevity in fully fed animals. Inhibition …

A Cytoplasm-Specific Activity Encoded By The Trithorax-Like Atx1 Gene, Ivan Ndamukong, Hanna Lapko, Ronald L. Cerny, Zoya Avramova

School of Biological Sciences: Faculty Publications

Eukaryotes produce multiple products from a single gene locus by alternative splicing, translation or promoter usage as mechanisms expanding the complexity of their proteome. Trithorax proteins, including the Arabidopsis Trithorax-like protein ATX1, are histone modifiers regulating gene activity. Here, we report that a novel member of the Trithorax family has a role unrelated to chromatin. It is encoded from an internal promoter in the ATX1 locus as an isoform containing only the SET domain (soloSET). It is located exclusively in the cytoplasm and its substrate is the elongation factor 1A (EF1A). Loss of SET, but not of the histone modifying …

Evidence For Air Movement Signals In The Agonistic Behaviour Of A Nocturnal Arachnid (Order Amblypygi), Roger D. Santer, Eileen A. Hebets

School of Biological Sciences: Faculty Publications

Many arthropods possess filiform hair sensilla (termed trichobothria in arachnids), which are extremely sensitive detectors of medium particle displacement. Electrophysiological evidence in some taxa suggests that these sensilla can detect air particle displacements resulting from intraspecific communication signals. However, it has not yet been shown for any species that the air particle displacements detected by the filiform hairs are themselves perceived as a ‘signal’ (i.e. that individuals make behavioural decisions based upon the responses of these organs to the displays of conspecifics). We investigate the agonistic behaviour of the whip spider Phrynus marginemaculatus and the role of its trichobothria in …

Composite Effects Of Polymorphisms Near Multiple Regulatory Elements Create A Major-Effect Qtl, Ryan D. Bickel, Artyom Kopp, Sergey V. Nuzhdin

School of Biological Sciences: Faculty Publications

Many agriculturally, evolutionarily, and medically important characters vary in a quantitative fashion. Unfortunately, the genes and sequence variants accounting for this variation remain largely unknown due to a variety of biological and technical challenges. Drosophila melanogaster contains high levels of sequence variation and low linkage disequilibrium, allowing us to dissect the effects of many causative variants within a single locus. Here, we take advantage of these features to identify and characterize the sequence polymorphisms that comprise major effect QTL alleles segregating at the bric-a-brac locus. We show that natural bric-a-brac alleles with large effects on cuticular pigmentation reflect a cumulative …

Epigenetic Regulatory Mechanisms In Plants, Zoya Avramova

School of Biological Sciences: Faculty Publications

Genomes are defined by their primary sequence, which provides the genetic blueprint of a species. Eukaryotic DNA functions within the context of chromatin, which provides additional layers of gene regulation referred to as “epigenetic.” The commonly found definition of epigenetics is that of a “study of heritable changes in genome function that occur without a change in DNA sequence.” However, evidence that neuronal gene-expression states are also regulated by epigenetic mechanisms, despite evidence that neuronal cells do not divide, has opened space for a broader unifying definition that keeps “the sense of prevailing usage but avoids constraints imposed by stringently …

Geographic Distribution: Osteopilus Septentrionalis (Cuban Treefrog). Usa: Florida: Bradford Co., Linda S. Stevenson, Louis A. Somma

Papers in Herpetology

OSTEOPILUS SEPTENTRIONALIS (Cuban Treefrog). USA: FLORIDA: B IlAI)flOIlD Co.: Starke. 703 South Orange Street (29.940 15"N, 82. 11532S'W; WGS84) . 12 December 2009. Linda S. Sleven son. Verified by Melvin P. Gra.mke. Florida Museum of Natural History. University of Florida. UF 162973. First county record (Meshaka et al. 2004. The Exotic Amphibians and Reptiles of Florida. Krieger Publ. Co., Malabar, Florida; Somma 2009. In Nonindigenous Aq uatic Species. USGS: hI rp: II nas.e r.usgs.gov I q ue ries! FactSheet. asp?specieslD=57). One adult collected from inside a mailbox on wall of a residence. Individ ual O. septentrionalis have been sighted at …

Complex Courtship Displays Facilitate Male Reproductive Success And Plasticity In Signaling Across Variable Environments, Dustin Wilgers, Eileen Hebets

Eileen Hebets Publications

Effective signal transmission is essential for communication. In environments where signal transmission is highly variable, signalers may utilize complex signals, which incorporate multiple components and modalities, to maintain effective communication. Male Rabidosa rabida wolf spiders produce complex courtship signals, consisting of both visual and seismic components. We test the hypothesis that the complex signaling of R. rabida contributes to male reproductive success in variable signaling environments. We first examine the condition-dependence of foreleg ornamentation (a presumed visual signal) and seismic signal components and find that both may provide potentially redundant information on foraging history. Next, we assessed reproductive success across …

The Degree Of Response To Increased Predation Risk Corresponds To Male Secondary Sexual Traits, Kasey Fowler-Finn, Eileen Hebets

Eileen Hebets Publications

Secondary sexual traits are expected to reflect a balance between sexual selection and natural selection. We test the hypothesis that plasticity in sexual advertisement behaviors can influence this trade-off, allowing showier traits than expected for a given level of predation risk. Specifically, we tested whether the degree of behavioral plasticity exhibited in response to chemical cues of a co-occurring predatory wolf spider corresponds to courtship rate and the degree of ornamentation in male wolf spiders. Both ornamented (brush-legged) males and non-ornamented males decreased locomotion, decreased their likelihood to court, and increased their time to initiate courtship in response to predator …

Sex Chromosome-Specific Regulation In The Drosophila Male Germline But Little Evidence For Chromosomal Dosage Compensation Or Meiotic Inactivation, Colin D. Meiklejohn, Emily L. Landeen, Jodi M. Cook, Sarah B. Kingan, Daven C. Presgraves

School of Biological Sciences: Faculty Publications

The evolution of heteromorphic sex chromosomes (e.g., XY in males or ZW in females) has repeatedly elicited the evolution of two kinds of chromosome-specific regulation: dosage compensation—the equalization of X chromosome gene expression in males and females— and meiotic sex chromosome inactivation (MSCI)—the transcriptional silencing and heterochromatinization of the X during meiosis in the male (or Z in the female) germline. How the X chromosome is regulated in the Drosophila melanogaster male germline is unclear. Here we report three new findings concerning gene expression from the X in Drosophila testes. First, X chromosome-wide dosage compensation appears to be absent from …

Dur3 Is The Major Urea Transporter In Candida Albicans And Is Co-Regulated With The Urea Amidolyase Dur1,2, Dhammika H. M. L. P Navarathna, Aditi Das, Joachim Morschhauser, Kenneth W. Nickerson, David D. Roberts

Kenneth Nickerson Papers

Hemiascomycetes, including the pathogen Candida albicans, acquire nitrogen from urea using the urea amidolyase Dur1,2, whereas all other higher fungi use primarily the nickel-containing urease. Urea metabolism via Dur1,2 is important for resistance to innate host immunity in C. albicans infections. To further characterize urea metabolism in C. albicans we examined the function of seven putative urea transporters. Gene disruption established that Dur3, encoded by orf 19.781, is the predominant transporter. [¹⁴C]Urea uptake was energy-dependent and decreased approximately sevenfold in a dur3D mutant. DUR1,2 and DUR3 expression was strongly induced by urea, whereas the other putative transporter genes …

Use Of Nape Tags For Marking Offspring Of Precocial Waterbirds, Todd W. Arnold, Daizaburo Shizuka, Bruce E. Lyon, Jeffrey T. Pelayo, Katherine R. Mehl, Joshua J. Traylor, Wendy L. Reed, Courtney L. Amundson

Papers in Ornithology

Individualized markers that allow organisms to be identified without recapture are invaluable for studies of survival, movement, and behavior. Nape tags consisting of brass safety pins with unique combinations of two or three colored plastic beads were used to mark 5,868 American Coot (Fulica americana) chicks and 331 Ruddy Duck (Oxyura jamaicensis), 157 King Eider (Somateria spectabilis) and 664 White-winged Scoter (Melanitta fusca deglandi) ducklings. These markers allowed for documentation of parent-offspring interactions, post-hatching survival, brood movements and brood-mixing behaviors. Nape tags were inexpensive, easy to make, easy to observe with binoculars …

Sparrows Use Multiple Status Signals In Winter Social Flocks, Alexis S. Chaine, Kris A. Tjernell, Daizaburo Shizuka, Bruce E. Lyon

Papers in Ornithology

Status signals are thought to reduce the potential costs of social conflict over resources by advertising social status to other group members and reducing unnecessary contests between individuals of differing abilities. Nearly all studies of status signals to date have focused on single signaling traits, and most studies that have investigated multiple traits did not examine whether different traits are used in different contexts, as is required for them to function as multiple signals. We examined the role of gold and black crown patches of wintering golden-crowned sparrows, Zonotrichia atricapilla, in determining social dominance during experimentally staged encounters between unfamiliar …

Arabidopsis G-Protein Interactome Reveals Connections To Cell Wall Carbohydrates And Morphogenesis, Karsten Klopffleisch, Nguyen Phan, Kelsey Augustin, Robert S. Bayne, Katherine S. Booker, Jose R. Botella, Nicholas C. Carpita, Tyrell Carr, Jin-Gui Chen, Thomas Ryan Cooke, Arwen Frick-Cheng, Erin J. Friedman, Brandon Fulk, Michael G. Hahn, Kun Jiang, Lucia Jorda, Lydia Kruppe, Chenggang Liu, Justine Lorek, Maureen C. Mccann, Antonio Molina, Etsuko N. Moriyama, M. Shahid Mukhtar, Yashwanti Mudgil, Sivakumar Pattathil, John Schwarz, Steven Seta, Matthew Tan, Ulrike Temp, Yuri Trusov, Daisuke Urano, Bastian Welter, Jing Yang, Ralph Panstruga, Joachim F. Uhrig, Alan M. Jones

School of Biological Sciences: Faculty Publications

The heterotrimeric G-protein complex is minimally composed of Ga, Gb, and Gc subunits. In the classic scenario, the G-protein complex is the nexus in signaling from the plasma membrane, where the heterotrimeric G-protein associates with heptahelical G-protein-coupled receptors (GPCRs), to cytoplasmic target proteins called effectors. Although a number of effectors are known in metazoans and fungi, none of these are predicted to exist in their canonical forms in plants. To identify ab initio plant G-protein effectors and scaffold proteins, we screened a set of proteins from the G-protein complex using two-hybrid complementation in yeast. After deep and exhaustive interrogation, we …

Search For First Generation Leptoquark Pair Production In The Electron + Missing Energy + Jets Final State, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, K. Devaughan, Aaron Dominguez, Michael Eads, D Johnston, Ioannis Katsanos, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

We present a search for the pair production of first generation scalar leptoquarks (LQ) in data corresponding to an integrated luminosity of 5.4 fb^-1 collected with the D0 detector at the Fermilab Tevatron Collider in pp collisions at √s= 1.96 TeV. In the channel LQLQ → eqv_eq¹, where q, q¹ are u or d quarks, no significant excess of data over background is observed, and we set a 95% C.L. lower limit of 326 GeV on the LQ mass, assuming equal probabilities of LQ decays to eq and v_{e …}

Measurement Of The T-Channel Single Top Quark Production Cross Section In Pp̅ Collisions At √S= 7 Tev, S. Chatrchyan, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, J Keller, T Kelly, Ilya Kravchenko, J. Lazo-Flores, Helena Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

Electroweak production of the top quark is measured for the first time in pp collisions at √s= 7 TeV, using a data set collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 36 pb^-1. With an event selection optimized for t-channel production, two complementary analyses are performed. The first one exploits the special angular properties of the signal, together with background estimates from the data. The second approach uses a multivariate analysis technique to probe the compatibility with signal topology expected from electroweak top-quark production. The combined measurement of the …

Search For New Physics With A Monojet And Missing Transverse Energy In Pp Collisions At √S= 7 Tev, S. Chatrchyan, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel Claes, Aaron Dominguez, Michael Eads, J Keller, T Kelly, Ilya Kravchenko, J. Lazo-Flores, Helena Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

A study of events with missing transverse energy and an energetic jet is performed using pp collision data at a center-of-mass energy of 7 TeV. The data were collected by the CMS detector at the LHC, and correspond to an integrated luminosity of 36 pb^-1. An excess of these events over standard model contributions is a signature of new physics such as large extra dimensions and unparticles. The number of observed events is in good agreement with the prediction of the standard model, and significant extension of the current limits on parameters of new physics benchmark models is …

Erection Of Ibirhynchus Gen. Nov. (Acanthocephala: Polymorphidae), Based On Molecular And Morphological Data, Martin Garcia-Varela, Gerardo Pérez-Ponce De León, Francisco J. Aznar, Steven A. Nadler

Harold W. Manter Laboratory of Parasitology: Faculty Publications

The genus Southwellina is composed of 3 described species, i.e., S. hispida (the type species), S. dimorpha, and S. macracanthus. All 3 are endoparasites of fish-eating birds that have worldwide distributions. Morphologically, the genus is characterized by possessing a short and compact trunk, 2 fields of spines in the anterior region of the trunk (in at least 1 sex), a short cylindrical proboscis (sometimes with a swollen region armed with numerous longitudinal rows of hooks), a double-walled proboscis receptacle, and 4 tubular cement glands in males. In the current study, specimens identified as S. dimorpha were collected from …

Helminths Of Squirrels (Sciuridae) From Mongolia, David S. Tinnin, Sumiya Ganzorig, Scott Lyell Gardner

Harold W. Manter Laboratory of Parasitology: Faculty Publications

Two species of ground squirrels, Urocitellus undulatus and Spermophilus alashanicus, were collected and examined for parasites from two localities in Mongolia in 1999. A total of 24 individuals of U. undulatus were examined resulting in a total of six taxa of helminths found, including: Ascaris tarbagan, Physaloptera massino, Streptopharagus kutassi, Anoplocephaloides transversaria, Hymenolepis suslica, and Moniliformis sp. This represents four new species records and an additional host record for the country. Two individuals of S. alashanicus were examined and found to be uninfected.

First-Principles Study Of Phase Stability Of Gd-Doped Euo And Eus, J. M. An, S. V. Barabash, Vidvuds Ozolins, Mark Van Schilfgaarde, Kirill D. Belashchenko

Kirill Belashchenko Publications

Phase diagrams of isoelectronic Eu_1−xGd_xO and Eu_1−x Gd_xS quasibinary alloy systems are constructed using first-principles calculations combined with a standard cluster-expansion approach and Monte Carlo simulations. The oxide system has a wide miscibility gap on the Gd-rich side but forms ordered compounds on the Eu-rich side, exhibiting a deep asymmetric convex hull in the formation enthalpy diagram. The sulfide system has no stable compounds. The large difference in the formation enthalpies of the oxide and sulfide compounds is attributed to the contribution of local lattice relaxation, which is sensitive to the anion size. …