Physical Sciences and Mathematics Commons^™

Distinct Pressure Evolution Of Coupled Nematic And Magnetic Orders In Fese, Anna E. Böhmer, Karunakar Kothapalli, Wageesha T. Jayasekara, John M. Wilde, Bing Li, Aashish Sapkota, Benjamin G. Ueland, Pinaki Das, Yumin Xiao, Wenli Bi, Jiyong Zhao, E. Ercan Alp, Sergey L. Bud’Ko, Paul C. Canfield, Alan I. Goldman, Andreas Kreyssig

A. I. Goldman

We present a microscopic study of nematicity and magnetism in FeSe over a wide temperature and pressure range using high-energy x-ray diffraction and time-domain Mössbauer spectroscopy. The low-temperature magnetic hyperfine field increases monotonically up to ∼ 6 GPa. The orthorhombic distortion initially decreases under increasing pressure but is stabilized at intermediate pressures by cooperative coupling to the pressure-induced magnetic order. Close to the reported maximum of the superconducting critical temperature at p = 6.8 GPa , the orthorhombic distortion suddenly disappears and a new tetragonal magnetic phase occurs. The pressure and temperature evolution of the structural and magnetic order parameters …

Heisenberg Model Analysis On Inelastic Powder Neutron Scattering Data Using Parent And K Doped Bamn2as2 Samples, Mehmet Ramazanoglu, Aashish Sapkota, Abhishek Pandey, Jagat Lamsal, Douglas L. Abernathy, Jennifer L. Niedziela, Matthew B. Stone, R. Salci, D. A. Acar, F. O. Oztirpan, Şener Ozonder, Andreas Kreyssig, Alan I. Goldman, David C. Johnston, Robert J. Mcqueeney

A. I. Goldman

Low temperature powder inelastic neutron scattering measurements were performed on three different powder samples; parent BaMn2As2,12.5% K-doped Ba0.875K0.125Mn2As2 and 25% K-doped Ba(0.75)K0.25Mn2As2. The Heisenberg Model involving J1‐J2‐Jz coupling constants were compared to the data by a powder integration routine using Monte Carlo integration methods. The best magnetic parameters were selected using a chi-square test where model intensities were compared to the full (q,E) dependence of magnetic scattering. A key step to this analysis is the characterization of the background which is formed mostly by phonon scattering intensities along with other sources including the magnetic impurity scattering events. The calculated powder …

Antiferromagnetic Stacking Of Ferromagnetic Layers And Doping-Controlled Phase Competition In Ca1−X Srx Co2−Y As2, Bing Li, Yuriy Sizyuk, Nediadath S. Sangeetha, John M. Wilde, Pinaki Das, W. Tian, David C. Johnston, Alan I. Goldman, Andreas Kreyssig, Peter P. Orth, Robert J. Mcqueeney, Benjamin G. Ueland

A. I. Goldman

In search of a quantum phase transition between the two-dimensional (2D) ferromagnetism of CaCo2−yAs2 and stripe-type antiferromagnetism in SrCo2 As2, we instead find evidence for 1D magnetic frustration between magnetic square Co layers. We present neutron-diffraction data for Ca1−x Srx Co2−y As2 that reveal a sequence of x -dependent magnetic transitions which involve different stacking of 2 D ferromagnetically aligned layers with different magnetic anisotropy. We explain the x-dependent changes to the magnetic order by utilizing classical analytical calculations of a 1D Heisenberg model where single-ion magnetic anisotropy and frustration of antiferromagnetic nearest- and next-nearest-layer exchange interactions are all composition …

Crystal Growth, Microstructure, And Physical Properties Of Srmnsb2, Yong Liu, Tao Ma, Warren E. Straszheim, Farhan Islam, Brandt A. Jensen, Wei Tian, Thomas Heitmann, R. A. Rosenberg, John M. Wilde, Bing Li, Andreas Kreyssig, Alan I. Goldman, Benjamin G. Ueland, Robert J. Mcqueeney, David Vaknin

A. I. Goldman

We report on the crystal and magnetic structures and magnetic and transport properties of SrMnSb2 single crystals grown by the self-flux method. Magnetic susceptibility measurements reveal an antiferromagnetic (AFM) transition at TN=295(3) K. Above TN, the susceptibility slightly increases and forms a broad peak at T∼420 K, which is a typical feature of two-dimensional magnetic systems. Neutron diffraction measurements on single crystals confirm the previously reported C-type AFM structure below TN. Both de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) effects are observed in SrMnSb2 single crystals. Analysis of the oscillatory component by a Fourier transform shows that the prominent …

Competing Magnetic Phases And Itinerant Magnetic Frustration In Srco2 As2, Bing Li, Benjamin G. Ueland, W. T. Jayasekara, D. L. Abernathy, N. S. Sangeetha, David C. Johnston, Qing-Ping Ding, Yuji Furukawa, Peter P. Orth, Andreas Kreyssig, Alan I. Goldman, Robert J. Mcqueeney

A. I. Goldman

Whereas magnetic frustration is typically associated with local-moment magnets in special geometric arrangements, here we show that SrCo2As2 is a candidate for frustrated itinerant magnetism. Using inelastic neutron scattering (INS), we find that antiferromagnetic (AF) spin fluctuations develop in the square Co layers of SrCo2As2 below T approximate to 100 K centered at the stripe-type AF propagation vector of (1/2, 1/2), and that their development is concomitant with a suppression of the uniform magnetic susceptibility determined via magnetization measurements. We interpret this switch in spectral weight as signaling a temperature-induced crossover from an instability toward ferromagnetism ordering to an instability …

United States Midwest Soil And Weather Conditions Influence Anaerobic Potentially Mineralizable Nitrogen, Jason D. Clark, Kristen S. Veum, Fabian G. Fernandez, James J. Camberato, Paul R. Carter, Richard B. Ferguson, David W. Franzen, Daniel E. Kaiser, Newell R. Kitchen, Carrie A.M. Laboski, Emerson D. Nafziger, John E. Sawyer, John F. Shanahan

Jason Clark

Nitrogen provided to crops through mineralization is an important factor in N management guidelines. Understanding of the interactive effects of soil and weather conditions on N mineralization needs to be improved. Relationships between anaerobic potentially mineralizable N (PMN_an) and soil and weather conditions were evaluated under the contrasting climates of eight US Midwestern states. Soil was sampled (0–30 cm) for PMN_an analysis before pre-plant N application (PP_0N) and at the V5 development stage from the pre-plant 0 (V5_0N) and 180 kg N ha⁻¹ (V5_180N) rates and incubated for 7, 14, …

Automated Monitoring Of Behaviour In Zebrafish After Invasive Procedures, Anthony G. Deakin, Jonathan Buckley, Hamzah S. Alzu'bi, Andrew R. Cossins, Joseph W. Spencer, Waleed Al'nuaimy, Iain S. Young, Jack S. Thomson, Lynne U. Sneddon

Lynne Sneddon, PhD

Fish are used in a variety of experimental contexts often in high numbers. To maintain their welfare and ensure valid results during invasive procedures it is vital that we can detect subtle changes in behaviour that may allow us to intervene to provide pain-relief. Therefore, an automated method, the Fish Behaviour Index (FBI), was devised and used for testing the impact of laboratory procedures and efficacy of analgesic drugs in the model species, the zebrafish. Cameras with tracking software were used to visually track and quantify female zebrafish behaviour in real time after a number of laboratory procedures including fin …

Synthesis And Evaluation Of Novel Silica Hydride-Based Stationary Phases For Bioanalytical Applications

Seiichiro Watanabe

Closed-Form Probability Distribution Of Number Of Infections At A Given Time In A Stochastic Sis Epidemic Model, Olusegun M. Otunuga

Olusegun Michael Otunuga

We study the effects of external fluctuations in the transmission rate of certain diseases and how these affect the distribution of the number of infected individuals over time. To do this, we introduce random noise in the transmission rate in a deterministic SIS model and study how the number of infections changes over time. The objective of this work is to derive and analyze the closed form probability distribution of the number of infections at a given time in the resulting stochastic SIS epidemic model. Using the Fokker-Planck equation, we reduce the differential equation governing the number of infections to …

Design Of Personnel Big Data Management System Based On Blockchain, Houbing Song, Jian Chen, Zhihan Lv

Houbing Song

With the continuous development of information technology, enterprises, universities and governments are constantly stepping up the construction of electronic personnel information management system. The information of hundreds of thousands or even millions of people’s information are collected and stored into the system. So much information provides the cornerstone for the development of big data, if such data is tampered with or leaked, it will cause irreparable serious damage. However, in recent years, electronic archives have exposed a series of problems such as information leakage, information tampering, and information loss, which has made the reform of personnel information management more and …

Adaboost‑Based Security Level Classifcation Of Mobile Intelligent Terminals, Feng Wang, Houbing Song, Dingde Jiang, Hong Wen

Houbing Song

With the rapid development of Internet of Things, massive mobile intelligent terminals are ready to access edge servers for real-time data calculation and interaction. However, the risk of private data leakage follows simultaneously. As the administrator of all intelligent terminals in a region, the edge server needs to clarify the ability of the managed intelligent terminals to defend against malicious attacks. Therefore, the security level classification for mobile intelligent terminals before accessing the network is indispensable. In this paper, we firstly propose a safety assessment method to detect the weakness of mobile intelligent terminals. Secondly, we match the evaluation results …

Millard Et Al. Pressure Dependence Of Magnesite Creep 2019 Geosciences.Pdf, Caleb Holyoke

Caleb Holyoke

No abstract provided.

Spanning Eulerian Subgraphs And Catlin’S Reduced Graphs, Wei-Guo Chen, Zhi-Hong Chen

Zhi-Hong Chen

A graph G is collapsible if for every even subset R ⊆ V (G), there is a spanning connected subgraph H_R of G whose set of odd degree vertices is R. A graph is reduced if it has no nontrivial collapsible subgraphs. Catlin [4] showed that the existence of spanning Eulerian subgraphs in a graph G can be determined by the reduced graph obtained from G by contracting all the collapsible subgraphs of G. In this paper, we present a result on 3-edge-connected reduced graphs of small orders. Then, we prove that a 3-edge-connected graph G of order n …

Properties Of Catlin’S Reduced Graphs And Supereulerian Graphs, Wei-Guo Chen, Zhi-Hong Chen, Mei Lu

Zhi-Hong Chen

A graph G is called collapsible if for every even subset R ⊆ V (G), there is a spanning connected subgraph H of G such that R is the set of vertices of odd degree in H. A graph is the reduction of G if it is obtained from G by contracting all the nontrivial collapsible subgraphs. A graph is reduced if it has no nontrivial collapsible subgraphs. In this paper, we first prove a few results on the properties of reduced graphs. As an application, for 3-edge-connected graphs G of order n with d(u) + d(v) ≥ 2(n/p − …

Lai’S Conditions For Spanning And Dominating Closed Trails, Wei-Guo Chen, Zhi-Hong Chen, Mei Lu

Zhi-Hong Chen

No abstract provided.

Taking The Metabolic Pulse Of The World's Coral Reefs, Tyler Cyronak, Andreas J. Andersson, Chris Langdon, Rebecca Albright, Nicholas R. Bates, Ken Caldeira, Renee Carlton, Jorge E. Corredor, Rob B. Dunbar, Ian Enochs, Jonathan Erez, Bradley D. Eyre, Jean-Pierre Gattuso, Dwight Gledhill, Hajime Kayanne, David I. Kline, David A. Koweek, Coulson Lantz, Boaz Lazar, Derek Manzello, Ashly Mcmahon, Melissa Melendez, Heather N. Page, Isaac R. Santos, Kai G. Schulz, Emily Shaw, Jacob Silverman, Atsushi Suzuki, Lida Teneva, Atsushi Watanabe, Shoji Yamamoto

Tyler Cyronak

Worldwide, coral reef ecosystems are experiencing increasing pressure from a variety of anthropogenic perturbations including ocean warming and acidification, increased sedimentation, eutrophication, and overfishing, which could shift reefs to a condition of net calcium carbonate (CaCO3) dissolution and erosion. Herein, we determine the net calcification potential and the relative balance of net organic carbon metabolism (net community production; NCP) and net inorganic carbon metabolism (net community calcification; NCC) within 23 coral reef locations across the globe. In light of these results, we consider the suitability of using these two metrics developed from total alkalinity (TA) and dissolved inorganic carbon (DIC) …

Temperature-Induced Viral Resistance In Emiliania Huxleyi (Prymnesiophyceae), B. Jacob Kendrick, Giacomo R. Ditullio, Tyler Cyronak, James M. Fulton, Benjamin A. S. Van Mooy, Kay D. Bidle

Tyler Cyronak

Annual Emiliania huxleyi blooms (along with other coccolithophorid species) play important roles in the global carbon and sulfur cycles. E. huxleyi blooms are routinely terminated by large, host-specific dsDNA viruses, (Emiliania huxleyi Viruses; EhVs), making these host-virus interactions a driving force behind their potential impact on global biogeochemical cycles. Given projected increases in sea surface temperature due to climate change, it is imperative to understand the effects of temperature on E. huxleyi’s susceptibility to viral infection and its production of climatically active dimethylated sulfur species (DSS). Here we demonstrate that a 3°C increase in temperature induces EhV-resistant phenotypes …

Nitrous Oxide And Methane Dynamics In A Coral Reef Lagoon Driven By Pore Water Exchange: Insights From Automated High‐Frequency Observations, Chiara O'Reilly, Isaac R. Santos, Tyler Cyronak, Ashly Mcmahon, Damien T. Maher

Tyler Cyronak

Automated cavity ring down spectroscopy was used to make continuous measurements of dissolved methane, nitrous oxide, and carbon dioxide in a coral reef lagoon for 2 weeks (Heron Island, Great Barrier Reef). Radon (²²²Rn) was used to trace the influence of tidally driven pore water exchange on greenhouse gas dynamics. Clear tidal variation was observed for CH₄, which correlated to ²²²Rn in lagoon waters. N2O correlated to ²²²Rn during the day only, which appears to be a response to coupled nitrification‐denitrification in oxic sediments, fueled by nitrate derived from bird guano. The lagoon was …

Permeable Coral Reef Sediment Dissolution Driven By Elevated Pco2 And Pore Water Advection, Tyler Cyronak, Isaac R. Santos, Bradley D. Eyre

Tyler Cyronak

Ocean acidification (OA) is expected to drive the transition of coral reef ecosystems from net calcium carbonate (CaCO₃) precipitating to net dissolving within the next century. Although permeable sediments represent the largest reservoir of CaCO₃ in coral reefs, the dissolution of shallow CaCO₃ sands under future pCO₂ levels has not been measured under natural conditions. In situ, advective chamber incubations under elevated pCO₂ (~800 µatm) shifted the sediments from net precipitating to net dissolving. Pore water advection more than doubled dissolution rates (1.10 g CaCO₃ m⁻² d⁻¹) when compared to …

Hysteresis Between Coral Reef Calcification And The Seawater Aragonite Saturation State, Ashly Mcmahon, Isaac R. Santos, Tyler Cyronak, Bradley D. Eyre

Tyler Cyronak

Some predictions of how ocean acidification (OA) will affect coral reefs assume a linear functional relationship between the ambient seawater aragonite saturation state (Ω_a) and net ecosystem calcification (NEC). We quantified NEC in a healthy coral reef lagoon in the Great Barrier Reef during different times of the day. Our observations revealed a diel hysteresis pattern in the NEC versus Ω_a relationship, with peak NEC rates occurring before the Ω_a peak and relatively steady nighttime NEC in spite of variable Ω_a. Net ecosystem production had stronger correlations with NEC than light, temperature, nutrients, pH, …

Groundwater And Porewater As Major Sources Of Alkalinity To A Fringing Coral Reef Lagoon (Muri Lagoon, Cook Islands), Tyler Cyronak, Isaac R. Santos, Dirk V. Erler, Bradley D. Eyre

Tyler Cyronak

To better predict how ocean acidification will affect coral reefs, it is important to understand how biogeochemical cycles on reefs alter carbonate chemistry over various temporal and spatial scales. This study quantifies the contribution of shallow porewater exchange (as quantified from advective chamber incubations) and fresh groundwater discharge (as traced by ²²²Rn) to total alkalinity (TA) dynamics on a fringing coral reef lagoon along the southern Pacific island of Rarotonga over a tidal and diel cycle. Benthic alkalinity fluxes were affected by the advective circulation of water through permeable sediments, with net daily flux rates of carbonate alkalinity ranging …

Expanding Aquatic Observations Through Recreation, Robert J. W. Brewin, Kieran Hyder, Andreas J. Andersson, Oliver Billson, Philip J. Bresnahan, Thomas G. Brewin, Tyler Cyronak, Giorgio Dall'olmo, Lee De Mora, George Graham, Thomas Jackson, Dionysios E. Raitsos

Tyler Cyronak

Accurate observations of the Earth system are required to understand how our planet is changing and to help manage its resources. The aquatic environment—including lakes, rivers, wetlands, estuaries, coastal and open oceans—is a fundamental component of the Earth system controlling key physical, biological, and chemical processes that allow life to flourish. Yet, this environment is critically undersampled in both time and space. New and cost-effective sampling solutions are urgently needed. Here, we highlight the potential to improve aquatic sampling by tapping into recreation. We draw attention to the vast number of participants that engage in aquatic recreational activities and argue, …

Drivers Of Pco2 Variability In Two Contrasting Coral Reef Lagoons: The Influence Of Submarine Groundwater Discharge, Tyler Cyronak, Isaac R. Santos, Dirk V. Erler, Damien T. Maher, Bradley D. Eyre

Tyler Cyronak

The impact of groundwater on pCO₂ variability was assessed in two coral reef lagoons with distinct drivers of submarine groundwater discharge (SGD). Diel variability of pCO₂ in the two ecosystems was explained by a combination of biological drivers and SGD inputs. In Rarotonga, a South Pacific volcanic island, ²²²Rn‐derived SGD was driven primarily by a steep terrestrial hydraulic gradient, and the water column was influenced by the high pCO₂ (5501 µatm) of the fresh groundwater. In Heron Island, a Great Barrier Reef coral cay, SGD was dominated by seawater recirculation through the sediments …

Enhanced Acidification Of Global Coral Reefs Driven By Regional Biogeochemical Feedbacks, Tyler Cyronak, Kai G. Schulz, Isaac R. Santos, Bradley D. Eyre

Tyler Cyronak

Physical uptake of anthropogenic CO₂ is the dominant driver of ocean acidification (OA) in the open ocean. Due to expected decreases in calcification and increased dissolution of CaCO₃ framework, coral reefs are thought to be highly susceptible to OA. However, biogeochemical processes can influence the pCO₂ and pH of coastal ecosystems on diel and seasonal time scales, potentially modifying the long‐term effects of increasing atmospheric CO₂. By compiling data from the literature and removing the effects of short‐term variability, we show that the average pCO₂ of coral reefs throughout the globe has increased ~3.5‐fold …

Coral Reef Carbonate Chemistry Variability At Different Functional Scales, Yuichiro Takeshita, Tyler Cyronak, Todd R. Martz, Theodor Kindeberg, Andreas J. Andersson

Tyler Cyronak

There is a growing recognition for the need to understand how seawater carbonate chemistry over coral reef environments will change in a high-CO₂ world to better assess the impacts of ocean acidification on these valuable ecosystems. Coral reefs modify overlying water column chemistry through biogeochemical processes such as net community organic carbon production (NCP) and calcification (NCC). However, the relative importance and influence of these processes on seawater carbonate chemistry vary across multiple functional scales (defined here as space, time, and benthic community composition), and have not been fully constrained. Here, we use Bermuda as a case study to …

Comparing Chemistry And Census-Based Estimates Of Net Ecosystem Calcification On A Rim Reef In Bermuda, Travis A. Courtney, Andreas J. Andersson, Nicholas R. Bates, Andrew R. Collins, Tyler Cyronak, Samantha J. De Putron, Bradley D. Eyre, Rebecca Garley, Eric J. Hochberg, Rodney Johnson, Sylvia Musielewicz, Tim J. Noyes, Christopher L. Sabine, Adrienne J. Sutton, Jessy Toncin, Aline Tribollet

Tyler Cyronak

Coral reef net ecosystem calcification (NEC) has decreased for many Caribbean reefs over recent decades primarily due to changes in benthic community composition. Chemistry-based approaches to calculate NEC utilize the drawdown of seawater total alkalinity (TA) combined with residence time to calculate an instantaneous measurement of NEC. Census-based approaches combine annual growth rates with benthic cover and reef structural complexity to estimate NEC occurring over annual timescales. Here, NEC was calculated for Hog Reef in Bermuda using both chemistry and census-based NEC techniques to compare the mass-balance generated by the two methods and identify the dominant biocalcifiers at Hog Reef. …

Analysis Of Flickr, Snapchat, And Twitter Use For The Modeling Of Visitor Activity In Florida State Parks, Hartwig H. Hochmair, Levente Juhasz

Levente Juhasz

Spatio-temporal information attached to social media posts allows analysts to study human activity and travel behavior. This study analyzes contribution patterns to the Flickr, Snapchat, and Twitter platforms in over 100 state parks in Central and Northern Florida. The first part of the study correlates monthly visitor count data with the number of Flickr images, snaps, or tweets, contributed within the park areas. It provides insight into the suitability of these different social media platforms to be used as a proxy for the prediction of visitor numbers in state parks. The second part of the study analyzes the spatial distribution …

Federal Protection Of Unique Environmental Interests: Endangered And Threatened Species, Ronald H. Rosenberg

Ronald H. Rosenberg

Endangered species protection has long been favored by many Americans, who watched regretfully as the numbers of American eagles, buffaloes and other species dwindled toward extinction. Only recently, however, has species protection become a matter of public controversy, subsumed in the more general "development v. environment" debate. In this Article, Professor Rosenberg surveys the federal government's role in species protection, with a special focus on the Endangered Species Act of 1973. Prompted by the much-publicized Supreme Court decision in the "snail darter case"--TVA v. Hill-Congress extensively amended the Act in 1978. After a detailed analysis of these amendments, Professor Rosenberg …

Molecular Recognition Of Methionine-Terminated Peptides By Cucurbit[8]Uril, Zoheb Hirani, Hailey F. Taylor, E. F. Babcock, Andrew T. Bockus, C. D. Varnado Jr., Christopher W. Bielawski, Adam R. Urbach

Adam R Urbach

This Article describes the molecular recognition of peptides containing an N-terminal methionine (Met) by the synthetic receptor cucurbit[8]-uril (Q8) in aqueous solution and with submicromolar affinity. Prior work established that Q8 binds with high affinity to peptides containing aromatic amino acids, either by simultaneous binding of two aromatic residues, one from each of two different peptides, or by simultaneous binding of an aromatic residue and its immediate neighbor on the same peptide. The additional binding interface of two neighboring residues suggested the possibility of targeting nonaromatic peptides, which have thus far bound only weakly to synthetic receptors. A peptide library …

Antagonistic Effects Of Ocean Acidification And Rising Sea Surface Temperature On The Dissolution Of Coral Reef Carbonate Sediments, Daniel Trnovsky, Laura Stoltenberg, Tyler Cyronak, Bradley D. Eyre

Tyler Cyronak

Increasing atmospheric CO₂ is raising sea surface temperature (SST) and increasing seawater CO₂ concentrations, resulting in a lower oceanic pH (ocean acidification; OA), which is expected to reduce the accretion of coral reef ecosystems. Although sediments comprise most of the calcium carbonate (CaCO₃) within coral reefs, no in situ studies have looked at the combined effects of increased SST and OA on the dissolution of coral reef CaCO₃ sediments. In situ benthic chamber incubations were used to measure dissolution rates in permeable CaCO₃ sands under future OA and SST scenarios in a coral reef …