Science.gov

Sample records for critical field study

  1. Anomalous critical fields in quantum critical superconductors

    PubMed Central

    Putzke, C.; Walmsley, P.; Fletcher, J. D.; Malone, L.; Vignolles, D.; Proust, C.; Badoux, S.; See, P.; Beere, H. E.; Ritchie, D. A.; Kasahara, S.; Mizukami, Y.; Shibauchi, T.; Matsuda, Y.; Carrington, A.

    2014-01-01

    Fluctuations around an antiferromagnetic quantum critical point (QCP) are believed to lead to unconventional superconductivity and in some cases to high-temperature superconductivity. However, the exact mechanism by which this occurs remains poorly understood. The iron-pnictide superconductor BaFe2(As1−xPx)2 is perhaps the clearest example to date of a high-temperature quantum critical superconductor, and so it is a particularly suitable system to study how the quantum critical fluctuations affect the superconducting state. Here we show that the proximity of the QCP yields unexpected anomalies in the superconducting critical fields. We find that both the lower and upper critical fields do not follow the behaviour, predicted by conventional theory, resulting from the observed mass enhancement near the QCP. Our results imply that the energy of superconducting vortices is enhanced, possibly due to a microscopic mixing of antiferromagnetism and superconductivity, suggesting that a highly unusual vortex state is realized in quantum critical superconductors. PMID:25477044

  2. Final report for the field-reversed configuration power plant critical-issue scoping study

    SciTech Connect

    Santarius, John F.; Mogahed, Elsayed A.; Emmert, Gilbert A.; Khater, Hesham Y.; Nguyen, Canh N.; Ryzhkov, Sergei V.; Stubna, Michael D.; Steinhauer, Loren C.; Miley, George H.

    2001-03-01

    This report describes research in which a team from the Universities of Wisconsin, Washington, and Illinois performed a scoping study of critical issues for field-reversed configuration (FRC) power plants. The key tasks for this research were (1) systems analysis of deuterium-tritium (D-T) FRC fusion power plants, and (2) conceptual design of the blanket and shield module for an FRC fusion core.

  3. Field-Reversed Configuration Power Plant Critical-Issue Scoping Study

    SciTech Connect

    Santarius, J. F.; Mogahed, E. A.; Emmert, G. A.; Khater, H. Y.; Nguyen, C. N.; Ryzhkov, S. V.; Stubna, M. D.

    2000-03-31

    A team from the Universities of Wisconsin, Washington, and Illinois performed an engineering scoping study of critical issues for field-reversed configuration (FRC) power plants. The key tasks for this research were (1) systems analysis for deuterium-tritium (D-T) FRC fusion power plants, and (2) conceptual design of the blanket and shield module for an FRC fusion core. For the engineering conceptual design of the fusion core, the project team focused on intermediate-term technology. For example, one decision was to use steele structure. The FRC systems analysis led to a fusion power plant with attractive features including modest size, cylindrical symmetry, good thermal efficiency (52%), relatively easy maintenance, and a high ratio of electric power to fusion core mass, indicating that it would have favorable economics.

  4. A Study on the Effect of Voluntary Retirement of Captains with Prior Service on Field Grade Officer Shortfalls in Critically Manned Mission Support Career Fields

    DTIC Science & Technology

    1989-05-01

    SHORTFALLS IN CRITICALLY (V) MANNED MISSION SUPPORT CAREER FIELDS N*. I LT COL DAVID P. CSINTYAN LT COL CHARLES K . LEONARD LT COL AARON B. ROGERS, JR...FIELDS by David P. Csintyan, Lt Col, USAF Charles K . Leonard, Lt Col, USAF Aaron B. Rogers, Jr., Lt Col, USAF A DEFENSE ANALYTICAL STUDY SUBMITTED TO...Officers School in 1975, Naval Command and Staff College in 1984, and Air War College in 1989. v BIOGRAPHICAL SKETCH Lieutenant Colonel Charles K

  5. Effects of mobile phone electromagnetic fields: critical evaluation of behavioral and neurophysiological studies.

    PubMed

    Kwon, Myoung Soo; Hämäläinen, Heikki

    2011-05-01

    For the last two decades, a large number of studies have investigated the effects of mobile phone radiation on the human brain and cognition using behavioral or neurophysiological measurements. This review evaluated previous findings with respect to study design and data analysis. Provocation studies found no evidence of subjective symptoms attributed to mobile phone radiation, suggesting psychological reasons for inducing such symptoms in hypersensitive people. Behavioral studies previously reported improved cognitive performance under exposure, but it was likely to have occurred by chance due to multiple comparisons. Recent behavioral studies and replication studies with more conservative statistics found no significant effects compared with original studies. Neurophysiological studies found no significant effects on cochlear and brainstem auditory processing, but only inconsistent results on spontaneous and evoked brain electrical activity. The inconsistent findings suggest possible false positives due to multiple comparisons and thus replication is needed. Other approaches such as brain hemodynamic response measurements are promising but the findings are few and not yet conclusive. Rigorous study design and data analysis considering multiple comparisons and effect size are required to reduce controversy in this important field of research.

  6. Outdoor urban nanomaterials: The emergence of a new, integrated, and critical field of study.

    PubMed

    Baalousha, Mohammed; Yang, Yi; Vance, Marina E; Colman, Benjamin P; McNeal, Samantha; Xu, Jie; Blaszczak, Joanna; Steele, Meredith; Bernhardt, Emily; Hochella, Michael F

    2016-07-01

    Engineered nanomaterials (ENMs) are currently widely incorporated in the outdoor urban environmental fabric and numerous new applications and products containing ENMs are expected in the future. As has been shown repeatedly, products containing ENMs have the potential, at some point in their lifetime, to release ENMs into their surrounding environment. However, the expanding body in environmental nanomaterial research has not yet shifted toward ENMs in the context of the complex outdoor urban environment. This is especially surprising because the world's human populations are on a steady march toward more and more urbanization and technological development, accompanied with increased applications for ENMs in the outdoor urban environment. Our objective for this paper is therefore to review, assess, and provide new information in this emerging field. We provide an overview of nanomaterials (NMs, encompassing both ENMs and incidental nanomaterials, INMs) that are likely to be released in the urban environment from outdoor sources by discussing 1) the applications of ENMs that may lead to release of ENMs in urban areas, 2) the recently published data on the release of ENMs from novel nano-enabled applications in the outdoor urban environment, 3) the available literature on the occurrence of INMs in the atmosphere and within/on dust particles, and 4) the potential pathways and fate of NMs in the outdoor urban environment. This review is then followed by three case studies demonstrating the importance of NMs in the outdoor urban environment. The first and second case studies illustrate the occurrence of NMs in urban dust and stormwater ponds, respectively, whereas the third case study discusses the lessons learned from the release of NMs (e.g. Pt, ph and Rh) from automotive vehicle catalytic convertors. This article ends with a discussion of the research priorities needed to advance this emerging field of "outdoor urban nanomaterials" and to assess the potential risks

  7. Critical analysis of soil invertebrate biomarkers: a field case study in Avonmouth, UK.

    PubMed

    Weeks, Jason M; Spurgeon, David J; Svendsen, Claus; Hankard, Peter K; Kammenga, Jan E; Dallinger, Reinhard; Köhler, Heinz-R; Simonsen, Vibeke; Scott-Fordsmand, Janeck

    2004-11-01

    During the period 1996-1999 a joint field research programme (BIOPRINT-II) funded by the European Union was undertaken. The main objective of this project was the deployment of biochemical fingerprint techniques of soil invertebrate biomarkers for assessing the exposure and effect of toxicants on soil invertebrates in the field. The aim was to apply these techniques in the field focusing on a a chronically polluted field near a lead and zinc smelter in Avonmouth (UK). Therefore six sites were selected from which organisms were either sampled or transplanted to or from the laboratory. The project has provided a unique opportunity to apply a series of biological test methodologies in order to determine the hazard posed to soil sustainability and by inference soil biodiversity and function. This work has attempted to understand the linkage between effects measured at the molecular or cellular level and relate these to changes at higher levels of biological organisation. Here we evaluated the links between biomarkers and soil function parameters. The paper aims to summarize and explore the necessary caveats that must be understood before soil biomarker test systems may be used to strengthen the risk assessment process.

  8. Upper critical field and AC-Susceptibility studies on FeTe0.5Se0.5 superconductor

    NASA Astrophysics Data System (ADS)

    Zargar, Rayees A.; Pal, Anand; Hafiz, A. K.; Awana, V. P. S.

    2015-06-01

    In this study we present synthesis and characterization of FeTe0.5Se0.5 sample that has been prepared by solid state reaction route by encapsulation of stoichiometric high purity (5N) ingredients in an evacuated quartz tube at 750 °C. The resultant compound is crystallized in single phase tetragonal structure with space group P4/nmm, having lattice parameters a = 3.792(1) Å and c = 6.0081(3) Å. The studied compound is superconducting at below 13K in both magnetic and transport measurements. Further superconductivity is barely affected by external applied magnetic field, giving rise to upper critical field of above 180 Tesla at 0 K. The sample is studied extensively for AC susceptibility measurements in superconducting state. The AC drive field and frequency are varied from 1-13 Oe and 33-9999 Hz respectively. It is concluded that though the grain boundaries of this superconductor are mainly metallic the minor (undetectable in XRD) foreign phases and the role of porosity cannot be ruled out completely. This is because both frequency and amplitude affects slightly the superconductivity coupling temperature of the grains.

  9. Trace Metal Bioremediation: Assessment of Model Components from Laboratory and Field Studies to Identify Critical Variables

    SciTech Connect

    Peter Jaffe; Herschel Rabitz

    2003-02-14

    The objective of this project was to gain an insight into the modeling support needed for the understanding, design, and operation of trace metal/radionuclide bioremediation. To achieve this objective, a workshop was convened to discuss the elements such a model should contain. A ''protomodel'' was developed, based on the recommendations of the workshop, and was used to perform sensitivity analysis as well as some preliminary simulations in support for bioremediation test experiments at UMTRA sites. To simulate the numerous biogeochemical processes that will occur during the bioremediation of uranium contaminated aquifers, a time-dependent one-dimensional reactive transport model has been developed. The model consists of a set of coupled, steady state mass balance equations, accounting for advection, diffusion, dispersion, and a kinetic formulation of the transformations affecting an organic substrate, electron acceptors, corresponding reduced species, and uranium. This set of equations is solved numerically, using a finite element scheme. The redox conditions of the domain are characterized by estimating the pE, based on the concentrations of the dominant terminal electron acceptor and its corresponding reduced specie. This pE and the concentrations of relevant species are passed to a modified version of MINTEQA2, which calculates the speciation and solubilities of the species of interest. Kinetics of abiotic reactions are described as being proportional to the difference between the actual and equilibrium concentration. A global uncertainty assessment, determined by Random Sampling High Dimensional Model Representation (RS-HDMR), was performed to attain a phenomenological understanding of the origins of output variability and to suggest input parameter refinements as well as to provide guidance for field experiments to improve the quality of the model predictions. Results indicated that for the usually high nitrate contents found ate many DOE sites, overall

  10. Critical Magnetic Field Determination of Superconducting Materials

    SciTech Connect

    Canabal, A.; Tajima, T.; Dolgashev, V.A.; Tantawi, S.G.; Yamamoto, T.; /Tsukuba, Natl. Res. Lab. Metrol.

    2011-11-04

    Superconducting RF technology is becoming more and more important. With some recent cavity test results showing close to or even higher than the critical magnetic field of 170-180 mT that had been considered a limit, it is very important to develop a way to correctly measure the critical magnetic field (H{sup RF}{sub c}) of superconductors in the RF regime. Using a 11.4 GHz, 50-MW, <1 {mu}s, pulsed power source and a TE013-like mode copper cavity, we have been measuring critical magnetic fields of superconductors for accelerator cavity applications. This device can eliminate both thermal and field emission effects due to a short pulse and no electric field at the sample surface. A model of the system is presented in this paper along with a discussion of preliminary experimental data.

  11. Flow Field Classification Using Critical Point Matching

    NASA Astrophysics Data System (ADS)

    Krueger, Paul S.; Williams, Sheila; Hahsler, Michael; Olinick, Eli V.

    2016-11-01

    Classification of flow fields according to topological similarities can help reveal features of the flow generation and evolution for bluff body flows, and characterize different swimming maneuvers in aquatic locomotion, to name a few. Rigorous classification can be challenging, however, especially when complex flows are distorted by measurement uncertainties or variable flow generating conditions. The present work uses critical points of the velocity field to characterize the global flow topology. Flow fields are compared by finding a best match of critical points in two flow fields based on topological and location characteristics of the critical points together with general point set distance measures. The similarity between the flow fields is quantified based on the matched critical points. Applying clustering algorithms to a set of flow fields with quantified similarity can then be used to group flows with similar characteristics. This approach has been applied to generic 2D flow fields constructed using potential flow results and is able to correctly identify similar flow fields even after large distortions (up to 20% of the vortex separation) have been applied to the flows. Support of NSF Grant Nos. 1115139 and 1557698, and the Lyle School of Engineering is gratefully acknowledged.

  12. Critical Density Interaction Studies

    SciTech Connect

    Young, P; Baldis, H A; Cheung, P; Rozmus, W; Kruer, W; Wilks, S; Crowley, S; Mori, W; Hansen, C

    2001-02-14

    Experiments have been performed to study the propagation of intense laser pulses to high plasma densities. The issue of self-focusing and filamentation of the laser pulse as well as developing predictive capability of absorption processes and x-ray conversion efficiencies is important for numerous programs at the Laboratory, particularly Laser Program (Fast Ignitor and direct-drive ICF) and D&NT (radiography, high energy backlighters and laser cutting). Processes such as resonance absorption, profile modification, linear mode conversion, filamentation and stimulated Brillouin scattering can occur near the critical density and can have important effects on the coupling of laser light to solid targets. A combination of experiments have been used to study the propagation of laser light to high plasma densities and the interaction physics of intense laser pulses with solid targets. Nonparaxial fluid codes to study nonstationary behavior of filamentation and stimulated Brillouin scattering at high densities have also been developed as part of this project.

  13. Magnetic-field induced critical endpoint

    NASA Astrophysics Data System (ADS)

    Rechenberger, Stefan

    2017-03-01

    The phase diagram of strong interaction matter is analyzed utilizing the Nambu-Jona-Lasinio model. Special emphasis is placed on its dependence on an external magnetic field and isospin chemical potential. Using flavor mixing induced by instanton effects the influence of isospin breaking due to the magnetic field and the isospin chemical potential is compared. It is found that at low temperatures and large quark chemical potential the magnetic field, depending on its strength, induces a new critical endpoint or a triple point.

  14. Upper critical field of copper molybdenum sulfide

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Woollam, J. A.

    1978-01-01

    The upper critical field of sintered and sputtered copper molybdenum sulfide Cu(x)Mo6S8 was measured and found to exceed the Werthamer, Helfand, and Hohenberg (1966) value for a type II superconductor characterized by dirty limit, weak isotropic electron phonon coupling, and no paramagnetic limiting. It is suggested that the enhancement results from anisotropy or clean limit or both. Other ternary molybdenum sulfides appear to show similar anomalies.

  15. Critical Number of Fields in Stochastic Inflation.

    PubMed

    Vennin, Vincent; Assadullahi, Hooshyar; Firouzjahi, Hassan; Noorbala, Mahdiyar; Wands, David

    2017-01-20

    Stochastic effects in generic scenarios of inflation with multiple fields are investigated. First passage time techniques are employed to calculate the statistical moments of the number of inflationary e-folds, which give rise to all correlation functions of primordial curvature perturbations through the stochastic δN formalism. The number of fields is a critical parameter. The probability of exploring arbitrarily large-field regions of the potential becomes nonvanishing when more than two fields are driving inflation. The mean number of e-folds can be infinite, depending on the number of fields; for plateau potentials, this occurs even with one field. In such cases, correlation functions of curvature perturbations are infinite. They can, however, be regularized if a reflecting (or absorbing) wall is added at large energy or field value. The results are found to be independent of the exact location of the wall and this procedure is, therefore, well defined for a wide range of cutoffs, above or below the Planck scale. Finally, we show that, contrary to single-field setups, multifield models can yield large stochastic corrections even at sub-Planckian energy, opening interesting prospects for probing quantum effects on cosmological fluctuations.

  16. Critical Number of Fields in Stochastic Inflation

    NASA Astrophysics Data System (ADS)

    Vennin, Vincent; Assadullahi, Hooshyar; Firouzjahi, Hassan; Noorbala, Mahdiyar; Wands, David

    2017-01-01

    Stochastic effects in generic scenarios of inflation with multiple fields are investigated. First passage time techniques are employed to calculate the statistical moments of the number of inflationary e -folds, which give rise to all correlation functions of primordial curvature perturbations through the stochastic δ N formalism. The number of fields is a critical parameter. The probability of exploring arbitrarily large-field regions of the potential becomes nonvanishing when more than two fields are driving inflation. The mean number of e -folds can be infinite, depending on the number of fields; for plateau potentials, this occurs even with one field. In such cases, correlation functions of curvature perturbations are infinite. They can, however, be regularized if a reflecting (or absorbing) wall is added at large energy or field value. The results are found to be independent of the exact location of the wall and this procedure is, therefore, well defined for a wide range of cutoffs, above or below the Planck scale. Finally, we show that, contrary to single-field setups, multifield models can yield large stochastic corrections even at sub-Planckian energy, opening interesting prospects for probing quantum effects on cosmological fluctuations.

  17. High-pressure study of the basal-plane anisotropy of the upper critical field of the topological superconductor SrxBi2Se3

    NASA Astrophysics Data System (ADS)

    Nikitin, A. M.; Pan, Y.; Huang, Y. K.; Naka, T.; de Visser, A.

    2016-10-01

    We report a high-pressure transport study of the upper-critical field Bc 2(T ) of the topological superconductor Sr0.15Bi2Se3 (Tc=3.0 K). Bc 2(T ) was measured for magnetic fields directed along two orthogonal directions, a and a*, in the trigonal basal plane. While superconductivity is rapidly suppressed at the critical pressure pc˜3.5 GPa, the pronounced two-fold basal-plane anisotropy Bc2 a/Bc2 a*=3.2 at T =0.3 K, recently reported at ambient pressure [Pan et al., Sci. Rep. 6, 28632 (2016), 10.1038/srep28632], is reinforced and attains a value of ˜5 at the highest pressure (2.2 GPa). The data reveal that the unconventional superconducting state with broken rotational symmetry is robust under pressure.

  18. Minimum Critical Values Study

    SciTech Connect

    Fox, P.B.

    2005-07-11

    This report provides minimum critical values for various 30-cm water-reflected uranium and plutonium oxide and nitrate aqueous mixtures as calculated by the SCALE CSAS1X sequence using the 238-group ENDF/B-V neutron cross-section library. The minimum values were determined through parametric searches in one-dimensional geometry. The calculations have been performed to obtain the minimum values: critical volume and mass for spheres, critical radius for cylinders, critical thickness for slabs, and minimum critical concentration (infinite geometry) for the following homogeneous mixtures: (1) UO{sub 2}-H{sub 2}O for 3, 4, 5, 20, and 100 wt % {sup 235}U; (2) UNH for 3, 4, 5, 20, and 100 wt % {sup 235}U; (3) PuO{sub 2}-H{sub 2}O for 100/0/0, 95/5/0, 90/5/5, 80/10/10, and 71/17/11/1 wt % of {sup 239}Pu/{sup 240}Pu/{sup 241}Pu(/{sup 242}Pu); and (4) PuNH for 100/0/0, 95/5/0, 90/5/5, 80/10/10, and 71/17/11/1 wt % of {sup 239}Pu/{sup 240}Pu/{sup 241}Pu(/{sup 242}Pu). All bounding surfaces were fully reflected by 30 cm of H{sub 2}O.

  19. Molecular dynamics study of combustion reactions in supercritical environment. Part 1: Carbon dioxide and water force field parameters refitting and critical isotherms of binary mixtures

    SciTech Connect

    Masunov, Artem E.; Atlanov, Arseniy Alekseyevich; Vasu, Subith S.

    2016-10-04

    Oxy-fuel combustion process is expected to drastically increase the energy efficiency and enable easy carbon sequestration. In this technology the combustion products (carbon dioxide and water) are used to control the temperature and nitrogen is excluded from the combustion chamber, so that nitrogen oxide pollutants do not form. Therefore, in oxycombustion the carbon dioxide and water are present in large concentrations in their transcritical state, and may play an important role in kinetics. The computational chemistry methods may assist in understanding these effects, and Molecular Dynamics with ReaxFF force field seem to be a suitable tool for such a study. Here we investigate applicability of the ReaxFF to describe the critical phenomena in carbon dioxide and water and find that several nonbonding parameters need adjustment. We report the new parameter set, capable to reproduce the critical temperatures and pressures. Furthermore, the critical isotherms of CO2/H2O binary mixtures are computationally studied here for the first time and their critical parameters are reported.

  20. Molecular dynamics study of combustion reactions in supercritical environment. Part 1: Carbon dioxide and water force field parameters refitting and critical isotherms of binary mixtures

    DOE PAGES

    Masunov, Artem E.; Atlanov, Arseniy Alekseyevich; Vasu, Subith S.

    2016-10-04

    Oxy-fuel combustion process is expected to drastically increase the energy efficiency and enable easy carbon sequestration. In this technology the combustion products (carbon dioxide and water) are used to control the temperature and nitrogen is excluded from the combustion chamber, so that nitrogen oxide pollutants do not form. Therefore, in oxycombustion the carbon dioxide and water are present in large concentrations in their transcritical state, and may play an important role in kinetics. The computational chemistry methods may assist in understanding these effects, and Molecular Dynamics with ReaxFF force field seem to be a suitable tool for such a study.more » Here we investigate applicability of the ReaxFF to describe the critical phenomena in carbon dioxide and water and find that several nonbonding parameters need adjustment. We report the new parameter set, capable to reproduce the critical temperatures and pressures. Furthermore, the critical isotherms of CO2/H2O binary mixtures are computationally studied here for the first time and their critical parameters are reported.« less

  1. Education Studies: Issues & Critical Perspectives

    ERIC Educational Resources Information Center

    Kassem, Derek; Mufti, Emmanuel; Robinson, John

    2006-01-01

    This major text for Education Studies students provides a critical account of key issues in education today. The text features: (1) A critical analysis of key issues in Education Studies to encourage students' thinking about education in the broadest terms; (2) Themed sections with introductions to link the issues discussed in each chapter; (3)…

  2. Critical endpoint behavior: A Wang Landau study

    NASA Astrophysics Data System (ADS)

    Landau, D. P.; Wang, Fugao; Tsai, Shan-Ho

    2008-07-01

    We study the critical endpoint behavior using an asymmetric Ising model with two- and three-body interactions on a triangular lattice, in the presence of an external field. The simulation method we use is Wang-Landau sampling in a two-dimensional parameter space. We observe a clear divergence of the curvature of the spectator phase boundary and of the magnetization coexistence diameter derivative at the critical endpoint, and the exponents for both divergences agree well with previous theoretical predictions.

  3. Critical behavior in black hole scalar field interaction

    NASA Astrophysics Data System (ADS)

    Crespo, J. A.; de Oliveira, H. P.

    2015-09-01

    We study the critical behavior at the threshold of black hole formation in a model consisting of a scalar field incident to a reflector barrier enclosing a Schwarzschild black hole. Weak incident scalar field waves disturb slightly the black hole spacetime and are completely radiated by the reflector, like water waves striking against the wall of a dam. Strong incident waves produce the formation of an apparent horizon outside the barrier. In this case, a fraction of scalar field crosses the horizon together with the barrier, whereas another fraction escapes to infinity. We have integrated the field equations using a Galerkin collocation code that allowed the necessary accuracy to investigate the behavior of the black hole masses for a broad range of scalar field initial amplitude. We have shown that a scaling law describes the black hole masses for amplitudes very close to the critical value. In the limit of very strong scalar fields, the black hole masses either scale linearly with the initial amplitude or saturate depending on the existence of the initial monopole moment.

  4. Retrospective dosimetry after criticality accidents using low-frequency EPR: a study of whole human teeth irradiated in a mixed neutron and gamma-radiation field.

    PubMed

    Zdravkova, M; Crokart, N; Trompier, F; Asselineau, B; Gallez, B; Gaillard-Lecanu, E; Debuyst, R

    2003-08-01

    In the context of accidental or intentional radiation exposures (nuclear terrorism), it is essential to separate rapidly those individuals with substantial exposures from those with exposures that do not constitute an immediate threat to health. Low-frequency electron paramagnetic resonance (EPR) spectroscopy provides the potential advantage of making accurate and sensitive measurements of absorbed radiation dose in teeth without removing the teeth from the potential victims. Up to now, most studies focused on the dose-response curves obtained for gamma radiation. In radiation accidents, however, the contribution of neutrons to the total radiation dose should not be neglected. To determine how neutrons contribute to the apparent dose estimated by EPR dosimetry, extracted whole human teeth were irradiated at the SILENE reactor in a mixed neutron and gamma-radiation field simulating criticality accidents. The teeth were irradiated in free air as well as in a paraffin head phantom. Lead screens were also used to eliminate to a large extent the contribution of the gamma radiation to the dose received by the teeth. The EPR signals, obtained with a low-frequency (1.2 GHz) spectrometer, were compared to dosimetry measurements at the same location. The contribution of neutrons to the EPR dosimetric signal was negligible in the range of 0 to 10 Gy and was rather small (neutron/gamma-ray sensitivity in the range 0-0.2) at higher doses. This indicates that the method essentially provides information on the dose received from the gamma-ray component of the radiation.

  5. Effective critical electric field for runaway-electron generation.

    PubMed

    Stahl, A; Hirvijoki, E; Decker, J; Embréus, O; Fülöp, T

    2015-03-20

    In this Letter we investigate factors that influence the effective critical electric field for runaway-electron generation in plasmas. We present numerical solutions of the kinetic equation and discuss the implications for the threshold electric field. We show that the effective electric field necessary for significant runaway-electron formation often is higher than previously calculated due to both (1) extremely strong dependence of primary generation on temperature and (2) synchrotron radiation losses. We also address the effective critical field in the context of a transition from runaway growth to decay. We find agreement with recent experiments, but show that the observation of an elevated effective critical field can mainly be attributed to changes in the momentum-space distribution of runaways, and only to a lesser extent to a de facto change in the critical field.

  6. Field Structure of a Quasisoliton Approaching the Critical Point

    NASA Astrophysics Data System (ADS)

    Gorshkov, K. A.; Soustova, I. A.; Ermoshkin, A. V.

    2016-03-01

    Within the framework of an approximate approach based on the representation of the Gardnerequation solitons as compound structures (different-polarity kinks), the non-quasistationary evolution of such solitary waves, which is stipulated by the variable quadratic-nonlinearity parameter α. The structure of the composite soliton is studied in cases that are critical for the quasistationary description where the predicted increase in the solitary-wave scales becomes unbounded on finite spatio-temporal intervals. The dependence of the spatial scales of the quasisoliton-field distribution on the quadratic-nonlinearity coefficient near the critical point for the power-law time dependence α(t) is studied in detail. The obtained solution is compared with the results of direct numerical simulation of the Gardner equation with variable coefficients.

  7. Technique development for uiper critical field studies of SmFeAs(O,F) in the 300T single turn system

    SciTech Connect

    Mcdonald, Ross D; Balakirev, F. F.; Altarawneh, M. M.; Betts, J; Mielke, C. H.; Moll, Philip Jw; Zhigadlo, N D; Karpinski, J; Batlogg, B.

    2011-01-14

    In high temperature superconductors, such as the most recent class of iron pnictides, extremely high upper critical fields H{sub c2} are common. The determination of H{sub c2}(T) is crucial to understand the detailed nature of the superconductor, in particular H{sub c2}(T = 0K) is of great interest. It is not only related to fundamental properties of the system, it is furthermore of great importance for materials science, as it is the ultimate limit of applicability of this superconductor in high field applications. However, this important quantity can only be estimated by extrapolation, as H{sub c2}(T = 0K) well exceeds hundreds of Tesla in optimally doped SillFeAs(O,F). We are developing methods to measure Ha(T) in direct transport in the extreme magnetic fields generated by the LANL single turn magnet.

  8. Determination of the Upper Critical Field of a Single Crystal LiFeAs: The Magnetic Torque Study up to 35 Tesla

    NASA Astrophysics Data System (ADS)

    Kurita, Nobuyuki; Kitagawa, Kentaro; Matsubayashi, Kazuyuki; Kismarahardja, Ade; Choi, Eun-Sang; Brooks, James S.; Uwatoko, Yoshiya; Uji, Shinya; Terashima, Taichi

    2011-01-01

    We report on the upper critical field Bc2 of a superconducting LiFeAs single crystal with Tc ˜ 16 K, determined from magnetic torque measurements in dc-magnetic fields up to 35 T and at temperatures down to 0.3 K. Bc2 at 0.3 K is obtained to be 26.4 and 15.5 T for the applied field Ba \\parallel ab and Ba \\parallel c, respectively. The anisotropy param eter Γ = Bc2ab/Bc2c is ˜3 at Tc and decreases to 1.7 as T → 0, showing rather isotropic superconductivity. While Bc2 is orbitally-limited for Ba \\parallel c, the spin-paramagnetic effect is evident in the temperature dependence of Bc2 for Ba \\parallel ab.

  9. Critical Theory and Information Studies: A Marcusean Infusion

    ERIC Educational Resources Information Center

    Pyati, Ajit K.

    2006-01-01

    In the field of library and information science, also known as information studies, critical theory is often not included in debates about the discipline's theoretical foundations. This paper argues that the critical theory of Herbert Marcuse, in particular, has a significant contribution to make to the field of information studies. Marcuse's…

  10. Profiling of energy deposition fields in a modular HTHR with annular core: Computational/experimental studies at the ASTRA critical facility

    SciTech Connect

    Boyarinov, V. F.; Garin, V. P.; Glushkov, E. S.; Zimin, A. A.; Kompaniets, G. V.; Nevinitsa, V. A.; Polyakov, D. N.; Ponomarev, A. S.; Ponomarev-Stepnoi, N. N.; Smirnov, O. N.; Fomichenko, P. A.; Chunyaev, E. I.; Marova, E. V.; Sukharev, Yu. P.

    2010-12-15

    The paper presents the results obtained from the computational/experimental studies of the spatial distribution of the {sup 235}U fission reaction rate in a critical assembly with an annular core and poison profiling elements inserted into the inner graphite reflector. The computational analysis was carried out with the codes intended for design computation of an HTHR-type reactor.

  11. Participative Critical Enquiry in Graduate Field-Based Learning

    ERIC Educational Resources Information Center

    Reilly, Kathy; Clavin, Alma; Morrissey, John

    2016-01-01

    This paper outlines a critical pedagogic approach to field-based learning (FBL) at graduate level. Drawing on student experience stemming from a FBL module and as part of an MA programme in Environment, Society and Development, the paper addresses the complexities associated with student-led, participative critical enquiry during fieldwork in…

  12. Zero-field quantum critical point in CeCoIn5.

    PubMed

    Tokiwa, Y; Bauer, E D; Gegenwart, P

    2013-09-06

    Quantum criticality in the normal and superconducting states of the heavy-fermion metal CeCoIn5 is studied by measurements of the magnetic Grüneisen ratio ΓH and specific heat in different field orientations and temperatures down to 50 mK. A universal temperature over magnetic field scaling of ΓH in the normal state indicates a hidden quantum critical point at zero field. Within the superconducting state, the quasiparticle entropy at constant temperature increases upon reducing the field towards zero, providing additional evidence for zero-field quantum criticality.

  13. Magnetic field dependence of critical currents in superconducting polycrystals

    SciTech Connect

    Kugel, K.I.; Lisovskaya, T.Y. ); Mints, R.G. )

    1992-02-10

    The authors study the dependence of critical current j{sub c} on magnetic field H in superconducting polycrystals which are considered as system of superconducting crystallites (isotropic or anisotropic) with Josephson contacts between them. Isotropy or anisotropy of contacts depends on the orientation of their crystallographic axes relatively to edges of contact planes. In this paper it is shown that for a system of randomly oriented isotropic contacts, the dependence j{sub c}(H) in a relatively wide field range has the asymptotic form j{sub c} {approximately} (InH)/H{sup 2}. This differs drastically from j{sub c}(H) for single contacts. Anisotropy effects due to large differences in London penetration depth {lambda} values corresponding to external magnetic field directed along different axes are analyzed in detail. It is shown that for uniaxal crystals with {lambda}{sub 1} = {lambda}{sub 2} {lt} {lambda}{sub 3}, this anisotropy leads to the relation j{sub c} {approximately} {radical}{lambda}{sub 3}/{lambda}{sub 1} for chaotic orientation of crystallites. The form of j{sub c}(H) curves for two different orientations of the magnetic field relatively to the transport current through the sample is found.

  14. Magnetic field and temperature dependence of the critical vortex velocity in type-II superconducting films.

    PubMed

    Grimaldi, G; Leo, A; Cirillo, C; Attanasio, C; Nigro, A; Pace, S

    2009-06-24

    We study the vortex dynamics in the instability regime induced by high dissipative states well above the critical current in Nb superconducting strips. The magnetic field and temperature behavior of the critical vortex velocity corresponding to the observed dynamic instability is ascribed to intrinsic non-equilibrium phenomena. The Larkin-Ovchinnikov (LO) theory of electronic instability in high velocity vortex motion has been applied to interpret the temperature dependence of the critical vortex velocity. The magnetic field dependence of the vortex critical velocity shows new features in the low-field regime not predicted by LO.

  15. Static Magnetic Field Therapy: A Critical Review of Treatment Parameters

    PubMed Central

    Wahbeh, Helané; Harling, Noelle; Connelly, Erin; Schiffke, Heather C.; Forsten, Cora; Gregory, William L.; Markov, Marko S.; Souder, James J.; Elmer, Patricia; King, Valerie

    2009-01-01

    Static magnetic field (SMF) therapy, applied via a permanent magnet attached to the skin, is used by people worldwide for self-care. Despite a lack of established SMF dosage and treatment regimens, multiple studies are conducted to evaluate SMF therapy effectiveness. Our objectives in conducting this review are to:(i) summarize SMF research conducted in humans; (ii) critically evaluate reporting quality of SMF dosages and treatment parameters and (iii) propose a set of criteria for reporting SMF treatment parameters in future clinical trials. We searched 27 electronic databases and reference lists. Only English language human studies were included. Excluded were studies of electromagnetic fields, transcranial magnetic stimulation, magnets placed on acupuncture points, animal studies, abstracts, posters and editorials. Data were extracted on clinical indication, study design and 10 essential SMF parameters. Three reviewers assessed quality of reporting and calculated a quality assessment score for each of the 10 treatment parameters. Fifty-six studies were reviewed, 42 conducted in patient populations and 14 in healthy volunteers. The SMF treatment parameters most often and most completely described were site of application, magnet support device and frequency and duration of application. Least often and least completely described were characteristics of the SMF: magnet dimensions, measured field strength and estimated distance of the magnet from the target tissue. Thirty-four (61%) of studies failed to provide enough detail about SMF dosage to permit protocol replication by other investigators. Our findings highlight the need to optimize SMF dosing parameters for individual clinical conditions before proceeding to a full-scale clinical trial. PMID:18955243

  16. Critical validation studies of neurofeedback.

    PubMed

    Gruzelier, John; Egner, Tobias

    2005-01-01

    The field of neurofeedback training has proceeded largely without validation. In this article the authors review studies directed at validating sensory motor rhythm, beta and alpha-theta protocols for improving attention, memory, and music performance in healthy participants. Importantly, benefits were demonstrable with cognitive and neurophysiologic measures that were predicted on the basis of regression models of learning to enhance sensory motor rhythm and beta activity. The first evidence of operant control over the alpha-theta ratio is provided, together with remarkable improvements in artistic aspects of music performance equivalent to two class grades in conservatory students. These are initial steps in providing a much needed scientific basis to neurofeedback.

  17. Quantum size effect on the paramagnetic critical field in free-standing superconducting nanofilms.

    PubMed

    Wójcik, P; Zegrodnik, M

    2014-11-12

    The quantum size effect on the in-plane paramagnetic critical field in Pb(1 1 1) free-standing nanofilms is investigated with the use of the spin-generalized Bogoliubov-de Gennes equations. It is shown that the critical field oscillates as a function of the nanofilm thickness with the period ∼ 2 ML (even-odd oscillations), modulated by the beating effect. The calculated values of the critical field for different nanofilm thicknesses are analyzed in the context of the Clogston-Chandrasekhar limit. It is found that the critical field for superconducting nanofilms differs from this limit. This phenomena is explained in terms of quantization of the electron energy caused by the confinement of electron motion in a direction perpendicular to the film. The thermal effect and thickness-dependence of electron-phonon coupling on the value of the critical magnetic field are also studied.

  18. Upper critical field of Mo-Ni heterostructures

    SciTech Connect

    Uher, C.; Watson, W.J.; Cohn, J.L.; Schuller, I.K.

    1985-12-01

    Upper critical field and its anisotropy have been measured on two very short wavelength Mo-Ni heterostructures of different degrees of perfection, lambda = 13.8A (disordered structure) and lambda = 16.6A (layered structure). In both cases the parallel critical field has an unexpected temperature dependence, a large and temperature dependent anisotropy, and over 60% enhancement over the Clogston-Chandrasekhar limit. Data are fit to the Werthamer-Helfand-Hohenberg theory and the spin-orbit scattering times are found to be 1.79 x 10 T s and 2 x 10 T s, respectively.

  19. Electric field measurements during the Condor critical velocity experiment

    NASA Technical Reports Server (NTRS)

    Kelley, M. C.; Pfaff, R. F.; Haerendel, G.

    1986-01-01

    The instrumentation of the Condor critical velocity Ba experiment (Wescott et al., 1986) for the measurements of the energetic particles and the electric field associated with a Ba explosion is described. The Ba explosion created a complex electric field pulse detected in situ by a single-axis double electric-field probe on a separate spacecraft. The measurements provide evidence of several important links in the critical-velocity chain, and are consistent with two hypotheses. The first hypothesis involves the creation of large polarization electric field due to charge separation; the second hypothesis implies a polarization of the beam by currents flowing across it. The chain of physical processes inferred from the observations is in agreement with most theories for the Alfven process.

  20. Unusual Critical Field Behavior in (TMTSF)_2X

    NASA Astrophysics Data System (ADS)

    Lee, I. J.; Naughton, M. J.; Danner, G. M.; Chaikin, P. M.

    1996-03-01

    Upper critical magnetic field phase diagrams have been determined along the three principal directions in the X=ClO4 and X=PF6 superconductors with high angular precision. In the ClO4 salt, we have previously shown that strong upward curvature is present in H_c2(T) for field aligned along the intermediate b direction.(I.J. Lee, et al., Synth.Met.70,747(1995); Appl.Superc.2,753(1995).) We present here new results on the PF6 system under pressure, via resistivity measurements. Near T_c=1.13K, the critical fields and their slopes are in the ratio H_a>H_b>H_c, as expected for these quasi-1D systems. However, an anisotropy crossover occurs near T/T_c=0.7, below which the critical field along b exceeds that along a. The resulting phase diagram is similar to that seen in UPt_3. In addition, H_c2(T) along b displays positive curvature at all fields and temperatures, with no sign of saturation to our highest and lowest (0.06K and 7T). We discuss these results in light of recent theories on superconductivity in high magnetic fields.(A.G. Lebed, JETP Lett. 44, 114 (1986); M. Rasolt and Z. Tesanovic, Rev. Mod. Phys. 64, 709 (1992); N. Dupuis, G. Montambaux and C. Sa de Melo, Phys. Rev. Lett. 70, 2613 (1993).)

  1. High upper critical field in disordered niobium nitride superconductor

    SciTech Connect

    Baskaran, R. Thanikai Arasu, A. V.; Amaladass, E. P.; Janawadkar, M. P.

    2014-10-28

    Superconducting Niobium Nitride thin films have been deposited on glass, aluminum nitride buffered glass, and oxidized silicon substrates by reactive DC magnetron sputtering at ambient substrate temperatures. The crystal structure of these thin films has been determined to be cubic fcc B1 structure by Glancing Incidence X-Ray Diffraction analysis. The superconducting transition temperatures of the thin films were measured to be greater than 11.6 K with a maximum of 13.4 K. The negative temperature coefficient of resistance observed in these thin films indicates the presence of disorder. Magneto-resistance measurements have been carried out on these thin films patterned into standard four probe geometry upto a maximum magnetic field of 12 T for two films and upto 15 T for the other two films. The dependence of transition temperature on the applied field is analyzed to estimate the upper critical field. The upper critical field for most of the films was estimated to exceed 35 T, while one of the most disordered films had an estimated upper critical field greater than 70 T.

  2. Teaching Critical Reflexivity in Short-Term International Field Courses: Practices and Problems

    ERIC Educational Resources Information Center

    Glass, Michael R.

    2015-01-01

    This study critiques the use of critical reflexivity in short-term international field courses. Critical reflexivity's benefits include preparing students for professional research, deepening their learning, and giving the chance to see how student perspectives on fieldwork sites are influenced by their own identity and positionality. I use an…

  3. Scalar field critical collapse in 2 +1 dimensions

    NASA Astrophysics Data System (ADS)

    JałmuŻna, Joanna; Gundlach, Carsten; Chmaj, Tadeusz

    2015-12-01

    We carry out numerical experiments in the critical collapse of a spherically symmetric massless scalar field in 2 +1 spacetime dimensions in the presence of a negative cosmological constant and compare them against a new theoretical model. We approximate the true critical solution as the n =4 Garfinkle solution, matched at the light cone to a Vaidya-like solution, and corrected to leading order for the effect of Λ <0 . This approximation is only C3 at the light cone and has three growing modes. We conjecture that pointwise it is a good approximation to a yet unknown true critical solution that is analytic with only one growing mode (itself approximated by the top mode of our amended Garfinkle solution). With this conjecture, we predict a Ricci-scaling exponent of γ =8 /7 and a mass-scaling exponent of δ =16 /23 , compatible with our numerical experiments.

  4. Critical suppression of spin Seebeck effect by magnetic fields

    NASA Astrophysics Data System (ADS)

    Kikkawa, Takashi; Uchida, Ken-ichi; Daimon, Shunsuke; Qiu, Zhiyong; Shiomi, Yuki; Saitoh, Eiji

    2015-08-01

    The longitudinal spin Seebeck effect (LSSE) in Pt /Y3Fe5O12(YIG ) junction systems has been investigated at various magnetic fields and temperatures. We found that the LSSE voltage in a Pt/YIG-slab system is suppressed by applying high magnetic fields and this suppression is critically enhanced at low temperatures. The field-induced suppression of the LSSE in the Pt/YIG-slab system is too large at around room temperature to be explained simply by considering the effect of the Zeeman gap in magnon excitation. This result requires us to introduce a magnon-frequency-dependent mechanism into the scenario of LSSE; low-frequency magnons dominantly contribute to the LSSE. The magnetic field dependence of the LSSE voltage was observed to change by changing the thickness of YIG, suggesting that the thermospin conversion by the low-frequency magnons is suppressed in thin YIG films due to the long characteristic lengths of such magnons.

  5. Criticality safety basics, a study guide

    SciTech Connect

    V. L. Putman

    1999-09-01

    This document is a self-study and classroom guide, for criticality safety of activities with fissile materials outside nuclear reactors. This guide provides a basic overview of criticality safety and criticality accident prevention methods divided into three parts: theory, application, and history. Except for topic emphasis, theory and history information is general, while application information is specific to the Idaho National Engineering and Environmental Laboratory (INEEL). Information presented here should be useful to personnel who must know criticality safety basics to perform their assignments safely or to design critically safe equipment or operations. However, the guide's primary target audience is fissile material handler candidates.

  6. Near field optical probe for critical dimension measurements

    DOEpatents

    Stallard, Brian R.; Kaushik, Sumanth

    1999-01-01

    A resonant planar optical waveguide probe for measuring critical dimensions on an object in the range of 100 nm and below. The optical waveguide includes a central resonant cavity flanked by Bragg reflector layers with input and output means at either end. Light is supplied by a narrow bandwidth laser source. Light resonating in the cavity creates an evanescent electrical field. The object with the structures to be measured is translated past the resonant cavity. The refractive index contrasts presented by the structures perturb the field and cause variations in the intensity of the light in the cavity. The topography of the structures is determined from these variations.

  7. Near field optical probe for critical dimension measurements

    DOEpatents

    Stallard, B.R.; Kaushik, S.

    1999-05-18

    A resonant planar optical waveguide probe for measuring critical dimensions on an object in the range of 100 nm and below is disclosed. The optical waveguide includes a central resonant cavity flanked by Bragg reflector layers with input and output means at either end. Light is supplied by a narrow bandwidth laser source. Light resonating in the cavity creates an evanescent electrical field. The object with the structures to be measured is translated past the resonant cavity. The refractive index contrasts presented by the structures perturb the field and cause variations in the intensity of the light in the cavity. The topography of the structures is determined from these variations. 8 figs.

  8. Gauge-field-assisted Kekulé quantum criticality

    NASA Astrophysics Data System (ADS)

    Scherer, Michael M.; Herbut, Igor F.

    2016-11-01

    We study the quantum phase transition of U (1 ) charged Dirac fermions Yukawa coupled to the Kekulé valence-bond-solid order parameter with Z3 symmetry of the honeycomb lattice. The symmetry allows for the presence of the term in the action which is cubic in the Kekulé order parameter and which is expected to prevent the quantum phase transition in question from being continuous. The Gross-Neveu-Yukawa theory for the transition is investigated using a perturbative renormalization group and within the ɛ expansion close to four space-time dimensions. For a vanishing U (1 ) charge we show that quantum fluctuations may render the phase transition continuous only sufficiently far away from 3+1 dimensions, where the validity of the conclusions based on the leading-order ɛ expansion appears questionable. In the presence of a fluctuating gauge field, on the other hand, we find quantum critical behavior even at weak coupling to appear close to 3+1 dimensions, that is, within the domain of validity of the perturbation theory. We also determine the renormalization-group scaling of the cubic coupling at higher-loop orders and for a large number of Dirac fermions for vanishing charge.

  9. Critical behavior in the presence of an order-parameter pinning field

    NASA Astrophysics Data System (ADS)

    Parisen Toldin, Francesco; Assaad, Fakher F.; Wessel, Stefan

    2017-01-01

    We apply a recently advocated simulation scheme that employs a local order-parameter pinning field to study quantum critical phenomena in the two-dimensional square-lattice bilayer quantum Heisenberg model. Using a world-line quantum Monte Carlo approach, we show that for this model, the pinning-field approach allows to locate the quantum critical point over a wide range of pinning-field strengths. However, the identification of the quantum critical scaling behavior is found to be hard since the pinning field introduces strong corrections to scaling. In order to further elucidate the scaling behavior in this situation, we also study an improved classical lattice model in the three-dimensional Ising universality class by means of Monte Carlo simulations on large lattice sizes, which allow us to employ refined finite-size scaling considerations. A renormalization group analysis exhibits the presence of an important crossover effect from the zero pinning-field to a critical adsorption fixed point. In line with field-theoretical results, we find that at the critical adsorption fixed point the short-distance expansion of the order-parameter profile exhibits a new universal critical exponent. This result also implies the presence of slowly decaying scaling corrections, which we analyze in detail.

  10. Magnetic-field-induced criticality in superconducting two-leg ladders

    NASA Astrophysics Data System (ADS)

    Vekua, Temo

    2017-03-01

    We study magnetic-field-induced critical singularities in the superconducting phase of the hole-doped Hubbard model of repulsively interacting electrons, defined on a two-leg ladder. We argue that, provided the low-energy spin excitations in doped ladders carry electric charge, the low-temperature thermodynamic quantities, such as the specific-heat coefficient and magnetic susceptibility, will show logarithmic singularities in the quantum critical regime. This behavior is in drastic contrast to the magnetic-field-induced criticality in undoped Mott insulator ladders, which is governed by the zero-scale-factor universality with its hallmark square-root singularities.

  11. Critical exact solutions for self-gravitating Dirac fields

    NASA Astrophysics Data System (ADS)

    Cianci, Roberto; Fabbri, Luca; Vignolo, Stefano

    2016-11-01

    We consider the Einstein-Dirac field equations describing a self-gravitating massive neutrino, looking for axially symmetric exact solutions; in the search of general solutions, we find some that are specific and which have critical features, such as the fact that the space-time curvature turns out to be flat and the spinor field gives rise to a vanishing bi-linear scalar overline{ψ }ψ =0 with non-vanishing bi-linear pseudo-scalar ioverline{ψ }γ ^5ψ not =0: because in quantum-field theory general computational methods are built on plane-wave solutions, for which the bi-linear pseudo-scalar vanishes while the bi-linear scalar does not vanish, then the solutions we found cannot be treated with the usual machinery of quantum-field theory. This means that for the Einstein-Dirac system there exist admissible solutions which nevertheless cannot be quantized with the common prescriptions; we regard this situation as yet another issue of tension between Einstein gravity and quantum principles. Possible ways to quench this tension can be seen either in enlarging the validity of quantum-field theory or by restricting the space of the solutions of the Einstein-Dirac system of field equations.

  12. Direct measurement of the upper critical field in cuprate superconductors

    PubMed Central

    Grissonnanche, G.; Cyr-Choinière, O.; Laliberté, F.; René de Cotret, S.; Juneau-Fecteau, A.; Dufour-Beauséjour, S.; Delage, M. -È.; LeBoeuf, D.; Chang, J.; Ramshaw, B. J.; Bonn, D. A.; Hardy, W. N.; Liang, R.; Adachi, S.; Hussey, N. E.; Vignolle, B.; Proust, C.; Sutherland, M.; Krämer, S.; Park, J. -H.; Graf, D.; Doiron-Leyraud, N.; Taillefer, Louis

    2014-01-01

    In the quest to increase the critical temperature Tc of cuprate superconductors, it is essential to identify the factors that limit the strength of superconductivity. The upper critical field Hc2 is a fundamental measure of that strength, yet there is no agreement on its magnitude and doping dependence in cuprate superconductors. Here we show that the thermal conductivity can be used to directly detect Hc2 in the cuprates YBa2Cu3Oy, YBa2Cu4O8 and Tl2Ba2CuO6+δ, allowing us to map out Hc2 across the doping phase diagram. It exhibits two peaks, each located at a critical point where the Fermi surface of YBa2Cu3Oy is known to undergo a transformation. Below the higher critical point, the condensation energy, obtained directly from Hc2, suffers a sudden 20-fold collapse. This reveals that phase competition—associated with Fermi-surface reconstruction and charge-density-wave order—is a key limiting factor in the superconductivity of cuprates. PMID:24518054

  13. Critical Studies in Art and Design Education.

    ERIC Educational Resources Information Center

    Thistlewood, David, Ed.

    This book brings together British and U.S. contributions to the debate of a critical studies approach to art and design education. The approach links practice and appreciation. But critical differences exist in definitions of the term design, with the U.S. recognition of design as the use of principles and elements of art in works and a British…

  14. Critical O (N ) models in the complex field plane

    NASA Astrophysics Data System (ADS)

    Litim, Daniel F.; Marchais, Edouard

    2017-01-01

    Local and global scaling solutions for O (N ) symmetric scalar field theories are studied in the complexified field plane with the help of the renormalization group. Using expansions of the effective action about small, large, and purely imaginary fields, we obtain and solve exact recursion relations for all couplings and determine the 3 d Wilson-Fisher fixed point analytically. For all O (N ) universality classes, we further establish that Wilson-Fisher fixed point solutions display singularities in the complex field plane, which dictate the radius of convergence for real-field expansions of the effective action. At infinite N , we find closed expressions for the convergence-limiting singularities and prove that local expansions of the effective action are powerful enough to uniquely determine the global Wilson-Fisher fixed point for any value of the fields. Implications of our findings for interacting fixed points in more complicated theories are indicated.

  15. Critical temperature and upper critical field of Li2Pd3-xCuxB (x=0.0, 0.1, 0.2) superconductors

    NASA Astrophysics Data System (ADS)

    Castro, A. A.; Olicón, O.; Escamilla, R.; Morales, F.

    2017-04-01

    We studied the effects of substitution of Pd by Cu on the upper critical field of the noncentrosymmetric superconductor Li2Pd3-xCuxB, with x=0.0, 0.1 and 0.2. The upper critical field as a function of temperature was determined by resistance measurements at different magnetic fields. We found that the superconducting transition temperature decreases as the Cu content increases. Moreover, the temperature dependence of the upper critical field is linear in the range of the temperature studied and, at low temperature, is enhanced compared with the prediction of the Werthamer-Helfan-Hohenberg theory. This indicates that the breaking of Cooper pairs by spin orbit scattering and Pauli paramagnetism is negligible, and that the upper critical field enhancement is mainly because the electron-phonon coupling and disorder.

  16. Pilot Field Test Study

    NASA Technical Reports Server (NTRS)

    Sherriff, Abigail

    2015-01-01

    The Field Test study is currently in full swing, preceded by the successful completion of the Pilot Field Test study that paved the way for collecting data on the astronauts in the medical tent in Kazakhstan. Abigail Sherriff worked alongside Logan Dobbe on one Field Test aspect to determine foot clearance over obstacles (5cm, 10cm, and 15cm) using APDM Inc. Internal Measurement Units (IMU) worn by the astronauts. They created a program to accurately calculate foot clearance using the accelerometer, magnetometer, and gyroscope data with the IMUs attached to the top of the shoes. To validate the functionality of their program, they completed a successful study on test subjects performing various tasks in an optical motion studio, considered a gold standard in biomechanics research. Future work will include further validation and expanding the program to include other analyses.

  17. Critical electric field strengths of onion tissues treated by pulsed electric fields.

    PubMed

    Asavasanti, Suvaluk; Ersus, Seda; Ristenpart, William; Stroeve, Pieter; Barrett, Diane M

    2010-09-01

    The impact of pulsed electric fields (PEF) on cellular integrity and texture of Ranchero and Sabroso onions (Allium cepa L.) was investigated. Electrical properties, ion leakage rate, texture, and amount of enzymatically formed pyruvate were measured before and after PEF treatment for a range of applied field strengths and number of pulses. Critical electric field strengths or thresholds (E(c)) necessary to initiate membrane rupture were different because dissimilar properties were measured. Measurement of electrical characteristics was the most sensitive method and was used to detect the early stage of plasma membrane breakdown, while pyruvate formation by the enzyme alliinase was used to identify tonoplast membrane breakdown. Our results for 100-μs pulses indicate that breakdown of the plasma membrane occurs above E(c)= 67 V/cm for 10 pulses, but breakdown of the tonoplast membrane is above either E(c)= 200 V/cm for 10 pulses or 133 V/cm for 100 pulses. This disparity in field strength suggests there may be 2 critical electrical field strengths: a lower field strength for plasma membrane breakdown and a higher field strength for tonoplast membrane breakdown. Both critical electric field strengths depended on the number of pulses applied. Application of a single pulse at an electric field up to 333 V/cm had no observable effect on any measured properties, while significant differences were observed for n≥10. The minimum electric field strength required to cause a measurable property change decreased with the number of pulses. The results also suggest that PEF treatment may be more efficient if a higher electric field strength is applied for a fewer pulses.

  18. Critical behavior of entropy production and learning rate: Ising model with an oscillating field

    NASA Astrophysics Data System (ADS)

    Zhang, Yirui; Barato, Andre C.

    2016-11-01

    We study the critical behavior of the entropy production of the Ising model subject to a magnetic field that oscillates in time. The mean-field model displays a phase transition that can be either first or second-order, depending on the amplitude of the field and on the frequency of oscillation. Within this approximation the entropy production rate is shown to have a discontinuity when the transition is first-order and to be continuous, with a jump in its first derivative, if the transition is second-order. In two dimensions, we find with numerical simulations that the critical behavior of the entropy production rate is the same, independent of the frequency and amplitude of the field. Its first derivative has a logarithmic divergence at the critical point. This result is in agreement with the lack of a first-order phase transition in two dimensions. We analyze a model with a field that changes at stochastic time-intervals between two values. This model allows for an informational theoretic interpretation, with the system as a sensor that follows the external field. We calculate numerically a lower bound on the learning rate, which quantifies how much information the system obtains about the field. Its first derivative with respect to temperature is found to have a jump at the critical point.

  19. Microbial field pilot study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.

    1991-12-06

    The objective of this project is to perform a microbial enhanced oil recovery field pilot test in the Southeast Vassar Vertz Sand Unit (SEVVSU) in Payne County, Oklahoma. Indigenous, anaerobic, nitrate-reducing bacteria will be stimulated to selectively plug flow paths which have been preferentially swept by a prior waterflood. This will force future flood water to invade bypassed regions of the reservoir and increase sweep efficiency. During this quarter an additional tracer study was performed in the field to determine pre-treatment flow paths and the first nutrients were injected. 2 figs.

  20. Field studies courses open

    NASA Astrophysics Data System (ADS)

    Fourteen month-long courses combining applied academics with training in field research methodology are being offered this summer by the School for Field Studies. The courses, held in eight countries during May, June, July, and August, provide unique opportunities for participants to work as a team under primitive conditions.‘Our courses bind together the academic challenge of the research problem, the physical challenge of the site itself, and the interpersonal challenge of the expedition team in a dynamic way so that both cognitive and affective learning are accelerated,’ according to Jim Elder, the school's director.

  1. Dimension dependence of the critical phenomena in gravitational collapse of massless scalar field

    NASA Astrophysics Data System (ADS)

    Bland, Jason Bryan

    2007-12-01

    A study of the critical behaviour which is observed in numerical calculations of spherically symmetric scalar field collapse has been performed. The gravitational collapse calculations are carried out using the field equations of Einstein's general theory of relativity in the context of a two dimensional dilaton gravity theory. The problem is formulated by considering a spherically symmetric matter distribution in an arbitrary number of space-time dimensions greater than three. A spherical distribution will only depend on two space-time coordinates, therefore, the action of the model can be reduced to a specific case of a 1 + 1 dilaton gravity theory. The evolution equations of the problem are simplified by carrying out a conformal transformation of the metric field. The number of space-time dimensions then appears as an input parameter of the field equations. Initial data is defined on a discrete space-time grid and numerical simulations of gravitational collapse are carried out. The computer code is optimized to increase numerical stability near the critical solutions. Discrete self-similarity and mass scaling in the near critical solutions are observed for each of the dimensions studied. The critical phenomena are described with a high level of confidence by smooth functions of space-time dimension. It is hypothesized that the critical solution of the theory at the limit of large dimension is discretely self-similar with a period of 5/2 and contains critical scaling with a constant of 1/2. Evidence will also be presented which suggests the critical solution in three dimensions with zero cosmological constant is not discretely self-similar but contains a critical scaling constant of approximately 0.11.

  2. A theoretical study on critical phenomena of magnetic soft modes

    NASA Astrophysics Data System (ADS)

    Zeng, Xiaoyan; Yang, Guohong; Yan, Ming

    2017-02-01

    Below a threshold magnetic field, domain structures in ferromagnetic samples may start to nucleate from the initially saturated state via either continuous or discontinuous phase transitions. Such processes are usually accompanied by the occurrence of soft spin-wave modes at the critical point. In this paper, we present a theoretical study on the critical phenomena of uniform soft modes in a macrospin model and spatially non-uniform ones in ferromagnetic thin films. The critical exponents of the mode frequency and its polarization are derived. The value is found to be equal to one half, which is directly related to the breaking of a reflection-symmetry in the phase transition. At the critical point, the soft mode becomes linearly polarized, which provides an additional measurable effect of the critical phenomena.

  3. Forms of crystal field Hamiltonians - A critical review

    NASA Astrophysics Data System (ADS)

    Rudowicz, C.; Gnutek, P.; Karbowiak, M.

    2011-08-01

    Our survey reveals that various disparate forms, both compact and expanded ones, of crystal field (CF) Hamiltonians, HCF, expressed in the Wybourne notation have been used in the literature. It turns out that the disparities in the symbolic explicit forms of HCF are especially important for monoclinic and triclinic site symmetry. The extent of the inconsistencies identified in selected papers has prompted us to embark on a systematic critical review of the HCF forms employed in optical spectroscopy and related areas. Most crucial results of this survey are presented here. Comparative analysis has been carried out to establish the interrelations between CF parameters (CFPs) expressed in disparate forms. The usage of inconsistent or confusing HCF forms has implications also for CFP conversions between the Stevens and Wybourne notations as well as for theoretical modeling of CFPs. This review reveals that comparison of CFP data taken from various sources should be carried out with special care, especially for low symmetry cases.

  4. Upper critical fields of periodic and quasiperiodic Nb-Ta superlattices

    SciTech Connect

    Cohn, J.L.; Lin, J.J.; Lamelas, F.J.; He, H.; Clarke, R.; Uher, C.

    1988-08-01

    Upper critical fields have been studied for two series of Nb-Ta superlattices grown by molecular-beam epitaxy with both periodic and quasiperiodic (Fibonacci sequence) layering. X-ray results are presented to characterize the nature and quality of the layering. Positive curvature in the perpendicular upper critical field (H/sub c//sub 2//sub perpendicular/), pronounced negative curvature near T/sub c/ in the parallel upper critical field (H/sub c//sub 2//sub X/), and dimensional crossover are observed in both types of samples. For quasiperiodic samples two upturns are observed in H/sub c//sub 2//sub X/ with decreasing temperature. These are shown to be associated with dimensional crossover occurring twice as the superconducting coherence length in the growth direction, xi/sub perpendicular/, samples the two length scales, 2d/sub Nb/ and d/sub Nb/, that are present in these structures.

  5. Upper critical fields of periodic and quasiperiodic Nb-Ta superlattices

    NASA Astrophysics Data System (ADS)

    Cohn, J. L.; Lin, J. J.; Lamelas, F. J.; He, H.; Clarke, R.; Uher, C.

    1988-08-01

    Upper critical fields have been studied for two series of Nb-Ta superlattices grown by molecular-beam epitaxy with both periodic and quasiperiodic (Fibonacci sequence) layering. X-ray results are presented to characterize the nature and quality of the layering. Positive curvature in the perpendicular upper critical field (Hc2⊥), pronounced negative curvature near Tc in the parallel upper critical field (Hc2), and dimensional crossover are observed in both types of samples. For quasiperiodic samples two upturns are observed in Hc2 with decreasing temperature. These are shown to be associated with dimensional crossover occurring twice as the superconducting coherence length in the growth direction, ξ⊥, samples the two length scales, 2dNb and dNb, that are present in these structures.

  6. Magnetic field orientation dependence of critical current in industrial Nb 3Sn strands

    NASA Astrophysics Data System (ADS)

    Schild, T.; Cloez, H.

    In usual superconducting devices such as magnets for NMR, the magnetic field is perpendicular to the superconducting strand axis. But in some special devices, such as magnets for the toroidal field system of fusion machines, the strands can experience any field orientation. For NbTi strands, the pinning force is dependent on the field orientation because of the drawing process (Takacs, S., Polak, M. and Krempasky, L., Critical currents of NbTi tapes with differently oriented anisotropic defects, Cryogenics, 1983, 23, 153-159). In the case of Nb 3Sn strands, the draw and react process suggests that the pinning force is isotropic. In fact, preliminary experiments have shown the contrary, which is why the magnetic field orientation dependence of the critical current for two types of industrial Nb 3Sn strands has been measured. These measurements have been performed for seven field orientations at field strengths up to 20 T. A clear anisotropic effect has been observed, which cannot be explained by Kramer's pinning law. The results are in very good agreement with an empirical law proposed in a recent study by Takayasu et al. (Takayasu, M., Montgomery, D.B. and Minervini, J.V., Effect of magnetic field direction on the critical current of twisted multifilamentary superconducting wires, Inst. of Phys. Conf. Ser., 1997, 158, 917-920). The parameters to be used in this law could be specific to the manufacturing process.

  7. Microbial field pilot study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Coates, J.D.; Chisholm, J.L.

    1993-05-01

    A multi-well microbially enhanced oil recovery field pilot has been performed in the Southeast Vassar Vertz Sand Unit in Payne County, Oklahoma. The primary emphasis of the experiment was preferential plugging of high permeability zones for the purpose of improving waterflood sweep efficiency. Studies were performed to determine reservoir chemistry, ecology, and indigenous bacteria populations. Growth experiments were used to select a nutrient system compatible with the reservoir that encouraged growth of a group of indigenous nitrate-using bacteria and inhibit growth of sulfate-reducing bacteria. A specific field pilot area behind an active line drive waterflood was selected. Surface facilities were designed and installed. Injection protocols of bulk nutrient materials were prepared to facilitate uniform distribution of nutrients within the pilot area. By the end of December, 1991, 82.5 tons (75.0 tonnes) of nutrients had been injected in the field. A tracer test identified significant heterogeneity in the SEVVSU and made it necessary to monitor additional production wells in the field. The tracer tests and changes in production behavior indicate the additional production wells monitored during the field trial were also affected. Eighty two and one half barrels (13.1 m[sup 3]) of tertiary oil have been recovered. Microbial activity has increased CO[sub 2] content as indicated by increased alkalinity. A temporary rise in sulfide concentration was experienced. These indicate an active microbial community was generated in the field by the nutrient injection. Pilot area interwell pressure interference test results showed that significant permeability reduction occurred. The interwell permeabilities in the pilot area between the injector and the three pilot production wells were made more uniform which indicates a successful preferential plugging enhanced oil recovery project.

  8. Structural Stability of Planar Homogeneous Polynomial Vector Fields: Applications to Critical Points and to Infinity

    NASA Astrophysics Data System (ADS)

    Llibre, Jaume; Pérez del Río, Jesús S.; Rodríguez, José Angel

    1996-03-01

    LetHmbe the space of planar homogeneous polynomial vector fields of degreemendowed with the coefficient topology. We characterize the setΩmof the vector fields ofHmthat are structurally stable with respect to perturbations inHmand we determine the exact number of the topological equivalence classes inΩm. The study of structurally stable homogeneous polynomial vector fields is very useful for understanding some interesting features of inhomogeneous vector fields. Thus, by using this characterization we can do first an extension of the Hartman-Grobman Theorem which allows us to study the critical points of planar analytical vector fields whosek-jets are zero for allkstudy of the flows of the planar polynomial vector fields in a neighborhood of the infinity also under generic assumptions.

  9. Assessment of critical thinking: a Delphi study.

    PubMed

    Paul, Sheila A

    2014-11-01

    Nurse educators are responsible for preparing nurses who critically analyze patient information and provide meaningful interventions in today's complex health care system. By using the Delphi research method, this study, utilized the specialized and experiential knowledge of Certified Nurse Educators. This original Delphi research study asked Certified Nurse Educators how to assess the critical-thinking ability of nursing students in the clinical setting. The results showed that nurse educators need time, during the clinical experience, to accurately assess each individual nursing student. This study demonstrated the need for extended student clinical time, and a variety of clinical learning assessment tools.

  10. Electric field effects on a near-critical fluid in microgravity

    NASA Technical Reports Server (NTRS)

    Zimmerli, G.; Wilkinson, R. A.; Ferrell, R. A.; Hao, H.; Moldover, M. R.

    1994-01-01

    The effects of an electric field on a sample of SF6 fluid in the vicinity of the liquid-vapor critical point is studied. The isothermal increase of the density of a near-critical sample as a function of the applied electric field was measured. In agreement with theory, this electrostriction effect diverges near the critical point as the isothermal compressibility diverges. Also as expected, turning on the electric field in the presence of density gradients can induce flow within the fluid, in a way analogous to turning on gravity. These effects were observed in a microgravity environment by using the Critical Point Facility which flew onboard the Space Shuttle Columbia in July 1994 as part of the Second International Microgravity Laboratory Mission. Both visual and interferometric images of two separate sample cells were obtained by means of video downlink. The interferometric images provided quantitative information about the density distribution throughout the sample. The electric field was generated by applying 500 Volts to a fine wire passing through the critical fluid.

  11. Microbial Field Pilot Study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1990-11-01

    This report covers progress made during the first year of the Microbial Field Pilot Study project. Information on reservoir ecology and characterization, facility and treatment design, core experiments, bacterial mobility, and mathematical modeling are addressed. To facilitate an understanding of the ecology of the target reservoir analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. A preliminary design of facilities for the operation of the field pilot test was prepared. In addition, procedures for facilities installation and for injection treatments are described. The Southeast Vassar Vertz Sand Unit (SEVVSU), the site of the proposed field pilot study, is described physically, historically, and geologically. The fields current status is presented and the ongoing reservoir simulation is discussed. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. Two possible mechanisms, relative permeability effects and changes in the capillary number, are discussed and related to four Berea core experiments' results. The experiments were conducted at reservoir temperature using SEVVSU oil, brine, and bacteria. The movement and activity of bacteria in porous media were investigated by monitoring the growth of bacteria in sandpack cores under no flow conditions. The rate of bacteria advancement through the cores was determined. A mathematical model of the MEOR process has been developed. The model is a three phase, seven species, one dimensional model. Finite difference methods are used for solution. Advection terms in balance equations are represented with a third- order upwind differencing scheme to reduce numerical dispersion and oscillations. The model is applied to a batch fermentation example. 52 refs., 26 figs., 21 tabs.

  12. Microbial field pilot study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1992-03-01

    The objective of this project is to perform a microbial enhanced oil recovery field pilot in the Southeast Vassar Vertz Sand Unit (SEVVSU) in Payne County, Oklahoma. Indigenous, anaerobic, nitrate reducing bacteria will be stimulated to selectively plug flow paths which have been referentially swept by a prior waterflood. This will force future flood water to invade bypassed regions of the reservoir and increase sweep efficiency. This report covers progress made during the second year, January 1, 1990 to December 31, 1990, of the Microbial Field Pilot Study project. Information on reservoir ecology, surface facilities design, operation of the unit, core experiments, modeling of microbial processes, and reservoir characterization and simulation are presented in the report. To better understand the ecology of the target reservoir, additional analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. The results of the produced and injected water analysis show increasing sulfide concentrations with respect to time. In March of 1990 Mesa Limited Partnership sold their interest in the SEVVSU to Sullivan and Company. In April, Sullivan and Company assumed operation of the field. The facilities for the field operation of the pilot were refined and implementation was begun. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. The experiments were performed at SEVVSU temperature using fluids and inoculum from the unit. The model described in last year's report was further validated using results from a core flood experiment. The model was able to simulate the results of one of the core flood experiments with good quality.

  13. Microbial field pilot study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1992-03-01

    The objective of this project is to perform a microbial enhanced oil recovery field pilot in the Southeast Vassar Vertz Sand Unit (SEVVSU) in Payne County, Oklahoma. Indigenous, anaerobic, nitrate reducing bacteria will be stimulated to selectively plug flow paths which have been referentially swept by a prior waterflood. This will force future flood water to invade bypassed regions of the reservoir and increase sweep efficiency. This report covers progress made during the second year, January 1, 1990 to December 31, 1990, of the Microbial Field Pilot Study project. Information on reservoir ecology, surface facilities design, operation of the unit, core experiments, modeling of microbial processes, and reservoir characterization and simulation are presented in the report. To better understand the ecology of the target reservoir, additional analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. The results of the produced and injected water analysis show increasing sulfide concentrations with respect to time. In March of 1990 Mesa Limited Partnership sold their interest in the SEVVSU to Sullivan and Company. In April, Sullivan and Company assumed operation of the field. The facilities for the field operation of the pilot were refined and implementation was begun. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. The experiments were performed at SEVVSU temperature using fluids and inoculum from the unit. The model described in last year`s report was further validated using results from a core flood experiment. The model was able to simulate the results of one of the core flood experiments with good quality.

  14. Critical Studies and the Drumcroon Experience.

    ERIC Educational Resources Information Center

    Taylor, Rod

    1987-01-01

    Describes the residency teaching experience of graduate students involved in the Drumcroon Critical Studies in Art Education Project. Focuses on three-way relationship between pupil, artist, and environment showing how this relationship helped produce a successful program. Graduate students are "practically" educating students in…

  15. AYURVEDA AND MODERN MEDICE: (A critical study)

    PubMed Central

    Majumdar, Kaviraj A.

    1989-01-01

    The author highlights in this paper the differences between Ayurveda and Western medicine in the approach to healing process. Also the paper examines relevance of Ayurveda to the present day life style and thus, makes a critical study of both medical systems quoting references from various modern authors. PMID:22557648

  16. Critical Quantitative Study of Immigrant Students

    ERIC Educational Resources Information Center

    Conway, Katherine M.

    2014-01-01

    The author discusses the importance of critical quantitative research for studies of immigrant students, a large and growing group, whose higher education experience is crucial to the future of the United States. The author outlines some of the distinctions to be made among immigrant students and recommends areas of future inquiry.

  17. Critical wetting of a class of nonequilibrium interfaces: a mean-field picture.

    PubMed

    de Los Santos, Francisco; Romera, Elvira; Al Hammal, Omar; Muñoz, Miguel Angel

    2007-03-01

    A self-consistent mean-field method is used to study critical wetting transitions under nonequilibrium conditions by analyzing Kardar-Parisi-Zhang (KPZ) interfaces in the presence of a bounding substrate. In the case of positive KPZ nonlinearity a single (Gaussian) regime is found. On the contrary, interfaces corresponding to negative nonlinearities lead to three different regimes of critical behavior for the surface order parameter: (i) a trivial Gaussian regime, (ii) a weak-fluctuation regime with a trivially located critical point and nontrivial exponents, and (iii) a highly nontrivial strong-fluctuation regime, for which we provide a full solution by finding the zeros of parabolic-cylinder functions. These analytical results are also verified by solving numerically the self-consistent equation in each case. Analogies with and differences from equilibrium critical wetting as well as nonequilibrium complete wetting are also discussed.

  18. Review of Yucca Mountain Disposal Criticality Studies

    SciTech Connect

    Scaglione, John M; Wagner, John C

    2011-01-01

    The U.S. Department of Energy (DOE), Office of Civilian Radioactive Waste Management, submitted a license application for construction authorization of a deep geologic repository at Yucca Mountain, Nevada, in June of 2008. The license application is currently under review by the U.S. Nuclear Regulatory Commission. However,on March 3, 2010 the DOE filed a motion requesting withdrawal of the license application. With the withdrawal request and the development of the Blue Ribbon Commission to seek alternative strategies for disposing of spent fuel, the status of the proposed repository at Yucca Mountain is uncertain. What is certain is that spent nuclear fuel (SNF) will continue to be generated and some long-lived components of the SNF will eventually need a disposition path(s). Strategies for the back end of the fuel cycle will continue to be developed and need to include the insights from the experience gained during the development of the Yucca Mountain license application. Detailed studies were performed and considerable progress was made in many key areas in terms of increased understanding of relevant phenomena and issues regarding geologic disposal of SNF. This paper reviews selected technical studies performed in support of the disposal criticality analysis licensing basis and the use of burnup credit. Topics include assembly misload analysis, isotopic and criticality validation, commercial reactor critical analyses, loading curves, alternative waste package and criticality control studies, radial burnup data and effects, and implementation of a conservative application model in the criticality probabilistic evaluation as well as other information that is applicable to operations regarding spent fuel outside the reactor. This paper summarizes the work and significant accomplishments in these areas and provides a resource for future, related activities.

  19. A Critical Analysis of Transverse Dispersivity Field Data

    NASA Astrophysics Data System (ADS)

    Attinger, Sabine; Zech, Alraune; Bellin, Alberto; Cvetkovic, Vladimir; Dagan, Gedeon; Dietrich, Peter; Fiori, Aldo; Teutsch, Georg

    2016-04-01

    Spreading of solute plumes in groundwater is often quantified by macrodispersivity. Thereby, the transverse αT and vertical αV characterize the broadening of the plume in the vertical plane, perpendicular to the flow direction. Determining αT and αV from field experiments is difficult and costly. Still, it is an important parameter for making predictions of contaminant transport e.g. for stationary contamination plumes, bio-degradation and natural attenuation. Measured values of αT and αV at field scale are only available for a few sites. Gelhar and coworkers classified in 1992 the values into three reliability groups: highly, moderately and lowly reliable. Only recently, we could show for the longitudinal macrodispersivity αL, that the values of low reliability need to be excluded for further analysis, based on a re-evaluation of the experiments. Furthermore, new studies emerged in the meantime, which requires evaluation of reliability and incorporation, when appropriate. This work focuses on collecting reliable field data of transverse and vertical macrodispersivities. The ensemble of reliable αT and αV values is then used to answer the following questions: (i) Is there an upper limit of αT and αV or the tendency of increasing values with increasing travel distance of tracer plumes? (ii) Can the field data be predicted by theoretical models? (iii) What can we learn from the field based ratios αV/αT and αT/αL? The investigation may provide valuable information for modeling and predicting contaminant transport in groundwater.

  20. Shift of the critical mixing temperature in strong electric fields. Theory and experiment.

    PubMed

    Orzechowski, Kazimierz; Adamczyk, Mariusz; Wolny, Alicja; Tsori, Yoav

    2014-06-26

    We study the shift in the critical temperature T(c) in binary mixtures in strong electric fields. In experiments we measure the nonlinear dielectric effect (NDE) in a mixture of nitrobenze and n-octane and calculate Piekara's factor. We find that the critical anomaly of Piekara's factor is a function of an electric field strength. We propose to explain this observation as a result of a downward shift of T(c), and this allows us to calculate (∂T(c)/∂E(2)) = (-22 ± 10) × 10(-16) (K m(2))/V(2). In the theoretical part we amend Landau and Lifshitz's formula and show that the downward shift of Tc can be estimated from a simple mean-field theory taking into account the linear and quadratic terms in an expansion of the constitutive relation ε(x) between the electric constant ε and mixture composition x.

  1. Magnetic field oscillations of the critical current in long ballistic graphene Josephson junctions

    NASA Astrophysics Data System (ADS)

    Rakyta, Péter; Kormányos, Andor; Cserti, József

    2016-06-01

    We study the Josephson current in long ballistic superconductor-monolayer graphene-superconductor junctions. As a first step, we have developed an efficient computational approach to calculate the Josephson current in tight-binding systems. This approach can be particularly useful in the long-junction limit, which has hitherto attracted less theoretical interest but has recently become experimentally relevant. We use this computational approach to study the dependence of the critical current on the junction geometry, doping level, and an applied perpendicular magnetic field B . In zero magnetic field we find a good qualitative agreement with the recent experiment of M. Ben Shalom et al. [Nat. Phys. 12, 318 (2016), 10.1038/nphys3592] for the length dependence of the critical current. For highly doped samples our numerical calculations show a broad agreement with the results of the quasiclassical formalism. In this case the critical current exhibits Fraunhofer-like oscillations as a function of B . However, for lower doping levels, where the cyclotron orbit becomes comparable to the characteristic geometrical length scales of the system, deviations from the results of the quasiclassical formalism appear. We argue that due to the exceptional tunability and long mean free path of graphene systems a new regime can be explored where geometrical and dynamical effects are equally important to understand the magnetic field dependence of the critical current.

  2. The Collaborative Pediatric Critical Care Research Network (CPCCRN) Critical Pertussis Study: Collaborative Research in Pediatric Critical Care Medicine

    PubMed Central

    Burr, Jeri S.; Jenkins, Tammara L.; Harrison, Rick; Meert, Kathleen; Anand, K.J.S.; Berger, John T.; Zimmerman, Jerry; Carcillo, Joseph; Dean, J. Michael; Newth, Christopher J. L.; Willson, Douglas F.; Sanders, Ronald C.; Pollack, Murray M.; Harvill, Eric; Nicholson, Carol E.

    2012-01-01

    Objective To provide an updated overview of critical pertussis to the pediatric critical care community and describe a study of critical pertussis recently undertaken. Setting The six sites, seven hospitals of the Collaborative Pediatric Critical Care Research Network and 17 outside sites at academic medical centers with PICUs. Results Despite high coverage for childhood vaccination, pertussis causes substantial morbidity and mortality in United States children, especially among infants. In pediatric intensive care units, Bordetella pertussis is a community-acquired pathogen associated with critical illness and death. The incidence of medical and developmental sequelae in critical pertussis survivors remains unknown, and the appropriate strategies for treatment and support remain unclear. The CPCCRN Critical Pertussis Study has begun to evaluate critical pertussis in a prospective cohort. Conclusion Research is urgently needed to provide an evidence base that might optimize management for critical pertussis, a serious, disabling, and too often fatal illness for United States children, and those in the developing world. PMID:21057366

  3. Critical Development? Using a Critical Theory Lens to Examine the Current Role of Evaluation in the Youth-Development Field

    ERIC Educational Resources Information Center

    Zeller-Berkman, Sarah

    2010-01-01

    A critical theory lens is used to explore the role of evaluation in youth development, a field aimed at recognizing youth as assets. A theory of change in the field is questioned for its emphasis on individual youth outcomes as programmatic outcome measures. A review of 209 evaluations of 131 programs in the Harvard Family Research Project's…

  4. Critical field enhancement of asymptotic optical bound states in the continuum

    PubMed Central

    Yoon, Jae Woong; Song, Seok Ho; Magnusson, Robert

    2015-01-01

    We study spectral singularities and critical field enhancement factors associated with embedded photonic bound states in subwavelength periodic Si films. Ultrahigh-Q resonances supporting field enhancement factor exceeding 108 are obtained in the spectral vicinity of exact embedded eigenvalues in spite of deep surface modulation and vertical asymmetry of the given structure. Treating relations between the partial resonance Q and field enhancement factors with an analytical coupled-mode model, we derive a general strategy to maximize the field enhancement associated with these photonic bound states in the presence of material dissipation. The analytical expression for the field enhancement quantitatively agrees with rigorous numerical calculations. Therefore, our results provide a general knowledge for designing practical resonance elements based on optical bound states in the continuum in various applications. PMID:26673548

  5. High magnetic-field scales and critical currents in SmFeAs(O, F) crystals

    NASA Astrophysics Data System (ADS)

    Moll, Philip J. W.; Puzniak, Roman; Balakirev, Fedor; Rogacki, Krzysztof; Karpinski, Janusz; Zhigadlo, Nikolai D.; Batlogg, Bertram

    2010-08-01

    With the discovery of new superconducting materials, such as the iron pnictides, exploring their potential for applications is one of the foremost tasks. Even if the critical temperature Tc is high, intrinsic electronic properties might render applications difficult, particularly if extreme electronic anisotropy prevents effective pinning of vortices and thus severely limits the critical current density, a problem well known for cuprates. Although many questions concerning microscopic electronic properties of the iron pnictides have been successfully addressed and estimates point to a very high upper critical field, their application potential is less clear. Thus, we focus here on the critical currents, their anisotropy and the onset of electrical dissipation in high magnetic fields up to 65T. Our detailed study of the transport properties of SmFeAsO0.7F0.25 single crystals reveals a promising combination of high (>2×106Acm-2) and nearly isotropic critical current densities along all crystal directions. This favourable intragrain current transport in SmFeAs(O, F), which shows the highest Tc of 54K at ambient pressure, is a crucial requirement for possible applications. Essential in these experiments are four-probe measurements on focused-ion-beam-cut single crystals with a sub-square-micrometre cross-section, with current along and perpendicular to the crystallographic c axis.

  6. Electron profile stiffness and critical gradient studies

    SciTech Connect

    DeBoo, J. C.; Petty, C. C.; Burrell, K. H.; Smith, S. P.; White, A. E.; Doyle, E. J.; Hillesheim, J. C.; Rhodes, T. L.; Schmitz, L.; Wang, G.; Zeng, L.; Holland, C.; McKee, G. R.

    2012-08-15

    Electron profile stiffness was studied in DIII-D L-mode discharges by systematically varying the heat flux in a narrow region with electron cyclotron heating and measuring the local change produced in {nabla}T{sub e}. Electron stiffness was found to slowly increase with toroidal rotation velocity. A critical inverse temperature gradient scale length 1/L{sub C} {approx} 3 m{sup -1} was identified at {rho}=0.6 and found to be independent of rotation. Both the heat pulse diffusivity and the power balance diffusivity, the latter determined by integrating the measured dependence of the heat pulse diffusivity on -{nabla}T{sub e}, were fit reasonably well by a model containing a critical inverse temperature gradient scale length and varying linearly with 1/L{sub T} above the threshold.

  7. Electromagnetic Field Penetration Studies

    NASA Technical Reports Server (NTRS)

    Deshpande, M.D.

    2000-01-01

    A numerical method is presented to determine electromagnetic shielding effectiveness of rectangular enclosure with apertures on its wall used for input and output connections, control panels, visual-access windows, ventilation panels, etc. Expressing EM fields in terms of cavity Green's function inside the enclosure and the free space Green's function outside the enclosure, integral equations with aperture tangential electric fields as unknown variables are obtained by enforcing the continuity of tangential electric and magnetic fields across the apertures. Using the Method of Moments, the integral equations are solved for unknown aperture fields. From these aperture fields, the EM field inside a rectangular enclosure due to external electromagnetic sources are determined. Numerical results on electric field shielding of a rectangular cavity with a thin rectangular slot obtained using the present method are compared with the results obtained using simple transmission line technique for code validation. The present technique is applied to determine field penetration inside a Boeing-757 by approximating its passenger cabin as a rectangular cavity filled with a homogeneous medium and its passenger windows by rectangular apertures. Preliminary results for, two windows, one on each side of fuselage were considered. Numerical results for Boeing-757 at frequencies 26 MHz, 171-175 MHz, and 428-432 MHz are presented.

  8. Influence of a Critically Oriented Methods Course and Early Field Experience on Preservice Teachers' Conceptions of Teaching

    ERIC Educational Resources Information Center

    Curtner-Smith, Matthew D.; Sofo, Seidu

    2004-01-01

    In recent years there has been a growing interest in arming physical education teachers with critical pedagogies. The purpose of this study was to determine the influence of a critically oriented methods course and early field experience (EFE) on 20 preservice teachers' (PTs) conceptions of the teaching-learning process. Data were collected using…

  9. [Contributions from the critical leisure field to the health promotion].

    PubMed

    Bacheladenski, Miguel Sidenei; Matiello Júnior, Edgard

    2010-08-01

    The studies about leisure for health promotion still tend to choose the active body occupation in the free-time (leisure activities), revealing the influence of the functionalist way of thinking, which trying to reduce the links between society and health-disease process, undoubtedly do not keep with the purpose of population health promotion. Focusing on this idea, and keeping in mind the premise that in the Brazilian physical training there are different opinions since the earliest 80s which try to achieve the purpose to avoid the ideas of the functionalist way of thinking. However, those opinions are almost unknown both in the Brazilian public health system and the collective health system, once the bibliography revision about leisure activities development was made in the country, looking for ideas taken in common knowledge for health promotion presuppositions, this report has the aim to show critical and alternatives concepts of leisure in the way it is linked to healthy as a real social change, using a political-pedagogical proposal called lazerania. In general, this is an emancipatory concept of leisure, which comes from the sport phenomenon as a problem and provides the feeling, thinking and behavior of the population, trying to build a society based on solidarity and consumer participation.

  10. Second-order magnetic critical points at finite magnetic fields: Revisiting Arrott plots

    NASA Astrophysics Data System (ADS)

    Bustingorry, S.; Pomiro, F.; Aurelio, G.; Curiale, J.

    2016-06-01

    The so-called Arrott plot, which consists in plotting H /M against M2, with H the applied magnetic field and M the magnetization, is used to extract valuable information in second-order magnetic phase transitions. Besides, it is widely accepted that a negative slope in the Arrott plot is indicative of a first-order magnetic transition. This is known as the Banerjee criterion. In consequence, the zero-field transition temperature T* is reported as the characteristic first-order transition temperature. By carefully analyzing the mean-field Landau model used for studying first-order magnetic transitions, we show in this work that T* corresponds in fact to a triple point where three first-order lines meet. More importantly, this analysis reveals the existence of two symmetrical second-order critical points at finite magnetic field (Tc,±Hc) . We then show that a modified Arrott plot can be used to obtain information about these second-order critical points. To support this idea we analyze experimental data on La2 /3Ca1 /3MnO3 and discuss an estimate for the location of the triple point and the second-order critical points.

  11. Baja California: Field Study

    ERIC Educational Resources Information Center

    Frey, John; Stewart, Jack

    1974-01-01

    Describes how to plan and execute an extended field trip which provides first hand observation of biological and cultural systems. Socialization of the participants was achieved through common planning and goal achievement. (BR)

  12. The distribution of 3D superconductivity near the second critical field

    NASA Astrophysics Data System (ADS)

    Kachmar, Ayman; Nasrallah, Marwa

    2016-09-01

    We study the minimizers of the Ginzburg-Landau energy functional with a uniform magnetic field in a three dimensional bounded domain. The functional depends on two positive parameters, the Ginzburg-Landau parameter and the intensity of the applied magnetic field, and acts on complex-valued functions and vector fields. We establish a formula for the distribution of the L 2-norm of the minimizing complex-valued function (order parameter). The formula is valid in the regime where the Ginzburg-Landau parameter is large and the applied magnetic field is close to and strictly below the second critical field—the threshold value corresponding to the transition from the superconducting to the normal phase in the bulk of the sample. Earlier results are valid in 2D domains and for the L 4-norm in 3D domains.

  13. Fielding: A Collection of Critical Essays. Twentieth Century Views Series.

    ERIC Educational Resources Information Center

    Paulson, Ronald, Ed.

    One of a series of works aimed at presenting contemporary critical opinion on major authors, this collection includes essays by Ronald Paulson, A. R. Humphreys, Winfield H. Rogers, Ian Watt, Maynard Mack, Mark Spilka, Aurelien Digeon, Andre Gide, Arnold Kettle, John Middleton Murry, William Empson, George Sherburn, and John S. Coolidge--all…

  14. The Field of Educational Development: Histories and Critical Questions

    ERIC Educational Resources Information Center

    Manathunga, Catherine

    2011-01-01

    The field of educational development has a 40-year history of providing continuing education or professional development for academic staff, particularly focusing on improving teaching and learning. However, little has yet been written on the historical origins and development of this field, apart from content analyses of some key journals and…

  15. Curator and Critic: Role of the Assessor in Aesthetic Fields

    ERIC Educational Resources Information Center

    Jacobs, Rachael

    2012-01-01

    Assessment in aesthetic fields presents a myriad of challenges in the higher education environment. This paper uses a metaphorical representation to explore the role of assessors within aesthetic assessment settings in higher education. It begins with a discussion of aesthetic fields and an exploration of the role of assessment in this area.…

  16. Notions of Criticality: Singaporean Teachers' Perspectives of Critical Thinking in Social Studies

    ERIC Educational Resources Information Center

    Baildon, Mark C.; Sim, Jasmine B.-Y.

    2009-01-01

    In this article we explore the ways critical thinking is conceived by a group of Singaporean social studies teachers, what they see as its purposes as well as perceived constraints to critical thinking and teaching critical thinking in Singapore's schools. Using a case study research design and constant comparative method we analysed data from…

  17. Double criticality in the magnetic field driven transition of a high-TC superconductor

    NASA Astrophysics Data System (ADS)

    Leridon, Brigitte; Vanacken, Johan; Moshchalkov, V. V.; Vignolle, Baptiste; Porwal, Rajni; Budhani, R. C.

    2015-03-01

    The magnetic-field driven transition of a set of high critical temperature La2 - x Srx CuO4 superconducting thin films has been investigated using high pulsed magnetic fields. For the underdoped samples, the existence of two distinct critical regions in the superconductor/insulator transition has been evidenced for the first time. The first quantum critical region is observed at intermediate magnetic fields (~= 19 T)and temperatures and gives way at lower temperature to a quantum critical point at about twice critical magnetic field and resistance per square. The critical exponents inferred from scaling behaviour are markedly different for the two regions. We attribute this behaviour to the existence of a clean/dirty crossover due to the presence of electronic inhomogeneities. This work has been supported by a SESAME grant from Region Ile-de-France. Part of the experiments at KULeuven have been founded by EuroMagNET II under the EU Contract Number 228043.

  18. Critical point scaling of Ising spin glasses in a magnetic field

    NASA Astrophysics Data System (ADS)

    Yeo, Joonhyun; Moore, M. A.

    2015-03-01

    Critical point scaling in a field H applies for the limits t →0 (where t =T /Tc-1 ) and H →0 but with the ratio R =t /H2 /Δ finite. Δ is a critical exponent of the zero-field transition. We study the replicon correlation length ξ and from it the crossover scaling function f (R ) defined via 1 /(ξ H4 /(d +2 -η )) ˜f (R ) . We have calculated analytically f (R ) for the mean-field limit of the Sherrington-Kirkpatrick model. In dimension d =3 , we have determined the exponents and the critical scaling function f (R ) within two versions of the Migdal-Kadanoff (MK) renormalization group procedure. One of the MK versions gives results for f (R ) in d =3 in reasonable agreement with those of the Monte Carlo simulations at the values of R for which they can be compared. If there were a de Almeida-Thouless (AT) line for d ≤6 , it would appear as a zero of the function f (R ) at some negative value of R , but there is no evidence for such behavior. This is consistent with the arguments that there should be no AT line for d ≤6 , which we review.

  19. Particle and flow field holography: A critical survey

    NASA Technical Reports Server (NTRS)

    Trolinger, James D.

    1987-01-01

    A brief background is provided for the fields of particle and flow visualization holography. A summary of methods currently in use is given, followed by a discussion of more recent and unique applications. The problem of data reduction is discussed. A state of the art summary is then provided with a prognosis of the future of the field. Particle and flow visualization holography are characterized as powerful tools currently in wide use and with significant untapped potential.

  20. Automated Critical Peak Pricing Field Tests: Program Descriptionand Results

    SciTech Connect

    Piette, Mary Ann; Watson, David; Motegi, Naoya; Kiliccote, Sila; Xu, Peng

    2006-04-06

    California utilities have been exploring the use of critical peak prices (CPP) to help reduce needle peaks in customer end-use loads. CPP is a form of price-responsive demand response (DR). Recent experience has shown that customers have limited knowledge of how to operate their facilities in order to reduce their electricity costs under CPP (Quantum 2004). While the lack of knowledge about how to develop and implement DR control strategies is a barrier to participation in DR programs like CPP, another barrier is the lack of automation of DR systems. During 2003 and 2004, the PIER Demand Response Research Center (DRRC) conducted a series of tests of fully automated electric demand response (Auto-DR) at 18 facilities. Overall, the average of the site-specific average coincident demand reductions was 8% from a variety of building types and facilities. Many electricity customers have suggested that automation will help them institutionalize their electric demand savings and improve their overall response and DR repeatability. This report focuses on and discusses the specific results of the Automated Critical Peak Pricing (Auto-CPP, a specific type of Auto-DR) tests that took place during 2005, which build on the automated demand response (Auto-DR) research conducted through PIER and the DRRC in 2003 and 2004. The long-term goal of this project is to understand the technical opportunities of automating demand response and to remove technical and market impediments to large-scale implementation of automated demand response (Auto-DR) in buildings and industry. A second goal of this research is to understand and identify best practices for DR strategies and opportunities. The specific objectives of the Automated Critical Peak Pricing test were as follows: (1) Demonstrate how an automated notification system for critical peak pricing can be used in large commercial facilities for demand response (DR). (2) Evaluate effectiveness of such a system. (3) Determine how customers

  1. Finite-size critical scaling in Ising spin glasses in the mean-field regime

    NASA Astrophysics Data System (ADS)

    Aspelmeier, T.; Katzgraber, Helmut G.; Larson, Derek; Moore, M. A.; Wittmann, Matthew; Yeo, Joonhyun

    2016-03-01

    We study in Ising spin glasses the finite-size effects near the spin-glass transition in zero field and at the de Almeida-Thouless transition in a field by Monte Carlo methods and by analytical approximations. In zero field, the finite-size scaling function associated with the spin-glass susceptibility of the Sherrington-Kirkpatrick mean-field spin-glass model is of the same form as that of one-dimensional spin-glass models with power-law long-range interactions in the regime where they can be a proxy for the Edwards-Anderson short-range spin-glass model above the upper critical dimension. We also calculate a simple analytical approximation for the spin-glass susceptibility crossover function. The behavior of the spin-glass susceptibility near the de Almeida-Thouless transition line has also been studied, but here we have only been able to obtain analytically its behavior in the asymptotic limit above and below the transition. We have also simulated the one-dimensional system in a field in the non-mean-field regime to illustrate that when the Imry-Ma droplet length scale exceeds the system size one can then be erroneously lead to conclude that there is a de Almeida-Thouless transition even though it is absent.

  2. Probability and critical electric field for electron runaway

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Brennan, Dylan; Boozer, Allen; Bhattacharjee, Amitava

    2015-11-01

    It is very important that we understand the physics of the runaway electron avalanche, both due to the need for runaway mitigation in disruptions in ITER, and the pure scientific merit. In this work we developed a new method to obtain the probability of an electron in momentum space to run away, by solving a time-independent PDE, alleviating the need for Monte-Carlo simulation. This PDE turns out to be adjoint to the electron kinetic equation. The new method is applied to calculate the avalanche growth rate and the threshold electric field. The results show that in the presence of synchrotron radiation and pitch angle scattering, the threshold electric field for the avalanche growth will increase to a value that is higher than the Connor-Hastie electric field. A series of kinetic simulations are conducted which confirms the findings. We also did a time-dependent simulation with increasing plasma density to simulate the gas-puffing runaway electron experiments in DIII-D, and the hard X-ray signal result shows qualitative agreement with the experiments for the threshold electric field.

  3. Critical Multicultural Education Competencies Scale: A Scale Development Study

    ERIC Educational Resources Information Center

    Acar-Ciftci, Yasemin

    2016-01-01

    The purpose of this study is to develop a scale in order to identify the critical mutlicultural education competencies of teachers. For this reason, first of all, drawing on the knowledge in the literature, a new conceptual framework was created with deductive method based on critical theory, critical race theory and critical multicultural…

  4. Structural versus dynamical origins of mean-field behavior in a self-organized critical model of neuronal avalanches.

    PubMed

    Moosavi, S Amin; Montakhab, Afshin

    2015-01-01

    Critical dynamics of cortical neurons have been intensively studied over the past decade. Neuronal avalanches provide the main experimental as well as theoretical tools to consider criticality in such systems. Experimental studies show that critical neuronal avalanches show mean-field behavior. There are structural as well as recently proposed [Phys. Rev. E 89, 052139 (2014)] dynamical mechanisms that can lead to mean-field behavior. In this work we consider a simple model of neuronal dynamics based on threshold self-organized critical models with synaptic noise. We investigate the role of high-average connectivity, random long-range connections, as well as synaptic noise in achieving mean-field behavior. We employ finite-size scaling in order to extract critical exponents with good accuracy. We conclude that relevant structural mechanisms responsible for mean-field behavior cannot be justified in realistic models of the cortex. However, strong dynamical noise, which can have realistic justifications, always leads to mean-field behavior regardless of the underlying structure. Our work provides a different (dynamical) origin than the conventionally accepted (structural) mechanisms for mean-field behavior in neuronal avalanches.

  5. Computational and experimental analysis of TMS-induced electric field vectors critical to neuronal activation

    NASA Astrophysics Data System (ADS)

    Krieg, Todd D.; Salinas, Felipe S.; Narayana, Shalini; Fox, Peter T.; Mogul, David J.

    2015-08-01

    Objective. Transcranial magnetic stimulation (TMS) represents a powerful technique to noninvasively modulate cortical neurophysiology in the brain. However, the relationship between the magnetic fields created by TMS coils and neuronal activation in the cortex is still not well-understood, making predictable cortical activation by TMS difficult to achieve. Our goal in this study was to investigate the relationship between induced electric fields and cortical activation measured by blood flow response. Particularly, we sought to discover the E-field characteristics that lead to cortical activation. Approach. Subject-specific finite element models (FEMs) of the head and brain were constructed for each of six subjects using magnetic resonance image scans. Positron emission tomography (PET) measured each subject’s cortical response to image-guided robotically-positioned TMS to the primary motor cortex. FEM models that employed the given coil position, orientation, and stimulus intensity in experimental applications of TMS were used to calculate the electric field (E-field) vectors within a region of interest for each subject. TMS-induced E-fields were analyzed to better understand what vector components led to regional cerebral blood flow (CBF) responses recorded by PET. Main results. This study found that decomposing the E-field into orthogonal vector components based on the cortical surface geometry (and hence, cortical neuron directions) led to significant differences between the regions of cortex that were active and nonactive. Specifically, active regions had significantly higher E-field components in the normal inward direction (i.e., parallel to pyramidal neurons in the dendrite-to-axon orientation) and in the tangential direction (i.e., parallel to interneurons) at high gradient. In contrast, nonactive regions had higher E-field vectors in the outward normal direction suggesting inhibitory responses. Significance. These results provide critical new

  6. [Research in two-dimensional critical phenomena and conformal field theory]. Final report

    SciTech Connect

    Not Available

    1990-12-31

    A very theoretical description is given of research in two- dimensional critical phenomena and conformal field theory. Major progress is reported in the field of fluctuating two-dimensional surfaces. A discretized representation of fluctuating geometry is used where surfaces are represented by triangulations; continuum surfaces are recovered by taking the size of the triangles to zero. One of the central goals of the theory of critical phenomena is to find all possible universality classes of n-dimensional critical phenomena; this goal has been translated into the problem of clasifying all possible scale-invariant euclidean quantum field theories. (RWR)

  7. Coding Major Fields of Study.

    ERIC Educational Resources Information Center

    Bobbitt, L. G.; Carroll, C. D.

    The National Center for Education Statistics conducts surveys which require the coding of the respondent's major field of study. This paper presents a new system for the coding of major field of study. It operates on-line i a Computer Assisted Telephone Interview (CATI) environment and allows conversational checks to verify coding directly from…

  8. Leading Critically: A Grounded Theory of Applied Critical Thinking in Leadership Studies

    ERIC Educational Resources Information Center

    Jekins, Daniel M.; Cutchens, Amanda B.

    2011-01-01

    This study describes the development of a grounded theory of applied critical thinking in leadership studies and examines how student-centered experiential learning in leadership education bridged critical thinking with action. Over three semester undergraduate students in an upper level leadership studies course at a large four-year public…

  9. Nonmonotonic pressure evolution of the upper critical field in superconducting FeSe

    DOE PAGES

    Kaluarachchi, Udhara S.; Taufour, Valentin; Böhmer, Anna E.; ...

    2016-02-01

    The pressure dependence of the upper critical field, Hc2,c, of single crystalline FeSe was studied using measurements of the interplane resistivity, ρc, in magnetic fields parallel to tetragonal c axis. Hc2,c(T) curves obtained under hydrostatic pressures up to 1.56 GPa, the range over which the superconducting transition temperature, Tc, of FeSe exhibits a nonmonotonic dependence with local maximum at p1 ≈ 0.8 GPa and local minimum at p2 ≈ 1.2 GPa. The slope of the upper critical field at Tc,(dHc2,c/dT)Tc, also exhibits a nonmonotonic pressure dependence with distinct changes at p1 and p2. For p < p1 the slope canmore » be described within a multiband orbital model. For both p1 < p < p2 and p > p2 the slope is in good semiquantitative agreement with a single band, orbital Helfand-Werthamer theory with Fermi velocities determined from Shubnikov–de Haas measurements. Lastly, this finding indicates that Fermi surface changes are responsible for the local minimum of Tc(p) at p2 ≈ 1.2 GPa.« less

  10. Nonmonotonic pressure evolution of the upper critical field in superconducting FeSe

    SciTech Connect

    Kaluarachchi, Udhara S.; Taufour, Valentin; Böhmer, Anna E.; Tanatar, Makariy A.; Bud'ko, Sergey L.; Kogan, Vladimir G.; Prozorov, Ruslan; Canfield, Paul C.

    2016-02-01

    The pressure dependence of the upper critical field, Hc2,c, of single crystalline FeSe was studied using measurements of the interplane resistivity, ρc, in magnetic fields parallel to tetragonal c axis. Hc2,c(T) curves obtained under hydrostatic pressures up to 1.56 GPa, the range over which the superconducting transition temperature, Tc, of FeSe exhibits a nonmonotonic dependence with local maximum at p1 ≈ 0.8 GPa and local minimum at p2 ≈ 1.2 GPa. The slope of the upper critical field at Tc,(dHc2,c/dT)Tc, also exhibits a nonmonotonic pressure dependence with distinct changes at p1 and p2. For p < p1 the slope can be described within a multiband orbital model. For both p1 < p < p2 and p > p2 the slope is in good semiquantitative agreement with a single band, orbital Helfand-Werthamer theory with Fermi velocities determined from Shubnikov–de Haas measurements. Lastly, this finding indicates that Fermi surface changes are responsible for the local minimum of Tc(p) at p2 ≈ 1.2 GPa.

  11. When Sex and Power Collide: An Argument for Critical Sexuality Studies.

    PubMed

    Fahs, Breanne; McClelland, Sara I

    2016-01-01

    Attentive to the collision of sex and power, we add momentum to the ongoing development of the subfield of critical sexuality studies. We argue that this body of work is defined by its critical orientation toward the study of sexuality, along with a clear allegiance to critical modalities of thought, particularly feminist thought. Critical sexuality studies takes its cues from several other critical moments in related fields, including critical psychology, critical race theory, critical public health, and critical youth studies. Across these varied critical stances is a shared investment in examining how power and privilege operate, understanding the role of historical and epistemological violence in research, and generating new models and paradigms to guide empirical and theoretical research. With this guiding framework, we propose three central characteristics of critical sexuality studies: (a) conceptual analysis, with particular attention to how we define key terms and conceptually organize our research (e.g., attraction, sexually active, consent, agency, embodiment, sexual subjectivity); (b) attention to the material qualities of abject bodies, particularly bodies that are ignored, overlooked, or pushed out of bounds (e.g., viscous bodies, fat bodies, bodies in pain); and (c) heteronormativity and heterosexual privilege, particularly how assumptions about heterosexuality and heteronormativity circulate in sexuality research. Through these three critical practices, we argue that critical sexuality studies showcases how sex and power collide and recognizes (and tries to subvert) the various power imbalances that are deployed and replicated in sex research.

  12. Universal self-field critical current for thin-film superconductors.

    PubMed

    Talantsev, E F; Tallon, J L

    2015-08-04

    For any practical superconductor the magnitude of the critical current density, Jc, is crucially important. It sets the upper limit for current in the conductor. Usually Jc falls rapidly with increasing external magnetic field, but even in zero external field the current flowing in the conductor generates a self-field that limits Jc. Here we show for thin films of thickness less than the London penetration depth, λ, this limiting Jc adopts a universal value for all superconductors-metals, oxides, cuprates, pnictides, borocarbides and heavy Fermions. For type-I superconductors, it is Hc/λ where Hc is the thermodynamic critical field. But surprisingly for type-II superconductors, we find the self-field Jc is Hc1/λ where Hc1 is the lower critical field. Jc is thus fundamentally determined and this provides a simple means to extract absolute values of λ(T) and, from its temperature dependence, the symmetry and magnitude of the superconducting gap.

  13. Mean-field behavior as a result of noisy local dynamics in self-organized criticality: Neuroscience implications

    NASA Astrophysics Data System (ADS)

    Moosavi, S. Amin; Montakhab, Afshin

    2014-05-01

    Motivated by recent experiments in neuroscience which indicate that neuronal avalanches exhibit scale invariant behavior similar to self-organized critical systems, we study the role of noisy (nonconservative) local dynamics on the critical behavior of a sandpile model which can be taken to mimic the dynamics of neuronal avalanches. We find that despite the fact that noise breaks the strict local conservation required to attain criticality, our system exhibits true criticality for a wide range of noise in various dimensions, given that conservation is respected on the average. Although the system remains critical, exhibiting finite-size scaling, the value of critical exponents change depending on the intensity of local noise. Interestingly, for a sufficiently strong noise level, the critical exponents approach and saturate at their mean-field values, consistent with empirical measurements of neuronal avalanches. This is confirmed for both two and three dimensional models. However, the addition of noise does not affect the exponents at the upper critical dimension (D =4). In addition to an extensive finite-size scaling analysis of our systems, we also employ a useful time-series analysis method to establish true criticality of noisy systems. Finally, we discuss the implications of our work in neuroscience as well as some implications for the general phenomena of criticality in nonequilibrium systems.

  14. High-field magnets using high-critical-temperature superconducting thin films

    DOEpatents

    Mitlitsky, F.; Hoard, R.W.

    1994-05-10

    High-field magnets fabricated from high-critical-temperature superconducting ceramic (HTSC) thin films which can generate fields greater than 4 Tesla are disclosed. The high-field magnets are made of stackable disk-shaped substrates coated with HTSC thin films, and involves maximizing the critical current density, superconducting film thickness, number of superconducting layers per substrate, substrate diameter, and number of substrates while minimizing substrate thickness. The HTSC thin films are deposited on one or both sides of the substrates in a spiral configuration with variable line widths to increase the field. 4 figures.

  15. High-field magnets using high-critical-temperature superconducting thin films

    DOEpatents

    Mitlitsky, Fred; Hoard, Ronald W.

    1994-01-01

    High-field magnets fabricated from high-critical-temperature superconducting ceramic (HTSC) thin films which can generate fields greater than 4 Tesla. The high-field magnets are made of stackable disk-shaped substrates coated with HTSC thin films, and involves maximizing the critical current density, superconducting film thickness, number of superconducting layers per substrate, substrate diameter, and number of substrates while minimizing substrate thickness. The HTSC thin films are deposited on one or both sides of the substrates in a spiral configuration with variable line widths to increase the field.

  16. Magnetic relaxation and lower critical field in MgB2 wires

    NASA Astrophysics Data System (ADS)

    Y, Feng; G, Yan; Y, Zhao; Pradhan, A. K.; F, Liu C.; X, Zhang P.; L, Zhou

    2003-09-01

    Magnetic relaxation behaviour, critical current density Jc and lower critical field Hc1 have been investigated in MgB2/Ta/Cu wires. It is found that Jc and Hc1 decrease linearly with temperature in the whole temperature region below Tc. The relaxation rate is very small and has a weak temperature dependence compared to high-Tc superconductors. Also, the pinning potential is much larger and the temperature and field dependences of the pinning potential are briefly discussed.

  17. Critical Discourse Analysis and Critical Thinking: An Experimental Study in an EFL Context

    ERIC Educational Resources Information Center

    Hashemi, Mohammad Reza; Ghanizadeh, Afsaneh

    2012-01-01

    The present study investigated the impact of critical discourse analysis (CDA) on TEFL students' critical thinking (CT) ability in "Reading Journalistic Texts" classes. In so doing, the study utilized an experimental design with 24 participants in the control group and 29 participants in the experimental group. The results of a pretest indicated…

  18. Critical Curriculum Studies: Education, Consciousness, and the Politics of Knowing. Critical Social Thought

    ERIC Educational Resources Information Center

    Au, Wayne

    2011-01-01

    "Critical Curriculum Studies" offers a novel framework for thinking about how curriculum relates to students' understanding of the world around them. Wayne Au brings together curriculum theory, critical educational studies, and feminist standpoint theory with practical examples of teaching for social justice to argue for a transformative…

  19. Magnetic Field Dependence of the Critical Current in S-N Bilayer Thin Films

    NASA Technical Reports Server (NTRS)

    Sadleir, John E.; Lee, Sang-Jun; Smith, Stephen James; Bandler, Simon; Chervenak, James; Kilbourne, Caroline A.; Finkbeiner, Fred M.; Porter, Frederick S.; Kelley, Richard L.; Adams, Joseph S.; Eckart, Megan E.; Busch, Sarah; Porst, Jan-Patrick

    2013-01-01

    Here we investigate the effects a non-uniform applied magnetic field has on superconducting transition-edge sensors (TESs) critical current. This has implications on TES optimization. It has been shown that TESs resistive transition can be altered by magnetic fields. We have observed critical current rectification effects and explained these effects in terms of a magnetic self-field arising from asymmetric current injection into the sensor. Our TES physical model shows that this magnetic self-field can result in significantly degraded or improved TES performance. In order for this magnetically tuned TES strategy to reach its full potential we are investigating the effect a non-uniform applied magnetic field has on the critical current.

  20. Misogynists All; A Study in Critical Classification

    ERIC Educational Resources Information Center

    Foskett, A. C.

    1971-01-01

    In theory, classificationists avoid critical classification: that is, the introduction of their own bias and prejudices into the schemes they compile. In practice, all the schemes reflect the prejudices of their origins. No solution is proposed, but it is important that librarians be aware of the problems. (Author/NH)

  1. Effect of a pinning field on the critical current density for current-induced domain wall motion in perpendicular magnetic anisotropy nanowires.

    PubMed

    Ooba, Ayaka; Fujimura, Yuma; Takahashi, Kota; Komine, Takashi; Sugita, Ryuji

    2012-09-01

    In this study, the effect of a pinning field on the critical current density for current-induced domain wall motion in nanowires with perpendicular magnetic anisotropy was investigated using micromagnetic simulations. In order to estimate the pinning field in notched nanowires, we conducted wall energy calculations for nanowires with various saturation magnetizations. The pinning field increased as the notch size increased. The pinning field decreased as the saturation magnetization decreased. As a result, the decreased in the pinning field causes the reduction of the critical current density. Therefore, a significant reduction of the critical current density can be obtained by decreasing the saturation magnetization, even if wall pinning occurs.

  2. Upper critical fields and critical current densities of Fe-based superconductors as compared to those of other technical superconductors

    NASA Astrophysics Data System (ADS)

    Pallecchi, I.; Tropeano, M.; Lamura, G.; Pani, M.; Palombo, M.; Palenzona, A.; Putti, M.

    2012-11-01

    Three years since the discovery by the Hosono's group of Fe-based superconductors, an enormous number of compounds, belonging to several different families have been discovered and fundamental properties have been deeply investigated in order to clarify the interplay between magnetisms and superconductivity in these compounds. Indeed, the actual potential of these compounds for practical applications remains still unclear. Fe-based superconductors are midway between high temperature superconductors (HTSCs) and MgB2. In Fe-based superconductors the critical current is rather independent of the field, similarly to HTSCs, as a consequence of the exceptionally high upper critical field and strong pinning associated with nm-scale local modulations of the order parameter. They exhibit low anisotropy of the critical current with respect to the crystalline directions, as in the case of MgB2, which allows current flow along the c-axis. However, Fe-based superconductor polycrystalline materials currently available still exhibit electromagnetic granularity, like the HTSCs, which suppresses superconducting current flow over long length. Whether the nature of such granularity is extrinsic, as due to spurious phases or cracks between grains or intrinsic, as related to misalignment of adjacent grains, is under debate. These aspects will be reviewed in the light of the recent literature.

  3. Static magnetic fields: animal studies.

    PubMed

    Saunders, Richard

    2005-01-01

    Various experimental studies carried out over the last 30-40 years have examined the effects of the chronic or acute exposure of laboratory animals to static magnetic fields. Many of the earlier studies have been adequately reviewed elsewhere; few adverse effects were identified. This review focuses on studies carried out more recently, mostly those using vertebrates, particularly mammals. Four main areas of investigation have been covered, viz., nervous system and behavioural studies, cardiovascular system responses, reproduction and development, and genotoxicity and cancer. Work on the role of the natural geomagnetic field in animal orientation and migration has been omitted. Generally, the acute responses found during exposure to static fields above about 4 T are consistent with those found in volunteer studies, namely the induction of flow potentials around the heart and the development of aversive/avoidance behaviour resulting from body movement in such fields. No consistently demonstrable effects of exposure to fields of approximately 1T and above have been seen on other behavioural or cardiovascular endpoints. In addition, no adverse effects of such fields on reproduction and development or on the growth and development of tumours have been firmly established. Overall, however, far too few animal studies have been carried out to reach any firm conclusions.

  4. Evidence of Magnetic Breakdown on the Defects With Thermally Suppressed Critical Field in High Gradient SRF Cavities

    SciTech Connect

    Eremeev, Grigory; Palczewski, Ari

    2013-09-01

    At SRF 2011 we presented the study of quenches in high gradient SRF cavities with dual mode excitation technique. The data differed from measurements done in 80's that indicated thermal breakdown nature of quenches in SRF cavities. In this contribution we present analysis of the data that indicates that our recent data for high gradient quenches is consistent with the magnetic breakdown on the defects with thermally suppressed critical field. From the parametric fits derived within the model we estimate the critical breakdown fields.

  5. A critical review of the genotoxic potential of electric and magnetic fields. Final report

    SciTech Connect

    McCann, J.; Dietrich, F.M.; Martin, A.

    1993-12-01

    Fifty five published articles were identified which reported results of tests of ELF (extremely low frequency) or static electric or magnetic fields for genotoxic effects. An additional 35 articles involving microwave or radiofrequency exposures were also identified. Primary emphasis was given to the electric and magnetic field studies. The analysis of microwave and radio frequency studies is presented in Appendix A. The biological assays used spanned a wide range, including microbial systems, plants, Drosophila, mammalian and human cells in vitro and in vivo. Experimental results were grouped into four exposure categories: ELF Electric; ELF Magnetic; Static Electric; and Static Magnetic. The internal electric fields present in media (for in vitro experiments) and in the torso and extremities (for in vivo experiments) were estimated, providing an index of comparison. All experiments were critically analyzed with respect to basic data quality criteria. Experiments within each exposure category were then compared to determine if results reinforced or contradicted one another. The preponderance of evidence suggests that neither ELF or static electric or magnetic fields have a clearly demonstrated potential to cause genotoxic effects. However, there may be weak genotoxic activity from exposure under conditions where phenomena auxiliary to an electric field, such as spark discharges, electrical shocks, or corona can occur. In addition, two unconfirmed reports suggest the genotoxic potential of certain chemical mutagens or ionizing radiation may be weakly affected by co-exposure to electric or magnetic fields. Certain exposure categories are not represented or are under-represented by tests in some genotoxicity test systems that are usually included in minimal test batteries as specified by EPA for chemicals. It is suggested that consideration be given to whether additional genotoxicity testing is warranted to fill these gaps.

  6. Critical Thinking and Online Supplemental Instruction: A Case Study

    ERIC Educational Resources Information Center

    Shaw, Cassandra S.; Holmes, Karen E.

    2014-01-01

    A wealth of research is available regarding supplemental instruction; however, a dearth exists regarding online supplemental instruction and critical thinking. This case study explored what was assumed to be known of critical thinking and investigated the extent to which critical thought was promoted within a university's online supplemental…

  7. Selective Critical Thinking: A Textbook Analysis of Education for Critical Thinking in Norwegian Social Studies

    ERIC Educational Resources Information Center

    Børhaug, Kjetil

    2014-01-01

    Current Norwegian curricular guidelines oblige schools to educate citizens with a critical perspective on society. From a discourse theoretical perspective, this obligation implies that various school subjects, and in particular social studies, offer discourses on social issues that allow for different points of view and critical evaluation.…

  8. Upper critical field and anisotropy in carbon alloyed MgB2 thin films

    NASA Astrophysics Data System (ADS)

    Li, Qi; Ferrando, Valeria; Chen, Jun; Pogrebnyakov, Alexej; Redwing, Joan; Xi, Xiaoxing; Gurevich, Alex; Larbalestier, David; Betts, J. B.; Mielke, C. H.

    2006-03-01

    We have studied the upper critical field and its anisotropy γ of C-alloyed MgB2 thin films grown on (0001) SiC single crystal substrates by hybrid physical-chemical vapor deposition (HPCVD). Different concentrations of C were introduced during the deposition, which increased the residual resistivity systematically but did not affect Tc seriously. The upper critical field was found to increase to above 60 T for H parallel to the ab plane and up to ˜ 40T for H parallel to the c axis with even moderate amounts of C doping. Moreover, we show that Hc2 stays at these levels in a wide range of C doping. The Hc2 anisotropy was found to decrease as the C concentration increases. The Hc2(T) curves for both H ab and H c directions were explained by a theoretical model of dirty limit two band superconductivity, which takes into account different scattering rates in π and σ bands, as well as interband scattering. The differences in the Hc2(T) and γ(T) for different samples can be explained by the differences of the relative scattering rates in each band which make it possible to adjust the π and σ scattering such that Hc2 perpendicular to ab can attain almost 20T at 20K.

  9. Critical review of studies on atmospheric dispersion in coastal regions

    SciTech Connect

    Shearer, D.L.; Kaleel, R.J.

    1982-09-01

    This study effort was required as a preliminary step prior to initiation of field measurements of atmospheric dispersion in coastal regions. The Nuclear Regulatory Commission (NRC) is in the process of planning an extensive field measurement program to generate data which will serve as improved data bases for licensing decisions, confirmation of regulations, standards, and guides, and for site characterizations. The study being reported here is an effort directed to obtaining as much information as is possible from existing studies that is relevant toward NRC's objectives. For this study, reports covering research and meteorological measurements conducted for industrial purposes, utility needs, military objectives, and academic studies were obtained and critically reviewed in light of NRC's current data needs. This report provides an interpretation of the extent of existing usable information, an indication of the potential for tailoring existing research toward current NRC information needs, and recommendations for several follow-on studies which could provide valuable additional information through reanalysis of the data. Recommendations are also offered regarding new measurement programs. Emphasis is placed on the identification and acquisition of data from atmospheric tracer studies conducted in coastal regions. A total of 225 references were identified which deal with the coastal atmosphere, including meteorological and tracer measurement programs, theoretical descriptions of the relevant processes, and dispersion models.

  10. On the magnon interaction in Haematite. 2: Magnon energy of the acoustical mode and magnetic critical fields

    NASA Technical Reports Server (NTRS)

    Bonavito, N. L.; Nagai, O.; Tanaka, T.

    1975-01-01

    Previous spin wave theories of the antiferromagnet hematite were extended. The behavior of thermodynamic quantities around the Morin transition temperature was studied, and the latent heat of the Morin transition was calculated. The temperature dependence of the antiferromagnetic resonance frequency and the parallel and perpendicular critical spin-flop magnetic fields were calculated. It was found that the theory agrees well with experiment.

  11. Critical Point Cancellation in 3D Vector Fields: Robustness and Discussion.

    PubMed

    Skraba, Primoz; Rosen, Paul; Wang, Bei; Chen, Guoning; Bhatia, Harsh; Pascucci, Valerio

    2016-02-29

    Vector field topology has been successfully applied to represent the structure of steady vector fields. Critical points, one of the essential components of vector field topology, play an important role in describing the complexity of the extracted structure. Simplifying vector fields via critical point cancellation has practical merit for interpreting the behaviors of complex vector fields such as turbulence. However, there is no effective technique that allows direct cancellation of critical points in 3D. This work fills this gap and introduces the first framework to directly cancel pairs or groups of 3D critical points in a hierarchical manner with a guaranteed minimum amount of perturbation based on their robustness, a quantitative measure of their stability. In addition, our framework does not require the extraction of the entire 3D topology, which contains non-trivial separation structures, and thus is computationally effective. Furthermore, our algorithm can remove critical points in any subregion of the domain whose degree is zero and handle complex boundary configurations, making it capable of addressing challenging scenarios that may not be resolved otherwise. We apply our method to synthetic and simulation datasets to demonstrate its effectiveness.

  12. Critical current density and current distribution in field cooled superconducting disks

    NASA Astrophysics Data System (ADS)

    Bernstein, Pierre; Noudem, Jacques; Dupont, Louis

    2016-07-01

    Applications of bulk superconductors concern superconducting motors and generators, the levitation of vehicles, the generation of high magnetic fields with small size cryo-magnets, the shielding of magnetic fields and other applications. For all of them, it is essential to determine the critical current density, and to understand the effect of the shape and size of the bulks on the properties of interest. In this contribution, we show how the combination of levitation force and trapped field measurements allow one to determine the characteristics and the potential performances of superconducting disks using analytical modeling. As examples of applications we detail the effects of the magnetizing field and of the bulk sheet critical current density on the levitation force. An important result of the reported measurements is that in field-cooled samples, the shielding currents possibly do not flow along the whole thickness of the disks.

  13. Field-induced magnetization jumps and quantum criticality in the 2D J-Q model

    NASA Astrophysics Data System (ADS)

    Iaizzi, Adam; Sandvik, Anders

    The J-Q model is a `designer hamiltonian' formed by adding a four spin `Q' term to the standard antiferromagnetic S = 1 / 2 Heisenberg model. The Q term drives a quantum phase transition to a valence-bond solid (VBS) state: a non-magnetic state with a pattern of local singlets which breaks lattice symmetries. The elementary excitations of the VBS are triplons, i.e. gapped S=1 quasiparticles. There is considerable interest in the quantum phase transition between the Néel and VBS states as an example of deconfined quantum criticality. Near the phase boundary, triplons deconfine into pairs of bosonic spin-1/2 excitations known as spinons. Using exact diagonalization and the stochastic series expansion quantum monte carlo method, we study the 2D J-Q model in the presence of an external magnetic field. We use the field to force a nonzero density of magnetic excitations at T=0 and look for signatures of Bose-Einstein condensation of spinons. At higher magnetic fields, there is a jump in the induced magnetization caused by the onset of an effective attractive interaction between magnons on a ferromagnetic background. We characterize the first order quantum phase transition and determine the minimum value of the coupling ratio q ≡ Q / J required to produce this jump. Funded by NSF DMR-1410126.

  14. Quantum anomalous Hall effect with field-tunable Chern number near Z2 topological critical point

    NASA Astrophysics Data System (ADS)

    Duong, Le Quy; Lin, Hsin; Tsai, Wei-Feng; Feng, Yuan Ping

    We study the practicability of achieving quantum anomalous Hall (QAH) effect with field-tunable Chern number in a magnetically doped, topologically trivial insulating thin film. Specifically in a candidate material, TlBi(S1-δSeδ)2, we demonstrate that the QAH phases with different Chern numbers can be achieved by means of tuning the exchange field strength or the sample thickness near the Z2 topological critical point. Our physics scenario successfully reduces the necessary exchange coupling strength for a targeted Chern number. This QAH mechanism differs from the traditional QAH picture with a magnetic topological insulating thin film, where the ``surface'' states must involve and sometimes complicate the realization issue. Furthermore, we find that a given Chern number can also be tuned by a perpendicular electric field, which naturally occurs when a substrate is present. High-Chern number QAH phase obtained from magnetically doped topological crystalline insulator thin films will also be discussed. Support by the Singapore National Research Foundation under NRF Award No. NRF-NRFF2013-03 is acknowledged.

  15. High agreement between laboratory and field estimates of critical power in cycling.

    PubMed

    Karsten, B; Jobson, S A; Hopker, J; Jimenez, A; Beedie, C

    2014-04-01

    The purpose of this study was to investigate the level of agreement between laboratory-based estimates of critical power (CP) and results taken from a novel field test. Subjects were fourteen trained cyclists (age 40±7 yrs; body mass 70.2±6.5 kg; VO2max 3.8±0.5 L · min-1). Laboratory-based CP was estimated from 3 constant work-rate tests at 80%, 100% and 105% of maximal aerobic power (MAP). Field-based CP was estimated from 3 all-out tests performed on an outdoor velodrome over fixed durations of 3, 7 and 12 min. Using the linear work limit (Wlim) vs. time limit (Tlim) relation for the estimation of CP1 values and the inverse time (1/t) vs. power (P) models for the estimation of CP2 values, field-based CP1 and CP2 values did not significantly differ from laboratory-based values (234±24.4 W vs. 234±25.5 W (CP1); P<0.001; limits of agreement [LOA], -10.98-10.8 W and 236±29.1 W vs. 235±24.1 W (CP2); P<0.001; [LOA], -13.88-17.3 W. Mean prediction errors for laboratory and field estimates were 2.2% (CP) and 27% (W'). Data suggest that employing all-out field tests lasting 3, 7 and 12 min has potential utility in the estimation of CP.

  16. Critical temperature for {alpha}-particle condensation within a momentum-projected mean-field approach

    SciTech Connect

    Sogo, T.; Roepke, G.; Lazauskas, R.

    2009-05-15

    {alpha}-particle (quartet) condensation in homogeneous spin-isospin symmetric nuclear matter is investigated. The usual Thouless criterion for the critical temperature is extended to the quartet case. The in-medium four-body problem is strongly simplified by the use of a momentum-projected mean-field ansatz for the quartet. The self-consistent single-particle wave functions are shown and discussed for various values of the density at the critical temperature. Excellent agreement of the critical temperature with a numerical solution of the Faddeev-Yakubovsky equation is obtained.

  17. Flux Pinning and Enhanced Critical Current in Magnetic Field by Artificial Pinning Centers.#

    NASA Astrophysics Data System (ADS)

    Wang, J.-Q.; Rizzo, N. D.; McCambridge, J. D.; Prober, D. E.; Motowidlo, L. R.; Zeitlin, B. A.

    1996-03-01

    Flux pinning to enhance critical currents (Jc) in type II superconductors (NbTi) in a magnetic field was studied, using nanometer sized artificial pins. From consideration of free energy and proximity effects, we compare pinning by various materials, ranging from weak superconductors (Nb), normal metals (Ti, Cu), to ferromagnets (Ni, Fe). A trade-off is found between induced superconductivity in the pin and a reduction of superconductivity in the NbTi. Thus, a normal metal can have stronger pinning than a similar-sized void. This idea is supported by our finding that Ti provides the strongest pinning in multilayer film systems. Pinning mechanisms by ferromagnetic (FM) pins are also discussed, along with results of Jc for NbTiTa wires with FM artificial pinning centers. #Support by CT Dept. Econ. Dev. Grant 94G014 and IGC-AS. *present address: Westinghouse STC, Pittsburgh, PA

  18. A study of critical thinking and research utilization among nurses.

    PubMed

    Profetto-McGrath, Joanne; Hesketh, Kathryn L; Lang, Sarah; Estabrooks, Carole A

    2003-04-01

    Previous studies have suggested that critical thinking influences research utilization; however, empirical support for the link between critical thinking dispositions and research utilization is nonexistent. In this article, critical thinking dispositions and research utilization habits are detailed, and the relationship of critical thinking dispositions to research utilization in a sample of 141 nurses working on two acute surgical units and five pediatric units in four tertiary care hospitals are examined. Results indicate a significant positive correlation between the total critical thinking disposition score and overall research utilization. Overall critical thinking disposition correlates significantly with all forms of research utilization, with the exception of symbolic research utilization. These findings indicate a need to foster critical thinking in both nursing education and the work environment.

  19. Self-Magnetic Field Effects on Electron Emission as the Critical Current is Approached

    SciTech Connect

    Ottinger, P. F.; Cooperstein, G.; Schumer, J. W.; Swanekamp, S. B.

    2001-09-28

    The self-magnetic field associated with the current in a planar diode is shown to reduce electron emission below the Child-Langmuir current density. As the magnetic field increases, the diode current is limited to the critical current. Here, a ID analysis is carried out to calculate the suppressed current density in the presence of a transverse magnetic field. The problem is shown to be similar to that of the limiting current (i.e., Hull current) calculated in a crossed field gap, in which a constant transverse magnetic field is applied across the gap to insulate the electron flow. In the case considered here, the magnetic field is produced by the diode current itself and this self-magnetic field decreases with distance along the gap. It is shown that the emitted current density is only modestly reduced from the Child-Langmuir current density. The 1-D analysis remains valid until critical current is approached, at which point orbit crossing occurs and a 2-D kinetic analysis is required. The minimum diode length required to reach critical current is also derived.

  20. A Critical Analysis of IQ Studies of Adopted Children

    ERIC Educational Resources Information Center

    Richardson, Ken; Norgate, Sarah H.

    2006-01-01

    The pattern of parent-child correlations in adoption studies has long been interpreted to suggest substantial additive genetic variance underlying variance in IQ. The studies have frequently been criticized on methodological grounds, but those criticisms have not reflected recent perspectives in genetics and developmental theory. Here we apply…

  1. Benchmark field study of deep neutron penetration

    SciTech Connect

    Morgan, J.F.; Sale, K. ); Gold, R.; Roberts, J.H.; Preston, C.C. )

    1991-06-10

    A unique benchmark neutron field has been established at the Lawrence Livermore National Laboratory (LLNL) to study deep penetration neutron transport. At LLNL, a tandem accelerator is used to generate a monoenergetic neutron source that permits investigation of deep neutron penetration under conditions that are virtually ideal to model, namely the transport of mono-energetic neutrons through a single material in a simple geometry. General features of the Lawrence Tandem (LATAN) benchmark field are described with emphasis on neutron source characteristics and room return background. The single material chosen for the first benchmark, LATAN-1, is a steel representative of Light Water Reactor (LWR) Pressure Vessels (PV). Also included is a brief description of the Little Boy replica, a critical reactor assembly designed to mimic the radiation doses from the atomic bomb dropped on Hiroshima, and its us in neutron spectrometry. 18 refs.

  2. Advertisement Analysis: A Comparative Critical Study

    ERIC Educational Resources Information Center

    Abdelaal, Noureldin Mohamed; Sase, Amal Saleh

    2014-01-01

    This study aimed at analyzing two advertisements, and investigating how advertisers use discourse and semiotics to make people and customers buy into their ideas, beliefs, or simply their products. The two advertisements analyzed are beauty products which have been selected from internet magazines. The methodology adopted in this study is…

  3. Universal self-field critical current for thin-film superconductors

    PubMed Central

    Talantsev, E. F.; Tallon, J. L.

    2015-01-01

    For any practical superconductor the magnitude of the critical current density, Jc, is crucially important. It sets the upper limit for current in the conductor. Usually Jc falls rapidly with increasing external magnetic field, but even in zero external field the current flowing in the conductor generates a self-field that limits Jc. Here we show for thin films of thickness less than the London penetration depth, λ, this limiting Jc adopts a universal value for all superconductors—metals, oxides, cuprates, pnictides, borocarbides and heavy Fermions. For type-I superconductors, it is Hc/λ where Hc is the thermodynamic critical field. But surprisingly for type-II superconductors, we find the self-field Jc is Hc1/λ where Hc1 is the lower critical field. Jc is thus fundamentally determined and this provides a simple means to extract absolute values of λ(T) and, from its temperature dependence, the symmetry and magnitude of the superconducting gap. PMID:26240014

  4. New Spinor Field Realizations of the Non-Critical W3 String

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Jie; Liu, Yu-Xiao; Ren, Ji-Rong

    2006-04-01

    We investigate the new spinor field realizations of the W3 algebra, making use of the fact that the W3 algebra can be linearized by the addition of a spin-1 current. We then use these new realizations to build the nilpotent Becchi-Rouet-Stora-Tyutin charges of the spinor non-critical W3 string.

  5. Policy, Practice and Purpose in the Field of Education: A Critical Review

    ERIC Educational Resources Information Center

    Blackmore, Jill

    2010-01-01

    This paper provides a critical review of papers in this special issue on Bourdieu and practice. What is different about this collection is that, in analysing policy and practice through a Bourdieusian lens, the thinking tools of field, disposition (collective and individual), logics of practice and doxa have been mobilised with regard to the…

  6. Specific features of the states of cobalt fluoride in the vicinity of the critical field

    NASA Astrophysics Data System (ADS)

    Medvedovskaya, O. G.; Fedorenko, T. A.; Chepurnykh, G. K.

    2016-12-01

    The state of cobalt fluoride in the vicinity of the critical value H c of a longitudinal magnetic field H, in which the magnetic subsystem of a CoF2 crystal with a strong Dzyaloshinskii interaction is transformed from the antiferromagnetic phase into the canted phase, has been investigated taking into account the increasing number of experimental studies related to the use of cobalt fluoride. It has been found that, despite the unusually high magnetic anisotropy of the crystal, the state of the magnetic subsystem at H = H c is extremely sensitive to a small deviation of the vector H from the C 4 axis. Another feature is that the high sensitivity disappears with an increase or decrease in the magnetic field by only a few thousandths of H c . The results of the investigations performed in this work are applicable to magnetically ordered crystals FeF3 and Cu2OSeO3, which, as well as the CoF2 crystals, are characterized by a strong Dzyaloshinskii interaction and a significant magnetic anisotropy. The revealed anomaly in the reduction of the effective magnetic anisotropy is of interest in connection with numerous attempts to decrease the magnetic anisotropy in crystals with giant magnetostriction, which are necessary for the use as sensors and vibrators.

  7. Magnetic Field Dependence of the Critical Current of Planar Geometry Josephson Junctions

    NASA Astrophysics Data System (ADS)

    Ma, Meng; Cho, Ethan; Huynh, Chuong; Cybart, Shane; Dynes, Robert

    2015-03-01

    We report a study on the magnetic field dependence of the critical current of planar geometry Josephson junctions. We have fabricated Josephson junctions by using a focused helium ion beam to irradiate a narrow barrier in the plane of a 25 nm thick Y-Ba-Cu-O film. The London penetration depth λL is large (~1 μm) because of the ultra-thin thickness of the film. As a result, calculations of the Josephson penetration depth λJ are not realistic nor physical. Therefore in this work, we measure λJ experimentally. We tested devices with bridge widths ranging from 4 to 50 μm, and present measurements of the Fraunhofer quantum diffraction pattern (IC (B)). We observe a crossover from short to long junction behavior, which gives an experimentally measured λJ that ranges between 3 μm to 5 μm. The shape of the IC (B) pattern is strongly affected by the width of the bridge because of self-field effects. As the bridge width increases, Josephson vortices enter the junction and skew the patterns. This work shows that the electronic properties of the planar junctions are very different than those classical ``sandwich'' junctions due to the differences in geometry.

  8. Critical Appraisal of Mixed Methods Studies

    ERIC Educational Resources Information Center

    Heyvaert, Mieke; Hannes, Karin; Maes, Bea; Onghena, Patrick

    2013-01-01

    In several subdomains of the social, behavioral, health, and human sciences, research questions are increasingly answered through mixed methods studies, combining qualitative and quantitative evidence and research elements. Accordingly, the importance of including those primary mixed methods research articles in systematic reviews grows. It is…

  9. Promoting Critical Thinking through an Interdisciplinary Study Abroad Program

    ERIC Educational Resources Information Center

    Cai, WeiWei; Sankaran, Gopal

    2015-01-01

    This paper discusses the promotion of critical thinking through an interdisciplinary curriculum design using multidisciplinary faculty as well as details the implementation of an experiential short-term study abroad program in China. To achieve this educational goal of critical thinking, along with meeting the requirements specific to each course,…

  10. Electromagnetic waves destabilized by runaway electrons in near-critical electric fields

    SciTech Connect

    Komar, A.; Pokol, G. I.; Fueloep, T.

    2013-01-15

    Runaway electron distributions are strongly anisotropic in velocity space. This anisotropy is a source of free energy that may destabilize electromagnetic waves through a resonant interaction between the waves and the energetic electrons. In this work, we investigate the high-frequency electromagnetic waves that are destabilized by runaway electron beams when the electric field is close to the critical field for runaway acceleration. Using a runaway electron distribution appropriate for the near-critical case, we calculate the linear instability growth rate of these waves and conclude that the obliquely propagating whistler waves are most unstable. We show that the frequencies, wave numbers, and propagation angles of the most unstable waves depend strongly on the magnetic field. Taking into account collisional and convective damping of the waves, we determine the number density of runaways that is required to destabilize the waves and show its parametric dependences.

  11. Critical factors affecting field-scale losses of nitrogen and phosphorus in spring snowmelt runoff in the canadian prairies.

    PubMed

    Liu, Kui; Elliott, Jane A; Lobb, David A; Flaten, Don N; Yarotski, Jim

    2013-01-01

    A long-term, field-scale study in southern Manitoba, Canada, was used to identify the critical factors controlling yearly transport of nitrogen (N) and phosphorus (P) by snowmelt runoff. Flow monitoring and water sampling for total and dissolved N and P were performed at the edge of field. The flow-weighted mean concentrations and loads of N and P for the early (the first half of yearly total volume of snowmelt runoff), late (the second half of yearly total volume of snowmelt runoff), and yearly snowmelt runoff were calculated as response variables. A data set of management practices, weather variables, and hydrologic variables was generated and used as predictor variables. Partial least squares regression analysis indicated that critical factors affecting the water chemistry of snowmelt runoff depended on the water quality variable and stage of runoff. Management practices within each year, such as nitrogen application rate, number of tillage passes, and residue burial ratio, were critical factors for flow-weighted mean concentration of N, but not for P concentration or nutrient loads. However, the most important factors controlling nutrient concentrations and loads were those related to the volume of runoff, including snow water equivalent, flow rate, and runoff duration. The critical factors identified for field-scale yearly snowmelt losses provide the basis for modeling of nutrient losses in southern Manitoba and potentially throughout areas with similar climate in the northern Great Plains region, and will aid in the design of effective practices to reduce agricultural nonpoint nutrient pollution in downstream waters.

  12. Magnetic-field-tuned quantum criticality of the heavy-fermion system YbPtBi

    SciTech Connect

    Mun, E. D.; Budko, Serguei L.; Martin, Catalin; Kim, Hyong June; Tanatar, Makariy A.; Park, J.-H.; Murphy, T.; Schmiedeshoff, G. M.; Dilley, N.; Prozorov, Ruslan; Canfield, Paul C.

    2013-02-15

    In this paper, we present systematic measurements of the temperature and magnetic field dependencies of the thermodynamic and transport properties of the Yb-based heavy fermion YbPtBi for temperatures down to 0.02 K with magnetic fields up to 140 kOe to address the possible existence of a field-tuned quantum critical point. Measurements of magnetic-field- and temperature-dependent resistivity, specific heat, thermal expansion, Hall effect, and thermoelectric power indicate that the AFM order can be suppressed by an applied magnetic field of Hc~4 kOe. In the H-T phase diagram of YbPtBi, three regimes of its low-temperature states emerge: (I) AFM state, characterized by a spin density wave-like feature, which can be suppressed to T=0 by the relatively small magnetic field of Hc~4 kOe; (II) field-induced anomalous state in which the electrical resistivity follows Δρ(T)∝T1.5 between Hc and ~8 kOe; and (III) Fermi liquid (FL) state in which Δρ(T)∝T2 for H≥8 kOe. Regions I and II are separated at T=0 by what appears to be a quantum critical point. Whereas region III appears to be a FL associated with the hybridized 4f states of Yb, region II may be a manifestation of a spin liquid state.

  13. Field-dependent critical state of high-Tc superconducting strip simultaneously exposed to transport current and perpendicular magnetic field

    SciTech Connect

    Xue, Cun; He, An; Yong, Huadong; Zhou, Youhe

    2013-12-15

    We present an exact analytical approach for arbitrary field-dependent critical state of high-T{sub c} superconducting strip with transport current. The sheet current and flux-density profiles are derived by solving the integral equations, which agree with experiments quite well. For small transport current, the approximate explicit expressions of sheet current, flux-density and penetration depth for the Kim model are derived based on the mean value theorem for integration. We also extend the results to the field-dependent critical state of superconducting strip in the simultaneous presence of applied field and transport current. The sheet current distributions calculated by the Kim model agree with experiments better than that by the Bean model. Moreover, the lines in the I{sub a}-B{sub a} plane for the Kim model are not monotonic, which is quite different from that the Bean model. The results reveal that the maximum transport current in thin superconducting strip will decrease with increasing applied field which vanishes for the Bean model. The results of this paper are useful to calculate ac susceptibility and ac loss.

  14. Criticality features in ULF magnetic fields prior to the 2011 Tohoku earthquake

    PubMed Central

    HAYAKAWA, Masashi; SCHEKOTOV, Alexander; POTIRAKIS, Stelios; EFTAXIAS, Kostas

    2015-01-01

    The criticality of ULF (Ultra-low-frequency) magnetic variations is investigated for the 2011 March 11 Tohoku earthquake (EQ) by natural time analysis. For this attempt, some ULF parameters were considered: (1) Fh (horizontal magnetic field), (2) Fz (vertical magnetic field), and (3) Dh (inverse of horizontal magnetic field). The first two parameters refer to the ULF radiation, while the last parameter refers to another ULF effect of ionospheric signature. Nighttime (L.T. = 3 am ± 2 hours) data at Kakioka (KAK) were used, and the power of each quantity at a particular frequency band of 0.03–0.05 Hz was averaged for nighttime hours. The analysis results indicate that Fh fulfilled all criticality conditions on March 3–5, 2011, and that the additional parameter, Dh reached also a criticality on March 6 or 7. In conclusion, criticality has reached in the pre-EQ fracture region a few days to one week before the main shock of the Tohoku EQ. PMID:25743063

  15. Malaria resurgence in India: a critical study.

    PubMed

    Sharma, V P; Mehrotra, K N

    1986-01-01

    mention that malaria resurgence occurred in towns where the control measures were non-insecticidal and in regions which were not under the influence of insecticide-resistant vectors. The study also revealed that resurgence occurred before the introduction of high-yielding varieties programme in the country, and had no relationship to either the cotton or rice growing or intensive agriculture.

  16. Magnetic-field-induced quantum criticality in a planar ferromagnet with single-ion anisotropy

    NASA Astrophysics Data System (ADS)

    Mercaldo, M. T.; Rabuffo, I.; De Cesare, L.; Caramico D'Auria, A.

    2014-08-01

    We analyze the effects induced by single-ion anisotropy on quantum criticality in a d-dimensional spin-3/2 planar ferromagnet. To tackle this problem we employ the two-time Green's function method, using the Tyablikov decoupling for exchange interactions and the Anderson-Callen decoupling for single-ion anisotropy. In our analysis the role of non-thermal control parameter which drives the quantum phase transition is played by a longitudinal external magnetic field. We find that the single-ion anisotropy has substantial effects on the structure of the phase diagram close to the quantum critical point.

  17. Low field critical current density of titanium sheathed magnesium diboride wires

    NASA Astrophysics Data System (ADS)

    Rostila, L.; Grasso, G.; Demenčík, E.; Tumino, A.; Brisigotti, S.; Kováč, P.

    2010-06-01

    Magnesium diboride (MgB2) is replacing some of the conventional superconductors due to its low cost and availability in kilometer lengths. MgB2 has also been considered for AC applications. In order to model the AC losses and the critical currents of the applications, intrinsic Jc(B)-dependence is an important factor also at low fields. In this work Jc(B)-dependence of an MgB2 sample is extracted from the standard in field voltage-current measurements. The proposed method is applied to a non magnetic titanium sheathed sample at 16 and 20 K and a simple formula for Jc(B) aligns with the measurements. In the fitting process, the critical current distribution inside the wire is numerically simulated in order to take the self field of the sample into account. Moreover, the same formula aligns with measurements of a different sample. These critical current measurements, performed at 4.2 K, were based on magnetization. In the self field computations, the superconducting cross section must be determined accurately. Therefore, we tailored an image processing tool for MgB2 wires to obtain the geometry from a photograph.

  18. Identifying critical source areas for phosphorus loss in Ireland using field and catchment scale ranking schemes

    NASA Astrophysics Data System (ADS)

    Hughes, K. J.; Magette, W. L.; Kurz, I.

    2005-03-01

    Phosphorus (P) in agricultural runoff is a major pollutant in many of Ireland's surface waters. Identification of areas that are at a high risk for P loss to surface waters is a critical component of river basin management. Two P ranking schemes (PRS's) were developed for Ireland, based on multi-criteria analysis approaches proposed in both the US and Europe, to predict the relative likelihood of P loss at both the field and catchment scales. The Field PRS was evaluated by comparing predicted rankings of potential P loss and transport against measured edge-of-field Dissolved Reactive P (DRP) loss for three fields with varying soil P levels. Qualitatively, results indicated that the Field PRS rankings corresponded to the magnitudes of measured P loss for the field sites, as well as to a reasoned evaluation of the relative likelihood that the fields would lose P that would subsequently make its way to surface water. The Catchment PRS was evaluated on a total of 31 catchments and sub-catchments by comparing predicted rankings of potential P loss and transport against measured in-stream median Molybdate Reactive P (MRP). Rankings of the relative likelihood of P loss and transport predicted by the Catchment PRS were positively correlated with median in-stream MRP ( r=0.51, P<0.05). Although the data available for these evaluations were limited, especially at field scale, and further research may identify the opportunity for modifications, both field and catchment scale P ranking schemes demonstrated a potential for identifying critical P source areas within catchments dominated by grass-based agricultural production systems, such as those in Ireland.

  19. Seven-Step Framework for Critical Analysis and Its Application in the Field of Physical Therapy.

    PubMed

    Nixon, Stephanie A; Yeung, Euson; Shaw, James A; Kuper, Ayelet; Gibson, Barbara E

    2016-09-29

    Critical analysis (or the ability to recognize taken-for-granted assumptions and their effects) is a skill that requires teaching and practice. The purpose of this article is to introduce a framework for critically analyzing assumptions within physical therapy and illustrate its utility through application to 2 examples: a physical therapy clinic logo and an outcome measure for health-related quality of life (HRQOL). This 7-step framework for critical analysis was created for a pilot project to develop reflexivity among senior physical therapist students and further developed through an iterative process of reflecting on its utility for advancing the field of physical therapy. The 7-step framework is an iterative process involving a cascade of 7 steps: (1) name the specific aspect of practice being analyzed, (2) identify the intended purposes of this aspect of practice, (3) uncover the assumptions that support these intended purposes, (4) identify who benefits, (5) identify who is disadvantaged, (6) link these specific ideas to society-level patterns, and (7) conceive of alternatives that mitigate actual or potential harms. It is emphasized that being theoretically critical does not equate to being negative. Rather, the word "critical" is used in the sense of thinking deeply and carefully about the intended and unintended consequences of actions (including common professional practices, ways of speaking, and visual representations) in order to reflect on and mature the field of physical therapy. The purpose of critical analysis is to invite and promote dialogue that assists physical therapist clinicians, researchers, and students to arrive at new insights about the impacts of their day-to-day actions.

  20. Scaling laws for the critical current density of NbN films in high magnetic fields

    SciTech Connect

    Hampshire, D.P. . Dept. of Physics); Gray, K.E.; Kampwirth, R.T. )

    1992-08-01

    We have measured the critical current density (Jc) of two NbN films (500 {Angstrom} and 1550 {Angstrom} thick) as a function of temperature in magnetic fields up to 25 Tesla using transport measurements. In both films, the functional form of the volume pinning force F{sub p} obeys the Fietz - Webb scaling law throughout the entire magnetic field and temperature range such that: F{sub p}=J{sub c} {times} B= {alpha}B{sub c2}{sup m}(T)b{sup {1/2}} (1-b){sup 2} = {alpha}*(1-T/T{sub c}){sup m}b{sup {1/2}}(1-b){sup 2} where {alpha} and {alpha}* are constants dependent on the film, B{sub c2}(T) is the upper critical field, b = B/B{sub c2}(T) is the reduced magnetic field, {Tc} is the critical temperature and we find m = 2.7 {plus minus} 0.1. Over a limited range of magnetic fields close to B{sub c2}(T), we can approximate this functional form by: F{sub p} = {Beta}B{sub c2}{sup M}(T)b(1-b){sup 2}={Beta}*(1-T/{Tc}){sup M}b(1-b){sup 2} where {Beta} and {Beta}* are constants and we find M = 2.6{plus minus}0.2. Values of J{sub c} derived from D.C. magnetisation data obtained using Bean's model show qualitative agreement with the transport measurements throughout the superconducting phase. Despite the marked granularity in the microstructure of these films, we interpret our results as evidence that a flux pinning mechanism determines the transport current density in NbN films in high magnetic fields.

  1. Scaling laws for the critical current density of NbN films in high magnetic fields

    SciTech Connect

    Hampshire, D.P.; Gray, K.E.; Kampwirth, R.T.

    1992-08-01

    We have measured the critical current density (Jc) of two NbN films (500 {Angstrom} and 1550 {Angstrom} thick) as a function of temperature in magnetic fields up to 25 Tesla using transport measurements. In both films, the functional form of the volume pinning force F{sub p} obeys the Fietz - Webb scaling law throughout the entire magnetic field and temperature range such that: F{sub p}=J{sub c} {times} B= {alpha}B{sub c2}{sup m}(T)b{sup {1/2}} (1-b){sup 2} = {alpha}*(1-T/T{sub c}){sup m}b{sup {1/2}}(1-b){sup 2} where {alpha} and {alpha}* are constants dependent on the film, B{sub c2}(T) is the upper critical field, b = B/B{sub c2}(T) is the reduced magnetic field, {Tc} is the critical temperature and we find m = 2.7 {plus_minus} 0.1. Over a limited range of magnetic fields close to B{sub c2}(T), we can approximate this functional form by: F{sub p} = {Beta}B{sub c2}{sup M}(T)b(1-b){sup 2}={Beta}*(1-T/{Tc}){sup M}b(1-b){sup 2} where {Beta} and {Beta}* are constants and we find M = 2.6{plus_minus}0.2. Values of J{sub c} derived from D.C. magnetisation data obtained using Bean`s model show qualitative agreement with the transport measurements throughout the superconducting phase. Despite the marked granularity in the microstructure of these films, we interpret our results as evidence that a flux pinning mechanism determines the transport current density in NbN films in high magnetic fields.

  2. Quasiperiodic superconducting V/Zr multilayers: critical magnetic fields and crossover

    NASA Astrophysics Data System (ADS)

    Fogel, N. Ya.; Cherkasova, V. G.; Mikhailov, M. Yu.; Bomze, Yu. V.; Yuzephovich, O. I.; Dmitrenko, I. M.; Stetsenko, A. N.

    1998-08-01

    Critical magnetic fields parallel and perpendicular to the planes of quasiperiodic superconducting Fibonacci multilayers (ML) consisting of vanadium and zirconium are measured. The temperature dependence of the parallel critical field Hc∥ displays two crossovers. The Hc∥(T) dependence is of square-root type in the vicinity of the transition temperature Tc and linear at low temperatures. Between these temperature intervals, the dependence follows a power law: Hc∥˜(1-T/Tc)α, α=0,78±0,02. The complex nature of this dependence can be explained in the framework of the Ginzburg-Landau theory for a quasiperiodic ML, as well as by the scaling theory for fractal multilayers which takes into account the different structure length scales in the case of ML with a complex sequence of layers.

  3. Studying critical values: adverse event identification following a critical laboratory values study at the ohio state university medical center.

    PubMed

    Jenkins, James J; Mac Crawford, J; Bissell, Michael G

    2007-10-01

    No study to date has used laboratory critical values to evaluate variations in patient adverse events. We retrospectively analyzed a database of critical values to determine their distribution by hospital unit over time. The data were drawn from the Ohio State University Medical Center Information Warehouse (Columbus) for a 58-month period. Critical values were plotted over time on statistical control charts and analyzed for unusual peaks in monthly occurrence rates. Chart review of individual patient results yielded several predictor variables for the unusual peaks. Of these, occurrence of patient adverse events was the most relevant independent predictor variable for a month with an unusual number of critical values vs a normal month. This result epidemiologically confirms the basic premise of critical value reporting and suggests that the control-chart method of this type could be a new statistical tool to compare clinical activity of different hospital locations at different times.

  4. Testing electromagnetic fields for potential carcinogenic activity: a critical review of animal models.

    PubMed Central

    McCann, J; Kavet, R; Rafferty, C N

    1997-01-01

    In order to assess the potential of electromagnetic fields (EMF) to influence the process of carcinogenesis, it will be necessary to supplement epidemiological studies with controlled laboratory studies in animals. There are now a number of suitable assays available that focus on different histopathological forms of cancer and on different stages of carcinogenesis--induction, promotion, progression. In this review we discuss eight major systems in the context of this generalized carcinogenesis paradigm. Our aim is to bring together what is currently known about the biology of carcinogenesis in these systems in order to provide a context for evaluating EMF results as they become available. We also critically discuss EMF test results that have so far been obtained in the animal models reviewed. Most of the 19 completed studies identified were negative. However, suggestive positive results were reported in three promotion assays (in rat mammary gland, in rat liver, and in mouse skin), and in one multigeneration study in mice. Results in the rat liver assay and in the multigeneration study have only been reported in abstract form and cannot be adequately evaluated. Positive results reported in both the rat mammary gland and the mouse skin systems are of weak statistical significance and have not been independently replicated. However, it may be of interest that effects in both systems appear primarily to involve the progression stage of carcinogenesis. We suggest that more definitive conclusions as to the carcinogenic potential of EMF may require expanded test protocols that reinforce traditional carcinogenesis end points with biochemical or other parameters reflective of biological processes known to be associated with carcinogenesis in the different systems. PMID:9114279

  5. Anomalous behaviour of critical fields near a superconducting quantum critical point in BaFe2(As1-xPx)2

    NASA Astrophysics Data System (ADS)

    Putzke, C.; Carrington, A.; Walmsley, P.; Malone, L.; Fletcher, J. D.; See, P.; Vignolles, D.; Proust, C.; Badoux, S.; Kasahara, S.; Mazukami, Y.; Shibauchi, T.; Matsuda, Y.

    2014-03-01

    BaFe2(As1-xPx)2 presents one of the cleanest and clearest systems in which to study the influence of quantum critical fluctuations on high temperature superconductivity. In this material a sharp maximum in the magnetic penetration depth has been found at the quantum critical point (QCP x = 0 . 3) where Tc is maximal1. Specific heat and de Haas-van Alphen effect measurements2 show that this peak is driven by a corresponding increase in the quasiparticle effective mass. Based on these previous results a simple one-band theory would suggest that at the QCP we should expect a large increase in Hc 2 and a corresponding dip in Hc 1 . Actual measurements of these critical fields, which we present here, shows quite different behavior which we suggest is caused by an anomalous enhancement in the vortex core energy close to the QCP. 1 K.Hashimoto et.al., Science 336, 1554 (2012) 2 P.Walmsley, C.Putzke et.al., Phys. Rev. Lett. 110, 257002 (2013) This work was supported by the Engineering and Physical Sciences Research Council, EuroMagNET II, and KAKENHI from JSPS.

  6. Critical Current Test of Liquid Hydrogen Cooled HTC Superconductors under External Magnetic Field

    NASA Astrophysics Data System (ADS)

    Shirai, Yasuyuki; Shiotsu, Masahiro; Tatsumoto, Hideki; Kobayashi, Hiroaki; Naruo, Yoshihiro; Nonaka, Satoshi; Inatani, Yoshifumi

    High-Tc (HTC) superconductors including MgB2 will show excellent properties under temperature of Liquid Hydrogen (LH2:20K), which has large latent heat and low viscosity coefficient. In order to design and fabricate the LH2 cooled superconducting energy devices, we must clear the cooling property of LH2 for superconductors, the cooling system and safety design of LH2 cooled superconducting devices and electro-magnetic property evaluation of superconductors (BSCCO, REBCO and MgB2) and their magnets cooled by LH2. As the first step of the study, an experimental setup which can be used for investigating heat transfer characteristics of LH2 in a pool and also in forced flow (circulation loop with a pump), and also for evaluation of electro-magnetic properties of LH2 cooled superconductors under external magnetic field (up to 7 T). In this paper, we will show a short sketch of the experimental set-up, practical experiences in safety operation of liquid hydrogen cooling system and example test results of critical current evaluation of HTC superconductors cooled by LH2.

  7. Investigation of radiation fields outside the Sub-critical Assembly in Dubna.

    PubMed

    Seltbor, P; Lopatkin, A; Gudowski, W; Shvetsov, V; Polanski, A

    2005-01-01

    The radiation fields outside the planned experimental Sub-critical Assembly in Dubna (SAD) have been studied in order to provide a basis for the design of the concrete shielding that cover the reactor core. The effective doses around the reactor, induced by leakage of neutrons and photons through the shielding, have been determined for a shielding thickness varying from 100 to 200 cm. It was shown that the neutron flux and the effective dose is higher above the shielding than at the side of it, owing to the higher fraction of high-energy spallation neutrons emitted in the direction of the incident beam protons. At the top, the effective dose was found to be -150 microSv s(-1) for a concrete thickness of 100 cm, while -2.5 microSv s(-1) for a concrete thickness of 200 cm. It was also shown that the high-energy neutrons (> 10 MeV), which are created in the proton-induced spallation interactions in the target, contribute for the major part of the effective doses outside the reactor.

  8. [Introduction to critical reading of articles: study design and biases].

    PubMed

    García Villar, C

    2015-01-01

    The critical evaluation of an article enables professionals to make good use of the new information and therefore has direct repercussions for the benefit of our patients. Before undertaking a detailed critical reading of the chosen article, we need to consider whether the study used the most appropriate design for the question it aimed to answer (i.e., whether the level of evidence is adequate). To do this, we need to know how to classify studies in function of their design (descriptive or analytical; prospective or retrospective; cross-sectional or longitudinal) as well as their correlation with the levels of evidence. In critical reading it is also important to know the main systematic errors or biases that can affect a study. Biases can appear in any phase of a study; they can affect the sample, the development of the study, or the measurement of the results.

  9. Superconductivity with extremely large upper critical fields in Nb2Pd0.81S5

    NASA Astrophysics Data System (ADS)

    Zhang, Qiu; Li, Gang; Rhodes, Daniel; Kiswandhi, Andhika; Basara, Tiglet; Sung, J.; Siegrist, Theo; Johannes, Michelle; Balicas, Luis

    2013-03-01

    Here, we report the discovery of superconductivity in a new transition metal-chalcogenide compound, i.e. Nb2Pd0.81S5, with a transition temperature Tc ≅ 6.6 K. Despite its relatively low Tc, it displays remarkably high and anisotropic superconducting upper critical fields, e.g. μ0Hc 2 (T --> 0 K) > 37 T for fields applied along the crystallographic b-axis. This value is considerably larger than the value reported for the technologically relevant Nb3Sn compound (μ0Hc 2 ~ 30 T, with Tc = 18 K)1,2. Its ratio of μ0Hc 2 (T --> 0 K) to Tc, is also larger than those of the new Fe based superconductors, e.g. β-FeSe (20 T/8.7 K)3, Ba1-xKxFe2As2 (~ 70 T/28 K)4, and even higher than the reported ratio for the Chevrel-phase PbMo6S8(60T/13.3 K)5 compound. For a field applied perpendicularly to the b-axis, μ0Hc 2 shows a linear dependence in temperature which coupled to a temperature-dependent anisotropy of the upper critical fields, suggests that Nb2Pd0.81S5 is a multi-band superconductor. This is confirmed by band structure calculations which reveal nearly cylindrical and quasi-one-dimensional Fermi surface sheets having hole and electron character, respectively.

  10. Field-structured composite studies.

    SciTech Connect

    Martin, James Ellis; Williamson, Rodney L.

    2004-04-01

    Field-structured composites (FSCs) were produced by hosting micron-sized gold-coated nickel particles in a pre-polymer and allowing the mixture to cure in a magnetic field environment. The feasibility of controlling a composite's electrical conductivity using feedback control applied to the field coils was investigated. It was discovered that conductivity in FSCs is primarily determined by stresses in the polymer host matrix due to cure shrinkage. Thus, in cases where the structuring field was uniform and unidirectional so as to produce chainlike structures in the composite, no electrical conductivity was measured until well after the structuring field was turned off at the gel point. In situations where complex, rotating fields were used to generate complex, three-dimensional structures in a composite, very small, but measurable, conductivity was observed prior to the gel point. Responsive, sensitive prototype chemical sensors were developed based on this technology with initial tests showing very promising results.

  11. Kiloampere, Variable-Temperature, Critical-Current Measurements of High-Field Superconductors

    PubMed Central

    Goodrich, LF; Cheggour, N; Stauffer, TC; Filla, BJ; Lu, XF

    2013-01-01

    5 K to those measured on the same specimen in flowing helium gas (“gas” or Ic gas) at the same temperature. These comparisons indicate the temperature control is effective over the superconducting wire length between the voltage taps, and this condition is valid for all types of sample investigated, including Nb-Ti, Nb3Sn, and MgB2 wires. The liquid/gas comparisons are used to study the variable-temperature measurement protocol that was necessary to obtain the “correct” critical current, which was assumed to be the Ic liq. We also calibrated the magnetoresistance effect of resistive thermometers for temperatures from 4 K to 35 K and magnetic fields from 0 T to 16 T. This calibration reduces systematic errors in the variable-temperature data, but it does not affect the liquid/gas comparison since the same thermometers are used in both cases. PMID:26401435

  12. Magnetic Field Dependence of Excitations Near Spin-Orbital Quantum Criticality

    NASA Astrophysics Data System (ADS)

    Biffin, A.; Rüegg, Ch.; Embs, J.; Guidi, T.; Cheptiakov, D.; Loidl, A.; Tsurkan, V.; Coldea, R.

    2017-02-01

    The spinel FeSc2 S4 has been proposed to realize a near-critical spin-orbital singlet (SOS) state, where entangled spin and orbital moments fluctuate in a global singlet state on the verge of spin and orbital order. Here we report powder inelastic neutron scattering measurements that observe the full bandwidth of magnetic excitations and we find that spin-orbital triplon excitations of an SOS state can capture well key aspects of the spectrum in both zero and applied magnetic fields up to 8.5 T. The observed shift of low-energy spectral weight to higher energies upon increasing applied field is naturally explained by the entangled spin-orbital character of the magnetic states, a behavior that is in strong contrast to spin-only singlet ground state systems, where the spin gap decreases upon increasing applied field.

  13. Nonprofessional Care in Chronic Critically Ill Patient: A Qualitative Study

    PubMed Central

    Dehkordi, Leila Mardanian; Babashahi, Monireh; Irajpour, Alireza

    2016-01-01

    Background: Decision-making about patients with critical condition transfer from Intensive Care Unit to the general wards be delegated to their families. The aim of the study was explaining the experiences of family caregiver's about care of chronic critically ill patient. Methods: This study was conducted with a qualitative content analysis using unstructured interview. Participants were selected purposively from May 2014 to May 2015 and data collection continued until data saturation. Analysis was based on conventional content analysis. Results: Participants’ experiences classified into three main categories as following: nonprofessional care, enhancing factors of care, and inhibiting factors of care. Conclusions: Finding of the current study showed different aspects of care. Care of chronic critically ill patients is a long-term process that affected by different factors. It seems that the exploration of caregivers needs and planning supportive interventions based on their needs improve the quality of care. PMID:28028426

  14. Josephson critical current of long SNS junctions in the presence of a magnetic field

    NASA Astrophysics Data System (ADS)

    Meier, Hendrik; Fal'Ko, Vladimir I.; Glazman, Leonid I.

    We evaluate the Josephson critical current of a long and wide two-dimensional superconductor-normal metal-superconductor (SNS) junction, taking into account the effect of electron reflection off the side edges of the junction. Considering clean junctions, we find that the effect of edges alters the usual Fraunhofer-like dependence of the Josephson critical current Ic on the magnetic flux Φ. At relatively weak fields, B <~Φ0 /W2 , the edge effect lifts zeros of the Ic (Φ) dependence and gradually shifts the maxima of that function by Φ0 / 2 . (Here W is the width of the junction and Φ0 the magnetic flux quantum.) At higher fields, B >~Φ0 /W2 , the edge effect leads to an accelerated decay of the critical current Ic (Φ) with increasing Φ. Our results are robust with respect to the roughness of realistic boundaries. Finally, we discuss the role of mesoscopic fluctuations of Ic (Φ) originating from the scattering off the edges, and compare our findings to recent experiments.

  15. White Lies: A Critical Race Study of Power and Privilege

    ERIC Educational Resources Information Center

    Brainard, Patricia Jones

    2009-01-01

    This was a phenomenological study of racial privilege as experienced by White people who have struggled to become more racially aware and socially active in dismantling racism and White privilege. The primary conceptual framework for this study was Critical Race Theory with Transformative Learning theory and Racial Identity Development as…

  16. Classical-to-quantum crossover in the critical behavior of the transverse-field Sherrington-Kirkpatrick spin glass model.

    PubMed

    Mukherjee, Sudip; Rajak, Atanu; Chakrabarti, Bikas K

    2015-10-01

    We study the critical behavior of the Sherrington-Kirkpatrick model in transverse field (at finite temperature) using Monte Carlo simulation and exact diagonalization (at zero temperature). We determine the phase diagram of the model by estimating the Binder cumulant. We also determine the correlation length exponent from the collapse of the scaled data. Our numerical studies here indicate that critical Binder cumulant (indicating the universality class of the transition behavior) and the correlation length exponent cross over from their "classical" to "quantum" values at a finite temperature (unlike the cases of pure systems, where such crossovers occur at zero temperature). We propose a qualitative argument supporting such an observation, employing a simple tunneling picture.

  17. Finite-temperature scaling at the quantum critical point of the Ising chain in a transverse field

    NASA Astrophysics Data System (ADS)

    Haelg, Manuel; Huvonen, Dan; Guidi, Tatiana; Quintero-Castro, Diana Lucia; Boehm, Martin; Regnault, Louis-Pierre; Zheludev, Andrey

    2015-03-01

    Inelastic neutron scattering is used to study the finite-temperature scaling behavior of spin correlations at the quantum critical point in an experimental realization of the one-dimensional Ising model in a transverse field. The target compound is the well-characterized, anisotropic and bond-alternating Heisenberg spin-1 chain material NTENP. The validity and the limitations of the dynamic structure factor scaling are tested, discussed and compared to theoretical predictions. For this purpose neutron data have been collected on the three-axes spectrometers IN14 at ILL and FLEXX at HZB as well as on the time of flight multi-chopper spectrometer LET at ISIS. In addition to the general statement about quantum criticality and universality, present study also reveals new insight into the properties of the spin chain compound NTENP in particular.

  18. Classical-to-quantum crossover in the critical behavior of the transverse-field Sherrington-Kirkpatrick spin glass model

    NASA Astrophysics Data System (ADS)

    Mukherjee, Sudip; Rajak, Atanu; Chakrabarti, Bikas K.

    2015-10-01

    We study the critical behavior of the Sherrington-Kirkpatrick model in transverse field (at finite temperature) using Monte Carlo simulation and exact diagonalization (at zero temperature). We determine the phase diagram of the model by estimating the Binder cumulant. We also determine the correlation length exponent from the collapse of the scaled data. Our numerical studies here indicate that critical Binder cumulant (indicating the universality class of the transition behavior) and the correlation length exponent cross over from their "classical" to "quantum" values at a finite temperature (unlike the cases of pure systems, where such crossovers occur at zero temperature). We propose a qualitative argument supporting such an observation, employing a simple tunneling picture.

  19. Effectively Integrating an International Field Study into the EMBA Curriculum

    ERIC Educational Resources Information Center

    Cotner, John; Jones, Raymond; Kashlak, Roger

    2003-01-01

    An international field study (IFS) is an integral part of the EMBA program because of the various critical roles it plays. This international travel experience is a value-added activity not only as "stand alone" vehicle for understanding macro-level environments and firm-level strategic initiatives, but also as a tool that integrates other pieces…

  20. Field theory of bicritical and tetracritical points. IV. Critical dynamics including reversible terms

    NASA Astrophysics Data System (ADS)

    Folk, R.; Holovatch, Yu.; Moser, G.

    2012-02-01

    This article concludes a series of papers [Folk, Holovatch, and Moser, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.78.04112478, 041124 (2008); Folk, Holovatch, and Moser, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.78.04112578, 041125 (2008); Folk, Holovatch, and Moser, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.79.03110979, 031109 (2009)] where the tools of the field theoretical renormalization group were employed to explain and quantitatively describe different types of static and dynamic behavior in the vicinity of multicritical points. Here we give the complete two-loop calculation and analysis of the dynamic renormalization-group flow equations at the multicritical point in anisotropic antiferromagnets in an external magnetic field. We find that the time scales of the order parameters characterizing the parallel and perpendicular ordering with respect to the external field scale in the same way. This holds independent whether the Heisenberg fixed point or the biconical fixed point in statics is the stable one. The nonasymptotic analysis of the dynamic flow equations shows that due to cancellation effects the critical behavior is described, in distances from the critical point accessible to experiments, by the critical behavior qualitatively found in one-loop order. Although one may conclude from the effective dynamic exponents (taking almost their one-loop values) that weak scaling for the order parameter components is valid, the flow of the time-scale ratios is quite different, and they do not reach their asymptotic values.

  1. Field-theoretical Renormalization-Group approach to critical dynamics of crosslinked polymer blends

    NASA Astrophysics Data System (ADS)

    Benhamou, M.; Chahid, M.

    2008-09-01

    We consider a crosslinked polymer blend that may undergo a microphase separation. When the temperature is changed from an initial value towards a final one very close to the spinodal point, the mixture is out equilibrium. The aim is the study of dynamics at a given time t , before the system reaches its final equilibrium state. The dynamics is investigated through the structure factor, S(q, t) , which is a function of the wave vector q , temperature T , time t , and reticulation dose D . To determine the phase behavior of this dynamic structure factor, we start from a generalized Langevin equation (model C) solved by the time composition fluctuation. Beside the standard de Gennes Hamiltonian, this equation incorporates a Gaussian local noise, ζ . First, by averaging over ζ , we get an effective Hamiltonian. Second, we renormalize this dynamic field theory and write a Renormalization-Group equation for the dynamic structure factor. Third, solving this equation yields the behavior of S(q, t) , in space of relevant parameters. As result, S(q, t) depends on three kinds of lengths, which are the wavelength q-1, a time length scale R(t) thicksim t1/z , and the mesh size ξ* . The scale R(t) is interpreted as the size of growing microdomains at time t . When R(t) becomes of the order of ξ* , the dynamics is stopped. The final time, t * , then scales as t * thicksim ξ{ast z} , with the dynamic exponent z = 6 - η . Here, η is the usual Ising critical exponent. Since the final size of microdomains ξ* is very small (few nanometers), the dynamics is of short time. Finally, all these results we obtained from renormalization theory are compared to those we stated in some recent work using a scaling argument.

  2. Nurses' Error Management in Critical Care Units: A Qualitative Study.

    PubMed

    Nasrabadi, Alireza Nikbakht; Peyrovi, Hamid; Valiee, Sina

    Nursing errors are common in critical care units, and nurses are in the first line of confrontation. The purpose of this study was to explore the processes of managing nursing errors in critical care units in Iran and to develop a theoretical explanation of the phenomenon. This was a grounded theory study. We recruited a sample of 18 critical care nurses for the study. The sampling method was purposive and then changed to theoretical. The data were collected through in-depth interviews. For data analysis, we employed the constant comparative analysis technique. The core category of the study was "continuous situational analysis." The main categories were situational analysis and error removal. When nurses confronted an error, they opted for analyzing the error situation in terms of the nature of error, probable consequences, monitoring, and life threat. Accordingly, they employed error removal strategies such as self-action, cooperation, notifying, and censoring. These steps happened concurrently, successively, or cyclically. To manage their committed errors, nurses usually go through an informal process. Nurse-managers need to design effective error management strategies and require the practicing nurses to adhere to them. A practical model for effective prevention and management of nursing errors in critical care units is necessary.

  3. [Brucellosis zoonoses in Tunisia: critical study of sanitary legislation].

    PubMed

    Gharbi, Mohamed

    2002-07-01

    The author presents a critical study of the sanitary legal texts of zoonotic brucellosis control. The tunisian legal texts are sometimes incomplete and old. The review of these texts, in order to improve the legal frame of control, is now necessary.

  4. Post-Fordism, Political Economy, and Critical Organizational Communication Studies.

    ERIC Educational Resources Information Center

    Nadesan, Majia Holmer

    2001-01-01

    Introduces readers to the literature on post-Fordism by first describing the social and economic phenomena that it seeks to explain and then by introducing the divergent research approaches that contest the scope and effects of post-Fordist phenomena. Suggests that critical organizational communication studies has much to gain, analytically and…

  5. Constructing Critical Autoethnographic Self-Studies with White Educators

    ERIC Educational Resources Information Center

    Pennington, Julie L.; Brock, Cynthia H.

    2012-01-01

    Autoethnography was used as a tool for white in-service elementary teachers to examine their racial identity from a Critical White Studies (CWS) perspective. Two white in-service teachers participated in two yearlong university courses focused on teaching linguistically and culturally diverse students. Each teacher collected their own data at…

  6. Interpretive and Critical Phenomenological Crime Studies: A Model Design

    ERIC Educational Resources Information Center

    Miner-Romanoff, Karen

    2012-01-01

    The critical and interpretive phenomenological approach is underutilized in the study of crime. This commentary describes this approach, guided by the question, "Why are interpretive phenomenological methods appropriate for qualitative research in criminology?" Therefore, the purpose of this paper is to describe a model of the interpretive…

  7. Towards Socially Just Pedagogies: Deleuzoguattarian Critical Disability Studies

    ERIC Educational Resources Information Center

    Goodley, Dan

    2007-01-01

    Socially just pedagogies call for sensitivity to politics and culture. In this paper I will uncover some key challenges in relation to working pedagogically with disabled people through the exploration of a critical disability studies perspective. First, I will unpack some of the assumptions that underpin educational understandings of…

  8. Disability and Diversity on CSU Websites: A Critical Discourse Study

    ERIC Educational Resources Information Center

    Gabel, Susan L.; Reid, Denise; Pearson, Holly; Ruiz, Litzy; Hume-Dawson, Rodney

    2016-01-01

    With more than 325,000 students, the California State University (CSU) system is 1 of the largest in the United States, making it a useful unit of analysis for studying disability and diversity. Using a critical discourse theoretical framework and borrowing strategies from Astroff (2001) and Pauwells (2012), we found disability information on CSU…

  9. Critical Practice in Teacher Education: A Study of Professional Learning

    ERIC Educational Resources Information Center

    Heilbronn, Ruth, Ed.; Yandell, John, Ed.

    2010-01-01

    This timely book uncovers all of the processes that should be considered when high-quality teacher education is designed, delivered and studied around the world. Written by experienced teacher educators, this book shows what critical practice is and how it can be used to facilitate a deeper understanding of practice that draws upon personal…

  10. Critical materials and dissipative losses: a screening study.

    PubMed

    Zimmermann, Till; Gößling-Reisemann, Stefan

    2013-09-01

    This study deals with dissipative losses of critical materials between the life-cycle stages of manufacturing and end-of-life. Following the EU definition for critical materials, a screening of dissipative losses for the respective materials has been performed based on existing data and the most significant data gaps have been identified. Furthermore, a classification scheme for dissipative losses (dissipation into environment, dissipation into other material flows, dissipation to landfills) and for assessing their degree has been developed and a first qualitative assessment applying this classification scheme has been performed. In combination with existing criticality assessments, the results can be used to generate a map of metals indicating future research needs for analyzing metal dissipation in detail. The results include quantitative estimates of dissipative losses (where feasible) along the chosen life-cycle stages, and discuss research needs for analysis and avoidance of dissipative losses for improved resource efficiency.

  11. Promoting Critical Multicultural Citizenship: A Case Study of Preparing Social Studies Teachers

    ERIC Educational Resources Information Center

    Castro, Antonio Jamie

    2009-01-01

    Given the growing cultural and economic diversity of today's students, this qualitative case study investigates how 4 social studies preservice teachers taught for critical multicultural citizenship during their student teaching semester. The tenets of critical citizenship emerge out of the intersection of critical pedagogy and multicultural…

  12. Aperiodic sequences and magnetic models: non-universal critical behavior within mean-field approximation

    NASA Astrophysics Data System (ADS)

    Branco, Nilton; Faria, Maicon; Tragtenberg, Marcelo

    2007-03-01

    We study the Ising model on a Bethe lattice, such that the exchange constant can assume two values, according to two-letter aperiodic sequences. Critical temperatures and exponents are calculated for three different sequences: Fibonacci, period-doubling and two-letter Rudin-Shapiro ones. These sequences are found to be irrelevant, marginal, and relevant, respectively, in the renormalization-group sense. The Fibonacci sequence presents the same critical behavior as for the uniform model and no log-periodic behavior is observed. For the marginal sequence, critical exponents depend on the ratio between the two possible exchange constants and a log-periodic behavior is clearly determined. Due to computational constraints, our results are not as precise for the Rudin-Shapiro sequence but we obtain evidence that the exponents are different from the classical ones and do not depend on the ratio between the exchange constants.

  13. Ion Dynamics and Field Structure of Quasi-perpendicular Collisionless Shocks near the Critical Mach Number

    NASA Astrophysics Data System (ADS)

    Balikhin, M. A.; Malkov, M.; Sagdeev, R.; Dudnikova, G.

    2015-12-01

    The structure of subcritical (laminar) collisionless shocks has been understood long time ago. When the Mach number exceeds a critical value, some of the incident ions are reflected. This needs to be included into the description of the shock structure and entropy production at the shock front. We present an analytical model of ion reflection from a quasi-perpendicular collisionless shock and the formation of the foot region associated with this reflection. Reflected ions perturb the electrostatic and magnetic fields in the foot region which we self-consistently include in determining the fraction of reflected ions, depending on the Mach number of the shock. The subsequent motion of the shock reflected ions downstream and formation of the downstream field structure is analyzed. Models for thermalization of the downstream plasma and approaches to Rankine-Hugoniot relations will also be discussed. The obtained overall shock structure is compared with the Cluster observations.

  14. Growth and decay of runaway electrons above the critical electric field under quiescent conditions

    SciTech Connect

    Paz-Soldan, C.; Eidietis, N. W.; Wesley, J. C.; Granetz, R.; Hollmann, E. M.; Moyer, R. A.; Zhang, J.; Crocker, N. A.; Austin, M. E.; Wingen, A.; Zhu, Y.

    2014-02-15

    Extremely low density operation free of error field penetration supports the excitation of trace-level quiescent runaway electron (RE) populations during the flat-top of DIII-D Ohmic discharges. Operation in the quiescent regime allows accurate measurement of all key parameters important to RE excitation, including the internal broadband magnetic fluctuation level. RE onset is characterized and found to be consistent with primary (Dreicer) generation rates. Impurity-free collisional suppression of the RE population is investigated by stepping the late-time main-ion density, until RE decay is observed. The transition from growth to decay is found to occur 3–5 times above the theoretical critical electric field for avalanche growth and is thus indicative of anomalous RE loss. This suggests that suppression of tokamak RE avalanches can be achieved at lower density than previously expected, though extrapolation requires predictive understanding of the RE loss mechanism and magnitude.

  15. [Research in two-dimensional critical phenomena and conformal field theory]. [Rutgers, The State Univ. , New Brunswick, New Jersey

    SciTech Connect

    Not Available

    1990-01-01

    A very theoretical description is given of research in two- dimensional critical phenomena and conformal field theory. Major progress is reported in the field of fluctuating two-dimensional surfaces. A discretized representation of fluctuating geometry is used where surfaces are represented by triangulations; continuum surfaces are recovered by taking the size of the triangles to zero. One of the central goals of the theory of critical phenomena is to find all possible universality classes of n-dimensional critical phenomena; this goal has been translated into the problem of clasifying all possible scale-invariant euclidean quantum field theories. (RWR)

  16. Microstructure, critical current density and trapped field experiments in IG-processed Y-123

    NASA Astrophysics Data System (ADS)

    Muralidhar, M.; Ide, N.; Koblischka, M. R.; Diko, P.; Inoue, K.; Murakami, M.

    2016-05-01

    In this paper, we adapted the top-seeded infiltration growth ‘IG’ technique and produced several YBa2Cu3O y ‘Y-123’ samples with an addition of Y2BaCuO5 ‘Y-211’ secondary phase particles with varying sizes by the sintering process and the ball milling technique. For the first set of samples, Y-211 disks were sintered at temperatures ranging between 900 °C and 1100 °C and were used for the production of Y-123 material by the IG process. Magnetization measurements showed a sharp superconducting transition with an onset T c at around 92 K, irrespective of the sintering temperature. However, the trapped field and critical current density (J c) values were dependent on the sintering temperature and it was found that the best temperature is around 925 °C. Further, the trapped field distribution measurements at 77 K indicated that all samples are of single grain nature. The highest trapped field was recorded around 0.31 T at 77 K for the Y-123 sample with 20 mm in diameter and 5 mm thickness produced by Y-211 pre-from around 925 °C. On the other hand, a second set of samples Y-211 were controlled by ball milling technique combined with an optimized slow cooling process. As a result, the critical current density (J c) at 77 K and zero field was determined to be 225 kA cm-2. The improved performance of the Y-123 material can be understood in terms of homogeneous distribution of fine secondary phase particles which is demonstrated by AFM micrographs.

  17. Positive-overlap transition and critical exponents in mean field spin glasses

    NASA Astrophysics Data System (ADS)

    Agostini, Alessandra; Barra, Adriano; DeSanctis, Luca

    2006-11-01

    In this paper we obtain two results for the Sherrington-Kirkpatrick (SK) model, and we show that they both emerge from a single approach. First, we prove that the average of the overlap takes positive values when it is non-zero. More specifically, the average of the overlap, which is naively expected to take values in the whole interval [-1,+1], becomes positive if we 'first' apply an external field, so as to destroy the gauge invariance of the model, and 'then' remove it in the thermodynamic limit. This phenomenon emerges at the critical point. This first result is weaker than the one obtained by Talagrand (not limited to the average of the overlap), but we show here that, at least on average, the overlap is proven to be non-negative with no use of the Ghirlanda-Guerra identities. The latter are instead needed to obtain the second result, which is to control the behaviour of the overlap at the critical point: we find the critical exponents of all the overlap correlation functions.

  18. Conformal field theory of critical Casimir forces between surfaces with alternating boundary conditions in two dimensions

    NASA Astrophysics Data System (ADS)

    Dubail, J.; Santachiara, R.; Emig, T.

    2017-03-01

    Systems as diverse as binary mixtures and inclusions in biological membranes, and many more, can be described effectively by interacting spins. When the critical fluctuations in these systems are constrained by boundary conditions, critical Casimir forces (CCF) emerge. Here we analyze CCF between boundaries with alternating boundary conditions in two dimensions, employing conformal field theory (CFT). After presenting the concept of boundary changing operators, we specifically consider two different boundary configurations for a strip of critical Ising spins: (I) alternating equi-sized domains of up and down spins on both sides of the strip, with a possible lateral shift, and (II) alternating domains of up and down spins of different size on one side and homogeneously fixed spins on the other side of the strip. Asymptotic results for the CCF at small and large distances are derived. We introduce a novel modified Szegö formula for determinants of real antisymmetric block Toeplitz matrices to obtain the exact CCF and the corresponding scaling functions at all distances. We demonstrate the existence of a surface renormalization group flow between universal force amplitudes of different magnitude and sign. The Casimir force can vanish at a stable equilibrium position that can be controlled by parameters of the boundary conditions. Lateral Casimir forces assume a universal simple cosine form at large separations.

  19. High critical current density and enhanced irreversibility field in superconducting MgB2 thin films

    NASA Astrophysics Data System (ADS)

    Eom, C. B.; Lee, M. K.; Choi, J. H.; Belenky, L. J.; Song, X.; Cooley, L. D.; Naus, M. T.; Patnaik, S.; Jiang, J.; Rikel, M.; Polyanskii, A.; Gurevich, A.; Cai, X. Y.; Bu, S. D.; Babcock, S. E.; Hellstrom, E. E.; Larbalestier, D. C.; Rogado, N.; Regan, K. A.; Hayward, M. A.; He, T.; Slusky, J. S.; Inumaru, K.; Haas, M. K.; Cava, R. J.

    2001-05-01

    The discovery of superconductivity at 39K in magnesium diboride offers the possibility of a new class of low-cost, high-performance superconducting materials for magnets and electronic applications. This compound has twice the transition temperature of Nb3Sn and four times that of Nb-Ti alloy, and the vital prerequisite of strongly linked current flow has already been demonstrated. One possible drawback, however, is that the magnetic field at which superconductivity is destroyed is modest. Furthermore, the field which limits the range of practical applications-the irreversibility field H*(T)-is approximately 7T at liquid helium temperature (4.2K), significantly lower than about 10T for Nb-Ti (ref. 6) and ~20T for Nb3Sn (ref. 7). Here we show that MgB2 thin films that are alloyed with oxygen can exhibit a much steeper temperature dependence of H*(T) than is observed in bulk materials, yielding an H* value at 4.2K greater than 14T. In addition, very high critical current densities at 4.2K are achieved: 1MAcm-2 at 1T and 105Acm-2 at 10T. These results demonstrate that MgB2 has potential for high-field superconducting applications.

  20. Quantum entanglement and criticality of the antiferromagnetic Heisenberg model in an external field.

    PubMed

    Liu, Guang-Hua; Li, Ruo-Yan; Tian, Guang-Shan

    2012-06-27

    By Lanczos exact diagonalization and the infinite time-evolving block decimation (iTEBD) technique, the two-site entanglement as well as the bipartite entanglement, the ground state energy, the nearest-neighbor correlations, and the magnetization in the antiferromagnetic Heisenberg (AFH) model under an external field are investigated. With increasing external field, the small size system shows some distinct upward magnetization stairsteps, accompanied synchronously with some downward two-site entanglement stairsteps. In the thermodynamic limit, the two-site entanglement, as well as the bipartite entanglement, the ground state energy, the nearest-neighbor correlations, and the magnetization are calculated, and the critical magnetic field h(c) = 2.0 is determined exactly. Our numerical results show that the quantum entanglement is sensitive to the subtle changing of the ground state, and can be used to describe the magnetization and quantum phase transition. Based on the discontinuous behavior of the first-order derivative of the entanglement entropy and fidelity per site, we think that the quantum phase transition in this model should belong to the second-order category. Furthermore, in the magnon existence region (h < 2.0), a logarithmically divergent behavior of block entanglement which can be described by a free bosonic field theory is observed, and the central charge c is determined to be 1.

  1. Critical behavior of the spin-1 and spin-3/2 Baxter-Wu model in a crystal field.

    PubMed

    Dias, D A; Xavier, J C; Plascak, J A

    2017-01-01

    The phase diagram and the critical behavior of the spin-1 and the spin-3/2 two-dimensional Baxter-Wu model in a crystal field are studied by conventional finite-size scaling and conformal invariance theory. The phase diagram of this model, for the spin-1 case, is qualitatively the same as those of the diluted 4-states Potts model and the spin-1 Blume-Capel model. However, for the present case, instead of a tricritical point one has a pentacritical point for a finite value of the crystal field, in disagreement with previous work based on finite-size calculations. On the other hand, for the spin-3/2 case, the phase diagram is much richer and can present, besides a pentacritical point, an additional multicritical end point. Our results also support that the universality class of the critical behavior of the spin-1 and spin-3/2 Baxter-Wu model in a crystal field is the same as the pure Baxter-Wu model, even at the multicritical points.

  2. Critical behavior of the spin-1 and spin-3/2 Baxter-Wu model in a crystal field

    NASA Astrophysics Data System (ADS)

    Dias, D. A.; Xavier, J. C.; Plascak, J. A.

    2017-01-01

    The phase diagram and the critical behavior of the spin-1 and the spin-3/2 two-dimensional Baxter-Wu model in a crystal field are studied by conventional finite-size scaling and conformal invariance theory. The phase diagram of this model, for the spin-1 case, is qualitatively the same as those of the diluted 4-states Potts model and the spin-1 Blume-Capel model. However, for the present case, instead of a tricritical point one has a pentacritical point for a finite value of the crystal field, in disagreement with previous work based on finite-size calculations. On the other hand, for the spin-3/2 case, the phase diagram is much richer and can present, besides a pentacritical point, an additional multicritical end point. Our results also support that the universality class of the critical behavior of the spin-1 and spin-3/2 Baxter-Wu model in a crystal field is the same as the pure Baxter-Wu model, even at the multicritical points.

  3. Towards a controlled study of the QCD critical point

    NASA Astrophysics Data System (ADS)

    de Forcrand, Ph; Philipsen, O.

    2008-10-01

    The phase diagram of QCD, as a function of temperature T and quark chemical potential μ, may contain a critical point (μE, TE) whose non-perturbative nature makes it a natural object of lattice studies. However, the sign problem prevents the application of standard Monte Carlo techniques at nonzero baryon density. We have been pursuing an approach free of the sign problem, where the chemical potential is taken as imaginary and the results are Taylor expanded in μ/T about μ = 0, then analytically continued to real μ. Within this approach we have determined the sensitivity of the critical chemical potential μE to the quark mass, d(\\mu_E)^2/dm_q|_{\\mu_E=0} . Our study indicates that the critical point moves to a larger chemical potential as the quark mass decreases. This finding, contrary to common wisdom, implies that the deconfinement crossover, which takes place in QCD at μ = 0 when the temperature is raised, will remain a crossover in the μ-region where our Taylor expansion can be trusted. If this result, obtained on a coarse lattice, is confirmed by simulations on finer lattices now in progress, then we predict that no chiral critical point will be found for μB lsim 500 MeV, unless the phase diagram contains additional transitions.

  4. Analysis and prediction of the critical regions of antimicrobial peptides based on conditional random fields.

    PubMed

    Chang, Kuan Y; Lin, Tung-pei; Shih, Ling-Yi; Wang, Chien-Kuo

    2015-01-01

    Antimicrobial peptides (AMPs) are potent drug candidates against microbes such as bacteria, fungi, parasites, and viruses. The size of AMPs ranges from less than ten to hundreds of amino acids. Often only a few amino acids or the critical regions of antimicrobial proteins matter the functionality. Accurately predicting the AMP critical regions could benefit the experimental designs. However, no extensive analyses have been done specifically on the AMP critical regions and computational modeling on them is either non-existent or settled to other problems. With a focus on the AMP critical regions, we thus develop a computational model AMPcore by introducing a state-of-the-art machine learning method, conditional random fields. We generate a comprehensive dataset of 798 AMPs cores and a low similarity dataset of 510 representative AMP cores. AMPcore could reach a maximal accuracy of 90% and 0.79 Matthew's correlation coefficient on the comprehensive dataset and a maximal accuracy of 83% and 0.66 MCC on the low similarity dataset. Our analyses of AMP cores follow what we know about AMPs: High in glycine and lysine, but low in aspartic acid, glutamic acid, and methionine; the abundance of α-helical structures; the dominance of positive net charges; the peculiarity of amphipathicity. Two amphipathic sequence motifs within the AMP cores, an amphipathic α-helix and an amphipathic π-helix, are revealed. In addition, a short sequence motif at the N-terminal boundary of AMP cores is reported for the first time: arginine at the P(-1) coupling with glycine at the P1 of AMP cores occurs the most, which might link to microbial cell adhesion.

  5. Automated Critical PeakPricing Field Tests: 2006 Pilot ProgramDescription and Results

    SciTech Connect

    Piette, Mary Ann; Watson, David; Motegi, Naoya; Kiliccote, Sila

    2007-06-19

    During 2006 Lawrence Berkeley National Laboratory (LBNL) and the Demand Response Research Center (DRRC) performed a technology evaluation for the Pacific Gas and Electric Company (PG&E) Emerging Technologies Programs. This report summarizes the design, deployment, and results from the 2006 Automated Critical Peak Pricing Program (Auto-CPP). The program was designed to evaluate the feasibility of deploying automation systems that allow customers to participate in critical peak pricing (CPP) with a fully-automated response. The 2006 program was in operation during the entire six-month CPP period from May through October. The methodology for this field study included site recruitment, control strategy development, automation system deployment, and evaluation of sites' participation in actual CPP events through the summer of 2006. LBNL recruited sites in PG&E's territory in northern California through contacts from PG&E account managers, conferences, and industry meetings. Each site contact signed a memorandum of understanding with LBNL that outlined the activities needed to participate in the Auto-CPP program. Each facility worked with LBNL to select and implement control strategies for demand response and developed automation system designs based on existing Internet connectivity and building control systems. Once the automation systems were installed, LBNL conducted communications tests to ensure that the Demand Response Automation Server (DRAS) correctly provided and logged the continuous communications of the CPP signals with the energy management and control system (EMCS) for each site. LBNL also observed and evaluated Demand Response (DR) shed strategies to ensure proper commissioning of controls. The communication system allowed sites to receive day-ahead as well as day-of signals for pre-cooling, a DR strategy used at a few sites. Measurement of demand response was conducted using two different baseline models for estimating peak load savings. One was the CPP

  6. Mixed method nursing studies: a critical realist critique.

    PubMed

    Lipscomb, Martin

    2008-01-01

    Mixed method study designs are becoming increasingly popular among nurse researchers. Mixed studies can have advantages over single method or methodological investigative designs. However, these advantages may be squandered where researchers fail to think through and justify their theoretic decisions. This paper argues that nurse researchers do not always pay sufficient heed to the philosophic and theoretic elements of research design and, in consequence, some mixed study reports lack argumentative coherence and validity. It is here suggested that Hempel's concept of equivalence can be stretched to usefully illustrate one of the main threats to argumentative coherence in mixed study design. The critical realist theory of Roy Bhaskar is then introduced and this, it is proposed, offers one means by which Hempel's equivalence dilemma can be overcome. Critical realists recognize the existence of logical connections between the ontological, epistemological, and methodological premises that underpin their work. They are therefore more likely to produce coherent studies than uncritical pragmatists who ignore such linkages and, paradoxically, critical realists can be epistemological pluralists because, in re-conceptualizing the ontological basis of inquiry, problems associated with the mixing of alternative metaphysics are circumvented.

  7. Reflective practice: a critical analysis of data-based studies and implications for nursing education.

    PubMed

    Ruth-Sahd, Lisa A

    2003-11-01

    Reflective practice has become part of the discourse of nursing education classrooms, conferences, and journals, and are popular features of nursing continuing education programs. Yet, the idea of reflective practice has become increasingly more disparate. This critical analysis examines data-based studies and provides an overview of reflective practice, discusses common themes that emerged from the studies, and identifies implications for reflective practice in the field of nursing education.

  8. Upper Critical Field, Critical Current Density and Activation Energy of the New La1-xSmxO0.5F0.5BiS2 (x = 0.2, 0.8) Superconductors

    NASA Astrophysics Data System (ADS)

    Kalai Selvan, Ganesan; Singh Thakur, Gohil; Manikandan, Krishnan; Uwatoko, Yoshia; Haque, Zeba; Gupta, Laxmi Chand; Ganguli, Ashok Kumar; Arumugam, Sonachalam

    2015-12-01

    Critical current density (Jc), thermal activation energy (U0), and upper critical field (Hc2) of La1-xSmxO0.5F0.5BiS2 (x = 0.2, 0.8) superconductors are investigated from magnetic field dependent ρ(T) studies. The estimated upper critical field (Hc2) has low values of 1.04 T for x = 0.2 and 1.41 T for x = 0.8. These values are lower than Sm free LaO0.5F0.5BiS2 superconductor (1.9 T). The critical current density (Jc) is estimated to be 1.35 × 105 and 5.07 × 105 A/cm2 (2 K) for x = 0.2 and 0.8 respectively, using the Bean's model. The thermal activation energy (U0/kB) is 61 K for x = 0.2 and 140 K for x = 0.8 as calculated from Arrhenius plots at low magnetic field (1 T) and indicates a strong flux pinning potential which might be co-existing with applied magnetic field.

  9. Temperature and angular dependence of the upper critical field in K2Cr3As3

    NASA Astrophysics Data System (ADS)

    Zuo, Huakun; Bao, Jin-Ke; Liu, Yi; Wang, Jinhua; Jin, Zhao; Xia, Zhengcai; Li, Liang; Xu, Zhuan; Kang, Jian; Zhu, Zengwei; Cao, Guang-Han

    2017-01-01

    We report measurements of the upper critical field Hc 2 as functions of temperature T , polar angle θ (of the field direction with respect to the crystallographic c axis), and azimuthal angle ϕ (of the field direction relative to the a axis within the a b plane) for the Cr-based superconductor K2Cr3As3 with a quasi-one-dimensional and noncentrosymmetric crystal structure. We confirm that the anisotropy in Hc 2(T ) becomes inverse with decreasing temperature. At low temperatures, Hc 2(θ ) data are featured by two maxima at θ =0 (H ∥c ) and π /2 (H ⊥ c ), which can be quantitatively understood only if uniaxial effective-mass anisotropy and absence of Pauli paramagnetic effect for H ⊥ c are taken simultaneously into consideration. The in-plane Hc 2(ϕ ) profile shows a unique threefold modulation especially at low temperatures. Overall, the characteristics of the Hc 2(θ ,ϕ ,T ) data mostly resemble those of the heavy-fermion superconductor UPt3, and we argue in favor of a dominant spin-triplet superconductivity with odd parity in K2Cr3As3 .

  10. Field and temperature scaling of the critical current density in commercial REBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Senatore, Carmine; Barth, Christian; Bonura, Marco; Kulich, Miloslav; Mondonico, Giorgio

    2016-01-01

    Scaling relations describing the electromagnetic behaviour of coated conductors (CCs) greatly simplify the design of REBCO-based devices. The performance of REBCO CCs is strongly influenced by fabrication route, conductor architecture and materials, and these parameters vary from one manufacturer another. In the present work we have examined the critical surface for the current density, J c(T, B, θ), of coated conductors from six different manufacturers: American Superconductor Co. (US), Bruker HTS GmbH (Germany), Fujikura Ltd (Japan), SuNAM Co. Ltd (Korea), SuperOx ZAO (Russia) and SuperPower Inc. (US). Electrical transport and magnetic measurements were performed at temperatures between 4.2 K and 77 K and in magnetic fields of up to 19 T. Experiments were conducted at three different orientations of the field with respect to the crystallographic c-axis of the REBCO layer, θ = 0°, 45° and 90°, in order to probe the angular anisotropy of J c. In spite of the large variability of the CCs’ performance, we show here that field and temperature dependences of J c at a given angle can be reproduced over wide ranges using a scaling relation based only on three parameters. Furthermore, we present and validate a new approach combining magnetic and transport measurements for the determination of the scaling parameters with minimal experimental effort.

  11. Correlation of Electric Field and Critical Design Parameters for Ferroelectric Tunable Microwave Filters

    NASA Technical Reports Server (NTRS)

    Subramanyam, Guru; VanKeuls, Fred W.; Miranda, Felix A.; Canedy, Chadwick L.; Aggarwal, Sanjeev; Venkatesan, Thirumalai; Ramesh, Ramamoorthy

    2000-01-01

    The correlation of electric field and critical design parameters such as the insertion loss, frequency ability return loss, and bandwidth of conductor/ferroelectric/dielectric microstrip tunable K-band microwave filters is discussed in this work. This work is based primarily on barium strontium titanate (BSTO) ferroelectric thin film based tunable microstrip filters for room temperature applications. Two new parameters which we believe will simplify the evaluation of ferroelectric thin films for tunable microwave filters, are defined. The first of these, called the sensitivity parameter, is defined as the incremental change in center frequency with incremental change in maximum applied electric field (EPEAK) in the filter. The other, the loss parameter, is defined as the incremental or decremental change in insertion loss of the filter with incremental change in maximum applied electric field. At room temperature, the Au/BSTO/LAO microstrip filters exhibited a sensitivity parameter value between 15 and 5 MHz/cm/kV. The loss parameter varied for different bias configurations used for electrically tuning the filter. The loss parameter varied from 0.05 to 0.01 dB/cm/kV at room temperature.

  12. Use of intuition by critical care nurses: a phenomenological study

    PubMed Central

    Hassani, Parkhide; Abdi, Alireza; Jalali, Rostam; Salari, Nader

    2016-01-01

    Background Intuition is defined as an irrational unconscious type of knowing. This concept was incorporated into nursing discipline for 3 decades, but nowadays its application is uncertain and ignored by educational institutions. Therefore, this study aimed to explore critical care nurses’ understanding of the use of intuition in clinical practice. Materials and methods In a descriptive phenomenological study, 12 nurses employed in critical care units of the hospitals affiliated with Kermanshah University of Medical Sciences, were recruited to a study using purposive, semistructured interviews, which were then written down verbatim. The data were managed by MaxQDA 10 software and analyzed as qualitative, with Colaizzi’s seven-stage approach. Results Of the 12 nurses who participated in the study, seven (58.3%) were female and married, 88.3% (ten) had a Bachelor of Nursing (BSc) degree, and the means ± SD of age, job experience, and critical care experience were 36.66±7.01, 13.75±6.82, and 7.66±3.36 years, respectively. We extracted three main themes, namely “patient conditions”, “nurse readiness”, and “outcome”, and seven subthemes – including “clinical signs”, “patient behaviors”, “prognosis”, “being sensitive”, “desire to act”, “prediction”, and “satisfaction” – integral to understanding the use of intuition in clinical practice by critical care nurses. Conclusion The findings showed that some nurses were attracted by the patients’ conditions and were more intuitive about them, and following their intuition prepared the nurses to under-take more appropriate measures. The positive results that the majority of the nurses experienced convinced them to follow their intuitions more often. PMID:26929677

  13. Numerical study of multicomponent droplet vaporization at near critical conditions

    NASA Technical Reports Server (NTRS)

    Hsieh, Kwang-Chung; Shuen, Jian-Shun; Yang, Vigor

    1988-01-01

    A comprehensive numerical analysis of multicomponent droplet vaporization at near critical conditions has been carried out. The model is based on the full time-dependent conservation equations and accommodates various important high-pressure phenomena. As an example, the case involving a two-component (n-pentane and n-octane) fuel droplet in nitrogen gas is studied. The influences of transient effects, surface regression, ambient gas solubility, and phase-equilibrium relations on vaporization mechanisms are examined in detail.

  14. Mentoring Field Directors: A National Exploratory Study

    ERIC Educational Resources Information Center

    Ellison, Martha L.; Raskin, Miriam S.

    2014-01-01

    In social work field education, mentoring is underused and lacks research data. There is a paucity of research that examines the effect mentoring has on social work field directors who administer field programs at the undergraduate and/or graduate level. This exploratory study fills this void by examining the mentoring opportunities and…

  15. Field Guides in Academe: A Citation Study

    ERIC Educational Resources Information Center

    Schmidt, Dianne

    2006-01-01

    Field guides are common in libraries but are generally not considered scholarly. This study examines citations to fifty field guides to determine how they were used in scholarly publications, finding that field guides are frequently cited as a source of data on the ranges, habits, and descriptions of plants and animals.

  16. Cancer support groups: a critical review of empirical studies.

    PubMed

    Gottlieb, Benjamin H; Wachala, Elizabeth D

    2007-05-01

    Support groups for adults affected by cancer are widely offered by local community and national agencies in North America. This type of psychosocial intervention is defined in terms of its structure and functions, and its theoretical underpinnings and models of practice are described. Forty-four empirical studies of professionally led cancer support groups are summarized and critically reviewed. These studies include 32 outcome evaluations of randomized controlled trials, two process evaluations, and 10 consumer satisfaction studies. The findings reveal high levels of consumer satisfaction, and the outcome evaluations substantiate the morale and other quality of life benefits short of prolonging life. Discussion centers on priorities for future research and practice.

  17. Mean-field dynamic criticality and geometric transition in the Gaussian core model

    NASA Astrophysics Data System (ADS)

    Coslovich, Daniele; Ikeda, Atsushi; Miyazaki, Kunimasa

    2016-04-01

    We use molecular dynamics simulations to investigate dynamic heterogeneities and the potential energy landscape of the Gaussian core model (GCM). Despite the nearly Gaussian statistics of particles' displacements, the GCM exhibits giant dynamic heterogeneities close to the dynamic transition temperature. The divergence of the four-point susceptibility is quantitatively well described by the inhomogeneous version of the mode-coupling theory. Furthermore, the potential energy landscape of the GCM is characterized by large energy barriers, as expected from the lack of activated, hopping dynamics, and display features compatible with a geometric transition. These observations demonstrate that all major features of mean-field dynamic criticality can be observed in a physically sound, three-dimensional model.

  18. Universal Signatures of Quantum Critical Points from Finite-Size Torus Spectra: A Window into the Operator Content of Higher-Dimensional Conformal Field Theories

    NASA Astrophysics Data System (ADS)

    Schuler, Michael; Whitsitt, Seth; Henry, Louis-Paul; Sachdev, Subir; Läuchli, Andreas M.

    2016-11-01

    The low-energy spectra of many body systems on a torus, of finite size L , are well understood in magnetically ordered and gapped topological phases. However, the spectra at quantum critical points separating such phases are largely unexplored for (2 +1 )D systems. Using a combination of analytical and numerical techniques, we accurately calculate and analyze the low-energy torus spectrum at an Ising critical point which provides a universal fingerprint of the underlying quantum field theory, with the energy levels given by universal numbers times 1 /L . We highlight the implications of a neighboring topological phase on the spectrum by studying the Ising* transition (i.e. the transition between a Z2 topological phase and a trivial paramagnet), in the example of the toric code in a longitudinal field, and advocate a phenomenological picture that provides qualitative insight into the operator content of the critical field theory.

  19. Universal Signatures of Quantum Critical Points from Finite-Size Torus Spectra: A Window into the Operator Content of Higher-Dimensional Conformal Field Theories.

    PubMed

    Schuler, Michael; Whitsitt, Seth; Henry, Louis-Paul; Sachdev, Subir; Läuchli, Andreas M

    2016-11-18

    The low-energy spectra of many body systems on a torus, of finite size L, are well understood in magnetically ordered and gapped topological phases. However, the spectra at quantum critical points separating such phases are largely unexplored for (2+1)D systems. Using a combination of analytical and numerical techniques, we accurately calculate and analyze the low-energy torus spectrum at an Ising critical point which provides a universal fingerprint of the underlying quantum field theory, with the energy levels given by universal numbers times 1/L. We highlight the implications of a neighboring topological phase on the spectrum by studying the Ising* transition (i.e. the transition between a Z_{2} topological phase and a trivial paramagnet), in the example of the toric code in a longitudinal field, and advocate a phenomenological picture that provides qualitative insight into the operator content of the critical field theory.

  20. Triplet generation and upper critical field in superconducting spin valves based on CrO2

    NASA Astrophysics Data System (ADS)

    Voltan, S.; Singh, A.; Aarts, J.

    2016-08-01

    It has been recently reported that a superconducting triplet spin valve (TSV) based on the half-metallic CrO2 can show "colossal" variations of the critical temperature, up to more than 1 K. This can be achieved when the magnetic noncollinearity between the mixer (F1) and the drainage ferromagnetic layer (F) is maximized. In this work we investigate further such TSV devices looking at two aspects: first, we present the dependence of the TSV effect on the thickness of the mixer layer; second, we look at the perpendicular upper critical field Hc 2 ⊥ as a function of the temperature. The thickness dependence, which is nonmonotonic as expected, represents a further proof that the effect is due to the generation of equal-spin triplet Cooper pairs, while what we observe for the Hc 2 ⊥ versus T curves is an interesting and peculiar behavior: there is a clear deviation from the universal linear dependence and the average slope is suppressed much more than what can be described with the formalism used for conventional proximized structures.

  1. Investigation on critical breakdown electric field of hot carbon dioxide for gas circuit breaker applications

    NASA Astrophysics Data System (ADS)

    Sun, Hao; Rong, Mingzhe; Wu, Yi; Chen, Zhexin; Yang, Fei; Murphy, Anthony B.; Zhang, Hantian

    2015-02-01

    Sulfur hexafluoride (SF6) gas is widely used in high-voltage circuit breakers, but due to its high global warming potential, substitutes are being sought. CO2 has been investigated as a candidate based on its arc interruption performance. The hot gas in the circuit breaker after current zero, with a complicated species composition caused by the dissociation and many other reactions, will lead to the electrical breakdown, which is one of the major concerns in assessing the arc interruption performance. Despite this, little research has been reported on the dielectric strength of hot CO2. In this paper, the dielectric properties of hot CO2 related to the dielectric recovery phase of the circuit breaker were investigated in the temperature range from 300 to 4000 K and in the pressure range from 0.01 to 1.0 MPa. Under the assumptions of local thermodynamic equilibrium (LTE) and local chemical equilibrium (LCE), the equilibrium compositions of hot CO2 were obtained based on Gibbs free energy minimization. The cross sections for interactions between electrons and the species are presented. The critical reduced electric field strength of CO2 was determined by balancing electron generation and loss. These were evaluated using the electron energy distribution function (EEDF) derived from the two-term Boltzmann transport equation. The result indicates that unlike SF6 or air, in hot CO2 the reduced critical electric field strength does not change monotonically with increasing heavy-particle temperature from 300 to 4000 K. CO2 has a superior dielectric strength to pure SF6 above 2500 K at 0.5 MPa, which means it has the potential to improve the interruption performance of the circuit breakers, while reducing the global warming effect. Good agreement was found with published experimental results and calculations for CO2 at room temperature, and with previous calculations for hot CO2.

  2. Incubating knowledge: A critical exploration with teachers studying live chickens

    NASA Astrophysics Data System (ADS)

    Rauchwerk, Susan I.

    This thesis documents a professional development workshop conducted with eight teachers who worked at Drumlin Farm, an outdoor education center, organic farm and wildlife sanctuary (Appendix C). The participants studied live chickens for eight consecutive workshop sessions. Seven years later the same group met for two follow-up sessions to discuss the effects of the workshop on their teaching practice. The workshop and follow-up sessions were conducted using a teaching-research method developed by Eleanor Duckworth called critical exploration (Duckworth, in press). In this thesis, findings from the eight-week workshop and the two followup sessions are documented in a narrative format showing how and what individuals and the group as a whole, came to understand from studying live chickens, as well as the process and application of the critical exploration method. Over the course of the workshop and the follow-up sessions, group explorations focused on the biological concept of broodiness (the desire to sit, tend, and hatch eggs) in domestic laying hens. In the process of developing and investigating their questions about broodiness, the participants developed and used a scientific process. Their experiences as learners in critical exploration with chickens as the subject matter, resulted in participants both thinking about, and modifying, their ideas about teaching and learning.

  3. Self-organized criticality as Witten-type topological field theory with spontaneously broken Becchi-Rouet-Stora-Tyutin symmetry

    SciTech Connect

    Ovchinnikov, Igor V.

    2011-05-15

    Here, a scenario is proposed, according to which a generic self-organized critical (SOC) system can be looked upon as a Witten-type topological field theory (W-TFT) with spontaneously broken Becchi-Rouet-Stora-Tyutin (BRST) symmetry. One of the conditions for the SOC is the slow driving noise, which unambiguously suggests Stratonovich interpretation of the corresponding stochastic differential equation (SDE). This, in turn, necessitates the use of Parisi-Sourlas-Wu stochastic quantization procedure, which straightforwardly leads to a model with BRST-exact action, i.e., to a W-TFT. In the parameter space of the SDE, there must exist full-dimensional regions where the BRST symmetry is spontaneously broken by instantons, which in the context of SOC are essentially avalanches. In these regions, the avalanche-type SOC dynamics is liberated from overwise a rightful dynamics-less W-TFT, and a Goldstone mode of Fadeev-Popov ghosts exists. Goldstinos represent moduli of instantons (avalanches) and being gapless are responsible for the critical avalanche distribution in the low-energy, long-wavelength limit. The above arguments are robust against moderate variations of the SDE's parameters and the criticality is 'self-tuned'. The proposition of this paper suggests that the machinery of W-TFTs may find its applications in many different areas of modern science studying various physical realizations of SOC. It also suggests that there may in principle exist a connection between some SOC's and the concept of topological quantum computing.

  4. Magnetic-field-induced quantum criticality in a spin- S planar ferromagnet with single-ion anisotropy

    NASA Astrophysics Data System (ADS)

    Mercaldo, M. T.; Rabuffo, I.; De Cesare, L.; Caramico D'Auria, A.

    2013-08-01

    The effects of single-ion anisotropy on quantum criticality in a d-dimensional spin- S planar ferromagnet is explored by means of the two-time Green's function method. We work at the Tyablikov decoupling level for exchange interactions and the Anderson-Callen decoupling level for single-ion anisotropy. In our analysis a longitudinal external magnetic field is used as the non-thermal control parameter and the phase diagram and the quantum critical properties are established for suitable values of the single-ion anisotropy parameter D. We find that the single-ion anisotropy has sensible effects on the structure of the phase diagram close to the quantum critical point. However, for values of the uniaxial crystal-field parameter below a positive threshold, the conventional magnetic-field-induced quantum critical scenario remains unchanged.

  5. A Multinational Study of Thromboprophylaxis Practice in Critically Ill Children*

    PubMed Central

    Faustino, Edward Vincent S.; Hanson, Sheila; Spinella, Philip C.; Tucci, Marisa; O'Brien, Sarah H.; Nunez, Antonio Rodriguez; Yung, Michael; Truemper, Edward; Qin, Li; Li, Simon; Marohn, Kimberly; Randolph, Adrienne G.

    2015-01-01

    Objectives Although critically ill children are at increased risk for developing deep venous thrombosis, there are few pediatric studies establishing the prevalence of thrombosis or the efficacy of thromboprophylaxis. We tested the hypothesis that thromboprophylaxis is infrequently used in critically ill children even for those in whom it is indicated. Design Prospective multinational cross-sectional study over four study dates in 2012. Setting Fifty-nine PICUs in Australia, Canada, New Zealand, Portugal, Singapore, Spain, and the United States. Patients All patients less than 18 years old in the PICU during the study dates and times were included in the study, unless the patients were 1) boarding in the unit waiting for a bed outside the PICU or 2) receiving therapeutic anticoagulation. Interventions None. Measurements and Main Results Of 2,484 children in the study, 2,159 (86.9%) had greater than or equal to 1 risk factor for thrombosis. Only 308 children (12.4%) were receiving pharmacologic thromboprophylaxis (e.g., aspirin, low-molecular-weight heparin, or unfractionated heparin). Of 430 children indicated to receive pharmacologic thromboprophylaxis based on consensus recommendations, only 149 (34.7%) were receiving it. Mechanical thromboprophylaxis was used in 156 of 655 children (23.8%) 8 years old or older, the youngest age for that device. Using nonlinear mixed effects model, presence of cyanotic congenital heart disease (odds ratio, 7.35; p < 0.001) and spinal cord injury (odds ratio, 8.85; p = 0.008) strongly predicted the use of pharmacologic and mechanical thromboprophylaxis, respectively. Conclusions Thromboprophylaxis is infrequently used in critically ill children. This is true even for children at high risk of thrombosis where consensus guidelines recommend pharmacologic thromboprophylaxis. PMID:24351371

  6. Soil Production and Transport Perspectives on Critical Zone Studies

    NASA Astrophysics Data System (ADS)

    Heimsath, A. M.; Foster, M.; Whipple, K. X.

    2015-12-01

    Quantifying soil production and transport rates and processes is a key aspect of most critical zone studies. Methodologies range from relatively straightforward, low cost studies like sediment traps and basin volume estimates to sophisticated and expensive studies using chemical and physical tracers and isotope geochemistry. Inherent in all methodologies are assumptions and simplifications that enable any measurement to be translated to a rate and interpreted in terms of process mechanics. For example, quantifying soil production using in situ cosmogenic nuclides measured in the parent material beneath an upland mobile regolith mantle depends on assuming a locally steady state soil thickness (i.e. neither thinning or thickening with time). Similarly, utilizing hillslope-scale sediment traps or landscape-scale basin analyses depends on assumptions of steady state processes and constraining the timescales represented by the captured sediment. As our analyses of landscapes have expanded into the details of how spatial and temporal gradients of all driving variables (lithology, climate, tectonics, distribution of biota, etc.) influence landscape evolution, our adherence to the assumptions and simplifications necessitated by our methods becomes questionable. Here we provide content analyses of recent and ongoing studies quantifying soil production and transport processes across a range of climatic, geologic and tectonic regimes. We code the studies for their inclusion and use of assumptions and simplifications necessary to ensure that the methodologies apply to their intended use. These analyses provide an important perspective on the use of quantitative methods and offer both a complimentary and cautionary views on critical zone studies in general.

  7. Upper critical field and Raman spectra of MgB2 thin films irradiated with low energy oxygen ion

    NASA Astrophysics Data System (ADS)

    Wang, J.; Zhuang, C. G.; Li, J.; Wang, Y. Z.; Feng, Q. R.; Zheng, D. N.

    2009-11-01

    The structure, upper critical field, and Raman spectrum of epitaxial MgB2 thin films irradiated by 300 keV O2+ ions have been investigated. Lattice parameter c expands after irradiation. There is a significant increase in upper critical field in the moderately irradiated films, while the critical temperature is reduced slightly. The values of critical field at zero temperature exhibit a maximum for samples with a moderate irradiation level for the applied magnetic field both perpendicular and parallel to the film surface. The temperature dependence of the anisotropy parameter, which is defined as the ratio of the upper critical field with the field parallel to the film surface and perpendicular to the film surface, reveals that oxygen ion irradiation mainly affects the σ band at a low irradiation level. With increasing irradiation level, π band scattering is strongly enhanced, and finally both bands are in the dirty limit. A broad peak centered around 570 cm-1 is observed in the Raman spectrum of the unirradiated films, and the peak position has a visible redshift in the irradiated samples. In particular, high-frequency spectral structures appear and become dominant, while the E2g broad band diminishes gradually with increasing irradiation fluence. The results are discussed by considering the disorder-induced change in carrier scattering within and between the σ and π bands and a violation of the Raman selection rules due to oxygen ion irradiation.

  8. Upper critical field and quantum oscillations in tetragonal superconducting FeS

    NASA Astrophysics Data System (ADS)

    Terashima, Taichi; Kikugawa, Naoki; Lin, Hai; Zhu, Xiyu; Wen, Hai-Hu; Nomoto, Takuya; Suzuki, Katsuhiro; Ikeda, Hiroaki; Uji, Shinya

    2016-09-01

    The magnetoresistance and magnetic torque of FeS are measured in magnetic fields B of up to 18 T down to a temperature of 0.03 K. The superconducting transition temperature is found to be Tc=4.1 K , and the anisotropy ratio of the upper critical field Bc 2 at Tc is estimated from the initial slopes to be Γ (Tc)=6.9 . Bc 2(0 ) is estimated to be 2.2 and 0.36 T for B ∥a b and c , respectively. Quantum oscillations are observed in both the resistance and torque. Two frequencies F =0.15 and 0.20 kT are resolved and assigned to a quasi-two-dimensional Fermi surface cylinder. The carrier density and Sommerfeld coefficient associated with this cylinder are estimated to be 5.8 ×10-3 carriers/Fe and 0.48 mJ /(K2mol ) , respectively. Other Fermi surface pockets still remain to be found. Band-structure calculations are performed and compared to the experimental results.

  9. Critical Pertussis Illness in Children, A Multicenter Prospective Cohort Study

    PubMed Central

    Berger, John T.; Carcillo, Joseph A.; Shanley, Thomas P.; Wessel, David L.; Clark, Amy; Holubkov, Richard; Meert, Kathleen L.; Newth, Christopher J.L.; Berg, Robert A.; Heidemann, Sabrina; Harrison, Rick; Pollack, Murray; Dalton, Heidi; Harvill, Eric; Karanikas, Alexia; Liu, Teresa; Burr, Jeri S.; Doctor, Allan; Dean, J. Michael; Jenkins, Tammara L.; Nicholson, Carol E.

    2013-01-01

    Objective Pertussis persists in the United States despite high immunization rates. The present report characterizes the presentation and acute course of critical pertussis by quantifying demographic data, laboratory findings, clinical complications, and critical care therapies required among children requiring admission to the pediatric intensive care unit (PICU). Design Prospective cohort study. Setting Eight PICUs comprising the Eunice Kennedy Shriver National Institute for Child Health and Human Development Collaborative Pediatric Critical Care Research Network and 17 additional PICUs across the United States. Patients Eligible patients had laboratory confirmation of pertussis infection, were < 18 years of age, and died in the PICU or were admitted to the PICU for at least 24 hours between June 2008 and August 2011. Interventions None. Measurements and Main Results 127 patients were identified. Median age was 49 days, and 105 (83%) patients were < 3 months of age. Fifty-five (43%) required mechanical ventilation. Twelve (9.4%) died during initial hospitalization. Pulmonary hypertension was found in 16 patients (12.5%), and was present in 75% of patients who died, compared with 6% of survivors (p< 0.001). Median white blood cell count (WBC) was significantly higher in those requiring mechanical ventilation (p<0.001), those with pulmonary hypertension (p<0.001) and non-survivors (p<0.001). Age, sex and immunization status did not differ between survivors and non-survivors. Fourteen patients received leukoreduction therapy (exchange transfusion (12), leukopheresis (1) or both (1)). Survival benefit was not apparent. Conclusions Pulmonary hypertension may be associated with mortality in pertussis critical illness. Elevated WBC is associated with the need for mechanical ventilation, pulmonary hypertension, and mortality risk. Research is indicated to elucidate how pulmonary hypertension, immune responsiveness, and elevated WBC contribute to morbidity and mortality

  10. Study on the critical properties of thin magnetic films using the clock model

    NASA Astrophysics Data System (ADS)

    Nguyen, T.-L. H.; Thanh Ngo, V.

    2017-03-01

    We study the critical behaviour of very thin magnetic films. This system can be described by the q-state clock model. In order to determine the critical exponents of the system when there exists the Berezinskii–Kosterlitz–Thouless phase between the two phase transitions, we introduce a new technique for calculating the order parameter. The simulation is performed by very high-resolution Monte Carlo method with including the Wang–Landau algorithm. The results showed that the Berezinskii–Kosterlitz–Thouless phase starts to occur when q≥slant 3 with a small symmetry breaking field. We obtained not only the critical exponents of a common transition at high temperature but also the ones of unclear transition at low temperature.

  11. Simulation study of the ionizing front in the critical ionization velocity phenomenon

    NASA Technical Reports Server (NTRS)

    Machida, S.; Goertz, C. K.; Lu, G.

    1988-01-01

    The simulation of the critical ionization velocity for a neutral gas cloud moving across the static magnetic field is presented. A low-beta plasma is studied, using a two and a half-dimensional electrostatic code linked with the Plasma and Neutral Interaction Code (Goertz and Machida, 1987). The physics of the ionizing front and the instabilities which occur there are discussed. Results are presented from four numerical runs designed so that the effects of the charge separation field can be distinguished from the wave heating.

  12. Currents of Trans/National Criticism in Indigenous Literary Studies

    ERIC Educational Resources Information Center

    Justice, Daniel Heath

    2011-01-01

    Recently, when preparing course materials for English graduate students on the practical skills and theoretical dimensions of teaching literature, the author surveyed the literature on the "state of the field" of literary studies in English (and the entire concept of a liberal arts education), ranging from high-profile monographs to various…

  13. Effect of two bands on critical fields in MgB2 thin films with various resistivity values

    NASA Astrophysics Data System (ADS)

    Ferrando, V.; Manfrinetti, P.; Marré, D.; Putti, M.; Sheikin, I.; Tarantini, C.; Ferdeghini, C.

    2003-09-01

    Upper critical fields of four MgB2 thin films were measured up to 28 T at Grenoble High Magnetic Field Laboratory. The films were grown by pulsed laser deposition and showed critical temperatures ranging between 29.5 and 38.8 K and resistivities at 40 K varying from 5 to 50 μΩ cm. The critical fields in the perpendicular direction turned out to be in the 13 24 T range while they were estimated to be in 42 57 T range for ab planes. In contrast to the prediction of the BCS theory, we did not observe any saturation at low temperatures: a linear temperature dependence is exhibited even at lowest temperatures at which we made the measurements. Moreover, the critical field values seemed not to depend on the normal state resistivity value. In this paper, we analyze these data considering the multiband nature of superconductivity in MgB2. We will show how the scattering mechanisms that determine critical fields and resistivity can be different.

  14. A Critical Review of Some Ecological Studies on Scientific Journals

    NASA Astrophysics Data System (ADS)

    Yamazaki, Shigeaki

    There have been hot discussions about the number and the rate of growth of scientific journals. The purpose of this review is intended to provide a critical assessment of those ecological studies on scientific journals. In 1961, Price presented his famous graph curve, and noted that rate of growth of journals had been fairly consisted at 5 per cent annum for nearly 300 years. But Price's graph curve has some primary error, and the author suggest to examine carefully his study. There is another problem that the loose definition of scientific journals is used. The author try to give a clear definition on the term ‘scientific journals’, and try to reestimate historically the growth rate in numbers of current scientific journals, referring several reliable studies previously conducted. The Author's estimation is about 1.85 per cent a year from the last of 18 century.

  15. Analytical study of the critical behavior of the nonlinear pendulum

    NASA Astrophysics Data System (ADS)

    Lima, F. M. S.

    2010-11-01

    The dynamics of a simple pendulum consisting of a small bob and a massless rigid rod has three possible regimes depending on its total energy E: Oscillatory (when E is not enough for the pendulum to reach the top position), "perpetual ascent" when E is exactly the energy needed to reach the top, and nonoscillatory for greater energies. In the latter regime, the pendulum rotates periodically without velocity inversions. In contrast to the oscillatory regime, for which an exact analytic solution is known, the other two regimes are usually studied by solving the equation of motion numerically. By applying conservation of energy, I derive exact analytical solutions to both the perpetual ascent and nonoscillatory regimes and an exact expression for the pendulum period in the nonoscillatory regime. Based on Cromer's approximation for the large-angle pendulum period, I find a simple approximate expression for the decrease of the period with the initial velocity in the nonoscillatory regime, valid near the critical velocity. This expression is used to study the critical slowing down, which is observed near the transition between the oscillatory and nonoscillatory regimes.

  16. Study of the critical behavior of the driven lattice gas model with limited nonequilibrium dynamics

    NASA Astrophysics Data System (ADS)

    Saracco, Gustavo P.; Rubio Puzzo, M. Leticia; Bab, Marisa A.

    2017-02-01

    In this paper the nonequilibrium critical behavior is investigated using a variant of the well-known two-dimensional driven lattice gas (DLG) model, called modified driven lattice gas (MDLG). In this model, the application of the external field is regulated by a parameter p ɛ [ 0 , 1 ] in such a way that if p = 0, the field is not applied, and it becomes the Ising model, while if p = 1, the DLG model is recovered. The behavior of the model is investigated for several values of p by studying the dynamic evolution of the system within the short-time regime in the neighborhood of a phase transition. It is found that the system experiences second-order phase transitions in all the interval of p for the density of particles ρ = 0.5. The determined critical temperatures Tc(p) are greater than the critical temperature of the Ising model TcI, and increase with p up to the critical temperature of the DLG model in the limit of infinite driving fields. The dependence of Tc(p) on p is compatible with a power-law behavior whose exponent is ψ = 0.27(3) . Furthermore, the complete set of the critical and the anisotropic exponents is estimated. For the smallest value of p, the ​dynamics and β exponents are close to that calculated for the Ising model, and the anisotropic exponent Δ is near zero. As p is increased, the exponents and Δ change, meaning that the anisotropy effects increase. For the largest value investigated, the set of exponents approaches to that reported by the most recent theoretical framework developed for the DLG model.

  17. Shell thickness and dynamic magnetic field effects on the critical phenomena of magnetic core-shell nanoparticles with spherical geometry

    NASA Astrophysics Data System (ADS)

    Yüksel, Yusuf

    2017-03-01

    By using Monte Carlo simulations for classical Heisenberg spins, we study the critical phenomena and ferrimagnetic properties of spherical nanoparticles with core-shell geometry. The particle core is composed of ferromagnetic spins, and it is coated by a ferromagnetic shell. Total size of the particle is fixed but the thickness of the shell is varied in such a way that the shell layer is grown at the expense of the core. Effects of the shell thickness, as well as dynamic magnetic field parameters such as oscillation period and field amplitude on the magnetization profiles, dynamic hysteresis loops and phase diagrams have been investigated for the present system. It has been found that as the shell thickness varies then the easy axis magnetization of the overall system may exhibit Q-, P-, L- and N- type behaviors based on the Neél terminology. We also found that three distinct anomalies originate in the thermal variation of specific heat with increasing field period. Dynamic hysteresis loops corresponding to off-axial magnetization components exhibit unconventional behavior such as double rings with symmetric shapes around the vertical axis over the h (t) = 0 line which may originate due to the stochastic resonance behavior of these components.

  18. Developing Critical Thinking through the Study of Paranormal Phenomena.

    ERIC Educational Resources Information Center

    Wesp, Richard; Montgomery, Kathleen

    1998-01-01

    Argues that accounts of paranormal phenomena can serve as an ideal medium in which to encourage students to develop critical-thinking skills. Describes a cooperative-learning approach used to teach critical thinking in a course on paranormal events. Reports that critical-thinking skills increased and that the course received favorable student…

  19. Superconductivity and critical fields in undoped and Sn-doped MoSr 2YCu 2O 8-δ

    NASA Astrophysics Data System (ADS)

    Balchev, N.; Nenkov, K.; Antonov, V.; Pirov, J.; Kunev, B.

    2010-12-01

    Samples with nominal compositions MoSn xSr 2YCu 2O 8-δ (0 ⩽ x ⩽ 0.075) were synthesized and their superconducting and magnetotransport properties were investigated. It was established that the optimum Sn-doping ( x = 0.02 and 0.03) increases the T c of the undoped MoSr 2YCu 2O 8-δ. The upper critical fields of the samples were determined using magnetization, susceptibility and resistivity measurements. It was established that the Sn-doping weakly affects the first and the intragrain second critical field of Mo-1212 but enhances the extrapolated to T = 0 (i.e. the intergrain) upper critical field. The observed phenomena were discussed on the basis of the Josephson-junction-arrays model. A phenomenological expression describing the temperature dependency of the susceptibility of Mo-1212 was found.

  20. Naturalistic Field Studies of Sleep and Performance

    DTIC Science & Technology

    2010-05-01

    AD_________________ Award Number: W81XWH-05-1-0099 TITLE: Naturalistic Field Studies of Sleep and...5a. CONTRACT NUMBER Naturalistic Field Studies of Sleep and Performance 5b. GRANT NUMBER W81XWH-05-1-0099 5c. PROGRAM ELEMENT NUMBER 6...Center (SPRC) conducts human and animal  studies  in laboratory and field settings in support of basic and applied sleep  research at Washington State

  1. Determination of the critical coupling of explosive synchronization transitions in scale-free networks by mean-field approximations.

    PubMed

    Peron, Thomas Kauê Dal'maso; Rodrigues, Francisco A

    2012-11-01

    An explosive synchronization can be observed in scale-free networks when Kuramoto oscillators have natural frequencies equal to their number of connections. The present paper reports on mean-field approximations to determine the critical coupling of such explosive synchronization. It has been verified that the equation obtained for the critical coupling has an inverse dependence on the network average degree. This expression differs from those whose frequency distributions are unimodal and even. In this case, the critical coupling depends on the ratio between the first and second statistical moments of the degree distribution. Numerical simulations were also conducted to verify our analytical results.

  2. Quantum criticality in a magnetic chain with two- and four-spin interactions in a transverse field

    NASA Astrophysics Data System (ADS)

    de Alcantara Bonfim, O. F.; Saguia, A.; Boechat, B.; Florencio, J.

    2015-03-01

    We use entanglement entropy and finite-size scaling methods to investigate the ground-state properties of a spin - 1 / 2 Ising chain with two-spin (J2) and four-spin (J4) interactions in a transverse magnetic field (B). We concentrate our study on the unexplored critical region B = 1 and obtain the phase diagram of the model in the (J4-J2) plane. The phases found include ferromagnetic (F), antiferromagnetic (AF), as well as more complex phases involving spin configurations with multiple periodicity. The system presents both first and second order transitions separated by tricritical points. We find an unusual phase boundary on the semi-infinite segment (J4 < - 1 , J2 =0) separating the F and AF phases.

  3. Study on contaminants on flight and other critical surfaces

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Hughes, Charles; Arendale, William F.

    1994-01-01

    The control of surface contamination in the manufacture of space hardware can become a critical step in the production process. Bonded surfaces have been shown to be affected markedly by contamination. It is important to insure surface cleanliness by preventing contamination prior to bonding. In this vein techniques are needed in which the contamination which may affect bonding are easily found and removed. Likewise, if materials which are detrimental to bonding are not easily removed, then they should not be used in the manufacturing process. This study will address the development of techniques to locate and quantify contamination levels of particular contaminants. With other data becoming available from MSFC and its contractors, this study will also quantify how certain contaminants affect bondlines and how easily they are removed in manufacturing.

  4. Magnetic-field-induced quantum criticality in a spin-1 planar ferromagnet with single-ion anisotropy

    NASA Astrophysics Data System (ADS)

    Mercaldo, Maria Teresa; Rabuffo, Ileana; Decesare, Luigi; Caramicod'Auria, Alvaro

    2014-03-01

    The effects of single-ion anisotropy on field-induced quantum criticality in spin-1 planar ferromagnet is explored by means of the two-time Green's function method. We work at the Tyablikov decoupling level for exchange interactions and the Anderson-Callen decoupling level for single-ion anisotropy. In our analysis a longitudinal external magnetic field is used as the non-thermal control parameter and the phase diagram and the quantum critical properties are established for suitable values of the single-ion anisotropy parameter. We find that the single-ion anisotropy has sensible effects on the structure of the phase diagram close to the quantum critical point. Indeed, for values of the uniaxial crystal-field parameter above a positive threshold a re-entrant behavior appears for the critical line, while above this value the conventional magnetic-field-induced quantum critical scenario remains unchanged. M. T. Mercaldo, I. Rabuffo, L. De Cesare, A. Caramico D'Auria, Eur. Phys. J. B 86, 340 (2013)

  5. Application of the string method to the study of critical nuclei in capillary condensation.

    PubMed

    Qiu, Chunyin; Qian, Tiezheng; Ren, Weiqing

    2008-10-21

    We adopt a continuum description for liquid-vapor phase transition in the framework of mean-field theory and use the string method to numerically investigate the critical nuclei for capillary condensation in a slit pore. This numerical approach allows us to determine the critical nuclei corresponding to saddle points of the grand potential function in which the chemical potential is given in the beginning. The string method locates the minimal energy path (MEP), which is the most probable transition pathway connecting two metastable/stable states in configuration space. From the MEP, the saddle point is determined and the corresponding energy barrier also obtained (for grand potential). Moreover, the MEP shows how the new phase (liquid) grows out of the old phase (vapor) along the most probable transition pathway, from the birth of a critical nucleus to its consequent expansion. Our calculations run from partial wetting to complete wetting with a variable strength of attractive wall potential. In the latter case, the string method presents a unified way for computing the critical nuclei, from film formation at solid surface to bulk condensation via liquid bridge. The present application of the string method to the numerical study of capillary condensation shows the great power of this method in evaluating the critical nuclei in various liquid-vapor phase transitions.

  6. Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors

    PubMed Central

    Kasahara, Y.; Takeuchi, Y.; Zadik, R. H.; Takabayashi, Y.; Colman, R. H.; McDonald, R. D.; Rosseinsky, M. J.; Prassides, K.; Iwasa, Y.

    2017-01-01

    Controlled access to the border of the Mott insulating state by variation of control parameters offers exotic electronic states such as anomalous and possibly high-transition-temperature (Tc) superconductivity. The alkali-doped fullerides show a transition from a Mott insulator to a superconductor for the first time in three-dimensional materials, but the impact of dimensionality and electron correlation on superconducting properties has remained unclear. Here we show that, near the Mott insulating phase, the upper critical field Hc2 of the fulleride superconductors reaches values as high as ∼90 T—the highest among cubic crystals. This is accompanied by a crossover from weak- to strong-coupling superconductivity and appears upon entering the metallic state with the dynamical Jahn–Teller effect as the Mott transition is approached. These results suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity with high-Tc and high-Hc2. PMID:28211544

  7. Disordered nanocrystalline superconducting PbMo6S8 with a very large upper critical field.

    PubMed

    Niu, H J; Hampshire, D P

    2003-07-11

    Large increases in the upper critical field B(C2)(0) are reported in bulk superconductors that demonstrate another novel property for nanocrystalline materials. Disordered nanocrystalline PbMo6S8 superconductors were fabricated by mechanical milling and hot isostatic pressing. Conventional PbMo6S8 has B(C2)(0) approximately 50 T. The nanocrystalline materials have higher resistivity (rho(N)) and B(C2)(0) approximately 100 T. The disorder produced in these nanocrystalline materials is significantly different from that produced by doping because it increases rho(N) and, hence, B(C2)(0) without significantly reducing the electronic density of states or superconducting transition temperature (T(C)). Furthermore, the disorder reduces the electron mean-free path to approximately 1 nm which is more than an order of magnitude smaller than the grain size and necessary to achieve the unprecedented increase in B(C2)(0).

  8. Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors.

    PubMed

    Kasahara, Y; Takeuchi, Y; Zadik, R H; Takabayashi, Y; Colman, R H; McDonald, R D; Rosseinsky, M J; Prassides, K; Iwasa, Y

    2017-02-17

    Controlled access to the border of the Mott insulating state by variation of control parameters offers exotic electronic states such as anomalous and possibly high-transition-temperature (Tc) superconductivity. The alkali-doped fullerides show a transition from a Mott insulator to a superconductor for the first time in three-dimensional materials, but the impact of dimensionality and electron correlation on superconducting properties has remained unclear. Here we show that, near the Mott insulating phase, the upper critical field Hc2 of the fulleride superconductors reaches values as high as ∼90 T-the highest among cubic crystals. This is accompanied by a crossover from weak- to strong-coupling superconductivity and appears upon entering the metallic state with the dynamical Jahn-Teller effect as the Mott transition is approached. These results suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity with high-Tc and high-Hc2.

  9. Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors

    NASA Astrophysics Data System (ADS)

    Kasahara, Y.; Takeuchi, Y.; Zadik, R. H.; Takabayashi, Y.; Colman, R. H.; McDonald, R. D.; Rosseinsky, M. J.; Prassides, K.; Iwasa, Y.

    2017-02-01

    Controlled access to the border of the Mott insulating state by variation of control parameters offers exotic electronic states such as anomalous and possibly high-transition-temperature (Tc) superconductivity. The alkali-doped fullerides show a transition from a Mott insulator to a superconductor for the first time in three-dimensional materials, but the impact of dimensionality and electron correlation on superconducting properties has remained unclear. Here we show that, near the Mott insulating phase, the upper critical field Hc2 of the fulleride superconductors reaches values as high as ~90 T--the highest among cubic crystals. This is accompanied by a crossover from weak- to strong-coupling superconductivity and appears upon entering the metallic state with the dynamical Jahn-Teller effect as the Mott transition is approached. These results suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity with high-Tc and high-Hc2.

  10. Assessing monoclonal antibody product quality attribute criticality through clinical studies.

    PubMed

    Goetze, Andrew M; Schenauer, Matthew R; Flynn, Gregory C

    2010-01-01

    Recombinant therapeutic proteins, including antibodies, contain a variety of chemical and physical modifications. Great effort is expended during process and formulation development in controlling and minimizing this heterogeneity, which may not affect safety or efficacy, and, therefore, may not need to be controlled. Many of the chemical conversions also occur in vivo, and knowledge about the alterations can be applied to assessment of the potential impact on characteristics and the biological activity of therapeutic proteins. Other attributes may affect the drug clearance and thereby alter drug efficacy. In this review article, we describe attribute studies conducted using clinical samples and how information gleaned from them is applied to attribute criticality assessment. In general, how fast attributes change in vivo compared to the rate of mAb elimination is the key parameter used in these evaluations. An attribute with more rapidly changing levels may have greater potential to affect safety or efficacy and thereby reach the status of a Critical Quality Attribute (CQA) that should be controlled during production and storage, but the effect will depend on whether compositional changes are due to chemical conversion or differential clearance.

  11. Field-induced magnetic instability and quantum criticality in the antiferromagnet CeCu2Ge2.

    PubMed

    Liu, Yi; Xie, Donghua; Wang, Xiaoying; Zhu, Kangwei; Yang, Ruilong

    2016-01-13

    The magnetic quantum criticality in strongly correlated electron systems has been considered to be closely related with the occurrence of unconventional superconductivity. Control parameters such as magnetic field, pressure or chemical doping are frequently used to externally tune the quantum phase transition for a deeper understanding. Here we report the research of a field-induced quantum phase transition using conventional bulk physical property measurements in the archetypal antiferromagnet CeCu2Ge2, which becomes superconductive under a pressure of about 10 GPa with Tc ~ 0.64 K. We offer strong evidence that short-range dynamic correlations start appearing above a magnetic field of about 5 T. Our demonstrations of the magnetic instability and the field-induced quantum phase transition are crucial for the quantum criticality, which may open a new route in experimental investigations of the quantum phase transition in heavy-fermion systems.

  12. Critical study of the B{yields}K{pi} puzzle

    SciTech Connect

    Kim, C.S.; Oh, Sechul; Yu, Chaehyun

    2005-10-01

    In the light of new experimental results on B{yields}K{pi} decays, we critically study the decay processes B{yields}K{pi} in a phenomenological way. Using the quark diagram approach and the currently available data, we determine the allowed values of the relevant theoretical parameters, corresponding to the electroweak (EW) penguin, the color-suppressed tree contribution, etc. In order to find the most likely values of the parameters in a statistically reliable way, we use the {chi}{sup 2} minimization technique. Our result shows that the current data for B{yields}K{pi} decays strongly indicate (large) enhancements of both the EW penguin and the color-suppressed tree contributions. In particular, the color-suppressed tree effect needs to be enhanced by about an order of magnitude to fit the present data.

  13. Coping with traumatic stress in journalism: a critical ethnographic study.

    PubMed

    Buchanan, Marla; Keats, Patrice

    2011-04-01

    Journalists who witness trauma and disaster events are at risk for physical, emotional, and psychological injury. The purpose of this paper is to present the results of a critical ethnographic study among 31 Canadian journalists and photojournalists with regard to coping strategies used to buffer the effects of being exposed to trauma and disaster events and work-related stress. The findings are the result of in-depth individual interviews and six workplace observations with journalists across Canada. The most commonly reported coping strategies were: avoidance strategies at work, use of black humor, controlling one's emotions and memories, exercise and other physical activities, focusing on the technical aspects, and using substances. Recommendations for addressing the effects of work-related stress within this population are provided.

  14. Critical behavior of k -core percolation: Numerical studies

    NASA Astrophysics Data System (ADS)

    Lee, Deokjae; Jo, Minjae; Kahng, B.

    2016-12-01

    k -core percolation has served as a paradigmatic model of discontinuous percolation for a long time. Recently it was revealed that the order parameter of k -core percolation of random networks additionally exhibits critical behavior. Thus k -core percolation exhibits a hybrid phase transition. Unlike the critical behaviors of ordinary percolation that are well understood, those of hybrid percolation transitions have not been thoroughly understood yet. Here, we investigate the critical behavior of k -core percolation of Erdős-Rényi networks. We find numerically that the fluctuations of the order parameter and the mean avalanche size diverge in different ways. Thus, we classify the critical exponents into two types: those associated with the order parameter and those with finite avalanches. The conventional scaling relations hold within each set, however, these two critical exponents are coupled. Finally we discuss some universal features of the critical behaviors of k -core percolation and the cascade failure model on multiplex networks.

  15. A CRITICAL ASSESSMENT OF NONLINEAR FORCE-FREE FIELD MODELING OF THE SOLAR CORONA FOR ACTIVE REGION 10953

    SciTech Connect

    DeRosa, Marc L.; Schrijver, Carolus J.; Aschwanden, Markus J.; Cheung, Mark C. M.; Lites, Bruce W.; Amari, Tahar; Canou, Aurelien; McTiernan, James M.; Regnier, Stephane; Thalmann, Julia K.; Wiegelmann, Thomas; Inhester, Bernd; Tadesse, Tilaye; Valori, Gherardo; Wheatland, Michael S.; Conlon, Paul A.; Fuhrmann, Marcel

    2009-05-10

    Nonlinear force-free field (NLFFF) models are thought to be viable tools for investigating the structure, dynamics, and evolution of the coronae of solar active regions. In a series of NLFFF modeling studies, we have found that NLFFF models are successful in application to analytic test cases, and relatively successful when applied to numerically constructed Sun-like test cases, but they are less successful in application to real solar data. Different NLFFF models have been found to have markedly different field line configurations and to provide widely varying estimates of the magnetic free energy in the coronal volume, when applied to solar data. NLFFF models require consistent, force-free vector magnetic boundary data. However, vector magnetogram observations sampling the photosphere, which is dynamic and contains significant Lorentz and buoyancy forces, do not satisfy this requirement, thus creating several major problems for force-free coronal modeling efforts. In this paper, we discuss NLFFF modeling of NOAA Active Region 10953 using Hinode/SOT-SP, Hinode/XRT, STEREO/SECCHI-EUVI, and SOHO/MDI observations, and in the process illustrate three such issues we judge to be critical to the success of NLFFF modeling: (1) vector magnetic field data covering larger areas are needed so that more electric currents associated with the full active regions of interest are measured, (2) the modeling algorithms need a way to accommodate the various uncertainties in the boundary data, and (3) a more realistic physical model is needed to approximate the photosphere-to-corona interface in order to better transform the forced photospheric magnetograms into adequate approximations of nearly force-free fields at the base of the corona. We make recommendations for future modeling efforts to overcome these as yet unsolved problems.

  16. The upper critical field and its anisotropy in (Li1-x Fe x )OHFe1-y Se

    NASA Astrophysics Data System (ADS)

    Wang, Zhaosheng; Yuan, Jie; Wosnitza, J.; Zhou, Huaxue; Huang, Yulong; Jin, Kui; Zhou, Fang; Dong, Xiaoli; Zhao, Zhongxian

    2017-01-01

    The temperature dependence of the upper critical field (H c2) in a (Li1-x Fe x )OHFe1-y Se single crystal ({{T}\\text{c}}≈ 40 K) has been determined by means of magnetotransport measurements down to 1.4 K both for inter-plane (H\\parallel c , H\\text{c2}//c ) and in-plane (H\\parallel ab , H\\text{c2}//ab ) field directions in static magnetic fields up to 14 T and pulsed magnetic fields up to 70 T. H\\text{c2}//c exhibits a quasilinear increase with decreasing temperature below the superconducting transition and can be described well by an effective two-band model with unbalanced diffusivity, while H\\text{c2}//ab shows a flattening below 35 K and follows the Werthamer-Helfand-Hohenberg (WHH) model incorporating orbital pair-breaking and spin-paramagnetic effects, yielding zero-temperature critical fields of H\\text{c2}//c(0)≈ 67 T and H\\text{c2}//ab(0)≈ 98 T. The anisotropy of the upper critical fields, γ (T)=H\\text{c2}//ab/H\\text{c2}//c monotonically decreases with decreasing temperature from about 7 near T c to 1.5 at 0 K. This reduced anisotropy, observed in most Fe-based superconductors, is caused by the Pauli limitation of H\\text{c2}//ab .

  17. Critical reading and critical thinking--study design and methodology: a personal approach on how to read the clinical literature.

    PubMed

    Lipman, Timothy O

    2013-04-01

    The volume of medical literature grows exponentially. Yet we are faced with the necessity to make clinical decisions based on the availability and quality of scientific information. The general strength (reliability, robustness) of any interpretation that guides us in clinical decision making is dependent on how information was obtained. All information and medical studies and, consequently, all conclusions are not created equal. It is incumbent upon us to be able to assess the quality of the information that guides us in the care of our patients. Being able to assess medical literature critically requires use of critical reading and critical thinking skills. To achieve these skills, to be able to analyze medical literature critically, takes a combination of education and practice, practice, and more practice.

  18. "What Is Critical Whiteness Doing in Our Nice Field Like Critical Race Theory?" Applying CRT and CWS to Understand the White Imaginations of White Teacher Candidates

    ERIC Educational Resources Information Center

    Matias, Cheryl E.; Viesca, Kara Mitchell; Garrison-Wade, Dorothy F.; Tandon, Madhavi; Galindo, Rene

    2014-01-01

    Critical Race Theory (CRT) revolutionized how we investigate race in education. Centralizing counter-stories from people of color becomes essential for decentralizing white normative discourse--a process we refer to as realities within the Black imagination. Yet, few studies examine how whites respond to centering the Black imagination, especially…

  19. Investigating Students' Critical Thinking in Weblogs: An Exploratory Study in a Singapore Secondary School

    ERIC Educational Resources Information Center

    Wang, Qiyun; Woo, Huay Lit

    2010-01-01

    Critical thinking is an essential competency in the new information age. But research shows that students commonly lack critical thinking skills and hence promoting students' critical thinking becomes crucial. This exploratory study investigated the extent to which secondary school students' critical thinking could be promoted by writing…

  20. A Critical Literacy Perspective for Teaching and Learning Social Studies

    ERIC Educational Resources Information Center

    Soares, Lina Bell; Wood, Karen

    2010-01-01

    In a time of increasing plurality in today's public schools, it is essential that students become critically competent citizens by examining current and historical social justice issues. The purpose of this manuscript is to provide the research, theory, and practice for teachers to help students take a critical stance as they read and respond to…

  1. Critical Incident Analysis through Narrative Reflective Practice: A Case Study

    ERIC Educational Resources Information Center

    Farrell, Thomas S. C.

    2013-01-01

    Teachers can reflect on their practices by articulating and exploring incidents they consider critical to themselves or others. By talking about these critical incidents, teachers can make better sense of seemingly random experiences that occur in their teaching because they hold the real inside knowledge, especially personal intuitive knowledge,…

  2. Groundwater protection and unconventional gas extraction: the critical need for field-based hydrogeological research.

    PubMed

    Jackson, R E; Gorody, A W; Mayer, B; Roy, J W; Ryan, M C; Van Stempvoort, D R

    2013-01-01

    Unconventional natural gas extraction from tight sandstones, shales, and some coal-beds is typically accomplished by horizontal drilling and hydraulic fracturing that is necessary for economic development of these new hydrocarbon resources. Concerns have been raised regarding the potential for contamination of shallow groundwater by stray gases, formation waters, and fracturing chemicals associated with unconventional gas exploration. A lack of sound scientific hydrogeological field observations and a scarcity of published peer-reviewed articles on the effects of both conventional and unconventional oil and gas activities on shallow groundwater make it difficult to address these issues. Here, we discuss several case studies related to both conventional and unconventional oil and gas activities illustrating how under some circumstances stray or fugitive gas from deep gas-rich formations has migrated from the subsurface into shallow aquifers and how it has affected groundwater quality. Examples include impacts of uncemented well annuli in areas of historic drilling operations, effects related to poor cement bonding in both new and old hydrocarbon wells, and ineffective cementing practices. We also summarize studies describing how structural features influence the role of natural and induced fractures as contaminant fluid migration pathways. On the basis of these studies, we identify two areas where field-focused research is urgently needed to fill current science gaps related to unconventional gas extraction: (1) baseline geochemical mapping (with time series sampling from a sufficient network of groundwater monitoring wells) and (2) field testing of potential mechanisms and pathways by which hydrocarbon gases, reservoir fluids, and fracturing chemicals might potentially invade and contaminate useable groundwater.

  3. Spacelab experiment definition study on phase transition and critical phenomena in fluids: Interim report on experimental justification

    NASA Technical Reports Server (NTRS)

    Moldover, M. R.; Hocken, M. R.; Gammon, R. W.; Sengers, J. V.

    1976-01-01

    Pure fluids and fluid mixtures near critical points are identified and are related to the progress of several disciplines. Consideration is given to thermodynamic properties, transport properties, and the complex nonlinear phenomena which occur when fluids undergo phase transitions in the critical region. The distinction is made between practical limits which may be extended by advances in technology and intrinsic ones which arise from the modification of fluid properties by the earth's gravitational field. The kinds of experiments near critical points which could best exploit the low gravity environment of an orbiting laboratory are identified. These include studies of the index of refraction, constant volume specific heat, and phase separation.

  4. Indigenous Studies as an International Field.

    ERIC Educational Resources Information Center

    Pino-Robles, Rodolfo

    This paper proposes the development of Indigenous Studies as an international field, both in the sense of advancing the discipline internationally, wherever there are Indigenous peoples, and in the sense of incorporating international perspectives into curricula. In Canada, Indigenous Studies has been and is still treated as something to be done…

  5. A Critical Study of Agglomerated Multigrid Methods for Diffusion

    NASA Technical Reports Server (NTRS)

    Nishikawa, Hiroaki; Diskin, Boris; Thomas, James L.

    2011-01-01

    Agglomerated multigrid techniques used in unstructured-grid methods are studied critically for a model problem representative of laminar diffusion in the incompressible limit. The studied target-grid discretizations and discretizations used on agglomerated grids are typical of current node-centered formulations. Agglomerated multigrid convergence rates are presented using a range of two- and three-dimensional randomly perturbed unstructured grids for simple geometries with isotropic and stretched grids. Two agglomeration techniques are used within an overall topology-preserving agglomeration framework. The results show that multigrid with an inconsistent coarse-grid scheme using only the edge terms (also referred to in the literature as a thin-layer formulation) provides considerable speedup over single-grid methods but its convergence deteriorates on finer grids. Multigrid with a Galerkin coarse-grid discretization using piecewise-constant prolongation and a heuristic correction factor is slower and also grid-dependent. In contrast, grid-independent convergence rates are demonstrated for multigrid with consistent coarse-grid discretizations. Convergence rates of multigrid cycles are verified with quantitative analysis methods in which parts of the two-grid cycle are replaced by their idealized counterparts.

  6. A Critical Study of Agglomerated Multigrid Methods for Diffusion

    NASA Technical Reports Server (NTRS)

    Thomas, James L.; Nishikawa, Hiroaki; Diskin, Boris

    2009-01-01

    Agglomerated multigrid techniques used in unstructured-grid methods are studied critically for a model problem representative of laminar diffusion in the incompressible limit. The studied target-grid discretizations and discretizations used on agglomerated grids are typical of current node-centered formulations. Agglomerated multigrid convergence rates are presented using a range of two- and three-dimensional randomly perturbed unstructured grids for simple geometries with isotropic and highly stretched grids. Two agglomeration techniques are used within an overall topology-preserving agglomeration framework. The results show that multigrid with an inconsistent coarse-grid scheme using only the edge terms (also referred to in the literature as a thin-layer formulation) provides considerable speedup over single-grid methods but its convergence deteriorates on finer grids. Multigrid with a Galerkin coarse-grid discretization using piecewise-constant prolongation and a heuristic correction factor is slower and also grid-dependent. In contrast, grid-independent convergence rates are demonstrated for multigrid with consistent coarse-grid discretizations. Actual cycle results are verified using quantitative analysis methods in which parts of the cycle are replaced by their idealized counterparts.

  7. Planning and setting objectives in field studies: Chapter 2

    USGS Publications Warehouse

    Fisher, Robert N.; Dodd, C. Kenneth

    2016-01-01

    This chapter enumerates the steps required in designing and planning field studies on the ecology and conservation of reptiles, as these involve a high level of uncertainty and risk. To this end, the chapter differentiates between goals (descriptions of what one intends to accomplish) and objectives (the measurable steps required to achieve the established goals). Thus, meeting a specific goal may require many objectives. It may not be possible to define some of them until certain experiments have been conducted; often evaluations of sampling protocols are needed to increase certainty in the biological results. And if sampling locations are fixed and sampling events are repeated over time, then both study-specific covariates and sampling-specific covariates should exist. Additionally, other critical design considerations for field study include obtaining permits, as well as researching ethics and biosecurity issues.

  8. Study on the limiting factor of critical current in Ag-Bi2223 tapes

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Ding, S. Y.; Luo, H.; Leng, X.; Lin, J. W.

    2003-04-01

    The silver sheathed tapes of Ag-Bi 2- xPb xSr 2Ca 2-Cu 3O 7- y (Ag-Bi2223) were fabricated by usual process. The limiting factor of the critical current density jc of the tapes was studied. V- I characteristic was performed for the tapes immersed in liquid nitrogen with and without magnetic fields. Hysteresis loop of V- I curve was observed. A model based on polycrystalline superconductors was proposed to account for this kind of hysteresis. The result shows that in our Ag-Bi2223 tapes the weak link is the key factor limiting the global critical current. The measurement of V- I loop can be an effective method to check whether there exist harmful weak links in polycrystalline samples.

  9. Study of Unrecovered Strain and Critical Stresses in One-Way Shape Memory Nitinol

    NASA Astrophysics Data System (ADS)

    Honarvar, Mohammad; Datla, Naresh V.; Konh, Bardia; Podder, Tarun K.; Dicker, Adam P.; Yu, Yan; Hutapea, Parsaoran

    2014-08-01

    Unique thermomechanical properties of Nitinol known as shape memory and superelasticity make it applicable for different fields such as biomedical, structural, and aerospace engineering. These unique properties are due to the comparatively large recoverable strain, which is being produced in a martensitic phase transformation. However, under certain ranges of stresses and temperatures, Nitinol wires exhibit unrecovered strain. For cyclic applications, it is important to understand the strain behavior of Nitinol wires. In this study, the unrecovered strain of different Nitinol wire diameters was investigated using constant stress experiment. Uniaxial tensile test has been also performed to find the range of critical stresses. It was observed that the unrecovered strain produced in the first loading-unloading cycle affects the total strain in the subsequent cycles. Moreover, a critical range of stress was found beyond which the unrecovered strain was negligible while the wires heated up to the range of 70-80°C, depending on the wire diameters. The unrecovered strain of wire diameters of 0.19 mm and less was found to be sensitive to the critical stress. On the other hand, for wire diameters bigger than 0.19 mm this connection between the unrecovered strain and the critical stress was not observed for the same range of heating temperature.

  10. Pressure Evolution of a Field-Induced Fermi Surface Reconstruction and of the Neel Critical Field in CeIn3

    SciTech Connect

    Petrovic, C.; Purcell, K.M.; Graf, D.; Kano, M.; Bourg, J.; Palm, E.C.; Murphy, T.; McDonald, R.; Mielke, C.H.; Altarawneh, M.M.; Hu, R.; Ebihara, T.; Cooley, J.; Schlottmann, P.; Tozer, S.W.

    2009-06-01

    We report high-pressure skin-depth measurements on the heavy fermion material CeIn{sub 3} in magnetic fields up to 64 T using a self-resonant tank circuit based on a tunnel diode oscillator. At ambient pressure, an anomaly in the skin depth is seen at 45 T. The field where this anomaly occurs decreases with applied pressure until approximately 1.0 GPa, where it begins to increase before merging with the antiferromagnetic phase boundary. Possible origins for this transport anomaly are explored in terms of a Fermi surface reconstruction. The critical magnetic field at which the Neel-ordered phase is suppressed, is also mapped as a function of pressure and extrapolates to the previous ambient-pressure measurements at high magnetic fields and high-pressure measurements at zero magnetic field.

  11. Studying electric fields in dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2014-11-01

    In Earth's magnetotail, sharp increases in the magnetic field known as dipolarization fronts are associated with high-speed plasma flows that connect Earth's ionosphere via electric currents. Some aspects of these dipolarization fronts have puzzled scientists; in particular, the dip in magnetic field that occurs just ahead of the dipolarization front layer is not well understood. Sun et al. analyze observations made using the Cluster satellites to elucidate the details of electric fields associated with dipolarization fronts. The study shows that a type of electric current known as a Hall current dominates in the dipolarization front region and in the region where the magnetic field dips, but this current flows in opposite directions in these two regions.

  12. Tri-critical behavior of the Blume-Emery-Griffiths model on a Kagomé lattice: Effective-field theory and Rigorous bounds

    NASA Astrophysics Data System (ADS)

    Santos, Jander P.; Sá Barreto, F. C.

    2016-01-01

    Spin correlation identities for the Blume-Emery-Griffiths model on Kagomé lattice are derived and combined with rigorous correlation inequalities lead to upper bounds on the critical temperature. From the spin correlation identities the mean field approximation and the effective field approximation results for the magnetization, the critical frontiers and the tricritical points are obtained. The rigorous upper bounds on the critical temperature improve over those effective-field type theories results.

  13. "Cultural Criticism": A Social Approach to Studying Writing.

    ERIC Educational Resources Information Center

    Bizzell, Patricia

    1989-01-01

    Explores the social circumstances of academic writing. Looks at student and professional academic writers and readers as participants in a complex literary genre, with its own conventions, ideological assumptions, and epistemological implications. Argues that academics must become cultural critics. (RAE)

  14. Structure of fluctuations near mean-field critical points and spinodals and its implication for physical processes.

    PubMed

    Klein, W; Gould, Harvey; Gulbahce, Natali; Rundle, J B; Tiampo, K

    2007-03-01

    We analyze the structure of fluctuations near critical points and spinodals in mean-field and near-mean-field systems. Unlike systems that are non-mean-field, for which a fluctuation can be represented by a single cluster in a properly chosen percolation model, a fluctuation in mean-field and near-mean-field systems consists of a large number of clusters, which we term fundamental clusters. The structure of the latter and the way that they form fluctuations has important physical consequences for phenomena as diverse as nucleation in supercooled liquids, spinodal decomposition and continuous ordering, and the statistical distribution of earthquakes. The effects due to the fundamental clusters implies that they are physical objects and not only mathematical constructs.

  15. Transient critical heat flux and blowdown heat-transfer studies

    SciTech Connect

    Leung, J.C.

    1980-05-01

    Objective of this study is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. To accomplish this task, a predictional method has been developed. Basically it involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous ''local-conditions'' hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. The prediction results are summarized in a table in which both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF that occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the x = 1.0 criterion; this is certainly indicative of an annular-flow dryout-type crisis. The delay CHF occurred at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis.

  16. 𝜖-expansion in critical ϕ3-theory on real projective space from conformal field theory

    NASA Astrophysics Data System (ADS)

    Hasegawa, Chika; Nakayama, Yu

    2017-03-01

    We use a compatibility between the conformal symmetry and the equations of motion to solve the one-point function in the critical ϕ3-theory (a.k.a. the critical Lee-Yang model) on the d = 6 ‑ 𝜖 dimensional real projective space to the first nontrivial order in the 𝜖-expansion. It reproduces the conventional perturbation theory and agrees with the numerical conformal bootstrap result.

  17. A Critical Fast Ion Beta in the Madison Symmetric Torus Reversed Field Pinch

    NASA Astrophysics Data System (ADS)

    Capecchi, William J.

    The first fast-ion profile measurements have been made in a reversed-field pinch (RFP) plasma. A large population of fast-ions are deposited in the core of the Madison Symmetric Torus (MST) through use of a 1 MW neutral beam injector (NBI) giving rise to a variety of beam-driven instabilities. One such mode, the energetic-particle mode (EPM) has been shown to reduce fast-ion content in MST, evident through drops in signal levels of the advanced neutral particle analyzer (ANPA). EPMs in MST appear as bursts of magnetic fluctuations at a lab frequency of ˜100 kHz reaching peak amplitude and decaying away within 100 microseconds. A burst ensemble of the neutron data does not reveal a drop in neutron emission across a burst, implying the population of fast-ions transported by a burst constitute a small fraction of the total. The burst may also pitch-angle scatter out of the ANPA phase space or be transported to mid-radius where charge-exchange with the background neutrals or fast-ion orbit stochasticity may reduce fast-ion confinement. Data gathered from the expanded neutron diagnostic suite including a new collimated neutron detector (CiNDe) was used to reconstruct the fast-ion profile in MST and measure critical fast-ion beta quantities. Measurements were made in plasma conditions with varying magnetic field strength in order to investigate the interplay between the energetic particle (EP) drive and Alfven continuum damping. The measured values of the core fast-ion beta (7.5% (1.2%) in 300 (500) kA plasmas) are reduced from classical predictions (TRANSP predicts up to 10% core value) due to EPM activity. The frequency, magnitude, and rate of occurrence of the bursts depends on the tearing mode amplitude, Alfven continuum damping rate, fast-ion profile shape, and resonant orbit dynamics. Marginal stability was reached in both moderate- (300 kA) and high- (500 kA) current discharges, marked by sustained EPM activity and a saturated global neutron signal during NBI

  18. All-loop order critical exponents for massless scalar field theory with Lorentz violation in the BPHZ method

    NASA Astrophysics Data System (ADS)

    Carvalho, Paulo R. S.

    2016-12-01

    We compute analytically the all-loop level critical exponents for a massless thermal Lorentz-violating (LV) O(N) self-interacting λϕ4 scalar field theory. For that, we evaluate, firstly explicitly up to next-to-leading loop order and later in a proof by induction up to any loop level, the respective β-function and anomalous dimensions in a theory renormalized in the massless BPHZ method, where a reduced set of Feynman diagrams to be calculated is needed. We investigate the effect of the Lorentz violation in the outcome for the critical exponents and present the corresponding mathematical explanation and physical interpretation.

  19. Landau-like theory for universality of critical exponents in quasistationary states of isolated mean-field systems.

    PubMed

    Ogawa, Shun; Yamaguchi, Yoshiyuki Y

    2015-06-01

    An external force dynamically drives an isolated mean-field Hamiltonian system to a long-lasting quasistationary state, whose lifetime increases with population of the system. For second order phase transitions in quasistationary states, two nonclassical critical exponents have been reported individually by using a linear and a nonlinear response theories in a toy model. We provide a simple way to compute the critical exponents all at once, which is an analog of the Landau theory. The present theory extends the universality class of the nonclassical exponents to spatially periodic one-dimensional systems and shows that the exponents satisfy a classical scaling relation inevitably by using a key scaling of momentum.

  20. Critical current densities and n-values of MgB2 strands over a wide range of temperatures and fields

    NASA Astrophysics Data System (ADS)

    Li, G. Z.; Yang, Y.; Susner, M. A.; Sumption, M. D.; Collings, E. W.

    2012-02-01

    Transport measurements of critical current density, Jct, in monocore powder-in-tube MgB2 strands have been carried out at temperatures, T, of from 4.2 to 40 K, and in transverse fields, B, of up to 14 T. Processing methods used were conventional continuous tube forming/filling (CTFF) and internal magnesium diffusion (IMD). Strands with several powder compositions were measured, including binary (undoped) MgB2, 2% carbon doped MgB2, and 3% carbon doped MgB2. Magnetization loops (M-B) were also measured, and magnetic critical current density, Jcm, values extracted from them. The transport, Jct(B) and magnetic, Jcm(B), critical current densities were compared. Also studied was the influence of doping on the resistively measured irreversibility field, Birr, and upper critical field, Bc2. Critical current densities, Jct, and n-values were extracted from transport measurements and were found to be universally related (for all B and T) according to n\\propto {J}_{{ct}}^{m} in which m = 0.52 ± 0.11. Likewise n was found to be related to B according to n ∝ B-p with a T-dependent p in the range of about 0.08-0.21. Further analysis of the field (B) and temperature (T) dependences of n-value resulted in an expression that enabled n(B,T), for all B and T, to be estimated for a given strand based on the results of transport Jct(B) measurements made at one arbitrarily chosen temperature.

  1. Reading the World's Classics Critically: A Keyword-Based Approach to Literary Analysis in Foreign Language Studies

    ERIC Educational Resources Information Center

    García, Nuria Alonso; Caplan, Alison

    2014-01-01

    While there are a number of important critical pedagogies being proposed in the field of foreign language study, more attention should be given to providing concrete examples of how to apply these ideas in the classroom. This article offers a new approach to the textual analysis of literary classics through the keyword-based methodology originally…

  2. Conceptualising Higher Education Research and/or Academic Development as "Fields": A Critical Analysis

    ERIC Educational Resources Information Center

    Clegg, Sue

    2012-01-01

    This paper calls into question the idea that we can simply think about higher education as a research field and explores different meanings of the term field. It asks whether there are related fields: research into higher education, academic development and disciplinary teaching research, rather than one. The approach of the paper is conceptual,…

  3. Critical points of the cosmic velocity field and the uncertainties in the value of the Hubble constant

    NASA Astrophysics Data System (ADS)

    Liu, Hao; Mohayaee, Roya; Naselsky, Pavel

    2016-06-01

    The existence of critical points for the peculiar velocity field is a natural feature of the correlated vector field. These points appear at the junctions of velocity domains with different orientations of their averaged velocity vectors. Since peculiar velocities are the important cause of the scatter in the Hubble expansion rate, we propose that a more precise determination of the Hubble constant can be made by restricting analysis to a subsample of observational data containing only the zones around the critical points of the peculiar velocity field, associated with voids and saddle points. On large-scales the critical points, where the first derivative of the gravitational potential vanishes, can easily be identified using the density field and classified by the behavior of the Hessian of the gravitational potential. We use high-resolution N-body simulations to show that these regions are stable in time and hence are excellent tracers of the initial conditions. Furthermore, we show that the variance of the Hubble flow can be substantially minimized by restricting observations to the subsample of such regions of vanishing velocity instead of aiming at increasing the statistics by averaging indiscriminately using the full data sets, as is the common approach.

  4. Rotational symmetry breaking in the topological superconductor SrxBi2Se3 probed by upper-critical field experiments

    PubMed Central

    Pan, Y.; Nikitin, A. M.; Araizi, G. K.; Huang, Y. K.; Matsushita, Y.; Naka, T.; de Visser, A.

    2016-01-01

    Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms. PMID:27350295

  5. Rotational symmetry breaking in the topological superconductor SrxBi2Se3 probed by upper-critical field experiments.

    PubMed

    Pan, Y; Nikitin, A M; Araizi, G K; Huang, Y K; Matsushita, Y; Naka, T; de Visser, A

    2016-06-28

    Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms.

  6. Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214

    SciTech Connect

    Finnemore, Douglas K.

    2001-01-01

    Thermodynamics has been studied systematically for the high temperature cuprate superconductor La2-xSrxCuO4-δ, La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H $\\parallel$ c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below Tc, magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the Tc0 vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La2-xSrxCuO4 (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to Tc. The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance ξc becomes comparable to the spacing between adjacent CuO2 layers s at sufficiently high magnetic field near Hc2.

  7. Common Group Problems: A Field Study.

    ERIC Educational Resources Information Center

    Weinberg, Sanford B.; And Others

    1981-01-01

    A field study of a naturally functioning group (N=125) was conducted to identify common group problems. Trained observers attended group meetings and described the problems encountered. Difficulties of cohesion, leadership, sub-group formation, and personality conflict were identified. (RC)

  8. Outdoor Education, Junior Biology Field Studies.

    ERIC Educational Resources Information Center

    Aikman, John H.; And Others

    Field studies for grade nine and ten biology students are developed in this teacher and student guide for outdoor education. A small section is devoted to teacher pre-planning and final sections are concerned with equipment, audio-visual resources, and a large booklist. Twenty-three investigations related to earth science and biology topics are…

  9. Jupiter Environmental Research & Field Studies Academy.

    ERIC Educational Resources Information Center

    Huttemeyer, Bob

    1996-01-01

    Describes the development and workings of the Jupiter Environmental Research and Field Studies Academy that focuses on enabling both teachers and students to participate in real-life learning experiences. Discusses qualifications for admittance, curriculum, location, ongoing projects, students, academics, preparation for life, problem solving, and…

  10. Case studies of first-year critical science teachers

    NASA Astrophysics Data System (ADS)

    Love, Kurt A.

    Brent Davis and Dennis Sumara (1997) performed a study of themselves and another professor who took a sabbatical to work in an elementary school for a year. Their intentions, as professors focused on cognition, was to create a change in teaching practices throughout the school that aligned more closely with social cognitive research. However, their experiences did not go as planned. Each found that he could not just simply bring their philosophies into their classrooms independent of the sociocultural context of the school. They found very quickly that none of them could act as fully autonomous agents. They described their experiences as being part of the sociocultural fabric of the school because each of their teaching practices changed in ways that they did not anticipate and in ways that were not philosophically aligned. However, they also found that this was a two-way relationship. They were not describing completely deterministic experiences. Davis and Sumara described observing colleagues changing their practices in ways that did incorporate some of the philosophies that they espoused during their tenure at the elementary school. They explain their experience as one where they were pushed and pulled by the sociocultural context and they also pushed and pulled on the sociocultural context. This dissertation focuses on three first-year science teachers (a 4 th grade teacher and two high school science teachers) who identified as wanting to bring critical, feminist, and ecojustice perspectives into their teaching practices. Each enacts these practices much differently in the context of the sociocultural contexts of their own schools, and often changed their teaching practices in ways that seemed to more closely align with those contexts. Each of the three dealt with external and internal hegemonic pressures that caused them to align more closely with their contexts. The philosophical foundations of their sociocultural contexts were manifested externally through

  11. Mean-field calculation of critical parameters and log-periodic characterization of an aperiodic-modulated model.

    PubMed

    Oliveira, T P; Branco, N S

    2012-01-01

    We employ a mean-field approximation to study the Ising model with aperiodic modulation of its interactions in one spatial direction. Two different values for the exchange constant, J(A) and J(B), are present, according to the Fibonacci sequence. We calculate the pseudocritical temperatures for finite systems and extrapolate them to the thermodynamic limit. We explicitly obtain the exponents β, δ, and γ and, from the usual scaling relations for anisotropic models at the upper critical dimension (assumed to be 4 for the model we treat), we calculate α, ν, ν(∥), η, and η(∥). Within the framework of a renormalization-group approach, the Fibonacci sequence is a marginal one and we obtain exponents that depend on the ratio r≡J(B)/J(A), as expected; however, the scaling relation γ=β(δ-1) is obeyed for all values of r we studied. We characterize some thermodynamic functions as log-periodic functions of their arguments, as expected for aperiodic-modulated models, and obtain precise values for the exponents from this characterization.

  12. Critical Schwinger pair production. II. Universality in the deeply critical regime

    NASA Astrophysics Data System (ADS)

    Gies, Holger; Torgrimsson, Greger

    2017-01-01

    We study electron-positron pair production by spatially inhomogeneous electric fields. Depending on the localization of the field, a critical point (critical surface) exists in the space of field configurations where the pair production probability vanishes. Near criticality, pair production exhibits universal properties similar to those of continuous phase transitions. We extend results previously obtained in the semiclassical (weak-field) critical regime to the deeply critical regime for arbitrary peak field strength. In this regime, we find an enhanced universality, featuring a unique critical exponent β =3 for all sufficiently localized fields. For a large class of field profiles, we also compute the nonuniversal amplitudes.

  13. Upper critical field and Kondo effects in Fe(Te0.9Se0.1) thin films by pulsed field measurements

    DOE PAGES

    Salamon, Myron B.; Cornell, Nicholas; Jaime, Marcelo; ...

    2016-02-10

    The transition temperatures of epitaxial films of Fe(Te0:9Se0:1) are remarkably insensitive to applied magnetic field, leading to predictions of upper critical fields Bc2(T = 0) in excess of 100 T. Using pulsed magnetic fields, we find Bc2(0) to be on the order of 45 T, similar to values in bulk material and still in excess of the paramagnetic limit. The same films show strong magnetoresistance in fields above Bc2(T), consistent with the observed Kondo minimum seen above Tc. Fits to the temperature dependence in the context of the WHH model, using the experimental value of the Maki parameter, require anmore » effective spin-orbit relaxation parameter of order unity. Lastly, we suggest that Kondo localization plays a similar role to spin-orbit pair breaking in making WHH fits to the data.« less

  14. Gate dependence of upper critical field in superconducting (110) LaAlO3/SrTiO3 interface

    PubMed Central

    Shen, S. C.; Chen, B. B.; Xue, H. X.; Cao, G.; Li, C. J.; Wang, X. X.; Hong, Y. P.; Guo, G. P.; Dou, R. F.; Xiong, C. M.; He, L.; Nie, J. C.

    2016-01-01

    The fundamental parameters of the superconducting state such as coherence length and pairing strength are essential for understanding the nature of superconductivity. These parameters can be estimated by measuring critical parameters such as upper critical field, Hc2. In this work, Hc2 of a superconducting (110) LaAlO3/SrTiO3 interface is determined through magnetoresistive measurements as a function of the gate voltage, VG. When VG increases, the critical temperature has a dome-like shape, while Hc2 monotonically decreases. This relationship of independence between the variation of Tc and of Hc2 suggests that the Cooper pairing potential is stronger in the underdoped region and the coherence length increases with the increase of VG. The result is as for high temperature superconducting cuprates and it is different than for conventional low temperature superconductors. PMID:27378271

  15. Enhancement of the critical current density in FeO-coated MgB2 thin films at high magnetic fields

    PubMed Central

    Surdu, Andrei E; Hamdeh, Hassan H; Al-Omari, I A; Sellmyer, David J; Socrovisciuc, Alexei V; Prepelita, Andrei A; Koparan, Ezgi T; Yanmaz, Ekrem; Ryazanov, Valery V; Hahn, Horst

    2011-01-01

    Summary The effect of depositing FeO nanoparticles with a diameter of 10 nm onto the surface of MgB2 thin films on the critical current density was studied in comparison with the case of uncoated MgB2 thin films. We calculated the superconducting critical current densities (J c) from the magnetization hysteresis (M–H) curves for both sets of samples and found that the J c value of FeO-coated films is higher at all fields and temperatures than the J c value for uncoated films, and that it decreases to ~105 A/cm2 at B = 1 T and T = 20 K and remains approximately constant at higher fields up to 7 T. PMID:22259764

  16. Recognizing Point of View: A Critical Reading Skill in the Social Studies.

    ERIC Educational Resources Information Center

    Fleming, Dan B.; Weber, Larry J.

    1980-01-01

    Stresses the importance of critical reading skills for high school students in social studies courses. Suggests that educators develop social studies materials dealing with critical reading and that they undertake research to develop better methods of instruction in critical reading. (DB)

  17. Field-controlled spin-density-wave order and quantum critically in Sr3 Ru2 O7

    NASA Astrophysics Data System (ADS)

    Hayden, Stephen

    The quasi-2D metamagnetic perovskite metal Sr3Ru2O7 has been an enigma for the last decade. The application of a large magnetic field of 8T parallel to the c-axis creates a new phase at low temperatures. This phase shows ``electronic nematic'' properties in that strong anisotropy its resistivity can be created by tilting the field away from the c-axis. In addition, measurement of transport and thermodynamic properties suggest that the phase is at the centre of a quantum critical region. Here we use neutron scattering to show that the magnetic field actually induces spin-density-wave magnetic order in the proximity of a metamagnetic critical endpoint. In fact, Sr3Ru2O7 can be tuned through two magnetically-ordered SDW states which exist over relatively small ranges in field (< 0.4 T). Their origin is probably due to the electronic fine structure near the Fermi energy. The magnetic field direction is shown to control the SDW domain populations which naturally explains the strong resistivity anisotropy or ''electronic nematic'' behaviour observed in this material. We find that Sr3Ru2O7 is also unique in that its the quantum critical region is controlled by overdamped incommensurate low-energy spin fluctuations with a diverging relaxation time. The low-energy electronic properties reflect the presence of these fluctuations and, in particular, the field-dependent low-temperature specific heat is proportional to the spin relaxation rate. [Based on C. Lester, S. Ramos, R. S. Perry at el. Natural Materials 14, 373 (2015).

  18. Upper critical field, pressure-dependent superconductivity and electronic anisotropy of Sm4Fe2As2Te(1-x)O(4-y)F(y).

    PubMed

    Pisoni, A; Katrych, S; Szirmai, P; Náfrádi, B; Gaál, R; Karpinski, J; Forró, L

    2016-03-23

    We present a detailed study of the electrical transport properties of a recently discovered iron-based superconductor: Sm4Fe2As2Te0.72O2.8F1.2. We followed the temperature dependence of the upper critical field by resistivity measurement of single crystals in magnetic fields up to 16 T, oriented along the two main crystallographic directions. This material exhibits a zero-temperature upper critical field of 90 T and 65 T parallel and perpendicular to the Fe2As2 planes, respectively. An unprecedented superconducting magnetic anisotropy γH=H(c2)(ab)/H(c2)(c) ~ 14 is observed near Tc, and it decreases at lower temperatures as expected in multiband superconductors. Direct measurement of the electronic anisotropy was performed on microfabricated samples, showing a value of ρ(c)/ρ(ab)(300K) ~ 5 that rises up to 19 near Tc . Finally, we have studied the pressure and temperature dependence of the in-plane resistivity. The critical temperature decreases linearly upon application of hydrostatic pressure (up to 2 GPa) similarly to overdoped cuprate superconductors. The resistivity shows saturation at high temperatures, suggesting that the material approaches the Mott-Ioffe-Regel limit for metallic conduction. Indeed, we have successfully modelled the resistivity in the normal state with a parallel resistor model that is widely accepted for this state. All the measured quantities suggest strong pressure dependence of the density of states.

  19. Field-induced quantum critical point in planar Heisenberg ferromagnets with long-range interactions: Two-time Green's function framework

    NASA Astrophysics Data System (ADS)

    Campana, L. S.; de Cesare, L.; Esposito, U.; Mercaldo, M. T.; Rabuffo, I.

    2010-07-01

    The two-time Green’s function method is used to study the critical properties and crossover phenomena near the field-induced quantum critical point (QCP) of a d -dimensional spin- S planar Heisenberg ferromagnet with long-range interactions decaying as r-α (with α>d ) with the distance r between spins. We adopt the Callen scheme for spin S and the Tyablikov decoupling procedure which is expected to provide suitable results at low temperatures. Different quantum critical regimes are found in the (α,d) plane and the global structure of the phase diagram is determined showing the typical V-shaped region close to the QCP. Depending on the values of α , we find that also for dimensionalities d⩽2 a finite-temperature critical line, ending in the QCP, exists with asymptotic behaviors and crossovers which can be employed as a useful guide for experimental studies. Moreover, these crossovers are shown to be suitably described in terms of (α,d) -dependent scaling functions and effective critical exponents.

  20. Fermi surface topology and the upper critical field in two-band superconductors: application to MgB2.

    PubMed

    Dahm, T; Schopohl, N

    2003-07-04

    Recent measurements of the anisotropy of the upper critical field B(c2) on MgB2 single crystals have shown a puzzling strong temperature dependence. Here, we present a calculation of the upper critical field based on a detailed modeling of band structure calculations that takes into account both the unusual Fermi surface topology and the two gap nature of the superconducting order parameter. Our results show that the strong temperature dependence of the B(c2) anisotropy can be understood as an interplay of the dominating gap on the sigma band, which possesses a small c-axis component of the Fermi velocity, with the induced superconductivity on the pi-band possessing a large c-axis component of the Fermi velocity. We provide analytic formulas for the anisotropy ratio at T=0 and T=T(c) and quantitatively predict the distortion of the vortex lattice based on our calculations.

  1. Temperature and Magnetic Field Dependence of Critical Current Density of YBCO with Varying Flux Pinning Additions (POSTPRINT)

    DTIC Science & Technology

    2010-03-01

    coverage corresponding to M phase 1 nm thickness was found to be necessary to increase compared to YBCO . The op- timal layer thickness for each M phase was...kept constant in this experiment: , Y211 0.8 nm , and [17]. Using the optimal M phase thickness, the YBCO layer was also systematically varied for...AFRL-RZ-WP-TP-2010-2083 TEMPERATURE AND MAGNETIC FIELD DEPENDENCE OF CRITICAL CURRENT DENSITY OF YBCO WITH VARYING FLUX PINNING ADDITIONS

  2. Ethical Dilemmas of Turkish Counsellors: A Critical Incidents Study

    ERIC Educational Resources Information Center

    Sivis-Cetinkaya, Rahsan

    2015-01-01

    Ethical dilemmas from a national purposive sample of Turkish counsellors (N = 172) were collected using critical incidents technique. Content analysis was performed with open coding guided by the classification of American Counseling Association code of ethics. Incidents regarding confidentiality and privacy (56.4%), with 37.1% involving incidents…

  3. DEVELOPMENT OF PROTOCOLS TO STUDY TO IDENTIFY CRITICAL ECOSYSTEMS

    EPA Science Inventory

    Healthy, functioning ecosystems are critical to the sustainability of human and natural communities, but the identification of areas of healthy ecosystems in an area as large as Region 5 is difficult due to time and information constraints. Geographic Information Systems (GIS) a...

  4. Writing and Power: A Critical Introduction to Composition Studies

    ERIC Educational Resources Information Center

    Mitchell, Candace

    2004-01-01

    This book offers a much needed alternative to the more traditional texts used to teach writing instruction. Grounded in history, the book clarifies changing theoretical and practical approaches to teaching writing, critically assessing each approach in relation to the social and political movements of the day, both within and beyond the…

  5. Is There Room for Criticism of Studies of Psychodynamic Psychotherapy?

    ERIC Educational Resources Information Center

    Thombs, Brett D.; Jewett, Lisa R.; Bassel, Marielle

    2011-01-01

    Comments on the original article, "The efficacy of psychodynamic psychotherapy," by J. Shedler. Shedler declared unequivocally that "empirical evidence supports the efficacy of psychodynamic therapy" (p. 98). He did not mention any specific criticisms that have been made of evidence on psychodynamic psychotherapies or address possible distinctions…

  6. Rhetorical Criticism of Interpersonal Discourse: An Exploratory Study.

    ERIC Educational Resources Information Center

    Glaser, Susan R.; Frank, David A.

    1982-01-01

    Demonstrates how rhetorical criticism can be utilized to clarify the rhetorical nature of interpersonal discourse. Synthesizes the following theories to explain the nature and form of selected portions of taped and transcribed interpersonal dialog: Lloyd Bitzer's situational theory, Ernest Bormann's fantasy theme analysis, and Carroll Arnold's…

  7. Connecting Critical Theory of Technology to Educational Studies

    ERIC Educational Resources Information Center

    Kruger-Ross, Matthew James

    2013-01-01

    In this article, I explore how transformative learning theory, an approach to educating drawn from adult education, can be used to provide access to the critical theory of technology for educators. Rather than focusing primarily on K-12 teachers and educational systems or higher education and other postsecondary instruction, I connect learning as…

  8. AFM nano-plough planar YBCO micro-bridges: critical currents and magnetic field effects.

    PubMed

    Elkaseh, A A O; Perold, W J; Srinivasu, V V

    2010-10-01

    The critical current (Ic) of YBa2Cu3O7-x (YBCO) AFM plough micro-constrictions is measured as a function of temperature, width and the magnetic flux density (B), which was applied perpendicular to the YBCO ab-plane and surface of the bridges. C-axis oriented thin films of YBa2Cu3O7-x were deposited on MgO substrates using an inverted cylindrical magnetron (ICM) sputtering technique. The films were then patterned into 8-10 micron size strips, using standard photolithography and dry etching processes. Micro-bridges with widths between 1.9 microm to 4.1 microm were fabricated by using atomic force microscope (AFM) nanolithography techniques. Critical current versus temperature data shows a straight-line behavior, which is typical of constriction type Josephson junctions. The Ic versus B characteristics exhibited a modulation, and a suppression of the critical current of up to 84%. It was also found that the critical current increases with increasing constriction width.

  9. Foundations Symposium: A Continued Dialogue on Critical Theory, Cultural Analysis, and Ethical Aspects of the Field.

    ERIC Educational Resources Information Center

    Anderson, Jane; And Others

    Seven articles are presented from a symposium on critical theory, cultural analysis, and the ethical aspects of the use of educational technology. Two papers deal with the educational philosophy of two modern thinkers, and others focus on educational technology in the modern or postmodern era. The following papers are included: (1) "Foucault…

  10. Positivism, Postmodernism, or Critical Theory? A Case Study of Communications Students' Understandings of Criticism

    ERIC Educational Resources Information Center

    Fuchs, Christian; Sandoval, Marisol

    2008-01-01

    Neoliberalism has resulted in a large-scale economization and capitalization of society that has also permeated the academic system. The paper at hand provides the result of a case study that analyzed how students, who are today frequently confronted by the combination of studying and precarious labour and insecure job perspectives, assess the…

  11. Microbial field pilot study. Final report

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Coates, J.D.; Chisholm, J.L.

    1993-05-01

    A multi-well microbially enhanced oil recovery field pilot has been performed in the Southeast Vassar Vertz Sand Unit in Payne County, Oklahoma. The primary emphasis of the experiment was preferential plugging of high permeability zones for the purpose of improving waterflood sweep efficiency. Studies were performed to determine reservoir chemistry, ecology, and indigenous bacteria populations. Growth experiments were used to select a nutrient system compatible with the reservoir that encouraged growth of a group of indigenous nitrate-using bacteria and inhibit growth of sulfate-reducing bacteria. A specific field pilot area behind an active line drive waterflood was selected. Surface facilities were designed and installed. Injection protocols of bulk nutrient materials were prepared to facilitate uniform distribution of nutrients within the pilot area. By the end of December, 1991, 82.5 tons (75.0 tonnes) of nutrients had been injected in the field. A tracer test identified significant heterogeneity in the SEVVSU and made it necessary to monitor additional production wells in the field. The tracer tests and changes in production behavior indicate the additional production wells monitored during the field trial were also affected. Eighty two and one half barrels (13.1 m{sup 3}) of tertiary oil have been recovered. Microbial activity has increased CO{sub 2} content as indicated by increased alkalinity. A temporary rise in sulfide concentration was experienced. These indicate an active microbial community was generated in the field by the nutrient injection. Pilot area interwell pressure interference test results showed that significant permeability reduction occurred. The interwell permeabilities in the pilot area between the injector and the three pilot production wells were made more uniform which indicates a successful preferential plugging enhanced oil recovery project.

  12. Disrupting Racialization: Considering Critical Leadership in the Field of Physical Education

    ERIC Educational Resources Information Center

    Fitzpatrick, Katie; Santamaría, Lorri J.

    2015-01-01

    Background: The field of physical education (PE), overlapping as it does with the field of sport, has been critiqued for marginalizing those positioned as "different". This difference is typically conceptualized in regard to a white, masculine, heterosexual, and able-bodied norm. Students who do not identify as white are not represented…

  13. Language as a Field of Energy: A Critical Question for Language Pedagogy

    ERIC Educational Resources Information Center

    Soter, Anna O.; Connors, Sean P.

    2017-01-01

    This essay offers a reorientation of our views on the interrelationships of language and thought as a field of constantly reprogrammable energy, and provides an argument as to why we believe this new metaphor (i.e., language as a field of energy) matters in language pedagogy, in classrooms at all levels, as well as within teacher education and…

  14. Sitting in the Waiting Room: Paulo Freire and the Critical Turn in the Field of Education

    ERIC Educational Resources Information Center

    Gottesman, Isaac

    2010-01-01

    Although it is commonly assumed that Paulo Freire was widely influential in the field of education in the United States immediately upon publication of his classic work, "Pedagogy of the Oppressed", in 1970, the historical evidence indicates otherwise. In fact, Freire's work only began to gain wide reception in the field in the mid- and late…

  15. Can an Observational Field Model Enhance Critical Thinking and Generalist Practice Skills?

    ERIC Educational Resources Information Center

    Carey, Maureen E.; McCardle, Melissa

    2011-01-01

    This article examines how a baccalaureate program initiated an introductory field experience in an attempt to improve 2 frequently identified impediments to quality field experiences, namely the lack of a complete generalist practice experience and the lack of opportunities for integration of theory into practice. The key components to this…

  16. Quantum Monte Carlo studies of quantum criticality in low-dimensional spin systems

    NASA Astrophysics Data System (ADS)

    Tang, Ying

    Strongly correlated low-dimensional quantum spin models provide a well-established frame- work to study magnetic properties of insulators, and are of great theoretical interest and experimental relevance in condensed-matter physics. In this thesis, I use quantum Monte Carlo methods to numerically study quantum critical behavior in low-dimensional quantum spin models and wavefunctions. First, I study spinons---emergent spin-1/2 bosonic excitations---at certain one- and two-dimensional quantum phase transitions (QPTs) in spin models, by characterizing their size and confinement length quantitatively. In particular, I focus on the QPT from an antiferromagnetic (AFM) phase into a valence-bond solid (VBS) phase, which is an example of a violation of the standard Landau-Ginzburg-Wilson paradigm for phase transitions. This transition in two dimensions (2D) is instead likely described by a novel theory called "deconfined quantum criticality" (DQC). According to the theory, spinons should be deconfined. The degree of deconfinement is quantified in my calculations. Second, I present a comprehensive study of so-called short-bond resonating-valence-bond (RVB) spin liquids in 2D, which have been suggested as a good starting point for understanding the spin physics of high-temperature cuprates. I find that these RVB states can also be classified as quantum-critical VBS states, which indicates that RVB is less disordered than expected. This work suggests a possible mapping from the quantum RVB states to classical dimer models via a classical continuum field theory---the height model. This map explicitly bridges well-established classical results to future quantum studies. Third, I consider 1D amplitude product (AP) states, which are generalized versions of RVB states, with different wavefunction weightings of bonds according to their lengths. AP states constitute a good ansatz for certain Hamiltonians and are of broad interest in quantum magnetism. I study phase transitions from

  17. ICU telemedicine and critical care mortality: a national effectiveness study

    PubMed Central

    Kahn, Jeremy M; Le, Tri Q.; Barnato, Amber E.; Hravnak, Marilyn; Kuza, Courtney C.; Pike, Francis; Angus, Derek C.

    2015-01-01

    Background Intensive care unit (ICU) telemedicine is an increasingly common strategy for improving the outcome of critical care, but its overall impact is uncertain. Objectives To determine the effectiveness of ICU telemedicine in a national sample of hospitals and quantify variation in effectiveness across hospitals. Research design We performed a multi-center retrospective case-control study using 2001–2010 Medicare claims data linked to a national survey identifying United States hospitals adopting ICU telemedicine. We matched each adopting hospital (cases) to up to 3 non-adopting hospitals (controls) based on size, case-mix and geographic proximity during the year of adoption. Using ICU admissions from 2 years before and after the adoption date, we compared outcomes between case and control hospitals using a difference-in-differences approach. Results 132 adopting case hospitals were matched to 389 similar non-adopting control hospitals. The pre- and post-adoption unadjusted 90-day mortality was similar in both case hospitals (24.0% vs. 24.3%, p=0.07) and control hospitals (23.5% vs. 23.7%, p<0.01). In the difference-in-differences analysis, ICU telemedicine adoption was associated with a small relative reduction in 90-day mortality (ratio of odds ratios: 0.96, 95% CI = 0.95–0.98, p<0.001). However, there was wide variation in the ICU telemedicine effect across individual hospitals (median ratio of odds ratios: 1.01; interquartile range 0.85–1.12; range 0.45–2.54). Only 16 case hospitals (12.2%) experienced statistically significant mortality reductions post-adoption. Hospitals with a significant mortality reduction were more likely to have large annual admission volumes (p<0.001) and be located in urban areas (p=0.04) compared to other hospitals. Conclusions Although ICU telemedicine adoption resulted in a small relative overall mortality reduction, there was heterogeneity in effect across adopting hospitals, with large-volume urban hospitals

  18. Field Studies of Exercise and Food Deprivation

    DTIC Science & Technology

    2006-08-01

    limit to fat reserves in physically active underfed young adult men, and in response to exercise and underfeeding, women used more fat mass and less fat...a shift to increased fat utilization, appear to be enhanced by concurrent physical activity . Exercise , diet and reproductive function Controlled... physically active and undernourished humans should help guide strategies to manage obesity safely and effectively. This review focuses on field studies

  19. The Relationship between Athletic Training Student Critical Thinking Skills and Clinical Instructor Supervision: A Pilot Study

    ERIC Educational Resources Information Center

    Kabay, Michele R.

    2013-01-01

    The purpose of this study was to 1) assess the critical thinking skill level of the athletic training student at onset and end of the clinical education experience 2) to examine the influence of the students' critical thinking skills and the CIs' supervision responses to the changes in the students' critical thinking skills and 3) to compare the…

  20. Transformation and Stasis: Two Case Studies of Critical Teacher Education in TESOL

    ERIC Educational Resources Information Center

    Nuske, Kyle

    2015-01-01

    Considering the prominent position of critical work in TESOL and Applied Linguistics, there is a need for detailed investigations of apprentice practitioners' formative interactions with critical ideas in graduate programs and how these affect their willingness to cultivate their own critical pedagogical repertories. Adopting a case study design,…

  1. Academic Writing as Genre: A Case Study of New Critical Writing Practices

    ERIC Educational Resources Information Center

    Ludewig, Julia

    2016-01-01

    The dissertation paints a cultural-historical portrait of the New Criticism, a formalist school of twentieth-century literary criticism. My case study revisits the trajectory of this vital school of thought through a fine-grained textual comparison of critical essays produced by principal affiliates. Using "genre" as a guiding concept, I…

  2. Perceptions of Writing Confidence, Critical Thinking, and Writing Competence among Registered Nurse-Learners Studying Online

    ERIC Educational Resources Information Center

    Carter, Lorraine

    2008-01-01

    Historically, nursing education has recognized that writing enhances critical thinking, the basis of the clinical reasoning process. The online learning recently adopted by Nursing involves considerable writing, which may enhance critical thinking more than face-to-face courses. In the study reported here, the critical thinking and writing…

  3. Comment on "Critical point scaling of Ising spin glasses in a magnetic field"

    NASA Astrophysics Data System (ADS)

    Temesvári, T.

    2016-11-01

    In a section of a recent paper [Phys. Rev. B 91, 104432 (2015), 10.1103/PhysRevB.91.104432], the authors discuss some of the arguments in the paper by Parisi and Temesvári [Nucl. Phys. B 858, 293 (2012), 10.1016/j.nuclphysb.2012.01.014]. In this Comment, it is shown how these arguments are misinterpreted and the existence of the Almeida-Thouless transition in the upper critical dimension six reasserted.

  4. Field-induced quantum critical point in the pressure-induced superconductor CeRhIn5

    SciTech Connect

    Bauer, Eric D; Park, Tuson; Tokiwa, Yoshifumi; Ronning, Filip; Lee, Han O; Movshovich, Roman; Thompson, Joe D

    2009-01-01

    When subjected to pressure, the prototypical heavy-fermion antiferromagnet CeRhIn{sub 5} becomes superconducting, forming a broad dome of superconductivity centered around 2.35 GPa (=P2) with maximal T{sub c} of 2.3 K. Above the superconducting dome, the normal state shows strange metallic behaviors, including a divergence in the specific heat and a sub-T-linear electrical resistivity. The discovery of a field-induced magnetic phase that coexists with superconductivity for a range of pressures P {le} P2 has been interpreted as evidence for a quantum phase transition, which could explain the non-Fenni liquid behavior observed in the normal state. Here we report electrical resistivity measurements of CeRhIn{sub 5} under magnetic field at P2, where the resistivity is sub-T-linear for fields less than H{sub c2}(0) and a T{sup 2}-coefficient A found above H{sub c2}(0) diverges as H{sub c2} is approached. These results are similar to the field-induced quantum critical compound Ce-CoIn{sub 5} and confirm the presence of a quantum critical point in the pressure-induced superconductor CeRhIn{sub 5}.

  5. Critical point in the strong-field magnetotransport of a three-dimensional binary disordered composite medium

    NASA Astrophysics Data System (ADS)

    Magier, Ronen; Bergman, David J.

    2008-04-01

    The electrical response of a three-dimensional composite medium composed of two isotropic conductors with charge carriers of the same sign is investigated. We consider such mixtures when subject to a strong magnetic field. First, an asymptotic analysis of a self-consistent effective medium approximation (SEMA) is applied for this purpose. A critical point in the behavior of the effective transverse Ohmic resistivity is predicted. At this critical point, occurring when the Hall resistivities of the two constituents are equal, the dependence of the induced magnetoresistance on the externally applied magnetic field changes from nonsaturating to saturating. The crossover between these distinct strong-field behaviors is characterized by a closed-form function of an appropriate scaling variable. An analogy is found between the investigated composite and a parallel-slabs composite. This provides physical insight into some of the results found using SEMA and indicates that their validity transcends that of SEMA. It also leads to some surprising predictions regarding the distributions of the local electric field and current density in the system.

  6. Promotion of critical thinking by using case studies as teaching method.

    PubMed

    Popil, Inna

    2011-02-01

    This paper examines the use of case studies as teaching strategies to promote critical thinking. Critical thinking and case studies are defined as teaching method. The benefits and limitations of case studies are also discussed. The literature review investigates research studies that have indicated how case studies facilitate and promote active learning, help clinical problem solving, and encourage the development of critical thinking skills. Using case studies in teaching will assist nurse educators in promoting active learning; furthermore, it will help in developing critical thinking skills, which are extremely important for nurses and other health care professionals.

  7. Effects of macroscopic inhomogeneities on the magnetoresistivity of simple metals and critical field anisotropy in granular aluminum

    NASA Astrophysics Data System (ADS)

    Loeffler, K. M.

    The effects of macroscopic voids on the high field thermal magnetoresistivity of the simple metals, including the effects of the lattice conductivity were determined. The calculations were performed using a Green's function approach and a boundary value method. The presence of the lattice conductivity causes large deviations from the linear term evident in the electrical magnetoresistivity. The thermal magnetoresistivity, both transverse and longitudinal, saturates in sufficiently strong fields. The deviation from linearity occurs for 10 is equal to or less than omega sub c tau is equal to or less than 100 depending upon the magnitude of k sub g. The Righi-Leduc coefficient was determined and it was found that the voids caused light increase. The magnetoresistance anomalies of potassium cannot be explained by the presence of voids. Critical field and fluctuation conductivity for extreme type 2 granular aluminum films were measured and found to exhibit a strong temperature dependent anisotropy.

  8. Cancer risk assessment of extremely low frequency electric and magnetic fields: a critical review of methodology.

    PubMed Central

    McCann, J

    1998-01-01

    This review provides a discussion of cancer risk assessment methodology pertinent to developing a strategy for extremely low frequency electric and magnetic fields (EMF). Approaches taken for chemical agents or ionizing radiation in six key topic areas are briefly reviewed, and then those areas are examined from the perspective of EMF, identifying issues to be addressed in developing a risk assessment strategy. The following recommendations are offered: 1) risk assessment should be viewed as an iterative process that informs an overall judgment as to health risk and consists of a complex of related activities incorporating both positive and negative data, tumor and nontumor end points, and human and nonhuman sources of information; 2) a hazard identification resulting in a conclusion of weak or null effects, such as may be associated with EMF, will need to assign significant weight to animal cancer bioassays conducted under defined exposure conditions as well as to human epidemiologic studies; 3) a default factor to account for possible age differences in sensitivity to carcinogenesis should be included in an EMF risk assessment; 4) lack of evidence of dose response and the apparent lack of DNA reactivity of EMF suggest that a safety (or uncertainty) factor or margin of exposure type of risk characterization may be most appropriate; and 5) an EMF risk assessment should permit at least tentative conclusions to be reached as to the limits of carcinogenic risk from exposure to EMF, and should also define an efficient research agenda aimed at clarifying uncertainties appropriate to a more complete assessment. PMID:9799185

  9. Teachers' Perceptions of Critical Thinking: A Study of Jordanian Secondary School Social Studies Teachers

    ERIC Educational Resources Information Center

    Alazzi, Khaled F.

    2008-01-01

    The author conducted research in Jordan, where he interviewed secondary school social studies teachers about their perspectives on teaching critical-thinking skills in their classrooms. All interviews were audiotaped or videotaped in Arabic and later translated into English. The author qualitatively analyzed data, including the translations of the…

  10. Criticality safety study of the MSRE auxiliary charcoal bed

    SciTech Connect

    Hollenbach, D.F.; Hopper, C.M.

    1996-09-01

    The Molten Salt Reactor Experiment (MSRE) was operated from June 1965 to December 1969. The objective of the experiment was to investigate the practicality of developing a power reactor consisting of a graphite lattice with circulating molten uranium salt as fuel for application in central power stations. When the experiment was terminated in 1969, approximately 4710 kg of salt containing approximately 36.3 kg of uranium, 675 g of plutonium, and various fission products were transferred to two fuel drain tanks (FDTs). The almost 30.5 kg of Uranium 233 in the salt is the primary fissile constituent, but about 0.93 kg of Uranium 235 is also present. In April 1994, a gas sample from the MSRE off-gas system (OGS) indicated that uranium had migrated from the FDTs into the OGS. Further investigation revealed a likely accumulation of approximately 2.6 kg of uranium in the auxiliary charcoal bed (ACB), which is located in the concrete-lined charcoal bed cell (CBC) below ground level outside the MSRE building. The nuclear criticality safety (NCS) situation was further complicated by the CBC being filled with water up to the overflow pipe, which completely submerged the ACB. Thus there was not only an increased risk of criticality because of water reflection in the ACB, but also because of potential moderation in the ACB in case of water inleakage. Leakage into the ACB would result in a direct path for water between the CBC and the OGS or FDTs, thus increasing the risk of criticality in these areas. When uranium was discovered in the ACB, a number of steps, detailed in this report, were immediately taken to try to understand and ameliorate the situation. After all the actions were completed, a validation of the results obtained for the ACB was performed.

  11. Field study plan for alternate barriers

    SciTech Connect

    Freeman, H.D.; Gee, G.W.; Relyea, J.F.

    1989-05-01

    Pacific Northwest Laboratory (PNL) is providing technical assistance in selecting, designing, evaluating, and demonstrating protective barriers. As part of this technical assistance effort, asphalt, clay, and chemical grout will be evaluated for use as alternate barriers. The purpose of the subsurface layer is to reduce the likelihood that extreme events (i.e., 100-year maximum storms, etc.) will cause significant drainage through the barrier. The tests on alternate barriers will include laboratory and field analysis of the subsurface layer performance. This field test plan outlines the activities required to test and design subsurface moisture barriers. The test plan covers activities completed in FY 1988 and planned through FY 1992 and includes a field-scale test of one or more of the alternate barriers to demonstrate full-scale application techniques and to provide performance data on a larger scale. Tests on asphalt, clay, and chemical grout were initiated in FY 1988 in small (30.5 cm diameter) tube-layer lysimeters. The parameters used for testing the materials were different for each one. The tests had to take into account the differences in material characteristics and response to change in conditions, as well as information provided by previous studies. 33 refs., 8 figs., 1 tab.

  12. Covariance matrices for use in criticality safety predictability studies

    SciTech Connect

    Derrien, H.; Larson, N.M.; Leal, L.C.

    1997-09-01

    Criticality predictability applications require as input the best available information on fissile and other nuclides. In recent years important work has been performed in the analysis of neutron transmission and cross-section data for fissile nuclei in the resonance region by using the computer code SAMMY. The code uses Bayes method (a form of generalized least squares) for sequential analyses of several sets of experimental data. Values for Reich-Moore resonance parameters, their covariances, and the derivatives with respect to the adjusted parameters (data sensitivities) are obtained. In general, the parameter file contains several thousand values and the dimension of the covariance matrices is correspondingly large. These matrices are not reported in the current evaluated data files due to their large dimensions and to the inadequacy of the file formats. The present work has two goals: the first is to calculate the covariances of group-averaged cross sections from the covariance files generated by SAMMY, because these can be more readily utilized in criticality predictability calculations. The second goal is to propose a more practical interface between SAMMY and the evaluated files. Examples are given for {sup 235}U in the popular 199- and 238-group structures, using the latest ORNL evaluation of the {sup 235}U resonance parameters.

  13. Numerical simulation of aerodynamic derivatives and critical wind speed for long-span bridges based on simplified steady wind field

    NASA Astrophysics Data System (ADS)

    Xin, Dabo; Ou, Jinping

    2007-06-01

    Combining the computational fluid dynamics-based numerical simulation with the forced vibration technique for extraction of aerodynamic derivatives, an approach for calculating the aerodynamic derivatives and the critical flutter wind speed for long-span bridges is presented in this paper. The RNG k-ɛ turbulent model is introduced to establish the governing equations, including the continuity equation and the Navier-Stokes equations, for solving the wind flow field around a two-dimensional bridge section. To illustrate the effectiveness and accuracy of the proposed approach, a simple application to the Hume Bridge in China is provided, and the numerical results show that the aerodynamic derivatives and the critical flutter wind speed obtained agree well with the wind tunnel test results.

  14. Poststructuralism, Politics, and Education. Critical Studies in Education and Culture.

    ERIC Educational Resources Information Center

    Peters, Michael

    This book provides an introduction to poststructuralism by examining a range of interrelated themes central to the field of education that focus on the critique of reason and the problematic nature of the subject. The first chapter examines the history of poststructuralism in terms of the broader canvas of European formalism, futurism, surrealism,…

  15. Vadose Zone Transport Field Study: Summary Report

    SciTech Connect

    Ward, Andy L.; Conrad, Mark E.; Daily, William D.; Fink, James B.; Freedman, Vicky L.; Gee, Glendon W.; Hoversten, Gary M.; Keller, Jason M.; Majer, Ernest L.; Murray, Christopher J.; White, Mark D.; Yabusaki, Steven B.; Zhang, Z. F.

    2006-07-31

    From FY 2000 through FY 2003, a series of vadose zone transport field experiments were conducted as part of the U.S. Department of Energy’s Groundwater/Vadose Zone Integration Project Science and Technology Project, now known as the Remediation and Closure Science Project, and managed by the Pacific Northwest National Laboratory (PNNL). The series of experiments included two major field campaigns, one at a 299-E24-11 injection test site near PUREX and a second at a clastic dike site off Army Loop Road. The goals of these experiments were to improve our understanding of vadose zone transport processes; to develop data sets to validate and calibrate vadose zone flow and transport models; and to identify advanced monitoring techniques useful for evaluating flow-and-transport mechanisms and delineating contaminant plumes in the vadose zone at the Hanford Site. This report summarizes the key findings from the field studies and demonstrates how data collected from these studies are being used to improve conceptual models and develop numerical models of flow and transport in Hanford’s vadose zone. Results of these tests have led to a better understanding of the vadose zone. Fine-scale geologic heterogeneities, including grain fabric and lamination, were observed to have a strong effect on the large-scale behavior of contaminant plumes, primarily through increased lateral spreading resulting from anisotropy. Conceptual models have been updated to include lateral spreading and numerical models of unsaturated flow and transport have revised accordingly. A new robust model based on the concept of a connectivity tensor was developed to describe saturation-dependent anisotropy in strongly heterogeneous soils and has been incorporated into PNNL’s Subsurface Transport Over Multiple Phases (STOMP) simulator. Application to field-scale transport problems have led to a better understanding plume behavior at a number of sites where lateral spreading may have dominated waste

  16. Field studies in geophysical diffraction tomography

    SciTech Connect

    Witten, A.J.; Stevens, S.S. ); King, W.C. . Dept. of Geography and Environmental Engineering); Ursic, J.R. . Region V)

    1992-01-01

    Geophysical diffraction tomography (GDT) is a quantitative, high- resolution technique for subsurface imaging. This method has been used in a number of shallow applications to image buried waste, trenches, soil strata, tunnels, synthetic magma chambers, and the buried skeletal remains of seismosaurus, the longest dinosaur ever discovered. The theory associated with the GDT inversion and implementing software have been developed for acoustic and scalar electromagnetic waves for bistatic and monostatic measurements in cross-borehole, offset vertical seismic profiling and reflection geometries. This paper presents an overview of some signal processing algorithms, a description of the instrumentation used in field studies, and selected imaging results.

  17. Field studies in geophysical diffraction tomography

    SciTech Connect

    Witten, A.J.; Stevens, S.S.; King, W.C.; Ursic, J.R.

    1992-07-01

    Geophysical diffraction tomography (GDT) is a quantitative, high- resolution technique for subsurface imaging. This method has been used in a number of shallow applications to image buried waste, trenches, soil strata, tunnels, synthetic magma chambers, and the buried skeletal remains of seismosaurus, the longest dinosaur ever discovered. The theory associated with the GDT inversion and implementing software have been developed for acoustic and scalar electromagnetic waves for bistatic and monostatic measurements in cross-borehole, offset vertical seismic profiling and reflection geometries. This paper presents an overview of some signal processing algorithms, a description of the instrumentation used in field studies, and selected imaging results.

  18. Planned waveguide electric field breakdown studies

    SciTech Connect

    Wang Faya; Li Zenghai

    2012-12-21

    This paper presents an experimental setup for X-band rf breakdown studies. The setup is composed of a section of WR90 waveguide with a tapered pin located at the middle of the waveguide E-plane. Another pin is used to rf match the waveguide so it operates in a travelling wave mode. By adjusting the penetration depth of the tapered pin, different surface electric field enhancements can be obtained. The setup will be used to study the rf breakdown rate dependence on power flow in the waveguide for a constant maximum surface electric field on the pin. Two groups of pins have been designed. The Q of one group is different and very low. The other has a similar Q. With the test of the two groups of pins, we should be able to discern how the net power flow and Q affect the breakdown. Furthermore, we will apply an electron beam treatment to the pins to study its effect on breakdown. Overall, these experiments should be very helpful in understanding rf breakdown phenomena and could significantly benefit the design of high gradient accelerator structures.

  19. Planetary geomorphology field studies: Washington and Alaska

    NASA Technical Reports Server (NTRS)

    Malin, M. C.

    1984-01-01

    Field studies of terrestrial landforms and the processes that shape them provide new directions to the study of planetary features. Investigations discussed address principally mudflow phenomena and drainage development. At the Valley of 10,000 Smokes (Katmai, AK) and Mount St. Helens, WA, studies of the development of erosional landforms (in particular, drainage) on fresh, new surfaces permitted analysis of the result of competition between geomorphic processes. Of specific interest is the development of stream pattern as a function of the competition between perennial seepage overland flow (from glacial or groundwater sources), ephemeral overland flow (from pluvial or seasonal melt sources), and ephemeral/perennial groundwater sapping, as a function of time since initial resurfacing, material properties, and seasonal/annual environmental conditions.

  20. Planetary geomorphology field studies: Iceland and Antarctica

    NASA Technical Reports Server (NTRS)

    Malin, M. C.

    1984-01-01

    Field studies of terrestrial landforms and the processes that shape them provide new directions to the study of planetary features. These studies, conducted in Iceland and in Antarctica, investigated physical and chemical weathering mechanisms and rates, eolitan processes, mudflow phenomena, drainage development, and catastrophic fluvial and volcanic phenomena. Continuing investigations in Iceland fall in three main catagories: (1) catastrophic floods of the Jokulsa a Fjollum, (2) lahars associated with explosive volcanic eruptions of Askja caldera, and (3) rates of eolian abrasion in cold, volcanic deserts. The ice-free valleys of Antarctica, in particular those in South Victoria Land, have much is common with the surface of Mars. In addition to providing independent support for the application of the Iceland findings to consideration of the martian erosional system, the Antarctic observations also provide analogies to other martian phenomena. For example, a family of sand dunes in Victoria Valley are stabilized by the incorporation of snow as beds.

  1. Satellite to study earth's magnetic field

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The Magnetic Field Satellite (Magsat) designed to measure the near earth magnetic field and crustal anomalies is briefly described. A scalar magnetometer to measure the magnitude of the earth's crustal magnetic field and a vector magnetometer to measure magnetic field direction as well as magnitude are included. The mission and its objectives are summarized along with the data collection and processing system.

  2. The Field Trip Book: Study Travel Experiences in Social Studies

    ERIC Educational Resources Information Center

    Morris, Ronald V.

    2010-01-01

    Looking for social studies adventures to help students find connections to democratic citizenship? Look no further! This book provides just the answer teachers need for engaging students in field trips as researching learners with emphasis on interdisciplinary social studies plus skills in collecting and reporting data gathered from field…

  3. Studies of the Martian Magnetic Field

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1998-01-01

    This report covers two awards: the first NAGW-2573 was awarded to enable participation in the Mars 94 mission that slipped to become the Mars 96 mission. Upon the unfortunate failure of Mars 96 to achieve its intended trajectory, the second grant was awarded to closeout the Mars 96 activities. Our initial efforts concentrated on assisting our colleagues: W. Riedler, K. Schwingenschuh, K. Gringanz, M. Verigin and Ye. Yeroshenko with advice on the development of the magnetic field portion of the investigation and to help them with test activities. We also worked with them to properly analyze the Phobos magnetic field and plasma data in order to optimize the return from the Mars 94/96 mission. This activity resulted in 18 papers on Mars scientific topics, and two on the instrumentation. One of these latter two papers was the last of the papers written, and speaks to the value of the closeout award. These 20 papers are listed in the attached bibliography. Because we had previously studied Venus and Titan and since it was becoming evident that the magnetic field was very weak, we compared the various properties of the Martian interaction with those of the analogous interactions at Venus and Titan while other papers simply analyzed the properties of the interaction as Phobos 2 observed them. One very interesting observation was the identification of ions picked up in the solar wind, originating in Mars neutral atmosphere. These had been predicted by our earlier observation of cyclotron waves at the proton gyrofrequency in the region upstream from Mars in the solar wind. Of course, the key question we addressed was that of the intrinsic or induced nature of the Martian magnetic field. We found little evidence for the former and much for the latter point of view. We also discussed the instrumentation planned for the Mars balloon and the instrumentation on the orbiter. In all these studies were very rewarding despite the short span of the Phobos data. Although they did not

  4. Field testing plan for unsaturated zone monitoring and field studies

    SciTech Connect

    Young, M.H.; Wierenga, P.J.; Warrick, A.W.

    1996-10-01

    The University of Arizona, in cooperation with the Bureau of Economic Geology at The University of Texas at Austin, and Stephens and Associates in Albuquerque, New Mexico has developed a field testing plan for evaluating subsurface monitoring systems. The U.S. Nuclear Regulatory Commission has requested development of these testing plans for low-level radioactive waste disposal sites (LLW) and for monitoring at decommissioned facilities designated under the {open_quotes}Site Decommissioning Management Plan{close_quotes} (SDMP). The tests are conducted on a 50 m by 50 m plot on the University of Arizona`s Maricopa Agricultural Center. Within the 50 m by 50 m plot one finds: (1) an instrumented buried trench, (2) monitoring islands similar to those proposed for the Ward Valley, California LLW Facility, (3) deep borehole monitoring sites, (4) gaseous transport monitoring, and (5) locations for testing non-invasive geophysical measurement techniques. The various subplot areas are instrumented with commercially available instruments such as neutron probes, time domain reflectometry probes, tensiometers, psychrometers, heat dissipation sensors, thermocouples, solution samplers, and cross-hole geophysics electrodes. Measurement depths vary from ground surface to 15 m. The data from the controlled flow and transport experiments, conducted over the plot, will be used to develop an integrated approach to long-term monitoring of the vadose zone at waste disposal sites. The data will also be used to test field-scale flow and transport models. This report describes in detail the design of the experiment and the methodology proposed for evaluating the data.

  5. Impact of a high magnetic field on the orientation of gravitactic unicellular organisms--a critical consideration about the application of magnetic fields to mimic functional weightlessness.

    PubMed

    Hemmersbach, Ruth; Simon, Anja; Waßer, Kai; Hauslage, Jens; Christianen, Peter C M; Albers, Peter W; Lebert, Michael; Richter, Peter; Alt, Wolfgang; Anken, Ralf

    2014-03-01

    The gravity-dependent behavior of Paramecium biaurelia and Euglena gracilis have previously been studied on ground and in real microgravity. To validate whether high magnetic field exposure indeed provides a ground-based facility to mimic functional weightlessness, as has been suggested earlier, both cell types were observed during exposure in a strong homogeneous magnetic field (up to 30 T) and a strong magnetic field gradient. While swimming, Paramecium cells were aligned along the magnetic field lines; orientation of Euglena was perpendicular, demonstrating that the magnetic field determines the orientation and thus prevents the organisms from the random swimming known to occur in real microgravity. Exposing Astasia longa, a flagellate that is closely related to Euglena but lacks chloroplasts and the photoreceptor, as well as the chloroplast-free mutant E. gracilis 1F, to a high magnetic field revealed no reorientation to the perpendicular direction as in the case of wild-type E. gracilis, indicating the existence of an anisotropic structure (chloroplasts) that determines the direction of passive orientation. Immobilized Euglena and Paramecium cells could not be levitated even in the highest available magnetic field gradient as sedimentation persisted with little impact of the field on the sedimentation velocities. We conclude that magnetic fields are not suited as a microgravity simulation for gravitactic unicellular organisms due to the strong effect of the magnetic field itself, which masks the effects known from experiments in real microgravity.

  6. Impact of a High Magnetic Field on the Orientation of Gravitactic Unicellular Organisms—A Critical Consideration about the Application of Magnetic Fields to Mimic Functional Weightlessness

    PubMed Central

    Simon, Anja; Waßer, Kai; Hauslage, Jens; Christianen, Peter C.M.; Albers, Peter W.; Lebert, Michael; Richter, Peter; Alt, Wolfgang; Anken, Ralf

    2014-01-01

    Abstract The gravity-dependent behavior of Paramecium biaurelia and Euglena gracilis have previously been studied on ground and in real microgravity. To validate whether high magnetic field exposure indeed provides a ground-based facility to mimic functional weightlessness, as has been suggested earlier, both cell types were observed during exposure in a strong homogeneous magnetic field (up to 30 T) and a strong magnetic field gradient. While swimming, Paramecium cells were aligned along the magnetic field lines; orientation of Euglena was perpendicular, demonstrating that the magnetic field determines the orientation and thus prevents the organisms from the random swimming known to occur in real microgravity. Exposing Astasia longa, a flagellate that is closely related to Euglena but lacks chloroplasts and the photoreceptor, as well as the chloroplast-free mutant E. gracilis 1F, to a high magnetic field revealed no reorientation to the perpendicular direction as in the case of wild-type E. gracilis, indicating the existence of an anisotropic structure (chloroplasts) that determines the direction of passive orientation. Immobilized Euglena and Paramecium cells could not be levitated even in the highest available magnetic field gradient as sedimentation persisted with little impact of the field on the sedimentation velocities. We conclude that magnetic fields are not suited as a microgravity simulation for gravitactic unicellular organisms due to the strong effect of the magnetic field itself, which masks the effects known from experiments in real microgravity. Key Words: Levitation—Microgravity—Gravitaxis—Gravikinesis—Gravity. Astrobiology 14, 205–215. PMID:24621307

  7. Leishmaniasis entomological field studies: ethical issues.

    PubMed

    Andrade-Narvaez, Fernando; Canto-Lara, Silvia B; Del Rosario Garcia-Miss, Maria

    2009-12-01

    Occupational health remains neglected in developing countries because of competing social, economic and political challenges. Ethical issues in the workplace related to the hazards and risks of becoming infected by Leishmania (Leishmania) mexicana, through the bite of naturally infected sand flies, is another area of concern that has been neglected as well. We report here the results of reviewing two entomological field studies carried out in our research center from 2003 to 2006. Eight students from our School of Biology were invited to catch sand flies. A total of six of the eight (75%) developed a typical clinical picture of Localized Cutaneous Leishmaniasis (LCL) caused by L. (L.) mexicana. In this article we identify the ethical issues related to these kinds of studies and propose some guidelines for conducting them.

  8. Critical realism: a philosophical framework for the study of gender and mental health.

    PubMed

    Bergin, Michael; Wells, John S G; Owen, Sara

    2008-07-01

    This paper explores gender and mental health with particular reference to the emerging philosophical field of critical realism. This philosophy suggests a shared ontology and epistemology for the natural and social sciences. Until recently, most of the debate surrounding gender and mental health has been guided either implicitly or explicitly within a positivist or constructivist philosophy. With this in mind, key areas of critical realism are explored in relation to gender and mental health, and contrasted with the positions of positivism and constructivism. It is argued that critical realism offers an alternative philosophical framework for the exploration of gender issues within mental health care.

  9. Irreversible mean-field model of the critical behavior of charge-density waves below the threshold for sliding

    NASA Astrophysics Data System (ADS)

    Sornette, Didier

    1993-05-01

    A mean-field (MF) model of the critical behavior of charge-density waves below the threshold for sliding is proposed, which replaces the combined effect of the pinning force and of the forces exerted by the neighbors on a given particle n by an effective force threshold Xn. It allows one to rationalize the numerical results of Middleton and Fisher [Phys. Rev. Lett. 66 (1991) 92] on the divergence of the polarization and of the largest correlation length and of Pla and Nori [Phys. Rev. Lett. 67 (1991) 919] on the distribution D( d) of sliding bursts of size d, measured in narrow intervals of driving fields E at a finite distance below the threshold Ec.

  10. Long-term field studies: positive impacts and unintended consequences.

    PubMed

    Strier, Karen B

    2010-09-01

    Long-term field studies of wild primates can have far-reaching impacts that transcend their contributions to science. These impacts can benefit not only the study animals, study areas, and local human communities, but they can also have unintended, potentially negative consequences. Examples of some of the positive impacts from the Northern Muriqui Project of Caratinga, in Minas Gerais, Brazil, include contributions to conservation efforts on behalf of this critically endangered species, capacity building through the training of Brazilian students, and employment opportunities for local people through our collaboration with a locally administered NGO that is facilitating ecotourism, education, and reforestation programs. Some concerns about unintended consequences of the research include the effects of our trails and trail traffic on surrounding vegetation and other aspects of the environmental "footprints" that both long-term researchers and short-term visitors may leave. In addition, although precautions against potential health risks from routine exposure to human observers are now standard protocol, little is known about the other ways in which our long-term research presence can affect the primates' experiences or alter their perceptions of their social and ecological environments. Risk analysis, which weighs both the positive and negative impacts can provide useful perspectives for addressing the ethical considerations that can arise during long-term field studies.

  11. Upper critical field and Kondo effects in Fe(Te0.9Se0.1) thin films by pulsed field measurements

    SciTech Connect

    Salamon, Myron B.; Cornell, Nicholas; Jaime, Marcelo; Balakirev, Fedor F.; Zakhidov, Anvar; Huang, Jijie; Wang, Haiyan

    2016-02-10

    The transition temperatures of epitaxial films of Fe(Te0:9Se0:1) are remarkably insensitive to applied magnetic field, leading to predictions of upper critical fields Bc2(T = 0) in excess of 100 T. Using pulsed magnetic fields, we find Bc2(0) to be on the order of 45 T, similar to values in bulk material and still in excess of the paramagnetic limit. The same films show strong magnetoresistance in fields above Bc2(T), consistent with the observed Kondo minimum seen above Tc. Fits to the temperature dependence in the context of the WHH model, using the experimental value of the Maki parameter, require an effective spin-orbit relaxation parameter of order unity. Lastly, we suggest that Kondo localization plays a similar role to spin-orbit pair breaking in making WHH fits to the data.

  12. This Isn't Business, It's Personal: Personal Narratives in the Field of Composition Studies

    ERIC Educational Resources Information Center

    Golar, Norman

    2010-01-01

    I focus on three critical autobiographies in the field of composition studies: Mike Rose's "Lives on the Boundary: A Moving Account of the Struggles and Achievements of America's Educationally Underprepared," Keith Gilyard's "Voices of the Self: A Study of Language Competence," and Victor Villanueva, Jr.'s "Bootstraps: From an American Academic of…

  13. Lower critical field and intragrain critical current density in the ruthenate-cuprate RuSr2Gd1.5Ce0.5Cu2O10

    NASA Astrophysics Data System (ADS)

    Das Virgens, M. G.; Garcia, S.; Ghivelder, L.

    2006-01-01

    The lower critical field of the grains, Hc1, and the intragrain critical current density, Jc, were determined for the superconducting ruthenate-cuprate RuSr2Gd1.5Ce0.5Cu2O10-δ [Ru-1222(Gd)] through a systematic study of the hysteresis in magnetoresistance loops. A reliable method, based on the effects of the magnetization of the grains on the net local field at the intergranular junctions is provided, circumventing the problem of the strong masking of the superconducting diamagnetic signal by the ferromagnetic background. The temperature dependency of Hc1 and Jc both exhibit a smooth increase on cooling without saturation down to T/T_{SC} \\cong 0.2. The obtained Hc1 values vary between 150 and 1500 Oe in the 0.2 ≤ T/TSC ≤0.4 interval, for samples annealed in an oxygen flow; oxygenation under high pressure (50 atm) leads to a further increase. These values are much larger than the previously reported rough assessments (25 50 Oe), using conventional magnetization measurements. High Jc values of 107 A/cm2, comparable to the high-Tc cuprates, were obtained. The Hc1(T) and Jc(T) dependencies are explained in the context of a magnetic phase separation scenario.

  14. Critical behavior of the random-bond Ashkin-Teller model: A Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Wiseman, Shai; Domany, Eytan

    1995-04-01

    The critical behavior of a bond-disordered Ashkin-Teller model on a square lattice is investigated by intensive Monte Carlo simulations. A duality transformation is used to locate a critical plane of the disordered model. This critical plane corresponds to the line of critical points of the pure model, along which critical exponents vary continuously. Along this line the scaling exponent corresponding to randomness φ=(α/ν) varies continuously and is positive so that the randomness is relevant, and different critical behavior is expected for the disordered model. We use a cluster algorithm for the Monte Carlo simulations based on the Wolff embedding idea, and perform a finite size scaling study of several critical models, extrapolating between the critical bond-disordered Ising and bond-disordered four-state Potts models. The critical behavior of the disordered model is compared with the critical behavior of an anisotropic Ashkin-Teller model, which is used as a reference pure model. We find no essential change in the order parameters' critical exponents with respect to those of the pure model. The divergence of the specific heat C is changed dramatically. Our results favor a logarithmic type divergence at Tc, C~lnL for the random-bond Ashkin-Teller and four-state Potts models and C~ln lnL for the random-bond Ising model.

  15. Critical Current of Superconducting Rutherford Cable in High Magnetic Fields with Transverse Pressure

    SciTech Connect

    Dietderich, D.R.; Scanlan, R.M.; Walsh, R.P.; Miller, J.R.

    1998-09-01

    For high energy physics applications superconducting cables are subjected to large stresses and high magnetic fields during service. It is essential to know how these cables perform in these operating conditions. A loading fixture capable of applying loads of up to 700 kN has been developed by NHMFL for LBNL. This fixture permits uniform loading of straight cables over a 122 mm length in a split-pair solenoid in fields up to 12 T at 4.2 K. The first results from this system for Rutherford cables of internal-tin and modified jelly roll strand of Nb{sub 3}Sn produced by IGC and TWC showed that little permanent degradation occurs up to 210 MPa. However, the cable made from internal-tin strand showed a 40% reduction in K{sub c} at 11T and 210 MPa while a dable made from modified jelly roll material showed only a 15% reduction in I{sub c} at 11T and 185 MPa.

  16. Gyrokinetic studies of microinstabilities in the reversed field pinch

    SciTech Connect

    Carmody, D.; Pueschel, M. J.; Terry, P. W.

    2013-05-15

    An analytic equilibrium, the Toroidal Bessel Function Model, is used in conjunction with the gyrokinetic code GYRO to investigate the nature of microinstabilities in a reversed field pinch plasma. The effect of the normalized electron plasma pressure β on the characteristics of the microinstabilities is studied. At a β of 4.5%, a transition between an ion temperature gradient (ITG) and a microtearing mode is observed. Suppression of the ITG mode occurs as in the tokamak, through coupling to shear Alfvén waves, with a critical β for stability higher than its tokamak equivalent due to a shorter parallel connection length. A steep dependence of the microtearing growth rate on the temperature gradient suggests high profile stiffness. There is evidence for a collisionless microtearing mode. The properties of this mode are investigated, and it is found that electron curvature drift plays an important role in the instability.

  17. Non-perturbative corrections to mean-field critical behavior: the spherical model on a spider-web graph

    NASA Astrophysics Data System (ADS)

    Balram, Ajit C.; Dhar, Deepak

    2012-03-01

    We consider the spherical model on a spider-web graph. This graph is effectively infinite dimensional, similar to the Bethe lattice, but has loops. We show that these lead to non-trivial corrections to the simple mean-field behavior. We first determine all normal modes of the coupled springs problem on this graph, using its large symmetry group. In the thermodynamic limit, the spectrum is a set of δ-functions, and all the modes are localized. The fractional number of modes with frequency less than ω varies as exp ( - C/ω) for ω tending to zero, where C is a constant. For an unbiased random walk on the vertices of this graph, this implies that the probability of return to the origin at time t varies as exp ( - C‧t1/3), for large t, where C‧ is a constant. For the spherical model, we show that while the critical exponents take the values expected from the mean-field theory, the free energy per site at temperature T, near and above the critical temperature Tc, also has an essential singularity of the type exp [ - K(T - Tc)-1/2].

  18. Pauli-limited Upper Critical Field of Fe1+yTe1−xSex

    SciTech Connect

    Petrovic, C.; Lei, H.; Hu, R.; Choi, E.S.; Warren, J.B.

    2010-01-11

    In this work, we investigated the temperature dependence of the upper critical field {mu}{sub 0}H{sub c2}(T) of Fe1.02(3)Te0.61(4)Se0.39(4) and Fe1.05(3)Te0.89(2)Se0.11(2) single crystals by measuring the magnetotransport properties in stable dc magnetic fields up to 35 T. Both crystals show that {mu}{sub 0}H{sub c2}(T) in the ab plane and along the c-axis exhibit saturation at low temperatures. The anisotropy of {mu}{sub 0}H{sub c2}(T) decreases with decreasing temperature, becoming nearly isotropic when the temperature T {yields} 0. Furthermore, {mu}{sub 0}H{sub c2}(0) deviates from the conventional Werthamer-Helfand-Hohenberg theoretical prediction values for both field directions. Our analysis indicates that the spin-paramagnetic pair-breaking effect is responsible for the temperature-dependent behavior of {mu}{sub 0}H{sub c2}(T) in both field directions.

  19. Critical Thinking: Discovery of a Misconception

    ERIC Educational Resources Information Center

    Rohrer, Sandie

    2014-01-01

    Critical thinking skills in the healthcare field are imperative when making quick-thinking decisions. This descriptive comparative study investigated to what extent completing a critical thinking course improved college students' critical thinking skills. The study further investigated whether the instructors' critical thinking skills were…

  20. The Challenge of Critical Pedagogy as a Social Studies Teacher Educator

    ERIC Educational Resources Information Center

    Wylie, Scott

    2014-01-01

    This study examines the evolution of my understanding of critical pedagogy as I work alongside my students to co-construct the curriculum in our social studies teacher education course. As a critical pedagogue, I seek to challenge traditional structures of power and control in the classroom and problematize the ideas and discourses that define our…

  1. How to Teach Critical-Thinking in Social Studies Education: An Examination of Three NCSS Journals

    ERIC Educational Resources Information Center

    Karabulut, Ülkü S.

    2012-01-01

    Problem Statement: Teaching a student critical-thinking skills has always been an important mission of social studies education. Over the years, literature and scholarly interest in critical-thinking in social studies have grown sporadically. Nevertheless, growing interest in the literature and commitment among the scholars did not ensure…

  2. Critical Studies: From the Theory of Ideology to Power/Knowledge.

    ERIC Educational Resources Information Center

    Sholle, David J.

    1988-01-01

    Examines theories of ideology as presented in Marxist-based critical studies; how these theories serve a strategic function within Marxist theory; and, by way of the work of Michel Foucault, the inadequacies of this discourse of "ideological" analysis. Proposes that critical studies of the media move toward the concept of…

  3. A Study of Self-Regulated Learning Strategies as Predictors of Critical Reading

    ERIC Educational Resources Information Center

    Aregu, Bekele Birhanie

    2013-01-01

    The study examines the effects of use of self-regulated learning strategies on critical reading performance among second year distance education students taking critical reading course. It also analyzes correlations of the variables treated. In this study, 140 participants, who were interested to participate, were included. To gather data, scales…

  4. Managing Criticism in Ph.D. Supervision: A Qualitative Case Study

    ERIC Educational Resources Information Center

    Li, Sarah; Seale, Clive

    2007-01-01

    This article is part of a larger study which presents findings from an in-depth longitudinal case study of a student's Ph.D. journey. It shows how criticism is produced and managed in the supervisory relationship. As well as an overview of types of criticism produced across a range of supervisory interactions, the article presents a micro-analysis…

  5. Content Analysis of the Studies in Turkey on the Ability of Critical Thinking

    ERIC Educational Resources Information Center

    Polat, Seyat

    2015-01-01

    Critical thinking, along with other skills, is included as a basic skill in the constructive education program that has been in use in Turkey since 2005. Therefore, a large increase has been observed in studies on critical thinking skills since 2005. In this frame, the present study was conducted in order to systematically examine research papers…

  6. Utilization of critical periods during development to study the effects of low levels of environmental agents

    SciTech Connect

    Russell, L. B.

    1980-01-01

    Careful definition of critical periods in the development of selected characters can result in experimental systems that may be highly useful in studying risk at low levels of exposure. Three examples are presented. Epidemiological investigations can lose much of their value unless critical periods are known for the end points being studied.

  7. Upper critical field, pressure-dependent superconductivity and electronic anisotropy of Sm4Fe2As2Te1-x O4-y F y

    NASA Astrophysics Data System (ADS)

    Pisoni, A.; Katrych, S.; Szirmai, P.; Náfrádi, B.; Gaál, R.; Karpinski, J.; Forró, L.

    2016-03-01

    We present a detailed study of the electrical transport properties of a recently discovered iron-based superconductor: Sm4Fe2As2Te0.72O2.8F1.2. We followed the temperature dependence of the upper critical field by resistivity measurement of single crystals in magnetic fields up to 16 T, oriented along the two main crystallographic directions. This material exhibits a zero-temperature upper critical field of 90 T and 65 T parallel and perpendicular to the Fe2As2 planes, respectively. An unprecedented superconducting magnetic anisotropy {γH}=Hc2ab/Hc2c˜ 14 is observed near T c , and it decreases at lower temperatures as expected in multiband superconductors. Direct measurement of the electronic anisotropy was performed on microfabricated samples, showing a value of {ρc}/{ρab}≤ft(300 \\text{K}\\right)˜ 5 that rises up to 19 near T c . Finally, we have studied the pressure and temperature dependence of the in-plane resistivity. The critical temperature decreases linearly upon application of hydrostatic pressure (up to 2 GPa) similarly to overdoped cuprate superconductors. The resistivity shows saturation at high temperatures, suggesting that the material approaches the Mott-Ioffe-Regel limit for metallic conduction. Indeed, we have successfully modelled the resistivity in the normal state with a parallel resistor model that is widely accepted for this state. All the measured quantities suggest strong pressure dependence of the density of states.

  8. Fabrication of Chemically Doped, High Upper Critical Field Magnesium Diboride Superconducting Wires

    SciTech Connect

    Marzik, James, V.

    2005-10-13

    Controlled chemical doping of magnesium diboride (MgB2) has been shown to substantially improve its superconducting properties to the levels required for high field magnets, but the doping is difficult to accomplish through the usual route of solid state reaction and diffusion. Further, superconducting cables of MgB2 are difficult to fabricate because of the friable nature of the material. In this Phase I STTR project, doped and undoped boron fibers were made by chemical vapor deposition (CVD). Several >100m long batches of doped and undoped fiber were made by CVD codeposition of boron plus dopants. Bundles of these fibers infiltrated with liquid magnesium and subsequently converted to MgB2 to form Mg-MgB2 metal matrix composites. In a parallel path, doped boron nano-sized powder was produced by a plasma synthesis technique, reacted with magnesium to produce doped MgB2 superconducting ceramic bodies. The doped powder was also fabricated into superconducting wires several meters long. The doped boron fibers and powders made in this program were fabricated into fiber-metal composites and powder-metal composites by a liquid metal infiltration technique. The kinetics of the reaction between boron fiber and magnesium metal was investigated in fiber-metal composites. It was found that the presence of dopants had significantly slowed the reaction between magnesium and boron. The superconducting properties were measured for MgB2 fibers and MgB2 powders made by liquid metal infiltration. Properties of MgB2 products (Jc, Hc2) from Phase I are among the highest reported to date for MgB2 bulk superconductors. Chemically doped MgB2 superconducting magnets can perform at least as well as NbTi and NbSn3 in high magnetic fields and still offer an improvement over the latter two in terms of operating temperature. These characteristics make doped MgB2 an effective material for high magnetic field applications, such as magnetic confined fusion, and medical MRI devices. Developing

  9. Mass univariate analysis of event-related brain potentials/fields I: a critical tutorial review.

    PubMed

    Groppe, David M; Urbach, Thomas P; Kutas, Marta

    2011-12-01

    Event-related potentials (ERPs) and magnetic fields (ERFs) are typically analyzed via ANOVAs on mean activity in a priori windows. Advances in computing power and statistics have produced an alternative, mass univariate analyses consisting of thousands of statistical tests and powerful corrections for multiple comparisons. Such analyses are most useful when one has little a priori knowledge of effect locations or latencies, and for delineating effect boundaries. Mass univariate analyses complement and, at times, obviate traditional analyses. Here we review this approach as applied to ERP/ERF data and four methods for multiple comparison correction: strong control of the familywise error rate (FWER) via permutation tests, weak control of FWER via cluster-based permutation tests, false discovery rate control, and control of the generalized FWER. We end with recommendations for their use and introduce free MATLAB software for their implementation.

  10. Critical current densities and irreversibility fields of MgB 2 bulks

    NASA Astrophysics Data System (ADS)

    Kumakura, H.; Takano, Y.; Fujii, H.; Togano, K.; Kito, H.; Ihara, H.

    2001-11-01

    We prepared two MgB 2 bulks by applying conventional sintering and high-pressure sintering methods, and compared the current carrying properties. Jc obtained by the resistive method was larger than that obtained by the magnetic method. Jc- B curves obtained by the resistive method showed no history effect. These results indicate that most of the superconducting currents flowing in the MgB 2 bulks were intergrain (transport) currents and intragrain currents were negligibly small. The high-pressure sintered sample with smaller grain size showed smaller field dependence of Jc and higher Birr than the conventionally sintered sample with larger grain size. This behavior can be explained by the grain boundary flux pinning.

  11. Comparison study of toroidal-field divertors for a compact reversed-field pinch reactor

    SciTech Connect

    Bathke, C.G.; Krakowski, R.A.; Miller, R.L.

    1985-01-01

    Two divertor configurations for the Compact Reversed-Field Pinch Reactor (CRFPR) based on diverting the minority (toroidal) field have been reported. A critical factor in evaluating the performance of both poloidally symmetric and bundle divertor configurations is the accurate determination of the divertor connection length and the monitoring of magnetic islands introduced by the divertors, the latter being a three-dimensional effect. To this end the poloidal-field, toroidal-field, and divertor coils and the plasma currents are simulated in three dimensions for field-line tracings in both the divertor channel and the plasma-edge regions. The results of this analysis indicate a clear preference for the poloidally symmetric toroidal-field divertor. Design modifications to the limiter-based CRFPR design that accommodate this divertor are presented.

  12. Critical review of epidemiologic studies related to ingested asbestos

    SciTech Connect

    Marsh, G.M.

    1983-11-01

    Thirteen epidemiologic studies of ingested asbestos conducted in five areas of the US and Canada were evaluated for the definitiveness and applicability regarding the development of ambient water quality standards. Associations between asbestos in water supplies and cancer mortality or incidence in humans were found in one or more studies dealing with neoplasms in the esophagus, stomach, small intestine, colon, rectum, gallbaldder, pancreas, peritoneum, lungs, pleura, prostate, kidneys, brain and thyroid as well as leukemia. However, no single study nor aggregate of studies existed that would establish risk levels from ingested asbestos. It is recommended that the integrated ecologic data to date be used to generate a rough priority of specific etiologic hypotheses that should be tested in the original settings or in independent study populations using studies designed at the more definitive individual level, such as case-control studies. 25 references, 7 tables.

  13. Dynamical percolation transition in the Ising model studied using a pulsed magnetic field.

    PubMed

    Biswas, Soumyajyoti; Kundu, Anasuya; Chandra, Anjan Kumar

    2011-02-01

    We study the dynamical percolation transition of the geometrical clusters in the two-dimensional Ising model when it is subjected to a pulsed field below the critical temperature. The critical exponents are independent of the temperature and pulse width and are different from the (static) percolation transition associated with the thermal transition. For a different model that belongs to the Ising universality class, the exponents are found to be same, confirming that the behavior is a common feature of the Ising class. These observations, along with a universal critical Binder cumulant value, characterize the dynamical percolation of the Ising universality class.

  14. Critical Pedagogy in the Twenty-First Century: A New Generation of Scholars. Critical Constructions: Studies on Education and Society

    ERIC Educational Resources Information Center

    Malott, Curry Stephenson, Ed.; Porfilio, Bradley, Ed.

    2011-01-01

    This book simultaneously provides multiple analyses of critical pedagogy in the twenty-first century while showcasing the scholarship of this new generation of critical scholar-educators. Needless to say, the writers herein represent just a small subset of a much larger movement for critical transformation and a more humane, less Eurocentric, less…

  15. Len Barton, Inclusion and Critical Disability Studies: Theorising Disabled Childhoods

    ERIC Educational Resources Information Center

    Goodley, Dan; Runswick-Cole, Katherine

    2010-01-01

    Len Barton has pioneered the sociological study of education in the areas of disability studies and inclusive education. This paper addresses an argument developed by Len Barton that social exclusion, of which disablism is one element, (1) has many compounding forms of differing exclusions, (2) is not a natural but a socially constructed process,…

  16. Critical Elements of Student Assistance Programs: A Qualitative Study

    ERIC Educational Resources Information Center

    Torres-Rodriguez, Leslie; Beyard, Karen; Goldstein, Marc B.

    2010-01-01

    Student assistance programs (SAPs) are one approach for using teams to respond to student needs, but there is little research on SAP implementation and whether SAPs function as intended. The authors present findings from a study of two SAPs that use a model developed by Connecticut's Governor's Prevention Partnership. The study focused on…

  17. Some Reflections on and Criticisms of China's Educational Management Studies

    ERIC Educational Resources Information Center

    Yang, Tian-ping

    2007-01-01

    In spite of having undergone one century's vicissitude, China's educational management studies are still lagging behind those abroad. Two research lines, one being induction and generalization, another being deduction and transplantation, have been roughly evolved over these studies. Both of them have reached the level of empirical science. Since…

  18. Comments on the diphoton excess: critical reappraisal of effective field theory interpretations

    NASA Astrophysics Data System (ADS)

    Kamenik, Jernej F.; Safdi, Benjamin R.; Soreq, Yotam; Zupan, Jure

    2016-07-01

    We consider the diphoton excess observed by ATLAS and CMS using the most up-to-date data and estimate the preferred enhancement in the production rate between 8 TeV and 13 TeV. Within the framework of effective field theory (EFT), we then show that for both spin-0 and spin-2 Standard Model (SM) gauge-singlet resonances, two of the three processes S → ZZ, S → Zγ, and S → W W must occur with a non-zero rate. Moreover, we demonstrate that these branching ratios are highly correlated in the EFT. Couplings of S to additional SM states may be constrained and differentiated by comparing the S production rates with and without the vector-boson fusion (VBF) cuts. We find that for a given VBF to inclusive production ratio there is maximum rate of S to gauge bosons, boverline{b} , and lighter quark anti-quark pairs. Simultaneous measurements of the width and the VBF ratio may be able to point towards the existence of hidden decays.

  19. Laser-assisted field evaporation of metal oxides: A time-dependent density functional theory study

    NASA Astrophysics Data System (ADS)

    Xia, Yu; Li, Zhibing

    2016-11-01

    To understand laser-assisted field evaporation of semiconductors and insulators at the microscopic level, we study the time evolution of the electronic and atomic structure of a MgO cluster in high electrostatic fields subjected to strong laser pulses. We find that the critical laser intensity for evaporation decreases linearly as the electrostatic field strength increases. The optical absorption enhancement in high electrostatic field is confirmed by the redshift of the optical absorption spectra, the reduction of the energy gap, and the increase of the absorption cross section.

  20. Summary of modeling studies of the Krafla geothermal field, Iceland

    SciTech Connect

    Bodvarsson, G.S.; Pruess, K.; Stefansson, V.; Eliasson, E.T.

    1983-08-01

    A comprehensive modeling study of the Krafla geothermal field in Iceland has been carried out. The study consists of four tasks: the analysis of well test data, modeling of the natural state of the field, the determination of the generating capability of the field, and modeling of well performance. The results of all four tasks are consistent with field observations.

  1. A small-amplitude study of solitons near critical plasma compositions

    NASA Astrophysics Data System (ADS)

    Olivier, Carel P.; Verheest, Frank; Maharaj, Shimul K.

    2016-12-01

    The properties of small-amplitude solitons are established near critical plasma compositions in a generalized fluid plasma with an arbitrary number of species. The study is conducted via a Taylor series expansion of the Sagdeev potential. It is shown that there are two types of critical compositions, namely rich critical and poor critical compositions. The coexistence of positive and negative polarity solitons is shown to arise at rich critical compositions and near rich critical compositions. At poor critical compositions, no small-amplitude solitons exist, while weak double layers arise near poor critical compositions. A novel analytical expression is obtained for a small-amplitude acoustic speed soliton solution near rich critical compositions. These solitons have a Lorentzian shape with much fatter tails than regular solitons. A case study is also performed for a simple fluid model consisting of cold ions and two Boltzmann electron species. Exact agreement is obtained between the Sagdeev analysis and reductive perturbation theory. For the first time, we derive the same Lorentzian acoustic speed soliton from reductive perturbation theory.

  2. Lifshitz critical point in the cuprate superconductor YBa2Cu3Oy from high-field Hall effect measurements

    NASA Astrophysics Data System (ADS)

    Leboeuf, David; Doiron-Leyraud, Nicolas; Vignolle, B.; Sutherland, Mike; Ramshaw, B. J.; Levallois, J.; Daou, R.; Laliberté, Francis; Cyr-Choinière, Olivier; Chang, Johan; Jo, Y. J.; Balicas, L.; Liang, Ruixing; Bonn, D. A.; Hardy, W. N.; Proust, Cyril; Taillefer, Louis

    2011-02-01

    The Hall coefficient RH of the cuprate superconductor YBa2Cu3Oy was measured in magnetic fields up to 60 T for a hole concentration p from 0.078 to 0.152 in the underdoped regime. In fields large enough to suppress superconductivity, RH(T) is seen to go from positive at high temperature to negative at low temperature, for p>0.08. This change of sign is attributed to the emergence of an electron pocket in the Fermi surface at low temperature. At p<0.08, the normal-state RH(T) remains positive at all temperatures, increasing monotonically as T→0. We attribute the change of behavior across p=0.08 to a Lifshitz transition, namely a change in Fermi-surface topology occurring at a critical concentration pL=0.08, where the electron pocket vanishes. The loss of the high-mobility electron pocket across pL coincides with a tenfold drop in the conductivity at low temperature, revealed in measurements of the electrical resistivity ρ at high fields, showing that the so-called metal-insulator crossover of cuprates is in fact driven by a Lifshitz transition. It also coincides with a jump in the in-plane anisotropy of ρ, showing that without its electron pocket, the Fermi surface must have strong twofold in-plane anisotropy. These findings are consistent with a Fermi-surface reconstruction caused by a unidirectional spin-density wave or stripe order.

  3. High critical current density and low anisotropy in textured Sr₁-xKxFe₂As₂ tapes for high field applications.

    PubMed

    Gao, Zhaoshun; Ma, Yanwei; Yao, Chao; Zhang, Xianping; Wang, Chunlei; Wang, Dongliang; Awaji, Satoshi; Watanabe, Kazuo

    2012-01-01

    From the application point of view, large critical current densities J(c) (H) for superconducting wires are required, preferably for magnetic fields higher than 5 T. Here we show that strong c-axis textured Sr(1-x)K(x)Fe(2)As(2) tapes with nearly isotropic transport J(c) were fabricated by an ex-situ powder-in-tube (PIT) process. At 4.2 K, the J(c) values show extremely weak magnetic field dependence and reach high values of 1.7 × 10(4) A/cm(2) at 10 T and 1.4 × 10(4) A/cm(2) at 14 T, respectively, these values are by far the highest ever reported for iron based wires and approach the J(c) level desired for practical applications. Transmission electron microscopy investigations revealed that amorphous oxide layers at grain boundaries were significantly reduced by Sn addition which resulted in greatly improved intergranular connectivity. Our results demonstrated the strong potential of using iron based superconductors for high field applications.

  4. Field-induced quantum criticality and universal temperature dependence of the magnetization of a spin-1/2 heisenberg chain.

    PubMed

    Kono, Y; Sakakibara, T; Aoyama, C P; Hotta, C; Turnbull, M M; Landee, C P; Takano, Y

    2015-01-23

    High-precision dc magnetization measurements have been made on Cu(C4H4N2) (NO3)2 in magnetic fields up to 14.7 T, slightly above the saturation field Hs=13.97  T, in the temperature range from 0.08 to 15 K. The magnetization curve and differential susceptibility at the lowest temperature show excellent agreement with exact theoretical results for the spin-1/2 Heisenberg antiferromagnet in one dimension. A broad peak is observed in magnetization measured as a function of temperature, signaling a crossover to a low-temperature Tomonaga-Luttinger-liquid regime. With an increasing field, the peak moves gradually to lower temperatures, compressing the regime, and, at Hs, the magnetization exhibits a strong upturn. This quantum critical behavior of the magnetization and that of the specific heat withstand quantitative tests against theory, demonstrating that the material is a practically perfect one-dimensional spin-1/2 Heisenberg antiferromagnet.

  5. Effect of starting composition and annealing temperature on irreversibility field and critical current density in Mg xB 2

    NASA Astrophysics Data System (ADS)

    Xu, G. J.; Pinholt, R.; Bilde-Sørensen, J.; Grivel, J.-C.; Abrahamsen, A. B.; Andersen, N. H.

    2006-02-01

    Bulk samples of MgxB2 with starting composition of 0.5 ⩽ x ⩽ 1.3 were prepared using a solid-state reaction route. Their structure and critical current density (Jc) were investigated. The experimental results show that the starting composition MgxB2, as well as the sintering temperature, has a significant influence on Jc and Hirr. The lattice parameter a increases with x and c shows a maximum value around x = 0.9. All the samples possess a Jc value about 106 A/cm2 in self-field for x > 0.5. However, at high magnetic field the Mg-deficient samples exhibit higher Jc values. The highest irreversibility field of Hirr = 5.2 T at 20 K was reached for x = 0.8 with sintering temperature of 800 °C, which is 0.8 T higher than that of the stoichiometric MgB2 sample. It is suggested that the formation of MgB4 nanoparticles is responsible for the increase of Hirr and Jc.

  6. Effects of concept map teaching on students' critical thinking and approach to learning and studying.

    PubMed

    Chen, Shiah-Lian; Liang, Tienli; Lee, Mei-Li; Liao, I-Chen

    2011-08-01

    The purpose of this study was to explore the effects of concept mapping in developing critical thinking ability and approach to learning and studying. A quasi-experimental study design with a purposive sample was drawn from a group of nursing students enrolled in a medical-surgical nursing course in central Taiwan. Students in the experimental group were taught to use concept mapping in their learning. Students in the control group were taught by means of traditional lectures. After the intervention, the experimental group had better overall critical thinking scores than did the control group, although the difference was not statistically significant. After controlling for the effects of age and the pretest score on critical thinking using analysis of covariance, the experimental group had significantly higher adjusted mean scores on inference and overall critical thinking compared with the control group. Concept mapping is an effective tool for improving students' ability to think critically.

  7. Listening to Hear: Critical Allies in Indigenous Studies

    ERIC Educational Resources Information Center

    McGloin, Colleen

    2015-01-01

    This paper reflects on a particular class in an undergraduate seminar in Australian Indigenous Studies where anecdote played a crucial role and where both the teacher and learners were challenged to consider their implication as racialised subjects in the teaching and learning process. The paper argues that student anecdote can be a vital bridge…

  8. Developing Critical Thinking in E-Learning Environment: Kuwait University as a Case Study

    ERIC Educational Resources Information Center

    Al-Fadhli, Salah; Khalfan, Abdulwahed

    2009-01-01

    This article investigated the impact of using e-learning models' with the principles of constructivism to enhance the critical thinking skills of students in higher education institutions. The study examines the effectiveness of e-learning model in enhancing critical thinking of students at university level. This effectiveness is measured by a…

  9. Critical Reflection as a Learning Tool for Nurse Supervisors: A Hermeneutic Phenomenological Study

    ERIC Educational Resources Information Center

    Urbas-Llewellyn, Agnes

    2013-01-01

    Critical reflection as a learning tool for nursing supervisors is a complex and multifaceted process not completely understood by healthcare leadership, specifically nurse supervisors. Despite a multitude of research studies on critical reflection, there remains a gap in the literature regarding the perceptions of the individual, the support…

  10. The Souls of White Folk: Critical Pedagogy, Whiteness Studies, and Globalization Discourse.

    ERIC Educational Resources Information Center

    Leonardo, Zeus

    2002-01-01

    Critical pedagogy benefits from an intersectional understanding of whiteness studies and globalization discourse. As capitalism spreads, its partnership with race relations evolves into a formidable force. Defines a global approach to race, suggesting that problems with white privilege transcend the nation state. A critical pedagogy of whiteness…

  11. A Critical Thinking Benchmark for a Department of Agricultural Education and Studies

    ERIC Educational Resources Information Center

    Perry, Dustin K.; Retallick, Michael S.; Paulsen, Thomas H.

    2014-01-01

    Due to an ever changing world where technology seemingly provides endless answers, today's higher education students must master a new skill set reflecting an emphasis on critical thinking, problem solving, and communications. The purpose of this study was to establish a departmental benchmark for critical thinking abilities of students majoring…

  12. Integrating Direct and Inquiry-Based Instruction in the Teaching of Critical Thinking: An Intervention Study

    ERIC Educational Resources Information Center

    Ku, Kelly Y. L.; Ho, Irene T.; Hau, Kit-Tai; Lai, Eva C. M.

    2014-01-01

    Critical thinking is a unifying goal of modern education. While past research has mostly examined the efficacy of a single instructional approach to teaching critical thinking, recent literature has begun discussing mixed teaching approaches. The present study examines three modes of instruction, featuring the direct instruction approach and the…

  13. A Study to Compare the Critical Thinking Dispositions between Chinese and American College Students

    ERIC Educational Resources Information Center

    Dennett, Susan K.

    2014-01-01

    The purpose of this quantitative research study was to compare Chinese and American students' inclined level of critical thinking using the California Critical Thinking Disposition Inventory (CCTDI) (Insight Assessment, 2013). The literature of Paul and Elder (1996, 2000, 2005, 2010), Facione and Facione (1992, 1996) and Brookfield (2005, 2010,…

  14. Integrating Critical Thinking Instruction and Assessment into Online University Courses: An Action Research Study

    ERIC Educational Resources Information Center

    Mason Heinrichs, Kim R.

    2016-01-01

    Universities claim that improved critical thinking ability is an educational outcome for their graduates, but they seldom create a path for students to achieve that outcome. In this practitioner action research study, the author created a job aid, entitled "Critical Thinking as a Differentiator for Distinguished Performance," to help…

  15. The Praxis of Ethnic Studies: Transforming Second Sight into Critical Consciousness

    ERIC Educational Resources Information Center

    Cammarota, Julio

    2016-01-01

    This article focuses on a youth participatory action research (YPAR) program called the Social Justice Education Project (SJEP) that fostered young people of color's critical consciousness. Their critical consciousness emerged through praxis (reflection/action) while focusing on preserving ethnic studies in Tucson, Arizona. Because the SJEP home…

  16. The Relationship between Global Competence and Language Learning Motivation: An Empirical Study in Critical Language Classrooms

    ERIC Educational Resources Information Center

    Semaan, Gaby; Yamazaki, Kasumi

    2015-01-01

    This article examines the relationship between global competence and second language learning motivation in critical language classrooms. Data were collected from 137 participants who were studying critical languages (Arabic, Chinese, Japanese, Korean, Persian) at two universities on the East and West Coasts of the United States, using a 30-item…

  17. Art as Critical Public Pedagogy: A Qualitative Study of Luis Camnitzer and His Conceptual Art

    ERIC Educational Resources Information Center

    Zorrilla, Ana; Tisdell, Elizabeth J.

    2016-01-01

    This qualitative study explored the connection between art and adult education for critical consciousness from the perspective and work of conceptual artist, Luis Camnitzer. The theoretical framework is grounded in the critical public pedagogy literature. Data collection methods included interviews with conceptual artist Luis Camnitzer and with…

  18. A Case Study of an EFL Teacher's Critical Literacy Teaching in a Reading Class in Taiwan

    ERIC Educational Resources Information Center

    Ko, Mei-Yun

    2013-01-01

    This qualitative case study describes in detail a college teacher's experience in teaching critical literacy to English major students in Taiwan. A qualitative analysis of the data collected from classroom observation, class discussion and interviews shows that the teacher struck a balance between language skills teaching and critical literacy…

  19. Field studies of the electrification of thunderstorms

    NASA Technical Reports Server (NTRS)

    Christian, H.; Holmes, C. R.; Moore, C. B.; Gaskell, W.; Illingworth, A. J.; Latham, J.

    1979-01-01

    Many theories have been advanced to explain the development of electric fields in thunderstorms, culminating in lightning, but thorough appraisal of these has been hampered by the lack of reliable and comprehensive observational data on the electrical characteristics, microphysical properties and dynamical behavior of the storms. A major field experiment (the Thunderstorm Research International Project) has been in progress for three years, in an effort to remedy this deficiency, and this paper describes some of this work and the results emanating from it. Major tools in this investigation are: an instrumented aircraft capable of penetrating the clouds; dual-Doppler and fast scanning radars; field-change and precipitation-recording networks; and an acoustic system for reconstructing the location of points on the lightning channels. The early results indicate a strong correlation between updraughts, precipitation and high fields. Circumstantial evidence points towards the presence of ice as being crucial to rapid field growth.

  20. A Critical Appraisal of Issues in Differential Response: Moving the Field Forward

    ERIC Educational Resources Information Center

    Winokur, Marc A.; Gabel, George

    2013-01-01

    This reaction article highlights areas of agreement and disagreement with the study conducted by Hughes, Rycus, Saunders-Adams, Hughes, and Hughes on the current state of research and practice in differential response (DR). Overall, we agree with several of the arguments put forth by Hughes et al. regarding the limitations of DR research and the…

  1. Measuring Critical Thinking: Results from an Art Museum Field Trip Experiment

    ERIC Educational Resources Information Center

    Kisida, Brian; Bowen, Daniel H.; Greene, Jay P.

    2016-01-01

    Research shows that participation in school-based arts education has declined over the past decade. A problem for the arts' role in education has been a lack of rigorous scholarship that demonstrates educational benefits. A component of this problem has been a lack of available data. In this study, we use original data collected through a…

  2. Pandemrix™ and narcolepsy: A critical appraisal of the observational studies

    PubMed Central

    Verstraeten, Thomas; Cohet, Catherine; Dos Santos, Gaël; Ferreira, Germano LC; Bollaerts, Kaatje; Bauchau, Vincent; Shinde, Vivek

    2016-01-01

    A link between Pandemrix™ (AS03-adjuvanted H1N1 pandemic influenza vaccine, GSK Vaccines, Belgium) and narcolepsy was first suspected in 2010 in Sweden and Finland following a number of reports in children and adolescents. Initial scepticism about the reported association faded as additional countries reported similar findings, leading several regulatory authorities to restrict the use of Pandemrix™. The authors acknowledge that currently available data suggest an increased risk of narcolepsy following vaccination with Pandemrix™; however, from an epidemiologist's perspective, significant methodological limitations of the studies have not been fully addressed and raise questions about the reported risk estimates. We review the most important biases and confounders that potentially occurred in 12 European studies of the observed association between Pandemrix™ and narcolepsy, and call for further analyses and debate. PMID:26379011

  3. Pandemrix™ and narcolepsy: A critical appraisal of the observational studies.

    PubMed

    Verstraeten, Thomas; Cohet, Catherine; Dos Santos, Gaël; Ferreira, Germano Lc; Bollaerts, Kaatje; Bauchau, Vincent; Shinde, Vivek

    2016-01-01

    A link between Pandemrix™ (AS03-adjuvanted H1N1 pandemic influenza vaccine, GSK Vaccines, Belgium) and narcolepsy was first suspected in 2010 in Sweden and Finland following a number of reports in children and adolescents. Initial scepticism about the reported association faded as additional countries reported similar findings, leading several regulatory authorities to restrict the use of Pandemrix™. The authors acknowledge that currently available data suggest an increased risk of narcolepsy following vaccination with Pandemrix™; however, from an epidemiologist's perspective, significant methodological limitations of the studies have not been fully addressed and raise questions about the reported risk estimates. We review the most important biases and confounders that potentially occurred in 12 European studies of the observed association between Pandemrix™ and narcolepsy, and call for further analyses and debate.

  4. TCDD and cancer: A critical review of epidemiologic studies

    PubMed Central

    Boffetta, Paolo; Mundt, Kenneth A; Adami, Hans-Olov; Cole, Philip; Mandel, Jack S

    2011-01-01

    The authors reviewed the epidemiologic studies on exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and cancer risk, published since the last full-scale review made by the International Agency for Research on Cancer Monographs program in 1997. The update of a cohort of US herbicide producers generated negative results overall; the internal analysis provided evidence of an increased “all-cancer” risk in the highest exposure category, with a statistically significant exposure-response association in some of the many analyses performed.The update of a similar Dutch cohort did not confirm the previously observed association with TCDD exposure. The updated surveillance of the Seveso population provided evidence of increased all-cancer mortality 15-20 years after exposure among those living in the most contaminated area but might also reflect random variation, as overall excesses in the most recent follow-up were not observed. Corresponding data on cancer incidence offer little support to the mortality results. Updated results from cohort studies of Vietnam veterans potentially exposed to TCDD did not consistently suggest an increased risk of cancer. Results of additional, smaller studies of other occupational groups potentially exposed to TCDD, and of community-based case-control studies, did not provide consistent evidence of an increased cancer risk. In conclusion, recent epidemiological evidence falls far short of conclusively demonstrating a causal link between TCDD exposure and cancer risk in humans. The emphasis on results for overall cancer risk—rather than risk for specific neoplasms—is notjustified on epidemiologic grounds and is nota reason for ignoring the weaknesses of the available evidence. PMID:21718216

  5. Combined Effect of Upper Critical Field and Flux Pinning on Enhancing Critical Current Density of In-situ MgB2/Fe Tapes with Various Carbon Sources Simultaneously Doped

    NASA Astrophysics Data System (ADS)

    Pan, Xifeng; Matsumoto, Akiyoshi; Kumakura, Hiroaki; Zhao, Yong; Yan, Guo; Feng, Yong

    2012-01-01

    MgB2/Fe tapes with various forms of mono- and co-doped C sources were prepared by an in-situ powder-in-tube (PIT) method to study the effect of different C sources on the transport critical current density Jc behavior of MgB2. A remarkable Jc improvement at 4.2 K under higher fields and a significant increase in the actual content of C substitution for B were achieved for the tapes with various C sources co-doped. For these co-doped tapes, both enhanced Hc2 and flux pinning properties are responsible for their Jc improvement in this work. Comparing the 4 wt % C9H11NO doped tape with the 20 wt % malic acid doped tape, the latter possesses much better in-field Jc performance at 4.2 K and 10 T and sharper field dependence of Jc, which suggests that the flux pinning plays a crucial role in determining its Jc behavior.

  6. Delirium epidemiology in critical care (DECCA): an international study

    PubMed Central

    2010-01-01

    Introduction Delirium is a frequent source of morbidity in intensive care units (ICUs). Most data on its epidemiology is from single-center studies. Our aim was to conduct a multicenter study to evaluate the epidemiology of delirium in the ICU. Methods A 1-day point-prevalence study was undertaken in 104 ICUs from 11 countries in South and North America and Spain. Results In total, 975 patients were screened, and 497 fulfilled inclusion criteria and were enrolled (median age, 62 years; 52.5% men; 16.7% and 19.9% for ICU and hospital mortality); 64% were admitted to the ICU because of medical causes, and sepsis was the main diagnosis (n = 76; 15.3%). In total, 265 patients were sedated with the Richmond agitation and sedation scale (RASS) deeper than -3, and only 232 (46.6%) patients could be evaluated with the confusion-assessment method for the ICU. The prevalence of delirium was 32.3%. Compared with patients without delirium, those with the diagnosis of delirium had a greater severity of illness at admission, demonstrated by higher sequential organ-failure assessment (SOFA (P = 0.004)) and simplified acute physiology score 3 (SAPS3) scores (P < 0.0001). Delirium was associated with increased ICU (20% versus 5.7%; P = 0.002) and hospital mortality (24 versus 8.3%; P = 0.0017), and longer ICU (P < 0.0001) and hospital length of stay (LOS) (22 (11 to 40) versus 7 (4 to 18) days; P < 0.0001). Previous use of midazolam (P = 0.009) was more frequent in patients with delirium. On multivariate analysis, delirium was independently associated with increased ICU mortality (OR = 3.14 (1.26 to 7.86); CI, 95%) and hospital mortality (OR = 2.5 (1.1 to 5.7); CI, 95%). Conclusions In this 1-day international study, delirium was frequent and associated with increased mortality and ICU LOS. The main modifiable risk factors associated with the diagnosis of delirium were the use of invasive devices and sedatives (midazolam). PMID:21092264

  7. Nonperturbative studies in quantum field theory

    SciTech Connect

    Abada, A.

    1992-01-01

    This dissertation is composed of three different research topics. The first part deals with the Study of the so-called local lattice Yukawa theory. The motivation for this study is to investigate the interior of the phase diagram of this theory. A strong y expansion (y being the bare Yukawa coupling) is performed of the partition function and show that within the (finite) range of convergence of the series expansion, the lattice Yukawa theory is equivalent to a purely bosonic theory, with a shifted action. The author explicitly calculated the shifted action to the fourth order in 1/y and find that it is composed of competing interactions. This suggests that away from y = [infinity] towards the interior of the phase diagram, there is a more complicated ordering than simple ferromagnetic or antiferromagnetic. In the second part, the question is addressed of formation of bound states out of constituent fields in an exactly soluble theory, i.e. multifermion electro-dynamics in two space-time dimensions. The author exactly calculates the correlation function corresponding to a neutral composite fermion operator and discuss the pole structure of its Fourier transform. It does not exhibit a simple pole in p[sup 2], hence the corresponding neutral composite operator does not create an asymptotic state in the spectrum of the theory. In part three, the author puts multifermion QED[sub 2] in a heat bath and address the same question as in part two. The author first exactly calculates a bosonic correlation function at finite temperature and density, and discuss its behavior. The author then exactly calculates the correlation function corresponding to the neutral composite fermion operator at finite temperature and density and discusses its behavior. It is concluded that the temperature does not help the composite fermion operator create a particle in the spectrum of the theory.

  8. Nurse educators' perceptions of critical thinking in developing countries: Ghana as a case study.

    PubMed

    Boso, Christian Makafui; Gross, Janet J

    2015-01-01

    The ability to critically evaluate information for the purpose of rendering health care is a prerequisite for modern nurses in a complex and ever-changing health care environment. The nurse educators' perceptions influence the utilization of critical thinking strategies in the classroom. The purpose of this study was to assess nursing faculty's perceptions of critical thinking. Using a questionnaire 106 nurse educators from two types of nursing educational program self-reported their perceptions. Data were collected from November 2013 to March 2014. Results were presented using frequencies, percentages, and t-test. The findings revealed that majority (95.3%) of nurse educators could not provide definitions that captured both affective and cognitive aspects of critical thinking. However, the majority of nurse educators had positive perceptions of critical thinking. Nurse educators in universities had more positive perceptions of critical thinking than those in the nurses' training colleges (P=0.007). The results suggested that the current nursing programs are not preparing nurses with the necessary critical thinking skills for the complex health care environment. Professional development programs in critical thinking should be instituted for nurse educators to assist them in developing appropriate teaching strategies to foster students' acquisition of critical thinking skills.

  9. Study of critical dimension uniformity (CDU) using a mask inspector

    NASA Astrophysics Data System (ADS)

    Lin, Mei-Chun; Yu, Ching-Fang; Lai, Mei-Tsu; Hsu, Luke T. H.; Chin, Angus; Yen, Anthony

    2012-11-01

    This paper studies the repeatability and the reliability of CDUs from a mask inspector and their correlation with CD SEM measurements on various pattern attributes such as feature sizes, tones, and orientations. Full-mask image analysis with a mask inspector is one of potential solutions for overcoming the sampling rate limitation of a mask CD SEM. By comparing the design database with the inspected dimension, the complete CDU behavior of specific patterns can be obtained without extra work and tool time. These measurements can be mapped and averaged over various spatial lengths to determine changes in relative CDU across the mask. Eventually, success of this methodology relies on the optical system of the inspector being highly stable.

  10. A study of critical reasoning in online learning: application of the Occupational Performance Process Model.

    PubMed

    Mitchell, Anita Witt; Batorski, Rosemary E

    2009-01-01

    This study examined the effect of an online guided independent study on critical reasoning skills. Twenty-one first-semester Master of Occupational Therapy students completed an online assignment designed to facilitate application of the Occupational Performance Process Model (Fearing & Clark) and kept reflective journals. Data from the journals were analyzed in relation to the three sets of questions, question type and results of the Watson-Glaser Critical Thinking Appraisal (WGCTA). This assignment appeared to be effective for enhancing awareness and use of critical reasoning skills. Differences in patterns of critical reasoning between students with high and low WGCTA scores and results of an inductive analysis of the journal entries are discussed. Future research investigating the types of feedback that effectively facilitate development of critical reasoning and whether students with high and low WGCTA scores might benefit from different types of instruction and/or feedback is recommended.

  11. Forced flow He vapor cooled critical current testing facility for measurements of superconductors in a wide temperature and magnetic field range

    NASA Astrophysics Data System (ADS)

    Baskys, Algirdas; Hopkins, Simon C.; Bader, Jakob; Glowacki, Bartek A.

    2016-10-01

    As superconducting materials find their way into applications, there is increasing need to verify their performance at operating conditions. Testing of critical current with respect to temperature and magnetic field is of particular importance. However, testing facilities covering a range of temperatures and magnetic fields can be costly, especially when considering the cooling power required in the cryogenic system in the temperature range below 65 K (inaccessible for LN2). Critical currents in excess of 500 A are common for commercial samples, making the testing of such samples difficult in setups cooled via a cryocooler, moreover it often does not represent the actual cooling conditions that the sample will experience in service. This work reports the design and operation of a low-cost critical current testing facility, capable of testing samples in a temperature range of 10-65 K, with magnetic field up to 1.6 T and measuring critical currents up to 900 A with variable cooling power.

  12. Combustion Safety Simplified Test Protocol Field Study

    SciTech Connect

    Brand, L.; Cautley, D.; Bohac, D.; Francisco, P.; Shen, L.; Gloss, S.

    2015-11-01

    Combustions safety is an important step in the process of upgrading homes for energy efficiency. There are several approaches used by field practitioners, but researchers have indicated that the test procedures in use are complex to implement and provide too many false positives. Field failures often mean that the house is not upgraded until after remediation or not at all, if not include in the program. In this report the PARR and NorthernSTAR DOE Building America Teams provide a simplified test procedure that is easier to implement and should produce fewer false positives. A survey of state weatherization agencies on combustion safety issues, details of a field data collection instrumentation package, summary of data collected over seven months, data analysis and results are included. The project team collected field data on 11 houses in 2015.

  13. Field Ecology Studies in the Rocky Mountains.

    ERIC Educational Resources Information Center

    Robertson, Philip A.

    1978-01-01

    Describes a six-week field plant ecology course in Montana which is offered by the Botany Department at Southern Illinois University. The goals of the course, how it is taught, and student evaluation are also presented. (HM)

  14. Plant Taxonomy as a Field Study

    ERIC Educational Resources Information Center

    Dalby, D. H.

    1970-01-01

    Suggests methods of teaching plant identification and taxonomic theory using keys, statistical analyses, and biometrics. Population variation, genotype- environment interaction and experimental taxonomy are used in laboratory and field. (AL)

  15. Millimeter wave near-field study

    NASA Technical Reports Server (NTRS)

    Kefauver, Neill

    1990-01-01

    The possibility is evaluated of current technology measuring large aperture millimeter wave antennas. Included are a mathematical modeling of system errors, experimental data supporting error model, predictions of system accuracy at millimeter wavelengths, advantage of near-field measurements, and a cost estimate for a facility upgrade. The use is emphasized of software compensation and other inexpensive alternatives to develop a near optimum solution to near-field measurement problems at millimeter wavelengths.

  16. [Communication denied: a pilot study on critical relationship in nursing].

    PubMed

    Cotichelli, Giordano

    2014-01-01

    INTRODUCTION. In letteratura sono pressoché assenti studi sula comunicazione infermieristica quando viene negata, ciò fa sorgere il quesito sul perché rifuggire la relazione con il paziente. OBIETTIVI. Valutare le criticità nella comunicazione infermieristica al fine di costruire una base analitica per uno studio più approfondito. MATERIALI E METODI. Osservazione partecipata (cover) durante uno stage di tirocinio, utilizzando un diario dell’osservazione e prendendo in esame il contesto di lavoro e relazionale di un reparto internistico. RISULTATI. Nella maggioranza dei casi si rifugge la comunicazione, riducendo i tempi di contatto con i pazienti, in altri la si ricerca anche quando non espressamente richiesta dal paziente. CONCLUSIONI. Fuggire la relazione può essere un indicatore di insicurezza professionale. L’Altro significativo cui si nega la relazione, diventa lo specchio in cui il professionista ritrova le sue debolezze. Considerare questi elementi favorisce la dimensione terapeutica. Lo studio si rivela elemento di partenza potenziale per un lavoro che possa avere maggior peso con un campione più ampio e in contesti più articolati.

  17. Critical study of Jara (aging) and its management.

    PubMed

    Parmar, Nisha; Vyas, Mahesh; Vyas, Hitesh

    2012-04-01

    Jara Avastha (stage of old age) is the later phase of life in which maximum decline of bodily elements is observed. Paramanuvibhaga (cell division) takes place at every moment; particularly in old age, it will be fast in comparison with other phases of life. Some organ related changes also take place during this period, which are the decades of Balya, Vridhhi, Chhavi, Medha, Twak, etc., In this study, applied aspects of Medha Hani, Twak Hani, and Drishti Hani were evaluated subjectively as well as objectively. Patients were selected from the OPD of Department of Basic Principles, I.P.G.T. and R.A., Gujarat Ayurved University, Jamnagar, irrespective of their sex, caste, religion, etc., and randomly divided into two groups. Patients in Group A were treated with Panchagavya Ghrita and Group B with plain Go Ghrita for 90 days and the dose of drug was 10 g/day at Nirannakala (early morning with empty stomach). Both groups showed significant results, the difference in between the groups is statistically insignificant.

  18. Critical study of Jara (aging) and its management

    PubMed Central

    Parmar, Nisha; Vyas, Mahesh; Vyas, Hitesh

    2012-01-01

    Jara Avastha (stage of old age) is the later phase of life in which maximum decline of bodily elements is observed. Paramanuvibhaga (cell division) takes place at every moment; particularly in old age, it will be fast in comparison with other phases of life. Some organ related changes also take place during this period, which are the decades of Balya, Vridhhi, Chhavi, Medha, Twak, etc., In this study, applied aspects of Medha Hani, Twak Hani, and Drishti Hani were evaluated subjectively as well as objectively. Patients were selected from the OPD of Department of Basic Principles, I.P.G.T. and R.A., Gujarat Ayurved University, Jamnagar, irrespective of their sex, caste, religion, etc., and randomly divided into two groups. Patients in Group A were treated with Panchagavya Ghrita and Group B with plain Go Ghrita for 90 days and the dose of drug was 10 g/day at Nirannakala (early morning with empty stomach). Both groups showed significant results, the difference in between the groups is statistically insignificant. PMID:23559801

  19. Reactor physics studies in the GCFR Phase III critical assembly

    SciTech Connect

    Morman, J A

    1980-03-01

    The third phase of the gas cooled fast reactor (GCFR) program, ZPR-9 Assembly 30, is based on a multi-zoned core of PuO/sub 2/-UO/sub 2/ with radial and axial blankets of UO/sub 2/. Studies performed in this assembly will be compared to the previous phases of the GCFR program and will help to define parameters in this power-flattened demonstration plant-type core. Measurements in the Phase III program included small sample reactivity worths of various materials, central reaction rates and reaction rate distributions, absorption-to-fission ratios and the central point conversion ratio and the worth of steam entry into a small central zone. The reactivity change associated with the construction of a central pin zone in the core and axial blanket was measured. Reaction rate and steam entry measurements were repeated in the pin environment. Standard analysis methods using ENDF/B-IV data are described and the results are compared to measurements performed during the program.

  20. Study of variables affecting critical value notification in a laboratory catering to tertiary care hospital.

    PubMed

    Agarwal, Rachna; Chhillar, Neelam; Tripathi, Chandra B

    2015-01-01

    During post-analytical phase, critical value notification to responsible caregiver in a timely manner has potential to improve patient safety which requires cooperative efforts between laboratory personnel and caregivers. It is widely accepted by hospital accreditors that ineffective notification can lead to diagnostic errors that potentially harm patients and are preventable. The objective of the study was to assess the variables affecting critical value notification, their role in affecting it's quality and approaches to improve it. In the present study 1,187 critical values were analysed in the Clinical Chemistry Laboratory catering to tertiary care hospital for neuropsychiatric diseases. During 25 months of study period, we evaluated critical value notification with respect to clinical care area, caregiver to whom it was notified and timeliness of notification. During the study period (25 months), the laboratory obtained 1,279 critical values in clinical chemistry. The analytes most commonly notified were sodium and potassium (20.97 & 20.8 % of total critical results). Analysis of critical value notification versus area of care showed that critical value notification was high in ICU and emergency area followed by inpatients and 64.61 % critical values were notified between 30 and 120 min after receiving the samples. It was found that failure to notify the responsible caregiver in timely manner represent an important patient safety issue and may lead to diagnostic errors. The major area of concern are notification of critical value for outpatient samples, incompleteness of test requisition forms regarding illegible writing, lack of information of treating physician and location of test ordering and difficulty in contacting the responsible caregiver.

  1. Field data reveal low critical chemical concentrations for river benthic invertebrates.

    PubMed

    Berger, Elisabeth; Haase, Peter; Oetken, Matthias; Sundermann, Andrea

    2016-02-15

    River ecosystems are of immense ecological and social importance. Despite the introduction of wastewater treatment plants and advanced chemical authorization procedures in Europe, chemical pollution is still a major threat to freshwater ecosystems. Here, large-scale monitoring data was exploited to identify taxon-specific chemical concentrations beyond which benthic invertebrate taxa are unlikely to occur using Threshold Indicator Taxa Analysis (TITAN). 365 invertebrate taxa and 25 organic chemicals including pesticides, pharmaceuticals, plasticisers, flame retardants, complexing agents, a surfactant and poly- and monocyclic aromatic hydrocarbons from a total of 399 sites were analysed. The number of taxa that responded to each of these chemicals varied between 0% and 21%. These sensitive taxa belonged predominantly to the groups Plecoptera, Coleoptera, Trichoptera, Ephemeroptera, Turbellaria, Megaloptera, Crustacea, and Diptera. Strong effects were observed in response to wastewater-associated compounds, confirming that wastewater is an important cause of biological degradation. The majority of change points identified for each compound were well below predicted no-effect concentrations derived from laboratory toxicity studies. Thus, the results show that chemicals are likely to induce effects in the environment at concentrations much lower than expected based on laboratory experiments. Overall, it is confirmed that chemical pollution is still an important factor shaping the distribution of invertebrate taxa, suggesting the need for continued efforts to reduce chemical loads in rivers.

  2. Preliminary Evaluation of a Field and Non-Field Based Social Studies Preservice Teacher Education Program

    ERIC Educational Resources Information Center

    Napier, John D.; Vansickle, Ronald L.

    1978-01-01

    Comparison of pre-service social studies teachers in field and non-field based methods courses indicated no significant differences with regard to teaching skills, attitudes, or behaviors teachers should exhibit in the classroom. (Author/DB)

  3. Characterization of YBa2Cu3O7, including critical current density Jc, by trapped magnetic field

    NASA Technical Reports Server (NTRS)

    Chen, In-Gann; Liu, Jianxiong; Weinstein, Roy; Lau, Kwong

    1992-01-01

    Spatial distributions of persistent magnetic field trapped by sintered and melt-textured ceramic-type high-temperature superconductor (HTS) samples have been studied. The trapped field can be reproduced by a model of the current consisting of two components: (1) a surface current Js and (2) a uniform volume current Jv. This Js + Jv model gives a satisfactory account of the spatial distribution of the magnetic field trapped by different types of HTS samples. The magnetic moment can be calculated, based on the Js + Jv model, and the result agrees well with that measured by standard vibrating sample magnetometer (VSM). As a consequence, Jc predicted by VSM methods agrees with Jc predicted from the Js + Jv model. The field mapping method described is also useful to reveal the granular structure of large HTS samples and regions of weak links.

  4. Analysis of Magnetic Critical Fields in Iron-Based SmFeAsO0.85 HIGH-Tc Superconductor

    NASA Astrophysics Data System (ADS)

    Ahmad, Dawood; Song, Tae Kwon; Park, In Suk; Kim, G. C.; Ren, Zhi-An; Kim, Y. C.

    The magnetic properties of the newly discovered iron-oxypnictide SmFeAsO0.85 high-Tc superconductor with a Tc of around 55 K were investigated. Bulk SmFeAsO0.85 was prepared by a method for high-pressure synthesis. The lower critical field Hc1 was estimated from the magnetization at low fields; Hc1(0) was measured to be 212 Oe. A linear temperature dependence instead of saturation at low temperatures in Hc1(T) revealed unconventional superconductivity with a nodal gap structure in our SmFeAsO0.85 superconductor. The results showed that the well-known secondary peak in the temperature dependence of the critical current density Jc is absent in the SmFeAsO0.85 high-Tc superconductor. The irreversibility line Birr was fitted well by the power law dependence (1 - T/Tc)n with n ~ 1.5. This is indicative of the flux creep phenomena in the SmFeAsO0.85 high-Tc superconductor. In addition, within the range of measurement temperatures in this study, no crossover was observed in the temperature dependence of the irreversibility line Birr which may be due to low anisotropy in our SmFeAsO0.85 superconductor.

  5. A quantitative study relating observed shear in photospheric magnetic fields to repeated flaring

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; Teuber, D.; West, E. A.; Smith, J. B.

    1984-01-01

    In this paper a quantitative evaluation of the shear in the magnetic field along the neutral line in an active region during an epoch of flare activity is presented. Shear is defined as the angular difference in the photosphere between the potential magnetic field, which fits the boundary conditions imposed by the observed line-of-sight field, and the observed magnetic field. For the active region studied, this angular difference (shear) is non-uniform along the neutral line with maxima occurring at the locations of repeated flare onsets. It is suggested that continued magnetic evolution causes the field's maximum shear to exceed a critical value of shear, resulting in a flare around the site of maximum shear. Evidently, the field at the site of the flare must relax to a state of shear somewhat below the critical value (but still far from potential), with subsequent evolution returning the field to the critical threshold. This inference is drawn because several flares occured at sites of maximum photospheric shear which were persistent in location.

  6. Critical state and low-field electrodynamics in LaO{sub 0.85}F{sub 0.15}FeAs superconductor polycrystals

    SciTech Connect

    Gerashchenko, O. V.; Kholmetskii, A. L.; Mashlan, M.; Yarman, T.; Aldushchenkov, A. V.; Okunev, I. S.; Lomonosov, V. A.; Makhnach, L. V.

    2015-06-15

    The penetration of a weak magnetic field into LaO{sub 0.85}F{sub 0.15}FeAs polycrystalline superconductors is investigated using two mutually complementing techniques: measurement of the higher harmonics of nonlinear magnetization and the current-voltage characteristics. The dependences of the critical current density and resistivity on the temperature and magnetic field strength are determined. The results confirm the theory of the critical state in the low-field electrodynamics of a Josephson medium. The universality of this theoretical concept is demonstrated for a new class of ceramic superconductors.

  7. Two-band and pauli-limiting effects on the upper critical field of 112-type iron pnictide superconductors

    PubMed Central

    Xing, Xiangzhuo; Zhou, Wei; Wang, Jinhua; Zhu, Zengwei; Zhang, Yufeng; Zhou, Nan; Qian, Bin; Xu, Xiaofeng; Shi, Zhixiang

    2017-01-01

    The temperature dependence of upper critical field μ0Hc2 of Ca0.83La0.17FeAs2 and Ca0.8La0.2Fe0.98Co0.02As2 single crystals are investigated by measuring the resistivity for the inter-plane (H//c) and in-plane (H//ab) directions in magnetic fields up to 60 T. It is found that μ0Hc2(T) of both crystals for H//c presents a sublinear temperature dependence with decreasing temperature, whereas the curve of μ0Hc2(T) for H//ab has a convex curvature and gradually tends to saturate at low temperatures. μ0Hc2(T) in both crystals deviates from the conventional Werthamer-Helfand-Hohenberg (WHH) theoretical model without considering spin paramagnetic effect for H//c and H//ab directions. Detailed analyses show that the behavior of μ0Hc2(T) in 112-type Iron-based superconductors (IBSs) is similar to that of most IBSs. Two-band model is required to fully reproduce the behavior of μ0Hc2(T) for H//c, while the effect of spin paramagnetic effect is responsible for the behavior of μ0Hc2(T) for H//ab. PMID:28383529

  8. Three-dimensional critical phase diagram of the Ising antiferromagnet CeRh2Si2 under intense magnetic field and pressure

    NASA Astrophysics Data System (ADS)

    Knafo, W.; Settai, R.; Braithwaite, D.; Kurahashi, S.; Aoki, D.; Flouquet, J.

    2017-01-01

    Using novel instrumentation to combine extreme conditions of intense pulsed magnetic field up to 60 T and high pressure up to 4 GPa, we have established the three-dimensional (3D) magnetic field-pressure-temperature phase diagram of a pure stoichiometric heavy-fermion antiferromagnet (CeRh2Si2 ). We find a temperature- and pressure-dependent decoupling of the critical and pseudometamagnetic fields at the borderlines of antiferromagnetism and strongly-correlated paramagnetism. This 3D phase diagram is representative of a class of heavy-fermion Ising antiferromagnets, where long-range magnetic ordering is decoupled from a maximum in the magnetic susceptibility. The combination of extreme conditions enabled us to characterize different quantum phase transitions, where peculiar quantum critical properties are revealed. The interest to couple the effects of magnetic field and pressure on quantum-critical correlated-electron systems is stressed.

  9. Critical Careers.

    ERIC Educational Resources Information Center

    Bowles, Roger A.

    2001-01-01

    Reports the critical shortage of qualified equipment technicians, especially in biomedical equipment. Cites the importance of encouraging careers in this field and describes a source of occupational information. (SK)

  10. Maternal critical care: what can we learn from patient experience? A qualitative study

    PubMed Central

    Hinton, Lisa; Locock, Louise; Knight, Marian

    2015-01-01

    Objective For every maternal death, nine women develop severe maternal morbidity. Many of those women will need care in an intensive care unit (ICU) or high dependency unit (HDU). Critical care in the context of pregnancy poses distinct issues for staff and patients, for example, with breastfeeding support and separation from the newborn. This study aimed to understand the experiences of women who experience a maternal near miss and require critical care after childbirth. Setting Women and some partners from across the UK were interviewed as part of a study of experiences of near-miss maternal morbidity. Design A qualitative study, using semistructured interviews. Participants A maximum variation sample was recruited of 35 women and 11 partners of women who had experienced a severe maternal illness, which without urgent medical attention would have led to her death. 18 of the women were admitted to ICU or HDU. Results The findings are presented in three themes: being in critical care; being a new mother in critical care; transfer and follow-up after critical care. The study highlights the shock of requiring critical care for new mothers and the gulf between their expectations of birth and what actually happened; the devastation of being separated from their baby, how valuable access to their newborn was, if possible, and the importance of breast feeding; the difficulties of transfer and the need for more support; the value of follow-up and outreach to this population of critical care patients. Conclusions While uncommon, critical illness in pregnancy can be devastating for new mothers and presents a challenge for critical care and maternity staff. This study provides insights into these challenges and recommendations for overcoming them drawn from patient experiences. PMID:25916486

  11. Simulation study of the critical current density of YBa2Cu3O7 ceramics

    NASA Astrophysics Data System (ADS)

    Cai, Zhi-Xiong; Welch, David O.

    1992-02-01

    A two-dimensional Josephson-junction-array model is used to study the effect of grain boundaries on the critical current density of YBa2Cu3O7 superconducting ceramics. The model represents a network of superconducting grains with a distribution of tilt angles θ. Each grain boundary has a critical current density Jc(θ) and normal-state resistance R(θ). The current-voltage characteristics are calculated numerically for different tilt-angle distributions. The scaling law and statistics of extremes, introduced by Duxbury, Beale, and Leath for general breakdown behavior, based on the most critical defect (normal region) in the network, are tested and found to be accurate for the predicted critical-current distribution of random samples. When the applied current is larger than but close to its critical value, there is a periodic V(t) with discrete power spectra. When the applied current gets larger, chaotic behavior appears with nearly continuous power spectra.

  12. Preliminary criticality study supporting transuranic waste acceptance into the plasma hearth process

    SciTech Connect

    Slate, L.J.; Santee, G.E. Jr.

    1996-12-31

    This study documents preliminary scoping calculations to address criticality issues associated with the processing of transuranic (TRU) waste and TRU mixed waste in the Plasma Hearth Process (PHP) Test Project. To assess the criticality potential associated with processing TRU waste, the process flow in the PHP is evaluated to identify the stages where criticality could occur. A criticality analysis methodology is then formulated to analyze the criticality potential. Based on these analyses, TRU acceptance criteria can be defined for the PHP. For the current level of analysis, the methodology only assesses the physical system as designed and does not address issues associated with the criticality double contingency principle. The analyses suggest that criticality within the PHP system and within the planned treatment residue (stag) containers does not pose a criticality hazard even when processing waste feed drums containing a quantity of TRU greater than would be reasonably expected. The analyses also indicate that the quantity of TRU that can be processed during each batch is controlled by moving and storage conditions for the resulting slag collection drums.

  13. A Critical Appraisal of Quantitative Studies of Protein Degradation in the Framework of Cellular Proteostasis

    PubMed Central

    Alvarez-Castelao, Beatriz; Ruiz-Rivas, Carmen; Castaño, José G.

    2012-01-01

    Protein homeostasis, proteostasis, is essential to understand cell function. Protein degradation is a crucial component of the proteostatic mechanisms of the cell. Experiments on protein degradation are nowadays present in many investigations in the field of molecular and cell biology. In the present paper, we focus on the different experimental approaches to study protein degradation and present a critical appraisal of the results derived from steady-state and kinetic experiments using detection of unlabelled and labelled protein methodologies with a proteostatic perspective. This perspective allows pinpointing the limitations in interpretation of results and the need of further experiments and/or controls to establish “definitive evidence” for the role of protein degradation in the proteostasis of a given protein or the entire proteome. We also provide a spreadsheet for simple calculations of mRNA and protein decays for mimicking different experimental conditions and a checklist for the analysis of experiments dealing with protein degradation studies that may be useful for researchers interested in the area of protein turnover. PMID:23119163

  14. Bianisotropic-critical-state model to study flux cutting in type-II superconductors at parallel geometry

    NASA Astrophysics Data System (ADS)

    Romero-Salazar, C.

    2016-04-01

    A critical-state model is postulated that incorporates, for the first time, the structural anisotropy and flux-line cutting effect in a type-II superconductor. The model is constructed starting from the theoretical scheme of Romero-Salazar and Pérez-Rodríguez to study the anisotropy induced by flux cutting. Here, numerical calculations of the magnetic induction and static magnetization are presented for samples under an alternating magnetic field, orthogonal to a static dc-bias one. The interplay of the two anisotropies is analysed by comparing the numerical results with available experimental data for an yttrium barium copper oxide (YBCO) plate, and a vanadium-titanium (VTi) strip, subjected to a slowly oscillating field {H}y({H}z) in the presence of a static field {H}z({H}y).

  15. Combustion Safety Simplified Test Protocol Field Study

    SciTech Connect

    Brand, L; Cautley, D.; Bohac, D.; Francisco, P.; Shen, L.; Gloss, S.

    2015-11-05

    "9Combustions safety is an important step in the process of upgrading homes for energy efficiency. There are several approaches used by field practitioners, but researchers have indicated that the test procedures in use are complex to implement and provide too many false positives. Field failures often mean that the house is not upgraded until after remediation or not at all, if not include in the program. In this report the PARR and NorthernSTAR DOE Building America Teams provide a simplified test procedure that is easier to implement and should produce fewer false positives. A survey of state weatherization agencies on combustion safety issues, details of a field data collection instrumentation package, summary of data collected over seven months, data analysis and results are included. The project provides several key results. State weatherization agencies do not generally track combustion safety failures, the data from those that do suggest that there is little actual evidence that combustion safety failures due to spillage from non-dryer exhaust are common and that only a very small number of homes are subject to the failures. The project team collected field data on 11 houses in 2015. Of these homes, two houses that demonstrated prolonged and excessive spillage were also the only two with venting systems out of compliance with the National Fuel Gas Code. The remaining homes experienced spillage that only occasionally extended beyond the first minute of operation. Combustion zone depressurization, outdoor temperature, and operation of individual fans all provide statistically significant predictors of spillage.

  16. Toward a Field of Interfaith Studies

    ERIC Educational Resources Information Center

    Patel, Eboo

    2013-01-01

    Scholars from a range of fields have long taken an interest in how people who orient around religion differently interact with one another. Indeed, this phenomenon has been the subject of important works in political science ("The Clash of Civilizations" by Samuel Huntington), sociology ("American Grace" by Robert Putnam and…

  17. Frozen-wave instability in near-critical hydrogen subjected to horizontal vibration under various gravity fields.

    PubMed

    Gandikota, G; Chatain, D; Amiroudine, S; Lyubimova, T; Beysens, D

    2014-01-01

    The frozen-wave instability which appears at a liquid-vapor interface when a harmonic vibration is applied in a direction tangential to it has been less studied until now. The present paper reports experiments on hydrogen (H2) in order to study this instability when the temperature is varied near its critical point for various gravity levels. Close to the critical point, a liquid-vapor density difference and surface tension can be continuously varied with temperature in a scaled, universal way. The effect of gravity on the height of the frozen waves at the interface is studied by performing the experiments in a magnetic facility where effective gravity that results from the coupling of the Earth's gravity and magnetic forces can be varied. The stability diagram of the instability is obtained. The experiments show a good agreement with an inviscid model [Fluid Dyn. 21 849 (1987)], irrespective of the gravity level. It is observed in the experiments that the height of the frozen waves varies weakly with temperature and increases with a decrease in the gravity level, according to a power law with an exponent of 0.7. It is concluded that the wave height becomes of the order of the cell size as the gravity level is asymptotically decreased to zero. The interface pattern thus appears as a bandlike pattern of alternate liquid and vapor phases, a puzzling phenomenon that was observed with CO2 and H2 near their critical point in weightlessness [Acta Astron. 61 1002 (2007); Europhys. Lett. 86 16003 (2009)].

  18. Distributions of Personalities Within Occupations and Fields of Study

    ERIC Educational Resources Information Center

    Holland, John L.; Holland, Joan E.

    1977-01-01

    Self Directed Search (SDS) and Vocational Preference Inventory (VPI) results occupations and fields of study were organized to show the distributions of personalities within an occupation or field of study. The results show that single fields tolerate several types, but some types occur only infrequently. (Author)

  19. Critical thinking instruction and technology enhanced learning from the student perspective: A mixed methods research study.

    PubMed

    Swart, Ruth

    2017-03-01

    Critical thinking is acclaimed as a valuable asset for graduates from higher education programs. Technology has advanced in quantity and quality; recognized as a requirement of 21st century learners. A mixed methods research study was undertaken, examining undergraduate nursing student engagement with critical thinking instruction, platformed on two technology-enhanced learning environments: a classroom response system face-to-face in-class and an online discussion forum out-of-class. The Community of Inquiry framed the study capturing constructivist collaborative inquiry to support learning, and facilitate critical thinking capability. Inclusion of quantitative and qualitative data sources aimed to gather a comprehensive understanding of students' development of critical thinking and engagement with technology-enhanced learning. The findings from the students' perspectives were positive toward the inclusion of technology-enhanced learning, and use in supporting their development of critical thinking. Students considered the use of two forms of technology beneficial in meeting different needs and preferences, offering varied means to actively participate in learning. They valued critical thinking instruction being intentionally aligned with subject-specific content facilitating understanding, application, and relevance of course material. While the findings are limited to student participants, the instructional strategies and technology-enhanced learning identified as beneficial can inform course design for the development of critical thinking.

  20. First-principles study of the critical thickness in asymmetric ferroelectric tunnel junctions

    SciTech Connect

    Cai Mengqiu; Du Yong; Huang Boyun

    2011-03-07

    The absent critical thickness of fully relaxed asymmetric ferroelectric tunnel junctions is investigated by first-principles calculations. The results show that PbTiO{sub 3} thin film between Pt and SrRuO{sub 3} electrodes can still retain a significant and stable polarization down to thicknesses as small as 0.8 nm, quite unlike the case of symmetric ferroelectric tunnel junctions. We trace this surprising result to the generation of a large electric field by the charge transfer between the electrodes caused by their different electronic environments, which acts against the depolarization field and enhances the ferroelectricity, leading to the reduction, or even complete elimination, for the critical thickness.

  1. Critical Illness Outcome Study: An Observational Study on Protocols and Mortality in Intensive Care Units

    PubMed Central

    Ali, Naeem A.; Gutteridge, David; Shahul, Sajid; Checkley, William; Sevransky, Jonathan; Martin, Greg S.

    2014-01-01

    Introduction Many individual Intensive Care Unit (ICU) characteristics have been associated with patient outcomes, including staffing, expertise, continuity and team structure. Separately, many aspects of clinical care in ICUs have been operationalized through the development of complex treatment protocols. The United State Critical Illness and Injury Trials Group-Critical Illness Outcomes Study (USCIITG-CIOS) was designed to determine whether the extent of protocol availability and use in ICUs is associated with hospital survival in a large cohort of United States ICUs. Here, we describe the study protocol and analysis plan approved by the USCIITG-CIOS Steering Committee. Methods USCIITG-CIOS is a prospective, observational, ecological multi-centered “cohort” study of mixed ICUs in the U.S. The data collected include organizational information for the ICU (e.g., protocol availability and utilization, multi-disciplinary staffing assessment) and patient level information (e.g. demographics, acute and chronic medical conditions). The primary outcome is all-cause hospital mortality, with the objective being to determine whether there is an association between protocol number and hospital mortality for ICU patients. USCIITG-CIOS is powered to detect a 3% difference in crude hospital mortality between high and low protocol use ICUs, dichotomized according to protocol number at the median. The analysis will utilize regression modeling to adjust for outcome clustering by ICU, with secondary linear analysis of protocol number and mortality and a variety of a priori planned ancillary studies. There are presently 60 ICUs participating in USCIITG-CIOS to enroll approximately 6,000 study subjects. Conclusions USCIITG-CIOS is a large multicentric study examining the effect of ICU protocol use on patient outcomes. The primary results of this study will inform our understanding of the relationship between protocol availability, use, and patient outcomes in the ICU. Moreover

  2. 3D-xy critical properties of YBa2Cu4O8 and magnetic-field-induced 3D to 1D crossover

    NASA Astrophysics Data System (ADS)

    Weyeneth, S.; Schneider, T.; Bukowski, Z.; Karpinski, J.; Keller, H.

    2008-08-01

    We present reversible magnetization data of a YBa2Cu4O8 single crystal and analyze the evidence for 3D-xy critical behavior and a magnetic-field-induced 3D to 1D crossover. Remarkable consistency with these phenomena is observed in agreement with a magnetic-field-induced finite size effect, whereupon the correlation length transverse to the applied magnetic field cannot grow beyond the limiting magnetic length scale LH = (Φ0/(aH))1/2. By applying the appropriate scaling form we obtain the zero-field critical temperature, the 3D to 1D crossover, the vortex melting line and the universal ratios of the related scaling variables. Accordingly there is no continuous phase transition in the (H,T) plane along the Hc2 lines as predicted by the mean-field treatment.

  3. Study of Critical Behavior in Amorphous Fe85Sn5Zr10 Alloy Ribbon

    NASA Astrophysics Data System (ADS)

    Han, L. A.; Hua, X. H.; Zhu, H. Z.; Yang, J.; Yang, H. P.; Yan, Z. X.; Zhang, T.

    2017-02-01

    We have investigated the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon prepared using a single-roller melt-spinning method. This alloy shows a second-order magnetic transition from paramagnetic to ferromagnetic (FM) state at the Curie temperature T C (˜306 K). To obtain more information on the features of the magnetic transition, a detailed critical exponent study was carried out using isothermal magnetization M ( H, T) data in the vicinity of the T C. Modified Arrott plot, Kouvel-Fisher plot, Widom's scaling relation and critical isotherm analysis techniques were used to investigate the critical behavior of this alloy system around its phase transition point. The values of critical exponents determined using the above methods are self-consistent. The estimated critical exponents are fairly close to the theoretical prediction of the three-dimensional (3D) Heisenberg model, implying that short-range FM interactions dominate the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon.

  4. Critical Pedagogy in Health Education

    ERIC Educational Resources Information Center

    Matthews, Catherine

    2014-01-01

    Objective: This review investigated how the three-phase model of critical pedagogy, based on the writings of Paulo Freire, can be put into practice in health education. Design: The study considers literature related to the fields of health education, health promotion and critical pedagogy. Setting: The study is a scholarly review completed as part…

  5. The generation of tens kT magnetic fields by transport instability of laser generated electrons in a near critical preformed plasma

    NASA Astrophysics Data System (ADS)

    Toncian, Toma; Hegelich, Bjorn Manuel; Willi, Oswald; Lehmann, Goetz

    2014-10-01

    First direct measurements of the electron transport along extended wire targets by Quinn et al. [PRL 102 (2009)] revealed a charging current and associated magnetic field moving close to the speed of light away from focal volume of the employed heating laser. The motion of the electrons is bound electrostatic to the proximity of the solid. A return current compensating the escaping charge is formed at the surface of the solid, the overall current loop sustaining kT magnetic fields, with traversal decay lengths of μm. In our study we show by means of numerical 2 dimensional particle in cell simulations that the motion of the hot electrons and dynamic of the charge compensating return current can be dramatically affected by a preformed μm scale length plasma gradient on the solid surface. In particularly the two velocities distribution and two antiparallel currents developing in the near critical plasma are unstable in respect of two stream and Kevin Helmholtz instability. The particle motion becomes locally magnetized resulting in current eddies trapping particles and localized magnetic and electric fields with values of tens of kT and TV/m sustained on μm scales and with characteristic decay times of ps.

  6. Field study on moving force identification

    NASA Astrophysics Data System (ADS)

    Chan, Hung-tin Tommy; Yung, Tak H.; Law, S. S.

    2001-08-01

    A field measurement to validate a moving force identification method was carried out on an existing prestressed concrete highway bridge with a span length of 28 m. The test bridge is located at Ma Tau Wai, Kowloon, Hong Kong. A heavy 2-axle truck with known axle loads was used as a control vehicle. Besides the control vehicle, axle load data of in-service vehicles were also collected. The bridge responses acquired for the identification were indirectly measured using strain gauges. Results show that dynamic axle loads induced from both control and in-service vehicles can be identified indicating the method is valid for identification of moving forces.

  7. Highly enhanced in-field critical current density of MgB 2 superconductor by combined addition of burned rice husk and nano Ho 2O 3

    NASA Astrophysics Data System (ADS)

    Vinod, K.; Varghese, Neson; Sundaresan, A.; Syamaprasad, U.

    2010-04-01

    With the aim of improving flux pinning and in-field critical current density [ JC( H)], two physically and chemically different additives - burned rice husk (BRH) and nano Ho 2O 3 were introduced into in situ MgB 2 superconductor. The effects of the above two additives were studied individually and combinedly. Ho 2O 3 decomposed and reacted with B to form HoB 4, without any substitution. BRH caused considerable amount of C substitution at B site and formed Mg 2Si and Mg 2C 3 secondary phases. Addition of Ho 2O 3 improved the JC( H) only marginally, but BRH improved the JC( H) strongly. Combined addition of Ho 2O 3 with BRH was found to be much more effective than their solo addition for the enhancement of JC( H) of MgB 2.

  8. Training of Critical Thinking Skills in Teacher Candidates and Placebo Effect: A Quasi-Experimental Study

    ERIC Educational Resources Information Center

    Demirbag, Betul; Unisen, Ali; Yesilyurt, Abdullah

    2016-01-01

    Problem Statement: In recent years many different studies have examined critical thinking disposition; however, these studies focus on investigating the variables that are related to this subject. There are actually few empirical studies in the literature. It is clear that there is a need for experimental research in order to comprehend the…

  9. The genesis of Typhoon Nuri as observed during the Tropical Cyclone Structure 2008 (TCS-08) field experiment - Part 1: The role of the easterly wave critical layer

    NASA Astrophysics Data System (ADS)

    Montgomery, M. T.; Lussier, L. L., III; Moore, R. W.; Wang, Z.

    2010-10-01

    An observational and real-time model forecast study of the genesis of Typhoon Nuri during the Tropical Cyclone Structure 2008 (TCS-08) field campaign in the western North Pacific sector is presented. Analysis and observational data show that the surrounding base state is an easterly trade wind flow and the precursor disturbance to Typhoon Nuri is an easterly wave that originates in the ITCZ in the Central Pacific. This disturbance can be tracked more than 10 days prior to tropical storm formation. An overview of the field data is presented here using a newly proposed dynamical framework for tropical cyclone formation within the critical layer of an easterly wave. Despite propagating through a hostile environment ripe with strong vertical wind shear and relatively dry air, the easterly wave critical layer protects the proto-vortex and allows it to gestate until it reaches a more favorable environment. Within this protective "Kelvin cat's eye flow" located within the wave's critical layer existed a sweet spot, defined as the intersection between the wave trough and critical latitude, which is the preferred location for tropical cyclogenesis. Global Forecast System Final Analyses and IR satellite imagery, which shows convective bands wrapping around the sweet spot as genesis nears, confirm that this sweet spot is the location where Typhoon Nuri's dominant low-level circulation emerges. United States Air Force C130 and Naval Research Laboratory P3 research flights on 16 and 17 August collected flight-level, dropwindsonde, and Doppler radar data that allowed an evaluation of the dynamic and thermodynamic processes within the cat's eye circulation. The dropwindsonde analyses identifies the precursor easterly wave disturbance on 16 August and identifies an area of weak low-level cyclonic circulation on 17 August. Real-time forecasts were produced using operational global prediction model data to support scientific missions during TCS-08. These forecasts were found to be

  10. The genesis of Typhoon Nuri as observed during the Tropical Cyclone Structure 2008 (TCS-08) field experiment - Part 1: The role of the easterly wave critical layer

    NASA Astrophysics Data System (ADS)

    Montgomery, M. T.; Lussier, L. L., III; Moore, R. W.; Wang, Z.

    2009-09-01

    An observational and real-time model forecast study of the genesis of Typhoon Nuri during the Tropical Cyclone Structure 2008 (TCS-08) field campaign in the western North Pacific sector is presented. Analysis and observational data show that the surrounding base state flow was an easterly trade wind flow and the precursor disturbance to Typhoon Nuri was an easterly wave that originated in the ITCZ in the Central Pacific and can be tracked more than 10 days prior to tropical storm formation. An overview of the field data is presented here using a newly proposed dynamical framework for tropical cyclone formation within the critical layer of an easterly wave. Despite propagating through a hostile environment ripe with strong vertical wind shear and relatively dry air, the easterly wave critical layer protected the proto-vortex and allowed it to gestate until it reached a more favorable environment. Within this protective "Kelvin's cat's eye flow" located within the wave's critical layer existed a "sweet spot", defined as the intersection between the wave trough and critical latitude, which was the preferred location for tropical cyclogenesis. Global Forecast System Final Analyses and IR satellite imagery, which shows convective bands wrapping around the sweet spot as genesis nears, confirm that this sweet spot is the location where Typhoon Nuri's dominant low-level circulation emerges. United States Air Force C130 and Naval Research Laboratory P3 research flights on 16 and 17 August collected flight-level, dropwindsonde, and Doppler radar data that allowed an evaluation of the dynamic and thermodynamic processes within the cat's eye. The dropwindsonde analyses identified the precursor easterly wave disturbance on 16 August and identified an area of weak low-level cyclonic circulation on 17 August. During the TCS-08 experiment "real-time forecasts" were produced in real-time using operational global prediction model data to support scientific missions. These forecasts

  11. Geosynthetic clay liners - slope stability field study

    SciTech Connect

    Carson, D.A.; Daniel, D.E.; Koerner, R.M.; Bonaparte, R.

    1997-12-31

    A field research project was developed to examine the internal shear performance of geosynthetic clay liners (GCLs). Several combinations of cross sections were assembled using GCL materials that were available at the time of project initiation. The cross sections utilized were intended to simulate landfill cover applications. Thirteen (13) resulting test plots were constructed on two different slope angles, and each plot is instrumented for physical displacement and soil moisture characteristics. Test plots were constructed in a manner that dictated the shear plane in the clay portion of the GCL product. The project purpose is to assess field performance and to verify design parameters associated with the application of GCLs in waste containment applications. Interim research data shows that test slopes on 2H:1V show global deformation, but little internal shear evidence, and the 3H:1V slopes show little deformation at approximately 650 days. The research is ongoing, and this paper presents the most recent information available from the project.

  12. High Critical Field Superconductivity in FeSe0.1 Te0.9 Coated Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Haiyan; Cornell, Nicholas; Huang, Jijie; Salamon, Myron; Zakhidov, Anvar; Anvar Zakhidov; Haiyan Wang Team; Utd; Tamu Afosr Team

    2015-03-01

    Thin films of FeSe0.1Te0.9, grown on SrTi03, have been shown to possess an increased critical temperature, field, and current relative to both bulk samples of FeSe0.1Te0.9 and thin films of the related compound FeSe0.5Te0.5. Empirical measurement of FeSe0.1Te0.9 thin films reveal a zero temperature Hc2(0) ~ 45T. Carbon nanotubes are a promising lightweight flexible material for superconducting applications and have proven a robust substrate when conformally coated by superconducting MgB2. Thin film coatings of FeSe0.1Te0.9 have been deposited via pulsed laser deposition on dry- drawn multiwall carbon nanotube sheets drawn from CVD grown forests. While true zero resistance isn't achieved due to inter-connectivity issues or junction effects in multiwall CNT case, clear superconducting transitions with R reaching zero can be seen on other single wall CNT, and non-oriented carbon nanotube substrates. Properties of these superconducting FeSe0.1Te0.9@SWCNT thin films are discussed.

  13. Geometrical thermodynamics and P-V criticality of the black holes with power-law Maxwell field

    NASA Astrophysics Data System (ADS)

    Hendi, S. H.; Panah, B. Eslam; Panahiyan, S.; Talezadeh, M. S.

    2017-02-01

    We study the thermodynamical structure of Einstein black holes in the presence of power Maxwell invariant nonlinear electrodynamics for two different cases. The behavior of temperature and conditions regarding the stability of these black holes are investigated. Since the language of geometry is an effective method in general relativity, we concentrate on the geometrical thermodynamics to build a phase space for studying thermodynamical properties of these black holes. In addition, taking into account the denominator of the heat capacity, we use the proportionality between cosmological constant and thermodynamical pressure to extract the critical values for these black holes. Besides, the effects of the variation of different parameters on the thermodynamical structure of these black holes are investigated. Furthermore, some thermodynamical properties such as the volume expansion coefficient, speed of sound, and isothermal compressibility coefficient are calculated and some remarks regarding these quantities are given.

  14. Validation studies based on critical experiments performed with fuel pin arrays moderated by Pu + U solutions

    SciTech Connect

    Smolen, G.R.; Matsumoto, T. )

    1989-01-01

    This paper outlines the results of a calculational study that was performed to validate the SCALE computer code system using data from critical experiments performed with fuel pin arrays moderated by mixed Pu + U aqueous solutions. A companion paper describes the experiments and discusses the criticality data that were obtained. These experimental activities are part of a joint exchange program between the US Department of Energy (DOE) and the Power Reactor and Nuclear Fuel Development Corporation of Japan in the area of criticality data development. The Consolidated fuel Reprocessing Program (CFRP) at Oak Ridge National Laboratory (ORNL) manages the program for the DOE. The experiments were conducted at the Battelle Pacific Northwest Laboratories-Critical Mass Laboratory (PNL-CML).

  15. NASA Computational Case Study: Modeling Planetary Magnetic and Gravitational Fields

    NASA Technical Reports Server (NTRS)

    Simpson, David G.; Vinas, Adolfo F.

    2014-01-01

    In this case study, we model a planet's magnetic and gravitational fields using spherical harmonic functions. As an exercise, we analyze data on the Earth's magnetic field collected by NASA's MAGSAT spacecraft, and use it to derive a simple magnetic field model based on these spherical harmonic functions.

  16. Comparative Study of Bacterial Growth in Magnet Fields

    NASA Astrophysics Data System (ADS)

    Smith, Derek; Masood, Samina

    It has been shown that magnetic fields affect bacterial growth. A comparative study of growth rates for gram-positive and gram-negative bacteria with different types of magnetic fields is done. Special focus is placed upon growth within liquid media, and the effect of magnetic fields relative to the chosen growth medium is considered.

  17. Critical current densities and irreversibility field of high-Tc Ba2Ca3Cu4O(O,F)2 superconductor

    NASA Astrophysics Data System (ADS)

    Shirage, P. M.; Iyo, A.; Shivagan, D. D.; Tanaka, Y.

    2008-03-01

    The superconductivity in apical fluorine system of Ba2Ca3Cu4O10-yFy: the fourth member of Ba2Can-1CunO2n(O,F)2 homologous series is significant to study as it deals with the novel phenomenon of superconductivity like co-existence of superconductivity and antiferromagnetism, in-equivalent and non-similar charge distribution in the CuO2 planes in a unit cell etc. The polycrystalline samples of Ba2Ca3Cu4O8(O,F)2 (F-0234) were synthesized under high pressure and showed sharp superconducting transitions temperature at 105 K. From the DA magnetization hysteresis loops, we determined the intragrain critical current density (Jc) and irreversibility field (Birr) using Bean's critical state model. The irreversibility line(IL) of F-0234 is higher than that for optimally-doped Bi-2212. However, IL much lower than that of Cu-1212 (Y-123) although the spacing of F-0234 (7.3 Å) is much thinner than that of Cu-1212.

  18. Assessing Critical Thinking Outcomes of Dental Hygiene Students Utilizing Virtual Patient Simulation: A Mixed Methods Study.

    PubMed

    Allaire, Joanna L

    2015-09-01

    Dental hygiene educators must determine which educational practices best promote critical thinking, a quality necessary to translate knowledge into sound clinical decision making. The aim of this small pilot study was to determine whether virtual patient simulation had an effect on the critical thinking of dental hygiene students. A pretest-posttest design using the Health Science Reasoning Test was used to evaluate the critical thinking skills of senior dental hygiene students at The University of Texas School of Dentistry at Houston Dental Hygiene Program before and after their experience with computer-based patient simulation cases. Additional survey questions sought to identify the students' perceptions of whether the experience had helped develop their critical thinking skills and improved their ability to provide competent patient care. A convenience sample of 31 senior dental hygiene students completed both the pretest and posttest (81.5% of total students in that class); 30 senior dental hygiene students completed the survey on perceptions of the simulation (78.9% response rate). Although the results did not show a significant increase in mean scores, the students reported feeling that the use of virtual patients was an effective teaching method to promote critical thinking, problem-solving, and confidence in the clinical realm. The results of this pilot study may have implications to support the use of virtual patient simulations in dental hygiene education. Future research could include a larger controlled study to validate findings from this study.

  19. THE FIELD STUDY NOTEBOOK FOR THE OUTDOOR SCHOOL.

    ERIC Educational Resources Information Center

    BURGESS, ROBERT A.; GILFILLAN, WARREN C.

    THE "FIELD STUDY NOTEBOOK" HAS BEEN PREPARED FOR USE BY PAROCHIAL AND PUBLIC ELEMENTARY SCHOOL STUDENTS FOR STUDYING ECOLOGY AT AN OUTDOOR SCHOOL. THE NOTEBOOK EMPHASIZES COMMUNITY DYNAMICS THROUGH STUDENT ACTIVITIES THAT ILLUSTRATE ECOLOGICAL RELATIONSHIPS. INFORMATION IS PROVIDED ON THE ORGANIZATION OF A FIELD STUDY AND ON PERFORMING…

  20. NAFTA Guidance Document for Conducting Terrestrial Field Dissipation Studies

    EPA Pesticide Factsheets

    Harmonized guidance for TFD studies that demonstrate transformation, transport and fate of pesticides under representative actual use conditions. Field studies substantiate physicochemical, mobility and biotransformation data from laboratory studies.

  1. Group Work and the Learning of Critical Thinking in the Hong Kong Secondary Liberal Studies Curriculum

    ERIC Educational Resources Information Center

    Fung, Dennis; Howe, Christine

    2014-01-01

    This article reports the findings of a one-year longitudinal study that investigated the impact of group work on the development of students' critical thinking in Hong Kong secondary schools. It explores whether the participation of teachers in a group-based teaching intervention adapted from an earlier study conducted in the United Kingdom (UK)…

  2. Liberal Studies in Hong Kong: A New Perspective on Critical Thinking through Group Work

    ERIC Educational Resources Information Center

    Fung, Dennis; Howe, Christine

    2012-01-01

    This article reports research that is contextualised within reforms of secondary education in Hong Kong and the reintroduction of Liberal Studies, which jointly emphasise the need for a learning environment that facilitates the practice of group work and the development of critical thinking. A study is described that explores the relevance of…

  3. Virtuous Subjects: A Critical Analysis of the Affective Substance of Social Studies Education

    ERIC Educational Resources Information Center

    Helmsing, Mark

    2014-01-01

    This essay invites social studies educators to consider critical theoretical insights related to affect, emotions, and feelings from what has been termed "the affective turn" in social sciences and humanities scholarship. Developments in theorizing affect and recent research in social studies education are related to affective elements…

  4. Whose Knowledge Is Valued: A Critical Study of Knowledge in Elementary School Textbooks in China

    ERIC Educational Resources Information Center

    Wang, Yuxiang; Phillion, JoAnn

    2010-01-01

    This study critically examines knowledge in elementary school textbooks in China. Language analysis and story-line analysis are used to examine how the knowledge related to minority groups and how the knowledge related to the Han group are introduced and interpreted. This study finds that the Han knowledge dominates elementary school textbooks in…

  5. Smartness as Property: A Critical Exploration of Intersections between Whiteness and Disability Studies

    ERIC Educational Resources Information Center

    Leonardo, Zeus; Broderick, Alicia A.

    2011-01-01

    Background/Context: Two scholars who each primarily identify as a scholar of critical race/whiteness studies and a scholar of disability studies, respectively, engage in this article in a purposeful dialogue that responds to the invitation put forth by Baglieri, Bejoian, Broderick, Connor, and Valle to engage with the construct of inclusive…

  6. Digital Storytelling and American Studies: Critical Trajectories from the Emotional to the Epistemological

    ERIC Educational Resources Information Center

    Oppermann, Matthias

    2008-01-01

    In recent years, digital storytelling has emerged as an alternative medium of knowledge production for students in American studies. A growing number of faculty are creating assignments which combine methodological markers of American studies and reinvented notions of critical pedagogy in a multimedia learning environment. Based on an analysis of…

  7. Integrating Black Consciousness and Critical Race Feminism into Family Studies Research

    ERIC Educational Resources Information Center

    Few, April L.

    2007-01-01

    The author examines the advantages and challenges of using Black feminist theory and critical race feminist theory to study the lives of Black women and families in family studies. The author addresses the ways in which these perspectives, both of which are intentional in their analyses of intersectionality and the politics of location, are also…

  8. Neuroscientific Studies of Mathematical Thinking and Learning: A Critical Look from a Mathematics Education Viewpoint

    ERIC Educational Resources Information Center

    Verschaffel, Lieven; Lehtinen, Erno; Van Dooren, Wim

    2016-01-01

    In this commentary we take a critical look at the various studies being reported in this issue about the relationship between cognitive neuroscience and mathematics, from a mathematics education viewpoint. After a discussion of the individual contributions, which we have grouped into three categories--namely neuroscientific studies of (a)…

  9. A Study on the Link between Moral Judgment Competences and Critical Thinking Skills

    ERIC Educational Resources Information Center

    Samanci, Nilay Keskin

    2015-01-01

    Although many studies have established a direct link between moral judgment competences and critical thinking skills, none has been found to reveal the nature of the link between these two skills in the national and international literature. The present study looked at biology and primary education teacher candidates' moral judgment and critical…

  10. Back to OZ? Rethinking the Literary in a Critical Study of Reading

    ERIC Educational Resources Information Center

    Hicks, Deborah

    2004-01-01

    Drawing on data gathered during a fourteen-month study of reading practices among poor and working-class girls, this essay explores the challenges of creating a responsive and critical reading pedagogy across boundaries of class. Set largely in a summer and after-school reading program for pre-teen girls, the study addressed the question of how a…

  11. Textual Concept Critical Analysis: Toward a Research Approach for Language Studies

    ERIC Educational Resources Information Center

    Osborn, Terry A.; Reagan, Timothy G.; Freiberg, Jo Ann

    2011-01-01

    When the International Society for Language Studies (ISLS) was founded in 2002 and the journal that is now "Critical Inquiry in Language Studies (CILS)" was in the planning stages, we recognized a need for an interdisciplinary, or perhaps even transdisciplinary (see Kaufman, Moss, & Osborn, 2003), venue for the publication of research on language…

  12. Master Teachers' Critical Practice and Student Learning Strategies: A Case Study in an Urban School District

    ERIC Educational Resources Information Center

    Paulmann, Greg

    2009-01-01

    Job embedded professional development in the K-12 education setting has long been discussed and debated. This study builds on standards of critical reflection and thinking using the National Institute for Excellence in Education's Teacher Advancement Program's master teacher model as a conduit between theory and practice. A study of professional…

  13. Social Studies: A Field of Dreams?

    ERIC Educational Resources Information Center

    Larrabee, Larry J.

    1991-01-01

    Discusses the development of social studies from the social upheaval of the industrial revolution to the present. Defines social studies as an integrated, interdisciplinary curriculum for instruction in citizenship education. Lists objectives as gaining necessary knowledge, developing skill in processing information, examining one's own beliefs,…

  14. Field of Study in College and Lifetime Earnings in the United States

    PubMed Central

    Kim, ChangHwan; Tamborini, Christopher R.; Sakamoto, Arthur

    2016-01-01

    Our understanding about the relationship between education and lifetime earnings often neglects differences by field of study. Utilizing data that matches respondents in the Survey of Income and Program Participation to their longitudinal earnings records based on administrative tax information, we investigate the trajectories of annual earnings following the same individuals over 20 years and then estimate the long-term effects of field of study on earnings for U.S. men and women. Our results provide new evidence revealing large lifetime earnings gaps across field of study. We show important differences in individuals’ earnings trajectories across the different stages of the work-life by field of study. In addition, the gaps in 40-year (i.e., ages 20 to 59) median lifetime earnings among college graduates by field of study are larger, in many instances, than the median gap between high school graduates and college graduates overall. Significant variation is also found among graduate degree holders. Our results uncover important similarities and differences between men and women with regard to the long-term earnings differentials associated with field of study. In general, these findings underscore field of study as a critical dimension of horizontal stratification in educational attainment. Other implications of the empirical findings are also discussed. PMID:28042177

  15. Simulated Laboratory/Field Study of Evolution.

    ERIC Educational Resources Information Center

    Dubowsky, Nathan; Hartman, Elliott M., Jr.

    1986-01-01

    Immediately following a lecture discussion on early hominid characteristics and behavior, students participate in a laboratory study of bipedal locomotion based on an analysis of footprints. The development and use of this simulation are described. (JN)

  16. Correlation between in-field critical currents in Zr-added (Gd, Y)Ba2Cu3Ox superconducting tapes at 30 and 77 K

    SciTech Connect

    Selvamanickam, V; Xu, A; Liu, Y; Khatri, ND; Lei, C; Chen, Y; Galstyan, E; Majkic, G

    2014-03-11

    Critical current (I-c) values of 1384 Lambda/12 mm, corresponding to a critical current density of 12.47 MA cm(-2) and a pinning force of 374 GN m(-3), have been achieved at 30 K, 3 T in the orientation of field parallel to the c axis (B parallel to c) in (Gd, Y)BaCuO tapes with 15 mol% Zr addition made by metal organic chemical vapor deposition (MOCVD). These tapes show pinning force levels as high as 453 GN m(-3) at 30 K. An analysis of the properties of 24-28 (Gd, Y)BaCuO tapes with 15 mol% Zr addition showed a lack of correlation between their critical currents at 30 K, 3 T (B parallel to c) and I-c values both at 77 K, zero field and at 77 K, 1 T (B parallel to c). However, a strong correlation was found between the critical currents at 30 K, 3 T and at 77 K, 3 T (B parallel to c). It has also been discovered that the minimum critical current (I-c, (min)) value at 77 K, 3 T has no influence on the I-c,I- (min) value at 30 K, 3 T, and it in turn depends on the ratio of the I-c values in the orientations of field parallel and perpendicular to the c axis at 77 K, 3 T.

  17. A cross-sectional study examining factors related to critical thinking in nursing.

    PubMed

    Lang, Gary Morris; Beach, Nick Lee; Patrician, Patricia A; Martin, Cheryl

    2013-01-01

    The purpose of this study was to examine critical thinking skills among registered nurses who work in a military hospital. Sixty-five nurses were administered the Health Sciences Reasoning Test to obtain scores in inductive reasoning, deductive reasoning, interpretation, analysis, and evaluation skills. Results showed no significant association between critical thinking skills and years of experience; however, differences were identified among racial/ethnic groups. It is hoped that findings from this study create a platform for dialogue among staff development nurses who are best situated to develop strategies that address these issues.

  18. Critical points in the 16-moment approximation. [plasma flow in laboratory and space plasmas study

    NASA Technical Reports Server (NTRS)

    Yasseen, F.; Retterer, J. M.

    1991-01-01

    The singular points in steady state, field-aligned plasma transport models based on velocity moment theory are examined. In particular, two separate singular points in the equations obtained from the 16-moment approximation are identified. These equations are presented in a form that makes the singularities apparent, and they are solved in a simple illustrative case. The singular points, one occurring at the sonic point and the other at a critical value of the parallel heat flux, give rise to different outflow regimes, characterized generically by different asymptotic behavior. The existence of the different outflow regimes separated by the heat flux critical point has been only hinted at in previous discussions of numerical simulation of the polar wind.

  19. Spinor Field Realizations of Non-critical W2,4 String Based on Linear W1,2,4 Algebra

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Jie; Liu, Yu-Xiao

    2006-10-01

    In this paper, we investigate the spinor field realizations of the W2,4 algebra, making use of the fact that the W2,4 algebra can be linearized through the addition of a spin-1 current. And then the nilpotent BRST charges of the spinor non-critical W2,4 string were built with these realizations.

  20. Temperature dependence of the upper critical field of high- Tc superconductors from isothermal magnetization data: influence of a temperature dependent Ginzburg-Landau parameter

    NASA Astrophysics Data System (ADS)

    Landau, I. L.; Ott, H. R.

    2003-11-01

    We show that the scaling procedure, recently proposed for the evaluation of the temperature variation of the normalized upper critical field of type-II superconductors, may easily be modified in order to take into account a possible temperature dependence of the Ginzburg-Landau parameter κ. As an example we consider κ( T) as it follows from the microscopic theory of superconductivity.

  1. Framing in the Field: A Case Study

    ERIC Educational Resources Information Center

    Benjamin, Diane

    2009-01-01

    Strategic Frame Analysis can inform the daily practice of policy advocates by bringing an evidence-based communications approach to their work. This case study of FrameWorks' decade-long association with the national Kids Count Network shares stories from advocates who are transforming their communications strategies, resulting in more effective…

  2. Effective field study of ising model on a double perovskite structure

    NASA Astrophysics Data System (ADS)

    Ngantso, G. Dimitri; El Amraoui, Y.; Benyoussef, A.; El Kenz, A.

    2017-02-01

    By using the effective field theory (EFT), the mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model adapted to a double perovskite structure has been studied. The EFT calculations have been carried out from Ising Hamiltonian by taking into account first and second nearest-neighbors interactions and the crystal and external magnetic fields. Both first- and second-order phase transitions have been found in phase diagrams of interest. Depending on crystal-field values, the thermodynamic behavior of total magnetization indicated the compensation phenomenon existence. The hysteresis behaviors are studied by investigating the reduced magnetic field dependence of total magnetization and a series of hysteresis loops are shown for different reduced temperatures around the critical one.

  3. Studies on Quantum Field Theory and Statistical Mechanics

    NASA Astrophysics Data System (ADS)

    Zhang, Shoucheng

    This dissertation is a summary of research in various areas of theoretical physics and is divided into three parts. In the first part, quantum fluctuations of the recently proposed superconducting cosmic strings are studied. It is found that vortices on the string world sheet represent an important class of fluctuation modes which tend to disorder the system. Both heuristic arguments and detailed renormalization group analysis reveal that these vortices do not appear in bound pairs but rather form a gas of free vortices. Based on this observation we argue that this fluctuation mode violates the topological conservation law on which superconductivity is based. Anomalies and topological aspects of supersymmetric quantum field theories are studied in the second part of this dissertation. Using the superspace formulation of the N = 1 spinning string, we obtain a path integral measure which is free from the world-sheet general coordinate as well as the supersymmetry anomalies and therefore determine the conformal anomaly and critical dimension of the spinning string. We also apply Fujikawa's formalism to computer the chiral anomaly in conformal as well as ordinary supergravity. Finally, we given a Noether-method construction of the supersymmetrized Chern-Simons term in five dimensional supergravity. In the last part of this dissertation, the soliton excitations in the quarter-filled Peierls-Hubbard model are investigated in both the large and the small U limit. For a strictly one dimensional system at zero temperature, we find that solitons in both limits are in one-to-one correspondence, while in the presence of weak three dimensional couplings or at finite temperature, the large U systems differ qualitatively from the small U systems in that the spin associated with the solitons ceases to be a sharp quantum observable.

  4. Vadose Zone Transport Field Study: Status Report

    SciTech Connect

    Gee, Glendon W.; Ward, Anderson L.

    2001-11-30

    Studies were initiated at the Hanford Site to evaluate the process controlling the transport of fluids in the vadose zone and to develop a reliable database upon which vadose-zone transport models can be calibrated. These models are needed to evaluate contaminant migration through the vadose zone to underlying groundwaters at Hanford. A study site that had previously been extensively characterized using geophysical monitoring techniques was selected in the 200 E Area. Techniques used previously included neutron probe for water content, spectral gamma logging for radionuclide tracers, and gamma scattering for wet bulk density. Building on the characterization efforts of the past 20 years, the site was instrumented to facilitate the comparison of nine vadose-zone characterization methods: advanced tensiometers, neutron probe, electrical resistance tomography (ERT), high-resolution resistivity (HRR), electromagnetic induction imaging (EMI), cross-borehole radar (XBR), and cross-borehole seismic (XBS). Soil coring was used to obtain soil samples for analyzing ionic and isotopic tracers.

  5. Adaptive radiations: From field to genomic studies

    PubMed Central

    Hodges, Scott A.; Derieg, Nathan J.

    2009-01-01

    Adaptive radiations were central to Darwin's formation of his theory of natural selection, and today they are still the centerpiece for many studies of adaptation and speciation. Here, we review the advantages of adaptive radiations, especially recent ones, for detecting evolutionary trends and the genetic dissection of adaptive traits. We focus on Aquilegia as a primary example of these advantages and highlight progress in understanding the genetic basis of flower color. Phylogenetic analysis of Aquilegia indicates that flower color transitions proceed by changes in the types of anthocyanin pigments produced or their complete loss. Biochemical, crossing, and gene expression studies have provided a wealth of information about the genetic basis of these transitions in Aquilegia. To obtain both enzymatic and regulatory candidate genes for the entire flavonoid pathway, which produces anthocyanins, we used a combination of sequence searches of the Aquilegia Gene Index, phylogenetic analyses, and the isolation of novel sequences by using degenerate PCR and RACE. In total we identified 34 genes that are likely involved in the flavonoid pathway. A number of these genes appear to be single copy in Aquilegia and thus variation in their expression may have been key for floral color evolution. Future studies will be able to use these sequences along with next-generation sequencing technologies to follow expression and sequence variation at the population level. The genetic dissection of other adaptive traits in Aquilegia should also be possible soon as genomic resources such as whole-genome sequencing become available. PMID:19528644

  6. Coastal Studies in a Comprehensive Summer Field Geology Course.

    ERIC Educational Resources Information Center

    Cameron, Barry; Jones, Richard J.

    1979-01-01

    Describes a college geology course that incorporates a coastal segment. Field studies are done on Plum Island and include examining beaches, dune fields, and an adjacent marsh and spit. Topics include sedimentation, coastal geomorphology, botanical effects, and coastal studies methodology. (MA)

  7. Field Study Manual to Freshwater and Estuarine Habitats.

    ERIC Educational Resources Information Center

    Georgia State Dept. of Education, Atlanta.

    This field studies manual, developed by biology students in the 1971 Georgia Governor's Honors Program, was designed for collection of data pertinent to freshwater and estuarine habitats. In addition to the various methods of sampling the ecosystem and for quantification of the data, instructions for dividing the field study into three logical…

  8. The Use of Interrupted Case Studies to Enhance Critical Thinking Skills in Biology

    PubMed Central

    White, Tracy K.; Whitaker, Paul; Gonya, Terri; Hein, Richard; Kroening, Dubear; Lee, Kevin; Lee, Laura; Lukowiak, Andrea; Hayes, Elizabeth

    2009-01-01

    There has been a dramatic increase in the availability of case studies for use in the biology classroom, and perceptions of the effectiveness of case-study-based learning are overwhelmingly positive. Here we report the results of a study in which we evaluated the ability of interrupted case studies to improve critical thinking in the context of experimental design and the conventions of data interpretation. Students were assessed using further case studies designed to evaluate their ability to recognize and articulate problematic approaches to these elements of experimentation. Our work reveals that case studies have broad utility in the classroom. In addition to demonstrating a small but statistically significant increase in the number of students capable of critically evaluating selected aspects of experimental design, we also observed increased student engagement and documented widespread misconceptions regarding the conventions of data acquisition and analysis. PMID:23653687

  9. Large field-induced irreversibility in Ni-Mn based Heusler shape-memory alloys: A pulsed magnetic field study

    NASA Astrophysics Data System (ADS)

    Nayak, A. K.; Mejia, C. Salazar; D'Souza, S. W.; Chadov, S.; Skourski, Y.; Felser, C.; Nicklas, M.

    2014-12-01

    We present a pulsed magnetic field study on the magnetic and magnetostriction properties of Ni-Mn-Z (Z =In , Sn, and Sb) based Heusler shape-memory alloys. These materials generally display a field-induced magnetostructural transition that could lead to an irreversible phase transition, when measured near the martensitic transition temperature. Here, we show that independently of the transition temperature, the critical field for the phase transition sensitively depends on the main-group element in the sample. Irrespective of their compositions, all samples display a magnetization of around 2 μB/f .u . in the martensite phase and about 6 μB/f .u . in the cubic austenite phase. Our magnetic and magnetostriction measurements at low temperatures exhibit a partial or complete arrest of the high-field austenite phase below the reverse martensitic transition. This results in a large irreversibility with a hysteresis width as high as 24 T. We introduce a theoretical model to discuss the experimental results.

  10. Study of Several Potentials as Scalar Field Dark Matter Candidates

    SciTech Connect

    Matos, Tonatiuh; Vazquez-Gonzalez, Alberto; Magan a, Juan

    2008-12-04

    In this work we study several scalar field potentials as a plausible candidate to be the dark matter in the universe. The main idea is the following; if the scalar field is an ultralight boson particle, it condensates like a Bose-Einstein system at very early times and forms the basic structure of the Universe. Real scalar fields collapse in equilibrium configurations which oscillate in space-time (oscillatons). The cosmological behavior of the field equations are solved using the dynamical system formalism. We use the current cosmological parameters as constraints for the free parameters of the scalar field potentials. We are able to reproduce very well the cosmological predictions of the standard {lambda}CDM model with some scalar field potentials. Therefore, scalar field dark matter seems to be a good alternative to be the nature of the dark matter of the universe.

  11. Flow-Field Simulations and Hemolysis Estimates for the Food and Drug Administration Critical Path Initiative Centrifugal Blood Pump.

    PubMed

    Heck, Margaret L; Yen, Allen; Snyder, Trevor A; O'Rear, Edgar A; Papavassiliou, Dimitrios V

    2017-02-07

    The design of blood pumps for use in ventricular assist devices, which provide life-saving circulatory support in patients with heart failure, require remarkable precision and attention to detail to replicate the functionality of the native heart. The United States Food and Drug Administration (FDA) initiated a Critical Path Initiative to standardize and facilitate the use of computational fluid dynamics in the study and development of these devices. As a part of the study, a simplified centrifugal blood pump model generated by computer-aided design was released to universities and laboratories nationwide. The effects of changes in fluid rheology due to temperature, hematocrit, and turbulent flow on key metrics of the FDA pump were examined in depth using results from a finite volume-based commercial computational fluid dynamics code. Differences in blood damage indices obtained using Eulerian and Lagrangian formulations were considered. These results are presented and discussed awaiting future validation using experimental results, which will be released by the FDA at a future date.

  12. High School Research and Critical Literacy: Social Studies with and Despite Wikipedia

    ERIC Educational Resources Information Center

    Harouni, Houman

    2009-01-01

    Drawing on experiences in his social studies classroom, Houman Harouni evaluates both the challenges and possibilities of helping high school students develop critical research skills. The author describes how he used Wikipedia to design classroom activities that address issues of authorship, neutrality, and reliability in information gathering.…

  13. Critical Issues in K-12 Service-Learning: Case Studies and Reflections.

    ERIC Educational Resources Information Center

    Gulati-Partee, Gita, Ed.; Finger, William R., Ed.

    This compilation includes practical and transferable principles that can be used by service-learning practitioners. The 39 case studies and personal essays in the compilation are organized around critical issues in strengthening long-term institutional and community support for K-12 service-learning programs. Each article describes how the issue…

  14. Developing Critical and Historical Thinking Skills in Middle Grades Social Studies

    ERIC Educational Resources Information Center

    Waring, Scott M.; Robinson, Kirk S.

    2010-01-01

    The author describes a social studies unit designed to help students develop critical thinking skills. The lessons give students opportunities to analyze multiple perspectives, use multiple sources when conducting research, and construct historical narratives through the creation of a digital historical biography.

  15. The Case Study Method: Critical Thinking Enhanced by Effective Teacher Questioning Skills.

    ERIC Educational Resources Information Center

    Wood, Alexander T.; Anderson, Carol H.

    A diverse body of educational research provides strong theoretical support for the development of higher order cognitive learning skills through case teaching. Case study teachers can improve their questioning skills to enhance students' critical thinking. The theoretical background for questioning in case method teaching and learning is traceable…

  16. The Experience of Critical Self-Reflection by Life Coaches: A Phenomenological Study

    ERIC Educational Resources Information Center

    Shaw, Deanna Lynn

    2012-01-01

    The purpose of this study was to describe the experience of critical self-reflection by life coaches. Life coaching is expanding within many disciplines including education, health care, business, social work, and wellness. Life coaching involves a coach working with an individual or groups aimed at effecting change for professional and personal…

  17. Nuclear-criticality-safety studies of interest to TMI-2 recovery operations

    SciTech Connect

    Thomas, J.T.

    1982-10-01

    A series of criticality calculations was made on simple systems representative of possible situations that may be found during recovery operations at TMI-2. While not specific to physical conditions that may be encountered, the effect of oxide fines on the neutron multiplication factor may be estimated from the relative effects observed in the systems studied.

  18. Writing Shapes Thinking: Investigative Study of Preservice Teachers Reading, Writing to Learn, and Critical Thinking

    ERIC Educational Resources Information Center

    Sanchez, Bernice; Lewis, Katie D.

    2014-01-01

    Teacher Preparation Programs must work towards not only preparing preservice teachers to have knowledge of classroom pedagogy but also must expand preservice teachers understanding of content knowledge as well as to develop higher-order thinking which includes thinking critically. This mixed methods study examined how writing shapes thinking and…

  19. The Process of Stress Assignment in Reading Aloud: Critical Issues from Studies on Italian

    ERIC Educational Resources Information Center

    Sulpizio, Simone; Burani, Cristina; Colombo, Lucia

    2015-01-01

    In polysyllabic languages the assignment of stress is crucial for understanding the reading process. Here we review empirical evidence, drawn mainly from studies on Italian, and discuss critical issues in understanding reading. We first discuss the lexical and sublexical mechanisms responsible for stress assignment and propose that the former is…

  20. Transforming Teaching and Learning in ELT through Critical Pedagogy: An International Study

    ERIC Educational Resources Information Center

    Jeyaraj, Joanna Joseph; Harland, Tony

    2014-01-01

    In this study, the voices of academics who use critical pedagogy in English language teaching have been brought together to shed light on how this practice transforms teaching and learning. Data were collected through semistructured interviews with academics from Canada, Hong Kong, Korea, Malaysia, New Zealand, United Kingdom, United States, and…