Science.gov

Sample records for critical field study

  1. Anomalous critical fields in quantum critical superconductors.

    PubMed

    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(As(1-x)P(x))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. 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

  3. 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.

  4. Heat transport study of field-tuned quantum criticality in CeIrIn5

    NASA Astrophysics Data System (ADS)

    Shakeripour, H.; Tanatar, M. A.; Petrovic, C.; Taillefer, Louis

    2016-02-01

    The in-plane electrical resistivity, ρ , and thermal conductivity, κ , of the heavy-fermion superconductor CeIrIn5 were measured down to 40 mK in magnetic fields up to 11 T applied along the c axis. For all fields above Hc 2=4 T of filamentary superconductivity, we find that the ratio of heat and charge conductivities in the T →0 limit obeys the Wiedemann-Franz law, κ /T =L0/ρ , where L0=2.45 ×10-8 WΩ K-2 is the Sommerfeld value of the Lorenz number. The temperature-dependent parts of both the electrical and thermal resistivity, w ≡T /L0κ , follow the functional dependence expected for the Fermi liquid theory of metals with ρ -ρ0=A T2 , w -w0=B T2 , with ρ0=w0 and B ≈2 A . The coefficient B does not show a significant field dependence even upon approaching Hc 2=0.4 T of the bulk superconducting state. The weak response to the magnetic field is in stark contrast with the behavior found in the closely related CeCoIn5, in which the field-tuned quantum critical point coincides with Hc 2. The value of the electron-electron mass enhancement, as judged by the A and B coefficients, is about one order of magnitude reduced in CeIrIn5 as compared to CeCoIn5 (in spite of the fact that the zero field γ0 in CeIrIn5 is twice as large as γ0 in CeCoIn5), which suggests that the material is significantly farther away from the magnetic quantum critical point at bulk Hc 2 and at all of the studied fields. A suppressed Kadowaki-Woods ratio in CeIrIn5 compared to CeCoIn5 suggests a notably more localized nature of f electrons in the compound.

  5. 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.

  6. Critical temperature enhancement of topological superconductors: A dynamical mean-field study

    NASA Astrophysics Data System (ADS)

    Nagai, Yuki; Hoshino, Shintaro; Ota, Yukihiro

    2016-06-01

    We show that a critical temperature Tc for spin-singlet two-dimensional superconductivity is enhanced by a cooperation between the Zeeman magnetic field and the Rashba spin-orbit coupling, where a superconductivity becomes topologically nontrivial below Tc. The dynamical mean-field theory with the segment-based hybridization-expansion continuous-time quantum Monte Carlo impurity solver is used for accurately evaluating a critical temperature, without any fermion sign problem. A strong-coupling approach shows that spin-flip-driven local pair hopping leads to part of this enhancement, especially effects of the magnetic field. We propose physical settings suitable for verifying the present calculations, a one-atom-layer system on Si(111) and ionic-liquid-based electric double-layer transistors.

  7. Studies of the critical electric field and L valley offset of a semiconductor characterized by terahertz radiation

    NASA Astrophysics Data System (ADS)

    Hwang, J. S.; Lin, H. C.; Chang, C. K.; Wang, T. S.; Lin, K. I.; Chang, L. S.; Lu, Y. T.

    2007-02-01

    The amplitudes of terahertz radiation are measured for a series of GaAs surface intrinsic-n + (SIN +) structures with various built-in surface electric fields as the bias. As the surface field is lower than the so-called "critical electric field" related with the energy difference between the Γ to L valley of the semiconductor, the amplitude is proportional to the product of the surface field and the number of photo-excited carriers. As the intensity of surface field exceeds the critical field, the THz amplitude is independent of the surface field but proportional the number of the photo-excited carriers. Our study proposed two optimal conditions for an SIN + structure to serve as a THz emitter: the width of its intrinsic layer is nearly equal to the penetration depth of the pump beam, and the intensity of built-in electric field is nearly equal to the critical electric field. Notably, the critical field determined from the THz amplitude under various electric fields provides one way to estimate the Γ to L valley splitting in semiconductors.

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. Superconductivity in Strong Magnetic Field (Greater Than Upper Critical Field)

    SciTech Connect

    Tessema, G.X.; Gamble, B.K.; Skove, M.J.; Lacerda, A.H.; Mielke, C.H.

    1998-08-22

    The National High Magnetic Field Laboratory, funded by the National Science Foundation and other US federal Agencies, has in recent years built a wide range of magnetic fields, DC 25 to 35 Tesla, short pulse 50 - 60 Tesla, and quasi-continuous 60 Tesla. Future plans are to push the frontiers to 45 Tesla DC and 70 to 100 Tesla pulse. This user facility, is open for national and international users, and creates an excellent tool for materials research (metals, semiconductors, superconductors, biological systems ..., etc). Here we present results of a systematic study of the upper critical field of a novel superconducting material which is considered a promising candidate for the search for superconductivity beyond H{sub c2} as proposed by several new theories. These theories predict that superconductors with low carrier density can reenter the superconducting phase beyond the conventional upper critical field H{sub c2}. This negates the conventional thinking that superconductivity and magnetic fields are antagonistic.

  13. 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

  14. Critical Education Studies

    ERIC Educational Resources Information Center

    Boxley, Simon

    2015-01-01

    Education Studies as an academic discipline within HE in the UK is a contested area. One thing most Education Studies programmes might agree on is that they are "critical". But what is a genuinely critical Education Studies degree? And, how could such a programme survive within the hostile neoliberal environment of the contemporary UK?…

  15. 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.

  16. The Use of Critical Thinking in Social Science Textbooks of High School: A Field Study of Fars Province in Iran

    ERIC Educational Resources Information Center

    Hashemi, Seyed Ahmad

    2011-01-01

    This study aims at investigating the use of critical thinking in high school social science textbooks based on Fars Province teachers' attitudes in order to present a model for textbook development. To achieve this goal, the use of the following skills in the social science textbooks was analyzed: reasoning, questioning, assessment of examples and…

  17. 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.

  18. Bridging Fields at a Critical Time

    ERIC Educational Resources Information Center

    Baggaley, Jon

    2014-01-01

    The launch of the "Journal of Learning for Development" occurs at a critical time for the education and development field. The "massive open online course" concept currently being implemented by Western educators is considered as a potential cost-saver in developing nations also. MOOCs based on reliable pedagogical principles…

  19. Solid-liquid surface tensions of critical nuclei and nucleation barriers from a phase-field-crystal study of a model binary alloy using finite system sizes.

    PubMed

    Choudhary, Muhammad Ajmal; Kundin, Julia; Emmerich, Heike; Oettel, Martin

    2014-08-01

    Phase-field-crystal (PFC) modeling has emerged as a computationally efficient tool to address crystal growth phenomena on atomistic length and diffusive time scales. We use a two-dimensional phase-field-crystal model for a binary system based on Elder et al. [Phys. Rev. B 75, 064107 (2007)] to study critical nuclei and their liquid-solid phase boundaries, in particular the nucleus size dependence of the liquid-solid interface tension as well as of the nucleation barrier. Critical nuclei are stabilized in finite systems of various sizes, however, the extracted interface tension as function of the nucleus radius r is independent of system size. We suggest a phenomenological expression to describe the dependence of the extracted interface tension on the nucleus radius r for the liquid-solid system. Moreover, the numerical PFC results show that this dependency can not be fully described by the nonclassical Tolman formula. PMID:25215738

  20. Solid-liquid surface tensions of critical nuclei and nucleation barriers from a phase-field-crystal study of a model binary alloy using finite system sizes

    NASA Astrophysics Data System (ADS)

    Choudhary, Muhammad Ajmal; Kundin, Julia; Emmerich, Heike; Oettel, Martin

    2014-08-01

    Phase-field-crystal (PFC) modeling has emerged as a computationally efficient tool to address crystal growth phenomena on atomistic length and diffusive time scales. We use a two-dimensional phase-field-crystal model for a binary system based on Elder et al. [Phys. Rev. B 75, 064107 (2007), 10.1103/PhysRevB.75.064107] to study critical nuclei and their liquid-solid phase boundaries, in particular the nucleus size dependence of the liquid-solid interface tension as well as of the nucleation barrier. Critical nuclei are stabilized in finite systems of various sizes, however, the extracted interface tension as function of the nucleus radius r is independent of system size. We suggest a phenomenological expression to describe the dependence of the extracted interface tension on the nucleus radius r for the liquid-solid system. Moreover, the numerical PFC results show that this dependency can not be fully described by the nonclassical Tolman formula.

  1. 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.

  2. 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.

  3. Further Evidence for Weak Field Critical Adsorption

    NASA Astrophysics Data System (ADS)

    Franck, Carl; Peach, Sarah; Polak, Robert D.

    1997-03-01

    Following our unexpected discovery of weak short-range surface field effects on the critical mixing transition of a binary liquid,(N.S. Desai, S. Peach, and C. Franck, Phys. Rev. E52), 4129 (1995) we have directly addressed our concern that these results might have been affected by surface heterogeneity. We have used octadecyltrichlorosilane (OTS) to cover borosilicate glass surfaces with partial monolayers. Reference substrates with identical treatment had OTS patches no larger than the bulk correlation length within 40 mK of the critical transition. The present reflectivity experiment employs uncovered reference surfaces for comparison in a single sample cell. We confirm our earlier discovery of a persistent (down to 3 mK above the critical point) deviation of the degree of critical adsorption from the maximum value expected. We have also improved our earlier analysis in order to examine the scaling behavior. Supported by the NSF under DMR-9320910, and through central facilities of the Materials Science Center at Cornell Univ.

  4. 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

  5. A Critically Reflective Social Studies?

    ERIC Educational Resources Information Center

    Clarke, Marge

    1990-01-01

    Examines social studies in the twenty-first century from a critical theory perspective. Traces critical reflection's origins from Marxist educational theories to Jurgen Habermas's critical theory. Highlights Fred Newmann's curricular model, "Education for Citizen Action," for developing competent action in public affairs. Advocates infusing…

  6. Conformal field theory of critical Casimir forces

    NASA Astrophysics Data System (ADS)

    Emig, Thorsten; Bimonte, Giuseppe; Kardar, Mehran

    2015-03-01

    Thermal fluctuations of a critical system induce long-ranged Casimir forces between objects that couple to the underlying field. For two dimensional conformal field theories (CFT) we derive exact results for the Casimir interaction for a deformed strip and for two compact objects of arbitrary shape in terms of the free energy of a standard region (circular ring or flat strip) whose dimension is determined by the mutual capacitance of two conductors with the objects' shape; and a purely geometric energy that is proportional to conformal charge of the CFT, but otherwise super-universal in that it depends only on the shapes and is independent of boundary conditions and other details. The effect of inhomogenous boundary conditions is also discussed.

  7. Three studies in quantum criticality

    NASA Astrophysics Data System (ADS)

    Ramazashvili, Revaz

    This thesis has been unified by the general topic of quantum criticality, an area of active current research which draws inspiration from the ongoing experiments on a host of T = 0 transitions of various nature, such as magnetic transitions, metal-insulator and superconductor-insulator transitions, Quantum Hall plateau-to-plateau transitions, and many others. In addition to the experimental motivation, the field is being driven by the internal demands of the theory, as many fundamental questions regarding e.g. the nature of the order parameter or the effects of disorder still remain to be answered. Chapter 1, the Introduction, briefly covers the key theoretical concepts and describes relevant materials. In Chapter 2 of the thesis, it is shown that, for a superconductor with a gap which is odd with respect to reflection in the Fermi surface, it is possible to suppress the transition temperature to zero without violating either the time reversal or the translational invariance. This feature is a qualitative hallmark of such superconductors, distinguishing them from isotropic BCS superconductors as well as from superconductors with anisotropic pairing. The pair propagator is calculated dose to this quantum critical point along with several observable quantities. It is argued that experimental studies of a superconducting quantum critical point in clean materials may provide a diagnostic tool for unusual mechanisms of superconductivity. Chapter 3 of the thesis concentrates on an s-wave superconductor near a quantum critical point driven by pairbreaking disorder. The disorder average of the pair propagator is calculated diagrammatically, and the low-temperature thermodynamic and transport properties are evaluated. It is argued that, in the absence of the effects of glassiness, this description should hold equally well for a strong-coupling superconductor at a quantum critical point. Chapter 4 presents a phenomenological theory of the quantum critical point observed in

  8. The critical level of water deficit causing a decrease in human exercise performance: a practical field study.

    PubMed

    Yoshida, Tetsuya; Takanishi, Toshimasa; Nakai, Seiichi; Yorimoto, Akira; Morimoto, Taketoshi

    2002-10-01

    To analyse the critical level of water deficit which causes a decrease in aerobic and anaerobic exercise performance, a step test score (STS) and 10 s maximal anaerobic power (MAP) output during cycling exercise were measured in two experiments (Ex-1, n=7, and Ex-2, n=9), before and after baseball practice, using subjects who played regularly. The measurements in both Ex-1 and Ex-2 were repeated under four conditions of fluid ingestion (FI) (FI of 80%, 60%, 40%, and 20% of the total sweat loss) on hot summer days. The subjects were allowed free access to a sports beverage, maintained at 10-15 degrees C, within any given FI condition during the exercise. The [mean (SEM)] duration of the exercise and the environmental conditions (wet bulb globe temperature) were similar between Ex-1 [3.52 (0.14) h and 29.2 (0.6) degrees C, respectively] and Ex-2 [3.82 (0.12) h and 29.2 (0.4) degrees C, respectively]. In both Ex-1 and Ex-2, the loss of body mass (Delta m(b)) increased significantly as FI decreased. In Ex-1, the STS significantly decreased ( P<0.05) at values of delta m(b) in excess of 2.4 (0.2)% (40%FI). In Ex-2, the MAP remained unchanged at values of delta m(b) up to 2.5 (0.3)% (40%FI), while the MAP significantly decreased ( P<0.05) at values of delta m(b) of 3.9 (0.2)% (20%FI). These results suggest that there is a critical level of water deficit at which a decrease in aerobic and anaerobic performance occurs, and that aerobic performance may be more adversely influenced by dehydration than anaerobic power output during exercise-induced dehydration.

  9. 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)…

  10. Upper critical field study in organic superconductor beta"-(ET) sulfur pentafluoride methylene difluoromethylene sulfur trioxide: Possibility of the FFLO state

    NASA Astrophysics Data System (ADS)

    Cho, Kyuil

    2009-07-01

    We conducted in-plane rf penetration depth measurements by using the tunnel diode oscillator technique. In the metal-free-all-organic superconductor beta"-(ET) 2SF5CH2 CF2SO3 the penetration depth measurements were carried out by changing the strength and direction of the magnetic field. When the magnetic field is applied perpendicular to the conducting planes, the Shubnikov-de Haas quantum oscillations are observed revealing the geometry of the Fermi surface. When the magnetic field is applied parallel to the conducting planes, the low temperature upper critical fields are found to exceed the Pauli paramagnetic limiting field calculated by using a semi-empirical method. Furthermore, we found the possible existence of an additional superconducting state which stablizes above the Pauli limiting field when the superconducting order parameter lowers its free energy by becoming spatially inhomogeneous in a high magnetic field. The additional superconducting state is called the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state and was predicted independently by Fulde and Ferrell [10] and by Larkin and Ovchinnikov [11] in 1964. The signature of the FFLO state observed in this thesis occurs as a kink during the superconducting vortex state (SCVS)-to-FFLO phase transition. In organic superconductors there have been several reports of the possible existence of the FFLO state [23, 24, 25, 62]. Even though these reports are all based on the fact that the upper critical field increases as the temperature decreases down to very low temperature, the obvious phase transition between the SCVS and the FFLO states has not been observed. To our best knowledge, the FFLO observation in beta"-(ET)2SF5CH2 CF2SO3 in this thesis is the first clear success which shows both the upper critical field enhancement at low temperature and the phase transition between the SCVS and the FFLO states.

  11. Identification of nematic superconductivity from the upper critical field

    NASA Astrophysics Data System (ADS)

    Venderbos, Jörn W. F.; Kozii, Vladyslav; Fu, Liang

    2016-09-01

    Recent nuclear magnetic resonance and specific heat measurements have provided concurring evidence of spontaneously broken rotational symmetry in the superconducting state of the doped topological insulator CuxBi2Se3 . This suggests that the pairing symmetry corresponds to a two-dimensional representation of the D3 d crystal point group, and that CuxBi2Se3 is a nematic superconductor. In this paper, we present a comprehensive study of the upper critical field Hc 2 of nematic superconductors within Ginzburg-Landau (GL) theory. Contrary to typical GL theories which have an emergent U(1) rotational symmetry obscuring the discrete symmetry of the crystal, the theory of two-component superconductors in trigonal D3 d crystals reflects the true crystal rotation symmetry. This has direct implications for the upper critical field. First, Hc 2 of trigonal superconductors with D3 d symmetry exhibits a sixfold anisotropy in the basal plane. Second, when the degeneracy of the two components is lifted by, e.g., uniaxial strain, Hc 2 exhibits a twofold anisotropy with characteristic angle and temperature dependence. Our thorough study shows that measurement of the upper critical field is a direct method of detecting nematic superconductivity, which is directly applicable to recently-discovered trigonal superconductors CuxBi2Se3 , SrxBi2Se3 , NbxBi2Se3 , and TlxBi2Te3 .

  12. The upper critical field in doped MgCNi 3

    NASA Astrophysics Data System (ADS)

    Andrzejewski, Bartłomiej; Klimczuk, Tomasz; Cava, Robert J.

    2007-09-01

    The upper critical field (Hc2) in the doped and undoped intermetallic superconductor MgCNi3 is studied. In MgCNi3-xMx (M = Ru, Fe), Hc2 decreases monotonically as x increases. In the case of Fe doping, Hc2 changes most dramatically: from 10.7 T at x = 0 to 7.9 T at x = 0.015, which might be caused by the fact that the 3d electrons in Fe break superconducting Cooper-pairs. Although, doping carbon on the boron site in Mg(B1-xCx)2 has a substantial effect on the upper critical field, here we report that for MgC1-xBxNi3, boron substitution slightly increases Hc2 for the lowest B doping level, x = 0.04, only. For x > 0.04 the upper critical field decreases slowly as x increases. The initial slope of Hc2(T) in MgC0.96B0.04Ni3 is nearly the same as that of pure MgCNi3.

  13. 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.

  14. Thermodynamic critical fields in high T c superconductivity

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.; Johnson, Keith H.

    1988-06-01

    Using the free electron approximation, a real space mechanism of how magnetic fields of sufficient strength destroy the superconducting state is outlined. Using the resultant equation together with the molecular orbital model of superconductivity 1,2, the thermodynamic critical magnetic field is calculated and compared to experiment for type I elemental superconductors and type II superconductors, including high-Tc superconductors. The expression for critical field compares favorably with an expression derived by Schrieffer.

  15. Critical Assessment of Current Force Fields. Short Peptide Test Case.

    PubMed

    Vymětal, Jiří; Vondrášek, Jiří

    2013-01-01

    The applicability of molecular dynamics simulations for studies of protein folding or intrinsically disordered proteins critically depends on quality of energetic functions-force fields. The four popular force fields for biomolecular simulations, CHARMM22/CMAP, AMBER FF03, AMBER FF99SB, and OPLS-AA/L, were compared in prediction of conformational propensities of all common proteinogenic amino acids. The minimalistic model of terminally block amino acids (dipeptides) was chosen for assessment of side chain effects on backbone propensities. The precise metadynamics simulations revealed striking inconsistency of trends in conformational preferences as manifested by investigated force fields for both backbone and side chains. To trace this disapproval between force fields, the two related AMBER force fields were studied more closely. In the cases of FF99SB and FF03, we uncovered that the distinct tends were driven by different charge models. Additionally, the effects of recent correction for side chain torsion (FF99SB-ILDN) were examined on affected amino acids and exposed significant coupling between free energy profiles and propensities of backbone and side chain conformers. These findings have important consequences for further force field development.

  16. 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…

  17. 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.

  18. Upper Critical Fields of Moleular-Based Spin Ladders

    NASA Astrophysics Data System (ADS)

    Keith, Brian; Landee, Chris; Turnbull, Mark; Harrison, Neil

    2010-03-01

    The upper critical (saturation) fields of several spin ladders was found using a high field, short pulse magnet at LANL. These compounds include Cu(Quinoxaline)Cl2, Cu(Quinoxaline)Br2, Cu(2,3 dimethylpyrazine)Cl2, Cu(2,3 dimethylpyrazine)Br2, Cu(methylpyrazine)Br2, and Cu(methylpyrazine)Cl2. The data were taken at temperatures as low as 460 mK with a pulsed field strength as high as 57 tesla. The upper critical fields were estimated by considerations of overcoming the exchange energies associated with all the compounds. These energies were extracted from model fits to the susceptibility data. These estimations agree reasonably well with the experimentally observed upper critical fields. We report on these results and compare the data to simulations of the magnetization as a function of field as a further check to confirm that these compounds obey the associated model systems.

  19. Upper critical field of the noncentrosymmetric superconductor BiPd

    NASA Astrophysics Data System (ADS)

    Peets, Darren C.; Maldonado, Ana; Enayat, Mostafa; Sun, Zhixiang; Wahl, Peter; Schnyder, Andreas P.

    2016-05-01

    The superconducting parameters and upper critical field of the noncentrosymmetric superconductor BiPd have proven contentious. This material is of particular interest because it is a rare example of a 4 f -electron-free noncentrosymmetric superconductor of which crystals may be grown and cleaved, enabling surface-sensitive spectroscopies. Here, using bulk probes augmented by tunneling data on defects, we establish that the lower of the previously reported upper critical fields corresponds to the bulk transition. The material behaves as a nearly weak-coupled BCS s -wave superconductor, and we report its superconducting parameters as drawn from the bulk upper critical field. Possible reasons behind the order-of-magnitude discrepancy in the reported upper critical fields are discussed.

  20. 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…

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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. PMID:25318561

  6. Anisotropic Upper Critical Field of Iron-Based Superconductors

    NASA Astrophysics Data System (ADS)

    Huang, Ruiqi; She, Weilong

    2016-09-01

    The upper critical field and its anisotropy are the easiest properties to examine in the research of iron-based superconductors. Based on warped cylindrical Fermi surface models, we investigate the temperature and angle dependence of the upper critical field in detail by employing the quasi-classical formalism of the Werthamer-Helfand-Hohenberg (WHH) theory. Our numerical results reveal the anisotropy of the upper critical field, which may be caused by an anisotropic gap function (e.g., d-wave pairing) or an anisotropic Fermi surface, respectively. Further, according to our analysis, this anisotropy can be modulated by the deformation of the Fermi surface and will be strongly suppressed by the Pauli paramagnetic effect.

  7. Electric field obtained from an elliptic critical-state model for anisotropic type-II superconductors

    NASA Astrophysics Data System (ADS)

    Romero-Salazar, C.; Hernández-Flores, O. A.

    2016-02-01

    The conventional elliptic critical-state models (ECSM) establish that the electric field vector is zero when it flows a critical current density in a type-II superconductor. This proposal incorporates a finite electric field on the ECSM to study samples with anisotropic-current-carrying capacity. Our theoretical scheme has the advantage of being able to dispense of a material law which drives the electric field magnitude, however, it does not consider the magnetic history of the superconductor.

  8. 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.

  9. 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.

  10. Electromagnetic Near Field Measurements of Two Critical Assemblies

    NASA Astrophysics Data System (ADS)

    Goettee, Jeffrey; Goorley, Tim; Mayo, Douglas; Myers, William; Goda, Joetta; Sage, Frank

    2015-04-01

    Preliminary measurements of the fast metal nuclear reactors at the National Criticality Experiments Research Center (NCERC) and at White Sands Missile Range (WSMR) within the past year characterize the very near field environment of these critical assemblies. Both reactors are fast, highly enriched uranium metal reactors and can be operated in a burst mode above prompt supercritical. Initial measurements of the electric and the magnetic fields within the reactor cell are consistent between the two facilities, and begin to describe the dependance on distance and polarization as might be assumed from initial Monte Carlo modelling of these facilities. The amplitude and time variation of the electric and magnetic fields are consistent with burst time scales. The polarization is consistent with the geometry of the source and with Compton scattering from fission gammas as the dominant ionization mechanism. An overview of the two fast neutron sources and the excursion dynamics, the experimental details, and summary of the modelling calculations will be provided as background.

  11. 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…

  12. 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.

  13. 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.

  14. High critical field NbC superconductor on carbon spheres.

    PubMed

    Bhattacharjee, Kaustav; Pati, Satya Prakash; Maity, Arjun

    2016-06-01

    Niobium carbide (NbC) nanoparticles embedded on the surface of carbon spheres (CS) were synthesized at 1350 °C by the carbothermal reduction of niobium oxide precursor in flowing argon (Nbc@CS). The morphology, crystal structure, and magnetic properties of the hybrid nanocomposite were investigated by means of electron microscopy, X-ray diffraction and a superconducting quantum interference device. It was found that the NbC@CS nanocomposites exhibit type-II superconductivity with a critical temperature (Tc) of 8-12 K, typical for stoichiometric NbC. The superconducting hysteresis loop reveals several interesting traits, including strong vortex pinning, the presence of asymmetry and a high penetration field. Moreover, the sample shows much improved irreversible (Hirr), lower (Hc1) and upper (Hc2) critical fields. The coherence length (ξ), penetration depth (λ), and Ginzburg-Landau (κ) parameters for the sample were estimated to be 9.78 nm, 33 nm and 3.39, respectively.

  15. 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.

  16. 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.

  17. Conformal field theory of critical Casimir interactions in 2D

    NASA Astrophysics Data System (ADS)

    Bimonte, G.; Emig, T.; Kardar, M.

    2013-10-01

    Thermal fluctuations of a critical system induce long-ranged Casimir forces between objects that couple to the underlying field. For two-dimensional (2D) conformal field theories (CFT) we derive an exact result for the Casimir interaction between two objects of arbitrary shape, in terms of 1) the free energy of a circular ring whose radii are determined by the mutual capacitance of two conductors with the objects' shape; and 2) a purely geometric energy that is proportional to the conformal charge of the CFT, but otherwise super-universal in that it depends only on the shapes and is independent of boundary conditions and other details.

  18. 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

  19. 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…

  20. Apparent anisotropy effects of upper critical field in high- textured superconducting Nb-Ti tapes

    NASA Astrophysics Data System (ADS)

    Guryev, V. V.; Shavkin, S. V.; Kruglov, V. S.; Volkov, P. V.; Vasiliev, A. L.; Ovcharov, A. V.; Likhachev, I. A.; Pashaev, E. M.; Svetogorov, R. D.; Zubavichus, Y. V.

    2016-09-01

    Analysis of the voltage-field characteristics of superconducting niobium-titanium tapes is the objective of this work. We used both the original cold-rolled and heat-treated tapes, whose structure and texture we had studied in detail. We observed anisotropy in the upper critical field and the reduction of the transition width with increasing angle between the plane of tape and the direction of the magnetic field. In addition, we have registered a significant difference of the upper critical field values, obtained from the voltage-field characteristics and field dependence of the pinning force. Considering our results, we suggest an explanation of the observed features within the macro-inhomogeneity model.

  1. High critical field NbC superconductor on carbon spheres.

    PubMed

    Bhattacharjee, Kaustav; Pati, Satya Prakash; Maity, Arjun

    2016-06-01

    Niobium carbide (NbC) nanoparticles embedded on the surface of carbon spheres (CS) were synthesized at 1350 °C by the carbothermal reduction of niobium oxide precursor in flowing argon (Nbc@CS). The morphology, crystal structure, and magnetic properties of the hybrid nanocomposite were investigated by means of electron microscopy, X-ray diffraction and a superconducting quantum interference device. It was found that the NbC@CS nanocomposites exhibit type-II superconductivity with a critical temperature (Tc) of 8-12 K, typical for stoichiometric NbC. The superconducting hysteresis loop reveals several interesting traits, including strong vortex pinning, the presence of asymmetry and a high penetration field. Moreover, the sample shows much improved irreversible (Hirr), lower (Hc1) and upper (Hc2) critical fields. The coherence length (ξ), penetration depth (λ), and Ginzburg-Landau (κ) parameters for the sample were estimated to be 9.78 nm, 33 nm and 3.39, respectively. PMID:27212586

  2. Field and Classroom Strategies for Improving Critical Thinking on Introductory Geoscience Field Trips

    NASA Astrophysics Data System (ADS)

    Boryta, M. D.; Walker, B.; Long, T.

    2011-12-01

    Although field experiences for introductory geoscience students have tremendous potential with respect to recruiting and retaining majors and enriching their understanding of geologic concepts, implementing field trips that promote critical thinking for introductory students is challenging. After observing that many of our students struggled at applying concepts they learned in the classroom to unfamiliar field areas, we developed teaching strategies and instructional materials for the classroom and the field to promote critical thinking and self-directed learning on field trips. We assessed the effectiveness of these modifications using video, interviews, student field trip reports and field notebooks. Student co-inquirers played a vital role during the project in field instruction and data analysis. We will discuss think-alouds, the importance of repetition in the classroom, allowing adequate processing time, field trip preparation exercises for the classroom, and other significant pedagogical changes that we made. Video of students in the field at the beginning, middle, and end of the project will be shown to illustrate the progressive changes in students' approaches to outcrop analysis over the course of the project.

  3. 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.

  4. Acquired visual field defects rehabilitation: critical review and perspectives.

    PubMed

    Pouget, M-C; Lévy-Bencheton, D; Prost, M; Tilikete, C; Husain, M; Jacquin-Courtois, S

    2012-02-01

    Visual field deficit (VFD) is one of the most commonly observed symptoms following brain injury. Persistent VFD and defective exploratory oculomotor scanning patterns often cause severe impairment in daily activities, particularly as regards visual exploration and reading. Homonymous hemianopia is consequently a powerful negative predictor of patient outcome. In spite of these quantitative and qualitative factors, there currently exists no consensus on rehabilitative therapy and treatment. Different approaches have nevertheless been developed, all of them having one therapeutic principle in common; repeated practice of a specific visual task, with the hope/expectation that improved performance will extend to a wide range of ecologically useful visual functions. The four main available methods aim at replacing part of the intact visual field with part of the damaged visual field (optical therapy using prisms), at partially restoring the lost visual field region (restorative therapies), at stimulating detection capacities in the blind field (stimulation or blindsight) or at substituting for the lost region by reorganizing the control of visual information processing and eye movements (compensatory therapies). This review explores the key data relative to these different approaches in terms of behavioral or imagery results. It also aims at critically analyzing the advantages and limits of each one. The importance of strict assessment in terms of deficiencies or disabilities is underlined. Finally, upon consideration of these data taken as a whole, it is suggested that efficient treatment would probably have to associate general components and more specific elements, according to what may be done with regard to other aspects of cognitive rehabilitation.

  5. Magnetic behavior of dirty multiband superconductors near the upper critical field

    NASA Astrophysics Data System (ADS)

    Silaev, Mikhail

    2016-06-01

    Magnetic properties of dirty multiband superconductors near the upper critical field are studied. The parameter κ2 characterizing magnetization slope is shown to have a significant temperature variation which is quite sensitive to the pairing interactions and relative strengths of intraband impurity scattering. In contrast to single-band superconductors the increase of κ2 at low temperatures can be arbitrarily large determined by the ratio of maximal and minimal diffusion coefficients in different bands. Temperature dependencies of κ2(T ) in two-band MgB2 and iron-based superconductors are shown to be much more sensitive to the multiband effects than the upper critical field Hc 2(T ) .

  6. 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.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1994-04-01

    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.

  9. Upper critical field of electron-doped Pr2-xCexCuO4-δ in parallel magnetic fields

    NASA Astrophysics Data System (ADS)

    Li, Pengcheng; Balakirev, F. F.; Greene, R. L.

    2007-05-01

    We report a systematic study of the resistive superconducting transition in the electron-doped cuprates Pr2-xCexCuO4-δ down to 1.5K for magnetic field up to 58T applied parallel to the conducting ab planes. We find that the zero-temperature parallel critical field [Hc2‖ab(0)] exceeds 58T for the underdoped and optimally doped films. For the overdoped films, 58T is sufficient to suppress the superconductivity. We also find that the Zeeman energy μBHc2‖ab(0) reaches the superconducting gap (Δ0) , i.e., μBHc2‖ab(0)≃Δ0 , for all the dopings, strongly suggesting that the parallel critical field is determined by the Pauli paramagnetic limit in electron-doped cuprates.

  10. 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.

  11. Critical currents of YBCO tapes and Bi-2212 wires at different temperatures and magnetic fields

    SciTech Connect

    Lombardo, V.; Barzi, e.; Turrioni, D.; Zlobin, A.V.; /Fermilab

    2010-08-01

    Design studies for the cooling channel of a Muon Collider call for straight and helical solenoids generating field well in excess of the critical fields of state of the art Low Temperature Superconductors (LTS) such as Nb{sub 3}Sn or NbTi. Therefore, High Temperature Superconductors (HTS) will need to be used for the manufacturing of all or certain sections of such magnets to be able to generate and withstand the field levels at the cryogenic temperatures required by the new machine. In this work, two major High Temperature Superconductors - Bi2212 round wires and YBCO coated conductor tapes - are investigated to understand how critical current density of such conductors scales as a function of external field and operating temperature. This is vital information to make conductor choices depending on the application and to proceed with the design of such magnets.

  12. 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.

  13. How self-organized criticality works: A unified mean-field picture

    NASA Astrophysics Data System (ADS)

    Vespignani, Alessandro; Zapperi, Stefano

    1998-06-01

    We present a unified dynamical mean-field theory, based on the single site approximation to the master-equation, for stochastic self-organized critical models. In particular, we analyze in detail the properties of sandpile and forest-fire (FF) models. In analogy with other nonequilibrium critical phenomena, we identify an order parameter with the density of ``active'' sites, and control parameters with the driving rates. Depending on the values of the control parameters, the system is shown to reach a subcritical (absorbing) or supercritical (active) stationary state. Criticality is analyzed in terms of the singularities of the zero-field susceptibility. In the limit of vanishing control parameters, the stationary state displays scaling characteristics of self-organized criticality (SOC). We show that this limit corresponds to the breakdown of space-time locality in the dynamical rules of the models. We define a complete set of critical exponents, describing the scaling of order parameter, response functions, susceptibility and correlation length in the subcritical and supercritical states. In the subcritical state, the response of the system to small perturbations takes place in avalanches. We analyze their scaling behavior in relation with branching processes. In sandpile models, because of conservation laws, a critical exponents subset displays mean-field values (ν=12 and γ=1) in any dimensions. We treat bulk and boundary dissipation and introduce a critical exponent relating dissipation and finite size effects. We present numerical simulations that confirm our results. In the case of the forest-fire model, our approach can distinguish between different regimes (SOC-FF and deterministic FF) studied in the literature, and determine the full spectrum of critical exponents.

  14. 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.

  15. 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.

  16. 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.

  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. Phase Correlations at Neighboring Intensity Critical Points in Gaussian Random Wave Fields

    NASA Astrophysics Data System (ADS)

    Freund, Isaac

    1998-11-01

    Phase correlations are studied for neighboring critical points of the intensity in an isotropic Gaussian random wave field. Significant correlations and anticorrelations are found that extend out to at least the fifth nearest neighbors. A theoretical interpretation of the empirical data is attempted within the framework of the phase autocorrelation and the probability-density functions of extended two-dimensional random phase fields. It is found, however, that adaptations of these theoretical models are unable to account satisfactorily, or even qualitatively, for the extensive phase correlations that are present in these fields.

  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. Non-mean-field critical exponent in a mean-field model: dynamics versus statistical mechanics.

    PubMed

    Ogawa, Shun; Patelli, Aurelio; Yamaguchi, Yoshiyuki Y

    2014-03-01

    Mean-field theory tells us that the classical critical exponent of susceptibility is twice that of magnetization. However, linear response theory based on the Vlasov equation, which is naturally introduced by the mean-field nature, makes the former exponent half of the latter for families of quasistationary states having second order phase transitions in the Hamiltonian mean-field model and its variances, in the low-energy phase. We clarify that this strange exponent is due to the existence of Casimir invariants which trap the system in a quasistationary state for a time scale diverging with the system size. The theoretical prediction is numerically confirmed by N-body simulations for the equilibrium states and a family of quasistationary states. PMID:24730814

  1. Upper critical field in electron-doped Pr2-xCexCuO4-δ in parallel magnetic fields

    NASA Astrophysics Data System (ADS)

    Li, Pengcheng; Balakirev, F. F.; Greene, R. L.

    2007-03-01

    We report a comprehensive study of the resistive superconducting transition in the electron-doped Pr2-xCexCuO4-δ films down to 1.5K for magnetic field up to 58T applied parallel to the conducting ab-planes. We find that the parallel critical field (Hc2//ab) exceeds 58T for underdoped and optimally doped films. For the overdoped films, 58T is sufficient to suppress the superconductivity. An Hc2//ab -T phase diagram is established. A comparison between our experimental results and theories for orbital and spin pairbreaking effects will be presented.

  2. 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.

  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. Electron profile stiffness and critical gradient studies

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

    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 ∇Te. Electron stiffness was found to slowly increase with toroidal rotation velocity. A critical inverse temperature gradient scale length 1/LC ˜ 3 m-1 was identified at ρ =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 -∇Te, were fit reasonably well by a model containing a critical inverse temperature gradient scale length and varying linearly with 1/LT above the threshold.

  5. 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.

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

    PubMed

    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 10(8) 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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.

  8. 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

  9. 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.

  10. [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.

  11. 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.

  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. 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.…

  15. 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…

  16. Superconducting critical fields of alkali and alkaline-earth intercalates of MoS2

    NASA Technical Reports Server (NTRS)

    Woollam, J. A.; Somoano, R. B.

    1976-01-01

    Results are reported for measurements of the critical-field anisotropy and temperature dependence of group-VIB semiconductor MoS2 intercalated with the alkali and alkaline-earth metals Na, K, Rb, Cs, and Sr. The temperature dependences are compared with present theories on the relation between critical field and transition temperature in the clean and dirty limits over the reduced-temperature range from 1 to 0.1. The critical-field anisotropy data are compared with predictions based on coupled-layers and thin-film ('independent-layers') models. It is found that the critical-field boundaries are steep in all cases, that the fields are greater than theoretical predictions at low temperatures, and that an unusual positive curvature in the temperature dependence appears which may be related to the high anisotropy of the layer structure. The results show that materials with the largest ionic intercalate atom diameters and hexagonal structures (K, Rb, and Cs compounds) have the highest critical temperatures, critical fields, and critical-boundary slopes; the critical fields of these materials are observed to exceed the paramagnetic limiting fields.

  17. 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.

  18. The infinite-range quantum transverse Ising spin glass: new estimate of the critical line via thermo-field method

    NASA Astrophysics Data System (ADS)

    Kopeć, T. K.; Büttner, G.; Usadel, K. D.

    1990-10-01

    The infinite-range quantum Ising spin glass in a transverse field Γ is studied by means of the thermo-field dynamics as a substitute for the n-replica trick. A new estimate of the critical line Tc(Γ) is obtained by the improved treatment of the dynamic self-interaction - in considerable agreement with the Trotter-Suzuki method.

  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. Critical-field theory of the Kondo lattice model in two dimensions

    SciTech Connect

    Kim, Ki-Seok

    2005-05-15

    In the context of the U(1) slave-boson theory we derive a critical-field theory near the quantum-critical point of the Kondo lattice model in two spatial dimensions. First, we argue that strong gauge fluctuations in the U(1) slave-boson theory give rise to confinement between spinons and holons, thus causing 'neutralized' spinons in association with the slave-boson U(1) gauge field. Second, we show that critical fluctuations of Kondo singlets near the quantum-critical point result in a new U(1) gauge field. This emergent gauge field has nothing to do with the slave-boson U(1) gauge field. Third, we find that the slave-boson U(1) gauge field can be exactly integrated out in the low-energy limit. As a result we find a critical-field theory in terms of renormalized conduction electrons and neutralized spinons interacting via the new emergent U(1) gauge field. Based on this critical-field theory we obtain the temperature dependence of the specific heat and the imaginary part of the self-energy of the renormalized electrons. These quantities display non-Fermi-liquid behavior near the quantum-critical point.

  1. 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

  2. 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…

  3. Microbial field pilot study

    SciTech Connect

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

    1991-01-01

    The objective of this project is to perform a microbially 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 or the reservoir and increase sweep efficiency. Injection of nutrient stimulates the growth and metabolism of reservoir bacteria, which produces beneficial products to enhance oil recovery. Sometimes, chemical treatments are used to clean or condition injection water. Such a chemical treatment has been initiated by Sullivan and Company at the Southeast Vassar Vertz Sand Unit. The unit injection water was treated with a mixture of water, methanol, isopropyl alcohol, and three proprietary chemicals. To determine if the chemicals would have an impact on the pilot, it was important to determine the effects of the chemical additives on the growth and metabolism of the bacteria from wells in this field. Two types of media were used: a mineral salts medium with molasses and nitrate, and this medium with 25 ppm of the treatment chemicals added. Samples were collected anaerobically from each of two wells, 1A-9 and 7-2. A sample from each well was inoculated and cultured in the broth tubes of molasses-nitrate medium with and without the chemicals. Culturing temperature was 35{degrees}C. Absorbance, pressure and cell number were checked to determine if the chemicals affected the growth and metabolism of bacteria in the brine samples. 12 figs.

  4. Force-Field Analysis: Incorporating Critical Thinking in Goal Setting.

    ERIC Educational Resources Information Center

    Hustedde, Ron; Score, Michael

    1995-01-01

    Force field analysis encourages members to examine the probability of reaching agreed-upon goals. It can help groups avoid working toward goals that are unlikely to be reached. In every situation are three forces: forces that encourage maintenance of the status quo or change; driving or helping forces that push toward change; and restraining…

  5. 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.

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

    PubMed

    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. PMID:27078308

  7. 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

  8. Intermittent criticality revealed in ULF magnetic fields prior to the 11 March 2011 Tohoku earthquake (MW = 9)

    NASA Astrophysics Data System (ADS)

    Contoyiannis, Y.; Potirakis, S. M.; Eftaxias, K.; Hayakawa, M.; Schekotov, A.

    2016-06-01

    The ultra-low-frequency (ULF) magnetic variations recorded prior to the 11 March 2011 Tohoku earthquake (EQ) are analyzed using the method of critical fluctuations (MCF). The first application of this specific method to ULF magnetic variations is performed on the unprocessed H- (horizontal) and Z- (vertical) components, as well as on the unprocessed total intensity, F, of the recorded magnetic field. The motivation for the present study was given by recent research results reporting criticality features in the ULF magnetic fields prior to the 2011 Tohoku EQ. These results call for a further analysis in order to verify the existence of criticality embedded in the specific ULF recordings using an independent method, as well as to investigate the type of the embedded criticality. The application of MCF indeed verifies the existence of criticality in the ULF magnetic fields a few days to one week before the occurrence of the main shock. Specifically, clear signatures of intermittent criticality are found in the recordings of 4 March 2011, while indications of critical behavior are also found in 3 and 6 March recordings, although not of the "stability" of those of 4 March. Moreover, it is found that only the ULF data of the nearest, to the epicenter of the EQ, geomagnetic observatory presented criticality. This finding further corroborates the view that the presented signal is indeed a precursor to the specific EQ.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Moosavi, S. Amin; Montakhab, Afshin

    2015-11-01

    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), 10.1103/PhysRevE.89.052139] 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.

  11. 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. PMID:26651741

  12. Field-induced quadrupolar quantum criticality in PrV2Al20

    NASA Astrophysics Data System (ADS)

    Shimura, Yasuyuki; Tsujimoto, Masaki; Zeng, Bin; Balicas, Luis; Sakai, Akito; Nakatsuji, Satoru

    2015-06-01

    PrV2Al20 is a heavy-fermion superconductor based on the cubic Γ3 doublet that exhibits nonmagnetic quadrupolar ordering below ˜0.6 K. Our magnetotransport study on PrV2Al20 reveals field-induced quadrupolar quantum criticality at μ0Hc˜11 T applied along the [111] direction. Near the critical field μ0Hc required to suppress the quadrupolar state, we find a marked enhancement of the resistivity ρ (H ,T ) , a divergent quasiparticle effective mass and concomitant non-Fermi-liquid (NFL) behavior [i.e., ρ (T ) ∝Tn with n ≤0.5 ]. We also observe the Shubnikov-de Haas effect above μ0Hc , indicating effective mass enhancement or m*/m0˜10 . This reveals the competition between the nonmagnetic Kondo effect and the intersite quadrupolar coupling which leads to pronounced NFL behavior in an extensive region of T and μ0H emerging from the quantum-critical point.

  13. 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…

  14. Deviation from mean-field behavior in a low molecular weight critical polymer blend

    NASA Astrophysics Data System (ADS)

    Hair, D. W.; Hobbie, E. K.; Nakatani, A. I.; Han, C. C.

    1992-06-01

    A deviation from mean-field behavior is observed in the static susceptibility and correlation length measured with small angle neutron scattering as a function of temperature near the phase boundary of a relatively low molecular weight critical polymer mixture. The possibility of a fluctuation influenced crossover from mean-field to nonmean-field behavior is considered.

  15. 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.

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

    DOE PAGES

    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 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

  17. Researching Critical Literacy: A Critical Study of Analysis of Classroom Discourse

    ERIC Educational Resources Information Center

    Van Sluys, Katie; Lewison, Mitzi; Flint, Amy Seely

    2006-01-01

    Studying critical literacies includes examining how research practices influence what is learned about classroom activity and the world. This article highlights the processes and practices used in studying 1 classroom conversation. The data, drawn from an elementary school classroom of a Critical Literacy in Action teacher-researcher group member,…

  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. 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…

  20. Critical language and discourse study: their transformative relevance for critical nursing inquiry.

    PubMed

    Boutain, D M

    1999-03-01

    A pragmatic view of language and a critical study of discourse can advance nursing inquiry toward the study of racism, heterosexism, classism, and health. In critical language inquiry notions about humans, health and illness are seen as constructed in societal discourses. Critical language inquiry challenges nurse researchers to theorize not which research questions to ask, but how to ask research questions that broaden knowledge about the interconnections among language, discourse, health, and society. Critical discourse analysis, as a methodology, can be of significant utility in exploring the relationships among health, discourse, power, and society.

  1. 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.

  2. Statistics of Critical Points of Gaussian Fields on Large-Dimensional Spaces

    SciTech Connect

    Bray, Alan J.; Dean, David S.

    2007-04-13

    We calculate the average number of critical points of a Gaussian field on a high-dimensional space as a function of their energy and their index. Our results give a complete picture of the organization of critical points and are of relevance to glassy and disordered systems and landscape scenarios coming from the anthropic approach to string theory.

  3. 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.

  4. 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.

  5. Critical loss radius in a Penning trap subject to multipole fields

    SciTech Connect

    Fajans, J.; Madsen, N.; Robicheaux, F.

    2008-03-15

    When particles in a Penning trap are subject to a magnetic multipole field, those beyond a critical radius will be lost. The critical radius depends on the history by which the field is applied, and can be much smaller if the particles are injected into a preexisting multipole than if the particles are subject to a ramped multipole. Both cases are relevant to ongoing experiments designed to trap antihydrogen.

  6. Pressure-dependent upper critical field of FeSe superconductor

    NASA Astrophysics Data System (ADS)

    Kaluarachchi, Udhara; Taufour, Valentin; Böhmer, Anna; Tanatar, Makariy; Bud'Ko, Sergey; Kogan, Vladimir; Prozorov, Ruslan; Canfield, Paul

    In FeSe, the superconducting transition temperature Tc (~ 9 K at ambient pressure) has a complicated pressure dependence with a local maximum near p1 ~ 0.8 GPa and a local minimum at p2 ~ 1.2GPa. In this work, we study the upper critical field, Hc 2 , c (T) , of FeSe using c-axis resistivity measurements under hydrostatic pressure up to 1.56 GPa with the magnetic field H ∥c. Application of both current and magnetic field along the same axis reduces the flux flow motion and give sharper transition in applied fields. We observe a non-monotonic evolution of the slope of Hc 2 , c (T) |Tc with pressure, with changes around p1 and p2. We employ two-band orbital Hc 2 , c calculation to show that the data can be explained using the Fermi velocities extracted from the recent quantum oscillations study [ 1 ] over the whole pressure range. [ 1 ] Terashima et al. arXiv:1510.01840v1 [cond-mat.supr-con] (2015) This work is supported by the US DOE, Basic Energy Sciences under Contract No. DE-AC02-07CH11358.

  7. 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.

  8. 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.…

  9. 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…

  10. Through Queers' Eyes: Critical Educational Ethnography in Queer Studies

    ERIC Educational Resources Information Center

    Chang, Yin-Kun

    2005-01-01

    In this paper, the author provides an overview of the theoretical background of critical educational research--namely, critical pedagogy--and discusses the relationship between critical pedagogy and queer issues. In doing this, the author addresses the current strengths and weaknesses of queer studies in education. The author suggests that making…

  11. 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.

  12. 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.

  13. Critical Thinking in Adult Education: An Elusive Quest for a Definition of the Field.

    ERIC Educational Resources Information Center

    Vaske, Joann M.

    A study attempted to derive the meaning of critical thinking in adult education through exploration of graduate faculty members' perceptions and perceived practices of critical thinking in adult education. Grounded theory methodology was used to explain the meaning of critical thinking to adult educators. The primary data sources were unstructured…

  14. Quantum oscillations of the critical current and high-field superconducting proximity in ballistic graphene

    NASA Astrophysics Data System (ADS)

    Ben Shalom, M.; Zhu, M. J.; Fal'Ko, V. I.; Mishchenko, A.; Kretinin, A. V.; Novoselov, K. S.; Woods, C. R.; Watanabe, K.; Taniguchi, T.; Geim, A. K.; Prance, J. R.

    2016-04-01

    Graphene-based Josephson junctions provide a novel platform for studying the proximity effect due to graphene’s unique electronic spectrum and the possibility to tune junction properties by gate voltage. Here we describe graphene junctions with a mean free path of several micrometres, low contact resistance and large supercurrents. Such devices exhibit pronounced Fabry-Pérot oscillations not only in the normal-state resistance but also in the critical current. The proximity effect is mostly suppressed in magnetic fields below 10 mT, showing the conventional Fraunhofer pattern. Unexpectedly, some proximity survives even in fields higher than 1 T. Superconducting states randomly appear and disappear as a function of field and carrier concentration, and each of them exhibits a supercurrent carrying capacity close to the universal quantum limit. We attribute the high-field Josephson effect to mesoscopic Andreev states that persist near graphene edges. Our work reveals new proximity regimes that can be controlled by quantum confinement and cyclotron motion.

  15. 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.

  16. Possibility of critical field enhancement due to field penetration in high-T/sub c/ sponges and thin films

    SciTech Connect

    Collings, E.W.; Markworth, A.J.; Marken, K.R. Jr.

    1989-03-01

    Magnetic susceptibility measurements of a sample of sintered high-T/sub c/ ceramic superconductor of nominal composition Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-y/ were conducted as function of temperature from liquid-He temperatures to T/sub c/. The fitted form of the susceptibility temperature dependence yielded a sample particle size that was only a few times larger than the field-penetration depth. The particle size was much less than the grain size and commensurate with the thickness of the optical twins. The occurence of field penetration between lamina about 0.2 to 0.7 /mu/m in half-thickness was predicted to lead to a small enhancement of the lower critical field. This prediction was compared with the results of an experiment in which the M(H) field sweep, initially +- 100 gauss, was incremented in small steps up to several kgauss. The results of the enhancement studies are also discussed in the light of Bean's early experiments on Pb sponges (in this case /lambda/ >> particle size) which exhibited spectacular enhancements of H/sub c/ in association with flux trapping at or between the Pb filaments. It is predicted that it should be possible, using presently available film-deposition techniques, to produce high-T/sub c/ films possessing several-fold enhancements of H/sub cl/ beyond the bulk value; and that as with the Pb sponges, the magnetization loops, even when taken within what passes for the Meissner state in such materials, will by hysteretic.

  17. Fluid phase separation inside a static periodic field: an effectively two-dimensional critical phenomenon.

    PubMed

    Vink, Richard L C; Neuhaus, Tim; Löwen, Hartmut

    2011-05-28

    When a fluid with a bulk liquid-vapor critical point is placed inside a static external field with spatial periodic oscillations in one direction, a new phase arises. This new phase-the so-called "zebra" phase-is characterized by an average density roughly between that of the liquid and vapor phases. The presence of the zebra phase gives rise to two new phase transitions: one from the vapor to the zebra phase, and one from the zebra to the liquid phase. At appropriate values of the temperature and chemical potential, the latter two transitions become critical. This phenomenon is called laser-induced condensation [I. O. Götze, J. M. Brader, M. Schmidt, and H. Löwen, Mol. Phys. 101, 1651 (2003)]. The purpose of this paper is to elucidate the nature of the critical points, using density functional theory and computer simulation of a colloid-polymer mixture. The main finding is that critical correlations develop in two-dimensional sheets perpendicular to the field direction, but not in the direction along the field: the critical correlations are thus effectively two-dimensional. Hence, static periodic fields provide a means to confine a fluid to effectively two dimensions. Away from criticality, the vapor-zebra and liquid-zebra transitions become first-order, but the associated surface tensions are extremely small. The consequences of the extremely small surface tensions on the nature of the two-phase coexistence regions are analyzed in detail.

  18. The Relation between Critical Thinking Abilities and Student Study Strategies.

    ERIC Educational Resources Information Center

    Hager, Paul; And Others

    1994-01-01

    A study of 54 first-year engineering students at an Australian university investigated their critical thinking skills as related to 3 kinds of study strategy: surface strategy; deep strategy; and achieving strategy. Results indicated a negative correlation between critical thinking ability and the achieving study strategy. Implications for…

  19. 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.

  20. Improved upper critical field in bulk-form magnesium diboride by mechanical alloying with carbon

    NASA Astrophysics Data System (ADS)

    Senkowicz, B. J.; Giencke, J. E.; Patnaik, S.; Eom, C. B.; Hellstrom, E. E.; Larbalestier, D. C.

    2005-05-01

    High-energy milling of magnesium diboride (MgB2) prereacted powder renders the material largely amorphous through extreme mechanical deformation and is suitable for mechanically alloying MgB2 with dopants including carbon. Bulk samples of milled carbon and MgB2 powders subjected to hot isostatic pressing and Mg vapor annealing have achieved upper critical fields in excess of 32T and critical current density approaching 106A /cm2.

  1. 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.

  2. 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.

  3. Critical behavior in a massless scalar field collapse with self-interaction potential

    NASA Astrophysics Data System (ADS)

    Zhang, Xuefeng; Lü, H.

    2015-02-01

    We examine a one-parameter family of analytical solutions representing spherically symmetric collapse of a nonlinear massless scalar field with self-interaction in an asymptotically flat spacetime. The time evolution exhibits a type of critical behavior. Depending on the scalar charge parameter q as compared to a critical value q*, the incoming scalar wave collapses either to a globally naked central singularity if q field) or to a scalar-hairy black hole if q >q* (strong field), both having finite asymptotic masses. Near the critical evolution, the black hole mass follows a product-logarithmic scaling law: -M2ln M ˜q -q* with 0 q*. The solution admits no self-similarity and satisfies the null and the strong energy conditions.

  4. 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.

  5. 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…

  6. Variation of critical current and n-value of 2G HTS tapes in external magnetic fields of different orientation

    NASA Astrophysics Data System (ADS)

    Sychugov, V. V.; Degtyarenko, P. N.; Ovcharov, A. V.; Shavkin, S. V.; Kruglov, V. S.; Vasiliev, A. L.; Volkov, P. V.; Chesnokov, Yu M.

    2016-09-01

    The in-field orientation dependence of critical current and n-value in second generation high temperature superconductive tapes was investigated. The samples were manufactured by Metalorganic Chemical Vapour Deposition method with BaZrO3 inclusions (SuperPower Inc.) and Pulsed Laser Deposition method (Bruker HTS). For samples of each kind of fabrication techniques we observed higher critical current value in the case of external magnetic field aligned along (or nearby) c-axis direction in comparison with one aligned along ab-plane. We analysed possible reasons for this effect. Angular dependences of the critical current and n-value were investigated. The microstructure images of superconductive layer of studied samples show tilt of BaZrO3 nanorods in MOCVD sample and high density of structural defects for PLD sample.

  7. Determination of the critical ionization distance and ionization zone during high-temperature field evaporation of molybdenum

    NASA Astrophysics Data System (ADS)

    Blashenkov, N. M.; Golubev, O. L.

    2016-07-01

    Steady-state field evaporation of molybdenum at high emitter temperatures ( T ˜ 2000 K) has been studied using a magnetic mass spectrometer equipped with a field ion source. Only low-charge ions (Mo+2 and Mo+) have been observed in the course of evaporation. The measured ion energies and evaporating field strengths ( F ev) were used to determine the critical ionization distances ( x cr) and ionization zones (Δ) for singly and doubly charged ions. The obtained x cr and Δ values show that the formation of ions takes place at a certain distance from the emitter surface.

  8. 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.

  9. Continuum theory of critical phenomena in polymer solutions: Formalism and mean field approximation

    NASA Astrophysics Data System (ADS)

    Goldstein, Raymond E.; Cherayil, Binny J.

    1989-06-01

    A theoretical description of the critical point of a polymer solution is formulated directly from the Edwards continuum model of polymers with two- and three-body excluded-volume interactions. A Hubbard-Stratonovich transformation analogous to that used in recent work on the liquid-vapor critical point of simple fluids is used to recast the grand partition function of the polymer solution as a functional integral over continuous fields. The resulting Landau-Ginzburg-Wilson (LGW) Hamiltonian is of the form of a generalized nonsymmetric n=1 component vector model, with operators directly related to certain connected correlation functions of a reference system. The latter is taken to be an ensemble of Gaussian chains with three-body excluded-volume repulsions, and the operators are computed in three dimensions by means of a perturbation theory that is rapidly convergent for long chains. A mean field theory of the functional integral yields a description of the critical point in which the power-law variations of the critical polymer volume fraction φc, critical temperature Tc, and critical amplitudes on polymerization index N are essentially identical to those found in the Flory-Huggins theory. In particular, we find φc ˜N-1/2, Tθ-Tc˜N-1/2 with (Tθ the theta temperature), and that the composition difference between coexisting phases varies with reduced temperature t as N-1/4t1/2. The mean field theory of the interfacial tension σ between coexisting phases near the critical point, developed by considering the LGW Hamiltonian for a weakly inhomogeneous solution, yields σ˜N-1/4t3/2, with the correlation length diverging as ξ˜N1/4t-1/2 within the same approximation, consistent with the mean field limit of de Gennes' scaling form. Generalizations to polydisperse systems are discussed.

  10. On the Second Critical Field for a Ginzburg-Landau Model with Ferromagnetic Interactions

    NASA Astrophysics Data System (ADS)

    Alama, Stan; Bronsard, Lia

    We consider a two-dimensional Ginzburg-Landau model for superconductors which exhibit ferromagnetic ordering in the superconducting phase, introduced by physicists to describe unconventional p-wave superconductors. In this model the magnetic field is directly coupled to a vector-valued order parameter in the energy functional. We show that one effect of spin coupling is to increase the second critical field Hc2, the value of the applied magnetic field at which superconductivity is lost in the bulk. Indeed, when the spin coupling is strong we show that the upper critical field is no longer present, confirming predictions in the physics literature. We treat the energy density as a measure, and show that the order parameter converges (as the Ginzburg-Landau parameter κ→∞) in an average sense to a constant determined by the average energy.

  11. 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…

  12. Secularism, Criticism, and Religious Studies Pedagogy

    ERIC Educational Resources Information Center

    Britt, Brian

    2006-01-01

    Secularization, the idea that religion would gradually diminish over time, was once widely assumed to be true by scholars of religion, but the unexpected resurgence of religious traditions has called it into question. Related debates on the distinction between religion and the secular have destabilized religious studies further. What does the…

  13. Stochastic geometry of critical curves, Schramm Loewner evolutions and conformal field theory

    NASA Astrophysics Data System (ADS)

    Gruzberg, Ilya A.

    2006-10-01

    Conformally invariant curves that appear at critical points in two-dimensional statistical mechanics systems and their fractal geometry have received a lot of attention in recent years. On the one hand, Schramm (2000 Israel J. Math. 118 221 (Preprint math.PR/9904022)) has invented a new rigorous as well as practical calculational approach to critical curves, based on a beautiful unification of conformal maps and stochastic processes, and by now known as Schramm-Loewner evolution (SLE). On the other hand, Duplantier (2000 Phys. Rev. Lett. 84 1363; Fractal Geometry and Applications: A Jubilee of Benot Mandelbrot: Part 2 (Proc. Symp. Pure Math. vol 72) (Providence, RI: American Mathematical Society) p 365 (Preprint math-ph/0303034)) has applied boundary quantum gravity methods to calculate exact multifractal exponents associated with critical curves. In the first part of this paper, I provide a pedagogical introduction to SLE. I present mathematical facts from the theory of conformal maps and stochastic processes related to SLE. Then I review basic properties of SLE and provide practical derivation of various interesting quantities related to critical curves, including fractal dimensions and crossing probabilities. The second part of the paper is devoted to a way of describing critical curves using boundary conformal field theory (CFT) in the so-called Coulomb gas formalism. This description provides an alternative (to quantum gravity) way of obtaining the multifractal spectrum of critical curves using only traditional methods of CFT based on free bosonic fields.

  14. 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,…

  15. 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.

  16. 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

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

    PubMed

    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

  18. Fabrication and characterization of scanning tunneling microscopy superconducting Nb tips having highly enhanced critical fields

    NASA Astrophysics Data System (ADS)

    Kohen, A.; Noat, Y.; Proslier, T.; Lacaze, E.; Aprili, M.; Sacks, W.; Roditchev, D.

    2005-02-01

    We report a simple method for the fabrication of Niobium superconducting (SC) tips for scanning tunneling microscopy which allow atomic resolution. The tips, formed in situ by the mechanical breaking of a niobium wire, reveal a clear SC gap of 1.5 meV and a critical temperature Tc = 9.2 ± 0.3 K, as deduced from Superconductor Insulator Normal metal (SIN) and Superconductor Insulator Superconductor (SIS) spectra. These match the values of bulk Nb samples. We systematically find an enhanced value of the critical magnetic field in which superconductivity in the tip is destroyed (around 1 T for some tips) up to five times larger than the critical field of bulk Nb (0.21 T). Such enhancement is attributed to a size effect at the tip apex.

  19. 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…

  20. Critical Points of the Electric Field from a Collection of Point Charges

    SciTech Connect

    Max, N; Weinkauf, T

    2007-02-16

    The electric field around a molecule is generated by the charge distribution of its constituents: positively charged atomic nuclei, which are well approximated by point charges, and negatively charged electrons, whose probability density distribution can be computed from quantum mechanics. For the purposes of molecular mechanics or dynamics, the charge distribution is often approximated by a collection of point charges, with either a single partial charge at each atomic nucleus position, representing both the nucleus and the electrons near it, or as several different point charges per atom. The critical points in the electric field are useful in visualizing its geometrical and topological structure, and can help in understanding the forces and motion it induces on a charged ion or neutral dipole. Most visualization tools for vector fields use only samples of the field on the vertices of a regular grid, and some sort of interpolation, for example, trilinear, on the grid cells. There is less risk of missing or misinterpreting topological features if they can be derived directly from the analytic formula for the field, rather than from its samples. This work presents a method which is guaranteed to find all the critical points of the electric field from a finite set of point charges. To visualize the field topology, we have modified the saddle connector method to use the analytic formula for the field.

  1. 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.

  2. 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.

  3. 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.

  4. EDF field operation computerization study

    SciTech Connect

    Guillot, L.; Pirus, D.

    2006-07-01

    The main control room has been the subject of extensive research and actions into improved operations assistance. On the other hand, few studies concern the need for field operation improvements, which have few assistance resources adapted to working requirements. Why? Past studies have shown the inability of technology to assume job constraints (insufficient screen readability, excessive equipment weight, prohibitive response times). Nevertheless, today new technologies can be adapted to field operations, and they justify further study. Real needs exist: local operations are often complex and are led in difficult environments where conditions prevent the use of paper-based documents. The issue is a significant risk of error which might impact plant reliability. The cumbersome nature of paper procedures, the working environment and the operational feed-back of experience led us to concentrate on the field operation to identify how it may be improved by the use of these new technologies. Such equipment would allow a better traceability and quality of actions. Possibility of communications with other plant personnel and information sharing may be also immediately available for all. This paper presents a study which intends to collect assistance requirements through an analysis of working practices and organizations with local personnel. Our aim is to identify which of those might benefit from IT support. This collection was obtained through interviews and observations. These two methods helped us to define potential needs, constraints and consequences for work organization. This paper presents the study results and findings, identifies professions which may benefit from the use of wearable computers and describes how the reliability and efficiency of human actions would be improved. Finally we identify design requirements and criteria to be used for writing the technical specifications for a test prototype. (authors)

  5. Critical Studies, the Liberal Arts, and Journalism Education.

    ERIC Educational Resources Information Center

    Parisi, Peter

    1992-01-01

    Discusses the relationship between journalism education and the liberal arts. Contends that critical, cultural, or qualitative studies provide a powerful focus for linking journalism education more firmly to the liberal arts. (SR)

  6. Discourse and Criticism in the Social Studies Classroom.

    ERIC Educational Resources Information Center

    Cherryholms, Cleo H.

    1982-01-01

    Examines the causes of student passivity in social studies classes. The need for more classroom discourse and free-flowing, critical inquiry into controversies is stressed. Strategies for improving classroom conditions to promote discourse are described. (AM)

  7. 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

  8. Field-induced quantum critical route to a Fermi liquid in high-temperature superconductors

    PubMed Central

    Shibauchi, Takasada; Krusin-Elbaum, Lia; Hasegawa, Masashi; Kasahara, Yuichi; Okazaki, Ryuji; Matsuda, Yuji

    2008-01-01

    In high-transition-temperature (Tc) superconductivity, charge doping is a natural tuning parameter that takes copper oxides from the antiferromagnet to the superconducting region. In the metallic state above Tc, the standard Landau's Fermi-liquid theory of metals as typified by the temperature squared (T2) dependence of resistivity appears to break down. Whether the origin of the non-Fermi-liquid behavior is related to physics specific to the cuprates is a fundamental question still under debate. We uncover a transformation from the non-Fermi-liquid state to a standard Fermi-liquid state driven not by doping but by magnetic field in the overdoped high-Tc superconductor Tl2Ba2CuO6+x. From the c-axis resistivity measured up to 45 T, we show that the Fermi-liquid features appear above a sufficiently high field that decreases linearly with temperature and lands at a quantum critical point near the superconductivity's upper critical field—with the Fermi-liquid coefficient of the T2 dependence showing a power-law diverging behavior on the approach to the critical point. This field-induced quantum criticality bears a striking resemblance to that in quasi-two-dimensional heavy-Fermion superconductors, suggesting a common underlying spin-related physics in these superconductors with strong electron correlations. PMID:18480261

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

    NASA Astrophysics Data System (ADS)

    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.

  10. 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.

  11. Hysteresis, critical fields and superferromagnetism of the film with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Kalita, V. M.; Kulyk, M. M.; Ryabchenko, S. M.

    2016-08-01

    This paper is focused on the analysis of hysteresis and critical phenomena of magnetization reversal of superferromagnetic (SFM) state in nanogranular (NG) Co/Al2O3 film with perpendicular anisotropy. It was demonstrated that the transition from the multidomain SFM state to the homogeneous SFM state, during the magnetization process, occurs critically. The value of the field of critical transition to the homogeneous state depends on the demagnetization field, granular anisotropy and interparticle exchange anisotropy. It turned out that the temperature dependence of the coercive force of the film, despite its SFM state, accords with the Neel-Brown formula for anisotropic single-domain ferromagnetic particles, but has an anomalous angular dependence. It was concluded that domain wall motion affects these features of the coercive field. The domain wall movement may occur due to the overturn of magnetic moments of particles in the boundaries between the superdomains. At the same time, the main factors influencing the coercivity are the anisotropy of the particles, which blocks their magnetic moment reorientation, and demagnetizing factor of the film. Together they lead to the anomalous angular dependence of the coercive field.

  12. Role of critical points of the skin friction field in formation of plumes in thermal convection

    NASA Astrophysics Data System (ADS)

    Bandaru, Vinodh; Kolchinskaya, Anastasiya; Padberg-Gehle, Kathrin; Schumacher, Jörg

    2015-10-01

    The dynamics in the thin boundary layers of temperature and velocity is the key to a deeper understanding of turbulent transport of heat and momentum in thermal convection. The velocity gradient at the hot and cold plates of a Rayleigh-Bénard convection cell forms the two-dimensional skin friction field and is related to the formation of thermal plumes in the respective boundary layers. Our analysis is based on a direct numerical simulation of Rayleigh-Bénard convection in a closed cylindrical cell of aspect ratio Γ =1 and focused on the critical points of the skin friction field. We identify triplets of critical points, which are composed of two unstable nodes and a saddle between them, as the characteristic building block of the skin friction field. Isolated triplets as well as networks of triplets are detected. The majority of the ridges of linelike thermal plumes coincide with the unstable manifolds of the saddles. From a dynamical Lagrangian perspective, thermal plumes are formed together with an attractive hyperbolic Lagrangian coherent structure of the skin friction field. We also discuss the differences from the skin friction field in turbulent channel flows from the perspective of the Poincaré-Hopf index theorem for two-dimensional vector fields.

  13. 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.

  14. 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.

  15. 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.

  16. Factors influencing job valuation: a comparative study of critical care and non-critical care nurses.

    PubMed

    Chaboyer, W; Najman, J; Dunn, S

    2001-04-01

    This study sought to identify the relationship between three predictor variables, perceived collaboration with medical staff, autonomy and independent actions and an outcome, the value hospital nurses placed on their work. In total 189 critical care and 366 non-critical care nurses completed a mailed survey. Critical care nurses perceived themselves to have a more collaborative relationship with the medical staff, described performing actions independent of medical orders more frequently and perceived their jobs to have more value than non-critical care nurses. However the latter group perceived themselves to have more autonomy in their work. Within both groups collaboration and autonomy were significantly, but weak to moderately correlated with job valuation. Simply expanding the work hospital nurses do is unlikely to result in nurses valuing their jobs more, however promoting an environment of respect and sharing between the medical and nursing staff and supporting nurses when they act in an autonomous fashion may positively influence nurses' perceptions of their work. PMID:11223056

  17. Anisotropies of the lower and upper critical fields in MgB2 single crystals.

    PubMed

    Lyard, L; Szabó, P; Klein, T; Marcus, J; Marcenat, C; Kim, K H; Kang, B W; Lee, H S; Lee, S I

    2004-02-01

    The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately 5 and approximately 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter gamma(H) (=lambda(c)/lambda(ab)=xi(ab)/xi(c)) that increases from Gamma(H(c1)) at low field to Gamma(H(c2)) at high field.

  18. Poverty in Latin America: A Critical Analysis of Three Studies.

    ERIC Educational Resources Information Center

    Boltvinik, Julio

    1996-01-01

    Critically evaluates the methodologies used in three recent studies on poverty in Latin America. Maintains that some studies measure the relative nature of nutritional poverty while others record the absolute nature of nutritional poverty (physical survival). Includes a comparative analysis of the studies' results. (MJP)

  19. [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.

  20. [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. PMID:25458123

  1. 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.

  2. Dipolar field effects on the critical current for spin transfer switch of iron and permalloy nanoelements

    SciTech Connect

    Oliveira, L. L.; Dantas, J. T. S.; Souza, R. M.; Carriço, A. S.; Dantas, Ana L.

    2014-05-07

    We report a theoretical study of dipolar effects on the switching current density of soft ferromagnetic elliptical nanoelements. Relevant changes on the critical current value are found according to the orientation of the magnetization and the spin polarization with the major axis. We show that the critical current density may be reduced by as much as 92% for thin nanoelements magnetized along the minor axis direction, using in-plane spin polarization parallel to the magnetization.

  3. 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. PMID:16604676

  4. 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.

  5. 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…

  6. Quantum criticality in the ferromagnetic superconductor UCoGe under pressure and magnetic field

    NASA Astrophysics Data System (ADS)

    Bastien, Gaël; Braithwaite, Daniel; Aoki, Dai; Knebel, Georg; Flouquet, Jacques

    2016-09-01

    The pressure-temperature phase diagram of the orthorhombic ferromagnetic superconductor UCoGe was determined by resistivity measurements up to 10.5 GPa . The Curie temperature TC is suppressed with pressure and vanishes at the critical pressure pc≈1 GPa . Superconductivity is observed in both the ferromagnetic state at low pressure, and in the paramagnetic state above pc up to about 4 GPa . Non-Fermi-liquid behavior appears in a large pressure range. The resistivity varies linearly with temperature around pc and evolves continuously with pressure to a T2 Fermi-liquid behavior for p ⪆5 GPa. The residual resistivity as a function of pressure shows a maximum far above pc at p=7.2 GPa and the amplitude of the inelastic scattering term of the resistivity decreases by more than one order in magnitude at p, which appears to mark the entrance into a weakly correlated regime. The pressure dependence of the upper critical field for magnetic field applied along the b and c axis illustrates the drastic difference in the field dependence of the ferromagnetic superconducting pairing. While for H ∥b axis Hc 2(T ) is driven by the suppression of the ferromagnetic order, it is dominated by the strong initial suppression of the ferromagnetic fluctuations for a field applied in the easy magnetization axis c .

  7. Using Critical Incident Reflections: A Self-Study as a Mathematics Teacher Educator

    ERIC Educational Resources Information Center

    Goodell, Joanne E.

    2006-01-01

    In this paper, I report the results of a 4-year study into how my students learn to become mathematics teachers during the combined 15-week methods and field placement course I teach. At the start of most weekly methods class meetings, groups of three or four students reported their critical incidents to each other, and then chose one incident to…

  8. A Critical Study of the Subject of Education at Graduate Level in Karachi

    ERIC Educational Resources Information Center

    Shakil, Anila Fatima; Faizi, Waqar Un Nisa; Ahmed, Syed Munir; Jabeen, Farkhanda

    2015-01-01

    This research is a critical study of instructional topics and their effectiveness in the subject of Education taught in colleges at graduate level vis-à-vis our current needs and the advancements in this field through research in all over the world. It also emphasizes the importance of curriculum review and revision for overcoming obstacles in…

  9. 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

  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. Magnetic field tuned quantum criticality of heavy fermion system YbPtBi

    NASA Astrophysics Data System (ADS)

    Mun, Eundeok

    2014-03-01

    Quantum criticality triggers an emergence of new quantum phase of matters due to the critical behavior of quantum fluctuations. Heavy fermion (HF) compounds have provided the cleanest evidence for the quantum phase transition. The face-centered cubic YbPtBi is one of the few frustrated stoichiometric Yb-based HF compounds. Measurements of magnetic field and temperature dependent resistivity, specific heat, thermal expansion, Hall effect, and thermoelectric power indicate that the antiferromagnetic (AFM) order (TN ~ 0.4 K) can be suppressed by applied magnetic field of Hc ~ 4 kOe. In the H- T phase diagram of YbPtBi, three regimes of its low temperature states emerges: (I) AFM state, characterized by spin density wave (SDW) 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 ρ(T) ~T 1 . 5 between Hc and ~ 8 kOe, and (III) Fermi liquid (FL) state in which ρ(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 4 f states of Yb, region II may be a manifestation of a spin liquid state. Work was supported by the US Department of Energy, Office of Basic Energy Science, Division of Materials Sciences and Engineering. Ames Laboratory is operated for the US Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358.

  12. 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.

  13. 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.

  14. 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.

  15. Anisotropy in upper critical field of FeTe{sub 0.55}Se{sub 0.45}

    SciTech Connect

    Shruti,; Sharma, G.; Patnaik, S.

    2015-06-24

    The anisotropic properties of FeTe{sub 0.55}Se{sub 0.45} single crystals are studied using transport measurements. FeTe{sub 0.55}Se{sub 0.45} shows onset superconducting transition at 14.2 K. The data measured on single crystals give a high upper critical field H{sub c2}(0) equal to 93.95 T and 67.32 T for magnetic field applied perpendicular and parallel to c axis of the sample respectively. Corresponding electronic anisotropy is estimated to be γ∼1.4 and Ginzburg-Landau coherence lengths are ξ{sub ab}=22.12 Å and ξ{sub c}=15.8 Å. Temperature and field dependent specific heat data are also reported.

  16. The applicability of current slimhole hydraulics algorithms under field conditions-a critical review

    SciTech Connect

    Thonhauser, G.; Millheim, K.K.; Spoerker, H.F.

    1995-12-31

    Numerous publications have addressed the problems inherent to calculating well hydraulics in slimhole applications. Accurate grasp of well hydraulics is of increased importance under slimhole conditions. Most models are valid in a controlled environment, but fail to fulfill the expectations under field conditions. Factors influencing the hydraulic behavior of the well have to be critically examined, and the accuracy of these factors entering into the calculations has to be quantified together with their relative impact on the results. This work has compared several {open_quotes}established{close_quotes} approaches with field data from five deep slimhole wells, and critically reviewed limitations and possible advances in slimhole hydraulics` calculations. Analyzing field data showed phenomena that are not considered in existing simulations. This work tries to define these phenomena and evaluate their impact on future simulations. These factors influencing pressure loss and ECD development are listed and quantified, and examples from well data are presented. A successful development of simulators of such complex systems is demanding a new way of thinking, away from the deterministic towards a probabilistic view of the problem.

  17. Field measurement of critical shear stress for erosion and deposition of fine muddy sediments

    NASA Astrophysics Data System (ADS)

    Salehi, M.; Strom, K. B.; Field Study

    2010-12-01

    The movement of muddy sediment from one region to another is linked to the fate and transport of pollutants that can be attached to this sediment. Important in understanding this movement is the need to know the critical conditions for erosion and deposition of the fine muddy sediment. For non-cohesion sediment, such as sands and gravels, reasonable estimates for the critical conditions can often be made theoretically without in situ measurements of the critical fluid condition or sediment transport rate. However, the shear stress needed for the incipient motion of the mud (cohesive sediments) is inherently difficult to calculate theoretically or in research flumes due to the influence of (1) flow history; (2) local sediment composition; (3) biological activity within the bed; (4) water content of the bed; and (5) salinity of the water column. The complexity of the combination of these factors makes the field measurement necessary. A field experiment was conducted under tidal flow in the region surrounding the Houston Ship Channel (near Houston, TX) to determine these conditions. Observations were made using single point, simultaneous, in situ measurement of turbulent flow and suspended sediment concentration within bottom boundary layer. Measurements were primarily made with a 6 MHz Nortek Vector velocimeter (ADV). The ADV was programmed to record 3-minute turbulent velocity with 32 Hz frequency every 10 minute. The suspended sediment concentration (SSC) was measured using the calibration of acoustic backscatter recorded by ADV against sample derived SSC. Different methods such as turbulent kinetic energy (TKE), TKEw and direct covariance method (COV) are compared together. TKE showed much more reasonable estimation on bed shear stress. Combination of time varying SSC, distance from the bed to the sampling volume recorded by ADV and calculation of shear stress made the determination of critical conditions for erosion and deposition possible.

  18. 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…

  19. Critical History: Implications for History/Social Studies Education.

    ERIC Educational Resources Information Center

    Segall, Avner

    1999-01-01

    Examines ways in which history/social studies educators might respond to the challenges posed by the critical literature in and about history in order to reconsider why we learn history, what we do (and could do) with it, and for what (and whose) purposes. (CMK)

  20. Going Critical: The Problem of Problematizing Knowledge in Education Studies

    ERIC Educational Resources Information Center

    Moore, Rob

    2007-01-01

    This paper raises the issue of what it is to be "critical" in education studies and in social theory more generally. It argues that this idea has for a long time been associated with forms of social constructionism and sociological reductionism. These understand the idea that knowledge is social in terms of reducing it to the experiences and…

  1. 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…

  2. 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…

  3. 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 "disability"…

  4. 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…

  5. 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…

  6. Studying fringe field effect of a field emitter array

    NASA Astrophysics Data System (ADS)

    Sayfullin, M. F.; Nikiforov, K. A.

    2014-10-01

    Field emitter arrays on heavy As-doped Si wafer are studied in vacuum nanoelectronics diode configuration. Different shapes of emitters are considered: cone-shaped point-emitters and cylinder-shaped sharp-edge-emitters are compared. Micro scale field enhancement factor on the edge of cylindrical emitter was calculated via home-developed Matlab application and the results are presented. Two types of anode geometry are proposed: plane anode and spherical anode. Experimental and modelling results of surface electric field distribution are presented. The spherical shape of anode allows higher voltage (and higher field emission current) without destructive arcs risk.

  7. Critical fields of Fe{sub 4}N/NbN ferromagnetic/superconducting multilayers

    SciTech Connect

    Mattson, J.E.; Potter, C.D.; Conover, M.J.; Sowers, C.H.; Bader, S.D.

    1997-01-01

    Structural, magnetic, and superconducting properties of ferromagnetic/superconducting multilayers of Fe{sub 4}N/NbN are explored for a variety of thickness combinations. The superconducting properties show that 11 {Angstrom} ferromagnetic layers are sufficient to decouple the superconducting layers and to yield anisotropic behavior. The upper critical field data are well described by theory for ferromagnetic/superconducting multilayers. This analysis yields an interfacial parameter which characterizes the electron scattering at the ferromagnetic/superconducting boundary. {copyright} {ital 1997} {ital The American Physical Society}

  8. Oscillations of critical superconducting current in thin doubly-connected Sn films in an external perpendicular magnetic field

    NASA Astrophysics Data System (ADS)

    Sivakov, A. G.; Pokhila, A. S.; Glukhov, A. M.; Kuplevakhsky, S. V.; Omelyanchouk, A. N.

    2014-05-01

    We report the results of experimental and theoretical studies of critical current oscillations in thin doubly-connected Sn films in an external perpendicular magnetic field. The experiments were performed on samples that consisted of two wide electrodes joined together by two narrow channels. The length of the channels l satisfied the condition l ≫ ξ (ξ is the Ginzburg-Landau coherence length). At temperatures close to the critical temperature Tc, the dependence of the critical current Ic on average external magnetic flux Φ¯e has the form of a piecewise linear function, periodic with respect to the flux quantum Φ0. The amplitude of the Ic oscillation at a given temperature is proportional to the factor ξ/l. Moreover, the dependence Ic=Ic(Φ ¯e) is found to be multivalued, hence indicating the presence of metastable states. Based on the Ginzburg-Landau approximation, a theory was constructed that explains the above features of the oscillation phenomenon taking a perfectly symmetric system as an example. Further, the experiments displayed the effects related to the critical currents imbalance between the superconducting channels, i.e., shift of the maxima of the dependence Ic=Ic(Φ ¯e) accompanied by an asymmetry with respect to the transport current direction.

  9. 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.

  10. 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.

  11. 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.

  12. Critical behavior of a tumor growth model: Directed percolation with a mean-field flavor

    NASA Astrophysics Data System (ADS)

    Lipowski, Adam; Ferreira, António Luis; Wendykier, Jacek

    2012-10-01

    We examine the critical behavior of a lattice model of tumor growth where supplied nutrients are correlated with the distribution of tumor cells. Our results support the previous report [Ferreira , Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.010901 85, 010901(R) (2012)], which suggested that the critical behavior of the model differs from the expected directed percolation (DP) universality class. Surprisingly, only some of the critical exponents (β, α, ν⊥, and z) take non-DP values while some others (β', ν||, and spreading-dynamics exponents Θ, δ, z') remain very close to their DP counterparts. The obtained exponents satisfy the scaling relations β=αν||, β'=δν||, and the generalized hyperscaling relation Θ+α+δ=d/z, where the dynamical exponent z is, however, used instead of the spreading exponent z'. Both in d=1 and d=2 versions of our model, the exponent β most likely takes the mean-field value β=1, and we speculate that it might be due to the roulette-wheel selection, which is used to choose the site to supply a nutrient.

  13. Critical RSOS and minimal models: fermionic paths, Virasoro algebra and fields

    NASA Astrophysics Data System (ADS)

    Feverati, Giovanni; Pearce, Paul A.

    2003-07-01

    A framework is presented to extend the finitized characters and recursion methods of (off-critical) corner transfer matrices (CTMs), in a self-consistent fashion, to the calculation of CFT characters and conformal partition functions. More specifically, in this paper we consider sℓ(2) minimal conformal field theories on a cylinder from a lattice perspective. We argue that a general energy-preserving bijection exists between the one-dimensional configuration paths of the AL restricted solid-on-solid (RSOS) lattice models and the eigenstates of their double row transfer matrices and exhibit this bijection for the critical and tricritical Ising models in the vacuum sector. To each allowed one-dimensional configuration path we associate a physical state and a monomial in a finite fermionic algebra. The orthonormal states produced by the action of these monomials on the primary states | h> generate finite Virasoro modules with dimensions given by the finitized Virasoro characters χ( N) h( q). These finitized characters are the generating functions for the double row transfer matrix spectra of the critical RSOS models. We also propose a general level-by-level algorithm to build matrix representations of the Virasoro generators and chiral vertex operators (CVOs). The algorithm employs a distinguished basis which we call the L1-basis. Our results extend to ZL-1 parafermion models by duality.

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

    PubMed

    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

    2001-05-31

    The discovery of superconductivity at 39 K 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 7 T at liquid helium temperature (4.2 K), significantly lower than about 10 T for Nb-Ti (ref. 6) and approximately 20 T 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 4.2 K greater than 14 T. In addition, very high critical current densities at 4.2 K are achieved: 1 MA cm-2 at 1 T and 105 A cm-2 at 10 T. These results demonstrate that MgB2 has potential for high-field superconducting applications.

  15. 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.

  16. Analysis and Prediction of the Critical Regions of Antimicrobial Peptides Based on Conditional Random Fields

    PubMed Central

    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. PMID:25803302

  17. 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

  18. Quantum criticality in single crystalline YFe2 Al10 determined from zero-field and longitudinal-field muon spin relaxation

    NASA Astrophysics Data System (ADS)

    Huang, Kevin; Tan, Cheng; Zhang, Jian; Ding, Zhaofeng; Maclaughlin, Douglas; Bernal, Oscar; Ho, Pei-Chun; Wu, Liusuo; Aronson, Meigan; Shu, Lei

    Muon spin relaxation (μSR) measurements were performed on single crystalline YFe2Al10 down to 19 mK and in magnetic fields up to ~100 Oe. Zero-field- μSR measurements showed no evidence of magnetic order down to 19 mK, consistent with previous measurements. However, we also find that the depolarization rate Λ is temperature independent above 1 K but increases in an exponential behavior for T < 1 K. Longitudinal-field μSR measurements also reveals a time-field scaling where G (t , H) = G (t /Hγ), with γ = 0.67. This is further confirmed from the magnetic field dependence of Λ, which finds Λ (H) ~H0. 67 at 19 mK. This is further evidence that single crystalline YFe2Al10 is in close proximity to a ferromagnetic quantum critical point. The research performed in this study was supported by the National NSF of China under Grant No. 11474060 and STCSM of China (No. 15XD1500200). Work at CSULA funded by NSF/DMR-1105380. Research at CSU-Fresno is supported by NSF DMR-1506677.

  19. Electronic structure, spin polarization and high critical fields in Chevrel compounds

    NASA Astrophysics Data System (ADS)

    Jarlborg, T.; Freeman, A. J.

    1982-05-01

    Results are presented of an extensive theoretical study of the origin of high field superconductivity and/or magnetism in a number of Chevrel phase ternary compounds, MMo 6X 8 (with M=Sn, Eu, Gd and X=S and/or Se) based on self-consistent linear muffin-tin orbital (LMTO) energy band calculations using the local density approach (Hedin et al. exchange correlation) for the paramagnetic structures and local spin density formalism (Gunnarsson and Lundqvist) for the ferromagnetic structures. All electrons and all 15 atoms/cell are included with the core electrons (including the 4f's) recalculated in each iteration in a fully relativistic representation and the conduction electrons treated semirelativistically (all relativistic terms except spin-orbit). Superconductivity is found to be due to the high Mo d-band density of states (DOS) at E F resulting from the unusual large charge transfer of Mo electrons to the chalcogen sites. There is also a large charge transfer from the metal site to the cluster (≈2 electrons in Sn and Eu) giving essentially no occupied conduction bands, for example, at the Eu site and a divalent ion isomer shift in very good agreement with the experiments of Dunlap et al. The conduction-electron DOS at the Eu site is found to be reduced by an order of magnitude from its metallic state value - in close agreement with their spin - lattice relaxation rate measurements. This low conduction-electron DOS yields very weak coupling of the 4f electrons to the conduction electrons and only a very weak Ruderman-Kittel-Kasuya-Yosida magnetic interaction showing why all the Chevrel rare-earth compounds - except Ce and Eu - are superconducting despite their having large local magnetic moments. The unusually high upper critical fields, Hc 2, in these materials is found to be due to the unusully flat energy bands near F F. The ferromagnetic (spin polarized) results for the Eu- and Gd-compounds show a net small but positive magnetic moment on the metal site and a

  20. Superconductivity and Critical Current of Iron-Based Superconductors in High Field

    NASA Astrophysics Data System (ADS)

    Li, Qiang

    2014-03-01

    Although high-temperature superconducting cuprates have been discovered for more than 26 years, high-field applications are still based on low-temperature superconductors (LTS), such as Nb3Sn. The high anisotropies, brittle textures and high manufacturing costs limit the applicability of the cuprates. Recently, we demonstrated that the iron superconductors, without most of the drawbacks of the cuprates, have a superior high-field performance over LTS at 4.2 K [Nat. Commun. 4:1347 (2013); Rep. Prog. Phys. 74 124510 (2011)]. In this presentation, I will discuss recent progress aimed at understanding the relationships between superconductivity, critical current, and nano-scaled structure defects in iron-based superconductors, with emphasis on the properties of superconducting iron chalcogenide films. Critical current densities Jc ~ 107 A/cm2 were observed in FeSe0.5Te0.5 films grown on CeO2 buffered single-crystalline and flexible metal substrates. These films are capable of carrying Jc exceeding 105 A/cm2 under 30 T magnetic fields. Furthermore, we found that these films have significantly higher Tc (>20K) as compared to bulk samples (bulk Tc ~ 15 K) for the entire doping regime of FeSe1-xTex. Structural analysis revealed that these films generally have significantly smaller c-axis and a-axis lattice constant than the bulk value, suggesting that the crystal structure changes have a dominating impact on the superconducting transition in iron-based superconductors. Large Jc enhancement can also be realized in iron based superconductors by irradiation with proton and heavy ions that opens a new avenue for a tailored landscape of effective vortex pinning defects.

  1. 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.

  2. 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

  3. Temperature and Magnetic Field Dependence of Critical Currents in YBCO Coated Conductors with Processing-Induced Variations in Pinning Properties

    SciTech Connect

    Gapud, Albert Agcaoili; Feenstra, Roeland; Christen, David K; Thompson, James R; Holesinger, T. G.

    2005-01-01

    Several applications of high-temperature super-conducting wire require high currents at intermediate magnetic fields B and over a range of orientations; however, such conditions are at present achievable only at low temperatures (-30 K). The goal of this study is to determine the feasibility of higher operating temperatures for these applications by investigating temperature dependent, low- and high-field pinning properties of YBCO coated conductor samples. The YBCO films were grown on RABiTS templates by a PVD ex situ BaF{sub 2} process. Variations in pinning properties were induced by introducing excess yttrium (Y) in the precursor and controllably increasing the growth rate. The main result is a more uniform dependence of J{sub c} over all orientations of B, along with high irreversibility field B{sub irr} and high critical current densities J{sub c}. Results also show that for films with various pinning properties and processed under different conditions the self-field J{sub c} at 77 K is an effective indicator of performance in the temperatures and fields of interest.

  4. Field-line Torsion (FLT) / (SOC) Self-Organized Criticality Correspondence and Duality

    NASA Astrophysics Data System (ADS)

    Bekhor, S. H.

    2008-12-01

    Magnetic potential energy is stored when an incident disturbance such as the propagating solar wind interacts with the undisturbed magnetosphere resulting in the twisting and bending of the Earth's magnetic field. The energy that is stored in turn becomes a reservoir for dissipative wave interactions and instabilities that ultimately result in auroral phenomena that are observed on Earth. The topological structure of the Earth's magnetic field can provide clues about the timing and intensity of these events even during relatively quiescent periods. In particular, the presence of magnetic field-line torsion (FLT), a putative signature of magnetic storms and sub-storms, results in an increase in the fundamental standing Alfvén wave (SAW) field-line resonance (FLR) frequencies corresponding to a particular Alfvén speed profile. These frequencies can be dynamically calculated in an arbitrary boundary-constrained non-orthogonal geomagnetic flux coordinate (GFC) system in conjunction with chronological magnetic field data, provided by magnetospheric models such as BATSRUS and Tsyganenko (T05). A comparison of these frequencies to those computed in a purely meridional geometry yields a parameter that is useful in forecasting the triggering and evolution of ionospheric phenomena, such as the formation of localized auroral density cavities, which interact with lower and upper hybrid waves or Z modes resulting in mode conversion processes that lead to the formation of discrete auroral arcs via an escaping electromagnetic mode. There is strong evidence that this evolution describes a dynamical self-organized critical (SOC) phase transition due to an abrupt change in the pressure distribution in the near-Earth plasma sheet and the intrusion of convective flows into the inner magnetosphere.

  5. 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.

  6. Studies in Quantum Field Theory

    NASA Astrophysics Data System (ADS)

    Bastianelli, Fiorenzo

    We analyze several topics in quantum field theory, mainly motivated by their role in the formulation of string theories. The common theme in what follows is the implementation of symmetries, such as local supersymmetry or BRST symmetry, through an action principle and the analysis of anomalies, the latter describing the breakdown of these symmetries at the quantum level. In the first part of this dissertation, we analyze "chiral bosons", i.e. massless scalar fields in a two -dimensional spacetime propagating in only one of the two light-cone directions. We present a general method for constructing couplings for chiral bosons and give details for the coupling to supergravity. The notion of a two dimensional chiral boson is generalized in d = 4k + 2 spacetime dimensions to that of a self-dual antisymmetric tensor field. We derive the coupling to gravity and compute the gravitational anomalies using the Feynman rules obtained from the action. We find agreement with the important work of Alvarez-Gaume and Witten, who conjectured the relevant Feynman rules. Our result therefore completes and justifies the Alvarez-Gaume-Witten findings. For the case of d = 2 we also show how to use the method of Fujikawa for computing anomalies from the non-invariance of the path integral measure. We obtain the full effective action by integrating the anomaly equation. In the second part we focus on a method for computing the consistent anomalies in the Fujikawa scheme. In a first application, we derive the consistent regulators for the various fields of the quantum action of the spinning string in superspace. These regulators produce the anomalies which satisfy the Wess-Zumino consistency conditions. In a second application, we analyze the anomalous structure of the Green-Schwarz formulation of the heterotic string. We find anomalies which generically do not cancel on an arbitrary world-sheet manifold. This raises questions concerning the possible validity of such a formulation of

  7. 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.

  8. Novel near-field optical probe for 100-nm critical dimension measurements

    SciTech Connect

    Stallard, B.R.; Kaushik, S.

    1997-06-01

    Although the theoretical resolution for a conventional optical microscope is about 300 nm, it is normally difficult to obtain satisfactory critical dimension (CD) measurements below about 600 nm. E-beam technology has been popular for sub-500 nm metrology but also has well known limitations. Scanning probe and near-field optical methods have high spatial resolution. Yet they are ill-suited for routine CD metrology of high aspect ratio features because of a combination of short working distances (< 10 nm) and large tips. In this paper the authors present the concept and initial modeling results for a novel near-field optical probe that has the potential of overcoming these limitations. The idea is to observe resonance shifts in a waveguide cavity that arise from the coupling of the evanescent field of the waveguide to perturbations beneath the waveguide plane. The change in resonance frequency is detected as a change in the transmission of a monochromatic probe beam through the waveguide. The transmitted intensity, together with the appropriate signal processing, gives the topography of the perturbation. The model predicts that this probe is capable of determining the width of photoresist lines as small as 100 nm. The working distance is much more practical than other probe techniques at about 100 to 250 nm.

  9. 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.

  10. 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.

  11. Recent biophysical studies in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Maret, Georg

    1990-06-01

    A brief overview of biophysical effects of steady magnetic fields is given. The need of high field strength is illustrated by several recent diamagnetic orientation experiments. They include rod-like viruses, purple membranes and chromosomes. Results of various studies on bees, quails, rats and pigeons exposed to fields above 7 T are also resumed.

  12. 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…

  13. Behavior analytic studies of creativity: A critical review.

    PubMed

    Winston, A S; Baker, J E

    1985-01-01

    Studies that treat creativity as operant behavior were critically reviewed. Of the twenty studies, most met minimal requirements for methodological adequacy; all provided at least some evidence for increased creative responding. Major difficulties involved potential confounds between instructions and contingencies, lack of an independent record of the training interaction, lack of social validation data, and very limited evidence for generalization. Several issues were discussed: problems in the behavioral definition of creativity, objections to the use of contingent reinforcement, and the need for empirical analysis of the creative process.

  14. On some p-Laplacian equation with electromagnetic fields and critical nonlinearity in ℝN

    NASA Astrophysics Data System (ADS)

    Liang, Sihua; Zhang, Jihui

    2015-04-01

    In this paper, we consider the existence and multiplicity of solutions for p-Laplacian equation with electromagnetic fields and critical nonlinearity in ℝN: - ɛ p Δ p , A u + V ( x ) |u| p - 2 u = |u| p* - 2 u + h ( x , |u| p ) |u| p - 2 u for x ∈ ℝN, where Δ p , A u ( x ) ≔ div ( |u ∇ u + i A ( x ) u | p - 2 ( ∇ u + i A ( x ) u ) . By using Lions' second concentration compactness principle and concentration compactness principle at infinity to prove that the (PS)c condition holds locally and by variational method, we show that this equation has at least one solution provided that ɛ < E , for any m ∈ ℕ, it has m pairs of solutions if ɛ < E m , where E and E m are sufficiently small positive numbers.

  15. Microstructural understanding and critical current optimization of advanced high field superconductors

    SciTech Connect

    Bonney, L.A.; Willis, T.C.; Larbalestier, D.C.

    1993-01-01

    It is of great importance to improve critical current density, J[sub c] in A15 superconductors for high field magnet applications. Most current work to improve J[sub c] in A15 wires concentrates on increasing the overall J[sub c] by increasing the fraction of superconducting phase in the wire, by improving the uniformity of the superconductor cross section along the length of the wire and by adjusting the strainstate of the A15 layer. The goal of the A15 work in this group was to investigate the intrinsic J[sub c] of the A15 layer itself. To do this, a better understanding of factors controlling the intrinsic J[sub c]of the Nb[sub 3]Sn was pursued.

  16. 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.

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

    PubMed

    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. PMID:27176347

  18. 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.

  19. 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.

  20. 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.

  1. Critical care physician cognitive task analysis: an exploratory study

    PubMed Central

    Fackler, James C; Watts, Charles; Grome, Anna; Miller, Thomas; Crandall, Beth; Pronovost, Peter

    2009-01-01

    Introduction For better or worse, the imposition of work-hour limitations on house-staff has imperiled continuity and/or improved decision-making. Regardless, the workflow of every physician team in every academic medical centre has been irrevocably altered. We explored the use of cognitive task analysis (CTA) techniques, most commonly used in other high-stress and time-sensitive environments, to analyse key cognitive activities in critical care medicine. The study objective was to assess the usefulness of CTA as an analytical tool in order that physician cognitive tasks may be understood and redistributed within the work-hour limited medical decision-making teams. Methods After approval from each Institutional Review Board, two intensive care units (ICUs) within major university teaching hospitals served as data collection sites for CTA observations and interviews of critical care providers. Results Five broad categories of cognitive activities were identified: pattern recognition; uncertainty management; strategic vs. tactical thinking; team coordination and maintenance of common ground; and creation and transfer of meaning through stories. Conclusions CTA within the framework of Naturalistic Decision Making is a useful tool to understand the critical care process of decision-making and communication. The separation of strategic and tactical thinking has implications for workflow redesign. Given the global push for work-hour limitations, such workflow redesign is occurring. Further work with CTA techniques will provide important insights toward rational, rather than random, workflow changes. PMID:19265517

  2. 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

  3. Critical sampling points methodology: case studies of geographically diverse watersheds.

    PubMed

    Strobl, Robert O; Robillard, Paul D; Debels, Patrick

    2007-06-01

    Only with a properly designed water quality monitoring network can data be collected that can lead to accurate information extraction. One of the main components of water quality monitoring network design is the allocation of sampling locations. For this purpose, a design methodology, called critical sampling points (CSP), has been developed for the determination of the critical sampling locations in small, rural watersheds with regard to total phosphorus (TP) load pollution. It considers hydrologic, topographic, soil, vegetative, and land use factors. The objective of the monitoring network design in this methodology is to identify the stream locations which receive the greatest TP loads from the upstream portions of a watershed. The CSP methodology has been translated into a model, called water quality monitoring station analysis (WQMSA), which integrates a geographic information system (GIS) for the handling of the spatial aspect of the data, a hydrologic/water quality simulation model for TP load estimation, and fuzzy logic for improved input data representation. In addition, the methodology was purposely designed to be useful in diverse rural watersheds, independent of geographic location. Three watershed case studies in Pennsylvania, Amazonian Ecuador, and central Chile were examined. Each case study offered a different degree of data availability. It was demonstrated that the developed methodology could be successfully used in all three case studies. The case studies suggest that the CSP methodology, in form of the WQMSA model, has potential in applications world-wide.

  4. 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.

  5. Criticality calculations and criticality monitoring studies of the slagging pyrolysis incinerator facility

    SciTech Connect

    Close, D.A.; Booth, T.E.; Caldwell, J.T.

    1981-01-01

    It was determined that the criticality hazard associated with the Slagging Pyrolysis Incinerator (SPI) Facility would be minimal if a three-level criticality-hazard prevention program were implemented. The first strategy consists of screening all incoming wastes for fissile content. The second prevention level is provided by introducing a small concentration of a neutron-absorbing compound, such as B/sub 2/O/sub 3/, into the input waste stream. The third prevention level is provided by direct criticality-hazard monitoring using sensitive neutron detectors in all regions of the facility where a significant hazard has been identified - principally the drying, pyrolysis, and slag regions. The facility could be shut down rapidly for cleanout if the measurements indicate an unsafe condition is developing. The criticality safety provided by the product of these three independent measures should reduce the hazard to a negligible level.

  6. Cost-of-illness studies: a guide to critical evaluation.

    PubMed

    Larg, Allison; Moss, John R

    2011-08-01

    Cost-of-illness (COI) studies aim to assess the economic burden of health problems on the population overall, and they are conducted for an ever widening range of health conditions and geographical settings. While they attract much interest from public health advocates and healthcare policy makers, inconsistencies in the way in which they are conducted and a lack of transparency in reporting have made interpretation difficult, and have ostensibly limited their usefulness. Yet there is surprisingly little in the literature to assist the non-expert in critically evaluating these studies. This article aims to provide non-expert readers with a straightforward guide to understanding and evaluating traditional COI studies. The intention is to equip a general audience with an understanding of the most important issues that influence the validity of a COI study, and the ability to recognize the most common limitations in such work.

  7. Muscle channelopathies and critical points in functional and genetic studies

    PubMed Central

    Jurkat-Rott, Karin; Lehmann-Horn, Frank

    2005-01-01

    Muscle channelopathies are caused by mutations in ion channel genes, by antibodies directed against ion channel proteins, or by changes of cell homeostasis leading to aberrant splicing of ion channel RNA or to disturbances of modification and localization of channel proteins. As ion channels constitute one of the only protein families that allow functional examination on the molecular level, expression studies of putative mutations have become standard in confirming that the mutations cause disease. Functional changes may not necessarily prove disease causality of a putative mutation but could be brought about by a polymorphism instead. These problems are addressed, and a more critical evaluation of the underlying genetic data is proposed. PMID:16075040

  8. [Economic evaluation studies in diagnostic imaging: justification and critical reading].

    PubMed

    Rueda Martínez de Santos, J R

    2015-11-01

    First, this article describes the concepts and tools most widely used for economic evaluation in healthcare. Second, it discusses some elements that must be taken into account in the social decision about how much we are willing to spend to prolong a person's life by one year. Third, it describes the criteria recommended for the critical analysis of publications that evaluate the economic aspects of health interventions. Finally, several studies about ultrasound screening for aneurysms of the abdominal aorta are used as illustrative examples to show how these elements and criteria can be applied. PMID:26563613

  9. 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.

  10. 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…

  11. Upper critical field of high temperature Y(1.2)Ba(0.8)CuO(4-delta) superconductor

    NASA Technical Reports Server (NTRS)

    Hor, P. H.; Meng, R. L.; Huang, J. Z.; Chu, C. W.; Huang, C. Y.

    1987-01-01

    A 20-T high-field magnet is used to measure electrical resistance as a function of temperature in the Y(1.2)Ba(0.8)CuO(4-delta) superconductor. The temperature dependence of the critical field, Hc2(T), is obtained from the superconduction transition. A Hc2(O) value of 166T is determined which is the highest critical field yet reported. Results show Y(1.2)Ba(0.8)CuO(4-delta) to be a 90K Type-II superconductor, with a lower critical field Hc1(O) of about 0.2T and a penetration depth of about 290 A.

  12. 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.

  13. Critical component of the interplanetary magnetic field responsible for large geomagnetic effects in the polar cap

    NASA Technical Reports Server (NTRS)

    Friis-Christensen, E.; Lassen, K.; Wilhjelm, J.; Wilcox, J. M.; Gonzalez, W.; Colburn, D. S.

    1972-01-01

    An observed influence is studied of the interplanetary magnetic sector structure on the geomagnetic variations in the polar cap which appears to be due to the component of the interplanetary magnetic field near the ecliptic perpendicular to the earth-sun direction. It is suggested that the observed effect on the ground originates in the front of the magnetosphere.

  14. 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.

  15. Non-monotonic changes in critical solidification rates for stability of liquid-solid interfaces with static magnetic fields

    PubMed Central

    Ren, W. L.; Fan, Y. F.; Feng, J. W.; Zhong, Y. B.; Yu, J. B.; Ren, Z. M.; Liaw, P. K.

    2016-01-01

    We report the magnetic field dependence of the critical solidification rate for the stability of liquid-solid interfaces. For a certain temperature gradient, the critical solidification rate first increases, then decreases, and subsequently increases with increasing magnetic field. The effect of the magnetic field on the critical solidification rate is more pronounced at low than at high temperature gradients. The numerical simulations show that the magnetic-field dependent changes of convection velocity and contour at the interface agree with the experimental results. The convection velocity first increases, then decreases, and finally increases again with increasing the magnetic field intensity. The variation of the convection contour at the interface first decreases, then increases slightly, and finally increases remarkably with increasing the magnetic field intensity. Thermoelectromagnetic convection (TEMC) plays the role of micro-stirring the melt and is responsible for the increase of interface stability within the initially increasing range of magnetic field intensity. The weak and significant extents of the magneto-hydrodynamic damping (MHD)-dependent solute build-up at the interface front result, respectively, in the gradual decrease and increase of interfacial stability with increasing the magnetic field intensity. The variation of the liquid-side concentration at the liquid-solid interface with the magnetic field supports the proposed mechanism. PMID:26846708

  16. Disorder-induced enhancement and critical scaling of spontaneous magnetization in random-field quantum spin systems

    NASA Astrophysics Data System (ADS)

    Bera, Anindita; Rakshit, Debraj; Lewenstein, Maciej; SenDe, Aditi; Sen, Ujjwal; Wehr, Jan

    2016-07-01

    We investigate the effect of a unidirectional quenched random field on the anisotropic quantum spin-1/2 X Y model, which magnetizes spontaneously in the absence of the random field. We adopt a mean-field approach for this analysis. In general, the models considered have Ising symmetry, and as such they exhibit ferromagnetic order in two and three dimensions in the presence of not too large disorder. Even in the special case when the model without disorder has U(1 ) symmetry, a small U(1 ) -symmetry-breaking random field induces ferromagnetic long-range order in two dimensions. The mean-field approach, consequently, provides a rather good qualitative and even quantitative description when applied not too close to the criticality. We show that spontaneous magnetization persists even in the presence of the random field, but the magnitude of magnetization gets suppressed due to disorder, and the system magnetizes in the directions parallel and transverse to the random field. Our results are obtained via analytical calculations within a perturbative framework and by numerical simulations. Interestingly, we show that it is possible to enhance a component of magnetization in the presence of the disorder field provided that we apply an additional constant field in the X Y plane. Moreover, we derive generalized expressions for the critical temperature and the scalings of the magnetization near the critical point for the X Y spin system with arbitrary fixed quantum spin angular momentum.

  17. 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…

  18. Computer Simulations of Critical Phenomena in Systems with Long-Range Interactions: a Study of Ising Dipoles and Self-Organized Criticality in Earthquakes.

    NASA Astrophysics Data System (ADS)

    Xu, Huang-Jian

    This thesis discusses scaling and critical behavior of two different models. One model describes Ising dipoles, originates in condensed matter physics, and depicts equilibrium critical phenomena. The other model, taken from the earth sciences, describes faulting instabilities and the resulting earthquakes, and involves self-organized criticality--a non-equilibrium phenomenon. Both models are characterized by long range interactions, with a resulting sensitivity to boundary conditions. The ordering properties of Ising dipoles on lattices are studied in a mean field theory and by Monte Carlo simulations. The mean field theory is manifestly shape independent in zero external field. In the case of dipoles on a diluted lattice the mean field theory predicts a critical concentration above which the low temperature phase is ferroelectric (or anti-ferroelectric depending on the lattice structure). Extensive Monte Carlo simulation results are in agreement with those of mean field theory. We propose a finite size scaling form that includes logarithmic corrections for systems at the critical dimensionality. In the case of dipoles on a body centered tetragonal lattice we found that the finite scaling form significantly improved the data collapse over the scaling form with mean field exponents. With lattice parameters appropriate to the Ising ferromagnetic compound LiHoF_4, we obtain a ferromagnetic transition temperature T -1.51 K in excellent agreement with experiment. This indicates that the material LiHoF_4 is dominated by the dipole-dipole interaction: since in the simulations we only include dipole dipole interactions. For dipoles on the simple cubic lattice, the ordered state is made up of anti-ferromagnetic rows. The critical exponents obtained by finite size scaling are beta~ 1/7, gamma ~ 8/7 and o~ 1/7. These results are in good agreement with those of high temperature series expansions. A model of self-organized ruptures in an elastic medium is developed; and applied

  19. 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.

  20. Quantum criticality and coexistence of spontaneous ferromagnetism and field- induced metamagnetism in triple-layered Sr4Ru3O10

    NASA Astrophysics Data System (ADS)

    Chikara, Shalinee; Durairaj, Vinobalan; Cao, Gang; Brill, Joseph W.; Schlottmann, Pedro

    2007-03-01

    Results of a thermodynamic and transport study of Sr4Ru3O10 as a function of temperature and magnetic field are presented. The central results of this work include growing specific heat C with increasing field B, divergent magnetic contribution to C at low temperatures, an abrupt jump and a peak in C/T at B=2.90 T and =7 T for B||ab-plane and B||c-axis, respectively, and corresponding changes in the power law of resistivity. All results provide not only strong evidence for metamagnetic quantum criticality but also quantum fluctuations in a spontaneously ferromagnetic state. The novelty of this work lies in the fact that the quantum criticality occurs in a system that shows both intralayer metamagnetism and interlayer spontaneous ferromagnetism, a feature characteristically different from all other relevant systems involving quantum criticality.

  1. 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.

  2. Critical behaviors of transverse crystal field and bimodal magnetic field mixed spin Ising model with bond dilution or bond percolation threshold

    NASA Astrophysics Data System (ADS)

    Xu, C. Q.; Yan, S. L.

    2016-10-01

    Within the effective field theory, we investigate critical behaviors of transverse crystal field and bimodal magnetic field mixed spin-1/2 and spin-1 Ising model with bond dilution or percolation threshold on a simple cubic lattice. A-type double tricritical points and zigzag reentrant phenomenon can be found at pure bond and large bimodal magnetic field status. The ordered phase is impaired sharply due to bond dilution. The positive transverse crystal field can induce ordered phase at ordinary bond percolation threshold. The bimodal magnetic field can suppress the induced ordered phase and form a series of closed ordered regions. An extraordinary bond percolation threshold is determined, at which the induced ordered phase vanishes completely. The different effects of bimodal magnetic field and bond percolation threshold on induced ordered phase are discussed.

  3. Studying children's religious knowledge: contributions of ethnography and the clinical-critical method.

    PubMed

    García Palacios, Mariana; Castorina, José Antonio

    2014-12-01

    We analyze different methodological and conceptual contributions of anthropology and psychogenetic theory to the research of children's religious knowledge. We argue that for the study of children's points of view it is possible to build an approach that links aspects studied by both disciplinary fields. With this aim, we revise some of their basic theoretical assumptions and recent reviews as well as their methodological proposals. Then we review the core characteristics of ethnography and the clinical-critical method-proposed by Piaget's psychogenetic theory-with the goal of stressing their potentialities as well as their limitations in research. We argue that within an ethnographic approach, we must establish certain restrictions on the clinical-critical method following basic premises of social anthropology. This approach lets us demonstrate the importance of understanding children's constructions by placing them within social relations that children produce and update in everyday interactions.

  4. Molecular approaches to field studies of malaria.

    PubMed

    Beck, Hans-Peter; Tetteh, Kevin

    2008-12-01

    The third 'Molecular Approaches to Malaria' conference was held in Lorne, Australia, in February 2008 and provided extensive information on the application of molecular tools in field studies on malaria. In recent years, technological advances and capacity building in malaria-endemic countries have permitted molecular tools to be applied much more frequently and successfully with exciting new findings. In this review, Hans-Peter Beck and Kevin Tetteh report on the most recent findings using molecular tools in field studies.

  5. Compound Lava Flow Fields on Planetary Surfaces: Hawaiian Analogue Studies

    NASA Astrophysics Data System (ADS)

    Crown, D. A.; Byrnes, J. M.; Ramsey, M. S.

    2002-12-01

    Quantitative, process-oriented analyses of planetary volcanism have primarily been based on analogue studies of single-lobed lava flows emplaced as discrete units. Comparative analyses of compound lava flow fields on the Earth and terrestrial planets are being conducted in order to include volcanic styles characterized by complex distributary systems, stratigraphic relationships, and emplacement histories. Field observations, differential Global Positioning Systems (dGPS) measurements, and visible, thermal, and radar remote sensing are being used to characterize Hawaiian lava flow fields and develop techniques for analyses of planetary flow fields using datasets with high spatial and/or spectral resolution, such as MOC and THEMIS. These terrestrial studies allow flow field surface morphology, topography, and lava textures as well as detailed maps of distributary networks to be used to examine flow field growth and development. Information on flow field evolution is provided by delineating relationships between remote sensing signatures, surface morphology, and lava transport processes and by identifying input parameters for flowfield emplacement models. Investigations of the Mauna Ulu (1969-1974) and Puu Oo (1983-present) flow fields (Kilauea Volcano, HI) have focused on understanding the nature of distributary networks at various scales in order to determine spatial and temporal variations in lava transport. Initial work at Mauna Ulu has included analyses of 1) the distribution, network morphometry, and volumetric significance of lava channels in the medial zone of the flow field, and 2) the distribution, lava texture, and volumetric significance of breakouts from surface conduits and subsurface storage. Analyses of the temporal evolution of individual conduit systems provide the basis for interpretation of complex patterns of overlapping surface units that characterize local flow stratigraphy. Reconstruction of lava transport networks and relationships to surface

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    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.

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

    PubMed Central

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

    2016-01-01

    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. PMID:26758347

  8. 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.

  9. 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…

  10. 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…

  11. Identification of the critical elements of environmental literacy: A Delphi study

    NASA Astrophysics Data System (ADS)

    Hoffmann, Johannes Oswald

    The overall purpose of this study was to obtain the opinions of environmental experts regarding the three identified levels of environmental literacy: nominal, functional, and operational. Specifically, this study was performed to identify and rank for importance the critical elements of environmental literacy as perceived by practicing environmental professionals. The Delphi technique was utilized to identify and refine the critical elements of environmental literacy by eliciting the opinions of experts in the environmental field. The research was conducted as a two-phase project. Phase I employed environmental experts who were Certified Environmental Professionals (CEPs) of the National Association of Environmental Professionals. In Phase II, the elements identified by Panel I were compared with the opinions elicited from Panel II, a group of managers and educators from Texas. Median scores were used to rank the elements. Elements meeting the criteria for inclusion became the final list of critical elements. The results of this study revealed that of the 79 critical elements of environmental literacy suggested by research sources and Panel I, 59 were rated for inclusion in the final list of elements. A significant difference (p < .05) was found for only 10 of the 79 elements by Panel II. Research involving environmental problems and issues indicated that in order for environmental-education programs to be successful, environmental literacy must be clearly identified and defined. As a statement of group opinion among a national panel of practicing environmental professionals, the Delphi technique produced a list of 59 critical elements of environmental literacy, and the importance of each element was determined by the use of the median. A comparison of results between Rounds 2 and 3 and the follow-up study revealed limited significant differences in median ratings. It was concluded that the final list of elements and their rankings represent the opinions of

  12. "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…

  13. Renyi entanglement entropies of descendant states in critical systems with boundaries: conformal field theory and spin chains

    NASA Astrophysics Data System (ADS)

    Taddia, Luca; Ortolani, Fabio; Pálmai, Tamás

    2016-09-01

    We discuss the Renyi entanglement entropies of descendant states in critical one-dimensional systems with boundaries, that map to boundary conformal field theories in the scaling limit. We unify the previous conformal-field-theory approaches to describe primary and descendant states in systems with both open and closed boundaries. We provide universal expressions for the first two descendants in the identity family. We apply our technique to critical systems belonging to different universality classes with non-trivial boundary conditions that preserve conformal invariance, and find excellent agreement with numerical results obtained for finite spin chains. We also demonstrate that entanglement entropies are a powerful tool to resolve degeneracy of higher excited states in critical lattice models.

  14. 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.

  15. 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.

  16. Influence of the upper critical-field anisotropy on the transport properties of polycrystalline MgB{sub 2}

    SciTech Connect

    Eisterer, M.; Krutzler, C.; Weber, H.W.

    2005-08-01

    The intrinsic properties of MgB{sub 2} form the basis for all applications of this superconductor. We wish to emphasize that the application range of polycrystalline MgB{sub 2} is limited by the upper critical field H{sub c2} and its anisotropy. In wires or tapes, the MgB{sub 2} grains are randomly oriented or only slightly textured and the anisotropy of the upper critical field leads to different transport properties in different grains, if a magnetic field is applied and the current transport becomes percolative. The irreversibility line is caused by the disappearance of a continuous superconducting current path and not by depinning as in high-temperature superconductors. Based on a percolation model, we demonstrate how the changes of the upper critical field and its anisotropy and how the changes of flux pinning will influence the critical currents of a wire or a tape. These predictions are compared to results of neutron irradiation experiments, where these parameters were changed systematically.

  17. Critical Issues in the Measurement of Ethnic and Racial Identity: A Referendum on the State of the Field

    ERIC Educational Resources Information Center

    Cokley, Kevin

    2007-01-01

    Ethnic and racial identity are among the most researched topics in the multicultural counseling literature. The popularity of these constructs, combined with ongoing controversies surrounding their measurement, warrants a critical examination by scholars in the field. The author contends that a combination of science and ideology has influenced…

  18. Embedding Culture in a Field Experience Seminar: Lessons Learned about Promoting Preservice Teacher Critical Consciousness in an Urban School Partnership

    ERIC Educational Resources Information Center

    Jacobs, Jennifer; Casciola, Vanessa; Arndt, Katie; Mallory, Mashainah

    2015-01-01

    This article reports the research findings of teacher educator inquiry using qualitative methods examining how incorporating the topic of culture into the field seminar component of a newly developed urban school-university partnership influenced preservice teachers' abilities to become critically conscious. After analyzing preservice teacher…

  19. 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. PMID:23745972

  20. 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.

  1. 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.

  2. Influence of Critical Current Density on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

    NASA Astrophysics Data System (ADS)

    Longcai, Zhang; Jianguo, Kong

    2012-07-01

    Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to AC external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay of the YBCO bulk over the NdFdB guideway used in the High-temperature superconducting maglev vehicle system with the application of the AC external magnetic field, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of the critical current density on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and try to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with lower critical current density. Therefore, we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by improving critical current density of the bulk.

  3. 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

  4. A Field Study on the Raindrop Fall Velocity

    NASA Astrophysics Data System (ADS)

    Rahman, Kalimur; Testik, Firat

    2016-04-01

    Raindrop fall velocity is a critical parameter in various rainfall related applications such as dual-polarization radar rainfall estimation. In such applications, it is typically assumed that raindrops fall at terminal velocity. Recent field observations, however, challenged this assumption of terminal raindrops. In this study, we investigated raindrop fall velocity in rainfall events using a new optical-type disdrometer called the High-speed Optical Disdrometer (HOD). We developed the HOD recently for precipitation microphysical observations, in particular for investigating raindrop dynamics including raindrop fall velocity. Our field observations showed clear deviations of raindrop fall velocities from predicted terminal velocities. These new field observations and our ongoing efforts to elucidate raindrop fall velocity characteristics will be discussed. This material is based upon work supported by the National Science Foundation under Grant No. AGS-1612681.

  5. Epigenetics of Osteoporosis: Critical Analysis of Epigenetic Epidemiology Studies

    PubMed Central

    Riancho, José A.

    2015-01-01

    Osteoarthritis (OA) is an age-related disease with poorly understood pathogenesis. Recent studies have demonstrated that miRNA might play a key role in OA initiation and development. We reviewed recent publications and elucidated the connection between miRNA and OA cartilage anabolic and catabolic signals, including four signaling pathways: TGF-β/Smads and BMPs signaling, associated with cartilage anabolism; and MAPK and NF-KB signaling, associated with cartilage catabolism. We also explored the relationships with MMP, ADAMTS and NOS (NitricOxide Synthases) families, as well as with the catabolic cytokines IL-1 and TNF-α. The potential role of miRNAs in biological processes such as cartilage degeneration, chondrocyte proliferation, and differentiation is discussed. Collective evidence indicates that miRNAs play a critical role in cartilage degeneration. These findings will aid in understanding the molecular network that governs articular cartilage homeostasis and in to elucidate the role of miRNA in the pathogenesis of OA. PMID:27019615

  6. 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.

  7. [Critical study of radiculomedullary and neuromuscular complications of ankylosing spondylitis].

    PubMed

    Serratrice, G; Acquaviva, P; Pouget, J; Guerra, L

    1987-03-01

    Medullo-radicular and neuro-muscular involvements of ankylosing spondylarthritis, often reported in an analytic fashion in the literature, deserve to be the subject of a critical study. Various neurological manifestations secondary to exceptional atlo-occipital and sometimes axis-atlas subluxations and medullary lesions as well as syndromes of the cauda equina. The medullary lesions have an epidural origin (3 cases in the literature, 2 cases from the authors) or are secondary to a spondylodiscitis (4 cases in the literature) or secondary to both (1 case reported by the authors). As for syndromes of the cauda equina the authors report 3 cases to be added to the 55 published previously. It concerns always old spondylarthritis. The lesions combine posterior diverticula and lesions of the lamina. The treatment is usually ineffective. A special case is represented by forms with trophic disorders. More debatable are the radicular lesions, which, except for intercostal pain, should be linked to local pain. Electromyographic abnormalities are of no significance. Alterations of the paravertebral muscles viewed on the scanner X have, for now, an uncertain significance. Finally, various associations, without significance such as multiple sclerosis, diffuse muscular lesions and the classic spondylotic pseudo-tabes, should be rejected.

  8. "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)

  9. Lessons from a Dominican Republic Field Study

    ERIC Educational Resources Information Center

    Gunter, Michael M., Jr.

    2010-01-01

    Utilizing student-centered pedagogy, this case study explores an increasingly prominent and instructive addition to traditional academic coursework--the field study experience. This is particularly true in the arena of environmental education where students learn best by experiencing environmental problems first-hand and then interacting with…

  10. 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…

  11. Vector Fields Simplification-A Case Study of Visualizing Climate Modeling and Simulation Data Sets

    SciTech Connect

    Wong, Pak C.; Foote, Harlan P.; Leung, Lai R.; Jurrus, Elizabeth R.; Adams, Daniel R.; Thomas, James J.

    2006-10-01

    In our study of regional climate modeling and simulation, we frequently encounter vector fields that are crowded with large numbers of critical points. A critical point in a flow is where vector field vanishes. While these critical points accurately reflect topology of the vector fields, in our study only a subset them is worth further investigation. We present a filtering tech-nique based on the vorticity of the vector fields to eliminate less interesting and sometimes sporadic critical points in a mul-tiresolution fashion. The neighboring regions of the preserved features, which are characterized by strong shear and circulation, potential locations of weather instability. We apply our fea-ture-filtering technique to a regional climate modeling data covering East Asia in the summer of 1991.

  12. 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.

  13. Interaction Between Flames and Electric Fields Studied

    NASA Technical Reports Server (NTRS)

    Yuan, Zeng-Guang; Hegde, Uday

    2003-01-01

    The interaction between flames and electric fields has long been an interesting research subject that has theoretical importance as well as practical significance. Many of the reactions in a flame follow an ionic pathway: that is, positive and negative ions are formed during the intermediate steps of the reaction. When an external electric field is applied, the ions move according to the electric force (the Coulomb force) exerted on them. The motion of the ions modifies the chemistry because the reacting species are altered, it changes the velocity field of the flame, and it alters the electric field distribution. As a result, the flame will change its shape and location to meet all thermal, chemical, and electrical constraints. In normal gravity, the strong buoyant effect often makes the flame multidimensional and, thus, hinders the detailed study of the problem.

  14. 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

  15. 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…

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Yung Moo Huh

    2001-05-01

    Thermodynamics has been studied systematically for the high temperature cuprate superconductor La{sub 2-x}Sr{sub x}CuO{sub 4-{delta}}, 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 T{sub c}, 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 T{sub c0} 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 La{sub 2-x}Sr{sub x}CuO{sub 4} (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 T{sub c}. 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 {zeta}{sub c} becomes comparable to the spacing between adjacent CuO{sub 2} layers s at sufficiently high magnetic fields near H{sub c2}.

  18. 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

    2016-01-01

    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

  19. 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

  20. 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

    2016-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    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.

  2. Criticality safety study of shutdown diffusion cascade coolers

    SciTech Connect

    Paschal, L.S.; Basoglu, B.; Bentley, C.L.; Dunn, M.E.

    1996-12-31

    Gaseous diffusion plants use cascade coolers in the production of highly enriched uranium (HEU) to remove heat from the enriched stream of UF{sub 6}. The cascade coolers operate like shell and tube heat exchangers with the UF{sub 6} on the shell side and Freon on the tube side. Recirculating cooling water (RCW) in condensers is used to cool the Freon. A criticality safety analysis was previously performed for cascade coolers during normal operation. The purpose of this paper is to evaluate several different hypothetical accidents regarding RCW ingress into the cooler to determine whether criticality safety concerns exist.

  3. Assessment of critical factors affecting the performance of trapped field magnets using thin film superconductor tapes

    NASA Astrophysics Data System (ADS)

    Selva, Kavita; Li, Xiao-Fen; Majkic, Goran; Masson, Philippe

    2015-12-01

    Trapped field magnets have been investigated using Zr-added (Gd,Y)Ba-Cu-O thin film superconductor tapes. Trapped field profiles were examined both experimentally and by simulation over a temperature range of 30 to 77 K. A good match is found between experimental and simulation trapped field data at 77 K and 65 K, but higher trapped field values were obtained experimentally at lower temperatures. Trapped field values up to 1.55 T were measured in an 11 mm thick stack of 55 μm thick superconductor tapes arranged in a crisscross fashion with three tapes per layer. A substantial increase in the trapped field values was found by simulation, in tape stacks made with 20 μm thick tapes. Using such thin tapes, trapped field values of nearly 2 T is predicted in ∼ 13 mm thick tape stacks at 77 K.

  4. Marine and Environmental Studies Field Manual.

    ERIC Educational Resources Information Center

    Cranston School Dept., RI.

    This laboratory manual was developed for a field-oriented high school oceanology program. The organization of the units includes a selection of supplementary activities to allow students to explore ocean studies in more depth. Included are 19 units. The units include biological oceanography, physical oceanography, and some social science topics. A…

  5. 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…

  6. 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…

  7. Matching field effects at tesla-level magnetic fields in critical current density in high-Tc superconductors containing self-assembled columnar defects

    SciTech Connect

    Sinclair, J.; Zuev, Yuri L; Cantoni, Claudia; Wee, Sung Hun; Varanasi, C. V.; Thompson, James R; Christen, David K

    2012-01-01

    We have investigated the superconductive transport properties of YBa2Cu3O7 films containing self-assembled columnar arrays of second phase SrZrO3 or BaSnO3 precipitates. A matching condition between columnar pinning sites (aligned at or near the c axis) and external magnetic flux, tilted with respect to them, is identified in the critical current JC.H/ data. The results for the material containing SrZrO3-based pins are analyzed within a simple intuitive model. At matching, the critical current is enhanced above the model prediction. In complementary contact-free investigations of BaSnO3-doped material, matching effects are observed over a wide range of temperatures in the field dependence of JC.H/. The deduced matching fields agree reasonably well with the densities of columnar pins directly observed by scanning electron microscopy.

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

    PubMed

    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

  9. 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

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

    NASA Astrophysics Data System (ADS)

    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.

    2016-07-01

    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.

  11. 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; 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 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

  12. 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…

  13. 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...

  14. Critical-Cultural Studies in Research and Instruction.

    ERIC Educational Resources Information Center

    Switzer, Les; McNamara, John; Ryan, Michael

    1999-01-01

    Outlines two paradigms in critical-cultural analysis that seek to identify and explain the meaning of phenomena that make a culture, focusing on their relevance to research and teaching in journalism and mass communication. Identifies key issues and implications for mass communication research and teaching. Suggests ways educators can apply…

  15. The Evaluation of HRD: A Critical Study with Applications

    ERIC Educational Resources Information Center

    Tome, Eduardo

    2009-01-01

    Purpose: The purpose of this paper is to analyze critically the most important methods that are used in the evaluation of human resource development (HRD). Design/methodology/approach: The approach is to ask two questions: What are the methods available to define the impact of HRD in the economy? How can we evaluate the evaluations that have been…

  16. 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…

  17. 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…

  18. 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…

  19. 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).

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

    PubMed

    Dahm, T; Schopohl, N

    2003-07-01

    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. In-field critical current of type-II superconductors caused by strain from nanoscale columnar inclusions

    NASA Astrophysics Data System (ADS)

    Rodriguez, J. P.; Barnes, P. N.; Varanasi, C. V.

    2008-08-01

    The results of a linear elasticity analysis yields that nanorod inclusions aligned along the c axis of a thin film of YBa2Cu3O7-δ , such as BaZrO3 and BaSnO3 , squeeze that matrix by pure shear. The sensitivity of the superconducting critical temperature in that material to the latter implies that the phase boundary separating the nanorod inclusion from the superconductor acts as a collective pinning center for the vortex lattice that appears in external magnetic field. A dominant contribution to the in-field critical current can result. The elasticity analysis also yields that the growth of nanorod inclusions can be weakly metastable when the inclusion is softer than the matrix.

  2. 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. PMID:26895190

  3. Terahertz radiation from InAlAs and GaAs surface intrinsic-N+ structures and the critical electric fields of semiconductors

    NASA Astrophysics Data System (ADS)

    Hwang, J. S.; Lin, H. C.; Lin, K. I.; Zhang, X. C.

    2005-09-01

    This study examines terahertz radiation from a series of In0.52Al0.48As and GaAs surface-intrinsic-N+ structures (SIN+) with surface-intrinsic layers of various thicknesses. The built-in electric fields in the SIN+ structures are used as the bias. Experimental results indicate that the amplitudes of the THz emission are independent of the built-in electric fields in the emitters when the built-in electric fields exceed the corresponding critical electric fields of the semiconductors. In contrast, the amplitudes of the THz emission are proportional to the thickness of the intrinsic layer and, therefore, the number of photo-excited charged carriers.

  4. Field-induced magnetostructural transition in Gd5ge4 studied by pulsed magnetic fields

    SciTech Connect

    Ouyang, Z.W.; Nojiri, H.; Yoshii, S.; Rao, G.H.; Wang, Y.C.; Pecharsky, V.K.; Gschneidner Jr., K.A.

    2008-05-22

    The field-induced magnetostructural transformation in Gd{sub 5}Ge{sub 4} was examined by magnetization measurements in pulsed magnetic fields. The low-temperature irreversibility of the transition can be destroyed by the magnetocaloric effect, and depending on the heat exchange between the sample and its surroundings, the irreversibility (or kinetic arrest) can also be retained. Measurements by using various magnetic-field sweep rates were conducted to examine the dynamic response of the system in the transition region. The critical fields for the magnetostructural transition below 20 K are field sweep rate dependent--the larger the field sweep rate, the higher the critical field. However, this rate dependence is readily suppressed with increasing temperature.

  5. Assessing the spatial and field dependence of the critical current density in YBCO bulk superconductors by scanning Hall probes

    NASA Astrophysics Data System (ADS)

    Hengstberger, F.; Eisterer, M.; Zehetmayer, M.; Weber, H. W.

    2009-02-01

    Although the flux density map of a bulk superconductor provides in principle sufficient information for calculating the magnitude and the direction of the supercurrent flow, the inversion of the Biot-Savart law is ill conditioned for thick samples, thus rendering this method unsuitable for state of the art bulk superconductors. If a thin (<1 mm) slab is cut from the bulk, the inversion is reasonably well conditioned and the variation of the critical current density in the sample can be calculated with adequate spatial resolution. Therefore a novel procedure is employed, which exploits the symmetry of the problem and solves the equations non-iteratively, assuming a planar thickness-independent current density. The calculated current density at a certain position is found to depend on the magnetic induction. In this way the average field dependence of the critical current density Jc(B) is also obtained at low fields, which is not accessible to magnetization measurements due to the self-field of the sample. It is further shown that an evaluation of magnetization loops, taking the self-field into account, results in a similar dependence in the field range accessible to this experiment.

  6. 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 and…

  7. Robust superconductivity with large upper critical field in Nb{sub 2}PdS{sub 5}

    SciTech Connect

    Jha, Rajveer; Tiwari, Brajesh; Rani, Poonam; Kishan, Hari; Awana, V. P. S.

    2014-06-07

    We report synthesis, structural details, and complete superconducting characterization of very recently discovered [Q. Zhang, Sci. Rep. 3, 1446 (2013)] Nb{sub 2}PdS{sub 5} new superconductor. The synthesized compound is crystallized in monoclinic structure with C2/m (#12) space group. Bulk superconductivity is seen in both ac/dc magnetic susceptibility and electrical resistivity measurements with superconducting transition temperature (T{sub c}) at 6 K. The upper critical field (H{sub c2}) being estimated from high field magneto-transport [ρ(T)H] measurements is above 240 kOe. The estimated H{sub c2}(0) is clearly above the Pauli paramagnetic limit of ∼1.84T{sub c}. Heat capacity (C{sub p}) measurements show clear transition with well defined peak at T{sub c}, but with lower jump than as expected for a Bardeen–Cooper–Schrieffer type superconductor. The Sommerfeld constant (γ) and Debye temperature (Θ{sub D}) as determined from low temperature fitting of C{sub P}(T) data are 32 mJ/mole-K{sup 2} and 263 K, respectively. Hall coefficients and resistivity in conjugation with electronic heat capacity indicates multiple gap superconductivity signatures in Nb{sub 2}PdS{sub 5}. We also studied the impact of hydrostatic pressure (0–1.97 Gpa) on superconductivity of Nb{sub 2}PdS{sub 5} and found nearly no change in T{sub c} for the given pressure range.

  8. Study of density distribution in a near-critical simple fluid (19-IML-1)

    NASA Technical Reports Server (NTRS)

    Michels, Teun

    1992-01-01

    This experiment uses visual observation, interferometry, and light scattering techniques to observe and analyze the density distribution in SF6 above and below the critical temperature. Below the critical temperature, the fluid system is split up into two coexisting phases, liquid and vapor. The spatial separation of these phases on earth, liquid below and vapor above, is not an intrinsic property of the fluid system; it is merely an effect of the action of the gravity field. At a fixed temperature, the density of each of the coexisting phases is in principle fixed. However, near T sub c where the fluid is strongly compressible, gravity induced hydrostatic forces will result in a gradual decrease in density with increasing height in the sample container. This hydrostatic density profile is even more pronounced in the one phase fluid at temperatures slightly above T sub c. The experiment is set up to study the intrinsic density distributions and equilibration rates of a critical sample in a small container. Interferometry will be used to determine local density and thickness of surface and interface layers. The light scattering data will reveal the size of the density fluctuations on a microscopic scale.

  9. 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…

  10. 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…

  11. 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…

  12. 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…

  13. 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…

  14. 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,…

  15. 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.

  16. Enhancement of the high-magnetic-field critical current density of superconducting MgB2 by proton irradiation.

    PubMed

    Bugoslavsky, Y; Cohen, L F; Perkins, G K; Polichetti, M; Tate, T J; Gwilliam, R; Caplin, A D

    2001-05-31

    Magnesium diboride, MgB2, has a relatively high superconducting transition temperature, placing it between the families of low- and high-temperature (copper oxide based) superconductors. Supercurrent flow in MgB2 is unhindered by grain boundaries, making it potentially attractive for technological applications in the temperature range 20-30 K. But in the bulk material, the critical current density (Jc) drops rapidly with increasing magnetic field strength. The magnitude and field dependence of the critical current are related to the presence of structural defects that can 'pin' the quantized magnetic vortices that permeate the material, and a lack of natural defects in MgB2 may be responsible for the rapid decline of Jc with increasing field strength. Here we show that modest levels of atomic disorder induced by proton irradiation enhance the pinning of vortices, thereby significantly increasing Jc at high field strengths. We anticipate that either chemical doping or mechanical processing should generate similar levels of disorder, and so achieve performance that is technologically attractive in an economically viable way.

  17. 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}.

  18. Early prenatal critical period for chorda tympani nerve terminal field development.

    PubMed

    Krimm, R F; Hill, D L

    1997-02-10

    In order to determine whether the developing central gustatory system responds to dietary manipulation during restricted developmental periods, terminal fields of the chorda tympani nerve within the nucleus of the solitary tract were investigated via anterograde transport of horseradish peroxidase in control rats and in rats in which a low sodium diet was systematically fed during specific periods of development. Rats fed a low sodium diet (0.03% NaCl) from embryonic day 3 (E3) to day E12 and then fed a sodium replete diet to at least 60 days postnatal exhibited enlarged and irregularly shaped chorda tympani terminal fields. Specifically, the dorsal zone of the field was the smallest in controls, whereas it was the largest in restricted rats, occupying more territory within the nucleus. This alteration in the terminal field was apparent in all groups of rats fed the low-NaCl diet beginning at E3, and continuing beyond E12. In contrast, no effects of the dietary manipulation on the developing chorda tympani field was evident when it occurred from E3 to day E9, from E0 to day E9 or when it occurred at adulthood only. Therefore, only 9 days of maternal exposure to a sodium-restricted diet is required for a permanent expansion of the chorda tympani terminal field in the offspring. Moreover, a brief period from E9 to E12 must be included within the 9-day dietary restriction to yield the expanded field. Since this period is before taste receptors appear on the tongue, it is likely that nonactivity-dependent factors determine the formation of the chorda tympani terminal field during later development.

  19. Connection between in-plane upper critical field Hc 2 and gap symmetry in layered d -wave superconductors

    NASA Astrophysics Data System (ADS)

    Wang, Jing-Rong; Liu, Guo-Zhu; Zhang, Chang-Jin

    2016-07-01

    Angle-resolved upper critical field Hc 2 provides an efficient tool to probe the gap symmetry of unconventional superconductors. We revisit the behavior of in-plane Hc 2 in d -wave superconductors by considering both the orbital effect and Pauli paramagnetic effect. After carrying out systematic analysis, we show that the maxima of Hc 2 could be along either nodal or antinodal directions of a d -wave superconducting gap, depending on the specific values of a number of tuning parameters. This behavior is in contrast to the common belief that the maxima of in-plane Hc 2 are along the direction where the superconducting gap takes its maximal value. Therefore, identifying the precise d -wave gap symmetry through fitting experiments results of angle-resolved Hc 2 with model calculations at a fixed temperature, as widely used in previous studies, is difficult and practically unreliable. However, our extensive analysis of angle-resolved Hc 2 show that there is a critical temperature T*: in-plane Hc 2 exhibits its maxima along nodal directions at T studies on the gap symmetry of CeCu2Si2 are unreliable and need to be reexamined, and also provide a candidate solution to an experimental discrepancy in the angle-resolved Hc 2 in CeCoIn5.

  20. 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

  1. 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.

  2. 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,…

  3. Critical thinking and clinical competence: a study of their relationship in BSN seniors.

    PubMed

    May, B A; Edell, V; Butell, S; Doughty, J; Langford, C

    1999-03-01

    National nursing organizations and nurses in the workplace identify critical thinking skills as essential to competent nursing practice. This study sets out to test the relationship between critical thinking skills and clinical competence because it seems that competent practice depends on critical thinking abilities. This study focuses on one school of nursing's response to the challenge of defining and measuring critical thinking and clinical competence and examining their relationship. An exploratory nonexperimental design was used with a heterogeneous sample consisting of two graduating nursing classes (N = 143). While the group of participants was able to think critically and practice competently according to set standards, there were no statistically significant correlations between critical thinking and clinical competence total scores. One conclusion for these findings is that critical thinking may not emerge as an associated factor with clinical competence until some time after nursing students become practicing nurses. PMID:10102507

  4. [Study on critical loads of sulfur and nitrogen in the Pearl River Delta].

    PubMed

    Sun, Cheng-Ling; Xie, Shao-Dong

    2014-04-01

    Supported by the geographical information system (ArcGIS), critical loads and exceedances of critical loads of sulfur and nitrogen in the Pearl River Delta (PRD) were calculated using Steady-state Mass Balance method with current deposition data, vegetation data and soil data obtained by field sampling and laboratory analysis. Results showed that the present critical loads of sulfur were high in the eastern PRD and low in the west. Higher critical loads occurred in most of Huizhou, north-central Guangzhou, Dongguan and south Zhongshan. The critical loads of these regions were mostly larger than 15 keq x (hm2 x a)(-1). Regions with lower critical loads included most of Jiangmen, most of Zhaoqing and part of Shenzhen with critical loads less than 2 keq x (hm2 x a)(-1). Critical loads of nitrogen were mainly in the range of 1.0-2.5 keq x (hm2 x a)(-1) while values lower than 1.0 keq x (hm2 x a)(-1) were found in Zhaoqing. According to the results of critical load exceedances, in several regions the sulfur deposition exceeded the critical loads whereas in most regions the nitrogen deposition exceeded the critical loads. With the reduction of particulate concentrations in atmosphere in the future, critical loads of sulfur would decrease and sulfur depositions in most regions would exceed their critical loads. Therefore, the control over nitrogen deposition should be strengthened in the present situation and special attention should be paid to the control of sulfur deposition with the reduction of particulate concentrations in the future.

  5. Obtaining a critical care pharmacist position: a marketing case study.

    PubMed

    Stratton, T P; Wu, B; Nakagawa, R S

    1993-06-01

    Marketing theory is used to explain how Pharmacy Department managers at a Vancouver-area hospital secured a new ICU pharmacist position in a period of severe fiscal constraint. Market segmentation, target marketing and pull marketing strategy were combined to obtain support for the new position. Improved drug information services for ICU nurses were promoted to Nursing Administration and enhanced pharmacotherapy monitoring was promoted to the two critical care physicians primarily responsible for patient care in the ICU. These physicians and Nursing Administration voiced their support for the new position to the V.P. of Nursing (the functional officer for Pharmacy), who then promoted the new position to Hospital Administration. A half-time DUR commitment by the ICU pharmacist was offered to Hospital Administration, expanding this already successful service and guaranteeing cost recovery for the new position. Hospital Administration approved the new ICU clinical pharmacist position in a budget which saw other hospital departments lose several positions.

  6. The buried reference electrode: A critical long term performance study

    SciTech Connect

    Leon, T.; Geyer, W.

    1998-12-31

    Accurate monitoring of cathodic protection relies upon the proficiency of the test personnel and the proper operation of the required equipment. The equipment consists of properly insulated test leads, an electronic volt meter with a known internal circuit resistance, and a reference electrode. The proper operation of each piece of equipment is critical to the accuracy of the cathodic protection test results. However, the reference electrode is not often suspected of being responsible for unexpected cathodic protection readings. This paper will provide background on the use of portable reference electrodes and data used to evaluate the performance of buried reference electrodes installed adjacent to a single, catholically protected, underground storage tank. Data accumulated at the test site clearly indicates that not all buried reference electrodes provide identical results.

  7. Critical component of the interplanetary magnetic field responsible for large geomagnetic effects in the polar cap.

    NASA Technical Reports Server (NTRS)

    Friis-Christensen, E.; Lassen, K.; Wilhjelm, J.; Wilcox, J. M.; Gonzalez, W.; Colburn, D. S.

    1972-01-01

    An observed influence of the interplanetary magnetic-sector structure on the geomagnetic variations in the polar cap appears to be due to the component of the interplanetary magnetic field near the ecliptic perpendicular to the earth-sun direction. This suggests that the observed effect on the ground originates in the front of the magnetosphere.

  8. Critical and umbilical points of a non-Gaussian random field

    NASA Astrophysics Data System (ADS)

    Beuman, T. H.; Turner, A. M.; Vitelli, V.

    2013-07-01

    Random fields in nature often have, to a good approximation, Gaussian characteristics. For such fields, the number of maxima and minima are the same. Furthermore, the relative densities of umbilical points, topological defects which can be classified into three types, have certain fixed values. Phenomena described by nonlinear laws can, however, give rise to a non-Gaussian contribution, causing a deviation from these universal values. We consider a random surface, whose height is given by a nonlinear function of a Gaussian field. We find that, as a result of the non-Gaussianity, the density of maxima and minima no longer match and we calculate the relative imbalance between the two. We also calculate the change in the relative density of umbilics. This allows us not only to detect a perturbation, but to determine its size as well. This geometric approach offers an independent way of detecting non-Gaussianity, which even works in cases where the field itself can not be probed directly.

  9. Low-magnetic-field operations of intrinsic Josephson junctions with a long c-axis periodicity by artificial critical-current modulations

    NASA Astrophysics Data System (ADS)

    Sakai, Shigeki; Zhao, Xia

    2007-02-01

    Flux-flow cavity resonances in intrinsic Josephson junctions (IJJs) with long c-axis periodicity by artificial critical-current (Jc) modulation are studied numerically and theoretically. For an n-1-n-1-n-1-n IJJ system with n-layer high-Jc and one-layer low-Jc alternately stacked, numerical simulation confirms fluxon penetration only in the low-Jc junctions under proper low magnetic fields. The simulation also shows pronounced cavity-resonance steps in the I-V curves of the low-Jc junctions, meaning that fluxon dynamics can be generated under much lower magnetic fields, compared to the fields for usual IJJs with homogeneous Jc. A theoretical method for describing the flux-flow cavity-resonance properties is presented. The general disperse k-ω relationship shows that, at low-k regions, the critical-current-modulated junction system can be regarded as simple homogeneous stacked junctions with a new effective thickness and a new inductive coupling strength. For general-k cases, the cavity-resonant voltage steps on the I-V curves at various magnetic fields can be well indexed by integers, which means excellent agreement between the theoretical analysis and the numerical simulations.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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…

  16. 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.

  17. 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

  18. Numerical quasi-linear study of the critical ionization velocity phenomenon

    NASA Technical Reports Server (NTRS)

    Moghaddam-Taaheri, E.; Goertz, C. K.

    1993-01-01

    The critical ionization velocity (CIV) for a neutral barium (Ba) gas cloud moving across the static magnetic field is studied numerically using quasi-linear equations and a parameter range which is typical for the shaped-charge Ba gas release experiments in space. For consistency the charge exchange between the background oxygen ions and neutral atoms and its reverse process, as well as the excitation of the neutral Ba atoms, are included. The numerical results indicate that when the ionization rate due to CIV becomes comparable to the charge exchange rate the energy lost to the ionization and excitation collisions by the superthermal electrons exceeds the energy gain from the waves that are excited by the ion beam. This results in a CIV yield less than the yield by the charge exchange process.

  19. A critical study of Rasamritam and it’s applied aspects

    PubMed Central

    Mohapatra, Sudhaldev; Gupta, Ramesh K.; Reddy, K.R.C.; Jha, Chandra Bhushan

    2012-01-01

    Historical studies of Rasa shastra reveal the use of metals and minerals, both for alchemical and therapeutical purposes in ancient past. But, gradually the alchemical use of the subject, declines and the therapeutical use takes over. Rasamritam is the latest doctrine in the field of Rasa shastra which compiles the extract of the older books and adopted some new and contemporary concepts. The practical aspects of this text influence both the academicians as well as physicians in large extent. Keeping the wealthier, timely concept of this text in mind, we are trying to review and analyze it critically for the benefit of researchers and practitioners and hope the idea will be fruitful. PMID:23559787

  20. Dielectrophoretic spectra of translational velocity and critical frequency for a spheroid in traveling electric field.

    PubMed

    Bunthawin, Sakshin; Wanichapichart, Pikul; Tuantranont, Adisorn; Coster, Hans G L

    2010-01-13

    An analysis has been made of the dielectrophoretic (DEP) forces acting on a spheroidal particle in a traveling alternating electric field. The traveling field can be generated by application of alternating current signals to an octapair electrode array arranged in phase quadrature sequence. The frequency dependent force can be resolved into two orthogonal forces that are determined by the real and the imaginary parts of the Clausius-Mossotti factor. The former is determined by the gradient in the electric field and directs the particle either toward or away from the tip of the electrodes in the electrode array. The force determined by the imaginary component is in a direction along the track of the octapair interdigitated electrode array. The DEP forces are related to the dielectric properties of the particle. Experiments were conducted to determine the DEP forces in such an electrode arrangement using yeast cells (Saccharomyces cervisiate TISTR 5088) with media of various conductivities. Experimental data are presented for both viable and nonviable cells. The dielectric properties so obtained were similar to those previously reported in literature using other DEP techniques.

  1. Nonlinear Force-Free Magnetic Field Modeling of AR 10953: A Critical Assessment

    NASA Astrophysics Data System (ADS)

    De Rosa, Marc L.; Schrijver, C. J.; Barnes, G.; Leka, K. D.; Lites, B. W.; Aschwanden, M. J.; Amari, T.; Canou, A.; McTiernan, J. M.; Régnier, S.; Thalmann, J. K.; Valori, G.; Wheatland, M. S.; Wiegelmann, T.; Cheung, M. C. M.; Conlon, P. A.; Fuhrmann, M.; Inhester, B.; Tadesse, T.

    2009-05-01

    Nonlinear force-free field (NLFFF) modeling seeks to provide accurate representations of the structure of the magnetic field above solar active regions, from which estimates of physical quantities of interest (e.g., free energy and helicity) can be made. However, the suite of NLFFF algorithms have failed to arrive at consistent solutions when applied to (thus far, two) cases using the highest-available-resolution vector magnetogram data from Hinode/SOT-SP (in the region of the modeling area of interest) and line-of-sight magnetograms from SOHO/MDI (where vector data were not available). One issue is that NLFFF models require consistent, force-free vector magnetic boundary data, and vector magnetogram data sampling the photosphere do not satisfy this requirement. Consequently, several problems have arisen that are believed to affect such modeling efforts. We use AR 10953 to illustrate these problems, namely: (1) some of the far-reaching, current-carrying connections are exterior to the observational field of view, (2) the solution algorithms do not (yet) incorporate the measurement uncertainties in the vector magnetogram data, and/or (3) a better way is needed to account for the Lorentz forces within the layer between the photosphere and coronal base. In light of these issues, we conclude that it remains difficult to derive useful and significant estimates of physical quantities from NLFFF models.

  2. Nonlinear Force-Free Magnetic Field Modeling of the Solar Corona: A Critical Assessment

    NASA Astrophysics Data System (ADS)

    De Rosa, M. L.; Schrijver, C. J.; Barnes, G.; Leka, K. D.; Lites, B. W.; Aschwanden, M. J.; McTiernan, J. M.; Régnier, S.; Thalmann, J.; Valori, G.; Wheatland, M. S.; Wiegelmann, T.; Cheung, M.; Conlon, P. A.; Fuhrmann, M.; Inhester, B.; Tadesse, T.

    2008-12-01

    Nonlinear force-free field (NLFFF) modeling promises to provide accurate representations of the structure of the magnetic field above solar active regions, from which estimates of physical quantities of interest (e.g., free energy and helicity) can be made. However, the suite of NLFFF algorithms have so far failed to arrive at consistent solutions when applied to cases using the highest-available-resolution vector magnetogram data from Hinode/SOT-SP (in the region of the modeling area of interest) and line-of-sight magnetograms from SOHO/MDI (where vector data were not been available). It is our view that the lack of robust results indicates an endemic problem with the NLFFF modeling process, and that this process will likely continue to fail until (1) more of the far-reaching, current-carrying connections are within the observational field of view, (2) the solution algorithms incorporate the measurement uncertainties in the vector magnetogram data, and/or (3) a better way is found to account for the Lorentz forces within the layer between the photosphere and coronal base. In light of these issues, we conclude that it remains difficult to derive useful and significant estimates of physical quantities from NLFFF models.

  3. Theoretical studies of transient criticality of irradiated fuel elements

    SciTech Connect

    Barbry, F.; Bonhomme, C.; Hague, P.; Mather, D.J.; Shaw, P.M.

    1987-01-01

    The use of transport flasks containing irradiated fuel is a common event, and their movements are strictly regulated by the national competent authority in order that an acceptable level of control of radiation hazards be maintained. Nonetheless it has been considered prudent to quantify the consequences of a particular hypothetical accident involving a transport package. The particular accident examined assumed that recriticality occurs during the refilling of a flask, and for the Commissariat a l'Energie Atomique (CEA) scenario, for which flasks are transported dry, the hypothetical accident occurs as the flask is slowly lowered into a storage pond. An alternative UK scenario assumes that the flask is being refilled, following breach, by a high-pressure hose. Thus, the consequences of such an accident were estimated by developing computer codes, Chateau by the CEA and Sartemp by the UK Atomic Energy Authority (UKAEA). This and other results show that the hypothetical accident in which a transport flask is brought to critical by the reentry of water gives at most a relatively mild event. In view of the considerably unlikely circumstances and conservative aspects introduced, this result shows that such an accident can be safely contained.

  4. Geometrical study of nanoscale field effect diodes

    NASA Astrophysics Data System (ADS)

    Manavizadeh, Negin; Raissi, Farshid; Asl Soleimani, Ebrahim; Pourfath, Mahdi

    2012-04-01

    In this paper, the previously proposed side-contacted field effect diode (FED) is carefully studied and its characteristic is compared against that of a modified FED and a metal oxide semiconductor field effect transistor (MOSFET). The influences of the body thickness, each gate length and access resistance are investigated. The figures of merit including intrinsic gate delay time and energy-delay product, which represent the speed and switching energy of the device, respectively, are studied. Our results highlight that FEDs are good candidates for obtaining a high Ion/Ioff ratio with a relatively short delay time compared to conventional FEDs and MOSFETs. We show that by a careful scaling of the source-drain region, the access resistance can be optimized. We demonstrate that a well-tempered device with a high switching response and a lower energy consumption can be achieved with a 30 nm body thickness, 85 nm source-drain length and a drain gate length longer than the source gate length.

  5. 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.

  6. Metamagnetic quantum criticality in Sr3Ru2O7 studied by thermal expansion.

    PubMed

    Gegenwart, P; Weickert, F; Garst, M; Perry, R S; Maeno, Y

    2006-04-01

    We report low-temperature thermal expansion measurements on the bilayer ruthenate Sr3Ru2O7 as a function of magnetic field applied perpendicular to the ruthenium-oxide planes. The field dependence of the c-axis expansion coefficient indicates the accumulation of entropy close to 8 T, related to an underlying quantum critical point. The latter is masked by two first-order metamagnetic transitions which bound a regime of enhanced entropy. Outside this region the singular thermal expansion behavior is compatible with the predictions of the itinerant theory for a two-dimensional metamagnetic quantum critical end point. PMID:16712009

  7. 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

  8. 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.

  9. Fourfold symmetry in the ab-plane of the upper critical field for the high-T{sub c} cuprates

    SciTech Connect

    Noji, T.; Koike, Y.; Nishizaki, T.; Kobayashi, N.

    1996-11-01

    The authors have found clear anisotropy in the ab plane with fourfold symmetry of the resistive superconducting transition under magnetic fields for single-crystal Pb{sub 2}Sr{sub 2}Y{sub 0.62}Ca{sub 0.38}Cu{sub 3}O{sub 8}, which is regarded as anisotropy of the upper critical field Hc{sub 2}. This is not only qualitatively but also quantitatively similar to that formerly observed in La{sub 1.86}Sr{sub 0.14}CuO{sub 4}. The observed fourfold symmetry is explained as being mainly due to the anisotropy of the superconducting energy gap owing to d{sub x{sup 2}{minus}y{sup 2}} pairing. H{sub c2}, one of the bulk properties, supports d{sub x{sup 2}{minus}y{sup 2}} pairing in the high-T{sub c} superconductivity.

  10. Effect of disorder on the decreasing the critical value of magnetic field in proximity induced topological superconductors

    NASA Astrophysics Data System (ADS)

    Alavirad, Yahya; Chiu, Ching-Kai; Sau, Jay

    Here we investigate how adding disorder changes the critical value of magnetic field Bc required to observe the topological phase transition in proximity induced topological superconductors .We consider disordered topological superconductors in D = 1 , 2 spatial dimensions and use numerical analysis to directly calculate the topological invariant.Qualitatively different behavior are found depending on the dimensionality of the system. In contrast to D = 2 for D = 1 we show that adding disorder gradually decreases Bc from the clean the case limit of Bc =√{μ2 +Δ2 } to Bc = Δ . A discussion of why these results are expected is provided. These findings, specially in D = 1 dimension are of experimental interest since they show that the topological phase transition might be observable at values of magnetic field Bc much smaller than previously expected. This work was supported by LPS-CMTC, JQI-NSF-PFC and University of Maryland startup grants.

  11. Estimate of the critical exponents from the field-theoretical renormalization group: mathematical meaning of the 'Standard Values'

    SciTech Connect

    Pogorelov, A. A.; Suslov, I. M.

    2008-06-15

    New estimates of the critical exponents have been obtained from the field-theoretical renormalization group using a new method for summing divergent series. The results almost coincide with the central values obtained by Le Guillou and Zinn-Justin (the so-called standard values), but have lower uncertainty. It has been shown that usual field-theoretical estimates implicitly imply the smoothness of the coefficient functions. The last assumption is open for discussion in view of the existence of the oscillating contribution to the coefficient functions. The appropriate interpretation of the last contribution is necessary both for the estimation of the systematic errors of the standard values and for a further increase in accuracy.

  12. Laboratory studies in search of the critical hydrogen concentration

    NASA Astrophysics Data System (ADS)

    Kanjana, Kotchaphan; Haygarth, Kyle S.; Wu, Weiqiang; Bartels, David M.

    2013-01-01

    Addition of H2 to primary coolant water is widely used in the nuclear reactor industry to suppress water radiolysis and lower the corrosion potential. The critical hydrogen concentration (CHC) - the minimum concentration of excess H2 that can completely suppress O2, H2O2, and H2 formation from water radiolysis - is an important quantity for the management of reactor water chemistry. For the design of future supercritical water cooled reactors, we have investigated whether water radiolysis can be suppressed with a reasonable overpressure of H2. Experiments were carried out using 2.5-2.8 MeV electrons from a van de Graaff accelerator, which can easily produce dose rates on the order of one kilogray/second, typical of power reactors. Radiolytic H2 and O2 production was measured as a function of excess dissolved H2. The results indicate that net radiolysis of water can be suppressed in supercritical water. Anomalous high H2 concentrations were obtained using metal (hastelloy or titanium) irradiation tubing rather than sapphire or silica. We ascribe these results to a radiation-stimulated corrosion process at high temperature. Throughout the subcritical temperature regime, almost no oxygen is measured, even though kinetic modeling suggests there should be concentrations well above our detection threshold. To explain this result we recommend that unmeasured rate constants for •H+O2- and (e-)aq+O2- should be considered completely diffusion-limited. At 300 °C, the (high dose rate) steady state H2 concentration in pure water is almost completely determined by the equilibrium H2+•OH⇔•H+H2O. The measured steady-state H2 is in good agreement with the recent equilibrium constant estimate of Bartels (Radiation Physics and Chemistry 78(3): 191-194, (2009)).

  13. Quantization of charged fields in the presence of critical potential steps

    NASA Astrophysics Data System (ADS)

    Gavrilov, S. P.; Gitman, D. M.

    2016-02-01

    QED with strong external backgrounds that can create particles from the vacuum is well developed for the so-called t -electric potential steps, which are time-dependent external electric fields that are switched on and off at some time instants. However, there exist many physically interesting situations where external backgrounds do not switch off at the time infinity. E.g., these are time-independent nonuniform electric fields that are concentrated in restricted space areas. The latter backgrounds represent a kind of spatial x -electric potential steps for charged particles. They can also create particles from the vacuum, the Klein paradox being closely related to this process. Approaches elaborated for treating quantum effects in the t -electric potential steps are not directly applicable to the x -electric potential steps and their generalization for x -electric potential steps was not sufficiently developed. We believe that the present work represents a consistent solution of the latter problem. We have considered a canonical quantization of the Dirac and scalar fields with x -electric potential step and have found in- and out-creation and annihilation operators that allow one to have particle interpretation of the physical system under consideration. To identify in- and out-operators we have performed a detailed mathematical and physical analysis of solutions of the relativistic wave equations with an x -electric potential step with subsequent QFT analysis of correctness of such an identification. We elaborated a nonperturbative (in the external field) technique that allows one to calculate all characteristics of zero-order processes, such, for example, scattering, reflection, and electron-positron pair creation, without radiation corrections, and also to calculate Feynman diagrams that describe all characteristics of processes with interaction between the in-, out-particles and photons. These diagrams have formally the usual form, but contain special

  14. 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…

  15. 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.

  16. 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…

  17. 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 power/knowledge. (SD)

  18. 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…

  19. Innovations in technology--Novalung iLA: challenges for the field of critical care nursing.

    PubMed

    Gordon, Elizabeth

    2009-01-01

    The Novalung interventional lung assist (iLA) device is a new pumpless extracorporeal gas exchange device that imitates the native lung because it allows for protective mechanical ventilation by the reduction of tidal volumes and decreased end expiratory pressures. It is a rescue device for patients with refractory lung failure, as well as a bridge to lung transplantation. While used in Europe for some years, the Novalung iLA has been recently approved by both Health Canada and our facility, as a bridge to lung transplantation. In this article, the author discusses the introduction of this new advancement in extracorporeal gas exchange into an adult critical care setting. First, the author presents an overview of this new technology and how it differs from the traditional model of extracorporeal membrane oxygenation, and then shares the process in which the anticipated challenges of this device introduction were addressed in one institution. Particular attention is paid to the education of the nursing staff. A plan was developed to deliver information, education and training guidelines to prepare for patients requiring a bridge to lung transplantation with this device within the medical surgical intensive care unit in our hospital. Subsequently, these initiatives have expanded to include a workshop and a simulation experience.

  20. Fractal analysis for the ULF data during the 1993 Guam earthquake to study prefracture criticality

    NASA Astrophysics Data System (ADS)

    Ida, Y.; Hayakawa, M.

    2006-08-01

    An extremely large earthquake (with magnitude of 8.2) happened on 8 August 1993 near the Guam island, and ultra-low-frequency (ULF) (frequency less than 1 Hz) electromagnetic fields were measured by 3-axis induction magnetometers at an observing station (with the epicentral distance of 65 km) with sampling frequency of 1 Hz. In order to study electromagnetic signature of prefracture criticality, we have undertaken the fractal (mono-fractal) analysis by means of the Higuchi's method for the ULF data during the 1993 Guam earthquake. Then, it is found that the fractal dimension exhibits five maxima 99, 75, 52, 21, and 9-4 days before the earthquake main shock, which suggests the ULF electromagnetic signature of nonlinear evolution (in the sense of self-organized criticality) taking place in the lithosphere just before the 1993 large Guam earthquake. That is, there take place step-like changes in the lithosphere during the long-term of the order of several months before the main shock.

  1. Dual rover human habitation field study

    NASA Astrophysics Data System (ADS)

    Litaker, Harry L.; Thompson, Shelby G.; Szabo, Richard; Twyford, Evan S.; Conlee, Carl S.; Howard, Robert L.

    2013-10-01

    For the last 3 years, the National Aeronautics and Space Administration (NASA) has been testing a pressurized rover prototype in the deserts of Arizona to obtain human-in-the-loop performance data. This year's field trial consisted of operating two rovers simultaneously while embarking on two 7-day flight-like exploration missions. During the 2010 Desert Research and Technology Studies (DRATS) at Black Point Lava Flow and SP Mountain in Arizona, NASA human factors investigators, in cooperation with other engineers and scientists, collected data on both the daily living and working within and around the Space Exploration Vehicle (SEV). Both objective and subjective data were collected using standard human factors metrics. Over 305 h of crew habitability data were recorded during the field trial with 65 elements of habitation examined. Acceptability of the vehicles over the course of the missions was considered satisfactory by the majority of the crews. As with previous testing, habitation was considered acceptable by the crews, but some issues concerning stowage, Waste Containment System (WCS) volume, and sleep curtains need to be considered for redesign for the next generation vehicle.

  2. 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…

  3. 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

  4. 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…

  5. How to Critically Evaluate Case Studies in Social Work

    ERIC Educational Resources Information Center

    Lee, Eunjung; Mishna, Faye; Brennenstuhl, Sarah

    2010-01-01

    The purpose of this article is to develop guidelines to assist practitioners and researchers in evaluating and developing rigorous case studies. The main concern in evaluating a case study is to accurately assess its quality and ultimately to offer clients social work interventions informed by the best available evidence. To assess the quality of…

  6. 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.

  7. 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…

  8. ERICA plans for winter storms field study

    NASA Astrophysics Data System (ADS)

    Hadlock, Ron

    The Experiment on Rapidly Intensifying Cyclones over the Atlantic (ERICA) field study will be conducted between December 1, 1988, and February 28, 1989. The oceanic area that is approximately bounded by t he Gulf Stream and North America, from coastal Carolina to just east of Newfoundland, will be the region for special observations obtained by recently developed measurement systems, including high-resolution and safe Loran-C dropwindsondes, CLASS rawinsondes, an array of drifting data buoys, and multiple airborne Doppler radars. The special observations will be acquired within a framework of all conventional operational data available for the eastern United States and Canada, including that from the National Weather Service's land sites (plus supplemental rawinsonde observations), ocean platforms, U.S. Air Force WC-130 National Winter Storms Operations Plan reconnaissance flights, and civilian and military weather satellites. Satellite imagery and soundings willl be available in real time and archived through facilities of NOAA and the military.

  9. Coulomb Glass: a Mean Field Study

    NASA Astrophysics Data System (ADS)

    Mandra, Salvatore; Palassini, Matteo

    2012-02-01

    We study the Coulomb glass model of disordered localized electrons with long-range Coulomb interaction, which describes systems such as disordered insulators, granular metals, amorphous semiconductors, or doped crystalline semiconductors. Long ago Efros and Shklovskii showed that the long-range repulsion induces a soft Coulomb gap in the single particle density of states at low temperatures. Recent works suggested that this gap is associated to a transition to a glass phase, similar to the Almeida-Thouless transition in spin glasses. In this work, we use a mean field approach to characterize several physical properties of the Coulomb glass. In particular, following a seminal work of Bray and Moore, we show that the Edward-Anderson parameter qEA and the spin glass susceptibility χSG are directly related to spectrum distribution of the Hessian matrix around free energy minima. Using this result, we show that no glass transition is associated to the gap formation.

  10. Cliffs' GRE StudyWare Package: A Critical Evaluation.

    ERIC Educational Resources Information Center

    Brooke, Stephanie L.

    1995-01-01

    Provides evaluation of Cliffs' GRE StudyWare package (Bobrow, 1992). Discusses the educational implications of using Cliffs' approach, in addition to focusing on software considerations. Makes recommendations concerning Cliffs' method for Graduate Record Examination (GRE) preparation. (Author/LKS)

  11. 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.

  12. [Control of infection in the odontostomatologic field. Possibility of decontamination of critical surfaces].

    PubMed

    Sebastiani Annicchiarico, L; Cacciotti, G P; Lepri, B; Malangola, C; Curcio, M L

    1989-01-01

    After a brief description of the sources and procedures of transmission of infections in the odontostomatological field, the Authors illustrate the degree of contamination of a range of surfaces presented by odontological instruments. This is followed by a description of the possibility of a disinfecting treatment using two products one based on iodoform and the other on quaternary ammonium. Prior to this disinfection treatment, the surfaces examined presented a level of microbial contamination (according to the Griffiths scale) for the most part defined as "acceptable with certain reservations" or as "unacceptable", with the almost constant finding of Staphylococci (S. Haemolyticus, aureus, hominis and cohnii) and very frequently of Acinetobacter calcoaceticus, as well as various types of Pseudomonas (Ps. cepacea, maltophilia, and aeruginosa). The disinfection treatment carried out on these same surfaces had a positive effect, leading to a reduction in microbial findings of at least 98% both using energetic disinfectants based on iodoform products, and also milder disinfectants based on quaternary ammonium. Accordingly since both substances used almost constantly reduced the microbial presence despite the different disinfecting action involved, the Authors conclude that not only the use of specific substances but even the mere action of mechanical cleaning may play a fundamental role in the decontamination of surfaces.

  13. Pharmacometrics: a multidisciplinary field to facilitate critical thinking in drug development and translational research settings.

    PubMed

    Barrett, Jeffrey S; Fossler, Michael J; Cadieu, K David; Gastonguay, Marc R

    2008-05-01

    Pharmacometrics has evolved beyond quantitative analysis methods used to facilitate decision making in drug development, although the application of the discipline in this arena continues to represent the primary emphasis of scientists calling themselves pharmacometricians. While related fields populate and interface with pharmacometrics, there is a natural synergy with clinical pharmacology due to common areas of research and the decision-making expectation with respect to evolving conventional and translational research paradigms. Innovative and adaptable training programs and resources are essential in this regard as both disciplines promise to be key elements of the clinical research workplace of the future. The demand for scientists with pharmacometrics skills has risen substantially. Likewise, the salary garnered by those with these skills appears to be surpassing their counterparts without such backgrounds. Given the paucity of existing training programs, available training materials, and academic champions, a virtual faculty and online curriculum would allow students to matriculate into one of several programs associated with their advisor but take instruction from faculty at multiple institutions, including instructors in both industrial and regulatory settings. Flexibility in both the curriculum and the governance of the degree would provide the greatest hope of addressing the short supply of trained pharmacometricians. PMID:18440922

  14. 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…

  15. 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.

  16. 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…

  17. National Longitudinal Study of the High School Class of 1972: Critical Data Base. 22U-884.

    ERIC Educational Resources Information Center

    Talbert, Robin

    The National Longitudinal Study of the High School Class of 1972 (NLS) critical data base contains 151 items (plus background information) from the base year and followup questionnaires; about thirty-seven percent of all items. This set of critical items consists of: (1) basic demographic variables; (2) items necessary for defining activity states…

  18. 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…

  19. 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…

  20. 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…

  1. 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…

  2. 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,…

  3. 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…

  4. Pathologic Metabolism: An Exploratory Study of the Plasma Metabolome of Critical Injury

    PubMed Central

    Peltz, Erik D.; D’Alessandro, Angelo; Moore, Ernest E.; Chin, Theresa; Silliman, Christopher C.; Sauaia, Angela; Hansen, Kirk C.; Banerjee, Anirban

    2015-01-01

    BACKGROUND Severe trauma is associated with massive alterations in metabolism. Thus far, investigations have relied upon traditional bio-analytical approaches including calorimetry or nuclear magnetic resonance. However, recent strides in the field of mass spectrometry (MS)-based metabolomics present enhanced analytic opportunities to characterize a wide range of metabolites in the critical care setting. METHODS MS-based metabolomics analyses were performed on plasma samples from severely injured patients trauma-activation field blood (TAFB) and plasma samples obtained during emergency department thoracotomy (EDT). These were compared against the metabolic profiles of healthy controls. RESULTS Few significant alterations were observed between TAFB and EDT patients. On the other hand, we identified trauma-dependent metabolic signatures which support a state of hypercatabolism, driven by sugar consumption, lipolysis and fatty acid utilization, accumulation of ketone bodies, proteolysis and nucleoside breakdown which provides carbon and nitrogen sources to compensate for trauma-induced energy consumption and negative nitrogen balance. Unexpectedly, metabolites of bacterial origin (including tricarballylate and citramalate) were detected in plasma from trauma patients. CONCLUSIONS In the future, the correlation between metabolomics adaptation and recovery outcomes could be studied by MS-based approaches and this work can provide a method for assessing the efficacy of alternative resuscitation strategies. PMID:25807403

  5. Using tissue samples for proteomic studies-critical considerations.

    PubMed

    Becker, Karl-Friedrich

    2015-04-01

    From my experience of 22 years working in a pathology research laboratory and overseeing dozens of collaborations with research groups from basic sciences and industry, I have the impression that researchers are rarely aware of the special issues related to acquisition and processing of frozen or formalin-fixed tissue samples for proteomic analysis. While challenges are expected for formalin-fixed tissues because of the cross-linking activities of formaldehyde, researchers believe when using frozen tissue samples they are safe and always have excellent material to analyze-but this is not always the case. It is alarming that many researchers do not question the quality of the tissue samples they are analyzing and focus only on their analytical technique. Standardization of the entire workflow from test ordering to the report of the proteomic assay, with special emphasis on the preanalytical phase, is crucial for successful integration of proteomic studies in the clinic as protein profiles may change due to sample processing before the proteomic analysis is performed. The aim of this review is to discuss the progress of proteomic studies with human tissues and to highlight the challenges that must be understood and addressed for successful translation of proteomic methods to clinical practice.

  6. 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…

  7. 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…

  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. PMID:26379453

  9. 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.

  10. Low-field Tails in EuBCO Vortex Field Distributions: a T-dependence muSR Study*

    NASA Astrophysics Data System (ADS)

    Tien, Y.; Ruiz, E. J.; Aslanian, H. H.; Santiago, R. D.; Li, Y.; Boekema, C.

    2002-03-01

    Muon-Spin-Rotation (muSR) vortex data ranging from 3.5 K to roomtemperature of EuBa2Cu3O7 have been analyzed using a Maximum-Entropy (ME) technique [1-3]. With a 1-kOe applied field, anomalous low-field tails [1, 4] stretching from about 0.5 kOe to 0.8 kOe are observed for magnetic field distributions below 40 K. The muSR time-histogram data are weighted with a Gaussian filter. The low-field tail in the vortex field distribution is best viewed within a filter-time interval, determined to lie between 0.73 and 0.95 microseconds. As temperature decreases, an increase in the low-field tail intensity is observed. We note, the presence of the low-field tail indicates that extra superconductivity could exist in the CuO-chain layers well below critical temperature. Currently, we are studying the temperature dependence of the low-field tail by fitting the ME transforms with a tail function and two Gaussians (representing the main vortex and grainboundary signals [1]). Fit-analysis results and comparison with YBCO vortex-tail behavior [1, 2] are reported. [1] Santiago et al, Phys Rev B63 132509 (2001); [2] Alves et al, Phys Rev B49 12396 (1994); [3] Cooke et al, Phys Rev B39 2748 (1989); [4] Aslanian et al, Physica C364-365 582 (2001).

  11. 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. PMID:23559801

  12. 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.

  13. Microstructural understanding and critical current optimization of advanced high field superconductors. Progress report, February 1, 1991--March 31, 1993

    SciTech Connect

    Bonney, L.A.; Willis, T.C.; Larbalestier, D.C.

    1993-04-01

    It is of great importance to improve critical current density, J{sub c} in A15 superconductors for high field magnet applications. Most current work to improve J{sub c} in A15 wires concentrates on increasing the overall J{sub c} by increasing the fraction of superconducting phase in the wire, by improving the uniformity of the superconductor cross section along the length of the wire and by adjusting the strainstate of the A15 layer. The goal of the A15 work in this group was to investigate the intrinsic J{sub c} of the A15 layer itself. To do this, a better understanding of factors controlling the intrinsic J{sub c}of the Nb{sub 3}Sn was pursued.

  14. Examination of a Model for Field Studies in Science

    ERIC Educational Resources Information Center

    Riban, David M.

    1976-01-01

    Discusses ways to increase the effectiveness of field studies as an instructional method. Describes a study in which high school students who completed a geological field study scored higher on an earth science test than students who had not participated in the field study. (MLH)

  15. Studies on soliton energy at critical and noncritical densities of negative ions in an inhomogeneous magnetized warm plasma

    NASA Astrophysics Data System (ADS)

    Singh, Dhananjay K.; Malik, Hitendra K.

    2007-11-01

    Considering an inhomogeneous plasma having finite-temperature negative and positive ions, and the isothermal electrons in the presence of an external magnetic field, the solitons at noncritical and critical densities of the negative ions are studied through Korteweg-deVries (KdV) and modified Korteweg-deVries (mKdV) equations, respectively. The compressive (rarefactive) KdV solitons are found to propagate when the negative ion concentration is less (greater) than the critical density of the negative ions. At the critical density, both the compressive and the rarefactive solitons of equal amplitudes are found to occur. The energies of the compressive KdV soliton and the mKdV solitons are found to increase and that of the rarefactive KdV soliton is found to decrease with the negative ion density. Soliton energy for both the KdV and the mKdV solitons gets lowered under the effect of stronger magnetic field. The effect of ion temperature is to increase the energy of the compressive KdV soliton, whereas the energy of the rarefactive KdV soliton as well as of the mKdV solitons gets decreased. The variation of the energy with the obliqueness of the magnetic field is different for the KdV and the mKdV solitons.

  16. Studies on soliton energy at critical and noncritical densities of negative ions in an inhomogeneous magnetized warm plasma

    SciTech Connect

    Singh, Dhananjay K.; Malik, Hitendra K.

    2007-11-15

    Considering an inhomogeneous plasma having finite-temperature negative and positive ions, and the isothermal electrons in the presence of an external magnetic field, the solitons at noncritical and critical densities of the negative ions are studied through Korteweg-deVries (KdV) and modified Korteweg-deVries (mKdV) equations, respectively. The compressive (rarefactive) KdV solitons are found to propagate when the negative ion concentration is less (greater) than the critical density of the negative ions. At the critical density, both the compressive and the rarefactive solitons of equal amplitudes are found to occur. The energies of the compressive KdV soliton and the mKdV solitons are found to increase and that of the rarefactive KdV soliton is found to decrease with the negative ion density. Soliton energy for both the KdV and the mKdV solitons gets lowered under the effect of stronger magnetic field. The effect of ion temperature is to increase the energy of the compressive KdV soliton, whereas the energy of the rarefactive KdV soliton as well as of the mKdV solitons gets decreased. The variation of the energy with the obliqueness of the magnetic field is different for the KdV and the mKdV solitons.

  17. 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.

  18. 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. PMID:26706759

  19. 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.

  20. 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)

  1. 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)

  2. 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.

  3. 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

  4. 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.

  5. 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)

  6. Critical state and low-field electrodynamics in LaO0.85F0.15FeAs superconductor polycrystals

    NASA Astrophysics Data System (ADS)

    Gerashchenko, O. V.; Kholmetskii, A. L.; Mashlan, M.; Yarman, T.; Aldushchenkov, A. V.; Okunev, I. S.; Lomonosov, V. A.; Makhnach, L. V.

    2015-06-01

    The penetration of a weak magnetic field into LaO0.85F0.15FeAs 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. 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.

  8. Magnetic measurements of the upper critical field, irreversibility line, anisotropy, and magnetic penetration depth of grain-aligned YBa sub 2 Cu sub 4 O sub 8

    SciTech Connect

    Lee, W.C.; Ginsberg, D.M. )

    1992-04-01

    We have measured the upper critical field and the irreversibility line of grain-aligned YBa{sub 2}Cu{sub 4}O{sub 8}, with the magnetic field oriented perpendicular to the CuO{sub 2} planes. The upper critical field's slope, {ital dH}{sub {ital c}2}/{ital dT}, is {minus}1.57 T/K, corresponding to a zero-temperature Ginzburg-Landau (GL) coherence length of 19.5 A. The irreversibility line obeys a power-law behavior similar to that of 90-K YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}. Using the lower-critical-field data, we obtain the zero-temperature magnetic penetration depth {lambda}{sub {ital a}{ital b}}(0)=1960 A and GL parameter {kappa}{sub {ital c}}=100.

  9. 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).

  10. 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)].

  11. 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)]. PMID:24580229

  12. 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.

  13. 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…

  14. Geology Field Trip Studies to New England

    ERIC Educational Resources Information Center

    Wood, John H.

    1976-01-01

    A two week, 3,000 mile, geology field trip for secondary school earth science students through New England is discussed. Student expenses, preparation details, accommodations, meals, transportation, course credit, and fieldwork are considered. A detailed trip itinerary is included. (BT)

  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. 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

  17. Critical analysis of studies concerning reports of respiratory sensitization to certain wood dusts.

    PubMed

    Williams, P Brock

    2005-01-01

    Studies have been published reporting that exposures to certain wood dusts are sensitizing, resulting in respiratory symptoms in susceptible individuals. Many of the publications in this field are case reports that collectively have a number of important shortcomings. Illuminating these should further our understanding of whether respiratory sensitization results from occupational exposure to particular wood dusts. The aim of this study was to critically review and understand the evidence to date regarding reported respiratory sensitization in connection with wood dusts from oak, beech, pine, ash, and western red cedar. Publications dealing with these commercially important woods in North America have been selected from the Pubmed/Medline database (1966 to the present) using the key word, wood dust. These articles, along with supporting references on procedures and techniques, are reviewed according to the strengths and weaknesses of evidence and conclusions presented. Evidence from skin testing, specific immunoglobulin E measurements, and basophil histamine release tests suggests that reported symptoms are not likely to be immunologically derived. Because of methodological problems, challenge tests with specific wood dusts do not support the conclusion that reactions to certain wood dusts are specific. Experiments with nonspecific bronchoconstrictive agents indicate that a number of study subjects possess hyperresponsive airways. Thus, select individuals can demonstrate various respiratory symptoms in the woodworking industry, but any specificity or direct cause is currently unproved. Current studies do not support that exposure to wood dusts from a number of common North American wood species causes immunologic sensitization in woodworkers. Rather, symptoms reported in some studies of exposed workers seem to follow the paradigm for nonspecific respiratory responses in individuals with hyperresponsive airways.

  18. Critical analysis of studies concerning reports of respiratory sensitization to certain wood dusts.

    PubMed

    Williams, P Brock

    2005-01-01

    Studies have been published reporting that exposures to certain wood dusts are sensitizing, resulting in respiratory symptoms in susceptible individuals. Many of the publications in this field are case reports that collectively have a number of important shortcomings. Illuminating these should further our understanding of whether respiratory sensitization results from occupational exposure to particular wood dusts. The aim of this study was to critically review and understand the evidence to date regarding reported respiratory sensitization in connection with wood dusts from oak, beech, pine, ash, and western red cedar. Publications dealing with these commercially important woods in North America have been selected from the Pubmed/Medline database (1966 to the present) using the key word, wood dust. These articles, along with supporting references on procedures and techniques, are reviewed according to the strengths and weaknesses of evidence and conclusions presented. Evidence from skin testing, specific immunoglobulin E measurements, and basophil histamine release tests suggests that reported symptoms are not likely to be immunologically derived. Because of methodological problems, challenge tests with specific wood dusts do not support the conclusion that reactions to certain wood dusts are specific. Experiments with nonspecific bronchoconstrictive agents indicate that a number of study subjects possess hyperresponsive airways. Thus, select individuals can demonstrate various respiratory symptoms in the woodworking industry, but any specificity or direct cause is currently unproved. Current studies do not support that exposure to wood dusts from a number of common North American wood species causes immunologic sensitization in woodworkers. Rather, symptoms reported in some studies of exposed workers seem to follow the paradigm for nonspecific respiratory responses in individuals with hyperresponsive airways. PMID:16270718

  19. 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.

    2016-10-01

    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.

  20. Studying critical string emerging from non-Abelian vortex in four dimensions

    NASA Astrophysics Data System (ADS)

    Koroteev, P.; Shifman, M.; Yung, A.

    2016-08-01

    Recently a special vortex string was found [5] in a class of soliton vortices supported in four-dimensional Yang-Mills theories that under certain conditions can become infinitely thin and can be interpreted as a critical ten-dimensional string. The appropriate bulk Yang-Mills theory has the U (2) gauge group and the Fayet-Iliopoulos term. It supports semilocal non-Abelian vortices with the world-sheet theory for orientational and size moduli described by the weighted CP (2 , 2) model. The full target space is R4 ×Y6 where Y6 is a non-compact Calabi-Yau space. We study the above vortex string from the standpoint of string theory, focusing on the massless states in four dimensions. In the generic case all massless modes are non-normalizable, hence, no massless gravitons or vector fields are predicted in the physical spectrum. However, at the selfdual point (at strong coupling) weighted CP (2 , 2) admits deformation of the complex structure, resulting in a single massless hypermultiplet in the bulk. We interpret it as a composite "baryon."

  1. Preparing for biofilm studies in the field.

    PubMed

    McLean, Robert J C; Simpson, Thomas R

    2008-08-01

    In their natural environments, microorganisms are under constant environmental selection to form biofilms. Using aquatic biofilms as an example, this unit illustrates general concepts in field biology and practical suggestions for designing, conducting, and analyzing biofilm experiments at varying distances from the laboratory. The unit also addresses an example of a special situation (space flight) where experimentation must be done by proxy through another individual or machine.

  2. Critical Knowledge of Curriculum in Practice: The Case of Social Studies.

    ERIC Educational Resources Information Center

    Thornton, Stephen J.

    This paper has two purposes: (1) to describe how qualitative studies, drawing on educational criticism, have thrown into relief some salient features of curriculum and instruction in social studies; and (2) to compare and contrast the current reform proposal to upgrade geography education. The qualitative studies that are reviewed are the…

  3. 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…

  4. Neutron spin-echo study of the critical dynamics of spin-5/2 antiferromagnets in two and three dimensions

    NASA Astrophysics Data System (ADS)

    Tseng, K. F.; Keller, T.; Walters, A. C.; Birgeneau, R. J.; Keimer, B.

    2016-07-01

    We report a neutron spin-echo study of the critical dynamics in the S =5/2 antiferromagnets MnF2 and Rb2MnF4 with three-dimensional (3D) and two-dimensional (2D) spin systems, respectively, in zero external field. Both compounds are Heisenberg antiferromagnets with a small uniaxial anisotropy resulting from dipolar spin-spin interactions, which leads to a crossover in the critical dynamics close to the Néel temperature, TN. By taking advantage of the μ eV energy resolution of the spin-echo spectrometer, we have determined the dynamical critical exponents z for both longitudinal and transverse fluctuations. In MnF2, both the characteristic temperature for crossover from 3D Heisenberg to 3D Ising behavior and the exponents z in both regimes are consistent with predictions from the dynamical scaling theory. The amplitude ratio of longitudinal and transverse fluctuations also agrees with predictions. In Rb2MnF4 , the critical dynamics crosses over from the expected 2D Heisenberg behavior for T ≫TN to a scaling regime with exponent z =1.387 (4 ) , which has not been predicted by theory and may indicate the influence of long-range dipolar interactions.

  5. 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…

  6. 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).

  7. Prediction of critical illness in elderly outpatients using elder risk assessment: a population-based study

    PubMed Central

    Biehl, Michelle; Takahashi, Paul Y; Cha, Stephen S; Chaudhry, Rajeev; Gajic, Ognjen; Thorsteinsdottir, Bjorg

    2016-01-01

    Rationale Identifying patients at high risk of critical illness is necessary for the development and testing of strategies to prevent critical illness. The aim of this study was to determine the relationship between high elder risk assessment (ERA) score and critical illness requiring intensive care and to see if the ERA can be used as a prediction tool to identify elderly patients at the primary care visit who are at high risk of critical illness. Methods A population-based historical cohort study was conducted in elderly patients (age >65 years) identified at the time of primary care visit in Rochester, MN, USA. Predictors including age, previous hospital days, and comorbid health conditions were identified from routine administrative data available in the electronic medical record. The main outcome was critical illness, defined as sepsis, need for mechanical ventilation, or death within 2 years of initial visit. Patients with an ERA score of 16 were considered to be at high risk. The discrimination of the ERA score was assessed using area under the receiver operating characteristic curve. Results Of the 13,457 eligible patients, 9,872 gave consent for medical record review and had full information on intensive care unit utilization. The mean age was 75.8 years (standard deviation ±7.6 years), and 58% were female, 94% were Caucasian, 62% were married, and 13% were living in nursing homes. In the overall group, 417 patients (4.2%) suffered from critical illness. In the 1,134 patients with ERA >16, 154 (14%) suffered from critical illness. An ERA score ≥16 predicted critical illness (odds ratio 6.35; 95% confidence interval 3.51–11.48). The area under the receiver operating characteristic curve was 0.75, which indicated good discrimination. Conclusion A simple model based on easily obtainable administrative data predicted critical illness in the next 2 years in elderly outpatients with up to 14% of the highest risk population suffering from critical illness

  8. 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.

  9. Angular Dependence of Transport AC Losses in Superconducting Wire with Position-Dependent Critical Current Density in a DC Magnetic Field

    NASA Astrophysics Data System (ADS)

    Su, Xing-liang; Xiong, Li-ting; Gao, Yuan-wen; Zhou, You-he

    2013-07-01

    Transport AC losses play a very important role in high temperature superconductors (HTSs), which usually carry AC transport current under applied magnetic field in typical application-like conditions. In this paper, we propose the analytical formula for transport AC losses in HTS wire by considering critical current density of both inhomogeneous and anisotropic field dependent. The angular dependence of critical current density is described by effective mass theory, and the HTS wire has inhomogeneous distribution cross-section of critical current density. We calculate the angular dependence of normalized AC losses under different DC applied magnetic fields. The numerical results of this formula agree well with the experiment data and are better than the results of Norris formula. This analytical formula can explain the deviation of experimental transport current losses from the Norris formula and apply to calculate transport AC losses in realistic practical condition.

  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.

    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

  11. 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

  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. Upper critical field of KFe2As2 under pressure: A test for the change in the superconducting gap structure

    SciTech Connect

    Taufour, Valentin; Foroozani, Neda; Tanatar, Makariy A.; Lim, Jinhyuk; Kaluarachchi, Udhara; Kim, Stella K.; Liu, Yong; Lograsso, Thomas A.; Kogan, Vladimir G.; Prozorov, Ruslan; Bud'ko, Sergey L.; Schilling, James S.; Canfield, Paul C.

    2014-06-01

    We report measurements of electrical resistivity under pressure to 5.8 GPa, magnetization to 6.7 GPa, and ac susceptibility to 7.1 GPa in KFe2As2. The previously reported change of slope in the pressure dependence of the superconducting transition temperature Tc(p) at a pressure p*~1.8 GPa is confirmed, and Tc(p) is found to be nearly constant above p* up to 7.1 GPa. The T-p phase diagram is very sensitive to the pressure conditions as a consequence of the anisotropic uniaxial pressure dependence of Tc. Across p*, a change in the behavior of the upper critical field is revealed through a scaling analysis of the slope of Hc2 with the effective mass as determined from the A coefficient of the T2 term of the temperature-dependent resistivity. We show that this scaling provides a quantitative test for the changes of the superconducting gap structure and suggests the development of a kz modulation of the superconducting gap above p* as a most likely explanation.

  14. Study of HTS Wires at High Magnetic Fields

    SciTech Connect

    Turrioni, D.; Barzi, E.; Lamm, M.J.; Yamada, R.; Zlobin, A.V.; Kikuchi, A.; /Fermilab

    2009-01-01

    Fermilab is working on the development of high field magnet systems for ionization cooling of muon beams. The use of high temperature superconducting (HTS) materials is being considered for these magnets using Helium refrigeration. Critical current (I{sub c}) measurements of HTS conductors were performed at FNAL and at NIMS up to 28 T under magnetic fields at zero to 90 degree with respect to the sample face. A description of the test setups and results on a BSCCO-2223 tape and second generation (2G) coated conductors are presented.

  15. 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.

  16. Analytical and numerical study of Gauss-Bonnet holographic superconductors with Power-Maxwell field

    NASA Astrophysics Data System (ADS)

    Sheykhi, Ahmad; Salahi, Hamid Reza; Montakhab, Afshin

    2016-04-01

    We provide an analytical as well as a numerical study of the holographic s-wave superconductors in Gauss-Bonnet gravity with Power-Maxwell electrodynamics. We limit our study to the case where scalar and gauge fields do not have an effect on the background metric. We use a variational method, based on Sturm-Liouville eigenvalue problem for our analytical study, as well as a numerical shooting method in order to compare with our analytical results. Interestingly enough, we observe that unlike Born-Infeld-like nonlinear electrodynamics which decrease the critical temperature compared to the linear Maxwell field, the Power-Maxwell electrodynamics is able to increase the critical temperature of the holographic superconductors in the sublinear regime. We find that requiring the finite value for the gauge field on the asymptotic boundary r → ∞, restricts the power parameter, q, of the Power-Maxwell field to be in the range 1 /2 < q < ( d - 1) /2. Our study indicates that it is quite possible to make condensation easier as q decreases in its allowed range. We also find that for all values of q, the condensation can be affected by the Gauss-Bonnet coefficient α. However, the presence of the Gauss-Bonnet term makes the transition slightly harder. Finally, we obtain an analytic expression for the order parameter and thus obtain the associated critical exponent near the phase transition. We find that the critical exponent has its universal value of β = 1 /2 regardless of the parameters q, α as well as dimension d, consistent with mean-field values obtained in previous studies.

  17. 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.

  18. Chemical instrumentation for field studies of atmospheric wet deposition processes

    SciTech Connect

    Tanner, R.L.

    1986-04-01

    Field studies of wet deposition processes require the differentiation and determination of many trace reactive species in the atmosphere. The species may be present in clear-air-gaseous or aerosol phases, or they may be distributed between cloudwater or precipitation and interstitial gaseous phases. Analytical requirement on existing techniques have been extremely rigorous and, in several cases, have required development of new approaches to the sampling and determination of critical species. This paper views these developments with respect to airborne sampling in the following general areas: determination of sub-ppb levels of nitrogen oxides (NO, NO/sub x/, HNO/sub 3/) in real-time using ozone chemiluminescence; determination of sub-ppb levels of sulfur dioxide and aersol sulfate in real-time using the flame photometric detector; determination of oxidants (ozone, PAN, H/sub 2/O/sub 2/) in gaseous and aqueous phases; determination of organic species (hydrocarbons, aldehydes, acids in gaseous and aqueous phases; cloud/raindrop - free air sampling; collection of aqueous liquid and solid samples; direct measurement of particle size distributions (aerosols, cloud droplets, rain droplets.)

  19. The Design of a Critical Thinking Test on Appraising Observations. Studies in Critical Thinking, Research Report No. 1.

    ERIC Educational Resources Information Center

    Norris, Stephen P.; King, Ruth

    This report describes the design of a test of one aspect of critical thinking ability, the ability to correctly appraise observations. Intended for classroom use with senior high school students, the 50 item Test on Appraising Observations is based on a comprehensive set of principles modified from Robert Ennes' conception of good observation…

  20. Quantum critical point of Dirac fermions studied using efficient continuous-time projector quantum Monte Carlo method

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Iazzi, Mauro; Corboz, Philippe; Troyer, Matthias

    2015-03-01

    Quantum phase transition (QPT) of Dirac fermions is a fascinating topic both in condensed matter and in high energy physics. Besides its immediate connection to fundamental problems like mass generation and exotic phases of matter, it provides a common playground where state of the art numerical simulations can be crosschecked with various effective field theory predictions, thus deepen our understanding of both fields. The universality class of the QPT is fundamentally different from the usual bosonic field theory because of the coupling to the gapless fermionic mode at the critical point. We study lattice models with spinless and multi-flavor Dirac fermions using the newly developed efficient continuous-time projector quantum Monte Carlo method. Besides eliminating the Trotter error, the method also enables us to directly calculate derivative observables in a continuous range of interaction strengths, thus greatly enhancing the resolution of the quantum critical region. Compatible results are also obtained from infinite projected entangled-pair states calculations. We compare these numerical results with predictions of the Gross-Neveu theory and discuss their physical implications.

  1. Study Skills and Critical Thinking Curriculum for Adolescents in a Psychiatric Treatment Center.

    ERIC Educational Resources Information Center

    Peniston, Lorraine C.

    This report discusses the need to teach critical thinking and study skill strategies to improve the problem-solving ability, study habits, and knowledge of subject content to students in psychiatric treatment centers. The report asserts that this type of curriculum will assist students in comprehending new information and utilizing thinking skills…

  2. 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…

  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. 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)…

  5. A Study of Ideational Metafunction in Joseph Conrad's "Heart of Darkness": A Critical Discourse Analysis

    ERIC Educational Resources Information Center

    Alaei, Mahya; Ahangari, Saeideh

    2016-01-01

    The linguistic study of literature or critical analysis of literary discourse is no different from any other textual description; it is not a new branch or a new level or a new kind of linguistics but the application of existing theories and methods (Halliday, 2002). This study intends to determine how ideology or opinion is expressed in Joseph…

  6. 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…

  7. 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…

  8. 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…

  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. 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…

  11. 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…

  12. Challenges and opportunities associated with studying sleep in critically ill adults.

    PubMed

    Redeker, Nancy S

    2008-01-01

    Disturbances in sleep associated with sleep deprivation, disorders in circadian rhythms, and sleep-disordered breathing are common in critical care settings and may have a significant impact on physiologic, behavioral, and functional outcomes, as well as patient satisfaction and utilization of healthcare resources. Despite growth in awareness of the potential importance of sleep in the critical setting over the past 30 years, many questions about the nature of sleep, the predictors and consequences of sleep disturbance, and the efficacy of sleep promotion interventions in critically ill patients remain unanswered. Most of the studies of sleep in critical care settings have used small, nonrandom samples and descriptive or explanatory designs; many have not considered multifactorial explanatory variables; and clinical trials are rare. These gaps in quantity and quality of research findings are barriers to the delivery of evidence-based sleep promotion interventions and may be partially explained by conceptual and methodological challenges associated primarily with the nature of sleep measurement and characteristics of critically ill patients and the critical care environment. This article will explore these concerns and propose strategies to deal with them. Research exemplars from the literature will be used to illustrate key points. PMID:18560287

  13. Study on internal waves generated by tidal flow over critical topography

    NASA Astrophysics Data System (ADS)

    Jia, Xiaona; Chen, Xu; Li, Qun; Li, Qiang

    2014-10-01

    Resonance due to critical slope makes the internal wave generation more effectively than that due to supercritical or subcritical slopes (Zhang et al., 2008). Submarine ridges make a greater contribution to ocean mixing than continental margins in global oceans (Müller, 1977; Bell, 1975; Baines, 1982; Morozov, 1995). In this paper, internal wave generation driven by tidal flow over critical topography is examined in laboratory using Particle Image Velocimetry (PIV) and synthetic schlieren methods in synchrony. Non-tidal baroclinic velocities and vertical isopycnal displacements are observed in three representative regions, i.e., critical, outward-propagating, and reflection regions. Temporal and spatial distributions of internal wave rays are analyzed using the time variations of baroclinic velocities and vertical isopycnal displacement, and the results are consistent with those by the linear internal wave theory. Besides, the width of wave beam changes with the outward propagation of internal waves. Finally, through monitoring the uniformly-spaced 14 vertical profiles in the x-z plane, the internal wave fields of density and velocity fields are constructed. Thus, available potential energy, kinetic energy and energy fluxes are determined quantitatively. The distributions of baroclinic energy and energy fluxes are confined along the internal wave rays. The total depth averaged energy and energy flux of vertical profiles away from a ridge are both larger than those near the ridge.

  14. 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.

  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. 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.

  17. 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 VARIOUS…

  18. Global and site specific multimedia (field) studies

    SciTech Connect

    Cutshall, N.H.; Guerin, M.R.

    1987-01-01

    Experience with radioactive fallout, with organic contaminants and with heavy metals has amply demonstrated that cross-media transfers are common and that understanding the transport, cycling, and fate of these contaminants requires a multimedia approach. Nonetheless, pollutants with similar physical and chemical attributes may follow markedly different pathways. The frequency of exceptions to predictions based on simplistic models is also sufficient to show that direct investigation of environmental contamination is essential to confirm validity of models used for conceptualizing a problem or for control. Modeling based on multimedia premises and regulatory controls that encompass multimedia considerations are challenged by a dilemma, however. First, the development of multimedia models or regulatory frameworks represents simplification and generalization. This is true for several reasons: (1) inadequate understanding of physical and environmental factors which control specific cross-media transfer; (2) the absence of specific data on certain multimedia pollutant concentrations; (3) even the most powerful computers do not have sufficient speed and capacity to deal with the known complexities of natural systems. On the other hand, for contaminants such as mercury, it may be necessary to include great detail; the overall distribution in the environment may be less important than the rate of some minor process. With sufficient experience and good judgment of what can be ignored, the simplifications and generalizations can be made. For the present, and for the foreseeable future, however, they absolutely must be accompanied by thorough field validation and monitoring.

  19. Studies on Highly Anisotropic Conductors and Superconductors in High Magnetic Fields and Low Temperatures.

    NASA Astrophysics Data System (ADS)

    Yu, Rangchen

    1990-08-01

    Transport properties in high magnetic field and low temperature have been studied in a number of highly anisotropic organic superconductors and high Tc cuprate superconductors. The magnetothermopower of (TMTSF)_2 ClO_4 has been systematically studied in high field and low temperature through the entire range of magnetic field induced spin-density-wave (FISDW) transitions. Our data provide strong evidence of the collective nature of the extremely stable state between 8 to 25 Tesla resembling the 1/3 fractional quantized Hall effect. A new phase transition into a semiconducting state at 2.6K in field of 30 Tesla has been identified. The FISDW phase diagram in the field range of 15-18 Tesla has been studied in detail to sort out the relationship between the "fast oscillations (FO)" and the reentrant FISDW. Our experiment show that there are no oscillations in the phase boundary correlated to the FO, in contrast to a theory proposed by Lebed and Bak which claimed that the reentrance of FISDW and FO are due to oscillations in the FISDW phase boundary resulting from the competition of two SDW modes originated from the anion ordering gap. Transport properties of the high T_ c superconductors are systematically studied. The temperature and carrier concentration dependence of the thermopower suggested that the cuprates were strongly correlated systems. The thermopower of La_{1.85 }Sr_{0.15}CuO _4 in strong magnetic field was studied to test the correlated hopping model. We find that thermopower of La_{1.85}Sr_{0.15 }CuO_4 is independent of magnetic field in field up to 30 Tesla and temperature down to 40K. Our results question the validity of this model, and lends support to the theories of carriers without spin, or of strong spin exchange interactions. The dimensionality of superconductivity of YBa _2Cu_3O _7 and Bi_{2.2} Sr_{1.9}CaCu _2O_{8+x} was studied by the orientational dependence of the critical field. While the critical field of YBa_2 Cu_3O_7 can be described by

  20. 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)

  1. Upper critical fields and superconducting transition temperatures of some zirconium-base amorphous transition-metal alloys

    NASA Astrophysics Data System (ADS)

    Karkut, M. G.; Hake, R. R.

    1983-08-01

    Superconducting upper critical fields Hc2(T), transition temperatures Tc and normal-state electrical resistivities ρn have been measured in the amorphous transition-metal alloy series Zr1-xCox, Zr1-xNix, (Zr1-xTix)0.78Ni0.22, and (Zr1-xNbx)0.78Ni0.22. Structural integrity of these melt-spun alloys is indicated by x-ray, density, bend-ductility, normal-state electrical resistivity, superconducting transition width, and mixed-state flux-pinning measurements. The specimens display Tc=2.1-3.8 K, ρn=159-190 μΩ cm, and |(dHc2dT)Tc|=28-36 kG/K. These imply electron mean free paths l~2-6 Å, zero-temperature Ginzburg-Landau coherence distances ξG0~50-70 Å, penetration depths λG0~(7-10)×103 Å, and extremely high dirtiness parameters ξ0l~300-1300. All alloys display Hc2(T) curves with negative curvature and (with two exceptions) fair agreement with the standard dirty-limit theory of Werthamer, Helfand, Hohenberg, and Maki (WHHM) for physically reasonable values of spin-orbit-coupling induced, electron-spin-flip scattering time τso. This is in contrast to the anomalously elevated Hc2(T) behavior which is nearly linear in T that is observed by some, and the unphysically low-τso fits to WHHM theory obtained by others, for various amorphous alloys. Current ideas that such anomalies may be due to alloy inhomogeneity are supported by present results on two specimens for which relatively low-τso fits of Hc2(T) to WHHM theory are coupled with superconductive evidence for inhomogeneity: relatively broad transitions at Tc and Hc2 current-density-dependent transitions at Hc2 and (in one specimen) a J-dependent, high-H (>Hc2), resistive "beak effect." In the Zr1-xCox and Zr1-xNix series, Tc decreases linearly with x (and with unfilled-shell average electron-to-atom ratio < ea > in the range 5.05<=< ea ><=6.40 in fair agreement with previous results for these systems and contrary to the Tc vs < ea > behavior of both amorphous and crystalline transition-metal alloys formed

  2. Quantitative imaging of sheet resistance, permittivity, and ferroelectric critical phenomena with a near-field scanning microwave microscope

    NASA Astrophysics Data System (ADS)

    Steinhauer, David Ethan

    I describe the design and use of a near-field scanning microwave microscope to make quantitative measurements of sample properties, such as sheet resistance and permittivity. The system consists of a resonator contained in a coaxial cable, terminated at one end with an open-ended coaxial probe. When a sample is brought near the probe tip, the resonant frequency and quality factor are perturbed depending on the local properties of the sample. The spatial resolution depends on the diameter of the probe's center conductor, which can be in the range 1-500 μm. This versatile technique is nondestructive, and has broadband (0.1-50 GHz) capability. Quantitative imaging of the sheet resistance of conducting thin films can be achieved through a thin-film calibration sample. To reinforce our understanding of the physical mechanisms of the measurement, I use a physical model for the system based on microwave transmission line theory. I demonstrate the technique at 7.5 GHz by imaging the sheet resistance of a variable-thickness YBa2Cu3O7-δ thin film on a sapphire substrate at room temperature. Using a probe with a sharp, protruding center conductor held in contact with the sample, high-resolution (1 μm) imaging can be accomplished. I use a finite element calculation of the electric field near the probe tip, combined with perturbation theory, to make quantitative linear and nonlinear dielectric measurements of thin films and crystals. I demonstrate this capability by imaging the dielectric permittivity and nonlinearity of a (Ba,Sr)TiO3 thin film. The microscope can also be used to image domains in ferroelectric crystals such as lithium niobate, barium titanate, and deuterated triglycine sulfate (DTGS). Critical phenomena can be investigated by varying the temperature of the sample. I measured the permittivity, dielectric nonlinearity, and domain relaxation time of DTGS as a function of temperature near the ferroelectric transition. For permittivity measurements, I found

  3. Effect of mosaicity in x-ray studies of critical behavior at the nematic to smectic-A transition.

    PubMed

    Primak, Andrew; Fisch, Michael; Kumar, Satyendra

    2002-11-01

    Previous studies of critical behavior at the nematic to smectic-A transition by high-resolution x-ray scattering were performed using low magnetic fields of 0.1-0.8 T. In those studies, the transverse resolution was limited by the sample mosaicity which complicated data analysis. In order to understand the effect of sample mosaicity on the measured values of critical exponents, the divergence of the smectic order correlation lengths xi(||, perpendicular ) and susceptibility sigma(o) was studied in a magnetic field ranging from 0.25 to 5 T. The use of high (5 T) field reduced the sample mosaicity and improved the effective transverse resolution by almost two orders of magnitude. Three liquid crystals, two mixtures of 6th and 7th homologs of 4,4(')-dialkylazoxybenzene (DnAOB) and 4-n-octylcyanobiphenyl (8CB) were studied. 15 wt% (D6.15AOB) and 40 wt% (D6.4AOB) mixtures of D7AOB in D6AOB have a wide nematic range, while 8CB has a narrow nematic range. Analysis of the data at different fields revealed a different and proper way to apply the mosaicity correction. The Gaussian mosaicity correction was found to be temperature independent but significantly ( approximately 3.5 times) smaller than the width of the sharpest q( perpendicular )-scan, which has traditionally been used for mosaicity correction in all previous studies. The values of the critical exponents measured over almost four decades of reduced temperature were: nu(||)=0.79+/-0.02, nu( perpendicular )=0.69+/-0.02, gamma=1.46+/-0.04 for D6.15AOB; nu(||)=0.79+/-0.02, nu( perpendicular )=0.67+/-0.02, gamma=1.44+/-0.04 for D6.4AOB; and nu(||)=0.70+/-0.02, nu( perpendicular )=0.52+/-0.02, gamma=1.24+/-0.04 for 8CB. The results for the two mixtures suggest that in wide temperature range nematics, far from the tricritical point, the exponents may be material independent. No significant effects of mosaicity on the values of the coefficient c of the fourth-order term in the structure factor were observed.

  4. 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…

  5. Time-Critical Studies: Rapid response to Transient Dynamic Mid-Ocean Ridge Events

    NASA Astrophysics Data System (ADS)

    Cowen, J. P.; Baker, E. T.; Dziak, R. P.; Lilley, M. M.

    2003-12-01

    The Time-Critical Studies (TCS) Theme of Ridge 2000 focuses on observations of the immediate geochemical and geobiological consequences of magmatic and tectonic events along the global mid-ocean ridge system. To date funding has centered on the Juan de Fuca and Gorda Ridges which are within the range of the U.S. Navy's Northeast Pacific Sound Surveillance System (SOSUS). NOAA's T-Phase Monitoring Program has accessed SOSUS in real-time since 1993, providing the TCS community with detection of seismicity associated with eruptive or tectonic activity along these two ridges. This remote detection of earthquake swarms along the N.E. Pacific mid-ocean ridge coupled to NSF funding for pre-event staging equipment and supplies has allowed directed and increasingly well-organized field responses to the event site. Major rapid and follow-up response cruises have been successfully mounted to 1993 CoAxial, 1996 and 2001 Gorda Ridge, the 1998 Axial Volcano, and 2001 Middle Valley magmatic episodes. The logistical approach required to study these events has been greatly facilitated by the RIDGE/Ridge 2000 programs and collaboration between university, NOAA and Canadian investigators. Not only have our studies of these events significantly impacted our ideas on the nature of crustal accretion, but they also have led to the discovery and preliminary documentation of a previously unrecognized biomass reservoir that lives below the seafloor and is swept out during these cataclysmic events, and to increased appreciation of the formation and thermal, chemical and biogeochemical implications of the 'Event Plumes' commonly associated with sea floor magmatic events. Rapid shore-to-event site response is an important aspect of TCS. Proposals to enhance the event detection and response effort are welcome at any Ridge 2000 target date. The Ridge 2000 program recognizes that even the most rapid ship response will miss the earliest subsurface and water column expressions of magmatic events

  6. Field calibration studies for ionisation chambers in mixed high-energy radiation fields.

    PubMed

    Theis, C; Forkel-Wirth, D; Fuerstner, M; Mayer, S; Otto, Th; Roesler, S; Vincke, H

    2007-01-01

    The monitoring of ambient doses at work places around high-energy accelerators is a challenging task due the complexity of the mixed stray radiation fields encountered. At CERN, mainly Centronics IG5 high-pressure ionisation chambers are used to monitor radiation exposure in mixed fields. The monitors are calibrated in the operational quantity ambient dose equivalent H*(10) using standard, source-generated photon- and neutron fields. However, the relationship between ionisation chamber reading and ambient dose equivalent in a mixed high-energy radiation field can only be assessed if the spectral response to every component and the field composition is known. Therefore, comprehensive studies were performed at the CERN-EU high-energy reference field facility where the spectral fluence for each particle type has been assessed with Monte Carlo simulations. Moreover, studies have been performed in an accessible controlled radiation area in the vicinity of a beam loss point of CERN's proton synchrotron. The comparison of measurements and calculations has shown reasonable agreement for most exposure conditions. The results indicate that conventionally calibrated ionisation chambers can give satisfactory response in terms of ambient dose equivalent in stray radiation fields at high-energy accelerators in many cases. These studies are one step towards establishing a method of 'field calibration' of radiation protection instruments in which Monte Carlo simulations will be used to establish a correct correlation between the response of specific detectors to a given high-energy radiation field.

  7. 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.

  8. Women Teaching for Change: Gender, Class & Power. Critical Studies in Education Series.

    ERIC Educational Resources Information Center

    Weiler, Kathleen

    This study of feminist high school teachers investigates and analyzes individual action within the bounds of structural constraints. The book draws on feminist theory that has addressed the role of schools in reproducing the inequality and oppression of women. Chapter One, "Critical Educational Theory," examines the implications and value of…

  9. An Exploratory Study on the Application of Conceptual Knowledge and Critical Thinking to Technological Issues

    ERIC Educational Resources Information Center

    Yu, Kuang-Chao; Lin, Kuen-Yi; Fan, Szu-Chun

    2015-01-01

    This study explored how senior high school students apply their conceptual knowledge, consisting of theoretical and system knowledge, to think critically when confronted with technological issues. We employed a curriculum on the history of communication technology to teach students about basic concepts in communication technology and to cultivate…

  10. PBL and Critical Thinking Disposition in Chinese Medical Students--A Randomized Cross-Sectional Study

    ERIC Educational Resources Information Center

    Du, XiangYun; Emmersen, Jeppe; Toft, Egon; Sun, Baozhi

    2013-01-01

    The purpose of this study was to explore the relationship of problem-based learning (PBL) and the development of critical thinking disposition (CT) and academic achievement in Chinese medical students using a cross-sectional randomized design. Medical students from China Medical University (CMU) were randomized to PBL or non-PBL teaching at the…

  11. An Exploratory Study of Criticism Realization Strategies Used By NS and NNS of New Zealand English

    ERIC Educational Resources Information Center

    Nguyen, Thi Thuy Minh

    2013-01-01

    This study explores how a group of learners of English as a second language (ESL) criticize in everyday situations compared to the native speaker (NS) with a view to expanding the range of speech acts under inquiry in the interlanguage pragmatics (ILP) literature. Data were collected from five NSs of New Zealand English and five intermediate…

  12. Critical Evaluation as an Aid to Improved Report Writing: A Case Study

    ERIC Educational Resources Information Center

    Walker, Mirabelle; Williams, Judith

    2014-01-01

    Report writing is an important employability skill for Engineers and Technologists, and this case study describes how a Technology degree module took a novel approach to developing students' report writing skills. Students learned how to use a criterion-referenced critical evaluation framework for reports and other technological documents.…

  13. Research Review: A Critical Review of Studies on the Developmental Trajectories of Antisocial Behavior in Females

    ERIC Educational Resources Information Center

    Fontaine, Nathalie; Carbonneau, Rene; Vitaro, Frank; Barker, Edward D.; Tremblay, Richard E.

    2009-01-01

    Background: Knowledge on the onset and the development of antisocial behavior in females is limited, because most of the research in this domain is based on males. Methods: We critically reviewed 46 empirical studies that examined developmental trajectories of antisocial behavior in females, notably to help determine whether or not an…

  14. Towards a Decolonising Pedagogy: Understanding Australian Indigenous Studies through Critical Whiteness Theory and Film Pedagogy

    ERIC Educational Resources Information Center

    Hook, Genine

    2012-01-01

    This article explores student and teacher engagement with Australian Indigenous Studies. In this article I identify key themes in the film "September" (2007) that demonstrate how the film can be used as a catalyst for student learning and discussion. Critical whiteness theory provides a framework to explore three themes, the invisibility of…

  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. 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.

  17. Making Critical Connections between Social Studies Teaching and Student Achievement Using NAEP Data Explorer

    ERIC Educational Resources Information Center

    Fitchett, Paul G.; Heafner, Tina L.

    2013-01-01

    In this analysis of promising practice, we demonstrate how social studies methods instructors can incorporate data analysis of the 2010 United States History National Assessment of Educational Progress (NAEP-USH) to facilitate pedagogical aims, engage teacher candidates in critical discourse, and investigate the contexts of teaching and learning.…

  18. 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.…

  19. The Narrative Turn and the Poetics of Resistance: Towards a New Language for Critical Educational Studies

    ERIC Educational Resources Information Center

    Peters, Michael A.; Besley, Tina

    2012-01-01

    This article argues for the adoption of a new language in critical educational studies through the "narrative turn", a turn that politicizes knowledge by drawing attention to questions concerning the meaning, construction and authorship of narratives. In the authors' interpretation going back to the poetics of early narrative forms they…

  20. 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…