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.

Dome of magnetic order inside the nematic phase of sulfur-substituted FeSe under pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiang, Li; Kaluarachchi, Udhara; Bohmer, Anna

2017-07-18

The pressure dependence of the structural, magnetic, and superconducting transitions and of the superconducting upper critical field were studied in sulfur-substituted Fe ( Se 1 - x S x ) . We performed resistance measurements on single crystals with three substitution levels ( x = 0.043 , 0.096, 0.12) under hydrostatic pressures up to 1.8 GPa and in magnetic fields up to 9 T and were compared to data on pure FeSe. Our results illustrate the effects of chemical and physical pressure on Fe ( Se 1 - x S x ). Furthermore, on increasing sulfur content, magnetic order inmore » the low-pressure range is strongly suppressed to a small domelike region in the phase diagrams. But, T s is much less suppressed by sulfur substitution, and T c of Fe ( Se 1 - x S x ) exhibits similar nonmonotonic pressure dependence with a local maximum and a local minimum present in the low-pressure range for all x . The local maximum in T c coincides with the emergence of the magnetic order above T c . At this pressure the slope of the upper critical field decreases abruptly, which may indicate a Fermi-surface reconstruction. The minimum of T c correlates with a broad maximum of the upper critical field slope normalized by T c .« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agosta, C. C.; Jin, J.; Coniglio, W. A.

We present upper critical field data for {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2} with the magnetic field close to parallel and parallel to the conducting layers. We show that we can eliminate the effect of vortex dynamics in these layered materials if the layers are oriented within 0.3-inch of parallel to the applied magnetic field. Eliminating vortex effects leaves one remaining feature in the data that corresponds to the Pauli paramagnetic limit (H{sub p}). We propose a semiempirical method to calculate the H{sub p} in quasi-2D superconductors. This method takes into account the energy gap of each of the quasi-2D superconductors, which ismore » calculated from specific-heat data, and the influence of many-body effects. The calculated Pauli paramagnetic limits are then compared to critical field data for the title compound and other organic conductors. Many of the examined quasi-2D superconductors, including the above organic superconductors and CeCoIn{sub 5}, exhibit upper critical fields that exceed their calculated H{sub p} suggesting unconventional superconductivity. We show that the high-field low-temperature state in {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2} is consistent with the Fulde-Ferrell-Larkin-Ovchinnikov state.« less

Upper critical field and Kondo effects in Fe(Te 0.9Se 0.1) thin films by pulsed field measurements

DOE PAGES

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

2016-02-10

The transition temperatures of epitaxial films of Fe(Te 0:9Se 0:1) are remarkably insensitive to applied magnetic field, leading to predictions of upper critical fields B c2(T = 0) in excess of 100 T. Using pulsed magnetic fields, we find B c2(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 B c2(T), consistent with the observed Kondo minimum seen above T c. Fits to the temperature dependence in the context of the WHH model, using the experimental valuemore » of the Maki parameter, require an effective spin-orbit relaxation parameter of order unity. Lastly, we suggest that Kondo localization plays a similar role to spin-orbit pair breaking in making WHH fits to the data.« less

Unusual two-dimensional behavior of iron-based superconductors with low anisotropy

NASA Astrophysics Data System (ADS)

Kalenyuk, A. A.; Pagliero, A.; Borodianskyi, E. A.; Aswartham, S.; Wurmehl, S.; Büchner, B.; Chareev, D. A.; Kordyuk, A. A.; Krasnov, V. M.

2017-10-01

We study angular-dependent magnetoresistance in iron-based superconductors Ba1 -xNaxFe2As2 and FeTe1 -xSex . Both superconductors have relatively small anisotropies γ ˜2 and exhibit a three-dimensional (3D) behavior at low temperatures. However, we observe that they start to exhibit a profound two-dimensional behavior at elevated temperatures and in applied magnetic field parallel to the surface. We conclude that the unexpected two-dimensional (2D) behavior of the studied low-anisotropic superconductors is not related to layeredness of the materials, but is caused by appearance of surface superconductivity when magnetic field exceeds the upper critical field Hc 2(T ) for destruction of bulk superconductivity. We argue that the corresponding 3D-2D bulk-to-surface dimensional transition can be used for accurate determination of the upper critical field.

Dimensional Crossover and Its Interplay with In-Plane Anisotropy of Upper Critical Field in β-(BDA-TTP)2SbF6

NASA Astrophysics Data System (ADS)

Yasuzuka, Syuma; Koga, Hiroaki; Yamamura, Yasuhisa; Saito, Kazuya; Uji, Shinya; Terashima, Taichi; Akutsu, Hiroki; Yamada, Jun-ichi

2017-08-01

Resistance measurements have been performed to investigate the dimensionality and the in-plane anisotropy of the upper critical field (Hc2) for β-(BDA-TTP)2SbF6 in fields H up to 15 T and at temperatures T from 1.5 to 7.5 K, where BDA-TTP stands for 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene. The upper critical fields parallel and perpendicular to the conduction layer are determined and dimensional crossover from anisotropic three-dimensional behavior to two-dimensional behavior is found at around 6 K. When the direction of H is varied within the conducting layer at 6.0 K, Hc2 shows twofold symmetry: Hc2 along the minimum Fermi wave vector (maximum Fermi velocity) is larger than that along the maximum Fermi wave vector (minimum Fermi velocity). The normal-state magnetoresistance has twofold symmetry similar to Hc2 and shows a maximum when the magnetic field is nearly parallel to the maximum Fermi wave vector. This tendency is consistent with the Fermi surface anisotropy. At 3.5 K, we found clear fourfold symmetry of Hc2 despite the fact that the normal-state magnetoresistance shows twofold symmetry arising from the Fermi surface anisotropy. The origin of the fourfold symmetry of Hc2 is discussed in terms of the superconducting gap structure in β-(BDA-TTP)2SbF6.

Anisotropic upper critical magnetic fields in Rb 2 Cr 3 As 3 superconductor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Zhang-Tu; Liu, Yi; Bao, Jin-Ke

Rb2Cr3As3 is a structurally one-dimensional superconductor containing Cr3As3 chains with a superconducting transition temperature of T-c = 4.8 K. Here we report the electrical resistance measurements for Rb2Cr3As3 single crystals, under magnetic fields up to 29.5 T and at temperatures down to 0.36 K, from which the upper critical fields, H-c2(T), can be obtained in a broad temperature range. For field parallel to the Cr3As3 chains, H-c2(parallel to)(T) is paramagnetically limited with an initial slope of mu(0)dH(c2)(parallel to)/dT|T-c = - 16 T K-1 and a zero-temperature upper critical field of mu H-0(c2)parallel to(0) = 17.5 T. For field perpendicular tomore » the Cr3As3 chains, however, H-c2(perpendicular to)(T) is only limited by orbital pair-breaking effect with mu(0)dH(c2)(perpendicular to)/dT|(Tc) = - 3 T K-1. As a consequence, the anisotropy gamma H = H-c2(parallel to)/H-c2(perpendicular to) decreases sharply near T-c and reverses below 2 K. Remarkably, the low- temperature H-c2(perpendicular to)(T) down to 0.075 T-c remains to increase linearly up to over three times the Pauli paramagnetic limit, which strongly suggests dominant spin-triplet superconductivity in Rb2Cr3As3.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Breznay, Nicholas P.; Tendulkar, Mihir; Zhang, Li

Here, we study the two-dimensional superconductor-insulator transition (SIT) in thin films of tantalum nitride. At zero magnetic field, films can be disorder-tuned across the SIT by adjusting thickness and film stoichiometry; insulating films exhibit classical hopping transport. Superconducting films exhibit a magnetic-field-tuned SIT, whose insulating ground state at high field appears to be a quantum-corrected metal. Scaling behavior at the field-tuned SIT shows classical percolation critical exponents zν ≈ 1.3, with a corresponding critical field H c << H c2, the upper critical field. The Hall effect exhibits a crossing point near H c, but with a nonuniversal critical valuemore » ρ c xy comparable to the normal-state Hall resistivity. We propose that high-carrier-density metals will always exhibit this pattern of behavior at the boundary between superconducting and (trivially) insulating ground states.« less

Superconductor to weak-insulator transitions in disordered tantalum nitride films

NASA Astrophysics Data System (ADS)

Breznay, Nicholas P.; Tendulkar, Mihir; Zhang, Li; Lee, Sang-Chul; Kapitulnik, Aharon

2017-10-01

We study the two-dimensional superconductor-insulator transition (SIT) in thin films of tantalum nitride. At zero magnetic field, films can be disorder-tuned across the SIT by adjusting thickness and film stoichiometry; insulating films exhibit classical hopping transport. Superconducting films exhibit a magnetic-field-tuned SIT, whose insulating ground state at high field appears to be a quantum-corrected metal. Scaling behavior at the field-tuned SIT shows classical percolation critical exponents z ν ≈1.3 , with a corresponding critical field Hc≪Hc 2 , the upper critical field. The Hall effect exhibits a crossing point near Hc, but with a nonuniversal critical value ρxy c comparable to the normal-state Hall resistivity. We propose that high-carrier-density metals will always exhibit this pattern of behavior at the boundary between superconducting and (trivially) insulating ground states.

Iron chalcogenide superconductors at high magnetic fields

PubMed Central

Lei, Hechang; Wang, Kefeng; Hu, Rongwei; Ryu, Hyejin; Abeykoon, Milinda; Bozin, Emil S; Petrovic, Cedomir

2012-01-01

Iron chalcogenide superconductors have become one of the most investigated superconducting materials in recent years due to high upper critical fields, competing interactions and complex electronic and magnetic phase diagrams. The structural complexity, defects and atomic site occupancies significantly affect the normal and superconducting states in these compounds. In this work we review the vortex behavior, critical current density and high magnetic field pair-breaking mechanism in iron chalcogenide superconductors. We also point to relevant structural features and normal-state properties. PMID:27877518

Synthesis, anisotropy, and superconducting properties of LiFeAs single crystal

NASA Astrophysics Data System (ADS)

Song, Yoo Jang; Ghim, Jin Soo; Min, Byeong Hun; Kwon, Yong Seung; Jung, Myung Hwa; Rhyee, Jong-Soo

2010-05-01

A LiFeAs single crystal with Tconset˜19.7 K was grown in a sealed tungsten crucible using the Bridgeman method. The electrical resistivity experiments revealed a ratio of room temperature to residual resistivity of approximately 46 and 18 for the in-plane and out-of plane directions, respectively. The estimated anisotropic resistivity, γρ=ρc/ρab, was approximately 3.3 at Tconset. The upper critical fields had large Hc2∥ab and Hc2∥c values of 83.4 T and 72.5 T, respectively, and an anisotropy ratio is γH=Hc2∥ab/Hc2∥c˜1.15. The high upper critical field value and small anisotropy highlight the potential use of LiFeAs in a variety of applications. The calculated critical current density (Jc) from the M-H loop is approximately 103 A/cm2

Critical Two-Point Function for Long-Range O( n) Models Below the Upper Critical Dimension

NASA Astrophysics Data System (ADS)

Lohmann, Martin; Slade, Gordon; Wallace, Benjamin C.

2017-12-01

We consider the n-component |φ|^4 lattice spin model (n ≥ 1) and the weakly self-avoiding walk (n=0) on Z^d, in dimensions d=1,2,3. We study long-range models based on the fractional Laplacian, with spin-spin interactions or walk step probabilities decaying with distance r as r^{-(d+α )} with α \\in (0,2). The upper critical dimension is d_c=2α . For ɛ >0, and α = 1/2 (d+ɛ ), the dimension d=d_c-ɛ is below the upper critical dimension. For small ɛ , weak coupling, and all integers n ≥ 0, we prove that the two-point function at the critical point decays with distance as r^{-(d-α )}. This "sticking" of the critical exponent at its mean-field value was first predicted in the physics literature in 1972. Our proof is based on a rigorous renormalisation group method. The treatment of observables differs from that used in recent work on the nearest-neighbour 4-dimensional case, via our use of a cluster expansion.

Superconductor to weak-insulator transitions in disordered tantalum nitride films

DOE PAGES

Breznay, Nicholas P.; Tendulkar, Mihir; Zhang, Li; ...

2017-10-31

Here, we study the two-dimensional superconductor-insulator transition (SIT) in thin films of tantalum nitride. At zero magnetic field, films can be disorder-tuned across the SIT by adjusting thickness and film stoichiometry; insulating films exhibit classical hopping transport. Superconducting films exhibit a magnetic-field-tuned SIT, whose insulating ground state at high field appears to be a quantum-corrected metal. Scaling behavior at the field-tuned SIT shows classical percolation critical exponents zν ≈ 1.3, with a corresponding critical field H c << H c2, the upper critical field. The Hall effect exhibits a crossing point near H c, but with a nonuniversal critical valuemore » ρ c xy comparable to the normal-state Hall resistivity. We propose that high-carrier-density metals will always exhibit this pattern of behavior at the boundary between superconducting and (trivially) insulating ground states.« less

Quantum oscillations and upper critical magnetic field of the iron-based superconductor FeSe

NASA Astrophysics Data System (ADS)

Audouard, Alain; Duc, Fabienne; Drigo, Loïc; Toulemonde, Pierre; Karlsson, Sandra; Strobel, Pierre; Sulpice, André

2015-01-01

Shubnikov-de Haas (SdH) oscillations and upper critical magnetic field (Hc2) of the iron-based superconductor FeSe (Tc = 8.6 \\text{K}) have been studied by tunnel diode oscillator-based measurements in magnetic fields of up to 55 T and temperatures down to 1.6 K. Several Fourier components enter the SdH oscillations spectrum with frequencies definitely smaller than predicted by band structure calculations indicating band renormalization and reconstruction of the Fermi surface at low temperature, in line with previous ARPES data. The Werthamer-Helfand-Hohenberg model accounts for the temperature dependence of (Hc2) for magnetic field applied both parallel (\\textbf{H} \\| ab) and perpendicular (\\textbf{H} \\| c) to the iron conducting plane, suggesting that one band mainly controls the superconducting properties in magnetic fields despite the multiband nature of the Fermi surface. Whereas Pauli pair breaking is negligible for \\textbf{H} \\| c , a Pauli paramagnetic contribution is evidenced for \\textbf{H} \\| ab with Maki parameter α = 2.1 , corresponding to Pauli field HP = 36.5 \\text{T} .

An antithetic variate to facilitate upper-stem height measurements for critical height sampling with importance sampling

Treesearch

Thomas B. Lynch; Jeffrey H. Gove

2013-01-01

Critical height sampling (CHS) estimates cubic volume per unit area by multiplying the sum of critical heights measured on trees tallied in a horizontal point sample (HPS) by the HPS basal area factor. One of the barriers to practical application of CHS is the fact that trees near the field location of the point-sampling sample point have critical heights that occur...

Reversal of the Upper Critical Field Anisotropy and Spin-Locked Superconductivity in K 2Cr 3As 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balakirev, Fedor Fedorovich; Kong, T.; Jaime, Marcelo

2016-02-08

Recently, superconductivity in K 2Cr 3As 3 (T c =6.1 K) was discovered. The crystalline lattice contains an array of weakly coupled, double well [(Cr 3As 3) 2-] ∞ linkages stretched along the c axis, suggesting the possibility of quasi-one-dimensional superconductivity. Moderately anisotropic upper critical field was revealed in single crystals, with very large initial slopes, dH ∥ c2 /dT=12 T/K along the Cr chains and dH perpendicular c2 /dT =7 T/K perpendicular to the chains. Given the ambiguity of conclusions based on the extrapolations of H c2(T) measured near T c to low temperatures, we performed high-field measurements ofmore » H c2(T) on K 2Cr 3As 3 single crystals in pulsed magnetic fields which enabled us to reveal the full anisotropic H c2(T) curves from T c down to 600 mK.« less

Statistics of Statisticians: Critical Mass of Statistics and Operational Research Groups

NASA Astrophysics Data System (ADS)

Kenna, Ralph; Berche, Bertrand

Using a recently developed model, inspired by mean field theory in statistical physics, and data from the UK's Research Assessment Exercise, we analyse the relationship between the qualities of statistics and operational research groups and the quantities of researchers in them. Similar to other academic disciplines, we provide evidence for a linear dependency of quality on quantity up to an upper critical mass, which is interpreted as the average maximum number of colleagues with whom a researcher can communicate meaningfully within a research group. The model also predicts a lower critical mass, which research groups should strive to achieve to avoid extinction. For statistics and operational research, the lower critical mass is estimated to be 9 ± 3. The upper critical mass, beyond which research quality does not significantly depend on group size, is 17 ± 6.

Quantum criticality and nodal superconductivity in the FeAs-based superconductor KFe2As2.

PubMed

Dong, J K; Zhou, S Y; Guan, T Y; Zhang, H; Dai, Y F; Qiu, X; Wang, X F; He, Y; Chen, X H; Li, S Y

2010-02-26

The in-plane resistivity rho and thermal conductivity kappa of the FeAs-based superconductor KFe2As2 single crystal were measured down to 50 mK. We observe non-Fermi-liquid behavior rho(T) approximately T{1.5} at H{c{2}}=5 T, and the development of a Fermi liquid state with rho(T) approximately T{2} when further increasing the field. This suggests a field-induced quantum critical point, occurring at the superconducting upper critical field H{c{2}}. In zero field, there is a large residual linear term kappa{0}/T, and the field dependence of kappa_{0}/T mimics that in d-wave cuprate superconductors. This indicates that the superconducting gaps in KFe2As2 have nodes, likely d-wave symmetry. Such a nodal superconductivity is attributed to the antiferromagnetic spin fluctuations near the quantum critical point.

Quantum Monte Carlo study of the transverse-field quantum Ising model on infinite-dimensional structures

NASA Astrophysics Data System (ADS)

Baek, Seung Ki; Um, Jaegon; Yi, Su Do; Kim, Beom Jun

2011-11-01

In a number of classical statistical-physical models, there exists a characteristic dimensionality called the upper critical dimension above which one observes the mean-field critical behavior. Instead of constructing high-dimensional lattices, however, one can also consider infinite-dimensional structures, and the question is whether this mean-field character extends to quantum-mechanical cases as well. We therefore investigate the transverse-field quantum Ising model on the globally coupled network and on the Watts-Strogatz small-world network by means of quantum Monte Carlo simulations and the finite-size scaling analysis. We confirm that both of the structures exhibit critical behavior consistent with the mean-field description. In particular, we show that the existing cumulant method has difficulty in estimating the correct dynamic critical exponent and suggest that an order parameter based on the quantum-mechanical expectation value can be a practically useful numerical observable to determine critical behavior when there is no well-defined dimensionality.

Supercondutivity at 9K in Mo 5PB 2 with evidence for multiple gaps

DOE PAGES

McGuire, Michael A.; Parker, David S.

2016-02-09

Superconductivity is observed with critical temperatures near 9 K in the tetragonal compound Mo 5PB 2. This material adopts the Cr 5B 3 structure type common to superconducting Nb 5Si 3–xBx, Mo 5SiB 2, and W 5SiB 2, which have critical temperatures of 5.8–7.8 K. We have synthesized polycrystalline samples of the compound, made measurements of electrical resistivity, magnetic susceptibility, and heat capacity, and performed first-principles electronic structure calculations. The highest T c value (9.2 K) occurs in slightly phosphorus rich samples, with composition near Mo 5P 1.1B 1.9, and the upper critical field H c2 at T = 0more » is estimated to be ≈17 kOe. Together, the measurements and band-structure calculations indicate intermediate coupling (λ=1.0), phonon mediated superconductivity. Here, the temperature dependence of the heat capacity and upper critical field H c2 below T c suggest multiple superconducting gaps may be present.« less

Upper critical fields in Ba2Ti2Fe2As4O single crystals: Evidence for dominant Pauli paramagnetic effect

NASA Astrophysics Data System (ADS)

Abdel-Hafiez, M.; Brisbois, J.; Zhu, Z.; Adamski, A.; Hassen, A.; Vasiliev, A. N.; Silhanek, A. V.; Krellner, C.

2018-03-01

We report on magneto-optical imaging and the temperature dependency of the upper critical fields Hc2 c(T ) parallel to the c axis and Hc2 a b(T ) parallel to the a b plane in Ba2Ti2Fe2As4O single crystals. These data were inferred from the measurements of the temperature-dependent resistance in static magnetic fields up to 14 T and magnetoresistance in pulsed fields up to 60 T. Hc 2 values are found to be 52 and 50 T for H ∥a b and H ∥c , respectively. These values are 1.2-1.35 times larger than the weak-coupling Pauli paramagnetic limit (Hp˜1.84 Tc ), indicating that enhanced paramagnetic limiting is essential and this superconductor is unconventional. Our observations of strong bending in the Hc2 a b(T ) curves and a nearly isotropic maximum upper critical field Hc2 a b(0 ) ≈Hc2 c(0 ) support the presence of a strong Pauli paramagnetic effect. We show that the Werthamer-Helfand-Hohenberg (WHH) formula that includes the spin-orbit scattering can effectively describe the Hc2 a b(T ) curve, whereas Hc 2 deviates from the conventional WHH theoretical model without considering the spin paramagnetic effect for the H ∥c and H ∥a b directions. For H ∥c , a two-band model is required to fully reproduce the behavior of Hc 2, while for H ∥a b the spin paramagnetic effect is responsible for the behavior of Hc 2. The anisotropy of Hc 2 is close to 3 near Tc and decreases rapidly at lower temperatures.

Vortex pinning and irreversibility fields in FeS1-xSex (x = 0, 0.06)

NASA Astrophysics Data System (ADS)

Wang, Aifeng; Petrovic, C.

2017-06-01

We report strong vortex pinning and large irreversibility fields in single crystals of tetragonal FeS1-xSex (x = 0, 0.06). Vortex dynamics is characterized by crossover in field dependence of the depinning energy U0, indicative of single flux surface pinning to the region of collective flux pinning on point-like defects. The close proximity of the irreversibility lines to the upper critical field (Hc2) is consistent with strong pinning in FeS and FeS0.94Se0.06, pointing that new materials with building-blocks of FeS4 tetrahedra are likely to host high critical currents.

Anisotropic upper critical fields up to 63 T in CaKFe 4As 4 single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kong, T.; Balakirev, Fedor Fedorovich; Meier, W. R.

2017-02-13

The discovery of Fe-based superconductors (FBS) has intensified research on mechanisms of hightemperature superconductivity as well as searches for materials with higher superconducting transition temperatures, Tc. Among many different classes of FBS, the so called “122” family is one of the most well studied systems. However, superconductivity in “122” systems is often stabilized via chemical substitution, which inevitably invites chemical disorder. Recently, a new compound, CaKFe 4As 4, with a well ordered structure that is essentially composed of alternating “122” layers, was discovered with a T c of 35 K. We were able to perform the first single crystal studymore » and measured the anisotropic upper critical fields, H c2, up to 63 T.« less

Superconducting properties of molybdenum ruthenium alloy Mo0.63Ru0.37

NASA Astrophysics Data System (ADS)

Wei, Wensen; Ge, Min; Wang, Shasha; Zhang, Lei; Han, Yuyan; Du, Haifeng; Tian, Mingliang; Zhang, Yuheng

2018-03-01

Resistance, magnetization and specific heat measurements were performed on Mo0.63Ru0.37 alloy. All of them confirm that Mo0.63Ru0.37 becomes superconducting at about 7.0 K with bulk nature. Its upper critical field behavior fits to Werthamer-Helfand-Hohenberg (WHH) model quite well, with an upper critical field of μ0Hc2(0) = 8.64 T, less than its Pauli limit. Its electronic specific heat is reproduced by Bardeen-Cooper-Schriffer (BCS)-based α-model with a gap ratio Δ0 = 1.88kBTc, which is a little larger than the standard BCS value of 1.76. We concluded that Mo0.63Ru0.37 is a fully gapped isotropic s-wave superconductor, with its features are mostly consistent with the conventional theory.

Tuning Ising superconductivity with layer and spin-orbit coupling in two-dimensional transition-metal dichalcogenides.

PubMed

de la Barrera, Sergio C; Sinko, Michael R; Gopalan, Devashish P; Sivadas, Nikhil; Seyler, Kyle L; Watanabe, Kenji; Taniguchi, Takashi; Tsen, Adam W; Xu, Xiaodong; Xiao, Di; Hunt, Benjamin M

2018-04-12

Systems simultaneously exhibiting superconductivity and spin-orbit coupling are predicted to provide a route toward topological superconductivity and unconventional electron pairing, driving significant contemporary interest in these materials. Monolayer transition-metal dichalcogenide (TMD) superconductors in particular lack inversion symmetry, yielding an antisymmetric form of spin-orbit coupling that admits both spin-singlet and spin-triplet components of the superconducting wavefunction. Here, we present an experimental and theoretical study of two intrinsic TMD superconductors with large spin-orbit coupling in the atomic layer limit, metallic 2H-TaS 2 and 2H-NbSe 2 . We investigate the superconducting properties as the material is reduced to monolayer thickness and show that high-field measurements point to the largest upper critical field thus reported for an intrinsic TMD superconductor. In few-layer samples, we find the enhancement of the upper critical field is sustained by the dominance of spin-orbit coupling over weak interlayer coupling, providing additional candidate systems for supporting unconventional superconducting states in two dimensions.

Effects of magnetic impurities on upper critical fields in the high-T c superconductor La-doped CaFe2As2

NASA Astrophysics Data System (ADS)

Jung, Soon-Gil; Shin, Soohyeon; Jang, Harim; Mikheenko, Pavlo; Johansen, Tom H.; Park, Tuson

2017-08-01

We investigate the effects of magnetic impurities on the upper critical field (μ 0 H c2) in La-doped CaFe2As2 (LaCa122) single crystals. The magnetic field dependency of the superconducting transition temperature (T c) for LaCa122 is rapidly suppressed at low fields up to ˜1 kOe despite its large μ 0 H c2(0) value on the order of tens of Tesla, resulting in a large positive curvature of μ 0 H c2(T) near T c. The magnetization hysteresis (M-H) loop at temperatures above T c shows a ferromagnetic-like signal and the M(H) value rapidly increases with increasing magnetic field up to ˜1 kOe. Taken together with the linear suppression of T c with the magnetization in the normal state, these results suggest that the large upward curvature of μ 0 H c2(T) near T c in La-doped CaFe2As2 mainly originates from the suppression of superconductivity due to the presence of magnetic impurities.

Superconducting properties of Ba(Fe1-xNix)2As2 thin films in high magnetic fields

NASA Astrophysics Data System (ADS)

Richter, Stefan; Kurth, Fritz; Iida, Kazumasa; Pervakov, Kirill; Pukenas, Aurimas; Tarantini, Chiara; Jaroszynski, Jan; Hänisch, Jens; Grinenko, Vadim; Skrotzki, Werner; Nielsch, Kornelius; Hühne, Ruben

2017-01-01

We report on the electrical transport properties of epitaxial Ba(Fe1-xNix)2As2 thin films grown by pulsed laser deposition in static magnetic fields up to 35 T. The thin film shows a critical temperature of 17.2 K and a critical current density of 5.7 × 105 A/cm2 in self field at 4.2 K, while the pinning is dominated by elastic pinning at two-dimensional nonmagnetic defects. Compared to the single-crystal data, we find a higher slope of the upper critical field for the thin film at a similar doping level and a small anisotropy. Also, an unusual small vortex liquid phase was observed at low temperatures, which is a striking difference to Co-doped BaFe2As2 thin films.

Enhanced superconducting transition temperature in electroplated rhenium

NASA Astrophysics Data System (ADS)

Pappas, D. P.; David, D. E.; Lake, R. E.; Bal, M.; Goldfarb, R. B.; Hite, D. A.; Kim, E.; Ku, H.-S.; Long, J. L.; McRae, C. R. H.; Pappas, L. D.; Roshko, A.; Wen, J. G.; Plourde, B. L. T.; Arslan, I.; Wu, X.

2018-04-01

We show that electroplated Re films in multilayers with noble metals such as Cu, Au, and Pd have an enhanced superconducting critical temperature relative to previous methods of preparing Re. The dc resistance and magnetic susceptibility indicate a critical temperature of approximately 6 K. The magnetic response as a function of field at 1.8 K demonstrates type-II superconductivity, with an upper critical field on the order of 2.5 T. Critical current densities greater than 107 A/m2 were measured above liquid-helium temperature. Low-loss at radio frequency was obtained below the critical temperature for multilayers deposited onto resonators made with Cu traces on commercial circuit boards. These electroplated superconducting films can be integrated into a wide range of standard components for low-temperature electronics.

Spin susceptibility of charge-ordered YBa2Cu3Oy across the upper critical field

NASA Astrophysics Data System (ADS)

Zhou, Rui; Hirata, Michihiro; Wu, Tao; Vinograd, Igor; Mayaffre, Hadrien; Krämer, Steffen; Reyes, Arneil P.; Kuhns, Philip L.; Liang, Ruixing; Hardy, W. N.; Bonn, D. A.; Julien, Marc-Henri

2017-12-01

The value of the upper critical field Hc2, a fundamental characteristic of the superconducting state, has been subject to strong controversy in high-Tc copper oxides. Since the issue has been tackled almost exclusively by macroscopic techniques so far, there is a clear need for local-probe measurements. Here, we use 17O NMR to measure the spin susceptibility χspin of the CuO2 planes at low temperature in charge-ordered YBa2Cu3Oy. We find that χspin increases (most likely linearly) with magnetic field H and saturates above field values ranging from 20 T to 40 T. This result is consistent with the lowest Hc2 values claimed previously and with the interpretation that the charge density wave (CDW) reduces Hc2 in underdoped YBa2Cu3Oy. Furthermore, the absence of marked deviation in χspin(H) at the onset of long-range CDW order indicates that this Hc2 reduction and the Fermi-surface reconstruction are primarily rooted in the short-range CDW order already present in zero field, not in the field-induced long-range CDW order. Above Hc2, the relatively low values of T= 2 K show that the pseudogap is a ground-state property, independent of the superconducting gap.

Critical fields and vortex pinning in overdoped Ba 0.2 K 0.8 Fe 2 As 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, B.; Leroux, M.; Wang, Y. L.

2015-05-19

We determine the upper and lower critical fields, the penetration depth and the vortex pinning characteristics of single crystals of overdoped Ba 0.2K 0.8Fe 2As 2 with T c ~ 10 K. We find that bulk vortex pinning is weak and vortex dynamics to be dominated by the geometrical surface barrier. The temperature dependence of the lower critical field, H c1, displays a distinctive upturn at low temperatures, which is suggestive of two distinct superconducting gaps. Furthermore, the penetration depth, λ, varies linearly with temperature below 4 K indicative of line nodes in the superconducting gap. As a result, thesemore » observations can be well described in a model based on a multi-band nodal superconducting gap.« less

Hc2(0) and the Kondo Effect in FeSe0.1Te0.9 Epitaxial Films

NASA Astrophysics Data System (ADS)

Cornell, Nicholas; Zakhidov, Anvar; Jaime, Marcelo; Huang, Jijie; Wang, Hayan; Salamon, Myron

2015-03-01

High-quality, [001]-oriented epitaxial films of FeSe0.1Te0.9 have been grown on SrTiO3. They are found to have increased critical temperatures and critical fields relative to both bulk samples and thin films of the sister compound, FeSe0.5Te0.5. Critical field values in excess of 114 T have been reported based on WHH theory. In addition to these improved properties, most samples show resistance minima above Tc, reminiscent of the Kondo effect, presumably from excess Fe. We report results of a high field investigation of these thin films that reveals an empirical zero-temperature value of Hc2(0) ~ 46 T along [001], significantly less than the WHH estimate, but still exceeding the maximum strong coupling correction to the Pauli limit. Large negative magnetoresistance above the critical field confirms the presence of Kondo behavior in the normal state and persists without saturation up to 60 T. Why the measured critical field exceeds the paramagnetic limit remains a question. However, a Kondo temperature that exceeds the superconducting Tc can lead to overestimated WHH upper critical fields and could explain the wide variation in Tc and Hc2 among the ``11'' iron chalcogenides.

Doping evolution of the anisotropic upper critical fields in the iron-based superconductor Ba 1-xK xFe 2As 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanatar, Makariy A.; Liu, Yong; Jaroszynski, J.

In-plane resistivity measurements as a function of temperature and magnetic field up to 35 T with precise orientation within the crystallographic ac plane were used to study the upper critical field H c2 of the hole-doped iron-based superconductor Ba 1–xK xFe 2As 2. Compositions of the samples studied spanned from under- doped x=0.17 (T c=12 K) and x=0.22 (T c=20 K), both in the coexistence range of stripe magnetism and superconductivity, through optimal doping x=0.39 (T c=38.4 K) and x=0.47 (T c=37.2 K), to overdoped x=0.65 (T c=22 K) and x=0.83 (T c=10 K). Here, we find notable doping asymmetrymore » of the shapes of the anisotropic H c2(T), suggesting the important role of paramagnetic limiting effects in the H∥a configuration in overdoped compositions and multiband effects in underdoped compositions.« less

Doping evolution of the anisotropic upper critical fields in the iron-based superconductor Ba 1-xK xFe 2As 2

DOE PAGES

Tanatar, Makariy A.; Liu, Yong; Jaroszynski, J.; ...

2017-11-14

In-plane resistivity measurements as a function of temperature and magnetic field up to 35 T with precise orientation within the crystallographic ac plane were used to study the upper critical field H c2 of the hole-doped iron-based superconductor Ba 1–xK xFe 2As 2. Compositions of the samples studied spanned from under- doped x=0.17 (T c=12 K) and x=0.22 (T c=20 K), both in the coexistence range of stripe magnetism and superconductivity, through optimal doping x=0.39 (T c=38.4 K) and x=0.47 (T c=37.2 K), to overdoped x=0.65 (T c=22 K) and x=0.83 (T c=10 K). Here, we find notable doping asymmetrymore » of the shapes of the anisotropic H c2(T), suggesting the important role of paramagnetic limiting effects in the H∥a configuration in overdoped compositions and multiband effects in underdoped compositions.« less

Critical current measurements of high-temperature superconducting short samples at a wide range of temperatures and magnetic fields.

PubMed

Ma, Hongjun; Liu, Huajun; Liu, Fang; Zhang, Huahui; Ci, Lu; Shi, Yi; Lei, Lei

2018-01-01

High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (H c2 ) and critical temperature (T c ). The critical current (I c ) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new I c measurement system that can carry out accurate I c measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The I c measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa 2 Cu 3 O 7-x (YBCO) tapes I c determination with different temperatures and magnetic fields.

Critical current measurements of high-temperature superconducting short samples at a wide range of temperatures and magnetic fields

NASA Astrophysics Data System (ADS)

Ma, Hongjun; Liu, Huajun; Liu, Fang; Zhang, Huahui; Ci, Lu; Shi, Yi; Lei, Lei

2018-01-01

High-Temperature Superconductors (HTS) are potential materials for high-field magnets, low-loss transmission cables, and Superconducting Magnetic Energy Storage (SMES) due to their high upper critical magnetic field (Hc2) and critical temperature (Tc). The critical current (Ic) of HTS, which is one of the most important parameters for superconductor application, depends strongly on the magnetic fields and temperatures. A new Ic measurement system that can carry out accurate Ic measurement for HTS short samples with various temperatures (4.2-80 K), magnetic fields (0-14 T), and angles of the magnetic field (0°-90°) has been developed. The Ic measurement system mainly consists of a measurement holder, temperature-control system, background magnet, test cryostat, data acquisition system, and DC power supply. The accuracy of temperature control is better than ±0.1 K over the 20-80 K range and ±0.05 K when measured below 20 K. The maximum current is over 1000 A with a measurement uncertainty of 1%. The system had been successfully used for YBa2Cu3O7-x(YBCO) tapes Ic determination with different temperatures and magnetic fields.

High field superconducting properties of Ba(Fe1-xCox)2As2 thin films

NASA Astrophysics Data System (ADS)

Hänisch, Jens; Iida, Kazumasa; Kurth, Fritz; Reich, Elke; Tarantini, Chiara; Jaroszynski, Jan; Förster, Tobias; Fuchs, Günther; Hühne, Ruben; Grinenko, Vadim; Schultz, Ludwig; Holzapfel, Bernhard

2015-11-01

In general, the critical current density, Jc, of type II superconductors and its anisotropy with respect to magnetic field orientation is determined by intrinsic and extrinsic properties. The Fe-based superconductors of the ‘122’ family with their moderate electronic anisotropies and high yet accessible critical fields (Hc2 and Hirr) are a good model system to study this interplay. In this paper, we explore the vortex matter of optimally Co-doped BaFe2As2 thin films with extended planar and c-axis correlated defects. The temperature and angular dependence of the upper critical field is well explained by a two-band model in the clean limit. The dirty band scenario, however, cannot be ruled out completely. Above the irreversibility field, the flux motion is thermally activated, where the activation energy U0 is going to zero at the extrapolated zero-kelvin Hirr value. The anisotropy of the critical current density Jc is both influenced by the Hc2 anisotropy (and therefore by multi-band effects) as well as the extended planar and columnar defects present in the sample.

Mixed-order phase transition in a colloidal crystal.

PubMed

Alert, Ricard; Tierno, Pietro; Casademunt, Jaume

2017-12-05

Mixed-order phase transitions display a discontinuity in the order parameter like first-order transitions yet feature critical behavior like second-order transitions. Such transitions have been predicted for a broad range of equilibrium and nonequilibrium systems, but their experimental observation has remained elusive. Here, we analytically predict and experimentally realize a mixed-order equilibrium phase transition. Specifically, a discontinuous solid-solid transition in a 2D crystal of paramagnetic colloidal particles is induced by a magnetic field [Formula: see text] At the transition field [Formula: see text], the energy landscape of the system becomes completely flat, which causes diverging fluctuations and correlation length [Formula: see text] Mean-field critical exponents are predicted, since the upper critical dimension of the transition is [Formula: see text] Our colloidal system provides an experimental test bed to probe the unconventional properties of mixed-order phase transitions.

Mixed-order phase transition in a colloidal crystal

NASA Astrophysics Data System (ADS)

Alert, Ricard; Tierno, Pietro; Casademunt, Jaume

2017-12-01

Mixed-order phase transitions display a discontinuity in the order parameter like first-order transitions yet feature critical behavior like second-order transitions. Such transitions have been predicted for a broad range of equilibrium and nonequilibrium systems, but their experimental observation has remained elusive. Here, we analytically predict and experimentally realize a mixed-order equilibrium phase transition. Specifically, a discontinuous solid-solid transition in a 2D crystal of paramagnetic colloidal particles is induced by a magnetic field H. At the transition field Hs, the energy landscape of the system becomes completely flat, which causes diverging fluctuations and correlation length ξ∝|H2-Hs2|-1/2. Mean-field critical exponents are predicted, since the upper critical dimension of the transition is du=2. Our colloidal system provides an experimental test bed to probe the unconventional properties of mixed-order phase transitions.

Exponential nonlinear electrodynamics and backreaction effects on holographic superconductor in the Lifshitz black hole background

NASA Astrophysics Data System (ADS)

Sherkatghanad, Z.; Mirza, B.; Lalehgani Dezaki, F.

We analytically describe the properties of the s-wave holographic superconductor with the exponential nonlinear electrodynamics in the Lifshitz black hole background in four-dimensions. Employing an assumption the scalar and gauge fields backreact on the background geometry, we calculate the critical temperature as well as the condensation operator. Based on Sturm-Liouville method, we show that the critical temperature decreases with increasing exponential nonlinear electrodynamics and Lifshitz dynamical exponent, z, indicating that condensation becomes difficult. Also we find that the effects of backreaction has a more important role on the critical temperature and condensation operator in small values of Lifshitz dynamical exponent, while z is around one. In addition, the properties of the upper critical magnetic field in Lifshitz black hole background using Sturm-Liouville approach is investigated to describe the phase diagram of the corresponding holographic superconductor in the probe limit. We observe that the critical magnetic field decreases with increasing Lifshitz dynamical exponent, z, and it goes to zero at critical temperature, independent of the Lifshitz dynamical exponent, z.

Spin susceptibility of charge-ordered YBa2Cu3Oy across the upper critical field

PubMed Central

Zhou, Rui; Hirata, Michihiro; Wu, Tao; Vinograd, Igor; Mayaffre, Hadrien; Krämer, Steffen; Reyes, Arneil P.; Kuhns, Philip L.; Liang, Ruixing; Hardy, W. N.; Bonn, D. A.; Julien, Marc-Henri

2017-01-01

The value of the upper critical field Hc2, a fundamental characteristic of the superconducting state, has been subject to strong controversy in high-Tc copper oxides. Since the issue has been tackled almost exclusively by macroscopic techniques so far, there is a clear need for local-probe measurements. Here, we use 17O NMR to measure the spin susceptibility χspin of the CuO2 planes at low temperature in charge-ordered YBa2Cu3Oy. We find that χspin increases (most likely linearly) with magnetic field H and saturates above field values ranging from 20 T to 40 T. This result is consistent with the lowest Hc2 values claimed previously and with the interpretation that the charge density wave (CDW) reduces Hc2 in underdoped YBa2Cu3Oy. Furthermore, the absence of marked deviation in χspin(H) at the onset of long-range CDW order indicates that this Hc2 reduction and the Fermi-surface reconstruction are primarily rooted in the short-range CDW order already present in zero field, not in the field-induced long-range CDW order. Above Hc2, the relatively low values of χspin at T= 2 K show that the pseudogap is a ground-state property, independent of the superconducting gap. PMID:29183974

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

DOE PAGES

Kasahara, Y.; Takeuchi, Y.; Zadik, R. H.; ...

2017-02-17

Controlled access to the border of the Mott insulating state by variation of control parameters offers exotic electronic states such as anomalous and possibly high-transition-temperature (T c) superconductivity. The alkali-doped fullerides show a transition from a Mott insulator to a superconductor for the first time in three-dimensional materials, but the impact of dimensionality and electron correlation on superconducting properties has remained unclear. Here we show that, near the Mott insulating phase, the upper critical field H c2 of the fulleride superconductors reaches values as high as ~90 T—the highest among cubic crystals. This is accompanied by a crossover from weak-more » to strong-coupling superconductivity and appears upon entering the metallic state with the dynamical Jahn–Teller effect as the Mott transition is approached. Lastly, these results suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity with high-T c and high-H c2.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasahara, Y.; Takeuchi, Y.; Zadik, R. H.

Controlled access to the border of the Mott insulating state by variation of control parameters offers exotic electronic states such as anomalous and possibly high-transition-temperature (T c) superconductivity. The alkali-doped fullerides show a transition from a Mott insulator to a superconductor for the first time in three-dimensional materials, but the impact of dimensionality and electron correlation on superconducting properties has remained unclear. Here we show that, near the Mott insulating phase, the upper critical field H c2 of the fulleride superconductors reaches values as high as ~90 T—the highest among cubic crystals. This is accompanied by a crossover from weak-more » to strong-coupling superconductivity and appears upon entering the metallic state with the dynamical Jahn–Teller effect as the Mott transition is approached. Lastly, these results suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity with high-T c and high-H c2.« less

Effect of equatorial line nodes on the upper critical field and London penetration depth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kogan, V G; Prozorov, R

2014-09-01

The upper critical field Hc2 and its anisotropy are calculated for order parameters with line nodes at the equators, kz=0, of the Fermi surface of uniaxial superconductors. It is shown that characteristic features found in Fe-based materials (a nearly linear Hc2(T) in a broad T domain, a low and increasing on warming anisotropy γH=Hc2,ab/Hc2,c) can be caused by competing effects of the equatorial nodes and of the Fermi surface anisotropy. For certain material parameters, γH(T)-1 may change sign upon warming, in agreement with the recorded behavior of FeTeS systems. It is also shown that the anisotropy of the penetration depthmore » γλ=λc/λab decreases upon warming to reach γH at Tc, in agreement with data available. For some materials γλ(T) may change upon warming, from γλ>1 at low Ts to γλ<1 at high Ts.« less

Calculative techniques for transonic flows about certain classes of wing body combinations

NASA Technical Reports Server (NTRS)

Stahara, S. S.; Spreiter, J. R.

1972-01-01

Procedures based on the method of local linearization and transonic equivalence rule were developed for predicting properties of transonic flows about certain classes of wing-body combinations. The procedures are applicable to transonic flows with free stream Mach number in the ranges near one, below the lower critical and above the upper critical. Theoretical results are presented for surface and flow field pressure distributions for both lifting and nonlifting situations.

Evidence of incomplete annealing at 800 °C and the effects of 120 °C baking on the crystal orientation and the surface superconducting properties of cold-worked and chemically polished Nb

NASA Astrophysics Data System (ADS)

Sung, Z.-H.; Dzyuba, A.; Lee, P. J.; Larbalestier, D. C.; Cooley, L. D.

2015-07-01

High-purity niobium rods were cold-worked by wire-drawing, followed by various combinations of chemical polishing and high-vacuum baking at 120 °C or annealing at 800 °C in order to better understand changes to the surface superconducting properties resulting from typical superconducting radio-frequency cavity processing. AC susceptibility measurements revealed an enhanced upper transition Tc at ˜ 9.3-9.4 K in all samples that was stable through all annealing steps, a value significantly above the accepted Tc of 9.23 K for pure annealed niobium. Corresponding elevations were seen in the critical fields, the ratio of the surface critical field Hc3 to the bulk upper critical field Hc2 rising to 2.3, well above the Ginzburg-Landau value of 1.695. Orientation imaging revealed an extensive dislocation rich sub-grain structure in the as-drawn rods, a small reduction of the surface strain after baking at 120 °C, and a substantial but incomplete recrystallization near the surface after annealing at 800 °C. We interpret these changes in surface superconducting and structural properties to extensive changes in the near-surface interstitial contamination produced by baking and annealing and to synergistic interactions between H and surface O introduced during electropolishing and buffered chemical polishing.

Critical and Griffiths-McCoy singularities in quantum Ising spin glasses on d-dimensional hypercubic lattices: A series expansion study.

PubMed

Singh, R R P; Young, A P

2017-08-01

We study the ±J transverse-field Ising spin-glass model at zero temperature on d-dimensional hypercubic lattices and in the Sherrington-Kirkpatrick (SK) model, by series expansions around the strong-field limit. In the SK model and in high dimensions our calculated critical properties are in excellent agreement with the exact mean-field results, surprisingly even down to dimension d=6, which is below the upper critical dimension of d=8. In contrast, at lower dimensions we find a rich singular behavior consisting of critical and Griffiths-McCoy singularities. The divergence of the equal-time structure factor allows us to locate the critical coupling where the correlation length diverges, implying the onset of a thermodynamic phase transition. We find that the spin-glass susceptibility as well as various power moments of the local susceptibility become singular in the paramagnetic phase before the critical point. Griffiths-McCoy singularities are very strong in two dimensions but decrease rapidly as the dimension increases. We present evidence that high enough powers of the local susceptibility may become singular at the pure-system critical point.

Critical and Griffiths-McCoy singularities in quantum Ising spin glasses on d -dimensional hypercubic lattices: A series expansion study

NASA Astrophysics Data System (ADS)

Singh, R. R. P.; Young, A. P.

2017-08-01

We study the ±J transverse-field Ising spin-glass model at zero temperature on d -dimensional hypercubic lattices and in the Sherrington-Kirkpatrick (SK) model, by series expansions around the strong-field limit. In the SK model and in high dimensions our calculated critical properties are in excellent agreement with the exact mean-field results, surprisingly even down to dimension d =6 , which is below the upper critical dimension of d =8 . In contrast, at lower dimensions we find a rich singular behavior consisting of critical and Griffiths-McCoy singularities. The divergence of the equal-time structure factor allows us to locate the critical coupling where the correlation length diverges, implying the onset of a thermodynamic phase transition. We find that the spin-glass susceptibility as well as various power moments of the local susceptibility become singular in the paramagnetic phase before the critical point. Griffiths-McCoy singularities are very strong in two dimensions but decrease rapidly as the dimension increases. We present evidence that high enough powers of the local susceptibility may become singular at the pure-system critical point.

Mixed-order phase transition in a colloidal crystal

PubMed Central

Tierno, Pietro; Casademunt, Jaume

2017-01-01

Mixed-order phase transitions display a discontinuity in the order parameter like first-order transitions yet feature critical behavior like second-order transitions. Such transitions have been predicted for a broad range of equilibrium and nonequilibrium systems, but their experimental observation has remained elusive. Here, we analytically predict and experimentally realize a mixed-order equilibrium phase transition. Specifically, a discontinuous solid–solid transition in a 2D crystal of paramagnetic colloidal particles is induced by a magnetic field H. At the transition field Hs, the energy landscape of the system becomes completely flat, which causes diverging fluctuations and correlation length ξ∝|H2−Hs2|−1/2. Mean-field critical exponents are predicted, since the upper critical dimension of the transition is du=2. Our colloidal system provides an experimental test bed to probe the unconventional properties of mixed-order phase transitions. PMID:29158388

High field superconducting properties of Ba(Fe1−xCox)2As2 thin films

PubMed Central

Hänisch, Jens; Iida, Kazumasa; Kurth, Fritz; Reich, Elke; Tarantini, Chiara; Jaroszynski, Jan; Förster, Tobias; Fuchs, Günther; Hühne, Ruben; Grinenko, Vadim; Schultz, Ludwig; Holzapfel, Bernhard

2015-01-01

In general, the critical current density, Jc, of type II superconductors and its anisotropy with respect to magnetic field orientation is determined by intrinsic and extrinsic properties. The Fe-based superconductors of the ‘122’ family with their moderate electronic anisotropies and high yet accessible critical fields (Hc2 and Hirr) are a good model system to study this interplay. In this paper, we explore the vortex matter of optimally Co-doped BaFe2As2 thin films with extended planar and c-axis correlated defects. The temperature and angular dependence of the upper critical field is well explained by a two-band model in the clean limit. The dirty band scenario, however, cannot be ruled out completely. Above the irreversibility field, the flux motion is thermally activated, where the activation energy U0 is going to zero at the extrapolated zero-kelvin Hirr value. The anisotropy of the critical current density Jc is both influenced by the Hc2 anisotropy (and therefore by multi-band effects) as well as the extended planar and columnar defects present in the sample. PMID:26612567

Pressure-temperature phase diagrams of CaK(Fe1 -xNix)4As4 superconductors

NASA Astrophysics Data System (ADS)

Xiang, Li; Meier, William R.; Xu, Mingyu; Kaluarachchi, Udhara S.; Bud'ko, Sergey L.; Canfield, Paul C.

2018-05-01

The pressure dependence of the magnetic and superconducting transitions and that of the superconducting upper critical field are reported for CaK (Fe1-xNix) 4As4 , the first example of an Fe-based superconductor with spin-vortex-crystal-type magnetic ordering. Resistance measurements were performed on single crystals with two substitution levels (x =0.033 ,0.050 ) under hydrostatic pressures up to 5.12 GPa and in magnetic fields up to 9 T. Our results show that, for both compositions, magnetic transition temperatures TN are suppressed upon applying pressure; the superconducting transition temperatures Tc are suppressed by pressure as well, except for x =0.050 in the pressure region where TN and Tc cross. Furthermore, the pressure associated with the crossing of the TN and Tc lines also coincides with a minimum in the normalized slope of the superconducting upper critical field, consistent with a likely Fermi-surface reconstruction associated with the loss of magnetic ordering. Finally, at p ˜4 GPa, both Ni-substituted CaK (Fe1-xNix) 4As4 samples likely go through a half-collapsed-tetragonal phase transition, similar to the parent compound CaKFe4As4 .

Coexistence of charge density wave and superconductivity in Cu0.10TiSe2

NASA Astrophysics Data System (ADS)

Jat, K. S.; Nagpal, V.; Sagar, A. D.; Neha, P.; Patnaik, S.

2018-04-01

We report the synthesis and characterization of Cu intercalated TiSe2 superconductor. The resistivity variation with temperature indicates superconducting transition onset at 3.1K and resistivity drops down to zero at 2.1K. The magnetization measurement provides the diamagnetic transition at 3 K. The upper critical field Hc2, lower critical field Hc1, Ginzburg Landau coherence length (ξ) and penetration depth(λ) are estimated to be 0.93 T, 0.01T, 18.8 nm and 181.5 nm respectively. At 100K, CDW type feature is observed. The coexistence of CDW phase and superconductivity is summarized.

Electron transport and electron energy distributions within the wurtzite and zinc-blende phases of indium nitride: Response to the application of a constant and uniform electric field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siddiqua, Poppy; Hadi, Walid A.; Salhotra, Amith K.

2015-03-28

Within the framework of an ensemble semi-classical three-valley Monte Carlo electron transport simulation approach, we critically contrast the nature of the electron transport that occurs within the wurtzite and zinc-blende phases of indium nitride in response to the application of a constant and uniform electric field. We use the electron energy distribution and its relationship with the electron transport characteristics in order to pursue this analysis. For the case of zinc-blende indium nitride, only a peak corresponding to the electrons within the lowest energy conduction band valley is observed, this peak being seen to broaden and shift to higher energiesmore » in response to increases in the applied electric field strength, negligible amounts of upper energy conduction band valley occupancy being observed. In contrast, for the case of wurtzite indium nitride, in addition to the aforementioned lowest energy conduction band valley peak in the electron energy distribution, and its broadening and shifting to higher energies in response to increases in the applied electric field strength, beyond a certain critical electric field strength, 30 kV/cm for the case of this particular material, upper energy conduction band valley occupancy is observed, this occupancy being further enhanced in response to further increases in the applied electric field strength. Reasons for these results are provided. The potential for device consequences is then commented upon.« less

[Tests of hand functionality in upper limb amputation with prosthesis].

PubMed

Bazzini, G; Orlandini, D; Moscato, T A; Nicita, D; Panigazzi, M

2007-01-01

The need for standardized instruments for clinical measurements has become pressing in the fields of occupational rehabilitation and ergonomics. This is particularly the case for instruments that allow a quantitative evaluation of upper limb function, and especially hand function in patients who have undergone an amputation and then application of an upper limb prosthesis. This study presents a review of the main tests used to evaluate hand function, with a critical analysis of their use in subjects with an upper limb prosthesis. The tests are divided into: tests to evaluate strength, tests to evaluate co-ordination and dexterity, tests of global or overall function, and tests proposed specifically for subjects with an upper limb prosthesis. Of the various tests presented, the authors give their preference to the Bimanual Functional Assessment, Abilhand and/or the ADL Questionnaire, because of the practical usefulness, clinimetric features, simplicity and ease of administration of these tests.

Retrogressive Failures in Sand Deposits of the Mississippi River. Report 1. Field Investigations, Laboratory Studies and Analysis of the Hypothesized Failure Mechanism

DTIC Science & Technology

1988-06-01

densities of Mississippi River point bar sands . 73. It is particularly conclusive to compare the available critical void ratio data for point bar sands on... River encounters the difficulty that the density of large parts of Zone A sands is between the upper and lower critical densities . All laboratory... sands of the Lower Mississippi River point bar deposits generally contain some strata of subcritical density , and the initial tendenc% of such sands

Evidence of incomplete annealing at 800 °C and the effects of 120 °C baking on the crystal orientation and the surface superconducting properties of cold-worked and chemically polished Nb

DOE PAGES

Sung, Z. -H.; Dzyuba, A.; Lee, P. J.; ...

2015-07-01

High-purity niobium rods were cold-worked by wire-drawing, followed by various combinations of chemical polishing and high-vacuum baking at 120 °C or annealing at 800 °C in order to better understand changes to the surface superconducting properties resulting from typical superconducting radio-frequency cavity processing. AC susceptibility measurements revealed an enhanced upper transition T c at ~ 9.3–9.4 K in all samples that was stable through all annealing steps, a value significantly above the accepted T c of 9.23 K for pure annealed niobium. Corresponding elevations were seen in the critical fields, the ratio of the surface critical field H c3 tomore » the bulk upper critical field H c2 rising to 2.3, well above the Ginzburg–Landau value of 1.695. Orientation imaging revealed an extensive dislocation rich sub-grain structure in the as-drawn rods, a small reduction of the surface strain after baking at 120 °C, and a substantial but incomplete recrystallization near the surface after annealing at 800 °C. We interpret these changes in surface superconducting and structural properties to extensive changes in the near-surface interstitial contamination produced by baking and annealing and to synergistic interactions between H and surface O introduced during electropolishing and buffered chemical polishing.« less

Evidence of incomplete annealing at 800 °C and the effects of 120 °C baking on the crystal orientation and the surface superconducting properties of cold-worked and chemically polished Nb

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sung, Z. -H.; Dzyuba, A.; Lee, P. J.

High-purity niobium rods were cold-worked by wire-drawing, followed by various combinations of chemical polishing and high-vacuum baking at 120 °C or annealing at 800 °C in order to better understand changes to the surface superconducting properties resulting from typical superconducting radio-frequency cavity processing. AC susceptibility measurements revealed an enhanced upper transition T c at ~ 9.3–9.4 K in all samples that was stable through all annealing steps, a value significantly above the accepted T c of 9.23 K for pure annealed niobium. Corresponding elevations were seen in the critical fields, the ratio of the surface critical field H c3 tomore » the bulk upper critical field H c2 rising to 2.3, well above the Ginzburg–Landau value of 1.695. Orientation imaging revealed an extensive dislocation rich sub-grain structure in the as-drawn rods, a small reduction of the surface strain after baking at 120 °C, and a substantial but incomplete recrystallization near the surface after annealing at 800 °C. We interpret these changes in surface superconducting and structural properties to extensive changes in the near-surface interstitial contamination produced by baking and annealing and to synergistic interactions between H and surface O introduced during electropolishing and buffered chemical polishing.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mcdonald, Ross David

The alkali-doped fullerides provide the first example of a transition from a three-dimensional Mott insulator to a superconductor, enabling the effects of both dimensionality and electron correlation on superconductivity to be explored. Chemically the alkali species tunes the superconductivity in the vicinity of the the Mott transition via sample volume. Measuring the relationship between the superconducting transition temperature and upper critical field reveals a crossover from weak- to strong-coupling associated with the dynamical Jahn–Teller effect as the Mott transition is approached. The use of pulsed magnets is required because the upper critical field is enhanced in the vicinity of themore » Mott insulating phase, reaching 90 T for RbxCs3-xC60 — the highest among cubic crystals. This required close collaboration between Prof Kasahara’s group and the Mag Lab to design rf-measurements compatible with sample encapsulation in an inert atmosphere. The concomitant increase of pairing strength with lattice volume near the Mott transition suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity (with high-T C and high-H C2).« less

Quantum Critical Quasiparticle Scattering within the Superconducting State of CeCoIn_{5}.

PubMed

Paglione, Johnpierre; Tanatar, M A; Reid, J-Ph; Shakeripour, H; Petrovic, C; Taillefer, Louis

2016-07-01

The thermal conductivity κ of the heavy-fermion metal CeCoIn_{5} was measured in the normal and superconducting states as a function of temperature T and magnetic field H, for a current and field parallel to the [100] direction. Inside the superconducting state, when the field is lower than the upper critical field H_{c2}, κ/T is found to increase as T→0, just as in a metal and in contrast to the behavior of all known superconductors. This is due to unpaired electrons on part of the Fermi surface, which dominate the transport above a certain field. The evolution of κ/T with field reveals that the electron-electron scattering (or transport mass m^{⋆}) of those unpaired electrons diverges as H→H_{c2} from below, in the same way that it does in the normal state as H→H_{c2} from above. This shows that the unpaired electrons sense the proximity of the field-tuned quantum critical point of CeCoIn_{5} at H^{⋆}=H_{c2} even from inside the superconducting state. The fact that the quantum critical scattering of the unpaired electrons is much weaker than the average scattering of all electrons in the normal state reveals a k-space correlation between the strength of pairing and the strength of scattering, pointing to a common mechanism, presumably antiferromagnetic fluctuations.

Adiabatic physics of an exchange-coupled spin-dimer system: Magnetocaloric effect, zero-point fluctuations, and possible two-dimensional universal behavior

DOE PAGES

Brambleby, J.; Goddard, P. A.; Singleton, John; ...

2017-01-05

We present the magnetic and thermal properties of the bosonic-superfluid phase in a spin-dimer network using both quasistatic and rapidly changing pulsed magnetic fields. The entropy derived from a heat-capacity study reveals that the pulsed-field measurements are strongly adiabatic in nature and are responsible for the onset of a significant magnetocaloric effect (MCE). In contrast to previous predictions we show that the MCE is not just confined to the critical regions, but occurs for all fields greater than zero at sufficiently low temperatures. We explain the MCE using a model of the thermal occupation of exchange-coupled dimer spin states andmore » highlight that failure to take this effect into account inevitably leads to incorrect interpretations of experimental results. In addition, the heat capacity in our material is suggestive of an extraordinary contribution from zero-point fluctuations and appears to indicate universal behavior with different critical exponents at the two field-induced critical points. Finally, the data at the upper critical point, combined with the layered structure of the system, are consistent with a two-dimensional nature of spin excitations in the system.« less

Effect of Electropolishing and Low-Temperature Baking on the Superconducting Properties of Large-Grain Niobium

DOE Office of Scientific and Technical Information (OSTI.GOV)

A. S. Dhavale, G. Ciovati, G. R. Myneni

Measurements of superconducting properties such as bulk and surface critical fields and thermal conductivity have been carried out in the temperature range from 2 K to 8 K on large-grain samples of different purity and on a high-purity fine-grain sample, for comparison. The samples were treated by electropolishing and low temperature baking (120° C, 48 h). While the residual resistivity ratio changed by a factor of ~3 among the samples, no significant variation was found in their superconducting properties. The onset field for flux penetration at 2 K, Hffp, measured within a ~30 µm depth from the surface, was ~160more » mT, close to the bulk value. The baking effect was mainly to increase the field range up to which a coherent superconducting phase persists on the surface, above the upper critical field.« less

Approaching isotropy in the vortex system of SmFeAs(O,F) at extreme magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moll, Philip J.W.; Zhidadlo, Nikolai D.; Karpinski, J.

2014-01-07

The role of anisotropy in the iron-pnictides is one of the key questions in understanding their high-temperature superconductivity. The inherent layeredness of these systems, consisting of FeAs layers separated by various layers, gives rise to an upper critical field anisotropy γ(T c) ~ 3 in the “122” system (i.e. (Ba,K)Fe 2As 2) and up to 6-8 in the “1111” system (i.e. SmFeAs(O,F)). In the “122” compounds, this anisotropy is known to decrease upon cooling, converging to almost isotropic superconductivity at lowest temperatures[1]. This can be understood through a particular temperature dependence of the inter- and intra-band scattering. The “1111” classmore » is naturally more anisotropic due to the thicker SmO blocking layer, and the much higher upper critical fields (H c2, HIIab(0)>>100T) cannot be reached at low temperature. Despite this challenging field requirement, the aim of this project is to discern whether this emergent isotropy in the “122” materials is a property of all FeAs classes. Focused Ion Beam (FIB) micromachined samples have in the past proven to be particularly well suited for pulsed magnetic fields[2]. Employing the micrometer precision of the FIB, we fabricated three individual samples on a 2x2 mm chip and thus maximized the acquired transport data per pulse.« less

Pressure-temperature phase diagrams of CaK ( Fe 1 – x Ni x ) 4 As 4 superconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiang, Li; Meier, William R.; Xu, Mingyu

Here, the pressure dependence of the magnetic and superconducting transitions and that of the superconducting upper critical field are reported for CaK(Fe 1–xNi x) 4As 4, the first example of an Fe-based superconductor with spin-vortex-crystal-type magnetic ordering. Resistance measurements were performed on single crystals with two substitution levels (x = 0.033,0.050) under hydrostatic pressures up to 5.12 GPa and in magnetic fields up to 9 T. Our results show that, for both compositions, magnetic transition temperatures T N are suppressed upon applying pressure; the superconducting transition temperatures T c are suppressed by pressure as well, except for x = 0.050more » in the pressure region where T N and T c cross. Furthermore, the pressure associated with the crossing of the T N and T c lines also coincides with a minimum in the normalized slope of the superconducting upper critical field, consistent with a likely Fermi-surface reconstruction associated with the loss of magnetic ordering. Lastly, at p ~ 4 GPa, both Ni-substituted CaK(Fe 1–xNi x) 4As 4 samples likely go through a half-collapsed-tetragonal phase transition, similar to the parent compound CaKFe 4As 4.« less

Directional asymmetries in human smooth pursuit eye movements.

PubMed

Ke, Sally R; Lam, Jessica; Pai, Dinesh K; Spering, Miriam

2013-06-27

Humans make smooth pursuit eye movements to bring the image of a moving object onto the fovea. Although pursuit accuracy is critical to prevent motion blur, the eye often falls behind the target. Previous studies suggest that pursuit accuracy differs between motion directions. Here, we systematically assess asymmetries in smooth pursuit. In experiment 1, binocular eye movements were recorded while observers (n = 20) tracked a small spot of light moving along one of four cardinal or diagonal axes across a featureless background. We analyzed pursuit latency, acceleration, peak velocity, gain, and catch-up saccade latency, number, and amplitude. In experiment 2 (n = 22), we examined the effects of spatial location and constrained stimulus motion within the upper or lower visual field. Pursuit was significantly faster (higher acceleration, peak velocity, and gain) and smoother (fewer and later catch-up saccades) in response to downward versus upward motion in both the upper and the lower visual fields. Pursuit was also more accurate and smoother in response to horizontal versus vertical motion. CONCLUSIONS. Our study is the first to report a consistent up-down asymmetry in human adults, regardless of visual field. Our findings suggest that pursuit asymmetries are adaptive responses to the requirements of the visual context: preferred motion directions (horizontal and downward) are more critical to our survival than nonpreferred ones.

Normal state above the upper critical field in Fe 1 + y Te 1 - x ( Se , S ) x

DOE PAGES

Wang, Aifeng; Kampert, Erik; Saadaoui, H.; ...

2017-05-03

Here, we have investigated the magnetotransport above the upper critical field ( H c 2 ) in Fe 1.14 Te 0.7 Se 0.3 , Fe 1.02 Te 0.61 Se 0.39 , Fe 1.05 Te 0.89 Se 0.11 , and Fe 1.06 Te 0.86 S 0.14 . The μ SR measurements confirm electronic phase separation in Fe 1.06 Te 0.86 S 0.14 , similar to Fe 1 + y Te 1 - x Se x . We found that superconductivity is suppressed in high magnetic fields above 60 T, allowing us to gain insight into the normal-state properties below the zero-fieldmore » superconducting transition temperature ( T c ). We also show that the resistivity of Fe 1.14 Te 0.7 Se 0.3 and Fe 1.02 Te 0.61 Se 0.39 above H c 2 is metallic as T → 0 , just like the normal-state resistivity above T c . On the other hand, the normal-state resistivity in Fe 1.05 Te 0.89 Se 0.11 and Fe 1.06 Te 0.86 S 0.14 is nonmetallic down to lowest temperatures, reflecting the superconductor-insulator transition due to electronic phase separation.« less

Pressure-temperature phase diagrams of CaK ( Fe 1 – x Ni x ) 4 As 4 superconductors

DOE PAGES

Xiang, Li; Meier, William R.; Xu, Mingyu; ...

2018-05-22

Here, the pressure dependence of the magnetic and superconducting transitions and that of the superconducting upper critical field are reported for CaK(Fe 1–xNi x) 4As 4, the first example of an Fe-based superconductor with spin-vortex-crystal-type magnetic ordering. Resistance measurements were performed on single crystals with two substitution levels (x = 0.033,0.050) under hydrostatic pressures up to 5.12 GPa and in magnetic fields up to 9 T. Our results show that, for both compositions, magnetic transition temperatures T N are suppressed upon applying pressure; the superconducting transition temperatures T c are suppressed by pressure as well, except for x = 0.050more » in the pressure region where T N and T c cross. Furthermore, the pressure associated with the crossing of the T N and T c lines also coincides with a minimum in the normalized slope of the superconducting upper critical field, consistent with a likely Fermi-surface reconstruction associated with the loss of magnetic ordering. Lastly, at p ~ 4 GPa, both Ni-substituted CaK(Fe 1–xNi x) 4As 4 samples likely go through a half-collapsed-tetragonal phase transition, similar to the parent compound CaKFe 4As 4.« less

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.

Direct measurement of the Bose-Einstein condensation universality class in NiCl2-4SC(NH2)2 at ultralow temperatures.

PubMed

Yin, L; Xia, J S; Zapf, V S; Sullivan, N S; Paduan-Filho, A

2008-10-31

In this work, we demonstrate field-induced Bose-Einstein condensation (BEC) in the organic compound NiCl2-4SC(NH2)_{2} using ac susceptibility measurements down to 1 mK. The Ni S=1 spins exhibit 3D XY antiferromagnetism between a lower critical field H_{c1} approximately 2 T and a upper critical field H_{c2} approximately 12 T. The results show a power-law temperature dependence of the phase transition line H_{c1}(T)-H_{c1}(0)=aT;{alpha} with alpha=1.47+/-0.10 and H_{c1}(0)=2.053 T, consistent with the 3D BEC universality class. Near H_{c2}, a kink was found in the phase boundary at approximately 150 mK.

Vortex pinning properties in Fe-chalcogenides

NASA Astrophysics Data System (ADS)

Leo, A.; Grimaldi, G.; Guarino, A.; Avitabile, F.; Nigro, A.; Galluzzi, A.; Mancusi, D.; Polichetti, M.; Pace, S.; Buchkov, K.; Nazarova, E.; Kawale, S.; Bellingeri, E.; Ferdeghini, C.

2015-12-01

Among the families of iron-based superconductors, the 11-family is one of the most attractive for high field applications at low temperatures. Optimization of the fabrication processes for bulk, crystalline and/or thin film samples is the first step in producing wires and/or tapes for practical high power conductors. Here we present the results of a comparative study of pinning properties in iron-chalcogenides, investigating the flux pinning mechanisms in optimized Fe(Se{}1-xTe x ) and FeSe samples by current-voltage characterization, magneto-resistance and magnetization measurements. In particular, from Arrhenius plots in magnetic fields up to 9 T, the activation energy is derived as a function of the magnetic field, {U}0(H), whereas the activation energy as a function of temperature, U(T), is derived from relaxation magnetization curves. The high pinning energies, high upper critical field versus temperature slopes near critical temperatures, and highly isotropic pinning properties make iron-chalcogenide superconductors a technological material which could be a real competitor to cuprate high temperature superconductors for high field applications.

Unusual superconducting behavior in HfV2Ga4

NASA Astrophysics Data System (ADS)

Santos, F. B.; Correa, L. E.; de Lima, B. S.; Cigarroa, O. V.; da Luz, M. S.; Grant, T.; Fisk, Z.; Machado, A. J. S.

2018-04-01

Bulk superconductivity in HfV2Ga4 with critical temperature close to 4.1 K was determined via magnetic susceptibility, electrical resistivity and specific heat measurements. Both the upper and lower critical field dependence with reduced temperature (T /Tc) exhibit non-conventional behavior. The electronic component of specific heat shows a double-jump, the first close to Tc and the other close to 0.75Tc. We speculate about the nature of the douple jump observed in specific heat considering two plausable scenarios: bulk inhomogeneities and the existence of a second gap.

New Fe-based superconductors: properties relevant for applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putti, M; Pallecchi, I; Bellingeri, E

2009-01-01

Less than two years after the discovery of high temperature superconductivity in oxypnictide LaFeAs(O, F) several families of superconductors based on Fe layers (1111, 122, 11, 111) are available. They share several characteristics with cuprate superconductors that compromise easy applications, such as the layered structure, the small coherence length and unconventional pairing. On the other hand, the Fe-based superconductors have metallic parent compounds and their electronic anisotropy is generally smaller and does not strongly depend on the level of doping, and the supposed order parameter symmetry is s-wave, thus in principle not so detrimental to current transmission across grain boundaries.more » From the application point of view, the main efforts are still devoted to investigate the superconducting properties, to distinguish intrinsic from extrinsic behaviors and to compare the different families in order to identify which one is the fittest for the quest for better and more practical superconductors. The 1111 family shows the highest T{sub c}, huge but also the most anisotropic upper critical field and in-field, fan-shaped resistive transitions reminiscent of those of cuprates. On the other hand, the 122 family is much less anisotropic with sharper resistive transitions as in low temperature superconductors, but with about half the T{sub c} of the 1111 compounds. An overview of the main superconducting properties relevant to applications will be presented. Upper critical field, electronic anisotropy parameter, and intragranular and intergranular critical current density will be discussed and compared, where possible, across the Fe-based superconductor families.« less

Nontrivial Critical Fixed Point for Replica-Symmetry-Breaking Transitions.

PubMed

Charbonneau, Patrick; Yaida, Sho

2017-05-26

The transformation of the free-energy landscape from smooth to hierarchical is one of the richest features of mean-field disordered systems. A well-studied example is the de Almeida-Thouless transition for spin glasses in a magnetic field, and a similar phenomenon-the Gardner transition-has recently been predicted for structural glasses. The existence of these replica-symmetry-breaking phase transitions has, however, long been questioned below their upper critical dimension, d_{u}=6. Here, we obtain evidence for the existence of these transitions in d

Quantum critical quasiparticle scattering within the superconducting state of CeCoIn 5

DOE PAGES

Paglione, Johnpierre; Tanatar, M. A.; Reid, J.-Ph.; ...

2016-06-27

Here, the thermal conductivity κ of the heavy-fermion metal CeCoIn 5 was measured in the normal and superconducting states as a function of temperature T and magnetic field H, for a current and field parallel to the [100] direction. Inside the superconducting state, when the field is lower than the upper critical field H c2, κ/T is found to increase as T→0, just as in a metal and in contrast to the behavior of all known superconductors. This is due to unpaired electrons on part of the Fermi surface, which dominate the transport above a certain field. The evolution ofmore » κ/T with field reveals that the electron-electron scattering (or transport mass m*) of those unpaired electrons diverges as H→H c2 from below, in the same way that it does in the normal state as H→H c2 from above. This shows that the unpaired electrons sense the proximity of the field-tuned quantum critical point of CeCoIn 5 at H*=H c2 even from inside the superconducting state. In conclusion, the fact that the quantum critical scattering of the unpaired electrons is much weaker than the average scattering of all electrons in the normal state reveals a k-space correlation between the strength of pairing and the strength of scattering, pointing to a common mechanism, presumably antiferromagnetic fluctuations.« less

Uniaxial Pressure and High-Field Effects on Superconducting Single-Crystal CeCoIn5

NASA Astrophysics Data System (ADS)

Johnson, Scooter David

We have measured the a.c. susceptibility response of single-crystal CeCoIn 5 under uniaxial pressure up to 4.07 kbar and in d.c. field parallel to the c axis up to 5 T. From these measurements we report on several pressure and field characteristics of the superconducting state. The results are divided into 3 chapters: (1) We find a non-linear dependence of the superconducting transition temperature Tc on pressure, with a maximum close to 2 kbar. The transition also broadens significantly as pressure increases. We model the broadening as a product of non-uniform pressure and discuss its implications for the pressure dependence of the transition temperature. We relate our measurements to previous theoretical work. (2) We provided evidence and pressure dependence for the FFLO phase with field and pressure along the c axis. The FFLO phase boundary is temperature independent and tracks with the suppression to lower fields of the upper critical field with pressure. We also report the strengthening of the Pauli-limited field in this orientation by calculating the increase of the orbitally-limited field with uniaxial pressure. (3) We extract the critical current using the Bean critical state model and compare it to the expected Ginzberg-Landau behavior. We find that the exponent of the critical current depends on uniaxial pressure and d.c. field. Within a d.c. field the pressure dependence of the exponent may be obscured by the field effect. We have also measured resistivity, susceptibility, and specific heat of high-quality single-crystal YIn3 below 1 K and present a refinement of Tc from previous measurements. We make suggestions for experimental comparisons to the heavy fermion family CeXIn5, (X = Rh, Ir, Co) and the parent compound CeIn3.

Thermodynamic glass transition in a spin glass without time-reversal symmetry

PubMed Central

Baños, Raquel Alvarez; Cruz, Andres; Fernandez, Luis Antonio; Gil-Narvion, Jose Miguel; Gordillo-Guerrero, Antonio; Guidetti, Marco; Iñiguez, David; Maiorano, Andrea; Marinari, Enzo; Martin-Mayor, Victor; Monforte-Garcia, Jorge; Muñoz Sudupe, Antonio; Navarro, Denis; Parisi, Giorgio; Perez-Gaviro, Sergio; Ruiz-Lorenzo, Juan Jesus; Schifano, Sebastiano Fabio; Seoane, Beatriz; Tarancon, Alfonso; Tellez, Pedro; Tripiccione, Raffaele; Yllanes, David

2012-01-01

Spin glasses are a longstanding model for the sluggish dynamics that appear at the glass transition. However, spin glasses differ from structural glasses in a crucial feature: they enjoy a time reversal symmetry. This symmetry can be broken by applying an external magnetic field, but embarrassingly little is known about the critical behavior of a spin glass in a field. In this context, the space dimension is crucial. Simulations are easier to interpret in a large number of dimensions, but one must work below the upper critical dimension (i.e., in d < 6) in order for results to have relevance for experiments. Here we show conclusive evidence for the presence of a phase transition in a four-dimensional spin glass in a field. Two ingredients were crucial for this achievement: massive numerical simulations were carried out on the Janus special-purpose computer, and a new and powerful finite-size scaling method. PMID:22493229

Two-step solar filament eruptions

NASA Astrophysics Data System (ADS)

Filippov, B.

2018-04-01

Coronal mass ejections (CMEs) are closely related to eruptive filaments and usually are the continuation of the same eruptive process into the upper corona. There are failed filament eruptions when a filament decelerates and stops at some greater height in the corona. Sometimes the filament after several hours starts to rise again and develops into the successful eruption with a CME formation. We propose a simple model for the interpretation of such two-step eruptions in terms of equilibrium of a flux rope in a two-scale ambient magnetic field. The eruption is caused by a slow decrease of the holding magnetic field. The presence of two critical heights for the initiation of the flux-rope vertical instability allows the flux rope to stay after the first jump some time in a metastable equilibrium near the second critical height. If the decrease of the ambient field continues, the next eruption step follows.

Upper critical field measurements in high-Tc superconducting oxides

NASA Astrophysics Data System (ADS)

Ousset, J. C.; Bobo, J. F.; Ulmet, J. P.; Rakoto, H.; Cheggour, N.

We present upper critical field measurements on the superconducting oxides RE Ba2Cu3O7-δ (RE = Y, Gd) performed in a pulsed magnetic field up to 43 T. Values for Hc2 as high as 52 T and 77 T for Y and Gd respectively, are expected at 77 K. However, in order to observe no resistive behaviour up to 43 T the temperature must be decreased down to 50 K. In the case of oxygen deficient systems the magnetoresistance reveals two superconducting phases wich could be related to two different orders of oxygen vacancies. Nous présentons des mesures de champ critique Hc2 sur les supraconducteurs TR Ba 2Cu3O7-δ (TR = Y, Gd) réalisées en champ magnétique pulsé jusqu'à 43 T. Elles permettent de prévoir des valeurs de H c2 de 52 T et 77 T respectivement pour Y et Gd à 77 K. Cependant, pour ne pas observer de comportement résistif jusqu'au champ maximum, il est nécessaire de refroidir l'échantillon jusqu'à 50 K. Dans le cas des systèmes déficients en oxygène (δ important) nous mettons en évidence l'existence de deux phases supraconductrices qui pourraient être dues à deux ordres différents des lacunes d'oxygène.

Hydrostatic pressure-induced huge enhancement of critical current density and flux pinning in Fe1-x Co x Se0.5Te0.5 single crystals

NASA Astrophysics Data System (ADS)

Sang, Lina; Shabbir, Babar; Maheshwari, Pankaj; Qiu, Wenbin; Ma, Zongqing; Dou, Shixue; Cai, Chuanbing; Awana, V. P. S.; Wang, Xiaolin

2018-07-01

We performed a systematic study of the hydrostatic pressure (HP) effect on the supercon-ducting transition temperature (T c), critical current density (J c), irreversibility field (H irr), upper critical field (H c2), and flux pinning mechanism in un-doped and 3 at.% Co-doped FeSe0.5Te0.5 crystals. We found that T c is increased from 11.5 to 17 K as HP increases from 0 to 1.2 GPa. Remarkably, the J c is significantly enhanced by a factor of 3 to 100 for low and high temperature and field, and the H irr line is shifted to higher fields by HP up to 1.2 GPa. Based on the collective pinning model, the δl pinning associated with charge-carrier mean free path fluctuation is responsible for the pinning mechanism of Fe1-x Co x Se0.5Te0.5 samples with or without pressure. A comprehensive vortex phase diagram in the mixed state is constructed and analysed for the 3 at.% Co-doped sample.

Evidence of new pinning centers in irradiated MgB2

NASA Astrophysics Data System (ADS)

Tarantini, C.; Martinelli, A.; Manfrinetti, P.; Palenzona, A.; Pallecchi, I.; Putti, M.; Ferdeghini, C.; Cimberle, M. R.

2008-03-01

It has been shown that C or SiC addictions can strongly enhance upper critical field of MgB2, leading to an in-field increase of critical current, but without introducing pinning centers other than grain boundaries. On the contrary neutron irradiation introduces new pinning centers, as highlighted by a significant shift of the maximum of pinning force and by a strong improvement of Jc at high field. This effect can be correlated to the defects that neutron irradiation produces. In fact TEM images show the presence of nanometric amorphous regions whose sizes are compatible with the coherence length and such as to act as pinning centers through two different mechanisms. The influence that neutron irradiation induces on MgB2 is also confirmed by magnetization decays that, differently by doped samples, show an important enhancement of pinning energies at high field. These measurements highlight as the increase of pinning energy with irradiation fluence is strongly correlated with Jc improvement.

Strongly enhanced current densities in Sr0.6K0.4Fe2As2 + Sn superconducting tapes.

PubMed

Lin, He; Yao, Chao; Zhang, Xianping; Zhang, Haitao; Wang, Dongliang; Zhang, Qianjun; Ma, Yanwei; Awaji, Satoshi; Watanabe, Kazuo

2014-03-25

Improving transport current has been the primary topic for practical application of superconducting wires and tapes. However, the porous nature of powder-in-tube (PIT) processed iron-based tapes is one of the important reasons for low critical current density (Jc) values. In this work, the superconducting core density of ex-situ Sr0.6K0.4Fe2As2 + Sn tapes, prepared from optimized precursors, was significantly improved by employing a simple hot pressing as an alternative route for final sintering. The resulting samples exhibited optimal critical temperature (Tc), sharp resistive transition, small resistivity and high Vickers hardness (Hv) value. Consequently, the transport Jc reached excellent values of 5.1 × 10(4) A/cm(2) in 10 T and 4.3 × 10(4) A/cm(2) in 14 T at 4.2 K, respectively. Our tapes also exhibited high upper critical field Hc2 and almost field-independent Jc. These results clearly demonstrate that PIT pnictide wire conductors are very promising for high-field magnet applications.

Strongly enhanced current densities in Sr0.6K0.4Fe2As2 + Sn superconducting tapes

PubMed Central

Lin, He; Yao, Chao; Zhang, Xianping; Zhang, Haitao; Wang, Dongliang; Zhang, Qianjun; Ma, Yanwei; Awaji, Satoshi; Watanabe, Kazuo

2014-01-01

Improving transport current has been the primary topic for practical application of superconducting wires and tapes. However, the porous nature of powder-in-tube (PIT) processed iron-based tapes is one of the important reasons for low critical current density (Jc) values. In this work, the superconducting core density of ex-situ Sr0.6K0.4Fe2As2 + Sn tapes, prepared from optimized precursors, was significantly improved by employing a simple hot pressing as an alternative route for final sintering. The resulting samples exhibited optimal critical temperature (Tc), sharp resistive transition, small resistivity and high Vickers hardness (Hv) value. Consequently, the transport Jc reached excellent values of 5.1 × 104 A/cm2 in 10 T and 4.3 × 104 A/cm2 in 14 T at 4.2 K, respectively. Our tapes also exhibited high upper critical field Hc2 and almost field-independent Jc. These results clearly demonstrate that PIT pnictide wire conductors are very promising for high-field magnet applications. PMID:24663054

Strongly enhanced current densities in Sr0.6K0.4Fe2As2 + Sn superconducting tapes

NASA Astrophysics Data System (ADS)

Lin, He; Yao, Chao; Zhang, Xianping; Zhang, Haitao; Wang, Dongliang; Zhang, Qianjun; Ma, Yanwei; Awaji, Satoshi; Watanabe, Kazuo

2014-03-01

Improving transport current has been the primary topic for practical application of superconducting wires and tapes. However, the porous nature of powder-in-tube (PIT) processed iron-based tapes is one of the important reasons for low critical current density (Jc) values. In this work, the superconducting core density of ex-situ Sr0.6K0.4Fe2As2 + Sn tapes, prepared from optimized precursors, was significantly improved by employing a simple hot pressing as an alternative route for final sintering. The resulting samples exhibited optimal critical temperature (Tc), sharp resistive transition, small resistivity and high Vickers hardness (Hv) value. Consequently, the transport Jc reached excellent values of 5.1 × 104 A/cm2 in 10 T and 4.3 × 104 A/cm2 in 14 T at 4.2 K, respectively. Our tapes also exhibited high upper critical field Hc2 and almost field-independent Jc. These results clearly demonstrate that PIT pnictide wire conductors are very promising for high-field magnet applications.

A Longitudinal Examination of the Effects of Computer Self-Efficacy Growth on Performance during Technology Training

ERIC Educational Resources Information Center

Downey, James P.; Kher, Hemant V.

2015-01-01

Technology training in the classroom is critical in preparing students for upper level classes as well as professional careers, especially in fields such as technology. One of the key enablers to this process is computer self-efficacy (CSE), which has an extensive stream of empirical research. Despite this, one of the missing pieces is how CSE…

Radio frequency self-resonant coil for contactless AC-conductivity in 100 T class ultra-strong pulse magnetic fields

NASA Astrophysics Data System (ADS)

Nakamura, D.; Altarawneh, M. M.; Takeyama, S.

2018-03-01

A contactless measurement system of electrical conductivity was developed for application under pulsed high magnetic fields over 100 T by using a self-resonant-type, high-frequency circuit. Electromagnetic fields in the circuit were numerically analysed by the finite element method, to show how the resonant power spectra of the circuit depends on the electrical conductivity of a sample set on the probe-coil. The performance was examined using a high-temperature cuprate superconductor, La2-x Sr x CuO4, in magnetic fields up to 102 T with a high frequency of close to 800 MHz. As a result, the upper critical field could be determined with a good signal-to-noise ratio.

Bak-Tang-Wiesenfeld model in the upper critical dimension: Induced criticality in lower-dimensional subsystems

NASA Astrophysics Data System (ADS)

Dashti-Naserabadi, H.; Najafi, M. N.

2017-10-01

We present extensive numerical simulations of Bak-Tang-Wiesenfeld (BTW) sandpile model on the hypercubic lattice in the upper critical dimension Du=4 . After re-extracting the critical exponents of avalanches, we concentrate on the three- and two-dimensional (2D) cross sections seeking for the induced criticality which are reflected in the geometrical and local exponents. Various features of finite-size scaling (FSS) theory have been tested and confirmed for all dimensions. The hyperscaling relations between the exponents of the distribution functions and the fractal dimensions are shown to be valid for all dimensions. We found that the exponent of the distribution function of avalanche mass is the same for the d -dimensional cross sections and the d -dimensional BTW model for d =2 and 3. The geometrical quantities, however, have completely different behaviors with respect to the same-dimensional BTW model. By analyzing the FSS theory for the geometrical exponents of the two-dimensional cross sections, we propose that the 2D induced models have degrees of similarity with the Gaussian free field (GFF). Although some local exponents are slightly different, this similarity is excellent for the fractal dimensions. The most important one showing this feature is the fractal dimension of loops df, which is found to be 1.50 ±0.02 ≈3/2 =dfGFF .

Bak-Tang-Wiesenfeld model in the upper critical dimension: Induced criticality in lower-dimensional subsystems.

PubMed

Dashti-Naserabadi, H; Najafi, M N

2017-10-01

We present extensive numerical simulations of Bak-Tang-Wiesenfeld (BTW) sandpile model on the hypercubic lattice in the upper critical dimension D_{u}=4. After re-extracting the critical exponents of avalanches, we concentrate on the three- and two-dimensional (2D) cross sections seeking for the induced criticality which are reflected in the geometrical and local exponents. Various features of finite-size scaling (FSS) theory have been tested and confirmed for all dimensions. The hyperscaling relations between the exponents of the distribution functions and the fractal dimensions are shown to be valid for all dimensions. We found that the exponent of the distribution function of avalanche mass is the same for the d-dimensional cross sections and the d-dimensional BTW model for d=2 and 3. The geometrical quantities, however, have completely different behaviors with respect to the same-dimensional BTW model. By analyzing the FSS theory for the geometrical exponents of the two-dimensional cross sections, we propose that the 2D induced models have degrees of similarity with the Gaussian free field (GFF). Although some local exponents are slightly different, this similarity is excellent for the fractal dimensions. The most important one showing this feature is the fractal dimension of loops d_{f}, which is found to be 1.50±0.02≈3/2=d_{f}^{GFF}.

Spreading dynamics of forget-remember mechanism

NASA Astrophysics Data System (ADS)

Deng, Shengfeng; Li, Wei

2017-04-01

We study extensively the forget-remember mechanism (FRM) for message spreading, originally introduced in Eur. Phys. J. B 62, 247 (2008), 10.1140/epjb/e2008-00139-4. The freedom of specifying forget-remember functions governing the FRM can enrich the spreading dynamics to a very large extent. The master equation is derived for describing the FRM dynamics. By applying the mean field techniques, we have shown how the steady states can be reached under certain conditions, which agrees well with the Monte Carlo simulations. The distributions of forget and remember times can be explicitly given when the forget-remember functions take linear or exponential forms, which might shed some light on understanding the temporal nature of diseases like flu. For time-dependent FRM there is an epidemic threshold related to the FRM parameters. We have proven that the mean field critical transmissibility for the SIS model and the critical transmissibility for the SIR model are the lower and the the upper bounds of the critical transmissibility for the FRM model, respectively.

Dramatic enhancement of superconductivity in single-crystalline nanowire arrays of Sn

PubMed Central

Zhang, Ying; Wong, Chi Ho; Shen, Junying; Sze, Sin Ting; Zhang, Bing; Zhang, Haijing; Dong, Yan; Xu, Hui; Yan, Zifeng; Li, Yingying; Hu, Xijun; Lortz, Rolf

2016-01-01

Sn is a classical superconductor on the border between type I and type II with critical temperature of 3.7 K. We show that its critical parameters can be dramatically increased if it is brought in the form of loosely bound bundles of thin nanowires. The specific heat displays a pronounced double phase transition at 3.7 K and 5.5 K, which we attribute to the inner ‘bulk’ contribution of the nanowires and to the surface contribution, respectively. The latter is visible only because of the large volume fraction of the surface layer in relation to the bulk volume. The upper transition coincides with the onset of the resistive transition, while zero resistance is gradually approached below the lower transition. In contrast to the low critical field Hc = 0.03 T of Sn in its bulk form, a magnetic field of more than 3 T is required to fully restore the normal state. PMID:27595646

Critical field-exponents for secure message-passing in modular networks

NASA Astrophysics Data System (ADS)

Shekhtman, Louis M.; Danziger, Michael M.; Bonamassa, Ivan; Buldyrev, Sergey V.; Caldarelli, Guido; Zlatić, Vinko; Havlin, Shlomo

2018-05-01

We study secure message-passing in the presence of multiple adversaries in modular networks. We assume a dominant fraction of nodes in each module have the same vulnerability, i.e., the same entity spying on them. We find both analytically and via simulations that the links between the modules (interlinks) have effects analogous to a magnetic field in a spin-system in that for any amount of interlinks the system no longer undergoes a phase transition. We then define the exponents δ, which relates the order parameter (the size of the giant secure component) at the critical point to the field strength (average number of interlinks per node), and γ, which describes the susceptibility near criticality. These are found to be δ = 2 and γ = 1 (with the scaling of the order parameter near the critical point given by β = 1). When two or more vulnerabilities are equally present in a module we find δ = 1 and γ = 0 (with β ≥ 2). Apart from defining a previously unidentified universality class, these exponents show that increasing connections between modules is more beneficial for security than increasing connections within modules. We also measure the correlation critical exponent ν, and the upper critical dimension d c , finding that ν {d}c=3 as for ordinary percolation, suggesting that for secure message-passing d c = 6. These results provide an interesting analogy between secure message-passing in modular networks and the physics of magnetic spin-systems.

Anisotropic two-gap superconductivity and the absence of a Pauli paramagnetic limit in single-crystalline LaO0.5F0.5BiS2

NASA Astrophysics Data System (ADS)

Chan, Y. C.; Yip, K. Y.; Cheung, Y. W.; Chan, Y. T.; Niu, Q.; Kajitani, J.; Higashinaka, R.; Matsuda, T. D.; Yanase, Y.; Aoki, Y.; Lai, K. T.; Goh, Swee K.

2018-03-01

Ambient-pressure-grown LaO0.5F0.5BiS2 with a superconducting transition temperature Tc˜3 K possesses a highly anisotropic normal state. By a series of electrical resistivity measurements with a magnetic-field direction varying between the crystalline c axis and the a b plane, we present datasets displaying the temperature dependence of the out-of-plane upper critical field Hc2 ⊥(T ) , the in-plane upper critical field Hc2 ∥(T ) , as well as the angular dependence of Hc 2 at fixed temperatures for ambient-pressure-grown LaO0.5F0.5BiS2 single crystals. The anisotropy of the superconductivity, Hc2 ∥/Hc2 ⊥ , reaches ˜16 on approaching 0 K, but it decreases significantly near Tc. A pronounced upward curvature of Hc2 ∥(T ) is observed near Tc, which we analyze using a two-gap model. Moreover, Hc2 ∥(0 ) is found to exceed the Pauli paramagnetic limit, which can be understood by considering the strong spin-orbit coupling associated with Bi as well as the breaking of the local inversion symmetry at the electronically active BiS2 bilayers. Hence, LaO0.5F0.5BiS2 with a centrosymmetric lattice structure is a unique platform to explore the physics associated with local parity violation in the bulk crystal.

Effects of high-energy proton irradiation on the superconducting properties of Fe(Se,Te) thin films

NASA Astrophysics Data System (ADS)

Sylva, G.; Bellingeri, E.; Ferdeghini, C.; Martinelli, A.; Pallecchi, I.; Pellegrino, L.; Putti, M.; Ghigo, G.; Gozzelino, L.; Torsello, D.; Grimaldi, G.; Leo, A.; Nigro, A.; Braccini, V.

2018-05-01

In this paper we explore the effects of 3.5 MeV proton irradiation on Fe(Se,Te) thin films grown on CaF2. In particular, we carry out an experimental investigation with different irradiation fluences up to 7.30 · 1016 cm‑2 and different proton implantation depths, in order to clarify whether and to what extent the critical current is enhanced or suppressed, what are the effects of irradiation on the critical temperature, resistivity, and critical magnetic fields, and finally what is the role played by the substrate in this context. We find that the effect of irradiation on superconducting properties is generally small compared to the case of other iron-based superconductors. The irradiation effect is more evident on the critical current density Jc, while it is minor on the transition temperature Tc, normal state resistivity ρ, and on the upper critical field Hc2 up to the highest fluences explored in this work. In more detail, our analysis shows that when protons implant in the substrate far from the superconducting film, the critical current can be enhanced up to 50% of the pristine value at 7 T and 12 K; meanwhile, there is no appreciable effect on critical temperature and critical fields together with a slight decrease in resistivity. On the contrary, when the implantation layer is closer to the film–substrate interface, both critical current and temperature show a decrease accompanied by an enhancement of the resistivity and lattice strain. This result evidences that possible modifications induced by irradiation in the substrate may affect the superconducting properties of the film via lattice strain. The robustness of the Fe(Se,Te) system to irradiation-induced damage makes it a promising compound for the fabrication of magnets in high-energy accelerators.

Electric Field Induced Interfacial Instabilities

NASA Technical Reports Server (NTRS)

Kusner, Robert E.; Min, Kyung Yang; Wu, Xiao-lun; Onuki, Akira

1999-01-01

The study of the interface in a charge-free, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In this paper, the flat interface of a marginally polar binary fluid mixture is stressed by a perpendicular alternating electric field and the resulting instability is characterized by the critical electric field E(sub c) and the pattern observed. The character of the surface dynamics at the onset of instability is found to be strongly dependent on the frequency f of the field applied. The plot of E(sub c) vs. f for a fixed temperature shows a sigmoidal shape, whose low and high frequency limits are well described by a power-law relationship, E(sub c) = epsilon(exp zeta) with zeta = 0.35 and zeta = 0.08, respectively. The low-limit exponent compares well with the value zeta = 4 for a system of conducting and non-conducting fluids. On the other hand, the high-limit exponent coincides with what was first predicted by Onuki. The instability manifests itself as the conducting phase penetrates the non-conducting phase. As the frequency increases, the shape of the pattern changes from an array of bifurcating strings to an array of column-like (or rod-like) protrusions, each of which spans the space between the plane interface and one of the electrodes. For an extremely high frequency, the disturbance quickly grows into a parabolic cone pointing toward the upper plate. As a result, the interface itself changes its shape from that of a plane to that of a high sloping pyramid.

Cirrus Susceptibility to Changes in Ice Nuclei: Physical Processes, Model Uncertainties, and Measurement Needs

NASA Technical Reports Server (NTRS)

Jensen, Eric

2017-01-01

In this talk, I will begin by discussing the physical processes that govern the competition between heterogeneous and homogeneous ice nucleation in upper tropospheric cirrus clouds. Next, I will review the current knowledge of low-temperature ice nucleation from laboratory experiments and field measurements. I will then discuss the uncertainties and deficiencies in representations of cirrus processes in global models used to estimate the climate impacts of changes in cirrus clouds. Lastly, I will review the critical field measurements needed to advance our understanding of cirrus and their susceptibility to changes in aerosol properties.

Evidence from EXAFS for Different Ta/Ti Site Occupancy in High Critical Current Density Nb3Sn Superconductor Wires.

PubMed

Heald, Steve M; Tarantini, Chiara; Lee, Peter J; Brown, Michael D; Sung, ZuHawn; Ghosh, Arup K; Larbalestier, David C

2018-03-19

To meet critical current density, J c , targets for the Future Circular Collider (FCC), the planned replacement for the Large Hadron Collider (LHC), the high field performance of Nb 3 Sn must be improved, but champion J c values have remained static for the last 10 years. Making the A15 phase stoichiometric and enhancing the upper critical field H c2 by Ti or Ta dopants are the standard strategies for enhancing high field performance but detailed recent studies show that even the best modern wires have broad composition ranges. To assess whether further improvement might be possible, we employed Extended X-ray Absorption Fine Structure (EXAFS) to determine the lattice site location of dopants in modern high-performance Nb 3 Sn strands with J c values amongst the best so far achieved. Although Ti and Ta primarily occupy the Nb sites in the A15 structure, we also find significant Ta occupancy on the Sn site. These findings indicate that the best performing Ti-doped stand is strongly sub-stoichiometric in Sn and that antisite disorder likely explains its high average H c2 behavior. These new results suggest an important role for dopant and antisite disorder in minimizing superconducting property distributions and maximizing high field J c properties.

Evidence from EXAFS for Different Ta/Ti Site Occupancy in High Critical Current Density Nb 3Sn Superconductor Wires

DOE PAGES

Heald, Steve M.; Tarantini, Chiara; Lee, Peter J.; ...

2018-03-19

To meet critical current density, Jc, targets for the Future Circular Collider (FCC), the planned replacement for the Large Hadron Collider (LHC), the high field performance of Nb 3Sn must be improved, but champion J c values have remained static for the last 10 years. Making the A15 phase stoichiometric and enhancing the upper critical field H c2 by Ti or Ta dopants are the standard strategies for enhancing high field performance but detailed recent studies show that even the best modern wires have broad composition ranges. To assess whether further improvement might be possible, we employed EXAFS to determinemore » the lattice site location of dopants in modern high-performance Nb 3Sn strands with J c values amongst the best so far achieved. Although Ti and Ta primarily occupy the Nb sites in the A15 structure, we also find significant Ta occupancy on the Sn site. These findings indicate that the best performing Ti-doped stand is strongly sub-stoichiometric in Sn and that antisite disorder likely explains its high average H c2 behavior. These new results suggest an important role for dopant and antisite disorder in minimizing superconducting property distributions and maximizing high field J c properties.« less

Evidence from EXAFS for Different Ta/Ti Site Occupancy in High Critical Current Density Nb 3Sn Superconductor Wires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heald, Steve M.; Tarantini, Chiara; Lee, Peter J.

To meet critical current density, Jc, targets for the Future Circular Collider (FCC), the planned replacement for the Large Hadron Collider (LHC), the high field performance of Nb 3Sn must be improved, but champion J c values have remained static for the last 10 years. Making the A15 phase stoichiometric and enhancing the upper critical field H c2 by Ti or Ta dopants are the standard strategies for enhancing high field performance but detailed recent studies show that even the best modern wires have broad composition ranges. To assess whether further improvement might be possible, we employed EXAFS to determinemore » the lattice site location of dopants in modern high-performance Nb 3Sn strands with J c values amongst the best so far achieved. Although Ti and Ta primarily occupy the Nb sites in the A15 structure, we also find significant Ta occupancy on the Sn site. These findings indicate that the best performing Ti-doped stand is strongly sub-stoichiometric in Sn and that antisite disorder likely explains its high average H c2 behavior. These new results suggest an important role for dopant and antisite disorder in minimizing superconducting property distributions and maximizing high field J c properties.« less

Unusually high critical current of clean P-doped BaFe2As2 single crystalline thin film

NASA Astrophysics Data System (ADS)

Kurth, F.; Tarantini, C.; Grinenko, V.; Hänisch, J.; Jaroszynski, J.; Reich, E.; Mori, Y.; Sakagami, A.; Kawaguchi, T.; Engelmann, J.; Schultz, L.; Holzapfel, B.; Ikuta, H.; Hühne, R.; Iida, K.

2015-02-01

Microstructurally clean, isovalently P-doped BaFe2As2 (Ba-122) single crystalline thin films have been prepared on MgO (001) substrates by molecular beam epitaxy. These films show a superconducting transition temperature (Tc) of over 30 K although P content is around 0.22, which is lower than the optimal one for single crystals (i.e., 0.33). The enhanced Tc at this doping level is attributed to the in-plane tensile strain. The strained film shows high transport self-field critical current densities (Jc) of over 6 MA/cm2 at 4.2 K, which are among the highest for Fe based superconductors (FeSCs). In-field Jc exceeds 0.1 MA/cm2 at μ 0 H = 35 T for H ‖ a b and μ 0 H = 18 T for H ‖ c at 4.2 K, respectively, in spite of moderate upper critical fields compared to other FeSCs with similar Tc. Structural investigations reveal no defects or misoriented grains pointing to strong pinning centers. We relate this unexpected high Jc to a strong enhancement of the vortex core energy at optimal Tc, driven by in-plane strain and doping. These unusually high Jc make P-doped Ba-122 very favorable for high-field magnet applications.

Frequency bandwidth limitation of external pulse electric fields in cylindrical micro-channel electrophoresis with analyte velocity modulation.

PubMed

Wang, Shau-Chun; Chen, Hsiao-Ping; Lee, Chia-Yu; Yeo, Leslie Y

2005-04-15

In capillary electrophoresis, effective optical signal quality improvement is obtained when high frequency (>100 Hz) external pulse fields modulate analyte velocities with synchronous lock-in detection. However, the pulse frequency is constrained under a critical value corresponding to the time required for the bulk viscous flow, which arises due to viscous momentum diffusion from the electro-osmotic slip in the Debye layer, to reach steady-state. By solving the momentum diffusion equation for transient bulk flow in the micro-channel, we show that this set-in time to steady-state and hence, the upper limit for the pulse frequency is dependent on the characteristic diffusion length scale and therefore the channel geometry; for cylindrical capillaries, the set-in time is approximately one half of that for rectangular slot channels. From our estimation of the set-in time and hence the upper frequency modulation limit, we propose that the half width of planar channels does not exceed 100 microm and that the radii of cylindrical channels be limited to 140 microm such that there is a finite working bandwidth range above 100 Hz and below the upper limit in order for flicker noise to be effectively suppressed.

Niobium-germanium superconducting tapes for high-field magnet applications

NASA Technical Reports Server (NTRS)

Braginski, A. I.; Roland, G. W.; Daniel, M. R.; Woolam, J. A.

1977-01-01

A process of fabricating superconducting Nb3Ge tapes by chemical vapor deposition (CVD) has been developed and tapes up to 10 meters long fabricated. The typical properties achieved were: critical temperature T sub c = 20 K, upper critical field H sub c2 = 29 tesla at 4.2 K, and J sub c = 3 to 4 x 10 to the 8th power A m(-2) at 4.2 K, 18 tesla. The relative depression of T sub c and H sub c2 compared with the best thin film samples sputtered on sapphire was due to the presence of Nb5Ge3 second-phase particles used as flux pinning centers and to strains induced by thermal mixmatch with Hastelloy B tape substrates. A peculiar field dependence of flux pinning force that was observed in both CVD and sputtered Nb3Ge indicated a premature pin-breaking mechanism or a phase inhomogeneity. Directions of further optimization work were defined.

New Transition in the Vortex Liquid State: intrinsic limit of the irreversibility line

NASA Astrophysics Data System (ADS)

Kwok, Wai-Kwong; Paulius, Lisa; Figueras, Jordi

2005-03-01

We have carried out angular dependent magneto-transport measurements on optimally doped, untwinned YBCO crystals irradiated with high energy heavy ions to determine the onset of vortex line tension in the vortex liquid state. The matching field was controlled and kept at a low level to partially preserve the first order vortex lattice melting transition. A Bose glass transition is observed below the lower critical point which then transforms into a first order phase transition near 5 Tesla. The locus of points which indicate the onset of vortex line tension overlaps with the Bose glass transition line at low fields and then deviates at higher fields, indicating a new transition line in the vortex liquid state. This new line in the vortex liquid phase extends beyond the upper critical point.This work was supported by the U.S. Department of Energy, BES, Materials Science under Contract No. W-31-109-ENG-38 at Argonne National Laboratory.

Critical current scaling and the pivot-point in Nb3Sn strands

NASA Astrophysics Data System (ADS)

Tsui, Y.; Hampshire, D. P.

2012-05-01

Detailed measurements are provided of the engineering critical current density (Jc) and the index of transition (n-value) of two different types of advanced ITER Nb3Sn superconducting strand for fusion applications. The samples consist of one internal-tin strand (OST) and two bronze-route strands (BEAS I and BEAS II—reacted using different heat treatments). Tests on different sections of these wires show that prior to applying strain, Jc is homogeneous to better than 2% along the length of each strand. Jc data have been characterized as a function of magnetic field (B ≤ 14.5 T), temperature (4.2 K ≤ T ≤ 12 K) and applied axial strain ( - 1% ≤ ɛA ≤ 0.8%). Strain-cycling tests demonstrate that the variable strain Jc data are reversible to better than 2% when the applied axial strain is in the range of - 1% ≤ ɛA ≤ 0.5%. The wires are damaged when the intrinsic strain (ɛI) is ɛI ≥ 0.55% and ɛI ≥ 0.23% for the OST and BEAS strands, respectively. The strain dependences of the normalized Jc for each type of strand are similar to those of prototype strands of similar design measured in 2005 and 2008 to about 2% which makes them candidate strands for a round-robin interlaboratory comparison. The Jc data are described by Durham, ITER and Josephson-junction parameterizations to an accuracy of about 4%. For all of these scaling laws, the percentage difference between the data and the parameterization is larger when Jc is small, caused by high B, T or |ɛI|. The n-values can be described by a modified power law of the form n=1+r{I}_{{c}}^{s}, where r and s are approximately constant and Ic is the critical current. It has long been known that pivot-points (or cross-overs) in Jc occur at high magnetic field and temperature. Changing the magnetic field or temperature from one side of the pivot-point to the other changes the highest Jc sample to the lowest Jc sample and vice versa. The pivot-point follows the B-T phase boundary associated with the upper critical field and is usually attributed to the different tin content profiles and pinning properties of internal-tin and bronze-route strands. We report that the strain dependence of the pivot-point in these strands is quite different from that of the upper critical field and suggest that its origin in optimized high tin content strands is the proximity of the tetragonal Nb3Sn phase, which has low superconducting critical parameters.

Heisenberg spin-glass behaviour in Ga0.99Yb0.01FeO3

NASA Astrophysics Data System (ADS)

Neacsa, Daniela Maria; Gruener, Gisèle; Hebert, Sylvie; Soret, Jean-Claude

2017-06-01

The dynamic and static magnetic properties of Ga0.99Yb0.01FeO3 are studied in detail using ac susceptibility and dc magnetization measurements. The study shows that the compound undergoes a spin-glass freezing at Tg ≈ 213 K . The dynamic scaling analysis of ac susceptibility data reveals typical features characteristic of canonical spin-glasses, i.e., relaxation time τ∗ ∼10-14 s , critical exponent νz = 4.1 ± 0.2 , and frequency sensitivity parameter δf ∼10-3 within three frequency decades. The analysis of the critical behaviour of the static nonlinear susceptibility yields the critical exponents γ = 4.3 ± 0.1, β = 1.0 ± 0.1 , and δ = 5.5 ± 0.5 , which lie between those typical of three-dimensional (3D) weakly anisotropic Heisenberg and Ising spin glasses. The analysis of the field-cooled and zero-field-cooled magnetization data allows to define two characteristic temperatures depending on the applied magnetic field. The upper one, Tirr(H) , is the threshold temperature corresponding to the appearance of weak irreversibility, whereas the lower one, Ts(H) , marks the onset of strong irreversibility. The resulting field-temperature phase diagram turns out to be in good quantitative agreement with the mean-field predictions for 3D Heisenberg spin-glass with random magnetic anisotropy, and appears consistent with the chiral driven freezing scenario.

Spectro-polarimetric observation in UV with CLASP to probe the chromosphere and transition region

NASA Astrophysics Data System (ADS)

Kano, Ryouhei; Ishikawa, Ryohko; Winebarger, Amy R.; Auchère, Frédéric; Trujillo Bueno, Javier; Narukage, Noriyuki; Kobayashi, Ken; Bando, Takamasa; Katsukawa, Yukio; Kubo, Masahito; Ishikawa, Shin-Nosuke; Giono, Gabriel; Hara, Hirohisa; Suematsu, Yoshinori; Shimizu, Toshifumi; Sakao, Taro; Tsuneta, Saku; Ichimoto, Kiyoshi; Goto, Motoshi; Cirtain, Jonathan W.; De Pontieu, Bart; Casini, Roberto; Manso Sainz, Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi, Luca; Carlsson, Mats

2016-05-01

The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a NASA sounding-rocket experiment that was performed in White Sands in the US on September 3, 2015. During its 5-minute ballistic flight, CLASP successfully made the first spectro-polarimetric observation in the Lyman-alpha line (121.57 nm) originating in the chromosphere and transition region. Since the Lyman-alpha polarization is sensitive to magnetic field of 10-100 G by the Hanle effect, we aim to infer the magnetic field information in such upper solar atmosphere with this experiment.The obtained CLASP data showed that the Lyman-alpha scattering polarization is about a few percent in the wings and the order of 0.1% in the core near the solar limb, as it had been theoretically predicted, and that both polarization signals have a conspicuous spatio-temporal variability. CLASP also observed another upper-chromospheric line, Si III (120.65 nm), whose critical field strength for the Hanle effect is 290 G, and showed a measurable scattering polarization of a few % in this line. The polarization properties of the Si III line could facilitate the interpretation of the scattering polarization observed in the Lyman-alpha line.In this presentation, we would like to show how the upper chromosphere and transition region are seen in the polarization of these UV lines and discuss the possible source of these complicated polarization signals.

Functional Specialization in the Lower and Upper Visual Fields in Humans: Its Ecological Origins and Neurophysiological Implications

DTIC Science & Technology

1990-01-01

in that the with this hypothesis are the many reports (e.g., Adler - crossed-disparity system does appear to develop first Grinberg & Stark 1978... Rodman et al. 1986) that survives as independent of hemispheric asymmetries and additive to striate lesions critically depends on the superior...Perfomance. IRAAI human brain. No longer can visual cortical physiology Adler -Grinberg, D. & Stark, L. (1978) Eye movements, scanpaths, and dyslexia

New types of high field pinning centers and pinning centers for the peak effect

NASA Astrophysics Data System (ADS)

Gajda, Daniel; Zaleski, Andrzej; Morawski, Andrzej; Hossain, Md Shahriar A.

2017-08-01

In this article, we report the results of a study that shows the existence of pinning centers inside grains and between grains in NbTi wires. We accurately show the ranges of magnetic fields in which the individual pinning centers operate. The pinning centers inside grains are activated in high magnetic fields above 6 T. We show the range of magnetic fields in which individual defects, dislocations, precipitates inside grains and substitutions in the crystal lattice can operate. We show the existence of a new kind of high field pinning center, which operates in high magnetic fields from 8 to ˜9.5 T. We indicate that dislocations create pinning centers in the range of magnetic fields from 6 to 8 T. In addition, our measurements suggest that the peak effect (increased critical current density (J c) near the upper critical field (B c2)) could be attributed to martensitic (needle-shaped) α‧-Ti inclusions inside grains. These centers are very important because they work very effectively in magnetic fields above 9.5-10 T. We also show that the α-Ti precipitates (between grains) with a thickness similar to the coherence length create pinning centers which work very effectively in magnetic fields from 3 to 6 T. In magnetic fields below 3 T, they act very efficiently in grain boundaries. The measurements indicate that the pinning centers created by dislocations only can be tested by transport measurements. This indicates that dislocations do not increase the magnetic critical current density (J cm). Cold drawing improves pinning centers at grain boundaries and increases the dislocation density, and cold-drawing pinning centers are responsible for the peak effect.

Fundamental study on the magnetic field control method using multiple HTS coils for Magnetic Drug Delivery System

NASA Astrophysics Data System (ADS)

Hirano, R.; Kim, S. B.; Nakagawa, T.; Tomisaka, Y.; Ueda, H.

2017-07-01

The magnetic drug delivery system (MDDS) is a key technology to reduce the side effects in the medical applications, and the magnetic force control is very important issue in MDDS. In this application, the strength of magnetic field and gradient required to MDDS devices are 54 mT and 5.5 T/m, respectively. We proposed the new magnetic force control system that consists of the multiple racetrack HTS magnets. We can control the magnetic field gradient along the longitudinal direction by the arrangement of the multiple racetrack HTS magnets and operating current of each magnet. When the racetrack HTS magnets were used, the critical current was reduced by the self-magnetic field. Therefore, the shape design of HTS magnet to reduce the magnet field into the surface of HTS tapes was required. Therefore, the electromagnetic analysis based on finite element method (FEM) was carried out to design and optimize the shape of multiple racetrack HTS magnet. We were able to suppress the reduction of critical current by placing the magnetic substance at upper and lower side of the HTS magnets. It was confirmed that obtained maximum values of magnetic field strength and field gradient were 33 mT and 0.18 T/m, respectively.

Unusual Magnetic Response of an S = 1 Antiferromagetic Linear-Chain Material

NASA Astrophysics Data System (ADS)

Xia, Jian-Sheng; Ozarowski, Andrzej; Spurgeon, Peter M.; Graham, Adora G.; Manson, Jamie L.; Meisel, Mark W.

2018-03-01

An S = 1 antiferromagnetic polymeric chain, [Ni(HF2)(3-Clpy)4]BF4 (py = pyridine), also referred to as NBCT, has previously been identified to have intrachain, nearest-neighbor antiferromagnetic interaction strength J/k B = 4.86 K and single-ion anisotropy (zero-field splitting) D/k B = 4.3 K, so the ratio D/J = 0.88 places this system close to the D/J ≈ 1 gapless critical point between the topologically distinct Haldane and Large-D phases. The magnetization was studied over a range of temperatures, 50 mK ≤ T ≤ 1 K, and magnetic fields, B ≤ 10 T, in an attempt to identify a critical field, B c, associated with the closing of a gap, and the present work places an upper bound of B c ≤ (35 ± 10) mT. At higher fields, the observed magnetic response is qualitatively similar to the “excess” signal observed by other workers at 0.5 K and below 3 T. The high-field (up to 14.5 T), multi-frequency (nominally 200 GHz to 425 GHz) ESR spectra at 3 K reveal several features associated with the sample.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grinenko, V.; Iida, K.; Kurth, F.

A quantum critical point (QCP) is currently being conjectured for the BaFe 2(As 1-xP x) 2 system at the critical value x c ≈ 0.3. In the proximity of a QCP, all thermodynamic and transport properties are expected to scale with a single characteristic energy, given by the quantum fluctuations. Such a universal behavior has not, however, been found in the superconducting upper critical field H c2. Here we report H c2 data for epitaxial thin films extracted from the electrical resistance measured in very high magnetic fields up to 67 Tesla. Using a multi-band analysis we find that Hmore » c2 is sensitive to the QCP, implying a significant charge carrier effective mass enhancement at the doping-induced QCP that is essentially band-dependent. Our results point to two qualitatively different groups of electrons in BaFe 2(As 1-xP x) 2. The first one (possibly associated to hot spots or whole Fermi sheets) has a strong mass enhancement at the QCP, and the second one is insensitive to the QCP. The observed duality could also be present in many other quantum critical systems.« less

Lung and Upper Aerodigestive Cancer | Division of Cancer Prevention

Cancer.gov

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Selective mass enhancement close to the quantum critical point in BaFe 2(As 1-xP x) 2

DOE PAGES

Grinenko, V.; Iida, K.; Kurth, F.; ...

2017-07-04

A quantum critical point (QCP) is currently being conjectured for the BaFe 2(As 1-xP x) 2 system at the critical value x c ≈ 0.3. In the proximity of a QCP, all thermodynamic and transport properties are expected to scale with a single characteristic energy, given by the quantum fluctuations. Such a universal behavior has not, however, been found in the superconducting upper critical field H c2. Here we report H c2 data for epitaxial thin films extracted from the electrical resistance measured in very high magnetic fields up to 67 Tesla. Using a multi-band analysis we find that Hmore » c2 is sensitive to the QCP, implying a significant charge carrier effective mass enhancement at the doping-induced QCP that is essentially band-dependent. Our results point to two qualitatively different groups of electrons in BaFe 2(As 1-xP x) 2. The first one (possibly associated to hot spots or whole Fermi sheets) has a strong mass enhancement at the QCP, and the second one is insensitive to the QCP. The observed duality could also be present in many other quantum critical systems.« less

Thermal conductivity of layered organic superconductor β-(BDA-TTP)2SbF6 in a parallel magnetic field: Anomalous effect of coreless vortices

NASA Astrophysics Data System (ADS)

Tanatar, M. A.; Ishiguro, T.; Toita, T.; Yamada, J.

2005-01-01

Thermal conductivity κ of the organic superconductor β-(BDA-TTP)2SbF6 was studied down to 0.3 K in magnetic fields H of varying orientation with respect to the superconducting plane. Anomalous plateau shape of the field dependence, κ vs H , is found for orientation of magnetic fields precisely parallel to the plane, in contrast to usual behavior observed in the perpendicular fields. We show that the lack of magnetic-field effect on the heat conduction results from coreless structure of vortices, causing both negligible scattering of phonons and constant in field electronic conduction up to the fields close to the upper critical field Hc2 . Usual behavior is recovered on approaching Hc2 and on slight field inclination from parallel direction, when normal cores are restored. This behavior points to the lack of bulk quasiparticle excitations induced by magnetic field, consistent with the conventional superconducting state.

Ideal charge-density-wave order in the high-field state of superconducting YBCO

DOE PAGES

Jang, H.; Lee, W. -S.; Nojiri, H.; ...

2016-12-05

The existence of charge-density-wave (CDW) correlations in cuprate superconductors has now been established. However, the nature of the CDW ground state has remained uncertain because disorder and the presence of superconductivity typically limit the CDW correlation lengths to only a dozen unit cells or less. Here we explore the field-induced 3D CDW correlations in extremely pure detwinned crystals of YBa 2Cu 3O 2 (YBCO) ortho-II and ortho-VIII at magnetic fields in excess of the resistive upper critical field ( H c2) where superconductivity is heavily suppressed. We observe that the 3D CDW is unidirectional and possesses a long in-plane correlationmore » length as well as significant correlations between neighboring CuO 2 planes. It is significant that we observe only a single sharply defined transition at a critical field proportional to H c2, given that the field range used in this investigation overlaps with other high-field experiments including quantum oscillation measurements. The correlation volume is at least two to three orders of magnitude larger than that of the zero-field CDW. Furthermore, this is by far the largest CDW correlation volume observed in any cuprate crystal and so is presumably representative of the high-field ground state of an “ideal” disorder-free cuprate.« less

Physical property characterization of Fe-tube encapsulated and vacuum annealed bulk MgB 2

NASA Astrophysics Data System (ADS)

Awana, V. P. S.; Rawat, Rajeev; Gupta, Anurag; Isobe, M.; Singh, K. P.; Vajpayee, Arpita; Kishan, H.; Takayama-Muromachi, E.; Narlikar, A. V.

2006-08-01

We report the phase formation, and present a detailed study of magnetization and resistivity under magnetic field of MgB 2 polycrystalline bulk samples prepared by the Fe-tube encapsulated and vacuum (10 -5 Torr) annealed (750 ∘C) route. Zero-field-cooled magnetic susceptibility (χ) measurements exhibited a sharp transition to the superconducting state with a sizeable diamagnetic signal at 39 K (Tc). The measured magnetization loops of the samples, despite the presence of flux jumps, exhibited a stable current density (Jc) of around 2.4×10 5 A/cm 2 in up to 2 T (Tesla) field and at temperatures (T) up to 10 K. The upper critical field is estimated from resistivity measurements in various fields and shows a typical value of 8 T at 21 K. Further, χ measurements at an applied field of 0.1 T reveal a paramagnetic Meissner effect (PME) that is briefly discussed.

Pairing transition, coherence transition, and the irreversibility line in granular GdBa2Cu3O7-δ

NASA Astrophysics Data System (ADS)

Roa-Rojas, J.; Menegotto Costa, R.; Pureur, P.; Prieto, P.

2000-05-01

We report on electrical magnetoconductivity experiments near the superconducting transition of a granular sample of GdBa2Cu3O7-δ. The measurements were performed in magnetic fields ranging from 0 to 500 Oe applied parallel to the current orientation. The results show that the transition proceeds in two steps. When the temperature is decreased we first observe the pairing transition, which stabilizes superconductivity within the grains at a temperature practically coincident with the bulk critical temperature Tc. Analysis of the fluctuation contributions to the conductivity shows that the universality class for this transition is that of the three dimensional (3D)-XY model in the ordered case, with dynamic critical exponent z=3/2. Close to the zero-resistance state, the measurements reveal the occurrence of a coherence transition, where the phases of the order parameter in individual grains become long-range ordered. The critical temperature Tco for this transition is close to the point where the resistivity vanishes. A strong enlargement of the fluctuation interval preceding the coherence transition is caused by the applied magnetic field. In this region, a 3D-Gaussian regime and an asymptotic critical regime were clearly identified. The critical conductivity behavior for the coherence transition is interpreted within a 3D-XY model where disorder and frustration are relevant. The irreversibility line is determined from magnetoconductivity measurements performed according to the zero-field-cooled (ZFC) and field-cooled data collected on cooling (FCC) recipes. The locus of this line coincides with the upper temperature limit for the fluctuation region above the coherence transition. The irreversibility line is interpreted as an effect of the formation of small clusters with closed loops of Josephson-coupled grains.

Finite-size scaling above the upper critical dimension in Ising models with long-range interactions

NASA Astrophysics Data System (ADS)

Flores-Sola, Emilio J.; Berche, Bertrand; Kenna, Ralph; Weigel, Martin

2015-01-01

The correlation length plays a pivotal role in finite-size scaling and hyperscaling at continuous phase transitions. Below the upper critical dimension, where the correlation length is proportional to the system length, both finite-size scaling and hyperscaling take conventional forms. Above the upper critical dimension these forms break down and a new scaling scenario appears. Here we investigate this scaling behaviour by simulating one-dimensional Ising ferromagnets with long-range interactions. We show that the correlation length scales as a non-trivial power of the linear system size and investigate the scaling forms. For interactions of sufficiently long range, the disparity between the correlation length and the system length can be made arbitrarily large, while maintaining the new scaling scenarios. We also investigate the behavior of the correlation function above the upper critical dimension and the modifications imposed by the new scaling scenario onto the associated Fisher relation.

Huge critical current density and tailored superconducting anisotropy in SmFeAsO₀.₈F₀.₁₅ by low-density columnar-defect incorporation.

PubMed

Fang, L; Jia, Y; Mishra, V; Chaparro, C; Vlasko-Vlasov, V K; Koshelev, A E; Welp, U; Crabtree, G W; Zhu, S; Zhigadlo, N D; Katrych, S; Karpinski, J; Kwok, W K

2013-01-01

Iron-based superconductors could be useful for electricity distribution and superconducting magnet applications because of their relatively high critical current densities and upper critical fields. SmFeAsO₀.₈F₀.₁₅ is of particular interest as it has the highest transition temperature among these materials. Here we show that by introducing a low density of correlated nano-scale defects into this material by heavy-ion irradiation, we can increase its critical current density to up to 2 × 10⁷ A cm⁻² at 5 K--the highest ever reported for an iron-based superconductor--without reducing its critical temperature of 50 K. We also observe a notable reduction in the thermodynamic superconducting anisotropy, from 8 to 4 upon irradiation. We develop a model based on anisotropic electron scattering that predicts that the superconducting anisotropy can be tailored via correlated defects in semimetallic, fully gapped type II superconductors.

Tuning the critical solution temperature of polymers by copolymerization

NASA Astrophysics Data System (ADS)

Schulz, Bernhard; Chudoba, Richard; Heyda, Jan; Dzubiella, Joachim

2015-12-01

We study statistical copolymerization effects on the upper critical solution temperature (CST) of generic homopolymers by means of coarse-grained Langevin dynamics computer simulations and mean-field theory. Our systematic investigation reveals that the CST can change monotonically or non-monotonically with copolymerization, as observed in experimental studies, depending on the degree of non-additivity of the monomer (A-B) cross-interactions. The simulation findings are confirmed and qualitatively explained by a combination of a two-component Flory-de Gennes model for polymer collapse and a simple thermodynamic expansion approach. Our findings provide some rationale behind the effects of copolymerization and may be helpful for tuning CST behavior of polymers in soft material design.

Measurements of the Magnetic Field of the Upper Chromosphere with Polarimetry

NASA Technical Reports Server (NTRS)

Rachmeler, Laurel; Mckenzie, David; Winebarger, Amy; Kobayashi, Ken; Ishikawa, Ryohko; Kubo, Masahito; Narukage, Noriyuki; Bueno, Trujillo, Javier; Auchere, Frederic

2017-01-01

A major remaining challenge for heliophysics is to decipher the magnetic structure of the chromosphere. The chromosphere is the critical interface between the Sun's photosphere and corona: it contains more mass than the entire interplanetary heliosphere, requires a heating rate that is larger than that of the corona, and mediates all the energy driving the solar wind, solar atmospheric heating and solar eruptions. While measurements of the magnetic field in the photosphere are routine, the chromosphere poses several extra challenges. The magnetically sensitive lines formed in the upper chromosphere are in the ultraviolet, so space-based observations are required. The lines are often formed over a range of heights, sampling different plasma which complicates the inversion process. These lines are sensitive to the magnetic field via polarized light that is created or modified through the Hanle and Zeeman effects. There are a few observations of these lines, and a significant challenge remains in extracting the magnetic field from the polarization measurements, as detailed model atmospheres with advanced radiative transfer physics are needed. Real progress is obtained by a simultaneous improvement in both the observational side and the modeling side. We present information on the CLASP (Chromospheric LAyer Spectro-Polarimeter) sounding rocket program, and future prospects for these types of measurements.

Anaemia only causes a small reduction in the upper critical temperature of sea bass: is oxygen delivery the limiting factor for tolerance of acute warming in fishes?

PubMed

Wang, Tobias; Lefevre, Sjannie; Iversen, Nina K; Findorf, Inge; Buchanan, Rasmus; McKenzie, David J

2014-12-15

To address how the capacity for oxygen transport influences tolerance of acute warming in fishes, we investigated whether a reduction in haematocrit, by means of intra-peritoneal injection of the haemolytic agent phenylhydrazine, lowered the upper critical temperature of sea bass. A reduction in haematocrit from 42±2% to 20±3% (mean ± s.e.m.) caused a significant but minor reduction in upper critical temperature, from 35.8±0.1 to 35.1±0.2°C, with no correlation between individual values for haematocrit and upper thermal limit. Anaemia did not influence the rise in oxygen uptake between 25 and 33°C, because the anaemic fish were able to compensate for reduced blood oxygen carrying capacity with a significant increase in cardiac output. Therefore, in sea bass the upper critical temperature, at which they lost equilibrium, was not determined by an inability of the cardio-respiratory system to meet the thermal acceleration of metabolic demands. © 2014. Published by The Company of Biologists Ltd.

Superconducting properties of ion-implanted gold-silicon thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jisrawi, N.M.

The superconducting properties of thin Au{sub x}Si{sub 1{minus}x}, films prepared by ion beam implantation and ion beam mixing are studied. The films are prepared by evaporation of single Au layers on Si substrates and mixing them with Si, Ar, or Xe, or by Xe beam mixing of alternate multilayers of Au and Si sputtered on Al{sub 2}O{sub 3} substrates. The superconducting transition temperature and upper critical fields are determined by measuring the temperature and magnetic field dependence of resistivity. Temperatures as low as 20mK and magnetic fields as high as 8 T were used. Superconductivity in these films is discussedmore » in connection with metastable metallic phases that are reportedly produced in the Au-Si system by high quenching rate preparation techniques like quenching from the vapor or the melt or ion implantation. Preliminary structural studies provide evidence for the existence of these phases and near-edge X-ray absorption and X-ray photoelectron spectroscopy measurements indicate a metallic type of bonding from which compound formation is inferred. The quality of the films is strongly dependent on the conditions of implantation. The maximum superconducting transition temperature attained is about 1.2 K. The upper critical fields have a maximum of 6T. An unusual double transition in the field dependence of resistivity is observed at low temperatures. The effect is very pronounced at compositions near x = 0.5 where the maximum {Tc} occurs. A model is presented to explain this result which invokes the properties of the metastable metallic phases and assumes the formation of more than two such phases in the same sample as the implantation dose increases. The Si-Au interface plays an important role in understanding the model and in interpreting the results of this thesis in general.« less

Hybrid robotic systems for upper limb rehabilitation after stroke: A review.

PubMed

Resquín, Francisco; Cuesta Gómez, Alicia; Gonzalez-Vargas, Jose; Brunetti, Fernando; Torricelli, Diego; Molina Rueda, Francisco; Cano de la Cuerda, Roberto; Miangolarra, Juan Carlos; Pons, José Luis

2016-11-01

In recent years the combined use of functional electrical stimulation (FES) and robotic devices, called hybrid robotic rehabilitation systems, has emerged as a promising approach for rehabilitation of lower and upper limb motor functions. This paper presents a review of the state of the art of current hybrid robotic solutions for upper limb rehabilitation after stroke. For this aim, studies have been selected through a search using web databases: IEEE-Xplore, Scopus and PubMed. A total of 10 different hybrid robotic systems were identified, and they are presented in this paper. Selected systems are critically compared considering their technological components and aspects that form part of the hybrid robotic solution, the proposed control strategies that have been implemented, as well as the current technological challenges in this topic. Additionally, we will present and discuss the corresponding evidences on the effectiveness of these hybrid robotic therapies. The review also discusses the future trends in this field. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Management by the intensivist of gastrointestinal bleeding in adults and children

PubMed Central

2012-01-01

Intensivists are regularly confronted with the question of gastrointestinal bleeding. To date, the latest international recommendations regarding prevention and treatment for gastrointestinal bleeding lack a specific approach to the critically ill patients. We present recommendations for management by the intensivist of gastrointestinal bleeding in adults and children, developed with the GRADE system by an experts group of the French-Language Society of Intensive Care (Société de Réanimation de Langue Française (SRLF), with the participation of the French Language Group of Paediatric Intensive Care and Emergencies (GFRUP), the French Society of Emergency Medicine (SFMU), the French Society of Gastroenterology (SNFGE), and the French Society of Digestive Endoscopy (SFED). The recommendations cover five fields of application: management of gastrointestinal bleeding before endoscopic diagnosis, treatment of upper gastrointestinal bleeding unrelated to portal hypertension, treatment of upper gastrointestinal bleeding related to portal hypertension, management of presumed lower gastrointestinal bleeding, and prevention of upper gastrointestinal bleeding in intensive care. PMID:23140348

Inflation with a graceful exit in a random landscape

NASA Astrophysics Data System (ADS)

Pedro, F. G.; Westphal, A.

2017-03-01

We develop a stochastic description of small-field inflationary histories with a graceful exit in a random potential whose Hessian is a Gaussian random matrix as a model of the unstructured part of the string landscape. The dynamical evolution in such a random potential from a small-field inflation region towards a viable late-time de Sitter (dS) minimum maps to the dynamics of Dyson Brownian motion describing the relaxation of non-equilibrium eigenvalue spectra in random matrix theory. We analytically compute the relaxation probability in a saddle point approximation of the partition function of the eigenvalue distribution of the Wigner ensemble describing the mass matrices of the critical points. When applied to small-field inflation in the landscape, this leads to an exponentially strong bias against small-field ranges and an upper bound N ≪ 10 on the number of light fields N participating during inflation from the non-observation of negative spatial curvature.

Fluid elasticity and the transition to chaos in thermal convection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khayat, R.E.

1995-01-01

The influence of fluid elasticity on the onset of aperiodic or chaotic motion of an upper-convected Maxwellian fluid is examined in the context of the Rayleigh-Benard thermal convection problem. A truncated Fourier representation of the flow and temperature fields leads to a four-dimensional dynamical system that constitutes a generalization of the classical Lorenz system for Newtonian fluids. It is found that, to the order of the present truncation and above a critical value of the Deborah number De[sup [ital c

Introduction to the problem

NASA Technical Reports Server (NTRS)

Ramohalli, Kumar

1989-01-01

Solid propellant rockets were used extensively in space missions ranging from large boosters to orbit-raising upper stages. The smaller motors find exclusive use in various earth-based applications. The advantage of the solids include simplicity, readiness, volumetric efficiency, and storability. Important recent progress in related fields (combustion, rheology, micro-instrumentation/diagnostics, and chaos theory) can be applied to solid rockets to derive maximum advantage and avoid waste. Main objectives of research in solid propellants include: to identify critical parameters, to establish specification rules, and to develop quantitative criteria.

High-field transport properties of a P-doped BaFe2As2 film on technical substrate

PubMed Central

Iida, Kazumasa; Sato, Hikaru; Tarantini, Chiara; Hänisch, Jens; Jaroszynski, Jan; Hiramatsu, Hidenori; Holzapfel, Bernhard; Hosono, Hideo

2017-01-01

High temperature (high-Tc) superconductors like cuprates have superior critical current properties in magnetic fields over other superconductors. However, superconducting wires for high-field-magnet applications are still dominated by low-Tc Nb3Sn due probably to cost and processing issues. The recent discovery of a second class of high-Tc materials, Fe-based superconductors, may provide another option for high-field-magnet wires. In particular, AEFe2As2 (AE: Alkali earth elements, AE-122) is one of the best candidates for high-field-magnet applications because of its high upper critical field, Hc2, moderate Hc2 anisotropy, and intermediate Tc. Here we report on in-field transport properties of P-doped BaFe2As2 (Ba-122) thin films grown on technical substrates by pulsed laser deposition. The P-doped Ba-122 coated conductor exceeds a transport Jc of 105 A/cm2 at 15 T for main crystallographic directions of the applied field, which is favourable for practical applications. Our P-doped Ba-122 coated conductors show a superior in-field Jc over MgB2 and NbTi, and a comparable level to Nb3Sn above 20 T. By analysing the E − J curves for determining Jc, a non-Ohmic linear differential signature is observed at low field due to flux flow along the grain boundaries. However, grain boundaries work as flux pinning centres as demonstrated by the pinning force analysis. PMID:28079117

High-field transport properties of a P-doped BaFe2As2 film on technical substrate

NASA Astrophysics Data System (ADS)

Iida, Kazumasa; Sato, Hikaru; Tarantini, Chiara; Hänisch, Jens; Jaroszynski, Jan; Hiramatsu, Hidenori; Holzapfel, Bernhard; Hosono, Hideo

2017-01-01

High temperature (high-Tc) superconductors like cuprates have superior critical current properties in magnetic fields over other superconductors. However, superconducting wires for high-field-magnet applications are still dominated by low-Tc Nb3Sn due probably to cost and processing issues. The recent discovery of a second class of high-Tc materials, Fe-based superconductors, may provide another option for high-field-magnet wires. In particular, AEFe2As2 (AE: Alkali earth elements, AE-122) is one of the best candidates for high-field-magnet applications because of its high upper critical field, Hc2, moderate Hc2 anisotropy, and intermediate Tc. Here we report on in-field transport properties of P-doped BaFe2As2 (Ba-122) thin films grown on technical substrates by pulsed laser deposition. The P-doped Ba-122 coated conductor exceeds a transport Jc of 105 A/cm2 at 15 T for main crystallographic directions of the applied field, which is favourable for practical applications. Our P-doped Ba-122 coated conductors show a superior in-field Jc over MgB2 and NbTi, and a comparable level to Nb3Sn above 20 T. By analysing the E - J curves for determining Jc, a non-Ohmic linear differential signature is observed at low field due to flux flow along the grain boundaries. However, grain boundaries work as flux pinning centres as demonstrated by the pinning force analysis.

AC-electric field dependent electroformation of giant lipid vesicles.

PubMed

Politano, Timothy J; Froude, Victoria E; Jing, Benxin; Zhu, Yingxi

2010-08-01

Giant vesicles of larger than 5 microm, which have been of intense interest for their potential as drug delivery vehicles and as a model system for cell membranes, can be rapidly formed from a spin-coated lipid thin film under an electric field. In this work, we explore the AC-field dependent electroformation of giant lipid vesicles in aqueous media over a wide range of AC-frequency from 1 Hz to 1 MHz and peak-to-peak field strength from 0.212 V/mm to 40 V/mm between two parallel conducting electrode surfaces. By using fluorescence microscopy, we perform in-situ microscopic observations of the structural evolution of giant vesicles formed from spin-coated lipid films under varied uniform AC-electric fields. The real-time observation of bilayer bulging from the lipid film, vesicle growth and fusing further examine the critical role of AC-induced electroosmotic flow of surrounding fluids for giant vesicle formation. A rich AC-frequency and field strength phase diagram is obtained experimentally to predict the AC-electroformation of giant unilamellar vesicles (GUVs) of l-alpha-phosphatidylcholine, where a weak dependence of vesicle size on AC-frequency is observed at low AC-field voltages, showing decreased vesicle size with a narrowed size distribution with increased AC-frequency. Formation of vesicles was shown to be constrained by an upper field strength of 10 V/mm and an upper AC-frequency of 10 kHz. Within these parameters, giant lipid vesicles were formed predominantly unilamellar and prevalent across the entire electrode surfaces. Copyright 2010 Elsevier B.V. All rights reserved.

Quantum critical scaling in beta-YbAlB4 and theoretical implications

NASA Astrophysics Data System (ADS)

Nevidomskyy, Andriy

2012-02-01

Emergent phenomena in quantum materials are subject of intense experimental and theoretical research at present. A wonderful example thereof are the sister phases of YbAlB4 - a newly discovered heavy fermion material [1]. While one phase (α-YbAlB4) is a heavy Fermi liquid, its sibling β-YbAlB4 is quantum critical, supporting an unconventional superconductivity with a tiny transition temperature of ˜80 mK. Latest experiments [2] uncover the quantum critical T/B-scaling in β-YbAlB4 and prove that superconductivity emerges from a strange metal governed by an extremely fragile quantum criticality, which apparently occurs at zero field, without any external tuning. Here, we will present a theoretical perspective on the quantum critical scaling in β-YbAlB4 and will show that the critical exponents can be derived from the nodal structure of the hybridization matrix between Yb f-band and the conduction electrons. It follows that the free energy at low temperatures can be written in a scaling form F[(kBT)^2 + (gμBB)^2]^3/4, which predicts the divergent Sommerfeld coefficient γ and quasi-particle effective mass as B->0: γ˜m^*/m B-1/2. This is indeed observed in the experiment [1,2], which places a tiny upper bound on the critical magnetic field Bc<0.2 mT. We will discuss theoritical implications of this fragile intrinsic quantum criticality in β-YbAlB4 and discuss the possibility of a quantum critical phase, rather than a quantum critical point, in this material. [1] S. Nakatsuji et al., Nature Physics 4, 603 (2008). [2] Y. Matsumoto, S. Nakatsuji, K. Kuga, Y. Karaki, Y. Shimura, T. Sakakibara, A. H. Nevidomskyy, and P. Coleman, Science 331, 316 (2011).

Fluctuation-induced conductivity analyses of Be-doped (Bi0.25Cu0.25Li0.25Tl0.25)Ba2Ca2Cu3O10-δ superconductors in the critical regime and beyond

NASA Astrophysics Data System (ADS)

Khan, Nawazish A.; Qurat-ul-Ain; Firdous, Umber; Shaheryar

2012-02-01

We have successfully synthesized (Bi0.25Cu0.25Li0.25Tl0.25)Ba2Ca2Cu3O10-δ and (Bi0.25Cu0.25Li0.25Tl0.25)Ba2(Ca1.5Be0.5)Cu3O10-δ samples and studied their excess conductivity analyses (fluctuation-induced conductivity) of resistivity data. The main objective of such analyses is to investigate the influence of Be-substitution on the superconductivity parameters at the microscopic level. The width of the 3D-2D Lawrence-Doniach regime is increased with the doping of Be at the Ca sites. The energy required to break apart the Cooper pairs is increased from 0.03 eV to 0.08 eV in Be-doped samples. Using the Ginzburg-Landau number (NG) and GL equations, the thermodynamic critical magnetic field Bc(0), the lower critical field Bc1(0), the upper critical field Bc2(0), the critical current density Jc(0), and penetration depth λp.d are also calculated from these analyses. The values of critical fields [Bc(0) Bc1(0)], Jc(0), and phase relaxation time τϕ are increased whereas the penetration depth λp.d and κ values are suppressed with Be-doping. It is most likely that as a result of the enhancement in the density of the carriers in the (Bi0.25Cu0.25Li0.25Tl0.25)Ba2(Ca1.5Be0.5)Cu3O10-δ sample, this charge density gap is suppressed, which in turn suppresses the pseudo-gap resulting into enhancement of Bc (0), Bc1(0), and Jc(0).

Lambert-Beer law in ocean waters: optical properties of water and of dissolved/suspended material, optical energy budgets.

PubMed

Stavn, R H

1988-01-15

The role of the Lambert-Beer law in ocean optics is critically examined. The Lambert-Beer law and the three-parameter model of the submarine light field are used to construct an optical energy budget for any hydrosol. It is further applied to the analytical exponential decay coefficient of the light field and used to estimate the optical properties and effects of the dissolved/suspended component in upper ocean layers. The concepts of the empirical exponential decay coefficient (diffuse attenuation coefficient) of the light field and a constant exponential decay coefficient for molecular water are analyzed quantitatively. A constant exponential decay coefficient for water is rejected. The analytical exponential decay coefficient is used to analyze optical gradients in ocean waters.

Scanning tunneling spectroscopy and vortex imaging in the iron pnictide superconductor BaFe1.8Co0.2As2.

PubMed

Yin, Yi; Zech, M; Williams, T L; Wang, X F; Wu, G; Chen, X H; Hoffman, J E

2009-03-06

We present an atomic resolution scanning tunneling spectroscopy study of superconducting BaFe1.8Co0.2As2 single crystals in magnetic fields up to 9 T. At zero field, a single gap with coherence peaks at Delta=6.25 meV is observed in the density of states. At 9 and 6 T, we image a disordered vortex lattice, consistent with isotropic, single flux quantum vortices. Vortex locations are uncorrelated with strong-scattering surface impurities, demonstrating bulk pinning. The vortex-induced subgap density of states fits an exponential decay from the vortex center, from which we extract a coherence length xi=27.6+/-2.9 A, corresponding to an upper critical field Hc2=43 T.

Patterns in Soil Electrical Resistivity Across Land Uses in the Calhoun Critical Zone Observatory Landscape

NASA Astrophysics Data System (ADS)

Markewitz, D.; Sutter, L.; Richter, D. D., Jr.

2017-12-01

Soil Electrical Resistivity Tomography (ERT) was measured across the Calhoun Critical Zone Observatory in relation to land use cover. ERT can help identify patterns in soil and saprolite physical attributes and moisture content through multiple meters. ERT data were generated with an AGI Supersting R8 with a 28 probe dipole-dipole array on a 1.5 meter spacing providing information through the upper 9 m. In Nov/Dec 2016 ten soil pits were dug to 3m depth in agricultural fields, pine forests, and hardwood forests across the CCZO and ERT measures were taken centered on these pits. ERT values ranged from 200 to 2500 Ohm-m. ERT patterns in the agricultural field demonstrated a limited resistivity gradient (200-700 Ohm-m) appearing moist throughout. In contrast, research areas under pine and hardwood forest had stronger resistivity gradients reflecting both moisture and physical attributes (i.e., texture or rock content). For example, research area 2 under pine had an area of higher resistivity that correlated with a band of saprolite that was readily visible in the exposed profile. In research area 7 and 8 that included both pine and hardwood forest resistivity gradients had contradictory patterns of high to low resistivity from top to bottom. In research area 7 resistivity was highest at the surface and decreased with depth, a common pattern when water table is at depth. In research area 8 the inverse was observed with low resistivity above and resistivity increasing with depth, a pattern observed in upper landscape positions on ridges with moist clay above dry saprolite. ERT patterns did reflect a large difference in the measured agricultural fields compared to forest while other difference appeared to reflect landscape position.

Probing transport mechanisms of BaFe₂As₂ superconducting films and grain boundary junctions by noise spectroscopy.

PubMed

Barone, C; Romeo, F; Pagano, S; Adamo, M; Nappi, C; Sarnelli, E; Kurth, F; Iida, K

2014-08-22

An important step forward for the understanding of high-temperature superconductivity has been the discovery of iron-based superconductors. Among these compounds, iron pnictides could be used for high-field magnet applications, resulting more advantageous over conventional superconductors, due to a high upper critical field as well as its low anisotropy at low temperatures. However, the principal obstacle in fabricating high quality superconducting wires and tapes is given by grain boundaries. In order to study these effects, the dc transport and voltage-noise properties of Co-doped BaFe₂As₂ superconducting films with artificial grain boundary junctions have been investigated. A specific procedure allows the separation of the film noise from that of the junction. While the former shows a standard 1/f behaviour, the latter is characterized by an unconventional temperature-dependent multi-Lorentzian voltage-spectral density. Moreover, below the film superconducting critical temperature, a peculiar noise spectrum is found for the grain boundary junction. Possible theoretical interpretation of these phenomena is proposed.

Enhancement of the in-field Jc of MgB2 via SiCl4 doping

NASA Astrophysics Data System (ADS)

Wang, Xiao-Lin; Dou, S. X.; Hossain, M. S. A.; Cheng, Z. X.; Liao, X. Z.; Ghorbani, S. R.; Yao, Q. W.; Kim, J. H.; Silver, T.

2010-06-01

We present the following results. (1) We introduce a doping source for MgB2 , liquid SiCl4 , which is free of C, to significantly enhance the irreversibility field (Hirr) , the upper critical field (Hc2) , and the critical current density (Jc) with a little reduction in the critical temperature (Tc) . (2) Although Si can not be incorporated into the crystal lattice, a significant reduction in the a -axis lattice parameter was found, to the same extent as for carbon doping. (3) Based on the first-principles calculation, it is found that it is reliable to estimate the C concentration just from the reduction in the a -lattice parameter for C-doped MgB2 polycrystalline samples that are prepared at high sintering temperatures, but not for those prepared at low sintering temperatures. Strain effects and magnesium deficiency might be reasons for the a -lattice reduction in non-C or some of the C-added MgB2 samples. (4) The SiCl4 -doped MgB2 shows much higher Jc with superior field dependence above 20 K compared to undoped MgB2 and MgB2 doped with various carbon sources. (5) We introduce a parameter, RHH (Hc2/Hirr) , which can clearly reflect the degree of flux-pinning enhancement, providing us with guidance for further enhancing Jc . (6) It was found that spatial variation in the charge-carrier mean free path is responsible for the flux-pinning mechanism in the SiCl4 treated MgB2 with large in-field Jc .

Quasilinear quantum magnetoresistance in pressure-induced nonsymmorphic superconductor chromium arsenide

NASA Astrophysics Data System (ADS)

Niu, Q.; Yu, W. C.; Yip, K. Y.; Lim, Z. L.; Kotegawa, H.; Matsuoka, E.; Sugawara, H.; Tou, H.; Yanase, Y.; Goh, Swee K.

2017-06-01

In conventional metals, modification of electron trajectories under magnetic field gives rise to a magnetoresistance that varies quadratically at low field, followed by a saturation at high field for closed orbits on the Fermi surface. Deviations from the conventional behaviour, for example, the observation of a linear magnetoresistance, or a non-saturating magnetoresistance, have been attributed to exotic electron scattering mechanisms. Recently, linear magnetoresistance has been observed in many Dirac materials, in which the electron-electron correlation is relatively weak. The strongly correlated helimagnet CrAs undergoes a quantum phase transition to a nonmagnetic superconductor under pressure. Here we observe, near the magnetic instability, a large and non-saturating quasilinear magnetoresistance from the upper critical field to 14 T at low temperatures. We show that the quasilinear magnetoresistance may arise from an intricate interplay between a nontrivial band crossing protected by nonsymmorphic crystal symmetry and strong magnetic fluctuations.

Superconductivity in the ternary germanide La3 Pd4 Ge4

NASA Astrophysics Data System (ADS)

Fujii, H.; Mochiku, T.; Takeya, H.; Sato, A.

2005-12-01

The ternary germanide La3Pd4Ge4 has been prepared by arc melting. This compound takes a body-centered lattice with an orthorhombic unit cell with the lattice parameters of a=4.2200(3)Å,b=4.3850(3)Å , and c=25.003(2)Å . The crystal structure of La3Pd4Ge4 is U3Ni4Si4 -type with the space group of Immm , consisting of the combination of structural units of AlB2 -type and BaAl4 -type layers. This compound is a type-II superconductor with a critical temperature (Tc) of 2.75 K. The lower critical field Hc1(0) is estimated to be 54 Oe. The upper critical field Hc2(0) estimated by linear extrapolation of the Hc2(T) curves is about 4.0 kOe, whereas the Werthamer-Hefland-Hohemberg theory gives Hc2(0)WHH=3.0kOe . This is an interesting observation of superconductivity in the compounds with U3Ni4Si4 -type structure. The coherence length ξ(0) of 330 Å and the penetration depth λ(0) of 2480 Å are derived.

Intrinsic pinning and the critical current scaling of clean epitaxial Fe(Se,Te) thin films

NASA Astrophysics Data System (ADS)

Iida, Kazumasa; Hänisch, Jens; Reich, Elke; Kurth, Fritz; Hühne, Ruben; Schultz, Ludwig; Holzapfel, Bernhard; Ichinose, Ataru; Hanawa, Masafumi; Tsukada, Ichiro; Schulze, Michael; Aswartham, Saicharan; Wurmehl, Sabine; Büchner, Bernd

2013-03-01

We report on the transport properties of clean, epitaxial Fe(Se,Te) thin films prepared on Fe-buffered MgO (001) single crystalline substrates by pulsed laser deposition. Near Tc a steep slope of the upper critical field for H||ab was observed (74.1 T/K), leading to a very short out-of-plane coherence length, ξc(0), of 0.2 nm, yielding 2ξc(0)≈0.4nm. This value is shorter than the interlayer distance (0.605 nm) between the Fe-Se(Te) planes, indicative of modulation of the superconducting order parameter along the c axis. An inverse correlation between the power law exponent N of the electric field-current density(E-J) curve and the critical current density Jc has been observed at 4 K, when the orientation of H was close to the ab plane. These results prove the presence of intrinsic pinning in Fe(Se,Te). A successful scaling of the angular dependent Jc and the corresponding exponent N can be realized by the anisotropic Ginzburg Landau approach with appropriate Γ values 2˜3.5. The temperature dependence of Γ behaves almost identically to that of the penetration depth anisotropy.

DOWNWARD CATASTROPHE OF SOLAR MAGNETIC FLUX ROPES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Quanhao; Wang, Yuming; Hu, Youqiu

2016-07-10

2.5-dimensional time-dependent ideal magnetohydrodynamic (MHD) models in Cartesian coordinates were used in previous studies to seek MHD equilibria involving a magnetic flux rope embedded in a bipolar, partially open background field. As demonstrated by these studies, the equilibrium solutions of the system are separated into two branches: the flux rope sticks to the photosphere for solutions at the lower branch but is suspended in the corona for those at the upper branch. Moreover, a solution originally at the lower branch jumps to the upper, as the related control parameter increases and reaches a critical value, and the associated jump ismore » here referred to as an upward catastrophe. The present paper advances these studies in three aspects. First, the magnetic field is changed to be force-free; the system still experiences an upward catastrophe with an increase in each control parameter. Second, under the force-free approximation, there also exists a downward catastrophe, characterized by the jump of a solution from the upper branch to the lower. Both catastrophes are irreversible processes connecting the two branches of equilibrium solutions so as to form a cycle. Finally, the magnetic energy in the numerical domain is calculated. It is found that there exists a magnetic energy release for both catastrophes. The Ampère's force, which vanishes everywhere for force-free fields, appears only during the catastrophes and does positive work, which serves as a major mechanism for the energy release. The implications of the downward catastrophe and its relevance to solar activities are briefly discussed.« less

Upper Ocean Momentum Response to Hurricane Forcing

NASA Astrophysics Data System (ADS)

Shay, L. K.; Jaimes de la Cruz, B.; Uhlhorn, E.

2016-02-01

The oceanic velocity response of the Loop Current (LC) and its complex warm and cold eddy field to hurricanes is critical to evaluate coupled operational forecast models. Direct velocity measurements of ocean current (including temperature and salinity) fields during hurricanes are needed to understand these complex interaction processes. As part of NOAA Intensity Forecasting Experiments, airborne expendable bathythermographs (AXBT), Conductivity-Temperature-Depth (AXCTD), and Current Profilers (AXCP) probes have been deployed in several major hurricanes from the NOAA research aircraft over the Gulf. Over the last decade, profilers were deployed in Isidore and Lili, Katrina and Rita, Gustav and Ike and Isaac-all of which interacted with the LC and warm eddy field. Central to these interactions under hurricane forcing is the level of sea surface cooling (typically about 1oC) induced by the wind-forced current response in the LC complex. Vertical current shear and instability (e.g., Richardson number) at the base of the oceanic mixed layer is often arrested by the strong upper ocean currents associated with the LC of 1 to 1.5 m s-1. By contrast, the SST cooling response often exceeds 3.5 to 4oC away from the LC complex in the Gulf Common Water. A second aspect of the interaction between the surface wind field and the LC is that the vorticity of the background flows (based on altimetry) enhances upwelling and downwelling processes by projecting onto the wind stress. This process modulates vertical mixing process at depth by keeping the Richardson numbers above criticality. Thus, the ocean cooling is less in the LC complex allowing for a higher and more sustained enthalpy flux as determined from global positioning system sondes deployed in these storms. This level of cooling (or lack thereof) in the LC complex significant impacts hurricane intensity that often reaches severe status which affects offshore structures and coastal communities at landfall in the northern Gulf of Mexico.

High-field transport properties of a P-doped BaFe2As2 film on technical substrate.

PubMed

Iida, Kazumasa; Sato, Hikaru; Tarantini, Chiara; Hänisch, Jens; Jaroszynski, Jan; Hiramatsu, Hidenori; Holzapfel, Bernhard; Hosono, Hideo

2017-01-12

High temperature (high-T c ) superconductors like cuprates have superior critical current properties in magnetic fields over other superconductors. However, superconducting wires for high-field-magnet applications are still dominated by low-T c Nb 3 Sn due probably to cost and processing issues. The recent discovery of a second class of high-T c materials, Fe-based superconductors, may provide another option for high-field-magnet wires. In particular, AEFe 2 As 2 (AE: Alkali earth elements, AE-122) is one of the best candidates for high-field-magnet applications because of its high upper critical field, H c2 , moderate H c2 anisotropy, and intermediate T c . Here we report on in-field transport properties of P-doped BaFe 2 As 2 (Ba-122) thin films grown on technical substrates by pulsed laser deposition. The P-doped Ba-122 coated conductor exceeds a transport J c of 10 5  A/cm 2 at 15 T for main crystallographic directions of the applied field, which is favourable for practical applications. Our P-doped Ba-122 coated conductors show a superior in-field J c over MgB 2 and NbTi, and a comparable level to Nb 3 Sn above 20 T. By analysing the E - J curves for determining J c , a non-Ohmic linear differential signature is observed at low field due to flux flow along the grain boundaries. However, grain boundaries work as flux pinning centres as demonstrated by the pinning force analysis.

Electronic structure, irreversibility line and magnetoresistance of Cu 0.3Bi 2Se 3 superconductor

DOE PAGES

Hemian, Yi; Gu, Genda; Chen, Chao -Yu; ...

2015-06-01

Cu xBi 2Se 3 is a superconductor that is a potential candidate for topological superconductors. We report our laser-based angle-resolved photoemission measurement on the electronic structure of the Cu xBi 2Se 3 superconductor, and a detailed magneto-resistance measurement in both normal and superconducting states. We find that the topological surface state of the pristine Bi 2Se 3 topological insulator remains robust after the Cu-intercalation, while the Dirac cone location moves downward due to electron doping. Detailed measurements on the magnetic field-dependence of the resistance in the superconducting state establishes an irreversibility line and gives a value of the upper criticalmore » field at zero temperature of ~4000 Oe for the Cu 0.3Bi 2Se 3 superconductor with a middle point T c of 1.9K. The relation between the upper critical field Hc2 and temperature T is different from the usual scaling relation found in cuprates and in other kinds of superconductors. Small positive magneto-resistance is observed in Cu 0.3Bi 2Se 3 superconductors up to room temperature. As a result, these observations provide useful information for further study of this possible candidate for topological superconductors.« less

Compilation of NRL Publications on High Temperature Superconductivity.

DTIC Science & Technology

1987-01-01

Fig. 2. The upper critical field as a function of .R. Beasley: Phys. Rev 11(1979) 4545. temperature for Ial.8Sro.2Cu04 (left) and 10) A. Junod , A...commuication 10) T.P. Orlando. E.J. McNiff. Jr.. S. Foner. and M.R. Beasley: Fhys. Rev 9(1979) 4545.-,, 11) A. Junod . A. Bezinge. T. Graf. J.L. Jorda. J...of MRS meeting (Anaheim, i Uchida et al. Jpn. J. of Apph Phys. 26, L443 (1987). -s 1987; in press). 12. H. Junod et al. (preprint

Magnetoresistance measurements of superconducting molybdenum nitride thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baskaran, R., E-mail: baskaran@igcar.gov.in; Arasu, A. V. Thanikai; Amaladass, E. P.

2016-05-23

Molybdenum nitride thin films have been deposited on aluminum nitride buffered glass substrates by reactive DC sputtering. GIXRD measurements indicate formation of nano-crystalline molybdenum nitride thin films. The transition temperature of MoN thin film is 7.52 K. The transition width is less than 0.1 K. The upper critical field Bc{sub 2}(0), calculated using GLAG theory is 12.52 T. The transition width for 400 µA current increased initially upto 3 T and then decreased, while that for 100 µA current transition width did not decrease.

Observation of superconducting vortex clusters in S/F hybrids

DOE PAGES

Di Giorgio, C.; Bobba, F.; Cucolo, A. M.; ...

2016-12-09

While Abrikosov vortices repel each other and form a uniform vortex lattice in bulk type-II superconductors, strong confinement potential profoundly affects their spatial distribution eventually leading to vortex cluster formation. The confinement could be induced by the geometric boundaries in mesoscopic-size superconductors or by the spatial modulation of the magnetic field in superconductor/ ferromagnet (S/F) hybrids. Here we study the vortex confinement in S/F thin film heterostructures and we observe that vortex clusters appear near magnetization inhomogeneities in the ferromagnet, called bifurcations. We use magnetic force microscopy to image magnetic bifurcations and superconducting vortices, while high resolution scanning tunneling microscopymore » is used to obtain detailed information of the local electronic density of states outside and inside the vortex cluster. We find an intervortex spacing at the bifurcation shorter than the one predicted for the same superconductor in a uniform magnetic field equal to the thermodynamical upper critical field H c2. This result is due to a local enhanced stray field and a competition between vortex-vortex repulsion and Lorentz force. Here, our findings suggest that special magnetic topologies could result in S/F hybrids that support superconductivity even when locally the vortex density exceeds the thermodynamic critical threshold value beyond which the superconductivity is destroyed.« less

Observation of superconducting vortex clusters in S/F hybrids.

PubMed

Di Giorgio, C; Bobba, F; Cucolo, A M; Scarfato, A; Moore, S A; Karapetrov, G; D'Agostino, D; Novosad, V; Yefremenko, V; Iavarone, M

2016-12-09

While Abrikosov vortices repel each other and form a uniform vortex lattice in bulk type-II superconductors, strong confinement potential profoundly affects their spatial distribution eventually leading to vortex cluster formation. The confinement could be induced by the geometric boundaries in mesoscopic-size superconductors or by the spatial modulation of the magnetic field in superconductor/ferromagnet (S/F) hybrids. Here we study the vortex confinement in S/F thin film heterostructures and we observe that vortex clusters appear near magnetization inhomogeneities in the ferromagnet, called bifurcations. We use magnetic force microscopy to image magnetic bifurcations and superconducting vortices, while high resolution scanning tunneling microscopy is used to obtain detailed information of the local electronic density of states outside and inside the vortex cluster. We find an intervortex spacing at the bifurcation shorter than the one predicted for the same superconductor in a uniform magnetic field equal to the thermodynamical upper critical field H c2 . This result is due to a local enhanced stray field and a competition between vortex-vortex repulsion and Lorentz force. Our findings suggest that special magnetic topologies could result in S/F hybrids that support superconductivity even when locally the vortex density exceeds the thermodynamic critical threshold value beyond which the superconductivity is destroyed.

Observation of superconducting vortex clusters in S/F hybrids

PubMed Central

Di Giorgio, C.; Bobba, F.; Cucolo, A. M.; Scarfato, A.; Moore, S. A.; Karapetrov, G.; D’Agostino, D.; Novosad, V.; Yefremenko, V.; Iavarone, M.

2016-01-01

While Abrikosov vortices repel each other and form a uniform vortex lattice in bulk type-II superconductors, strong confinement potential profoundly affects their spatial distribution eventually leading to vortex cluster formation. The confinement could be induced by the geometric boundaries in mesoscopic-size superconductors or by the spatial modulation of the magnetic field in superconductor/ferromagnet (S/F) hybrids. Here we study the vortex confinement in S/F thin film heterostructures and we observe that vortex clusters appear near magnetization inhomogeneities in the ferromagnet, called bifurcations. We use magnetic force microscopy to image magnetic bifurcations and superconducting vortices, while high resolution scanning tunneling microscopy is used to obtain detailed information of the local electronic density of states outside and inside the vortex cluster. We find an intervortex spacing at the bifurcation shorter than the one predicted for the same superconductor in a uniform magnetic field equal to the thermodynamical upper critical field Hc2. This result is due to a local enhanced stray field and a competition between vortex-vortex repulsion and Lorentz force. Our findings suggest that special magnetic topologies could result in S/F hybrids that support superconductivity even when locally the vortex density exceeds the thermodynamic critical threshold value beyond which the superconductivity is destroyed. PMID:27934898

Considerations for Assessing Maximum Critical Temperatures in Small Ectothermic Animals: Insights from Leaf-Cutting Ants

PubMed Central

Ribeiro, Pedro Leite; Camacho, Agustín; Navas, Carlos Arturo

2012-01-01

The thermal limits of individual animals were originally proposed as a link between animal physiology and thermal ecology. Although this link is valid in theory, the evaluation of physiological tolerances involves some problems that are the focus of this study. One rationale was that heating rates shall influence upper critical limits, so that ecological thermal limits need to consider experimental heating rates. In addition, if thermal limits are not surpassed in experiments, subsequent tests of the same individual should yield similar results or produce evidence of hardening. Finally, several non-controlled variables such as time under experimental conditions and procedures may affect results. To analyze these issues we conducted an integrative study of upper critical temperatures in a single species, the ant Atta sexdens rubropiosa, an animal model providing large numbers of individuals of diverse sizes but similar genetic makeup. Our specific aims were to test the 1) influence of heating rates in the experimental evaluation of upper critical temperature, 2) assumptions of absence of physical damage and reproducibility, and 3) sources of variance often overlooked in the thermal-limits literature; and 4) to introduce some experimental approaches that may help researchers to separate physiological and methodological issues. The upper thermal limits were influenced by both heating rates and body mass. In the latter case, the effect was physiological rather than methodological. The critical temperature decreased during subsequent tests performed on the same individual ants, even one week after the initial test. Accordingly, upper thermal limits may have been overestimated by our (and typical) protocols. Heating rates, body mass, procedures independent of temperature and other variables may affect the estimation of upper critical temperatures. Therefore, based on our data, we offer suggestions to enhance the quality of measurements, and offer recommendations to authors aiming to compile and analyze databases from the literature. PMID:22384147

Iron Isotope Fractionation in the Bushveld Igneous Complex Provide Insight into Fractional Crystallization

NASA Astrophysics Data System (ADS)

Rios, K. L.; Feineman, M. D.; Bybee, G. M.

2016-12-01

Dated at 2.056 Ga and encompassing an estimated 65,000 km2 in surface area and 650,000 km3 in volume the Bushveld Igneous Complex in South Africa contains the largest and most unique layered mafic intrusion in the world. It contains 80-90% of the world's minable platinum group elements. Scientists are interested in understanding the origin of this intrusion due to its massive size, unique assemblage of minerals, and strongly zoned stratigraphy. Iron isotopes may help us to understand the roles of partial mantle melting and fractional crystallization in magma genesis and differentiation. For example, it may be possible to determine what role fractional crystallization of oxides and sulfides played in the formation of the Rustenburg Layered Suite (RLS) by comparing δ56Fe in samples from the Lower, Critical, Main and Upper Zones. The use of MC-ICPMS has made it more routine to study the fractionation of stable iron isotopes in natural systems; however, this technique has only been applied in a few studies of the RLS, mostly restricted to the Upper Main and Upper Zones. In this study δ56Fe was determined in Upper Zone magnetite, Critical Zone chromitite and Critical Zone sulfides using MC-ICP-MS. Previous research has shown that early crystallizing mafic phases incorporate the lighter 54Fe isotope leaving a residual magma with a higher δ56Fe value. Therefore, if the Upper Zone magma represents a high-degree differentiate of the parental Bushveld magma, then magmas from the Upper Zone would be expected to have a higher δ56Fe than magmas contributing to the Lower, Critical and Main Zones. The results of this experiment were indeed consistent with this hypothesis. The δ56Fe values recorded for the three sample types were: magnetite 0.19 ±0.03‰; sulfides -0.45 ±0.03‰ to -0.81 ±0.03‰; and chromitite 0.03 ±0.05‰. The sulfides of the Critical Zone are isotopically lighter than would be predicted based on equilibrium sulfide-melt fractionation, if the parental melt of the Critical Zone were in equilibrium with previously published whole rock data for Upper Zone. This is consistent with interpretations of the Upper Zone as a high degree differentiate of the Bushveld Parental Magma.

Electron spin resonance shifts in S=1 antiferromagnetic chains

NASA Astrophysics Data System (ADS)

Furuya, Shunsuke C.; Maeda, Yoshitaka; Oshikawa, Masaki

2013-03-01

We discuss electron spin resonance (ESR) shifts in spin-1 Heisenberg antiferromagnetic chains with a weak single-ion anisotropy, based on several effective field theories: the O(3) nonlinear sigma model (NLSM) in the Haldane phase, free-fermion theories around the lower and the upper critical fields. In the O(3) NLSM, the single-ion anisotropy corresponds to a composite operator which creates two magnons at the same time and position. Therefore, even inside a parameter range where free magnon approximation is valid for thermodynamics, we have to take interactions among magnons into account in order to include the single-ion anisotropy as a perturbation. Although the O(3) NLSM is only valid in the Haldane phase, an appropriate translation of Faddeev-Zamolodchikov operators of the O(3) NLSM to fermion operators enables one to treat ESR shifts near the lower critical field in a similar manner to discussions in the Haldane phase. Our theory gives quantitative agreements with a numerical evaluation using quantum Monte Carlo simulation, and also with recent ESR experimental results on a spin-1 chain compound Ni(C5H14N2)2N3(PF6).

Evaluation of pediatric upper extremity peripheral nerve injuries.

PubMed

Ho, Emily S

2015-01-01

The evaluation of motor and sensory function of the upper extremity after a peripheral nerve injury is critical to diagnose the location and extent of nerve injury as well as document functional recovery in children. The purpose of this paper is to describe an approach to the evaluation of the pediatric upper extremity peripheral nerve injuries through a critical review of currently used tests of sensory and motor function. Outcome studies on pediatric upper extremity peripheral nerve injuries in the Medline database were reviewed. The evaluation of the outcome in children less than 10 years of age with an upper extremity peripheral nerve injury includes careful observation of preferred prehension patterns, examination of muscle atrophy and sudomotor function, provocative tests, manual muscle testing and tests of sensory threshold and tactile gnosis. The evaluation of outcome in children with upper extremity peripheral nerve injuries warrants a unique approach. Copyright © 2015 Hanley & Belfus. Published by Elsevier Inc. All rights reserved.

Critical constraint on inflationary magnetogenesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujita, Tomohiro; Yokoyama, Shuichiro, E-mail: tomohiro.fujita@ipmu.jp, E-mail: shu@icrr.u-tokyo.ac.jp

2014-03-01

Recently, there are several reports that the cosmic magnetic fields on Mpc scale in void region is larger than ∼ 10{sup −15}G with an uncertainty of a few orders from the current blazar observations. On the other hand, in inflationary magnetogenesis models, additional primordial curvature perturbations are inevitably produced from iso-curvature perturbations due to generated electromagnetic fields. We explore such induced curvature perturbations in a model independent way and obtained a severe upper bound for the energy scale of inflation from the observed cosmic magnetic fields and the observed amplitude of the curvature perturbation , as ρ{sub inf}{sup 1/4}

Quasiparticle Excitations in the Superconducting State of FeSe Probed by Thermal Hall Conductivity in the Vicinity of the BCS-BEC Crossover

NASA Astrophysics Data System (ADS)

Watashige, Tatsuya; Arsenijević, Stevan; Yamashita, Takuya; Terazawa, Daiki; Onishi, Takafumi; Opherden, Lars; Kasahara, Shigeru; Tokiwa, Yoshifumi; Kasahara, Yuichi; Shibauchi, Takasada; von Löhneysen, Hilbert; Wosnitza, Jochen; Matsuda, Yuji

2017-01-01

There is growing evidence that the superconducting semimetal FeSe (Tc ˜ 8 K) is in the crossover regime between weak-coupling Bardeen-Cooper-Schrieffer (BCS) and strong-coupling Bose-Einstein-condensate (BEC) limits. We report on longitudinal and transverse thermal conductivities, κxx and κxy, respectively, in magnetic fields up to 20 T. The field dependences of κxx and κxy imply that a highly anisotropic small superconducting gap forms at the electron Fermi-surface pocket whereas a more isotropic and larger gap forms at the hole pocket. Below ˜1.0 K, both κxx and κxy exhibit distinct anomalies (kinks) at the upper critical field Hc2 and at a field H* slightly below Hc2. The analysis of the thermal Hall angle (κxy/κxx) indicates a change of the quasiparticle scattering rate at H*. These results provide strong support to the previous suggestion that above H* a distinct field-induced superconducting phase emerges with an unprecedented large spin imbalance.

Strain-induced intervortex interaction and vortex lattices in tetragonal superconductors

DOE PAGES

Lin, Shi -Zeng; Kogan, Vladimir G.

2017-02-22

In superconductors with strong coupling between superconductivity and elasticity manifested in a strong dependence of transition temperature on pressure, there is an additional contribution to intervortex interactions due to the strain field generated by vortices. When vortex lines are along the c axis of a tetragonal crystal, a square vortex lattice (VL) is favored at low vortex densities, because the vortex-induced strains contribution to the intervortex interactions is long range. At intermediate magnetic fields, the triangular lattice is stabilized. Furthermore, the triangular lattice evolves to the square lattice upon increasing magnetic field, and eventually the system locks to the squaremore » structure. We argue, however, that as magnetic field approaches the upper critical field H c2 the elastic intervortex interactions disappear faster than the standard London interactions, so that VL should return to the triangular structure. Our results are compared to VLs observed in the heavy fermion superconductor CeCoIn 5.« less

Nanoscale-SiC doping for enhancing Jc and Hc2 in superconducting MgB2

NASA Astrophysics Data System (ADS)

Dou, S. X.; Braccini, V.; Soltanian, S.; Klie, R.; Zhu, Y.; Li, S.; Wang, X. L.; Larbalestier, D.

2004-12-01

The effect of nanoscale-SiC doping of MgB2 was investigated in comparison with undoped, clean-limit, and Mg-vapor-exposed samples using transport and magnetic measurements. It was found that there are two distinguishable but related mechanisms that control the critical current-density-field Jc(H ) behavior: increase of upper critical field Hc2 and improvement of flux pinning. There is a clear correlation between the critical temperature Tc, the resistivity ρ, the residual resistivity ratio RRR =R(300K)/R(40K), the irreversibility field H*, and the alloying state in the samples. The Hc2 is about the same within the measured field range for both the Mg-vapor-treated and the SiC-doped samples. However, the Jc(H ) for the latter is higher than the former in a high-field regime by an order of magnitude. Mg vapor treatment induced intrinsic scattering and contributed to an increase in Hc2. SiC doping, on the other hand, introduced many nanoscale precipitates and disorder at B and Mg sites, provoking an increase of ρ(40K ) from 1μΩcm (RRR=15) for the clean-limit sample to 300μΩcm (RRR=1.75) for the SiC-doped sample, leading to significant enhancement of both Hc2 and H * with only a minor effect on Tc. Electron energy-loss spectroscope and transmission electron microscope analysis revealed impurity phases: Mg2Si, MgO, MgB4, BOx, SixByOz, and BC at a scale below 10nm and an extensive domain structure of 2-4-nm domains in the doped sample, which serve as strong pinning centers.

Absolute versus convective helical magnetorotational instability in a Taylor-Couette flow.

PubMed

Priede, Jānis; Gerbeth, Gunter

2009-04-01

We analyze numerically the magnetorotational instability of a Taylor-Couette flow in a helical magnetic field [helical magnetorotational instability (HMRI)] using the inductionless approximation defined by a zero magnetic Prandtl number (Pr_{m}=0) . The Chebyshev collocation method is used to calculate the eigenvalue spectrum for small-amplitude perturbations. First, we carry out a detailed conventional linear stability analysis with respect to perturbations in the form of Fourier modes that corresponds to the convective instability which is not in general self-sustained. The helical magnetic field is found to extend the instability to a relatively narrow range beyond its purely hydrodynamic limit defined by the Rayleigh line. There is not only a lower critical threshold at which HMRI appears but also an upper one at which it disappears again. The latter distinguishes the HMRI from a magnetically modified Taylor vortex flow. Second, we find an absolute instability threshold as well. In the hydrodynamically unstable regime before the Rayleigh line, the threshold of absolute instability is just slightly above the convective one although the critical wavelength of the former is noticeably shorter than that of the latter. Beyond the Rayleigh line the lower threshold of absolute instability rises significantly above the corresponding convective one while the upper one descends significantly below its convective counterpart. As a result, the extension of the absolute HMRI beyond the Rayleigh line is considerably shorter than that of the convective instability. The absolute HMRI is supposed to be self-sustained and, thus, experimentally observable without any external excitation in a system of sufficiently large axial extension.

Constraints from Naturally Deformed Peridotites on Controls on Olivine Lattice Preferred Orientation

NASA Astrophysics Data System (ADS)

Bernard, R. E.; Behr, W. M.

2016-12-01

Seismic anisotropy in the upper mantle is produced primarily by lattice preferred orientations (LPO) in olivine formed during viscous deformation. Because seismic anisotropy is one of the principal means of characterizing upper mantle flow directions, it is critical to understand how LPO is affected by deformation conditions. Laboratory experiments suggest that water content and stress magnitude each play key roles in the development of LPO in olivine under experimental conditions, but it is unclear to what extent these results apply to natural conditions. We use peridotite xenoliths from a wide range of tectonic settings (Lunar Craters, Geronimo, and San Carlos volcanic fields in the Basin and Range; Cima and Deadman Lake volcanic fields in the Mojave; the Navajo Volcanic field in the Colorado Plateau; and the Potrillo volcanic field in the Rio Grande Rift region) to investigate correlations between water content, stress, and olivine LPO in natural rocks. Water contents were measured using Secondary Ion Mass Spectrometry, stress magnitudes using paleopiezometry, and LPOs using electron backscatter diffraction. The samples examined exhibit a range of fabric types, including A-, B-, C-, and E-type LPOs. Mojave xenoliths show no difference in water content between A- and E-type LPO; instead, differences in fabric type appear to reflect variations in strain magnitude. Samples from the Navajo volcanic field do show a correlation between water influx and stress magnitude as they exhibit abundant hydrous minerals and high water contents, stress magnitudes greater than 250 MPa and B-type olivine LPOs. Additional results from other xenolith suites will be presented at the meeting.

Probing transport mechanisms of BaFe2As2 superconducting films and grain boundary junctions by noise spectroscopy

PubMed Central

Barone, C.; Romeo, F.; Pagano, S.; Adamo, M.; Nappi, C.; Sarnelli, E.; Kurth, F.; Iida, K.

2014-01-01

An important step forward for the understanding of high-temperature superconductivity has been the discovery of iron-based superconductors. Among these compounds, iron pnictides could be used for high-field magnet applications, resulting more advantageous over conventional superconductors, due to a high upper critical field as well as its low anisotropy at low temperatures. However, the principal obstacle in fabricating high quality superconducting wires and tapes is given by grain boundaries. In order to study these effects, the dc transport and voltage-noise properties of Co-doped BaFe2As2 superconducting films with artificial grain boundary junctions have been investigated. A specific procedure allows the separation of the film noise from that of the junction. While the former shows a standard 1/f behaviour, the latter is characterized by an unconventional temperature-dependent multi-Lorentzian voltage-spectral density. Moreover, below the film superconducting critical temperature, a peculiar noise spectrum is found for the grain boundary junction. Possible theoretical interpretation of these phenomena is proposed. PMID:25145385

Synthesis and characterization of indium doped La{sub 3}Co{sub 4}Sn{sub 13} skutterudite superconductor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neha, P.; Srivastava, P.; Shruti,

2016-05-06

We report the synthesis and characterization of a novel superconductor La{sub 3}Co{sub 4}Sn{sub 12.35}In{sub 0.65} by Indium doping at Tin site in parent compound La{sub 3}Co{sub 4}Sn{sub 13}. We observe enhanced T{sub c} along with improved superconducting properties as onset compared to parent compound. By transport measurements we get superconducting transition with T{sub c}{sup onset} = 4.7 K and T{sub c}{sup zero} = 3.2 K. In magnetization measurements (ZFC-FC) superconducting transition is observed at 5.1 K. Upper critical field (H{sub c2}) and lower critical field (H{sub c1}) calculated by magneto resistance and M-H loop measurement are found to be 1.65more » T and 0.0026 T respectively. Hall measurement shows the majority charge carrier as electrons with carrier density of the order of 10{sup 19} cm{sup −3}. TEP measurement also support the Hall data as the Seebeck coefficient is negative over whole temperature range of measurement.« less

Conservatism of lizard thermal tolerances and body temperatures across evolutionary history and geography.

PubMed

Grigg, Joseph W; Buckley, Lauren B

2013-04-23

Species may exhibit similar thermal tolerances via either common ancestry or environmental filtering and local adaptation, if the species inhabit similar environments. We ask whether upper and lower thermal limits (critical thermal maxima and minima) and body temperatures are more strongly conserved across evolutionary history or geography for lizard populations distributed globally. We find that critical thermal maxima are highly conserved with location accounting for a higher proportion of the variation than phylogeny. Notably, thermal tolerance breadth is conserved across the phylogeny despite critical thermal minima showing little niche conservatism. Body temperatures observed during activity in the field show the greatest degree of conservatism, with phylogeny accounting for most of the variation. This suggests that propensities for thermoregulatory behaviour, which can buffer body temperatures from environmental variation, are similar within lineages. Phylogeny and geography constrain thermal tolerances similarly within continents, but variably within clades. Conservatism of thermal tolerances across lineages suggests that the potential for local adaptation to alleviate the impacts of climate change on lizards may be limited.

Substorm-associated large-scale magnetic field changes in the magnetotail: a prerequisite for magnetotail deflation events

NASA Astrophysics Data System (ADS)

Nakai, H.; Kamide, Y.

2003-04-01

An attempt is made to search for a critical condition in the lobe magnetic field to initiate large-scale magnetic field changes associated with substorm expansions. Using data from ISEE-1 for 1978, sudden decreases in the lobe magnetic field accompanied by magnetic field dipolarizations are identified. In this study, such events are designated as the magnetotail deflation. The magnetic field component parallel to the equatorial plane, BE , is normalized to a fixed geocentric distance, BEN , and is corrected for the compression effect of the solar wind dynamic pres-sure, BENC . It is shown that the BENC value just prior to a magnetotail deflation correlates well with the Dst index; BENC = 37.5 - 0.217 Dst0, where Dst0 denotes the Dst value corrected for the solar wind dynamic pressure. This regression function appears to delineate the upper limit of BENC values, when they are sorted by the Dst0 index. On the basis of this finding it is suggested that a prerequisite condition for magnetotail deflations must exist in the magnetosphere.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madaric, Juraj, E-mail: jurmad@hotmail.com; Klepanec, Andrej; Mistrik, Martin

Induction of therapeutic angiogenesis by autologous bone marrow mononuclear cell transplantation has been identified as a potential new option in patients with advanced lower-limb ischemia. There is little evidence of the benefit of intra-arterial cell application in upper-limb critical ischemia. We describe a patient with upper-extremity critical limb ischemia with digital gangrene resulting from hypothenar hammer syndrome successfully treated by intra-arterial autologous bone marrow mononuclear cell transplantation.

Polarisation of the Balmer-α emission in crossed electric and magnetic fields

NASA Astrophysics Data System (ADS)

Thorman, Alex

2018-03-01

An analysis of the polarisation structure of the Balmer-α emission in the presence of electric and magnetic fields is presented, with an emphasis on motional Stark effect polarimetry for fusion plasma diagnostics. When the fields are orthogonal, as is the case for neutral heating beams injected into a magnetised plasma, some degeneracy remains in the Stark-Zeeman energy levels and the magnetic quantum number is not well defined. The polarisation structure from the degenerate states is underdetermined and therefore volatile to weaker interactions that resolve this degeneracy, a critical subtlety that has previously been overlooked. A perturbation theory analysis finds distinct polarisation structures for the σ emission that apply when the fine-structure and microscopic electric fields are considered. It is found that only the σ ± 1 polarisation orientation is sensitive to upper-state populations (which are non-statistically weighted for neutral beam injection into a target gas), but with appropriate viewing geometries and beam injection directions the effect can be made negligible.

Low-temperature rapid synthesis and superconductivity of Fe-based oxypnictide superconductors.

PubMed

Fang, Ai-Hua; Huang, Fu-Qiang; Xie, Xiao-Ming; Jiang, Mian-Heng

2010-03-17

Fe-based oxypnictide superconductors were successfully synthesized at lower reaction temperatures and with shorter reaction times made possible by starting with less stable compounds, which provide a larger driving force for reactions. Using ball-milled powders of intermediate compounds, phase-pure superconductors with T(c) above 50 K were synthesized at 1173 K in 20 min. This method is particularly advantageous for retaining F, a volatile dopant that enhances superconductivity. Bulk superconductivity and high upper critical fields up to 392 T in Sm(0.85)Nd(0.15)FeAsO(0.85)F(0.15) were demonstrated.

Theory of High-T{sub c} Superconducting Cuprates Based on Experimental Evidence

DOE R&D Accomplishments Database

Abrikosov, A. A.

1999-12-10

A model of superconductivity in layered high-temperature superconducting cuprates is proposed, based on the extended saddle point singularities in the electron spectrum, weak screening of the Coulomb interaction and phonon-mediated interaction between electrons plus a small short-range repulsion of Hund's, or spin-fluctuation, origin. This permits to explain the large values of T{sub c}, features of the isotope effect on oxygen and copper, the existence of two types of the order parameter, the peak in the inelastic neutron scattering, the positive curvature of the upper critical field, as function of temperature etc.

Early optical polarization of a gamma-ray burst afterglow.

PubMed

Mundell, Carole G; Steele, Iain A; Smith, Robert J; Kobayashi, Shiho; Melandri, Andrea; Guidorzi, Cristiano; Gomboc, Andreja; Mottram, Chris J; Clarke, David; Monfardini, Alessandro; Carter, David; Bersier, David

2007-03-30

We report the optical polarization of a gamma-ray burst (GRB) afterglow, obtained 203 seconds after the initial burst of gamma-rays from GRB 060418, using a ring polarimeter on the robotic Liverpool Telescope. Our robust (2sigma) upper limit on the percentage of polarization, less than 8%, coincides with the fireball deceleration time at the onset of the afterglow. The combination of the rate of decay of the optical brightness and the low polarization at this critical time constrains standard models of GRB ejecta, ruling out the presence of a large-scale ordered magnetic field in the emitting region.

A generalized public goods game with coupling of individual ability and project benefit

NASA Astrophysics Data System (ADS)

Zhong, Li-Xin; Xu, Wen-Juan; He, Yun-Xin; Zhong, Chen-Yang; Chen, Rong-Da; Qiu, Tian; Shi, Yong-Dong; Ren, Fei

2017-08-01

Facing a heavy task, any single person can only make a limited contribution and team cooperation is needed. As one enjoys the benefit of the public goods, the potential benefits of the project are not always maximized and may be partly wasted. By incorporating individual ability and project benefit into the original public goods game, we study the coupling effect of the four parameters, the upper limit of individual contribution, the upper limit of individual benefit, the needed project cost and the upper limit of project benefit on the evolution of cooperation. Coevolving with the individual-level group size preferences, an increase in the upper limit of individual benefit promotes cooperation while an increase in the upper limit of individual contribution inhibits cooperation. The coupling of the upper limit of individual contribution and the needed project cost determines the critical point of the upper limit of project benefit, where the equilibrium frequency of cooperators reaches its highest level. Above the critical point, an increase in the upper limit of project benefit inhibits cooperation. The evolution of cooperation is closely related to the preferred group-size distribution. A functional relation between the frequency of cooperators and the dominant group size is found.

Interface induced high temperature superconductivity in single unit-cell FeSe on SrTiO{sub 3}(110)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Guanyu; Zhang, Ding; Liu, Chong

2016-05-16

We report high temperature superconductivity in one unit-cell (1-UC) FeSe films grown on SrTiO{sub 3} (STO)(110) substrate by molecular beam epitaxy. By in-situ scanning tunneling microscopy measurement, we observe a superconducting gap as large as 17 meV on the 1-UC FeSe films. Transport measurements on 1-UC FeSe/STO(110) capped with FeTe layers reveal superconductivity with an onset transition temperature (T{sub C}) of 31.6 K and an upper critical magnetic field of 30.2 T. We also find that T{sub C} can be further increased by external electric field although the effect is weaker than that on STO(001) substrate.

How Hives Collapse: Allee Effects, Ecological Resilience, and the Honey Bee

PubMed Central

Dennis, Brian; Kemp, William P.

2016-01-01

We construct a mathematical model to quantify the loss of resilience in collapsing honey bee colonies due to the presence of a strong Allee effect. In the model, recruitment and mortality of adult bees have substantial social components, with recruitment enhanced and mortality reduced by additional adult bee numbers. The result is an Allee effect, a net per-individual rate of hive increase that increases as a function of adult bee numbers. The Allee effect creates a critical minimum size in adult bee numbers, below which mortality is greater than recruitment, with ensuing loss of viability of the hive. Under ordinary and favorable environmental circumstances, the critical size is low, and hives remain large, sending off viably-sized swarms (naturally or through beekeeping management) when hive numbers approach an upper stable equilibrium size (carrying capacity). However, both the lower critical size and the upper stable size depend on many parameters related to demographic rates and their enhancement by bee sociality. Any environmental factors that increase mortality, decrease recruitment, or interfere with the social moderation of these rates has the effect of exacerbating the Allee effect by increasing the lower critical size and substantially decreasing the upper stable size. As well, the basin of attraction to the upper stable size, defined by the model potential function, becomes narrower and shallower, indicating the loss of resilience as the hive becomes subjected to increased risk of falling below the critical size. Environmental effects of greater severity can cause the two equilibria to merge and the basin of attraction to the upper stable size to disappear, resulting in collapse of the hive from any initial size. The model suggests that multiple proximate causes, among them pesticides, mites, pathogens, and climate change, working singly or in combinations, could trigger hive collapse. PMID:26910061

Prevention of upper gastrointestinal bleeding in critically ill Chinese patients: a randomized, double-blind study evaluating esomeprazole and cimetidine.

PubMed

Lou, Wenhui; Xia, Ying; Xiang, Peng; Zhang, Liangqing; Yu, Xiangyou; Lim, Sam; Xu, Mo; Zhao, Lina; Rydholm, Hans; Traxler, Barry; Qin, Xinyu

2018-04-20

To assess the efficacy and safety of esomeprazole in preventing upper gastrointestinal (GI) bleeding in critically ill Chinese patients, using cimetidine as an active comparator. A pre-specified non-inferiority limit (5%) was used to compare rates of significant upper GI bleeding in this randomized, double-blind, parallel-group, phase 3 study across 27 intensive care units in China. Secondary endpoints included safety and tolerability measures. Patients required mechanical ventilation and had at least one additional risk factor for stress ulcer bleeding. Patients were randomized to receive either active esomeprazole 40 mg, as a 30-min intravenous (IV) infusion twice daily, and an IV placebo cimetidine infusion or active cimetidine 50 mg/h, as a continuous infusion following an initial bolus of 300 mg, and placebo esomeprazole injections, given up to 14 days. Patients were blinded using this double-dummy technique. Of 274 patients, 2.7% with esomeprazole and 4.6% with cimetidine had significant upper GI bleeding (bright red blood in the gastric tube not clearing after lavage or persistent Gastroccult-positive "coffee grounds" material). Non-inferiority of esomeprazole to cimetidine was demonstrated. The safety profiles of both drugs were similar and as expected in critically ill patients. Esomeprazole is effective in preventing upper GI bleeding in critically ill Chinese patients, as demonstrated by the non-inferiority analysis using cimetidine as an active control. ClinicalTrials.gov identifier NCT02157376.

Drying and wetting transitions of a Lennard-Jones fluid: Simulations and density functional theory

NASA Astrophysics Data System (ADS)

Evans, Robert; Stewart, Maria C.; Wilding, Nigel B.

2017-07-01

We report a theoretical and simulation study of the drying and wetting phase transitions of a truncated Lennard-Jones fluid at a flat structureless wall. Binding potential calculations predict that the nature of these transitions depends on whether the wall-fluid attraction has a long ranged (LR) power law decay or is instead truncated, rendering it short ranged (SR). Using grand canonical Monte Carlo simulation and classical density functional theory, we examine both cases in detail. We find that for the LR case wetting is first order, while drying is continuous (critical) and occurs exactly at zero attractive wall strength, i.e., in the limit of a hard wall. In the SR case, drying is also critical but the order of the wetting transition depends on the truncation range of the wall-fluid potential. We characterize the approach to critical drying and wetting in terms of the density and local compressibility profiles and via the finite-size scaling properties of the probability distribution of the overall density. For the LR case, where the drying point is known exactly, this analysis allows us to estimate the exponent ν∥, which controls the parallel correlation length, i.e., the extent of vapor bubbles at the wall. Surprisingly, the value we obtain is over twice that predicted by mean field and renormalization group calculations, despite the fact that our three dimensional system is at the upper critical dimension where mean field theory for critical exponents is expected to hold. Possible reasons for this discrepancy are discussed in the light of fresh insights into the nature of near critical finite-size effects.

Drying and wetting transitions of a Lennard-Jones fluid: Simulations and density functional theory.

PubMed

Evans, Robert; Stewart, Maria C; Wilding, Nigel B

2017-07-28

We report a theoretical and simulation study of the drying and wetting phase transitions of a truncated Lennard-Jones fluid at a flat structureless wall. Binding potential calculations predict that the nature of these transitions depends on whether the wall-fluid attraction has a long ranged (LR) power law decay or is instead truncated, rendering it short ranged (SR). Using grand canonical Monte Carlo simulation and classical density functional theory, we examine both cases in detail. We find that for the LR case wetting is first order, while drying is continuous (critical) and occurs exactly at zero attractive wall strength, i.e., in the limit of a hard wall. In the SR case, drying is also critical but the order of the wetting transition depends on the truncation range of the wall-fluid potential. We characterize the approach to critical drying and wetting in terms of the density and local compressibility profiles and via the finite-size scaling properties of the probability distribution of the overall density. For the LR case, where the drying point is known exactly, this analysis allows us to estimate the exponent ν ∥ , which controls the parallel correlation length, i.e., the extent of vapor bubbles at the wall. Surprisingly, the value we obtain is over twice that predicted by mean field and renormalization group calculations, despite the fact that our three dimensional system is at the upper critical dimension where mean field theory for critical exponents is expected to hold. Possible reasons for this discrepancy are discussed in the light of fresh insights into the nature of near critical finite-size effects.

Key factors for the implementation of successful, stand-alone village electrification schemes in Peru

NASA Astrophysics Data System (ADS)

Sanchez-Campos, Teodoro

The hypothesis of this work is that there are social, financial, technical, managerial institutional and political key factors that may either support or prevent the success of small stand alone energy systems in rural areas. This research work aims at contributing to the identification of such factors and study their relevance to the performance and sustainability of stand alone energy systems in rural areas; to meet its purpose, a wide range of literature was reviewed including rural electrification programmes and projects, research and development projects on access to electricity in rural areas, impact studies and others, and a field research survey was done the Andes and Upper Jungle regions in Peru. Nineteen possible critical factors were identified, thirteen with relevance at the local context (the community or village), and six with relevance at the national (or wider) context. From literature review it was found that the possible local critical factors were relevant only to four categories of factors instead of the six considered initially (i.e. social, financial, technological and managerial): the other two categories, political and institutional were found to be more relevant to the national context, therefore those were included in the group of possible critical factors of wider context. A series of questionnaires were designed to collect field data information, which was later used to analyse and establish the relation of each identified factor with the success of the systems studied. The survey research was implemented in 14 villages, 7 with small diesel sets and 7 with small hydropower schemes, all spread in the Andes and Upper Jungle of Peru, which were carefully selected to be representative of regions with isolated stand alone systems and with different socioeconomic background. Out of the 13 possible critical factors of local context, it was found that only 3 are really critical, the others are important but not critical; one of them (technical assistance) was found to be closely linked to national capacity, therefore for practical reasons both are considered as one critical factor or wider context. Although more research study is needed to establish a more clearer result on the factors of wider context (national context), it was found that out of the 6 factors of wider context only one appears to be critical, the other 5 are important but not critical. Therefore the summary of critical factors is as follows: a) Critical Factors of Local Context o Management o Local capacity b) Critical Factors of National Context o Technical Support/national capacity On the local factors, management appears to be the most critical of all factors, because with good management, most of the other factors can be overcome. It was also found that "The small enterprise model" tested by Practical Action on small scale hydropower schemes is proving to be successful and other organisations are starting to use it in different contexts. Therefore future research is recommended on this particular management model in order to be useful for rural electrification programmes based on decentralised energy generation systems.

Upward shift of the vortex solid phase in high-temperature-superconducting wires through high density nanoparticle addition

DOE PAGES

Miura, Masashi; Maiorov, Boris; Balakirev, Fedor F.; ...

2016-02-08

Here, we show a simple and effective way to improve the vortex irreversibility line up to very high magnetic fields (60T) by increasing the density of second phase BaZrO 3 nanoparticles. (Y 0.77,Gd 0.23)Ba 2Cu 3O y films were grown on metal substrates with different concentration of BaZrO 3 nanoparticles by the metal organic deposition method. We find that upon increase of the BaZrO 3 concentration, the nanoparticle size remains constant but the twin-boundary density increases. Up to the highest nanoparticle concentration (n ~ 1.3 × 10 22/m 3), the irreversibility field (H irr) continues to increase with no signmore » of saturation up to 60 T, although the vortices vastly outnumber pinning centers. We find extremely high H irr, namely H irr = 30 T (H||45°) and 24 T (H||c) at 65 K and 58 T (H||45°) and 45 T (H||c) at 50K. The difference in pinning landscape shifts the vortex solid-liquid transition upwards, increasing the vortex region useful for power applications, while keeping the upper critical field, critical temperature and electronic mass anisotropy unchanged.« less

Acoustic explorations of the upper ocean boundary layer

NASA Astrophysics Data System (ADS)

Vagle, Svein

2005-04-01

The upper ocean boundary layer is an important but difficult to probe part of the ocean. A better understanding of small scale processes at the air-sea interface, including the vertical transfer of gases, heat, mass and momentum, are crucial to improving our understanding of the coupling between atmosphere and ocean. Also, this part of the ocean contains a significant part of the total biomass at all trophic levels and is therefore of great interest to researchers in a range of different fields. Innovative measurement plays a critical role in developing our understanding of the processes involved in the boundary layer, and the availability of low-cost, compact, digital signal processors and sonar technology in self-contained and cabled configurations has led to a number of exciting developments. This talk summarizes some recent explorations of this dynamic boundary layer using both active and passive acoustics. The resonant behavior of upper ocean bubbles combined with single and multi-frequency broad band active and passive devices are now giving us invaluable information on air-sea gas transfer, estimation of biological production, marine mammal behavior, wind speed and precipitation, surface and internal waves, turbulence, and acoustic communication in the surf zone.

Multicritical scalar theories with higher-derivative kinetic terms: A perturbative RG approach with the ɛ -expansion

NASA Astrophysics Data System (ADS)

Safari, M.; Vacca, G. P.

2018-02-01

We employ perturbative renormalization group and ɛ -expansion to study multicritical single-scalar field theories with higher derivative kinetic terms of the form ϕ (-□)kϕ . We focus on those with a Z2-symmetric critical point which are characterized by an upper critical dimension dc=2 n k /(n -1 ) accumulating at even integers. We distinguish two types of theories depending on whether or not the numbers k and n -1 are relatively prime. When they are, the critical theory involves a marginal powerlike interaction ϕ2 n and the deformations admit a derivative expansion that at leading order involves only the potential. In this case we present the beta functional of the potential and use this to calculate some anomalous dimensions and operator product expansion coefficients. These confirm some conformal field theory data obtained using conformal-block techniques, while giving new results. In the second case where k and n -1 have a common divisor, the theories show a much richer structure induced by the presence of marginal derivative operators at criticality. We study the case k =2 with odd values of n , which fall in the second class, and calculate the functional flows and spectrum. These theories have a phase diagram characterized at leading order in ɛ by four fixed points which apart from the Gaussian UV fixed point include an IR fixed point with a purely derivative interaction.

Enhancement of Hc2 and Jc by carbon-based chemical doping

NASA Astrophysics Data System (ADS)

Yeoh, W. K.; Dou, S. X.

2007-06-01

In the past 5 years, various kinds of doping of MgB 2, including single elements (metal and non-metal), silicates, various carbon sources, and other compounds have been investigated and reported. Most nanoparticle doping leads to improvement of critical current density, Jc( H), and performance, but some types show a negative effect. In this paper, the effect of carbon doping on Jc and the upper critical field, Hc2, of MgB 2 is reviewed. Carbon substitution effects make two distinguishable contributions to the enhancement of Jc field performance: increase of Hc2 and improvement of flux pinning, both because carbon substitutes for boron in the MgB 2 lattice. Among all the carbon sources so far, nano-SiC has been confirmed to be the most effective dopant to enhance the Jc in magnetic fields and Hc2. An irreversibility field, Hirr, of 10 T has been achieved with nano-SiC doping at 20 K, exceeding Hirr of NbTi at 4.2 K. Besides that, Hc2 of carbon alloyed MgB 2 film has reached the value of 71 T. The significant enhancement in Jc( H) and Hc2 via carbon substitution has provided great potential for practical applications of MgB 2. The dual reaction model proposed by the authors’ group provides a comprehensive understanding of the mechanism of enhancement in Jc and Hc2 by chemical doping. Further improvement in self-field Jc performance while maintaining the already achieved in-field performance remains as a major challenge in the development of MgB 2.

Numerical modeling of the equatorial ionization anomaly (EIA), equatorial temperature and wind anomaly (ETWA) and equatorial electron temperature anomaly (EETA) on the basis of the GSM TIP

NASA Astrophysics Data System (ADS)

Klimenko, M. V.; Klimenko, V. V.; Bryukhanov, V. V.

On the basis of Global Self-consistent Model of Thermosphere Ionosphere and Protonosphere GSM TIP developed in WD IZMIRAN the calculations of the behavior of thermosphere F-region and upper ionosphere parameters at middle and low geomagnetic latitudes are carried out The calculations were carried out with use the new block of the calculation of electric fields in the ionosphere in which the decision of the three-dimensional equation describing the law of the conservation of the full current density in the ionosphere of the Earth is realized by adduction it to the two-dimensional by integration on the thickness of the current conductive layer of the ionosphere along equipotential geomagnetic field lines The calculations of the neutral atmosphere composition and temperature were executed with use of the MSIS model The quite geomagnetic conditions of the equinox were considered in the minimum of the solar activity There are presented the calculated global distributions of the critical frequency of the F2-layer of ionosphere for the different moments UT the latitudinal course of the N e and T e in the F-region and upper ionosphere in the vicinity of geomagnetic equator and unrolling on UT of the calculated velocities of zonal component of the thermospheric wind and ion temperature in the F-region of ionosphere as well as critical frequency and height of the F2-layer maximum of the ionosphere at three longitude chains of the stations Brazilian -- Fortaleza 4 0 r S 38 0 r W Jicamarca 11 9 r S 76 0 r W Cachoeira

Hydraulic complexity, larval drift, and endangered species recovery in the Upper Missouri River

NASA Astrophysics Data System (ADS)

Erwin, S. O.; Bulliner, E. A., IV; Jacobson, R. B.; Fischenich, C. J.; Braaten, P.

2016-12-01

Connectivity is recognized as an important attribute of river ecosystems. In highly fragmented rivers restoring longitudinal connectivity is often difficult or impossible. In systems where removal of dams is not viable and bypass does not address needs of target fish species, manipulation of flows to meet requirements of aquatic organisms may aid species recovery. Such is the case in the Missouri River basin, where dams and reservoirs impede fish migration and larval drift, critical life history events for many species, notably the endangered pallid sturgeon. In 2016, we conducted a large-scale dye-trace experiment in the Upper Missouri River downstream from Fort Peck Reservoir, MT. A slug injection of Rhodamine WT was tracked and measured over a 135-km reach. Direct measurements of downstream dye concentrations were used to calibrate a one-dimensional advection-dispersion model, which is being used to explore alternative reservoir operations for Fort Peck and the downstream reservoir, Lake Sakakawea. Results are used to evaluate the effects of flow regulation on dispersal of endangered sturgeon larvae. Additionally, we employ a two-dimensional hydrodynamic model to evaluate particle residence times and inform understanding of hydraulic processes that may control the shape of breakthrough curves observed from the field experiment. Lateral connectivity also has a potential role in river management and species recovery. Reservoir management can determine whether flow is contained within the channel, where dispersion is low, or laterally connected to rough floodplains which can result in high dispersion, long-tailed particle residence times, and greater opportunities for drifting larvae to transition to exogenous feeding and survive. We discuss our findings in the context of basin-wide restoration efforts and highlight the critical contributions of both large-scale field experiments and numerical modeling to inform management.

The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP)

NASA Technical Reports Server (NTRS)

Ishikawa, Shin-nosuke; Kano, R.; Kobayashi, K.; Bando, T.; Narukage, N..; Ishikawa, R.; Kubo, M.; Katsukawa, Y.; Suematsu, Y.; Hara, H.;

Middle and upper Miocene natural gas sands in onshore and offshore Alabama

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mink, R.M.; Mancini, E.A.; Bearden, B.L.

1988-09-01

Thirty Miocene natural gas fields have been established in onshore and offshore Alabama since the discovery of Miocene gas in this area in 1979. These fields have produced over 16 bcf of natural gas from the middle Miocene Amos sand (24 fields) and upper Miocene Luce (3 fields), Escambia (1 field), and Meyer (3 fields) sands. Production from the Amos transgressive sands represents over 92% of the cumulative shallow Miocene natural gas produced in onshore and offshore Alabama. In addition, over 127 bcf of natural gas has been produced from upper Miocene sands in the Chandeleur area. The productive Miocenemore » section in onshore and coastal Alabama is interpreted to present transgressive marine shelf and regressive shoreface sands. The middle Miocene Amos sand bars are the most productive reservoirs of natural gas in onshore and coastal Alabama, principally due to the porous and permeable nature of these transgressive sands and their stratigraphic relationship to the underlying basinal clays in this area. In offshore Alabama the upper Miocene sands become thicker and are generally more porous and permeable than their onshore equivalents. Because of their deeper burial depth in offshore Alabama, these upper Miocene sands are associated with marine clays that are thermally more mature. The combination of reservoir grade lithologies associated with moderately mature petroleum source rocks enhances the natural gas potential of the upper Miocene sands in offshore Alabama.« less

Outcome following nonoperative treatment of brachial plexus birth injuries.

PubMed

DiTaranto, Patricia; Campagna, Liliana; Price, Andrew E; Grossman, John A I

2004-02-01

Ninety-one infants who sustained a brachial plexus birth injury were treated with only physical and occupational therapy. The children were evaluated at 3-month intervals and followed for a minimum of 2 years. Sixty-three children with an upper or upper-middle plexus injury recovered good to excellent shoulder and hand function. In all of these children, critical marker muscles recovered M4 by 6 months of age. Twelve infants sustained a global palsy, with critical marker muscles remaining at M0-M1 at 6 months, resulting in a useless extremity. Sixteen infants with upper and upper-middle plexus injuries failed to recover greater than M1-M2 deltoid and biceps by 6 months, resulting in a very poor final outcome. These data provide useful guidelines for selection of infants for surgical reconstruction to improve ultimate outcome.

Upper bound of abutment scour in laboratory and field data

USGS Publications Warehouse

Benedict, Stephen

2016-01-01

The U.S. Geological Survey, in cooperation with the South Carolina Department of Transportation, conducted a field investigation of abutment scour in South Carolina and used those data to develop envelope curves that define the upper bound of abutment scour. To expand on this previous work, an additional cooperative investigation was initiated to combine the South Carolina data with abutment scour data from other sources and evaluate upper bound patterns with this larger data set. To facilitate this analysis, 446 laboratory and 331 field measurements of abutment scour were compiled into a digital database. This extensive database was used to evaluate the South Carolina abutment scour envelope curves and to develop additional envelope curves that reflected the upper bound of abutment scour depth for the laboratory and field data. The envelope curves provide simple but useful supplementary tools for assessing the potential maximum abutment scour depth in the field setting.

Pressure-induced superconductivity in semimetallic 1 T -TiTe2 and its persistence upon decompression

NASA Astrophysics Data System (ADS)

Dutta, U.; Malavi, P. S.; Sahoo, S.; Joseph, B.; Karmakar, S.

2018-02-01

Pristine 1 T -TiTe2 single crystal has been studied for resistance and magnetoresistance behavior under quasihydrostatic and nonhydrostatic compressions. While the semimetallic state is retained in nearly hydrostatic pressures, small nonhydrostatic compression leads to an abrupt change in low-temperature resistance, a signature of possible charge density wave (CDW) ordering, that eventually collapses above 6.2 GPa. Superconductivity emerges at ˜5 GPa, rapidly increasing to a critical temperature (Tc) of 5.3 K at 12 GPa, irrespective of pressure condition. Pressure studies thus evidence that 1 T -TiTe2 exhibits superconductivity irrespective of the formation of the CDW-like state, implying the existence of phase-separated domains. Most surprisingly, the superconducting state persists upon decompression, establishing a novel phase diagram with suppressed P scale. The pressure quenchable superconductivity, of multiband nature and relatively high upper critical field, makes 1 T -TiTe2 unique among other layered dichalcogenides.

Altered saccadic targets when processing facial expressions under different attentional and stimulus conditions.

PubMed

Boutsen, Frank A; Dvorak, Justin D; Pulusu, Vinay K; Ross, Elliott D

2017-04-01

Depending on a subject's attentional bias, robust changes in emotional perception occur when facial blends (different emotions expressed on upper/lower face) are presented tachistoscopically. If no instructions are given, subjects overwhelmingly identify the lower facial expression when blends are presented to either visual field. If asked to attend to the upper face, subjects overwhelmingly identify the upper facial expression in the left visual field but remain slightly biased to the lower facial expression in the right visual field. The current investigation sought to determine whether differences in initial saccadic targets could help explain the perceptual biases described above. Ten subjects were presented with full and blend facial expressions under different attentional conditions. No saccadic differences were found for left versus right visual field presentations or for full facial versus blend stimuli. When asked to identify the presented emotion, saccades were directed to the lower face. When asked to attend to the upper face, saccades were directed to the upper face. When asked to attend to the upper face and try to identify the emotion, saccades were directed to the upper face but to a lesser degree. Thus, saccadic behavior supports the concept that there are cognitive-attentional pre-attunements when subjects visually process facial expressions. However, these pre-attunements do not fully explain the perceptual superiority of the left visual field for identifying the upper facial expression when facial blends are presented tachistoscopically. Hence other perceptual factors must be in play, such as the phenomenon of virtual scanning. Published by Elsevier Ltd.

Numerical modelling of iron-pnictide bulk superconductor magnetization

NASA Astrophysics Data System (ADS)

Ainslie, Mark D.; Yamamoto, Akiyasu; Fujishiro, Hiroyuki; Weiss, Jeremy D.; Hellstrom, Eric E.

2017-10-01

Iron-based superconductors exhibit a number of properties attractive for applications, including low anisotropy, high upper critical magnetic fields (H c2) in excess of 90 T and intrinsic critical current densities above 1 MA cm-2 (0 T, 4.2 K). It was shown recently that bulk iron-pnictide superconducting magnets capable of trapping over 1 T (5 K) and 0.5 T (20 K) can be fabricated with fine-grain polycrystalline Ba0.6K0.4Fe2As2 (Ba122). These Ba122 magnets were processed by a scalable, versatile and low-cost method using common industrial ceramic processing techniques. In this paper, a standard numerical modelling technique, based on a 2D axisymmetric finite-element model implementing the H -formulation, is used to investigate the magnetisation properties of such iron-pnictide bulk superconductors. Using the measured J c(B, T) characteristics of a small specimen taken from a bulk Ba122 sample, experimentally measured trapped fields are reproduced well for a single bulk, as well as a stack of bulks. Additionally, the influence of the geometric dimensions (thickness and diameter) on the trapped field is analysed, with a view of fabricating larger samples to increase the magnetic field available from such trapped field magnets. It is shown that, with current state-of-the-art superconducting properties, surface trapped fields >2 T could readily be achieved at 5 K (and >1 T at 20 K) with a sample of diameter 50 mm. Finally, an aspect ratio of between 1 and 1.5 for R/H (radius/thickness) would be an appropriate compromise between the accessible, surface trapped field and volume of superconducting material for bulk Ba122 magnets.

Superconducting phase transitions in mK temperature range in splat-cooled U0.85Pt0.15 alloys

NASA Astrophysics Data System (ADS)

Kim-Ngan, N.-T. H.; Tarnawski, Z.; Chrobak, M.; Sowa, S.; Duda, A.; Paukov, M.; Buturlim, V.; Havela, L.

2018-05-01

We present the temperature and magnetic-field dependence of the electrical resistivity (ρ(T,B)) in the mK temperature range used as a diagnostic tool for the superconductivity of U-Pt alloys prepared by splat-cooling technique. In most of the investigated alloys, a single resistivity drop was observed at the superconducting transition. For splat-cooled U0.85Pt0.15 (U-15 at% Pt) alloys, two drops were revealed around 0.6 K and 1 K tentatively attributed to the superconducting phase transitions of the γ-U phase and α-U phase. The ρ(T,B) characteristics were found to depend on the cooling rate. The superconductivity is characterized by very high upper critical fields, reaching 4.5 T in the 0 K limit.

The effects of annealing temperature on the in-field Jc and surface pinning in silicone oil doped MgB2 bulks and wires

NASA Astrophysics Data System (ADS)

Hossain, M. S. A.; Motaman, A.; Çiçek, Ö.; Ağıl, H.; Ertekin, E.; Gencer, A.; Wang, X. L.; Dou, S. X.

2012-12-01

The effects of sintering temperature on the lattice parameters, full width at half maximum (FWHM), strain, critical temperature (Tc), critical current density (Jc), irreversibility field (Hirr), upper critical field (Hc2), and resistivity (ρ) of 10 wt.% silicone oil doped MgB2 bulk and wire samples are investigated in state of the art by this article. The a-lattice parameter of the silicone oil doped samples which were sintered at different temperatures was drastically reduced from 3.0864 Å to 3.0745 Å, compared to the un-doped samples, which indicates the substitution of the carbon (C) into the boron sites. It was found that sintered samples at the low temperature of 600 °C shows more lattice distortion by more C-substitution and higher strain, lower Tc, higher impurity scattering, and enhancement of both magnetic Jc and Hc2, compared to those sintered samples at high temperatures. The flux pinning mechanism has been analyzed based on the extended normalized pinning force density fp = Fp/Fp,max scaled with b = B/Bmax. Results show that surface pinning is the dominant pinning mechanism for the doped sample sintered at the low temperature of 600 °C, while point pinning is dominant for the un-doped sample. The powder in tube (PIT) MgB2 wire was also fabricated by using of this liquid doping and found that both transport Jc and n-factor increased which proves this cheap and abundant silicone oil doping can be a good candidate for industrial application.

Ares I-X Upper Stage Simulator Residual Stress Analysis

NASA Technical Reports Server (NTRS)

Raju, Ivatury S.; Brust, Frederick W.; Phillips, Dawn R.; Cheston, Derrick

2008-01-01

The structural analyses described in the present report were performed in support of the NASA Engineering and Safety Center (NESC) Critical Initial Flaw Size (CIFS) assessment for the Ares I-X Upper Stage Simulator (USS) common shell segment. An independent assessment was conducted to determine the critical initial flaw size (CIFS) for the flange-to-skin weld in the Ares I-X Upper Stage Simulator (USS). The Ares system of space launch vehicles is the US National Aeronautics and Space Administration s plan for replacement of the aging space shuttle. The new Ares space launch system is somewhat of a combination of the space shuttle system and the Saturn launch vehicles used prior to the shuttle. Here, a series of weld analyses are performed to determine the residual stresses in a critical region of the USS. Weld residual stresses both increase constraint and mean stress thereby having an important effect on fatigue and fracture life. The results of this effort served as one of the critical load inputs required to perform a CIFS assessment of the same segment.

HOMOGENEOUS NUCLEAR REACTOR

DOEpatents

Hammond, R.P.; Busey, H.M.

1959-02-17

Nuclear reactors of the homogeneous liquid fuel type are discussed. The reactor is comprised of an elongated closed vessel, vertically oriented, having a critical region at the bottom, a lower chimney structure extending from the critical region vertically upwardly and surrounded by heat exchanger coils, to a baffle region above which is located an upper chimney structure containing a catalyst functioning to recombine radiolyticallydissociated moderator gages. In operation the liquid fuel circulates solely by convection from the critical region upwardly through the lower chimney and then downwardly through the heat exchanger to return to the critical region. The gases formed by radiolytic- dissociation of the moderator are carried upwardly with the circulating liquid fuel and past the baffle into the region of the upper chimney where they are recombined by the catalyst and condensed, thence returning through the heat exchanger to the critical region.

A scaling law for the critical current of Nb3Sn stands based on strong-coupling theory of superconductivity

NASA Astrophysics Data System (ADS)

Oh, Sangjun; Kim, Keeman

2006-02-01

We study the transition temperature Tc, the thermodynamic critical field Bc, and the upper critical field Bc2 of Nb3Sn with Eliashberg theory of strongly coupled superconductors using the Einstein spectrum α2(ω)F(ω)=λ<ω2>1/2δ(ω-<ω2>1/2). The strain dependences of λ(ɛ) and <ω2>1/2(V) are introduced from the empirical strain dependence of Tc(V) for three model cases. It is found that the empirical relation Tc(V)/Tc(0)=[Bc2(4.2 K,V)/Bc2(4.2 K,0)]1/w (w~3) is mainly due to the low-energy-phonon mode softening. We derive analytic expressions for the strain and temperature dependences of Bc(T,V) and Bc2(T,V) and the Ginzburg-Landau parameter κ(T,V) from the numerical calculation results. The Summers refinement on the temperature dependence of κ(T) shows deviation from our calculation results. We propose a unified scaling law of flux pinning in Nb3Sn strands in the form of the Kramer model with the analytic expressions of Bc2(T,V) and κ(T,V) derived in this work. It is shown that the proposed scaling law gives a reasonable fit to the reported data with only eight fitting parameters.

Superconducting and charge density wave transition in single crystalline LaPt2Si2

NASA Astrophysics Data System (ADS)

Gupta, Ritu; Dhar, S. K.; Thamizhavel, A.; Rajeev, K. P.; Hossain, Z.

2017-06-01

We present results of our comprehensive studies on single crystalline LaPt2Si2. Pronounced anomaly in electrical resistivity and heat capacity confirms the bulk nature of superconductivity (SC) and charge density wave (CDW) transition in the single crystals. While the charge density wave transition temperature is lower, the superconducting transition temperature is higher in single crystal compared to the polycrystalline sample. This result confirms the competing nature of CDW and SC. Another important finding is the anomalous temperature dependence of upper critical field H C2(T). We also report the anisotropy in the transport and magnetic measurements of the single crystal.

Vertical Distribution of Pasteuria penetrans Parasitizing Meloidogyne incognita on Pittosporum tobira in Florida.

PubMed

Baidoo, Richard; Mengistu, Tesfamariam Mekete; Brito, Janete A; McSorley, Robert; Stamps, Robert H; Crow, William T

2017-09-01

Pasteuria penetrans is considered as the primary agent responsible for soil suppressiveness to root-knot nematodes widely distributed in many agricultural fields. A preliminary survey on a Pittosporum tobira field where the grower had experienced a continuous decline in productivity caused by Meloidogyne incognita showed that the nematode was infected with Pasteuria penetrans . For effective control of the nematode, the bacterium and the host must coexist in the same root zone. The vertical distribution of Pasteuria penetrans and its relationship with the nematode host in the soil was investigated to identify (i) the vertical distribution of P. penetrans endospores in an irrigated P. tobira field and (ii) the relationship among P. penetrans endospore density, M. incognita J2 population density, and host plant root distribution over time. Soil bioassays revealed that endospore density was greater in the upper 18 cm of the top soil compared with the underlying depths. A correlation analysis showed that the endospore density was positively related to the J2 population density and host plant root distribution. Thus, the vertical distribution of P. penetrans was largely dependent on its nematode host which in turn was determined by the distribution of the host plant roots. The Pasteuria was predominant mostly in the upper layers of the soil where their nematode host and the plant host roots are abundant, a factor which may be a critical consideration when using P. penetrans as a nematode biological control agent.

Vertical Distribution of Pasteuria penetrans Parasitizing Meloidogyne incognita on Pittosporum tobira in Florida

PubMed Central

Baidoo, Richard; Mengistu, Tesfamariam Mekete; Brito, Janete A.; McSorley, Robert; Stamps, Robert H.; Crow, William T.

2017-01-01

Pasteuria penetrans is considered as the primary agent responsible for soil suppressiveness to root-knot nematodes widely distributed in many agricultural fields. A preliminary survey on a Pittosporum tobira field where the grower had experienced a continuous decline in productivity caused by Meloidogyne incognita showed that the nematode was infected with Pasteuria penetrans. For effective control of the nematode, the bacterium and the host must coexist in the same root zone. The vertical distribution of Pasteuria penetrans and its relationship with the nematode host in the soil was investigated to identify (i) the vertical distribution of P. penetrans endospores in an irrigated P. tobira field and (ii) the relationship among P. penetrans endospore density, M. incognita J2 population density, and host plant root distribution over time. Soil bioassays revealed that endospore density was greater in the upper 18 cm of the top soil compared with the underlying depths. A correlation analysis showed that the endospore density was positively related to the J2 population density and host plant root distribution. Thus, the vertical distribution of P. penetrans was largely dependent on its nematode host which in turn was determined by the distribution of the host plant roots. The Pasteuria was predominant mostly in the upper layers of the soil where their nematode host and the plant host roots are abundant, a factor which may be a critical consideration when using P. penetrans as a nematode biological control agent. PMID:29062154

High transport current superconductivity in powder-in-tube Ba0.6K0.4Fe2As2 tapes at 27 T

NASA Astrophysics Data System (ADS)

Huang, He; Yao, Chao; Dong, Chiheng; Zhang, Xianping; Wang, Dongliang; Cheng, Zhe; Li, Jianqi; Awaji, Satoshi; Wen, Haihu; Ma, Yanwei

2018-01-01

The high upper critical field and low anisotropy of iron-based superconductors (IBS) make them particularly attractive for high-field applications, especially for the construction of next-generation nuclear magnetic resonance spectrometers, particle accelerators and high-field magnets. However, for practical use it is essential to make IBS materials into wire and tape conductors with sufficient current carrying capability, which is limited by misaligned grains inside the conductors. Here, based on a simple and low-cost powder-in-tube (PIT) method, we demonstrate a high transport critical current density (J c) reaching 1.5 × 105 A cm-2 (I c = 437 A) at 4.2 K and 10 T in Ba0.6K0.4Fe2As2 (Ba-122) tapes by texturing the grain orientation with optimized hot-press technique. The transport J c measured at 4.2 K under high magnetic fields of 27 T is still on the level of 5.5 × 104 A cm-2. Moreover, at 20 K and 5 T the transport J c is also as high as 5.4 × 104 A cm-2, showing a promising application potential in moderate temperature range which can be reached by liquid hydrogen or cryogenic cooling. All these J c values are the highest ever reported for IBS wires and tapes. The high-performance PIT Ba-122 tapes in this work suggest IBS to be a strong potential competitor of cuprate superconductors for the race of high-field applications in the future.

Perception of Words and Non-Words in the Upper and Lower Visual Fields

ERIC Educational Resources Information Center

Darker, Iain T.; Jordan, Timothy R.

2004-01-01

The findings of previous investigations into word perception in the upper and the lower visual field (VF) are variable and may have incurred non-perceptual biases caused by the asymmetric distribution of information within a word, an advantage for saccadic eye-movements to targets in the upper VF and the possibility that stimuli were not projected…

Low Cost, Upper Stage-Class Propulsion

NASA Technical Reports Server (NTRS)

Vickers, John

2015-01-01

The low cost, upper stage-class propulsion (LCUSP) element will develop a high strength copper alloy additive manufacturing (AM) process as well as critical components for an upper stage-class propulsion system that will be demonstrated with testing. As manufacturing technologies have matured, it now appears possible to build all the major components and subsystems of an upper stage-class rocket engine for substantially less money and much faster than traditionally done. However, several enabling technologies must be developed before that can happen. This activity will address these technologies and demonstrate the concept by designing, manufacturing, and testing the critical components of a rocket engine. The processes developed and materials' property data will be transitioned to industry upon completion of the activity. Technologies to enable the concept are AM copper alloy process development, AM post-processing finishing to minimize surface roughness, AM material deposition on existing copper alloy substrate, and materials characterization.

Cascades on a stochastic pulse-coupled network

NASA Astrophysics Data System (ADS)

Wray, C. M.; Bishop, S. R.

2014-09-01

While much recent research has focused on understanding isolated cascades of networks, less attention has been given to dynamical processes on networks exhibiting repeated cascades of opposing influence. An example of this is the dynamic behaviour of financial markets where cascades of buying and selling can occur, even over short timescales. To model these phenomena, a stochastic pulse-coupled oscillator network with upper and lower thresholds is described and analysed. Numerical confirmation of asynchronous and synchronous regimes of the system is presented, along with analytical identification of the fixed point state vector of the asynchronous mean field system. A lower bound for the finite system mean field critical value of network coupling probability is found that separates the asynchronous and synchronous regimes. For the low-dimensional mean field system, a closed-form equation is found for cascade size, in terms of the network coupling probability. Finally, a description of how this model can be applied to interacting agents in a financial market is provided.

Cascades on a stochastic pulse-coupled network

PubMed Central

Wray, C. M.; Bishop, S. R.

2014-01-01

While much recent research has focused on understanding isolated cascades of networks, less attention has been given to dynamical processes on networks exhibiting repeated cascades of opposing influence. An example of this is the dynamic behaviour of financial markets where cascades of buying and selling can occur, even over short timescales. To model these phenomena, a stochastic pulse-coupled oscillator network with upper and lower thresholds is described and analysed. Numerical confirmation of asynchronous and synchronous regimes of the system is presented, along with analytical identification of the fixed point state vector of the asynchronous mean field system. A lower bound for the finite system mean field critical value of network coupling probability is found that separates the asynchronous and synchronous regimes. For the low-dimensional mean field system, a closed-form equation is found for cascade size, in terms of the network coupling probability. Finally, a description of how this model can be applied to interacting agents in a financial market is provided. PMID:25213626

One-per-mil tumescent technique for upper extremity surgeries: broadening the indication.

PubMed

Prasetyono, Theddeus O H; Biben, Johannes A

2014-01-01

We studied the effect of 1:1,000,000 epinephrine concentration (1 per mil) to attain a bloodless operative field in hand and upper extremity surgery and to explore its effectiveness and safety profile. This retrospective observational study enrolled 45 consecutive patients with 63 operative fields consisting of various hand and upper extremity problems. One-per-mil solution was injected into the operative field with tumescent technique to create a bloodless operating field without tourniquet. The solution was formulated by adding a 1:1,000,000 concentration of epinephrine and 100 mg of lidocaine into saline solution to form 50 mL of tumescent solution. Observation was performed on the clarity of the operative field, which we described as totally bloodless, minimal bleeding, acceptable bleeding, or bloody. The volume of tumescent solution injected, duration of surgery, and surgical outcome were also reviewed. The tumescent technique with 1-per-mil solution achieved 29% totally bloodless, 48% minimal bleeding, 22% acceptable bleeding, and 2% bloody operative fields in cases that included burn contracture and congenital hand and upper extremity surgeries. One-per-mil tumescent solution created a clear operative field in hand and upper extremity surgery. It proved safe and effective for a wide range of indications. Therapeutic IV. Copyright © 2014 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Stabilization of composition fluctuations in mixed membranes by hybrid lipids

NASA Astrophysics Data System (ADS)

Safran, Samuel; Palmieri, Benoit

2013-03-01

A ternary mixture model is proposed to describe composition fluctuations in mixed membranes composed of saturated, unsaturated and hybrid lipids. The asymmetric hybrid lipid has one saturated and one unsaturated hydrocarbon chain and it can reduce the packing incompatibility between saturated and unsaturated lipids. A methodology to recast the free-energy of the lattice in terms of a continuous isotropic field theory is proposed and used to analyze composition fluctuations above the critical temperature. The effect of hybrid lipids on fluctuations domains rich in saturated/unsaturated lipids is predicted. The correlation length of such fluctuations decreases significantly with increasing amounts of hybrids even if the temperature is maintained close to the critical temperature. This provides an upper bound for the domain sizes expected in rafts stabilized by hybrids, above the critical temperature. When the hybrid composition of the membrane is increased further, a crossover value is found above which ``stripe-like'' fluctuations are observed. The wavelength of these fluctuations decreases with increasing hybrid fraction and tends toward a molecular size in a membrane that contains only hybrids.

Nonequilibrium quantum mechanics: A "hot quantum soup" of paramagnons

NASA Astrophysics Data System (ADS)

Scammell, H. D.; Sushkov, O. P.

2017-01-01

Motivated by recent measurements of the lifetime (decay width) of paramagnons in quantum antiferromagnet TlCuCl3, we investigate paramagnon decay in a heat bath and formulate an appropriate quantum theory. Our formulation can be split into two regimes: (i) a nonperturbative, "hot quantum soup" regime where the paramagnon width is comparable to its energy; (ii) a usual perturbative regime where the paramagnon width is significantly lower than its energy. Close to the Neel temperature, the paramagnon width becomes comparable to its energy and falls into the hot quantum soup regime. To describe this regime, we develop a new finite frequency, finite temperature technique for a nonlinear quantum field theory; the "golden rule of quantum kinetics." The formulation is generic and applicable to any three-dimensional quantum antiferromagnet in the vicinity of a quantum critical point. Specifically, we apply our results to TlCuCl3 and find agreement with experimental data. Additionally, we show that logarithmic running of the coupling constant in the upper critical dimension changes the commonly accepted picture of the quantum disordered and quantum critical regimes.

Two-gap superconductivity in Mo8Ga41 and its evolution upon vanadium substitution

NASA Astrophysics Data System (ADS)

Verchenko, V. Yu.; Khasanov, R.; Guguchia, Z.; Tsirlin, A. A.; Shevelkov, A. V.

2017-10-01

Zero-field and transverse-field muon spin rotation/relaxation (μ SR ) experiments were undertaken in order to elucidate the microscopic properties of a strongly coupled superconductor Mo8Ga41 with Tc=9.8 K. The upper critical field extracted from the transverse-field μ SR data exhibits significant reduction with respect to the data from thermodynamic measurements indicating the coexistence of two independent length scales in the superconducting state. Accordingly, the temperature-dependent magnetic penetration depth of Mo8Ga41 is described using a model in which two s wave superconducting gaps are assumed. A V for Mo substitution in the parent compound leads to the complete suppression of one superconducting gap, and Mo7VGa41 is well described within the single s wave gap scenario. The reduction in the superfluid density and the evolution of the low-temperature resistivity upon V substitution indicate the emergence of a competing state in Mo7VGa41 that may be responsible for the closure of one of the superconducting gaps.

Effect of Ce Substitution on the Magnetoresistivity and Flux Pinning Energy of the Bi2Sr2Ca1- x Ce x Cu2O8+ δ Superconductors

NASA Astrophysics Data System (ADS)

Özçelik, B.; Kaya, C.; Gündoğmuş, H.; Sotelo, A.; Madre, M. A.

2014-02-01

In this study, the effect of Ce doping on the properties of Bi2Sr2Ca1- x Ce x Cu2O8+ δ ceramic superconductors, with x=0.0, 0.01, 0.05, 0.1, and 0.25, has been investigated. Samples' precursors were prepared using the conventional solid state method and subsequently textured using the Laser Floating Zone technique. The magnetoresistance measurements were studied under various applied magnetic fields. The activation energies, irreversibility fields ( H irr ), upper critical fields ( H c2) and coherence lengths at 0 K ( ξ(0)) were calculated from the resistivity versus temperature ( ρ- T) curves, under DC magnetic fields up to 5 T. The thermally activated flux flow model has been applied in order to calculate the flux pinning energies. The results indicated that H c2(0) varied from 416.19 to 115 T and the flux pinning energies varied from 1.46 to 0.042 eV at 0 T.

Scattering by multiple cylinders located on both sides of an interface

NASA Astrophysics Data System (ADS)

Lee, Siu-Chun

2018-07-01

The solution for scattering by multiple parallel infinite cylinders located in adjacent half spaces with dissimilar refractive index is presented in this paper. The incident radiation is an arbitrarily polarized plane wave propagating in the upper half space in the plane perpendicular to the axis of the cylinders. The formulation of the electromagnetic field vectors utilized Hertz potentials that are expressed in terms of an expansion of cylindrical wave functions. It accounts for the near-field multiple scattering, Fresnel effect at the interface, and interaction between cylinders in both half spaces. Analytical formulas are derived for the electromagnetic field and Poynting vector in the far-field. The present solution provides the theoretical framework for deducing the solutions for scattering by cylinders located on either side of an interface irradiated by a propagating or an evanescent incident wave. Deduction of these solutions from the present formulation is demonstrated. Numerical results are presented to illustrate the frustration of total internal reflection and scattering of light beyond the critical angle by nanocylinders located in either or both half spaces.

Superconducting symmetries and magnetic responses of uranium heavy-fermion systems UBe13 and UPd2Al3

NASA Astrophysics Data System (ADS)

Shimizu, Yusei; Kittaka, Shunichiro; Sakakibara, Toshiro; Aoki, Dai

2018-05-01

Low-temperature thermodynamic investigation for UBe13 and UPd2Al3 were performed in order to gain insight into their unusual ground states of 5 f electrons. Our heat-capacity data for the cubic UBe13 strongly suggest that nodal quasiparticles are absent and its superconducting (SC) gap is fully open over the Fermi surface. Moreover, two unusual thermodynamic anomalies are also observed in UBe13 at ∼ 3 T and ∼ 9 T; the lower-field anomaly is seen only in the SC mixed state by dc magnetization M (H) as well as heat-capacity C (H) , while the higher-field anomaly appears for C (H) in the normal phase above the upper critical field. On the other hand, field-orientation dependence of the heat capacity in the hexagonal UPd2Al3 shows a significantly anisotropic behavior of C (H) ∝H 1 / 2 , reflecting the nodal gap structure of this system. Our result strongly suggests the presence of a horizontal line node on the Fermi surface with heavy effective mass in UPd2Al3.

Upper South Platte Watershed Protection and Restoration Project

Treesearch

Steve Culver; Cindy Dean; Fred Patten; Jim Thinnes

2001-01-01

The Upper South Platte Basin is a critical watershed in Colorado. Nearly 80 percent of the water used by the 1.5 million Denver metropolitan residents comes from or is transmitted through this river drainage. The Colorado Unified Watershed Assessment identified the Upper South Platte River as a Category 1 watershed in need of restoration. Most of the river basin is...

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…

Assessment of impact of mass movements on the upper Tayyah valley's bridge along Shear escarpment highway, Asir region (Saudi Arabia) using remote sensing data and field investigation

NASA Astrophysics Data System (ADS)

Youssef, A. M.; Al-Kathery, M.; Pradhan, B.

2015-01-01

Escarpment highways, roads and mountainous areas in Saudi Arabia are facing landslide hazards that are frequently occurring from time to time causing considerable damage to these areas. Shear escarpment highway is located in the north of the Abha city. It is the most important escarpment highway in the area, where all the light and heavy trucks and vehicle used it as the only corridor that connects the coastal areas in the western part of the Saudi Arabia with the Asir and Najran Regions. More than 10 000 heavy trucks and vehicles use this highway every day. In the upper portion of Tayyah valley of Shear escarpment highway, there are several landslide and erosion potential zones that affect the bridges between tunnel 7 and 8 along the Shear escarpment Highway. In this study, different types of landslides and erosion problems were considered to access their impacts on the upper Tayyah valley's bridge along Shear escarpment highway using remote sensing data and field investigation. These landslides and erosion problems have a negative impact on this section of the highway. Results indicate that the areas above the highway and bridge level between bridge 7 and 8 have different landslides including planar, circular, rockfall failures and debris flows. In addition, running water through the gullies cause different erosional (scour) features between and surrounding the bridge piles and culverts. A detailed landslides and erosion features map was created based on intensive field investigation (geological, geomorphological, and structural analysis), and interpretation of Landsat image 15 m and high resolution satellite image (QuickBird 0.61 m), shuttle radar topography mission (SRTM 90 m), geological and topographic maps. The landslides and erosion problems could exhibit serious problems that affect the stability of the bridge. Different mitigation and remediation strategies have been suggested to these critical sites to minimize and/or avoid these problems in the future.

The generalization of upper atmospheric wind and temperature based on the Voigt line shape profile.

PubMed

Zhang, Chunmin; He, Jian

2006-12-25

The principle of probing the upper atmospheric wind field, which is the Voigt profile spectral line shape, is presented for the first time. By the Fourier Transform of Voigt profile, with the Imaging Spectroscope and the Doppler effect of electromagnetic wave, the distribution and calculation formulae of the velocity field, temperature field, and pressure field of the upper atmosphere wind field are given. The probed source is the two major aurora emission lines originated from the metastable O(1S) and O(1D) at 557.7nm and 630.0nm. From computer simulation and error analysis, the Voigt profile, which is the correlation of the Gaussian profile and Lorentzian profile, is closest to the actual airglow emission lines.

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

Monthly mean large-scale analyses of upper-tropospheric humidity and wind field divergence derived from three geostationary satellites

NASA Technical Reports Server (NTRS)

Schmetz, Johannes; Menzel, W. Paul; Velden, Christopher; Wu, Xiangqian; Vandeberg, Leo; Nieman, Steve; Hayden, Christopher; Holmlund, Kenneth; Geijo, Carlos

1995-01-01

This paper describes the results from a collaborative study between the European Space Operations Center, the European Organization for the Exploitation of Meteorological Satellites, the National Oceanic and Atmospheric Administration, and the Cooperative Institute for Meteorological Satellite Studies investigating the relationship between satellite-derived monthly mean fields of wind and humidity in the upper troposphere for March 1994. Three geostationary meteorological satellites GOES-7, Meteosat-3, and Meteosat-5 are used to cover an area from roughly 160 deg W to 50 deg E. The wind fields are derived from tracking features in successive images of upper-tropospheric water vapor (WV) as depicted in the 6.5-micron absorption band. The upper-tropospheric relative humidity (UTH) is inferred from measured water vapor radiances with a physical retrieval scheme based on radiative forward calculations. Quantitative information on large-scale circulation patterns in the upper-troposphere is possible with the dense spatial coverage of the WV wind vectors. The monthly mean wind field is used to estimate the large-scale divergence; values range between about-5 x 10(exp -6) and 5 x 10(exp 6)/s when averaged over a scale length of about 1000-2000 km. The spatial patterns of the UTH field and the divergence of the wind field closely resemble one another, suggesting that UTH patterns are principally determined by the large-scale circulation. Since the upper-tropospheric humidity absorbs upwelling radiation from lower-tropospheric levels and therefore contributes significantly to the atmospheric greenhouse effect, this work implies that studies on the climate relevance of water vapor should include three-dimensional modeling of the atmospheric dynamics. The fields of UTH and WV winds are useful parameters for a climate-monitoring system based on satellite data. The results from this 1-month analysis suggest the desirability of further GOES and Meteosat studies to characterize the changes in the upper-tropospheric moisture sources and sinks over the past decade.

On the assessment of coordination between upper extremities: towards a common language between rehabilitation engineers, clinicians and neuroscientists.

PubMed

Shirota, Camila; Jansa, Jelka; Diaz, Javier; Balasubramanian, Sivakumar; Mazzoleni, Stefano; Borghese, N Alberto; Melendez-Calderon, Alejandro

2016-09-08

Well-developed coordination of the upper extremities is critical for function in everyday life. Interlimb coordination is an intuitive, yet subjective concept that refers to spatio-temporal relationships between kinematic, kinetic and physiological variables of two or more limbs executing a motor task with a common goal. While both the clinical and neuroscience communities agree on the relevance of assessing and quantifying interlimb coordination, rehabilitation engineers struggle to translate the knowledge and needs of clinicians and neuroscientists into technological devices for the impaired. The use of ambiguous definitions in the scientific literature, and lack of common agreement on what should be measured, present large barriers to advancements in this area. Here, we present the different definitions and approaches to assess and quantify interlimb coordination in the clinic, in motor control studies, and by state-of-the-art robotic devices. We then propose a taxonomy of interlimb activities and give recommendations for future neuroscience-based robotic- and sensor-based assessments of upper limb function that are applicable to the everyday clinical practice. We believe this is the first step towards our long-term goal of unifying different fields and help the generation of more consistent and effective tools for neurorehabilitation.

Literature Review on Needs of Upper Limb Prosthesis Users.

PubMed

Cordella, Francesca; Ciancio, Anna Lisa; Sacchetti, Rinaldo; Davalli, Angelo; Cutti, Andrea Giovanni; Guglielmelli, Eugenio; Zollo, Loredana

2016-01-01

The loss of one hand can significantly affect the level of autonomy and the capability of performing daily living, working and social activities. The current prosthetic solutions contribute in a poor way to overcome these problems due to limitations in the interfaces adopted for controlling the prosthesis and to the lack of force or tactile feedback, thus limiting hand grasp capabilities. This paper presents a literature review on needs analysis of upper limb prosthesis users, and points out the main critical aspects of the current prosthetic solutions, in terms of users satisfaction and activities of daily living they would like to perform with the prosthetic device. The ultimate goal is to provide design inputs in the prosthetic field and, contemporary, increase user satisfaction rates and reduce device abandonment. A list of requirements for upper limb prostheses is proposed, grounded on the performed analysis on user needs. It wants to (i) provide guidelines for improving the level of acceptability and usefulness of the prosthesis, by accounting for hand functional and technical aspects; (ii) propose a control architecture of PNS-based prosthetic systems able to satisfy the analyzed user wishes; (iii) provide hints for improving the quality of the methods (e.g., questionnaires) adopted for understanding the user satisfaction with their prostheses.

Literature Review on Needs of Upper Limb Prosthesis Users

PubMed Central

Cordella, Francesca; Ciancio, Anna Lisa; Sacchetti, Rinaldo; Davalli, Angelo; Cutti, Andrea Giovanni; Guglielmelli, Eugenio; Zollo, Loredana

2016-01-01

The loss of one hand can significantly affect the level of autonomy and the capability of performing daily living, working and social activities. The current prosthetic solutions contribute in a poor way to overcome these problems due to limitations in the interfaces adopted for controlling the prosthesis and to the lack of force or tactile feedback, thus limiting hand grasp capabilities. This paper presents a literature review on needs analysis of upper limb prosthesis users, and points out the main critical aspects of the current prosthetic solutions, in terms of users satisfaction and activities of daily living they would like to perform with the prosthetic device. The ultimate goal is to provide design inputs in the prosthetic field and, contemporary, increase user satisfaction rates and reduce device abandonment. A list of requirements for upper limb prostheses is proposed, grounded on the performed analysis on user needs. It wants to (i) provide guidelines for improving the level of acceptability and usefulness of the prosthesis, by accounting for hand functional and technical aspects; (ii) propose a control architecture of PNS-based prosthetic systems able to satisfy the analyzed user wishes; (iii) provide hints for improving the quality of the methods (e.g., questionnaires) adopted for understanding the user satisfaction with their prostheses. PMID:27242413

The path integral on the Poincaré upper half-plane with a magnetic field and for the Morse potential

NASA Astrophysics Data System (ADS)

Grosche, Christian

1988-10-01

Rigorous path integral treatments on the Poincaré upper half-plane with a magnetic field and for the Morse potential are presented. The calculation starts with the path integral on the Poincaré upper half-plane with a magnetic field. By a Fourier expansion and a non-linear transformation this problem is reformulated in terms of the path integral for the Morse potential. This latter problem can be reduced by an appropriate space-time transformation to the path integral for the harmonic oscillator with generalised angular momentum, a technique which has been developed in recent years. The well-known solution for the last problem enables one to give explicit expressions for the Feynman kernels for the Morse potential and for the Poincaré upper half-plane with magnetic field, respectively. The wavefunctions and the energy spectrum for the bound and scattering states are given, respectively.

Social class and family size as determinants of attributed machismo, femininity, and family planning: a field study in two South American communities.

PubMed

Nicassio, P M

1977-12-01

A study was conducted to determine the way in which stereotypes of machismo and femininity are associated with family size and perceptions of family planning. A total of 144 adults, male and female, from a lower class and an upper middle class urban area in Colombia were asked to respond to photographs of Colombian families varying in size and state of completeness. The study illustrated the critical role of sex-role identity and sex-role organization as variables having an effect on fertility. The lower-class respondents described parents in the photographs as significantly more macho or feminine because of their children than the upper-middle-class subjects did. Future research should attempt to measure when this drive to sex-role identity is strongest, i.e., when men and women are most driven to reproduce in order to "prove" themselves. Both lower- and upper-middle-class male groups considered male dominance in marriage to be directly linked with family size. Perceptions of the use of family planning decreased linearly with family size for both social groups, although the lower-class females attributed more family planning to spouses of large families than upper-middle-class females. It is suggested that further research deal with the ways in which constructs of machismo and male dominance vary between the sexes and among socioeconomic groups and the ways in which they impact on fertility.

Monitoring tropical cyclone intensity using wind fields derived from short-interval satellite images

NASA Technical Reports Server (NTRS)

Rodgers, E. B.; Gentry, R. C.

1981-01-01

Rapid scan visible images from the Visible Infrared Spin Scan Radiometer sensor on board SMS-2 and GOES-1 were used to derive high resolution upper and lower tropospheric environmental wind fields around three western Atlantic tropical cyclones (1975-78). These wind fields were used to derive upper and lower tropospheric areal mean relative vorticity and their differences, the net relative angular momentum balance and upper tropospheric mass outflow. These kinematic parameters were shown by studies using composite rawinsonde data to be strongly related to tropical cyclone formation and intensity changes. Also, the role of forced synoptic scale subsidence in tropical cyclone formation was examined. The studies showed that satellite-derived lower and upper tropospheric wind fields can be used to monitor and possibly predict tropical cyclone formation and intensity changes. These kinematic analyses showed that future changes in tropical cyclone intensity are mainly related to the "spin-up" of the storms by the net horizontal transport of relative angular momentum caused by convergence of cyclonic vorticity in the lower troposphere and to a lesser extent the divergence of anticyclone vorticity in the upper troposphere.

The upper bound of abutment scour defined by selected laboratory and field data

USGS Publications Warehouse

Benedict, Stephen; Caldwell, Andral W.

2015-01-01

The U.S. Geological Survey, in cooperation with the South Carolina Department of Transportation, conducted a field investigation of abutment scour in South Carolina and used that data to develop envelope curves defining the upper bound of abutment scour. To expand upon this previous work, an additional cooperative investigation was initiated to combine the South Carolina data with abutment-scour data from other sources and evaluate the upper bound of abutment scour with the larger data set. To facilitate this analysis, a literature review was made to identify potential sources of published abutment-scour data, and selected data, consisting of 446 laboratory and 331 field measurements, were compiled for the analysis. These data encompassed a wide range of laboratory and field conditions and represent field data from 6 states within the United States. The data set was used to evaluate the South Carolina abutment-scour envelope curves. Additionally, the data were used to evaluate a dimensionless abutment-scour envelope curve developed by Melville (1992), highlighting the distinct difference in the upper bound for laboratory and field data. The envelope curves evaluated in this investigation provide simple but useful tools for assessing the potential maximum abutment-scour depth in the field setting.

Coexistence of multiphase superconductivity and ferromagnetism in lithiated iron selenide hydroxide [(L i1 -xF ex) OH ]FeSe

NASA Astrophysics Data System (ADS)

Urban, Christian; Valmianski, Ilya; Pachmayr, Ursula; Basaran, Ali C.; Johrendt, Dirk; Schuller, Ivan K.

2018-01-01

We present experimental evidence for (a) multiphase superconductivity and (b) coexistence of magnetism and superconductivity in a single structural phase of lithiated iron selenide hydroxide [(L i1 -xF ex )OH]FeSe. Magnetic field modulated microwave spectroscopy data confirms superconductivity with at least two distinct transition temperatures attributed to well-defined superconducting phases at TSC 1=40 ±2 K and TSC 2=35 ±2 K. Magnetometry data for the upper critical fields reveal a change in the magnetic order (TM=12 K) below TSC 1 and TSC 2 that is consistent with ferromagnetism. This occurs because the superconducting coherence length is much smaller than the structural coherence length, allowing for several different electronic and magnetic states on a single crystallite. The results give insight into the physics of complex multinary materials, where several phenomena governed by different characteristic length scales coexist.

Calorimetric determination of the magnetic phase diagram of underdoped ortho II YBa2Cu3O6.54 single crystals

PubMed Central

Marcenat, C.; Demuer, A.; Beauvois, K.; Michon, B.; Grockowiak, A.; Liang, R.; Hardy, W.; Bonn, D. A.; Klein, T.

2015-01-01

The recent discovery of a charge order in underdoped YBa2Cu3Oy raised the question of the interplay between superconductivity and this competing phase. Understanding the normal state of high-temperature superconductors is now an essential step towards the description of the pairing mechanism in those materials and determining the upper critical field is therefore of fundamental importance. We present here a calorimetric determination of the field–temperature phase diagram in underdoped YBa2Cu3Oy single crystals. We show that the specific heat saturates in high magnetic fields. This saturation is consistent with a normal state without any significant superconducting contribution and a total Sommerfeld coefficient γN∼6.5±1.5 mJ mol−1 K−2 putting strong constraints on the theoretical models for the Fermi surface reconstruction. PMID:26294047

CLASP2: The Chromospheric LAyer Spectro-Polarimeter

NASA Technical Reports Server (NTRS)

Mckenzie, D. E.; Ishikawa, R.; Bueno, J. Trujillo; Auchere, F.; Rachmeler, L.; Kubo, M.; Kobayashi, K.; Winebarger, A.; Bethge, C.; Narukage, N.;

CLASP2: The Chromospheric LAyer Spectro-Polarimeter

NASA Technical Reports Server (NTRS)

McKenzie, D. E.; Ishikawa, R.; Bueno, J. Trujillo; Auchere, F.; Rachmeler, L; Kudo, M.; Kobayashi, K.; Winebarger, A.; Bethge, C.; Narukage, N.;

Polydisperse sphere packing in high dimensions, a search for an upper critical dimension

NASA Astrophysics Data System (ADS)

Morse, Peter; Clusel, Maxime; Corwin, Eric

2012-02-01

The recently introduced granocentric model for polydisperse sphere packings has been shown to be in good agreement with experimental and simulational data in two and three dimensions. This model relies on two effective parameters that have to be estimated from experimental/simulational results. The non-trivial values obtained allow the model to take into account the essential effects of correlations in the packing. Once these parameters are set, the model provides a full statistical description of a sphere packing for a given polydispersity. We investigate the evolution of these effective parameters with the spatial dimension to see if, in analogy with the upper critical dimension in critical phenomena, there exists a dimension above which correlations become irrelevant and the model parameters can be fixed a priori as a function of polydispersity. This would turn the model into a proper theory of polydisperse sphere packings at that upper critical dimension. We perform infinite temperature quench simulations of frictionless polydisperse sphere packings in dimensions 2-8 using a parallel algorithm implemented on a GPGPU. We analyze the resulting packings by implementing an algorithm to calculate the additively weighted Voronoi diagram in arbitrary dimension.

Superconductivity in two-dimensional NbSe2 field effect transistors

NASA Astrophysics Data System (ADS)

El-Bana, Mohammed S.; Wolverson, Daniel; Russo, Saverio; Balakrishnan, Geetha; Mck Paul, Don; Bending, Simon J.

2013-12-01

We describe investigations of superconductivity in few molecular layer NbSe2 field effect transistors. While devices fabricated from NbSe2 flakes less than eight molecular layers thick did not conduct, thicker flakes were superconducting with an onset Tc that was only slightly depressed from the bulk value for 2H-NbSe2 (7.2 K). The resistance typically showed a small, sharp high temperature transition followed by one or more broader transitions which usually ended in a wide tail to zero resistance at low temperatures. We speculate that these multiple resistive transitions are related to disorder in the layer stacking. The behavior of several flakes has been characterized as a function of temperature, applied field and back-gate voltage. We find that the conductance in the normal state and transition temperature depend weakly on the gate voltage, with both conductivity and Tc decreasing as the electron concentration is increased. The application of a perpendicular magnetic field allows the evolution of different resistive transitions to be tracked and values of the zero temperature upper critical field, Hc2(0), and coherence length, ξ(0), to be independently estimated. Our results are analyzed in terms of available theories for these phenomena.

The effect of growth temperature on the irreversibility line of MPMG YBCO bulk with Y2O3 layer

NASA Astrophysics Data System (ADS)

Kurnaz, Sedat; Çakır, Bakiye; Aydıner, Alev

2017-07-01

In this study, three kinds of YBCO samples which are named Y1040, Y1050 and Y1060 were fabricated by Melt-Powder-Melt-Growth (MPMG) method without a seed crystal. Samples seem to be single crystal. The compacted powders were located on a crucible with a buffer layer of Y2O3 to avoid liquid to spread on the furnace plate and also to support crystal growth. YBCO samples were investigated by magnetoresistivity (ρ-T) and magnetization (M-T) measurements in dc magnetic fields (parallel to c-axis) up to 5 T. Irreversibility fields (Hirr) and upper critical fields (Hc2) were obtained using 10% and 90% criteria of the normal state resistivity value from ρ-T curves. M-T measurements were carried out using the zero field cooling (ZFC) and field cooling (FC) processes to get irreversible temperature (Tirr). Fitting of the irreversibility line results to giant flux creep and vortex glass models were discussed. The results were found to be consistent with the results of the samples fabricated using a seed crystal. At the fabrication of MPMG YBCO, optimized temperature for crystal growth was determined to be around 1050-1060 °C.

Transport properties of epitaxial films for superconductor NbN and half-metallic Heusler alloy Co2MnSi under high magnetic fields

NASA Astrophysics Data System (ADS)

Shigeta, Iduru; Kubota, Takahide; Sakuraba, Yuya; Kimura, Shojiro; Awaji, Satoshi; Takanashi, Koki; Hiroi, Masahiko

2018-05-01

Transport properties were investigated for epitaxial films of superconductor NbN and half-metallic Heusler alloy Co2MnSi under high magnetic fields up to 17 T. The superconducting transition temperature Tc of NbN/Co2MnSi/Au trilayer films was determined to be 16.1 K in the absence of magnetic field. Temperature dependence of the resistivity ρ (T) was measured in both magnetic fields parallel and perpendicular to the surface of NbN/Co2MnSi/Au trilayer films. The activation energy U0 (H) for vortex motion of the trilayer films in both magnetic fields was well fitted above 5 T by the similar model with the exponents in the field dependence of the pinning force density. From the resistivity ρ (T) measurements under high magnetic fields, the upper critical field Hc2 (0) at 0 K was also deduced to be μ0 Hc2 ∥ (0) = 23.2 T for the parallel magnetic filed and μ0 Hc2 ⊥ (0) = 15.8 T for the perpendicular magnetic field, respectively. The experimental results under magnetic fields revealed the superconductivity of the NbN layer was affected by the interplay between the superconducting NbN layer and the half-metallic Co2MnSi layer.

Enstrophy-based proper orthogonal decomposition of flow past rotating cylinder at super-critical rotating rate

NASA Astrophysics Data System (ADS)

Sengupta, Tapan K.; Gullapalli, Atchyut

2016-11-01

Spinning cylinder rotating about its axis experiences a transverse force/lift, an account of this basic aerodynamic phenomenon is known as the Robins-Magnus effect in text books. Prandtl studied this flow by an inviscid irrotational model and postulated an upper limit of the lift experienced by the cylinder for a critical rotation rate. This non-dimensional rate is the ratio of oncoming free stream speed and the surface speed due to rotation. Prandtl predicted a maximum lift coefficient as CLmax = 4π for the critical rotation rate of two. In recent times, evidences show the violation of this upper limit, as in the experiments of Tokumaru and Dimotakis ["The lift of a cylinder executing rotary motions in a uniform flow," J. Fluid Mech. 255, 1-10 (1993)] and in the computed solution in Sengupta et al. ["Temporal flow instability for Magnus-robins effect at high rotation rates," J. Fluids Struct. 17, 941-953 (2003)]. In the latter reference, this was explained as the temporal instability affecting the flow at higher Reynolds number and rotation rates (>2). Here, we analyze the flow past a rotating cylinder at a super-critical rotation rate (=2.5) by the enstrophy-based proper orthogonal decomposition (POD) of direct simulation results. POD identifies the most energetic modes and helps flow field reconstruction by reduced number of modes. One of the motivations for the present study is to explain the shedding of puffs of vortices at low Reynolds number (Re = 60), for the high rotation rate, due to an instability originating in the vicinity of the cylinder, using the computed Navier-Stokes equation (NSE) from t = 0 to t = 300 following an impulsive start. This instability is also explained through the disturbance mechanical energy equation, which has been established earlier in Sengupta et al. ["Temporal flow instability for Magnus-robins effect at high rotation rates," J. Fluids Struct. 17, 941-953 (2003)].

Pathways and pipelines: Self-reported critical experiences for expert and novice geologists

NASA Astrophysics Data System (ADS)

LaDue, N.; Pacheco, H. A.

2011-12-01

The recruitment and retention of geology students has received attention due to pressure from industry to replenish an aging workforce nearing retirement (Gonzales and Keane, 2010). Thorough, qualitative studies have been conducted using critical incident methodology to understand what experiences cause various groups of people to choose careers in the geosciences or geoscience degree programs (Levine et al., 2007; Houlton, 2010). This study both builds upon earlier studies and provides new insights about capacity building in the geosciences. Individuals who have been successfully pipelined into the geosciences ranging from upper-level undergraduates to decades-long professionals, were selected for an expert-novice study about field mapping. All of the 38 participants have field-mapping experience and were selected to achieve a balance of age, gender and experience in the sample and secondarily based on geographic diversity. Participants were asked how they became interested in geology as the last question of an interview about the other tasks during the study. Participants were surficially probed, in contrast to in-depth interviews conducted using critical incident methods. Remarkably, though the interview question was unstructured and open ended, the three persistent themes that emerged are consistent with previous studies of women geologists (Holmes and O'Connell, 2003), under-represented minorities (Levine et al., 2007), and undergraduate geoscience majors (Houlton, 2010): Role or influence of academic experience, influence of and/or connections with people and connections with Earth. Additionally, individual participant comments are well aligned the proposed framework by Kraft et al. (2011) for engaging geoscience students through the affective domain. We suggest that future studies should examine whether these findings are consistent across geologists from sub-domains that are less field-based and involve primarily modeling, or other computer- and lab-based activities.

Ageostrophic winds and vertical motion fields accompanying upper level jet streak propagation during the Red River Valley tornado outbreak

NASA Technical Reports Server (NTRS)

Moore, J. T.; Squires, M. F.

1982-01-01

Preliminary results are shown relating the ageostrophic wind field, through the terms of a semigeostrophic wind equation (assuming adiabatic conditions and the geostrophic momentum approximation) to both air parcel trajectories and their vertical motion fields computed from the parcels' displacement on isentropic surfaces, with respect to pressure. The analysis of results considers both upper-level (324 K) ageostrophic fields and low-level (304 K) fields. Preliminary results tend to support Uccellini and Johnson's (1979) hypothesis concerning upper-level-jet/low-level-jet (ULJ/LLJ) coupling in the exit region of the ULJ. Future plans are described briefly for research intended to clarify the mechanism behind ULJ streak propagation, LLJ development and their relationship to the initiation of severe convection.

Cirrus Cloud Retrieval Using Infrared Sounding Data: Multilevel Cloud Errors.

NASA Astrophysics Data System (ADS)

Baum, Bryan A.; Wielicki, Bruce A.

1994-01-01

In this study we perform an error analysis for cloud-top pressure retrieval using the High-Resolution Infrared Radiometric Sounder (HIRS/2) 15-µm CO2 channels for the two-layer case of transmissive cirrus overlying an overcast, opaque stratiform cloud. This analysis includes standard deviation and bias error due to instrument noise and the presence of two cloud layers, the lower of which is opaque. Instantaneous cloud pressure retrieval errors are determined for a range of cloud amounts (0.1 1.0) and cloud-top pressures (850250 mb). Large cloud-top pressure retrieval errors are found to occur when a lower opaque layer is present underneath an upper transmissive cloud layer in the satellite field of view (FOV). Errors tend to increase with decreasing upper-cloud elective cloud amount and with decreasing cloud height (increasing pressure). Errors in retrieved upper-cloud pressure result in corresponding errors in derived effective cloud amount. For the case in which a HIRS FOV has two distinct cloud layers, the difference between the retrieved and actual cloud-top pressure is positive in all casts, meaning that the retrieved upper-cloud height is lower than the actual upper-cloud height. In addition, errors in retrieved cloud pressure are found to depend upon the lapse rate between the low-level cloud top and the surface. We examined which sounder channel combinations would minimize the total errors in derived cirrus cloud height caused by instrument noise and by the presence of a lower-level cloud. We find that while the sounding channels that peak between 700 and 1000 mb minimize random errors, the sounding channels that peak at 300—500 mb minimize bias errors. For a cloud climatology, the bias errors are most critical.

Unified Scaling Law for flux pinning in practical superconductors: II. Parameter testing, scaling constants, and the Extrapolative Scaling Expression

NASA Astrophysics Data System (ADS)

Ekin, Jack W.; Cheggour, Najib; Goodrich, Loren; Splett, Jolene; Bordini, Bernardo; Richter, David

2016-12-01

A scaling study of several thousand Nb3Sn critical-current (I c) measurements is used to derive the Extrapolative Scaling Expression (ESE), a relation that can quickly and accurately extrapolate limited datasets to obtain full three-dimensional dependences of I c on magnetic field (B), temperature (T), and mechanical strain (ɛ). The relation has the advantage of being easy to implement, and offers significant savings in sample characterization time and a useful tool for magnet design. Thorough data-based analysis of the general parameterization of the Unified Scaling Law (USL) shows the existence of three universal scaling constants for practical Nb3Sn conductors. The study also identifies the scaling parameters that are conductor specific and need to be fitted to each conductor. This investigation includes two new, rare, and very large I c(B,T,ɛ) datasets (each with nearly a thousand I c measurements spanning magnetic fields from 1 to 16 T, temperatures from ˜2.26 to 14 K, and intrinsic strains from -1.1% to +0.3%). The results are summarized in terms of the general USL parameters given in table 3 of Part 1 (Ekin J W 2010 Supercond. Sci. Technol. 23 083001) of this series of articles. The scaling constants determined for practical Nb3Sn conductors are: the upper-critical-field temperature parameter v = 1.50 ± 0.04 the cross-link parameter w = 3.0 ± 0.3 and the strain curvature parameter u = 1.7 ± 0.1 (from equation (29) for b c2(ɛ) in Part 1). These constants and required fitting parameters result in the ESE relation, given by I c ( B , T , ɛ ) B = C [ b c 2 ( ɛ ) ] s ( 1 - t 1.5 ) η - μ ( 1 - t 2 ) μ b p ( 1 - b ) q with reduced magnetic field b ≡ B/B c2*(T,ɛ) and reduced temperature t ≡ T/T c*(ɛ), where: B c 2 * ( T , ɛ ) = B c 2 * ( 0 , 0 ) ( 1 - t 1.5 ) b c 2 ( ɛ ) T c * ( ɛ ) = T c * ( 0 ) [ b c 2 ( ɛ ) ] 1/3 and fitting parameters: C, B c2*(0,0), T c*(0), s, either η or μ (but not both), plus the parameters in the strain function b c2(ɛ). The pinning-force shape parameters p and q are also preferably fitted (simultaneously with the other parameters), but default values p = 0.5 and q = 2.0 also give high fitting accuracy when the range of relative magnetic fields is not extensive. Default values are also essential when the magnetic field data range is insufficient to determine p and q. The scaling constants are remarkably stable (changes less than ˜1%) with respect to different values of p and q, Nb3Sn conductor configurations, magnetic self-field corrections, and pinning-force trim values. The results demonstrate that the scaling of transport critical current holds down to the lowest temperatures measured ˜2.2 K, for both magnetic self-field corrected and uncorrected data. An initial comparison is also made between transport and magnetization scaling data in matched Nb3Sn samples and significant differences are found, especially for the upper critical field B c2*(T,ɛ), which may be a result of inhomogeneous shielding currents. In Part 3 of this topical review series (Ekin J W 2017 Supercond. Sci. Technol. at press), the smallest practical minimum dataset for extrapolating full I c(B,T,ɛ) datasets is derived. Application of the ESE relation is illustrated in several new areas, including full characterization of Nb3Sn conductors from as little as a single I c(B) curve when a few core parameters have been determined for similar conductors.

Rate of progression of total, upper, and lower visual field defects in patients with open-angle glaucoma and high myopia.

PubMed

Yoshino, Takaiko; Fukuchi, Takeo; Togano, Tetsuya; Sakaue, Yuta; Seki, Masaaki; Tanaka, Takayuki; Ueda, Jun

2016-03-01

We evaluated the rate of progression of total, upper, and lower visual field defects in patients with treated primary open-angle glaucoma (POAG) with high myopia (HM). Seventy eyes of 70 POAG patients with HM [≤-8 diopters (D)] were examined. The mean deviation (MD) slope and the upper and lower total deviation (upper TD, lower TD) slopes of the Humphrey Field Analyzer were calculated in patients with high-tension glaucoma (HTG) (>21 mmHg) versus normal-tension glaucoma (NTG) (≤21 mmHg). The mean age of all the patients (29 eyes with HTG and 41 eyes with NTG) was 48.5 ± 9.6 years. The MD slope, and upper and lower TD slopes of the HM group were compared to those of the non-HM group (NHM) (>-8 D) selected from 544 eyes in 325 age-matched POAG patients. In all, 70 eyes with HM and NHM were examined. The mean MD slope was -0.33 ± 0.33 dB/year in the HM, and -0.38 ± 0.49 dB/year in the NHM. There were no statistical differences between the HM and NHM (p = 0.9565). In the comparison of HTG versus NTG patients in both groups, the MD slope, and upper and lower TD slopes were similar. The rate of progression of total, upper, and lower visual field defects was similar among patients with HM and NHM. Although HM is a risk factor for the onset of glaucoma, HM may not be a risk factor for progression of visual field defects as assessed by the progression rate under treatment.

Superconducting and Magnetic Properties of Vanadium/iron Superlattices.

NASA Astrophysics Data System (ADS)

Wong, Hong-Kuen

A novel ultrahigh vacuum evaporator was constructed for the preparation of superlattice samples. The thickness control was much better than an atomic plane. With this evaporator we prepared V/Fe superlattice samples on (0001) sapphire substrates with different thicknesses. All samples showed a good bcc(110) structure. Mossbauer experiments showed that the interface mixing extended a distance of about one atomic plane indicating an almost rectangular composition profile. Because of this we were able to prepare samples with layer thickness approaching one atomic plane. Even with ultrathin Fe layers, the samples are ferromagnetic, at least at lower temperatures. Superparamagnetism and spin glass states were not seen. In the absence of an external field, the magnetic moments lie close to the film plane. In addition to this shape anisotropy, there is some uniaxial anisotropy. No magnetic dead layers have been observed. The magnetic moments within the Fe layers vary little with the distance from the interfaces. At the interfaces the Fe moment is reduced and an antiparallel moment is induced on the vanadium atoms. It is observed that ultrathin Fe layers behave in a 2D fashion when isolated by sufficiently thick vanadium layers; however, on thinning the vanadium layers, a magnetic coupling between the Fe layers has been observed. We also studied the superconducting properties of V/Fe sandwiches and superlattices. In both cases, the Fe layer, a strong pair-breaker, suppresses the superconducting transition temperature consistent with the current knowledge of the magnetic proximity effect. For the sandwiches with thin (thick) vanadium layers, the temperature dependence of the upper critical fields is consistent with the simple theory for a 2D (3D) superconductor. For the superlattices, when the vanadium layer is on the order of the BCS coherence length and the Fe layer is only a few atomic planes thick, a 2D-3D crossover has been observed in the temperature dependence of the parallel upper critical field. This implies the coexistence of superconductivity and ferromagnetism. We observe three dimensional behavior for thinner Fe layers ((TURN)1 atomic plane) and two dimensional behavior for thicker Fe layers (greater than 10 atomic planes).

Selenium capped monolayer NbSe 2 for two-dimensional superconductivity studies

DOE PAGES

Onishi, Seita; Ugeda, Miguel M.; Zhang, Yi; ...

2016-08-01

Superconductivity in monolayer niobium diselenide (NbSe 2) on bilayer graphene is studied by electrical transport. Monolayer NbSe 2 is grown on bilayer graphene by molecular beam epitaxy and capped with a selenium film to avoid degradation in air. The selenium capped samples have T C = 1.9 K. In situ measurements down to 4 K in ultrahigh vacuum show that the effect of the selenium layer on the transport is negligible. Lastly, the superconducting transition and upper critical fields in air exposed and selenium capped samples are compared. Schematic of monolayer NbSe 2/bilayer graphene with selenium capping layer and electricalmore » contacts.« less

New Discoveries Resulted from Lidar Investigation of Middle and Upper Atmosphere Temperature, Composition, Chemistry and Dynamics at McMurdo, Antarctica

NASA Astrophysics Data System (ADS)

Chu, X.; Yu, Z.; Fong, W.; Chen, C.; Huang, W.; Lu, X.; Gardner, C. S.; McDonald, A.; Fuller-Rowell, T. J.; Vadas, S.

2013-12-01

The scientific motivation to explore the neutral properties of the polar middle and upper atmosphere is compelling. Human-induced changes in the Earth's climate system are one of the most challenging social and scientific issues in this century. Besides monitoring climate change, to fully explore neutral-ion coupling in the critical region between 100 and 200 km is an objective of highest priority for the upper atmosphere science community. Meteorological sources of wave energy from the lower atmosphere are responsible for producing significant variability in the upper atmosphere. Energetic particles and fields originating from the magnetosphere regularly alter the state of the ionosphere. These influences converge through the tight coupling between the ionosphere plasma and neutral thermosphere gas in the space-atmosphere interaction region (SAIR). Unfortunately measurements of the neutral thermosphere are woefully incomplete and in critical need to advance our understanding of and ability to predict the SAIR. Lidar measurements of neutral thermospheric winds, temperatures and species can enable these explorations. To help address these issues, in December 2010 we deployed an Fe Boltzmann temperature lidar to McMurdo (77.8S, 166.7E), Antarctica via collaboration between the United States Antarctic Program and Antarctica New Zealand. Since then an extensive dataset (~3000 h) has been collected by this lidar during its first 32 months of operation, leading to several important new discoveries. The McMurdo lidar campaign will continue for another five years to acquiring long-term datasets for polar geospace research. In this paper we provide a comprehensive overview of the lidar campaign and scientific results, emphasizing several new discoveries in the polar middle and upper atmosphere research. In particular, the lidar has detected neutral Fe layers reaching 170 km in altitude, and derived neutral temperature from 30 to 170 km for the first time in the world. Such discoveries may have opened the new door to observing the neutral thermosphere with ground-based instruments. Extreme Fe events in summer were observed and understood as the interesting interactions among the meteoric metal atoms, sub-visible ice particles and energetic particles during aurora precipitation. Furthermore, the McMurdo middle and upper atmosphere is found to be very dynamical, especially in winter when inertia-gravity waves and eastward propagating planetary waves are predominant in the mesosphere and lower thermosphere and in the stratosphere, respectively. Despite small amplitudes below 100 km, the diurnal and semidiurnal tidal amplitudes exhibit fast growth from 100 to 110 km depending on the geomagnetic activities. These observations pose great challenges to our understanding of the Earth's upper atmosphere but also provide excellent opportunities to exploring how the electrodynamics and neutral dynamics work together at this high southern latitude to produce many intriguing geophysical phenomena.

Quantifying the relationship between vehicle interior geometry and child restraint systems.

PubMed

Sherwood, C P; Abdelilah, Y; Crandall, J R

2006-01-01

The prevention of interactions of children or child restraints with other vehicle structures is critical to child passenger safety. Fifteen current vehicles and seven rear and forward facing child restraint systems were measured in an attempt to quantify the available distance between child restraints and these vehicle structures. Rear facing child restraints exhibited such small amounts of clearance that contact would be expected in the majority of frontal crashes. Upper tethers are critical in the prevention of head contact, while head contact is likely when the upper tether is not used.

Intrinsic Magnetic Properties of the Lunar Body

NASA Technical Reports Server (NTRS)

Behannon, Kenneth W.

1968-01-01

Preliminary analysis of magnetic measurements by Explorer 35 in lunar orbit suggested an upper limit of 4 x 10(exp 20) gauss-cm3 for the magnetic moment of the moon. A more detailed analysis of a larger body of Explorer 35 data from measurements in the earth's magnetic tail has subsequently been performed. Reversal of the ambient tail field by 180deg when the moon and spacecraft traverse the neutral sheet permits a separation of permanent and induced field contributions to the total field observed near the moon. When compared to calculated permanent and induced field effects, the results of this analysis lead to new upper limits of 102' gauss-cm3 on the lunar magnetic moment and 4y on the lunar surface field. Limiting the moment induced in the moon by the magnetotail field permits an upper limit of 1.8 to be set on the bulk relative magnetic permeability of the moon.

Disruption of circumstellar discs by large-scale stellar magnetic fields

NASA Astrophysics Data System (ADS)

ud-Doula, Asif; Owocki, Stanley P.; Kee, Nathaniel Dylan

2018-05-01

Spectropolarimetric surveys reveal that 8-10% of OBA stars harbor large-scale magnetic fields, but thus far no such fields have been detected in any classical Be stars. Motivated by this, we present here MHD simulations for how a pre-existing Keplerian disc - like that inferred to form from decretion of material from rapidly rotating Be stars - can be disrupted by a rotation-aligned stellar dipole field. For characteristic stellar and disc parameters of a near-critically rotating B2e star, we find that a polar surface field strength of just 10 G can significantly disrupt the disc, while a field of 100 G, near the observational upper limit inferred for most Be stars, completely destroys the disc over just a few days. Our parameter study shows that the efficacy of this magnetic disruption of a disc scales with the characteristic plasma beta (defined as the ratio between thermal and magnetic pressure) in the disc, but is surprisingly insensitive to other variations, e.g. in stellar rotation speed, or the mass loss rate of the star's radiatively driven wind. The disc disruption seen here for even a modest field strength suggests that the presumed formation of such Be discs by decretion of material from the star would likely be strongly inhibited by such fields; this provides an attractive explanation for why no large-scale fields are detected from such Be stars.

String scattering amplitudes and deformed cubic string field theory

NASA Astrophysics Data System (ADS)

Lai, Sheng-Hong; Lee, Jen-Chi; Lee, Taejin; Yang, Yi

2018-01-01

We study string scattering amplitudes by using the deformed cubic string field theory which is equivalent to the string field theory in the proper-time gauge. The four-string scattering amplitudes with three tachyons and an arbitrary string state are calculated. The string field theory yields the string scattering amplitudes evaluated on the world sheet of string scattering whereas the conventional method, based on the first quantized theory brings us the string scattering amplitudes defined on the upper half plane. For the highest spin states, generated by the primary operators, both calculations are in perfect agreement. In this case, the string scattering amplitudes are invariant under the conformal transformation, which maps the string world sheet onto the upper half plane. If the external string states are general massive states, generated by non-primary field operators, we need to take into account carefully the conformal transformation between the world sheet and the upper half plane. We show by an explicit calculation that the string scattering amplitudes calculated by using the deformed cubic string field theory transform into those of the first quantized theory on the upper half plane by the conformal transformation, generated by the Schwarz-Christoffel mapping.

Conference in Rhetorical Criticism: Address of the Conference and Commended Papers (2nd, Hayward, Calif., May 1967).

ERIC Educational Resources Information Center

Barrett, Harold, Ed.; And Others

At the second annual Cal-State Hayward Conference in Rhetorical Criticism, upper division and graduate students from 17 colleges and universities presented papers on the theory, history, and criticism of rhetoric. Panels of faculty members from the same colleges and universities, serving as editor-critics, judged the six papers in this volume as…

Petroleum geology of the Cusiana Field, Llanos Basin Foothills, Colombia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cazier, E.C.; Hayward, A.B.; Espinosa, G.

1995-10-01

Cusiana field is located in the Llanos Foothills, 150 mi (240km) northeast of Bogota, Colombia. Light oil, gas, and condensate in Cusiana occur at drilling depths that average 15,000 ft (4575 m) in an asymmetric, hanging-wall anticlinal trap 15 mi (25 km) long and 3-4 mi (5-6 km) across, formed during the Miocene-Holocene deformation of the Eastern Cordillera. Top and lateral seals are provided by marine mudstones of the Oligocene Carbonera Group, and support a hydrocarbon column of over 1500 ft (460 m). Biomarker data from the hydrocarbons indicate a marine mudstone source interpreted to be the Turonian-Coniacian Gacheta Formation.more » Over 50% of the reserves occur in upper Eocene Mirador Formation sandstones, which were deposited predominantly in estuarine environments. Additional, deeper reservoirs include estuarine sandstones of the Paleocene Barco Formation and the shallow-marine Santonian-Campanian Upper Guadalupe Sandstone. Porosity in Cusiana is relatively low. Good permeability is retained, however, because the reservoirs are pure quartz-cemented quartzarenites that lack permeability-reducing authigenic clays and carbonate cements. Core and well test analyses indicate matrix permeability, not fracture permeability, provides the high deliverability of Cusiana wells. Cusiana hydrocarbon phases exist in a near-miscible, critical-point state. Reservoir simulation indicates very high liquid hydrocarbon recoveries should be possible from all reservoirs by using the reinjection of produced gas to maintain reservoir pressure and to vaporize residual liquids. The field contains up to 1.5 MSTB of hydrocarbon liquid reserves and 3.4 Tcf of gas.« less

Reaching with cerebral tunnel vision.

PubMed

Rizzo, M; Darling, W

1997-01-01

We studied reaching movements in a 48-year-old man with bilateral lesions of the calcarine cortex which spared the foveal representation and caused severe tunnel vision. Three-dimensional (3D) reconstruction of brain MR images showed no evidence of damage beyond area 18. The patient could not see his hand during reaching movements, providing a unique opportunity to test the role of peripheral visual cues in limb control. Optoelectronic recordings of upper limb movements showed normal hand paths and trajectories to fixated extrinsic targets. There was no slowing, tremor, or ataxia. Self-bound movements were also preserved. Analyses of limb orientation at the endpoints of reaches showed that the patient could transform an extrinsic target's visual coordinates to an appropriate upper limb configuration for target acquisition. There was no disadvantage created by blocking the view of the reaching arm. Moreover, the patient could not locate targets presented in the hemianopic fields by pointing. Thus, residual nonconscious vision or 'blindsight' in the aberrant fields was not a factor in our patient's reaching performance. The findings in this study show that peripheral visual cues on the position and velocity of the moving limb are not critical to the control of goal directed reaches, at least not until the hand is close to target. Other cues such as kinesthetic feedback can suffice. It also appears that the visuomotor transformations for reaching do not take place before area 19 in humans.

High Temperature Superconductivity in Praseodymium Doped (0%, 2%, 4%) in Melt-Textured Y(1-x)Pr(x)Ba2Cu3O(7-delta) Systems

NASA Technical Reports Server (NTRS)

James, Claudell

1995-01-01

A study of the magnetic and structural properties of the alloy Y(1-x)Pr(x)Ba2Cu3O(7-delta) of 0%, 2%, and 4% doping of praseodymium is presented. The resulting oxides of the alloy series are a high-temperature superconductor Y-Ba-Cu-O, which has an orthorhombic superconducting crystal-lattice. Magnetic relaxation studies have been performed on the Y-Pr-Ba-CuO bulk samples for field orientation parallel to the c-axis, using a vibrating sample magnetometer. Relaxation was measured at several temperatures to obtain the irreversible magnetization curves used for the Bean model. Magnetization current densities were derived from the relaxation data. Field and temperature dependence of the logarithmic flux-creep relaxation was measured in critical state. The data indicates that the effective activation energy U(eff) increases with increasing T between 77 K and 86 K. Also, the data shows that U(eff)(T) and superconducting transition temperature, Tc, decreased as the lattice parameters increased with increasing Pr ion concentration, x, for the corresponding Y(1-x)Pr(x)Ba(x)Cu3O(7-delta) oxides. One contribution to Tc decrease in this sampling is suspected to be due to the larger ionic radius of the Pr(3+) ion. The upper critical field (H(sub c2)) was measured in the presence of magnetic field parallel to the c axis. A linear temperature dependence with H(sub c2) was obtained.

Effect of α-particle irradiation on a NdFeAs(O,F) thin film

NASA Astrophysics Data System (ADS)

Tarantini, C.; Iida, K.; Sumiya, N.; Chihara, M.; Hatano, T.; Ikuta, H.; Singh, R. K.; Newman, N.; Larbalestier, D. C.

2018-07-01

The effect of α-particle irradiation on a NdFeAs(O,F) thin film has been investigated to determine how the introduction of defects affects basic superconducting properties, including the critical temperature T c and the upper critical field H c2, and properties more of interest for applications, like the critical current density J c and the related pinning landscape. The irradiation-induced suppression of the film T c is significantly smaller than on a similarly damaged single crystal. Moreover H c2 behaves differently, depending on the field orientation: for H//c the H c2 slope monotonically increases with increasing disorder, whereas for H//ab it remains constant at low dose and it increases only when the sample is highly disordered. This suggests that a much higher damage level is necessary to drive the NdFeAs(O,F) thin film into the dirty limit. Despite the increase in the low temperature H c2, the effects on the J c(H//c) performances are moderate in the measured temperature and field ranges, with a shifting of the pinning force maximum from 4.5 to 6 T after an irradiation of 2 × 1015 cm-2. On the contrary, J c(H//ab) is always suppressed. The analysis demonstrates that irradiation does introduce point defects (PD) acting as pinning centres proportionally to the irradiation fluence but also suppresses the effectiveness of c-axis correlated pinning present in the pristine sample. We estimate that significant performance improvements may be possible at high field or at temperatures below 10 K. The suppression of the J c(H//ab) performance is not related to a decrease of the J c anisotropy as found in other superconductors. Instead it is due to the presence of PD that decrease the efficiency of the ab-plane intrinsic pinning typical of materials with a layered structure.

The deep thermal field of the Upper Rhine Graben

NASA Astrophysics Data System (ADS)

Freymark, Jessica; Sippel, Judith; Scheck-Wenderoth, Magdalena; Bär, Kristian; Stiller, Manfred; Fritsche, Johann-Gerhard; Kracht, Matthias

2017-01-01

The Upper Rhine Graben has a significant socioeconomic relevance as it provides a great potential for geothermal energy production. The key for the utilisation of this energy resource is to understand the controlling factors of the thermal field in this area. We have therefore built a data-based lithospheric-scale 3D structural model of the Upper Rhine Graben and its adjacent areas. In addition, 3D gravity modelling was performed to constrain the internal structure of the crystalline crust consistent with seismic information. Based on this lithosphere scale 3D structural model the present-day conductive thermal field was calculated and compared to measured temperatures. Our results show that the regional thermal field is mainly controlled by the configuration of the upper crust, which has different thermal properties characteristic for the Variscan and Alpine domains. Temperature maxima are predicted for the Upper Rhine Graben where thick insulating Cenozoic sediments cause a thermal blanketing effect and where the underlying crustal units are characterised by high radiogenic heat production. The comparison of calculated and measured temperatures overall shows a reasonable fit, while locally occuring model deviations indicate where a larger influence of groundwater flow may be expected.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, P.

A model of the solar chromosphere that consists of two fundamentally different regions, a lower region and an upper region, is proposed. The lower region is covered mostly by weak locally closed magnetic field and small network areas of extremely strong, locally open field. The field in the upper region is relatively uniform and locally open, connecting to the corona. The chromosphere is heated by strong collisional damping of Alfvén waves, which are driven by turbulent motions below the photosphere. The heating rate depends on the field strength, wave power from the photosphere, and altitude in the chromosphere. The wavesmore » in the internetwork area are mostly damped in the lower region, supporting radiation in the lower chromosphere. The waves in the network area, carrying more Poynting flux, are only weakly damped in the lower region. They propagate into the upper region. As the thermal pressure decreases with height, the network field expands to form the magnetic canopy where the damping of the waves from the network area supports radiation in the whole upper region. Because of the vertical stratification and horizontally nonuniform distribution of the magnetic field and heating, one circulation cell is formed in each of the upper and lower regions. The two circulation cells distort the magnetic field and reinforce the funnel-canopy-shaped magnetic geometry. The model is based on classical processes and is semi-quantitative. The estimates are constrained according to observational knowledge. No anomalous process is invoked or needed. Overall, the heating mechanism is able to damp 50% of the total wave energy.« less

The upper bound of Pier Scour defined by selected laboratory and field data

USGS Publications Warehouse

Benedict, Stephen; Caldwell, Andral W.

2015-01-01

The U.S. Geological Survey, in cooperation with the South Carolina Department of Transportation, conducted several field investigations of pier scour in South Carolina (Benedict and Caldwell, 2006; Benedict and Caldwell, 2009) and used that data to develop envelope curves defining the upper bound of pier scour. To expand upon this previous work, an additional cooperative investigation was initiated to combine the South Carolina data with pier-scour data from other sources and evaluate the upper bound of pier scour with this larger data set. To facilitate this analysis, a literature review was made to identify potential sources of published pier-scour data, and selected data were compiled into a digital spreadsheet consisting of approximately 570 laboratory and 1,880 field measurements. These data encompass a wide range of laboratory and field conditions and represent field data from 24 states within the United States and six other countries. This extensive database was used to define the upper bound of pier-scour depth with respect to pier width encompassing the laboratory and field data. Pier width is a primary variable that influences pier-scour depth (Laursen and Toch, 1956; Melville and Coleman, 2000; Mueller and Wagner, 2005, Ettema et al. 2011, Arneson et al. 2012) and therefore, was used as the primary explanatory variable in developing the upper-bound envelope curve. The envelope curve provides a simple but useful tool for assessing the potential maximum pier-scour depth for pier widths of about 30 feet or less.

Decoding facial blends of emotion: visual field, attentional and hemispheric biases.

PubMed

Ross, Elliott D; Shayya, Luay; Champlain, Amanda; Monnot, Marilee; Prodan, Calin I

2013-12-01

Most clinical research assumes that modulation of facial expressions is lateralized predominantly across the right-left hemiface. However, social psychological research suggests that facial expressions are organized predominantly across the upper-lower face. Because humans learn to cognitively control facial expression for social purposes, the lower face may display a false emotion, typically a smile, to enable approach behavior. In contrast, the upper face may leak a person's true feeling state by producing a brief facial blend of emotion, i.e. a different emotion on the upper versus lower face. Previous studies from our laboratory have shown that upper facial emotions are processed preferentially by the right hemisphere under conditions of directed attention if facial blends of emotion are presented tachistoscopically to the mid left and right visual fields. This paper explores how facial blends are processed within the four visual quadrants. The results, combined with our previous research, demonstrate that lower more so than upper facial emotions are perceived best when presented to the viewer's left and right visual fields just above the horizontal axis. Upper facial emotions are perceived best when presented to the viewer's left visual field just above the horizontal axis under conditions of directed attention. Thus, by gazing at a person's left ear, which also avoids the social stigma of eye-to-eye contact, one's ability to decode facial expressions should be enhanced. Published by Elsevier Inc.

Pre-Service Teachers Teaching Critical Literacy through Microteaching: Possibilities and Constraints

ERIC Educational Resources Information Center

Ng, Chiew Hong

2017-01-01

In this paper I explore four groups of pre-service teachers' teaching of critical literacy in microteaching to examine how they translated critical literacy into teaching practice for secondary/upper middle grade students (the role played by peers undergoing microteaching). Firstly I discuss some key concepts and outline the pedagogical framework…

Conference in Rhetorical Criticism: Commended Papers (6th, Hayward, California, May 1, 1971).

ERIC Educational Resources Information Center

Peat, Stephen D., Ed.; And Others

At the sixth annual Cal-State Hayward Conference in Rhetorical Criticism, upper division and graduate students from 11 western colleges and universities presented papers on the theory, history, and criticism of rhetoric. Panels of faculty members from the same colleges and universities selected the three best papers for commendation and…

Upper Primary Level History Teachers' Attitudes toward the Use of School Field Trips as an Educational Aid throughout Schools in Irbid First Education Directorate

ERIC Educational Resources Information Center

Menazel, Basil H.

2015-01-01

The study aimed to identify upper primary level History teachers' attitudes toward the use of school field trips as an educational aid throughout schools in the Irbid First Education Directorate, through exploring the importance of school field trips in the creation of an interactive atmosphere and to encourage school administration attitudes…

Evaluating the Sonic Layer Depth Relative to the Mixed Layer Depth

DTIC Science & Technology

2008-07-24

upper ocean to trap acoustic energy in a surface duct while MLD characterizes upper ocean mixing. The SLD is computed from temperature and salinity...and compared over the annual cycle. The SLD characterizes the potential of the upper ocean to trap acoustic energy in a surface duct while MLD...exists a tropical cyclone formation [e.g., Mao et al., 2000], to Minimum acoustic Cutoff Frequency (MCF) above which phytoplankton bloom critical depth

Airfoil shape for flight at subsonic speeds

DOEpatents

Whitcomb, Richard T.

1976-01-01

An airfoil having an upper surface shaped to control flow accelerations and pressure distribution over the upper surface and to prevent separation of the boundary layer due to shock wave formulation at high subsonic speeds well above the critical Mach number. A highly cambered trailing edge section improves overall airfoil lifting efficiency.

Mechanical and Hydrologic Effects of Riparian Vegetation on Critical Conditions for Streambank Stability: Upper Truckee River, California

NASA Astrophysics Data System (ADS)

Simon, A.; Pollen, N. L.; Langendoen, E. J.

2005-05-01

The Upper Truckee River is the single largest contributor of sediment to Lake Tahoe with a large proportion of the suspended-sediment load coming from eroding streambanks. Recent advances in quantifying streambank processes highlight the combined effects of hydraulic erosion at the bank toe with geotechnical stability of the upper part of the bank and resulted in the development of a deterministic model of bank-toe erosion and streambank stability (Simon et al., 1999). The use of riparian vegetation in schemes of bank stabilization and stream restoration have become popular but are often implemented on a trial and error basis because of a lack of quantifiable information on the mechanical and hydrologic effects of vegetation on bank stability. This study, conducted along an unstable reach of the Upper Truckee River, combines field data with numerical modeling to quantify (1) hydraulic and geotechnical driving and resisting forces that control bank failures, (2) the mechanical and hydrologic effects of vegetation on shear strength, and (3) the critical conditions for bank stability with and without indigenous riparian species. Tests were conducted using three top-bank treatments: bare (control), Lemmon's willow, and young Lodgepole pine. The susceptibility of the bank toe to erosion by hydraulic forces was quantified by conducting submerged jet tests of in situ material to determine the erodibility coefficient (k) and the critical shear stress of the material. Drained, shear-strength parameters (cohesion and friction angle) of the banks were determined from borehole shear tests at various depths. Pore-water pressure and matric suction were monitored at three depths (30, 100, and 150 cm) with digital tensiometers to calculate changes in apparent cohesion for the period (September 2003 - May 2004) and to differentiate between the hydrologic effects of the two species. Root reinforcement of the two species was quantified by determining the relation between root-tensile strength and root diameter and integrating this with root distribution. Bank failures occurred during winter and spring, brought on by repeated basal melting of snow packs and rain-on-snow events. Lemmon's willow provided an order of magnitude more root-reinforcement (5.5 kPa) than the young Lodgepole pines (0.5 kPa). This difference is not related to differences in root strength, but to the far greater number of roots associated with Lemmon's willow. The hydrologic effects of the species varied spatially and temporally, were beneficial (drier) at depths of 100 and 150 cm but disadvantageous (wetter) near the surface (30 cm). In total, these effects were generally smaller in magnitude than the mechanical effects. Lemmon's willow provided a significant increase in bank strength to streambanks along the Upper Truckee River. Model runs conducted with the hydrologic and mechanical effects of Lemmon's willow included, showed no failures during the simulation period. Overall, Lemmon's willow provided a significant increase in bank strength, reducing the frequency of bank failures and delivery of fine-grained sediment to the study reach of the Upper Truckee River. The use of Lemmon's willow in a bank-stabilization scheme was found to be numerically equivalent to reducing the angle of the entire bank 10-15 degrees.

Superconducting and magnetic properties of Sr 3 Ir 4 Sn 13

DOE PAGES

Biswas, P. K.; Amato, A.; Khasanov, R.; ...

2014-10-10

In this research, magnetization and muon spin relaxation or rotation (µSR) measurements have been performed to study the superconducting and magnetic properties of Sr₃Ir₄Sn₁₃. From magnetization measurements the lower and upper critical fields of Sr₃Ir₄Sn₁₃ are found to be 81(1) Oe and 14.4(2) kOe, respectively. Zero-field µSR data show no sign of any magnetic ordering or weak magnetism in Sr₃Ir₄Sn₁₃. Transverse-field µSR measurements in the vortex state provided the temperature dependence of the magnetic penetration depth λ. The dependence of λ⁻² with temperature is consistent with the existence of single s-wave energy gap in the superconducting state of Sr₃Ir₄Sn₁₃ withmore » a gap value of 0.82(2) meV at absolute zero temperature. The magnetic penetration depth at zero temperature λ(0) is 291(3) nm. The ratio Δ(0)/k BT c = 2.1(1) indicates that Sr₃Ir₄Sn₁₃ should be considered as a strong-coupling superconductor.« less

The Hazards of Our Star

NASA Technical Reports Server (NTRS)

Klimchuk, James A.

2011-01-01

The Sun's magnetic field permeates its atmosphere - ranging from the solar photosphere (the visible "surface") to the corona above. Think of this field as a collection of invisible rubber bands that are slowly stretched and twisted until they eventually reach a breaking point, When the field breaks, it releases a small amount of energy, known as a nanoflare. Millions of nanoflares occur every second, and the combined effect heats the solar corona to more than 1 million kelvins, hundreds of times hotter than the photosphere. The super-heated gas emits X-ray and ultraviolet radiation; Earth's upper atmosphere absorbs it, which changes our atmosphere's properties. This can disrupt communication, navigation, and surveillance systems, and also alter the orbits of satellites. On much larger scales, huge sections of the corona explosively erupt in coronal mass ejections (CMEs) and solar flares. CMEs directed toward Earth cause geomagnetic storms, which can wreck havoc on electrical power grids and produce widespread blackouts. Highly energetic particles can damage or even disable critical spacecraft components. Intense radiation from flares has the same effects as nanoflares, but to a greater degree. The need to understand how solar phenomena impact Earth has led to an important science field called space weather.

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 between near neighbors in the Periodic Table. Upper-critical-field and normal-state electrical resistivity measurements suggest that the molar electronic specific-heat coefficient γm decreases with x in parallel with Tc in the Zr1-xCox and Zr1-xNix series. In the equal-< ea > (Zr1-xTix)0.78Ni0.22 system, Tc decreases with x; in the (Zr1-xNbx)0.78Ni0.22 system, Tc first increases and then decreases with x (hence with < ea >). These diverse < ea > dependencies of Tc appear consistent with the ultraviolet-photoemission-spectroscopy indicated split-band model of such amorphous transition-metal alloys and the associated idea that the alloying dependence of Tc cannot be described by general Tc vs < ea > rules.

Role of Earth's plasmasphere in coupling of upper atmosphere

NASA Astrophysics Data System (ADS)

Singh, A. K.; Mishra, Sandhya; Dohare, S. K.

2010-02-01

The near-Earth space environment is a complex, ever changing system of magnetized plasmas whose behaviour has a profound impact upon our technology dependent society. The exploration of the cold, relatively dense, inner region of upper atmosphere (the plasmasphere) and its unexpectedly sharp outer boundary (the plasma pause) has proceeded through a combination of in-situ observations and ground based whistler observations. Studies have shown that plasmasphere is highly variable both spatially and temporally responding to changes in geomagnetic indices, ring current, penetration and shielding electric fields and subauroral electric fields. Consequently the plasmasphere exhibits erosion, emptying and refilling during active times. Infact, it is the electric field that plays one of the most important roles in coupling of upper atmosphere. The atmospheric dynamo is the main generator of the large-scale electric field in the upper atmosphere. It arises because of a special situation which electrons and ions move with different velocities across the magnetic field because of different collisions between electrons and neutral particles and ions with neutral particles. This process leads to charge separation and consequently to an electric field. In the present paper, storm/ quiet period VLF whistler data recorded at lower latitudes/mid latitudes are analyzed and attempt has been made to look at plasmasphere response on coupling of ionosphere and magnetosphere.

Annual Conference in Rhetorical Criticism: Commended Papers (6th, California State Univ., Hayward, May, 1972).

ERIC Educational Resources Information Center

Chalip, Alice Grace, Ed.

At this 1972 conference, upper division and graduate students from nine western colleges submitted papers on the theory, history, and criticism of rhetoric. Three of them are published in this conference report, along with the principal address. In "Rhetorical Criticism as Argument," the principal address, Wayne Brockriede suggests that useful…

Conference in Rhetorical Criticism: Commended Papers, 1970 (5th, Hayward, California, May 9, 1970).

ERIC Educational Resources Information Center

Rose, Doreen K. F., Ed.; And Others

At the fifth annual Cal-State Hayward Conference in Rhetorical Criticism, upper division and graduate students from 14 western colleges and universities presented papers on the theory, history, and criticism of rhetoric. Panels of faculty members from the same colleges and universities selected the three best papers for commendation and…

Solar magnetism eXplorer (SolmeX). Exploring the magnetic field in the upper atmosphere of our closest star

NASA Astrophysics Data System (ADS)

Peter, Hardi; Abbo, L.; Andretta, V.; Auchère, F.; Bemporad, A.; Berrilli, F.; Bommier, V.; Braukhane, A.; Casini, R.; Curdt, W.; Davila, J.; Dittus, H.; Fineschi, S.; Fludra, A.; Gandorfer, A.; Griffin, D.; Inhester, B.; Lagg, A.; Landi Degl'Innocenti, E.; Maiwald, V.; Sainz, R. Manso; Martínez Pillet, V; Matthews, S.; Moses, D.; Parenti, S.; Pietarila, A.; Quantius, D.; Raouafi, N.-E.; Raymond, J.; Rochus, P.; Romberg, O.; Schlotterer, M.; Schühle, U.; Solanki, S.; Spadaro, D.; Teriaca, L.; Tomczyk, S.; Trujillo Bueno, J.; Vial, J.-C.

2012-04-01

The magnetic field plays a pivotal role in many fields of Astrophysics. This is especially true for the physics of the solar atmosphere. Measuring the magnetic field in the upper solar atmosphere is crucial to understand the nature of the underlying physical processes that drive the violent dynamics of the solar corona—that can also affect life on Earth. SolmeX, a fully equipped solar space observatory for remote-sensing observations, will provide the first comprehensive measurements of the strength and direction of the magnetic field in the upper solar atmosphere. The mission consists of two spacecraft, one carrying the instruments, and another one in formation flight at a distance of about 200 m carrying the occulter to provide an artificial total solar eclipse. This will ensure high-quality coronagraphic observations above the solar limb. SolmeX integrates two spectro-polarimetric coronagraphs for off-limb observations, one in the EUV and one in the IR, and three instruments for observations on the disk. The latter comprises one imaging polarimeter in the EUV for coronal studies, a spectro-polarimeter in the EUV to investigate the low corona, and an imaging spectro-polarimeter in the UV for chromospheric studies. SOHO and other existing missions have investigated the emission of the upper atmosphere in detail (not considering polarization), and as this will be the case also for missions planned for the near future. Therefore it is timely that SolmeX provides the final piece of the observational quest by measuring the magnetic field in the upper atmosphere through polarimetric observations.

Impacts of space weather events on the structure of the upper atmosphere

NASA Astrophysics Data System (ADS)

Lee, Y.; Mahaffy, P. R.; Benna, M.; Elrod, M. K.

2017-12-01

Due to the absence of the intrinsic magnetic field, Mars' upper atmosphere is vulnerable to the solar wind, which directly strips away the Martian upper atmosphere via various mechanisms, resulting in interesting global phenomena that are observable. The Mars Atmosphere and Volatile EvolutioN (MAVEN) has observed the responses of the upper atmosphere such as Interplanetary Coronal Mass Ejections (ICMEs) and Solar flare events spanning from November 2014 to the present. A comprehensive set of observations taken by the MAVEN instrument package enables the better characterization of the thermospheric and ionospheric behavior affected by various space weather events. The observed impacts include changes in the upper atmospheric and ionospheric density and temperature, enhancements of atmospheric loss rate of ions and neutrals, and changes in important boundary layers. The measurements by plasma and field instruments allows the upstream monitoring of the solar EUV, solar energetic particles, and Interplanetary Magnetic Field (IMF) simultaneously and provide additional information of the near-Mars space weather disturbances. In addition, at low altitudes near the periapsis of the spacecraft, the simultaneous measurements of the magnetic field and properties of the thermosphere and ionosphere allow the analysis of the effects of the local crustal magnetic fields. Here, adding to the reported MAVEN observations of the space weather impacts at Mars, we analyze the responses of the upper atmosphere to the mars-impacting space weather events observed by MAVEN. We focus mainly on the responses of the density and temperature structures, which in turn allow us to examine the effects on the important atmospheric layers such as the M2 layer and transition region from the thermosphere to exosphere.

Vorticity and Vertical Motions Diagnosed from Satellite Deep-Layer Temperatures. Revised

NASA Technical Reports Server (NTRS)

Spencer, Roy W.; Lapenta, William M.; Robertson, Franklin R.

1994-01-01

Spatial fields of satellite-measured deep-layer temperatures are examined in the context of quasigeostrophic theory. It is found that midtropospheric geostrophic vorticity and quasigeostrophic vertical motions can be diagnosed from microwave temperature measurements of only two deep layers. The lower- ( 1000-400 hPa) and upper- (400-50 hPa) layer temperatures are estimated from limb-corrected TIROS-N Microwave Sounding Units (MSU) channel 2 and 3 data, spatial fields of which can be used to estimate the midtropospheric thermal wind and geostrophic vorticity fields. Together with Trenberth's simplification of the quasigeostrophic omega equation, these two quantities can be then used to estimate the geostrophic vorticity advection by the thermal wind, which is related to the quasigeostrophic vertical velocity in the midtroposphere. Critical to the technique is the observation that geostrophic vorticity fields calculated from the channel 3 temperature features are very similar to those calculated from traditional, 'bottom-up' integrated height fields from radiosonde data. This suggests a lack of cyclone-scale height features near the top of the channel 3 weighting function, making the channel 3 cyclone-scale 'thickness' features approximately the same as height features near the bottom of the weighting function. Thus, the MSU data provide observational validation of the LID (level of insignificant dynamics) assumption of Hirshberg and Fritsch.

Small anisotropy, weak thermal fluctuations, and high field superconductivity in Co-doped iron pnictide Ba(Fe1-xCox)2As2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamamoto, A.; Jaroszynski, J.; Tarantini, C.

2009-01-01

We performed high-field magnetotransport and magnetization measurements on a single crystal of the 122-phase iron pnictide Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2}. Unlike the high-temperature superconductor cuprates and 1111-phase oxypnictides, Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} showed practically no broadening of the resistive transitions under magnetic fields up to 45 T. We report the temperature dependencies of the upper critical field H{sub c2} both parallel and perpendicular to the c-axis, the irreversibility field H{sub irr}{sup c}(T), and a rather unusual symmetric volume pinning force curve F{sub p}(H) suggestive of a strong pinning nanostructure. The anisotropy parameter {gamma} = H{sub c2}{sup ab}/H{sub c2}{supmore » c} deduced from the slopes of dH{sub c2}{sup ab}/dT = 4.9 T/K and dH{sub c2}{sup c}/dT = 2.5 T/K decreases from -2 near T{sub c}, to -1.5 at lower temperatures, much smaller than {gamma} for 1111 pnictides and high-T{sub c} cuprates.« less

Ductile alloy and process for preparing composite superconducting wire

DOEpatents

Verhoeven, John D.; Finnemore, Douglas K.; Gibson, Edwin D.; Ostenson, Jerome E.

1983-03-29

An alloy for the commercial production of ductile superconducting wire is prepared by melting together copper and at least 15 weight percent niobium under non-oxygen-contaminating conditions, and rapidly cooling the melt to form a ductile composite consisting of discrete, randomly distributed and orientated dendritic-shaped particles of niobium in a copper matrix. As the wire is worked, the dendritric particles are realigned parallel to the longitudinal axis and when drawn form a plurality of very fine ductile superconductors in a ductile copper matrix. The drawn wire may be tin coated and wound into magnets or the like before diffusing the tin into the wire to react with the niobium. Impurities such as aluminum or gallium may be added to improve upper critical field characteristics.

Effect of neutron irradiation on the London penetration depth for polycrystalline Bi(1.8)Pb(0.3)Sr2Ca2Cu3O10 superconductor

NASA Technical Reports Server (NTRS)

Ossandon, J. G.; Thompson, J. R.; Sun, Yang Ren; Christen, D. K.; Chakoumakos, B. C.

1995-01-01

Magnetization studies of polycrystalline Bi(1.8)Pb(0.3)Sr2Ca2Cu3O10 superconductor, prior to and after neutron irradiation, showed an increase in J(sub c) due to irradiation damage. Analysis of the equilibrium magnetization revealed significant increases in other more fundamental properties. In particular, the London penetration depth increased by approximately 15 percent following irradiation with 8 x 10(exp 16) neutrons/sq cm. Corresponding changes were observed in the upper critical magnetic field H(sub c2). However, the most fundamental thermodynamic property, the superconductive condensation energy F(sub c), was unaffected by the moderate level of neutron-induced damage.

On the robustness of the primordial power spectrum in renormalized Higgs inflation

NASA Astrophysics Data System (ADS)

Bezrukov, Fedor; Pauly, Martin; Rubio, Javier

2018-02-01

We study the cosmological consequences of higher-dimensional operators respecting the asymptotic symmetries of the tree-level Higgs inflation action. The main contribution of these operators to the renormalization group enhanced potential is localized in a compact field range, whose upper limit is close to the end of inflation. The spectrum of primordial fluctuations in the so-called universal regime turns out to be almost insensitive to radiative corrections and in excellent agreement with the present cosmological data. However, higher-dimensional operators can play an important role in critical Higgs inflation scenarios containing a quasi-inflection point along the inflationary trajectory. The interplay of radiative corrections with this quasi-inflection point may translate into a sizable modification of the inflationary observables.

Ductile alloy and process for preparing composite superconducting wire

DOEpatents

Verhoeven, J.D.; Finnemore, D.K.; Gibson, E.D.; Ostenson, J.E.

An alloy for the commercial production of ductile superconducting wire is prepared by melting together copper and at least 15 weight percent niobium under non-oxygen-contaminating conditions, and rapidly cooling the melt to form a ductile composite consisting of discrete, randomly distributed and oriented dendritic-shaped particles of niobium in a copper matrix. As the wire is worked, the dendritic particles are realigned parallel to the longitudinal axis and when drawn form a plurality of very fine ductile superconductors in a ductile copper matrix. The drawn wire may be tin coated and wound into magnets or the like before diffusing the tin into the wire to react with the niobium. Impurities such as aluminum or gallium may be added to improve upper critical field characteristics.

On the stellar rotation-activity connection

NASA Technical Reports Server (NTRS)

Rosner, R.

1983-01-01

The relationship between rotation rates and surface activity in late-type dwarf stars is explored in a survey of recent theoretical and observational studies. Current theoretical models of stellar-magnetic-field production and coronal activity are examined, including linear kinematic dynamo theory, nonlinear dynamos using approximations, and full numerical simulations of the MHD equations; and some typical results are presented graphically. The limitations of the modeling procedures and the constraints imposed by the physics are indicated. The statistical techniques used in establishing correlations between various observational parameters are analyzed critically, and the methods developed for quasar luminosity functions by Avni et al. (1980) are used to evaluate the effects of upper detection bounds, incomplete samples, and missing data for the case of rotation and X-ray flux data.

Superconducting FeSe0.1Te0.9 thin films integrated on Si-based substrates

NASA Astrophysics Data System (ADS)

Huang, Jijie; Chen, Li; Li, Leigang; Qi, Zhimin; Sun, Xing; Zhang, Xinghang; Wang, Haiyan

2018-05-01

With the goal of integrating superconducting iron chalcogenides with Si-based electronics, superconducting FeSe0.1Te0.9 thin films were directly deposited on Si and SiOx/Si substrates without any buffer layer by a pulsed laser deposition (PLD) method. Microstructural characterization showed excellent film quality with mostly c-axis growth on both types of substrates. Superconducting properties (such as superconducting transition temperature T c and upper critical field H c2) were measured to be comparable to that of the films on single crystal oxide substrates. The work demonstrates the feasibility of integrating superconducting iron chalcogenide (FeSe0.1Te0.9) thin films with Si-based microelectronics.

Assessing the dynamics of the upper soil layer relative to soil management practices

USDA-ARS?s Scientific Manuscript database

The upper layer of the soil is the critical interface between the soil and the atmosphere and is the most dynamic in response to management practices. One of the soil properties is the stability of the aggregates because this property controls infiltration of water and exchange of gases. An aggregat...

Portrait of a Geothermal Spring, Hunter's Hot Springs, Oregon.

PubMed

Castenholz, Richard W

2015-01-27

Although alkaline Hunter's Hot Springs in southeastern Oregon has been studied extensively for over 40 years, most of these studies and the subsequent publications were before the advent of molecular methods. However, there are many field observations and laboratory experiments that reveal the major aspects of the phototrophic species composition within various physical and chemical gradients of these springs. Relatively constant temperature boundaries demark the upper boundary of the unicellular cyanobacterium, Synechococcus at 73-74 °C (the world-wide upper limit for photosynthesis), and 68-70 °C the upper limit for Chloroflexus. The upper limit for the cover of the filamentous cyanobacterium, Geitlerinema (Oscillatoria) is at 54-55 °C, and the in situ lower limit at 47-48 °C for all three of these phototrophs due to the upper temperature limit for the grazing ostracod, Thermopsis. The in situ upper limit for the cyanobacteria Pleurocapsa and Calothrix is at ~47-48 °C, which are more grazer-resistant and grazer dependent. All of these demarcations are easily visible in the field. In addition, there is a biosulfide production in some sections of the springs that have a large impact on the microbiology. Most of the temperature and chemical limits have been explained by field and laboratory experiments.

Portrait of a Geothermal Spring, Hunter’s Hot Springs, Oregon

PubMed Central

Castenholz, Richard W.

2015-01-01

Although alkaline Hunter’s Hot Springs in southeastern Oregon has been studied extensively for over 40 years, most of these studies and the subsequent publications were before the advent of molecular methods. However, there are many field observations and laboratory experiments that reveal the major aspects of the phototrophic species composition within various physical and chemical gradients of these springs. Relatively constant temperature boundaries demark the upper boundary of the unicellular cyanobacterium, Synechococcus at 73–74 °C (the world-wide upper limit for photosynthesis), and 68–70 °C the upper limit for Chloroflexus. The upper limit for the cover of the filamentous cyanobacterium, Geitlerinema (Oscillatoria) is at 54–55 °C, and the in situ lower limit at 47–48 °C for all three of these phototrophs due to the upper temperature limit for the grazing ostracod, Thermopsis. The in situ upper limit for the cyanobacteria Pleurocapsa and Calothrix is at ~47–48 °C, which are more grazer-resistant and grazer dependent. All of these demarcations are easily visible in the field. In addition, there is a biosulfide production in some sections of the springs that have a large impact on the microbiology. Most of the temperature and chemical limits have been explained by field and laboratory experiments. PMID:25633225

A prototype data assimilation framework for generating spatiotemporally continuous SWOT data products

NASA Astrophysics Data System (ADS)

Andreadis, K.; Margulis, S. A.; Li, D.; Lettenmaier, D. P.

2017-12-01

The Surface Water and Ocean Topography (SWOT) satellite will provide critical surface water observations for the hydrologic community. However, production of key SWOT variables, such as river discharge and surface inundation, as well as lake, reservoir, and wetland storage change will be complicated by the discontinuity of the observations in space and time. A methodology that generates products with spatially and temporally continuous fields based on SWOT observables would be highly desirable. Data assimilation provides a mechanism for merging observations from SWOT with model predictions in order to produce estimates of quantities such as river discharge, storage change, and water heights for locations and times when there is no satellite overpass or other constraints (such as layover) render the measurement unusable. We describe here a prototype assimilation system with application to the Upper Mississippi basin, implemented using synthetic SWOT observations. We use a hydrologic model (VIC) coupled with a hydrodynamic model (LISFLOOD-FP) which generates "true" fields of surface water variables. The true fields are then used to generate synthetic SWOT observations using the SWOT Instrument Simulator. We also perform a "first-guess" (or open-loop) simulation with the coupled model using a configuration that contains errors representative of the imperfect knowledge of parameters and input data, including channel topography, bankfull widths and depths, and inflows, to create an ensemble of 20 model trajectories. Subsequently we assimilate the synthetic SWOT observations into the open-loop model results to estimate water surface elevation, discharge, and storage change. Our preliminary results using three data assimilation strategies show that all improve the water surface elevation estimate accuracy by 25% - 35% for a river reach of the upper Mississippi River. Ongoing work is examining whether the improved water surface elevation estimates propagate to improvements in river discharge.

Investigating the FUV Emission of Young M dwarfs with FUMES: the Far Ultraviolet M-dwarf Evolution Survey

NASA Astrophysics Data System (ADS)

Pineda, John

2016-10-01

M dwarf stars have become attractive candidates for exoplanet searches and will be a main focus of the upcoming TESS mission, with the continued search for nearby potentially habitable worlds. However, the atmospheric characterization of these exoplanetary systems depends critically on the high energy stellar radiation environment from X-ray to NUV. Strong radiation at these energies can lead to atmospheric mass loss and is a strong driver of photochemistry in planetary atmospheres. Recently, the MUSCLES Treasury Survey (Cycles 19, 22) provided the first comprehensive assessment of the high energy radiation field around old, planet hosting M dwarfs. However, the habitability and potential for such exoplanetary atmospheres to develop life also depends on the evolution of the atmosphere and hence the evolution of the incident radiation field. The strong high energy spectrum of young M dwarfs can have devastating consequences for the potential habitability of a given system. We, thus, propose the Far Ultraviolet M-dwarf Evolution Survey (FUMES) to measure the strong FUV coronal/chromospheric emission features of young M dwarfs (12 - 650 Myr), e.g. He II, C IV, and S IV. FUMES will observe objects with a wide range of rotation rates to directly connect the emission features to the evolution of coronal heating and upper atmospheric structure, and provide observational benchmarks at young ages for models of M dwarf upper atmospheres. Building on results from MUSCLES, we will be able to estimate the whole high energy radiation field and establish the evolutionary picture of the incident radiation throughout the lifetime of exoplanetary systems around early-mid M dwarf hosts.

Bulk superconductivity in bismuth oxysulfide Bi4O4S3.

PubMed

Singh, Shiva Kumar; Kumar, Anuj; Gahtori, Bhasker; Shruti; Sharma, Gyaneshwar; Patnaik, Satyabrata; Awana, Veer P S

2012-10-10

A very recent report on the observation of superconductivity in Bi(4)O(4)S(3) [Mizuguchi, Y.; http://arxiv.org/abs/1207.3145] could potentially reignite the search for superconductivity in a broad range of layered sulfides. We report here the synthesis of Bi(4)O(4)S(3) at 500 °C by a vacuum encapsulation technique and its basic characterizations. The as-synthesized Bi(4)O(4)S(3) was contaminated with small amounts of Bi(2)S(3) and Bi impurities. The majority phase was found to be tetragonal (space group I4/mmm) with lattice parameters a = 3.9697(2) Å and c = 41.3520(1) Å. Both AC and DC magnetization measurements confirmed that Bi(4)O(4)S(3) is a bulk superconductor with a superconducting transition temperature (T(c)) of 4.4 K. Isothermal magnetization (M-H) measurements indicated closed loops with clear signatures of flux pinning and irreversible behavior. The lower critical field (H(c1)) at 2 K for the new superconductor was found to be ~15 Oe. Magnetotransport measurements showed a broadening of the resistivity (ρ) and a decrease in T(c) (ρ = 0) with increasing magnetic field. The extrapolated upper critical field H(c2)(0) was ~31 kOe with a corresponding Ginzburg-Landau coherence length of ~100 Å . In the normal state, the ρ ~ T(2) dependence was not indicated. Hall resistivity data showed a nonlinear magnetic field dependence. Our magnetization and electrical transport measurements substantiate the appearance of bulk superconductivity in as-synthesized Bi(4)O(4)S(3). On the other hand, Bi heat-treated at the same temperature is not superconducting, thus excluding the possibility of impurity-driven superconductivity in the newly discovered superconductor Bi(4)O(4)S(3).

The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx): Goals, platforms, and field operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, R.; Springston, S.; Mechoso, C. R.

2011-01-21

The VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) was an international field program designed to make observations of poorly understood but critical components of the coupled climate system of the southeast Pacific. This region is characterized by strong coastal upwelling, the coolest SSTs in the tropical belt, and is home to the largest subtropical stratocumulus deck on Earth. The field intensive phase of VOCALS-REx took place during October and November 2008 and constitutes a critical part of a broader CLIVAR program (VOCALS) designed to develop and promote scientific activities leading to improved understanding, model simulations, and predictions of the southeastern Pacificmore » (SEP) coupled ocean-atmosphere-land system, on diurnal to interannual timescales. The other major components of VOCALS are a modeling program with a model hierarchy ranging from the local to global scales, and a suite of extended observations from regular research cruises, instrumented moorings, and satellites. The two central themes of VOCALS-REx focus upon (a) links between aerosols, clouds and precipitation and their impacts on marine stratocumulus radiative properties, and (b) physical and chemical couplings between the upper ocean and the lower atmosphere, including the role that mesoscale ocean eddies play. A set of hypotheses designed to be tested with the combined field, monitoring and modeling work in VOCALS is presented here. A further goal of VOCALS-REx is to provide datasets for the evaluation and improvement of large-scale numerical models. VOCALS-REx involved five research aircraft, two ships and two surface sites in northern Chile. We describe the instrument payloads and key mission strategies for these platforms and give a summary of the missions conducted.« less

The Combined Effect of Mere Exposure, Counterattitudinal Advocacy, and Art Criticism Methodology on Upper Elementary and Junior High Students' Affect Toward Art Works.

ERIC Educational Resources Information Center

Hollingsworth, Patricia

1983-01-01

Results indicated that, for elementary students, art criticism was more effective than a combination of methodologies for developing positive affect toward art works. For junior high students, the combination methodology was more effective than art criticism, the exposure method, or the counterattitudinal advocacy method. (Author/SR)

Hyperscaling breakdown and Ising spin glasses: The Binder cumulant

NASA Astrophysics Data System (ADS)

Lundow, P. H.; Campbell, I. A.

2018-02-01

Among the Renormalization Group Theory scaling rules relating critical exponents, there are hyperscaling rules involving the dimension of the system. It is well known that in Ising models hyperscaling breaks down above the upper critical dimension. It was shown by Schwartz (1991) that the standard Josephson hyperscaling rule can also break down in Ising systems with quenched random interactions. A related Renormalization Group Theory hyperscaling rule links the critical exponents for the normalized Binder cumulant and the correlation length in the thermodynamic limit. An appropriate scaling approach for analyzing measurements from criticality to infinite temperature is first outlined. Numerical data on the scaling of the normalized correlation length and the normalized Binder cumulant are shown for the canonical Ising ferromagnet model in dimension three where hyperscaling holds, for the Ising ferromagnet in dimension five (so above the upper critical dimension) where hyperscaling breaks down, and then for Ising spin glass models in dimension three where the quenched interactions are random. For the Ising spin glasses there is a breakdown of the normalized Binder cumulant hyperscaling relation in the thermodynamic limit regime, with a return to size independent Binder cumulant values in the finite-size scaling regime around the critical region.

Proton pump inhibitors versus histamine 2 receptor antagonists for stress ulcer prophylaxis in critically ill patients: a systematic review and meta-analysis.

PubMed

Alhazzani, Waleed; Alenezi, Farhan; Jaeschke, Roman Z; Moayyedi, Paul; Cook, Deborah J

2013-03-01

Critically ill patients may develop bleeding caused by stress ulceration. Acid suppression is commonly prescribed for patients at risk of stress ulcer bleeding. Whether proton pump inhibitors are more effective than histamine 2 receptor antagonists is unclear. To determine the efficacy and safety of proton pump inhibitors vs. histamine 2 receptor antagonists for the prevention of upper gastrointestinal bleeding in the ICU. We searched Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, ACPJC, CINHAL, online trials registries (clinicaltrials.gov, ISRCTN Register, WHO ICTRP), conference proceedings databases, and reference lists of relevant articles. Randomized controlled parallel group trials comparing proton pump inhibitors to histamine 2 receptor antagonists for the prevention of upper gastrointestinal bleeding in critically ill patients, published before March 2012. Two reviewers independently applied eligibility criteria, assessed quality, and extracted data. The primary outcomes were clinically important upper gastrointestinal bleeding and overt upper gastrointestinal bleeding; secondary outcomes were nosocomial pneumonia, ICU mortality, ICU length of stay, and Clostridium difficile infection. Trial authors were contacted for additional or clarifying information. Fourteen trials enrolling a total of 1,720 patients were included. Proton pump inhibitors were more effective than histamine 2 receptor antagonists at reducing clinically important upper gastrointestinal bleeding (relative risk 0.36; 95% confidence interval 0.19-0.68; p = 0.002; I = 0%) and overt upper gastrointestinal bleeding (relative risk 0.35; 95% confidence interval 0.21-0.59; p < 0.0001; I = 15%). There were no differences between proton pump inhibitors and histamine 2 receptor antagonists in the risk of nosocomial pneumonia (relative risk 1.06; 95% confidence interval 0.73-1.52; p = 0.76; I = 0%), ICU mortality (relative risk 1.01; 95% confidence interval 0.83-1.24; p = 0.91; I = 0%), or ICU length of stay (mean difference -0.54 days; 95% confidence interval -2.20 to 1.13; p = 0.53; I = 39%). No trials reported on C. difficile infection. In critically ill patients, proton pump inhibitors seem to be more effective than histamine 2 receptor antagonists in preventing clinically important and overt upper gastrointestinal bleeding. The robustness of this conclusion is limited by the trial methodology, differences between lower and higher quality trials, sparse data, and possible publication bias. We observed no differences between drugs in the risk of pneumonia, death, or ICU length of stay.

Dense lower crust elevates long-term earthquake rates in the New Madrid seismic zone

USGS Publications Warehouse

Levandowski, William Brower; Boyd, Oliver; Ramirez-Guzman, Leonardo

2016-01-01

Knowledge of the local state of stress is critical in appraising intraplate seismic hazard. Inverting earthquake moment tensors, we demonstrate that principal stress directions in the New Madrid seismic zone (NMSZ) differ significantly from those in the surrounding region. Faults in the NMSZ that are incompatible with slip in the regional stress field are favorably oriented relative to local stress. We jointly analyze seismic velocity, gravity, and topography to develop a 3-D crustal and upper mantle density model, revealing uniquely dense lower crust beneath the NMSZ. Finite element simulations then estimate the stress tensor due to gravitational body forces, which sums with regional stress. The anomalous lower crust both elevates gravity-derived stress at seismogenic depths in the NMSZ and rotates it to interfere more constructively with far-field stress, producing a regionally maximal deviatoric stress coincident with the highest concentration of modern seismicity. Moreover, predicted principal stress directions mirror variations (observed independently in moment tensors) at the NMSZ and across the region.

Superconductivity and strong intrinsic defects in LaPd1-xBi2

NASA Astrophysics Data System (ADS)

Han, Fei; Malliakas, Christos D.; Stoumpos, Constantinos C.; Sturza, Mihai; Claus, Helmut; Chung, Duck Young; Kanatzidis, Mercouri G.

2013-10-01

Two new phases LaPd1-xBi2 and CePd1-xBi2 were obtained by growing single crystals in Bi flux. They adopt the tetragonal ZrCuSi2-type structure and feature Bi-square nets and PbO-type PdBi layers with significant partial Pd occupancy. Bulk superconductivity at 2.1 K and metallic behavior above Tc are observed in LaPd1-xBi2. A small residual resistance ratio (RRR) indicates a strong scattering effect induced by the Pd vacancies, which implies an s-wave pairing symmetry in LaPd1-xBi2. The broadening of the resistivity transition was measured under different magnetic fields demonstrating a high upper critical field of 3 T. Hall effect measurements reveal dominantly electron-like charge carriers and single-band transport behavior in LaPd1-xBi2. The paramagnetic CePd1-xBi2 is nonsuperconducting but shows antiferromagnetic ordering below 6 K.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolff-Fabris, F.; Lei, Hechang; Wosnitza, J.

We have studied the temperature dependence of the upper critical fields μ 0 H c 2 of K x Fe 2 - y Se 2 - z S z single crystals up to 60 T. The μ 0 H c 2 for H ∥ a b and H ∥ c decrease with increasing sulfur content. The detailed analysis using Werthamer-Helfand-Hohenberg theory including the Pauli spin-paramagnetic effect shows that μ 0 H c 2 for H ∥ a b is dominated by the spin-paramagnetic effect, which diminishes with higher S content, whereas μ 0 H c 2 for H ∥ cmore » shows a linear temperature dependence with an upturn at high fields. The latter observation can be ascribed to multiband effects that become weaker for higher S content. This results in an enhanced anisotropy of μ 0 H c 2 for high S content due to the different trends of the spin-paramagnetic and multiband effect for H ∥ a b and H ∥ c , respectively.« less

Spectral properties of Pauli operators on the Poincaré upper-half plane

NASA Astrophysics Data System (ADS)

Inahama, Yuzuru; Shirai, Shin-ichi

2003-06-01

We investigate the essential spectrum of the Pauli operators (and the Dirac and the Schrödinger operators) with magnetic fields on the Poincaré upper-half plane. The magnetic fields under consideration are asymptotically constant (which may be equal to zero), or diverge at infinity. Moreover, the Aharonov-Casher type result is also considered.

The effects of prism glasses and intensive upper limb exercise on hemineglect, upper limb function, and activities of daily living in stroke patients: a case series.

PubMed

Oh, Se-Il; Kim, Jin-Kyung; Park, So-Yeon

2015-12-01

[Purpose] This study aimed to examine the effects of visual field with prism glasses, and intensive upper limb functional training on reduction of hemineglect and improvement in upper limb function and activities of daily living in three stroke patients with hemineglect. [Subjects] This study included three stroke patients hospitalized in a sanatorium. [Methods] Intervention treatment involving prism glass use for 12 hours and 30 minutes and paretic side upper limb training was conducted 5 days a week for 15 weeks. Three upper limb training tasks (hitting a balloon, passing through a ring, and reading a newspaper) were performed for 10 minutes each session, for a total of 30 minutes. Line by Section, Motor-Free Visual Perception Test-3 (MVPT-3), Manual Function Test (MFT), Box & Block Test (BBT), and Assessment of Motor and Process Skills (AMPS) were conducted before and after intervention. [Results] Subjects' hemineglect decreased and upper limb function on the paretic side improved after intervention, which enhanced activities of daily living. [Conclusion] Prism glass use and paretic upper limb functional training effectively ameliorated stroke patients' hemineglect and improved upper limb function. Future research should focus on prism glasses that provide a wide visual field for use in patients with different conditions.

Convection in three dimensions with surface plates - Generation of toroidal flow

NASA Technical Reports Server (NTRS)

Gable, Carl W.; O'Connell, Richard J.; Travis, Bryan J.

1991-01-01

This work presents numerical calculations of mantle convection that incorporate some of the basic observational constraints imposed by plate tectonics. The model is three-dimensional and includes surface plates; it allows plate velocity to change dynamically according to the forces which result from convection. It is shown that plates are an effective means of introducing a toroidal component into the flow field. After initial transients the plate motion is nearly parallel to transform faults and in the direction that tends to minimize the toroidal flow field. The toroidal field decays with depth from its value at the surface; the poloidal field is relatively constant throughout the layer but falls off slightly at the top and bottom boundaries. Layered viscosity increasing with depth causes the toroidal field to decay more rapidly, effectively confining it to the upper, low-viscosity layer. The effect of viscosity layering on the poloidal field is relatively small, which is attributed to its generation by temperature variations distributed throughout the system. The generation of toroidal flow by surface plates would seem to account for the observed nearly equal energy of toroidal and poloidal fields of plate motions on the earth. A low-viscosity region in the upper mantle will cause the toroidal flow to decay significantly before reaching the lower mantle. The resulting concentration of toroidal flow in the upper mantle may result in more thorough mixing there and account for some of the geochemical and isotopic differences proposed to exist between the upper and lower mantles.

Suppression of the Hall number due to charge density wave order in high-Tc cuprates

NASA Astrophysics Data System (ADS)

Sharma, Girish; Nandy, S.; Taraphder, A.; Tewari, Sumanta

2018-05-01

Understanding the pseudogap phase in hole-doped high-temperature cuprate superconductors remains a central challenge in condensed-matter physics. From a host of recent experiments there is now compelling evidence of translational-symmetry-breaking charge density wave (CDW) order in a wide range of doping inside this phase. Two distinct types of incommensurate charge order, bidirectional at zero or low magnetic fields and unidirectional at high magnetic fields close to the upper critical field Hc 2, have been reported so far in approximately the same doping range between p ≃0.08 and p ≃0.16 . In concurrent developments, recent high-field Hall experiments have also revealed two indirect but striking signatures of Fermi surface reconstruction in the pseudogap phase, namely, a sign change of the Hall coefficient to negative values at low temperatures in the intermediate range of hole doping and a rapid suppression of the positive Hall number without a change in sign near optimal doping p ˜0.19 . We show that the assumption of a unidirectional incommensurate CDW (with or without a coexisting weak bidirectional order) at high magnetic fields near optimal doping and the coexistence of both types of orders of approximately equal magnitude at high magnetic fields in the intermediate range of doping may help explain the striking behavior of the low-temperature Hall effect in the entire pseudogap phase.

Vlasov Simulations of Ionospheric Heating Near Upper Hybrid Resonance

NASA Astrophysics Data System (ADS)

Najmi, A. C.; Eliasson, B. E.; Shao, X.; Milikh, G. M.; Papadopoulos, K.

2014-12-01

It is well-known that high-frequency (HF) heating of the ionosphere can excite field- aligned density striations (FAS) in the ionospheric plasma. Furthermore, in the neighborhood of various resonances, the pump wave can undergo parametric instabilities to produce a variety of electrostatic and electromagnetic waves. We have used a Vlasov simulation with 1-spatial dimension, 2-velocity dimensions, and 2-components of fields, to study the effects of ionospheric heating when the pump frequency is in the vicinity of the upper hybrid resonance, employing parameters currently available at ionospheric heaters such as HAARP. We have found that by seeding theplasma with a FAS of width ~20% of the simulation domain, ~10% depletion, and by applying a spatially uniform HF dipole pump electric field, the pump wave gives rise to a broad spectrum of density fluctuations as well as to upper hybrid and lower hybrid oscillating electric fields. We also observe collisionless bulk-heating of the electrons that varies non-linearly with the amplitude of the pump field.

Spatial and Temporal Patterns of Nitrification Rates in Forested Floodplain Wetland Soils of Upper Mississippi River Pool 8, Journal Article

EPA Science Inventory

Overbank flooding is thought to be a critical process controlling nitrogen retention and cycling. In this study we investigated the effects of season and flood frequency on soil nitrification rates at ten sites in forested floodplains of Upper Mississippi River, Pool 8...A rough ...

Large-cell renormalisation and systems of dimensionality larger than the upper marginal dimension

NASA Technical Reports Server (NTRS)

Nakanishi, H.

1984-01-01

A recent argument dismissing the applicability of large-cell renormalization schemes to systems whose dimensionality is larger than the upper marginal dimension is critically discussed. In this connection, new large-cell renormalization results for the random walk for a dimensionality of 3 and 4 are presented which indicate convergence to the correct results.

Effect of parallel refraction on magnetospheric upper hybrid waves

NASA Technical Reports Server (NTRS)

Engel, J.; Kennel, C. F.

1984-01-01

Large amplitude (not less than 10 mV/m) electrostatic plasma waves near the upper hybrid (UH) frequency have been observed from 0 to 50 deg magnetic latitude (MLAT) during satellite plasma-pause crossings. A three-dimensional numerical ray-tracing calculation, based on an electron distribution measured during a GEOS 1 dayside intense upper-hybrid wave event, suggests how UH waves might achieve such large amplitudes away from the geomagnetic equator. Refractive effects largely control the wave amplification and, in particular, the unavoidable refraction due to parallel geomagnetic field gradients restricts growth to levels below those observed. However, a cold electron density gradient parallel to the field can lead to upper hybrid wave growth that can account for the observed emission levels.

Upper bound of pier scour in laboratory and field data

USGS Publications Warehouse

Benedict, Stephen; Caldwell, Andral W.

2016-01-01

The U.S. Geological Survey (USGS), in cooperation with the South Carolina Department of Transportation, conducted several field investigations of pier scour in South Carolina and used the data to develop envelope curves defining the upper bound of pier scour. To expand on this previous work, an additional cooperative investigation was initiated to combine the South Carolina data with pier scour data from other sources and to evaluate upper-bound relations with this larger data set. To facilitate this analysis, 569 laboratory and 1,858 field measurements of pier scour were compiled to form the 2014 USGS Pier Scour Database. This extensive database was used to develop an envelope curve for the potential maximum pier scour depth encompassing the laboratory and field data. The envelope curve provides a simple but useful tool for assessing the potential maximum pier scour depth for effective pier widths of about 30 ft or less.

Asymptotics of the evolution semigroup associated with a scalar field in the presence of a non-linear electromagnetic field

NASA Astrophysics Data System (ADS)

Albeverio, Sergio; Tamura, Hiroshi

2018-04-01

We consider a model describing the coupling of a vector-valued and a scalar homogeneous Markovian random field over R4, interpreted as expressing the interaction between a charged scalar quantum field coupled with a nonlinear quantized electromagnetic field. Expectations of functionals of the random fields are expressed by Brownian bridges. Using this, together with Feynman-Kac-Itô type formulae and estimates on the small time and large time behaviour of Brownian functionals, we prove asymptotic upper and lower bounds on the kernel of the transition semigroup for our model. The upper bound gives faster than exponential decay for large distances of the corresponding resolvent (propagator).

Self field triggered superconducting fault current limiter

DOEpatents

Tekletsadik, Kasegn D [Rexford, NY

2008-02-19

A superconducting fault current limiter array with a plurality of superconductor elements arranged in a meanding array having an even number of supconductors parallel to each other and arranged in a plane that is parallel to an odd number of the plurality of superconductors, where the odd number of supconductors are parallel to each other and arranged in a plane that is parallel to the even number of the plurality of superconductors, when viewed from a top view. The even number of superconductors are coupled at the upper end to the upper end of the odd number of superconductors. A plurality of lower shunt coils each coupled to the lower end of each of the even number of superconductors and a plurality of upper shunt coils each coupled to the upper end of each of the odd number of superconductors so as to generate a generally orthoganal uniform magnetic field during quenching using only the magenetic field generated by the superconductors.

Initial Assessment of the Ares I-X Launch Vehicle Upper Stage to Vibroacoustic Flight Environments

NASA Technical Reports Server (NTRS)

Larko, Jeffrey M.; Hughes, William O.

2008-01-01

The Ares I launch vehicle will be NASA s first new launch vehicle since 1981. Currently in design, it will replace the Space Shuttle in taking astronauts to the International Space Station, and will eventually play a major role in humankind s return to the Moon and eventually to Mars. Prior to any manned flight of this vehicle, unmanned test readiness flights will be flown. The first of these readiness flights, named Ares I-X, is scheduled to be launched in April 2009. The NASA Glenn Research Center is responsible for the design, manufacture, test and analysis of the Ares I-X upper stage simulator (USS) element. As part of the design effort, the structural dynamic response of the Ares I-X launch vehicle to its vibroacoustic flight environments must be analyzed. The launch vehicle will be exposed to extremely high acoustic pressures during its lift-off and aerodynamic stages of flight. This in turn will cause high levels of random vibration on the vehicle's outer surface that will be transmitted to its interior. Critical flight equipment, such as its avionics and flight guidance components are susceptible to damage from this excitation. This study addresses the modelling, analysis and predictions from examining the structural dynamic response of the Ares I-X upper stage to its vibroacoustic excitations. A statistical energy analysis (SEA) model was used to predict the high frequency response of the vehicle at locations of interest. Key to this study was the definition of the excitation fields corresponding to lift off acoustics and the unsteady aerodynamic pressure fluctuations during flight. The predicted results will be used by the Ares I-X Project to verify the flight qualification status of the Ares I-X upper stage components.

Materials and Physics in Pnictide Superconductors

NASA Astrophysics Data System (ADS)

Wen, Hai-Hu

2009-03-01

Superconductivity in the pnictides has shown itself to be very interesting and attractive. Some experimental results have revealed that the superconducting mechanism could be unconventional. In this talk I will survey our recent progress of both material synthesizing and physical properties of this rich family. We have made several major contributions to the synthesizing of new pnictide superconductors. (1) Fabrication of the hole doped RE1-xSrxFeAsO samples (RE=La and Pr); (2) Fabrication of a series of new parent compounds DvFeAsF (Dv=divalent metals: Sr, Ca, Eu etc.) and many new superconductors with Tc beyond 50 K by doping electrons into the system; (3) Invention of the new material (Sr3Sc2O5)Fe2As2 with rather large spacing distance between the FeAs planes. We have successfully grown the NdFeAsO1-xFx and Ba1-xKxFe2As2 single crystals. It is found that the anomalous electron scattering in the normal state cannot be simply attributed to the multiband effect. The influence given by the magnetic correlation may play an important role. Specific heat, lower critical field and point contact tunneling all indicate the unconventional superconductivity and multigap features, while the paring symmetry of the superconducting gap may be a non-trivial issue. In the 1111 phase, the superfluid density is rather low and contains probably a nodal feature. While in the 122 phase, both the superfluid density and the quasiparticle density of states is about 5-10 times higher than that in the 1111 phase. An s-wave component was found in the 122 phase. I will also report the measurements on anisotropy, critical current density, critical fields and vortex phase diagram. Small anisotropy, high upper critical field and fish-tail effect (in 122) were observed. All these suggest very good potential applications. In collaboration with Gang Mu, Zhaosheng Wang, Huiqian Luo, Huan Yang, Xiyu Zhu, Ying Jia, Yonglei Wang, Fei Han, Bing Zeng, Bing Shen, Cong Ren, Lei Shan.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Negus-De Wys, J.; Dixon, J. M.; Evans, M. A.

This document consists of the following papers: inorganic geochemistry studies of the Eastern Kentucky Gas Field; lithology studies of upper Devonian well cuttings in the Eastern Kentucky Gas Field; possible effects of plate tectonics on the Appalachian Devonian black shale production in eastern Kentucky; preliminary depositional model for upper Devonian Huron age organic black shale in the Eastern Kentucky Gas Field; the anatomy of a large Devonian black shale gas field; the Cottageville (Mount Alto) Gas Field, Jackson County, West Virginia: a case study of Devonian shale gas production; the Eastern Kentucky Gas Field: a geological study of the relationshipsmore » of Ohio Shale gas occurrences to structure, stratigraphy, lithology, and inorganic geochemical parameters; and a statistical analysis of geochemical data for the Eastern Kentucky Gas Field.« less

NOAA/NWS Storm Prediction Center

Science.gov Websites

Thunderstorm/Tornado Watches Mesoscale Discussions Convective Outlooks Thunderstorm Outlook Fire Weather Analysis Sounding Climatology Upper-Air Maps HREF HRRR Browser SREF SREF Plumes Fire Weather Composite Maps Convective Outlook. Critical fire weather conditions are forecast today. See details... Critical fire weather

Predicting the Mobility and Burial of Underwater Unexploded Ordnance (UXO) using the UXO Mobility Model. Field Test Report (PMRF Barking Sands, Kauai, Hawaii)

DTIC Science & Technology

2008-05-20

of the demonstration; yellow stars indicate the inshore and offshore fields. ................. 39 Figure 19. Wave height (upper) and current...demonstration; yellow stars indicate the inshore and offshore fields. 40 Figure 19. Wave height (upper) and current magnitude (lower) measured...State Park to Barking Sands, are composed of material eroded from the Kokee Highlands, remnant of a shield volcano that is dissected on its western side

A Semiarid Long-Term Hydrologic Observatory at the Continental Scale: The Upper Río Grande Basin

NASA Astrophysics Data System (ADS)

Hogan, J. F.; Vivoni, E. R.; Bowman, R. S.; Coonrod, J.; Thomson, B. M.; Samani, Z.; Ferre, P. T.; Phillips, F. M.; Rango, A.; Rasmussen, R.; Springer, E. P.; Small, E. E.

2004-12-01

Water availability is critical in arid and semiarid regions, which comprise 35 percent of the land area of the globe. In the Southwestern US, climate variability and landscape heterogeneity lead to strong gradients in hydrological processes, which in turn impact land-atmosphere interactions, ecological dynamics, biogeochemical cycles and geomorphic change. This complexity presents a fundamental challenge to our understanding of hydrology, one that is best addressed through long-term, systematic field and remote-sensing observations and numerical-model investigations. In this poster, we will present our plans to study the interaction of climate-landscape-vegetation and water using a nested set of instrumented sites within the Upper Río Grande, a continental-scale semiarid watershed. This complex watershed extends from the snow-dominated headwater basins in San Juan Mountains of southern Colorado, through the Chihuahuan Desert in New Mexico, Texas and Mexico, to the desert valley alluvial basins southeast of El Paso, Texas. As part of the Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) plan for a network of Long-Term Hydrologic Observatories (LTHOs), the Upper Río Grande would represent the combination of mountain landscapes, semiarid to arid alluvial basin aquifers and riparian corridors that are characteristic of the Western United States. We will describe existing hydrologic, ecologic and atmospheric measurement infrastructure in the watershed and discuss plans for integrating these into a coherent network that provides a core set of scientific data products for the hydrologic community. Data products generated by the Upper Río Grande LTHO will also aid in the testing of coupled numerical models of the atmosphere-surface-groundwater system applied at high resolution over the region. The Upper Río Grande presents unique opportunities to test hydrologic hypotheses concerning surface water-groundwater interactions and their control on runoff response, solute transport and reactivity, and riparian ecological communities

Inner core boundary topography explored with reflected and diffracted P waves

NASA Astrophysics Data System (ADS)

deSilva, Susini; Cormier, Vernon F.; Zheng, Yingcai

2018-03-01

The existence of topography of the inner core boundary (ICB) can affect the amplitude, phase, and coda of body waves incident on the inner core. By applying pseudospectral and boundary element methods to synthesize compressional waves interacting with the ICB, these effects are predicted and compared with waveform observations in pre-critical, critical, post-critical, and diffraction ranges of the PKiKP wave reflected from the ICB. These data sample overlapping regions of the inner core beneath the circum-Pacific belt and the Eurasian, North American, and Australian continents, but exclude large areas beneath the Pacific and Indian Oceans and the poles. In the pre-critical range, PKiKP waveforms require an upper bound of 2 km at 1-20 km wavelength for any ICB topography. Higher topography sharply reduces PKiKP amplitude and produces time-extended coda not observed in PKiKP waveforms. The existence of topography of this scale smooths over minima and zeros in the pre-critical ICB reflection coefficient predicted from standard earth models. In the range surrounding critical incidence (108-130 °), this upper bound of topography does not strongly affect the amplitude and waveform behavior of PKIKP + PKiKP at 1.5 Hz, which is relatively insensitive to 10-20 km wavelength topography height approaching 5 km. These data, however, have a strong overlap in the regions of the ICB sampled by pre-critical PKiKP that require a 2 km upper bound to topography height. In the diffracted range (>152°), topography as high as 5 km attenuates the peak amplitudes of PKIKP and PKPCdiff by similar amounts, leaving the PKPCdiff/PKIKP amplitude ratio unchanged from that predicted by a smooth ICB. The observed decay of PKPCdiff into the inner core shadow and the PKIKP-PKPCdiff differential travel time are consistent with a flattening of the outer core P velocity gradient near the ICB and iron enrichment at the bottom of the outer core.

A Hybrid Sport Education-Games for Understanding Striking/Fielding Unit for Upper Elementary Pupils

ERIC Educational Resources Information Center

Curtner-Smith, Matthew

2004-01-01

This article describes a hybrid Sport Education-Games for Understanding unit through which upper elementary pupils can learn to play basic striking/fielding games. The unit is written for a class of 30 pupils. The twenty-five lesson unit is described in detail within 10 stages: (1) Getting started and early skill, strategy, rule, and role work…

The essential spectrum of Schrödinger operators with asymptotically constant magnetic fields on the Poincaré upper-half plane

NASA Astrophysics Data System (ADS)

Inahama, Yuzuru; Shirai, Shin-ichi

2003-01-01

We study the essential spectrum of the magnetic Schrödinger operators on the Poincaré upper-half plane and establish a hyperbolic analog of Iwatsuka's result [J. Math. Kyoto Univ. 23(3), 475-480 (1983)] on the stability of the essential spectrum under perturbations from constant magnetic fields.

Superconducting properties of NbN film, bridge and meanders

NASA Astrophysics Data System (ADS)

Joshi, Lalit M.; Verma, Apoorva; Gupta, Anurag; Rout, P. K.; Husale, Sudhir; Budhani, R. C.

2018-05-01

The transport properties of superconducting NbN nanostructures in the form of thin film, bridge of width (w) = 50 μm and three meanders of w = 500, 250 and 100 nm have been investigated by resistance (R) measurements in temperature (T) range = 2 -300 K and magnetic field (B) range = 0 - 7 Tesla. The nanostructuring was carried out using Focused Ion Beam (FIB) milling. Reduction of sample width results in significant changes in the normal and superconducting state properties. For instance, the observed metallic behavior in the thin film sample is lost and the normal state resistance increases drastically from 2.4 Ω to 418 kΩ for the 100 nm meander. In the superconducting state, the value of critical temperature Tc (upper critical field Bc2 at T = 0 K) reduces gradually with width reduction, it changes from 13.15 K (42.8 Tesla) in the case of thin film sample to 5.7 K (12.7 Tesla) for the 100 nm meander sample. The superconducting transitions are found to get broader for the bridge sample and the meanders additionally show low-temperature resistive tails. In case of all the samples with reduced width, the transition onsets are found to be rounded at surprisingly high values of T ˜ 25 K >> Tc. These results are discussed in terms of the possible effects of FIB processing and weak localization in our samples.

Agricultural Intensification in the Amazon: Tracking Nitrogen Fertilizer from Soy-Maize Double Cropping to Streams

NASA Astrophysics Data System (ADS)

Cabrera, V. D.; Jankowski, K.; Neill, C.; Macedo, M.; Deegan, L.; Brando, P. M.; Nascimento, S.; Nascimento, E.; Rocha, S.; Coe, M. T.; Nunes, D.

2015-12-01

Globalization and the increasing demand for food create pressure to both expand and intensify agriculture. These changes have potentially large consequences for the solute concentrations and functioning of streams. In the Brazilian Amazon, crop agriculture expanded greatly during the last 20 years. More recently, farmers have intensified production on existing cropland by double cropping of soy and maize during the same year. Maize, a novel crop for the region, requires much higher applications of nitrogen (N) fertilizer than soybeans. To determine whether this novel land use and associated N addition influenced N concentrations in groundwater and stream water, we measured N concentrations in groundwater wells and streams from small headwater watersheds across three land uses (soy-maize, soy, and tropical forest) in the Upper Xingu Basin, a region of rapid cropland intensification in the southern Amazon. Each watershed contained six groundwater wells arranged in a transect reaching cropland field edge on either side of the stream. Total inorganic N concentrations were higher in wells adjacent to fields where double cropping occurred, while stream concentrations did not differ overall among land uses. This suggests the riparian zones are critical in the removal of N, but as the intensification of agriculture continues the ability of the riparian zone to prevent N from traveling to streams is unknown. Their protection is critical to the functioning of tropical watersheds.

Mixing Layer Formation near the Tropopause Due to Gravity Wave Critical Level Interactions in a Cloud-Resolving Model.

NASA Astrophysics Data System (ADS)

Moustaoui, Mohamed; Joseph, Binson; Teitelbaum, Hector

2004-12-01

A plausible mechanism for the formation of mixing layers in the lower stratosphere above regions of tropical convection is demonstrated numerically using high-resolution, two-dimensional (2D), anelastic, nonlinear, cloud-resolving simulations. One noteworthy point is that the mixing layer simulated in this study is free of anvil clouds and well above the cloud anvil top located in the upper troposphere. Hence, the present mechanism is complementary to the well-known process by which overshooting cloud turrets causes mixing within stratospheric anvil clouds. The paper is organized as a case study verifying the proposed mechanism using atmospheric soundings obtained during the Central Equatorial Pacific Experiment (CEPEX), when several such mixing layers, devoid of anvil clouds, had been observed. The basic dynamical ingredient of the present mechanism is (quasi stationary) gravity wave critical level interactions, occurring in association with a reversal of stratospheric westerlies to easterlies below the tropopause region. The robustness of the results is shown through simulations at different resolutions. The insensitivity of the qualitative results to the details of the subgrid scheme is also evinced through further simulations with and without subgrid mixing terms. From Lagrangian reconstruction of (passive) ozone fields, it is shown that the mixing layer is formed kinematically through advection by the resolved-scale (nonlinear) velocity field.

Enhanced detection of a low-frequency signal by using broad squeezed light and a bichromatic local oscillator

NASA Astrophysics Data System (ADS)

Li, Wei; Jin, Yuanbin; Yu, Xudong; Zhang, Jing

2017-08-01

We experimentally study a protocol of using the broadband high-frequency squeezed vacuum to detect the low-frequency signal. In this scheme, the lower sideband field of the squeezed light carries the low-frequency modulation signal, and the two strong coherent light fields are applied as the bichromatic local oscillator in the homodyne detection to measure the quantum entanglement of the upper and lower sideband for the broadband squeezed light. The power of one of the local oscillators for detecting the upper sideband can be adjusted to optimize the conditional variance in the low-frequency regime by subtracting the photocurrent of the upper sideband field of the squeezed light from that of the lower sideband field. By means of the quantum correlation of the upper and lower sideband for the broadband squeezed light, the low-frequency signal beyond the standard quantum limit is measured. This scheme is appropriate for enhancing the sensitivity of the low-frequency signal by the aid of the broad squeezed light, such as gravitational waves detection, and does not need to directly produce the low-frequency squeezing in an optical parametric process.

Groundwater conditions and studies in the Augusta–Richmond County area, Georgia, 2008–2009

USGS Publications Warehouse

Gonthier, Gerard; Lawrence, Stephen J.; Peck, Michael F.; Holloway, O. Gary

2011-01-01

Groundwater studies and monitoring efforts conducted during 2008–2009, as part of the U.S. Geological Survey (USGS) Cooperative Water Program with the City of Augusta in Richmond County, Georgia, provided data for the effective management of local water resources. During 2008–2009 the USGS completed: (1) installation of three monitoring wells and the collection of lithologic and geophysical logging data to determine the extent of hydrogeologic units, (2) collection of continuous groundwater-level data from wells near Well Fields 2 and 3, (3) collection of synoptic groundwater-level measurements and construction of potentiometric-surface maps in Richmond County to establish flow gradients and groundwater-flow directions in the Dublin and Midville aquifer systems, (4) completion of a 24-hour aquifer test to determine hydraulic characteristics of the lower Dublin aquifer, and upper and lower Midville aquifers in Well Field 2, and (5) collection of groundwater samples from selected wells in Well Field 2 for laboratory analysis of volatile organic compounds and groundwater tracers to assess groundwater quality and estimate the time of groundwater recharge. Potentiometric-surface maps of the Dublin and Midville aquifer systems for 2008–2009 indicate that the general groundwater flow direction within Richmond County is eastward toward the Savannah River, with the exception of the area around Well Field 2, where pumping interrupts the eastward flow of water toward the Savannah River and causes flow lines to bend toward the center of pumping. Results from a 24-hour aquifer test conducted in 2009 within the upper and lower Midville aquifers at Well Field 2 indicated a transmissivity and storativity for the upper and lower Midville aquifers, combined, of 4,000 feet-squared per day and 2x10-4, respectively. The upper and lower Midville aquifers and the middle lower Midville confining unit, which is 85-feet thick in this area, yielded horizontal hydraulic conductivity and specific storage values of about 45 feet per day and 2x10-6 ft-1, respectively. Results from the 24-hour aquifer test also indicate a low horizontal hydraulic conductivity for the lower Dublin aquifer of less than 1 foot per day. Of the 35 volatile organic compounds (VOCs) analyzed in 23 groundwater samples during 2008–2009, only six were detected above laboratory reporting limits in samples from eight wells. No concentration in groundwater samples collected during 2008–2009 exceeded drinking water standards. Trichloroethene had the maximum VOC concentration (1.9 micrograms per liter) collected from a water sample during 2008–2009. Water-quality sampling of several wells near Well Field 2 indicate that, while in operation, the northernmost production well might have diverted groundwater, containing low levels of trichloroethene from at least two other production wells. Analysis of sulfur hexafluoride data indicate the average year of recharge ranges between 1981 and 1984 for water samples from five wells open to the upper and lower Midville aquifers, and 1991 for a water sample from one shallow well open to the lower Dublin aquifer. All of these ages suggest a short flow path and nearby source of contamination. The actual source of low levels of VOCs at Well Field 2 remains unknown. Three newly installed monitoring wells indicate that hydrogeologic units beneath Well Fields 2 and 3 are composed of sand and clay layers. Hydrogeologic units, encountered at Well Field 2, in order of increasing depth are the lower Dublin confining unit, lower Dublin aquifer, upper Midville confining unit, upper Midville aquifer, lower Midville confining unit, and lower Midville aquifer. West of Well Field 3, hydrogeologic units, in order of increasing depth are the Upper Three Runs aquifer, Gordon confining unit, Gordon aquifer, lower Dublin confining unit, lower Dublin aquifer, upper Midville confining unit, upper Midville aquifer, lower Midville confining unit, and lower Midville aquifer.

Microstructure and trapped field of YBCO bulk single-grain superconductors prepared by interior seeding

NASA Astrophysics Data System (ADS)

Radusovska, M.; Diko, P.; Piovarci, S.; Park, S.-D.; Jun, B.-H.; Kim, C.-J.

2017-10-01

The microstructural analyses of YBCO bulk single-grain superconductors grown by interior seeding with taller and shorter upper pellets have shown that a suitable upper pellet height can lower the porosity in the upper part of the sample, produce a more appropriate distribution of pinning centres in the form of Y-211 particles and suppress subgrain formation with a higher crystal misalignment in the c-growth sector (c-GS), which can lead to a higher measured trapped magnetic field and a more uniform cone of the trapped-field profile. The observed bulging of the sample surface at the c-GS can be explained by the edge melt distribution model, which shows that macroscopic mass transport to the growth sector occurs with higher growth rates.

In/Visible Dimensions: Framing the Intercultural Communication Course through a Critical Intercultural Communication Framework

ERIC Educational Resources Information Center

Halualani, Rona Tamiko

2011-01-01

This article highlights how course material on "culture" and "intercultural communication" faces a distinctive challenge in crafting an engaged power-focused positionality for students. I discuss the importance of incorporating a "critical intercultural communication perspective and practice" into an upper-division diversity/intercultural…

Cases on Critical and Qualitative Perspectives in Online Higher Education

ERIC Educational Resources Information Center

Orleans, Myron, Ed.

2014-01-01

Online education continues to permeate mainstream teaching techniques in higher education settings. Teaching upper-level classes in an online setting is having a major impact on education as a whole and is fundamentally altering global learning. "Cases on Critical and Qualitative Perspectives in Online Higher Education" offers a…

Responses to Comments

DTIC Science & Technology

1989-04-01

34, New Phytology ., Vol. 79, pp 95-106. Davis, R. D., and P. H. T. Beckett. 1978. "Upper Critical Levels of Toxic Elements in Plants. II. Critical...Levels of Copper in Young Barley, Wheat, Rape, Lettuce, and Ryegrass, and of Nickel and Zinc in Young Barley and Ryegrass", New Phytology , Vol. 80, pp 23

Superconductivity in the system Mo{sub x}C{sub y}Ga{sub z}O{sub δ} prepared by focused ion beam induced deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weirich, P. M., E-mail: p.weirich@Physik.uni-frankfurt.de; Schwalb, C. H.; Winhold, M.

2014-05-07

We have prepared the new amorphous superconductor Mo{sub x}C{sub y}Ga{sub z}O{sub δ} with a maximum critical temperature T{sub c} of 3.8 K by the direct-write nano-patterning technique of focused (gallium) ion beam induced deposition (FIBID) using Mo(CO){sub 6} as precursor gas. From a detailed analysis of the temperature-dependent resistivity and the upper critical field, we found clear evidence for proximity of the samples to a disorder-induced metal-insulator transition. We observed a strong dependence of T{sub c} on the deposition parameters and identified clear correlations between T{sub c}, the localization tendency visible in the resistance data and the sample composition. By anmore » in-situ feedback-controlled optimization process in the FIB-induced growth, we were able to identify the beam parameters which lead to samples with the largest T{sub c}-value and sharpest transition into the superconducting state.« less

Heat treatment influence on the superconducting properties of nanometric-scale Nb3Sn wires with Cu-Sn artificial pinning centers

NASA Astrophysics Data System (ADS)

Da Silva, L. B. S.; Rodrigues, C. A.; Oliveira, N. F., Jr.; Bormio-Nunes, C.; Rodrigues, D., Jr.

2010-11-01

Since the discovery of Nb3Sn superconductors many efforts have been expended to improve the transport properties in these materials. In this work, the heat treatment profiles for Nb3Sn superconductor wires with Cu(Sn) artificial pinning centers (APCs) with nanometric-scale sizes were analyzed in an attempt to improve the critical current densities and upper critical magnetic field. The methodology to optimize the heat treatment profiles in respect to the diffusion, reaction and formation of the superconducting phases is described. Microstructural characterization, transport and magnetic measurements were performed in an attempt to relate the microstructure to the pinning mechanisms acting in the samples. It was concluded that the maximum current densities occur due to normal phases (APCs) that act as the main pinning centers in the global behavior of the Nb3Sn superconducting wire. The APC technique was shown to be very powerful because it permitted mixing of the pinning mechanism. This achievement was not possible in other studies in Nb3Sn wires reported up to now.

Numerical simulation of soft palate movement and airflow in human upper airway by fluid-structure interaction method

NASA Astrophysics Data System (ADS)

Sun, Xiuzhen; Yu, Chi; Wang, Yuefang; Liu, Yingxi

2007-08-01

In this paper, the authors present airflow field characteristics of human upper airway and soft palate movement attitude during breathing. On the basis of the data taken from the spiral computerized tomography images of a healthy person and a patient with Obstructive Sleep Apnea-Hypopnea Syndrome (OSAHS), three-dimensional models of upper airway cavity and soft palate are reconstructed by the method of surface rendering. Numerical simulation is performed for airflow in the upper airway and displacement of soft palate by fluid-structure interaction analysis. The reconstructed three-dimensional models precisely preserve the original configuration of upper airways and soft palate. The results of the pressure and velocity distributions in the airflow field are quantitatively determined, and the displacement of soft palate is presented. Pressure gradients of airway are lower for the healthy person and the airflow distribution is quite uniform in the case of free breathing. However, the OSAHS patient remarkably escalates both the pressure and velocity in the upper airway, and causes higher displacement of the soft palate. The present study is useful in revealing pathogenesis and quantitative mutual relationship between configuration and function of the upper airway as well as in diagnosing diseases related to anatomical structure and function of the upper airway.

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.

Limitations of the background field method applied to Rayleigh-Bénard convection

NASA Astrophysics Data System (ADS)

Nobili, Camilla; Otto, Felix

2017-09-01

We consider Rayleigh-Bénard convection as modeled by the Boussinesq equations, in the case of infinite Prandtl numbers and with no-slip boundary condition. There is a broad interest in bounds of the upwards heat flux, as given by the Nusselt number Nu, in terms of the forcing via the imposed temperature difference, as given by the Rayleigh number in the turbulent regime Ra ≫ 1 . In several studies, the background field method applied to the temperature field has been used to provide upper bounds on Nu in terms of Ra. In these applications, the background field method comes in the form of a variational problem where one optimizes a stratified temperature profile subject to a certain stability condition; the method is believed to capture the marginal stability of the boundary layer. The best available upper bound via this method is Nu ≲Ra/1 3 ( ln R a )/1 15 ; it proceeds via the construction of a stable temperature background profile that increases logarithmically in the bulk. In this paper, we show that the background temperature field method cannot provide a tighter upper bound in terms of the power of the logarithm. However, by another method, one does obtain the tighter upper bound Nu ≲ Ra /1 3 ( ln ln Ra ) /1 3 so that the result of this paper implies that the background temperature field method is unphysical in the sense that it cannot provide the optimal bound.

A high precision, compact electromechanical ground rotation sensor

NASA Astrophysics Data System (ADS)

Dergachev, V.; DeSalvo, R.; Asadoor, M.; Bhawal, A.; Gong, P.; Kim, C.; Lottarini, A.; Minenkov, Y.; Murphy, C.; O'Toole, A.; Peña Arellano, F. E.; Rodionov, A. V.; Shaner, M.; Sobacchi, E.

2014-05-01

We present a mechanical rotation sensor consisting of a balance pivoting on a tungsten carbide knife edge. These sensors are important for precision seismic isolation systems, as employed in land-based gravitational wave interferometers and for the new field of rotational seismology. The position sensor used is an air-core linear variable differential transformer with a demonstrated noise floor of {1}{ × 10^{-11}}textrm { m}/sqrt{textrm {Hz}}. We describe the instrument construction and demonstrate low noise operation with a noise floor upper bound of {5.7}{ × 10^{-9}}textrm { rad}/sqrt{textrm {Hz}} at 10 mHz and {6.4}{ × 10^{-10}}textrm { rad}/sqrt{textrm {Hz}} at 0.1 Hz. The performance of the knife edge hinge is compatible with a behaviorur free of noise from dislocation self-organized criticality.

Magnetosphere - Ionosphere - Thermosphere (MIT) Coupling at Jupiter

NASA Astrophysics Data System (ADS)

Yates, J. N.; Ray, L. C.; Achilleos, N.

2017-12-01

Jupiter's upper atmospheric temperature is considerably higher than that predicted by Solar Extreme Ultraviolet (EUV) heating alone. Simulations incorporating magnetosphere-ionosphere coupling effects into general circulation models have, to date, struggled to reproduce the observed atmospheric temperatures under simplifying assumptions such as azimuthal symmetry and a spin-aligned dipole magnetic field. Here we present the development of a full three-dimensional thermosphere model coupled in both hemispheres to an axisymmetric magnetosphere model. This new coupled model is based on the two-dimensional MIT model presented in Yates et al., 2014. This coupled model is a critical step towards to the development of a fully coupled 3D MIT model. We discuss and compare the resulting thermospheric flows, energy balance and MI coupling currents to those presented in previous 2D MIT models.

A critical velocity interaction between fast barium and strontium atoms and the terrestial ionospheric plasma

NASA Technical Reports Server (NTRS)

Deehr, C. S.; Wescott, E. M.; Stenbaek-Nielsen, H.; Romick, G. J.; Hallinan, T. J.; Foeppl, H.

1982-01-01

A disk of barium and strontium vapor traveling radially outward, perpendicular to the geomagnetic field lines, may be created by the detonation of a high-explosive, radially shaped charge with a liner composed of the two metals in the upper atmosphere. Because of solar radiation resonance, both the barium and the strontium may be optically tracked. Observations indicate the early formation of the metal ions thus evolved into a disk-shaped, stellate structure with a dark hole at the center of a radial structure. The results of these experiments indicate that the process could occur on a cosmic scale, and that unconfirmed aspects of the theory relating to this process could be determined through variation of the parameters in future radial rocket experiments.

Reliability enhancement through optimal burn-in

NASA Astrophysics Data System (ADS)

Kuo, W.

1984-06-01

A numerical reliability and cost model is defined for production line burn-in tests of electronic components. The necessity of burn-in is governed by upper and lower bounds: burn-in is mandatory for operation-critical or nonreparable component; no burn-in is needed when failure effects are insignificant or easily repairable. The model considers electronic systems in terms of a series of components connected by a single black box. The infant mortality rate is described with a Weibull distribution. Performance reaches a steady state after burn-in, and the cost of burn-in is a linear function for each component. A minimum cost is calculated among the costs and total time of burn-in, shop repair, and field repair, with attention given to possible losses in future sales from inadequate burn-in testing.

Exact coherent structures in an asymptotically reduced description of parallel shear flows

NASA Astrophysics Data System (ADS)

Beaume, Cédric; Knobloch, Edgar; Chini, Gregory P.; Julien, Keith

2015-02-01

A reduced description of shear flows motivated by the Reynolds number scaling of lower-branch exact coherent states in plane Couette flow (Wang J, Gibson J and Waleffe F 2007 Phys. Rev. Lett. 98 204501) is constructed. Exact time-independent nonlinear solutions of the reduced equations corresponding to both lower and upper branch states are found for a sinusoidal, body-forced shear flow. The lower branch solution is characterized by fluctuations that vary slowly along the critical layer while the upper branch solutions display a bimodal structure and are more strongly focused on the critical layer. The reduced equations provide a rational framework for investigations of subcritical spatiotemporal patterns in parallel shear flows.

Surface waves generated by shallow underwater explosions

NASA Technical Reports Server (NTRS)

Falade, A.; Holt, M.

1978-01-01

Surface water waves generated by surface and near surface point explosions are calculated. Taking the impulse distribution imparted at the water surface by the explosion as the overriding mechanism for transferring energy of the explosive to surface wave motion, the linearized theory of Kranzer and Keller is used to obtain the wave displacement in the far field. The impulse distribution is obtained by integrating the pressure wave over an appropriate time interval on a horizontal surface just beneath the undisturbed water surface. For surface explosions, a modified form of the similarity method first used by Collins and Holt is used to obtain the flow field. In the case of submerged explosions, the flow field is estimated by making necessary modifications to Sedov's similarity solution to account for the venting that accompanies the interaction of the leading (blast) wave with the ocean surface. Surface waves generated by a charge at six depths of placement (0.15 m, 0.30 m, 0.61 m, 0.91 m, 1.37 m, 3.05 m) are considered in addition to surface explosions. The results seem to support the existence of an upper critical depth phenomenon (of the type already established for chemical explosions) for point (nuclear) explosions.

Non-Solenoidal Startup Research Directions on the Pegasus Toroidal Experiment

NASA Astrophysics Data System (ADS)

Fonck, R. J.; Bongard, M. W.; Lewicki, B. T.; Reusch, J. A.; Winz, G. R.

2017-10-01

The Pegasus research program has been focused on developing a physical understanding and predictive models for non-solenoidal tokamak plasma startup using Local Helicity Injection (LHI). LHI employs strong localized electron currents injected along magnetic field lines in the plasma edge that relax through magnetic turbulence to form a tokamak-like plasma. Pending approval, the Pegasus program will address a broader, more comprehensive examination of non-solenoidal tokamak startup techniques. New capabilities may include: increasing the toroidal field to 0.6 T to support critical scaling tests to near-NSTX-U field levels; deploying internal plasma diagnostics; installing a coaxial helicity injection (CHI) capability in the upper divertor region; and deploying a modest (200-400 kW) electron cyclotron RF capability. These efforts will address scaling of relevant physics to higher BT, separate and comparative studies of helicity injection techniques, efficiency of handoff to consequent current sustainment techniques, and the use of ECH to synergistically improve the target plasma for consequent bootstrap and neutral beam current drive sustainment. This has an ultimate goal of validating techniques to produce a 1 MA target plasma in NSTX-U and beyond. Work supported by US DOE Grant DE-FG02-96ER54375.

Assessment of upper airway mechanics during sleep.

PubMed

Farré, Ramon; Montserrat, Josep M; Navajas, Daniel

2008-11-30

Obstructive sleep apnea, which is the most prevalent sleep breathing disorder, is characterized by recurrent episodes of upper airway collapse and reopening. However, the mechanical properties of the upper airway are not directly measured in routine polysomnography because only qualitative sensors (thermistors for flow and thoraco-abdominal bands for pressure) are used. This review focuses on two techniques that quantify upper airway obstruction during sleep. A Starling model of collapsible conduit allows us to interpret the mechanics of the upper airway by means of two parameters: the critical pressure (Pcrit) and the upstream resistance (Rup). A simple technique to measure Pcrit and Rup involves the application of different levels of continuous positive airway pressure (CPAP) during sleep. The forced oscillation technique is another non-invasive procedure for quantifying upper airway impedance during the breathing cycle in sleep studies. The latest developments in these two methods allow them to be easily applied on a routine basis in order to more fully characterize upper airway mechanics in patients with sleep breathing disorders.

The Study of the plasmaspheric refilling using the data from the ERG, the VAPs, the ground-based magnetometers and the IPE model

NASA Astrophysics Data System (ADS)

Obana, Y.; Maruyama, N.; Masahito, N.; Matsuoka, A.; Teramoto, M.; Nomura, R.; Fujimoto, A.; Tanaka, Y.; Shinohara, M.; Kasahara, Y.; Matsuda, S.; Kumamoto, A.; Tsuchiya, F.; Yoshizumi, M.; Shinohara, I.

2017-12-01

Earth's inner magnetosphere is a complex dynamical region of geo space comprising plasma populations with wide energy ranges, the plasmasphere, ring current, and radiation belts. They form a closely coupled system, thus, the plasmasphere is the lowest energy population in the inner magnetosphere, but the accurate prediction of the evolution of the plasmasphere is critical in understanding the dynamics of the inner magnetosphere, which include even the highest energy population, the radiation belts. In this study, we study plasmaspheric refilling following geomagnetic storms using data from ERG-MGF, ERG-PWE, RBSP-EMFISIS and Ground-based magneto­meters. DC magnetic field data measured by ERG-MGF, RBSP-EMFISIS and ground-based magnetometers provides the frequency of the toroidal mode field line resonances. From this information, the equatorial plasma mass density is estimated by solving the MHD wave equation for suitable models of the magnetic field and the field line density distribution. ERG-PWE and RBSP-EMFISIS provide measurements of wave electric and magnetic field, thus we can estimate the local electron density from the plasma wave spectrograms by identifying narrow-band emission at the upper-hybrid resonance frequency. Furthermore, using Ionosphere Plasmasphere Electrodynamics Model (IPE), we calculate the plasmaspheric refilling rates and evaluate the relative contribution of various mechanisms (heating, neutral particle density, composition and wings, etc.) to the refilling rate.

Two Types of Long-duration Quasi-static Evolution of Solar Filaments

NASA Astrophysics Data System (ADS)

Xing, C.; Li, H. C.; Jiang, B.; Cheng, X.; Ding, M. D.

2018-04-01

In this Letter, we investigate the long-duration quasi-static evolution of 12 pre-eruptive filaments (four active region (AR) and eight quiescent filaments), mainly focusing on the evolution of the filament height in 3D and the decay index of the background magnetic field. The filament height in 3D is derived through two-perspective observations of Solar Dynamics Observatory (SDO) and Solar TErrestrial RElations Observatory (STEREO). The coronal magnetic field is reconstructed using the potential field source surface model. A new finding is that the filaments we studied show two types of long-duration evolution: one type comprises a long-duration static phase and a short, slow rise phase with a duration of less than 12 hr and a speed of 0.1–0.7 km s‑1, while the other one only presents a slow rise phase but with an extremely long duration of more than 60 hr and a smaller speed of 0.01–0.2 km s‑1. At the moment approaching the eruption, the decay index of the background magnetic field at the filament height is similar for both AR and quiescent filaments. The average value and upper limit are ∼0.9 and ∼1.4, close to the critical index of torus instability. Moreover, the filament height and background magnetic field strength are also found to be linearly and exponentially related with the filament length, respectively.

Instability of a cantilevered flexible plate in viscous channel flow

NASA Astrophysics Data System (ADS)

Balint, T. S.; Lucey, A. D.

2005-10-01

The stability of a flexible cantilevered plate in viscous channel flow is studied as a representation of the dynamics of the human upper airway. The focus is on instability mechanisms of the soft palate (flexible plate) that cause airway blockage during sleep. We solve the Navier Stokes equations for flow with Reynolds numbers up to 1500 fully coupled with the dynamics of the plate motion solved using finite-differences. The study is 2-D and based upon linearized plate mechanics. When both upper and lower airways are open, the plate is found to lose its stability through a flutter mechanism and a critical Reynolds number exists. When one airway is closed, the plate principally loses its stability through a divergence mechanism and a critical flow speed exists. However, below the divergence-onset flow speed, flutter can exist for low levels of structural damping in the flexible plate. Our results serve to extend understanding of flow-induced instability of cantilevered flexible plates and will ultimately improve the diagnosis and treatment of upper-airway disorders.

Formation and dissociation of dust molecules in dusty plasma

NASA Astrophysics Data System (ADS)

Yan, Jia; Feng, Fan; Liu, Fucheng; Dong, Lifang; He, Yafeng

2016-09-01

Dust molecules are observed in a dusty plasma experiment. By using measurements with high spatial resolution, the formation and dissociation of the dust molecules are studied. The ion cloud in the wake of an upper dust grain attracts the lower dust grain nearby. When the interparticle distance between the upper dust grain and the lower one is less than a critical value, the two dust grains would form a dust molecule. The upper dust grain always leads the lower one as they travel. When the interparticle distance between them is larger than the critical value, the dust molecule would dissociate. Project supported by the National Natural Science Foundation of China (Grant Nos. 11205044 and 11405042), the Natural Science Foundation of Hebei Province, China (Grant Nos. A2011201006 and A2012201015), the Research Foundation of Education Bureau of Hebei Province, China (Grant No. Y2012009), the Program for Young Principal Investigators of Hebei Province, China, and the Midwest Universities Comprehensive Strength Promotion Project, China.

Thermal biology, population fluctuations and implications of temperature extremes for the management of two globally significant insect pests.

PubMed

Nyamukondiwa, Casper; Weldon, Christopher W; Chown, Steven L; le Roux, Peter C; Terblanche, John S

2013-12-01

The link between environmental temperature, physiological processes and population fluctuations is a significant aspect of insect pest management. Here, we explore how thermal biology affects the population abundance of two globally significant pest fruit fly species, Ceratitis capitata (medfly) and C. rosa (Natal fruit fly), including irradiated individuals and those expressing a temperature sensitive lethal (tsl) mutation that are used in the sterile insect technique. Results show that upper and lower lethal temperatures are seldom encountered at the field sites, while critical minimum temperatures for activity and lower developmental thresholds are crossed more frequently. Estimates of abundance revealed that C. capitata are active year-round, but abundance declines markedly during winter. Temporal autocorrelation of average fortnightly trap captures and of development time, estimated from an integrated model to calculate available degree days, show similar seasonal lags suggesting that population increases in early spring occur after sufficient degree-days have accumulated. By contrast, population collapses coincide tightly with increasing frequency of low temperature events that fall below critical minimum temperatures for activity. Individuals of C. capitata expressing the tsl mutation show greater critical thermal maxima and greater longevity under field conditions than reference individuals. Taken together, this evidence suggests that low temperatures limit populations in the Western Cape, South Africa and likely do so elsewhere. Increasing temperature extremes and warming climates generally may extend the season over which these species are active, and could increase abundance. The sterile insect technique may prove profitable as climates change given that laboratory-reared tsl flies have an advantage under warmer conditions. Copyright © 2013 Elsevier Ltd. All rights reserved.

Bulk Kosterlitz-Thouless Type Molecular Superconductor β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]·18-crown-6.

PubMed

Martin, Lee; Lopez, Jordan R; Akutsu, Hiroki; Nakazawa, Yasuhiro; Imajo, Shusaku

2017-11-20

A new molecular superconductor, β″-(BEDT-TTF) 2 [(H 2 O)(NH 4 ) 2 Cr(C 2 O 4 ) 3 ]·18-crown-6, has been synthesized from the organic donor molecule BEDT-TTF with the anion Cr(C 2 O 4 ) 3 3- . The crystal structure consists of conducting organic layers of BEDT-TTF molecules which adopt the β″ packing motif (layer A), layers of NH 4 + and Λ-Cr(C 2 O 4 ) 3 3- (layer B), layers of (H 2 O)(NH 4 )18-crown-6 (layer C), and layers of NH 4 + and Δ-Cr(C 2 O 4 ) 3 3- (layer D) which produce a superstructure with a repeating pattern of ABCDABCDA. As a result of this packing arrangement, this is the 2D superconductor with the widest gap between conducting layers where only a single donor packing motif is present (β″). Superconducting critical temperatures at ambient pressure observed by electrical transport and magnetic measurements are 4.0-4.9 and 2.5 K, respectively. The strong 2D nature of this system, the broad transition to T zero at 1.8K, and the transition of α of V ∝ I α from 1 to 3 on I-V curves strongly suggest that the superconducting transition is very close to a Kosterlitz-Thouless transition. The magnetic field dependence of the superconducting critical temperature parallel to the conducting plane gives an upper critical field μ 0 H c2∥ > 8 T, which is over the calculated Pauli-Clogston limit for this material.

[Research on output and quality of Panax notoginseng and annual change characteristics of N, P and K nutrients of planting soil under stereo-cultivation].

PubMed

Huang, Chun-mei; Cui, Xiu-ming; Lan, Lei; Chen, Wei-dong; Wang, Cheng-xiao; Yang, Xiao-yan; Lu, Da-hui; Yang, Ye

2015-08-01

The output and agronomic characters of 3-year-old Panax notoginseng cultured under stereo structure (upper, middle and down layers) were investigated, and the annual change of N, P and K of its planting soil were also studied. Results showed that, compared with field cultured Panax notoginseng, growth vigour and output of stereo-cultivation were significantly lower. But the total production of the 3 layers was 1.6 times of field. The growth vigor and production of P. notoginseng was in the order of upper layer > middle layer > down layer. The content of ginsenoside in rhizome, root tuber and hair root of P. notoginseng was in the order of upper layer > field > middle layer > down layer. Organic matter content and pH of stereo-cultivation soil decreased with the prolonging of planting time, which with the same trend of yield. Organic matter content of stereo-cultivation soil was significantly higher than field, but the pH was significantly lower. Contents of total and available N, P and K in stereo-cultivation soil and field decreased with the prolonging of planting time. The content of N and P were in the order of upper layer > middle layer > yield > down layer, the content of K was in the order of upper layer > middle layer > down layer > yield. Compared with field, the proportion of N and P in the organ of underground (rhizome, root tuber and hair root) of upper layer were increased, while decreased in middle and down layers. Proportion of K in underground decreased significantly of the 3 layers. In conclusion, the agronomic characters and production of stereo-cultivation were significantly lower than that of yield. But the total production of the 3 layers were significantly higher than field of unit area. And the aim of improving land utilization efficiency was achieved. Nutritions in the soil of stereo-cultivation were enough to support the development of P. notoginseng, which was not the cause of weak growth and low production. The absorbing ability of P. notoginseng to N, P and K nutrients was decreased by stereo-cultivation mode. So, improve the growth vigour of P. notoginseng from the perspective of adjusting the stereo-cultivation mode so as to improve the nutrient absorption capacity is the future direction.

A quasi-static model of global atmospheric electricity. II - Electrical coupling between the upper and lower atmosphere

NASA Technical Reports Server (NTRS)

Roble, R. G.; Hays, P. B.

1979-01-01

The paper presents a model of global atmospheric electricity used to examine the effect of upper atmospheric generators on the global electrical circuit. The model represents thunderstorms as dipole current generators randomly distributed in areas of known thunderstorm frequency; the electrical conductivity in the model increases with altitude, and electrical effects are coupled with a passive magnetosphere along geomagnetic field lines. The large horizontal-scale potential differences at ionospheric heights map downward into the lower atmosphere where the perturbations in the ground electric field are superimposed on the diurnal variation. Finally, changes in the upper atmospheric conductivity due to solar flares, polar cap absorptions, and Forbush decreases are shown to alter the downward mapping of the high-latitude potential pattern and the global distribution of fields and currents.

Installation of the Canadian Muon Cargo Inspection System at CRL

DTIC Science & Technology

2014-04-01

2-3 2.4 Critical Infrastructure Protection ...................................................................... 2-4 2.5 Other Applications...of muon tomography .......................................................... 2-4 2.5.1 Imaging Critical Facilities...cosmic radiation with the upper layer of the atmosphere. They are charged like the electron, which makes them easy to detect, but have a large mass

Aligning Best Practices to Develop Targeted Critical Thinking Skills and Habits

ERIC Educational Resources Information Center

Heft, Ilea E.; Scharff, Lauren F. V.

2017-01-01

This project evaluated the effectiveness of a course design within an upper-level biology course that incorporated what prior scholarship of teaching and learning (SoTL) research has suggested to be best practices for developing critical thinking skills while also managing the grading load on the instructor. These efforts centered on the…

Two Configurations for Accessing Classroom Computers: Differential Impact on Students' Critical Reflections and Their Empowerment

ERIC Educational Resources Information Center

Solhaug, T.

2009-01-01

The context of this article is the new technological environment and the struggle to use meaningful teaching practices in Norwegian schools. Students' critical reflections in two different technological learning environments in six upper secondary schools are compared. Three of these schools offer Internet-connected computers in special computer…

Hemispheric differences in recognizing upper and lower facial displays of emotion.

PubMed

Prodan, C I; Orbelo, D M; Testa, J A; Ross, E D

2001-01-01

To determine if there are hemispheric differences in processing upper versus lower facial displays of emotion. Recent evidence suggests that there are two broad classes of emotions with differential hemispheric lateralization. Primary emotions (e.g. anger, fear) and associated displays are innate, are recognized across all cultures, and are thought to be modulated by the right hemisphere. Social emotions (e.g., guilt, jealousy) and associated "display rules" are learned during early child development, vary across cultures, and are thought to be modulated by the left hemisphere. Display rules are used by persons to alter, suppress or enhance primary emotional displays for social purposes. During deceitful behaviors, a subject's true emotional state is often leaked through upper rather than lower facial displays, giving rise to facial blends of emotion. We hypothesized that upper facial displays are processed preferentially by the right hemisphere, as part of the primary emotional system, while lower facial displays are processed preferentially by the left hemisphere, as part of the social emotional system. 30 strongly right-handed adult volunteers were tested tachistoscopically by randomly flashing facial displays of emotion to the right and left visual fields. The stimuli were line drawings of facial blends with different emotions displayed on the upper versus lower face. The subjects were tested under two conditions: 1) without instructions and 2) with instructions to attend to the upper face. Without instructions, the subjects robustly identified the emotion displayed on the lower face, regardless of visual field presentation. With instructions to attend to the upper face, for the left visual field they robustly identified the emotion displayed on the upper face. For the right visual field, they continued to identify the emotion displayed on the lower face, but to a lesser degree. Our results support the hypothesis that hemispheric differences exist in the ability to process upper versus lower facial displays of emotion. Attention appears to enhance the ability to explore these hemispheric differences under experimental conditions. Our data also support the recent observation that the right hemisphere has a greater ability to recognize deceitful behaviors compared with the left hemisphere. This may be attributable to the different roles the hemispheres play in modulating social versus primary emotions and related behaviors.

Boeing CST-100 Starliner Processing

NASA Image and Video Library

2018-04-26

Boeing’s CST-100 Starliner Orbital Flight Test vehicle will fly the first test flight to space on an uncrewed mission to the International Space Station. Here you see the spacecraft’s upper dome undergoing the final preparations before the upper and lower dome are mated for a pressure test, and then the two domes will move on to be populated with avionics, life support and other critical hardware.

Discussion Starter: The Case for Duplexing without Channel Flow During the Development and Emplacement of the Himalayan Middle Crust

NASA Astrophysics Data System (ADS)

Webb, A. G.; He, D.; Yu, H.

2015-12-01

This presentation and another presentation led by Dawn Kellett will preface a ten-minute open discussion on how the Himalayan middle crust was developed and emplaced. Current hypotheses are transitioning from a set including wedge extrusion, channel flow with focused denudation, and tectonic wedging to a revised dichotomy: models with intense upper plate out-of-sequence activity (i.e., tunneling of channel flow, and critical taper wedge behavior) versus models in which the upper plate mainly records basal accretion of horses (i.e., duplexing). Critical taper and duplexing offer a simple contrast that can be illustrated via food analogies. If a wedge is critical, it churns internally like a pile of CheeriosTM cereal pushed up an inclined plane. Stacking of a duplex acts like a deli meat-slicing machine: slice after slice is cut from the intact block to a stack of slices, but neither the block (~down-going plate) nor the stack (~upper plate) features much internal deformation. Thus critical taper and channel tunneling models predict much processing via out-of-sequence deformation, whereas duplexing predicts in-sequence thrusting. The two concepts may be considered end-members. Recent work shows that the Himalayan middle crust has been assembled along a series of mainly southwards-younging thrust faults. The thrust faults separate 1-5 km thick panels that experienced similar metamorphic cycles during different time periods. Out-of-sequence deformation is rare, with its apparent significance enhanced because of the high throw-to-heave ratio of out-of-sequence thrusting. Flattening fabrics developed prior to thrusting have been interpreted to record either (1) southwards channel tunneling across the upper plate, or (2) fabric development during metamorphism of the down-going plate. We will argue that the thrust faults dominantly represent in-sequence duplexing, and therefore conclude that the Himalaya and analogous hot orogens behave like other accretionary orogens.

Application of Kite Based Aerial Photography to Resolve Short Term Sediment Exchanges Between a Dissipative Beach and Densely Vegetated Dunes

NASA Astrophysics Data System (ADS)

Conlin, M.; Cohn, N.; Ruggiero, P.

2016-12-01

Sand dunes provide coastal communities critical protection from flooding and erosion, as well as a habitat for a range of species- some threatened or endangered. As such, it is of importance to develop a quantitative understanding of the processes through which these systems evolve at a variety of temporal and spatial scales. During summer 2016, a large field campaign in southwest Washington called the Sandbar-aEolian Dune EXchange EXperiment (SEDEX2) focused on developing a suite of data sets fundamental to improving our understanding of the ways in which beaches and dunes grow during fair weather conditions. As part of this experiment, daily to bi-weekly measurements of upper-beach and vegetated dune morphology were collected by post-processing images acquired using a consumer grade kite-based aerial photography system with low-cost Agisoft Photoscan Structure from Motion (SfM) software. Under the appropriate environmental conditions (e.g., sufficient wind, no precipitation, and minimal fog), kite-based SfM techniques minimize survey effort and time as compared to traditional coastal surveying methods such as RTK DGPS and Terrestrial Laser Scanning (TLS), making this approach ideally suited for frequent surveys of small ( < 5 km2) coastal areas. However, while the dominant grass in the area, A. breviligulta (American Beachgrass), is critical for perturbing the wind field, impacting sediment transport processes, and partially dictating dune morphology, it grows densely and therefore complicates the development of aerial photography derived bare-earth digital elevation models. Here we document daily-to-weekly-scale upper beach and dune evolution using kite-based SfM techniques, focusing particularly on improving the efficacy of this technology both in vegetated areas and over short timescales. Our kite-based SfM approach, validated by concurrent RTK DGPS surveys, TLS scans, and dune vegetation surveys, is allowing us to develop quantitative estimates of the sediment exchange between the back-beach and dunes. Other data collected during SEDEX2 are being utilized to determine the primary drivers of these observed changes.

Effects of upper mantle heterogeneities on the lithospheric stress field and dynamic topography

NASA Astrophysics Data System (ADS)

Osei Tutu, Anthony; Steinberger, Bernhard; Sobolev, Stephan V.; Rogozhina, Irina; Popov, Anton A.

2018-05-01

The orientation and tectonic regime of the observed crustal/lithospheric stress field contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. In this study, we analyze the influence of the thermal and density structure of the upper mantle on the lithospheric stress field and topography. We use a 3-D lithosphere-asthenosphere numerical model with power-law rheology, coupled to a spectral mantle flow code at 300 km depth. Our results are validated against the World Stress Map 2016 (WSM2016) and the observation-based residual topography. We derive the upper mantle thermal structure from either a heat flow model combined with a seafloor age model (TM1) or a global S-wave velocity model (TM2). We show that lateral density heterogeneities in the upper 300 km have a limited influence on the modeled horizontal stress field as opposed to the resulting dynamic topography that appears more sensitive to such heterogeneities. The modeled stress field directions, using only the mantle heterogeneities below 300 km, are not perturbed much when the effects of lithosphere and crust above 300 km are added. In contrast, modeled stress magnitudes and dynamic topography are to a greater extent controlled by the upper mantle density structure. After correction for the chemical depletion of continents, the TM2 model leads to a much better fit with the observed residual topography giving a good correlation of 0.51 in continents, but this correction leads to no significant improvement of the fit between the WSM2016 and the resulting lithosphere stresses. In continental regions with abundant heat flow data, TM1 results in relatively small angular misfits. For example, in western Europe the misfit between the modeled and observation-based stress is 18.3°. Our findings emphasize that the relative contributions coming from shallow and deep mantle dynamic forces are quite different for the lithospheric stress field and dynamic topography.

Quality of economically extractable coal beds in the Gillette coal field as compared with other Tertiary coal beds in the Powder River basin, Wyoming and Montana

USGS Publications Warehouse

Ellis, Margaret S.

2002-01-01

The Powder River Basin, and specifically the Gillette coal field, contains large quantities of economically extractable coal resources. These coal resources have low total sulfur content and ash yield, and most of the resources are subbituminous in rank. A recent U.S Geological Survey study of economically extractable coal in the Gillette coal field focused on five coal beds, the Wyodak rider, Upper Wyodak, Canyon, Lower Wyodak-Werner, and Gates/Kennedy. This report compares the coal quality of these economically extractable coal beds to coal in the Wyodak-Anderson coal zone in the Powder River Basin and in the Gillette coal field (Flores and others, 1999) and other produced coal in the Gillette coal field (Glass, 2000). The Upper Wyodak, Canyon, and Lower Wyodak/Werner beds are within the Wyodak-Anderson coal zone. Compared with all coal in the Wyodak-Anderson coal zone, both throughout the Powder River Basin and just within the Gillette coal field; the thick, persistent Upper Wyodak coal bed in the Gillette coal field has higher mean gross calorific value (8,569 Btu/lb), lower mean ash yield (5.8 percent), and lower mean total sulfur content (0.46 percent).

Anisotropy and multiband superconductivity in Sr 2 RuO 4 determined by small-angle neutron scattering studies of the vortex lattice [Anisotropy and multiband superconductivity in Sr 2 RuO 4

DOE PAGES

Kuhn, S. J.; Morgenlander, W.; Louden, E. R.; ...

2017-11-14

Despite numerous studies the exact nature of the order parameter in superconducting Sr 2RuO 4 remains unresolved. We have extended previous small-angle neutron scattering studies of the vortex lattice in this material to a wider field range, higher temperatures, and with the field applied close to both the <100> and <110> basal plane directions. Measurements at high field were made possible by the use of both spin polarization and analysis to improve the signal-to-noise ratio. Rotating the field towards the basal plane causes a distortion of the square vortex lattice observed for H // <001> and also a symmetry changemore » to a distorted triangular symmetry for fields close to <100>.The vortex lattice distortion allows us to determine the intrinsic superconducting anisotropy between the c axis and the Ru-O basal plane, yielding a value of ~60 at low temperature and low to intermediate fields. This greatly exceeds the upper critical field anisotropy of ~20 at low temperature, reminiscent of Pauli limiting. Indirect evidence for Pauli paramagnetic effects on the unpaired quasiparticles in the vortex cores are observed, but a direct detection lies below the measurement sensitivity. The superconducting anisotropy is found to be independent of temperature but increases for fields > 1 T, indicating multiband superconductvity in Sr 2RuO 4. Lastly, the temperature dependence of the scattered intensity provides further support for gap nodes or deep minima in the superconducting gap.« less

Anisotropy and multiband superconductivity in Sr 2 RuO 4 determined by small-angle neutron scattering studies of the vortex lattice [Anisotropy and multiband superconductivity in Sr 2 RuO 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuhn, S. J.; Morgenlander, W.; Louden, E. R.

Despite numerous studies the exact nature of the order parameter in superconducting Sr 2RuO 4 remains unresolved. We have extended previous small-angle neutron scattering studies of the vortex lattice in this material to a wider field range, higher temperatures, and with the field applied close to both the <100> and <110> basal plane directions. Measurements at high field were made possible by the use of both spin polarization and analysis to improve the signal-to-noise ratio. Rotating the field towards the basal plane causes a distortion of the square vortex lattice observed for H // <001> and also a symmetry changemore » to a distorted triangular symmetry for fields close to <100>.The vortex lattice distortion allows us to determine the intrinsic superconducting anisotropy between the c axis and the Ru-O basal plane, yielding a value of ~60 at low temperature and low to intermediate fields. This greatly exceeds the upper critical field anisotropy of ~20 at low temperature, reminiscent of Pauli limiting. Indirect evidence for Pauli paramagnetic effects on the unpaired quasiparticles in the vortex cores are observed, but a direct detection lies below the measurement sensitivity. The superconducting anisotropy is found to be independent of temperature but increases for fields > 1 T, indicating multiband superconductvity in Sr 2RuO 4. Lastly, the temperature dependence of the scattered intensity provides further support for gap nodes or deep minima in the superconducting gap.« less

Quantum oscillations in strong magnetic fields, berry phase, and superconductivity in three-dimensional topological Bi{sub 2–x}Cu{sub x}Se{sub 3} insulators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vedeneev, S. I., E-mail: vedeneev@sci.lebedev.ru; Knyazev, D. A.; Prudkoglyad, V. A.

2015-07-15

Two-dimensional (2D) Shubnikov–de Haas oscillations and 2D Hall oscillations are observed in 3D copper-doped Bi{sub 2}Se{sub 3} single crystals in magnetic fields up to 19.5 T at temperatures down to 0.3 K. Three samples with a high bulk carrier concentration (n ≈ 10{sup 19}–10{sup 20} cm{sup –3}) are studied. The rotation of the samples in a magnetic field shows that these oscillations are related to numerous parallel 2D conducting channels 1–5 nm thick. Their basic kinetic parameters are found. Quantized Hall resistance R{sub xy} is detected in 1-nm-thick 2D conducting channels at high fields. The distance Δ(1/R{sub xy}) between themore » steps in the field dependence of 1/R{sub xy} is found to be constant for different Landau levels, 1.3e{sup 2}/h per 1-nm-thick layer. The constructed fan diagrams of 2D Landau levels for various angles of sample inclination with respect to the magnetic field direction allowed us to conclude that the Berry phase in the 2D conducting channels is γ ≈ π and independent of the magnetic field direction. When studying the angular dependence of upper resistive critical magnetic field H{sub c2} in one of the superconducting samples, we showed that it can be considered as a bulk superconductor consisting of superconducting layers with an effective thickness of about 50 nm.« less

Fulde-Ferrell-Larkin-Ovchinnikov superconductivity in the layered organic superconductor β "-(BEDT-TTF ) 4[(H3O ) Ga (C2O4)3] C6H5NO2

NASA Astrophysics Data System (ADS)

Uji, S.; Iida, Y.; Sugiura, S.; Isono, T.; Sugii, K.; Kikugawa, N.; Terashima, T.; Yasuzuka, S.; Akutsu, H.; Nakazawa, Y.; Graf, D.; Day, P.

2018-04-01

Resistance and magnetic torque measurements are reported in a layered organic superconductor, β "-(BEDT-TTF ) 4[(H3O ) Ga (C2O4)3] C6H5NO2 with Tc=4.8 K, where BEDT-TTF stands for bis(ethylenedithio)tetrathiafulvalene. Because of the large anion between the BEDT-TTF conducting layers, the superconductivity of this salt is highly anisotropic. In magnetic fields parallel to the conducting layers for T =0.4 K, the magnetic torque shows a large diamagnetic signal associated with hysteresis up to ˜21 T, suggesting the upper critical field Hc 2≳21 T at 0.4 K. The large reduction of the diamagnetic signal is observed above 16 T, which shows a Fulde and Ferrell and Larkin and Ovchinnikov (FFLO) phase transition. For T =0.5 K, the interlayer resistance has nonzero value in a wide field region up to Hc 2, arising from the Josephson vortex dynamics. Successive dips in the second derivative curves of the resistance are observed between 16 T and Hc 2, which are ascribed to the commensurability effect between the Josephson vortex lattice and the order parameter oscillation of the FFLO phase. The commensurability effect is observed only in nearly parallel fields, showing that the FFLO phase is stable in a very limited field angle region. The temperature-field phase diagram is determined.

An evaluation of corn earworm damage and thresholds in soybean

NASA Astrophysics Data System (ADS)

Adams, Brian Patrick

Interactions between corn earworm, Helicoverpa zea (Boddie), and soybean, Glycine max L. (Merrill), were investigated in the Mid-South to evaluate thresholds and damage levels. Field studies were conducted in both indeterminate and determinate modern cultivars to evaluate damage, critical injury levels, and soybean response to simulated corn earworm injury. Field studies were also conducted to evaluate the response of indeterminate cultivars to infestations of corn earworm. Field studies were also conducted to investigate the relationship between pyrethroid insecticide application and corn earworm oviposition in soybean. Results of field studies involving simulated corn earworm damage indicated the need for a dynamic threshold that becomes more conservative as soybean phenology progressed through the reproductive growth stages. This suggested that soybean was more tolerant to fruit loss during the earlier reproductive stages and was able to compensate for fruit loss better during this time than at later growth stages. Results of field studies involving infestations of corn earworm indicated that current thresholds are likely too liberal. This resulted in economic injury level tables being constructed based upon a range of crop values and control costs, however, a general action threshold was also recommended for indeterminate soybean in the Mid-South. Field study results investigating the relationship of pyrethroid application and corn earworm oviposition indicated that even in the presence of an insecticide, corn earworm prefers to oviposit in the upper portion of the canopy, as well as on the leaves as opposed to all other plant parts, consistent with all previous literature.

4-D permafrost thaw observations from ambient road traffic noise and a very dense distributed fiber optic sensing array

NASA Astrophysics Data System (ADS)

Lindsey, N.; Dou, S.; Martin, E. R.; Wagner, A. M.; Ajo Franklin, J. B.

2017-12-01

How does frozen soil thaw? The answer to this question affects hydrology, ecology, climate, and human infrastructure. We are using the local ambient noise field from a road recorded on a distributed fiber optic acoustic sensing (DAS) array to monitor the evolution in seismic parameters related to the top-down permafrost thaw process in the upper 10 m. Our field experiment demonstrates the advantages of "Large N" ambient noise studies using DAS, particularly to probe near surface critical zone dynamics. Over 60 days beginning in August 2016, we made continuous seismic recordings with a >4000 channel trenched fiber optic DAS dataset above a controlled permafrost warming demonstration experiment in Fairbanks, AK. The warming experiment accelerated the state of permafrost degradation by approximately two decades in a small 15 m x 20 m area, deepening the permafrost table from 4 m to 5.5 m. Continuous seismic DAS recording of high frequency surface waves (5-30 Hz) generated by vehicles traveling along a nearby road enables our investigation of hypothesized shear wave speed and attenuation changes, which lab measurements suggest may result from decreasing shear modulus and increasing saturation. We develop daily auto- and crosscorrelation function estimates using combinations of horizontal inline, collinear, and crossline DAS sensor orientations and vertical component geophone data, and then invert for maps of Love and Rayleigh wave speed that are sensitive to the upper 30 m. Many issues related to the accuracy, stability, and repeatability of the recovered empirical Green's tensor, as well as the sensitivity of the DAS sensor network will be considered.

Reduced-Order Biogeochemical Flux Model for High-Resolution Multi-Scale Biophysical Simulations

NASA Astrophysics Data System (ADS)

Smith, Katherine; Hamlington, Peter; Pinardi, Nadia; Zavatarelli, Marco

2017-04-01

Biogeochemical tracers and their interactions with upper ocean physical processes such as submesoscale circulations and small-scale turbulence are critical for understanding the role of the ocean in the global carbon cycle. These interactions can cause small-scale spatial and temporal heterogeneity in tracer distributions that can, in turn, greatly affect carbon exchange rates between the atmosphere and interior ocean. For this reason, it is important to take into account small-scale biophysical interactions when modeling the global carbon cycle. However, explicitly resolving these interactions in an earth system model (ESM) is currently infeasible due to the enormous associated computational cost. As a result, understanding and subsequently parameterizing how these small-scale heterogeneous distributions develop and how they relate to larger resolved scales is critical for obtaining improved predictions of carbon exchange rates in ESMs. In order to address this need, we have developed the reduced-order, 17 state variable Biogeochemical Flux Model (BFM-17) that follows the chemical functional group approach, which allows for non-Redfield stoichiometric ratios and the exchange of matter through units of carbon, nitrate, and phosphate. This model captures the behavior of open-ocean biogeochemical systems without substantially increasing computational cost, thus allowing the model to be combined with computationally-intensive, fully three-dimensional, non-hydrostatic large eddy simulations (LES). In this talk, we couple BFM-17 with the Princeton Ocean Model and show good agreement between predicted monthly-averaged results and Bermuda testbed area field data (including the Bermuda-Atlantic Time-series Study and Bermuda Testbed Mooring). Through these tests, we demonstrate the capability of BFM-17 to accurately model open-ocean biochemistry. Additionally, we discuss the use of BFM-17 within a multi-scale LES framework and outline how this will further our understanding of turbulent biophysical interactions in the upper ocean.

Reduced-Order Biogeochemical Flux Model for High-Resolution Multi-Scale Biophysical Simulations

NASA Astrophysics Data System (ADS)

Smith, K.; Hamlington, P.; Pinardi, N.; Zavatarelli, M.; Milliff, R. F.

2016-12-01

Biogeochemical tracers and their interactions with upper ocean physical processes such as submesoscale circulations and small-scale turbulence are critical for understanding the role of the ocean in the global carbon cycle. These interactions can cause small-scale spatial and temporal heterogeneity in tracer distributions which can, in turn, greatly affect carbon exchange rates between the atmosphere and interior ocean. For this reason, it is important to take into account small-scale biophysical interactions when modeling the global carbon cycle. However, explicitly resolving these interactions in an earth system model (ESM) is currently infeasible due to the enormous associated computational cost. As a result, understanding and subsequently parametrizing how these small-scale heterogeneous distributions develop and how they relate to larger resolved scales is critical for obtaining improved predictions of carbon exchange rates in ESMs. In order to address this need, we have developed the reduced-order, 17 state variable Biogeochemical Flux Model (BFM-17). This model captures the behavior of open-ocean biogeochemical systems without substantially increasing computational cost, thus allowing the model to be combined with computationally-intensive, fully three-dimensional, non-hydrostatic large eddy simulations (LES). In this talk, we couple BFM-17 with the Princeton Ocean Model and show good agreement between predicted monthly-averaged results and Bermuda testbed area field data (including the Bermuda-Atlantic Time Series and Bermuda Testbed Mooring). Through these tests, we demonstrate the capability of BFM-17 to accurately model open-ocean biochemistry. Additionally, we discuss the use of BFM-17 within a multi-scale LES framework and outline how this will further our understanding of turbulent biophysical interactions in the upper ocean.

Developmental Strategy For Effective Sampling To Detect Possible Nutrient Fluxes In Oligotrophic Coastal Reef Waters In The Caribbean

NASA Astrophysics Data System (ADS)

Mendoza, W. G.; Corredor, J. E.; Ko, D.; Zika, R. G.; Mooers, C. N.

2008-05-01

The increasing effort to develop the coastal ocean observing system (COOS) in various institutions has gained momentum due to its high value to climate, environmental, economic, and health issues. The stress contributed by nutrients to the coral reef ecosystem is among many problems that are targeted to be resolved using this system. Traditional nutrient sampling has been inadequate to resolve issues on episodic nutrient fluxes in reef regions due to temporal and spatial variability. This paper illustrates sampling strategy using the COOS information to identify areas that need critical investigation. The area investigated is within the Puerto Rico subdomain (60-70oW, 15-20oN), and Caribbean Time Series (CaTS), World Ocean Circulation Experiment (WOCE), Intra-America Sea (IAS) ocean nowcast/forecast system (IASNFS), and other COOS-related online datasets are utilized. Nutrient profile results indicate nitrate is undetectable in the upper 50 m apparently due to high biological consumption. Nutrients are delivered in Puerto Rico particularly in the CaTS station either via a meridional jet formed from opposing cyclonic and anticyclonic eddies or wind-driven upwelling. The strong vertical fluctuation in the upper 50 m demonstrates a high anomaly in temperature and salinity and a strong cross correlation signal. High chlorophyll a concentration corresponding to seasonal high nutrient influx coincides with higher precipitation accumulation rates and apparent riverine input from the Amazon and Orinoco Rivers during summer (August) than during winter (February) seasons. Non-detectability of nutrients in the upper 50 m is a reflection of poor sampling frequency or the absence of a highly sensitive nutrient analysis method to capture episodic events. Thus, this paper was able to determine the range of depths and concentrations that need to be critically investigated to determine nutrient fluxes, nutrient sources, and climatological factors that can affect nutrient delivery. It also provides some insight into needed sampling rates and temporal and spatial domain choices. Finally, it demonstrates a scientific reconnaissance for a field study that is now possible with online in-situ and remote sensing observations and numerical simulations, as a consequence of IOOS in general and COOS in particular.

Effects of Lightning in the Upper Atmosphere

NASA Astrophysics Data System (ADS)

Sentman, Davis D.; Pasko, Victor P.; Morrill, Jeff S.

2010-02-01

AGU Chapman Conference on Effects of Thunderstorms and Lightning in the Upper Atmosphere; University Park, Pennsylvania, 10-14 May 2009; The serendipitous observation in 1989 of electrical discharge in the high atmosphere induced by thundercloud lightning launched a new field of geophysical investigation. From this single unexpected observation sprang a vigorous and fertile new research field that simultaneously encompasses geophysical disciplines that are normally pursued independently, such as meteorology and lightning, plasma and gas discharge physics, atmospheric chemistry, ionospheric physics, and energetic particle physics. Transient electrical discharge in the upper atmosphere spans the full range of altitudes between the tropopause and the ionosphere and takes a variety of forms that carry the whimsical names red sprites, blue jets, gigantic jets, elves (emissions of light and very low frequency perturbations from electromagnetic pulse sources), and sprite halos, collectively known as transient luminous events (TLEs). To date, TLEs have been observed from ground and airborne or spaceborne platforms above thunderstorm systems worldwide, and radio observations made concomitantly with optical observations have shown that they are produced by the transient far fields of thundercloud lightning. TLEs appear to be large-scale (tens of kilometers in dimension), upper atmospheric versions of conventional gas discharge akin to weakly ionized, collision-dominated systems found in laboratory discharge devices (millimeter-centimeter dimensions), with characteristic energies of a few electron volts. The dominant physical processes have been identified as described by the familiar kinetic theory of the photochemistry of the upper atmosphere, but with electric field-driven electron impact ionization playing the role of photolysis or energetic precipitating particle-induced ionization.

Solar Magnetism eXplorer (Solme X)

NASA Technical Reports Server (NTRS)

Peter, Hardi; Abbo, L.; Andretta, V.; Auchere, F.; Bemporad, A.; Berrilli, F.; Bommier, V.; Cassini, R.; Curdt, W.; Davila, J.;

The direct reaction field hamiltonian: Analysis of the dispersion term and application to the water dimer

NASA Astrophysics Data System (ADS)

Thole, B. T.; Van Duijnen, P. Th.

1982-10-01

The induction and dispersion terms obtained from quantum-mechanical calculations with a direct reaction field hamiltonian are compared to second order perturbation theory expressions. The dispersion term is shown to give an upper bound which is a generalization of Alexander's upper bound. The model is illustrated by a calculation on the interactions in the water dimer. The long range Coulomb, induction and dispersion interactions are reasonably reproduced.

Critical Features of Visualizations of Transport through the Cell Membrane--an Empirical Study of Upper Secondary and Tertiary Students' Meaning-Making of a Still Image and an Animation

ERIC Educational Resources Information Center

Rundgren, Carl-Johan; Tibell, Lena A. E.

2010-01-01

Images, diagrams, and other forms of visualization are playing increasingly important roles in molecular life science teaching and research, both for conveying information and as conceptual tools, transforming the way we think about the events and processes the subject covers. This study examines how upper secondary and tertiary students interpret…

Validity of Alternative Fitnessgram Upper Body Tests of Muscular Strength and Endurance among Seventh and Eighth Grade Males and Females

ERIC Educational Resources Information Center

Hobayan, Kalani; Patterson, Debra; Sherman, Clay; Wiersma, Lenny

2014-01-01

In a society in which obesity levels have tripled in the past 30 years, the importance of increased fitness levels within the academic setting has become even more critical. The purpose of this study was to investigate the validity of alternative Fitnessgram upper body tests of muscular strength and endurance among seventh and eighth grade males…

The Impact of Concept Mapping on EFL Learners' Critical Thinking Ability

ERIC Educational Resources Information Center

Khodadady, Ebrahim; Ghanizadeh, Afsaneh

2011-01-01

The present study investigated the influence of concept mapping as a post-reading strategy on EFL learners' critical thinking ability. The study utilized a pretest-posttest control and experimental group design. To do so, thirty six EFL learners at upper intermediate and advanced levels were randomly assigned to experimental (n=18) and control…

Assessment of a Novel Group-Centered Testing Schema in an Upper-Level Undergraduate Molecular Biotechnology Course

ERIC Educational Resources Information Center

Srougi, Melissa C.; Miller, Heather B.; Witherow, D. Scott; Carson, Susan

2013-01-01

Providing students with assignments that focus on critical thinking is an important part of their scientific and intellectual development. However, as class sizes increase, so does the grading burden, prohibiting many faculty from incorporating critical thinking assignments in the classroom. In an effort to continue to provide our students with…

An Analysis of the Teaching of Critical Thinking Skills in History in Postsecondary Education

ERIC Educational Resources Information Center

Arrington, Walter T. Ted

2017-01-01

This study is an investigation and analysis of the teaching of critical thinking skills in eight public universities in Texas, in particular the History, Education, and Business departments. The study is, in part, a document analysis of the universities' mission statements, the departments' stated learning objectives, and two upper level…

Achievement as Resistance: The Development of a Critical Race Achievement Ideology among Black Achievers

ERIC Educational Resources Information Center

Carter, Dorinda J.

2008-01-01

In this article, Dorinda Carter examines the embodiment of a critical race achievement ideology in high-achieving black students. She conducted a yearlong qualitative investigation of the adaptive behaviors that nine high-achieving black students developed and employed to navigate the process of schooling at an upper-class, predominantly white,…

Quantitative analysis of surface deformation and ductile flow in complex analogue geodynamic models based on PIV method.

NASA Astrophysics Data System (ADS)

Krýza, Ondřej; Lexa, Ondrej; Závada, Prokop; Schulmann, Karel; Gapais, Denis; Cosgrove, John

2017-04-01

Recently, a PIV (particle image velocimetry) analysis method is optical method abundantly used in many technical branches where material flow visualization and quantification is important. Typical examples are studies of liquid flow through complex channel system, gas spreading or combustion problematics. In our current research we used this method for investigation of two types of complex analogue geodynamic and tectonic experiments. First class of experiments is aimed to model large-scale oroclinal buckling as an analogue of late Paleozoic to early Mesozoic evolution of Central Asian Orogenic Belt (CAOB) resulting from nortward drift of the North-China craton towards the Siberian craton. Here we studied relationship between lower crustal and lithospheric mantle flows and upper crustal deformation respectively. A second class of experiments is focused to more general study of a lower crustal flow in indentation systems that represent a major component of some large hot orogens (e.g. Bohemian massif). The most of simulations in both cases shows a strong dependency of a brittle structures shape, that are situated in upper crust, on folding style of a middle and lower ductile layers which is influenced by rheological, geometrical and thermal conditions of different parts across shortened domain. The purpose of PIV application is to quantify material redistribution in critical domains of the model. The derivation of flow direction and calculation of strain-rate and total displacement field in analogue experiments is generally difficult and time-expensive or often performed only on a base of visual evaluations. PIV method operates with set of images, where small tracer particles are seeded within modeled domain and are assumed to faithfully follow the material flow. On base of pixel coordinates estimation the material displacement field, velocity field, strain-rate, vorticity, tortuosity etc. are calculated. In our experiments we used velocity field divergence to quantify the redistribution and flow of anatectic lower crust and to evaluate upper crust thickenning and topography evolution. As this method is very sensitive to resolution and color contrast of obtained images and used materials are mostly uniform within individual rheological layers and domains, we utilized various markers as flakes of a fluorescent wax or glitter to increase overall sensitivity. Applying this method to oroclinal buckling experiments we derived velocity field divergence associated with upper crustal deformation and evolution of topography. Scaled, dimensionless negative values of divergence reach minimum (˜ -1) in two elongated domains propagating from inflection area of modeled orocline. These values correlate with significant upper crust material removing and-or with redistribution of crustal material associated with formed pop-up and pop-down structures. Maximum positive values (˜ 0.1) correspond with material spreading alongside forming platforms that are situated in foreland of maximum elevations. Application of PIV method on lateral view, where ductile middle and lower crust is vertically folded during lithosphere shortening and indentation, revealed possibility to track melt migration from base of lower crust through interlimb area towards hinge zone of individual folds. Simultaneously with folds locking and material accumulation, whole structures are exhumed at the middle crust level. Melt flow and heat exchange with surrounding environment is responsible for increased plasticity of the middle crust marked by higher strain-rates observed inside fold envelope. It is also responsible for significant elevation above hinges during later stages of model evolution. Heterogeneous nature of deformation is well documented by heterogeneities in derived divergence field within folds interiors. Our results show distinct advantages of PIV method for post-processing of geodynamic and tectonic analogue models and demonstrate great potential of this method for quantitative processing of wide spectrum of analogue approaches to different natural systems.

Strong anisotropy effect in an iron-based superconductor CaFe0.882Co0.118AsF

NASA Astrophysics Data System (ADS)

Ma, Yonghui; Ji, Qiucheng; Hu, Kangkang; Gao, Bo; Li, Wei; Mu, Gang; Xie, Xiaoming

2017-07-01

The anisotropy of iron-based superconductors is much smaller than that of the cuprates and that predicted by theoretical calculations. A credible understanding for this experimental fact is still lacking up to now. Here we experimentally study the magnetic-field-angle dependence of electronic resistivity in the superconducting phase of an iron-based superconductor CaFe{}0.882Co{}0.118AsF, and find the strongest anisotropy effect of the upper critical field among the iron-based superconductors based on the framework of Ginzburg-Landau theory. The evidence of the energy band structure and charge density distribution from electronic structure calculations demonstrates that the observed strong anisotropic effect mainly comes from the strong ionic bonding in between the ions of Ca2+ and F-, which weakens the interlayer coupling between the layers of FeAs and CaF. This finding provides a significant insight into the nature of the experimentally-observed strong anisotropic effect of electronic resistivity, and also paves the way for designing exotic two-dimensional artificial unconventional superconductors in the future.

Observation of superconductivity in BaNb2S5

NASA Astrophysics Data System (ADS)

Smith, M. G.; Neumeier, J. J.

2018-06-01

Bulk superconductivity is reported in BaNb2S5 at the transition temperature Tc = 0.85(1) K. The electrical resistivity ρ versus T is metallic with ρ(2 K) = 42.4 μΩ cm. The magnetic susceptibility is paramagnetic, with temperature-independent contributions due to diamagnetism, Pauli paramagnetism, and Van Vleck paramagnetism; a Curie-Weiss contribution appears to be impurity related. Hall effect measurements show that the majority charge carriers are electrons with charge-carrier concentration n(3 K) = 2.40(2) × 1021 cm-3. Specific heat measurements reveal an electronic specific heat coefficient γ = 11.2(1) mJ/mol K2, a Debye temperature ΘD = 126.4(8) K, and an energy gap associated with the superconducting state of Eg = 0.184(4) meV. Measurements of ρ(T) in magnetic field provide the upper critical magnetic field of about 3055(74) Oe as T → 0 K, which was used to estimate the coherence length ξ = 6.21(15) nm. The results allow classification of BaNb2S5 as a Type II, BCS superconductor in the dirty limit.

Superconductor-insulator transition in quasi-one-dimensional single-crystal Nb₂PdS₅ nanowires.

PubMed

Ning, Wei; Yu, Hongyan; Liu, Yequn; Han, Yuyan; Wang, Ning; Yang, Jiyong; Du, Haifeng; Zhang, Changjin; Mao, Zhiqiang; Liu, Ying; Tian, Mingliang; Zhang, Yuheng

2015-02-11

Superconductor-insulator transition (SIT) in one-dimensional (1D) nanowires attracts great attention in the past decade and remains an open question since contrasting results were reported in nanowires with different morphologies (i.e., granular, polycrystalline, or amorphous) or environments. Nb2PdS5 is a recently discovered low-dimensional superconductor with typical quasi-1D chain structure. By decreasing the wire diameter in the range of 100-300 nm, we observed a clear SIT with a 1D transport character driven by both the cross-sectional area and external magnetic field. We also found that the upper critical magnetic field (Hc2) decreases with the reduction of nanowire cross-sectional area. The temperature dependence of the resistance below Tc can be described by the thermally activated phase slip (TAPS) theory without any signature of quantum phase slips (QPS). These findings demonstrated that the enhanced Coulomb interactions with the shrinkage of the wire diameter competes with the interchain Josephson-like coupling may play a crucial role on the SIT in quasi-1D system.

'One physical system': Tansley's ecosystem as Earth's critical zone.

PubMed

Richter, Daniel deB; Billings, Sharon A

2015-05-01

Integrative concepts of the biosphere, ecosystem, biogeocenosis and, recently, Earth's critical zone embrace scientific disciplines that link matter, energy and organisms in a systems-level understanding of our remarkable planet. Here, we assert the congruence of Tansley's (1935) venerable ecosystem concept of 'one physical system' with Earth science's critical zone. Ecosystems and critical zones are congruent across spatial-temporal scales from vegetation-clad weathering profiles and hillslopes, small catchments, landscapes, river basins, continents, to Earth's whole terrestrial surface. What may be less obvious is congruence in the vertical dimension. We use ecosystem metabolism to argue that full accounting of photosynthetically fixed carbon includes respiratory CO₂ and carbonic acid that propagate to the base of the critical zone itself. Although a small fraction of respiration, the downward diffusion of CO₂ helps determine rates of soil formation and, ultimately, ecosystem evolution and resilience. Because life in the upper portions of terrestrial ecosystems significantly affects biogeochemistry throughout weathering profiles, the lower boundaries of most terrestrial ecosystems have been demarcated at depths too shallow to permit a complete understanding of ecosystem structure and function. Opportunities abound to explore connections between upper and lower components of critical-zone ecosystems, between soils and streams in watersheds, and between plant-derived CO₂ and deep microbial communities and mineral weathering. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Correlation of Tc and coefficient of T 2 resistivity term of Fe-based pnictide & chalcogenide superconductors

NASA Astrophysics Data System (ADS)

Castro, P. B.; Ferreira, J. L.; Silva Neto, M. B.; ElMassalami, M.

2018-03-01

Normal-state of many Fe-based pnictides and chalcogenides superconductors exhibit a quadratic-in-temperature, ρtot – ρo – ρ ph = AT 2, over wide ranges of temperature and pressure. Moreover, these systems exhibit a correlation between their T c and A, namely ln(Tc /θ)∝ A ‑1/2(θ is an energy scale parameter), even when a control parameter such as pressure is widely varied. This manifestation, as well as that of \\frac{1}{{T}c}{≤ft(-\\frac{d{H}c2}{dT}\\right)}{Tc}\\propto \\frac{A}{n} [Phys. Rev. B 89, 220509 (2014), n is charge density, H c2 is the upper critical field] suggests a common Landau Fermi Liquid scenario for both superconductivity and quadratic-in-T contribution.

Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}} As a Model System for Fundamental Studies of High Temperature Superconductivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Z.F.; Wang, J.H.

2000-05-22

During the past year, the Principal Investigator (PI) (Z. F. Ren) moved from SUNY-Buffalo to Boston College as an Associate Professor in the Department of Physics to further enhance the future success of this program. Due to the moving and set up of the new laboratory at Boston College, the project was slowed down in some extent. Nevertheless, the PI and his associates have been able to accomplish the following: (1) The upper critical field study has been carried out on the early samples (made when the PI was still with SUNY-Buffalo). Those samples have either high {Tc} (>20K) withmore » single transition or low TC but with double transitions. Therefore, there has no definitive conclusion been drawn yet. (2) X-ray photoemission has been used to study the Tl-2201 thin films. (3) In addition, J. Y. Lao has synthesized the epitaxial thallium-containing 1212 films with critical current density up to 10{sup 6}/cm{sup 2} at 77K and zero magnetic field as part of his Ph.D thesis. The success of this research has enabled us to consider using this material as an alternative for Yba{sub 2}Cu{sub 3}O{sub 7} (YBCO) or TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 9} (Tl-1223) for long length wire development for applications such as transmission cables, motors, generators, etc.« less

Heavy fermions, quantum criticality, and unconventional superconductivity in filled skutterudites and related materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andraka, Bohdan

2015-05-14

The main goal of this program was to explore the possibility of novel states and behaviors in Pr-based system exhibiting quantum critical behavior, PrOs₄Sb₁₂. Upon small changes of external parameter, such as magnetic field, physical properties of PrOs₄Sb₁₂ are drastically altered from those corresponding to a superconductor, to heavy fermion, to field-induced ordered phase with primary quadrupolar order parameter. All these states are highly unconventional and not understood in terms of current theories thus offer an opportunity to expand our knowledge and understanding of condensed matter. At the same time, these novel states and behaviors are subjects to intense internationalmore » controversies. In particular, two superconducting phases with different transition temperatures were observed in some samples and not observed in others leading to speculations that sample defects might be partially responsible for these exotic behaviors. This work clearly established that crystal disorder is important consideration, but contrary to current consensus this disorder suppresses exotic behavior. Superconducting properties imply unconventional inhomogeneous state that emerges from unconventional homogeneous normal state. Comprehensive structural investigations demonstrated that upper superconducting transition is intrinsic, bulk, and unconventional. The high quality of in-house synthesized single crystals was indirectly confirmed by de Haas-van Alphen quantum oscillation measurements. These measurements, for the first time ever reported, spanned several different phases, offering unprecedented possibility of studying quantum oscillations across phase boundaries.« less

Insights into the Earth System mass variability from CSR-RL05 GRACE gravity fields

NASA Astrophysics Data System (ADS)

Bettadpur, S.

2012-04-01

The next-generation Release-05 GRACE gravity field data products are the result of extensive effort applied to the improvements to the GRACE Level-1 (tracking) data products, and to improvements in the background gravity models and processing methodology. As a result, the squared-error upper-bound in RL05 fields is half or less than the squared-error upper-bound in RL04 fields. The CSR-RL05 field release consists of unconstrained gravity fields as well as a regularized gravity field time-series that can be used for several applications without any post-processing error reduction. This paper will describe the background and the nature of these improvements in the data products, and provide an error characterization. We will describe the insights these new series offer in measuring the mass flux due to diverse Hydrologic, Oceanographic and Cryospheric processes.

The Superconductors That Magnets Really Want: What Stands in the Way? (Superconductors for Accelerator Use: What Next and How Close is the Ideal Conductor?)

ScienceCinema

Larbalestier, David

2018-01-11

There are over 5000 superconducting materials but only about 5 have ever been useful for applications in magnets, while HEP, which has been so vital for the development of superconducting magnet technology has made virtually every magnet out of just one, the simple bcc alloy Nb-Ti with Tc of 9 K and upper critical field ~ 14T (at 2K). Significant demonstrations of the capability of the brittle intermetallic Nb3Sn have shown that fields of more than 15 T can be generated in dipole form. But Nb-Ti and Nb3Sn are staid, conventional superconductors, far from the cutting edge of superconducting science research where cuprates like YBa2Cu3O7-x and Bi2Sr2CaCu2Ox remain at the scientific forefront and in 2008 were joined by the recently discovered Fe-As pnictide superconductors. What could it mean to have materials for magnets with 10 times the Tc of Nb-Ti (90-120 K) and 3 or more times the critical field (100-240 T)? One enormous barrier is that higher Tc so far always means more complexity and a more localized superconducting interaction which is sensitive to local loss of superconductivity. The issue that has made the cuprate high temperature superconductors so hard to apply is that grain boundaries which form a 3D network in any practical wire form, easily acquire degraded superconducting properties. But conductors can now be made with extreme texture so that grain boundaries are minimized. Moreover almost practical conductors of Bi2Sr2CaCu2Ox and YBa2Cu3O7-x are now are in production and in late 2008 we were, at the Magnet Lab, able to make small solenoids operating at high current density in fields of 32 and almost 34 T respectively. Within the HEP community, there is enthusiasm to embrace HTS conductors for new very high field machines that could, like the Muon Collider, use fields of 30-50 T. In my talk I would like to explore the underlying science controlling such potential applications.

Equilibrium properties of superconducting niobium at high magnetic fields: A possible existence of a filamentary state in type-II superconductors [Possible existence of a filamentary state in type-II superconductors

DOE PAGES

Kozhevnikov, V.; Valente-Feliciano, A. -M.; Curran, P. J.; ...

2017-05-17

The standard interpretation of the phase diagram of type-II superconductors was developed in the 1960s and has since been considered a well-established part of classical superconductivity. However, upon closer examination a number of fundamental issues arises that leads one to question this standard picture. To address these issues we studied equilibrium properties of niobium samples near and above the upper critical field H c2 in parallel and perpendicular magnetic fields. The samples investigated were very high quality films and single-crystal disks with the Ginzburg-Landau parameters 0.8 and 1.3, respectively. A range of complementary measurements has been performed, which include dcmore » magnetometry, electrical transport, muon spin rotation spectroscopy, and scanning Hall-probe microscopy. Contrary to the standard scenario, we observed that a superconducting phase is present in the sample bulk above H c2 and the field H c3 is the same in both parallel and perpendicular fields. Our findings suggest that above H c2 the superconducting phase forms filaments parallel to the field regardless of the field orientation. Near H c2 the filaments preserve the hexagonal structure of the preceding vortex lattice of the mixed state, and the filament density continuously falls to zero at H c3. Finally, our paper has important implications for the correct interpretation of the properties of type-II superconductors and can be essential for practical applications of these materials.« less

Methane Bubbles Transport Particles From Contaminated Sediment to a Lake Surface

NASA Astrophysics Data System (ADS)

Delwiche, K.; Hemond, H.

2017-12-01

Methane bubbling from aquatic sediments has long been known to transport carbon to the atmosphere, but new evidence presented here suggests that methane bubbles also transport particulate matter to a lake surface. This transport pathway is of particular importance in lakes with contaminated sediments, as bubble transport could increase human exposure to toxic metals. The Upper Mystic Lake in Arlington, MA has a documented history of methane bubbling and sediment contamination by arsenic and other heavy metals, and we have conducted laboratory and field studies demonstrating that methane bubbles are capable of transporting sediment particles over depths as great as 15 m in Upper Mystic Lake. Methane bubble traps were used in-situ to capture particles adhered to bubble interfaces, and to relate particle mass transport to bubble flux. Laboratory studies were conducted in a custom-made 15 m tall water column to quantify the relationship between water column height and the mass of particulate transport. We then couple this particle transport data with historical estimates of ebullition from Upper Mystic Lake to quantify the significance of bubble-mediated particle transport to heavy metal cycling within the lake. Results suggest that methane bubbles can represent a significant pathway for contaminated sediment to reach surface waters even in relatively deep water bodies. Given the frequent co-occurrence of contaminated sediments and high bubble flux rates, and the potential for human exposure to heavy metals, it will be critical to study the significance of this transport pathway for a range of sediment and contaminant types.

Effects of a Weak Planetary Field on a Model Venus Ionosphere

NASA Astrophysics Data System (ADS)

Luhmann, Janet G.; Ma, Yingjuan; Villarreal, Michaela

2014-05-01

There are a number of attributes of the near-Venus space environment and upper atmosphere that remain mysterious, including occasional large polar magnetic field stuctures seen on VEX and nightside ionospheric holes seen on PVO. We have been exploring the consequences of a weak global dipole magnetic field of Venus using results of BATS-R-US MHD simulations. An advantage of these models is that they include the effects on a realistic ionosphere. We compare some of the weak magnetosphere's ionospheric properties with the typical unmagnetized ionsphere case. The results show the differences can be quite subtle for dipole fields less than ~10 nT at the equator, as might be expected. Nevertheless the dipole fields do produce distinctive details, especially in the upper regions.

On the limit of field-aligned current intensity in the polar magnetosphere

NASA Technical Reports Server (NTRS)

Cole, Keith D.

1991-01-01

Field-aligned current (FAC) is here defined by 4 pi j = alpha B, where alpha is constant along a magnetic field line. The upper limit value of alpha in the polar magnetosphere, possible source regions of the strongest FAC and the relationship of them to some auroral and ionospheric irregularity cross-field scale sizes are discussed. Cross-field dimensions of the strongest FAC are related to the gyroradii of source particles (O(+), He(2+), He(+), H(+), e) in the current-generating region. It is suggested that experimental determination, and mapping of the values of alpha, may assist with the search for the generators of such currents in near-earth space including in the nearby solar wind. The upper limit of alpha is associated with the breakup of FAC systems.

Integral Color Anodizing of Aluminum Alloy 7075-T6 Upper Receivers of the M16A1 Rifle

DTIC Science & Technology

1981-06-01

and control upper receivers were carried, fired, and maintained by soldiers in the field undergoing basic and advanced Infantry training and by other...soldiers undergoing Ranger training . The test and control items were subjected to typical field usage conditions involving rough handhng, firing...ICA hardcoat treatment will provide a longer inservice life for the M16A1 rifle receivers than will the low- temperature hardcoat process. 12

Characterization of Seismic Noise at Selected Non-Urban Sites

DTIC Science & Technology

2010-03-01

Field sites for seismic recordings: Scottish moor (upper left), Enfield, NH (upper right), and vicinity of Keele, England (bottom). ERDC...three sites. The sites are: a wind farm on a remote moor in Scotland, a ~13 acre field bounded by woods in a rural Enfield, NH neigh- borhood, and a site...in a rural Enfield, NH, neighborhood, and a site transitional from developed land to farmland within 1 km of the six-lane M6 motorway near Keele

SU-F-BRE-01: A Rapid Method to Determine An Upper Limit On a Radiation Detector's Correction Factor During the QA of IMRT Plans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamio, Y; Bouchard, H

2014-06-15

Purpose: Discrepancies in the verification of the absorbed dose to water from an IMRT plan using a radiation dosimeter can be wither caused by 1) detector specific nonstandard field correction factors as described by the formalism of Alfonso et al. 2) inaccurate delivery of the DQA plan. The aim of this work is to develop a simple/fast method to determine an upper limit on the contribution of composite field correction factors to these discrepancies. Methods: Indices that characterize the non-flatness of the symmetrised collapsed delivery (VSC) of IMRT fields over detector-specific regions of interest were shown to be correlated withmore » IMRT field correction factors. The indices introduced are the uniformity index (UI) and the mean fluctuation index (MF). Each one of these correlation plots have 10 000 fields generated with a stochastic model. A total of eight radiation detectors were investigated in the radial orientation. An upper bound on the correction factors was evaluated by fitting values of high correction factors for a given index value. Results: These fitted curves can be used to compare the performance of radiation dosimeters in composite IMRT fields. Highly water-equivalent dosimeters like the scintillating detector (Exradin W1) and a generic alanine detector have been found to have corrections under 1% over a broad range of field modulations (0 – 0.12 for MF and 0 – 0.5 for UI). Other detectors have been shown to have corrections of a few percent over this range. Finally, a full Monte Carlo simulations of 18 clinical and nonclinical IMRT field showed good agreement with the fitted curve for the A12 ionization chamber. Conclusion: This work proposes a rapid method to evaluate an upper bound on the contribution of correction factors to discrepancies found in the verification of DQA plans.« less

Preliminary stratigraphy and facies analysis of the Upper Cretaceous Kaguyak Formation, including a brief summary of newly discovered oil stain, upper Alaska Peninsula

USGS Publications Warehouse

Wartes, Marwan A.; Decker, Paul L.; Stanley, Richard G.; Herriott, Trystan M.; Helmold, Kenneth P.; Gillis, Robert J.

2013-01-01

The Alaska Division of Geological and Geophysical Surveys has an ongoing program aimed at evaluating the Mesozoic forearc stratigraphy, structure, and petroleum systems of lower Cook Inlet. Most of our field studies have focused on the Jurassic component of the petroleum system (this report). However, in late July and early August of 2012, we initiated a study of the stratigraphy and reservoir potential of the Upper Cretaceous Kaguyak Formation. The Kaguyak Formation is locally well exposed on the upper Alaska Peninsula (fig. 25) and was named by Keller and Reiser (1959) for a sequence of interbedded siltstone and sandstone of upper Campanian to Maastrichtian age that they estimated to be 1,450 m thick.Subsequent work by Detterman and Miller (1985) examined 900 m of section and interpreted the unit as the record of a prograding submarine fan.This interpretation of deep-water deposition contrasts with other Upper Cretaceous rocks exposed along the Alaska Peninsula and lower Cook Inlet that are generally described as nonmarine to shallow marine (Detterman and others, 1996; LePain and others, 2012).Based on foraminifera and palynomorphs from the COST No. 1 well, Magoon (1986) concluded that the Upper Cretaceous rocks were deposited in a variety of water depths and environments ranging from upper bathyal to nonmarine. During our recent fieldwork west and south of Fourpeaked Mountain, we similarly encountered markedly varying lithofacies in the Kaguyak Formation (fig. 25), and we also found oil-stained rocks that are consistent with the existence of an active petroleum system in Upper Cretaceous rocks on the upper Alaska Peninsula and in lower Cook Inlet. These field observations are summarized below.

Assessment for Qualification and Certification in Upper Secondary Education: A Review of Country Practices and Research Evidence. OECD Education Working Papers, No. 83

ERIC Educational Resources Information Center

Dufaux, Stefanie

2012-01-01

Within the policy field of student assessment, the assessment of students for qualification and certification in upper secondary education has special importance since key decisions for the progression of students may be taken on the basis of assessment results. Students in most OECD countries face increased specialisation in upper secondary…

Upper-Tropospheric Winds Derived from Geostationary Satellite Water Vapor Observations

NASA Technical Reports Server (NTRS)

Velden, Christopher S.; Hayden, Christopher M.; Nieman, Steven J.; Menzel, W. Paul; Wanzong, Steven; Goerss, James S.

1997-01-01

The coverage and quality of remotely sensed upper-tropospheric moisture parameters have improved considerably with the deployment of a new generation of operational geostationary meteorological satellites: GOES-8/9 and GMS-5. The GOES-8/9 water vapor imaging capabilities have increased as a result of improved radiometric sensitivity and higher spatial resolution. The addition of a water vapor sensing channel on the latest GMS permits nearly global viewing of upper-tropospheric water vapor (when joined with GOES and Meteosat) and enhances the commonality of geostationary meteorological satellite observing capabilities. Upper-tropospheric motions derived from sequential water vapor imagery provided by these satellites can be objectively extracted by automated techniques. Wind fields can be deduced in both cloudy and cloud-free environments. In addition to the spatially coherent nature of these vector fields, the GOES-8/9 multispectral water vapor sensing capabilities allow for determination of wind fields over multiple tropospheric layers in cloud-free environments. This article provides an update on the latest efforts to extract water vapor motion displacements over meteorological scales ranging from subsynoptic to global. The potential applications of these data to impact operations, numerical assimilation and prediction, and research studies are discussed.

Evaluation of the value of ENI in radiotherapy for cervical and upper thoracic esophageal cancer: a retrospective analysis.

PubMed

Liu, Mina; Zhao, Kuaile; Chen, Yun; Jiang, Guo-Liang

2014-10-25

A retrospective study to compare the failure patterns and effects of elective nodal irradiation (ENI) or involved field irradiation (IFI) for cervical and upper thoracic esophageal squamous cell carcinoma (SCC) patients. One hundred and sixty nine patients with the cervical and upper thoracic esophageal SCC were analyzed retrospectively; 99 patients (59%) underwent IFI and 70 patients (41%) received ENI. We defined "Out-PTVifi in-PTVeni metastasis" as lymph node metastasis occurring in the cervical prophylactic field of PTVeni thus out of PTVifi. Out-PTVifi in-PTVeni cervical node metastasis occurred in 8% of patients in the IFI group, all within 2 years after treatment. However, it occurred in 10% of patients in the ENI group, and these failures happened gradually since one year after treatments. No difference was found in OS and the incidences of Grade ≥ 3 treatment-related esophageal and lung toxicities between the two groups. ENI for cervical and upper thoracic esophageal SCC patients did not bring longer OS and better long-term control of cervical lymph nodes. Although ENI might delay cervical nodes progression in elective field; it could not decrease the incidence of these failures.

Is the inherent potential of maize roots efficient for soil phosphorus acquisition?

PubMed

Deng, Yan; Chen, Keru; Teng, Wan; Zhan, Ai; Tong, Yiping; Feng, Gu; Cui, Zhenling; Zhang, Fusuo; Chen, Xinping

2014-01-01

Sustainable agriculture requires improved phosphorus (P) management to reduce the overreliance on P fertilization. Despite intensive research of root adaptive mechanisms for improving P acquisition, the inherent potential of roots for efficient P acquisition remains unfulfilled, especially in intensive agriculture, while current P management generally focuses on agronomic and environmental concerns. Here, we investigated how levels of soil P affect the inherent potential of maize (Zea mays L.) roots to obtain P from soil. Responses of root morphology, arbuscular mycorrhizal colonization, and phosphate transporters were characterized and related to agronomic traits in pot and field experiments with soil P supply from deficiency to excess. Critical soil Olsen-P level for maize growth approximated 3.2 mg kg(-1), and the threshold indicating a significant environmental risk was about 15 mg kg(-1), which represented the lower and upper levels of soil P recommended in current P management. However, most root adaptations involved with P acquisition were triggered when soil Olsen-P was below 10 mg kg(-1), indicating a threshold for maximum root inherent potential. Therefore, to maintain efficient inherent potential of roots for P acquisition, we suggest that the target upper level of soil P in intensive agriculture should be reduced from the environmental risk threshold to the point maximizing the inherent potential of roots.

Is the Inherent Potential of Maize Roots Efficient for Soil Phosphorus Acquisition?

PubMed Central

Deng, Yan; Chen, Keru; Teng, Wan; Zhan, Ai; Tong, Yiping; Feng, Gu; Cui, Zhenling; Zhang, Fusuo; Chen, Xinping

2014-01-01

Sustainable agriculture requires improved phosphorus (P) management to reduce the overreliance on P fertilization. Despite intensive research of root adaptive mechanisms for improving P acquisition, the inherent potential of roots for efficient P acquisition remains unfulfilled, especially in intensive agriculture, while current P management generally focuses on agronomic and environmental concerns. Here, we investigated how levels of soil P affect the inherent potential of maize (Zea mays L.) roots to obtain P from soil. Responses of root morphology, arbuscular mycorrhizal colonization, and phosphate transporters were characterized and related to agronomic traits in pot and field experiments with soil P supply from deficiency to excess. Critical soil Olsen-P level for maize growth approximated 3.2 mg kg−1, and the threshold indicating a significant environmental risk was about 15 mg kg−1, which represented the lower and upper levels of soil P recommended in current P management. However, most root adaptations involved with P acquisition were triggered when soil Olsen-P was below 10 mg kg−1, indicating a threshold for maximum root inherent potential. Therefore, to maintain efficient inherent potential of roots for P acquisition, we suggest that the target upper level of soil P in intensive agriculture should be reduced from the environmental risk threshold to the point maximizing the inherent potential of roots. PMID:24594677

Literature Review on the Effects of tDCS Coupled with Robotic Therapy in Post Stroke Upper Limb Rehabilitation

PubMed Central

Simonetti, Davide; Zollo, Loredana; Milighetti, Stefano; Miccinilli, Sandra; Bravi, Marco; Ranieri, Federico; Magrone, Giovanni; Guglielmelli, Eugenio; Di Lazzaro, Vincenzo; Sterzi, Silvia

2017-01-01

Today neurological diseases such as stroke represent one of the leading cause of long-term disability. Many research efforts have been focused on designing new and effective rehabilitation strategies. In particular, robotic treatment for upper limb stroke rehabilitation has received significant attention due to its ability to provide high-intensity and repetitive movement therapy with less effort than traditional methods. In addition, the development of non-invasive brain stimulation techniques such as transcranial Direct Current Stimulation (tDCS) has also demonstrated the capability of modulating brain excitability thus increasing motor performance. The combination of these two methods is expected to enhance functional and motor recovery after stroke; to this purpose, the current trends in this research field are presented and discussed through an in-depth analysis of the state-of-the-art. The heterogeneity and the restricted number of collected studies make difficult to perform a systematic review. However, the literature analysis of the published data seems to demonstrate that the association of tDCS with robotic training has the same clinical gain derived from robotic therapy alone. Future studies should investigate combined approach tailored to the individual patient's characteristics, critically evaluating the brain areas to be targeted and the induced functional changes. PMID:28588467

Prospects and applications near ferroelectric quantum phase transitions: a key issues review.

PubMed

Chandra, P; Lonzarich, G G; Rowley, S E; Scott, J F

2017-11-01

The emergence of complex and fascinating states of quantum matter in the neighborhood of zero temperature phase transitions suggests that such quantum phenomena should be studied in a variety of settings. Advanced technologies of the future may be fabricated from materials where the cooperative behavior of charge, spin and current can be manipulated at cryogenic temperatures. The progagating lattice dynamics of displacive ferroelectrics make them appealing for the study of quantum critical phenomena that is characterized by both space- and time-dependent quantities. In this key issues article we aim to provide a self-contained overview of ferroelectrics near quantum phase transitions. Unlike most magnetic cases, the ferroelectric quantum critical point can be tuned experimentally to reside at, above or below its upper critical dimension; this feature allows for detailed interplay between experiment and theory using both scaling and self-consistent field models. Empirically the sensitivity of the ferroelectric T c 's to external and to chemical pressure gives practical access to a broad range of temperature behavior over several hundreds of Kelvin. Additional degrees of freedom like charge and spin can be added and characterized systematically. Satellite memories, electrocaloric cooling and low-loss phased-array radar are among possible applications of low-temperature ferroelectrics. We end with open questions for future research that include textured polarization states and unusual forms of superconductivity that remain to be understood theoretically.

Prospects and applications near ferroelectric quantum phase transitions: a key issues review

NASA Astrophysics Data System (ADS)

Chandra, P.; Lonzarich, G. G.; Rowley, S. E.; Scott, J. F.

2017-11-01

The emergence of complex and fascinating states of quantum matter in the neighborhood of zero temperature phase transitions suggests that such quantum phenomena should be studied in a variety of settings. Advanced technologies of the future may be fabricated from materials where the cooperative behavior of charge, spin and current can be manipulated at cryogenic temperatures. The progagating lattice dynamics of displacive ferroelectrics make them appealing for the study of quantum critical phenomena that is characterized by both space- and time-dependent quantities. In this key issues article we aim to provide a self-contained overview of ferroelectrics near quantum phase transitions. Unlike most magnetic cases, the ferroelectric quantum critical point can be tuned experimentally to reside at, above or below its upper critical dimension; this feature allows for detailed interplay between experiment and theory using both scaling and self-consistent field models. Empirically the sensitivity of the ferroelectric T c’s to external and to chemical pressure gives practical access to a broad range of temperature behavior over several hundreds of Kelvin. Additional degrees of freedom like charge and spin can be added and characterized systematically. Satellite memories, electrocaloric cooling and low-loss phased-array radar are among possible applications of low-temperature ferroelectrics. We end with open questions for future research that include textured polarization states and unusual forms of superconductivity that remain to be understood theoretically.

Recent Topics of Organic Superconductors

NASA Astrophysics Data System (ADS)

Ardavan, Arzhang; Brown, Stuart; Kagoshima, Seiichi; Kanoda, Kazushi; Kuroki, Kazuhiko; Mori, Hatsumi; Ogata, Masao; Uji, Shinya; Wosnitza, Jochen

2012-01-01

Recent developments in research into superconductivity in organic materials are reviewed. In the epoch-defining quasi-one-dimensional TMTSF superconductors with Tc ˜ 1 K, Tc decreases monotonically with increasing pressure, as do signatures of spin fluctuations in the normal state, providing good evidence for magnetically-mediated pairing. Upper critical fields exceed the Zeeman-limiting field by several times, suggesting triplet pairing or a transition to an inhomogeneous superconducting state at high magnetic fields, while triplet pairing is ruled out at low fields by NMR Knight-shift measurements. Evidence for a spatially inhomogeneous superconducting state, Fulde--Ferrel--Larkin--Ovchinnikov state, which has long been sought in various superconducting systems, is now captured by thermodynamic and transport measurements for clean and highly two-dimensional BEDT-TTF and BETS superconductors. Some of the layered superconductors also serve as model systems for Mott physics on anisotropic triangular lattice. For example, the Nernst effect and the pseudo-gap behavior in NMR relaxation are enhanced near to the Mott transition. In the case of increasing spin frustration, the superconducting transition temperature is depressed, and antiferromagnetic ordering is eliminated altogether in the adjacent Mott insulating phase. There is an increasing number of materials exhibiting superconductivity in competition or cooperation with charge order. Theoretical studies shed light on the role of spin and/or charge fluctuations for superconductivity appearing under conditions close to those of correlation-induced insulating phases in the diversity of organic materials.

Safety and Mission Assurance for In-House Design Lessons Learned from Ares I Upper Stage

NASA Technical Reports Server (NTRS)

Anderson, Joel M.

2011-01-01

This viewgraph presentation identifies lessons learned in the course of the Ares I Upper Stage design and in-house development effort. The contents include: 1) Constellation Organization; 2) Upper Stage Organization; 3) Presentation Structure; 4) Lesson-Importance of Systems Engineering/Integration; 5) Lesson-Importance of Early S&MA Involvement; 6) Lesson-Importance of Appropriate Staffing Levels; 7) Lesson-Importance S&MA Team Deployment; 8) Lesson-Understanding of S&MA In-Line Engineering versus Assurance; 9) Lesson-Importance of Close Coordination between Supportability and Reliability/Maintainability; 10) Lesson-Importance of Engineering Data Systems; 11) Lesson-Importance of Early Development of Supporting Databases; 12) Lesson-Importance of Coordination with Safety Assessment/Review Panels; 13) Lesson-Implementation of Software Reliability; 14) Lesson-Implementation of S&MA Technical Authority/Chief S&MA Officer; 15) Lesson-Importance of S&MA Evaluation of Project Risks; 16) Lesson-Implementation of Critical Items List and Government Mandatory Inspections; 17) Lesson-Implementation of Critical Items List Mandatory Inspections; 18) Lesson-Implementation of Test Article Safety Analysis; and 19) Lesson-Importance of Procurement Quality.

Physical property and electronic structure characterization of bulk superconducting Bi3Ni

NASA Astrophysics Data System (ADS)

Kumar, Jagdish; Kumar, Anuj; Vajpayee, Arpita; Gahtori, Bhasker; Sharma, Devina; Ahluwalia, P. K.; Auluck, S.; Awana, V. P. S.

2011-07-01

We report the experimental and theoretical study of the magnetic nature of the Bi3Ni system. The structure is found to be orthorhombic (Pnma) with lattice parameters a = 8.879 Å, b = 4.0998 Å and c = 4.099 Å. The title compound is synthesized via a solid state reaction route by quartz vacuum encapsulation of 5 N purity stoichiometric ingredients of Ni and Bi. The superconducting transition temperature is found to be 4.1 K as confirmed from magnetization and specific heat measurements. The lower critical field (Hc1) and irreversibility field (Hirr) are around 150 and 3000 Oe respectively at 2 K. Upper critical field (Hc2), as determined from in-field (up to 4 T) ac susceptibility, is found to be around 2 T at 2 K. The normal state specific heat is fitted using the Sommerfeld-Debye equation C(T) = γT + βT3 + δT5 and the parameters obtained are γ = 11.08 mJ mol - 1 K - 2, β = 3.73 mJ mol - 1 K - 4 and δ = 0.0140 mJ mol - 1 K - 6. The calculated electronic density of states (DOS) at the Fermi level N(EF) and Debye temperature ΘD are 4.697 states/eV/f.u. and 127.7 K respectively. We also estimated the value of the electron-phonon coupling constant (λ) to be 1.23, which when substituted in the MacMillan equation gives Tc = 4.5 K. Density functional theory (DFT) based calculations for experimentally determined lattice parameters show that Ni in this compound is non-magnetic and ferromagnetic interactions seem to play no role. The Stoner condition IN(EF) = 0.136 per Ni atom also indicates that the system cannot have any ferromagnetism. The fixed spin moment (FSM) calculations, by fixing total magnetic moment on the unit cell, also suggested that this system does not exhibit any signatures of ferromagnetism.

The critical velocity of a body towed by a cable from an airplane

NASA Technical Reports Server (NTRS)

Koning, C; De Haas, T P

1937-01-01

It is sufficient to consider only the equations of motion of the towed body whereas those of the cable may be left out of consideration. The result obtained makes it possible to determine which factors affect the critical velocity and what modifications of the instrument are necessary for extending the upper limit of that velocity.

Critical Literacy and Transgender Topics in an Upper Elementary Classroom: A Portrait of Possibility

ERIC Educational Resources Information Center

Hermann-Wilmarth, Jill M.; Lannen, Rosemary; Ryan, Caitlin L.

2017-01-01

In this paper, we explore the intersection of critical literacy pedagogy, queer pedagogy, and transgender topics by turning our attention to the learning that supported the writing of an acrostic poem about Title IX and transgender students. We examine how this writing, in turn, created additional content and context that spurred others' learning.…

First-order chiral to non-chiral transition in the angular dependence of the upper critical induction of the Scharnberg-Klemm p-wave pair state

NASA Astrophysics Data System (ADS)

Klemm, Richard; Zhang, Jingchuan; Lorscher, Christopher; Gu, Qiang

2014-03-01

We calculate the temperature T and angular (θ , ϕ) dependence of the upper critical induction Bc 2(θ , ϕ , T) for parallel-spin superconductors with an axially symmetric p-wave pairing interaction pinned to the lattice and a dominant ellipsoidal Fermi surface (FS). When both parallel-spin states are allowed, the chiral Scharnberg-Klemm state Bc 2(θ , ϕ , T) exceeds that of the chiral Anderson-Brinkman-Morel state for all FS anisotropies, and exhibits a kink at θ =θ*(T , ϕ) , indicative of a first-order transition from its chiral, nodal-direction behavior to its non-chiral, antinodal-direction behavior. Potential applicability to Sr2RuO4, UCoGe, and topological superconductors is discussed.

The Dirac Experiments - Results and Challenges

NASA Astrophysics Data System (ADS)

Clark, R. G.; O'Brien, J. L.; Dzurak, A. S.; Kane, B. E.; Lumpkin, N. E.; Reilley, D. J.; Starrett, R. P.; Rickel, D. G.; Goettee, J. D.; Campbell, L. J.; Fowler, C. M.; Mielke, C.; Harrison, N.; Zerwekh, W. D.; Clark, D.; Bartram, B. D.; King, J. C.; Parkin, D.; Nakagawa, H.; Miura, N.

2004-11-01

The 1997 international Dirac II Series held at Los Alamos National Laboratory involved low temperature electrical transport and optical experiments in magnetic fields exceeding 800 T, produced by explosive flux compression using Russian MC-1 generators. An overview of the scientific and technical advances achieved in this Series is given, together with a strategy for future work in this challenging experimental environment. A significant outcome was achieved in transport studies of microfabricated thin-film YBCO structures with the magnetic field in the CuO plane. Using a GHz transmission line technique at an ambient temperature of 1.6 K, an onset of dissipation was observed at 150 T (a new upper bound for superconductivity in any material), with a saturation of resistivity at 240 T. Comparison with the Pauli limit expected at B - 155 T in this material suggests that the critical field in this geometry is limited by spin paramagnetism. In preparation for a Dirac III series, a systematic temperature-dependent transport study of YBCO using in-plane magnetic fields of 150 T generated by single-turn coils, at temperatures over the range 10-100 K, has been undertaken in collaboration with the Japanese Megagauss Laboratory. The objective is to map out the phase diagram for this geometry, which is expected to be significantly different than the Werthamer-Helfand-Hohenberg model due to the presence of paramagnetic limiting. Nanofabricated magnetometers have also been developed in a UNSW-LANL collaboration for use in Dirac III for Fermi surface measurements of YBCO in megagauss fields, which are described.

Physics and material science of ultra-high quality factor superconducting resonator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vostrikov, Alexander

2015-08-01

The nitrogen doping into niobium superconducting radio frequency cavity walls aiming to improve the fundamental mode quality factor is the subject of the research in the given work. Quantitative nitrogen diffusion into niobium model calculating the concentration profile was developed. The model estimations were confirmed with secondary ion mass spectrometry technique measurements. The model made controlled nitrogen doping recipe optimization possible. As a result the robust reproducible recipe for SRF cavity walls treatment with nitrogen doping was developed. The cavities produced with optimized recipe met LCLS–II requirements on quality factor of 2.7 ∙ 10 10 at acceleration field of 16more » MV/m. The microscopic effects of nitrogen doping on superconducting niobium properties were studied with low energy muon spin rotation technique and magnetometer measurements. No significant effect of nitrogen on the following features was found: electron mean free path, magnetic field penetration depth, and upper and surface critical magnetic fields. It was detected that for nitrogen doped niobium samples magnetic flux starts to penetrate inside the superconductor at lower external magnetic field value compared to the low temperature baked niobium ones. This explains lower quench field of SRF cavities treated with nitrogen. Quality factor improvement of fundamental mode forced to analyze the high order mode (HOM) impact on the particle beam dynamics. Both resonant and cumulative effects caused by monopole and dipole HOMs respectively are found to be negligible within the requirements for LCLS–II.« less

Field-induced superconducting phase of FeSe in the BCS-BEC cross-over

PubMed Central

Kasahara, Shigeru; Watashige, Tatsuya; Hanaguri, Tetsuo; Kohsaka, Yuhki; Yamashita, Takuya; Shimoyama, Yusuke; Mizukami, Yuta; Endo, Ryota; Ikeda, Hiroaki; Aoyama, Kazushi; Terashima, Taichi; Uji, Shinya; Wolf, Thomas; von Löhneysen, Hilbert; Shibauchi, Takasada; Matsuda, Yuji

2014-01-01

Fermi systems in the cross-over regime between weakly coupled Bardeen–Cooper–Schrieffer (BCS) and strongly coupled Bose–Einstein-condensate (BEC) limits are among the most fascinating objects to study the behavior of an assembly of strongly interacting particles. The physics of this cross-over has been of considerable interest both in the fields of condensed matter and ultracold atoms. One of the most challenging issues in this regime is the effect of large spin imbalance on a Fermi system under magnetic fields. Although several exotic physical properties have been predicted theoretically, the experimental realization of such an unusual superconducting state has not been achieved so far. Here we show that pure single crystals of superconducting FeSe offer the possibility to enter the previously unexplored realm where the three energies, Fermi energy εF, superconducting gap Δ, and Zeeman energy, become comparable. Through the superfluid response, transport, thermoelectric response, and spectroscopic-imaging scanning tunneling microscopy, we demonstrate that εF of FeSe is extremely small, with the ratio Δ/εF∼1(∼0.3) in the electron (hole) band. Moreover, thermal-conductivity measurements give evidence of a distinct phase line below the upper critical field, where the Zeeman energy becomes comparable to εF and Δ. The observation of this field-induced phase provides insights into previously poorly understood aspects of the highly spin-polarized Fermi liquid in the BCS-BEC cross-over regime. PMID:25378706

Saturn's very axisymmetric magnetic field: No detectable secular variation or tilt

NASA Astrophysics Data System (ADS)

Cao, Hao; Russell, Christopher T.; Christensen, Ulrich R.; Dougherty, Michele K.; Burton, Marcia E.

2011-04-01

Saturn is the only planet in the solar system whose observed magnetic field is highly axisymmetric. At least a small deviation from perfect symmetry is required for a dynamo-generated magnetic field. Analyzing more than six years of magnetometer data obtained by Cassini close to the planet, we show that Saturn's observed field is much more axisymmetric than previously thought. We invert the magnetometer observations that were obtained in the "current-free" inner magnetosphere for an internal model, varying the assumed unknown rotation rate of Saturn's deep interior. No unambiguous non-axially symmetric magnetic moment is detected, with a new upper bound on the dipole tilt of 0.06°. An axisymmetric internal model with Schmidt-normalized spherical harmonic coefficients g10 = 21,191 ± 24 nT, g20 = 1586 ± 7 nT. g30 = 2374 ± 47 nT is derived from these measurements, the upper bounds on the axial degree 4 and 5 terms are 720 nT and 3200 nT respectively. The secular variation for the last 30 years is within the probable error of each term from degree 1 to 3, and the upper bounds are an order of magnitude smaller than in similar terrestrial terms for degrees 1 and 2. Differentially rotating conducting stable layers above Saturn's dynamo region have been proposed to symmetrize the magnetic field (Stevenson, 1982). The new upper bound on the dipole tilt implies that this stable layer must have a thickness L >= 4000 km, and this thickness is consistent with our weak secular variation observations.

Electric field controlled emulsion phase contactor

DOEpatents

Scott, Timothy C.

1995-01-01

A system for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity.

Method of using an electric field controlled emulsion phase contactor

DOEpatents

Scott, Timothy C.

1993-01-01

A system for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity.

Electric field controlled emulsion phase contactor

DOEpatents

Scott, T.C.

1995-01-31

A system is described for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity. 5 figs.

GLAG theory for superconducting property variations with A15 composition in Nb3Sn wires.

PubMed

Li, Yingxu; Gao, Yuanwen

2017-04-25

We present a model for the variation of the upper critical field H c2 with Sn content in A15-type Nb-Sn wires, within the Ginzburg-Landau-Abrikosov-Gor'kov (GLAG) theory frame. H c2 at the vicinity of the critical temperature T c is related quantitatively to the electrical resistivity ρ, specific heat capacity coefficient γ and T c . H c2 versus tin content is theoretically formulated within the GLAG theory, and generally reproduces the experiment results. As Sn content gradually approaches the stoichiometry, A15-type Nb-Sn undergoes a transition from the dirty limit to clean limit, split by the phase transformation boundary. The H-T phase boundary and pinning force show different behaviors in the cubic and tetragonal phase. We dipict the dependence of the composition gradient on the superconducting properties variation in the A15 layer, as well as the curved tail at vicinity of H c2 in the Kramer plot of the Nb 3 Sn wire. This helps understanding of the inhomogeneous-composition inducing discrepancy between the results by the state-of-art scaling laws and experiments.

Multilevel eEmpirical Bayes modeling for improved estimation of toxicant formulations tosuppress parasitic sea lamprey in the Upper Great Lakes

USGS Publications Warehouse

Hatfield, Laura A.; Gutreuter, Steve; Boogaard, Michael A.; Carlin, Bradley P.

2011-01-01

Estimation of extreme quantal-response statistics, such as the concentration required to kill 99.9% of test subjects (LC99.9), remains a challenge in the presence of multiple covariates and complex study designs. Accurate and precise estimates of the LC99.9 for mixtures of toxicants are critical to ongoing control of a parasitic invasive species, the sea lamprey, in the Laurentian Great Lakes of North America. The toxicity of those chemicals is affected by local and temporal variations in water chemistry, which must be incorporated into the modeling. We develop multilevel empirical Bayes models for data from multiple laboratory studies. Our approach yields more accurate and precise estimation of the LC99.9 compared to alternative models considered. This study demonstrates that properly incorporating hierarchical structure in laboratory data yields better estimates of LC99.9 stream treatment values that are critical to larvae control in the field. In addition, out-of-sample prediction of the results of in situ tests reveals the presence of a latent seasonal effect not manifest in the laboratory studies, suggesting avenues for future study and illustrating the importance of dual consideration of both experimental and observational data.

On the behavior of the leading eigenvalue of Eigen's evolutionary matrices.

PubMed

Semenov, Yuri S; Bratus, Alexander S; Novozhilov, Artem S

2014-12-01

We study general properties of the leading eigenvalue w¯(q) of Eigen's evolutionary matrices depending on the replication fidelity q. This is a linear algebra problem that has various applications in theoretical biology, including such diverse fields as the origin of life, evolution of cancer progression, and virus evolution. We present the exact expressions for w¯(q),w¯(')(q),w¯('')(q) for q = 0, 0.5, 1 and prove that the absolute minimum of w¯(q), which always exists, belongs to the interval (0, 0.5]. For the specific case of a single peaked landscape we also find lower and upper bounds on w¯(q), which are used to estimate the critical mutation rate, after which the distribution of the types of individuals in the population becomes almost uniform. This estimate is used as a starting point to conjecture another estimate, valid for any fitness landscape, and which is checked by numerical calculations. The last estimate stresses the fact that the inverse dependence of the critical mutation rate on the sequence length is not a generally valid fact. Copyright © 2014 Elsevier Inc. All rights reserved.

CLASP2: The Chromospheric LAyer Spectro-Polarimeter

NASA Astrophysics Data System (ADS)

Rachmeler, Laurel; E McKenzie, David; Ishikawa, Ryohko; Trujillo Bueno, Javier; Auchère, Frédéric; Kobayashi, Ken; Winebarger, Amy; Bethge, Christian; Kano, Ryouhei; Kubo, Masahito; Song, Donguk; Narukage, Noriyuki; Ishikawa, Shin-nosuke; De Pontieu, Bart; Carlsson, Mats; Yoshida, Masaki; Belluzzi, Luca; Stepan, Jiri; del Pino Alemná, Tanausú; Ballester, Ernest Alsina; Asensio Ramos, Andres

2017-08-01

We present the instrument, science case, and timeline of the CLASP2 sounding rocket mission. The successful CLASP (Chromospheric Lyman-Alpha Spectro-Polarimeter) sounding rocket flight in 2015 resulted in the first-ever linear polarization measurements of solar hydrogen Lyman-alpha line, which is sensitive to the Hanle effect and can be used to constrain the magnetic field and geometric complexity of the upper chromosphere. Ly-alpha is one of several upper chromospheric lines that contain magnetic information. In the spring of 2019, we will re-fly the modified CLASP telescope to measure the full Stokes profile of Mg II h & k near 280 nm. This set of lines is sensitive to the upper chromospheric magnetic field via both the Hanle and the Zeeman effects.

Arc dynamics of a pulsed DC nitrogen rotating gliding arc discharge

NASA Astrophysics Data System (ADS)

Zhu, Fengsen; Zhang, Hao; Li, Xiaodong; Wu, Angjian; Yan, Jianhua; Ni, Mingjiang; Tu, Xin

2018-03-01

In this study, a novel pulsed direct current (DC) rotating gliding arc (RGA) plasma reactor co-driven by an external magnetic field and a tangential gas flow has been developed. The dynamic characteristics of the rotating gliding arc have been investigated by means of numerical simulation and experiment. The simulation results show that a highly turbulent vortex flow can be generated at the bottom of the RGA reactor to accelerate the arc rotation after arc ignition, whereas the magnitude of gas velocity declined significantly along the axial direction of the RGA reactor. The calculated arc rotation frequency (14.4 Hz) is reasonably close to the experimental result (18.5 Hz) at a gas flow rate of 10 l min-1. In the presence of an external magnet, the arc rotation frequency is around five times higher than that of the RGA reactor without using a magnet, which suggests that the external magnetic field plays a dominant role in the maintenance of the arc rotation in the upper zone of the RGA reactor. In addition, when the magnet is placed outside the reactor reversely to form a reverse external magnetic field, the arc can be stabilized at a fixed position in the inner wall of the outer electrode at a critical gas flow rate of 16 l min-1.

Pressure induced superconductivity in the antiferromagnetic Dirac material BaMnBi2.

PubMed

Chen, Huimin; Li, Lin; Zhu, Qinqing; Yang, Jinhu; Chen, Bin; Mao, Qianhui; Du, Jianhua; Wang, Hangdong; Fang, Minghu

2017-05-09

The so-called Dirac materials such as graphene and topological insulators are a new class of matter different from conventional metals and (doped) semiconductors. Superconductivity induced by doing or applying pressure in these systems may be unconventional, or host mysterious Majorana fermions. Here, we report a successfully observation of pressure-induced superconductivity in an antiferromagnetic Dirac material BaMnBi 2 with T c of ~4 K at 2.6 GPa. Both the higher upper critical field, μ 0 H c2 (0) ~ 7 Tesla, and the measured current independent of T c precludes that superconductivity is ascribed to the Bi impurity. The similarity in ρ ab (B) linear behavior at high magnetic fields measured at 2 K both at ambient pressure (non-superconductivity) and 2.6 GPa (superconductivity, but at the normal state), as well as the smooth and similar change of resistivity with pressure measured at 7 K and 300 K in zero field, suggests that there may be no structure transition occurred below 2.6 GPa, and superconductivity observed here may emerge in the same phase with Dirac fermions. Our findings imply that BaMnBi 2 may provide another platform for studying SC mechanism in the system with Dirac fermions.

In situ synthesis and superconducting properties of MgB 2 fibers

NASA Astrophysics Data System (ADS)

Kim, J. H.; Yoon, H. R.; Jo, W.; Kim, J. W.; Kim, K. H.

2006-10-01

Superconducting MgB2 fibers are grown by a diffusion method, in which B filaments are exposed to Mg vapor inside a folded Ta foil over a wide range of temperature and growth time. The as-grown wires with a diameter of about 110 μm are characterized by scanning electron microscopy and energy dispersive X-ray analysis. Surface morphology of the fibers turns out to be dependent on growth temperature and mixing ratio of Mg and B. Radial distribution of Mg ions into B is observed over the cross-sectional area. Transport properties of the MgB2 fibers are investigated in magnetic fields from 0 to 8 T by use of a physical property measurement system. MgB2 fibers grown at 900 °C for 2 h show a superconducting transition at 38.1 K with an onset temperature as 41.7 K and ΔTc < 3.03 K. Resistance of the MgB2 fiber at room temperature is 4 Ω and residual resistivity ratio (RRR) is estimated as 4.72. It is estimated that the upper critical field Hc2 at 4 K is more than 16 T. In addition, a small amount of magneto-resistance is detected at high magnetic fields.

Biodegradation kinetics for pesticide exposure assessment.

PubMed

Wolt, J D; Nelson, H P; Cleveland, C B; van Wesenbeeck, I J

2001-01-01

Understanding pesticide risks requires characterizing pesticide exposure within the environment in a manner that can be broadly generalized across widely varied conditions of use. The coupled processes of sorption and soil degradation are especially important for understanding the potential environmental exposure of pesticides. The data obtained from degradation studies are inherently variable and, when limited in extent, lend uncertainty to exposure characterization and risk assessment. Pesticide decline in soils reflects dynamically coupled processes of sorption and degradation that add complexity to the treatment of soil biodegradation data from a kinetic perspective. Additional complexity arises from study design limitations that may not fully account for the decline in microbial activity of test systems, or that may be inadequate for considerations of all potential dissipation routes for a given pesticide. Accordingly, kinetic treatment of data must accommodate a variety of differing approaches starting with very simple assumptions as to reaction dynamics and extending to more involved treatments if warranted by the available experimental data. Selection of the appropriate kinetic model to describe pesticide degradation should rely on statistical evaluation of the data fit to ensure that the models used are not overparameterized. Recognizing the effects of experimental conditions and methods for kinetic treatment of degradation data is critical for making appropriate comparisons among pesticide biodegradation data sets. Assessment of variability in soil half-life among soils is uncertain because for many pesticides the data on soil degradation rate are limited to one or two soils. Reasonable upper-bound estimates of soil half-life are necessary in risk assessment so that estimated environmental concentrations can be developed from exposure models. Thus, an understanding of the variable and uncertain distribution of soil half-lives in the environment is necessary to estimate bounding values. Statistical evaluation of measures of central tendency for multisoil kinetic studies shows that geometric means better represent the distribution in soil half-lives than do the arithmetic or harmonic means. Estimates of upper-bound soil half-life values based on the upper 90% confidence bound on the geometric mean tend to accurately represent the upper bound when pesticide degradation rate is biologically driven but appear to overestimate the upper bound when there is extensive coupling of biodegradation with sorptive processes. The limited data available comparing distribution in pesticide soil half-lives between multisoil laboratory studies and multilocation field studies suggest that the probability density functions are similar. Thus, upper-bound estimates of pesticide half-life determined from laboratory studies conservatively represent pesticide biodegradation in the field environment for the purposes of exposure and risk assessment. International guidelines and approaches used for interpretations of soil biodegradation reflect many common elements, but differ in how the source and nature of variability in soil kinetic data are considered. Harmonization of approaches for the use of soil biodegradation data will improve the interpretative power of these data for the purposes of exposure and risk assessment.

Correlation between topological structure and its properties in dynamic singular vector fields.

PubMed

Vasilev, Vasyl; Soskin, Marat

2016-04-20

A new technique for establishment of topology measurements for static and dynamic singular vector fields is elaborated. It is based on precise measurement of the 3D landscape of ellipticity distribution for a checked singular optical field with C points on the tops of ellipticity hills. Vector fields possess three-component topology: areas with right-hand (RH) and left-hand (LH) ellipses, and delimiting those L lines as the singularities of handedness. The azimuth map of polarization ellipses is common for both RH and LH ellipses of vector fields and do not feel L lines. The strict rules were confirmed experimentally, which define the connection between the sign of underlying optical vortices and morphological parameters of upper-lying C points. Percolation phenomena explain their realization in-between singular vector fields and long duration of their chains of 10³  s order.

Anisotropy of the upper critical field and its thickness dependence in superconducting FeSe electric-double-layer transistors

NASA Astrophysics Data System (ADS)

Shiogai, Junichi; Kimura, Shojiro; Awaji, Satoshi; Nojima, Tsutomu; Tsukazaki, Atsushi

2018-05-01

Anisotropy of superconductivity is one of the fundamental physical parameters for understanding layered iron-based superconductors (IBSs). Here we investigated the anisotropic response of resistive transition as a function of thickness (d ) in iron selenide (FeSe) based electric-double-layer transistors (EDLTs) on SrTi O3 , which exhibit superconducting transition temperatures Tc as high as 40 K below d =10 nm . According to the analyses of the in-plane (Hc2 //) and out-of-plane (Hc2 ⊥) upper critical fields (Hc 2) and the magnetic field angle dependence of the resistance (Rs-θ ) in ultrathin condition, we found that the anisotropy factor ɛ0=Hc2 ///Hc2 ⊥ is 7.4 in the thin limit of d ˜1 nm , which is larger than that of bulk IBSs. In addition, we observed the shorter out-of-plane coherence length ξc of 0.19 nm compared to the c -axis lattice constant, which implies the confinement of the order parameter in the one unit cell FeSe. These findings suggest that high-Tc superconductivity in the ultrathin FeSe-EDLT exhibits an anisotropic three-dimensional (3D) or quasi-two-dimensional (2D) nature rather than the pure 2D one, leading to the robust superconductivity. Moreover, we carried out the systematic evaluation of the anisotropic Hc 2 against thickness reduction in the FeSe channel. The in-plane Hc 2 as a function of normalized temperature T /Tc is almost independent of d until the thin limit condition. On the other hand, the out-of-plane Hc 2 near T /Tc˜1 decreases with increasing d , resulting in the increase of ɛ0 at around Tc to 32.0 at the thick condition of d =9.3 nm , which is also confirmed by Rs-θ measurements. The counterintuitive behavior can be attributed to the degree of coupling strength between two electron-rich layers possessing a high superconducting order parameter induced by electrostatic gating at the top interface and charge transfer from SrTi O3 substrates at the bottom interface. Besides a large Hc2 ⊥ for d =9.3 nm exceeding 20 T even at T =0.8 Tc , we observe the decoupling crossover of the two superconducting layers at low temperature, which is a unique feature for the high-Tc FeSe-EDLT on SrTi O3 .

Role of nonlinear refraction in the generation of terahertz field pulses by light fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zabolotskii, A. A., E-mail: zabolotskii@iae.nsk.su

2013-07-15

The generation of microwave (terahertz) pulses without any envelope in a four-level quasi-resonant medium is considered. Two intense quasi-monochromatic laser fields lead to a partial upper-level population. Microwave field pulses cause the transition between these levels. For appropriately chosen scales, the evolution of the fields is shown to be described by the pseudo-spin evolution equations in a microwave field with the inclusion of nonlinear refraction caused by an adiabatic upper-level population. The evolution of terahertz field pulses is described outside the scope of the slow-envelope approximation. When a number of standard approximations are taken into account, this system of equationsmore » is shown to be equivalent to an integrable version of the generalized reduced Maxwell-Bloch equations or to the generalized three-wave mixing equations. The soliton solution found by the inverse scattering transform method is used as an example to show that nonlinear refraction leads to a strong compression of the microwave (terahertz) field soliton.« less

Decay of superconducting correlations for gauged electrons in dimensions D ≤ 4

NASA Astrophysics Data System (ADS)

Tada, Yasuhiro; Koma, Tohru

2018-03-01

We study lattice superconductors coupled to gauge fields, such as an attractive Hubbard model in electromagnetic fields, with a standard gauge fixing. We prove upper bounds for a two-point Cooper pair correlation at finite temperatures in spatial dimensions D ≤ 4. The upper bounds decay exponentially in three dimensions and by power law in four dimensions. These imply the absence of the superconducting long-range order for the Cooper pair amplitude as a consequence of fluctuations of the gauge fields. Since our results hold for the gauge fixing Hamiltonian, they cannot be obtained as a corollary of Elitzur's theorem.

Useful field of view in simulated driving: Reaction times and eye movements of drivers

PubMed Central

Seya, Yasuhiro; Nakayasu, Hidetoshi; Yagi, Tadasu

2013-01-01

To examine the spatial distribution of a useful field of view (UFOV) in driving, reaction times (RTs) and eye movements were measured in simulated driving. In the experiment, a normal or mirror-reversed letter “E” was presented on driving images with different eccentricities and directions from the current gaze position. The results showed significantly slower RTs in the upper and upper left directions than in the other directions. The RTs were significantly slower in the left directions than in the right directions. These results suggest that the UFOV in driving may be asymmetrical among the meridians in the visual field. PMID:24349688

A Study on Water Surface Profiles of Rivers with Constriction

NASA Astrophysics Data System (ADS)

Qian, Chaochao; Yamada, Tadashi

2013-04-01

Water surface profile of rivers with constrictions is precious in both classic hydraulics and river management practice. This study was conducted to clarify the essences of the water surface profiles. 3 cases of experiments and 1D numerical calculations with different discharges were made in the study and analysis solutions of the non-linear basic equation of surface profile in varied flow without considering friction were derived. The manning's number was kept in the same in each case by using crosspiece roughness. We found a new type of water surface profile of varied flow from the results of 1D numerical calculation and that of experiments and named it as Mc curve because of its mild condition with constriction segment. This kind of curves appears as a nature phenomenon ubiquitously. The process of water surface forming is dynamic and bore occurs at the upper side of constriction during increasing discharge before the surface profile formed. As a theoretical work, 3 analysis solutions were derived included 2 physical-meaning solutions in the study by using Man-Machine system. One of the derived physical-meaning solutions was confirmed that it is validity by comparing to the results of 1D numerical calculation and that of experiments. The solution represents a flow profile from under critical condition at the upper side to super critical condition at the down side of constriction segment. The other derived physical-meaning solution represents a flow profile from super critical condition at the upper side to under critical condition at the down side of constriction segment. These two kinds of flow profiles exist in the nature but no theoretical solution can express the phenomenon. We find the depth distribution only concerned with unit width discharge distribution and critical depth under a constant discharge from the derived solutions. Therefor, the profile can be gained simply and precisely by using the theoretical solutions instead of numerical calculation even in practice.

Time of day affects the frequency and duration of breathing events and the critical closing pressure during NREM sleep in participants with sleep apnea.

PubMed

El-Chami, Mohamad; Shaheen, David; Ivers, Blake; Syed, Ziauddin; Badr, M Safwan; Lin, Ho-Sheng; Mateika, Jason H

2015-09-15

We investigated if the number and duration of breathing events coupled to upper airway collapsibility were affected by the time of day. Male participants with obstructive sleep apnea completed a constant routine protocol that consisted of sleep sessions in the evening (10 PM to 1 AM), morning (6 AM to 9 AM), and afternoon (2 PM to 5 PM). On one occasion the number and duration of breathing events was ascertained for each sleep session. On a second occasion the critical closing pressure that demarcated upper airway collapsibility was determined. The duration of breathing events was consistently greater in the morning compared with the evening and afternoon during N1 and N2, while an increase in event frequency was evident during N1. The critical closing pressure was increased in the morning (2.68 ± 0.98 cmH2O) compared with the evening (1.29 ± 0.91 cmH2O; P ≤ 0.02) and afternoon (1.25 ± 0.79; P ≤ 0.01). The increase in the critical closing pressure was correlated to the decrease in the baseline partial pressure of carbon dioxide in the morning compared with the afternoon and evening (r = -0.73, P ≤ 0.005). Our findings indicate that time of day affects the duration and frequency of events, coupled with alterations in upper airway collapsibility. We propose that increases in airway collapsibility in the morning may be linked to an endogenous modulation of baseline carbon dioxide levels and chemoreflex sensitivity (12), which are independent of the consequences of sleep apnea.

Seismic model study of Patrick Draw field, Wyoming: a stratigraphic trap in the Upper Cretaceous Almond Formation

USGS Publications Warehouse

Anderson, Robert C.; Ryder, Robert T.

1978-01-01

The Patrick Draw field, located on the eastern flank of the Rock Springs uplift in the Washakie basin of southwestern Wyoming, was discovered in 1959 without the use of geophysical methods. The field is a classic example of a stratigraphic trap, where Upper Cretaceous porous sandstone units pinch out on a structural nose. Two-dimensional seismic modeling was used to construct the seismic waveform expressions of the Patrick Draw field, and to better understand how to explore for other 'Patrick Draw' fields. Interpretation of the model shows that the detection of the reservoir sand is very difficult, owing to a combination of acoustic contrasts and bed thickness. Because the model included other major stratigraphic units in the subsurface, several stratigraphic traps are suggested as potential exploration targets.

ON THE MISALIGNMENT BETWEEN CHROMOSPHERIC FEATURES AND THE MAGNETIC FIELD ON THE SUN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martínez-Sykora, Juan; Pontieu, Bart De; Hansteen, Viggo

2016-11-01

Observations of the upper chromosphere show an enormous amount of intricate fine structure. Much of this comes in the form of linear features, which are most often assumed to be well aligned with the direction of the magnetic field in the low plasma β regime that is thought to dominate the upper chromosphere. We use advanced radiative magnetohydrodynamic simulations, including the effects of ion-neutral interactions (using the generalized Ohm’s law) in the partially ionized chromosphere, to show that the magnetic field is often not well aligned with chromospheric features. This occurs where the ambipolar diffusion is large, i.e., ions andmore » neutral populations decouple as the ion-neutral collision frequency drops, allowing the field to slip through the neutral population; where currents perpendicular to the field are strong; and where thermodynamic timescales are longer than or similar to those of ambipolar diffusion. We find this often happens in dynamic spicule or fibril-like features at the top of the chromosphere. This has important consequences for field extrapolation methods, which increasingly use such upper chromospheric features to help constrain the chromospheric magnetic field: our results invalidate the underlying assumption that these features are aligned with the field. In addition, our results cast doubt on results from 1D hydrodynamic models, which assume that plasma remains on the same field lines. Finally, our simulations show that ambipolar diffusion significantly alters the amount of free energy available in the coronal part of our simulated volume, which is likely to have consequences for studies of flare initiation.« less

Effect of quasi-hydrostatical radial pressure on Ic of Nb3Sn wires

NASA Astrophysics Data System (ADS)

Mondonico, G.; Seeber, B.; Ferreira, A.; Bordini, B.; Oberli, L.; Bottura, L.; Ballarino, A.; Flükiger, R.; Senatore, C.

2012-11-01

High-performance Nb3Sn conductors are intended to be used in large-scale magnets like the International Thermonuclear Experimental Reactor (ITER) and in the upgrade of the Large Hadron Collider (LHC). Due to the occurrence of high electromagnetic forces, a detailed knowledge of the response of the critical current to the three-dimensional mechanical loads acting on the wires inside the cables is required. A detailed analysis of transverse stress effects on the critical current for powder-in-tube and bronze route Nb3Sn wires is presented. In an earlier publication, we have described the effect of transverse stress exerted on a Nb3Sn wire by means of two parallel plates. In the present paper, we analyse the effect of transverse stress exerted simultaneously by four walls on a wire being confined in a U-shaped groove. In order to get a more realistic picture of the situation of wires embedded in a Rutherford cable, the compression by four walls was also performed after impregnating the wire with epoxy in the same U-shaped groove. The result is very different from the case of pressing by means of two walls: the effect of pressure on Ic is now strongly reduced, which is attributed to the almost hydrostatic pressure in the U-shaped groove. This is further confirmed by the comparison between the effects of axial and transverse loads on the upper critical field and the pinning force. The present data are also compared against the effects of mechanical load on the critical current of cables in large-scale magnets.

Low-Stress Upper Plate Near Subduction Zones and Implications for Temporal Changes in Loading Forces

NASA Astrophysics Data System (ADS)

Wang, K.; Hu, Y.; Yoshida, K.

2016-12-01

Subduction megathrusts are weak, often with effective friction coefficients as low as 0.03. Consequently, differential stress (S1 - S3) in the nearby upper plate is low. Compression due to plate coupling and tension due to gravity are in a subtle balance that can be tipped by small perturbations. For example, the 2011 M=9 Tohoku-oki earthquake, which has a rupture-zone-average stress drop of only a few MPa, switched offshore margin-normal stress from compression to tension and affected seismicity pattern and stress directions of various parts of the land area. The low differential stress is also reflected in spatial variations of stresses, such as with changes in topography. In the Andes, crustal earthquake focal mechanisms change from thrust-faulting in low-elevation areas to normal-faulting in high-elevation areas. Given the lack of evidence for a pervasively weak crust, the low differential stress may indicate that in general the crust near subduction zones is not critically stressed. If so, crustal earthquakes do not represent pervasive failure but only local failure due to stress, material, and fluid pressure heterogeneity. If distributed permanent deformation that creates topography is not the norm, it either happens in brief episodes or took place in the past. The outer wedge may enter a compressively or extensionally critical state due to coseismic strengthening or weakening, respectively, of the shallow megathrust in largest interplate earthquakes. Temporal changes in loading forces must occur also at much larger temporal and spatial scales in response to changes in the nature of the subducting plate and other tectonic conditions. We propose that submarine wedges and high topography in the upper plate attain their geometry in geologically brief episodes of high differential stress. They normally stay in a low-stress stable state, but their geometry often reflects high-stress episodes of critical states in the past. In other words, rocks have a sustained memory for the most traumatic moments. Except for the weaker outer wedge, the upper plate does not switch from one critical state to another in megathrust earthquake cycles, such as from compressional failure to gravitational collapse.

Airfoil shape for flight at subsonic speeds. [design analysis and aerodynamic characteristics of the GAW-1 airfoil

NASA Technical Reports Server (NTRS)

Whitcomb, R. T. (Inventor)

1976-01-01

An airfoil is examined that has an upper surface shaped to control flow accelerations and pressure distribution over the upper surface and to prevent separation of the boundary layer due to shock wave formulation at high subsonic speeds well above the critical Mach number. A highly cambered trailing edge section improves overall airfoil lifting efficiency. Diagrams illustrating supersonic flow and shock waves over the airfoil are shown.

Space Experiments with Particle Accelerators: SEPAC

NASA Technical Reports Server (NTRS)

Burch, J. L.; Roberts, W. T.; Taylor, W. W. L.; Kawashima, N.; Marshall, J. A.; Moses, S. L.; Neubert, T.; Mende, S. B.; Choueiri, E. Y.

1994-01-01

The Space Experiments with Particle Accelerators (SEPAC), which flew on the Atmospheric Laboratory for Applications and Science (ATLAS) 1 mission, used new techniques to study natural phenomena in the Earth's upper atmosphere, ionosphere and magnetosphere by introducing energetic perturbations into the system from a high power electron beam with known characteristics. Properties of auroras were studied by directing the electron beam into the upper atmosphere while making measurements of optical emissions. Studies were also performed of the critical ionization velocity phenomenon.

SU-F-J-13: Choosing An IMRT Technique in the Treatment of Head and Neck Cancer with Daily Localization Uncertainties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, T; Wang, L; Galloway, T

Purpose: Head and Neck cancer treatment with IMRT/VMAT has two choices: split-filed IMRT(SFI), in which the LAN is treated with a separate anterior field and the extended whole-field IMRT(WFI) in which LAN is included with the IMRT/VMAT field. This study shows that under the same dose limit criteria, choosing the technique becomes a critical issue if daily localization and immobilization altered the dose distribution. Methods: Nine common head-and-neck cancer cases were chosen to illustrate how the daily localization and immobilization uncertainties affect to choose between SFI and WFI. Both SFI and WFI at upper target coverage were generated with VMAT.more » For each case, the same planning criteria were applied to the target and critical structures; therefore, similar target coverage and dose falloff can be observed in both techniques. Thirty days of kV cone beam CT(CBCT) images on each case were also delineated with contralateral and ipsilateral target as well as larynx as critical structure. About 300 CBCT images with daily delivered doses were analyzed and compared in a form of dose-volume histograms. Results: While both plans for SFI and WFI with VMAT planning utilized and meet the criteria of D95>prescription dose and for not-involved larynx with mean dose <35Gy and V55<10%, the daily localization and immobilization has a great contribution to the resulted dose delivery. With WFI, the better daily contralateral and ipsilateral neck target coverage can reflect a simpler or shorter localization; however, a much superior avoidance (WFI: mean dose a 42.5Gy; SFI: mean dose a 18.9Gy) of the non-involved larynx from the SFI is preferred. Conclusion: Dosimetrically, SFI and WFI are equally well for head and Neck cancer treatment with VMAT technique; however, if considering the contribution of daily localization(CBCT) method uncertainties, SFI is better with sparing non-involved larynx and WFI has better target coverage.« less

Stratigraphy of Citronelle Oil Field, AL: Perspectives from Enhanced Oil Recovery and Potential CO2 Sequestration

NASA Astrophysics Data System (ADS)

Hills, D. J.; Pashin, J. C.; Kopaska-Merkel, D. C.; Esposito, R. A.

2008-12-01

The Citronelle Dome is a giant salt-cored anticline in the eastern Mississippi Interior Salt Basin of south Alabama. The dome forms an elliptical structural closure containing multiple opportunities for enhanced oil recovery (EOR) and large-capacity saline reservoir CO2 sequestration. The Citronelle Oil Field, which is on the crest of the dome, has produced more than 168 MMbbl of 42° gravity oil from marginal marine sandstone in the Lower Cretaceous Donovan Sand. Recently, EOR field tests have begun in the northeastern part of the oil field. Citronelle Unit B-19-10 #2 well (Alabama State Oil and Gas Board Permit No. 3232) will serve as the CO2 injector for the first field test. CO2 will be injected into the Upper Donovan 14-1 and 16-2 sandstone units. All well logs in the 4-square-mile area surrounding the test site have been digitized and used to construct a network of nineteen stratigraphic cross sections correlating Sands 12 through 20A in the Upper Donovan. Detailed study of Citronelle cores has shown that depositional environments in the Donovan Sand differed significantly from the earlier model that has guided past development of the Citronelle Field. The cross sections demonstrate the extreme facies heterogeneity of the Upper Donovan, and this heterogeneity is well expressed within the five-spot well pattern where the field test will be conducted. Many other features bearing on the performance of the CO2 injection test have been discovered. Of particular interest is the 16-2 sand, which is interpreted as a composite of two tiers of channel fills. Pay strata are typically developed in the lower tier, and this is where CO2 will be injected. The upper tier is highly heterogeneous and is interpreted to contain sandstone fills of variable reservoir quality, as well as mudstone plugs.

Effect of Balloon Pulmonary Angioplasty on Respiratory Function in Patients With Chronic Thromboembolic Pulmonary Hypertension.

PubMed

Akizuki, Mina; Serizawa, Naoki; Ueno, Atsuko; Adachi, Taku; Hagiwara, Nobuhisa

2017-03-01

Balloon pulmonary angioplasty (BPA) in chronic thromboembolic pulmonary hypertension (CTEPH) improves hemodynamics and exercise capacity. However, its effect on respiratory function is unclear. Our objective was to investigate the effect of BPA on respiratory function. We enrolled patients with inoperable CTEPH who underwent BPA primarily in lower lobe arteries (first series) and upper and middle lobe arteries (second series). We compared changes in hemodynamics and respiratory function between different BPA fields. Sixty-two BPA sessions were performed in 13 consecutive patients. Mean pulmonary arterial pressure and pulmonary vascular resistance significantly improved from 44 ± 8 to 23 ± 5 mm Hg and 818 ± 383 to 311 ± 117 dyne/s/cm -5 . The percent predicted diffusion capacity of lung for carbon monoxide (Dlco) decreased after BPA in the lower lung field (from 60% ± 8% to 54% ± 8%) with no recovery. Percent Dlco increased after BPA in the upper middle lung field (from 53% ± 6% to 58% ± 6%) and continued to improve during the follow-up (from 58% ± 6% to 64% ± 11%). The ventilation/Co 2 production (V˙e/V˙co 2 ) slope significantly improved after BPA in the lower lung field (from 51 ± 13 to 41 ± 8) and continued to improve during the follow-up (from 41 ± 8 to 35 ± 7); however, the V˙e/V˙co 2 slope remained unchanged after BPA in the upper/middle lung field. Changes in % Dlco and the V˙e/V˙co 2 slope differed significantly between lower and upper/middle lung fields. The effect of BPA on respiratory function in patients with CTEPH differed depending on the lung field. Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

Revisiting Virtual Field Trips: Perspectives of College Science Instructors

ERIC Educational Resources Information Center

Lei, Simon A.

2015-01-01

Field trips are an important component of upper undergraduate and graduate-level science courses, especially in the fields of biology, geoscience, and environmental science. Field trips can provide a new perspective to a course's content and quality. Science field trips can facilitate active student learning, yet often can be constrained by time,…

Constraining Crustal Anisotropy by Receiver Functions at the Deep Continental Drilling Site KTB in Southern Germany

NASA Astrophysics Data System (ADS)

Bianchi, Irene; Qorbani, Ehsan; Bokelmann, Götz

2016-04-01

As one of the rare observational tools for studying deformation and stress within the Earth, seismic anisotropy has been one of the focuses of geophysical studies over the last decade. In order to unravel the anisotropic properties of the crust, the teleseismic receiver functions (RF) methodology has started to be widely applied recently. Such effects of anisotropy on RF were illustrated in theoretical studies, showing the strong backazimuthal dependence of RF on the 3D characteristics of the media sampled by the waves. The use of teleseismic RF has the advantage of not being affected by a heterogeneous depth distribution of local earthquakes, since teleseismic rays sample the entire crust beneath the stations. The application of this technique however, needs to be critically assessed using a suitable field test. To test the technique, we need a crustal block where the underground structure is reasonably well-known, e.g., where there is extensive knowledge from local seismic experiments and drilling. A field experiment has thus been carried out around the KTB (Kontinental Tiefbohrung) site in the Oberpfalz area in Southeastern Germany, in order to compare with previous results from deep drilling, and high-frequency seismic experiments around the drill site. The investigated region has been studied extensively by local geophysical experiments, and geological studies. The deep borehole was placed into gneiss rocks of the Zone Erbendorf-Vohenstrauss. The drilling activity lasted from 1987 to 1994, and descended down to a depth of 9101 meters, sampling an alternating sequence of paragneiss and amphibolite, with metamorphism of upper amphibolite facies conditions, and ductile deformation produced a strong foliation of the rocks. The application of the RFs reveals strong seismic anisotropy in the upper crust related to the so-called Erbendorf body. The SKS shear-wave splitting method has been applied as well, revealing coherent results for the whole region with exception of the southernmost station, for which the seismic waves show larger delays. We use the RF observations to test the effect of crustal anisotropy on the SKS records, which sample entire crust and upper mantle.

Comparisons of observed seasonal climate features with a winter and summer numerical simulation produced with the GLAS general circulation model

NASA Technical Reports Server (NTRS)

Halem, M.; Shukla, J.; Mintz, Y.; Wu, M. L.; Godbole, R.; Herman, G.; Sud, Y.

1979-01-01

Results are presented from numerical simulations performed with the general circulation model (GCM) for winter and summer. The monthly mean simulated fields for each integration are compared with observed geographical distributions and zonal averages. In general, the simulated sea level pressure and upper level geopotential height field agree well with the observations. Well simulated features are the winter Aleutian and Icelandic lows, the summer southwestern U.S. low, the summer and winter oceanic subtropical highs in both hemispheres, and the summer upper level Tibetan high and Atlantic ridge. The surface and upper air wind fields in the low latitudes are in good agreement with the observations. The geographical distirbutions of the Earth-atmosphere radiation balance and of the precipitation rates over the oceans are well simulated, but not all of the intensities of these features are correct. Other comparisons are shown for precipitation along the ITCZ, rediation balance, zonally averaged temperatures and zonal winds, and poleward transports of momentum and sensible heat.

Heavy Metal Content in Terraced Rice Fields at Sruwen Tengaran Semarang - Indonesia

NASA Astrophysics Data System (ADS)

Hindarwati, Yulis; Soeprobowati, Tri Retnaningsih; Sudarno

2018-02-01

The presence of heavy metal on agricultural soils can be caused not only natural factors but also due to human intervention. Differences in management and lack of understanding of farmers in the production input of fertilizers and pesticides ensued in land ravaged. Periodic testing of paddy fields is necessary to minimize the contaminants from being absorbed by plants that will have an impact on health decline. The purpose of the assessment was to identify the heavy metal content in the terraced rice field in Sruwen Village, Tengaran District, Semarang Regency. Survey was conducted in February 2017. Sampling on terraced rice fields of different heights consisted of upper, middle, and upper down. Taken as many as eight single points and composed at a depth of 0-20 cm and 20-40 cm. The identification results showed that heavy metal content of Pb, Cd, and Cu were present at all altitudes. Heavy Metals Pb and Cd at a depth of 0-20 cm were higher from 20-40 cm in the upper and lower rice fields but lower in the middle rice field. Cu heavy metal at a depth of 0-20 cm was higher than 20-40 cm in all altitude land. The heavy metal content of Pb, Cd, and Cu was still below the heavy metal standard set by the European Union and India.

Anisotropies in the perceived spatial displacement of motion-defined contours: opposite biases in the upper-left and lower-right visual quadrants.

PubMed

Fan, Zhao; Harris, John

2010-10-12

In a recent study (Fan, Z., & Harris, J. (2008). Perceived spatial displacement of motion-defined contours in peripheral vision. Vision Research, 48(28), 2793-2804), we demonstrated that virtual contours defined by two regions of dots moving in opposite directions were displaced perceptually in the direction of motion of the dots in the more eccentric region when the contours were viewed in the right visual field. Here, we show that the magnitude and/or direction of these displacements varies in different quadrants of the visual field. When contours were presented in the lower visual field, the direction of perceived contour displacement was consistent with that when both contours were presented in the right visual field. However, this illusory motion-induced spatial displacement disappeared when both contours were presented in the upper visual field. Also, perceived contour displacement in the direction of the more eccentric dots was larger in the right than in the left visual field, perhaps because of a hemispheric asymmetry in attentional allocation. Quadrant-based analyses suggest that the pattern of results arises from opposite directions of perceived contour displacement in the upper-left and lower-right visual quadrants, which depend on the relative strengths of two effects: a greater sensitivity to centripetal motion, and an asymmetry in the allocation of spatial attention. Copyright © 2010 Elsevier Ltd. All rights reserved.

Innovations in prosthetic interfaces for the upper extremity.

PubMed

Kung, Theodore A; Bueno, Reuben A; Alkhalefah, Ghadah K; Langhals, Nicholas B; Urbanchek, Melanie G; Cederna, Paul S

2013-12-01

Advancements in modern robotic technology have led to the development of highly sophisticated upper extremity prosthetic limbs. High-fidelity volitional control of these devices is dependent on the critical interface between the patient and the mechanical prosthesis. Recent innovations in prosthetic interfaces have focused on several control strategies. Targeted muscle reinnervation is currently the most immediately applicable prosthetic control strategy and is particularly indicated in proximal upper extremity amputations. Investigation into various brain interfaces has allowed acquisition of neuroelectric signals directly or indirectly from the central nervous system for prosthetic control. Peripheral nerve interfaces permit signal transduction from both motor and sensory nerves with a higher degree of selectivity. This article reviews the current developments in each of these interface systems and discusses the potential of these approaches to facilitate motor control and sensory feedback in upper extremity neuroprosthetic devices.

Influence of field dependent critical current density on flux profiles in high Tc superconductors

NASA Technical Reports Server (NTRS)

Takacs, S.

1990-01-01

The field distribution for superconducting cylinders and slabs with field dependent critical current densities in combined DC and AC magnetic fields and the corresponding magnetic fluxes are calculated. It is shown that all features of experimental magnetic-field profile measurements can be explained in the framework of field dependent critical current density. Even the quantitative agreement between the experimental and theoretical results using Kim's model is very good.

The biomechanics of upper extremity kinematic and kinetic modeling: applications to rehabilitation engineering.

PubMed

Slavens, Brooke A; Harris, Gerald F

2008-01-01

Human motion analysis has evolved from the lower extremity to the upper extremity. Rehabilitation engineering is reliant upon three-dimensional biome-chanical models for a thorough understanding of upper body motions and forces in order to improve treatment methods, rehabilitation strategies and to prevent injury. Due to the complex nature of upper body movements, a standard biomechanical model does not exist. This paper reviews several kinematic and kinetic rehabilitation engineering models from the literature. These models may capture a single joint; multijoints such as the shoulder, elbow and wrist; or a combination of joints and an ambulatory aid, which serves as the extension of the upper arm. With advances in software and hardware, new models continuously arise due to the clinical questions at hand. When designing a biomechanical upper extremity model, several key components must be determined. These include deciding on the anatomic segments of the model, the number of markers and placement on bony landmarks, the definition of joint coordinate systems, and the description of the joint motions. It is critical to apply the proper model to further our understanding of pathologic populations.

Critical electric field for maximum tunability in nonlinear dielectrics

NASA Astrophysics Data System (ADS)

Akdogan, E. K.; Safari, A.

2006-09-01

The authors develop a self-consistent thermodynamic theory to compute the critical electric field at which maximum tunability is attained in a nonlinear dielectric. They then demonstrate that the stored electrostatic free energy functional has to be expanded at least up to the sixth order in electric field so as to define the critical field, and show that it depends solely on the fourth and sixth order permittivities. They discuss the deficiency of the engineering tunability metric in describing nonlinear dielectric phenomena, introduce a critical field renormalized tunability parameter, and substantiate the proposed formalism by computing the critical electric field for prototypical 0.9Pb(Mg1/3,Nb2/3)-0.1PbTiO3 and Ba(Ti0.85,Sn0.15)O3 paraelectrics.

High-field superconductivity in the Nb-Ti-Zr ternary system

NASA Astrophysics Data System (ADS)

Ralls, K. M.; Rose, R. M.; Wulff, J.

1980-06-01

Resistive critical current densities, critical fields, and normal-state electrical resistivities were obtained at 4.2 °K for 55 alloys in the Nb-Ti-Zr ternary alloy system, excepting Ti-Zr binary compositions. The resistive critical field as a function of ternary composition has a saddle point between the Nb-Ti and Nb-Zr binaries, so that ternary alloying in this system is not expected to result in higher critical fields than the binary alloys.

Surface-Modified Nanocarriers for Nose-to-Brain Delivery: From Bioadhesion to Targeting

PubMed Central

Clementino, Adryana; Buttini, Francesca; Colombo, Gaia; Pescina, Silvia; Stanisçuaski Guterres, Silvia; Nicoli, Sara

2018-01-01

In the field of nasal drug delivery, nose-to-brain delivery is among the most fascinating applications, directly targeting the central nervous system, bypassing the blood brain barrier. Its benefits include dose lowering and direct brain distribution of potent drugs, ultimately reducing systemic side effects. Recently, nasal administration of insulin showed promising results in clinical trials for the treatment of Alzheimer’s disease. Nanomedicines could further contribute to making nose-to-brain delivery a reality. While not disregarding the need for devices enabling a formulation deposition in the nose’s upper part, surface modification of nanomedicines appears the key strategy to optimize drug delivery from the nasal cavity to the brain. In this review, nanomedicine delivery based on particle engineering exploiting surface electrostatic charges, mucoadhesive polymers, or chemical moieties targeting the nasal epithelium will be discussed and critically evaluated in relation to nose-to-brain delivery. PMID:29543755

Superconductivity induced by In substitution into the topological crystalline insulator Pb0.5Sn0.5Te

NASA Astrophysics Data System (ADS)

Zhong, R. D.; Schneeloch, J. A.; Liu, T. S.; Camino, F. E.; Tranquada, J. M.; Gu, G. D.

2014-07-01

Indium substitution turns the topological crystalline insulator (TCI) Pb0.5Sn0.5Te into a possible topological superconductor. To investigate the effect of the indium concentration on the crystal structure and superconducting properties of (Pb0.5Sn0.5)1-xInxTe, we have grown high-quality single crystals using a modified floating-zone method and have performed systematic studies for indium content in the range 0≤x≤0.35. We find that the single crystals retain the rocksalt structure up to the solubility limit of indium (x ˜0.30). Experimental dependencies of the superconducting transition temperature (Tc) and the upper critical magnetic field (Hc2) on the indium content x have been measured. The maximum Tc is determined to be 4.7 K at x =0.30, with μ0Hc2(T =0)≈5 T.

Superconducting thin films of (100) and (111) oriented indium doped topological crystalline insulator SnTe

DOE PAGES

Si, W.; Zhang, C.; Wu, L.; ...

2015-09-01

Recent discovery of the topological crystalline insulator SnTe has triggered a search for topological superconductors, which have potential application to topological quantum computing. The present work reports on the superconducting properties of indium doped SnTe thin films. The (100) and (111) oriented thin films were epitaxially grown by pulsed-laser deposition on (100) and (111) BaF2 crystalline substrates respectively. The onset superconducting transition temperatures are about 3.8 K for (100) and 3.6 K for (111) orientations, slightly lower than that of the bulk. Magneto-resistive measurements indicate that these thin films may have upper critical fields higher than that of the bulk.more » With large surface-to-bulk ratio, superconducting indium doped SnTe thin films provide a rich platform for the study of topological superconductivity and potential device applications based on topological superconductors.« less

A study of hear sink performance in air and soil for use in a thermoelectric energy harvesting device

NASA Technical Reports Server (NTRS)

Snyder, J.; Lawrence, E. E.

2002-01-01

A suggested application of a thermoelectric generator is to exploit the natural temperature difference between the air and the soil to generate small amounts of electrical energy. Since the conversion efficiency of even the best thermoelectric generators available is very low, the performance of the heat sinks providing the heat flow is critical. By providing a constant heat input to various heat sinks, field tests of their thermal conductances in soil and in air were performed. Aprototype device without a thermoelectric generator was constructed, buried, and monitored to experimentally measure the heat flow achievable in such a system. Theoretical considerations for design and selection of improved heat sinks are also presented. In particular, the method of shape factoranalysis is used to give rough estimates and upper bounds for the thermal conductance of a passive heat sink buried in soil.

Superconducting thin films of (100) and (111) oriented indium doped topological crystalline insulator SnTe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Si, Weidong, E-mail: wds@bnl.gov, E-mail: qiangli@bnl.gov; Zhang, Cheng; Wu, Lijun

2015-08-31

Recent discovery of the topological crystalline insulator SnTe has triggered a search for topological superconductors, which have potential application to topological quantum computing. The present work reports on the superconducting properties of indium doped SnTe thin films. The (100) and (111) oriented thin films were epitaxially grown by pulsed-laser deposition on (100) and (111) BaF{sub 2} crystalline substrates, respectively. The onset superconducting transition temperatures are about 3.8 K for (100) and 3.6 K for (111) orientations, slightly lower than that of the bulk. Magneto-resistive measurements indicate that these thin films may have upper critical fields higher than that of the bulk. Withmore » large surface-to-bulk ratio, superconducting indium doped SnTe thin films provide a rich platform for the study of topological superconductivity and potential device applications based on topological superconductors.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naritsuka, M.; Rosa, P. F. S.; Luo, Yongkang

Unconventional superconductivity and magnetism are intertwined on a microscopic level in a wide class of materials. A new approach to this most fundamental and hotly debated issue focuses on the role of interactions between superconducting electrons and bosonic fluctuations at the interface between adjacent layers in heterostructures. In this paper, we fabricate hybrid superlattices consisting of alternating atomic layers of the heavy-fermion superconductormore » $${\\mathrm{CeCoIn}}_{5}$$ and antiferromagnetic (AFM) metal $${\\mathrm{CeRhIn}}_{5}$$, in which the AFM order can be suppressed by applying pressure. We find that the superconducting and AFM states coexist in spatially separated layers, but their mutual coupling via the interface significantly modifies the superconducting properties. An analysis of upper critical fields reveals that, upon suppressing the AFM order by applied pressure, the force binding superconducting electron pairs acquires an extreme strong-coupling nature. Finally, this demonstrates that superconducting pairing can be tuned nontrivially by magnetic fluctuations (paramagnons) injected through the interface.« less

Fe substitution and pressure effects on superconductor Re6Hf

NASA Astrophysics Data System (ADS)

Yang, Jinhu; Guo, Yang; Wang, Hangdong; Chen, Bin

2018-04-01

Polycrystalline samples of (Re1-xFex) 6Hf were synthesized by arc-melting method and the phase purity of the samples was confirmed by powder X-ray diffraction method. In this paper, we report the Fe substitution and pressure effect on non-centrosymmetric superconductor Re6Hf. The superconducting transition temperature, TC, is confirmed by the measurements of magnetic susceptibility, electrical resistivity for x ≤ 0.22 samples with the temperature down to 2 K. We find that the TC is suppressed with the increase of Fe content. The upper critical field Hc2 is larger than the value predicted by the WHH theory and shows a linear temperature dependence down to 2 K. When upon the application of external pressure up to 2.5 GPa, the TC decreases monotonically at a rate dlnTC/dP of 0.01 GPa-1.

Superconducting Properties of CeIr3 Single Crystal

NASA Astrophysics Data System (ADS)

Sato, Yoshiki J.; Nakamura, Ai; Shimizu, Yusei; Maurya, Arvind; Homma, Yoshiya; Li, Dexin; Honda, Fuminori; Aoki, Dai

2018-05-01

Superconducting properties of CeIr3 single crystal with rhombohedral structure were examined for the first time using DC magnetization, specific heat, and electrical resistivity measurements. A bulk type-II superconductivity was clearly detected at Tc = 3.4 K, which is the second highest Tc among Ce-based intermetallic compounds. The thermodynamic properties as well as an upper critical field Hc2(0) ˜ 46.5 kOe for the H || c-axis are fully consistent with the weak-coupling BCS regime. The observed √{H} variation of C(H)/T becomes less pronounced upon cooling, possibly suggesting a suppression of low-energy quasiparticle excitations in an anisotropic s-wave gap in CeIr3, as observed in CeRu2. The origin of superconductivity is discussed from the viewpoints of the valence of Ce atom and Ir 5d-electron with a strong spin-orbit coupling.

Plasma-enhanced pulsed-laser deposition of single-crystalline M o2C ultrathin superconducting films

NASA Astrophysics Data System (ADS)

Zhang, Fan; Zhang, Zhi; Wang, Huichao; Chan, Cheuk Ho; Chan, Ngai Yui; Chen, Xin Xin; Dai, Ji-Yan

2017-08-01

Transition-metal carbides (TMCs) possess many intriguing properties and inspiring application potentials, and recently the study of a two-dimensional form of TMCs has attracted great attention. Herein, we report successful fabrication of continuous M o2C ultrathin single-crystalline films at 700 ∘C with an approach of plasma-enhanced pulsed-laser deposition. By sophisticated structural analyses, the M o2C films are characterized as single crystal with a rarely reported face-centered cubic structure. In further electrical transport measurements, superconductivity observed in the M o2C films demonstrates a typical two-dimensional feature, which is consistent with Berezinskii-Kosterlitz-Thouless transitions. Besides, large upper critical magnetic fields are discovered in this system. Our work offers an approach to grow large-area and high-quality TMCs at relatively low temperatures. This study may stimulate more related investigations on the synthesis, characterizations, and applications of two-dimensional TMCs.

Systematic study of vortex pinning and liquid-glass phase transition in BaFe2-x Ni x As2 single crystals

NASA Astrophysics Data System (ADS)

Vlasenko, V. A.; Sobolevskiy, O. A.; Sadakov, A. V.; Pervakov, K. S.; Gavrilkin, S. Yu.; Dik, A. V.; Eltsev, Yu. F.

2018-01-01

The vortex pinning and liquid-glass transition have been studied in BaFe2-x Ni x As2 single crystals with different doping levels (x = 0.065; 0.093; 0.1; 0.14; 0.18). We found that Ni-doped Ba-122 has rather narrow vortex-liquid state region. Our results show that the temperature dependence of the resistivity as well as I-V characteristics of Ni-doped Ba-122 is consistent with 3D vortex-glass model. It was found that δl-pinning gives the main contribution to overall pinning in 122 Ni-doped system. The vortex phase diagrams for different doping levels were built based on the obtained data of temperature of the vortex-glass transition T g and the upper critical magnetic field H c2.

Towards a Model Climatology of Relative Humidity in the Upper Troposphere for Estimation of Contrail and Contrail-Induced Cirrus

NASA Technical Reports Server (NTRS)

Selkirk, Henry B.; Manyin, M.; Ott, L.; Oman, L.; Benson, C.; Pawson, S.; Douglass, A. R.; Stolarski, R. S.

2011-01-01

The formation of contrails and contrail cirrus is very sensitive to the relative humidity of the upper troposphere. To reduce uncertainty in an estimate of the radiative impact of aviation-induced cirrus, a model must therefore be able to reproduce the observed background moisture fields with reasonable and quantifiable fidelity. Here we present an upper tropospheric moisture climatology from a 26-year ensemble of simulations using the GEOS CCM. We compare this free-running model's moisture fields to those obtained from the MLS and AIRS satellite instruments, our most comprehensive observational databases for upper tropospheric water vapor. Published comparisons have shown a substantial wet bias in GEOS-5 assimilated fields with respect to MLS water vapor and ice water content. This tendency is clear as well in the GEOS CCM simulations. The GEOS-5 moist physics in the GEOS CCM uses a saturation adjustment that prevents supersaturation, which is unrealistic when compared to in situ moisture observations from MOZAIC aircraft and balloon sondes as we will show. Further, the large-scale satellite datasets also consistently underestimate super-saturation when compared to the in-situ observations. We place these results in the context of estimates of contrail and contrail cirrus frequency.

Method of using an electric field controlled emulsion phase contactor

DOEpatents

Scott, T.C.

1993-11-16

A system is described for contacting liquid phases comprising a column for transporting a liquid phase contacting system, the column having upper and lower regions. The upper region has a nozzle for introducing a dispersed phase and means for applying thereto a vertically oriented high intensity pulsed electric field. This electric field allows improved flow rates while shattering the dispersed phase into many micro-droplets upon exiting the nozzle to form a dispersion within a continuous phase. The lower region employs means for applying to the dispersed phase a horizontally oriented high intensity pulsed electric field so that the dispersed phase undergoes continuous coalescence and redispersion while being urged from side to side as it progresses through the system, increasing greatly the mass transfer opportunity. 5 figures.

Noise characteristics of upper surface blown configurations. Experimental program and results

NASA Technical Reports Server (NTRS)

Brown, W. H.; Searle, N.; Blakney, D. F.; Pennock, A. P.; Gibson, J. S.

1977-01-01

An experimental data base was developed from the model upper surface blowing (USB) propulsive lift system hardware. While the emphasis was on far field noise data, a considerable amount of relevant flow field data were also obtained. The data were derived from experiments in four different facilities resulting in: (1) small scale static flow field data; (2) small scale static noise data; (3) small scale simulated forward speed noise and load data; and (4) limited larger-scale static noise flow field and load data. All of the small scale tests used the same USB flap parts. Operational and geometrical variables covered in the test program included jet velocity, nozzle shape, nozzle area, nozzle impingement angle, nozzle vertical and horizontal location, flap length, flap deflection angle, and flap radius of curvature.

An Upper Bound on High Speed Satellite Collision Probability When Only One Object has Position Uncertainty Information

NASA Technical Reports Server (NTRS)

Frisbee, Joseph H., Jr.

2015-01-01

Upper bounds on high speed satellite collision probability, PC †, have been investigated. Previous methods assume an individual position error covariance matrix is available for each object. The two matrices being combined into a single, relative position error covariance matrix. Components of the combined error covariance are then varied to obtain a maximum PC. If error covariance information for only one of the two objects was available, either some default shape has been used or nothing could be done. An alternative is presented that uses the known covariance information along with a critical value of the missing covariance to obtain an approximate but potentially useful Pc upper bound.

Initial Assessment and Resuscitation in Nonvariceal Upper Gastrointestinal Bleeding.

PubMed

Simon, Tracey G; Travis, Anne C; Saltzman, John R

2015-07-01

Acute nonvariceal upper gastrointestinal bleeding remains an important cause of hospital admission with an associated mortality of 2-14%. Initial patient evaluation includes rapid hemodynamic assessment, large-bore intravenous catheter insertion and volume resuscitation. A hemoglobin transfusion threshold of 7 g/dL is recommended, and packed red blood cell transfusion may be necessary to restore intravascular volume and improve tissue perfusion. Patients should be risk stratified into low- and high-risk categories, using validated prognostic scoring systems such as the Glasgow-Blatchford, AIMS65 or Rockall scores. Effective early management of acute, nonvariceal upper gastrointestinal hemorrhage is critical for improving patient outcomes. Copyright © 2015 Elsevier Inc. All rights reserved.

Stress Analysis for the Critical Metal Structure of Bridge Crane

NASA Astrophysics Data System (ADS)

Ling, Zhangwei; Wang, Min; Xia, Junfang; Wang, Songhua; Guo, Xiaolian

2018-01-01

Based on the type of connection between the main girder and end beam of electrical single beam crane, the finite element analysis model of a full portal crane was established. The stress distribution of the critical structure under different loading conditions was analyzed. The results shown that the maximum Mises stress and deflection of the main girder were within the allowable range. And the connecting location between end beam web and main girder had higher stress than other region, especially at the lower edge and upper edge of the end beam web and the area near the bolt hole of upper wing panel. Therefore it is important to inspect the connection status, the stress condition and the crack situation nearing connection location during the regular inspection process to ensure the safety of the connection between the main girder and end beam.

Modifying upper-limb inter-joint coordination in healthy subjects by training with a robotic exoskeleton.

PubMed

Proietti, Tommaso; Guigon, Emmanuel; Roby-Brami, Agnès; Jarrassé, Nathanaël

2017-06-12

The possibility to modify the usually pathological patterns of coordination of the upper-limb in stroke survivors remains a central issue and an open question for neurorehabilitation. Despite robot-led physical training could potentially improve the motor recovery of hemiparetic patients, most of the state-of-the-art studies addressing motor control learning, with artificial virtual force fields, only focused on the end-effector kinematic adaptation, by using planar devices. Clearly, an interesting aspect of studying 3D movements with a robotic exoskeleton, is the possibility to investigate the way the human central nervous system deals with the natural upper-limb redundancy for common activities like pointing or tracking tasks. We asked twenty healthy participants to perform 3D pointing or tracking tasks under the effect of inter-joint velocity dependant perturbing force fields, applied directly at the joint level by a 4-DOF robotic arm exoskeleton. These fields perturbed the human natural inter-joint coordination but did not constrain directly the end-effector movements and thus subjects capability to perform the tasks. As a consequence, while the participants focused on the achievement of the task, we unexplicitly modified their natural upper-limb coordination strategy. We studied the force fields direct effect on pointing movements towards 8 targets placed in the 3D peripersonal space, and we also considered potential generalizations on 4 distinct other targets. Post-effects were studied after the removal of the force fields (wash-out and follow up). These effects were quantified by a kinematic analysis of the pointing movements at both end-point and joint levels, and by a measure of the final postures. At the same time, we analysed the natural inter-joint coordination through PCA. During the exposition to the perturbative fields, we observed modifications of the subjects movement kinematics at every level (joints, end-effector, and inter-joint coordination). Adaptation was evidenced by a partial decrease of the movement deviations due to the fields, during the repetitions, but it occurred only on 21% of the motions. Nonetheless post-effects were observed in 86% of cases during the wash-out and follow up periods (right after the removal of the perturbation by the fields and after 30 minutes of being detached from the exoskeleton). Important inter-individual differences were observed but with small variability within subjects. In particular, a group of subjects showed an over-shoot with respect to the original unexposed trajectories (in 30% of cases), but the most frequent consequence (in 55% of cases) was the partial persistence of the modified upper-limb coordination, adopted at the time of the perturbation. Temporal and spatial generalizations were also evidenced by the deviation of the movement trajectories, both at the end-effector and at the intermediate joints and the modification of the final pointing postures towards targets which were never exposed to any field. Such results are the first quantified characterization of the effects of modification of the upper-limb coordination in healthy subjects, by imposing modification through viscous force fields distributed at the joint level, and could pave the way towards opportunities to rehabilitate pathological arm synergies with robots.

Hydrogen Radicals, Nitrogen Radicals, and the Production of Ozone in the Middle and Upper Troposphere

NASA Technical Reports Server (NTRS)

Bui, T. P.

1997-01-01

The concentrations of hydrogen radicals, OH and HO2, in the middle and upper troposphere were measured simultaneously with those of NO, O3,CO, H20, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field.

Simulating TGF and gamma ray emission above and within stormclouds due to the interaction of TeV cosmic ray shower electrons/positrons/photons with plausible electric field geometries generated in stormclouds.

NASA Astrophysics Data System (ADS)

Connell, P. H.

2017-12-01

The University of Valencia has developed a software simulator LEPTRACK to simulate lepton and photon scattering in any kind of media with a variable density, and permeated by electric/magnetic fields of any geometry, and which can handle an exponential runaway avalanche. Here we show results of simulating the interaction of electrons/positrons/photons in an incoming TeV cosmic ray shower with the kind of electric fields expected in a stormcloud after a CG discharge which removes much of the positive charge build up at the centre of the cloud. The point is to show not just a Relativistic Runaway Electron Avalanche (RREA) above the upper negative shielding layer at 12 km but other gamma ray emission due to electron/positron interaction in the remaining positive charge around 9km and the lower negative charge at 6km altitude. We present here images, lightcurves, altitude profiles, spectra and videos showing the different ionization, excitation and photon density fields produced, their time evolution, and how they depend critically on where the cosmic ray shower beam intercepts the electric field geometry. We also show a new effect of incoming positrons, which make up a significant fraction of the shower, where they appear to "orbit" within the high altitude negative shielding layer, and which has been conjectured to produce significant microwave emission, as well as a short range 511 keV annihilation line. The interesting question is if this conjectured emission can be observed and correlated with TGF orbital observations to prove that a TGF originates in the macro-fields of stormclouds or the micro-fields of light leaders and streamers where this "positron orbiting" is not likely to occur.

[Optimal lymphadenectomy for thoracic esophageal cancer: three-field or modified two-field lymphadenectomy].

PubMed

Liu, Shuoyan; Wang, Zhen; Wang, Feng

2016-09-25

Differences in operative procedure and knowledge of esophageal cancer exist among surgeons from different countries and regions. There is controversy in the surgical treatment of esophageal cancer, especially in the extent of lymphadenectomy. Until now, results of the three-field lymphadenectomy and two-field lymphadenectomy are mostly reported by retrospective studies from Japan and China. Three-field lymphadenectomy has been initiated in Fujian Provincial Cancer Hospital since 1990s. After evaluating our database, we found that three-field was superior to two-field lymphadenectomy in terms of long-term survival for patients with upper thoracic esophageal cancer, whereas for those with middle or lower thoracic esophageal cancer, the survival benefit of three-field lymphadenectomy was reduced. Therefore, we propose to perform three-field lymphadenectomy for upper thoracic esophageal cancer. In middle or lower thoracic esophageal cancer, we suggest to perform modified two-field lymphadenectomy in most cases, and three-field lymphadenectomy in selective cases. Video-assisted two-field lymphadenectomy is feasible. Based on the national condition of China, we advise to perform thoracic duct removal only in patients with posterior mediastinal or peri-ductus node metastasis to achieve curative effect.

Magnetic field orientations in Saturn's upper ionosphere inferred from Voyager radio occultations

NASA Technical Reports Server (NTRS)

Hinson, D. P.

1984-01-01

The radio scintillations observed during occultations of Voyagers 1 and 2 by Saturn are analyzed to determine the morphology of plasma irregularities and hence the magnetic field orientation in Saturn's upper atmosphere. The measurement techniques, the weak scattering theory, and the method used to relate the observed radio scintillations to physical properties of the ionospheric irregularities are briefly described. Results on the spatial characteristics of the irregularities are presented, and the magnetic field orientation in Saturn's ionosphere is inferred. Although the occultation measurements generally confirm the accuracy of the Saturnian magnetic field model of Connerney et al. (1982), it is found that a small adjustment of the coefficients in that model's zonal harmonic expansion would remove the discrepancy between the model predictions and the measurements. A strategy for obtaining improved measurements of Saturn's magnetic field from radio occultation observations of scintillations and Faraday rotation using an orbiting spacecraft is briefly discussed.

Evolution of the soil cover of soccer fields

NASA Astrophysics Data System (ADS)

Belobrov, V. P.; Zamotaev, I. V.

2014-04-01

A soccer field can be considered a soil-like technogenic formation (STF). According to the theory of soil cover patterns, the artificially constructed (anthropogenic) soil cover of a soccer field is an analogue of a relatively homogeneous elementary soil area. However, the spatial homogeneity of the upper part (50-80 cm) of the STF of soccer fields is unstable and is subjected to gradual transformation under the impact of pedogenetic processes, agrotechnical loads, and mechanical loads during the games. This transformation is favored by the initial heterogeneity of the deep (buried) parts of the STF profile. The technogenic factors and elementary pedogenetic processes specify the dynamic functioning regime of the STF. In 50-75 years, the upper part of the STF is transformed into soil-like bodies with properties close to those in zonal soils. Certain micro- and nanopatterns of the soil cover are developed within the field creating its spatial heterogeneity.

Elastic - Plastic Fracture Mechanics. A Critical Review. Part 1

DTIC Science & Technology

1990-04-01

Rolfe and Novak (86) developed the following correlations for upper shelf toughness in steels: (KIC) 2 (CVN S) (3.301 where KiC is in ksi , CVN is in ft...lb, and ys isin ksi. The good correlation with Rolfe and Novak’s experimental data was attributed to upper shelf fracture not being as sensitive to...Pisarski (84) pointed out that much of Rolfe and Novak’s data did not meet the KIC size requirements and were therefore not valid. Rolfe and Barsom (87

Deconfinement phase transition in a magnetic field in 2 + 1 dimensions from holographic models

NASA Astrophysics Data System (ADS)

M. Rodrigues, Diego; Capossoli, Eduardo Folco; Boschi-Filho, Henrique

2018-05-01

Using two different models from holographic quantum chromodynamics (QCD) we study the deconfinement phase transition in 2 + 1 dimensions in the presence of a magnetic field. Working in 2 + 1 dimensions lead us to exact solutions on the magnetic field, in contrast with the case of 3 + 1 dimensions where the solutions on the magnetic field are perturbative. As our main result we predict a critical magnetic field Bc where the deconfinement critical temperature vanishes. For weak fields meaning B Bc we find that the critical temperature raises with growing field showing a magnetic catalysis (MC). These results for IMC and MC are in agreement with the literature.

Correlation Functions of σ Fields with Values in a Hyperbolic Space

NASA Astrophysics Data System (ADS)

Haba, Z.

It is shown that the functional integral for a σ field with values in the Poincare upper half-plane (and some other hyperbolic spaces) can be performed explicitly resulting in a conformal invariant noncanonical field theory in two dimensions.

"Ring rain" on Saturn's ionosphere: densities and temperatures from 2011 observations and re-detection in 2013 observations

NASA Astrophysics Data System (ADS)

O'Donoghue, J.; Moore, L.; Melin, H.; Connerney, J. E. P.; Oliversen, R. J.

2017-12-01

In ground-based observations using the 10 meter W. M. Keck telescope in 2011, we discovered that the "ring rain" which falls on Saturn from the rings (along magnetic field lines) leaves an imprint on the upper-atmospheric H3+ ion. H3+ emissions were brightest where water products are expected to fall. Through subsequent modeling of the upper atmosphere, it became clear that an influx of water products (e.g. H2O+, O+, etc.) would act to soak up electrons - something that would otherwise destroy H3+ through recombination - and lead to a higher H3+ density and therefore emission. Here we present the first re-detections of the imprint of "ring rain" on Saturn's ionospheric H3+ from ground-based Keck telescope data from 2013. Observed intensities at low-latitudes decreased by an order of magnitude from 2011 to 2013, likely due to a decrease in upper atmospheric temperature by 100 K. A new analysis of 2011 observations revealed temperatures and densities as a function of latitude on Saturn for the first time. Where water influx is expected, H3+ column densities are high (as models predicted) and temperatures are low. While the latter was unexpected, the effect of ring rain on electron densities is stronger at lower altitudes. Therefore, as ring rain enhances density at lower altitudes where the temperature is lower, it should result in the emitting column of H3+ having a lower average temperature. These results come at a critical time as the Cassini spacecraft completes all orbits between planet and rings, with the opportunity to sample the forces and material fluxes related to ring rain.

An Assessment of Upper Tropospheric Water Vapor in the MERRA-2 Reanalysis: Comparisons with MLS and In Situ Water Vapor Measurements

NASA Astrophysics Data System (ADS)

Selkirk, H. B.; Molod, A.; Pawson, S.; Douglass, A. R.; Voemel, H.; Hurst, D. F.; Jiang, J. H.; Read, W. G.; Schwartz, M. J.; Manyin, M.

2015-12-01

The recently released MERRA-2 reanalysis represents a significant evolution of the GEOS-5 atmospheric general circulation model and data assimilation system since the original MERRA project, and it is expected that MERRA-2 will be widely used in climate change studies as has its predecessor. A number of studies have demonstrated critical sensitivities of the climate system to the water vapor content of the upper troposphere and lower stratosphere (UT/LS) and it is therefore important to assess how well the MERRA-2 reanalysis represents the mean structure and variability of water vapor in this part of the atmosphere. Recent comparisons with MLS water vapor indicate that the ECMWF and original MERRA reanalyses overestimate water vapor throughout the global upper troposphere by 50-80%. These overestimates are particularly acute at 147 hPa and 215 hPa and occur in all seasons. In this presentation, we analyze differences between the MLS v.4.2 water vapor data and the new MERRA-2 reanalysis to assess improvements in the treatment of water vapor in the GEOS-5 system since MERRA. We also include in our analysis a comparison of MERRA-2 profiles with water vapor and relative humidity profiles from frostpoint hygrometers at five sites with long-term records and a sixth with an intensive campaign of one month. Three of the long-term sites, Boulder, Colorado, Lindenburg, Germany and Lauder, New Zealand, lie in middle latitudes, and two sites, San José, Costa Rica and Hilo, Hawaii, are in the tropics and subtropics, respectively. The campaign-only database is from the NASA SEAC4RS mission at Ellington Field, Houston, TX in 2013.

Great River Environmental Action Team (GREAT II) Upper Mississippi River (Guttenberg, Iowa to Saverton, Missouri). Appendix. Fish and Wildlife Management Work Group.

DTIC Science & Technology

1980-12-01

evaluate silt tolerance and growing success of tree, shrub , vine , grass, and shrub species that are beneficial to wildlife. Additional information will...including plowed fields 4. Levee - levees and areas adjacent to levees usually consisting of grasses, forbs, vines , shrubs , and a few trees 5. Old field...of the river- can b~e measured by the many uses man dcniiads of its waters, its hoeins and its rloxlplain. Population ex- pansion in the Upper Midwest

Environmental Education in High Schools in Kosovo—A teachers' perspective

NASA Astrophysics Data System (ADS)

Hyseni Spahiu, Mimoza; Korca, Bardha; Lindemann-Matthies, Petra

2014-11-01

The integration of education for sustainable development (ESD) into all levels of education is a key priority in Kosovo's environmental action plan. However, at present it is not even known how environmental education (EE) is integrated in the country's educational system. With the help of a written questionnaire and in-depth interviews with 18 teachers, this study investigated the integration of EE in high schools (optional upper secondary education) in Kosovo. The representative sample of biology, geography, chemistry, and civic education teachers (244 persons) focused on various kinds of pollution and hazards of pollutants. Teachers' choice of topics was highly relevant, place-based, and linked to the experiences of students, but excluded sustainability issues such as the loss of biodiversity. EE was approached in three ways. The first approach critically reflected links between the natural, social, and cultural environment, while the second approach was characterized by knowledge submission of environmental facts. The third approach aimed at capacity-building and, in the sense of ESD, understood learning as process-oriented, participatory, and action-oriented. However, this approach was rather uncommon, most likely due to insufficient teacher preparation, large classes (up to 50 students), and little time (just one hour per week for EE). Class size and time also restricted outdoor activities, in particular field work. Nevertheless, in view of the interviewees, ideal EE would mean outdoor education, field work and other place-based, capacity-building practical experiences, and the development of critical thinking skills. This exemplifies that approaches to ESD may find support from dedicated teachers in Kosovo.

Superconductivity in the Nb-Ru-Ge σ phase

DOE PAGES

Carnicom, Elizabeth M.; Xie, Weiwei; Sobczak, Zuzanna; ...

2017-12-07

Here, we show that the previously unreported ternary σ-phase material Nb 20.4Ru 5.7Ge 3.9 (Nb 0.68Ru 0.19Ge 0.13) is a superconductor with a critical temperature of 2.2 K. Temperature-dependent magnetic susceptibility, resistance, and specific heat measurements were used to characterize the superconducting transition. The Sommerfeld constant γ for Nb 20.4Ru 5.7Ge 3.9 is 91 mJ mol-f.u. -1K -2 (~3 mJ mol-atom -1K -2) and the specific heat anomaly at the superconducting transition, ΔC/γT c, is approximately 1.38. The zero-temperature upper critical field (µ 0Hc 2(0)) was estimated to be 2 T by resistance data. Field-dependent magnetization data analysis estimated µmore » 0Hc 1(0) to be 5.5 mT. Thus, the characterization shows Nb 20.4Ru 5.7Ge 3.9 to be a type II BCS superconductor. This material appears to be the first reported ternary phase in the Nb-Ru-Ge system, and the fact that there are no previously reported binary Nb-Ru, Nb-Ge, or Ru-Ge σ-phases shows that all three elements are necessary to stabilize the material. An analogous σ-phase in the Ta-Ru-Ge system did not display superconductivity above 1.7 K, which suggests that electron count cannot govern the superconductivity observed. Preliminary characterization of a possible superconducting σ-phase in the Nb-Ru-Ga system is also reported.« less

Upper extremity transplantation: current concepts and challenges in an emerging field.

PubMed

Elliott, River M; Tintle, Scott M; Levin, L Scott

2014-03-01

Loss of an isolated upper limb is an emotionally and physically devastating event that results in significant impairment. Patients who lose both upper extremities experience profound disability that affects nearly every aspect of their lives. While prosthetics and surgery can eventually provide the single limb amputee with a suitable assisting hand, limited utility, minimal haptic feedback, weight, and discomfort are persistent problems with these techniques that contribute to high rates of prosthetic rejection. Moreover, despite ongoing advances in prosthetic technology, bilateral amputees continue to experience high levels of dependency, disability, and distress. Hand and upper extremity transplantation holds several advantages over prosthetic rehabilitation. The missing limb is replaced with one of similar skin color and size. Sensibility, voluntary motor control, and proprioception are restored to a greater degree, and afford better dexterity and function than prosthetics. The main shortcomings of transplantation include the hazards of immunosuppression, the complications of rejection and its treatment, and high cost. Hand and upper limb transplantation represents the most commonly performed surgery in the growing field of Vascularized Composite Allotransplantation (VCA). As upper limb transplantation and VCA have become more widespread, several important challenges and controversies have emerged. These include: refining indications for transplantation, optimizing immunosuppression, establishing reliable criteria for monitoring, diagnosing, and treating rejection, and standardizing outcome measures. This article will summarize the historical background of hand transplantation and review the current literature and concepts surrounding it.

Sensitivity-Uncertainty Techniques for Nuclear Criticality Safety

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Forrest B.; Rising, Michael Evan; Alwin, Jennifer Louise

2017-08-07

The sensitivity and uncertainty analysis course will introduce students to k eff sensitivity data, cross-section uncertainty data, how k eff sensitivity data and k eff uncertainty data are generated and how they can be used. Discussion will include how sensitivity/uncertainty data can be used to select applicable critical experiments, to quantify a defensible margin to cover validation gaps and weaknesses, and in development of upper subcritical limits.

Microwave Power Transmission Workshop summary

NASA Technical Reports Server (NTRS)

Freeman, J. W.

1980-01-01

The assumptions, methodologies, and conclusions of the NASA SPS studies were assessed and criticized to identify critical issues and to make recommendations for follow-on works. An assessment of the following items was made: beam forming and control, microwave amplifiers, radiating elements, and the rectenna. It was concluded that top priority should be given to determining an upper limit for permissible microwave power density which can be sent through the ionosphere.

Tectonic stresses in the lithosphere: constraints provided by the experimental deformation of rocks.

USGS Publications Warehouse

Kirby, S.H.

1980-01-01

The strengths of rocks clearly place an upper limit on the stress that can be sustained by the upper half of the lithosphere. Laboratory data on rock rheology are generally lacking at intermediate temperatures and pressures on the important rock types expected in the lithosphere, so a definitive accounting of the strength distribution with depth in the upper lithosphere is presently unattainable. Analogies are drawn between the fragmentary strength data on slicates at intermediate temperature and the more extensive experimental data on marble and limestone, and several tentative conclusions are drawn: First, brittle processes, such as faulting and cataclasis, are expected to control rock strength at low pressures and temperatures. The strengths associated with these brittle mechanisms increase rapidly with increasing effective pressure and are relatively insensitive to temperature and strain rate. Second, the transitions between brittle and ductile processes occur at critical values of the least principal stress sigma3. I suggest that the concept of the deformation mechanism map of Ashby (1972) be extended to brittle-ductile transitions by normalizing the applied differential stress sigma by sigma3, i.e., the transitions occur at critical values of sigma/sigma3. -from Author

Crytometia Does Not Survive in the Upper Coastal Plain of Georgia

Treesearch

Timothy La Farge

1980-01-01

Nine seed sources of Ctyptomeriojaponicafrom the northern portion of its range in Japan were tested in the Upper Coastal Plain of central Georgia. Although these sources varied significantly in their rates of growth in the nursery, only 3 of 180 trees survived after 5 years in the field.

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.;

Effect of intrinsic magnetic field decrease on the low- to middle-latitude upper atmosphere dynamics simulated by GAIA

NASA Astrophysics Data System (ADS)

Tao, C.; Jin, H.; Shinagawa, H.; Fujiwara, H.; Miyoshi, Y.

2017-12-01

The effects of decreasing the intrinsic magnetic field on the upper atmospheric dynamics at low to middle latitudes are investigated using the Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA). GAIA incorporates a meteorological reanalysis data set at low altitudes (<30 km), which enables us to investigate the atmospheric response to various waves under dynamic and chemical interactions with the ionosphere. In this simulation experiment, we reduced the magnetic field strength to as low as 10% of the current value. The averaged neutral velocity, density, and temperature at low to middle latitudes at 300 km altitude show little change with the magnetic field variation, while the dynamo field, current density, and the ionospheric conductivities are modified significantly. The wind velocity and tidal wave amplitude in the thermosphere remain large owing to the small constraint on plasma motion for a small field. On the other hand, the superrotation feature at the dip equator is weakened by 20% for a 10% magnetic field because the increase in ion drag for the small magnetic field prevents the superrotation.

Effect of intrinsic magnetic field decrease on the low- to middle-latitude upper atmosphere dynamics simulated by GAIA

NASA Astrophysics Data System (ADS)

Tao, Chihiro; Jin, Hidekatsu; Shinagawa, Hiroyuki; Fujiwara, Hitoshi; Miyoshi, Yasunobu

2017-09-01

The effects of decreasing the intrinsic magnetic field on the upper atmospheric dynamics at low to middle latitudes are investigated using the Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy (GAIA). GAIA incorporates a meteorological reanalysis data set at low altitudes (<30 km), which enables us to investigate the atmospheric response to various waves under dynamic and chemical interactions with the ionosphere. In this simulation experiment, we reduced the magnetic field strength to as low as 10% of the current value. The averaged neutral velocity, density, and temperature at low to middle latitudes at 300 km altitude show little change with the magnetic field variation, while the dynamo field, current density, and the ionospheric conductivities are modified significantly. The wind velocity and tidal wave amplitude in the thermosphere remain large owing to the small constraint on plasma motion for a small field. On the other hand, the superrotation feature at the dip equator is weakened by 20% for a 10% magnetic field because the increase in ion drag for the small magnetic field prevents the superrotation.

Critical 2-D Percolation: Crossing Probabilities, Modular Forms and Factorization

NASA Astrophysics Data System (ADS)

Kleban, Peter

2007-03-01

We first consider crossing probabilities in critical 2-D percolation in rectangular geometries, derived via conformal field theory. These quantities are shown to exhibit interesting modular behavior [1], although the physical meaning of modular transformations in this context is not clear. We show that in many cases these functions are completely characterized by very simple transformation properties. In particular, Cardy's function for the percolation crossing probability (including the conformal dimension 1/3), follows from a simple modular argument. We next consider the probability of crossing between various points for percolation in the upper half-plane. For two points, with the point x an edge of the system, the probability is P(x,z)= k 1y^5/48 φ(x,z)^1/3 where φ is the potential at z of a 2-D dipole located at x, and k is a non-universal constant. For three points, one finds the exact and universal factorization [2,3] P(x1,x2,z)= C ; √P(x1,z)P(x2,z)P(x1,x2) with C= 8 √2; &5/2circ;3^3/4 ; γ(1/3)^9/2. These results are calculated by use of conformal field theory. Computer simulations verify them very precisely. Furthermore, simulations show that the same factorization holds asymptotically, with the same value of C, when one or both of the points xi are moved from the edge into the bulk.1.) Peter Kleban and Don Zagier, Crossing probabilities and modular forms, J. Stat. Phys. 113, 431-454 (2003) [arXiv: math-ph/0209023].2.) Peter Kleban, Jacob J. H. Simmons, and Robert M. Ziff, Anchored critical percolation clusters and 2-d electrostatics, Phys. Rev. Letters 97,115702 (2006) [arXiv: cond-mat/0605120].3.) Jacob J. H. Simmons and Peter Kleban, in preparation.

Performance analysis for the cryogenic etalon spectrometer on the Upper Atmospheric Research Satellite

NASA Technical Reports Server (NTRS)

Roche, A. E.; Forney, P. B.; Kumer, J. B.; Naes, L. G.; Nast, T. C.

1983-01-01

The Upper Atmospheric Research Satellite (UARS) program has the objective of providing an 18-month to 2-year platform for observations of the upper atmosphere, giving particular attention to the stratosphere, mesosphere, and lower thermosphere. The primary aims of the mission are related to the measurement of the solar energy input between 120 and 500 km, the acquisition of global maps of the vertical and horizontal distribution of a series of critical trace and minor species, and the investigation of the dynamics of the upper atmosphere. One of several instruments designed to perform neutral species measurements on board the satellite is the Cryogenic Limb Array Etalon Spectrometer (CLAES). The CLAES experiment is concerned with measurements of concentrations of species of interest to the ozone layer balance. Attention is given to the performance requirements of the instrument and the effects of these requirements on the cryogenic design.

The Pioneer 11 high-field fluxgate magnetometer

NASA Technical Reports Server (NTRS)

Acuna, M. H.; Ness, N. F.

1973-01-01

The High Field Fluxgate Magnetometer Experiment flow aboard the Pioneer 11 spacecraft to investigate Jupiter's magnetic field is described. The instrument extends the spacecraft's upper limit measurement capability by more than an order of magnitude to 17.3 gauss with minimum power and volume requirements.

Gas, Oil, and Water Production from Jonah, Pinedale, Greater Wamsutter, and Stagecoach Draw Fields in the Greater Green River Basin, Wyoming

USGS Publications Warehouse

Nelson, Philip H.; Ewald, Shauna M.; Santus, Stephen L.; Trainor, Patrick K.

2010-01-01

Gas, oil, and water production data were compiled from selected wells in four gas fields in rocks of Late Cretaceous age in southwestern Wyoming. This study is one of a series of reports examining fluid production from tight-gas reservoirs, which are characterized by low permeability, low porosity, and the presence of clay minerals in pore space. Production from each well is represented by two samples spaced five years apart, the first sample typically taken two years after commencement of production. For each producing interval, summary diagrams of oil versus gas and water versus gas production show fluid production rates, the change in rates during five years, the water-gas and oil-gas ratios, and the fluid type. These diagrams permit well-to-well and field-to-field comparisons. Fields producing water at low rates (water dissolved in gas in the reservoir) can be distinguished from fields producing water at moderate or high rates, and the water-gas ratios are quantified. The ranges of first-sample gas rates in Pinedale field and Jonah field are quite similar, and the average gas production rate for the second sample, taken five years later, is about one-half that of the first sample for both fields. Water rates are generally substantially higher in Pinedale than in Jonah, and water-gas ratios in Pinedale are roughly a factor of ten greater in Pinedale than in Jonah. Gas and water production rates from each field are fairly well grouped, indicating that Pinedale and Jonah fields are fairly cohesive gas-water systems. Pinedale field appears to be remarkably uniform in its flow behavior with time. Jonah field, which is internally faulted, exhibits a small spread in first-sample production rates. In the Greater Wamsutter field, gas production from the upper part of the Almond Formation is greater than from the main part of the Almond. Some wells in the main and the combined (upper and main parts) Almond show increases in water production with time, whereas increases in water production are rare in the upper part of the Almond, and a higher percentage of wells in the upper part of the Almond show water decreasing at the same rate as gas than in the main or combined parts of the Almond. In Stagecoach Draw field, the gas production rate after five years is about one-fourth that of the first sample, whereas in Pinedale, Jonah, and Greater Wamsutter fields, the production rate after five years is about one-half that of the first sample. The more rapid gas decline rate seems to be the outstanding feature distinguishing Stagecoach Draw field, which is characterized as a conventional field, from Pinedale, Jonah, and Greater Wamsutter fields, which are generally characterized as tight-gas accumulations. Oil-gas ratios are fairly consistent within Jonah, Pinedale, and Stagecoach Draw fields, suggesting similar chemical composition and pressure-temperature conditions within each field, and are less than the 20 bbl/mmcf upper limit for wet gas. However, oil-gas ratios vary considerably from one area to another in the Greater Wamsutter field, demonstrating a lack of commonality in either chemistry or pressure-temperature conditions among the six areas. In all wells in all four fields examined here, water production commences with gas production-there are no examples of wells with water-free production and no examples where water production commences after first-sample gas production. The fraction of records with water production higher in the second sample than in the first sample varies from field to field, with Pinedale field showing the lowest percentage of such cases and Jonah field showing the most. Most wells have water-gas ratios exceeding the amount that could exist dissolved in gas at reservoir pressure and temperature.

Responsive upper limb and cognitive fatigue measures during light precision work: an 8-hour simulated micro-pipetting study.

PubMed

Yung, Marcus; Wells, Richard P

2017-07-01

Many contemporary occupations are characterised by long periods of low loads. These lower force levels, which are relevant to the development of work-related musculoskeletal disorders, are usually not the focus of fatigue studies. In studies that did measure fatigue in light manual or precision work, within and between measurement responses were inconsistent. The aim of this study was to identify fatigue measures that were responsive at lower force levels (<10% MVC) over the course of an 8-h period. A complementary set of fatigue measures, reflecting both neuromuscular and cognitive mechanisms, was measured during a light precision micro-pipetting task performed by 11 participants. Nine measures were found to be significantly responsive over the 8-h period, including: ratings of perceived fatigue, postural tremor, blink frequency and critical flicker fusion frequency threshold. Common field measures, specifically electromyography RMS amplitude and maximum voluntary contractions, did not lead to extraordinary time effects. Practitioner summary: The findings provide insight towards the responsiveness of a complementary set of field usable fatigue measures at low work intensities Although commonly used measures did not reveal significant increases in fatigue, nine alternative measures were significantly responsive over the 8-h period.

Selenium doping NaCl-type superconductor: SnAs1-xSex (x=0-0.13)

NASA Astrophysics Data System (ADS)

He, Jianqiao; Zhang, Xian; Lai, Xiaofang; Huang, Fuqiang

2017-08-01

Selenium doped NaCl-type superconductor SnAs1-xSex (x=0-0.13) were made through solid state reaction. EDS results show that Se content increases with Se doping until over doped in SnAs0.9Se0.1 and SnAs0.87Se0.13 (around 2.7%). PXRD patterns confirmed the main phase of the six doped samples are SnAs. The cell parameters of doped SnAs were calculated using Rietveld refinements. Their cell parameters increase almost linearly with x until x reaches 13%. Single crystal diffraction measurement results show that there are no interstitial atom in doped SnAs. We conclude that Se atoms are substitutional atoms in SnAs. The superconducting onset temperatures (Tconset, under a magnetic field of 10 Oe) of SnAs increased from 3.8 K to 4.5 K by 10% Se doping. ρ-T curves of 1%, 5% and 10% Se doped samples show that all the three samples are metallic. Upper critical field Hc2(0) of 1%, 5% and 10% Se doped samples are 294 Oe, 649 Oe and 1011 Oe, respectively.

Phase-field model with plastic flow for grain growth in nanocrystalline material

NASA Astrophysics Data System (ADS)

Steinbach, Ingo; Song, Xiaoyan; Hartmaier, Alexander

2010-01-01

A phase-field model is presented which considers the accumulation of structural defects in grain boundaries by an isotropic eigenstrain associated with the grain boundaries. It is demonstrated that the elastic energy caused by dilatation of the grain boundary with respect to the bulk crystal contributes largely to the grain boundary energy. The sign of this contribution can be both positive and negative dependent on the local stress state in the grain boundary. Self-diffusion of atoms is taken into account to relax the stress caused by the dilatation of the grain boundary. Application of the model to discontinuous grain growth in pure nanocrystalline cobalt material is presented. Linear grain growth is found in the nanocrystalline state, which is explained by the interpretation of grain boundary motion as a diffusive process defining an upper limit of the grain boundary velocity independent of the grain boundary curvature but dependent on temperature. The transition to regular grain growth at a critical temperature, as observed experimentally, is explained by the drop of theoretical grain boundary velocity due to its mean curvature during coarsening of the nanograin structure below the maximum velocity.

Quantum critical dynamics of the boson system in the Ginzburg-Landau model

NASA Astrophysics Data System (ADS)

Vasin, M. G.

2014-12-01

The quantum critical dynamics of the quantum phase transitions is considered. In the framework of the unified theory, based on the Keldysh technique, we consider the crossover from the classical to the quantum description of the boson many-body system dynamics close to the second order quantum phase transition. It is shown that in this case the upper critical space dimension of this model is dc+=2, therefore the quantum critical dynamics approach is useful in case of d<2. In the one-dimension system the phase coherence time does diverge at the quantum critical point, gc, and has the form of τ∝-ln∣g-gc∣/∣g-gc∣, the correlation radius diverges as rc∝∣g-gc∣(ν=0.6).

Xenoliths from Bunyaruguru volcanic field: Some insights into lithology of East African Rift upper mantle

NASA Astrophysics Data System (ADS)

Muravyeva, N. S.; Senin, V. G.

2018-01-01

The mineral composition of mantle xenoliths from kamafugites of the Bunyaruguru volcanic field has been determined. The major and some trace elements (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, Cr, Ni, Ba, Sr, La, Ce, Nd, Nb) has been analyzed in olivine, clinopyroxene, phlogopite, Cr-spinel, titanomagnetite, perovskite and carbonates of xenoliths and their host lavas. Bunyaruguru is one of three (Katwe-Kikorongo, Fort Portal and Bunyaruguru) volcanic fields included in the Toro-Ankole province located on the North end of the West Branch of the East African Rift. The xenoliths from three craters within the Bunyaruguru volcanic field revealed the different character of metasomatic alteration, reflecting the heterogeneity of the mantle on the kilometer scale. The most unusual finding was composite glimmerite-wehrlite xenolith from the crater Kazimiro, which contains the fresh primary high-Mg olivine with inclusions of Cr-spinel that had not been previously identified in this area. The different composition of phenocryst and xenolith minerals indicates that the studied xenoliths are not cumulus of enclosing magma, but the composition of xenoliths characterizes the lithology of the upper mantle of the area. The carbonate melt inclusions in olivine Fo90 demonstrate the existence of primary carbonatitic magmas in Bunyaruguru upper mantle. The results of texture and chemical investigation of the xenolith minerals indicate the time sequence of metasomatic alteration of Bunyaruguru upper mantle: MARID metasomatism at the first stage followed by carbonate metasomatism. The abundances of REE in perovskites from kamafugite are 2-4 times higher than similar values for xenolith. Therefore the kamafugite magma was been generated from a more enriched mantle source than the source of the xenoliths. The evaluation of P-T conditions formation of clinopyroxene xenolith revealed the range of pressure 20-65 kbar and the temperatures range 830-1040 °C. The pressure of clinopyroxene phenocryst crystallization differs from pressure of formation the xenoliths clinopyroxene: it may be higher or lower of it. The results of our investigation have shown that olivine can play a noticeable role in the lithology of the upper mantle Bunyaruguru volcanic field.