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ABSTRACT: Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most damaging diseases of wheat worldwide. It is essential to identify new genes for effective resistance against the disease. Durum wheat PI 480148, originally from Ethiopia, was resistant in all seedling tests with several predominant Pst races in the US under controlled greenhouse conditions and at multiple locations subject to natural infection for several years. To map the resistance gene(s) and to transfer it to common wheat, a cross was made between PI 480148 and susceptible common wheat genotype Avocet S (AvS). Resistant F(3) plants with 42 chromosomes were selected cytologically and by testing with Pst race PST-100. A total of 157 F(4) plants from a single F(3) plant with 2n = 42 tested with PST-100 segregated in a 3 resistant: 1 susceptible ratio, indicating that a single dominant gene from PI 480148 conferred resistance. Using the F(3:4) population and the resistance gene-analog polymorphism (RGAP) and simple sequence repeat (SSR) markers, the gene was mapped to the long arm of chromosome 2B. SSR marker Xwmc441 and RGAP marker XLRRrev/NLRRrev ( 350 ) flanked the resistance gene by 5.6 and 2.7 cM, respectively. The effective resistance of the gene to an Australian Pst isolate virulent to Yr5, which is also located on 2BL and confers resistance to all US Pst races, together with an allelism test of the two genes, indicated that the gene from PI 480148 is different from Yr5 and should be a new and useful gene for resistance to stripe rust. Resistant common wheat lines with plant types similar to AvS were selected for use in breeding programs.
Theoretical and Applied Genetics 10/2012; · 3.30 Impact Factor
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Malvina Andris,
M C Arias,
Brandon L Barthel,
Burton H Bluhm,
Joël Bried,
D Canal,
X M Chen, P Cheng,
Marina B Chiappero,
Manuela M Coelho, [......],
J H Sarasola,
D R See,
Seifu Seyoum,
Mónica C Silva,
C Solaro,
Krystal A Tolley,
Michael D Tringali,
A Vasemägi,
L S Xu,
J I Zanón-Martínez
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ABSTRACT: This article documents the addition of 171 microsatellite marker loci and 27 pairs of single nucleotide polymorphism (SNP) sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Bombus pauloensis, Cephalorhynchus heavisidii, Cercospora sojina, Harpyhaliaetus coronatus, Hordeum vulgare, Lachnolaimus maximus, Oceanodroma monteiroi, Puccinia striiformis f. sp. tritici, Rhea americana, Salmo salar, Salmo trutta, Schistocephalus solidus, Sousa plumbea and Tursiops aduncus. These loci were cross-tested on the following species: Aquila heliaca, Bulweria bulwerii, Buteo buteo, Buteo swainsoni, Falco rusticolus, Haliaeetus albicilla, Halobaena caerulea, Hieraaetus fasciatus, Oceanodroma castro, Puccinia graminis f. sp. Tritici, Puccinia triticina, Rhea pennata and Schistocephalus pungitii. This article also documents the addition of 27 sequencing primer pairs for Puffinus baroli and Bulweria bulwerii and cross-testing of these loci in Oceanodroma castro, Pelagodroma marina, Pelecanoides georgicus, Pelecanoides urinatrix, Thalassarche chrysostoma and Thalassarche melanophrys.
Molecular Ecology Resources 05/2012; 12(4):779-81. · 3.06 Impact Factor
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Malvina Andris,
M C Arias,
Brandon L Barthel,
Burton H Bluhm,
Jo L Bried,
D Canal,
X M Chen, P Cheng,
Marina B Chiappero,
Manuela M Coelho, [......],
J H Sarasola,
D R See,
Seifu Seyoum,
C Silva,
C Solaro,
Krystal A Tolley,
Michael D Tringali,
L S Xu,
J I Zan,
N-Mart Nez
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ABSTRACT: This article documents the addition of 171 microsatellite marker loci and 27 pairs of single nucleotide polymorphism (SNP)
sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Bombus
pauloensis, Cephalorhynchus heavisidii, Cercospora sojina, Harpyhaliaetus coronatus, Hordeum vulgare, Lachnolaimus maximus,
Oceanodroma monteiroi, Puccinia striiformis f. sp. tritici, Rhea americana, Salmo salar, Salmo trutta, Schistocephalus
solidus, Sousa plumbea and Tursiops aduncus. These loci were cross-tested on the following species: Aquila heliaca, Bulweria
bulwerii, Buteo buteo, Buteo swainsoni, Falco rusticolus, Haliaeetus albicilla, Halobaena caerulea, Hieraaetus fasciatus,
Oceanodroma castro, Puccinia graminis f. sp. Tritici, Puccinia triticina, Rhea pennata and Schistocephalus pungitii. This article
also documents the addition of 27 sequencing primer pairs for Puffinus baroli and Bulweria bulwerii and cross-testing
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ABSTRACT: We determined the optical conductivity of Bi2Sr2-xLaxCuO6 at dopings covering the phase diagram from the underdoped to the overdoped regimes. The frequency-dependent scattering rate shows a pseudogap extending into the overdoped regime. We found that the effective mass enhancement calculated from the optical conductivity is constant throughout the phase diagram. Conversely, the effective optical charge density varies almost linearly with doping. Our results suggest that the low-frequency electrodynamics of Bi2Sr2-xLaxCuO6 is not strongly affected by the long-range Mott transition.
Phys. Rev. B. 03/2012; 85(9).
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C. Tarantini,
M. Putti,
A. Gurevich,
Y. Shen,
R.K. Singh,
J.M. Rowell,
N. Newman,
D.C. Larbalestier, P. Cheng,
Y. Jia,
and H-H Wen
Physical Review Letters 01/2012; 104(087002). · 7.37 Impact Factor
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T. Qian,
N. Xu,
Y.-B. Shi,
K. Nakayama,
P. Richard,
T. Kawahara,
T. Sato,
T. Takahashi,
M. Neupane,
Y.-M. Xu,
X.-P. Wang,
G. Xu,
X. Dai,
Z. Fang, P. Cheng,
H.-H. Wen,
H. Ding
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ABSTRACT: We have performed an angle-resolved photoemission spectroscopy study of the iron-based superconductor (SC) Sr2VFeAsO3. While V 3d orbitals are found to be in a Mott-insulating state and show an incoherent peak at ~1 eV below the Fermi level, the dispersive Fe 3d bands form several hole- and electronlike Fermi surfaces (FSs), some of which are quasinested by the (π,0) wave vector. This differs from the local-density approximation (LDA) calculations, which predict non-nested FSs for this material. However, LDA + U with a large effective Hubbard energy U on V 3d electrons can reproduce the experimental observation reasonably well. The observed fermiology in SC Sr2VFeAsO3 strongly supports that (π,0) interband scattering between quasinested FSs may play an important role for SC in pnictides.
Physical Review B 04/2011; 83(14). · 3.69 Impact Factor
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ABSTRACT: Scanning tunneling spectroscopic studies of Ba(Fe(1-x)Co(x))(2)As(2) (x=0.06, 0.12) single crystals reveal direct evidence for predominantly two-gap superconductivity. These gaps decrease with increasing temperature and vanish above the superconducting transition T(c). The two-gap nature and the slightly doping- and energy-dependent quasiparticle scattering interferences near the wave vectors (±π, 0) and (0, ±π) are consistent with sign-changing s-wave superconductivity. The excess zero-bias conductance and the large gap-to-T(c) ratios suggest dominant unitary impurity scattering.
Physical Review Letters 02/2011; 106(8):087004. · 7.37 Impact Factor
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T. Qian,
N Xu,
Y. -B. Shi,
K Nakayama,
P. Richard,
T Kawahara,
T Sato,
T Takahashi,
M. Neupane,
Y. -M. Xu,
X. -P. Wang,
G Xu,
X Dai,
Z Fang, P Cheng,
H. H. Wen,
H Ding
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ABSTRACT: We have performed an angle-resolved photoemission spectroscopy study of a new
iron-based superconductor Sr4V2O6Fe2As2. While V 3d orbitals are found to be in
a Mott insulator state and show an incoherent peak at ~ 1 eV below the Fermi
level, the dispersive Fe 3d bands form several hole- and electron-like Fermi
surfaces (FSs), some of which are quasi-nested by the (pi, 0) wave vector. This
differs from the local density approximation (LDA) calculations, which predict
non-nested FSs for this material. However, LDA+U with a large effective Hubbard
energy U on V 3d electrons can reproduce the experimental observation
reasonably well. The observed fermiology in superconducting Sr4V2O6Fe2As2
strongly supports that (pi, 0) interband scattering between quasi-nested FSs is
indispensable to superconductivity in pnictides.
08/2010;
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ABSTRACT: We report the first NMR investigation of spin dynamics in the overdoped nonsuperconducting regime of Ba(Fe1-xCox)2As2 up to x=0.26. We demonstrate that the absence of interband transitions with large momentum transfer Q{AF} approximately (pi/a,0) between the hole and electron Fermi surfaces results in complete suppression of antiferromagnetic spin fluctuations for x greater than or approximately 0.15. Our experimental results provide direct evidence for a correlation between T{c} and the strength of Q{AF} antiferromagnetic spin fluctuations.
Physical Review Letters 01/2010; 104(3):037001. · 7.37 Impact Factor
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M Putti,
I Pallecchi,
E Bellingeri,
M Tropeano,
C Ferdeghini,
A Palenzona C Tarantini,
A Yamamoto,
J Jiang,
J Jaroszynski,
F Kametani, [......],
R Jin,
B C Sales,
A S Sefat,
M A McGuire,
D Mandrus, P Cheng,
Y Jia,
H H Wen,
S Lee,
C B Eom
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ABSTRACT: 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, the supposed order parameter symmetry is s wave, thus
in principle not so detrimental to current transmission across grain
boundaries. From the application point of view, the main efforts are still
devoted to investigate the superconducting properties, to distinguish intrinsic
from extrinsic behaviours 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 Tc, huge but also the most
anisotropic upper critical field and in-field, fan-shaped resistive transitions
reminiscent of those of cuprates, while the 122 family is much less anisotropic
with sharper resistive transitions as in low temperature superconductors, but
with about half the Tc of the 1111 compounds. An overview of the main
superconducting properties relevant to applications will be presented. Upper
critical field, electronic anisotropy parameter, intragranular and
intergranular critical current density will be discussed and compared, where
possible, across the Fe-based superconductor families.
10/2009;
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ABSTRACT: We will examine the possible link between spin fluctuations and the superconducting mechanism in the iron-based high temperature superconductor Ba(Fe,Co)2As2 based on NMR and high pressure transport measurements. Comment: Invited paper to m2s-IX (2009)
10/2009;
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ABSTRACT: The in-plane thermal conductivity $\kappa$ of overdoped FeAs-based superconductor BaFe$_{1.73}$Co$_{0.27}$As$_2$ ($T_c$ = 8.1 K) single crystal was measured down to 80 mK. In zero field, the residual linear term $\kappa_0/T$ is negligible, suggesting a nodeless superconducting gap in the $ab$-plane. In magnetic field, $\kappa_0/T$ increases rapidly, very different from that of conventional s-wave superconductors. This anomalous $\kappa_0/T(H)$ may reveal an exotic superconducting gap structure in overdoped BaFe$_{1.73}$Co$_{0.27}$As$_2$: the vanishing hole ($\beta$) pocket has a much larger gap than the electron ($\gamma$ and $\delta$) pockets which contain most of the carriers. Such an exotic gap structure is an evidence for superconducting state induced by interband interactions, in which the band with the {\it smaller} density of states has a {\it larger} gap. Comment: 5 pages, 3 figures
08/2009;
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ABSTRACT: We report the first NMR investigation of spin dynamics in the overdoped non-superconducting regime of Ba(Fe[1-x]Co[x])2As2 up to x =0.26. We demonstrate that the absence of inter-band transitions with large momentum transfer Q(AF) ~ (pi, 0) between the hole and electron Fermi surfaces results in complete suppression of antiferromagnetic spin fluctuations for x > 0.15. Our experimental results provide direct evidence for a correlation between Tc and the strength of Q(AF) antiferromagnetic spin fluctuations. Comment: Accepted for publication in Phys. Rev. Lett
07/2009;
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J. Jaroszynski,
F. Hunte,
L. Balicas,
Youn-jung Jo,
I. Raičević,
A. Gurevich,
D. C. Larbalestier,
F. F. Balakirev,
L. Fang, P. Cheng,
Y. Jia,
H. H. Wen
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ABSTRACT: We present detailed measurements of the longitudinal resistivity ρxx(T,H) and the upper critical field Hc2 of NdFeAsO0.7F0.3 single crystals in strong dc and pulsed magnetic fields up to 45 and 60 T, respectively. We found that the field scale of Hc2 is comparable to Hc2∼100 T of high-Tc cuprates. Hc2(T) parallel to the c axis exhibits a pronounced upward curvature similar to what was extracted from earlier measurements on polycrystalline LaFeAs(O,F), NdFeAs(O,F), and SmFeAs(O,F) samples. Thus, this behavior of Hc2⊥(T) is indeed an intrinsic feature of oxypnictides rather than manifestation of vortex lattice melting or granularity. The orientational dependence of Hc2(θ) as a function of the angle θ between H and the c axis shows deviations from the one-band Ginzburg-Landau scaling. The mass anisotropy parameter γ(T)=(mc/mab)1/2=Hc2∥/Hc2⊥ obtained from these measurements decreases as temperature decreases from γ≃9.2 at 44 K to γ≃5 at 34 K, where ∥ and ⊥ correspond to H parallel and perpendicular to the ab planes, respectively. Spin-dependent magnetoresistance and nonlinearities in the Hall coefficient suggest contribution to the conductivity from electron-electron interactions modified by disorder reminiscent of that in diluted magnetic semiconductors. The Ohmic resistivity ρxx(T,H) measured below Tc but above the irreversibility field exhibits a clear Arrhenius thermally-activated behavior ρ=ρ0 exp[−Ea(T,H)/T] over 4–5 decades of ρxx. The activation energy Ea(T,H) has very different field dependencies for H∥ab and H⊥ab varying from 4×103 K at H=0.2 T to ∼200 K at H=35 T. We discuss to what extent different pairing scenarios suggested in the literature can manifest themselves in the observed behavior of Hc2, using the two-band model of superconductivity in oxypnictides. The results indicate the importance of paramagnetic effects on Hc2(T) in oxypnictides, which may significantly reduce Hc2(0) as compared to Hc2(0)∼200–300 T based on extrapolations of Hc2(T) near Tc down to low temperatures.
Phys. Rev. B. 11/2008; 78(17).
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J. Jaroszynski,
F. Hunte,
L. Balicas,
Youn-jung Jo,
I. Raicevic,
A. Gurevich,
D. C. Larbalestier,
F. F. Balakirev,
L Fang, P Cheng,
Y Jia,
H. H. Wen
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ABSTRACT: We present measurements of the resistivity and the upper critical field H_c2 of Nd(O_0.7F_0.3)FeAs single crystals in strong DC and pulsed magnetic fields up to 45 T and 60 T, respectively. We found that the field scale of H_c2 is comparable to ~100 T of high T_c cuprates. H_c2(T) parallel to the c-axis exhibits a pronounced upward curvature similar to what was extracted from earlier measurements on polycrystalline samples. Thus this behavior is indeed an intrinsic feature of oxypnictides, rather than manifestation of vortex lattice melting or granularity. The orientational dependence of H_c2 shows deviations from the one-band Ginzburg-Landau scaling. The mass anisotropy decreases as T decreases, from 9.2 at 44K to 5 at 34K. Spin dependent magnetoresistance and nonlinearities in the Hall coefficient suggest contribution to the conductivity from electron-electron interactions modified by disorder reminiscent that of diluted magnetic semiconductors. The Ohmic resistivity measured below T_c but above the irreversibility field exhibits a clear Arrhenius thermally activated behavior over 4-5 decades. The activation energy has very different field dependencies for H||ab and H\perp ab. We discuss to what extent different pairing scenarios can manifest themselves in the observed behavior of H_{c2}, using the two-band model of superconductivity. The results indicate the importance of paramagnetic effects on H_c2(T),which may significantly reduce H_c2(0) as compared toH_c2(0)~200-300 T based on extrapolations of H_c2(T) near T_c down to low temperatures.
11/2008;
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ABSTRACT: We report plane-polarized Raman scattering spectra of iron oxypnictide superconductor NdFeAsO$_{1-x}$F$_x$ single crystals with varying fluorine $x$ content. The spectra exhibit sharp and symmetrical phonon lines with a weak dependence on fluorine doping $x$. The temperature dependence does not show any phonon anomaly at the superconducting transition. The Fe related phonon intensity shows a strong resonant enhancement below 2 eV. We associate the resonant enhancement to the presence of an interband transition around 2 eV observed in optical conductivity. Our results point to a rather weak coupling between Raman-active phonons and electronic excitations in iron oxypnictides superconductors. Comment: 4 pages, 3 figures, to appear in Phys. Rev. B
10/2008;
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ABSTRACT: We present heat capacity measurements of the upper critical fields of single-crystal NdFeAsO1-xFx. In zero-magnetic field a clear step in the heat capacity is observed at Tc = 47K . In fields applied perpendicular to the FeAs-layers the step broadens significantly whereas for the in-plane orientation the field effects are small. This behavior is reminiscent of the CuO2-high-Tc superconductors and is a manifestation of pronounced fluctuation effects. Using an entropy conserving construction we determine the transition temperatures in applied fields and the upper critical field slopes of dHc2,a = -0.72 T/K and dHc2,ab = -3.1 T/K. Zero-temperature coherence lengths of xiab = 3.7 nm and xic = 0.9 nm and a modest superconducting anisotropy of gamma ~ 4 can be deduced in a single-band model. Comment: 15 pages with 4 figures
07/2008;
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ABSTRACT: We present heat-capacity measurements of the upper critical fields of single-crystal NdFeAsO1−xFx. In zero-magnetic field a clear step in the heat capacity is observed at Tc≈47 K. In fields applied perpendicular to the FeAs layers the step broadens significantly whereas for the in-plane orientation the field effects are small. This behavior is reminiscent of the CuO2-high-Tc superconductors and is a manifestation of pronounced fluctuation effects. Using an entropy conserving construction we determine the transition temperatures in applied fields and the upper critical-field slopes of ∂Hc2c/∂T=−0.72 T/K and ∂Hc2ab/∂T=−3.1 T/K. Zero-temperature coherence lengths of ξab≈3.7 nm and ξc≈0.9 nm and a modest superconducting anisotropy of λ∼4 can be deduced in a single-band model.
Phys. Rev. B. 78(14).
