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  • 1
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    Price Explosiveness, Speculation, and Grain Futures Prices (2014)
    Oxford University Press
    Details
    Publication Date: 2014-12-13
    Description: A recently developed testing procedure is used to detect and date-stamp explosive episodes ("bubbles") in corn, soybean, and wheat futures markets during 2004–2013. We find that the markets experienced price explosiveness only approximately two percent of the time and, when bubbles do occur, they are generally short-lived and small in magnitude. The correspondence between observed price spikes and bubbles is rather low, with a large portion of the price explosiveness occurring during downward price movements. Commodity index trader positions do not significantly affect the probability of a positive bubble occurring in grain futures markets, which directly contradicts the argument (the "Masters Hypothesis") that waves of index investment distorted underlying supply-and-demand relationships and led to a series of massive bubbles in agricultural futures markets. In addition, commodity index trader positions tend to reduce negative bubble occurrence, while general speculative activity as measured by Working's T reduces the probability of a positive bubble. There is some evidence that the positions of noncommercial traders have a direct effect on positive bubble occurrence, but the effect declines when accounting for the composition of other traders in the market. Overall, speculation has little effect or negative effects on price explosiveness. Finally, positive bubbles are more likely to occur in the presence of low inventories, strong exports, a weak U.S. dollar, and booming economic growth, whereas negative bubbles are more likely to occur with large inventories, weak exports, and stagnant economic growth.
    Keywords: D84 - Expectations ; Speculations, G12 - Asset Pricing ; Trading volume ; Bond Interest Rates, G13 - Contingent Pricing ; Futures Pricing, G14 - Information and Market Efficiency ; Event Studies, Q13 - Agricultural Markets and Marketing ; Cooperatives ; Agribusiness, Q41 - Demand and Supply
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by Oxford University Press
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  • 2
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    Nonlinear optical properties of bulk cuprous oxide using single beam Z-scan at 790 nm (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-11-12
    Description: The two-photon absorption (TPA) coefficient β and the nonlinear index of refraction n 2 for bulk cuprous oxide (Cu 2 O) direct gap semiconductor single crystal have been measured by using a balance-detection Z-scan single beam technique, with an excellent signal to noise ratio. Both coefficients were measured at 790 nm using a 65 fs laser pulse at a repetition rate of 90.9 MHz, generated by a Ti:Sapphire laser oscillator. The experimental values for β were explained by using a model that includes allowed-allowed, forbidden-allowed, and forbidden-forbidden transitions. It was found that the forbidden-forbidden transition is the dominant mechanism, which is consistent with the band structure of Cu 2 O. The low value for β found in bulk, as compared with respect to thin film, is explained in terms of the structural change in thin films that result in opposite parities of the conduction and valence band. The n 2 is also theoretically calculated by using the TPA dispersion curve and the Kramers-Kronig relations for nonlinear optics.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 3
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    Genome-wide copy number variation study in anorectal malformations (2013)
    Oxford University Press
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    Publication Date: 2013-01-12
    Description: Anorectal malformations (ARMs, congenital obstruction of the anal opening) are among the most common birth defects requiring surgical treatment (2–5/10 000 live-births) and carry significant chronic morbidity. ARMs present either as isolated or as part of the phenotypic spectrum of some chromosomal abnormalities or monogenic syndromes. The etiology is unknown. To assess the genetic contribution to ARMs, we investigated single-nucleotide polymorphisms and copy number variations (CNVs) at genome-wide scale. A total of 363 Han Chinese sporadic ARM patients and 4006 Han Chinese controls were included. Overall, we detected a 1.3-fold significant excess of rare CNVs in patients. Stratification of patients by presence/absence of other congenital anomalies showed that while syndromic ARM patients carried significantly longer rare duplications than controls ( P = 0.049), non-syndromic patients were enriched with both rare deletions and duplications when compared with controls ( P = 0.00031). Twelve chromosomal aberrations and 114 rare CNVs were observed in patients but not in 868 controls nor 11 943 healthy individuals from the Database of Genomic Variants. Importantly, these aberrations were observed in isolated ARM patients. Gene-based analysis revealed 79 genes interfered by CNVs in patients only. In particular, we identified a de novo DKK4 duplication . DKK4 is a member of the WNT signaling pathway which is involved in the development of the anorectal region. In mice, Wnt disruption results in ARMs. Our data suggest a role for rare CNVs not only in syndromic but also in isolated ARM patients and provide a list of plausible candidate genes for the disorder.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
    Published by Oxford University Press
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  • 4
    Electronic Resource
    Electronic Resource
    Ab initio studies of the reactions of Cu(2S, 2D, and 2P) with SiH4 and GeH4 (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 928-935 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The interactions of Cu(2S:3d104s1, 2D:3d94s2, and 2P:3d104p1) with SiH4 and GeH4 were studied by means of Hartree–Fock–SCF and multiconfigurational-SCF followed by variational and multireference second order Möller–Plesset perturbational configuration interaction (CIPSI) calculations, using relativistic effective core potentials. The Cu atom in its 2P(3d104p1) state is inserted in the Si–H and Ge–H bonds. In both interactions their corresponding 5 2A′ potential energy surfaces are initially attractive and become repulsive only after having encountered the avoided crossing region with the initially repulsive 4 2A′ surface adiabatically linked with the Cu(2D:3d94s2)–SiH4(GeH4) fragments. The three 2A′ curves derived from the interaction of the Cu(2D:3d94s2) atom with silicon (or germane) molecule are initially repulsive. Each one of them shows two avoided crossings and its lowest lying 2 2A′ curve goes sharply down until it meets the X 2A′ curve adiabatically linked with the Cu(2S:3d104s1)+SiH4(GeH4) asymptotes. The 2 2A′ curve becomes repulsive after the avoided crossing with the X 2A′ curve. The lowest-lying X 2A′ potential leads to the HCuZH3 X 2A1 (Z=Si, Ge) intermediate molecule. This intermediate molecule, diabatically correlated with the Cu(2P:3d104p1)+ZH4 fragments which lie 5.8 and 1.6 kcal/mol, respectively, above the ground state reactants, have been carefully characterized as well as the dissociation channels leading to the CuH+ZH3 and H+CuZH3 products. These products are reached from the HCuZH3 intermediates without activation barriers. This work suggests that the simultaneous photoexcitation of the Cu atom in presence of silane and germane molecules in the gas phase could be used to produce better quality a-SiGe:H thin films. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1427713
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  • 5
    Electronic Resource
    Electronic Resource
    Ab initio studies of the reactions of M(1S,3P, and 1P) with GeH4 (M=Cd, Hg) (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 2647-2652 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The interaction of Cd(1S:5s2, 3,1P:5s15p1) and Hg(1S:6s2, 1,3P:6s16p1) with GeH4 were studied by means of Hartree–Fock self-consistent field (SCF) and multiconfigurational SCF plus variational and multireference second order Möller–Plesset perturbational configuration interaction (CIPSI) calculations, using relativistic effective core potentials. It was found that both metal atoms in their 3P(ns1np1) state break spontaneously the Ge–H bond of the germane molecule, giving place to the MH+GeH3 (M=Cd, Hg) final products. For both atoms, the 1P(ns1np1) state is also inserted in the Ge–H bond and the corresponding interaction surface shows an avoided crossing with the lowest-lying X 1A′ potential surface adiabatically linked with the M(1S:ns2)+GeH4. This interaction leads eventually to the MH+GeH3 products. The HMGeH3 X 1A1 (M=Cd, Hg) intermediate molecules, diabatically correlated with the M(1P:ns1np1)+GeH4, which lie 13.6 and 21 kcal/mol, respectively, above the ground state reactants, have been carefully characterized as well as the dissociation channels leading to the MH+GeH3 and H+MGeH3 products. These products are reached from the HMGeH3 intermediates without activation barriers. Accurate energy differences for all these species are reported. This work suggests that the simultaneous photoexcitation of Cd and Hg atoms in the presence of silane and germane molecules in the gas phase could be used to produce better quality a-SiGe:H thin films. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1337863
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  • 6
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    Search for liquids electrospraying the smallest possible nanodrops in vacuo (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-12-11
    Description: Prior work with electrosprays in vacuum of mixtures of ionic liquids (ILs) and the moderately high boiling point (T b ) solvents formamide (FM) and propylene carbonate (PC) (T b of 210 and 241 °C) has shown that the charged drops produced have reasonably narrow charge/mass distributions, controllable over a wide mass/charge range. This enables their use as propellants in electrical propulsion with specific impulse I sp varying from a few hundred to a few thousand seconds (10 kV beam energy) and with excellent propulsion efficiency. However, some limitations are imposed by the finite room temperature volatility of FM and PC. Here, we seek improved performance from propellants based on the polar but viscous solvent Sulfolane (SF; ε = 43.2, μ = 10.3 cP) and the low viscosity but less polar solvent tributyl phosphate (TBP; ε = 8.9, μ = 3.4 cP), both with T b  〉 280 °C. Neither TBP nor its low viscosity mixtures with SF achieve the electrical conductivities needed to yield high I sp . Most ILs used in SF/IL mixtures tested were based on the 1-ethyl-3-methylimidazolium (EMI) or 1,3-dimethylimidazolium (DMI) cations, including EMI-BF 4 , EMI-N(CN) 2 , and DMI-N(CN) 2 . These combinations reach high conductivities, some approaching 3 S/m, but have limited propulsive performance because evaporation of ions directly from the electrified meniscus produces undesirable mixed beams of drops and ions. Exceptional characteristics are found in mixtures of SF with ethylammonium nitrate (EAN), where the small EA + cation is strongly bound to the solvent, greatly delaying ion evaporation from the meniscus. Evidence on the formation of nano-jets with diameters as small as 1 nm is seen. Although unprecedented, this finding agrees with what would be expected if ion evaporation were suppressed. SF/EAN mixtures thus provide the best available sources to produce the smallest possible nanodrops, minimally polluted by ions.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 7
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    Dynamics of nonstructural carbohydrates and biomass yield in a fodder legume tree at different harvest intensities (2001)
    Oxford University Press
    Details
    Publication Date: 2001-05-01
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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