1,489 research outputs found
Nitrogen retention and plant uptake on a highly weathered central Amazonian Ferralsol amended with compost and charcoal.
Inspired by the sustained fertility of anthropogenic Terra Preta soils in the central Amazon Basin, we studied the effect of charcoal as soil amendment
Non-parametric comparison of histogrammed two-dimensional data distributions using the Energy Test
When monitoring complex experiments, comparison is often made between regularly acquired histograms of data and reference histograms which represent the ideal state of the equipment. With the larger HEP experiments now ramping up, there is a need for automation of this task since the volume of comparisons could overwhelm human operators. However, the two-dimensional histogram comparison tools available in ROOT have been noted in the past to exhibit shortcomings. We discuss a newer comparison test for two-dimensional histograms, based on the Energy Test of Aslan and Zech, which provides more conclusive
discrimination between histograms of data coming from different distributions than methods provided in a recent ROOT release.The Science and Technology Facilities Council, U
Corte e carbonização como uma alternativa ao corte e queima: estudos na Amazônia.
Neste capítulo são apresentados vários estudos realizados em Manaus cujo principal objetivo foi verificar o efeito da aplicação de carvão vegetal no manejo do Latossolo Amarelo (xanthic Ferralsol) na terra firme em Manaus - Brasil. Os estudos foram conduzidos na Estação Experimental da Embrapa Amazônia Ocidental no km 30 da Rodovia AM-010. Também é descrito uma forma de manejo indígena da fertilidade do solo pela queima e uso de fontes orgânica
Oxygen-isotope effect on the in-plane penetration depth in underdoped Y_{1-x}Pr_xBa_2Cu_3O_{7-delta} as revealed by muon-spin rotation
The oxygen-isotope (^16O/^18O) effect (OIE) on the in-plane penetration depth
in underdoped Y_{1-x}Pr_xBa_2Cu_3O_{7-delta} was studied by
muon-spin rotation. A pronounced OIE on was observed
with a relative isotope shift of
=-5(2)% for x =0.3 and -9(2)% for
x=0.4. It arises mainly from the oxygen-mass dependence of the in-plane
effective mass . The OIE exponents of T_{c} and of
exhibit a relation that appears to be generic for
cuprate superconductors.Comment: 4 pages, 4 eps figures, RevTex
Superconducting Magnetization above the Irreversibility Line in Tl2Ba2CuO6
Piezolever torque magnetometry has been used to measure the magnetization of
superconducting Tl2Ba2CuO6. Three crystals with different levels of oxygen
overdoping were investigated in magnetic fields up to 10 Tesla. In all cases,
the magnetization above the irreversibility line was found to depart from the
behaviour M ~ ln(Hc2/H) of a simple London-like vortex liquid. In particular,
for a strongly overdoped (Tc = 15K) crystal, the remnant superconducting order
above the irreversibility line is characterized by a linear diamagnetic
response (M ~ H) that persists well above Tc and also up to the highest field
employed.Comment: RevTeX, 11 pages, 7 encapsulated PostScript figures, submitted to
Physical Review
Investigation of A1g phonons in YBa2Cu3O7 by means of LAPW atomic-force calculations
We report first-principles frozen-phonon calculations for the determination
of the force-free geometry and the dynamical matrix of the five Raman-active
A1g modes in YBa2Cu3O7. To establish the shape of the phonon potentials atomic
forces are calculated within the LAPW method. Two different schemes - the local
density approximation (LDA) and a generalized gradient approximation (GGA) -
are employed for the treatment of electronic exchange and correlation effects.
We find that in the case of LDA the resulting phonon frequencies show a
deviation from experimental values of approximately -10%. Invoking GGA the
frequency values are significantly improved and also the eigenvectors are in
very good agreement with experimental findings.Comment: 15 page
Coupling to optical phonons in the one-dimensional t-J model: Effects on superconducting fluctuations and phase separation
The one-dimensional (1D) - Holstein model is studied by exact
diagonalization of finite rings using a variational approximation for the
phonon states. Due to renormalization effects induced by the phonons, for
intermediate electron-phonon coupling, the phase separation (PS) boundary, and
with it the region of dominating superconducting fluctuations is shifted
substantially to smaller values of as compared to the pure - model.
Superconducting correlations are weakened through charge density wave
interactions mediated by the phonons. Possible consequences for the high
oxides are discussed.Comment: 4 pages, Latex2
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