269 research outputs found
Ladder operators for subtle hidden shape invariant potentials
Ladder operators can be constructed for all potentials that present the
integrability condition known as shape invariance, satisfied by most of the
exactly solvable potentials. Using the superalgebra of supersymmetric quantum
mechanics we construct the ladder operators for two exactly solvable potentials
that present a subtle hidden shape invariance.Comment: 9 pages, based on the talk given at International Conference Progress
in Supersymmetric Quantum Mechanics (PSQM03), Valladolid, Spain, 15-19 July,
2003, to appear in a Special Issue of J. Phys. A: Math. Ge
The impact of increased atmospheric carbon dioxide on microbial community dynamics in the rhizosphere
Rising atmospheric CO2 levels are predicted to have major consequences upon carbon cycle feedbacks and the overall functioning of terrestrial ecosystems. Photosynthetic activity and the structure of terrestrial macrophytes is expected to change, but it remains uncertain how this will affect soil-borne communities dependent on plant-derived carbon, and their feedbacks on ecosystem function. Our main objective is to assess the impact of increased atmospheric carbon dioxide on microbial community dynamics in the rhizosphere. Using a controlled growth system, we examined the short-term and long-term impact of elevated atmospheric CO2 on soil-borne microbial communities by comparing belowground community responses associated with plants grown under ambient versus double ambient CO2 environments. Results on the structure and dynamics of broad and specific microbial groups provided insight into the plant-microbe interactions of the r hizosphere under elevated CO2. We also showed that the specific microbial groups are affected by elevated CO2 and demonstrate that presumably rhizo-competent bacteria and fungi are most highly affected by increased atmospheric CO2. These patterns were consistent with observed changes in the density of antibiotic production genes as well as changes in exudation patterns. The results demonstrate that elevated CO2 influenced different parts of the soil microbial community, but that the effects depend on the plant species and soil type. Pulse labelling studies demonstrates that elevated atmospheric CO2 increases translocation of plant-fixed carbon, via arbuscular mycorrhizal fungi (AMF), and that distinct microbial populations incorporate plant-derived carbon under different levels of atmospheric CO2. As opposed to simply increasing the activity of soil-borne microbes resident at ambient CO2 conditions, elevated atmospheric CO2 clearly selects for opportunistic plant-associated microbial communities, with a shift in dominant AMF species, as well as rhizosphere bacterial and fungal populations. These experiments also showed that AMF are the main conduit in the transfer of carbon between plants and soil. The microbial carbon dynamic model derived from our results provides a general framework for reappraising our view of carbon flow paths in soils and their effects on soil biodiversity under elevated atmospheric CO2 concentration.NWO and KNAWUBL - phd migration 201
Supersymmetric solutions of PT-/non-PT-symmetric and non-Hermitian Screened Coulomb potential via Hamiltonian hierarchy inspired variational method
The supersymmetric solutions of PT-symmetric and Hermitian/non-Hermitian
forms of quantum systems are obtained by solving the Schrodinger equation for
the Exponential-Cosine Screened Coulomb potential. The Hamiltonian hierarchy
inspired variational method is used to obtain the approximate energy
eigenvalues and corresponding wave functions.Comment: 13 page
Utilization of the wastes of vital activity
The recycling of wastes from the biological complex for use in life-support systems is discussed. Topics include laboratory equipment, heat treatment of waste materials, mineralization of waste products, methods for production of ammonium hydroxide and nitric acid, the extraction of sodium chloride from mineralized products, and the recovery of nutrient substances for plants from urine
Rapid incorporation of carbon from ectomycorrhizal mycelial necromass into soil fungal communities
Peer reviewedPublisher PD
Upper critical magnetic field in Ba_0.68K_0.32Fe_2As_2 and Ba(Fe_0.93Co_0.07)_2As_2
We report measurements of the temperature dependence of the radio-frequency
magnetic penetration depth in Ba_0.68K_0.32Fe_2As_2 and
Ba(Fe_0.93Co_0.07)_2As_2 single crystals in pulsed magnetic fields up to 60 T.
From our data, we construct an H-T phase diagram for the inter-plane (H || c)
and in-plane (H || ab) directions for both compounds. For both field
orientations in Ba_0.68K_0.32Fe_2As_2, we find a concave curvature of the
Hc2(T) lines with decreasing anisotropy and saturation towards lower
temperature. Taking into account Pauli spin paramagnetism we can describe
Hc2(T) and its anisotropy. In contrast, we find that Pauli paramagnetic pair
breaking is not essential for Ba(Fe_0.93Co_0.07)_2As_2. For this electron-doped
compound, the data support a Hc2(T) dependence that can be described by the
Werthamer Helfand Hohenberg model for H || ab and a two-gap behavior for H ||
c.Comment: 7 pages, 8 figure
Evidence for antiferromagnetism coexisting with charge order in the trilayer cuprate HgBaCaCuO
Multilayered cuprates possess not only the highest superconducting
temperature transition but also offer a unique platform to study disorder-free
CuO planes and the interplay between competing orders with
superconductivity. Here, we study the underdoped trilayer cuprate
HgBaCaCuO and we report the first quantum oscillation
and Hall effect measurements in magnetic field up to 88 T. A careful analysis
of the complex spectra of quantum oscillations strongly supports the
coexistence of an antiferromagnetic order in the inner plane and a charge order
in the outer planes. The presence of an ordered antiferromagnetic metallic
state that extends deep in the superconducting phase is a key ingredient that
supports magnetically mediated pairing interaction in cuprates.Comment: 6+5 pages, 4+6 figure
An Algebraic q-Deformed Form for Shape-Invariant Systems
A quantum deformed theory applicable to all shape-invariant bound-state
systems is introduced by defining q-deformed ladder operators. We show these
new ladder operators satisfy new q-deformed commutation relations. In this
context we construct an alternative q-deformed model that preserve the
shape-invariance property presented by primary system. q-deformed
generalizations of Morse, Scarf, and Coulomb potentials are given as examples
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