355 research outputs found
Topology Induced Spatial Bose-Einstein Condensation for Bosons on Star-Shaped Optical Networks
New coherent states may be induced by pertinently engineering the topology of
a network. As an example, we consider the properties of non-interacting bosons
on a star network, which may be realized with a dilute atomic gas in a
star-shaped deep optical lattice. The ground state is localized around the star
center and it is macroscopically occupied below the Bose-Einstein condensation
temperature T_c. We show that T_c depends only on the number of the star arms
and on the Josephson energy of the bosonic Josephson junctions and that the
non-condensate fraction is simply given by the reduced temperature T/T_c.Comment: 20 Pages, 5 Figure
Solitary Waves and Compactons in a class of Generalized Korteweg-DeVries Equations
We study the class of generalized Korteweg-DeVries equations derivable from
the Lagrangian: L(l,p) = \int \left( \frac{1}{2} \vp_{x} \vp_{t} - {
{(\vp_{x})^{l}} \over {l(l-1)}} + \alpha(\vp_{x})^{p} (\vp_{xx})^{2} \right)
dx, where the usual fields of the generalized KdV equation are
defined by u(x,t) = \vp_{x}(x,t). This class contains compactons, which are
solitary waves with compact support, and when , these solutions have the
feature that their width is independent of the amplitude. We consider the
Hamiltonian structure and integrability properties of this class of KdV
equations. We show that many of the properties of the solitary waves and
compactons are easily obtained using a variational method based on the
principle of least action. Using a class of trial variational functions of the
form we
find soliton-like solutions for all , moving with fixed shape and constant
velocity, . We show that the velocity, mass, and energy of the variational
travelling wave solutions are related by , where , independent of .\newline \newline PACS numbers: 03.40.Kf,
47.20.Ky, Nb, 52.35.SbComment: 16 pages. LaTeX. Figures available upon request (Postscript or hard
copy
The Endolog system for moderate-to-severe hallux valgus
Purpose. To report the midterm outcome of the Endolog system for correction of moderate-to-severe hallux valgus. Methods. 23 women and 2 men (33 feet) aged 35 to 80 (mean, 52) years underwent minimally invasive surgery for moderate (n=25) and severe (n=8) hallux valgus using the Endolog system. The hallux valgus angle (HVA), the intermetatarsal angle (IMA), and the proximal articular set angle (PASA) were measured on radiographs. The feet were also assessed based on the American Orthopaedic Foot and Ankle Society (AOFAS) scale. Results. The mean follow-up duration was 18.2 (range, 12–36) months. The mean HVA, IMA, PASA, and the mean AOFAS score improved significantly after surgery (all p<0.0001). Periosteal reaction was noted by week 4, and callus formation after 3 months. There were no delayed or non-union or other complications. Conclusion. The Endolog system achieved good outcome for moderate-to-severe hallux valgus
The Chiral Condensate of Strongly Coupled QCD in the 't Hooft Limit
Using the recently proposed generalization to an arbitrary number of colors
of the strong coupling approach to lattice gauge
theories\cite{Grignani:2003uv}, we compute the chiral condensate of massless
QCD in the 't Hooft limit.Comment: 12 pages, revtex
Finite-Temperature Renormalization Group Analysis of Interaction Effects in 2D Lattices of Bose-Einstein Condensates
By using a renormalization group analysis, we study the effect of
interparticle interactions on the critical temperature at which the
Berezinskii-Kosterlitz-Thouless (BKT) transition occurs for Bose-Einstein
condensates loaded at finite temperature in a 2D optical lattice. We find that
the critical temperature decreases as the interaction energy decreases; when
U/J=36/\pi one has a vanishing critical temperature, signaling the possibility
of a quantum phase transition of BKT type
Observable Signature of the Berezinskii-Kosterlitz-Thouless Transition in a Planar Lattice of Bose-Einstein Condensates
We investigate the possibility that Bose-Einstein condensates (BECs), loaded
on a 2D optical lattice, undergo - at finite temperature - a
Berezinskii-Kosterlitz-Thouless (BKT) transition. We show that - in an
experimentally attainable range of parameters - a planar lattice of BECs is
described by the XY model at finite temperature. We demonstrate that the
interference pattern of the expanding condensates provides the experimental
signature of the BKT transition by showing that, near the critical temperature,
the k=0 component of the momentum distribution and the central peak of the
atomic density profile sharply decrease. The finite-temperature transition for
a 3D optical lattice is also discussed, and the analogies with superconducting
Josephson junction networks are stressed through the text
Dissolved organic carbon retention by coprecipitation during the oxidation of ferrous iron (EGU2018-3906)
Although the importance of Fe (hydr)oxides for soil organic matter (OM) stabilization and C retention by surface adsorption is well known, only recently has coprecipitation been recognized as an important process responsible for C storage in hydromorphic soils, such as rice paddy soils. Under periodic fluctuations in redox conditions the interaction between dissolved organic carbon (DOC) and Fe (hydr)oxides may not only involve organic coatings
on mineral surfaces, but also Fe-DOC coprecipitates that form during the oxidation of soil solutions containing important amounts of DOC and Fe2+.
The aim of this work was to provide new insights into the mechanisms involved, and the amount and selectivity of C retained during the coprecipitation process. A series of Fe-OM associations with increasing C loading was synthesized at pH 6 by surface adsorption or coprecipitation (oxidation of ferrous iron) utilizing rice-straw derived dissolved organic matter. The kinetics of Fe2+ oxidation and complexation, and the total and selective retention of DOC during the coprecipitation process were evaluated. Moreover, synthesized associations, as well as a field coprecipitate collected in situ from a paddy soil, were studied by X-ray diffraction, N2 gas adsorption-desorption isotherms, electrophoretic mobility measurements and thermogravimetric analyses. Coprecipitation resulted in higher organic C contents (49-213 mg g-1) with respect to adsorbed systems (18-47 mg g-1), and favoured the inclusion of OM within highly aggregated associations having particularly low BET specific surface areas. Coprecipitates sampled in situ also showed a similar retention of organic C confirming that this process may contribute significantly to the OM stabilization in paddy topsoils. The mechanisms involved in the retention of straw-derived DOM during coprecipitation were shown to be strongly dependent on C/Fe ratio of the solution. Although the overall coprecipitation process was highly selective for aromatic constituents, initial complexation of Fe2+ and precipitation as C-rich metal salts involved the selective interaction with aliphatic carboxylic constituents. The contribution of the latter mechanism to total C retention during coprecipitation was shown to increase with increasing solution C/Fe ratios. These aliphatic complexes formed during coprecipitation may play an important, though often underestimated, role in C stabilization in hydromorphic. The process-related selectivity of specific constituents of DOM during coprecipitation highlights the involvement of specific mechanisms, i.e. complexation, adsorption, salt precipitation, while ruling out non-selective, physical occlusion of OM within the forming coprecipitat
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