2,444 research outputs found
Torsion-induced persistent current in a twisted quantum ring
We describe the effects of geometric torsion on the coherent motion of
electrons along a thin twisted quantum ring. The geometric torsion inherent in
the quantum ring triggers a quantum phase shift in the electrons' eigenstates,
thereby resulting in a torsion-induced persistent current that flows along the
twisted quantum ring. The physical conditions required for detecting the
current flow are discussed.Comment: 9 pages, 3 figure
How far can Tarzan jump?
The tree-based rope swing is a popular recreation facility, often installed
in outdoor areas, giving pleasure to thrill-seekers. In the setting, one drops
down from a high platform, hanging from a rope, then swings at a great speed
like "Tarzan", and finally jumps ahead to land on the ground. The question now
arises: How far can Tarzan jump by the swing? In this article, I present an
introductory analysis of the Tarzan swing mechanics, a big pendulum-like swing
with Tarzan himself attached as weight. The analysis enables determination of
how farther forward Tarzan can jump using a given swing apparatus. The
discussion is based on elementary mechanics and, therefore, expected to provide
rich opportunities for investigations using analytic and numerical methods.Comment: 8 pages, 4 figure
Local pore size correlations determine flow distributions in porous media
The relationship between the microstructure of a porous medium and the
observed flow distribution is still a puzzle. We resolve it with an analytical
model, where the local correlations between adjacent pores, which determine the
distribution of flows propagated from one pore downstream, predict the flow
distribution. Numerical simulations of a two-dimensional porous medium verify
the model and clearly show the transition of flow distributions from
-function-like via Gaussians to exponential with increasing disorder.
Comparison to experimental data further verifies our numerical approach.Comment: 5 pages, 3 figures, supplemental materia
The dynamic exponent of the Ising model on negatively curved surfaces
We investigate the dynamic critical exponent of the two-dimensional Ising
model defined on a curved surface with constant negative curvature. By using
the short-time relaxation method, we find a quantitative alteration of the
dynamic exponent from the known value for the planar Ising model. This
phenomenon is attributed to the fact that the Ising lattices embedded on
negatively curved surfaces act as ones in infinite dimensions, thus yielding
the dynamic exponent deduced from mean field theory. We further demonstrate
that the static critical exponent for the correlation length exhibits the mean
field exponent, which agrees with the existing results obtained from canonical
Monte Carlo simulations.Comment: 14 pages, 3 figures. to appear in J. Stat. Mec
Geometric effects on critical behaviours of the Ising model
We investigate the critical behaviour of the two-dimensional Ising model
defined on a curved surface with a constant negative curvature. Finite-size
scaling analysis reveals that the critical exponents for the zero-field
magnetic susceptibility and the correlation length deviate from those for the
Ising lattice model on a flat plane. Furthermore, when reducing the effects of
boundary spins, the values of the critical exponents tend to those derived from
the mean field theory. These findings evidence that the underlying geometric
character is responsible for the critical properties the Ising model when the
lattice is embedded on negatively curved surfaces.Comment: 16 pages, 6 figures, to appear in J. Phys. A: Math. Ge
Phase Transition of XY Model in Heptagonal Lattice
We numerically investigate the nature of the phase transition of the XY model
in the heptagonal lattice with the negative curvature, in comparison to other
interaction structures such as a flat two-dimensional (2D) square lattice and a
small-world network. Although the heptagonal lattice has a very short
characteristic path length like the small-world network structure, it is
revealed via calculation of the Binder's cumulant that the former exhibits a
zero-temperature phase transition while the latter has the finite-temperature
transition of the mean-field nature. Through the computation of the vortex
density as well as the correlation function in the low-temperature
approximation, we show that the absence of the phase transition originates from
the strong spinwave-type fluctuation, which is discussed in relation to the
usual 2D XY model.Comment: 5 pages, 6 figures, to be published in Europhys. Let
Metastatic Squamous Cell Carcinoma in a Northern Brown Bandicoot (<i>Isoodon macrourus</i>)
Aside from a handful of notable exceptions, neoplasia is not reported as a major cause of mortality in wild animal populations and often goes undetected. For northern brown bandicoots specifically, there are few reported tumors in the literature and on file in the Australian Registry of Wildlife Health. This report describes a case of squamous cell carcinoma in a northern brown bandicoot (Isoodon macrourus), with metastases to the draining lymph nodes and lung. This neoplasm consisted predominantly of well-differentiated squamous cells and multifocal keratin pearls, with areas possibly consistent with epithelial to mesenchymal transition, as identified by positive immunohistochemical staining by both pancytokeratin (AE1/AE3) and vimentin. Additional investigations were negative for bandicoot papillomatosis carcinomatosis viruses
Manipulating the Tomonaga-Luttinger exponent by electric field modulation
We establish a theoretical framework for artificial control of the power-law
singularities in Tomonaga-Luttinger liquid states. The exponent governing the
power-law behaviors is found to increase significantly with an increase in the
amplitude of the periodic electric field modulation applied externally to the
system. This field-induced shift in the exponent indicates the tunability of
the transport properties of quasi-one-dimensional electron systems.Comment: 7 pages, 3 figure
PEGylated DOTA-AHA-based Gd(III) chelates â A relaxometric study
Three PEGylated derivatives of 1,4,7,10-tetraazacyclododecane-1-((6-amino)hexanoic)-4,7,10-triacetic acid) (DOTA-AHA) with different molecular weights were prepared and characterized. Their Gd(III) chelates were studied in aqueous solution using variable-temperature 1H nuclear magnetic relaxation dispersion (NMRD) and 17ONMR spectroscopy in view of the determination of their relaxivity and the parameters that govern it. The relaxivity varied from 5.1 to 6.5 mM-1.s-1 (37 ÂșC and 60 MHz) with the increasing molecular weight of the PEG chain, being slightly higher than that of the parent chelate Gd(DOTA-AHA), due to a small contribution of a slow global rotation of the complexes.
A variable temperature 1H NMR study of several Ln(III) chelates of DOTA-A(PEG750)HA allowed the determination of the isomeric M/m ratio (M = square antiprismatic isomer and m = twisted square antiprismatic isomer, the latter presenting a much faster water exchange) which for the Gd(III) chelate was estimated in circa 1:0.2, very close to that of [Gd(DOTA)]-. This explains why the PEGylated Gd(III) chelate has a water rate exchange similar to that of [Gd(DOTA)]-. The predominance of the M isomer is a consequence of the bulky PEG moiety which does not favor the stabilization of the m isomer in sterically crowded systems at the substituent site, contrary to what happens with less packed asymmetrical DOTA-type chelates with substitution in one of the four acetate C(α) atoms.The authors thank the Foundation for Science and Technology (FCTâPortugal) for financial support through the NMR Portuguese network (Bruker 400 Avance III-Univ Minho); FCT and FEDER (European Fund for Regional Development)-COMPETE/QREN/EU for financial support through the research unity PEst-C/QUI/UI686/2013 and the PhD grant attributed to AndrĂ© Fontes (SFRH/BD/63676/2009) also financed by the POPH and FSE
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