3,713 research outputs found
A dislocation dynamics study of the strength of stacking fault tetrahedra. Part II: interactions with mixed and edge dislocations
In this paper we present the sequel to Part I and present a comprehensive dislocation dynamics study of the strength of stacking fault tetrahedra to mixed and edge dislocation glides in fcc Cu
Polaronic state and nanometer-scale phase separation in colossal magnetoresistive manganites
High resolution topographic images obtained by scanning tunneling microscope
in the insulating state of Pr0.68Pb0.32MnO3 single crystals showed regular
stripe-like or zigzag patterns on a width scale of 0.4 - 0.5 nm confirming a
high temperature polaronic state. Spectroscopic studies revealed inhomogeneous
maps of zero-bias conductance with small patches of metallic clusters on length
scale of 2 - 3 nm only within a narrow temperature range close to the
metal-insulator transition. The results give a direct observation of polarons
in the insulating state, phase separation of nanometer-scale metallic clusters
in the paramagnetic metallic state, and a homogeneous ferromagnetic state
A One-Dimensional Model for Many-Electron Atoms in Extremely Strong Magnetic Fields: Maximum Negative Ionization
We consider a one-dimensional model for many-electron atoms in strong
magnetic fields in which the Coulomb potential and interactions are replaced by
one-dimensional regularizations associated with the lowest Landau level. For
this model we show that the maximum number of electrons is bounded above by
2Z+1 + c sqrt{B}.
We follow Lieb's strategy in which convexity plays a critical role. For the
case of two electrons and fractional nuclear charge, we also discuss the
critical value at which the nuclear charge becomes too weak to bind two
electrons.Comment: 23 pages, 5 figures. J. Phys. A: Math and General (in press) 199
Evidence for a Kondo destroying quantum critical point in YbRh2Si2
The heavy-fermion metal YbRhSi is a weak antiferromagnet below
K. Application of a low magnetic field T () is sufficient to continuously suppress the antiferromagnetic (AF) order.
Below K, the Sommerfeld coefficient of the electronic specific
heat exhibits a logarithmic divergence. At K, (), while the electrical resistivity
(: residual resistivity). Upon
extrapolating finite- data of transport and thermodynamic quantities to , one observes (i) a vanishing of the "Fermi surface crossover" scale
, (ii) an abrupt jump of the initial Hall coefficient and
(iii) a violation of the Wiedemann Franz law at , the field-induced
quantum critical point (QCP). These observations are interpreted as evidence of
a critical destruction of the heavy quasiparticles, i.e., propagating Kondo
singlets, at the QCP of this material.Comment: 20 pages, 8 figures, SCES 201
Anomalous scaling in random shell models for passive scalars
A shell-model version of Kraichnan's (1994 {\it Phys. Rev. Lett. \bf 72},
1016) passive scalar problem is introduced which is inspired from the model of
Jensen, Paladin and Vulpiani (1992 {\it Phys. Rev. A\bf 45}, 7214). As in the
original problem, the prescribed random velocity field is Gaussian,
delta-correlated in time and has a power-law spectrum ,
where is the wavenumber. Deterministic differential equations for second
and fourth-order moments are obtained and then solved numerically. The
second-order structure function of the passive scalar has normal scaling, while
the fourth-order structure function has anomalous scaling. For the
anomalous scaling exponents are determined for structure functions up
to by Monte Carlo simulations of the random shell model, using a
stochastic differential equation scheme, validated by comparison with the
results obtained for the second and fourth-order structure functions.Comment: Plain LaTex, 15 pages, 4 figure available upon request to
[email protected]
Parameterized complexity of the MINCCA problem on graphs of bounded decomposability
In an edge-colored graph, the cost incurred at a vertex on a path when two
incident edges with different colors are traversed is called reload or
changeover cost. The "Minimum Changeover Cost Arborescence" (MINCCA) problem
consists in finding an arborescence with a given root vertex such that the
total changeover cost of the internal vertices is minimized. It has been
recently proved by G\"oz\"upek et al. [TCS 2016] that the problem is FPT when
parameterized by the treewidth and the maximum degree of the input graph. In
this article we present the following results for the MINCCA problem:
- the problem is W[1]-hard parameterized by the treedepth of the input graph,
even on graphs of average degree at most 8. In particular, it is W[1]-hard
parameterized by the treewidth of the input graph, which answers the main open
problem of G\"oz\"upek et al. [TCS 2016];
- it is W[1]-hard on multigraphs parameterized by the tree-cutwidth of the
input multigraph;
- it is FPT parameterized by the star tree-cutwidth of the input graph, which
is a slightly restricted version of tree-cutwidth. This result strictly
generalizes the FPT result given in G\"oz\"upek et al. [TCS 2016];
- it remains NP-hard on planar graphs even when restricted to instances with
at most 6 colors and 0/1 symmetric costs, or when restricted to instances with
at most 8 colors, maximum degree bounded by 4, and 0/1 symmetric costs.Comment: 25 pages, 11 figure
A prospective cohort study of safety and patient satisfaction of voluntary medical male circumcision in Botswana
Randomized trials have shown that voluntary medical male circumcision (VMMC) significantly reduces the risk of HIV acquisition in men. However, the rate of complications associated with the surgical procedure varies from 0.7% to 37.4% in real-world settings. We assessed the frequency, type and severity of adverse events following VMMC among 427 adult men surgically circumcised in southeastern Botswana; 97% completed ≥1 follow-up visit within seven days post-circumcision. Thirty moderate AEs were observed in 28 men resulting in an overall AE rate of 6.7%. Patient satisfaction was high: >95% were very or somewhat satisfied with the procedure and subsequent follow-up care
Multifrequency Study of The Radio Galaxy NGC326
We present the results of a multi-frequency study of the inversion symmetric
radio galaxy NGC326 based on Very Large Array observations at 1.4, 1.6, 4.8,
8.5 and 14.9 GHz. The morphological, spectral and polarization properties of
this peculiar object are studied at different levels of spatial resolutions.
The interpretation of the data will be discussed in forthcoming papers.Comment: 15 pages, 15 ps figures, accepted by A&
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