46,463 research outputs found
Factorization in hard diffraction
In this talk, I reviewed the role of factorization in diffraction hard
scattering.Comment: Talk presented at the Ringberg Workshop on ``New Trends in HERA
Physics 2001''. 10 pages, 6 postscript figures. Misprints correcte
Contact tracing and epidemics control in social networks
A generalization of the standard susceptible-infectious-removed (SIR)
stochastic model for epidemics in sparse random networks is introduced which
incorporates contact tracing in addition to random screening. We propose a
deterministic mean-field description which yields quantitative agreement with
stochastic simulations on random graphs. We also analyze the role of contact
tracing in epidemics control in small-world networks and show that its
effectiveness grows as the rewiring probability is reduced.Comment: 4 pages, 4 figures, submitted to PR
Data-driven Design of Engineering Processes with COREPROModeler
Enterprises increasingly demand IT support for the coordination of their engineering processes, which often consist of hundreds up to thousands of sub-processes. From a technical viewpoint, these sub-processes have to be concurrently executed and synchronized considering numerous interdependencies.
So far, this coordination has mainly been accomplished manually, which has resulted in errors and inconsistencies. In order to deal with this problem, we have to better understand the interdependencies between the subprocesses to be coordinated. In particular, we can benefit from the fact that sub-processes are often correlated to the assembly of a product (represented by a product data structure). This information can be utilized for the modeling and execution of so-called data-driven process structures. In this paper, we present the COREPRO demonstrator that supports the data-driven modeling of these process structures. The approach explicitly establishes a close linkage between product data structures and engineering processes
Thermodynamics of the frustrated - Heisenberg ferromagnet on the body-centered cubic lattice with arbitrary spin
We use the spin-rotation-invariant Green's function method as well as the
high-temperature expansion to discuss the thermodynamic properties of the
frustrated spin- - Heisenberg magnet on the body-centered
cubic lattice. We consider ferromagnetic nearest-neighbor bonds and
antiferromagnetic next-nearest-neighbor bonds and arbitrary spin
. We find that the transition point between the ferromagnetic ground
state and the antiferromagnetic one is nearly independent of the spin ,
i.e., it is very close to the classical transition point . At finite temperatures we focus on the parameter regime
with a ferromagnetic ground-state. We calculate the Curie
temperature and derive an empirical formula describing the
influence of the frustration parameter and spin on . We find
that the Curie temperature monotonically decreases with increasing frustration
, where very close to the -curve exhibits a
fast decay which is well described by a logarithmic term
. To characterize the magnetic ordering
below and above , we calculate the spin-spin correlation functions
, the spontaneous
magnetization, the uniform static susceptibility as well as the
correlation length . Moreover, we discuss the specific heat and the
temperature dependence of the excitation spectrum. As approaching the
transition point some unusual features were found, such as negative
spin-spin correlations at temperatures above even though the ground state
is ferromagnetic or an increase of the spin stiffness with growing temperature.Comment: 19 pages, 10 figures, version as in EPJ
(l) as a sociolinguistic variable in Francoprovençal
This article argues for (l) as a sociolinguistic variable in Francoprovençal: (l) refers to variable palatalisation of /l/ in obstruent + lateral onset clusters (/kl, ɡl, pl, bl, fl/), a feature that has long been the subject of metalinguistic commentary, but no systematic analysis. Our data, which come from a larger study of Francoprovençal (FP), show significant intraspeaker variation. Sociolinguistic interviews were carried out in the Lyonnais region of France among 21 FP speakers with different acquisition routes. /l/-palatalisation is far from categorical in our sample, with increased rates of the French variant [l] over the traditional [j] variant. We interpret these data as contact-induced change: phonological leveling is underway, with convergence towards French. These findings are consistent with the language death literature, and are now widely reported in the context of other minority varieties spoken in the Hexagon. Conversely, some new speakers show different patterns with a greater range of palatalised variants. These findings add to a growing body of evidence that suggest laterals to be a locus for socio-indexical cues cross-linguistically
--Oscillations for Correlated Electron Pairs in Disordered Mesoscopic Rings
The full spectrum of two interacting electrons in a disordered mesoscopic
one--dimensional ring threaded by a magnetic flux is calculated numerically.
For ring sizes far exceeding the one--particle localization length we
find several --periodic states whose eigenfunctions exhibit a pairing
effect. This represents the first direct observation of interaction--assisted
coherent pair propagation, the pair being delocalized on the scale of the whole
ring.Comment: 4 pages, uuencoded PostScript, containing 5 figures
NanoSQUID magnetometry of individual cobalt nanoparticles grown by focused electron beam induced deposition
We demonstrate the operation of low-noise nano superconducting quantum
interference devices (SQUIDs) based on the high critical field and high
critical temperature superconductor YBaCuO (YBCO) as
ultra-sensitive magnetometers for single magnetic nanoparticles (MNPs). The
nanoSQUIDs exploit the Josephson behavior of YBCO grain boundaries and have
been patterned by focused ion beam milling. This allows to precisely define the
lateral dimensions of the SQUIDs so as to achieve large magnetic coupling
between the nanoloop and individual MNPs. By means of focused electron beam
induced deposition, cobalt MNPs with typical size of several tens of nm have
been grown directly on the surface of the sensors with nanometric spatial
resolution. Remarkably, the nanoSQUIDs are operative over extremely broad
ranges of applied magnetic field (-1 T 1 T) and temperature (0.3
K 80 K). All these features together have allowed us to perform
magnetization measurements under different ambient conditions and to detect the
magnetization reversal of individual Co MNPs with magnetic moments (1 - 30)
. Depending on the dimensions and shape of the
particles we have distinguished between two different magnetic states yielding
different reversal mechanisms. The magnetization reversal is thermally
activated over an energy barrier, which has been quantified for the (quasi)
single-domain particles. Our measurements serve to show not only the high
sensitivity achievable with YBCO nanoSQUIDs, but also demonstrate that these
sensors are exceptional magnetometers for the investigation of the properties
of individual nanomagnets
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