739 research outputs found
Operative Therapie der spezifischen und unspezifischen Spondylodiszitis
Evaluation der klinischen und radiologischen Ergebnisse bei operativer Therapie der Spondylodiszitis nach einzeitiger dorsaler extrafokaler Stabilisierung, ventralem Débridement und Rekonstruktion der ventralen Säule mittels Cage-Implantation oder Knocheninterposition. Zur Beurteilung des Wirbelsäulenprofils erfolgte eine radiometrische Analyse. Der neurologische Status wurde mit Frankel-Score, rückenschmerzbedingte Funktionseinschränkungen mit Roland-Morris-Score erhoben. Radiographisch fand sich aktuell in allen Fällen eine knöcherne Fusion. Der segmentale Korrekturverlust war nach Cage-Interposition signifikant geringer als nach Spaninterposition. Titan-Cages bieten insbesondere im Falle größerer Substanzdefekte biomechanische Vorteile und gehen nicht mit einer gegenüber autologen Knocheninterponaten erhöhten Infektpersistenz oder Reinfektionsrate einher
Der Einfluss von Corticosteroiden auf das Biopsieergebnis bei Verdacht auf Arteriitis temporalis
Beim Auftreten okulärer Symptome einer Arteriitis temporalis ist vor allem die zeitnahe Therapie mit hochdosierten Cortisonen erfolgsversprechend. Als wegweisende diagnostische Maßnahme gilt die Biopsie der Temporalarterie.
Inwiefern wird das histologische Bild bei einer erst später durchgeführten Biopsie durch die Medikamente verändert und in welchem Zeitintervall sollte biopsiert werden. Die retrospektive Studie, in der die Patientendaten aus über 20 Jahren ausgewertet wurden, zeigt u.a., dass bereits nach dem dritten Tag der Cortisongabe die Wahrscheinlichkeit signifikant ansteigt, dass das Biopsieergebnis falsch negativ ausfällt. Des Weiteren werden zahlreiche statistische Daten dargelegt, welche einen Einblick in diese komplexe Krankheit gewŠhren
Characterizing implementable allocation rules in multi-dimensional environments
We study characterizations of implementable allocation rules when types are multi-dimensional, monetary transfers are allowed, and agents have quasi-linear preferences over outcomes and transfers. Every outcome is associated with a continuous valuation function that maps an agent's type to his value for this outcome. Sets of types are assumed to be convex. Our main characterization theorem implies that allocation rules are implementable if and only if they are implementable on any two-dimensional convex subset of the type set. For finite sets of outcomes, they are implementable if and only if they are implementable on every one-dimensional subset of the type set. Our results complement and extend significantly a characterization result by Saks and Yu, as well as follow-up results thereof. Contrary to our model, this stream of literature identifies types with valuation vectors. In such models, convexity of the set of valuation vectors allows for a similar characterization as ours. Furthermore, implementability on one-dimensional subsets of valuation vectors is equivalent to monotonicity. We show by example that the latter does not hold anymore in our more general setting. Our proofs demonstrate that the linear programming approach to mechanism design, pioneered in Gui et al. and Vohra, can be extended from models with linear valuation functions to arbitrary continuous valuation functions. This provides a deeper understanding of the role of monotonicity and local implementation. In particular, we provide a new, simple proof of the Saks and Yu theorem, and generalizations thereof. Modeling multi-dimensional mechanism design the way we propose it here is of relevance whenever types are given by few parameters, while the set of possible outcomes is large, and when values for outcomes are non-linear functions in types
Phase Synchronization in Railway Timetables
Timetable construction belongs to the most important optimization problems in
public transport. Finding optimal or near-optimal timetables under the
subsidiary conditions of minimizing travel times and other criteria is a
targeted contribution to the functioning of public transport. In addition to
efficiency (given, e.g., by minimal average travel times), a significant
feature of a timetable is its robustness against delay propagation. Here we
study the balance of efficiency and robustness in long-distance railway
timetables (in particular the current long-distance railway timetable in
Germany) from the perspective of synchronization, exploiting the fact that a
major part of the trains run nearly periodically. We find that synchronization
is highest at intermediate-sized stations. We argue that this synchronization
perspective opens a new avenue towards an understanding of railway timetables
by representing them as spatio-temporal phase patterns. Robustness and
efficiency can then be viewed as properties of this phase pattern
Magnetic anomalies in the spin chain system, SrCuZnIrO
We report the results of ac and dc magnetization (M) and heat-capacity (C)
measurements on the solid solution, SrCuZnIrO. While the Zn
end member is known to form in a rhombohedral pseudo one-dimensional
KCdCl structure with an antiferromagnetic ordering temperature of
(T =) 19 K, the Cu end member has been reported to form in a monoclinically
distorted form with a Curie temperature of (T =) 19 K. The magnetism of the
Zn compound is found to be robust to synthetic conditions and is broadly
consistent with the behavior known in the literature. However, we find a lower
magnetic ordering temperature (T) for our Cu compound (~ 13 K), thereby
suggesting that T is sensitive to synthetic conditions. The Cu sample
appears to be in a spin-glass-like state at low temperatures, judged by a
frequency dependence of ac magnetic susceptibility and a broadening of the C
anomaly at the onset of magnetic ordering, in sharp contrast to earlier
proposals. Small applications of magnetic field, however, drive this system to
ferromagnetism as inferred from the M data. Small substitutions for Cu/Zn (x =
0.75 or 0.25) significantly depress magnetic ordering; in other words, T
varies non-monotonically with x (T ~ 6, 3 and 4 K for x = 0.25, 0.5, and
0.67 respectively). The plot of inverse susceptibility versus temperature is
non-linear in the paramagnetic state as if correlations within (or among) the
magnetic chains continuously vary with temperature. The results establishComment: 7 pages, 7 figures, Revte
Continuum-mechanical, Anisotropic Flow model for polar ice masses, based on an anisotropic Flow Enhancement factor
A complete theoretical presentation of the Continuum-mechanical, Anisotropic
Flow model, based on an anisotropic Flow Enhancement factor (CAFFE model) is
given. The CAFFE model is an application of the theory of mixtures with
continuous diversity for the case of large polar ice masses in which induced
anisotropy occurs. The anisotropic response of the polycrystalline ice is
described by a generalization of Glen's flow law, based on a scalar anisotropic
enhancement factor. The enhancement factor depends on the orientation mass
density, which is closely related to the orientation distribution function and
describes the distribution of grain orientations (fabric). Fabric evolution is
governed by the orientation mass balance, which depends on four distinct
effects, interpreted as local rigid body rotation, grain rotation, rotation
recrystallization (polygonization) and grain boundary migration (migration
recrystallization), respectively. It is proven that the flow law of the CAFFE
model is truly anisotropic despite the collinearity between the stress deviator
and stretching tensors.Comment: 22 pages, 5 figure
Semiclassical theory of transport in a random magnetic field
We study the semiclassical kinetics of 2D fermions in a smoothly varying
magnetic field . The nature of the transport depends crucially on
both the strength of the random component of and its mean
value . For , the governing parameter is ,
where is the correlation length of disorder and is the Larmor radius
in the field . While for the Drude theory applies, at
most particles drift adiabatically along closed contours and are
localized in the adiabatic approximation. The conductivity is then determined
by a special class of trajectories, the "snake states", which percolate by
scattering at the saddle points of where the adiabaticity of their
motion breaks down. The external field also suppresses the diffusion by
creating a percolation network of drifting cyclotron orbits. This kind of
percolation is due only to a weak violation of the adiabaticity of the
cyclotron rotation, yielding an exponential drop of the conductivity at large
. In the regime the crossover between the snake-state
percolation and the percolation of the drift orbits with increasing
has the character of a phase transition (localization of snake states) smeared
exponentially weakly by non-adiabatic effects. The ac conductivity also
reflects the dynamical properties of particles moving on the fractal
percolation network. In particular, it has a sharp kink at zero frequency and
falls off exponentially at higher frequencies. We also discuss the nature of
the quantum magnetooscillations. Detailed numerical studies confirm the
analytical findings. The shape of the magnetoresistivity at is
in good agreement with experimental data in the FQHE regime near .Comment: 22 pages REVTEX, 14 figure
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