950 research outputs found
Idiopathische thrombozytopenische Purpura im Kindesalter
Zusammenfassung: Die idiopathische thrombozytopenische Purpura (ITP) ist eine Blutungskrankheit, die durch eine verkürzte Lebensdauer der Thrombozyten charakterisiert ist. Sie ist heterogen ausgeprägt und wird durch endogene und erworbene Faktoren beeinflusst. Sie ist eine Ausschlussdiagnose, deren Differenzialdiagnose stets bedacht werden muss. Die Unkenntnis der Ätiologie und der Mangel an klinischen Daten aus kontrollierten prospektiven Studien haben Kontroversen hinsichtlich Diagnose und Behandlung zur Folge. Die bisherigen prospektiven Therapiestudien haben die Beschleunigung des Thrombozytenanstiegs zum Ziel. Diese Zielsetzung wird oft in den klinischen Alltag übertragen, ohne dass bisher gezeigt werden konnte, dass ein rascher Thrombozytenanstieg von klinischem Wert ist. Bei der Behandlung des Patienten mit ITP ist meist eine Vorbeugung vor fatalen Blutungen beabsichtigt. Diese sind aber im Kindesalter sehr selten. Die Therapieziele im klinischen Alltag, aber auch in klinischen Studien müssen überdacht werden. Andere wichtige Gesichtspunkte sind Blutungen, die Lebensqualität des Patienten und seiner Angehörigen, Nebenwirkungen von Medikamenten und ökonomische Aspekt
No singular modulus is a unit
A result of the second-named author states that there are only finitely many
CM-elliptic curves over whose -invariant is an algebraic unit.
His proof depends on Duke's Equidistribution Theorem and is hence
non-effective. In this article, we give a completely effective proof of this
result. To be precise, we show that every singular modulus that is an algebraic
unit is associated with a CM-elliptic curve whose endomorphism ring has
discriminant less than . Through further refinements and
computer-assisted computations, we eventually rule out all remaining cases,
showing that no singular modulus is an algebraic unit. This allows us to
exhibit classes of subvarieties in not containing any special
points.Comment: Dedicated to David Masser on the occasion of his 70th birthday.
Version 2 has a new title, updated references, and contains minor
corrections. 31 pages, to appear in IMRN. Link to scripts
https://github.com/philipphabegger/Effective-Bounds-for-Singular-Unit
Quantum critical dynamics of a S = 1/2 antiferromagnetic Heisenberg chain studied by 13C-NMR spectroscopy
We present a 13C-NMR study of the magnetic field driven transition to
complete polarization of the S=1/2 antiferromagnetic Heisenberg chain system
copper pyrazine dinitrate Cu(C_4H_4N_2)(NO_3)_2 (CuPzN). The static local
magnetization as well as the low-frequency spin dynamics, probed via the
nuclear spin-lattice relaxation rate 1/T_1, were explored from the low to the
high field limit and at temperatures from the quantum regime (k_B T << J) up to
the classical regime (k_B T >> J). The experimental data show very good
agreement with quantum Monte Carlo calculations over the complete range of
parameters investigated. Close to the critical field, as derived from static
experiments, a pronounced maximum in 1/T_1 is found which we interpret as the
finite-temperature manifestation of a diverging density of zero-energy magnetic
excitations at the field-driven quantum critical point.Comment: 5 pages, 4 figure
Dynamics of a Heisenberg spin chain in the quantum critical regime: NMR experiment versus effective field theory
A comprehensive comparison between the magnetic field- and
temperature-dependent low frequency spin dynamics in the antiferromagnetic
spin-1/2 Heisenberg chain (AFHC) system copper pyrazine dinitrate, probed via
the 13C-nuclear magnetic resonance (NMR) relaxation rate 1/T1, and the field
theoretical approach in the Luttinger liquid (LL) regime has been performed. We
have found a very good agreement between the experiment and theory in the
investigated temperature and field range. Our results demonstrate how strongly
the quantum critical point affects the spin dynamics of Heisenberg spin chain
compounds.Comment: 5 pages, 3 figure
Cavity-enhanced optical Hall effect in two-dimensional free charge carrier gases detected at terahertz frequencies
The effect of a tunable, externally coupled Fabry-P\'{e}rot cavity to
resonantly enhance the optical Hall effect signatures at terahertz frequencies
produced by a traditional Drude-like two-dimensional electron gas is shown and
discussed in this communication. As a result, the detection of optical Hall
effect signatures at conveniently obtainable magnetic fields, for example by
neodymium permanent magnets, is demonstrated. An AlInN/GaN-based high electron
mobility transistor structure grown on a sapphire substrate is used for the
experiment. The optical Hall effect signatures and their dispersions, which are
governed by the frequency and the reflectance minima and maxima of the
externally coupled Fabry-P\'{e}rot cavity, are presented and discussed. Tuning
the externally coupled Fabry-P\'{e}rot cavity strongly modifies the optical
Hall effect signatures, which provides a new degree of freedom for optical Hall
effect experiments in addition to frequency, angle of incidence and magnetic
field direction and strength
Circular dichroism of magneto-phonon resonance in doped graphene
Polarization resolved, Raman scattering response due to E phonon in
monolayer graphene has been investigated in magnetic fields up to 29 T. The
hybridization of the E phonon with only the fundamental inter Landau
level excitation (involving the n=0 Landau level) is observed and only in one
of the two configurations of the circularly crossed polarized excitation and
scattered light. This polarization anisotropy of the magneto-phonon resonance
is shown to be inherent to relatively strongly doped graphene samples, with
carrier concentration typical for graphene deposited on SiO
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