High incidence of Angina pectoris in patients treated with 5-fluorouracil - A planned surveillance study with 102 patients

Objective: Angina pectoris, arrhythmic sudden death and myocardial infarction, all these cardiac events have occasionally been reported during 5-fluorouracil (5-FU) chemotherapy. Underlying mechanisms leading to these events are unknown; damage to the myocytes or vasospasms have been discussed. Methods: 102 consecutive and unselected patients were monitored with 12-lead ECG, echocardiography and radionuclide ventriculography prior to the first cycle of 5-FU chemotherapy and 3 months from baseline. Results: 19% of the patients developed reversible symptoms of angina pectoris during treatment which lasted up to 12 h after cessation of the infusion. Most of the 19 patients showed corresponding ECG changes. 6 out of the 19 patients with severe angina pectoris had subsequent coronary angiography. In none of these patients the coronary angiography showed coronary artery disease, but it showed low ventricular function (ejection fraction <50%) in 2 patients. The ejection fraction did not increase overtime. Arrhythmias were screened for with Holter monitoring during 5-FU chemotherapy. The frequency of bradycardia and ventricular extrasystoles increased significantly (p < 0.05) during treatment compared to arrhythmias in Holter monitoring 3 months later. Furthermore the Qtc time in the ECG 3 months later was significantly prolonged (p < 0.05) compared to baseline values. Conclusions:The incidence of angina pectoris in patients during 5-FU treatment seems higher than previously suspected. As myocardial ischemia can be fatal, attentiveness to these symptoms and immediate treatment are crucial. Copyright (C) 2003 S. Karger AG, Basel

Gain in quantum cascade lasers and superlattices: A quantum transport theory

Gain in current-driven semiconductor heterostructure devices is calculated within the theory of nonequilibrium Green functions. In order to treat the nonequilibrium distribution self-consistently the full two-time structure of the theory is employed without relying on any sort of Kadanoff-Baym Ansatz. The results are independent of the choice of the electromagnetic field if the variation of the self-energy is taken into account. Excellent quantitative agreement is obtained with the experimental gain spectrum of a quantum cascade laser. Calculations for semiconductor superlattices show that the simple 2-time miniband transport model gives reliable results for large miniband widths at room temperatureComment: 8 Pages, 4 Figures directly included, to appear in Physical Review

Probing confined phonon modes by transport through a nanowire double quantum dot

Strong radial confinement in semiconductor nanowires leads to modified electronic and phononic energy spectra. We analyze the current response to the interplay between quantum confinement effects of the electron and phonon systems in a gate-defined double quantum dot in a semiconductor nanowire. We show that current spectroscopy of inelastic transitions between the two quantum dots can be used as an experimental probe of the confined phonon environment. The resulting discrete peak structure in the measurements is explained by theoretical modeling of the confined phonon mode spectrum, where the piezoelectric coupling is of crucial importance.Comment: 4 pages, 4 figures; final versio

Tunneling through nanosystems: Combining broadening with many-particle states

We suggest a new approach for transport through finite systems based on the Liouville equation. By working in a basis of many-particle states for the finite system, Coulomb interactions are taken fully into account and correlated transitions by up to two different contact states are included. This latter extends standard rate equation models by including level-broadening effects. The main result of the paper is a general expression for the elements of the density matrix of the finite size system, which can be applied whenever the eigenstates and the couplings to the leads are known. The approach works for arbitrary bias and for temperatures above the Kondo temperature. We apply the approach to standard models and good agreement with other methods in their respective regime of validity is found.Comment: 9 pages, 5 figures included to tex

Current-voltage characteristic and stability in resonant-tunneling n-doped semiconductor superlattices

We review the occurrence of electric-field domains in doped superlattices within a discrete drift model. A complete analysis of the construction and stability of stationary field profiles having two domains is carried out. As a consequence, we can provide a simple analytical estimation for the doping density above which stable stable domains occur. This bound may be useful for the design of superlattices exhibiting self-sustained current oscillations. Furthermore we explain why stable domains occur in superlattices in contrast to the usual Gunn diode.Comment: Tex file and 3 postscript figure

A hybrid model for chaotic front dynamics: From semiconductors to water tanks

We present a general method for studying front propagation in nonlinear systems with a global constraint in the language of hybrid tank models. The method is illustrated in the case of semiconductor superlattices, where the dynamics of the electron accumulation and depletion fronts shows complex spatio-temporal patterns, including chaos. We show that this behavior may be elegantly explained by a tank model, for which analytical results on the emergence of chaos are available. In particular, for the case of three tanks the bifurcation scenario is characterized by a modified version of the one-dimensional iterated tent-map.Comment: 4 pages, 4 figure

Correlation-induced conductance suppression at level degeneracy in a quantum dot

The large, level-dependent g-factors in an InSb nanowire quantum dot allow for the occurrence of a variety of level crossings in the dot. While we observe the standard conductance enhancement in the Coulomb blockade region for aligned levels with different spins due to the Kondo effect, a vanishing of the conductance is found at the alignment of levels with equal spins. This conductance suppression appears as a canyon cutting through the web of direct tunneling lines and an enclosed Coulomb blockade region. In the center of the Coulomb blockade region, we observe the predicted correlation-induced resonance, which now turns out to be part of a larger scenario. Our findings are supported by numerical and analytical calculations.Comment: 5 pages, 4 figure