Stochastic Resonance in Chaotic Spin-Wave Dynamics

We report the first experimental observation of noise-free stochastic resonance by utilizing the intrinsic chaotic dynamics of the system. To this end we have investigated the effect of an external periodic modulation on intermittent signals observed by high power ferromagnetic resonance in yttrium iron garnet spheres. Both the signal-to-noise ratio and the residence time distributions show the characteristic features of stochastic resonance. The phenomena can be explained by means of a one-dimensional intermittent map. We present analytical results as well as computer simulations.Comment: 4 pages, revtex, 5 eps figures included, also available "via www http://athene.fkp.physik.th-darmstadt.de/public/wolfram.html" or "via ftp ftp://athene.fkp.physik.th-darmstadt.de/pub/publications/wolfram/", Phys. Rev. Lett. in pres

Noise reduction in chaotic time series by a local projection with nonlinear constraints

On the basis of a local-projective (LP) approach we develop a method of noise reduction in time series that makes use of nonlinear constraints appearing due to the deterministic character of the underlying dynamical system. The Delaunay triangulation approach is used to find the optimal nearest neighboring points in time series. The efficiency of our method is comparable to standard LP methods but our method is more robust to the input parameter estimation. The approach has been successfully applied for separating a signal from noise in the chaotic Henon and Lorenz models as well as for noisy experimental data obtained from an electronic Chua circuit. The method works properly for a mixture of additive and dynamical noise and can be used for the noise-level detection.Comment: 11 pages, 12 figures. See http://www.chaosandnoise.or

Delayed feedback control of periodic orbits in autonomous systems

For controlling periodic orbits with delayed feedback methods the periodicity has to be known a priori. We propose a simple scheme, how to detect the period of orbits from properties of the control signal, at least if a periodic but nonvanishing signal is observed. We analytically derive a simple expression relating the delay, the control amplitude, and the unknown period. Thus, the latter can be computed from experimentally accessible quantities. Our findings are confirmed by numerical simulations and electronic circuit experimentsComment: 4 pages, Revtex, manuscript also available at ftp://athene.fkp.physik.th-darmstadt.de/pub/publications/wolfram/prl_98a/ or at http://athene.fkp.physik.th-darmstadt.de/public/wolfram_publ.htm

Generation of spin-wave envelope dark solitons

We demonstrate that in nonlinear systems with small group velocity any (odd or even) number of dark solitons can be generated by an input pulse without initially introduced phase modulation. We propose a theoretical explanation of the earlier reported experimental results on the generation of magnetic envelope dark solitons

Chaos suppression in the parametrically driven Lorenz system

We predict theoretically and verify experimentally the suppression of chaos in the Lorenz system driven by a high-frequency periodic or stochastic parametric force. We derive the theoretical criteria for chaos suppression and verify that they are in a good agreement with the results of numerical simulations and the experimental data obtained for an analog electronic circuit

Generation of spin-wave dark solitons with phase engineering

We generate experimentally spin-wave envelope dark solitons from rectangular high-frequency dark input pulses with externally introduced phase shifts in yttrium-iron garnet magnetic fims. We observe the generation of both odd and even numbers of magnetic dark solitons when the external phase shift varies. The experimental results are in a good qualitative agreement with the theory of the dark-soliton generation in magnetic films developed earlier [Phys. Rev. Lett. 82, 2583 (1999)].Comment: 6 pages, including 7 figures, submitted to Phys. Rev.

On the Mechanism of Time--Delayed Feedback Control

The Pyragas method for controlling chaos is investigated in detail from the experimental as well as theoretical point of view. We show by an analytical stability analysis that the revolution around an unstable periodic orbit governs the success of the control scheme. Our predictions concerning the transient behaviour of the control signal are confirmed by numerical simulations and an electronic circuit experiment.Comment: 4 pages, REVTeX, 4 eps-figures included Phys. Rev. Lett., in press also available at http://athene.fkp.physik.th-darmstadt.de/public/wolfram.htm

Lenalidomide and dexamethasone in relapsed/refractory immunoglobulin light chain (AL) amyloidosis: results from a large cohort of patients with long follow-up.

SummaryLenalidomide and dexamethasone (RD) is a standard treatment in relapsed/refractory immunoglobulin light chain (AL) amyloidosis (RRAL). We retrospectively investigated toxicity, efficacy and prognostic markers in 260 patients with RRAL. Patients received a median of two prior treatment lines (68% had been bortezomib‐refractory; 33% had received high‐dose melphalan). The median treatment duration was four cycles. The 3‐month haematological response rate was 31% [very good haematological response (VGHR) in 18%]. The median follow‐up was 56·5 months and the median overall survival (OS) and haematological event‐free survival (haemEFS) were 32 and 9 months. The 2‐year dialysis rate was 15%. VGHR resulted in better OS (62 vs. 26 months, P < 0·001). Cardiac progression predicted worse survival (22 vs. 40 months, P = 0·027), although N‐terminal prohormone of brain natriuretic peptide (NT‐proBNP) increase was frequently observed. Multivariable analysis identified these prognostic factors: NT‐proBNP for OS [hazard ratio (HR) 1·71; P < 0·001]; gain 1q21 for haemEFS (HR 1·68, P = 0·014), with a trend for OS (HR 1·47, P = 0·084); difference between involved and uninvolved free light chains (dFLC) and light chain isotype for OS (HR 2·22, P < 0·001; HR 1·62, P = 0·016) and haemEFS (HR 1·88, P < 0·001; HR 1·59, P = 0·008). Estimated glomerular filtration rate (HR 0·71, P = 0·004) and 24‐h proteinuria (HR 1·10, P = 0·004) were prognostic for renal survival. In conclusion, clonal and organ biomarkers at baseline identify patients with favourable outcome, while VGHR and cardiac progression define prognosis during RD treatment