4,311 research outputs found
GONG p-mode frequency changes with solar activity
We present a correlation analysis of GONG p-mode frequencies with nine solar
activity indices for the period 1995 August to 1997 August. This study includes
spherical harmonic degree in the range 2 to 150 and the frequency range of
1500-3500 \mu Hz. Using three statistical tests, the measured mean frequency
shifts show strong to good correlation with activity indices. A decrease of
0.06 \mu Hz in frequency, during the descending phase of solar cycle 22 and an
increase of 0.04 \mu Hz in the ascending phase of solar cycle 23 is observed.
These results provide the first evidence for change in p-mode frequencies
around the declining phase of solar cycle 22 and beginning of new cycle 23.
This analysis further confirms that the temporal behaviour of the solar
frequency shifts closely follow the phase of the solar activity cycle.Comment: 14 pages, 3 figures. To appear in Ap.
The diffusion coefficient of propagating fronts with multiplicative noise
Recent studies have shown that in the presence of noise both fronts
propagating into a metastable state and so-called pushed fronts propagating
into an unstable state, exhibit diffusive wandering about the average position.
In this paper we derive an expression for the effective diffusion coefficient
of such fronts, which was motivated before on the basis of a multiple scale
ansatz. Our systematic derivation is based on the decomposition of the
fluctuating front into a suitably positioned average profile plus fluctuating
eigenmodes of the stability operator. While the fluctuations of the front
position in this particular decomposition are a Wiener process on all time
scales, the fluctuations about the time averaged front profile relax
exponentially.Comment: 4 page
Roughness of Sandpile Surfaces
We study the surface roughness of prototype models displaying self-organized
criticality (SOC) and their noncritical variants in one dimension. For SOC
systems, we find that two seemingly equivalent definitions of surface roughness
yields different asymptotic scaling exponents. Using approximate analytical
arguments and extensive numerical studies we conclude that this ambiguity is
due to the special scaling properties of the nonlinear steady state surface. We
also find that there is no such ambiguity for non-SOC models, although there
may be intermediate crossovers to different roughness values. Such crossovers
need to be distinguished from the true asymptotic behaviour, as in the case of
a noncritical disordered sandpile model studied in [10].Comment: 5 pages, 4 figures. Accepted for publication in Phys. Rev.
Prolonged survival of patients receiving trastuzumab beyond disease progression for HER2 overexpressing metastatic breast cancer (MBC)
Background: The aim of this retrospective analysis was to evaluate the impact of trastuzumab-based regimens on the survival of patients with HER2-overexpressing metastatic breast cancer (MBC). The study specifically focussed on the influence of the continuation of trastuzumab-based treatment despite tumor progression on survival. Patients and Methods: Patients with HER2 overexpressing MBC were included in this retrospective analysis. HER2 overexpression was determined by the immunohistochemical staining score (DAKO Hercep Test (TM)). Trastuzumab was applied at a loading dose of 4 mg/kg and a maintenance dose of 2 mg/kg. Results: Among 136 HER2 overexpressing patients (DAKO score 3+), 66 patients received first-line trastuzumab, 47 patients received trastuzumab as second-line therapy and 23 patients received trastuzumab beyond disease progression. There was no significant difference regarding the duration of trastuzumab-based treatment (first-line: 29.5 weeks vs. second-line: 25 weeks). Moreover, there was no difference in the response rate (first-line: 37.9% vs. second-line: 35.7%) or the median survival (p = 0.47 log rank). Patients who received >= 2 trastuzumab-based regimens for MBC survived significantly longer compared to those who had received only 1 regimen (>= 2 regimens: 62.4 months vs. 1 regimen: 38.5 months; p = 0.01 log rank). Conclusions: Trastuzumab is highly effective in the treatment of HER2 overexpressing MBC. Compared to historical controls, overall survival appears to be markedly prolonged, particularly in patients who received sequential trastuzumab-based treatment beyond disease progression
The universality class of fluctuating pulled fronts
It has recently been proposed that fluctuating ``pulled'' fronts propagating
into an unstable state should not be in the standard KPZ universality class for
rough interface growth. We introduce an effective field equation for this class
of problems, and show on the basis of it that noisy pulled fronts in {\em d+1}
bulk dimensions should be in the universality class of the {\em (d+1)+1}D KPZ
equation rather than of the {\em d+1}D KPZ equation. Our scenario ties together
a number of heretofore unexplained observations in the literature, and is
supported by previous numerical results.Comment: 4 pages, 2 figure
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