PubMed · 12349644
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C Bright. The nemesis effect.. https://pubmed.ncbi.nlm.nih.gov/12349644/
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Among noise-induced cooperative phenomena a peculiar relevance is played by stochastic resonance. In this paper we offer evidence that geomagnetic polarity reversals may be due to a stochastic resonance process. In detail, analyzing the distribution function P(tau) of polarity residence times (chrons), we found the evidence of a stochastic synchronization process, i.e., a series of peaks in the P(tau) at T(n) approximately (2n+1)T(Omega)/2 with n=0,1,...,j and T(omega) approximately 0.1 Myr. This result is discussed in connection with both the typical time scale of Earth's orbit eccentricity variation and the recent results on the typical time scale of climatic long-term variation.
It was tested with 5 different types of mammography films in which manner the values of "Lightspeed" (LS) and "Lightcontrast" (LC), according DIN V 6868-55 will be changed, when preexposed film strips are used, stored at different climates and spaces of time in comparison to strips, which are exposed immediately before processing. It was proved, that the value LS of preexposed film strips in general will be lowered with increasing storage time compared to freshly exposed film strips, when both strips are processed simultaneously. This drift will be enhanced with increasing rel.humidity levels during storage. The value of LC increases in general with longer storage time and higher rel.humidity levels. The tested film types have all individual drifts in LS and LC. The precision of a single measurement using preexposed film strips was established over all different types of films at in about: Delta LS=0.06 and Delta LC (%)=16% [in the borders of 2 sigma (sigma)]. This uncertainty includes solely the precision of sensitometer, densitometer, the method to establish sensitometric values and unavoidable statistical fluctuations. Even when the systematic drift of the used film type is well established, the required precision, restricted to the listed items and prescribed in DIN V 6868-55, table D.1 to determine the values of LS with Delta LS=0.039 and the values of LC with Delta LC=7.2% is overstepped in so far, that it is impossible to draw a precise conclusion from the measured values to the performance of the subsystem film and processing. If any exceeding of the dose in image receptor plane is monitored, there is no tracking possible to a misadjustment of the subsystem film and processing.