Calculating Internal Avalanche Velocities from Correlation with Error Analysis

Velocities inside avalanches have been calculated for many years by calculatingthe cross-correlation between opto-electronic sensors using a method pioneered by inlinecite Nishimura et al. and Dent et al. Their approachhas been widely adopted but there has been little discussion of the optimal designof such instruments and the best analysis techniques. This paper discusses some ofthe different sources of error that arise and how these can be mitigated. A statisticalframework that describes such instruments is developed and used to quantify the errors.     

North European last glacial–interglacial transition (LGIT; 15–9 ka) tephrochronology: extended limits and new events

High‐precision correlation of palaeoclimatic and palaeoenvironmental records is crucial for testing hypotheses of synchronous change. Although radiocarbon is the traditional method for dating late Quaternary sedimentary sequences, particularly during the last glacial–interglacial transition (LGIT; 15–9 ka), there are inherent problems with the method, particularly during periods of climate change which are often accompanied by major perturbations in atmospheric radiocarbon content. An alternative method is the use of tephras that act as time‐parallel marker horizons. Within Europe, numerous volcanic centres are known to have erupted during the LGIT, providing considerable potential for high‐precision correlation independent of past radiocarbon fluctuations. Here we report the first identification of the Vedde Ash and Askja Tephra in Ireland, significantly extending the known provenance of these events. We have also identified two new horizons (the Roddans Port Tephras A and B) and tentatively recognise an additional horizon from Vallensgård Mose (Denmark) that provide crucial additional chronological control for the LGIT. Two phases of the Laacher See Tephra (LST) are reported, the lower Laacher See Tephra (LLST) and probably the C2 phase of the Middle Laacher See Tephra (MLST‐C2) indicating a more northeasterly distribution of this fan than reported previously. Copyright © 2006 John Wiley & Sons, Ltd.     

Dynamics of Two Planets in the 3/2 Mean-motion Resonance: Application to the Planetary System of the Pulsar PSR B1257+12

This paper considers the dynamics of two planets, as the planets B and C of the pulsar PSR B1257+12, near a 3/2 mean-motion resonance. A two-degrees-of-freedom model, in the framework of the general three-body planar problem, is used and the solutions are analyzed through surfaces of section and Fourier techniques in the full phase space of the system.On the possibility of existence of a fourth planet in distant orbit, see Wolszczan et al., 2000     

Quintessential inflation models with a nonminimally coupled scalar field

The evolution of a homogeneous, isotropic cosmological model driven by a nonminimally coupled scalar field is studied. The potential for the quintessential inflation model proposed by Peebles and Vilenkin is selected as a scalar potential. Possible scenarios for the cosmological dynamics are described in the conformal Einstein and Jordan representations. It is shown that, unlike in models with a minimal scalar field, here a class of solutions exists for which the scalar field is fixed at finite values during cosmological expansion. __________ Translated from Astrofizika, Vol. 49, No. 3, pp. 487–498 (August 2006).     

Observational Test of an Accretion Model of Star Formation in Galactic Clusters

Theoretical predictions of an accretion model of star formation in galactic clusters, published quite long ago, which is found to have some relevance with the current picture of star formation have been tested with observation of seven clusters of young and intermediate ages. It is found that the agreement between the theory and observation is very good.     

Distance estimate and progenitor characteristics of SN 2005cs in M51

We present the excitation energies and lifetimes for the  3 s 3 p 3 d  ⁴ F  _7/2,9/2  levels for five aluminium-like ions of the iron group. Apart from the wavelengths, this also includes the transition probabilities and branching ratios for the electric-dipole allowed (E1) and forbidden (M1, E2, M2) lines into the energetically lower lying levels of the  3 s ²3 d , 3 s 3 p ²  and  3 s 3 p 3 d   configurations. Applying systematically enlarged multiconfiguration Dirac–Fock (MCDF) wavefunctions, here the effects of relativity and the electron–electron correlation are treated within the same (computational) model.