About the problem of motion of n gyrostats: I. The first integrals

In this paper, the problem of the motion of n gyrostats in a central field, with relative momenta _k ^r (k=1, 2, ..., n) functions of the time, is considered.In these conditions, the existence of the linear and angular momentum integrals is established.Moreover, a sufficient condition for the existence of the Jacobi's Integral is given. This study generalizes the results given by Duboshin for n rigid bodies.     

Calculated and observed seismic behaviour of exposed upper mantle

In order to determine the seismic properties of rocks representing the continental crust/upper mantle transition, a structural and petrographical study of peridotites of the Ivrea-Verbano zone (N. Italy) has been undertaken. The seismic behaviour (Vp, Vs, birefringence, orientation of the fast shear-wave polarisation plane) has been calculated from the modal composition of rock samples, together with the crystallographic preferred orientation and the single crystal elastic constants, using the methods of Mainprice (1990). It is shown that the intrinsic anisotropy of peridotites is mainly due to the lattice preferred orientation (LPO) of olivine and to the competing effects due to the LPO of orthopyroxene. If present, well-oriented hydrous phases such as phlogopite, leads to both P- and S-waves velocities becoming drastically reduced, but the anisotropy and the S-wave splitting (mainly on the foliation plane) is increased. An attempt has been made to apply this petrologic and microstructural approach to understand the seismic properties of ultramafic rocks with the aid of a mobile seismic network set up in the Ivrea-Verbano zone. Five recording units with 3-component geophones were installed on the most representative lithologies of the Ivrea-Verbano zone: kinzigites, gabbros, stronalites, and on metapelites of the adjacent outcrop of the Serie dei Laghi. During five months the seismic network recorded 49 events that were mainly regional earthquakes. The preliminary analysis of the first arrival revealed a high-velocity anomaly near the Finero ultramafic massif. Rough calculations indicated that this anomaly could be due to a shallow-depth, peridotitic body about six kilometres thick. S-wave polarisation analysis was carried out on the horizontal components of the seismograms of four regional earthquakes that showed a first arrival propagating almost vertically at the recording sites. Four earthquakes were chosen in order to reconstruct the orientation of the polarisation plane of the shear phases. The preliminary results of this analysis have shown a qualitatively good agreement between the orientation of the polarisation plane of the fast shear-wave and the strike of the foliation at the station near Finero, located on kinzigites of the Ivrea-Verbano zone, although the relationships between the local structural setting and the polarisation orientations at the other recording sites is not yet so clear.     

Diffusive-Shock-Accelerated Interplanetary Ions At Several Energies During the Solar Cycle 21 Maximum

The most intense energetic particle (mainly proton) events in the energy range 36–1600 keV, during the years of maximum activity of solar cycle 21 (1978 to 1982), have been studied with regard to their spectra, temporal profiles, source location at the Sun, interplanetary plasma parameters and interplanetary magnetic field topology. In all the events, the particles were accelerated by the 'Diffusive Shock' acceleration mechanism, because all the events were 'long-duration events', shock-associated, and their spectra fitted to a power-law energetic particle spectrum dJ/dE E^-\gamma with the exponent values ranging from 1.25 up to 1.94, with a mean value of 1.60 ± 0.06. We also show that the spectral indexes are related to the shock properties by a linear expression. The solar sources were located on a wide longitudinal belt extending from 50^ W up to 73^ E. Neither the spectral indexes nor the shock parameters present any dependence on the source location at the Sun. Finally, only one event showed the complete set of properties that characterize the presence of a magnetic cloud associated with the event.     

Multiwavelength study of the nuclei of a volume-limited sample of galaxies – II. Optical, infrared and radio observations

We present optical and infrared broad-band images, radio maps, and optical spectroscopy for the nuclear region of a sample of nearby galaxies. The galaxies have been drawn from a complete volume-limited sample for which we have already presented X-ray imaging. We modelled the stellar component of the spectroscopic observations to determine the star formation history of our targets. Diagnostic diagrams were used to classify the emission-line spectra and determine the ionizing mechanism driving the nuclear regions. All those sources classified as active galactic nuclei present small Eddington ratios  (∼10⁻³–10⁻⁶)  , implying a very slow growth rate of their black holes. We finally investigate the relative numbers of active and normal nuclei as a function of host galaxy luminosity and find that the fraction of active galaxies slowly rises as a function of host absolute magnitude in the   M _B ∼−12  to −22 range.     

Ag-rich Tetrahedrite in the El Zancudo Deposit,Colombia: Occurrence,Chemical Compositions and Genetic Temperatures

Chemical compositions of tetrahedrite—Ag-rich tetrahedrite—freibergite solid solutions (Ag-rich tetrahedrite_ss) and homogenization temperatures of fluid inclusions in quartz and carbonates of seventeen samples from nine veins in the El Zancudo deposit, Antioquia, Colombia, were investigated to reveal the origin of silver in Ag-rich tetrahedrite_ss, to derive their crystallization temperatures and to examine the relationship between chemical compositions of Ag-rich tetrahedrite_ss and their crystallization temperatures. The ores consist of arsenopyrite, pyrite, sphalerite, Ag-rich tetrahedrite_ss, galena, boulangerite, andorite, owyheeite, diaphorite, jamesonite, miargyrite, bournonite, chalcopyrite, and electrum. Ag-rich tetrahedrite_ss forms about 10 volume % of the total ores and is one of the most common and widely distributed sulfosalts in this deposit. Ag-rich tetrahedrite_ss is rich in Ag (1.13 to 31.02 wt%) and Sb (22.93 to 29.82 wt%), and poor in As (0.06 to 2.43 wt%), consistent with the reported incompatibilities of Ag and As in Ag-rich tetrahedrite_ss. The Zn/(Zn + Fe)-, Ag/(Ag + Cu)- and Sb/(Sb + As + Bi)-atomic ratios exhibit some variations among the veins. Ag-rich tetrahedrite_ss with higher Ag/(Ag + Cu) ratios coexist with diaphorite, whereas those with lower ratios are not associated with this sulfosalt. Ag-rich tetrahedrite_ss in the assemblages of Ag-rich tetrahedrite_ss+ sphalerite and of Ag-rich tetrahedrite_ss+ bournonite + galena shows no Zn ↔ Fe and Cu ↔ Ag variations between core and rim, respectively, negating the possibility of solid state reaction during cooling. Ag-rich tetrahedrite_ss is thus regarded as primary phase. Homogenization temperatures of primary fluid inclusions in quartz and carbonates co-existing with Ag-rich tetrahedrite_ss define the mineralization temperatures of 134 to 263°C. Independent crystallization temperatures of Ag-rich tetrahedrite estimated based on Zn/(Zn + Fe) and Ag/(Ag + Cu) ratios of the Ag-rich tetrahedrite_ss associated with silver minerals such as miargyrite, andorite and diaphorite using Sack's thermochemical database lie in a range between 170 and ∼250°C. Both results are thus in good agreement.     

Paleolithic vs. Epipaleolithic fisheries in northern Iberia

A comparison of Paleolithic and Epipaleolithic fisheries in NW Iberia shows an overall high trophic level of catch. Freshwater fisheries (and thus their impacts) are ca. 8000 yr older than marine fisheries and have suffered virtually no changes in the region except for the increase in numbers, being focused on two families (Salmonidae, and Anguillidae to a very minor extent). Marine fisheries in the Paleolithic likely had a low impact but rapidly increased in importance, raising the average trophic level of the catch, the number of affected taxa and the proportion of marine to freshwater fisheries with time.     

Regularization and linearization of the equations of motion in central force-fields

Within the framework of linear and regular celestial mechanics, a wide class of central force field problems are considered. We take as potential function a polynomial whose variable is the reciprocal of the distance from the origin, and, as regularizing function the square root of a certain reciprocal polynomial, related to the potential function. The relations between the coefficients of both functions, in order to arrive to linear equations, are given. In particular, the case of a quintic polynomial is analyzed, and an application is made to artificial earth satellites considering harmonicsJ ₂,J ₃,J ₄.     

Intercomparison of measurements of bulk snow density and water equivalent of snow cover with snow core samplers: Instrumental bias and variability induced by observers

Manually collected snow data are often considered as ground truth for many applications such as climatological or hydrological studies. However, there are many sources of uncertainty that are not quantified in detail. For the determination of water equivalent of snow cover (SWE), different snow core samplers and scales are used, but they are all based on the same measurement principle. We conducted two field campaigns with 9 samplers commonly used in observational measurements and research in Europe and northern America to better quantify uncertainties when measuring depth, density and SWE with core samplers. During the first campaign, as a first approach to distinguish snow variability measured at the plot and at the point scale, repeated measurements were taken along two 20 m long snow pits. The results revealed a much higher variability of SWE at the plot scale (resulting from both natural variability and instrumental bias) compared to repeated measurements at the same spot (resulting mostly from error induced by observers or very small scale variability of snow depth). The exceptionally homogeneous snowpack found in the second campaign permitted to almost neglect the natural variability of the snowpack properties and focus on the separation between instrumental bias and error induced by observers. Reported uncertainties refer to a shallow, homogeneous tundra-taiga snowpack less than 1 m deep (loose, mostly recrystallised snow and no wind impact). Under such measurement conditions, the uncertainty in bulk snow density estimation is about 5% for an individual instrument and is close to 10% among different instruments. Results confirmed that instrumental bias exceeded both the natural variability and the error induced by observers, even in the case when observers were not familiar with a given snow core sampler.