Corrections of Systematic Errors, Data Homogenisation and Climatic Analysis of the Padova Pressure Series (1725-1999)

A short history of the series with daily observations of barometric pressure in Padova (since 1725) is made, with special reference to the types of barometers used, their locations, the types of corrections (which were only partial in the early period), the calibrations and the comparison with primary instruments. The paper also describes the homogenisation of the series and the procedures used to fill the small gaps. The Padova series was compared with previously well investigated series from the ADVICE and IMPROVE projects and especially with the nearby Milan series in order to check its reliability. Trend analysis shows an increase in pressure (some 1 hPa) during the last a hundred year. This trend is a common feature for Northern Italy. An effect of the increased air pressure is a local lowering of the Northern Mediterranean Sea level by 1 cm. The part of the year mostly affected by this increase is from late spring to August and corresponds to an extension of the hot season, characterised by an earlier start, and longer duration of the Azores Anticyclone. This reduces the penetration of the Atlantic disturbances in the Northern Mediterranean and the precipitation associated with the passage of fronts. This change is associated with an increase in thermoconvective activity with thunderstorms and heavy precipitation. This explains why, in the last decades, the annual total amount of precipitation is slightly decreased and at the same time the frequency of intense rainfall is increased. Moreover, a comparison of the day-to-day pressure variability with the Western Mediterranean Oscillation (WeMO) indicates a significant positive correlation during the late autumn-early winter period. An increase of the WeMO index means a strengthening of the baric dipole from Azores to Northern Italy, that could be explained by a deepening of the cyclonic circulation over northern Italy from November to January.     

Determination of the distribution of size of irregularly shaped particles from laser diffractometer measurements

The formal stereological transformation equation for particle sieve size distribution from measurements in lower dimensional spaces is applied to laser diffractometer measurements. The transformation function for iron ore particles is measured experimentally, and modeled. The solution is tested against the measured transformation function data as well as synthetic composite distributions of the original sample. The natural size distribution of a sample taken from a grinding circuit stream was measured by a combination of standard sieving and cyclosizer, and the result is compared to the transformed size distribution calculated from laser diffractometer measurements. The stereological transformation technique performed well in all cases.     

Late Pleistocene–Holocene environments in Valle Carbajal, Tierra del Fuego, Argentina

The authors discuss Late Pleistocene–Holocene depositional environments in one of the Fuegian Andes valleys on the basis of palynological, geomorphological, and sedimentological analyses from two sites located near the Beagle Channel. The results obtained at these localities reinforce and refine the Late Pleistocene–Holocene climatic pattern previously recorded there. A colder period, associated with the Younger Dryas stadial event, is suggested by low Nothofagus pollen frequency, and communities of grass, low scrub, and shrub heath expanded into the low/middle slopes (10,310 ¹⁴C yr BP). By ca. 9500 ¹⁴C yr BP, warmer and drier conditions occurred, as evidenced by the development of open-grown vegetation in the valley floors (pollen zone O-3), followed by the expansion of open Nothofagus woodland (pollen zone O-2) in the middle Holocene. The milder climate subsequently changed, as indicated by the spreading of the closed forest and mire (pollen zone O-1), to more humid and cooler conditions during the last ca. 5000 yr BP.     

Sensitivity analysis of seismic hazard for Western Liguria (North Western Italy): A first attempt towards the understanding and quantification of hazard uncertainty

The use of logic trees in probabilistic seismic hazard analyses often involves a large number of branches that reflect the uncertainty in the selection of different models and in the selection of the parameter values of each model. The sensitivity analysis, as proposed by Rabinowitz and Steinberg [Rabinowitz, N., Steinberg, D.M., 1991. Seismic hazard sensitivity analysis: a multi-parameter approach. Bull. Seismol. Soc. Am. 81, 796–817], is an efficient tool that allows the construction of logic trees focusing attention on the parameters that have greater impact on the hazard.In this paper the sensitivity analysis is performed in order to identify the parameters that have the largest influence on the Western Liguria (North Western Italy) seismic hazard. The analysis is conducted for six strategic sites following the multi-parameter approach developed by Rabinowitz and Steinberg [Rabinowitz, N., Steinberg, D.M., 1991. Seismic hazard sensitivity analysis: a multi-parameter approach. Bull. Seismol. Soc. Am. 81, 796–817] and accounts for both mean hazard values and hazard values corresponding to different percentiles (e.g., 16%-ile and 84%-ile). The results are assessed in terms of the expected PGA with a 10% probability of exceedance in 50 years for rock conditions and account for both the contribution from specific source zones using the Cornell approach [Cornell, C.A., 1968. Engineering seismic risk analysis. Bull. Seismol. Soc. Am. 58, 1583–1606] and the spatially smoothed seismicity [Frankel, A., 1995. Mapping seismic hazard in the Central and Eastern United States. Seismol. Res. Lett. 66, 8–21]. The influence of different procedures for calculating seismic hazard, seismic catalogues (epicentral parameters), source zone models, frequency–magnitude parameters, maximum earthquake magnitude values and attenuation relationships is considered. As a result, the sensitivity analysis allows us to identify the parameters with higher influence on the hazard. Only these parameters should be subjected to careful discussion or further research in order to reduce the uncertainty in the hazard while those with little or no effect can be excluded from subsequent logic-tree-based seismic hazard analyses.     

Structural control of Au–Pd mineralization (Jacutinga): An example from the Cauê Mine, Quadrilátero Ferrífero, Brazil

Precambrian banded iron formations (BIFs) in the Quadrilátero Ferrífero host a special kind of Au–Pd mineralization known as Jacutinga. The main orebodies are hosted within the Cauê Syncline, a SW-verging fold that involves Paleoproterozoic metasedimentary rocks in the Itabira District, a regional synclinorium with BIFs in the core of synclinal folds in the northeastern part of Quadrilatéro Ferrífero, Minas Gerais. Structural analysis reveals two important features of the district: the polydeformed character of the rocks and the importance of brittle structures in the control of the orebodies. Two deformational events are recognized in this area. The first event developed the main foliation, S1, that is the enveloping surface of the Cauê Syncline. The second event is better defined in the northern boundary of the structure where it is represented by a right-lateral wrench fault zone that has developed a foliation, S2, that truncates S1. This wrench fault was also responsible for the development of a system of fractures (Frm) that host the Au–Pd mineralization. The auriferous bodies of Cauê Syncline (Y, X, Área Central, Aba Norte, Noroeste and Aba Leste/Aba Leste Inferior) were generated during this second event. Shear fractures (R, R′ and P) and tension fractures (T) developed in response to the wrench fault system under brittle conditions. The best-developed, and most commonly mineralized fractures are R and T in all auriferous bodies. Elsewhere, the best mineralization occurs in the contacts of hematite bodies (soft/hard) and intrusive rocks with fractured itabirites. Other mineralization (Aba Norte, Área Central and X) is hosted on the contacts of other units.A system of fractures, as well as their intersections, thus represents the structural control on Jacutinga bodies and is responsible for the geometry of the orebodies. Of importance, there is no control by mineral/stretching lineations, fold axes and other ductile structure on the geometry and plunge of the orebodies.     

Line emission from accretion discs around black holes: the analytic approach

The broad X-ray iron line observed in many active galactic nuclei spectra is thought to originate from the accretion disc surrounding the putative supermassive black hole. We show here how to perform the analytical integration of the geodesic equations that describe the photon trajectories in the general case of a rotating black hole (Kerr metric), in order to write a fast and efficient numerical code for modelling emission line profiles from accretion discs.     

Airborne gravimetry used in precise geoid computations by ring integration

Two detailed geoids have been computed in the region of North Jutland. The first computation used marine data in the offshore areas. For the second computation the marine data set was replaced by the sparser airborne gravity data resulting from the AGMASCO campaign of September 1996. The results of comparisons of the geoid heights at on-shore geometric control showed that the geoid heights computed from the airborne gravity data matched in precision those computed using the marine data, supporting the view that airborne techniques have enormous potential for mapping those unsurveyed areas between the land-based data and the off-shore marine or altimetrically derived data. Received: 7 July 1997 / Accepted: 22 April 1998     

Plate Tectonics and mineralization in the Tethyan region

The association between mineralization and plate movements is becoming evident in the American Cordillera and the Pacific Island Arcs. This paper attempts to show how these ideas apply to the zone along which the Eurasian and Afro-Arabia plates collided during the late Mesozoic, between the Alps and the Himalayas. The study highlights some of the outstanding problems concerned with plate collision and the important question of the origin of ophiolite complexes. Some of the major mineralized districts in Greece, Turkey and Iran can be related to active plate edges, to island arc development and to related tectonism around pre-Mesozoic crystalline massifs. The study reinforces the view that the younger tectonic zones traversing the Middle East will become major mineral-producing areas in the future.     

Dynamics of a particle in a gravitational field of a homogeneous annulus disk

We formulate the problem of an infinitesimal particle moving in the space under the influence of the gravitational force induced by a homogeneous annulus disk fixed on a plane. We compute using different coordinates and in terms of an elliptic integral the potential associated to this problem. Also we study the symmetries of the associated potential. After that, we look at the dynamics in some particular cases, namely: in the line perpendicular to the plane that contains the annulus disk and passes through the center of the ring and on the plane that contains the massive annulus.