Continental drift and rotation of the Earth

It is shown, based on certain simplifying assumptions, that an island the size of Greenland, drifting across the North Atlantic at 10 m/century produces a change in secular rotation T=0.01 s.Presented at the Symposium Star Catalogues, Positional Astronomy and Celestial Mechanics, held in honor of Paul Herget at the U.S. Naval Observatory, Washington, November 30, 1978.     

Formation and stability of mixed Mg/Ca/phytate species in synthetic seawater media: Consequences on ligand speciation

The results of a potentiometric investigation (by ISE-H⁺, glass electrode) on the speciation of phytate ion (Phy¹²⁻) in an ionic medium simulating the major components (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻ and SO₄²⁻) of natural seawater, at different salinities and t = 25 °C, are reported. The work was particularly aimed at determining the possible formation of mixed Ca²⁺–Mg²⁺–phytate ion pairs, and to establish how including the formation of these mixed species would affect the speciation modeling in seawater media. After testing various speciation models, that considering the formation of the MgCaH₃Phy⁵⁻, MgCaH₄Phy⁴⁻, Mg₂CaH₃Phy³⁻ and Mg₂CaH₄Phy²⁻ species was accepted, and corresponding stability constants were determined at two salinities (S = 5, 10). A discussion is reported both on the choice of the experimental conditions and on the possibility to extend these results to those typical of real seawater. A detailed procedure is also described to demonstrate that the stability of these species is higher than that statistically predicted. As reported in literature, a parameter, namely log X, has been determined in order to quantify this extra stability for the formation of each mixed species at various salinities. For example, at S = 10, log X₁₁₃ = 2.67 and log X₁₁₄ = 1.37 for MgCaH₃Phy⁵⁻ and MgCaH₄Phy⁴⁻ (statistical value is log X_stat = 0.60), and log X₂₁₃ = 6.11 and log X₂₁₄ = 2.15 for Mg₂CaH₃Phy³⁻ and Mg₂CaH₄Phy²⁻ (log X_stat = 1.43), respectively. Results obtained also showed that the formation of these species may occur even in conditions of low salinity (i.e. low concentration of alkaline earth cations) and low pH (i.e., more protonated ligand).     

Solar irradiance in NW Italy

Summary An analysis is made of the monthly mean global and diffuse irradiance values recorded by the Genoa University Geophysical Institute radiation network to derive characteristic elements of the solar climate in four typical NW Italy locations. Diffuse irradiation was estimated for the stations where diffuse irradiation data were not recorded, by using correlations between measured data with clearness parameter and sunshine index. Local factors which affect the attenuation of global irradiance under cloudless skies are discussed.

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Zusammenfassung Die vom Strahlungsaufzeichnungsnetz der Geophysikalischen Hochschule Genua aufgenommenen monatlichen Mittelwerte der Global- und Himmelsstrahlung werden untersucht, wobei charakteristische Elemente des Sonnenklimas von vier typischen Stationen in NW-Italien deduziert werden. Die Himmelsstrahlung wird für diejenigen Stationen, wo diese nicht aufgenommen wird, durch Anwendung von Korrelationen zwischen Meßwerten und einem Klarheitsparameter bzw. einer Sonnenscheinzahl geschätzt. Außerdem werden örtliche Faktoren diskutiert, die die Schwächung der Globalstrahlung unter wolkenlosem Himmel bestimmen.

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This paper is dedicated to the memory of Prof. Mario Bossolasco of whom the author had the honour of being a pupil.

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With 2 Figures     

Detecting patterns of climate change in long-term forecasts of marine environmental parameters

ABSTRACT

Forecasting environmental parameters in the distant future requires complex modelling and large computational resources. Due to the sensitivity and complexity of forecast models, long-term parameter forecasts (e.g. up to 2100) are uncommon and only produced by a few organisations, in heterogeneous formats and based on different assumptions of greenhouse gases emissions. However, data mining techniques can be used to coerce the data to a uniform time and spatial representation, which facilitates their use in many applications. In this paper, streams of big data coming from AquaMaps and NASA collections of 126 long-term forecasts of nine types of environmental parameters are processed through a cloud computing platform in order to (i) standardise and harmonise the data representations, (ii) produce intermediate scenarios and new informative parameters, and (iii) align all sets on a common time and spatial resolution. Time series cross-correlation applied to these aligned datasets reveals patterns of climate change and similarities between parameter trends in 10 marine areas. Our results highlight that (i) the Mediterranean Sea may have a standalone ‘response’ to climate change with respect to other areas, (ii) the Poles are most representative of global forecasted change, and (iii) the trends are generally alarming for most oceans.     

Inconstancy in predator/prey ratios in Quaternary large mammal communities of Italy, with an appraisal of mechanisms

Constancy in predator/prey ratio (PPR) is a controversial issue in ecological research. Published reports support both constancy and inconstancy of the ratio in animal communities. Only a few studies, however, specifically address its course through time. Here we study the course of predator/prey ratio in communities of large Plio-Pleistocene mammals in Italy. After controlling for taphonomic biases, we find strong support for PPR inconstancy through time. Extinction, dispersal events, and differences in body size trends between predators and their prey were found to affect the ratio, which was distributed almost bimodally. We suggest that this stepwise dynamic in PPR indicates changes in ecosystem functioning. Prey richness was controlled by predation when PPR was high and by resources when PPR was low.     

Jet breaks at the end of the slow decline phase of Swift GRB light curves

The Swift mission has discovered an intriguing feature of gamma-ray burst (GRBs) afterglows, a phase of shallow decline of the flux in the X-ray and optical light curves. This behaviour is typically attributed to energy injection into the burst ejecta. At some point this phase ends, resulting in a break in the light curve, which is commonly interpreted as the cessation of the energy injection. In a few cases, however, while breaks in the X-ray light curve are observed, optical emission continues its slow flux decline. This behaviour suggests a more complex scenario. In this paper, we present a model that invokes a double component outflow, in which narrowly collimated ejecta are responsible for the X-ray emission while a broad outflow is responsible for the optical emission. The narrow component can produce a jet break in the X-ray light curve at relatively early times, while the optical emission does not break due to its lower degree of collimation. In our model both components are subject to energy injection for the whole duration of the follow-up observations. We apply this model to GRBs with chromatic breaks, and we show how it might change the interpretation of the GRBs canonical light curve. We also study our model from a theoretical point of view, investigating the possible configurations of frequencies and the values of GRB physical parameters allowed in our model.     

Forest structure of a maple old-growth stand: a case study on the Apennines mountains (Southern Italy)

In Europe, very small forest areas can be considered to be old-growth, and they are mainly located in Eastern Europe. The typical structures of old growth forests infrequently occur in Mediterranean mountainous environments, since they have been affected by human activities for centuries. This study focused on a remote and almost pure Italian maple stand located in southern Italy, which has not been managed for long time due to its inaccessibility. The effects of natural evolution on the forest stand were evaluated through the analysis of the spatial and chronological structure and the regeneration patterns, then estimating the amounts and quality of deadwood occurrence. Across the whole stand, all the trees with DBH (diameter at breast height) larger than 50 cm (LLT, large living trees) were measured (DBH and height) and age was also determined through a dendrochronological approach. The diameters observed ranged between 50 and 145 cm with ages of 120 to 250 years. The Latham index calculated for trees within the sample plot highlighted a multilayered canopy with a dominant layer of large living trees (age > 120 years). The size-class distribution of stems had a reverse-J shape, and basal area was 52 m² ha^-1. Deadwood was exclusively constituted by standing dead trees and CWD and its volume was on average 31 m³ ha^-1.Pure Italian maple forests are generally rare in Europe, and it was unexpected to find a forest stand characterized by a so complex structure with old growth attributes. The study of complex forest stand, even if small, could give precious information on the forest evolution, clarifying also diverse auto-ecological traits of tree species that usually are not common in our forests.