Solar constant and sunspots

Summary The relationship, already found by the authors, between sunspot numbers and the solar constant, as deduced from the highest global irradiance values at noon, is here reexamined and confirmed. Some attempts at explanation and further inferences are presented.     

Middle-Late Pleistocene polycyclic evolution of a stable coastal area (southern Apulia, Italy)

The Otranto–Leuca coastal tract is marked by the presence of numerous sea caves placed close to present sea level. They are located generally at the back of a shore platform covered by a sequence of breccia deposits, marine sediments and speleothems. At Grotta di Masseria dell'Orte, marine cemented sands rest on a narrow shore platform at about 6.2 m above mean sea level and are covered by speleothems older than 185 ka. At Grotta del Diavolo, which is mostly filled by breccia deposits, three beach levels have been detected at about 3.0, 3.5 and 5.9 m above msl. They are either covered by or overlie speleothems that yield an U/Th age of 340, 78 ka and between 170.3 and 146.5, respectively. Geomorphological evidence and radiometric ages indicate that the area after a period of uplift has been tectonically stable since the last part of the Middle Pleistocene so that marine landforms close to the present shoreline underwent a polycyclic evolution. The sedimentary fills of sea caves formed during Middle-Late Pleistocene glacial stages, when arid or semiarid conditions promoted the removal of regolith and the development of thick breccia deposits. During Marine Isotope Stages (MIS) 9.3, 5.5 and 5.1, cave sediments were partially eroded whereas beach layers and related speleothems developed. These are, in fact, the only marine isotope stages marked by a sea level position which in this Mediterranean region was either close to, or slightly higher than, the present one.     

Deciphering late Quaternary land snail shell δO and δC from Franchthi Cave (Argolid,Greece)

This paper investigates the stable isotopic composition from late Pleistocene–Holocene (~ 13 to ~ 10.5 cal ka BP) shells of the land snail Helix figulina, from Franchthi Cave (Greece). It explores the palaeoclimatic and palaeoenvironmental implications of the isotope palaeoecology of archaeological shells at the time of human occupation of the cave. Modern shells from around the cave were also analysed and their isotopic signatures compared with those of the archaeological shells. The carbon isotope composition of modern shells depicts the consumption of C₃ vegetation. Shell oxygen isotopic values are consistent with other Mediterranean snail shells from coastal areas. Combining empirical linear regression and an evaporative model, the δ¹⁸Os suggest that modern snails in the study area are active during periods of higher relative humidity and lower rainfall δ¹⁸O, probably at night. Late glacial and early Holocene δ¹⁸Os show lower values compared to modern ones. Early Holocene δ¹⁸Os values likely track enhanced moisture and isotopic changes in the precipitation source. By contrast, lower late glacial δ¹⁸O could reflect lower temperatures and δ¹⁸Op, compared to the present day. Shell carbon isotope values indicate the presence of C₃ vegetation as main source of carbon to late glacial and early Holocene snails.     

An elastoplastic strainhardening model for soil allowing for hydraulic bonding–debonding effects

The paper presents a strainhardening constitutive model for unsaturated soil behaviour based on energy conjugated stress variables in the framework of superposed continua. The proposed constitutive law deals with hydro‐mechanical coupling phenomena. The main purpose is to develop within a consistent framework a model that can deal with possible mechanical instabilities occurring in partially saturated materials. The loss of capillary effects during wetting processes can, in fact, play a central role in unstable processes. Therefore, it will be shown that the bonding effects due to surface tensions can be described in a mathematical framework similar to that employed for bonded geomaterials to model weathering or diagenesis effects, either mechanically or chemically induced. The results of several simulations of common laboratory tests on partially saturated soil specimens are shown. The calculated behaviour appears to be in good qualitative agreement with that observed in the laboratory. In particular it is shown that volumetric collapse phenomena due to hydraulic debonding effects can be successfully described by the model. Finally, it will be highlighted the ability of the model to naturally capture the transition to a fully saturated condition and to deal with possible mechanical instabilities in the unsaturated regime. Copyright © 2008 John Wiley & Sons, Ltd.     

Thermodynamics of rare events and impulsive relaxation events in the magnetospheric substorm dynamics

The magnetosphere dynamics shows fast relaxation events following power-law distribution for many observable quantities during magnetic substorms. The emergence of such power-law distributions has been widely discussed in the framework of self-organized criticality and/or turbulence. Here, a different approach to the statistical features of these impulsive dynamical events is proposed in the framework of the thermodynamics of rare events [Lavenda, B.H., Florio, A., 1992. Thermodynamics of rare events, Int. J. Theor. Phys. 31, 1455–1475; Lavenda, B.H., 1995. Thermodynamics of Extremes. Albion]. In detail, an application of such a novel approach to the magnetospheric substorm avalanching dynamics as monitored by the auroral electroject index is discussed.     

Natural background levels and threshold values derivation for naturally As, V and F rich groundwater bodies: a methodological case study in Central Italy

Natural background levels (NBL) and threshold values (TV) derivation is an important task for EU Member States to correctly assess the chemical status of groundwater bodies within the context of the recently adopted Groundwater Directive. Attempts are being made both by water authorities and scientific community to test application viability of proposed methods to different real situations and to develop tailored adjustments and refinements. The aim of this paper is to describe a methodological case study of NBL and TV determination in a large area (5,500 km²) located in Central Italy where both natural and anthropogenic contamination occurs, resulting in several substances be detected in ground waters with concentration frequently exceeding drinking water standards. This paper shows the key role played in the determination process by knowledge on the hydrogeological setting and hydrogeochemical features. The adoption of appropriate pre-selection criteria of samples, the establishment of TV at the groundwater body scale for natural origin substances, and the evaluation of TVs exceedances in a multiparameter context are experimentally discussed. Beyond the critical evaluation of NBL and TV determination method, this research aims at increasing consciousness in the water management agencies that groundwater status assessment should be conceived as a scientific evaluation procedure and not as a mere technical/administrative exercise to be performed using any set of available data. As such, it should be supported by adequate knowledge of hydrogeological setting, hydrochemical processes occurring in groundwater bodies, and human activities acting overland to be progressively verified.     

Research progress in volcanology in the Neapolitan area, southern Italy: a review and some alternative views

Comprehensive reviews are given for the major volcanic systems that occur in the greater metropolitan area of Naples, southern Italy; Mt. Somma-Vesuvius to the east and the Campi Flegrei volcanic system to the west. Also included in the review is a detailed discussion of the large, highly explosive Campania Volcanic Zone (CVZ) ignimbrite events. These volcanic areas have been studied for more than 100 years, yet significant differences of opinion exist related to fundamental issues of origin and distribution. We present some alternative views related to petrogenesis on some issues based on more than 25 years of research. The relationship between risk assessment and management that impacts the threatened society or culture and the past and ongoing fundamental volcanological research is an essential part of the science. Countries with limited resources may be forced to accept an increased risk but even highly industrialized societies may not be able to completely eliminate deaths from volcanic eruptions. Scientific studies of the hazardous regions should be comprehensive and include reasonable alternative interpretations as this information reveals the level of confidence that must be conveyed to the public officials. The authors review the state of the art of risk assessment and management of the volcanic hazards in the Neapolitan region in light of the review of research.     

Low multipath antennas for GNSS-based attitude determination systems applied to high-altitude platforms

High-altitude platforms (HAPs) are a flexible and attractive technology for providing innovative wireless services. These aerial platforms can be successfully employed for mobile or broadband communications and for disaster monitoring or response. However, one of the open issues is whether HAP stations can provide reliable services without temporal outages owing to stratospheric winds that can cause positional and attitude instabilities thus affecting the communication system operation. To counteract this issue, one possible solution is to use reconfigurable antennas whose pointing direction can be adjusted depending on the platform spatial orientation. However, this would require real-time three-axial attitude data. As a possible solution, this paper will review the potential of GNSS-based attitude determination systems with reference to HAP stations. In particular, it will be shown how the use of a particular class of low multipath and lightweight antennas can provide a high degree of accuracy without altering the avionic ballast.     

Conditioning clayey soils with a dispersant agent for Deep Soil Mixing application: laboratory experiments and artificial neural network interpretation

Acta Geotechnica - Plasticity of clays makes Deep Soil Mixing (DSM) problematic due to the tendency of the material to congest the rotating blades, reduce mixing efficiency and remain...