Aluminum in quartz as a geothermometer

Quartz forming in aluminum-saturated environments has a trace aluminum content which varies linearly and directly with its temperature of crystallization. The aluminum content varies at a rate of approximately 1 ppm Al per 3.6° C change in temperature. Use of this geothermometer gives temperatures which are consistent with those expected by geologic reasoning or through the use of other geothermometers.     

The ionosphere over Genova during the solar eclipse of February 15, 1961

Summary The behaviour of the ionosphere over Genova during the solar eclipse of February 15, 1961 is investigated. For theE-layer the effect was very marked, but the value obtained for the recombination coefficient is above normal. The effect of the eclipse was also observed on theF2 layer; however, the behaviour here appears affected by the simultaneous occurrence of an ionospheric perturbation. Finally, the maximum reduction of the ionospheric absorption on 2 and 3 Mc/s during the eclipse was found to be of the order of about 12 db.This report belongs to a set of investigations on geophysical effects of the solar eclipse of February 15th, 1961 carried out by the «Istituto Geofisico, Università di Genova», and made possible through a financial support of the «Consiglio Nazionale delle Ricerche».     

Abbassamento elettroosmotico della superficie piezometrica in un suolo saturo d'acqua

Riassunto Si studia il fenomeno di elettroprosciugamento di un terreno, in un caso particolare di disposizione elettrodica (piano-parallela, e parallela alla superficie del suolo), con particolare riguardo all'abbassarsi nel tempo del limite fra terreno saturo d'acqua e terreno asciutto. Si scrivono formule che forniscono i tempi di prosciugamento, e l'espressione dell'energia elettrica assorbita dal processo.

---

Summary In present paper the A. deals with the electro-drainage phenomenon, on account of a particular distribution of the electrodes (plane-parallel, and parallel to soil surface), in regard chiefly to the lowering, relative to time, of the boundary between the zone of water-saturated soil and the zone of dry soil. Formulae are given in order to evaluate the duration of electro-drainage and the amount of electric energy taken over by the process.

     

L'énergie des perturbations et les deux régimes du mouvement des fluides en météorologie synoptique

Résumé On commence par déduire l'équation thermo-hydrodynamique d'une masse finie quelconque du fluide. Cette équation réalise la synthèse des équations du mouvement, de l'équation de continuité, de l'équation qui exprime le premier principe de la thermodynamique et de l'équation d'état. Sous sa forme première, elle ne se prête pas, pour plusieurs raisons; à l'étude des transformations d'énergie dans une masse donnée. En considérant cependant la décomposition du mouvement réel en mouvement de base et perturbation, et en appliquant l'équation thermo-hydrodynamique à une même masse dans le mouvement réel et dans le mouvement de base (c'est-à-dire, à une masse dont la surface limite se déplace de la même manière dans le mouvement réel et dans le mouvement de base), on arrive facilement à une nouvelle forme beaucoup plus simple, quoique rigoureuse, de l'équation thermohydrodynamique. Cette nouvelle forme exprime la perturbation de l'énergie cinétique du mouvement autour du centre de gravité de la masse en fonction de la perturbation de son enthalpie (terme margulésien) et de la perturbation de la dissipation d'énergie dans la masse par les efforts de frottement. D'où un premier résultat central du mémoire qui s'énonce en disant que la perturbation de la dissipation d'énergie contribue nécessairement et efficacement, dans certains volumes de l'atmosphère, à une augmentation de l'énergie cinétique des perturbations.La variation de l'enthalpie peut être exprimée en fonction du mouvement du centre de gravité de la masse. On montre alors que la variation temporelle de la perturhation de l'enthalpie est nulle pour toute masse dont le mouvement de la surface limite n'a pas de perturbation. Ceci conduit au deuxième résultat central, d'après lequel la variation de la perturbation de l'énergie cinétique du mouvement autour du centre de gravité dans und telle masse est égale à la perturbation, changée de signe, de la vitesse de dissipation d'énergie par les efforts de frottement.Ces deux résultats impliquent, selon l'auteur, un changement radical dans la manière de traiter le problème de l'origine de l'énergie des perturbations. En particulier ils montrent qu'il faut rejeter les modèles margulésiens ou margulésiens généralisés, selon lesquels toute perturbation est essentiellement un mécanisme qui emprunte son énergie cinétique à l'enthalpie de la masse.Le mouvement de base, produit directement par l'ensemble des actions extérieures thermodynamiques et mécaniques qui agissent sur le fluide, doit être considéré comme étant celui qui réalise à chaque instant, pour ses différentes propriétés, le minimum de variation temporelle. Ceci implique l'existence, en chaque point du fluide, d'une fonction de dissipation essentiellement positive, d'où résulte que la loi des efforts de frottement dans le mouvement de base est nécessairement une loi de Hooke isotrope. Sous l'influence des mêmes actions extérieures, le fluide prend cependant un mouvement différent du mouvement de base (en d'autres termes, il se superpose à celui-ci une perturbation) parce que la loi réelle des efforts de frottement n'est pas rigoureusement une loi de Hooke isotrope. La perturbation est donc, à chaque instant, la résultat de l'action, étendue à tout le passé du fluide, de la différence des deux lois des efforts de frottement.En négligeant cependant différentiellement, à un instant donné, la partie des efforts de frottement qui ne correspond pas à une loi de Hooke isotrope, on arrive facilement à une généralisation du théorème de Helmholtz sur la fonction de dissipation, et l'on montre que la condition nécessaire et suffisante pour qu'il existe une perturbation non nulle est que le mouvement de base soit rotationnel ou divergent.

---

Summary The thermo-hydrodynamical equation for an arbitrary finite mass of the fluid is first of all deduced. This equation realizes the synthesis of the equations of motion, the equation of continuity, the equation expressing the first principle of thermodynamics and the equation of state. In its primary form, the thermo-hydrodynamical equation cannot be easily applied, for several reasons, to the investigation of the energy transformations in a given mass. However, by considering the separation of the motion in a basic motion and a perturbation, and applying the thermo-hydrodynamical equation to the same mass in the real and the basic motion (in other words, to a mass with the same displacements of its boundary surface in the real as in the basic motions), a much more simple (but still exact) form of this equation can be derived. This new form expresses the perturbation of the kinetic energy of the motion around the gravity centre of the mass as a function of the perturbation of its enthalpy (margulesian term) and the perturbation of the energy dissipation inside the mass by the frictional stresses. A first result follows from this equation, which states that the perturbation of the energy dissipation by the frictional stresses must necessarily and efficiently contribute, in some volumes of the fluid, to an increase of the kinetic energy of the perturbations.The enthalpy variation can be expressed as a function of the motion of the gravity centre of the mass. It can then be shown that the temporal variation of the enthalpy perturbation must vanish for any mass with no perturbation of the motion of its boundary surface. This property then leads to the second central result of the paper, which states that the temporal variation of the perturbation of the kinetic energy of the motion around the gravity centre of such a mass is due solely to the perturbation of the rate of energy dissipation by the frictional stresses.In the author's opinion, these results lead to a radical change of attitude towards the fundamental problem of the origin of the energy of the perturbations. They show, for instance, that any margulesian or generalized margulesian perturbation model, consisting essentially in a mechanism borrowing its kinetic energy from the enthalpy of the mass, should be rejected.The basic motion is the direct effect of the thermodynamical and mechanical external actions and must be considered as the motion which realizes, at any moment, a condition of minimum temporal variation for its properties. Consequently, an essentially positive dissipation function must exist at any point in the basic motion. The corresponding law for the frictional stresses is necessarily an isotropic Hooke's law. The real motion of the fluid, under the influence of the same external actions, differs from the basic motion because the real law of the frictional stresses is not strictly an isotropic Hooke's law. At any moment, the perturbation is the integrated result, for all the life history of the fluid, of the difference between the two laws of the frictional stresses.Neglecting however differentially, at a given moment, the part of the frictional stresses not corresponding to an isotropic Hooke's law, a generalization of Helmholtz theorem on the dissipation function can be derived, with the consequence that the necessary and sufficient condition for a non vanishing perturbation is a rotational or divergent basic motion.

---

---

Communication à la 3ème Assemblée de la «Società Italiana di Geofisica e Meteorologia» (Gênes, 15–17 Avril 1955).     

Flow toward periodic tile drains

The method of conformal mapping is applied to the analysis of transient flow toward parallel periodic drains in a semi-infinite aquifer taking into consideration the non-linear boundary conditions on the free surface. The mapping function is expressed as a power series in time and the seepage domain is mapped onto a domain of an auxiliary complex variable. Mapping is performed in such a manner that the free surface will always remain the real axis. Calculations are carried out for different ratios of drain depth to drain spacing using various drain diameter to depth ratios.     

Small-scale spatial variation of macrobenthic community structure

Examination of small-scale spatial variation in essential to understanding the relationships between environmental factors and benthic community structure in estuaries. A sampling experiment was performed in October 1993 to measure infauna association with sediment composition and salinity gradients in Nueces Bay, Texas, USA. The bay was partitioned into four salinity zones and three sediment types. Higher densities of macrofaua, were found in sediments with greater sand content and in areas with higher salinity. High diversity was also associated with high homogeneous salinity (31–33‰) and greater sand content. Macrofauna biomass and diversity were positively correlated with bottom salinity, porewater salinity, and bottom dissolved inorganic nitrogen (DIN). Furthermore, species dominance shifted along the estuarine gradient.Streblospio benedicti dominated at lower salinity, but,Mediomatsus ambiseta andMulinia lateralis were the dominant species at higher salinity. Statistical analyses revealed significant correlations for sediment characteristics (i.e., increased fine sediments, water content, and total organic carbon) with decreased total abundance and diversity. Increased salinity and DIN were correlated with increased total biomass, diversity, and macrofauma community structure. These physico-chemical variables are regulated by freshwater inflow, so inflow is an important factor influencing macrofauna community structure by indirectly influencing the physico-chemical environment.     

Survival of crucian carp,Carassius carassius,exposed to a high low-molecular weight inorganic aluminium challenge

Crucian carp were exposed to three combinations of pH and inorganic aluminium concentrations for 25 days. Mortality, plasma chloride and haematocrit, and gill aluminium content were investigated. No mortality was observed in any of the three exposures. Crucian carp survived acidic Al-rich water (pH 5.17) with a high concentration of low-molecular weight inorganic Al species (242 µgl^–1) for 25 days. These fish had lowered plasma chloride levels and high amounts of aluminium on their gills compared to fish exposed to acidic Al-poor water (pH 5.16 and 12 µgl^–1 Al_i) and control water (pH 6.29 and 4 µgl^–1 Al_i). Haematocrit was the same in all three exposures. Because aluminium was not acutely toxic to the anoxia tolerant crucian carp, the present results give support to the hypothesis that Al polymerization with subsequent hypoxia is of high importance for the mechanism of acute Al toxicity to fish.     

Global lumped-parameter model with physical representation for unbounded medium

A systematic procedure to construct a consistent global lumped-parameter model consisting of springs, dashpots and possibly masses with frequency-independent coefficients connecting the degrees of freedom of the nodes of any structure-medium interface for the unbounded medium is presented. The dynamic-stiffness matrix is first diagonalized which then permits each term to be modelled independently from the others. Physical insight is thus provided. Alternatively, the (symmetric) static-stiffness and damping matrices and possibly mass matrix of the unbounded medium can be established directly.     

Geochronological constraints on the evolution of a suture: the Ossa-Morena/Central Iberian contact (Variscan Belt,south-west Iberian Peninsula)

One of the main tectonic boundaries of the Variscan Belt in the Iberian Peninsula is the Ossa-Morena/Central Iberian contact. This contact is marked by a highly deformed unit (Central Unit) which recorded an initial high-pressure/high-temperature metamorphic evolution. Rb-Sr whole-rock isotopic data from three gneissic bodies cropping out in the Central Unit yield two Late Proterozoic ages (690 ± 134 and 632 ± 103 Ma) and an early Palaeozoic age (495 ± 13 Ma), which we interpret as protolith ages. The two Late Proterozoic orthogneisses show initial ⁸⁷Sr/⁸⁶Sr ratios typical of mantle-derived materials or those with significant mantle participation (⁸⁷Sr/⁸⁶Sr > 0.709). These new radiometric data, together with ages previously published and the structural evolution of the Central Unit, lead to the conclusions that: (1) there are magmatic protoliths of Late Proterozoic and Early Palaeozoic ages; (2) the metamorphic evolution of this area, including the high-pressure event, belongs to the Variscan orogenic cycle; (3) the deformations observed affect the rocks of the entire Central Unit, accordingly they are post-Ordovician, i.e. Variscan; and (4) consequently, the Ossa-Morena/Central Iberian contact is interpreted here as a Variscan suture.