Macroscopically‐Zoned Grandite from the Garnetite Skarn of Meka Presedla (Kopaonik Mountain,Serbia)

The macroscopically-zoned grandite from the garnetite skarn of Meka Presedla (Kopaonik Mountain, Serbia) was studied with optical microscopy, electron microprobe analysis (EMPA), Fourier transform infra-red (FT–IR), and Raman methods. The EMPA results indicate that the main core–rim compositional variations (Ca2.93–2.97Mn0.05–0.06Mg0.00–0.01Al1.14–1.26Fe3+0.72–0.83Ti0.00–0.02Si2.97–3.02O12) slightly differ along the zones, showing evidence for a quasi-cyclic alternation of the oscillatory zoning nature. Among this, considerable variation is observed only by the Al–Fe3+ substitutions in the octahedral site. The EMPA also indicate that the grandite zones compositionally vary, mostly within ±1 and ±2 mol% of the homogeneity level range, that is, Grs64±1Adr36±1Sps2 (A), Grs62±1Adr38±1Sps2 (B), Grs59±2Adr40±2Sps2 (C), Grs58±2Adr41±2Sps2 (D), and Grs58±1Adr41±1Sps2 (E). Therefore, the investigated garnet can be considered as relatively highly homogeneous. The majority of compositions lie within the narrow miscibility region of 0.58±2相似文献   

On the First Anthropic Argument in Astrobiology

We consider the little-known anthropic argument of Fontenelledealing with the nature of cometary orbits, given a year before the publication of Newton'sPrincipia. This is particularly interesting in view of the rapid development of therecently resurgent theories of cometary catastrophism and their role in the modern astrobiologicaldebates, for instance in the ``rare Earth' hypothesis of Ward and Brownlee.     

Characterization and seasonal variations of surface active substances in the natural sea surface micro-layers of the coastal Middle Adriatic stations

Surface micro-layer (ML) samples were collected in different seasons over a long time period in the coastal area of the Middle Adriatic Sea including the seawater Rogoznica lake location and the semi-enclosed estuarine Martinska station. Natural surface micro-layers were studied as original samples and as ex-situ reconstructed films after previous extraction by organic solvents of different polarities (n-hexane and dichloromethane). Using alternating current (AC) voltammetry (out-of-phase mode) the concentration of surface active substances (SAS) in original ML of both locations was determined, and the enrichment factor (EF) in the ML was related to the underlayer water (ULW) samples collected at 0.5 m depth. Seasonal variability of SAS concentrations of the ML was observed at both locations. The ex-situ films were studied using a modified AC voltammetry method (out-of-phase mode) transferring an organic extract of natural micro-layers spread onto electrolyte from the air-water interface to the mercury electrode surface. The comparison of adsorption characteristics for model lipids of different polarities and those of transferred ex-situ reconstructed films has revealed that different types of lipid material were present in each ex-situ film of the same micro-layer. Additional characterization of the surface active material of natural MLs was carried out by AC voltammetry (in-phase mode) using cathodic reduction of cadmium ions as an indicator of permeability of different films adsorbed at the mercury electrode. The SAS of ML of both investigated locations induced an inhibition effect to the reduction of cadmium ions. Seasonal variations of inhibition have also been noticed. The electrochemical study contributed to the physicochemical characterization of the surface active matter of the surface micro-layer with the emphasis to the role of lipids which, although they represent a minor fraction of the total micro-layer organic material, contribute considerably to the micro-layer formation and stabilization at the air–water interface.     

Dynamical evolution of the Hungaria asteroids

The Hungarias are a stable asteroid group orbiting between Mars and the main asteroid belt, with high inclinations (16–30°), low eccentricities (e < 0.18), and a narrow range of semi-major axes (1.78–2.06 AU). In order to explore the significance of thermally-induced Yarkovsky drift on the population, we conducted three orbital simulations of a 1000-particle grid in Hungaria a–e–i space. The three simulations included asteroid radii of 0.2, 1.0, and 5.0 km, respectively, with run times of 200 Myr. The results show that mean motion resonances—martian ones in particular—play a significant role in the destabilization of asteroids in the region. We conclude that either the initial Hungaria population was enormous, or, more likely, Hungarias must be replenished through collisional or dynamical means. To test the latter possibility, we conducted three more simulations of the same radii, this time in nearby Mars-crossing space. We find that certain Mars crossers can be trapped in martian resonances, and by a combination of chaotic diffusion and the Yarkovsky effect, can be stabilized by them. Therefore, some Hungarias (around 5% of non-family members with absolute magnitudes H < 15.5 and 10% for H < 17) may represent previously transient Mars crossers that have been adopted in this manner.     

Deficit and surplus of precipitation as a continuous function of time

The quantitative measure of drought is a complex problem. A common factor in all types of drought is that they originate from a deficiency of precipitation. The difference between the real and potentially expected daily precipitation amount is what we have used to define the continuous function of daily deficit and surplus of precipitation (DSP). We have also defined the monthly and yearly DSP. We tested the precipitation data series for the normal climatic period 1961–1990 observed at the Meteorological Observatory of Belgrade. The DSP considers that the intensity of drought during the current period is dependent upon the current precipitation plus the cumulative precipitation of the previous period. When applied to longer periods, this function denotes dry and wet periods.     

Sensitivity analysis of the 1-D convective cloud model outputs on the dynamical parameters

Summary Forced 1-D time-dependent numerical model of Cb cloud is used to analyse the sensitivity of the model products on dynamical parameters. The model considers the processes of horizontal entrainment, forced lifting through the cloud base as well as the six forms of water substance: water vapour, cloud water, cloud ice, rain, snow and hail. Atmospheric soundings for deep storm situation are used as initial and evironmental conditions.The maxima model values of vertical velocity, cloud water, rain water and ice mixing ratios, temperature excess, cloud top height and radar reflectivity are under the strong influence of the parameters of entrainment, amplitude of initial vertical velocity and forced vertical velocity. The most visible influence is that of forced vertical velocity on the ice content.The model values agree well with observations in one case for selected dynamical conditions.

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Zusammenfassung Ein 1-D-zeitabhängiges numerisches Modell einer Cumulonimbuswolke wird für eine Sensitivitätsanalyse der Modellergebnisse nach dynamischen Parametern herangezogen. Im Modell werden Prozesse des horizontalen Entrainments und der erzwungenen Hebung durch die Wolkenbasis sowie Wasser in sechs Erscheinungsformen beachtet: Wasserdampf, Wolkenwasser, Wolkeneis, Regen, Schnee und Hagel. Atmosphärische Sondierungen von heftigen Sturmsituationen werden als Anfangs- und Randbedingungen verwendet.Die maximalen Modellwerte der Vertikalgeschwindigkeit, des Wolken- und Regenwassers und des Eismischungsverhältnisses, des Temperaturüberschusses, der Höhe der Wolkenobergrenze und der Radarreflektivität werden stark von den Entrainmentparametern und der Amplitude der ursprünglichen wie der erzwungenen Vertikalgeschwindigkeit beeinflußt. Am sichtbarsten ist der Einfluß der erzwungenen Vertikalgeschwindigkeit auf den Eisgehalt.Die Modellwerte stimmen gut mit Beobachtungen für einen Fall mit ausgesuchten dynamischen Bedingungen überein.

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Sensitivity study of the influence of cloud droplet concentration on hail suppression effectiveness

A cloud-resolving mesoscale model with a two-moment microphysical scheme has been used. The software package for cloud seeding and two categories of precipitation elements (graupel and frozen raindrops) are incorporated in the model. The aim of this study was to investigate the impact of cloud droplet concentration on hail suppression effectiveness. The concentration level of cloud droplets is prescribed in the model. We performed sensitivity tests of precipitation amounts (rain and hail) on the cloud droplet concentration in unseeded and seeded cases. We demonstrated for the unseeded case that increasing the concentration of cloud droplets created a reduction in rain accumulation, while the amount of hail accumulation increased. It is necessary to understand whether natural diversity in the cloud droplet concentration can affect the effectiveness of hail suppression. For operational cloud seeding activities, it would be helpful to determine whether it is possible to suppress hail if we know the optimal level of concentration for cloud droplets. Our study showed that hail suppression effectiveness had the greatest influence on lowering cloud droplet concentration levels; suppression effectiveness decreased as the cloud droplet concentration increased.     

Cooling Radius vs. Absorption Size of Galaxies

The discussion of the relationship between cooling radius in two-phaseadiabatic halo models and observationally established maximal radiusof absorption in luminous galaxies at low redshift is presented. It isof paramount importance that any viable model of the halo is able toreproduce empirical value of the absorption cross-section of normalgalaxies and its scaling with luminosity. Several ways for bringingthe theoretical and observational values into agreement are outlined.It is of great methodological importance to fully assess the difficultiesany model is likely to encounter when testing predicted extent ofabsorption and column density distribution against recently obtainedlow-redshift Ly absorption data.     

Seasonal and interannual variations in pigments in the Adriatic Sea

Spatial and temporal variability of pigments was studied from the CZCS satellite data and fromin situ chlorophyll and transparency for the period 1979-1985. The three Adriatic sites, Northern, Middle, and Southern Adriatic are differently influenced by meteorological, hydrological and oceanographic parameters. The differences between seasonalin situ chlorophyll and remotely sensed pigment concentrations (from CZCS satellite data) from the Adriatic are large in winter. Through the correlation analysis, pigments were compared to meteo-oceanographic and hydrological parameters from different Adriatic sites. The PCA (principal component analysis) was applied to the pigment data series and significant components were compared. Different correlations are obtained for warm and cold periods of the year pointing to seasonal differences in the underlying mechanism of pigment variability. The first PC is influenced mainly by temperature. In the warm period more parameters seem to influence the pigment field, than in the cold period. The pigments in the Adriatic are in good correlation to a number of hydrologic and meteo-oceanographic factors.