Venus: Cloud optical depth and surface albedo from Venera 8

We have used the measurements of the solar flux obtained by the Venera 8 spacecraft inside the atmosphere of Venus and the values of the Venus spherical albedo to deduce the characteristics of the clouds and of the ground. The method used is the exponential kernel approximation and the results have been tested by exact computations with the spherical harmonics method.A cloud layer with an optical thickness $\text{τ}{}_1\text{? 144}$, an albedo for single scattering $\text{ω}{}_0\text{= 0.9998}$ in the rear infrared, above a Rayleigh layer between 0 and 32 km and a ground of reflectivity ? = 0.4, gives a good agreement with the experimental results. A model with two cloud layers is also discussed.     

An efficient clean-up method for the GC-MS determination of methylsulfonyl-PCBs/DDEs extracted from various marine mammal tissues

Existing methods for analyzing methylsulfonyl-PCBs in animal tissues require multiple laborious clean-up steps prior to quantitation. In this paper, we report a new, efficient method for the isolation and determination of methylsulfonyl-PCB metabolites in the blubber, liver, kidney, lung, and milk from mammals of marine origin using: solvent extraction, GPC fractionation, and clean-up on an adsorption chromatography column prior to analysis by gas chromatography-mass spectrometry. The method is rapid and can be completed in about half the analysis time required by most other reported methods. The method exhibits excellent analyte recoveries (89-95%), and good reproducibilities with CV's ranging from 3-12% depending on analyte concentration. Detection limits are approximately 1 ng/g lipid. The method is further validated by comparing its quantitative results to that of an independent reference analytical method for several different marine mammal blubber samples. Finally, the method is applied to profile the distribution of methylsulfones among the various tissue types studied for a single bottle-nose dolphin (Tursiops truncatus) sample. In addition, the extent of their transplacental transfer from mother to unborn fetus for several pilot whale (Globicephala melaena) mother-fetus pairs is examined.     

Phase-decoupled refraction–diffraction for spectral wave models

Conventional spectral wave models, which are used to determine wave conditions in coastal regions, can account for all relevant processes of generation, dissipation and propagation, except diffraction. To accommodate diffraction in such models, a phase-decoupled refraction–diffraction approximation is suggested. It is expressed in terms of the directional turning rate of the individual wave components in the two-dimensional wave spectrum. The approximation is based on the mild-slope equation for refraction–diffraction, omitting phase information. It does therefore not permit coherent wave fields in the computational domain (harbours with standing-wave patterns are excluded). The third-generation wave model SWAN (Simulating WAves Nearshore) was used for the numerical implementation based on a straightforward finite-difference scheme. Computational results in extreme diffraction-prone cases agree reasonably well with observations, analytical solutions and solutions of conventional refraction–diffraction models. It is shown that the agreement would improve further if singularities in the wave field (e.g., at the tips of breakwaters) could be properly accounted for. The implementation of this phase-decoupled refraction–diffraction approximation in SWAN shows that diffraction of random, short-crested waves, based on the mild-slope equation can be combined with the processes of refraction, shoaling, generation, dissipation and wave–wave interactions in spectral wave models.     

Petrological, organic geochemical and geochemical characteristics of coal from the Soko mine, Serbia

A petrological, organic geochemical and geochemical study was performed on coal samples from the Soko Mine, Soko Banja basin, Serbia. Ten coal and two carbonaceous clay samples were collected from fresh, working faces in the underground brown coal mine from different parts of the main coal seam. The Lower Miocene, low-rank coal of the Soko Mine is a typical humic coal with huminite concentrations of up to 76.2 vol.%, liptinite less than 14 vol.% and inertinite less than 11 vol.%. Ulminite is the most abundant maceral with variable amounts of densinite and clay minerals. Sporinite and resinite are the most common macerals of the liptinite group. Inertodetrinite is the most abundant maceral of the inertinite group. The mineral-bituminous groundmass identified in some coal samples, and carbonaceous marly clay, indicate sub-aquatic origin and strong bacterial decomposition. The mean random huminite reflectance (ulminite B) for the main coal seam is 0.40 ± 0.05% Rr, which is typical for an immature to early mature stage of organic matter.The extract yields from the coal of the Soko Banja basin ranges from 9413 to 14,096 ppm, in which alkanes constituted 1.0–20.1%, aromatics 1.3–14.7%, asphaltenes 28.1–76.2% and resins 20.2–43.5%. The saturated hydrocarbon fractions included n-C₁₅ to n-C₃₂, with an odd carbon number that predominate in almost all the samples. The contents of n-C₂₇ and n-C₂₉ alkanes are extremely high in some samples, as a contribution of epicuticular waxes from higher plants. Acyclic isoprenoid hydrocarbons are minor constituents in the aliphatic fraction, and the pristane/phytane (Pr/Ph) ratio varies between 0.56 and 3.13, which implies anaerobic to oxic conditions during sedimentation. The most abundant diterpanes were abietane, dehydroabietane and 16α(H)-phyllocladane. In samples from the upper part of the coal seam, diterpanes are the dominant constituents of the alkane fraction. Polycyclic alkanes of the triterpane type are important constituents of alkane fractions. The occurrence of ββ- and αβ-type hopanes from C₂₇ to C₃₁, but without C₂₈, is typical for the Soko Banja coals.The major and trace elements in the coal were analysed using X-ray fluorescence (XRF), and inductively coupled plasma-mass spectrometry (ICP-MS). In comparison with world lignites, using the geometric mean value, the coal from the Soko Banja Basin has a high content of strontium (306.953 mg/kg). Higher values than the world lignites were obtained for Mo (3.614 mg/kg), Ni (8.119 mg/kg), Se (0.884 mg/kg), U (2.642 mg/kg) and W (0.148 mg/kg). Correlation analysis shows inorganic affinity for almost all the major and trace elements, except for S, which has an organic affinity.     

Sub-pixel classification of SPOT-VEGETATION time series for the assessment of regional crop areas in Belgium

Global time series of low resolution images are available with high repeat frequency and at low cost, but their analysis is hampered by the presence of mixed pixels and the difficulty in locating detailed spatial features. This study examined the potential of sub-pixel classification for regional crop area estimation using time series of monthly NDVI-composites of the 1 km resolution sensor SPOT-VEGETATION. Belgium was selected as test zone, because of the availability of ample reference data in the form of a vectorial GIS with the boundaries and cover type of the large majority of agricultural fields. Two different methods were investigated: the linear mixture model and neural networks. Both result in area fraction images (AFIs), which contain for each 1 km pixel the estimated area proportions occupied by the different cover types (crops or other land use). Both algorithms were trained with part of the reference data and validated with the remainder. Validation was repeated at three different levels: the 1 km pixel, the municipality and the agro-statistical district. In general, the neural network outperformed the linear mixture model. For the major classes (winter wheat, maize, forest) the obtained acreage estimates showed good agreement with the true values, especially when aggregated to the level of the municipality (R² ≈ 85%) or district (R² ≈ 95%). The method seems attractive for wide-scale, regional area estimation in data-poor countries.     

Empirical regression models using NDVI, rainfall and temperature data for the early prediction of wheat grain yields in Morocco

In Morocco, no operational system actually exists for the early prediction of the grain yields of wheat (Triticum aestivum L.). This study proposes empirical ordinary least squares regression models to forecast the yields at provincial and national levels. The predictions were based on dekadal (10-daily) NDVI/AVHRR, dekadal rainfall sums and average monthly air temperatures. The Global Land Cover raster map (GLC2000) was used to select only the NDVI pixels that are related to agricultural land. Provincial wheat yields were assessed with errors varying from 80 to 762 kg ha⁻¹, depending on the province. At national level, wheat yield was predicted at the third dekad of April with 73 kg ha⁻¹ error, using NDVI and rainfall. However, earlier forecasts are possible, starting from the second dekad of March with 84 kg ha⁻¹ error, at least 1 month before harvest. At the provincial and national levels, most of the yield variation was accounted for by NDVI. The proposed models can be used in an operational context to early forecast wheat yields in Morocco.     

Dissolution kinetics of dolomite: Effects of lithology and fluid flow velocity

The dissolution kinetics of three stoichiometric dolomite specimens (hydrothermal single crystal, microcrystalline sedimentary rock, coarse-grained marble) were studied in aqueous carbonate solutions. Hydrodynamic conditions were controlled through use of a rotating dolomite disk in which one face was exposed to solution and fluid flow regime was defined by spinning rate. The resulting mass transfer properties were uniform across the disk surface. The dissolution experiments were begun at an initially undersaturated condition set by CO₂ at ~ 1 atm dissolved in deionized water. The reaction was followed by measuring concentrations of Ca²⁺, Mg²⁺, HCO₃^?, and pH over time in a free-drift type of experiment at 0, 15, and 25°C.Dissolution rates for all three samples were similar in form and value; grain size effects were insignificant. Ca/Mg was constant throughout each run at 0.81–0.96. From initial conditions, the dissolution rate decreased as the solution became more saturated. At solution conditions still far from equilibrium (ion activity product = 10^?19), rate dropped off sharply to a very low value. Surface morphology, determined by SEM, showed deep narrow holes in the single crystal, while the rocks dissolved along grain boundaries. These features suggested preferential dissolution of energetically favored sites and surface reaction rate control. Initial rates were used to calculate an apparent activation energy of 32 kJ mol^?1 (sedimentary dolomite) and 27 kJ mol^?1 (single crystal).Initial dissolution rates at 25°C and pH ~ 4 for all samples varied with spinning speed and ranged from 1–3 μmol m^?2 s^?1 for laminar flow conditions to almost 3–6 μmol m^?2 s^?1 as the transition to turbulence began. At lower temperatures, the rate was lower, and increasing spinning velocity had less effect. The strongest spinning rate dependence occurred far from equilibrium, and it became a less important factor as the saturation state increased.     

On the use of meiofauna in ecological monitoring: Who needs taxonomy?

Taxonomic problems have hindered the widespread use of meiobenthos for the purpose of pollution monitoring despite its potential usefulness. The question whether it is necessary to go down to species level in order to distinguish assemblages and stations was studied using data on meiofauna densities available from a GEEP-workshop held in Norway, August 1986.

Using the complete species list of harpacticoid copepod and nematode species, the six stations could be clearly separated by different multivariate techniques (TWINSPAN, DCA, MDS, Clustering). The abundance data of the genera, the families and even the orders (in the case of nematodes) still allowed a more or less clear separation of the stations, although their relative relationships were sometimes distorted. Thus, from a practical point of view, it may be sufficient to identify the animals to genus or family level.

It is proven that this result is not due to ecological similarities between congeneric or confamiliar species. The species groups typifying the stations in the TWINSPAN analysis did not contain more confamiliar species pairs than expected from random sorting. Randomly assembled ‘families’ allowed a separation of the stations as clear as that based on taxonomic groups.

We conclude that the information contained in species abundances was preserved, at least partially, when the species are grouped, even at random. The grouping in higher taxonomic categories was as good as any, and more convenient than all the others. However, within the (limited) range of habitats studied, ecological adaptation is achieved nearly exclusively on the species level.     

Comparative paleofloristics of the Albian-early Paleocene in the Anadyr-Koryak and North Alaska Subregions,Part 1: The Anadyr-Koryak Subregion

A high-resolution phytostratigraphic scheme based on plant macrofossils is suggested for the first time for the Albian and Upper Cretaceous of the Anadyr-Koryak Subregion of the North Pacific. Seven phytostratigraphic horizons of the subregion are distinguished based on successive stages in flora evolution substantiated by comprehensive data on described floral assemblages.