Interpretation of petrographic anisotropy in ornamental granites based on P wave velocity measurements

The existence of a possible anisotropy, determined by the orientation of any mineral or by micro­crack network in granite rock, isn´t easily detected by the naked eye. Five granitic rocks from Galicia (Spain), namely Albero, Gris Alba, Gris Mondariz, Rosa Porriño and Traspielas, were characterized petrographically by means of textural and mineralogical studies, using optical polarizing microscopy, and fractographic studies were carried out under scanning electron microscopy. Longitudinal wave propagation velocity was measured in three orthogonal directions on cubic samples, oriented according to rift surface (known in quarry works like the preferential partition surface visible in the blocks). Vp was measured on dry and water saturated samples. All the dry samples showed an anisotropic behaviour of Vp. Models of microcrack network distribution and possible mineral grain orientation were developed based on the obtained data.

Characterisation and Modelling of Gravity Pre-Concentration Amenability Using LST Fluidisation in a REFLUXTM Classifier

Samples of the feed, underflow and overflow from water-based separations conducted using a continuous REFLUXTM Classifier involving inclined channels with a 3 mm spacing have been fractionated. Another REFLUXTM Classifier operating in a semi-batch configuration using a dense fluidising medium of lithium heteropolytungstates (LST) was used to determine the density distributions of the three streams. The partition surface of the separator was quantified, and the technique was validated against sink/float data for a −300 + 38 µm chromite ore separation. It was found that the LST flow fractionation determined the D50 with remarkable accuracy across the entire size range, with the Ep values also very good above 75 µm. For water-based continuous separations involving a gold ore covering the size range −1.0 + 0.090 mm, the D50 varied with particle size to the power −0.22 and the Ep remained relatively constant at approximately 170 kg/m3 for each of the narrow particle size ranges. These results were consistent with the partition surface validated based on the much finer size range of the higher density chromite ore. The performance of the continuous system was then modelled, with the results shown to agree well with separations conducted on the feed. This approach has been developed as an alternative to using the sink/float test, thus offering a new option with both a lower cost and minimal health and environmental risk. The findings from this study can in turn be used to assess the amenability of a given ore to gravity pre-concentration.

Determination of partition surface of grained material by means of non-classical approximation methods of distributions functions of particle size and density

In this paper, the grained material analyzed was hard coal collected from one of the mines located in Upper Silesia. Material was collected from a dust jig where it was separated in industrial conditions by concentrate and waste. It was then screened in sieves and it was separated in dense media into density fractions. Both particle size distribution and particle density distribution for feed and concentrate were approximated by several classical distribution functions. The best results were obtained by means of the Weibull (RRB) distribution function. However, because of the unsatisfying quality of approximations it was decided to apply non-parametric statistical methods, which became more and more popular alternative methods in conducting statistical investigations. In the paper, the kernel methods were applied to this purpose and the Gauss kernel was accepted as the kernel function. Kernel method, which is relatively new, gave much better results than classical distribution functions by means of the least squared method. Both classical and non-parametric obtained distribution functions were evaluated by means of mean standard error, the values of which proved that they sufficiently well approximate the empirical data. Such function forms were then applied to determine the theoretical distribution function for vector (D, P), where D is the random variable describing particle size and P – its density. This approximation was sufficiently acceptable. That is why it served to determine the equation of partition surface dependent on particle size and particle density describing researched material. The obtained surface proves that it is possible to evaluate material separation which occurs during mineral processing operations, such as jigging, by means of more than one feature of researched material. Furthermore, its quality confirms that it is justified to apply non-parametric statistical methods instead of commonly used classical ones.

The Stratiform and Convective Components of Surface Precipitation

One year of precipitation records taken from a subset of the World Meteorological Organization (WMO) global rain gauge network has been analyzed. This analysis has shown that the distribution of accumulation of precipitation with the rainfall rate is characterized by an exponential law. This relationship seems to be universal and is present regardless of the averaging interval considered. The data structure suggests that this exponential distribution can be used as a basic state to partition surface precipitation into stratiform and convective components. The physical basis of this approach is investigated and discussed using Monte Carlo simulations based on a simple cloud model. The methodology is validated using a Fourier analysis in time, and average global monthly maps of convective and stratiform precipitation are presented to illustrate the feasibility of the technique.

Surface heterogeneity of rat sperm during maturation

Rat sperm isolated from the caput and caudal epididymis and the vas deferens were subjected to multiple partition in aqueous two-phase systems. The technique was used to reveal heterogeneity of a sperm population with respect to particular surface properties. Sperm from all three regions gave broad distributions indicative of heterogeneous cell populations. Greatest heterogeneity was observed for cauda sperm with caput and was sperm producing similar distributions. Following multiple partition sperm from different regions of the distribution profiles were immunostained with three antibodies known to recognise maturation antigens. The results show that some antigens are acquired during epididymal transit whilst others are present throughout. The partition (surface heterogeneity) seen cannot therefore be explained solely by the distribution of the antigens recognised by 2D6, 6B2 and 3D5.