Extracting flow structures from tracer data

A method of visualizing structures in closed chaotic flows out of homogenous particle distributions is presented in the example of models of a meandering jet. To this end, the system will be leaked or opened up by defining a region of the flow, so that a particle is considered to be escaped if it leaves this region. By applying this method to an ensemble of nonescaped tracers, we are able to characterize mixing processes by visualizing the converging and stretching filamentations (stable and unstable manifolds) in the flow without using additional mathematical tools. The possibility of applying the algorithm to analyze buoy data, and a comparison with the finite time manifolds are discussed.     

Assessment of evaporation and water fluxes in a column of dry saline soil subject to different water table levels

Dry saline soils are common in the arid and hyper‐arid basins located in the Chilean Altiplano, where evaporation from shallow groundwater is typically the major component of the water balance. Thus, a good understanding of evaporation processes is necessary for improving water resource planning and management in these regions. In this study, we conducted laboratory experiments with a natural saline soil column to estimate evaporation rates and assess the liquid and water vapor fluxes under different water table levels. Water content, electrical conductivity and temperature at different depths were utilized to assess the liquid and water vapor fluxes in the soil column. We observed movement of water that dissolves salts from the soil and transports them to areas in the column where they accumulate. Isothermal liquid flux was predominant, while thermal and isothermal liquid and thermal water vapor fluxes were negligible, except for deep water table levels where isothermal and thermal water vapor fluxes had similar magnitude but opposite directions. Differences observed in total fluxes for all water table levels were due to different upward and downward fluxes, which depend on changes in water content and temperature within the soil profile. Both the vapor flux magnitude and direction were found to be very sensitive to the choice of empirical parameters used in flux quantification, such as tortuosity and the enhancement factor for local temperature gradients in the air phase within the column. Copyright © 2013 John Wiley & Sons, Ltd.     

Mhd Leaky Waves in a Layered Plasma: II Mechanisms of Leakage

The application of Fourier analysis to study leaky waves has the advantage of simplicity, but it is not clear why the complex roots of the dispersion relations represent leaky waves, nor how the leakage occurs. We investigate the different kinds of leakage that can occur in a three layer plasma, and to which Fourier pseudomodes they are associated. We find four basic mechanisms, called surface mode ..., single interface ..., trapped wave ... and lost insulation leakage. These mechanisms appear in pure form only near certain limiting cases, in which the parameters of the problem take some special values. As soon as the parameters depart significantly from the limiting values, the behavior of the leaky wave complicates and mixtures of the mechanisms occur, in varying amounts. In consequence different points of the same complex branch of the spectrum may correspond to different mechanisms. All the complex branches of the spectrum correspond to leaky waves, but in general it is not possible to classify them according to type of leakage, except close to a limiting case. Since in a three layer configuration there are many of these, the spectrum of leaky waves is very complicated.     

Spatial distribution and ecotoxicity of petroleum hydrocarbons in sediments from the Galicia continental shelf (NW Spain) after the Prestige oil spill

The distribution of aliphatic and aromatic hydrocarbons was determined in surface sediments collected at 36 stations along the Galicia continental shelf (NW Spain), following the Prestige oil spill. Sampling was performed in December 2002, just after the accident, and in February and September 2003. Concentrations of PAHs (summation operator 13 parent components) were in the range of 0.9-422 microg/kgdw, the highest values being close to coastal urban areas (e.g. Pontevedra and A Coru?a), whereas in the stations of the area most heavily impacted by the spill (off Costa da Morte) concentrations were in the range of 14.8-89.6 microg/kgdw, with a certain predominance of alkylated compounds, which may suggest a mixture of petrogenic and pyrolytic sources. The detailed study of petrogenic molecular markers (e.g. steranes and triterpanes) showed the occurrence of an old (weathered) petrogenic chronic pollution in the shelf sediments but not of the Prestige oil, with the possible exception of few stations in the area of Costa da Morte. This was attributed to the heavy nature of the spilled oil that was barely dispersed in the water column and mainly stranded on the coast or sedimented in the form of oil patches. The addition of increasing amounts of fuel oil to a representative sediment sample showed that the molecular indices were indicative of the presence of the Prestige oil when the amount was above 1g/kg of sediment. The toxicity of selected samples (showing the higher PAH concentrations) was tested using the bivalve embryogenesis bioassay. Embryogenesis success reached high values in all cases (80-88%, with 86% in the control), indicating a lack of toxicity in the sediments and supporting the conclusion that the patchiness of the fuel eventually reaching the seafloor reduced its impact on the benthic communities of the Galician shelf.     

Griquait mit rhombischem Pyroxen (Granatwebsterit) von Borek bei Stupná bei Křemže (Krems) in Böhmen

Zusammenfassung Es wird das Vorkommen von Griquait mit rhombischem Pyroxen (Granatwebsterit) von einem Feld am Borekwald, kaum 1 km westlich von der Gemeinde Stupná bei Keme südöstlich von eské Budjovice (Böhm. Budweis), beschrieben. Den Mineralgehalt des untersuchten Gesteines bilden Enstatit, Endiopsid, Pyrop, Amphibol, Spinell, Plagioklas und ein Mineralgemengteil in Form von Kelyphit oder Symplektit. Das Gestein fällt durch seinen hohen Gehalt an Magnesium auf. Es wird für saures Äquivalent der Peridotite gehalten.

---

Griquaite with orthorhombic pyroxene (Garnetic Websterite) from Borek at Stupná near Keme in Bohemia

Summary The occurrence of griquaite with orthorhombic pyroxene (garnetic websterite) is described; it lies in a field near the Borek forest, scarcely 1 km west of the village Stupná near Keme, SE of eské Budjovice (South Bohemia). The mineral content of the rock studied consists of enstatite, endiopside, pyrope, amphibole, spinel, plagioclase and a mixture of minerals in the form of kelyphite or symplectite. The rock is interesting because of its high magnesium content. It is considered to be an acid equivalent of peridotite.

---

---

Mit 1 Abbildung     

Andalusite in granulites of the bohemian massif

Summary In granulites of South-Bohemia not only the usually occurring Al₂SiO₅ polymorphs, kyanite and sillimanite, were found but also andalusite. Its presence indicates that the metamorphic development of these granulites is characterized by a high PT-gradient. The granulitic rocks of the Bohemian Massif can be regarded as a facies series ranging from the granulite facies through the amphibolite facies to the hornblende-hornfels facies. The lower limit of the PT-conditions of this series should be placed below the position of the triple point of Al₂SiO₅.

---

Andalusit in Granuliten der Böhmischen Masse

Zusammenfassung In den Mineralparagenesen der südböhmischen Granulite wurde neben den üblicherweise auftretenden Al₂SiO₅-Modifikationen, Disthen und Sillimanit, auch Andalusit gefunden. Seine Anwesenheit weist darauf hin, daß die metamorphe Entwicklung der erwähnten Granulite durch einen ausgeprägten PT-Gradienten gekennzeichnet wurde. Die Granulitgesteine der Böhmischen Masse kann man als eine Faziesserie ansehen, die von der Granulitfazies über die Amphibolitfazies bis in die Hornblende-Hornfelsfazies reicht. Die untere Grenze der PT-Bedingungen dieser Serie ist unter die Lage des Tripelpunktes von Al₂SiO₅ zu setzen.

---

---

With 5 Figures     

Shortage in the midst of plenty: Labour strategies in four Central and Eastern European cities

Labour shortage was an integral feature of the communist system of economic management and one that seemed most unlikely to persist in the face of systemic transformation. A casual examination of the unemployment rates that have emerged throughout most of Central and Eastern Europe (CEE) during the course of the past decade might suggest that this early assumption was correct. However, within the region the aggregate rate of joblessness, as well as the behaviour of national output, mask the fact that certain, major urban centres appear to have weathered well the storms caused by exposure to western markets and stringent fiscal and monetary policies. In these centres transformation has meant, to a greater or lesser degree, industrial modernisation and this begs the question of whether the human capital portfolios of the inherited labour force match up to the requirements of the new environment. This paper examines the meaning of the concept of labour shortage and presents the findings from a survey of employers in four leading cities of three major CEE economies designed to elicit if, and how, manpower requirements are being met in the present climate. The results indicate that, somewhat paradoxically, labour shortage persists in the more flexible markets of the post-communist era and that firms do not expect the situation to change radically in the near future. This revised version was published online in July 2006 with corrections to the Cover Date.     

Use of Noise to Augment Training Data: A Neural Network Method of Mineral–Potential Mapping in Regions of Limited Known Deposit Examples

One of the main factors that affects the performance of MLP neural networks trained using the backpropagation algorithm in mineral-potential mapping isthe paucity of deposit relative to barren training patterns. To overcome this problem, random noise is added to the original training patterns in order to create additional synthetic deposit training data. Experiments on the effect of the number of deposits available for training in the Kalgoorlie Terrane orogenic gold province show that both the classification performance of a trained network and the quality of the resultant prospectivity map increasesignificantly with increased numbers of deposit patterns. Experiments are conducted to determine the optimum amount of noise using both uniform and normally distributed random noise. Through the addition of noise to the original deposit training data, the number of deposit training patterns is increased from approximately 50 to 1000. The percentage of correct classifications significantly improves for the independent test set as well as for deposit patterns in the test set. For example, using ±40% uniform random noise, the test-set classification performance increases from 67.9% and 68.0% to 72.8% and 77.1% (for test-set overall and test-set deposit patterns, respectively). Indices for the quality of the resultant prospectivity map, (i.e. D/A, D × (D/A), where D is the percentage of deposits and A is the percentage of the total area for the highest prospectivity map-class, and area under an ROC curve) also increase from 8.2, 105, 0.79 to 17.9, 226, 0.87, respectively. Increasing the size of the training-stop data set results in a further increase in classification performance to 73.5%, 77.4%, 14.7, 296, 0.87 for test-set overall and test-set deposit patterns, D/A, D × (D/A), and area under the ROC curve, respectively.