Exoplanet Transit Database. Reduction and processing of the photometric data of exoplanet transits

We demonstrate the newly developed resource for exoplanet researchers – The Exoplanet Transit Database. This database is designed to be a web application and it is open for any exoplanet observer. It came on-line in September 2008. The ETD consists of three individual sections. One serves for predictions of the transits, the second one for processing and uploading new data from the observers. We use a simple analytical model of the transit to calculate the central time of transit, its duration and the depth of the transit. These values are then plotted into the observed–computed diagrams (O–C), that represent the last part of the application.     

Physical and mechanical properties of the repaired sandstone ashlars in the facing masonry of the Charles Bridge in Prague (Czech Republic) and an analytical study for the causes of its rapid decay

The facing masonry of the Gothic Charles Bridge in Prague (Czech Republic) has been largely altered during nineteenth and twentieth century repairs, due to extensive replacements of weathered sandstone ashlar blocks. Natural stone varieties used during these replacements show different responses to a variety of weathering processes which lead to their rapid decay. The decay of the newer stone has been accelerated by use of Portland cement paste as the binding and fill material, instead of the original hydraulic lime-based and cocciopesto-type mortars. The hardened Portland cement paste makes an almost impermeable barrier, with permeability three to four orders of magnitude lower, compared to the original mortars and natural stone. The low permeability of this new alien material results in the accumulation of water-soluble salts (specifically nitrates, but also sulphates and chlorides) in the facing masonry ashlars, with their crystallisation coming in the form of both sub- and efflorescence, as well as the development of various decay forms (blistering, granular disintegration and/or scaling and flaking). The source of the water-soluble salts can be traced back to previous restoration attempts. These included chemical cleaning (black crust removal) by nitric acid, ammonium hydroxide (‘ammonium water’), or ammonium hydrogen carbonate, all which can be linked to high nitrate content in the efflorescence.     

Geomorphological research of large-scale slope instability at Machu Picchu, Peru

A multidisciplinary approach has been adopted to study the slope movements and landscape evolution at the archaeological site of Machu Picchu and its immediate surroundings. The basic event in the paleogeomorphological evolution of the area was the large-scale slope movement, which destroyed the originally higher ridge between Mt. Machupicchu and Mt. Huaynapicchu. Within remnants of that primary deformation, several younger generations of slope movements occurred. The laboratory analyses of granitoids revealed highly-strained zones on the slopes of Mt. Machupicchu, which strongly affect the largest slope deformation. The borders of the largest slope deformation are structurally predisposed by the existence of fault zones. The majority of various types of slope movements on the so-called Front Slope (E facing) and Back Slope (W facing) are influenced by the alignment between topography and joints. Along with slope movements, fluvial erosion and tectonic disturbance of the rocks have been affecting the evolution of the landscape. A monitoring network for dilatometric and extensometric measurements was used to detect the present-day activity of rock displacements within the archaeological site. In addition to standard mapping of surface hydrogeological phenomena, eleven express slug tests were conducted to verify the infiltration potential of precipitation. The results of these surveys indicate that recent large-scale slope movement as suggested by some previous studies is doubtful, and the detected movements can be explained by individual movements of rock blocks or several other mechanisms including sinking of archaeological structures, subsurface erosion and annual changes in the water content of the soils.     

On the uniqueness of image reconstruction from the amplitude of radiointerferometric response

The theorem is proved that presents a rigorous foundation of the possibility of unique reconstruction of the radio-image of the sourceI(r) from the modulus of visibility function |V(b|=|Î(r)|. This results gives a rigorous explanation of the efficiency of different numerical methods of the image reconstruction using only amplitude data which are widespread in radio-astronomy.     

Long term mobilisation of chemical elements in tephra-rich peat (NE Iceland)

This paper presents geochemical profiles of a tephra-bearing minerotrophic peat column from NE-Iceland obtained using various elemental analyses of the solid phase and the pore water. The influence of tephra grain size, thickness and composition of each tephra on the peat geochemistry was investigated. Interpretations are supported by a statistical approach, in particular by autocorrelation, and by microscopy observations. Minerotrophic peat geochemistry may be strongly dependent upon post-depositional mobilization and possible leaching of elements as demonstrated by Fe and trace metal concentration profiles. Chemical elements, and more specifically potentially harmful metals, can be slowly leached out of volcanic falls during their weathering and re-accumulate downwards. It is emphasised that a tephra deposit can act as an active geochemical barrier, blocking downward elemental movements and leading to the formation of enriched layers. In this study, the formation of poorly amorphous Fe phases above the Hekla 3 tephra is shown. These poorly crystalline Fe phases scavenged Ni.     

Landslide susceptibility assessment using SVM machine learning algorithm

This paper introduces the current machine learning approach to solving spatial modeling problems in the domain of landslide susceptibility assessment. The latter is introduced as a classification problem, having multiple (geological, morphological, environmental etc.) attributes and one referent landslide inventory map from which to devise the classification rules. Three different machine learning algorithms were compared: Support Vector Machines, Decision Trees and Logistic Regression. A specific area of the Fruška Gora Mountain (Serbia) was selected to perform the entire modeling procedure, from attribute and referent data preparation/processing, through the classifiers' implementation to the evaluation, carried out in terms of the model's performance and agreement with the referent data. The experiments showed that Support Vector Machines outperformed the other proposed methods, and hence this algorithm was selected as the model of choice to be compared with a common knowledge-driven method – the Analytical Hierarchy Process – to create a landslide susceptibility map of the relevant area. The SVM classifier outperformed the AHP approach in all evaluation metrics (κ index, area under ROC curve and false positive rate in stable ground class).     

Review of solutions for 3D hydrodynamic modeling applied to aquaculture in South Pacific atoll lagoons

A workshop organized in French Polynesia in November 2004 allowed reviewing the current methods to model the three-dimensional hydrodynamic circulation in semi-enclosed atoll lagoons for aquaculture applications. Mollusk (e.g. pearl oyster, clam) aquaculture is a major source of income for South Pacific countries such as French Polynesia or Cook Islands. This aquaculture now requires a better understanding of circulation patterns to improve the spatial use of the lagoons, especially to define the best area to set larvae collectors. The pelagic larval duration of the relevant species (<20 days) and the size of the semi-closed lagoons (few hundreds of km2) drive the specifications of the model in terms of the spatial and temporal scale. It is considered that, in contrast with fish, mollusk larvae movements are limited and that their cycle occurs completely in the lagoon, without an oceanic stage. Atolls where aquaculture is productive are generally well-bounded, or semi-closed, without significant large and deep openings to the ocean. Nevertheless part of the lagoon circulation is driven by oceanic water inputs through the rim, ocean swells, tides and winds. Therefore, boundary conditions of the lagoon system are defined by the spatial structure of a very shallow rim (exposition and number of hoas), the deep ocean swell climate, tides and wind regimes. To obtain a realistic 3D numerical model of lagoon circulation with adequate forcing, it is thus necessary to connect in an interdisciplinary way a variety of methods (models, remote sensing and in situ data collection) to accurately represent the different components of the lagoon system and its specific boundary conditions. We review here the current methods and tools used to address these different components for a hypothetical atoll of the Tuamotu Archipelago (French Polynesia), representative of the semi-closed lagoons of the South Pacific Ocean. We hope this paper will serve as a guide for similar studies elsewhere and we provide guidelines in terms of costs for all the different stages involved.     

Review: Hydrogeology of weathered crystalline/hard-rock aquifers—guidelines for the operational survey and management of their groundwater resources

Hard rocks or crystalline rocks (i.e., plutonic and metamorphic rocks) constitute the basement of all continents, and are particularly exposed at the surface in the large shields of Africa, India, North and South America, Australia and Europe. They were, and are still in some cases, exposed to deep weathering processes. The storativity and hydraulic conductivity of hard rocks, and thus their groundwater resources, are controlled by these weathering processes, which created weathering profiles. Hard-rock aquifers then develop mainly within the first 100 m below ground surface, within these weathering profiles. Where partially or noneroded, these weathering profiles comprise: (1) a capacitive but generally low-permeability unconsolidated layer (the saprolite), located immediately above (2) the permeable stratiform fractured layer (SFL). The development of the SFL’s fracture network is the consequence of the stress induced by the swelling of some minerals, notably biotite. To a much lesser extent, further weathering, and thus hydraulic conductivity, also develops deeper below the SFL, at the periphery of or within preexisting geological discontinuities (joints, dykes, veins, lithological contacts, etc.). The demonstration and recognition of this conceptual model have enabled understanding of the functioning of such aquifers. Moreover, this conceptual model has facilitated a comprehensive corpus of applied methodologies in hydrogeology and geology, which are described in this review paper such as water-well siting, mapping hydrogeological potentialities from local to country scale, quantitative management, hydrodynamical modeling, protection of hard-rock groundwater resources (even in thermal and mineral aquifers), computing the drainage discharge of tunnels, quarrying, etc.

     

Formation and shock impact history of the Csatalja ordinary chondrite

The analysis of the Csatalja H4 chondrite (which was found in August 2012) suggests shock-related textures and spatial inhomogeneities, indicating a complex geological history. In the most heavily fractured and sheared units, small opaque grains and older fractures have locally enhanced the shock effect, producing melt. While the impact textures were evident in most units of the meteorite, mechanical shearing is apparent in only two units, suggesting that these units might have been present at somewhat different locations inside the parent body. Shearing also occurred at the border of the so-called xenolith unit, confirming its mechanical mixing with the other units. Besides fragmentation and melting, chemical changes due to impact have also been identified, producing compositional homogenization of olivines in 30% of the investigated area of the sample's thin section (23 mm²), and moderate accumulation of Fe, Ca, and Na in the strongly shocked zones, initiating crystallization of feldspar in veins with a specific spatial distribution (feldspar glass with metal–sulfide globules). Analyzing the high P–T minerals, the peak shock pressure and temperature values differed substantially in the various units, ranging between 2 and 17 GPa, 100 and >1200 °C. The xenolith unit crystallized more slowly after the impact event and does not show shock impact alterations, suggesting that it was formed in a deeper region of the parent body. This was later shifted to its current surroundings and was lithified (fixed) to the rest of the sample. This “randomly selected” Csatalja sample provides information on the range of the formation temperatures, pressures, and processes that contributed to the heterogeneity of meteorites at the mm spatial scale, in general. The identified heterogeneity is a result not purely of the shock effects but also of the different pre-shock structural characteristics. The shock also mixed fragments mechanically that have been formed at different environments, with at least several dozens or even 100 m depth in the parent body.     

Actual state of European wetlands and their possible future in the context of global climate change

The present area of European wetlands is only a fraction of their area before the start of large-scale human colonization of Europe. Many European wetlands have been exploited and managed for various purposes. Large wetland areas have been drained and reclaimed mainly for agriculture and establishment of human settlements. These threats to European wetlands persist. The main responses of European wetlands to ongoing climate change will vary according to wetland type and geographical location. Sea level rise will probably be the decisive factor affecting coastal wetlands, especially along the Atlantic coast. In the boreal part of Europe, increased temperatures will probably lead to increased annual evapotranspiration and lower organic matter accumulation in soil. The role of vast boreal wetlands as carbon sinks may thus be suppressed. In central and western Europe, the risk of floods may support the political will for ecosystem-unfriendly flood defence measures, which may threaten the hydrology of existing wetlands. Southern Europe will probably suffer most from water shortage, which may strengthen the competition for water resources between agriculture, industry and settlements on the one hand and nature conservancy, including wetland conservation, on the other.