Three-dimensional Travel-time Calculation Based on Fermat's Principle

— We present a new travel-time calculation method based on Fermat's principle. In the method, travel times are recursively calculated on horizontal planes of increasing depth. For typical configurations of exploration geophysics, the distance between the planes is on the order of 100 m. The travel times on the first plane are calculated by connecting straight ray segments from the source point to the grid points on the plane and integrating the slowness along each segment. The times on the other planes are calculated by finding the minimum of the combination of the times on the plane above plus the additional time along segments connecting grid points on the two planes. The travel-time calculation method is designed for calculating either the first arrival times, or the time of the shortest travel path arrival. The method is extended to handle vertically transverse isotropic (VTI) media by an approach which increases the computing time only slightly. The algorithm is tested against synthetic examples for isotropic and VTI wave propagation.     

Geology and characterisation of the Pecket coal deposit, Magellan Region, Chile

The geology, petrography and chemical variation of the Pecket coal sequence, Magellan Region (52°57′S, 71°10′W), the only Chilean coal used for electricity generation on a large scale, has been studied in order to predict their combustion behaviour, especially in coal blends. The depositional environment of formation of the coal seams was a swamp rarely exposed to subaerial conditions and was associated with the development of the folded foreland of the Magellan basin during the Tertiary (Oligo–Miocene). The general tectonic regime of the collision of the Antarctic and South American plates is reflected by a system of joints with 40°N–50°W strike. The maceral composition of all six seams studied indicates high contents of vitrinite (>90%), minor content of liptinite (4.7%) and inertinite (<2%). Occurrence of tonstein horizons altered to kaolinite indicates a distal volcanism during peat accumulation. Coal rank varies between lignite and subbituminous (Ro=0.28–0.42%) with an average dry basis calorific value of 5450 kcal/kg, 17 wt.% moisture, 41 wt.% volatile matter, and sulphur content below 0.5 wt.%. The mineral matter (LTA) associated with the coal shows a dominance of kaolinite with quartz, smectite, and minor basanite. SiO₂/Al₂O₃ and Fe₂O₃/CaO ratios of the ashes diminish towards the lower seams. With respect to the utilisation of Pecket coals in combustion, base/acid ratios (B/A) and silica ratios (SR) indicate potential fouling for seams 1, 2, 5, and 6i, with high fouling indexes (Rf) for seams 2 and 5. Pecket coal is excellent for blend combustion due to its low sulphur content.     

Sebkhas as ecological archives and the vegetation and landscape history of southeastern Tunisia during the last two millennia

Sebkhas are temporary lacustrine systems depending on the number and extension of floodings. They may create laminated sediments which can be exploited as ecological archives. Contrary to those of meromictic lakes they are seasonal but not annual. After each flooding a detritus layer and a plasmo-condensed layer of bacteria and algae are formed in the water body or film and during the subsequent dessication a third subaeric layer of evaporites is build up. These laminae show a quasi-textile fabric and they can trap and conserve any dust and fine grained material. A high resolution pollendiagram covering the last two millennia as well as geochemical analysis from a southeastern Tunisian sebkha demonstrate the potentials of these ecological archives.     

Interaction of Aquatic Dissolved Organic Matter(DOM) with Amitrole: The Nature of the Bound Residues

In this study the binding behaviour of the herbicide amitrole with humic substances respectively dissolved organic matter (DOM) is presented. The results of the binding and release experiments using radio actively ¹⁴C-labelled amitrole ledto the conclusion that the binding of amitrole is very low. About 70% of amitrole bound to humic substances was not extractable. The releasable amitrole portion of the purified DOM-amitrolecomplexes led to a harmful effect in the cress test. Solid-state cross polarisation (CP) magic angle spinning (MAS) ¹⁵N-NMR spectroscopy is a powerful spectroscopic method to elucidate the structure of bound xenobiotics. In addition extraction experiments were used resulting in a binding scheme of amitrole to DOM, where above all the covalent bonding occurred via acid amide bonds.     

A long-term photometric study of the pre-main-sequence star V 350 Cep

Results from photographic and CCD photometric observations of the pre-main sequence star V 350 Cep are presented. A continued gradual rise of brightness resembling the light curves of the FUOR type stars is observed. A search in the WFPDB was made to find old photographic observations of V 350 Cep.     

Analysis of Gable-Roofed Building Signature in Multiaspect InSAR Data

The spatial resolution of state-of-the-art synthetic aperture radar sensors enables the structure analysis of urban areas. The appearance of buildings in magnitude images in settlements is dominated by the effects of the inherent oblique scene illumination. In urban residential districts, salient pairs of parallel lines of bright magnitude are often caused by direct reflection and double-bounce signal at gable-roofed buildings. In this letter, the magnitude and interferometric phase signature of gable-roofed buildings are discussed to extract reliable building features for reconstruction. The analysis contains signature changes by varying illumination and building geometry. The presented approach is aiming at the reconstruction of gable-roofed buildings by a knowledge-based analysis considering the discussed effects. The reconstruction results are assessed by using a high-resolution LIDAR surface model as ground truth.      

The Origin and Distribution of Salts on Alluvial Fans in The Atacama Desert,Northern Chile

The Atacama Desert has been predominantly hyperarid since the middle Miocene. Combined ionic and X-ray diffraction analysis shows that calcium sulphate is prevalent on three similar alluvial fans in salar basins across a transect of different environments in Antofagasta Province, northern Chile. Differences between the fans were largely due to the effect of local factors on salt input, secondary redistribution and deposit preservation. Thus carbonate was notable in the High Andes (fan C) and Pre-Cordillera (fan B), whereas in the Central Valley (fan A) greater qualities of the more soluble salts (chlorides and nitrates) probably reflect the higher level of aridity and an oceanic source (the camanchaca). Calcium sulphate distribution on the alluvial fans and on adjacent hilltops indicates an aeolian origin. Evidence from the Pre-Cordillera (fan B), however, suggests that salt input may have been episodic, related to changes in conditions within the general aridity and possibly to stone pavement and soil development. Calcium sulphate sources range from an input in Andean precipitation and the camanchaca to abundant regional evaporite deposits. It is probable, however, that products of Andean volcanism constitute the dominant primary source of calcium sulphate, and that the salt has subsequently been distributed widely within the endoreic basins of the region by a combination of groundwater, surface flow and the wind. © 1997 John Wiley & Sons, Ltd.     

Groundwater recharge estimation from ephemeral streams. Case study: Wadi Tabalah,Saudi Arabia

Estimation of groundwater recharge to an unconfined aquifer is studied using analytical and numerical techniques and results are compared with field observations. There is an acute need for such estimation in water balance studies in arid climates, and the case study in this paper is for such a region. The wetting front movement in the unsaturated zone depends on antecedent soil moisture, the ponded water depth and its duration, and on the position of the water table and the hydraulic properties of the unsaturated zone. A hydraulic connection between the recharge basin and the aquifer is not immediately established because the wetting front is unsaturated. A numerical model is applied to estimate recharge in an arid-zone wadi, and its validity is tested by comparing it with an analytical solution of the equations. The calculated recharge values matched the piezometric levels observed at a well site at the edge of the wadi channel. The total recharge depths found by integration in the time domain provided a good estimate of the transmitted volume of water per unit length of wadi channel. The findings were confirmed by runoff volume measurements at gauging stations located in the basin. © 1997 John Wiley & Sons, Ltd.     

Colluvial deposits in northwest Deccan,India: their significance in the interpretation of Late Quaternary history

The Deccan Trap region exhibits an erosional landscape over a relatively ancient and stable Deccan shield. The Quaternary history of the area has been reconstructed on the basis of evidence from alluvial deposits occurring along the major rivers. However, recent investigations have revealed that evidence for geo-environmental change during the Quaternary Period is also contained in the colluvial deposits that occur in the foothill zones. The colluvial deposits, ranging in thickness from 1 to 10 m, invariably occupy gently inclined pediment slopes. The sediments are presently deeply dissected by gullies, and the process of colluviation has almost ceased. These deposits are best preserved in the semi-arid parts of the region. Detailed textural, geochemical and stratigraphical studies at four different sites reveal similar input processes, the slight variations being attributed to local environmental factors. Scanning electron microscopy studies of some grains indicate marginal contribution of aeolian processes at the time of deposition. Mesolithic artefacts and a few U/Th dates indicate that the colluviation took place during the Late Quaternary. The properties of the deposits suggest relatively high energy conditions as well as a remarkable variability in the intensity of hillslope processes. These properties are indicative of semi-arid conditions during which the regolith was stripped from devegetated hillslopes and was deposited on the pediments. A variety of evidence indicates that the period of colluviation coincided with arid conditions during the Last Glacial Maximum. The geomorphological and archaeological evidence also indicates that incision by gully systems was initiated during the early Holocene humid phase. The environmental conditions deduced for the study area are similar to those reported for other parts of the intertropical zone. © 1997 John Wiley & Sons, Ltd.     

Antiproliferative and apoptosis-inducing potential of 3β-hydroxy-△5-steroidal congeners purified from the soft coral Dendronephthya putteri

The exploration and identification of antiproliferative phytochemicals have received increased attention in medicinal chemistry.In particular,research focused on the toxicology of marine natural products has increased in recent years.Terpenoids,among many secondary metabolites,have been demonstrated to act as effective anticancer agents.Soft corals,a group of marine invertebrates,produce a variety of terpenoids with biofunctional properties.The current study presents the extraction,purification,and identification of sterol congeners from the soft coral Dendronephthya putteri.The method involves 50%chloro form-methanol extraction,polar column fractionation,and analy sis through GC-MS~n.Do se-dependent antiproliferative activity was observed within the sterol-rich fraction(DPCMH 2-4),which consisted of3β-hydroxy-A5-steroidal congeners.This fraction inhibited the growth of HL-60 and MCF-7 cells with IC_(50) values of 25.27±1.43 and 22.81±0.15 μg/mL,respectively.Apoptotic body formation,DNA damage,cell cycle arrest,and apoptotic cell signaling pathway activation were also observed,reinforcing the dosedependent antiproliferative and apoptosis-inducing activity of 3β-hydroxy-A5-steroidal congeners.To our knowledge,this is the first report of anticancer agent identification from the soft coral D.putteri.Based on the observations,these steroidal congeners are promising candidates for the development of anticancer drugs.