Ore lead isotope variations in the Proterozoic massive pyrite deposit at Näsliden,Skellefte district,Sweden

The ore lead isotope ratios from the Näsliden deposit are mantle-like in terms of the idealized plumbotectonics model. They suggest that the Näsliden deposit was formed in the Proterozoic equivalent of a Phanerozoic primitive island arc. The mantle-like nature of the lead and its homogeneity indicate that crustal lead does not constitute the major component of the ore lead. Crustal lead contamination is suggested to be the cause of divergences in ore lead isotopic compositions associated with later veins in the deposit.     

Speckle filtering of Synthetic Aperture Radar images using filters with object-size-adapted windows

Speckle degrades the radiometric quality of a Synthetic Aperture Radar (SAR) image. Previous methods for speckle reduction have used a fixed-size window for filtering the entire image. This, however, may not be effective for the entire image, as land covers of different sizes require different filtering windows. In this paper, a novel method is proposed by which each pixel in the image is filtered with a window appropriate for the size of object within it. The real in-phase and the imaginary quadrature components of the SAR images determine the best window size and the pixels in the intensity image are filtered using their own optimal windows. The proposed method is presented for both single- and multi-polarized SAR images, and the results of several common filters that were modified are presented. This approach is applied to two RADARSAT-2 images: one over San Francisco, California, USA and the other over St. John’s, Newfoundland and Labrador, Canada, producing results that were similar to, or outperformed, comparable filters while retaining details and suppressing speckle effectively. While the method was successful for single-look intensity data, it offers great potential for multi-look and amplitude data as well.     

Characterizing proteases in an Antarctic Janthinobacterium sp. isolate：Evidence of a protease horizontal gene transfer event

We report the isolation of a cold-adapted bacterium belonging to the genus Janthinobacterium (named AU11), from a water sample collected in Lake Uruguay (King George Island, South Shetlands). AU11 (gro...     

Macrobenthic surf zone communities of temperate sandy beaches: spatial and temporal patterns

The spatial and temporal patterns within the surf zone epibenthic assemblages were studied in a coastal fringe of Argentina to determine whether assemblage compositions, abundance, species richness and diversity vary spatially and temporarily. Sampling was conducted seasonally in two sandy beaches over 2 years with a benthic sledge used to collect the fauna in the upper centimeters of soft bottom sediments and the epifauna on the sediment surface. Physical variables were measured in the same coastal sites where biological sampling was conducted. A total of 58 morphospecies were collected. Peracarid crustaceans were the most abundant group. The mysid Pseudobranchiomysis arenae (new genus–new species) (29.73 ± 17.79 ind. per sample) and the isopod Leptoserolis bonaerensis (51.54 ± 22.35 ind. per sample) were the most abundant and common species and were present regularly throughout the sampling period. Differences in the surf zone community composition were found between the beaches; these differences could be related to variation in physical parameters such as sand grain size and wave climate, indicating the possible influence of the morphodynamic state of the beaches on the epibenthic assemblages. A seasonal abundance trend was detected, reflecting the changes in abundance of the two dominant species; the richness pattern was not easily detectable due to the sporadic appearance of non‐resident species in the surf zone, probably due to different causes, including dispersion by entry of water from surrounding areas, littoral currents and storms. The surf zone studied presents a complex and dynamic epibenthic community that appears to be influenced by the morphodynamic state of the beach and the dynamic of non‐resident species.     

Reconstruction of Holocene sea-surface salinity in the Skagerrak–Kattegat: a climatic and environmental record of Scandinavia

Holocene sea-surface salinity in the Skagerrak–Kattegat is reconstructed using weighted averaging regression and calibration (WA) of diatom data from core Skagen 3. Diatom data from surface sediments together with 10-yr mean values of salinity and water temperature were used as a modern training set. Canonical correspondence analysis (CCA) was used to identify statistically significant directions of variation within the training set. The results of forward selection of the environmental variables and associated Monte Carlo permutation tests of the statistical significance of each variable, the canonical coefficients, and the intraset correlations of the environmental variables with the CCA axes suggest that summer and winter sea-surface salinities (SSS, WSS) are potentially reconstructable from fossil diatom assemblages. The changes in sea-surface salinity during the Holocene can be correlated with changes in climate of the circum-Baltic area, the current patterns of the Skagerrak–Kattegat, and the development of the Baltic Sea. Generally low SSS and large differences between WSS and SSS (ΔSw-s) during 9000–6000 yr BP might have resulted from a climate with higher precipitation than today in the circum-Baltic area and its catchment, or a climate with maximum precipitation in late spring or early summer. The mechanism behind these patterns may be the combination of the northward shift of the jet stream and a stronger surface westerly penetration into the continent caused by a reduced latitudinal insolation gradient and enhanced land–sea contrast in the early to middle Holocene. It was, however, complicated by local events such as changes in the strength of various currents in the Skagerrak–Kattegat, successions of Baltic brackish and freshwater phases, and hydrodynamic conditions in the circum-Baltic area. © 1998 John Wiley & Sons, Ltd.     

Wave Energy from the North Sea: Experiences from the Lysekil Research Site

This paper provides a status update on the development of the Swedish wave energy research area located close to Lysekil on the Swedish West coast. The Lysekil project is run by the Centre for Renewable Electric Energy Conversion at Uppsala University. The project was started in 2004 and currently has permission to run until the end of 2013. During this time period 10 grid-connected wave energy converters, 30 buoys for studies on environmental impact, and a surveillance tower for monitoring the interaction between waves and converters will be installed and studied. To date the research area holds one complete wave energy converter connected to a measuring station on shore via a sea cable, a Wave Rider? buoy for wave measurements, 25 buoys for studies on environmental impact, and a surveillance tower. The wave energy converter is based on a linear synchronous generator which is placed on the sea bed and driven by a heaving point absorber at the ocean surface. The converter is directly driven, i.e. it has no gearbox or other mechanical or hydraulic conversion system. This results in a simple and robust mechanical system, but also in a somewhat more complicated electrical system.     

Empirical Orthogonal Function Analysis of Daily Rainfall in the Upper Reaches of the Huai River Basin, China

Summary  The design and operation of hydro-structures for flood control and water conservation bring a need for improved characterization of precipitation patterns. A 73 000 km² study area in East Central China is situated in the East Asian monsoon region and experiences a strong seasonality in the rainfall regime. The characteristics of daily rainfall from 230 gauges during 1967–1986 were investigated for four periods in the summer monsoon season using empirical orthogonal function analysis (EOF) and extended empirical orthogonal function analysis (EEOF). The EOF analysis showed that for all four periods most of the variance was explained by an elongated spatial rainfall pattern. The pattern varied in direction, from roughly west-east to southwest-northeast, in the different periods. The zonally oriented patterns were interpreted as being caused by the stationary Mei-Yu front and the southwest-northeast patterns interpreted as cold fronts in cyclones that were developing over the study area. The latitude of the rain belt described by the first mode moved slightly northward with the advance of the East Asian monsoon from the first period, 9–22 June, to the third period, 23 July–5 August, and then withdrew southward again in accordance with the known seasonal movement of the Mei-Yu front. The EEOF analysis was used to show the development of the rainfall area over sequences of three days. During all four periods rainfall intensified on the second day, compared to the first and third days. During the first and last periods, 9–22 June and 5 August–30 September, respectively, there appeared to be little movement in the rainfall. During the second and third periods, the patterns were interpreted as a cold front in a developing cyclone. The results show the connection between the temporal variation in rainfall intensity and the temporal succession of spatial patterns over three day periods and should be used in the construction of design rainfalls for the study area. Received February 10, 1998 Revised June 23, 1998     

Vertical migrations of the mangrove snail Cerithidea decollata (L.) (Potamididae) through a synodic month

The vertical migration on mangrove trunks of the gastropod Cerithidea decollata was followed for 5 weeks, in a Kenyan mangrove. Most of the times, snails forage on the mud surface, during low tide, and climb back on trees well before the incoming tide. As soon as the sea retreats, the downward migration takes place and the snails spread again on the ground. The migratory behaviour of snails can vary widely, depending on the relative tide intensity, and different strategies can be exhibited. Individuals can spend several days on trees without migrating to the ground, around Spring Tides, or else, they might remain on the ground without bothering to migrate upwards, during Neap Tides, when the study area is not reached by the water. These irregular animal behaviours, relating to the complicated tide succession, can hardly be explained by the sole presence of an internal clock, and direct cues seem necessary to switch between different strategies, tuning the snails migratory behaviour to the actual local sea conditions.