The Virtual Solar Observatory—A Resource for International Heliophysics Research

The Virtual Solar Observatory (VSO) has been developed to allow researchers, educators, and the general public to access data and images from the major sources of on-line solar data. The VSO substantially reduces the effort required to locate disparate data sets, and removes the need for the user to locate the data and learn multiple interfaces. The VSO provides a single interface to about 60 geographically distributed data sets including space- and ground-based sources. These data sets incorporate several physical variables including magnetic field, intensity, Doppler velocity, etc., and all wavelengths from X-ray to radio. All layers of the sun, from the interior to the corona, are included. In this paper we describe the system and present the interface that the user will encounter. We also discuss future enhancements planned for the system.     

Elevation of cytochrome P450-immunopositive protein and DNA damage in mussels (Mytilus edulis) transplanted to a contaminated site

Mytilus edulis were collected from a reference site (Port Quin) and an urban/industrial contaminated site (New Brighton) in the UK during June 1999. Levels of PCBs (sigma7 congeners) and CB-138 were determined to be, respectively, 21 fold and 16 fold higher in the mussel digestive glands from New Brighton. Levels of CYPIA-immunopositive protein were 1.5 fold higher (P < 0.05) at the polluted site but the levels of DNA strand breaks were 1.3 fold higher (P<0.05) at the reference site. Mussels from Port Quin were placed in cages at both sites and both transplanted and indigenous populations sampled in September (13 weeks). Mussels transplanted from the reference site to the industrial site, reported elevated levels of CYP1A-immunopositive protein (1.4 fold; P < 0.05) and higher levels of DNA damage (1.2 fold; P < 0.05) compared to caged populations at the reference site and a PCB loading similar to the populations from the polluted site. Moreover, transplanted mussels had DNA damage 1.8 fold greater (P < 0.05) than indigenous mussels at the transplant site. These changes were small but significant when compared to the observed temporal changes in the indigenous populations.     

A Search for Freshwater in the Saline Aquifer of Coastal Bangladesh

In the polder region of coastal Bangladesh, shallow groundwater is primarily brackish with unpredictable occurrence of freshwater pockets. Delta building processes, including the codeposition of fresh-to-saline porewater and sediments, have formed the shallow aquifer. Impermeable clay facies and the lack of a topographical gradient limit the flow of groundwater and its mixing with surface water so controls on spatial variability of salinity are not obvious. By characterizing groundwater-surface water (GW-SW) interactions, this study attempted to identify areas of potable groundwater for the polder communities. We used transects of piezometers, cores, electromagnetic induction, and water chemistry surveys to explore two sources of potential fresh groundwater: (1) tidal channel-aquifer exchange and (2) meteoric recharge. Fresh groundwater proved difficult to find due to heterogeneous subsurface lithology, asymmetrical tidal dynamics, extreme seasonal fluctuations in rainfall, and limited field data. Geophysical observations suggest substantial lateral variability in shallow subsurface conductivity profiles. Piezometers show varying degrees of tidal pressure attenuation away from the channels. Nevertheless, the active exchange of freshwater appears to be limited due to low permeability of banks and surface sediments. Results indicate that pockets of fresh groundwater cannot be identified using readily available hydrogeological methods, so alternative drinking water sources should be pursued. By better understanding the hydrogeology of the system, however, communities will be better equipped to redirect water management resources to more feasible and sustainable drinking water options.     

Temporal patterns in macrograzer effects on epilithic algae and meiofauna: a comparative approach to test for single species and whole grazer community effects

Within the shallow littoral zones of lakes, periphyton is an essential component, representing an important source of primary production and a food resource for herbivores. Periphytic communities are abundantly inhabited by meiofaunal organisms, which are mostly dominated by nematodes. During the last 3 decades, consumer–resource interactions between herbivore consumers and periphytic components (mainly algae) have been intensively studied. Although whole grazer community and single species effects on periphyton are known from field and laboratory experiments, the importance of single, dominant grazer taxa in direct comparison to whole community impacts is unknown. To investigate the continuity of grazing effects of a single, dominant macrograzer (Theodoxus fluviatilis, Gastropoda, Prosobranchia) on epilithic meiofauna and algae with respect to the whole grazer community, a temporally structured field experiment was carried out in Lake Erken (Sweden). Grazer impacts on periphytic algae and meiofauna were tested by controlling macrograzer access to littoral periphyton communities for 8 weeks in an exclosure/enclosure experimental design. Overall, the results showed macrograzer presence to have temporally constant, strongly negative effects on algal biomass as well as meiofaunal abundance and community composition. Moreover, T. fluviatilis alone accounted for up to 80% of the grazing effects, indicative of their ability to regulate periphytic communities in lakes. The present study yields new insights into the effects of a single grazer species and stressed temporal patterns of consumer–resource interactions in freshwater lakes.     

CYP1A- and CYP3A-immunopositive protein levels in digestive gland of the mussel Mytilus galloprovincialis from the Mediterranean Sea

CYP1A-immunopositive protein can be elevated in response to planar PAHs and PCBs in Mytilus sp. digestive gland whilst CYP3A-immunopositive protein has been associated with testosterone 6beta-hydroxylation in fish. Levels of CYP1A- and CYP3A-immunopositive protein were determined in Mytilus galloprovincialis digestive gland microsomes collected from 12 sites in the Mediterranean Sea during May and September 2001. CYP1A-immunopositive protein was significantly highest at contaminated sites whilst CYP3A-immunopositive protein was significantly lowest. A weak negative correlation (r2 = 0.21) was seen between CYP1A- and CYP3A-immunopositive protein. Little evidence of differences at the different sampling times was observed. These results confirm previous work indicating elevation of CYP1A-immunopositive protein in Mytilus sp. digestive gland at contaminated sites. Further study is required to characterise CYP3A-like expression in Mytilus and to elucidate the consequences of possible CYP3A-like down-regulation at contaminated sites.     

Bioaccumulation and histopathological effects of oil on a stony coral

Colonies of the shallow-water Caribbean coral Manicina areolata incorporated petroleum hydrocarbons into their tissues during exposure to water accommodated fractions of No. 2 fuel oil for three months. This contamination was not removed after depuration periods of up to two weeks. Although these corals remained alive, evidence of pathological responses was found which included impaired development of reproductive tissues, degeneration and loss of symbiotic zooxanthellae, and atrophy of mucous secretory cells and muscle bundles.     

Deep-sea sediments in the eastern equatorial Atlantic off the African coast and meteorological flow patterns over the Sahel

Deep-sea mineral dust deposits are a powerful tool allowing to deduct atmospheric flow patterns. Here deep-sea sediments from the eastern tropical Atlantic were used to derive climatic conditions over the African continent where in summer the dust is lifted in the transition zone of the Sahara and the Sahel. The meteorological process causing this aeolian dust injection are the squall lines, the rain bearing disturbances of the Sahel. They produce a high surface wind velocity area in their northern vicinity. The deep-sea deposits of sediments and their spatial patterns allowed to conclude that the dust raising mechanism connected with the squall lines were similar for present day conditions and for the time of the last glacial maximum. The Saharan trades and the African monsoon had about the same extension in either time slice coupled with an identical travel belt of the squall lines. However, the intensity and the frequency of the squall lines were lower in glacial times.

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Zusammenfassung Tiefseesedimente liefern interessante und wertvolle Aufschlüsse über atmosphärische Strömungsbedingungen. Hier werden die Sedimente aus dem Gebiet des östlichen tropischen Nordatlantiks verwendet, um klimatische Angaben über die Strömungsverhältnisse über dem afrikanischen Kontinent zu gewinnen, da die Quelle des Staubes auf dem Kontinent im Übergangsbereich zwischen der Sahara und dem Sahel zu suchen ist. Die meteorologische Ursache des systematischen Staubeintrages in die Atmosphäre sind die regenbringenden sommerlichen Störungen des Sahel («>squall lines»<), die in ihrem nördlichen Randbereich ein Gebiet hoher Windgeschwindigkeit am Boden aufweisen, so daß es hier regelmäßig zu Staubaufwirbelungen kommt. Mit Hilfe der räumlichen und zeitlichen Verteilung der Tiefseesedimente konnte schon früher gezeigt werden, daß während der Periode des letzten Hochglazials die Lage der Grenzzone zwischen Passat und afrikanischem Monsun sich im Vergleich zur Gegenwart nicht verändert hat. Hier wird nun zusätzlich deutlich, daß sowohl die Intensität als auch die Frequenz der «>squall lines»< zum Höhepunkt der Vereisung geringer was als heute.

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Résumé Les sédiments amenés par le vent dans les mers profondes fournissent de précieuses indications sur la distribution des courants atmosphériques. Dans cette note, les sédiments de la partie orientale de l'Atlantique tropical sont examinés en vue de déduire les conditions climatiques régnant sur le continent africain, où la source de la poussière est située entre le Sahara et le Sahel. En effet, l'origine météorologique des apports éoliens sont les pertubations pluvieuses (lignes de grains) qui sont accompagnées sur leur bordure nord de vents de grande vitesse au sol. La distribution des sédiments sur le fond océanique a déjà permis de conclure que le mécanisme de transport était, lors de la dernière glaciation (18.000 ans), semblable à ce qu'il est aujourd'hui. Toutefois, l'intensité et la frequence des perturbations étaient plus faibles qu'aujourd'hui.

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Macroscale friction of granular soils under monotonic and cyclic loading based upon micromechanical determination of dissipated energy

Macroscopic frictional behavior of granular materials is of great importance for studying several complex problems associated with fault slip and landslides. The main objective of this study is to model the macroscale frictional behavior of granular soils under monotonic and cyclic loadings based upon micromechanical determination of dissipated energy at particle contacts. This study is built on the general observation that the externally computed energy dissipation should be equal to the total internal energy dissipation derived from inter-particle sliding and rolling, energy losses from inter-particle collisions, and damping. For this purpose, the discrete element method is used to model a granular soil and determine the stored, dissipated, and damping energies associated with shear loading for applied monotonic and cyclic velocities. These energies are then related to the friction by an application of the Taylor-critical state power balance relationship. Also, the contributions of the different modes of energy dissipation (normal, shear, and rolling) to the total frictional resistance were studied. By changing the inter-particle friction, the simulations showed that the macroscopic friction was nearly constant, the slip friction increased almost linearly with increasing inter-particle friction, and the difference between the two was attributed to the non-energy dissipating dilatancy component. By providing a clear relationship between energy dissipated by micro-scale mechanisms versus the traditional engineering definition based on macro-scale (continuum) parameters, this study provides a means to develop a better understanding for the frictional behavior of granular media.

     

Analysis of rainfall and temperature time series to detect long-term climatic trends and variability over semi-arid Botswana

Arid and semi-arid environments have been identified with locations prone to impacts of climate variability and change. Investigating long-term trends is one way of tracing climate change impacts. This study investigates variability through annual and seasonal meteorological time series. Possible inhomogeneities and years of intervention are analysed using four absolute homogeneity tests. Trends in the climatic variables were determined using Mann–Kendall and Sen’s Slope estimator statistics. Association of El Niño Southern Oscillation (ENSO) with local climate is also investigated through multivariate analysis. Results from the study show that rainfall time series are fully homogeneous with 78.6 and 50% of the stations for maximum and minimum temperature, respectively, showing homogeneity. Trends also indicate a general decrease of 5.8, 7.4 and 18.1% in annual, summer and winter rainfall, respectively. Warming trends are observed in annual and winter temperature at 0.3 and 1.5% for maximum temperature and 1.7 and 6.5% for minimum temperature, respectively. Rainfall reported a positive correlation with Southern Oscillation Index (SOI) and at the same time negative association with Sea Surface Temperatures (SSTs). Strong relationships between SSTs and maximum temperature are observed during the El Niño and La Niña years. These study findings could facilitate planning and management of agricultural and water resources in Botswana.