Observations of helium and hydrogen emission in quiescent prominences

Observations of a number of helium triplet ( 10830, 4713, 4471, 3889, 4026) and hydrogen (H, , , ) emission line intensities in six quiescent prominences are presented. The regions of prominence and neighboring corona were raster-scanned by the telescope, and all lines were measured concurrently at each point. The instrumental field of view was 5 × 20. The results are compared with previous observations and theory. In particular, the intensity of the 10830 emission relative to the other triplets is found to differ strongly from the predictions of the recent detailed calculations of Heasley et al. (1974) for model quiescent prominences.     

Pelagic trophic transfer efficiency in an oligotrophic, dimictic deep lake (Lake Stechlin, Germany) and its relation to fisheries yield

We investigated trophic transfer efficiency in the pelagic food chain of deep, oligotrophic Lake Stechlin (Germany) by analyses of the primary, secondary, and fish production. Primary production between April and November 2000 was estimated at 78 g C m⁻², pelagic secondary production at 14 g C m⁻², and production of the main planktivorous fish species [European cisco, Coregonus albula (L.)] at 0.77 g C m⁻². Thus, trophic transfer efficiency between primary and pelagic secondary production was around 18%, whereas between pelagic and fish production around 6%. The high efficiency at the first step of the chain is discussed to be due to the high food quality in oligotrophic lakes due to the dominance of Bacillariophyceae and Chlorophyceae rich in essential fatty acids. In turn, the relatively low trophic transfer efficiency between the secondary and the fish production is mainly explained by the avoidance of calanoid copepods as food source by the ciscoes. Concerning the trophic transfer efficiency, results from this study support the general assumption of a 10% transfer between neighbouring trophic levels within ecosystems.     

Geochemistry of peridotites and mafic igneous rocks from the Central Dinaric Ophiolite Belt,Yugoslavia

In the Central Dinaric Ophiolite Belt (CDOB) peridotites and associated metamorphic rocks of various grades tectonically overlie an olistostrome melange of middle to late Jurassic age. Peridotites and underlying slices of mafic granulites (partially transformed to gamet amphibolites) are intruded by doleritic dikes which do not occur in the melange. The melange contains blocks of subgreywackes and cherts as well as those of pillow lavas and massive diabase (spilites). CDOB peridotites are in the spinel peridotite facies, but locally spinel-plagioclase peridotites occur as well. All peridotites have lherzolitic compositions showing several significant element correlations: Al₂O₃, CaO, TiO₂, Na₂O and Cu are negatively correlated and Ni is positively correlated with MgO. Recent estimates of primitive mantle compositions lie near the low-MgO end point of each correlation trend. Al/Ti and Ca/Al ratios of CDOB lherzolites are for the most part higher than the range observed in chondrites. However, when a few samples with extreme compositions are excluded, Al/Ti and Ca/Al are positively correlated with MgO, and the samples at the low-MgO end have near-chondritic Ca/Al but slightly higher than chondritic Al/Ti ratios. Chondrite-normalized REE patterns of CDOB lherzolites show extreme depletions in LREE providing strong evidence for the absence of any metasomatic renrichment. The lack of correlation between highly incompatible elements (LREE) and moderately incompatible elements (HREE, Ti, Na, Al, Ca) together with the extremely low La/Sm ratios suggest that fractional or very small increment melt removal played a role in the genesis of these lherzolites. Four out of five lherzolites yield and apparent Sm-Nd isochron age of 136±15 Ma with an Nb of 6.0±1.1 (bulk rocks and clinopyroxene separates). One sample has an exceptionally high Nd of about 23. The mafic igneous rocks scatter around the lower end of the 136 Ma reference isochron allowing, but not proving, a genetic relationship with a mantle having a Nd isotopic composition which is similar to that of CDOB lherzolites. LIL element abundances of spilites and doleritic dike rocks suggest some hydrothermal alteration. In primitive mantle-normalized concentration diagrams none of these mafic igneous rocks shows a significant negative Nb-Ta anomaly. Chondrite-normalized REE patterns of both rock types are essentially flat. Whereas the inferred primary compositions of the spilites compare well with those of E-type MORBs, the doleritic dike rocks show elemental ratios similar to those normally found in back-arc basin tholeiites.     

Late quaternary organic carbon cycles and paleoproductivity in the Labrador Sea

Accumulation rates of (marine) organic carbon and estimates of paleoproductivity from organic carbon data indicate distinct late Quaternary glacial/interglacial cycles at Ocean Drilling Program (ODP) Site 646. During the last 240,000 years, surface-water productivity was significantly higher in the northern Labrador Sea during interglacial than during glacial times (70 to 170 gC/m²/yr vs. 30 to 70 gC/m²/yr). The reduced glacial productivity is probably caused by a closed sea-ice cover dominating the northern Labrador Sea during glacial intervals.     

Deposit Feeding and Sediment:

Abstract. The feeding of the epibenthic deposit-feeder Holothuria tubulosa GMELIN and its influence on sediment metabolism was investigated from February 1988 to February 1989. Water samples, specimens of H. tubulosa , and samples of freshly egested feces were taken by SCUBA diving in a 5 m deep seagrass bed at the Island of Ischia in the Gulf of Naples (Italy). Particulate organic carbon (POC), particulate organic nitrogen (PON), total particulate carbohydrates (PCHO), and bacterial biomass exhibited higher values in the foregut than in the surrounding sediment. Even the freshly egested feces were richer in the organic components than the sediment. The percentage of growing bacterial cells increased from 4.1 % in the sediment to 12.2 % in the foregut and declined to 11.6 % in the hindgut and 6.2 % in freshly egested feces.
On an annual average, absorption efficiency was highest for bacteria (x = 71%); for PON we calculated a mean absorption efficiency of 20.9%, for PCHO 19.5%. It was estimated that bacterial biomass supplied between 4 and 25 % of the respiratory carbon demand of H. tubulosa. We present evidence that the feeding activity of H. tubulosa stabilizes the bacterial community in the sediment. Furthermore, our data indicate that H. tubulosa reacts quickly to changing conditions, such as sedimented phytoplankton blooms.     

Common-reflection-surface stack — a real data example

The simulation of a zero-offset (ZO) stack section from multi-coverage reflection data is a standard imaging method in seismic processing. It significantly reduces the amount of data and increases the signal-to-noise ratio due to constructive interference of correlated events. Conventional imaging methods, e.g., normal moveout (NMO)/dip moveout (DMO)/stack or pre-stack migration, require a sufficiently accurate macro-velocity model to yield appropriate results, whereas the recently introduced common-reflection-surface stack does not depend on a macro-velocity model. For two-dimensional seismic acquisition, its stacking operator depends on three wavefield attributes and approximates the kinematic multi-coverage reflection response of curved interfaces in laterally inhomogeneous media. The common-reflection-surface stack moveout formula defines a stacking surface for each particular sample in the ZO section to be simulated. The stacking surfaces that fit best to actual events in the multi-coverage data set are determined by means of coherency analysis. In this way, we obtain a coherency section and a section of each of the three wavefield attributes defining the stacking operator. These wavefield attributes characterize the curved interfaces and, thus, can be used for a subsequent inversion. In this paper, we focus on an application to a real land data set acquired over a salt dome. We propose three separate one-parametric search and coherency analyses to determine initial common-reflection-surface stack parameters. Optionally, a subsequent optimization algorithm can be performed to refine these initial parameters. The simulated ZO section obtained by the common-reflection-surface stack is compared to the result of a conventional NMO/DMO/stack processing sequence. We observe an increased signal-to-noise ratio and an improved continuity along the events for our proposed method — without loss of lateral resolution.     

Dimensional analysis of two-phase flow including a rate-dependent capillary pressure–saturation relationship

The macroscopic modelling of two-phase flow processes in subsurface hydrosystems or industrial applications on the Darcy scale usually requires a constitutive relationship between capillary pressure and saturation, the P_c(S_w) relationship. Traditionally, it is assumed that a unique relation between P_c and S_w exists independently of the flow conditions as long as hysteretic effects can be neglected. Recently, this assumption has been questioned and alternative formulations have been suggested. For example, the extended P_c(S_w) relationship by Hassanizadeh and Gray [Hassanizadeh SM, Gray WG. Mechanics and thermodynamics of multiphase flow in porous media including interphase boundaries. Adv Water Resources 1990;13(4):169–86] proposes that the difference between the phase pressures to the equilibrium capillary pressure is a linear function of the rate of change of saturation, thereby introducing a constant of proportionality, the coefficient τ. It is desirable to identify cases where the extended relationship needs to be considered. Consequently, a dimensional analysis is performed on the basis of the two-phase balance equations. In addition to the well-known capillary and gravitational number, the dimensional analysis yields a new dimensionless number. The dynamic number Dy quantifies the ratio of dynamic capillary to viscous forces. Relating the dynamic to the capillary as well as the gravitational number gives the new numbers DyC and DyG, respectively. For given sets of fluid and porous medium parameters, the dimensionless numbers Dy and DyC are interpreted as functions of the characteristic length and flow velocity. The simulation of an imbibition process provides insight into the interpretation of the characteristic length scale. The most promising choice for this length scale seems to be the front width. We conclude that consideration of the extended P_c(S_w) relationship may be important for porous media with high permeability, small entry pressure and high coefficient τ when systems with a small characteristic length (e.g. steep front) and small characteristic time scale are under investigation.     

Could surface roughness be a poor proxy for landslide age? Results from the Swabian Alb,Germany

The potential of surface roughness to quantify geomorphological landforms and processes has been enhanced with the availability of high‐resolution digital terrain models (DTM). Recent studies that attempt to identify landslide features with surface roughness have suggested that this measure of topographic heterogeneity may also be applied to estimate the relative age of landslides. This is a provisional study that explores the potential of this relationship by assessing the ability of surface roughness to act as a proxy for relative landslide age. The surface roughness for a set of 12 dated landslides in the Swabian Alb that occurred between 1789 and 1985 was calculated from a 1 m² spatial resolution LiDAR DTM with three algorithms: root‐mean‐square‐height (RMSH), standard deviation of slope (SDS), and direction cosine eigenvalue ratios (DCE). Scale‐dependence was analysed by calculating surface roughness for a range of moving window sizes (3 × 3, 5 × 5, 9 × 9 and 15 × 15), and surface roughness for each landslide was summarized by the median and upper quartile. Only weak correlations (best Spearman's rho 0.58) were present between landslide age and surface roughness. This correlation becomes weaker with increasing moving window size. Given weak observed associations and discussed challenges pertaining to the complexities of landslide morphology change over time, we currently find that surface roughness alone may not be justifiable to act as a proxy for landslide age for our study region. Furthermore, we recommend future studies should focus on addressing possible natural and anthropogenic factors such as land use change that may alter surface roughness. These studies may focus on one of the three roughness measures used here as they are strongly correlated. Copyright © 2014 John Wiley & Sons, Ltd.