bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recruitment, kin and the spatial genetic structure of a caddisfly Plectrocnemia conspersa in a southern English stream
Authors: WILCOCK HELEN R. , BRUFORD MICHAEL W. , HILDREW ALAN G. , NICHOLS RICHARD A. 
Published: August 2005

Summary1. Our objectives were to examine small‐scale patterns in oviposition and genetic relatedness in a population of the stream‐dwelling caddis Plectrocnemia conspersa and, in particular, to look for any evidence of the spatial proximity of close kin and, therefore, ‘patchy recruitment’.2. In order to examine the distribution of related larvae at the beginning of the aquatic phase, we searched the stream for egg masses. Spatially and temporally structured samples of larvae were then collected from the stream over four sample dates within one generation. The genetic relatedness of these field‐collected larvae, estimated using six polymorphic microsatellite loci, was subsequently compared with that of larvae reared from individual egg masses in the laboratory.3. Egg masses were laid in clusters or ‘hot spots’ along the stream. The mean relatedness coefficient within reared egg masses ranged from 0.327 to 0.525, and differed significantly from that estimated for the population as a whole (0.070), indicating that the markers were sufficiently powerful to identify groups of siblings. Each egg mass was likely to be the progeny of one father, although the possibility of a small contribution from a second male could not be excluded for a few masses.4. Mean relatedness within the spatially structured groups of larvae in the stream, even those in close proximity to each other, did not differ from the background population level estimate, suggesting that siblings disperse away from each other very quickly and that kin structure does not persist over time.5. Changes in spatial genetic structure late in the larval life indicated that neighbouring larvae were less closely related than the population overall, possibly suggesting some direct or indirect means of avoiding kin when approaching the onset of pupation.6. Our counts of egg masses suggested that survival through the egg stage and early larval life was apparently very high (>50%) for a non‐social insect, and may be a consequence of the colonial net that is briefly occupied by first instar larvae.7. The number of egg masses laid in the stream (approximately 400 in the sample year), the lack of a spatial genetic structure showing evidence of families even early in larval life, and the high survival of eggs and early instar larvae, all refute the ‘patchy recruitment hypothesis’ for this species.
Meiobenthic response to river‐borne benthic particulate matter – a microcosm experiment
Authors: WITTHÖFT‐MÜHLMANN ANDRÉ , TRAUNSPURGER WALTER , ROTHHAUPT KARL OTTO 
Published: August 2005

Summary1. Benthic communities inhabiting river–lake interfaces are confronted with temporal variation in the import of river‐borne material to the associated littoral zone. The primary objective of this study was to evaluate the exposure to river‐borne benthic particulate matter as a force shaping the meiofauna of the river–lake interface.2. In a 2 × 2 factorial design, combinations of strongly and weakly river‐influenced communities (near or far from the river mouth) with and without river‐borne benthic particulate matter enrichment were studied in laboratory microcosms to assess the response of the heterotrophic meiobenthos to river‐borne matter.3. Nematodes dominated both habitat types and were the only meiofaunal taxon that responded to the enrichment.4. A strong interactive effect between experimental enrichment and location of site was observed. Whereas nematodes from the littoral habitat close to the river mouth responded to the enrichment only marginally, nematodes from the remote site were strongly affected in the presence of river‐borne particulate matter.5. In the non‐enriched samples of the remote site, the number of nematodes increased greatly over time. Among nematode feeding types, deposit feeders dominated over chewers at the beginning of the experiment but both types were equally abundant at the end. In the presence of river‐borne matter the increase of chewers ceased and a shift in feeding type composition did not occur.6. It was shown that for river–lake interface meiofaunal assemblages in relative proximity, the same taxon might respond differently if exposed to an external pressure, e.g. river‐borne components. These components may have a stronger influence on taxa with longer life cycles.
Orthogonal vibroseis sweeps
Authors: Xia J. , Geier N.A. , Miller R.D. , Tapie C.R. 
Published: August 2005

ABSTRACTVibroseis is a method that imparts coded seismic energy into the ground. The energy is recorded with geophones and then processed using the known (coded) input signal. The resulting time‐domain representation of vibroseis data is an impulsive wavetrain with wavelet properties consistent with the coded input signal convolved with the earth's reflectivity series. Historically, vibratory seismic surveys collect data from one source location at a time, summing one or more sources at each location. We present a method of designing orthogonal sweeps using the concept of combisweeps. The orthogonal sweeps allow simultaneous recording and later separation of two or more unique source locations. Orthogonality of sweeps permits separation of the data into unique source‐location field records by a conventional correlation procedure. The separation power of the orthogonal sweeps is demonstrated by a comparison between separated data and data acquired with one vibrator. Separation noise was at a negligible level for our demonstration data sets when two vibrators were located 50 m to 200 m apart. Coincident generation and recording of two vibroseis sweeps at different locations would allow almost double the amount of data to be recorded for a given occupation time and requires only half the storage medium.
τ‐migration and velocity analysis: application to data from the Red Sea
Authors: Alkhalifah Tariq 
Published: August 2005

ABSTRACTImaging pre‐salt reflections for data acquired from the coastal region of the Red Sea is a task that requires prestack migration velocity analysis. Conventional post‐stack time processing lacks the lateral inhomogeneity capability, necessary for such a problem. Prestack migration velocity analysis in the vertical time domain reduces the velocity–depth ambiguity that usually hampers the performance of prestack depth‐migration velocity analysis. In prestack τ‐migration velocity analysis, the interval velocity model and the output images are defined in τ (i.e. vertical time). As a result, we avoid placing reflectors at erroneous depths during the velocity analysis process and thus avoid inaccurately altering the shape of the velocity model, which in turn speeds up the convergence to the true model. Using a 1D velocity update scheme, the prestack τ‐migration velocity analysis produces good images of data from the Midyan region of the Red Sea. For the first seismic line from this region, only three prestack τ‐migration velocity analysis iterations were required to focus pre‐salt reflections in τ. However, the second line, which crosses the first line, is slightly more complicated and thus required five iterations to reach the final, reasonably focused, τ‐image. After mapping the images for the two crossing lines to depth, using the final velocity models, the placements of reflectors in the two 2D lines were consistent at their crossing point. Some errors occurred due to the influence of out‐of‐plane reflections on 2D imaging. However, such errors are identifiable and are generally small.
An enhanced method for source parameter imaging of magnetic data collected for mineral exploration
Authors: Smith Richard S. , Salem Ahmed , Lemieux Jean 
Published: August 2005

ABSTRACTWe have developed a method for imaging magnetic data collected for mineral exploration to yield the following structural information: depth, model type (structural index) and susceptibility. The active nature of mineral exploration data requires we derive the structural information from a robust quantity: we propose that the first‐ or second‐order analytic‐signal amplitude is suitably stable. The procedure is to normalize the analytic‐signal amplitude by the peak value and then use non‐linear inversion to estimate the depth and the structural index for each anomaly. In our field example, different results are obtained depending on whether we inverted for the first‐ or second‐order analytic‐signal amplitude. This is probably because the two‐dimensional contact, thin sheet or horizontal cylinder models we have assumed are not appropriate. In cases such as these, when our model assumptions are not correct, the results should not be interpreted quantitatively, but they might be useful for giving a qualitative indication of how the structure might vary.With a priori information, it is possible to assume a model type (i.e. set the structural index) and generate estimates of the depth and susceptibility. These data can then be gridded and imaged. If a contact is assumed, the susceptibility contrast is estimated; for the dike model, the susceptibility‐thickness is estimated; for the horizontal cylinder, the susceptibility‐area is estimated. To emphasize that the results are dependent on our assumed model, we advocate prefixing any derived quantity by the term ‘apparent’.
Seismic anisotropy of shales
Authors: Sayers C.M. 
Published: August 2005

ABSTRACTShales are a major component of sedimentary basins, and they play a decisive role in fluid flow and seismic‐wave propagation because of their low permeability and anisotropic microstructure. Shale anisotropy needs to be quantified to obtain reliable information on reservoir fluid, lithology and pore pressure from seismic data, and to understand time‐to‐depth conversion errors and non‐hyperbolic moveout. A single anisotropy parameter, Thomsen's δ parameter, is sufficient to explain the difference between the small‐offset normal‐moveout velocity and vertical velocity, and to interpret the small‐offset AVO response. The sign of this parameter is poorly understood, with both positive and negative values having been reported in the literature. δ is sensitive to the compliance of the contact regions between clay particles and to the degree of disorder in the orientation of clay particles. If the ratio of the normal to shear compliance of the contact regions exceeds a critical value, the presence of these regions acts to increase δ, and a change in the sign of δ, from the negative values characteristic of clay minerals to the positive values commonly reported for shales, may occur. Misalignment of the clay particles can also lead to a positive value of δ. For transverse isotropy, the elastic anisotropy parameters can be written in terms of the coefficients W200 and W400 in an expansion of the clay‐particle orientation distribution function in generalized Legendre functions. For a given value of W200, decreasing W400 leads to an increase in δ, while for fixed W400, δ increases with increasing W200. Perfect alignment of clay particles with normals along the symmetry axis corresponds to the maximum values of W200 and W400, given by and . A comparison of the predictions of the theory with laboratory measurements shows that most shales lie in a region of the (W200, W400)‐plane defined by W400/W200≤Wmax400/Wmax200.
Elastic properties of double‐porosity rocks using the differential effective medium model
Authors: Markov M. , Levine V. , Mousatov A. , Kazatchenko E. 
Published: August 2005

ABSTRACTAn approach to determining the effective elastic moduli of rocks with double porosity is presented. The double‐porosity medium is considered to be a heterogeneous material composed of a homogeneous matrix with primary pores and inclusions that represent secondary pores. Fluid flows in the primary‐pore system and between primary and secondary pores are neglected because of the low permeability of the primary porosity. The prediction of the effective elastic moduli consists of two steps. Firstly, we calculate the effective elastic properties of the matrix with the primary small‐scale pores (matrix homogenization). The porous matrix is then treated as a homogeneous isotropic host in which the large‐scale secondary pores are embedded. To calculate the effective elastic moduli at each step, we use the differential effective medium (DEM) approach. The constituents of this composite medium – primary pores and secondary pores – are approximated by ellipsoidal or spheroidal inclusions with corresponding aspect ratios.We have applied this technique in order to compute the effective elastic properties for a model with randomly orientated inclusions (an isotropic medium) and aligned inclusions (a transversely isotropic medium). Using the special tensor basis, the solution of the one‐particle problem with transversely isotropic host was obtained in explicit form.The direct application of the DEM method for fluid‐saturated pores does not account for fluid displacement in pore systems, and corresponds to a model with isolated pores or the high‐frequency range of acoustic waves. For the interconnected secondary pores, we have calculated the elastic moduli for the dry inclusions and then applied Gassmann's tensor relationships. The simulation of the effective elastic characteristic demonstrated that the fluid flow between the connected secondary pores has a significant influence only in porous rocks containing cracks (flattened ellipsoids). For pore shapes that are close to spherical, the relative difference between the elastic velocities determined by the DEM method and by the DEM method with Gassmann's corrections does not exceed 2%. Examples of the calculation of elastic moduli for water‐saturated dolomite with both isolated and interconnected secondary pores are presented. The simulations were verified by comparison with published experimental data.
Instantaneous polarization attributes in the time–frequency domain and wavefield separation
Authors: Diallo M.S. , Kulesh M. , Holschneider M. , Scherbaum F. 
Published: August 2005

ABSTRACTWe introduce a method of wavefield separation from multicomponent data sets based on the use of the continuous wavelet transform. Our method is a further generalization of the approach proposed by Morozov and Smithson, in that by using the continuous wavelet transform, we can achieve a better separation of wave types by designing the filter in the time–frequency domain. Furthermore, using the instantaneous polarization attributes defined in the wavelet domain, we show how to construct filters tailored to separate different wave types (elliptically or linearly polarized), followed by an inverse wavelet transform to obtain the desired wave type in the time domain. Using synthetic and experimental data, we show how the present method can be used for wavefield separation.
Spatial and structural uniformity of lowland agricultural grassland in England: a context for low biodiversity
Authors: Tallowin J. R. B. , Smith R. E. N. , Goodyear J. , Vickery J. A. 
Published: August 2005

AbstractThe contention that agricultural grassland within the UK is spatially and structurally uniform across wide differences in livestock farming intensity is examined. Total nitrogen (N) input was used as a surrogate for management intensity. Farms with average annual N inputs of >200 kg ha−1 were categorized as highly intensive, those with N inputs of 50–200 kg N ha−1 as moderately intensive and those with inputs of <50 kg N ha−1 were categorized as extensive. Four farms within each management category were selected in two discrete regions: one in south‐west England, typifying a landscape dominated by agricultural grassland, the other in south‐east England with a more mixed‐farming landscape. Specific N input and management data, and sward botanical composition and structure, were obtained on four fields per farm. The south‐west region had a higher proportion of farms with dairy cattle than in the south‐east England region. The average N input and stocking rates were higher within the intensive‐management category farms in south‐west England than in south‐east England. Old permanent grasslands contained variable amounts of sown species, such as Lolium perenne, and were dominated by a few (generally <5) non‐sown grass species. Grassland that received >75 kg N ha −1 year−1 contained <7 plant species and <3 forb species m−2. Grassland communities with >12 plant species and >5 forb species m−2 were only found in study fields that received <50 kg N ha−1 year−1. Grasslands with >10 forb species m−2 were found only in sites receiving <15 kg N ha−1. Of importance at a landscape scale was ubiquity of species‐poor and similar grassland plant communities across the management intensity range within and between livestock farms. Grassland in the extensive management category was similar in structure in terms of sward height and/or sward density to more intensively managed grasslands. This study revealed, albeit in two lowland sample regions in the UK, the ubiquity of grass‐dominated, species‐poor and structurally uniform grasslands, irrespective of apparently broad differences in farming intensity. The consequences of this spatial uniformity on grassland biodiversity are likely to be profound.
Use of a systems synthesis approach to model nitrogen losses from dairy farms in south‐west England
Authors: Cuttle S. P. , Jarvis S. C. 
Published: August 2005

AbstractNitrogen (N) budgets were determined for six typical, moderately intensive dairy farms in south‐west England. Proportionately, only 0·12–0·17 of the N input to the farms was recovered in agricultural products, leaving annual N surpluses equivalent to 249–376 kg N ha−1. A sequence of models (MANNER, NCYCLE and SUNDIAL) was used, together with the estimated N balance of the dairy cows and standard ammonia emission factors, to estimate N losses for each farm. Total estimated losses were equivalent to 137–220 kg N ha−1 year−1. Leaching accounted for 0·26–0·45 of the total loss, ammonia volatilization for 0·27–0·39 and denitrification for 0·17–0·36. When residual N from manure applications was included, there appeared to be an annual accumulation of soil N, equivalent to 66–158 kg N ha−1 when averaged over the whole farm area. The amounts of N lost by leaching, volatilization and denitrification, and accumulated as soil‐N, were determined by a combination of farm properties, including N input, soil type, drainage, characteristics of the manure produced and type of fertilizer. The sum of estimated losses and change in N retained on the farm was between 0·85 and 1·11 of the N surplus (input minus output) determined from the farm budget. This suggests that losses and the change in soil‐N were underestimated on some farms and overestimated on others (by up to −50 and +23 kg N ha−1 respectively). Much of the discrepancy between estimates and the surplus was attributed to difficulties of fully integrating inputs and outputs between the different models and stages of the modelling procedure.
Effects of perennial ryegrass (Lolium perenne L.) cultivars on herbage production, nutritional quality and herbage intake of grazing dairy cows
Authors: Smit H. J. , Tas B. M. , Taweel H. Z. , Tamminga S. , Elgersma A. 
Published: August 2005

AbstractFour perennial ryegrass (Lolium perenne L.) cultivars were compared for differences in herbage production, nutritive value and herbage intake of dry matter (DM) during the summers of 2002 and 2003. Two paddocks were sown with pure stands of four cultivars in a randomized block design with three replicates. Each plot was subdivided into fourteen subplots (22 m × 6 m) which were grazed by one cow during 24 h. Twelve lactating dairy cows were assigned to one cultivar for a period of 2 weeks in a 4 × 4 Latin square experimental design; the experiment lasted 8 weeks in each year. Sward structure (sward surface height, DM yield, green leaf mass, bulk density and tiller density) and morphological characteristics were measured. The ash, neutral‐detergent fibre, acid‐detergent lignin, crude protein and water‐soluble carbohydrate concentrations, and in vitro digestibility of the herbage were measured. The sward was also examined for infestation by crown rust (Puccinia coronata f. sp. lolii). Herbage intake of dairy cows was estimated using the n‐alkane technique. Cultivar differences for all sward structural characteristics were found except for bulk density and tiller density in 2003. Cultivars differed for proportions of pseudostem, stem (in 2003 only) and dead material. The chemical composition of the herbage was different among cultivars, with the water‐soluble carbohydrate concentration showing large variation (>0·35). Cultivars differed in susceptibility to crown rust. Herbage intake differed among cultivars in 2002 (>2 kg DM) but not in 2003. Herbage intake was positively associated with sward height, DM yield and green leaf mass. Canopy morphology did not affect herbage intake. Crown rust affected herbage intake negatively. It was concluded that options for breeders to select for higher intake were limited. High‐yielding cultivars and cultivars highly resistant to crown rust were positively related with a high herbage intake.
Differential responses of cord and adult blood‐derived dendritic cells to dying cells
Authors: Wong On Hang , Huang Fang‐Ping , Chiang Alan K. S. 
Published: August 2005

SummaryNormal turnover of body tissues yields apoptotic cells while infections cause tissue injuries and cell necrosis. The interaction of these dying cells with dendritic cells (DCs) may provide immunological instructions leading to either immune tolerance or activation. We hypothesize that neonatal and adult DCs differ in their responses to dying cells, thereby contributing to the observed differences in immune responses between neonates and adults. We compare the outcome of interaction of cord and adult blood‐derived DCs with dying Epstein–Barr‐virus‐transformed lymphoblastoid cells (LCLs) and the responsiveness to lipopolysaccharide. While cord DCs were able to phagocytose both apoptotic and necrotic LCLs, the subsequent responses differed significantly from those of adult DCs. Interaction of adult DCs with necrotic but not early apoptotic LCLs resulted in high expression of DC costimulatory molecules (CD80/CD86) and activation markers (CD83), production of both proinflammatory and anti‐inflammatory cytokines (tumour necrosis factor‐α, interleukin‐10), and strong T‐cell‐stimulating activities. In contrast, in response to either necrotic or apoptotic LCLs, cord DCs had minimal up‐regulation of those DC functional markers, little cytokine production and poor stimulation on T‐cell proliferation. In response to lipopolysaccharide, however, both adult and cord DCs produced comparable levels of tumour necrosis factor‐α and interleukin‐10, but only adult DCs produced interleukin‐12(p70). Taken together, these results suggest that neonatal DCs generally favour immune tolerance with minimal activation and cytokine production, except in extremely dangerous situations, such as bacterial sepsis, when neonatal DCs may produce certain types of cytokines and stimulate T‐cell proliferation.