bluuebunny/crossref_metadata_2025_split huggingface dataset:
Handling dip discrimination phenomenon in common‐reflection‐surface stack via combination of output‐imaging‐scheme and migration/demigration
Authors: Yang Kai , Chen Bao‐shu , Wang Xiao‐jiang , Yang Xiao‐chun , Liu Jun‐rong 
Published: September 2011

ABSTRACTIn the application of a conventional common‐reflection‐surface (CRS) stack, it is well‐known that only one optimum stacking operator is determined for each zero‐offset sample to be simulated. As a result, the conflicting dip situations are not taken into account and only the most prominent event contributes to any a particular stack sample. In this paper, we name this phenomenon caused by conflicting dip problems as ‘dip discrimination phenomenon’. This phenomenon is not welcome because it not only leads to the loss of weak reflections and tips of diffractions in the final zero‐offset‐CRS stacked section but also to a deteriorated quality in subsequent migration.The common‐reflection‐surface stack with the output imaging scheme (CRS‐OIS) is a novel technique to implement a CRS stack based on a unified Kirchhoff imaging approach. As far as dealing with conflicting dip problems is concerned, the CRS‐OIS is a better option than a conventional CRS stack. However, we think the CRS‐OIS can do more in this aspect. In this paper, we propose a workflow to handle the dip discrimination phenomenon based on a cascaded implementation of prestack time migration, CRS‐OIS and prestack time demigration. Firstly, a common offset prestack time migration is implemented. Then, a CRS‐OIS is applied to the time‐migrated common offset gather. Afterwards, a prestack time demigration is performed to reconstruct each unmigrated common offset gather with its reflections being greatly enhanced and diffractions being well preserved.Compared with existing techniques dealing with conflicting dip problems, the technique presented in this paper preserves most of the diffractions and accounts for reflections from all possible dips properly. More importantly, both the post‐stacked data set and prestacked data set can be of much better quality after the implementation of the presented scheme. It serves as a promising alternative to other techniques except that it cannot provide the typical CRS wavefield attributes. The numerical tests on a synthetic Marmousi data set and a real 2D marine data set demonstrated its effectiveness and robustness.
Break through the limits of vibroseis data quality
Authors: Wei Zhouhong , Phillips Thomas F. 
Published: September 2011

ABSTRACTThe vibroseis method has become the principal data acquisition method in land seismic exploration. It seems that this method has been extended to its limits as the search for energy resources continues. Many practical issues arising from field operations have remained theoretically unexplained, for example, variations in wavelet arrival time, inaccurate wavelet estimation and harmonics in the wavelet itself. The focus of this paper is the proposal of a new model, which is referred to as the vibrator‐coupled ground model, to simulate the filtering effects of a complex coupling system consisting of the coupling between the baseplate and the ground as well as the coupling between the captured ground mass near the vibrator baseplate and the surrounding earth. With this vibrator‐coupled ground model many of the practical issues mentioned above were reasonably addressed. Furthermore, it was demonstrated from experimental tests that both the pilot sweep and the weighted‐sum groundforce, when filtered by the vibrator‐coupled ground model, are proportional to the far‐field particle velocity whereas the unfiltered signals are not. The harmonics on the filtered weighted‐sum groundforce successfully maintain a proportional relationship with the harmonics seen in the far‐field signal.
Joint inversion of rock properties from sonic, resistivity and density well‐log measurements
Authors: Dell’Aversana Paolo , Bernasconi Giancarlo , Miotti Fabio , Rovetta Diego 
Published: September 2011

ABSTRACTWell‐log data are processed in order to derive subsurface physical parameters, namely rock porosity, fluid saturations and permeability. This step involves the selection and inversion of experimental constitutive equations, which are the link between the rock parameters and geophysical measurements. In this paper we investigate the rock parameter observability and the reliability of well‐log data processing. We present a visual analysis of the constitutive equations and of the inverse problem conditioning, when using independently, or jointly, log data from different domains. The existence of a common set of rock properties (cross‐properties) that influence different measurements, makes it possible to reduce the ambiguities of the interpretation. We select a test case in a reservoir scenario and we explore how to determine rock porosity and fluid saturation from sonic, conductivity and density logs. We propose a Bayesian joint inversion procedure, which is able to control the conditioning problems, to efficiently take into account input data and model uncertainty and to provide a confidence interval for the solution. The inversion procedure is validated on a real well‐log data set.
Reconstruction of geologic bodies in depth associated with a sedimentary basin using gravity and magnetic data
Authors: Barbosa Valéria C. F. , Silva João B. C. 
Published: September 2011

ABSTRACTWe present a comprehensive review of the most common gravity and magnetic interpretation methods to in depth retrieval of the geometry of geologic bodies associated with a sedimentary basin. We identify three types of bodies: 1) the sedimentary basement relief, 2) salt bodies and 3) mafic intrusions in a sedimentary section. In reconstructing basement topography through gravity and/or magnetic data we identify three groups of methods: the automatic, the spectral and the nonspectral methods. The reconstruction of salt bodies from gravity data usually uses interactive forward modelling but recently gravity inversion methods have been developed to interpret this kind of geologic environment. Finally, the problem of reconstructing intrusive bodies using magnetic and/or gravity data employs three strategies to interpret mafic or ultramafic intrusions in a sedimentary section: the automatic methods, interactive forward modelling and the inversion methods.
Hybrid modelling of gravity, gravity gradients and magnetic fields
Authors: Schmidt S. , Plonka C. , Götze H.‐J. , Lahmeyer B. 
Published: September 2011

ABSTRACTModern geophysical interpretation requires an interdisciplinary approach and software capable of handling multiple geophysical data types such as seismic, full tensor gravity gradiometry, magnetics and magnetotellurics. We use the IGMAS+ (Interactive Gravity and Magnetic Application System) geo‐modelling software that is designed for 3D gravity, gravity gradient and magnetic modelling. This paper deals with a special aspect of potential field modelling, combining conventional triangulated model geometries (building polyhedrons) with voxel cubes.The hybrid modelling combines the advantages of both the vector and raster modelling system: both may be used alone (polyhedrons without voxels, voxels without polyhedrons) or simultaneously by superposition of both effects, which provides flexibility towards full interoperability. The key idea of our approach is, on the one hand to use two different, completely independent geometries (vector and raster) and give on the other hand the possibility to link both on demand for either editing the voxel model or to combine a large number of voxel cells under a common physical parameter function – which results in more reliable parameter inversion results.
Traveltime parameters in a tilted elliptical anisotropic medium‡
Authors: Golikov Pavel , Stovas Alexey 
Published: September 2011

ABSTRACTIn this paper, we derive analytical expressions for one‐way and two‐way kinematical parameters in elliptical tilted transverse isotropy media. We show that the homogeneous elliptical tilted transverse isotropy models result in hyperbolic moveout with a reflection point sideslip x0, which can be considered as an additional traveltime parameter for one‐way wave propagation. For homogeneous elliptical tilted transverse isotropy models we show that the inversion of one‐way traveltime parameters suffers from the ambiguity for large tilts. It is shown that the accuracy of the inversion is sensitive to the error in x0. We also derive and invert the traveltime parameters for a vertically heterogeneous elliptical tilted transverse isotropy model with a tilt gradually changing with depth. The a priori knowledge of parameter δ is very important for inversion. The wrong choise of this parameter results in significant errors in inverted model parameters.
Fire‐induced tree mortality in a neotropical forest: the roles of bark traits, tree size, wood density and fire behavior
Authors: Brando Paulo M. , Nepstad Daniel C. , Balch Jennifer K. , Bolker Benjamin , Christman Mary C. , Coe Michael , Putz Francis E. 
Published: September 2011

AbstractLarge‐scale wildfires are expected to accelerate forest dieback in Amazônia, but the fire vulnerability of tree species remains uncertain, in part due to the lack of studies relating fire‐induced mortality to both fire behavior and plant traits. To address this gap, we established two sets of experiments in southern Amazonia. First, we tested which bark traits best predict heat transfer rates (R) through bark during experimental bole heating. Second, using data from a large‐scale fire experiment, we tested the effects of tree wood density (WD), size, and estimated R (inverse of cambium insulation) on tree mortality after one to five fires. In the first experiment, bark thickness explained 82% of the variance in R, while the presence of water in the bark reduced the difference in temperature between the heat source and the vascular cambium, perhaps because of high latent heat of vaporization. This novel finding provides an important insight for improving mechanistic models of fire‐induced cambium damage from tropical to temperate regions. In the second experiment, tree mortality increased with increasing fire intensity (i.e. as indicated by bark char height on tree boles), which was higher along the forest edge, during the 2007 drought, and when the fire return interval was 3 years instead of one. Contrary to other tropical studies, the relationship between mortality and fire intensity was strongest in the year following the fires, but continued for 3 years afterwards. Tree mortality was low (≤20%) for thick‐barked individuals (≥18 mm) subjected to medium‐intensity fires, and significantly decreased as a function of increasing tree diameter, height and wood density. Hence, fire‐induced tree mortality was influenced not only by cambium insulation but also by other traits that reduce the indirect effects of fire. These results can be used to improve assessments of fire vulnerability of tropical forests.
Bacterial killing by several root filling materials and methods in an ex vivo infected root canal model
Authors: Özcan E. , Eldeniz A. U. , Arı H. 
Published: September 2011

Özcan E, Eldeniz AU, Arı H. Bacterial killing by several root filling materials and methods in an ex vivo infected root canal model. International Endodontic Journal, 44, 1102–1109, 2011.AbstractAim  To evaluate the ability of two root canal sealers (Epoxy resin‐based AH Plus® or polydimethylsiloxane‐based GuttaFlow®) and five root filling techniques (continuous wave of condensation, Thermafil®, lateral condensation, matched taper single gutta‐percha point, laterally condensed‐matched taper gutta‐percha point) to kill bacteria in experimentally infected dentinal tubules.Methodology  An infected dentine block model was used. One hundred and twenty extracted, single‐rooted human teeth were randomly divided into 10 test (n = 10) and 2 control (n = 10) groups. The roots, except negative controls, were infected with Enterococcus faecalis for 21 days. The root canals were then filled using the test materials and methods. Positive controls were not filled. Sterile roots were used as negative controls. Dentine powder was obtained from all root canals using gates glidden drills using a standard method. The dentine powder was diluted and inoculated into bacterial growth media. Total colony‐forming units (CFU) were calculated for each sample. Statistical analysis was performed using the Kruskal–Wallis and Mann–Whitney U test.Results  The epoxy resin‐based sealer was effective in killing E. faecalis except when using Thermafil (P < 0.05), but the polydimethylsiloxane‐based sealer was not effective in killing this microorganism except in the continuous wave group (P < 0.05).Conclusions  In the test model, AH Plus killed bacteria in infected dentine more effectively than GuttaFlow. The filling method was less important than the sealer material.
A triadic interplay between academics, practitioners and students in the nursing theory and practice dialectic
Authors: Chan Engle Angela , Chan Kitty , Liu Yat Wa Justina 
Published: September 2011

chan e.a., chan k. & liu y.w.j. (2011) A triadic interplay between academics, practitioners and students in the nursing theory and practice dialectic. Journal of Advanced Nursing 68(5), 1038–1049.AbstractAim.  This article is a report of a descriptive study of the effectiveness of classroom teaching by clinical nurse specialists on students’ transfer of theory into practice.Background.  Ongoing concern about a theory‐practice merger in nursing has led to collaborative initiatives between academics and practitioners globally. There are different forms of collaborative efforts, but information on their evaluation is scarce and inconclusive. Integration of theory and practice is important for an outcome‐based approach, which emphasizes students’ clinical competence as the measure of success. The limited nursing discussion on theory and practice collaboration in education was our impetus for the study.Methods.  Between 2007 and 2008, focus group interviews were held, first with 75 and then with 35 from the same group of first‐year students, regarding their learning experience from the lectures of the two clinical nurse specialists in diabetes and colostomy care, respectively, prior to and after their clinical placements. Six of their clinical instructors and the two clinical nurse specialists were also interviewed. The audiotaped interviews were transcribed verbatim and analysed using content analysis.Findings.  Three themes were identified: impact of students’ vicarious learning from clinical nurse specialists’ stories of experience; improving the collaboration between clinical nurse specialists and subject lecturers for junior students’ learning experience; continuity in the clinical integration of theory‐practice as dialectic through an interplay between academics, practitioners and students.Conclusion.  The theory and practice issue is best addressed as a triadic paradigm in a community of practice with the collaboration among academics, practitioners and students.
A comparison of patient and family caregiver prospective control over lung cancer
Authors: Lobchuk Michelle M. , McPherson Christine J. , McClement Susan E. , Cheang Mary 
Published: September 2011

lobchuk m.m., mcpherson c.j., mcclement s.e. & cheang m. (2011) A comparison of patient and family caregiver prospective control over lung cancer. Journal of Advanced Nursing 68(5), 1122–1133.AbstractAim.  This paper is a report of our secondary analysis of patient and family caregiver prospective control in lung cancer.Background.  Control beliefs underlie self‐care in sickness and health. Self‐care often involves ‘shared’ activities between the afflicted individual and caregiving family and friends. However, depending on how control is perceived, conflicts can occur in decision‐making thus jeopardizing optimal self‐care. We need to comprehend how control beliefs compare between patients and caregivers and how their control beliefs are linked with dealing with serious illness.Methods.  Based on questionnaire data collected in our larger study between September 2005 and February 2009, we conducted exploratory comparative analyses of 304 patients’ and caregivers’ control beliefs in managing lung cancer. Eight 5‐point response items captured prospective control. Exploratory factor analysis with promax rotation was conducted to compare dyadic perceptions on the dimensionality of prospective control. We also conducted exploratory correlations between control beliefs and smoking cessation, attributional reactions, caregiver helping and symptom reports.Results.  Principal component analysis identified the same factors for patients and caregivers: factor 1, Fate control and factor 2, Team control. Patient and caregiver ‘Fate’ and ‘Team’ control sub‐scales were respectively associated with hope, caregiver helping and patient smoking cessation.Conclusion.  Clinicians need to support, adapt or develop a philosophy of cancer care that is inclusive of partnerships, drawing on beliefs of patients and caregivers that controlling lung cancer is a team effort which in turn is tentatively linked to patient smoking cessation, positive emotions and caregiver helping.
Bayesian inference on age‐specific survival for censored and truncated data
Authors: Colchero Fernando , Clark James S. 
Published: September 2011

Summary1. Traditional estimation of age‐specific survival and mortality rates in vertebrates is limited to individuals with known age. Although this subject has been studied extensively using effective capture–recapture and capture–recovery models, inference remains challenging because of large numbers of incomplete records (i.e. unknown age of many individuals) and because of the inadequate duration of the studies.2. Here, we present a hierarchical model for capture–recapture/recovery (CRR) data sets with large proportions of unknown times of birth and death. The model uses a Bayesian framework to draw inference on population‐level age‐specific demographic rates using parametric survival functions and applies this information to reconstruct times of birth and death for individuals with unknown age.3. We simulated a set of CRR data sets with varying study span and proportions of individuals with known age, and varying recapture and recovery probabilities. We used these data sets to compare our method to a traditional CRR model, which requires knowledge of individual ages. Subsequently, we applied our method to a subset of a long‐term CRR data set on Soay sheep.4. Our results show that this method performs better than the common CRR model when sample sizes are low. Still, our model is sensitive to the choice of priors with low recapture probability and short studies. In such cases, priors that overestimate survival perform better than those that underestimate it. Also, the model was able to estimate accurately ages at death for Soay sheep, with an average error of 0·94 years and to identify differences in mortality rate between sexes.5. Although many of the problems in the estimation of age‐specific survival can be reduced through more efficient sampling schemes, most ecological data sets are still sparse and with a large proportion of missing records. Thus, improved sampling needs still to be combined with statistical models capable of overcoming the unavoidable limitations of any fieldwork. We show that our approach provides reliable estimates of parameters and unknown times of birth and death even with the most incomplete data sets while being flexible enough to accommodate multiple recapture probabilities and covariates.
Phylogeography at large spatial scales: incongruent patterns of population structure and demography of Pan‐American butterflies associated with weedy habitats
Authors: Runquist Erik B. , Forister Matthew L. , Shapiro Arthur M. 
Published: September 2011

AbstractAim  Few studies of comparative phylogeography have been conducted at very large spatial scales, encompassing species that are distributed across multiple continents. Several Pan‐American butterfly species associated with weedy, human‐modified habitats were studied using comparative phylogeographic tools to test for the congruence of demographic histories across a range of spatial scales and to investigate the effects of human‐facilitated range expansion.Location  North and South America, mainly the southern United States, Brazil and Argentina.Methods  The mitochondrial DNA cytochrome c oxidase subunit II region (COII) was sequenced for Hylephila phyleus, Lerodea eufala, Erynnis funeralis and Agraulis vanillae across their North and South American ranges. Data from these conspecifics were compared with variation in COII sequences between allopatric congener pairs on both continents whose ranges approximate the conspecifics and also share similar weedy habitat associations: Ancyloxypha numitor versus Ancyloxypha nitedula, Vanessa annabella versus Vanessa carye, and Euptoieta claudia versus Euptoieta hortensia. We tested for similarities in demographic histories within and across continents for each species using pairwise distances, population genetic statistics, mismatch distributions and deviations from mutation‐drift equilibrium.Results  Mean pairwise divergence across continents was lower for Lerodea eufala and Hylephila phyleus (with several shared Pan‐American haplotypes each) compared with Erynnis funeralis and Agraulis vanillae (both with no shared haplotypes). Differentiation between congeneric species pairs was generally significantly higher than conspecific divergence across continents, but North and South American populations of A. vanillae were more divergent than V. annabella and V. carye. We found deviations from mutation‐drift equilibrium in A. vanillae. Population‐level variation was greater than the variation across continents for H. phyleus and L. eufala.Main conclusions  We find little congruence in phylogeographic patterns among these taxa across continents, although similar demographic patterns can be detected at smaller regional levels. Except for Californian populations of some species, the North American distributions of these weedy butterfly species appear to largely pre‐date the influences of human‐facilitated range expansion.