bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a Fully Implicit, Parallel, EOS Compositional Simulator to Model Asphaltene Precipitation in Petroleum Reservoirs
Authors: Fazelipour Waleed , Pope Gary A. , Sepehrnoori Kamy 
Published: September 2008

Abstract
A serious and complex problem in hydrocarbon recovery is the asphaltene precipitation since it affects all aspects of petroleum production, processing, and consequently transportation. It is very desireable to predict and simulate the asphaltene precipitation during upstream recovery processes from oil and gas reservoirs. Many models have been developed to predict the precipitation behavior of asphaltenes.
We present implementation of an asphaltene precipitation model into a fully implicit, 3D, parallel, multiphase, multicomponent, EOS compositional simulator called GPAS developed at the Center for Petroleum and Geosystems Engineering to model the phase behavior and simulate the dynamic aspects of the asphaltene precipitation problem that occurs in oil and gas reservoirs.
After studying many models for asphaltene precipitation available in the petroleum engineering literature, testing and utilizing various simulators (e.g. ECLIPSE, CMG, VIP) to simulate the problem under primary depletion, CO2 and water flooding scenarios, a particular thermodynamic approach was chosen to be implemented in the GPAS simulator. This model treats the precipitating asphaltene as a single component residing in a pure solid phase, while hydrocarbon phases are modeled with an EOS.
The primary goal of GPAS, currently under development, is to support realistic, high-resolution reservoir studies using millions of gridcells on massively parallel computers. Key features for this simulator include the ability to handle multiple physical models, multiple fault blocks, and flexible gridding.
With the incorporation of asphaltene simulation into GPAS, many equations in the original code were modified, added, and implemented including the phase equilibrium, volume constraint, and mass conservation equations. Multiphase flash calculations were developed to predict the onset point and the amount of asphaltene precipitation throughout the life of a reservoir. Since this phenomenon severely damages the physical properties of formation, models were also implemented to estimate the effects on porosity, relative permeability, and wettability. The fully implicit formulations of GPAS added a great deal to the complexity of the formulations.
Simulation results indicate that asphaltene precipitation reduces oil production. A key conclusion of the achivements is the capability to predict the detrimental effects of asphaltenes in reservoirs without the need for data generation from expensive downhole samples. This research also led to a more powerful reservoir simulator that can be used by E&P companies to predict asphaltene precipitation in reservoirs and help with the design of primary and secondary recovery processes on their desktops or clusters of computers to solve E&P challenges of the future.
Accurate Streamline Tracing on Three-Dimensional Tetrahedral and Hexahedral Grids
Authors: Matringe Sébastien F. 
Published: September 2008

Abstract
Modern reservoir simulation grids are geometrically complex (distorted or unstructured grids) and often populated with tensor permeabilities. The solution of the flow problem on these advanced grids requires accurate finite volume methods such as the multipoint flux approximation (MPFA) schemes. Existing streamline tracing algorithms do not preserve the accuracy of the MPFA solutions and therefore represent a source of errors for the streamline method.
Very recently, MPFA methods have been related to mixed finite element methods (MFEM) on 3D tetrahedral and hexahedral grids. This link equips MPFA with a new mathematical framework that we exploit to design a new streamline tracing method. Our approach was already used successfully in 2D and this paper presents the extension to 3D of the previous work by the authors.
In the new method, the velocity field is interpolated from the MPFA subfluxes using mixed finite element velocity shape functions. The streamlines are then integrated to arbitrary accuracy. The method is the natural extension of Pollock's (1988) tracing method for general tetrahedral or hexahedral grids. The new method presents two major advantages over the streamline tracing methods developed for MPFA by Prévost et al.1 and Hægland et al.2 First, our algorithm provides more accurate streamlines and second, the direct interpolation of the velocity from the MPFA subfluxes avoids the expensive flux postprocessing used by the other methods. After a detailed description of the theory and implementation of our streamline tracing method, we use challenging test cases to compare its accuracy and efficiency to other existing streamline tracing methods.
Unusual intragenomic and interspecific variability of Geobacillus 16S-23S rRNA internal transcribed spacers
Authors: Kuisiene Nomeda , Raugalas Juozas , Chitavichius Donaldas 
Published: September 2008

Abstract
The aim of this study was to evaluate the inter-and intraspecific as well as intragenomic variability of Geobacillus 16S–23S rRNA internal transcribed spacers without tRNA genes and to compare these sequences with sequences bearing tRNA genes. In this study the structural analysis was performed in a unique way because the length and the sequence of the structural blocks were adjusted to fit the structure of 16S–23S rRNA internal transcribed spacers of five different Geobacillus species. Our study demonstrated the mosaic-like structure of 16S–23S rRNA internal transcribed spacers in Geobacillus. Some characteristics of these spacers of geobacilli were not previously reported for other bacteria: unusually short conserved sequence in the 5′ end region, some identical conserved blocks in both 5′ and 3′ regions of 16S–23S rRNA internal transcribed spacers, the same sequence blocks in both 16S–23S and 23S–5S rRNA intergenic spacers. Our study demonstrated quite uniform arrangement of the sequence blocks in Geobacillus thermodenitrificans. This species diverged early in the phylogenetic tree of the genus Geobacillus. For the phylogenetically recent species Geobacillus kaustophilus and Geobacillus lituanicus the low inter-and intraspecific, but high intragenomic variability, as a consequence of recent phylogenetic events, was established.
Recent Applications of Conjugated Polyelectrolytes in Optoelectronic Devices
Authors: Hoven Corey V. , Garcia Andres , Bazan Guillermo C. , Nguyen Thuc‐Quyen 
Published: September 2008

AbstractConjugated polyelectrolytes comprise an electronically delocalized backbone with pendant groups bearing ionic functionalities. Important new developments regarding their use to improve charge injection from metallic electrodes into organic semiconductors, a key requirement in emissive devices, have recently appeared. This article provides an overview of recent studies concerning the basic properties of conjugated polyelectrolytes as a function of molecular structure, and of optoelectronic devices with conjugated polyelectrolytes as essential functional components. Processes where more insightful mechanistic understanding is needed and areas of opportunity are discussed.
Hollow Micro‐/Nanostructures: Synthesis and Applications
Authors: Lou Xiong Wen (David) , Archer Lynden A. , Yang Zichao 
Published: September 2008

AbstractHollow micro‐/nanostructures are of great interest in many current and emerging areas of technology. Perhaps the best‐known example of the former is the use of fly‐ash hollow particles generated from coal power plants as partial replacement for Portland cement, to produce concrete with enhanced strength and durability. This review is devoted to the progress made in the last decade in synthesis and applications of hollow micro‐/nanostructures. We present a comprehensive overview of synthetic strategies for hollow structures. These strategies are broadly categorized into four themes, which include well‐established approaches, such as conventional hard‐templating and soft‐templating methods, as well as newly emerging methods based on sacrificial templating and template‐free synthesis. Success in each has inspired multiple variations that continue to drive the rapid evolution of the field. The Review therefore focuses on the fundamentals of each process, pointing out advantages and disadvantages where appropriate. Strategies for generating more complex hollow structures, such as rattle‐type and nonspherical hollow structures, are also discussed. Applications of hollow structures in lithium batteries, catalysis and sensing, and biomedical applications are reviewed.
Type II autosomal recessive cutis laxa: Report of another patient and molecular studies concerning three candidate genes
Authors: Scherrer Daniel Zanetti , Alexandrino Fabiana , Cintra Maria Letícia , Sartorato Edi Lúcia , Steiner Carlos Eduardo 
Published: September 2008

AbstractCutis laxa is a rare disorder of connective tissue in which the skin sags excessively, giving the individual an aged appearance. In the present study we analyzed three unrelated families with type II autosomal recessive cutis laxa for mutations in three genes implicated in other forms of cutis laxa; LOX, FBLN4, and FBLN5 genes. Two individuals have been previously reported, and the third case is described in detail. No causative mutations were identified. © 2008 Wiley‐Liss, Inc.
The Matthew effect defined and tested for the 100 most prolific economists
Authors: Tol Richard S.J. 
Published: September 2008

AbstractThe Matthew effect has that recognition is bestowed on researchers of already high repute. If recognition is measured by citations, this means that often‐cited papers or authors are cited more often. I use the statistical theory of the growth of firms to test whether the fame of papers and authors indeed exhibits increasing returns to scale, and confirm this hypothesis for the 100 most prolific economists.
Influence of measurement errors and deviations from Tully‐Fisher relationship on multipole structure of bulk galaxy motion
Authors: Parnovsky S.L. , Parnowski A.S. 
Published: September 2008

AbstractThe velocity field of large‐scale non‐Hubble galaxy motion recovered from peculiar velocities of spiral galaxies is distorted due to measurement errors and deviations from Tully‐Fisher relationship. To figure out how this affects the multipole structure we use the Monte‐Carlo approach and simulate errors and deviations. We use the galaxies from the Revised Flat Galaxy Catalogue subsample and the generalized Tully‐Fisher relationship in the ‘H I line width–angular diameter’ version. The analysis of the multipole structure has shown that the dipole velocity component (bulk motion) is underestimated, and the characteristic values of the quadrupole component are overestimated. The directions of the quadrupole component's eigenvectors can be determined precisely enough. Typical deviation angles of bulk motion apices lie between 17 and 40.. The main input is caused by errors in the measurement of the angular diameter. The probability of the quadrupole component being incidental can be estimated at the 4 per cent level. For the octopole component, it can be estimated at the 7–10 per cent level. This is essentially higher than the estimations less than 1 per cent due to the Fisher test. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An interpretation of rapid changes in the magnetic field associated with solar flares
Authors: Oreshina I.V. , Somov B.V. 
Published: September 2008

AbstractThe energy source of a flare is the magnetic field in the corona. A topological model of the magnetic field is used here for interpreting the recently discovered drastic changes in magnetic field associated with solar flares. The following observational results are self‐consistently explained: (1) the transverse field strength decreases at outer part of active regions and increases significantly in their centers; (2) the center‐of‐mass positions of opposite magnetic polarities converge towards the magnetic neutral line just after flares onset; (3) the magnetic flux of active regions decreases steadily during the course of flares. For X‐class flares, almost 50% events show such changes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The main sequence from F to K stars of the solar neighbourhood in SDSS colours
Authors: Just A. , Jahreiß H. 
Published: September 2008

AbstractFor an understanding of Galactic stellar populations in the SDSS filter system well defined stellar samples are needed. The nearby stars provide a complete stellar sample representative for the thin disc population. We compare the filter transformations of different authors applied to the main sequence stars from F to K dwarfs to SDSS filter system and discuss the properties of the main sequence. The location of the mean main sequence in colour‐magnitude diagrams is very sensitive to systematic differences in the filter transformation. A comparison with fiducial sequences of star clusters observed in g ′, r ′, and i ′ show good agreement. Theoretical isochrones from Padua and from Dartmouth have still some problems, especially in the (r – i) colours. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The problem of phase mixed shear Alfvén waves in the solar corona revisited
Authors: Mocanu G. , Marcu A. , Ballai I. , Orza B. 
Published: September 2008

AbstractThe problem of phase mixing of shear Alfvén waves is revisited taking into account dissipative phenomena specific for the solar corona. In regions of space plasmas where the dynamics is controlled by the magnetic field, transport coefficients become anisotropic with transport mechanism having different behavior and magnitude depending on the orientation with respect to the ambient magnetic field. Taking into account realistic values for dissipative coefficients we obtain that the previous results derived in context of torsional Alfvén wave phase mixing are actually heavily underestimated so phase mixing cannot be used to explain the damping of torsional Alfvén waves and heating of open coronal structures. The presented results indicate that in order for phase mixing to still be a viable mechanism to explain heating or wave damping unrealistic assumptions have to be made. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐resolution observations of extremely bright penumbral grains
Authors: Denker C. , Tritschler A. , Deng N. 
Published: September 2008

AbstractWe observed a cluster of extremely bright penumbral grains located at the inner limb‐side penumbra of the leading sunspot in active region NOAA 10892. The penumbral grains in the cluster showed a typical peak intensity of 1.58 times the intensityI0of the granulation surrounding the sunspot. The brightest specimen even reached values of 1.8–2.0I0, thus, exceeding the temperatures of the brightest granules in the immediate surroundings of the sunspot. We find that the observed sample of extremely bright penumbral grains is an intermittent phenomenon, that disappears on time scales of hours. Horizontal flow maps indicating proper motions reveal that the cluster leaves a distinct imprint on the penumbral flow field. We find that the divergence line co‐located with the cluster is displaced from the middle penumbra closer towards the umbra and that the radial outflow velocities are significantly increased to speeds in excess of 2 km s–1. The extremely bright penumbral grains, which are located at the inner limb‐side penumbra, are also discernible in offband Hαimages down to Hα± 0.045 nm. We interpret the observations in the context of themoving flux tubemodel arguing that hotter than normal material is rapidly ascending along the inner footpoint of the embedded flux tube, i.e., the ascending hot material is the cause of the extremely bright penumbral grains. This study is based on speckle‐reconstructed broad‐band images taken at 600 nm and chromospheric Hαobservations obtained with two‐dimensional spectroscopy. All data were taken with adaptive optics under very good seeing conditions at the Dunn Solar Telescope, National Solar Observatory/Sacramento Peak, New Mexico on 2006 June 10. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hydrogen production by photoautotrophic sulfur‐deprived Chlamydomonas reinhardtii pre‐grown and incubated under high light
Authors: Tolstygina Irina V. , Antal Taras K. , Kosourov Sergey N. , Krendeleva Tatyana E. , Rubin Andrey B. , Tsygankov Anatoly A. 
Published: September 2008

AbstractWe have previously demonstrated that Chlamydomonas reinhardtii can produce hydrogen under strictly photoautotrophic conditions during sulfur deprivation [Tsygankov et al. (2006); Int J Hydrogen Energy 3:1574–1584]. The maximum hydrogen photoproduction was achieved by photoautotrophic cultures pre‐grown under a low light regime (25 µE m−2 s−1). We failed to establish sustained hydrogen production from cultures pre‐grown under high light (100 µE m−2 s−1). A new approach for sustained hydrogen production by these cultures is presented here. Assuming that stable and reproducible transition to anerobiosis as well as high starch accumulation are important for hydrogen production, the influence of light intensity and dissolved oxygen concentration during the oxygen evolving stage of sulfur deprivation were investigated in cultures pre‐grown under high light. Results showed that light higher than 175 µE m−2 s−1 during sulfur deprivation induced reproducible transition to anerobiosis, although the total amount of starch accumulation and hydrogen production were insignificant. The potential PSII activity measured in the presence of an artificial electron acceptor (DCBQ) and an inhibitor of electron transport (DBMIB) did not change in cultures pre‐grown under 20 µE m−2 s−1 and incubated under 150 µE m−2 s−1 during sulfur deprivation. In contrast, the potential PSII activity decreased in cultures pre‐grown under 100 µE m−2 s−1 and incubated under 420 µE m−2 s−1. This indicates that cultures grown under higher light experience irreversible inhibition of PSII in addition to reversible down regulation. High dissolved O2 content during the oxygen evolving stage of sulfur deprivation has a negative regulatory role on PSII activity. To increase hydrogen production by C. reinhardtii pre‐grown under 100 µE m−2 s−1, cultures were incubated under elevated PFD and decreased oxygen pressure during the oxygen evolving stage. These cultures reproducibly reached anaerobic stage, accumulated significant quantities of starch and produced significant quantities of H2. It was found that elevation of pH from 7.4 to 7.7 during the oxygen producing stage of sulfur deprivation led to a significant increase of accumulated starch. Thus, control of pH during sulfur deprivation is a possible way to further optimize hydrogen production by photoautotrophic cultures. Biotechnol. Bioeng. 2009;102: 1055–1061. © 2008 Wiley Periodicals, Inc.
Complete versus incomplete revascularization in patients with multivessel disease undergoing percutaneous coronary intervention with drug‐eluting stents
Authors: Tamburino Corrado , Angiolillo Dominick J. , Capranzano Piera , Dimopoulos Konstantinos , La Manna Alessio , Barbagallo Rossella , Tagliareni Francesco , Mangiafico Sarah , Guzman Luis A. , Galassi Alfredo R. , Bass Theodore A. 
Published: September 2008

AbstractObjectives:To investigate the long‐term prognostic implications of complete versus incomplete revascularization in multivessel coronary artery disease (MVD) patients undergoing percutaneous coronary intervention (PCI) with drug‐eluting stent (DES).Background:Coronary artery bypass grafting (CABG) in patients with MVD provides better outcomes when complete revascularization is achieved. There is a paucity of data on the outcomes of complete versus incomplete revascularization of MVD patients undergoing PCI, and currently there is no data available with DES.Methods:Patients with MVD undergoing PCI with DES (sirolimus‐ or paclitaxel‐eluting stent) were included. Comparisons of long‐term outcomes between completely versus incompletely revascularized patients were made. The primary outcome measure was the composite of cardiac death, nonfatal myocardial infarction (MI), or any revascularization. Secondary endpoints were the components of the composite endpoint.Results:A total of 508 patients were considered for this analysis: 212 (41.7%) and 296 (58.3%) had complete and incomplete revascularization, respectively. The median follow‐up was 27.0 (interquartile range: 23.0–37.1) months. After adjusting for baseline characteristics, the hazard ratio (HR, 95% confidence interval) for complete revascularization was 0.43 (0.29–0.63,P< 0.0001) for the primary composite endpoint. Complete revascularization was associated with better outcomes for components of the composite endpoint: 0.37 (0.15–0.92,P= 0.03) for cardiac death, 0.34 (0.16–0.75P= 0.008) for the composite of cardiac death or MI and 0.45 (0.29–0.69,P= 0.0003) for any repeat revascularization. This association was confirmed in a propensity‐matched population.Conclusions:Complete revascularization with DES of MVD patients is associated with lower rates of long‐term adverse events. © 2008 Wiley‐Liss, Inc.
Prevention and management of transcatheter balloon‐expandable aortic valve malposition
Authors: Ali Abdullah M. Al , Altwegg Lukas , Horlick Eric M. , Feindel Christopher , Thompson Christopher R. , Cheung Anson , Carere Ronald G. , Humphries Karin , Ye Jian , Masson Jean‐Bernard , Webb John G. 
Published: September 2008

AbstractObjectives:Early clinical outcomes in selected high‐risk patients undergoing catheter‐based aortic valve replacement (AVR) compare favorably with conventional surgical AVR. Improved understanding of the mechanisms of success and failure of transcatheter AVR will likely improve outcomes further. To this end, we examined our experience during the developmental phases of transcatheter AVR and describe the causes and management of prosthetic valve malposition.Methods:Transcatheter balloon‐expandable AVR was performed in 170 patients at two centers. Malposition was defined as prosthetic valve implantation in a location other than within the native valve. Patients were prospectively identified and followed as part of an ongoing database.Results:Valve malposition occurred in 9 of 170 patients (5.3%). Final position was supravalvular in eight of nine cases. In all cases, embolization to the ascending aorta occurred within a few cardiac cycles following deployment. Importantly, late embolization was not observed. In most cases, the prosthesis was uneventfully repositioned in the more distal aorta. Positioning was subvalvular in one patient (0.6%), resulting in a severe regurgitation with residual native valve stenosis. Implantation of a second transcatheter valve was attempted in six patients and was successful in all. Conventional AVR was performed in two patients, with early mortality in one. At late follow‐up (mean 412 days), seven of nine patients remain alive (78%) with a functioning prosthesis and relief of aortic stenosis.Conclusions:Malposition of current balloon‐expandable aortic valves is a largely preventable complication. An improved understanding of the procedure will likely minimize this possibility and mitigate the consequences should malposition occur. © 2008 Wiley‐Liss, Inc.