bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling of In, Tl, Ga, Sb, and Pd as lanthanides binding agents in U-Zr metallic nuclear fuels
Authors: Bozzolo Guillermo , Yacout Abdellatif M. , Hofman Gerard L. , Mosca H. O. 
Published: November 2012

ABSTRACTAtomistic modeling is used to study the role of different alloying additions to metallic U-Zr nuclear fuels in terms of their ability to reduce lanthanide migration to the outer surface of the fuel and thus reduce their interaction with cladding. The Bozzolo-Ferrante-Smith (BFS) method for alloys is used to examine the behavior of each addition, the resulting phase structure, and the evolution of the fuel surface. Different behaviors are observed for each of the additives (In, Tl, Ga, Sb, Pd), all a result of the competition between the formation of bulk precipitates and the tendency of each additive to segregate to the surface. For each case, characteristic temperatures are determined indicating the range of temperatures in which each additive performs a different role. Sb and Pd additives are determined to be the most effective additions, properly balancing their ability to bind lanthanides in the fuel with their own segregating tendencies.
Electronic Structure of Compressed Americium Metal
Authors: Kolorenc Jindrich , Shick Alexander B. , Caciuffo Roberto 
Published: November 2012

ABSTRACTWe report a theoretical investigation of changes in the electronic structure of americium metal due to applied pressure. We employ a variant of the LDA+DMFT method that takes into account not only the correlations among the 5f electrons, but also the feedback of these correlations on the rest of the system by means of an appropriate adjustment of the electronic charge density. We observe only minor modification of the electronic structure in the compressed lattice, which is in accord with recent resonant x-ray spectroscopy experiments.
Systematic Trends in Non-resonant Inelastic X-ray Scattering of Actinides
Authors: van der Laan Gerrit 
Published: November 2012

ABSTRACTNonresonant inelastic x-ray scattering (NIXS) measurements probing the 5d→ 5felectronic transitions at the uraniumO4,5edges in a localized electron system such as UO2show a good agreement with many-electron atomic spectral calculations. The higher multipole spectra are split into two peaks that can be assigned as the 5d5/2and 5d3/2structures, despite the large electrostatic interactions. A new sum rule for the branching ratio of spin-orbit split core levels in electric multipole spectra, which generalizes the sum rule for dipole transitions in x-ray absorption spectroscopy, allows for a systematic analysis of the NIXS spectra. The branching ratio is linearly proportional to the expectation value of the angular part of the spin-orbit interaction in the initial state, where the rank of the multipole determines the coefficient of the linear dependence. This spin-orbit sum rule can be an important diagnostic tool for high-energy spectroscopies.
Ab Initio Study of Advanced Metallic Nuclear Fuels for Fast Breeder Reactors
Authors: Landa Alexander , Söderlind Per. , Grabowski Blazej , Turchi Patrice E.A. , Ruban Andrei V. , Vitos Levente 
Published: November 2012

ABSTRACTDensity-functional formalism is applied to study the ground state properties of γ-U-Zr and γ-U-Mo solid solutions. Calculated heats of formation are compared with CALPHAD assessments. We discuss how the heat of formation in both alloys correlates with the charge transfer between the alloy components. The decomposition curves for γ-based U-Zr and U-Mo solid solutions are derived from Ising-type Monte Carlo simulations. We explore the idea of stabilization of the δ-UZr2 compound against the α-Zr (hcp) structure due to increase of Zr d-band occupancy by the addition of U to Zr. We discuss how the specific behavior of the electronic density of states in the vicinity of the Fermi level promotes the stabilization of the U2Mo compound. The mechanism of possible Am redistribution in the U-Zr and U-Mo fuels is also discussed.
Protective Mechanisms of Simvastatin in Experimental Periodontal Disease
Authors: Dalcico Roberta , de Menezes Adriana M. A. , Deocleciano Otacilio B. , Oriá Reinaldo B. , Vale Mariana L. , Ribeiro Ronaldo A. , Brito Gerly A. de C. 
Published: November 2012

Background: Simvastatin is a cholesterol‐lowering drug whose pleiotropic effects may have a therapeutic impact on bone. This study evaluates the effect of simvastatin on rats subjected to experimental periodontal disease.Methods: Periodontitis was induced by ligature placement around the maxillary left second molar of rats for 11 days. Groups of six animals received oral saline or simvastatin (3, 10, and 30 mg/kg/day) until sacrifice on day 11. Alveolar bone loss was determined by macroscopic and histologic examination. The serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and total alkaline phosphatase (TAP) were evaluated. Gingival myeloperoxidase activity and gingival levels of interleukin‐1β (IL‐1β), tumor necrosis factor‐α, IL‐10, reduced glutathione, malonaldehyde, and nitrate/nitrite were analyzed to investigate oxidative stress and inflammation. Expression of inducible nitric oxide synthase (iNOS), matrix metalloproteinases 1 and 8 (MMP‐1 and ‐8), bone morphogenetic protein‐2 (BMP‐2), receptor activator of nuclear factor κB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) were also investigated by immunohistochemistry to assess bone turnover and metabolism. Immunofluorescence microscopy was used to confirm the expression of RANKL in rats’ maxillae.Results: Treatment with simvastatin improved alveolar bone loss within all of the parameters studied, thus demonstrating anti‐inflammatory and antioxidant activity. Simvastatin reduced expression of iNOS, MMP‐1 and ‐8, RANK, and RANKL and increased BMP‐2 and OPG levels in the periodontal tissue. Simvastatin (30 mg/kg) increased TAP activity on day 11 compared with the saline group. No differences were found in the levels of AST and ALT in any of the groups studied.Conclusion: The present data suggest that simvastatin prevents inflammatory bone resorption in experimental periodontitis, which may be mediated by its anti‐inflammatory and antioxidant properties.
Influence of Periodontal Status and Periodontopathogens on Levels of Oral Human β‐Defensin‐2 in Saliva
Authors: Pereira Alexandre L. , Franco Gilson C. , Cortelli Sheila C. , Aquino Davi R. , Costa Fernando O. , Raslan Suzane A. , Cortelli José R. 
Published: November 2012

Background: Expression patterns of human β‐defensin‐2 (HBD‐2) mRNA or HBD‐2 protein concentration and periodontal diseases have been a focus of scientific research. This study compares the salivary levels of HBD‐2 protein concentration of healthy patients and patients with gingivitis and chronic periodontitis (CP) and correlates these levels with the presence of periodontopathogens.Methods: A total of 89 patients were enrolled in this study: 31 periodontally healthy, 27 with gingivitis, and 31 with CP. Plaque and gingival indices, probing depth, and clinical attachment level were measured. The presence of Campylobacter rectus, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, and Prevotella intermedia was evaluated qualitatively by conventional polymerase chain reaction. HBD‐2 quantification in saliva was performed using an immune enzymatic assay. Frequency of periodontopathogens and HBD‐2 protein concentration was assessed. Association between HBD‐2 protein concentration (≥100 pg/mL) and the simultaneous presence of one to two, three to four, or five to six periodontopathogens was tested.Results: Although periodontally healthy individuals and patients with gingivitis showed similar HBD‐2 levels, the CP group displayed an increased level of HBD‐2. P. gingivalis, P. intermedia, T. forsythia, and T. denticola were more prevalent in CP; however, their mere presence was not related to the increased levels of HBD‐2 (Pearson correlation and multinomial logistic regression model).Conclusions: Salivary HBD‐2 protein concentration was higher in patients with CP compared with healthy individuals or patients with gingivitis. These different protein concentrations were not related to the frequency of periodontopathogens. Clinical inflammatory profile had a higher impact on salivary HBD‐2 levels than bacteria.
Blocking Proinflammatory Cytokine Release Modulates Peripheral Blood Mononuclear Cell Response to Porphyromonas gingivalis
Authors: Berker Ezel , Kantarci Alpdogan , Hasturk Hatice , Van Dyke Thomas E. 
Published: November 2012

Background: Chronic periodontitis (CP) is an inflammatory disease in which cytokines play a major role in the progression of disease. Anti‐inflammatory cytokines (interleukin 4 [IL‐4] and IL‐10) were reported to be absent or reduced in diseased periodontal tissues, suggesting an imbalance between the proinflammatory and anti‐inflammatory mediators. This study tests the hypothesis that there is cellular crosstalk mediated by proinflammatory and anti‐inflammatory cytokines and that blocking proinflammatory cytokine (tumor necrosis factor‐α [TNF‐α] and IL‐1) production will enhance anti‐inflammatory cytokine (IL‐4 and IL‐10) production from peripheral blood mononuclear cells (PBMCs) in response to Porphyromonas gingivalis.Methods: PBMCs were isolated from individuals diagnosed with CP or healthy individuals and cultured for 24 hours. Concanavalin A (ConA) was used as an activator of lymphocyte function. Live and heat‐killed P. gingivalis or lipopolysaccharide from P. gingivalis were used as the bacterial stimulants. TNF‐α and IL‐1 production was neutralized by specific antibodies against TNF‐α and IL‐1α or IL‐β. Culture supernatants were evaluated by enzyme‐linked immunosorbent assay for TNF‐α, IL‐1β, IL‐4, and IL‐10 production.Results: Live P. gingivalis did not result in any significant IL‐10 or IL‐4 release, whereas heat‐killed P. gingivalis led to a significant increase in IL‐10 levels compared with unstimulated or live P. gingivalis–stimulated cells from both healthy individuals or those with CP. Overall, PBMCs from patients with CP produced significantly lower IL‐10 in response to ConA and P. gingivalis, suggesting chronic suppression of the anti‐inflammatory cytokine production. Blocking the proinflammatory cytokine response did not result in any substantial change in IL‐10 or IL‐4 response to live P. gingivalis. Blocking the proinflammatory cytokine response restored IL‐10 production by cells from CP in response to P. gingivalis lipopolysaccharide.Conclusions: These findings suggest that PBMCs from patients with CP have suppressed anti‐inflammatory cytokine production that can, in part, be restored by neutralizing proinflammatory cytokines. Monocytes are an important source of IL‐10 production, and monocyte‐derived IL‐10 might play a regulatory role in the pathogenesis of CP.
Effect of Live Crude on Alkaline/Surfactant Polymer Formulations: Implications for Final Formulation Design
Authors: Southwick Jeffrey G. , Svec Yi , Chilek Greg , Shahin Gordon T. 
Published: November 2012

Summary
Phase-behavior experiments have identified several surfactant systems that develop high solubilization ratios and low interfacial tension (IFT) with a specific dead paraffinic crude oil at specific salinities.
The purpose of this work is to test these surfactant systems with reconstituted live crude. Emulsion-screening tests were performed in sight cells where an equilibrium amount of solution gas is dissolved in the crude at reservoir pressure (1,100 psi). The results indicate that the surfactant is relatively more soluble in the oil phase under these conditions. Thus, a formulated chemical slug for field conditions should contain either less salinity or a more hydrophilic surfactant system than that used in formulations with dead crude. Phase-behavior measurements estimate this offset to be approximately 0.25% less NaCl for the particular live crude in this study. The relevance of this offset is shown by comparing the results of dead-crude corefloods with a live-crude coreflood. A control experiment pressurizing oil with nitrogen at the same condition, 1,100 psi, did not show enhanced relative surfactant solubility in the oil phase.
Hydrate Decomposition and Its Material Balance in a Volumetric Tilted Hydrate-Capped Gas Reservoir by Method of Depressurization
Authors: Tabatabaie S. Hamed , Pooladi-Darvish M.. 
Published: November 2012

Summary
The decline in conventional hydrocarbon resources coupled with the increase in energy demand has encouraged the development of unconventional gas resources. One specific type of unconventional gas is the natural-gas hydrate. It is expected that the substantial size of this hydrate resource will be a motivating factor in its development. In the early phases of development of hydrate reservoirs, data are limited and a large number of sensitivity studies are required. Efficient and accurate analytical models are suitable for such sensitivity studies. One such model is presented in this work.
An analytical solution is developed to model the rate of gas generation and hydrate recovery when gas is produced from a tilted hydrate-capped gas reservoir in which the geothermal gradient is accounted for. As a result of the variation in temperature within the hydrate column, the size of the decomposing area increases with continued production.
Development of the analytical model in this work is based on a material-balance equation that is combined with the solution for the temperature of the decomposed zone and the hydrate-equilibrium curve. The three equations are solved simultaneously for the gas-generation rate. To validate the assumptions made in the development of the analytical model, a numerical simulator was used that does not make the assumptions of the analytical model. A close agreement is shown between the two models, validating the assumptions made in the analytical solution. The effects of different reservoir parameters on the reservoir performance were investigated by performing sensitivity analyses. The sensitivity results show how a steeper reservoir that extends closer to the base of the permafrost leads to less recovery or how a thicker hydrate cap could maintain the reservoir pressure for a longer time.
The model developed in this study can be used as an approximate engineering tool to evaluate the role of hydrates in improving the productivity and extending the life of tilted hydrate-capped gas reservoirs.
Novel Drag-Reducing Agents for Fracturing Treatments Based on Polyacrylamide Containing Weak Labile Links in the Polymer Backbone
Authors: Kot E.. , Saini R.K.. K. , Norman L.R.. R. , Bismarck A.. 
Published: November 2012

Summary
Water-soluble polymers have found extensive use in the oil and gas industry. For instance, high-molecular-weight polymers are very efficient drag-/friction-reducing agents and viscosifiers. Unfortunately, the adsorption of the polymer on the reservoir formation reduces the effectiveness of the recovery of oil and gas from low-permeability formations, such as shale. The availability of water-soluble polymers containing weak links in the backbone of the polymer that can be degraded upon experiencing a certain trigger, such as temperature, pH, or reducing agent, would be very advantageous. Because of the ability of weak links to degrade under certain conditions, such polymers can be used for their intended application and can afterward be degraded in a controlled and predetermined way. The resulting lower-molecular-weight fractions of that polymer lead to a reduced viscosity and quick partitioning into the water phase, and they are also less likely to adsorb onto formation surfaces. Additionally, no oxidizers need to be pumped to break or clean the deposited polymer, thus saving treatment time.
It has been proved that using a bifunctional reducing agent containing degradable groups and oxidizing metal ions as a redox couple is an effective method to initiate free-radical polymerization and build degradable groups into the backbone of vinyl polymers. Temperature-degradable but hydrolytically stable azo groups showed the most-desirable results. The presence of azo groups in the backbone of the synthesized polyacrylamide (PAM) was confirmed by H1-NMR spectra and differential scanning calorimetry (DSC). The degradation behavior of the PAM with temperature-sensitive azo groups was characterized using gel permeation chromatography (GPC) and proved that multiple labile links were built into the polymer backbone. It was also found that PAM with azo links in the polymer backbone is as good a drag-reducing agent as pure PAM. However, PAM with azo links in the backbone loses its drag-reduction properties once subjected to elevated temperatures, which for some applications is viewed as an advantage.
Wettability Alteration and Foam Mobility Control in a Layered, 2D Heterogeneous Sandpack
Authors: Li Robert F. , Hirasaki George J. , Miller Clarence A. , Masalmeh Shehadeh K. 
Published: November 2012

Summary
In a layered, 2D heterogeneous sandpack with a 19:1 permeability contrast that was preferentially oil-wet, the recovery by waterflood was only 49.1% of original oil in place (OOIP) because of injected water flowing through the high-permeability zone, leaving the low-permeability zone unswept. To enhance oil recovery, an anionic surfactant blend (NI) was injected that altered the wettability and lowered the interfacial tension (IFT). Once IFT was reduced to ultralow values, the adverse effect of capillarity retaining oil was eliminated. Gravity-driven vertical countercurrent flow then exchanged fluids between high- and low-permeability zones during a 42-day system shut-in. Cumulative recovery after a subsequent foam flood was 94.6% OOIP, even though foam strength was weak. Recovery with chemical flood (incremental recovered oil/waterflood remaining oil) was 89.4%. An alternative method is to apply foam mobility control as a robust viscous-force-dominant process with no initial surfactant injection and shut-in. The light crude oil studied in this paper was extremely detrimental to foam generation. However, the addition of lauryl betaine to NI (NIB) at a weight ratio of 1:2 (NI:lauryl betaine) made the new blend a good foaming agent with and without the presence of the crude oil. NIB by itself as an IFT-reducing and foaming agent is shown to be effective in various secondary and tertiary alkaline/surfactant/foam (ASF) processes in water-wet 1D homogeneous sandpacks and in an oil-wet heterogeneous layered system with a 34:1 permeability ratio.
Sequential Quadratic Programming for Solving Constrained Production Optimization–Case Study From Brugge Field
Authors: Dehdari Vahid , Oliver Dean S. 
Published: November 2012

Summary
Normally only approximately 30% of the oil in a reservoir is extracted during primary production, but using secondary-production methods such as water or gas injection, it is often possible to increase that percentage significantly and maintain the production rate of a reservoir over a longer period of time. In reservoirs under water or gas injection, additional gains can be obtained through an efficient strategy for management of front movement and reservoir sweep. The objective of reservoir production optimization is to maximize an outcome such as sweep efficiency or net present value (NPV) through the control of completion rates or pressures. Using optimization methods, it is possible to compute control settings that result in increased oil production and decreased water production compared with production from standard practices. In this paper, we focus on optimization using sequential quadratic programming (SQP) with an ensemble-based approach to estimate the gradient for the optimization. Although uncertainty in reservoir properties is usually important for the computation of optimal controls, here we use a single realization of the reservoir to evaluate the efficiency of the optimization algorithm.
The most expensive aspect of gradient-based optimization is usually the computation of gradients. Most practical production-optimization problems involve large-scale, highly complex reservoir models with thousands of constraints, which makes numerical calculation of the gradient time consuming. Here, we use an ensemble-based approach for finding gradients and use localization to improve estimation of the gradient from a small number of realizations. The Broyden-Fletcher-Goldfarb-Shanno (BFGS) method is used for maximizing the objective function, with the Hessian estimated from a sequence of estimates of the gradient. Improving the gradient approximation using localization results in improvement to the Hessian approximation. A second important aspect of the efficiency of the method is the identification of active constraints. In this paper, we use a method for eliminating nonnegativity constraints to decrease computation time and an updating procedure to solve each iteration of SQP much faster than the base case. Both the speed of the algorithm and the final NPV were increased significantly.
We evaluate the method by applying it to optimization of control settings in the Brugge field. Brugge is a 3D synthetic model designed by TNO with 20 vertical producers and 10 vertical peripheral water injectors. All of the producers and injectors are smart wells whose downhole chokes must be adjusted to optimize NPV. The total number of completion flow rates to be controlled is 84 at each timestep, with 40 timesteps (every 6 months). There are 1,200 inequality constraints on total well liquid rates and 3,360 nonnegativity constraints on completion liquid rates. There are also inequality constraints on the bottomhole pressure (BHP) for wells at each time period.
Modeling and Simulation of Nitrate Injection for Reservoir Souring Remediation
Authors: Haghshenas Mehdi , Sepehrnoori Kamy , Bryant Steven L. , Farhadinia Mohammad Ali 
Published: November 2012

Summary
Reservoir souring refers to the onset of hydrogen sulfide (H2S) production during waterflooding. Besides health and safety issues, H2S content reduces the value of the produced hydrocarbon. Nitrate injection is an effective method to prevent the formation of H2S. Designing this process requires the modeling of a complicated set of biogeochemical reactions involved in the production of H2S and its inhibition. This paper describes the modeling and simulation of biological reactions associated with the injection of nitrate to inhibit reservoir souring. The model is implemented in a general-purpose adaptive reservoir simulator (GPAS). To the best of our knowledge, GPAS is the first field-scale reservoir simulator that models reservoir souring treatment.
The basic mechanism in the biologically mediated generation of H2S is the reaction between sulfate in the injection water and fatty acids in the formation water in the presence of sulfate-reducing bacteria (SRB). There are proposed mechanisms that describe the effect of nitrate injection on souring remediation. Depending on the circumstances, more than one mechanism may occur at the same time. These mechanisms include the inhibitory effect of nitrite on sulfate reduction, the competition between SRB and nitrate-reducing bacteria (NRB), and the stimulation of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB). For each mechanism, we specify the biological species and chemical components involved and determine the role of each component in the biological reaction. For every biological reaction, a set of ordinary differential equations along with differential equations for the transport of chemical and biological species are solved.
The results of reported experiments in the literature are used to find the input parameters for field-scale simulations. This reservoir simulator can then predict the onset of reservoir souring and the effectiveness of nitrate injection and helps in the design of the process. The comprehensive modeling accounts for variation in biological system characteristics and reservoir conditions that affect the production and remediation of H2S.