bluuebunny/crossref_metadata_2025 huggingface dataset:
Actinide Response under Pressure Probed by Inelastic X-ray Scattering
Authors: Rueff J.-P.
Published: November 2012

The electronic response of actinide systems under high-pressure conditions is undoubtedly of broad scientific interest but simultaneously very difficult to qualify. We will focus here on the use of inelastic x-ray scattering and its significance for actinides research through recent examples. IXS indeed combines several advantages that turn it into a powerful probe of the electronic and valence properties of f-electron systems. Besides element and orbital selectivity, resonant IXS can overcome core-hole lifetime broadening thus providing sharper spectral features and finer details about the electronic structure. Second, non-dipolar transitions are allowed in non-resonant IXS at high momentum transfer; thus “giant dipolar” Fano-like resonances that overwhelms the electron response at the O4,5 edges can be avoided. Recent results of IXS under pressure in Am and U under pressure are presented along with perspectives for actinides research at SOLEIL synchrotron.
Influence of Carbonate on Uranium Solubility in the WIPP
Authors: Lucchini Jean-Francois , Ballard Sally , Khaing Hnin
Published: November 2012

In the performance assessment (PA) for the Waste Isolation Pilot Plant (WIPP), the solubility of uranium (VI) was conservatively set at 10-3 M for all expected WIPP conditions, including the potential and likely effects of carbonate complexation [1]. Under WIPP-relevant conditions, long-term experiments were performed to establish the uranium (VI) solubility limits in WIPP-simulated brine over a broad range of pCH+ values [7.5-12.5] and to evaluate the contribution of carbonate complexation and hydrolysis to uranium (VI) speciation. Data obtained in carbonate-free ERDA-6 brine, a simulated WIPP brine, were reported earlier [2]. In the absence of carbonate, uranium solubility approached 10-7 M at the expected pCH+ in the WIPP (~ 9.5). In the presence of a significant amount of carbonate (millimole levels), recent experimental results showed that uranium (VI) concentrations will not exceed 10-4M. This measured solubility limit is an order of magnitude lower than the uranium solubility value currently used in the WIPP PA [3]. A small effect of borate complexation was found in the pCH+ range [7.5-10]. At pCH+ ≥ 10, hydrolysis overwhelmed carbonate effects, and no amphoteric effect was observed.
Silicon Carbide Waveguides for Optogenetic Neural Stimulation
Authors: Register Joseph , Muller Andreas , King Justin , Weeber Edwin , Frewin Christopher L. , Saddow Stephen E.
Published: November 2012

In this paper we present a microfabricated SiC based alternative to glass-fiber optogenetic stimulation. The glass fiber system currently used for stimulation has numerous drawbacks. First, the very presence of glass can evoke an immune response in cortical tissue that can impede the light-to-neuron optical interface. This glial scarring of brain tissue effectively lowers the spatial resolution and power output of the system. Second, the fragility of an implanted glass fiber is a problem that has yet to be fully addressed. Using SiC the proposed optical structure will address these problems by significantly lowering the amount glial scarring and astrocytic activity expressed as a result of the implant. In addition, single crystal SiC allows for a flexible device that can move with the surrounding tissue without fracturing. Finally, the current glass fibers tend be single channel devices with a single ended emitter. The proposed microfabricated device will allow for multiple channels, multiple wavelengths of stimulation, and electrical feedback on each channel improving upon the current standard.
Characterization of 3C-SiC (100) as a platform for detecting the onset of acute myocardial infarction (AMI)
Authors: Oliveros Alexandra , Guiseppi-Elie Anthony , Jaroszeski Mark , Saddow Stephen E.
Published: November 2012

In this work we describe the characterization of anti-myoglobin immobilization on 3C-SiC (100) by means of surface modification with 3-aminopropyltriethoxysilane (APTES). Surface water contact angle measurements were used to compare the wettability of 3C-SiC (100) before (16 ±3°) and after APTES layer formation (61 ±1°). Atomic force microscopy (AFM) was used to confirm the homogenous formation of APTES and anti-myoglobin immobilization with EDC-sulfo NHS coupling. For the APTES surfaces no significant change in the surface roughness was obtained whereas with anti-myoglobin surfaces, particles on the order of ∼60 nm in diameter with a globular shape were observed.
Polymeric Nanospheres Containing Rare Earth Complexes and Colloidal Crystals with Luminescent Properties
Authors: Yang Xudong , Zhao Zixi , Shen Bowen , Lin Quan , Yang Bai
Published: November 2012

Colloidal particles (CPs) have been the subject of intensive studies and have attracted increasing attention from the scientific community. In this contribution, we present the design and synthesis of luminescent colloidal crystal films. Rare earth complexes as the photoluminescent source is introduced into the polymeric nanospheres system, the diameter can be controlled by changing the polymeric reaction condition, which can act as building blocks to prepare diverse functional materials. Further, three-dimensional (3-D) colloidal crystal films with excellent fluorescent properties are fabricated by self-organization of the monodispersed polymeric nanospheres. The colloidal crystal film indicates a photonic band gap, which depends on the diameter and size-dispersing of the nanospheres building blocks. It shows potential applications in fabricating optical devices, data storage, chemical and biological sensors, and color displays.
Uncooled microbolometers with hydrogenated amorphous germanium-silicon films: Different device configurations and improvements on the thermosensing films
Authors: Moreno Mario , Torres Alfonso , Ambrosio Roberto , Rosales Pedro , Kosarev Andrey , Reyes Claudia , Zuniga Carlos , Calleja Wilfrido , de la Hidalga Wade Francisco J. , Dominguez Miguel A.
Published: November 2012

We report our main results on the development of un-cooled microbolometers based on hydrogenated amorphous Germanium-Silicon (a-GexSiy:H) thermo-sensing films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD). Our research has been conducted to improve both, the structure of the devices (pixels) and the performance characteristics of the amorphous Germanium-Silicon thermosensing films.

Our motivation is to produce microbolometers with much better performance characteristics (larger thermal coefficient of resistance, larger conductivity and better stability) than those available in commercial microbolometer arrays, based on boron doped hydrogenated amorphous silicon (a-Si:H,B).

As part of our latest research, we also report the study of what we believe is the next generation of thermosensing films based on Silicon and Geranium amorphous films with embedded nanocrystals in the amorphous matrix (polymorphous films). Those materials have several advantages over amorphous, as a lower defect density, better stability and better transport properties.
Longevity of Plutonium 238 Heat Sources
Authors: Mulford Roberta N. , Richardson Paul D. , Hickey Joseph , Chavarria Rene
Published: November 2012

Plutonium oxide heat sources are used to power space missions. The heat produced by alpha decay of the 238 isotope of Pu is converted to electricity in a thermopile, providing electricity during a substantial fraction of the 88 year half-life of the isotope. Decay of the Pu produces helium and uranium, and a fraction of the evolved helium is captured in the oxide matrix. All of the helium produced in decay can in principle be contained in the oxide lattice, where it occupies the tetrahedral sites. Some helium diffuses out at a rate that is somewhat dependent on the form and morphology of the fuel. Rates have previously been measured for oxide aged about 1 year. Current measurements on sealed heat sources as old as 34 years indicate that the rate of diffusion has changed only slightly over time. Possible mechanisms for helium release include bubble diffusion, point defect migration, agglomeration and movement of He at grain boundaries, and volume diffusion through the lattice sites. We observe primarily diffusion from site to site within the lattice, with an activation energy of 18.7 kcal/mole, independent of point defect movement, despite the rising concentration of helium in the lattice over time and the accumulation of radiation damage within the lattice. Because of the slow diffusion of helium from the fuel to the headspace, heat sources are anticipated to be stable over a long lifetime.
Synthesis of FeS2 Nano Crystals for Ink-Based Solar Cells
Authors: Ganta Lakshmi Kanth , Dhakal Tara P. , Rajendran Surya , Westgate Charles R.
Published: November 2012

Although pyrite (FeS2) is abundant, getting a single-phase pyrite thin film is difficult due to the coexistence of various phases of iron and sulfur in nature. We propose an ink-based process for attaining the pyrite phase of iron sulfide. This work involves degassing Iron (II) chloride in an octadecylamine solution and later reflux with addition of sulfur in diphenyl ether at 200°C. The process yielded phase-pure single crystalline pyrite nanocrystals which were later cleaned and dispersed in chloroform for uniform suspension. Thus obtained nanocrystals were deposited as thin films using drop casting and spin coating. Solar cells were fabricated using CdS as an n-type window layer in a superstrate configuration. When tested, the superstrate type FeS2 nanoparticle cell showed 0.03% with high Voc of 565 mV.
Pulmonary Toxicity of Indium Tin Oxide and Copper Indium Gallium Diselenide
Authors: Tanaka Akiyo , Hirata Miyuki , Koga Kazunori , Nakano Makiko , Omae Kazuyuki , Kiyohara Yutaka
Published: November 2012

The aim of this review is to introduce the adverse health effects of indium compounds. This review consists of 2 parts: (1) a study of the toxic effects in indium compounds in humans, and (2) a study of the toxic effects of indium tin oxide (ITO) and copper indium gallium diselenide (CIGS) in animals.

To date, 4 epidemiological surveys have been conducted of indium-handling workers in Japan, and all who were studied showed that exposure to indium compounds caused pulmonary interstitial and emphysematous changes. There were clear dose-response and dose-effect relationships between the serum indium levels and the levels of Krebs von den Lungen-6 (KL-6), which is a serological indicator of interstitial pneumonia up until 2011, 8 cases of interstitial pneumonia in Japanese indium-exposed workers, 2 cases of pulmonary alveolar proteinosis (PAP) in US indium-exposed workers, and 1 case of PAP in a Chinese indium-exposed worker have been reported.

In animals studies, it has been clearly demonstrated that ITO and CIGS particles cause pulmonary toxicity and that the dissolution of ITO and CIGS particles in the lungs is considerably slow when repeated intratracheal instillations were given to experimental animals.

Thus, more studies are needed on the effects of human exposure to indium compounds.
Magnetic Hardening of Mechanically Alloyed Pr2Co7
Authors: Bessais L. , Fersi R. , Cabié M. , Mliki N.
Published: November 2012

The Pr2Co7 alloys are known to crystallize in two polymorphic forms: a hexagonal of the Ce2Ni7 type structure and a rhombohedral of the Gd2Co7 one. They were synthesized by mechanical milling and subsequent annealing in high vacuum. In this work, we focus on the structural study of these phases using X-ray diffraction and transmission electron microscopy. Also, we present the evolution of magnetic properties of these compounds vs the annealing temperature. The coercivity increases with annealing temperature reaching a maximum for TA = 800 °C. The highest is equal to 18 kOe at 293 K and 23 kOe at 10 K. The high magnetic properties observed in these nanostructured Pr2Co7 intermetallic alloys have their origin in its relatively high uniaxial magnetocrystalline anisotropy field, and in the homogeneous nanostructure developed by mechanical milling process and subsequent annealing. This high coercivity is attributed to the high anisotropy field of the Pr2Co7 phase and its nanoscale grain size. This leads to the formation of a magnetically hard Pr2Co7 phase.
Sb-Te Phase-change Nanowires by Templated Electrodeposition
Authors: Ihalawela C. A. , Cook R. E. , Lin X. M. , Wang H. H. , Chen G.
Published: November 2012

Phase-change memory materials (PCMMs) are semiconductors that exhibit rapid order-disorder transition under electrical or optical pulse excitation. Currently thin-film-based PCMMs play a dominant role in fabrication of non-volatile memory devices. In contrast, phase-change nanowires (PCNWs) have the potential to overcome future challenges such as high data density and low power consumption. Among the various methods to synthesize PCNWs, the vapor-liquid-solid method has been reported previously. In this paper, we report synthesis of Sb-Te PCNWs using a templated electrochemical method. Nanoporous anodic aluminum oxide (AAO) was used as a template for the growth of nanowires. Sb-Te PCNWs with different compositions, diameters and aspect ratios were grown inside the AAO template by electrodeposition. Composition and structure of these nanowires were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction, and scanning and transmission electron microscopy. It is found that electrodeposition through nanosized channels results in materials that are quite different from those electrodeposited on unrestricted surface. The mechanism of nanowire formation inside the channels of AAO template is discussed.
Localization vs delocalization of 5f electrons in actinides: Dual nature and electron spectroscopies
Authors: Zwicknagl Gertrud
Published: November 2012

Intermetallic compounds containing actinide ions exhibit a broad spectrum of different physical phenomena at low temperatures. The latter include heavy quasiparticles, unconventional superconductivity and various forms of magnetic ordering. The complex and sometimes enigmatic properties of these compounds derive from the strong correlations among the 5f electrons. Previous model calculations suggested that the intra-atomic Hund’s rule-type correlations may lead to partial localization which is reflected e. g. in the co-existence of itinerant 5f-derived heavy quasiparticles and local magnetic excitations. The conjectured "dual nature" of 5f electrons which is closely related to the question of the 5f valence of the actinide ions is not directly probed by ground state properties and the low-energy excitations. Here we present microscopic calculations for core-level spectroscopy emphasizing the consequences of strong intra-atomic correlations of the 5f shell.
Synchrotron Topography Studies of Growth and Deformation-Induced Dislocations in 4H-SiC
Authors: Dudley M. , Wang H. , Wu F. , Byrappa S. , Shun S. , Raghothamachar B. , Sanchez E. K. , Chung G. , Hansen D. , Mueller S. G. , Loboda M. J.
Published: November 2012

Synchrotron topography studies are presented of the behavior of growth dislocations and deformation-induced dislocations in 4H-SiC single crystals. The growth dislocations include those in threading orientation with line directions approximately along c with Burgers vectors of a, c, and na+mc (where n and m are integers) while the deformation-induced dislocations include those with line directions confined to the basal plane with Burgers vectors of a and Shockley partial dislocations with Burgers vectors of 1/3<1-100> as well as those with line directions in the {1-100} prismatic planes with Burgers vectors of a. Processes leading to the nucleation of the growth dislocations are discussed as well as their deflection onto the basal plane during crystal growth in a reversible process. This latter process can lead to the conversion of segments of the deflected growth dislocations into deformation induced dislocations. In some cases this can lead to dislocation multiplication via the Hopping Frank-Read source mechanism and in others to the motion of single Shockley partial dislocations leading to Shockley stacking fault expansion. Studies are also presented of interactions between threading growth dislocations with c-component of Burger’s vector facilitated by climb processes which are mediated by interactions with non-equilibrium concentrations of vacancies. This can lead to reactions whereby complete or partial dislocation Burgers vector annihilation occurs.
Highly resolved synchrotron-based investigations related to nuclear waste disposal
Authors: Denecke Melissa A. , Borchert Manuela , Denning Robert G. , de Nolf Wout , Falkenberg Gerald , Hönig Susanne , Klinkenberg Martina , Kvashnina Kristina , Neumeier Stefan , Patommel Jens , Petersmann Tobias , Pruessmann Tim , Ritter Stephan , Schroer Christian G. , Stephan Sandra , Villanova Julie , Vitova Tonya , Wellenreuther Gerd
Published: November 2012

Synchrotron-based X-ray techniques are used increasingly to characterize actinide element speciation in heterogeneous media related to nuclear waste disposal safety. Especially techniques offering added temporal, spatial and energy resolved information are advancing our understanding of f-element physics and chemistry in general and of actinide element waste disposal in particular. Examples of investigations of uranium containing systems using both highly (energy) resolved X-ray emission spectroscopy (HRXES) techniques and spatially resolved techniques with focused X-ray beams are presented in this paper: polarization dependent partial fluorescence yield X-ray absorption near edge structure (PD-PFY-XANES) spectroscopic studies of a single Cs2UO2Cl4 crystal, which experimentally reveal a splitting of the σ, π, and δ components of the 6d valence states [1], and characterization of UO2/Mo thin films prepared on different substrates using a combination of techniques (2D and 3D micro- and nano-X-ray fluorescence, XANES and both holographic and ptychographic tomography).
Models of Mixed Metal-Oxide Interfaces for Atomistic Materials Simulations
Authors: Valone Steven M.
Published: November 2012

Nuclear fuels and materials present special problems to atomistic-scale modeling. At a metal-metal-oxide interface, the metal centers are charged on the oxide side, but neutral on the metallic side. The intimate contact necessitates that atomistic models for these materials be both compatible and consistent with one another at some level. A new "fragment’’ Hamiltonian (FH) model, at the atomistic level, is presented that reduces qualitatively to existing, successful models for metals, such as the embedded atom method, and ceramics, such as the charge equilibration models. Moreover, the FH model possesses both electron hopping and fundamental gaps that appear as separate terms in a generalized embedding function. The electron hopping contributions come from both one-electron and two-electron sources. These contributions appear as a result of the FH point of view, rather than being postulated. The model obeys certain wellknown theoretical limits that come from the nonlinearity of electron hopping processes as the volume of a crystal is changed. The generalized notion of embedding entails two variables instead of one. The ability to account for multiple charge states in the cations leads to the capability within the model to distinguish the qualitative differences among metallic, ionic, and covalent bonding environments. The details of all of these energies, among with fragmentfragment interactions, combine to determine the state of the atom in the material.
Oxygen potentials of PuO2-x
Authors: Komeno Akira , Kato Masato , Hirooka Shun , Sunaoshi Takeo
Published: November 2012

Oxygen potentials of PuO2-x were measured at temperatures of 1473 - 1873 K by thermo-gravimetry. The oxygen potentials were determined by in situ analysis as functions of oxygen-to-metal ratio and temperature. The measurement data were analyzed on the basis of defect chemistry and an approximate equation was derived to represent the relationship among temperature, oxygen partial pressure, and deviation x in PuO2-x.
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

Atomistic 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

We 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

Nonresonant 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

Density-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.
Hydration mechanism of tricalcium silicate (alite)
Authors: Noor-ul-Amin  , Alam Sultan , Gul Saeed , Muhammad Khan
Published: November 2012

In this review paper, the hydration of alite with reference to its stages and mechanism is discussed. The overall hydration process of alite is divided in four stages: period of initial reaction, period of slow reaction, acceleration period and deceleration period. The addition of calcium sulfate modifies the hydration process of alite, the rate of reaction of tricalcium aluminate, the interactions of silicates and aluminates and the kinetics of the deceleration period. Different hydration products are obtained in the presence of calcium chloride, which not only activate the hydration process but improve the strength of cement mortar.
Lifecycle management of footbridges: a framework
Authors: Ho Lok Hang
Published: November 2012

Little effort has been made to develop a life-cycle management system for small or medium-scale projects, such as the provision of footbridges. As the number of footbridges keeps increasing, there is a need to develop an optimal management strategy to optimise the cost of design and construction, as well as the cost of future actions such as maintenance, inspection and repair. However, while footbridges tend to be built in the form of networks, in most existing life-cycle management system research and practice, bridges are treated individually rather than as a bridge network. A new life-cycle management system for footbridges is therefore needed. The objective of this paper is to propose a framework for a life-cycle management system of footbridges which consists of three management levels – component level, project level and network level – in order to manage footbridges as a united network. The management approach and the dominant components of the proposed framework are introduced and application of the framework to Hong Kong provides an illustrative example.
Concrete bridge deck stresses induced by stay-in-place forms
Authors: Riad Mourad Y. , William Gergis W. , Shoukry Samir N.
Published: November 2012

In this study, the restraining actions induced by stay-in-place metal forms to concrete bridge decks are examined. A comparison between the behaviour of a concrete deck section constructed with regular stay-in-place metal forms and that constructed on a flat-bed geometry where the corrugations in the stay-in-place forms are filled with extruded polystyrene foam is conducted. Data consisting of three-dimensional concrete deck strains, thermal gradient profiles through the deck thickness, deck deflection profiles and reinforcement strains were recorded through a long-term sensory system consisting of 340 sensors embedded within the deck since construction. Analysis of stresses developed in the concrete deck material indicates that using the foam material to fill the corrugations proved to be successful in reducing the concrete shrinkage stresses at early age and also in reducing the constraining effects of the stay-in-place forms on deck expansion and contraction within the monitoring period of about 1 year.
Delivering London 2012: Contaminated soil treatment at the Olympic Park
Authors: Mead Ian , Apted James , Sharif Saphina
Published: November 2012

The creation of the Olympic Park, commenced with the formation of the development platform, on which the venues and infrastructure was built. This was part of the enabling works, and included 2 million m3 of excavation, and the remediation of contamination. To enable the contaminated soils to be reused, a number of soil treatment techniques were adopted: soil washing, bioremediation, chemical stabilisation and material sorting. Soil washing was the main technique, treating around 700 000 m3 of soil by mixing it with water. This removed the fine grained fractions on which the contaminants were predominantly based, creating a filter cake, typically around 20% of the total volume of soil washed. Bioremediation and chemical stabilisation together treated less than 100 000 m3 of soil. A regime of chemical testing was established to test the materials at the excavation stage, manage the treatment and finally validate the final material. With the exception of the final validation, testing was carried out off site in MCERTS accredited laboratories, the bulk of the testing was undertaken in the site laboratory, which also handled geotechnical testing.
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

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

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

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

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

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.