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Sample records for enhanced wellbore stabilization

  1. Coupled wellbore erosion and stability analysis

    NASA Astrophysics Data System (ADS)

    Stavropoulou, M.; Papanastasiou, P.; Vardoulakis, I.

    1998-09-01

    This paper extends earlier work on sand erosion and presents an attempt to couple sand erosion to mechanical damage of rock around a wellbore. Porosity which evolves in time and space as surface erosion progresses, is chosen as the coupling parameter. Both rock elasticity and strength (cohesion) are assumed to depend on porosity in such a way that the material becomes weaker with increasing porosity. The mathematical model, consists of erosion equations, mixture flow equations and stress equilibrium equations, is solved numerically by Galerkin finite element method. Numerical results suggest that erosion, resulting in sand production, is high close to the free surface. Erosion is accompained by changes in porosity and a significant permeability increase. Erosion in the vicinity of the wellbore induces alterations in the mechanical behaviour of the medium. Weakening of rock stiffness leads to severe alteration of both effective stresses and pore pressure near the cavity. Since cohesion decreases with increasing porosity, one can also identify the time instant at which rock mechanical failure starts.

  2. A Wellbore Stability Model for a Deviated Well in a Transversely Isotropic Formation Considering Poroelastic Effects

    NASA Astrophysics Data System (ADS)

    Liu, Ming; Jin, Yan; Lu, Yunhu; Chen, Mian; Hou, Bing; Chen, Wenyi; Wen, Xin; Yu, Xiaoning

    2016-09-01

    To analyse wellbore stability phenomena when drilling through a transversely isotropic formation such as shale, a wellbore stability model is developed based on the coordinate transformation method and complex variable elasticity theory. In order to comprehensively consider the anisotropies in the transversely isotropic formation, the model includes the followings: 1. the elastic anisotropy due to the sedimentation effect and naturally developed fractures and 2. the strength anisotropy due to the poor cementation between bedding planes and natural fractures. The model is further generalized by accounting for an arbitrary wellbore trajectory under an arbitrary in situ stress orientation. Next, the model is used in a parametric study that includes factors such as elastic anisotropy, strength anisotropy, multiple weak planes, in situ stress anisotropy, and poroelastic anisotropy, all of which can have a great influence on wellbore stability. Finally, a correction for a frequently used failure criterion has been made to ensure that the newly developed model is comprehensive and accurate for wellbore stability analyses in highly heterogeneous formations.

  3. A study of wellbore stability in shales including poroelastic, chemical, and thermal effects

    NASA Astrophysics Data System (ADS)

    Chen, Guizhong

    Shale is always a troublesome rock during oil and gas drilling operations. Shale (in)stability has been of great concern in the oil industry for decades. It has also been a costly problem and has perplexed the industry for many years. A better understanding of the wellbore stability mechanism in shales is imperative. The object of this study is to develop a comprehensive model to deal with borehole instability problems in shales. Wellbore stability problems are caused by changes in near wellbore pore pressure and rock stresses. The excess of rock effective stresses over the rock strength can cause collapse (shear) or breakdown (tensile) failure of the drilled formation. This imbalance between the rock stress and rock strength always happens when the in-situ rock is drilled out and is replaced by the drilling fluid. Pore pressure alterations due to osmotic effects are a function of the water activity in the drilling fluid and the membrane efficiency of the shale. In this work, thermo-mechanical stresses coupled with the osmotic contributions are used to compute conditions under which the wellbore becomes unstable. The osmotic contribution is added to the hydraulic potential to form the net driving force of the fluid flow. Changes in pore pressure have been observed in shale experiments. An alteration of the shale strength was also observed when shales are exposed to different drilling fluids. It is necessary to consider shale strength alterations when inspecting the wellbore stability status and determining critical mud weights. Thermal diffusion inside the drilled formation induces additional pore pressure and rock stress changes and consequently affects shale stability. Thermal effects are important because thermal diffusion into shale formations occurs more quickly than hydraulic diffusion and thereby dominates during early times. Rock temperature and pore pressure can be partially decoupled for shale formations. The partially decoupled problem can be solved

  4. Wellbore stability in oil and gas drilling with chemical-mechanical coupling.

    PubMed

    Yan, Chuanliang; Deng, Jingen; Yu, Baohua

    2013-01-01

    Wellbore instability in oil and gas drilling is resulted from both mechanical and chemical factors. Hydration is produced in shale formation owing to the influence of the chemical property of drilling fluid. A new experimental method to measure diffusion coefficient of shale hydration is given, and the calculation method of experimental results is introduced. The diffusion coefficient of shale hydration is measured with the downhole temperature and pressure condition, then the penetration migrate law of drilling fluid filtrate around the wellbore is calculated. Furthermore, the changing rules of shale mechanical properties affected by hydration and water absorption are studied through experiments. The relationships between shale mechanical parameters and the water content are established. The wellbore stability model chemical-mechanical coupling is obtained based on the experimental results. Under the action of drilling fluid, hydration makes the shale formation softened and produced the swelling strain after drilling. This will lead to the collapse pressure increases after drilling. The study results provide a reference for studying hydration collapse period of shale. PMID:23935430

  5. Application of in situ stress estimation methods in wellbore stability analysis under isotropic and anisotropic conditions

    NASA Astrophysics Data System (ADS)

    Gholami, Raoof; Rasouli, Vamegh; Aadnoy, Bernt; Mohammadi, Ramin

    2015-08-01

    Estimation of in situ stresses is a key step in many petroleum engineering applications, ranging from wellbore stability to sanding analysis and hydraulic fracturing design. Direct techniques conventionally used to determine in situ stresses are indeed very time consuming and expensive. These measurements would also be restricted as to the depth of acquisition, and generalization of the results to entire rock masses may not yield representative results. In this paper, applications of three indirect methods-Zoback’s polygon, shear moduli, and poroelastic-are studied to assess their applicability in providing reliable stress estimation under isotropic and anisotropic conditions. Determination of elastic, strength, and in situ stress parameters according to the assumption of each method for one of the vertical wells drilled in south Iran indicated that the shear moduli method is an appropriate approach for prediction of maximum horizontal stress within an interval where sufficient field data including leak-off tests are acquired. However, the poroelastic method seems to be a better method in prediction of in situ stresses under anisotropic conditions. This might be due to the presence of excessive shale formations in subsurface layers, causing structural or intrinsic anisotropy-based methods such as poroelastic equations to deliver more accurate results. However, making general conclusions based on studying a single vertical wellbore may not be sufficient, and therefore further studies are required.

  6. Laboratory measurements of seismic velocity anisotropy of salt diapirs: Implications for wellbore stability and seismic processing

    NASA Astrophysics Data System (ADS)

    Vargas-Meleza, Liliana; Healy, David

    2013-04-01

    A set of ten evaporite samples collected from outcrops in a single diapiric province in Cape Breton Island (Canada) have been tested for seismic velocity anisotropy using three methods: 1) conventional ultrasonic pulse transmission method, where velocities are found from the travel times and the known dimensions of the samples. In order to obtain the entire suite of elastic constants, both P- and S-wave velocity measurements were taken in three different directions of cuboid rock samples. Velocities have been measured under dry, ambient conditions of temperature and pressure in halite-, gypsum- and anhydrite-dominated samples; 2) optical microscopy and scanning electron microscopy on thin sections to define the spatial distribution of minerals, their crystallographic preferred orientations (CPO); and 3) a numerical 'rock-recipe' approach based on Tatham et al. (2008) to calculate seismic velocity anisotropy using arbitrary composites of evaporite minerals and different CPOs. These three methods are then compared to understand the controlling factors of the anisotropic elastic properties. The elasticity data are used to guide geomechanical modeling for wellbore stability and to provide insights for the seismic data processing and seismic imaging of salt diapirs. Reference Tatham, D.J., Lloyd, G.E., Butler, R.W.H. and Casey, M, 2008, Amphibole and lower crustal seismic properties: Earth and Planetary Science Letters, 267, 118-128.

  7. Implementation of Bounding Surface Model into ABAQUS and Its Application to Wellbore Stability Analysis

    NASA Astrophysics Data System (ADS)

    Chen, S.; Al-Muntasheri, G.; Abousleiman, Y. N.

    2014-12-01

    The critical state concept based bounding surface model is one of the most widely used elastoplastic constitutive models for geomaterials, attributed mainly to its essential feature of allowing plastic deformation to occur for stress points within the bounding surface and thus the capability to represent the realistic non-recoverable behaviour of soils and rocks observed under the cyclic loading. This paper develops an implicit integration algorithm for the bounding surface model, using the standard return mapping approach (elastic predictor-plastic corrector), to obtain the updated stresses for the given strain increments. The formulation of the constitutive integration requires the derivation of a supplementary differential equation to describe the evolution of a key variable, i.e., the ratio between the image stress and the current stress quantities. It is essentially an extension of the integration scheme presented in an earlier work used for the simple bounding surface version of modified Cam Clay associated with a substantially simplified hardening rule. The integration algorithm for the bounding surface model is implemented into the finite element analysis commercial program, ABAQUS, through the material interface of UMAT (user defined material subroutine), and then used for the analysis of wellbore stability problem. The predictions from the ABAQUS simulations are generally in excellent agreement with the available analytical solutions, thus demonstrating the accuracy and robustness of the proposed integration scheme.

  8. Wellbore pressure transducer

    DOEpatents

    Shuck, Lowell Z.

    1979-01-01

    Subterranean earth formations containing energy values are subjected to hydraulic fracturing procedures to enhance the recovery of the energy values. These fractures are induced in the earth formation by pumping liquid into the wellbore penetrating the earth formation until the pressure of the liquid is sufficient to fracture the earth formation adjacent to the wellbore. The present invention is directed to a transducer which is positionable within the wellbore to generate a signal indicative of the fracture initiation useful for providing a timing signal to equipment for seismic mapping of the fracture as it occurs and for providing a measurement of the pressure at which the fracture is initiated.

  9. Weatherford Inclined Wellbore Construction

    SciTech Connect

    Schulte, R.

    2002-08-19

    The Rocky Mountain Oilfield Testing Center (RMOTC) has recently completed construction of an inclined wellbore with seven (7) inch, twenty-three (23) pound casing at a total depth of 1296 feet. The inclined wellbore is near vertical to 180 feet with a build angle of approximately 4.5 degrees per hundred feet thereafter. The inclined wellbore was utilized for further proprietary testing after construction and validation. The wellbore is available to other companies requiring a cased hole environment with known deviation out to fifty degrees (50) from vertical. The wellbore may also be used by RMOTC for further deepening into the fractured shales of the Steele and Niobrara formation.

  10. Process and composition to enhance removal of polymer-containing filter cakes from wellbores

    SciTech Connect

    Mondshine, T.C.; Benta, G.R.

    1993-08-24

    A method is described for removing the filter cake from the surface of a hydrocarbon-containing subterranean formation, the filter cake comprising bridging particles and at least one polysaccharide polymer, which comprises contacting the filter cake with a solution comprising an aqueous brine, a peroxide selected from the group consisting of alkaline earth metal peroxides, zinc peroxide, and mixtures thereof, and an acidic substance to provide the soak solution with a pH in the range from about 1 to about 8, for a period of time at least sufficient to decompose the polysaccharide polymers therein to such an extent that the filter cake forms a loosely adherent mass on the surface of the formation, and thereafter contacting the filter cake with a wash solution in which the bridging particles are soluble to remove the remaining filter cake solids. A composition is described for decomposing polysaccharide polymers contained within filter cakes on the sides of a borehole, the filter cake containing at least one polysaccharide polymer and bridging particles, which comprises an aqueous brine in which the bridging particles are not appreciably soluble, an alkaline earth metal peroxide in an amount from about 2.8 kg/m[sup 3] to about 57 kg/m[sup 3], a soluble activator to enhance the rate of decomposition of the polysaccharide, and an acidic substance to provide the composition with a pH in the range from about 1 to about 8.

  11. Wellbore simulation - case studies

    SciTech Connect

    Freeston, Derek; Gunn, Calum

    1993-01-28

    The use of a wellbore simulator, WELLSIM, to characterise the effects of multi-feed inflow on wellbore pressure-temperature characteristics, and diameter changes to a well on the deliverability curve, is discussed. Matching analyses are performed with the simulator on a well which has a number of two-phase and liquid infeeds, and it is demonstrated that good matches to both pressure and temperature profiles can be achieved. The significance of the reservoir/feed response curve for a steam well is illustrated, and the optimisation of wellbore diameter is shown to be related to whether the discharge is wellbore or reservoir controlled.

  12. Wellbore Integrity Network

    SciTech Connect

    Carey, James W.; Bachu, Stefan

    2012-06-21

    In this presentation, we review the current state of knowledge on wellbore integrity as developed in the IEA Greenhouse Gas Programme's Wellbore Integrity Network. Wells are one of the primary risks to the successful implementation of CO{sub 2} storage programs. Experimental studies show that wellbore materials react with CO{sub 2} (carbonation of cement and corrosion of steel) but the impact on zonal isolation is unclear. Field studies of wells in CO{sub 2}-bearing fields show that CO{sub 2} does migrate external to casing. However, rates and amounts of CO{sub 2} have not been quantified. At the decade time scale, wellbore integrity is driven by construction quality and geomechanical processes. Over longer time-scales (> 100 years), chemical processes (cement degradation and corrosion) become more important, but competing geomechanical processes may preserve wellbore integrity.

  13. Enhanced Wellbore Stabilization and Reservoir Productivity with Aphron Drilling Fluid Technology

    SciTech Connect

    Tatiana Hoff; Fred Growcock

    2004-12-30

    Core Leak-off tests are commonly used to ascertain the ability of a drilling fluid to seal permeable rock under downhole conditions. Unfortunately, these tests are expensive and require a long time to set up. To monitor fluid invasion trends and to evaluate potential treatments for reducing fluid invasion on location, a simpler screening test is highly desirable. The Capillary Suction Time (CST) Test has been used since the 1970's as a fast, yet reliable, method for characterizing fluid filterability and the condition of colloidal materials in water treatment facilities and drilling fluids. For the latter, it has usually been applied to determine the state of flocculation of clay-bearing fluids and to screen potential shale inhibitors. In this work, the CST method was evaluated as a screening tool for predicting relative invasion rates of drilling fluids in permeable cores. However, the drilling fluids examined--DRILPLEX, FLOPRO, and APHRON ICS--are all designed to generate low fluid loss and give CST values that are so high that fluid invasion comes to be dominated by experimental artifacts, such as fluid evaporation. As described in this work, the CST procedure was modified so as to minimize such artifacts and permit differentiation of the fluids under investigation.

  14. Enhanced Wellbore Stabilization and Reservoir Productivity with Aphron Drilling Fluid Technology

    SciTech Connect

    Fred Growcock

    2004-03-31

    During this second Quarter of the Project, the first four tasks of Phase I--all focusing on the behavior of aphrons--were continued: (a) Aphron Visualization--evaluate and utilize various methods of monitoring and measuring aphron size distribution at elevated pressure; (b) Fluid Density--investigate the effects of pressure, temperature and chemical composition on the survivability of aphrons; (c) Aphron Air Diffusivity--determine the rate of loss of air from aphrons during pressurization; and (d) Pressure Transmissibility--determine whether aphron bridges created in fractures and pore throats reduce fracture propagation. The project team expanded the laboratory facilities and purchased a high-pressure system to measure bubble size distribution, a dissolved oxygen (DO) probe and computers for data acquisition. Although MASI Technologies LLC is not explicitly ISO-certified, all procedures are being documented in a manner commensurate with ISO 9001 certification, including equipment inventory and calibration, data gathering and reporting, chemical inventory and supplier data base, waste management procedures and emergency response plan. Several opportunities presented themselves to share the latest aphron drilling fluid technology with potential clients, including presentation of papers and working exhibit booths at the IADC/SPE Drilling Conference and the SPE Coiled Tubing Conference & Exhibition. In addition, a brief trip to the Formation Damage Symposium resulted in contacts for possible collaboration with ActiSystems, the University of Alberta and TUDRP/ACTS at the University of Tulsa. Preliminary results indicate that the Aphron Visualization and Pressure Transmissibility tasks should be completed on time. Although the Aphron Air Diffusivity task has been impeded by the lack of a suitable DO probe, it is hoped to be completed on time, too. The Fluid Density task, on the other hand, has had significant delays caused by faulty equipment and will likely require an additional month of work. Meanwhile, an assessment of potential methodologies for the Aphron Hydrophobicity project has been initiated and is now focused on measuring wettability of the aphron surface rather than interfacial tension.

  15. Enhanced Wellbore Stabilization and Reservoir Productivity with Aphron Drilling Fluid Technology

    SciTech Connect

    Fred Growcock

    2003-12-31

    During this first Quarter of the Project, a team of five individuals was formed to characterize aphron drilling fluids, with the ultimate objectives to gain acceptance for this novel technology and decrease the costs of drilling mature and multiple-pressure formations in oil and gas wells. Aphron drilling fluids are very high low-shear-rate viscosity fluids laden with specially designed microbubbles, or ''aphrons.'' The focus of the Project is to develop some understanding of the aphron structure and how aphrons and base fluid behave under downhole conditions. Four tasks were begun during this Quarter. All of these focus on the behavior of aphrons: (a) Aphron Visualization - to evaluate various methods of measuring bubble size distribution, especially Acoustic Bubble Spectroscopy (ABS), in aphron drilling fluids at elevated pressure; (b) Fluid Density - to investigate the effects of pressure, temperature and chemical composition on the survivability of aphrons; (c) Aphron Air Diffusivity - to determine the rate of loss of air from aphrons during pressurization; and (d) Pressure Transmissibility - to determine whether aphron networks (similar to foams) in fractures and pore networks reduce fracture propagation. The project team installed laboratory facilities and purchased most of the equipment required to carry out the tasks described above. Then work areas were combined to permit centralized data acquisition and communication with internal and external file servers, and electronic and hard copy filing systems were set up to be compatible with ISO 9001 guidelines. Initial feasibility tests for all four tasks were conducted, which led to some modification of the experimental designs so as to enable measurements with the required accuracy and precision. Preliminary results indicate that the Aphron Visualization, Aphron Air Diffusivity and Pressure Transmissibility tasks should be completed on time. The Fluid Density task, on the other hand, has some fundamental problems that may preclude realization of its objectives; alternative experimental approaches and methods of analysis will be explored during the next Quarter.

  16. Enhanced Wellbore Stabilization and Reservoir Productivity with Aphron Drilling Fluid Technology

    SciTech Connect

    Arkadiy Belkin; Fred Growcock

    2004-07-31

    The rate and amplitude of pressure transmission of various drilling fluids--particularly aphron drilling fluids--are measured in a long conduit and in sand packs to determine how pressure transmissibility can affect fluid invasion.

  17. Enhanced Wellbore Stabilization and Reservoir Productivity with Aphron Drilling Fluid Technology

    SciTech Connect

    Maribella Irving; Fred Growcock

    2004-11-30

    A method is developed to monitor the rate of loss of air from aphrons at elevated pressures. This technique is used to study the effects of pressure, fluid composition and rates of pressurization and depressurization on the kinetics of air loss from aphrons in APHRON ICS{trademark} drilling fluids.

  18. Enhanced Wellbore Stabilization and Reservoir Productivity with Aphron Drilling Fluid Technology

    SciTech Connect

    Miranda Fosdick; Fred Growcock

    2004-10-30

    Various methods were investigated to measure the oil-wetting character of transient bubbles under static and dynamic conditions, in order to determine the roles played by bubble and micellar agglomeration, coalescence and adhesion to mineral surfaces.

  19. Enhanced Wellbore Stabilization and Reservoir Productivity With Aphron Drilling Fluid Technology

    SciTech Connect

    Bob O'Connor; Fred Growcock

    2004-12-01

    The Acoustic Bubble Spectrometer has been identified as a potential method for monitoring the size distribution of aphrons in situ, such as in an oil well drilling fluid flowline.1 Research was continued from Task 1.1 of this Project, Aphron Visualization,2 in which ABS was tested against laser light scattering (Coulter Counter) and optical (visual) imaging to determine the bubble size distribution (BSD) of the aphrons at ambient temperature and pressure. Task 2.1 continued this investigation by measuring the bubble size distribution via ABS and optical imaging at elevated pressures up to 2000 psig.

  20. Ras enhances Myc protein stability.

    PubMed

    Sears, R; Leone, G; DeGregori, J; Nevins, J R

    1999-02-01

    Various experiments have demonstrated a collaborative action of Myc and Ras, both in normal cell growth control as well as during oncogenesis. We now show that Ras enhances the accumulation of Myc activity by stabilizing the Myc protein. Whereas Myc has a very short half-life when produced in the absence of mitogenic signals, due to degradation by the 26S proteasome, the half-life of Myc increases markedly in growth-stimulated cells. This stabilization is dependent on the Ras/Raf/MAPK pathway and is not augmented by proteasome inhibition, suggesting that Ras inhibits the proteasome-dependent degradation of Myc. We propose that one aspect of Myc-Ras collaboration is an ability of Ras to enhance the accumulation of transcriptionally active Myc protein.

  1. Advanced Wellbore Thermal Simulator

    1992-03-04

    GEOTEMP2, which is based on the earlier GEOTEMP program, is a wellbore thermal simulator designed for geothermal well drilling and production applications. The code treats natural and forced convection and conduction within the wellbore and heat conduction within the surrounding rock matrix. A variety of well operations can be modeled including injection, production, forward and reverse circulation with gas or liquid, gas or liquid drilling, and two-phase steam injection and production. Well completion with severalmore » different casing sizes and cement intervals can be modeled. The code allows variables, such as flow rate, to change with time enabling a realistic treatment of well operations. Provision is made in the flow equations to allow the flow areas of the tubing to vary with depth in the wellbore. Multiple liquids can exist in GEOTEMP2 simulations. Liquid interfaces are tracked through the tubing and annulus as one liquid displaces another. GEOTEMP2, however, does not attempt to simulate displacement of liquids with a gas or two-phase steam or vice versa. This means that it is not possible to simulate an operation where the type of drilling fluid changes, e.g. mud going to air. GEOTEMP2 was designed primarily for use in predicting the behavior of geothermal wells, but it is flexible enough to handle many typical drilling, production, and injection problems in the oil industry as well. However, GEOTEMP2 does not allow the modeling of gas-filled annuli in production or injection problems. In gas or mist drilling, no radiation losses are included in the energy balance. No attempt is made to model flow in the formation. Average execution time is 50 CP seconds on a CDC CYBER170. This edition of GEOTEMP2 is designated as Version 2.0 by the contributors.« less

  2. Analysis of the Wellbore Seal at Well 49-6 in the SACROC CO2 Enhanced Oil Recovery Field, West Texas

    NASA Astrophysics Data System (ADS)

    Carey, J. W.; Wigand, M.; Chipera, S.; Woldegabriel, G.; Pawar, R.; Lichtner, P. C.; Wehner, S.; Raines, M.; Guthrie, G. D.

    2005-12-01

    Long-term integrity of wellbore cements is one of the major concerns for geologic sequestration of CO2. This paper presents analyses of cement core recovered from a well used in a long-term CO2 enhanced oil recovery operation. A sidetrack system was used to obtain core from a 55 year-old well with 30 years of CO2 exposure as both an injector and a producer at the SACROC unit (Permian Basin, Texas). The mineralogy, chemistry, and hydrologic properties were evaluated for evidence of degradation by CO2. The recovered samples were located ~ 3 m above the contact with the reservoir. The recovered cement had permeabilities in the milliDarcy range and thus retained its capacity to prevent significant flow of CO2. There was evidence for CO2 migration along the casing-cement and cement-shale interfaces. The casing interface had a 1-2 mm thick rind of calcite-aragonite-halite. The CO2 producing this rind may have traveled up the casing wall or may have infiltrated through the casing threads. The cement in contact with the shale (within 1 cm) was heavily carbonated to an assemblage of calcite, aragonite, vaterite and amorphous alumino-silica residue and was transformed to a distinctive orange color. The heavily carbonated region is separated from less altered cement by a narrow, dense zone of silica and carbonate deposition. The CO2 for this carbonation process migrated from the cement-shale interface where the presence of shale fragments (wall cake) may have provided a fluid pathway. The carbonation reaction was associated with only small changes in the original cement chemistry including an increase in Na2O and decrease in CaO and MgO with a slight enrichment in SiO2. The carbonated zone also has a distinct carbon and oxygen stable isotope signature. Although the observed carbonation was intense, the measured hydrologic properties of the carbonated zone were not significantly different from those of relatively unaltered cement in adjacent parts of the core. Textural

  3. Transient Wellbore Fluid Flow Model

    1982-04-06

    WELBORE is a code to solve transient, one-dimensional two-phase or single-phase non-isothermal fluid flow in a wellbore. The primary thermodynamic variables used in solving the equations are the pressure and specific energy. An equation of state subroutine provides the density, quality, and temperature. The heat loss out of the wellbore is calculated by solving a radial diffusion equation for the temperature changes outside the bore. The calculation is done at each node point in themore » wellbore.« less

  4. Ranging methods for developing wellbores in subsurface formations

    DOEpatents

    MacDonald, Duncan

    2011-09-06

    A method for forming two or more wellbores in a subsurface formation includes forming a first wellbore in the formation. A second wellbore is directionally drilled in a selected relationship relative to the first wellbore. At least one magnetic field is provided in the second wellbore using one or more magnets in the second wellbore located on a drilling string used to drill the second wellbore. At least one magnetic field is sensed in the first wellbore using at least two sensors in the first wellbore as the magnetic field passes by the at least two sensors while the second wellbore is being drilled. A position of the second wellbore is continuously assessed relative to the first wellbore using the sensed magnetic field. The direction of drilling of the second wellbore is adjusted so that the second wellbore remains in the selected relationship relative to the first wellbore.

  5. Loading of wellbores with explosives

    SciTech Connect

    Loving, F.A.; Simmons, W.J.

    1983-04-26

    Bags of explosive are loaded rapidly into deep wellbores by suspending a rigid positioning tube partway into the wellbore, and loading the bags into the tube, the bags being prevented from dropping through the open bottom end of the tube by a cord attached to the lowermost bag and secured at the upper end of the tube when the tube-suspending cable is in tension by a cordsecuring/releasing means, E.G., a pivotable bar having a hook on one end. When the bag-laden tube is lowered to the bottom of the wellbore, or to a column of bags previously placed therein, the tension on the cable is relaxed and the cord is released, allowing the positioning tube thereafter to be raised to the surface for re-use, leaving the cord and bags in the wellbore. Freedom of the bag-supporting cord to move with respect to the positioning tube when the latter is raised to the surface is assured by threading the cord through plastic tubing mounted to the wall of the positioning tube and releasable therefrom for reuse.

  6. Rational Design of Biobetters with Enhanced Stability.

    PubMed

    Courtois, Fabienne; Schneider, Curtiss P; Agrawal, Neeraj J; Trout, Bernhardt L

    2015-08-01

    Biotherapeutics are the fastest growing class of pharmaceutical with a rapidly evolving market facing the rise of biosimilar and biobetter products. In contrast to a biosimilar, which is derived from the same gene sequence as the innovator product, a biobetter has enhanced properties, such as enhanced efficacy or reduced immunogenicity. Little work has been carried out so far to increase the intrinsic stability of biotherapeutics via sequence changes, even though, aggregation, the primary degradation pathway of proteins, leads to issues ranging from manufacturing failure to immunological response and to loss of therapeutic activity. Using our spatial aggregation propensity tool as a first step to a rational design approach to identify aggregation-prone regions, biobetters of rituximab have been produced with enhanced stability by introducing site-specific mutations. Significant stabilization against aggregation was achieved for rituximab with no decrease in its binding affinity to the antigen.

  7. Compressor Stability Enhancement Using Discrete Tip Injection

    NASA Technical Reports Server (NTRS)

    Suder, Kenneth L.; Hathaway, Michael D.; Thorp, Scott A.; Strazisar, Anthony J.; Bright, Michelle B.

    2001-01-01

    Mass injection upstream of the tip of a high-speed axial compressor rotor is a stability enhancement approach known to be effective in suppressing small in tip-critical rotors. This process is examined in a transonic axial compressor rotor through experiments and time-averaged Navier-Stokes CFD simulations. Measurements and simulations for discrete injection are presented for a range of injection rates and distributions of injectors around the annulus. The simulations indicate that tip injection increases stability by unloading the rotor tip and that increasing injection velocity improves the effectiveness of tip injection. For the tested rotor, experimental results demonstrate that at 70 percent speed the stalling flow coefficient can be reduced by 30 percent using an injected mass- flow equivalent to 1 percent of the annulus flow. At design speed, the stalling flow coefficient was reduced by 6 percent using an injected mass-fiow equivalent to 2 percent of the annulus flow. The experiments show that stability enhancement is related to the mass-averaged axial velocity at the tip. For a given injected mass-flow, the mass-averaged axial velocity at the tip is increased by injecting flow over discrete portions of the circumference as opposed to full-annular injection. The implications of these results on the design of recirculating casing treatments and other methods to enhance stability will be discussed.

  8. Wellbore failure mechanisms in shales: Prediction and prevention

    SciTech Connect

    Gazaniol, D.; Forsans, T.; Boisson, M.J.F.; Piau, J.M.

    1995-07-01

    Shale stability is still one of the most important problems faced during drilling. Until recently, stability problems were most often attributed to shale swelling; however, recent research shows that several mechanisms are involved and that their relative importance can be estimated. This paper presents a review of these mechanisms, including pore-pressure diffusion, plasticity, anisotropy, capillary effects, osmosis, and physicochemical alteration. Pore-pressure diffusion into the rock in the vicinity of the wellbore (transition from undrained to drained behavior) appears to be of major importance in these very-low-permeability rocks. Plasticity is discussed in terms of modeling. Compared with simple elastic models, modeling of plasticity can simulate the actual behavior of wellbore better. The behavior of different types of muds is discussed while taking these phenomena into consideration, and the practical use of rock-mechanics models is also addressed.

  9. Heating production fluids in a wellbore

    DOEpatents

    Orrego, Yamila; Jankowski, Todd A.

    2016-07-12

    A method for heating a production fluid in a wellbore. The method can include heating, using a packer fluid, a working fluid flowing through a first medium disposed in a first section of the wellbore, where the first medium transfers heat from the packer fluid to the working fluid. The method can also include circulating the working fluid into a second section of the wellbore through a second medium, where the second medium transfers heat from the working fluid to the production fluid. The method can further include returning the working fluid to the first section of the wellbore through the first medium.

  10. Three-dimensional, transient natural convection in inclined wellbores

    SciTech Connect

    McEligot, D.M. . Oceanic Div.); Denbow, D.A. ); Murphy, H.D. )

    1990-01-01

    The occurrence of natural conduction in a wellbore can affect geothermal gradient measurements and heat flow estimates. In the Hot Dry Rock geothermal concept, the wellbores are purposely inclined in the deep regions to enhance heat production. To simulate natural convection flow patterns in directionally drilled wellbores, experiments and analyses were conducted for a circular tube with length to diameter (L/D) ratio of 36 at angles of 0{degrees}, 20{degrees}, and 35{degrees} from the vertical. The tube was heated at the bottom and cooled at the top, and the insulation was adjusted so that approximately one- to two-thirds of the power dissipated was transferred through the tube wall to the surroundings. An aqueous solution of polyvinyl alcohol was employed as the working fluid in order to obtain low Rayleigh numbers corresponding to conditions in geothermal wellbores. Temperature distributions were measured for the three orientations and for several heating rates to demonstrate the effects of tube angle and Rayleigh number. Comparison with measurements showed good agreement of the predicted temperature levels for the maximum inclination and slightly poorer agreement for the other limit, a vertical tube. 50 refs., 9 figs.

  11. Enhanced Product Stability in the Hammerhead Ribozyme†

    PubMed Central

    Shepotinovskaya, Irina; Uhlenbeck, Olke C.

    2010-01-01

    The rate of dissociation of P1, the 5′ product of hammerhead cleavage, is 100–300-fold slower in full-length hammerheads than in hammerheads that either lack or have disrupting mutations in the loop-loop tertiary interaction. The added stability requires the presence of residue 17 at the 3′ terminus of P1 but not the 2′, 3′ terminal phosphate. Since residue 17 is buried within the catalytic core of the hammerhead in the x-ray structure, we propose that the enhanced P1 stability is the result of the cooperative folding of the hammerhead around this residue. However, since the P1 is fully stabilized above 2.5 mM MgCl2 while hammerhead activity continues to increase with increasing MgCl2, it is clear that the hammerhead structure in the transition state must differ from that of the product complex. The product stabilization assay is used to test our earlier proposal that different tertiary interactions modulate the cleavage rate by differentially stabilizing the core. PMID:20423112

  12. Drilling subsurface wellbores with cutting structures

    DOEpatents

    Mansure, Arthur James; Guimerans, Rosalvina Ramona

    2010-11-30

    A system for forming a wellbore includes a drill tubular. A drill bit is coupled to the drill tubular. One or more cutting structures are coupled to the drill tubular above the drill bit. The cutting structures remove at least a portion of formation that extends into the wellbore formed by the drill bit.

  13. Methods for forming wellbores in heated formations

    DOEpatents

    Guimerans, Rosalvina Ramona; Mansure, Arthur James

    2012-09-25

    A method for forming a wellbore in a heated formation includes flowing liquid cooling fluid to a bottom hole assembly in a wellbore in a heated formation. At least a portion of the liquid cooling fluid is vaporized at or near a region to be cooled. Vaporizing the liquid cooling fluid absorbs heat from the region to be cooled.

  14. Enhanced stabilization of collagen by furfural.

    PubMed

    Lakra, Rachita; Kiran, Manikantan Syamala; Usha, Ramamoorthy; Mohan, Ranganathan; Sundaresan, Raja; Korrapati, Purna Sai

    2014-04-01

    Furfural (2-furancarboxaldehyde), a product derived from plant pentosans, has been investigated for its interaction with collagen. Introduction of furfural during fibril formation enhanced the thermal and mechanical stability of collagen. Collagen films treated with furfural exhibited higher denaturation temperature (Td) (p<0.04) and showed a 3-fold increase in Young's modulus (p<0.04) at higher concentration. Furfural and furfural treated collagen films did not have any cytotoxic effect. Rheological characterization showed an increase in shear stress and shear viscosity with increasing shear rate for treated collagen. Circular dichroism (CD) studies indicated that the furfural did not have any impact on triple helical structure of collagen. Scanning electron microscopy (SEM) of furfural treated collagen exhibited small sized porous structure in comparison with untreated collagen. Thus this study provides an alternate ecologically safe crosslinking agent for improving the stability of collagen for biomedical and industrial applications.

  15. Development of a Standalone Thermal Wellbore Simulator

    NASA Astrophysics Data System (ADS)

    Xiong, Wanqiang

    With continuous developments of various different sophisticated wells in the petroleum industry, wellbore modeling and simulation have increasingly received more attention. Especially in unconventional oil and gas recovery processes, there is a growing demand for more accurate wellbore modeling. Despite notable advancements made in wellbore modeling, none of the existing wellbore simulators has been as successful as reservoir simulators such as Eclipse and CMG's and further research works on handling issues such as accurate heat loss modeling and multi-tubing wellbore modeling are really necessary. A series of mathematical equations including main governing equations, auxiliary equations, PVT equations, thermodynamic equations, drift-flux model equations, and wellbore heat loss calculation equations are collected and screened from publications. Based on these modeling equations, workflows for wellbore simulation and software development are proposed. Research works are conducted in key steps for developing a wellbore simulator: discretization, a grid system, a solution method, a linear equation solver, and computer language. A standalone thermal wellbore simulator is developed by using standard C++ language. This wellbore simulator can simulate single-phase injection and production, two-phase steam injection and two-phase oil and water production. By implementing a multi-part scheme which divides a wellbore with sophisticated configuration into several relative simple simulation running units, this simulator can handle different complex wellbores: wellbore with multistage casings, horizontal wells, multilateral wells and double tubing. In pursuance of improved accuracy of heat loss calculations to surrounding formations, a semi-numerical method is proposed and a series of FLUENT simulations have been conducted in this study. This semi-numerical method involves extending the 2D formation heat transfer simulation to include a casing wall and cement and adopting new

  16. Ceramic membranes with enhanced thermal stability

    DOEpatents

    Anderson, Marc A.; Xu, Qunyin; Bischoff, Brian L.

    1993-01-01

    A method of creating a ceramic membrane with enhanced thermal stability is disclosed. The method involves combining quantities of a first metal alkoxide with a second metal, the quantities selected to give a preselected metal ratio in the resultant membrane. A limited amount of water and acid is added to the combination and stirred until a colloidal suspension is formed. The colloid is dried to a gel, and the gel is fired at a temperature greater than approximately 400.degree. C. The porosity and surface area of ceramic membranes formed by this method are not adversely affected by this high temperature firing.

  17. General single phase wellbore flow model

    SciTech Connect

    Ouyang, Liang-Biao; Arbabi, S.; Aziz, K.

    1997-02-05

    A general wellbore flow model, which incorporates not only frictional, accelerational and gravitational pressure drops, but also the pressure drop caused by inflow, is presented in this report. The new wellbore model is readily applicable to any wellbore perforation patterns and well completions, and can be easily incorporated in reservoir simulators or analytical reservoir inflow models. Three dimensionless numbers, the accelerational to frictional pressure gradient ratio R{sub af}, the gravitational to frictional pressure gradient ratio R{sub gf}, and the inflow-directional to accelerational pressure gradient ratio R{sub da}, have been introduced to quantitatively describe the relative importance of different pressure gradient components. For fluid flow in a production well, it is expected that there may exist up to three different regions of the wellbore: the laminar flow region, the partially-developed turbulent flow region, and the fully-developed turbulent flow region. The laminar flow region is located near the well toe, the partially-turbulent flow region lies in the middle of the wellbore, while the fully-developed turbulent flow region is at the downstream end or the heel of the wellbore. Length of each region depends on fluid properties, wellbore geometry and flow rate. As the distance from the well toe increases, flow rate in the wellbore increases and the ratios R{sub af} and R{sub da} decrease. Consequently accelerational and inflow-directional pressure drops have the greatest impact in the toe region of the wellbore. Near the well heel the local wellbore flow rate becomes large and close to the total well production rate, here R{sub af} and R{sub da} are small, therefore, both the accelerational and inflow-directional pressure drops can be neglected.

  18. Method for hydraulic fracturing cased wellbores

    SciTech Connect

    Schmidt, J.H.

    1991-12-24

    This patent describes a method of hydraulically fracturing a cased wellbore in an earth formation. It comprises determining the angle with respect to the wellbore axis and a reference point on the circumference of the wellbore which will provide for initiation of a hydraulic fracture in the formation which will turn with the largest radius of curvature into a fracture plane normal to the minimum in situ stress in the formation; perforating the wellbore casing at the angle with respect to the reference point; initiating a hydraulic fracture in the formation by pumping a liquid through the perforation and into the formation to force the initiation of a fracture in the formation at a point which develops the highest tensile stress in the formation in relation to increasing the hydraulic pressure in the wellbore; extending the fracture by pumping a relatively proppant-free quantities of proppant per unit volume of pumped fluid and in successive discrete stages of increasing proppant density to provide a propped portion of increasing proppant density to provide a propped portion of the fracture in the near wellbore region of the fracture which will prevent reclosing of the fracture in the near wellbore region.

  19. Photovoltaic panel having enhanced conversion efficiency stability

    SciTech Connect

    Cannella, V. D.

    1985-10-01

    A photovoltaic panel for converting light into electrical energy has enhanced energy conversion efficiency stability. The panel includes a photovoltaic device having an active region formed from a semiconductor material which exhibits an energy conversion efficiency stability directly related to the operating temperature of the device. The panel also includes means for maintaining the operating temperature of the device upon exposure to light at an elevated temperature above the ambient temperature external to the device. The active region semiconductor material is preferably an amorphous semiconductor alloy such as, for example, an amorphous silicon alloy. The operating temperature elevating means can include a thermal insulating material such as glass wool, styrofoam, or cork applied to the back side of the device to minimize heat conduction from the device. The panel can also include an enclosure for enclosing the device having a transparent cover overlying the device to seal the enclosure and provide a still air space adjacent the device. The panel is thereby arranged to maintain the operating temperature of the device at a temperature which is from about twenty degrees Centigrade to about one hundred and fifty degrees Centigrade above the ambient temperature external to the device.

  20. Design, implementation, and completion of a horizontal tight gas wellbore - case study: Green River Basin, Wyoming

    SciTech Connect

    Billingsley, R.L.; Evans, L.W.; Anderson, T.M.

    1995-06-01

    In September, 1993 Amoco Production Company began drilling the Champlin 254B No. 2H, a horizontal well test located near the Wamsutter Arch, southwestem Wyoming. The Champlin 254B No. 2H was designed to confirm a fractured reservoir concept and to test the economic viability of a horizontal wellbore in the Almond fm.. The wellbore was designed to determine real-time, the fracture direction and the optimum horizontal leg direction within the confines of the drilling permit. A deviated pilot hole was drilled to optimize our ability to cross vertical natural fractures. MWD gamma-ray, oriented core, a vertical seismic profile, Formation Microimager, and a robust suite of electric logs were obtained to gain information on the presence and orientation of fractures before kickoff for the horizontal leg. Electromagnetic goniometry was used onsite to orient fractures in core. Log and core data were consistent and a wellbore trajectory of due South was chosen. A two thousand foot horizontal wellbore was drilled, 1700 feet of which is in the upper Almond formation productive zone. MWD gamma-ray, three 30` cores, Formation Microscanner logs, and a density-neutron log were obtained in the horizontal hole. This wellbore was completed open-hole with a stabilized gas rate of 1 mmcfd. In May, 1994 a portion of the original wellbore collapsed and a replacement horizontal leg was drilled. Oil-based mud and rotary BOP`s were utilized to minimize damage and invasion to the reservoir. Reservoir pressures encountered in the redrill indicate that depletion along the original wellbore had begun. The redrill was completed open-hole with a pre-perforated (every third joint) 5 1/2 inches liner and also stabilized at a rate of 1 mmcfd.

  1. Microseismic monitoring of CO2 injection at the Penn West Enhanced Oil Recovery pilot project, Canada: implications for detection of wellbore leakage.

    PubMed

    Martínez-Garzón, Patricia; Bohnhoff, Marco; Kwiatek, Grzegorz; Zambrano-Narváez, Gonzalo; Chalaturnyk, Rick

    2013-09-02

    A passive seismic monitoring campaign was carried out in the frame of a CO2-Enhanced Oil Recovery (EOR) pilot project in Alberta, Canada. Our analysis focuses on a two-week period during which prominent downhole pressure fluctuations in the reservoir were accompanied by a leakage of CO2 and CH4 along the monitoring well equipped with an array of short-period borehole geophones. We applied state of the art seismological processing schemes to the continuous seismic waveform recordings. During the analyzed time period we did not find evidence of induced micro-seismicity associated with CO2 injection. Instead, we identified signals related to the leakage of CO2 and CH4, in that seven out of the eight geophones show a clearly elevated noise level framing the onset time of leakage along the monitoring well. Our results confirm that micro-seismic monitoring of reservoir treatment can contribute towards improved reservoir monitoring and leakage detection.

  2. Wellbore inertial directional surveying system

    DOEpatents

    Andreas, Ronald D.; Heck, G. Michael; Kohler, Stewart M.; Watts, Alfred C.

    1991-01-01

    A wellbore inertial directional surveying system for providing a complete directional survey of an oil or gas well borehole to determine the displacement in all three directions of the borehole path relative to the well head at the surface. The information generated by the present invention is especially useful when numerous wells are drilled to different geographical targets from a single off-shore platform. Accurate knowledge of the path of the borehole allows proper well spacing and provides assurance that target formations are reached. The tool is lowered down into a borehole on the electrical cable. A computer positioned on the surface communicates with the tool via the cable. The tool contains a sensor block which is supported on a single gimbal, the rotation axis of which is aligned with the cylinder axis of the tool and, correspondingly, the borehole. The gyroscope measurement of the sensor block rotation is used in a null-seeking servo loop which essentially prevents rotation of the sensor block aboutthe gimbal axis. Angular rates of the sensor block about axes which are perpendicular to the gimbal axis are measured by gyroscopes in a manner similar to a strapped-down arrangement. Three accelerometers provide acceleration information as the tool is lowered within the borehole. The uphole computer derives position information based upon acceleration information and anular rate information. Kalman estimation techniques are used to compensate for system errors.

  3. Wellbore inertial directional surveying system

    DOEpatents

    Andreas, R.D.; Heck, G.M.; Kohler, S.M.; Watts, A.C.

    1982-09-08

    A wellbore inertial directional surveying system for providing a complete directional survey of an oil or gas well borehole to determine the displacement in all three directions of the borehole path relative to the well head at the surface. The information generated by the present invention is especially useful when numerous wells are drilled to different geographical targets from a single offshore platform. Accurate knowledge of the path of the borehole allows proper well spacing and provides assurance that target formations are reached. The tool is lowered down into a borehole on an electrical cable. A computer positioned on the surface communicates with the tool via the cable. The tool contains a sensor block which is supported on a single gimbal, the rotation axis of which is aligned with the cylinder axis of the tool and, correspondingly, the borehole. The gyroscope measurement of the sensor block rotation is used in a null-seeking servo loop which essentially prevents rotation of the sensor block about the gimbal axis. Angular rates of the sensor block about axes which are perpendicular to te gimbal axis are measured by gyroscopes in a manner similar to a strapped-down arrangement. Three accelerometers provide acceleration information as the tool is lowered within the borehole. The uphole computer derives position information based upon acceleration information and angular rate information. Kalman estimation techniques are used to compensate for system errors. 25 figures.

  4. Passive Endwall Treatments for Enhancing Stability

    NASA Technical Reports Server (NTRS)

    Hathaway, Michael D.

    2007-01-01

    These lecture notes were presented at the von Karman Institutes lecture series on Advances in Axial Compressor Aerodynamics, May 2006. They provide a fairly extensive overview of what's been learned from numerous investigations of various passive casing endwall technologies that have been proposed for alleviating the stall limiting physics associated with the compressor endwall flow field. The lecture notes are organized to give an appreciation for the inventiveness and understanding of the earliest compressor technologists and to provide a coherent thread of understanding that has arisen out of the early investigations. As such the lecture notes begin with a historical overview of casing treatments from their infancy through the earliest proposed concepts involving blowing, suction and flow recirculation. A summary of lessons learned from these early investigations is provided at the end of this section. The lecture notes then provide a somewhat more in-depth overview of recent advancements in the development of passive casing treatments from the late 1990's through 2006, including advancements in understanding the flow mechanism of circumferential groove casing treatments, and the development of discrete tip injection and self-recirculating casing treatments. At the conclusion of the lecture notes a final summary of lessons learned throughout the history of the development of passive casing treatments is provided. Finally, a list of future needs is given. It is hoped that these lecture notes will be a useful reference for future research endeavors to improve our understanding of the fluid physics of passive casing treatments and how they act to enhance compressor stability, and that they will perhaps provide a springboard for future research activities in this area of interest

  5. Factors Controlling Wellbore Imaging of Fractures

    NASA Astrophysics Data System (ADS)

    Al-Fahmi, M. M.; Cartwright, J. A.

    2015-12-01

    There are many scientific and engineering methods in petroleum industry for collecting data about small fractures in subsurface. The acquired data is predominantly indirect, and constrained by the bounds of technology and the subtle nature of small fractures. Among the various data types, cores and wellbore images reliably provide the data to observe small fractures, and help characterize important fracture properties such as density, geometry and aperture. There is, however, a major uncertainty about how thorough is the illustration of the small fractures in the wellbore electrical images which are widely used instead of cutting core for practical and economical grounds. We present novel results to help with understanding the potential and limits of wellbore electrical imagers to detect small fractures. We compare and discuss observations from high-quality microresistivity images and their equivalent core samples that are obtained from sub-horizontal wells drilled into carbonate hydrocarbon reservoirs in eastern Arabia. We observed that the wellbore images give limited and inconsistent fracture sampling. The reduction in fracture sampling is related to the fracture nature that defies the imager-resolution capacity. We propose that the imaging capacity is constrained by: 1) degree of fracture roughness, 2) contrast between resistivity and conductivity of the geologic features, 3) effective stress action that is increasing and decreasing fracture aperture, and 4) fracture intake of drilling fluids under a variable fluid pressure balancing between wellbore and reservoir. The wellbore imaging outcomes influence fracture studies, particularly the areas of measuring static and dynamic properties of reservoir fractures and estimating trends and magnitudes of in situ stress.

  6. Depth enhanced and content aware video stabilization

    NASA Astrophysics Data System (ADS)

    Lindner, A.; Atanassov, K.; Goma, S.

    2015-03-01

    We propose a system that uses depth information for video stabilization. The system uses 2D-homographies as frame pair transforms that are estimated with keypoints at the depth of interest. This makes the estimation more robust as the points lie on a plane. The depth of interest can be determined automatically from the depth histogram, inferred from user input such as tap-to-focus, or selected by the user; i.e., tap-to-stabilize. The proposed system can stabilize videos on the fly in a single pass and is especially suited for mobile phones with multiple cameras that can compute depth maps automatically during image acquisition.

  7. Proceedings of the wellbore sampling workshop

    SciTech Connect

    Traeger, R.K.; Harding, B.W.

    1987-11-01

    Representatives from academia, industry and research laboratories participated in an intensive two-day review to identify major technological limitations in obtaining solid and fluid samples from wellbores. Top priorities identified for further development include: coring of hard and unconsolidated materials; flow through fluid samplers with borehole measurements T, P and pH; and nonintrusive interrogation of pressure cores.

  8. Cementing a wellbore using cementing material encapsulated in a shell

    DOEpatents

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael

    2016-08-16

    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  9. Enhancing probiotic stability in industrial processes

    PubMed Central

    Gueimonde, Miguel; Sánchez, Borja

    2012-01-01

    Background Manufacture of probiotic products involves industrial processes that reduce the viability of the strains. This lost of viability constitutes an economic burden for manufacturers, compromising the efficacy of the product and preventing the inclusion of probiotics in many product categories. Different strategies have been used to improve probiotic stability during industrial processes. These include technological approaches, such as the modification of production parameters or the reformulation of products, as well as microbiological approaches focused on the strain intrinsic resistance. Among the later, both selection of natural strains with the desired properties and stress-adaptation of strains have been widely used. Conclusion During recent years, the knowledge acquired on the molecular basis of stress-tolerance of probiotics has increased our understanding on their responses to industrial stresses. This knowledge on stress-response may nowadays be used for the selection of the best strains and industrial conditions in terms of probiotic stability in the final product. PMID:23990824

  10. Mechanisms and enhancement of flame stabilization

    SciTech Connect

    Law, C.K.

    1993-01-01

    During the reporting period, useful contributions have been made in understanding the structure of laminar premixed and diffusion flames, with emphasis on the influence of aerodynamics and chemical kinetics. These contributions include (1) derivation of the missing closure condition for the activation energy asymptotic analysis of premixed flames, (2) identification of a dual extinction mode for radiation-affected flames, (3) formulation of a unified theory of fundamental flammability limits, and (4) demonstration that flame stabilization can be achieved in the absence of heat loss. These investigations have been conducted via experimental, analytical and computational approaches, with strong coupling between the individual components.

  11. Enhancing protein stability with extended disulfide bonds.

    PubMed

    Liu, Tao; Wang, Yan; Luo, Xiaozhou; Li, Jack; Reed, Sean A; Xiao, Han; Young, Travis S; Schultz, Peter G

    2016-05-24

    Disulfide bonds play an important role in protein folding and stability. However, the cross-linking of sites within proteins by cysteine disulfides has significant distance and dihedral angle constraints. Here we report the genetic encoding of noncanonical amino acids containing long side-chain thiols that are readily incorporated into both bacterial and mammalian proteins in good yields and with excellent fidelity. These amino acids can pair with cysteines to afford extended disulfide bonds and allow cross-linking of more distant sites and distinct domains of proteins. To demonstrate this notion, we preformed growth-based selection experiments at nonpermissive temperatures using a library of random β-lactamase mutants containing these noncanonical amino acids. A mutant enzyme that is cross-linked by one such extended disulfide bond and is stabilized by ∼9 °C was identified. This result indicates that an expanded set of building blocks beyond the canonical 20 amino acids can lead to proteins with improved properties by unique mechanisms, distinct from those possible through conventional mutagenesis schemes.

  12. Fluctuation-enhanced stability of a metapopulation

    NASA Astrophysics Data System (ADS)

    Nie, Lin-Ru; Mei, Dong-Cheng

    2007-11-01

    The simplified incidence function model with cross-correlated noises was employed to study the stability of a metapopulation perturbed by environments. Through numerically computing the stationary probability distribution function (PDF) and stochastically simulating the extinction time of a metapopulation, we found that: (i) The multiplicative noise intensity D inhibits the fluctuation of dynamic variable while the additive noise intensity α intensifies it, whether there is a correlation between the multiplicative noise and the additive noise; (ii) As the correlation strength (λ) between them is greater than zero, there is an optimal D in which the PDF curve deviates furthest from the extinction position, and another optimal D which maximally delays the extinction time of a metapopulation; (iii) For the constant D and α, the increment of λ not only upgrades the probability that patches are occupied by a metapopulation, but also delays the time that a metapopulation goes to extinction.

  13. Geomechanical Modeling to Predict Wellbore Stresses and Strains for the Design of Wellbore Seal Repair Materials

    NASA Astrophysics Data System (ADS)

    Gomez, S. P.; Sobolik, S. R.; Matteo, E. N.; Dewers, T. A.; Taha, M. R.; Stormont, J. C.

    2013-12-01

    A critical aspect of designing effective wellbore seal repair materials is predicting thermo-mechanical perturbations in local stress that can compromise seal integrity. For the DOE-NETL project 'Wellbore Seal Repair Using Nanocomposite Materials,' we are especially interested in the stress-strain history of abandoned wells, as well as changes in local pressure, stress, and temperature conditions that accompany carbon dioxide injection or brine extraction. Building on existing thermo-hydro-mechanical (THM) finite element modeling of wellbore casings subject to significant tensile and shear loads, we advance a conceptual and numerical methodology to assess responses of annulus cement and casing. Bench-scale models complement bench-top experiments of an integrated seal system in an idealized scaled wellbore mock-up being used to test candidate seal repair materials. Field scale models use the stratigraphy from a pilot CO2 injection operation to estimate the necessary mechanical properties needed for a successful repair material. We report on approaches used for adapting existing wellbore models and share preliminary results of field scale models. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND Number: 2013-6241A.

  14. A multi-feedzone wellbore simulator

    SciTech Connect

    Bjornsson, G.; Bodvarsson, G.S.

    1987-06-01

    A multi-feedzone wellbore simulator has been developed. This computer code is quite general as it enables one to compute downhole conditions in wells with an arbitrary number of feedzones during discharge or injection. The simulator is applied to flowing pressure and temperature surveys from various wells in Mexico, Iceland and Kenya. It is demonstrated that such a model can be used to estimate flow rates and enthalpies of individual feedzones.

  15. Method of repairing a wellbore liner for sand control

    SciTech Connect

    Dees, J.M.

    1992-10-13

    This patent describes a method of repairing a damaged wellbore liner for controlling sand and other fine materials. It comprises: positioning a quantity of fluid resin material in alignment with the portion of the wellbore liner to be repaired; positioning a gas generator in proximity with the fluid resin material; actuating the gas generator to increase wellbore pressure in a substantially instantaneous manner to a pressure substantially in excess of well pressure to force the fluid resin material from the wellbore into the damaged area of the wellbore liner; and subsequently polymerizing the resin material to form a consolidated, porous permeable matrix that allows the flow of production fluid into the well while preventing the flow of sand, or other fine materials into the well through the previously damaged area of the wellbore liner.

  16. Enhanced thermal stability of Ag nanorods through capping

    SciTech Connect

    Bachenheimer, Lou; Elliott, Paul; Stagon, Stephen; Huang, Hanchen

    2014-11-24

    Ag nanorods may serve as sensors in the detection of trace amounts of chemical agents, even single molecules, through surface enhanced Raman spectroscopy (SERS). However, thermal coarsening of Ag nanorods near room temperature limits their applications. This letter proposes the use of a thin oxide capping layer to enhance the thermal stability of Ag nanorods beyond 100 °C. Using electron microscopy characterization and SERS tests, the authors show that the proposed method is effective in stabilizing both morphology and sensitivity of Ag nanorods. The results of this work extend the applicability of Ag nanorods as chemical sensors to higher temperatures.

  17. Tethered naphthalene diimide intercalators enhance DNA triplex stability.

    PubMed

    Gianolio, D A; McLaughlin, L W

    2001-09-01

    Naphthalene diimides function as effective intercalators and when tethered to the 5'-terminus of a pyrimidine-rich oligonucleotide can contribute significantly to the overall stabilization of DNA triplexes. This stabilization can be further enhanced by alterations to the linker tethering the DNA sequence and the intercalator. Less flexible linkers, and particularly one with a phenyl ring present, appear to permit the stabilization afforded by the bound intercalator to be transferred more effectively to the three-stranded complex. The conjugate containing the phenyl linker exhibits a T(M) value that is increased by 28 degrees C relative to the unconjugated triplex. That the linker itself contributes to the observed stabilization is clear since introduction of the phenyl linker increases the observed T(M) by 11 degrees C relative to a simple flexible linker.

  18. A multi-feedzone geothermal wellbore simulator

    SciTech Connect

    Bjornsson, G.

    1987-05-01

    The main objective of this work is to develop a multiple feedzone wellbore model for single- or two-phase flow in vertical wells. It has been demonstrated in various fields (e.g., oil and gas and geothermal) that multiple feedzones with different pressure potentials can significantly effect the well performance in the long run. Very little work in this subject has been done to date, but the importance of the subject is becoming more and more evident. 55 refs., 33 figs., 4 tabs.

  19. Enhanced Luminescent Stability through Particle Interactions in Silicon Nanocrystal Aggregates.

    PubMed

    Miller, Joseph B; Dandu, Naveen; Velizhanin, Kirill A; Anthony, Rebecca J; Kortshagen, Uwe R; Kroll, Daniel M; Kilina, Svetlana; Hobbie, Erik K

    2015-10-27

    Close-packed assemblies of ligand-passivated colloidal nanocrystals can exhibit enhanced photoluminescent stability, but the origin of this effect is unclear. Here, we use experiment, simulation, and ab initio computation to examine the influence of interparticle interactions on the photoluminescent stability of silicon nanocrystal aggregates. The time-dependent photoluminescence emitted by structures ranging in size from a single quantum dot to agglomerates of more than a thousand is compared with Monte Carlo simulations of noninteracting ensembles using measured single-particle blinking data as input. In contrast to the behavior typically exhibited by the metal chalcogenides, the measured photoluminescent stability shows an enhancement with respect to the noninteracting scenario with increasing aggregate size. We model this behavior using time-dependent density functional theory calculations of energy transfer between neighboring nanocrystals as a function of nanocrystal size, separation, and the presence of charge and/or surface-passivation defects. Our results suggest that rapid exciton transfer from "bright" nanocrystals to surface trap states in nearest-neighbors can efficiently fill such traps and enhance the stability of emission by promoting the radiative recombination of slowly diffusing excited electrons.

  20. Patterned Si thin film electrodes for enhancing structural stability.

    PubMed

    Cho, Gyu-Bong; Noh, Jung-Pil; Sung, Ho-Jin; Lee, Sang-Hun; Im, Yeon-Min; Ahn, Hyo-Jun; Kim, Ki-Won

    2012-01-01

    A patterned film (electrode) with lozenge-shaped Si tiles could be successfully fabricated by masking with an expanded metal foil during film deposition. Its electrochemical properties and structural stability during the charge-discharge process were examined and compared with those of a continuous (conventional) film electrode. The patterned electrode exhibited a remarkably improved cycleability (75% capacity retention after 120 cycles) and an enhanced structural stability compared to the continuous electrode. The good electrochemical performance of the patterned electrode was attributed to the space between Si tiles that acted as a buffer against the volume change of the Si electrode. PMID:22221620

  1. Patterned Si thin film electrodes for enhancing structural stability

    NASA Astrophysics Data System (ADS)

    Cho, Gyu-Bong; Noh, Jung-Pil; Sung, Ho-Jin; Lee, Sang-Hun; Im, Yeon-Min; Ahn, Hyo-Jun; Kim, Ki-Won

    2012-01-01

    A patterned film (electrode) with lozenge-shaped Si tiles could be successfully fabricated by masking with an expanded metal foil during film deposition. Its electrochemical properties and structural stability during the charge-discharge process were examined and compared with those of a continuous (conventional) film electrode. The patterned electrode exhibited a remarkably improved cycleability (75% capacity retention after 120 cycles) and an enhanced structural stability compared to the continuous electrode. The good electrochemical performance of the patterned electrode was attributed to the space between Si tiles that acted as a buffer against the volume change of the Si electrode.

  2. Wellbore flow model for carbon dioxide and brine

    SciTech Connect

    Pan, L.; Oldenburg, C.M.; Wu, Y.-S.; Pruess, K.

    2008-11-01

    Wellbores have been identified as the most likely conduit for CO{sub 2} and brine leakage from geologic carbon sequestration (GCS) sites, especially those in sedimentary basins with historical hydrocarbon production. In order to quantify the impacts of leakage of CO{sub 2} and brine through wellbores, we have developed a wellbore simulator capable of describing non-isothermal open well flow dynamics of CO{sub 2}-brine mixtures. The mass and thermal energy balance equations are solved numerically by a finite difference scheme with wellbore heat transmission handled semianalytically. This new wellbore simulator can take as input the pressure, saturation, and composition conditions from reservoir simulators and calculate CO{sub 2} and brine fluxes needed to assess impacts to vulnerable resources. This new capability is being incorporated into the Certification Framework (CF) developed for risk assessment of GCS sites.

  3. Enhanced Mechanical Stability of Gold Nanotips through Carbon Nanocone Encapsulation

    NASA Astrophysics Data System (ADS)

    Cano-Marquez, Abraham G.; Schmidt, Wesller G.; Ribeiro-Soares, Jenaina; Gustavo Cançado, Luiz; Rodrigues, Wagner N.; Santos, Adelina P.; Furtado, Clascidia A.; Autreto, Pedro A. S.; Paupitz, Ricardo; Galvão, Douglas S.; Jorio, Ado

    2015-06-01

    Gold is a noble metal that, in comparison with silver and copper, has the advantage of corrosion resistance. Despite its high conductivity, chemical stability and biocompatibility, gold exhibits high plasticity, which limits its applications in some nanodevices. Here, we report an experimental and theoretical study on how to attain enhanced mechanical stability of gold nanotips. The gold tips were fabricated by chemical etching and further encapsulated with carbon nanocones via nanomanipulation. Atomic force microscopy experiments were carried out to test their mechanical stability. Molecular dynamics simulations show that the encapsulated nanocone changes the strain release mechanisms at the nanoscale by blocking gold atomic sliding, redistributing the strain along the whole nanostructure. The carbon nanocones are conducting and can induce magnetism, thus opening new avenues on the exploitation of transport, mechanical and magnetic properties of gold covered by sp2 carbon at the nanoscale.

  4. Enhanced Mechanical Stability of Gold Nanotips through Carbon Nanocone Encapsulation

    PubMed Central

    Cano-Marquez, Abraham G.; Schmidt, Wesller G.; Ribeiro-Soares, Jenaina; Gustavo Cançado, Luiz; Rodrigues, Wagner N.; Santos, Adelina P.; Furtado, Clascidia A.; Autreto, Pedro A.S.; Paupitz, Ricardo; Galvão, Douglas S.; Jorio, Ado

    2015-01-01

    Gold is a noble metal that, in comparison with silver and copper, has the advantage of corrosion resistance. Despite its high conductivity, chemical stability and biocompatibility, gold exhibits high plasticity, which limits its applications in some nanodevices. Here, we report an experimental and theoretical study on how to attain enhanced mechanical stability of gold nanotips. The gold tips were fabricated by chemical etching and further encapsulated with carbon nanocones via nanomanipulation. Atomic force microscopy experiments were carried out to test their mechanical stability. Molecular dynamics simulations show that the encapsulated nanocone changes the strain release mechanisms at the nanoscale by blocking gold atomic sliding, redistributing the strain along the whole nanostructure. The carbon nanocones are conducting and can induce magnetism, thus opening new avenues on the exploitation of transport, mechanical and magnetic properties of gold covered by sp2 carbon at the nanoscale. PMID:26083864

  5. Enhancement of stability in systems with metastable states

    SciTech Connect

    Spagnolo, B.; Augello, G.; Pizzolato, N.; Valenti, D.; Fiasconaro, A.

    2007-12-06

    The investigation of noise-induced phenomena in far from equilibrium systems is one of the approach used to understand the behaviour of physical and biological complex systems. Metastability is a generic feature of many nonlinear systems, and the problem of the lifetime of metastable states involves fundamental aspects of nonequilibrium statistical mechanics. The enhancement of the life-time of metastable states through the noise enhanced stability effect and the role played by the resonant activation phenomenon will be discussed in models of interdisciplinary physics: (i) Ising model (ii) Josephson junction; (iii) stochastic FitzHugh-Nagumo model; (iv) a population dynamics model, and (v) a market model with stochastic volatility.

  6. Enhancing stability of industrial turbines using adjustable partial arc bearings

    NASA Astrophysics Data System (ADS)

    Chasalevris, Athanasios; Dohnal, Fadi

    2016-09-01

    The paper presents the principal of operation, the simulation and the characteristics of two partial-arc journal bearings of variable geometry and adjustable/controllable stiffness and damping properties. The proposed journals are supposed to consist of a scheme that enables the periodical variation of bearing properties. Recent achievements of suppressing rotor vibrations using plain circular journal bearings of variable geometry motivate the further extension of the principle to bearings of applicable geometry for industrial turbines. The paper describes the application of a partial-arc journal bearing to enhance stability of high speed industrial turbines. The proposed partial-arc bearings with adjustable/controllable properties enhance stability and they introduce stable margins in speeds much higher than the 1st critical.

  7. Biochemical stabilization enhances red blood cell recovery and stability following cryopreservation.

    PubMed

    Wagner, Christopher T; Martowicz, Melissa L; Livesey, Stephen A; Connor, Jerome

    2002-10-01

    Glycerolized red blood cells (RBC) are approved for long-term cryopreservation. However, the need to remove the glycerol cryoprotectant prior to transfusion has limited the usefulness of this cryopreservation method. This report describes using non-cryoprotectant biochemical stabilization techniques to substitute for the standard glycerol cryoprotectant. The glycerolized RBC method was compared to a newly developed LC-V method that combines transfusable cryoprotectants (hydroxyethyl starch and dextran) and specific non-cryoprotectant biochemical stabilizers (nicotinamide, nifedipine, and flurbiprofen). Results demonstrate that the biochemical stabilizers significantly reduce cryopreservation-induced hemolysis compared to cryopreservation in their absence and that thaw hemolysis levels approach those of standard 40% (w/v) glycerolized RBC (3.1+/-0.2% for 40% glycerol compared to 8.7+/-0.9% for the LC-V protocol). Furthermore, LC-V cryopreserved RBC exhibit a significantly enhanced post-thaw stability compared to glycerolized RBC as determined by osmotic fragility index (0.557+/-0.034 for 40% glycerol compared to 0.478+/-0.016 for the LC-V protocol). Analysis of biochemically stabilized RBC proteins revealed a transient translocation of carbonic anhydrase to the membrane fraction. However, the enhanced RBC recovery and stability could not be attributed to this event. Finally, DSC analysis demonstrated that the biochemical stabilizers of the LC-V process were not functioning as surrogate cryoprotectants in that they did not affect the quantity or quality of ice formed. Overall, this work demonstrates that cryopreservation-induced RBC damage may be corrected or prevented through specific biochemical stabilization and represents a significant step toward a directly transfusable cryopreserved RBC product.

  8. Enhanced catalyst stability for cyclic co methanation operations

    DOEpatents

    Risch, Alan P.; Rabo, Jule A.

    1983-01-01

    Carbon monoxide-containing gas streams are passed over a catalyst to deposit a surface layer of active surface carbon thereon essentially without the formation of inactive coke. The active carbon is thereafter reacted with steam or hydrogen to form methane. Enhanced catalyst stability for long term, cyclic operation is obtained by the incorporation of an alkali or alkaline earth dopant in a silica binding agent added to the catalyst-support additive composition.

  9. Investigation of wellbore cooling by circulation and fluid penetration into the formation using a wellbore thermal simulator computer code

    SciTech Connect

    Duda, L.E.

    1987-01-01

    The high temperatures of geothermal wells present severe problems for drilling, logging, and developing these reservoirs. Cooling the wellbore is perhaps the most common method to solve these problems. However, it is usually not clear what may be the most effective wellbore cooling mechanism for a given well. In this paper, wellbore cooling by the use of circulation or by fluid injection into the surrounding rock is investigated using a wellbore thermal simulator computer code. Short circulation times offer no prolonged cooling of the wellbore, but long circulation times (greater than ten or twenty days) greatly reduce the warming rate after shut-in. The dependence of the warming rate on the penetration distance of cooler temperatures into the rock formation (as by fluid injection) is investigated. Penetration distances of greater than 0.6 m appear to offer a substantial reduction in the warming rate. Several plots are shown which demonstrate these effects.

  10. Dispersive Elements for Enhanced Laser Gyroscopy and Cavity Stabilization

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Chang, Hongrok; Diels, J. C.

    2007-01-01

    We analyze the effect of a highly dispersive element placed inside a modulated optical cavity on the frequency and amplitude of the modulation to determine the conditions for cavity self-stabilization and enhanced gyroscopic sensitivity. We find an enhancement in the sensitivity of a laser gyroscope to rotation for normal dispersion, while anomalous dispersion can be used to self-stabilize an optical cavity. Our results indicate that atomic media, even coherent superpositions in multilevel atoms, are of limited use for these applications, because the amplitude and phase filters work against one another, i.e., decreasing the modulation frequency increases its amplitude and vice-versa. On the other hand, for optical resonators the dispersion reversal associated with critical coupling enables the amplitude and phase filters to work together. We find that for over-coupled resonators, the absorption and normal dispersion on-resonance increase the contrast and frequency of the beat-note, respectively, resulting in a substantial enhancement of the gyroscopic response. Under-coupled resonators can be used to stabilize the frequency of a laser cavity, but result in a concomitant increase in amplitude fluctuations. As a more ideal solution we propose the use of a variety of coupled-resonator-induced transparency that is accompanied by anomalous dispersion.

  11. Enhanced enzyme stability through site-directed covalent immobilization.

    PubMed

    Wu, Jeffrey Chun Yu; Hutchings, Christopher Hayden; Lindsay, Mark Jeffrey; Werner, Christopher James; Bundy, Bradley Charles

    2015-01-10

    Breakthroughs in enzyme immobilization have enabled increased enzyme recovery and reusability, leading to significant decreases in the cost of enzyme use and fueling biocatalysis growth. However, current enzyme immobilization techniques suffer from leaching, enzyme stability, and recoverability and reusability issues. Moreover, these techniques lack the ability to control the orientation of the immobilized enzymes. To determine the impact of orientation on covalently immobilized enzyme activity and stability, we apply our PRECISE (Protein Residue-Explicit Covalent Immobilization for Stability Enhancement) system to a model enzyme, T4 lysozyme. The PRECISE system uses non-canonical amino acid incorporation and the Huisgen 1,3-dipolar cycloaddition "click" reaction to enable directed enzyme immobilization at rationally chosen residues throughout an enzyme. Unlike previous site-specific systems, the PRECISE system is a truly covalent immobilization method. Utilizing this system, enzymes immobilized at proximate and distant locations from the active site were tested for activity and stability under denaturing conditions. Our results demonstrate that orientation control of covalently immobilized enzymes can provide activity and stability benefits exceeding that of traditional random covalent immobilization techniques. PRECISE immobilized enzymes were 50 and 73% more active than randomly immobilized enzymes after harsh freeze-thaw and chemical denaturant treatments.

  12. Enhanced photo-stability, thermal-stability and aqueous-stability of indocyanine green in polymeric nanoparticulate systems.

    PubMed

    Saxena, Vishal; Sadoqi, Mostafa; Shao, Jun

    2004-03-19

    Photo-degradation, thermal-degradation and aqueous-instability of indocyanine green (ICG) limits its application as a fluorescence contrast agent for imaging purposes. Thus, the objective of this study is to develop polymeric nanoparticles entrapping ICG and to establish its effectiveness in providing photo-stability, thermal stability and aqueous stability to ICG. Nanoparticles entrapping ICG were engineered, characterized and the degradation kinetics of ICG in the nanoparticles was investigated in aqueous media. The entrapment of ICG in the nanoparticles causes a shift in its wavelength of peak fluorescence and a decrease in its peak fluorescence intensity. The degradation of ICG in aqueous nanoparticle suspension followed first-order kinetics for the time period studied. ICG entrapment in the nanoparticles enhanced aqueous-stability of ICG (half-life, t(1/2) was 72.2+/-6.1 h for ICG in the nanoparticles as compared to 16.8+/-1.5 h for free ICG solution), photo-stability of ICG (t(1/2) was 73.7+/-7.5 h for ICG in the nanoparticles as compared to 14.4+/-2.4 h for free ICG solution when exposed to room light from two 32 W normal fluorescent tubes) and thermal-stability of ICG (t(1/2) of ICG at 42 degrees C was 62.4+/-1.7 h for ICG in the nanoparticles as compared to 10.1+/-0.6 h for free ICG solution).

  13. Enhancement of thermal stability in microwave applicators by mismatching and detuning

    SciTech Connect

    Nelson, E.M.

    1996-07-01

    Many microwave applicator systems experiencing thermal runaway can be stabilized by mismatching and/or detuning the system. The stability of the systems is discussed qualitatively and a conservative guide for adjusting microwave applicators for enhanced stability is described.

  14. Enhanced thermal stability of phosphate capped magnetite nanoparticles

    SciTech Connect

    Muthukumaran, T.; Philip, John

    2014-06-14

    We have studied the effect of phosphate capping on the high temperature thermal stability and magnetic properties of magnetite (Fe{sub 3}O{sub 4}) nanoparticles synthesized through a single-step co-precipitation method. The prepared magnetic nanoparticles are characterized using various techniques. When annealed in air, the phosphate capped nanoparticle undergoes a magnetic to non-magnetic phase transition at a temperature of 689 °C as compared to 580 °C in the uncoated nanoparticle of similar size. The observed high temperature phase stability of phosphate capped nanoparticle is attributed to the formation of a phosphocarbonaceous shell over the nanoparticles, which acts as a covalently attached protective layer and improves the thermal stability of the core material by increasing the activation energy. The phosphocarbonaceous shell prevents the intrusion of heat, oxygen, volatiles, and mass into the magnetic core. At higher temperatures, the coalescence of nanoparticles occurs along with the restructuring of the phosphocarbonaceous shell into a vitreous semisolid layer on the nanoparticles, which is confirmed from the small angle X-ray scattering, Fourier transform infra red spectroscopy, and transmission electron microscopy measurements. The probable mechanism for the enhancement of thermal stability of phosphocarbonaceous capped nanoparticles is discussed.

  15. Chemical Effect on Wellbore Instability of Nahr Umr Shale

    PubMed Central

    Nie, Zhen

    2013-01-01

    Wellbore instability is one of the major problems that hamper the drilling speed in Halfaya Oilfield. Comprehensive analysis of geological and engineering data indicates that Halfaya Oilfield features fractured shale in the Nahr Umr Formation. Complex accidents such as wellbore collapse and sticking emerged frequently in this formation. Tests and theoretical analysis revealed that wellbore instability in the Halfaya Oilfield was influenced by chemical effect of fractured shale and the formation water with high ionic concentration. The influence of three types of drilling fluids on the rock mechanical properties of Nahr Umr Shale is tested, and time-dependent collapse pressure is calculated. Finally, we put forward engineering countermeasures for safety drilling in Halfaya Oilfield and point out that increasing the ionic concentration and improving the sealing capacity of the drilling fluid are the way to keep the wellbore stable. PMID:24282391

  16. Optimized Design and Use of Induced Complex Fractures in Horizontal Wellbores of Tight Gas Reservoirs

    NASA Astrophysics Data System (ADS)

    Zeng, F. H.; Guo, J. C.

    2016-04-01

    Multistage hydraulic fracturing is being increasing use in the establishment of horizontal wells in tight gas reservoirs. Connecting hydraulic fractures to natural and stress-induced fractures can further improve well productivity. This paper investigates the fracture treatment design issues involved in the establishment of horizontal wellbores, including the effects of geologic heterogeneity, perforation parameters, fracturing patterns, and construction parameters on stress anisotropy during hydraulic fracturing and on natural fractures during hydraulic fracture propagation. The extent of stress reversal and reorientation was calculated for fractures induced by the creation of one or more propped fractures. The effects of stress on alternate and sequential fracturing horizontal well and on the reservoir's mechanical properties, including the spatial extent of stress reorientation caused by the opening of fractures, were assessed and quantified. Alternate sequencing of transverse fractures was found to be an effective means of enhancing natural fracture stimulation by allowing fractures to undergo less stress contrast during propagation. The goal of this paper was to present a new approach to design that optimizes fracturing in a horizontal wellbore from the perspectives of both rock mechanics and fluid production. The new design is a modified version of alternate fracturing, where the fracture-initiation sequence was controlled by perforation parameters with a staggered pattern within a horizontal wellbore. Results demonstrated that the modified alternate fracturing performed better than original sequence fracturing and that this was because it increased the contact area and promoted more gas production in completed wells.

  17. Dramatic pressure-driven enhancement of bulk skyrmion stability.

    PubMed

    Levatić, I; Popčević, P; Šurija, V; Kruchkov, A; Berger, H; Magrez, A; White, J S; Rønnow, H M; Živković, I

    2016-01-01

    The recent discovery of magnetic skyrmion lattices initiated a surge of interest in the scientific community. Several novel phenomena have been shown to emerge from the interaction of conducting electrons with the skyrmion lattice, such as a topological Hall-effect and a spin-transfer torque at ultra-low current densities. In the insulating compound Cu2OSeO3, magneto-electric coupling enables control of the skyrmion lattice via electric fields, promising a dissipation-less route towards novel spintronic devices. One of the outstanding fundamental issues is related to the thermodynamic stability of the skyrmion lattice. To date, the skyrmion lattice in bulk materials has been found only in a narrow temperature region just below the order-disorder transition. If this narrow stability is unavoidable, it would severely limit applications. Here we present the discovery that applying just moderate pressure on Cu2OSeO3 substantially increases the absolute size of the skyrmion pocket. This insight demonstrates directly that tuning the electronic structure can lead to a significant enhancement of the skyrmion lattice stability. We interpret the discovery by extending the previously employed Ginzburg-Landau approach and conclude that change in the anisotropy is the main driver for control of the size of the skyrmion pocket. PMID:26892190

  18. Dramatic pressure-driven enhancement of bulk skyrmion stability

    PubMed Central

    Levatić, I.; Popčević, P.; Šurija, V.; Kruchkov, A.; Berger, H.; Magrez, A.; White, J. S.; Rønnow, H. M.; Živković, I.

    2016-01-01

    The recent discovery of magnetic skyrmion lattices initiated a surge of interest in the scientific community. Several novel phenomena have been shown to emerge from the interaction of conducting electrons with the skyrmion lattice, such as a topological Hall-effect and a spin-transfer torque at ultra-low current densities. In the insulating compound Cu2OSeO3, magneto-electric coupling enables control of the skyrmion lattice via electric fields, promising a dissipation-less route towards novel spintronic devices. One of the outstanding fundamental issues is related to the thermodynamic stability of the skyrmion lattice. To date, the skyrmion lattice in bulk materials has been found only in a narrow temperature region just below the order-disorder transition. If this narrow stability is unavoidable, it would severely limit applications. Here we present the discovery that applying just moderate pressure on Cu2OSeO3 substantially increases the absolute size of the skyrmion pocket. This insight demonstrates directly that tuning the electronic structure can lead to a significant enhancement of the skyrmion lattice stability. We interpret the discovery by extending the previously employed Ginzburg-Landau approach and conclude that change in the anisotropy is the main driver for control of the size of the skyrmion pocket. PMID:26892190

  19. Method for enhancing stability in multi-beam microscopy

    NASA Astrophysics Data System (ADS)

    Huang, Yujia; Wang, Yifan; Kuang, Cuifang; Liu, Xu

    2016-10-01

    A method based on close loop control of four degrees of freedom (4DF) is proposed to enhance angular and translational stability of beams in multi-beam microscopy including STED, RESOLFT and CARS, etc. Deviations of multi-beams can be measured and corrected by our module, which is composed of four degrees of freedom position sensitive detectors (4DF PSD) and two actuator mirrors (AM) with motor and piezo servos. An output crosslink matrix obtained by a self-learning process is used to control four actuators to compensate for 4DF independently in beam deviations. We realize a standard deviation within about 2 µm at the entrance pupil plane (a spatial optical path of 180 cm for the whole system) using a compact stabilization system, which is equivalent to around 3 nm at the sample plane under the 100×  objective lens with a focal length of 2 mm, corresponding to an improvement of stability by an order of magnitude. Our method can react fast in real time and compensate for large disturbances caused by air agitation or temperature variation.

  20. Glucocorticoids enhance stability of human growth hormone mRNA.

    PubMed Central

    Paek, I; Axel, R

    1987-01-01

    We have studied the control of expression of the human growth hormone (hGH) gene introduced into the chromosomes of mouse fibroblasts. Cell lines transformed with the hGH gene expressed low levels of intact hGH mRNA and secreted hGH protein into the medium. Although the level of expression of hGH mRNA was low, the gene remained responsive to induction by glucocorticoid hormones. To localize the sequences responsible for induction and to determine the mechanism by which these cis-acting sequences enhance gene expression, we have constructed a series of fusion genes between the hGH gene and the herpes simplex virus (HSV) thymidine kinase (tk) gene. We have demonstrated that a fusion gene in which hGH cDNA is flanked at its 5' terminus by an HSV tk promoter and is flanked at its 3' terminus by 3' HSV tk DNA remains inducible by glucocorticoids. Our studies indicate that the hGH exons contain sequences which are responsible for glucocorticoid hormone induction. Pulse-chase experiments, in vitro nuclear transcription, and approach to steady-state measurements indicate that the mechanisms responsible for induction of the hGH cDNA fusion gene operate posttranscriptionally to enhance the stability of hGH mRNA. Moreover, this increased stability was associated with an increase in the length of the 3' poly(A) tail on hGH mRNA. Images PMID:3037323

  1. Stability Enhancement of Polymeric Sensing Films Using Fillers

    NASA Technical Reports Server (NTRS)

    Lin, Brian; Shevade, Abhijit; Ryan, Margaret Amy; Kisor, Adam; Yen, Shiao-Pin; Manatt, Kenneth; Homer, Margie; Fleurial, Jean-Pierre

    2006-01-01

    Experiments have shown the stability enhancement of polymeric sensing films on mixing the polymer with colloidal filler particles (submicron-sized) of carbon black, silver, titanium dioxide, and fumed silicon dioxide. The polymer films are candidates for potential use as sensing media in micro/nano chemical sensor devices. The need for stability enhancement of polymer sensing films arises because such films have been found to exhibit unpredictable changes in sensing activity over time, which could result in a possible failure of the sensor device. The changes in the physical properties of a polymer sensing film caused by the sorption of a target molecule can be measured by any of several established transduction techniques: electrochemical, optical, calorimetric, or piezoelectric, for example. The transduction technique used in the current polymer stability experiments is based on piezoelectric principles using a quartz-crystal microbalance (QCM). The surface of the QCM is coated with the polymer, and the mass uptake by the polymer film causes a change in the oscillating frequency of the quartz crystal. The polymer used for the current study is ethyl cellulose. The polymer/ polymer composite solutions were prepared in 1,3 dioxolane solvent. The filler concentration was fixed at 10 weight percent for the composites. The polymer or polymer composite solutions were cast on the quartz crystal having a fundamental frequency of about 6 MHz. The coated crystal was subjected to a multistage drying process to remove all measurable traces of the solvent. In each experiment, the frequency of oscillation was measured while the QCM was exposed to clean, dry, flowing air for about 30 minutes, then to air containing a known concentration of isopropanol for about 30 minutes, then again to clean dry air for about 30 minutes, and so forth. This cycle of measurements for varying isopropanol concentrations was repeated at intervals for several months. The figure depicts some of the

  2. Experimental and Computational Studies of Coupled Geomechanical and Hydrologic Processes in Wellbore Systems (Invited)

    NASA Astrophysics Data System (ADS)

    Carey, J. W.; Mori, H.; Porter, M. L.; Lewis, K. C.; Kelkar, S.

    2013-12-01

    cement, the cement-rock interface, caprock, and reservoir rock. We used a model that is 1 m in radius, and extends 5 m along the wellbore. The model consisted of a lower storage aquifer, a caprock and an upper aquifer that received leaking fluids. We coupled flow and geomechanics using a shear-failure model that represents shear-induced damage and is similar to a Mohr-Coulomb slip mechanism. In this model, damage occurs for any excess shear stress with permeability enhancement a function of stress with a maximum magnitude set by the user. Stresses were induced by application of an elevated constant pressure within the injection reservoir representing a far-field injection process. The initial permeability of the cement was 1 mD and stress-enhanced permeability was limited to an increase by a factor of 10-100. The simulations show that shear-failure modes lead to enhanced permeability of the wellbore system. Continuing work will examine sensitivity of the results to mechanical properties and initial permeability distributions, the impact of relative permeability models, and the development of permeability-stress models including an aperture-opening tensile-failure model.

  3. Low dose tunicamycin enhances atherosclerotic plaque stability by inducing autophagy.

    PubMed

    Ma, Meijuan; Song, Liqiang; Yan, Hao; Liu, Min; Zhang, Le; Ma, Ying; Yuan, Jian; Hu, Jianhua; Ji, Zhaole; Zhang, Rongqing; Li, Congye; Wang, Haichang; Tao, Ling; Zhang, Yingmei; Li, Yan

    2016-01-15

    After decades of indolent progression, atherosclerosis may cause unheralded events, such as myocardial infarction, acute coronary syndrome and stroke due to sudden rupture of atherosclerotic plaques, and pharmacologically modulating plaque stability would reduce the risk of cardiovascular diseases. Endoplasmic reticulum stress (ERS) is responsible for the vulnerability of plaques. However, the underlying mechanism has not been fully elucidated. In this work, ApoE(-/-) mice underwent perivascular carotid collar placement surgeries or sham operations were given higher (3.0mg/kg) and lower (0.3mg/kg) doses of tunicamycin (TM), and plaque stability was evaluated. It was shown that lower TM-treated animals exhibited reduced plaque areas and necrotic cores as well as fibrous cap thickness accompanied by a lower percentage of infiltrates and foam cells than the sham-operated and higher TM treated animals. Lower TM had a profound inhibitory effect on plasma inflammatory response and lipid profile in atherosclerotic ApoE(-/-) mice. In addition, we found that the ApoE(-/-) mice presented higher autophagy activity in response to lower TM administration while apoptosis was reduced. An in vitro study in murine macrophages revealed that lower TM could markedly reduce lipid uptake and accumulation and cell apoptosis while significantly upregulated the expression of Atg7. However, higher TM had adverse effects. Finally, mild induction of ERS by lower TM inhibits AKT-TSC-mTOR cascades to increase cellular autophagy. However, high TM failed to enhance autophagy and equilibrate elevated CHOP-mediated cell death in spite of the inhibition of AKT-TSC-mTOR signaling. In conclusion, lower TM stabilized plaques by activating autophagy through AKT-TSC-mTOR signaling. PMID:26616221

  4. Low dose tunicamycin enhances atherosclerotic plaque stability by inducing autophagy.

    PubMed

    Ma, Meijuan; Song, Liqiang; Yan, Hao; Liu, Min; Zhang, Le; Ma, Ying; Yuan, Jian; Hu, Jianhua; Ji, Zhaole; Zhang, Rongqing; Li, Congye; Wang, Haichang; Tao, Ling; Zhang, Yingmei; Li, Yan

    2016-01-15

    After decades of indolent progression, atherosclerosis may cause unheralded events, such as myocardial infarction, acute coronary syndrome and stroke due to sudden rupture of atherosclerotic plaques, and pharmacologically modulating plaque stability would reduce the risk of cardiovascular diseases. Endoplasmic reticulum stress (ERS) is responsible for the vulnerability of plaques. However, the underlying mechanism has not been fully elucidated. In this work, ApoE(-/-) mice underwent perivascular carotid collar placement surgeries or sham operations were given higher (3.0mg/kg) and lower (0.3mg/kg) doses of tunicamycin (TM), and plaque stability was evaluated. It was shown that lower TM-treated animals exhibited reduced plaque areas and necrotic cores as well as fibrous cap thickness accompanied by a lower percentage of infiltrates and foam cells than the sham-operated and higher TM treated animals. Lower TM had a profound inhibitory effect on plasma inflammatory response and lipid profile in atherosclerotic ApoE(-/-) mice. In addition, we found that the ApoE(-/-) mice presented higher autophagy activity in response to lower TM administration while apoptosis was reduced. An in vitro study in murine macrophages revealed that lower TM could markedly reduce lipid uptake and accumulation and cell apoptosis while significantly upregulated the expression of Atg7. However, higher TM had adverse effects. Finally, mild induction of ERS by lower TM inhibits AKT-TSC-mTOR cascades to increase cellular autophagy. However, high TM failed to enhance autophagy and equilibrate elevated CHOP-mediated cell death in spite of the inhibition of AKT-TSC-mTOR signaling. In conclusion, lower TM stabilized plaques by activating autophagy through AKT-TSC-mTOR signaling.

  5. Enhanced Raman sensitivity using an actively stabilized external resonator

    NASA Astrophysics Data System (ADS)

    Taylor, David J.; Glugla, Manfred; Penzhorn, Ralf-Dieter

    2001-04-01

    An enhancement up to 250-fold in laser Raman signals for real-time gas analysis has been achieved within an actively stabilized external resonator (ASER), whose length is actively matched to the single-frequency excitation laser using the Pound-Drever technique. With the Raman cell present, enhancements up to 50-fold are achieved, and the resulting detection limit for hydrogen in ambient-pressure gas mixtures is about ten parts-per-million in a 1 min analysis period at unity signal-to-noise ratio. Based upon the recent development of a fiber-pumped Nd:YVO4 laser with single-frequency output exceeding 5 W at 532 nm, this highly sensitive instrument is applied to detection of tritiated gases, wherein the compactness and low heat of this laser head permit placing the entire optical system, including laser head, charge coupled Raman detector, and ASER, within the glove box necessary for secondary containment of tritium, thereby accomplishing a robust, highly sensitive Raman analytical system for hazardous substances.

  6. Mental training enhances attentional stability: neural and behavioral evidence.

    PubMed

    Lutz, Antoine; Slagter, Heleen A; Rawlings, Nancy B; Francis, Andrew D; Greischar, Lawrence L; Davidson, Richard J

    2009-10-21

    The capacity to stabilize the content of attention over time varies among individuals, and its impairment is a hallmark of several mental illnesses. Impairments in sustained attention in patients with attention disorders have been associated with increased trial-to-trial variability in reaction time and event-related potential deficits during attention tasks. At present, it is unclear whether the ability to sustain attention and its underlying brain circuitry are transformable through training. Here, we show, with dichotic listening task performance and electroencephalography, that training attention, as cultivated by meditation, can improve the ability to sustain attention. Three months of intensive meditation training reduced variability in attentional processing of target tones, as indicated by both enhanced theta-band phase consistency of oscillatory neural responses over anterior brain areas and reduced reaction time variability. Furthermore, those individuals who showed the greatest increase in neural response consistency showed the largest decrease in behavioral response variability. Notably, we also observed reduced variability in neural processing, in particular in low-frequency bands, regardless of whether the deviant tone was attended or unattended. Focused attention meditation may thus affect both distracter and target processing, perhaps by enhancing entrainment of neuronal oscillations to sensory input rhythms, a mechanism important for controlling the content of attention. These novel findings highlight the mechanisms underlying focused attention meditation and support the notion that mental training can significantly affect attention and brain function.

  7. Plasma deposited stability enhancement coating for amorphous ketoprofen.

    PubMed

    Bosselmann, Stephanie; Owens, Donald E; Kennedy, Rachel L; Herpin, Matthew J; Williams, Robert O

    2011-05-01

    A hydrophobic fluorocarbon coating deposited onto amorphous ketoprofen via pulsed plasma-enhanced chemical vapor deposition (PPECVD) significantly prolonged the onset of recrystallization compared to uncoated drug. Rapid freezing (RF) employed to produce amorphous ketoprofen was followed by PPECVD of perfluorohexane. The effect of coating thickness on the recrystallization and dissolution behavior of ketoprofen was investigated. Samples were stored in open containers at 40°C and 75% relative humidity, and the onset of recrystallization was monitored by DSC. An increase in coating thickness provided enhanced stability against recrystallization for up to 6 months at accelerated storage conditions (longest time of observation) when compared to three days for uncoated ketoprofen. Results from XPS analysis demonstrated that an increase in coating thickness was associated with improved surface coverage thus enabling superior protection. Dissolution testing showed that at least 80% of ketoprofen was released in buffer pH 6.8 from all coated samples. Overall, an increase in coating thickness resulted in a more complete drug release due to decreased adhesion of the coating to the substrate.

  8. Regional-scale advective, diffusive, and eruptive dynamics of CO2 and brine leakage through faults and wellbores

    NASA Astrophysics Data System (ADS)

    Jung, Na-Hyun; Han, Weon Shik; Han, Kyungdoe; Park, Eungyu

    2015-05-01

    Regional-scale advective, diffusive, and eruptive transport dynamics of CO2 and brine within a natural analogue in the northern Paradox Basin, Utah, were explored by integrating numerical simulations with soil CO2 flux measurements. Deeply sourced CO2 migrates through steeply dipping fault zones to the shallow aquifers predominantly as an aqueous phase. Dense CO2-rich brine mixes with regional groundwater, enhancing CO2 dissolution. Linear stability analysis reveals that CO2 could be dissolved completely within only ~500 years. Assigning lower permeability to the fault zones induces fault-parallel movement, feeds up-gradient aquifers with more CO2, and impedes down-gradient fluid flow, developing anticlinal CO2 traps at shallow depths (<300 m). The regional fault permeability that best reproduces field spatial CO2 flux variation is estimated 1 × 10-17 ≤ kh < 1 × 10-16 m2 and 5 × 10-16 ≤ kv < 1 × 10-15 m2. The anticlinal trap serves as an essential fluid source for eruption at Crystal Geyser. Geyser-like discharge sensitively responds to varying well permeability, radius, and CO2 recharge rate. The cyclic behavior of wellbore CO2 leakage decreases with time.

  9. Microwave Heating of Functionalized Graphene Nanoribbons in Thermoset Polymers for Wellbore Reinforcement.

    PubMed

    Kim, Nam Dong; Metzger, Andrew; Hejazi, Vahid; Li, Yilun; Kovalchuk, Anton; Lee, Seoung-Ki; Ye, Ruquan; Mann, Jason A; Kittrell, Carter; Shahsavari, Rouzbeh; Tour, James M

    2016-05-25

    Here, we introduce a systematic strategy to prepare composite materials for wellbore reinforcement using graphene nanoribbons (GNRs) in a thermoset polymer irradiated by microwaves. We show that microwave absorption by GNRs functionalized with poly(propylene oxide) (PPO-GNRs) cured the composite by reaching 200 °C under 30 W of microwave power. Nanoscale PPO-GNRs diffuse deep inside porous sandstone and dramatically enhance the mechanics of the entire structure via effective reinforcement. The bulk and the local mechanical properties measured by compression and nanoindentation mechanical tests, respectively, reveal that microwave heating of PPO-GNRs and direct polymeric curing are major reasons for this significant reinforcement effect. PMID:27140722

  10. The influence of wellbore inflow on electromagnetic borehole flowmeter measurements

    USGS Publications Warehouse

    Clemo, T.; Barrash, W.; Reboulet, E.C.; Johnson, T.C.; Leven, C.

    2009-01-01

    This paper describes a combined field, laboratory, and numerical study of electromagnetic borehole flowmeter measurements acquired without the use of a packer or skirt to block bypass flow around the flowmeter. The most significant finding is that inflow through the wellbore screen changes the ratio of flow through the flowmeter to wellbore flow. Experiments reveal up to a factor of two differences in this ratio for conditions with and without inflow through the wellbore screen. Standard practice is to assume the ratio is constant. A numerical model has been developed to simulate the effect of inflow on the flowmeter. The model is formulated using momentum conservation within the borehole and around the flowmeter. The model is embedded in the MODFLOW-2000 ground water flow code. ?? 2009 National Ground Water Association.

  11. Controls of wellbore flow regimes on pump effluent composition.

    PubMed

    Martin-Hayden, James M; Plummer, Mitchell; Britt, Sanford L

    2014-01-01

    Where well water and formation water are compositionally different or heterogeneous, pump effluent composition will vary due to partial mixing and transport induced by pumping. Investigating influences of purging and sampling methodology on composition variability requires quantification of wellbore flow regimes and mixing. As a basis for this quantification, analytical models simulating Poiseuille flow were developed to calculate flow paths and travel times. Finite element modeling was used to incorporate influences of mixing. Parabolic velocity distributions within the screened interval accelerate with cumulative inflow approaching the pump intake while an annulus of inflowing formation water contracts uniformly to displace an axial cylinder of pre-pumping well water as pumping proceeds. Increased dispersive mixing forms a more diffuse formation water annulus and the contribution of formation water to pump effluent increases more rapidly. Models incorporating viscous flow and diffusion scale mixing show that initially pump effluent is predominantly pre-pumping well water and compositions vary most rapidly. After two screen volumes of pumping, 94% of pump effluent is inflowing formation water. Where the composition of formation water and pre-pumping well water are likely to be similar, pump effluent compositions will not vary significantly and may be collected during early purging or with passive sampling. However, where these compositions are expected to be considerably different or heterogeneous, compositions would be most variable during early pumping, that is, when samples are collected during low-flow sampling. Purging of two screen volumes would be required to stabilize the content and collect a sample consisting of 94% formation water.

  12. Controls of Wellbore Flow Regimes on Pump Effluent Composition

    SciTech Connect

    James Martin-Hayden; plummer; Sanford Britt

    2014-01-01

    Where well water and formation water are compositionally different or heterogeneous, pump effluent composition will vary due to partial mixing and transport induced by pumping. Investigating influences of purging and sampling methodology on composition variability requires quantification of wellbore flow regimes and mixing. As a basis for this quantification, analytical models simulating Poiseuille flow were developed to calculate flow paths and travel times. Finite element modeling was used to incorporate influences of mixing. Parabolic velocity distributions within the screened interval accelerate with cumulative inflow approaching the pump intake while an annulus of inflowing formation water contracts uniformly to displace an axial cylinder of pre-pumping well water as pumping proceeds. Increased dispersive mixing forms a more diffuse formation water annulus and the contribution of formation water to pump effluent increases more rapidly. Models incorporating viscous flow and diffusion scale mixing show that initially pump effluent is predominantly pre-pumping well water and compositions vary most rapidly. After two screen volumes of pumping, 94% of pump effluent is inflowing formation water. Where the composition of formation water and pre-pumping well water are likely to be similar, pump effluent compositions will not vary significantly and may be collected during early purging or with passive sampling. However, where these compositions are expected to be considerably different or heterogeneous, compositions would be most variable during early pumping, that is, when samples are collected during low-flow sampling. Purging of two screen volumes would be required to stabilize the content and collect a sample consisting of 94% formation water.

  13. Enhanced photoacoustic stability of gold nanorods by silica matrix confinement.

    PubMed

    Chen, Leng-Chun; Wei, Chen-Wei; Souris, Jeffrey S; Cheng, Shih-Hsun; Chen, Chin-Tu; Yang, Chung-Shi; Li, Pai-Chi; Lo, Leu-Wei

    2010-01-01

    Photoacoustic tomography (PAT) has garnered much attention for its high contrast and excellent spatial resolution of perfused tissues. Gold nanorods (GNRs) have been employed to further enhance the imaging contrast of PAT. However, the photon fluences typically needed for PA wave induction often also result in GNR shape changes that significantly reduce the efficiency of acoustic wave generation. In this work, we propose, synthesize, and evaluate amorphous silica-coated gold nanorods (GNR-Si) in an effort to improve contrast agent stability and ameliorate efficiency loss during photoacoustic (PA) wave induction. TEM and optical absorption spectra measurements of GNR and GNR-Si show that encasing GNRs within amorphous silica provides substantial protection of nanorod conformation from thermal deformation. PA signals generated by GNR-Si demonstrate considerably greater resistance to degradation of signal intensity with repetitive pulsing than do uncoated GNRs, thereby enabling much longer, high-contrast imaging sessions than previously possible. The prolongation of high-contrast imaging, and biocompatibility and easy surface functionalization for targeting ligands afforded by amorphous silica, suggest GNR-Si to be potentially significant for the clinical translation of PAT. PMID:20210456

  14. CO2-saturated brine reactivity at the Portland cement-shale interface and the integrity of wellbore systems

    NASA Astrophysics Data System (ADS)

    Carey, J. W.; Lichtner, P. C.; Wigand, M. O.

    2006-12-01

    Long-term geologic storage of CO2 requires trapping the buoyant CO2 plume beneath impermeable caprocks such as shale. Given a high-quality caprock, wells that penetrate the caprock represent the most significant potential leak point in the sequestration system. This is particularly so because the Portland cement used to create the primary fluid barrier in the wellbore system is reactive with CO2 and may degrade over time. In this study, we used a combination of field observations obtained at the SACROC Unit in West Texas (the oldest CO2-enhanced oil recovery field in the US), experimental studies of cement-CO2-brine interactions, and numerical modeling to investigate the stability of the primary seal. The field observations and the recognition of the large thickness of Portland cement used in the wellbore annulus shows that the primary concern for potential leakage is not matrix flow due to carbonation of the Portland cement, but is the interfaces between the casing and cement and the cement and caprock. We focused on the dynamics of the cement- caprock interface in this study. Both field observations and experiments show that cement carbonation is accompanied by loss of primary cement phases such as portlandite and their replacement by a combination of carbonate minerals (calcite, aragonite, vaterite, and dolomite) and an amorphous alumino-silica residue. The carbonation reaction is accompanied by a transformation of the cement to a distinctive orange color. We have used the field and laboratory observations to construct a numerical model of carbonation at the cement-shale interface. The initial focus was on obtaining an adequate simulation of the cement alteration mineralogy with a 1-D, diffusion-based model. The primary variables controlling the reaction characteristics were porosity, tortuosity, and mineral reaction rates. By suitable adjustment of these parameters, the model successfully reproduces many of the alteration features of the cement including the

  15. Wellbore Models GWELL, GWNACL, and HOLA User's Guide

    SciTech Connect

    Aunzo, Z.P.; Bjornsson, G.; Bodvarsson, G.S.

    1991-10-01

    This report describes three multi-component, multi-feedzone geothermal wellbore simulators developed. These simulators reproduce the measured flowing temperature and pressure profiles in flowing wells and determine the relative contribution, fluid properties (e.g. enthalpy, temperature) and fluid composition (e.g. CO{sub 2}, NaCl) of each feedzone for a given discharge condition. The three related wellbore simulators that will be discussed here are HOLA, GWELL and GWNACL. HOLA is a multi-feedzone geothermal wellbore simulator for pure water, modified after the wellbore simulator developed by Bjornsson, 1987 and can now handle deviated wells. The other two simulators GWELL (see also Aunzo, 1990) and GWNACL are modified versions of HOLA that can handle H{sub 2}O-CO{sub 2} and H{sub 2}O-NaCl systems, respectively. These simulators can handle both single and two-phase flows in vertical and inclined pipes and calculate the flowing temperature and pressure profiles in the well. The simulators solve numerically the differential equations that describe the steady-state energy, mass and momentum flow in a pipe. The codes allow for multiple feedzones, variable grid spacing and well radius. These codes were developed using FORTRAN language on the UNIX system.

  16. Wellbore models GWELL, GWNACL, and HOLA: User's guide

    SciTech Connect

    Aunzo, Z.P. . Geothermal Div.); Bjornsson, G. ); Bodvarsson, G.S. )

    1991-10-01

    This report describes three multi-component, multi-feedzone geothermal wellbore simulators developed. These simulators reproduce the measured flowing temperature and pressure profiles in flowing wells and determine the relative contribution, fluid properties (e.g., enthalpy, temperature) and fluid composition (e.g. CO{sub 2}, NaCl) of each feedzone for a given discharge condition. The three related wellbore simulators that will be discussed here are HOLA, GWELL and GWNACL. HOLA is a multi-feedzone geothermal wellbore simulator for pure water, modified after the wellbore simulator developed by Bjornsson, 1987 and can now handle deviated wells. The other two simulators GWELL and GWNACL are modified versions of HOLO that can handle H{sub 2}O CO{sub 2} and H{sub 2}O-NaCl systems, respectively. These simulators can handle both single and two-phase flows in vertical and inclined pipes and calculate the flowing temperature and pressure profiles in the well. The simulators solve numerically the differential equations that describe the steady-state energy, mass and momentum flow in a pipe. The codes allow for multiple feedzones, variable grid spacing and well radius. Theses codes were developed using FORTRAN language on the UNIX system.

  17. Method of placing magnetic markers on collarless cased wellbores

    SciTech Connect

    Wilson, J.G.; Crawford, G.J.

    1986-02-25

    This patent describes a method of marking a wellbore casing in a manner such that the mark can be subsequently detected by a casing collar locator comprising placing a horseshoe-shaped electromagnet adjacent to the casing and energizing the electromagnet producing a magnetic marker at a location between the poles of the electromagnet.

  18. Controlling the pressure within an annular volume of a wellbore

    DOEpatents

    Hermes, Robert E.; Gonzalez, Manuel E.; Llewellyn, Brian C.; Bloys, James B.

    2011-01-18

    A process is described for replacing at least a portion of the liquid within the annular volume of a casing system within a wellbore with a second liquid. The second liquid is preselected to provide a measure of control of the pressure within the annular volume as the fluid within the volume is being heated.

  19. Controlling the pressure within an annular volume of a wellbore

    DOEpatents

    Hermes, Robert E.; Gonzalez, Manuel E.; Llewellyn, Brian C.; Bloys, James B.; Coates, Don M.

    2011-06-21

    A process is described for replacing at least a portion of the liquid within the annular volume of a casing system within a wellbore with a second liquid. The second liquid is preselected to provide a measure of control of the pressure within the annular volume as the fluid within the volume is being heated.

  20. Controlling the pressure within an annular volume of a wellbore

    DOEpatents

    Hermes, Robert E.; Gonzalez, Manuel E.; Llewellyn, Brian C.; Bloys, James B.

    2010-06-29

    A process is described for replacing at least a portion of the liquid within the annular volume of a casing system within a wellbore with a second liquid. The second liquid is preselected to provide a measure of control of the pressure within the annular volume as the fluid within the volume is being heated.

  1. Controlling the pressure within an annular volume of a wellbore

    DOEpatents

    Hermes, Robert E.; Gonzalez, Manuel E.; Llewellyn, Brian C.; Bloys, James B.

    2008-10-28

    A process is described for replacing at least a portion of the liquid within the annular volume of a casing system within a wellbore with a second liquid. The second liquid is preselected to provide a measure of control of the pressure within the annular volume as the fluid within the volume is being heated.

  2. Controlling the pressure within an annular volume of a wellbore

    DOEpatents

    Hermes, Robert E.; Gonzalez, Manuel E.; Llewellyn, Brian C.; Bloys, James B.; Coates, Don M.

    2011-05-31

    A process is described for replacing at least a portion of the liquid within the annular volume of a casing system within a wellbore with a second liquid. The second liquid is preselected to provide a measure of control of the pressure within the annular volume as the fluid within the volume is being heated.

  3. Effect of CO2-induced reactions on the mechanical behaviour of fractured wellbore cement

    NASA Astrophysics Data System (ADS)

    Wolterbeek, Timotheus; Hangx, Suzanne; Spiers, Christopher

    2016-04-01

    Geomechanical damage, such as fracturing of wellbore cement, can severely impact well integrity in CO2 storage fields. Chemical reactions between the cement and CO2-bearing fluids may subsequently alter the cement's mechanical properties, either enhancing or inhibiting damage accumulation during ongoing changes in wellbore temperature and stress-state. To evaluate the potential for such effects, we performed triaxial compression tests on Class G Portland cement, conducted at down-hole temperature (80 ° C) and effective confining pressures ranging from 1 to 25 MPa. After deformation, samples displaying failure on localised shear fractures were reacted with CO2-H2O, and then subjected to a second triaxial test to assess changes in mechanical properties. Using results from the first phase of deformation, baseline yield and failure criteria were constructed for virgin cement. These delineate stress conditions where unreacted cement is most prone to dilatational (permeability-enhancing) failure. Once shear-fractures formed, later reaction with CO2 did not produce further geomechanical weakening. Instead, after six weeks of reaction, we observed up to 83% recovery of peak-strength and increased frictional strength (15-40%) in the post-failure regime, due to calcium carbonate precipitation in the fractures. As such, our results suggest more or less complete mechanical healing on timescales of the order of months.

  4. Mechanism study on stability enhancement of adefovir dipivoxil by cocrystallization: Degradation kinetics and structure-stability correlation.

    PubMed

    Lin, Rui-Zhen; Sun, Peng-Jie; Tao, Qian; Yao, Jia; Chen, Jia-Mei; Lu, Tong-Bu

    2016-03-31

    The purpose of this study is to determine the mechanism by which cocrystallization can enhance the stability of adefovir dipivoxil (AD), a diester prodrug of adefovir with known chemical stability problem. Three multi-component crystals of AD with biologically safe coformers, including gallic acid cocrystal hydrate (1:1:1), salicylate salt (1:1), and maleate salt (1:1) were prepared and characterized by thermal analysis, infrared spectroscopy, powder and single crystal X-ray diffraction. DVS measurements and stability tests were applied to evaluate the stability. The new crystalline phases exhibit improved stability compared to pure drug in the order AD gallic acid cocrystal>AD maleate>AD salicylate>AD form I. Degradation kinetics and structure-stability correlation studies demonstrate that the stability enhancement mechanism by cocrystallization involves (1) inhibition of hydrolysis of AD by replacement of drug-drug homosynthons by stronger drug-coformer heterosynthons at adenine fragments; (2) suppression of dimerization of AD by separation of adenine fragments by inserting coformers in crystal lattices; (3) further reducing rates of hydrolysis by forming hydrogen bonds with hydrate water at phosphoryl fragments. This study has important implications for use of cocrystallization approach to some easily degradable drugs in pharmaceutical. PMID:26462447

  5. Enhancing the stability of the synchronization of multivariable coupled oscillators

    NASA Astrophysics Data System (ADS)

    Sevilla-Escoboza, R.; Gutiérrez, R.; Huerta-Cuellar, G.; Boccaletti, S.; Gómez-Gardeñes, J.; Arenas, A.; Buldú, J. M.

    2015-09-01

    Synchronization processes in populations of identical networked oscillators are the focus of intense studies in physical, biological, technological, and social systems. Here we analyze the stability of the synchronization of a network of oscillators coupled through different variables. Under the assumption of an equal topology of connections for all variables, the master stability function formalism allows assessing and quantifying the stability properties of the synchronization manifold when the coupling is transferred from one variable to another. We report on the existence of an optimal coupling transference that maximizes the stability of the synchronous state in a network of Rössler-like oscillators. Finally, we design an experimental implementation (using nonlinear electronic circuits) which grounds the robustness of the theoretical predictions against parameter mismatches, as well as against intrinsic noise of the system.

  6. Enhancement of ferroelectric polarization stability by interface engineering.

    PubMed

    Lu, H; Liu, X; Burton, J D; Bark, C-W; Wang, Y; Zhang, Y; Kim, D J; Stamm, A; Lukashev, P; Felker, D A; Folkman, C M; Gao, P; Rzchowski, M S; Pan, X Q; Eom, C-B; Tsymbal, E Y; Gruverman, A

    2012-03-01

    By using theoretical predictions based on first-principle calculations, we explore an interface engineering approach to stabilize polarization states in ferroelectric heterostructures with a thickness of just several nanometers. PMID:22278910

  7. Enhancing the stability of the synchronization of multivariable coupled oscillators.

    PubMed

    Sevilla-Escoboza, R; Gutiérrez, R; Huerta-Cuellar, G; Boccaletti, S; Gómez-Gardeñes, J; Arenas, A; Buldú, J M

    2015-09-01

    Synchronization processes in populations of identical networked oscillators are the focus of intense studies in physical, biological, technological, and social systems. Here we analyze the stability of the synchronization of a network of oscillators coupled through different variables. Under the assumption of an equal topology of connections for all variables, the master stability function formalism allows assessing and quantifying the stability properties of the synchronization manifold when the coupling is transferred from one variable to another. We report on the existence of an optimal coupling transference that maximizes the stability of the synchronous state in a network of Rössler-like oscillators. Finally, we design an experimental implementation (using nonlinear electronic circuits) which grounds the robustness of the theoretical predictions against parameter mismatches, as well as against intrinsic noise of the system.

  8. Enhancing synchronization stability in a multi-area power grid.

    PubMed

    Wang, Bing; Suzuki, Hideyuki; Aihara, Kazuyuki

    2016-01-01

    Maintaining a synchronous state of generators is of central importance to the normal operation of power grids, in which many networks are generally interconnected. In order to understand the condition under which the stability can be optimized, it is important to relate network stability with feedback control strategies as well as network structure. Here, we present a stability analysis on a multi-area power grid by relating it with several control strategies and topological design of network structure. We clarify the minimal feedback gain in the self-feedback control, and build the optimal communication network for the local and global control strategies. Finally, we consider relationship between the interconnection pattern and the synchronization stability; by optimizing the network interlinks, the obtained network shows better synchronization stability than the original network does, in particular, at a high power demand. Our analysis shows that interlinks between spatially distant nodes will improve the synchronization stability. The results seem unfeasible to be implemented in real systems but provide a potential guide for the design of stable power systems. PMID:27225708

  9. Enhanced muscle activity during lumbar extension exercise with pelvic stabilization.

    PubMed

    Lee, Ho-Seong

    2015-12-01

    The purpose of this study was to investigate whether pelvic stabilization affects multifidus (MF) and iliocostalis lumborum (IL) muscle activities during dynamic extension exercise. Nine males (age, 25.1±6.3 yr; height, 176.6±2.4 cm; body mass, 74.9±6.7 kg) performed an isometric lumbar extension strength test and dynamic exercise in an upright seated position with or without pelvic stabilization. The electromyography and muscle strength of the MF and IL muscles were measured when the subjects performed the isometric lumbar extension strength test at the trunk angle 110°, 146°, and 182°. In addition, the trunk extensor muscle activities were measured using 50% muscle strength of maximum isometric strength during a dynamic trunk extension exercise. The MF and IL muscle activities were significantly higher at 110°, 146°, and 182° with pelvic stabilization than that without pelvic stabilization during the isometric lumbar extension strength test (P<0.05) and the dynamic exercise (P<0.05). These results suggest that the lumbar extension exercise with pelvic stabilization may be more effective for MF and IL muscle activity compared to that without pelvic stabilization.

  10. Enhancing synchronization stability in a multi-area power grid

    PubMed Central

    Wang, Bing; Suzuki, Hideyuki; Aihara, Kazuyuki

    2016-01-01

    Maintaining a synchronous state of generators is of central importance to the normal operation of power grids, in which many networks are generally interconnected. In order to understand the condition under which the stability can be optimized, it is important to relate network stability with feedback control strategies as well as network structure. Here, we present a stability analysis on a multi-area power grid by relating it with several control strategies and topological design of network structure. We clarify the minimal feedback gain in the self-feedback control, and build the optimal communication network for the local and global control strategies. Finally, we consider relationship between the interconnection pattern and the synchronization stability; by optimizing the network interlinks, the obtained network shows better synchronization stability than the original network does, in particular, at a high power demand. Our analysis shows that interlinks between spatially distant nodes will improve the synchronization stability. The results seem unfeasible to be implemented in real systems but provide a potential guide for the design of stable power systems. PMID:27225708

  11. Enhanced muscle activity during lumbar extension exercise with pelvic stabilization

    PubMed Central

    Lee, Ho-Seong

    2015-01-01

    The purpose of this study was to investigate whether pelvic stabilization affects multifidus (MF) and iliocostalis lumborum (IL) muscle activities during dynamic extension exercise. Nine males (age, 25.1±6.3 yr; height, 176.6±2.4 cm; body mass, 74.9±6.7 kg) performed an isometric lumbar extension strength test and dynamic exercise in an upright seated position with or without pelvic stabilization. The electromyography and muscle strength of the MF and IL muscles were measured when the subjects performed the isometric lumbar extension strength test at the trunk angle 110°, 146°, and 182°. In addition, the trunk extensor muscle activities were measured using 50% muscle strength of maximum isometric strength during a dynamic trunk extension exercise. The MF and IL muscle activities were significantly higher at 110°, 146°, and 182° with pelvic stabilization than that without pelvic stabilization during the isometric lumbar extension strength test (P<0.05) and the dynamic exercise (P<0.05). These results suggest that the lumbar extension exercise with pelvic stabilization may be more effective for MF and IL muscle activity compared to that without pelvic stabilization. PMID:26730390

  12. Enhancing synchronization stability in a multi-area power grid

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Suzuki, Hideyuki; Aihara, Kazuyuki

    2016-05-01

    Maintaining a synchronous state of generators is of central importance to the normal operation of power grids, in which many networks are generally interconnected. In order to understand the condition under which the stability can be optimized, it is important to relate network stability with feedback control strategies as well as network structure. Here, we present a stability analysis on a multi-area power grid by relating it with several control strategies and topological design of network structure. We clarify the minimal feedback gain in the self-feedback control, and build the optimal communication network for the local and global control strategies. Finally, we consider relationship between the interconnection pattern and the synchronization stability; by optimizing the network interlinks, the obtained network shows better synchronization stability than the original network does, in particular, at a high power demand. Our analysis shows that interlinks between spatially distant nodes will improve the synchronization stability. The results seem unfeasible to be implemented in real systems but provide a potential guide for the design of stable power systems.

  13. Structural basis for the enhanced stability of highly fluorinated proteins

    PubMed Central

    Buer, Benjamin C.; Meagher, Jennifer L.; Stuckey, Jeanne A.; Marsh, E. Neil G.

    2012-01-01

    Noncanonical amino acids have proved extremely useful for modifying the properties of proteins. Among them, extensively fluorinated (fluorous) amino acids seem particularly effective in increasing protein stability; however, in the absence of structural data, the basis of this stabilizing effect remains poorly understood. To address this problem, we solved X-ray structures for three small proteins with hydrophobic cores that are packed with either fluorocarbon or hydrocarbon side chains and compared their stabilities. Although larger, the fluorinated residues are accommodated within the protein with minimal structural perturbation, because they closely match the shape of the hydrocarbon side chains that they replace. Thus, stability increases seem to be better explained by increases in buried hydrophobic surface area that accompany fluorination than by specific fluorous interactions between fluorinated side chains. This finding is illustrated by the design of a highly fluorinated protein that, by compensating for the larger volume and surface area of the fluorinated side chains, exhibits similar stability to its nonfluorinated counterpart. These structure-based observations should inform efforts to rationally modulate protein function using noncanonical amino acids. PMID:22411812

  14. Enhanced stability of hillslopes and channel beds to mass failure

    NASA Astrophysics Data System (ADS)

    Prancevic, Jeff; Lamb, Michael; Palucis, Marisa; Venditti, Jeremy

    2016-04-01

    The stability of inclined, unconsolidated sediments subjected to groundwater flow on hillslopes and steep channel beds is important for both landscape evolution and natural hazards. Force-balance models have been used for seven decades to predict the stability of slopes, but they generally underpredict the degree of saturation required to destabilize the sediment. Researchers often appeal to heightened stabilizing forces from root and mineral cohesion, and friction acting on the margins of the failure to explain this underprediction. Surprisingly, infinite-slope stability models in their simplest form have never been tested under controlled laboratory conditions. To address this gap in data, we perform a set of controlled laboratory experiments with slope-parallel seepage in the simplest possible configuration. We performed 47 experiments in a 5 m laboratory flume with 4 grain sizes (D50 = 0.7, 2, 5, and 15 mm) and a wide range in bed angles (20° to 43°), spanning both Darcian and turbulent subsurface flow regimes. Our experiments show that granular slopes were more stable than predicted by simple force balance models in experiments that lack root or mineral cohesion. Despite the smooth plastic walls and the long aspect ratio of our flume, we calculate wall and toe friction to be important. Including these additional resistance terms in the model reduces the model misfit with our experimental results. However, there is considerable remaining misfit (up to 50% underestimation of the saturation level required for failure). We investigate two explanations of this heightened stability: 1) standard frictional resistance terms are underestimated, and 2) seepage stresses are overestimated. Both explanations require that we modify the models used to predict slope stability.

  15. New Insight into Cataract Formation: Enhanced Stability through Mutual Attraction

    SciTech Connect

    Stradner, A.; Schurtenberger, P.; Foffi, G.; Dorsaz, N.; Thurston, G.

    2007-11-09

    Small-angle neutron scattering experiments and molecular dynamics simulations combined with an application of concepts from soft matter physics to complex protein mixtures provide new insight into the stability of eye lens protein mixtures. Exploring this colloid-protein analogy we demonstrate that weak attractions between unlike proteins help to maintain lens transparency in an extremely sensitive and nonmonotonic manner. These results not only represent an important step towards a better understanding of protein condensation diseases such as cataract formation, but provide general guidelines for tuning the stability of colloid mixtures, a topic relevant for soft matter physics and industrial applications.

  16. Advanced wellbore thermal simulator GEOTEMP2 user manual

    SciTech Connect

    Mondy, L.A.; Duda, L.E.

    1984-11-01

    GEOTEMP2 is a wellbore thermal simulator computer code designed for geothermal drilling and production applications. The code treats natural and forced convection and conduction within the wellbore and heat conduction within the surrounding rock matrix. A variety of well operations can be modeled including injection, production, forward, and reverse circulation with gas or liquid, gas or liquid drilling, and two-phase steam injection and production. Well completion with several different casing sizes and cement intervals can be modeled. The code allows variables suchas flow rate to change with time enabling a realistic treatment of well operations. This user manual describes the input required to properly operate the code. Ten sample problems are included which illustrate all the code options. Complete listings of the code and the output of each sample problem are provided.

  17. Quantifying drag on wellbore casings in moving salt sheets

    NASA Astrophysics Data System (ADS)

    Weijermars, R.; Jackson, M. P. A.; Dooley, T. P.

    2014-08-01

    Frontier hydrocarbon development projects in the deepwater slopes of the Gulf of Mexico Basin, Santos Basin and Lower Congo Basin all require wells to cross ductile layers of autochthonous or allochthonous salt moving at peak rates of 100 mm yr-1. The Couette-Poiseuille number is introduced here to help pinpoint the depth of shear stress reversal in such salt layers. For any well-planned through salt, the probable range of creep forces of moving salt needs to be taken into account when designing safety margins and load-factor tolerance of the well casing. Drag forces increase with wellbore diameter, but more significantly with effective viscosity and speed of the creeping salt layer. The potential drag forces on cased wellbores in moving salt sheets are estimated analytically using a range of salt viscosities (1015-1019 Pa s) and creep rates (0-10 mm yr-1). Drag on perfectly rigid casing of infinite strength may reach up to 13 Giga Newton per meter wellbore length in salt having a viscosity of 1019 Pa s. Well designers may delay stress accumulations due to salt drag when flexible casing accommodates some of the early displacement and strain. However, all creeping salt could displace, fracture and disconnect well casing, eventually. The shear strength of typical heavy duty well casing (about 1000 MPa) can be reached due to drag by moving salt. Internal flow of salt will then fracture the casing near salt entry and exit points, but the structural damage is likely to remain unnoticed early in the well-life when the horizontal shift of the wellbore is still negligibly small (at less than 1 cm yr-1). Disruption of casing and production flow lines within the anticipated service lifetime of a well remains a significant risk factor within distinct zones of low-viscosity salt which may reach ultrafast creep rates of 100 mm yr-1.

  18. High-energy gas fracturing in cased and perforated wellbores

    SciTech Connect

    Cuderman, J.F.

    1986-06-01

    A propellant-based technology, High-Energy Gas Fracturing (HEGF), has been applied to fracturing through perforations in cased boreholes. HEGF is a tailored-pulse fracturing technique originally developed by Sandia National Laboratories for application in uncased, liquid-free gas wells in Appalachian Devonian shales. Because most oil and gas wells are liquid filled as well as cased and perforated, the potential impact of present research is significantly broader. A number of commercial tailored-pulse fracturing services, using a variety of explosives or propellants, are currently available. Present research provides valuable insight into phenomena that occur in those stimulations. The use of propellants that deflagrate or burn rather than detonate, as do high-order explosives, permits controlled buildup of pressure in the wellbore. The key to successful stimulation in cased and perforated wellbores is to control the pressure buildup of the combustion gases to maximize fracturing without destroying the casing. Eight experiments using cased and perforated wellbore were conducted in a tunnel complex at the Department of Energy's Nevada Test Site, which provides a realistic in situ stress environment (4 to 10 MPa (600 to 1500 psi)) and provides access for mineback to directly observe fracturing obtained. Primary variables in the experiments include propellant burn rate and amount of propellant used, presence or absence of liquid in the wellbore, in situ stress orientation, and perforation diameter, density, and phasing. In general, the presence of liquid in the borehole results in a much faster pressure risetime and a lower peak pressure for the same propellant charge. Fracture surfaces proceed outward along lines of perforations as determined by phasing, then gradually turn toward the hydraulic fracture direction. 8 refs., 23 figs., 3 tabs.

  19. Carbonate scaling characteristics in Dixie Valley, Nevada geothermal wellbores

    SciTech Connect

    Benoit, W.R. )

    1989-01-01

    Calcite scale deposits in seven wellbores were logged with Schlumberger's multifinger caliper. The bottom of the scale is found at the deepest flash point. It thickens to a maximum in 46 to 107 m and then diminishes over a total length of 290 to 518 m. Scale deposition rates range from 267 to 911 kg of fluid produced for each cm/sup 3/ of scale deposited. The dominant variable controlling the deposition rate is the pre-flash calcium content which increases with decreasing fluid entry temperature. Data from one pair of wells indicates a 22.44 cm (I.D.) wellbore can have an initial scale deposition rate about 30% greater than a 31.53 cm wellbore. Downward movement of the flash point lengthens the scaled interval. Estimated times between scale cleanouts should be 3 to 4 months for wells with 22.44 cm production casing and 6 to 12 months for wells with 31.53 cm casing.

  20. Optimal mistuning for enhanced aeroelastic stability of transonic fans

    NASA Technical Reports Server (NTRS)

    Hall, K. C.; Crawley, E. F.

    1983-01-01

    An inverse design procedure was developed for the design of a mistuned rotor. The design requirements are that the stability margin of the eigenvalues of the aeroelastic system be greater than or equal to some minimum stability margin, and that the mass added to each blade be positive. The objective was to achieve these requirements with a minimal amount of mistuning. Hence, the problem was posed as a constrained optimization problem. The constrained minimization problem was solved by the technique of mathematical programming via augmented Lagrangians. The unconstrained minimization phase of this technique was solved by the variable metric method. The bladed disk was modelled as being composed of a rigid disk mounted on a rigid shaft. Each of the blades were modelled with a single tosional degree of freedom.

  1. Stability Enhancement of Lean, Premixed Flames by Flameholder Heating

    NASA Astrophysics Data System (ADS)

    Hermanson, James C.; Demmons, Nathaniel

    2001-11-01

    The effects of flameholder heating on the stability and emissions of lean, premixed, turbulent flames were examined experimentally. The flames were stabilized by an axial, cylindrical bluff-body flameholder 6.4 mm in diameter made of copper or stainless steel. In some cases, the stainless flameholder was heated electrically. The flame was at atmospheric pressure. The premixed ethylene/air mixture upstream of the flameholder was unheated and had an equivalence ratio of 0.37 to 0.87. The cold gas flow velocities ranged from 5.0 to 10.5 m/s to give Reynolds numbers at the flameholder tip from 3,250 to 6,700. The impact of flameholder heating on the lean-blow off limit was determined visually. Heating the flameholder to yield a local mixture temperature of 190 C resulted in a decrease in the equivalence ratio at lean blow-off of approximately 20%. This decrease in equivalence ratio resulted in up to a 26% decrease in exhaust-plane NOx emissions and a 51 K reduction in the exhaust-plane gas temperature. These reductions were consistent with the lower equivalence ratios attainable by the localized mixture preheating. At the same time, the exhaust concentrations of CO and unburned hydrocarbons increased by a factor of approximately two. A smaller increase in lean flame stability was seen for the unheated stainless flameholder versus the copper flameholder.

  2. Method for enhancing stability of high explosives, for purposes of transport or storage, and the stabilized high explosives

    DOEpatents

    Nutt, Gerald L.

    1991-01-01

    The stability of porous solid high explosives, for purposes of transport or storage, is enhanced by reducing the sensitivity to shock initiation of a reaction that leads to detonation. The pores of the explosive down to a certain size are filled under pressure with a stable, low melt temperature material in liquid form, and the combined material is cooled so the pore filling material solidifies. The stability can be increased to progressively higher levels by filling smaller pores. The pore filling material can be removed, at least partially, by reheating above its melt temperature and drained off so that the explosive is once more suitable for detonation.

  3. Hydraulic fracturing model featuring initiation beyond the wellbore wall for directional well in coal bed

    NASA Astrophysics Data System (ADS)

    Li, Yuwei; Jia, Dan; Wang, Meng; Liu, Jia; Fu, Chunkai; Yang, Xinliang; Ai, Chi

    2016-08-01

    In developing internal fracture systems in coal beds, the initiation mechanism differs greatly from that of conventional ones and initiations may be produced beyond the wellbore wall. This paper describes the features of the internal structure of coal beds and RFPA2D simulation is used to attest the possible occurrence of initiation beyond the wellbore wall in coal bed hydraulic fracturing. Using the theory of elasticity and fracture mechanics, we analyse the stress distribution in the vicinal coal rock. Then by taking into consideration the effects of the spatial relationship between coal bed cleats and the wellbore, we establish a model for calculating both tensile and shear initiation pressure that occur along cleats beyond the wellbore wall. The simulation in this paper indicates that for shear initiations that happen along coal cleats, the pressure required to initiate fracture for cleats beyond the wellbore wall is evidently lower than that on the wellbore wall, thus it is easier to initiate shear fractures for cleats beyond the wellbore wall. For tensile failure, the pressure required to initiate tensile fracture for cleats beyond the wellbore wall is obviously higher than that for cleats at the wellbore wall, thus it is easier to initiate tensile fractures for cleats at the wellbore wall. On the one hand, this paper has proved the possible occurrence of initiations beyond the wellbore wall and has changed the current assumption that hydraulic fractures can only occur at the wellbore wall. On the other hand, the established theoretical model provides a new approach to calculating the initiation pressure in hydraulic fracturing.

  4. Synthesis and Characterization of Processable Polyimides with Enhanced Thermal Stability

    NASA Technical Reports Server (NTRS)

    Harris, Frank W.

    1999-01-01

    The following is a summary report of the research carried out under NASA Grant NAG-1-448. The work was divided into four major areas: 1) Enhanced polyimide processing through the use of reactive plasticizers 2) Development of processable polyhenylquinoxalines 3) Synthesis and characterization of perfluorovinylether-terminated imide oligomers and 4) Fluorosilicones containing perfuorocyclobutane rings.

  5. Microwave axial free-electron laser with enhanced phase stability

    SciTech Connect

    Carlsten, B.; Fazio, M.; Haynes, W.

    1995-12-31

    Free-electron laser (FEL) amplifiers have demonstrated high efficiencies and high output power at microwave wavelengths. However, measurements and simulations have indicated that the present level of phase stability for these devices is not sufficient for driving linear accelerators. Fluctuations in the diode voltage, which is needed to accelerate the electron beam, are the largest cause of the shifts in the phase of the output power. Pulse-power technology cannot keep the voltage fluctuations less than 1/4%. However, we have found a scheme that will make the output phase much less sensitive to these fluctuations by exploiting the traveling wave nature of the FEL interaction. In this paper we study the phase stability issue by analyzing the dispersion relation for an axial FEL, in which the rf field is transversely wiggled and the electron trajectories are purely longitudinal. The advantage of using the axial FEL interaction instead of the common transverse FEL interaction is that (1) the dispersion relation is not additionally complicated by how the transverse electron motion depends on the diode voltage and (2) such a device is simpler and less expensive to construct than a transverse-coupling FEL because there is no wiggler. The axial FEL interaction is with a fast wave and does involve axial bunching of the electron beam, so the results found for this device also apply to transverse-coupling FELs. By examination of the dispersion relation it is found that the effect of the phase dependency on the beam`s velocity can be cancelled by the effect of the phase dependency on the beam`s plasma wave, for an annular electron beam. By changing the annulus radius, exact cancellation can be found for a variety of beam voltages and currents in the ranges of 0.5-1.0 MV and 1-5 kA. This cancellation leads to first-order phase stability, which is not possible for standing-wave devices, such as klystrons.

  6. Microwave axial free-electron laser with enhanced phase stability

    SciTech Connect

    Carlsten, B.E.; Fortgang, C.M.; Fazio, M.V.; Haynes, W.B.; May, L.M.; Potter, J.M.

    1995-09-01

    Free-electron lasers (FELs) amplifiers have demonstrated high efficiencies and high output power at microwave wavelengths. However, measurements and simulations have indicated that the present level of phase stability for these devices is not sufficient for driving linear accelerators. Fluctuations in the diode voltage, which is needed to accelerate the electron beam, are the largest cause of the shifts in the phase of the output power. Present-day pulse-power technology cannot keep the voltage fluctuations less than 1/4%. However, we have found a scheme that win make the output phase much less sensitive to these fluctuations by exploiting the traveling-wave nature of the FEL interaction. In this paper we study the phase stability issue by analyzing the dispersion relation for an axial FEL, in which the rf field is transversely wiggled and the electron trajectories are purely longitudinal. The advantage of using the axial FEL interaction instead of the common transverse FEL interaction is that the dispersion relation is not additionally complicated by how the transverse electron motion depends on the diode voltage and such a device is simpler and less expensive to construct than a transverse-coupling FEL because there is no wiggler. By examination of the dispersion relation it is found that the effect of the phase dependency on the beam`s velocity can be cancelled by the effect of the phase dependency on the beam`s plasma wave, for an annular electron beam. This cancellation leads to first-order phase stability, which is not possible for standing-wave devices, such as klystrons. Detailed particle-in-cell simulations are included to demonstrate the transverse wiggling of the rf mode and the axial FEL interaction.

  7. Adaptive forward-inverse modeling of reservoir fluids away from wellbores

    SciTech Connect

    Ziagos, J P; Gelinas, R J; Doss, S K; Nelson, R G

    1999-07-30

    This Final Report contains the deliverables of the DeepLook Phase I project entitled, ''Adaptive Forward-Inverse Modeling of Reservoir Fluids Away from Wellbores''. The deliverables are: (i) a description of 2-D test problem results, analyses, and technical descriptions of the techniques used, (ii) a listing of program setup commands that construct and execute the codes for selected test problems (these commands are in mathematical terminology, which reinforces technical descriptions in the text), and (iii) an evaluation and recommendation regarding continuance of this project, including considerations of possible extensions to 3-D codes, additional technical scope, and budget for the out-years. The far-market objective in this project is to develop advanced technologies that can help locate and enhance the recovery of oil from heterogeneous rock formations. The specific technical objective in Phase I was to develop proof-of-concept of new forward and inverse (F-I) modeling techniques [Gelinas et al, 1998] that seek to enhance estimates (images) of formation permeability distributions and fluid motion away from wellbore volumes. This goes to the heart of improving industry's ability to jointly image reservoir permeability and flow predictions of trapped and recovered oil versus time. The estimation of formation permeability away from borehole measurements is an ''inverse'' problem. It is an inseparable part of modeling fluid flows throughout the reservoir in efforts to increase the efficiency of oil recovery at minimum cost. Classic issues of non-uniqueness, mathematical instability, noise effects, and inadequate numerical solution techniques have historically impeded progress in reservoir parameter estimations. Because information pertaining to fluid and rock properties is always sampled sparsely by wellbore measurements, a successful method for interpolating permeability and fluid data between the measurements must be: (i) physics-based, (ii) conditioned by

  8. Tuneable enhancement of the salt and thermal stability of polymeric micelles by cyclized amphiphiles

    PubMed Central

    Honda, Satoshi; Yamamoto, Takuya; Tezuka, Yasuyuki

    2013-01-01

    Cyclic molecules provide better stability for their aggregates. Typically in nature, the unique cyclic cell membrane lipids allow thermophilic archaea to inhabit extreme conditions. By mimicking the biological design, the robustness of self-assembled synthetic nanostructures is expected to be improved. Here we report topology effects by cyclized polymeric amphiphiles against their linear counterparts, demonstrating a drastic enhancement in the thermal, as well as salt stability of self-assembled micelles. Furthermore, through coassembly of the linear and cyclic amphiphiles, the stability was successfully tuned for a wide range of temperatures and salt concentrations. The enhanced thermal/salt stability was exploited in a halogen exchange reaction to stimulate the catalytic activity. The mechanism for the enhancement was also investigated. These topology effects by the cyclic amphiphiles offer unprecedented opportunities in polymer materials design unattainable by traditional means. PMID:23481382

  9. Enhanced Thermal Stability of Polylactide by Terminal Conjugation Groups

    NASA Astrophysics Data System (ADS)

    Tran, Hang Thi; Matsusaki, Michiya; Akashi, Mitsuru; Vu, Ngo Dinh

    2016-05-01

    Various acids such as aliphatic or carbocyclic fatty or aromatic acids were successfully conjugated into the ending hydroxyl group of poly( l-lactide) (PLLA). The chemical structures of various acid-PLLAs were confirmed by Fourier transform infrared and proton nuclear magnetic resonance analysis. The crystallinity and solubility of the original PLLA were maintained after the terminal conjugation of various acids. The thermal properties were significantly improved, especially the 10% weight-loss temperature that showed an increase of over 80°C for conjugation of aliphatic or aromatic acids as compared to that of the corresponding original PLLA. In addition, more than 60 wt.% of the aliphatic acid-PLLAs was pyrolyzed, and aromatic acid-PLLAs degraded only about 10 wt.% for 150 min, although the original PLLA was pyrolyzed completely at 250°C for 7 min. The thermal stability of PLLA was controlled by the conjugation of aliphatic or aromatic acids into a chain end. These acid-PLLAs may be useful as materials with high thermal stability for various application fields.

  10. Geochemistry of Wellbore Integrity in CO2 Sequestration: Portland Cement-Steel-Brine-CO2 Interactions (Invited)

    NASA Astrophysics Data System (ADS)

    Carey, J. W.

    2013-12-01

    Effective geologic sequestration of CO2 requires long-term storage with very low leak rates. Numerous studies have identified wells as one of the key risk factors for CO2 leakage including purpose-built injection and monitoring wells in addition to older wells in and above the storage reservoir. All wells have the potential to leak due to faulty construction or other defects. However, geochemical reactions induced by CO2 could result in damage to Portland cement and steel that are used in the well to isolate reservoir fluids from underground drinking water sources and the surface. This concern is based on the thermodynamic incompatibility of CO2-saturated aqueous fluids with Portland cement and steel, which leads to relatively rapidly reactions that form, principally, calcium carbonate and iron carbonate. Despite this thermodynamic fate, wellbore materials perform and maintain zonal isolation in field and experimental observations. This is understood as a consequence of coupled behavior between flow of reactants (CO2-water) and the rate of dissolution and precipitation of cement or corrosion of steel. In the restricted flow environments found in wellbore systems, cements are carbonated but do not suffer significant deterioration of hydrologic or mechanical properties. In fact, cement carbonation often results in reduced permeability and enhanced mechanical strength. While steel is susceptible to corrosion, wellbore environments allow development of protective iron carbonate scale. In addition, the presence of Portland cement, even carbonated cement, provides protection against significant rates of corrosion. The impact of geochemical reactions in the wellbore environment cannot be separated from coupled flow, thermal and mechanical processes. CO2-induced chemical reactions migrating upward from a storage reservoir will not result in the creation of defects or the wholesale dissolution of cement or steel. Defects must exist that allow CO2×brine to flow and to come

  11. Visual stabilization dynamics are enhanced by standing flight velocity.

    PubMed

    Theobald, Jamie C; Ringach, Dario L; Frye, Mark A

    2010-06-23

    A flying insect must travel to find food, mates and sites for oviposition, but for a small animal in a turbulent world this means dealing with frequent unplanned deviations from course. We measured a fly's sensory-motor impulse response to perturbations in optic flow. After an abrupt change in its apparent visual position, a fly generates a compensatory dynamical steering response in the opposite direction. The response dynamics, however, may be influenced by superimposed background velocity generated by the animal's flight direction. Here we show that constant forward velocity has no effect on the steering responses to orthogonal sideslip perturbations, whereas constant parallel sideslip substantially shortens the lags and relaxation times of the linear dynamical responses. This implies that for flies stabilizing in sideslip, the control effort is strongly affected by the direction of background motion.

  12. Synthesis and characterization of processable polyimides with enhanced thermal stability

    NASA Technical Reports Server (NTRS)

    Harris, Frank W.

    1987-01-01

    Many of the emerging applications of polymers on space vehicles require materials with outstanding thermal stability. These polymers must also be readily processable in order to facilitate their use. The syntheses and polymerization of a cardo dianhydride were investigated. This monomer was prepared via the reaction of N-methyl 4-nitrophthalimide with a cardo diol. Polyimides containing oxyalkylene linkages were studied. The effects of two additional structural modifications on the polymers' properties were investigated. The effects of carrying out the preparation of poly(amic acid)s under non-equilibrium conditions were examined. Approaches that were investigated included the in-situ neutralization of the generated amic acid and its in-situ esterification.

  13. Soy protein polymers: Enhancing the water stability property

    NASA Astrophysics Data System (ADS)

    Srinivasan, Gowrishankar

    Soy protein based plastics have been processed in the past by researchers for various short-term applications; however a common issue is the high water sensitivity of these plastics. This work concentrates on resolving this water sensitivity issue of soy protein polymers by employing chemical and mechanical interaction at the molecular level during extrusion. The primary chemical interactions employed were anhydride chemistries such as maleic anhydride (MA), phthalic anhydride (PTA), and butylated hydroxyanisole (BHA). These were respectively used in conjunction with glycerol as a plasticizer to produce relatively water stable soy protein based plastics. Formulations with varying additive levels of the chemistries were extruded and injection molded to form the samples for characterization. The additive levels of anhydrides were varied between 3-10% tw/tw (total mass). Results indicated that phthalic anhydride formulations resulted in highest water stability. Plastic formulations with concentration up to 10% phthalic anhydride were observed to have water absorption as low as 21.5% after 24 hrs of exposure to water with respect to 250% for the control formulation. Fourier transform infrared spectroscopy (FTIR) was utilized to characterize and confirm the fundamental mechanisms of water stability achieved by phthalic and maleic anhydride chemistries. In addition, the anhydride formulations were modified by inclusion of cotton fibers and pretreated cotton powder in order to improve mechanical properties. The incorporation of cotton fibers improved the dry strength by 18%, but did not significantly improve the wet state strength of the plastics. It was also observed that the butylated-hydroxy anisole (BHA) formulation exhibited high extension values in the dry state and had inferior water absorption properties in comparison with anhydride formulations.

  14. Thermal effects in borehole stability

    NASA Astrophysics Data System (ADS)

    Tran, Dung Trung

    An accurate wellbore stability analysis depends strongly on the state of knowledge of the problem at hand. Almost in all cases, the state of knowledge for wellbore stability analyses is poor. Values of many parameters and variables (so-called prior geological information) are poorly constrained and various assumptions of the adopted wellbore models are easily violated. The dilema is that using a model requiring few input parameters would suffer from a large number of model assumptions and simplifications; while using a complex model requiring a large number of input parameters which have wide ranges of possible values. Therefore, assessing the uncertainty (or degree of confidence) for different possible wellbore stability/instability scenarios remains difficult. Current sensitivity analyses, which consider varying possible values of one parameter while keeping others constant, are suboptimal and may not provide the correct effects of the parameters' uncertainties on the overall uncertainty of the wellbore stability prediction. Recent technological advances such as logging-while-drilling (LWD) and measuring-while-drilling (MWD) enable real-time updating of measured rock properties values and in-situ conditions. This means the ranges and uncertainties of parameters for wellbore stability analyses can be adjusted in real-time, during drilling. This aspect has not been developed into a self-updating, real-time wellbore stability analysis approach yet. As a step toward that goal, this dissertation presents several studies covering different aspects of wellbore stability. In particular, the uncertainties of input parameters and selected models are treated using a probabilistic framework combining Monte Carlo simulations and Bayesian statistics. The uncertain nature of both input parameters and model assumptions and their effects on the uncertainties of wellbore stability predictions are investigated. It is shown that, depending on the severity of parameters

  15. Response surfaces for CO2 leakage from geologic storage along abandoned wellbores

    NASA Astrophysics Data System (ADS)

    Jordan, A.; Carey, J. W.; Pawar, R. J.; Stauffer, P. H.

    2011-12-01

    The storage of carbon dioxide (CO2) in geologic reservoirs that have previously been drilled for oil and gas exploration is under investigation worldwide as an option for reducing the amount of anthropogenic carbon introduced to the atmosphere. Reservoirs that have already been tapped for hydrocarbon production have several benefits over development of new sites: they tend to be geologically well-understood, with existing wellbore data to help further characterize the local geologic framework; are known to be conducive to trapping buoyant or pressurized fluids; may have infrastructure in place; and are likely to be already impacted ecologically as compared to pristine sites. One downside to using depleted hydrocarbon reservoirs is the potential for CO2 leakage along pre-existing wellbores that were either not designed for CO2 sequestration or have been improperly plugged and abandoned. The primary goal of this study is to develop estimates of possible wellbore leakage rates of CO2 from storage reservoirs to the surface and/or into overlaying aquifers, as a function of wellbore properties and the surrounding geologic framework. The Finite Element Heat and Mass transfer code (FEHM) was used to perform Monte Carlo simulations of multiphase flow along wellbores across a wide range of geologic and wellbore parameters. Several wellbore scenarios were studied, including a simple wellbore between the CO2 storage reservoir and the surface; a wellbore intersecting a saline aquifer ("thief zone"); and a wellbore intersecting both a thief zone and a freshwater aquifer. The Problem Solving environment for Uncertainty Analysis and Design Exploration (PSUADE) software was used to analyze results and produce response surfaces for the estimation of wellbore flow rate as a function of the primary factors that influence leakage. These results will be used to develop abstractions for leakage rates to be incorporated in performance assessments of geologic CO2 storage, which will help

  16. Enhanced weathering strategies for stabilizing climate and averting ocean acidification

    NASA Astrophysics Data System (ADS)

    Taylor, Lyla L.; Quirk, Joe; Thorley, Rachel M. S.; Kharecha, Pushker A.; Hansen, James; Ridgwell, Andy; Lomas, Mark R.; Banwart, Steve A.; Beerling, David J.

    2016-04-01

    Chemical breakdown of rocks, weathering, is an important but very slow part of the carbon cycle that ultimately leads to CO2 being locked up in carbonates on the ocean floor. Artificial acceleration of this carbon sink via distribution of pulverized silicate rocks across terrestrial landscapes may help offset anthropogenic CO2 emissions. We show that idealized enhanced weathering scenarios over less than a third of tropical land could cause significant drawdown of atmospheric CO2 and ameliorate ocean acidification by 2100. Global carbon cycle modelling driven by ensemble Representative Concentration Pathway (RCP) projections of twenty-first-century climate change (RCP8.5, business-as-usual; RCP4.5, medium-level mitigation) indicates that enhanced weathering could lower atmospheric CO2 by 30-300 ppm by 2100, depending mainly on silicate rock application rate (1 kg or 5 kg m-2 yr-1) and composition. At the higher application rate, end-of-century ocean acidification is reversed under RCP4.5 and reduced by about two-thirds under RCP8.5. Additionally, surface ocean aragonite saturation state, a key control on coral calcification rates, is maintained above 3.5 throughout the low latitudes, thereby helping maintain the viability of tropical coral reef ecosystems. However, we highlight major issues of cost, social acceptability, and potential unanticipated consequences that will limit utilization and emphasize the need for urgent efforts to phase down fossil fuel emissions.

  17. Enhanced Weathering Strategies for Stabilizing Climate and Averting Ocean Acidification

    NASA Technical Reports Server (NTRS)

    Taylor, Lyla L.; Quirk, Joe; Thorley, Rachel M. S.; Kharecha, Pushker A.; Hansen, James; Ridgwell, Andy; Lomas, Mark R.; Banwart, Steve A.; Beerling, David J.

    2015-01-01

    Chemical breakdown of rocks, weathering, is an important but very slow part of the carbon cycle that ultimately leads to CO2 being locked up in carbonates on the ocean floor. Artificial acceleration of this carbon sink via distribution of pulverized silicate rocks across terrestrial landscapes may help offset anthropogenic CO2 emissions. We show that idealized enhanced weathering scenarios over less than a third of tropical land could cause significant drawdown of atmospheric CO2 and ameliorate ocean acidification by 2100. Global carbon cycle modelling driven by ensemble Representative Concentration Pathway (RCP) projections of twenty-first-century climate change (RCP8.5, business-as-usual; RCP4.5, medium-level mitigation) indicates that enhanced weathering could lower atmospheric CO2 by 30-300 ppm by 2100, depending mainly on silicate rock application rate (1 kg or 5 kg m(exp -2) yr (exp -1)) and composition. At the higher application rate, end-of-century ocean acidification is reversed under RCP4.5 and reduced by about two-thirds under RCP8.5. Additionally, surface ocean aragonite saturation state, a key control on coral calcification rates, is maintained above 3.5 throughout the low latitudes, thereby helping maintain the viability of tropical coral reef ecosystems. However, we highlight major issues of cost, social acceptability, and potential unanticipated consequences that will limit utilization and emphasize the need for urgent efforts to phase down fossil fuel emissions.

  18. A Quasi-Steady Flexible Launch Vehicle Stability Analysis Using Steady CFD with Unsteady Aerodynamic Enhancement

    NASA Technical Reports Server (NTRS)

    Bartels, Robert E.

    2011-01-01

    Launch vehicles frequently experience a reduced stability margin through the transonic Mach number range. This reduced stability margin is caused by an undamping of the aerodynamics in one of the lower frequency flexible or rigid body modes. Analysis of the behavior of a flexible vehicle is routinely performed with quasi-steady aerodynamic lineloads derived from steady rigid computational fluid dynamics (CFD). However, a quasi-steady aeroelastic stability analysis can be unconservative at the critical Mach numbers where experiment or unsteady computational aeroelastic (CAE) analysis show a reduced or even negative aerodynamic damping. This paper will present a method of enhancing the quasi-steady aeroelastic stability analysis of a launch vehicle with unsteady aerodynamics. The enhanced formulation uses unsteady CFD to compute the response of selected lower frequency modes. The response is contained in a time history of the vehicle lineloads. A proper orthogonal decomposition of the unsteady aerodynamic lineload response is used to reduce the scale of data volume and system identification is used to derive the aerodynamic stiffness, damping and mass matrices. The results of the enhanced quasi-static aeroelastic stability analysis are compared with the damping and frequency computed from unsteady CAE analysis and from a quasi-steady analysis. The results show that incorporating unsteady aerodynamics in this way brings the enhanced quasi-steady aeroelastic stability analysis into close agreement with the unsteady CAE analysis.

  19. Feasibility of Biogeochemical Sealing of Wellbore Cements: Lab and Simulation Tests

    NASA Astrophysics Data System (ADS)

    Colwell, F. S.; Verba, C.; Thurber, A. R.; Alleau, Y.; Koley, D.; Peszynska, M.; Torres, M. E.

    2014-12-01

    To ensure permanence of carbon dioxide stored in a geologic formation it is essential to maintain wellbore integrity to prevent leakage of gas to the surface or surficial aquifers. Among others, the Mt. Simon Sandstone of the Illinois Basin has been targeted by DOE partnerships for supercritical CO2 injection. In this study, we used lab experiments to test the feasibility of microbially-mediated sealing of a leaking wellbore and then used the data to model the biofilm growth and calcite precipitation while accounting for over nine chemical reactions. Sporosarcina pasteurii was investigated for its ability to precipitate calcium carbonate to seal fractures in cement or within the Mt. Simon Sandstone formation, at variable pressure and temperature conditions. S. pasteurii cultures were studied in a rocking autoclave at temperature (ca. 40oC) and pressure (ca. 12 MPa) consistent with the geologic formation at depth and surficial changes were characterized before and after experimental incubations using scanning electron microscopy (SEM) and scanning electrochemical microscopy (SECM). At temperatures up to 40oC, atmospheric pressure, and in the presence of the Mt. Simon brine (1.016 M NaCl, 0.171M CaCl2, 0.067 M MgCl2, 0.017 M Na2SO4, 0.006 M NaHCO3), S. pasteurii thrived and showed evidence of biofilm formation using SECM. These data are the first to be applied to the newly developed computational model that extends a singular and degenerate model of biofilm growth and incorporates a variational inequality to remove the singularity. This study extends our knowledge of the stability of biologically generated carbonate species, and the associated biota, in pore-space and fractures of pertinent geological strata and cement under conditions consistent with deep storage of CO2.

  20. Glycosylation of the enhanced aromatic sequon is similarly stabilizing in three distinct reverse turn contexts.

    PubMed

    Price, Joshua L; Powers, David L; Powers, Evan T; Kelly, Jeffery W

    2011-08-23

    Cotranslational N-glycosylation can accelerate protein folding, slow protein unfolding, and increase protein stability, but the molecular basis for these energetic effects is incompletely understood. N-glycosylation of proteins at naïve sites could be a useful strategy for stabilizing proteins in therapeutic and research applications, but without engineering guidelines, often results in unpredictable changes to protein energetics. We recently introduced the enhanced aromatic sequon as a family of portable structural motifs that are stabilized upon glycosylation in specific reverse turn contexts: a five-residue type I β-turn harboring a G1 β-bulge (using a Phe-Yyy-Asn-Xxx-Thr sequon) and a type II β-turn within a six-residue loop (using a Phe-Yyy-Zzz-Asn-Xxx-Thr sequon) [Culyba EK, et al. (2011) Science 331:571-575]. Here we show that glycosylating a new enhanced aromatic sequon, Phe-Asn-Xxx-Thr, in a type I' β-turn stabilizes the Pin 1 WW domain. Comparing the energetic effects of glycosylating these three enhanced aromatic sequons in the same host WW domain revealed that the glycosylation-mediated stabilization is greatest for the enhanced aromatic sequon complementary to the type I β-turn with a G1 β-bulge. However, the portion of the stabilization from the tripartite interaction between Phe, Asn(GlcNAc), and Thr is similar for each enhanced aromatic sequon in its respective reverse turn context. Adding the Phe-Asn-Xxx-Thr motif (in a type I' β-turn) to the enhanced aromatic sequon family doubles the number of proteins that can be stabilized by glycosylation without having to alter the native reverse turn type. PMID:21825145

  1. Enhanced hydrolytic stability of dental composites by use of fluoroalkyltrimethoxysilanes.

    PubMed

    Nihei, T; Kurata, S; Kondo, Y; Umemoto, K; Yoshino, N; Teranaka, T

    2002-07-01

    The hydrolytic stability of a group of experimental composite materials was evaluated. Seven distinct composites were formed by the mixing of a resin monomer mixture with silica filler that had been pre-treated with one of 7 different ethanol solutions. In one case, the filler was treated with an ethanol solution that contained only 3-methacryloyloxypropyltrimethoxysilane. In 5 cases, it was treated with solution containing a mixture of 3-methacryloyloxypropyltrimethoxysilane and one of the following hydrophobic fluoroalkyltrimethoxysilanes: trifluoropropyl-, nonafluorohexyl-, tridecafluorooctyl-, heptadecafluorodecyl-, and henicosafluorododecyl-trimethoxysilane. The tensile strength, after being immersed in water for 1800 days, of 2 of the experimental composites, whose pre-treatment regimen had included a fluoroalkyltrimethoxysilane, was significantly higher than that of the composite whose pre-treatment regimen had not included a fluoroalkyltrimethoxysilane. Moreover, there was no significant difference between the tensile strength of fresh samples of these 2 composites and the tensile strength of identically produced samples that had remained under water for 1800 days or that had been subjected to 30,000 cycles of thermal stress.

  2. Enhanced stability of skyrmions in magnets with broken mirror symmetry

    NASA Astrophysics Data System (ADS)

    Rowland, James; Banerjee, Sumilan; Randeria, Mohit

    Most previous work on skyrmion phases in chiral magnets with Dzyaloshinkii Moriya interactions (DMI) focuses on the case of broken bulk inversion symmetry. The skyrmion crystal is then stable only in a limited range of parameter space with easy-axis anisotropy. In this talk I will describe the effects of including broken mirror or surface inversion symmetry which leads to a Rashba DMI, in addition to the Dresselhaus DMI arising from broken bulk inversion. I will show that increasing Rashba DMI leads to a progressively larger domain of stability for skyrmions, especially in the easy-plane anisotropy regime. In the latter regime the topological charge density shows an unusual internal structure, and isolated skyrmions cannot be embedded in a ferromagnetic background. Thus the homotopy group π2 (S2) method of classifying skyrmions fails. I will discuss a Chern number classification of these non-trivial skyrmions using maps from the 2-torus (the unit cell for skyrmion crystals) to the 2-sphere in spin space. Finally, I will discuss the elliptic cone phase, a new state that emerges for easy-axis anisotropy and broken mirror symmetry. We acknowledge support by the National Science Foundation by the NSF Graduate Research Fellowship Program Grant No. DGE-1343012 (JR), by an NSF Grant DMR-1410364 (MR), and by the CEM, an NSF MRSEC, under Grant DMR-1420451.

  3. Wellbore inertial navigation system (WINS) software development and test results

    SciTech Connect

    Wardlaw, R. Jr.

    1982-09-01

    The structure and operation of the real-time software developed for the Wellbore Inertial Navigation System (WINS) application are described. The procedure and results of a field test held in a 7000-ft well in the Nevada Test Site are discussed. Calibration and instrumentation error compensation are outlined, as are design improvement areas requiring further test and development. Notes on Kalman filtering and complete program listings of the real-time software are included in the Appendices. Reference is made to a companion document which describes the downhole instrumentation package.

  4. Enhancement of stability of various nZVI suspensions used in groundwater remediation with environmentally friendly organic stabilizers

    NASA Astrophysics Data System (ADS)

    Schmid, Doris; Wagner, Stephan; Velimirović, Milica; Laumann, Susanne; Micić, Vesna; Hofmann, Thilo

    2014-05-01

    The use of nanoscale zero-valent iron (nZVI) particles for in situ remediation of polluted soil and groundwater has been shown as one of the most promising techniques [1]. The success of this technology depends on the mobility, reactivity, and longevity of nZVI particles. The mobility of nZVI particles depends on the properties of the single particles, stability of the particle suspension, and the aquifer material [1,2]. In order to enhance the mobility of nZVI, the mobility-decisive properties of the nZVI particles in suspension such as concentration, size distribution, surface charge, and sedimentation rate have to be investigated and optimized. Previous studies showed that pristine nZVI particles aggregate rapidly in water, reducing the particles radius of influence after injection [3]. In order to prevent aggregation and sedimentation of the nZVI particles, and consequently improve the stability of nZVI suspension and therefore the mobility of the nZVI particles, surface stabilizers can be used to provide electrostatic repulsion and steric or electrosteric stabilization [3,4]. The objective of this lab-scale study is to investigate the potential for enhancing the stability of different nZVI suspensions by means of environmentally friendly organic stabilizers, including carboxymethyl cellulose, pectin, alginate, xanthan, and guar gum. The different nZVI particles used included pristine and polyacrylic acid-coated nZVI particles provided in suspension (Nanofer 25 and Nanofer 25S, respectively, NANOIRON s.r.o., Czech Republic), air-stable nZVI particles (Nanofer Star, (NANOIRON s.r.o., Czech Republic), and milled iron flakes (UVR-FIA, Germany). In order to study the enhancement of nZVI stability (1 g L-1 total iron) different concentrations of organic stabilizers (1-20 wt.%) were applied in these nZVI suspensions. Each nZVI suspension was freshly prepared and treated for 10 minutes with Ultra-Turrax (15 000 rpm) and 10 minutes ultrasonic bath prior to

  5. Wellbore failures and its constraints on the in-situ stress state in the Nankai Trough accretionary prism, Site C0002, IODP Expedition 348

    NASA Astrophysics Data System (ADS)

    Sone, H.; Jurado, M. J.; Boston, B.; Yamamoto, Y.; Tobin, H. J.; Saffer, D. M.; Hirose, T.

    2014-12-01

    The International Ocean Discovery Program (IODP) Expedition 348 extended the borehole of Site C0002, Nankai Trough, down to over 3000 meters below sea floor (mbsf) collecting core samples and in-situ geophysical data from the inner accretionary prism. In order to investigate the in-situ stress state within the prism, we characterized the occurrence and shapes of wellbore failures as observed by resistivity image logs and sonic caliper logs collected in the vertical well of Hole C0002P. Most wellbore failures were observed in the top 70 meters of Hole C0002P (2150 to 2218.5 mbsf), where resistivity images were acquired several days after the borehole was initially exposed by previous drilling and coring runs. Wide breakouts spanning up to 140 degrees are observed in the NW/SE to NNW/SSE direction suggesting that the maximum horizontal principal stress in the cored interval is in the direction generally consistent with those observed in the shallower sections of Site C0002 from earlier expeditions. In the remaining section of the borehole below, wellbore failures are much sparse and subtle in the resistivity image possibly due to the short exposure time between drilling and image acquisition (about 2 hours). Preliminary examination suggest that these features are breakouts aligned in the direction consistent with the upper section, but examination in combination with the sonic caliper data is required for further confirmation. These observations suggest that the occurrence of breakouts exhibit significant time-dependence due to processes such as pore pressure diffusion or time-dependent rock deformation. Moreover, sonic caliper data suggests that shapes and width of the wellbore failures in the studied dataset is influenced by the formation strength anisotropy (in the horizontal direction) enhanced by the steeply dipping bedding planes (60-90 degrees). Thus, constraints on in-situ stress magnitudes will be provided through comparison of wellbore failures, borehole

  6. Mechanical expansion of steel tubing as a solution to leaky wellbores.

    PubMed

    Radonjic, Mileva; Kupresan, Darko

    2014-01-01

    Wellbore cement, a procedural component of wellbore completion operations, primarily provides zonal isolation and mechanical support of the metal pipe (casing), and protects metal components from corrosive fluids. These are essential for uncompromised wellbore integrity. Cements can undergo multiple forms of failure, such as debonding at the cement/rock and cement/metal interfaces, fracturing, and defects within the cement matrix. Failures and defects within the cement will ultimately lead to fluid migration, resulting in inter-zonal fluid migration and premature well abandonment. Currently, there are over 1.8 million operating wells worldwide and over one third of these wells have leak related problems defined as Sustained Casing Pressure (SCP). The focus of this research was to develop an experimental setup at bench-scale to explore the effect of mechanical manipulation of wellbore casing-cement composite samples as a potential technology for the remediation of gas leaks. The experimental methodology utilized in this study enabled formation of an impermeable seal at the pipe/cement interface in a simulated wellbore system. Successful nitrogen gas flow-through measurements demonstrated that an existing microannulus was sealed at laboratory experimental conditions and fluid flow prevented by mechanical manipulation of the metal/cement composite sample. Furthermore, this methodology can be applied not only for the remediation of leaky wellbores, but also in plugging and abandonment procedures as well as wellbore completions technology, and potentially preventing negative impacts of wellbores on subsurface and surface environments. PMID:25490436

  7. Mechanical expansion of steel tubing as a solution to leaky wellbores.

    PubMed

    Radonjic, Mileva; Kupresan, Darko

    2014-11-20

    Wellbore cement, a procedural component of wellbore completion operations, primarily provides zonal isolation and mechanical support of the metal pipe (casing), and protects metal components from corrosive fluids. These are essential for uncompromised wellbore integrity. Cements can undergo multiple forms of failure, such as debonding at the cement/rock and cement/metal interfaces, fracturing, and defects within the cement matrix. Failures and defects within the cement will ultimately lead to fluid migration, resulting in inter-zonal fluid migration and premature well abandonment. Currently, there are over 1.8 million operating wells worldwide and over one third of these wells have leak related problems defined as Sustained Casing Pressure (SCP). The focus of this research was to develop an experimental setup at bench-scale to explore the effect of mechanical manipulation of wellbore casing-cement composite samples as a potential technology for the remediation of gas leaks. The experimental methodology utilized in this study enabled formation of an impermeable seal at the pipe/cement interface in a simulated wellbore system. Successful nitrogen gas flow-through measurements demonstrated that an existing microannulus was sealed at laboratory experimental conditions and fluid flow prevented by mechanical manipulation of the metal/cement composite sample. Furthermore, this methodology can be applied not only for the remediation of leaky wellbores, but also in plugging and abandonment procedures as well as wellbore completions technology, and potentially preventing negative impacts of wellbores on subsurface and surface environments.

  8. Enhanced Immunogenicity of Stabilized Trimeric Soluble Influenza Hemagglutinin

    PubMed Central

    Weldon, William C.; Wang, Bao-Zhong; Martin, Maria P.; Koutsonanos, Dimitrios G.; Skountzou, Ioanna; Compans, Richard W.

    2010-01-01

    Background The recent swine-origin H1N1 pandemic illustrates the need to develop improved procedures for rapid production of influenza vaccines. One alternative to the current egg-based manufacture of influenza vaccine is to produce a hemagglutinin (HA) subunit vaccine using a recombinant expression system with the potential for high protein yields, ease of cloning new antigenic variants, and an established safety record in humans. Methodology/Principal Findings We generated a soluble HA (sHA), derived from the H3N2 virus A/Aichi/2/68, modified at the C-terminus with a GCN4pII trimerization repeat to stabilize the native trimeric structure of HA. When expressed in the baculovirus system, the modified sHA formed native trimers. In contrast, the unmodified sHA was found to present epitopes recognized by a low-pH conformation specific monoclonal antibody. We found that mice primed and boosted with 3 µg of trimeric sHA in the absence of adjuvants had significantly higher IgG and HAI titers than mice that received the unmodified sHA. This correlated with an increased survival and reduced body weight loss following lethal challenge with mouse-adapted A/Aichi/2/68 virus. In addition, mice receiving a single vaccination of the trimeric sHA in the absence of adjuvants had improved survival and body weight loss compared to mice vaccinated with the unmodified sHA. Conclusions/Significance Our data indicate that the recombinant trimeric sHA presents native trimeric epitopes while the unmodified sHA presents epitopes not exposed in the native HA molecule. The epitopes presented in the unmodified sHA constitute a “silent face” which may skew the antibody response to epitopes not accessible in live virus at neutral pH. The results demonstrate that the trimeric sHA is a more effective influenza vaccine candidate and emphasize the importance of structure-based antigen design in improving recombinant HA vaccines. PMID:20824188

  9. An assessment of the mechanical stability of wells offshore Nigeria

    SciTech Connect

    Lowrey, J.P.; Ottesen, S.

    1995-03-01

    In 1991 lost time due to stuck pipe related drilling problems accounted for approximately 18% of total drilling time in Mobil Producing Nigeria Ultd.`s (MPN) offshore operations. The primary cause of stuck pipe was identified as mechanical wellbore instability. This paper presents an assessment of the mechanical stability of MPN`s wells offshore Nigeria. The objectives of the study were to: (1) determine the magnitude of the in-situ principal stresses and material properties of the troublesome Intra-Biafra and Qua Iboe shale sequences; (2) quantify the drilling fluid densities required to drill mechanically stable wells through these formations; (3) review and recommend well planning and operational parameters which aid in minimizing wellbore stability-related drilling problems. The well-bore stability assessment was carried out with the aid of a 3-dimensional wellbore stability model using field derived data from the study area to corroborate the results. The collection and analysis of drilling data (borehole geometry and density logs, pore pressure, leak-off tests, local geology and other relevant well records) to determine the magnitude of the in-situ principal stresses, together with compressive strength tests on formation cores are discussed. Minimum safe drilling fluid densities to promote wellbore stability as a function of well geometry and depth are presented for the most troublesome shales drilled in the study area. Implementation of the results reduced wellbore stability related problems and associated trouble time to less than 5% in 1992.

  10. Enhanced Physical Stability of Amorphous Drug Formulations via Dry Polymer Coating.

    PubMed

    Capece, Maxx; Davé, Rajesh

    2015-06-01

    Although amorphous solid drug formulations may be advantageous for enhancing the bioavailability of poorly soluble active pharmaceutical ingredients, they exhibit poor physical stability and undergo recrystallization. To address this limitation, this study investigates stability issues associated with amorphous solids through analysis of the crystallization behavior for acetaminophen (APAP), known as a fast crystallizer, using a modified form of the Avrami equation that kinetically models both surface and bulk crystallization. It is found that surface-enhanced crystallization, occurring faster at the free surface than in the bulk, is the major impediment to the stability of amorphous APAP. It is hypothesized that a novel use of a dry-polymer-coating process referred to as mechanical-dry-polymer-coating may be used to inhibit surface crystallization and enhance stability. The proposed process, which is examined, simultaneously mills and coats amorphous solids with polymer, while avoiding solvents or solutions, which may otherwise cause stability or crystallization issues during coating. It is shown that solid dispersions of APAP (64% loading) with a small particle size (28 μm) could be prepared and coated with the polymer, carnauba wax, in a vibratory ball mill. The resulting amorphous solid was found to have excellent stability as a result of inhibition of surface crystallization. PMID:25902736

  11. Enhanced Physical Stability of Amorphous Drug Formulations via Dry Polymer Coating.

    PubMed

    Capece, Maxx; Davé, Rajesh

    2015-06-01

    Although amorphous solid drug formulations may be advantageous for enhancing the bioavailability of poorly soluble active pharmaceutical ingredients, they exhibit poor physical stability and undergo recrystallization. To address this limitation, this study investigates stability issues associated with amorphous solids through analysis of the crystallization behavior for acetaminophen (APAP), known as a fast crystallizer, using a modified form of the Avrami equation that kinetically models both surface and bulk crystallization. It is found that surface-enhanced crystallization, occurring faster at the free surface than in the bulk, is the major impediment to the stability of amorphous APAP. It is hypothesized that a novel use of a dry-polymer-coating process referred to as mechanical-dry-polymer-coating may be used to inhibit surface crystallization and enhance stability. The proposed process, which is examined, simultaneously mills and coats amorphous solids with polymer, while avoiding solvents or solutions, which may otherwise cause stability or crystallization issues during coating. It is shown that solid dispersions of APAP (64% loading) with a small particle size (28 μm) could be prepared and coated with the polymer, carnauba wax, in a vibratory ball mill. The resulting amorphous solid was found to have excellent stability as a result of inhibition of surface crystallization.

  12. Geomechanical analyses to investigate wellbore/mine interactions in the Potash Enclave of Southeastern New Mexico.

    SciTech Connect

    Ehgartner, Brian L.; Bean, James E.; Arguello, Jose Guadalupe, Jr.; Stone, Charles Michael

    2010-04-01

    Geomechanical analyses have been performed to investigate potential mine interactions with wellbores that could occur in the Potash Enclave of Southeastern New Mexico. Two basic models were used in the study; (1) a global model that simulates the mechanics associated with mining and subsidence and (2) a wellbore model that examines the resulting interaction impacts on the wellbore casing. The first model is a 2D approximation of a potash mine using a plane strain idealization for mine depths of 304.8 m (1000 ft) and 609.6 m (2000 ft). A 3D wellbore model then considers the impact of bedding plane slippage across single and double cased wells cemented through the Salado formation. The wellbore model establishes allowable slippage to prevent casing yield.

  13. Reduction of Wellbore Positional Uncertainty During Directional Drilling

    NASA Astrophysics Data System (ADS)

    Hadavand, Zahra

    Magnetic measurement errors significantly affect the wellbore positional accuracy in directional drilling operations taken by Measurement While Drilling (MWD) sensors. Therefore this research has provided a general overview of error compensation models for magnetic surveys and elaborated the most accurate calibration methods of hard- and soft-iron, as well as multiple-survey correction for compensating drilling assembly magnetic interference to solve the problem of wellbore positional uncertainty and provide accurate surveying solution downhole. The robustness of hard- and soft-iron calibration algorithm was validated through an iterative least-squares estimator initialized using a two-step linear solution. A case study of a well profile, a simulated well profile and a set of experimental data are utilized to perform a comparison study. The comparison analysis outcomes imply that position accuracy gained by multistation analysis surpasses hard- and soft-iron compensation results. Utilization of multiple-survey correction in conjunction with real-time geomagnetic referencing to monitor geomagnetic disturbances, such as diurnal effects, as well as changes in the local field by providing updated components of reference geomagnetic field, provide superior accuracy.

  14. Development of an Ultrasonic Phased Array System for Wellbore Integrity Evaluation and Near-Wellbore Fracture Network Mapping of Injection and Production Wells in Geothermal Energy Systems

    SciTech Connect

    Almansouri, Hani; Foster, Benjamin; Kisner, Roger A; Polsky, Yarom; Bouman, Charlie

    2016-01-01

    This paper documents our progress developing an ultrasound phased array system in combination with a model-based iterative reconstruction (MBIR) algorithm to inspect the health of and characterize the composition of the near-wellbore region for geothermal reservoirs. The main goal for this system is to provide a near-wellbore in-situ characterization capability that will significantly improve wellbore integrity evaluation and near well-bore fracture network mapping. A more detailed image of the fracture network near the wellbore in particular will enable the selection of optimal locations for stimulation along the wellbore, provide critical data that can be used to improve stimulation design, and provide a means for measuring evolution of the fracture network to support long term management of reservoir operations. Development of such a measurement capability supports current hydrothermal operations as well as the successful demonstration of Engineered Geothermal Systems (EGS). The paper will include the design of the phased array system, the performance specifications, and characterization methodology. In addition, we will describe the MBIR forward model derived for the phased array system and the propagation of compressional waves through a pseudo-homogenous medium.

  15. Observations of wellbore failure in the Toa Baja Well—Implications for the state of stress in the North Coast Tertiary Basin, Puerto Rico

    NASA Astrophysics Data System (ADS)

    Moos, Daniel; Morin, Roger H.

    Borehole televiewer (BHTV) and 4-arm caliper (dipmeter) logs were obtained in the Toa Baja well (drilled to a depth of 2704 m into sediments of the North Coast Tertiary Basin, Puerto Rico) from 704 to 2676 m depth. The only observations suggesting that stress-induced wellbore failure (breakouts) had occurred were small intermittent features at a depth of approximately 2600 m with azimuths of 70° and 250° and the fact that, during drilling, wellbore stability became a problem near total depth. An increase in mud weight to 10 Lb/gal required to stabilize the deteriorating wellbore was accompanied by loss of drilling fluid into the formation, suggesting that hydraulic fracturing or the reopening of pre-existing near vertical fractures had occurred. A series of vertical fractures at a variety of azimuths (averaging N3l°W) was detected by the BHTV. The loss of circulation due to an increase in mud weight, combined with the absence of well-developed breakouts, enables us to estimate stress magnitudes near the well for reasonable values of rock strength: S1=Sv; S3=Shmin ≈ 0.5v; SHmax ≈ (0.55-0.63)Sv, and an associated incipient normal faulting stress regime. This stress regime is consistent with focal mechanisms determined for earthquakes with epicenters near the drillsite.

  16. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion.

    PubMed

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W; Liu, Yan; Walter, Nils G; Yan, Hao

    2016-02-10

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology.

  17. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion

    PubMed Central

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W.; Liu, Yan; Walter, Nils G.; Yan, Hao

    2016-01-01

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology. PMID:26861509

  18. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion

    NASA Astrophysics Data System (ADS)

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W.; Liu, Yan; Walter, Nils G.; Yan, Hao

    2016-02-01

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology.

  19. Enhanced Enzyme Kinetic Stability by Increasing Rigidity within the Active Site*

    PubMed Central

    Xie, Yuan; An, Jiao; Yang, Guangyu; Wu, Geng; Zhang, Yong; Cui, Li; Feng, Yan

    2014-01-01

    Enzyme stability is an important issue for protein engineers. Understanding how rigidity in the active site affects protein kinetic stability will provide new insight into enzyme stabilization. In this study, we demonstrated enhanced kinetic stability of Candida antarctica lipase B (CalB) by mutating the structurally flexible residues within the active site. Six residues within 10 Å of the catalytic Ser105 residue with a high B factor were selected for iterative saturation mutagenesis. After screening 2200 colonies, we obtained the D223G/L278M mutant, which exhibited a 13-fold increase in half-life at 48 °C and a 12 °C higher T5015, the temperature at which enzyme activity is reduced to 50% after a 15-min heat treatment. Further characterization showed that global unfolding resistance against both thermal and chemical denaturation also improved. Analysis of the crystal structures of wild-type CalB and the D223G/L278M mutant revealed that the latter formed an extra main chain hydrogen bond network with seven structurally coupled residues within the flexible α10 helix that are primarily involved in forming the active site. Further investigation of the relative B factor profile and molecular dynamics simulation confirmed that the enhanced rigidity decreased fluctuation of the active site residues at high temperature. These results indicate that enhancing the rigidity of the flexible segment within the active site may provide an efficient method for improving enzyme kinetic stability. PMID:24448805

  20. Enhancement of amorphous celecoxib stability by mixing it with octaacetylmaltose: the molecular dynamics study.

    PubMed

    Grzybowska, K; Paluch, M; Wlodarczyk, P; Grzybowski, A; Kaminski, K; Hawelek, L; Zakowiecki, D; Kasprzycka, A; Jankowska-Sumara, I

    2012-04-01

    In this paper, we present a novel way of stabilization of amorphous celecoxib (CEL) against recrystallization by preparing binary amorphous celecoxib-octaacetylmaltose (CEL-acMAL) systems by quench-cooling of the molten phase. As far as we know this is the first application of carbohydrate derivatives with acetate groups to enhance the stability of an amorphous drug. We found that CEL in the amorphous mixture with acMAL is characterized by a much better solubility than pure CEL. We report very promising results of the long-term measurements of stability of the CEL-acMAL binary amorphous system with small amount of stabilizer during its storage at room temperature. Moreover, we examined the effect of adding acMAL on molecular dynamics of CEL in the wide temperature range in both the supercooled liquid and glassy states. We found that the molecular mobility of the mixture of CEL with 10 wt % acMAL in the glassy state is much more limited than that in the case of pure CEL, which correlates with the better stability of the amorphous binary system. By dielectric measurements and theoretical calculations within the framework of density functional theory (DFT), we studied the role of acMAL in enhancing the stability of amorphous CEL in mixtures and postulated which interactions between CEL and acMAL molecules can be responsible for preventing devitrification. PMID:22384922

  1. Geochemical and Geomechanical Effects on Wellbore Cement Fractures

    SciTech Connect

    Um, Wooyong; Jung, Hun Bok; Kabilan, Senthil; Fernandez, Carlos A.; Brown, Christopher F.

    2014-12-31

    Experimental studies were conducted using batch reactors, X-ray microtomograpy (XMT), and computational fluid dynamics (CFD) simulation to determine changes in cement fracture surfaces, fluid flow pathways, and permeability with geochemical and geomechanical processes. Composite Portland cement-basalt caprock core with artificial fractures was prepared and reacted with CO2-saturated groundwater at 50°C and 10 MPa for 3 to 3.5 months under static conditions to understand the geochemical and geomechanical effects on the integrity of wellbores containing defects. Cement-basalt interface samples were subjected to mechanical stress at 2.7 MPa before the CO2 reaction. XMT provided three-dimensional (3-D) visualization of the opening and interconnection of cement fractures due to mechanical stress. After the CO2 reaction, XMT images revealed that calcium carbonate precipitation occurred extensively within the fractures in the cement matrix, but only partially along fractures located at the cement-basalt interface. The permeability calculated based on CFD simulation was in agreement with the experimentally measured permeability. The experimental results imply that the wellbore cement with fractures is likely to be healed during exposure to CO2-saturated groundwater under static conditions, whereas fractures along the cement-caprock interface are still likely to remain vulnerable to the leakage of CO2. CFD simulation for the flow of different fluids (CO2-saturated brine and supercritical CO2) using a pressure difference of 20 kPa and 200 kPa along ~2 cm-long cement fractures showed that a pressure gradient increase resulted in an increase of CO2 fluids flux by a factor of only ~3-9 because the friction of CO2 fluids on cement fracture surfaces increased with higher flow rate as well. At the same pressure gradient, the simulated flow rate was higher for supercritical CO2 than CO2-saturated brine by a factor of only ~2-3, because the viscosity of supercritical CO2 is much

  2. Geochemical and Geomechanical Effects on Wellbore Cement Fractures

    DOE PAGESBeta

    Um, Wooyong; Jung, Hun Bok; Kabilan, Senthil; Fernandez, Carlos A.; Brown, Christopher F.

    2014-12-31

    Experimental studies were conducted using batch reactors, X-ray microtomograpy (XMT), and computational fluid dynamics (CFD) simulation to determine changes in cement fracture surfaces, fluid flow pathways, and permeability with geochemical and geomechanical processes. Composite Portland cement-basalt caprock core with artificial fractures was prepared and reacted with CO2-saturated groundwater at 50°C and 10 MPa for 3 to 3.5 months under static conditions to understand the geochemical and geomechanical effects on the integrity of wellbores containing defects. Cement-basalt interface samples were subjected to mechanical stress at 2.7 MPa before the CO2 reaction. XMT provided three-dimensional (3-D) visualization of the opening and interconnectionmore » of cement fractures due to mechanical stress. After the CO2 reaction, XMT images revealed that calcium carbonate precipitation occurred extensively within the fractures in the cement matrix, but only partially along fractures located at the cement-basalt interface. The permeability calculated based on CFD simulation was in agreement with the experimentally measured permeability. The experimental results imply that the wellbore cement with fractures is likely to be healed during exposure to CO2-saturated groundwater under static conditions, whereas fractures along the cement-caprock interface are still likely to remain vulnerable to the leakage of CO2. CFD simulation for the flow of different fluids (CO2-saturated brine and supercritical CO2) using a pressure difference of 20 kPa and 200 kPa along ~2 cm-long cement fractures showed that a pressure gradient increase resulted in an increase of CO2 fluids flux by a factor of only ~3-9 because the friction of CO2 fluids on cement fracture surfaces increased with higher flow rate as well. At the same pressure gradient, the simulated flow rate was higher for supercritical CO2 than CO2-saturated brine by a factor of only ~2-3, because the viscosity of supercritical CO2 is

  3. Enhancing the stability and antibiofilm activity of DspB by immobilization on carboxymethyl chitosan nanoparticles.

    PubMed

    Tan, Yulong; Ma, Su; Liu, Chenguang; Yu, Wengong; Han, Feng

    2015-09-01

    A β-N-acetyl-glucosaminidase (DspB) from Aggregatibacter actinomycetemcomitans CU1000 has been proved to inhibit and detach the biofilms formed by Staphylococcus epidermidis, Staphylococcus aureus and A. actinomycetemcomitans. However, the application of this enzyme is limited by its poor stability. In the present study, a β-N-acetyl-glucosaminidase encoding gene, dspB, was cloned from A. actinomycetemcomitans HK1651 and expressed in Escherichia coli. The recombinant DspB was loaded on hydrogel nanoparticles, which was prepared by using linoleic acid (LA) modified carboxymethyl chitosan (CMCS) after sonication. The nanoparticles were almost saturated by DspB at 0.3 mg/ml, which gave a loading capacity of 76.7%. The immobilization enhanced thermal stability, storage stability and reusability of DspB significantly. Moreover, it also increased antibiofilm activity due to the dual mechanism, including the improvement of the enzyme stability and the antibiofilm activity of CMCS nanoparticles. PMID:26302845

  4. Synthesis and Characterisation of Biocompatible Polymer-Conjugated Magnetic Beads for Enhancement Stability of Urease.

    PubMed

    Doğaç, Yasemin Ispirli; Teke, Mustafa

    2016-04-01

    We reported natural polymer-conjugated magnetic featured urease systems for removal of urea effectively. The optimum temperature (20-60 °C), optimum pH (3.0-10.0), kinetic parameters, thermal stability (4-70 °C), pH stability (4.0-9.0), operational stability (0-250 min), reusability (18 times) and storage stability (24 weeks) were studied for characterisation of the urease-encapsulated biocompatible polymer-conjugated magnetic beads. Also, the surface groups and chemical structure of the magnetic beads were determined by using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The all urease-encapsulated magnetic beads protected their stability of 30-45 % relative activity at 70 °C. A significant increase was observed at their pH stability compared with the free urease for both acidic and alkaline medium. Besides this, their repeatability activity were approximately 100 % during 4(th) run. They showed residual activity of 50 % after 16 weeks. The importance of this work is enhancement stability of immobilised urease by biocompatible polymer-conjugated magnetic beads for the industrial application based on removal of urea.

  5. Effective Permeability Change in Wellbore Cement with Carbon Dioxide Reaction

    SciTech Connect

    Um, Wooyong; Jung, Hun Bok; Martin, Paul F.; McGrail, B. Peter

    2011-11-01

    Portland cement, a common sealing material for wellbores for geological carbon sequestration was reacted with CO{sub 2} in supercritical, gaseous, and aqueous phases at various pressure and temperature conditions to simulate cement-CO{sub 2} reaction along the wellbore from carbon injection depth to the near-surface. Hydrated Portland cement columns (14 mm diameter x 90 mm length; water-to-cement ratio = 0.33) including additives such as steel coupons and Wallula basalt fragments were reacted with CO{sub 2} in the wet supercritical (the top half) and dissolved (the bottom half) phases under carbon sequestration condition with high pressure (10 MPa) and temperature (50 C) for 5 months, while small-sized hydrated Portland cement columns (7 mm diameter x 20 mm length; water-to-cement ratio = 0.38) were reacted with CO{sub 2} in dissolved phase at high pressure (10 MPa) and temperature (50 C) for 1 month or with wet CO{sub 2} in gaseous phase at low pressure (0.2 MPa) and temperature (20 C) for 3 months. XMT images reveal that the cement reacted with CO{sub 2} saturated groundwater had degradation depth of {approx}1 mm for 1 month and {approx}3.5 mm for 5 month, whereas the degradation was minor with cement exposure to supercritical CO{sub 2}. SEM-EDS analysis showed that the carbonated cement was comprised of three distinct zones; the innermost less degraded zone with Ca atom % > C atom %, the inner degraded zone with Ca atom % {approx} C atom % due to precipitation of calcite, the outer degraded zone with C atom % > Ca atom % due to dissolution of calcite and C-S-H, as well as adsorption of carbon to cement matrix. The outer degraded zone of carbonated cement was porous and fractured because of dissolution-dominated reaction by carbonic acid exposure, which resulted in the increase in BJH pore volume and BET surface area. In contrast, cement-wet CO{sub 2}(g) reaction at low P (0.2 MPa)-T (20 C) conditions for 1 to 3 months was dominated by precipitation of micron

  6. Potential of hydraulically induced fractures to communicate with existing wellbores

    NASA Astrophysics Data System (ADS)

    Montague, James A.; Pinder, George F.

    2015-10-01

    The probability that new hydraulically fractured wells drilled within the area of New York underlain by the Marcellus Shale will intersect an existing wellbore is calculated using a statistical model, which incorporates: the depth of a new fracturing well, the vertical growth of induced fractures, and the depths and locations of existing nearby wells. The model first calculates the probability of encountering an existing well in plan view and combines this with the probability of an existing well-being at sufficient depth to intersect the fractured region. Average probability estimates for the entire region of New York underlain by the Marcellus Shale range from 0.00% to 3.45% based upon the input parameters used. The largest contributing parameter on the probability value calculated is the nearby density of wells meaning that due diligence by oil and gas companies during construction in identifying all nearby wells will have the greatest effect in reducing the probability of interwellbore communication.

  7. AnalyzeHOLE: An Integrated Wellbore Flow Analysis Tool

    SciTech Connect

    Keith J. Halford

    2009-10-01

    Conventional interpretation of flow logs assumes that hydraulic conductivity is directly proportional to flow change with depth. However, well construction can significantly alter the expected relation between changes in fluid velocity and hydraulic conductivity. Strong hydraulic conductivity contrasts between lithologic intervals can be masked in continuously screened wells. Alternating intervals of screen and blank casing also can greatly complicate the relation between flow and hydraulic properties. More permeable units are not necessarily associated with rapid fluid-velocity increases. Thin, highly permeable units can be misinterpreted as thick and less permeable intervals or not identified at all. These conditions compromise standard flow-log interpretation because vertical flow fields are induced near the wellbore. AnalyzeHOLE, an integrated wellbore analysis tool for simulating flow and transport in wells and aquifer systems, provides a better alternative for simulating and evaluating complex well-aquifer system interaction. A pumping well and adjacent aquifer system are simulated with an axisymmetric, radial geometry in a two-dimensional MODFLOW model. Hydraulic conductivities are distributed by depth and estimated with PEST by minimizing squared differences between simulated and measured flows and drawdowns. Hydraulic conductivity can vary within a lithology but variance is limited with regularization. Transmissivity of the simulated system also can be constrained to estimates from single-well, pumping tests. Water-quality changes in the pumping well are simulated with simple mixing models between zones of differing water quality. These zones are differentiated by backtracking thousands of particles from the well screens with MODPATH. An Excel spreadsheet is used to interface the various components of AnalyzeHOLE by (1) creating model input files, (2) executing MODFLOW, MODPATH, PEST, and supporting FORTRAN routines, and (3) importing and graphically

  8. AnalyzeHOLE - An Integrated Wellbore Flow Analysis Tool

    USGS Publications Warehouse

    Halford, Keith

    2009-01-01

    Conventional interpretation of flow logs assumes that hydraulic conductivity is directly proportional to flow change with depth. However, well construction can significantly alter the expected relation between changes in fluid velocity and hydraulic conductivity. Strong hydraulic conductivity contrasts between lithologic intervals can be masked in continuously screened wells. Alternating intervals of screen and blank casing also can greatly complicate the relation between flow and hydraulic properties. More permeable units are not necessarily associated with rapid fluid-velocity increases. Thin, highly permeable units can be misinterpreted as thick and less permeable intervals or not identified at all. These conditions compromise standard flow-log interpretation because vertical flow fields are induced near the wellbore. AnalyzeHOLE, an integrated wellbore analysis tool for simulating flow and transport in wells and aquifer systems, provides a better alternative for simulating and evaluating complex well-aquifer system interaction. A pumping well and adjacent aquifer system are simulated with an axisymmetric, radial geometry in a two-dimensional MODFLOW model. Hydraulic conductivities are distributed by depth and estimated with PEST by minimizing squared differences between simulated and measured flows and drawdowns. Hydraulic conductivity can vary within a lithology but variance is limited with regularization. Transmissivity of the simulated system also can be constrained to estimates from single-well, pumping tests. Water-quality changes in the pumping well are simulated with simple mixing models between zones of differing water quality. These zones are differentiated by backtracking thousands of particles from the well screens with MODPATH. An Excel spreadsheet is used to interface the various components of AnalyzeHOLE by (1) creating model input files, (2) executing MODFLOW, MODPATH, PEST, and supporting FORTRAN routines, and (3) importing and graphically

  9. Emissions of Methane and Other Hydrocarbons Due to Wellbore Leaks

    NASA Astrophysics Data System (ADS)

    Lyman, S. N.; Mansfield, M. L.

    2013-12-01

    The explosive growth of oil and gas production in the United States has focused public and regulatory attention on environmental impacts of hydrocarbon extraction, including air quality and climate impacts. However, EPA and others have acknowledged that current air emissions factors and inventories for many oil and gas-related source categories are inadequate or lacking entirely. One potentially important emissions source is leakage of natural gas from wellbores. This phenomenon has long been recognized to occur, but no attempt has been made to quantify emission rates of gas leaked from wellbores to the atmosphere. Soil gas measurements carried out by USGS over the last several years in Utah's oil and gas fields have shown that, while concentrations of methane in soils near many wells are low, soil gas near some wells can contain more than 10% methane, indicating that underground leakage is occurring. In summer 2013 we carried out a campaign to measure the emission rate of methane and other hydrocarbons from soils near wells in two oil and gas fields in Utah. We measured emissions from several locations on some well pads to determine the change in emission rate with distance from well heads, and we measured at non-well sites in the same fields to determine background emission rates. Methane emission rates at some wells exceeded 3 g m-2 h-1, while emission rates at other wells were similar to background levels, and a correlation was observed between soil gas methane concentrations and methane emission rates from the soil. We used these data to estimate total methane and hydrocarbon emission rates from these two fields.

  10. Field tests indicate tubing is main source of iron precipitation in the wellbore

    SciTech Connect

    Coulter, A.W.; Gougler, P.D.

    1984-09-03

    Among the many problems that arise in a producing well is the production decline from impairment of near-wellbore permeability. This can result from a number of causes, including particle migration, water saturation, or precipitation of a mineral scale in the flow channels. Efforts to overcome the decline normally utilize acid. Acid introduces another possible problem, the precipitation of dissolved iron near the wellbore. Although many investigators have considered the danger of iron precipitation near the wellbore, very few have considered rust and debris from the tubing as the primary source of the problem.

  11. Enhancing Intrinsic Stability of Hybrid Perovskite Solar Cell by Strong, yet Balanced, Electronic Coupling

    NASA Astrophysics Data System (ADS)

    El-Mellouhi, Fedwa; Bentria, El Tayeb; Rashkeev, Sergey N.; Kais, Sabre; Alharbi, Fahhad H.

    2016-07-01

    In the past few years, the meteoric development of hybrid organic–inorganic perovskite solar cells (PSC) astonished the community. The efficiency has already reached the level needed for commercialization; however, the instability hinders its deployment on the market. Here, we report a mechanism to chemically stabilize PSC absorbers. We propose to replace the widely used methylammonium cation (CH3NH3+) by alternative molecular cations allowing an enhanced electronic coupling between the cation and the PbI6 octahedra while maintaining the band gap energy within the suitable range for solar cells. The mechanism exploits establishing a balance between the electronegativity of the materials’ constituents and the resulting ionic electrostatic interactions. The calculations demonstrate the concept of enhancing the electronic coupling, and hence the stability, by exploring the stabilizing features of CH3PH3+, CH3SH2+, and SH3+ cations, among several other possible candidates. Chemical stability enhancement hence results from a strong, yet balanced, electronic coupling between the cation and the halides in the octahedron. This shall unlock the hindering instability problem for PSCs and allow them to hit the market as a serious low-cost competitor to silicon based solar cell technologies.

  12. Enhancing Intrinsic Stability of Hybrid Perovskite Solar Cell by Strong, yet Balanced, Electronic Coupling.

    PubMed

    El-Mellouhi, Fedwa; Bentria, El Tayeb; Rashkeev, Sergey N; Kais, Sabre; Alharbi, Fahhad H

    2016-01-01

    In the past few years, the meteoric development of hybrid organic-inorganic perovskite solar cells (PSC) astonished the community. The efficiency has already reached the level needed for commercialization; however, the instability hinders its deployment on the market. Here, we report a mechanism to chemically stabilize PSC absorbers. We propose to replace the widely used methylammonium cation (CH3NH3(+)) by alternative molecular cations allowing an enhanced electronic coupling between the cation and the PbI6 octahedra while maintaining the band gap energy within the suitable range for solar cells. The mechanism exploits establishing a balance between the electronegativity of the materials' constituents and the resulting ionic electrostatic interactions. The calculations demonstrate the concept of enhancing the electronic coupling, and hence the stability, by exploring the stabilizing features of CH3PH3(+), CH3SH2(+), and SH3(+) cations, among several other possible candidates. Chemical stability enhancement hence results from a strong, yet balanced, electronic coupling between the cation and the halides in the octahedron. This shall unlock the hindering instability problem for PSCs and allow them to hit the market as a serious low-cost competitor to silicon based solar cell technologies. PMID:27457130

  13. VMCast: A VM-Assisted Stability Enhancing Solution for Tree-Based Overlay Multicast.

    PubMed

    Gu, Weidong; Zhang, Xinchang; Gong, Bin; Zhang, Wei; Wang, Lu

    2015-01-01

    Tree-based overlay multicast is an effective group communication method for media streaming applications. However, a group member's departure causes all of its descendants to be disconnected from the multicast tree for some time, which results in poor performance. The above problem is difficult to be addressed because overlay multicast tree is intrinsically instable. In this paper, we proposed a novel stability enhancing solution, VMCast, for tree-based overlay multicast. This solution uses two types of on-demand cloud virtual machines (VMs), i.e., multicast VMs (MVMs) and compensation VMs (CVMs). MVMs are used to disseminate the multicast data, whereas CVMs are used to offer streaming compensation. The used VMs in the same cloud datacenter constitute a VM cluster. Each VM cluster is responsible for a service domain (VMSD), and each group member belongs to a specific VMSD. The data source delivers the multicast data to MVMs through a reliable path, and MVMs further disseminate the data to group members along domain overlay multicast trees. The above approach structurally improves the stability of the overlay multicast tree. We further utilized CVM-based streaming compensation to enhance the stability of the data distribution in the VMSDs. VMCast can be used as an extension to existing tree-based overlay multicast solutions, to provide better services for media streaming applications. We applied VMCast to two application instances (i.e., HMTP and HCcast). The results show that it can obviously enhance the stability of the data distribution.

  14. VMCast: A VM-Assisted Stability Enhancing Solution for Tree-Based Overlay Multicast

    PubMed Central

    Gu, Weidong; Zhang, Xinchang; Gong, Bin; Zhang, Wei; Wang, Lu

    2015-01-01

    Tree-based overlay multicast is an effective group communication method for media streaming applications. However, a group member’s departure causes all of its descendants to be disconnected from the multicast tree for some time, which results in poor performance. The above problem is difficult to be addressed because overlay multicast tree is intrinsically instable. In this paper, we proposed a novel stability enhancing solution, VMCast, for tree-based overlay multicast. This solution uses two types of on-demand cloud virtual machines (VMs), i.e., multicast VMs (MVMs) and compensation VMs (CVMs). MVMs are used to disseminate the multicast data, whereas CVMs are used to offer streaming compensation. The used VMs in the same cloud datacenter constitute a VM cluster. Each VM cluster is responsible for a service domain (VMSD), and each group member belongs to a specific VMSD. The data source delivers the multicast data to MVMs through a reliable path, and MVMs further disseminate the data to group members along domain overlay multicast trees. The above approach structurally improves the stability of the overlay multicast tree. We further utilized CVM-based streaming compensation to enhance the stability of the data distribution in the VMSDs. VMCast can be used as an extension to existing tree-based overlay multicast solutions, to provide better services for media streaming applications. We applied VMCast to two application instances (i.e., HMTP and HCcast). The results show that it can obviously enhance the stability of the data distribution. PMID:26562152

  15. Enhancing Intrinsic Stability of Hybrid Perovskite Solar Cell by Strong, yet Balanced, Electronic Coupling

    PubMed Central

    El-Mellouhi, Fedwa; Bentria, El Tayeb; Rashkeev, Sergey N.; Kais, Sabre; Alharbi, Fahhad H.

    2016-01-01

    In the past few years, the meteoric development of hybrid organic–inorganic perovskite solar cells (PSC) astonished the community. The efficiency has already reached the level needed for commercialization; however, the instability hinders its deployment on the market. Here, we report a mechanism to chemically stabilize PSC absorbers. We propose to replace the widely used methylammonium cation (CH3NH3+) by alternative molecular cations allowing an enhanced electronic coupling between the cation and the PbI6 octahedra while maintaining the band gap energy within the suitable range for solar cells. The mechanism exploits establishing a balance between the electronegativity of the materials’ constituents and the resulting ionic electrostatic interactions. The calculations demonstrate the concept of enhancing the electronic coupling, and hence the stability, by exploring the stabilizing features of CH3PH3+, CH3SH2+, and SH3+ cations, among several other possible candidates. Chemical stability enhancement hence results from a strong, yet balanced, electronic coupling between the cation and the halides in the octahedron. This shall unlock the hindering instability problem for PSCs and allow them to hit the market as a serious low-cost competitor to silicon based solar cell technologies. PMID:27457130

  16. VMCast: A VM-Assisted Stability Enhancing Solution for Tree-Based Overlay Multicast.

    PubMed

    Gu, Weidong; Zhang, Xinchang; Gong, Bin; Zhang, Wei; Wang, Lu

    2015-01-01

    Tree-based overlay multicast is an effective group communication method for media streaming applications. However, a group member's departure causes all of its descendants to be disconnected from the multicast tree for some time, which results in poor performance. The above problem is difficult to be addressed because overlay multicast tree is intrinsically instable. In this paper, we proposed a novel stability enhancing solution, VMCast, for tree-based overlay multicast. This solution uses two types of on-demand cloud virtual machines (VMs), i.e., multicast VMs (MVMs) and compensation VMs (CVMs). MVMs are used to disseminate the multicast data, whereas CVMs are used to offer streaming compensation. The used VMs in the same cloud datacenter constitute a VM cluster. Each VM cluster is responsible for a service domain (VMSD), and each group member belongs to a specific VMSD. The data source delivers the multicast data to MVMs through a reliable path, and MVMs further disseminate the data to group members along domain overlay multicast trees. The above approach structurally improves the stability of the overlay multicast tree. We further utilized CVM-based streaming compensation to enhance the stability of the data distribution in the VMSDs. VMCast can be used as an extension to existing tree-based overlay multicast solutions, to provide better services for media streaming applications. We applied VMCast to two application instances (i.e., HMTP and HCcast). The results show that it can obviously enhance the stability of the data distribution. PMID:26562152

  17. Enhancement of colour stability of anthocyanins in model beverages by gum arabic addition.

    PubMed

    Chung, Cheryl; Rojanasasithara, Thananunt; Mutilangi, William; McClements, David Julian

    2016-06-15

    This study investigated the potential of gum arabic to improve the stability of anthocyanins that are used in commercial beverages as natural colourants. The degradation of purple carrot anthocyanin in model beverage systems (pH 3.0) containing L-ascorbic acid proceeded with a first-order reaction rate during storage (40 °C for 5 days in light). The addition of gum arabic (0.05-5.0%) significantly enhanced the colour stability of anthocyanin, with the most stable systems observed at intermediate levels (1.5%). A further increase in concentration (>1.5%) reduced its efficacy due to a change in the conformation of the gum arabic molecules that hindered their exposure to the anthocyanins. Fluorescence quenching measurements showed that the anthocyanin could have interacted with the glycoprotein fractions of the gum arabic through hydrogen bonding, resulting in enhanced stability. Overall, this study provides valuable information about enhancing the stability of anthocyanins in beverage systems using natural ingredients.

  18. Enhanced planar hall sensitivity with better thermal stability by introducing interfacial modification of Au spacer

    NASA Astrophysics Data System (ADS)

    Li, Xu-Jing; Feng, Chun; Chen, Xi; Zhang, Jing-Yan; Liu, Yi-Wei; Jiang, Shao-Long; Liu, Yang; Li, Ming-Hua; Yu, Guang-Hua

    2015-05-01

    This paper reports an enhancement of planar Hall sensitivity in NiFe/Au/IrMn multilayers by introducing interfacial modification. The improvement of the sensitivity derives from the increase of resistivity change (Δρ), which is attributed to strengthened spin-asymmetry of polarized electrons in NiFe layer induced by strong spin-orbit scattering of Au layer. Furthermore, the NiFe/Au/IrMn structure based sensor exhibits good thermal stability. The high sensitivity together with good thermal stability makes the NiFe/Au/IrMn structure based sensor very promising for bio-detections.

  19. Biodiversity simultaneously enhances the production and stability of community biomass, but the effects are independent.

    PubMed

    Cardinale, Bradley J; Gross, Kevin; Fritschie, Keith; Flombaum, Pedro; Fox, Jeremy W; Rixen, Christian; van Ruijven, Jasper; Reich, Peter B; Scherer-Lorenzen, Michael; Wilsey, Brian J

    2013-08-01

    To predict the ecological consequences of biodiversity loss, researchers have spent much time and effort quantifying how biological variation affects the magnitude and stability of ecological processes that underlie the functioning of ecosystems. Here we add to this work by looking at how biodiversity jointly impacts two aspects of ecosystem functioning at once: (1) the production of biomass at any single point in time (biomass/area or biomass/ volume), and (2) the stability of biomass production through time (the CV of changes in total community biomass through time). While it is often assumed that biodiversity simultaneously enhances both of these aspects of ecosystem functioning, the joint distribution of data describing how species richness regulates productivity and stability has yet to be quantified. Furthermore, analyses have yet to examine how diversity effects on production covary with diversity effects on stability. To overcome these two gaps, we reanalyzed the data from 34 experiments that have manipulated the richness of terrestrial plants or aquatic algae and measured how this aspect of biodiversity affects community biomass at multiple time points. Our reanalysis confirms that biodiversity does indeed simultaneously enhance both the production and stability of biomass in experimental systems, and this is broadly true for terrestrial and aquatic primary producers. However, the strength of diversity effects on biomass production is independent of diversity effects on temporal stability. The independence of effect sizes leads to two important conclusions. First, while it may be generally true that biodiversity enhances both productivity and stability, it is also true that the highest levels of productivity in a diverse community are not associated with the highest levels of stability. Thus, on average, diversity does not maximize the various aspects of ecosystem functioning we might wish to achieve in conservation and management. Second, knowing how

  20. Fabrication of amorphous curcumin nanosuspensions using β-lactoglobulin to enhance solubility, stability, and bioavailability.

    PubMed

    Aditya, N P; Yang, Hanjoo; Kim, Saehoon; Ko, Sanghoon

    2015-03-01

    Curcumin has low aqueous stability and solubility in its native form. It also has a low bioavailability which presents a major barrier to its use in fortifying food products. The aim of this work was to reduce the size of curcumin crystals to the nanoscale and subsequently stabilize them in an amorphous form. To this end, amorphous curcumin nanosuspensions were fabricated using the antisolvent precipitation method with β-lactoglobulin (β-lg) as a stabilizer. The resulting amorphous curcumin nanosuspensions were in the size range of 150-175 nm with unimodal size distribution. The curcumin particles were amorphous and were molecularly dispersed within the β-lg as confirmed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. The solubility of the amorphous curcumin nanosuspension was enhanced ∼35-fold due to the reduced size and lower crystallinity. Among the formulations, the amorphous curcumin nanosuspensions stabilized with β-lg and prepared at pH 3.4 (β-lg-cur 3.4), showed maximum aqueous stability which was >90% after 30 days. An in vitro study using Caco-2 cell lines showed a significant increase in curcumin bioavailability after stabilization with β-lg.

  1. A comparison of analytical approaches for wellbore heat transmission in layered formations

    SciTech Connect

    Wu, Yu-Shu.

    1988-08-01

    This report presents an analytical method for determining wellbore heat transmission during liquid or gas flow along the tubing. The mathematical model describes the heat transfer between the flowing fluid in the wellbore and in the surrounding formation as one whole physical system. The transient heat transfer equations in the two regions with coupling at the sandface are solved simultaneously. Non-homogeneous formations are treated which consist of several layers with different physical properties and arbitrary initial temperature distributions in the vertical direction. Closed form analytical solutions are obtained in real space and in Laplace space, which can be used to calculate the temperature distribution along the wellbore and in the formation, and to evaluate heat transfer rate and cumulative heat exchange between wellbore and formation. A more accurate formula is given for the widely-used transient heat conduction function f(t{sub D}) of thermal resistance. 14 refs., 12 figs., 1 tab.

  2. Numerical Simulation on Open Wellbore Shrinkage and Casing Equivalent Stress in Bedded Salt Rock Stratum

    PubMed Central

    Liu, Jianjun

    2013-01-01

    Most salt rock has interbed of mudstone in China. Owing to the enormous difference of mechanical properties between the mudstone interbed and salt rock, the stress-strain and creep behaviors of salt rock are significantly influenced by neighboring mudstone interbed. In order to identify the rules of wellbore shrinkage and casings equivalent stress in bedded salt rock stratum, three-dimensional finite difference models were established. The effects of thickness and elasticity modulus of mudstone interbed on the open wellbore shrinkage and equivalent stress of casing after cementing operation were studied, respectively. The results indicate that the shrinkage of open wellbore and equivalent stress of casings decreases with the increase of mudstone interbed thickness. The increasing of elasticity modulus will reduce the shrinkage of open wellbore and casing equivalent stress. Research results can provide the scientific basis for the design of mud density and casing strength. PMID:24198726

  3. Numerical simulation on open wellbore shrinkage and casing equivalent stress in bedded salt rock stratum.

    PubMed

    Liu, Jianjun; Zhang, Linzhi; Zhao, Jinzhou

    2013-01-01

    Most salt rock has interbed of mudstone in China. Owing to the enormous difference of mechanical properties between the mudstone interbed and salt rock, the stress-strain and creep behaviors of salt rock are significantly influenced by neighboring mudstone interbed. In order to identify the rules of wellbore shrinkage and casings equivalent stress in bedded salt rock stratum, three-dimensional finite difference models were established. The effects of thickness and elasticity modulus of mudstone interbed on the open wellbore shrinkage and equivalent stress of casing after cementing operation were studied, respectively. The results indicate that the shrinkage of open wellbore and equivalent stress of casings decreases with the increase of mudstone interbed thickness. The increasing of elasticity modulus will reduce the shrinkage of open wellbore and casing equivalent stress. Research results can provide the scientific basis for the design of mud density and casing strength.

  4. Development of New Geothermal Wellbore Holdup Correlations Using Flowing Well Data

    SciTech Connect

    Sabodh K. Garg; John W. Pritchett; James H. Alexander; Joel Renner

    2004-03-01

    Geothermal well performances depend primarily on four factors: reservoir pressure, permeability, temperature and wellbore size. The ability to predict both the quantity of fluid that can be produced and its thermodynamic state (pressure, temperature, enthalpy, gas content, salinity, etc.) is essential for estimating the total usable energy of a geothermal resource. Numerical reservoir simulators can be utilized to calculate the thermodynamic state of the fluid in the reservoir when it enters the wellbore. To compute the fluid properties as it travels up the wellbore to the well-head given certain reservoir conditions the use of a wellbore simulator is needed. This report contains new correlations for flowing geothermal wells to accurately estimate produced fluid properties.

  5. Permeability-dependent propagation of polyacrylamides under near-wellbore flow conditions

    SciTech Connect

    Zitha, P.; Chauveteau, G.; Zaitoun, A.

    1995-11-01

    A new type of polyacrylamide flow-induced retention has been observed in core experiments simulating near-wellbore flow conditions. The retention is due to the bridging of pore throats by adsorbed macromolecules previously stretched under elongational flow. It occurs in low-to-medium permeability granular packs (up to k = 1,000 mD in the test conditions) and leads to progressive but severe plugging. The present paper shows that polymer placement in the reservoir surrounding the wellbore can be very different from what is predicted from stable values of polymer mobility. In heterogeneous reservoirs, polymer penetration in low-permeability layers is expected to be strongly reduced, thus allowing a deeper penetration into higher permeability zones. The polymer can thus improve reservoir conformance around the wellbore when injected directly through the entire opened interval. Near-wellbore polymer or gel treatments may thus not require zone isolation to be efficient.

  6. Zwitterionic gel encapsulation promotes protein stability, enhances pharmacokinetics, and reduces immunogenicity

    PubMed Central

    Zhang, Peng; Sun, Fang; Tsao, Caroline; Liu, Sijun; Jain, Priyesh; Sinclair, Andrew; Hung, Hsiang-Chieh; Bai, Tao; Wu, Kan; Jiang, Shaoyi

    2015-01-01

    Advances in protein therapy are hindered by the poor stability, inadequate pharmacokinetic (PK) profiles, and immunogenicity of many therapeutic proteins. Polyethylene glycol conjugation (PEGylation) is the most successful strategy to date to overcome these shortcomings, and more than 10 PEGylated proteins have been brought to market. However, anti-PEG antibodies induced by treatment raise serious concerns about the future of PEGylated therapeutics. Here, we demonstrate a zwitterionic polymer network encapsulation technology that effectively enhances protein stability and PK while mitigating the immune response. Uricase modified with a comprehensive zwitterionic polycarboxybetaine (PCB) network exhibited exceptional stability and a greatly prolonged circulation half-life. More importantly, the PK behavior was unchanged, and neither anti-uricase nor anti-PCB antibodies were detected after three weekly injections in a rat model. This technology is applicable to a variety of proteins and unlocks the possibility of adopting highly immunogenic proteins for therapeutic or protective applications. PMID:26371311

  7. Transient stability enhancement of electric power generating systems by 120-degree phase rotation

    DOEpatents

    Cresap, Richard L.; Taylor, Carson W.; Kreipe, Michael J.

    1982-01-01

    A method and system for enhancing the transient stability of an intertied three-phase electric power generating system. A set of power exporting generators (10) is connected to a set of power importing generators (20). When a transient cannot be controlled by conventional stability controls, and imminent loss of synchronism is detected (such as when the equivalent rotor angle difference between the two generator sets exceeds a predetermined value, such as 150 degrees), the intertie is disconnected by circuit breakers. Then a switch (30) having a 120-degree phase rotation, or a circuit breaker having a 120-degree phase rotation is placed in the intertie. The intertie is then reconnected. This results in a 120-degree reduction in the equivalent rotor angle difference between the two generator sets, making the system more stable and allowing more time for the conventional controls to stabilize the transient.

  8. Enhanced stability of black phosphorus field-effect transistors with SiO2 passivation

    NASA Astrophysics Data System (ADS)

    Wan, Bensong; Yang, Bingchao; Wang, Yue; Zhang, Junying; Zeng, Zhongming; Liu, Zhongyuan; Wang, Wenhong

    2015-10-01

    Few-layer black phosphorus (BP) has attracted much attention due to its high mobility and suitable band gap for potential applic5ations in optoelectronics and flexible devices. However, its instability under ambient conditions limits its practical applications. Our investigations indicate that by passivation of the mechanically exfoliated BP flakes with a SiO2 layer, the fabricated BP field-effect transistors (FETs) exhibit greatly enhanced environmental stability. Compared to the unpassivated BP devices, which show a fast drop of on/off current ratio by a factor of 10 after one week of ambient exposure, the SiO2-passivated BP devices display a high retained on/off current ratio of over 600 after one week of exposure, just a little lower than the initial value of 810. Our investigations provide an effective route to passivate the few-layer BPs for enhancement of their environmental stability.

  9. Enhanced stability of black phosphorus field-effect transistors with SiO₂ passivation.

    PubMed

    Wan, Bensong; Yang, Bingchao; Wang, Yue; Zhang, Junying; Zeng, Zhongming; Liu, Zhongyuan; Wang, Wenhong

    2015-10-30

    Few-layer black phosphorus (BP) has attracted much attention due to its high mobility and suitable band gap for potential applic5ations in optoelectronics and flexible devices. However, its instability under ambient conditions limits its practical applications. Our investigations indicate that by passivation of the mechanically exfoliated BP flakes with a SiO2 layer, the fabricated BP field-effect transistors (FETs) exhibit greatly enhanced environmental stability. Compared to the unpassivated BP devices, which show a fast drop of on/off current ratio by a factor of 10 after one week of ambient exposure, the SiO2-passivated BP devices display a high retained on/off current ratio of over 600 after one week of exposure, just a little lower than the initial value of 810. Our investigations provide an effective route to passivate the few-layer BPs for enhancement of their environmental stability.

  10. Core stabilization exercises enhance lactate clearance following high-intensity exercise.

    PubMed

    Navalta, James W; Hrncir, Stephen P

    2007-11-01

    Dynamic activities such as running, cycling, and swimming have been shown to effectively reduce lactate in the postexercise period. It is unknown whether core stabilization exercises performed following an intense bout would exhibit a similar effect. Therefore, this study was designed to assess the extent of the lactate response with core stabilization exercises following high-intensity anaerobic exercise. Subjects (N = 12) reported twice for testing, and on both occasions baseline lactate was obtained after 5 minutes of seated rest. Subjects then performed a 30-second Wingate anaerobic cycle test, immediately followed by a blood lactate sample. In the 5-minute postexercise period, subjects either rested quietly or performed core stabilization exercises. A final blood lactate sample was obtained following the 5-minute intervention period. Analysis revealed a significant interaction (p = 0.05). Lactate values were similar at rest (core = 1.4 +/- 0.1, rest = 1.7 +/- 0.2 mmol x L(-1)) and immediately after exercise (core = 4.9 +/- 0.6, rest = 5.4 +/- 0.4 mmol x L(-1)). However, core stabilization exercises performed during the 5-minute postexercise period reduced lactate values when compared to rest (5.9 +/- 0.6 vs. 7.6 +/- 0.8 mmol x L(-1)). The results of this study show that performing core stabilization exercises during a recovery period significantly reduces lactate values. The reduction in lactate may be due to removal via increased blood flow or enhanced uptake into the core musculature. Incorporation of core stability exercises into a cool-down period following muscular work may result in benefits to both lactate clearance as well as enhanced postural control.

  11. Error-in-variables for failure criteria applied to the near-wellbore region

    NASA Astrophysics Data System (ADS)

    Zambrano Mendoza, Orlando

    envelopes have been fitted by other methods. This work is limited to the processing of data obtained in experiments conducted in homogenous, isotropic rock at isothermal conditions. Sedimentary rocks such as sandstone are the focus of this study because of their importance in near-wellbore reservoir rock stability problems. Nevertheless, the methodology developed in this work is not limited to this type of rock.

  12. Pulse testing in the presence of wellbore storage and skin effects

    SciTech Connect

    Ogbe, D.O.; Brigham, W.E.

    1984-08-01

    A pulse test is conducted by creating a series of short-time pressure transients in an active (pulsing) well and recording the observed pressure response at an observation (responding) well. Using the pressure response and flow rate data, the transmissivity and storativity of the tested formation can be determined. Like any other pressure transient data, the pulse-test response is significantly influenced by wellbore storage and skin effects. The purpose of this research is to examine the influence of wellbore storage and skin effects on interference testing in general and on pulse-testing in particular, and to present the type curves and procedures for designing and analyzing pulse-test data when wellbore storage and skin effects are active at either the responding well or the pulsing well. A mathematical model for interference testing was developed by solving the diffusivity equation for radial flow of a single-phase, slightly compressible fluid in an infinitely large, homogeneous reservoir. When wellbore storage and skin effects are present in a pulse test, the observed response amplitude is attenuated and the time lag is inflated. Consequently, neglecting wellbore storage and skin effects in a pulse test causes the calculated storativity to be over-estimated and the transmissivity to be under-estimated. The error can be as high as 30%. New correlations and procedures are developed for correcting the pulse response amplitude and time lag for wellbore storage effects. Using these correlations, it is possible to correct the wellbore storage-dominated response amplitude and time lag to within 3% of their expected values without wellbore storage, and in turn to calculate the corresponding transmissivity and storativity. Worked examples are presented to illustrate how to use the new correction techniques. 45 references.

  13. Cavity Self-Stabilization and Enhancement of Laser Gyroscopes by (Coupled) Optical Resonators

    NASA Technical Reports Server (NTRS)

    Smith, David D.

    2006-01-01

    We analyze the effect of a highly dispersive element placed inside a modulated optical cavity on the frequency and amplitude of the modulation to determine the conditions for cavity self-stabilization and enhanced gyroscopic sensitivity. Hence, we model cavity rotation or instability by an arbitrary AM/FM modulation, and the dispersive element as a phase and amplitude filter. We find that anomalous dispersion may be used to self-stabilize a laser cavity, provided the magnitude of the group index of refraction is smaller than the phase index of refraction in the cavity. The optimal stabilization is found to occur when the group index is zero. Group indices with magnitudes larger than the phase index (both normal and anomalous dispersion) are found to enhance the sensitivity of a laser gyroscope to rotation. Furthermore, our results indicate that atomic media, even coherent superpositions in multilevel atoms, are not useful for these applications, because the amplitude and phase filters work against one another, i.e., decreasing the modulation frequency increases its amplitude and vice versa, with one exception: negative group indices whose magnitudes are larger than the phase index result in negative, but enhanced, beat frequencies. On the other hand, for optical resonators the dispersion reversal associated with critical coupling enables the amplitude and phase filters to work together under a greater variety of circumstances than for atomic media. We find that for single over-coupled resonators, or in the case of under-coupled coupled-resonator-induced absorption, the absorption and normal dispersion on-resonance increase the contrast and frequency of the beat-note, respectively, resulting in a substantial enhancement of the gyroscopic response. Moreover, for cavity self-stabilization, we propose the use of a variety of coupled-resonator induced transparency that is accompanied by anomalous dispersion.

  14. Chemical derivatization to enhance chemical/oxidative stability of resorcinol-formaldehyde resin

    SciTech Connect

    Hubler, T.

    1996-10-01

    The purpose of this work is to develop modified resorcinol-formaldehyde (R-F) resin with enhanced chemical/oxidative stability in conditions typically encountered in the remediation of radioactive waste tanks. R-F resin is a regenerable organic ion-exchanger developed at Savannah River Technology Center that is being considered for use in the selective removal of radioactive cesium from alkaline waste tank supernates at both the Hanford and Savannah River sites.

  15. Lipid Cross-Linking of Nanolipoprotein Particles Substantially Enhances Serum Stability and Cellular Uptake.

    PubMed

    Gilmore, Sean F; Blanchette, Craig D; Scharadin, Tiffany M; Hura, Greg L; Rasley, Amy; Corzett, Michele; Pan, Chong-Xian; Fischer, Nicholas O; Henderson, Paul T

    2016-08-17

    Nanolipoprotein particles (NLPs) consist of a discoidal phospholipid lipid bilayer confined by an apolipoprotein belt. NLPs are a promising platform for a variety of biomedical applications due to their biocompatibility, size, definable composition, and amphipathic characteristics. However, poor serum stability hampers the use of NLPs for in vivo applications such as drug formulation. In this study, NLP stability was enhanced upon the incorporation and subsequent UV-mediated intermolecular cross-linking of photoactive DiynePC phospholipids in the lipid bilayer, forming cross-linked nanoparticles (X-NLPs). Both the concentration of DiynePC in the bilayer and UV exposure time significantly affected the resulting X-NLP stability in 100% serum, as assessed by size exclusion chromatography (SEC) of fluorescently labeled particles. Cross-linking did not significantly impact the size of X-NLPs as determined by dynamic light scattering and SEC. X-NLPs had essentially no degradation over 48 h in 100% serum, which is a drastic improvement compared to non-cross-linked NLPs (50% degradation by ∼10 min). X-NLPs had greater uptake into the human ATCC 5637 bladder cancer cell line compared to non-cross-linked particles, indicating their potential utility for targeted drug delivery. X-NLPs also exhibited enhanced stability following intravenous administration in mice. These results collectively support the potential utility of X-NLPs for a variety of in vivo applications. PMID:27411034

  16. Protection enhances community and habitat stability: evidence from a mediterranean marine protected area.

    PubMed

    Fraschetti, Simonetta; Guarnieri, Giuseppe; Bevilacqua, Stanislao; Terlizzi, Antonio; Boero, Ferdinando

    2013-01-01

    Rare evidences support that Marine Protected Areas (MPAs) enhance the stability of marine habitats and assemblages. Based on nine years of observation (2001-2009) inside and outside a well managed MPA, we assessed the potential of conservation and management actions to modify patterns of spatial and/or temporal variability of Posidonia oceanica meadows, the lower midlittoral and the shallow infralittoral rock assemblages. Significant differences in both temporal variations and spatial patterns were observed between protected and unprotected locations. A lower temporal variability in the protected vs. unprotected assemblages was found in the shallow infralittoral, demonstrating that, at least at local scale, protection can enhance community stability. Macrobenthos with long-lived and relatively slow-growing invertebrates and structurally complex algal forms were homogeneously distributed in space and went through little fluctuations in time. In contrast, a mosaic of disturbed patches featured unprotected locations, with small-scale shifts from macroalgal stands to barrens, and harsh temporal variations between the two states. Opposite patterns of spatial and temporal variability were found for the midlittoral assemblages. Despite an overall clear pattern of seagrass regression through time, protected meadows showed a significantly higher shoot density than unprotected ones, suggesting a higher resistance to local human activities. Our results support the assumption that the exclusion/management of human activities within MPAs enhance the stability of the structural components of protected marine systems, reverting or arresting threat-induced trajectories of change. PMID:24349135

  17. Protection enhances community and habitat stability: evidence from a mediterranean marine protected area.

    PubMed

    Fraschetti, Simonetta; Guarnieri, Giuseppe; Bevilacqua, Stanislao; Terlizzi, Antonio; Boero, Ferdinando

    2013-01-01

    Rare evidences support that Marine Protected Areas (MPAs) enhance the stability of marine habitats and assemblages. Based on nine years of observation (2001-2009) inside and outside a well managed MPA, we assessed the potential of conservation and management actions to modify patterns of spatial and/or temporal variability of Posidonia oceanica meadows, the lower midlittoral and the shallow infralittoral rock assemblages. Significant differences in both temporal variations and spatial patterns were observed between protected and unprotected locations. A lower temporal variability in the protected vs. unprotected assemblages was found in the shallow infralittoral, demonstrating that, at least at local scale, protection can enhance community stability. Macrobenthos with long-lived and relatively slow-growing invertebrates and structurally complex algal forms were homogeneously distributed in space and went through little fluctuations in time. In contrast, a mosaic of disturbed patches featured unprotected locations, with small-scale shifts from macroalgal stands to barrens, and harsh temporal variations between the two states. Opposite patterns of spatial and temporal variability were found for the midlittoral assemblages. Despite an overall clear pattern of seagrass regression through time, protected meadows showed a significantly higher shoot density than unprotected ones, suggesting a higher resistance to local human activities. Our results support the assumption that the exclusion/management of human activities within MPAs enhance the stability of the structural components of protected marine systems, reverting or arresting threat-induced trajectories of change.

  18. Enhancing enzyme stability and metabolic functional ability of β-galactosidase through functionalized polymer nanofiber immobilization.

    PubMed

    Misson, Mailin; Jin, Bo; Chen, Binghui; Zhang, Hu

    2015-10-01

    A functionalized polystyrene nanofiber (PSNF) immobilized β-galactosidase assembly (PSNF-Gal) was synthesized as a nanobiocatalyst aiming to enhance the biocatalyst stability and functional ability. The PSNF fabricated by electrospinning was functionalized through a chemical oxidation method for enzyme binding. The bioengineering performance of the enzyme carriers was further evaluated for bioconversion of lactose to galacto-oligosaccharides (GOS). The modified PSNF-Gal demonstrated distinguished performances to preserve the same activity as the free β-galactosidase at the optimum pH of 7.0, and to enhance the enzyme stability of PSNF-Gal in an alkaline condition up to pH 10. The PSNF assembly demonstrated improved thermal stability from 37 to 60 °C. The nanobiocatalyst was able to retain 30 % of its initial activity after ninth operation cycles comparing to four cycles with the unmodified counterpart. In contrast with free β-galactosidase, the modified PSNF-Gal enhanced the GOS yield from 14 to 28 %. These findings show the chemically modified PSNF-based nanobiocatalyst may be pertinent for various enzyme-catalysed bioprocessing applications.

  19. Distributed Multi-Agent-Based Protection Scheme for Transient Stability Enhancement in Power Systems

    NASA Astrophysics Data System (ADS)

    Rahman, M. S.; Mahmud, M. A.; Pota, H. R.; Hossain, M. J.; Orchi, T. F.

    2015-04-01

    This paper presents a new distributed agent-based scheme to enhance the transient stability of power systems by maintaining phase angle cohesiveness of interconnected generators through proper relay coordination with critical clearing time (CCT) information. In this distributed multi-agent infrastructure, intelligent agents represent various physical device models to provide dynamic information and energy flow among different physical processes of power systems. The agents can communicate with each other in a distributed manner with a final aim to control circuit breakers (CBs) with CCT information as this is the key issue for maintaining and enhancing the transient stability of power systems. The performance of the proposed scheme is evaluated on a standard IEEE 39-bus New England benchmark system under different large disturbances such as three-phase short-circuit faults and changes in loads within the systems. From the simulation results, it is found that the proposed scheme significantly enhances the transient stability of power systems as compared to a conventional scheme of static CB operation.

  20. Protection Enhances Community and Habitat Stability: Evidence from a Mediterranean Marine Protected Area

    PubMed Central

    Fraschetti, Simonetta; Guarnieri, Giuseppe; Bevilacqua, Stanislao; Terlizzi, Antonio; Boero, Ferdinando

    2013-01-01

    Rare evidences support that Marine Protected Areas (MPAs) enhance the stability of marine habitats and assemblages. Based on nine years of observation (2001–2009) inside and outside a well managed MPA, we assessed the potential of conservation and management actions to modify patterns of spatial and/or temporal variability of Posidonia oceanica meadows, the lower midlittoral and the shallow infralittoral rock assemblages. Significant differences in both temporal variations and spatial patterns were observed between protected and unprotected locations. A lower temporal variability in the protected vs. unprotected assemblages was found in the shallow infralittoral, demonstrating that, at least at local scale, protection can enhance community stability. Macrobenthos with long-lived and relatively slow-growing invertebrates and structurally complex algal forms were homogeneously distributed in space and went through little fluctuations in time. In contrast, a mosaic of disturbed patches featured unprotected locations, with small-scale shifts from macroalgal stands to barrens, and harsh temporal variations between the two states. Opposite patterns of spatial and temporal variability were found for the midlittoral assemblages. Despite an overall clear pattern of seagrass regression through time, protected meadows showed a significantly higher shoot density than unprotected ones, suggesting a higher resistance to local human activities. Our results support the assumption that the exclusion/management of human activities within MPAs enhance the stability of the structural components of protected marine systems, reverting or arresting threat-induced trajectories of change. PMID:24349135

  1. Geomechanical analysis to predict the oil leak at the wellbores in Big Hill Strategic Petroleum Reserve

    SciTech Connect

    Park, Byoung Yoon

    2014-02-01

    Oil leaks were found in wellbores of Caverns 105 and 109 at the Big Hill Strategic Petroleum Reserve site. According to the field observations, two instances of casing damage occurred at the depth of the interbed between the caprock bottom and salt top. A three dimensional finite element model, which contains wellbore element blocks and allows each cavern to be configured individually, is constructed to investigate the wellbore damage mechanism. The model also contains element blocks to represent interface between each lithology and a shear zone to examine the interbed behavior in a realistic manner. The causes of the damaged casing segments are a result of vertical and horizontal movements of the interbed between the caprock and salt dome. The salt top subsides because the volume of caverns below the salt top decrease with time due to salt creep closure, while the caprock subsides at a slower rate because the caprock is thick and stiffer. This discrepancy yields a deformation of the well. The deformed wellbore may fail at some time. An oil leak occurs when the wellbore fails. A possible oil leak date of each well is determined using the equivalent plastic strain failure criterion. A well grading system for a remediation plan is developed based on the predicted leak dates of each wellbore.

  2. Facile Synthesis of Phosphatidyl Saccharides for Preparation of Anionic Nanoliposomes with Enhanced Stability

    PubMed Central

    Song, Shuang; Cheong, Ling-Zhi; Falkeborg, Mia; Liu, Lei; Dong, Mingdong; Jensen, Henrik Max; Bertelsen, Kresten; Thorsen, Michael; Tan, Tianwei; Xu, Xuebing; Guo, Zheng

    2013-01-01

    Physical stability during storage and against processing such as dehyration/rehydration are the cornerstone in designing delivery vehicles. In this work, mono-, di- and tri-saccharides were enzymatically conjugated to phosphatidyl group through a facile approach namely phospholipase D (PLD) mediated transphosphatidylation in a biphasic reaction system. The purified products were structurally identified and the connectivities of carbohydrate to phosphatidyl moiety precisely mapped by 1H, 31P, 13C NMR pulse sequences and LC-ESI-FTMS. The synthetic phosphatidyl saccharides were employed as the sole biomimetic component for preparation of nanoliposomes. It was found that the critical micelle concentration (CMC) of phosphatidyl saccharides increases as more bulky sugar moiety (mono- to tri-) is introduced. Phosphatidyl di-saccharide had the largest membrane curvature. In comparison to the zwitterionic phosphatidylcholine liposome, all phosphatidyl saccharides liposomes are anionic and demonstrated significantly enhanced stability during storage. According to the confocal laser scan microscopy (CLSM) and atom force microscopy (AFM) analyses, the nanoliposomes formed by the synthetic phosphatidyl saccharides also show excellent stability against dehydration/rehydration process in which most of the liposomal structures remained intact. The abundance hydroxyl groups in the saccharide moieties might provide sufficient H-bondings for stabilization. This work demonstrated the synthesized phosphatidyl saccharides are capable of functioning as enzymatically liable materials which can form stable nanoliposomes without addition of stabilizing excipients. PMID:24069243

  3. Co-composting solid biowastes with alkaline materials to enhance carbon stabilization and revegetation potential.

    PubMed

    Chowdhury, Saikat; Bolan, Nanthi S; Seshadri, Balaji; Kunhikrishnan, Anitha; Wijesekara, Hasintha; Xu, Yilu; Yang, Jianjun; Kim, Geon-Ha; Sparks, Donald; Rumpel, Cornelia

    2016-04-01

    Co-composting biowastes such as manures and biosolids can be used to stabilize carbon (C) without impacting the quality of these biowastes. This study investigated the effect of co-composting biowastes with alkaline materials on C stabilization and monitored the fertilization and revegetation values of these co-composts. The stabilization of C in biowastes (poultry manure and biosolids) was examined by their composting in the presence of various alkaline amendments (lime, fluidized bed boiler ash, flue gas desulphurization gypsum, and red mud) for 6 months in a controlled environment. The effects of co-composting on the biowastes' properties were assessed for different physical C fractions, microbial biomass C, priming effect, potentially mineralizable nitrogen, bioavailable phosphorus, and revegetation of an urban landfill soil. Co-composting biowastes with alkaline materials increased C stabilization, attributed to interaction with alkaline materials, thereby protecting it from microbial decomposition. The co-composted biowastes also increased the fertility of the landfill soil, thereby enhancing its revegetation potential. Stabilization of biowastes using alkaline materials through co-composting maintains their fertilization value in terms of improving plant growth. The co-composted biowastes also contribute to long-term soil C sequestration and reduction of bioavailability of heavy metals. PMID:26381784

  4. Flash Nanoprecipitation: Prediction and Enhancement of Particle Stability via Drug Structure

    PubMed Central

    2015-01-01

    Flash nanoprecipitation (FNP) can generate hydrophobic drug nanoparticles in ∼100 nm with a much higher drug loading (e.g., > 40 wt %) than traditional nanocarriers (e.g., < 20 wt %). This paper studies the effects of drug molecules on nanoparticle stability made via FNP and demonstrates that chemically bonding a drug compound (e.g., paclitaxel) with a cleavable hydrophobic moiety of organosilicate (e.g., triethoxysilicate) is able to enhance the particle size stability. A nonionic amphiphilic diblock copolymer, poly(lactic-co-glycolic acid)-block-poly(ethylene glycol) (PLGA-b-PEG), is used as a model surfactant to provide steric stabilization. The experiments here show that the lower the drug solubility in the aqueous medium, the more stable the particles in terms of Ostwald ripening, which are consistent with the prediction by the LSW theory. The initial particle size distribution is sufficiently narrow and of insignificance to Ostwald ripening. To correlate the particle stability with hydrophobicity, this study introduces the n-octanol/water partition coefficient (LogP), a hydrophobicity indication, into the FNP technique. A comparison of various drugs and their analogues shows that LogP of a drug is a better hydrophobicity indication than the solubility parameter (δ) and correlates well with the particle stability. Empirically, with ACDLogP > ∼12, nanoparticles have good stability; with ∼2 < ACDLogP < ∼9, nanoparticles show fast Ostwald ripening and interparticle recrystallization; with ACDLogP < ∼2, the drug is very likely difficult to form nanoparticles. This rule creates a quick way to predict particle stability for a randomly selected drug structure and helps to enable a fast preclinical drug screen. PMID:24484077

  5. Decreased aperture surface energy enhances electrical, mechanical, and temporal stability of suspended lipid membranes

    PubMed Central

    Bright, Leonard K.; Baker, Christopher A.; Agasid, Mark T.; Ma, Lin; Aspinwall, Craig A.

    2013-01-01

    The development of next-generation transmembrane protein-based biosensors relies heavily on the use of black lipid membranes (BLMs); however, electrical, mechanical, and temporal instability of BLMs pose a limiting challenge to biosensor development. In this work, micron-sized glass apertures were modified with silanes of different chain length and fluorine composition, including 3-cyanopropyldimethychlorosilane (CPDCS), ethyldimethylchlorosilane (EDCS), n-octyldimethylchlorosilane (ODCS), (tridecafluoro 1, 1, 2, 2-tetrahydrooctyl)dimethylchlorosilane (PFDCS) or (heptadecafluoro-1,1,2,2-tetrahydrodecyl)dimethylchlorosilane (PFDDCS) to explore the effect of substrate surface energy on BLM stability. Low energy silane-modified surfaces promoted enhanced lipid-substrate interactions that facilitate the formation of low-leakage, stable BLMs. The surface energies of silane-modified substrates were 30 ± 3, 16 ± 1, 14 ± 2, 11 ± 1 and 7.1 ± 2 mJ m−2 for CDCS, EDCS, ODCS, PFDCS and PFDDCS, respectively. Decreased surface energy directly correlated to improved electrical, mechanical, and temporal BLM stability. Amphiphobic perfluorinated surface modifiers yielded superior performance compared to traditional hydrocarbon modifiers in terms of stability and BLM formation, with only marginal effects on BLM membrane permeability. Leakage currents obtained for PFDCS and PFDDCS BLMs were elevated only 10-30%, though PFDDCS modification yielded > 5-fold increase in electrical stability as indicated by breakdown voltage (> 2000 mV vs. 418 ± 73 mV), and > 25-fold increase in mechanical stability as indicated by air-water transfers (> 50 vs. 2 ± 0.2) when compared to previously reported CPDCS modification. Importantly, the dramatically improved membrane stabilities were achieved with no deleterious effects on reconstituted ion channel function as evidenced by α-hemolysin activity. Thus, this approach provides a simple, low cost and broadly applicable alternative for BLM

  6. Flash nanoprecipitation: prediction and enhancement of particle stability via drug structure.

    PubMed

    Zhu, Zhengxi

    2014-03-01

    Flash nanoprecipitation (FNP) can generate hydrophobic drug nanoparticles in ∼ 100 nm with a much higher drug loading (e.g., > 40 wt %) than traditional nanocarriers (e.g., < 20 wt %). This paper studies the effects of drug molecules on nanoparticle stability made via FNP and demonstrates that chemically bonding a drug compound (e.g., paclitaxel) with a cleavable hydrophobic moiety of organosilicate (e.g., triethoxysilicate) is able to enhance the particle size stability. A nonionic amphiphilic diblock copolymer, poly(lactic-co-glycolic acid)-block-poly(ethylene glycol) (PLGA-b-PEG), is used as a model surfactant to provide steric stabilization. The experiments here show that the lower the drug solubility in the aqueous medium, the more stable the particles in terms of Ostwald ripening, which are consistent with the prediction by the LSW theory. The initial particle size distribution is sufficiently narrow and of insignificance to Ostwald ripening. To correlate the particle stability with hydrophobicity, this study introduces the n-octanol/water partition coefficient (LogP), a hydrophobicity indication, into the FNP technique. A comparison of various drugs and their analogues shows that LogP of a drug is a better hydrophobicity indication than the solubility parameter (δ) and correlates well with the particle stability. Empirically, with ACDLogP > ∼ 12, nanoparticles have good stability; with ∼ 2 < ACDLogP < ∼ 9, nanoparticles show fast Ostwald ripening and interparticle recrystallization; with ACDLogP < ∼ 2, the drug is very likely difficult to form nanoparticles. This rule creates a quick way to predict particle stability for a randomly selected drug structure and helps to enable a fast preclinical drug screen.

  7. Flash nanoprecipitation: prediction and enhancement of particle stability via drug structure.

    PubMed

    Zhu, Zhengxi

    2014-03-01

    Flash nanoprecipitation (FNP) can generate hydrophobic drug nanoparticles in ∼ 100 nm with a much higher drug loading (e.g., > 40 wt %) than traditional nanocarriers (e.g., < 20 wt %). This paper studies the effects of drug molecules on nanoparticle stability made via FNP and demonstrates that chemically bonding a drug compound (e.g., paclitaxel) with a cleavable hydrophobic moiety of organosilicate (e.g., triethoxysilicate) is able to enhance the particle size stability. A nonionic amphiphilic diblock copolymer, poly(lactic-co-glycolic acid)-block-poly(ethylene glycol) (PLGA-b-PEG), is used as a model surfactant to provide steric stabilization. The experiments here show that the lower the drug solubility in the aqueous medium, the more stable the particles in terms of Ostwald ripening, which are consistent with the prediction by the LSW theory. The initial particle size distribution is sufficiently narrow and of insignificance to Ostwald ripening. To correlate the particle stability with hydrophobicity, this study introduces the n-octanol/water partition coefficient (LogP), a hydrophobicity indication, into the FNP technique. A comparison of various drugs and their analogues shows that LogP of a drug is a better hydrophobicity indication than the solubility parameter (δ) and correlates well with the particle stability. Empirically, with ACDLogP > ∼ 12, nanoparticles have good stability; with ∼ 2 < ACDLogP < ∼ 9, nanoparticles show fast Ostwald ripening and interparticle recrystallization; with ACDLogP < ∼ 2, the drug is very likely difficult to form nanoparticles. This rule creates a quick way to predict particle stability for a randomly selected drug structure and helps to enable a fast preclinical drug screen. PMID:24484077

  8. Effect of pH and penetration enhancers on cysteamine stability and trans-corneal transport.

    PubMed

    Pescina, Silvia; Carra, Federica; Padula, Cristina; Santi, Patrizia; Nicoli, Sara

    2016-10-01

    Ocular cystinosis is a rare metabolic disorder characterized by the presence of insoluble cystine crystals inside the corneal stroma, with consequent photophobia, keratopathies and frequent corneal erosions. The current therapy consists in the lifetime ophthalmic administration of cysteamine, drug characterized by extremely high hydrophilicity, low molecular weight (77g/mol), and easy oxidization to disulfide. Ocular delivery of cysteamine is very challenging, for its poor permeability and stability in solution. The purpose of the present paper was to study the impact of formulation pH and composition on (1) the trans-corneal delivery and (2) the stability in solution of cysteamine, with particular focus on the use of alpha-cyclodextrin (α-CD), benzalkonium chloride (BAC) and disodium edetate (EDTA). Permeation experiments were performed ex vivo through freshly excised porcine cornea; stability was evaluated for six months at -20°, +4° and +25°C; irritation potential was evaluated using HET-CAM assay. The results showed that cysteamine trans-corneal diffusion is strictly dependent on both pH (7.4 preferred to 4.2) and buffering capacity, that negatively impact on the permeation; EDTA did not enhance the trans-corneal diffusion of cysteamine neither at pH 7.4 nor at pH 4.2, while benzalkonium chloride (BAC), antimicrobial agent present within commercial eye-drops, significantly enhanced it. Notably, α-CD was able to promote the trans-corneal diffusion of cysteamine and, at a 5.5%, a 4-fold higher penetration compared to the BAC-containing formulation was obtained. EDTA and acidic pH demonstrated to be essential for cysteamine stability. The formulation obtained by combining α-CD and EDTA was characterized by significant permeation, good stability profile, and no irritation potential, even if the tolerability should be further confirmed by in vivo test. PMID:27395395

  9. Enhanced Performance and Stability in Polymer Photovoltaic Cells Using Ultraviolet-Treated PEDOT:PSS

    NASA Astrophysics Data System (ADS)

    Xu, Xue-Jian; Yang, Li-Ying; Tian, Hui; Qin, Wen-Jing; Yin, Shou-Gen; Zhang, Fengling

    2013-07-01

    We investigate the effects of ultraviolet (UV) irradiation treatment with varying irradiation intensities for different treatment times of poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film on the performance and stability of polymer solar cells (PSCs) based on regioregular poly(3-hexylthiophene) (P3HT) and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend. Ultraviolet-visible transmission spectra, x-ray photoelectron spectroscopy, contact angle measurement, atomic force microscopy and the Kelvin probe method are conducted to characterize the UV-treated PEDOT:PSS film. The results demonstrate that UV treatment can improve the power conversion efficiency (PCE) and stability of PSCs effectively. The best performance is achieved under 1200 μW/cm2 UV treatment for 50 min. Compared to the control device, the optimized device exhibits enhanced performance with a Voc of 0.59 V, Jsc of 12.3 mA/cm2, fill factor of 51%, and PCE of 3.64%, increased by 3.5%, 33%, 8.7% and 50%, respectively. The stability of the PSCs is enhanced by 2.5 times simply through the UV treatment on the PEDOT:PSS buffer layer. The improvement in the device performance and stability is attributed to the improvement in the wettability property and the increase in the work function of the PEDOT:PSS film by UV treatment, while the impact of UV treatment on the transparency of the PEDOT:PSS film is negligible. The strategy of using UV treatment to improve device performance and stability is attractive due to its simplicity, cost-effectiveness, and because it is suitable for large-scale commercial production.

  10. Vertical Wellbore Flow Monitoring for Assessing Spatial and Temporal Flow Relationships with a Dynamic River Boundary

    SciTech Connect

    Newcomer, Darrell R.; Bjornstad, Bruce N.; Vermeul, Vincent R.

    2010-10-01

    A useful tool for identifying the temporal and spatial ambient wellbore flow relationships near a dynamic river boundary is to continuously monitor ambient vertical wellbore flow with an electromagnetic borehole flowmeter (EBF). This is important because the presence of the wellbore can result in significant mixing or exchange of groundwater vertically across the aquifer. Mixing or exchanging groundwater within the well-screen section can have significant impacts on the distribution of contaminants within the aquifer and adverse effects on the representativeness of groundwater samples collected from the monitoring well. EBF monitoring data collected from long, fully screened wells at Hanford’s 300-Area Integrated Field Research Challenge (IFRC) site, located ~260 to 290 m from the Columbia River, demonstrate that ambient vertical wellbore flow exhibits both a positive (direct) and inverse temporal relationship with periodic river-stage fluctuations over short distances. The ambient flow monitoring wells fully penetrate a highly transmissive unconfined aquifer that consists of unconsolidated coarse sediments of the Hanford formation. The spatial distribution of ambient vertical wellbore flows across the IFRC’s ~2,200 m2 well-field size indicates two general regions of inverse ambient wellbore flow behavior. The western region of the IFRC site is characterized by ambient vertical wellbore flows that are positively related to river-stage fluctuations. In contrast, the eastern region of the site exhibits ambient wellbore flows that are inversely related to river-stage fluctuations. The cause of this opposite relationship between ambient wellbore flows and river-stage changes is not completely understood; however, the positive relationships appear to be associated with high-energy Hanford formation flood deposits. These flood deposits have a well-defined northwest-southeast trend and are believed to coincide with a local paleochannel. This local paleochannel bisects

  11. Investigation of Possible Wellbore Cement Failures During Hydraulic Fracturing Operations

    SciTech Connect

    Kim, Jihoon; Moridis, George

    2014-11-01

    We model and assess the possibility of shear failure, using the Mohr-Coulomb model ? along the vertical well by employing a rigorous coupled flow-geomechanic analysis. To this end, we vary the values of cohesion between the well casing and the surrounding cement to representing different quality levels of the cementing operation (low cohesion corresponds to low-quality cement and/or incomplete cementing). The simulation results show that there is very little fracturing when the cement is of high quality.. Conversely, incomplete cementing and/or weak cement can causes significant shear failure and the evolution of long fractures/cracks along the vertical well. Specifically, low cohesion between the well and cemented areas can cause significant shear failure along the well, but the same cohesion as the cemented zone does not cause shear failure. When the hydraulic fracturing pressure is high, low cohesion of the cement can causes fast propagation of shear failure and of the resulting fracture/crack, but a high-quality cement with no weak zones exhibits limited shear failure that is concentrated near the bottom of the vertical part of the well. Thus, high-quality cement and complete cementing along the vertical well appears to be the strongest protection against shear failure of the wellbore cement and, consequently, against contamination hazards to drinking water aquifers during hydraulic fracturing operations.

  12. Simulation of altering residual water saturation near wellbore for CO2 injectivity

    NASA Astrophysics Data System (ADS)

    Park, Y.; Lee, T.; Lee, S.; Park, K.

    2014-12-01

    Volumetric CO2 storage capacity in brine aquifers is one of the most important factor for large scale CCS projects. The maximum sustainable injection rate or the injectivity is another important criterion which is dependent on many reservoir specific properties including permeability, porosity, formation thickness, areal extent, pressure and relative permeability. Among those parameters, we focused on the residual wetting phase saturation expressed in relative permeability curve. From previous experiments, residual brine saturation is typically between 0.4 and 0.6. Higher displacement efficiency cannot be expected with those values because the displacement efficiency is inversely proportional to the residual oil saturation. Also, it is natural that the end-point relative permeability for CO2 should be low. The reason is that the high CO2-brine interfacial tension disturbs CO2 invasion into small pores. In this study, chemical flooding was assumed with surfactants or intermediate fluid which is miscible with both water and CO2 to reduce the interfacial tension. We didn't use the chemicals to improve the displacement efficiency all over the field but intend to improve the injectivity at least near the wellbore region swept by the chemicals. Once lower residual brine saturation was achieved, the higher CO2 saturation could be maintained and the better CO2 injectivity was shown. Injection tests using a commercial model showed that the increase of the injectivity was not very high but the enhancement was meaningful.

  13. Enhanced Performance of Plasmid DNA Polyplexes Stabilized by a Combination of Core Hydrophobicity and Surface PEGylation

    PubMed Central

    Adolph, Elizabeth J.; Nelson, Christopher E.; Werfel, Thomas A.; Guo, Ruijing; Davidson, Jeffrey M.; Duvall, Craig L.

    2014-01-01

    Nonviral gene therapy has high potential for safely promoting tissue restoration and for treating various genetic diseases. One current limitation is that conventional transfection reagents such as polyethylenimine (PEI) form electrostatically stabilized plasmid DNA (pDNA) polyplexes with poor colloidal stability. In this study, a library of poly(ethylene glycol-b-(dimethylaminoethyl methacrylate-co-butyl methacrylate)) [poly(EG-b-(DMAEMA-co-BMA))] polymers were synthesized and screened for improved colloidal stability and nucleic acid transfection following lyophilization. When added to pDNA in the appropriate pH buffer, the DMAEMA moieties initiate formation of electrostatic polyplexes that are internally stabilized by hydrophobic interactions of the core BMA blocks and sterically stabilized against aggregation by a PEG corona. The BMA content was varied from 0% to 60% in the second polymer block in order to optimally tune the balance of electrostatic and hydrophobic interactions in the polyplex core, and polymers with 40 and 50 mol% BMA achieved the highest transfection efficiency. Diblock copolymers were more stable than PEI in physiologic buffers. Consequently, diblock copolymer polyplexes aggregated more slowly and followed a reaction-limited colloidal aggregation model, while fast aggregation of PEI polyplexes was governed by a diffusion-limited model. Polymers with 40% BMA did not aggregate significantly after lyophilization and produced up to 20-fold higher transfection efficiency than PEI polyplexes both before and after lyophilization. Furthermore, poly(EG-b-(DMAEMA-co-BMA)) polyplexes exhibited pH-dependent membrane disruption in a red blood cell hemolysis assay and endosomal escape as observed by confocal microscopy.Lyophilized polyplexes made with the lead candidate diblock copolymer (40% BMA) also successfully transfected cells in vitro following incorporation into gas-foamed polymeric scaffolds. In summary, the enhanced colloidal stability

  14. Validation of enhanced stabilization of municipal solid waste under controlled leachate recirculation using FTIR and XRD.

    PubMed

    Sethi, Sapna; Kothiyal, N C; Nema, Arvind K

    2012-07-01

    Leachate recirculation at neutral PH accompanied with buffer/nutrients addition has been used successfully in earlier stabilization of municipal solid waste in bioreactor landfills. In the present study, efforts were made to enhance the stabilization rate of municipal solid waste (MSW) and organic solid waste (OSW) in simulated landfill bioreactors by controlling the pH of recirculated leachate towards slightly alkaline side in absence of additional buffer and nutrients addition. Enhanced stabilization in waste samples was monitored with the help of analytical tools like Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). Predominance of bands assigned to inorganic compounds and comparatively lower intensities of bands for organic compounds in the FTIR spectra of waste samples degraded with leachate recirculation under controlled pH confirmed higher rate of biodegradation and mineralization of waste than the samples degraded without controlled leachate recirculation. XRD spectra also confirmed to a greater extent of mineralization in the waste samples degraded under leachate recirculation with controlled pH. Comparison of XRD spectra of two types of wastes pointed out higher degree of mineralization in organic solid waste as compared to municipal solid waste. PMID:24749191

  15. Intestine-Specific Delivery of Hydrophobic Bioactives from Oxidized Starch Microspheres with an Enhanced Stability.

    PubMed

    Wang, Shanshan; Chen, Yuying; Liang, Hao; Chen, Yiming; Shi, Mengxuan; Wu, Jiande; Liu, Xianwu; Li, Zuseng; Liu, Bin; Yuan, Qipeng; Li, Yuan

    2015-10-01

    An intestine-specific delivery system for hydrophobic bioactives with improved stability was developed. It consists of oxidized potato starch polymers, where the carboxyl groups were physically cross-linked via ferric ions. The model hydrophobic ingredients (β-carotene) were incorporated inside the starch microspheres via a double-emulsion method. Confocal laser scanning microscopy images showed that β-carotene were distributed homogeneously in the inner oil phase of the starch microspheres. The negative value of the ζ-potential of microspheres increased with increasing pH and decreasing ionic strength. In vitro release experiments showed that the microspheres were stable at acidic stomach conditions (pH < 2), whereas at neutral intestinal conditions (pH 7.0), they rupture to release the loaded β-carotene. The 1,1-diphenyl-2-picrylhydrazyl radical, 2,2-diphenyl-1-(2,4,6-trinitriphenyl), scavenging activity results suggested that microsphere-encapsulated β-carotene had an improved activity after thermal treatment at 80 °C. The storage stability of encapsulated β-carotene at room temperature was also enhanced. The starch microspheres showed potential as intestine-specific carriers with an enhanced stability.

  16. Chemical stability of plasmon-active silver tips for tip-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Kalbacova, Jana; Rodriguez, Raul D.; Desale, Vivek; Schneider, Maximilian; Amin, Ihsan; Jordan, Rainer; Zahn, Dietrich R. T.

    2015-01-01

    Silver nanostructures are used in tip- and surface-enhanced Raman spectroscopy due to their high electric field enhancement over almost the entire visible spectral range. However, the low chemical stability of silver, compared to other noble metals, promotes silver sulfide and sulfate formation which decreases its plasmonic activity. This is why silver tips are usually prepared on the same day of the experiments or are disregarded in favour of gold that is chemically more stable. Since silver degradation cannot be avoided, we hypothesized that a protection layer may be able to minimize or control degradation. In this contribution, we report the successful preparation of 4-biphenylthiol and 4'-nitro-4-biphenylthiol self-assembled monolayers on silver tips in order to protect them against tarnishing and to investigate the effect on the life-time of the plasmonic activity. The electrochemically etched wire surface was probed via Raman spectroscopy and scanning electron microscopy. The best long term stability and resistance against corrosion was shown by a monolayer of 4-biphenylthiol formed from dimethylformamide which did not display any degradation of the metallic tip during the observed period. Here, we demonstrate an easy and straightforward approach towards increasing the chemical stability of silver TERS-active probes.

  17. Dual enhancement of electroluminescence efficiency and operational stability by rapid upconversion of triplet excitons in OLEDs

    PubMed Central

    Furukawa, Taro; Nakanotani, Hajime; Inoue, Munetomo; Adachi, Chihaya

    2015-01-01

    Recently, triplet harvesting via a thermally activated delayed fluorescence (TADF) process has been established as a realistic route for obtaining ultimate internal electroluminescence (EL) quantum efficiency in organic light-emitting diodes (OLEDs). However, the possibility that the rather long transient lifetime of the triplet excited states would reduce operational stability due to an increased chance for unwarranted chemical reactions has been a concern. Herein, we demonstrate dual enhancement of EL efficiency and operational stability in OLEDs by employing a TADF molecule as an assistant dopant and a fluorescent molecule as an end emitter. The proper combination of assistant dopant and emitter molecules realized a “one-way” rapid Förster energy transfer of singlet excitons from TADF molecules to fluorescent emitters, reducing the number of cycles of intersystem crossing (ISC) and reverse ISC in the TADF molecules and resulting in a significant enhancement of operational stability compared to OLEDs with a TADF molecule as the end emitter. In addition, we found that the presence of this rapid energy transfer significantly suppresses singlet-triplet annihilation. Using this finely-tuned rapid triplet-exciton upconversion scheme, OLED performance and lifetime was greatly improved. PMID:25673259

  18. Origin of Shear Stability and Compressive Ductility Enhancement of Metallic Glasses by Metal Coating

    PubMed Central

    Sun, B. A.; Chen, S. H.; Lu, Y. M.; Zhu, Z. G.; Zhao, Y. L.; Yang, Y.; Chan, K. C.; Liu, C. T.

    2016-01-01

    Metallic glasses (MGs) are notorious for the poor macroscopic ductility and to overcome the weakness various intrinsic and extrinsic strategies have been proposed in past decades. Among them, the metal coating is regarded as a flexible and facile approach, yet the physical origin is poorly understood due to the complex nature of shear banding process. Here, we studied the origin of ductile enhancement in the Cu-coating both experimentally and theoretically. By examining serrated shear events and their stability of MGs, we revealed that the thin coating layer plays a key role in stopping the final catastrophic failure of MGs by slowing down shear band dynamics and thus retarding its attainment to a critical instable state. The mechanical analysis on interplay between the coating layer and shear banding process showed the enhanced shear stability mainly comes from the lateral tension of coating layer induced by the surface shear step and the bonding between the coating layer and MGs rather than the layer thickness is found to play a key role in contributing to the shear stability. PMID:27271435

  19. Origin of Shear Stability and Compressive Ductility Enhancement of Metallic Glasses by Metal Coating.

    PubMed

    Sun, B A; Chen, S H; Lu, Y M; Zhu, Z G; Zhao, Y L; Yang, Y; Chan, K C; Liu, C T

    2016-01-01

    Metallic glasses (MGs) are notorious for the poor macroscopic ductility and to overcome the weakness various intrinsic and extrinsic strategies have been proposed in past decades. Among them, the metal coating is regarded as a flexible and facile approach, yet the physical origin is poorly understood due to the complex nature of shear banding process. Here, we studied the origin of ductile enhancement in the Cu-coating both experimentally and theoretically. By examining serrated shear events and their stability of MGs, we revealed that the thin coating layer plays a key role in stopping the final catastrophic failure of MGs by slowing down shear band dynamics and thus retarding its attainment to a critical instable state. The mechanical analysis on interplay between the coating layer and shear banding process showed the enhanced shear stability mainly comes from the lateral tension of coating layer induced by the surface shear step and the bonding between the coating layer and MGs rather than the layer thickness is found to play a key role in contributing to the shear stability. PMID:27271435

  20. Silica Cladding of Ag Nanoparticles for High Stability and Surface-Enhanced Raman Spectroscopy Performance

    NASA Astrophysics Data System (ADS)

    Zhao, Miaomiao; Guo, Hao; Liu, Wenyao; Tang, Jun; Wang, Lei; Zhang, Binzhen; Xue, Chenyang; Liu, Jun; Zhang, Wendong

    2016-09-01

    For high-precision biochemical sensing, surface-enhanced Raman spectroscopy (SERS) has been demonstrated to be a highly sensitive spectroscopic analytical method and Ag is considered to be the best material for SERS performance. Due to the high surface activity of Ag nanoparticles, the high stability of Ag nanostructures, especially in moist environments, is one of the key issues that need to be solved. A method for silica (SiO2) cladding of Ag nanoparticles (NPs) is demonstrated here for high sensitivity and long-term stability when putted in aqueous solution. The chemically inert, transparent, hydrophilic, and bio-compatible SiO2 surface acts as the protection layer for the Ag nanoparticles, which can also enhance the Raman intensity to a certain extent. In our study, the Ag@SiO2 core-shell substrate can detect crystal violet solutions with molar concentrations down to 10-12 M. After 24 h of immersion, the reduction in Raman scattering intensity is about 85 % for sole Ag NP films, compared to 12 % for the Ag coated with a 10-nm SiO2 layer. This thickness was found to be optimum for Ag@SiO2 core-shell substrates with long-term stability and high SERS activity.

  1. Origin of Shear Stability and Compressive Ductility Enhancement of Metallic Glasses by Metal Coating

    NASA Astrophysics Data System (ADS)

    Sun, B. A.; Chen, S. H.; Lu, Y. M.; Zhu, Z. G.; Zhao, Y. L.; Yang, Y.; Chan, K. C.; Liu, C. T.

    2016-06-01

    Metallic glasses (MGs) are notorious for the poor macroscopic ductility and to overcome the weakness various intrinsic and extrinsic strategies have been proposed in past decades. Among them, the metal coating is regarded as a flexible and facile approach, yet the physical origin is poorly understood due to the complex nature of shear banding process. Here, we studied the origin of ductile enhancement in the Cu-coating both experimentally and theoretically. By examining serrated shear events and their stability of MGs, we revealed that the thin coating layer plays a key role in stopping the final catastrophic failure of MGs by slowing down shear band dynamics and thus retarding its attainment to a critical instable state. The mechanical analysis on interplay between the coating layer and shear banding process showed the enhanced shear stability mainly comes from the lateral tension of coating layer induced by the surface shear step and the bonding between the coating layer and MGs rather than the layer thickness is found to play a key role in contributing to the shear stability.

  2. Validation of enhanced stabilization of municipal solid waste under controlled leachate recirculation using FTIR and XRD.

    PubMed

    Sethi, Sapna; Kothiyal, N C; Nema, Arvind K

    2012-07-01

    Leachate recirculation at neutral PH accompanied with buffer/nutrients addition has been used successfully in earlier stabilization of municipal solid waste in bioreactor landfills. In the present study, efforts were made to enhance the stabilization rate of municipal solid waste (MSW) and organic solid waste (OSW) in simulated landfill bioreactors by controlling the pH of recirculated leachate towards slightly alkaline side in absence of additional buffer and nutrients addition. Enhanced stabilization in waste samples was monitored with the help of analytical tools like Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). Predominance of bands assigned to inorganic compounds and comparatively lower intensities of bands for organic compounds in the FTIR spectra of waste samples degraded with leachate recirculation under controlled pH confirmed higher rate of biodegradation and mineralization of waste than the samples degraded without controlled leachate recirculation. XRD spectra also confirmed to a greater extent of mineralization in the waste samples degraded under leachate recirculation with controlled pH. Comparison of XRD spectra of two types of wastes pointed out higher degree of mineralization in organic solid waste as compared to municipal solid waste.

  3. Silica Cladding of Ag Nanoparticles for High Stability and Surface-Enhanced Raman Spectroscopy Performance.

    PubMed

    Zhao, Miaomiao; Guo, Hao; Liu, Wenyao; Tang, Jun; Wang, Lei; Zhang, Binzhen; Xue, Chenyang; Liu, Jun; Zhang, Wendong

    2016-12-01

    For high-precision biochemical sensing, surface-enhanced Raman spectroscopy (SERS) has been demonstrated to be a highly sensitive spectroscopic analytical method and Ag is considered to be the best material for SERS performance. Due to the high surface activity of Ag nanoparticles, the high stability of Ag nanostructures, especially in moist environments, is one of the key issues that need to be solved. A method for silica (SiO2) cladding of Ag nanoparticles (NPs) is demonstrated here for high sensitivity and long-term stability when putted in aqueous solution. The chemically inert, transparent, hydrophilic, and bio-compatible SiO2 surface acts as the protection layer for the Ag nanoparticles, which can also enhance the Raman intensity to a certain extent. In our study, the Ag@SiO2 core-shell substrate can detect crystal violet solutions with molar concentrations down to 10(-12) M. After 24 h of immersion, the reduction in Raman scattering intensity is about 85 % for sole Ag NP films, compared to 12 % for the Ag coated with a 10-nm SiO2 layer. This thickness was found to be optimum for Ag@SiO2 core-shell substrates with long-term stability and high SERS activity. PMID:27637895

  4. Enhanced stability of low fouling zwitterionic polymer brushes in seawater with diblock architecture.

    PubMed

    Quintana, Robert; Gosa, Maria; Jańczewski, Dominik; Kutnyanszky, Edit; Vancso, G Julius

    2013-08-27

    The successful implementation of zwitterionic polymeric brushes as antifouling materials for marine applications is conditioned by the stability of the polymer chain and the brush-anchoring segment in seawater. Here we demonstrate that robust, antifouling, hydrophilic polysulfobetaine-based brushes with diblock architecture can be fabricated by atom-transfer radical polymerization (ATRP) using initiator-modified surfaces. Sequential living-type polymerization of hydrophobic styrene or methyl methacrylate and commercially available hydrophilic sulfobetaine methacrylamide (SBMAm) monomer is employed. Stability enhancement is accomplished by protecting the siloxane anchoring bond of brushes on the substrate, grafted from silicon oxide surfaces. The degradation of unprotected PSBMAm brushes is clearly evident after a 3 month immersion challenge in sterilized artificial seawater. Ellipsometry and atomic force microscopy (AFM) measurements are used to follow changes in coating thickness and surface morphology. Comparative stability results indicate that surface-tethered poly(methyl methacrylate) and polystyrene hydrophobic blocks substantially improve the stability of zwitterionic brushes in an artificial marine environment. In addition, differences between the hydration of zwitterionic brushes in fresh and salt water are discussed to provide a better understanding of hydration and degradation processes with the benefit of improved design of polyzwitterionic coatings. PMID:23876125

  5. Enhanced stability of uncemented canine femoral components by bone ingrowth into the porous coatings.

    PubMed

    Jasty, M; Bragdon, C R; Zalenski, E; O'Connor, D; Page, A; Harris, W H

    1997-01-01

    The following questions were answered in this study: (1) What is the initial stability of proximally porous-coated canine femoral components? (2) Does bone ingrowth occur under these conditions? (3) Is the stability enhanced by tissue ingrowth in vivo? The stability of proximally porous-coated femoral components of canine total hip arthroplasties after 6 months to 2 years of in vivo service in dogs was measured in vitro using displacement transducers under loads simulating canine midstance. This was compared with the stability of identical components under the same loading conditions immediately after implantation in vitro in the contralateral femurs. The femurs were then sectioned and bone ingrowth into the porous coatings was quantified. The results showed that immediately after implantation the implants can move as much as 50 microns, but that the bone ingrowth into porous coatings of canine femoral components can occur even under such conditions. These data also suggested that the relative motion existing at the time of insertion can be reduced to very small amounts (< 10 microns) by bone ingrowth. PMID:9021510

  6. The role of glycerol and phosphatidylcholine in solubilizing and enhancing insulin stability in reverse hexagonal mesophases.

    PubMed

    Amar-Yuli, Idit; Azulay, Doron; Mishraki, Tehila; Aserin, Abraham; Garti, Nissim

    2011-12-15

    The potential of reverse hexagonal mesophases based on monoolein (GMO) and glycerol (as cosolvent) to facilitate the solubilization of proteins, such as insulin was explored. H(II) mesophases composed of GMO/decane/water were compared to GMO/decane/glycerol/water and GMO/phosphatidylcholine (PC)/decane/glycerol/water systems. The stability of insulin was tested, applying external physical modifications such as low pH and heat treatment (up to 70°C), in which insulin is known to form ordered amyloid-like aggregates (that are associated with several neurodegenerative diseases) with a characteristic cross β-pleated sheet structure. The impact of insulin confinement within these carriers on its stability, unfolding, and aggregation pathways was studied by combining SAXS, FTIR, and AFM techniques. These techniques provided a better insight into the molecular level of the "component interplay" in solubilizing and stabilizing insulin and its conformational modifications that dictate its final aggregate morphology. PC enlarged the water channels while glycerol shrank them, yet both facilitated insulin solubilization within the channels. The presence of glycerol within the mesophase water channels led to the formation of stronger hydrogen bonds with the hosting medium that enhanced the thermal stability of the protein and remarkably affected the unfolding process even after heat treatment (at 70°C for 60 min).

  7. Enhancement of stability of aqueous suspension of alumina nanoparticles by femtosecond laser irradiation

    SciTech Connect

    Seo, Youngsang; Ha, Jeonghong; Kim, Dongsik; Choi, Tae-Youl; Jeong, Dae-Yong; Lee, Seung Yong

    2015-09-21

    In this work, we report substantially enhanced colloidal stability of aqueous nanoparticle suspensions by ultrashort laser pulse irradiation. A Ti:Sapphire femtosecond laser (wavelength: 800 nm; pulse duration: 50 fs at full width at half maximum) was used to modify the electrochemical properties of nanoparticle suspensions at laser fluences below the particle ablation threshold. The colloidal stability of the suspension was evaluated by zeta potential and dynamic light scattering (DLS). The DLS results along with the images from transmission electron microscopy revealed that the laser irradiation caused no distinct morphological change to the individual alumina particles, but a substantial portion of the clustered particles was fragmented by the laser pulses, decreasing the apparent size of the suspended particles. Also, X-ray photoelectron spectroscopy analysis indicates that the laser irradiation modified the surface chemistry of the alumina particles. The stabilizing capability of the proposed technique was turned out to be better than that of conventional ultrasonic treatments. The stability of the laser-treated sample with no added surfactant was maintained for up to 30 days, without requiring an additional homogenizing process such as magnetic stirring.

  8. Enhanced Hydrolytic Stability of Siliceous Surfaces Modified with Pendant Dipodal Silanes

    PubMed Central

    Arkles, Barry; Pan, Youlin; Larson, Gerald L; Singh, Mani

    2014-01-01

    Dipodal silanes possess two silicon atoms that can covalently bond to a surface. They offer a distinct advantage over conventional silanes commonly used for surface modification in terms of maintaining the integrity of surface coatings, adhesive primers, and composites in aqueous environments. New nonfunctional and functional dipodal silanes with structures containing “pendant” rather than “bridged” organofunctionality are introduced. The stability of surfaces in aqueous environments prepared from dipodal silanes with hydrophobic alkyl functionality is compared to the stability of similar surfaces prepared from the conventional silanes. In strongly acidic and brine environments, surfaces modified with dipodal silanes demonstrate markedly improved resistance to hydrolysis compared to surfaces prepared from conventional silanes. Pendant dipodal silanes exhibit greater stability than bridged dipodal silanes. The apparent equilibrium constant for the formation of silanol species by the hydrolysis of a disiloxane bond was determined as Kc=[SiOH]2/[Si-O-Si][H2O]=6±1×10−5 and is helpful in understanding the enhanced hydrolytic stability of surfaces modified with dipodal silanes. PMID:25043315

  9. Enhancing stability of poly(1,3-cyclohexadiene)-based materials by bromination and dehydrobromination

    SciTech Connect

    Huang, Tianzi; Wang, Xiaojun; Malmgren, Thomas W; Mays, Jimmy

    2012-01-01

    In order to improve their thermal stability, poly(1,3-cyclohexadiene) (PCHD) homopolymer, diblock copolymer of PCHD with styrene (PCHD-b-PS), and crosslinked PCHD membranes were dehydrogenated by addition of bromine to the polymer in solution, followed by dehydrobromination using an isothermal treatment at elevated temperature. The brominated PCHD materials thus obtained were characterized via FT-IR and thermogravimetric analysis (TGA) before and after dehydrobromination. Dehydrobromination was performed inside a TGA instrument, allowing insight into thermal stability of the analytes to be obtained. The dehydrobrominated PCHD samples were characterized using elemental analysis, and it was found the dehydrogenation of PCHD to polyphenylene was not complete. Nevertheless, some aromatization did occur, and the thermal stability of the treated polymer was greatly enhanced as compared to its PCHD precursor. Such materials may thus be of interest as high carbon content, graphene-like films. Crosslinked PCHD membranes and PCHD-b-PS diblock copolymers were treated via the same bromination/pyrolysis process, which resulted in markedly improved thermal stabilities for these materials as well.

  10. Thermal stability enhancement of modified carboxymethyl cellulose films using SnO2 nanoparticles.

    PubMed

    Baniasad, Arezou; Ghorbani, Mohsen

    2016-05-01

    In this study, in-situ and ex-situ hydrothermal synthesis procedures were applied to synthesize novel CMC/porous SnO2 nanocomposites from rice husk extracted carboxymethyl cellulose (CMC) biopolymer. In addition, the effects of SnO2 nanoparticles on thermal stability of the prepared nanocomposite were specifically studied. Products were investigated in terms of morphology, particle size, chemical structure, crystallinity and thermal stability by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Presence of characteristic bands in the FTIR spectra of samples confirmed the successful formation of CMC and CMC/SnO2 nanocomposites. In addition, FESEM images revealed four different morphologies of porous SnO2 nanoparticles including nanospheres, microcubes, nanoflowers and olive-like nanoparticles with hollow cores which were formed on CMC. These nanoparticles possessed d-spacing values of 3.35Å. Thermal stability measurements revealed that introduction of SnO2 nanoparticles in the structure of CMC enhanced stability of CMC to 85%.

  11. Geomechanical Modeling of CO2 Injection Site to Predict Wellbore Stresses and Strains for the Design of Wellbore Seal Repair Materials

    NASA Astrophysics Data System (ADS)

    Sobolik, S. R.; Matteo, E. N.; Dewers, T. A.; Newell, P.; Gomez, S. P.; Stormont, J.

    2014-12-01

    This paper will present the results of large-scale three-dimensional calculations simulating the hydrological-mechanical behavior of a CO2 injection reservoir and the resulting effects on wellbore casings and sealant repair materials. A critical aspect of designing effective wellbore seal repair materials is predicting thermo-mechanical perturbations in local stress that can compromise seal integrity. The DOE-NETL project "Wellbore Seal Repair Using Nanocomposite Materials," is interested in the stress-strain history of abandoned wells, as well as changes in local pressure, stress, and temperature conditions that accompany carbon dioxide injection or brine extraction. Two distinct computational models comprise the current modeling effort. The first is a field scale model that uses the stratigraphy, material properties, and injection history from a pilot CO2 injection operation in Cranfield, MS to develop a stress-strain history for wellbore locations from 100 to 400 meters from an injection well. The results from the field scale model are used as input to a more detailed model of a wellbore casing. The 3D wellbore model examines the impacts of various loading scenarios on a casing structure. This model has been developed in conjunction with bench-top experiments of an integrated seal system in an idealized scaled wellbore mock-up being used to test candidate seal repair materials. The results from these models will be used to estimate the necessary mechanical properties needed for a successful repair material. This material is based upon work supported by the U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL) under Grant Number DE-FE0009562. This project is managed and administered by the University of New Mexico and funded by DOE/NETL and cost-sharing partners. This work was funded in part by the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of

  12. Geomechanical Modeling of CO2 Injection Site to Predict Wellbore Stresses and Strains for the Design of Wellbore Seal Repair Materials

    NASA Astrophysics Data System (ADS)

    Sobolik, S. R.; Gomez, S. P.; Matteo, E. N.; Stormont, J.

    2014-12-01

    This paper will present the results of large-scale three-dimensional calculations simulating the hydrological-mechanical behavior of a CO2injection reservoir and the resulting effects on wellbore casings and sealant repair materials. A critical aspect of designing effective wellbore seal repair materials is predicting thermo-mechanical perturbations in local stress that can compromise seal integrity. The DOE-NETL project "Wellbore Seal Repair Using Nanocomposite Materials," is interested in the stress-strain history of abandoned wells, as well as changes in local pressure, stress, and temperature conditions that accompany carbon dioxide injection or brine extraction. Two distinct computational models comprise the current modeling effort. The first is a field scale model that uses the stratigraphy, material properties, and injection history from a pilot CO2injection operation in Cranfield, MS to develop a stress-strain history for wellbore locations from 100 to 400 meters from an injection well. The results from the field scale model are used as input to a more detailed model of a wellbore casing. The 3D wellbore model examines the impacts of various loading scenarios on a casing structure. This model has been developed in conjunction with bench-top experiments of an integrated seal system in an idealized scaled wellbore mock-up being used to test candidate seal repair materials. The results from these models will be used to estimate the necessary mechanical properties needed for a successful repair material. This material is based upon work supported by the US Department of Energy (DOE) National Energy Technology Laboratory (NETL) under Grant Number DE-FE0009562. This project is managed and administered by the Storage Division of the NETL and funded by DOE/NETL and cost-sharing partners. This work was funded in part by the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science

  13. Geomechanical Modeling of CO2 Injection Site to Predict Wellbore Stresses and Strains for the Design of Wellbore Seal Repair Materials

    NASA Astrophysics Data System (ADS)

    Sobolik, S. R.; Gomez, S. P.; Matteo, E. N.; Stormont, J.

    2015-12-01

    This paper will present the results of large-scale three-dimensional calculations simulating the hydrological-mechanical behavior of a CO2injection reservoir and the resulting effects on wellbore casings and sealant repair materials. A critical aspect of designing effective wellbore seal repair materials is predicting thermo-mechanical perturbations in local stress that can compromise seal integrity. The DOE-NETL project "Wellbore Seal Repair Using Nanocomposite Materials," is interested in the stress-strain history of abandoned wells, as well as changes in local pressure, stress, and temperature conditions that accompany carbon dioxide injection or brine extraction. Two distinct computational models comprise the current modeling effort. The first is a field scale model that uses the stratigraphy, material properties, and injection history from a pilot CO2injection operation in Cranfield, MS to develop a stress-strain history for wellbore locations from 100 to 400 meters from an injection well. The results from the field scale model are used as input to a more detailed model of a wellbore casing. The 3D wellbore model examines the impacts of various loading scenarios on a casing structure. This model has been developed in conjunction with bench-top experiments of an integrated seal system in an idealized scaled wellbore mock-up being used to test candidate seal repair materials. The results from these models will be used to estimate the necessary mechanical properties needed for a successful repair material. This material is based upon work supported by the US Department of Energy (DOE) National Energy Technology Laboratory (NETL) under Grant Number DE-FE0009562. This project is managed and administered by the Storage Division of the NETL and funded by DOE/NETL and cost-sharing partners. This work was funded in part by the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science

  14. Anomalously enhanced hydration of aqueous electrolyte solution in hydrophobic carbon nanotubes to maintain stability.

    PubMed

    Ohba, Tomonori

    2014-02-24

    An understanding of the structure and behavior of electrolyte solutions in nanoenvironements is crucial not only for a wide variety of applications, but also for the development of physical, chemical, and biological processes. We demonstrate the structure and stability of electrolyte in carbon nanotubes using hybrid reverse Monte Carlo simulations of X-ray diffraction patterns. Hydrogen bonds between water are adequately formed in carbon nanotubes, although some hydrogen bonds are restricted by the interfaces of carbon nanotubes. The hydrogen bonding network of water in electrolyte in the carbon nanotubes is further weakened. On the other hand, formation of the ion hydration shell is significantly enhanced in the electrolyte in the carbon nanotubes in comparison to ion hydration in bulk electrolyte. The significant hydrogen bond and hydration shell formation are a result of gaining stability in the hydrophobic nanoenvironment.

  15. Engineering bright solitons to enhance the stability of two-component Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Radha, R.; Vinayagam, P. S.; Sudharsan, J. B.; Liu, Wu-Ming; Malomed, Boris A.

    2015-12-01

    We consider a system of coupled Gross-Pitaevskii (GP) equations describing a binary quasi-one-dimensional Bose-Einstein condensate (BEC) with intrinsic time-dependent attractive interactions, placed in a time-dependent expulsive parabolic potential, in a special case when the system is integrable (a deformed Manakov's system). Since the nonlinearity in the integrable system which represents binary attractive interactions exponentially decays with time, solitons are also subject to decay. Nevertheless, it is shown that the robustness of bright solitons can be enhanced in this system, making their respective lifetime longer, by matching the time dependence of the interaction strength (adjusted with the help of the Feshbach-resonance management) to the time modulation of the strength of the parabolic potential. The analytical results, and their stability, are corroborated by numerical simulations. In particular, we demonstrate that the addition of random noise does not impact the stability of the solitons.

  16. Enhancing the thermal stability of inulin fructotransferase with high hydrostatic pressure.

    PubMed

    Li, Yungao; Miao, Ming; Liu, Miao; Chen, Xiangyin; Jiang, Bo; Feng, Biao

    2015-03-01

    The thermal stability of inulin fructotransferase (IFTase) subjected to high hydrostatic pressure (HHP) was studied. The value of inactivation rate of IFTase in the range of 70-80°C decreased under the pressure of 100 or 200 MPa, indicating that the thermostability of IFTase under high temperature was enhanced by HHP. Far-UV CD and fluorescence spectra showed that HHP impeded the unfolding of the conformation of IFTase under high temperature, reflecting the antagonistic effect between temperature and pressure on IFTase. The new intramolecular disulfide bonds in IFTase were formed under a combination of HHP and high temperature. These bonds might be related to the stabilization of IFTase at high temperature. All the above results suggested that HHP had the protective effect on IFTase against high temperature.

  17. Fullerene mixtures enhance the thermal stability of a non-crystalline polymer solar cell blend

    NASA Astrophysics Data System (ADS)

    Lindqvist, Camilla; Bergqvist, Jonas; Bäcke, Olof; Gustafsson, Stefan; Wang, Ergang; Olsson, Eva; Inganäs, Olle; Andersson, Mats R.; Müller, Christian

    2014-04-01

    Printing of polymer:fullerene solar cells at high speed requires annealing at temperatures up to 140 °C. However, bulk-heterojunction blends that comprise a non-crystalline donor polymer often suffer from insufficient thermal stability and hence rapidly coarsen upon annealing above the glass transition temperature of the blend. In addition, micrometer-sized fullerene crystals grow, which are detrimental for the solar cell performance. In this manuscript, we present a strategy to limit fullerene crystallization, which is based on the use of fullerene mixtures of the two most common derivatives, PC61BM and PC71BM, as the acceptor material. Blends of this fullerene mixture and a non-crystalline thiophene-quinoxaline copolymer display considerably enhanced thermal stability and largely retain their photovoltaic performance upon annealing at elevated temperatures as high as 170 °C.

  18. Enhancing Stability of Perovskite Solar Cells to Moisture by the Facile Hydrophobic Passivation.

    PubMed

    Hwang, Insung; Jeong, Inyoung; Lee, Jinwoo; Ko, Min Jae; Yong, Kijung

    2015-08-12

    In this study, a novel and facile passivation process for a perovskite solar cell is reported. Poor stability in ambient atmosphere, which is the most critical demerit of a perovskite solar cell, is overcome by a simple passivation process using a hydrophobic polymer layer. Teflon, the hydrophobic polymer, is deposited on the top of a perovskite solar cell by a spin-coating method. With the hydrophobic passivation, the perovskite solar cell shows negligible degradation after a 30 day storage in ambient atmosphere. Suppressed degradation of the perovskite film is proved in various ways: X-ray diffraction, light absorption spectrum, and quartz crystal microbalance. This simple but effective passivation process suggests new kind of approach to enhance stability of perovskite solar cells to moisture.

  19. Aeroelastic Tailoring for Stability Augmentation and Performance Enhancements of Tiltrotor Aircraft

    NASA Technical Reports Server (NTRS)

    Nixon, Mark W.; Piatak, David J.; Corso, Lawrence M.; Popelka, David A.

    1999-01-01

    The requirements for increased speed and productivity for tiltrotors has spawned several investigations associated with proprotor aeroelastic stability augmentation and aerodynamic performance enhancements. Included among these investigations is a focus on passive aeroelastic tailoring concepts which exploit the anisotropic capabilities of fiber composite materials. Researchers at Langley Research Center and Bell Helicopter have devoted considerable effort to assess the potential for using these materials to obtain aeroelastic responses which are beneficial to the important stability and performance considerations of tiltrotors. Both experimental and analytical studies have been completed to examine aeroelastic tailoring concepts for the tiltrotor, applied either to the wing or to the rotor blades. This paper reviews some of the results obtained in these aeroelastic tailoring investigations and discusses the relative merits associated with these approaches.

  20. Screening of polysaccharides for preparation of α-amylase conjugate to enhance stability and storage life.

    PubMed

    Jadhav, Swati B; Singhal, Rekha S

    2013-02-15

    Nine polysaccharides differing in structure and chemical nature were screened for their ability to conjugate with α-amylase by covalent binding for enhancing the thermal and pH stability of α-amylase. Among these polysaccharides, agar, dextran, pectin and xanthan showed better results but dextran stood out among all the polysaccharide for providing both thermal and pH stability to α-amylase. α-Amylase conjugated with agar, dextran, pectin and xanthan showed antimicrobial property with added preservative (0.2% sodium benzoate) in liquid formulation of α-amylase challenged with Bacillus subtilis and Escherichia coli. Dextran was the only polysaccharide which showed significant reduction of microbial growth of challenged organisms and aerobic flora without any preservative added. Aerobic flora could flourish well in the liquid α-amylase, but low temperature (4 °C), dextran, and preservative showed synergistic effect in efficiently increasing the storage life of liquid α-amylase.

  1. Enhanced stability of steep channel beds to mass failure and debris flow initiation

    NASA Astrophysics Data System (ADS)

    Prancevic, J.; Lamb, M. P.; Ayoub, F.; Venditti, J. G.

    2015-12-01

    Debris flows dominate bedrock erosion and sediment transport in very steep mountain channels, and are often initiated from failure of channel-bed alluvium during storms. While several theoretical models exist to predict mass failures, few have been tested because observations of in-channel bed failures are extremely limited. To fill this gap in our understanding, we performed laboratory flume experiments to identify the conditions necessary to initiate bed failures in non-cohesive sediment of different sizes (D = 0.7 mm to 15 mm) on steep channel-bed slopes (S = 0.45 to 0.93) and in the presence of water flow. In beds composed of sand, failures occurred under sub-saturated conditions on steep bed slopes (S > 0.5) and under super-saturated conditions at lower slopes. In beds of gravel, however, failures occurred only under super-saturated conditions at all tested slopes, even those approaching the dry angle of repose. Consistent with theoretical models, mass failures under super-saturated conditions initiated along a failure plane approximately one grain-diameter below the bed surface, whereas the failure plane was located near the base of the bed under sub-saturated conditions. However, all experimental beds were more stable than predicted by 1-D infinite-slope stability models. In partially saturated sand, enhanced stability appears to result from suction stress. Enhanced stability in gravel may result from turbulent energy losses in pores or increased granular friction for failures that are shallow with respect to grain size. These grain-size dependent effects are not currently included in stability models for non-cohesive sediment, and they may help to explain better the timing and location of debris flow occurrence.

  2. Noise‐enhanced postural stability in subjects with functional ankle instability

    PubMed Central

    Ross, Scott E

    2007-01-01

    Objective To examine the effects of stochastic resonance (SR) stimulation on the postural stability of subjects with functional ankle instability (FAI). Design Experimental research design. Setting Sports medicine research laboratory. Participants 12 subjects with FAI who reported a history of recurrent ankle sprains and “giving way” sensations at the ankle. Interventions Subjects performed 20 s single‐leg balance tests under SR stimulation at 0.05 mA and 0.01 mA and under control conditions. Testing order was randomised. Stimulators that delivered subsensory stimulation to ankle muscles and ligaments were worn. Subjects were blinded to the test conditions, as SR stimulation was subsensory and stimulators were turned off during the control condition. Main outcome measures Anterior/posterior and medial/lateral centre‐of‐pressure velocities (COPVs) were combined to form a resultant vector (COPV‐R). The COPV‐R differences between the optimal SR stimulation and control conditions were analysed. Optimal SR stimulation was defined as the SR stimulation input intensity level (0.05 mA or 0.01 mA) that produced the greatest percentage improvement in postural stability compared with the control condition. Slower velocities indicated enhanced postural stability. Results The optimal input intensity was 0.05 mA for nine subjects and 0.01 mA for the other three. The optimal SR stimulation significantly (p<0.05) improved COPV‐R compared with the control condition (6.60 (1.06) vs 7.20 (1.03) cm/s; mean (SD)). Conclusion SR stimulation may enhance signal detection of sensorimotor signals associated with postural stability. This result has clinical relevance as improvements in postural instability associated with FAI may decrease ankle sprain injury. PMID:17550917

  3. Enhancing enzyme stability by construction of polymer-enzyme conjugate micelles for decontamination of organophosphate agents.

    PubMed

    Suthiwangcharoen, Nisaraporn; Nagarajan, Ramanathan

    2014-04-14

    Enhancing the stability of enzymes under different working environments is essential if the potential of enzyme-based applications is to be realized for nanomedicine, sensing and molecular diagnostics, and chemical and biological decontamination. In this study, we focus on the enzyme, organophosphorus hydrolase (OPH), which has shown great promise for the nontoxic and noncorrosive decontamination of organophosphate agents (OPs) as well as for therapeutics as a catalytic bioscavanger against nerve gas poisoning. We describe a facile approach to stabilize OPH using covalent conjugation with the amphiphilic block copolymer, Pluronic F127, leading to the formation of F127-OPH conjugate micelles, with the OPH on the micelle corona. SDS-PAGE and MALDI-TOF confirmed the successful conjugation, and transmission electron microscopy (TEM) and dynamic light scattering (DLS) revealed ∼100 nm size micelles. The conjugates showed significantly enhanced stability and higher activity compared to the unconjugated OPH when tested (i) in aqueous solutions at room temperature, (ii) in aqueous solutions at higher temperatures, (iii) after multiple freeze/thaw treatments, (iv) after lyophilization, and (v) in the presence of organic solvents. The F127-OPH conjugates also decontaminated paraoxon (introduced as a chemical agent simulant) on a polystyrene film surface and on a CARC (Chemical Agent Resistant Coating) test panel more rapidly and to a larger extent compared to free OPH. We speculate that, in the F127-OPH conjugates (both in the micellar form as well as in the unaggregated conjugate), the polypropylene oxide block of the copolymer interacts with the surface of the OPH and this confinement of the OPH reduces the potential for enzyme denaturation and provides robustness to OPH at different working environments. The use of such polymer-enzyme conjugate micelles with improved enzyme stability opens up new opportunities for numerous civilian and Warfighter applications.

  4. Apoferritin Nanoparticle: A Novel and Biocompatible Carrier for Enzyme Immobilization with Enhanced Activity and Stability

    SciTech Connect

    Zhang, Youyu; Tang, Zhiwen; Wang, Jun; Wu, Hong J.; Lin, Chiann Tso; Lin, Yuehe

    2011-11-01

    Apoferritin is a nanostructured material with a uniform size and spherical structure, and it has excellent bio-compatibility. In this work, we report the use of apoferritin as a novel and biocompatible carrier for stabilizing enzymes and their activities. We used glucose oxidase (GOx) as a model enzyme. GOx was immobilized on the surface of the apoferritin through a green synthetic approach taking advantage of bioaffinity binding between streptavidin and biotin. As a result, a glucose oxidase-biotin/streptavidin/biotin-apoferritin conjugate (Apo-GOx) was prepared using streptavidin as a bridge. The synthesized Apo-GOx was characterized with transmission electron microscopy, ultraviolet, and fluorescence spectroscopy. The activity and stability of GOx on the surface of the apoferritin were studied in different environments, such as temperature, chemicals, and pH, in comparison with the biotinylated GOx (B-GOx). The results showed that the activity of GOx on the apoferritin surface was significantly enhanced. The thermal and chemical stability of the GOx on the apoferritin was also greatly improved compared to free B-GOx in a solution. It was found that the activity of the GOx on the apoferritin only lost 30% in comparison to a 70% loss of free B-GOx after a 2 h incubation at 50oC. There was almost no decrease in activity for the GOx on the apoferritin as compared to an 80% activity decrease for free B-GOx after 30 min incubation in a 5 M urea solution. Glucose detection was used as a model application for the enzyme immobilization method developed in this work. The GOx immobilized apoferritin nanoparticles exhibited high sensitivity for glucose detection with a detection limit of 3 nM glucose. This work offers a novel approach for immobilizing enzymes with enhanced stability and activity, and this method may find a number of applications, such as in enzyme catalysis, DNA assays and immunoassays.

  5. Glyceryl monooleate cubic phase gel as chemical stability enhancer of cefazolin and cefuroxime.

    PubMed

    Sadhale, Y; Shah, J C

    1998-11-01

    The primary objective of this study was to determine the ability of the glyceryl monooleate (GMO) cubic phase gel to protect drugs from chemical instability reactions such as hydrolysis and oxidation. Stability was assessed on cefazolin incorporated in cubic phase gel and in solution at two different concentrations (200 and 50 micrograms/g), at 22, 37, and 50 degrees C. Degradation profiles, plotting percent cefazolin remaining on a logarithmic scale versus time, were constructed and the degradation rate constants calculated from the slopes. At both concentrations, degradation of cefazolin was found to be slower in the cubic phase gel than in solution at 22 and 37 degrees C, but not at 50 degrees C. The degradation rate constants were 3- to 18-fold lower in the gel than in solution at low concentration of cefazolin. At 22 and 37 degrees C, the kinetics of degradation at high concentration of cefazolin was not first-order but showed a lag phase followed by an exponential loss of cefazolin, typical of oxidation. The potential oxidation of the thioether moiety of cefazolin was confirmed by its 18-fold higher stability in the presence of ethylenediaminetetraacetic acid (EDTA) and nitrogen in solution. Cefuroxime, a cephalosporin which degrades solely via beta-lactam hydrolysis, degraded twice as fast in solution as it did in the gel. The enhanced stability of cefazolin and cefuroxime in the GMO cubic phase gel shows its potential as a chemical stability enhancer and this is the first report to demonstrate oxidation, in addition to beta-lactam hydrolysis, as a mechanism for degradation of cefazolin.

  6. Correction: Enhanced photocatalytic activity of a self-stabilized synthetic flavin anchored on a TiO2 surface.

    PubMed

    Pandiri, Manjula; Shaham-Waldmann, Nurit; Hossain, Mohammad S; Foss, Frank W; Rajeshwar, Krishnan; Paz, Yaron

    2016-09-14

    Correction for 'Enhanced photocatalytic activity of a self-stabilized synthetic flavin anchored on a TiO2 surface' by Manjula Pandiri et al., Phys. Chem. Chem. Phys., 2016, 18, 18575-18583. PMID:27509005

  7. X-ray source assembly having enhanced output stability, and fluid stream analysis applications thereof

    DOEpatents

    Radley, Ian; Bievenue, Thomas J.; Burdett Jr., John H.; Gallagher, Brian W.; Shakshober, Stuart M.; Chen, Zewu; Moore, Michael D.

    2007-04-24

    An x-ray source assembly (2700) and method of operation are provided having enhanced output stability. The assembly includes an anode (2125) having a source spot upon which electrons (2120) impinge and a control system (2715/2720) for controlling position of the anode source spot relative to an output structure. The control system can maintain the anode source spot location relative to the output structure (2710) notwithstanding a change in one or more operating conditions of the x-ray source assembly. One aspect of the disclosed invention is most amenable to the analysis of sulfur in petroleum-based fuels.

  8. X-ray source assembly having enhanced output stability, and fluid stream analysis applications thereof

    DOEpatents

    Radley, Ian; Bievenue, Thomas J.; Burdett, John H.; Gallagher, Brian W.; Shakshober, Stuart M.; Chen, Zewu; Moore, Michael D.

    2008-06-08

    An x-ray source assembly and method of operation are provided having enhanced output stability. The assembly includes an anode having a source spot upon which electrons impinge and a control system for controlling position of the anode source spot relative to an output structure. The control system can maintain the anode source spot location relative to the output structure notwithstanding a change in one or more operating conditions of the x-ray source assembly. One aspect of the disclosed invention is most amenable to the analysis of sulfur in petroleum-based fuels.

  9. Fluorous metal-organic frameworks with enhanced stability and high H2/CO2 storage capacities.

    PubMed

    Zhang, Da-Shuai; Chang, Ze; Li, Yi-Fan; Jiang, Zhong-Yi; Xuan, Zhi-Hong; Zhang, Ying-Hui; Li, Jian-Rong; Chen, Qiang; Hu, Tong-Liang; Bu, Xian-He

    2013-11-22

    A new class of metal-organic frameworks (MOFs) has been synthesized by ligand-functionalization strategy. Systematic studies of their adsorption properties were performed at low and high pressure. Importantly, when fluorine was introduced into the framework via the functionalization, both the framework stabilities and adsorption capacities towards H2/CO2 were enhanced significantly. This consequence can be well interpreted by theoretical studies of these MOFs structures. In addition, one of these MOFs TKL-107 was used to fabricate mixed matrix membranes, which exhibit great potential for the application of CO2 separation.

  10. Fluorous Metal-Organic Frameworks with Enhanced Stability and High H2/CO2 Storage Capacities

    PubMed Central

    Zhang, Da-Shuai; Chang, Ze; Li, Yi-Fan; Jiang, Zhong-Yi; Xuan, Zhi-Hong; Zhang, Ying-Hui; Li, Jian-Rong; Chen, Qiang; Hu, Tong-Liang; Bu, Xian-He

    2013-01-01

    A new class of metal-organic frameworks (MOFs) has been synthesized by ligand-functionalization strategy. Systematic studies of their adsorption properties were performed at low and high pressure. Importantly, when fluorine was introduced into the framework via the functionalization, both the framework stabilities and adsorption capacities towards H2/CO2 were enhanced significantly. This consequence can be well interpreted by theoretical studies of these MOFs structures. In addition, one of these MOFs TKL-107 was used to fabricate mixed matrix membranes, which exhibit great potential for the application of CO2 separation. PMID:24264725

  11. Enhancement of thermal stability of porous bodies comprised of stainless steel or an alloy

    DOEpatents

    Bischoff, Brian L.; Sutton, Theodore G.; Judkins, Roddie R.; Armstrong, Timothy R.; Adcock, Kenneth D.

    2010-11-09

    A method for treating a porous item constructed of metal powder, such as a powder made of Series 400 stainless steel, involves a step of preheating the porous item to a temperature of between about 700 and 900.degree. C. degrees in an oxidizing atmosphere and then sintering the body in an inert or reducing atmosphere at a temperature which is slightly below the melting temperature of the metal which comprises the porous item. The thermal stability of the resulting item is enhanced by this method so that the item retains its porosity and metallic characteristics, such as ductility, at higher (e.g. near-melting) temperatures.

  12. Enhanced stability and antibacterial efficacy of a traditional Chinese medicine-mediated silver nanoparticle delivery system.

    PubMed

    Sun, Wenjie; Qu, Ding; Ma, Yihua; Chen, Yan; Liu, Congyan; Zhou, Jing

    2014-01-01

    Silver nanoparticles (AgNPs) are widely used as antibacterial products in various fields. Recent studies have suggested that AgNPs need an appropriate stabilizer to improve their stability. Some antibacterial traditional Chinese medicines (TCMs) contain various reductive components, which can not only stabilize AgNPs but also enhance their antimicrobial activity. In this study, we developed a series of novel AgNPs using a TCM extract as a stabilizer, reducing agent, and antimicrobial agent (TCM-AgNPs). A storage stability investigation of the TCM-AgNPs suggested a significant improvement when compared with bare AgNPs. Further, conjugation of TCMs onto the AgNP surface resulted in stronger antimicrobial potency on antibacterial evaluation using Pseudomonas aeruginosa, Staphylococcus epidermidis, and Staphylococcus aureus with minimum inhibitory concentration 50% (MIC50) ratios (and minimum bactericidal concentration 90% [MBC90] ratios) of AgNPs to respective TCM-AgNPs as assessment indices. Among these, P. cuspidatum Sieb. et-conjugated AgNPs (P.C.-AgNPs) had the advantage of a combination of TCMs and AgNPs and was studied in detail with regard to its synthesis and characterization. The extraction time, reaction temperature, and concentrations of AgNO3 and Polygonum cuspidatum Sieb. et extract were critical factors in the preparation of P.C.-AgNPs. Further, the results of X-ray diffraction and Fourier transform infrared spectroscopy indicated successful preparation of P.C.-AgNPs. In representative studies, P.C.-AgNPs showed a well-defined spherical shape, a homogeneous small particle size (36.78 nm), a narrow polydispersity index (0.105), and a highly negative zeta potential (-23.6 mV) on transmission electron microscopy and dynamic light scattering. These results indicate that TCM-AgNPs have a potential role as antibacterial agents in the clinic setting. PMID:25473286

  13. Contributors to Enhanced CO2 Electroreduction Activity and Stability in a Nanostructured Au Electrocatalyst.

    PubMed

    Kim, Haeri; Jeon, Hyo Sang; Jee, Michael Shincheon; Nursanto, Eduardus Budi; Singh, Jitendra Pal; Chae, Keunhwa; Hwang, Yun Jeong; Min, Byoung Koun

    2016-08-23

    The formation of a nanostructure is a popular strategy for catalyst applications because it can generate new surfaces that can significantly improve the catalytic activity and durability of the catalysts. However, the increase in the surface area resulting from nanostructuring does not fully explain the substantial improvement in the catalytic properties of the CO2 electroreduction reaction, and the underlying mechanisms have not yet been fully understood. Here, based on a combination of extended X-ray absorption fine structure analysis, X-ray photoelectron spectroscopy, and Kelvin probe force microscopy, we observed a contracted Au-Au bond length and low work function with the nanostructured Au surface that had enhanced catalytic activity for electrochemical CO2 reduction. The results may improve the understanding of the enhanced stability of the nanostructured Au electrode based on the resistance of cation adhesion during the CO2 reduction reaction. PMID:27466025

  14. Enhanced stability and activity of an antimicrobial peptide in conjugation with silver nanoparticle.

    PubMed

    Pal, Indrani; Brahmkhatri, Varsha P; Bera, Swapna; Bhattacharyya, Dipita; Quirishi, Yasrib; Bhunia, Anirban; Atreya, Hanudatta S

    2016-12-01

    The conjugation of nanoparticles with antimicrobial peptides (AMP) is emerging as a promising route to achieve superior antimicrobial activity. However, the nature of peptide-nanoparticle interactions in these systems remains unclear. This study describes a system consisting of a cysteine containing antimicrobial peptide conjugated with silver nanoparticles, in which the two components exhibit a dynamic interaction resulting in a significantly enhanced stability and biological activity compared to that of the individual components. This was investigated using NMR spectroscopy in conjunction with other biophysical techniques. Using fluorescence assisted cell sorting and membrane mimics we carried out a quantitative comparison of the activity of the AMP-nanoparticle system and the free peptide. Taken together, the study provides new insights into nanoparticle-AMP interactions at a molecular level and brings out the factors that will be useful for consideration while designing new conjugates with enhanced functionality. PMID:27585423

  15. Subsurface fracture mapping from geothermal wellbores. Final report

    SciTech Connect

    Hartenbaum, B.A.; Rawson, G.

    1983-08-01

    To advance the state-of-the-art in Hot Dry Rock technology, and evaluation is made of (1) the use of both electromagnetic and acoustic radar to map far-field fractures, (2) the use of more than twenty different conventional well logging tools to map borehole-fracture intercepts, (3) the use of magnetic dipole ranging to determine the relative positions of the injection well and the production well within the fractured zone, (4) the use of passive microseismic methods to determine the orientation and extent of hydraulic fractures, and (5) the application of signal processing techniques to fracture mapping including tomography, holography, synthetic aperture, image reconstruction, and the relative importance of phase and amplitude information. It is found that according to calculations, VHF backscatter radar has the potential for mapping fractures within a distance of 50 +- 20 meters from the wellbore. A new technique for improving fracture identification is presented. The range of acoustic radar is five to seven times greater than that of VHF radar when compared on the basis of equal resolution, i.e., equal wavelengths. Analyses of extant data indicate that when used synergistically the (1) caliper, (2) resistivity dipmeter, (3) televiewer, (4) television, (5) impression packer, and (6) acoustic transmission are useful for mapping borehole-fracture intercepts. A new model of hydraulic fracturing is presented which indicates that a hydraulic fracture is dynamically unstable; consequently, improvements in locating the crack tip may be possible. The importance of phase in signal processing is stressed and those techniques which employ phase data are emphasized for field use.

  16. Enhancing stability of octahedral PtNi nanoparticles for oxygen reduction reaction by halide treatment

    NASA Astrophysics Data System (ADS)

    Choi, Juhyuk; Lee, Youhan; Kim, Jihan; Lee, Hyunjoo

    2016-03-01

    Because a reduction in the amount of Pt catalysts is essential for the commercialization of fuel cells, various approaches have been tested to maximize the mass activity of Pt-based catalysts. Among these, the most successful results so far were obtained using shaped PtNi alloy nanoparticles, preferably with PtNi(111) facets. However, these nanoparticles typically suffer from much lower activity after the durability tests due to the leaching out of the surface Ni during the oxygen reduction reaction (ORR), which leads to the disappearance of the activity-enhancing effect caused by electronic structure modification. Here, we showed that halide treatment of the octahedral PtNi nanoparticles could significantly enhance their durability. Halides are adsorbed on surface Ni more strongly than on surface Pt, and the surface halides are found to preserve the surface Ni that induces the ORR activity enhancement. Especially, Br can preserve the surface Ni effectively. Durability testing by repeating cyclic voltammetry 10,000 times in the 0.6-1.1 V range showed that the mass activity decreased by 52.6% for the as-prepared PtNi octahedral nanoparticles, whereas the mass activity decreased by only 15.0% for the Br-treated PtNi nanoparticles. The simple treatment significantly enhanced the long-term stability of the highly active PtNi alloy nano-octahedra.

  17. Lasic -Cavity-enhanced molecular iodine laser frequency stabilization for space projects

    NASA Astrophysics Data System (ADS)

    Turazza, Oscar; Acef, O.; Auger, G.; Halloin, H.; Duburck, F.; Plagnol, E.; Holleville, D.; Dimarcq, N.; Binetruy, P.; Brillet, A.; Lemonde, P.; Devismes, E.; Prat, P.; Lours, M.; Tuckey, P.; Argence, B.

    We present work in progress at SYRTE, APC and ARTEMIS aiming at stabilizing the frequency of a Nd:YAG laser using saturated absorption spectroscopy of molecular iodine 127I2. The novel design of the LASIC project allows for robustness and compacity while achieving high-performance phase noise suppression. The project is a follow-up of the laser stabilization work started at Artemis and continued at APC. The use of a low-finesse bow-tie optical cavity around the iodine absorber, combined with an adapted high-frequency modulation of the laser phase -NICE-OHMS technique-yields shot-noise limited saturated absorption signals with cavity-enhanced signal-to-noise ratios. Residual fractional frequency instability in terms of Allan Std. Deviation is expected below 10-14 @1s integration time and down to 10-15 over several hours. The compact iodine / cavity design, and performance well above LISA requirements make this project an interesting candidate for the space-based Gravitational Waves detector. We discuss the scientific background and outline of this project within the LISA framework, as well as its potential impact on other stringent technical requirements of the LISA project (e.g. U.S.O. clock-stability, arm-length measurements. . . ). We also present other possible applications for space projects involving interferometry, laser ranging or onboard ultrastable oscillators.

  18. Using detrended fluctuation analysis (DFA) to analyze whether vibratory insoles enhance balance stability for elderly fallers.

    PubMed

    Wang, Chien-Chih; Yang, Wen-Hung

    2012-01-01

    Falls are a common and devastating problem among elderly people. In a previous study, vibratory insoles were developed to improve postural stability for elderly fallers. To verify the effects of vibratory insoles, a two-stage experiment was conducted to collect center of pressure (COP) signals from 26 elderly fallers and 16 healthy young subjects while standing still. The DFA is used to analyze the behavior of different time-series data obtained from the trajectory of COP. Postural stability was compared by the DFA scaling exponent between a control condition (before using vibratory insoles) and a vibration condition (after using vibratory insoles). For elderly fallers, DFA scaling exponents 95% confidence interval were [1.434, 1.547] and [1.329, 1.451] under control and vibration conditions in the anteroposterior (AP) direction, respectively. The experimental results revealed that temporary stimuli of appropriate amplitude produced by vibration insoles enhanced postural stability in elderly fallers and was more obvious in the AP direction.

  19. Enhanced capacity and stability for the separation of cesium in electrically switched ion exchange

    SciTech Connect

    Tawfic, A.F.; Dickson, S.E.; Kim, Y.; Mekky, W.

    2015-03-15

    Electrically switched ion exchange (ESIX) can be used to separate ionic contaminants from industrial wastewater, including that generated by the nuclear industry. The ESIX method involves sequential application of reduction and oxidation potentials to an ion exchange film to induce the respective loading and unloading of cesium. This technology is superior to conventional methods (e.g electrodialysis reversal or reverse osmosis) as it requires very little energy for ionic separation. In previous studies, ESIX films have demonstrated relatively low ion exchange capacities and limited film stabilities over repeated potential applications. In this study, the methodology for the deposition of electro-active films (nickel hexacyanoferrate) on nickel electrodes was modified to improve the ion exchange capacity for cesium removal using ESIX. Cyclic voltammetry was used to investigate the ion exchange capacity and stability. Scanning electron microscopy (SEM) was used to characterize the modified film surfaces. Additionally, the films were examined for the separation of cesium ions. This modified film preparation technique enhanced the ion exchange capacity and improves the film stability compared to previous methods for the deposition of ESIX films. (authors)

  20. Enhanced Stability of Skyrmions in Two-Dimensional Chiral Magnets with Rashba Spin-Orbit Coupling

    NASA Astrophysics Data System (ADS)

    Banerjee, Sumilan; Rowland, James; Erten, Onur; Randeria, Mohit

    2014-07-01

    Recent developments have led to an explosion of activity on skyrmions in three-dimensional (3D) chiral magnets. Experiments have directly probed these topological spin textures, revealed their nontrivial properties, and led to suggestions for novel applications. However, in 3D the skyrmion crystal phase is observed only in a narrow region of the temperature-field phase diagram. We show here, using a general analysis based on symmetry, that skyrmions are much more readily stabilized in two-dimensional (2D) systems with Rashba spin-orbit coupling. This enhanced stability arises from the competition between field and easy-plane magnetic anisotropy and results in a nontrivial structure in the topological charge density in the core of the skyrmions. We further show that, in a variety of microscopic models for magnetic exchange, the required easy-plane anisotropy naturally arises from the same spin-orbit coupling that is responsible for the chiral Dzyaloshinskii-Moriya interactions. Our results are of particular interest for 2D materials like thin films, surfaces, and oxide interfaces, where broken surface-inversion symmetry and Rashba spin-orbit coupling naturally lead to chiral exchange and easy-plane compass anisotropy. Our theory gives a clear direction for experimental studies of 2D magnetic materials to stabilize skyrmions over a large range of magnetic fields down to T=0.

  1. A computational study on the enhanced stabilization of aminophenol derivatives by internal hydrogen bonding

    NASA Astrophysics Data System (ADS)

    Gomes, José R. B.; Ribeiro da Silva, Manuel A. V.

    2006-05-01

    The stabilization of aminophenol derivatives and their radicals due to internal hydrogen bonding has been analyzed by means of density functional theory and by topological electron density analysis. The calculations have been carried out at the B3LYP level of theory, using several basis sets, and by means of the CBS-4M composite approach. A strong O-H⋯NH 2 hydrogen bond is found to stabilize the aminophenol with the lone-pair of the nitrogen atom co-planar with the aromatic ring, contrasting with the optimized structure found for aniline. The effect of electron donors and electron acceptors on the strength of the internal hydrogen bond is also analyzed. For one of the species studied, 2,6-diaminophenol, the computed O-H bond dissociation enthalpy is only 300 kJ/mol, the lowest value found so far for phenol and other compounds containing the O-H bond, almost 25 kJ/mol lower than those found experimentally for pyrogallol and for vitamin E. The explanation for such a small value comes from the enhanced stabilization of the corresponding radical species by internal hydrogen bonding, combined with a decrease of the steric effects caused by rotation of the amino groups.

  2. Improving the durability of a drag-reducing nanocoating by enhancing its mechanical stability.

    PubMed

    Cheng, Mengjiao; Zhang, Songsong; Dong, Hongyu; Han, Shihui; Wei, Hao; Shi, Feng

    2015-02-25

    The durability of superhydrophobic surface is a major problem to restrict industrial application of superhydrophobic materials from laboratory research, which can be attributed to a more general issue of mechanical stability for superhydrophobic coatings. Therefore, in order to handle this issue, we have fabricated a mechanically stable drag-reducing coating composed of elastic polydimethylsiloxane (PDMS) and hydrophobic copper particles on model ships, which can resist mechanical abrasion and has displayed a durable drag-reducing effect. In comparison with normal Au superhydrophobic coatings, the as-prepared PDMS/copper coatings showed durable drag reduction performance with a similar drag-reducing rate before (26%) and after (24%) mechanical abrasion. The mechanism for the enhanced mechanical stability and maintained drag reduction of the superhydrophobic surfaces was investigated through characterizations of surface morphology, surface wettability, and water adhesive force evaluation before and after abrasion. This is the first demonstration to realize the application of durable drag reduction by improving the mechanical stability of superhydrophobic coatings. We do believe that superhydrophobic surfaces with good resistance to mechanical abrasion or scratching may draw wide attention and gain significant applications with durable drag-reducing properties.

  3. Shaped Apertures in Photoresist Films Enhance the Lifetime and Mechanical Stability of Suspended Lipid Bilayers

    PubMed Central

    Kalsi, Sumit; Powl, Andrew M.; Wallace, B.A.; Morgan, Hywel; de Planque, Maurits R.R.

    2014-01-01

    Planar lipid bilayers suspended in apertures provide a controlled environment for ion channel studies. However, short lifetimes and poor mechanical stability of suspended bilayers limit the experimental throughput of bilayer electrophysiology experiments. Although bilayers are more stable in smaller apertures, ion channel incorporation through vesicle fusion with the suspended bilayer becomes increasingly difficult. In an alternative bilayer stabilization approach, we have developed shaped apertures in SU8 photoresist that have tapered sidewalls and a minimum diameter between 60 and 100 μm. Bilayers formed at the thin tip of these shaped apertures, either with the painting or the folding method, display drastically increased lifetimes, typically >20 h, and mechanical stability, being able to withstand extensive perturbation of the buffer solution. Single-channel electrical recordings of the peptide alamethicin and of the proteoliposome-delivered potassium channel KcsA demonstrate channel conductance with low noise, made possible by the small capacitance of the 50 μm thick SU8 septum, which is only thinned around the aperture, and unimpeded proteoliposome fusion, enabled by the large aperture diameter. We anticipate that these shaped apertures with micrometer edge thickness can substantially enhance the throughput of channel characterization by bilayer lipid membrane electrophysiology, especially in combination with automated parallel bilayer platforms. PMID:24739164

  4. Iridium-Tin oxide solid-solution nanocatalysts with enhanced activity and stability for oxygen evolution

    NASA Astrophysics Data System (ADS)

    Li, Guangfu; Yu, Hongmei; Yang, Donglei; Chi, Jun; Wang, Xunying; Sun, Shucheng; Shao, Zhigang; Yi, Baolian

    2016-09-01

    Addressing major challenges from the material cost, efficiency and stability, it is highly desirable to develop high-performance catalysts for oxygen evolution reaction (OER). Herein we explore a facile surfactant-assisted approach for fabricating Irsbnd Sn (Ir/Sn = 0.6/0.4, by mol.) nano-oxide catalysts with good morphology control. Direct proofs from XRD and X-ray photoelectron spectra indicate hydrophilic triblock polymer (TBP, like Pluronic® F108) surfactant can boost the formation of stable solid-solution structure. With the TBP hydrophilic and block-length increase, the fabricated Irsbnd Sn oxides undergoing the rod-to-sphere transition obtain the relatively lower crystallization, decreased crystallite size, Ir-enriched surface and incremental available active sites, all of which can bolster the OER activity and stability. Meanwhile, it is observed that the coupled Ir oxidative etching takes a crucial role in determining the material structure and performance. Compared with commercial Ir black, half-cell tests confirm F108-assistant catalysts with over 40 wt% Ir loading reduction show 2-fold activity enhancement as well as significant stability improvement. The lowest cell voltage using 0.88 mg cm-2 Ir loading is only 1.621 V at 1000 mA cm-2 and 80 °C with a concomitant energy efficiency of 75.8% which is beyond the DOE 2017 efficiency target of 74%.

  5. ITO/ATO bilayer transparent electrodes with enhanced light scattering, thermal stability and electrical conductance

    NASA Astrophysics Data System (ADS)

    Guillén, C.; Montero, J.; Herrero, J.

    2016-10-01

    Transparent electrodes based on In2O3:Sn (ITO) and SnO2:Sb (ATO) thin films have been deposited by sputtering at room temperature on soda lime glass (SLG) substrates. The preparation conditions were adjusted to obtain 250 nm-thick ITO layers with high conductivity and textured ATO coatings with various thicknesses from 80 to 200 nm. These ITO and ATO films have been combined to enhance the optical scattering and the electrical conductivity of the bilayer electrodes. Besides, a suitable ATO coating can prevent the oxidation of the ITO underlayer, thus increasing the stability of the overall electrical performance. With this purpose the structure, morphology, optical and electrical properties have been analysed comparatively for SLG/ITO, SLG/ATO and SLG/ITO/ATO samples after heating in air at 500 °C, studying the influence of the ATO layer thickness on the light scattering and thermal stability of the electrodes. In this way, a minimum sheet resistance of 8 Ω/sq has been achieved with a 120 nm-thick ATO film deposited on the 250 nm-thick ITO layer; such stacked electrode has visible transmittance near 80% and average haze HT = 10%, showing superior stability, light scattering and electrical performance than the isolated ITO and ATO films.

  6. Self aligning electron beam gun having enhanced thermal and mechanical stability

    DOEpatents

    Scarpetti, Jr., Raymond D.; Parkison, Clarence D.; Switzer, Vernon A.; Lee, Young J.; Sawyer, William C.

    1995-01-01

    A compact, high power electron gun having enhanced thermal and mechanical stability which incorporates a mechanically coupled, self aligning structure for the anode and cathode. The enhanced stability, and reduced need for realignment of the cathode to the anode and downstream optics during operation are achieved by use of a common support structure for the cathode and anode which requires no adjustment screws or spacers. The electron gun of the present invention also incorporates a modular design for the cathode, in which the electron emitter, its support structure, and the hardware required to attach the emitter assembly to the rest of the gun are a single element. This modular design makes replacement of the emitter simpler and requires no realignment after a new emitter has been installed. Compactness and a reduction in the possibility of high voltage breakdown are achieved by shielding the "triple point" where the electrode, insulator, and vacuum meet. The use of electric discharge machining (EDM) for fabricating the emitter allows for the accurate machining of the emitter into intricate shapes without encountering the normal stresses developed by standard emitter fabrication techniques.

  7. Self aligning electron beam gun having enhanced thermal and mechanical stability

    DOEpatents

    Scarpetti, R.D. Jr.; Parkison, C.D.; Switzer, V.A.; Lee, Y.J.; Sawyer, W.C.

    1995-05-16

    A compact, high power electron gun is disclosed having enhanced thermal and mechanical stability which incorporates a mechanically coupled, self aligning structure for the anode and cathode. The enhanced stability, and reduced need for realignment of the cathode to the anode and downstream optics during operation are achieved by use of a common support structure for the cathode and anode which requires no adjustment screws or spacers. The electron gun of the present invention also incorporates a modular design for the cathode, in which the electron emitter, its support structure, and the hardware required to attach the emitter assembly to the rest of the gun are a single element. This modular design makes replacement of the emitter simpler and requires no realignment after a new emitter has been installed. Compactness and a reduction in the possibility of high voltage breakdown are achieved by shielding the ``triple point`` where the electrode, insulator, and vacuum meet. The use of electric discharge machining (EDM) for fabricating the emitter allows for the accurate machining of the emitter into intricate shapes without encountering the normal stresses developed by standard emitter fabrication techniques. 12 Figs.

  8. Neomycin enhances extracellular matrix stability of glutaraldehyde crosslinked bioprosthetic heart valves.

    PubMed

    Friebe, Vincent M; Mikulis, Brandon; Kole, Sourav; Ruffing, Christy S; Sacks, Michael S; Vyavahare, Naren R

    2011-11-01

    Glutaraldehyde (GLUT) crosslinked porcine aortic heart valves are continued to be extensively used in heart valve replacement surgeries. GLUT does not crosslink glycosaminoglycans in the tissue and we have demonstrated that GAG loss is associated with tissue degeneration. In this study, we examined the ability of neomycin to enhance GLUT crosslinking to stabilize GAGs, as well as provide evidence of improved functional integrity. Neomycin enhanced GLUT crosslinked (NG) leaflets exposed to collagenase and elastase enzymes exhibited an increased resistance to proteolytic degradation. Furthermore, NG leaflets exhibited small but significant increases in collagen denaturation temperatures when compared to that of standard GLUT crosslinked BHVs. NG leaflets subjected to storage, accelerated cyclic fatigue, and in vitro enzyme mediated GAG degradation revealed improved GAG stabilization versus standard GLUT crosslinked valves, which sustained substantial decreases in GAG content. Ultrastructural analysis using transmission electron microscopy qualitatively confirmed NG leaflets preserved GAGs after enzymatic degradation. Biomechanical analyses demonstrated that NG leaflets were functionally similar to GLUT tissues but were slightly stiffer under both planar biaxial tension and under flexure. Interestingly, after GAGase treatment, GLUT tissues showed increased areal compliance and reduced hysteresis, while NG leaflets were unchanged. Collectively, NG cross-linking functionally insulated the tissue from GAG digestion, and imparted modest additional matrix stiffness but maintained tissue hysteresis properties.

  9. Enhancing stability and efficiency of perovskite solar cells with crosslinkable silane-functionalized and doped fullerene

    PubMed Central

    Bai, Yang; Dong, Qingfeng; Shao, Yuchuan; Deng, Yehao; Wang, Qi; Shen, Liang; Wang, Dong; Wei, Wei; Huang, Jinsong

    2016-01-01

    The instability of hybrid perovskite materials due to water and moisture arises as one major challenge to be addressed before any practical application of the demonstrated high efficiency perovskite solar cells. Here we report a facile strategy that can simultaneously enhance the stability and efficiency of p–i–n planar heterojunction-structure perovskite devices. Crosslinkable silane molecules with hydrophobic functional groups are bonded onto fullerene to make the fullerene layer highly water-resistant. Methylammonium iodide is introduced in the fullerene layer for n-doping via anion-induced electron transfer, resulting in dramatically increased conductivity over 100-fold. With crosslinkable silane-functionalized and doped fullerene electron transport layer, the perovskite devices deliver an efficiency of 19.5% with a high fill factor of 80.6%. A crosslinked silane-modified fullerene layer also enhances the water and moisture stability of the non-sealed perovskite devices by retaining nearly 90% of their original efficiencies after 30 days' exposure in an ambient environment. PMID:27703136

  10. Enhancing stability and efficiency of perovskite solar cells with crosslinkable silane-functionalized and doped fullerene

    NASA Astrophysics Data System (ADS)

    Bai, Yang; Dong, Qingfeng; Shao, Yuchuan; Deng, Yehao; Wang, Qi; Shen, Liang; Wang, Dong; Wei, Wei; Huang, Jinsong

    2016-10-01

    The instability of hybrid perovskite materials due to water and moisture arises as one major challenge to be addressed before any practical application of the demonstrated high efficiency perovskite solar cells. Here we report a facile strategy that can simultaneously enhance the stability and efficiency of p-i-n planar heterojunction-structure perovskite devices. Crosslinkable silane molecules with hydrophobic functional groups are bonded onto fullerene to make the fullerene layer highly water-resistant. Methylammonium iodide is introduced in the fullerene layer for n-doping via anion-induced electron transfer, resulting in dramatically increased conductivity over 100-fold. With crosslinkable silane-functionalized and doped fullerene electron transport layer, the perovskite devices deliver an efficiency of 19.5% with a high fill factor of 80.6%. A crosslinked silane-modified fullerene layer also enhances the water and moisture stability of the non-sealed perovskite devices by retaining nearly 90% of their original efficiencies after 30 days' exposure in an ambient environment.

  11. Effect of ultrasound-enhanced fat separation on whey powder phospholipid composition and stability.

    PubMed

    Torkamani, Amir E; Juliano, Pablo; Fagan, Peter; Jiménez-Flores, Rafael; Ajlouni, Said; Singh, Tanoj K

    2016-06-01

    Fat from freshly pasteurized liquid whey was partially separated by gravity for 5, 10, and 30min, with and without simultaneous application of ultrasound. Ultrasound treatments were carried out at 400 and 1,000 kHz at different specific energy inputs (23-390 kJ/kg). The fat-enriched top layers (L1) and the fat-depleted bottom layers (L2) were separately removed and freeze-dried. Nonsonicated and sonicated L2 powders were stored for 14d at ambient temperature to assess their oxidative stability. Creaming was enhanced at both frequencies and fat separation increased with higher ultrasonic energy, extended sonication, or both. The oxidative volatile compound content decreased in defatted whey powders below published odor detection threshold values for all cases. Sonication had a minor influence on the partitioning of phospholipids with fat separation. The current study suggested that ultrasonication at high frequency enhanced fat separation from freshly pasteurized whey while improving whey powder oxidative stability. PMID:27060816

  12. Delay and noise induced regime shift and enhanced stability in gene expression dynamics

    NASA Astrophysics Data System (ADS)

    Yang, Tao; Zhang, Chun; Zeng, Chunhua; Zhou, Guoqiong; Han, Qinglin; Tian, Dong; Zhang, Huili

    2014-12-01

    A quantitative model of autoregulatory gene expression involving a single gene with time delays and cross-correlated noise sources is investigated. The probability density and mean first passage time (MFPT) of the protein concentration are obtained. The impacts of multiplicative (σM) and additive (σA) noise intensities, cross-correlation intensity λ between two noises, time delays τ in the degradation process and θ in the synthesis process and time delay β in both processes on the probability density and MFPT of the regime shifts between high and low protein concentration states are discussed, respectively. These results indicate that (i) the regime shifts from a high (or low) protein concentration state to a low (or high) one can be induced by σM, λ and θ (or σA and β) (ii) the MFPT as a function of the noise intensity σM or σA exhibits one maximum value in the case of λ > 0 or θ > 0, this maximum is a signature of the noise's enhanced stability phenomenon for high protein concentration state; and (iii) τ and β can weaken the stability of high protein concentration state but, in contrast, λ and θ can enhance it in the gene expression dynamics.

  13. Enhanced thermal- and photo-stability of acid yellow 17 by incorporation into layered double hydroxides

    SciTech Connect

    Wang Qian; Feng Yongjun; Feng Junting; Li Dianqing

    2011-06-15

    2,5-dichloro-4-(5-hydroxy-3-methyl-4-(sulphophenylazo) pyrazol-1-yl) benzenesulphonate (DHSB) anions, namely acid yellow 17 anions, have been successfully intercalated into Zn-Al layered double hydroxides (LDH) to produce a novel organic-inorganic pigment by a simple method involving separate nucleation and aging steps (SNAS), and the dye-intercalated LDH was analyzed by various techniques, e.g., XRD, SEM, FT-IR, TG-DTA and ICP. The d-spacing of the prepared LDH is 2.09 nm. Furthermore, the incorporation of the DHSB aims to enhance the thermal- and photo-stability of the guest dye molecule, for example, the less color change after accelerated thermal- and photo-aging test. - Graphical abstract: Acid yellow anions were successfully assembled into ZnAl layered double hydroxides (LDH) to produce a novel organic-inorganic composite pigment by a simple method involving separate nucleation and aging steps (SNAS). Highlights: > Acid yellow 17 was directly intercalated into ZnAl-LDH to form a novel pigment. > The pigment was prepared by a method involving separate nucleation and aging steps. > The intercalation of dye anions enhances its thermal- and photo-stability.

  14. Thermostable α-amylase immobilization: Enhanced stability and performance for starch biocatalysis.

    PubMed

    Kumar, Gudi Satheesh; Rather, Gulam Mohmad; Gurramkonda, Chandrasekhar; Reddy, Bontha Rajasekhar

    2016-01-01

    The uses of thermostable starch hydrolytic biocatalysts are steadily increasing for the industrial application because of their obvious need for biocatalytic performance at elevated temperatures. The starch liquefaction and saccharification can be carried out simultaneously by the use of thermostable starch hydrolytic biocatalysts, thus minimizing the unit operations, time, and efforts. The cost factor hampers the industrialization of expensive soluble (free) enzymes for biocatalytic applications and the immobilization of enzymes offers promising alternative to the hurdle. The present investigation was aimed for immobilization of thermostable α-amylase using calcium alginate, and statistical optimization studies were carried out for enhanced biocatalytic performance. Initially, one-parameter at a time optimization studies were carried out for identification of significant factors influencing the immobilization. Furthermore, a statistical approach, response surface methodology, was applied for immobilization of α-amylase. The immobilized α-amylase in alginate microbeads showed enhanced stability to temperature and reusable property for up to seven cycles (with the retention of 50% initial activity). Finally, the kinetic behavior of free and immobilized enzyme showed the Km value of 1.2% and 2.6% (w/v) and Vmax of 1,020 and 1,030 U, respectively. Fifty percent reduction in affinity of the immobilized enzyme toward substrate was compensated by its longer stability. PMID:25604037

  15. Thermostable α-amylase immobilization: Enhanced stability and performance for starch biocatalysis.

    PubMed

    Kumar, Gudi Satheesh; Rather, Gulam Mohmad; Gurramkonda, Chandrasekhar; Reddy, Bontha Rajasekhar

    2016-01-01

    The uses of thermostable starch hydrolytic biocatalysts are steadily increasing for the industrial application because of their obvious need for biocatalytic performance at elevated temperatures. The starch liquefaction and saccharification can be carried out simultaneously by the use of thermostable starch hydrolytic biocatalysts, thus minimizing the unit operations, time, and efforts. The cost factor hampers the industrialization of expensive soluble (free) enzymes for biocatalytic applications and the immobilization of enzymes offers promising alternative to the hurdle. The present investigation was aimed for immobilization of thermostable α-amylase using calcium alginate, and statistical optimization studies were carried out for enhanced biocatalytic performance. Initially, one-parameter at a time optimization studies were carried out for identification of significant factors influencing the immobilization. Furthermore, a statistical approach, response surface methodology, was applied for immobilization of α-amylase. The immobilized α-amylase in alginate microbeads showed enhanced stability to temperature and reusable property for up to seven cycles (with the retention of 50% initial activity). Finally, the kinetic behavior of free and immobilized enzyme showed the Km value of 1.2% and 2.6% (w/v) and Vmax of 1,020 and 1,030 U, respectively. Fifty percent reduction in affinity of the immobilized enzyme toward substrate was compensated by its longer stability.

  16. Enhancement of folate content and its stability using food grade elicitors in coriander (Coriandrum sativum L.).

    PubMed

    Puthusseri, Bijesh; Divya, Peethambaran; Lokesh, Veeresh; Neelwarne, Bhagyalakshmi

    2012-06-01

    Folate (vitamin B₉) content was evaluated in 10 varieties of coriander with the aim of enhancing its concentration and stability, because of three reasons: 1) coriander is among a few widely used greens in the world and suits many cuisines, 2) folate deficiency is prevalent in developing countries causing anaemia, infant mortality and neural tube closure defects, and 3) natural folate is preferred due to doubts about health risks associated with the synthetic form. In C. sativum, the highest folate content of 1,577 μg/100 g DW was found in var. GS4 Multicut foliage of mature plants (marketable stage) with an insignificantly higher content (1,599.74 μg/100 g DW) at flowering, which is a stage not preferred in markets. In callus cultures treated with plant growth regulators (GRs) (6-benzylaminopurine, kinetin and abscisic acid) substantial increase in folate occurred after 6 h, whereas elicitors (methyl jasmonate and salicylic acid) caused rapid 2-fold increase of folate, particularly in response to salicylic acid. Based on these observations, foliar applications were done for in vivo plants, where salicylic acid (250 μM, 24 h) also enhanced folate level by 2-folds (3,112.33 μg/100 g DW), although the content varied with diurnal rhythms. Stability of folates in treated coriander foliage was 10 % higher than in untreated foliage when stored at 25 °C and 4 °C. This study has established for the first time that coriander foliage is rich in folates, which can be doubled by elicitation and impart 10 % more stability than control during processing and storage.

  17. Problems associated with application of a wellbore heat transmission computer code

    SciTech Connect

    Dash, Z.V.; Zyvoloski, G.A.

    1982-01-01

    An analysis of the discrepancies between actual temperature surveys and results obtained from a wellbore heat transmission computer code are presented for recent workover operations in well EE-2 at the Fenton Hill Hot Dry Rock Geothermal site. Several sources of error in modeling the thermal behavior of wellbores are considered. These are errors in the estimation of in-situ properties, particularly thermal conductivity, the failure to include frictional heating effects when high flow rates are involved, and error in reporting the flow rate history. These errors were also found to have a cumulative effect. A sensitivity analysis of the computed results to each error type is presented for countercurrent flow. It is concluded that all the errors considered can cause temperature discrepancies between measured and computed temperature. Wellbore codes should have provisions for variable thermal properties and frictional heating. In addition, modeling efforts should be coordinated with periodic temperature surveys so cumulative errors can be minimized.

  18. SiC-dopped MCM-41 materials with enhanced thermal and hydrothermal stabilities

    SciTech Connect

    Wang, Yingyong; Jin, Guoqiang; Tong, Xili; Guo, Xiangyun

    2011-11-15

    Graphical abstract: Novel SiC-dopped MCM-41 materials were synthesized by adding silicon carbide suspension in the molecular sieve precursor solvent followed by in situ hydrothermal synthesis. The dopped materials have a wormhole-like mesoporous structure and exhibit enhanced thermal and hydrothermal stabilities. Highlights: {yields} SiC-dopped MCM-41 was synthesized by in situ hydrothermal synthesis of molecular sieve precursor combined with SiC. {yields} The dopped MCM-41 materials show a wormhole-like mesoporous structure. {yields} The thermal stability of the dopped materials have an increment of almost 100 {sup o}C compared with the pure MCM-41. {yields} The hydrothermal stability of the dopped materials is also better than that of the pure MCM-41. -- Abstract: SiC-dopped MCM-41 mesoporous materials were synthesized by the in situ hydrothermal synthesis, in which a small amount of SiC was added in the precursor solvent of molecular sieve before the hydrothermal treatment. The materials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N{sub 2} physical adsorption and thermogravimetric analysis, respectively. The results show that the thermal and hydrothermal stabilities of MCM-41 materials can be improved obviously by incorporating a small amount of SiC. The structure collapse temperature of SiC-dopped MCM-41 materials is 100 {sup o}C higher than that of pure MCM-41 according to the differential scanning calorimetry analysis. Hydrothermal treatment experiments also show that the pure MCM-41 will losses it's ordered mesoporous structure in boiling water for 24 h while the SiC-dopped MCM-41 materials still keep partial porous structure.

  19. Enhanced dissolution and stability of Tanshinone IIA base by solid dispersion system with nano-hydroxyapatite

    PubMed Central

    Jiang, Yan-rong; Zhang, Zhen-hai; Huang, Sai-yan; Lu, Yan; Ma, Tian-tian; Jia, Xiao-bin

    2014-01-01

    Background: Tanshinone IIA (TSIIA) exhibits a variety of cardiovascular effects; however, it has low solubility in water. The preparation of poorly soluble drugs for oral delivery is one of the greatest challenges in the field of formulation research. Among the approaches available, solid dispersion (SD) technique has proven to be one of the most commonly used these methods for improving dissolution and bioavailability of drugs, because of its relative simplicity and economy in terms of both preparation and evaluation. Objective: This study was aimed at investigating the dissolution behavior and physical stability of SDs of TSIIA by employing nano-hydroxyapatite (n-HAp). Materials and Methods: The TSIIA SDs was prepared to use a spray-drying method. First, an in vitro dissolution test was performed to assess dissolution characteristics. Next, a set of complementary techniques (differential scanning calorimetry, scanning electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy) was used to monitor the physicochemical properties of the SDs. The SDs was stored at 40°C/75% relative humidity for 6 months, after which their stability was assessed. Results: TSIIA dissolution remarkably improved because of the formulation of the SDs with n-HAp particles. Comparisons with the corresponding physical mixtures revealed changes in the SDs and explained the formation of the amorphous phase. In the stability test, virtually no time-dependent decrease was observed in either in vitro drug dissolution or drug content. Conclusion: SD formulation with n-HAp may be a promising approach for enhancing the dissolution and stability of TSIIA. PMID:25210322

  20. Dissolution enhancement of gliclazide using ultrasound waves and stabilizers in liquid anti-solvent precipitation.

    PubMed

    Al-Nimry, S S; Qandil, A M; Salem, M S

    2014-12-01

    The absorption rate of gliclazide is slow and variable among subjects probably due to poor dissolution from the dosage form. The objective of this study was to enhance the dissolution rate of gliclazide by reducing the particle size. Gliclazide was precipitated from an acetone solution by adding an antisolvent (water) containing stabilizers. A combination of jets (flow rate of 20 ml/min), ultrasound, HPMC 4000, and sodium dodecyl sulfate was used to control particle size and particle size distribution. The effects of concentration of stabilizers, initial drug concentration in solution, time of insonation, antisolvent-to-solvent ratio, and ultrasound power on particle size and particle size distribution were studied. Precipitated drug particles were characterized by laser diffraction particle size analysis, SEM, FTIR spectroscopy, DSC, powder x-ray diffraction and in-vitro dissolution. With increasing almost all the studied parameters, the particle size of gliclazide initially decreased, exhibited a minimum, and then increased. Drug particles of glicazide with a mean particle size of 1.56 ± 0.09 μm and a narrow size distribution (d10/d50/d90 = 0.67/1.67/2.26) were precipitated as compared to unprocessed gliclazide with a mean particle size of 10.67 ± 0.04 μm and a wide size distribution (d10/ds50/d90 = 4.53/9.88/18.03). SEM images indicated changes in the particle morphology. Powder x-ray diffraction patterns and DSC curves indicated no changes in the chemical properties but only decrease in crystallinity and/or particle size. The dissolution rate was enhanced 2.55-fold. In conclusion, drug particles with small size and narrow size distribution were precipitated by selecting favorable process conditions, and dissolution was enhanced several folds.

  1. Enhanced exo-inulinase activity and stability by fusion of an inulin-binding module.

    PubMed

    Zhou, Shun-Hua; Liu, Yuan; Zhao, Yu-Juan; Chi, Zhe; Chi, Zhen-Ming; Liu, Guang-Lei

    2016-09-01

    In this study, an inulin-binding module from Bacillus macerans was successfully fused to an exo-inulinase from Kluyveromyces marxianus, creating a hybrid functional enzyme. The recombinant exo-inulinase (rINU), the hybrid enzyme (rINUIBM), and the recombinant inulin-binding module (rIBM) were, respectively, heterologously expressed and biochemically characterized. It was found that both the inulinase activity and the catalytic efficiency (k cat/K m(app)) of the rINUIBM were considerably higher than those of rINU. Though the rINU and the rINUIBM shared the same optimum pH of 4.5, the optimum temperature of the rINUIBM (60 °C) was 5 °C higher than that of the rINU. Notably, the fused IBM significantly enhanced both the pH stability and the thermostability of the rINUIBM, suggesting that the rINUIBM obtained would have more extensive potential applications. Furthermore, the fusion of the IBM could substantially improve the inulin-binding capability of the rINUIBM, which was consistent with the determination of the K m(app). This meant that the fused IBM could play a critical role in the recognition of polysaccharides and enhanced the hydrolase activity of the associated inulinase by increasing enzyme-substrate proximity. Besides, the extra supplement of the independent non-catalytic rIBM could also improve the inulinase activity of the rINU. However, this improvement was much better in case of the fusion. Consequently, the IBM could be designated as a multifunctional domain that was responsible for the activity enhancement, the stabilization, and the substrate binding of the rINUIBM. All these features obtained in this study make the rINUIBM become an attractive candidate for an efficient inulin hydrolysis. PMID:27164865

  2. Enhanced exo-inulinase activity and stability by fusion of an inulin-binding module.

    PubMed

    Zhou, Shun-Hua; Liu, Yuan; Zhao, Yu-Juan; Chi, Zhe; Chi, Zhen-Ming; Liu, Guang-Lei

    2016-09-01

    In this study, an inulin-binding module from Bacillus macerans was successfully fused to an exo-inulinase from Kluyveromyces marxianus, creating a hybrid functional enzyme. The recombinant exo-inulinase (rINU), the hybrid enzyme (rINUIBM), and the recombinant inulin-binding module (rIBM) were, respectively, heterologously expressed and biochemically characterized. It was found that both the inulinase activity and the catalytic efficiency (k cat/K m(app)) of the rINUIBM were considerably higher than those of rINU. Though the rINU and the rINUIBM shared the same optimum pH of 4.5, the optimum temperature of the rINUIBM (60 °C) was 5 °C higher than that of the rINU. Notably, the fused IBM significantly enhanced both the pH stability and the thermostability of the rINUIBM, suggesting that the rINUIBM obtained would have more extensive potential applications. Furthermore, the fusion of the IBM could substantially improve the inulin-binding capability of the rINUIBM, which was consistent with the determination of the K m(app). This meant that the fused IBM could play a critical role in the recognition of polysaccharides and enhanced the hydrolase activity of the associated inulinase by increasing enzyme-substrate proximity. Besides, the extra supplement of the independent non-catalytic rIBM could also improve the inulinase activity of the rINU. However, this improvement was much better in case of the fusion. Consequently, the IBM could be designated as a multifunctional domain that was responsible for the activity enhancement, the stabilization, and the substrate binding of the rINUIBM. All these features obtained in this study make the rINUIBM become an attractive candidate for an efficient inulin hydrolysis.

  3. In-situ Mechanical Manipulation of Wellbore Cements as a Solution to Leaky Wells

    NASA Astrophysics Data System (ADS)

    Kupresan, D.; Radonjic, M.; Heathman, J.

    2013-12-01

    Wellbore cement provides casing support, zonal isolation, and casing protection from corrosive fluids, which are essential for wellbore integrity. Cements can undergo one or more forms of failure such as debonding at cement/formation and cement/casing interface, fracturing and defects within cement matrix. Failures and defects within cement will ultimately lead to fluids migration, resulting in inter-zonal fluid migration and premature well abandonment. There are over 27,000 abandoned oil and gas wells only in The Gulf of Mexico (some of them dating from the late 1940s) with no gas leakage monitoring. Cement degradation linked with carbon sequestration can potentially lead to contamination of fresh water aquifers with CO2. Gas leaks can particularly be observed in deviated wells used for hydraulic fracking (60% leakage rate as they age) as high pressure fracturing increases the potential for migration pathways. Experimental method utilized in this study enables formation of impermeable seals at interfaces present in a wellbore by mechanically manipulating wellbore cement. Preliminary measurements obtained in bench scale experiments demonstrate that an impermeable cement/formation and cement/casing interface can be obtained. In post-modified cement, nitrogen gas flow-through experiments showed complete zonal isolation and no permeability in samples with pre-engineered microannulus. Material characterization experiments of modified cement revealed altered microstructural properties of cement as well as changes in mineralogical composition. Calcium-silicate-hydrate (CSH), the dominant mineral in hydrated cement which provides low permeability of cement, was modified as a result of cement pore water displacement, resulting in more dense structures. Calcium hydroxide (CH), which is associated with low resistance of cement to acidic fluids and therefore detrimental in most wellbore cements, was almost completely displaced and/or integrated in CSH as a result of

  4. Impact of Wellbore Cement Degradation on CO2 Storage Integrity

    NASA Astrophysics Data System (ADS)

    Kutchko, B.; Strazisar, B.; Lowry, G.; Dzombak, D.; Thaulow, N.

    2007-12-01

    The sequestration of CO2 in underground geologic formations requires a thorough evaluation of potential leakage of the sequestered CO2 through the numerous existing wellbores which penetrate them. Leakage rates of less than 1% per 100 years have been deemed necessary for geologic sequestration to be viable. Well bores are of particular interest because the cement used to line and/or plug the well, may be vulnerable to acid attack. Injected CO2 will dissolve, becoming carbonic acid, which can readily react with calcium hydroxide and calcium silicate hydrate, key components in hardened cement. Laboratory experiments have been performed in order to determine the physical and chemical changes, as well as the rate of degradation of the cement under simulated sequestration reservoir conditions, including both aqueous and supercritical CO2. Upon exposure to aqueous CO2, hardened cement formed well-defined reaction zones by a 2-step process. The first step is the dissolution of Ca(OH) 2 (s) and subsequent precipitation of CaCO3 (s). The formation of CaCO3 (s) has been reported to decrease cement permeability and increase its compressive strength. The second step is the dissolution of CaCO3 (s) resulting in a leaching of calcium from the cement matrix. The resulting cement paste has a significant increase in porosity, is primarily composed of amorphous silica gel, and lacks structural integrity. Although it is clear that cement is degraded, the results of this study suggest that the reactions involved are slow. In fact, long term experiments show that the rate of degradation decreases over time, likely due to the precipitation of CaCO3 (s) within the pore space of the cement. This phenomenon should limit the negative impact that chemical degradation will have on well bores. Supercritical CO2 exposure (saturated with water vapor) led to a very different process by which CaCO3 (s) was deposited throughout the matrix and on the surface, rather than within an isolated reaction

  5. The deubiquitinase Usp27x stabilizes the BH3-only protein Bim and enhances apoptosis.

    PubMed

    Weber, Arnim; Heinlein, Melanie; Dengjel, Jörn; Alber, Claudia; Singh, Prafull Kumar; Häcker, Georg

    2016-05-01

    Bim is a pro-apoptotic Bcl-2 family member of the BH3-only protein subgroup. Expression levels of Bim determine apoptosis susceptibility in non-malignant and in tumour cells. Bim protein expression is downregulated by proteasomal degradation following ERK-dependent phosphorylation and ubiquitination. Here, we report the identification of a deubiquitinase, Usp27x, that binds Bim upon its ERK-dependent phosphorylation and can upregulate its expression levels. Overexpression of Usp27x reduces ERK-dependent Bim ubiquitination, stabilizes phosphorylated Bim, and induces apoptosis in PMA-stimulated cells, as well as in tumour cells with a constitutively active Raf/ERK pathway. Loss of endogenous Usp27x enhances the Bim-degrading activity of oncogenic Raf. Overexpression of Usp27x induces low levels of apoptosis in melanoma and non-small cell lung cancer (NSCLC) cells and substantially enhances apoptosis induced in these cells by the inhibition of ERK signalling. Finally, deletion of Usp27x reduces apoptosis in NSCLC cells treated with an EGFR inhibitor. Thus, Usp27x can trigger via its proteolytic activity the deubiquitination of Bim and enhance its levels, counteracting the anti-apoptotic effects of ERK activity, and therefore acts as a tumour suppressor.

  6. The deubiquitinase Usp27x stabilizes the BH3-only protein Bim and enhances apoptosis.

    PubMed

    Weber, Arnim; Heinlein, Melanie; Dengjel, Jörn; Alber, Claudia; Singh, Prafull Kumar; Häcker, Georg

    2016-05-01

    Bim is a pro-apoptotic Bcl-2 family member of the BH3-only protein subgroup. Expression levels of Bim determine apoptosis susceptibility in non-malignant and in tumour cells. Bim protein expression is downregulated by proteasomal degradation following ERK-dependent phosphorylation and ubiquitination. Here, we report the identification of a deubiquitinase, Usp27x, that binds Bim upon its ERK-dependent phosphorylation and can upregulate its expression levels. Overexpression of Usp27x reduces ERK-dependent Bim ubiquitination, stabilizes phosphorylated Bim, and induces apoptosis in PMA-stimulated cells, as well as in tumour cells with a constitutively active Raf/ERK pathway. Loss of endogenous Usp27x enhances the Bim-degrading activity of oncogenic Raf. Overexpression of Usp27x induces low levels of apoptosis in melanoma and non-small cell lung cancer (NSCLC) cells and substantially enhances apoptosis induced in these cells by the inhibition of ERK signalling. Finally, deletion of Usp27x reduces apoptosis in NSCLC cells treated with an EGFR inhibitor. Thus, Usp27x can trigger via its proteolytic activity the deubiquitination of Bim and enhance its levels, counteracting the anti-apoptotic effects of ERK activity, and therefore acts as a tumour suppressor. PMID:27013495

  7. Wellbore cement fracture evolution at the cement–basalt caprock interface during geologic carbon sequestration

    SciTech Connect

    Jung, Hun Bok; Kabilan, Senthil; Carson, James P.; Kuprat, Andrew P.; Um, Wooyong; Martin, Paul F.; Dahl, Michael E.; Kafentzis, Tyler A.; Varga, Tamas; Stephens, Sean A.; Arey, Bruce W.; Carroll, KC; Bonneville, Alain; Fernandez, Carlos A.

    2014-08-07

    Composite Portland cement-basalt caprock cores with fractures, as well as neat Portland cement columns, were prepared to understand the geochemical and geomechanical effects on the integrity of wellbores with defects during geologic carbon sequestration. The samples were reacted with CO2-saturated groundwater at 50 ºC and 10 MPa for 3 months under static conditions, while one cement-basalt core was subjected to mechanical stress at 2.7 MPa before the CO2 reaction. Micro-XRD and SEM-EDS data collected along the cement-basalt interface after 3-month reaction with CO2-saturated groundwater indicate that carbonation of cement matrix was extensive with the precipitation of calcite, aragonite, and vaterite, whereas the alteration of basalt caprock was minor. X-ray microtomography (XMT) provided three-dimensional (3-D) visualization of the opening and interconnection of cement fractures due to mechanical stress. Computational fluid dynamics (CFD) modeling further revealed that this stress led to the increase in fluid flow and hence permeability. After the CO2-reaction, XMT images displayed that calcium carbonate precipitation occurred extensively within the fractures in the cement matrix, but only partially along the fracture located at the cement-basalt interface. The 3-D visualization and CFD modeling also showed that the precipitation of calcium carbonate within the cement fractures after the CO2-reaction resulted in the disconnection of cement fractures and permeability decrease. The permeability calculated based on CFD modeling was in agreement with the experimentally determined permeability. This study demonstrates that XMT imaging coupled with CFD modeling represent a powerful tool to visualize and quantify fracture evolution and permeability change in geologic materials and to predict their behavior during geologic carbon sequestration or hydraulic fracturing for shale gas production and enhanced geothermal systems.

  8. Computational studies of two-phase cement-CO2-brine interaction in wellbore environments

    SciTech Connect

    Carey, James William; Lichtner, Peter C

    2009-01-01

    Wellbore integrity is essential to ensuring long-term isolation of buoyant supercritical CO{sub 2} during geologic sequestration of CO{sub 2}. In this report, we summarize recent progress in numerical simulations of cement-brine-CO{sub 2} interactions with respect to migration of CO{sub 2} outside of casing. Using typical values for the hydrologic properties of cement, caprock (shale) and reservoir materials, we show that the capillary properties of good quality cement will prevent flow of CO{sub 2} into and through cement. Rather, CO{sub 2}, if present, is likely to be confined to the casing-cement or cement-formation interfaces. CO{sub 2} does react with the cement by diffusion from the interface into the cement, in which case it produces distinct carbonation fronts within the cement. This is consistent with observations of cement performance at the CO{sub 2}-enhanced oil recovery SACROC Unit in West Texas (Carey et al. 2007). For poor quality cement, flow through cement may occur and would produce a pattern of uniform carbonation without reaction fronts. We also consider an alternative explanation for cement carbonation reactions as due to CO{sub 2} derived from caprock. We show that carbonation reactions in cement are limited to surficial reactions when CO{sub 2} pressure is low (< 10 bars) as might be expected in many caprock environments. For the case of caprock overlying natural CO{sub 2} reservoirs for millions of years, we consider Scherer and Huet's (2009) hypothesis of diffusive steady-state between CO{sub 2} in the reservoir and in the caprock. We find that in this case, the aqueous CO{sub 2} concentration would differ little from the reservoir and would be expected to produce carbonation reaction fronts in cements that are relatively uniform as a function of depth.

  9. The processes controlling damage zone propagation induced by wellbore fluid injection

    NASA Astrophysics Data System (ADS)

    Shalev, Eyal; Lyakhovsky, Vladimir

    2013-04-01

    Induced seismicity by wellbore fluid injection is an important tool for enhancing permeability in hydrocarbon and geothermal reservoirs. We model nucleation and propagation of damage zones and seismicity patterns for two-dimensional plane strain configuration at a depth of 5 km using novel numerical software developed in the course of this study. Simulations include the coupling of poro-elastic deformation and groundwater flow with damage evolution (weakening and healing) and its effect on the elastic and hydrologic parameters. Results show that the process occurring during fluid injection can be divided into four stages. The duration of each stage depends on the hydrological and mechanical parameters. Initially, fluid flows into the rock with no seismic events (5 to 20 hr). At this stage, damage increases from 0 to 1 creating two sets of conjugate zones (four narrow damage zones). Thereafter, the occurrence of seismic events and faulting begins and accelerates for the next 20 to 70 hr. At the initial part of this stage, two of the damage zones create stress shadows on the other two damage zones that stop progressing. The velocity of the advancing damage is limited only by the rock parameters controlling damage evolution. At the third stage, which lasts for the following 20-30 hr, damage acceleration decreases because fluid transport becomes a limiting factor as the damage zones are too long to efficiently transfer the pressure from the well to the tip of the damage zones. Finally, the damage decelerates and even stops in some cases. The propagation of damage is controlled and limited by fluid transport from the injection well to the tip of the damage zones because fluid transport does not keep up with the dilatancy of the damage zones. The time and distance of propagation depend on the damage-permeability coupling and the remote shear stress. Higher remote shear stress causes shorter initial periods of no seismicity; strong damage-permeability coupling causes

  10. Enhance ferromagnetism by stabilizing the cation vacancies in GaN

    NASA Astrophysics Data System (ADS)

    Tang, Zhen-kun; Zhang, Deng-Yu; Tang, Li-Ming; Wang, Ling-Ling; Chen, Ke-Qiu

    2013-06-01

    The magnetic properties related to cation vacancies in GaN are investigated by first-principles calculations. The results show that a neutral Ga-vacancy induces 3 μ B magnetic moment in GaN, but is difficult to form due to the high formation energy. It is found that the Ga-vacancy formation energy can be reduced by adding electrons with uniform compensating positive background charge, by nano-structure engineering, or by co-doping donor-like defects. The Ga-vacancy induced colossal magnetic moment in Gd-doped GaN can be modulated by co-doping the donor like defects. It is suggested that ferromagnetism enhanced by stabilizing the cation vacancies may be applied to other wide band-gap semiconductors as well.

  11. Local order origin of thermal stability enhancement in amorphous Ag doping GeTe

    NASA Astrophysics Data System (ADS)

    Xu, L.; Li, Y.; Yu, N. N.; Zhong, Y. P.; Miao, X. S.

    2015-01-01

    We demonstrate the impacts of Ag doping on the local atomic structure of amorphous GeTe phase-change material. The variations of phonon vibrational modes, boding nature, and atomic structure are shown by Raman, X-ray photoelectron spectroscopy, and ab initio calculation. Combining the experiments and simulations, we observe that the number of Ge atoms in octahedral site decreases and that in tetrahedral site increases. This modification in local order of GeTe originating from the low valence element will affect the crystallization behavior of amorphous GeTe, which is verified by differential scanning calorimetry and transmission electron microscope results. This work not only gives the analysis on the structural change of GeTe with Ag dopants but also provides a method to enhance the thermal stability of amorphous phase-change materials for memory and brain-inspired computing applications.

  12. Local order origin of thermal stability enhancement in amorphous Ag doping GeTe

    SciTech Connect

    Xu, L.; Li, Y.; Yu, N. N.; Zhong, Y. P.; Miao, X. S.

    2015-01-19

    We demonstrate the impacts of Ag doping on the local atomic structure of amorphous GeTe phase-change material. The variations of phonon vibrational modes, boding nature, and atomic structure are shown by Raman, X-ray photoelectron spectroscopy, and ab initio calculation. Combining the experiments and simulations, we observe that the number of Ge atoms in octahedral site decreases and that in tetrahedral site increases. This modification in local order of GeTe originating from the low valence element will affect the crystallization behavior of amorphous GeTe, which is verified by differential scanning calorimetry and transmission electron microscope results. This work not only gives the analysis on the structural change of GeTe with Ag dopants but also provides a method to enhance the thermal stability of amorphous phase-change materials for memory and brain-inspired computing applications.

  13. Aqueous solutions of acidic ionic liquids for enhanced stability of polyoxometalate-carbon supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Hu, Chenchen; Zhao, Enbo; Nitta, Naoki; Magasinski, Alexandre; Berdichevsky, Gene; Yushin, Gleb

    2016-09-01

    Nanocomposites based on polyoxometalates (POMs) nanoconfined in microporous carbons have been synthesized and used as electrodes for supercapacitors. The addition of the pseudocapacitance from highly reversible redox reaction of POMs to the electric double-layer capacitance of carbon lead to an increase in specific capacitance of ∼90% at 1 mV s-1. However, high solubility of POM in traditional aqueous electrolytes leads to rapid capacity fading. Here we demonstrate that the use of aqueous solutions of protic ionic liquids (P-IL) as electrolyte instead of aqueous sulfuric acid solutions offers an opportunity to significantly improve POM cycling stability. Virtually no degradation in capacitance was observed in POM-based positive electrode after 10,000 cycles in an asymmetric capacitor with P-IL aqueous electrolyte. As such, POM-based carbon composites may now present a viable solution for enhancing energy density of electrical double layer capacitors (EDLC) based on pure carbon electrodes.

  14. Development of bubble chambers with enhanced stability and sensitivity to low-energy nuclear recoils

    SciTech Connect

    Bolte, W.J.; Collar, Juan I.; Crisler, M.; Hall, J.; Holmgren, D.; Nakazawa, D.; Odom, B.; O'Sullivan, K.; Plunkett, R.; Ramberg, E.; Raskin, A.; Sonnenschein, A.; Vieira, J.D.; /Chicago U., EFI /KICP, Chicago /Fermilab

    2005-03-01

    The viability of using a Bubble Chamber for rare event searches and in particular for the detection of dark matter particle candidates is considered. Techniques leading to the deactivation of inhomogeneous nucleation centers and subsequent enhanced stability in such a detector are described. Results from prototype trials indicate that sensitivity to low-energy nuclear recoils like those expected from Weakly Interacting Massive Particles can be obtained in conditions of near total insensitivity to minimum ionizing backgrounds. An understanding of the response of superheated heavy refrigerants to these recoils is demonstrated within the context of existing theoretical models. We comment on the prospects for the detection of supersymmetric dark matter particles with a large CF{sub 3}I chamber.

  15. Enhancing the stability of microplasma device utilizing diamond coated carbon nanotubes as cathode materials

    SciTech Connect

    Chang, Tinghsun; Sankaran, Kamatchi Jothiramalingam; Tai, Nyanhwa E-mail: inanlin@mail.tku.edu.tw; Kunuku, Srinivasu; Leou, Keh-Chyang; Lin, I-Nan E-mail: inanlin@mail.tku.edu.tw

    2014-06-02

    This paper reports the enhanced stability of a microplasma device by using hybrid-granular-structured diamond (HiD) film coated carbon nanotubes (CNTs) as cathode, which overcomes the drawback of short life time in the CNTs-based one. The microplasma device can be operated more than 210 min without showing any sign of degradation, whereas the CNTs-based one can last only 50 min. Besides the high robustness against the Ar-ion bombardment, the HiD/CNTs material also possesses superior electron field emission properties with low turn-on field of 3.2 V/μm, which is considered as the prime factor for the improved plasma illumination performance of the devices.

  16. Remarkable enhancement of O₂ activation on yttrium-stabilized zirconia surface in a dual catalyst bed.

    PubMed

    Richard, Mélissandre; Can, Fabien; Duprez, Daniel; Gil, Sonia; Giroir-Fendler, Anne; Bion, Nicolas

    2014-10-13

    Yttrium-stabilized zirconia (YSZ) has been extensively studied as an electrolyte material for solid oxide fuel cells (SOFC) but its performance in heterogeneous catalysis is also the object of a growing number of publications. In both applications, oxygen activation on the YSZ surface remains the step that hinders utilization at moderate temperature. It was demonstrated by oxygen isotope exchange that a dual catalyst bed system consisting of two successive LaMnO3 and YSZ beds without intimate contact drastically enhances oxygen activation on the YSZ surface at 698 K. It can be concluded that LaMnO3 activates the triplet ground-state of molecular oxygen into a low-lying singlet state, thereby facilitating the activation of the O2 molecule on the YSZ oxygen vacancy sites. This phenomenon is shown to improve the catalytic activity of the LaMnO3-Pd/YSZ system for the partial oxidation of methane.

  17. RF plasma enhanced MOCVD of yttria stabilized zirconia thin films using octanedionate precursors and their characterization

    NASA Astrophysics Data System (ADS)

    Chopade, S. S.; Nayak, C.; Bhattacharyya, D.; Jha, S. N.; Tokas, R. B.; Sahoo, N. K.; Deo, M. N.; Biswas, A.; Rai, Sanjay; Thulasi Raman, K. H.; Rao, G. M.; Kumar, Niranjan; Patil, D. S.

    2015-11-01

    Yttria stabilized zirconia thin films have been deposited by RF plasma enhanced MOCVD technique on silicon substrates at substrate temperature of 400 °C. Plasma of precursor vapors of (2,7,7-trimethyl-3,5-octanedionate) yttrium (known as Y(tod)3), (2,7,7-trimethyl-3,5-octanedionate) zirconium (known as Zr(tod)4), oxygen and argon gases is used for deposition. To the best of our knowledge, plasma assisted MOCVD of YSZ films using octanediaonate precursors have not been reported in the literature so far. The deposited films have been characterized by GIXRD, FTIR, XPS, FESEM, AFM, XANES, EXAFS, EDAX and spectroscopic ellipsometry. Thickness of the films has been measured by stylus profilometer while tribological property measurement has been done to study mechanical behavior of the coatings. Characterization by different techniques indicates that properties of the films are dependent on the yttria content as well as on the structure of the films.

  18. Enhanced silencing and stabilization of siRNA polyplexes by histidine-mediated hydrogen bonds

    PubMed Central

    Chou, Szu-Ting; Hom, Kellie; Zhang, Daoning; Leng, Qixin; Tricoli, Lucas J.; Hustedt, Jason M.; Lee, Amy; Shapiro, Michael J.; Seog, Joonil; Kahn, Jason D.; Mixson, A. James

    2013-01-01

    Branched peptides containing histidines and lysines (HK) have been shown to be effective carriers for DNA and siRNA. We anticipate that elucidation of the binding mechanism of HK with siRNA will provide greater insight into the self-assembly and delivery of the HK:siRNA polyplex. Non-covalent bonds between histidine residues and nucleic acids may enhance the stability of siRNA polyplexes. We first compared the polyplex biophysical properties of a branched HK with those of branched asparagines-lysine peptide (NK). Consistent with siRNA silencing experiments, gel electrophoresis demonstrated that the HK siRNA polyplex maintained its integrity with prolonged incubation in serum, whereas siRNA in complex with NK was degraded in a time-dependent manner. Isothermal titration calorimetry of various peptides binding to siRNA at pH 7.3 showed that branched polylysine, interacted with siRNA was initially endothermic, whereas branched HK exhibited an exothermic reaction at initial binding. The exothermic interaction indicates formation of non-ionic bonds between histidines and siRNA; purely electrostatic interaction is entropy-driven and endothermic. To investigate the type of non-ionic bond, we studied the protonation state of imidazole rings of a selectively 15N labeled branched HK by heteronuclear single quantum coherence NMR. The peak of Nδ1-H tautomers of imidazole shifted downfield (in the direction of deprotonation) by 0.5 to 1.0 ppm with addition of siRNA, providing direct evidence that histidines formed hydrogen bonds with siRNA at physiological pH. These results establish that histidine-rich peptides form hydrogen bonds with siRNA, thereby enhancing the stability and biological activity of the polyplex in vitro and in vivo. PMID:24161165

  19. IQGAP1 interacts with Aurora-A and enhances its stability and its role in cancer

    SciTech Connect

    Yin, Ning; Shi, Ji; Wang, Dapeng; Tong, Tong; Wang, Mingrong; Fan, Feiyue; Zhan, Qimin

    2012-04-27

    Highlights: Black-Right-Pointing-Pointer IQGAP1 interacts with Aurora-A through its RGCt domain. Black-Right-Pointing-Pointer Overexpression of IQGAP1 prevents ubiquitination of Aurora-A. Black-Right-Pointing-Pointer Overexpression of IQGAP1 enhances the protein stability of Aurora-A. Black-Right-Pointing-Pointer Overexpression of IQGAP1 promotes the kinase activity of Aurora-A. -- Abstract: IQGAP1, a ubiquitously expressed scaffold protein, has been identified in a wide range of organisms. It participates in multiple aspects of cellular events by binding to and regulating numerous interacting proteins. In our present study, we identified a new IQGAP1 binding protein named Aurora-A which is an oncogenic protein and overexpressed in various types of human tumors. In vitro analysis with GST-Aurora-A fusion proteins showed a physical interaction between Aurora-A and IQGAP1. Moreover, the binding also occurred in HeLa cells as endogenous Aurora-A co-immunoprecipitated with IQGAP1 from the cell lysates. Overexpression of IQGAP1 resulted in an elevation of both expression and activity of Aurora-A kinase. Endogenous IQGAP1 knockdown by siRNA promoted Aurora-A degradation whereas IQGAP1 overexpression enhanced the stability of Aurora-A. Additionally, we documented that the IQGAP1-induced cell proliferation was suppressed by knocking down Aurora-A expression. Taken together, our results showed an unidentified relationship between Aurora-A and IQGAP1, and provided a new insight into the molecular mechanism by which IQGAP1 played a regulatory role in cancer.

  20. Hydrocaffeic acid-chitosan nanoparticles with enhanced stability, mucoadhesion and permeation properties.

    PubMed

    Soliman, Ghareb M; Zhang, Yu Ling; Merle, Geraldine; Cerruti, Marta; Barralet, Jake

    2014-11-01

    Catechol-containing molecules, such as hydrocaffeic acid (HCA) have been shown to increase the mucoadhesion of several polymers. We report here a simple and bioinspired approach to enhance chitosan (CS) mucoadhesion and stabilize it in nanoparticulate form by preparing HCA-CS conjugates. HCA-CS conjugates containing 6 and 15mol% HCA were synthesized and characterized by FT-IR, (1)H NMR and UV-vis spectrophotometry. HCA-CS nanoparticles prepared by ionic gelation with sodium tripolyphosphate (TPP) ranged in size between 100 and 250nm depending on the polymer and TPP/CS weight ratio. In contrast to CS nanoparticles, which aggregate at pH>6.5, HCA-CS nanoparticles did not show any sign of aggregation or precipitation over the 4-10 pH range and maintain their size. Unexpectedly, HCA-CS nanoparticles also maintained their size and polydispersity index at pH 7.4 and NaCl concentrations of up to 500mM. Partial oxidation of HCA resulted in nanoparticle cross-linking and improved stability at pH<4. HCA-CS mucoadhesion to rabbit small intestine was 6 times higher than unmodified CS. CS and HCA-CS nanoparticles were able to induce reversible tight junction opening in Caco-2 cell monolayers. Tight junction opening facilitated the permeability of a model hydrophilic molecule, fluorescein isothiocyanate-labeled dextran (FD4) and was 3 times higher in the cells treated with HCA-CS 15% nanoparticles compared to control groups. HCA-CS conjugates were found to be excellent candidates for stable nanodelivery systems with enhanced oral absorption of hydrophilic molecules.

  1. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties.

    PubMed

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Huang, Jingfeng; Tan, Dunlin; Zhang, Bowei; Teo, Edwin Hang Tong; Tok, Alfred Iing Yoong

    2016-06-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ∼4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (∼60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications. PMID:27227818

  2. Formation of disulfide bonds in insect prophenoloxidase enhances immunity through improving enzyme activity and stability.

    PubMed

    Lu, Anrui; Peng, Qin; Ling, Erjun

    2014-06-01

    Type 3 copper proteins, including insect prophenoloxidase (PPO), contain two copper atoms in the active site pocket and can oxidize phenols. Insect PPO plays an important role in immunity. Insects and other invertebrates show limited recovery from pathogen invasion and wounds if phenoloxidase (PO) activity is low. In most insect PPOs, two disulfide bonds are present near the C-terminus. However, in Pimpla hypochondriaca (a parasitoid wasp), each PPO contains one disulfide bond. We thus questioned whether the formation of two sulfide bonds in insect PPOs improved protein stability and/or increased insect innate immunity over time. Using Drosophila melanogaster PPO1 as a model, one or two disulfide bonds were deleted to evaluate the importance of disulfide bonds in insect immunity. rPPO1 and mutants lacking disulfide bonds could be expressed and showed PO activity. However, the PO activities of mutants lacking one or two disulfide bonds significantly decreased. Deletion of disulfide bonds also reduced PPO thermostability. Furthermore, antibacterial activities against Escherichia coli and Bacillus subtilis significantly decreased when disulfide bonds were deleted. Therefore, the formation of two disulfide bond(s) in insect PPO enhances antibacterial activity by increasing PO activity and stability.

  3. α-SNAP Enhances SNARE Zippering by Stabilizing the SNARE Four-Helix Bundle.

    PubMed

    Ma, Lu; Kang, Yuhao; Jiao, Junyi; Rebane, Aleksander A; Cha, Hyo Keun; Xi, Zhiqun; Qu, Hong; Zhang, Yongli

    2016-04-19

    Intracellular membrane fusion is mediated by dynamic assembly and disassembly of soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptors (SNAREs). α-SNAP guides NSF to disassemble SNARE complexes after membrane fusion. Recent experiments showed that α-SNAP also dramatically enhances SNARE assembly and membrane fusion. How α-SNAP is involved in these opposing activities is not known. Here, we examine the effect of α-SNAP on the stepwise assembly of the synaptic SNARE complex using optical tweezers. We found that α-SNAP destabilized the linker domain (LD) of the SNARE complex but stabilized its C-terminal domain (CTD) through a conformational selection mechanism. In contrast, α-SNAP minimally affected assembly of the SNARE N-terminal domain (NTD), indicating that α-SNAP barely bound the partially assembled trans-SNARE complex. Thus, α-SNAP recognizes the folded CTD for SNARE disassembly with NSF and subtly modulates membrane fusion by altering the stabilities of the SNARE CTD and LD.

  4. Urease immobilized polymer hydrogel: Long-term stability and enhancement of enzymatic activity.

    PubMed

    Kutcherlapati, S N Raju; Yeole, Niranjan; Jana, Tushar

    2016-02-01

    A method has been developed in which an enzyme namely urease was immobilized inside hydrogel matrix to study the stability and enzymatic activity in room temperature (∼27-30°C). This urease coupled hydrogel (UCG) was obtained by amine-acid coupling reaction and this procedure is such that it ensured the wider opening of mobile flap of enzyme active site. A systematic comparison of urea-urease assay and the detailed kinetic data clearly revealed that the urease shows activity for more than a month when stored at ∼27-30°C in case of UCG whereas it becomes inactive in case of free urease (enzyme in buffer solution). The aqueous microenvironment inside the hydrogel, unusual morphological features and thermal behaviour were believed to be the reasons for unexpected behaviour. UCG displayed enzyme activity at basic pH and up to 60°C. UCG showed significant enhancement in activity against thermal degradation compared to free urease. In summary, this method is a suitable process to stabilize the biomacromolecules in standard room temperature for many practical uses.

  5. Bee species diversity enhances productivity and stability in a perennial crop.

    PubMed

    Rogers, Shelley R; Tarpy, David R; Burrack, Hannah J

    2014-01-01

    Wild bees provide important pollination services to agroecoystems, but the mechanisms which underlie their contribution to ecosystem functioning--and, therefore, their importance in maintaining and enhancing these services-remain unclear. We evaluated several mechanisms through which wild bees contribute to crop productivity, the stability of pollinator visitation, and the efficiency of individual pollinators in a highly bee-pollination dependent plant, highbush blueberry. We surveyed the bee community (through transect sampling and pan trapping) and measured pollination of both open- and singly-visited flowers. We found that the abundance of managed honey bees, Apis mellifera, and wild-bee richness were equally important in describing resulting open pollination. Wild-bee richness was a better predictor of pollination than wild-bee abundance. We also found evidence suggesting pollinator visitation (and subsequent pollination) are stabilized through the differential response of bee taxa to weather (i.e., response diversity). Variation in the individual visit efficiency of A. mellifera and the southeastern blueberry bee, Habropoda laboriosa, a wild specialist, was not associated with changes in the pollinator community. Our findings add to a growing literature that diverse pollinator communities provide more stable and productive ecosystem services. PMID:24817218

  6. Bee Species Diversity Enhances Productivity and Stability in a Perennial Crop

    PubMed Central

    Rogers, Shelley R.; Tarpy, David R.; Burrack, Hannah J.

    2014-01-01

    Wild bees provide important pollination services to agroecoystems, but the mechanisms which underlie their contribution to ecosystem functioning—and, therefore, their importance in maintaining and enhancing these services—remain unclear. We evaluated several mechanisms through which wild bees contribute to crop productivity, the stability of pollinator visitation, and the efficiency of individual pollinators in a highly bee-pollination dependent plant, highbush blueberry. We surveyed the bee community (through transect sampling and pan trapping) and measured pollination of both open- and singly-visited flowers. We found that the abundance of managed honey bees, Apis mellifera, and wild-bee richness were equally important in describing resulting open pollination. Wild-bee richness was a better predictor of pollination than wild-bee abundance. We also found evidence suggesting pollinator visitation (and subsequent pollination) are stabilized through the differential response of bee taxa to weather (i.e., response diversity). Variation in the individual visit efficiency of A. mellifera and the southeastern blueberry bee, Habropoda laboriosa, a wild specialist, was not associated with changes in the pollinator community. Our findings add to a growing literature that diverse pollinator communities provide more stable and productive ecosystem services. PMID:24817218

  7. In vitro hyperthermia with improved colloidal stability and enhanced SAR of magnetic core/shell nanostructures.

    PubMed

    Patil, R M; Thorat, N D; Shete, P B; Otari, S V; Tiwale, B M; Pawar, S H

    2016-02-01

    Magnetic core/shell nanostructures of Fe3O4 nanoparticles coated with oleic acid and betaine-HCl were studied for their possible use in magnetic fluid hyperthermia (MFH). Their colloidal stability and heat induction ability were studied in different media viz. phosphate buffer solution (PBS), saline solution and glucose solution with different physiological conditions and in human serum. The results showed enhanced colloidal stability in these media owing to their high zeta potential values. Heat induction studies showed that specific absorption rates (SAR) of core/shells were 82-94W/g at different pH of PBS and concentrations of NaCl and glucose. Interestingly, core/shells showed 78.45±3.90W/g SAR in human serum. The cytotoxicity of core/shells done on L929 and HeLa cell lines using 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide and trypan blue dye exclusion assays showed >89% and >80% cell viability for 24 and 48h respectively. Core/shell structures were also found to be very efficient for in vitro MFH on cancer cell line. About 95% cell death was occurred in 90min after hyperthermia treatment. The mechanism of cell death was found to be elevated ROS generation in cells after exposure to core/shells in external magnetic field. This study showed that these core/shells have a great potential to be used in in vivo MFH. PMID:26652424

  8. Nanoalloy Printed and Pulse-Laser Sintered Flexible Sensor Devices with Enhanced Stability and Materials Compatibility.

    PubMed

    Zhao, Wei; Rovere, Thomas; Weerawarne, Darshana; Osterhoudt, Gavin; Kang, Ning; Joseph, Pharrah; Luo, Jin; Shim, Bonggu; Poliks, Mark; Zhong, Chuan-Jian

    2015-06-23

    While conformal and wearable devices have become one of the most desired formats for printable electronics, it is challenging to establish a scalable process that produces stable conductive patterns but also uses substrates compatible with widely available wearable materials. Here, we describe findings of an investigation of a nanoalloy ink printed and pulsed-laser sintered conductive patterns as flexible functional devices with enhanced stability and materials compatibility. While nanoparticle inks are desired for printable electronics, almost all existing nanoparticle inks are based on single-metal component, which, as an electronic element, is limited by its inherent stabilities of the metal such as propensity of metal oxidation and mobility of metal ions, especially in sintering processes. The work here has demonstrated the first example in exploiting plasmonic coupling of nanoalloys and pulsed-laser energy with controllable thermal penetration. The experimental and theoretical results have revealed clear correlation between the pulsed laser parameters and the nanoalloy structural characteristics. The superior performance of the resulting flexible sensor device, upon imparting nanostructured sensing materials, for detecting volatile organic compounds has significant implications to developing stable and wearable sensors for monitoring environmental pollutants and breath biomarkers. This simple "nanoalloy printing-laser sintering-nanostructure printing" process is entirely general to many different sensor devices and nanostructured sensing materials, enabling the ability to easily construct sophisticated sensor array.

  9. Urease immobilized polymer hydrogel: Long-term stability and enhancement of enzymatic activity.

    PubMed

    Kutcherlapati, S N Raju; Yeole, Niranjan; Jana, Tushar

    2016-02-01

    A method has been developed in which an enzyme namely urease was immobilized inside hydrogel matrix to study the stability and enzymatic activity in room temperature (∼27-30°C). This urease coupled hydrogel (UCG) was obtained by amine-acid coupling reaction and this procedure is such that it ensured the wider opening of mobile flap of enzyme active site. A systematic comparison of urea-urease assay and the detailed kinetic data clearly revealed that the urease shows activity for more than a month when stored at ∼27-30°C in case of UCG whereas it becomes inactive in case of free urease (enzyme in buffer solution). The aqueous microenvironment inside the hydrogel, unusual morphological features and thermal behaviour were believed to be the reasons for unexpected behaviour. UCG displayed enzyme activity at basic pH and up to 60°C. UCG showed significant enhancement in activity against thermal degradation compared to free urease. In summary, this method is a suitable process to stabilize the biomacromolecules in standard room temperature for many practical uses. PMID:26520823

  10. Nanoalloy Printed and Pulse-Laser Sintered Flexible Sensor Devices with Enhanced Stability and Materials Compatibility

    SciTech Connect

    Zhao, Wei; Rovore, Thomas; Weerawarne, Darshana; Osterhoudt, Gavin; Kang, Ning; Joseph, Pharrah; Luo, Jin; Shim, Bonggu; Poliks, Mark; Zhong, Chuan-Jian

    2015-06-02

    While conformal and wearable devices have become one of the most desired formats for printable electronics, it is challenging to establish a scalable process that produces stable conductive patterns but also uses substrates compatible with widely available wearable materials. Here, we describe findings of an investigation of a nanoalloy ink printed and pulsed laser sintered conductive patterns as flexible functional devices with enhanced stability and materials compatibility. While nanoparticle inks are desired for printable electronics, almost all existing nanoparticle inks are based on single-metal component, which, as an electronic element, is limited by its inherent stabilities of the metal such as propensity of metal oxidation and mobility of metal ions, especially in sintering processes. The work here has demonstrated the first example in exploiting plasmonic coupling of nanoalloys and pulsed-laser energy with controllable thermal penetration. The experimental and theoretical results have revealed clear correlation between the pulsed laser parameters and the nanoalloy structural characteristics. The superior performance of the resulting flexible sensor device, upon imparting nanostructured sensing materials, for detecting volatile organic compounds has significant implications to developing stable and wearable sensors for monitoring environmental pollutants and breath biomarkers. This simple “nanoalloy printing 'laser sintering' nanostructure printing” process is entirely general to many different sensor devices and nanostructured sensing materials, enabling the ability to easily construct sophisticated sensor array.

  11. Development of New Geothermal Wellbore Holdup Correlations Using Flowing Well Data

    SciTech Connect

    Garg, S.K.; Pritchett, J.W.; Alexander, J.H.

    2004-03-01

    An ability to predict both the quantity of fluid that can be produced and its thermodynamic state (pressure, temperature, enthalpy, gas content, salinity, etc.) is essential for estimating the total usable energy of a geothermal resource. Numerical reservoir simulators can be utilized to calculate the thermodynamic state of the fluid at the underground feed-zone(s) at which the fluid enters the wellbore. The computation of the well-head fluid properties from a given underground state (or vice-versa) requires the use of a wellbore simulator. The fluid flow in the wellbore is not amenable to strict analytical treatment. Depending upon the relative amounts of gas and liquid, a variety of flow patterns can occur in the pipe. At small gas loadings, bubble flow takes place. An increase in gas flow rate can result in slug, churn or annular flow. Existing methods for treating two-phase flow in a wellbore require use of empirical correlations for action factor and for liquid hold-up.

  12. Enhanced stability of multilayer graphene-supported catalysts for polymer electrolyte membrane fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Marinkas, A.; Hempelmann, R.; Heinzel, A.; Peinecke, V.; Radev, I.; Natter, H.

    2015-11-01

    One of the biggest challenges in the field of polymer electrolyte membrane fuel cells (PEMFC) is to enhance the lifetime and the long-term stability of PEMFC electrodes, especially of cathodes, furthermore, to reduce their platinum loading, which could lead to a cost reduction for efficient PEMFCs. These demands could be achieved with a new catalyst support architecture consisting of a composite of carbon structures with significant different morphologies. A highly porous cathode catalyst support layer is prepared by addition of various carbon types (carbon black particles, multi-walled carbon nanotubes (MWCNT)) to multilayer graphene (MLG). The reported optimized cathodes shows extremely high durability and similar performance to commercial standard cathodes but with 89% lower Pt loading. The accelerated aging protocol (AAP) on the membrane electrode assemblies (MEA) shows that the presence of MLG increases drastically the durability and the Pt-extended electrochemical surface area (ECSA). In fact, after the AAP slightly enhanced performance can be observed for the MLG-containing cathodes instead of a performance loss, which is typical for the commercial carbon-based cathodes. Furthermore, the presence of MLG drastically decreases the ECSA loss rate. The MLG-containing cathodes show up to 6.8 times higher mass-normalized Pt-extended ECSA compared to the commercial standard systems.

  13. Sweeter and stronger: enhancing sweetness and stability of the single chain monellin MNEI through molecular design

    PubMed Central

    Leone, Serena; Pica, Andrea; Merlino, Antonello; Sannino, Filomena; Temussi, Piero Andrea; Picone, Delia

    2016-01-01

    Sweet proteins are a family of proteins with no structure or sequence homology, able to elicit a sweet sensation in humans through their interaction with the dimeric T1R2-T1R3 sweet receptor. In particular, monellin and its single chain derivative (MNEI) are among the sweetest proteins known to men. Starting from a careful analysis of the surface electrostatic potentials, we have designed new mutants of MNEI with enhanced sweetness. Then, we have included in the most promising variant the stabilising mutation E23Q, obtaining a construct with enhanced performances, which combines extreme sweetness to high, pH-independent, thermal stability. The resulting mutant, with a sweetness threshold of only 0.28 mg/L (25 nM) is the strongest sweetener known to date. All the new proteins have been produced and purified and the structures of the most powerful mutants have been solved by X-ray crystallography. Docking studies have then confirmed the rationale of their interaction with the human sweet receptor, hinting at a previously unpredicted role of plasticity in said interaction. PMID:27658853

  14. Chitosan nanocomposite films: enhanced electrical conductivity, thermal stability, and mechanical properties.

    PubMed

    Marroquin, Jason B; Rhee, K Y; Park, S J

    2013-02-15

    A novel, high-performance Fe(3)O(4)/MWNT/Chitosan nanocomposite has been prepared by a simple solution evaporation method. A significant synergistic effect of Fe(3)O(4) and MWNT provided enhanced electrical conductivity, mechanical properties, and thermal stability on the nanocomposites. A 5% (wt) loading of Fe(3)O(4)/MWNT in the nanocomposite increased conductivity from 5.34×10(-5) S/m to 1.49×10(-2) S/m compared to 5% (wt) MWNT loadings. The Fe(3)O(4)/MWNT/Chitosan films also exhibited increases in tensile strength and modulus of 70% and 155%, respectively. The integral procedure decomposition temperature (IPDT) was enhanced from 501 °C to 568 °C. These effects resulted from a number of factors: generation of a greater number of conductive channels through interactions between MWNT and Fe(3)O(4) surfaces, a higher relative crystallinity, the antiplasticizing effects of Fe(3)O(4), a restricted mobility and hindrance of depolymerization of the Chitosan chain segments, as well as uniform distribution, improved dispersion, and strong interfacial adhesion between the MWNT and Chitosan matrix.

  15. Enhanced stability and local structure in biologically relevant amorphous materials containing pyrophosphate

    SciTech Connect

    Slater, Colin; Laurencin, Danielle; Burnell, Victoria; Smith, Mark E.; Grover, Liam M.; Hriljac, Joseph A.; Wright, Adrian J.

    2012-10-25

    There is increasing evidence that amorphous inorganic materials play a key role in biomineralisation in many organisms, however the inherent instability of synthetic analogues in the absence of the complex in vivo matrix limits their study and clinical exploitation. To address this, we report here an approach that enhances long-term stability to >1 year of biologically relevant amorphous metal phosphates, in the absence of any complex stabilizers, by utilizing pyrophosphates (P{sub 2}O{sub 7}{sup 4-}); species themselves ubiquitous in vivo. Ambient temperature precipitation reactions were employed to synthesise amorphous Ca{sub 2}P{sub 2}O{sub 7}.nH{sub 2}O and Sr{sub 2}P{sub 2}O{sub 7}.nH{sub 2}O (3.8 < n < 4.2) and their stability and structure were investigated. Pair distribution functions (PDF) derived from synchrotron X-ray data indicated a lack of structural order beyond 8 {angstrom} in both phases, with this local order found to resemble crystalline analogues. Further studies, including {sup 1}H and {sup 31}P solid state NMR, suggest the unusually high stability of these purely inorganic amorphous phases is partly due to disorder in the P-O-P bond angles within the P{sub 2}O{sub 7} units, which impede crystallization, and to water molecules, which are involved in H-bonds of various strengths within the structures and hamper the formation of an ordered network. In situ high temperature powder X-ray diffraction data indicated that the amorphous nature of both phases surprisingly persisted to 450 C. Further NMR and TGA studies found that above ambient temperature some water molecules reacted with P{sub 2}O{sub 7} anions, leading to the hydrolysis of some P-O-P linkages and the formation of HPO{sub 4}{sup 2-} anions within the amorphous matrix. The latter anions then recombined into P{sub 2}O{sub 7} ions at higher temperatures prior to crystallization. Together, these findings provide important new materials with unexplored potential for enzyme

  16. Iron casein succinylate-chitosan coacervate for the liquid oral delivery of iron with bioavailability and stability enhancement.

    PubMed

    Min, Kyoung Ah; Cho, Jung-Hye; Song, Yun-Kyoung; Kim, Chong-Kook

    2016-01-01

    Iron casein succinylate (ICS) liquid oral preparation as iron supplement has uncomfortable taste after a long period of storage because of its stability, and poor bioavailability of iron compared to any other iron preparations. To improve the chemical stability of ICS and enhance the bioavailability of iron, chitosan-ICS nanoparticles (NPs) were prepared by complex coacervation method and stabilized with polyethylene glycol (PEG) 400. NPs were spherical (mean diameter of 830-1070 nm) with positive charge (+30-60 mV) depending on the composition of NPs. Addition of PEG400 (2 w/v %) increased the zeta potential (26-50 %) and physical stability of chitosan-ICS NPs suspension. Also, NPs decreased iron release compared to ICS after 7-weeks of storage at 4 °C. NPs markedly increased the permeability of iron in Caco-2 cell up to 32-38-fold compared to ICS, while physical mixture of chitosan and ICS increased the iron permeability only 2.5-fold. In summary, NPs improved the physicochemical stability and enhanced the transport of iron compared to other iron preparations in Caco-2 cell model. Thus, chitosan-ICS coacervate might be a promising candidate as a liquid oral iron delivery system for iron deficiency patients with stability and bioavailability enhancement.

  17. Improved Modeling of Naturally Fractured Reservoirs by Quantitatively Handling Flow Convergence into the Wellbore

    NASA Astrophysics Data System (ADS)

    Stadelman, M.; Crandall, D.; Sams, W. N.; Bromhal, G. S.

    2015-12-01

    Complex fractured networks in the subsurface control the flow of fluids in many applications, and accurately modeling their interaction with wells is critical to understanding their behavior. For tight sand and shale formations, fluid flow is primarily restricted to fractures within each rock layer. NFFLOW was designed by the Department of Energy to model gas well production from naturally fractured reservoirs. NFFLOW is a discrete fracture simulator, with every fracture and rock matrix in the domain handled individually. One-dimensional models are used calculate the flow through connected fractures and flow from the surrounding rocks into fractures. Flow into wellbores are determined from the combined flux from connecting fractures and adjacent rock matrices. One-dimensional fluid flow equations are used because they are extremely fast to solve and represent a reasonable approximation of the physical behavior of fluids in most of the reservoir. However, near the wellbore those models become inaccurate due to gas flow convergence, which is a multidimensional situation. We present a method to correct the one-dimensional models, using data from two-dimensional fluid flow models, while maintaining the original simulator speed. By applying corrections from the two-dimensional model, the one-dimensional models can better account for gas flow convergence into the wellbore as well as the location of the wellbore within the rock strata. Corrections were successful in scaling the one-dimensional flow rates to match the two dimensional values over a wide range of parameters for both fracture flow and porous media flow into the wellbore. This is shown to increase the accuracy of history matching to production data for a wide range of wells, allowing for better modeling and prediction of future productivity. With an accurate history match established, NFFLOW can then be used to investigate issues such as the ability of the formation to sequester carbon dioxide or the effects

  18. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties

    NASA Astrophysics Data System (ADS)

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Huang, Jingfeng; Tan, Dunlin; Zhang, Bowei; Teo, Edwin Hang Tong; Tok, Alfred Iing Yoong

    2016-05-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ~4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (~60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications.Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability

  19. Stability and solubility enhancement of ellagic acid in cellulose ester solid dispersions.

    PubMed

    Li, Bin; Harich, Kim; Wegiel, Lindsay; Taylor, Lynne S; Edgar, Kevin J

    2013-02-15

    Structurally varied, carboxyl-containing cellulose derivatives were evaluated for their ability to form amorphous solid dispersions (ASD) with ellagic acid (EA), in order to improve the solubility of this high-melting, poorly bioavailable, but highly bioactive natural flavonoid compound. ASDs of EA with carboxymethylcellulose acetate butyrate (CMCAB), cellulose acetate adipate propionate (CAAdP), and hydroxypropylmethylcellulose acetate succinate (HPMCAS) were prepared, and EA dissolution from these ASDs was compared with that from pure crystalline EA and from EA/poly(vinylpyrrolidinone) (PVP) solid dispersions (SD). Polymer/drug mixtures were characterized by powder X-ray diffraction (XRPD), modulated differential scanning calorimetry (MDSC), nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FT-IR). The XRPD and FT-IR results indicated that EA was amorphous in solid dispersions with EA concentration up to 25 wt%. The stability against crystallization and solution concentrations of EA from these solid dispersions were significantly higher than those observed for physical mixtures and pure crystalline EA. HPMCAS stabilized EA most effectively, among the polymers tested, against both chemical degradation and recrystallization. The relative ability to solubilize EA from ASDs at pH 6.8 was PVP>HPMCAS>CMCAB. EA dissolves from ASD in PVP quickly and completely (maximum 92%) at pH 6.8, but EA is also released from PVP at pH 1.2, and then crystallizes rapidly. Therefore PVP is not a practical candidate for EA ASD. In contrast, the cellulose derivative ASDs show very slow EA release at pH 1.2 (<4%) and faster but still incomplete drug release at pH 6.8 (maximum 35% for HPMCAS SD). The pH-triggered drug release from HPMCAS ASD makes HPMCAS a practical choice for EA solubility enhancement. PMID:23399175

  20. Flow-Enhanced Stability of Rolling Adhesion through E-Selectin.

    PubMed

    Li, Quhuan; Wayman, Annica; Lin, Jiangguo; Fang, Ying; Zhu, Cheng; Wu, Jianhua

    2016-08-23

    Selectin-ligand interactions mediate tethering and rolling of circulating leukocytes on the vessel wall during inflammation. Extensive study has been devoted to elucidating the kinetic and mechanical constraints of receptor-ligand-interaction-mediated leukocyte adhesion, yet many questions remain unanswered. Here, we describe our design of an inverted flow chamber to compare adhesions of HL-60 cells to E-selectin in the upright and inverted orientations. This new, to our knowledge, design allowed us to evaluate the effect of gravity and to investigate the mechanisms of flow-enhanced adhesion. Cell rolling in the two orientations was qualitatively similar, and the quantitative differences can be explained by the effect of gravity, which promotes free-flowing cells to tether and detached cells to reattach to the surface in the upright orientation but prevents such attachment from happening in the inverted orientation. We characterized rolling stability by the lifetime of rolling adhesion and detachment of rolling cells, which could be easily measured in the inverted orientation, but not in the upright orientation because of the reattachment of transiently detached cells. Unlike the transient tether lifetime of E-selectin-ligand interaction, which exhibited triphasic slip-catch-slip bonds, the lifetime of rolling adhesion displayed a biphasic trend that first increased with the wall shear stress, reached a maximum at 0.4 dyn/cm(2), and then decreased gradually. We have developed a minimal mathematical model for the probability of rolling adhesion. Comparison of the theoretical predictions to data has provided model validation and allowed evaluation of the effective two-dimensional association on-rate, kon, and the binding affinity, Ka, of the E-selectin-ligand interaction. kon increased with the wall shear stress from 0.1 to 0.7 dyn/cm(2). Ka first increased with the wall shear stress, reached a maximum at 0.4 dyn/cm(2), and then decreased gradually. Our results

  1. Oxidative-stability enhancement and charge transport mechanism in glyme-lithium salt equimolar complexes.

    PubMed

    Yoshida, Kazuki; Nakamura, Megumi; Kazue, Yuichi; Tachikawa, Naoki; Tsuzuki, Seiji; Seki, Shiro; Dokko, Kaoru; Watanabe, Masayoshi

    2011-08-24

    The oxidative stability of glyme molecules is enhanced by the complex formation with alkali metal cations. Clear liquid can be obtained by simply mixing glyme (triglyme or tetraglyme) with lithium bis(trifluoromethylsulfonyl)amide (Li[TFSA]) in a molar ratio of 1:1. The equimolar complex [Li(triglyme or tetraglyme)(1)][TFSA] maintains a stable liquid state over a wide temperature range and can be regarded as a room-temperature ionic liquid consisting of a [Li(glyme)(1)](+) complex cation and a [TFSA](-) anion, exhibiting high self-dissociativity (ionicity) at room temperature. The electrochemical oxidation of [Li(glyme)(1)][TFSA] takes place at the electrode potential of ~5 V vs Li/Li(+), while the oxidation of solutions containing excess glyme molecules ([Li(glyme)(x)][TFSA], x > 1) occurs at around 4 V vs Li/Li(+). This enhancement of oxidative stability is due to the donation of lone pairs of ether oxygen atoms to the Li(+) cation, resulting in the highest occupied molecular orbital (HOMO) energy level lowering of a glyme molecule, which is confirmed by ab initio molecular orbital calculations. The solvation state of a Li(+) cation and ion conduction mechanism in the [Li(glyme)(x)][TFSA] solutions is elucidated by means of nuclear magnetic resonance (NMR) and electrochemical methods. The experimental results strongly suggest that Li(+) cation conduction in the equimolar complex takes place by the migration of [Li(glyme)(1)](+) cations, whereas the ligand exchange mechanism is overlapped when interfacial electrochemical reactions of [Li(glyme)(1)](+) cations occur. The ligand exchange conduction mode is typically seen in a lithium battery with a configuration of [Li anode|[Li(glyme)(1)][TFSA]|LiCoO(2) cathode] when the discharge reaction of a LiCoO(2) cathode, that is, desolvation of [Li(glyme)(1)](+) and insertion of the resultant Li(+) into the cathode, occurs at the electrode-electrolyte interface. The battery can be operated for more than 200 charge

  2. Photo-cross-linking approach to engineering small tyrosine-containing peptide hydrogels with enhanced mechanical stability.

    PubMed

    Ding, Yin; Li, Ying; Qin, Meng; Cao, Yi; Wang, Wei

    2013-10-29

    Peptide-based supramolecular hydrogels have been extensively explored in biomaterials owing to their unique bioactive, stimulus-responsive, and biocompatible features. However, peptide-based hydrogels often have low mechanical stability with storage moduli of 10-1000 Pa. They are susceptible to mechanical destruction and solvent erosion, greatly hindering their practical application. Here, we present a photo-cross-linking strategy to enhance the mechanical stability of a peptide-based hydrogel by 10(4)-fold with a storage modulus of ~100 kPa, which is one of the highest reported so far for hydrogels made of small peptide molecules. This method is based on the ruthenium-complex-catalyzed conversion of tyrosine to dityrosine upon light irradiation. The reinforcement of the hydrogel through photo-cross-linking can be achieved within 2 min thanks to the fast reaction kinetics. The enhancement of the mechanical stability was due to the formation of a densely entangled fibrous network of peptide dimers through a dityrosine linkage. We showed that in order to implement this method successfully, the peptide sequence should be rationally designed to avoid the cross talk between self-assembly and cross-linking. This method is convenient and versatile for the enhancement of the mechanical stability of tyrosine-containing peptide-based hydrogels. We anticipate that the photo-cross-linked supramolecular hydrogels with much improved mechanical stability will find broad applications in tissue engineering and drug controlled release.

  3. Fluoride enhances transfection activity of carbonate apatite by increasing cytoplasmic stability of plasmid DNA

    SciTech Connect

    Chowdhury, E.H.

    2011-06-17

    Highlights: {yields} Cytoplasmic stability of plasmid DNA is enhanced by fluoride incorporation into carbonate apatite carrier. {yields} Fluoridated carbonate apatite promotes a robust increase in transgene expression. {yields} Controlled dissolution of fluoridated carbonate apatite in endosomal acidic environment might buffer the endosomes and prevent degradation of the released DNA. -- Abstract: Intracellular delivery of a functional gene or a nucleic acid sequence to specifically knockdown a harmful gene is a potential approach to precisely treat a critical human disease. The intensive efforts in the last few decades led to the development of a number of viral and non-viral synthetic vectors. However, an ideal delivery tool in terms of the safety and efficacy has yet to be established. Recently, we have developed pH-sensing inorganic nanocrystals of carbonate apatite for efficient and cell-targeted delivery of gene and gene-silencing RNA. Here we show that addition of very low level of fluoride to the particle-forming medium facilitates a robust increase in transgene expression following post-incubation of the particles with HeLa cells. Confocal microscopic observation and Southern blotting prove the cytoplasmic existence of plasmid DNA delivered by likely formed fluoridated carbonate apatite particles while degradation of plasmid DNA presumably by cytoplasmic nucleases was noticed following delivery with apatite particles alone. The beneficial role of fluoride in enhancing carbonate apatite-mediated gene expression might be due to the buffering potential of generated fluoridated apatite in endosomal acidic environment, thereby increasing the half-life of delivered plasmid DNA.

  4. Wellbore failure mechanisms in shales: Prediction and prevention

    SciTech Connect

    Gazaniol, D.; Forsans, T.; Boisson, M.J.F.; Piau, J.M.

    1994-12-31

    Shales stability is still one of the most important problems faced during drilling. Until recently, stability problems were attributed, most often to the swelling of shales. Recent research work performed by Elf and others shows that several mechanisms are involved, and that their relative importance can be estimated. A review of these mechanisms is presented here. More precisely, pore pressure diffusion, plasticity, anisotropy, capillary effects, osmosis, and physicochemical alteration are discussed. Considering all these phenomena, the way of acting of different kinds of muds is discussed. The practical use of rock mechanics models is also addressed.

  5. Array-level stability enhancement of 50 nm AlxOy ReRAM

    NASA Astrophysics Data System (ADS)

    Iwasaki, Tomoko Ogura; Ning, Sheyang; Yamazawa, Hiroki; Takeuchi, Ken

    2015-12-01

    ReRAM's low voltage and low current programmability are attractive features to solve the scaling issues of conventional floating gate Flash. However, read instability in ReRAM is a critical issue, due to random telegraph noise (RTN), sensitivity to disturb and retention. In this work, the array-level characteristics of read stability in 50 nm AlxOy ReRAM are investigated and a circuit technique to improve stability is proposed and evaluated. First, in order to quantitatively assess memory cell stability, a method of stability characterization is defined. Next, based on this methodology, a proposal to improve read stability, called "stability check loop" is evaluated. The stability check loop is a stability verification procedure, by which, instability improvement of 7×, and read error rate improvement of 40% are obtained.

  6. Ultrasound-enhanced drug delivery in prostate cancer xenografts by nanoparticles stabilizing microbubbles.

    PubMed

    Eggen, Siv; Fagerland, Stein-Martin; Mørch, Ýrr; Hansen, Rune; Søvik, Kishia; Berg, Sigrid; Furu, Håkon; Bøhn, Audun Dybvik; Lilledahl, Magnus B; Angelsen, Anders; Angelsen, Bjørn; de Lange Davies, Catharina

    2014-08-10

    The delivery of nanoparticles to solid tumors is often ineffective due to the lack of specificity towards tumor tissue, limited transportation of the nanoparticles across the vascular wall and poor penetration through the extracellular matrix of the tumor. Ultrasound is a promising tool that can potentially improve several of the transportation steps, and the interaction between sound waves and microbubbles generates biological effects that can be beneficial for the successful delivery of nanocarriers and their contents. In this study, a novel platform consisting of nanoparticle-stabilized microbubbles has been investigated for its potential for ultrasound-enhanced delivery to tumor xenografts. Confocal laser scanning microscopy was used to study the supply of nanoparticles from the vasculature and to evaluate the effect of different ultrasound parameters at a microscopic level. The results demonstrated that although the delivery is heterogeneous within tumors, there is a significant improvement in the delivery and the microscopic distribution of both nanoparticles and a released model drug when the nanoparticles are combined with microbubbles and ultrasound. The mechanisms that underlie the improved delivery are discussed.

  7. Silver-mediated base pairings: towards dynamic DNA nanostructures with enhanced chemical and thermal stability

    NASA Astrophysics Data System (ADS)

    Swasey, Steven M.; Gwinn, Elisabeth G.

    2016-04-01

    The thermal and chemical fragility of DNA nanomaterials assembled by Watson-Crick (WC) pairing constrain the settings in which these materials can be used and how they can be functionalized. Here we investigate use of the silver cation, Ag+, as an agent for more robust, metal-mediated self-assembly, focusing on the simplest duplex building blocks that would be required for more elaborate Ag+-DNA nanostructures. Our studies of Ag+-induced assembly of non-complementary DNA oligomers employ strands of 2-24 bases, with varied base compositions, and use electrospray ionization mass spectrometry to determine product compositions. High yields of duplex products containing narrowly distributed numbers of Ag+ can be achieved by optimizing solution conditions. These Ag+-mediated duplexes are stable to at least 60 mM Mg2+, higher than is necessary for WC nanotechnology schemes such as tile assemblies and DNA origami, indicating that sequential stages of Ag+-mediated and WC-mediated assembly may be feasible. Circular dichroism spectroscopy suggests simple helical structures for Ag+-mediated duplexes with lengths to at least 20 base pairs, and further indicates that the structure of cytosine-rich duplexes is preserved at high urea concentrations. We therefore propose an approach towards dynamic DNA nanomaterials with enhanced thermal and chemical stability through designs that combine sturdy silver-mediated ‘frames’ with WC paired ‘pictures’.

  8. Functionalization of Metal-Organic Frameworks for Enhanced Stability under Humid Carbon Dioxide Capture Conditions.

    PubMed

    Andirova, Dinara; Lei, Yu; Zhao, Xiaodan; Choi, Sunho

    2015-10-26

    Metal-organic frameworks (MOFs) have been highlighted recently as promising materials for CO2 capture. However, in practical CO2 capture processes, such as capture from flue gas or ambient air, the adsorption properties of MOFs tend to be harmed by the presence of moisture possibly because of the hydrophilic nature of the coordinatively unsaturated sites (CUSs) within their framework. In this work, the CUSs of the MOF framework are functionalized with amine-containing molecules to prevent structural degradation in a humid environment. Specifically, the framework of the magnesium dioxybenzenedicarboxylate (Mg/DOBDC) MOF was functionalized with ethylenediamine (ED) molecules to make the overall structure less hydrophilic. Structural analysis after exposure to high-temperature steam showed that the ED-functionalized Mg/DOBDC (ED-Mg/DOBDC) is more stable under humid conditions, than Mg/DOBDC, which underwent drastic structural changes. ED-Mg/DOBDC recovered its CO2 adsorption capacity and initial adsorption rate quite well as opposed to the original Mg/DOBDC, which revealed a significant reduction in its capture capacity and kinetics. These results suggest that the amine-functionalization of the CUSs is an effective way to enhance the structural stability of MOFs as well as their capture of humid CO2 . PMID:26367016

  9. Enhanced surface transfer doping of diamond by V2O5 with improved thermal stability

    NASA Astrophysics Data System (ADS)

    Crawford, Kevin G.; Cao, Liang; Qi, Dongchen; Tallaire, Alexandre; Limiti, E.; Verona, C.; Wee, Andrew T. S.; Moran, David A. J.

    2016-01-01

    Surface transfer doping of hydrogen-terminated diamond has been achieved utilising V2O5 as a surface electron accepting material. Contact between the oxide and diamond surface promotes the transfer of electrons from the diamond into the V2O5 as revealed by the synchrotron-based high resolution photoemission spectroscopy. Electrical characterization by Hall measurement performed before and after V2O5 deposition shows an increase in hole carrier concentration in the diamond from 3.0 × 1012 to 1.8 × 1013 cm-2 at room temperature. High temperature Hall measurements performed up to 300 °C in atmosphere reveal greatly enhanced thermal stability of the hole channel produced using V2O5 in comparison with an air-induced surface conduction channel. Transfer doping of hydrogen-terminated diamond using high electron affinity oxides such as V2O5 is a promising approach for achieving thermally stable, high performance diamond based devices in comparison with air-induced surface transfer doping.

  10. Enhanced flame stability and soot radiation using electric fields. Annual report, July 1987-July 1988

    SciTech Connect

    Berman, C.H.; Gill, R.J.; Calcote, H.F.

    1988-10-01

    Enhanced stabilization of methane-air flames was achieved by application of dc electric fields of only a few thousand volts with a minimum electric-power dissipation, about 0.01% of the combustion power being controlled. Both the lean blowoff composition and the maximum blowoff velocity are markedly affected. The mechanism for this phenomenon is discussed in terms of an effect of the electric field on the boundary velocity gradient. The electric field applies an electric force on the chemiions in the flame, producing an electric wind which forces the flame closer to the burner rim both reducing the dead space and decreasing the boundary velocity gradient. The 'boiling' effect on a flat flame due to the application of an electric field, reported previously, is explained by an electron-cascade effect in which thermally produced electrons are accelerated by the electric field producing more charged soot particles. In a counterflow flame, periodic waves are produced by the electric field; an explanation has not been developed. The counterflow and flat flame apparatus, including the laser optical system for particle measurements in the flame has been completely redesigned for more rapid and especially more accurate data collection.

  11. Enhanced flame stability and soot radiation using electric fields. Final report, July 1986-January 1989

    SciTech Connect

    Berman, C.H.; Gill, R.J.; Calcote, H.F.

    1989-06-01

    Enhanced stabilization of methane-air flames was achieved by application of dc electric fields of only a few thousand volts with a minimum electric power dissipation, about 0.01% of the combustion power being controlled. Both the lean-blowoff composition and the maximum blowoff velocity are markedly affected. The mechanism for the phenomenon is discussed in terms of an effect of the electric field on the boundary velocity gradient. The electric field applies an electric force on the chemiions in the flame, producing an electric wind that forces the flame closer to the burner rim both reducing the dead space and decreasing the boundary velocity gradient. The boiling effect on a flat flame due to the application of an electric field, reported previously, is explained by an electron cascade effect in which thermally produced electrons are accelerated by the electric field producing more charged soot particles. In a counterflow flame, periodic waves are produced by the electric field; an explanation has not been developed. The counterflow and flat flame apparatus, including the laser optical system for particle measurements in the flame has been completely redesigned for more rapid and especially more accurate data collection.

  12. Baicalin loaded in folate-PEG modified liposomes for enhanced stability and tumor targeting.

    PubMed

    Chen, Yiyin; Minh, Le Van; Liu, Jianwen; Angelov, Borislav; Drechsler, Markus; Garamus, Vasil M; Willumeit-Römer, Regine; Zou, Aihua

    2016-04-01

    Bioavailability of baicalin (BAI), an example of traditional Chinese medicine, has been modified by loading into liposome. Several liposome systems of different composition i.e., lipid/cholesterol (L), long-circulating stealth liposome (L-PEG) and folate receptor (FR)-targeted liposome (L-FA) have been used as the drug carrier for BAI. The obtained liposomes were around 80 nm in diameter with proper zeta potentials about -25 mV and sufficient physical stability in 3 months. The entrapment efficiency and loading efficiency of BAI in the liposomes were 41.0-46.4% and 8.8-10.0%, respectively. The morphology details of BAI lipsosome systems i.e., formation of small unilamellar vesicles, have been determined by cryogenic transmission electron microscopy (cryo-TEM) and small angle X-ray scattering (SAXS). In vitro cytotoxicity of BAI liposomes against HeLa cells was evaluated by MTT assay. BAI loaded FR-targeted liposomes showed higher cytotoxicity and cellular uptake compared with non-targeted liposomes. The results suggested that L-FA-BAI could enhance anti-tumor efficiency and should be an effective FR-targeted carrier system for BAI delivery.

  13. Conjugation of curcumin onto alginate enhances aqueous solubility and stability of curcumin.

    PubMed

    Dey, Soma; Sreenivasan, K

    2014-01-01

    Curcumin is a potential drug for various diseases including cancer. Prime limitations associated with curcumin are low water solubility, rapid hydrolytic degradation and poor bioavailability. In order to redress these issues we developed Alginate-Curcumin (Alg-Ccm) conjugate which was characterized by FTIR and (1)H NMR spectroscopy. The conjugate self-assembled in aqueous solution forming micelles with an average hydrodynamic diameter of 459 ± 0.32 nm and negative zeta potential. The spherical micelles were visualized by TEM. The critical micelle concentration (CMC) of Alg-Ccm conjugate was determined. A significant enhancement in the aqueous solubility of curcumin was observed upon conjugation with alginate. Formation of micelles improved the stability of curcumin in water at physiological pH. The cytotoxic activity of Alg-Ccm was quantified by MTT assay using L-929 fibroblast cells and it was found to be potentially cytotoxic. Hence, Alg-Ccm could be a promising drug conjugate as well as a nanosized delivery vehicle.

  14. Managing compost stability and amendment to soil to enhance soil heating during soil solarization.

    PubMed

    Simmons, Christopher W; Guo, Hongyun; Claypool, Joshua T; Marshall, Megan N; Perano, Kristen M; Stapleton, James J; Vandergheynst, Jean S

    2013-05-01

    Soil solarization is a method of soil heating used to eradicate plant pathogens and weeds that involves passive solar heating of moist soil mulched (covered) with clear plastic tarp. Various types of organic matter may be incorporated into soil prior to solarization to increase biocidal activity of the treatment process. Microbial activity associated with the decomposition of soil organic matter may increase temperatures during solarization, potentially enhancing solarization efficacy. However, the level of organic matter decomposition (stability) necessary for increasing soil temperature is not well characterized, nor is it known if various amendments render the soil phytotoxic to crops following solarization. Laboratory studies and a field trial were performed to determine heat generation in soil amended with compost during solarization. Respiration was measured in amended soil samples prior to and following solarization as a function of soil depth. Additionally, phytotoxicity was estimated through measurement of germination and early growth of lettuce seedlings in greenhouse assays. Amendment of soil with 10%(g/g) compost containing 16.9 mg CO2/gdry weight organic carbon resulted in soil temperatures that were 2-4 °C higher than soil alone. Approximately 85% of total organic carbon within the amended soil was exhausted during 22 days of solarization. There was no significant difference in residual respiration with soil depth down to 17.4 cm. Although freshly amended soil proved highly inhibitory to lettuce seed germination and seedling growth, phytotoxicity was not detected in solarized amended soil after 22 days of field solarization.

  15. Noise-enhanced stability and double stochastic resonance of active Brownian motion

    NASA Astrophysics Data System (ADS)

    Zeng, Chunhua; Zhang, Chun; Zeng, Jiakui; Liu, Ruifen; Wang, Hua

    2015-08-01

    In this paper, we study the transient and resonant properties of active Brownian particles (ABPs) in the Rayleigh-Helmholtz (RH) and Schweitzer-Ebeling-Tilch (SET) models, which is driven by the simultaneous action of multiplicative and additive noise and periodic forcing. It is shown that the cross-correlation between two noises (λ) can break the symmetry of the potential to generate motion of the ABPs. In case of no correlation between two noises, the mean first passage time (MFPT) is a monotonic decrease depending on the multiplicative noise, however in case of correlation between two noises, the MFPT exhibits a maximum, depending on the multiplicative noise for both models, this maximum for MFPT identifies the noise-enhanced stability (NES) effect of the ABPs. By comparing with case of no correlation (λ =0.0 ), we find two maxima in the signal-to-noise ratio (SNR) depending on the cross-correlation intensity, i.e. the double stochastic resonance is shown in both models. For the RH model, the SNR exhibits two maxima depending on the multiplicative noise for small cross-correlation intensity, while in the SET model, it exhibits only a maximum depending on the multiplicative noise. Whether λ =0.0 or not, the MFPT is a monotonic decrease, and the SNR exhibits a maximum, depending on the additive noise in both models.

  16. Functionally graded bioactive glass coating on magnesia partially stabilized zirconia (Mg-PSZ) for enhanced biocompatibility.

    PubMed

    Rahaman, Mohamed N; Li, Yadong; Bal, B Sonny; Huang, Wenhai

    2008-06-01

    The coating of magnesia partially stabilized zirconia (Mg-PSZ) with a bioactive glass was investigated for enhancing the bioactivity and bone-bonding ability of Mg-PSZ orthopedic implants. Individual coatings of three different bioactive glasses were prepared by depositing a concentrated suspension of the glass particles on Mg-PSZ substrates, followed by sintering at temperatures between 750 degrees C and 850 degrees C. Two silicate-based glass compositions (designated 13-93 and 6P68), and a borosilicate glass composition (H12) were investigated. The microstructure and adhesive strength of the coatings were characterized, and the in vitro bioactivity of the glasses was compared by measuring their conversion kinetics to hydroxyapatite in an aqueous phosphate solution at 37 degrees C. The 6P68 glass provided the highest adhesive strength (40 +/- 2 MPa) but showed very limited bioactivity, whereas the H12 glass had lower adhesive strength (18 +/- 2 MPa) but the highest bioactivity. A functionally graded coating, consisting of a 6P68 interfacial layer and an H12 surface layer, was developed to provide a coating with high adhesive strength coupled with rapid in vitro bioactivity.

  17. IκB kinases increase Myc protein stability and enhance progression of breast cancer cells

    PubMed Central

    2011-01-01

    Background Both IκB kinase (IKK) complex and oncgenic protein Myc play important roles in cancer progression, including cancer cell invasiveness and metastasis. The levels of Myc is regulated by the phosphorylation of Myc at Thr58 and Ser62. Results In this study, we show that the expression of Myc is associated with IKKα and IKKβ in breast cancers and that Myc is an IKKs substrate. Suppression of IKK activity by either chemical inhibitor or transfection of kinase-dead mutants decreases the phosphorylation of Myc at Ser62 and enhances the degradation of Myc. Consequently, these treatments decrease the tumorigenic and invasive ability of breast cancer cells. Furthermore, doxorubicin, a frequently used anticancer drug in breast cancer, activates IKKs and Myc, thereby increasing invasiveness and tumorigenesis of breast carcinoma MCF7 cells. Inhibition of IKKs prevents these doxorubicin-induced effects. Conclusions Our study indicates that IKKs tightly regulate Myc expression through prolonging protein stability, and suggests that IKKs are potentially therapeutic targets and that suppression of IKKs may be used following chemotherapy to reduce the risk of treatment-induced tumor progression. PMID:21575199

  18. Managing compost stability and amendment to soil to enhance soil heating during soil solarization.

    PubMed

    Simmons, Christopher W; Guo, Hongyun; Claypool, Joshua T; Marshall, Megan N; Perano, Kristen M; Stapleton, James J; Vandergheynst, Jean S

    2013-05-01

    Soil solarization is a method of soil heating used to eradicate plant pathogens and weeds that involves passive solar heating of moist soil mulched (covered) with clear plastic tarp. Various types of organic matter may be incorporated into soil prior to solarization to increase biocidal activity of the treatment process. Microbial activity associated with the decomposition of soil organic matter may increase temperatures during solarization, potentially enhancing solarization efficacy. However, the level of organic matter decomposition (stability) necessary for increasing soil temperature is not well characterized, nor is it known if various amendments render the soil phytotoxic to crops following solarization. Laboratory studies and a field trial were performed to determine heat generation in soil amended with compost during solarization. Respiration was measured in amended soil samples prior to and following solarization as a function of soil depth. Additionally, phytotoxicity was estimated through measurement of germination and early growth of lettuce seedlings in greenhouse assays. Amendment of soil with 10%(g/g) compost containing 16.9 mg CO2/gdry weight organic carbon resulted in soil temperatures that were 2-4 °C higher than soil alone. Approximately 85% of total organic carbon within the amended soil was exhausted during 22 days of solarization. There was no significant difference in residual respiration with soil depth down to 17.4 cm. Although freshly amended soil proved highly inhibitory to lettuce seed germination and seedling growth, phytotoxicity was not detected in solarized amended soil after 22 days of field solarization. PMID:23422041

  19. Functionalization of Metal-Organic Frameworks for Enhanced Stability under Humid Carbon Dioxide Capture Conditions.

    PubMed

    Andirova, Dinara; Lei, Yu; Zhao, Xiaodan; Choi, Sunho

    2015-10-26

    Metal-organic frameworks (MOFs) have been highlighted recently as promising materials for CO2 capture. However, in practical CO2 capture processes, such as capture from flue gas or ambient air, the adsorption properties of MOFs tend to be harmed by the presence of moisture possibly because of the hydrophilic nature of the coordinatively unsaturated sites (CUSs) within their framework. In this work, the CUSs of the MOF framework are functionalized with amine-containing molecules to prevent structural degradation in a humid environment. Specifically, the framework of the magnesium dioxybenzenedicarboxylate (Mg/DOBDC) MOF was functionalized with ethylenediamine (ED) molecules to make the overall structure less hydrophilic. Structural analysis after exposure to high-temperature steam showed that the ED-functionalized Mg/DOBDC (ED-Mg/DOBDC) is more stable under humid conditions, than Mg/DOBDC, which underwent drastic structural changes. ED-Mg/DOBDC recovered its CO2 adsorption capacity and initial adsorption rate quite well as opposed to the original Mg/DOBDC, which revealed a significant reduction in its capture capacity and kinetics. These results suggest that the amine-functionalization of the CUSs is an effective way to enhance the structural stability of MOFs as well as their capture of humid CO2 .

  20. Fused kinase is stabilized by Cdc37/Hsp90 and enhances Gli protein levels

    SciTech Connect

    Kise, Yoshiaki; Takenaka, Kei; Tezuka, Tohru; Yamamoto, Tadashi; Miki, Hiroaki . E-mail: miki@ims.u-tokyo.ac.jp

    2006-12-08

    Serine/threonine kinase Fused (Fu) is an essential component of Hedgehog (Hh) signaling in Drosophila, but the biochemical functions of Fu remain unclear. Here, we have investigated proteins co-precipitated with mammalian Fu and identified a kinase-specific chaperone complex, Cdc37/Hsp90, as a novel-binding partner of Fu. Inhibition of Hsp90 function by geldanamycin (GA) induces rapid degradation of Fu through a ubiquitin-proteasome pathway. We next show that co-expression of Fu with transcription factors Gli1 and Gli2 significantly increases their protein levels and luciferase reporter activities, which are blocked by GA. These increases can be ascribed to Fu-mediated stabilization of Gli because co-expression of Fu prolongs half-life of Gli1 and reduces polyubiquitination of Gli1. Finally, we show that GA inhibits proliferation of PC3, a Hh signaling-activated prostate cancer cell line. This growth inhibition is partially rescued by expression of ectopic Gli1, suggesting that Fu may contribute to enhance Hh signaling activity in cancer cells.

  1. Baicalin loaded in folate-PEG modified liposomes for enhanced stability and tumor targeting.

    PubMed

    Chen, Yiyin; Minh, Le Van; Liu, Jianwen; Angelov, Borislav; Drechsler, Markus; Garamus, Vasil M; Willumeit-Römer, Regine; Zou, Aihua

    2016-04-01

    Bioavailability of baicalin (BAI), an example of traditional Chinese medicine, has been modified by loading into liposome. Several liposome systems of different composition i.e., lipid/cholesterol (L), long-circulating stealth liposome (L-PEG) and folate receptor (FR)-targeted liposome (L-FA) have been used as the drug carrier for BAI. The obtained liposomes were around 80 nm in diameter with proper zeta potentials about -25 mV and sufficient physical stability in 3 months. The entrapment efficiency and loading efficiency of BAI in the liposomes were 41.0-46.4% and 8.8-10.0%, respectively. The morphology details of BAI lipsosome systems i.e., formation of small unilamellar vesicles, have been determined by cryogenic transmission electron microscopy (cryo-TEM) and small angle X-ray scattering (SAXS). In vitro cytotoxicity of BAI liposomes against HeLa cells was evaluated by MTT assay. BAI loaded FR-targeted liposomes showed higher cytotoxicity and cellular uptake compared with non-targeted liposomes. The results suggested that L-FA-BAI could enhance anti-tumor efficiency and should be an effective FR-targeted carrier system for BAI delivery. PMID:26741267

  2. Polyacrylonitrile nanofibers with added zeolitic imidazolate frameworks (ZIF-7) to enhance mechanical and thermal stability

    SciTech Connect

    Lee, Min Wook; An, Seongpil; Song, Kyo Yong; Joshi, Bhavana N.; Jo, Hong Seok; Yoon, Sam S. E-mail: ayarin@uic.edu; Al-Deyab, Salem S.; Yarin, Alexander L. E-mail: ayarin@uic.edu

    2015-12-28

    Zeolitic imidazolate framework 7/polyacrylonitrile (ZIF-7/PAN) nanofiber mat of high porosity and surface area can be used as a flexible fibrous filtration membrane that is subjected to various modes of mechanical loading resulting in stresses and strains. Therefore, the stress-strain relation of ZIF-7/PAN nanofiber mats in the elastic and plastic regimes of deformation is of significant importance for numerous practical applications, including hydrogen storage, carbon dioxide capture, and molecular sensing. Here, we demonstrated the fabrication of ZIF-7/PAN nanofiber mats via electrospinning and report their mechanical properties measured in tensile tests covering the elastic and plastic domains. The effect of the mat fabrication temperature on the mechanical properties is elucidated. We showed the superior mechanical strength and thermal stability of the compound ZIF-7/PAN nanofiber mats in comparison with that of pure PAN nanofiber mats. Material characterization including scanning electron microscope, energy-dispersive X-ray spectroscopy, tensile tests, differential scanning calorimetry, and Fourier transform infrared spectroscopy revealed the enhanced chemical bonds of the ZIF-7/PAN complex.

  3. Polyacrylonitrile nanofibers with added zeolitic imidazolate frameworks (ZIF-7) to enhance mechanical and thermal stability

    NASA Astrophysics Data System (ADS)

    Lee, Min Wook; An, Seongpil; Song, Kyo Yong; Joshi, Bhavana N.; Jo, Hong Seok; Al-Deyab, Salem S.; Yoon, Sam S.; Yarin, Alexander L.

    2015-12-01

    Zeolitic imidazolate framework 7/polyacrylonitrile (ZIF-7/PAN) nanofiber mat of high porosity and surface area can be used as a flexible fibrous filtration membrane that is subjected to various modes of mechanical loading resulting in stresses and strains. Therefore, the stress-strain relation of ZIF-7/PAN nanofiber mats in the elastic and plastic regimes of deformation is of significant importance for numerous practical applications, including hydrogen storage, carbon dioxide capture, and molecular sensing. Here, we demonstrated the fabrication of ZIF-7/PAN nanofiber mats via electrospinning and report their mechanical properties measured in tensile tests covering the elastic and plastic domains. The effect of the mat fabrication temperature on the mechanical properties is elucidated. We showed the superior mechanical strength and thermal stability of the compound ZIF-7/PAN nanofiber mats in comparison with that of pure PAN nanofiber mats. Material characterization including scanning electron microscope, energy-dispersive X-ray spectroscopy, tensile tests, differential scanning calorimetry, and Fourier transform infrared spectroscopy revealed the enhanced chemical bonds of the ZIF-7/PAN complex.

  4. Micro Mechanics and Microstructures of Major Subsurface Hydraulic Barriers: Shale Caprock vs Wellbore Cement

    NASA Astrophysics Data System (ADS)

    Radonjic, M.; Du, H.

    2015-12-01

    Shale caprocks and wellbore cements are two of the most common subsurface impermeable barriers in the oil and gas industry. More than 60% of effective seals for geologic hydrocarbon bearing formations as natural hydraulic barriers constitute of shale rocks. Wellbore cements provide zonal isolation as an engineered hydraulic barrier to ensure controlled fluid flow from the reservoir to the production facilities. Shale caprocks were deposited and formed by squeezing excess formation water and mineralogical transformations at different temperatures and pressures. In a similar process, wellbore cements are subjected to compression during expandable tubular operations, which lead to a rapid pore water propagation and secondary mineral precipitation within the cement. The focus of this research was to investigate the effect of wellbore cement compression on its microstructure and mechanical properties, as well as a preliminary comparison of shale caprocks and hydrated cement. The purpose of comparative evaluation of engineered vs natural hydraulic barrier materials is to further improve wellbore cement durability when in contact with geofluids. The micro-indentation was utilized to evaluate the change in cement mechanical properties caused by compression. Indentation experiments showed an overall increase in hardness and Young's modulus of compressed cement. Furthermore, SEM imaging and Electron Probe Microanalysis showed mineralogical alterations and decrease in porosity. These can be correlated with the cement rehydration caused by microstructure changes as a result of compression. The mechanical properties were also quantitatively compared to shale caprock samples in order to investigate the similarities of hydraulic barrier features that could help to improve the subsurface application of cement in zonal isolation. The comparison results showed that the poro-mechanical characteristics of wellbore cement appear to be improved when inherent pore sizes are shifted to

  5. Amino acids as co-amorphous stabilizers for poorly water soluble drugs--Part 1: preparation, stability and dissolution enhancement.

    PubMed

    Löbmann, Korbinian; Grohganz, Holger; Laitinen, Riikka; Strachan, Clare; Rades, Thomas

    2013-11-01

    Poor aqueous solubility of an active pharmaceutical ingredient (API) is one of the most pressing problems in pharmaceutical research and development because up to 90% of new API candidates under development are poorly water soluble. These drugs usually have a low and variable oral bioavailability, and therefore an unsatisfactory therapeutic effect. One of the most promising approaches to increase dissolution rate and solubility of these drugs is the conversion of a crystalline form of the drug into its respective amorphous form, usually by incorporation into hydrophilic polymers, forming glass solutions. However, this strategy only led to a small number of marketed products usually because of inadequate physical stability of the drug (crystallization). In this study, we investigated a fundamentally different approach to stabilize the amorphous form of drugs, namely the use of amino acids as small molecular weight excipients that form specific molecular interactions with the drug resulting in co-amorphous forms. The two poorly water soluble drugs carbamazepine and indomethacin were combined with amino acids from the binding sites of the biological receptors of these drugs. Mixtures of drug and the amino acids arginine, phenylalanine, tryptophan and tyrosine were prepared by vibrational ball milling. Solid-state characterization with X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) revealed that the various blends could be prepared as homogeneous, single phase co-amorphous formulations indicated by the appearance of an amorphous halo in the XRPD diffractograms and a single glass transition temperature (Tg) in the DSC measurements. In addition, the Tgs of the co-amorphous mixtures were significantly increased over those of the individual drugs. The drugs remained chemically stable during the milling process and the co-amorphous formulations were generally physically stable over at least 6 months at 40 °C under dry conditions. The

  6. Supplement to wellbore models GWELL, GWNACL, and HOLA User`s Guide

    SciTech Connect

    Hadgu, T.; Bodvarsson, G.S.

    1992-09-01

    A study was made on improving the applicability and ease of usage of the wellbore simulators HOLA, GWELL and GWNACL (Bjornsson, 1987; Aunzo et al., 1991). The study concentrated mainly on the usage of Option 2 (please refer to the User`s Guide; Aunzo et al., 1991) and modeling flow of superheated steam when using these computer codes. Amendments were made to the simulators to allow implementation of a variety of input data. A wide range of input data was used to test the modifications to the codes. The study did not attempt to modify or improve the physics or formulations which were used in the models. It showed that a careful check of the input data is required. This report addresses these two areas of interest: usage of Option 2, and simulation of wellbore flow of superheated steam.

  7. Determination of Diffusion Profiles in Altered Wellbore Cement Using X-ray Computed Tomography Methods

    SciTech Connect

    Mason, Harris E.; Walsh, Stuart D. C.; DuFrane, Wyatt L.; Carroll, Susan A.

    2014-06-17

    The development of accurate, predictive models for use in determining wellbore integrity requires detailed information about the chemical and mechanical changes occurring in hardened Portland cements. X-ray computed tomography (XRCT) provides a method that can nondestructively probe these changes in three dimensions. Here, we describe a method for extracting subvoxel mineralogical and chemical information from synchrotron XRCT images by combining advanced image segmentation with geochemical models of cement alteration. The method relies on determining “effective linear activity coefficients” (ELAC) for the white light source to generate calibration curves that relate the image grayscales to material composition. The resulting data set supports the modeling of cement alteration by CO2-rich brine with discrete increases in calcium concentration at reaction boundaries. The results of these XRCT analyses can be used to further improve coupled geochemical and mechanical models of cement alteration in the wellbore environment.

  8. Pulling tool for use with reeled tubing and method for operating tools from wellbores

    SciTech Connect

    Pleasants, C.W.

    1991-08-20

    This patent describes a tool for latching to and/or pulling a well operating tool having a fishing neck from a downhole location in pipe in a well bore. It comprises an elongated tubular housing assembly defining a longitudinal bore; means connecting the housing assembly to an end of a string of reeled tubing for passing the housing assembly through the wellbore and into contact with the fishing neck and for introducing fluid into the longitudinal bore; means disposed on the housing assembly for automatically latching to the fishing neck upon the housing assembly engaging the fishing neck; means responsive to a predetermined fluid condition in the bore for releasing the latching means from the fishing neck to permit the tool to be removed from the wellbore; and means responsive to a predetermined mechanical force exerted, via the reeled tubing, on the housing assembly and on the fishing neck for releasing the latching means from the fishing neck.

  9. Drilling forces in high-curvature wellbores: A comparison of analytical model results with MWD data

    SciTech Connect

    Rocheleau, D.N.; Zhao, M.

    1997-07-01

    Horizontal drilling is commonly used to reach lateral targets in oil and gas reservoirs. A method is presented which predicts the drilling forces encountered while tripping-in and tripping-out of high-curvature wellbores during horizontal and extended reach drilling. The method is based on modeling the drillstring as a set of continuous beams using Timoshenko beam theory. The paper first describes how the drillstring is modeled; it then develops the analytical equations of the model and outlines a computer implementation of these equations. Lastly, the results predicted by the analytical model are compared with actual field results based on measurement while drilling (MWD) data obtained from high-curvature wellbores in the Gulf of Mexico.

  10. Determination of diffusion profiles in altered wellbore cement using X-ray computed tomography methods.

    PubMed

    Mason, Harris E; Walsh, Stuart D C; DuFrane, Wyatt L; Carroll, Susan A

    2014-06-17

    The development of accurate, predictive models for use in determining wellbore integrity requires detailed information about the chemical and mechanical changes occurring in hardened Portland cements. X-ray computed tomography (XRCT) provides a method that can nondestructively probe these changes in three dimensions. Here, we describe a method for extracting subvoxel mineralogical and chemical information from synchrotron XRCT images by combining advanced image segmentation with geochemical models of cement alteration. The method relies on determining "effective linear activity coefficients" (ELAC) for the white light source to generate calibration curves that relate the image grayscales to material composition. The resulting data set supports the modeling of cement alteration by CO2-rich brine with discrete increases in calcium concentration at reaction boundaries. The results of these XRCT analyses can be used to further improve coupled geochemical and mechanical models of cement alteration in the wellbore environment. PMID:24869420

  11. Wellbore enlargement investigation: Potential analogs to the Waste Isolation Pilot Plant during inadvertent intrusion of the repository

    SciTech Connect

    Boak, D.M.; Dotson, L.; Aguilar, R.

    1997-01-01

    This study involved the evaluation and documentation of cases in which petroleum wellbores were enlarged beyond the nominal hole diameter as a consequence of erosion during exploratory drilling, particularly as a function of gas flow into the wellbore during blowout conditions. A primary objective was to identify analogs to potential wellbore enlargement at the Waste Isolation Pilot Plant (WIPP) during inadvertent human intrusion. Secondary objectives were to identify drilling scenarios associated with enlargement, determine the physical extent of enlargement, and establish the physical properties of the formation in which the enlargement occurred. No analogs of sufficient quality to establish quantitative limits on wellbore enlargement at the WIPP disposal system were identified. However, some information was obtained regarding the frequency of petroleum well blowouts and the likelihood that such blowouts would bridge downhole, self-limiting the surface release of disposal-system material. Further work would be necessary, however, to determine the conditions under which bridging could occur and the extent to which the bridging might be applicable to WIPP. In addition, data on casing sizes of petroleum boreholes in the WIPP vicinity support the use of a 12-{1/4} inch borehole size in WIPP performance assessment calculations. Finally, although data are limited, there was no evidence of significant wellbore enlargement in any of three blowouts that occur-red in wellbores in the Delaware Basin (South Culebra Bluff Unit No. 1, Energy Research and Development Administration (ERDA) 6, and WIPP 12).

  12. Study on Enhancement Principle and Stabilization for the Luminol-H2O2-HRP Chemiluminescence System

    PubMed Central

    Yang, Lihua; Jin, Maojun; Du, Pengfei; Chen, Ge; Zhang, Chan; Wang, Jian; Jin, Fen; Shao, Hua; She, Yongxin; Wang, Shanshan; Zheng, Lufei; Wang, Jing

    2015-01-01

    A luminol-H2O2-HRP chemiluminescence system with high relative luminescent intensity (RLU) and long stabilization time was investigated. First, the comparative study on the enhancement effect of ten compounds as enhancers to the luminol-H2O2-HRP chemiluminescence system was carried out, and the results showed that 4-(imidazol-1-yl)phenol (4-IMP), 4-iodophenol (4-IOP), 4-bromophenol (4-BOP) and 4-hydroxy-4’-iodobiphenyl (HIOP) had the best performance. Based on the experiment, the four enhancers were dissolved in acetone, acetonitrile, methanol, and dimethylformamide (DMF) with various concentrations, the results indicated that 4-IMP, 4-IOP, 4-BOP and HIOP dissolved in DMF with the concentrations of 0.2%, 3.2%, 1.6% and 3.2% could get the highest RLU values. Subsequently, the influences of pH, ionic strength, HRP, 4-IMP, 4-IOP, 4-BOP, HIOP, H2O2 and luminol on the stabilization of the luminol-H2O2-HRP chemiluminescence system were studied, and we found that pH value, ionic strength, 4-IMP, 4-IOP, 4-BOP, HIOP, H2O2 and luminol have little influence on luminescent stabilization, while HRP has a great influence. In different ranges of HRP concentration, different enhancers should be selected. When the concentration is within the range of 0~6 ng/mL, 4-IMP should be selected. When the concentration of HRP ranges from 6 to 25ng/mL, 4-IOP was the best choice. And when the concentration is within the range of 25~80 ng/mL, HIOP should be selected as the enhancer. Finally, the three well-performing chemiluminescent enhanced solutions (CESs) have been further optimized according to the three enhancers (4-IMP, 4-IOP and HIOP) in their utilized HRP concentration ranges. PMID:26154162

  13. Study on Enhancement Principle and Stabilization for the Luminol-H2O2-HRP Chemiluminescence System.

    PubMed

    Yang, Lihua; Jin, Maojun; Du, Pengfei; Chen, Ge; Zhang, Chan; Wang, Jian; Jin, Fen; Shao, Hua; She, Yongxin; Wang, Shanshan; Zheng, Lufei; Wang, Jing

    2015-01-01

    A luminol-H2O2-HRP chemiluminescence system with high relative luminescent intensity (RLU) and long stabilization time was investigated. First, the comparative study on the enhancement effect of ten compounds as enhancers to the luminol-H2O2-HRP chemiluminescence system was carried out, and the results showed that 4-(imidazol-1-yl)phenol (4-IMP), 4-iodophenol (4-IOP), 4-bromophenol (4-BOP) and 4-hydroxy-4'-iodobiphenyl (HIOP) had the best performance. Based on the experiment, the four enhancers were dissolved in acetone, acetonitrile, methanol, and dimethylformamide (DMF) with various concentrations, the results indicated that 4-IMP, 4-IOP, 4-BOP and HIOP dissolved in DMF with the concentrations of 0.2%, 3.2%, 1.6% and 3.2% could get the highest RLU values. Subsequently, the influences of pH, ionic strength, HRP, 4-IMP, 4-IOP, 4-BOP, HIOP, H2O2 and luminol on the stabilization of the luminol-H2O2-HRP chemiluminescence system were studied, and we found that pH value, ionic strength, 4-IMP, 4-IOP, 4-BOP, HIOP, H2O2 and luminol have little influence on luminescent stabilization, while HRP has a great influence. In different ranges of HRP concentration, different enhancers should be selected. When the concentration is within the range of 0~6 ng/mL, 4-IMP should be selected. When the concentration of HRP ranges from 6 to 25 ng/mL, 4-IOP was the best choice. And when the concentration is within the range of 25~80 ng/mL, HIOP should be selected as the enhancer. Finally, the three well-performing chemiluminescent enhanced solutions (CESs) have been further optimized according to the three enhancers (4-IMP, 4-IOP and HIOP) in their utilized HRP concentration ranges.

  14. Stability enhancement of an electrically tunable colloidal photonic crystal using modified electrodes with a large electrochemical potential window

    SciTech Connect

    Shim, HongShik; Gyun Shin, Chang; Heo, Chul-Joon; Jeon, Seog-Jin; Jin, Haishun; Woo Kim, Jung; Jin, YongWan; Lee, SangYoon; Gyu Han, Moon E-mail: jinklee@snu.ac.kr; Lim, Joohyun; Lee, Jin-Kyu E-mail: jinklee@snu.ac.kr

    2014-02-03

    The color tuning behavior and switching stability of an electrically tunable colloidal photonic crystal system were studied with particular focus on the electrochemical aspects. Photonic color tuning of the colloidal arrays composed of monodisperse particles dispersed in water was achieved using external electric field through lattice constant manipulation. However, the number of effective color tuning cycle was limited due to generation of unwanted ions by electrolysis of the water medium during electrical switching. By introducing larger electrochemical potential window electrodes, such as conductive diamond-like carbon or boron-doped diamond, the switching stability was appreciably enhanced through reducing the number of ions generated.

  15. Bioengineered Human Arginase I with Enhanced Activity and Stability Controls Hepatocellular and Pancreatic Carcinoma Xenografts1

    PubMed Central

    Glazer, Evan S; Stone, Everett M; Zhu, Cihui; Massey, Katherine L; Hamir, Amir N; Curley, Steven A

    2011-01-01

    Hepatocellular carcinoma (HCC) and pancreatic carcinoma (PC) cells often have inherent urea cycle defects rendering them auxotrophic for the amino acid l-arginine (l-arg). Most HCC and PC require extracellular sources of l-arg and undergo cell cycle arrest and apoptosis when l-arg is restricted. Systemic, enzyme-mediated depletion of l-arg has been investigated in mouse models and human trials. Non-human enzymes elicit neutralizing antibodies, whereas human arginases display poor pharmacological properties in serum. Co2+ substitution of the Mn2+ metal cofactor in human arginase I (Co-hArgI) was shown to confer more than 10-fold higher catalytic activity (kcat/Km) and 5-fold greater stability. We hypothesized that the Co-hArgI enzyme would decrease tumor burden by systemic elimination of l-arg in a murine model. Co-hArgI was conjugated to 5-kDa PEG (Co-hArgI-PEG) to enhance circulation persistence. It was used as monotherapy for HCC and PC in vitro and in vivo murine xenografts. The mechanism of cell death was also investigated. Weekly treatment of 8 mg/kg Co-hArgI-PEG effectively controlled human HepG2 (HCC) and Panc-1 (PC) tumor xenografts (P = .001 and P = .03, respectively). Both cell lines underwent apoptosis in vitro with significant increased expression of activated caspase-3 (P < .001). Furthermore, there was evidence of autophagy in vitro and in vivo. We have demonstrated that Co-hArgI-PEG is effective at controlling two types of l-arg-dependent carcinomas. Being a nonessential amino acid, arginine deprivation therapy through Co-hArgI-PEG holds promise as a new therapy in the treatment of HCC and PC. PMID:21633669

  16. A facile approach to enhance the high temperature stability of magnetite nanoparticles with improved magnetic property

    NASA Astrophysics Data System (ADS)

    Pati, S. S.; Philip, John

    2013-01-01

    We study the effect of Zn2+ doping on crystal structure, magnetic properties, blocking and Curie temperatures, and the high temperature phase stability of magnetite nanoparticles under air and vacuum annealing. The Zn2+ doped nanoparticles (ZnxFe3-xO4 with x = 0, 0.2, 0.4, and 0.6) are prepared by simple co-precipitation technique and are characterized by high temperature X-ray powder diffraction (HTXRD), vibrating sample magnetometer, small angle X-ray scattering, thermogravimetry, differential scanning calorimetry (DSC), and transmission electron microscopy. Our HTXRD studies show that the decomposition temperature of pure magnetite (Fe3O4) in vacuum is increased by 300 °C (from 700 to 1000 °C), with 0.2 fraction of Zn2+ doping. The DSC studies under air environment also show that the γ-Fe2O3 to α-Fe2O3 phase transition temperature increases with the zinc fraction. The increase in transition temperature is attributed to the increase in the activation energy of the maghemite to hematite phase transition after the replacement of Fe3+ with larger diameter Zn2+ in the A site. Interestingly, the saturation magnetization increases from 61 to 69 emu/g upon 0.2 fraction of Zn2+, which augments the utility of the doped compound for practical applications. While the Curie temperature is found to increase with doping concentration, the blocking temperature shows an opposite trend. The blocking temperature values were found to be 262, 196, 144, and 153 K for 0, 0.2, 0.4, and 0.6 fraction of zinc, respectively. The reduction in TB is attributed to weak dipole-dipole interactions and local exchange coupling between nanoparticles. All the Zn2+ doped samples show superparamagnetic nature. These findings are extremely useful in producing superparamagnetic nanoparticles with enhanced magnetic properties for high temperature applications.

  17. Ultrasound-assisted butyl acetate synthesis catalyzed by Novozym 435: enhanced activity and operational stability.

    PubMed

    Martins, Andréa B; Schein, Mirela F; Friedrich, John L R; Fernandez-Lafuente, Roberto; Ayub, Marco A Z; Rodrigues, Rafael C

    2013-09-01

    The influence of low-frequency ultrasound (40 kHz) in the esterification reaction between acetic acid and butanol for flavor ester synthesis catalyzed by the commercial immobilized lipase B from Candida antarctica (Novozym 435) was evaluated. A central composite design and the response surface methodology were used to analyze the effects of the reaction parameters (temperature, substrate molar ratio, enzyme content and added water) and their response (yields of conversion in 2.5 h of reaction). The reaction was carried out using n-hexane as solvent. The optimal conditions for ultrasound-assisted butyl acetate synthesis were found to be: temperature of 46 °C; substrate molar ratio of 3.6:1 butanol:acetic acid; enzyme content of 7%; added water of 0.25%, conditions that are slightly different from those found using mechanical mixing. Over 94% of conversion was obtained in 2.5h under these conditions. The optimal acid concentration for the reaction was determined to be 2.0 M, compared to 0.3 M without ultrasound treatment. Enzyme productivity was significantly improved to around 7.5-fold for each batch when comparing ultrasound and standard mechanical agitation. The biocatalyst could be directly reused for 14 reactions cycles keeping around 70% of its original activity, while activity was virtually zeroed in the third cycle using the standard mixing system. Thus, compared to the traditional mechanical agitation, ultrasound technology not only improves the process productivity, but also enhances enzyme recycling and stability in the presence of acetic acid, being a powerful tool to improve biocatalyst performance in this type of reaction. PMID:23453821

  18. Multiple Unit Particles System of Ramipril: An Approach to Enhance Stability

    PubMed Central

    Patel, HP; Patel, JK; Patel, MP; Patel, RR

    2011-01-01

    The present invention relates to produce multiple unit particle system (MUPS) of stabilized ramipril pellets, hydrochlorothiazide, diluents, superdisintegrants, and lubricants which produce better dissolution of the system for better bioavailability with improving stability and bioavailability of ramipril. More particularly, the present invention is directed for stabilized ramipril against decomposition into degradation products, namely ramipril-DKP and ramipril-diacid, during formulation and storage conditions. Simple ramipril formulation shows 15.15% related impurities after 3-month accelerated stability study, which was minimized to the 2.07% related impurities in ramipril pellets after 6 month accelerated stability study. By making MUPS of ramipril pellets, Hydrochlorothiazide and other excipients show better dissolution (100.4% of ramipril and 97.9% of hydrochlorothiazide within 60 min) to produce better bioavailability. So, making MUPS containing ramipril pellets with polymer coating and hydrochlorothiazide and other excipients shows better stability of ramipril along degradation and synergistic effect among hypertension in immediate delivery. PMID:21731352

  19. Interbed Modeling to Predict Wellbore Damage for Big Hill Strategic Petroleum Reserve

    NASA Astrophysics Data System (ADS)

    Park, Byoung Yoon

    2014-09-01

    Oil leaks were found in wellbores of Caverns 105 and 109 at the Big Hill Strategic Petroleum Reserve site. According to the field observations, two instances of casing damage occurred at the depth of the interbed between the caprock bottom and salt top. A three-dimensional finite element model, which allows each cavern to be configured individually, was constructed to investigate horizontal and vertical displacements in each well as it crosses the various interbeds. The model contains interfaces between each lithology and a shear zone (fault) to examine the interbed behavior in a realistic manner. This analysis results indicate that the casings of Caverns 105 and 109 failed, respectively, from shear stress that exceeded the casing shear strength due to the horizontal movement of the salt top relative to the caprock and tensile stress due to the downward movement of the salt top from the caprock. The wellbores of Caverns 114 and 104, located at the far end of the field and near the fault, respectively, are predicted to fail by shear stress in the near future. The wellbores of inmost Caverns 107 and 108 are predicted to fail by tensile stress in the near future. The salt top subsides because the volumes of caverns in the salt dome decrease with time due to salt creep closure, while the caprock does not subside at the same rate as the salt top because the caprock is thick and stiff. This discrepancy yields deformation of the well.

  20. Analytical solution for two-phase flow in a wellbore using the drift-flux model

    SciTech Connect

    Pan, L.; Webb, S.W.; Oldenburg, C.M.

    2011-11-01

    This paper presents analytical solutions for steady-state, compressible two-phase flow through a wellbore under isothermal conditions using the drift flux conceptual model. Although only applicable to highly idealized systems, the analytical solutions are useful for verifying numerical simulation capabilities that can handle much more complicated systems, and can be used in their own right for gaining insight about two-phase flow processes in wells. The analytical solutions are obtained by solving the mixture momentum equation of steady-state, two-phase flow with an assumption that the two phases are immiscible. These analytical solutions describe the steady-state behavior of two-phase flow in the wellbore, including profiles of phase saturation, phase velocities, and pressure gradients, as affected by the total mass flow rate, phase mass fraction, and drift velocity (i.e., the slip between two phases). Close matching between the analytical solutions and numerical solutions for a hypothetical CO{sub 2} leakage problem as well as to field data from a CO{sub 2} production well indicates that the analytical solution is capable of capturing the major features of steady-state two-phase flow through an open wellbore, and that the related assumptions and simplifications are justified for many actual systems. In addition, we demonstrate the utility of the analytical solution to evaluate how the bottomhole pressure in a well in which CO{sub 2} is leaking upward responds to the mass flow rate of CO{sub 2}-water mixture.

  1. Enhanced water splitting stability with controlled NiO co-catalyst on GaN photoanode.

    PubMed

    Kim, Soo Hee; Kang, Jin-Ho; Ryu, Sang-Wan

    2014-10-01

    Arrayed NiO co-catalyst on GaN is proposed to improve water splitting efficiency and to obtain stable photoelectrolysis without dissolution of photoanode. The characteristics of photoanodes were investigated by changing the height of NiO on n-GaN. The photoanode stability and performance of GaN with NiO was significantly improved compared to the reference GaN at zero bias. SEM measurements showed negligible etching of NiO and GaN surfaces, which confirmed considerably improved stability compared to the reference n-GaN. In summary, enhanced water splitting efficiency and photoanode stability were achieved by combining GaN with NiO co-catalyst which are advantageous for water splitting applications.

  2. Enhanced tunability of thermodynamic stability of complex hydrides by the incorporation of H{sup –} anions

    SciTech Connect

    Takagi, Shigeyuki; Humphries, Terry D.; Miwa, Kazutoshi; Orimo, Shin-ichi

    2014-05-19

    First-principles calculations were employed to investigate hypothetical complex hydrides (M,M{sup ′}){sub 4}FeH{sub 8} (M = Na, Li; M{sup ′}=Mg, Zn, Y, Al). Besides complex anion [FeH{sub 6}]{sup 4–}, these materials contain two H{sup –} anions, which raise the total anionic charge state from tetravalent to hexavalent, and thereby significantly increasing the number of combinations of countercations. We have determined that similar to complex hydrides (M,M{sup ′}){sub 2}FeH{sub 6} containing only [FeH{sub 6}]{sup 4–}, the thermodynamic stability is tuned by the average cation electronegativity. Thus, the chemical flexibility provided by incorporating H{sup –} enhances the tunability of thermodynamic stability, which will be beneficial in obtaining optimal stability for hydrogen storage materials.

  3. Strain-induced stabilization of Al functionalization in graphene oxide nanosheet for enhanced NH{sub 3} storage

    SciTech Connect

    Li, Yunguo; De Sarkar, Abir; Pathak, Biswarup; Ahuja, Rajeev

    2013-06-17

    Strain effects on the stabilization of Al ad-atom on graphene oxide (GO) nanosheet as well as its implications for NH{sub 3} storage have been investigated using first-principles calculations. Tensile strain is found to be very effective in stabilizing the Al ad-atom on GO. It strengthens the C-O bonds through an enhanced charge transfer from C to O atoms. Interestingly, Al's stability is governed by the bond strength of C-O rather than that of Al-O. Optimally strained Al-functionalized GO binds up to 6 NH{sub 3} molecules, while it binds no NH{sub 3} molecule in unstrained condition.

  4. Enhanced Organic Solar Cell Stability through the Effective Blocking of Oxygen Diffusion using a Self-Passivating Metal Electrode.

    PubMed

    Lee, Hansol; Jo, Sae Byeok; Lee, Hyo Chan; Kim, Min; Sin, Dong Hun; Ko, Hyomin; Cho, Kilwon

    2016-03-01

    A new and simple strategy for enhancing the stability of organic solar cells (OSCs) was developed by using self-passivating metal top electrodes. Systematic investigations on O2 permeability of Al top electrodes revealed that the main pathways for oxidation-induced degradation could be greatly suppressed by simply controlling the nanoscale morphology of the Al electrode. The population of nanoscale pinholes among Al grains, which critically decided the diffusion of O2 molecules toward the Al-organic interfaces that are vulnerable to oxidation, was successfully regulated by rapidly depositing Al or promoting lateral growth among the Al grains, accompanied by increasing the deposition thickness. Our observations suggested that the stability of OSCs with conventional architectures might be greatly enhanced simply by controlling the fabrication conditions of the Al top electrode, without the aid of additional secondary treatments.

  5. Binary functionalization of H:Si(111) surfaces by alkyl monolayers with different linker atoms enhances monolayer stability and packing.

    PubMed

    Arefi, Hadi H; Nolan, Michael; Fagas, Giorgos

    2016-05-14

    Alkyl monolayer modified Si forms a class of inorganic-organic hybrid materials with applications across many technologies such as thin-films, fuel/solar-cells and biosensors. Previous studies have shown that the linker atom, through which the monolayer binds to the Si substrate, and any tail group in the alkyl chain, can tune the monolayer stability and electronic properties. In this paper we study the H:Si(111) surface functionalized with binary SAMs: these are composed of alkyl chains that are linked to the surface by two different linker groups. Aiming to enhance SAM stability and increase coverage over singly functionalized Si, we examine with density functional theory simulations that incorporate vdW interactions, a range of linker groups which we denote as -X-(alkyl) with X = CH2, O(H), S(H) or NH(2) (alkyl = C6 and C12 chains). We show how the stability of the SAM can be enhanced by adsorbing alkyl chains with two different linkers, e.g. Si-[C, NH]-alkyl, through which the adsorption energy is increased compared to functionalization with the individual -X-alkyl chains. Our results show that it is possible to improve stability and optimum coverage of alkyl functionalized SAMs linked through a direct Si-C bond by incorporating alkyl chains linked to Si through a different linker group, while preserving the interface electronic structure that determines key electronic properties. This is important since any enhancement in stability and coverage to give more densely packed monolayers will result in fewer defects. We also show that the work function can be tuned within the interval of 3.65-4.94 eV (4.55 eV for bare H:Si(111)).

  6. Enhancing stability and expression of recombinant human hemoglobin in E. coli: Progress in the development of a recombinant HBOC source.

    PubMed

    Graves, Philip E; Henderson, Douglas P; Horstman, Molly J; Solomon, Brian J; Olson, John S

    2008-10-01

    The commercial feasibility of recombinant human Hb (rHb) as an O(2) delivery pharmaceutical is limited by the production yield of holoprotein in E. coli. Currently the production of rHb is not cost effective for use as a source in the development of third and fourth generation Hb-based oxygen carriers (HBOCs). The major problems appear to be aggregation and degradation of apoglobin at the nominal expression temperatures, 28-37 degrees C, and the limited amount of free heme that is available for holohemoglobin assembly. One approach to solve the first problem is to inhibit apoglobin precipitation by a comparative mutagenesis strategy to improve apoglobin stability. alpha Gly15 to Ala and beta Gly16 to Ala mutations have been constructed to increase the stability of the alpha helices of both subunits of HbA, based on comparison with the sequences of the more stable sperm whale hemoglobin subunits. Fetal hemoglobin is also known to be more stable than human HbA, and sequence comparisons between human beta and gamma (fetal Hb) chains indicate several substitutions that stabilize the alpha1beta1 interface, one of which, beta His116 to Ile, increases resistance to denaturation and enhances expression in E. coli. These favorable effects of enhanced globin stability can be augmented by co-expression of bacterial membrane heme transport systems to increase the rate and extent of heme uptake through the bacterial cell membranes. The combination of increased apoglobin stability and active heme transport appear to enhance holohemoglobin production to levels that may make rHb a plausible starting material for all extracellular Hb-based oxygen carriers.

  7. Enhanced Stability and Controllability of an Ionic Diode Based on Funnel-Shaped Nanochannels with an Extended Critical Region.

    PubMed

    Xiao, Kai; Xie, Ganhua; Zhang, Zhen; Kong, Xiang-Yu; Liu, Qian; Li, Pei; Wen, Liping; Jiang, Lei

    2016-05-01

    The enhanced stability and controllability of an ionic diode system based on funnel-shaped nanochannels with a much longer critical region is reported. The polarity of ion transport switching from anion/cation-selective to ambipolar can be controlled by tuning the length and charge of the critical region. This nanofluidic structure anticipates potential applications in single-molecule biosensing, water resource monitoring, and healthcare.

  8. Enhanced Recyclability, Stability, and Selectivity of CdS/C@Fe3O4 Nanoreactors for Orientation Photodegradation of Ciprofloxacin.

    PubMed

    Lu, Ziyang; Zhao, Xiaoxu; Zhu, Zhi; Yan, Yongsheng; Shi, Weidong; Dong, Hongjun; Ma, Zhongfei; Gao, Nailing; Wang, Youshan; Huang, Hai

    2015-12-14

    A unique CdS/C@Fe3O4 nanoreactor was fabricated by the surface-imprinting technique, which effectively enhances the recyclability, stability, and selectivity for orientation recognition and photodegradation of ciprofloxacin in the binary mixed solution under visible-light irradiation. This work not only puts forward a novel design idea that develops the potential application value of CdS, but also provides a new approach for inhibiting its secondary pollution.

  9. Structural Basis of Duplex Thermodynamic Stability and Enhanced Nuclease Resistance of 5'-C-Methyl Pyrimidine-Modified Oligonucleotides.

    PubMed

    Kel'in, Alexander V; Zlatev, Ivan; Harp, Joel; Jayaraman, Muthusamy; Bisbe, Anna; O'Shea, Jonathan; Taneja, Nate; Manoharan, Rajar M; Khan, Saeed; Charisse, Klaus; Maier, Martin A; Egli, Martin; Rajeev, Kallanthottathil G; Manoharan, Muthiah

    2016-03-18

    Although judicious use of chemical modifications has contributed to the success of nucleic acid therapeutics, poor systemic stability remains a major hurdle. The introduction of functional groups around the phosphate backbone can enhance the nuclease resistance of oligonucleotides (ONs). Here, we report the synthesis of enantiomerically pure (R)- and (S)-5'-C-methyl (C5'-Me) substituted nucleosides and their incorporation into ONs. These modifications generally resulted in a decrease in thermal stability of oligonucleotide (ON) duplexes in a manner dependent on the stereoconfiguration at C5' with greater destabilization characteristic of (R)-epimers. Enhanced stability against snake venom phosphodiesterase resulted from modification of the 3'-end of an ON with either (R)- or (S)-C5'-Me nucleotides. The (S)-isomers with different 2'-substituents provided greater resistance against 3'-exonucleases than the corresponding (R)-isomers. Crystal structure analyses of RNA octamers with (R)- or (S)-5'-C-methyl-2'-deoxy-2'-fluorouridine [(R)- or (S)-C5'-Me-2'-FU, respectively] revealed that the stereochemical orientation of the C5'-Me and the steric effects that emanate from the alkyl substitution are the dominant determinants of thermal stability and are likely molecular origins of resistance against nucleases. X-ray and NMR structural analyses showed that the (S)-C5'-Me epimers are spatially and structurally more similar to their natural 5' nonmethylated counterparts than the corresponding (R)-epimers.

  10. Structural Basis of Duplex Thermodynamic Stability and Enhanced Nuclease Resistance of 5'-C-Methyl Pyrimidine-Modified Oligonucleotides.

    PubMed

    Kel'in, Alexander V; Zlatev, Ivan; Harp, Joel; Jayaraman, Muthusamy; Bisbe, Anna; O'Shea, Jonathan; Taneja, Nate; Manoharan, Rajar M; Khan, Saeed; Charisse, Klaus; Maier, Martin A; Egli, Martin; Rajeev, Kallanthottathil G; Manoharan, Muthiah

    2016-03-18

    Although judicious use of chemical modifications has contributed to the success of nucleic acid therapeutics, poor systemic stability remains a major hurdle. The introduction of functional groups around the phosphate backbone can enhance the nuclease resistance of oligonucleotides (ONs). Here, we report the synthesis of enantiomerically pure (R)- and (S)-5'-C-methyl (C5'-Me) substituted nucleosides and their incorporation into ONs. These modifications generally resulted in a decrease in thermal stability of oligonucleotide (ON) duplexes in a manner dependent on the stereoconfiguration at C5' with greater destabilization characteristic of (R)-epimers. Enhanced stability against snake venom phosphodiesterase resulted from modification of the 3'-end of an ON with either (R)- or (S)-C5'-Me nucleotides. The (S)-isomers with different 2'-substituents provided greater resistance against 3'-exonucleases than the corresponding (R)-isomers. Crystal structure analyses of RNA octamers with (R)- or (S)-5'-C-methyl-2'-deoxy-2'-fluorouridine [(R)- or (S)-C5'-Me-2'-FU, respectively] revealed that the stereochemical orientation of the C5'-Me and the steric effects that emanate from the alkyl substitution are the dominant determinants of thermal stability and are likely molecular origins of resistance against nucleases. X-ray and NMR structural analyses showed that the (S)-C5'-Me epimers are spatially and structurally more similar to their natural 5' nonmethylated counterparts than the corresponding (R)-epimers. PMID:26940174

  11. Use of Modified Phenolic Thyme Extracts (Thymus vulgaris) with Reduced Polyphenol Oxidase Substrates as Anthocyanin Color and Stability Enhancing Agents.

    PubMed

    Aguilar, Oscar; Hernández-Brenes, Carmen

    2015-01-01

    Residual enzymatic activity in certain foods, particularly of polyphenoloxidase (PPO), is responsible for the majority of anthocyanin degradation in food systems, causing also parallel losses of other relevant nutrients. The present work explored the feasibility of modifying phenolic profiles of thyme extracts, by use of chromatographic resins, to obtain phenolic extracts capable of enhancing anthocyanin colour and stability in the presence of PPO activity. Results indicated that pretreatment of thyme extracts with strong-anion exchange resins (SAE) enhanced their copigmentation abilities with strawberry juice anthocyanins. Phenolic chromatographic profiles, by HPLC-PDA, also demonstrated that thyme extracts subjected to SAE treatments had significantly lower concentrations of certain phenolic compounds, but extracts retained their colour enhancing and anthocyanin stabilization capacities though copigmentation. Additional testing also indicated that SAE modified extract had a lower ability (73% decrease) to serve as PPO substrate, when compared to the unmodified extract. Phenolic profile modification process, reported herein, could be potentially used to manufacture modified anthocyanin-copigmentation food and cosmetic additives for colour-stabilizing applications with lower secondary degradation reactions in matrixes that contain PPO activity. PMID:26694329

  12. Colour stabilities of sour cherry juice concentrates enhanced with gallic acid and various plant extracts during storage.

    PubMed

    Navruz, Ayşe; Türkyılmaz, Meltem; Özkan, Mehmet

    2016-04-15

    Gallic acid (GA) and pomegranate rind extract (PRE), cherry stem extract (CSE) and green tea extract (GTE) were added to sour cherry juice concentrates (SCJCs) to enhance the colour. Effects of these copigment sources on anthocyanins, colour and turbidity were investigated during storage at -20, 4 and 20°C for 110 days. Cyanidin-3-glucosylrutinoside (cyd-3-glu-rut, 75%) was the major anthocyanin, followed by cyanidin-3-rutinoside (cyd-3-rut, 23%) and cyanidin-3-sophoroside (cyd-3-soph, 2%). While GA (37-53%), PRE (27-77%) and GTE (44-119%) increased the stabilities of cyd-3-rut and cyd-3-glu-rut, CSE reduced (12-24%) the stabilities of all anthocyanins. Polymeric colour and turbidity values increased after the addition of all extracts and GA. The lowest turbidity value after 110 days of storage at 20°C was determined in the SCJC enhanced with PRE. We recommend the addition of PRE to SCJC for the enhancement of anthocyanin stability and colour intensity, and the reduction in turbidity. PMID:26616935

  13. Colour stabilities of sour cherry juice concentrates enhanced with gallic acid and various plant extracts during storage.

    PubMed

    Navruz, Ayşe; Türkyılmaz, Meltem; Özkan, Mehmet

    2016-04-15

    Gallic acid (GA) and pomegranate rind extract (PRE), cherry stem extract (CSE) and green tea extract (GTE) were added to sour cherry juice concentrates (SCJCs) to enhance the colour. Effects of these copigment sources on anthocyanins, colour and turbidity were investigated during storage at -20, 4 and 20°C for 110 days. Cyanidin-3-glucosylrutinoside (cyd-3-glu-rut, 75%) was the major anthocyanin, followed by cyanidin-3-rutinoside (cyd-3-rut, 23%) and cyanidin-3-sophoroside (cyd-3-soph, 2%). While GA (37-53%), PRE (27-77%) and GTE (44-119%) increased the stabilities of cyd-3-rut and cyd-3-glu-rut, CSE reduced (12-24%) the stabilities of all anthocyanins. Polymeric colour and turbidity values increased after the addition of all extracts and GA. The lowest turbidity value after 110 days of storage at 20°C was determined in the SCJC enhanced with PRE. We recommend the addition of PRE to SCJC for the enhancement of anthocyanin stability and colour intensity, and the reduction in turbidity.

  14. Use of Modified Phenolic Thyme Extracts (Thymus vulgaris) with Reduced Polyphenol Oxidase Substrates as Anthocyanin Color and Stability Enhancing Agents.

    PubMed

    Aguilar, Oscar; Hernández-Brenes, Carmen

    2015-12-14

    Residual enzymatic activity in certain foods, particularly of polyphenoloxidase (PPO), is responsible for the majority of anthocyanin degradation in food systems, causing also parallel losses of other relevant nutrients. The present work explored the feasibility of modifying phenolic profiles of thyme extracts, by use of chromatographic resins, to obtain phenolic extracts capable of enhancing anthocyanin colour and stability in the presence of PPO activity. Results indicated that pretreatment of thyme extracts with strong-anion exchange resins (SAE) enhanced their copigmentation abilities with strawberry juice anthocyanins. Phenolic chromatographic profiles, by HPLC-PDA, also demonstrated that thyme extracts subjected to SAE treatments had significantly lower concentrations of certain phenolic compounds, but extracts retained their colour enhancing and anthocyanin stabilization capacities though copigmentation. Additional testing also indicated that SAE modified extract had a lower ability (73% decrease) to serve as PPO substrate, when compared to the unmodified extract. Phenolic profile modification process, reported herein, could be potentially used to manufacture modified anthocyanin-copigmentation food and cosmetic additives for colour-stabilizing applications with lower secondary degradation reactions in matrixes that contain PPO activity.

  15. Generation of enhanced stability factor VIII variants by replacement of charged residues at the A2 domain interface.

    PubMed

    Wakabayashi, Hironao; Varfaj, Fatbardha; Deangelis, Jennifer; Fay, Philip J

    2008-10-01

    Factor VIII consists of a heavy chain (A1A2B domains) and light chain (A3C1C2 domains), whereas the contiguous A1A2 domains are separate subunits in the cofactor, factor VIIIa. The intrinsic instability of the cofactor results from weak affinity interactions of the A2 subunit within factor VIIIa. The charged residues Glu272, Asp519, Glu665, and Glu1984 appear buried at the interface of the A2 domain with either the A1 or A3 domain, and thus may impact protein stability. To determine the effects of these residues on procofactor/cofactor stability, these residues were individually replaced with either Ala or Val, and stable BHK cell lines expressing the B-domainless proteins were prepared. Specific activity and thrombin generation parameters for 7 of the 8 variants were more than 80% the wild-type value. Factor VIII activity at 52 degrees C to 60 degrees C and the decay of factor VIIIa activity after thrombin activation were monitored. Six of the 7 variants showing wild-type-like activity demonstrated enhanced stability, with the Glu1984Val variant showing a 2-fold increase in thermostability and an approximately 4- to 8-fold increase in stability of factor VIIIa. These results indicate that replacement of buried charged residues is an effective alternative to covalent modification in increasing factor VIII (VIIIa) stability. PMID:18650448

  16. Optimization of operation conditions for preventing sludge bulking and enhancing the stability of aerobic granular sludge in sequencing batch reactors.

    PubMed

    Zhou, Jun; Wang, Hongyu; Yang, Kai; Ma, Fang; Lv, Bin

    2014-01-01

    Sludge bulking caused by loss of stability is a major problem in aerobic granular sludge systems. This study investigated the feasibility of preventing sludge bulking and enhancing the stability of aerobic granular sludge in a sequencing batch reactor by optimizing operation conditions. Five operation parameters have been studied with the aim to understand their impact on sludge bulking. Increasing dissolved oxygen (DO) by raising aeration rates contributed to granule stability due to the competition advantage of non-filamentous bacteria and permeation of oxygen at high DO concentration. The ratio of polysaccharides to proteins was observed to increase as the hydraulic shear force increased. When provided with high/low organic loading rate (OLR) alternately, large and fluffy granules disintegrated, while denser round-shape granules formed. An increase of biomass concentration followed a decrease at the beginning, and stability of granules was improved. This indicated that aerobic granular sludge had the resistance of OLR. Synthetic wastewater combined highly and slowly biodegradable substrates, creating a high gradient, which inhibited the growth of filamentous bacteria and prevented granular sludge bulking. A lower chemical oxygen demand/N favored the hydrophobicity of granular sludge, which promoted with granule stability because of the lower diffusion rate of ammonia. The influence of temperature indicated a relatively low temperature was more suitable.

  17. Hot melt extrusion for amorphous solid dispersions: temperature and moisture activated drug-polymer interactions for enhanced stability.

    PubMed

    Sarode, Ashish L; Sandhu, Harpreet; Shah, Navnit; Malick, Waseem; Zia, Hossein

    2013-10-01

    Hot melt extrudates (HMEs) of indomethacin (IND) with Eudragit EPO and Kollidon VA 64 and those of itraconazole (ITZ) with HPMCAS-LF and Kollidon VA 64 were manufactured using a Leistritz twin screw extruder. The milled HMEs were stored at controlled temperature and humidity conditions. The samples were collected after specified time periods for 3 months. The stability of amorphous HMEs was assessed using moisture analysis, thermal evaluation, powder X-ray diffraction, FTIR, HPLC, and dissolution study. In general, the moisture content increased with time, temperature, and humidity levels. Amorphous ITZ was physically unstable at very high temperature and humidity levels, and its recrystallization was detected in the HMEs manufactured using Kollidon VA 64. Although physical stability of IND was better sustained by both Eudragit EPO and Kollidon VA 64, chemical degradation of the drug was identified in the stability samples of HMEs with Eudragit EPO stored at 50 °C. The dissolution rates and the supersaturation levels were significantly decreased for the stability samples in which crystallization was detected. Interestingly, the supersaturation was improved for the stability samples of IND:Eudragit EPO and ITZ:HPMCAS-LF, in which no physical or chemical instability was observed. This enhancement in supersaturation was attributed to the temperature and moisture activated electrostatic interactions between the drugs and their counterionic polymers. PMID:23961978

  18. High carotenoid bioaccessibility through linseed oil nanoemulsions with enhanced physical and oxidative stability.

    PubMed

    Sotomayor-Gerding, Daniela; Oomah, B Dave; Acevedo, Francisca; Morales, Eduardo; Bustamante, Mariela; Shene, Carolina; Rubilar, Mónica

    2016-05-15

    Carotenoid (astaxanthin or lycopene) emulsions obtained by high pressure homogenization were investigated for their physical, oxidative and storage stability and biological fate on an in vitro digestion model of bioaccessibility. Emulsion stability evaluated at various processing environments (20-50°C, 2-10 pH, 0-500 mM NaCl, and 0-35 days storage at 25°C) depended on carotenoid and homogenization pressures (5, 10, 100 MPa). Trolox increased the oxidative stability of nanoemulsions (100 MPa) and acted synergistically with BHT in increasing the stability of lycopene nanoemulsion. Intestinal digestibility depended on homogenization pressures with the fastest release and lower amount of free fatty acids observed at 100 MPa. Carotenoid nanoemulsions (100 MPa) were partially (66%) digested and highly bioaccessible (>70%). Therefore, nanoemulsions provide an effective and stable system for efficient astaxanthin or lycopene delivery and bioavailability in foods, beverages, nutraceuticals and/or other agriproducts.

  19. The Or gene enhances carotenoid accumulation and stability during post-harvest storage of potato tubers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Provitamin A carotenoids in staple crops are not very stable during storage and their loss compromises nutritional quality. To elucidate the fundamental mechanisms underlying carotenoid accumulation and stability, we investigated transgenic potato tubers that express the cauliflower Orange (Or) gene...

  20. Enhanced thermal stability of lysosomal beta-D-galactosidase in parenchymal cells of tumour bearing mice.

    PubMed Central

    Lenti, L.; Lipari, M.; Lombardi, D.; Zicari, A.; Dotta, A.; Pontieri, G. M.

    1986-01-01

    The thermal stability of the enzyme beta-D-galactosidase varies among different organs in normal C57Bl/6 mice, and increases in the same organs in mice with Lewis Lung carcinoma. Thermal stability of this enzyme is also increased by treatment of the mice with cell-free extracts of tumour cells or with inflammatory compounds such as carrageenan or orosomucoid. After desialylation, orosomucoid more effectively increases the heat stability of the enzyme. By contrast talc, which has no galactosyl groups, is without effect on the stability of the enzyme in vivo. Macrophages of tumour bearing mice release into the culture medium a more heat resistant enzyme than macrophages from control mice. In both cases the heat resistance of the secreted enzyme is higher when fetal calf serum is present in the culture medium. Bovine serum does not modify the thermal stability of beta-D-galactosidase in this system. Incubation of lysosomal fractions of various organs with the synthetic beta-D-galactosidase substrate, p-nitrophenyl-galactopyranoside, also strongly increases the heat resistance of the enzyme. The results suggest that one factor influencing the heat resistance of this enzyme may be complex formation between the enzyme and its substrates, an example of substrate protection of the enzyme. This may not be the only factor involved in enzyme stabilization in vivo. PMID:3099822

  1. Stabilization and enhanced reactivity of actinorhodin polyketide synthase minimal complex in polymer-nucleotide coacervate droplets.

    PubMed

    Crosby, John; Treadwell, Tom; Hammerton, Michelle; Vasilakis, Konstantinos; Crump, Matthew P; Williams, David S; Mann, Stephen

    2012-12-18

    Compartmentalization of the minimal complex of actinorhodin polyketide synthase in coacervate liquid droplets produces enhanced yields of shunt polyketides under conditions of low and high ionic strength.

  2. Encapsulation of biophenolic phytochemical EGCG within lipid nanoparticles enhances its stability and cytotoxicity against cancer.

    PubMed

    Radhakrishnan, Rasika; Kulhari, Hitesh; Pooja, Deep; Gudem, Sagarika; Bhargava, Suresh; Shukla, Ravi; Sistla, Ramakrishna

    2016-06-01

    Epigallocatechin gallate (EGCG), a green tea polyphenolic catechin, has been known to possess a variety of beneficial biological activities. The in-vitro anti-cancer activity of EGCG is well documented. However, the use of EGCG in modern therapeutics is limited due to its poor bioavailability and limited stability at physiological pH. In this study, we have investigated the stability profiles of EGCG in aqueous solutions using UV-vis spectroscopy. Stability results showed very low stability profile of EGCG at physiological pH with rapid degradation under alkaline conditions. Therefore, we have encapsulated EGCG in solid lipid nanoparticles to increase its stability and evaluated for anticancer activity. The lipid core of nanoparticles not only provides an additional structural reinforcement to the nanoparticle assembly, but also makes it biologically compatible, thereby enabling a stealth vehicle for efficient drug delivery. EGCG loaded nanoparticles (EGCG-SLN) were characterized using dynamic light scattering, Fourier transform infrared spectroscopy and differential scanning calorimetry. EGCG and EGCG-SLN were evaluated for their anticancer activities by cellular proliferation. The cytotoxicity of EGCG-SLN was found to be 8.1 times higher against MDA-MB 231 human breast cancer cells and 3.8 times higher against DU-145 human prostate cancer cells than that of the pure EGCG. PMID:27234272

  3. Chemical modification of turnip peroxidase with methoxypolyethylene glycol enhances activity and stability for phenol removal using the immobilized enzyme.

    PubMed

    Quintanilla-Guerrero, F; Duarte-Vázquez, M A; Tinoco, R; Gómez-Suárez, M; García-Almendárez, B E; Vazquez-Duhalt, R; Regalado, C

    2008-09-10

    Peroxidase from turnip roots (TP) was isolated followed by modification with methoxypolyethylene glycol (MPEG). The catalytic activity of the modified TP (MTP) on ABTS increased 2.5 times after 80 min of reaction. MTP showed a KM similar value to that of TP, but a significantly greater kcat for ABTS oxidation, in aqueous buffer. Chemical modification produced an enhanced stability in organic solvents and increased thermal stability of about 4 times that of TP, in aqueous buffer at 70 degrees C. Circular dichroism showed that MPEG modification decreased TP alpha-helical structure from 26 to 16% and increased beta-turns from 26 to 34%, resulting in an enhanced conformational stability. The temperature at the midpoint of thermal denaturation (melting temperature) increased from 57 to 63 degrees C after modification. MTP was immobilized in alginate beads (IMTP) and tested for oxidative polymerization of concentrated phenolic synthetic solutions, achieving 17 effective contact cycles removing >65% phenols. IMTP may be useful for the development of an enzymatic process for wastewater effluent treatment. PMID:18698787

  4. Fabrication of Dendrimer-Based Polyion Complex Submicrometer-Scaled Structures with Enhanced Stability under Physiological Conditions.

    PubMed

    Naoyama, Kenshiro; Mori, Takeshi; Katayama, Yoshiki; Kishimura, Akihiro

    2016-07-01

    Submicrometer-scaled (subμ-) self-assembled materials have been developed based on polyion complex (PIC) formation, in particular for biomedical-applications. However, sufficient stability under physiological conditions is required for their practical use. In this study, PIC formation behavior is examined using a block aniomer, poly(ethylene glycol)-b-poly(aspartic acid), and homocatiomers, poly(l-lysine) (LPK) and dendritic poly(l-lysine) (DPK) with different generations, to elucidate the contribution of the dendritic architecture to stability enhancement. LPK-based PIC shows a subμ-vesicular structure only at 25 °C in the absence of NaCl; in contrast, DPK-based PIC forms a subμ-structure under physiological salt concentration and temperature conditions, even when the number of charges of a single molecule is much smaller than that of LPK. Moreover, the formation of subμ-vesicular and -spherical micellar structures is dependent on DPK generation. Thus, the molecular backbone architecture of the PIC component plays an important role not only in expanding the preparation conditions and enhancing stability, but also in controlling the self-assembled structures, mainly due to the spatially restricted structures of dendrimers. PMID:27191793

  5. Polymer-Enhanced Stability of Inorganic Perovskite Nanocrystals and Their Application in Color Conversion LEDs.

    PubMed

    Meyns, Michaela; Perálvarez, Mariano; Heuer-Jungemann, Amelie; Hertog, Wim; Ibáñez, Maria; Nafria, Raquel; Genç, Aziz; Arbiol, Jordi; Kovalenko, Maksym V; Carreras, Josep; Cabot, Andreu; Kanaras, Antonios G

    2016-08-01

    Cesium lead halide (CsPbX3, X = Cl, Br, I) nanocrystals (NCs) offer exceptional optical properties for several potential applications but their implementation is hindered by a low chemical and structural stability and limited processability. In the present work, we developed a new method to efficiently coat CsPbX3 NCs, which resulted in their increased chemical and optical stability as well as processability. The method is based on the incorporation of poly(maleic anhydride-alt-1-octadecene) (PMA) into the synthesis of the perovskite NCs. The presence of PMA in the ligand shell stabilizes the NCs by tightening the ligand binding, limiting in this way the NC surface interaction with the surrounding media. We further show that these NCs can be embedded in self-standing silicone/glass plates as down-conversion filters for the fabrication of monochromatic green and white light emitting diodes (LEDs) with narrow bandwidths and appealing color characteristics. PMID:27454750

  6. Fuzzy wavelet plus a quantum neural network as a design base for power system stability enhancement.

    PubMed

    Ganjefar, Soheil; Tofighi, Morteza; Karami, Hamidreza

    2015-11-01

    In this study, we introduce an indirect adaptive fuzzy wavelet neural controller (IAFWNC) as a power system stabilizer to damp inter-area modes of oscillations in a multi-machine power system. Quantum computing is an efficient method for improving the computational efficiency of neural networks, so we developed an identifier based on a quantum neural network (QNN) to train the IAFWNC in the proposed scheme. All of the controller parameters are tuned online based on the Lyapunov stability theory to guarantee the closed-loop stability. A two-machine, two-area power system equipped with a static synchronous series compensator as a series flexible ac transmission system was used to demonstrate the effectiveness of the proposed controller. The simulation and experimental results demonstrated that the proposed IAFWNC scheme can achieve favorable control performance. PMID:26363960

  7. Modification of PEGylated enzyme with glutaraldehyde can enhance stability while avoiding intermolecular crosslinking†

    PubMed Central

    McShane, M. J.

    2015-01-01

    We demonstrate an enzyme stabilization approach whereby a model enzyme is PEGylated, followed by controlled chemical modification with glutaraldehyde. Using this stabilization strategy, size increases and aggregation due to intermolecular crosslinking are avoided. Immediately following synthesis, the PEGylated enzyme with and without glutaraldehyde modification possessed specific activities of 372.9 ± 20.68 U/mg and 373.9 ± 15.14 U/mg, respectively (vs. 317.7 ± 19.31 U/mg for the native enzyme). The glutaraldehyde-modified PEGylated enzyme retains 73% original activity after 4 weeks at 37 °C (vs. 2% retention for control). PMID:26052433

  8. A Numerical Simulation for Movement of Contaminated Water through a Wellbore

    NASA Astrophysics Data System (ADS)

    Stanko, Z. P.; Nishikawa, T.; Teague, N. F.; Izbicki, J. A.

    2014-12-01

    A 3D groundwater-flow model was developed using MODFLOW and MODPATH particle tracking to simulate movement of water through a 293-m public-supply well under unpumped and pumped conditions. The well, located in the Rialto-Colton groundwater basin in Southern Calif., penetrates two water-bearing units, separated by a low-permeability layer, and has been inactive for 8 years as a result of perchlorate contamination; field data show 13 kg of perchlorate is redistributed annually through the well from the upper to the lower unit. The local-scale (13.7 km2) model included one pumping well and was calibrated to wellbore flow and head data. The parameter-estimation software, PEST, was used to estimate hydraulic conductivities (K) for each of 18 homogeneous and isotropic model layers. The PEST problem was ill-posed, which was partially mitigated by applying singular value decomposition and Tikhonov regularization. Prior information included lithology from drillers' logs and approximate regional water-level gradients. The model simulated: 1) unpumped wellbore flow and contaminant redistribution from the upper, contaminated unit to the lower, uncontaminated unit; and 2) pumped wellbore flow and contaminant recapture. Model results indicated that a vertical head gradient of about 1% could vertically redistribute the perchlorate through the unpumped well. The longitudinal extent of the redistributed contaminant plume in the direction of the regional horizontal gradient was strongly dependent on the calibrated K values. In addition, the simulated horizontal distribution of contaminants in the transverse direction matched observed concentrations collected from a nearby well at various depths. Under pumped conditions, 67% of the tracked particles were recaptured within 10 years of resuming pumping at 13,250 L/min. Sensitivity analyses revealed that perchlorate recapture estimates are unaffected by small uncertainties in K or the regional gradient imposed by the boundary conditions.

  9. Shale-Gas Experience as an Analog for Potential Wellbore Integrity Issues in CO2 Sequestration

    SciTech Connect

    Carey, James W.; Simpson, Wendy S.; Ziock, Hans-Joachim

    2011-01-01

    Shale-gas development in Pennsylvania since 2003 has resulted in about 19 documented cases of methane migration from the deep subsurface (7,0000) to drinking water aquifers, soils, domestic water wells, and buildings, including one explosion. In all documented cases, the methane leakage was due to inadequate wellbore integrity, possibly aggravated by hydrofracking. The leakage of methane is instructive on the potential for CO{sub 2} leakage from sequestration operations. Although there are important differences between the two systems, both involve migrating, buoyant gas with wells being a primary leakage pathway. The shale-gas experience demonstrates that gas migration from faulty wells can be rapid and can have significant impacts on water quality and human health and safety. Approximately 1.4% of the 2,200 wells drilled into Pennsylvania's Marcellus Formation for shale gas have been implicated in methane leakage. These have resulted in damage to over 30 domestic water supplies and have required significant remediation via well repair and homeowner compensation. The majority of the wellbore integrity problems are a result of over-pressurization of the wells, meaning that high-pressure gas has migrated into an improperly protected wellbore annulus. The pressurized gas leaks from the wellbore into the shallow subsurface, contaminating drinking water or entering structures. The effects are localized to a few thousands of feet to perhaps two-three miles. The degree of mixing between the drinking water and methane is sufficient that significant chemical impacts are created in terms of elevated Fe and Mn and the formation of black precipitates (metal sulfides) as well as effervescing in tap water. Thus it appears likely that leaking CO{sub 2} could also result in deteriorated water quality by a similar mixing process. The problems in Pennsylvania highlight the critical importance of obtaining background data on water quality as well as on problems associated with

  10. Chemical and Physical Reactions of Wellbore Cement under CO2 Storage Conditions: Effects of Cement Additives

    NASA Astrophysics Data System (ADS)

    Kutchko, B. G.; Strazisar, B. R.; Huerta, N.; Lowry, G. V.; Dzombak, D. A.; Thaulow, N.

    2008-12-01

    Sequestration of CO2 into geologic formations requires long-term storage and low leakage rates to be effective. Active and abandoned wells in candidate storage formations must be evaluated as potential leakage points. Wellbore integrity is an important part of an overall integrated assessment program being developed at NETL to assess potential risks at CO2 storage sites. Such a program is needed for ongoing policy and regulatory decisions for geologic carbon sequestration. The permeability and integrity of the cement in the well is a primary factor affecting its ability to prevent leakage. Cement must be able to maintain low permeability over lengthy exposure to reservoir conditions in a CO2 injection and storage scenario. Although it is known that cement may be altered by exposure to CO2, the results of ongoing research indicate that cement curing conditions, fluid properties, and cement additives play a significant role in the rate of alteration and reaction. The objective of this study is to improve understanding of the factors affecting wellbore cement integrity for large-scale geologic carbon sequestration projects. Due to the high frequency use of additives (pozzolan) in wellbore cement, it is also essential to understand the reaction of these cement-pozzolan systems upon exposure to CO2 under sequestration conditions (15.5 MPa and 50°C). Laboratory experiments were performed to determine the physical and chemical changes, as well as the rate of alteration of commonly used pozzolan-cement systems under simulated sequestration reservoir conditions, including both supercritical CO2 and CO2-saturated brine. The rate of alteration of the cement-pozzolan systems is considerably faster than with neat cement. However, the alteration of physical properties is much less significant with the pozzolanic blends. Permeability of a carbonated pozzolanic cement paste remains sufficiently small to block significant vertical migration of CO2 in a wellbore. All of the

  11. Modeling Methane Leakage from Faulty Wellbores in the Denver-Julesburg Basin, Colorado

    NASA Astrophysics Data System (ADS)

    Lackey, G.; Rajaram, H.; Karra, S.; Sherwood, O.; Burke, T. L.

    2015-12-01

    Regulations in the state of Colorado mandate that all oil and gas wells be constructed with surface casings that extend 50 feet below the depth of the deepest potable aquifer, and production casings that are cemented to at least 200 feet above the shallowest producing formation. Building wells in accordance with the minimum regulations leaves an uncemented annulus between the production casing and the surrounding rock matrix, extending from the bottom of the surface casing to the top of the production casing cement. In Colorado, this annulus is sealed at the ground surface by the "bradenhead valve". Stray methane can enter the uncemented annulus through faulty cement in the producing formation or an intermediate gas-bearing zone and migrate upwards along the production casing. The gas dissolves into the annular fluid and accumulates below the bradenhead valve building pressure. Data from the Colorado Oil and Gas Conservation Commission (COGCC) indicates that 1,492 wells in the Denver-Julesburg (DJ) Basin have recorded bradenhead pressures greater than 20 psi since 2007. A leak of this kind creates the potential for both the single-phase transport of dissolved methane and the multiphase transport of methane gas away from the well. The degree to which methane transport occurs depends not only on the size of the leak but also the construction of the wellbore. In Colorado, the definition of potable groundwater has changed with time. To meet increasing demands for water, drinking water wells have been drilled deeper. As a result, there are potentially 4,144 wells in the DJ Basin with surface casings too shallow to protect the deepest potable aquifer. In this work, we investigate how a methane leak into the open annulus of an oil and gas wellbore, could result in the transport of dissolved and gas phase methane into a nearby drinking water aquifer. We construct a multiphase wellbore model that computes the pressure distribution and gas fraction along the uncemented

  12. Ionic Polymer-Coated Laccase with High Activity and Enhanced Stability: Application in the Decolourisation of Water Containing AO7

    PubMed Central

    Zhang, Xiaolin; Hua, Ming; Lv, Lu; Pan, Bingcai

    2015-01-01

    Eliminating dyes in environmental water purification remains a formidable challenge. Laccase is a unique, environmentally friendly and efficient biocatalyst that can degrade pollutants. However, the use of laccase for the degradation of pollutants is considerably limited by its susceptibility to environmental changes and its poor reusability. We fabricated a novel biocatalyst (LacPG) by coating polyethylenimine onto the native laccase (Lac) followed by crosslinking with glutaraldehyde. The stability of the resulting LacPG was highly enhanced against pH variations, thermal treatments and provided better long-term storage with a negligible loss in enzymatic activity. Compared to Lac, LacPG exhibited significantly higher decolourisation efficiency in the degradation of a representative azo dye, acid orange 7 (AO7), which resulted from the electrostatic attraction between the coating and AO7. LacPG was separated from the AO7 solution using an ultrafiltration unit. The increased size and modified surface chemistry of LacPG facilitated ultrafiltration and reduced membrane fouling. LacPG exhibited enhanced stability, high catalytic activity and favourable properties for membrane separation; therefore, LacPG could be continuously reused in an enzymatic membrane reactor with a high efficiency for decolourising water containing AO7. The developed strategy appears to be promising for enhancing the applicability of laccase in practical water treatment. PMID:25652843

  13. Enhanced physical stabilization of fenofibrate nanosuspensions via wet co-milling with a superdisintegrant and an adsorbing polymer.

    PubMed

    Azad, Mohammad; Afolabi, Afolawemi; Bhakay, Anagha; Leonardi, Jonathan; Davé, Rajesh; Bilgili, Ecevit

    2015-08-01

    Drug nanoparticles in suspensions can form aggregates leading to physical instability, which is traditionally mitigated using soluble polymers and surfactants. The aim of this paper was to explore common superdisintegrants, i.e., sodium starch glycolate (SSG), croscarmellose sodium (CCS), and crospovidone (CP), as novel class of dispersants for enhanced stabilization of fenofibrate (FNB), a model BCS Class II drug, suspensions. FNB was wet-milled with superdisintegrants along with hydroxypropyl methylcellulose (HPMC), a soluble adsorbing polymer, in a stirred media mill. For comparison, FNB was also milled in the presence of HPMC and/or SDS (sodium dodecyl sulfate) without superdisintegrants. Laser diffraction, scanning electron microscopy, viscometry, differential scanning calorimetry, and powder X-ray diffraction were used to characterize the suspensions. The results show that 2% HPMC along with 1% SSG or 1% CCS mitigated the aggregation of FNB nanoparticles significantly similar to the use of either 5% HPMC or 1% HPMC-0.075% SDS, whereas CP was not effective due to its low swelling capacity. CCS/SSG enhanced steric-kinetic stabilization of the FNB suspensions owing to their high swelling capacity, viscosity enhancement, and physical barrier action. Overall, this study provides a mechanistic basis for a novel method of formulating surfactant-free drug nanosuspensions with co-milled superdisintegrants. PMID:26079832

  14. Ionic Polymer-Coated Laccase with High Activity and Enhanced Stability: Application in the Decolourisation of Water Containing AO7

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaolin; Hua, Ming; Lv, Lu; Pan, Bingcai

    2015-02-01

    Eliminating dyes in environmental water purification remains a formidable challenge. Laccase is a unique, environmentally friendly and efficient biocatalyst that can degrade pollutants. However, the use of laccase for the degradation of pollutants is considerably limited by its susceptibility to environmental changes and its poor reusability. We fabricated a novel biocatalyst (LacPG) by coating polyethylenimine onto the native laccase (Lac) followed by crosslinking with glutaraldehyde. The stability of the resulting LacPG was highly enhanced against pH variations, thermal treatments and provided better long-term storage with a negligible loss in enzymatic activity. Compared to Lac, LacPG exhibited significantly higher decolourisation efficiency in the degradation of a representative azo dye, acid orange 7 (AO7), which resulted from the electrostatic attraction between the coating and AO7. LacPG was separated from the AO7 solution using an ultrafiltration unit. The increased size and modified surface chemistry of LacPG facilitated ultrafiltration and reduced membrane fouling. LacPG exhibited enhanced stability, high catalytic activity and favourable properties for membrane separation; therefore, LacPG could be continuously reused in an enzymatic membrane reactor with a high efficiency for decolourising water containing AO7. The developed strategy appears to be promising for enhancing the applicability of laccase in practical water treatment.

  15. Ionic polymer-coated laccase with high activity and enhanced stability: application in the decolourisation of water containing AO7.

    PubMed

    Zhang, Xiaolin; Hua, Ming; Lv, Lu; Pan, Bingcai

    2015-01-01

    Eliminating dyes in environmental water purification remains a formidable challenge. Laccase is a unique, environmentally friendly and efficient biocatalyst that can degrade pollutants. However, the use of laccase for the degradation of pollutants is considerably limited by its susceptibility to environmental changes and its poor reusability. We fabricated a novel biocatalyst (LacPG) by coating polyethylenimine onto the native laccase (Lac) followed by crosslinking with glutaraldehyde. The stability of the resulting LacPG was highly enhanced against pH variations, thermal treatments and provided better long-term storage with a negligible loss in enzymatic activity. Compared to Lac, LacPG exhibited significantly higher decolourisation efficiency in the degradation of a representative azo dye, acid orange 7 (AO7), which resulted from the electrostatic attraction between the coating and AO7. LacPG was separated from the AO7 solution using an ultrafiltration unit. The increased size and modified surface chemistry of LacPG facilitated ultrafiltration and reduced membrane fouling. LacPG exhibited enhanced stability, high catalytic activity and favourable properties for membrane separation; therefore, LacPG could be continuously reused in an enzymatic membrane reactor with a high efficiency for decolourising water containing AO7. The developed strategy appears to be promising for enhancing the applicability of laccase in practical water treatment.

  16. Enhancement stabilization of heavy metals (Zn, Pb, Cr and Cu) during vermifiltration of liquid-state sludge.

    PubMed

    Yang, Jian; Zhao, Chunhui; Xing, Meiyan; Lin, Yanan

    2013-10-01

    This paper illustrated the potential effect of earthworms on heavy metal stabilization after vermifiltration of liquid-state sludge. Significant enhancement of organics degradation in sludge caused an increase of heavy metal concentrations in VF effluent sludge. However, the analysis of heavy metal chemical speciation indicated earthworms made unstable fractions of heavy metals transformed into stable fractions. Further investigation using principal component analysis revealed that transformations of heavy metal fractions were mainly due to the changes in sludge physico-chemical properties of pH, soluble chemical oxygen demand and available phosphorus. The bioassay of earthworms indicated that only zinc was accumulated by earthworms because the unstable fraction was its main chemical speciation. Furthermore, risk analysis demonstrated that earthworm activities weakened heavy metal risk due to the formation of stable fractions although their total concentrations increased. These results indicated that earthworms in vermifilter had a positive role in stabilizing heavy metals in sewage sludge.

  17. Enhancement of thermal stability and water resistance in yttrium-doped GeO{sub 2}/Ge gate stack

    SciTech Connect

    Lu, Cimang Hyun Lee, Choong; Zhang, Wenfeng; Nishimura, Tomonori; Nagashio, Kosuke; Toriumi, Akira

    2014-03-03

    We have systematically investigated the material and electrical properties of yttrium-doped GeO{sub 2} (Y-GeO{sub 2}) on Germanium (Ge). A significant improvement of both thermal stability and water resistance were demonstrated by Y-GeO{sub 2}/Ge stack, compared to that of pure GeO{sub 2}/Ge stack. The excellent electrical properties of Y-GeO{sub 2}/Ge stacks with low D{sub it} were presented as well as enhancement of dielectric constant in Y-GeO{sub 2} layer, which is beneficial for further equivalent oxide thickness scaling of Ge gate stack. The improvement of thermal stability and water resistance are discussed both in terms of the Gibbs free energy lowering and network modification of Y-GeO{sub 2}.

  18. High stability of the hinge region in the membrane-active peptide helix of zervamicin: paramagnetic relaxation enhancement studies.

    PubMed

    Shenkarev, Zakhar O; Paramonov, Alexander S; Balashova, Tamara A; Yakimenko, Zoya A; Baru, Michael B; Mustaeva, Leila G; Raap, Jan; Ovchinnikova, Tatyana V; Arseniev, Alexander S

    2004-12-17

    Zervamicin IIB is a 16 amino acid peptaibol that forms voltage dependent ion channels with multilevel conductance states in planar lipid bilayers and vesicular systems. Stability of the hinge region and intermolecular interactions were investigated in the N- and C-terminally spin-labelled peptide analogues. Intermolecular and intramolecular paramagnetic enhancement indicates that zervamicin behaves as a rigid helical rod in methanol solution. There are no high amplitude hinge-bending motions, and the peptaibol is monomeric up to concentration 1.5 mM. Stability of the hinge region illustrates the helix stabilising propensity of the Pro residue in membrane mimic environments and implies absence of significant conformational rearrangement due to voltage peptaibol activation.

  19. Cross-linking oppositely charged oil-in-water emulsions to enhance heteroaggregate stability.

    PubMed

    Maier, Christiane; Oechsle, Anja M; Weiss, Jochen

    2015-11-01

    The formation and subsequent enzymatic and chemical cross-linking of heteroaggregates from oppositely charged oil-in-water (O/W) emulsions was investigated. For this purpose, 10% (w/w) oil-in-water emulsions (d43<1 μm) were prepared at pH 4 using a positively charged emulsifier (Nα-lauroyl-L-arginine ethyl ester (LAE), cold water fish gelatin, or whey protein isolate) or a negatively charged one (sugar beet pectin or Quillaja saponins). The oppositely charged emulsions were then combined at a volume ratio of 1:1 and treated with laccase or glutaraldehyde in order to further stabilize the electrostatically attached aggregates by covalently cross-linking the oppositely charged membranes. Emulsions and heteroaggregates were characterized by their rheological properties, their surface charge, particle size distribution, and microstructure using dynamic and static light scattering as well as confocal laser scanning microscopy. Prior to cross-linking, the emulsifiers' stabilization mechanism were found to greatly influence the formation of heteroaggregates. Laccase treatment (1.34 mU/mL) increased aggregate expansion by ca. 30% for the combined emulsions stabilized by Quillaja saponins/whey protein isolate, while combined Quillaja saponins/fish gelatin stabilized emulsions remained unaffected. When combined emulsions were treated with 50mM glutaraldehyde, aggregate size significantly increased 2- and 3-fold, respectively. Thus, our study provides novel insights into the enzymatic and chemical cross-linking of heteroaggregates composed of oppositely charged O/W emulsions.

  20. Hollow mesoporous ceria nanoreactors with enhanced activity and stability for catalytic application.

    PubMed

    Liu, Baocang; Yu, Shengli; Wang, Qin; Hu, Wenting; Jing, Peng; Liu, Yang; Jia, Wenjing; Liu, Yongxin; Liu, Lixia; Zhang, Jun

    2013-05-01

    Novel hollow mesoporous @M/CeO(2) (M = Au, Pd, and Au-Pd) nanospheres are created. The nanospheres can be used as effective nanoreactors with superior catalytic activity and stability for reduction of 4-nitrophenol due to their hollow mesoporous structural features.

  1. Cross-linking oppositely charged oil-in-water emulsions to enhance heteroaggregate stability.

    PubMed

    Maier, Christiane; Oechsle, Anja M; Weiss, Jochen

    2015-11-01

    The formation and subsequent enzymatic and chemical cross-linking of heteroaggregates from oppositely charged oil-in-water (O/W) emulsions was investigated. For this purpose, 10% (w/w) oil-in-water emulsions (d43<1 μm) were prepared at pH 4 using a positively charged emulsifier (Nα-lauroyl-L-arginine ethyl ester (LAE), cold water fish gelatin, or whey protein isolate) or a negatively charged one (sugar beet pectin or Quillaja saponins). The oppositely charged emulsions were then combined at a volume ratio of 1:1 and treated with laccase or glutaraldehyde in order to further stabilize the electrostatically attached aggregates by covalently cross-linking the oppositely charged membranes. Emulsions and heteroaggregates were characterized by their rheological properties, their surface charge, particle size distribution, and microstructure using dynamic and static light scattering as well as confocal laser scanning microscopy. Prior to cross-linking, the emulsifiers' stabilization mechanism were found to greatly influence the formation of heteroaggregates. Laccase treatment (1.34 mU/mL) increased aggregate expansion by ca. 30% for the combined emulsions stabilized by Quillaja saponins/whey protein isolate, while combined Quillaja saponins/fish gelatin stabilized emulsions remained unaffected. When combined emulsions were treated with 50mM glutaraldehyde, aggregate size significantly increased 2- and 3-fold, respectively. Thus, our study provides novel insights into the enzymatic and chemical cross-linking of heteroaggregates composed of oppositely charged O/W emulsions. PMID:26298085

  2. Nanocrystalline brookite with enhanced stability and photocatalytic activity: influence of lanthanum(III) doping.

    PubMed

    Perego, Céline; Wang, Yu-Heng; Durupthy, Olivier; Cassaignon, Sophie; Revel, Renaud; Jolivet, Jean-Pierre

    2012-02-01

    Metastable TiO(2) polymorphs are more promising materials than rutile for specific applications such as photocatalysis or catalysis support. This was clearly demonstrated for the anatase phase but still under consideration for brookite, which is difficult to obtain as pure phase. Moreover, the surface doping of anatase with lanthanum ions is known to both increase the thermal stability of the metastable phase and improve its photocatalytic activity. In this study, TiO(2) nanoparticles of almost only the brookite structure were prepared by a simple sol-gel procedure in aqueous solution. The nanoparticles were then doped with lanthanum(III) ions. The thermal stability of the nanoparticles was analyzed by X-ray diffraction and kinetic models were successfully applied to quantify phases evolutions. The presence of surface-sorbed lanthanum(III) ions increased the phase stability of at least 200 °C and this temperature shift was attributed to the selective phase stabilization of metastable TiO(2) polymorphs. Moreover, the combination of the surface doping ions and the thermal treatment induces the vanishing of the secondary anatase phase, and the photocatalytic tests on the doped brookite nanoparticles demonstrated that the doping increased photocatalytic activity and that the extent depended on the duration of the sintering treatment.

  3. Enhancement of the chemical stability in confined δ-Bi2O3

    NASA Astrophysics Data System (ADS)

    Sanna, Simone; Esposito, Vincenzo; Andreasen, Jens Wenzel; Hjelm, Johan; Zhang, Wei; Kasama, Takeshi; Simonsen, Søren Bredmose; Christensen, Mogens; Linderoth, Søren; Pryds, Nini

    2015-05-01

    Bismuth-oxide-based materials are the building blocks for modern ferroelectrics, multiferroics, gas sensors, light photocatalysts and fuel cells. Although the cubic fluorite δ-phase of bismuth oxide (δ-Bi2O3) exhibits the highest conductivity of known solid-state oxygen ion conductors, its instability prevents use at low temperature. Here we demonstrate the possibility of stabilizing δ-Bi2O3 using highly coherent interfaces of alternating layers of Er2O3-stabilized δ-Bi2O3 and Gd2O3-doped CeO2. Remarkably, an exceptionally high chemical stability in reducing conditions and redox cycles at high temperature, usually unattainable for Bi2O3-based materials, is achieved. Even more interestingly, at low oxygen partial pressure the layered material shows anomalous high conductivity, equal or superior to pure δ-Bi2O3 in air. This suggests a strategy to design and stabilize new materials that are comprised of intrinsically unstable but high-performing component materials.

  4. Gold nanoparticles coated with polysarcosine brushes to enhance their colloidal stability and circulation time in vivo.

    PubMed

    Chen, Ying; Xu, Zhengqing; Zhu, Difeng; Tao, Xinfeng; Gao, Yuqian; Zhu, Hong; Mao, Zhengwei; Ling, Jun

    2016-12-01

    Polysarcosine (PS), a non-ionic hydrophilic polypeptoid whose structure is similar to polypeptides, bearing repeating units of natural α-amino acid, has been used to stabilize gold nanoparticles (AuNPs) due to its excellent hydrophilicity and biocompatibility. Disulfide functionalized polysarcosines with different molecular weight were synthesized and used to cap AuNPs by traditional ligand exchange. The grafting of PS on AuNPs was evidenced by Fourier transform infrared (FTIR) spectroscopy and the alternation of surface zeta potential. The polysarcosine coated AuNPs (Au@PS) showed good stabilities in wide pH range and saline condition. They had strong resistance to ligand competition of dithiothreitol (DTT). They showed good stability in serum, with a molecular weight dependent interaction pattern with proteins. The Au@PS had very low cytotoxicity and cell uptake in vitro. Based on the results in vitro, polysarcosine with molecular weight of 5kD with the best ability to stabilize AuNPs was used for in vivo test. The Au@PS had a longer circulation time in blood after intravenous injection than that of Au@PEG, indicating a better stealth-like property of polysarcosine. The Au@PS did not cause obvious toxicity in vivo, suggesting potential applications in disease diagnosis and therapy. PMID:27552428

  5. Enhanced slippery behavior and stability of lubricating fluid infused nanostructured surfaces

    NASA Astrophysics Data System (ADS)

    Pant, Reeta; Ujjain, Sanjeev Kumar; Nagarajan, Arun Kumar; Khare, Krishnacharya

    2016-07-01

    Stability of lubricating fluid infused slippery surfaces is a concern for scientists and engineers and attempts are being made for its improvement. Lubricating oil coated slippery surface for aqueous drops is one of the important candidates in this class and their stability needs be improved to make them useful for practical applications. Cloaking of water drops with thin lubricant layer results in the loss of lubricant leading to deterioration of slippery behavior. Surface roughness or porosity provides larger surface area to the lubricating fluid and would to affect the stability of the lubricating film. Here we report the effect of surface roughness, from tens of nanometer to few microns, on the stability of slippery surface. Samples with small nanoscale roughness show improved performance in terms of contact angle hysteresis, critical tilt angle and slip velocity. Whereas large roughness samples show poorer performance compared to small nanoscale roughness and smooth samples. Small nanoscale roughness samples also show relatively slower deterioration against loss of lubricant during water flow. Once completely lost, the slippery behavior can be restored again simply by coating the sample again by the lubricating fluid.

  6. Coating with mesoporous silica remarkably enhances the stability of the highly active yet fragile flower-like MgO catalyst for dimethyl carbonate synthesis.

    PubMed

    Cui, Zhi-Min; Chen, Zhe; Cao, Chang-Yan; Song, Wei-Guo; Jiang, Lei

    2013-07-11

    Flower-like MgO is a highly effective catalyst for the synthesis of dimethyl carbonate through the transesterification method, and coating the catalyst with mesoporous silica significantly enhances the stability of the MgO catalyst.

  7. Fracture Characterization in Enhanced Geothermal Systems by Wellbore and Reservoir Analysis

    SciTech Connect

    Horne, Roland N.; Li, Kewen; Alaskar, Mohammed; Ames, Morgan; Co, Carla; Juliusson, Egill; Magnusdottir, Lilja

    2012-06-30

    This report highlights the work that was done to characterize fractured geothermal reservoirs using production data. That includes methods that were developed to infer characteristic functions from production data and models that were designed to optimize reinjection scheduling into geothermal reservoirs, based on these characteristic functions. The characterization method provides a robust way of interpreting tracer and flow rate data from fractured reservoirs. The flow-rate data are used to infer the interwell connectivity, which describes how injected fluids are divided between producers in the reservoir. The tracer data are used to find the tracer kernel for each injector-producer connection. The tracer kernel describes the volume and dispersive properties of the interwell flow path. A combination of parametric and nonparametric regression methods were developed to estimate the tracer kernels for situations where data is collected at variable flow-rate or variable injected concentration conditions. The characteristic functions can be used to calibrate thermal transport models, which can in turn be used to predict the productivity of geothermal systems. This predictive model can be used to optimize injection scheduling in a geothermal reservoir, as is illustrated in this report.

  8. Introduction of d-Glutamate at a Critical Residue of Aβ42 Stabilizes a Prefibrillary Aggregate with Enhanced Toxicity.

    PubMed

    Warner, Christopher J A; Dutta, Subrata; Foley, Alejandro R; Raskatov, Jevgenij A

    2016-08-16

    The amyloid beta peptide 42 (Aβ42) is an aggregation-prone peptide that plays a pivotal role in Alzheimer's disease. We report that a subtle perturbation to the peptide through a single chirality change at glutamate 22 leads to a pronounced delay in the β-sheet adoption of the peptide. This was accompanied by an attenuated propensity of the peptide to form fibrils, which was correlated with changes at the level of the fibrillary architecture. Strikingly, the incorporation of d-glutamate was found to stabilize a soluble, ordered macromolecular assembly with enhanced cytotoxicity to PC12 cells, highlighting the importance of advanced prefibrillary Aβ aggregates in neurotoxicity.

  9. Numerical analysis of wellbore integrity: results from a field study of a natural CO2 reservoir production well

    NASA Astrophysics Data System (ADS)

    Crow, W.; Gasda, S. E.; Williams, D. B.; Celia, M. A.; Carey, J. W.

    2008-12-01

    An important aspect of the risk associated with geological CO2 sequestration is the integrity of existing wellbores that penetrate geological layers targeted for CO2 injection. CO2 leakage may occur through multiple pathways along a wellbore, including through micro-fractures and micro-annuli within the "disturbed zone" surrounding the well casing. The effective permeability of this zone is a key parameter of wellbore integrity required for validation of numerical models. This parameter depends on a number of complex factors, including long-term attack by aggressive fluids, poor well completion and actions related to production of fluids through the wellbore. Recent studies have sought to replicate downhole conditions in the laboratory to identify the mechanisms and rates at which cement deterioration occurs. However, field tests are essential to understanding the in situ leakage properties of the millions of wells that exist in the mature sedimentary basins in North America. In this study, we present results from a field study of a 30-year-old production well from a natural CO2 reservoir. The wellbore was potentially exposed to a 96% CO2 fluid from the time of cement placement, and therefore cement degradation may be a significant factor leading to leakage pathways along this wellbore. A series of downhole tests was performed, including bond logs and extraction of sidewall cores. The cores were analyzed in the laboratory for mineralogical and hydrologic properties. A pressure test was conducted over an 11-ft section of well to determine the extent of hydraulic communication along the exterior of the well casing. Through analysis of this pressure test data, we are able estimate the effective permeability of the disturbed zone along the exterior of wellbore over this 11-ft section. We find the estimated range of effective permeability from the field test is consistent with laboratory analysis and bond log data. The cement interfaces with casing and/or formation are

  10. Enhancement of Aviation Fuel Thermal Stability Characterization Through Application of Ellipsometry

    NASA Technical Reports Server (NTRS)

    Browne, Samuel Tucker; Wong, Hubert; Hinderer, Cameron Branch; Klettlinger, Jennifer

    2012-01-01

    ASTM D3241/Jet Fuel Thermal Oxidation Tester (JFTOT) procedure, the standard method for testing thermal stability of conventional aviation turbine fuels is inherently limited due to the subjectivity in the color standard for tube deposit rating. Quantitative assessment of the physical characteristics of oxidative fuel deposits provides a more powerful method for comparing the thermal oxidation stability characteristics of fuels, especially in a research setting. We propose employing a Spectroscopic Ellipsometer to determine the film thickness and profile of oxidative fuel deposits on JFTOT heater tubes. Using JP-8 aviation fuel and following a modified ASTM D3241 testing procedure, the capabilities of the Ellipsometer will be demonstrated by measuring oxidative fuel deposit profiles for a range of different deposit characteristics. The testing completed in this report was supported by the NASA Fundamental Aeronautics Subsonics Fixed Wing Project

  11. Enhancement of Voltage Stability of DC Smart Grid During Islanded Mode by Load Shedding Scheme

    NASA Astrophysics Data System (ADS)

    Nassor, Thabit Salim; Senjyu, Tomonobu; Yona, Atsushi

    2015-10-01

    This paper presents the voltage stability of a DC smart grid based on renewable energy resources during grid connected and isolated modes. During the islanded mode the load shedding, based on the state of charge of the battery and distribution line voltage, was proposed for voltage stability and reservation of critical load power. The analyzed power system comprises a wind turbine, a photovoltaic generator, storage battery as controllable load, DC loads, and power converters. A fuzzy logic control strategy was applied for power consumption control of controllable loads and the grid-connected dual active bridge series resonant converters. The proposed DC Smart Grid operation has been verified by simulation using MATLAB® and PLECS® Blockset. The obtained results show the effectiveness of the proposed method.

  12. Enhancing the natural folate level in wine using bioengineering and stabilization strategies.

    PubMed

    Liu, Yazheng; Walkey, Christopher J; Green, Timothy J; van Vuuren, Hennie J J; Kitts, David D

    2016-03-01

    Folate deficiency is linked to many diseases, some of which may have higher probability in individuals with alcohol-induced alterations in one-carbon metabolism. Our study shows that folate content in commercial wine is not related to white or red varieties, but associated with the yeast that is used to produce the wine. The stability of folate in these wines, once opened for consumption, did not correlate with total phenolic or sulfite content. In addition, we employed yeast bioengineering to fortify wine with folate. We confirmed by overexpression that FOL2 was the key gene encoding the rate-limiting step of folate biosynthesis in wine yeast. In this study, we also show that overexpression of other folate biosynthesis genes, including ABZ1, ABZ2, DFR1, FOL1 and FOL3, had no effect on folate levels in wine. Ensuring stability of the increased natural folate in all wines was achieved by the addition of ascorbate.

  13. Enhanced Air Stability in REPb3 (RE = Rare Earths) by Dimensional Reduction Mediated Valence Transition.

    PubMed

    Subbarao, Udumula; Sarkar, Sumanta; Jana, Rajkumar; Bera, Sourav S; Peter, Sebastian C

    2016-06-01

    We conceptually selected the compounds REPb3 (RE = Eu, Yb), which are unstable in air, and converted them to the stable materials in ambient conditions by the chemical processes of "nanoparticle formation" and "dimensional reduction". The nanoparticles and the bulk counterparts were synthesized by the solvothermal and high-frequency induction furnace heating methods, respectively. The reduction of the particle size led to the valence transition of the rare earth atom, which was monitored through magnetic susceptibility and X-ray absorption near edge spectroscopy (XANES) measurements. The stability was checked by X-ray diffraction and thermogravimetric analysis over a period of seven months in oxygen and argon atmospheres and confirmed by XANES. The nanoparticles showed outstanding stability toward aerial oxidation over a period of seven months compared to the bulk counterpart, as the latter one is more prone to the oxidation within a few days. PMID:27187579

  14. Enhanced solid waste stabilization in aerobic landfills using low aeration rates and high density compaction.

    PubMed

    El Fadel, Mutasem; Fayad, Wissam; Hashisho, Jihan

    2013-01-01

    Historically, municipal solid waste landfills have been designed and operated as storage facilities with suboptimal degradation under anaerobic conditions resulting in slow waste stabilization, gaseous emissions and leachate formation. This article examines the aerobic bioreactor alternative combining the recirculation of high strength leachate [chemical oxygen demand (COD): 89,000-95,600 mg/l; biological oxygen demand (BOD): 75,700-80,000 mg/l)] with low aeration rates (0.0125-0.05 l/min.kg) at high initial waste compaction (657-875 kg/m3) to promote and control biodegradation of solid waste in laboratory-scale columns (diameter = 60 cm, height = 1 m). Low aeration rates coupled with high initial density demonstrated improved performance with increased levels of stabilization with COD and BOD attenuation reaching up to 96%, final C:N ratio of 25 and waste settlement up to 55%. PMID:22878935

  15. Enhanced Heat Stability of α-Chymotrypsin through Single-Enzyme Confinement in Attoliter Liposomes.

    PubMed

    Yoshimoto, Makoto; Yamada, Jun; Baba, Misaki; Walde, Peter

    2016-07-01

    The entrapment of α-chymotrypsin (α-CT) within 70-140 nm liposomes formed from POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) leads to an unexpected and remarkable increase in the thermal stability of the enzyme. This finding is based on the observation that heating aqueous suspensions of α-CT-containing POPC liposomes to 80 °C for 30 minutes resulted in partial enzyme inactivation, whereas the same treatment of aqueous solutions of free α-CT inactivated the enzyme completely. The stabilizing effect of enzyme confinement in the attoliter volumes of the liposomes was found to increase with decreasing numbers of α-CT molecules per liposome. Single-enzyme confinement was particularly effective, as intermolecular interactions between heat-denatured α-CT molecules (causing irreversible inactivation) are not possible. PMID:27124158

  16. Simultaneous enhancements of conductivity and stability for anion exchange membranes (AEMs) through precise structure design.

    PubMed

    Ran, Jin; Wu, Liang; Wei, Bing; Chen, Yaoyao; Xu, Tongwen

    2014-09-26

    Polymeric materials as anion exchange membranes (AEMs) play an essential role in the field of energy and environment. The achievement of high performance AEMs by the precise manipulation of macromolecular architecture remains a daunting challenge. Herein, we firstly report a novel rod-coil graft copolymer AEM, possessing rigid hydrophobic main chains and soft hydrophilic graft chains. The low graft density, which can alleviate the adverse influences of ionic graft chains on the main chains, was obtained by using the living polymerization technique. Consequently, the grafted ionic groups which result in the degradation of polymer backbone was decreased to a small degree. Moreover, the relatively long graft chains induced the nanophase separation between the hydrophobic polymer chains and hydrophilic graft chains, which creates a convenient pathway for high hydroxide ion mobility. Such an accurate molecular design simultaneously improves the hydroxide ion conductivity and alkaline stability as well as dimensional stability.

  17. Mesoscale Origin of the Enhanced Cycling-Stability of the Si-Conductive Polymer Anode for Li-ion Batteries

    PubMed Central

    Gu, Meng; Xiao, Xing-Cheng; Liu, Gao; Thevuthasan, Suntharampillai; Baer, Donald R.; Zhang, Ji-Guang; Liu, Jun; Browning, Nigel D.; Wang, Chong-Min

    2014-01-01

    Electrode used in lithium-ion battery is invariably a composite of multifunctional components. The performance of the electrode is controlled by the interactive function of all components at mesoscale. Fundamental understanding of mesoscale phenomenon sets the basis for innovative designing of new materials. Here we report the achievement and origin of a significant performance enhancement of electrode for lithium ion batteries based on Si nanoparticles wrapped with conductive polymer. This new material is in marked contrast with conventional material, which exhibit fast capacity fade. In-situ TEM unveils that the enhanced cycling stability of the conductive polymer-Si composite is associated with mesoscale concordant function of Si nanoparticles and the conductive polymer. Reversible accommodation of the volume changes of Si by the conductive polymer allows good electrical contact between all the particles during the cycling process. In contrast, the failure of the conventional Si-electrode is probed to be the inadequate electrical contact. PMID:24418812

  18. Facile formation of dendrimer-stabilized gold nanoparticles modified with diatrizoic acid for enhanced computed tomography imaging applications

    NASA Astrophysics Data System (ADS)

    Peng, Chen; Li, Kangan; Cao, Xueyan; Xiao, Tingting; Hou, Wenxiu; Zheng, Linfeng; Guo, Rui; Shen, Mingwu; Zhang, Guixiang; Shi, Xiangyang

    2012-10-01

    We report a facile approach to forming dendrimer-stabilized gold nanoparticles (Au DSNPs) through the use of amine-terminated fifth-generation poly(amidoamine) (PAMAM) dendrimers modified by diatrizoic acid (G5.NH2-DTA) as stabilizers for enhanced computed tomography (CT) imaging applications. In this study, by simply mixing G5.NH2-DTA dendrimers with gold salt in aqueous solution at room temperature, dendrimer-entrapped gold nanoparticles (Au DENPs) with a mean core size of 2.5 nm were able to be spontaneously formed. Followed by an acetylation reaction to neutralize the dendrimer remaining terminal amines, Au DSNPs with a mean size of 6 nm were formed. The formed DTA-containing [(Au0)50-G5.NHAc-DTA] DSNPs were characterized via different techniques. We show that the Au DSNPs are colloid stable in aqueous solution under different pH and temperature conditions. In vitro hemolytic assay, cytotoxicity assay, flow cytometry analysis, and cell morphology observation reveal that the formed Au DSNPs have good hemocompatibility and are non-cytotoxic at a concentration up to 3.0 μM. X-ray absorption coefficient measurements show that the DTA-containing Au DSNPs have enhanced attenuation intensity, much higher than that of [(Au0)50-G5.NHAc] DENPs without DTA or Omnipaque at the same molar concentration of the active element (Au or iodine). The formed DTA-containing Au DSNPs can be used for CT imaging of cancer cells in vitro as well as for blood pool CT imaging of mice in vivo with significantly improved signal enhancement. With the two radiodense elements of Au and iodine incorporated within one particle, the formed DTA-containing Au DSNPs may be applicable for CT imaging of various biological systems with enhanced X-ray attenuation property and detection sensitivity.We report a facile approach to forming dendrimer-stabilized gold nanoparticles (Au DSNPs) through the use of amine-terminated fifth-generation poly(amidoamine) (PAMAM) dendrimers modified by diatrizoic acid

  19. Towards practical Baeyer-Villiger-monooxygenases: design of cyclohexanone monooxygenase mutants with enhanced oxidative stability.

    PubMed

    Opperman, Diederik J; Reetz, Manfred T

    2010-12-10

    Baeyer-Villiger monooxygenases (BVMOs) catalyze the conversion of ketones and cyclic ketones into esters and lactones, respectively. Cyclohexanone monooxygenase (CHMO) from Acinetobacter sp. NCIMB 9871 is known to show an impressive substrate scope as well as exquisite chemo-, regio-, and enantioselectivity in many cases. Large-scale synthetic applications of CHMO are hampered, however, by the instability of the enzyme. Oxidation of cysteine and methionine residues contributes to this instability. Designed mutations of all the methionine and cysteine residues in the CHMO wild type (WT) showed that the amino acids labile towards oxidation are mostly either surface-exposed or located within the active site, whereas the two methionine residues identified for thermostabilization are buried within the folded protein. Combinatorial mutations gave rise to two stabilized mutants with either oxidative or thermal stability, without compromising the activity or stereoselectivity of the enzyme. The most oxidatively stabilized mutant retained nearly 40 % of its activity after incubation with H(2)O(2) (0.2 M), whereas the wild-type enzyme's activity was completely abolished at concentrations as low as 5 mM H(2)O(2). We propose that oxidation-stable mutants might well be a "prerequisite" for thermostabilization, because laboratory-evolved thermostability in CHMO might be masked by a high degree of oxidation instability.

  20. Enhanced production and organic solvent stability of a protease from Brevibacillus laterosporus strain PAP04.

    PubMed

    Anbu, P

    2016-01-01

    A bacterial strain (PAP04) isolated from cattle farm soil was shown to produce an extracellular, solvent-stable protease. Sequence analysis using 16S rRNA showed that this strain was highly homologous (99%) to Brevibacillus laterosporus. Growth conditions that optimize protease production in this strain were determined as maltose (carbon source), skim milk (nitrogen source), pH 7.0, 40°C temperature, and 48 h incubation. Overall, conditions were optimized to yield a 5.91-fold higher production of protease compared to standard conditions. Furthermore, the stability of the enzyme in organic solvents was assessed by incubation for 2 weeks in solutions containing 50% concentration of various organic solvents. The enzyme retained activity in all tested solvents except ethanol; however, the protease activity was stimulated in benzene (74%) followed by acetone (63%) and chloroform (54.8%). In addition, the plate assay and zymography results also confirmed the stability of the PAP04 protease in various organic solvents. The organic solvent stability of this protease at high (50%) concentrations of solvents makes it an alternative catalyst for peptide synthesis in non-aqueous media. PMID:27007657

  1. Enhanced In Vitro Skin Deposition Properties of Retinyl Palmitate through Its Stabilization by Pectin.

    PubMed

    Suh, Dong-Churl; Kim, Yeongseok; Kim, Hyeongmin; Ro, Jieun; Cho, Seong-Wan; Yun, Gyiae; Choi, Sung-Up; Lee, Jaehwi

    2014-01-01

    The purpose of this study was to examine the effect of stabilization of retinyl palmitate (RP) on its skin permeation and distribution profiles. Skin permeation and distribution study were performed using Franz diffusion cells along with rat dorsal skin, and the effect of drug concentration and the addition of pectin on skin deposition profiles of RP was observed. The skin distribution of RP increased in a concentration dependent manner and the formulations containing 0.5 and 1 mg of pectin demonstrated significantly increased RP distributions in the epidermis. Furthermore, it was found that skin distribution of RP could be further improved by combined use of pectin and ascorbyl palmitate (AP), due largely to their anti-oxidative effect. These results clearly demonstrate that the skin deposition properties of RP can be improved by stabilizing RP with pectin. Therefore, it is strongly suggested that pectin could be used in the pharmaceutical and cosmetic formulations as an efficient stabilizing agent and as skin penetration modulator. PMID:24596625

  2. Enhanced In Vitro Skin Deposition Properties of Retinyl Palmitate through Its Stabilization by Pectin

    PubMed Central

    Suh, Dong-Churl; Kim, Yeongseok; Kim, Hyeongmin; Ro, Jieun; Cho, Seong-Wan; Yun, Gyiae; Choi, Sung-Up; Lee, Jaehwi

    2014-01-01

    The purpose of this study was to examine the effect of stabilization of retinyl palmitate (RP) on its skin permeation and distribution profiles. Skin permeation and distribution study were performed using Franz diffusion cells along with rat dorsal skin, and the effect of drug concentration and the addition of pectin on skin deposition profiles of RP was observed. The skin distribution of RP increased in a concentration dependent manner and the formulations containing 0.5 and 1 mg of pectin demonstrated significantly increased RP distributions in the epidermis. Furthermore, it was found that skin distribution of RP could be further improved by combined use of pectin and ascorbyl palmitate (AP), due largely to their anti-oxidative effect. These results clearly demonstrate that the skin deposition properties of RP can be improved by stabilizing RP with pectin. Therefore, it is strongly suggested that pectin could be used in the pharmaceutical and cosmetic formulations as an efficient stabilizing agent and as skin penetration modulator. PMID:24596625

  3. Enhancement of pedicle screw stability using calcium phosphate cement in osteoporotic vertebrae: in vivo biomechanical study.

    PubMed

    Taniwaki, Yoshimichi; Takemasa, Ryuichi; Tani, Toshikazu; Mizobuchi, Hiroo; Yamamoto, Hiroshi

    2003-01-01

    We conducted an experimental study using female beagles with and without ovariectomy-induced osteoporosis to determine the effect of calcium phosphate cement (CPC) on the mechanical stability of inserted pedicle screws. A drill hole was created from the base of the transverse process to the vertebral body; CPC was injected into the hole, and then a screw was inserted into the same hole. In the presence of osteoporosis evidenced by dual X-ray absorptiometry, the stability of the inserted screw augmented by CPC against pull-out and cephalocaudal forces were significantly greater by 28% and 54% at 1 week after operation, 48% and 71% at 2 weeks, and 56% and 68% at 4 weeks compared with those without CPC. The pull-out strength increased progressively with time after surgery, probably reflecting new-bone growth from the surrounding cancellous bone, which was in direct contact with the CPC, as shown in the histologic study. At each time point the cephalocaudal rigidity was similar and the pull-out strength greater than that for the screws inserted without CPC in nonporotic dogs. These findings suggest that CPC augments the stability of the inserted pedicle screws and increases the stiffness of fixed osteoporotic motion segments using instrumentation. PMID:12768486

  4. Polymer Encapsulation of an Amorphous Pharmaceutical by initiated Chemical Vapor Deposition for Enhanced Stability.

    PubMed

    Christian, Paul; Ehmann, Heike M A; Coclite, Anna Maria; Werzer, Oliver

    2016-08-24

    The usage of amorphous solids in practical applications, such as in medication, is commonly limited by the poor long-term stability of this state, because unwanted crystalline transitions occur. In this study, three different polymeric coatings are investigated for their ability to stabilize amorphous films of the model drug clotrimazole and to protect against thermally induced transitions. For this, drop cast films of clotrimazole are encapsulated by initiated chemical vapor deposition (iCVD), using perfluorodecyl acrylate (PFDA), hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA). The iCVD technique operates under solvent-free conditions at low temperatures, thus leaving the solid state of the encapsulated layer unaffected. Optical microscopy and X-ray diffraction data reveal that at ambient conditions of about 22 °C, any of these iCVD layers extends the lifetime of the amorphous state significantly. At higher temperatures (50 or 70 °C), the p-PFDA coating is unable to provide protection, while the p-HEMA and p-MAA strongly reduce the crystallization rate. Furthermore, p-HEMA and p-MAA selectively facilitate a preferential alignment of clotrimazole and, interestingly, even suppress crystallization upon a temporary, rapid temperature increase (3 °C/min, up to 150 °C). The results of this study demonstrate how a polymeric coating, synthesized directly on top of an amorphous phase, can act as a stabilizing agent against crystalline transitions, which makes this approach interesting for a variety of applications. PMID:27467099

  5. Polymer Encapsulation of an Amorphous Pharmaceutical by initiated Chemical Vapor Deposition for Enhanced Stability

    PubMed Central

    2016-01-01

    The usage of amorphous solids in practical applications, such as in medication, is commonly limited by the poor long-term stability of this state, because unwanted crystalline transitions occur. In this study, three different polymeric coatings are investigated for their ability to stabilize amorphous films of the model drug clotrimazole and to protect against thermally induced transitions. For this, drop cast films of clotrimazole are encapsulated by initiated chemical vapor deposition (iCVD), using perfluorodecyl acrylate (PFDA), hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA). The iCVD technique operates under solvent-free conditions at low temperatures, thus leaving the solid state of the encapsulated layer unaffected. Optical microscopy and X-ray diffraction data reveal that at ambient conditions of about 22 °C, any of these iCVD layers extends the lifetime of the amorphous state significantly. At higher temperatures (50 or 70 °C), the p-PFDA coating is unable to provide protection, while the p-HEMA and p-MAA strongly reduce the crystallization rate. Furthermore, p-HEMA and p-MAA selectively facilitate a preferential alignment of clotrimazole and, interestingly, even suppress crystallization upon a temporary, rapid temperature increase (3 °C/min, up to 150 °C). The results of this study demonstrate how a polymeric coating, synthesized directly on top of an amorphous phase, can act as a stabilizing agent against crystalline transitions, which makes this approach interesting for a variety of applications. PMID:27467099

  6. Stabilization of engineered zero-valent nanoiron with Na-acrylic copolymer enhances spermiotoxicity.

    PubMed

    Kadar, Eniko; Tarran, Glenn A; Jha, Awadhesh N; Al-Subiai, Sherain N

    2011-04-15

    Studies were carried out to assess the effects of stabilized (i.e., coated with organic polyacrylic stabilizer) and nonstabilized forms of zero-valent nanoiron (nZVI) on the development of Mytilus galloprovincialis embryos following 2 h exposure of the sperm prior to in vitro fertilization. Both forms of nZVI caused serious disruption of development, consisting of 30% mortality among spermatozoa with subsequent 20% decline in fertilization success, and delay in development, i.e., over 50% of the larvae were suspended in the trochophore stage. Significant DNA damage was also detected in sperm exposed to the highest exposure concentrations (10 mg L(-1)). Distinct dose response to the two different types of nZVI observed are linked to aggregation behavior that is controlled by the surface stabilizers. This work reports on conventional biomarkers (for membrane integrity, genotoxicity, and developmental toxicity) applied for the rapid assessment of toxicity of nZVI, which are able to detect surface property-related effects to meet the requirements of risk assessments for nanotechnology. The study highlights the potential ecotoxicological impact of an environmentally relevant engineered nanoparticle. Implications of the NOM-nZVI interactions regarding soil and groundwater remediation and wastewater treatment are discussed.

  7. Experimental evaluation of wellbore integrity along the cement-rock boundary.

    PubMed

    Newell, Dennis L; Carey, J William

    2013-01-01

    Leakage of CO(2) and brine from geologic storage reservoirs along wellbores is a major risk factor to the success of geologic carbon sequestration. We conducted multiphase [supercritical (sc)CO(2)-brine] coreflood experiments that simulate a leakage pathway along the cement/rock interface. A composite core constructed of oil-well cement and siltstone separated by a simulated damage zone (defect) containing ground cement and siltstone was flooded with brine + scCO(2) at 10 MPa and 60 °C parallel to the defect. During coinjection of scCO(2), the effective brine permeability decreased from ~200 to 90 mD due to transition to two-phase flow and then further declined to 35 mD. CO(2) injection resulted in a pH drop from 11 to 4 and carbonate-undersaturated conditions in the produced brine. Microscopy revealed leaching and erosion along the defect, a carbonation front extending 5 mm into the cement, parallel to the damage zone, and no change in the dimensions of the defect. Carbonation of cement does not appear to explain the permeability drop, which is attributed to the migration and reprecipitation of alteration products derived from cement within the defect. This study shows the potential for self-limiting flow along wellbore defects despite flow of aggressive scCO(2)-brine mixtures.

  8. Impacts of shaking Bengkulus seismicity to subsurface Wellbore in the XX area

    NASA Astrophysics Data System (ADS)

    Rusli, Saifatur; Pratama, M. Ardian; Mardiyan, Hilman; Mirza, Finisha, Brian

    2016-05-01

    Bengkulu earthquake was happened on Wednesday, May 5th 2010 at 23:29:03 WIB (UTC-7) with magnitude 6.5 Richter scale. The Epicentrum was very close to Mentawai Fault System located on latitude 4.063°S and longitude 101.085°E with depth subsurface 27 kms. It was occurred the result of the Indian Ocean Plate-Australia's activity with low angled-subducted beneath the island of Sumatra. Shaking Bengkulus seismicity impacted subsurface in the XX Area which situated on South Palembang Sub-Basin part of South Sumatra Basin (SSB) about 200 kms far away from the epicentrum. Due to XX Area has some producing wells so that the seismicity activities as hypothetically impacts to Subsurface Wellbore which has caused some wells casing problems in the same depth. The wells casing problem shown after conducted routine sand bailer by Sand Line Unit, it was a downhole device used to remove debris sands or similar small particles around the fishingnecks of downhole tools or equipment in the wellbore, and then Sand Bailer tools got scratch at one side body. Similarly, Sand Bailer tools couldnt lowered until Total Depth and got samples sands slightly. At the end, it has impacted to well performance to produce oil in the XX Area.

  9. Theoretical assessment of James' method for the determination of geothermal wellbore discharge characteristics

    SciTech Connect

    Karamarakar, M.; Cheng, P.

    1980-11-01

    A theoretical study based on two-phase critical flow models has been performed to evaluate James' empirical method for the determination of geothermal wellbore discharge characteristics. The following conclusions are obtained: the James' empirical method for the determination of stagnation enthalpy, steam quality, and total flow rate are within 8% from results predicted from one-component two-phase critical flow models of Fauske, Moody, and Levy. When the wellbore discharge contains a substantial amount of CO{sub 2}, the determination of discharge characteristics based on the modified James' method agree with those predicted based on a modification of Fauske's model to the same degree of accuracy. An extension of Fauske's theory shows that if a large amount of dissolved salts exists in the discharge, the straight-forward application of James' method for the determination of discharge characteristics will lead to serious errors. When the lip pressure is low and the discharge pipe diameter is equal to or larger than 6-inches in diameter, the pressure gradient in the approach region of the critical flow is small such that the lip pressure measurements taken within 1/4-inch from the exit would not affect the accuracy of the determination of the critical flow rate.

  10. Explaining Spatial Variability in Wellbore Impairment Risk for Pennsylvania Oil and Gas Wells, 2000-2014

    NASA Astrophysics Data System (ADS)

    Santoro, R.; Ingraffea, A. R.

    2015-12-01

    Previous modeling (ingraffea et al. PNAS, 2014) indicated roughly two-times higher cumulative risk for wellbore impairment in unconventional wells, relative to conventional wells, and large spatial variation in risk for oil and gas wells drilled in the state of Pennsylvania. Impairment risk for wells in the northeast portion of the state were found to be 8.5-times greater than that of wells drilled in the rest of the state. Here, we set out to explain this apparent regional variability through Boosted Regression Tree (BRT) analysis of geographic, developmental, and general well attributes. We find that regional variability is largely driven by the nature of the development, i.e. whether conventional or unconventional development is dominant. Oil and natural gas market prices and total well depths present as major influences in wellbore impairment, with moderate influences from well densities and geologic factors. The figure depicts influence paths for predictors of impairments for the state (top left), SW region (top right), unconventional/NE region (bottom left) and conventional/NW region (bottom right) models. Influences are scaled to reflect percent contributions in explaining variability in the model.

  11. Assessment of crude glycerol for Enhanced Biological Phosphorus Removal: Stability and role of long chain fatty acids.

    PubMed

    Tayà, Carlota; Guerrero, Javier; Suárez-Ojeda, María Eugenia; Guisasola, Albert; Baeza, Juan Antonio

    2015-12-01

    Enhanced Biological Phosphorus Removal (EBPR) of urban wastewaters is usually limited by the available carbon source required by Polyphosphate Accumulating Organisms (PAO). External carbon sources as volatile fatty acids (VFA) or other pure organic compounds have been tested at lab scale demonstrating its ability to enhance PAO activity, but the application of this strategy at full-scale WWTPs is not cost-effective. The utilization of industrial by-products with some of these organic compounds provides lower cost, but it has the possible drawback of having inhibitory or toxic compounds to PAO. This study is focused on the utilization of crude glycerol, the industrial by-product generated in the biodiesel production, as a possible carbon source to enhance EBPR in carbon-limited urban wastewaters. Crude glycerol has non-negligible content of other organic compounds as methanol, salts, VFA and long chain fatty acids (LCFA). VFA and methanol have been demonstrated to enhance PAO activity, but there is no previous study about the effect of LCFA on PAO. This work presents the operation of an EBPR SBR system using crude glycerol as sole carbon source, studying also its long-term stability. The effect of LCFA is evaluated at short and long-term operation, demonstrating for the first time EBPR activity with LCFA as sole carbon source and its long-term failure due to the increased hydrophobicity of the sludge. PMID:26092200

  12. Assessment of crude glycerol for Enhanced Biological Phosphorus Removal: Stability and role of long chain fatty acids.

    PubMed

    Tayà, Carlota; Guerrero, Javier; Suárez-Ojeda, María Eugenia; Guisasola, Albert; Baeza, Juan Antonio

    2015-12-01

    Enhanced Biological Phosphorus Removal (EBPR) of urban wastewaters is usually limited by the available carbon source required by Polyphosphate Accumulating Organisms (PAO). External carbon sources as volatile fatty acids (VFA) or other pure organic compounds have been tested at lab scale demonstrating its ability to enhance PAO activity, but the application of this strategy at full-scale WWTPs is not cost-effective. The utilization of industrial by-products with some of these organic compounds provides lower cost, but it has the possible drawback of having inhibitory or toxic compounds to PAO. This study is focused on the utilization of crude glycerol, the industrial by-product generated in the biodiesel production, as a possible carbon source to enhance EBPR in carbon-limited urban wastewaters. Crude glycerol has non-negligible content of other organic compounds as methanol, salts, VFA and long chain fatty acids (LCFA). VFA and methanol have been demonstrated to enhance PAO activity, but there is no previous study about the effect of LCFA on PAO. This work presents the operation of an EBPR SBR system using crude glycerol as sole carbon source, studying also its long-term stability. The effect of LCFA is evaluated at short and long-term operation, demonstrating for the first time EBPR activity with LCFA as sole carbon source and its long-term failure due to the increased hydrophobicity of the sludge.

  13. Suxiaojiuxin pill enhances atherosclerotic plaque stability by modulating the MMPs/TIMPs balance in ApoE-deficient mice.

    PubMed

    Zhang, Jinbao; Zhuang, Pengwei; Lu, Zhiqiang; Zhang, Mixia; Zhang, Teng; Zhang, Yanjun; Wang, Jinlei; Liu, Dan; Tong, Yongling

    2014-08-01

    : Suxiaojiuxin pill (SX) is a famous Chinese formulated product, which has been used to treat coronary heart disease and angina pectoris in China. This study was carried out to investigate the effect and possible mechanism of SX on the stability of atherosclerotic plaque in ApoE-deficient mice. ApoE-/- mice of 6-8 weeks old were fed with high-fat diet for developing artherosclerosis. After oral administration of SX for 8 weeks, histopathology of aortic plaque was performed by Sudan III and hematoxylin-eosin staining, and muscle protein was detected by Western blotting (WB). The mRNA and proteins associated with aortic plaque stability were detected by reverse transcription-polymerase chain reaction and WB, respectively. SX treatment could not only reduce serum triglyceride level and plaque area but also increase fibrous cap thickness and collagen content compared with the model group. WB results showed that SX could increase α-smooth muscle actin, tissue inhibitor of metalloproteinase 1 (TIMP-1), and TIMP-2 protein expression, whereas decrease matrix metalloproteinase 2 (MMP-2) and MMP-9 protein expression. Moreover, SX could upregulate the expression of α-smooth muscle actin mRNA and downregulate the expression of vascular endothelial growth factor mRNA. These results showed that SX could enhance atherosclerotic plaque stability in ApoE-deficient mice. The mechanism may be associated with modulating the MMPs/TIMPs balance.

  14. Understanding the mechanism of surface modification through enhanced thermal and electrochemical stabilities of N-doped graphene oxide

    NASA Astrophysics Data System (ADS)

    Mehetre, Shantilal S.; Maktedar, Shrikant S.; Singh, Man

    2016-03-01

    The kinetically active two dimensional surface of graphene oxide (GrO) plays an important role in understanding the chemistry of graphene. The GrO is comprises of carbon and oxygen while the f-(6-AIND) GrO contains nitrogen along with carbon and oxygen. The prominent thermal instability of GrO is widely explored. However, due to the synergistic impact of their constituting elements, the thermal and electrochemical stability of f-(6-AIND) GrO enhances after N-doping with nitrogen containing heterocycles like 6-Aminoindazole. Hence it is essential to probe the mutual impact of various functionalities present over the surface of GrO, to understand the mechanism of direct functionalization of GrO with thermal and electrochemical stabilities. Therefore, the decomposition kinetics of discrete atomic domains and their effect on thermal stability of f-(6-AIND) GrO was revealed with spectroscopic analysis and thermal assessment. Additionally, the mechanism of thermal transformation is precisely developed to demonstrate the impact of heat on weight loss due to the mass transfer. Likewise, the electrochemical properties can be well understood with the help of mechanism of electrochemical activity and cyclic voltammetry experiments. Also, the f-(6-AIND) GrO is confirmed with the help of various surface analysis techniques like FTIR, EDS, HR-XPS, HR-TEM, CV, SAED, TGA, DSC and UV-vis.

  15. Mussel-Inspired Polydopamine Coating for Enhanced Thermal Stability and Rate Performance of Graphite Anodes in Li-Ion Batteries.

    PubMed

    Park, Seong-Hyo; Kim, Hyeon Jin; Lee, Junmin; Jeong, You Kyeong; Choi, Jang Wook; Lee, Hochun

    2016-06-01

    Despite two decades of commercial history, it remains very difficult to simultaneously achieve both high rate capability and thermal stability in the graphite anodes of Li-ion batteries because the stable solid electrolyte interphase (SEI) layer, which is essential for thermal stability, impedes facile Li(+) ion transport at the interface. Here, we resolve this longstanding challenge using a mussel-inspired polydopamine (PD) coating via a simple immersion process. The nanometer-thick PD coating layer allows the formation of an SEI layer on the coating surface without perturbing the intrinsic properties of the SEI layer of the graphite anodes. PD-coated graphite exhibits far better performances in cycling test at 60 °C and storage test at 90 °C than bare graphite. The PD-coated graphite also displays superior rate capability during both lithiation and delithiation. As evidenced by surface free energy analysis, the enhanced performance of the PD-coated graphite can be ascribed to the Lewis basicity of the PD, which scavenges harmful hydrofluoric acid and forms an intermediate triple-body complex among a Li(+) ion, solvent molecules, and the PD's basic site. The usefulness of the proposed PD coating can be expanded to various electrodes in rechargeable batteries that suffer from poor thermal stability and interfacial kinetics. PMID:27183170

  16. In situ growth of hollow gold-silver nanoshells within porous silica offers tunable plasmonic extinctions and enhanced colloidal stability.

    PubMed

    Li, Chien-Hung; Jamison, Andrew C; Rittikulsittichai, Supparesk; Lee, Tai-Chou; Lee, T Randall

    2014-11-26

    Porous silica-coated hollow gold-silver nanoshells were successfully synthesized utilizing a procedure where the porous silica shell was produced prior to the transformation of the metallic core, providing enhanced control over the structure/composition of the bimetallic hollow core. By varying the reaction time and the precise amount of gold salt solution added to a porous silica-coated silver-core template solution, composite nanoparticles were tailored to reveal a readily tunable surface plasmon resonance that could be centered across the visible and near-IR spectral regions (∼445-800 nm). Characterization by X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed that the synthetic methodology afforded particles having uniform composition, size, and shape. The optical properties were evaluated by absorption/extinction spectroscopy. The stability of colloidal solutions of our composite nanoparticles as a function of pH was also investigated, revealing that the nanoshells remain intact over a wide range of conditions (i.e., pH 2-10). The facile tunability, enhanced stability, and relatively small diameter of these composite particles (∼110 nm) makes them promising candidates for use in tumor ablation or as photothermal drug-delivery agents. PMID:25321928

  17. Enhancing the water stability of Al-MIL-101-NH2 via postsynthetic modification.

    PubMed

    Wittmann, Thomas; Siegel, Renée; Reimer, Nele; Milius, Wolfgang; Stock, Norbert; Senker, Jürgen

    2015-01-01

    The resistance of metal-organic frameworks towards water is a very critical issue concerning their practical use. Recently, it was shown for microporous MOFs that the water stability could be increased by introducing hydrophobic pendant groups. Here, we demonstrate a remarkable stabilisation of the mesoporous MOF Al-MIL-101-NH2 by postsynthetic modification with phenyl isocyanate. In this process 86 % of the amino groups were converted into phenylurea units. As a consequence, the long-term stability of Al-MIL-101-URPh in liquid water could be extended beyond a week. In water saturated atmospheres Al-MIL-101-URPh decomposed at least 12-times slower than the unfunctionalised analogue. To study the underlying processes both materials were characterised by Ar, N2 and H2 O sorption measurements, powder X-ray diffraction, thermogravimetric and chemical analysis as well as solid-state NMR and IR spectroscopy. Postsynthetic modification decreased the BET equivalent surface area from 3363 to 1555 m(2)  g(-1) for Al-MIL-101-URPh and reduced the mean diameters of the mesopores by 0.6 nm without degrading the structure significantly and reducing thermal stability. In spite of similar water uptake capacities, the relative humidity-dependent uptake of Al-MIL-101-URPh is slowed and occurs at higher relative humidity values. In combination with (1) H-(27) Al D-HMQC NMR spectroscopy experiments this favours a shielding mechanism of the Al clusters by the pendant phenyl groups and rules out pore blocking. PMID:25352494

  18. Enhanced stability of tristetraprolin mRNA protects mice against immune-mediated inflammatory pathologies

    PubMed Central

    Patial, Sonika; Curtis, Alan D.; Lai, Wi S.; Stumpo, Deborah J.; Hill, Georgette D.; Flake, Gordon P.; Mannie, Mark D.; Blackshear, Perry J.

    2016-01-01

    Tristetraprolin (TTP) is an inducible, tandem zinc-finger mRNA binding protein that binds to adenylate-uridylate–rich elements (AREs) in the 3′-untranslated regions (3′UTRs) of specific mRNAs, such as that encoding TNF, and increases their rates of deadenylation and turnover. Stabilization of Tnf mRNA and other cytokine transcripts in TTP-deficient mice results in the development of a profound, chronic inflammatory syndrome characterized by polyarticular arthritis, dermatitis, myeloid hyperplasia, and autoimmunity. To address the hypothesis that increasing endogenous levels of TTP in an intact animal might be beneficial in the treatment of inflammatory diseases, we generated a mouse model (TTPΔARE) in which a 136-base instability motif in the 3′UTR of TTP mRNA was deleted in the endogenous genetic locus. These mice appeared normal, but cultured fibroblasts and macrophages derived from them exhibited increased stability of the otherwise highly labile TTP mRNA. This resulted in increased TTP protein expression in LPS-stimulated macrophages and increased levels of TTP protein in mouse tissues. TTPΔARE mice were protected from collagen antibody-induced arthritis, exhibited significantly reduced inflammation in imiquimod-induced dermatitis, and were resistant to induction of experimental autoimmune encephalomyelitis, presumably by dampening the excessive production of proinflammatory mediators in all cases. These data suggest that increased systemic levels of TTP, secondary to increased stability of its mRNA throughout the body, can be protective against inflammatory disease in certain models and might be viewed as an attractive therapeutic target for the treatment of human inflammatory diseases. PMID:26831084

  19. End-use load control for power system dynamic stability enhancement

    SciTech Connect

    Dagle, J.E.; Winiarski, D.W.; Donnelly, M.K.

    1997-02-01

    Faced with the prospect of increasing utilization of the transmission and distribution infrastructure without significant upgrade, the domestic electric power utility industry is investing heavily in technologies to improve network dynamic performance through a program loosely referred to as Flexible AC Transmission System (FACTS). Devices exploiting recent advances in power electronics are being installed in the power system to offset the need to construct new transmission lines. These devices collectively represent investment potential of several billion dollars over the next decade. A similar development, designed to curtail the peak loads and thus defer new transmission, distribution, and generation investment, falls under a category of technologies referred to as demand side management (DSM). A subset of broader conservation measures, DSM acts directly on the load to reduce peak consumption. DSM techniques include direct load control, in which a utility has the ability to curtail specific loads as conditions warrant. A novel approach has been conceived by Pacific Northwest National Laboratory (PNNL) to combine the objectives of FACTS and the technologies inherent in DSM to provide a distributed power system dynamic controller. This technology has the potential to dramatically offset major investments in FACTS devices by using direct load control to achieve dynamic stability objectives. The potential value of distributed versus centralized grid modulation has been examined by simulating the western power grid under extreme loading conditions. In these simulations, a scenario is analyzed in which active grid stabilization enables power imports into the southern California region to be increased several hundred megawatts beyond present limitations. Modeling results show distributed load control is up to 30 percent more effective than traditional centralized control schemes in achieving grid stability.

  20. Stability Enhancing N-Terminal PEGylation of Oxytocin Exploiting Different Polymer Architectures and Conjugation Approaches.

    PubMed

    Collins, Jennifer; Kempe, Kristian; Wilson, Paul; Blindauer, Claudia A; McIntosh, Michelle P; Davis, Thomas P; Whittaker, Michael R; Haddleton, David M

    2016-08-01

    Oxytocin, a cyclic nine amino acid neurohypophyseal hormone therapeutic, is effectively used in the control of postpartum hemorrhaging (PPH) and is on the WHO List of Essential Medicines. However, oxytocin has limited shelf life stability in aqueous solutions, particularly at temperatures in excess of 25 °C and injectable aqueous oxytocin formulations require refrigeration (<8 °C). This is particularly problematic in the hot climates often found in many developing countries where daytime temperatures can exceed 40 °C and where reliable cold-chain storage is not always achievable. The purpose of this study was to develop N-terminal amine targeted PEGylation strategies utilizing both linear PEG and polyPEG "comb" polymers as an effective method for stabilizing solution formulations of this peptide for prolonged storage in the absence of efficient cold-chain storage. The conjugation chemistries investigated herein include irreversible amine targeted conjugation methods utilizing NHS ester and aldehyde reductive amination chemistry. Additionally, one reversible conjugation method using a Schiff base approach was explored to allow for the release of the native peptide, thus, ensuring that biological activity remains unaffected. The reversibility of this approach was investigated for the different polymer architectures, alongside a nonpolymer oxytocin analogue to monitor how pH can tune native peptide release. Elevated temperature degradation studies of the polymer conjugates were evaluated to assess the stability of the PEGylated analogues in comparison to the native peptide in aqueous formulations to mimic storage conditions in developing nations and regions where storage under appropriate conditions is challenging. PMID:27419537

  1. Toward interfacing organic semiconductors with ferromagnetic transition metal substrates: enhanced stability via carboxylate anchoring.

    PubMed

    Han, R; Blobner, F; Bauer, J; Duncan, D A; Barth, J V; Feulner, P; Allegretti, F

    2016-07-28

    We demonstrate that chemically well-defined aromatic self-assembled monolayers (SAMs) bonded via a carboxylate head group to surfaces of ferromagnetic (FM = Co, Ni, Fe) transition metals can be prepared at ambient temperature in ultra-high vacuum and are thermally stable up to 350-400 K (depending on the metal). The much superior stability over thiolate-bonded SAMs, which readily decompose above 200 K, and the excellent electronic communication guaranteed by the carboxylate bonding render benzoate/FM-metal interfaces promising candidates for application in spintronics. PMID:27417687

  2. Protein thermal stability enhancement by designing salt bridges: a combined computational and experimental study.

    PubMed

    Lee, Chi-Wen; Wang, Hsiu-Jung; Hwang, Jenn-Kang; Tseng, Ching-Ping

    2014-01-01

    Protein thermal stability is an important factor considered in medical and industrial applications. Many structural characteristics related to protein thermal stability have been elucidated, and increasing salt bridges is considered as one of the most efficient strategies to increase protein thermal stability. However, the accurate simulation of salt bridges remains difficult. In this study, a novel method for salt-bridge design was proposed based on the statistical analysis of 10,556 surface salt bridges on 6,493 X-ray protein structures. These salt bridges were first categorized based on pairing residues, secondary structure locations, and Cα-Cα distances. Pairing preferences generalized from statistical analysis were used to construct a salt-bridge pair index and utilized in a weighted electrostatic attraction model to find the effective pairings for designing salt bridges. The model was also coupled with B-factor, weighted contact number, relative solvent accessibility, and conservation prescreening to determine the residues appropriate for the thermal adaptive design of salt bridges. According to our method, eight putative salt-bridges were designed on a mesophilic β-glucosidase and 24 variants were constructed to verify the predictions. Six putative salt-bridges leaded to the increase of the enzyme thermal stability. A significant increase in melting temperature of 8.8, 4.8, 3.7, 1.3, 1.2, and 0.7°C of the putative salt-bridges N437K-D49, E96R-D28, E96K-D28, S440K-E70, T231K-D388, and Q277E-D282 was detected, respectively. Reversing the polarity of T231K-D388 to T231D-D388K resulted in a further increase in melting temperatures by 3.6°C, which may be caused by the transformation of an intra-subunit electrostatic interaction into an inter-subunit one depending on the local environment. The combination of the thermostable variants (N437K, E96R, T231D and D388K) generated a melting temperature increase of 15.7°C. Thus, this study demonstrated a novel

  3. Rapid Small-Signal Stability Assessment and Enhancement Following Changes in Topology

    SciTech Connect

    Saric, AT; Stankovic, AM

    2015-05-01

    The paper proposes a scalable and tractable algorithm for dynamic topology optimization of power systems involving changes in branch on/off status, while respecting small-signal stability (SSS) constraints. A procedure for fast updates of the system matrices (in descriptor form) and without additional full matrix inversions is proposed. To additionally reduce the computation time, only critical eigenvalues (right-most or those in a specified damping ratio and frequency range) are calculated. A quadratic optimization approach is proposed for optimized generation re-dispatch to satisfy SSS constraints. The approach is applied to two (medium- and large-scale) real-world test power systems.

  4. Mechanisms and enhancement of flame stabilization. Annual report, January 15, 1992--January 14, 1993

    SciTech Connect

    Law, C.K.

    1993-02-01

    During the reporting period, useful contributions have been made in understanding the structure of laminar premixed and diffusion flames, with emphasis on the influence of aerodynamics and chemical kinetics. These contributions include (1) derivation of the missing closure condition for the activation energy asymptotic analysis of premixed flames, (2) identification of a dual extinction mode for radiation-affected flames, (3) formulation of a unified theory of fundamental flammability limits, and (4) demonstration that flame stabilization can be achieved in the absence of heat loss. These investigations have been conducted via experimental, analytical and computational approaches, with strong coupling between the individual components.

  5. Protein Thermal Stability Enhancement by Designing Salt Bridges: A Combined Computational and Experimental Study

    PubMed Central

    Hwang, Jenn-Kang; Tseng, Ching-Ping

    2014-01-01

    Protein thermal stability is an important factor considered in medical and industrial applications. Many structural characteristics related to protein thermal stability have been elucidated, and increasing salt bridges is considered as one of the most efficient strategies to increase protein thermal stability. However, the accurate simulation of salt bridges remains difficult. In this study, a novel method for salt-bridge design was proposed based on the statistical analysis of 10,556 surface salt bridges on 6,493 X-ray protein structures. These salt bridges were first categorized based on pairing residues, secondary structure locations, and Cα–Cα distances. Pairing preferences generalized from statistical analysis were used to construct a salt-bridge pair index and utilized in a weighted electrostatic attraction model to find the effective pairings for designing salt bridges. The model was also coupled with B-factor, weighted contact number, relative solvent accessibility, and conservation prescreening to determine the residues appropriate for the thermal adaptive design of salt bridges. According to our method, eight putative salt-bridges were designed on a mesophilic β-glucosidase and 24 variants were constructed to verify the predictions. Six putative salt-bridges leaded to the increase of the enzyme thermal stability. A significant increase in melting temperature of 8.8, 4.8, 3.7, 1.3, 1.2, and 0.7°C of the putative salt-bridges N437K–D49, E96R–D28, E96K–D28, S440K–E70, T231K–D388, and Q277E–D282 was detected, respectively. Reversing the polarity of T231K–D388 to T231D–D388K resulted in a further increase in melting temperatures by 3.6°C, which may be caused by the transformation of an intra-subunit electrostatic interaction into an inter-subunit one depending on the local environment. The combination of the thermostable variants (N437K, E96R, T231D and D388K) generated a melting temperature increase of 15.7°C. Thus, this study

  6. Steric hindrance and the enhanced stability of light rare-earth elements in hydrothermal fluids

    USGS Publications Warehouse

    Mayanovic, Robert A.; Anderson, Alan J.; Bassett, William A.; Chou, I.-Ming

    2009-01-01

    A series of X-ray absorption spectroscopy (XAS) experiments were made to determine the structure and stability of aqueous REE (La, Nd, Gd, and Yb) chloride complexes to 500 ??C and 520 MPa. The REE3+ ions exhibit inner-sphere chloroaqua complexation with a steady increase of chloride coordination with increasing temperature in the 150 to 500 ??C range. Furthermore, the degree of chloride coordination of REE3+ inner-sphere chloroaqua complexes decreases significantly from light to heavy REE. These results indicate that steric hindrance drives the reduction of chloride coordination of REE3+ inner-sphere chloroaqua complexes from light to heavy REE. This results in greater stability and preferential transport of light REE3+ over heavy REE3+ ions in saline hydrothermal fluids. Accordingly, the preferential mobility of light REE directly influences the relative abundance of REE in rocks and minerals and thus needs to be considered in geochemical modeling of petrogenetic and ore-forming processes affected by chloride-bearing hydrothermal fluids.

  7. A rapid preparation of acicular Ni impregnated anode with enhanced conductivity and operational stability

    NASA Astrophysics Data System (ADS)

    Zhu, Xingbao; Guan, Chengzhi; Lü, Zhe; Wei, Bo; Li, Yiqian; Su, Wenhui

    2014-06-01

    A novel method for fabricating Ni(NO3)2 solution impregnated YSZ (YSZ: Yttria Stabilized Zirconia) anodes for solid oxide fuel cells (SOFCs) is presented. In order to reduce the impregnation cycles and increase the reliability of the YSZ membrane, a YSZ support with a porosity of ∼60% is soaked in a saturated Ni(NO3)2 solution with an increased temperature of 80 °C. The impregnated anode is dried in a vacuum drying device without heating, resulting in a flower-like Ni(NO3)2·6H2O crystal. The formed porous structure is likely to facilitate the impregnating process and considered to be the key to success of the impregnation process with saturated solution. After heating at 700 °C, a novel needle-shaped NiO is presented, which exhibits some advantages including fast preparation, high connectivity, large specific surface area and high operational stability (i.e. high aggregation resistance). For the purpose of comparison, Ni(NO3)2 solution impregnated YSZ anodes prepared through the conventional impregnation process are also characterized under the same conditions.

  8. The Bilayer Enhances Rhodopsin Kinetic Stability in Bovine Rod Outer Segment Disk Membranes

    PubMed Central

    Corley, Scott C.; Sprangers, Peter; Albert, Arlene D.

    2011-01-01

    Rhodopsin is a kinetically stable protein constituting >90% of rod outer segment disk membrane protein. To investigate the bilayer contribution to rhodopsin kinetic stability, disk membranes were systematically disrupted by octyl-β-D-glucopyranoside. Rhodopsin kinetic stability was examined under subsolubilizing (rhodopsin in a bilayer environment perturbed by octyl-β-D-glucopyranoside) and under fully solubilizing conditions (rhodopsin in a micelle with cosolubilized phospholipids). As determined by DSC, rhodopsin exhibited a scan-rate-dependent irreversible endothermic transition at all stages of solubilization. The transition temperature (Tm) decreased in the subsolubilizing stage. However, once the rhodopsin was in a micelle environment there was little change of the Tm as the phospholipid/rhodopsin ratio in the mixed micelles decreased during the fully solubilized stage. Rhodopsin thermal denaturation is consistent with the two-state irreversible model at all stages of solubilization. The activation energy of denaturation (Eact) was calculated from the scan rate dependence of the Tm and from the rate of rhodopsin thermal bleaching at all stages of solubilization. The Eact as determined by both techniques decreased in the subsolubilizing stage, but remained constant once fully solubilized. These results indicate the bilayer structure increases the Eact to rhodopsin denaturation. PMID:21689528

  9. Variable prey development time suppresses predator-prey cycles and enhances stability.

    PubMed

    Cronin, James T; Reeve, John D; Xu, Dashun; Xiao, Mingqing; Stevens, Heidi N

    2016-03-01

    Although theoretical models have demonstrated that predator-prey population dynamics can depend critically on age (stage) structure and the duration and variability in development times of different life stages, experimental support for this theory is non-existent. We conducted an experiment with a host-parasitoid system to test the prediction that increased variability in the development time of the vulnerable host stage can promote interaction stability. Host-parasitoid microcosms were subjected to two treatments: Normal and High variance in the duration of the vulnerable host stage. In control and Normal-variance microcosms, hosts and parasitoids exhibited distinct population cycles. In contrast, insect abundances were 18-24% less variable in High- than Normal-variance microcosms. More significantly, periodicity in host-parasitoid population dynamics disappeared in the High-variance microcosms. Simulation models confirmed that stability in High-variance microcosms was sufficient to prevent extinction. We conclude that developmental variability is critical to predator-prey population dynamics and could be exploited in pest-management programs.

  10. Enhanced thermal stability and pH behavior of glucose oxidase on electrostatic interaction with polyethylenimine.

    PubMed

    Padilla-Martínez, Silvia G; Martínez-Jothar, Lucía; Sampedro, José G; Tristan, Ferdinando; Pérez, Elías

    2015-04-01

    Electrostatic interactions, mediated by ionic-exchange, between polyethylenimine (PEI) and glucose oxidase (GOx) were used to form GOx-PEI macro-complex, which were evaluated for pH and thermal stability of GOx. Under the experimental conditions, the complex had a dominant GOx presence on its surface and a hydrodynamic diameter of 205 ± 16 nm. Activity was evaluated from 40 to 75 °C, and at pH from 2 to 12. GOx activity in complex was maintained up to 70 °C and it was lost at 75 °C. In contrast, free GOx showed a maximum activity at 50 °C, which was completely lost at 70 °C. This difference, observed by fluorescence analysis, was associated with the compact unfolded structure of GOx in the complex. This GOx stability was not observed under pH variations, and complex formation was only possible at pH ≥ 5 where enzymatic activity was diminished by the presence of PEI.

  11. Enhanced Hydrothermal Stability and Catalytic Performance of HKUST-1 by Incorporating Carboxyl-Functionalized Attapulgite.

    PubMed

    Yuan, Bo; Yin, Xiao-Qian; Liu, Xiao-Qin; Li, Xing-Yang; Sun, Lin-Bing

    2016-06-29

    Much attention has been paid to metal-organic frameworks (MOFs) due to their large surface areas, tunable functionality, and diverse structure. Nevertheless, most reported MOFs show poor hydrothermal stability, which seriously hinders their applications. Here a strategy is adopted to tailor the properties of MOFs by means of incorporating carboxyl-functionalized natural clay attapulgite (ATP) into HKUST-1, a well-known MOF. A new type of hybrid material was thus fabricated from the hybridization of HKUST-1 and ATP. Our results indicated that the hydrothermal stability of the MOFs as well as the catalytic performance was apparently improved. The frameworks of HKUST-1 were severely destroyed after hydrothermal treatment (hot water vapor, 60 °C), while that of the hybrid materials was maintained. For the hybrid materials containing 8.4 wt % of ATP, the surface area reached 1302 m(2)·g(-1) and was even higher than that of pristine HKUST-1 (1245 m(2)·g(-1)). In the ring-opening of styrene oxide, the conversion reached 98.9% at only 20 min under catalysis from the hybrid material, which was obviously higher than that over pristine HKUST-1 (80.9%). Moreover, the hybrid materials showed excellent reusability and the catalytic activity was recoverable without loss after six cycles. Our materials provide promising candidates for heterogeneous catalysis owing to the good catalytic activity and reusability. PMID:27268731

  12. Biomass retention on electrodes rather than electrical current enhances stability in anaerobic digestion.

    PubMed

    De Vrieze, Jo; Gildemyn, Sylvia; Arends, Jan B A; Vanwonterghem, Inka; Verbeken, Kim; Boon, Nico; Verstraete, Willy; Tyson, Gene W; Hennebel, Tom; Rabaey, Korneel

    2014-05-01

    Anaerobic digestion (AD) is a well-established technology for energy recovery from organic waste streams. Several studies noted that inserting a bioelectrochemical system (BES) inside an anaerobic digester can increase biogas output, however the mechanism behind this was not explored and primary controls were not executed. Here, we evaluated whether a BES could stabilize AD of molasses. Lab-scale digesters were operated in the presence or absence of electrodes, in open (no applied potential) and closed circuit conditions. In the control reactors without electrodes methane production decreased to 50% of the initial rate, while it remained stable in the reactors with electrodes, indicating a stabilizing effect. After 91 days of operation, the now colonized electrodes were introduced in the failing AD reactors to evaluate their remediating capacity. This resulted in an immediate increase in CH4 production and VFA removal. Although a current was generated in the BES operated in closed circuit, no direct effect of applied potential nor current was observed. A high abundance of Methanosaeta was detected on the electrodes, however irrespective of the applied cell potential. This study demonstrated that, in addition to other studies reporting only an increase in methane production, a BES can also remediate AD systems that exhibited process failure. However, the lack of difference between current driven and open circuit systems indicates that the key impact is through biomass retention, rather than electrochemical interaction with the electrodes.

  13. A simple composite protective layer coating that enhances the cycling stability of lithium metal batteries

    NASA Astrophysics Data System (ADS)

    Lee, Hongkyung; Lee, Dong Jin; Kim, Yun-Jung; Park, Jung-Ki; Kim, Hee-Tak

    2015-06-01

    Metallic lithium is the most promising negative electrode for high-energy rechargeable batteries due to its extremely high specific capacity and its extremely low redox potential. However, the low cycle efficiency and lithium dendrite formation during the charge/discharge processes consistently hinder its practical application. In this report, we present a stabilized Li electrode on which a Li+ ion conductive inorganic/organic composite protective layer (CPL) is coated. With the introduction of the CPL, the Li dendrite growth and electrolyte decomposition are effectively suppressed; consequently, stable Li plating/stripping at high current densities up to 10 mA cm-2 is possible. Nanoindentation tests demonstrate that the shear modulus of the CPL at narrow indentations is 1.8 times higher than that of the Li metal, which provides a theoretical understanding for its efficacy. Moreover, the LiCoO2/Li cell incorporating CPL exhibits excellent cycling stability up to 400 cycles at 1 mA cm-2 (1 C-rate), which demonstrates practical applicability in Li ion batteries through replacing the graphite anode with a CPL-coated Li metal anode.

  14. Limpets compensate sea urchin decline and enhance the stability of rocky subtidal barrens.

    PubMed

    Piazzi, Luigi; Bulleri, Fabio; Ceccherelli, Giulia

    2016-04-01

    Understanding the mechanisms that regulate shifts among alternative ecosystems has become a priority for ecologists and environmental scientists. This study assessed the relative importance of different herbivorous invertebrates (urchins and limpets) in regulating transitions from barren to vegetated states on Mediterranean rocky reefs, under different levels of nutrient availability. Nutrient concentration and the herbivore assemblage were manipulated to test i) whether limpets can compensate for the decline or loss of sea urchin populations, thereby contributing to the persistence of barrens, ii) whether limpet effects vary according to nutrient availability and iii) whether limpets affect the structure of the algal assemblage. The complete removal of sea urchins was not sufficient to trigger the recovery of erect and turf-forming macroalgae if limpets were left at natural density, suggesting that these herbivores play an important role in the stability of the barren state. The effect of these mesograzers was particularly important under oligotrophic conditions. This suggests that limpets play an important role in sustaining the stability of the barren state. A more comprehensive assessment of top-down forces, implying the quantification of the relative effect of different herbivore guilds, is therefore necessary to estimate the strength of hysteresis and to identify critical thresholds at which shifts back to the vegetated state are initiated. PMID:26874891

  15. Heat inactivation kinetics of Hypocrea orientalis β-glucosidase with enhanced thermal stability by glucose.

    PubMed

    Xu, Xin-Qi; Shi, Yan; Wu, Xiao-Bing; Zhan, Xi-Lan; Zhou, Han-Tao; Chen, Qing-Xi

    2015-11-01

    Thermal inactivation kinetics of Hypocrea orientalis β-glucosidase and effect of glucose on thermostability of the enzyme have been determined in this paper. Kinetic studies showed that the thermal inactivation was irreversible and first-order reaction. The microscopic rate constants for inactivation of free enzyme and substrate-enzyme complex were both determined, which suggested that substrates can protect β-glucosidase against thermal deactivation effectively. On the other hand, glucose was found to protect β-glucosidase from heat inactivation to remain almost whole activity below 70°C at 20mM concentration, whereas the apparent inactivation rate of BG decreased to be 0.3×10(-3)s(-1) in the presence of 5mM glucose, smaller than that of sugar-free enzyme (1.91×10(-3)s(-1)). The intrinsic fluorescence spectra results showed that glucose also had stabilizing effect on the conformation of BG against thermal denaturation. Docking simulation depicted the interaction mode between glucose and active residues of the enzyme to produce stabilizing effect.

  16. Enhanced thermal stability of functionally graded sandwich cylindrical shells by shape memory alloys

    NASA Astrophysics Data System (ADS)

    Asadi, H.; Akbarzadeh, A. H.; Chen, Z. T.; Aghdam, M. M.

    2015-04-01

    The present paper deals with the nonlinear thermal instability of geometrically imperfect sandwich cylindrical shells under uniform heating. The sandwich shells are made of a shape memory alloy (SMA)-fiber-reinforced composite and functionally graded (FG) face sheets (FG/SMA/FG). The Brinson phenomenological model is used to express the constitutive characteristics of SMA fibers. The governing equations are established within the framework of the third-order shear deformation shell theory by taking into account the von Karman geometrical nonlinearity and initial imperfection. The material properties of constituents are assumed to be temperature dependent. The Galerkin technique is utilized to derive expressions of the bifurcation points and bifurcation paths of the sandwich cylindrical shells. Using the developed closed-form solutions, extensive numerical results are presented to provide an insight into the influence of the SMA fiber volume fraction, SMA pre-strain, core thickness, non-homogeneity index, geometrical imperfection, geometry parameters of sandwich shells and temperature dependency of materials on the stability of shells. The results reveal that proper application of SMA fibers postpones the thermal bifurcation point and dramatically decreases thermal post-buckling deflection. Moreover, the induced tensile recovery stress of SMA fibers could also stabilize the geometrically imperfect shells during the inverse martensite phase transformation.

  17. Mesoporous CLEAs-silica composite microparticles with high activity and enhanced stability

    PubMed Central

    Cui, Jiandong; Jia, Shiru; Liang, Longhao; Zhao, Yamin; Feng, Yuxiao

    2015-01-01

    A novel enzyme immobilization approach was used to generate mesoporous enzymes-silica composite microparticles by co-entrapping gelatinized starch and cross-linked phenylalanine ammonia lyase (PAL) aggregates (CLEAs) containing gelatinized starch into biomemitic silica and subsequently removing the starch by α-amylase treatment. During the preparation process, the gelatinzed starch served as a pore-forming agent to create pores in CLEAs and biomimetic silica. The resulting mesoporous CLEAs-silica composite microparticles exhibited higher activity and stability than native PAL, conventional CLEAs, and PAL encapsulated in biomimetic silica. Furthermore, the mesoporous CLEAs-silica composite microparticles displayed good reusability due to its suitable size and mechanical properties, and had excellent stability for storage. The superior catalytic performances were attributed to the combinational unique structure from the intra-cross-linking among enzyme aggregates and hard mesoporous silica shell, which not only decreased the enzyme-support negative interaction and mass-transfer limitations, but also improved the mechanical properties and monodispersity. This approach will be highly beneficial for preparing various bioactive mesoporous composites with excellent catalytic performance. PMID:26374188

  18. Combining the hok/sok, parDE, and pnd postsegregational killer loci to enhance plasmid stability.

    PubMed

    Pecota, D C; Kim, C S; Wu, K; Gerdes, K; Wood, T K

    1997-05-01

    To enhance plasmid segregational stability in bacterial cells, two pairs of independent postsegregational killing loci (genes which induce host killing upon plasmid loss) isolated from plasmids R1, R483, or RP4 (hok+/sok+ pnd+ or hok+/sok+ parDE+) were cloned into a common site of the beta-galactosidase expression vector pMJR1750 (ptac::lacZ+) to form a series of plasmids in which the effect of one or two stability loci on segregational plasmid stability could be discerned. Adding two antisense killer loci (hok+/sok+ pnd+) decreased the specific growth rate by 50% though they were more effective at reducing segregational instability than hok+/sok+ alone. With the ptac promoter induced fully (2.0 mM isopropyl-beta-D-thiogalactopyranoside) and no antibiotic selection pressure, the combination of a proteic killer locus (parDE+) with antisense killer loci (hok+/sok+) had a negligible impact on specific growth rate, maintained high beta-galactosidase expression, and led to a 30 and 190% increase in segregational stability (based on stable generations) as compared to plasmids containing either hok+/sok+ or parDE+ alone, respectively. Use of hok+/sok+ or parDE+ alone with high cloned-gene expression led to ninefold and fourfold increases in the number of stable generations, respectively. Two convenient cloning cassettes have been constructed to facilitate cloning the dual hok+/sok+ parDE+ and hok+/sok+ pnd+ killer systems. PMID:9143123

  19. Alumina over-coating on Pd nanoparticle catalysts by atomic layer deposition : enhanced stability and reactivity.

    SciTech Connect

    Feng, H.; Lu, J.; Stair, P. C.; Elam, J. W.

    2011-04-01

    ALD Alumina was utilized as a protective layer to inhibit the sintering of supported nano-sized ALD Pd catalysts in the methanol decomposition reaction carried out at elevated temperatures. The protective ALD alumina layers were synthesized on Pd nanoparticles (1-2 nm) supported on high surface area alumina substrates. Up to a certain over-coat thickness, the alumina protective layers preserved or even slightly enhanced the catalytic activity and prevented sintering of the Pd nanoparticles up to 500 C.

  20. Stability or variation? Patterns of lactase gene and its enhancer region distributions in Brazilian Amerindians.

    PubMed

    Friedrich, Deise C; Callegari-Jacques, Sidia M; Petzl-Erler, M Luiza; Tsuneto, Luiza; Salzano, Francisco M; Hutz, Mara H

    2012-03-01

    Lactase persistence (LP) is the phenotypic trait in which lactase secretion is maintained during adulthood. LP is due to mutations in the LCT enhancer region, located 14-kb upstream of the gene. In Europeans, the -13910*T allele is associated with LP. In Africans this allele is rare while other mutations in this same region were related to LP. The LCT is highly polymorphic in human populations, but so far Brazilian Amerindians had not been investigated for these polymorphisms or for the presence of LP mutations. We describe the genetic diversity of the LCT region and the presence of LP enhancer mutations in four native Brazilian populations (Guarani-Kaiowá, Guarani-Ñandeva, Kaingang, and Xavante). Twelve polymorphisms were genotyped by PCR-based methods. The -13910*T allele varied from 0.5% in the Xavante to 7.6% in the Guarani-Ñandeva. These frequencies probably derive from European sources and they correlate with non-native admixture proportions previously estimated for these groups. But since admixture is virtually absent in the Xavante, we suggest that the presence of the LP allele could have been determined by a de novo mutation. No other mutations in the -14 kb enhancer region were found. The LCT was highly polymorphic in the present sample showing 15 haplotypes with a heterogeneous distribution among the four Amerindian populations. This diversity could be due to drift, as indicated by the neutrality test performed. PMID:22271590

  1. Stability or variation? Patterns of lactase gene and its enhancer region distributions in Brazilian Amerindians.

    PubMed

    Friedrich, Deise C; Callegari-Jacques, Sidia M; Petzl-Erler, M Luiza; Tsuneto, Luiza; Salzano, Francisco M; Hutz, Mara H

    2012-03-01

    Lactase persistence (LP) is the phenotypic trait in which lactase secretion is maintained during adulthood. LP is due to mutations in the LCT enhancer region, located 14-kb upstream of the gene. In Europeans, the -13910*T allele is associated with LP. In Africans this allele is rare while other mutations in this same region were related to LP. The LCT is highly polymorphic in human populations, but so far Brazilian Amerindians had not been investigated for these polymorphisms or for the presence of LP mutations. We describe the genetic diversity of the LCT region and the presence of LP enhancer mutations in four native Brazilian populations (Guarani-Kaiowá, Guarani-Ñandeva, Kaingang, and Xavante). Twelve polymorphisms were genotyped by PCR-based methods. The -13910*T allele varied from 0.5% in the Xavante to 7.6% in the Guarani-Ñandeva. These frequencies probably derive from European sources and they correlate with non-native admixture proportions previously estimated for these groups. But since admixture is virtually absent in the Xavante, we suggest that the presence of the LP allele could have been determined by a de novo mutation. No other mutations in the -14 kb enhancer region were found. The LCT was highly polymorphic in the present sample showing 15 haplotypes with a heterogeneous distribution among the four Amerindian populations. This diversity could be due to drift, as indicated by the neutrality test performed.

  2. Use of coal ash for enhancing biocrust development in stabilizing sand dunes

    NASA Astrophysics Data System (ADS)

    Zaady, Eli; Katra, Itzhak; Sarig, Shlomo

    2015-04-01

    In dryland environments, biocrusts are considered ecosystem engineers since they play significant roles in ecosystem processes. In the successional pathway of crust communities, the new areas are colonized after disturbance by pioneers such as filamentous cyanobacteria - Microcoleus spp. This stage is followed by colonization of green algae, mosses, and lichens. Aggregation of soil granules is caused by metabolic polysaccharides secreted by cyanobacteria and green algae, gluing the soil particles to form the crust layer. It was suggested that incorporating dust into the biocrusts encourages the growth of cyanobacteria, leading to a strengthening of the biocrusts' cohesion. Moreover, biocrusts cover a larger portion of the surface when the soil contains finer particles, and it was observed that at least 4-5% of clay and silt is required to support a measurable biocrust. While natural and undisturbed sand dunes are generally stabilized by biocrusts in the north-western Negev desert, stabilization of disturbed and movable sand dunes is one of the main problems in this desertified land, as in vast areas in the world. Daily breezes and seasonal wind storms transport sand particles to populated and agricultural areas causing damages to field crops and livelihood. Moving sand dunes consist of relatively coarse grains (250-2000 μm) with a low percent of clay and silt. This phenomenon negatively affects cyanobacterial colonization rate, even in relatively wet desert areas (100-250 mm rainfalls). In order to face the problem it was suggested to enrich the dune surface by using coal fly-ash. The research was conducted in two stages: first, examining the feasibility in Petri-dishes in laboratory conditions and in Experimental Aeolian Greenhouse conditions. The results showed that adding coal fly-ash and biocrust inoculum increased aggregate stability, penetration resistance and shear strength, as opposed to the control-sand plot. Using mobile wind-tunnel simulations, sand

  3. Uricase alkaline enzymosomes with enhanced stabilities and anti-hyperuricemia effects induced by favorable microenvironmental changes.

    PubMed

    Zhou, Yunli; Zhang, Mi; He, Dan; Hu, Xueyuan; Xiong, Huarong; Wu, Jianyong; Zhu, Biyue; Zhang, Jingqing

    2016-01-01

    Enzyme therapy is an effective strategy to treat diseases. Three strategies were pursued to provide the favorable microenvironments for uricase (UCU) to eventually improve its features: using the right type of buffer to constitute the liquid media where catalyze reactions take place; entrapping UCU inside the selectively permeable lipid vesicle membranes; and entrapping catalase together with UCU inside the membranes. The nanosized alkaline enzymosomes containing UCU/(UCU and catalase) (ESU/ESUC) in bicine buffer had better thermal, hypothermal, acid-base and proteolytic stabilities, in vitro and in vivo kinetic characteristics, and uric acid lowering effects. The favorable microenvironments were conducive to the establishment of the enzymosomes with superior properties. It was the first time that two therapeutic enzymes were simultaneously entrapped into one enzymosome having the right type of buffer to achieve added treatment efficacy. The development of ESU/ESUC in bicine buffer provides valuable tactics in hypouricemic therapy and enzymosomal application. PMID:26823332

  4. Natural deep eutectic solvents providing enhanced stability of natural colorants from safflower (Carthamus tinctorius).

    PubMed

    Dai, Yuntao; Verpoorte, Robert; Choi, Young Hae

    2014-09-15

    A certain combination of natural products in the solid state becomes liquid, so called natural deep eutectic solvents (NADES). Recently, they have been considered promising new green solvents for foods, cosmetics and pharmaceuticals due to their unique solvent power which can dissolve many non-water-soluble compounds and their low toxicity. However, in addition to the features as solvents, the stabilisation ability of NADES for compounds is important for their further applications. In the study, the stability analysis demonstrates that natural pigments from safflower are more stable in sugar-based NADES than in water or 40% ethanol solution. Notably, the stabilisation capacity of NADES can be adjusted by reducing water content with increasing viscosity. The strong stabilisation ability is due to the formation of strong hydrogen bonding interactions between solutes and NADES molecules. The stabilising ability of NADES for phenolic compounds shows great promise for their applications in food, cosmetic and pharmaceutical industries.

  5. SO2-catalyzed steam pretreatment enhances the strength and stability of softwood pellets.

    PubMed

    Tooyserkani, Zahra; Kumar, Linoj; Sokhansanj, Shahab; Saddler, Jack; Bi, Xiaotao T; Lim, C Jim; Lau, Anthony; Melin, Staffan

    2013-02-01

    Densification can partially resolve the logistical challenges encountered when large volumes of biomass are required for bioconversion processes to benefit from economies-of-scale. Despite the higher bulk density of pellets, their lower mechanical strength and sensitivity to moisture are still recurring issues hindering long term transportation and storage. In this study, we have evaluated the potential benefits of SO(2)-catalyzed steam treatment to achieve both the needed size reduction prior to pelletization while improving the stability of the produced pellets. This pretreatment substantially reduced the particle size of the woodchips eliminating any further grinding. The treated pellets had a higher density and exhibited a two-time higher mechanical strength compared to untreated pellets. Despite a higher moisture adsorption capacity, treated pellets remained intact even under highly humid conditions. The high heating values, low ash content and good overall carbohydrate recovery of treated pellets indicated their potential suitability for both biochemical and thermochemical applications.

  6. Timing stability enhancement of an Erbium Doped mode locked Fiber Laser using SESAM mirror

    NASA Astrophysics Data System (ADS)

    Afifi, G.; Khedr, M. Atta; Badr, Y.; Danailov, M.; Sigalotti, P.; Cinquegrana, P.; Alsous, M. B.; Galaly, A. R.

    2016-05-01

    We report on an examination of pulse timing stability of a home built Erbium Doped Fiber Laser (EDFL) passively mode locked via nonlinear polarization rotation by inserting semiconductor saturable absorber mirror (SESAM) in laser cavity. A very low root mean square (RMS) timing jitter (less than 27 fsec) and faster self-starting mode locking have been established. In order to get clear, low noise signal for time resolving measurements, synchronization of EDFL laser with an external high precision electronic oscillator have been established. Subsequently, it is synchronized and optically cross-correlated with a Ti:Sapphire laser source (Micra). The measured relative timing jitter was found to be less than 65 fsec. In this way, the two, well synchronized Ti:Sapphire and EDFL laser pulses prove to be a powerful tool for time resolving measurements.

  7. Enhancing Chemical Stability of Electroplated Cu Films by Engineering Electrolyte Chemistry and Twinning Structure

    NASA Astrophysics Data System (ADS)

    Yang, Chih-Jie; Huang, Chun-Lung; Liao, Chien-Neng

    2015-07-01

    The effects of an electrolyte additive and twinning structure on the corrosion characteristics of electroplated Cu films have been investigated. Four different Cu films were individually deposited with and without benzotriazole (BTA) in the electrolyte using the direct-current (DC) and pulsed-current (PC) plating techniques. The Cu films plated with BTA additive showed improved corrosion resistance according to electrochemical polarization testing and postetching morphological inspection. Moreover, the PC-plated films that had dense nanoscale twin boundaries appeared to have higher chemical stability than the DC-plated ones. It is proposed that the presence of twin-modified grain boundary segments suppresses corrosion along the grain boundary network and improves the corrosion resistance of electroplated Cu films.

  8. Enhancement of the Stability of Fluorine Atoms on Defective Graphene and at Graphene/Fluorographene Interface.

    PubMed

    Ao, Zhimin; Jiang, Quanguo; Li, Shuang; Liu, Hao; Peeters, Francois M; Li, Sean; Wang, Guoxiu

    2015-09-01

    Fluorinated graphene is one of the most important derivatives of graphene and has been found to have great potential in optoelectronic and photonic nanodevices. However, the stability of F atoms on fluorinated graphene under different conditions, which is essential to maintain the desired properties of fluorinated graphene, is still unclear. In this work, we investigate the diffusion of F atoms on pristine graphene, graphene with defects, and at graphene/fluorographene interfaces by using density functional theory calculations. We find that an isolated F atom diffuses easily on graphene, but those F atoms can be localized by inducing vacancies or absorbates in graphene and by creating graphene/fluorographene interfaces, which would strengthen the binding energy of F atoms on graphene and increase the diffusion energy barrier of F atoms remarkably.

  9. Propagation stability of self-reconstructing Bessel beams enables contrast-enhanced imaging in thick media

    NASA Astrophysics Data System (ADS)

    Fahrbach, Florian O.; Rohrbach, Alexander

    2012-01-01

    Laser beams that can self-reconstruct their initial beam profile even in the presence of massive phase perturbations are able to propagate deeper into inhomogeneous media. This ability has crucial advantages for light sheet-based microscopy in thick media, such as cell clusters, embryos, skin or brain tissue or plants, as well as scattering synthetic materials. A ring system around the central intensity maximum of a Bessel beam enables its self-reconstruction, but at the same time illuminates out-of-focus regions and deteriorates image contrast. Here we present a detection method that minimizes the negative effect of the ring system. The beam's propagation stability along one straight line enables the use of a confocal line principle, resulting in a significant increase in image contrast. The axial resolution could be improved by nearly 100% relative to the standard light-sheet techniques using scanned Gaussian beams, while demonstrating self-reconstruction also for high propagation depths.

  10. Hyperbranched polycarbonate-based multimolecular micelle with enhanced stability and loading efficiency.

    PubMed

    Su, Wei; Luo, Xiao-Hua; Wang, Hua-Fen; Li, Lei; Feng, Jun; Zhang, Xian-Zheng; Zhuo, Ren-Xi

    2011-02-16

    We herein develop a facile catalyst-free method to prepare hyperbranched hydroxyl-enriched aliphatic polycarbonate according to SCROP strategy. PEG-attached multiarm hyperbranched copolymer HEHDO-star-mPEG was further designed. It was found that HEHDO-star-mPEG can self-assemble into supramolecular multimolecular micelles in water. HEHDO-star-mPEG micelle showed excellent stability with respect to micellar size upon dilution, and displayed good cell-biocompatibility. An anticancer drug of doxorubicin with hydrogen-bonding functionality was incorporated into obtained micelles to establish a drug delivery system model. A high drug-loading content as well as sustained release pattern for HEHDO-star-mPEG based delivery system was achieved.

  11. A Best Practices System to Enhance CFD Use in Stability and Control Applications

    NASA Technical Reports Server (NTRS)

    Morrison, Joseph H.; Mendenhall, Michael R.

    2004-01-01

    Successful use of CFD to provide aerodynamics for stability and control (S&C) applications will require that the traditional time and costs associated with CFD be reduced and that the errors and uncertainties currently associated with CFD be better understood. CFD will be required to work under a wide range of flow conditions and provide fast and reliable aerodynamics if it is to contribute to this next generation of S&C analyses. CFD solutions have errors and uncertainties due to poorly converged solutions, solution anomalies caused by grids, turbulence models, and parameter selection, and other manifold reasons. In addition to the above problems, there will be a requirement for communications between the CFD expert and the S&C expert and possibly experts from other related disciplines. The CFD expert may not understand the technical problems associated with S&C, and it is almost certain the converse is true.

  12. Propagation stability of self-reconstructing Bessel beams enables contrast-enhanced imaging in thick media.

    PubMed

    Fahrbach, Florian O; Rohrbach, Alexander

    2012-01-17

    Laser beams that can self-reconstruct their initial beam profile even in the presence of massive phase perturbations are able to propagate deeper into inhomogeneous media. This ability has crucial advantages for light sheet-based microscopy in thick media, such as cell clusters, embryos, skin or brain tissue or plants, as well as scattering synthetic materials. A ring system around the central intensity maximum of a Bessel beam enables its self-reconstruction, but at the same time illuminates out-of-focus regions and deteriorates image contrast. Here we present a detection method that minimizes the negative effect of the ring system. The beam's propagation stability along one straight line enables the use of a confocal line principle, resulting in a significant increase in image contrast. The axial resolution could be improved by nearly 100% relative to the standard light-sheet techniques using scanned Gaussian beams, while demonstrating self-reconstruction also for high propagation depths.

  13. Uricase alkaline enzymosomes with enhanced stabilities and anti-hyperuricemia effects induced by favorable microenvironmental changes

    PubMed Central

    Zhou, Yunli; Zhang, Mi; He, Dan; Hu, Xueyuan; Xiong, Huarong; Wu, Jianyong; Zhu, Biyue; Zhang, Jingqing

    2016-01-01

    Enzyme therapy is an effective strategy to treat diseases. Three strategies were pursued to provide the favorable microenvironments for uricase (UCU) to eventually improve its features: using the right type of buffer to constitute the liquid media where catalyze reactions take place; entrapping UCU inside the selectively permeable lipid vesicle membranes; and entrapping catalase together with UCU inside the membranes. The nanosized alkaline enzymosomes containing UCU/(UCU and catalase) (ESU/ESUC) in bicine buffer had better thermal, hypothermal, acid-base and proteolytic stabilities, in vitro and in vivo kinetic characteristics, and uric acid lowering effects. The favorable microenvironments were conducive to the establishment of the enzymosomes with superior properties. It was the first time that two therapeutic enzymes were simultaneously entrapped into one enzymosome having the right type of buffer to achieve added treatment efficacy. The development of ESU/ESUC in bicine buffer provides valuable tactics in hypouricemic therapy and enzymosomal application. PMID:26823332

  14. Enhanced stability of Bacillus licheniformis L-arabinose isomerase by immobilization with alginate.

    PubMed

    Zhang, Ye-Wang; Prabhu, Ponnandy; Lee, Jung-Kul; Kim, In-Won

    2010-01-01

    Recombinant Escherichia coli whole cells harboring Bacillus licheniformis L-arabinose isomerase (BLAI) were harvested to prepare alginate-immobilized biocatalysts. The operational conditions for immobilization were optimized according to relative activity and the cell leakage of the immobilized cell. The optimal conditions are as follows: alginate concentration, Ca(2+) concentration, cell mass loading, and curing time were 2% (w/v), 0.1 M, 50 g l(-1), and 4 hours, respectively. After immobilization, cross-linking with 0.1% glutaraldehyde significantly reduced cell leakage. The immobilized whole cells harboring BLAI were very stable with 89% residual activity remaining after 33 days of incubation at 50 degrees C and were much more stable than the free enzyme and cells. The results showed that immobilizing whole cells harboring BLAI is suitable for use as a biocatalyst in the production of L-ribulose, largely due to its high stability and low cost.

  15. Everolimus Stabilizes Podocyte Microtubules via Enhancing TUBB2B and DCDC2 Expression

    PubMed Central

    Jeruschke, Stefanie; Jeruschke, Kay; DiStasio, Andrew; Karaterzi, Sinem; Büscher, Anja K.; Nalbant, Perihan; Klein-Hitpass, Ludger; Hoyer, Peter F.; Weiss, Jürgen; Stottmann, Rolf W.; Weber, Stefanie

    2015-01-01

    Background Glomerular podocytes are highly differentiated cells that are key components of the kidney filtration units. The podocyte cytoskeleton builds the basis for the dynamic podocyte cytoarchitecture and plays a central role for proper podocyte function. Recent studies implicate that immunosuppressive agents including the mTOR-inhibitor everolimus have a protective role directly on the stability of the podocyte actin cytoskeleton. In contrast, a potential stabilization of microtubules by everolimus has not been studied so far. Methods To elucidate mechanisms underlying mTOR-inhibitor mediated cytoskeletal rearrangements, we carried out microarray gene expression studies to identify target genes and corresponding pathways in response to everolimus. We analyzed the effect of everolimus in a puromycin aminonucleoside experimental in vitro model of podocyte injury. Results Upon treatment with puromycin aminonucleoside, microarray analysis revealed gene clusters involved in cytoskeletal reorganization, cell adhesion, migration and extracellular matrix composition to be affected. Everolimus was capable of protecting podocytes from injury, both on transcriptional and protein level. Rescued genes included tubulin beta 2B class IIb (TUBB2B) and doublecortin domain containing 2 (DCDC2), both involved in microtubule structure formation in neuronal cells but not identified in podocytes so far. Validating gene expression data, Western-blot analysis in cultured podocytes demonstrated an increase of TUBB2B and DCDC2 protein after everolimus treatment, and immunohistochemistry in healthy control kidneys confirmed a podocyte-specific expression. Interestingly, Tubb2bbrdp/brdp mice revealed a delay in glomerular podocyte development as showed by podocyte-specific markers Wilm’s tumour 1, Podocin, Nephrin and Synaptopodin. Conclusions Taken together, our study suggests that off-target, non-immune mediated effects of the mTOR-inhibitor everolimus on the podocyte cytoskeleton

  16. Laccase encapsulation in chitosan nanoparticles enhances the protein stability against microbial degradation.

    PubMed

    Koyani, Rina D; Vazquez-Duhalt, Rafael

    2016-09-01

    A novel concept with the result of enzyme stabilization against microbial degradation in real bioremediation processes was developed through the encapsulation of laccase in chitosan nanoparticles. Besides of abundant information on laccase-chitosan conjugates, we report the laccase encapsulation into nanoparticles based in chitosan. The chitosan-tripolyphosphate technique was applied for the production of morphologically homogeneous enzymatic nanoparticles, with high enzyme encapsulation efficiency, small asymmetric sizes (from 40 to 90 nm), and rough surfaces. Contrary to macroscopic immobilized enzymes, temperature and pH activity profiles of nano-sized laccase were similar to those of free enzyme. The substrate affinity constant (K M) of nano-encapsulated laccase was similar to these from free enzyme, while its activity rate constant (k cat) represented 60 % of these obtained with free enzyme. Importantly, stability of nano-encapsulated laccase against microbial degradation in soil, compost, and wastewater was significantly increased. After 24 h exposure to wastewater from a treatment plant, the laccase activity of the nanoparticles was 82.8 % of initial activity, compared with only 7.8 % retained activity for free enzyme. After 36 h incubation in compost extract, the laccase nanoparticles showed 72.4 % of the initial activity, while the free enzyme was almost completely inactivated. Finally, after 84 h incubation in soil extract, the nanoparticles and free preparations showed 57.9 and 17.3 % of the initial activity, respectively. Thus, the nanoencapsulation of enzymes able to transform pollutants is an alternative to improve the operational lifetime of enzymes in real environmental applications.

  17. Laccase encapsulation in chitosan nanoparticles enhances the protein stability against microbial degradation.

    PubMed

    Koyani, Rina D; Vazquez-Duhalt, Rafael

    2016-09-01

    A novel concept with the result of enzyme stabilization against microbial degradation in real bioremediation processes was developed through the encapsulation of laccase in chitosan nanoparticles. Besides of abundant information on laccase-chitosan conjugates, we report the laccase encapsulation into nanoparticles based in chitosan. The chitosan-tripolyphosphate technique was applied for the production of morphologically homogeneous enzymatic nanoparticles, with high enzyme encapsulation efficiency, small asymmetric sizes (from 40 to 90 nm), and rough surfaces. Contrary to macroscopic immobilized enzymes, temperature and pH activity profiles of nano-sized laccase were similar to those of free enzyme. The substrate affinity constant (K M) of nano-encapsulated laccase was similar to these from free enzyme, while its activity rate constant (k cat) represented 60 % of these obtained with free enzyme. Importantly, stability of nano-encapsulated laccase against microbial degradation in soil, compost, and wastewater was significantly increased. After 24 h exposure to wastewater from a treatment plant, the laccase activity of the nanoparticles was 82.8 % of initial activity, compared with only 7.8 % retained activity for free enzyme. After 36 h incubation in compost extract, the laccase nanoparticles showed 72.4 % of the initial activity, while the free enzyme was almost completely inactivated. Finally, after 84 h incubation in soil extract, the nanoparticles and free preparations showed 57.9 and 17.3 % of the initial activity, respectively. Thus, the nanoencapsulation of enzymes able to transform pollutants is an alternative to improve the operational lifetime of enzymes in real environmental applications. PMID:27318485

  18. Enhancing the resonance stability of a high-Q micro/nanoresonator by an optical means

    NASA Astrophysics Data System (ADS)

    Sun, Xuan; Luo, Rui; Zhang, Xi-Cheng; Lin, Qiang

    2016-02-01

    High-quality optical resonators underlie many important applications ranging from optical frequency metrology, precision measurement, nonlinear/quantum photonics, to diverse sensing such as detecting single biomolecule, electromagnetic field, mechanical acceleration/rotation, among many others. All these applications rely essentially on the stability of optical resonances, which, however, is ultimately limited by the fundamental thermal fluctuations of the devices. The resulting thermo-refractive and thermo-elastic noises have been widely accepted for nearly two decades as the fundamental thermodynamic limit of an optical resonator, limiting its resonance uncertainty to a magnitude 10-12 at room temperature. Here we report a novel approach that is able to significantly improve the resonance stability of an optical resonator. We show that, in contrast to the common belief, the fundamental temperature fluctuations of a high-Q micro/nanoresonator can be suppressed remarkably by pure optical means without cooling the device temperature, which we term as temperature squeezing. An optical wave with only a fairly moderate power launched into the device is able to produce strong photothermal backaction that dramatically suppresses the spectral intensity of temperature fluctuations by five orders of magnitudes and squeezes the overall level (root-mean-square value) of temperature fluctuations by two orders of magnitude. The proposed approach is universally applicable to various micro/nanoresonator platforms and the optimal temperature squeezing can be achieved with an optical Q around 106-107 that is readily available in various current devices. The proposed photothermal temperature squeezing is expected to have profound impact on broad applications of high-Q cavities in sensing, metrology, and integrated nonlinear/quantum photonics.

  19. Wheat proteins enhance stability and function of adhesion molecules in cryopreserved hepatocytes.

    PubMed

    Grondin, Mélanie; Hamel, Francine; Averill-Bates, Diana A; Sarhan, Fathey

    2009-01-01

    Cryopreserved hepatocytes with good hepatospecific functions upon thawing are important for clinical transplantation and for in vitro drug toxicity testing. However, cryopreservation reduces viability and certain hepatospecific functions, but the most pronounced change is diminished attachment efficiency of hepatocytes. Adhesion of cells to the extracellular matrix and cell-cell contacts are crucial for many aspects of cellular function. These processes are partly mediated and controlled by cellular adhesion molecules. The mechanisms responsible for reduced attachment efficiency of cryopreserved hepatocytes are not well understood. To address this question, we investigated the effect of a new cryopreservation procedure, using wheat proteins (WPs) or mixtures of recombinant forms of wheat freezing tolerance-associated proteins, on the stability of three important adhesion molecules (beta1-integrin, E-cadherin, and beta-catenin). Immunoblot analyses revealed that the levels of beta1-integrin, E-cadherin, and beta-catenin were much lower in cryopreserved rat hepatocytes, when compared to fresh cells. Protein expression of the adhesion molecules was generally lower in cells cryopreserved with DMSO, compared to WPs. Moreover, the stability of the adhesion molecules was not affected by cryopreservation to the same degree, with more pronounced decreases occurring for beta1-integrin (62-74%) > beta-catenin (51-58%) > E-cadherin (21-37%). However, when hepatocytes were cryopreserved with partially purified WPs (SulWPE, AcWPE) or with mixtures of recombinant wheat proteins, there was a clear protective effect against the loss of protein expression of beta1-integrin, E-cadherin, and beta-catenin. Protein expression was only 10-20% lower than that observed in fresh hepatocytes. These findings clearly demonstrate that WPs, and more particularly, partially purified WPs and recombinant wheat proteins, were more efficient for cryopreservation of rat hepatocytes by maintaining good

  20. Mesoporous silica sub-micron spheres as drug dissolution enhancers: Influence of drug and matrix chemistry on functionality and stability.

    PubMed

    Brigo, Laura; Scomparin, Elisa; Galuppo, Marco; Capurso, Giovanni; Ferlin, Maria Grazia; Bello, Valentina; Realdon, Nicola; Brusatin, Giovanna; Morpurgo, Margherita

    2016-02-01

    Mesoporous silica particles prepared through a simplified Stöber method and low temperature solvent promoted surfactant removal are evaluated as dissolution enhancers for poorly soluble compounds, using a powerful anticancer agent belonging to pyrroloquinolinones as a model for anticancer oral therapy, and anti-inflammatory ibuprofen as a reference compound. Mesoporous powders composed of either pure silica or silica modified with aminopropyl residues are produced. The influence of material composition and drug chemical properties on drug loading capability and dissolution enhancement are studied. The two types of particles display similar size, surface area, porosity, erodibility, drug loading capability and stability. An up to 50% w/w drug loading is reached, showing correlation between drug concentration in adsorption medium and content in the final powder. Upon immersion in simulating body fluids, immediate drug dissolution occurred, allowing acceptor solutions to reach concentrations equal to or greater than drug saturation limits. The matrix composition influenced drug solution maximal concentration, complementing the dissolution enhancement generated by a mesoporous structure. This effect was found to depend on both matrix and drug chemical properties allowing us to hypothesise general prediction behaviour rules. PMID:26652411

  1. Molecular complexation of curcumin with pH sensitive cationic copolymer enhances the aqueous solubility, stability and bioavailability of curcumin.

    PubMed

    Kumar, Sunny; Kesharwani, Siddharth S; Mathur, Himanshi; Tyagi, Mohit; Bhat, G Jayarama; Tummala, Hemachand

    2016-01-20

    Curcumin is a natural dietary compound with demonstrated potential in preventing/treating several chronic diseases in animal models. However, this success is yet to be translated to humans mainly because of its poor oral bioavailability caused by extremely low water solubility. This manuscript demonstrates that water insoluble curcumin (~1μg/ml) forms highly aqueous soluble complexes (>2mg/ml) with a safe pH sensitive polymer, poly(butyl-methacrylate-co-(2-dimethylaminoethyl) methacrylate-co-methyl-methacrylate) when precipitated together in water. The complexation process was optimized to enhance curcumin loading by varying several formulation factors. Acetone as a solvent and polyvinyl alcohol as a stabilizer with 1:2 ratio of drug to polymer yielded complexes with relatively high loading (~280μg/ml) and enhanced solubility (>2mg/ml). The complexes were amorphous in solid and were soluble only in buffers with pHs less than 5.0. Hydrogen bond formation and hydrophobic interactions between curcumin and the polymer were recorded by infrared spectroscopy and nuclear magnetic resonance spectroscopy, respectively. Molecular complexes of curcumin were more stable at various pHs compared to unformulated curcumin. In mice, these complexes increased peak plasma concentration of curcumin by 6 times and oral bioavailability by ~20 times. This is a simple, economic and safer strategy of enhancing the oral bioavailability of curcumin.

  2. Mesoporous silica sub-micron spheres as drug dissolution enhancers: Influence of drug and matrix chemistry on functionality and stability.

    PubMed

    Brigo, Laura; Scomparin, Elisa; Galuppo, Marco; Capurso, Giovanni; Ferlin, Maria Grazia; Bello, Valentina; Realdon, Nicola; Brusatin, Giovanna; Morpurgo, Margherita

    2016-02-01

    Mesoporous silica particles prepared through a simplified Stöber method and low temperature solvent promoted surfactant removal are evaluated as dissolution enhancers for poorly soluble compounds, using a powerful anticancer agent belonging to pyrroloquinolinones as a model for anticancer oral therapy, and anti-inflammatory ibuprofen as a reference compound. Mesoporous powders composed of either pure silica or silica modified with aminopropyl residues are produced. The influence of material composition and drug chemical properties on drug loading capability and dissolution enhancement are studied. The two types of particles display similar size, surface area, porosity, erodibility, drug loading capability and stability. An up to 50% w/w drug loading is reached, showing correlation between drug concentration in adsorption medium and content in the final powder. Upon immersion in simulating body fluids, immediate drug dissolution occurred, allowing acceptor solutions to reach concentrations equal to or greater than drug saturation limits. The matrix composition influenced drug solution maximal concentration, complementing the dissolution enhancement generated by a mesoporous structure. This effect was found to depend on both matrix and drug chemical properties allowing us to hypothesise general prediction behaviour rules.

  3. Monetizing Leakage Risk of Geologic CO2 Storage using Wellbore Permeability Frequency Distributions

    NASA Astrophysics Data System (ADS)

    Bielicki, Jeffrey; Fitts, Jeffrey; Peters, Catherine; Wilson, Elizabeth

    2013-04-01

    Carbon dioxide (CO2) may be captured from large point sources (e.g., coal-fired power plants, oil refineries, cement manufacturers) and injected into deep sedimentary basins for storage, or sequestration, from the atmosphere. This technology—CO2 Capture and Storage (CCS)—may be a significant component of the portfolio of technologies deployed to mitigate climate change. But injected CO2, or the brine it displaces, may leak from the storage reservoir through a variety of natural and manmade pathways, including existing wells and wellbores. Such leakage will incur costs to a variety of stakeholders, which may affect the desirability of potential CO2 injection locations as well as the feasibility of the CCS approach writ large. Consequently, analyzing and monetizing leakage risk is necessary to develop CCS as a viable technological option to mitigate climate change. Risk is the product of the probability of an outcome and the impact of that outcome. Assessment of leakage risk from geologic CO2 storage reservoirs requires an analysis of the probabilities and magnitudes of leakage, identification of the outcomes that may result from leakage, and an assessment of the expected economic costs of those outcomes. One critical uncertainty regarding the rate and magnitude of leakage is determined by the leakiness of the well leakage pathway. This leakiness is characterized by a leakage permeability for the pathway, and recent work has sought to determine frequency distributions for the leakage permeabilities of wells and wellbores. We conduct a probabilistic analysis of leakage and monetized leakage risk for CO2 injection locations in the Michigan Sedimentary Basin (USA) using empirically derived frequency distributions for wellbore leakage permeabilities. To conduct this probabilistic risk analysis, we apply the RISCS (Risk Interference of Subsurface CO2 Storage) model (Bielicki et al, 2013a, 2012b) to injection into the Mt. Simon Sandstone. RISCS monetizes leakage risk

  4. Permeability Changes on Wellbore Cement Fractures Modified by Geochemical and Geomechanical Processes

    NASA Astrophysics Data System (ADS)

    Rod, K. A.; Um, W.

    2015-12-01

    Experimental studies were conducted using batch reactors, X-ray microtomography (XMT), and computational fluid dynamics (CFD) modeling to determine changes in cement fracture surfaces, fluid flow pathways and permeability, and cement fracture propagation with geochemical and geomechanical processes. Portland cement-basalt interface sample with artificial fractures was prepared to study the geochemical and geomechanical effects on the integrity of wellbores containing defects caused by subsurface activities. Cement-basalt interface sample was subjected to mechanical stress at 2.7 MPa before the chemical reaction. CFD modeling was performed to simulate flow of supercritical CO2 within the fractures before and after the application of mechanical stress. The model results highlighted the complex flow characteristics within the fracture and also changes in flow patterns due to application of geomechanical stress. The CFD model predicted ~45% increase in permeability after the application of geomechanical force, which increases the fracture aperture. The same sample was reacted with CO2-saturated groundwater with impurity H2S (1 wt.%) at 50°C and 10 MPa for 3 to 3.5 months under static conditions. XMT provided three-dimensional (3-D) visualization of the opening and interconnection of cement fractures due to mechanical stress. Even after a 3.5-month reaction with CO2-H2S-saturated groundwater at 50°C and 10 MPa, CaCO3 (s) precipitation occurred more extensively within the cement fracture rather than along the cement-basalt interfaces. Micro X-ray diffraction analysis also showed that major cement carbonation products of CO2-saturated groundwater reacting with impurity H2S were calcite, aragonite, and vaterite, consistent with cement carbonation by pure CO2-saturated groundwater, while pyrite was not identified due to low H2S content. The experimental results imply that the wellbore cement with fractures is likely to be healed during exposure to CO2-saturated

  5. Hydro-mechanical simulations of well abandonment at the Ketzin pilot site for CO2 storage verify wellbore system integrity

    NASA Astrophysics Data System (ADS)

    Unger, Victoria; Kempka, Thomas

    2015-04-01

    In geological underground utilisation, operating and abandoned wells have been identified as a main potential leakage pathways for reservoir fluids. In the scope of the well abandonment procedure currently carried out at the Ketzin pilot site for CO2 storage in Germany, a hydro-mechanical model was built to carry out a coupled analysis of the integrity in the entire wellbore system. The main aim of the present study was to assess the impacts of stress changes associated with CO2 injection as well as the cement backfill undertaken in the scope of well abandonment. A numerical model comprising cement sheaths, steel casings, tubing, multiple packers and wellbore annuli was implemented to enable a detailed representation of the entire wellbore system. The numerical model grid has a horizontal discretisation of 5 m x 5 m to focus on near wellbore effects, whereby element sizes increase with increasing distance from the wellbore. Vertical grid discretisation uses a tartan grid type over the entire model thickness of 1,500 m to ensure a sufficient discretisation of all wellbore system elements as well as of the reservoir unit. The total number of elements amounts to 210,672. Mechanical model parameters were taken from geological, drilling, logging and laboratory test data based on Ketzin pilot site-specific information as well as related literature (Kempka et al., 2014). The coupled calculations were performed using an elasto-plastic constitutive law, whereby an initial simulation run ensured a static mechanical equilibrium to represent the initial state before the start of CO2 injection. Thereto, gravitational load of the overburden rocks and pore pressure distribution following available well logs were integrated for initial model parameterisation including a normal faulting stress regime defined by a horizontal to vertical total stress ratio of 0.85. A correction accounting for the temperature and pressure dependent CO2 density was carried out in advance of each

  6. Enhanced Weathering Strategies for Stabilizing Climate and Averting Ocean Acidification - Supplementary Information

    NASA Technical Reports Server (NTRS)

    Taylor, Lyla L.; Quirk, Joe; Thorley, Rachel M. S.; Kharecha, Pushker A.; Hansen, James; Ridgwell, Andy; Lomas, Mark R.; Banwart, Steve A.; Beerling, David J.

    2015-01-01

    Chemical breakdown of rocks, weathering, is an important but very slow part of the carbon cycle that ultimately leads to CO2 being locked up in carbonates on the ocean floor. Artificial acceleration of this carbon sink via distribution of pulverized silicate rocks across terrestrial landscapes may help offset anthropogenic CO2 emissions. We show that idealized enhanced weathering scenarios over less than a third of tropical land could cause significant drawdown of atmospheric CO2 and ameliorate ocean acidification by 2100. Global carbon cycle modelling driven by ensemble Representative Concentration Pathway (RCP) projections of twenty-first-century climate change (RCP8.5, business-as-usual; RCP4.5, medium-level mitigation) indicates that enhanced weathering could lower atmospheric CO2 by 30-300 ppm by 2100, depending mainly on silicate rock application rate (1 kg or 5 kg m(exp. -2) yr (exp -1)) and composition. At the higher application rate, end-of-century ocean acidification is reversed under RCP4.5 and reduced by about two-thirds under RCP8.5. Additionally, surface ocean aragonite saturation state, a key control on coral calcification rates, is maintained above 3.5 throughout the low latitudes, thereby helping maintain the viability of tropical coral reef ecosystems. However, we highlight major issues of cost, social acceptability, and potential unanticipated consequences that will limit utilization and emphasize the need for urgent efforts to phase down fossil fuel emissions.

  7. Diels-Alder hydrogels with enhanced stability: First step toward controlled release of bevacizumab.

    PubMed

    Kirchhof, Susanne; Gregoritza, Manuel; Messmann, Viktoria; Hammer, Nadine; Goepferich, Achim M; Brandl, Ferdinand P

    2015-10-01

    Eight-armed PEG was functionalized with furyl and maleimide groups (8armPEG20k-Fur and 8armPEG20k-Mal); degradable hydrogels were obtained by cross-linking via Diels-Alder chemistry. To increase the stability to degradation, the macromonomers were modified by introducing a hydrophobic 6-aminohexanoic acid spacer between PEG and the reactive end-groups (8armPEG20k-Ahx-Fur and 8armPEG20k-Ahx-Mal). In an alternative approach, the number of reactive groups per macromonomer was increased by branching the terminal ends of eight-armed PEG with lysine (Lys) and Ahx residues (8armPEG20k-Lys-Ahx-Fur2 and 8armPEG20k-Lys-Ahx-Mal2). The hydrolytic resistance of the synthesized macromonomers was determined by UV spectroscopy; the obtained hydrogels were characterized by rheology and degradation studies. The degradation time of 5% (w/v) 8armPEG20k-Ahx hydrogels (28days) was twice as long as the degradation time of 5% (w/v) 8armPEG20k hydrogels (14days); this is explained by increased hydrolytic resistance of the maleimide group. Using dendritic 8armPEG20k-Lys-Ahx macromonomers substantially increased the stability of the resulting hydrogels; degradation of 5% (w/v) 8armPEG20k-Lys-Ahx hydrogels occurred after 34 weeks. 8armPEG20k hydrogels had the largest mesh size of all tested hydrogels, while hydrogels made from dendritic 8armPEG20k-Lys-Ahx macromonomers showed the smallest value. To evaluate their potential for the controlled release of therapeutic antibodies, the hydrogels were loaded with bevacizumab. The incorporated bevacizumab was released over 10 days (8armPEG20k) and 42days (8armPEG20k-Ahx), respectively; release from 8armPEG20k-Lys-Ahx hydrogels was not completed after 105 days. In summary, we believe that 8armPEG20k-Ahx or 8armPEG20k-Lys-Ahx hydrogels could serve as controlled release system for therapeutic antibodies such as bevacizumab.

  8. Enhancing Oxidative Stability of Sunflower Oil during Convective and Microwave Heating Using Grape Seed Extract

    PubMed Central

    Poiana, Mariana-Atena

    2012-01-01

    This study was performed to investigate the effectiveness of grape seed extract (GSE) compared to butylated hydroxytoluene (BHT) on retarding lipid oxidation of sunflower oil subjected to convection and microwave heating up to 240 min under simulated frying conditions. The progress of lipid oxidation was assessed in terms of peroxide value (PV), p-anisidine value (p-AV), conjugated dienes and trienes (CD, CT), inhibition of oil oxidation (IO) and TOTOX value. In addition, total phenolic content (TP) was evaluated in samples before and after heating in order to assess the changes in these compounds relative to the extent of lipid oxidation. The results of this study highlight that GSE showed a significantly inhibitory effect on lipid oxidation during both treatments, although to a different extent. This ability was dose-dependent; therefore, the extent of lipid oxidation was inversely related to GSE level. Convective heating, respective microwave exposure for 240 min of samples supplemented by GSE to a level of 1000 ppm, resulted in significant decreases of investigated indices relative to the control values as follows: PV (48%; 30%), p-AV (29%; 40%), CD (45%; 30%), CT (41%; 36%), TOTOX (35%; 37%). GSE to a level of 600–800 ppm inhibited the lipid oxidation in a similar manner to BHT. These results suggested that GSE can be used as a potential natural extract for improving oxidative stability of sunflower oil during thermal applications. PMID:22942764

  9. Immobilization of peroxidase enzyme onto the porous silicon structure for enhancing its activity and stability

    NASA Astrophysics Data System (ADS)

    Sahare, Padmavati; Ayala, Marcela; Vazquez-Duhalt, Rafael; Agrawal, Vivechana

    2014-08-01

    In this work, a commercial peroxidase was immobilized onto porous silicon (PS) support functionalized with 3-aminopropyldiethoxysilane (APDES) and the performance of the obtained catalytic microreactor was studied. The immobilization steps were monitored and the activity of the immobilized enzyme in the PS pores was spectrophotometrically determined. The enzyme immobilization in porous silicon has demonstrated its potential as highly efficient enzymatic reactor. The effect of a polar organic solvent (acetonitrile) and the temperature (up to 50°C) on the activity and stability of the biocatalytic microreactor were studied. After 2-h incubation in organic solvent, the microreactor retained 80% of its initial activity in contrast to the system with free soluble peroxidase that lost 95% of its activity in the same period of time. Peroxidase immobilized into the spaces of the porous silicon support would be perspective for applications in treatments for environmental security such as removal of leached dye in textile industry or in treatment of different industrial effluents. The system can be also applied in the field of biomedicine.

  10. Graphene/silicon nanocomposite anode with enhanced electrochemical stability for lithium-ion battery applications

    NASA Astrophysics Data System (ADS)

    Maroni, F.; Raccichini, R.; Birrozzi, A.; Carbonari, G.; Tossici, R.; Croce, F.; Marassi, R.; Nobili, F.

    2014-12-01

    A graphene/silicon nanocomposite has been synthesized, characterized and tested as anode active material for lithium-ion batteries. A morphologically stable composite has been obtained by dispersing silicon nanoparticles in graphene oxide, previously functionalized with low-molecular weight polyacrylic acid, in eco-friendly, low-cost solvent such as ethylene glycol. The use of functionalized graphene oxide as substrate for the dispersion avoids the aggregation of silicon particles during the synthesis and decreases the detrimental effect of graphene layers re-stacking. Microwave irradiation of the suspension, inducing reduction of graphene oxide, and the following thermal annealing of the solid powder obtained by filtration, yield a graphene/silicon composite material with optimized morphology and properties. Composite anodes, prepared with high-molecular weight polyacrylic acid as green binder, exhibited high and stable reversible capacity values, of the order of 1000 mAh g-1, when cycled using vinylene carbonate as electrolyte additive. After 100 cycles at a current of 500 mA g-1, the anode showed a discharge capacity retention of about 80%. The mechanism of reversible lithium uptake is described in terms of Li-Si alloying/dealloying reaction. Comparison of the impedance responses of cells tested in electrolytes with or without vinylene carbonate confirms the beneficial effects of the additive in stabilizing the composite anode.

  11. Stability enhancement of haptic interaction by analog input shaper and its application to scaled teleoperation

    NASA Astrophysics Data System (ADS)

    Lim, Yo-An; Kim, Jong-Phil; Ryu, Jeha

    2007-12-01

    This paper addresses an analog input shaper introduced in haptic control to improve the stability when interacting with virtual environments. High frequency inputs to a haptic device, which can occur in collision with a virtual wall with high stiffness, can bring limit cycle oscillations and instabilities. In order to reduce the high frequency input to an haptic device an analog input shaper is added to the control system. Since the input shaper acts as a low-pass filter, when a haptic pointer leaves the virtual wall with high stiffness, a user may feel slow decrease of impedance, moreover there may be negative impedance as if the wall is pulling. In order to prevent this, we add half-wave rectifiers which allow fast decrease of impedance and no negative input to a haptic device. The input shaper reduces the total energy supplied to a haptic device by preventing inputs with high frequency from flowing into a haptic device. Therefore it can be regarded as an artificial damping element. In order to apply the Energy-Bounding Algorithm (EBA),1 which can guarantee the stable haptic interaction, to a scaled teleoperation in a virtual nano-environment two scaling factors (velocity and force) are incorporated into EBA. By applying the analog input shaper to EBA in scaled teleoperation, the range of virtual wall stiffness which can be stably rendered by a haptic device is significantly extended.

  12. Fungal Isolate Optimized for Biogenesis of Silver Nanoparticles with Enhanced Colloidal Stability.

    PubMed

    Rajput, Sunil; Werezuk, Rodney; Lange, Ralph M; McDermott, Mark T

    2016-08-30

    Understanding the synthesis and properties of nanomaterials is critical for reliable applications. Biological systems, such as fungi, have been described as a "green" alternative to synthesis, yet knowledge gaps exist in terms of production variability, comparison with commercial products, and identifying a clear biological advantage over other synthesis methods. In this study, we evaluated 12 fungal isolates of Fusarium oxysporum for Ag nanoparticle production and characterized the resultant biologically produced (biogenic) nanoparticles. We show evidence that isolate selection, temperature, and pH can influence the quantity, size, and shape of nanoparticles. All F. oxysporum isolates produced Ag nanoparticles, but in varied quantities. Increasing incubation temperature increased the quantity, yet nanoparticle diameter was inversely related to temperature. Variations in pH predominately influenced nanoparticle morphology. A direct comparison with commercial, chemically produced Ag nanoparticles yielded physical similarities; however, important differences in surface chemistry are observed. Biogenic nanoparticles show a greater degree of colloidal stability in high-ionic-strength solutions, pointing to a biological advantage associated with the fungal produced layer (corona) surrounding the nanoparticles. It is clear that understanding the organic layer and interfacial interactions will be beneficial in developing innovative applications, particularly in the field of biosensing. PMID:27466012

  13. Noni puree (Morinda citrifolia) mixed in beef patties enhanced color stability.

    PubMed

    Tapp, W Nathan; Yancey, Janeal W S; Apple, Jason K; Dikeman, Michael E; Godbee, Richard G

    2012-06-01

    Ground beef, mixed with 0, 2, 4, and 6% Noni puree, was formed into 150-g patties, aerobically packaged, and displayed in retail for 5d. After 2 and 3d, patties with higher concentrations of Noni were perceived as redder and less discolored (P<0.05) by visual panelists. Noni patties were found to have greater (P<0.05) a* values than controls, even though all patties became less red during display. After 3 and 5d of retail display, patties with higher concentrations of Noni puree also had lower TBARS (were less oxidized; P<0.05). In fresh taste panels, panelists perceived the patties to have less beef flavor and greater incidence of off-flavors (P<0.05) as Noni puree concentration increased. The potential of Noni puree to improve the color stability and shelf life of fresh ground beef is very promising, but the flavors produced by the addition of Noni in ground beef may be detrimental to its use.

  14. Immobilization of peroxidase enzyme onto the porous silicon structure for enhancing its activity and stability

    PubMed Central

    2014-01-01

    In this work, a commercial peroxidase was immobilized onto porous silicon (PS) support functionalized with 3-aminopropyldiethoxysilane (APDES) and the performance of the obtained catalytic microreactor was studied. The immobilization steps were monitored and the activity of the immobilized enzyme in the PS pores was spectrophotometrically determined. The enzyme immobilization in porous silicon has demonstrated its potential as highly efficient enzymatic reactor. The effect of a polar organic solvent (acetonitrile) and the temperature (up to 50°C) on the activity and stability of the biocatalytic microreactor were studied. After 2-h incubation in organic solvent, the microreactor retained 80% of its initial activity in contrast to the system with free soluble peroxidase that lost 95% of its activity in the same period of time. Peroxidase immobilized into the spaces of the porous silicon support would be perspective for applications in treatments for environmental security such as removal of leached dye in textile industry or in treatment of different industrial effluents. The system can be also applied in the field of biomedicine. PMID:25221454

  15. Operational stability enhancement in organic light-emitting diodes with ultrathin Liq interlayers

    PubMed Central

    Tsang, Daniel Ping-Kuen; Adachi, Chihaya

    2016-01-01

    Organic light-emitting diodes (OLEDs) under constant current operation suffer from a decrease of luminance accompanied by an increase of driving voltage. We report a way to greatly improve the stability of OLEDs having a green emitter exhibiting thermally activated delayed fluorescence (TADF), (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl) isophthalonitrile (4CzIPN), by introducing ultrathin (1 to 3 nm) interlayers of 8-hydroxyquinolinato lithium (Liq) between hole-blocking layer and its surrounding emissive and electron-transport layers. Under constant current operation starting at a luminescence of 1,000 cd/m2, the time to reach 90% of initial luminance (LT90) increased eight times, resulting in LT90 = 1,380 hours after insertion of the interlayers. Combining this new concept and mixed host system, LT95 was further extended to 1315 hours that is 16 times of reference device. This is the best value reported for TADF-based OLEDs and is comparable to the operational lifetimes of well-established phosphorescence-based OLEDs. Thermally stimulated current measurements showed that the number of deep charge traps was reduced with the insertion of the ultrathin Liq interlayer, indicating that reducing the number of deep traps is important for improving the operational lifetime and that exciton-polaron annihilation may be a source of the device degradation. PMID:26926237

  16. Enhancing oxidative stability of sunflower oil during convective and microwave heating using grape seed extract.

    PubMed

    Poiana, Mariana-Atena

    2012-01-01

    This study was performed to investigate the effectiveness of grape seed extract (GSE) compared to butylated hydroxytoluene (BHT) on retarding lipid oxidation of sunflower oil subjected to convection and microwave heating up to 240 min under simulated frying conditions. The progress of lipid oxidation was assessed in terms of peroxide value (PV), p-anisidine value (p-AV), conjugated dienes and trienes (CD, CT), inhibition of oil oxidation (IO) and TOTOX value. In addition, total phenolic content (TP) was evaluated in samples before and after heating in order to assess the changes in these compounds relative to the extent of lipid oxidation. The results of this study highlight that GSE showed a significantly inhibitory effect on lipid oxidation during both treatments, although to a different extent. This ability was dose-dependent; therefore, the extent of lipid oxidation was inversely related to GSE level. Convective heating, respective microwave exposure for 240 min of samples supplemented by GSE to a level of 1000 ppm, resulted in significant decreases of investigated indices relative to the control values as follows: PV (48%; 30%), p-AV (29%; 40%), CD (45%; 30%), CT (41%; 36%), TOTOX (35%; 37%). GSE to a level of 600-800 ppm inhibited the lipid oxidation in a similar manner to BHT. These results suggested that GSE can be used as a potential natural extract for improving oxidative stability of sunflower oil during thermal applications.

  17. Selective crystallization of regioregularity controlled polythiophene for enhancing mechanical stability and electronic performance

    NASA Astrophysics Data System (ADS)

    Kim, Hyeong Jun; Yu, Hojeong; Kim, Jae-Han; Kim, Jin-Sung; Kim, Taek Soo; Oh, Joon Hak; Kim, Bumjoon

    Considering the many potential applications of organic electronics in portable electronic devices, it is of great importance to develop an electro-active material that possesses mechanical stability and high electronic performance. Coexistence of both properties, however, is very difficult to achieve because good electronic performance is associated with long conjugation length, and high crystallinity often results in stiffness and brittleness. Herein, we utilize P3HT with two different regioregularities: high RR (98) P3HT has high electronic properties but poor mechanical resilience, and low RR P3HT (68) exhibits high elasticity and ductility but poor electronic performance. Selective crystallization of high RR P3HT induced by solution assembly allows construction of percolated networks of high RR P3HT nanowires (NWs) embedded in low RR P3HT matrix. Only 5 wt high RR P3HT is required to reach a hole mobility comparable to that of high RR P3HT, and high RR NWs embedded in film exhibits 20 times higher elongation at break. Selective self-assembly allows us to overcome the fragile nature of highly crystalline conjugated polymers without losing their electronic properties.

  18. Selective crystallization of regioregularity controlled polythiophene for enhancing mechanical stability and electronic performance

    NASA Astrophysics Data System (ADS)

    Kim, Hyeong Jun; Yu, Hojeong; Kim, Jae Han; Kim, Jin-Sung; Kim, Taek Soo; Oh, Joon Hak; Kim, Bumjoon

    Considering the many potential applications of organic electronics in portable electronic devices, it is of great importance to develop an electro-active material that possesses mechanical stability and high electronic performance. Coexistence of both properties, however, is very difficult to achieve because good electronic performance is associated with long conjugation length, and high crystallinity often results in stiffness and brittleness. Herein, we utilize P3HT with two different regioregularities: high RR (98%) P3HT has high electronic properties but poor mechanical resilience, and low RR P3HT (68%) exhibits high elasticity and ductility but poor electronic performance. Selective crystallization of high RR P3HT induced by solution assembly allows construction of percolated networks of high RR P3HT nanowires (NWs) embedded in low RR P3HT matrix. Only 5 wt% high RR P3HT is required to reach a hole mobility comparable to that of high RR P3HT, and high RR NWs embedded in film exhibits 20 times higher elongation at break. Selective self-assembly allows us to overcome the fragile nature of highly crystalline conjugated polymers without losing their electronic properties.

  19. Stabilized Heptapeptide A7R for Enhanced Multifunctional Liposome-Based Tumor-Targeted Drug Delivery.

    PubMed

    Ying, Man; Shen, Qing; Liu, Yu; Yan, Zhiqiang; Wei, Xiaoli; Zhan, Changyou; Gao, Jie; Xie, Cao; Yao, Bingxin; Lu, Weiyue

    2016-06-01

    (L)A7R (ATWLPPR) is a heptapeptide with high binding affinity in vitro to vascular endothelial growth factor receptor 2 (VEGFR2) and neuropilin-1 (NRP-1) overexpressed on glioma, glioma vasculogenic mimicry and neovasculature. However, its tumor targeting efficacy is significantly reduced in vivo due to proteolysis in blood circulation. To improve the in vivo stability and targeting efficacy, the retro inverso isomer of (L)A7R ((D)A7R) was developed for glioma-targeted drug delivery. (D)A7R was expected to have a similar binding affinity to its receptors in vitro (VEGFR2 and NRP-1), which was experimentally confirmed. In vivo, (D)A7R-modified liposomes achieved improved glioma-targeted efficiency than did (L)A7R-modified liposomes. After loading a chemotherapeutic agent (doxorubicin), (D)A7R-modified liposomes significantly inhibited subcutaneous model tumor in comparison to free doxorubicin, plain liposomes and (L)A7R-modified liposomes. In summary, the present study presented the potential of a proteolytically stable d-peptide ligand for in vivo tumor-targeted drug delivery. PMID:27195531

  20. Synthesis and characterization of supported polysugar-stabilized palladium nanoparticle catalysts for enhanced hydrodechlorination of trichloroethylene.

    PubMed

    Bacik, Deborah B; Zhang, Man; Zhao, Dongye; Roberts, Christopher B; Seehra, Mohinar S; Singh, Vivek; Shah, Naresh

    2012-07-27

    Palladium (Pd) nanoparticle catalysts were successfully synthesized within an aqueous phase using sodium carboxymethyl cellulose (CMC) as a capping ligand which offers a green alternative to conventional nanoparticle synthesis techniques. The CMC-stabilized Pd nanoparticles were subsequently dispersed within support materials using the incipient wetness impregnation technique for utilization in heterogeneous catalyst systems. The unsuppo