bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of a protein S assay measuring the APC cofactor activity / Charakterisierung eines APC-Kofaktor basierten Protein S-Aktivitätstests
Authors: Patzke Jürgen , Merz Mechthild , Siegemund Annelie 
Published: December 2007

Abstract
The Protein S Ac activity assay is based on the role of protein S as a cofactor to activated protein C (APC). Tests performed on three coagulation analyzers were studied to determine assay performance characteristics. The overall mean imprecision was 5.5%, 5.0% and 7.5% for within-run coefficient of variation (CV), run-to-run CV and total CV, respectively. A total of 239 sample results yielded a correlation to the STA Protein S Clotting assay of r=0.92 (slope=0.96). A group of patients with APC resistance and additional underlying conditions, such as oral contraception, oral anticoagulation, pregnancy and recurrent thrombosis showed pathologically low protein S values with activity assays as well as with free antigen assays. To differentiate between the effects of APC resistance and other influencing factors, samples from healthy blood donors with APC resistance were measured with both assay types. Based on comparison of antigen and activity results, it can be concluded that APC resistance lowers protein S activity values by approximately 15% (rel.). No interference was observed from physiologically relevant concentration of factor V, factor VIII, triglycerides, hemoglobin, bilirubin and heparin (low molecular weight heparin and unfractionated heparin). When samples are to be frozen, double centrifugation is the best procedure to reduce the platelet count. The stability of the sample was at least 4 h at room temperature, regardless of whether fresh or frozen samples were tested. Freezing had no observable effect on samples stored for up to 12 months at −70°C.
Streptokokkenschnelltests / Rapid streptococcal antigen detection tests
Authors: Reinert Ralf René 
Published: December 2007

Zusammenfassung
Die konsequente antibiotische Behandlung von durch Streptococcus pyogenes hervorgerufener Tonsillo-Pharyngitis ist nach wie vor aufgrund der Folgeerkrankungen erforderlich. Die Diagnose der Streptokokken-Pharyngitis basierend allein auf klinischen Symptomen ist nicht zuverlässig möglich. Die klassische mikrobiologische Kultur erfordert ein bis drei Tage und wird den Anforderungen des klinischen Alltags aufgrund des Zeitbedarfes nicht gerecht. Daher haben einfach durchzuführende Streptokokkenschnelltests in den letzten Jahren zunehmend Verbreitung gefunden. Fast alle modernen Streptokokkenschnelltests besitzen eine hohe Spezifität (>95%), auch die Sensitivität wurde in den letzten Jahren aufgrund technischer Verbesserungen deutlich gesteigert (>85%). Große Sorgfalt muss auf bei der Auswahl des geeigneten Streptokokkenschnelltests für die entsprechende medizinische Einrichtung aufgewandt werden. Überlegungen zum Einsatz von Streptokokkenschnelltests sollten folgende Aspekte berücksichtigen: Art der Einrichtung (Krankenhaus, niedergelassene Praxis), Kosten und schnelle Verfügbarkeit eines mikrobiologischen Labors. Niedergelassenen Kinderärzten ist anzuraten, für die Zeit der Einführung eines neuen Tests, Schnelltest und klassische mikrobiologische Kultur parallel durchzuführen, bis man sich von hoher Spezifität und Sensitivität der neuen Testmethode im Rahmen der eigenen Einrichtung überzeugt hat. Der Einfluss, den Ausbildung und Training des technischen Personals auf die diagnostische Qualität des Tests haben, darf nicht unterschätzt werden. In besonderen Fällen sollte auf eine Empfindlichkeitsprüfung nicht verzichtet werden, da auch in Deutschland die Makrolidresistenz von Streptococcus pyogenes in den letzten Jahren deutlich zugenommen hat.
Administration route-dependent effects of estrogens on IGF-I levels during fixed GH replacement in women with hypopituitarism
Authors: van der Klaauw Agatha A , Biermasz Nienke R , Zelissen Pierre M J , Pereira Alberto M , Lentjes Eef G W M , Smit Johannes W A , van Thiel Sjoerd W , Romijn Johannes A , Roelfsema Ferdinand 
Published: December 2007

ObjectiveGH-deficient women using oral estradiol treatment require higher doses of recombinant human GH (rhGH) to achieve similar IGF-I levels when compared with men and women on transdermal estradiol replacement. The aim of this study was to evaluate the effects of oral versus transdermal estrogen administration at similar plasma estradiol levels on IGF-I, IGF-binding protein-3, and sex hormone-binding globulin (SHBG) concentrations.DesignParallel crossover study in which two groups of hypogonadal and GH-deficient women with fixed and stable rhGH replacement passed through four different estradiol treatment schemes (2 and 4 mg oral, and 50 and 100 μg transdermal estradiol) with a duration of four cycles each to ensure a new steady state. Group I (18 patients using oral estradiol prior to the study) was treated with oral followed by transdermal estradiol and group II (five patients with transdermal estradiol prior to inclusion) with transdermal followed by oral estradiol.ResultsEstradiol concentrations were lowest during 50 μg transdermal and highest during 4 mg oral estradiol treatment. Estradiol concentrations did not differ during 100 μg transdermal and 2 mg oral treatment. Nevertheless, IGF-I levels were significantly higher during 100 μg transdermal when compared with 2 mg oral treatment (P=0.005 in group I and 0.02 in group II), while SHBG levels were significantly lower (P=0.002 in group I and P=0.004 in group II). SHBG and IGF-I concentrations were negatively correlated (R=−0.41, P=0.0001).ConclusionDuring fixed GH replacement, the route of estrogen administration is a determinant of IGF-I levels in hypogonadal GH-deficient women.
Eliminating Human Error During Coiled Tubing Operations
Authors: Burgos Rex , Allcorn Marc , Mallalieu Robin , Vicens Jorge 
Published: December 2007

Summary
In the last decade, several successful initiatives have been introduced to mitigate the risk of coiled tubing pipe failure while performing interventions in oil and gas wells. Through the use of reasonably accurate computer modeling, the industry has seen a marked reduction in the number of pipe failures associated with material fatigue caused by the constant plastic deformation occur-ing during pipe-tripping operations. Similarly, the judicious practice of employing off-line pipe-quality inspection tools, as well as the availability of real-time monitoring of pipe geometry through a variety of devices has contributed to a more predictable and more favorable pipe performance.
A study of root causes for coiled tubing (CT) pipe failures during a 5-year period indicates that a substantial percentage of incidents were attributed to human error. This type of incident involves the application of excessive overpull, resulting in pipe necking or complete parting of the pipe because of tensile failure. Similarly, too much snubbing force will cause pipe buckling and compressive failure. Both have the undesirable result of a damaged CT string (at best) or a compromised well control security (at worst). Using a properly trained and fully competent crew can minimize such events. However, the arduous and stress-filled nature of live-well CT operations will limit the elimination of this human element.
This paper presents an effective means for eliminating the possibility of human error becoming a factor in conditions that could result in a pipe failure during normal CT operations. Through the incorporation of a specialized system in the coiled tubing unit controls, a safety device is put in place to provide a shutdown feature when specific job-designed setpoints are exceeded.
This paper provides a discussion of the features and capabilities of such a system. It cites details of recent experiences demonstrating the benefits with use of the device in actual CT interventions.
The Kinetics of Sulphate Deposition in Seeded and Unseeded Tests
Authors: Boak L. S. , Sorbie K. S. 
Published: December 2007

Summary
In a previous paper (Boak et al. 2005), we addressed the issue: What level of sulphate reduction is required to eliminate the need for scale inhibitor squeezing? In this earlier work, we developed the idea of a simple kinetic scheme for sulphate deposition on the basis of a "safe envelope" concept within which the system could operate. Central to the safe envelope approach is the choice of rate constant for barite deposition and this can be estimated experimentally under various conditions appropriate to the specific field application. Experimental results on kinetic barite deposition in low sulphate brine mixtures were presented previously (Boak et al. 2005). However, these previous results were carried out for unseeded solutions (i.e., no solid barite or sand particles were added to the scaling solutions). The following questions were raised
If barite particles were present, would this mean that the solution supersaturation (Sp) would reduce to 1 very rapidly thus over-ruling any kinetic deposition effects? Does the presence of sand particles have the same effect as barite particles? In the case of both barite or sand particles does the size of the particles (i.e. the surface area per unit mass) have any effect on the barite deposition rate?
In addition, a very simple kinetic model for bulk deposition of barite was used for which the long time behavior was that barite is deposited until the limiting ion was totally consumed. However, it is known that barite has some solubility at higher levels of sodium chloride and the kinetic model should limit to this value. This may be an important consideration especially in lower sulphate (or lower barium) brines.
Experimental results are presented in this paper which both address and answer the above questions, and extend the analysis with an improved kinetic model for barite deposition. Even in the presence of seed materials (barite and sand of various surface areas), clear rate effects can be observed and rate constants can be derived. As expected, barite seed material of higher surface area induces faster depletion of the scaling ions to a supersaturation ratio of 1 than barite of lower surface area. However, allowing for the effect of surface area, the barite seed material shows a clearly enhanced potential to induce scale formation than the sand. In addition, the safe envelope model is extended by considering a more accurate analytical kinetic model which limits correctly to the equilibrium solubility of barite at long times.
Alkaline Flood Prediction Studies, Ranger VII Pilot, Wilmington Field, California
Authors: Mayer E. H. , Breit V. S. 
Published: December 2007

Summary
This paper discusses the design of a simulator to model alkaline displacement mechanisms, along with the current understanding of in-situ caustic consumption. Assimilation of laboratory coreflood and rock consumption data, and their use in one- and two-dimensional (1D and 2D) limited-area simulations and in threedimensional (3D) model of the entire pilot project are given.
This paper also reports simulation studies of alkaline flood behavior in a small 2D area of a field for various concentrations, slug sizes, long-term consumption functions, and two relative-permeability adjustment mechanisms. The scale-up of 2D simulation results and their use in a 271-acre [1096.7-ha], seven-layered, 3D model of the pilot are also discussed and 3D simulator results are compared with initial field alkaline flood performance.
Finally, recommended additional applications of the simulator methods developed in this pilot and in other alkaline floods are discussed.
The Effect of Stress-Dependent Permeability on Gas Production and Well Testing
Authors: Ostensen R. W. 
Published: December 2007

Summary
The effect of stress-dependent permeability on gas production and well testing in tight gas sands was studied by use of a modified pseudopressure that included stress dependence. This work assumes that information on cores is applicable to reservoir behavior. Because microcracks are the primary path for flow through tight-gas-sand cores, average stress-dependent permeabilities were found as an average over all crack orientations in a nonuniform stress field, with a horizontal stress only 0.6 times the vertical one. Initial in-situ permeabilities are found to be two to five times the values obtained from uniformly restressed cores. Stress dependence decreases initial gas production by at most 30%, with the loss increasing with reservoir depletion. Buildup tests yield reliable results for the properties at average reservoir pressure. Drawdown tests are more sensitive to stress effects and are much less reliable.
Stress Gradient Affects the Height of Vertical Hydraulic Fractures
Authors: Thiercelin M. J. , Lemanczyk Z. R. 
Published: December 2007

Summary
Fracture height is a critical input variable in current hydraulic-fracturing-treatment design. This paper presents the results of a laboratory study regarding the effect of the in-situ horizontal stress gradient acting as a potential barrier in limiting the height of a hydraulically created vertical fracture. The experiments consisted of creating fractures in cylindrical samples of polymethylmethacrylate (PMMA) and measuring the ensuing heights. The stress gradient was induced by preventing any radial displacement at the sample ends while simultaneously applying an axial load. A two-dimensional (2D) analysis was used to predict the extent of crack development as a function of fluid pressure in the fracture. The experimental results confirm that high stress gradients can act as barriers in containing fracture height. Our experimental approach permits quantitative results to be obtained that are in good agreement with those predicted from the calculations.
Cyclic Steaming of Tar Sands Through Hydraulically Induced Fractures
Authors: Dietrich J. K. 
Published: December 2007

Summary
Fracture dimensions and process mechanisms that resulted from cyclic steam stimulation above fracturing pressure in German and Canadian tar sands are analyzed with numerical modeling. Horizontal fracture radii of 100 ft [30.5 m] and vertical fracture half-lengths of 250 ft [76.2 m] with fracture surface areas of 30,000 to 70,000 sq ft [2787 to 6503 m2] are sufficient to reproduce steam injectivity into reservoirs containing highly viscous oil and negligible amounts of movable water saturation. Mechanisms that are important during fluid loading and unloading of induced fractures include thermal expansion of tar oil, countercurrent imbibition of water and oil caused by capillary pressure effects, and fracture compressibility.
A New Approximate Analytic Solution for Finite-Conductivity Vertical Fractures
Authors: Lee Sheng-Tai , Brockenbrough John R. 
Published: December 2007

Summary
A new analytic solution, based on an approximate trilinear flow model, is developed to study the transient behavior of a well intercepted by a finite-conductivity vertical fracture. The solution accounts for the effects of skin, wellbore storage, and fracture storage. Both constant-pressure and constant-rate cases are considered. The solution is simple and reliable for short-time analysis. Combining this solution with a semilog asymptotic solution provides a reliable tool for analysis and formation evaluation of fractured wells. We also demonstrate that the optimization technique is a convenient means of formation parameter estimation. A set of early-time asymptotic solutions is also presented. These solutions provide qualitative and quantitative relations of the simultaneous influences of wellbore storage, fracture storage, and skin damage on early-time wellbore pressure behavior.
Rheological Study of Foam Fracturing Fluids Using Nitrogen and Carbon Dioxide
Authors: Reidenbach V. G. , Harris P. C. , Lee Y. N. , Lord D. L. 
Published: December 2007

SummaryA practical mathematical model based on experimental data is presented for calculation of rheological properties of N2 and CO2 foam stimulation fluids. The laminar flow model is a yield pseudoplastic type, with viscosity dependent on foam quality, yield point, base liquid consistency index (K′), and flow behavior index (n′). Turbulent foam flow data were analyzed with API RP39 procedures but were modified to include variable density effects of foam fluids.Water-based foam apparent viscosities compare closely to Mitchell's Bingham plastic model at high shear rates. The yield pseudoplastic model also includes viscous effects of gelling agents and measurement at much lower shear rates. Comparison of predicted pipe friction was made to actual field wellhead pressures with good agreement.
Using the Hollow-Core Test To Determine Acid Reaction Rates
Authors: Gdanski R. D. , Norman L. R. 
Published: December 2007

Summary
Effects of chemical additives on acid reaction rates may be determined by observation of acid reaction in hollow limestone cores. Reactivities of acids containing (1) surfactant gelling agents, (2) polymeric gelling agents, (3) crosslinked polymeric gelling agents, and (4) fluid loss additives were measured. Effects of chemical and filter cake retardation were assessed, and experiments were conducted with and without fluid leakoff at temperatures of 150 to 300°F [65 to 150°C].
A Numerical Technique for Tracking Sharp Fronts in Studies of Tertiary Oil-Recovery Pilots
Authors: Jensen O. K. , Finlayson B. A. 
Published: December 2007

Summary
A numerical front-tracking technique, based on a transformation of the governing equations into a moving coordinate system (MCS), is applied to a finite-element reservoir simulator. The method is especially suited for studies of tertiary oil-recovery pilots with chemical flooding and other miscible displacement processes. The new front-tracking technique is compared to conventional finite-element formulations with a uniform grid over the entire domain. Comparisons with other methods show that computer time can be greatly reduced with the same accuracy.
Through-Casing Reservoir Evaluation
Authors: Cannon Darrel E. , LaVigne Jack A. 
Published: December 2007

Summary
Evaluation of complex carbonates and formations with unknown formation water salinities is difficult though now possible. Processing of both elastic and inelastic spectra of pulsed-neutron gamma-ray spectrometry tools (GST's™) can provide lithologic information comparable to core and openhole logs and water saturation values in formations of unknown water salinity. Quick looks can be obtained from basic measurements, but quantitative values require processing. Saturation information improves as porosity increases.
Low-pH Methanol: An Alternative for Stimulation in Water-Sensitive, Tight, Dirty Sandstones
Authors: Ortiz J. , McLane J. E. 
Published: December 2007

Summary
Heavily clay-laden, low-permeability sandstones have always presented difficulties in stimulation. The most common treatment for such formations has been a crosslinked 40/60-lbm hydroxypropyl guar (HPG) in KCl water, but the results have not always reached expectations.
This paper characterizes one of these formations by scanning-electron-microscope/energy-dispersive-spectrometer (SEM/EDS) evaluation of mineralogy and lithology. The core samples were subjected to conventional and experimental treatment fluids by a nitrogen gas reference core-flow apparatus to find the optimum stimulation treatment.
Mechanical Degradation of Polyacrylamide Solutions in Core Plugs From Several Carbonate Reservoirs
Authors: Martin F. D. 
Published: December 2007

SummaryThis paper presents results of laboratory studies on mechanical degradation of partially hydrolyzed polyacrylamide (HPAM) solutions in core samples from several different carbonate reservoirs. Studies in carbonates are of particular importance because several of the larger polymer projects are in carbonate reservoirs and because data on carbonate rocks have not previously been available. Many of the data in the literature were obtained with solutions of polymer-in-brine. Because HPAM polymers are generally more efficient in fresh waters, lower-salinity waters were used for the bulk of the present study. Investigated variables included polymer molecular weight, polymer concentration, and salinity of the aqueous solvent. HPAM samples used were commercial products of various molecular weights. Results were compared with correlations previously developed for sandstone core plugs and unconsolidated sands. The extent of induced degradation was monitored by comparison of viscosities and screen factors before and after flow through the core plugs at various flow rates.During injection of low-salinity polymer solutions through low-permeability carbonate core plugs, the extent of induced mechanical degradation was higher than values estimated with existing correlations obtained with higher-permeability porous media. Severe nonuniformities in the low-permeability carbonate core caused difficulties in our attempts to relate the degradation of existing correlations. Thin sections of the core materials were very helpful in the qualitative understanding of the differences in injectivity and mechanical degradation for cores from the various reservoirs. Cores with relatively uniform porosity performed differently from those that were very nonuniform, even though the permeabilities were similar.The induced mechanical degradation of the polymer reduced the viscoelastic and pseudoplastic nature of the HPAM solutions. As expected, the extent of mechanical degradation increased as the polymer molecular weight increased. Residual viscosities and screen factors of the sheared solutions, however, were often greater for the higher-molecular-weight HPAM polymers. Higher salinities or calcium concentrations of the solvent resulted in increased degradation. Thus, use of low-salinity water or softened fresh water can reduce the level of irreversible shear degradation.
Factors Affecting Perforating Charge Performance and Relationship to Port Plug Condition
Authors: King G. E. , Bingham M. D. , Kidder R. W. 
Published: December 2007

Summary
A series of perforating tests was run in surface targets to determine whether the conditions of the port plug from a perforating gun could be used as a relative indication of entrance hole shape and perforation penetration. Tests that used centralized and decentralized guns in large cement targets showed that a strong correlation exists between casing-entrance hole shape and the shape of the hole in the port plug of the gun. Also, if the charge was misaligned or double-jetted, resulting in cutting of the side of the port plug or the gun, target penetration was sharply reduced. Data were also collected on such influences as gun clearance, charge weight and liner type, multiple casing strings, defective charges, and age of charges.
Cleaning and Testing of Used Submersible Pumps To Reduce Lifting Costs
Authors: Divine D. L. 
Published: December 2007

Summary
A technique has been developed to clean used submersible pumps chemically without the expense of tearing down the pump and rebuilding it. After the cleaning process, the pump is tested arid its performance is plotted against the manufacturer's catalog curve. More than 70% of the pumps put through this process have been rerun without being rebuilt, with substantial savings to the operator.
This paper discusses the process used in cleaning and inspection. The test bench will be described, along with the metering accuracy and calibration techniques. Use of the actual pump curve for improving production will be covered, along with statistical data on more than 1,200 new and used pumps.
Penetration-Rate Performance of Roller-Cone Bits
Authors: Warren T. M. 
Published: December 2007

Summary
The rate of penetration (ROP) obtained with a roller-cone bit is limited by either the cuttings-generation or cuttings-removal process. An ROP model that includes the effect of both the initial chip formation and cuttings-removal processes is presented. Laboratory observations show that the reduction in ROP at high borehole pressure is the result of both local cratering effects and global cleaning effects.