bluuebunny/crossref_metadata_2025_split huggingface dataset:
Equations and Type Curves for Predicting the Polymerization of Amorphous Silica in Geothermal Brines
Authors: Weres Oleh , Yee Andrew , Tsao Leon 
Published: December 2007

Abstract
The polymerization of dissolved silica in aqueous solutions up to 100°C and containing up to 1 M NaCl has been studied experimentally, and theoretically. In this paper, the results of this work are presented in a form suitable for practical use in interpreting and predicting the chemistry of silica in geothermal brines. Empirical equations for calculating the rate of molecular deposition of silica on surfaces as a function of silica concentration, temperature, pH, and salinity are presented. Theoretically calculated type curves that depict the decrease of dissolved silica concentration by homogeneous nuclea-tion and particle growth are presented, along with the procedures for using them to predict the course of this process under different conditions.
General Inflow Performance Relationship for Solution-Gas Reservoir Wells
Authors: Dias-Couto Luiz Evanio , Golan Michael 
Published: December 2007

Summary
Two equations are developed to describe the inflow performance relationship (IPR) of wells producing from solution-gas drive reservoirs. These are general equations (extensions of the currently available IPR's) that apply to wells with any drainage-area shape at any state of completion flow efficiency and any stage of reservoir depletion.

Introduction
The dimensionless IPR presented by Vogel1 was developed for flow of saturated oil from a solution-gas drive reservoir into an "ideal" well (a well without any negative or positive skin effect).
For real wells (damaged or stimulated), Standing2 developed a modification to Vogel's IPR and presented a set of dimensionless curves for a range of flow efficiencies different from one.
An analytical approach for flow efficiency correction of Vogel's IPR that provides a simple equation to calculate the productivities of real wells at present time was presented by Couto.3
Standing4 suggested a simple procedure to obtain the IPR of an ideal well at any future depletion stage.
Applying Couto's approach for flow efficiency correction to Standing's development of future IPR yields a more generalized single IPR equation that accounts for any state of completion flow efficiency and reservoir depletion.
A different approach to predict future IPR of a real well has been proposed by Fetkovich.5 His procedure can be rearranged to yield a single IPR equation somewhat similar to the general equation' derived from Vogel's approach.
Each of the two equations developed may be used to predict future-time IPR of small- to medium-capacity real wells.
Vogel's Present-Time Generalized IPR
According to Vogel, the present-time dimensionless IPR for an ideal well (in which flow efficiency E=1) may be expressed asEquation 1
Substituting the dimensionless bottom hole flowing pressure R=pwf/p in Eq. 1 yieldsEquation 2
Couto has shown that for real wells, in which E?1, Vogel's equation can be written for the ideal part of the pressure drawdown asEquation 3
where p'wf=pwf+Dps is the ideal bottom flowing pressure and j=(p-p'wf)/(p-pwf) is the actual flow efficiency of the real well. Eq. 3 applies for any p'wf/p 0.
Rewriting Eq. 3 in terms of the dimensionless ideal bottom hole flowing pressure R'=p'wf/p, we obtainEquation 4
which applies for any R' 0.
Representing Wells in Numerical Reservoir Simulation: Part 2 – Implementation
Authors: Chappelear John E. , Williamson Alexander S. 
Published: December 2007

Abstract
A reservoir simulation system uses an analytical model to represent flow within a grid block as it enters or leaves a well. This model is called a well model. This paper presents a succinct but comprehensive description of the installation of a well model in a simulator, including problems which may be encountered and possible remedies. This and the preceding paper, SPE 7697, present a unified viewpoint of material, some of which may be already familiar to simulator developers.
The Effect of Interfacial Tensions on Relative Oil/Water Permeabilities of Consolidated Porous Media
Authors: Amaefule Jude O. , Handy Lyman L. 
Published: December 2007

Abstract
Relative permeabilities of systems containing low-tension additives are needed to develop mechanistic insights as to how injected aqueous chemicals affect fluid distribution and flow behavior. This paper presents results of an experimental investigation of the effect of low interfacial tensions (IFT's) on relative oil/water permeabilities of consolidated porous media.
The steady- and unsteady-state displacement methods were used to generate relative permeability curves. Aqueous low-concentration surfactant systems were used to vary IFT levels. Empirical correlations were developed that relate the imbibition relative permeabilities, apparent viscosity, residual oil, and water saturations to the interfacial tension through the capillary number (Nc = vμ/σ). They require two empirical, experimentally generated coefficients.
The experimental results show that the relative oil/water permeabilities at any given saturation are affected substantially by IFT values lower than 10-1 mN/m. Relative oil/water permeabilities increased with decreasing IFT (increasing Nc). The residual oil and residual water saturations (Sor and Swr) decreased, while the total relative mobilities increased with decreasing IFT. The correlations predict values of relative oil/water permeability ratios, fractional flow, and residual saturations that agree with our experimental data. Apparent mobility design viscosities decreased exponentially with the capillary number.
The results of this study can be used with simulators to predict process performance and efficiency for enhanced oil-recovery projects in which chemicals are considered for use either as waterflood or steamflood additives. However, the combined effect of decreased interfacial tension and increased temperature on relative permeabilities has not yet been studied.
Gibbs Energy Analysis of Phase Equilibria
Authors: Baker Lee E. , Pierce Alan C. , Luks Kraemer D. 
Published: December 2007

Abstract
Equations of state are used to predict or to match equilibrium fluid phase behavior for systems as diverse as distillation columns and miscible gas floods of oil reservoirs. The success of such simulations depends on correct predictions of the number and the compositions of phases present at a given temperature, pressure, and overall fluid composition. For example, recent research has shown that three or more phases may exist in equilibrium in CO2 floods.
This paper shows why an equation of state can predict the incorrect number of phases or incorrect phase compositions. The incorrect phase descriptions still satisfy the usual restrictions on equality of chemical potentials of components in each phase and conservation of moles in the system. A new method and its mathematical proof are presented for determining when a phase equilibrium solution is incorrect.
Examples of instances where incorrect predictions may be made are described. These include a binary system in which a two-phase solution may be predicted for a single-phase fluid and a multicomponent CO2/reservoir oil system in which three or more phases may coexist.
Surfactant Flooding 2: The Effect of Alkaline Additives on Permeability and Sweep Efficiency
Authors: Krumrine Paul H. , Falcone James S. , Campbell Thomas C. 
Published: December 2007

Abstract
This paper is the second of a series of papers reporting our examinations of the effects alkaline additives have on dilute surfactant systems for low-tension waterflooding (LTWF). The first paper outlined the effects on interfacial tension (IFT), hardness removal, and surfactant retention by the core material, and how these parameters then affect overall recovery of oil from watered-out cores containing high-hardness brines. This study examines the effects of those chemicals on permeability, sweep efficiency, and sweep symmetry through multipermeable noncommunicating zones. Correlations and possible mechanisms are offered that relate these findings to the earlier work on surfactant retention and hardness removal.
The results of these studies indicate that each alkali behaves differently, but all are capable of enhancing the action of the dilute surfactant treatment. Sweep efficiency in three-dimensional (3D) patterns and sweep symmetry through multipermeable noncommunicating zones is increased by the alkaline chemicals. Selective permeability reduction, caused by the reaction with the residual hardness ions, is suspected as a mechanism. Overall, sodium silicate addition to the surfactant flood as a builder was found to produce the best performance because of its ability to inhibit surfactant retention, thereby increasing the recovery of crude before selective permeability reduction occurs. Overall permeability loss is only about 20 to 25% in a core initially containing 4,800 ppm of hardness as CaCOз under our experimental conditions.
Temperature Observations and Steam-Zone Rise in the Vicinity of a Steam-Heated Fracture
Authors: Closmann Philip J. , Smith Richard A. 
Published: December 2007

Abstract
Temperature observations taken in a well that traverses a steam-heated fracture in a tar sand formation allow estimates of the in-situ thermal parameters of the formation. They also indicate for the case presented the upward movement of a heat source at a constant velocity, suggesting the vertical growth of a permeable hot zone. This vertical movement can be modeled approximately with a thermal simulator. Comparison of numerical and analytic solutions, however, shows that very small finite-difference grid spacing is required to obtain the correct steam rise velocity with the simulator. The comparison between experimental and simulation results also provides an indication of the relative importance of the vertical reservoir permeability.
Vapor-Pressure Lowering in Geothermal Systems
Authors: Hsieh Chih-Hang , Ramey Henry J. 
Published: December 2007

Abstract
The water vapor-pressure lowering phenomenon in porous media was investigated for a range of temperatures by measuring vapor pressure vs. mass of water adsorbed in consolidated sandstone cores and unconsolidated silica sands. Experimental results showed that the mass of water adsorbed on the rock surface is much more than the amount of pore steam. Results also revealed that the water adsorption is caused mainly by micropores in the porous medium. Measurement of the mass of methane and ethane adsorbed on dry rocks showed that the amount of adsorption is not great in comparison with the pore gas.
It was found that adsorption data for water/sandstone core studies could be normalized with respect to temperature. Although this appears not to have been reported previously, it does agree in principle with findings for solid powders with micropores. Another interesting result was that reanalysis of previous studies of capillarity in sandstones indicates that experimental data probably were influenced mostly by adsorption.
Correlation of Crude Oil Steam Distillation Yields With Basic Crude Oil Properties
Authors: Wu Ching H. , Elder Robert B. 
Published: December 2007

AbstractSteam distillation can occur in reservoirs during steam injection and in-situ combustion processes. To estimate the amount of vaporized oil caused by steam distillation, we established correlations of steam distillation yields with the basic crude oil properties. These correlations were based on steam distillation tests performed on 16 crude oils from various parts of the U.S. The gravity of oils varied from 12 to 40°API [0.99 to 0.83 g/cm3]. The viscosity of oil ranged from 5 to 4,085 cSt [5 to 4085 mm2/s] at 100°F [38°C]. The steam distillations were performed at a saturated steam pressure of 220 psia [1.5 MPa]. One oil sample was used in experiments to investigate the effect of steam pressure (220 to 500 psia [1.5 to 3.4 MPa]) on the steam distillation yield.The experiments were carried out to a steam distillation factor (Vw/Voi) of 20, with the factor defined as the cumulative volume of condensed steam used in distillation, Vw, divided by the initial volume of oil, Voi. At a steam distillation factor of 20, the distillation yields ranged from 13 to 57% of the initial oil volume.Several basic crude oil properties can be used to predict steam distillation yields reasonably well. A correlation using oil viscosity in centistokes at 100°F [38°C] can be used to predict the steam distillation yield within a standard error of 4.3%. The API gravity can be used to estimate yields within 5.6%. A gas chromatographic analysis was made for each crude oil to obtain the component boiling points (simulated distillation temperatures). A correlation parameter was selected from the simulated distillation results that can be used to estimate the steam distillation yields within 4.5%.
A New Method To Measure Directional Permeability
Authors: Rose Walter D. 
Published: December 2007

Introduction and Theory
The problem of measuring directional permeability by applying Darcy's law has been known for a long time, but so far it has been left unresolved. Here we show that for two-dimensional cases of anisotropy, three measurements must be made on a laboratory sample to calculate the maximum and minimum permeability from the data. These are (1) Angle B, which shows the direction of flow with respect to the direction of maximum permeability, (2) Angle A, which shows the direction of permeability, (2) Angle A, which shows the direction of flow with respect to the direction of the driving force gradient, and (3) the R11 element of the resistivity tensor that appears when Darcy's law is given the special form
Rij qu=-grad p................... (1)
Here Rij is the second-rank (symmetric) resistivity tensor defined by the transformation rule
(2)
In Eq. 2, lambda ii and lambda jj are the direction cosines between an i, j-axis frame and any other i, j- (rotated-) axis frame. Specifically, it is clear that an angle, - B, always can be found such that Rij will take on a diagonalized form.
It and easy to prove that the inverses of R1 and R2, respectively, give the maximum and minimum Darcian permeabilities since the i, j-axis frame coincides with the permeabilities since the i, j-axis frame coincides with the principal directions of the permeability tensor. principal directions of the permeability tensor. JPT
P. 1142
“Decoding the Dots”: The ImageStream system (ISS) as a novel and powerful tool for flow cytometric analysis
Authors: Zuba-Surma Ewa , Kucia Magdalena , Ratajczak Mariusz 
Published: December 2007

Abstract
The aim of this article is to provide a brief review of the ImageStream system (ISS). The ISS technology was developed as a novel method for multiparameter cell analysis and subsequently as a supportive tool for flow cytometry (FC). ISS integrates the features of FC and fluorescent microscopy collecting images of acquired cells for offline digital image analysis. The article presents an overview of the main characteristics of ISS and a comparison between ISS, FC and the laser scanning cytometer (LSC). We reviewed ISS applications focusing on those involved in cellular phenotyping and provide our own experience with using ISS as a supportive tool to classical FC and demonstrate the compatibility between FC and ISS photometric analysis as well as the advantages of using ISS to confirm FC results.
DCC and TS protein expression in resected gastric cancer: A Hellenic Cooperative Oncology Group Study
Authors: Bamias Aristotle , Fountzilas George , Michael Michael , Konstantaras Christos , Vrettou Eleftheria , Eleftheriadis Efstathios , Papakostas Pavlos , Papadimitriou Konstantionos , Pavlidis Nicholas , Xiros Nikos , Bai Maria 
Published: December 2007

Abstract
There is a high risk of relapse after resection of gastric cancer. We studied the prognostic significance of the deleted colorectal cancer (DCC) gene and thymidylate synthase (TS) protein expression after resection of gastric cancer. Protein expression in the primary tumor of 146 patients with serosal and/or lymph node involvement was studied immunohistochemically by using anti-DCC and anti-TS monoclonal antibodies. DCC expression was found in 69.9%, while low TS staining intensity (0+,1+) and focal staining (<25% of tumor cells stained) were found in 44.6% and 33.8%, respectively. Overall survival (OS) was significantly longer in patients with DCC (p=0.014) negative tumors. TS expression was not an independent prognostic factor. Lack of DCC expression was associated with significantly longer cause-specific survival (CSS) (p=0.040) after curative resection. In conclusion, DCC expression is an independent prognostic factor in patients undergoing resection of gastric cancer while TS expression was not associated with the prognosis in our study.
Population-based cardiovascular risk factors in the elderly in Turkey: a cross-sectional survey
Authors: Ozkara Adem , Turgut Faruk , Kanbay Mehmet , Selcoki Yusuf , Akcay Ali 
Published: December 2007

AbstractHypertension, diabetes, hyperlipidaemia, obesity and smoking are known to be the most important modifiable risk factors for cardiovascular disease (CVD). Because the elderly population has been increasing globally, CVD may become a more important public health problem in the future. This report examines the prevalence of cardiovascular risk factors in the elderly in Ankara, Turkey. This was a cross-sectional survey and included a total of 2720 individuals living in the Ankara district. Trained research staff administered a standard questionnaire in the participants’ homes and worksites. The questionnaire collected information on clinical and demographic characteristics and a self-reported medical history, including past history of hypertension, diabetes, hyperlipidemia, coronary artery disease, coronary artery by-pass graft operation, and cerebrovascular accident. The mean age of the study participants was 69.5 ± 7.2 years. The study identified 1298 women (78.1%) and 753 men (71.2%) with hypertension, and the overall prevalence of hypertension was 75.4%. A total of 739 (27.2%) people had diabetes mellitus, and, of these people, 603 (81.6%) were hypertensive. A total of 1361 people had hyperlipidemia, and 1103 of these patients were also hypertensive. The overall prevalence of obesity was 27.2%. A total of 553 (20.3%) people were smokers. Our findings indicate that cardiovascular risk factors are very common in the elderly. To maximize risk reduction, physicians must take aggressive measures to decrease cardiovascular risk factors.
Coffee consumption and type 2 diabetes — An extensive review
Authors: Bidel Siamak , Hu Gang , Tuomilehto Jaakko 
Published: December 2007

Abstract
Coffee is a complex mixture of potentially active chemicals. It contains significant amounts of phenolic polymers, chlorogenic acid and also caffeine. Agricultural factors, roasting, blending, and brewing determine coffee’s chemical composition. Recent epidemiological studies suggest that habitual coffee consumption may help to prevent some chronic diseases including type 2 diabetes. Despite reports from the clinical trials of the effect of caffeine on decreasing insulin sensitivity, long-term prospective studies revealed that coffee may improve fasting glucose, glucose tolerance and insulin sensitivity as well. In the most recent publication habitual coffee drinkers have a lower total and cardiovascular mortality rate among diabetic subjects.
Comparative X-Ray study of galantamine and tacrine on the evacuatory function of rat gastrointestinal tract
Authors: Kristev Athanas , Sirakov Vladimir , Turiiski Valentin , Getova Damianka , Velkova Kichka 
Published: December 2007

Abstract
A The acetylcholinesterase inhibitors galantamine and tacrine are used to treat Alzheimer’s disease. However, these compounds also affect the gastrointestinal (GI) tract. Here, we compared and analyzed both the effects of galantamine-and tacrine on the evacuatory kinetics of the GI tract in rats. Rats were untreated (n=15) or treated with galantamine (one daily dose of 1 mg/kg per os for 21 days; n=17) or tacrine (one daily dose of 0.5 mg/kg per os for 21 days; n=13) and evacuatory kinetics were assessed using radiological methods. Galantamine initially slowed and then accelerated evacuation, which is characteristic of the majority of cholinesterase inhibitors and is a result of the endogenous acetylcholine accumulated in the GI tissues. In the tacrine-treated rats the contrast medium was kept in the stomach and cecum and its evacuation time was reliably increased. These results indicate that when administered for 20 days, galantamine and tacrine have different effects on motor and evacuatory function in the GI tract of rats, because at certain levels of the tract the tacrine-action is dominated by specific non-cholinergic and non-anticholinesterase mechanisms.
Theory of nonlinear Sagnac effect
Authors: Eliseev P. 
Published: December 2007

AbstractA nonlinear wave interaction is considered as a technique to increase the rotation sensitivity of the ring laser. The gyroscopic scale factor K is calculated in an active laser gyro with a dispersive medium. K is in reverse proportion to the group index n* = n + vdn/dv of the medium. In a monolithically-integrated GaAs ring laser, the value K ∼5000 is obtainable (radius ∼1 cm) in a linear case. In the presence of a strong wave, the dynamic nonlinear anomalous dispersion can provide an increase of K by 10–100 times in the vicinity of critical points where n* passes zero. An expression of K is derived for the nonlinear Sagnac effect. The nonlinear dispersion is discussed in terms of “slow/fast” light.
Temporal electrical response of chiral smectic liquid crystal displays with V/W-shaped electrooptical characteristic
Authors: Pena J. , Pérez I. , Urruchi V. , Torres J. , Otón J. 
Published: December 2007

AbstractChiral smectic liquid crystal cells showing V-shaped electrooptical switching have been reported as one of the most promising technologies for high-end display applications. In this work, time-resolved electrical behaviour of these devices has been obtained through a set of systematic measurements. The electrical equivalent circuit has been derived, a number of simulations at different frequencies have been performed using commercial software for analogue circuits. Performance of this electrical model to account for time domain variations of switching currents in chiral smectic LC displays with V/W-shaped electrooptical response has been analyzed as well.
Multiband Hubbard Models and the Transition Metals
Authors: Stollhoff Gernot 
Published: December 2007

AbstractCorrelation computations on multiband Hubbard Hamiltonians are presented. It is shown why the proper degeneracy is of vital importance and that the atomic exchange interaction plays a particular role. The different methods are connected, and their results are discussed. Many experimental properties for the elemental solids can be explained by single closely related sets of parameters each. There is an exception,Tcof Fe. Here, a novel feature of longer‐range interactions enters. Connections are made to LSDA calculations, and their seeming successes and deficiencies are explained.
Quantum
M
onte
C
arlo Methods
Authors: Assaad Fakher F. , Troyer Matthias 
Published: December 2007

Abstract
We present a review of quantum Monte Carlo algorithms for the simulation of quantum magnets. A general introduction to Monte Carlo sampling is followed by an overview of local updates, cluster updates, and generalized ensemble techniques such as multicanonical and Wang‐Landau sampling for classical magnets. For quantum systems we present two complementary approaches: world‐line methods in (i) a path‐integral and (ii) a stochastic series expansion (SSE) representation, which are best suited for pure spin Hamiltonians. Determinental quantum Monte Carlo algorithms are the methods of choice for the simulation of fermionic Hamiltonians, such as the Hubbard model. An overview of the methods is followed by a selection of typical applications.