bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alkylation of Isobutane with Butenes Catalyzed by a Cesium Hydrogen Salt of 12-Tungstophosphoric Acid
Authors: Okuhara Toshio , Yamashita Masayuki , Na Kyutae , Misono Makoto 
Published: April 2006

Abstract
A solid superacid, Cs2.5H0.5PW12O40, catalyzed the alkylation of isobutane with butenes at room temperature. Cs2.5H0.5PW12O40 was much more active than SO42−/ZrO2, a well-known solid superacid, and was highly selective.
A New Chiral Stationary Phase Bearing Both π-Acidic and π-Basic Sites Derived from (S)-Tyrosine for the Liquid Chromatographic Resolution of Racemates
Authors: Hyun Myung Ho , Min Chung-Sik 
Published: April 2006

Abstract
A new chiral stationary phase (CSP) bearing both π-acidic and π-basic sites for the chiral liquid chromatography has been prepared from (S)-tyrosine. This CSP has been found to be useful in resolving a variety of either π-basic or π-acidic racemates.
Influence of Added Saccharides on the Conformation of Boronic-Acid-Appended Poly(l-lysine). Attempts to Control a Helix-Coil Transition by Sugars
Authors: Nagasaki Takeshi , Kimura Taro , Arimori Susumu , Shinkai Seiji 
Published: April 2006

Abstract
Poly(l- and d-lysine)s (l- and d-1, respectively) were modified with a phenylboronic acid derivative which acts as a sugar-binding site. When monosaccharides were added to the l-1 solution, the helix content was increased and the pH which gives the maximum helix content shifted to lower pH region. The pH dependence in the presence of d-fructose was different, although slightly, between l- and d-1. This is a novel attempt toward the control of a polypeptide conformation by sugars.
Enantioselective Catalysis by Supramolecular Bilayer Membrane as Artificial Aminotransferase
Authors: Kikuchi Jun-ichi , Zhang Zhi-Yi , Murakami Yukito 
Published: April 2006

Abstract
A supramolecular bilayer assembly, composed of a cationic peptide lipid having an l-histidyl residue, a hydrophobic pyridoxamine derivative, and copper(II) ions, performed substrate-selective catalysis as a vitamin B6-dependent artificial aminotransferase to transform α-keto acids into the corresponding α-amino acids in an enantiomeric excess of the d-isomer.
Highly-Sensitive Measurement of Dihydroxyphenols Using Carbon Felt Electrode Impregnated with Fructose Dehydrogenase-Containing Solution
Authors: Mizutani Fumio , Yabuki Soichi 
Published: April 2006

Abstract
A carbon felt electrode impregnated with a fructose dehydrogenase/fructose-containing solution was used for measuring dihydroxyphenols (e.g., catechol and dopamine). Dihydroxyphenol molecules are oxidized on the electrode but regenerated by the enzyme reaction. The consumption/regeneration cycle for dihydroxyphenols resulted in an amplified electrode response. Further, the measuring method could be free from the electrochemical interference by oxidizable species such as l-ascorbic acid.
An Investigation of the Ionic Polarization of Carrageenans with Different Charge Densities
Authors: Ueda Kazuyoshi , Sato Shigenobu , Ochiai Hiroshi , Imamura Akira , Yamaoka Kiwamu 
Published: April 2006

Abstract
Counterion polarization of κ-, ι- and λ-carrageenans, which have different charge densities, in aqueous solution was investigated through the electric birefringence method. The data analysis by the Manning’s counterion condensation theory suggests that the loosely bound counterions mainly contribute to the ionic polarization.
The Emission Cross Section of the Paschen-α Line Produced in Electron-Hydrogen Collisions
Authors: Ogawa Teiichiro , Yonekura Nobuaki , Kido Masami , Furuya Kenji , Nakashima Keiji 
Published: April 2006

Abstract
The Paschen-α line (1875.1 nm) of the excited hydrogen atom produced in e-H2 collisions was observed with a grating spectrometer equipped with a PbS detector. The emission cross section was determined to be 0.95 × 10−19 cm2 at 100 eV.
Effect of Cu(II) Ion on the Polycondensation of Octadecyl Esters of Aromatic Amino Acids in Monolayers at the Air/Water Interface
Authors: Liu Ming-hua , Nakahara Hiroo , Shibasaki Yoshio , Fukuda Kiyoshige 
Published: April 2006

Abstract
Polycondensation of octadecyl esters of l-phenylalanine (l-PheC18), l-tyrosine (l-TyrC18) and l-tryptophan (l-TrpC18) in the monolayers on the subphase containing Cu(II) ion was significantly accelerated in comparison with those in the monolayers on phosphate buffer or in bulk phases. A reaction mechanism including formation of an intermediate complex and reorientation of the aromatic rings was proposed.
Fluorometric and Coulometric Analyses of Electron Transfer across Microdroplet/Water Interface
Authors: Nakatani Kiyoharu , Chikama Katsumi , Kim Haeng-Boo , Kitamura Noboru 
Published: April 2006

Abstract
Electron transfer between ferrocene (FeCp) and Fe(III) across the droplet/water interface was studied by an optically transparent thin-layer electrode method. A time dependence of the FeCp concentration in the droplets caused by the interfacial electron transfer was discussed on the basis of coulometric analysis of Fe(II) or Fe(III) in the water phase and fluorometric analysis of FeCp in the droplets.
Energy-Transfer Luminescence of Lanthanide Ions Encapsulated in Calix[4]arenes. Correlation between the Energy Level of Sensitizers and the Quantum Yield
Authors: Matsumoto Hitoshi , Shinkai Seiji 
Published: April 2006

Abstract
It was shown that the Tb3+ and Eu3+ complexes of 5,11,17,23-tetraacetyl-25,26,27,28-tetrakis(N,N-diethylaminocarbonylmethoxy)calix[4]arene give the high luminescence quantum yields (Φ = 0.164 for Tb3+ and 0.017 for Eu3+). The mechanistic investigations established that the high quantum yields are due to the energy level suitable to the energy-transfer and the presence of the carbonyl groups which mediate the intersystem crossing.
Selective Alkylation of p-Xylene with 2-Methylpropene by 12-Tungstophosphoric Acid
Authors: Soeda Hironobu , Okuhara Toshio , Misono Makoto 
Published: April 2006

Abstract
Solid H3PW12O40 catalyzed the alkylation of p-xylene with 2-methylpropene to t-butyl-p-xylene with 75%-selectivity, while the selectivity with H2SO4 was only 7%. The selectivity of heteropolyacids tended to increase with the acid strength.
Use of Sildenafil for Female Sexual Dysfunction
Authors: Shields Kelly M , Hrometz Sandra L 
Published: April 2006

Objective: To review the pathophysiology of female sexual dysfunction (FSD) and the literature regarding the use of sildenafil in its treatment. Data Sources: Literature was accessed through MEDLINE (1966—April 2006), Iowa Drug Information Service (1966—April 2006), EMBASE (1966—April 2006), and bibliographies of pertinent articles. Search terms included female sexual dysfunction; sexual dysfunction, psychological; phosphodiesterase inhibitors; and sildenafil. Data Synthesis: The lack of a clear understanding of FSD contributes to the limited treatment options available. Studies regarding the safety and efficacy of the phosphodiesterase 5 inhibitor sildenafil in the management of FSD were evaluated. Many trials have been of poor quality, making clinical application of their results difficult. The current literature does not show sildenafil to be an effective treatment option for FSD. Conclusions: Treatment of FSD should include both physical and psychological components. Based on the limited data available, it appears that sildenafil, while well tolerated, offers little or no benefit to most patients with FSD.
Contribution of the Monkey Frontal Eye Field to Covert Visual Attention
Authors: Wardak Claire , Ibos Guilhem , Duhamel Jean-René , Olivier Etienne 
Published: April 2006

The frontal eye field (FEF) has long been regarded as a cortical area critically involved in the execution of voluntary saccadic eye movements. However, recent studies have suggested that the FEF may also play a role in orienting attention. To address this issue, we reversibly inactivated the FEF using multiple microinjections of muscimol, a GABAAagonist, in two macaque monkeys performing visually guided saccades to a single target. The effects of FEF inactivation were also studied in a covert visual search task that required monkeys to search for a target presented among several distractors without making any eye movements.As expected, inactivating the FEF caused spatially selective deficits in executing visually guided saccades, but it also altered the ability to detect a visual target presented among distractors when no eye movements were permitted. These results allow us to conclude definitively to an involvement of the FEF in both oculomotor and attentional functions. Comparison of the present results with a similar experiment conducted in the lateral intraparietal cortex area revealed qualitatively different deficits, suggesting that the two areas may make distinct contributions to selective attention processes.
Effects of apple orchard management strategies on the great tit (Parus major) in southeastern france
Authors: Bouvier Jean-Charles , Toubon Jean-François , Boivin Thomas , Sauphanor Beno′t 
Published: April 2006

AbstractThe impact of conventional, organic, and integrated pest management (IPM) strategies of apple orchards on the reproduction of the great tit Parus major was investigated during a three-year period in southeastern France. The colonization process, egg-laying dates, clutch sizes, and fledging success were similar among pairs of P. major nesting in orchards conducted under the three studied management strategies. However, the mean number of young produced per ha (orchard productivity) was significantly higher in organic orchards than in both conventional and IPM orchards. Such divergences between both fledging success and orchard productivity primarily resulted from higher densities of P. major nesting pairs, but also from lower rates of nest abandonment during incubation in organic orchards. We suggest that intensive pesticide use under both IPM and conventional managements may have resulted in a substantial reduction in insect prey availability that enhanced intraspecific competition, which then led to failure in reproduction in pairs with low competitive ability. Our results highlight the relevance of P. major in assessing the environmental impact of apple orchard management strategies.
The Effect of Heterogeneity on In-Situ Combustion: Propagation of Combustion Fronts in Layered Porous Media
Authors: Akkutlu I. Yucel , Yortsos Yannis C. 
Published: April 2006

Summary
In-situ combustion is a potential method for the recovery of heavy oil. The effect of reservoir heterogeneity, a ubiquitous feature of oil reservoirs, on in-situ combustion has not been systematically addressed in prior studies, however. In this paper, we present analytical models for filtration combustion, namely the combustion of a stationary solid fuel, in the specific case where the reservoir consists of two layers of different permeability and thickness, separated by nearly impermeable shales. We investigate the conditions for the propagation of steady combustion fronts as a function of some key parameters, including the permeability-thickness contrast R between the layers, the thickness ratio η, and the external heat loss coefficient h.
We find that heterogeneity acts in two distinct ways: It reduces the temperature of the leading front in the high-permeability layer in all cases, and uncouples the propagation of the fronts in the two layers if R is smaller than a critical value Rc. The first effect may lead to low-temperature oxidation conditions, and therefore to the effective extinction of the front in the high-permeability layer. The second leads to a reduced sweep efficiency (and early breakthrough). However, if R exceeds the critical value, the fronts in the two layers travel coherently (with the same speed). This coherence is identified for the first time. The resulting thermal coupling greatly retards the front in the more permeable layer, and accelerates only slightly that in the less permeable one, until the two fronts reach a common velocity.
We study the effects of R, the heat loss rate, and the ratio of thickness η. The coupling is aided by moderate heat losses (small h), and smaller η, which affect the critical value Rc.Asinthe homogeneous case, at sufficiently high heat loss rates, steady front propagation cannot be sustained and the combustion process becomes extinct.
The work is useful for the understanding of the viability of in-situ combustion process in heterogeneous layered reservoirs and the effect of a number of injection, combustion, and reservoir parameters.
Modeling Coupled Fracture-Matrix Fluid Flow in Geomechanically Simulated Fracture Networks
Authors: Philip Zeno G. , Jennings James W. , Olson Jon E. , Laubach Stephen E. , Holder Jon 
Published: April 2006

Summary
In conventional reservoir simulations, gridblock permeabilities are frequently assigned values larger than those observed in core measurements to obtain reasonable history matches. Even then, accuracy with regard to some aspects of the performance such as water or gas cuts, breakthrough times, and sweep efficiencies may be inadequate. In some cases, this could be caused by the presence of substantial flow through natural fractures unaccounted for in the simulation. In this paper, we present a numerical investigation into the effects of coupled fracture-matrix fluid flow on equivalent permeability.
A fracture-mechanics-based crack-growth simulator, rather than a purely stochastic method, was used to generate fracture networks with realistic clustering, spacing, and fracture lengths dependent on Young's modulus, the subcritical crack index, the bed thickness, and the tectonic strain. Coupled fracture-matrix fluid-flow simulations of the resulting fracture patterns were performed with a finite-difference simulator to obtain equivalent permeabilities that can be used in a coarse-scale flow simulation. The effects of diagenetic cements completely filling smaller aperture fractures and partially filling larger aperture fractures were also studied.
Fractures were represented in finite-difference simulations both explicitly as grid cells and implicitly using nonneighbor connections (NNCs) between grid cells. The results indicate that even though fracture permeability is highly sensitive to fracture aperture, the computed equivalent permeabilities are more sensitive to fracture patterns and connectivity.
An Analytical Model for Cleanup of Yield-Stress Fluids in Hydraulic Fractures
Authors: Balhoff Matthew T. , Miller Matthew J. 
Published: April 2006

SummaryThe retention of fracturing fluid in a proppant pack reduces the dimensionless fracture conductivity, Fcd, resulting in poor well productivity regardless of fluid type (gelled oil, crosslinked polymers, viscoelastic surfactants, or foams). Analytical expressions derived in this paper can be used to calculate the extent of fracture cleanup under a set of production conditions. Several dimensionless parameters describing the fluid, fracture, and reservoir properties are introduced that affect the equilibrium cleanup. A second, transient, fracture-cleanup model is also proposed and is used to estimate the dimensionless-parameter values.The equilibrium model predicts that cleanup increases greatly with decreasing dimensionless yield stress of the fracturing fluid. The magnitude of cleanup is also greater for cases in which the permeability ratio of the clean portion of the fracture to the fouled portion is high. The cleanup is expected to increase with an increase in the ratio of reservoir and fracture mobility until an optimum is reached, and then decrease with increasing the mobility ratio. The critical process of parameter estimation is achieved by making experimental measurements and by history matching published fracture flowback data using the transient model.
Prediction of Capillary Fluid Interfaces During Gas or Water Coning in Vertical Wells
Authors: Johns Russell T. , Lake Larry W. , Ansari Rafay Z. , Delliste Arnaud M. 
Published: April 2006

Summary
Gas and water coning significantly reduce oil production while increasing production costs. Simulation and experimental methods, coupled with simple analytical solutions or correlations, are typically used to identify the oil rate that minimizes coning and maximizes recovery. Current analytical solutions, however, are overly simplified in that they assume negligible capillary pressure, which leads to segregated flow. This paper presents new benchmark analytical solutions that relax this assumption and also allow for simultaneous two-phase flow.
The new coning solutions apply to vertical wells where in-situ fluids are in vertical equilibrium. The development identifies the important dimensionless groups that control the effect of coning on oil recovery and illustrates how simultaneous two-phase flow affects capillary fluid levels in the formation. Dimensionless two-phase production windows are constructed to identify critical rates, the largest oil rate at which water (or gas) will not be produced. From comparisons to simulation, we show that critical flow rate estimates are accurate for aspect ratios greater than approximately 10. For aspect ratios less than 10, the critical rate estimates are always conservative.
Stability of a Multilateral Junction: Experimental Results and Numerical Modeling
Authors: Papanastasiou P. , Sibai M. , Heiland J. , Shao J. F. , Cook J. , Fourmaintraux D. , Onaisi A. , Jeffryes B. , Charlez P. 
Published: April 2006

Summary
We studied the stability of multilateral (ML) junctions in a combined experimental and numerical modeling program. The experiments were carried out in a true triaxial machine on large cubic blocks (40 cm) of weak triassic sandstone with two holes intersecting. Six tests have been performed with two different geometrical configurations and three different stress states. The experimental results are presented and compared with numerical modeling obtained with finite-element software developed for assessing the integrity of rock surrounding an ML junction.
High-Order Upwind Schemes for Two-Phase, Multicomponent Flow
Authors: Mallison B. T. , Gerritsen M. G. , Jessen K. , Orr F. M. 
Published: April 2006

Summary
In this paper, we investigate high-order finite-difference schemes for compositional simulation. Results presented for onedimensional (1D) gas-injection problems suggest that a third-order, essentially nonoscillatory scheme achieves accurate results more efficiently than first-order methods; leads to an improved treatment of phase behavior; and is more robust than traditional total variation diminishing schemes. We use phase diagrams as well as solution profiles to analyze discretization errors. Discretization errors can strongly affect the prediction of local displacement efficiency because of the nonlinear coupling introduced by the phase behavior in the system of governing equations. The study explains the ability of the numerical schemes to predict local displacement efficiency. In all of our tests, we compare numerical results to analytical and semianalytical solutions found through the method of characteristics. Our 1D results can be extended to 3D through conventional finite-difference approaches, but we plan to apply them in a streamline-based compositional simulator.
A Mechanistic Model for Horizontal Gravel-Pack Displacement
Authors: Martins A. L. , de Magalhães J. V. M. , Calderon A. , Chagas C. M. 
Published: April 2006

SummaryThis article presents the detailed formulation for each of the three steps of a horizontal gravel-pack displacement operation, including sand injection and alpha/beta waves propagation. The main core of the model, aiming to define alpha wave height, is based on a well known two-layer model. Initially developed for hydrotransport applications, this kind of model has been adapted by several authors for drilled cuttings transport analysis. Additionally, a comparison between theoretical predictions and pumping charts from a field operation performed in Campos basin is presented.
Effect of Crossflow on Foam-Induced Diversion in Layered Formations
Authors: Nguyen Quoc P. , Currie Peter K. , Zitha Pacelli L. J. 
Published: April 2006

SummaryFoams have been widely used to control fluid mobility in improved oil recovery as well as in near-wellbore production enhancement operations, such as acid diversion. The efficiency of fluid blockage and diversion depends strongly on the geological layering of the formation and on the occurrence of (viscous and capillary) crossflow. However, these effects have not been studied in detail in the literature. In this paper, we report an experimental study of foam-induced fluid diversion in isolated and capillarycommunicating double-layer cores. Sodium dodecyl sulfate (SDS) surfactant was used at just above its critical micelle concentration. Natural rocks were used to manufacture concentric double-layer cores, having final permeability contrasts in the range of 10 to 200. We also used capillary-communicating double-layer cores, obtained by sintering two homogeneous glass-bead layers. In addition to pressure-drop monitoring, the in-situ fluid saturation was visualized using X-ray computerized tomography. A range of foam qualities has been investigated.
A New Method for Measuring Solvent Diffusivity in Heavy Oil by Dynamic Pendant Drop Shape Analysis (DPDSA)
Authors: Yang Chaodong , Gu Yongan 
Published: April 2006

Summary
This paper presents a new experimental method and its computational scheme for measuring solvent diffusivity in heavy oil under practical reservoir conditions by DPDSA. In the experiment, a see-through windowed high-pressure cell is filled with a test solvent at desired pressure and temperature. Then, a heavy-oil sample is introduced through a syringe delivery system to form a pendant oil drop inside the pressure cell. The subsequent diffusion of the solvent into the pendant oil drop causes its shape and volume to change until an equilibrium state is reached. The sequential digital images of the dynamic pendant oil drop are acquired and digitized by applying computer-aided digital image-acquisition and-processing techniques. Physically, variations of the shape and volume of the dynamic pendant oil drop are attributed to the interfacial tension reduction and the well-known oil-swelling effect as the solvent gradually dissolves into heavy oil. Theoretically, the interfacial profile of the dynamic pendant oil drop is governed by the Laplace equation of capillarity, and the molecular diffusion process of the solvent into the pendant oil drop is described by the diffusion equation. An objective function is constructed to express the discrepancy between the numerically predicted and experimentally observed interfacial profiles of the dynamic pendant oil drop. The solvent diffusivity in heavy oil and the mass-transfer Biot number are used as adjustable parameters and thus are determined once the minimum objective function is achieved. This novel experimental technique is tested to measure diffusivities of carbon dioxide in a brine sample and a heavy-oil sample, respectively. It should be noted that, with the present technique, a single diffusivity measurement can be completed within an hour and only a small amount of oil sample is required. The interface mass-transfer coefficient at the solvent/heavy-oil interface can also be determined. In particular, this new technique allows the measurement of solvent diffusivity in an oil sample at constant prespecified high pressure and temperature. Therefore, it is especially suitable for studying the mass-transfer process of injected solvent into heavy oil during solvent-based post-cold heavy-oil production (post-CHOP).