bluuebunny/crossref_metadata_2025_split huggingface dataset:
On mechanism of fatigue fracture in interstitial free steel sheet
Authors: Majumdar S. , Bhattacharjee D. , Ray K. K. 
Published: April 2009

The mechanism of fatigue fracture in an interstitial free steel sheet has been studied. The process can be divided into four regimes: (i) the fatigue crack initiates on the specimen surface, from the mesocracks along the grain boundaries in stage I (ii) propagates mostly in an opening mode through grain boundaries in stage II (iii) propagates through microscopic striations and transverse intergranular cracking briefly in stage III (iv) the crack path changes from flat to slant along with through thickness necking and it propagates to failure through discrete crack jumps in stage IV. The crack jumps are associated with crack progression marks (CPMs), the spacing of which increases exponentially from few micrometres to few hundred micrometres with crack length.
Thermal tolerance of crustacean larvae (zoea I) in two different populations of the kelp crabTaliepus dentatus(Milne-Edwards)
Authors: Storch Daniela , Santelices Pedro , Barria Jessica , Cabeza Karla , Pörtner Hans-Otto , Fernández Miriam 
Published: April 2009

SUMMARYStudies of thermal tolerance in marine ectotherms are key in understanding climate effects on ecosystems; however, tolerance of their larval stages has rarely been analyzed. Larval stages are expected to be particularly sensitive. Thermal stress may affect their potential for dispersal and zoogeographical distribution. A mismatch between oxygen demand and the limited capacity of oxygen supply to tissues has been hypothesized to be the first mechanism restricting survival at thermal extremes. Therefore, thermal tolerance of stage zoea I larvae was examined in two populations of the Chilean kelp crab Taliepus dentatus, which are separated by latitude and the thermal regime. We measured temperature-dependent activity, oxygen consumption,cardiac performance, body mass and the carbon (C) and nitrogen (N) composition in order to: (1) examine thermal effects from organismal to cellular levels,and (2) compare the thermal tolerance of larvae from two environmental temperature regimes. We found that larval performance is affected at thermal extremes indicated by decreases in activity, mainly in maxilliped beat rates,followed by decreases in oxygen consumption rates. Cardiac stroke volume was almost temperature-independent. Through changes in heart rate, cardiac output supported oxygen demand within the thermal window whereas at low and high temperature extremes heart rate declined. The comparison between southern and central populations suggests the adaptation of southern larvae to a colder temperature regime, with higher cardiac outputs due to increased cardiac stroke volumes, larger body sizes but similar body composition as indicated by similar C:N ratios. This limited but clear differentiation of thermal windows between populations allows the species to widen its biogeographical range.
Determination of Binding Parameters and Mode of Ferrocenyl Chalcone–DNA Interaction
Authors: Shah Afzal , Qureshi Rumana , Khan Asad Muhammad , Ansari Farzana Latif , Ahmad Safeer 
Published: April 2009

Abstract
This paper reports that how the variation in peak current, absorbance, and viscosity of ferrocenyl chalcone (FC), chemically named as 1-ferrocenyl-3-(4-nitrophenyl)-2-propen-1-one, in 10% aqueous DMF upon addition of DNA can be used to probe the mode of interaction and binding parameters. Binding constant (K = 5.17 (±0.25) × 103 M−1), binding site size (s = 1.08 ± 0.05 bp) and diffusion coefficient of the free (Df = 5.22 × 10−7 cm2 s−1) and DNA bound drug (Db = 4.39 × 10−8 cm2 s−1) were determined from voltammetric data. The binding constant (K = 4.91 (±0.20) × 103 M−1) was also obtained from UV–vis absorption titration. Gibbs energy change (ΔG = −RT ln K) of −21.18 kJ mol−1 at 25 °C indicated the spontaneity of the binding interaction. The experimental results revealed intercalation of FC into DNA as the dominant mode of interaction. Furthermore, the radii of the free and DNA-bound drug were determined from viscosity measurements.
Formation and Decay Dynamics of Vitamin E Radical in the Antioxidant Reaction of Vitamin E
Authors: Mukai Kazuo , Ouchi Aya , Mitarai Akiko , Ohara Keishi , Matsuoka Chihiro 
Published: April 2009

Abstract
In order to understand the dynamics of antioxidant actions of vitamin E (α-, β-, γ-, and δ-tocopherols, TocH) in biological systems, kinetic study of the formation and decay reactions of vitamin E radicals (α-, β-, γ-, and δ-tocopheroxyls, Toc•) has been performed in organic solvents, using stopped-flow spectrophotometry. By mixing α-, β-, γ-, and δ-TocH with aryloxyl radical (ArO•) in ethanol, the peaks of the UV–vis absorption due to α-, β-, γ-, and δ-Toc• radical appeared rapidly at ca. 430–340 nm, showed maxima, and then decayed gradually. The second-order rate constants (kf and 2kd) for the formation and decay (that is, bimolecular disproportionation) reactions of α-Toc• were determined by comparing the observed curves with the simulation ones obtained by the numerical calculation of differential equations related to the above reactions. From the results, the wavelengths of absorption maxima (λmaxi) and molar extinction coefficients (εi) (i = 1–4) of the optical spectra were determined for α-Toc• radical. Notable solvent effects have been observed for the reaction rates (kf and 2kd) and absorption spectra (λmaxi and εi) of α-Toc• radical. The scheme of the formation and decay reactions of α-, β-, γ-, and δ-Toc• radicals has been discussed based on the results obtained.
Sensitization of NaMO3 (M: Nb and Ta) Photocatalysts with Wide Band Gaps to Visible Light by Ir Doping
Authors: Iwase Akihide , Saito Kenji , Kudo Akihiko 
Published: April 2009

Abstract
NiO/NaNbO3 (BG: 3.5 eV) showed photocatalytic activity for water splitting into H2 and O2 under UV irradiation. When NaMO3 (M: Nb and Ta) was codoped with iridium ions and alkaline earth metal ions or lanthanum ions, a new visible-light absorption band was observed in addition to the band gap absorption band of the host material. The codopants of alkaline earth metal and lanthanum ions contributed to maintaining the charge balance and forming of fine crystals of the NaMO3 powder. These NaNbO3 and NaTaO3 codoped with iridium ions and alkaline earth metal ions or lanthanum ions showed photocatalytic activities for H2 or O2 evolution from an aqueous solution containing a sacrificial reagent under visible light irradiation.
Pressure Dependence of Aggregation State of (DMPC/Cholesterol) Mixed Monolayer Based on AFM Observation
Authors: Tagami Yasunobu , Matsufuji Takashi , Ikigai Hajime , Narita Takayuki , Oishi Yushi 
Published: April 2009

Abstract
We investigated the aggregation state of a mixed monolayer of 1,2-dimyristoyl-sn-glycero-3-phospholine and cholesterol at different surface pressures by AFM. AFM images revealed a nanoscopically separated structure despite a macroscopic homogenization of the monolayer under compression.
Electronegative Oligothiophenes Having Difluorodioxocyclopentene-annelated Thiophenes as Solution-processable n-Type OFET Materials
Authors: Ie Yutaka , Okabe Makoto , Umemoto Yoshikazu , Tada Hirokazu , Aso Yoshio 
Published: April 2009

Abstract
Solution-processable electronegative oligothiophenes bearing difluorodioxocyclopentene-annelated thiophenes have been synthesized. The electronic properties of the oligomers were investigated by absorption spectroscopy and electrochemical measurements. Their films fabricated by spin-coating showed typical n-channel OFET behavior.
Electrochemical Sensing of Sulfate Using Mixed Thiol-derivatized β-Cyclodextrin/Pentanethiol Monolayers
Authors: Domi Yasuhiro , Shimazu Katsuaki , Porter Marc D 
Published: April 2009

Abstract
The oxidation of ferrocene on a defect-free mixed per-6-thio-β-cyclodextrin/pentanethiol monolayer in a NaClO4 solution was inhibited in the presence of sulfate. The peak current in differential pulse voltammograms linearly decreased with the logarithm of the sulfate concentration in an extremely wide range from 1 nM to 1 mM, showing the possible application as an electrochemical sensor of sulfate.
Simple Determination of Melamine Based on Self-assembly of Citrate-capped Gold Nanoparticles
Authors: Qin Zhu Hong , Zhao Hua Wen , Huang Cheng Zhi , Wu Li Ping 
Published: April 2009

Abstract
In the presence of melamine (2,4,6-triamino-s-triazine), citrate-capped gold nanoparticles (Au-NPs) can self-assemble and form a network structure through electrostatic interactions. A new absorption peak appears at approximately 700 nm, and the intensity is proportional to the concentration of melamine. Thus, a new simple method of detecting melamine is developed.
The Potential Use of Electricity to Control Burrowing Shrimp in Oyster Aquaculture Beds
Authors: Dumbauld Brett , Harlan Lisa 
Published: April 2009

Abstract
Thalassinidean shrimp cause significant problems for oyster aquaculture in the Pacific Northwest (USA), where oysters succumb to the physical sediment disruption generated by the burrowing activity of these animals. Although electrofishing is a commonly used technique to capture fish and some invertebrates in freshwater, applications in marine systems are limited due to the high conductivity of the water medium. Experiments conducted in aquaria showed that burrowing bay ghost shrimp Neotrypaea californiensis responded best (forced swimming with directed movement) to a pulsed DC waveform with optimal parameter settings of 1 V/cm, a frequency of 2 Hz, and a pulse width of 0.001–0.005 s. Unfortunately, when bay ghost shrimp were allowed to burrow into the substrate, they displayed a similar reaction but moved towards the bottom of their burrows, thus ruling out the envisioned use of this technique to attract them to the surface for capture. In experiments designed to induce mortality, it was possible to achieve paralysis or tetany by use of higher power with DC, pulsed DC, and AC, but the animals recovered unless (1) exposure time exceeded 60–100 s and (2) voltage exceeded 100 V (5 V/cm), frequency exceeded 120 Hz (pulsed DC), or both. These sustained levels would be difficult to achieve in the field due to the substrate, depth of the shrimp burrows, and high power necessary to obtain adequate field strength.
Inferring evolutionary modes in a fossil lineage (Bryozoa:Peronopora) from the Middle and Late Ordovician
Authors: Pachut Joseph F. , Anstey Robert L. 
Published: April 2009

Recent analytical advances have permitted quantitative evaluations of evolutionary mode in populations of fossil organisms by providing tests of the null hypothesis that patterns of stratigraphic character variation do not differ from the expectations of a random walk. If the hypothesis can be rejected, then stasis and anagenesis represent alternative evolutionary modes discernable using values of the Hurst estimate. We used this approach to evaluate evolutionary mode in the bryozoan genusPeronoporaacross 34 characters in eight unbranched, cladistically defined, evolutionary sequences. Eight monophyletic crown species and eight paraphyletic (phenetically distinct) metaspecies constitute 16 species-rank taxa within the genus.In seven of 15 species-rank transitions that had adequate sample sizes, significant character state changes—both phyletic gradualism and punctuated equilibrium—coincided with speciation events 11% of the time and were limited to more derived, crownward, ancestor-descendant pairs. Each of the 34 measured characters exhibited instances of transpecific stasis or anagenesis. Anagenesis of some characters persisted across unbranched lineages over 13 species (i.e., across 12 speciation events), whereas character stasis continued through unbranched lineages in up to 16 species (i.e., persisted unchanged across all 15 speciation events). Transpecific stasis and anagenesis were recognizable in over one-half of the data set, with stasis being approximately twice as common as anagenesis.Across all character state transitions, approximately one-half reflect stasis, 30% anagenesis, and 20% could not be differentiated from a random walk. Similarly, across species and metaspecies characterized by a single intraspecific mode, stasis was twice as common as anagenesis and three times more common than undifferentiated random walks. The remaining instances of multiple intraspecific evolutionary modes occurred more commonly within metaspecies than within species. This difference might reflect the more frequent presence of unrecognized cryptic species or subspecies within metaspecies ofPeronopora.Instantaneous rates of evolution can be estimated both within and between species ofPeronoporafor characters displaying anagenesis, potentially providing quantitative insights into evolutionary changes within the lineage.
A cautionary note on implications of the well-mixed compartment assumption as applied to mass balance models of chemical fate in flowing systems
Authors: Warren Christopher S. , Mackay Donald , Webster Eva , Arnot Jon A. 
Published: April 2009

AbstractA convenient, simple, and widely used approach for modeling the fate of a chemical in a flowing environmental or biological system is to simulate the system as comprising one or more well-mixed boxes, also known as continuous stirred tank reactors (CSTRs). In principle, any desired level of accuracy can be achieved by increasing the number of boxes. However, highly segmented systems require more input data, they are more computationally intensive, and the results may be more difficult to interpret. Thus there is a tendency to minimize the number of boxes, especially in screening level models. Whereas in the hydrology and engineering literature there is an appreciation of the mathematical errors associated with applying the well-mixed box concept, we believe that these errors are often underappreciated when modeling certain environmental systems. Here, we briefly review the implications of these errors in multimedia models, river and lake simulations, atmospheric transport, flow in soils, gastrointestinal absorption, and metabolism in the liver. The key conclusion is that if over 25% of the chemical entering a box is removed, applying this well-mixed assumption can lead to substantial error. We recommend that results obtained when this criterion is violated be treated with caution.
Verification and Proper Use of Water-Oil Transfer Function for Dual-Porosity and Dual-Permeability Reservoirs
Authors: Balogun A. , Kazemi H. , Ozkan E. , Al-Kobaisi M. , Ramirez B. 
Published: April 2009

Summary
Accurate calculation of multiphase fluid transfer between the fracture and matrix in naturally fractured reservoirs is a very crucial issue. In this paper, we will present the viability of the use of a simple transfer function to accurately account for fluid exchange resulting from capillary and gravity forces between fracture and matrix in dual-porosity and dual-permeability numerical models. With this approach, fracture- and matrix-flow calculations can be decoupled and solved sequentially, improving the speed and ease of computation. In fact, the transfer-function equations can be used easily to calculate the expected oil recovery from a matrix block of any dimension without the use of a simulator or oil-recovery correlations.
The study was accomplished by conducting a 3-D fine-grid simulation of a typical matrix block and comparing the results with those obtained through the use of a single-node simple transfer function for a water-oil system. This study was similar to a previous study (Al-kandari 2002) we had conducted for a 1D gas-oil system.
The transfer functions of this paper are specifically for the sugar-cube idealization of a matrix block, which can be extended to simulation of a match-stick idealization in reservoir modeling. The basic data required are: matrix capillary-pressure curves, densities of the flowing fluids, and matrix block dimensions.
Multiphysics and Multiscale Methods for Modeling Fluid Flow Through Naturally Fractured Carbonate Karst Reservoirs
Authors: Popov P. , Qin G. , Bi L. , Efendiev Y. , Kang Z. , Li J. 
Published: April 2009

Summary
Modeling and numerical simulations of Carbonate karst reservoirs is a challenging problem because of the presence of vugs and caves which are connected through fracture networks at multiple scales. In this paper, we propose a unified approach to this problem by using the Stokes-Brinkman equations which combine both Stokes and Darcy flows. These equations are capable of representing porous media (porous rock) as well as free-flow regions (fractures, vugs, and caves) in a single system of equations. The Stokes-Brinkman equations also generalize the traditional Darcy-Stokes coupling without sacrificing the modeling rigor. Thus, it allows us to use a single set of equations to represent multiphysics phenomena on multiple scales. The local Stokes-Brinkman equations are used to perform accurate scale-up. We present numerical results for permeable rock matrix populated with elliptical vugs and we consider upscaling to two different coarse-scale grids— 5×5 and 10×10. Both constant and variable background permeability matrices are considered and the effect the vugs have on the overall permeability is evaluated. The Stokes-Brinkman equations are also used to study several vug/cave configurations which are typical of Tahe oilfield in China.
A New Approach for Reliable Estimation of Hydraulic Fracture Properties Using Elliptical Flow Data in Tight Gas Wells
Authors: Cheng Yueming , Lee W. John , McVay Duane A. 
Published: April 2009

Summary
Gas wells in low-permeability formations usually require hydraulic fracturing to be commercially viable. Pressure transient analysis in hydraulically fractured tight gas wells is commonly based on analysis of three flow regimes: bilinear, linear, and pseudoradial. Without the presence of pseudoradial flow, neither reservoir permeability nor fracture half-length can be independently estimated. In practice, as pseudoradial flow is often absent, the resulting estimation is uncertain and unreliable. On the other hand, elliptical flow, which exists between linear flow and pseudoradial flow, is of long duration (typically months to years). We can acquire much rate and pressure data during this flow regime, but no practical well test analysis technique is currently available to interpret these data.
This paper presents a new approach to reliably estimate reservoir and hydraulic fracture properties from analysis of pressure data obtained during the elliptical flow period. The method is applicable to estimate fracture half-length, formation permeability, and skin factor independently for both infinite- and finite-conductivity fractures. It is iterative and features rapid convergence. The method can estimate formation permeability when pseudoradial flow does not exist. Coupled with stable deconvolution technology, which converts variable production-rate and pressure measurements into an equivalent constant-rate pressure drawdown test, this method can provide fracture-property estimates from readily available, noisy production data. We present synthetic and field examples to illustrate the procedures and demonstrate the validity and applicability of the proposed approach.
Stress-Dependent Directional Permeabilities of Two Analog Reservoir Rocks: A Prospective Study on Contribution of µ-Tomography and Pore Network Models
Authors: Dautriat J. , Gland N. , Youssef S. , Rosenberg E. , Bekri S. , Vizika O. 
Published: April 2009

SummaryTo predict the effects of stress on rock permeability, the authors propose an integrated approach based on an extended rock characterization, an experimental investigation of pressure dependency of directional rock permeabilities and finally a pore-scale simulation of this dependency using equivalent pore network extracted from microtomography analysis. This study has been conducted on two analog reservoir rock types: the high-permeability Bentheimer Sandstone and a dual-porosity bioclastic carbonate, the Estaillades Limestone, having an intermediate permeability. Compression tests have been conducted using a new triaxial cell specially designed to measure directional permeabilities along and transverse to direction of maximum stress application. We measured the pressure dependency of porosity, directional permeabilities, compressibilities, and elastic moduli of the tested samples. We also performed computed microtomography (CMT) imaging of the rock samples, from which we extracted the poral skeletons and the associated characteristics lengths. Then, we calculated the macroscopic transport properties using Pore Network Modeling (PNM) based on the real pore geometry. We included a model of pressure dependence of pore and throat sizes based on pressurized cavity models derived from elasticity theory to simulate the evolution of porosity and permeability with pressure. First, we show that the experimental determination of the evolution of directional permeabilities under hydrostatic and deviatoric loading is feasible. Finally, we show that the PNM coupled with μ-tomography can be a promising tool to forecast the evolution of transport properties under stresses representative of reservoir conditions, at the condition of integrating more advanced pore-scale compaction models.
Monitoring SAGD Steam Injection Using Microseismicity and Tiltmeters
Authors: Maxwell S. C. , Du J. , Shemeta J. , Zimmer U. , Boroumand N. , Griffin L. G. 
Published: April 2009

Summary
A combination of microseismic and surface-deformation monitoring with an array of tiltmeters was used to monitor the warm-up phase of a steam-assisted-gravity-drainage (SAGD) well pair. A sequence of microseismic events was recorded with signal characteristics that suggested deformation associated with thermal expansion of the wellbore, in addition to events apparently associated with induced fracturing in the reservoir. Integration of the microseismic data with volumetric strain, inverted from the measured surface deformation, indicates a discrete deforming region near the toe of the well. The volumetric strain also shows another region near the heel of the well, although the area is too far from the microseismic observation well for any associated microseismicity to be recorded. The central portion of the well pair did not have significant deformation, indicating poor steam conformance during this warm-up phase. A comparison of the temporal response of the microseismic deformation with the surface uplift suggests a lag between periods of accelerated seismic deformation followed by an associated period of accelerated uplift a few days later. This timing suggests the creation of a fracture network and related seismic deformation, which then fills with steam and starts to expand over a period of a few days. In a related paper (Du et al. 2007), stress changes associated with the volumetric strain are used to examine potential geomechanical failure zones that match the observed locations of microseisms. Together, the volumetric strain, computed stress changes, and failure zones could be used to calibrate a geomechanically linked reservoir simulator.