bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simulation Study of Performance Miscible Diplacement in El Gassi Field, Algeria
Authors: Merdaci C. , Tiab D. , Zhu T.
Published: March 2008

El Gassi is a volatile oil field located in the Algerian desert. The field has produced about 62 MMSTB oil since 1959, through primary depletion. Due to the heterogenity of producing formation, the total recovery during 45 years is only about 11%. The implementation of water-flood project was avoided due to low achievable water injection rate. A miscible gas injection project is examined in this study. The purpose of gas injection is to maintain reservoir pressure and improve the microscopic efficiency to increase the overall recovery in the field. A laboratory study revealed that the miscibility could be achieved with a pressure of about 241.4 bars (i.e. 3500 psia), which is below the reservoir average pressure in El Gassi field. Typical reservoir heterogeneities encountered in El Gassi field were incorporated into the simulation model. The study includes history matching of past reservoir performance, investigation of different injection scenarios, optimization of injection well number, optimization of gas injection and oil production rates, and the benefit of drilling infill wells. Edge line gas injection appeared to be promising.
Sustaining Fracture Conductivity Increases Cumulative Production in Tight–Gas Reservoir—A Case History
Authors: Luna Jose Balbino , Soriano D. Eduardo , Garcia Raul , R. Juan Galvan , C. Alejandro Barrera
Published: March 2008

The rapid post-fracture production rate decline observed in both oil and gas wells is normally associated with loss of fracture conductivity, often attributed to invasion of formation fines into the proppant pack, loss of fracture width caused by proppant flowback, and fines derived from proppant crushing. However, recent studies have indicated that solid material generated from a geochemical process in the fracture face known as proppant diagenesis has considerable impact on proppant conductivity.

Although diagenesis is a slow geological process, lab tests show that proppant diagenesis can occur in fractions of a year. Post-fracture rapid production decline in high-temperature/high-stress wells seems to be the main symptom of proppant diagenesis. Recent lab tests have shown that the process can be prevented by isolating the direct contact proppant/formation through the use of hydrophobic materials.

The liquid resin systems (LRS), a specific type of hydrophobic material, have been used in the industry to prevent proppant flowback. The proppant is coated on-the-fly on location with a LRS. This technology has also proved to increase and sustain fracture conductivity over time. The production data presented in this paper comes from some tight-gas fields located at the Burgos Basin in north Mexico. The formation fractured is an intermediate/high-temperature and high-stress sandstone. The wells previously fractured in these fields historically had a rapid post-fracture production decline rate.

The wells successfully treated with LRS material show a significant production increase compared to untreated offset wells because of a substantial change of the conductivity of the fracture. Based on laboratory experiments on proppant diagenesis and field results, it has been observed that the proppant diagenesis protection treatment provided by the LRS significantly contributed to the production increase of the treated wells.
Accomplishments and Challenges of Horizontal Well Technology in Hassi Messaoud Oilfield
Authors: Achi B.
Published: March 2008

At present, about half of Hassi Messaoud field output is being produced from hundreds of non-conventional wells. Two horizontal well (HW) applications are being used; new infill medium-radius horizontal wells in between productive zones and re-entry of dry-to-poor vertical producers all over the field using short-radius equipment.

The purpose of both projects is to recover incremental oil from poor-quality reservoir parts in order to boost overall production and improve oil recovery. Horizontal well technology has proven to be a good alternative to overcome reservoir areal heterogeneity and intercept natural fractures when present in the reservoir.

Although the two techniques have significantly improved production from marginal areas, several limitations and problems still have to be addressed. Challenges include weaker-than-expected productivities, rapid production decline rates in most wells, difficulties in data acquisition and inadequate completions for both remedial stimulation and zonal isolation. This study attempts to bridge production profiles with well and reservoir parameters such as; well length, permeability, vertical communication, lateral heterogeneity and anisotropy, near wellbore damage, pressure support, …etc.

The article presents a comprehensive analysis of horizontal wells in the field and investigates many aspects of the observed success and failure cases. It also discusses the benefits of underbalanced drilling and pre-perforated liner completions. By benchmarking current well performances, the paper draws some suggestions for well design and completion strategies for prospective wells.
Multi Lateral Horizontal Well Application for Improving the Oil Recovery of a Mature Field, Intisar N. Field, Concession 103— Libya
Authors: Gharsalla Mohamed M. , Elghmari Mohamed B.
Published: March 2008

This paper examines the performance of a horizontal well with multi-lateral completion in a mature thin carbonate reservoir. The Upper Sabil reservoir in Zelten formation of Paleocene age in Intisar 103N Field has a structure of anticline that housed 14.4 MMSTB of OOIP. The reservoir was highly under-saturated with oil of 42° API.

The initial field development with two vertical wells resulted in a poor recovery of only 9 % of OOIP. The recovery mechanism of Upper Sabil reservoir is mainly rock/fluid expansion with marginal support from flank aquifers. The poor recovery can be attributed to thin pay thickness, poor reservoir quality, large well spacing, and lack of pressure support from aquifers.

The existing two vertical wells revealed a near constant production rate for the last 17 years indicating the drainage area is much larger than the wells can deplete in a reasonable time frame. The incentive of reducing well spacing was there but the question was how to reduce the well spacing: by drilling many vertical wells or less number of horizontal wells.

A reservoir simulation study in 2003 indicated that drilling vertical wells in a very thin reservoir of poor quality was not cost effective and recommended drilling of horizontal well. Hence, a horizontal well was drilled and completed at the top of the porosity with two lateral legs.

The stabilized oil production rate of the horizontal well was approximately three times higher than that of the vertical well, whereas the drilling cost of the horizontal well was about 1.5 times higher. The production from the horizontal well showed no negative impact on the production performance of the existing vertical well and the reserve was doubled.
Imaging the Deep Mediterranean Through Multi-Azimuth Seismic Acquisition and Processing
Authors: Rietveld Walter , Keggin Jim , Benson Mark , Manning Ted , Page Chris
Published: March 2008

At a depth of around 3km across large areas of the Nile Delta in the Mediterranean, lies a thin but complex layer of partially eroded Miocene aged anhydrite and other facies, refered to as the Messinian. Wavefield distortion, attenuation and the generation of complex multiple diffraction noise cause the quality of the underlying seismic image to be highly variable (See Figure 1). Multi-azimuth (MAZ) seismic can help resolve these issues and improve the deep pre-Messinian image.

Here we discuss the acquisition and processing flow of a MAZ streamer datasets and show some of the results. The initial data analysis shows that MAZ greatly improves general image quality, signal-to-noise ratio, lateral resolution, as well as suppressing diffracted and other multiples effectively. Issues and challenges around this approach are discussed.
Optimizing Hydraulic Fracturing in a Mature Oil Reservoir in Algeria
Authors: Shaoul J. R. , Spitzer W. , Mendenhall S. , Soufi S. , Aloun S.
Published: March 2008

The El-Agreb field, located near Hassi Messaoud, Algeria, has been producing for over 40 years. Hydraulic fracturing was attempted in the mid 1990's with some success. This paper describes the results of a study of 11 stimulation treatments performed in the Agreb field from 1994-2003. Fracture modeling using net pressure history matching gave estimates of fracture dimensions and reservoir permeability. Fracture dimensions and conductivity data went into a reservoir simulator and the post-frac production was history matched by adjusting the effective proppant permeability.

Analysis of the pre and post-frac productivity indexes (PI) was done to determine the productivity improvement factor (PIF). This analysis showed a clear correlation between the PIF and the dimensionless fracture conductivity (FcD). Such a correlation would only be expected in the case of finite conductivity fractures. For all the propped fractures, the "ideal" fracture conductivity (assuming 50% proppant permeability damage) gave an FcD greater than 1.5 (with an average FcD of 12). History matching the actual post-frac production, however, required proppant damage factors up to 97%, giving effective FcD's as small as 0.1. The proppant damage factor needed to match post-frac production was a strong function of the "ideal" FcD of the fracture. This result indicates that for good cleanup of the gel in the proppant pack, higher fracture conductivity is necessary than what would be considered sufficient based only on reservoir permeability and ideal values of proppant permeability. Previous work has made this claim1, and this field data strongly supports the earlier work. A large number of El Agreb fracture treatments were analyzed and a calibrated fracture model developed, allowing more accurate design of tip screenout treatments. Due to the low reservoir pressure in this mature field, a large differential pressure drives fracture leakoff, making spurt loss important2. The calibrated model has been applied successfully to 14 new fracture treatments in 2003-2007 (11 producers and 3 injectors). The benefits of this approach are improved productivity and more rapid post-fracture cleanup. New wells drilled in the field are now usually immediately fracture stimulated.
A Thermal Recovery Method for Medium-Heavy Oil Reservoirs
Authors: de Zwart A. H. , Bakker P. , Glandt C. A. , Brooks A. D. , van Dorp J.
Published: March 2008

The primary recovery of a medium-heavy oil reservoir with a strong bottom aquifer is generally poor. The introduction of horizontal wells that are drilled at the top of the oil column has improved the oil recovery. However, even horizontal wells suffer from fast water breakthrough that leads to oil production at a high water cut. Given the low primary recoveries, such fields are attractive EOR targets.

In situ combustion (ISC) is a displacement process generally applied to medium-heavy oil reservoirs in order to increase oil production by reducing the oil viscosity. In thick reservoirs (thicker than 10 meters), oil recovery could be severely challenged by gravity override of the injected gasses. In reservoirs without active aquifers, a significant part of the incremental oil is produced by gravity drainage after breakthrough.

We propose an ISC strategy where an infill producer is drilled close to the oil-water contact so that a significant amount of heat can be rapidly deployed in the middle and upper sections of the reservoir. Subsequently, the aquifer is used to sweep the warm oil through the heated zone towards the producers. The ISC process is compared with steam injection that also employs an additional infill producer. ISC and steam injection are used to deploy heat in the reservoir.

Numerical simulations show that the oil is produced at much lower water cut compared to the cold case (50-60 % versus 95%). Simulated oil recoveries increase significantly for both ISC and steam injection. A detailed comparison of these two processes is presented in this paper.
Practical Aspects of Streamline Application to Water Injection Management of a Giant Carbonate Reservoir
Authors: Rodriguez Alfonso , Dawood Naseem J. , Soremi Yinka , Taiban A.
Published: March 2008

This paper presents how streamline technology in combination with conventional water injection management indicators was used to effectively manage water injection in a giant field. Describing the relationship between injectors and producers is obtained from a streamline simulation model. Adjusting injection requirements only, based on well streamline injection efficiencies, is not possible for all regions of the reservoir since a good history-match is not always achieved in all regions, particularly for a giant simulation model with 520 producers and 160 injectors. Thus, conventional water injection management indicators like injection/production ratio(IPR) target per segment, reservoir pressure distribution and maximum water injection plant facilities should be taken into consideration to distribute the water efficiently.

The new proposed methodology, through an iterative process, links the streamline simulation results to the practical aspects of conventional peripheral water injection management considering water injection facilities constraints and routine reservoir performance metrics. The new approach improves injection efficiency for all segments simultaneously in a single run. We have accounted for redistributing water injection among several segments connected to a single/multiple water injection plants (WIPs). Results indicated that a similar oil production rate can be obtained through optimization. The main benefit is that water injection is managed more effectively with the excess amount of water not injected in a particular month or quarter, could be transferred and injected into other fields.
The Role of Multi-Disciplinary Teams in Innovative Reservoir Management Projects
Authors: Thakur Ganesh
Published: March 2008

This paper documents the use of integrated reservoir management concepts during the application of innovative technology to improve oil production/recovery in both new and mature fields. It provides a number of examples of multi-disciplinary project teams working together in a motivated environment to optimize the asset value. These examples demonstrate the innovative use of existing technologies to increase asset productivity: 3D/4D seismic, geostatistics, characterization/simulation, horizontal drilling technology, and improved oil recovery (IOR)/enhanced oil recovery (EOR) techniques — dumpflooding, peripheral/pattern floods, water/gas injection, CO2/miscible gas, and steamflooding.

Adopting an integrated team approach is important because of the advanced level of expertise required in making large-scale primary, secondary and tertiary projects successful from both a technical and an economic point of view. Opportunities for improving recovery through synergistic activities among team members are numerous. The integrated team approach and innovative use of technologies have resulted in significant increase in production/recovery in each of the case studies. Moreover, multi-disciplinary functions can yield significant benefits and individual job satisfaction for the participating team members.

A team building approach that uses "in-house" reservoir management quality fitness reviews or mini-forums are often employed to facilitate communication among engineering, geosciences, and operations staff. Recommendations for project improvement are a natural outgrowth of these forums.

Our experience indicates that considerable corporate benefits can be derived from integrated, multi-disciplinary reservoir management activities for both new and mature fields, onshore or offshore.
Geomechanical Aspects of 15 Years Water Injection on a Field Complex: An Analysis of the Past to Plan the Future
Authors: Santarelli F. J. , Havmøller O. , Naumann M.
Published: March 2008

This paper presents an analysis of the water injection conditions on a vast oil field complex operated by StatoilHydro in the Norwegian sector of the North Sea over a fifteen years period. The injection data were analysed from a geomechanical perspective such as to identify the main parameters governing the variations of fracturing pressure over the life of the wells, which in turn governs efficient and safe water injection.

The data highlight the importance of thermal effects in fracturing pressure variations even in relatively weak formations, where theory would deem them small based upon laboratory measurements. The magnitude of thermal effects quantified from field measurements is about one order of magnitude larger than what was expected a-priori from laboratory measurements.

It was also possible to track the evolution of the fracturing pressure of single wells for various reservoir pressures during phases of reservoir re-pressurisation. Here again the field data indicate behaviours that were not expected from a theoretical point of view – i.e. a constant fracturing pressure during reservoir re-pressurisation, while theory would predict a significant increase.

The practical implications of the study when designing water injection schemes on new fields are highlighted and examples are given on how the current theoretical short-comings identified during the study can be successfully by-passed in real life engineering. The need for R&D efforts aimed at matching the gap between field observations and existing theories is also emphasised.
High Density Brine-Based Drill-In Fluid Improved Reservoir Producibility in Gas Field Offshore Egypt
Authors: Ezzat A. M. , Gamal Medhat , D'Angelo Stefano
Published: March 2008

Quick clean up and dramatic improvements in reservoir producibility have been achieved in gas wells located offshore Egypt. These wells were drilled and completed using an engineered drill-in fluid system. The fluid formulation was carefully designed and extensively tested in three different laboratories prior to the field applications to help ensure reproducibility of the data and to verify the non damaging characteristics of the fluid. These tests were conducted under simulated downhole conditions to help ensure fluid compatibility with the reservoir rock minerals and natural fluids.

To help minimize fluid invasion while drilling in the payzone section, the optimal concentration and particle size distribution (PSD) of the suspended bridging material were selected and maintained during the field applications. The PSD of pure ground marble was selected based on the reservoir rock morphology and average pore size to establish effective bridging near the wellbore and help ensure quick lift-off of the filter cake.

A high-density calcium chloride / calcium bromide brine blend (14-14.5 lb/gal ≃ 1.68 sp.gr.-1.74 sp.gr.) was used as the base fluid to achieve and maintain the required fluid density without additions of insoluble weight material. Optimal concentrations of non-damaging temperature-stable polymers were used to provide suspension and filtration control. The gas reservoir section was drilled and completed in several wells with the new system. Productivity index and flow rates exceeded the operator’s expectations without any stimulation treatments. Substantial savings were realized in terms of rig time and well completion costs.

This paper presents the laboratory and field-generated data and discusses the key issues in designing and monitoring the new drill-in fluid during the field applications.
Clearing the Air: The Evolution of Organized Labor's Role in Tobacco Control in the United States
Authors: Zelnick Jennifer , Campbell Richard , Levenstein Charles , Balbach Edith
Published: March 2008

As efforts to make U.S. worksites smoke-free took shape in the 1980s, the tobacco industry sought to defeat them by forming alliances with organized labor. The alliance between the tobacco industry and organized labor was based on framing the regulation of environmental tobacco smoke (ETS) as a threat to jobs, an example of management unilateralism, and an issue that divided smoking and nonsmoking union members. The dynamics of organized labor and tobacco control began to change in the late 1980s with attempts to ban smoking on airlines and in the hospitality industry. Flight attendants, bar and restaurant workers, and casino dealers—all subject to ETS in their work environments—confronted ETS as an occupational health issue. Against the backdrop of increasing awareness of the hazards of ETS, and the acceptance of tobacco control policy, this framing changed the basis of organized labor's role in tobacco control. Because service workers share the workplace with the general public, their occupational health issues are also public health issues. This fact presents new opportunities for coalition building to protect the health of service workers and the public alike.
Expansion of an ancient lake in the Kathmandu basin of Nepal during the Late Pleistocene evidenced by lacustrine sediment underlying piedmont slope
Authors: Saijo Kiyoshi , Kimura Kazuo
Published: March 2008

We investigated the geomorphology and surface geology of the piedmont slope on the margins of the Kathmandu basin in the Nepal Himalaya in order to establish Late Pleistocene geography and especially the extent of the ancient lake in the basin. The piedmont slope consists of detrital deposits of colluvial or fluvial origin, underlain and interfingered by organic muddy sediments with radiocarbon ages of about 30,000 yr BP. Detritus from the surrounding hillslopes and lacustrine sediments were alternately deposited as the lake level rose at about that time. The ancient lake in the Kathmandu basin thus reached a level of between 1400 and 1440 m at around 30,000 yr BP, when it covered almost the entire basin. Because the cols on the surrounding divide are higher than this estimated lake level, and because reddish soils and weathered bedrock are observed on these cols, we conclude that overflow from an outlet other than the Bagmati River probably did not occur. Drainage of the ancient lake by the Bagmati River began just after 30,000 yr BP.

Key words: Nepal, Kathmandu basin, piedmont slope, lacustrine, lake level change, Late Pleistocene

Himalayan Journal of Sciences Vol.4(6) 2007 p.41-48
Discrete versus In Situ‐Generated Aluminum‐Salen Catalysts in Enantioselective Cyanosilylation of Ketones: Role of Achiral Ligands
Authors: Alaaeddine Ali , Roisnel Thierry , Thomas Christophe M. , Carpentier Jean‐François
Published: March 2008

The monometallic species {Salen}AlX (X=Me, 2a,b; X=Cl, 4a,b; O‐i‐Pr, 5a,b) and open bimetallic species {Salen}[AlMe2]2 (3a,b) that result from binary combinations between an aluminum precursor [trimethylaluminum, dimethylaluminum chloride, aluminum tris(isopropoxide)] and a diprotio {Salen}H2 pro‐ligand 1a,b (a=1R,2R‐cyclohexyl‐salen; b=1R,2R‐diphenylethylene‐salen) have been isolated. The crystal structures of 3b, 4b and of μ‐oxo species [{diphenylethylene‐salen}Al]2O (6b) are reported. The discrete species 2–5a,b have been individually evaluated in the asymmetric cyanosilylation of acetophenone. It is shown that, in several cases, these discrete catalysts display dramatically different performances than the catalyst systems in situ‐generated from the binary combinations. The influence of the achiral ligand X on both the enantioselectivity and activity of the cyanosilylation reaction has been investigated, resulting in the definition of a highly active and productive hexafluoro‐2‐propoxide‐based catalyst for a variety of aryl alkyl ketones (TON up to 470, TOF up to 140 h−1 at −20 °C for acetophenone).
Synthetic Applications of Synergism using Catalytic Binuclear Elimination Reactions. Further Examples of Rhodium‐Manganese and Rhodium‐Rhenium‐Catalyzed Hydroformylations
Authors: Li Chuanzhao , Chen Li , Garland Marc
Published: March 2008

Synergism has been previously observed in both rhodium‐manganese‐ and rhodium‐rhenium‐catalyzed hydroformylation. Furthermore, detailed in situ spectroscopic investigations have conclusively shown that the phenomenological origin of this synergistic effect is catalytic binuclear elimination (J. Am. Chem. Soc. 2003, 125, 5540–5548; 2007, 129, 13327–13334). In the present contribution, further substrates are used in the hydroformylation reaction with both rhodium‐manganese and rhodium‐rhenium. In situ spectroscopic studies show that (i) significant rate enhancements occur in the mixed metal systems with the new substrates and (ii) the organometallics present in the active systems, and their concentration profiles are consistent with those present in the previously studied catalytic binuclear elimination reactions (CBER). It is therefore concluded that catalytic binuclear elimination is a rather general mechanism in mixed metal hydroformylations and is rather independent of the substrates used. Further discussion is given to mechanistic aspects, synthetic efficiency, and the possibility that such synergistic effects might be useful to other classes of organic syntheses.
Nanomaterials for Rechargeable Lithium Batteries
Authors: Bruce Peter G. , Scrosati Bruno , Tarascon Jean‐Marie
Published: March 2008

Energy storage is more important today than at any time in human history. Future generations of rechargeable lithium batteries are required to power portable electronic devices (cellphones, laptop computers etc.), store electricity from renewable sources, and as a vital component in new hybrid electric vehicles. To achieve the increase in energy and power density essential to meet the future challenges of energy storage, new materials chemistry, and especially new nanomaterials chemistry, is essential. We must find ways of synthesizing new nanomaterials with new properties or combinations of properties, for use as electrodes and electrolytes in lithium batteries. Herein we review some of the recent scientific advances in nanomaterials, and especially in nanostructured materials, for rechargeable lithium‐ion batteries.
Tetraoxaspiroalkanes for polymerization stress reduction of Silorane resins
Authors: Chappelow Cecil C. , Pinzino Charles S. , Chen Shin‐Shi , Kotha Shiva P. , Glaros Alan G. , Eick J. David
Published: March 2008

This study involved the synthesis and characterization of tetraoxaspiroalkane monomers and evaluated their potential to reduce polymerization stress when formulated in a Silorane resin system. The tetraoxaspiroalkane monomers had two main structural features (a) two different types of core ring structures (a 1,5,7,11‐tetraoxaspirocyclic ring or a 2,4,8,10‐tetraoxaspirocyclic ring) and (b) four different types of ring substituents (normal alkyl, allyloxyalkyl, trimethylsilylalkyl, or oxabicycloalkyl). The resin formulations contained (a) 20 mol % of a 1,5,7,11‐ or 2,4,8,10‐tetraoxaspiroalkyl monomer; (b) a phenylmethylsilane containing two oxabicycloheptyl groups; (c) a cyclotetrasiloxane containing four oxabicycloheptyl groups; and (d) a photocationic initiator system. Three main aspects were studied (a) the photoreactivity of the formulations using PDSC, (b) photopolymerization stress, and (c) mechanical properties (flexural elastic modulus, ultimate strength, and work of fracture) which were measured using an electromagnetic mechanical testing machine. The main findings were (a) formulations containing 2,4,8,10‐tetraoxaspiroalkane monomers had measured net enthalpies greater than those containing 1,5,7,11‐tetraoxaspiroalkane monomers, and above those calculated for addition of an inert diluent; (b) all formulations containing tetraoxaspiroalkane monomers exhibited photopolymerization stress values that were 40–99% less than the nonaddition control; (c) the formulation containing a 1,5,7,11‐tetraoxaspiroalkane monomer with an oxirane functionality had mechanical properties that were not significantly different from the nonaddition control. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Polymerization of acrylonitrile initiated by Ce(IV)‐sucrose redox system: A kinetic study
Authors: Mahadevaiah  , Demappa T. , Sangappa  , Katoon Bibi Ahamadi
Published: March 2008

The polymerization of acrylonitrile (M), initiated by the free radicals formed in situ in the Ce (IV)‐sucrose redox system, was studied in aqueous sulfuric acid medium under nitrogen atmosphere in the temperature range of 30–60°C. The rate of polymerization is proportional to [M]1.0, [R]0.76, [Ce(IV)]0.8, and [H+]−0.46. The rate of Ceric ion disappearance and the rate of polymerization Rp have been measured. The effects of some water–miscible organic solvents, surfactants, ionic strength, and complexing agents on the rate of polymerization were investigated. The temperature‐dependence of the rate was studied and the activation parameters were computed using the Arrhenius and Eyring plots. A mechanism consistent with the experimental data, involving Ce(IV)‐sucrose complex formation, which generates free radicals, is suggested. The chain termination step of the polymerization reaction was determined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis of PNIPA/PDMS‐g‐PAA core‐shell composites in supercritical carbon dioxide
Authors: Cao Li‐Qin , Chen Liu‐Ping , Cui Peng‐Yuan , Wang Ji‐De
Published: March 2008

Herein we report a means that has been developed to prepare smart polymeric microgels consisting of thermosensitive cores with pH‐sensitive shells. The microgels were obtained directly from seed polymerization of N‐isopropylacrylamide in supercritical carbon dioxide (scCO2). The effects of initial amounts of crosslinker, and Poly (dimethylsiloxane)‐graft‐polyacrylates (PDMS‐g‐PAA) on the yield and morphology of the resulting polymer were investigated. PDMS‐g‐PAA and crosslinker worked effectively as surfactant. PNIPA/PDMS‐g‐PAA particles with diameters in 50 nm were produced in scCO2, in high yield and in short reaction times. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation and electroanalytical characterization of polyaniline: Polyacrylonitrile composite films
Authors: Khatoon Atika , Khalid Mohd , Mohammad Faiz
Published: March 2008

Electrically conducting composite films of polyaniline:polyacyrlonitrile (PANI:PAN) prepared with varying composition ratios of aniline mixed with a fixed amount PAN. The films of optimum thicknesses (0.10 mm) were obtained using an electrically operated automatic pressure machine. The films polymerized by oxidative polymerization using 0.1M potassium persulphate (K2S2O8), undoped in 1M aqueous ammonia (NH4OH) and doped in 1M hydrochloric acid (HCl). The conductivity of composite films was studied by keeping it in 1M HCl for different time period using 4‐in‐line probe DC electrical conductivity measuring instrument and the temperature dependence of DC electrical conductivity was studied using isothermal technique. The PANI:PAN composite film is used as a working electrode in an electrochemical cell. Chemically doped composite film is used as cathode (working electrode), aluminum metal foil as anode (counter electrode) and platinum foil as reference electrode. The electrolyte is of 0.05M aluminum chloride (AlCl3) in dimethyl sulfoxide (DMSO). The voltage of the working electrode is stabilized with respect to the reference electrode and current applied between the working and counter electrode through a 9‐V battery. The change in voltage versus time is plotted as the discharge curve and reversing the cell processes results in the doping of the composite films. The diffusion coefficient of the dopant ion (Cl−) present in the fully doped films were estimated by the galvanostatic pulse technique and found to bedifferent in different samples in the range of 10−16 to 10−12 cm2 s−1. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of the template molecules and nonsolvent additives on the recognition property of molecular imprinted polyethersulfone particles
Authors: Yu Binyu , Zhang Xinlan , He Jie , Yang Kaiguang , Zhao Changsheng
Published: March 2008

In this study, molecular imprinted polyethersulfone (PES) particles were prepared by phase inversion technique. Bisphenol A, 4,4′‐biphenol, and phenol were used as the template molecules, and the functional binding performance in aqueous medium towards the template molecules was investigated. The nonsolvent additives such as ethanol, water, chloroform, and toluene had no effect on the recognition property of the PES particles. The resultant BPA imprinted particles showed the highest BPA recognition coefficient, which was 2.14 times higher than that for the nonimprinted ones. The 4,4′‐biphenol imprinted particles showed the highest binding ability towards the template which was 28.4 μmol/g. Scatchard analysis showed that there were two classes of binding sites formed in the imprinted particles, and the equilibrium dissociation constant of the highest affinity binding sites was estimated to be 9.2 μM. Finally, the interaction between PES and the templates was studied by Fourier transform infrared (FTIR) and NMR. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
The influence of study methods and knowledge processing on academic success and long‐term recall of anatomy learning by first‐year veterinary students
Authors: Ward Peter J. , Walker James J.
Published: March 2008

The purpose of this investigation was to quantitatively and qualitatively identify the study methods and learning strategies that veterinary students used to study anatomy during their first year of professional school and to correlate these with their academic achievement and long‐term recall of information. It was surmised that active study methods would be more beneficial than passive method, but this hypothesis was not supported. The activity or passivity of each study method was secondary to the way in which the students processed the learning. No single study method was associated with academic success or long‐term recall; instead, successful students used a multitude of study methods while the struggling students relied on a single method alone, although these methods varied from student to student. Students and their study methods were profiled using the qualitative technique known as phenomenographic analysis to find those who studied in a deep or surface way. The deep‐processing students, who commonly used multiple study methods, not only succeeded in the class but also had better recall. Students who relied on a memorization‐heavy surface approach to learning had limited recall and tended to perform poorly in the class. These results strongly suggest that by encouraging students to integrate their studying by using multiple methods educators can improve both student grades and recall of complex topics. Anat Sci Ed 1:68–74, 2008. © 2008 American Association of Anatomists.
Transforming clinical imaging data for virtual reality learning objects
Authors: Trelease Robert B. , Rosset Antoine
Published: March 2008

Advances in anatomical informatics, three‐dimensional (3D) modeling, and virtual reality (VR) methods have made computer‐based structural visualization a practical tool for education. In this article, the authors describe streamlined methods for producing VR “learning objects,” standardized interactive software modules for anatomical sciences education, from newer high‐resolution clinical imaging systems data. The key program is OsiriX, a free radiological image processing workstation software capable of directly reformatting and rendering volumetric 3D images. The transformed image arrays are then directly loaded into a commercial VR program to produce a variety of learning objects. Multiple types or “dimensions” of anatomical information can be embedded in these objects to provide different kinds of functions, including interactive atlases, examination questions, and complex, multistructure presentations. The use of clinical imaging data and workstation software speeds up the production of VR simulations, compared with reconstruction‐based modeling from segmented cadaver cross‐sections, while providing useful examples of normal structural variation and pathological anatomy. Anat Sci Ed 1:50–55, 2008. © 2008 American Association of Anatomists.
Anatomists debate the value of a teaching credential
Authors: Rizzolo Lawrence J. , Drake Richard L.
Published: March 2008

Fewer and fewer programs are training graduate students and postdoctoral fellows in the classical anatomical disciplines. Nonetheless, there remains a need at all levels of clinical and basic science education for skilled instructors of anatomy, histology, and embryology. Two sessions at the 2006 annual meeting of the American Association of Anatomists (AAA) explored whether a system of accreditation would benefit students, institutions, and training programs. Although the value of accreditation was controversial, three challenges for the various anatomical societies emerged from these discussions: (1) To identify the skills and knowledge that should be shared among all anatomists, and the more specific skills and knowledge needed for the diverse settings in which anatomists work. (2) To address the historical inattention of institutions to the training of educators. (3) To develop strategies to lobby institutions and national organizations to support the training and work of educators in the anatomical sciences. One approach to meeting these challenges would be to develop guidelines for training programs. These guidelines would help graduate students seek the training they need, provide institutions with a benchmark to assess or develop training programs, and provide the basis for focusing lobbying efforts targeted at institutions or existing accreditation bodies. Anat Sci Ed 1:60–67, 2008. © 2008 American Association of Anatomists.
Effects of instructional strategies using cross sections on the recognition of anatomical structures in correlated CT and MR images
Authors: Khalil Mohammed K. , Paas Fred , Johnson Tristan E. , Su Yung K. , Payer Andrew F.
Published: March 2008

This research is an effort to best utilize the interactive anatomical images for instructional purposes based on cognitive load theory. Three studies explored the differential effects of three computer‐based instructional strategies that use anatomical cross‐sections to enhance the interpretation of radiological images. These strategies include: (1) cross‐sectional images of the head that can be superimposed on radiological images, (2) transparent highlighting of anatomical structures in radiological images, and (3) cross‐sectional images of the head with radiological images presented side‐by‐side. Data collected included: (1) time spent on instruction and on solving test questions, (2) mental effort during instruction and test, and (3) students' performance to identify anatomical structures in radiological images. Participants were 28 freshmen medical students (15 males and 13 females) and 208 biology students (190 females and 18 males). All studies used posttest‐only control group design, and the collected data were analyzed by either t test or ANOVA. In self‐directed computer‐based environments, the strategies that used cross sections to improve students' ability to recognize anatomic structures in radiological images showed no significant positive effects. However, when increasing the complexity of the instructional materials, cross‐sectional images imposed a higher cognitive load, as indicated by higher investment of mental effort. There is not enough evidence to claim that the simultaneous combination of cross sections and radiological images has no effect on the identification of anatomical structures in radiological images for novices. Further research that control for students' learning and cognitive style is needed to reach an informative conclusion. Anat Sci Ed 1:75–83, 2008. © 2008 American Association of Anatomists.
Clarifying the roles of kinetics and diffusion in activated sludge filamentous bulking
Authors: Lou In Chio , de los Reyes Francis L.
Published: March 2008

We hypothesized that the growth rates of filaments and floc formers in activated sludge are affected by the combination of kinetic selection (Lou and de los Reyes, Biotechnol Bioeng 92(6): 729–739, 2005b) and substrate diffusion limitation (Martins et al., Water Res 37:2555–2570, 2003). To clarify the influence of these factors in explaining filamentous bulking, a conceptual framework was developed in this study. The framework suggests the existence of three different regions corresponding to bulking, non‐bulking, and intermediate regions, based on substrate concentration. In the bulking and non‐bulking regions, kinetic growth differences control the competition process, and filaments or floc formers dominate, respectively. In the intermediate region, substrate diffusion limitation, determined by the floc size, plays the major role in causing bulking. To test this framework, sequencing batch reactors (SBRs) were operated with influent COD of 100, 300, 600, and 1,000 mg/L, and the sludge settleability was measured at various floc size distributions that were developed using different mixing strengths. The experimental data in the bulking and intermediate regions supported the proposed framework. A model integrating the two factors was developed to simulate the substrate concentrations at different depths and floc sizes under intermittently feeding conditions. The modeling results confirmed that substrate diffusion limitation occurs inside the flocs at a certain range of activated sludge floc sizes over the operation cycle, and provided additional support for the proposed framework. Biotechnol. Bioeng. 2008;101: 327–336. © 2008 Wiley Periodicals, Inc.
Nutrient gradients in engineered cartilage: Metabolic kinetics measurement and mass transfer modeling
Authors: Zhou Shengda , Cui Zhanfeng , Urban Jill P.G.
Published: March 2008

Since tissue‐engineered cartilage is avascular, both nutrient supply and metabolic waste removal rely on diffusion. As a result, gradients of nutrients and wastes exist through the construct. Previous models usually calculate gradients of oxygen, glucose, and lactic acid separately, without taking into account the complex interdependence between concentrations of these substrates and rates of metabolism. In this study, these interactions were experimentally examined and incorporated into diffusion models. One‐dimensional diffusion‐reaction models were developed for three typical culture conditions, that is, static culture, perfusion culture, and suspended culture. The profiles of oxygen, glucose, lactic acid, and pH in the cultured constructs were calculated simultaneously using measured metabolic rates. The maximum construct size and cell density which could be supported before nutrients were depleted in the construct center was identified; a function predicting the relationship between construct dimension and the maximum viable cell density was developed. For constructs incubated under static culture the model demonstrated that the gradients which developed through the medium could not be neglected. Perfusion cultures could support a considerably higher cell density than static cultures, while for batch cultures in a rotating bioreactor, the volume of medium also influences the maximum cell density that could be supported. This study provides useful guidance for design of engineered cartilage constructs. Biotechnol. Bioeng. 2008;101: 408–421. © 2008 Wiley Periodicals, Inc.
The membrane bioreactor: A novel tool to grow anammox bacteria as free cells
Authors: van der Star Wouter R.L. , Miclea Andreea I. , van Dongen Udo G.J.M. , Muyzer Gerard , Picioreanu Cristian , van Loosdrecht Mark C.M.
Published: March 2008

In a membrane bioreactor (MBR), fast growth of anammox bacteria was achieved with a sludge residence time (SRT) of 12 days. This relatively short SRT resulted in a—for anammox bacteria—unprecedented purity of the enrichment of 97.6%. The absence of a selective pressure for settling, and dedicated cultivation conditions led to growth in suspension as free cells and the complete absence of flocs or granules. Fast growth, low levels of calcium and magnesium, and possibly the presence of yeast extract and a low shear stress are critical for the obtainment of a completely suspended culture consisting of free anammox cells. During cultivation, a population shift was observed from Candidatus “Brocadia” to Candidatus “Kuenenia stuttgartiensis.” It is hypothesized that the reason for this shift is the higher affinity for nitrite of “Kuenenia.” The production of anammox bacteria in suspension with high purity and productivity makes the MBR a promising tool for the cultivation and study of anammox bacteria. Biotechnol. Bioeng. 2008;101: 286–294. © 2008 Wiley Periodicals, Inc.
Specific Isotope Labeling of Colicin E1 and B Channel Domains For Membrane Topological Analysis by Oriented Solid‐State NMR Spectroscopy
Authors: Aisenbrey Christopher , Cusan Monica , Lambotte Stephan , Jasperse Pieter , Georgescu Julia , Harzer Ulrike , Bechinger Burkhard
Published: March 2008

An approach is presented to selectively label the methionines of the colicin E1 and B channel domains, each about 200 residues in size, and use them for oriented solid‐state NMR investigations. By combining site‐directed mutagenesis, bacterial overexpression in a methionine auxotroph E. coli strain and biochemical purification, quantitative amounts of the proteins for NMR structural investigations were obtained. The proteins were selectively labeled with 15N at only one, or at a few, selected sites. Multidimensional heteronuclear correlation high‐resolution NMR spectroscopy and mass spectrometry were used to monitor the quality of isotopic labeling. Thereafter the proteins were reconstituted into oriented phospholipid bilayers and investigated by proton‐decoupled 15N solid‐state NMR spectroscopy. The colicin E1 thermolytic fragment that carries a single 15N methionine within its hydrophobic helix 9 region exhibited 15N resonances that are characteristic of helices that are oriented predominantly parallel to the membrane surface at low temperature, and a variety of alignments and conformations at room temperature. This suggests that the protein can adopt both umbrella and pen‐knife conformations.
The life of π and σ—A tutorial review of the ubiquitous use of these symbols in Zeeman and magnetic‐resonance spectroscopy
Authors: Weil John Ashley
Published: March 2008

Certain concepts and symbolism as applied to electromagnetic radiation and especially the concept of photons are discussed and (perhaps) clarified. A useful summary of the properties of photons is provided, and the concept of polarization is discussed. In particular, the common usage in Zeeman and magnetic‐resonance (EPR and NMR) spectroscopy of the symbols π and σ is examined herein, both from the historical viewpoint and the scientific standpoint, and certain errors and fallacies are brought to attention. Brief reference to relevant recent work published on dynamic nuclear polarization and on pulse EPR is included. © 2008 Wiley Periodicals, Inc.Concepts Magn Reson Part A 32A: 134–142, 2008.