bluuebunny/crossref_metadata_2025 huggingface dataset:
Real-Time Diagnostics of Gas Lift Systems Using Intelligent Agents: A Case Study
Authors: Stephenson G. , Molotkov R. , De Guzman N. , Lafferty L.
Published: March 2010

This paper describes a new method to continuously monitor and diagnose the condition of wells producing through continuous gas lift. The paper describes the application of this system in a mature onshore gas lift field in the western United States and the results obtained. A central problem related to the operation of gas lift wells is the ability to identify underperforming wells and to address the underlying issues appropriately and in a timely manner. This problem is compounded by the trend toward leaner operations and relative scarcity of application-specific domain knowledge. The purpose of this method is to address these issues by leveraging real-time data, gas lift domain expertise, and proven steady-state analysis techniques in a desktop software application.

This system performs four key functions: Monitoring the wells' condition by collecting data, assessing the meaning of these data, recommending actions for correcting problems and responding to threats, and explaining recommendations.

The performance of the system has met initial expectations and has provided additional unforeseen benefits. This paper cites specific cases that compare agent predictions to expert diagnoses and quantify the benefits of taking the recommended actions. What was found was that while the correct diagnoses of well performance issues was beneficial, the real benefit was in allowing production engineers to analyze a greater number of wells in far less time. To that end, the paper will discuss the role of this system as it relates to the overall production management workflow.

The success of this project has demonstrated that intelligent agents can effectively perform functions historically performed by a handful of experts. The paper will discuss key system-design features that enable this level of functionality as well as other potential areas in which the technology can be extended in the future.
Improved Geosteering by Integrating in Real Time Images From Multiple Depths of Investigation and Inversion of Azimuthal Resistivity Signals
Authors: Chemali Roland , Bittar Michael , Hveding Frode , Wu Min , Dautel Mike
Published: March 2010

Optimal field development often entails placing the wells in prescribed locations within the reservoir. An error of a few meters in height above the oil/water contact or with respect to the roof may result in leaving behind a significant portion of the producible reserves. Driven by this key requirement, new technologies continue to emerge to help geologists, drillers, and reservoir engineers geosteer the wells. In recent years, two types of logging-whiledrilling (LWD) information have been used. On one hand, wellbore imaging can determine when a well path has left the reservoir and the angle of exit. On the other hand, traditional axisymmetrical resistivity logs help to quantify the distance to an approaching boundary through inversion, but fail to tell its azimuth.

A newly deployed azimuthal deep resistivity instrument recognizes an approaching geological event before it intersects the well while continually imaging it at multiple depths of investigation. Of particular interest is the azimuth of approach with respect to the well path, advising in real time the most favorable change of direction. In addition, a series of transverse electromagnetic measurements specific to azimuthal resistivity, called geosignals, are presented. Geosignals help to quantify the distance and the rate of approach with great accuracy, before the actual intersection could occur. With this real-time information, geosteering engineers can remain at prescribed distances from important boundaries, including oil/water contacts and overlying shale roofs. Modeling and actual logs demonstrate that the new LWD instrument performs at its best when the reservoir is overlaid by shale. Modeling suggests, however, that suboptimal performance occurs in reservoirs with very resistive caprock, such as anhydrite.
Fully Coupled Numerical Modelling of Ground Surface Uplift in Steam Injection
Authors: Yin Shunde , Dusseault Maurice B. , Rothenburg Leo
Published: March 2010

Abstract

In enhanced oil recovery, steam injection involves high stresses, pressures, temperatures and volume changes. Traditional reservoir simulation fails to predict associated transient ground surface movements because it does not consider coupled geomechanical effects. We present a fully-coupled, thermal half-space model using a hybrid DDFEM method, in which a simultaneous finite element method (FEM) solution is adopted for the reservoir and the surrounding thermally affected zone, and a displacement discontinuity (DD) method used for the elastic, non-thermal zone. This approach provides transient ground surface movements in a natural manner.

Introduction

Enhanced oil recovery (EOR) methods involving high pressures and steam injection (steamflooding, cyclic steam stimulation, steam-assisted gravity drainage) are accompanied by large volume changes in the reservoir horizon. Ground movements in excess of 300 mm heave or subsidence are registered during injection and production cycles. Reservoir simulation cannot address this phenomena without due consideration of geomechanical effects.

The earliest theory to account for coupled pore fluid behaviour and soil deformation was the Terzaghi one-dimensional consolidation theory, still used in soil mechanics. Since Biot's theory of consolidation(1) was introduced to petroleum engineering by Geertsma(2) with the coined term "poroelasticity,?? coupled analysis of petroleum geomechanics effects has been widely advocated(3-5). Coupled reservoir simulation can be carried out in a loosely coupled fashion(6, 7) or with a tightly coupled scheme(8-10), and comparisons of different coupling techniques can be found (11, 12).

In reservoir simulation, a coupled analysis demands simultaneous solution of changes in (p,T) and fluid flow as well as stress and strain. Computing challenges persist in large-scale 3D applications to real cases where there are a huge number of equations to solve iteratively; e.g. thermo-poro-elasto-plastic analyses involving several simultaneous diffusion processes (Darcy, Fourier, Fick). In regions of large pressure, temperature, concentration or stress gradients, accurate solution requires small-scale discretization. If the problem has strong non-linearity, such as changes in permeability, compressibility, or other properties arising from changes in pressure and effective stress, the computational effort increases by several orders of magnitude because multiple iteration loops are needed. These issues mean that accurate analysis of realistic complex 3D problems is challenging, and will so remain as we seek to solve larger and larger coupled problems involving non-linear responses.
Thermal Solvent Reflux and Thermal Solvent Hybrid Experiments
Authors: Ivory J. , Frauenfeld T. , Jossy C.
Published: March 2010

Abstract

The experiments and numerical simulations described in this paper were performed to determine the effectiveness of the thermal solvent reflux and steam solvent hybrid processes and to determine the key parameters involved in these two processes.

Steam-assisted gravity drainage (SAGD) is the current technology of choice for Athabasca reservoirs. It is commercially proven and delivers high oil rates and high ultimate recoveries. However, it is energy intensive. In addition, steam injection may be limited by lack of water, by regulatory issues or by the fact that some reservoirs are water sensitive.

Vapour-assisted petroleum extraction (VAPEX) does not have the energy and water problems associated with SAGD. However, it is inherently slower than SAGD.

One solution to the above difficulties is to combine processes by heating the horizontal wellbores. The heat serves to initiate communication between the injector and the producer. In addition, it will increase the rate of diffusion of the solvent into the oil. Heat may be applied by electric heaters, with a closed steam or glycol loop, or by direct injection of steam. In the first three of four experiments described in this report, the wells were electrically heated. In the fourth experiment, steam was co-injected with the solvent.

Two experiments using Hillmond oil showed that similar results were obtained whether heating was obtained by electrically heating the wells (thermal solvent reflux process) or by direct steam injection (steam solvent-hybrid process). For these two experiments, the oil rate and recovery were similar. Numerical simulations were used to history match the experiments and effective diffusivity values were estimated.

Introduction

The objective of the thermal solvent reflux experiments was to develop a solvent-assisted process for recovery of heavy oil from thick, cold reservoirs such as Cold Lake and Athabasca.

The thermal solvent process concept (Figure 1) is

• Inject solvent and produce oil through horizontal wells

• Heat the injection and production wells to reboil the solvent in situ (solvent reflux) (i.e., in-situ recycle of solvent)

The advantages of the thermal solvent reflux process are

• Requires less heat than SAGD

• Less steam plant emissions

• Smaller solvent recycle plant on surface

• Smaller injection facility needed

• Does not inject water into the reservoir

• Suitable for reactive reservoirs

• No treatment of boiler feed water required

• Minimal water disposal

• Minimal oil/water separation facilities required

• Heat will speed mass transfer over cold VAPEX
Is High-Pressure Air Injection (HPAI) Simply a Flue-Gas Flood?
Authors: Montes A.R. , Gutierrez D. , Moore R.G. , Mehta S.A. , Ursenbach M.G.
Published: March 2010

Abstract

High-pressure air injection (HPAI) is an enhanced oil recovery (EOR) process in which compressed air is injected into a deep, light-oil reservoir, with the expectation that the oxygen in the injected air will react with a fraction of the reservoir oil at an elevated temperature to produce carbon dioxide.

Over the years, HPAI has been considered a simple flue-gas flood, giving little credit to the thermal drive as a production mechanism. The truth is that, although early production during a HPAI process is mainly due to re-pressurization and gasflood effects, once a pore volume of air has been injected the combustion front becomes the main driving mechanism.

This paper presents laboratory and field evidence of the presence of a thermal front during HPAI operations, and of its beneficial impact on oil production. Production and injection data from the Buffalo Field, which comprises the oldest HPAI projects currently in operation, were gathered and analyzed for this purpose. These HPAI projects definitely do not behave as simple immiscible gasfloods.

This study shows that a HPAI project has the potential to yield higher recoveries than a simple immiscible gasflood. Furthermore, it gives recommendations about how to operate the process to take advantage of its full capabilities.

Introduction

High-Pressure Air Injection (HPAI) is an emerging technology for the enhanced oil recovery (EOR) of light oils that has proven to be a valuable process, especially in deep, thin, low-permeability reservoirs(1-7).

A number of successful high-pressure air injection projects in light oil reservoirs have been documented in the literature(8-10). Most of these projects have been operating for many years, attesting to their technical and economic success.

The improvement in recovery of light oil by HPAI involves a combination of complex processes, each contributing to the overall recovery. These processes include flue gas sweeping, field re-pressurization, oil swelling, viscosity reduction, stripping of the lighter components of the oil, and thermal effects. Early production during the HPAI process is related to re-pressurization and gasflood effects; hence, the influence of the thermal zone is secondary during the early life of an injector. The oil displaced directly by the thermal front will depend on the effectiveness of the generated flue gas on oil displacement from outside the thermal region.
Mechanisms of Heavy Oil Recovery by Low Rate Waterflooding
Authors: Mai A. , Kantzas A.
Published: March 2010

Abstract

At the conclusion of primary heavy oil production, significant volumes of oil still remain in the reservoir under depleted reservoir pressure. Waterfloods are often considered for additional oil recovery. It is accepted that conventional oil waterflooding theory is not applicable for heavy oil. However, there is a lack of understanding of how waterfloods should perform in these reservoirs, particularly after water breakthrough. In this study, waterfloods were performed at multiple rates in cores containing heavy oil and connate water. In some cores, oil was initially free of solution gas, and waterfloods were a primary recovery process. In other cores, waterfloods were performed after primary production. Experiments were performed in linear systems for a high-viscosity oil (11,500 mPa·s at 23°C), at different injection rates. The influence of viscous and capillary forces is studied in primary vs. secondary recovery systems. A common misconception is that capillary forces are negligible in heavy oil; however, this work shows that these forces are significant, and that water imbibition after water breakthrough can lead to improved oil recovery in both primary and secondary waterfloods.

Introduction

The Canadian deposits of heavy oil and bitumen are some of the largest in the world. Recent estimates by the Alberta Energy and Utilities Board(1) suggest that this resource could exceed 270 billion m³ in Alberta alone, with a significant portion of this oil located in reservoirs where energy-intensive thermal operations will not be economic. Heavy oil is a special class of this unconventional oil, which has viscosity ranging from 50 - 50,000 mPa·s (cp) and low API gravity. Heavy oil reservoirs are often high-porosity, high-permeability, unconsolidated sand deposits. Permeability of the sand averages in the range of 3D, but oil does not flow easily because of its high viscosity(2). The oil may contain dissolved solution gas at initial conditions; thus, a fraction of the oil can be recovered through solution gas drive. Primary production can recover around 5% of the oil in place(1), leaving significant oil volumes in the reservoir for potential secondary recovery.

Waterflooding is a common technique for secondary oil recovery in conventional oil reservoirs. In heavy oil systems, the extremely high oil viscosities lead to adverse mobility ratio conditions; thus, water will tend to "finger?? through the oil, and recoveries are expected to be extremely low(3,4). Despite the poor recoveries predicted theoretically, there have been numerous reports of heavy oil waterfloods performed in the literature(5-8). All of these studies report poor sweep efficiencies and low overall recovery. However, it is significant that in all cases some oil was still recovered, despite the highly adverse mobility ratios in the waterfloods.
Case Study of Multiple-Hydraulic-Fracture Completion in a Subsea Horizontal Well, Campos Basin
Authors: Neumann L.F. , Fernandes P.D. , Rosolen M.A. , Rodrigues V.F. , Silva Neto J.A. , Pedroso C.A. , Mendez A. , Torres D.
Published: March 2010

This paper provides a case history of the first hydraulic fracture on a subsea horizontal well in the Quissama formation, a low-permeability limestone reservoir in Campos basin, Brazil.

The well was drilled in the direction of the expected fracture growth, thus evolving longitudinal fractures along the horizontal section. It is part of a research project to evaluate selective stimulation methods for subsea horizontal wells. Every aspect since the drilling, completion, and evaluation of the well was handled with the end in mind of hydraulically fracturing it in several stages.

Hydraulically fracturing a horizontal well has become a more accepted practice in our industry. The procedures used in fracturing vertical wells must be taken into consideration when fracturing a horizontal well, to avoid refracturing work. Near-wellbore (NWB) problems are usually the main reason that fracturing work is not completed. This paper describes hydraulic-fracture treatments with detailed discussion on analysis of calibration tests, fluid-efficiency tests (FETs), and lessons learned.

Results of the pumping work will be presented showing theory and how common practices played a key role for a successful application of techniques used. Laboratory tests performed with cores taken from the well itself, such as rock mechanics, proppant embedment, compaction measurements, and basic mineralogy, are presented.

Production results will be presented and compared to conventional methods used on other subsea horizontal wells in Campos basin.
Comment on Casey Mulligan: Keynes in Both Fresh and Salt Water
Authors: Da Silva Sergio
Published: March 2010

Casey Mulligan suggested in The Economists' Voice that this recession was caused by "something [that] made real wages high and employment low." This coincides with his own view of the causes of the Great Depression. The similarity inevitably brings back General-Theory-Keynes, according to Da Silva, and justifies the suspicion of some salt water economists that Mulligan is blaming both downturns on laziness.
Influence of Light, Distance and Size on Recognition and Classification of Food Grains' Images
Authors: Anami Basavaraj S , Savakar Dayanand G
Published: March 2010

The paper presents an artificial neural network based approach to corroborate the effect of variations in illumination, distance of image acquisition and size on recognition and classification accuracies of bulk food grain image samples. Different food grains samples like Wheat, Groundnut, Green gram and Jowar are considered. The image samples are taken by varying acquisition distances, illumination and sizes. The natural light source and the minimum distance of 40 centimeters are ideal for image acquisition compared to other light sources and varying distance of image acquisition. The experimental results have shown a reduction in accuracy in all the cases other than natural lighting condition and fixed distance of acquisition. The same is true with human vision system too. Variations in image sizes also affect the recognition and classification accuracies. Hence, it is inferred that any variation in the size of the image and the distance of acquisition has an impact on the accuracy of recognition of food grain samples.
Photo-Fenton and photo-Fenton-like processes for the degradation of methyl orange in aqueous medium: Influence of oxidation states of iron
Authors: Devi L. , Kumar S. , Anantha Raju K. , Eraiah Rajashekhar K.
Published: March 2010

Degradation of methyl orange (MO) was carried out by the photo-Fenton process (Fe2+/H2O2/UV) and photo-Fenton-like processes (Fe3+/H2O2/UV, Fe2+/S2O82−/UV, and Fe3+/S2O82−/UV) at the acidic pH of 3 using hydrogen peroxide and ammonium persulfate (APS) as oxidants. Oxidation state of iron had a significant influence on the efficiency of photo-Fenton/photo-Fenton-like processes. It was found that a process with a source of Fe3+ ions as the catalyst showed higher efficiency compared to a process with the Fe2+ ion as the catalyst. H2O2 served as a better oxidant for both oxidation states of iron compared to APS. The lower efficiency of APS is attributed to the generation of excess protons which scavenges the hydroxyl radicals necessary for degradation. Further, the sulfate ions produced from S2O82− form a complex with Fe2+/Fe3+ ions thereby reducing the concentration of free iron ions in the solution. This process can also reduce the concentration of hydroxyl radicals in the solution. Efficiency of the various MO degradation processes follows the order: Fe3+/H2O2/UV, Fe3+/APS/UV, Fe2+/H2O2/UV, Fe2+/APS/UV.
Synthesis, spectral and electrochemical study of coordination molecules Cu4OX6L4: 3-cyanopyridine Cu4OBrnCl(6−n)(3-CNpy)4 complexes
Authors: Ondrejovič Gregor , Kotočová Adela , Koman Marian , Segľa Peter
Published: March 2010

Seven new 3-cyanopyridine Cu4OBrnCl(6−n)(3-CNpy)4 (n = 0–6) complexes were prepared and studied by infrared spectra, electronic spectra, and cyclic voltammetry. Infrared spectra revealed a distortion of the tetrahedral Cu4O core to C 2ν or C 3ν symmetries and a donor-acceptor vibrational coupling with the in-plane pyridine ring bending within the O-Cu-(pyridine ring)CN system involving the π-back bonding between Cu(II) atoms and 3-CNpy ligands. Bands of the electronic spectra and half-wave potentials of the complexes are consistent with the weak donor and strong acceptor behaviour of the 3-CNpy ligands. The results were compared with analogous complexes of pyridine, 3-substituted and 4-substituted pyridine ligands.
Beziehungen zwischen Baum- und Krautschicht in Buchenmischwäldern | Relations between tree and herb layer in mixed beech forests
Authors: Reusser Judith , Heiri Caroline , Weber Pascale , Bugmann Harald
Published: March 2010

Tree layer composition is a crucial factor for the stability and diversity of forest ecosystems, and many factors such as nutrient availability or the light regime are influenced by trees and their species-specific properties. The occurrence and abundance of herbs as indicators for site characteristics are likely to be related to the variability in tree layer diversity and changes in environmental variables. To test this hypothesis, the effect of tree layer composition on herb layer diversity was studied in mixed deciduous beech (Fagus sylvatica) forest reserves on the Swiss Plateau. Applying a transect design we recorded tree and herbaceous species composition and measured key top soil properties and light availability in seven forest reserves. Tree layer diversity did not affect herb layer diversity at the study sites. However, a species-specific influence of trees on the herb layer was evident: a high proportion of beech had a negative effect on herb layer diversity, and the presence of ash (Fraxinus excelsior) was correlated with a thick A h horizon and high soil pH, which enhanced herb layer diversity. Spruce (Picea abies) and pine (Pinus sylvestris) were related to a thick forest floor (litter) layer, which negatively affected herb layer diversity.
What Concepts Do: Preface to the Chinese Translation of A Thousand Plateaus
Authors: Massumi Brian
Published: March 2010

This essay suggests an approach to the reading of Deleuze and Guattari's A Thousand Plateaus, grasped as a philosophical event that is as directly pragmatic as it is abstract and speculative. A series of key Deleuzo-Guattarian concepts (in particular, multiplicity, minority and double becoming) are staged from the angle of philosophy's relation to its disciplinary outside. These concepts are then transferred to the relation between the authors' philosophical lineage and the new cultural outside into which the Chinese translation will propel their thought. Emphasis is placed on the writing – and reading – of philosophy as a creative act of collective import and ethical force.
Analogon Rationis: Baumgarten, Deleuze and the ‘Becoming Girl’ of Philosophy
Authors: Haferkamp Leyla
Published: March 2010

Baumgarten's Enlightenment Aesthetica provides an important philosophical analogon to Deleuze's alignment of the ‘logic of sense’ and the ‘logic of sensation’. By linking serious reason with its ‘other’, frivolous feeling, the book greatly influenced Herder and the Romantic movement. Baumgarten called aesthetics ‘logic's younger sister’. Like Deleuze he propagates nothing less than the ‘becoming-girl’ of philosophy.
Sense, Being and the Revelatory Event: Deleuze and Metamorphosis
Authors: Hertz-Ohmes Peter
Published: March 2010

Metamorphosis is a sudden change, a ‘becoming-other’ in life or in philosophical perspective. A revelatory event initiates in a double manner the move from Heidegger's futile search for a transcendental IT that delivers perceptible beings to the confident positing of Deleuze's transcendental empiricism, suffused with the IF of incorporeal sense. In the process Deleuze dramatically enacts his personal connection between sense (Sinn) and being (Sein).
Back to Life: Deleuze, Whitehead and Process
Authors: Robinson Keith
Published: March 2010

In this paper I argue that Deleuze's ‘thinking with’ Whitehead gives access to a range of novel conceptual resources that offer a route out of phenomenology and back to life, a movement beyond intentionality and back to things ‘in their free and wild state’. I lay out four conceptual and methodological markers (there are many more) – creativity, event, prehension, empiricism – that characterise Deleuze's metaphysics and provide a guide for showing how these develop through a sustained becoming with Whitehead. I conclude by looking at Deleuze and Guattari's use of the term most famously associated with Whitehead: the concept of ‘process’.
Alcoholism and Alternative Splicing of Candidate Genes
Authors: Sasabe Toshikazu , Ishiura Shoichi
Published: March 2010

Gene expression studies have shown that expression patterns of several genes have changed during the development of alcoholism. Gene expression is regulated not only at the level of transcription but also through alternative splicing of pre-mRNA. In this review, we discuss some of the evidence suggesting that alternative splicing of candidate genes such as DRD2 (encoding dopamine D2 receptor) may form the basis of the mechanisms underlying the pathophysiology of alcoholism. These reports suggest that aberrant expression of splice variants affects alcohol sensitivities, and alcohol consumption also regulates alternative splicing. Thus, investigations of alternative splicing are essential for understanding the molecular events underlying the development of alcoholism.
Implementation of a 3D Coupled Hydrodynamic and Contaminant Fate Model for PCDD/Fs in Thau Lagoon (France): The Importance of Atmospheric Sources of Contamination
Authors: Dueri Sibylle , Marinov Dimitar , Fiandrino Annie , Tronczyński Jacek , Zaldívar José-Manuel
Published: March 2010

A 3D hydrodynamic and contaminant fate model was implemented for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in Thau lagoon. The hydrodynamic model was tested against temperature and salinity measurements, while the contaminant fate model was assessed against available data collected at different stations inside the lagoon. The model results allow an assessment of the spatial and temporal variability of the distribution of contaminants in the lagoon, the seasonality of loads and the role of atmospheric deposition for the input of PCDD/Fs. The outcome suggests that air is an important source of PCDD/Fs for this ecosystem, therefore the monitoring of air pollution is very appropriate for assessing the inputs of these contaminants. These results call for the development of integrated environmental protection policies.
2-Methyl-7-(phenylsulfanylmethyl)naphthalene
Authors: Bogdanov Jane , Maslak Przemyslaw
Published: March 2010

A new sulfide, 2-methyl-7-(phenylsulfanylmethyl)naphthalene was synthesized and its MS, IR, 1H NMR, 13C NMR and DEPT-135 data are reported.
Magnetic Biotransport: Analysis and Applications
Authors: Furlani Edward P.
Published: March 2010

Magnetic particles are finding increasing use in bioapplications, especially as carrier particles to transport biomaterials such as proteins, enzymes, nucleic acids and whole cells etc. Magnetic particles can be prepared with biofunctional coatings to target and label a specific biomaterial, and they enable controlled manipulation of a labeled biomaterial using an external magnetic field. In this review, we discuss the use of magnetic nanoparticles as transport agents in various bioapplications. We provide an overview of the properties of magnetic nanoparticles and their functionalization for bioapplications. We discuss the basic physics and equations governing the transport of magnetic particles at the micro- and nanoscale. We present two different transport models: a classical Newtonian model for predicting the motion of individual particles, and a drift-diffusion model for predicting the behavior of a concentration of nanoparticles that takes into account Brownian motion. We review specific magnetic biotransport applications including bioseparation, drug delivery and magnetofection. We demonstrate the transport models via application to these processes.
Teratogenic Effects of Diatom Metabolites on Sea Urchin Paracentrotus lividus Embryos
Authors: Romano Giovanna , Miralto Antonio , Ianora Adrianna
Published: March 2010

The diatom-derived polyunsaturated aldehydes (PUAs), 2-trans,4-trans-decadienal, 2-trans,4-trans-octadienal, 2-trans,4-trans,7-octatrienal, 2-trans,4-trans-heptadienal, as well as tridecanal were tested on early and later larval development in the sea urchin Paracentrotus lividus. We also tested the effect of some of the more abundant diatom polyunsaturated fatty acids (PUFAs) on development, in particular 5,8,11,14,17-eicosapentaenoic acid (EPA), one of the main precursors of diatom PUAs, as well as 4,7,10,13,16,19-docosahexaenoic acid (DHA), 6,9,12,15-octadecatetraenoic acid (stearidonic acid), 6,9,12-octadecatrienoic acid (γ-linolenic acid) and 9,12-octadecadienoic acid (linoleic acid). PUAs blocked sea urchin cell cleavage in a dose dependent manner and with increasing chain length from C7 to C10 PUAs, with arrest occurring at 27.27 µM with heptadienal, 16.13 µM with octadienal, 11.47 µM with octatrienal and 5.26 mM with decadienal. Of the PUFAs tested, only EPA and stearidonic acid blocked cleavage, but at much higher concentrations compared to PUAs (331 μM for EPA and 181 μM for stearidonic acid). Sub-lethal concentrations of decadienal (1.32–5.26 μM) delayed development of embryos and larvae which showed various degrees of malformations depending on the concentrations tested. Sub-lethal concentrations also increased the proportion of TUNEL-positive cells indicating imminent death in embryos and larvae. Using decadienal as a model PUA, we show that this aldehyde can be detected spectrophotometrically for up to 14 days in f/2 medium.
The Heck Reaction in Ionic Liquids: Progress and Challenges
Authors: Bellina Fabio , Chiappe Cinzia
Published: March 2010

As the interest for environmental increases and environmental laws become more stringent, the need to replace existing processes with new more sustainable technologies becomes a primary objective. The use of ionic liquids to replace organic solvents in metal catalyzed reactions has recently gained much attention and great progress has been accomplished in this area in the last years. This paper reviews the recent developments in the application of ionic liquids and related systems (supported ionic liquids, ionic polymers, and so on) in the Heck reaction. Merits and achievements of ionic liquids were analyzed and discussed considering the possibility of increasing the effectiveness of industrial processes.
Synthesis of Dihydrouracils Spiro-Fused to Pyrrolidines: Druglike Molecules Based on the 2-Arylethyl Amine Scaffold
Authors: Blanco-Ania Daniel , Valderas-Cortina Carolina , Hermkens Pedro H.H. , Sliedregt Leo A.J.M. , Scheeren Hans W. , Rutjes Floris P.J.T.
Published: March 2010

The synthesis of a small library of dihydrouracils spiro-fused to pyrrolidines is described. These compounds are synthesized from b-aryl pyrrolidines, providing products with the 2-arylethyl amine moiety, a structural feature often encountered in compounds active in the central nervous system. The b-aryl pyrrolidines are synthesized through a three-step methodology that includes a Knoevenagel condensation reaction, a 1,3-dipolar cycloaddition reaction, and a nitrile reduction.
Implementation and Evaluation of the WADGPS System in the Taipei Flight Information Region
Authors: Jan Shau-Shiun , Lu Shih-Chieh
Published: March 2010

This paper describes the implementation of the Wide Area Differential Global Positioning System (WADGPS) system in order to evaluate the operational performance of a satellite based aviation navigation system within Taipei Flight Information Region (FIR). The main objective of the WADGPS is to provide real time integrity information regarding the use of GPS for civil aviation applications. This paper uses the e-GPS observation stations operated by the Taiwan Ministry of Interior (MOI) as the WADGPS reference stations to collect the L1-L2 dual-frequency GPS measurements. A WADGPS master station is also implemented to process all GPS measurements sent from each reference station, and then generate the vector corrections. These vector corrections consist of the satellite ephemeris and clock errors, and a grid of ionospheric delays. The data stream also includes confidence bounds for the corrections and “Use/Do Not Use” messages to provide integrity. These messages are then passed to the WADGPS user through the Internet. This paper discusses the WADGPS system architecture and the system performance analysis. A five-day operation performance in Taipei Flight Information Region (FIR) is presented in this paper. The results show that the WADGPS can improve the accuracy performance of GPS positioning and fulfill the integrity performance required by Non-Precision Approach (NPA) defined by the International Civil Aviation Organization (ICAO).
Data Centric Storage Technologies: Analysis and Enhancement
Authors: Rumín Ángel Cuevas , Pascual Manuel Urueña , Ortega Ricardo Romeral , López David Larrabeiti
Published: March 2010

This paper surveys the most relevant works of Data Centric Storage (DCS) for Wireless Sensor Networks. DCS is a research area that covers data dissemination and storage inside an ad-hoc sensor network. In addition, we present a Quadratic Adaptive Replication (QAR) scheme for DCS, which is a more adaptive multi-replication DCS system and outperforms previous proposals in the literature by reducing the overall network traffic that has a direct impact on energy consumption. Finally, we discuss the open research challenges for DCS.
HIV-1 Ribonuclease H: Structure, Catalytic Mechanism and Inhibitors
Authors: Beilhartz Greg L. , Götte Matthias
Published: March 2010

Since the human immunodeficiency virus (HIV) was discovered as the etiological agent of acquired immunodeficiency syndrome (AIDS), it has encouraged much research into antiviral compounds. The reverse transcriptase (RT) of HIV has been a main target for antiviral drugs. However, all drugs developed so far inhibit the polymerase function of the enzyme, while none of the approved antiviral agents inhibit specifically the necessary ribonuclease H (RNase H) function of RT. This review provides a background on structure-function relationships of HIV-1 RNase H, as well as an outline of current attempts to develop novel, potent chemotherapeutics against a difficult drug target.
SUBCONTRACTOR SELECTION PRACTICES IN INTERNATIONAL CONSTRUCTION PROJECTS
Authors: Ulubeyli Serdar , Manisali Ekrem , Kazaz Aynur
Published: March 2010

This paper presents a study of subcontractor selection practices of Turkish contractors in international projects. The results highlight the current subcontracting practices of main contracting firms that have resulted in a long‐lasting market share abroad. Toward this aim, a detailed questionnaire was administered to 96 construction companies. Turkish and host countries’ subcontractors were shown to be frequently employed in international projects. However, subcontracting firms from other countries were found to not be used. Main contracting companies generally select subcontractors in the periods after the main tender or after the project's start. Although many of them often work with previously known subcontracting companies and do not take into account the lowest bid price as the primary criterion, systematic processes or models are not used to select the best subcontractor. Most importantly, main contractors not only use subcontractors but also carry out activities using their in‐house resources. Hence, this study will not only be a step for further works that can be performed by potential researchers who may find interesting similarities or differences between their countries and Turkey, but also assist contractors who plan to strengthen their positions and to increase work opportunities in the international market. Santrauka Straipsnyje pateikiami Turkijos generaliniu rangovu praktiniai subrangovu parinkimo tyrimai, vykdant tarptautinius pro‐jektus. Akcentuojama dabartine generalinio rangovo imoniu subrangos praktika, kuri sudaro ilgalaike ir plačia rinkos dali. Šiam tikslui buvo išsamiai apklausta iki 96 statybos imoniu. Turkijos ir kitu vadovaujančiaja pozicija užimančiu šaliu subrangovai teige, kad dažnai dirba su tarptautiniais projektais. Tačiau kitu šaliu subrangos imones nedalyvauja toje veik‐loje. Generalines rangovo imones paprastai pasirenka subrangovus pateikus pagrindini pasiūlyma arba projekto pradžioje. Nors daugelis iš ju dažnai dirba su jau anksčiau žinomomis subrangos imonemis ir pasirinkdamos geriausia subrangova neatsižvelgia i pagrindini rodikli‐ žemiausia siūloma kaina, nenaudoja sisteminiu procesu ar modeliu. Svarbiausia, kad generaliniai rangovai naudojasi ne tik subrangovu paslaugomis, bet ir vykdo veikla, naudodamiesi ju turimais vidaus ištekliais. Taigi šis tyrimas bus ne tik potencialiu tyreju žingsnis igyvendinti ir rasti idomiu panašumu bei skirtumu tarp šiu šaliu ir Turkijos, bet ir padeti rangovams stiprinti savo pozicijas bei didinti isidarbinimo galimybes tarptautineje rin‐koje.
NFLUENCE OF QUALITY PERFORMANCE ON CLIENTS’ PATRONAGE OF INDIGENOUS AND EXPATRIATE CONSTRUCTION CONTRACTORS IN NIGERIA
Authors: Idoro Godwin Iroroakpo
Published: March 2010

Contractors operating in Nigeria are classified as either indigenous or expatriates. The latter is often giving preference over the former in the award of contracts and stakeholders consider this practice unhealthy for growth and development. This study evaluates the influence of the quality performance of the two categories of contractors on their patronage. The objectives are to determine the level and difference in the patronage and quality performance of indigenous and expatriate contractors and the correlation between clients’ assessment of the quality performance and patronage of indigenous and expatriate contractors in the Nigerian construction industry. To achieve these objectives, a field survey involving a sample of 43 clients selected from the population of organised clients in Nigeria was conducted. Structured questionnaires were used to collect data. The data collected were analysed to determine the ranking and test of difference in clients’ patronage and clients’ assessment of quality performance between the two categories of contractors using mean and t‐test respectively. The correlation between patronage and quality performance was analysed using Spearman correlation test. The study established that expatriate contractors are being giving preference in the award of contracts. It also established that clients perceive the quality performance of expatriate contractors to be better than that of indigenous contractors and attributed the preference in patronage to this difference. It suggested that indigenous contractors should embark on measures that will improve their quality performance in order to stop the preference for expatriate contractors. Santrauka Nigerijoje dirbantys rangovai klasifikuojami i vietinius ir emigravusius. Sudarant sutartis pastariesiems paprastai suteikiama pirmenybe. Tačiau laikoma, kad tokia praktika nera palanki augimui ir pletrai. Šiame tyrime vertinama abieju kategoriju rangovu darbo kokybes itaka klientams. Tikslas ‐ nustatyti vietiniu ir emigravusiu rangovu darbo kokybes lygi, kokybes skirtumus bei koreliacija tarp klientu ivertintos vietiniu ir emigravusiu rangovu, dirbančiu Nigerijos statybos pramoneje, kokybes. Šiam tikslui pasiekti atliktas tyrimas, apimantis 43 klientus, atrinktus iš Nigerijos klientu aibes. Duomenims rinkti naudoti klausimynai. Surinkti duomenys buvo analizuoti naudojant vidurkio ir t testo metodus, norint nustatyti reitingus bei patikrinti kokybes skirtumus tarp dvieju kategoriju rangovu. Koreliacija analizuota taikant Spir‐meno koreliacijos testa. Tyrimo metu nustatyta, kad konkursu metu pirmenybM suteikiama emigravusiems rangovams. Taip pat nustatyta klientus pastebint, jog emigravusiu rangovu darbo kokybe yra geresne nei vietiniu rangovu. Siūloma, kad vietiniai rangovai turetu atsižvelgti ityrimo rezultatus, ir tai galetu padeti gerinti ju darbu kokybe bei sumažinti emi‐gravusiu rangovu pranašuma.
CUSTOMER BEHAVIOR AND DECISION MAKING IN THE REFURBISHMENT INDUSTRY‐A DATA MINING APPROACH
Authors: Huang Chung-Fah , Hsueh Sung-Lin
Published: March 2010

The study of consumer behavior in the refurbishment industry is crucial to the business operation of firms, but there is a lack of research in this regard. With reference to the EKB model specific to consumer behavior, this paper discusses the relationship among consumption characteristics, firm selection behavior and satisfaction degree of refurbishment customers. 242 valid questionnaire copies were collected from refurbishment customers, and analyzed using Decision Tree Analysis and Association Rules in Data Mining. The research results show that, over half of the customers tend to entrust the refurbishment to well‐reputed firms. Moreover, the integrity of refurbishment equipment, response of refurbishment personnel, professionalism and confidence are key elements in service quality (SQ). The best marketing policy for the customers is one which provides more attractive services. These research findings may provide a useful reference for innovative refurbishment firms in their decision‐making. Santrauka Vartotoju elgsena, tiriant atnaujinima, yra labai svarbi verslo imoniu veiklai, tačiau stinga šiuo klausimu atliktu tyrimu. Remiantis EKB (Engel‐Kollat‐Blackwell) konkrečiu vartotoju elgsenos modeliu, straipsnyje aptariami ryšiai tarp vartojimo charakteristiku, imones pasirinkimo elgsenos ir atnaujinimo vartotoju ivertinimo laipsnio. Surinktos 242 galiojančios atsinaujinančiu vartotoju apklausos, kurios buvo nagrinejamos taikant sprendimu priemimo medi ir ryšiu taisykles gaunant duomenis. Tyrimu rezultatai rodo, kad daugiau kaip puse vartotojuyra linke patiketi atnaujinima žinomoms imonems. Dar daugiau, pagrindiniai elementai, užtikrinantys paslaugu kokybe (PK) ir atnaujinimo vientisuma, yra atnaujinančio personalo reakcija, jo profesionalumas ir pasitikejimas juo. Geriausia vartotoju rinkodaros politika ta, kuri suteikia daugiau patraukliu paslaugu. Šiu tyrimu rezultatai gali suteikti naudingos informacijos novatoriškoms atnaujinimo imonems ir ju sprendimams.
DESIGN OF PEOPLE EVACUATION FROM ROOMS AND BUILDINGS
Authors: Papinigis Vytautas , Geda Edgaras , Lukošius Kęstutis
Published: March 2010

There is a fire hazard in many civil buildings or engineering structures. Analysis of people evacuation time from the room or building is an important part of the designing process. Nevertheless, analysis of human behaviour in fire conditions is very complicated. Various factors should be evaluated, physical and even psychical, influencing safe evacuation of people from buildings. The analytical and calculating methods created are intended for analysis of people evacuation in fire conditions. Unfortunately, use of complicated calculations for determination of people evacuation requires too many resources; therefore, their application is limited. The calculation method for people evacuation presented in this paper is based on dependencies of the physical characteristics of people stream (density, intensity, movement speed) on people movement manner. The time required to evacuate people from people gathering room and building is determined in the numerical illustration of the method application. The article presents the comparison of simple calculation method and modeling with FDS+Evac software results of time for safe evacuation of people from rooms and buildings. Santrauka Daugelyje civiliniu pastatu ar inžineriniu statiniu kyla gaisro rizikos pavojus. Žmoniu evakuacijos laiko iš patalpos ar statinio analize yra svarbi projektavimo dalis. Tačiau žmoniu elgsenos gaisro salygomis analize yra labai sudetinga. Ivairūs fizikiniai ir netgi psichologiniai veiksniai, darantys itaka saugiai žmoniu evakuacijai iš statiniu, turi būti ivertinti. Išrasti analitiniai ir skaičiuojamieji metodai, skirti žmoniu evakuacijai gaisro salygomis analizuoti. Deja, sudetingu skaičiavimu metodu taikymas žmoniu evakuacijai nustatyti reikalauja pernelyg daug ištekliu, todel ju taikymas yra ribotas. Šiame straipsnyje pateikiamas žmoniu evakuacijos skaičiavimo metodas, paremtas fizikinemis žmoniu srauto charakteristikomis (tankiu, intensyvumu, judejimo greičiu), priklausomai nuo žmoniu judejimo būdo. Palyginti aprašyto ir sudetingojo žmoniu evakuacijos skaičiavimo metodu, naudojant FDS+Evac programine iranga, rezultatai.
NON-LINEAR ANALYSIS OF SUSPENSION BRIDGES WITH FLEXIBLE AND RIGID CABLES
Authors: Juozapaitis Algirdas , Idnurm Siim , Kaklauskas Gintaris , Idnurm Juhan , Gribniak Viktor
Published: March 2010

One of the main problems related to the design of suspension bridges is stabilisation of their initial form. The tendency of suspension bridges to deform is generally determined by the kinematical displacements of the suspension cable caused by asymmetrical loads rather than by the elastic deformations. There are some suspension bridges when the so‐called rigid (stiff in bending) cables instead of usual flexible cables are suggested for stabilisation of their initial form. The analysis methods of such suspension bridges with rigid cables are underdeveloped. For the analysis of classical suspension bridges analytical models can be applied. However, in case of concentrated forces, the numerical techniques are preferred. The article presents analytical expressions for the calculation of internal forces and displacements of suspension bridges with a rigid cable. The article also discusses the discrete calculation model for classical suspension bridges. Santrauka Viena iš pagrindiniu kabamuju tiltu projektavimo problemu yra pradinus ju formos stabilizavimas. Kabamuju tiltu deformatyvuma lemia iš esmes ne tiek tampriosios deformacijos, kiek asimetriniu apkrovu sukelti kinematiniai kabamojo lyno poslinkiai. Yra žinomi kabamieji tiltai, kuriu pradinei formai stabilizuoti siūloma vietoje iprastiniu lanksčiuju lynu taikyti vadinamuosius standžius lynus. Tokiu kabamuju tiltu su standžiaislynais skaičiavimo metodai nera iki galo parengti. Klasikiniams tiltams su lanksčiu lynu skaičiuoti taikomi daugiausia kontinualūs modeliai, kurie esant tam tikrai tilto sandarai ar veikiant sutelktoms apkrovoms nera pakankamai tikslūs. Straipsnyje pateikiamos analizines išraiškos kabamuju tiltu su standžiu lynu iražoms ir poslinkiams apskaičiuoti, aptariamas diskretusis klasikiniu kabamuju tiltu skaičiavimo modelis.