bluuebunny/crossref_metadata_2025 huggingface dataset:
Managed Pressure Drilling Applications Proves Successful in the Middle East and North Africa Region
Authors: Arnone M. , Vieira P. , Torres F. , Qutob H. , Babajan S.
Published: December 2009

There is no doubt that Managed Pressure Drilling (MPD) technology will to be applied in the near future as the conventional practice to drill what is today defined as undrillable, hazardous and expensive wells. The several analyzed cases, applications and results obtained in the Middle East and North Africa region clearly leads to this conclusion.

Managed Pressure Drilling, from the core concept point of view, is a collection of drilling optimization techniques that when correctly designed, planned and applied will improve the overall drilling performance, mitigate risks and reduce operating costs by proactively managing the hydraulic pressure profile and solving the problems associated with high Non Productive Time (NPT) commonly experienced with conventional drilling practices. This simple concept is what promotes this technology to be the new standard and conventional drilling practice in the near future.

From the technical point of view, IADC defines MPD as an adaptive drilling process used to precisely control the annular pressure profile throughout the drilled wellbore. The objectives are to ascertain the downhole pressure environment limits and to manage the annular hydraulic pressure profile accordingly, avoiding continuous influx of formation fluids to the surface. Any influx will be early detected, managed and safely contained. MPD may include semi-automatic or full automatic control of annular backpressure, fluid density, fluid rheology, annular fluid level, circulating friction, hole geometry or combination thereof. MPD represents the ability to dynamically control annular pressures, optimizing the drilling process facilitating what might otherwise be economically unattainable prospects.

This paper summarizes the process used to visualize the ideal prospects, the conceptual development including re-engineering planning and design phases, the process to implement the technology and the results obtained, lessons learned and the range of opportunities this technology has created in the Middle East and North Africa region from year 2007 to early 2009.
Improving Operations Through Increased Accuracy of Production Data
Authors: Wising U. , Kalitventzeff P.-B. , Campan J. , Vrielynck B.
Published: December 2009

Production Engineers have more and more information available and operating companies are trying to integrate that information and create an "integrated oil-field" with the main objectives of maximizing production and at the same time maximize recovery. One of the challenges in these types of approaches is the quality of production data. By not having accurate enough production data, the integration efforts are covered in a layer of haze, uncertainties. By combining advanced data validation and data reconciliation techniques it is possible to improve the quality of production data and quantifying all flows, temperatures, pressures and compositions throughout the production network.

This technology has been applied in the downstream area for years and are now more and more being deployed in oil and gas production. The main goal is to provide accurate flow of oil, gas and water in each production well, but it can and has been applied to water injection systems, gas fuel and flare systems, FPSO's etc.

It has been shown that it is possible to provide accurate production data in a production network. In particular, it has been shown that even on wells that do not have multi phase flow meters, it is possible to determine the flow of oil, gas and water with an uncertainty of less than 10%. In addition it provides other types of virtual meters, in general a production network with x measurement, would have another 2*x measurements validated and reconciled. Also by comparing measured data with validated and reconciled data it is possible to draw some conclusions; for example sensors and equipment that need maintenance can be identified much earlier and maintenance can move towards conditioned based, predictive maintenance.

This is a digital technology that can help operators have a better understanding of how their assets are performing and can help in increasing recovery from each well in the production network. Injection schemes can be performed more optimally and capacity from a field can be expanded in a cost effective way.
Formation Testing, Completion Integrity Evaluation and Geomechanical Applications Using a Wireline Cased-Hole Formation Tester
Authors: Ardila Mario , Achourov Vladislav , Gisolf Adriaan , Williams Stephen
Published: December 2009

Wireline formation testing is traditionally carried out in open-hole wells. Advances in formation tester technology have provided the industry with a new modular cased-hole formation tester (CHFT). In this new design a hole is drilled through the casing and cement, communication with the formation is then established enabling formation testing and sampling. The drilled hole is subsequently plugged.

This paper describes several case-studies from the North Sea where a full range of formation testing applications (that would traditionally be performed in open-hole) were made in casing using a cased-hole formation tester. In addition to pressure testing and sampling, three recent case studies demonstrate advanced applications.

The first example demonstrates zonal isolation behind casing and identifies communication between layers under injection. The reservoir consisted of two layers with significant permeability contrast. The CHFT was set at the bottom of the higher permeability zone and a hole was drilled thought the casing and annulus. The pressure was monitored while seawater was injected at increasing pressure steps into the lower permeabily zone. By analyzing the pressure response the degree of zonal communication and the maximum injection-rate were obtained.

In the second example, the CHFT was used to determine whether production wells could be drilled safely, and to evaluate bypassed reservoir layers. A very deep and deviated injection well completed and perforated over a long interval was tested with a CHFT deployed by tractor. Formation testing results provided a formation pressure profile in un-developed zones and showed that the injected interval was over-pressured and above the maximum safe pressure for drilling operations.

The final case study described in this paper shows an application of the CHFT for shale integrity testing. A poor cementing operation potentially left a production well without zonal isolation. The overburden shales are weak and prone to collapse. If the quality of the seal provided by the collapsed shale is tested for integrity and can be qualified as a barrier providing zonal isolation, the operator could avoid the expense of drilling a side-track. Two effective-stress testing cycles were made with the CHFT, which confirmed the integrity of the shale barrier, and quantified the minimum horizontal stress.
Deep Offshore Fracture Pressure Prediction in the Niger Delta - A New Approach
Authors: Ajienka Joseph , Egbon Franck , Onwuemena Uchechukwu
Published: December 2009

Drilling in deepwater is becoming more and more expensive. There is need to know before hand, for well planning purposes, the values of the fracture pressure. The Fracture pressure could be determined by predictive or verificative methods. Many correlations exists that can be used to predict the fracture pressure. However, they are mostly limited to onshore and shallow water fields. There is therefore the need to develop correlations that can reliably predict the fracture pressure for deep water fields.

This paper explores the concept of developing and possibly modifying some existing correlations to suit deep offshore needs as well as develop an Excel Spreadsheet and a V-Basic program that can be used to predict fracture pressure for deep offshore fields both in the Niger Delta region and the Gulf of Mexico. Furthermore, the predicted fracture gradient (LOT) values yielded by the various correlations were compared with actual LOT from a particular deep offshore field in the Niger Delta and the results analyzed.

The results of the analysis showed that some of the correlations studied, especially Matthew & Kelly, can be used to reliably predict the facture gradient for deep offshore fields.
Understanding Dynamic Simulation Results
Authors: Obidike Peter
Published: December 2009

Reservoir engineering tools applied in development planning or operations support ranges from material balance calculations to simulation studies. The results from a full 3D complex reservoir simulation study comprise a large amount of data. To better appreciate the result of the calculations, simulation packages make use of various visualization tools such as 2D plots or 3D displays. Properties such as water cut and sweep arrays can be visualized with the 2D or 3D displays respectively. These plots enable an understanding of the result of a reservoir simulation run. In some cases the results are easy to understand and appreciate, for example increasing well count you may likely recover more oil. In some other cases surprises may be resolved by investigating the underlying principles of fluid flow through the grid blocks. Because of the complexity of some reservoir models, a systematic approach may be necessary to understand what is going on in the system.

Developing these interpretation skills require hands-on assignment of reservoir simulation problems and coaching by more experienced reservoir engineers. Some cases that give insight to strategies in understanding the simulation output and making good engineering decisions are discussed in this paper.
First-Pass Screening of Reservoirs with Large Gas Caps for Oil Rim Development
Authors: Olamigoke Olugbenga , Peacock Anthony
Published: December 2009

Many gas reservoirs critical to providing a reliable supply of gas to the Nigeria Gas market have observed or potential oil rims where only a gas-down-to (GDT) has been logged. Development of these oil rims must be considered as part of the overall hydrocarbon maturation plans for the reservoir. Maturation studies of this type can take a long time and may lead to restrictions on the availability (quantity and timing) of the gas volumes to the market. This poses a serious challenge to maintaining gas supply and meeting contractual obligations.

Field performance of selected oil rim reservoirs in the Niger Delta have been analysed and presented in this work. The main factors that influence oil rim performance are highlighted and oil recovery trends have been established.

In addition, a generic simulation model has also been developed to analyse oil rim dynamics and assess the impact on oil and gas recovery for a range of sub-surface uncertainties. A range of alternate development strategies has been considered. Experimental design was used to obtain oil recovery correlations for each development strategy which has proven to be a useful first pass screening tool to make assessments of the likely oil recovery range from a specific oil rim reservoir. The oil recovery trends obtained from the simulation study have been found to be consistent with actual oil rim performance.

The result of this work is therefore useful for quick screening of oil rims for technical and economic feasibility to support key business decisions before embarking on costly detailed studies, if eventually required, subject to the complexity of the situation and decision required.
Maximising Production in Non-Mandrel Wells by the Insert Orifice Case Specific Design Approach - Case Histories
Authors: Afolabi Folorunso , Olayemi Sarah , Avre Paul , Iwuh Virgil , Iwuogu Augustine , Ekong Inem , Dennar Linda
Published: December 2009

Shell Petroleum Dev. Coy. onshore wells in Nigeria are from brown fields producing since 1960. The fields have about 300 flowing strings. The fields are characterized by various challenges including depleted reservoir pressures, some non-mandrel wells, single and dual string completion with or without sand control, old tubulars and low remaining oil reserves. The crude is medium to high API gravity, all ranges of viscosity and produced with high water cut in some cases.

These wells completed without mandrels were either not flowing because of one or a combination of 1) formation damage problems 2) vertical lift problems due to depleted reservoir pressures and increasing water cut and 3) high pressure drop across flow lines in wells far from the flow stations. Distance becomes a significant factor especially with remote manifold wells that also suffer high backpressures from healthy common manifold wells. The predominant damage mechanisms in these wells are fines migration, clay swelling, wettability changes, water block, inorganic and organic scale deposition.

Restoring the productivity of non-mandrel wells with vertical lift problems or insufficient energy to reach flow stations with the aid of artificial lift methods (gaslift being the most accessible and cheapest option) in these fields would normally require a workover rig. Wells were worked over and re-completed with gaslift mandrels when significant reserves still existed. An expensive uneconomical option in these brown fields with dwindling reserves. The alternative, which is the rimless pack-off mandrel or insert orifice, has not only been found economical but also a technically less risky and skilful approach to introduce gaslift assistance. At the onset of the introduction of the insert orifice technology in the fields, engineers were faced with the challenge of determining the best position in the tubing for inserting the gas lift orifice in order to maximize reserves recovery. Using the poor boy approach of creating an inlet for gaslift into the production tubing easily became a short term and un-sustained success.

The case specific insert orifice design was applied in old non-mandrel wells with single and dual string completions, with or with sand control in depleted reservoirs and with low remaining oil reserves. The results so far have been 100 percent success in production increase and reserves addition. 11 strings have been successfully put on gaslift using the case specific design insert orifice method. These wells have delivered over 3.3MMstb of oil at a low average Unit Technical Cost of ca. 0.8$/bbl. The approach has saved the company the high cost of workover operations that would otherwise have been required, increased ultimate recovery and also improved the insert orifice gas lift design in general.
One year monitoring of norovirus in a sewage treatment plant in Rio de Janeiro, Brazil
Authors: Victoria Matías , Guimarães Flávia Ramos , Fumian Tulio Machado , Ferreira Fabiana Fioretti Martins , Vieira Carmen Baur , Shubo Tatsuo , Leite José Paulo Gagliardi , Miagostovich Marize Pereira
Published: December 2009

Norovirus (NoV) is one of the most important aetiological agents of acute gastroenteritis both in developed and developing countries. NoV is shed in high concentrations by infected persons and contaminates recreational and drinking water through sewage discharge into the environment. The aim of this study was to determine the prevalence, genotypes and removal ratio of NoV by PCR, seminested-PCR and quantitative PCR (qPCR) assays in a sewage treatment plant in Rio de Janeiro city, Brazil, during one year of surveillance. NoV was detected in 7 (15%), 14 (29%) and 28 (58%) samples using PCR, seminested-PCR and qPCR, respectively. The mean removal ratio for the activated sludge process was 0.6 log10 for NoV genogroup I (GI) and 0.32 log10 for NoV genogroup II (GII). The peak NoV concentration was detected in the coldest months, with 53,300 genomic copies/litre. Nucleotide sequencing and phylogenetic analysis revealed that five strains clustered with GI strains and six with GII strains. This study demonstrates that NoV spreads into the environment despite the sewage treatment process and remains a source of waterborne outbreaks of acute gastroenteritis.
Effect of environmental factors on the fecundity, hatchability and survival of snail Lymnaea (Radix) acuminata (Lamarck): vector of fascioliasis
Authors: Jigyasu Harsh Vardhan , Singh Vinay Kumar
Published: December 2009

Lymnaea acuminata breeds round the year. The effect of pH, temperature, dissolved oxygen, carbon dioxide, light/dark period and clean/polluted water on the fecundity, hatchability and survival of young snails of L. acuminata were studied. It was observed that these environmental variant abiotic factors caused a significant variation in fecundity, hatchability and survival of young snails. Maximum reproduction of this snail was observed in the months of March to May. A significant positive correlation (p<0.05) between D.O. (3.1–7.7 ppm)/pH (7.01–8.96) of water with fecundity (6.0–196.33/20 snails), hatchability (54.69–96.91%) and survival (61.3–95.86%) of young snails was observed for each month and each interval of 24–72 h. In contrast, a significant negative correlation between dissolved CO2 (4.6–16.6 ppm)/temperature (16–37°C) of water was noted with fecundity, hatchability and survival of snails. Percent hatchability in the eggs in different regimens of water was between 96.91–54.69%. The hatching period was prolonged (2–14 days) in snail exposed to different groups of water compared to the control group (2–9 d). This study conclusively shows that variant abiotic factors in different months of the year can significantly alter the reproductive ability and development process in the snail Lymnaea acuminata.
The association of drinking water quality and sewage disposal with Helicobacter pylori incidence in infants: the potential role of water-borne transmission
Authors: Travis Penny B. , Goodman Karen J. , O'Rourke Kathleen M. , Groves Frank D. , Sinha Debajyoti , Nicholas Joyce S. , VanDerslice Jim , Lackland Daniel , Mena Kristina D.
Published: December 2009

The mode of transmission of Helicobacter pylori, a bacterium causing gastric cancer and peptic ulcer disease, is unknown although waterborne transmission is a likely pathway. This study investigated the hypothesis that access to treated water and a sanitary sewerage system reduces the H. pylori incidence rate, using data from 472 participants in a cohort study that followed children in Juarez, Mexico, and El Paso, Texas, from April 1998, with caretaker interviews and the urea breath test for detecting H. pylori infection at target intervals of six months from birth through 24 months of age. The unadjusted hazard ratio comparing bottled/vending machine water to a municipal water supply was 0.71 (95% confidence interval (CI): 0.50, 1.01) and comparing a municipal sewer connection to a septic tank or cesspool, 0.85 (95% CI: 0.60, 1.20). After adjustment for maternal education and country, the hazard ratios decreased slightly to 0.70 (95% confidence interval: 0.49, 1.00) and 0.77 (95% confidence interval: 0.50, 1.21), respectively. These results provide moderate support for potential waterborne transmission of H. pylori.
Simultaneous determination of 42 organic chemicals in bottled water by combining C18 extraction disk with GC-MS and LC/MS/MS technique
Authors: Jin Bao-hui , Xiao Feng , Chen Bo , Chen Pei-jin , Xie Li-qi
Published: December 2009

A method for the determination of 42 hazard residues required by ‘Japan Positive List System’ in bottled water was described. Hazard compounds in bottled water were extracted with a solid phase extraction step using C18 disks. Determination was carried out by gas chromatography/mass spectrometry (GC/MS) and liquid chromatography-tandem mass spectrometry (LC/MS/MS). The disk extraction has high throughput which is well adapted to isolate and enrich these compounds from large volumes of water. For the water sample spiked at three concentration levels (LOQ, 4 times LOQ and 8 times LOQ), the recoveries of all analytes ranged between 65% and 120% with a relative standard deviation < 24% (n=8).
Modelling latrine diffusion in Benin: towards a community typology of demand for improved sanitation in developing countries
Authors: Jenkins Marion W. , Cairncross Sandy
Published: December 2009

Latrine diffusion patterns across 502 villages in Benin, West Africa, were analysed to explore factors driving initial and increasing levels of household adoption in low-coverage rural areas of sub-Saharan Africa. Variables explaining adoption related to population density, size, infrastructure/services, non-agricultural occupations, road and urban proximity, and the nearby latrine adoption rate, capturing differences in the physical and social environment, lifestyles and latrine exposure involved in stimulating status/prestige and well-being reasons for latrine adoption. Contagion was most important in explaining adoption initiation. Cluster analysis revealed four distinct village typologies of demand for latrines which provide a framework for tailoring promotional interventions to better match the different sanitation demand characteristics of communities in scaling-up sanitation development and promotion programmes.
Applicability of quantitative PCR for determination of removal efficacy of enteric viruses and Cryptosporidium by water treatment processes
Authors: Ryu Hodon , Mayer Brooke , Abbaszadegan Morteza
Published: December 2009

This study aims to assess the applicability of quantitative PCR (qPCR) for removal studies of adenovirus, coxsackievirus, echovirus and Cryptosporidium by water treatment processes. Bench-scale coagulation jar tests were performed using the enteric viruses and Cryptosporidium. Standard methods (conventional cell-culture methods for the viruses and an immunofluorescence assay (IFA) for Cryptosporidium) were used to compare to qPCR. A significant correlation between microbial removals determined by qPCR and the standard detection methods and an approximate 1:1 correlation were observed for the challenge microorganisms. The results indicated that qPCR could be a satisfactory alternate for microbial removal studies using a relative quantification approach.
Are the defined substrate-based methods adequate to determine the microbiological quality of natural recreational waters?
Authors: Valente Marta Sofia , Pedro Paulo , Alonso M. Carmen , Borrego Juan J. , Dionísio Lídia
Published: December 2009

Monitoring the microbiological quality of water used for recreational activities is very important to human public health. Although the sanitary quality of recreational marine waters could be evaluated by standard methods, they are time-consuming and need confirmation. For these reasons, faster and more sensitive methods, such as the defined substrate-based technology, have been developed. In the present work, we have compared the standard method of membrane filtration using Tergitol-TTC agar for total coliforms and Escherichia coli, and Slanetz and Bartley agar for enterococci, and the IDEXX defined substrate technology for these faecal pollution indicators to determine the microbiological quality of natural recreational waters. ISO 17994:2004 standard was used to compare these methods. The IDEXX for total coliforms and E. coli, Colilert®, showed higher values than those obtained by the standard method. Enterolert® test, for the enumeration of enterococci, showed lower values when compared with the standard method. It may be concluded that more studies to evaluate the precision and accuracy of the rapid tests are required in order to apply them for routine monitoring of marine and freshwater recreational bathing areas. The main advantages of these methods are that they are more specific, feasible and simpler than the standard methodology.
Pressure sensor distribution for leak detection in Barcelona water distribution network
Authors: Pérez R. , Puig V. , Pascual J. , Peralta A. , Landeros E. , Jordanas Ll.
Published: December 2009

This paper proposes a leakage detection method based on detecting significant discrepancies between pressure measurements and their estimations obtained from the simulation of a calibrated water distribution network model. Every sensor in the network will allow to detect a discrepancy in pressure due to leakage depending on its location. Then, a set of well distributed pressure sensors will generate a leakage signature that allows leakage localisation. This paper presents the methodology used in the Barcelona network for distributing properly the sensors for a good discrimination in the leakage localisation process. The methodology for sensor placement uses the pressure sensitivity matrix to the leakage presence. This matrix is normalised and binarised in order to be used as a leakage signature matrix using the standard model based fault diagnosis approach. Sensors may be installed in any node and leakages are simulated as a constant demand that can appear in any node too. The problem of deciding which are the best localisations for a small number of sensors in order to detect and localise leakages is an inverse problem that should be solved using optimisation. The resulting optimisation problem is of discrete nature and very huge for a real network. This type of problem is, in general, hard to solve and very time consuming. The use of GA (Genetic Algorithms) has been proved adequate according to the formulation of the signatures in the sensitivity matrix.
Performance of new generation membrane distillation membranes
Authors: Zhang Jianhua , Duke Mikel , Ostarcevic Eddy , Dow Noel , Gray Stephen , Li Jun-de
Published: December 2009

Membrane distillation has been a known desalination process for many years, but its commercial implementation has been hampered by low water fluxes and the need for low cost heat sources. With greater emphasis being placed on energy efficiency, membrane distillation coupled with waste heat or solar heat sources to drive the process is being reconsidered. In particular, the use of membrane distillation to treat brine concentrates is receiving renewed attention, as it results in increased water recovery and lower brine discharges, and high salt concentrations do not increase the driving force requirements for membrane distillation. In this paper, four different membranes, one made of polyvinylidenefluoride (PVDF) and three made of polytetrafluoroethylene (PTFE) of different pore sizes, were assessed the performance in membrane distillation under different hot feed flow rates and inlet temperatures. The results show that the PTFE membranes had a much higher flux than that of PVDF at the same operational conditions, and PTFE membranes of large pore size produced higher flux than that of the small pore size. The results also showed that increasing the flow rate of the hot feed and its inlet temperature increased the flux, but the rates of increase decreased with increasing flow rate and inlet feed temperature.
Residential water demand in a transition economy: evidence from Poland
Authors: Bartczak Anna , Kopanska Agnieszka , Raczka Jan
Published: December 2009

This paper analyzes residential water demand in Poland and the determinants thereof, including both water tariffs and income levels. Information on the price and income elasticities of residential water demand is crucial for effective management of water demand. We carried out this empirical analysis using several panel-data models. The analysis is based on data provided by the urban municipalities, in which the number of the end-users connected to water supply networks exceeded 50,000. We focused on the larger cities to obtain sample homogeneity in terms of the access to water supply and sewage collection systems, as well as the income structure. We found that the indicators of price elasticity of residential water demand in Poland are similar to those being known from the relevant surveys conducted in Western Europe. However, the income elasticity is smaller in absolute terms when compared to that in countries with more developed economies. Based on the results obtained, our prediction is that the decreasing trend of individual water consumption in Poland will slow down in the next few years. Our study is one of the first to investigate the price and income elasticities of water demand in Poland, and also one of the first such ones carried out for economies in transition.
Improving water management efficiency by using optimization-based control strategies: the Barcelona case study
Authors: Ocampo-Martinez C. , Puig V. , Cembrano G. , Creus R. , Minoves M.
Published: December 2009

This paper describes the application of model-based predictive control (MPC) techniques to the flow management in large-scale drinking water networks including a telemetry/telecontrol system. MPC technique is used to generate flow control strategies from the sources to the consumer areas to meet future demands, optimizing performance indexes associated to operational goals such as economic cost, network safety volumes and flow control stability. The designed management strategies are applied to a real case study based on a representative model of the drinking water network of Barcelona (Spain).
The impact of Moringa oleifera as a coagulant aid on the removal of trihalomethane (THM) precursors and iron from drinking water
Authors: Kalibbala H. M. , Wahlberg O. , Hawumba T. J.
Published: December 2009

Chlorine is used as a disinfectant and an oxidant in drinking water treatment to protect the public health from pathogenic microorganisms. However, if applied to raw water with humic materials, it leads to the formation of halogenated organic compounds that are a potentially serious environmental and health problem. This renders pre-chlorination of raw waters to oxidise iron inappropriate. Coagulation, the principal treatment process for removal of THM precursors, is therefore essential for chlorination by-product control. In this study, the impact of pre-chlorination and the performance of Moringa oleifera as a coagulant aid at Masaka waterworks were assessed. An average increase of trihalomethanes of over 4,000% at aeration and pre-chlorination stage was observed at the plant. From the jar tests, alum with Moringa oleifera reduced dissolved organic concentration by 47.1%. The treated water after sedimentation tasted salty but after filtration and chlorination, the salty taste disappeared. Residual iron values of 1.38 mg/L and 3.05 mg/L were achieved with MOC-SC as coagulant aid and alum alone respectively. The jar test results indicated that use of alum with Moringa oleifera as coagulant aid is promising as a first stage in the treatment train for waters with humic materials and high content of iron.
Oxidation and immobilization of iron and manganese by a fluidized bed reactor
Authors: Huang Yao-Hui , Huang Chun-Ping , Lu Yu-Wen , Lo Chun-Yu
Published: December 2009

An iron and manganese species immobilization technology was developed in a fluidized bed reactor (FBR) with a new fluidized media, immobilized iron oxide (namely FeOx-30). The FeOx-30 catalyst exhibited excellent performance as a catalyst for the oxidation of Mn2 + . About 95% and 30% of the manganese species were immobilized on FeOx-30 and silica sand in FBR, respectively. The oxidation rates of Fe2 +  and Mn2 +  and the immobilization efficiencies of iron and manganese oxides strongly depend on pH value. Usually during oxidization the pH values of the solution containing Fe2 +  must be above 7, and Mn2 +  must be above 9. During this study, large amounts of iron species leached from the surface of FeOx-30 only when manganese was in the system. The surface of the FeOx-30 became fragile in a single system. However, the removal of iron and manganese species simultaneously was better than only the removal of manganese in an FBR. In the binary system, the optimum pH condition for immobilization of both iron and manganese species was pHi 9. The higher catalyst loading in the binary system led to a higher removal efficiency of iron and manganese.
Velocity-based self-cleaning residential drinking water distribution systems
Authors: Vreeburg J. H. G. , Blokker E. J. M , Horst P. , van Dijk J. C.
Published: December 2009

Resuspension of accumulated particles in residential networks is the main cause for customers to complain to the water company about the water quality. Preventing the particles from accumulating in these networks can be achieved by high velocities in pipes. Adding this velocity criterion to the conventional design criteria leads to a branched lay out of distribution networks, that perform better with respect to water quality, continuity of supply and investment costs. In close cooperation with fire brigades the conventional fire flow requirements were challenged. Based on modern building codes, it proved possible to reduce the capacity of fire-hydrants to 8.3 l/s (30 m3/h) in newly built areas. Six years after the introduction of the velocity criterion the characteristics of the newly laid networks have changed resulting in smaller diameter pipes and reduced length of networks. The amount of 100/110 mm pipes have dropped from 55% of the total length to 45% of total length. The total investment costs for new networks have dropped by 20% in the Netherlands.
Persistent organic pollutants (POPs) degradation in natural waters using a V-UV/UV/TiO2 reactor
Authors: Azrague K. , Osterhus S. W.
Published: December 2009

This paper presents the use of a V-UV/UV/TiO2 reactor (M300 water purifier®) for the removal of sulfamethoxazole and atrazine from natural water. The efficiency of the different processes (photolysis, Vacuum UV (V-UV) and photocatalysis) within the photoreactor was investigated using para-chlorobenzoic acid (pCBA) which is a good probe for hydroxyl radicals. The effect of pH, dissolved organic carbon (DOC) and total inorganic carbon (TIC) was also studied. V-UV was found to be the most efficient process for pCBA degradation within this unit. No photocatalytic degradation was observed. The water quality largely affected the efficiency of the system. Indeed, both DOC and TIC lowered the hydroxyl radical concentration in the system, but DOC did it to a larger extent. Atrazine and sulfamethoxazole, were successfully degraded, and as for pCBA, V-UV was the most efficient process. Sulfamethoxazole displayed a better removal by photocatalysis than atrazine and pCBA. In addition, there was a larger contribution of photolysis during the degradation of sulfamethoxazole than of atrazine. The UV254 nm absorbance of the water affected the photolysis of sulfamethoxazole which has a high molar extinction coefficient and quantum yield at 254 nm, while the DOC is mainly competing with the pollutants for the hydroxyl radicals.
The analysis of influential factors on the frequency of pipeline failures
Authors: Iličić K.
Published: December 2009

The aim of this paper is to research into the interactions of factors influencing the frequency of pipeline failures and to determine their impacts. The research was carried out on a representative part of the water supply system of Zagreb, the capital of Croatia, i.e. on a District Metered Area (DMA), using the log-linear analysis of frequency tables. The first influential factor that was analyzed was the condition of pressure regulation. The DMA was observed in the period when the system was not in the condition of pressure regulation (January 2005–March 2006) and in the period when the system was in the condition of pressure regulation (March 2006–September 2008). Other influential factors that were included into the analysis were the diameter, the material and the age of pipes. In addition to the main goal established in this general way, a specific goal related to the condition of regulation in interaction with remaining influential factors was also set. Using the log-linear analysis, general results about the influence of the interaction between observed factors were obtained. The specific goal was reached by conclusions made about the effect of the relation between the DMA condition of regulation and remaining influential factors, i.e. diameter, material and age of pipes on the frequency of pipeline failures.
The Credibility Imperative: The Political Dynamics of Retaliation in the World Trade Organization's Dispute Resolution Mechanism
Authors: Nzelibe Jide
Published: December 2009

Under the WTO’s dispute settlement procedures, a party that has been injured by a scofflaw state’s failure to comply with its trade obligations may retaliate against the scofflaw state by withdrawing equivalent trade concessions. Legal and economic commentators generally view retaliation as an economically perverse strategy for enforcing freetrade norms. This Article explores an alternative explanation, arguing that retaliation may provide the optimal enforcement mechanism for trade liberalization given the prevalence of low compliance incentives and high enforcement costs in international cooperation agreements. The Article argues that retaliation is superior to other remedial options because it enables an injured state to inflict maximum political costs on the scofflaw state by mobilizing powerful export groups in the scofflaw state against protectionist policies. Furthermore, this Article shows how the presence of significant protectionist groups in the injured state, which stand to benefit from retaliatory measures, also improves the injured state’s ability to commit to retaliation. Even if states have asymmetric preferences about protectionist policies, retaliation threats can still be credible since there is uncertainty about each state’s retaliation costs. Finally, the Article concludes that contrary to the conventional wisdom, the substantial role of uncertainty in this model indicates that specific performance, and not compensation, ought to be the goal of the WTO’s enforcement mechanism.
How Property Can Create, Maintain, or Destroy Community
Authors: Lehavi Amnon
Published: December 2009

Property law plays a crucial role in the ability of groups, especially ones composed of geographically-adjacent members, to establish and maintain significant forms of "community" around a shared social, economic, or ideological interest. Property may also, however, have the opposite effect of undermining or even destroying communities, particularly those that rely on fragile modes of cooperation. This Article identifies three major types of territorial communities: (1) Intentional Communities—close-knit groups that initially organize around a consolidating non-instrumental idea (such as cooperative Kibbutzim or religious communes) and employ sweeping internal norms to validate their communality. (2) Planned Communities — comprised mostly of residential developments of homeowners associations, which rely on a formal set of conditions, covenants, and restrictions incorporated in the association’s governing documents. (3) Spontaneous Communities — clusters of initially unorganized neighbors who succeed in cooperating and coordinating over time. The evolvement of such organizations may be essential to the creation of an interpersonal "social capital" and to a physical and functional improvement of the community’s surroundings. For each one of these types of communities, property law plays a very different role. Thus, while Intentional Communities do not strictly hinge upon the existence of a supportive property system to flourish, Planned Communities cannot be conceived without the security of an overt, formal, state-backed regime, and Spontaneous Communities may often need property law’s affirmative backing (providing what I term "Property Tailwind") to thrive and enjoy the social and economic benefits of sustainable collective action.
Corneal Molecular and Cellular Biology Update for the Refractive Surgeon
Authors: Salomao Marcella Q. , Wilson Steven E.
Published: December 2009

Purpose:

To review clinically relevant progress in understanding cellular and molecular interactions in the cornea that relate to refractive surgical outcomes in patients.

Methods:

Recent published literature focused on femtosecond LASIK and surface ablation procedures, such as photorefractive keratectomy, was reviewed and correlated with clinical results of surgery.

Results:

The femtosecond laser has a direct necrotic effect on stromal keratocytes, resulting in the release of cellular components that are chemotactic to bone marrow–derived inflammatory cells. Developments of the femtosecond laser led to lower energy delivery to the stroma and altered laser ablation profiles that decrease epithelial damage during the side-cut, and have markedly improved femtosecond LASIK to the point that the overall early postoperative healing response is indistinguishable from microkeratome LASIK. New studies have directly demonstrated the importance of surface irregularity and resulting structural and functional defects in the epithelial basement membrane, in the generation and persistence of anterior stromal myofibroblasts and haze following surface ablation procedures. These defects augment penetration of epithelium-derived TGF-β, which is a critical modulator of myofibroblast development in the stroma. Studies on the mechanism of action of mitomycin C treatment to prevent haze have confirmed that the most powerful effect is on stromal cell proliferation and, therefore, decreased population of the anterior stroma with myofibroblast progenitor cells. An undesirable long-term effect of mitomycin C is diminished anterior stromal keratocyte density due to diminished keratocyte re-population. This raises concerns regarding future corneal anomalies in treated corneas.

Conclusions:

Basic research studies of refractive procedures provide important insights into the effects of wound healing on surgical outcomes. [J Refract Surg.2009;25:459–466.]
Optical Performance in ReZoom and Array Multifocal Intraocular Lenses In Vitro
Authors: Kawamorita Takushi , Uozato Hiroshi , Aizawa Daisuke , Kamiya Kazutaka , Shimizu Kimiya
Published: December 2009

Purpose:

To investigate the modulation transfer function (MTF) of two refractive multifocal intraocular lenses (IOLs).

Methods:

The ReZoom and Array (AMO) multifocal IOLs were evaluated using the OPAL Vector system (Image Science Ltd) and a model eye with a variable aperture (2.1 to 5.5 mm). Modulation transfer functions were evaluated at distant, near, and intermediate (−1.50 diopter defocus) focus lengths.

Results:

The ReZoom IOL distant focus MTF for a 5.1-mm effective diameter was higher than that of the Array IOL. At intermediate distance, the ReZoom lens showed a slight increase compared with the Array. The near focus MTF for the ReZoom IOL began to increase at an effective diameter of 2.1 mm and remained constant for diameters >3.45 mm.

Conclusions:

The ReZoom IOL gave better image quality than the Array, particularly at distant focus. To enhance near vision with the ReZoom lens, the desirable real pupil diameter should be at least 3.45 mm. [
J Refract Surg.
2009;25:467–469.]
Wavefront-guided Photorefractive Keratectomy After Radial Keratotomy in Nine Eyes
Authors: Myrowitz Elliott H. , Kurwa Ambereen , Parker Jack , Chuck Roy S.
Published: December 2009

Purpose:

To investigate the refractive outcomes of wavefront-guided photorefractive keratectomy (PRK) in patients with previous radial keratotomy (RK).

Methods:

This study is a retrospective review of consecutive cases from August 2004 until February 2007 of PRK after RK. The VISX STAR S4 excimer laser was used. Visual acuity, manifest refraction, and slit-lamp microscopy were reviewed preoperatively and 3 and 12 months postoperatively.

Results:

Nine eyes, five hyperopic and four myopic, of six consecutively treated patients were evaluated. Myopic spherical equivalent refractive treatments averaged −2.08 diopters (D) (range: −0.80 to −3.36 D) and hyperopic treatments averaged +2.20 D (range: +1.28 to +3.12 D). No eyes lost any lines of Snellen best spectacle-corrected visual acuity (BSCVA) and three (33%) eyes gained one line of BSCVA. Two (22%) eyes showed grade 0.5 level haze (not in the visual axis) and the remaining seven eyes showed no haze. Seven (77%) of nine eyes were within ±0.25 D of the targeted spherical equivalent refraction at 3 months postoperative. Six (66%) of nine eyes had ⩾±0.50 D (range: +0.50 to +2.25) of astigmatism prior to PRK and all astigmatic errors were significantly reduced, with the highest residual astigmatic error of 0.75 D in one eye and 0.50 D in two eyes.

Conclusions:

Wavefront-guided PRK after RK for myopic, hyperopic, and astigmatic refractive errors targeting emmetropia in six eyes and myopia in three eyes yielded accurate refractive outcomes in this consecutive series. Three (33%) of nine eyes gained one line of BSCVA with no eyes losing BSCVA. Seven of nine eyes were within ±0.25 D of targeted spherical equivalent refraction at 3 months postoperative. [
J Refract Surg
. 2009;25:470–472.]
Problemas asociados al equilibrio en estructuras de membrana con bordes rígidos
Authors: Viglialoro G. , Murcia J. , Martínez F.
Published: December 2009

Este trabajo aborda el análisis del equilibrio de una membrana con borde rígido. La idea de utilizar las membranas en aplicaciones tales como las pasarelas, una nueva tecnología que se está desarrollando en España, requiere un análisis estructural muy ajustado. Debido a los esfuerzos de tracción, la membrana se identifi ca a una superficie con curvatura de Gauss negativa. De esta forma, el equilibrio se expresa directamente por medio de ecuaciones diferenciales en derivadas parciales, en términos de la forma de la membrana y del tensor de esfuerzos. A partir de dichas ecuaciones, se pueden considerar dos enfoques complementarios, aquí llamados problema directo y problema dual. Se analizan ambos problemas, estudiando sus posibles soluciones con el objetivo de obtener resultados prácticos. En particular, se profundizan los principales aspectos analíticos del problema directo, se propone un método numérico para la resolución y, fi nalmente, se presentan ejemplos de solución analítica y numérica.
Diagnóstico y análisis de estructuras de madera mediante técnicas no destructivas: aplicación a la Plaza Mayor de Chinchón (Madrid)
Authors: Basterra L. A. , Acuña L. , Casado M. , Ramón-Cueto G. , López G.
Published: December 2009

Este artículo muestra los trabajos de inspección, diagnóstico y propuesta de intervención sobre la estructura de madera vista de la plaza Mayor de Chinchón (Madrid). Se emplearon técnicas de reconocimiento visual y otras de tipo no destructivo y pseudo-no destructivo como la microfotografía, xilohigrometría, medición de la velocidad de ultrasonidos, arranque de tornillos y resistografía. Los trabajos permitieron identificar la especie leñosa original, caracterizar la madera estructural, señalar los daños y lesiones de diverso tipo que presenta y, finalmente, realizar una peritación estructural. Todo ello sirvió de base para establecer una propuesta de intervención basada en los datos obtenidos y los principios generales internacionalmente reconocidos, aplicados al caso particular. Aunque el estado general de la madera es relativamente bueno gracias a actuaciones realizadas anteriormente, se propusieron sugerencias de intervención constructiva y tratamientos contra daños bióticos y abióticos. Ha sido realizado por el Grupo de Investigación en Estructuras y Tecnología de la Madera de la Universidad de Valladolid (http://www.uva.es/maderas), que está integrado por profesionales e investigadores multidisciplinares, con experiencia en los campos de la construcción y restauración arquitectónica y la tecnología de la madera.