bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Calcium and Iron (II) Ions on the Precipitation of Calcium Carbonate and Ferrous Carbonate
Authors: Alsaiari H.A.. A. , Kan A.. , Tomson M.B.. B.
Published: March 2010

This work was intended to study the interaction between ferrous-iron and calcium ions simultaneously toward carbonate ions in supersaturated solution in a continuous stirred tank reactor (CSTR) and to establish an acceptable experimental design as a preparation step to study the kinetics of other types of ferrous iron salts. The experiments were conducted in 0.5 M NaCl solution at 55°C. The pH values were between 6.2 and 7.8. It was found that calcium ions have a strong influence in increasing the solubility of iron carbonate. On the other hand, ferrous iron did not affect the solubility of calcium carbonate significantly. This might be caused by increasing the stability of ferrous iron carbonate complexes in the presence of calcium. Also, the molar ratios of calcium to iron in the solution were compared with their molar ratios in the precipitated salts. It was found that the relation was greater than unity; Rsolid/Rsolution = 2.39. Thus, calcium carbonate has a preference to precipitate. This result seems to be in agreement with water dissolution rates of divalent ions and also with reaction-rate constants of iron carbonate and calcium carbonate reported in the literature.
A Successful Application of Fiber-Optic-Enabled Coiled Tubing With Distributed-Temperature Sensing Along With Pressures To Diagnose Production Decline in an Offshore Oil Well
Authors: Parta P.E.. E. , Parapat A.. , Burgos R.. , Christian J.. , Jamaluddin A.. , Rae G.. , Foo S.K.. K. , Ghani J.. , Musa M..
Published: March 2010

In this paper, we present a field example where pressure and distributed-temperature measurements enabled understanding of reservoir characteristics and fluid movement causing production hindrance in an offshore horizontal well. The field example has a horizontal well in the South China Sea that was completed as an openhole monobore oil producer using a slotted liner. The well began production with an initial oil rate of 1,800 B/D. Oil production quickly dropped to 1,000 B/D and gradually declined to 200 B/D. During this period, the gas/oil ratio (GOR) steadily increased from 200 scf/bbl to 2,200 scf/bbl. To arrest production decline, a chemical treatment was conducted to remove suspected emulsions and polymers assumed to have been deposited during drilling. Immediate post-treatment production increased to 3,700 B/D, but dropped dramatically and stabilized at pretreatment rates soon after. Formation of emulsions and asphaltenes were believed to be the cause of the production decline. However, with inadequate information, the diagnosis was inconclusive. Consequently, another chemical treatment was conducted and this time, a fiber-optic-enabled coiled-tubing (CT) string along with real-time bottomhole-pressure and temperature gauges were used to acquire distributed temperatures and pressures of the entire horizontal section of the wellbore.

Results of the pressure survey revealed that the well was receiving insufficient pressure support from the water injector, which was causing gas-cap expansion. The distributed-temperature survey indicated excessive gas production from the toe of the horizontal section as a result of this expansion, thus limiting liquid production. The combination of gas rates with oil and water production has also created tight emulsions, further hindering production performance. It was concluded that the high gas production from the toe could not be selectively shutoff or controlled in the horizontal openhole slotted-liner completion to perform an effective stimulation program and treat the tight viscous emulsions.
Polymer Flooding in Unconsolidated-Sand Formations: Fracturing and Geomechanical Considerations
Authors: Khodaverdian Mohamad , Sorop Tibi , Postif Sophie , Van den Hoek Paul
Published: March 2010

A study was carried out to determine the geomechanical effects of polymer flooding in an unconsolidated-sand reservoir. The work involved laboratory-scale polymer injections in unconsolidated- sand blocks to identify the injectivity mechanisms, numerical analyses for fracture prediction, and geomechanical modeling of the formation to examine the potential of shear failure and containment loss during flooding.

Laboratory tests under polyaxial conditions indicate that nearwellbore fracturing and permeability increase in unconsolidated sands occur at net injection pressures limited to 2.0 MPa. These findings were applied to fracture modeling. Geomechanical modeling suggests large-scale shear failure in the sand and in the bounding shale during polymer flooding. These are expected to affect both the fracture containment and the vertical-hole integrity. Finally, fracture predictions underscore the importance of the geomechanical considerations on determining the fracture dimensions and containment. Sensitivity analyses also point to the significance of binding several key parameters for fracture prediction. These include sand shale stress contrast, fluid quality and total-suspended-solids (TSS) content, fluid rheology and effective viscosity in the formation, and the filter-cake properties in the presence of polymer.

This paper provides a geomechanical perspective on the generally complex problem of polymer flooding in unconsolidated formations containing viscous oil. The work also offers some insights into the critical issues that must be examined in such situations to avoid catastrophic failures. It highlights the existing technological gaps in the current predictive capabilities.
Rapid Prediction of Carbon Dioxide Adsorption Isotherms for Molecular Sieves Using Simple Correlation
Authors: Bahadori Alireza , Vuthaluru Hari B.
Published: March 2010

Carbon dioxide (CO2) emission from burning fossil fuels has been identified as the major contributor to the increase in atmospheric CO2 levels that can potentially lead to global climate changes. Among main methods that are being developed for CO2 capture and separation (CCS), CO2 adsorption is of great interest because of its low energy consumption, low equipment cost, and ease of application. In this work, a new simple-to-use correlation, which is easier than current available models involving a large number of parameters and requiring more-complicated and longer computations, is presented to predict accurately the CO2 adsorption isotherms for a molecular sieve as a function of temperature and CO2 partial pressure. This correlation predicts the CO2 adsorzption isotherms for CO2 partial pressures and temperatures up to 120 kPa and 470 K, respectively. The promising method to develop correlation for accurate prediction of CO2 adsorption isotherms could be extended for CCS for the wide range of adsorbents, including various molecular sieves, simply by readjusting the tuned coefficients. The average absolute deviation between reported data and the proposed correlation is approximately 4%.
Retrofit Gas Lift System for Tension-Leg-Platform Wells
Authors: Babajide Abisoye , Hall Jim , Garrett Johnnie
Published: March 2010

When oil wells can no longer flow naturally at the desired rate, artificial-lift methods are often employed. Most mechanical installations of artificial-lift equipment require a complete workover of the well, involving pulling the well apart and rerunning the completion with additional artificial-lift components. These methods can prove prohibitively expensive and/or risky, and they may not pass the economic hurdle for implementation. A tubing punch and packoff gas lift system, also known as an "econo-gas lift" or retrofit gas lift system, may provide a less risky and more economically viable means of bringing dead wells back on production or optimizing flowing wells. To the best of our knowledge, the use of retrofit gas lift systems has been untested in a tension-leg-platform (TLP) environment and poses a new set of challenges as compared to its use onshore or in shallow-water locations. A case of the gas lift retrofit of an oil well on a TLP in the Gulf of Mexico (GOM) demonstrates the usefulness of the proposed method. This paper shows how a retrofit gas lift system was used for capturing remaining reserves from a loaded TLP well. The specific case relates to the Shell Ursa A9 well, and this paper presents the new technologies employed and the successes and challenges associated with bringing the well back on production.
Integrated Data Analysis and Dynamic Fracture Modeling Key To Understanding Complex Waterfloods: Case Study of the Pierce Field, North Sea
Authors: Hustedt B.. , Snippe J.R.. R.
Published: March 2010

The performance of many waterfloods [and enhanced-oil-recovery (EOR) schemes] is characterized by fluid injection under fracturing conditions. Especially when the geology is complex and the mobility of the reservoir is low, induced fractures can be of the same order as the well spacing, which has a significant (in general undesired) impact on both areal sweep and vertical conformance. Therefore, fluid injection needs to be actively managed and surveyed in order to design an appropriate injection strategy over time.

We have analyzed historical injection/production-test, injection step-rate-test, and falloff (FO) test (FOT) data of an existing complex waterflood in the Pierce field, North Sea. The mental subsurface model that emerged from this data analysis was developed further through a series of dynamic fracture-propagation simulations. While the data analysis was a relatively standard procedure, the fracture-modeling part was far from trivial and included simulations using a standalone fracture modeling tool and a more sophisticated coupled dynamic fracture-propagation reservoir simulator, both being in-house software tools.

The combined analysis was used to develop a better understanding of the waterflood performance. The main improvement compared to previous work was the integration of the data analysis and the dynamic modeling work rather than looking at each data source individually. In combination, a consistent explanation of the observed reservoir behavior was achieved. This has resulted in changes in the day-to-day water injection management and is expected to play a key role in longer-term development strategies
Understanding Volumetric Sweep Efficiency in SAGD Projects
Authors: Baker R. , Fong C. , Bowes C. , Toews M.
Published: March 2010

Abstract

An understanding of volumetric sweep and capture efficiency are critical to optimizing SAGD projects. Capture efficiency refers to how much mobilized and heated oil is actually produced. Volumetric sweep efficiency can be estimated reasonably well for SAGD pilots having an abundance of information. A rich data set may include geological, petrophysical, production, injection, pressure, temperature observation and 4D seismic data. With this information, excellent insight into steam chamber development can be assessed. However, determining volumetric sweep and op­timal strategies is a problem where data are sparse.

This paper summarizes analytical SAGD surveillance methods that estimate volumetric sweep and presents a work flow that can help optimize SAGD processes with limited data.

Although the methods each have their assumptions and are not perfect, there is general agreement. The various techniques are corroborated using public core, injection/production, temperature observation and 4D seismic for the Surmont and Christina Lake pilot projects.

Introduction

Evaluating reservoir performance through the surveillance of production data is an excellent reservoir management tool. For waterflooding, this can be achieved through a conformance plot(1) that indicates how efficiently net water throughput affects recovery. Associating a water balance with an oil balance enhances the understanding of the influx/efflux of fluids and outer boundary losses out of zones. The plot works well for waterfloods because of the low compressibility of the fluids. For SAGD, a similar surveillance principle using abundant data is applied. However, a material balance alone is not definitive because SAGD is an energy-intensive process where steam is required to reduce the oil viscosity to a point where it will flow. Therefore, accounting for the energy within the SAGD process provides a different perspective for multiple geologies and heterogeneities.

Typical objectives of SAGD surveillance using production and monitoring data are to determine:

Original oil in place (OOIP)

Remaining oil in place (ROIP)

Mobile ROIP distribution and current condition (saturation, temperature and pressure)

Limiting factors in recovery

Potential improvements to economic oil recovery

Recovery profile and optimizing recovery factor

Operating strategies to achieve better volumetric sweep
Role of Asphaltene Precipitation in VAPEX Process
Authors: Haghighat P. , Maini B.B.
Published: March 2010

Abstract

VAPEX (vapour extraction) is an oil recovery process, in which heavy oil or bitumen is mobilized by injection of a low molecular weight hydrocarbon solvent and is drained by gravity to a horizontal production well. It has attracted considerable attention because of its potential applicability to problematic reservoirs and the potential for in-situ upgrading of heavy oil during the process.

Oil drainage rate under VAPEX is controlled by the viscosity of solvent diluted oil and can be affected substantially by de-asphalting. In-situ de-asphalting can be advantageous because it reduces the oil viscosity and leads to production of upgraded oil. However, the precipitated asphaltenes can also plug the pores of the formation and cause severe damage to the permeability.

The objective of the current work was to determine whether the beneficial effects of asphaltene precipitation would outweigh any formation damage. The effects of in-situ precipitation and deposition of asphaltenes on the rate of oil drainage and the quality of the produced oil under different operating conditions were experimentally evaluated. The experiments were conducted in a physical model, packed with 140 - 200 mesh sand, and propane was used as the solvent. The quality of the produced oil samples was evaluated through the SARA technique and viscosity measurements.

The experimental results show that the oil produced at higher injection pressures was substantially upgraded, but the viscosity reduction by asphaltene precipitation did not lead to higher production rates. The effect of viscosity reduction was negated by the accompanying damage to formation permeability. The huff and puff injection of toluene into the production well, to remove damage from the near well zone, was tried but proved to be ineffective. It led to production of oil with higher asphaltene content with no improvement in the rate of oil production compared to the lower pressure operation without asphaltene precipitation. However, co-injection of toluene with propane was successful in increasing the rate of production and the extent of upgrading obtained was encouraging.
Experimental Investigations on the Flow Dynamics and Abandonment Pressure for CO2 Sequestration and Oil Recovery in Artificially Fractured Cores
Authors: Trivedi J.J. , Babadagli T.
Published: March 2010

Abstract

CO2 flooding in naturally fractured reservoirs is becoming increasingly more popular. The Midale Field is a good example of this phenomenon and has gained a great deal of interest, not only from enhanced oil recovery, but also from a CO2 sequestration point of view. To consider future opportunities for greenhouse sequestration in these types of reservoirs while improving oil recovery specifically in the Midale field, a series of experiments were performed.

The goal of this work was to study the effect of miscibility (miscible, immiscible and near-miscible regions) and injection rate on incremental oil recovery and sequestration during continuous injection in fractured porous media. Another important aspect considered was to analyze the effect of pressure drawdown or depletion on additional recovery with sequestration optimization. First, artificially fractured Berea sandstone samples were used. CO2 was injected at constant, slow rates into the fracture, while maintaining the high-pressure into the core and the system. At the end of the production life, the pressure into the system was released to different pressure steps and kept for a longer period of time at each of the reduced steps of pressure. In between two pressure steps, the system was shut down for enough time to observe the effect of CO2 and oil diffusion/back diffusion. After a series of Berea sandstone experiments, a few tests were conducted on the Midale cores, which were obtained from a good quality matrix part of the field. Injection and production data were collected using a continuous data logging system, an analysis of the produced liquids and measuring the gas production using a continuous flowmeter, which led to the understanding of the mechanism. The results showed that the pressure blowdown, followed by shut in after continuous injection, can increase oil recovery significantly until a certain critical pressure. Storage capacity of the rock with change in pressure and amount of oil recovered during blowdown period will lead to the critical understanding of abandonment pressure during the project life to achieve the goal of sequestration and recovery optimization.
Experimental Study of Solvent Flooding to Heavy Oil in Fractured Five-Spot Micro-Models: The Role of Fracture Geometrical Characteristics
Authors: Farzaneh S.A. , Kharrat R. , Ghazanfari M.H.
Published: March 2010

Abstract

The solvent-based process appears to be an increasingly feasible technology for the extraction of heavy oil reserves. However, there is a lack of fundamental understanding of how fracture geometrical characteristics control the oil recovery efficiency in this type of enhanced oil recovery (EOR) technique. In this work, a series of experiments were performed whereby the pure and mixed hydrocarbon solvents (HCS) displaced heavy oil in fractured five-spot glass micro-models. Successive images of the solvent injection process were recorded. The oil recovery factor, as a function of injected pore volume of solvents, was measured using image analysis of the provided pictures. It has been observed that the oil recovery decreased when the fractures' spacing, discontinuity, overlap, and distribution increased. In contrast, the oil recovery increased when the orientation angle, discontinuity-distribution and the number of fractures increased. Also, it has been found that there is an optimum solvent composition, which maximizes the oil recovery. Finally, some pore-level visualization representing the role of asphaltene precipitation during miscible injection was illustrated using these experiments. This study demonstrates the applicability of the micro-models for the fundamental studying of the solvent-based process in fractured five-spot systems, which are used to investigate the effect of fracture geometrical characteristics and their effect on oil recovery.

Introduction

Heavy oil and bitumen reserves represent a considerable portion of worldwide energy resources. It is estimated that these reservoirs contain six trillion barrels of oil originally in place (OOIP), which is much more than the total conventional oil reservoirs. Great consumption of light oil reserves and their resulting dramatic decline encourages more interest in exploitation of highly viscous oil and bitumen for future energy demands. For optimum conditions, the primary recovery of these reservoirs would not exceed 10% of the OOIP(1). A variety of thermal methods, including cyclic steam stimulation, in-situ combustion and steam assisted gravity drainage are currently being applied for extraction of these crudes. As far as the reservoir's oil is heated, the main fraction of thermal energy is used up in heating the formation itself. For the reservoirs with a thin pay zone, bottom water zone and/or overlying gas zone, excessive depths, low thermal conductivity of rock matrix, high water saturation, etc., the economical applicability of thermal methods is doubtful. With respect to current available recovery technologies, these reservoirs are categorized as problematic reservoirs(2,3).
Laboratory Studies of Producing Hydrogen and Incremental Oil From Light Oil Reservoirs Using Downhole Gasification
Authors: Greaves M. , Xia T.X.
Published: March 2010

Abstract

The idea of gasifying (reforming) a fraction of a light crude oil in the reservoir, was conceived originally by Davidson and Yule(1). This involved "stringing?? a series of downhole gasification (DHG) units along either a horizontal producer well or vertical producer well, or along some other suitable well arrangement.

Although catalytic steam reforming of naphtha practiced on a large scale has been extensively researched, such understanding is largely restricted to much lower pressures than those investigated in the present study. We present results obtained using a small, "pilot-scale?? DHG unit, or reforming reactor, operated at up to 100 bar pressure. The feed to this unit was a light naphtha fraction cut from Statfjord crude oil. The effect of pressure, catalyst loading, steam to hydrocarbon ratio and gasifier temperature were investigated.

Essentially, the conversion to inert gases, principally hydrogen and carbon dioxide, at high pressure was sufficiently high to make the process technically feasible in depleted light oil reservoirs. Furthermore, the economics of this novel enhanced oil recovery process, which also produces (and stores) hydrogen, appear to be very favourable. However, the experiments, which were conducted under pilot-scale conditions using a single-tube reactor unit, were not of sufficient duration time to test the long-term effects on catalyst activity owing to carbon fouling and sulphur poisoning. These factors (at least carbon deposition) can be controlled as demonstrated in the experiments by adjusting the steam-to-hydrocarbon ratio and the depth of naphtha-cut taken from the crude oil. These aspects of the process are to be further investigated in a Phase 2 project.

Introduction

Davidson and Yule(1) originally conceived the idea of a self-contained, downhole gasification (DHG) unit as a safer, "greener?? method for transporting oil out of environmentally sensitive areas, such as the Everglades, as gas. Subsequently, the focus was directed towards applying DHG in depleted light oil reservoirs. The inert gases generated by a downhole DHG unit(s) are directed into a gas cap, or used to create a gas cap (Figure 1). This would then allow gravity stabilized displacement (GSGI), WAG, or another assisted gas injection technique, to be implemented for the purpose of improved oil recovery. This is still a high priority, especially in such areas as the North Sea, and the many hundreds of depleted light oil fields in the US, where output continues to fall. The main IOR problem is the availability of a suitable gas to inject into the reservoir, especially offshore. Although the displacement dynamics are likely to be complex because of the hydrogen in the generated gas, it is estimated that valuable incremental oil can be gained using the DHG process.
Efficient Detection of Productive Intervals in Oil and Gas Reservoirs
Authors: Bouffin Nicolas , Jensen Jerry L.
Published: March 2010

The utility and evaluation of cutoff values for net pay or net-to-gross determination have been hotly debated topics since the 1950s. There are numerous subtleties to cutoffs, but exactly how the values are calculated has largely been overlooked. Most cutoff users have been content to use a regression line to calculate the cutoff value.

We show that cutoffs obtained using a regression line are likely to be inferior to estimates produced by other methods. When four methods were applied to two field datasets and compared, regression-based porosity cutoffs were between 1 and 2 pu different than the values that give the smallest number of errors. Monte Carlo simulations broadly support the results obtained from the datasets. One method, the "trial-and-error?? method, performed well through most of the tests, reducing errors by 40% from those obtained using the regression line-based cutoff.

All cutoff estimation methods have errors, caused by the imperfect relationships we have between variables, such as porosity and permeability. This study shows we have a choice of methods. Because the better method can be easily applied in spreadsheet software, this should be a valuable addition to the petrophysicist's toolbox.

Introduction

Net pay (NP) may be defined as any interval containing economically producible hydrocarbon using a specific production method. This represents the portion of the reservoir that contains sufficient porosity, permeability and hydrocarbons for economic exploitation. NP can be interpreted as an effective thickness that is pertinent to identification of flow units and target intervals for well completions and stimulation programs [Worthington and Cosen­tino(1)]. The associated net-to-gross ratio (NGR) corresponds to the proportion of the total or gross thickness, which is composed of net pay.

Numerous papers have reviewed and proposed methods for NP and NGR determination. Snyder(2) covers many of the methods in use up to the early 1970s, which used the self-potential (SP) or gamma ray (GR) logs and core analysis. More recent proposals include using capillary pressure [Vavra et al.(3)], probe permeameter measurements [Flølo et al.(4)] and percolation modelling [Li et al.(5)]. Of the large variety of possible methods, one approach is much more commonly discussed than any other. This method involves defining threshold values (or cutoffs) for the characteristics of interest and their surrogates. These limiting values are designed to define those rock intervals that show potential to contribute significantly to economic hydrocarbon production.
Durability of Oilwell Cement Formulations Aged in H2S-Containing Fluids
Authors: Lécolier E.. , Rivereau A.. , Ferrer N.. , Audibert A.. , Longaygue X..
Published: March 2010

In the next few decades, the production of oil fields with high contents of associated sour gases will increase. For instance, it is estimated that 40% of the world's remaining gas reserves contain more than 2% of carbon dioxide (CO2) and/or more than 100 ppm of hydrogen sulphide (H2S). Therefore, investigations on technologies to produce such fields are of utmost importance. Because of the presence of corrosive gas, special attention has to be paid to the design and the selection of materials (steel and cement) used for well construction. Corrosion of steel caused by acid-gas- containing brines is well documented in the literature, and to a lesser extent, data about the degradation by wet CO2 or wet H2S can be found. For cement-based materials, one can find abundant literature dealing with deterioration of cement pastes because of the CO2 environment. Published data on degradation mechanisms of cement-based materials exposed to H2S environments are more scarce. This paper addresses the problem of durability of oilwell cement in different H2S environments.

Different periods of time can be identified in the lifetime of the wells—the production period (typically between 20 and 40 years), the post-abandonment period (some tens of years following the permanent well abandonment), and the abandonment period (several centuries). For each period of time, cementing materials (primary cementing, plugs) are in contact with different types of fluids. Therefore, to correctly assess the behavior of oilwell cement, aging tests have to be carried out in fluids representative of these different periods of time. In this paper, we present both the methodology implemented under high-pressure/high-temperature conditions for testing materials in H2S-containing fluids and the results obtained on cement-based materials. Main physicochemical degradation mechanisms of cement-based materials caused by H2S are identified using various characterization techniques. Depending on the nature of the fluid in contact with cement materials, severe degradation can occur with a strong impairment of macroscopic properties.
A pilot study of anaerobic membrane digesters for concurrent thickening and digestion of waste activated sludge (WAS)
Authors: Dagnew Martha , Parker Wayne J. , Seto Peter
Published: March 2010

The increased interest in biomass energy provides incentive for the development of efficient and high throughput digesters such as anaerobic membrane bioreactors (AnMBRs) to stabilize waste activated sludge (WAS). This paper presents the results of a pilot and short term filtration study that was conducted to assess the performance of AnMBRs when treating WAS at a 15 day hydraulic retention time (HRT) and 30 day sludge retention time (SRT) in comparison to two conventional digesters running at 15 (BSR-15) and 30 days (BSR-30) HRT/SRT. At steady state, the AnMBR digester showed a slightly higher volatile solids (VS) destruction of 48% in comparison to 44% and 35.3% for BSR-30 and BSR-15, respectively. The corresponding values of specific methane production were 0.32, 0.28 and 0.21 m3 CH4/kg of VS fed. Stable membrane operation at an average flux of 40 ± 3.6 LM−2 H−1 (LMH) was observed when the digester was fed with a polymer-dosed thickened waste activated sludge (TWAS) and digester total suspended solids (TSS) concentrations were less than 15 gL−1. Above this solids concentration a flux decline to 24.1 ± 2.0 LM−2 H−1 was observed. Short term filtration tests conducted using sludge fractions of a 9.7 and 17.1 gL−1 TSS sludge indicated 84 and 70% decline in filtration performance to be associated with the supernatant fraction of the sludge. At a higher sludge concentration, the introduction of unique fouling control strategy to tubular membranes, a relaxed mode of operation (i.e. 5 minutes permeation and 1 minute relaxation by) significantly increased the flux from 23.8 ± 1.1 to 37.8 ± 2.3 LMH for a neutral membrane and from 25.7 ± 1.1 to 44.9 ± 2.9 LMH for a negatively charged membrane. The study clearly indicates that it is technically feasible to employ AnMBRs to achieve a substantial reduction in digester volumes.
Feasibility of bioflocculation in a high-loaded membrane bioreactor for improved energy recovery from sewage
Authors: Akanyeti Ime , Temmink Hardy , Remy Maxime , Zwijnenburg Arie
Published: March 2010

The feasibility of a high-loaded membrane bioreactor to improve methane recovery from sewage was investigated. Although the process needs further optimization, it already is feasible to recover at least 35% of the sewage COD. Important aspects for further research are the occurrence of membrane fouling, and the optimum process conditions for bioflocculation, i.e. the proper SRT/HRT ratio, dissolved oxygen concentration and shear and overall energy production and consumption under optimised conditions.
Application of library-independent microbial source tracking methods for identifying the sources of faecal contamination in coastal areas
Authors: Gourmelon M. , Caprais M. P. , Le Mennec C. , Mieszkin S. , Ponthoreau C. , Gendronneau M.
Published: March 2010

Faecal contamination sources were identified in coastal areas around the Guerande-Atlantique peninsula using two microbial source tracking (MST) methods: (i) Bacteroidales host-specific 16S rRNA gene markers measured by real-time PCR and (ii) F-specific bacteriophage (FRNAPH) genotyping. Both methods were used on 63 water samples from 7 water courses. HF183 marker and bacteriophage genogroup II (FRNAPH II) were detected in all water samples and in the majority of water samples, respectively, from La Torre stream (W5), Piriac (W2), R2000 (W3) and Mazy (W7) rain water drains, and also detected, less frequently, in Le Nau drain (W4), suggesting contamination by human faecal sources at these sites. These human markers were weakly detected in Pouliguen channel (W6). Furthermore, BacR and bacteriophage genogroup I (FRNAPH I) were also detected, but at lower concentration and frequency. So, site W6 seems to be contaminated by multiple sources, though mainly human. Finally, BacR was detected twice in Pont d'Armes channel (W1), whereas HF183 was not detected. FRNAPH I and II were detected in only 3 out of 12 water samples. Site W1 seems mainly contaminated by animal sources. As a result of our findings, actions were taken to remediate water and shellfish quality.
Emission standards versus immission standards for assessing the impact of urban drainage on ephemeral receiving water bodies
Authors: Freni Gabriele , Mannina Giorgio , Viviani Gaspare
Published: March 2010

In the past, emission standard indicators have been adopted by environmental regulation authorities in order to preserve the quality of a receiving water body. Such indicators are based on the frequency or magnitude of a polluted discharge that may be continuous or intermittent. In order to properly maintain the quality of receiving waters, the Water Framework Directive, following the basic ideas of British Urban Pollution Manual, has been established. The Directive has overtaken the emission-standard concept, substituting it with the stream-standard concept that fixes discharge limits for each polluting substance depending on the self-depurative characteristics of receiving waters. Stream-standard assessment requires the deployment of measurement campaigns that can be very expensive; furthermore, the measurement campaigns are usually not able to provide a link between the receiving water quality and the polluting sources. Therefore, it would be very useful to find a correlation between the quality status of the natural waters and the emission-based indicators. Thus, this study is aimed to finding a possible connection between the receiving water quality indicators drawn by environmental regulation authorities and emission-based indicators while considering both continuous (i.e. from the wastewater treatment plants) and intermittent pollution discharges (mainly from combined sewer overflows). Such research has been carried out by means of long-term analysis adopting a holistic modelling approach. The different parts of the integrated urban drainage system were modelled by a parsimonious integrated model. The analysis was applied to an ephemeral river bounding Bologna (Italy). The study concluded that the correlation between receiving water quality and polluting emissions cannot be generally stated. Nevertheless, specific analyses on polluting emissions were pointed out in the study highlighting cause—effect link between polluting sources and receiving water quality.
Wet hydrogen peroxide catalytic oxidation of phenol with FeAC (iron-embedded activated carbon) catalysts
Authors: Liou Rey-May , Chen Shih-Hsiung , Huang Cheng-Hsien , Hung Mu-Ya , Chang Jing-Song , Lai Cheng-Lee
Published: March 2010

This investigation aims at exploring the catalytic oxidation activity of iron-embedded activated carbon (FeAC) and the application for the degradation of phenol in the wet hydrogen peroxide catalytic oxidation (WHPCO). FeAC catalysts were prepared by pre-impregnating iron in coconut shell with various iron loadings in the range of 27.5 to 46.5% before they were activated. The FeAC catalysts were characterised by measuring their surface area, pore distribution, functional groups on the surface, and X-ray diffraction patterns. The effects of iron loading strongly inhibited the pore development of the catalyst but benefited the oxidation activity in WHPCO. It was found that the complete conversion of phenol was observed with all FeAC catalysts in oxidation. High level of chemical oxygen demand (COD) abatement can be achieved within the first 30 minutes of oxidation. The iron embedded in the activated carbon showed good performance in the degradation and mineralisation of phenol during the oxidation due to the active sites as iron oxides formed on the surface of the activated carbon. It was found that the embedding irons were presented in γ-Fe2O3, α-Fe2O3, and α-FeCOOH forms on the activated carbon. The aging tests on FeAC catalysts showed less activity loss, and less iron leaching was found after four oxidation runs.
Enhancement of Brønsted Acidity in Sulfate-Vanadium Treated Silica-Titania Aerogel as Oxidative-Acidic Bifunctional Catalyst
Authors: Lee Siew Ling , Wei Soo Chien , Nur Hadi , Hamdan Halimaton
Published: March 2010

Enhancement of Brønsted acidity in silica-titania aerogel was achieved by loading both sulfate and vanadium onto the material. This phenomena could be due to formation of V(OSi)2OH-O-SO3- in the resulted sample. In contrast, no noticeable Brønsted acidity was detected in vanadium loaded silica-titania aerogel (V/ST). UV-vis DR analysis results showed that the amount of hydrated tetrahedral titanium species, which acts as oxidative site, increased significantly upon sulfation and vanadium loading on the surface of the aerogel. However, presence of vanadium in the samples tended to transform framework tetrahedral titanium to extra framework octahedral titanium structure. The catalytic performance of the samples were evaluated in consecutive transformation of 1-octene to 1,2-octanediol through formation of 1,2-epoxyoctane using aqueous H2O2.
The Value of Layoffs and Labor Market Conditions as Signals of Worker Quality
Authors: Kosovich Stephen M
Published: March 2010

Empirical studies in the job displacement literature have found that workers face significant earnings losses on average when they are permanently displaced from jobs. Previous work also finds that the costliness of job loss varies widely and that some of this variation may result from the differences between layoffs and plant closings. Layoffs provide hiring firms worker specific information about productivity but plant closings do not. This paper extends the understanding of the costs of job loss by presenting a theoretical motivation that indicates that labor market conditions can influence the information contained in a layoff. The empirical results from the Displaced Worker Supplement support this model and suggest that when the local unemployment rate is high, less information is transmitted by a layoff concerning worker quality, for the sample of white-collar workers.
Contributions of Charles Townes’ research to nonlinear optics
Authors: Garmire Elsa
Published: March 2010

Nonlinear optics was profoundly influenced by early work of Charles Townes and his group at Massachusetts Institute of Technology from 1961 to 1967. His foundational contribution was the realization that coherent molecular oscillations resulted from stimulated Raman scattering, leading to the introduction of stimulated Brillouin scattering. Self-trapping of light beams and self-steeping of light pulses in nonlinear materials were two other important innovations. Some applications today of these early ideas are outlined.
Seam-tracking for high precision laser welding applications—Methods, restrictions and enhanced concepts
Authors: Regaard Boris , Kaierle Stefan , Poprawe Reinhart
Published: March 2010

Laser beam welding bears evident advantages regarding precision, quality, productivity, low heat input, and feasibility of automation. At the same time the process calls for high precision of the beam positioning on the workpiece, which therefore imposes high requirements of welding trajectory and feed rate accuracy; e.g., for butt welding the focal point of the laser beam with respect to the joint must be maintained within a typical accuracy better than 20–150 μm, depending on the focused beam radius. To meet these requirements, seam-tracking devices are used. A sensor measures the joint position and computes a correction vector to compensate the joint trajectory offset. The deviation is compensated either by a robot trajectory adjustment or by an additional tracking axis. This paper describes the basic concepts of seam tracking in detail and points out problems in the different control principles, which are evoked by the forerun of the sensor. State-of-the-art sensors and error compensating techniques are presented and analyzed. Further, a new approach for seam tracking is introduced. It uses a multisensor concept, which in addition to the seam position measures the relative displacement between the processing head and the workpiece. An integrated two-dimensional beam positioning system enables “self-guided” processing, which allows high-accuracy tracking of a joint independent of the motion system and disengages from time intensive sensor calibration and robot teaching necessity.
Spectroscopic characterization of halogen- and cyano-substituted pyridinevinylenes synthesized without catalyst or solvent
Authors: Percino M. , Chapela Víctor , Montiel Ling-Fa , Pérez-Gutiérrez Enrique , Maldonado José
Published: March 2010

An efficient Knoevenagel route using green chemistry conditions was applied for the synthesis of halogen- and cyano- substituted pyridinevinylene compounds. Absorption and fluorescence emission spectra of these conjugated compounds were recorded and compared in order to evaluate the effect of substituents on the electronic properties of pyridinevinylene compounds. The substituents studied were terminal Cl and F, two or three aromatic rings, as well as a cyano group attached to a C=C double bond. The compounds synthesized are: (E)-2-(4-fluorostyryl)pyridine, (E)-2-(4-chlorostyryl)pyridine, (E)-4-(4-chlorostyryl)pyridine, 2,3-diphenylacrylonitrile, 3-phenyl-2-(pyridin-2-yl)acrylonitrile, 3-phenyl-2-(pyridin-3-yl)acrylonitrile, 2-phenyl-3-(pyridin-2-yl)acrylonitrile, 3,3′-(1,4-phenylene)bis(2-phenylacrylonitrile), 3,3′-(1,4-phenylene)bis(2-(pyridin-2-yl)acrylonitrile), and 3,3′-(1,4-phenylene)bis(2-(pyridin-3-yl)acrylonitrile). The solvent-free method used in this work allows obtaining each compound by controlling the reaction temperature. The compounds were characterized by infrared spectroscopy and 1H-NMR spectroscopy.
Deposition and release of chlorhexidine from non-ionic and anionic polymer matrices
Authors: Musial Witold , Kokol Vanja , Voncina Bojana
Published: March 2010

Therapeutic activity of locally applied drugs depends on both the thermodynamic activity of the active molecule and the pharmaceutical system which enables the release of the molecule; also the vasoconstrictive activity of vessels plays an important role. In this study, the release of chlorhexidine was assessed considering the use of ionic and non-ionic polymeric carriers at temperatures in the range between 22°C and 42°C, including the temperature of 32°C as the reference surface body temperature. The obtained release rates and concentrations of chlorhexidine, loaded to methylcellulose and poly(acrylic acid) gels, were compared with respective viscositiy, pH, and conductivity of the assessed systems. The deposition patterns of chlorhexidine in the polymeric matrix were studied using energy dispersive X-ray spectrometry to evaluate the possible influence of chlorhexidine distribution in/on the carrier on the respective release rates. This study is significant for patients with various skin temperature conditions, who are required to receive local biocides applied on skin or into the oral cavity. The obtained precipitate of polyacrylic acid-chlorhexidine preparation was extensively studied to evaluate the chlorhexidine release and to develop an application in skin and dental care.
Immanence and Transcendence as Inseparable Processes: On the Relevance of Arguments from Whitehead to Deleuze Interpretation
Authors: Williams James
Published: March 2010

It is argued in this paper that recent work on immanence and transcendence in Whitehead scholarship, notably by Basile and Nobo, provides helpful guidelines and ideas for work on problems regarding immanence in Deleuze's philosophy. By following arguments on theism and naturalism in the reception of Whitehead, it argues that Deleuze's philosophy depends on reciprocal relations between that actual and the virtual such that they cannot be considered as separate without also being incomplete. It is then shown that Deleuze's philosophy allows for metaphysical terms such as ‘pure’ without having to concede a separate and self-sufficient pure realm.
Interstitial Life: Subtractive Vitalism in Whitehead and Deleuze
Authors: Shaviro Steven
Published: March 2010

Deleuze and Whitehead are both centrally concerned with the problem of how to reconcile the emergence of the New with the evident continuity and uniformity of the world through time. They resolve this problem through the logic of what Deleuze calls ‘double causality’, and Whitehead the difference between efficient and final causes. For both thinkers, linear cause-and-effect coexists with a vital capacity for desire and decision, guaranteeing that the future is not just a function of the past. The role of desire and decision can be seen in recent developments in biology.
Prevalence of Ocular, Respiratory and Cutaneous Symptoms in Indoor Swimming Pool Workers and Exposure to Disinfection By-Products (DBPs)
Authors: Fantuzzi Guglielmina , Righi Elena , Predieri Guerrino , Giacobazzi Pierluigi , Mastroianni Katia , Aggazzotti Gabriella
Published: March 2010

The objective of this cross-sectional study was to investigate the prevalence of self-reported respiratory, ocular and cutaneous symptoms in subjects working at indoor swimming pools and to assess the relationship between frequency of declared symptoms and occupational exposure to disinfection by-products (DBPs). Twenty indoor swimming pools in the Emilia Romagna region of Italy were included in the study. Information about the health status of 133 employees was collected using a self-administered questionnaire. Subjects working at swimming pools claimed to frequently experience the following symptoms: cold (65.4%), sneezing (52.6%), red eyes (48.9%) and itchy eyes (44.4%). Only 7.5% claimed to suffer from asthma. Red eyes, runny nose, voice loss and cold symptoms were declared more frequently by pool attendants (lifeguards and trainers) when compared with employees working in other areas of the facility (office, cafe, etc.). Pool attendants experienced generally more verrucas, mycosis, eczema and rash than others workers; however, only the difference in the frequency of self-declared mycosis was statistically significant (p = 0.010). Exposure to DBPs was evaluated using both environmental and biological monitoring. Trihalomethanes (THMs), the main DBPs, were evaluated in alveolar air samples collected from subjects. Swimming pool workers experienced different THM exposure levels: lifeguards and trainers showed the highest mean values of THMs in alveolar air samples (28.5 ± 20.2 µg/m3), while subjects working in cafe areas (17.6 ± 12.1 µg/m3), offices (14.4 ± 12.0 µg/m3) and engine rooms (13.6 ± 4.4 µg/m3) showed lower exposure levels. Employees with THM alveolar air values higher than 21 µg/m3 (median value) experienced higher risks for red eyes (OR 6.2; 95% CI 2.6–14.9), itchy eyes (OR 3.5; 95% CI 1.5–8.0), dyspnea/asthma (OR 5.1; 95% CI 1.0–27.2) and blocked nose (OR 2.2; 95% CI 1.0–4.7) than subjects with less exposure. This study confirms that lifeguards and trainers are more at risk for respiratory and ocular irritative symptoms and cutaneous diseases than subjects with other occupations at swimming pool facilities.
Photoinduced Surface Relief Grating Formation for a Single Crystal of 4-Aminoazobenzene
Authors: Nakano Hideyuki
Published: March 2010

Photoinduced surface relief grating (SRG) formation for a single crystal of 4-aminoazobenzene was investigated. It was found that SRG could be inscribed on the (001) surface of the crystal, which might suggest that the photoinduced SRG formation is a general phenomenon observed for single crystals of azobenzene-based molecules as well as for azobenzene-based amorphous systems. In addition, the dependences of the SRG formation upon the orientation of the sample crystal and upon the polarization of the writing beams were found to be different from those observed for previously reported crystalline systems.