bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-Lapse Effects in a Steam Flood Development in South Oman
Authors: Rocco G.. , Adawi R.. , Busaidi K.. , Rodriguez F.. , Busaidi S.. , Kindy F.. , Maamari A.. , Kiyashchenko D.. , Mehta K.. , Lopez J.. , Zwaan M.. , de Zwart B..
Published: July 2011

A steam flood re-development of a mature field in the South of Oman is well underway with the first pattern of steam injection active since late 2008. The areal surveillance programme designed by a joint effort between Petroleum Development Oman (PDO) and Shell International Exploration and Production (SIEP) includes the simultaneous recording of a variety of seismic methods of different resolution. The main purpose of the time-lapse work is to monitor the steam conformance and sweep efficiency as the steam is injected in this heavy oil reservoir over 1,000 m below surface. Key aspects of the data acquisition campaigns, state-of-the-art processing and time-lapse interpretation will be discussed. The ultimate objective of the programme is to evaluate the effectiveness of the techniques used in order to select the most appropriate and economically viable reservoir surveillance tools for full field deployment.
Miscible GOGD Using CO2 in One of the Iranian Fractured Reservoirs - A Case Study
Authors: Kamali Fatemeh , Khosravi Maryam , Vahidi Akram , Roayaei Emad
Published: July 2011

Advantages of CO2 in enhanced oil recovery for Iranian oil reservoirs offers a unique opportunity to boost incremental oil recovery and reducing emissions of greenhouse gas through geological sequestration. Moreover, because of the dominant role of gravity force in gas injection process in fractured reservoirs, and also relatively low minimum miscibility pressure (MMP) of CO2, therefore, miscible CO2 injection with Gas Oil Gravity Drainage (GOGD) mechanism can be considered as an efficient method in most carbonate reservoirs.

In this paper, different production strategies such as vertical and horizontal immiscible and miscible gas injection were applied to find the optimum EOR method in one of the under-saturated Iranian fractured reservoirs.

To aim this goal, a study with simulation approach was conducted while the effect of gravity drainage on recovery was investigated besides other mechanisms. A complete analysis of phase behavior, PVT properties of reservoir fluid and CO2 mixture was done. These data were applied in designing of the slim tube and full field simulation model. A fully compositional reservoir simulator was employed to understand the reservoir characteristics, also, verifying the suitability of CO2 injection.

Material balance analysis indicated the original oil in place (OOIP) is about 910 million STB with a relatively strong water support. The maximum oil production of 60,000 STB/D was assumed in all simulation cases. Reservoir simulation results revealed that additional oil recovery could be obtained from this fractured reservoir by miscible gas injection, while gravity drainage was the main displacement mechanism. In case of vertical well production, the model predicted an increase in oil recovery about 24 and 28% OOIP for immiscible and miscible CO2 injection respectively. Considering horizontal producers and gravity drainage as the dominant production mechanism, immiscible and miscible gas injection will enhance oil production more than 28 and 36% OOIP respectively.
Moving CO2 EOR Offshore
Authors: Goodyear S. G. , Koster M. P. , Marriott K. A. , Paterson A.. , Sipkema A. W. , Young I. M.
Published: July 2011

CO2 can be an effective EOR agent and is the dominant anthropogenic greenhouse gas driving global warming. Capturing CO2 from industrial sources in EOR projects can maximize hydrocarbon recovery and help provide a possible bridge to a lower carbon emissions future, by adding value through EOR production and field life extension, and providing long term secure storage post-EOR operations.

Shell is working to implement new generation CO2 projects, including offshore applications. Based on recent offshore project design experience, this paper describes the challenges in moving CO2 EOR from onshore to offshore and the solutions developed, in the key areas of safety, facilities, wells, subsurface and piloting. The overriding design principle in any project is HSE. Offshore operations brings a new set of challenges over inventory, pressure, confined spaces and evacuation, with conventional emergency procedures requiring modification because of the different physical characteristics of CO2 releases compared to hydrocarbon gas. Surface facilities need to be simple to minimise CAPEX, weight and space while maintaining flexibility, since there is less scope to incrementally evolve the surface facilities as is the case onshore. Balancing the tension between these objectives requires very close surface and subsurface integration to find optimal and cost-effective solutions. This is illustrated with three key decision areas: gas treatment options for back produced CO2 and hydrocarbon gas, artificial lift and facilities capacity.

A novel integrated CO2 gas lift system is described. This simplifies facilities and reduces CAPEX and OPEX, while at the same time providing a high degree of flexibility and risk management over the EOR life cycle in terms of subsurface uncertainty and reducing the issues around molecular weight variation in the recycled gas and the degree of turndown required in the facilities in the early years of EOR operations.
Simulation Study of Enhanced Gas Recovery Process Using a Compositional and a Black Oil Simulator
Authors: Rafiee M. M. , Ramazanian M..
Published: July 2011

Enhanced Gas Recovery (EGR) is a way of producing residual gas in depleted gas reservoirs. CO2 injection is a promising method for EGR by increasing the reservoir pressure and also gas-gas displacement. The miscibility of injected CO2 and residual gas in place is an important factor in this process.

The objective of this work is to investigate the miscibility process of CO2 injection into gas reservoirs using a compositional and a black oil reservoir simulator. A synthetic simulation model is built for this process having injection and production wells. The effect of gas miscibility is studied for both simulators and the results are compared to find optimum miscibility parameters.

The simulation results show that compositional result is similar to the black oil run, when the miscibility factor in the later case is almost half of the complete miscible process. In case of no miscibility the extension front is very sharp while for the case of complete miscibility the CO2 front is more advanced toward production well with wider length of miscible zone.

The findings of this paper could be beneficial for further pilot and field case study for monitoring of the observation and abandonment wells. Also the method is helpful in using black oil simulator as an alternative, less working effort and same reliable for CO2 sequestration in comparison to a compositional simulator.
Large Scale CO2 Flood Begins Along Texas Gulf Coast
Authors: Davis Darrell , Scott Mark , Roberson Kris , Robinson Adam
Published: July 2011

CO2 flooding of a strong waterdrive reservoir has begun along the Texas Gulf Coast. Ninety (90) million SCF of CO2 will be injected daily during 2011 to re-pressure the reservoir and rates as high as 1 billion SCF per day (including recycle) will ultimately be used to develop this giant oil field. Design of this CO2 flood at a depth of 6,000 feet has focused upon pattern design, operating pressure, and the impact of aquifer influence. Success of CO2 floods, hinges upon the ability to increase reservoir pressure to, or near, miscibility pressure and to effectively sweep the reservoir. Laboratory and field performance data have been utilized to improve the design of this continuous CO2 injection project.

Some of the largest oil reservoirs in the world are composed of high permeability sandstones with large aquifers. These reservoirs are attractive candidates for CO2 flooding due to the size of the initial oil deposits; however recoveries due to the strong waterdrive and good quality sands often result in low residual and/or remaining oil saturations. With oil zone thickness often exceeding 100 feet, significant challenges exist in developing optimum completion strategy and pattern selection. For the Hastings CO2 flood, five-spot injection patterns will be staggered so that the upper and lower portions of the reservoir have dedicated injectors and producers, thus improving vertical sweep. Water injection profiles have also shown that perforation shot density is key to insuring uniform vertical sweep given the minimal pressure drop across each perforation when low viscosity CO2 is injected. Reservoir pressure within the floodable area must also be maintained (preventing leakoff) in order to maximize displacement efficiency. This is accomplished by use of water injection wells placed downdip to act as a water curtain, thus reducing leakoff of pressure into the infinite acting aquifer. As expansion of the EOR project develops additional patterns downdip, water injectors will be placed further downdip, while the updip injectors will be placed on CO2.
Optimization of Solvent Additive SAGD Applications using Hybrid Optimization Techniques
Authors: Al-Gosayir Muhammad , Babadagli Tayfun , Leung Juliana
Published: July 2011

Heavy oil and bitumen recovery cost is excessive mainly due to high energy requirement to generate heat and its environmental impacts. Steam Assisted Gravity Drainage (SAGD) is an example of this case; the determination of optimal operating conditions, such as injection rates and well locations, based on reservoir and fluid characteristics is essential in the design of field applications.

Many Steam Assisted Gravity Drainage (SAGD) optimization studies published in the literature combined numerical simulation with graphical or analytical techniques for design and performance evaluation. There have been limited efforts that integrated the simulation exercise with global optimization algorithms. Some studies focused on optimization of cumulative steam-to-oil ratio (cSOR) in SAGD by altering steam injection rates, while others focused on optimization of cumulative net energy-to-oil ratio (cEOR) in solvent-additive SAGD by altering injection pressures and fraction of solvent in the injection stream. Typical scoring functions were the net present value per hectare of land (NPV/ha) by controlling steam and solvent rates. Several studies also considered total project net present value calculation by changing total project area, capital cost intensities, solvent prices, discount rate, and risk factors to determine the well spacing and drilling schedule. Optimization techniques commonly used in those studies were scattered search, simulated annealing, and genetic algorithm (GA). However, applications of hybrid genetic algorithm were rarely found.

In continuation of these efforts, we focused on optimizing the SAGD process and its extension to solvent-additive SAGD using hybrid genetic algorithm. The objective function was defined to obtain the lowest cumulative steam-oil ratio (cSOR) and highest recovery factor. It was used later as scoring function by changing operating pressure, solvent-to-steam ratio, and steam injection rates. The results in this paper can be implemented directly in the efforts of minimization of cost and environmental impacts while accelerating the recovery in SAGD.
Performance Study of a New Type Alkaline/Surfactant/Polymer Ternary Complex
Authors: Liu Yong , Lu Yi , Lin Weimin , Hu Xingqi
Published: July 2011

NaOH, which is used in traditional Alkaline/Surfactant/Polymer Flooding technique, can result in formation damage and equipment corrosion1, 2. In order to replace NaOH with Na2CO3, a new type Gemini surfactant-DEDS is synthesized. Its dose is very lower than traditional surfactant for ASP combination flooding. Rheological behavior of DEDS/AP-P4/Na2CO3 (ASP) aqueous solution and the effect of salt on it were studied. Conclusions are as follows: DEDS has the same influencent as inorganic electrolyte, and rheological behavior of ASP aqueous solution can be described with power law fluid mode. The apparent viscosity of ASP aqueous solution (AP-P4 2000mg/L, Na2CO3 1%, DEDS 0.423mmol/L and NaCl 1×104mg/L) is 3.88–8.11 that of ASP aqueous solution (AP-P4 2000mg/L, Na2CO3 1%, DEDS 0.423mmol/L), Rheological behavior of ASP solution exhibits a little character of Bingham fluid with the increasing of NaCl concentration. When DEDS concentration is 0.423mmol/L, and AP-P4 concentration is 1500mg/L, ASP ability emulsifing analog oil will enhance with the increasing of Na2CO3 concentration. When Na2CO3 concentration reaches 1%, ASP solution and analog oil is completely emulsified, IFT reaches 10−4mN/m, and ultra-low IFT is realized. Using ASP solution to drive homogeneous test core undergoing waterflooding, recovery efficiency increases about 18%; for nonhomogeneous test core, which permeability contrast is 1.76, its increment of tight permeability is more 6.8% than of high permeability, and ASP solution possesses better profile control property. In comparison with traditional surfactants, DEDS dosage can remarkably decrease, and weak alkaline ASP flooding can be achieved. Extent of formation damage and equipment corrosion of chemicals will obviously reduce, when it is used in field.
A Novel Alkaline-Surfactant-Foam EOR Process
Authors: Guo Hua , Faber Rien , Buijse Marten , Zitha Pacelli L.J.
Published: July 2011

This paper reports a laboratory study of a novel alkaline-surfactant-foam (ASF) process. The goal of the study was to investigate whether foaming a specially designed AS formulation could meet the two key requirements for a good enhanced oil recovery (EOR), i.e. lowering the interfacial tension (IFT) considerably and ensuring a good mobility control. The study included phase behavior tests, foam column tests and CT scan-aided core-floods. It was found that the IFT of the designed alkali-surfactant (AS) and a selected crude oil drops by four orders of magnitude at the optimum salinity. The AS proved to be a good foaming agent in the column tests and core-floods in absence of oil. The mobility reduction due to the AS foam was hardly sensitive to salinity and increased with decreasing foam quality. CT scanned core-floods demonstrated that AS foam following a small AS pre-flush recovered almost all the oil left after water-flooding. The oil recovery mechanism by ASF combines the formation of an oil bank and the transport of emulsified oil by flowing lamellae. Further optimization of the ASF is needed to ensure that the oil is produced exclusively by the oil bank.
Carbon Capture for Enhanced Oil Recovery in Niger Delta: A Case Study of Okota/Okpoputa Field in Offshore Niger Delta
Authors: Odesa David , Adewale Dosumnu
Published: July 2011

Carbon capture for enhanced oil recovery is a proven technology that holds the promise of increasing oil reserves, reducing greenhouse gas (GHG) emissions, diminish the concerns associated with the release of cocktail gases from gas flaring and reduce hostility in host communities. In this work, we considered the Okota/Okpoputa field in Offshore Niger Delta and covered areas of interest such as the post combustion capture using monoethanolamine (MEA), prognosis of storage site, increase production pressure, economics of the capture and assessment of the risk of leakage. With about 80 million tonnes of CO2 captured annually from flared flue gas, the CO2-enhanced oil recovery will yield 20–40% Original Oil in Place (OOIIP), and this will translate to a savings of $ 474,500,000 excluding commercial sales of CO2.
New Approach to Upgrade the Combustion In Situ Process by using an Emulsified Additive on Heavy Oil from Orinoco Belt
Authors: Arturo J.. , Mendoza R.. , Oliveros Deivi , Arellano Dixon , Perozo Héctor , Reinoza Jefferson , Rivas Ángel
Published: July 2011

The main challenge of the Venezuelan Oil Industry is focused in exploitation of the Orinoco Oil Belt (FPO), where potentiality are located the largest heavy oil reserves in the world. The heavy and extra heavy oil reservoirs are produced by its primary energy in some cases; in others depending on the oil viscosity enhanced oil recovery by thermal processes are applied. In Situ Combustion has been studied for more than four decade and there are reported several studies using additive in order to optimize it. However, a wide range of kind of additive has been studied and they evidence an increase of the recovery associated and upgrading to the oil produced.

The present approach has been visualized as a considerable opportunity to contact a bigger zone into the reservoir and major effectiveness of the reaction promote. In that sense, PDVSA Intevep is focused on optimizing the combustion process using non-conventional additive. The methodology used is based on the air injection into the reservoir and posterior heating for ignition, where the combustion front will face with the emulsified additive promoting a series of exothermic oxidation reactions which reduce oil viscosity, due to the additional energy generated by the presence of additive in the system. The results obtained in the combustion tests, showed front stability, a considerable increase in the reactions conversion, reduction of oil viscosity, an as a consequence major oil recovery and oil value for the marketing.
Production Optimization at Connacher’s Pod One (Great Divide) Oil Sands Project
Authors: Johnson M. D. , Hansen L. A. , Lau T.. , Phenix T. J. , Breen S. P.
Published: July 2011

Connacher’s first oil sands project, the Pod One facility at Great Divide, has been operational since 2007. The successful SAGD project has produced approximately 7 million barrels of bitumen. During the past three and a half years, the impacts of certain predicted reservoir challenges and opportunities have become apparent.

While the quality of the oil sands in this first phase of Pod One is generally good, Pad 101 South in particular has geological zones that affect SAGD operation. This includes a bitumen lean zone, and a gas cap overlying the main bitumen channel/s. Early field results matched with detailed simulations have shown positive results in maximizing well pair production. For the purposes of this paper a lean bitumen zone differs from an aquifer in two ways. The lean zone is not charged, and is limited in size. The operation is also complicated by the fact the gas bearing zone has been depleted through earlier production.

Connacher’s operating practice at Great Divide attempts to achieve a pressure balance between the 3 zones (rich oil sands, lean zone, gas cap) to reduce steam loss and maximize production rates. Reducing the pressure encourages steam chamber development growth horizontally and ensures that steam contacts the highly saturated bitumen areas. How this is achieved with the highest positive impact on well productivity is illustrated with operational data and analysis including the results of simulations that recommended the optimum operating strategies.
Improved Characterization of EOR Processes in 3D. Characterizing Mineralogy, Wettability and Residual Fluid Phases at the Pore Scale
Authors: Knackstedt Mark , Senden Tim , Carnerup Anna , Fogden Andrew
Published: July 2011

At the conclusion of flooding into an oil- or gas-bearing reservoir, a significant fraction of the original hydrocarbon in place remains as trapped residual phase. In addition to determining the amount of trapped phase, the microscopic distribution within the pore space of the reservoir rock is important to gain a better understanding of recovery mechanisms, and for the design and implementation of improved or enhanced recovery processes. While the importance of the mineralogy, wettability, pore scale structure and distribution of residual oil is widely acknowledged, little quantitative information on these properties has been directly available. We describe results from an ongoing interdisciplinary study of this problem bridging the molecular-scale, pore-scale and core-scale of rock structure using surface chemical techniques, pore scale x-ray microtomographic imaging, petrographical imaging and experimental analysis on reservoir carbonate material. We first describe the experimental techniques used in this study and review the registration technology which enables one to quantify mineralogy on 3D images through the integration of SEM-EDS with micro-CT methods. We then discuss methods to visualize pore scale oil and brine populations at the pore scale with a particular focus on characterizing native state plugs. In parallel, we characterize the physical and surface chemical characteristics of rock surfaces at the pore-scale and sub-pore scale, and consider the oil-brine-rock interactions giving rise to these states. This interdisciplinary approach provides the foundation for understanding recovery processes and for the development of strategies to alter wettability and improve recovery in reservoirs.
Using Core Data to Study and Optimize the Completion Strategy in EOR Operations
Authors: Nagineni Venu Gopal , D’Souza David F. , Holden Charles , Hughes Richard G.
Published: July 2011

Dykstra Parsons Coefficients and Lorenz Coefficients calculated from core data are traditionally used as indicators of heterogeneity in a reservoir. Modified Lorenz (ML) plots serve as an indicator of heterogeneity and also depict the transmissivity versus the storativity of the payzone. In this work, ML plots are used to study the flow capacity versus the storage capacity of a reservoir, and to divide the reservoir into individual flow units. Production and injection profile logs were used to verify the depths at which CO2 was actually being injected or produced and compared to the depths where a high flow capacity was observed on the ML Plot. Premature production of CO2 and high GOR on producing wells in CO2 floods is attributed to the CO2 being injected and produced in high permeability zones as compared to low or no CO2 injection in low permeability zones. This study proposes a well completion technique using well core data to normalize CO2 injection across various ML defined zones, and thereby improve CO2 conformance and recovery.

High GOR in CO2 flooded reservoirs increases the net and gross utilization of CO2 and may also result in lower vertical sweep efficiency. Controlling the preferential entry of CO2 into high flow capacity regions, and selectively controlling the injection rate into the various flow units of the reservoir can minimize CO2 utilization, increase volumetric sweep efficiency and recovery. This paper presents a simple well completion technique to selectively control CO2 injection into the reservoir for various flow units. The area of flow open to CO2 is controlled by the perforation density. For most practical applications, the perforation density for a flow unit should be inversely proportional to the slope of the flow unit characterized using the ML plots.
Evaluation and Optimization of Enhanced Oil Recovery by WAG Injection at Tapis and Guntong Fields, Malaysia
Authors: Selamat Samsuddin , Samsuddin Seri Ainatrah , Halim Nurazizi Abdul
Published: July 2011

EMEPMI and PETRONAS have recently concluded major simulation studies on the application of immiscible Water Alternating Gas (WAG) injection to enhance oil recovery for Tapis and Guntong fields, the two largest waterflooded fields operated by ExxonMobil in Malaysia. Both fields have been under waterflood operation for more than 25 years with about 40% original-oil-in-place (OOIP) recovered to-date.

Evaluations of immiscible WAG injection process application at Tapis and Guntong fields were carried out using full-field reservoir simulation models. The scope of the evaluation work included: a) assessment of additional recovery from enhancing waterflood operations, b) assessment of recovery uplift from WAG injection, c) WAG pattern and WAG ratio optimization, d) optimal WAG operating parameters and reservoir management strategy, and e) integrating production and injection well operating conditions with facilities process design.

The Tapis WAG evaluation study has supported ExxonMobil's plans to implement a WAG project at Tapis. The study has matured to the point of providing the subsurface design basis for the Project. The Guntong study has provided an initial assessment of WAG potential used for the conceptual WAG development and early project planning.
Residual Oil Saturation Determination for EOR Projects in a Mature West Texas Carbonate Field
Authors: Pathak Prabodh , Fitz Dale E. , Babcock Kenneth P.
Published: July 2011

The technical success of an Enhanced Oil Recovery (EOR) project depends on two main factors - first, the reservoir remaining oil saturation (ROS) after primary and secondary operations, and second, the recovery efficiency of the EOR process in mobilizing the ROS. These two interrelated parameters need to be estimated prior to embarking on a time-consuming and costly process for designing and implementing an EOR process. The oil saturation can vary areally and vertically within the reservoir, and the distribution of the ROS will determine the success of the EOR injectants in mobilizing the remaining oil.

There are many methods for determining the oil saturation (Chang et al. 1988, Pathak et al. 1989) and these include core analysis, well log analysis, Log-Inject-Log (LIL) procedures (Richardson 1973 and Reedy 1984), and Single Well Chemical Tracer Tests (SWCTT). These methods have different depths of investigation and different accuracies, and they all provide valuable information about the distribution of ROS. There is no single method that provides the best estimate of ROS, and a combination of all these methods is essential in developing a holistic picture of oil saturation and in assessing whether the oil in place is large enough to justify the application of an EOR process. As Teletzke et al. (2010) have shown, EOR implementation is a complex process, and a staged, disciplined approach to identifying the key uncertainties and acquiring data for alleviating the uncertainties is essential. The largest uncertainty in some cases is the remaining oil saturation in the reservoir.

This paper presents the results from a field-wide data acquisition program conducted in a West Texas carbonate reservoir to estimate ROS as part of an EOR project assessment. The Means field in West Texas has been producing for more than the past 75 years and the producing mechanisms have included primary recovery, secondary waterflooding and the application of a CO2 EOR process. The Means field is an excellent example of how the productive life and oil recovery can be increased by the application of new technology. The Means story is one of judicious application of appropriate EOR technology to the sustained development of a mature asset. The Means field is currently being evaluated for further expansion of the EOR process and it was imperative to evaluate the oil saturation in the lower, previously-undeveloped zones. This paper briefly outlines the production history, reservoir description and reservoir management of the Means field, but this paper concentrates on the Residual Oil Zone (ROZ) that underlies the Main Producing Zone (MPZ), and describes a recent data acquisition program to evaluate the oil saturation in the ROZ. We discuss three major methods for evaluating the ROS - core analysis, LIL tests and SWCTT tests.
High-Dimensional Regression and Variable Selection Using CAR Scores
Authors: Zuber Verena , Strimmer Korbinian
Published: July 2011

Variable selection is a difficult problem that is particularly challenging in the analysis of high-dimensional genomic data. Here, we introduce the CAR score, a novel and highly effective criterion for variable ranking in linear regression based on Mahalanobis-decorrelation of the explanatory variables. The CAR score provides a canonical ordering that encourages grouping of correlated predictors and down-weights antagonistic variables. It decomposes the proportion of variance explained and it is an intermediate between marginal correlation and the standardized regression coefficient. As a population quantity, any preferred inference scheme can be applied for its estimation. Using simulations, we demonstrate that variable selection by CAR scores is very effective and yields prediction errors and true and false positive rates that compare favorably with modern regression techniques such as elastic net and boosting. We illustrate our approach by analyzing data concerned with diabetes progression and with the effect of aging on gene expression in the human brain. The R package “care” implementing CAR score regression is available from CRAN.
Comment on Cramton and Katzman: Medicare Competitive Bidding Lowered Expenditures
Authors: Hoerger Thomas J
Published: July 2011

In contrast to Cramton and Katzmans assertion that Medicare encountered serious problems with its pilot competitive bidding program, Thomas Hoerger of RTI International cites his early evaluations that suggested strikingly positive results.
On Jensen's and related combinatorial identities
Authors: Guo Victor
Published: July 2011

Motivated by the recent work of Chu [Electron. J. Combin. 17 (2010), #N24],
we give simple proofs of Jensen's identity n?k=0 (x+kz/k)(y-kz/n-k = n?k=0
(x+y-k)/n-k)zk; and Chu's and Mohanty-Handa's generalizations of Jensen's
identity. We also give a quite simple proof of an equivalent form of
Graham-Knuth-Patashnik's identity ?k?0 (m+r/m-n-k) (n+k/n)xm-n-k yk = ?k?0
(-r/m-n-k)(n+k/n)(-x)m-n-k(x+y)k; which was rediscovered, respectively, by
Sun in 2003 and Munarini in 2005. Finally we give a multinomial coefficient
generalization of this identity.
Modeling Emergency Evacuation of Individuals with Disabilities in a Densely Populated Airport
Authors: Manley Matthew , Kim Yong Seog , Christensen Keith , Chen Anthony
Published: July 2011

Emergency evacuation from airports is an important consideration, given the continuing occurrence of natural and human-caused disasters affecting these locations. These incidents have focused attention on the needs of individuals with disabilities, who are more likely to suffer during emergency situations. The agent-based model presented in this paper can be used by engineering and management professionals in design and planning efforts to estimate the evacuation performance of heterogeneous populations from airports. The model classifies the environment according to accessibility characteristics encompassing various conditions that have a disproportionate effect on the behavior of individuals with disabilities during an evacuation. The results of a simulation experiment demonstrate some of the limitations of the pier airport design and identify which individuals are most at risk: those with lower stamina and those using wheelchairs. The results also reveal areas of the airport that are prone to bottlenecks or clogging.
Transition of the Rolling Dynamic Deflectometer Device from a Screening Tool to an Evaluation Tool for Rigid Airfield Pavement Projects
Authors: Nam Boo Hyun
Published: July 2011

For the past decade, the rolling dynamic deflectometer (RDD), a continuous deflection measurement device, has been used as a screening tool in identifying problematic airport pavements for repair. The RDD has not seen much use, however, as an evaluation tool to measure characteristics such as moduli of pavement layers and load-transfer efficiency (LTE). The primary goal of this research was to develop the hardware and software to take the RDD from a screening tool to an evaluation tool for airport pavement projects. In this study, the RDD as an evaluation tool could obtain (a) continuous measurement of rolling deflection basins (for the backcalculation of layer moduli to be studied) and (b) continuous evaluation of joint LTEs. Four subtasks were conducted: (a) investigation of parameters affecting the RDD measurements, (b) use of an increased number of rolling sensors, (c) improvement of RDD data processing (distance-based deflection profile with increased spatial resolution), and (d) a series of field tests with the RDD on a rigid airfield pavement. With all five sensors continuously monitored during rolling, the software that was developed was capable of selecting a zone of lateral uniformity over which it was appropriate to construct deflection basins. The improved data processing identified accurate locations of joints and properly positioned two rolling sensors on opposite sides of the adjacent slabs in the continuous deflection profile, producing a continuous LTE evaluation along the pavement. The RDD measurements (continuous deflection basins and LTEs) were compared with falling weight deflectometer measurements, and the comparison provided promising results.
Estimation and Comparison of Impact of Single Airport Delay on National Airspace System with Multivariate Simultaneous Models
Authors: Nayak Nagesh , Zhang Yu
Published: July 2011

U.S. air transport is under significant stress, experiencing frequent delays and high levels of congestion. At certain times, individual airports become bottlenecks within the National Airspace System (NAS). Major causes of flight delay at airports include overscheduling, en route convective weather, reduced ceiling and visibility around airports, and upstream delay propagation. Delay at one airport can be passed on to other airports in the NAS. Hence, to allocate resources for airport capacity expansion in an optimal way, the impact of single airport delay to the NAS and vice versa must be quantified. This research applies multivariate simultaneous regression models to quantify airport delay spillover effects across 34 of the 35 Operational Evolution Partnership airports and the rest of the NAS. This analysis considers such contributing factors as average daily arrival delay, deterministic queuing delay, weather patterns, aircraft equipment type, and others. The three-stage least-square method is used to regress the models and obtain coefficients for the multivariate equations. The outcomes are used to explain the interactions among airports in the NAS and to identify the major delay contributors at each.
Opportunities and Obstacles in Obtaining Air Connectivity for Residents of Federally Designated Essential Air Service Communities
Authors: Vaishnav Maulik
Published: July 2011

The Essential Air Service (EAS) program was established in 1978 to guarantee air connectivity for residents of small communities to the national air transportation system. Currently, more than half of EAS communities are within 70 highway miles of another airport, leading to passenger leakage at EAS airports and rising program costs. Five case studies of EAS communities examine the reasons for local support of air service that is rarely used. The case studies present three main findings: (a) the EAS program is a gateway to the federal airport infrastructure funds of the Airport Improvement Program; (b) there is an information gap between the U.S. Department of Transportation and the EAS communities regarding the existing risky alternate programs; and (c) local politics and airport administrators' concern about their professional future sustains support for local air service. EAS communities in a multi-airport region, therefore, are most susceptible to passenger leakage and continue to struggle in the program. The obstacles also deter the establishment of transportation options that best fit communities and their residents. The study provides insights into policy changes that address the importance of small airports and rural air connectivity.
Antimicrobial and Cytotoxicity Studies of the Aerial Part of Arachis hypogea Linn.
Authors: Parvin Most Nazma , Chowdhury Sadia Afreen
Published: July 2011

Key words: Arachis hypogea; Papilionaceae; Cytotoxicity; AntimicrobialDOI: http://dx.doi.org/10.3329/sjps.v3i2.8034 S.J. Pharm. Sci 3(2): 25-28
In vitro Antioxidant and Cytotoxic Activities of Methanolic Leaf Extract of Ficus hispida Linn.
Authors: Saha Moni Rani , Shill Manik Chandra , Biswas Subrata Kumar , Faruque Abdullah
Published: July 2011

Key words: Ficus Hispida Linn.; DPPH free radical scavenging; antioxidant; cytotoxicityDOI: http://dx.doi.org/10.3329/sjps.v3i2.8035 S.J. Pharm. Sci 3(2): 29-36
Antimicrobial Activity of Different Extracts of Geodorum densiflorum (Lam) Schltr. pseudobulb
Authors: Akter Saleha , Imam Mohammad Zafar , Akter Tahira
Published: July 2011

DOI: http://dx.doi.org/10.3329/sjps.v3i2.8037 S.J. Pharm. Sci 3(2): 47-48
The Coupled Effect of Mid-Tropospheric Moisture and Aerosol Abundance on Deep Convective Cloud Dynamics and Microphysics
Authors: Cui Zhiqiang , Carslaw Kenneth S. , Blyth Alan M.
Published: July 2011

The humidity of the mid troposphere has a significant effect on the development of deep convection. Dry layers (dry intrusions) can inhibit deep convection through the effect of a thermal inversion resulting from radiation and due to the reduction in buoyancy resulting from entrainment. Recent observations have shown that the sensitivity of cloud top height to changes in mid-tropospheric humidity can be larger than straightforward “parcel dilution” would lead us to expect. Here, we investigate how aerosol effects on cloud development and microphysics are coupled to the effects of mid-tropospheric dry air. The two effects are coupled because the buoyancy loss through entrainment depends on droplet evaporation, so is controlled both by the environmental humidity and by droplet sizes, which are, in turn, controlled in part by the aerosol size distribution. Previous studies have not taken these microphysical effects into account. Cloud development and microphysics are examined using a 2-D non-hydrostatic cloud model with a detailed treatment of aerosol, drop, and ice-phase hydrometeor size spectra. A moderately deep mixed-phase convective cloud that developed over the High Plains of the United States is simulated. We find that a dry layer in the mid troposphere leads to a reduction in cloud updraft strength, droplet number, liquid water content and ice mass above the layer. The effect of the dry layer on these cloud properties is greatly enhanced under elevated aerosol conditions. In an environment with doubled aerosol number (but still realistic for continental conditions) the dry layer has about a three-times larger effect on cloud drop number and 50% greater effect on ice mass compared to an environment with lower aerosol. In the case with high aerosol loading, the dry layer stops convective development for over 10 min, and the maximum cloud top height reached is lower. However, the effect of the dry layer on cloud vertical development is significantly reduced when aerosol concentrations are lower. The coupled effect of mid-tropospheric dry air and aerosol on convective development is an additional way in which long term changes in aerosol may impact planetary cloud processes and climate.
Soil Rhizosphere Microbial Communities and Enzyme Activities under Organic Farming in Alabama
Authors: Gardner Terrence , Acosta-Martinez V. , Senwo Zachary , Dowd Scot E.
Published: July 2011

Evaluation of the soil rhizosphere has been limited by the lack of robust assessments that can explore the vast complex structure and diversity of soil microbial communities. Our objective was to combine fatty acid methyl ester (FAME) and pyrosequencing techniques to evaluate soil microbial community structure and diversity. In addition, we evaluated biogeochemical functionality of the microbial communities via enzymatic activities of nutrient cycling. Samples were taken from a silt loam at 0–10 and 10–20 cm in an organic farm under lettuce (Lactuca sativa), potato (Solanum tuberosum), onion (Allium cepa L), broccoli (Brassica oleracea var. botrytis) and Tall fescue pasture grass (Festuca arundinacea). Several FAMEs (a15:0, i15:0, i15:1, i16:0, a17:0, i17:0, 10Me17:0, cy17:0, 16:1ω5c and 18:1ω9c) varied among the crop rhizospheres. FAME profiles of the soil microbial community under pasture showed a higher fungal:bacterial ratio compared to the soil under lettuce, potato, onion, and broccoli. Soil under potato showed higher sum of fungal FAME indicators compared to broccoli, onion and lettuce. Microbial biomass C and enzyme activities associated with pasture and potato were higher than the other rhizospheres. The lowest soil microbial biomass C and enzyme activities were found under onion. Pyrosequencing revealed significant differences regarding the maximum operational taxonomic units (OTU) at 3% dissimilarity level (roughly corresponding to the bacterial species level) at 0–10 cm (581.7–770.0) compared to 10–20 cm (563.3–727.7) soil depths. The lowest OTUs detected at 0–10 cm were under broccoli (581.7); whereas the lowest OTUs found at 10–20 cm were under potato (563.3). The predominant phyla (85%) in this soil at both depths were Bacteroidetes (i.e., Flavobacteria, Sphingobacteria), and Proteobacteria. Flavobacteriaceae and Xanthomonadaceae were predominant under broccoli. Rhizobiaceae, Hyphomicrobiaceae, and Acidobacteriaceae were more abundant under pasture compared to the cultivated soils under broccoli, potato, onion and lettuce. This study found significant differences in microbial community structure and diversity, and enzyme activities of nutrient cycling in this organic farming system under different rhizospheres, which can have implications in soil health and metabolic functioning, and the yield and nutritional value of each crop.
Species Richness and Community Structure on a High Latitude Reef: Implications for Conservation and Management
Authors: Jones Alison M. , Berkelmans Ray , Houston Wayne
Published: July 2011

In spite of the wealth of research on the Great Barrier Reef, few detailed biodiversity assessments of its inshore coral communities have been conducted. Effective conservation and management of marine ecosystems begins with fine-scale biophysical assessments focused on diversity and the architectural species that build the structural framework of the reef. In this study, we investigate key coral diversity and environmental attributes of an inshore reef system surrounding the Keppel Bay Islands near Rockhampton in Central Queensland, Australia, and assess their implications for conservation and management. The Keppels has much higher coral diversity than previously found. The average species richness for the 19 study sites was ~40 with representatives from 68% of the ~244 species previously described for the southern Great Barrier Reef. Using scleractinian coral species richness, taxonomic distinctiveness and coral cover as the main criteria, we found that five out of 19 sites had particularly high conservation value. A further site was also considered to be of relatively high value. Corals at this site were taxonomically distinct from the others (representatives of two families were found here but not at other sites) and a wide range of functionally diverse taxa were present. This site was associated with more stressful conditions such as high temperatures and turbidity. Highly diverse coral communities or biodiversity ‘hotspots’ and taxonomically distinct reefs may act as insurance policies for climatic disturbance, much like Noah’s Arks for reefs. While improving water quality and limiting anthropogenic impacts are clearly important management initiatives to improve the long-term outlook for inshore reefs, identifying, mapping and protecting these coastal ‘refugia’ may be the key for ensuring their regeneration against catastrophic climatic disturbance in the meantime.
Infection Dynamics Vary between Symbiodinium Types and Cell Surface Treatments during Establishment of Endosymbiosis with Coral Larvae
Authors: Bay Line Kolind , Cumbo Vivian Ruth , Abrego David , Kool Johnathan Travis , Ainsworth Tracy Danielle , Willis Bette Lynn
Published: July 2011

Symbioses between microbes and higher organisms underpin high diversity in many ecosystems, including coral reefs, however mechanisms underlying the early establishment of symbioses remain unclear. Here we examine the roles of Symbiodinium type and cell surface recognition in the establishment of algal endosymbiosis in the reef-building coral, Acropora tenuis. We found 20–70% higher infection success (proportion of larvae infected) and five-fold higher Symbiodinium abundance in larvae exposed to ITS-1 type C1 compared to ITS-1 type D in the first 96 h following exposure. The highest abundance of Symbiodinium within larvae occurred when C1-type cells were treated with enzymes that modified the 40–100 kD glycome, including glycoproteins and long chain starch residues. Our finding of declining densities of Symbiodinium C1 through time in the presence of intact cell surface molecules supports a role for cell surface recognition molecules in controlling post-phagocytosis processes, leading to rejection of some Symbiodinium types in early ontogeny. Reductions in the densities of unmodified C1 symbionts after 96 h, in contrast to increases in D symbionts may suggest the early initiation of a winnowing process contributing to the establishment of Symbiodinium D as the dominant type in one-month old juveniles of A. tenuis.
State Operator Correspondence and Entanglement in AdS2/CFT1
Authors: Sen Ashoke
Published: July 2011

Since Euclidean global AdS2 space represented as a strip has two boundaries, the state-operator correspondence in the dual CFT1 reduces to the standard map from the operators acting on a single copy of the Hilbert space to states in the tensor product of two copies of the Hilbert space. Using this picture we argue that the corresponding states in the dual string theory living on AdS2 × K are described by the twisted version of the Hartle–Hawking states, the twists being generated by a large unitary group of symmetries that this string theory must possess. This formalism makes natural the dual interpretation of the black hole entropy—as the logarithm of the degeneracy of ground states of the quantum mechanics describing the low energy dynamics of the black hole, and also as an entanglement entropy between the two copies of the same quantum theory living on the two boundaries of global AdS2 separated by the event horizon.
Partition Function of the Schwarzschild Black Hole
Authors: Mäkelä Jarmo
Published: July 2011

We consider a microscopic model of a stretched horizon of the Schwarzschild black hole. In our model the stretched horizon consists of a finite number of discrete constituents. Assuming that the quantum states of the Schwarzschild black hole are encoded in the quantum states of the constituents of its stretched horizon in a certain manner we obtain an explicit, analytic expression for the partition function of the hole. Our partition function predicts, among other things, the Hawking effect, and provides it with a microscopic, statistical interpretation.
Chitosan Interaction with Iron from Yoghurt Using an In Vitro Digestive Model: Comparative Study with Plant Dietary Fibers
Authors: Dello Staffolo Marina , Martino Miriam , Bevilacqua Alicia , Montero Mirta , Rodríguez María Susana , Albertengo Liliana
Published: July 2011

The objective of this work was to investigate the interaction of chitosan with iron from yoghurt by an in vitro gastrointestinal tract model. Taking into account that chitosan is a polysaccharide included in fiber definition by Codex Alimentarius; chitosan behavior was studied and compared with different plant fiber (wheat, bamboo, apple, psyllium and inulin) behaviors, in the same in vitro conditions. Ferrous sulfate was added to yoghurts with each type of fiber. The gastric environment was simulated with HCl (pH 1.0–2.0). The duodenal environment was simulated with NaHCO3 (pH 6.8–7.2) and a dialysis tubing cellulose membrane. Results showed that chitosan had the highest iron retention percentages (53.2% at 30 min; 56.8% at 60 min) interacting in a more pronounced manner with iron than the plant fibers used in this work.