bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigations of an SLA Support System for Cloud Computing (SLACC)
Authors: Machado Guilherme Sperb , Stiller Burkhard
Published: May 2011

Cloud Providers (CP) and Cloud Users (CU) need to agree on a set of parameters expressed through Service Level Agreements (SLA) for a given Cloud service. However, even with the existence of many CPs in the market, it is still impossible today to see CPs who guarantee, or at least offer, an SLA specification tailored to CU's interests: not just offering percentage of availability, but also guaranteeing, for example, specific performance parameters for a certain Cloud application. Due to (1) the huge size of CPs' IT infrastructures and (2) the high complexity with multiple inter-dependencies of resources (physical or virtual), the estimation of specific SLA parameters to compose Service Level Objectives (SLOs) with trustful Key Performance Indicators (KPIs) tends to be inaccurate. This paper investigates an SLA Support System for CC (SLACC) which aims to estimate in a formalized methodology – based on available Cloud Computing infrastructure parameters – what CPs will be able to offer/accept as SLOs or KPIs and, as a consequence, which increasing levels of SLA specificity for their customers can be reached.
Spontaneously hypertensive rat (SHR) as an animal model for ADHD: a short overview
Authors: Meneses Alfredo , Perez-Garcia Georgina , Ponce-Lopez Teresa , Tellez Ruth , Gallegos-Cari Andrea , Castillo Carlos
Published: May 2011

Diverse studies indicate that attention-deficit hyperactivity disorder (ADHD) is associated with alterations in encoding processes, including working or short-term memory. Some ADHD dysfunctional domains are reflected in the spontaneously hypertensive rat (SHR). Because ADHD, drugs and animal models are eliciting a growing interest, hence the aim of this work is to present a brief overview with a focus on the SHR as an animal model for ADHD and memory deficits. Thus, this paper reviews the concept of SHR as a model system for ADHD, comparing SHR, Wistar-Kyoto and Sprague-Dawley rats with a focus on the hypertension level and working, short-term memory and attention in different behavioral tasks, such as open field, five choice serial reaction time, water maze, passive avoidance, and autoshaping. In addition, drug treatments (d-amphetamine and methylphenidate) are evaluated.
When is adult hippocampal neurogenesis necessary for learning? Evidence from animal research
Authors: Castilla-Ortega Estela , Pedraza Carmen , Estivill-Torrús Guillermo , Santín Luis J.
Published: May 2011

The hippocampus is a key brain structure involved in the short- and long-term processing of declarative memory. Since adult hippocampal neurogenesis was first found, numerous studies have tried to establish the contribution of newborn neurons to hippocampus-dependent cognitive functions. However, this large amount of research has generated contradictory results. In this paper, we review the body of evidence investigating the relationship between hippocampal neurogenesis and learning to conclude the functional role of adult-born hippocampal neurons. First, factors that could explain discrepancies among experiments are taken into account. Then, in addition to methodological differences, we emphasize the importance of the age of the newborn neurons studied, as to how their maturation influences both their properties and potential functionality. Next, we discuss which declarative memory components could require involvement of adult hippocampal neurogenesis, taking into consideration the representational demands of the task, its difficulty and the level of performance reached by the subject. Finally, other factors that could modulate neurogenesis and memory, such as stress levels or previous experience of the animal, should also be taken into consideration in interpreting experiments focused on neurogenesis. In conclusion, our analysis of published studies suggests that new adult-born neurons, under certain circumstances, have a crucial and irreplaceable role in hippocampal learning.
Current perspectives on potential role of albumin in neuroprotection
Authors: Prajapati Kanaiyalal D. , Sharma Shyam S. , Roy Nilanjan
Published: May 2011

Albumin is the most abundant plasma protein synthesised mainly in the liver. It is also a major component of extracellular fluids including cerebrospinal fluid, interstitial fluid and lymph. Albumin has several biochemical properties including regulation of colloid osmotic pressure of plasma, transportation of hormones, fatty acids, drugs and metabolites across plasma, regulation of microvascular permeability, antioxidant activity, anti-thrombotic activity and anti-inflammatory activity. This multifunctional protein has been implicated in many neurological diseases owing to its ability to regulate hemodynamic properties of the brain circulation as well as the direct neuroprotective actions on neuronal and glial cells. In this review, we summarise various neuroprotective actions of the albumin in the brain. In experimental ischemic stroke, exogenous human serum albumin administration has been found to be neuroprotective via reducing brain swelling, prevention of post-ischemic thrombosis, anti-oxidant activity, hemodilution and increasing the perfusion to the ischemic tissue. Also, human serum albumin administration is currently under clinical trials for treatment of cerebral ischemia. In the experimental models of Alzheimer’s disease, albumin has been implicated in neuroprotection by inhibiting polymerisation and enhancing the clearance of amyloid β. The direct neuroprotective actions on neuronal and glial cells are mediated via endogenously produced albumin or cellular uptake of blood derived albumin. These neuroprotective effects of albumin are partly attributed to anti-oxidant property and modulation of intracellular signalling of neuronal or glial cells. The recent finding of de novo synthesis of albumin in microglial cells directs us to explore newer roles of this endogenously produced multifunctional protein in normal as well as pathological conditions of the brain.
Pathways of chemotherapy resistance in castration-resistant prostate cancer
Authors: Mahon Kate L , Henshall Susan M , Sutherland Robert L , Horvath Lisa G
Published: May 2011

Chemotherapy remains the major treatment option for castration-resistant prostate cancer (CRPC) and limited cytotoxic options are available. Inherent chemotherapy resistance occurs in half of all patients and inevitably develops even in those who initially respond. Docetaxel has been the mainstay of therapy for 6 years, providing a small survival benefit at the cost of significant toxicity. Cabazitaxel is a promising second-line agent; however, it is no less toxic, whereas mitoxantrone provides only symptomatic benefit. Multiple cellular pathways involving apoptosis, inflammation, angiogenesis, signalling intermediaries, drug efflux pumps and tubulin are implicated in the development of chemoresistance. A thorough understanding of these pathways is needed to identify biomarkers that predict chemotherapy resistance with the aim to avoid unwarranted toxicities in patients who will not benefit from treatment. Until recently, the search for predictive biomarkers has been disappointing; however, the recent discovery of macrophage inhibitory cytokine 1 as a marker of chemoresistance may herald a new era of biomarker discovery in CRPC. Understanding the interface between this complex array of chemoresistance pathways rather than their study in isolation will be required to effectively predict response and target the late stages of advanced disease. The pre-clinical evidence for these resistance pathways and their progress through clinical trials as therapeutic targets is reviewed in this study.
The RNA-binding protein Sam68 is a multifunctional player in human cancer
Authors: Bielli Pamela , Busà Roberta , Paronetto Maria Paola , Sette Claudio
Published: May 2011

Src associated in mitosis, of 68 kDa (Sam68) is a KH domain RNA-binding protein that belongs to the signal transduction and activation of RNA family. Although ubiquitously expressed, Sam68 plays very specialized roles in different cellular environments. In most cells, Sam68 resides in the nucleus and is involved in several steps of mRNA processing, from transcription, to alternative splicing, to nuclear export. In addition, Sam68 translocates to the cytoplasm upon cell stimulation, cell cycle transitions or viral infections, where it takes part to signaling complexes and associates with the mRNA translation machinery. Recent evidence has linked Sam68 function to the onset and progression of endocrine tumors, such as prostate and breast carcinomas. Notably, all the biochemical activities reported for Sam68 seem to be implicated in carcinogenesis. Herein, we review the recent advancement in the knowledge of Sam68 function and regulation and discuss it in the frame of its participation to neoplastic transformation and tumor progression.
Inositol 1,4,5-trisphosphate receptor 1 mutation perturbs glucose homeostasis and enhances susceptibility to diet-induced diabetes
Authors: Ye Risheng , Ni Min , Wang Miao , Luo Shengzhan , Zhu Genyuan , Chow Robert H , Lee Amy S
Published: May 2011

The inositol 1,4,5-trisphosphate receptors (IP3Rs) as ligand-gated Ca2+ channels are key modulators of cellular processes. Despite advances in understanding their critical role in regulating neuronal function and cell death, how this family of proteins impact cell metabolism is just emerging. Unexpectedly, a transgenic mouse line (D2D) exhibited progressive glucose intolerance as a result of transgene insertion. Inverse PCR was used to identify the gene disruption in the D2D mice. This led to the discovery that Itpr1 is among the ten loci disrupted in chromosome 6. Itpr1 encodes for IP3R1, the most abundant IP3R isoform in mouse brain and also highly expressed in pancreatic β-cells. To study IP3R1 function in glucose metabolism, we used the Itpr1 heterozygous mutant mice, opt/+. Glucose homeostasis in male mice cohorts was examined by multiple approaches of metabolic phenotyping. Under regular diet, the opt/+ mice developed glucose intolerance but no insulin resistance. Decrease in second-phase glucose-stimulated blood insulin level was observed in opt/+ mice, accompanied by reduced β-cell mass and insulin content. Strikingly, when fed with high-fat diet, the opt/+ mice were more susceptible to the development of hyperglycemia, glucose intolerance, and insulin resistance. Collectively, our studies identify the gene Itpr1 being interrupted in the D2D mice and uncover a novel role of IP3R1 in regulation of in vivo glucose homeostasis and development of diet-induced diabetes.
Rehabilitation of the Atrophic Posterior Maxilla With Pterygoid Implants: A Review
Authors: Candel Eugenia , Peñarrocha David , Peñarrocha Maria
Published: May 2011

The purpose of this article is to review the literature published and to assess the success of treatment of patients with atrophic posterior maxilla with pterygoid implants. Studies from 1992 to 2009 on patients with atrophic posterior maxilla rehabilitated with pterygoid implants were reviewed. Those reporting clinical series of at least 5 patients with atrophic posterior maxilla (Class IV and V of Cawood and Howell), rehabilitated with pterygoid implants and fixed prosthesis, and with 12 months minimum follow-up were included. In each study the following were assessed: number of patients, number of implants, surgical technique, prosthetic rehabilitation, success rate, bone loss, complications and patient satisfaction. Thirteen articles were included, reporting a total of 1053 pterygoid implants in 676 patients. The weighted average success of pterygoid implants was 90.7%; bone loss evaluated radiographically ranged between 0 and 4.5 mm. No additional complications compared with conventional implants were found, and patient satisfaction level with the prosthesis was high. Pterygoid implants have high success rates, similar bone loss levels to those of conventional implants, minimal complications and good acceptance by patients, being therefore an alternative to treat patients with atrophic posterior maxilla. Two anatomical locations in which implants are placed in the retromolar area can be distinguished: the pterygoid process and the pterygomaxillary region. Implant lengths and angulations vary between these two techniques.
A comparison of dynamic and quasi-static results for the flow towards a well
Authors: NADER J.J.
Published: May 2011

The present analysis takes into account the acceleration term in the differential equation of motion to obtain exact dynamic solutions concerning the groundwater flow towards a well in a confined aquifer. The results show that the error contained in the traditional quasi-static solution is very small in typical situations.
Chemo-mechanical effects in kaolinite. Part 1: prepared samples
Authors: WAHID A.S. , GAJO A. , DI MAGGIO R.
Published: May 2011

The results of laboratory tests on chemo-mechanical interactions in kaolinite samples prepared with inorganic, salt, acid and base solutions are presented. In particular, the effects of the different solutions on the liquid limit, one-dimensional compressibility, permeability and residual shear strength are considered. Kaolinite proves relatively insensitive to salt solutions, whereas variations in pore fluid pH cause large strength changes, associated with non-negligible changes in one-dimensional compressibility. The partly inconsistent effects induced by acids and bases on the residual shear strength and on the one-dimensional compressibility do not permit any easy interpretation of the experimental evidence. Mineral dissolution and the associated formation of new compounds are probably involved in the behaviour observed. These aspects will be investigated in part 2 of this paper.
Cone penetration tests in a virtual calibration chamber
Authors: ARROYO M. , BUTLANSKA J. , GENS A. , CALVETTI F. , JAMIOLKOWSKI M.
Published: May 2011

A virtual calibration chamber was built using a three-dimensional model based on the discrete-element method. The chamber was then filled with a scaled granular equivalent of Ticino sand, the material properties of which were selected by curve-fitting triaxial tests. Cone penetration tests were then performed under different initial densities and isotropic stresses. Penetration resistance in the virtual calibration chamber was affected by the same cone/chamber size effect that affects physical calibration chambers and was corrected accordingly. The corrected cone resistance obtained from the virtual calibration chamber cone penetration tests shows good quantitative agreement with correlations that summarise previous physical results.
Ultrasonic transducers characterisation for evaluation of stiff geomaterials
Authors: TALLAVO F. , CASCANTE G. , PANDEY M.D.
Published: May 2011

The pulse velocity test (PVT) is an ASTM standard for the dynamic characterisation of geomaterials such as stiff clays, cemented sands, rooks and concrete. The PVT is based on the first arrival of the compressional wave. The analysis of full waveforms in ultrasonic testing is important in evaluating the variation with frequency of the dynamic properties of materials (phase velocity and material damping). Reliable full waveforms are also required to calibrate numerical simulations for the interpretation of ultrasonic wave propagation in viscoelastic materials. However, the analysis of full waveforms is rarely performed in practice because of the difficulties involved in the characterisation of ultrasonic transducers and their coupling with the medium. This paper presents a new methodology for measurement of the frequency response and impulse response functions of ultrasonic transducers. The proposed methodology uses the complex exponential method to extract dynamic properties from impulse response functions. Ultrasonic tests and numerical simulations are conducted on a calibration aluminium bar and a cemented sand specimen to demonstrate the applicability of the new methodology. The results show that this methodology can be successfully used for dynamic characterisation of ultrasonic transducers for evaluation of the wave velocity and damping ratio of stiff geomaterials.
Changes to particle characteristics associated with the compression of sands
Authors: ALTUHAFI F.N. , COOP M.R.
Published: May 2011

It is commonly accepted that the onset of particle breakage in sands during compression marks the start of yielding. Although particle breakage is strongly associated with the tensile strength of a single soil grain, initial density and initial sample grading have great influence on the probability of particle breakage. This paper examines the effect of initial grading and density on the sample behaviour during one-dimensional compression for three sands with distinct mineralogies. It was found that a unique normal compression line is the outcome of a large amount of breakage in poorly graded samples and that by changing the initial grading to a better graded sample a significant reduction in particle breakage is observed, until for very well-graded samples no significant particle breakage can be measured. At this point a difficulty in defining a unique normal compression line for the sample was found and a transitional behaviour was identified. In addition to particle size, the paper examines the changes to some important particle characteristics such as particle shape and particle surface roughness in an attempt to relate the soil behaviour to the nature of the microscopic particle damage during yielding.
Social Smoking Among Young Adults: Investigation of Intentions and Attempts to Quit
Authors: Song Anna V. , Ling Pamela M.
Published: May 2011

Objectives. We compared the association between 3 different definitions of social smoking—a common pattern of smoking among young adults—and cessation indicators.

Methods. We used a Web-enabled, cross-sectional national survey of 1528 young adults (aged 18–25 years) from a panel (recruited by random-digit dialing) maintained by the research group Knowledge Networks.

Results. Among 455 smokers, 62% self-identified or behaved as social smokers. Compared with established smokers, self-identified social smokers were less likely to have cessation intentions (odds ratio [OR] = 0.83; 95% confidence interval [CI] = 0.70, 0.98) and cessation attempts lasting 1 month or longer (OR = 0.54; 95% CI = 0.45, 0.66). Behavioral social smokers (mainly or only smoking with others) were more likely than were self-identified social smokers (those who did not report these behavior patterns) to have cessation intentions (mainly ORmainly = 1.66; 95% CI = 1.05, 2.63; and ORonly = 2.02; 95% CI = 1.02, 3.97) and cessation attempts (ORmainly = 4.33; 95% CI = 2.68, 7.00; and ORonly = 6.82; 95% CI = 3.29, 14.15).

Conclusions. Self-identified social smokers may be considered a high-risk group with particular challenges for cessation. Behavioral social smokers may represent a group primed for cessation. Public health efforts should address these differences when developing smoking cessation strategies.
The Unique Authority of State and Local Health Departments to Address Obesity
Authors: Pomeranz Jennifer L.
Published: May 2011

The United States has 51 state health departments and thousands of local health agencies. Their size, structure, and authority differ, but they all possess unique abilities to address obesity. Because they are responsible for public health, they can take various steps themselves and can coordinate efforts with other agencies to further health in all policy domains.

I describe the value of health agencies' rule-making authority and clarify this process through 2 case studies involving menu-labeling regulations. I detail rule-making procedures and examine the legal and practical limitations on agency activity.

Health departments have many options to effect change in the incidence of obesity but need the support of other government entities and officials.
Effect of Health Care System Distrust on Breast and Cervical Cancer Screening in Philadelphia, Pennsylvania
Authors: Yang Tse-Chuan , Matthews Stephen A. , Hillemeier Marianne M.
Published: May 2011

Objectives. We investigated whether health care system distrust is a barrier to breast and cervical cancer screening and whether different dimensions of distrust—values and competence—have different impacts on cancer screening.

Methods. We utilized data on 5268 women aged 18 years and older living in Philadelphia, Pennsylvania, and analyzed their use of screening services via logistic and multinomial logistic regression.

Results. High levels of health care system distrust were associated with lower utilization of breast and cervical cancer screening services. The associations differed by dimensions of distrust. Specifically, a high level of competence distrust was associated with a reduced likelihood of having Papanicolaou tests, and women with high levels of values distrust were less likely to have breast examinations within the recommended time period. Independent of other covariates, individual health care resources and health status were associated with utilization of cancer screening.

Conclusions. Health care system distrust is a barrier to breast and cervical cancer screening even after control for demographic and socioeconomic determinants. Rebuilding confidence in the health care system may improve personal and public health by increasing the utilization of preventive health services.
Impact of a Malaria-Control Project in Benin That Included the Integrated Management of Childhood Illness Strategy
Authors: Rowe Alexander K. , Onikpo Faustin , Lama Marcel , Osterholt Dawn M. , Deming Michael S.
Published: May 2011

Objectives. To estimate the impact of the Integrated Management of Childhood Illness (IMCI) strategy on early-childhood mortality, we evaluated a malaria-control project in Benin that implemented IMCI and promoted insecticide-treated nets (ITNs).

Methods. We conducted a before-and-after intervention study that included a nonrandomized comparison group. We used the preceding birth technique to measure early-childhood mortality (risk of dying before age 30 months), and we used health facility surveys and household surveys to measure process indicators.

Results. Most process indicators improved in the area covered by the intervention. Notably, because ITNs were also promoted in the comparison area children's ITN use increased by about 20 percentage points in both areas. Regarding early-childhood mortality, the trend from baseline (1999–2001) to follow-up (2002–2004) for the intervention area (13.0% decrease; P < .001) was 14.1% (P < .001) lower than was the trend for the comparison area (1.3% increase; P = .46).

Conclusions. Mortality decreased in the intervention area after IMCI and ITN promotion. ITN use increased similarly in both study areas, so the mortality impact of ITNs in the 2 areas might have canceled each other out. Thus, the mortality reduction could have been primarily attributable to IMCI's effect on health care quality and care-seeking.
The Impact of Single-Payer Health Care on Physician Income in Canada, 1850–2005
Authors: Duffin Jacalyn
Published: May 2011

This study traces the average net income of Canadian physicians over 150 years to determine the impact of medicare. It also compares medical income in Canada to that in the United States. Sources include academic studies, government reports, Census data, taxation statistics, and surveys. The results show that Canadian doctors enjoyed a windfall in earnings during the early years of medicare and that, after a period of adjustment, medicare enhanced physician income. Except during the windfall boom, Canadian physicians have earned less than their American counterparts. Until at least 2005, however, the medical profession was the top-earning trade in Canada relative to all other professions.
Contribution of Water Pollution From Inadequate Sanitation and Housing Quality to Diarrheal Disease in Low-Cost Housing Settlements of Cape Town, South Africa
Authors: Govender Thashlin , Barnes Jo M. , Pieper Clarissa H.
Published: May 2011

Objectives. We investigated the effects of failing sanitation, poor housing conditions, and fecal pollution in runoff water on the health—particularly the incidence of diarrheal disease—of residents of low-cost housing settlements in Cape Town, South Africa.

Methods. In November 2009, we conducted a cross-sectional survey with structured interviews in 4 communities (n = 336 dwellings; 1080 persons). We used Colilert defined-substrate technology to determine Escherichia coli levels in runoff water samples taken from the study communities.

Results. Almost 15% of households disposed of soiled products in storm water drains and 6% disposed of soiled products in the street. In only 26% of the dwellings were toilets washed daily. Approximately 59% of dwellings lacked a tap near the toilet for hand washing, and 14% of respondents suffered 1 or more attacks of diarrhea in the 2 weeks preceding their interview. E.coli counts of runoff environmental water samples ranged from 750 to 1 580 000 000 per 100 milliliters.

Conclusions. A holistic and integrated approach is needed to improve housing quality and sanitation among Cape Town's low-income citizens.
Description and Evaluation of the 2009–2010 Pennsylvania Influenza Sentinel School Monitoring System
Authors: Short Vanessa L. , Marriott Chandra K. , Ostroff Stephen , Waller Kirsten
Published: May 2011

Objectives. We described and evaluated the 2009–2010 Pennsylvania Influenza Sentinel School Monitoring System, a voluntary sentinel network of schools that report data on school absenteeism and visits to the school nurse for influenza-like illness (ILI).

Methods. Participating schools provided daily absenteeism and ILI data on a weekly basis through an online survey. We used participation and weekly response rates to determine acceptability, timeliness, and simplicity. We assessed representativeness by comparing participating schools with nonparticipating schools. We compared monitoring system data with statewide reports of laboratory-confirmed influenza.

Results. Of the 3244 Pennsylvania public schools, 367 (11%) enrolled in the system. On average, 79% of enrolled schools completed the survey each week. Although the peak week of elevated absenteeism coincided with the peak of statewide laboratory-confirmed influenza cases, the correlation between absenteeism and state data was nonsignificant (correlation coefficient = 0.10; P = .56). Trends in ILI correlated significantly with state data (correlation coefficient = 0.67; P < .001).

Conclusions. The school-based sentinel system is a simple, acceptable, reliable device for tracking absenteeism and ILI in schools. Further analyses are necessary to determine the comparative value of this system and other influenza surveillance systems.
Racial and Ethnic Disparities in Uptake and Location of Vaccination for 2009-H1N1 and Seasonal Influenza
Authors: Uscher-Pines Lori , Maurer Jurgen , Harris Katherine M.
Published: May 2011

To learn more about racial and ethnic disparities in influenza vaccination during the 2009-H1N1 pandemic, we examined nationally representative survey data of US adults. We found disparities in 2009-H1N1 vaccine uptake between Blacks and Whites (13.8% vs 20.4%); Whites and Hispanics had similar 2009-H1N1 vaccination rates. Physician offices were the dominant location for 2009-H1N1 and seasonal influenza vaccinations, especially among minorities. Our results highlight the need for a better understanding of how communication methods and vaccine distribution strategies affect vaccine uptake within minority communities.
Quit Attempts and Quit Rates Among Menthol and Nonmenthol Smokers in the United States
Authors: Levy David T. , Blackman Kenneth , Tauras John , Chaloupka Frank J. , Villanti Andrea C. , Niaura Raymond S. , Vallone Donna M. , Abrams David B.
Published: May 2011

Objectives. We compared quit attempts and quit rates among menthol and nonmenthol cigarette smokers in the United States.

Methods. We used data from the 2003 and 2006–2007 waves of the large, nationally representative Tobacco Use Supplement to the Current Population Survey with control for state-level tobacco control spending, prices, and smoke-free air laws. We estimated mean prevalence, quit rates, and multivariate logistic regression equations by using self-respondent weights for menthol and nonmenthol smokers.

Results. In 2003 and 2007, 70% of smokers smoked nonmenthol cigarettes, 26% smoked menthol cigarettes, and 4% had no preference. Quit attempts were 4.3% higher in 2003 and 8.8% higher in 2007 among menthol than nonmenthol smokers. The likelihood of quitting was 3.5% lower for quitting in the past year and 6% lower for quitting in the past 5 years in menthol compared with nonmenthol smokers. Quit success in the past 5 years was further eroded among menthol-smoking Blacks and young adults.

Conclusions. Menthol smokers are more likely to make quit attempts, but are less successful at staying quit. The creation of menthol preference through marketing may reduce quit success.
Managed-Pressure Drilling: Using Model Predictive Control To Improve Pressure Control During Dual-Gradient Drilling
Authors: Breyholtz Øyvind , Nygaard Gerhard , Nikolaou Michael
Published: May 2011

Managed-pressure drilling (MPD) offers unprecedented capabilities for precise pressure control in drilling operations. This capability, created by the availability of new hardware tools, creates the need for tight coordination of such tools, to ensure reliable and safe operation. The use of model predictive control (MPC) is proposed as a multivariable control framework that can coordinate multiple variables to offer both better performance and higher reliability and safety compared with current practice.

A case study on a dual-gradient drilling system is presented to demonstrate how MPC can simultaneously control bottomhole pressure and hook position during drillstring movement, by simultaneously manipulating the main-pump flow rate, seabed-pump flow rate, and drillstring velocity. Simulations focusing on the robustness to modeling errors and noise sensitivity will also be presented. Computer simulations show that the proposed approach results in much lower bottomhole-pressure (BHP) deviations during drillstring movement than manual control of hook position alone. The sensitivity to errors in the MPC model and noise are found to be low. The implications of this study as well as future directions for integration of additional variables and use of appropriate MPC variants are discussed.
Ready for Gas Injection: Asphaltene Risk Evaluation by Mathematical Modeling of Asphaltene-Precipitation Envelope (APE) With Integration of All Laboratory Deliverables
Authors: Yonebayashi Hideharu , Masuzawa Tsutomu , Dabbouk Chawki , Urasaki Daisuke
Published: May 2011

An offshore carbonate oil field in the Arabian Gulf is exhibiting asphaltene deposition inside the tubing of production wells completed in one of two main producible limestone reservoirs. This problem significantly reduces well profitability because of production loss and frequent asphaltene-removal jobs (solvent soaking). Furthermore, future full-field enhanced-oil-recovery (EOR) development—namely gas injection—is now planned and might have a risk of enhancing the asphaltene problem. Therefore, comprehensive study has been carried out not only to establish a less-frequent and more-effective remedy than the current action but also to evaluate a future risk of gas injection.

The study was initiated with careful review of the fundamental measurements of asphaltene properties collected during the 20 years of production history—saturates, aromatics, resins, and asphaltenes (SARA); asphaltene contents; and asphaltene-onset-pressure (AOP). Subsequently, the mathematical modeling analysis using those properties was incorporated into the study for better understanding/predicting of asphaltene-precipitation behavior. This paper describes the integration/optimization of the asphaltene-precipitation-envelope (APE) modeling on the basis of all available laboratory data, and consequently suggests representative APE. The APE-model validity was evaluated by comparison with actual observation data in the problematic reservoir.

On the basis of the mathematical models established, several sensitivities (i.e., mixing with injection gas and blending oils produced from the two main producible reservoirs) were investigated to assess impacts of the future EOR on asphaltene risk from the subsurface and surface points of view. Several types of injection gas were examined, and their risks were compared and identified. Consequently, the surface-facility design was adequately modified and optimized in order to minimize asphaltene risk influenced by gas injection.
Design and Performance Evaluation of a Unique Deepwater Cement Slurry
Authors: Wang Chengwen , Wang Ruihe , Li Huazhou , Bu Yuhuan , Zhou Weidong
Published: May 2011

The exploration and development of deepwater hydrocarbon resources necessitate the fast evolution of drilling and completion technologies for deepwater wells. To drill and complete deepwater wells successfully, sophisticated technologies need to be developed to solve various problems arising from low temperature, weak formations, shallow water/gas flow, environmental protection, and high deepwater rig rate.

It is a challenge to develop a good cement slurry that can be used successfully for deepwater wells under low-temperature environment. Such cement slurry should have several distinct properties, such as a short thickening time, a fast transition from liquid to solid, a rapid development of compressive strength, and environmental friendliness. It usually takes a long time for conventional cement slurry to set and only limited compressive strength can be achieved at low temperatures. In addition, most additives used for the conventional cement have adverse effects on the environment. Therefore, it is of upmost importance to design an environmentally friendly and low-density cement slurry that is appropriate for deepwater wells.

In this paper, a new deepwater cement [sulfur polymer cement (SP-C)] was designed and tested for the first time. This new deepwater cement combines the advantages of the sulfoaluminate cement and Class G oilwell cement. Green cement additives including cement dispersant, fluid-loss-control agent, and accelerator were also developed. Consequently, a unique low-density cement slurry was obtained for deepwater-well applications. Laboratory tests showed that the low-density slurry exhibited favorable properties including the nonexistence of free fluid, an excellent fluid-loss-control capability, a short waiting-on-cement time at low temperatures, and a shortened transition time of critical gel strength. This new cement slurry can be easily prepared and applied in deepwater wells without adverse impacts on the marine environment.
Scale-Inhibitor Application in Northern Alberta: A Case History of an Ultrahigh-Temperature Scale-Inhibition Solution in Fire-Tube Heater Treaters
Authors: Wylde Jonathan J. , McMahon Jeff , Mayner Steve
Published: May 2011

This paper reports a challenging and unique scale-forming environment in northern Alberta, Canada. Calcite was forming on the fire tubes in a series of treaters. Bulk fluid temperature was 110°C, but skin temperature of the fire tubes was in excess of 450°C. This created an extremely high scaling potential.

The paper provides background on the field case history with a detailed description of the process and the scale-forming environment. An in-depth scale-modeling study characterizing the scaling up to 200°C is provided.

Further laboratory studies are reported, including performance testing on candidate scale inhibitors and differential scanning calorimetry (DSC) to determine their molecular stability. The testing looked at scale inhibitors and investigated the direct inhibition properties, as well as any dispersion properties to prevent surface adsorption of scale on the fire tubes.

The testing found that the incumbent scale inhibitor (phospho- nate based) was a good product for the bulk scale inhibition but was not stable at the temperature of the fire tubes. The most thermally stable scale inhibitors tested were polymaleic acid copolymers and polymeric acrylic acids of low-to-medium molecular weight. No scale inhibitors were tested to be fully stable up to 450°C, but it was found in field application that the best product identified through laboratory testing was sufficient to delay the scale formation on the fire tubes. It is hypothesized that the product was stable at high temperature for the residence time of fluid in the treaters or imparted some degree of scale inhibition even after thermal molecular scission.

The paper concludes with data of the fire-tube change-out history highlighting the step change in performance when applying the polymeric inhibitor quantified by change-out frequency and presence of hot spots.
Sour-Gas-Reservoir Exploitation in Croatia
Authors: Hrncevic L.. , Simon K.. , Kristafor Z.. , Malnar M..
Published: May 2011

Because fossil fuels are still dominant sources of energy supply, the petroleum industry is called upon not only to provide an effective management of oil and gas reserves in order to meet rising energy demand, but also to do that in a safe and efficient manner, with as small an ecological footprint as practically possible. Consequently, also taking into account the fact that conventional oil and gas reserves are declining, petroleum companies are forced to develop and adopt new technologies to increase oil and gas recovery and to expand their upstream activities to still unexploited areas, which often implies development of deep-buried oil and natural-gas reservoirs characterized by unfavorable reservoir conditions such as high temperature and pressure and even a certain amount of impurities.

Croatian experience with natural-gas production from deep-buried reservoirs is based on the development of several gas fields in the northwestern part of Croatia. The development of the largest natural-gas fields in Croatia—Molve, Stari Gradac, and Kalinovac gas fields—began at the beginning of the 1980s. The main characteristic of all the mentioned fields are extremely unfavorable reservoir conditions, with reservoir depth of more than 3000 m, high initial reservoir pressures (more than 450 bar), high temperature (180°C), and a significant share of CO2 (10 to 54%), H2S (800 ppm), and some other nonhydrocarbon compounds such as mercaptans (30 mg/m3) and mercury (1000 to 1500 μg/m3). Several other gas fields with similar reservoir conditions were discovered and developed in the last 25 years in the same region. Today, the petroleum industry in Croatia has almost 30 years of experience in processing sour natural gas with a well-established methodology of auditing processing-plant outlet-gas influences on the environment. These experiences and future plans regarding this subject will be presented in this paper.
Field Improvement of Water Handling Offshore Trinidad
Authors: Rampersad Kerry , Lom Shreeram , McLean Hadyn
Published: May 2011

This paper describes how it is possible to modify existing equipment and chemical treatment and effectively separate approximately 94% of water produced and treat it offshore. The goal is to separate water from oil on the platform abiding by environmental regulations and reduce operating costs with a defined budget. The engineering described is basically that of creating secondary and tertiary separation at each facility, improving chemical treatment and designing for redundancy and future production increases.
Reservoir Characterization and Flow Simulation of a Low-Permeability Gas Reservoir: An Integrated Approach for Modelling the Tommy Lakes Gas Field
Authors: Deng Jack H. , Aguilera Roberto , Alfarhan Mohammed , White Lionel , Oldow John S. , Aiken Carlos L.V.
Published: May 2011

The Tommy Lakes field is located in northeastern British Columbia, Canada, and is one of the largest Middle Triassic gas pools within the western Canada sedimentary basin (WCSB). The major gas-production formation (Halfway/Doig reservoirs) at the Tommy Lakes field corresponds to shoreface sands with permeabilities ranging between 0.1 and 3 md, and porosities of 3 to12%. For the purpose of production optimization and field development, a full-field reservoir model was developed with the integration of advanced reservoir characterization, hydraulic-fracture modelling, and history-matching techniques.

This study presents an integrated workflow for modelling the low-permeability Doig gas reservoir. A stochastic geostatistical reservoir model was developed on the basis of concepts emanating from an outcrop analogue analyzed with terrestrial light detection and ranging (LiDAR) technology and 60 wells that represent the fundamental rock characteristics, structure, facies? proportions, and petrophysical properties of the Doig anomalously thick sandstone bodies (ATSBs). Structural tops were interpreted from well logs and permeability/porosity relationships established from quantitative log analysis and core/log calibration. Facies were identified in cored intervals and were further grouped into four lithofacies. An artificial neural network (ANN) was used for training the logs of key wells [gamma ray (GR), neutron porosity (NPHI), and bulk density (RHOB)] and populating the facies distribution of uncored wells. Facies-based log-derived porosity, permeability, shale volume, and water saturation were assigned to gridblocks using sequential Gaussian simulation (SGS). Finally, the Monte Carlo simulation approach was used to rank the key variables affecting original gas in place (OGIP) in the uncertainty and optimization process.

Flow-based techniques were used for upscaling reservoir properties into the coarse simulation grid. The full-field simulation model was calibrated with buildup data and hydraulic-fracture modelling of single wells. Production of the Doig channel from commingled wells was allocated systematically in order to achieve a good match of the gas-production history and bottomhole pressures. Sensitivity analysis of fracture half-length and its impact on ultimate gas recovery was investigated. This concluded with an integrated development strategy.

It is concluded that integration of multiple domains leads to a valid full-field reservoir model, which is critical in developing an integrated strategy, predicting reservoir performance, and optimizing gas production.
Simulation of Deep-Coalbed-Methane Permeability and Production Assuming Variable Pore-Volume Compressibility
Authors: Tonnsen Robert R. , Miskimins Jennifer
Published: May 2011

One of the horizons of interest for future unconventional-resource development is deep- (> 5,000 ft) coalbed-methane (CBM) production. Unfortunately, coal permeability is highly sensitive to changes in stress, leading to the belief of limited permeability in deep coals. However, this conclusion is generally based on the assumption of constant pore-volume (PV) compressibility of a coal's porosity/cleat system during changing stress conditions.

Modelling the evolution of permeability within potential deep coal reservoirs is highly dependent on this assumption of constant or variable PV compressibility. This paper shows how this assumption affects modelled permeability changes and that permeability in deep coals may maintain much higher values during production than previously suggested. Using prior work and data, ideas are reorganized into an alternative view of deep-CBM permeability.

The modelled compressibility and permeability results are then applied to the simulation of deep-CBM reservoirs to discover the practical difference of the compressibility assumption on a coal's simulated production. Simulations show significant difference in production based on the two assumptions. Application of the simulation results may provide a justification for exploration into deeper CBM reservoirs.
Effects of Pre-Treatments and Air Drying Temperatures on Colour and Antioxidant Properties of Gac Fruit Powder
Authors: Kha Tuyen C , Nguyen Minh H , Roach Paul D
Published: May 2011

Gac fruit contains extraordinarily high levels of carotenoids that are well-known as strong antioxidants with an attractive yellow-orange-red colour. The aim of this study was to investigate the effects of different pre-treatments and air drying temperatures on colour characteristics, total carotenoid content (TCC) and total antioxidant activity (TAA) of resultant Gac fruit powder. Results showed that pre-soaking in solutions of ascorbic acid or bisulfite prior to air drying at low temperature of 40°C was effective in preserving TCC and TAA. Loss of TCC and TAA increased as drying temperatures increased (50, 60, 70, and 80°C). Moreover, the colour characteristics of Gac powder, such as chroma and hue angle, were not significantly affected by pre-treatments and air drying temperatures. The sorption isotherm curve of Gac aril powder has sigmoid shape.
Real-linear isometries between function algebras
Authors: Miura Takeshi
Published: May 2011

Let A and B be uniformly closed function algebras on locally compact Hausdorff spaces with Choquet boundaries Ch A and ChB, respectively. We prove that if T: A → B is a surjective real-linear isometry, then there exist a continuous function κ: ChB → {z ∈ ℂ: |z| = 1}, a (possibly empty) closed and open subset K of ChB and a homeomorphism φ: ChB → ChA such that T(f) = κ(f ∘φ) on K and $T\left( f \right) = \kappa \overline {fo\phi }$ on ChB \ K for all f ∈ A. Such a representation holds for surjective real-linear isometries between (not necessarily uniformly closed) function algebras.
On a class of nonlocal elliptic operators for compact Lie groups. Uniformization and finiteness theorem
Authors: Sternin Boris
Published: May 2011

We consider a class of nonlocal operators associated with an action of a compact Lie group G on a smooth closed manifold. Ellipticity condition and Fredholm property for elliptic operators are obtained. This class of operators is studied using pseudodifferential uniformization, which reduces the problem to a pseudodifferential operator acting in sections of infinite-dimensional bundles.
Scalar differential invariants of symplectic Monge-Ampère equations
Authors: Paris Alessandro , Vinogradov Alexandre
Published: May 2011

All second order scalar differential invariants of symplectic hyperbolic and elliptic Monge-Ampère equations with respect to symplectomorphisms are explicitly computed. In particular, it is shown that the number of independent second order invariants is equal to 7, in sharp contrast with general Monge-Ampère equations for which this number is equal to 2. We also introduce a series of invariant differential forms and vector fields which allow us to construct numerous scalar differential invariants of higher order. The introduced invariants give a solution of the symplectic equivalence of Monge-Ampère equations. As an example we study equations of the form u
xy + f(x, y, u
x, u
y) = 0 and in particular find a simple linearization criterion.
Diffractometric examination of the structure of heat-resisting steel-based coatings in different measurement geometries
Authors: Kucharska Barbara
Published: May 2011

Coatings of the composition of 310S heat-resisting steel dopped Al and Ir additions, deposited on a substrate of the same steel by the magnetron sputtering method, were examined. The measurements were made in the classical Bragg-Brentano geometry and by the GXRD method. With the fixed and different position of the coated sample by rotating the sample by angles ψ. The coating as deposited and after being soaked at 400°C for 15 minutes was subjected to examinations. The examination carried out have shown that coatings may have a unique, subtle structure which is metastable and undergoes irreversible changes in the temperatures up to 400°C. It has been found that in the outermost coating zones and zones closer to the substrate, areas occur in the coating structure, which have the different lattice parameter compared to the basic phase. Additionaly, the local period of the structure equal 5.9 nm was found.