bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of mannan antigen and anti-mannan antibodies in the diagnosis of invasive candidiasis: recommendations from the Third European Conference on Infections in Leukemia
Authors: Mikulska Małgorzata , Calandra Thierry , Sanguinetti Maurizio , Poulain Daniel , Viscoli Claudio ,   the Third European Conference on Infections in Leukemia Group
Published: July 2012

Abstract
Introduction
Timely diagnosis of invasive candidiasis (IC) remains difficult as the clinical presentation is not specific and blood cultures lack sensitivity and need a long incubation time. Thus, non-culture-based methods for diagnosing IC have been developed. Mannan antigen (Mn) and anti-mannan antibodies (A-Mn) are present in patients with IC. On behalf of the Third European Conference on Infections in Leukemia, the performance of these tests was analysed and reviewed.

Methods
The literature was searched for studies using the commercially available sandwich enzyme-linked immunosorbent assays (Platelia™, Bio-Rad Laboratories, Marnes-la-Coquette, France) for detecting Mn and A-Mn in serum. The target condition of this review was IC defined according to 2008 European Organization for Research and Treatment of Cancer/Mycoses Study Group criteria. Sensitivity, specificity and diagnostic odds ratios (DOR) were calculated for Mn, A-Mn and combined Mn/A-Mn testing.

Results
Overall, 14 studies that comprised 453 patients and 767 controls were reviewed. The patient populations included in the studies were mainly haematological and cancer cases in seven studies and mainly intensive care unit and surgery cases in the other seven studies. All studies but one were retrospective in design. Mn sensitivity was 58% (95% confidence interval [CI], 53-62); specificity, 93% (95% CI, 91-94) and DOR, 18 (95% CI 12-28). A-Mn sensitivity was 59% (95% CI, 54-65); specificity, 83% (95% CI, 79-97) and DOR, 12 (95% CI 7-21). Combined Mn/A-Mn sensitivity was 83% (95% CI, 79-87); specificity, 86% (95% CI, 82-90) and DOR, 58 (95% CI 27-122). Significant heterogeneity of the studies was detected. The sensitivity of both Mn and A-Mn varied for different Candida species, and it was the highest for C. albicans, followed by C. glabrata and C. tropicalis. In 73% of 45 patients with candidemia, at least one of the serological tests was positive before the culture results, with mean time advantage being 6 days for Mn and 7 days for A-Mn. In 21 patients with hepatosplenic IC, 18 (86%) had Mn or A-Mn positive test results at a median of 16 days before radiological detection of liver or spleen lesions.

Conclusions
Mn and A-Mn are useful for diagnosis of IC. The performance of combined Mn/A-Mn testing is superior to either Mn or A-Mn testing.
Mapping Shekgalagari in Southern Africa: a Sociohistorical and Linguistic Study
Authors: Chebanne A. M. , Monaka K. C. 
Published: July 2012

The Bakgalagari were classified by Guthrie (1948) as S30 and by Cole (1954) as 60/2/5. They incorporate ethnic groups such as Bangologa, Bashaga, Babolaongwe, Balala, Bakhena, Baritjhauba, and Bakgwatheng and Baphaleng, the latter of which do not speak Shekgalagari any more. At the moment, Bakgalagari are only found in Botswana. They are thought to have arrived in southern Africa more than 2000 years ago, together with other Bantu groups (Tlou/Campbell 1997:33), and were the earliest Sotho-Tswana group to inhabit the Madikwe and Limpopo river basins (Figure 1) around 900 and 1000 CE (Tlou/Campbell, 1997).Around 1200 CE, the Bakgalagari were already inhabiting the peripheries of this area as they migrated into Botswana, where they are estimated to have arrived around 1000 CE, as Figure 2 illustrates (cf. Tlou/Campbell, 1997:90). They would later be pushed into the Kgalagadi desert, which reinforced the peripheral and distant location of some of them from the rest of the Sotho-Tswana groups that subsequently inhabited the country.History suggests that there were ethnic rivalries amongst the Bakgalagari, and they consequently split into various ethnic groups (Tlou/Campbell, 1997:90). These ethnic groups were dispersed in various directions in the country at different times as shown in Figure 3. Figure 3 shows the historical base and the subsequent movements of the Bakgalagari starting earlier than 1400 CE. It is possible that these movements might have been reversed at various times, and also that some people at a later stage took the same directions to find their ethic counterparts (e.g., Babolaongwe at around 1650 CE).
Exotic Plants of Western Africa: Where They Came From and When
Authors: Alpern Stanley B. 
Published: July 2012

History in Africa carried an article in 1992 entitled “The European Introduction of Crops into West Africa in Precolonial Times.” I wrote this to correct an impression left by several historians that only maize and cassava were worth mentioning. My reading of precolonial African history had made it very clear that a great many new crops were brought to the continent during the slave-trade period. My initial geographical focus was what used to be called Lower Guinea, roughly the coast from Cape Palmas to Mt. Cameroon, but inevitably my research took in all of western Africa from Senegal to Angola and up to the southern fringe of the Sahara. My findings were admittedly interim, a sort of database for future refinement. And yet I was able to identify 86 introduced crops.It was ingenuous of me to expect that one paper would suffice to over-turn what had become conventional wisdom. In 1995 John Iliffe, in 1997 Elizabeth Isichei, in 1998 John Reader repeated the maize-cassava mantra. In 2002 Christopher Ehret expanded the duo of exotic crops to include tobacco, peanuts, New World beans, Asian rice and sugar cane. David W. Phillipson reiterated in 2005 what he had said 20 years earlier, citing only maize, cassava and bananas. And in 2006 James L.A. Webb Jr. named just four: maize, cassava, peanuts and potatoes.This pattern of minimization may reflect what seems to be a general disinclination of historians to dig deeply into botany. An important recent book titled Writing African History devotes only 17 of 510 pages to the subject.
Applying Simultaneous Variable Control Strategies for ROP Optimization and Offshore Well Costs Mitigation
Authors: Folsta M. G. , Martins A. L. 
Published: July 2012

Abstract
Process control strategies are widespread in the industry and provide cost reduction and reliability for different processes. Automation for Well construction technology is still an emerging technology, most probably due to data transmission limitations and to the several uncertainties inherent to the process. The elevated costs, especially in deepwater operations, and the society claims for safety improvement are the major drives for the increasing industrial efforts to overcome the steps for drilling automation. Several process can be controlled during well construction steps, such as: downhole pressure and torque on bit during drilling, bit cost minimization, keeping downhole pressures during influx circulations and tripping. The purpose of this article is to show a comprehensive analysis of the adequacy of different process control strategies to support the automation of the drilling process, with special focus on cost reduction. Initially, a traditional feed back approach was considered to compare different control methodologies, such as Proportional (P), Proportional-Integral (PI) and proportional - Integral- Differential (PID). Comparison in response times, attenuation rates and other control parameters are presented. Control stability performance was evaluated through the analysis of measurement and actuation delays, signal loss, magnitude of disturbs and other classic strategies. A multiple input single output analysis was included, introducing gains to the control process.
Development of a Software System for Drilling Optimization using Surface and Downhole Drilling Data Modeling a Human Process for Drilling Optimization
Authors: Hanley Chris , Stuart Simon , Bass Chad , Garcia Alexis 
Published: July 2012

Abstract
Software systems are developed with the intent of providing methods to perform specific business tasks. However, in actual use cases, additional human processes or supplemental software are often required to complete the business process. In ideal cases, the software would guide the user through the entire business process and significantly aid in the required decision making or analysis to complete the process.
This paper will present the development of a new drilling optimization software system ergonomically modeled on key business and analytical processes. These key processes have been organically developed over a number of years for a commercial drilling optimization service using data from downhole drilling dynamics recorders. A multi-disciplinary project team including business unit managers, project coordinators, data analysts, software architects and developers was assembled. The project team designed the new system to ensure it would fit the human processes that had historically been used to support the commercial service.
The new system models all of the key business processes associated with the commercial drilling optimization service. These processes include job setup, mobilization of tools, assignment of field personnel to the job, acquisition of all required data in the field, and reporting tools for field personnel.
The system also provides the user with an intuitive suite of data analysis and drilling optimization techniques. These include automated processes for handling, merging, analyzing, and presenting the surface drilling parameters and recorded downhole drilling dynamics data. Additionally, the user is provided with recommended data analysis and optimization routines from the system based on data entered throughout the business processes from job setup to field operations and based on trends identified in the surface parameters and recorded downhole drilling dynamics data imported into the system.
Case studies demonstrating the value-added to the users of the new system will be presented.
Second Generation Interval Control Valve (ICV) Enhances Operational Efficiency and Inflow Performance in Intelligent Completions
Authors: Rahman Jameel , Allen Clifford , Bhat Gireesh 
Published: July 2012

Abstract
Intelligent completions were introduced over a decade ago to address completions and reservoir management challenges arising from highly-deviated, extended-reach, multi-targeted, or multilateral wells. Recent advances in exploration and drilling technology are enabling the oil and gas industry to target reservoirs with stratigraphic and depositional complexities in deepwater, subsalt, arctic, and other extreme environments, resulting in the need to develop a new generation of intelligent completion tools. These reservoirs also may be characterized by HPHT, extreme HPHT, or ultra-HPHT environments with multiple components contributing to the uncertainty of recovery.
This paper describes how the requirements of current and future reservoir environments and a decade of operational experience have shaped the functional design and qualification of a new-generation Interval Control Valve (ICV) for intelligent completions. The new-generation ICV has higher pressure and temperature tolerances to cater to the new harsher environments while simplifying its operating mechanism and improving inflow performance and debris tolerance. The qualification program included metal-to-metal seal qualification, life-cycle testing, API 14A SCSSV class II- sand slurry based tests, flow coefficient (Cv) test, seal stack qualification, and erosion testing. Descriptions of each qualification test, acceptance criteria and test results that demonstrate the capability of the new generation of ICV to perform in severe service conditions are presented in this paper.
Field applications of the second generation valve have shown additional operational benefits not even considered during the design. Technologies such as real time ICV position feedback have further aided in maximizing efficiency by enabling the use of downhole or surface positioning. Surface positioning devices can choke flow by varying ICV positions. The use of surface positioning enhances reliability by reducing the number of tools required downhole. Finally the paper outlines the operational limits of the current design and discusses the design enhancements planned for the next generation ICV.
Effect of Liquid Invasion and Capillary Pressure on Wireline Formation Tester Measurements in Tight Gas Reservoirs
Authors: Andrews Joshua Thomas , Bahrami Hassan , Rezaee Reza , Mehmood Sultan , Salemi Hossein , Pourabed HamidReza 
Published: July 2012

Abstract
Wireline formation testing and measurement of true formation pressure can provide essential knowledge about the reservoir dynamic characteristics. In tight formations, a reliable determination of pressure and mobility gradients is challenging because of the tight nature of formation rock. Due to the very low reservoir permeability, the mud cake across wellbore is often ineffective in preventing filtrate invasion, thus causing the measured pressure to be higher than actual formation pressure as a result of supercharging effect. Wireline formation testing measurements are also influenced by the effects of filtrate invasion and capillary pressure, as the measured pressure is pressure of drilling fluid filtrate, the continuous phase present in the invaded region around wellbore. As a result, the measured pressure might be different to true formation pressure. This effect is more noticeable in tight gas reservoirs due to capillary pressure effect.
This paper looks into estimation of true formation pressure and evaluates the effect of filtrate invasion damage and supercharging on wireline formation tester measurements in tight gas reservoirs. Numerical simulation approach is used to build the reservoir model based on data acquired from a tight gas reservoir. The model undergoes water injection followed by gas production from different testing points along the wellbore, and the corresponding pressure gradients are plotted to check for pressure matching with that of the formation fluid in the virgin region. The results indicate the significant effects of supercharging, reservoir characteristics, capillary pressure and liquid invasion damage on wireline formation pressure measurements in tight gas reservoirs.
Challenges in Deep Shale Gas Drilling: A Case Study in Sichuan Basin
Authors: Li Gao , Liu Houbin , Meng Yingfeng , Leng Xueshuang , Jia Hongjun , Li Hongtao , Hu Jinke 
Published: July 2012

Abstract
As an unconventional gas resource, shale gas has been developed mostly in shallow reservoirs which are mainly buried in depth form 76 m to 2439 m in the world. However, the deep shale gas is drawing more attention as time goes by. In this paper, deep shale gas in Sichuan Basin is studied as an example where the shale gas reservoirs are mostly buried deep in depth from 2300 m to 4500 m. Because the shale gas in Sichuan Basin is buried deep with high formation pressure and the formation conditions are complex, there are many problems that will be encountered during drilling, such as wellbore instability, serious formation damage by high drilling fluid pressure, and low drilling efficiency, etc. In this paper, shale gas reservoir in Long maxi Group of Sichuan Basin is studied as a case for deep shale gas drilling. Basic characteristics of strata profile, lithological characteristics, formation fluids and formation pressure are analyzed combined with previous drilling data. Based on this, wellbore stability and formation damage are evaluated. The study indicates that in a relatively high borehole stress condition with a Mechanic-Chemical coupling, shale with lamellar, brittle and high clay content has a high collapse stress, and borehole trajectory design and drilling fluid performance are crucial to wellbore stabilization. Meanwhile, in deep shale drilling of this area, liquid phase will invade into bedding fissures and tectonic fractures to form a liquid phase trap between the fractures and matrix, so that the shale formation in near bore area will be isolated by the aqueous phase trapping and unable to penetrate, and it is the main formation damage. This will be helpful in improving wellbore stability in basin deep shale gas drilling, reducing formation damage, and promoting drilling and exploration efficiency.
Unique Flow-Back Chemistry for Enhancing Productivity of Low- Permeability Reservoir
Authors: Zhang Hui , Marinescu Pavel , Foxenberg William 
Published: July 2012

Abstract
Low-permeability reservoirs are highly sensitive to water saturation. When filtrate or clear brine is lost into these formations, capillary forces pull the fluid into pore spaces and prevent full displacement upon production. This paper illustrates how effective flowback chemistry reduces water saturation and enhances productivity. The authors initiated a study to evaluate chemistries that can be added to reservoir drill-in fluids, completion brines, and workover fluids to reduce capillary forces, recover invaded brine from the formation, and promote optimal productivity of the well. This paper introduces a unique flowback chemistry that not only provides excellent surface tension reduction and good thermal stability, but fulfills a challenge not met before; i.e., it is completely soluble and compatible with all common types of completion brines. Furthermore, this chemistry is not absorptive to solids in drilling fluids or a porous formation matrix, therefore low surface tension and low capillary pressure are maintained with mud filtrate or brine that is lost to the formation. Simple, low-cost, and innovative methodologies are presented to illustrate capillary pressure reduction and brine recovery in a simulated formation.
Due to the nature of surface activity, flowback treatments containing surfactants invariably generate strong and long-lived foam. If not controlled, foam can cause difficulties or even catastrophic outcomes for well service jobs including fluid transportation, well circulation, and brine reclamation. The flowback chemistry presented in this paper includes a new and very effective defoamer (or antifoamer,) which renders the flowback treatment non-foaming. Successful lab tests and field application are presented.
Pore Pressure and Fracture Gradient Prediction in Shale Gas Formations: Accounting for Complex Rock Properties and Anisotropies
Authors: Li Shuling , Purdy Cary , Wu Shiguo 
Published: July 2012

Abstract
The prediction of abnormal pore pressure is necessary for avoiding, or at least mitigating, drilling risks but is even more critical in shale gas formations where pore pressure can increase from normal pressure to an abnormally high pressure over a comparatively short depth interval. Arguably, the pore pressure prediction in shale gas plays offers even greater challenges than conventional reservoirs. There are numerous reasons why shale gas presents additional challenges. First, anisotropic rock properties in shale formations thataffect log responses will also affect pore pressure prediction. Second, the presence of gas in the shale causes the compressional interval travel time to read higher (slower), which affects derived rock properties, negatively impacting the accuracy of conventional pressure prediction techniques. Third, the geologically-old formations have higher resistivities with complex compaction and uplift histories. The same properties that create challenges with pore pressure prediction also cause uncertainties in fracture gradient prediction.
New pore pressure prediction methods have been developed to address the unique characteristics of unconventional gas plays. The new methods incorporate gas corrections in the calculation of pore pressure and fracture gradient. Becausethe shear wave velocity has a much smaller gas effect than the compressional wave, it is used to correct the compressional data. Based on the corrected compressional log data, a better pore pressure prediction can be achieved. For resistivity-based pore pressure prediction, a new depth-dependent compaction, which accounts for complex compaction and reduces the gas effect, is used for improved pore pressure prediction. Additional improvements in the prediction of pore pressures, fracture gradient, and minimum stress are achieved by characterizing the effects of shale property anisotropies (e.g., Poisson's Ratio). The improvements achieved with the new methods are demonstrated through comparative analyses with conventional methods in the Bossier and Haynesville shales.
Dynamic Modeling of Wellbore Pressures Allows Successful Drilling of a Narrow Margin HPHT Exploration Well in Malaysia
Authors: Nordin Noor Azree , Umar Lawrence , Aziz IntanAzianBt A , Nas Steve , Woo Wing Keat 
Published: July 2012

Abstract
Using a Dynamic Hydraulic and Well Control Simulator to predict and establish wellbore pressures in a narrow margin HPHT well has allowed the operator to set operational limits during drilling, tripping, casing and cementing operations. A previous attempt to reach the objectives for the well failed. A much more rigorous approach to wellbore pressure management was undertaken prior to drilling this second well. A complete review of the expected pressure limitations was conducted, this review included a detailed overview of pore and fracture pressures as well as casing setting depths, hole sizes, temperature effects and proposed mud weights. This resulted in an improved prediction of the pressure windows for each of the proposed hole sections. Each hole section was in turn reviewed for optimal mud weights and this included a detailed review of equivalent static, equivalent circulating and dynamic kick tolerance limitations for the proposed mud weights. Surge and Swab calculations then determined maximum tripping speeds and cementing calculations ensured that pore and fracture pressure limits were not breached with the proposed cement volumes and pump schedules.
This paper presents the approach that was taken in proving a complete pressure management system for a narrow margin HPHT exploration well. The use of dynamic hydraulic models allowed accurate predictions of down hole pressures during virtually all drilling operational phases a hole section. Calculated down hole pressures were compared to PWD tools, proving that the accuracy of the dynamic hydraulic predictions was within the required limits to allow drilling without a PWD tool if required. Combining the available pore pressure and fracture pressure data, with mud weight schedules, pump rates, tripping rates and cementing operations allowed optimization of the drilling parameters thus ensuring that this narrow margin HPHT well, was drilled successfully to its target depth and all of its objectives were met.