bluuebunny/crossref_metadata_2025_split huggingface dataset:
RNA switches regulate initiation of translation in bacteria
Authors: Marzi Stefano , Fechter Pierre , Chevalier Clément , Romby Pascale , Geissmann Thomas 
Published: March 2008

Abstract
A large variety of RNA-based mechanisms have been uncovered in all living organisms to regulate gene expression in response to internal and external changes, and to rapidly adapt cell growth in response to these signals. In bacteria, structural elements in the 5′ leader regions of mRNAs have direct effects on translation initiation of the downstream coding sequences. The docking and unfolding of these mRNAs on the 30S subunit are critical steps in the initiation process directly modulating and timing translation. Structural elements can also undergo conformational changes in response to environmental cues (i.e., temperature sensors) or upon binding of a variety of trans-acting factors, such as metabolites, non-coding RNAs or regulatory proteins. These RNA switches can temporally regulate translation, leading either to repression or to activation of protein synthesis.
Lipopolysaccharide: a tool and target in enterobacterial vaccine development
Authors: Nagy Gábor , Pál Tibor 
Published: March 2008

AbstractLipopolysaccharide (LPS) is an essential component of Gram-negative bacteria. While mutants exhibiting truncated LPS molecules are usually over-attenuated, alternative approaches that affect the extent or timing of LPS expression, as well as its modification may establish the optimal balance for a live vaccine strain of sufficient attenuation and retained immunogenicity. On the other hand, a specific immune response to LPS molecules in itself is capable of conferring protective immunity to certain enterobacterial pathogens. Therefore, purified LPS derivatives could be used as parenteral vaccines. This review summarizes various LPS-based vaccination strategies, as well as approaches that utilize LPS mutants as whole-cell vaccines.
Not to wake a sleeping giant: new insights into host-pathogen interactions identify new targets for vaccination against latentMycobacterium tuberculosisinfection
Authors: Lin May Young , Ottenhoff Tom H.M. 
Published: March 2008

AbstractMycobacterium tuberculosisis one of the worlds' most successful and sophisticated pathogens. It is estimated that over 2 billion people today harbour latentM. tuberculosisinfection without any clinical symptoms. As most new cases of active tuberculosis (TB) arise from this (growing) number of latently infected individuals, urgent measures to control TB reactivation are required, including post-exposure/therapeutic vaccines. The current bacille Calmette-Guérin (BCG) vaccine and all new generation TB vaccines being developed and tested are essentially designed as prophylactic vaccines. Unfortunately, these vaccines are unlikely to be effective in individuals already latently infected withM. tuberculosis. Here, we argue that detailed analysis ofM. tuberculosisgenes that are switched on predominantly during latent stage infection may lead to the identification of new antigenic targets for anti-TB strategies. We will describe essential host-pathogen interactions in TB with particular emphasis on TB latency and persistent infection. Subsequently, we will focus on novel groups of late-stage specific genes, encoded amongst others by theM. tuberculosisdormancy (dosR) regulon, and summarise recent studies describing human T-cell recognition of these dormancy antigens in relation to (latent)M. tuberculosisinfection. We will discuss the possible relevance of these new classes of antigens for vaccine development against TB.
Pre-clinical development of cell culture (Vero)-derived H5N1 pandemic vaccines
Authors: Howard M. Keith , Kistner Otfried , Barrett P. Noel 
Published: March 2008

Abstract
The rapid spread of avian influenza (H5N1) and its transmission to humans has raised the possibility of an imminent pandemic and concerns over the ability of standard influenza vaccine production methods to supply sufficient amounts of an effective vaccine. We report here on a robust and flexible strategy which uses wild-type virus grown in a continuous cell culture (Vero) system to produce an inactivated whole virus vaccine. Candidate vaccines based on clade 1 and clade 2 influenza H5N1 strains, produced at a variety of manufacturing scales, were demonstrated to be highly immunogenic in animal models without the need for adjuvant. The vaccines induce cross-neutralising antibodies and are protective in a mouse challenge model not only against the homologous virus but against other H5N1 strains, including those from other clades. These data indicate that cell culture-grown, whole virus vaccines, based on the wild-type virus, allow the rapid high-yield production of a candidate pandemic vaccine.
Microstructural Characterization of Oxides Formed on Model Zr Alloys Using Synchrotron Radiation
Authors: Motta A. T. , Gomes da Silva M. J. , Yilmazbayhan A. , Comstock R. J. , Cai Z. , Lai B. 
Published: March 2008

Abstract
To understand how alloy chemistry and microstructure impact corrosion performance, oxide layers formed at different stages of corrosion on various model zirconium alloys (Zr-xFe-yCr, Zr-xCu-yMo, for various x, y) and control materials (pure Zr, Zircaloy-4) were examined to determine their structure and the connection of such structure to corrosion kinetics and oxide stability. Microbeam synchrotron radiation diffraction and fluorescence of oxide cross sections were used to determine the oxide phases present, grain size, and orientation relationships as a function of distance from the oxide-metal interface. The results show a wide variation of corrosion behavior among the alloys, in terms of the pretransition corrosion kinetics and in terms of the oxide susceptibility to breakaway corrosion. The alloys that exhibited protective behavior at 500°C also were protective during 360°C corrosion testing. The Zr-0.4Fe-0.2Cr model ternary alloy showed protective behavior and stable oxide growth throughout the test. The results of the examination of the oxide layers with microbeam X-ray diffraction show clear differences in the structure of protective and nonprotective oxides both at the oxide-metal interface and in the bulk of the oxide layer. The nonprotective oxide interfaces show a smooth transition from metal to oxide with metal diffraction peaks disappearing as the monoclinic oxide peaks appear. In contrast, the protective oxides showed a complex structure near the oxide-metal interface, showing peaks from Zr3O suboxide and a highly oriented tetragonal oxide phase with specific orientation relationships with the monoclinic oxide and the base metal. The same interfacial structures are observed through their diffraction signals in protective oxide layers formed during both 360°C and 500°C corrosion testing. These diffraction peaks showed much higher intensities in the samples from 500°C testing. The results for the various model alloys are discussed to help elucidate the role of individual alloying elements in oxide formation and the influence of oxide microstructure on the corrosion mechanism.
Simple Expressions for the Evaluation of Stresses in Sphere-Loaded Disks Under Biaxial Flexure
Authors: Fett T. , Rizzi G. , Esfehanian M. , Oberacker R. 
Published: March 2008

Abstract
In testing ceramic materials, sphere-loaded disk tests are of increasing importance. Three different tests including one, four, and six spheres are addressed. For the first two tests, the maximum stress in the disk center was already studied in several papers. In this note, simple analytical relations for the distribution of the tangential stress will be given. The stress distribution in the center region is, for instance, necessary for the determination of effective surface and volume as used for Weibull statistics. For special applications also, stresses across larger distances from the center are desirable. As an example, strength tests on coarse-grained alumina are mentioned briefly which need a fracture mechanics evaluation for interpretation.
Analysis of Casing-Shift Problems in Compacting Reservoirs
Authors: Jinnai Yasuo , Morita Nobuo 
Published: March 2008

AbstractIn the past, casing shift problems were thought to be one of the causes of production decline. This motivated field engineers to investigate whether casing shift occurred or not by shooting radioactive bullets in productive layers and measuring the relative movement of casing and formation. However, the results were ambiguous due to the uncertainty of wire-line logging depth measurements during a long reservoir compaction period. In this paper, the following will be investigated: how the bonding of casing and formation breaks under confining stresses,how a casing slides after the bonding breaks,the magnitude of shear force required to induce casing shift.the magnitudes of casing shift for typical reservoir conditionsTo achieve the above objectives, the following laboratory measurements were performed. Construct test samples simulating casings bonded to formation with cement and mud cakeConduct experiments measuring shear force required to induce casing shift under confining stressSimulate the correlation of depth and shear and normal stresses around a cased hole using a finite element model for compacting reservoirsCompare the results of experiments with simulations to judge the magnitude of casing shiftThe laboratory experiments showed that a casing does not simply slip when a shear load is applied. It accompanies shear failure of cement sheath. Hence, when casing shift occurs, shear fractures are also induced in the cement, which may cause gas or liquid migration through the fracture network. Calculations are performed to estimate the shear stress induced at casing/cement and formation/cement interfaces during reservoir compaction using a finite element simulation model. Comparing the laboratory-measured sliding shear stress with the calculated shear stress, it is concluded that a small casing slippage may occur at casing/cement and formation/cement interfaces. The amount and distribution of slippage along casing/cement and formation/cement are also evaluated for typical reservoir conditions. The small slippage may be serious enough to cause production reduction. Hence, re-perforation at the expected shift intervals would recover productivity. In addition, the small slippage creates a shear fracture network which may cause gas or liquid migration. This work complements two previous works1,2,3 for casing/cement and formation/cement bond strengths using similar cement. Previous work determines cement shear and hydraulic bond strengths for those with small reservoir compaction while this work focuses on cement bond strength for more severe compactions where casing slippage or failure are initiated. Unlike the standard hydraulic and shear cement bond tests, the current test method closely simulates the in-situ conditions, clarifying the phenomena occurring during casing slippage. In addition, a rule of thumb and a practical method to evaluate the magnitude of casing shift are proposed.
Solid Expandable Tubular Technology Applications in Saudi Arabia: Lessons Learned
Authors: Al-Umran Mohammed I. , Al-Obaidi Ibrahim A. , Zhou Shaohua , Al-Nassir Abdulmohsin 
Published: March 2008

Abstract
Saudi Aramco started solid expandable tubular technology applications in mid-2003. Since then the company has become one of leading players worldwide in terms of field applications. So far, more than 130,000 ft of accumulative footage of expandable liners have been installed in about 70 wells.
The major benefits of utilizing solid expandable tubular as production liner have been realized by: Reviving dead or poor oil producers to prolific oil producers.Delivering MRC (maximum reservoir contact) wells with extended 5-1/2" laterals drilled by either slimhole rotary steerable system or directional drilling assembly.Allowing advanced completions (such as smart completion with interval control valves inside expanded 5-1/2" liner and slimhole packers and screen) to provide zonal isolation in 5-1/2" lateral or sidetrack aimed to shut off water production as well as inflow control.Allowing advanced completions such as open hole smart completion with interval control valves and slimhole packers to provide zonal isolation in 5-1/2" motherbore aimed to shut off water production as well as inflow control.
Success did not come without hard lessons learned over the last four years, including several expandable liner failures in the most challenging curved sections, located in the area from vertical to near horizontal hole.
Although the technology no doubt adds a great value to drilling and workover wells, it still requires more improvements before becoming a reliable and regular tool for Saudi Aramco's demanding application environment.
Drilling Difficult Formations Efficiently with the Use of an Antistall Tool
Authors: Selnes Knut Sigve , Clemmensen Carl , Reimers Nils 
Published: March 2008

Abstract
Anti Stall Technology (AST) is a mechanical downhole solution which aims to adjust the drilling torque automatically in real time. Originally, the tool was developed by Tomax AS for coiled tubing applications where it has proven its ability to successfully reduce vibrations, motor stalls, equipment failures and general wear, in addition to increasing the penetration rate and run length (Dagestad, V 2006). The tool was then developed further based on the need for a similar solution for rotary drilling. The goal was to eliminate cutter-induced torque variations and string stalls in difficult formations and resultant harmful effects. Prototype AST tools were made in sizes ranging from 6 ¾" to 8 ¼". The tools were then run in test wells and later in field operations with a variety of tool configurations until the database, in addition to two controlled trials, counted 25 regular jobs - mainly on the Norwegian Continental Shelf. The paper describes in detail, both based on theory and on field experience, how the bit-induced torque fluctuations are significantly decreased to improve penetration, and how BHA damage is prevented in order to increase run lengths.
Automatic Real-Time Drilling Supervision, Simulation, 3D Visualization and Diagnosis on Ekofisk
Authors: Rommetveit Rolv , Bjørkevoll Knut S. , Ødegård Sven Inge , Herbert Mike , Halsey George W. 
Published: March 2008

AbstracteDrilling is a new and innovative system for real time drilling simulation, 3D visualization and control from a remote drilling expert centre. The concept uses all available real time drilling data (surface and downhole) in combination with real time modeling to monitor and optimize the drilling process. This information is used to visualize the wellbore in 3D in real time. eDrilling has been implemented in an Onshore Drilling Center in Norway. The system is composed of the following elements, some of which are unique and ground-breaking: An advanced and fast Integrated Drilling Simulator which is capable to model the different drilling sub-processes dynamically, and also the interaction between these sub-processes in real time.Automatic quality check and corrections of drilling data; making them suitable for processing by computer modelsReal time supervision methodology for the drilling process using time based drilling data as well as drilling models / the integrated drilling simulatorMethodology for diagnosis of the drilling state and conditions. This is obtained from comparing model predictions with measured data.Advisory technology for more optimal drilling.A Virtual Wellbore, with advanced visualization of the downhole process.Data flow and computer infrastructureeDrilling has been implemented in an Onshore Drilling Center on Ekofisk in Norway. The system has been used on several drilling operations. Experiences from its use will be summarized and presented. This paper has main focus on utilization of an advanced flow model for real time supervision and control of ECD and ECD related effects.
Extended-Reach Drilling Offshore California: An Operator's Experience with Drilling a Record Extended Reach Well
Authors: Walker Michael W. 
Published: March 2008

Abstract
The "Spanish Bay" well was drilled from a production platform located offshore California in 1,075 ft of water. This record setting extended reach well overcame numerous technical and operational challenges and reached a total depth of 33,435-ft measured depth (MD) / 7,663-ft true vertical depth (TVD) with 29,720-ft displacement. This paper will highlight the rig package limitations and upgrades, describe key technical and operational challenges, discuss how the challenges were addressed, and describe key / unique operations.
A case history is presented describing the technical and operational challenges successfully overcome including limited hydraulics, high torque, pipe racking constraints, mud handling capacity, offshore logistics, and platform space limitations. As predicted by detailed torque and drag modeling, the well's 86° tangent angle required that drillpipe and casing be rotated into the hole to overcome the effects of negative weight. The 22,131-ft 9⅝ × 10¾-in. intermediate liner was successfully floated and rotated to 29,831ft MD / 5,525 ft TVD. The well established a new North American extended reach drilling (ERD) record and a new global ERD record from an offshore location.
How Drillstring Rotation Affects Critical Buckling Load?
Authors: Menand S. , Sellami H. , Akowanou J. , Simon C. , Macresy L. , Isambourg P. , Dupuis D. 
Published: March 2008

AbstractBuckling of tubulars inside wellbores has been the subject of many researches and articles in the past. However, these conservative theories have always followed the same assumptions: the wellbore has a perfect and unrealistic geometry (vertical, horizontal, deviated, curved), the friction and rotation effects are ignored, conditions relatively far from actual field conditions. How do tubulars buckle in actual field conditions, that is, in a naturally tortuous wellbore with friction and rotation ? Can we apply theories developed for perfect well conditions (no tortuosity, no friction, no rotation) to actual well conditions ?For the first time, this paper presents how the drillstring rotation affects the critical buckling load in actual field conditions. These new results have been obtained from an advanced model dedicated to drillstring mechanics successfully validated with laboratory tests.Firstly, this paper presents the new developments integrated in a recently advanced model for drillstring mechanics that enables to take into account the buckling phenomenon in any actual well trajectory. Indeed, some simultaneous torque-drag-buckling calculations are presented and allow to properly take into account the additional contact force generated in a post-buckling configuration, and as a consequence the additional torque at surface. Secondly, this paper shows the influence of friction and rotation on buckling loads for some practical and critical cases met in the drilling industry. These friction and rotation effects are demonstrated with an experimental set up that enables to confirm theoretical features. Lastly, this paper shows that using standard buckling criteria may lead to too conservative solutions, and that under specific circumstances, the drilling and completion engineer could safely operate in a buckling mode for a given time.These new results presented in this paper should improve significantly well planning and operational procedures to drill and operate more and more complex wells.
Mitigating Risks From Waste Subsurface Injection Through Accurate Downhole Pressure Measurement, Analysis, and Fracture Monitoring
Authors: Shokanov T. A. , Fragachan F. E. , Feyereisen S. B. , Greener J. M. 
Published: March 2008

Abstract
Enhanced environmental awareness and controls for new offshore and onshore field developments has increased the requirement for effective management of cuttings and associated drilling waste. Subsurface injection of these wastes has proven to be an environmentally sound alternative for waste management.
This paper describes the results of injection monitoring and in-depth fracture diagnostics pressure analysis for injection assurance in a dedicated waste injection well located offshore in the southern Caspian Sea. The benefits and value generated from real-time downhole pressure measurements recorded during subsurface waste injection and decline periods provided an insight into waste domain monitoring and obligatory waste management quality assurance. Precise interpretation and thorough evaluation of non-standard pressure signatures registered during regular injections provided critical information to reveal sub-surface injection pressure anomalies, potential impact on injection assurance and effectively mitigate associated potential risks.
Early in the project, fracture re-orientation into the horizontal plane as a result of injection wells being located in a tectonically active environment and on the flank of a compressional anticline with higher horizontal stresses, resulted in additional challenges for the injection assurance. This prompted the immediate need for close and continuous pressure monitoring and analysis. Detailed analysis of the downhole and surface pressure response coupled with regular collaboration of the operational team and subsurface geo-mechanics experts has contributed to the successful delivery of a waste management program. It is via an integrated team that has made the challenges and success of this project feasible.
This paper also includes the risks identified throughout the injection project as well as lessons learned from the experience. Downhole pressure measurements coupled with real-time injection monitoring provided the quality assurance required to meet zero discharge objectives in a tectonically active offshore environmental with complex in-situ conditions.
To date, more than 200,000 bbl of drilling waste have been safely disposed of in this well using subsurface injection.
Remote HP/HT Wells in Egypt
Authors: Bruce Tom 
Published: March 2008

Abstract
BP drilled and tested successfully the well Raven 1 in 2004. In 2006 BP mobilised into Mediterranean Sea the 15 K moored semi Pride North America. The wells to drill are deep HPHT exploration wells, it is the First Big Bore wells introduced in Egypt. Extensive learnings from Gom and Shah Deniz were transferred over.
The result of well Raven 2 confirmed the gas resources and the success of the design and the execution of a Big Bore well.
The leanings are: successful application of stress cage principle, under reaming performance, ECD management, well control equipment and operations, expandable contingencies actually used, Equipment integrity standards.
Specialized Equipment was implemented: Rig HPHT Monitoring System dedicated to HP HT drilling operation which meet The Institute of Petroleum model code of Practice, Total Waste Management Alliance system as no rejection is allowed, successful contingency deployment of Expandable Liner hanger at a depth of 4870 m (15978ft), such technology is considered for additional hole sections.
Personnel training was a key issue and put through and continually re-trained for HP HT operations. Joint Operations manual was created and strictly adhered to. Bi weekly well control drills were performed.