bluuebunny/crossref_metadata_2025_split huggingface dataset:
Triglyceride to HDL-C Ratio and Increased Arterial Stiffness in Children, Adolescents, and Young Adults
Authors: Urbina Elaine M. , Khoury Philip R. , McCoy Connie E. , Dolan Lawrence M. , Daniels Stephen R. , Kimball Thomas R. 
Published: March 2013

BACKGROUND AND OBJECTIVE:
Lipid levels are linked to early atherosclerosis. Risk stratification may be improved by using triglyceride to high-density lipoprotein cholesterol ratio (TG/HDL-C), which relates to arterial stiffness in adults. We tested whether TG/HDL-C was an independent predictor of arterial stiffness in youth.

METHODS:
Subjects 10 to 26 years old (mean 18.9 years, 39% male, 56% non-Caucasian, n = 893) had laboratory, anthropometric, blood pressure, and arterial stiffness data collected (brachial distensibility, augmentation index, carotid-femoral pulse-wave velocity). Subjects were stratified into tertiles of TG/HDL-C (low, n = 227; mid, n = 288; high, n = 379).

RESULTS:
There was a progressive rise in cardiovascular (CV) risk factors and arterial stiffness across TG/HDL-C ratio. The high TG/HDL-C ratio group had the stiffest vessels (all P &lt; .03 by analysis of variance). TG/HDL-C as a continuous variable was an independent determinant of brachial distensibility in CV risk factor adjusted model and for carotid-femoral pulse-wave velocity in obese subjects, with trend for higher augmentation index.

CONCLUSIONS:
TG/HDL-C, an estimate of small, dense low-density lipoprotein cholesterol, is an independent determinant of arterial stiffness in adolescents and young adults, especially in obese youth. These data suggest that use of TG/HDL-C may be helpful in identifying young adults requiring aggressive intervention to prevent atherosclerotic CV diseases.
Temperature dependent behavior of flat and bulk heterojunction organic solar cells
Authors: Widmer Johannes , Leo Karl , Riede Moritz 
Published: March 2013

ABSTRACTThe open-circuit voltage of an organic solar cell is increasing with decreasing temperature and with increasing illumination intensity. These dependencies are quantitatively investigated for two types of organic solar cells, one with a flat donor-acceptor heterojunction and one with a mixed layer bulk heterojunction. Zinc-phthalocyanine and C60 are used as donor and acceptor, respectively. A qualitative difference is found for the two geometries. We find that a logarithmic illumination intensity dependence with temperature as a linear pre-factor of the logarithm, which is commonly reported and observed, is applicable for the bulk heterojunction. The flat heterojunction, in contrast, shows a constant illumination intensity pre-factor which is independent of the temperature, and the temperature can be modeled as additional linear summand.
Hall Effect Measurement System for Characterization of Doped Single Crystal Diamond
Authors: Berkun Isil , Demlow Shannon N. , Suwanmonkha Nutthamon , Hogan Timothy P. , Grotjohn Timothy A. 
Published: March 2013

ABSTRACTA temperature dependent Hall Effect measurement system with software based data acquisition and control was built and tested. Transport measurements are shown for boron-doped single crystal diamond (SCD) films deposited in a microwave plasma-assisted chemical vapor deposition (MPCVD) reactor. The influence of Ohmic contacts and temperature control accuracy are studied. For a temperature range of 300K-700K IV curves, Hall mobilities and carrier concentrations are presented.
Plastic Deformation of Directionally-Solidified MoSi2/Mo5Si3 Eutectic Composites
Authors: Sasai Yuta , Inoue Atsushi , Fujiwara Kosuke , Kishida Kyosuke , Inui Haruyuki 
Published: March 2013

ABSTRACTDeformation behavior of the directionally-solidified MoSi2/Mo5Si3 eutectic composites has been investigated as a function of the average thickness of MoSi2 phase over a temperature range from 900 to 1500°C. The average thickness of both MoSi2 and Mo5Si3 phases in the directionally-solidified ingots with script-lamellar morphologies grown by optical floating zone method decreases with increasing the growth rate. Plastic deformation was observed above 1000°C for all the DS ingots grown at different growth rates when the loading axis is parallel to [1¯10]MoSi2 close to the growth direction. Yield stress decreases monotonically with increasing temperature. Yield stress at 1400°C increases drastically with decreasing the average thickness of MoSi2 phase.
Infrared and Raman Spectroscopic Study of Glasses in the Al2O3-B2O3-Fe2O3-Na2O-SiO2 System
Authors: Stefanovsky S.V. , Fox K.M. , Marra J.C. 
Published: March 2013

ABSTRACTGlasses in the Al2O3-B2O3-Fe2O3-Na2O-SiO2 system were produced at a temperature of 1150 °C, poured onto a metal plate and annealed. The nature of the structural units and their bonding in the structure were studied by infrared and Raman spectroscopic techniques. The structural network of all the glasses studied is built from major [SiO4] tetrahedra with 2-3 non-bridging oxygens (NBO). Incorporation of Fe2O3 offers a destructive effect in the glass network.
The Effects of Structure on the Formation of Schottky Barriers at Nanoparticle-Oxide Interfaces
Authors: Kraya Ramsey , Kraya Laura Y. 
Published: March 2013

ABSTRACTThe surface structure of oxide materials may be the limiting factor in controlling switching properties at interfaces. Here we investigate and correlate the surface structure and electronic properties of BaTiO3 substrates. By using low energy electron diffraction and scanning tunneling microscopy we are able to identify surface reconstructions based on annealing treatments. We then investigate the effect of contact size on the transport properties on oxide surfaces utilizing atomic force microscopy. Our results show the critical importance of controlling surface structure to optimize electronic properties at oxide interfaces.
Evolution of nucleation sites and bubble precursors in silicon as a function of helium implanted dose
Authors: Liu Changlong , Delamare R. , Ntsoenzok E. , Regula G. , Pichaud B. , Veen A.Van 
Published: March 2013

Abstract(111) oriented silicon samples were implanted at room temperature with 1.55 MeV 3He ions in the dose range of 5×1015 to 5×1016/cm2. Cross-sectional transmission electron microscopy (XTEM) was used to study the evolution of bubbles and extended defects during subsequent thermal annealing at 800°C and 900°C for 30min. The He desorption from bubbles and bubble precursors was measured by means of nuclear reaction analysis (NRA). TEM observations show that no bubbles were observed in Si implanted at doses lower than 1×1016/cm2, while a well-defined cavity band was formed after implantation at 5×1016/cm2 and subsequent thermal annealing. At the intermediary dose of 2×1016/cm2, however, the evolution of bubbles and extended defects is quite different. The bubbles prefer to nucleate in large planar clusters surrounded by a high density of dislocation loops emerging from them. The clusters of bubbles act as the sources of the dislocation loops. NRA measurements indicate that the He desorption behavior is also dose-dependent. The He desorption is achieved much faster in low dose implanted Si. The results are qualitatively discussed.
Drill Pipe Riser Intervention System Successful Experience in Offshore West Africa
Authors: Rohart Christophe , de Fonvielle Henri , Bordet Laurent , Campbell William , Susak Nenad , Marajh Mitra 
Published: March 2013

Abstract
While offshore intervention on subsea equipments is quite common, the increasingly deeper water operations require light weight intervention systems while meeting safe and stringent operating specification. For these new deep offshore challenges, the conventional risers are becoming a more costly and less desirable solution.
Starting with a recollection of the main drivers that motivated the development of drill pipe riser intervention systems (DPRISi), the paper details the technical and economical challenges in West Africa that have led to the design of such a solution. When non productive time and financial aspects are taken into account, it makes sense to develop a dedicated system in order to provide fast and reliable intervention.
Depending on the field requirements, two different types of drill pipe riser systems using a proprietary double shoulder connection were used by operators. A first solution was developed in 1999 featuring a seal ring close to the external shoulder. Subsequently, a new solution featuring a gas-tight metal to metal seal on the pin nose was developed in order to address increasingly demanding and challenging operations.
Intensively used in West Africa since 1999, the solution using the seal ring has shown robustness and reliability while being used for several projects in Angola such as Girassol and Rosa and now GirRI. The paper draws a summary of these operations and the feedback on the field use and maintenance. Also it emphasises the successful qualification process for the metal to metal seal solution that has been used in offshore Nigeria since 2010 for the USAN project.
Comparing Soft-String and Stiff-String Methods Used to Compute Casing Centralization
Authors: Gorokhova Lidia , Parry Andrew , Flamant Nicolas 
Published: March 2013

Abstract
Good casing centralization during cementing operations is a key factor for achieving proper mud displacement and obtaining hydraulic isolation in the annulus. To this end, centralizers are often placed along the casing to position it centrally in the borehole. The optimal number of centralizers and their spacing is determined with simulation software.
Until now, the industry has typically used calculation methods derived from API Spec. 10D to predict casing eccentricity in the wellbore. The calculations are based on an analytical soft-string method, which models an element of casing string between two centralizers as a bi-fixed beam.
However, in drilling operations, the use of a numerical stiff-string method to compute torque-and-drag forces is now becoming widespread. It accounts for tubular bending stiffness and provides a more realistic analysis of the stresses and loads acting upon the drillstring and the borehole. The stiff-string technique based on the finite-element method is thus proposed as an alternate and more effective solution for computing casing centralization for cementing operations.
Measured and calculated casing centralizations were compared in several field cases. The casing eccentricity was measured after the cement placement using recently developed ultrasonic logging tools and diagnostics. Discrepancies between analytical and numerical calculation methods were analyzed, then advantages and disadvantages to each method were assessed. The results of the calculation methods were used to formulate an optimal approach to casing centralization.
Optimal Bit, Reamer Selection and Operating Procedures Improve Hole Enlargement Performance in Deepwater Gulf of Mexico
Authors: Ho T. , Alferez C. , Cortez M. , Nott I. , McNary X. 
Published: March 2013

Abstract
Hole enlargement using underreamers has become a necessary drilling practice in deepwater Gulf of Mexico. Underreaming while drilling saves operators an extra trip to open a hole, and improves drilling budgets. Further benefits include better equivalent circulating density management and optimal cement jobs because of the bigger annulus. With these benefits come great challenges that can be categorized into three classes: 1) Drilling dynamics 2) Drilling performance and 3) Hole quality. These challenges, if not addressed during the planning and execution phase, can lead to tool failure, lower penetration rates, and hole angle deflection. This paper presents a deepwater Gulf of Mexico success story where a total systems optimization approach was utilized to overcome the previously mentioned challenges, generating a scalable improvement in drilling efficiency.
This paper presents the planning and results from two sections of the subject well - 18 1/8 x 21 in. and 16 ½ x 19 in. Each section had different sets of challenges. The first section was drilled through an inter-bedded formation entering at the top of the salt, while the second section was drilled entirely in salt. To overcome these challenges, an optimization approach was followed, which consisted of four steps - 1) Offset well analysis 2) Bit/underreamer selection 3) Development of optimum drilling parameters and 4) Roadmap to manage these parameters on the rig.
According to field results, this approach improved the ROP by more than 15% in the 18 1/8 x 21-in. salt section. Drilling efficiency for both sections was enhanced by more than 65% when compared to previous offsets. For both sections, the maximum hole inclination was 0.13° or less, keeping the well vertical. Furthermore, lower axial and lateral vibrations were observed, eliminating downhole tool failures while the bit and underreamer came out with better dull conditions compared to the offsets.
Wellbore Strengthening-Nano-Particle Drilling Fluid Experimental Design Using Hydraulic Fracture Apparatus
Authors: Nwaoji Charles O. , Hareland Geir , Husein Maen , Nygaard Runar , Zakaria Mohammad Ferdous 
Published: March 2013

Abstract
This paper introduces a novel LCM drilling fluid blend which has been used successfully in the laboratory to acheive wellbore strengthening results in permeable and impermeable formations for water based and invert emulsion (diesel oil) based drilling fluids.
Optimum combinations of standard LCM (graphite) and in-house prepared nanoparticles (NPs) (iron (III) hydroxide and calcium carbonate) have been established by running hydraulic fracture experiments on Roubidoux sandstone and impermeable concrete cores. Different blended fluids were used to prop open and seal fractures. The blends that gave the highest increase in fracture pressure with minimal distortion in mud rheological properties were selected for both drilling fluid type. The optimal fluid blend for water based mud was repeated using impermeable concrete core to test for consistency of result and possible application to shale wellbore strengthening.
The optimal blend (iron IH hydroxide NPs) and graphite increased the fracture pressure by 1,668 psi or by 70% over the unblended water based mud with moderate impact on mud rheology. The optimal blend (calcium carbonate NPs) and graphite increased the fracture pressure by 586 psi or by 36% over the unblended invert emulsion mud with moderate impact on mud rheology. Plastic viscosity and 10 min gel strength have been noted as important markers or indicators that show when the blended fluid will give very good wellbore strengthening result. Absolute fracture sealing was noticed in two of the samples (sandstone and concrete) while running the re-opening pressure cycle which shows the excellent propping and sealing properties of the blend. A 25% increase in fracture pressure over the unblended mud was achieved in impermeable concrete core showing the applicability of the designed fluid in shale wellbore strengthening.
Future work involves field verification of the laboratory results achieved with the designed LCM blends.
Full-scale Testing Shows Advantages of a Quantitative Approach to Interpreting Negative Pressure Tests
Authors: Rahmani Reza , Bourgoyne Darryl , Smith John Rogers 
Published: March 2013

Abstract
Negative pressure tests are an important step in proving well integrity for some well operations. Although the concept is straightforward, there are no standard procedures for conducting and interpreting negative tests. Recent industry experience has shown the potential for these tests to be misinterpreted with disastrous results. This paper describes proper quantitative interpretation of both successful and unsuccessful tests demonstrated on two full-scale test wells.
Tests with and without water leaks are simulated in two vertical wells with 2971ft and 5884ft depths. Test results are interpreted quantitatively to distinguish successes from failures. In addition, the impact of leak rate and the differential pressure between the leak source and well are investigated. The impacts of gas as a leak fluid, different well volumes, different surface piping arrangements, and different measuring tanks are also shown.
The success of a test should be verified with both flow and pressure checks. For the flow check, a trend between bleed off pressure and volume can be predicted based on fluid compressibility, tubing expansion, and drainage from surface piping. Deviations from that trend will identify the onset of a leak. Early detection and control of a high rate leak can reduce the formation fluid volume entering the well and the consequent risks. Detecting a low rate leak is difficult if the test duration is too short. Therefore, a 30 minute test duration was evaluated for detection of low rate leaks.
The fundamental differences between a leak and no leak are conclusively demonstrated with quantitative results. Approaches for overcoming complications to achieving conclusive tests are explained and demonstrated. These test results and the proposed interpretation methods are applicable to vertical wells. Drilling fluid properties, multiple fluids, and thermal expansion can also influence results but were not investigated in this study. Nevertheless, these results should provide a basis for improving field procedures and minimizing the risk of misinterpreting a leak as a successful test.
Shale Play Drilling Challenges: Case Histories and Lessons Learned
Authors: Jellison Michael , Brock Jim , Muradov Andrei , Morgan Dan , Rowell Jim 
Published: March 2013

Abstract
Shale drilling for both natural gas and hydrocarbon liquids has increased dramatically in North America over the last several years. Shale oil and gas deposits are known to exist all over the globe including Australia and the rest of the Asia Pacific. This paper discusses the requirements for drillpipe in shale drilling applications along with a review of some of the challenges and problems associated with the drillstring in these critical applications. Most wells are horizontal with long departures. Typical wells in the Bakken Shale are 17,000 ft MD, 11,000 ft TVD with a 6,000 ft horizontal reach. Drilling these wells puts huge demands on the drillpipe and rotary shoulder connections and pushes the drilling equipment and rig crews beyond the requirements of typical onshore well construction projects. Many, if not most, of the shale wells require advanced design, double shoulder connections (DSC) on the drillstring to provide the enhanced torsional strength and streamlined connection dimensions required to effectively drill these prospects. The paper presents connection design solutions along with considerations for safe and efficient running procedures. Although, the advanced DSCs are designed to be transparent to normal drilling operations, compared to standard API connections, some problems have been encountered. The paper addresses these running and handling issues and provides guidelines to mitigate these problems. Excessive tool joint and drillpipe body wear have also been encountered in several shale plays. This is discussed, along with recommendations to limit wear. Stick-slip has created drillstring problems on several wells. Stick-slip can cause damage to the drillpipe and, in the extreme, downhole connection back-offs have occurred. The paper looks at aspects of case histories to illustrate these issues and provides lessons learned to improve shale drilling operations in North America, the Asia Pacific and other regions of the world.
Cost Effective Ultra-Large Diameter PDC Bit Drilling in Deepwater Gulf of Mexico
Authors: D'Ambrosio Piero , Prochaska Ernest , Bouska Reisha , Tinsley Douglas , Hart Sofiri 
Published: March 2013

Abstract
Ultra-large diameter Polycrystalline Diamond Compact (PDC) bit drilling is a fast growing cost-effective solution in high-tier deepwater drilling operations in the U.S. Gulf of Mexico (GOM) where salt is encountered in the shallow part of the wellbore. Conventional design called for roller cone (RC) (IADC Code 111-115) drill bits on positive displacement motors (PDM) in these ultra-large diameter intervals. Cost savings on drilling fluid alone, in the form of Rate of Penetration (ROP) gains through the salt interval, has the industry trending to drill these riserless sections with the use of PDC drill bits on Rotary Steerable System (RSS) drilling assemblies.
New robust high torque capacity top drives, stronger drillpipe connections, larger diameter RSS tools and improved mud programs have all largely contributed to this step change in drilling performance. Additionally, evolved bit and BHA design, efficient operating parameters, improved hydraulics and vibration prediction modeling have all aided in the success of these runs.
Although this emerging new trend reduces drilling times and associated cost, experience has shown there are multiple challenges that must be overcome to complete a successful run in a single trip. These challenges vary from well to well and include, but are not limited to: BHA steerability, rig equipment limitations, efficient operating parameters, identification of both sediment and salt formations, hole cleaning and hydraulics, salt creep, drilling fluid displacement, drillpipe torque limitations, stabilization placement, lateral/ torsional BHA vibrations, and others.
This paper will concentrate on the multiple aspects of ultra-large diameter riserless PDC bit drilling applications and the considerations that have been used to optimize them. Prior SPE papers and data from previous deepwater GOM case histories were heavily researched and scrutinized to support the conclusions provided within the body of this paper. Together with industry experience available, these findings have resulted in a set of defined recommendations, providing operators with a guide to justify a lower cost per foot approach through the potential reduction of drilling time in these challenging applications.
Novell Drilling Fluid Design Enables Successful Drilling of Depleted Carbonate Reservoirs Offshore Republic of Congo
Authors: Thomas Seye , LELEUX Jerome , Delvaux Alex 
Published: March 2013

Abstract
A unique air-energized drilling fluid was developed that enabled all 13 wells in the development program of the Emeraude field, Offshore Pointe-Noire, Republic of Congo to be drilled with only 19-bbl downhole losses and zero non-productive time. The energized air-surfactant polymer drilling fluid used on the Emeraude field has potential for drilling similar depleted carbonate reservoirs in West Africa.
The Emeraude field is a major hydrocarbon accumulation lying offshore Pointe-Noire, Republic of Congo below water 60 to 75 m deep. The 150 m thick reservoir is a complex sequence of interbedded silt and fractured carbonates with an average reservoir pressure of 0.4 to 0.7 sg equivalent pressure. Such low reservoir pressures present considerable drilling challenges, including efficient hole cleaning in inclined wellbores up to 53°, minimizing stuck pipe risk from excessive overbalance pressures in permeable and depleted formations, and minimizing downhole fluid losses in fractured carbonate formations. Over fifty previous offset wells, which were drilled with various types of drilling fluids, suffered from total losses and subsequent poor cement jobs, as well as high water-cut hydrocarbon production.
The drilling program was very successful with very minimal downhole losses and zero non-productive time. Hole cleaning was excellent at all times as evidenced by low rotary torque, pick up and slack off weights while drilling and tripping out of hole. In addition, cementing operations were completed successfully with full returns, and initial production had zero water-cut.
This paper details case histories from the Emeraude field 13-well drilling program, focusing on the design elements of the novel drilling fluid. Best engineering practices adopted to successfully drill these challenging wells also are described in detail.