bluuebunny/crossref_metadata_2025 huggingface dataset:
Translating Perforating Laboratory Results to the Downhole Environment
Authors: Grove B. , Harvey J. , Zhan L. , Atwood D.
Published: June 2011

Perforating laboratory experiments are being conducted more frequently in recent years. In some instances, the goal is to qualitatively compare multiple candidate perforating techniques. In others, the goal is to obtain quantitative insight into likely flow performance in the field. Although the laboratory will never perfectly replicate the downhole environment, it can yield useful results which – if properly interpreted – can enable informed prediction of downhole flow performance.

A traditional flow lab experiment (along the lines of API RP-19B Section 4) yields many key results, four of which are required inputs to downhole inflow simulators. These are perforation tunnel length and diameter, and crushed zone thickness and permeability. In the case of natural completions, these parameters (in addition to other system and wellbore parameters), dictate the skin and ultimate flow performance of the completion.

Crushed zone permeability is typically inferred from core flow efficiency (CFE) and an assumed crushed zone thickness. As traditionally applied, this technique can yield values which are not accurate, and more significantly can produce misleading predictions of downhole performance.

To address this, we have developed new methods for both measuring and interpreting CFE. The new measurement technique yields CFE values which are more meaningful and relevant. The new interpretation technique provides a consistent method of translating CFE to crushed zone permeability, and is capable of accounting for the effect of partially plugged tunnels. This work clarifies and improves the link between lab and field performance of perforators, with the ultimate goal of increasing the value of downhole inflow performance predictions.

While other work is ongoing to challenge the framework of the conventional skin models, the present paper accepts these models as a premise. This work simply presents a coherent methodology of interpreting laboratory data, with the intent of generating the required inputs for skin models as they currently are. Furthermore, it is recommended that this workflow be considered for inclusion in any revisions to Section 4 testing protocol.
Size-Exclusion Particle Capture During Mono-Dispersed Suspension Flow in Porous Media
Authors: O'Reilly D. I. , Bedrikovetsky P. , Lee K. , Zakaria N.
Published: June 2011

In this work, we develop a new analytical solution for the problem of deep bed filtration under size-exclusion dominated particle capture. An uspcaled stochastic micro model has been derived that models individual particle-pore interactions. The solution is based upon mono-dispersed suspension injection into a medium with a known pore throat distribution. Ultimately, the model can be used for matching with laboratory corefloods, simulation of permeability decline or expected tracer breakthrough.

Size-exclusion particle capture during suspension transport in porous media takes place during drilling fluid penetration into oil bearing formations, sand production and the injection of poorly treated water. Straining particle capture can dominate over the particle attraction in cases of produced water injection, injection of produced water from aquifers, fines production in fractured wells and gravel packed horizontal wells. Deep bed filtration contributes highly to the problem of formation damage.

Planning and design of the above-mentioned oil production processes is based on reliable mathematical modeling. If compared with previous population balance models for the general case of particle capture, the current work discusses a particular case of pure straining. We show that in the case of particle-grain and particle-particle repulsion, the particles cannot be strained in pores larger than the particle size. The particles can be captured in thin pores only. These considerations change the expression for capture rate in the basic population balance model. In order to validate the proposed model by comparison with laboratory tests, we found a travelling wave solution. The comparison with 2 sets of laboratory data showed good agreement, which validated the proposed model.

The new solution has broad application to the petroleum industry. The developed model can be applied for: (1) Particle sizing for drilling fluids, (2) Log interpretation of filtrate penetration into the formation, (3) Design of injected water treatment and (4) The design of gravel packs to minimise fines production and formation damage.
Controlled Wellbore Implosions Show that Not All Damage is Bad – A New Technique to Increase Production from Damaged Wells
Authors: Al Busaidy Adil , Zaouali Zouhir , Baumann Carlos Erik , Vegliante Enzo
Published: June 2011

Near wellbore damage is often blamed for many production problems, it can manifest itself in many ways and is caused by almost anything that disturbs the formation; even producing hydrocarbons can lead to near wellbore damage. Knowing where the damage is and how it was produced can help prevent new occurrences, but oftentimes prevention is not possible. Perforation damage is one kind of damage that cannot be prevented; because the objective of perforating is to damage the formation by creating a tunnel as large and as deep as possible.

A new technique of consisting of producing controlled implosions constitutes the most effective way of removing perforation and other types of near wellbore damage, and this technique lends itself to provide quantitative values of well damage removal. This paper discusses how this new technique was developed, from concept and modeling to its effectiveness in the field as demonstrated by a number of jobs on wells with different types of damage. The results are extremely encouraging; in some wells production has increased by as much as three to four times, this production increase is sustained and the rate at which well formation damage occurs is significantly lower.

This paper presents field experiments conducted on four wells in the Libyan Desert, including logging data based on state of the art measurements, and giving new insights into near wellbore damage. Strategies are recommended to combat the effects of common near wellbore damage mechanisms and to address their root causes. These findings opened a debate that challenges some aspects of industry accepted perforation techniques, and presents conclusive evidence that some well damage is in fact beneficial.
Laboratory Evaluation of Organic Water Shut-off Gelling System for Carbonate Formations
Authors: Al-Anazi M. S. , Al-Mutairi S. H. , Al-Khaldi M. H. , Al-Zahrani A. A. , Al-Yami I. S. , Gurmen M. N.
Published: June 2011

Water production can reduce or block oil and gas production rates. In addition, the lifting, handling, and disposal of produced water negatively impact the hydrocarbon production economics. Among several techniques for water control, crosslinked polymer systems are the most effective for certain water shut-off projects. The objective of this paper is to assess the effectiveness of crosslinked polymer system for water control applications in carbonate formations and present its optimal formulation.

This paper presents a detailed lab testing of a cross-linked polymer system. The system includes a gelling agent, primary and secondary crosslinkers and an acidic activator. The evaluation covered extreme concentrations of all components, temperatures up to 212°F, differential pressures up to 1,500 psi, actual field water salinity, wide range of permeability, and extended testing time up to three months. Core-flood experiments along with Computerized Tomography Scanning and Environmental Scanning Electron Microscopy were used to assess the sweep efficiency and the strength of the gel inside the core plugs. Losses of active ingredients from effluent samples were measured using Thermal Gravimetric Analyzer. Results of carbonate core plugs were compared with that of Berea sandstone. Strength of the gel at different cross-linker and polymer concentrations was monitored using sealed glass ampoules. Gelation times were measured using bottle tests and rotational viscometers.

Extreme vertices design was used to optimize the experimental work and mixture triangle was used to represent the final results. An optimal gelling system with controlled gelation time and maximum performance was attained for the targeted formation at 212°F. It was found that the gelation time was affected by the three main components of the gelling system. The acetic acid-based activator was found to have the highest effect on the gelation time. However, this activator was not effective when the gelling system was tested in carbonate core plugs. A major effort of this work was to develop alternative strategies for the ineffectiveness of acidic activator in carbonaceous formations.
Sand Control Completions for Ormen Lange Big-Bore, High-Rate Gas Development, Evaluation of Concept Selection, Qualification, Execution and Well Performance
Authors: van Kranenburg A. , Twycross J. , Combe C. , Hals K.
Published: June 2011

Ormen Lange is the second-largest gas field in Norway, currently providing 20% of the domestic gas consumption for the UK. As one of the world's largest subsea big-bore gas wells - with production rates up to 350 MMscf/d per well, a 120-km tieback to shore, subzero seabed temperatures and a design life of more than 30 years - these wells provide unique technical challenges. Due to the low reservoir rock strength, high velocities and the life expectancy of these wells, sand control was identified as a prerequisite from day one.

This paper clarifies the logic of the selected sand control method and describes the extensive testing required to qualify the sand control hardware and associated completion fluids for the expected operating conditions. The execution of thirteen successful sand control completion installations will be discussed, including both ends of the success spectrum, and well performance will be covered.

Throughout the four-year installation campaign to date, a number of new technologies were qualified and successfully integrated into the lower completions. These included cableless gauges to provide data closer from the reservoir inflow area, tagged proppant for individual subsea well fingerprinting if proppant is found at the gas plant, and water-tracer technology to aid in identifying the subsea source of potential formation water breakthrough.

This subject explains the extent of the effort to progress an ambitious field development based on big-bore gas wells only (to reduce well count) from the drawing board to flawless execution and world-class production. Relevance also relates to other major big-bore, high-rate gas subsea developments with sand control requirements that are currently being pursued in similar harsh environments (deep water, Arctic conditions, sub-zero seabed) that might have interest in the application of Ormen Lange's successfully implemented technology.
A New technique to Characterize Drilling Fluid Filter Cake
Authors: Elkatatny S. M. , Mahmoud M. A. , Nasr-El-Din H. A.
Published: June 2011

Filter cake characterization is very important in drilling and completion operations. The homogeneity of the filter cake affects the properties of filtration process such as the volume of filtrate, the thickness of filter cake, and the way to remove it. Different models were used to determine the thickness and permeability of the filter cake. These models assume that the filter cake is homogeneous.

The objective of this study is to measure the filter cake thickness and permeability of water-based drilling fluids by a new approach and compare the results with previous models. A HPHT filter press was used to perform the filtration process under static conditions (225°F and 300 psi). CT (computed tomography) scan was used to measure the thickness and porosity of the filter cake. SEM was used to provide the morphology of the filter cake. Leica microscope was used to determine particle size distribution.

The results obtained from the CT scan showed that the filter cake was heterogeneous and contained two layers with different properties. The average thickness of the external layer was 0.1 in., which was greater than the average thickness of the internal layer (0.06 in.). Both the porosity and permeability of the external layer were zero, while the porosity of the internal layer ranged from 10 to 20 vol. %. SEM results showed that the two layers contained large and small particles but there was a very poor sorting in the external layer, which led to zero porosity in this layer. Previous models underestimated the thickness of the filter cake by almost 50%. A new method was developed to predict the thickness and permeability of the two-layer filter cake. This method predicted the experimental data very well.
Computational Fluid Dynamics for Reservoir and Well Fluid Flow Performance Modelling
Authors: Byrne M. , Jimenez M. A. , Rojas E. , Castillo E.
Published: June 2011

Computational Fluid Dynamics (CFD) has been used to model fluid behaviour in reservoirs, near wellbores and wells. More recently the CFD has been applied to more diverse challenges such as sand transport, coupled mechanical modelling of failing wellbores and gas well clean-up. CFD has been applied to model the crushed zone around perforation tunnels and also to predict well performance base on laboratory testing. Where the reservoir is involved in these models they are fully coupled and flow is enabled deep in the reservoir and in to every point along the well.

Capturing the simultaneous flow of fluids in the reservoir and in the well is essential to predict performance in wells and reservoirs with complex geometry. Cross flow between reservoir layers and the flow of fluids through and along the well length are real phenomena which if ignored, can lead to poor prediction of well performance. CFD modelling relies on fundamental physical properties and enables changes in flow restriction such as formation damage or matrix stimulation to be captured. This paper presents some recent case histories where model results are verified by real well performance and where traditional analytical model results are compared to fully coupled CFD reservoir and well models. The impact of formation damage is observed to produce very different results, depending on the model applied.

Case histories illustrating the application of innovative, rigorous modelling of formation damage from different drilling and completion fluids and practices are presented. Further advances that enable sand failure and sand transport to be modelled are also illustrated. The case is made for use of CFD or similar modelling processes where complex reservoirs or complex wells are considered.
New Approach for Completion Applications With Higher Internal Phase Inverts Utilizing Innovative Surfactants
Authors: Luyster Mark , Patel Arvind , Ravitz Ray , Lim Kim S.
Published: June 2011

A new surfactant capable of providing stable emulsions to as low as a 20/80 oil/water ratio while still maintaining a continuous oil phase is now possible. The new surfactant works in a variety of brines allowing flexibility in formulations and applications. The high internal phase emulsion allows formulations of higher density with less total solids. These high internal phase emulsions are stable at high temperatures and provide manageable (adequate) low-end rheological properties suitable for drilling and completion applications. This system demonstrates relatively less syneresis than a conventional invert. Using a higher internal phase requires less oil and subsequently lowers costs both from initial base fluid cost and final disposal of the base fluid. This new surfactant can also be used to formulate systems for conventional alpha-beta gravel packing, whereby the rheology profile approaches Newtonian properties.

This paper will detail the chemistry behind the new surfactant, initial laboratory assessments and the potential applications for this new technology.
Specially Formulated Delayed-Breaker System for Extended-Reach Injectors in a Viscous Oil Waterflood Application
Authors: Kim L. S. , Ravitz R. , Patel A. , Martens H. , Luyster M. , Kuck M.
Published: June 2011

Two wells have been designed and completed using a combination of monitoring, isolation and injection control equipment to provide an understanding of injection behavior in extended-reach laterals and possible matrix bypass events (MBE) in the Nikaitchug field in Northern Alaska. These lower completion designs also provided a means to evenly distribute injection along the length of the lateral section as well as a means of mitigation and control of water if necessary.

In order to facilitate direct injection, a specifically formulated breaker system was developed to provide a delay to allow spotting in the openhole horizontal prior to running the liner and lower completion injection control assemblies. The ability to place the breaker system after drilling the horizontal mitigated risk associated with temporary flowback when inflow control devices were installed. Both post intervention and flow back were not desired.

The breaker system was formulated to provide a delay and allow the liner and injection control assembly to be installed before degradation of the residual filtercake caused uncontrollable losses thus allowing the completion phase to proceed as planned. The filtercake was deposited by a reversible invert reservoir drill-in fluid system used to drill the horizontal sections. The breaker system was unique in that it was blended as an invert emulsion and consisting of an oil continuous phase and an aqueous discontinuous phase that included a glycol acid precursor. An oil-based system was desired to reduce friction thus facilitating the installation of the lower completion hardware for these extended-reach wells.

This paper discusses the upfront assessment process, the reversible invert drill-in fluid system, the chemistry and subsequent optimization of the breaker system to achieve the drilling and completion objectives. In addition, the actual field results and lessons learned will be discussed.
Stimulation Solutions for the High-Pressure, High-Temperature Naturally Fractured Carbonate Reservoirs in Mexico
Authors: Flores Jose G. , de Antunano Munoz Yuri , Diaz Vazquez Alan , Cruz Espinoza Leonardo
Published: June 2011

One of the components in PEMEX's strategy to offset the natural decline of some of Mexico's giant fields consists in the implementation of technological advances and best practices for mature fields. About 70% of the hydrocarbon produced in Mexico originates in naturally fractured, depleted carbonate reservoirs, with active aquifers and secondary gas caps, which makes it difficult to maintain production levels and increase recovery factors. To optimize the reservoir-well-facilities systems, in 2006 PEMEX established, in cooperation with service companies, multidisciplinary productivity teams to generate portfolios of opportunities in all its production assets nationwide. The selection and optimization of stimulation and matrix-acidizing treatments were identified as critical enablers for production enhancement.

The stimulation designs have evolved in several directions, including the utilization of energized fluids, the introduction of emulsified acids, and the application of high-dissolution systems for high-temperature wells. Fluid placement techniques for selective stimulation have improved with the assistance of high-hydraulic-impact tools, inflatable packers, downhole real-time monitoring, and chemical-mechanical self-diverting fluids with degradable fibers to treat high-temperature formations. These improvements and evolutions have brought about solutions to historical problems and made it possible to optimize stimulation treatments in complex carbonate reservoirs with superior production results, including: 1) identifying natural-fracture patterns in low-productivity areas to increase the well-formation contact by acid fracturing; 2) treating and optimizing wells with severe gas breakthrough with strong diversion mechanisms to temporarily isolate the gas channels and stimulate the producing zones; 3) employing selective diversion fluids and non-reactive systems to break emulsions and water blockages in wells with high water cuts; and 4) applying state-of-the art fluids to maximize productivity from new discoveries.

The application of PEMEX's Well Productivity strategy is successfully contributing to maintaining Mexico's hydrocarbon production levels. For example, in PEMEX's South Region, it is estimated that 50,000 BOPD is the average incremental production per year obtained by solving a historical scale and organics deposition problem, and that 35,000 BOPD is the average incremental obtained from new wells by successfully removing and bypassing the drilling-induced damage. This paper discusses the production enhancement workflows, milestones, examples, results, lessons learned and strategies established to meet the production targets in various naturally fractured carbonate fields in Mexico.
Laboratory Simulation of Flow through a Perforation
Authors: Brooks James E. , Haggerty Dennis
Published: June 2011

API RP 19B Section 4 tests were established to evaluate perforator performance at field conditions. The question of how well such a small-scale laboratory test translates to downhole reality has long been raised. Furthermore, how accurately are downhole dynamics reproduced in single-shot, Section 4 tests, when in practice, an extensive formation is perforated with multiple shots?

To address this question, flow fields for typical axial and radial API Section 4 flow targets were calculated using a general analytical model based on potential theory and compared with the calculated results of various downhole configurations with different shot densities. When compared with calculations of downhole flow, we show that both radial and axial API targets can yield flow patterns that differ considerably from those downhole, which could lead to erroneous interpretations of results and dynamic effects, such as cleanup. As expected, results show that a radial flow target tends to overestimate the flow into a downhole perforation depending on the shot density and that an axial flow target tends to underestimate the flow depending on target length.

We discuss how to modify the API test core by attaching a low-permeability sleeve to create a more accurate downhole flow simulation. The result is a more representative test that better reproduces the initial static reservoir pressure and the post-shot flowing pressure.

To illustrate the concept, we made several tests using modified and unmodified axial flow targets to compare flow efficiency through perforations. Initial results indicate a difference in flow between the two sets of targets, with the modified targets having lower flow efficiency. Finally, we offer some possible physical reasons to explain the difference.
Phase Boundaries of Microemulsion Systems Help to Increase Productivity
Authors: Quintero Lirio , Jones Thomas A. , Pietrangeli Gianna
Published: June 2011

Formation damage may be caused by in-situ emulsions, changes in wettability and by deposition of asphaltenes, wax and scales. It is widely recognized that these damage mechanisms may be removed by using microemulsion technology, resulting in enhanced productivity of oil and gas wells. It is also known that microemulsion systems are composed of surfactants, oil, brine and optional co-surfactants and acids. These systems can be very complex, due to the number of variables that influence formulation behavior, including temperature, type of oil, type and concentration of salt, surfactant, co-surfactant, and acid.

The development of microemulsions for specific oilfield applications requires a systematic study of phase behavior as a tool to select a treatment composition that satisfies specific parameters defined by the application. Phase behavior studies are necessary in order to identify microemulsion phase boundaries.

Phase behavior diagrams of microemulsion systems developed for wellbore damage remediation considered the following variables: temperature, type and concentration of co-surfactants, type and concentration of brine, oils, surfactants and acids. Laboratory studies of surfactant-oil-brine systems used successfully in the field confirm that they undergo phase transitions from Winsor I (oil-in-water with excess oil), to Winsor III (microemulsion), to Winsor II (water-in-oil with excess water).

This paper presents formulations positioned in an area of the phase diagram that correspond to maximum detergency and optimum interfacial properties required for field applications. The relationship between phase diagrams, interfacial properties (interfacial tension and contact angle) and well productivity are discussed.
Crude Oil Compatibility Method Significantly Minimizes Volumes Required
Authors: Schultz Katrina , Javora Paul H.
Published: June 2011

Crude oil compatibility testing with completion brine is necessary to prevent the formation of crude oil-brine emulsions that cause formation damage and limit hydrocarbon production. Furthermore, required remedial action is costly. Conventional testing for the formation of oil-brine emulsions requires large volumes of oil, typically 50 to 75 mL oil for each test. Completion brine projects can require more than forty tests to identify adequately all fluid compatibility issues, which translates to about three liters of crude oil. However, high profile projects often deliver only limited quantities of crude oil, sometimes only 500 milliliters or less are available for emulsion testing.

To accommodate the growing demand for oil volume, researchers developed a new high-shear method and apparatus that uses a total per test volume of 10 milliliters, including crude oil and brine, fracturing gels, fluid loss control gels, broken gels, filtrates or stimulation fluids, and combinations thereof. With this methodology, a series of 40 crude oil compatibility tests requires only 200 mL of crude oil. The apparatus is constructed from common laboratory equipment and readily available devices. Markedly, the equipment delivers consistent high-shear mixing, clear visualization of fluid interfaces, capacity to stack three or more test fluids in a single test, and the ability to heat age samples to about 82°C (180°F).

Testing demonstrated that the new high-shear method and device produce reliable results using small volumes of crude oil and compare positively with conventional test methods. Since this method is applicable to all fluid-fluid testing, a proposal will be presented for inclusion into ISO-13503-3 (API RP-13J), Testing of heavy brines.
Measuring Fluid Placement of Sand-Consolidation Treatments Using DTS
Authors: Villesca Josue , Glasbergen Gerard , Attaway David
Published: June 2011

The successful application of sand-consolidation treatments is, for a major portion, dependent on correct fluid placement of the consolidation material. It is crucial to achieve a uniform placement of the material and, therefore, techniques are needed to overcome natural or artificially created heterogeneities. Diversion methods such as foams are being used frequently. However, fluid-placement verification of these treatments is rare.

This paper discusses the placement of a novel sand-consolidation material using a foam diverter and the verification of the placement by using distributed temperature sensing (DTS). Two case histories are analyzed in detail and used for illustration. In both case histories, foam was used to place the sand-consolidation material in multilayer reservoirs, and DTS was used to verify the placement in real-time. Qualitative and quantitative fluid placement information was derived in both cases.

From the DTS data, the parts of the formation that were treated could be identified in both case histories. In one case history, recently placed hydraulic fractures were identified and were treated. In the other case, reservoir-pressure variations were determined and identified to be the reason for preferential fluid placement and diversion over time. The lessons learned from the case histories will lead to further improvement of fluid placement.
Defective Differentiation of Regulatory FoxP3+ T Cells by Small-Intestinal Dendritic Cells in Patients With Type 1 Diabetes
Authors: Badami Ester , Sorini Chiara , Coccia Margherita , Usuelli Vera , Molteni Laura , Bolla Andrea Mario , Scavini Marina , Mariani Alberto , King Cecile , Bosi Emanuele , Falcone Marika
Published: June 2011

OBJECTIVE

The gut environment modulates the pathogenesis of type 1 diabetes (T1D), but how it affects autoimmunity toward pancreatic β-cells, a self-tissue located outside the intestine, is still unclear. In the small intestine, lamina propria dendritic cells (LPDCs) induce peripheral differentiation of FoxP3+ regulatory T (Treg) cells. We tested the hypothesis that the intestinal milieu impinges on human T1D by affecting differentiation of FoxP3+ Treg cells.

RESEARCH DESIGN AND METHODS

We collected duodenal biopsies of 10 T1D patients, 16 healthy subjects, and 20 celiac individuals and performed a fluorescent-activated cell sorter analysis to measure percentages of various immune cell subsets, including CD4+ and CD8+ T cells, NK cells, γδ T cells, CD103+CD11c+ LPDCs, and CD4+CD25+FoxP3+CD127− Treg cells. In parallel, we assessed the tolerogenic function (i.e., capacity to induce differentiation of FoxP3+ Treg cells) by LPDCs of T1D patients and control subjects.

RESULTS

Our analysis revealed a significant reduction in the percentage of intestinal CD4+CD25+FoxP3+CD127− Treg cells in T1D patients compared with healthy subjects (P = 0.03) and celiac individuals (P = 0.003). In addition, we found that LPDCs from T1D patients completely lacked their tolerogenic function; they were unable to convert CD4+CD25− T cells into CD4+CD25+FoxP3+CD127− Treg cells.

CONCLUSIONS

Our data indicate that T1D patients have a reduced number of intestinal FoxP3+ Treg cells as a result of their defective differentiation in the gut. These findings suggest that intestinal immune regulation is not only calibrated to tolerate commensal bacteria and food components but also is instrumental in maintaining immune tolerance toward pancreatic β-cells and preventing T1D.
Tillage in Relation to Distribution of Nutrients and Organic Carbon in the Soil
Authors: Šoltysová Božena , Danilovič Martin
Published: June 2011

Tillage in Relation to Distribution of Nutrients and Organic Carbon in the Soil

Changes of total nitrogen, available phosphorus, available potassium and soil organic carbon were observed on gleyic Fluvisols (locality Milhostov) at the following crops: grain maize (2005), spring barley (2006), winter wheat (2007), soya (2008), grain maize (2009). The experiment was realized at three soil tillage technologies: conventional tillage, reduced tillage and no-tillage. Soil samples were collected from three depths (0-0.15 m; 0.15-0.30 m; 0.30-0.45 m). The ratio of soil organic carbon to total nitrogen was also calculated.

Soil tillage affects significantly the content of total nitrogen in soil. The difference between the convetional tillage and soil protective tillages was significant. The balance showed that the content of total nitrogen decreased at reduced tillage by 5.2 rel.%, at no-tillage by 5.1 rel.% and at conventional tillage by 0.7 rel.%.

Similarly, the content of organic matter in the soil was significantly affected by soil tillage. The content of soil organic carbon found at the end of the research period was lower by 4.1 rel.% at reduced tillage, by 4.8 rel.% at no-tillage and by 4.9 rel.% at conventional tillage compared with initial stage. The difference between the convetional tillage and soil protective tillages was significant.

Less significant relationship was found between the soil tillage and the content of available phosphorus. The balance showed that the content of available phosphorus was increased at reduced tillage (by 4.1 rel.%) and was decreased at no-tillage (by 9.5 rel.%) and at conventional tillage (by 3.3 rel.%).

Tillage did not significantly affect the content of available potassium in the soil.
Physical Game Demands in Elite Rugby Union: A Global Positioning System Analysis and Possible Implications for Rehabilitation
Authors: Coughlan Garrett F. , Green Brian S. , Pook Paul T. , Toolan Eoin , O'Connor Sean P.
Published: June 2011

Study Design

Descriptive.

Objectives

To evaluate the physical demands of an international Rugby Union-level game using a global positioning system (GPS).

Background

Elite Rugby Union teams currently employ the latest technology to monitor and evaluate physical demands of training and games on their players.

Methods

GPS data from 2 players, a back and a forward, were collected during an international Rugby Union game. Locomotion speed, total body load, and body load sustained in tackles and scrums were analyzed.

Results

Players completed an average distance of 6715 m and spent the major portion of the game standing or walking, interspersed with medium- and high-intensity running activities. The back performed a higher number of high-intensity sprints and reached a greater maximal speed. Body load data revealed that high levels of gravitational force are sustained in tackling and scrum tasks.

Conclusion

The current study provides a detailed GPS analysis of the physical demands of international Rugby Union players. These data, when combined with game video footage, may assist sports medicine professionals in understanding the demands of the game and mechanism of injury, as well as improving injury rehabilitation. J Orthop Sports Phys Ther 2011;41(8):600–605, Epub 7 June 2011. doi:10.2519/jospt.2011.3508
Factors Associated With Care Seeking From Physicians, Physical Therapists, or Chiropractors by Persons With Spinal Pain: A Population-Based Study
Authors: Chevan Julia , Riddle Daniel L.
Published: June 2011

Study Design

Secondary analysis of longitudinal population-based survey data.

Objectives

To investigate factors associated with care seeking for physician-referred physical therapy (MD/PT), as compared to physician-only (MD) or chiropractic-only (DC) care for spinal pain.

Background

Although a large proportion of ambulatory physical therapy visits are related to spinal pain, physical therapists are not the most commonly seen provider. The majority of visits are to physicians, followed by chiropractors. We attempted to understand more about this disparity by examining social and demographic factors that differentiate between persons who see these providers.

Methods

Episodes of care were constructed from participants in 2 panels from the Medical Expenditure Panel Survey who had spinal pain. The provider of care was identified for each episode, and logistic regression was used to determine factors associated with MD/PT use compared to MD use, and MD/PT use compared to DC use.

Results

The majority of patients (61%) received MD care for spinal pain, followed by those who received DC (28%) and MD/PT (11%) care. Female sex, higher levels of education, and higher income were significantly associated with MD/ PT care over MD care. Increased age, female sex, lower self-health rating, and presence of at least 1 disability day were all significantly associated with MD/PT care over DC care.

Conclusion

Sociodemographic and clinical factors are associated with those who get MD/PT care as compared to MD or DC care. We found evidence of an access disparity for physical therapy and identified population characteristics that both increase and reduce the likelihood of physical therapy service use. J Orthop Sports Phys Ther 2011;41(7):467–476, Epub 7 June 2011. doi:10.2519/jospt.2011.3637
Race, Sexual Orientation, Culture and Male Teacher Role Models: “Will Any Teacher Do as Long as They are Good?”
Authors: Gosse Douglas
Published: June 2011

There is a perceived shortage of males in education provincially and nationally in Canada, particularly at the elementary level. My theoretical framework derives from queer theory, questioning the fluidity of discourse and identities, and troubling accepted, commonplace beliefs, knowledge, and practices. To this end, I interpret data from an online survey of 223 male primary/junior schoolteachers in Ontario. In this paper, I address male primary-junior teachers as role models in relation to race, sexual orientation, and culture, regarding two popular ideologies. The first is that of good teachers who can supposedly teach all pupils regardless of their own identity markers and sense of agency, or those of their pupils and larger communities. The second reflects notions of diversity to offset hegemonic male gender expectations, and to better reflect diversity in the broader school and social populations, while counterbalancing the overwhelming numbers of female role models in school, and at home, for children.
Parametric Investigation of Optimum Thermal Insulation Thickness for External Walls
Authors: Kaynakli Omer
Published: June 2011

Numerous studies have estimated the optimum thickness of thermal insulation materials used in building walls for different climate conditions. The economic parameters (inflation rate, discount rate, lifetime and energy costs), the heating/cooling loads of the building, the wall structure and the properties of the insulation material all affect the optimum insulation thickness. This study focused on the investigation of these parameters that affect the optimum thermal insulation thickness for building walls. To determine the optimum thickness and payback period, an economic model based on life-cycle cost analysis was used. As a result, the optimum thermal insulation thickness increased with increasing the heating and cooling energy requirements, the lifetime of the building, the inflation rate, energy costs and thermal conductivity of insulation. However, the thickness decreased with increasing the discount rate, the insulation material cost, the total wall resistance, the coefficient of performance (COP) of the cooling system and the solar radiation incident on a wall. In addition, the effects of these parameters on the total life-cycle cost, payback periods and energy savings were also investigated.
Micro Electromechanical Systems (MEMS) Based Microfluidic Devices for Biomedical Applications
Authors: Ashraf Muhammad Waseem , Tayyaba Shahzadi , Afzulpurkar Nitin
Published: June 2011

Micro Electromechanical Systems (MEMS) based microfluidic devices have gained popularity in biomedicine field over the last few years. In this paper, a comprehensive overview of microfluidic devices such as micropumps and microneedles has been presented for biomedical applications. The aim of this paper is to present the major features and issues related to micropumps and microneedles, e.g., working principles, actuation methods, fabrication techniques, construction, performance parameters, failure analysis, testing, safety issues, applications, commercialization issues and future prospects. Based on the actuation mechanisms, the micropumps are classified into two main types, i.e., mechanical and non-mechanical micropumps. Microneedles can be categorized according to their structure, fabrication process, material, overall shape, tip shape, size, array density and application. The presented literature review on micropumps and microneedles will provide comprehensive information for researchers working on design and development of microfluidic devices for biomedical applications.
The Ground Zero Mosque Controversy: Implications for American Islam
Authors: Takim Liyakat
Published: June 2011

The controversy surrounding the “ground zero mosque” is part of a larger debate about the place of Islam in U.S. public space. The controversy also reveals the ways in which the boundaries of American identity continue to be debated, often through struggles over who counts as a “real” American. It further demonstrates the extent to which Islam is figured as un-American and militant, and also the extent to which all Muslims are required to account for the actions of those who commit violence under the rubric of Islam. This paper will discuss how, due to the events of September 11, 2001, Muslims have engaged in a process of indigenizing American Islam. It will argue that the Park51 Islamic Community Center (or Ground Zero mosque) is a reflection of this indigenization process. It will go on to argue that projects such as the Ground Zero mosque which try to establish Islam as an important part of the American religious landscape and insist on the freedom of worship as stated in the U.S. constitution, illustrate the ideological battlefield over the place of Islam in the U.S. The paper will also examine the possible ramifications of building the Park51 Islamic Community Center including how this will shape the role that Islam plays in the socio-political lives America Muslims.
Symmetry Groups for the Decomposition of Reversible Computers, Quantum Computers, and Computers in between
Authors: Vos Alexis De , Baerdemacker Stijn De
Published: June 2011

Whereas quantum computing circuits follow the symmetries of the unitary Lie group, classical reversible computation circuits follow the symmetries of a finite group, i.e., the symmetric group. We confront the decomposition of an arbitrary classical reversible circuit with w bits and the decomposition of an arbitrary quantum circuit with w qubits. Both decompositions use the control gate as building block, i.e., a circuit transforming only one (qu)bit, the transformation being controlled by the other w−1 (qu)bits. We explain why the former circuit can be decomposed into 2w − 1 control gates, whereas the latter circuit needs 2w − 1 control gates. We investigate whether computer circuits, not based on the full unitary group but instead on a subgroup of the unitary group, may be decomposable either into 2w − 1 or into 2w − 1 control gates.
Neuraminidase of 2007–2008 Influenza A(H1N1) Viruses Shows Increased Affinity for Sialic Acids Due to the D344N Substitution
Authors: Rameix-Welti Marie-Anne , Munier Sandie , Le Gal Sebastien , Cuvelier Frederique , Agou Fabrice , Enouf Vincent , Naffakh Nadia , van der Werf Sylvie
Published: June 2011

Background

During the 2007–2008 season, A(H1N1) viruses naturally resistant to oseltamivir due to an H275Y substitution in the neuraminidase emerged and spread in the human population. The neuraminidase of 2007–2008 A(H1N1) viruses has an increased affinity for sialic acids as compared with the N1 of previously circulating viruses.

Methods

Using site-directed mutagenesis analysis and an enzymatic assay on cells transiently expressing the viral neuraminidase, the amino acid changes that could account for the particular enzymatic properties of the neuraminidase of 2007–2008 A(H1N1) viruses were explored. The affinity for the substrate ( K m) and the inhibition constants for inhibitors ( K i) were determined for wild-type and mutated neuraminidases. Reverse genetics was used to produce 6:2 reassortant viruses expressing haemagglutinin and neuraminidase derived from A(H1N1) viruses of the 2007–2008 season or from a previously circulating H1N1 virus, in an A/WSN/33 background.

Results

The D344N substitution characteristic of the N1 of 2007–2008 A(H1N1) viruses was identified as a major determinant of its increased affinity for sialic acids. According to the viral plaque phenotype of the 6:2 reas-sortant viruses, the H275Y mutation was deleterious when the surface glycoproteins were derived from the H1N1 virus isolated in 2004, but not when they were derived from A(H1N1) viruses of the 2007–2008 season.

Conclusions

The D344N substitution, by modifying the enzymatic property of the N1, may have favoured the emergence and spread of viruses naturally resistant to oseltamivir.
The Tibial Sulcus as a Reference Point for Total Knee Arthroplasty
Authors: Kelmanovich Daniel J. , Russinoff Scott L. , Maldjian Catherine , Lucas Paul , Zelicof Steven B.
Published: June 2011

Determining the amount of tibial resection is an important aspect of knee arthroplasty. The tibial sulcus is a reference point that should be unaffected by degenerative processes. This study compared the tibial sulcus and plateau height for 50 arthritic knees to 50 normal knees on magnetic resonance imaging. The tibial sulcus measured 17.09 mm in arthritic knees and 17.88 mm in normal knees. Sulcus height differences were not statistically significant. Based on these findings, a tibial cut 12 to 14 mm from the sulcus is recommended as a reference point in arthritic knees. This measuring technique has application in limited incision knee arthroplasty.
Impaction Grafting for Femoral Component Revision in a Goat Model Using Washed Morselized Cancellous Allograft
Authors: Voor Michael J. , Madsen Robin , Malkani Arthur , Togawa Daisuke , Bauer Thomas W.
Published: June 2011

To determine whether washing morselized cancellous bone allograft in impaction grafting for revision hip arthroplasty would improve mechanical and biologic performance, left hip hemiarthroplasty with a collarless stem cemented into impacted morselized cancellous bone was performed in 22 goats. Washed allograft was used in the experimental group, and standard allograft was used in the control group. One of 11 experimental and 4 of 11 control implants were observed to be loose at 8 weeks. Washing allowed significantly more morselized cancellous bone to be placed in the experimental group compared to the control group (7.7±1.9 and 6.2±2.0 g, respectively,
P
<.05). Significantly less in vivo subsidence over the 8-week study period also was demonstrated in the experimental group compared to the control group (0.4±0.4 and 2.2±2.3 mm, respectively,
P
<.05). Angular motion during cyclic ±1.5 Nm loading demonstrated significant differences between the 2 groups at time zero (2.67°±1.02° for the control group and 1.98°±0.47° for the experimental group,
P
<.05) and at 8 weeks (2.40°±0.38° for the control group and 1.74°±0.55° for the experimental group,
P
<.05). Histology showed little difference between the 2 groups, but there was a trend toward less inflammation in the experimental group.
Grammont Inverted Prosthesis for the Treatment of Cuff Tear Arthropathy: A 6-Year Follow-up Study
Authors: de Cupis Vincenzo , Chillemi Claudio , Marinelli Mario
Published: June 2011

This study evaluated mid-term functional results of the Grammont inverted prosthesis for the treatment of shoulder osteoarthritis associated with massive cuff rupture. Twenty-eight patients with a minimum of 6 years of follow-up were evaluated. Clinical evaluation was performed on all patients preoperatively and at follow-up using the Constant score. Radiologic assessment included radiographs and magnetic resonance imaging preoperatively and radiographs at follow-up. Constant score improved from 27.4 preoperatively to 64.6 postoperatively. The inverted prosthesis is attractive and remains one of the options for treating cuff tear arthropathy. However, glenoid loosening remains a serious problem.
Complications of Cervical Halo-Vest Orthoses in Elderly Patients
Authors: Taitsman Lisa A. , Altman Daniel T. , Hecht Andrew C. , Pedlow Frank X.
Published: June 2011

Halo-vest orthoses have been associated with complications. Previous reports have suggested increased complications in elderly patients; however, data are limited. This study reviewed 75 patients ≥65 years with cervical spine fractures treated with halo-vest orthoses. Forty-one patients (55%) experienced at least 1 complication. Pin-site problems were the most frequent adverse outcome. Seventeen patients (23%) had significant pulmonary compromise. Pulmonary complications were associated with high morbidity. We found an 8% early mortality rate. Halo-vest orthoses are useful devises. However, adverse events experienced by elderly patients are common and may lead to significant morbidity and mortality.