bluuebunny/crossref_metadata_2025 huggingface dataset:
Fiber-Based Fracture Fluid Technology a First for Oil Reservoirs in Western Siberia
Authors: Oussoltsev D. , Butula K. K. , Klyubin A. , Gayfullin Albert , Senchenko Dmitry , Fayzullin Ildar
Published: February 2008

Successful hydraulic fracturing in various "risky" oil reservoirs has been the biggest challenge for fracturing engineers in the Western Siberia basin, as a significant number of the oil-bearing formations in the basin are located near a water zone. These hydraulic fracturing difficulties created a niche for technologies that offer fracture-geometry control without sacrificing proppant-pack conductivity.

The conventional approach is based on net pressure control. This can be achieved using low-viscosity fluids, such as viscoelastic systems, oil-based systems or reduced polymer systems. The fluid systems can then further be pumped as linear gel pad stages with cross-linked proppant stages with or without the use of materials for fracture height-growth control (HGC). The Yaraynerskoe oilfield case study documents the fiber assisted fracturing fluid technology used with HGC materials as a significant improvement in HGC solution. This technology combination additionally enhances fracture placement success.

As the treatments significantly differ from the regular fiber assisted application in tight gas formations, a series of experiments had to be performed to ensure full compatibility with formation fluid, resin-coated proppants, and treating fluids.

Characteristics such as leakoff behavior, viscosity development, settling rate for large-sized proppants, and fiber degradation in static and dynamic conditions were determined in various laboratory tests. This engineering work allowed fiber based fluids technology to be extended to moderate permeable oil reservoirs (1-20 md) and relatively cool formations (76–95°C), where fracturing treatments are regularly designed for tip-screenout treatments requiring fracture geometry control maximizing proppant pack permeability by increasing mesh size and proppant concentration.

The first five treatments performed have pushed the limits of the technology in regard to proppant size, type, concentration, and fracture fluid gel loading. Combining this solution with the use of advanced HGC materials offers unprecedented results in regard to fracture-height containment, where positive net pressures were obtained the first time. These operational results were confirmed by production measurements where the average water cut is 50% lower compared to the conventional treatments. Increases in productivity allowed up to a 37% increase in oil flow rate.
Adopting Aphron Fluid Technology for Completion and Workover Applications
Authors: MacPhail W. F , Cooper R. C. , Brookey T. , Paradis J.
Published: February 2008

The literature describes several applications where Aphron fluid technology has been applied in both drilling and re-entry scenarios and includes an extensive description of how this fluid system works. A highly efficient leak-off prevention mechanism makes aphron based fluid systems beneficial for certain completion and workover applications as well, where formation damage could be avoided by the practical elimination of fluid-fluid or fluid-rock interaction or where simply the workover objectives can be achieved by obtaining efficient circulation of fluid to surface. Completion and workover applications for this fluid system have not been extensively reported.

This paper reviews three applications of Aphron fluid technology in different completion and workover scenarios. The selected cases were reviewed to present some of the technical and operational lessons learned and to some extent discuss the observed formation cleanup behavior. The following three applications were reviewed: completion of a dual string sour gas well, using an oil based aphron system for kill fluid, with practically no kill fluid loss to a hydraulically fractured formation; the completion of additional zones within a depleted dolomitic limestone formation on two wells where the method of Aphron fluid placement was found to significantly affect fluid losses; and finally, the enabling of the provision of annular pressure support at pressures which approached the hydraulic fracture opening pressure of a shallow zone while hydraulically fracturing a deeper zone through tubing with a packer.
Continuous Pumping, Multistage, Hydraulic Fracturing in Kitina Field, Offshore Congo, West Africa
Authors: Casero Alberto , Pace Giamberardino , Malone Brad , Cantaloube Francois , Tealdi Loris , Malonga Henri , Seale Rocky
Published: February 2008

Many West Africa offshore fields are maturing and operators are completing secondary targets in their wells to maintain the economic operation of their valuable assets. Large quantities of reserves can be found in low permeability, consolidated, formations and new techniques are being investigated to improve the economic return of completing these formations.

The Kitina Field, offshore from Pointe Noire, Congo, is one such field. Deeper sands have been produced to economic depletion and the operator is looking for alternative production intervals.

The targeted reservoir is the 3A Sand at approximately 2200 meters TVD. The reservoir is a very heterogeneous lithology with varying quantities of siltstone, sandstone and calcite. The intervals of better porosity show a decrease in clay content, but the good "sands" can be either dominated by quartz or calcite with substantial variations with each meter of height.

Three candidate wells were selected for placing multiple propped fractures using a technique that has been used for six years in North America. This technique utilizes a series of mechanical packers and frac ports that are sequentially shifted "on the fly" allowing continuous placement of more than one hydraulic propped fracture without shutting down the pumping equipment.

During April to June of 2007, eight hydraulic propped fractures were placed in three re-completed, cased-hole wells in the Kitina Field with very encouraging production increases. During the first 90 days of post fracturing production, a production increase of 200% was achieved.

This paper will discuss the steps that were taken to place these propped fractures from an ocean going tender barge using skid equipment and recommendations for the future applications of this stimulation technique.
Effects of Crosslinker Type and Additives on the Performance of In-Situ Gelled Acids
Authors: Fatah W. Abdel , Nasr-El-Din H. A. , Moawad T. , Elgibaly A.
Published: February 2008

One of the most important factors that determine the outcome of matrix acidizing treatment is acid placement across the target zone. Chemical and mechanical means are used to enhance diversion during matrix acid treatment in various well completions; extended reach and multi-lateral wells. In-situ gelled acid that is based on polyacrylamide-based polymers has been used in the industry for several years.1,2 Previous studies highlighted that this acid can be used for diversion in formations with almost no hydrogen sulfide and permeability greater than 50 md.3

This acid consists of a polyacrylamide-based polymer, a cross linker, a buffer and a breaker. The cross-linker reacts with the polymer at a certain pH value and forms a gel, which helps in diverting the acid in tight or damaged zones. A breaker is used to reverse the gelation reaction at pH values that depend on the system. There are various cross-linkers available including those that are based on iron, aluminum and zirconium. The objective of this study is to examine the effect of type of cross linker and acid additives on the performance of in-situ gelled acids. Coreflood tests and rheological studies were conducted in this work.

The results obtained indicated that the gelation pH depends on the type of cross-linker used. Aluminum formed a gel at much higher pH values ((pH 4.3) compared the gel formed with iron (pH 2.6). Corrosion inhibitor reduced the pH of gelation in the case of iron, whereas an opposite effect was noted with the Al-based acid. Mutual solvent (ethylene glycol monobutylether) was very effective in reducing gel residue at pH values greater than 5.

Core tests indicated the in-situ gelled acid increased the permeability of tight cores from 35 to 2,000 md. Unlike previous studies, which showed damaged due to this system, no polymer residue was noted after flushing the core with mutual solvent solutions.
Effect of Droplet Size on the Reaction Kinetics of Emulsified Acid With Calcite
Authors: Al-Mutairi S. H. , Nasr-El-Din H. A. , Hill A. D. , Al-Aamri A. D.
Published: February 2008

Unlike other acid systems such as gelled and viscoelastic surfactant-based (VES) acids, where the mobility of hydrogen ion controls the overall rate of the reaction, emulsified acid/calcite reaction involves the transport of acid droplets in the diesel to the rock surface, breaking of acid droplets, and then the actual reaction on the surface. A limited number of papers have been published on the reaction kinetics of emulsified acid. However, none of the published work considered the effect of acid droplet size on the reaction of emulsified acid. The objective of this work is to examine the effect of acid droplet size on the reaction rate of emulsified acid with calcite.

The acid was 15 wt% HCl emulsified in diesel with 70 to 30 acid to diesel volume ratio. Emulsifier concentration was varied from 1 to 10 gpt. All emulsions were characterized by measuring the droplet size distribution, viscosity and thermal stability. Diffusivities were measured using the rotating disk device. Experiments were carried out at 25, 50 and 85°C, under 1,000 psi pressure, and disk rotational speeds from 100 to 1,000 rpm. Samples of the reacting acid were collected and analyzed for calcium concentration.

The effects of droplet size on the overall reaction rate were significant. Diffusion rate of acid droplets to the surface of the disk were found to decrease with increasing emulsifier concentration because of higher viscosities and smaller droplet sizes. Effective diffusion coefficient of emulsified acid was found to increase linearly with the average droplet size of the acid. Emulsions with low emulsifier concentrations (1 gpt) have average droplet sizes of nearly 13 µm. These emulsions were found to have high effective diffusion coeffeicents (5.093 ×10−9 cm2/s) and low retardation. On the other hand, emulsions with high emulsifier concentrations (10 gpt) have smaller average droplet sizes (nearly 6 µm) and found to have low effective diffusion coeffeicents (4.905 ×10−11 cm2/s) and high retardations.

The new sets of data can be used to determine the optimum emulsified acid formulation to yield deeper acid penetration in the formation. It is suggested that droplet size can be adjusted to produce the desired diffusion rate coefficients for acid fracturing treatments.
Sand Control Completion Failures: Can We Talk the Same Language?
Authors: Wagg Brian T. , Heseltine Jonathan L. , Faga Abraham T. , McKinzie Howard L.
Published: February 2008

Several operators have recently launched a new industry-wide initiative on sand control reliability. The aim of the initiative is to gain a better understanding of Sand Control Completion (SCC) systems, equipment performance, and reliability in a variety of applications. It focuses on assisting the industry to improve SCC performance and service life through sharing of reliability and failure information, operational practices, and other pertinent data. One of the key challenges in this effort is how to achieve consistency in the data collected by several operators.

This paper presents an approach to establish consistent practices for collecting, tracking and sharing SCC reliability and failure information. The approach is based on two key elements: (1) common data set; and (2) a standard nomenclature for coding SCC failure information. The general data set contains basic information on operating conditions, SCC systems and equipment, and the observed failures. While this data set is not overly detailed, in that the information is typically already collected by most operators and relatively easy to obtain, it is comprehensive enough so that meaningful analyses can be performed. The nomenclature standard builds on the International Standard IS0 14224 that stipulates broad definitions and failure attributes related to collection and exchange of reliability and maintenance data for equipment used in the petroleum industry.

The paper also provides a review of past industry efforts to track SCC system reliability in terms of the types of data collected, and the main types of analyses performed with the data. Comments are included on difficult issues such as how to define failure of a sand control completion.

It is hoped that the paper will encourage discussion on the topic, and help the industry share SCC reliability and failure data in a more consistent manner. The ultimate goals of this work are to assist the industry in improving SCC service life; improving the basis for selecting sand control systems and equipment; and better realizing the full potential of SCC technologies.
Gelled Scale Inhibitor Treatment for Improved Placement in Long Horizontal Wells at Norne and Heidrun fields
Authors: Selle Olav Martin , Springer Martin , Auflem Inge H. , Chen Ping , Matheson Rozenn , Mebratu Amare , Glasbergen Gerard
Published: February 2008

The success of a scale inhibitor treatment depends on the placement efficiency. The scale inhibitor should be placed so that all water producing intervals accept a sufficient quantity of the total treatment volume. If significant permeability or pressure variations are present in the interval to be treated, treatment fluid will enter the zones with the higher permeability and lower pressure leaving little fluid to treat the other zones, which can be potentially the water producing zones. The challenge is even greater in long horizontal wells with significant permeability and pressure contrast.

To achieve a more uniform fluid coverage, the original flow distribution across interval often needs to be altered. The methods used to alter this are called "diversion" methods. The purpose is to divert the flow from one portion of the interval to another.

In response to this challenge, a joint study with the objective of improving the placement of treatment fluids was initiated by a major operator in the North Sea and two service companies in 2002.

As a result of this work a fully viscosified scale inhibitor system is developed. The system comprises a purified xanthan viscosifying agent, a standard scale inhibitor for downhole scale squeezing and a breaker to achieve controlled gel breaking down hole.

The system has been field tested at Norne field in two long horizontal wells at Heidrun field in one long deviated well, all with significant permeability variations and cross flow. The operations were successful and the scale treatments have protected the wells from scaling. The paper describes the product qualification process, placement simulation, temperature prediction and gel breaking characteristics, case histories and post job evaluation.
Inflow Control Device and Near-Wellbore Interaction
Authors: Moen T. , Asheim H.
Published: February 2008

The optimization of inflow performance in long horizontal open hole completions involves several challenges. One is the formation damage and well clean-up. Another is the heel – toe effect caused by flow friction in the pipe, resulting in risk of gas or water coning in the heel and limited drainage from the toe. Due to such effects, horizontal wells may suffer from reduced PI and reserves left behind.

The introduction of Inflow Control Device (ICD) technology has proved to significantly increase the recoverable reserves from many fields. The ICD provides a controlled pressure drop which is a function of the flow rate. This restricts high producing zones and thus stimulates low producing zones, resulting in:

Improved well clean-up reducing the effect of formation damage caused by the drilling of the well. Equalizing the flux along the well path, giving reduced coning effects. Reduced annular flow. This reduces the risk of sand production behind the screen and subsequent plugging or erosion.

This paper is discussing how an ICD interacts with the reservoir and near well bore region. The first step is the dynamic of the clean-up process. The optimal differential pressure can now be applied to remove near well bore damage.

A model illustrating the propagation of this process will be described. This will be correlated with experimental results from clean-up of core plugs and practical field experience. The purpose of this work is to illustrate how the use of the ICD technology both improves the well PI and increases the recoverable reserves.
Evaluation of Formation Damage/Completion Impairment Following Dynamic Filter-Cake Deposition on Unconsolidated Sand
Authors: Constien V. G.
Published: February 2008

Evaluation of formation and completion (gravel pack and screen only) flow capacity damage in unconsolidated formation material has proven difficult in the laboratory because typical core flood equipment does not adequately confine the formation material to allow drilling and cleanup fluids to be circulated at representative shear rates and pressures over the formation face.

A testing protocol and equipment have been developed which allows dynamic flow and fluid loss across unconsolidated formation material at shear rates, temperatures, differential pressures, and times representative of mud circulation rates in the wellbore.

The dynamically prepared filtercakes grow to an equilibrium thickness depending on the shear rate, differential pressure, and temperature and are more representative in composition and mass to wellbore filtercakes so that their damage to formation, gravel packs and / or screens can be better evaluated. The effectiveness of cleanup systems can also be determined by circulating the fluids across the mud filtercakes at typical shear rates, differential pressures and temperatures before allowing static soak conditions.

At the end of the test, the screen and formation material or screen, gravel pack and formation material are stressed together simulating a wellbore collapse. The permeability of the formation plus gravel pack and screen or formation and screen only are then measured and compared to the initial values to determine flow capacity impairment.
Performance Evaluation of Ionic Liquids as a Clay Stabilizer and Shale Inhibitor
Authors: Berry Sandra L. , Boles Joel L. , Brannon Harold D. , Beall Brian B.
Published: February 2008

Most oil and gas producing formations contain clay minerals that were deposited during the sedimentation process, formed during the interaction of heat, pressure, and time on the naturally present minerals in the formation, or precipitated from fluids flowing from one area of the formation to others. The oil and gas industry has extensively investigated the role of these clay minerals during production and the potential permeability damage that can occur with swelling and migration of these clays. For many years, the effective use of salts such as KCl and NaCl in workover fluids for temporary clay stabilization has been well established. However, due to the potential environmental issues and the logistics of using large quantities of salts for this application, many operators have begun to search for alternative clay stabilizer products.

This project details the investigation and evaluation of ionic liquids as a clay stabilizer and shale inhibitor additive to prevent clay swelling and migration in comparison to the industry-standard clay stabilizers. Ionic liquids are compounds that are liquids at ambient temperatures and consist entirely of cations and anions, usually a organic cation and a inorganic anion.

Screening studies to determine the state of flocculation of clay-bearing fluids and to screen for shale inhibition were conducted with Capillary Suction Time tests (CST), Clay Pack Flow tests and core flow studies. This paper summarizes the results of the clay stabilizer screening studies conducted with ionic liquids and details the effectiveness of the ionic liquids as KCl substitutes, clay stabilizer additives, and shale inhibitors.
Associating Seasonal Range Characteristics With Survival of Female White‐Tailed Deer
Authors: KLAVER ROBERT W. , JENKS JONATHAN A. , DEPERNO CHRISTOPHER S. , GRIFFIN STEVEN L.
Published: February 2008

ABSTRACT  Delineating populations is critical for understanding population dynamics and managing habitats. Our objective was to delineate subpopulations of migratory female white‐tailed deer (Odocoileus virginianus) in the central Black Hills, South Dakota and Wyoming, USA, on summer and winter ranges. We used fuzzy classification to assign radiocollared deer to subpopulations based on spatial location, characterized subpopulations by trapping sites, and explored relationships among survival of subpopulations and habitat variables. In winter, Kaplan‐Meier estimates for subpopulations indicated 2 groups: high (S = 0.991 ± 0.005 [x̄ ± SE]) and low (S = 0.968 ± 0.007) weekly survivorship. Survivorship increased with basal area per hectare of trees, average diameter at breast height of trees, percent cover of slash, and total point‐center quarter distance of trees. Cover of grass and forbs were less for the high survivorship than the lower survivorship group. In summer, deer were spaced apart with mixed associations among subpopulations. Habitat manipulations that promote or maintain large trees (i.e., basal area = 14.8 m2/ha and average dbh of trees = 8.3 cm) would seem to improve adult survival of deer in winter.
Survival and Body Condition of Raccoons at the Edge of the Range
Authors: PITT JUSTIN A. , LARIVIÈRE SERGE , MESSIER FRANÇOIS
Published: February 2008

ABSTRACT We investigated the influence of intrinsic and extrinsic variables on overwinter survival of raccoons (Procyon lotor; n= 114) at the northern edge of their distribution. A Cox proportional hazard model identified winter severity as the variable with the greatest influence on raccoon survival (β = 1.08). Autumn body condition estimates (20.5 ± 0.46% total body fat) were relatively stable across years even though we observed large differences in autumn food indices. Variations in autumn body condition did not explain heterogeneity observed in overwinter survival nor the spring condition in which raccoons emerged. Relatively constant autumn body condition suggests reliable availability of anthropogenic food resources may negate variations observed in natural food items on which raccoons rely during hyperphagia. Conversely, spring body condition did vary among years and was highly correlated with winter severity. Accordingly, we also observed a strong inverse relationship with overwinter survival and winter severity. Our findings indicate winter climatic constraints are important factors governing the northern limit of raccoon distribution and changes in winter severity could have important implications in further range expansion of this species.
Habitat Selection and Movement of Pond‐Breeding Amphibians in Experimentally Fragmented Pine Forests
Authors: GRAETER GABRIELLE J. , ROTHERMEL BETSIE B. , GIBBONS J. WHITFIELD
Published: February 2008

ABSTRACT Population‐level responses of amphibians to forest management regimes are partly dictated by individual behavioral responses to habitat alteration. We examined the short‐term (i.e., 24‐hr) habitat choices and movement patterns of 3 amphibian species—southern leopard frogs (Rana sphenocephala), marbled salamanders (Ambystoma opacum), and southern toads (Bufo terrestris)—released on edges between forest habitats and recent clear‐cuts in the Upper Coastal Plain of South Carolina, USA. We predicted that adult frogs and salamanders would preferentially select forest using environmental cues as indicators of habitat suitability. We also predicted that movement patterns would differ in clear‐cuts relative to forests, resulting in lower habitat permeability of clear‐cuts for some or all of the species. Using fluorescent powder tracking, we determined that marbled salamanders selected habitat at random, southern toads preferred clear‐cuts, and southern leopard frogs initially selected clear‐cuts but ultimately preferred forests. Frogs exhibited long‐distance, directional movement with few turns. In contrast, toads exhibited wandering behavior and salamanders moved relatively short distances before locating cover. Southern toads and southern leopard frogs moved farther in forests, and all 3 species made more turns in clear‐cuts than in forests. Habitat selection by southern toads did not vary according to body size, sex, or the environmental cues we measured. However, marbled salamanders were more likely to enter clear‐cuts when soil moisture was high, and southern leopard frogs were more likely to enter clear‐cuts when relative humidity and air temperature were higher in the clear‐cut than in adjacent forest. Although we found evidence of reduced habitat permeability of clear‐cuts for southern leopard frogs and southern toads, none of the species exhibited strong behavioral avoidance of the small (4‐ha) clear‐cuts in our study. Further studies of long‐term habitat use and the potential physiological and other costs to individuals in altered forests are needed to understand the effects of forest management on population persistence. To reduce potentially detrimental effects of clear‐cutting on amphibians in the Southeast, wildlife managers should consider the vagility and behavior of species of concern, especially in relation to the size of planned harvests adjacent to breeding sites.
Screening Radiolocation Datasets for Movement Strategies With Time Series Segmentation
Authors: DETTKI HOLGER , ERICSSON GÖRAN
Published: February 2008

ABSTRACT  Classical home range analysis is tailored to meet requirements of data with few points per individual with relatively large intervals between observations. The swift rise in Global Positioning System (GPS)‐based studies requires the development of new analytical approaches because GPS data allow for more detailed analysis in time and space. The amount of data derived from GPS studies enhances the potential to more accurately separate movement strategies. We present a general, simple, conceptual approach to using large movement datasets to automatically screen and delimit spatial and temporal home ranges of individuals and movement strategies using time series segmentation. We used GPS data for moose (Alces alces) from a boreal Swedish population as an example. We tested predictions that our screening method could separate seasonal migration from dispersal and nomadic strategies by the movement profile, which includes several dimensions. Our analysis showed that broad strategies were detected using our simple analytical approach, which speeds up use of GPS data for management and research because the method can be used to calculate more objective spatial and temporal activity ranges in relation to movement strategies. Our examples illustrate the importance of using the time stamp on location data in describing home ranges and movements.
Proximate Cues for a Short‐Distance Migratory Species: an Application of Survival Analysis
Authors: MEUNIER JED , SONG RUI , LUTZ R. SCOTT , ANDERSEN DAVID E. , DOHERTY KEVIN E. , BRUGGINK JOHN G. , OPPELT EILEEN
Published: February 2008

ABSTRACT Investigation of bird migration has often highlighted the importance of external factors in determining timing of migration. However, little distinction has been made between short‐ and long‐distance migrants and between local and flight birds (passage migrants) in describing migration chronology. In addition, measures of food abundance as a proximate factor influencing timing of migration are lacking in studies of migration chronology. To address the relationship between environmental variables and timing of migration, we quantified the relative importance of proximate external factors on migration chronology of local American woodcock (Scolopax minor), a short distance migrant, using event‐time analysis methods (survival analysis). We captured 1,094 woodcock local to our study sites in Michigan, Minnesota, and Wisconsin (USA) during autumn 2002–2004 and documented 786 departure dates for these birds. Photoperiod appeared to provide an initial proximate cue for timing of departure. Moon phase was important in modifying timing of departure, which may serve as a navigational aid in piloting and possibly orientation. Local synoptic weather variables also contributed to timing of departure by changing the rate of departure from our study sites. We found no evidence that food availability influenced timing of woodcock departure. Our results suggest that woodcock use a conservative photoperiod‐controlled strategy with proximate modifiers for timing of migration rather than relying on abundance of their primary food, earthworms. Managing harvest pressure on local birds by adjusting season lengths may be an effective management tool with consistent migration patterns from year to year based on photoperiod.
Alternative Feeding Strategies and Potential Disease Transmission in Wisconsin White‐Tailed Deer
Authors: THOMPSON ABBEY K. , SAMUEL MICHAEL D. , VAN DEELEN TIMOTHY R.
Published: February 2008

ABSTRACT We conducted experimental feeding using 3 feeding methods (pile, spread, trough) and 2 quantities (rationed, ad libitum) of shelled corn to compare deer activity and behavior with control sites and evaluate potential direct and indirect transmission of infectious disease in white‐tailed deer (Odocoileus virginianus) in central Wisconsin, USA. Deer use was higher at 2 of the feeding sites than at natural feeding areas (P≤ 0.02). Deer spent a higher proportion of time (P< 0.01) feeding at pile (49%) and spread (61%) treatments than at natural feeding areas (36%). We found higher deer use for rationed than ad libitum feeding quantities and feeding intensity was greatest at rationed piles and lowest at ad libitum spreads. We also observed closer pairwise distances (≤0.3 m) among deer when corn was provided in a trough relative to spread (P=0.03). Supplemental feeding poses risks for both direct and indirect disease transmission due to higher deer concentration and more intensive use relative to control areas. Concentrated feeding and contact among deer at feeding sites can also increase risk for disease transmission. Our results indicated that restrictions on feeding quantity would not mitigate the potential for disease transmission. None of the feeding strategies we evaluated substantially reduced the potential risk for disease transmission and banning supplemental feeding to reduce transmission is warranted.
Cover Pole Design for Easy Transport, Assembly, and Field Use
Authors: DAVID TOLEDO P. , ABBOTT LAURIE B. , HERRICK JEFFREY E.
Published: February 2008

ABSTRACT Cover poles, also called Robel poles, are used to measure a variety of structural vegetation attributes commonly used in wildlife and livestock management. Although cover pole dimensions, measurement criteria, and interpretation of cover pole data vary depending on measurement objectives, the technical use of cover poles is fairly consistent. Practical use of cover poles requires that they are sturdy, lightweight, and easily transported. We describe a cover pole apparatus that can be easily constructed, transported, and assembled for use in remote locations. This self‐supporting cover pole enables one person to take measurements, and can be modified for use in multiple habitats and soil types.
A Returns-Based Representation of Earnings Quality
Authors: Ecker Frank , Francis Jennifer , Kim Irene , Olsson Per M. , Schipper Katherine
Published: February 2008

We examine the properties of a returns-based representation of earnings quality, estimated from firm-specific asset-pricing regressions augmented by an earnings quality mimicking factor. The coefficient on the earnings quality factor (the “e-loading”) captures the sensitivity of the firm's returns to earnings quality in a given year or quarter, analogous to beta as a measure of the sensitivity of returns to market movements. Relative to other proxies for earnings quality, e-loadings can be calculated for larger samples of firms and can be estimated for shorter intervals at any point in time. Along all dimensions examined, we find that e-loadings perform well in capturing notions of earnings quality.
Does Hiring a New CFO Change Things? An Investigation of Changes in Discretionary Accruals
Authors: Geiger Marshall A. , North David S.
Published: February 2008

The recent spate of fraudulent financial reporting in the U.S. has drawn attention to the fact that the Chief Financial Officer (CFO) has a substantial amount of control over a firm's reported financial results. This paper examines the changes in discretionary accruals surrounding the appointment of a new CFO. Using a sample of 712 companies that appointed a new CFO in the period 1994 to 2000, we find that discretionary accruals decreased significantly following the appointment of a new CFO. Our tests indicate that this reduction is significantly greater for our group of CFO-hiring firms than for a control group of non-hiring firms, and that the changes are not driven by a concurrent appointment of a new Chief Executive Officer (CEO). We also find that our results are largely driven by firms that hire a new CFO from outside the company. Our study extends earlier research by providing empirical evidence that individuals in CFO positions wield significant influence over the firm's reported financial results and that a firm's discretionary accruals are significantly reduced surrounding the appointment of a new CFO.
Organizational Slack in Decentralized Firms: The Role of Business Unit Controllers
Authors: Indjejikian Raffi J. , Mateˇjka Michal
Published: February 2008

We study the determinants of organizational slack in large decentralized firms and focus in particular on how management accounting systems (represented by business unit controllers) affect slack. We rely on an adverse selection model to derive several predictions and to motivate our tests. Consistent with this framework, we find that organizational slack (measured by achievability of business unit managers' performance targets) is higher in settings where business unit controllers focus relatively more on providing decision-making information to business unit managers than on providing information for corporate control. We also find that organizational slack is persistent over time and positively associated with business unit growth, our proxy for the extent of information asymmetry between corporate headquarters and local business unit management.
Performance Measure Properties and Delegation
Authors: Moers Frank
Published: February 2008

In this paper, I extend the organizational design literature by examining how the delegation choice is affected by the ability to resolve the incentive problem caused by this delegation. Based on the seminal papers by Grossman and Hart (1986) and Holmstrom and Milgrom (1994), I argue that the ability to resolve the incentive problem depends on the contractibility of financial performance measures versus nonfinancial performance measures, where the contractibility depends on the performance measure properties sensitivity, precision, and verifiability. The empirical results show that, if financial performance measures are “good” (“poor”) incentive measures, i.e., high (low) on sensitivity, precision, and verifiability, then using these measures for incentive purposes increases (decreases) delegation. Overall, the results are consistent with the argument that firms design their decision-making process around the quality of contractible performance measures.
The Perils of Pensions: Does Pension Accounting Lead Investors and Analysts Astray?
Authors: Picconi Marc
Published: February 2008

This paper explores the ability of investors and analysts to fully process available pension information when establishing prices and making earnings forecasts. I find that neither prices nor forecasts fully reflect the quantifiable future earnings effects of changes in pension information at the time it becomes publicly available in the firm's 10-K. Instead, the evidence suggests that investors and analysts only gradually incorporate this information into prices and forecasts as they observe the effects of the pension plan changes on subsequent quarterly earnings. The persistent tardiness of analysts to incorporate this relevant and economically significant information about earnings is surprising given that they are provided with pension information on a repeated and timely basis. Additionally, I find that the off-balance-sheet portion of the pension plan's funded status and the PBO are predictive of future returns while the on-balance-sheet portion of the funded status is not. This implies that investors do not accurately assess the long-run cash flow and earnings implications of these off-balance-sheet pension disclosures. The compensation rate is also predictive of future returns suggesting that it signals management's expectation of future performance.
Comments on Slavin: Through the Looking Glass: Experiments, Quasi-Experiments, and the Medical Model
Authors: Sloane Finbarr
Published: February 2008

Slavin (2008) has called for changing the criteria used for the inclusion of basic research in national research synthesis clearinghouses. The author of this article examines a number of the assumptions made by Slavin, provides critique with alternatives, and asks what it means to fully implement the medical model in educational settings.
Comments on Slavin: Bringing Answers to Educators: Guiding Principles for Research Syntheses
Authors: Dynarski Mark
Published: February 2008

Research syntheses are appealing because they enable decision makers to determine quickly whether policies, programs, and practices will have effects on student achievement and, if so, the magnitudes of the likely effects. Such syntheses should present objective, clear, scientifically accurate, and defensible evidence in terms that educators can use in making their decisions. The syntheses should also give the most weight to research with strong causal validity and should consider sources of bias and use procedures that reduce or eliminate bias. To that end, it is hoped that theoretical development of standards will help researchers to assess the trade-offs that need to be made in weighing the evidence to be used in syntheses. Creating methods for assessing the extent of evidence in syntheses will enhance their usefulness in evidence-informed decision making.
Long‐term seed bank dynamics in a temperate forest under conversion from coppice‐with‐standards to high forest management
Authors: van Calster Hans , Chevalier Richard , van Wyngene Bram , Archaux Frédéric , Verheyen Kris , Hermy Martin
Published: February 2008

Questions:How do changes in forest management, i.e. in disturbance type and frequency, influence species diversity, abundance and composition of the seed bank? How does the relationship between seed bank and vegetation change? What are the implications for seed bank dynamics?

Location:An ancientQuercus petraea — Carpinus betulusforest in conversion from coppice‐with‐standards to regularQuercushigh forest near Montargis, France.

Methods:Seed bank and vegetation were sampled in six replicated stand types, forming a chronosequence along the conversion pathway. The stand types represented mid‐successional stages of stands in transition from coppice‐with‐standards (to high forest (16 plots) and early‐ and mid‐successional high forest stands (32 plots).

Results:Seed bank density and species richness decreased with time since last disturbance. Adjusting for seed density effects obscured species richness differences between stand types, but species of later seres were nested subsets of earlier seres, implying concomitant shifts in species richness and composition with time since disturbance. Later seres were characterized by species with low seed weight and high seed longevity. Seed banks of early seres were more similar to vegetation than to later seres.

Conclusions:Abandonment of the coppice‐with‐standards regime altered the seed bank characteristics, as well as its relationship with vegetation. Longer management cycles under high forest yield impoverished seed banks. For their persistence, seed bank species will increasingly rely on management of permanently open areas in the forest landscape. Thus, revegetation at the beginning of new high‐forest cycles may increasingly depend on inflow from seed sources.
Long‐term after‐effects of fertilisation on the restoration of calcareous grasslands
Authors: Smits N.A.C. , Willems J.H. , Bobbink R.
Published: February 2008

Question: What are the long‐term implications of former fertilisation for the ecological restoration of calcareous grasslands?

Location: Gerendal, Limburg, The Netherlands.

Methods: In 1970, ten permanent plots were established in just abandoned agricultural calcareous grassland under a regime of annual mowing in August. From 1971 to 1979, two different fertiliser treatments were applied twice a year to a subset of the plots (artificial fertiliser with different proportions of nitrogen and phosphorus). The vegetation of the plots was recorded yearly and vegetation biomass samples were taken for peak standing crop and total amounts of nitrogen, phosphorus and potassium. Species composition and floristic diversity were analysed over the research period (1970–2006) and between the treatments, including the use of multivariate techniques (Detrended Correspondence Analysis).

Results: In terms of species number, there is a clear optimum 10 to 20 years after fertilisation has been terminated. Afterwards, there is a slow decrease; no new species appear and species of more nutrient‐rich conditions gradually disappear. For the fertilised plots that received a relatively high proportion of N, effects are found only in the first years, whereas, for the plots that received a relatively high proportion of P, long‐term after‐effects are found in species composition, peak standing crop, total amounts of phosphorus in biomass, and in soil phosphorus data.

Conclusions: The effect of artificial fertiliser with a large amount of nitrogen disappears in less than ten years when mown in August, including removal of the hay. This is a promising result for restoration of N‐enriched calcareous grasslands, as the applied dose of nitrogen in this experiment largely exceeds the extra input of nitrogen via atmospheric deposition. Application of fertiliser with a large amount of phosphorus, however, has effects even more than 25 years after the last addition. There are no prospects that this effect will become reduced in the near future under the current mowing management.
A Finite Element Formulation for Atrial Tissue Monolayer
Authors: Richter H. E. , Plank G. , Pfeifer B. , Tilg B. , Nowak C. N. , Fischer G. , Wieser L.
Published: February 2008

Objectives:
Using computer models for the study of complex atrial arrhythmias such as atrial fibrillation is computationally demanding as long observation periods in the order of tens of seconds are required. A well established approach for reducing computational workload is to approximate the thin atrial walls by curved monolayers. On the other hand, the finite element method (FEM) is a well established approach to solve the underlying partial differential equations.

Methods:
A generalized 2D finite element method (FEM) is presented which computes the corresponding stiffness and coupling matrix for arbitrarily shaped monolayers (ML). Compared to standard 2D FEM, only one additional coordinate transformation is required. This allows the use of existing FEM software with minor modifications. The algorithm was tested to simulate wave propagation in benchmark geometries and in a model of atrial anatomy.

Results:
The ML model was able to simulate electric activation in curved tissue with anisotropic conductivity. Simulations in branching tissue yielded slightly different patterns when compared to a volumetric model with finite thickness. In the model of atrial anatomy the computed activation times for five different pacing protocols displayed a correlation of 0.88 compared to clinical data.

Conclusions:
The presented method provides a useful and easily implemented approach to model wave propagation in MLs with a few restrictions to volumetric models.
Estimating Morbidity Ratesfrom Electronic Medical Records in General Practice
Authors: Verheij R. A. , de Bakker D. H. , Zielhuis G. A. , de Vries Robbé P. F. , Biermans M. C. J.
Published: February 2008

Objectives:
In this study, we evaluated the internal validity of EPICON, an application for grouping ICPCcoded diagnoses from electronic medical records into episodes of care. These episodes are used to estimate morbidity rates in general practice.

Methods:
Morbidity rates based on EPICON were compared to a gold standard; i.e. the rates from the second Dutch National Survey of General Practice. We calculated the deviation from the gold standard for 677 prevalence and 681 incidence rates, based on the full dataset. Additionally, we examined the effect of casebased reasoning within EPICON using a comparison to a simple, not case-based method (EPI-0). Finally, we used a split sample procedure to evaluate the performance of EPICON.

Results:
Morbidity rates that are based on EPICON deviate only slightly from the gold standard and show no systematic bias. The effect of case-based reasoning within EPICON is evident. The addition of case-based reasoning to the grouping system reduced both systematic and random error. Although the morbidity rates that are based on the split sample procedure show no systematic bias, they do deviate more from the gold standard than morbidity rates for the full dataset.

Conclusions:
Results from this study indicate that the internal validity of EPICON is adequate. Assuming that the standard is gold, EPICON provides valid outcomes for this study population. EPICON seems useful for registries in general practice for the purpose of estimating morbidity rates.
Size‐Dependent Catalytic Activity of Supported Palladium Nanoparticles for Aerobic Oxidation of Alcohols
Authors: Chen Jing , Zhang Qinghong , Wang Ye , Wan Huilin
Published: February 2008

Silica‐alumina (SiO2‐Al2O3)‐supported palladium catalysts prepared by adsorption of the tetrachloropalladate anion (PdCl42−) followed by calcination and reduction with either hexanol or hydrogen were studied for the aerobic oxidation of alcohols. The mean size of the Pd particles over the SiO2‐Al2O3 support was found to depend on the Si/Al ratio, and a decrease in the Si/Al ratio resulted in a decrease in the mean size of the Pd nanoparticles. By changing the Si/Al ratio, we obtained supported Pd nanoparticles with mean sizes ranging from 2.2 to 10 nm. The interaction between the Pd precursor and the support was proposed to play a key role in tuning the mean size of the Pd nanoparticles. The Pd/SiO2‐Al2O3 catalyst with an appropriate mean size of Pd particles could catalyze the aerobic oxidation of various alcohols to the corresponding carbonyl compounds, and this catalyst was particularly efficient for the solvent‐free conversion of benzyl alcohol. The intrinsic turnover frequency per surface Pd atom depended significantly on the mean size of Pd particles and showed a maximum at a medium mean size (3.6–4.3 nm), revealing that the aerobic oxidation of benzyl alcohol catalyzed by the supported Pd nanoparticles was structure‐sensitive.