bluuebunny/crossref_metadata_2025 huggingface dataset:
Class-Size Caps, Sorting, and the Regression-Discontinuity Design
Authors: Urquiola Miguel , Verhoogen Eric
Published: March 2009

This paper examines how schools' choices of class size and households' choices of schools affect regression-discontinuity-based estimates of the effect of class size on student outcomes. We build a model in which schools are subject to a class-size cap and an integer constraint on the number of classrooms, and higher-income households sort into higher-quality schools. The key prediction, borne out in data from Chile's liberalized education market, is that schools at the class-size cap adjust prices (or enrollments) to avoid adding an additional classroom, which generates discontinuities in the relationship between enrollment and household characteristics, violating the assumptions underlying regression-discontinuity research designs. (JEL D12, I21, I28, O15)
Taxes and Employment Subsidies in Optimal Redistribution Programs
Authors: Beaudry Paul , Blackorby Charles , Szalay Dezsö
Published: March 2009

This paper explores how to optimally set taxes and transfers when taxation authorities are uninformed about individuals' value of time in both market and nonmarket activities; and can observe both market-income and time allocated to market employment. We show that optimal redistribution in this environment involves a cutoff wage whereby workers above the cutoff are taxed as they increase their income, while workers earning a wage below the cutoff receive an income supplement as they increase their income. Finally, we show that the optimal program transfers zero income to individuals who choose not to work. (JEL D31, H21, H23, H24)
Rare Disasters, Asset Prices, and Welfare Costs
Authors: Barro Robert J
Published: March 2009

A representative-consumer model with Epstein-Zin-Weil preferences and i.i.d. shocks, including rare disasters, accords with observed equity premia and risk-free rates if the coefficient of relative risk aversion equals 3–4. If the intertemporal elasticity of substitution exceeds one, an increase in uncertainty lowers the price-dividend ratio for equity, and a rise in the expected growth rate raises this ratio. Calibrations indicate that society would willingly reduce GDP by around 20 percent each year to eliminate rare disasters. The welfare cost from usual economic fluctuations is much smaller, though still important, corresponding to lowering GDP by about 1.5 percent each year. (JEL E13, E21, E22, E32)
Cognition and Incomplete Contracts
Authors: Tirole Jean
Published: March 2009

Thinking about contingencies, designing covenants, and seeing through their implications is costly. Parties to a contract accordingly use heuristics and leave it incomplete. The paper develops a model of limited cognition and examines its consequences for contractual design. (JEL D23, D82, D86, L22)
The Value of Groups
Authors: Hargreaves Heap Shaun P , Zizzo Daniel John
Published: March 2009

We present the results of an experiment that attempts to measure the social value of groups. In the experiment, group membership is induced artificially: subjects interact with insiders and outsiders in trust games and periodically enter markets where they can trade group membership. We find that trust falls with groups because of negative discrimination against outsiders. Against this, however, there is evidence that group membership provides a psychological benefit, albeit one that may induce social inertia. Overall, the welfare effects of groups are at best neutral and could be negative. (JEL: D17, Z13)
The War on Drugs: Methamphetamine, Public Health, and Crime
Authors: Dobkin Carlos , Nicosia Nancy
Published: March 2009

In mid-1995, a government effort to reduce the supply of methamphetamine precursors successfully disrupted the methamphetamine market and interrupted a trajectory of increasing usage. The price of methamphetamine tripled and purity declined from 90 percent to 20 percent. Simultaneously, amphetamine-related hospital and treatment admissions dropped 50 percent and 35 percent, respectively. Methamphetamine use among arrestees declined 55 percent. Although felony methamphetamine arrests fell 50 percent, there is no evidence of substantial reductions in property or violent crime. The impact was largely temporary. The price returned to its original level within four months; purity, hospital admissions, treatment admissions, and arrests approached preinter-vention levels within eighteen months. (JEL I12, K42)
Insurer-Provider Networks in the Medical Care Market
Authors: Ho Katherine
Published: March 2009

I use data on the hospital networks offered by managed care health insurers to estimate the expected division of profits between insurers and providers. I include a simple profit-maximization framework and an additional effect: hospitals that can secure demand without contracting with all insurers (e.g., those most attractive to consumers and those that are capacity constrained) may demand high prices that some insurers refuse to pay. Hospital mergers may also affect price bargaining. I estimate that all three types of hospitals capture higher markups than other providers. These results provide information on the hospital investment incentives generated by bargaining. (JEL G22, G34, I11, L25)
Excise Taxes with Multiproduct Transactions
Authors: Hamilton Stephen F
Published: March 2009

I examine excise taxes levied on multiproduct retailers. Excise taxes reduce equilibrium output and decrease equilibrium product variety in the short run, but taxes can raise output per product in the long run and induce entry. Excise taxes are overshifted into prices in a wide range of cases, including under linear and concave demand conditions, and excise taxes shift less than one-for-one into prices only when demand is highly convex. Multiproduct transactions substantively alter the efficiency of ad valorem and specific forms of excise taxes and affect the comparison of relative tax performance over short-run and long-run time horizons. (JEL H25, H32, L11, L13, L81)
Liquidity Constraints and Imperfect Information in Subprime Lending
Authors: Adams William , Einav Liran , Levin Jonathan
Published: March 2009

We present new evidence on consumer liquidity constraints and the credit market conditions that might give rise to them. We analyze unique data from a large auto sales company serving the subprime market. Short-term liquidity appears to be a key driver of consumer behavior. Demand increases sharply during tax rebate season and purchases are highly sensitive to down-payment requirements. Lenders also face substantial informational problems. Default rates rise significantly with loan size, providing a rationale for loan caps, and higher-risk borrowers demand larger loans. This adverse selection is mitigated, however, by risk-based pricing. (JEL D14, D82, D83, G21)
Resolving complaints: a new model
Authors: Prentice Derek
Published: March 2009

The Dental Complaints Service allows patients across the UK to complain about any aspect of private dental care, treatment or service, involving any member of the dental team. It works with patients and dental professionals to help resolve complaints using a ‘common sense’ approach, recognizing that handling complaints badly can be damaging to all concerned.
Impairment of fitness to practise: has the pendulum swung?
Authors: Forde Martin
Published: March 2009

Practitioners and their legal advisers have struggled to interpret the nebulous concept of impairment of fitness to practise since its introduction in November 2004. Impairment of fitness to practise is not defined in the legislation or in the General Medical Council (Fitness to Practise) Rules 2004. This has led to competing arguments being raised before Fitness to Practise Panels regarding both the meaning of impairment of fitness to practise and the nature and quality of the evidence that can be relied upon as evidencing a lack of impairment of fitness to practise. A recent trilogy of High Court decisions appears to have provided the clarity so sadly lacking in the legislation. The cases of Cohen, Zygmunt and Azzam, all decided in 2008 in the High Court, may have provided greater protection to doctors.
Healthcare regulators and risk: assessing the evidence
Authors: Rudkin Duncan
Published: March 2009

The General Dental Council (GDC) is one of a number of healthcare regulators that manages risk on behalf of the public, in order to protect patients. However, it recognizes that it cannot take decisions on the basis of opinion, anecdote and assumptions about the public's appetite for risk. Basing how it manages risk on how it assesses risk – systematically – is preferable. A risk-based approach better serves the principles of better regulation: proportionality, accountability, consistency, transparency and targeting. The GDC has taken some steps towards this approach, working closely with stakeholders.
Experience in the USA
Authors: Mayer K H
Published: March 2009

In November 2006, the United States Centers for Disease Control and Prevention updated their recommendations for HIV-testing in healthcare settings in the USA. The new guidelines recommended routine HIV-testing not based on patient risk, opt-out testing, no separate consent for HIV-testing and no requirement for pretest counselling. Three cardinal points underlie the changes: risk-based testing has not identified all HIV-infected individuals in the USA, opportunities for diagnosis and management of HIV are being missed and routine HIV screening is cost-effective. Routine screening for HIV is desirable and should be achievable, but challenges still remain in introducing it in the USA. State-by-State changes in laws have had to be made, the impact on providers and payers must be considered and proactive screening programmes must be supported by faith and cultural leaders in the highly affected communities. Furthermore, non-specialist clinicians must be trained to deal with all aspects of HIV-testing in an appropriate and professional manner. Despite fears that the public would not accept the new approach, many Americans believe that HIV-testing is an appropriate part of a medical check-up. With the public's support, newly diagnosed HIV-infected individuals will benefit from treatment, and society will benefit because of reduced HIV transmission.
Experience in the UK
Authors: Fisher M , Delpech V
Published: March 2009

The number of new diagnoses of HIV in the UK is increasing, with most new diagnoses reported in men who have sex with men (MSM) and black African heterosexuals the later of whom usually acquire their infection abroad. Around 31 % of people infected with HIV in the UK are unaware of their diagnosis, and one in three are diagnosed for the first time with a CD4 count <200 cells/mm3 or with AIDS. Late diagnosis is the most important factor that explains most HIV-related causes of death in the UK. Strategies to increase HIV-testing include universal approaches in antenatal and STD clinics (known as genitourinary [GU] medicine clinics), but other opportunities for prompt diagnosis are often missed during secondary and primary consultations - even when patients present with HIV-related illnesses. Furthermore, a significant proportion of people with undiagnosed HIV who attend GU medicine clinics leave without being offered an HIV test or a diagnosis of HIV. Universal offer (opt-out testing) policies seem to work well - such as in the successful antenatal testing programme - but local strategies to increase HIV-testing and prompt diagnosis, such as training courses and rapid HIV-testing initiatives have met with varied success. New national guidelines for the UK have been published and, if successfully implemented, should help to address some of these issues.
Interventions for uncomplicated varicose veins
Authors: Bachoo P
Published: March 2009

Objective

To review the evidence regarding interventions (compression, sclerotherapy, surgery and endoluminal) for uncomplicated venous disease.

Method

A literature search of MEDLINE and EMBASE was performed. In addition, bibliographies of published data and the Cochrane Peripheral Vascular Review Group Specialist Register were examined. Publications describing an intervention for uncomplicated venous disease or trials comparing one intervention against another were considered.

Results

Uncomplicated but symptomatic varicose veins are associated with a significant reduction in quality of life (QoL). Evaluation must include a detailed history and examination supported by non-invasive imaging. Although HHD is useful, its utility is limited in the popliteal fossa. It can not provide morphological/anatomical detail when considering an endoluminal treatment option. Regardless of intervention, all treatments considered are associated with a significant improvement in QoL at acceptable cost.

Conclusion

Uncomplicated symptomatic varicose veins lead to a reduced QoL, which can be significantly improved by all interventions considered.
Radiofrequency ablation for uncomplicated varicose veins
Authors: Gohel M S , Davies A H
Published: March 2009

In recent years, minimally invasive endovenous treatments have gained popularity in the treatment of superficial venous reflux. The perceived advantages of endovenous therapy include reduced pain, high vein occlusion rates, and early return to work and normal activities. Endovenous radiofrequency ablation (RFA) involves the delivery of thermal energy from a bipolar catheter to the venous segment to be treated. This technique has been available since 1998 and numerous devices and catheters are now produced. Numerous prospective and randomized studies have compared the effectiveness of RFA with traditional and endovenous procedures. In this article, the available evidence for clinical effectiveness, quality of life and cost gains following endovenous RFA is summarized. The scientific principles behind RFA and technical procedural considerations are discussed and standards of care for the delivery of endovenous RFA are proposed.
Endovenous laser treatment for uncomplicated varicose veins
Authors: Darwood R J , Gough M J
Published: March 2009

Objective

Endovenous laser ablation (EVLA) of incompetent truncal veins has been proposed as a minimally invasive alternative to conventional surgery for varicose veins. Various strategies have been proposed for successful treatment and this study reviews the evidence for these.

Method

A Medline and ‘controlled trials online database’ search was performed to identify original articles and randomized controlled trials (RCTs) reporting outcomes for EVLA. Information on patient selection, equipment, technique and outcomes were recorded.

Results

Ninety-eight original studies, including five RCTs, were identified. RCT data indicate short-term outcomes (abolition of reflux, improvement in quality of life [QOL], patient satisfaction) were equivalent to those for surgery. Long-term follow-up is not available. A further RCT showed superior outcomes for ablation commencing at the lowest point of superficial venous reflux rather than at an arbitrary point (fewer residual varicosities, greater improvement in QOL). Non-randomized series suggest that laser energy of >60 J/cm results in reliable truncal vein occlusion and that longer wavelength lasers may be associated with less post-treatment discomfort.

Conclusion

In the short-term EVLA is a safe and effective treatment for patients with varicose veins. Long-term follow-up is still required.
Foam and liquid sclerotherapy for varicose veins
Authors: Smith P Coleridge
Published: March 2009

Objective

The objective of this study is to review the methods and outcome of ultrasound-guided foam sclerotherapy (UGFS) for the treatment of superficial venous incompetence.

Method

Medical literature databases including Medline were searched for recent literature concerning UGFS. Papers describing methods and outcome have been assessed and their main findings included in this summary. A detailed description of the methods used by the author has been included as an example of how successful the treatment may be achieved.

Results

A diverse range of practice is described in published literature in this field. Each group of authors used their own variation of the methods, described in the published literature, with good results. It is clear that foam sclerotherapy is far more effective than liquid sclerotherapy and that ultrasound imaging allows the treatment to be delivered accurately to affected veins. There is evidence that 3% policocanol foam is no more effective than 1% polidocanol foam. The optimum ratio of gas to liquid is 4:1, although a range of ratios is reported in published work. There is a wide variation in the volume used as well as the method by which it is injected. The use of carbon dioxide foam reduces the systemic complications, particularly visual disturbance, when compared with air foams. Very few serious adverse events have been reported in the literature despite the widespread use of this method. Rates of recanalization of saphenous trunks following UGFS are similar to those observed after endovenous laser and endovenous radiofrequency ablation of veins, as well as the residual incompetence after surgical treatment.

Conclusions

UGFS is a safe and effective method of treating varicose veins. The relative advantages or disadvantages of this treatment in the longer term are yet to be published.
Higher Milk Requirements for Bone Mineral Accrual in Adolescent Girls Bearing Specific Caucasian Genotypes in the VDR Promoter
Authors: Esterle Laure , Jehan Frederic , Sabatier Jean-Pierre , Garabedian Michele
Published: March 2009

Low milk intakes hamper bone mineral acquisition during adolescence, especially in European girls. We hypothesized that ethnic-specific polymorphisms of the vitamin D receptor gene promoter (VDRp) influence this milk/bone association. We evaluated lumbar spine BMC and BMD, milk/dairy products and calcium intakes, markers of P-Ca metabolism, and VDRp polymorphisms at the Cdx-2 binding (rs11568820) and −1012 (rs4516035) loci in 117 healthy European peri- and postmenarcheal girls (14.9 ± 1.6 yr) during a 4-yr follow-up. Calcium intakes from milk, nonmilk dairy products, and nondairy products averaged 199, 243, and 443 mg/d at the initiation of the study. Results show no association between milk intakes and bone mass accrual in girls bearing an A/A genotype at the −1012 VDRp locus (30% of the cohort). In contrast, A/G or G/G girls had lower spine BMC (−13%, p = 0.031), BMD (−10%, p = 0.004), and BMD Z-score (−0.84 SD, p = 0.0003) when their milk intakes were <260 ml/d compared with genotype-matched girls with higher milk intakes and with girls with an A/A genotype. The negative impact of low milk intake persisted up to 19.0 ± 1.7 yr. These findings suggest that European girls bearing a −1012 A/G or G/G VDRp genotype should have higher milk/calcium intakes for optimal vertebral mass accrual during adolescence than girls bearing an A/A genotype, a genotype found in 30% of European and 98% of Asian and Sub-Saharan African populations. VDRp genotype diversity may contribute to the ethnic differences observed in milk requirements for bone health during adolescence.
Adhesion Development of Organic and Silicone Sealants on Wet and Dry Concrete
Authors: Gubbels Frederic , Calvet Clementine
Published: March 2009

Reliability of a sealed joint is directly related to the durability of its adhesion to the substrate. The presence of moisture on the surface of porous substrates caused by changing weather conditions prior to the application of sealants, such as the wetting of concrete by rainfall, can lead to poor sealed joint durability due to adhesion loss. In an attempt to better understand this mechanism, a method of testing adhesion of sealants on wet concrete has been developed and the effect of changes in surface conditions on sealant adhesion has been evaluated during the various drying phases identified for concrete. In the first 2 h of drying, a significant reduction of the pH at the surface is observed, which is mirrored with a reduction of the surface humidity. Both of these properties seem to have reached their plateau value within that timeframe, but in the following hours of the drying process the concrete continues to lose weight through water evaporation. Sealants based on different chemistries have been applied at various stages of the drying process (t = 0, 0.33, 2, 8, 24, 56 h) showing that the critical time period affecting the development of adhesion is within the first 2 h of concrete drying. This indicates that the alkalinity, surface moisture, on both, are the major factors responsible for the poor adhesion obtained on wet porous substrates and this is also the same for adhesion development of a primer on the substrate. The different sealant technologies evaluated in this program were silicones, urethanes, acrylics, silyl-terminated polyether, and silyl-terminated polyurethanes. In terms of adhesion development on wet concrete, the results highlight that the differences are more related to formulation within a sealant family than to the binder chemistry itself.
Optimierte Modellierung von Füllständen in Regenüberlaufbecken mittels CI-basierter ParameterselektionOptimized Modelling of Fill Levels in Stormwater Tanks Using CI-based Parameter Selection Schemes
Authors: Konen Wolfgang , Zimmer Tobias , Bartz-Beielstein Thomas
Published: March 2009

Ziel dieses Beitrags ist die Prognose der Füllstände in Regenüberlaufbecken aufgrund von Regeneintrag und Bodenbeschaffenheit. Wir vergleichen verschiedene Prognoseverfahren und nutzen die Sequentielle Parameteroptimierung (SPO), um für jedes Verfahren in vergleichbarer Weise bestmögliche Parameter zu finden. Es zeigt sich, dass diverse Standard- und CI-basierte Verfahren der Modellierung mit intermittierenden Regenmessdaten als Input nicht gut zurecht kommen. Problemspezifische Modellierungen, die kausale Effekte erster Ordnung berücksichtigen, erzielen wesentlich kleinere Prognosefehler. Wichtige Resultate dieser Arbeit sind: (i) SPO lässt sich auf verschiedene Modellierungsverfahren gleichermaßen anwenden und automatisiert das manuell zeitaufwendige Parameter-Tuning, (ii) das beste manuell erzielte Ergebnis wurde mit SPO nochmals um ca. 30% verbessert und (iii) SPO analysiert in konsistenter Weise den Einfluss von Parametern und erlaubt so oftmals eine zielgerichtete Vereinfachung oder Verbesserung des Modellentwurfs.
Modellierung dynamischer Systeme mit zeitkontinuierlichen rekurrenten Fuzzy-SystemenModeling of Dynamical Systems Using Continuous-time Recurrent Fuzzy Systems
Authors: Adamy Jürgen , Schwung Andreas
Published: March 2009

In diesem Beitrag wird die Anwendung zeitkontinuierlicher rekurrenter Fuzzy-Systeme (KRFS) zur Modellbildung technischer Systeme beschrieben. Ausgehend von der Systembeschreibung rekurrenter Fuzzy-Systeme werden Verfahren vorgestellt, mit denen das KRFS das Verhalten des Prozesses anhand von Messdaten und qualitativem Prozesswissen erlernen kann. Die Leistungsfähigkeit wird anhand der Modellierung eines biotechnologischen Prozesses gezeigt.
Multikriterielle Optimierung mit λ-geregelten modellgestützten EvolutionsstrategienModel Assisted Multiobjective Optimization with λ-Control
Authors: Braun Jan , Hoffmann Frank , Krettek Johannes , Bertram Torsten
Published: March 2009

Evolutionäre Algorithmen benötigen für die Optimierung eine hohe Anzahl an Auswertungen der Gütefunktion. Dieser Aufwand limitiert ihre Anwendbarkeit bei der Hardware-in-the-Loop Optimierung und bei auf zeitaufwändigen Simulationen und Berechnungen basierenden Optimierungsaufgaben. Dieser Beitrag präsentiert einen neuartigen Ansatz zur Fitnessmodellierung, welcher die Anzahl an Güteauswertungen mit Hilfe einer Vorselektion deutlich reduziert. Die Innovation des Ansatzes besteht in der gezielten Regelung des Selektionsdrucks innerhalb der Vorselektion anhand der geschätzten Modellgüte. Diese sogenannte λ-Regelung garantiert gegenüber einer rein statischen Vorselektion eine effiziente Optimierung bezüglich der benötigten Güteauswertungen. Zudem erweitert die hier vorgestellte Methode die bekannten Ansätze zur modellgestützten, skalaren, evolutionären Optimierung auf multikriterielle Probleme. Die Optimierungsergebnisse an Benchmarkproblemen weisen eine verbesserte Konvergenz gegenüber herkömmlichen multikriteriellen Evolutionsstrategien auf und belegen die Effizienz der λ-geregelten Variante.
Zuordnen von linguistischen Ausdrücken zu Motiven in ZeitreihenMatching of Labeled Terms to Time Series Motifs
Authors: Moewes Christian , Kruse Rudolf
Published: March 2009

In diesem Aufsatz geht es um die Problematik, von Experten entworfene Versuche realen Beobachtungen anzunähern. Dazu wird dieses Problem in zwei kleinere Teilprobleme zerlegt: 1.) die Suche von wiederkehrenden Mustern in temporalen Sequenzen, sogenannten Motiven, die es gilt sowohl in den Versuchen als auch in der Realität zu entdecken, und 2.) das Zuordnen der Motive zu linguistischen Ausdrücken, die als Domänenwissen eventuell vorhanden sind. Dabei wird eine effektive Repräsentation von Zeitreihen beschrieben, welche die Suche nach diesen Motiven enorm beschleunigt. Einige Ansätze werden dargestellt, um mit den gefundenen Motiven die entworfenen Versuche zu korrigieren.
Larval Fish Transport and Retention and the Importance of Location for Juvenile Fish Recruitment in Upper Klamath Lake, Oregon
Authors: Markle Douglas F. , Reithel Susan A. , Crandall John , Wood Tammy , Tyler Torrey J. , Terwilliger Mark , Simon David C.
Published: March 2009

In the Upper Klamath Lake basin of Oregon, we applied the member‐vagrant hypothesis to larval lake fishes, documented marsh and hydrographic retention for larval shortnose suckersChasmistes brevirostrisand Lost River suckersDeltistes luxatus, and examined the effect of larval retention on the shoreline abundance of the juveniles of five species of fish in August. Emigration of larval suckers was highest from natal rivers, and immigration was highest in nonnatal areas downstream of the lake. Lake retention was facilitated by a wind‐generated gyre and advection by an eastern boundary current. Marshes and other shoreline irregularities acted as traps that slowed river and eastern boundary current advection and retained larvae, especially for shortnose suckers, for up to 3 weeks. The interaction of behavior, seasonal spawning, and seasonal system dynamics appears to drive retention patterns. For both species of suckers and three minnow species (fathead minnowPimephales promelas, blue chubGila coerulea, and tui chubG. bicolor), the abundance of juveniles along the shoreline increased with distance from the lake outlet and was weakly related to lake elevation, a surrogate for available habitat. For these five species, 45.5% of the variation in August juvenile abundance was determined by distance from the lake outlet. This work suggests that the nonbehavioral component of freshwater retention is complex and depends on hydrographic features, the boundary conditions of hydrographic features, and shoreline habitat.
Stage–discharge relationship for a triangular labyrinth spillway
Authors: Ghodsian M.
Published: March 2009

The labyrinth spillway is characterised by a broken axis in plan, generally triangular or trapezoidal, repeated periodically. Therefore, a labyrinth spillway will have longer crest length than a straight spillway and, for the same head the discharge per unit width, is substantially increased. The discharge over a labyrinth spillway is a function of the total head, the effective crest length and the discharge coefficient. The discharge coefficient depends on the total head, height of spillway, shape of crest and apex configuration of spillway. In this paper, results of experiments on a triangular labyrinth spillway are reported. The stage–discharge relationship for a triangular labyrinth spillway with different crest shapes is obtained. The discharge coefficient was related to the ratio of length of spillway to width of spillway, ratio of total head to spillway height and crest shape.
Impact of Kerogen Heterogeneity on Sorption of Organic Pollutants. 2. Sorption Equilibria
Authors: Yang Chen , Yu Zhiqiang , Xiao Baohua , Huang Weilin , Fu Jiamo , Dang Zhi
Published: March 2009

Phenanthrene and naphthalene sorption isotherms were measured for three different series of kerogen materials using completely mixed batch reactors. Sorption isotherms were nonlinear for each sorbate-sorbent system, and the Freundlich isotherm equation fit the sorption data well. The Freundlich isotherm linearity parameter n ranged from 0.192 to 0.729 for phenanthrene and from 0.389 to 0.731 for naphthalene. The n values correlated linearly with rigidity and aromaticity of the kerogen matrix, but the single-point, organic carbon-normalized distribution coefficients varied dramatically among the tested sorbents. A dual-mode sorption equation consisting of a linear partitioning domain and a Langmuir adsorption domain adequately quantified the overall sorption equilibrium for each sorbent-sorbate system. Both models fit the data well, with r2 values of 0.965 to 0.996 for the Freundlich model and 0.963 to 0.997 for the dual-mode model for the phenanthrene sorption isotherms. The dual-mode model fitting results showed that as the rigidity and aromaticity of the kerogen matrix increased, the contribution of the linear partitioning domain to the overall sorption equilibrium decreased, whereas the contribution of the Langmuir adsorption domain increased. The present study suggested that kerogen materials found in soils and sediments should not be treated as a single, unified, carbonaceous sorbent phase.
Interpreting the Hazardous Air Pollutants Area Source Rule
Authors: Holliday G. H.
Published: March 2009

On 3 January 2007 at 72 FR 26, EPA promulgated revisions to 40 CFR Part 63 Subpart HH to include Area Sources within the rule. This rule applies to emissions of benzene from triethylene glycol (TEG) dehydrators located at upstream oil and gas producing facilities and gas plants, which are not Major Sources. Area Source TEG dehydrators are placed into one of four groupings. 1) Black oil facilities, exempted from the rule. 2) Exempted facilities, not controlled because of low volume throughput. 3) Facilities Within UA plus offset and UC, e.g., TEG dehydrators located in Urbanized Areas (UA), plus a two-mile buffer zone (Offset) around each Urbanized Area, plus Urban Clusters (UC) containing ≤ 10,000 people, and 4) TEG dehydrators located outside of UA plus offset and UC.

For purposes of compliance, the term, Urban-1 County, appears in the rule and defined as a county containing a large Metropolitan Statistical Area. Most existing TEG dehydrators must implement the rule by January 2007. New TEG dehydrators must implement the rule before startup.

U.S. Census Bureau defines Urban Cluster as an urban area containing 2500 persons. Accordingly, the U.S. Census Bureau does not provide maps for Urban Cluster data in the "EPA 10,000 person" format. Therefore, API developed a computer program for locating dehydrators relative to the UA plus offset and UC. The computer method has not been implemented, because; no operator was willing sponsor the website. Accordingly, this paper provides a manual method of determining if a dehydrator is within or outside an UA plus offset and UC.

Area Source dehydrator emissions controls depend on facility location and throughput or emissions. Emissions controls range from doing nothing, to optimizing TEG flow rates, to add-on control equipment. Affected TEG dehydrators within UA plus offset and UC areas are required to install benzene emission control equipment and provide automatic surveillance recording. TEG dehydrators outside of the UA plus offset and UC areas must operate dehydrators at or less than the optimum glycol flow rates developed by EPA or decrease emissions to below 1-ton per year. It is doubtful if small operators are in compliance. The paper demonstrates the EPA "optimum glycol flow rate" proposal is so impractical as to be impossible to implement in the field.
Improving Equipment Safety While Reducing Diesel Exhaust during Well Service Operations
Authors: Neal Greg , Ingram Donald
Published: March 2009

Wellhead isolation tools (WIT) are used during frac jobs to protect the wellhead from excessive pressure and damage from proppant-chemical-laden fluids. Typically, these tools are installed onto the wellhead by a crane truck built for this purpose. There is usually a hydraulic system on the crane truck to operate the tool and to open and close the master valve on top of the tool. The controls for operating the crane, WIT, and master valve are typically all in the same area so that one operator can control the whole process. However, having all the controls in one place increases the likelihood that the operator might operate the wrong control. It is important that the master valve be opened and closed at the correct times to avoid injuring personnel working on the high-pressure manifold and to avoid equipment damage caused by closing the master valve during pumping. The current system also requires the operator to leave the crane truck engine running during the frac job to have the hydraulic system available to open and close the master valve as required. This prolonged idling of the truck engines can cause problems with the diesel particulate filter on newer truck diesel-engine emissions systems and adds CO2 to the atmosphere.

A new hydraulic system to actuate the valves was designed to eliminate some of the problems of the current system. The new system uses an electric motor to drive a hydraulic pump to open and close the master valve. The electric motor is powered from the truck batteries. This allows the engine to be shut down for the majority of the frac job, reducing the diesel exhaust emitted to the atmosphere and extending maintenance intervals for the engine. Having an electric system also allows the master-valve controls to be placed on the other side of the truck, greatly reducing the chance the master valve will be accidentally actuated during WIT installation and removal. Typically, this also places the operator on the side of the truck away from the wellhead, which is a safer position (Fig. 1).
The Impact of Carbon Geological Sequestration
Authors: Xie Xina , Economides Michael J.
Published: March 2009

Although CO2 geological sequestration is the most popular carbon storage method promoted and pilot tested, the economic feasibility and technical risks for commercial scale sequestration projects are rarely mentioned. More significant is that, apart from rhetorical pronouncements, the would-be impact of the operation on climate change is not discussed. This work studies the technical risks, regulatory issues, and economic burden of CO2 geological sequestration on the U.S. by using the Kyoto Protocol emission requirement as the base line. The potential effect of burying all the extra CO2 regulated by Kyoto Protocol on global temperature change is also evaluated.

The lack of regulatory framework is blamed as one of the obstacles for slowing or stopping CO2 geological sequestration practice. However, any regulatory issues are intertwined and dominated by the physics of the injection process itself and its economic viability. This study analyzes the uncertainty and/or risks caused by CO2 geological sequestration in oil and gas reservoirs, saline aquifers, and coalbeds. The work shows that the potential technical and legal risks and financial costs for sequestering CO2 underground make it impossible to promulgate any regulatory framework without causing detrimental effects on economic development and energy utilization. It is estimated that CO2 sequestration in U.S. will cost over $1 trillion annually for CO2 geological sequestration by complying with the Kyoto Protocol. Even if the global temperature increase of 0.7 degrees Celsius over the past 100 years is solely caused by anthropogenic CO2 emission, the change on the global temperature by sequestering all the CO2 emitted exceeding the 95% of 1990 level will be negligible. The dynamic climate and weather patterns on Earth will make it impossible to be verified.

This work gives a realistic situation on the potential impacts of commercial scale CO2 sequestration projects on economics, environment, and the global climate change. The findings of this study can be used to evaluate the risks of the CO2 geological sequestration projects.
New Tool Assists Informed Purchasing Decisions Based on Overall Cost and HSE Risk Potential of Well Construction Fluids
Authors: Gilbert Ylva , Kumpulainen Anna , Syrjanen Mikko
Published: March 2009

The well construction fluid (WCF) used in a particular operation influences the overall cost of the well construction both during and after the construction phase. The fluid can also be associated with a certain Cost at Risk potential, as unwanted incidents involving fluids may lead to consequences that carry costs. These costs can be related to the fluid's hazard level. The cost and risk related data requirements that support informed WCF choice decisions include direct fluid costs, but also cost items related to operational deployment and production stream treatment. Health, safety and environment (HSE) direct and indirect costs through risk and liability potential also form an important input into the decision making process. Identifying the most cost effective fluid that carries least risk potential may therefore significantly enhance overall well economics.

To compare overall fluid costs, the different fluid pricing models, overall operational costs and HSE related risk potential must be evaluated and summed in the same format. The Activity Based Costing (ABC) approach provides a valid framework for allocating indirect operational costs to each well construction activity and evaluating the overall operational expenditure per well. However, such overarching cost comparisons for WCF choice appear to be rare. This is considered partially attributable to a lack of a simple yet overarching cost and risk assessment tool. This paper presents the management advantages achievable from using a novel, decision supporting software tool for collating and analysing all charges related to the deployment of WCF.

The tool utilises operator, location and operation-specific data in a format that supports data collation across different asset team departments and budgets. This enables systematic, fast, repeatable yet operation-specific assessment and allows management to base decisions on the overall cost and HSE risk associated with the assessed WCF alternatives. The tool has been initially set up to compare high-density completion brines. It provides management with a clear overview of the overall financial implications and comparative HSE risks and advantages related to fluid choice. The approach is currently being adopted by a major oil company and integrated into their fluid decisions-analysis software.
Use of No-Purge Groundwater Sampling Techniques to Eliminate Health and Safety Concerns and Reduce Costs
Authors: Fields Karen
Published: March 2009

Semi-annual groundwater sampling is conducted at a petroleum facility in northern Kentucky. The site is situated on a very steep slope along the banks of the Ohio River. A near miss occurred in October 2006 when technicians were emptying a 325-gallon polytank containing purge water into an oil/water separator. A technician was lifting the tank to get the last few gallons of purge water out of the tank when the tank slipped and fell out of the truck bed, almost hitting a second technician. A root cause analysis was conducted and it brought to light the inherent risks associated with moving large volumes of water around the site. It was decided to use an alternative sampling technique (a no-purge sampling device called a HydraSleeve) to eliminate the generation of purge water, which in turn eliminated the safety concerns with hauling the purge water around the site. No-purge sampling has been shown to produce comparable results to standard purge and sample techniques for certain constituents. As an additional benefit, no-purge sampling has reduced the amount of time to conduct the sampling— from about 4-5 days to about 2 days; thereby also reducing the costs. Thus, an increased concern for safety doesn't have to lead to an increased cost.
Safety in Offshore Frac Hose Rig Hookups
Authors: Arceneaux Chris , DeKerlegand Kim
Published: March 2009

Large volume sand control and reservoir stimulation methods in the offshore market require connecting a heavy, low-yielding flexible hose from the service company stimulation vessel to the drilling rig or platform (Henceforth referred to as "rig"). From there it is typically connected to rigid high pressure treating line routed to a manifold. The use of a flexible hose anchoring point pre-installed on the rig greatly reduces exposure to accidents by eliminating dangerous chaining up methods to secure the hose to the rig. This device may remain on the rig for future pumping events.

The use of a flexible hose rig-anchoring point provides an engineered solution to reduced human, hands-on interaction when securing the treatment hose to the rig prior to a sand control or stimulation pumping event. Pinch points for hand and foot interactions are eliminated.

Placing workers in precarious situations on the outboard of the rig's handrail, high above the water surface is prevented by use of a "drop-in and lock-in" landing plate that supports the flexible hose and its connection flange in a vertical position.

This process saves time by eliminating repositioning measures when having to secure the flexible hose to some fixed object on the outboard side of the rig such as handrail posts or mooring cleats using chains.
Sustainability Assessment via Sustainable Value Added and Composite Sustainable Development Index on the Example of Petroleum Majors
Authors: Fries B.
Published: March 2009

Based on the rising social and political pressure regarding sustainable development of corporations, sustainability is getting a more and more significant issue for the business management. To control the sustainable development of a corporation it is essential to assess the performance for benchmarking purposes or to monitor the developments over time. In the last years several methods have been developed for this purpose. In this paper two methods, a monetary and a non-monetary, are introduced and applied to assess the sustainability performance of the petroleum majors.

The paper in hand presents the concept of sustainable development and explains two methods to assess the associated performance: the Sustainable Value Added (SVA) and the Composite Sustainable Development Index (CSDI). The SVA is a monetary approach, which compares the value creation resulting from the use of a resource with a benchmark according to the concept of opportunity costs and is able to combine the ecological, the social and the economic dimension in this way. The CSDI is a non-monetary method, which is based on the analytical hierarchical process determining the contribution of a single indicator of one of the three dimensions to the total sustainability. The result is a single aggregated measure, which can be compared with other companies or the last years.

Using the data of sustainability and annual reports, the two methods are applied to the petroleum majors: BP, Shell, Total, ExxonMobil, Chevron and ConocoPhillips. Based on the findings the approaches are compared and their applicability is discussed. A limitation of the paper is the data availability, for the application of the SVA-method the social dimension is neglected.

The results allow a critical review of the methods by comparing the results of the monetary and the non-monetary assessment and give answers about the expressiveness of the different approaches. The conclusions of the study should serve as a recommendation for petroleum companies, how to assess their sustainability performance or at least give an idea about potential assessment procedures in regard of sustainable development.
Institutionalization of HSE
Authors: Hallmark Ronald G.
Published: March 2009

The paper describes a road map to achieving "Institutionalization of HSE" which is defined as an organization or company which has a safety culture so engrained that HSE activities are performed by all levels of the organization as a part of their normal daily routine. The paper describes the characteristics of an institutionalized company and then lists the steps to achievement. This roadmap to "Institutionalization of HSE" can be applied to any organization. The examples upon which this author based the paper were oil & gas assets on 4 continents.

The author found that there are specific key characteristics common in organizations which achieve world class HSE performance. By listing the characteristics, one may compare them to their own organization to identify gaps. The world class performers all combine mandatory behaviors and reward mechanisms to achieve success which are highlighted in the paper.

Safety management systems have been around for decades but recently many companies are asking why their Safety systems and programs haven't achieved a definitive "Safety Culture". World Class HSE performers have already achieved "Safety Culture" and have moved to the next level, "Institutionalization of HSE".
Rig Safety and Reliability Incidents Caused by Software: How They Could Have Been Prevented
Authors: Shafer Don
Published: March 2009

The Canadian Defense Force and the US Coast Guard list software along with fire, explosion, flood, and earthquake as risks that produce extreme vulnerabilities to maritime technology systems. More than half the US's imported oil comes through the Gulf of Mexico. Fifteen percent of the US daily oil supply comes through the Louisiana Offshore Oil Port system just 20 miles off of New Orleans. Chances are the port won't be shut down by a bang but by a mere keystroke! The control software running these offshore oil and gas drilling and production platforms is extremely vulnerable to unproven, unmanaged and untested software releases.

These problems exist because the equipment manufacturers, maritime contractors and operators have very little incentive to fix the vulnerabilities. Their driving goal is to make their operations a profitable as possible while complying with the minimal HSSE rules and regulations. In most cases they have little knowledge of software and systems engineering and can neither evaluate vulnerabilities nor devise solutions once problems arise. Many organizations share the blame for this lack of incentive. This presentation will recount some recent safety disasters and near misses caused by software vulnerabilities. Attendees will learn how to ensure that complex software systems function not only on first use but throughout their life cycle. The author and his team have performed software verification and validation on systems from Norway to Singapore, from Brazil to Angola, and through out the Gulf of Mexico.