bluuebunny/crossref_metadata_2025 huggingface dataset:
Strategically Increasing Completion Efficiency by Applying a Customized Filtercake Breaker Solution
Authors: Alimuddin Sultan , Yewlekar Satish , Raman C. V. , Bais Shashi Kant , Anez Marcos , Ezeigbo Eze , Kishore Kunal , Patil Bhushan
Published: January 2016

This paper presents a comprehensive field study of an openhole completion with standalone screens using a unique filtercake breaker treatment, compatibility with reservoir fluids, cost effectiveness, and overall performance-based comparative results to meet the challenges of drilling and completing offshore wells.

In the offshore field of Krishna-Godavari Basin, Bay of Bengal, one of the most prolific hydrocarbon basins of India, synthetic-based reservoir drill-in fluids (SB-RDFs) were used to drill the reservoir section, which was then completed openhole using standalone sand-control screens. In order to control fluid invasion to the formation, a major cause of formation damage, the designed RDF created a filtercake at the sandface. However, high flow initiation pressure caused high skin effect and compromised completion efficiency. The primary challenge during completion was to clean up the SB- RDF filtercake from the reservoir section to remove near-wellbore damage and maximize productivity. Another challenge was to avoid the high potential of filtercake plugging of the screens, which could lead to higher drawdown pressures and possible early screen failure. To address these challenges, a filtercake breaker for the SB-RDF was developed to lower the skin factor thus maximizing production and mitigating the risks of plugging the sand-control screens. After implementing this customized breaker solution, combined with a precise placement program, the wells showed a tremendous reduction in the skin factor and a significant increase in completion efficiency, compared to wells with the same reservoir properties completed in earlier campaigns.

An organic acid pre-cursor enabled filtercake breaker placement and soaking without being chemically spent during circulation. Additional breaker design criteria included the ability to break the RDF emulsion, water-wet the solids in the filtercake, dissolve the calcium carbonate used as bridging material in the SB-RDF, and disperse the non-acid soluble material without plugging the screens.

The paper presents a detailed study of the main challenges while formulating and evaluating the filtercake breaker solution. Additionally, a production results comparison is made between the well using the customized filtercake breaker treatment and previous well completion and breaker treatments. The paper also discusses the comprehensive displacement program and required spacers for precise placement of the breaker in the openhole and offshore pit management.
Buoyancy Technology Used Effectively in Casing Running Operations: Case History of Record Length Two-Stage Production Casing String
Authors: Rogers Hank , Shaikh Alaa , Faraj Omar A. , Hasan Abdulaziz
Published: January 2016

Operators today face an ever increasing demand for locating commercial reserves and producing those reserves with attention to exploration and development costs. In addition to basic financial pressures, operators also strive to reduce the environmental impact of well construction and production operations. Extended-reach drilling technology allows operators to reach recoverable reserves that, in the past, were unreachable. Specifically, extended-reach drilling from a multi-pad wellsite allows significant portions of the well construction costs to be spread over multiple wells, rather than being carried by an individual wellbore. Also, the ability to drill multiple wells from a single pad helps reduce the environmental impact from the drilling operation.

Extending the wellbore reach from a given pad depends on the location of the target formation. Depth, horizontal distance, and production type significantly affect the type of drilling program as well as the casing running operation. In many wells, drag between the casing and wellbore prevents casing running operations from being performed. Casing flotation is a proven technology that has been deployed in multiple fields globally to extend the attainable lateral reach of the casing running operation.

This paper documents using flotation technology in combination with two-stage cementing tools in production wells where drag limits and subsequent casing lock up were averted to allow successful casing running operations to be performed. Detailed pre-job planning and computer simulations are provided to demonstrate the technical limits and step-out achieved with casing flotation.
Successful Use of Abrasive Tubing Punch Technology for Highly Deviated Wells in Saudi Arabia
Authors: Danish Syed Muhammad , Khan Faisal Zubair
Published: January 2016

The scope of this paper is to highlight the difficulties faced together with the respective solutions proposed and executed during the de-completion of a deviated well having complex horizontal internally plastic coated (IPC) completion during its work over phase, for a sour gas field. This was the first instance an abrasive jetting technology was used to punch a completion during a workover operation in Saudi Arabia.

In an unrelenting pursuit to reduce rig time per well, operators have to explore new innovative technologies that can reduce their reliance on multiple intervention techniques, subsequently saving rig stand by and operating hours by cutting unnecessary trips in and out of the wellbore.

In this candidate onshore well, the operator wanted to identify, isolate, and eliminate downhole tubing casing annulus (TCA) communication by changing the existing IPC completion. The production region was a deep horizontal openhole section with the reservoir having high gas oil ratio (GOR), based on previous experience the well was expected to produce sour gas any time even when it is killed. Initial operation on the rig was to nipple down (N/D) the wellhead (WH) and nipple up (N/U) the rig's blow out preventer (BOP) by loading up the well with kill fluid and setting secondary mechanical isolation barriers for well control. It was unfeasible to cure kill fluid losses using loss circulation material (LCM) because of the large openhole section, the highly deviated completion further limited slickline or wireline reach for barrier placement.

This paper explains the innovative solution devised and executed on this well, further covering the execution part of the operation, elaborating the combination of coiled tubing (CT) with slickline tools for intervention, tubing punch by abrasive sand blend jetted by means of specifically designed carbide nozzles, and the implementation of best practices to deliver a successful TCA isolation and well de-completion in record time.

The operation consisted of multiple CT runs, from cleaning out the completion of any residue plastic junk to lock mandrel enabled leak isolation, and mechanical plug barrier placement before abrasive jetting for tubing punch just above the packer with depth correlation by memory casing collar locator (CCL). Based on similar work performed on a nearby well, this innovative abrasive punch technology enabled the rig to save more than 40 hours of operating time on Well X.
Achieve Demanding Targets: Successful Well Placement With No Harm to the Environment. Case Study from Offshore Abu Dhabi
Authors: Al-Jaberi S. M. , Amer M. M. , Marrauld J. , Yuliandri Y. , Al-Braik S. , Baca Espinoza I. , Shoukry M. , Hammad T. K. , Jaorawala A. , Herz U. , El Masry H. , Saravanakumar K. , Potshangbam S.
Published: January 2016

Drilling and producing oil wells safely and with minimum risk of environmental hazards is crucial in Abu Dhabi offshore fields. A significant challenge to achieve this goal is steering in very selective sub-layers without conventional radioactive source porosity tools. Acquiring real-time data is critical, especially when drilling slim holes with long horizontal drains, and a well profile that targets several thin reservoir beds.

To meet this challenge, a nuclear magnetic resonance (NMR) sourceless porosity tool was introduced for the first time in this reservoir in a six-inch hole. Two lateral drains, each more than 3,000 ft., were drilled, targeting different reservoirs. As a part of the geosteering methodology, nearby offset well properties were incorporated to generate a forward model along the planned well trajectory. The forward integrated geosteering model was updated in real time with porosity and gamma ray data, resistivity images and, structure views, etc. Decisions were made from this input to place the trajectory in the optimum target zones, achieving the reservoir objectives.

This paper demonstrates the successful use of an NMR sourceless tool's real-time data acquisition that played a significant part in facilitating effective geosteering and well placement. Real-time NMR total porosity was critical to confirm optimum well placement, especially where lateral facies variations were expected and due to the limited availability data for such a green field. In addition, the available porosity distribution was used to estimate a permeability index. This index, after normalization to offset the well data, was used for selecting formation pressure while drilling and reservoir zonation.

The case study in this paper shows that with current advance technologies, incorporated data for available wells, and real-time technical support, the demands of sourceless drilling can be achieved to place the well in a precise target during slim borehole drilling.
Step Change in Drilling Efficiency
Authors: Salem Gamal
Published: January 2016

Step change in drilling effiency to enhance drilling performance in our field.

Our casing design in our field heavy casing design as drill 22″ hole and set 18.5/8″ casing at +/- 2000 ft and drill this phase with RSS to control the verticalitly in the hole as our wells drilled in cluster location the separation between each wells is 10 M only so the verticalitly is very important to avoid anti collsions between the wellsso 1st phase the quality to drill the hole and run casing is very important than make perfroamnce.

Second phace in our casing design is 16″ phase which will drill it deviated section up to +/- 9000 ftand will discuss it in detail after complete discsions the remain phases in our casing design.
Subsurface Wireless Intervention Technology Development for the Acquisition of Subsurface Static and Dynamic Fluid Level in Oil and Gas Wells
Authors: Littleford S. J. , Holyoak S. , Birch W. , Shepherd D.
Published: January 2016

This paper summarizes the results of an eight well field trial that utilized a wireless surveillance technique to measure real-time wellbore fluid interface depths. The measurement of fluid depth in oil and gas wells is widely used for calculating reservoir pressure in the absence of downhole gauges and for other well information requirements. As this innovative technology does not require well entry it reduces operational costs and exposure to HSE risks. Furthermore, this technique overcomes issues inherent in acoustic measurement, related to low-pressure environments and short distance measurement.

The novel Frequency and Time Domain Reflectometry (FDR/TDR) technique described in this paper utilizes Microwave (MW) and Radio Frequency (RF) to scan the inside of the tubing string from the wellhead to a subsurface feature. The scanning operation consists of injecting pulses of MW/RF frequencies through the wellhead via an antenna installed in a Tree Cap or the annulus. The core advantages of the technique are: Low energy MW/RF pulsesWell pressure control and well entry tooling requirements are minimizedPre-determined MW/RF frequencies for tubing scans are harmonized with completion geometry to optimize measurement efficiencyThe scanning process takes approximately one minuteData processing of the scan information identifies single and multiple fluid level interfaces in addition to other well features.The data is available immediately and displayed on a surface readout unit (SRU).

The average rig up to rig down time taken for each well was approximately forty minutes. The position and movement of the well bore fluid levels and other well features such as tubing joint identification were successfully measured providing data for the analysis of the well fluid inventory. The identification of individual casing and tubing joints allowed depth correlation to be verified to previously measured depths and provided a simple method of calibration. The technique provided accurate measurements over short and long distances.

The trial provides evidence of the successful development and implementation of a wireless field deployable subsurface well surveillance sensor. The sensor technology is designed for deployment in single and multiple well applications used for continuous monitoring of well integrity and for production optimization purposes.

Further development of the sensor has advanced by focusing on the introduction of the technology to multiple wells and remote surveillance real-time monitoring operations for both tubing and annulus fluid level measurements.
Combination of Foam Assisted Lift & Gas Lift (FAGL) to De-liquefy Gas Wells
Authors: Tayyab Imran , Uddin M. Farooq , Ahmed Qazi I. , Ibad-ur-Rehman M. , Azam Qazi Syed
Published: January 2016

Liquid loading is an ineluctable problem encountered by gas wells as their reservoir pressure declines and Gas-Liquid Ratio (GLR) increases. Foam Assisted Lift (FAL) is one of the modern methods for dewatering gas wells by reducing effective density and surface tension of produced fluid. Gas lift is also a widely used method that reduces flowing bottom-hole pressure by injecting gas in the well to lower hydrostatic head.

This paper proposes a combination of above mentioned technologies called Foam Assisted Gas Lift (FAGL) and recommends its' efficiency over two specific scenarios; a) when reservoir pressure is low and static liquid level remains below bottommost SPM, b) when there is a considerable liquid column in wellbore and gas injection pressures are limited due to surface constraints, injecting foam decreases the hydrostatic head and requires less gas injection pressure to offload the well. In either case, FAL can offload the well but the stabilized rates achieved are uneconomical compared to the soap requirement per day. FAGL is applied on mature wells having low reservoir pressures and completed with single SPM. These wells had frequent load-up issues and FAL/gas-lift failed due to low reservoir inflow. After FAGL is implemented, frequent load-up issues have been resolved and wells began to produce at increased stabilized rates. FAGL also emerged as an economical option because it reduced the soap /injected gas requirement per day and increased gas rates and overall recovery.

For wells with deep SPMs, depleted reservoir pressure and liquid loading problems, FAGL could be an economical de-liquefaction method when compared to standalone gas-lift or FAL due to its lower OPEX.
Manure and Inorganic Nitrogen Affect Irrigated Corn Yields and Soil Properties
Authors: Halvorson Ardell D. , Stewart Catherine E. , Del Grosso Stephen J.
Published: January 2016

Manure can substitute for inorganic N fertilizers and can mitigate potential soil deterioration under irrigated corn (Zea mays L.) silage production, but the impact on yields, soil C and N have not been thoroughly studied in the semiarid western United States. Five N source treatments (dairy manure [DM, 412 kg N ha−1], DM + AgrotainPlus [DM+AP], SuperU [SU, 179 kg N ha−1], urea [179 kg N ha−1], and control [no N applied]) were studied (3 yr) to determine effects on silage and grain yields, N uptake, and changes in soil properties (soil organic carbon [SOC], total soil nitrogen [TSN], nitrate‐nitrogen [NO3–N], and soil test phosphorus [STP]) in an irrigated, conventionally‐ tilled clay loam soil under continuous corn silage production. Silage, grain, and stover yields and N uptake were greater with N application than control, with no difference between DM, DM+AP, urea, and SU. Fall soil NO3–N was greater with N application than control (0–90‐cm depth), but lower with DM than for SU (0–180‐cm depth). Soil test P was seven times greater with DM than with inorganic P after 3 yr. The SOC and TSN were strongly related to root and DM inputs, increasing with DM application but decreasing or remaining constant for SU, urea, and control treatments. Dairy manure is a valuable source of C, N, and P for irrigated tilled corn silage production with minimal NO3–N leaching or excessive soil P after 3 yr and can ameliorate residue removal and tillage impacts.
Modeling of river flow rate as a function of rainfall and temperature using response surface methodology based on historical time series
Authors: Kostić Srđan , Stojković Milan , Prohaska Stevan , Vasović Nebojša
Published: January 2016

In the present paper we propose a new model of monthly river flow rate as a simple nonlinear function of air temperature and rainfall. Response surface methodology is used to analyze the observed monthly flow rates from 1950 to 1990 for Great Morava River, as the largest domestic river in Serbia. Obtained results indicate significant linear and quadratic effect of both individual factors, while two-factor interactions show significantly smaller influence, indicating occurrence of maximum flow rate for low temperature and high rainfall regime. Statistical reliability of the proposed model is verified by internal and external validation, the latter of which included comparison of predicted and observed values from 1991 to 2012. It is shown that predicted flow rates exhibit a similar statistical pattern as observed ones, with a satisfying value of Nash–Sutcliffe coefficient (NSE = 0.73), although the derived model cannot capture well the highest flow rates. Obtained results further indicate the sequence of residuals represents random time series, which is confirmed by appropriate test statistics and surrogate data testing. The advantage of using the derived model for hydrological simulations in river basins instead of existing ones lies in its explicit mathematical form, making it suitable for quick and reliable estimation and prediction of monthly flow rates.
Results of heavy metals and other water quality levels in tap water from Çan sourced from Ağı Dağı (Mt. Ağı) (Çanakkale, Turkey)
Authors: Kilinc Gamze , Yilmaz Selehattin , Turkoglu Muhammet , Erdugan Huseyin
Published: January 2016

In this study, the concentrations of heavy metals Pb, Cu, Zn, Cd, Ni, Fe, Mn and Cr were determined using an inductively coupled plasma and optical emission spectrophotometer (ICP-OES), and water quality parameters pH, temperature, and conductivity were measured using the YSI 556 MPS water probe. The water samples were collected monthly from five different street tap water points sourced from Mt. Agi (Ağı Dağı in Turkish) spring waters between May 2012 and February 2013 in Çan (Canakkale, Turkey). All results were compared with the drinking water standards of the Turkish Standards Institute (TSE 266), World Health Organization, European Union and US Environmental Protection Agency. While concentrations of Cu, Zn, Fe, and Mn were within limit values, Pb, Cd, Ni, and Cr were at undetectable limits. The highest concentrations of Cu, Zn, Fe, and Mn were 0.010 ppm, 0.018 ppm, 0.058 ppm, and 0.014 ppm, respectively. The findings revealed that although there was no public health risk in view of heavy metal concentrations, there was an acidity problem due to lower pH levels correlated with some heavy metals such as Cu (R = 0.419), Fe (R = –0.421) and Mn (R = –0.687).
Measuring the willingness to pay for drinking water quality improvements: results of a contingent valuation survey in Songzi, China
Authors: Jianjun Jin , Wenyu Wang , Ying Fan , Xiaomin Wang
Published: January 2016

The aim of this study is to elicit local residents' willingness to pay (WTP), by applying the contingent valuation method as a surcharge on their water bill, for a given improvement in the drinking water quality and the supply reliability. The mean WTP for the drinking water quality improvement program was estimated to be 16.71 yuan (0.3% of total household income). The results note that more educated respondents and households with higher income and with fewer household members are, on average, willing to pay more. This study also demonstrates that respondents' concerns regarding drinking water quality and perceptions of the health risk of drinking water quality can have significant positive impacts on people's WTP. The research results can help decision-makers understand the local population's demand for improved drinking water quality and undertake an environmental cost–benefit analysis.
Reducing Depression Through an Online Intervention: Benefits From a User Perspective
Authors: Crisp Dimity A , Griffiths Kathleen M
Published: January 2016

Background

Internet interventions are increasingly being recognized as effective in the treatment and prevention of mental health conditions; however, the usefulness of such programs from the perspective of the participants is often not reported.

Objective

This study explores the experiences of participants of a 12-week randomized controlled trial of an automated self-help training program (e-couch), with and without an Internet support group, targeting depression.

Methods

The study comprised a community sample of 298 participants who completed an online survey both prior to and on completion of an intervention for preventing or reducing depressive symptoms.

Results

Overall, participants reported a high level of confidence in the ability of an online intervention to improve a person’s understanding of depression. However, confidence that a website could help people learn skills for preventing depression was lower. Benefits reported by participants engaged in the intervention included increased knowledge regarding depression and its treatment, reduced depressive symptoms, increased work productivity, and improved ability to cope with everyday stress. A minority of participants reported concerns or problems resulting from participation in the interventions.

Conclusions

The findings provide consumer support for the effectiveness of this online intervention.

Trial Registration

International Standard Randomized Controlled Trial Number (ISRCTN): 65657330;http://www.isrctn.com/ISRCTN65657330 (Archived by WebCite at http://www.webcitation.org/6cwH8xwF0)
Characterization of cadmium substituted nickel ferrites prepared using auto-combustion technique
Authors: De Manojit , Mukherjee Aniruddha , Tewari Hari
Published: January 2016

In the present paper we have investigated synthesis of nickel ferrite
(NiFe2O4) and cadmium substituted nickel ferrite (Ni1-xCdxFe2O4) powders with
particles? size in nanometer range using auto combustion technique as well as
their sinterability. XRD analysis of the sintered samples confirmed the
formation of single phase materials and the lattice parameter was increased
with increase in cadmium concentration. It has also been observed that the
estimated bulk densities of the materials decrease with increase in cadmium
concentration, while they increase with the rise of sintering temperature.
Perceptions of Leadership: Comparing Canadian and Irish Physiotherapists' Views
Authors: McGowan Emer , Martin Gillian , Stokes Emma
Published: January 2016

Purpose: To contribute to the growing body of research on leadership in physiotherapy by comparing leadership-related perceptions of physiotherapists in Ireland and in Canada. Methods: This article compares the results of a survey of Canadian physiotherapists with those of the same survey administered to Irish physiotherapists. The results of both studies have previously been reported and are used here to allow a cultural comparison of the perceptions of physiotherapists. The present study used two-portion Z-tests to compare the percentage of physiotherapists in Ireland who self-declared as a leader with the percentage of physiotherapists in Canada who did so. Results: Physiotherapists in both Ireland and Canada most often rated communication and professionalism as extremely important characteristics. Physiotherapists in Canada were more likely than those in Ireland to perceive themselves as leaders (Z=2.67, p < 0.05; 95% CI: 1.33, 9.87). Factors associated with self-declaration as a leader differed between the two countries. Conclusion: Physiotherapists in Canada and Ireland showed both similarities and differences in their perceptions of leadership characteristics. Results from this study may aid the development of future leadership training programmes specifically targeted at physiotherapists.
Revenue and Policy Implications from Emerging Fuel Sale Trends in Metro Vancouver, British Columbia, Canada
Authors: King Fearghal , Fox Jacob
Published: January 2016

Taxes generated from fuel sales represent an important source of revenue throughout North America and are broadly used with other sources to maintain and develop transportation networks and associated infrastructure. Historically, these taxes have performed well in providing a secure source of revenue. However, recent factors such as improved vehicle fleet efficiency and declining vehicle kilometers traveled (VKT) on a per vehicle and per capita basis affect the volume of fuel sold and threaten the security of existing sources of revenue generated from fuel taxes. Notwithstanding the obvious environmental benefits to which these factors contribute, a need remains to ensure that revenue streams are able to keep pace with funding requirements, given that auto ownership continues to rise, which places pressure on total VKT. The result is a decoupling of road usage and the main source of road user payments. The traditional solution to maintaining or growing revenue streams in the region of Metro Vancouver, British Columbia, Canada, has been to increase the fuel tax. However, the decoupling problem is intensified in the region because of the proximity to the border with the United States, where fuel price differentials are placing pressure on such solutions. This paper explores a number of recent trends that affect fuel sales in Metro Vancouver. Revenue implications are outlined, and policy recommendations are made to strengthen the link between road usage and road user payments.
Case Studies in Transport Public–Private Partnerships
Authors: Roumboutsos Athena
Published: January 2016

Case research, the preferred research tool for public–private partnerships (PPP), is performed within a specific context, and any findings cannot be separated from that context. This drawback limits the exploitation of research findings. The present research proposes a methodological framework and process by which the contextual elements of the setting for a PPP transport infrastructure are described in respective typologies. A preliminary description of these typologies is presented. The proposed methodological framework is piloted by using 12 case studies from different countries and different transport modes (TMs). The results suggest the potential to transfer findings within groups of similar dimensions regardless of the physical location of implementation, the TM infrastructure, or even the actual business model. In addition, initial findings indicate the potential to transfer findings and knowledge over time. New hypotheses are generated, and their verification may have significant impact on the credit rating of PPP projects for transport infrastructure and, consequently, on the identification of alternative sources of finance.
Optimization Models for Public Transit Operations under Subsidization and Regulation
Authors: Sun Yanshuo , Schonfeld Paul M.
Published: January 2016

This paper presents a bilevel optimization framework for analyzing the effects of external subsidies and service policy constraints (i.e., fare and service frequency limits) on the operation of public transportation systems. After reviews of existing optimization models for public transit operations, a major deficiency within the centralized optimization framework is identified, namely, its inability to model decision interactions between multiple decision-making agents. A benchmark model that maximizes social welfare is formulated and then extended into a series of bilevel models with combinations of regulation policies and subsidization schemes to explore the relations between operators and government (both subsidizer and regulator). Single-level problems, including both the benchmark and those bilevel programs that can be reduced to one level, are solved analytically. Bilevel programs are solved with a hybrid method combining analytical and numerical techniques. Numerical evaluations that consider the cost of public funds show that ( a) the combination of regulation and subsidization scheme yields the highest social welfare, ( b) any subsidization scheme without regulation produces socially worse results than the benchmark, and ( c) two thresholds can be identified to distinguish the three proposed subsidization methods.
For Whom the Consumer Price Index Tolls: Reporting of Road Pricing in the consumer expenditure survey
Authors: Peters Jonathan , King David A. , Gordon Cameron , Santiago Nora Tabori
Published: January 2016

User fees have long been seen as an efficient financing mechanism because beneficiaries of services pay for the benefits received. This point of view is especially applicable to public services with commercial aspects and in situations for which links between consumption and price are relatively easy to make. However, road pricing, such as tolls, can be very high and important to local price levels. This paper examines the way in which expenditures on tolls are tracked and measured in the United States through the consumer expenditure survey (CES) run by the U.S. Bureau of Labor Statistics. The paper describes the CES and its methods, both generally and for tolls and road charges specifically, and compares those with estimates of U.S. tolls from other sources and from some micro-data the authors have compiled for the New York metropolitan area. The results suggest that the current CES underestimates consumer toll expenditures. Because the CES is a key background input into the consumer price index, the paper argues that flow-on effects continue through to measurement of U.S. inflation and gross domestic product as well.
Welfare Analysis using Logsum Differences versus Rule of Half: Series of Case Studies
Authors: Ma Shuhong , Kockelman Kara M. , Fagnant Daniel J.
Published: January 2016

Logsum differences and rule-of-half (ROH) calculations are two methods for estimating consumer surplus in transport economics. As a traditional and relatively straightforward (and potentially more robust) procedure, ROH is widely used in project investment and policy analysis, and much of the literature agrees that logsums are somewhat superior to ROH when user benefits are valued, at least when true travel behaviors stem from random-utility maximization with Gumbel error terms. This paper explores the differences in both methods through a careful review of literature and many case study results. The comparison of ROH and logsum methods relies on three specifications in order of increasing complexity: binary logit, multinomial logit, and nested logit models under a variety of settings and scenarios. This work offers a closer look at three numerical examples and concludes that the difference between ROH and logsum solutions rises with increases in travel times or costs and with changes in parameters. The monetized differences in logsums is usually smaller than the ROH solution for welfare changes under most situations and gives a more exact result for consumer surplus than ROH (which assumes a linear demand relationship with respect to cost). Larger coefficients on affected variables (such as travel time and cost) in the random-utility expressions tend to increase differences between logsum-and ROH-based estimates. Such findings should be of interest to policy makers and planners when they are developing transportation planning and land use models and interpreting their results for more accurate and rigorous and behaviorally defensible project evaluations.
Transport Infrastructure and Macroeconomic Performance in European Countries
Authors: Chi Junwook
Published: January 2016

The share of investment in transport infrastructure of the gross domestic product (GDP) has risen substantially in central and eastern European countries, and the effectiveness of public investment in transport infrastructure to improve economic performance is receiving increasing attention. This paper explores the dynamic impact of transport infrastructure on employment, GDP, exports, and industry production in European countries. With the use of data from 1995 to 2010, the paper analyzes the causality among variables in a dynamic panel framework. The results reveal that transport infrastructure and macroeconomic indicators are cointegrated and a significant unidirectional causal relationship exists from public investment in transport infrastructure to economic performance. The findings of this paper support the traditional notion that an increase in government spending on transport infrastructure contributes to economic growth. More specifically, the paper finds that transport infrastructure is a forcing variable of economic output and exports of European countries. Examination of the economic impacts of transport infrastructure between developed and developing economies shows that economic performance of central and eastern European countries is more sensitive to a change in investment in transport infrastructure than that of Western European countries. A major policy implication of these findings is that expanding transportation infrastructure could be an effective fiscal policy tool to boost economic performance of developing European economies.
Microsurgical resectability, outcomes, and tumor control in meningiomas occupying the cavernous sinus
Authors: Nanda Anil , Thakur Jai Deep , Sonig Ashish , Missios Symeon
Published: January 2016

OBJECTIVE

Cavernous sinus meningiomas (CSMs) represent a cohort of challenging skull base tumors. Proper management requires achieving a balance between optimal resection, restoration of cranial nerve (CN) function, and maintaining or improving quality of life. The objective of this study was to assess the pre-, intra-, and postoperative factors related to clinical and neurological outcomes, morbidity, mortality, and tumor control in patients with CSM.

METHODS

A retrospective review of a single surgeon's experience with microsurgical removal of CSM in 65 patients between January 1996 and August 2013 was done. Sekhar's classification, modified Kobayashi grading, and the Karnofsky Performance Scale were used to define tumor extension, tumor removal, and clinical outcomes, respectively.

RESULTS

Preoperative CN dysfunction was evident in 64.6% of patients. CN II deficits were most common. The greatest improvement was seen for CN V deficits, whereas CN II and CN IV deficits showed the smallest degree of recovery. Complete resection was achieved in 41.5% of cases and was not significantly associated with functional CN recovery. Internal carotid artery encasement significantly limited the complete microscopic resection of CSM (p < 0.0001). Overall, 18.5% of patients showed symptomatic recurrence after their initial surgery (mean follow-up 60.8 months [range 3–199 months]). The use of adjuvant stereotactic radiosurgery (SRS) after microsurgery independently decreased the recurrence rate (p = 0.009; OR 0.036; 95% CI 0.003–0.430).

CONCLUSIONS

Modified Kobayashi tumor resection (Grades I–IIIB) was possible in 41.5% of patients. CN recovery and tumor control were independent of extent of tumor removal. The combination of resection and adjuvant SRS can achieve excellent tumor control. Furthermore, the use of adjuvant SRS independently decreases the recurrence rates of CSM.
Skull base chordomas: clinical outcome in a consecutive series of 45 patients with long-term follow-up and evaluation of clinical and biological prognostic factors
Authors: Boari Nicola , Gagliardi Filippo , Cavalli Andrea , Gemma Marco , Ferrari Luca , Riva Paola , Mortini Pietro
Published: January 2016

OBJECTIVE

Skull base chordomas (SBCs) are rare dysembryogenetic invasive tumors with a variable tendency for recurrence. According to previous studies, the recurrence rate seems to be affected by both clinical variables and tumor biological features. The authors present the results of treatment of SBCs in a large series of patients and investigate the role of 1p36 chromosomal region loss of heterozygosity (LOH) as a prognostic factor.

METHODS

Between 1990 and 2011, 45 patients were treated for SBCs. The mean follow-up was 76 months (range 1–240 months). An LOH analysis was performed in 27 cases. Survival analysis was performed to determine clinical and biological parameters correlating with clinical outcome.

RESULTS

The 5- and 10-year overall survival rates were 67% and 57%, respectively. Five- and 10-year progression-free survival rates were 58% and 44%, respectively. Multivariate analysis showed that extent of resection, adjuvant radiation therapy, and absence of rhinopharynx invasion were positive independent predictors of overall survival. The latter 2 variables and a younger patient age were positive independent predictors of progression-free survival. Twenty-one patients showed 1p36 LOH. All events of recurrence and death clustered in the group of patients with 1p36 LOH; however, this biological marker was not statistically significant on multivariate analysis.

CONCLUSIONS

Resection is the treatment of choice in primary and recurrent SBC. Patient age, rhinopharynx invasion at diagnosis, extent of tumor removal, and postoperative radiation therapy influence SBC prognosis. Genetic analysis, even while showing interesting results, did not reveal 1p36 LOH as an independent predictor of clinical outcome.
Straight sinus: ultrastructural analysis aimed at surgical tumor resection
Authors: Amato Marcelo Campos Moraes , Tirapelli Luis Fernando , Carlotti Carlos Gilberto , Colli Benedicto Oscar
Published: January 2016

OBJECTIVE

Accurate knowledge of the anatomy of the straight sinus (SS) is relevant for surgical purposes. During one surgical procedure involving the removal of part of the SS wall, the authors observed that the venous blood flow was maintained in the SS, possibly through a vein-like structure within the dural sinus or dural multiple layers. This observation and its divergence from descriptions of the histological features of the SS walls motivated the present study. The authors aimed to investigate whether it is possible to dissect the SS walls while keeping the lumen intact, and to describe the histological and ultrastructural composition of the SS wall.

METHODS

A total of 22 cadaveric specimens were used. The SS was divided into three portions: anterior, middle, and posterior. The characteristics of the SS walls were analyzed, and the feasibility of dissecting them while keeping the SS lumen intact was assessed. The thickness and the number of collagen fibers and other tissues in the SS walls were compared with the same variables in other venous sinuses. Masson's trichrome and Verhoeff's stains were used to assess collagen and elastic fibers, respectively. The data were analyzed using Zeiss image analysis software (KS400).

RESULTS

A vein-like structure independent of the SS walls was found in at least one of the portions of the SS in 8 of 22 samples (36.36%). The inferior wall could be delaminated in at least one portion in 21 of 22 samples (95.45%), whereas the lateral walls could seldom be delaminated. The inferior wall of the SS was thicker (p < 0.05) and exhibited less collagen and greater amounts of other tissues—including elastic fibers, connective tissue, blood vessels, and nerve fibers (p < 0.05)—compared with the lateral walls. Transmission electron microscopy revealed the presence of muscle fibers at a level deeper than that of the subendothelial connective tissue in the inferior wall of the SS, extending from its junction with the great cerebral vein to the confluence of sinuses.

CONCLUSIONS

The presence of a structure within the SS that can maintain the venous blood flow despite the dural wall might be considered an anatomical variation. The greater thickness of the inferior wall of the SS compared with the lateral walls is mainly due to the presence of larger amounts of tissues other than collagen. Delamination of the inferior wall of the SS was mostly possible in its inferior wall, but an attempt to delaminate the lateral walls is not recommended. Ultrastructural assessment corroborated a recent report of the presence of muscle fibers in the inferior wall of the SS.
Temporary surgical clipping of flow-diverted arteries in an experimental aneurysm model
Authors: Darsaut Tim E. , Salazkin Igor , Gentric Jean-Christophe , Magro Elsa , Gevry Guylaine , Bojanowski Michel W. , Raymond Jean
Published: January 2016

OBJECTIVE

Surgical management of recurrent aneurysms following failed flow diversion may pose difficulties in securing vascular control with temporary clips. The authors tested the efficacy and impact of different types of aneurysm clips on flow-diverted arteries.

METHODS

Six wide-necked experimental aneurysms were created in canines and treated with Pipeline flow diverters. In 4 aneurysms, occlusion of the artery at the level of the proximal and distal landing zones (n = 2 per aneurysm) was attempted, using temporary, fenestrated, single, and double permanent aneurysm clips. Two aneurysms served as unclipped controls. Serial angiography was performed to investigate the efficacy of clip occlusion, flow diverter deformation, and thrombus formation. After the animals were killed, the flow-diverted aneurysm constructs were opened and photographed to determine neointimal or device damage as a result of clip placement.

RESULTS

Angiography-confirmed clip occlusion was only possible for 4 of 8 of the tested flow-diverted arterial segments. Clip application attempts led to filling defects consistent with thrombus formation in 2 of 4 flow-diverted constructs, and to minor damage of the flow diverter with neointimal fracture in 1 of 4 cases.

CONCLUSIONS

Aneurysm clips placed on canine parent arteries bearing a Pipeline flow diverter were unable to reliably stop blood flow. Application of aneurysm clips can cause mild damage to the device and neointima, which might translate into thromboembolic risks. If possible, vascular control should be sought beyond the terminal ends of the implanted device.
Supratentorial hemispheric ependymomas: an analysis of 109 adults for survival and prognostic factors
Authors: Hollon Todd , Nguyen Vincent , Smith Brandon W. , Lewis Spencer , Junck Larry , Orringer Daniel A.
Published: January 2016

OBJECTIVE

Survival rates and prognostic factors for supratentorial hemispheric ependymomas have not been determined. The authors therefore designed a retrospective study to determine progression-free survival (PFS), overall survival (OS), and prognostic factors for hemispheric ependymomas.

METHODS

The study population consisted of 8 patients from our institution and 101 patients from the literature with disaggregated survival information (n = 109). Patient age, sex, tumor side, tumor location, extent of resection (EOR), tumor grade, postoperative chemotherapy, radiation, time to recurrence, and survival were recorded. Kaplan-Meier survival analyses and Cox proportional hazard models were completed to determine survival rates and prognostic factors.

RESULTS

Anaplastic histology/WHO Grade III tumors were identified in 62% of cases and correlated with older age. Three-, 5-, and 10-year PFS rates were 57%, 51%, and 42%, respectively. Three-, 5-, and 10-year OS rates were 77%, 71%, and 58%, respectively. EOR and tumor grade were identified on both Kaplan-Meier log-rank testing and univariate Cox proportional hazard models as prognostic for PFS and OS. Both EOR and tumor grade remained prognostic on multivariate analysis. Subtotal resection (STR) predicted a worse PFS (hazard ratio [HR] 4.764, p = 0.001) and OS (HR 4.216, p = 0.008). Subgroup survival analysis of patients with STR demonstrated a 5- and 10-year OS of 28% and 0%, respectively. WHO Grade III tumors also had worse PFS (HR 10.2, p = 0.004) and OS (HR 9.1, p = 0.035). Patients with WHO Grade III tumors demonstrated 5- and 10-year OS of 61% and 46%, respectively. Postoperative radiation was not prognostic for PFS or OS.

CONCLUSIONS

A high incidence of anaplastic histology was found in hemispheric ependymomas and was associated with older age. EOR and tumor grade were prognostic factors for PFS and OS on multivariate analysis. STR or WHO Grade III pathology, or both, predicted worse overall prognosis in patients with hemispheric ependymoma.
Lateral orbitotomy for a maxillary nerve schwannoma: case report
Authors: Wallace Scott A. , Michael Meyer R. , Cirivello Michael J. , Cho Raymond I.
Published: January 2016

Authors of this report describe a Fukushima Type D(b) or Kawase Type ME2 trigeminal schwannoma involving the right maxillary division in a 59-year-old woman who presented with intermittent right-sided facial numbness and pain. This tumor was successfully resected via a right lateral orbitotomy without the need for craniotomy. This novel approach to a lesion of this type has not yet been described in the scientific literature. The outcome in this case was good, and the patient's intra- and postoperative courses proceeded without complication. The epidemiology of trigeminal schwannomas and some technical aspects of lateral orbitotomy, including potential advantages of this approach over traditional transcranial as well as fully endoscopic dissections in appropriately selected cases, are also briefly discussed.
Results of a prospective study (CATS) on the effects of thalamic stimulation in minimally conscious and vegetative state patients
Authors: Magrassi Lorenzo , Maggioni Giorgio , Pistarini Caterina , Di Perri Carol , Bastianello Stefano , Zippo Antonio G. , Iotti Giorgio A. , Biella Gabriele E. M. , Imberti Roberto
Published: January 2016

OBJECTIVE

Deep brain stimulation of the thalamus was introduced more than 40 years ago with the objective of improving the performance and attention of patients in a vegetative or minimally conscious state. Here, the authors report the results of the Cortical Activation by Thalamic Stimulation (CATS) study, a prospective multiinstitutional study on the effects of bilateral chronic stimulation of the anterior intralaminar thalamic nuclei and adjacent paralaminar regions in patients affected by a disorder of consciousness.

METHODS

The authors evaluated the clinical and radiological data of 29 patients in a vegetative state (unresponsive wakefulness syndrome) and 11 in a minimally conscious state that lasted for more than 6 months. Of these patients, 5 were selected for bilateral stereotactic implantation of deep brain stimulating electrodes into their thalamus. A definitive consensus for surgery was obtained for 3 of the selected patients. All 3 patients (2 in a vegetative state and 1 in a minimally conscious state) underwent implantation of bilateral thalamic electrodes and submitted to chronic stimulation for a minimum of 18 months and a maximum of 48 months.

RESULTS

In each case, there was an increase in desynchronization and the power spectrum of electroencephalograms, and improvement in the Coma Recovery Scale–Revised scores was found. Furthermore, the severity of limb spasticity and the number and severity of pathological movements were reduced. However, none of these patients returned to a fully conscious state.

CONCLUSIONS

Despite the limited number of patients studied, the authors confirmed that bilateral thalamic stimulation can improve the clinical status of patients affected by a disorder of consciousness, even though this stimulation did not induce persistent, clinically evident conscious behavior in the patients.

Clinical trial registration no.: NCT01027572 (ClinicalTrials.gov)