bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparative Assessment of 3-3/8-in. Perforators Using ‘Reactive’ and ‘Non-reactive’ Shaped Charges
Authors: Haggerty Dennis , Manning Doug , Leidel David , Barker James , Pettitt Andrew
Published: December 2009

Several recently introduced oilfield perforators incorporate reactive materials that are derivatives of military-based weapons technology. Perforator suppliers claim that using reactive charges facilitates tunnel cleanup creating optimized perforations, thus improving downhole performance leading to increased well productivity. To better understand and quantify differences in penetration and flow performance between reactive shaped charges and conventional shaped charges, a comprehensive test matrix was designed. The performance assessments of reactive versus nonreactive perforators were carried out under controlled conditions in an API Perforation Flow Laboratory (PFL) (API, 2006).

The Phase I tests for this study, which involved shooting into stressed rock under simulated downhole conditions, were conducted in Berea Sandstone targets with mineral-oil flow, to simulate a typical oil-bearing formation. Phase II testing will be conducted in Carbon Tan Sandstone with nitrogen flow, to simulate a typical gas-bearing formation. The Berea Sandstone represented moderate-to-high porosity and permeability rocks with high, unconfined compressive strength (UCS). The Carbon Tan Sandstone will represent low-permeability and medium-porosity rocks with moderate-UCS.

In order to further understand the contribution of the ‘reactive’ component, tests designed for this study are carried out in balanced, underbalanced and overbalanced conditions. Charge performance measurements are taken for both conventional and ‘reactive’ charges in each target reservoir rock. This paper describes the methodology used for the comparative tests between ‘reactive’ and ‘nonreactive’ perforators in the Berea Sandstone portion of the program and summarizes the observations of core penetration, tunnel cleanup and productivity.
Production Data Analysis of Fractured and Horizontal CBM Wells
Authors: Clarkson C. R. , Jordan C. L. , Ilk D. , Blasingame T. A.
Published: December 2009

In recent work, the authors (Clarkson et al 2008a; Clarkson et al 2007; Jordan et al 2006) demonstrated how modern production data analysis (PDA) methods, such as flowing material balance (FMB) and production type-curves, may be adapted to account for the unique reservoir characteristics of coalbed methane (CBM) reservoirs through the appropriate use of material balance and time transforms. Reservoir characteristics related to storage and fluid flow that were addressed included: adsorbed and free-gas storage; single-phase flow of water above desorption pressure (undersaturated coals); 2-phase flow of gas and water below desorption pressure (saturated coals); non-static absolute permeability during depletion; and multi-layer behavior. Example (field) applications of the new PDA methods were limited to vertical wells that were either openhole completed, or slightly stimulated with hydraulic fracturing methods.

In this work, new workflows and analytical approaches are provided for analyzing single- and multi-phase flow of CBM from vertical, hydraulically-fractured wells and horizontal wells. The workflow for single-phase CBM wells, which parallels that used in modern pressure transient analysis (well-testing), includes identification and analysis of flow regimes, followed by (model) type-curve matching and analytical (or numerical) modeling. Pseudotime is modified to account for instantaneous desorption. The analysis and methodology for 2-phase flow reservoirs is more complex, requiring additional modification of the pseudovariables to account for changes in effective permeability. A new workflow is introduced for 2-phase CBM wells that includes the transformation of the well production and flowing pressure data into dimensionless type-curve and flowing material balance coordinates using outputs from the simulator used to history-match the production data. Both simulated and field cases are analyzed to illustrate the new procedures and analytical techniques.

The primary contribution of the current work is the demonstration that modern production analysis methods, modified for CBM reservoir behavior and combined with analytical (or numerical) modeling, can be used to extract quantitative reservoir information from CBM reservoirs which exhibit a wide-range in production characteristics, and completed in a variety of styles. The methods are expected to be used as a pre-cursor to or in parallel with reservoir simulation, to assist with CBM development decisions.
A Probabilistic Approach to CO2 Corrosion Rate Assessment in Gas Pipelines
Authors: Omolegbe Anu , Appah Dulu
Published: December 2009

Extension of field life has resulted in pipelines carrying changing fluids compositions beyond the original designed life. New pipelines are also being constructed in increasingly challenging environment like deep offshore. Therefore, the need arises to ensure the integrity of these pipelines and reduce the uncertainties involved in predicting the future conditions.

The NORSOK CO2 corrosion rate calculation model is used calculate the CO2 corrosion rate in assessing failure of a pipeline. The probabilistic approach to assess pipeline corrosion risks deals with many of the uncertainties common to the data employed and those with regard to the NORSOK predictive model. Rather than consider each input parameter as an average value or "worst case?? value, this approach evaluates the possibility of having 10%, 50% and 90% chances of CO2 corrosion rates obtained from Monte Carlo simulation using Crystal ball®. The corresponding "years of failure?? for the pipeline using a straight line decline extrapolation of the thickness under varying operating conditions were also obtained.This approach reduces the uncertainties involved in predicting future conditions of pipelines based solely on a deterministic "worst case??.
Deepwater Petroleum Exploration and Development in Africa An Appraisal of Factors, Efforts, and Outcomes, 1998-2007
Authors: Iledare Omowumi , Pincomb Richard , Vitrano Derek
Published: December 2009

This paper describes qualitatively the key factors driving deepwater petroleum exploration and development prospectivity worldwide, including but not limited to global petroleum supply and demand fundamentals, availability and accessibility to petroleum resources, technology innovations and infrastructure development, and geopolitics and fiscal arrangements. Quantitative indicators are estimated to analyze these factors with respect to deepwater activity and outcomes in Africa using number of fields discovered, the number of producing and on-stream fields, the estimated average size of discoveries, instantaneous production flow estimates, completion techniques and methods, and capital expenditure compontents and trends. The paper evaluates and compares the attractiveness and prospectivity of the deepwater in Africa using the above empirical indicators by country.
Development & Implementation of a New Technology known as the "AEROS System"® (Airborne Robotic Oil Spill Recovery System) - Improving the State-of-the-Art of Offshore Oil Spill Emergency Response
Authors: Sullivan Myron
Published: December 2009

Our world is increasingly prone to environmental disasters with the public and governments worldwide demanding more effective solutions. Global Response Group "GRG" has proprietary technology that will contribute immensely to solving two serious global problems: large marine oil spills and global warming. GRG provides industry and governments the ability to quickly and effectively respond to large marine oil spills and to control destructive forest fires, (both on a global scale) using fleets of Lockheed L-100 and C-130 Hercules aircraft and crews integrated with GRG patented technology using satellite remote sensing/GPS/remote control/ telemetry systems.

The AEROS® Airborne Robotic Oil Spill Recovery System

Large offshore marine oil spills have never been effectively controlled and oil spill pollution remains a serious global problem. The ever-growing public concern for the environment will only escalate the costs and penalties of future spills. Therefore, GRG developed the AEROS® Robotic Oil Spill Recovery System, a truly effective and extremely rapid, robotic, satellite controlled oil spill containment and recovery system. AEROS© is demonstrated on the GRG web site: www.globalresponsegroup.com

Global Response Group (GRG) has invested approximately $10 Million to date in the development of GRG's AEROS Technology. The AEROS system, as shown on the GRG web site and CD ROM presentation, demonstrates GRG's ability to rapidly contain, recover and recycle a marine oil spill of any size with much higher recovery efficiencies than ever achieved by other systems currently on the market. Potential customers for AEROS include: all oil companies and tanker fleet owners; the governments of all oil producing and consuming countries with a shoreline; and, all offshore drilling and production rigs. Other customers include: the insurance underwriters industry; the entire merchant marine shipping industry; and, all private and public oil spill response organizations. GRG'S AEROS System combines proven technology that has already demonstrated its durability and effectiveness with a unique robotic oil spill recovery vehicle (patented). Another unique feature of the system is GRG's ability to rapidly deploy AEROS using Lockheed L-100 and C-130 Hercules aircraft and to control AEROS oil spill recovery operations with satellites.

Another significant operational capability of the AEROS System is its potential to fight malaria and dengue fever on a very large scale. GRG has developed a scientific business plan, called the "MEP" = Malaria Eradication Program. GRG's "MEP" has received indications of serious interest from the U.N. World Health Organization ("WHO"). Upon request, GRG can provide a detailed business plan for the "MEP" Malaria Eradication Program, as well as the credentials of the scientists who back this program.
Economic Viability of Gas-to-Liquids in Nigeria
Authors: Balogun O. M. , Onyekonwu M. O.
Published: December 2009

With recent oil price escalation, declining oil reserves and global warming, interest has been shown world-wide in the production of clean liquid fuels through Fischer-Tropsch (FT) Synthesis. FT Synthesis is a proven technology but development of commercial GTL has been very slow. For resource holders, the major challenge is economics thus, the economic viability of GTL calls for critical analysis.

This paper reviewed FT process and investigated its economics with principal interest in the production of Syncrude, DME and Methanol in Nigeria. A sound appraisal technique was later used to measure and rank GTL proposals with the LNG in Nigeria.

The results show that GTL-Diesel would be economically feasible when applied to a typical offshore Niger Delta resource at oil prices of above US$35/bbl and feedstock gas price in range of US$0.25-1.5/mmBtu. GTL-DME economics looks encouraging and could be introduced at a price lower than that of LPG. However GTL-Methanol will only be viable at a distress gas price of US$0.25-0.5/mmBtu and in a condition of preferential tax treatment. LNG and GTL-Syncude have the same value at discount rate of 16.84% with LNG giving higher profits if the cost of capital is less than 16.84%. The profitability of LNG and GTL (Syncrude and DME) is very close, with GTL having a potential superior return at high oil prices and preferable under conditions of limited capital. In Nigeria, GTL-Syncrude could be used to monetize "leftover" gas that doesn't merit a standalone new LNG train and provide the country an opportunity to enjoy direct exposure to oil price upsides.
Impact of Borehole Washout on Acoustic Logs and Well-to-Seismic Ties
Authors: Ugborugbo Omuvwie , Rao Tummala
Published: December 2009

Good well-to-seismic ties are key to proper seismic reservoir rock property characterisation. Acoustic log measurements are significantly affected by unstable hole conditions that can impact on the usual porosity computation from the sonic and density logs within these bad hole intervals. It is commonly assumed that sonic logs are not significantly impacted by these bad hole conditions.

In this study, sonic, density and caliper logs were each taken from one field located in the eastern and western Niger delta. The acoustic logs were recreated by a Neural Network technique in intervals where the hole indicates extensive wash out. Cross-plots of the acoustic logs against calipers were made for both the measured and recreated logs. Well-to-seismic ties were also completed using both the measured and the recreated logs.

In both fields, a dependence of sonic velocity on hole size was observed for the measured logs. Across washout regions, an improved well to seismic tie was obtained from the sonic and density logs when corrected for the effect of borehole washout. Cross-plots of p-impedance versus density using uncorrected logs showed no significant differentiation between sands and shales. However, sands and shales showed good separation in the reconstructed logs, enabling more accurate lithologic calls. It is concluded that hole washout affects sonic and density log readings more substantially than is commonly recognized, and that the quality of the sonic log has a significant impact on the quality of subsequent seismic to well ties and inversion results used in reservoir characterisation.
Improving the Reliability of Subsea Valves
Authors: Mamman Saidu , Andrawus Jesse A. , Iyalla Ibiye
Published: December 2009

Subsea valves are critical component used for the control of fluid flow in sub-sea Oil & Gas (O&G) production equipment. Subsea Valves are susceptible to early-life failure and, are increasingly utilised in production equipment due to the current deep water exploration of O&G. The reliability of valves is indispensable to the availability of sub-sea production equipment. Failure of subsea valves can have significant financial, environmental, health and safety consequences. Failure Mode and Effect Criticality Analysis (FMECA) is a technique that permits evaluation of assets functions to predict critical failure modes and the resultant consequences in order to determine appropriate maintenance tasks for the assets. In this paper, the technique of FMECA is used to assess the failure characteristics of sub-sea valves. Common and dominant failure modes of the valves are identified. The failure consequences are calculated in financial terms by taking into account production losses, intervention cost, repair and environmental cleaning costs. Failure Elimination and Prevention Strategy (FEPS) is designed to prevent early-life failures and improve the overall reliability of subsea valves.
Key Elements of Successful Well and Reservoir Management in the Bonga Field, Deepwater Nigeria
Authors: Sathyamoorthy S. , Olatunbosun O. , Sabatini D. , Orekyeh U. , Olaniyan E.
Published: December 2009

Production from the deepwater Bonga turbidite reservoirs was started in November 2005. As with all waterflood and Enhanced Oil Recovery schemes, ‘world-class’ Well and Reservoir Management (WRM) is the foundation of a successful project. A comprehensive WRM plan was defined for Bonga very early in the project, and its implementation from start-up has demonstrated tremendous value.

More than 220 MMstb have been produced as of March 2009 from 13 subsea producers, and reservoir pressures have been maintained by water injection from the start of production in 13 subsea high rate water injectors, allowing high field production rates to be sustained. Well and reservoir performance data obtained during the first three years of production, and information from 4 D seismic shot in early 2008 are now used to optimize the planning and drilling of additional wells as part of the Phase 2 development drilling project. Bonga is a ‘brownfield’ that is not immune to normal well and asset integrity issues, and declines in well injectivity and productivity. Ability to respond swiftly to these issues is part of the Bonga WRM Plan.

This paper presents key elements of successful WRM in Bonga. These include people factor and cross discipline integration, Smart Fields® capability, ‘live’ WRM Plan and monitoring, good understanding of subsurface, application of integrated production modelling, intervention readiness and effective well integrity management. The paper concludes on key learnings applicable to future deepwater waterflood projects.
Nigerian Gas Transmission Tariff Framework Study
Authors: Chilaka Augustine , Onyekonwu Mike
Published: December 2009

The Federal Government of Nigeria intends to develop the domestic gas market by opening investment opportunity for infrastructural development, and by including gas pipeline construction among her key projects in 2009 budget. The domestic gas market is estimated to have an annual growth potential of about 15% to 18%, which attests to its potential profitability.

In this study, we investigated the gas transmission tariff and profitability potential for investment in the gas transmission investment opportunity proposed in the Nigerian Gas Master Plan. The gas transmission systems are the South-North System, the Western System, and the Interconnector System.

Deterministic and stochastic methods were used for cashflow modeling and sensitivity analysis. Using 17% internal rate of returns, the resulting tariffs for the gas transmission systems were the following: $0.47/Mscf for the Western Pipeline System, $0.97/MScf for South-North pipeline system, and $0.34/MScf for Interconnector pipeline system. The most sensitive cost items to internal rate of returns for investment in the pipeline systems were determined as the peak flow of gas, gas pipeline costs, and installation costs.

The calculated tariffs could be coupled with the casing head gas price and processing fee to yield the likely price of the lean gas.
Pre-Drill Pore Pressure Prediction From 3-D Seismic Data in Parts of the Onshore Niger Delta Basin
Authors: Opara A. I. , Onuoha K. M.
Published: December 2009

Geopressured sedimentary formations are common within the more prolific deeper hydrocarbon reserves in the Niger Delta basin. While overpressured zones could serve as tools for hydrocarbon prospectivity evaluation, they are significant safety concern to the driller. Pre-drill pore pressure prediction using 3-D seismic data was carried out in the Niger Delta basin to predict subsurface pressure regimes and further applied in the determination of hydrocarbon column, reservoir continuity, fault seal and trap integrity. Results revealed that overpressures in the area are associated with simple rollover structures bounded by growth faults, especially at the hanging walls, while hydrostatic pressures are often observed in areas with k-faults and collapsed crested structures. The depth to top of mild overpressures(<0.71psi/ft) in the basin ranges from about 6000ftss to about 13000ft subsea. Similarly, the depth to top of hard overpressures(>0.71psi/ft) ranges from about 13000ftss to over 30000ftss(throughout the Akata Formation).Post-depositional faulting is believed to have controlled the configuration of the overpressure surface and has played later roles in modifying the present day depth to top of overpressures.
Time-Lapse Feasibility Studies of Two Fields in the Niger Delta
Authors: Osayande Francesca , Ugborugbo Omuvie
Published: December 2009

Time-lapse Feasibility Studies were carried out for two producing fields in the Niger Delta to assess the probabilities of success of acquiring 4D surveys. The two fields are located within onshore Niger Delta.

Agbada field is located on land 100km North West of Port Harcourt, Nigeria. The field was discovered in 1960 and has been producing since 1965. To date some 66 wells have been drilled in the field. It has a STOIIP of about 1.5 billion barrels. Current estimate of undeveloped hydrocarbon reserves stand at Expectation Volume of 285 MMbbl and 0.8 Tscf. However, the field is experiencing high water cut and declining production. Agbada Field is covered by several vintages of 2D lines and one vintage of higher quality 3D seismic data that was acquired in the 1993.

Kolo Creek field is located within the swamp, 110km South West of Port Harcourt, Nigeria. The field was discovered in 1961 but started production in 1973. It has a STOIIP of 495 MMSTB and an FGIIP of 1.3 TCF. Total Oil production to date is 254MMstb representing 45% of the STOIIP; and there has been no gas production. This field is also experiencing declining production and high water cut. It is also covered by several vintages of 2D lines and one vintage of higher quality 3D seismic data that was acquired in 1997.

For each of these fields, it was desired to determine whether time-lapse signals will be detectable and to ascertain the optimum time in which to carry out a time-lapse monitor survey. The history matched dynamic simulation models for each field were converted to acoustic properties through a suitable rock model, and resultant acoustic impedances were calculated. Synthetic seismograms were subsequently generated for several time steps and analyzed for production-induced 4D signals. The impact of various levels of random noise on the 4D response was also evaluated.

The results from both of these studies demonstrated that, even in the presence of significant random noise, production induced 4D changes should be observable if the monitor seismic survey is acquired in or beyond 2006. These results will be discussed.
Syncytial Knots as a Reflection of Placental Maturity: Reference Values for 20 to 40 Weeks' Gestational Age
Authors: Loukeris Krishna , Sela Raanan , Baergen Rebecca N.
Published: December 2009

Syncytiotrophoblastic knots or syncytial knots are aggregates of syncytial nuclei at the surface of terminal villi. In the term placenta, most syncytial knots are thought to be artifacts from tangential sectioning while the minority are syncytial sprouts, bridges, or apoptotic knots. Syncytial knots are consistently present, increasing with increasing gestational age, and can be used to evaluate villous maturity. Increased syncytial knots are associated with conditions of uteroplacental malperfusion and are important in placental examination. Although 30% of terminal villi with syncytial knots at term are often reported, no reference values have been developed for the percentage of villi with syncytial knots at different gestational ages. We counted the percentage of chorionic villi with syncytial knots at different gestational ages from 20 to 40 weeks using cases with no history of malperfusion or clinical conditions known to be associated with malperfusion. We provide normal reference data for the average percentage of syncytial knots for gestational ages ranging from 20 to 40 weeks. There was a significant positive correlation of gestational age with percentage of villi with syncytial knots. Term placentas (37–40 weeks) showed an average of 28% syncytial knots. A drop-off to a mean of 22.5% was noted at 36 weeks; at 26 to 33 weeks, syncytial knots varied from 10.8% to 14.7%; between 20 and 25 weeks, syncytial knots ranged between 5.2% and 9.1%. These reference data can facilitate histologic assessment of normal placental maturation as well as evaluation of placental morphology in placental malperfusion.
Synthesis of MSn(OH)6 (where M = Mg, Ca, Zn, Mn, or Cu) materials at room temperature
Authors: Kramer Jonathan , Kelly Brandon , Manivannan Venkatesan
Published: December 2009

Applying a metathesis approach (MCl2·xH2O+Na2SnO3·xH2O→MSn(OH)6+NaCl+xH2O), Schoenfliesite-type materials with general formula MSn(OH)6 (where M=Ca, Cu, Mg, Mn or Zn) were synthesized at room-temperature. The high lattice-energy of the by-product alkali halide NaCl drives the reaction in the forward direction leading to the formation of the desired materials. The materials synthesized were characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) to elucidate structural and micro structural features.
A Q-Ising model application for linear-time image segmentation
Authors: Bentrem Frank
Published: December 2009

A computational method is presented which efficiently segments digital grayscale images by directly applying the Q-state Ising (or Potts) model. Since the Potts model was first proposed in 1952, physicists have studied lattice models to gain deep insights into magnetism and other disordered systems. For some time, researchers have realized that digital images may be modeled in much the same way as these physical systems (i.e., as a square lattice of numerical values). A major drawback in using Potts model methods for image segmentation is that, with conventional methods, it processes in exponential time. Advances have been made via certain approximations to reduce the segmentation process to power-law time. However, in many applications (such as for sonar imagery), real-time processing requires much greater efficiency. This article contains a description of an energy minimization technique that applies four Potts (Q-Ising) models directly to the image and processes in linear time. The result is analogous to partitioning the system into regions of four classes of magnetism. This direct Potts segmentation technique is demonstrated on photographic, medical, and acoustic images.
Genesis and stability of accessory phosphates in silicic magmatic rocks: a Western Carpathian case study
Authors: Broska Igor , Petrík Igor
Published: December 2009

Genesis and stability of accessory phosphates in silicic magmatic rocks: a Western Carpathian case study

The formation of accessory phosphates in granites reflects many chemical and physical factors, including magma composition, oxidation state, concentrations of volatiles and degree of differentiation. The geotectonic setting of granites can be judged from the distribution and character of their phosphates. Robust apatite crystallization is typical of the early magmatic crystallization of I-type granitoids, and of late magmatic stages when increased Ca activity may occur due to the release of anorthite from plagioclase. Although S-type granites also accumulate apatite in the early stages, increasing phosphorus in late differentiates is common due to their high ASI. The apatite from the S-types is enriched in Mn compared to that in I-type granites. A-type granites characteristically contain minor amounts of apatite due to low P concentrations in their magmas. Monazite is typical of S-type granites but it can also become stable in late I-type differentiates. Huttonite contents in monazite correlate roughly positively with temperature. The cheralite molecule seems to be highest in monazite from the most evolved granites enriched in B and F. Magmatic xenotime is common mainly in the S-type granites, but crystallization of secondary xenotime is not uncommon. The formation of the berlinite molecule in feldspars in peraluminous melts may suppress phosphate precipitation and lead to distributional inhomogeneities. Phosphate mobility commonly leads to the formation of phosphate veinlets in and outside granite bodies. The stability of phosphates in the superimposed, metamorphic processes is restricted. Both monazite-(Ce) and xenotime-(Y) are unstable during fluid-activated overprinting. REE accessories, especially monazite and allanite, show complex replacement patterns culminating in late allanite and epidote formation.
Genetic Analysis of Inonotus Obliquus Strains by RAPD
Authors: Chen Yan-Qiu , Guo Xiao-Fan , Li Chang-Tian , Li Yu
Published: December 2009

Genetic Analysis ofInonotus ObliquusStrains by RAPD

RAPD profiling of eightInonotus obliquusstrains isolated from sclerotia collected from different areas of China was conducted to determine the genetic variability within this important medicinal fungus and to better define relationships between the genotype and geographical origins of isolation. Twelve 10-mer primers generated a total of 167 stable and reproducible DNA fragments, of which 101 (60.5%) were polymorphic. DNA fingerprints revealed genetic diversity among the strains tested, but there was the little intraspecific difference between the fingerprints of individual strains. A phenogram constructed based on UPGMA analysis of genetic distances calculated from RAPD fragment data identified three distinct groupings: (1) BCX01 and BCX02, (2) JL01, JL02, JL03, JL04 and JL05, (3) HLJ01. Our data confirm that the genetic variability among different strains may be a useful ancillary tool for identifyingl. obliquussclerotia of different geographical origins.
Comparison of Biochemical Markers of Bone Turnover in Patients on Continuous Ambulatory Peritoneal Dialysis and Maintenance Hemodialysis
Authors: Novaković Neda , Pejanović Svetlana , Jovanović Dijana , Majkić-Singh Nada
Published: December 2009

Comparison of Biochemical Markers of Bone Turnover in Patients on Continuous Ambulatory Peritoneal Dialysis and Maintenance Hemodialysis

The aim of this study was to compare the biochemical markers of bone formation - bone isoenzyme alkaline phosphatase, /BALP/ bone resorption - tartarat resistant acid phosphatase /TRAP/ and parameters of bone turnover (Ca, P and iPTH) between 108 patients on continuous ambulatory peritoneal dialysis (CAPD) and 112 patients on hemodialysis (HD). Parameters were determined by spectrophotometry (TRAP, Ca, P), electrochemiluminiscent method (iPTH) and electrophoresis (BALP). There was significant correlation between BALP levels of CAPD patients and Ca values of HD patients (r = 0.216, p < 0.05), but comparison of P, iPTH and BALP showed no significant difference between the groups. We found significant correlation between BALP and TRAP (r = 0.570, p < 0.01) and BALP and iPTH values (r = 0.551, p < 0.01) in HD patients. Also, significant correlations in CAPD patients between BALP and TRAP (r = 0.194, p < 0.05) and BALP and iPTH values (r = 0.283, p < 0.01) were found. Our results suggest that the effect of CAPD and HD on bone turnover may be monitored most conclusively via BALP levels. This biochemical marker is a very good index of bone turnover in patients undergoing dialysis and it could indicate an early stage of decreased bone turnover.
Cognitive Load and Dual-Task Performance During Locomotion Poststroke: A Feasibility Study Using a Functional Virtual Environment
Authors: Kizony Rachel , Levin Mindy F. , Hughey Lucinda , Perez Claire , Fung Joyce
Published: December 2009

Background

Gait and cognitive functions can deteriorate during dual tasking, especially in people with neurological deficits. Most studies examining the simultaneous effects of dual tasking on motor and cognitive aspects were not performed in ecological environments. Using virtual reality technology, functional environments can be simulated to study dual tasking.

Objectives

The aims of this study were to test the feasibility of using a virtual functional environment for the examination of dual tasking and to determine the effects of dual tasking on gait parameters in people with stroke and age-matched controls who were healthy.

Design

This was a cross-sectional observational study.

Methods

Twelve community-dwelling older adults with stroke and 10 age-matched older adults who were healthy participated in the study. Participants walked on a self-paced treadmill while viewing a virtual grocery aisle projected onto a screen placed in front of them. They were asked to walk through the aisle (single task) or to walk and select (“shop for”) items according to instructions delivered before or during walking (dual tasking).

Results

Overall, the stroke group walked slower than the control group in both conditions, whereas both groups walked faster overground than on the treadmill. The stroke group also showed larger variability in gait speed and shorter stride length than the control group. There was a general tendency to increase gait speed and stride length during dual-task conditions; however, a significant effect of dual tasking was found only in one dual-task condition for gait speed and stride duration variability. All participants were able to complete the task with minimal mistakes.

Limitations

The small size and heterogeneity of the sample were limitations of the study.

Conclusions

It is feasible to use a functional virtual environment for investigation of dual tasking. Different gait strategies, including an increase or decrease in gait speed, can be used to cope with the increase in cognitive demands required for dual tasking.
Use of an artificial neural network to predict head injury outcome
Authors: Rughani Anand I. , Dumont Travis M. , Lu Zhenyu , Bongard Josh , Horgan Michael A. , Penar Paul L. , Tranmer Bruce I.
Published: December 2009

Object

The authors describe the artificial neural network (ANN) as an innovative and powerful modeling tool that can be increasingly applied to develop predictive models in neurosurgery. They aimed to demonstrate the utility of an ANN in predicting survival following traumatic brain injury and compare its predictive ability with that of regression models and clinicians.

Methods

The authors designed an ANN to predict in-hospital survival following traumatic brain injury. The model was generated with 11 clinical inputs and a single output. Using a subset of the National Trauma Database, the authors “trained” the model to predict outcome by providing the model with patients for whom 11 clinical inputs were paired with known outcomes, which allowed the ANN to “learn” the relevant relationships that predict outcome. The model was tested against actual outcomes in a novel subset of 100 patients derived from the same database. For comparison with traditional forms of modeling, 2 regression models were developed using the same training set and were evaluated on the same testing set. Lastly, the authors used the same 100-patient testing set to evaluate 5 neurosurgery residents and 4 neurosurgery staff physicians on their ability to predict survival on the basis of the same 11 data points that were provided to the ANN. The ANN was compared with the clinicians and the regression models in terms of accuracy, sensitivity, specificity, and discrimination.

Results

Compared with regression models, the ANN was more accurate (p < 0.001), more sensitive (p < 0.001), as specific (p = 0.260), and more discriminating (p < 0.001). There was no difference between the neurosurgery residents and staff physicians, and all clinicians were pooled to compare with the 5 best neural networks. The ANNs were more accurate (p < 0.0001), more sensitive (p < 0.0001), as specific (p = 0.743), and more discriminating (p < 0.0001) than the clinicians.

Conclusions

When given the same limited clinical information, the ANN significantly outperformed regression models and clinicians on multiple performance measures. While this paradigm certainly does not adequately reflect a real clinical scenario, this form of modeling could ultimately serve as a useful clinical decision support tool. As the model evolves to include more complex clinical variables, the performance gap over clinicians and logistic regression models will persist or, ideally, further increase.
Cell Culture on MEMS Platforms: A Review
Authors: Ni Ming , Tong Wen Hao , Choudhury Deepak , Rahim Nur Aida Abdul , Iliescu Ciprian , Yu Hanry
Published: December 2009

Microfabricated systems provide an excellent platform for the culture of cells, and are an extremely useful tool for the investigation of cellular responses to various stimuli. Advantages offered over traditional methods include cost-effectiveness, controllability, low volume, high resolution, and sensitivity. Both biocompatible and bioincompatible materials have been developed for use in these applications. Biocompatible materials such as PMMA or PLGA can be used directly for cell culture. However, for bioincompatible materials such as silicon or PDMS, additional steps need to be taken to render these materials more suitable for cell adhesion and maintenance. This review describes multiple surface modification strategies to improve the biocompatibility of MEMS materials. Basic concepts of cell-biomaterial interactions, such as protein adsorption and cell adhesion are covered. Finally, the applications of these MEMS materials in Tissue Engineering are presented.
Cytotoxic Activity of Curcumin towards CCRF-CEM Leukemia Cells and Its Effect on DNA Damage
Authors: Kong Yu , Ma Wei , Liu Xia , Zu Yuangang , Fu Yujie , Wu Nan , Liang Lu , Yao Liping , Efferth Thomas
Published: December 2009

The cytotoxic activity of curcumin towards CCRF-CEM human T-cell leukemia cells was measured by the MTT assay. Tumor cells were more sensitive to the cytotoxic activity of curcumin or curcumin-Cu (II)compared to normal cells, and the IC50 ofcurcumin towards CCRF-CEM cells was 8.68 µM, and that ofcurcumin-Cu (II) was 8.14 µM. The cell cycle distribution of curcumin-treated CCRF-CEM cells was analyzed by flow cytometry. DNA damage induced by oxidants such as curcumin-Cu (II) ions is considered as one of the main causes of cell inactivation. Therefore, we analyzed the effect of curcumin on DNA damage by agarose gel electrophoresis and atomic force microscopy (AFM). Gel electrophoresis analyses showed that curcumin or Cu (II) alone failed to cause DNA damage in pBR322 plasmid DNA as compared with the normal plasmid. However, DNA plasmids were mostly damaged after treatment with curcumin of different concentrations in the presence of Cu (II). Two forms were observed by means of AFM: closed circular plasmids and linear plasmids. DNA damage induced by a combination of curcumin and Cu (II) was also found by agarose gel electrophoresis, which was applied as control method to verify the results obtained by AFM.
Synthesis and Biological Evaluation of Novel 1-Alkyltryptophan Analogs as Potential Antitumor Agents
Authors: Sun Ting , Li Zhao-Long , Tian Hua , Wang Shih-Chen , Cai Jiong
Published: December 2009

To seek novel antitumor agents, we designed and synthesized new 1-tryptophan analogs based on tryptophan catabolism. 1-Alkyltryptophan analogues including 1-ethyltryptophan (1-ET), 1-propyltryptophan (1-PT), 1-isopropyltryptophan (1-isoPT) and 1-butyltryptophan (1-BT) were synthesized from tryptophan. We examined whether those compounds had the antiproliferative effects on SGC7901 and HeLa cells line by using MTT assay in vitro, respectively. Compared to tryptophan, all targeted compounds efficiently inhibited proliferation of two cancer cell lines at 2 mmol/L for 48 hours. Among these tryptophan analogs, 1-BT showed the most powerful cytotoxicity against SGC7901 and HeLa cells at 1 mmol/L and 2 mmol/L concentration. These data suggest that some specific tryptophan analogs could be developed as potential anti-neoplastic agents.
Direct Georeferencing of Stationary LiDAR
Authors: Mohamed Ahmed , Wilkinson Benjamin
Published: December 2009

Unlike mobile survey systems, stationary survey systems are given very little direct georeferencing attention. Direct Georeferencing is currently being used in several mobile applications, especially in terrestrial and airborne LiDAR systems. Georeferencing of stationary terrestrial LiDAR scanning data, however, is currently performed indirectly through using control points in the scanning site. The indirect georeferencing procedure is often troublesome; the availability of control stations within the scanning range is not always possible. Also, field procedure can be laborious and involve extra equipment and target setups. In addition, the conventional method allows for possible human error due to target information bookkeeping. Additionally, the accuracy of this procedure varies according to the quality of the control used. By adding a dual GPS antenna apparatus to the scanner setup, thereby supplanting the use of multiple ground control points scattered throughout the scanning site, we mitigate not only the problems associated with indirect georeferencing but also induce a more efficient set up procedure while maintaining sufficient precision. In this paper, we describe a new method for determining the 3D absolute orientation of LiDAR point cloud using GPS measurements from two antennae firmly mounted on the optical head of a stationary LiDAR system. In this paper, the general case is derived where the orientation angles are not small; this case completes the theory of stationary LiDAR direct georeferencing. Simulation and real world field experimentation of the prototype implementation suggest a precision of about 0.05 degrees (~1 milli-radian) for the three orientation angles.
Field Measurements and Guidelines for the Application of Wireless Sensor Networks to the Environment and Security
Authors: Jiménez Víctor P. Gil , Armada Ana García
Published: December 2009

Frequently, Wireless Sensor Networks (WSN) are designed focusing on applications and omitting transmission problems in these wireless networks. In this paper, we present a measurement campaign that has been carried out using one of the most commonly used WSN platforms, the micaZ from Crossbow© . Based on these measurements, some guidelines to deploy a robust and reliable WSN are provided. The results are focused on security and environmental applications but can also be extrapolated to other scenarios. A main conclusion that can be extracted is that, from the transmission point of view, a dense WSN is one of the best choices to overcome many of the transmission problems such as the existence of a transitional region, redundance, forwarding, obstructions or interference with other systems.
Nanoreactors
Authors: Ostafin Agnes , Chen Yen‐Chi
Published: December 2009

Smaller, highly parallel chemical processing using nanosized reactors, or nanoreactors, is an emerging trend. The advantages of using nanoreactors includes improved control over reaction processes and yields, enhanced safety, versatility and cost effectiveness. Understanding chemical reactions inside nanoreactors requires a re‐examination of the basic assumption of reaction mechanisms and an awareness of how the nanoreactor itself alters the normal reaction outcome by virtue of thermodynamic and interfacial effects. This article outlines the basic reasons why nanoreactors are of interest in science and technology and reviews a few of the major classes of materials that are used as nanoreactors.
Effect of stereoregularity of polypropylene on flow instability in capillary extrusion
Authors: Suzuki Makoto , Ali Mohd Amran Md , Okamoto Kenzo , Taniike Toshiaki , Terano Minoru , Yamaguchi Masayuki
Published: December 2009

Rheological responses in capillary flow extrusion for syndiotactic polypropylene (sPP) are studied along with the linear viscoelastic properties. It is found that sPP produced by a metallocene catalyst shows a high level of the onset shear stress for flow instability as compared with conventional isotactic polypropylene. This should enable operation of extrusion processing at high output rates. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:185–191, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20159
Analysis of a pressure‐driven folding flow microreactor with nearly plug‐flow characteristics
Authors: Vikhansky A. , Macinnes J. M.
Published: December 2009

We discuss the possibility of designing a pressure‐driven single‐phase microreactor with characteristics similar to that in an ideal plug‐flow reactor. We consider equations for the moments of the residence time distribution and investigate the behavior of the solution in long spatially‐periodic channels. If the microreactor consists of a large number of folding flow elements, the chaotic advection plays a double role: it mixes the chemical species and suppresses the axial dispersion. It is shown using analytical estimates and numerical modeling that chemical reactions have different sensitivity to the axial dispersion and for some reactions the effect of dispersion can be successfully eliminated. © 2009 American Institute of Chemical Engineers AIChE J, 2010
Frustrierte Lewis‐Paare: metallfreie Wasserstoffaktivierung und mehr
Authors: Stephan Douglas W. , Erker Gerhard
Published: December 2009

Die Kombination sterisch gehinderter Lewis‐Säuren und ‐Basen führt nicht zur üblichen Neutralisationsreaktion unter Bildung der “klassischen” Lewis‐Säure/Base‐Addukte. Stattdessen stehen die Lewis‐Acidität und ‐Basizität solcher “frustrierten Lewis‐Paare” (FLPs) gemeinsam für die Durchführung ungewöhnlicher Reaktionen zur Verfügung. Typische Beispiele für FLPs bestehen aus inter‐ und intramolekularen Kombinationen sperriger Phosphine und Amine mit stark elektrophilen RB(C6F5)2‐Komponenten. Viele frustrierte Lewis‐Paare sind in der Lage, Wasserstoff heterolytisch zu spalten. Die resultierenden H+/H−‐Paare (z. B. stabilisiert in Form der entsprechenden Phosphonium‐Kation/Hydridoborat‐Anion‐Salze) fungieren als metallfreie Katalysatoren für die Hydrierung sperriger Imine, Enamine, Enolether usw. FLPs reagieren auch mit Alkenen, Carbonylverbindungen und einer Vielzahl anderer kleiner Moleküle, darunter auch Kohlendioxid, in vermutlich kooperativen Dreikomponentenreaktionen. Auf dieser Beobachtung lassen sich neue Synthesestrategien aufbauen.
A pharmacogenetic study of escitalopram in autism spectrum disorders
Authors: Owley Thomas , Brune Camille W. , Salt Jeff , Walton Laura , Guter Steve , Ayuyao Nelson , Gibbons Robert D. , Leventhal Bennett L. , Cook Edwin H.
Published: December 2009

Objective: To determine the effect of serotonin transporter polymorphism promoter region (5‐HTTPLR) genotypic variation (low, intermediate, and high expression groups) on response to escitalopram treatment of children and adolescents with autism spectrum disorders (ASDs). Method: The study used a forced titration, open label design, with genotype blind until study completion. Participants were children and adolescents aged 4–17 years of age with a confirmed ASD (autistic disorder, Asperger's disorder, or pervasive developmental disorder, not otherwise specified). Results: There was an interaction between genotype group and time on the Aberrant Behavior Checklist (ABC) Irritability Subscale (primary outcome variable) (linear maximum marginal likelihood estimation=−4.84, Z=−2.89, SE=1.67, P=0.004). Examination of baseline to last visit revealed that a genotype grouping based on a previous study of platelet 5‐HT uptake revealed less response in the genotype group that had S/S genotype for 5‐HTTLPR and did not have a diplotype in intron 1 previously shown to be associated with increased platelet 5‐HT uptake. Conclusion: This genotype‐blind, prospective pharmacogenetic study found the group of subjects with associated with the lowest platelet 5‐HT uptake from previous study had the smallest reduction in ABC‐Irritability scores after open label treatment with escitalopram. Replication is necessary to confirm these findings.