bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prevalence and factors associated with irritable bowel syndrome among medical students of Karachi, Pakistan: A cross-sectional study
Authors: Naeem Syed Saad , Siddiqui Efaza Umar , Kazi Abdul Nafey , Memon Akhtar Amin , Khan Sumaiya Tauseeq , Ahmed Bilal 
Published: June 2012

Abstract

Background
Irritable bowel syndrome (IBS) and its association with stress, has not been studied among university students in Pakistan. We investigated the prevalence and the pattern of anxiety related IBS symptoms among medical students of Karachi.

Findings
An observational case–control study was carried out at three medical colleges of Karachi, Pakistan. Random sampling was done on 360 medical students. Data was collected using validated tools “Rome III Criteria” and “Generalized Anxiety Disorder Questionnaire”. Participants with IBS were diagnosed on the criteria having experienced abdominal discomfort at least 2–3 days/month associated with high level of anxiety. The apparent prevalence of IBS was found to be 28.3%, with a predominance of 87 (85.29%) females (85.29%) over males (14.71%). The psychological symptoms of anxiety were encountered in 57 (55.8%) participants with IBS, among which males were 15.7% and females 84.2% respectively.

Conclusion
Students who more frequently suffer with mental stress and anxiety are more associated with IBS.
Effects of indole on drug resistance and virulence of Salmonella enterica serovar Typhimurium revealed by genome-wide analyses
Authors: Nikaido Eiji , Giraud Etienne , Baucheron Sylvie , Yamasaki Suguru , Wiedemann Agnès , Okamoto Kousuke , Takagi Tatsuya , Yamaguchi Akihito , Cloeckaert Axel , Nishino Kunihiko 
Published: June 2012

Abstract

Background
Many Gram-positive and Gram-negative bacteria produce large quantities of indole as an intercellular signal in microbial communities. Indole demonstrated to affect gene expression in Escherichia coli as an intra-species signaling molecule. In contrast to E. coli, Salmonella does not produce indole because it does not harbor tnaA, which encodes the enzyme responsible for tryptophan metabolism. Our previous study demonstrated that E. coli-conditioned medium and indole induce expression of the AcrAB multidrug efflux pump in Salmonella enterica serovar Typhimurium for inter-species communication; however, the global effect of indole on genes in Salmonella remains unknown.

Results
To understand the complete picture of genes regulated by indole, we performed DNA microarray analysis of genes in the S. enterica serovar Typhimurium strain ATCC 14028s affected by indole. Predicted Salmonella phenotypes affected by indole based on the microarray data were also examined in this study. Indole induced expression of genes related to efflux-mediated multidrug resistance, including ramA and acrAB, and repressed those related to host cell invasion encoded in the Salmonella pathogenicity island 1, and flagella production. Reduction of invasive activity and motility of Salmonella by indole was also observed phenotypically.

Conclusion
Our results suggest that indole is an important signaling molecule for inter-species communication to control drug resistance and virulence of S. enterica.
ERAP1 genetic variations associated with HLA-B27 interaction and disease severity of syndesmophytes formation in Taiwanese ankylosing spondylitis
Authors: Wang Chin-Man , Ho Huei-Huang , Chang Su-Wei , Wu Yeong-Jian Jan , Lin Jing-Chi , Chang Pi-Yueh , Wu Jianming , Chen Ji-Yih 
Published: June 2012

Abstract
Introduction
Ankylosing spondylitis (AS) is a familial, heritable disease specified by syndesmophyte formation leading to an ankylosed spine. Endoplasmic reticulum aminopeptidase 1 (ERAP1) genetic variations have been widely proved to be associated with AS in several ethnic populations. The aim of this study was to investigate whether ERAP1 single nucleotide polymorphisms (SNPs) are associated with AS susceptibility and disease severity in Taiwanese.

Methods
Four ERAP1 SNPs (rs27037, rs27980, rs27044 and rs30187) were genotyped in 797 Taiwanese AS patients and 1,150 healthy controls. Distributions of genotype and alleles were compared between AS patients and healthy controls, and among AS patients stratified by clinical parameters.

Results
The SNP rs27037T allele appeared to be a risk factor for AS susceptibility (P = 5.5 × 10-5, OR 1.30, 95% CI: 1.15 to 1.48; GT+TT vs. GG P = 9.3 × 10-5, OR 1.49, 95% CI: 1.22 to 1.82). In addition, the coding SNP (cSNP) rs27044G allele (P = 1.5 × 10-4, OR 1.28, 95% CI: 1.13 to 1.46; CG+GG vs. CC, P = 1.7 × 10-3, OR 1.44, 95% CI: 1.15 to 1.81) and the cSNP rs30187T allele (P = 1.7 × 10-3, OR 1.23, 95% CI: 1.08 to 1.40; CT+TT vs. CC P = 6.1 × 10-3, OR 1.38, 95% CI: 1.10 to 1.74) were predisposing factors for AS. Notably, the rs27044G allele carriers (CG+GG vs. CC, P = 0.015, OR 1.59, 95% CI: 1.33 to 2.30) and rs30187T allele carriers (CT+TT vs. CC, P = 0.011, OR 1.63, 95% CI: 1.12 to 2.38) were susceptible to syndesmophyte formation in AS patients. Furthermore, two cSNPs (rs27044 and rs30187) strongly associated with HLA-B27 positivity in AS patients. Finally, the ERAP1 SNP haplotype TCG (rs27037T/rs27980C/rs27044G) is a major risk factor for AS (adjusted P <0.00001, OR 1.38, 95% CI: 1.12 to 1.58) in Taiwanese.

Conclusions
This study provides the first evidence of ERAP1 SNPs involving syndesmophyte formation. The interactions between ERAP1 SNPs and HLA-B27 play critical roles in pMHC I pathway processing contributing to the pathogenesis of AS in multiple populations.
Determining Gas Flow Rate and Formation Thermal Conductivity from Pressure and Temperature Profiles in Vertical Well
Authors: Barrett E. , Abbasy I. , Wu C. R. , You Z. , Bedrikovetsky P. 
Published: June 2012

Abstract
The gas flow rate and the formation thermal conductivity distributions along the gas well have been determined from the measured pressure and temperature profiles using production logging tools, which is much cheaper and more precise than the traditional procedures of direct flow metering. An effective and robust method is proposed in this work: the system of governing equations for non-isothermal gas flow in vertical well is solved using the Runge-Kutta method; then the flow rate and formation thermal conductivity are obtained by optimising the modelled profiles of pressure and temperature based on the measured profiles. Application of the algorithm to field case shows good agreement between the directly measured and modelled pressure and temperature profiles; the flow rate prediction is consistent with flowmeter (PLT) data; the thermal conductivity profile is also in a good agreement with that obtained from lithology log. It validates the proposed method.
GPU-based Parallel Reservoir Simulation for Large-scale Simulation Problems
Authors: Yu Song , Liu Hui , Chen Zhangxin John , Hsieh Ben , Shao Lei 
Published: June 2012

Abstract
Reservoir simulation for a full field heterogeneous model with millions of grid blocks demands significant computational time so improving the computational efficiency becomes crucial in designing a reservoir simulator. Graphics Processing Unit (GPU), a new high-profile parallel processor with hundreds of microprocessors, stands out in parallel simulation because of its efficient power utilization and high computational efficiency. Also, its cost is relatively low, making large-scale parallel reservoir simulation possible for most of desktop users.
In this paper several GPU-based parallel preconditoners, in conjunction with a new GPU-based GMRES algorithm, are proposed and coupled with an in-house black-oil simulator to speedup reservoir simulation. In particular, massively parallel ILU preconditioners (ILU(0), ILUT, block ILU(0), block ILUT), which are usually regarded as data dependence and highly sequential preconditioners, are developed on GPUs.
In the numerical experiments performed, the SPE 10 problem, a 3D heterogeneous benchmark model with over one million grid blocks, is selected to test the speedup of our GPU solver and preconditioners. On the state-of-the-art CPU and GPU platform, the new GPU implementation can achieve a speedup of over eight times in solving linear systems arising from this SPE 10 problem compared with the CPU based serial solver. Moreover, our GPU solver is successfully coupled with the in-house black-oil simulator to test the performance of the whole parallel simulation process, with a speedup of about six times. The excellent speedup and accurate results demonstrate that the GPU-based parallel linear solver and preconditioners have the great potential in parallel reservoir simulation.
Challenges in High Performance Computing for Reservoir Simulation
Authors: Hayder Ehtesham M , Baddourah Majdi 
Published: June 2012

Abstract
High resolution reservoir modeling is necessary to analyze complex flow phenomena in reservoirs. As more powerful computing platforms become available, reservoir simulation engineers are building larger and higher resolution reservoir models to study giant fields. Large number of simulations is necessary to validate the model and to lower uncertainty in prediction results. It is a challenge to accurately model complex processes in the reservoir and also efficiently solve high resolution giant reservoir models on rapidly evolving hardware and software platforms. There are many challenges to get high performance in reservoir simulations on constantly evolving computing platforms. There are constraints which limit performance of large scale reservoir simulation. In this study, we review some of these constraints and show their effects on practical reservoir simulation. We review emerging computing platforms and highlight opportunities and challenges for reservoir simulation on those platforms. It is anticipated that management of data locality by the simulator will become very important on emerging computing platforms and there will be needs to manage locality to achieve good performance. Heterogeneity in the computing platform will make it difficult to get good performance without adoption of a hybrid parallelization style in the simulator. In this study, we analyze many benchmark results to illustrate challenges in high performance computations of reservoir simulation on current and emerging computing platforms.
Risk Evaluation Technique for Tubing-Conveyed Perforating
Authors: Baumann Carlos , Dutertre Antoine , Martin Andy , Williams Harvey 
Published: June 2012

Abstract
This paper presents one application of a simulation tool that predicts tubing-conveyed perforating gunshock loads reliably. The tool enables completion engineers to evaluate the sensitivity of gunshock loads to changes in gun type, charge type, shot density, tubing size and length, rathole length, use of shock absorbers, and placement of packers, among others.
The simulation tool described in this paper helps engineers to identify perforating jobs that have a risk of gunshock related damage, such as bent tubing and unset packers. When predicted gunshock loads are large, changes to the perforating equipment or job execution parameters are sought to reduce gunshock loads and the associated risks.
Comparisons between predicted wellbore pressure and actual fast-gauge pressure data are available in related SPE articles. These comparisons show that predicted wellbore pressure transients are very reliable both in magnitude and time. Peak sustained pressure amplitudes at the gauges are on average within 10% of software-simulated values. For cases where shock absorbers were used, residual deformations of crushable elements correlate well with the peak axial loads predicted by the software. The software is able to simulate perforating job designs in a short time, which allows engineers to optimize perforation jobs by reducing gunshock loads and equipment costs.
The ability to predict and reduce gunshock-induced damage in perforating operations is very important because of the high value of typical wells. With the software tool described in this paper engineers can optimize perforation jobs by minimizing the risk of gunshock-related damage and the associated non-productive time (NPT).
The Adaptive Well Log Data Interpretation in Geological Modeling
Authors: Kozhevnikov D. A. , Kovalenko K. V. , Deshenenkov I. S. 
Published: June 2012

Abstract
Widespread application of 3D geological modeling in oil and gas field development practices resulted in substantiation of the transition from the traditional concept of &quot;absolute pore space?? to the concept of &quot;effective pore space??. This could be achieved with the geophysical and well logging data interpretation algorithms and procedures focused on the determination of reservoirs dynamic characteristics with high vertical resolution and based on principles of adaptability and petrophysical invariance.
The adaptive log data interpretation technology provides analytical relations between log interpretative parameters and reservoir rocks properties in the generalized form. Proposed interpretative algorithms are implemented in the geological modeling software package and combined with standard geological modeling procedures to develop the three-dimensional distribution of reservoir properties.
Adaptive petrophysical models make possible the quantitative estimation of effective porosity and effective/phase/relative permeability. Formation parameters, which characterize the content of bound water in the framework and cement, maximum total porosity and effective porosity. Dependencies between effective porosity and effective permeability are estimated according to outcomes of petrophysical modeling. Effective porosity is calculated with the interpretation of standard log data. The distribution of reservoir properties in three-dimensional space is carried out with geostatistical simulation techniques. Application of effective porosity for prediction of relative permeability and capillary pressures with log data was realized as an important task for field development design.
The test of the proposed technology is conducted on a large number of wells worldwide (Western and Eastern Siberia, Caspian region, Middle East, Alaska, etc.). Formations consist of clastic fine-grained sandstones with cement and framework complex mineral composition. Application of proposed technology in geological modeling software packages represents an innovative direction of geological information technologies. It does not require any special capital expenditure with a significant economy of forces and operational time.
Will Gas Hydrate Lying On Oceanic Floors In India Solve Its Energy Problem? A Futuristic Approach
Authors: Jha Ashutosh Kumar , Bansal Gopal , Joshi Abhishek , Sangwai Jitendra Shital 
Published: June 2012

Abstract
India with the largest gas hydrate deposits in the world have potential of being the biggest global producer of NGH (a solidified form of gas lying on oceanic floors). 1.08 trillion cubic metres of the proven conventional natural gas reserves in India is around 1700 times less than the prognosticated gas hydrate resources of 1,894 trillion cubic metres lying in the deep water regions. Even the extraction of minor fraction of this resource can be the energy hunters for decades.This paper discusses the geological and geophysical aspects of marine gas hydrate distribution in India. Through a wide literature survey authors have shown the hurdles which are imposing constraints on the wide scale extraction of natural gas from NGH. The Indian exploration strategies to identify and quantify the gas hydrates by various seismic tools (e.g. seismic reflectors coincidence with the base of the gas hydrate stability zone (BGHSZ)) with its limitations are described in lucid manner. Also, the technical advancements are presented to eliminate the mentioned limitations. Well- based extraction technology (a drilling program) is discussed for safe and economically viable production of gas from gas hydrate reservoirs.India's 7500 km of coastline having a vast fuel reserve in the form of NGH can be a next generation energy source if mature extraction technology is developed to extract the gas from gas hydrate reservoirs.
A Comparative Studies and a Sensitivity Analysis for a Heavy-Oil Reservoir in GCC Region
Authors: Alajmi Haifaa , King Peter 
Published: June 2012

Abstract
In this paper we are continuing our previous works (SPE-143142 and WHOC11-353) to investigate the best development options for a major heavy oil reservoir within the GCC region. In the early stage of this work the most applicable EOR methods were selected, and several simulation runs were conducted to find the optimal injection scenarios and rank them based on the oil recovery factor (ORF). In this paper a comparative study and a sensitivity analysis of various operational conditions and reservoir parameters were conducted in order to (1) find the optimum conditions to achieve a high RF and (2) understand the effect of reservoir heterogeneity on the reservoir performance. The investigated operational parameters are the Steam injection rate, injection swapping time and the perforation location. The investigated reservoir parameters are oil viscosity, initial water saturation, porosity and permeability. In addition to investigating these reservoir parameters, the oil price sensitivity was investigated to evaluate the financial feasibility of the selected recovery methods within a historical and forecasted oil price range.
The preliminary results show that the RF is very sensitive to the oil viscosity value and the relation between them is a nonlinear relation. The Simulation results also indicate that the increase in the porosity and permeability accelerates performance; however, the opposite is not true for the initial water saturation value. From an economic perspective, production acceleration would improve overall project economics by mitigating the negative impact of discounting on the revenue stream due to the low oil price. Economically, all successive scenarios support a successful investment at the lowest (expected) oil price; in contrast, the continuous steam and hot-water flooding development options show a high economic risk after the second year, at all oil price scenarios.
Building Trust in History Matching: The Role of Multidimensional Projection
Authors: Hajizadeh Yasin , Amorim Elisa Portes , Costa Sousa Mario 
Published: June 2012

Abstract
Assisted history matching frameworks powered by stochastic population-based sampling algorithms have been a popular choice for real-life reservoir management problems for the past decade. These methods provide an ensemble of history-matched models which can be used to quantify the uncertainty of future field performance. As a critique, population-based algorithms are generally considered black-boxes with little knowledge of their performance during history matching. In most cases, the misfit value is used as the only criteria to monitor the sampling algorithms and assess their quality.
This paper applies three recently developed multidimensional projection schemes as a novel interactive, exploratory visualization tool for gaining insights to the sampling performance of population-based algorithms and comparing multiple runs in history matching. We use Least Square Projection (LSP), Projection by Clustering (ProjClus) and Principle Component Analysis (PCA) to examine the relationship between exploration of search space and the uncertainty in predictions of reservoir production. These projection techniques provide a mapping of the high dimensional search space into a 2D space by trying to maintain the distance relationships between sampled points. The application of multidimensional projection is illustrated for history matching of the benchmark PUNQ-S3 model using ant colony, differential evolution, particle swarm and the neighbourhood algorithms.
We conclude that multi-dimensional projection algorithms are valuable diagnostic tools that should accompany assisted history matching workflows in order to evaluate their performance and compare ensembles of history-matched models. Using the projection tools, we show that misfit value - as an indicator of match quality - is not the only important factor in making reliable predictions. We demonstrate that exploration of the search space is also a critical element in the uncertainty quantification workflow which can be monitored with multidimensional projection schemes.
Pressure Transient Analysis in Multiphase Multi Layer Reservoirs with Inter Layer Communication
Authors: Nikjoo Ehsan , Hashemi Abdolnabi 
Published: June 2012

Abstract
The focus of this study is on the investigation of multiphase flow effects on the pressure transient analysis in layered reservoirs with cross flow. Virtually all studies on the subject of multiphase well test analysis have been carried out in single layer reservoirs. However, many reservoirs are found to be composed of number of layers whose characteristics are different from each other and the wells in such reservoirs may be completed and produced from more than one layer.
A novel technique is proposed based on replacing multi-phase multi-layer reservoirs with cross flow with an equivalent single phase single layer reservoir. To validate the proposed method, several reservoirs with different saturations were studied numerically and were compared with the results of the proposed model. The reservoir parameters such as phase mobilities, skin factor and average reservoir pressure are compared with actual values. It was found that reservoir parameters can be obtained accurately with the equivalent single phase single layer model. However, care should be exercised when horizontal saturation gradient is significant.
A New Approach To Fracturing And Completion Operations In The Eagle Ford Shale
Authors: Fulks Robert , Smythe Steve 
Published: June 2012

Abstract
Completions and multizone fracturing operations in the Eagle Ford Shale are complex undertakings. Effectively managing hydraulic fracturing projects becomes even more complex when multiple service providers and suppliers are required to work in a coordinated sequential fashion. By late 2009 daylight completions work in the Eagle Ford evolved into 24 hour a day operations to maximize asset availability – primarily hydraulic horsepower.
Completions were accomplished in fewer days using the 24 hour approach, but efficiencies and safety suffered. However, a select group of Eagle Ford operators were concerned with the drop in performance. These operators chose to adopt an integrated services approach where one service company provided the majority of equipment and personnel on completions jobs. This new approach achieved both fewer days per completion and high KPI efficiency (e.g. stages per day, fewer safety incidents, etc.) as well as improving communication and teamwork. An explanation of this new approach is detailed here.