Simulation of surfactant based enhanced oil recovery

Surfactant flooding is an important process for enhanced oil recovery. A substantial amount of remaining oil resides in reservoirs especially in carbonate oil reservoirs that have low primary and water-flood oil recovery. Most of the surfactant flooding studies to date has been performed in water-wet sandstone reservoirs. As a result, the effects of heterogeneity and wettability of carbonates on surfactant flooding efficiency are fairly unknown. The purpose of this simulation study was to determine the effects of wettability and wettability alteration on Dodecylbenzene Sulfonate surfactant flooding in carbonate reservoirs. This study used the multi-phase, multi-component, surfactant flooding simulator called UTCHEM. The base case results showed that additional 27.8% of oil recovered after water-flooding process. Sensitivity analyses of key parameters such as chemical slug size and concentrations, salinity, reservoir heterogeneity and surfactant adsorption were performed to optimize a surfactant design for a mixed-wet dolomite reservoir. The study was then extended to simulating wettability alteration during the field scale surfactant flood. The results of modeling the wettability alteration showed that significant differences in injectivity and oil recovery are caused by the changes in the mobility of the injected fluid. As the use of surfactant flooding spreads into the reservoir especially oil-wet and mixed-wet reservoirs, the importance of surfactant-based wettability alteration will become important

Clinicopathologic Features and Treatment Outcomes in Differentiated Thyroid Carcinoma Patients with Concurrent Graves' Disease

The clinical behaviors and treatment outcomes of thyroid carcinomas in patients with Graves' disease is a matter of controversy. This study aimed to identify the clinicopathologic features, treatment outcome, and the indicators for predicting recurrence, and to suggest the optimal extent of surgery in these patients. We retrospectively analyzed data of 58 patients who underwent surgical treatment for differentiated thyroid cancer and concurrent Graves' disease. The follow-up period ranged from 23 to 260 months (mean±standard devuation, 116.8±54.0). In our series, the mean age was 40.8±12.7 yr (range, 15-70), with a male-to-female ratio of 1:6.25. The mean tumor size was 13±9 mm (range, 3-62). The surgical methods included 19 cases of total thyroidectomy, 38 cases of subtotal thyroidectomy, and 1 case of completion total thyroidectomy. Locoregional recurrence occurred in four patients (6.9%). The 10-yr overall survival and disease-free survival of patients were 95.8% and 91.1%, respectively. Age over 45 yr (p=0.031), tumor size over 10 mm (p=0.049), multiplicity (p=0.007), extracapsular invasion (p=0.021), and clinical cancer (p=0.035) were significantly more prevalent in patients with locoregional recurrence than in those without recurrence. We recommend that Graves' disease patients should undergo regular ultrasonography screening for early detection of thyroid carcinoma. We also suggest that the choice of extent of surgery should depend on the diagnostic timing (clinical or incidental) and factors for predicting recurrence

Assessment of the Type D Personality Construct in the Korean Population: A Validation Study of the Korean DS14

This study aimed to develop a Korean version of the Type D Personality Scale-14 (DS14) and evaluate the psychiatric symptomatology of Korean cardiac patients with Type D personality. Healthy control (n = 954), patients with a coronary heart disease (n = 111) and patients with hypertension and no heart disease (n = 292) were recruited. All three groups completed DS14, the Eysenck Personality Questionnaire (EPQ), the state subscale of Spielberger State and Trait Anxiety Inventory (STAI-S), the Center for Epidemiologic Studies Short Depression Scale (CESD), and the General Health Questionnaire (GHQ). The Korean DS14 was internally consistent and stable over time. 27% of the subjects were classified as Type D. Type D individuals had significantly higher mean scores on the STAI-S, CESD, and GHQ compared to non-Type D subjects in each group. The Korean DS14 was a valid and reliable tool for identifying Type D personality. The general population and cardiovascular patients with Type D personality showed higher rate of depression, anxiety and psychological distress regarding their health. Therefore, identifying Type D personality is important in clinical research and practice in chronic medical disorders, especially cardiovascular disease, in Korea

Status of Initiating Pattern of Hemodialysis: A Multi-center Study

This study was to evaluate the status of initiating pattern of hemodialysis (HD). Five hundred-three patients in 8 University Hospitals were included. Presentation mode (planned vs. unplanned), and access type (central venous catheters [CVC] vs. permanent access) at initiation of HD were evaluated, and the influence of predialysis care on determining the mode of HD and access type was also assessed. Most patients started unplanned HD (81.9%) and the most common initial access type was CVC (86.3%). The main reason for unplanned HD and high rate of CVC use was patient-related factors such as refusal of permanent access creation and failure to attend scheduled clinic appointments. Predialysis care was performed in 57.9% of patients and only 24.1% of these patients started planned HD and 18.9% used permanent accesses initially. Only a minority of patients initiated planned HD with permanent accesses in spite of predialysis care. To overcome this, efforts to improve the quality of predialysis care are needed

Carriage of the V279F Null Allele within the Gene Encoding Lp-PLA2 Is Protective from Coronary Artery Disease in South Korean Males

The Asia-specific PLA2G7 994G-T transversion leads to V279F substitution within the lipoprotein-associated phospholipase-A2 (Lp-PLA₂) and to absence of enzyme activity in plasma. This variant offers a unique natural experiment to assess the role of Lp-PLA₂ in the pathogenesis of coronary artery disease (CAD) in humans. Given conflicting results from mostly small studies, a large two-stage case-control study was warranted.PLA2G7 V279F genotypes were initially compared in 2890 male cases diagnosed with CAD before age 60 with 3128 male controls without CAD at age 50 and above and subsequently in a second independent male dataset of 877 CAD cases and 1230 controls. In the first dataset, the prevalence of the 279F null allele was 11.5% in cases and 12.8% in controls. After adjustment for age, body mass index, diabetes, smoking, glucose and lipid levels, the OR (95% CI) for CAD for this allele was 0.80 (0.66-0.97, p = 0.02). The results were very similar in the second dataset, despite lower power, with an allele frequency of 11.2% in cases and 12.5% in controls, leading to a combined OR of 0.80 (0.69-0.92), p = 0.002. The magnitude and direction of this genetic effect were fully consistent with large epidemiological studies on plasma Lp-PLA₂ activity and CAD risk.Natural deficiency in Lp-PLA₂ activity due to carriage of PLA2G7 279F allele protects from CAD in Korean men. These results provide evidence for a causal relationship between Lp-PLA₂ and CAD, and support pharmacological inhibition of this enzyme as an innovative way to prevent CAD

Carriage of the V279F Null Allele within the Gene Encoding Lp-PLA2 Is Protective from Coronary Artery Disease in South Korean Males

The Asia-specific PLA2G7 994G-T transversion leads to V279F substitution within the lipoprotein-associated phospholipase-A2 (Lp-PLA₂) and to absence of enzyme activity in plasma. This variant offers a unique natural experiment to assess the role of Lp-PLA₂ in the pathogenesis of coronary artery disease (CAD) in humans. Given conflicting results from mostly small studies, a large two-stage case-control study was warranted.PLA2G7 V279F genotypes were initially compared in 2890 male cases diagnosed with CAD before age 60 with 3128 male controls without CAD at age 50 and above and subsequently in a second independent male dataset of 877 CAD cases and 1230 controls. In the first dataset, the prevalence of the 279F null allele was 11.5% in cases and 12.8% in controls. After adjustment for age, body mass index, diabetes, smoking, glucose and lipid levels, the OR (95% CI) for CAD for this allele was 0.80 (0.66-0.97, p = 0.02). The results were very similar in the second dataset, despite lower power, with an allele frequency of 11.2% in cases and 12.5% in controls, leading to a combined OR of 0.80 (0.69-0.92), p = 0.002. The magnitude and direction of this genetic effect were fully consistent with large epidemiological studies on plasma Lp-PLA₂ activity and CAD risk.Natural deficiency in Lp-PLA₂ activity due to carriage of PLA2G7 279F allele protects from CAD in Korean men. These results provide evidence for a causal relationship between Lp-PLA₂ and CAD, and support pharmacological inhibition of this enzyme as an innovative way to prevent CAD

Intermediate storage and operation of periodic processes

Intermediate storage has an important role in improving the operating efficiency and reducing the capital cost of batch/semicontinuous processes by decoupling the operation of the adjacent trains. In addition, intermediate storage can mitigate the effects of process parameter variations, such as recipe inaccuracies and operator errors, to which batch operations are particularly susceptible. Viewed over a longer operating horizon, process variations must include not only short term parameter variations but also larger scale processing disruptions such as failure of batches of material in meeting product specifications and failures of the equipment items themselves. In this role too, intermediate storage can be useful by providing a buffer which can allow the properly functioning process trains to proceed with minimum disruption until the failed process components are restored. In this thesis, relations were developed for determining the storage requirements for the building block 1-1 system. Analytical expressions were obtained for the required limiting volume of intermediate storage as a function of the frequency of failure. For equipment failure, the analysis is developed in three parts. First, the 1-1 system is considered in which the upstream equipment is susceptible to failure while the downstream equipment is not. Then results for the converse case are developed, namely, reliable upstream unit and unreliable downstream system. Finally, these results were extended to treat the more usual case involving both types of failure. Next, the effects of variations of the failure occurrence frequency about its mean as well as of the duration of the time period before the resumption of normal production were considered. For the 1-1 case it is possible to develop analytical predictive relations for two cases: the case in which the variations are uniformly distributed over specified intervals and the case in which the variations are normally distributed with given mean and variance. In both cases, the design will be dependent on the desired confidence level for uninterrupted operation. From the above analysis, a dynamic operating policy was proposed which allowed the storage size to be selected less conservatively by exploiting the partial control of storage accumulation afforded by the adjustment in the processing rate of the up- or downstream unit. It was shown that for the same confidence level, the dynamic policy allows operation with a considerably decreased storage volume. Finally extensions of this policy to accommodate general serial process networks were studied. The results are illustrated with suitable examples

Potential of Polysorbate20 surfactant for enhanced oil recovery

Surfactant for enhanced oil recovery (EOR) has been applied for many years, particularly in the 1970's and 1980's when the technology was put on a sound scientific basis. Unfortunately, the economic reality of the process performance in field trials has precluded widespread deployment of this technology. Many surfactants have been evaluated for their ability to recover incremental oil and this study is focusing on Polysorbate20 as a candidate for this EOR application. This laboratory study aims to determine the characteristics of Polysorbate20 surfactant, in particular for its capabilities to create low interfacial tensions (IFT) with n-alkane hydrocarbons. Certain formulated surfactant and cosolvent exhibit low interfacial tension (IFT) values of 0.01 dyne/cm or less versus n-octane. This surfactant was tested for EOR using coreflood tests on Berea sandstones. Laboratory tests had confirmed that the useful property which is to reduce the IFT by using Polysorbate20 formulations can be largely independent of both salinity and temperature. Preliminary studies also suggest Polysorbate20 has only modest adsorption between 0.10 to 0.11 mg/g onto crushed sandstone and between 15.33 to 17.62 mg/g onto kaolinite clay

Pyrolysis of eucalyptus wood in a fluidized-bed reactor

Eucalyptus wood can be utilized as a biomass feedstock for conversion to bio-oil using a pyrolysis process. Eucalyptus wood samples were initially pyrolyzed on a laboratory-scale pyrolysis system at different values in the ranges of 300-800 °C and 0.050-0.300 L min-1 to determine the effects of operation temperature and N2 flow rate, respectively, on the yields of products. Then, the bio-oil in the highest yield (wB = 44.37 %), which was obtained at pyrolysis final temperature (450 °C), heating rate (35 °C min-1), particle size (850 lm), and sweeping flow rate (0.200 L min-1), was characterized by Fourier transform infra-red spectroscopy, gas chromatography/mass spectrometry and column chromatography. Subsequently, it was shown that the operating temperature and N2 gas flow rate parameters affected the product yields. Also, some important physico-chemical properties of the pyrolytic oil obtained in high yield were determined as a calorific value of 37.85 MJ kg-1, an empirical formula of CH1.651O0.105N0.042S 0.001, a rich chemical content containing many different chemical groups, a density of 981.48 kg m-3, and a viscosity of 61.24 mm 2 s-1. Based on the determined properties of the pyrolytic oil, it was concluded that the use of pyrolytic oil derived from Eucalyptus wood may be useful for the production of alternative liquid fuels and fine chemicals after the necessary improvements