bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of O2 Contamination on MMP and Core Flood Performance in Miscible and Immiscible CO2 WAG
Authors: Jiang Haifeng , Nuryaningsih Lily , Adidharma Hertanto
Published: April 2012

For a given oil and reservoir temperature, the CO2 Minimum Miscibility Pressure (MMP) is largely affected by the CO2 purity. A commonly found contamination gas in CO2 EOR is O2, the existence of which will influence the MMP and thus influence the CO2 Water Alternating Gas (WAG) performance.

Slim tube tests and core flood experiments are conducted in order to study the influence of O2 on the MMP and CO2 WAG performance. Both experiments utilize crude oil from South Slattery Field in Wyoming. The mole concentration of O2 in CO2 gas varies from 0 mol% to 5 and 10 mol% and the experimental temperature is set at 57 °C to mimic the reservoir condition. In the slim tube tests, the oil recoveries at gas breakthrough are used to interpret the MMP. All core flood experiments utilize Berea sandstone cores and synthetic brines. A pressure of 20% higher than the pure CO2 MMP is used to ensure miscible condition and a pressure of 50% of the pure CO2 MMP is used for the immiscible study. WAG is injected in the tertiary recovery mode and its parameters include a WAG ratio of 1:1, a half cycle slug size of 0.1 PV, and a total slug size of 2.0 PV. WAG performance, i.e., percent oil recovery, tertiary recovery factor, and CO2 utilization factor are determined.

Slim tube results show that the existence of O2 increases the CO2 MMP significantly. Five mol percent of O2 in CO2 gas increases its MMP by 20.88%, while 10 mol% of O2 increases it by 61.92%. Core flood results show that the existence of O2 in CO2 gas adversely influence the WAG performance. For miscible CO2 WAG flooding, the higher the O2 content, the lower the incremental recovery and tertiary recovery factor (TRF). The same results are also found in immiscible CO2 WAG with less significant effects.

Similar studies have been mainly focused on N2 and CH4, while the influence of O2 has never been experimentally investigated. This study is essential for better understanding the influence of CO2 contamination on WAG performance, which is a major concern in CO2 EOR utilizing unpurified CO2 gas sources.
ECO-GSAI "Gravity Stable Air Injection" Pilot Test, an Enhanced Oil Recovery Opportunity to be Implemented in Chichimene Field – Colombia
Authors: Ordoñez Aníbal , Trujillo Marta , Rodriguez Edwin , Belgrave John , Lobo Adriano , Fernández Fabián , Comas Juan , Bottia Hernando
Published: April 2012

In order to improve the oil production and recovery in Chichimene heavy oil field, an air injection process is planned to be implemented: GSAI (Gravity Stable Air Injection). The first step is to conduct a pilot test in the field with a startup planned for 2013. Laboratory work and analysis with analytical and numerical models indicated that the process can achieve of around 30% of additional recovery factor over primary production.

Chichimene is one of the Ecopetrol S.A heavy oil fields, located 50 km south of Villavicencio city, Meta. The field has been in production since 2002 from the T2 formation using vertical wells with conventional casing (approximately 20 wells), drilled on 40 acre spacing and without water production so far, API gravity of 10 °API and viscosity of 150 cp at reservoir conditions (185° F and 3600 psia). At such a reservoir conditions the crude has good mobility making it a good candidate for ECO-GSAI technology. A similar opportunity, but less favorable in Suplacu of Barcau (Romania), has shown improvement in the recovery factor of 9% to over 50%.

This paper presents the screening, reservoir characterization, laboratory work, numerical simulation, and other design considerations for planning and justification of the pilot.
Development of Thermally and Chemically Stable Large-Hydrophobe Alkoxy Carboxylate Surfactants
Authors: Adkins Stephanie , Arachchilage Gayani Pinnawala , Solairaj Sriram , Lu Jun , Weerasooriya Upali , Pope Gary
Published: April 2012

The Guerbet reaction produces large, branched hydrophobes through the dimerization of linear alcohols. High-performance, low-cost enhanced oil recovery (EOR) surfactants are produced by carboxylation (carboxymethylation) of large Guerbet alkoxylates. Alkoxy groups such as propylene oxide (PO) and ethylene oxide (EO) are incorporated as extenders to the Guerbet alcohol, followed by carboxylation to make the anionic surfactant. Previously, the use of low-cost Guerbet alkoxy sulfate surfactants for EOR applications at high temperatures was established by enhancing their thermal stability when the pH is maintained at 10–11. Alternative thermally and chemically stable anionic surfactant structures are highly desired, especially for application under conditions where alkali usage is prohibitive. These novel large-hydrophobe carboxylate surfactants meet this need. In addition, the Guerbet alkoxy carboxylate structure can be tailored to fit the specific EOR requirements. These surfactants are stable at elevated temperatures both with and without alkali, and furthermore they can be used in environments of high salinity and high hardness (high concentration of divalent ions). Carboxylate surfactants have been used in formulations to produce ultra-low interfacial tensions with low microemulsion viscosities for a wide variety of crude oils under a large range of reservoir conditions. A parallel paper titled "Novel Large-Hydrophobe Alkoxy Carboxylate Surfactants for Enhanced Oil Recovery" will discuss the application of these surfactants. Thus, the advent of this class of cost-effective surfactants greatly broadens the application of chemical EOR.
Novel Large-Hydrophobe Alkoxy Carboxylate Surfactants for Enhanced Oil Recovery
Authors: Lu Jun , Britton Christopher , Solairaj Sriram , Liyanage Pathma J. , Kim Do Hoon , Adkins Stephanie , Arachchilage Gayani W. , Weerasooriya Upali , Pope Gary A.
Published: April 2012

A new class of surfactants has been developed and tested for chemical enhanced oil recovery that shows excellent performance under harsh reservoir conditions. These novel Guerbet alkoxy carboxylate surfactants fulfill this need by providing large, branched hydrophobes, flexibility in the number of alkoxylate groups, and stability in both alkaline and non- alkaline environments at temperatures up to at least 120 °C. The new carboxylate surfactants perform better than previously available commercial surfactants, they can be used under harsh reservoir conditions, and they can be manufactured at a lower cost from widely available feedstocks. A formulation containing the combination of a carboxylate surfactant and a sulfonate co-surfactant resulted in a synergistic interaction that has the potential to further reduce the total chemical cost. Both ultra- low interfacial tension with the oils and a clear aqueous solution even under harsh conditions such as high salinity, high hardness and high temperature with or without alkali can be obtained using these new large-hydrophobe alkoxy carboxylate surfactants. Both sandstone and carbonate corefloods were conducted with excellent results. Formulations have been developed for both active oils (contains naturally occurring carboxylic acids) and inactive oils (oils that do not produce soap/carboxylic acid) with excellent results. The new class of surfactants is a major breakthrough that greatly increases the commercial potential of chemical enhanced oil recovery.
Optimal Injection Design Utilizing Tracer and Simulation in a Surfactant Pilot for a Fractured Carbonate Yates Field
Authors: Cheng A. M. , Kwan J. T.
Published: April 2012

Yates Field is a large, naturally fractured, carbonate reservoir in west Texas. The estimated recovery after 84 years of production since 1927 is about 35% after primary depletion, water and gas injections. Laboratory and field production data indicate that Yates is an oil-wet reservoir system. Consequently, it is expected that wettability alteration can improve Yates recovery by changing to more favorable water-wet condition. A field pilot with one injector and one producer using a new, anionic surfactant was performed in Yates to determine if the surfactant can improve oil production via lower interfacial tension and wettability alteration mechanisms. This paper shows a field case study of an integrated use of a geological model, reservoir simulator, tracer test data, and laboratory results to design a surfactant pilot in the fractured carbonate Yates Field. Reservoir simulation models were calibrated by matching the bromide tracer test results. The models were used to quantify the fracture properties and study different injection scenarios. The optimal schedule was to inject multiple cycles of a 3% surfactant, at a rate of 500 b/d for 12 hours, and then shut-in the injector for 12 hours. A total of 50,000 lb of surfactant was injected into the pilot area.
The Impact of Microemulsion Viscosity on Oil Recovery
Authors: Walker Dustin L. , Britton Christopher , Kim Do Hoon , Dufour Sophie , Weerasooriya Upali , Pope Gary A.
Published: April 2012

The physical structure of microemulsions and the degree to which ultra-low IFT is achieved is dependent on a number of parameters including the types and concentrations of surfactants, co-solvents and alkali, crude oil composition, brine composition, temperature and to a lesser extent, pressure. Modifying any one of these variables creates a microemulsion with different properties. The rheological properties of the microemulsion must be adjusted appropriately to achieve good performance under practical reservoir conditions. Two microemulsion properties of primary concern are undesirably high viscosity relative to oil viscosity and non-Newtonian behavior. The broader implications of injecting microemulsions with high viscosities or non-Newtonian behavior in the field include high surfactant retention, unsustainably high pressure gradients, reduced sweep efficiency and microemulsions that stagnate in the field due to high viscosity at low shear rates. The most common ways to reduce microemulsion viscosity are to optimize the surfactant formulation with a good co-solvent and/or by adding more branching to the surfactant hydrophobe. Adding co-solvent in appropriate concentrations makes a microemulsion much less viscous. However, co-solvents increase the cost and complexity and also tend to increase the IFT. A less conventional solution involves increasing the temperature of the injection water thereby lowering both the oil and microemulsion viscosity. This approach has been tested successfully in core floods using both surrogate and reservoir cores.
Recovery Mechanisms and Relative Permeability for Gas/Oil Systems at Near-miscible Conditions: Effects of Immobile Water Saturation, Wettability, Hysteresis and Permeability
Authors: Fatemi S. Mobeen , Sohrabi Mehran , Jamiolahmady Mahmoud , Ireland Shaun
Published: April 2012

Near-miscible gas injection represents a number of processes of great importance to reservoir engineers including hydrocarbon gas injection and CO2 flood. Very little experimental data is available in the literature on displacements involving very low-IFT (interfacial tension). In this paper, we present the results of a series of two-phase and three-phase gas injection (drainage) and oil injection (imbibition) core flood experiments for an gas/oil system at near-miscible (IFT= 0.04 mN.m‒1) conditions. Two different cores; a high-permeability (1000 mD) and a lower permeability (65 mD) core were used in the experiments and both water-wet and mixed-wet conditions were examined.

The results show that despite a very low gas-oil IFT, there is significant hysteresis between the imbibition and drainage oil and gas relative permeabilities (kr) curves in the 65mD core. Hysteresis was less for 1000mD core (compared to the 65 mD core) but it still could not be ignored. Near-miscible kr hysteresis was significant for both water-wet and mixed-wet systems. Presence of immobile water in the water-wet cores improved oil relative permeabilities but reduced gas relative permeabilities in both imbibition and drainage directions. As a result, oil recovery for gas injection experiments improved when the rock contained immobile water. Both oil and gas relative permeabilities reduced when the rock wettability was altered to mixed wet from water wet and as a result, oil recovery by gas injection in the mixed-wet rock was less than that obtained under water-wet conditions. We offer explanations for these observations based on our understanding of the pore-scale interactions and mechanisms, the distribution of fluid phases and their spreading bahaviour.

The results help us better understand the impact of some of the important parameters pertinent to kr and its hysteresis especially in very low IFT gas-oil systems and mixed-wet rocks. Understanding these effects and behavior is important for improved prediction of the performance of gas injection and water-alternating gas (WAG) injection in oil reservoirs.
Pore-Scale Modelling of Water Flooding in Mixed-Wet Rock Images: Effects of Initial Saturation and Wettability
Authors: Zhou Y. , Helland J. O. , Hatzignatiou D. G.
Published: April 2012

We simulate transient behaviour of viscous- and capillary-dominated water invasion at mixed-wet conditions directly in SEM images of Bentheim sandstone by treating the pore spaces as cross-sections of straight tubes. Initial conditions are established by drainage and wettability alteration. Constant rate or differential pressure is imposed between tube inlet and outlet. The phase pressures vary with positions along the tube length but remain unique in each cross-section, consistent with one-dimensional core-scale models. This leads to a nonlinear system of equations that are solved for the interface positions as a function of time. The cross-sectional fluid configurations are computed accurately at any capillary pressure and wetting condition by combining free energy minimisation with a menisci-determining procedure that identifies the intersections of two circles moving in opposite directions along the pore boundary. Circle rotation at pinned contact lines accounts for mixed-wet conditions. The fluid conductances are estimated by new explicit expressions that are shown to be in agreement with numerical computations performed directly in the cross-sectional fluid configurations.

An SEM image of Bentheim sandstone is taken as input to the developed model for simulating the evolution of saturation profiles during water floods for different flow rates and several mixed-wet conditions, which are established with different initial water saturations and contact angles. It is demonstrated that the simulated saturation profiles depend strongly on initial water saturation at mixed-wet conditions. The saturation profiles exhibit increasingly gradual behaviour in time as the contact angle, defined on the oil-wet solid surfaces, increases or the initial water saturation decreases. Front menisci associated with positive capillary pressures promote oil displacement by water, whereas for large and negative capillary pressures at small flow rates oil displaces water because the associated front menisci retract. This results in the development of pronounced gradual saturation fronts at mixed-wet conditions. The water floods simulated at conditions established with a large initial water saturation and small contact angle on the oil-wet solid surfaces, exhibit steep Buckley-Leverett saturation profiles for high flow rates because the capillary pressure is small and less important. The shape of the saturation profiles are interpreted based on the simulated capillary pressure curves and the corresponding fluid configurations occurring in the rock image.
The Design and Execution of an Alkaline-Surfactant-Polymer Pilot Test
Authors: Sharma A. , Azizi-Yarand A. , Clayton B. , Baker G. , McKinney P. , Britton C. , Delshad M. , Pope G.
Published: April 2012

A tertiary Alkaline-Surfactant-Polymer pilot flood was implemented during 2010 in the Illinois Basin of the United States and is continuing at this time. With initial discovery of the Bridgeport Sandstone formation in the early 1900's and over 60 years of waterflooding, the pilot was designed to demonstrate that ASP flooding could produce significant quantities of incremental oil in order to sanction a commercial project. Laboratory experiments including corefloods were done to determine the optimal chemical formulation for the pilot and to provide essential parameters for a numerical simulation model. Polymer injectivity tests, single well chemical tracer tests and an interwell tracer test program were all done to prepare for and support a full interpretation of the pilot results. A field laboratory was run through the duration of the pilot to monitor the quality the injection and production fluids, which turned out to be critical to the success of the pilot. We present the results and interpretation of the ASP pilot to date, the challenges faced during the project, and the lessons learnt from the field perspective.
Comparison of Various Gases for Enhanced Recovery from Shale Oil Reservoirs
Authors: Hoffman B. Todd
Published: April 2012

New technology in horizontal drilling and stimulation has caused production from ultra-tight oil formations to increase rapidly over the last decade. While initial rates are high, recovery factors for these types of reservoirs are predicted to be low, around 5–10%. Unlike conventional reservoirs, water flooding does not appear to be a viable secondary option due to its low injectivity. Recent analysis has shown that gas injection may be an effective alternative.

A 4-section area of the Elm Coulee field in eastern Montana is used to study the impact of different gas injection schemes: carbon dioxide, immiscible hydrocarbon and miscible hydrocarbon. This paper examines the difference in total recovery, production rate and efficiency using a flow simulation model. Recovery efficiency is similar for both miscible hydrocarbon gases and carbon dioxide with recoveries increasing from 6% on primary production to around 20% with gas injection.

While the increased recovery is encouraging, both methods have some practical limitations. Carbon dioxide is currently unavailable in many basins, and while hydrocarbon gases are available in most oil fields, they are rarely used as injectants because they are marketable. We performed a cost-benefit analysis of selling the hydrocarbon gas versus using it to increase oil production. We assumed a $10 million investment in compression and facilities for the 4-section area, and used a $5/mscf cost for the gas and $80/stb revenue for the oil. The net present value for these criteria in this area is $68 million and the rate of return is 83%.

The value of this work is that it demonstrates that injecting gas (both immiscible and especially miscible) will appreciably increase oil recovery in very low permeability reservoirs. These types of reservoirs are becoming more prevalent, and a large prize is available to those who find ways to increase recovery from them. In the case of hydrocarbon gas, the economics appear to be favorable for current commodity prices.
Self-Sustained CAGD Combustion Front Development; Experimental and Numerical Observations
Authors: Rahnema H. , Barrufet M. A. , Mamora D.
Published: April 2012

Using horizontal wells for In-Situ combustion operation brings new advantages. Horizontal wells provide larger contact area between the formation and combustion front. Mobilized oil does not necessarily should pass through cold oil bank to be produced and this improve the overall performance of the process. Combustion Assisted Gravity Drainage (CAGD) is an integrated horizontal well air injection process for in situ recovery and upgrading of heavy oil and tar sands bitumen. Short distance air injection and direct mobilized oil production are main features of this process that lead to stable sweep and high oil recovery. These characteristics identify CAGD process as a highly potential oil recovery method.

This paper summarizes recent experimental and numerical studies of CAGD process. In-Situ combustion experiments have been carried out using a rectangular 3D combustion cell with dimensions of 0.62 m, 0.41 m and 0.15 m. Enriched air (50% O2) has been injected to create and sustain the combustion front in the model. Experimental results showed that oil displacement occurs mainly by gravity drainage. Vigorous combustion was observed at the early stages near the heel of injection well, where peak temperature of about 690 °C was recorded. Moreover, a thermal simulator was used for history matching the laboratory data, while capturing the main mechanisms. Simulation results showed very good agreement between numerical and experimental data in terms of fluid production rate, combustion temperature and produced gas composition.
Effect of Neutral Salts and Temperature on the Partitioning Coefficient of Ethyl Formate Used for Enhanced Oil Recovery Assessment
Authors: Chavez-Majluf Nabil , Shiau B. J. , Harwell Jeffrey H. , Roberts Bruce L. , Lin Zhixun , Yuill Sean
Published: April 2012

Single well chemical tracer test is a technique for measuring residual oil saturation in a reservoir. For enhanced oil recovery applications, like waterflooding and chemical flooding (polymer/surfactant), it is essential to evaluate the efficiency of the process by determining the amount of oil displaced. This is where the single well chemical tracer test plays an important role. The partitioning coefficient of chemical tracers (K), a ratio of chemical tracer concentration in crude oil to concentration in brine, is a critical parameter for designing single well chemical tracer tests. Factors such as brine salinity, crude oil composition, and the procedures for measuring the K value can directly impact this critical parameter. The effect of the above-mentioned factors and reservoir temperature on the K value is studied and discussed in this work. Crude oil and brine from Oklahoma oil fields were used in the study along with decane and mimic brine. K value measurements at 30°C, and 60°C demonstrated that the temperature effect over K is minimal. In addition, the impact of brine minerals on the hydrolysis reaction of chemical tracers is also evaluated. K value measurements using different Oklahoma oil field brines and mimic brines with TDS ranging from 10,000 mg/L to 183,000 mg/L are also determined. The results clearly show a positive correlation between the K value and TDS. It is also observed that K values of mimic brines are particularly sensitive to changes in NaCl and MgCl2, whereas equivalent changes in CaCl2 and BaCl2 concentrations impact the K value less significantly. Ongoing tests are being carried on to continue to study of the effects of more brine components as wells as the effect of the crude oil composition over K. The results from this study can significantly help improve the protocol of single well chemical tracer tests.
Improved Reservoir Characterization using Petrophysical Classifiers within Electrofacies
Authors: Teh Woan Jing , Willhite G Paul , Doveton John H.
Published: April 2012

Estimation of permeability in a reservoir is necessary for simulation of production history. In mature fields, cores are limited so estimation of permeability is usually done from permeability-porosity correlations developed from cored wells. In this paper, a methodology is presented to predict permeability from well logs. The method groups the well logs into electrofacies, which are recognized to correspond with core lithofacies. The permeability-porosity correlations in the core data are developed using petrophysical classifiers - rock fabric number, rfn for dolomite and flow zone indicator, FZI for sandstone. The rfn and FZI are calculated for the cored wells and calibrated to the well log measurements within each electrofacies. The petrophysical classifiers extract the pore connectivity information from the well logs within each electrofacies, representing similar lithology. The permeability is then calculated from the porosity, using the petrophysical classifier values. Application of the methodology is demonstrated for dolomite and sandstone intervals in the Ogallah Field, Kansas. Permeabilities obtained from this approach closely matched core measurements.
Design and Development of Aqueous Colloidal Gas Aphrons for Enhanced Oil Recovery Applications
Authors: Samuel Shivana R. , Kuru Ergun , Trivedi Japan J
Published: April 2012

The problems associated with current chemical flooding technologies are based around inadequate sweep efficiencies and unfavorable mobility ratios which leave much of the recoverable oil left untouched in the pores of the reservoir. In order to address the low sweep efficiency and unfavorable mobility ratio issues, numerous formulations of polymer and surfactant base fluids have been used for enhanced oil recovery (EOR) applications with varying degree of success. The use of Colloidal Gas Aphrons (CGA) as an alternative chemical EOR technique is investigated in this study. Colloidal Gas Aphrons (CGA) are described as micro-bubbles which are 10 to 100 microns in size with a gas containing inner core encapsulated by a thin surfactant film. Aqueous CGA fluids are comprised of water, polymer and surfactant solutions.

An experimental study was conducted to determine the optimum surfactant and polymer concentrations which would yield stable micro-bubbles. The formulations of stable micro-bubbles were analyzed in terms of rheology, bubble size distribution and time stability.

In order to determine the displacement efficiency of CGA fluid in the EOR process, flooding experiments were conducted using a 2D linear model and 3D radial model, both packed with glass beads and saturated with mineral oil. Flooding experiments were performed using a) water, b) aqueous polymer solution, c) aqueous polymer and surfactant solution mixed at low shear rate, d) CGA fluid, e) water followed by CGA fluid, and f) water followed by polymer solution. Efficiency of oil recovery using the CGA fluid was compared to that of other fluids. All experiments were repeated to ensure consistent results. Less than 3 % variation in results was observed in all cases.

Pressure drop, ultimate recovery and injected fluid retention time data were measured during the flooding experiments. In addition, time-lapse images taken at regular intervals were analyzed to study frontal displacement patterns observed in 2-D experiments.

The results indicated that the CGA fluids showed more stable frontal displacement as compared to water flooding. The cumulative oil recovery performance of CGA fluids was comparable but slightly less than that of aqueous polymer solutions. CGA fluids, however, required significantly lower injection pressure as compared to aqueous polymer solutions. The breakthrough time of CGA fluids was longer than that of any of the other fluids tested indicating that CGAs have longer retention time.

Results from preliminary experiments encourage the further investigation of colloidal gas aphrons as an alternative EOR technique. The results will also be useful in designing an EOR process as an alternate to polymer, surfactant-polymer or WAG flood with particular importance to carbon sequestration as CO2 / flue gas can also be used in micro-bubble generation in place of air.
Experimental analysis of R.C. beam strengthened with discrete glass fiber
Authors: Ata Elkareim , Moustaf Osman
Published: April 2012

The usage of discrete glass fiber with concrete provides enhancement the
ductility and deformability. This study aims at understanding and evaluating
shear behavior of discrete glass fiber concrete beams. This paper presents an
experimental investigation carried out on reinforced concrete beams with
discrete glass fiber mixed randomly with concrete, with 150x150mm cross
section. The studied parameters included stirrups spacing (50, 75, and 100
mm) and weight percent of discrete glass fiber (0.0%, 0.75%, and 1.5%).
Experimental results indicated that the shear strength of beams was
significantly enhanced. Although, the number of cracks increased as a result
of using discrete fiber, they became finer. Moreover, the crack propagation
and its modes may be changed by using discrete fiber. The discrete glass
fiber increases ductility and prevents sudden failure due to shear.
Seismic hazard in the design of oil and gas pipelines
Authors: Zdravkovic Slavko , Mladenovic Biljana , Zlatkov Dragan
Published: April 2012

Criteria that are adopted in earthquake resistant design of pipelines and gas
lines have to take into account seismic movements and seismic generated
forces that are of significantly high probability level of appearance along
the length of pipeline. A choice of criteria has to include an acceptable
level of seismic hazard, while design criteria should be calculated. Seismic
hazard is defined as a part of natural hazard and means probability of
appearance of earthquake of corresponding characteristics in certain time and
place. For design needs and calculation of influences caused by seismic
forces the most important is seismic hazard of maximal horizontal
acceleration due to ground vibration during earthquake. The methodology of
seismic hazard calculation as base for micro seismic zoning is presented in
the paper. It is shown calculation of seismic hazard of maximal horizontal
acceleration due to ground vibration that is applied for 985 points at the
territory of Republic of Serbia, based on which maps for return periods of 50
and 200 years are drawn.
Minimum weather data requirements for estimating reference evapotranspiration
Authors: Trajkovic Slavisa , Stojnic Vladimir , Gocic Milan
Published: April 2012

The International Commission for Irrigation and Drainage (ICID) and Food and
Agriculture Organization of the United Nations (FAO) have proposed using the
Penman-Monteith method as the standard method for estimating reference
evapotranspiration (ET0), and for evaluating other methods. The FAO-56
Penman-Monteith (FAO-56 PM) method requires the numerous weather data that
are not available in the most of the stations. The objectives of this study
were: first, to estimate errors that can arise if some weather data are not
available and have to be estimated; second, to compare the FAO-56 PM ET0
values computed under various levels of data availability; and third, to
determine minimum weather data requirements for estimating ET0 without
decreasing the acceptable accuracy. For this study, full weather data sets
were collected from six humid weather stations from Serbia (Southeast
Europe).The main conclusion is that the minimum and maximum air temperature
and "local default" value of wind speed are the minimum data requirements
necessary to apply the FAO-56 PM method in humid climate.
Experimental - theoretical study of axially compressed cold formed steel profiles
Authors: Besevic Miroslav , Kukaras Danijel
Published: April 2012

Analysis of axially compressed steel members made of cold formed profiles
presented in this paper was conducted through both experimental and numerical
methods. Numerical analysis was conducted by means of "PAK" finite element
software designed for nonlinear static and dynamic analysis of structures.
Results of numerical analysis included ultimate bearing capacity with
corresponding middle section force-deflection graphs and buckling curves.
Extensive experimental investigation were also concentrated on determination
of bearing capacity and buckling curves. Experiments were conducted on five
series with six specimens each for slenderness values of 50, 70, 90, 110 and
120. Compressed simply supported members were analyzed on Amsler Spherical
pin support with unique electronical equipment and software. Besides
determination of forcedeflection curves, strains were measured in 18 or 12
cross sections along the height of the members. Analysis included comparisons
with results obtained by different authors in this field recently published
in international journals. Special attention was dedicated to experiments
conducted on high strength and stainless steel members.
Application of analogous models in civil engineering
Authors: Andjelkovic Vladimir , Lazarevic Zarko , Nedovic Velimir
Published: April 2012

The paper describes the results of making the mathematical and physical
models of the authors, by using analogous methods and materials. There is the
mathematical rock mass deformability model as a base for foundation
engineering a concrete arch dam and the physical rock slope model which was
tested by loading until failure and the results were compared with the
calculation procedure. In the first example the correlation is established
between the static and the analogous dynamic in situ investigations for
creating the mathematical rock mass deformability model. In the second
example there is application of the analogous materials for the discontinuity
shearing simulation on the physical slope model. The results of the
geotechnical in situ investigations and laboratory testing carried out in the
Institute for Development of Water Resources "Jaroslav Cerni" in Belgrade
were used for making the models.
Application of solar roof shallow pool at individual residental buildings
Authors: Gavrilovic Dragan
Published: April 2012

The paper discusses the possibility of applying shallow roof pools of water
on the basis of passive solar water capture functioning as thermal batteries
and thermal "regulators" in a "hot - cold" mode with individual residential
buildings. With this application, the utilization of the existing
functionality of the building roof area would improve and open up the
possibility of achieving better overall bio-climate individual object. By
using this system, a flat roof impassable "terrace" takes on a new,
additional energy function, which proves the ability to reduce overall energy
consumption of total conventional seasonal heating and cooling consumption of
a building. Supporting of this intention, the paper gives a variant solution
of an easily prefabricated reinforced concrete roof system of shallow water
pool that works on the principle of passive solar energy capture.
Impossible Alternatives to Tom Sawyer’s Delusions in Twain and Adorno
Authors: Morris Christopher D.
Published: April 2012

Theodor Adorno’s adaptation of Tom Sawyer depicts it as a precursor to his negative dialectic, which Derrida saw as resembling deconstruction in attempting to articulate the ‘possibility of the impossible.’ The lack of any authentic alternative to Tom, the epitome of America’s delusion, is allegorized when Joe is first posited as ‘wholly other,’ then contained by the hegemonic, referential discourses of St Petersburg. Adorno similarly makes clear that Huck, like Joe, can’t resist such assimilation. This reading of Tom Sawyer is consistent with Twain’s tall tales and travel writings. Unsuccessful efforts to imagine an alternative to Tom’s world also characterize the collusive voice of Twain the narrator of Tom Sawyer.
Release of Ciprofloxacin-HCl and Dexamethasone Phosphate by Hyaluronic Acid Containing Silicone Polymers
Authors: Nguyen Darrene , Hui Alex , Weeks Andrea , Heynen Miriam , Joyce Elizabeth , Sheardown Heather , Jones Lyndon
Published: April 2012

The purpose of this study was to determine the effect of the covalent incorporation of hyaluronic acid (HA) into conventional hydrogel and hydrogels containing silicone as models for contact lens materials on the uptake and release of the fluoroquinolone antibiotic ciprofloxacin and the anti-inflammatory steroid dexamethasone phosphate. A 3 mg/mL ciprofloxacin solution (0.3% w/v) and a 1 mg/mL dexamethasone phosphate solution (0.1%) was prepared in borate buffered saline. Three hydrogel material samples (pHEMA; pHEMA TRIS; DMAA TRIS) were prepared with and without the covalent incorporation of HA of molecular weight (MW) 35 or 132 kDa. Hydrogel discs were punched from a sheet of material with a uniform diameter of 5 mm. Uptake kinetics were evaluated at room temperature by soaking the discs for 24 h. Release kinetics were evaluated by placing the drug-loaded discs in saline at 34 °C in a shaking water bath. At various time points over 6–7 days, aliquots of the release medium were assayed for drug amounts. The majority of the materials tested released sufficient drug to be clinically relevant in an ophthalmic application, reaching desired concentrations for antibiotic or anti-inflammatory activity in solution. Overall, the silicone-based hydrogels (pHEMA TRIS and DMAA TRIS), released lower amounts of drug than the conventional pHEMA material (p < 0.001). Materials with HA MW132 released more ciprofloxacin compared to materials with HA MW35 and lenses without HA (p < 0.02). Some HA-based materials were still releasing the drug after 6 days.
Difference between early clinical features of swine origin A H1N1 influenza corfirmed and not confirmed infection in Mexico
Authors: Rodríguez-Valero Monica , Prado Calleros Hector Manuel , Bravo Escobar Gerardo Arturo , Valdez Vázquez Rafael Ricardo , Figueroa Moreno Rafael , Martínez Montes Guillermo , Kawa Karasik Simón
Published: April 2012

Introduction: The Swine Origin A H1N1 Influenza Virus (SOIV) pandemic emerged in April 2009 affecting people and health-care systems worldwide. This study examined the differences among the early clinical features presented in confirmed SOIV cases, those who tested negative for SOIV infection, fatalities, and hospitalized cases. Methodology: We reviewed 1,024 initial medical records of patients presenting with acute respiratory symptoms who attended the respiratory emergency room of a general hospital in Mexico and had a confirmatory test for influenza AH1N1 by RT-PCR from April to December 2009. Results: Out of 1,024 cases, 457 (44%) were men with a mean age of 31±17 years; however, of these, SOIV confirmed cases were younger (26±8, p=0.000). SOIV infection was confirmed in 36% of the patients. Most (%?) cases presented mild infection, 20% of the patients required hospitalization, and 0.09% patients died. Asthma was more frequent in confirmed cases (p=0.028). Presence of COPD, systemic arterial hypertension, and diabetes mellitus was significant in confirmed hospitalized cases. Pulmonary rales, wheezing, and sudden symptom onset were more frequent and statistically significant in confirmed patients. Influenza-like illness was more frequent in confirmed cases (p=0.049).  Conclusions: This study presents one of the largest series of the new SOIV infection confirmed by RT-PCR reported. This infection is frequently mild and affects mainly young adults. Sudden symptoms onset, pulmonary rales, and wheezing are early features of this infection. Asthma, COPD, systemic arterial hypertension, and diabetes mellitus should be identified to identify potentially severe and fatal cases. ILI helps distinguish SOIV infection.
Susceptibility of community associated methicillin resistant Staphylococcus aureus isolated from faeces to antiseptics
Authors: Akinkunmi Ezekiel Olugbenga , Lamikanra Adebayo
Published: April 2012

Introduction: The study aimed to investigate the resistance of methicillin resistant Staphylococcus aureus (MRSA), an indicator used in hospitals but isolated from faecal samples of children in the community, to commonly used antibiotics and antiseptic agents. Methodology: S. aureus isolates were identified by phenotypic and genotypic techniques such as biochemical tests and polymerase chain reaction. Antibiotic susceptibility was investigated using the disc diffusion technique while the agar dilution method was used to determine the minimum inhibitory concentration (MIC) of antiseptics. Results: MRSA showed considerably higher resistance to other antibiotics than methicillin sensitive Staphylococcus aureus (MSSA). Twelve percent of the MSSA were susceptible to all the antibiotics studied while none of the MRSA had this property. A significant difference in susceptibility between MRSA and MSSA to the three antiseptic agents was observed as 68.8%, 75.0% and 100% of MRSA were less susceptible to benzalkonium chloride, chlorhexidine and cetrimide respectively, while 32.0%, 28.0% and 56.0% of MSSA respectively were less susceptible to these agents compared with S. aureus NCTC 6571. Overall, the MICs for the antiseptics were 2-3 times greater in the MRSA than in the MSSA (p < 0.001). Conclusion: Results show that the concentration of antiseptics used in the prevention of the transmission of infectious agents may have to be raised to cope with the possible presence of MRSA in patients coming into hospital.
Chronic hepatitis b with type I diabetes mellitus and autoimmune thyroiditis development during interferon alpha therapy
Authors: Kose Sukran , Gozaydin Ayhan , Akkoclu Gulgun , Ece Gulfem
Published: April 2012

Interferon alpha is a molecule frequently used in the treatment of chronic hepatitis B, C, and D, with immunomodulatory and antiviral activity. It is also used in some cancer types. It has been widely claimed that interferon alpha triggers autoimmunity, with its broad adverse effect profile. Here we present the case of a 29-year-old male patient with chronic hepatitis B diagnosis who developed type 1 diabetes mellitus and autoimmune thyroiditis during treatment with interferon alfa-2b. Within four months of initiation of treatment with interferon alfa-2b, the patient presented to our clinic with dry mouth, urinary frequency (8 to 10 times per day), drinking plenty of water, night time urination, and tiredness. He was admitted to the clinic when his fasting blood glucose level was detected to be high. After examinations, the patient was diagnosed with type 1 diabetes and autoimmune thyroiditis and began to receive treatment with insulin and propranolol. Fasting blood glucose levels were controlled and thyroid hormones decreased to normal levels within one month after the treatments began. For patients who will receive treatment with interferon alpha, especially those individuals with chronic hepatitis, pancreatic autoantibodies should be checked and close monitoring should be performed as there may be glucose tolerance impairment in patients with high titers. In addition, follow-up with thyroid function tests should be performed prior to and during the treatment.
Oral care practice for the ventilated patients in intensive care units: a pilot survey
Authors: Soh Kim Lam , Shariff Ghazali Sazlina , Soh Kim Geok , Abdul Raman Rosna , Sharif Abdullah Sharifah Shafinaz , Ong Swee Leong
Published: April 2012

Introduction: Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in intensive care units (ICUs).  One factor causing VAP is aspiration of oral colonisation, which may result from poor oral care practice.  Oral care using tooth brushing can prevent formulation of dental plaque that can be a reservoir for microbes causing VAP. Methodology: A cross-sectional survey was conducted among 124 nurses, using a self-administered questionnaire, to determine methods used, frequency, and attitude of nurses toward oral care provided to mechanically ventilated patients in Malaysian ICUs.  Results: Methods for oral care and their frequency of use varied between nurses even in the same unit. Cotton with forceps was used by 73.4% of the nurses. Some nurses used forceps and gauze (65%) or spatulas and gauze (36%). Toothbrushes were used by 50.8% of the nurses. Nurses in this hospital reported to have positive attitude toward providing oral care. Conclusions: The survey showed the need to have standardised oral care protocols in ICUs to improve quality of oral care provided to ventilated patients.
Occult hepatitis B in Egyptian thalassemic children
Authors: Shaker Olfat , Ahmed Amal , Abdel Satar Inas , El Ahl Hamza , Shousha Wafaa , Doss Wahid
Published: April 2012

Introduction: Thalassemia is hereditary anemia which requires lifelong transfusion as treatment, and hepatitis viral infection is one of the risks of repeated transfusions. Hepatitis B outbreaks in health-care settings are still a serious public health concern worldwide. Blood samples negative for HBsAg but positive for HBV-DNA, with or without the presence of HBV antibodies, are classified as "occult" HBV infection (OBI). This study investigated the prevalence of occult HBV infection in Egyptian thalassemic children. Methodology:  Eighty patients admitted to the Faculty of Medicine, Cairo University Hospital, were involved in this prospective study. Strict inclusion criteria were set to nullify the effect of confounding variables and further minimize selection bias. The following laboratory investigations were performed: complete blood count (CBC); serum AST and ALT; albumin; bilirubin; HBsAg; HBeAg; HBcAb; HCV-RNA; and HBV-DNA. Results: All our patients had no clinical manifestation suggestive of hepatitis. Molecular biology studies revealed positivity for HCV and HBV at 25% and 32.5% respectively. Conclusion: The estimated risk of acquiring hepatitis B and C infection in children receiving multiple blood transfusions is surprisingly high. Moreover, occult hepatitis B infection is a considerably risk.
Prevalence of keratinophilic fungi in soils of St. Kitts and Nevis
Authors: Gugnani Harish Chander , Sharma Soni , Gupta Brijinder , Gaddam Srinivas
Published: April 2012

Introduction: Information on the prevalence of keratinophilic fungi in West Indies is scanty. Occurrence of keratinophilic fungi in soils of St. Kitts and Nevis has not been investigated previously. Methodology: The prevalence of keratinophilic fungi was investigated in 108 samples of soils of varying habitats from St. Kitts and 55 such samples from Nevis by hair-baiting technique. Fungal growths appearing on the hair baits after four to eight weeks of incubation at room temperature were microscopically examined and cultured on mycological media. Cultures were identified on the basis of colonial and microscopic features. Results: Forty-nine (45%) of the samples from St. Kitts and 38 (69%) from Nevis were positive for keratinophilic fungi. Microsporum gypseum complex, a well-known geophilic dermatophyte, was the most frequently recovered species being present in 15.7%  of soils of St. Kitts and 40% of soils of Nevis. The next commonest species recovered was Chrysosporium indicum, represented by 15 (13.9%) isolates from St. Kitts and seven (12.7%) isolates from Nevis. Other infrequently isolated keratinophilic species included Chrysosporium tropicum, Chrysosporium keratinophilum, and unidentified Chrysosporium species. Conclusions: This study is the first of its kind in the islands of St. Kitts and Nevis. A high incidence of M. gypseum complex in the soil of these islands is a noteworthy finding of public health significance.