Journal articles on the topic 'HP-HT Experimente'

Introduction: The Helicobacter pylori (HP) reinfection rate seems to be higher in developing countries than in developed ones. An increased seroprevalence of HP has also been reported in patients with type 1 diabetes (T1D) and Hashimoto’s thyroiditis (HT). Mycobacterium avium subsp. paratuberculosis (MAP) has been linked to both T1D and HT. Quite a few lines of evidence indicate that autoantibodies against several epitopes belonging to human zinc transporter 8 (ZnT8) cross-recognize the homologous MAP3865c epitopes in both T1D and HT patients. HP may play a role in HT disease, most likely acting through a molecular mimicry mechanism that targets ZnT8 as reported for MAP and the two autoimmune diseases. Methodology: An enzyme-linked immunosorbent assay (ELISA) has been developed for the detection of antibodies against several epitopes deriving from HP proteins, which are highly homologous to the immunodominant ZnT8 peptides previously identified: ZnT8178–186 and ZnT8186–194. Results: None of the HP peptides tested were significantly recognized when the humoral responses of 92 HT patients and 91 healthy volunteers were analyzed. Conclusions: These findings do not support a triggering role for HP (through ZnT8 mimicking) in HT. If a molecular mimicry phenomenon is taking place, it involves a different self-antigen. Moreover, the negative outcome of the experiments performed stresses the fact that sharing stretches of sequence homology is relevant, but not enough to trigger an antibody-mediated cross-recognition.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 20136, “Research and Application of Fracture Failure Control Technology for 13Cr Tubing in HP/HT Gas Wells,” by Lei Ma, Hongtao Liu, and Hailong Geng, PetroChina, et al., prepared for the 2020 International Petroleum Technology Conference, Dhahran, Saudi Arabia, 13-15 January. The paper has not been peer reviewed. Copyright 2020 International Petroleum Technology Conference. Reproduced by permission. Super 13Cr-110 tubing used in high-pressure, high-temperature (HP/HT) gas wells in the Tarim oil field has experienced numerous failures. After a series of investigations for root-cause analysis, the conclusion was that fracture of the tubing mechanistically is categorized as stress corrosion cracking (SCC) and is closely related to the application of phosphate-based completion fluid. Further tests indicated that Super 13Cr (S13Cr) tubing specimens experienced SCC with phosphate-based completion fluids contaminated with mud and oxygen, whereas formate-based completion fluid is compatible with S13Cr tubing. At present, 55 HP/HT gas wells in the field have used formate-based completion fluid with no tubing string fracture. Introduction Compared with the Gulf of Mexico, the North Sea, the South China Sea, the Qiongqiong Basin, and various Chinese oil and gas fields, the oil pipelines in the Tarim field are among the most difficult with regard to service conditions, which are characterized by extreme operating conditions such as high pump pressure and large displacement reform. Construction and high-yield alternating loads on tubing string and joint and a harsh, corrosive environment [chloride content greater than 80 000 mg/L, carbon dioxide (CO2) partial pressure greater than 1 MPa, and the presence of fresh and residual acid] pose significant challenges to the safe service of the tubing string. In the early stages of production, S13Cr oil pipe was selected as the completion string of the HP/HT gas well in the Kuqa mountain front, but in recent years, the S13Cr-110 pipe of the HP/HT gas well in the Tarim field has been continuously fractured. Failure accidents have caused serious economic losses. In the complete paper, through lateral comparison analysis of the failed tubing and indoor simulation experiments, the cause of the tubing fracture is discovered, solution measures are initiated, and good application results are achieved. Comparative Analysis of Oil-Pipe Failures Comparative Analysis of Fracture Macroscopic Morphology. When comparing the macroscopic topographic maps of oil-pipe failures seen in six studied wells, fracture locations of three wells are located in the coupling, while fracture locations of the other three wells are located on the body. In five wells (Wells A through E), the tubing fracture is neat, indicating brittle fracture with no plastic deformation. Well F, however, has a visible longitudinal crack on the surface of the tubing, and many burrs are visible at the fracture. Comparison and Analysis of Working Conditions of Failed Tubing. Through comparative analysis, it was determined that five of the six wells have under-gone acidification. The service shaft temperature, pressure, CO2 content, and formation water salinity of the failed wells differ, but, in five of the six wells, the tubing was exposed to a phosphate-based completion fluid.

Among the microstructure defects in hexagonal graphitic boron nitride, the basal plane corrugations are of high relevance for the sp2 to sp3 phase transition under high pressures (HP) and high temperatures (HT). A microstructure model is described, which is capable of quantifying the amplitude of the basal plane corrugations on the basis of the anisotropic X-ray diffraction line broadening. It is illustrated that this model correctly reproduces the specific shape of the diffraction lines from corrugated basal planes, i.e., the characteristic splitting of the 00l peaks. The results from XRD are verified by direct observation in the transmission electron microscope with high resolution. Subsequent HP/HT experiments were performed in order to highlight the difference in the phase transition kinetics between hexagonal boron nitride samples with different amount of basal plane corrugations. The effect of these microstructure defects on the conversion rate and on the obtained synthesis product is discussed.

The high-temperature clinoenstatite (HT-CEn) is one of the important MgSiO3 pyroxene polymorph. The single-crystal of C2/c HT-CEn endmember is firstly synthesized by rapid pressure-temperature quenching from 15-16 GPa and 900-19000C [1]. No report that it is produced as single crystal or large domain has been made on the MgSiO3 endmember. The HT-CEn-type modifications are observed in Ca-poor Mg-Fe clinoenstatite and pigeonite and are always found to be unquenchable in rapid cooling. The high pressure and high temperature experiments of MgSiO3 composition were carried out with a Kawai-type multi-anvil apparatus. The samples were quenched by rapidly releasing the oil pressure load and/or by blow out of anvil cell gasket. The space group of C2/c is strictly determined by Rigaku RAPID Weissenberg photographs and synchrotron radiation. Single-crystal X-ray diffraction experiments were performed at ambient conditions using a Rigaku AFC-5 four circle diffractometer. A total of 9383 reflections was measured and averaged in Laue symmetry 2/m to give 766 independent reflections used for the structure refinements. Final reliability factors converged smoothly to R = 0.029. The single-crystal diffraction analysis shows that the unusual bonding distances frozen in this metastable structure. The degree of kinking of the silicate tetrahedral chains is 1750for HT-CEn. The chain angle for HP-CEn is substantially smaller (1350) and the angle for L-CEn turned to the opposite direction at -1600(=2000). The degree of kinking increases by being curved in more than 1800in the transition from HT-CEn to L-CEn. As for the reverse change from the expansion to the stretch, a potential barrier exists in the point of the continuity. It is suggested that the reason which can quench structure under ambient conditions is the present HT-CEn single crystal was formed by the isosymmetric phase transition from HP-CEn. HT-CEn type single-crystals cannot be frozen without pressure.

Summary Matrix acidizing improves productivity in oil and gas wells. Hydrochloric acid (HCl), because of its many advantages such as its effectiveness, availability, and low cost, has been a typical first-choice fluid for acidizing operations. However, HCl in high-pressure/high-temperature (HP/HT) wells can be problematic because of its high reactivity, resulting in face dissolution, high corrosion rates, and high corrosion inhibition costs. Several alternatives to HCl have been tested; among them, emulsified acid is a favorable choice because of its inherent low corrosion rate, deeper penetration into the reservoir, fewer asphaltene/sludge problems, and better acid distribution due to its higher viscosity. The success of the new system is dependent upon the stability of the emulsion, especially at high temperatures. The emulsified acid must be stable until it is properly placed, and it must also be compatible with other additives in an acidizing package. This study develops a stable, emulsified acid system at 300°F using aliphatic nonionic surfactants. This paper introduces a new nonaromatic, nonionic surfactant to form an emulsified acid for HP/HT wells. The type and quality of the emulsified acid were assessed through conductivity measurements and drop tests. The thermal stability of the system was monitored as a function of time through the use of pressure tubes and a preheated oil bath at 300°F. A LUMisizer® (LUM GmbH, Berlin, Germany) and Turbiscan® (Formulaction, S. A., L’Union, France) were used to determine the stability and the average droplet size of the emulsion, respectively. The viscosity of the emulsified acid was measured at different temperatures up to 300°F as a function of shear rate (1 to 1,000 s−1). The microscopy study was used to examine the shape and the distribution of acid droplets in diesel. Coreflood studies at low and high flow rates were conducted to determine the performance of the newly developed stable emulsified acid in creating wormholes in carbonate rocks. Inductively coupled plasma and computed tomography (CT) scans were used to determine the dissolved cations and wormhole propagation, respectively. Superior stimulation results with a low pore volume of acid to breakthrough (PVBT) were achieved at 300°F with the newly developed emulsified acid system. The wormhole propagation was narrow and dominant compared to branched wormholes resulting from conventional emulsified acid systems. Results indicate that a nonionic surfactant with optimal chemistry, such as a suitable hydrophobe chain length and structure, can form a stable emulsified acid. In this study we introduce a new and effective aliphatic nonionic surfactant to create a stable emulsified acid system for matrix acidizing at HP/HT conditions, leading to a deeper penetration of acid with low pore volume to breakthrough. The successful core flood studies in the laboratory using carbonate cores suggest that the new emulsified acid system may efficiently stimulate HP/HT carbonate reservoirs.

Summary The water recovered from hydraulic-fracturing operations (i.e., flowback water) is highly saline, and can be analyzed for reservoir characterization. Past studies measured ion-concentration data during imbibition experiments to explain the production of saline flowback water. However, the reported laboratory data of ion concentration are approximately three orders of magnitude lower than those reported in the field. It has been hypothesized that the significant surface area created by hydraulic-fracturing operations is one of the primary reasons for the highly saline flowback water. In this study, we investigate shale/water interactions by measuring the mass of total ion produced (TIP) during water-imbibition experiments. We conduct two sets of imbibition experiments at low-temperature/low-pressure (LT/LP) and high-temperature and high-pressure (HT/HP) conditions. We study the effects of rock surface area (As), temperature, and pressure on TIP during imbibition experiments. Laboratory results indicate that pressure does not have a significant effect on TIP, whereas increasing As and temperature both increase TIP. We use the flowback-chemical data and the laboratory data of ion concentration to estimate the fracture surface area (Af) for two wells completed in the Horn River Basin (HRB), Canada. For both wells, the estimated Af values from LT/LP and HT/HP test results have similar orders of magnitude (approximately 5.0×106 m2) compared with those calculated from production and flowback rate-transient analysis (RTA) (approximately 106 m2). The proposed scaleup procedure can be used as an alternative approach for a quick estimation of Af using early-flowback chemical data.

This article describes the preparation of a series of inclusion complexes of anhydrolycorine with three cyclodextrins (CDs), namely β-CD, γ-CD, and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), and their successful characterization through UV, TG, DSC, XRD, SEM, 1H NMR, and 2D NMR spectroscopies. The results demonstrated that the water solubility of anhydrolycorine increased notably by about 23–42 times after the inclusion complexation with these CDs. Furthermore, preliminary in vitro cytotoxicity experiments on human colon cancer cell lines HT-29, SW480, HCT116, and DLD-1 were also performed, and the complexes showed remarkable anticancer activity against HT-29, SW480, and HCT116. These results suggested that the inclusion complexes would be potentially useful for applications for human colon cancer chemotherapy.

The structure and composition of the Earth’s mantle and of the terrestrial planets are considered in the light of the new scientific approaches. These data indicate on the further structural subdivision of the Earth’s inner geospheres and of the Moon’s deep seated zones. The results of HP- and HT-experiments related with the transformation of the main mantle’s and core’s components of the Earth, Moon, gaseus giants (Jupiter and Saturn) and ice giant planets (Uranus and Neptune) reveal the new structure and property changes.

When a condensate gas reservoir with gaseous water under high temperature and high pressure condition is producing, the gaseous water and nonequilibrium effect will have great influences on the phase behavior of condensate oil and gas system and the accumulation of condensate liquid near the wellbore area. Therefore, a series of experiments were performed to investigate phase behavior of the condensate gas reservoirs with gaseous water using a PVT cell, in which the constant volume depletion process of nonequilibrium pressure drop and equilibrium pressure drop within near wellbore zone was simulated. And using the modified PR EOS, PR EOS, and nonequilibrium effect theory, the authors calculated the content of condensate oil and condensate liquid of the nonequilibrium pressure drop and equilibrium pressure drop and compared the calculated results with the experimental data. The results show that the modified PR EOS combined with nonequilibrium effect theory is more suitable for representing phase behavior characteristics of the development process of condensate gas reservoir containing gaseous water, with the average relative error of 4.49%. Furthermore, choosing the appropriate exploiting opportunity and properly increasing the nonequilibrium effect are helpful to increase condensate oil and water recovery.

Summary As exploration for oil and gas continues, it becomes necessary to produce from deeper formations, and to meet the challenge of low permeability and higher temperatures. Unconventional shale formations are addressed with slickwater fracturing fluids, owing to the shale's unique geomechanical properties. On the other hand, conventional formations require crosslinked fracturing fluids to properly enhance productivity. Guar and its derivatives have a history of success in crosslinked hydraulic–fracturing fluids. However, they require higher polymer loading to withstand higher–temperature environments. This leads to an increase in mixing time and additive requirements. Most importantly, as a result of high polymer loading, they do not break completely and thus generate residual–polymer fragments that can plug the formation and significantly reduce fracture conductivity. In this work, a new hybrid dual–polymer hydraulic–fracturing fluid was developed. The fluid consists of a guar derivative and a polyacrylamide–based synthetic polymer. Compared with conventional fracturing fluids, this new system is easily hydrated, requires fewer additives, can be mixed “on the fly,” and is capable of maintaining excellent rheological performance at low polymer loadings. The polymer mixture solutions were prepared at a total polymer concentration of 20 to 40 lbm/1,000 gal at volume ratios of 2:1, 1:1, and 1:2. The fluids were crosslinked with a metallic crosslinker and broken with an oxidizer at 300°F. Testing focused on crosslinker/polymer–ratio analysis to effectively lower loading while maintaining sufficient performance to carry proppant at this temperature. A high–pressure/high–temperature (HP/HT) rheometer was used to measure viscosity, storage modulus, and fluid–breaking performance. An HP/HT aging cell and HP/HT see–through cell were used for proppant settling. Fourier–transform infrared (FTIR) spectroscopy, Cryo scanning electron microscopy (Cryo–SEM), and an HP/HT rheometer were also used to understand the interaction. Results indicated that the dual–polymer fracturing fluid was able to generate stable viscosity at 300°F and 100 s−1 as well as generate a higher viscosity compared with the individual–polymer fracturing fluid. Also, properly understanding and tuning the crosslinker to the polymer ratio generated excellent performance at 20 lbm/1,000 gal. The two polymers formed an improved crosslinking network that enhanced proppant–carrying properties. This fluid also demonstrated a clean and controlled breaking performance with an oxidizer. Extensive experiments were pursued to evaluate the new dual–polymer system for the first time. This system exhibited a positive interaction between the polysaccharide and polyacrylamide families and generated excellent rheological properties. The major benefit of using a mixed–polymer system is reduced polymer loading. Lower loading is highly desirable because it reduces material cost, eases field operation, and potentially lowers damage to the fracture face, proppant pack, and formation.

Summary Fluid-loss control is an essential property of oil-based mud (OBM) that can affect the success of drilling operations. This paper presents an investigation of the mitigation of lost circulation in OBM by use of leakoff-control-additive gilsonite. A simple physical model was developed to describe the static-filtration process considering the formation and properties of the filter cake. Both high-pressure/high-temperature (HP/HT) American Petroleum Institute (API) press and core-flow-filtration experiments were performed to evaluate the leakoff behavior of OBM. Core-filtration experiments were carried with the aid of a computerized-tomography (CT) scanner to monitor the invasion of the filtrate into the sandstone core at time intervals. In the long time limit, the model predicts that the fluid loss follows the classical Carter equation; that is, the volume of leakoff increases as the square root of time for the static filtration through a filter paper and through the sandstone core. Dual-mode filtration diminishes the rate of fluid loss considering the effect of emulsion. The model also provides a relation between pressure drop and filtrate rate, which can be used to estimate the permeability of filter cake in the experiment. The leakoff behavior with additive observed in the experiment is well-explained by the microstructure of rapid-buildup filter cake, which is mainly responsible for the control of fluid loss. The role of different components of OBM, such as solid particles, emulsion droplets, and additives, is discussed in light of our observations.

Summary This paper presents new technology for evaluating high-pressure gas-seal integrity of polymer ring seals used as secondary or backup pressure seals in casing and tubing threaded connections. This new technology may also enable the further consideration of API connections with ring seals, as an alternative to premium connections, for appropriate applications. A nonlinear elasto-viscoplastic constitutive model for the behavior of polymers and elastomers has been developed and extended to the specific application of analysis of casing and tubing connections with fiberglass-filled polytetrafluoroethylene (PTFE) ring seals. Procedures for modeling makeup of a connection including a fiberglass-filled PTFE ring seal have been developed using a finite-element model (FEM) of 10¾-in. OD, 45.5 lb/ft, P-110 API buttress thread casing-seal ring groove (BTC-SRG). The results of finite-element analysis (FEA) of makeup, followed by the application of thermal, axial, and internal pressure loads are presented in this paper. In addition, based on the interest in the development of gas-tight threaded connections for expandable casing, the FEM was subjected to a radial expansion of a 20% increase in the outside diameter. In this paper, the theory of the constitutive model is summarized and calibration of the model with experimental test and published data are presented. The focus of the FEA results is on the contact pressures between the ring seal, coupling groove, and pin threads. Historical Perspective FEA of threaded connections has been used for overcoming challenging well-design problems for many years (Crose et al. 1976). FEA has become an important part of the validation and service evaluation process of API and proprietary casing and tubing threaded connection designs, along with the physical testing procedures documented in API RP 5C5 (1996) and ISO 13679: 2002 (2002). Major advances have been achieved in design of premium connections through analysis of metal-to-metal seal contact stresses computed from FEM (Hilbert and Kalil 1992). Analysis and verification of the performance of threaded connections that include polymeric or elastomeric ring seals has been limited to full-scale physical testing (Payne 1988). Until now, only costly full-scale gas pressure tests have been used to evaluate ring seal integrity. Ring-seal design has been a trial and error process, with new ring-seal or pin and coupling dimensions prescribed only after failure of the seal in a proof test. In some cases, ring design or the effects of ring dimensions have been based on analytical calculations, relying on the bulk modulus of the material. When more advanced design tools, such as FEA, have been used, the pressure generated by entrapment of the ring seal has been estimated and then these pressures have been applied to the groove and pin thread surfaces to simulate the effect of the actual ring seal. The developments in the paper were motivated by a need to reduce the cost of connection qualification by reducing the number of tests and to improve the process of ring-seal design. Properties of PTFE PTFE is a thermoplastic fluorocarbon derived from the monomer tetrafluoroethylene (TFE). PTFE is a semi-crystalline polymer composed of crystalline and amorphous regions. Its molecular structure, shown in Fig. 1, consists of long chains of carbon atoms symmetrically surrounded by fluorine atoms. This structure imbues PTFE with unique mechanical and chemical properties. The straight "backbone" of carbon atoms provides PTFE with a high degree of chemical inertness, stability, and one of the lowest coefficients of friction of any commonly used material. PTFE is more commonly known by the trade name Teflon. In a moment of pure serendipity, in 1938 Roy Plunckett of DuPont discovered TFE when he was conducting experiments to develop nonflammable, nontoxic, colorless, and odorless refrigerants (Ebnesajjad 2000).

Summary Effective mitigation of fluid loss and prevention of formation damage are substantial concerns during well completion and workover in low-pressure, high-permeability, and/or fractured reservoirs, especially with high temperature (HT). In this paper, a highly elastic composite gel is developed on the basis of the solution blending for “intercalated crosslinking.” The mechanism is the intercalation of polymer and crosslinker into layered silicate material (LSM) using a specific procedure. The gel is composed of HT resistant copolymer, crosslinker polyethyleneimine (PEI), LSM, and antioxidant in freshwater. The effects of main variables on the gelation performance are investigated. The mature composite gel strength is noticeably improved with increasing temperature. The elastic modulus (G′) of the mature composite gel prepared at 160°C can reach up to 15 000 Pa, while only a value of 6000 Pa is obtained for the gel at 130°C. The composite gel remains robust after aging 10 days at 160°C. The pressure-bearing capacity and rigidity of the mature composite gel are noticeably improved with increasing layered silicate concentration. This unique feature can benefit stress buffering when the sealing operation is conducted under high differential pressure such as the case with a long hydrostatic column. Scanning electron microscope (SEM) is used to further reveal the intercalated crosslinking mechanism of the composite gel. A temporary plugging experiment for a fractured limestone core also supports the gel's high-pressure (HP) resistance and low adsorption and retention to alleviate formation damage. The composite gel is promising for fluid loss mitigation that could be extended to other related near-wellbore operations in HT wells.

After the discovery of C fullerenes and C nanotubes grown in the vapor phase, the formation of carbon onions [1] in the condensed phase from the irradiation of graphitic polyhedral particles with an intense electron beam gave further evidence that spherical carbon network can be favored under high temperature and strong irradiation regimes. Recently, BN and B-C-N hybrid nanotubes were synthetized. In spite of theoretical predictions, so far there has been no experimental evidence for the stability of B-N and B-C-N analogs of buckminster fullerenes. We exposed turbostratic BC2N and turbostratic BN samples to intense electron irradiation to study the ability of the honey comb network to include non hexagonal member rings and form curved structures.In the experiments described here, the BC2N starting materials were synthesized from vapor phase reaction (CVD) of BC13 and CH3CN. Such samples were then exposed to high temperature-high pressure (HT-HP) conditions at 7.7.

Summary Molecular diffusion plays a dominant role in various reservoir processes, especially in the absence of convective mixing. In general, gas diffusion in oils depends on several factors such as pressure, temperature, oil viscosity, and gas/oil ratio (GOR). Out of these factors, the effects of GOR and live-oil-compositional changes on diffusivity are rare or not available in the literature. The current work fills this gap and presents the experimental observations on the effect of GOR on gas diffusivity in reservoir-fluid systems. Synthetic live oils were created by combining stock-tank oil (STO) and methane in various ratios. Constant-composition-expansion (CCE) experiments were performed with these oils to obtain their bubblepoints and liquid densities in relation to GOR. Methane diffusivity in these oils was obtained from pressure-decay (PD) tests at high-pressure/high-temperature (HP/HT) conditions. The diffusion and solubility parameters were estimated from PD data using the diffusion model and integral-based linear regression presented in previous work (Ratnakar and Dindoruk 2015, 2018). The experimental and modeling methodologies are presented here in sufficient detail to allow readers to replicate and evaluate the results. In this work, we experimentally investigated the effect of GOR on methane diffusivity in oils at HP/HT conditions using PD tests. In particular, We present experimental data for bubblepoints and liquid density of synthetic oils with various GOR values. For the range of GORs considered, these measurements show that the bubblepoint pressure increases linearly with GOR. Late-transient solution (LTS) of the PD model was used to obtain diffusivity parameters by regressing against experimental data. It is found that as the GOR value increases (that is, when oil becomes lighter), the diffusivity value increases, which is in accordance with the Stokes-Einstein relation. Most importantly, an empirical correlation is developed on the basis of a limited data set to describe the variation in diffusivity values with GOR. This can be important when experimental data are available for the STO but not for the live oils. It can also be extremely useful in gas-injection processes where the amount of gas dissolved in the oil varies, leading to variations in diffusivity.

Hydraulic fracturing using water-soluble polymers has been extensively used to enhance the productivity of oil and gas wells. However, the production enhancement can be significantly impaired due to polymer residue generated within the proppant pack in the created fractures. This work describes an approach to establish a suitable fracturing fluid cleanup process by characterizing broken polymer residues generated from the use of different gel breaker types. Commonly used gel breakers such as inorganic oxidizers (bromate and persulfate salts), specific enzymes, and acids were evaluated in this work. The influence of each gel breaker was examined using High-Pressure/High-Temperature (HP/HT) rheometer, aging cells, zeta potential, Gel Permeation Chromatography (GPC), and Environmental Scanning Electron Microscope/Energy Dispersive X-ray Spectroscopy (ESEM/EDS). Experiments were performed on a carboxymethylhydroxypropyl guar (CMHPG) fracturing fluid at temperatures up to 300 °F. The developed GPC methodology showed that the size of the broken polymer chains was mainly dependent on the type of gel breakers used. Moreover, laboratory tests have revealed that some gel breakers may negatively influence the performance of polymeric clay stabilizers. Additionally, this work showed damaging precipitations that can be generated due to the interactions of gel breakers with H2S.

The present study focuses on the metallurgical and corrosion characterization of post weld heat treated duplex stainless steel joints. After friction welding, it was confirmed that there is an increase in ferrite content at weld interface due to dynamic recrystallization. This caused the weldments prone to pitting corrosion attack. Hence the post weld heat treatments were performed at three temperatures 1080[Formula: see text]C, 1150[Formula: see text]C and 1200[Formula: see text]C with 15[Formula: see text]min of aging time. This was followed by water and oil quenching. The volume fraction of ferrite to austenite ratio was balanced and highest pit nucleation resistance were achieved after PWHT at 1080[Formula: see text]C followed by water quench and at 1150[Formula: see text]C followed by oil quench. This had happened exactly at parameter set containing heating pressure (HP):40 heating time (HT):4 upsetting pressure (UP):80 upsetting time (UP):2 (experiment no. 5). Dual phase presence and absence of precipitates were conformed through TEM which follow Kurdjumov–Sachs relationship. PREN of ferrite was decreasing with increase in temperature and that of austenite increased. The equilibrium temperature for water quenching was around 1100[Formula: see text]C and that for oil quenching was around 1140[Formula: see text]C. The pit depths were found to be in the range of 100[Formula: see text]nm and width of 1.5–2[Formula: see text][Formula: see text]m.

Summary Acoustic velocity is one of the key thermodynamic properties that can supplement phase behavior or pressure/volume/temperature (PVT) measurements of pure substances and mixtures. Several important fluid properties are relatively difficult to obtain through traditional measurement techniques, correlations, or equation of state (EOS) models. Acoustic measurements offer a simpler method to obtain some of these properties. In this work, we used an experimental method based on ultrasonic pulse-echo measurements in a high-pressure/high-temperature (HP/HT) cell to estimate acoustic velocity in fluid mixtures. We used this technique to estimate related key PVT parameters (such as compressibility), thereby bridging gaps in essential data. In particular, the effect of dilution with methane (CH4) and carbon dioxide (CO2) at pressures from 15 to 62 MPa and temperatures from 313 to 344 K is studied for two reservoir fluid systems to capture the effect of the gas/oil ratio (GOR) and density variations on measured viscosity and acoustic velocity. Correlative analysis of the acoustic velocity and viscosity data were then performed to develop an empirical correlation that is a function of GOR. Such a correlation can be useful for improving the interpretation of the sonic velocity response and the calibration of viscosity changes when areal fluid properties vary with GOR, especially in disequilibrium systems. In addition, under isothermal conditions, the acoustic velocity of a live oil decreases monotonically with decreasing pressure until the saturation point where the trend is reversed. This observation can also be used as a technique to estimate the saturation pressure of a live oil or as a byproduct of the target experiments. It supplements the classical pressure/volume measurements to determine the bubblepoint pressure.

Summary Carboxybetaine viscoelastic surfactants have been applied in acid diversion and fracturing treatments in which high temperatures and low pH are usually involved. These surfactants are subjected to hydrolysis under such conditions because of the existence of a peptide group (-CO-NH-) in their molecules, leading to changes in the rheological properties of the acid. The objective of this paper is to study the impact of hydrolysis at high temperatures on the apparent viscosity of carboxybetaine viscoelastic surfactant-based acids, and propose the mechanism of viscosity changes by molecular dynamics (MD) simulations. Surfactant-acid solutions with different compositions (surfactant concentration varied from 4 to 8 wt%) were incubated at 190°F for 1 to 6 hours. Solutions were then partially spent by CaCO3 until the sample pH was 4.5, and the apparent viscosity was measured using a high-temperature/high-pressure (HT/HP) viscometer. To understand the mechanism for viscosity changes on the molecular level, MD simulations were carried out on spent surfactant-acid aqueous systems using the Materials Studio 5.0 Package. It was found that short-time hydrolysis at high temperatures (for example, 1 to 2 hours at 190°F) led to a significant increase in surfactant-acid viscosity. However, after incubation for 3 hours, phase separation occurred and the acid lost its viscosity. Simulation results showed that viscosity changes of amido-carboxybetaine surfactant acid by hydrolysis at high temperatures may be caused by different micellar structures formed by carboxybetaine and fatty acid soap, its hydrolysis product. The optimum molar ratio of amido-carboxybetaine and fatty acid soap to form wormlike micelles was found to be nearly 3:1 from our simulations. Our results indicate that hydrolysis at high temperatures has a great impact on surfactant-acid rheological properties. Short time viscosity build-up and effective gel breakdown can be achieved if surfactant-acid treatments are carefully designed; otherwise, unexpected viscosity reduction and phase separation may occur, which will affect the outcome of acid treatments.

Summary Typically, water-based fracturing treatments consume a large volume of fresh water. Providing consistent freshwater sources is difficult and sometimes not feasible, especially in remote areas and offshore operations. Therefore, several seawater-based fracturing fluids have been developed in an effort to preserve freshwater resources. However, none of these fluids minimizes fracture-face skin and proppant-conductivity impairment, which can be critical for unconventional well treatments. Several experiments and design iterations were conducted to tailor raw-seawater-based fracturing fluids. These fluids were designed to have rheological properties that can transport proppant under dynamic and static conditions. The optimized seawater-based fracturing-fluid formulas were developed such that no scale forms when additives are mixed in or when the fracturing-fluid filtrate is mixed with different formation brines. The tests were conducted using a high-pressure/high-temperature (HP/HT) rheometer, coreflood, and by aging cells at 250 to 300°F. The developed seawater-based fracturing fluids were optimized with an apparent viscosity greater than 100 cp at a shear rate of 100 seconds–1 and a temperature of 300°F for more than 1 hour. The use of polymeric- and phosphonate-based scale inhibitors (SIs) prevented the formation of severe calcium sulfate (CaSO4) scale in mixtures of seawater and formation brines at 300°F. Controlling the pH of fracturing fluids prevented magnesium and calcium hydroxide precipitation that occurs at a pH value of greater than 9.5. Most importantly, SIs had a negative effect on the viscosity of seawater fracturing fluid during testing because of their negative interaction with metallic crosslinkers. The developed seawater-based fracturing fluids were applied for the first time in an unconventional and a conventional carbonate well and showed very promising results; details of field treatments are discussed in this paper.

Abstract The solids sagging in high-pressure high-temperature (HP/HT) reservoirs is a common challenge associated with hematite drilling fluids. This study provides a solution to hematite sagging in invert emulsion mud for HP/HT wells, which involves the combination of Micromax (Mn3O4) with hematite. The particles of both weighting agents were characterized to address their mineralogical features. A field formulation of the mud was used over a range of Micromax/hematite ratios (0/100, 20/80, and 30/70%) in laboratory experiments to address the sag performance and determine the optimal combination ratio. Then, density, emulsion stability, rheology, viscoelasticity, and filtration performance for the formulated mud were addressed. The tests were conditioned to 500 psi and 350 °F. The acquired results of sag tests indicated that incorporation of 30% Micromax solved the hematite sagging issue and brought the sag tendency within the recommended safe range. An insignificant reduction in mud density was observed upon the inclusion of Micromax, while the emulsion stability was obviously improved from 551 to 614 volts with the 30% Micromax mixture. The recommended 30/70% combination had almost no effect on plastic viscosity and yield point since they were increased by one unit, but the gel strength was improved resulting in flat rheology and better solids suspension capacity. The filtration behavior of the formulation with 30% Micromax was enhanced compared to pure hematite as it resulted in 10% and 14% reduction of the filtrate volume and filter-cake thickness, respectively. This study contributes to improve and economize the drilling cost and time by formulating a stabilized and distinguished-performance drilling mud using combined weighting agents at HP/HT.

Background: Reperfusion following ischemia can lead to more injuries than ischemia itself especially in diabetic patients. The aim of this study was to evaluate the effect of dexmedetomidine on ischemia-reperfusion injury (IRI) in rats with have hepatic IRI and diabetes mellitus. Methodology: Twenty-eight Wistar Albino rats were randomised into four groups as control (C), diabetic (DC), diabetic with hepatic ischemia-reperfusion injury (DIR), and diabetic but administered dexmedetomidine followed by hepatic IRI (DIRD) groups. Hepatic tissue samples were evaluated histopathologically by semiquantitative methods. Malondialdehyde (MDA), superoxide dismutase (SOD), glutathion s-transpherase (GST), and catalase (CAT) enzyme levels were investigated in liver and kidney tissues as oxidative state parameters. Results: In Group DIR; hepatocyte degeneration, sinusoidal dilatation, pycnotic nucleus, and necrotic cells were found to be more in rat hepatic tissue; while mononuclear cell infiltration was higher in the parenchyme. MDA levels were significantly lower; but SOD levels were significantly higher in Group DIRD with regard to Group DIR. In the IRI induced diabetic rats’ hepatic and nephrotic tissues MDA levels, showing oxidative injury, were found to be lower. SOD levels, showing early antioxidant activity, were higher. Conclusion: The enzymatic findings of our study together with the hepatic histopathology indicate that dexmedetomidine has a potential role to decrease IRI. Key words: Hepatic ischemia reperfusion injury; Diabetes mellitus; Dexmedetomidine; Rat; MDA; SOD Citation: Sezen SC, Işık B, Bilge M, Arslan M, Çomu FM, Öztürk L, Kesimci E, Kavutçu M. Effect of dexmedetomidine on ischemia-reperfusion injury of liver and kidney tissues in experimental diabetes and hepatic ischemia-reperfusion injury induced rats. Anaesth Pain & Intensive Care 2016;20(2):143-149 Received: 21 November 2015; Reviewed: 10, 24 December 2015, 9, 10 June 2016; Corrected: 12 December 2015; Accepted: 10 June 2016 INTRODUCTİON Perioperative acute tissue injury induced by ischemia-reperfusion is a comman clinical event caused by reduced blood supply to the tissue being compromised during major surgery. Ischemia leads to cellular injury by depleting cellular energy deposits and resulting in accumulation of toxic metabolites. The reperfusion of tissues that have remained in ischemic conditions causes even more damage.1 Furthermore hepatic ischemia-reperfusion injury (IRI) demonstrates a strong relationship with peri-operative acute kidney injury.2 The etiology of diabetic complications is strongly associated with increased oxidative stress (OS). Diabetic patients are known to have a high risk of developing OS or IRI which results with tissue failure.3 The most important role in ischemia and reperfusion is played by free oxygen radicals.1 In diabetes, characterized by hyperglycemia, even more free oxygen radicals are produced due to oxidation of glucose and glycosylation of proteins.3 The structures which are most sensitive to free oxygen radicals in the cells are membrane lipids, proteins, nucleic acids and deoxyribonucleic acids.1 It has been reported that endogenous antioxidant enzymes [superoxide dismutase (SOD), glutathion s-transpherase (GST), catalase (CAT)] play an important role to alleviate IRI.4-8 Also some pharmacological agents have certain effects on IRI.1 The anesthetic agents influence endogenous antioxidant systems and free oxygen radical formation.9-12 Dexmedetomidine is a selective α-2 adrenoceptor agonist agent. It has been described as a useful and safe adjunct in many clinical applications. It has been found that it may increase urine output by considerably redistributing cardiac output, inhibiting vasopressin secretion and maintaining renal blood flow and glomerular filtration. Previous studies demonstrated that dexmedetomidine provides protection against renal, focal cerebral, cardiac, testicular, and tourniquet-induced IRI.13-18 Arslan et al observed that dexmedetomidine protected against lipid peroxidation and cellular membrane alterations in hepatic IRI, when given before induction of ischemia.17 Si et al18 demonstrated that dexmedetomidine treatment results in a partial but significant attenuation of renal demage induced by IRI through the inactivation of JAK/STAT signaling pathway in an in vivo model. The efficacy of the dexmedetomidine for IRI in diabetic patient is not resarched yet. The purpose of this experimental study was to evaluate the biochemical and histological effects of dexmedetomidine on hepatic IRI in diabetic rat’s hepatic and renal tissue. METHODOLOGY Animals and Experimental Protocol: This study was conducted in the Physiology Laboratory of Kirikkale University upon the consent of the Experimental Animals Ethics Committee of Kirikkale University. All of the procedures were performed according to the accepted standards of the Guide for the Care and Use of Laboratory Animals. In the study, 28 male Wistar Albino rats, weighing between 250 and 300 g, raised under the same environmental conditions, were used. The rats were kept under 20-21 oC at cycles of 12-hour daylight and 12-hour darkness and had free access to food until 2 hours before the anesthesia procedure. The animals were randomly separated into four groups, each containing 7 rats. Diabetes was induced by a single intraperitoneal injection of streptozotocin (Sigma Chemical, St. Louis, MO, USA) at a dose of 65 mg/kg body weight. The blood glucose levels were measured at 72 hrs following this injection. Rats were classified as diabetic if their fasting blood glucose (FBG) levels exceeded 250 mg/dl, and only animals with FBGs of > 250 mg/dl were included in the diabetic groups (dia­betes only, diabetes plus ischemia-reperfusion and diabetes plus dexmedetomidine-ischemia-reperfusion). The rats were kept alive 4 weeks after streptozotocin injection to allow development of chronic dia­betes before they were exposed to ischemia-reperfusion.(19) The rats were weighed before the study. Rats were anesthetized with intraperitoneal ketamine 100 mg/kg. The chest and abdomen were shaved and each animal was fixed in a supine position on the operating table. The abdomen was cleaned with 1% polyvinyl iodine and when dry, the operating field was covered with a sterile drape and median laparotomy was performed. There were four experimental groups (Group C (sham-control; n = 7), (Group DC (diabetes-sham-control; n = 7), Group DIR (diabetes-ischemia-reperfusion; n = 7), and Group DIRD (diabetes-ischemia-reperfusion-dexmedetomidine; n = 7). Sham operation was performed on the rats in Group C and Group DC. The sham operation consisted of mobilization of the hepatic pedicle only. The rats in this group were sacrificed 90 min after the procedure. Hepatic I/R injury was induced in Groups DIR and DIRD respectively with hepatic pedicle clamping using a vascular clamp as in the previous study of Arslan et al.(17) After an ischemic period of 45 min, the vascular clamp was removed. A reperfusion period was maintained for 45 min. In Group DIRD, dexmedetomidine hydrochloride 100 μg/kg, (Precedex 100 μg/2 ml, Abbott®, Abbott Laboratory, North Chicago, Illinois, USA) was administrated via intraperitoneal route 30 minutes before surgery. All the rats were given ketamine 100 mg/kg intraperitoneally and intracardiac blood samples were obtained. Preserving the tissue integrity by avoiding trauma, liver and renal biopsy samples were obtained. Biochemical Analysis: The liver and renal tissues were first washed with cold deionized water to discard blood contamination and then homogenized in a homogenizer. Measurements on cell contest require an initial preparation of the tissues. The preparation procedure may involve grinding of the tissue in a ground glass tissue blender using a rotor driven by a simple electric motor. The homogenizer as a tissue blender similar to the typical kitchen blender is used to emulsify and pulverize the tissue (Heidolph Instruments GMBH & CO KGDiax 900 Germany®) at 1000 U for about 3 min. After centrifugation at 10,000 g for about 60 min, the upper clear layer was taken. MDA levels were determined using the method of Van Ye et al,(20) based on the reaction of MDA with thiobarbituric acid (TBA). In the TBA test reaction, MDA and TBA react in acid pH to form a pink pigment with an absorption maximum at 532 nm. Arbitrary values obtained were compared with a series of standard solutions (1,1,3,3-tetraethoxypropane). Results were expressed as nmol/mg.protein. Part of the homogenate was extracted in ethanol/chloroform mixture (5/3 v/v) to discard the lipid fraction, which caused interferences in the activity measurements of T-SOD, CAT and GST activities. After centrifugation at 10.000 x g for 60 min, the upper clear layer was removed and used for the T-SOD, CAT, GST enzyme activity measurement by methods as described by Durak et al21, Aebi22 and Habig et al23 respectively. One unit of SOD activity was defined as the enzyme protein amount causing 50% inhibition in NBTH2 reduction rate and result were expressed in U/mg protein. The CAT activity method is based on the measurement of absorbance decrease due to H2O2 consumption at 240 nm. The GST activity method is based on the measurement of absorbance changes at 340 nm due to formation of GSH-CDNB complex. Histological determinations: Semiquantitative evaluation technique used by Abdel-Wahhab et al(24) was applied for interpreting the structural changes investigated in hepatic tissues of control and research groups. According to this, (-) (negative point) represents no structural change, while (+) (one positive point) represents mild, (++) (two positive points) medium and (+++) (three positive points) represents severe structural changes. Statistical analysis: The Statistical Package for the Social Sciences (SPSS, Chicago, IL, USA) 20.0 softwre was used for the statistical analysis. Variations in oxidative state parameters, and histopathological examination between study groups were assessed using the Kruskal-Wallis test. The Bonferroni-adjusted Mann-Whitney U-test was used after significant Kruskal-Wallis to determine which groups differed from the others. Results were expressed as mean ± standard deviation (Mean ± SD). Statistical significance was set at a p value < 0.05 for all analyses. RESULTS There was statistically significant difference observed between the groups with respect to findings from the histological changes in the rat liver tissue (hepatocyte degeneration, sinüsoidal dilatation, pycnotic nucleus, prenecrotic cell) determined by light microscopy according to semiquantitative evaluation techniques (p < 0.0001). In Group DIR, hepatocyte degeneration was significantly high compared to Group C, Group DC and Group DIRD (p < 0.0001, p < 0.0001, p = 0.002, respectively), (Table 1, Figure 1-4). Similarly, sinüsoidal dilatation was significantly higher in Group DIR (p < 0.0001, p = 0.004, p = 0.015, respectively). Although, pcynotic nucleus was decreased in Group DIRD, it did not make a significant difference in comparison to Group DIR (p = 0.053), (Table 1, Figure 1-4). The prenecrotic cells were significantly increased in Group DIR, with respect to Group C, Group DC and Group DIRD (p < 0.0001, p = 0.004, p < 0.0001, respectively), (Table 1, Figure 1-4). Table 1. The comparison of histological changes in rat hepatic tissue [Mean ± SD)] p**: Statistical significance was set at a p value < 0.05 for Kruskal-Wallis test *p < 0.05: When compared with Group DIR Figure 1: Light microscopic view of hepatic tissue of Group C (control). VC: vena centralis, *: sinusoids. ®: hepatocytes, k: Kupffer cells, G: glycogen granules, mc: minimal cellular changes, Hematoxilen & Eosin x 40 Figure 2: Light-microscopic view of hepatic tissue of Group DC (diabetes mellitus control) (G: Glycogen granules increased in number, (VC: vena centralis, *:sinusoids. ®:hepatocytes, k:Kupffer cells, G: glycogen granules, mc: minimal cellular changes; Hematoxylin & Eosin x 40) Figure 3: Light-microscopic view of hepatic tissue of Group DIR (Diabetes Mellitus and ischemia-reperfusion) (VC: vena centralis, (H) degenerative and hydrophic hepatocytes, (dej) vena centralis degeneration (centrolobar injury) (*): sinusoid dilatation. (←) pycnotic and hyperchromatic nuclei, MNL: mononuclear cell infiltration, (¯) congestion, K: Kupffer cell hyperplasia, (­) vacuolar degeneration (Hematoxylin & Eosin x 40) Figure 4: Light-microscopic view of hepatic tissue of Group DIRD (Diabetes Mellitus and ischemia-reperfusion together with dexmedetomidine applied group) (VC: vena centralis, (MNL) mononuclear cell infiltration, (dej) hydrophilic degeneration in hepatocytes around vena centralis, (conj) congestion, G: glycogen granules, (←) pycnotic and hyperchromatic nuclei, sinusoid dilatation (*) (Hematoxylin & Eosin x 40) Besides, in liver tissue parenchyma, MN cellular infiltration was a light microscopic finding; and showed significant changes among the groups (p < 0.0001). This was significantly higher in Group DIR, compared to Group C, DC, and DIRD (p < 0.0001, p=0.007, p = 0.007, respectively), (Table 1, Figure 1-4). The enzymatic activity of MDA, SOD and GST in hepatic tissues showed significant differences among the groups [(p = 0.019), (p = 0.034). (p = 0.008) respectively]. MDA enzyme activity was significantly incresed in Group DIR, according to Group C and Group DIRD (p = 0.011, p = 0.016, respectively), (Table 2). In Group DIR SOD enzyme activity was lower with respect to Group C and Group DIRD (p = 0.010, p = 0.038, respectively), (Table 2). The GST enzyme activity was significantly higher in Group DIR, when compared to Group C, DC and DIRD (p = 0.007, p = 0.038, p = 0.039, respectively), (Table 2). Table 2. Oxidative state parameters in rat hepatic tissue [Mean ± SD] p**: Statistical significance was set at a p value < 0.05 for Kruskal-Wallis test *p < 0.05: When compared with Group DIR The enzymatic activity of MDA, SOD in renal tissues, showed significant differences among the groups [(p < 0.0001), (p = 0.008) respectively ]. MDA enzyme activity was significantly incresed in Group DIR, according to Group C and Group DIRD (p < 0.0001, p < 0.0001, respectively). Also MDA enzyme activity level was significantly increased in Group DC, in comparison to Group C and Group DIRD (p = 0.003, p = 0.001, respectively), (Table 3). In Group DIR SOD enzyme activity was lower with respect to Group C and Group DIRD (p = 0.032, p = 0.013, respectively), (Table 3). The GST enzyme activity was significantly higher in Group DIR than the other three groups, however; CAT levels were similar among the groups (Table 3). Table 3: Oxidative state parameters in rat nephrotic tissue [Mean ± SD)] p**: Statistical significance was set at a p value < 0.05 for Kruskal-Wallis test *p < 0.05: When compared with Group DIR DISCUSSION In this study, we have reported the protective effect of dexmedetomidine in experimental hepatic and renal IRI model in the rat by investigating the MDA and SOD levels biochemically. Besides, hepatic histopathological findings also supported our report. Ischemic damage may occur with trauma, hemorrhagic shock, and some surgical interventions, mainly hepatic and renal resections. Reperfusion following ischemia results in even more injury than ischemia itself. IRI is an inflammatory response accompanied by free radical formation, leucocyte migration and activation, sinusoidal endothelial cellular damage, deteoriated microcirculation and coagulation and complement system activation.1 We also detected injury in hepatic and renal tissue caused by reperfusion following ischemia in liver. Experimental and clinical evidence indicates that OS is involved in both the pathogenesis and the complications of diabetes mellitus.25,26 Diabetes mellitus is a serious risk factor for the development of renal and cardiovascular disease. It is also related to fatty changes in the liver.27 Diabetes-related organ damage seems to be the result of multiple mechanisms. Diabetes has been associated with increased free radical reactions and oxidant tissue damage in STZ-induced diabetic rats and also in patients.26Oxidative stress has been implicated in the destruction of pancreatic β-cells28 and could largely contribute to the oxidant tissue damage associated with chronic hyperglycemia.29 A number of reports have shown that antioxidants can attenuate the complications of diabetes in patients30 and in experimental models.28,31 This study demonstrated that diabetes causes a tendency to increase the IRI. There is a lot of investigations related to the pharmacological agents or food supplements applied for decreasing OS and IRI. Antioxidant agents paly an important role in IRI by effecting antioxidant system or lessening the formation of ROS. It has been reported that anesthetic agents too, are effective in oxidative stress.1 During surgical interventions, it seems rational to get benefit from anesthetic agents in prevention of OS caused by IRI instead of using other agents. It has been declared that; dexmedetomidine; as an α-2 agonist with sedative, hypnotic properties; is important in prevention of renal, focal, cerebral, cardiac, testicular and tourniquet-induced IRI.13-18 On the other hand Bostankolu et al. concluded that dexmedetomidine did not have an additional protective role for tournique induced IRI during routine general anesthesia.32 In this study; we have shown that dexmedetomidine has a reducing effect in IRI in diabetic rats. Some biochemical tests and histopathological evaluations are applied for bringing up oxidative stress and IRI in the tissues. Reactive oxygen species (ROS) that appear with reperfusion injury damage cellular structures through the process of the lipid peroxidation of cellular membranes and yield toxic metabolites such as MDA.33 As an important intermidiate product in lipid peroxidation, MDA is used as a sensitive marker of IRI.34 ROS-induced tissue injury is triggered by various defense mechanisms.35 The first defence mechanisms include the antioxidant enzymes of SOD, CAT, and GPx. These endogenous antioxidants are the first lines of defence against oxidative stres and act by scavenging potentially damaging free radical moieties.36 There is a balance between ROS and the scavenging capacity of antioxidant enzymes.1-8 In this study, for evaluation of oxidative damage and antioxidant activity, MDS, SOD, GST and CAT levels were determined in liver and kidney tissues. MDA levels in hepatic and renal tissues were higher in Group DIR compared to Group C and Group DIRD. GST levels were higher in Group DIR compared to all the other three groups. When the groups were arranged from highest to lowest order, with respect to CAT levels, the order was; Group DIR, Group DIRD, Group DC and Group C. However, the difference was not significant. The acute phase reactant MDA, as a marker of OS, was found to be high in Group DIR and low in Group DIRD. This could be interpreted as the presence of protective effect of dexmedetomidine in IRI. IRI developing in splanchnic area causes injury also in the other organs.35 Leithead et al showed that clinically significant hepatic IRI demonstrates a strong relationship with peri-operative acute kidney injury.2 In our experimental research that showed correlation to that of research by Leithead et al. After hepatic IRI in diabetic rats renal OS marker MDA levels were significantly more in Group DIR than Group DIRD. In our study, we observed histopathological changes in the ischemic liver tissue and alterations in the level of MDA, SOD, GST and CAT levels which are OS markers. Histopathological changes of the liver tissues are hepatocyt degeneration, sinusoidal dilatation, nuclear picnosis, celluler necrosis, mononuclear cell infiltrationat paranchimal tissue. These histopathological injury scores were significantly lower in the Group DIRD than those in group DIR. LIMITATION Study limitation is there was no negative control group, as this type of surgical intervention is not possible in rats without anesthesia. CONCLUSION The enzymatic findings of our study together with the hepatic histopathology indicate that dexmedetomidine has a potential role to decrease ischemia-reperfusion injury. Conflict of interest and funding: The authors have not received any funding or benefits from industry or elsewhere to conduct this study. 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