Effect Of Fluid Composition Research Articles

Elastohydrodynamic Traction and Film Thickness at High Speeds

A renewed interest in elastohydrodynamic lubrication (EHL) phenomena at high speeds, for which thermal effects strongly influence both traction and film thickness, has grown out of the challenges presented by high-speed geared transmissions in electric vehicles. This study uses a new ball-on-disc set-up employing the well-known ultra-thin-film interferometry technique to simultaneously measure EHL film thickness and traction at entrainment speeds up to 20 m/s and slide-roll ratios up to 100%. The effect of fluid composition is examined for Group I, II and III mineral oils, for two polyalphaolefins in Group IV, and for the traction fluid Santotrac 50. The effect of viscosity in the range 4–180 mPa.s is investigated by varying bulk fluid temperature. At high speeds, both film thickness and traction are considerably lower than predicted by conventional EHL theory. The contact is seen to be fully-flooded for all conditions tested. The widely-used thermal EHL correction of Gupta is shown to overcorrect for the film thickness reduction even at modest SRRs. Finally, the influence of the sliding direction on traction and film thickness is discussed for this set-up, and a thermal model is proposed to explain the observed behaviour.Graphical abstract

A geochemical model for the transformation of gabbro into vesuvianite-bearing rodingite

Rodingite is a Ca-rich and Si-poor metasomatic rock commonly occurring in association with serpentinites. This rock is characterized by specific mineral assemblages consisting of hydrated garnet, diopside, vesuvianite, epidote-zoisite, chlorite, or prehnite. However, natural rodingites are significantly heterogeneous in mineral composition and vesuvianite occurs only in some extensively rodingitized rocks. Major factors controlling the mineral diversity as well as details on fluid-rock interactions leading to the evolution of mineral and chemical composition during rodingitization have not yet been fully constrained. In this work, we use PHREEQC software to present a geochemical model for the transformation of a mafic rock into vesuvianite-bearing rodingite at a temperature of 300 °C. Through these simulations, we investigate the effect of fluid composition and progress of the metasomatic process on rodingite formation. Our results show that rodingitization requires an open system with a high input of hydrothermal fluid. Additionally, a decrease in the Si/Ca ratio in the metasomatized rock is correlated to an increase in the volume of incoming fluid. Whole rock chemical and mineral composition in natural rodingites are well reproduced by the model. Furthermore, the diversity of mineral parageneses results mainly from different degrees of transformation and only to a lesser extent to the chemical composition of hydrothermal fluid or protolith. The hydrothermal fluid doesn't need to be especially rich in calcium to transform a mafic rock into rodingite, but it must be low in magnesium, silicon, and have a high pH, which is naturally controlled by serpentinization of surrounding ultramafic rocks.

Effects of fluid composition and salinity on subcritical crack growth in granite

Using the double-torsion technique, the fracture mechanical response of granite specimens was investigated under the influence of fluid with different electrolyte types and salinities. The fracture toughness (KIC) and critical mechanical energy release rate (G0) of the granite in electrolyte solution are weakened compared to those in distilled water. The KIC in all electrolyte solutions is 2.08–2.28 MPa·m1/2, which is 8.4 % − 16.5 % lower than that in distilled water, and it is insensitive to ion type and salinity. In contrast, the subcritical crack growth index (n) shows different salinity dependence in three salt (AlCl3, CaCl2, and NaCl) solutions. The slight increase in n with rising salinity of the AlCl3 solution is attributed to crack tip blunting caused by over-dissolution of minerals. The n and G0 decrease and then increase with rising salinity of CaCl2 solution, which may be related to the salinity-dependent dissolution rate of quartz and the weakening of repulsive force between crack surfaces. The n and G0 shows a negative correlation with salinity and decrease by 26.4 % and 15.4 %, respectively as the NaCl salinity increases from 0.1 M to 1.0 M. Limitations in the dissolution reactions of the main minerals (albite, biotite and diopside) is accountable for enhancement of n in silica solutions. Experimental results emphasize the critical and subcritical fracture behavior of the granite in response to chemically reactive fluids with implications for both hydraulic fracture stimulations in geothermal fields and caprock integrity for CO2 sequestration. In these applications, the fracture properties of the reservoir rock can be enhanced or weakened by changing the electrolyte type and salinity of the fluid, depending on the actual requirements.

Effects of fluid composition in fluid injection experiments in porous media

Experiments on fluid flow in porous media, using fluids loaded with solids of various grain sizes, have been conducted in a modified Hele-Shaw setup. This setup utilised weakly cemented porous media with specific hydraulic and mechanical properties. Fluid injection in coarse granular media with clean or low-concentration fine particles, results in infiltration only, with pressure close to the material tensile strength, while injection in finer granular material causes damage alongside infiltration, with the fluid pressure still close to the material tensile strength. When larger particle sizes or higher particle concentrations are used in the mixture, the fluid travels further within the porous medium, primarily influenced by the grain size of the granular medium. In the latter case, the Darcy flow equation with an effective permeability term can be employed to determine the pressure differential. For the largest particle sizes included in the fluid, the equation is still applicable, but the effective permeability requires adjustment for particle size within the fluid rather than the granular medium. This is crucial when the injection point is locally clogged. The experiments show that fracturing conditions are controlled by different mechanisms. Dimensional and statistical analysis was used to classify the injection pressures to regimes predicted by fracturing theory or by Darcy law with modified effective permeabilities. The findings show that both the material properties and fluid composition are important designing parameters.

Multistage hydration during oceanic serpentinisation revealed by in situ oxygen isotope and trace element analyses

Serpentinisation of mantle peridotites below the seafloor is the most important hydration reaction in the Earth's deep water cycle. This critical step in water–rock interaction occurs over multiple serpentinisation stages and at variable temperatures and fluid compositions. We present the first study using spatially coupled in-situ analysis of oxygen isotopes (secondary ionization mass spectrometry) and trace elements (laser ablation inductively coupled plasma mass spectrometry) to unravel the multistage hydration history of oceanic serpentinites. We study samples from the Newfoundland-Iberia extended passive margins, which represents a magma-poor ocean-continent transition zone (Ocean Drilling Program cores, Leg 173 Site 1070 from Iberia, Leg 210 Site 1277 from Newfoundland). The concentrations of the fluid mobile elements chlorine and boron in serpentine are used as a proxy for the salinity of the serpentinising fluid. The correlation of Cl/B with δ18Oserpentine compositions provides new insights to disentangle temperature from fluid composition effects. The transition metal composition (V, Co, Sc, Mn, Zn, Ni, Cr) of dominantly lizardite in mesh after olivine and in bastite after orthopyroxene shows a chemical redistribution between textural sites in the Newfoundland samples, indicating the simultaneous serpentinisation of olivine and orthopyroxene. This feature is not observed in the Iberian samples, for which we propose sequential reactions. Lizardite in samples from both localities varies considerably in oxygen isotope composition at the scale of tens of micrometres depending on texture, with a range in δ18O of 3.3–13.5‰ for Iberia samples and a more restricted range of 5.7–9.3‰ for Newfoundland samples. Temperatures calculated from the δ18Oserpentine corresponding to the lowest Cl/B ratio (interpreted as closest to seawater composition) indicate sequential serpentinisation with decreasing temperature from ∼190 to ∼60 °C in the Iberia setting. The Newfoundland samples were serpentinised at a lower temperature (100–130 °C), possibly at a shallower depth. Serpentinisation in the Newfoundland samples probably produced a concentrated amount of H2 in a shorter period of time, whereas in the Iberian samples a small but prolonged amount of H2 was produced, possibly creating more favourable conditions for microbial activity.

Insights into adsorption and diffusion behavior of shale oil in slit nanopores: A molecular dynamics simulation study

Nanoscale pores have been widely observed in shale plays. Within such a small scale pore, the interaction between fluid molecules and porewall surface becomes significant, and the adsorption state of shale fluids is quite different from that in conventional reservoirs. In this study, the method of molecular dynamics (MD) simulation is applied to address the adsorption and diffusion behavior of shale oil in slit nanopores. Firstly, two different models of organic graphene nanopore and inorganic quartz nanopore are constructed, and three typical components of alkanes (methane, propane, and n-octane) are selected to represent the shale oil fluids. Based on this model, the effects of fluid composition, nanopore type and porewall wettability on the adsorption and diffusion behavior of shale fluids are discussed. For the simulation method of hydrophilic porewall surface, in this study, a series of carbonyl functional group is grafted on graphene surface to enhance the hydrophilicity of porewall surface. Results indicate that the multicomponent alkanes in nanoscale pores can form a multilayer adsorption state. The heavy components will occupy the adsorption sites around the porewall surface. In contrast, the adsorbed amount of light components at porewall surface can be almost negligible. However, as the effect of multicomponent fluid is considered, a significant difference for the properties of adsorption layer and the mean square displacement (MSD) value can be observed compared with that of the pure component fluids. Similarly, shale fluids can also show a multilayer adsorption behavior of heavy components at the quartz nanopore wall surface, but the amount of adsorption is lower. Comparing the peak density of the first adsorption layer in organic matter pores with that in quartz nanopore, the former shows 1.87 times more than the latter for ternary mixture (C1-C3-C8). Furthermore, it can be also observed that the adsorption capacity of fluid in the nanopores with different wettabilities differs. As the O/C ratio in organic matter wall is above 15%, the peak density of adsorption layer is significantly increased with the carbonyl proportion increases. But this changing tendency is decreased as the O/C ratio reaches above 50.46%. Furthermore, from the simulation results, it is observed that with the carbonyl proportion increases, the fluid self-diffusion coefficient is gradually reduced. It indicates that the effect of rock wettability on the fluid diffusion behavior. This study can provide an important data support to understand the adsorption and diffusion behavior of shale oil in nanopores, which is important for the effective and efficient development of shale oil reservoirs.

Intravenous fluid therapy in sepsis.

Sepsis is the dysregulated immune response to severe infection that is common and lethal among critically ill patients. Fluid administration is a common treatment for hypotension and shock in early sepsis. Fluid therapy can also cause edema and organ dysfunction. Research on the best treatment strategies for sepsis has provided insights on the optimal timing, dose, and type of fluid to treat patients with sepsis. Initial research on early goal-directed therapy for sepsis included an initial bolus of 30 ml/kg of fluid, but more recent research has supported use of smaller volumes. After initial fluid resuscitation, minimizing additional fluid administration may be beneficial, but no single measure has been established as the best method to guide ongoing fluid management in sepsis. Dynamic measures of "fluid responsiveness" can predict which patients will experience an increase in cardiac output from a fluid bolus. Use of such a measure in clinical care remains limited by applicability to patient populations and uncertainty regarding the effect on clinical outcomes. Recent research informs the effect of fluid composition on outcomes for patients with sepsis. Current data support the use of balanced crystalloids, rather than saline, and the use of crystalloids, rather than semisynthetic colloids. The role for albumin administration in sepsis remains uncertain. Future research should focus on determining the optimal volume of fluid during sepsis resuscitation, the effectiveness of measures of "fluid responsiveness" in improving outcomes, the optimal composition of crystalloid solutions, the role of albumin, and the effects of "deresuscitation" after septic shock.

A Review of Crystallization Fouling in Heat Exchangers

A vast majority of heat exchangers suffer from unwanted deposition of material on the surface, which severely inhibits their performance and thus marks one of the biggest challenges in heat transfer. Despite numerous scientific investigations, prediction and prevention of fouling remain unresolved issues in process engineering and are responsible for large economic losses and environmental damage. This review article focuses specifically on crystallization fouling, providing a comprehensive overview of the state-of-the-art of fouling in heat exchangers. The fundamentals of the topic are discussed, as the term fouling resistance is introduced along with distinct fouling behaviour, observed in laboratory and industrial environments. Insight into subsequent phases of the fouling process is provided, along with the accompanying microscale events. Furthermore, the effects of fluid composition, temperature, flow velocity, surface condition, nucleate boiling and composite fouling are comprehensively discussed. Fouling modelling is systematically reviewed, from the early work of Kern and Seaton to recently used artificial neural networks and computational fluid dynamics. Finally, the most common fouling mitigation approaches are presented, including design considerations and various on-line strategies, as well as off-line cleaning. According to our review, several topics require further study, such as the initial stage of crystal formation, the effects of ageing, the interplay of two or more fouling mechanisms and the underlying phenomena of several mitigation strategies.

Can magma degassing at depth donate the metal budget of large hydrothermal Sb deposits?

A genetic link between Sb mineralization and magmatism has previously been proposed, yet little is known about the mobility of Sb during magma degassing. We have carried out a series of experiments to understand the effects of fluid composition, oxygen fugacity (fO2), pressure and temperature on the partitioning of Sb between magmatic fluids and a rhyolitic melt at crustal conditions (T = 850 °C, P = 200 MPa). The experiments were carried out in Molybdenum - Hafnium Carbide (MHC) pressure vessel assemblies at T = 850 to 1000 °C, P = 100 to 200 MPa and logfO2 from 1.64 log units below to 1.78 log units above the Ni-NiO buffer. Antimony partitions into aqueous chloride-bearing fluids weakly, with the fluid/silicate melt partition coefficient of Sb (DSbfluid/melt) increasing from 0.48 ± 0.11 (1σ) to only 0.85 ± 0.17 (1σ) as the total chlorine concentration in the fluid increases from 0.99 to 16.24 m, indicating the lack of significant Sb-chloride species in the fluid. In contrast, DSbfluid/melt increased from 0.89 ± 0.19 to 1.49 ± 0.19 as the aluminum saturation index (ASI) of the melt increased from 1.02 to 1.24. The moderate increase in DSbfluid/melt with increasing ASI of the melt (and HCl/metal chloride in the fluid) most likely relates to decreasing Sb solubility in the melt and further demonstrates the lack of significant chloride complexing of Sb. We also found that DSbfluid/melt is only slightly influenced by fO2 suggesting that Sb does not change oxidation state (Sb3+) at redox conditions typical of arc magmatism. Furthermore, the presence of reduced S species in the fluid phase caused only a minor increase in DSbfluid/melt indicating that Sb-sulfide complexes are not particularly stable in magmatic fluids. Our data also show that pressure and temperature, within the range of 100 to 200 MPa and 850 to 1000 °C, do not significantly influence DSbfluid/melt. Thus it is apparent that at most possible conditions at which rhyolitic melts degas in the upper crust, Sb will only weakly partition into the fluid phase and it is likely that the Sb budget of large epithermal Sb deposits is not directly derived from primary magmatic fluids.

The effects of fluid composition and shear conditions on bacterial adhesion to an antifouling peptide-coated surface

Abstract

Effect of S on the aqueous and gaseous transport of Cu in porphyry and epithermal systems: Constraints from in situ XAS measurements up to 600 °C and 300 bars

The effect of S on the solubility of Cu in high-temperature fluids at conditions relative to porphyry and epithermal ore deposit formation has been investigated conducting in situ X-ray absorption (XAS) and Raman spectroscopy from 325 to 600°C at 300bars. The experimental results identify the Cl or S-complexes responsible for Cu transport in high-temperature fluids and provide information on transport in porphyry/epithermal systems and the effect of fluid composition on the transfer of Cu from the porphyry to the epithermal environment.In S-free HCl solutions, Cu solubility is about 10 times higher in high-density (ρ>0.6g·cm−3) versus low-density (ρ<0.3g·cm−3) fluids. During the transition from high- to low-density, Cu speciation evolves from CuCl2− complexes to CuCl(H2O) or CuCl(HCl), depending on HCl concentrations. In sulfur-only solutions Cu solubility is extremely low. The addition of S to Cl-bearing fluids results in a drop of Cu solubility in high- and low-density fluids. Solubilities drop from weight percent levels (in Cl-only solutions) to hundreds of ppm in high-density fluids (containing sulfur). In low-density fluids, Cu concentrations similarly drop, from hundreds of ppm to below detection. The low Cu concentrations in the presence of sulfur preclude the characterization of Cu complexes, except in high-density Cl+S fluids, where CuCl2− is found to remain the dominant specie even for Cl concentrations <1wt%.Overall, these results suggest that the presence of S of mixed oxidation state (sulfide S2−, sulfite S4+ and sulfate S6+) limits transport of Cu in porphyry and epithermal systems and may even trigger Cu precipitation. Furthermore, these experiments provide evidence that the presence of the S3− ion does not increase Cu solubility in fluids. Thus, if present in such environments, S3− ion could fractionate Cu from Au in porphyry-epithermal environments.

Resuscitation fluid composition affects hepatic inflammation in a murine model of early sepsis

BackgroundFluid resuscitation is a crucial therapy for sepsis, and the use of balanced fluids and/or isotonic albumin may improve patient survival. We have previously demonstrated that resuscitation with normal saline results in increased hepatic leukocyte recruitment in a murine model of sepsis. Given that clinical formulations of albumin are in saline, our objectives were to develop a novel balanced electrolyte solution specifically for sepsis and to determine if supplementing this solution with albumin would improve the inflammatory response in sepsis.MethodsWe developed two novel buffered electrolyte solutions that contain different concentrations of acetate and gluconate, named Seplyte L and Seplyte H, and administered these solutions with or without 5% albumin. Normal saline with or without albumin and Ringer’s lactate served as controls. Sepsis was induced by cecal ligation and puncture (CLP), and the liver microvasculature was imaged in vivo at 6 h after CLP to quantify leukocyte recruitment. Hepatic cytokine expression and plasma cell-free DNA (cfDNA) concentrations were also measured.ResultsSeptic mice receiving either Seplyte fluid showed significant reductions in hepatic post-sinusoidal leukocyte rolling and adhesion compared to normal saline. Hepatic cytokine concentrations varied in response to different concentrations of acetate and gluconate in the novel resuscitation fluids but were unaffected by albumin. All Seplyte fluids significantly increased hepatic TNF-α levels at 6 h compared to control fluids. However, Seplyte H exhibited a similar cytokine profile to the control fluids for all other cytokines, whereas mice given Seplyte L had significantly elevated IL-6, IL-10, KC (CXCL1), and MCP-1 (CCL2). Plasma cfDNA was generally increased during sepsis, but resuscitation fluid composition did not significantly affect cfDNA concentrations.ConclusionsElectrolyte concentrations and buffer constituents of resuscitation fluids can modulate hepatic cytokine production and leukocyte recruitment in septic mice, while the effects of albumin are modest during early sepsis. Therefore, crystalloid fluid choice should be an important consideration for resuscitation in sepsis, and the effects of fluid composition on inflammation in other organ systems should be studied to better understand the physiological impact of this vital sepsis therapy.

The effect of fluid composition, salinity, and acidity on subcritical crack growth in calcite crystals

AbstractChemically activated processes of subcritical cracking in calcite control the time‐dependent strength of this mineral, which is a major constituent of the Earth's brittle upper crust. Here experimental data on subcritical crack growth are acquired with a double torsion apparatus to characterize the influence of fluid pH (range 5–7.5) and ionic strength and species (Na2SO4, NaCl, MgSO4, and MgCl2) on the propagation of microcracks in calcite single crystals. The effect of different ions on crack healing has also been investigated by decreasing the load on the crack for durations up to 30 min and allowing it to relax and close. All solutions were saturated with CaCO3. The crack velocities reached during the experiments are in the range 10−9–10−2 m/s and cover the range of subcritical to close to dynamic rupture propagation velocities. Results show that for calcite saturated solutions, the energy necessary to fracture calcite is independent of pH. As a consequence, the effects of fluid salinity, measured through its ionic strength, or the variation of water activity have stronger effects on subcritical crack propagation in calcite than pH. Consequently, when considering the geological sequestration of CO2 into carbonate reservoirs, the decrease of pH within the range of 5–7.5 due to CO2 dissolution into water should not significantly alter the rate of fracturing of calcite. Increase in salinity caused by drying may lead to further reduction in cracking and consequently a decrease in brittle creep. The healing of cracks is found to vary with the specific ions present.

Rutile solubility in NaF–NaCl–KCl-bearing aqueous fluids at 0.5–2.79 GPa and 250–650 °C

The complex nature of trace element mobility in subduction zone environments is thought to be primarily controlled by fluid–rock interactions, episodic behavior of fluids released, mineral assemblages, and element partitioning during phase transformations and mineral breakdown throughout the transition from hydrated basalt to blueschist to eclogite. Quantitative data that constrain the partitioning of trace elements between fluid(s) and mineral(s) are required in order to model trace element mobility during prograde and retrograde metamorphic fluid evolution in subduction environments. The stability of rutile has been proposed to control the mobility of HFSE during subduction, accounting for the observed depletion of Nb and Ta in arc magmas. Recent experimental studies demonstrate that the solubility of rutile in aqueous fluids at temperatures >700°C and pressures <2GPa increases by several orders of magnitude relative to pure H2O as the concentrations of ligands (e.g., F and Cl) in the fluid increase. Considering that prograde devolatilization in arcs begins at ∼300°C, there is a need for quantitative constraints on rutile solubility and the partitioning of HFSE between rutile and aqueous fluid over a wider range of temperature and pressure than is currently available. In this study, new experimental data are presented that quantify the solubility of rutile in aqueous fluids from 0.5 to 2.79GPa and 250 to 650°C. Rutile solubility was determined by using synchrotron X-ray fluorescence to measure the concentration of Zr in an aqueous fluid saturated with a Zr-bearing rutile crystal within a hydrothermal diamond anvil cell. At the PT conditions of the experiments, published diffusion data indicate that Zr is effectively immobile (logDZr ∼10−25m2/s at 650°C and ∼10−30m2/s at 250°C) with diffusion length-scales of <0.2μm in rutile for our run durations (<10h). Hence, the Zr/Ti ratio of the starting rutile, which was quantified, does not change during the experiment, and the measured concentration of Zr in the fluid was used to calculate the concentration of Ti (i.e., the solubility of rutile) in the fluid. The salts NaF, NaCl, and KCl were systematically added to the aqueous fluid, and the relative effects of fluid composition, pressure, and temperature on rutile solubility were quantified. The results indicate that fluid composition exerts the greatest control on rutile solubility in aqueous fluid, consistent with previous studies, and that increasing temperature has a positive, albeit less pronounced, effect. The solubility of Zr-rutile in aqueous fluid increases with the addition of halides in the following order: 2wt% NaF<30wt% KCl<30wt% NaCl<3wt% NaF<(10wt% NaCl+2wt% NaF)<4wt% NaF. The solubility of rutile in the fluid increases with the 2nd to 3rd power of the Cl− concentration, and the 3rd to 4th power of the F− concentration. These new data are consistent with observations from field studies of exhumed terranes that indicate that rutile is soluble in complex aqueous fluids, and that fluid composition is the primary control on rutile solubility and HFSE mobility.

Effect of fluid composition on growth rate of monazite in quartzite at 1.0 GPa and 1000 °C

The dependence of monazite coarsening rate on fluid composition was evaluated by performing growth experiments in a piston-cylinder apparatus at 1.0 GPa and 1000 °C. Results show that the rate of monazite coarsening in quartzite + fluid is strongly sensitive to fluid composition. Although other studies have shown that monazite solubility is higher in acidic fluid, addition of 2 m HCl to H2O decreased the growth rate. Textural observations and modeling indicate that monazite growth in 2 m HCl occurs through a combination of Ostwald ripening and coalescence. Addition of 2 m NaCl to H2O should have increased monazite aqueous solubility and made the fluid interconnected, but the expected increase in monazite growth rate did not occur, with monazite size distributions showing no change between 0 and 165 h and no measurable growth. Ion adsorption on the surface of monazite may have slowed the rate of monazite growth on addition of HCl and stopped growth on addition of NaCl. The strong dependence of monazite coarsening rate on fluid composition suggests that the size of crystals produced by metamorphic coarsening may not be a reliable indicator of duration of metamorphism, and that adsorption of ions on mineral surfaces may be significant even at 1000 °C.

Effect of components composition of condensate reservoirs on well test analysis: An experimental design approach

Gas condensate is a challenging fluid in reservoir due to difficulties arising from condensate dropout around the well. Condensate blockage complicates simulating the behavior of this fluid especially in well testing. The common approach in gas condensate well testing is using gas single-phase pseudo-pressure. In this study, statistical approach is applied to well test analysis in order to investigate the effect of fluid composition on reservoir behavior. Mixture design controls the number of otherwise numerous well testing of fluids to a limited number. The output data of well testings are then used for multivariable regression to create proxy models of reservoir and fluid properties including initial pressure of reservoir, gas permeability in condensate zone and maximum liquid dropout of fluids. Results show that proposed model efficiently simulates mentioned properties with high R-squared values. Results also show that the intensity of condensate formation in the reservoir is a strong function of rich components composition in the reservoir.

Randomized, Double-Blind Trial of the Effect of Fluid Composition on Electrolyte, Acid–Base, and Fluid Homeostasis in Patients Early After Subarachnoid Hemorrhage

Hyper- and hyponatremia are frequently observed in patients after subarachnoidal hemorrhage, and are potentially related to worse outcome. We hypothesized that the fluid regimen in these patients is associated with distinct changes in serum electrolytes, acid-base disturbances, and fluid balance. Thirty-six consecutive patients with SAH were randomized double-blinded to either normal saline and hydroxyethyl starch dissolved in normal saline (Voluven(®); saline) or balanced crystalloid and colloid solutions (Ringerfundin(®) and Tetraspan(®); balanced, n = 18, each) for 48 h. Laboratory samples and fluid balance were evaluated at baseline and at 24 and 48 h. Age [57 ± 13 years (mean ± SD; saline) vs. 56 ± 12 years (balanced)], SAPS II (38 ± 16 vs. 34 ± 17), Hunt and Hess [3 (1-4) (median, range) vs. 2 (1-4)], and Fischer scores [3.5 (1-4) vs. 3.5 (1-4)] were similar. Serum sodium, chloride, and osmolality increased in saline only (p ≤ 0.010, time-group interaction). More patients in saline had Cl >108 mmol/L [16 (89 %) vs. 8 (44 %); p = 0.006], serum osmolality >300 mosmol/L [10 (56 %) vs. 2 (11 %); p = 0.012], a base excess <-2 [12 (67 %) vs. 2 (11 %); p = 0.001], and fluid balance >1,500 mL during the first 24 h [11 (61 %) vs. 5 (28 %); p = 0.046]. Hyponatremia and hypo-osmolality were not more frequent in the balanced group. Treatment with saline-based fluids resulted in a greater number of patients with hyperchloremia, hyperosmolality, and positive fluid balance >1,500 mL early after SAH, while administration of balanced solutions did not cause more frequent hyponatremia or hypo-osmolality. These results should be confirmed in larger studies.

Working fluid composition effects on methane oxycombustion in an SI-engine: EGR vs. CO2

Reducing greenhouse-gas production through carbon capture is a key strategy in addressing global climate change. Oxycombustion using carbon dioxide, water, or a combination of the two as the diluent when burning hydrocarbon fuels with pure oxygen is an approach that allows for easy post-combustion carbon capture. In this work, oxycombustion experiments in a spark ignited engine using methane were conducted using carbon dioxide or EGR (in which exhaust water is not condensed out) as the working fluid. Between the two cases, EGR produced higher brake efficiencies and a lower coefficient of variation of the indicated mean effective pressure for similar operating conditions. For both working fluids it was necessary to have the oxygen concentration higher than 21%. Numerical modeling, using several mechanisms for comparison, indicates that the computed laminar flame speed with EGR is more than twice that using only carbon dioxide. However, for both EGR and carbon dioxide, laminar flame speeds were reduced significantly relative to methane-in-air combustion. Numerical modeling of the methane and oxygen with EGR working fluid provided good agreement with engine results. Based on this work, the use of oxycombustion in engines and other devices should consider including water in the working fluid to improve flame speed and combustion performance.

Effect of fluid composition on nanofinishing of single-crystal silicon by magnetic field-assisted finishing process

Magnetic field-assisted finishing is a deterministic process particularly used for finishing optical materials. The main component of this process is magnetorheological fluid which consists of magnetic particles, abrasive particles, carrier fluid such as water or oil, and some additives to impart stability. Under the influence of magnetic field (generated by either permanent magnet or electromagnet), magnetic particles form chain-like structure and support many abrasive particles to perform finishing of workpiece surface. Selection of abrasive and carrier fluid in this process is one of the major concerns which play vital role on finishing mechanism and surface quality. In the present experimental investigation, aluminum oxide and cerium oxide are chosen as abrasives while deionized water and paraffin oil are selected as carrier fluids. A set of experiments are carried out to study chemical interactions of abrasive and carrier fluid on the silicon surface. A rheological study is carried out to study behavior of magnetorheological fluid fluids under magnetic field.

Study of the PVT Properties of Gas—Synthetic-Drilling-Fluid Mixtures Applied to Well Control

Summary The study of the interaction between the formation gas and the drilling fluid during offshore operations as well as in high-pres- sure/high-temperature environments is essential to drill the pay zone of the well safely and economically. The environmental regulatory issues and the peculiar technical aspects involved in deep and ultradeep waters require low-toxicity synthetic drilling fluids. The main objective of this study was to understand the pressure/ volume/temperature (PVT) behavior of those fluids by the experimental determination and modeling of properties such as solubility, specific gravity, and formation volume factor of the fluid. Those properties have a direct impact on kick detection and circulation out of the well and should be addressed in well-control planning and execution. The experimental work was conducted in a PVT laboratory, using mixtures of methane and n-paraffin-based emulsions as unweighted drilling fluids, tested at temperatures of 158, 194, and 302°F. The pressure, temperature, and fluid-composition effects on those gas/liquid mixture properties were analyzed, and the experimental data for solubility and formation volume factor were compared to predictions considering the additivity hypothesis and mathematical fittings based on the experimental data. A model for the methane/n-paraffin system based on literature data and the Peng-Robinson equation of state has also been fitted to the data to discuss the application of the additivity hypothesis for the emulsions. Pit gain evaluation based on the correlated experimental data for the synthetic drilling fluid has been performed and compared to the values expected for water-based muds (WBMs).