Equilibrium Fluid Research Articles

Mathematical model of propagation of liquid vibrations in a tubing string

Effectiveness of wave processes in tubing strings, wells and long pipelines may be limited by damping of hydrodynamic waves along the length of the channel. Violation of thermodynamic equilibrium in reservoir fluids during their rise to the surface and in ground pipelines may be accompanied by the release of asphalt-resin-paraffin components in the flow of crystals due to a decrease in temperature and pressure. Subsequent depositing of crystals takes place as they grow, due to adhesion to the wall of pipes, the surface of equipment. Deposits are most intensified in areas of local expansion and narrowing of the cross-section area of the flow (occurrence of vortices).

Application of geothermal temperature scale method in temperature estimation of underground heat storage in Rizhao coastal area

Rizhao coastal area is located in the southeast of Shandong Province. The development and utilization of geothermal resources are relatively low, and there are few geothermal wells. The research on the deep thermal storage temperature is not high in general. Therefore, this paper attempts to use the geothermal temperature scale method to evaluate the deep thermal storage temperature in this area. Geothermal temperature scale is an economic and effective means to evaluate the temperature of deep thermal reservoir. At present, the commonly used geothermal temperature scales can be divided into four categories: silica geothermal scale, cationic geothermal thermometer, isotopic geothermal thermometer and gas geothermal thermometer. Silica geothermal thermometer and cationic geothermal thermometer are the most studied ones in China and abroad. The empirical formulas of various temperature scales are established by using the relationship between equilibrium reaction of corresponding components in aqueous solution and temperature. Therefore, it is necessary to carefully study the equilibrium state of hot water and minerals and select a reliable geothermal temperature scale. In this paper, the mineral fluid equilibrium of geothermal water in Rizhao coastal camel rock (LTS) and platform (PT) is determined by using Na-K-Mg trigonometry method and multi mineral equilibrium graphic method established by watch program. It is considered that the geothermal water is unbalanced water, which proves that chalcedony temperature scale is more suitable for estimating the heat storage temperature of geothermal system in this area.

F/OH ratio in a rare fluorine-poor blue topaz from Padre Para\xedso (Minas Gerais, Brazil) to unravel topaz\u2019s ambient of formation

Topaz [Al2SiO4(F,OH)2] is one of the main fluorine-bearing silicates occurring in environments where variably acidic (F)/aqueous (OH) fluids saturate the silicate system. In this work we fully characterized blue topaz from Padre Paraíso (Minas Gerais, Brazil) by means of in situ synchrotron X-Ray and neutron powder diffraction measurements (temperature range 298–1273 K) combined with EDS microanalyses. Understanding the role of OH/F substitution in topaz is important in order to determine the hydrophilicity and the exchange reactions of fluorine by hydroxyl groups, and ultimately to characterize the environmental redox conditions (H2O/F) required for mineral formation. The fluorine content estimated from neutron diffraction data is ~ 1.03 a.f.u (10.34 wt%), in agreement with the chemical data (on average 10.0 wt%). The XOH [OH/(OH + F)] (0.484) is close to the maximum XOH value (0.5), and represents the OH- richest topaz composition so far analysed in the Minas Gerais district. Topaz crystallinity and fluorine content sharply decrease at 1170 K, while mullite phase starts growing. On the basis of this behaviour, we suggest that this temperature may represent the potential initial topaz’s crystallization temperature from supercritical fluids in a pegmatite system. The log(fH2O/fHF)fluid (1.27 (0.06)) is coherent with the fluorine activity calculated for hydrothermal fluids (pegmatitic stage) in equilibrium with the forming mineral (log(fH2O/fHF)fluid = 1.2–6.5) and clearly different from pure magmatic (granitic) residual melts [log(fH2O/fHF)fluid < 1]. The modelled H2O saturated fluids with the F content not exceeding 1 wt% may represent an anomalous water-dominant / fluorine-poor pegmatite lens of the Padre Paraíso Pegmatite Field.

Phase Separation and Multibody Effects in Three-Dimensional Active Brownian Particles.

Simulation studies of the phase diagram of repulsive active Brownian particles in three dimensions reveal that the region of motility-induced phase separation between a high and low density phase is enclosed by a region of gas-crystal phase separation. Near-critical loci and structural crossovers can additionally be identified in analogy with simple fluids. Motivated by the striking similarity to the behavior of equilibrium fluids with short-ranged pairwise attractions, we show that a direct mapping to pair potentials in the dilute limit implies interactions that are insufficiently attractive to engender phase separation. Instead, this is driven by the emergence of multibody effects associated with particle caging that occurs at sufficiently high number density. We quantify these effects via information-theoretical measures of n-body effective interactions extracted from the configurational structure.

Effects of the repulsive and attractive forces on phase equilibrium and critical properties of two-dimensional non-conformal simple fluids

Molecular simulations in the canonical and isothermal-isobaric ensembles were performed for a two-dimensional simple fluid using a set of non conformal molecular interactions. The specific characteristics of this interaction model give it some advantages over other well known interaction potentials employed traditionally in the study of thermodynamic properties of soft matter systems. The functional form employed for modelling the effective potentials is the one proposed by the so-called ANC theory (Approximate Non-Conformal Theory), which allows to modify separately the contributions of the repulsive and attractive terms by means of a molecular parameter called softness. The effect of both, repulsive and attractive softness, on the liquid-vapour coexistence, liquid-solid transition and vaporization curve as well as on the value of the critical properties were explored. In fact, the linear dependence on the softness parameters exhibited by the critical properties, allows to extrapolate the linear correlations presented in this work, to reproduce the critical point of a two-dimensional Lennard-Jones fluid. With the aim of showing how versatile is the interaction model presented in this work, adequate values of the softness parameters were selected to reproduce qualitatively the liquid-vapour coexistence and critical points for both, a two-dimensional model fluid with a double exponential interaction potential, widely employed in molecular simulations of simple fluids; and a thin monolayer of methane molecules adsorbed on a planar graphite substrate, a system that can be considered in good approximation as two-dimensional and that has been studied in a lot of work for four decades. Finally, the effects of the dimensionality of the system was evaluated by quantifying the relative percentage differences exhibited by the thermodynamic properties explored in this paper with respect to its three-dimensional counterpart. The results presented in this work show not only the predictive capacity of the linear correlations mentioned, but the robustness of the ANC interactions to reproduce thermophysical properties and phase equilibria for model and real two-dimensional fluids. Discriminating the influence of repulsive and attractive contributions in molecular interaction models is undoubtedly of great relevance to have a better understanding of thermodynamic properties of simple and complex fluids.

Development of a Unique Organic Acid Solution for Removing Composite Field Scales.

Removal of oil field scales commonly requires low pH acid, which may cause many issues under downhole conditions. Because of the deposition of different scale types and the economic effect, there is a need to develop a remedial descaling fluid that can be effectively used to remove different types of scales at a different position in the well. This paper provides a new scale dissolver that is noncorrosive and has high scale dissolution performance for composite scales. This study shows a series of comprehensive experimental lab tests as scale characterization, equilibrium brine compositional analysis, fluid compatibility and stability, solubility test, precipitation tendency for the dissolved solids, corrosion test, and core flooding. The scale samples contain magnetite, kaolinite, calcium carbonate, and sulfate scales. The results showed that the dissolution rate was higher than 74% for composite field scale samples after 6 h at 70 °C, while the new dissolver completely dissolved the two samples at 100 °C after 5 h. The new dissolver outperformed the common commercial dissolver used in the oil and gas industry. The new dissolver has a pH of 9 and showed safe use regarding the precipitation of dissolved solids that can be produced during the scale treatment and a low corrosion rate of 0.063 kg/m2 at 6.9 MPa and 100 °C for 6 h. Also, the new dissolver was tested through core flooding for Indiana limestone and showed core permeability enhancement; the treatment with the new dissolver enhanced the core permeability from an initial value of 0.67 milliDarcy (mD) to record 1.29 mD.

Whiteschist genesis through metasomatism and metamorphism in the Monte Rosa nappe (Western Alps)

Whiteschists from the Monte Rosa Nappe were examined in the field as well as with petrographic, geochemical, and isotopic methods to constrain the controversial origin of these rocks in their Alpine metamorphic context. Whiteschists occur as ellipsoidal-shaped, decametric-sized bodies, within a Permian metagranite, and consist mainly of chloritoid, talc, phengite, and quartz. The transition from whiteschist to metagranite is marked by multiple sharp mineralogical boundaries defining concentric zones unrelated to Alpine deformation. The development of reaction zones, as well as the geometry of the whiteschist suggest a pervasive fluid infiltration, facilitated and canalized by reaction fingering. Whole-rock compositions of whiteschists and metagranites indicate an enrichment in MgO and H2O and depletion of Na2O, CaO, Ba, Sr, Pb, and Zn in the whiteschist relative to the metagranite. Trace- and rare-earth elements, together with all other major elements, notably K2O and SiO2, were within uncertainty not mobile. Such a K and Si saturated, Na undersaturated fluid is not compatible with previous interpretations of fluids derived from ultramafic rocks, evaporites, or Mg-enriched seawater due to mantle interactions. Together with the large variations in δD and δ18O values, this indicates large fluid fluxes during metasomatism. Calculated δD and δ18O values of fluids in equilibrium with the whiteschist support a magmatic–hydrothermal fluid source, as does the chemical alteration pattern. Bulk rock 87Sr/86Sr ratios in whiteschists confirm a pre-Alpine age of fluid infiltration. The 87Sr/86Sr ratios in whiteschists were subsequently partially homogenized in a closed system during Alpine metamorphism. In conclusion, the granite was locally affected by late magmatic–hydrothermal alteration, which resulted in sericite–chlorite alteration zones in the granite. The entire nappe underwent high-pressure metamorphism during the Alpine orogeny and the mineralogy of the whiteschist was produced during dehydration of the metasomatic assemblage under otherwise closed-system metamorphism. While each whiteschist locality needs to be studied in detail, this in-depth study suggests that many whiteschists found in granitic bodies in the Alps might be of similar origin.

Carbonate–Alkaline Metasomatites of the Peschanoe Uranium Occur (Western Baikal Region): Mineral-Geochemical and Isotope-Geochemical Characteristics

Abstract—Metasomatic alterations in cataclased granites of the Primorsky Complex PR1 in the Southern Siberian Craton are represented by albitization and riebeckitization, accompanied by microclinization, dolomitization and completed by the formation of hydrothermal quartz–carbonate veins. Albitization, epidotization, and carbonatization are occurred in the host metavolcanics. Mineral parageneses and mineral thermometry data indicate the occurrence of hydrothermal–metasomatic processes in the temperature range from 400–500 to 200‒250°С. Calcite deposited at an early stage has values of δ13С –(3.2–3.3)‰ and δ18O +(8.3–9.4)‰, ferruginous dolomite δ13С –(1.6–1.9)‰ and δ18O +(10.6–11.1)‰. The calculated values of δ13C in CO2 contained in the fluid from which calcite was deposited at 450°C (about –0.7 to 0.8‰) indicate marine carbonates as the source of CO2; the calculated values of δ18O in a fluid in equilibrium with calcite (from +5.4 to +6.5‰) show that the fluid underwent isotopic exchange with magmatic silicate rocks at elevated temperatures and a low fluid-rock ratio. The initial (87Sr/86Sr)t ratio in newly formed calcite (0.718087) and dolomite (0.712033) and eNdT = –(7.3–8.2) indicate the leading role of an upper crustal source of material. The maximum U concentration (52 ppm on average) contains albite–biotite–magnetite schists at the contact with altered granites. The U concentrators in metasomatically altered rocks are the crichtonite group minerals, zircon, and thorite.

The renin-angiotensin system in central nervous system tumors and degenerative diseases.

Despite their differences, central nervous system (CNS) tumors and degenerative diseases share important molecular mechanisms underlying their pathologies, due to their common anatomy. Here we review the role of the renin-angiotensin system (RAS) in CNS tumors and degenerative diseases, to highlight common molecular features and examine the potential merits in repurposing drugs that inhibit the RAS, its bypass loops, and converging signaling pathways. The RAS consists of key components, including angiotensinogen, (pro)renin receptor (PRR), angiotensin-converting enzyme 1 (ACE1), angiotensin-converting enzyme 2 (ACE2), angiotensin I (ATI), angiotensin II (ATII), ATII receptor 1 (AT1R), ATII receptor 2 (AT2R) and the Mas receptor (MasR). The RAS is integral to systemic and cellular pathways that regulate blood pressure and body fluid equilibrium and cellular homeostasis. The main effector of the RAS is ATII which exerts its effect by binding to AT1R and AT2R through two competitive arms: an ACE1/ATII/AT1R axis, which is involved in regulating oxidative stress and neuroinflammation pathways, and an ATII/AT2R and/or ATII/ACE2/Ang(1-7)/MasR axis that potentiates neuroprotection pathways. Alterations of these axes are associated with cellular dysfunction linked to CNS diseases. The generation of ATII is also influenced by proteases that constitute bypass loops of the RAS. These bypass loops include cathepsins B, D and G and chymase and aminopeptidases. The RAS is also influenced by converging pathways such as the Wnt/β-catenin pathway which sits upstream of the RAS via PRR, a key component of the RAS. We also discuss the co-expression of components of the RAS and markers of pluripotency, such as OCT4 and SOX2, in Parkinson's disease and glioblastoma, and their potential influences on transduction pathways involving the Wnt/β-catenin, MAPK/ERK, PI3K/AKT and vacuolar (H+) adenosine triphosphatase (V-ATPase) signaling cascades. Further research investigating modulation of the ACE1/ATII/AT1R and ACE2/Ang(1-7)/MasR axes with RAS inhibitors may lead to novel treatment of CNS tumors and degenerative diseases. The aim of this review article is to discuss and highlight experimental and epidemiological evidence for the role of the RAS, its bypass loops and convergent signaling pathways in the pathogenesis of CNS tumors and degenerative diseases, to direct research that may lead to the development of novel therapy.

Determination of hydrostatic pressure force on a spherical surface under conditions of relative equilibrium of fluid using method K123

Determination of hydrostatic pressure force on a spherical surface under conditions of relative equilibrium of fluid using method K123

Natural mineralized fractures from the Montney-Doig unconventional reservoirs (Western Canada Sedimentary Basin): Timing and controlling factors

Characterizing the origin of natural fractures in organic-rich fine-grained deposits is key to constraining permeability evolution in these potential source rocks and tight reservoirs, as well as to assess the hydraulic connectivity of the fluid systems in which they develop.Differently oriented calcite-filled fractures (i.e. veins), hosted by organic-rich mudrocks of the Lower-Middle Triassic Montney-Doig unconventional resource play (Western Canada Sedimentary Basin), were sampled in sub-surface well cores from British Columbia. A multidisciplinary approach (including sedimentology, Rock-Eval pyrolysis, petrography, O–C–Sr isotope geochemistry and fluid inclusion microthermometry) was applied to host-rocks and fracture filling calcites.The results demonstrate the relevance and usefulness of such multidisciplinary studies to gather insights on: 1) the lithology-related factors controlling fracture occurrence; 2) the timing of fracture opening and the origin of the circulating paleo-fluids; 3) the openness of the fluid system through time.More specifically, host-rock facies (particularly grain size) and vertical facies changes appear to be the leading factors controlling fracture occurrence. A less relevant role was played by the occurrence of diagenetic carbonates, while TOC possibly did not control fracture occurrence.Three generations of calcite cemented fractures were identified. Vertical fractures (first generation) post-dated the onset of oil generation (Late Cretaceous). Horizontal, bedding-parallel fractures (second generation) post-dated the onset of gas generation and possibly opened close to maximum burial, corresponding to peak hydrocarbon (CH4) generation (Late Cretaceous - Early Paleogene). Vertical fractures (third generation) post-dated the horizontal ones and opened during basin uplift (Middle to Late Paleogene).The consistent petrographic and geochemical features of all the calcite cements point to parent fluids in equilibrium with the host-rock lithologies, that possibly behaved as a closed hydraulic system during Late Cretaceous to Paleogene time; this would support the hypothesis that, at least in the portion of the basin investigated, the Montney Fm also acted as source rock of the unconventional system.

Mineralization and petrogenesis of the Qiongheba porphyry copper deposit in Mengxi district, East Junggar, China

The Qiongheba porphyry Cu deposit is characterized by geochemical features of island arc and adakitic intrusions with fractional crystallization playing a key role in the formation of the ore-bearing rocks. Calculated sulfur concentrations in silicate melts at sulfide saturation show that two-thirds of the sulfur was exsolved during the fractional crystallization process to contribute to the formation of sulfides. The ore-bearing rocks in the Qiongheba area yielded U-Pb zircon ages of 414–412 Ma coeval with the 412 Ma Re-Os age of molybdenite indicating that sulfide mineralization is broadly coeval with magmatic crystallization. The color cathodoluminescence of quartz (purple) and K-feldspar (pink) in the fibrous veins and miarolitic cavities (Qtz-2 and Kfs-2) are the same as those (Qtz-1 and Kfs-1) in the granitic porphyry whereas the hydrothermal quartz (Qtz-3) and K-feldspar (Kfs-3) are black and green, suggesting that the color cathodoluminescence can be used to unravel the paragenesis of PCD. The oxygen isotopic values of Qtz-1 and Qtz-2 range from 9.15 to 10.1‰ and 8.93 to 10.4‰ with calculated equilibrium fluid compositions of 9.86 to 11.7‰ and 10.5 to 12.0‰, respectively, indicating a magma-dominated fluid composition, whereas Qtz-3 veins have very low oxygen isotopic values from −4.60 to −1.25‰ with corresponding fluid compositions of −3.51 to −0.17‰, implying that the fluid formed via the mixing of magmatic and meteoric water. Titanium-in-quartz thermometry constrains the magmatic crystallization to 580–627 °C, whereas the magmatic to hydrothermal transition occurred at 523–613 °C.

Evolution of the Kiruna-type Gol-e-Gohar iron ore district, Sanandaj-Sirjan zone, Iran

The Gol-e-Gohar iron ore district in the Sanandaj-Sirjan zone of south-western Iran comprises six major ore bodies. The largest deposit is Gol-e-Gohar No. 3 (Gohar-Zamin) with about 643 Mt @ 53.1% Fe. The host rocks in this district are Late Neoproterozoic meta-sedimentary rocks (para-gneiss, marble), meta-basalt (ortho-amphibolite), and I-type meta-granite (ortho-gneiss). The district is characterized by potassic-sodic (albite-K-feldspar), phyllic (muscovite) and propylitic (chlorite-calcite-dolomite-magnesite with pyrite) hydrothermal alteration, and massive and brecciated Kiruna-type magnetite ± apatite mineralization. There is also boron (B) metasomatism, manifested as tourmaline blastesis. Gol-e-Gohar magnetite contains Mg, Ca and Si up to the percent range, V and Ti in the 100s ppm level, and low Cr, Co, Ni in the tens of ppm range, typical of skarn or IOCG mineralization. The oxygen isotope composition of magnetite is 4.9 ± 0.7‰ δ18O (n = 9) and the iron isotope composition is 0.49 ± 0.05‰ δ56Fe (n = 17). These data suggest that the magnetite ore formed from a magmatic-hydrothermal (high-T) fluid in equilibrium with a granitic source. The hydrothermal carbonate inclusions in late pyrite have δ11B values of 20.3 ± 2.4‰, indicating the imprint of fluids which interacted with the Early Cambrian marine country rocks of the district, such as limestone and/or evaporites. The Gol-e-Gohar iron ore district shows several similarities to the Bafq iron district, located about 400 km to the north, and seems to be a disrupted member of the Kashmar-Kerman arc.

Measurements of solidification kinetics for benzene in methane at high pressures and cryogenic temperatures

A stirred, high-pressure, visual microscopy-based apparatus was used to investigate solid-formation kinetics in LNG-relevant binary mixtures. The apparatus can detect solid crystals as small as 20 µm in a 3.5 mm field of view and is capable of measurements at temperatures as low as 90 K and pressures up to 20 MPa. The apparatus is described in detail and is presented alongside experimental results for two benzene + methane mixtures. Measurements of the solid–fluid equilibrium temperatures for the benzene + methane mixtures at 10 MPa were determined by raising the temperature of the mixture in (0.5 to 1)K steps and observing whether the crystals were still present after 2 h. The equilibrium temperatures were consistent with those predicted using the software package ThermoFAST within the combined experimental and model uncertainties. Formation measurements were carried out using a 100 ppm benzene-in-methane sample. Isobaric constant-cooling experiments at pressures of 8 and 10 MPa were used to construct subcooling formation-probability distributions for this mixture by identifying the temperature at which solid crystals were first observed to form on a copper substrate. The subcooling values at formation ranged from (4.4 to 11.0) K and were used to generate a cumulative probability of formation. The measured formation-probability distribution was fit to a model based on Classical Nucleation Theory to yield an estimate of 5 mJ/m2 for the effective surface free energy of solid benzene in liquid methane on the copper substrate. These results pave the way to probabilistic estimates of risk for solids formation in cryogenic heat exchangers.

Standardized histomorphological processing of peritoneal biopsies as part of the German Peritoneal Biopsy Registry (GRIP, German registry in PD)

Das Peritoneum stellt als seröse Haut, die mit ihrem viszeralen und parietalen Anteil den Bauchraum auskleidet, ein interessantes Organ dar, welches bei der sog. Peritoneal- oder Bauchfelldialyse (PD) klinische Beachtung findet. Bei diesem Nierenersatzverfahren wird die Semipermeabilität des Peritoneums genutzt, um mittels unterschiedlich osmolarer Dialyseflüssigkeiten die sog. harnpflichtigen Substanzen aus dem Körper zu eliminieren. Dies ist insbesondere bei jungen Patienten eine ideales Nierenersatzverfahren und funktioniert in der Regel zumindest einige Zeit sehr gut. Vorschäden des Peritoneums durch die Grunderkrankung der chronischen Niereninsuffizienz oder assoziierte Komorbiditäten sowie v. a. entzündliche Veränderungen während der PD führen zu einem morphologischen Umbau des Peritoneums mit der Konsequenz des Verlusts der Filtereigenschaften, sodass die PD beendet und auf ein anderes Nierenersatzverfahren gewechselt werden muss. Die Kenntnis des morphologischen Umbaus des Peritoneums sowie möglicher begünstigender Faktoren, zu denen es derzeit noch zu wenige Daten gibt, ist wichtig für die Therapie und Prognose der Patienten, die mit PD behandelt werden. Aus diesem Grund wurde vor einigen Jahren das Deutsche Peritonealbiopsieregister (GRIP, German Registry In PD) gegründet, das mittlerweile knapp 1700 Biopsate umfasst und an diesen standardisiert klinische und histomorphologische Parameter erhebt und dokumentiert.

Two Modes of Vibrational Double-Diffusive Instability in a Superposed Fluid-Porous Layer Heated from Below: The Effect of Buoyancy Ratio

The convective double-diffusive instability in a two-layer system consisting of a binary fluid layer overlaying a fluid-saturated porous layer is investigated numerically. The system moves periodically in a vertical direction under the conditions of gravity field. The layers are heated from below and oscillate with high frequency and small amplitude. The instability threshold for the convection onset and the wavelength of convective rolls, which induce as soon as the fluid equilibrium state has lost its stability, are found. The buoyancy ratio and vibrational parameter effects are studied. A region of parameters for the bimodal marginal stability curves is obtained and divided it into parts for the local and large-scale convection onset values. It is revealed that wavelength of stationary convection rolls varies non-monotonically as the buoyancy ratio decreases. The longitudinal scale of rolls reduces sharply at first and then increases gradually. Vibration produces the greatest stabilizing effect on the fluid equilibrium state in a narrow range of small negative and positive buoyancy ratios, which are responsible for a considerable change in the wavelength of rolls. The buoyancy ratio effect on the oscillatory convection rolls is rather weak. The vibration effect on their marginal stability threshold and wavelength is more pronounced.

Effects of turbulent environment on the surface roughening: The Kardar-Parisi-Zhang model coupled to the stochastic Navier–Stokes equation

The Kardar-Parisi-Zhang model of non-equilibrium critical behaviour (kinetic surface roughening) with turbulent motion of the environment taken into account is studied by the field theoretic renormalization group approach. The turbulent motion is described by the stochastic Navier–Stokes equation with the random stirring force whose correlation function includes two terms that allow one to account both for a turbulent fluid and for a fluid in thermal equilibrium. The renormalization group analysis performed in the leading order of perturbation theory (one-loop approximation) reveals six possible types of scaling behaviour (universality classes). The most interesting values of the spatial dimension d = 2 and 3 correspond to the universality class of a pure turbulent advection where the nonlinearity of the Kardar-Parisi-Zhang model is irrelevant.

Transient 3D conjugate heat transfer simulation of a rectangular GOX–GCH4 rocket combustion chamber and validation

This paper aims to predict the transient temperature fields of rocket combustion chambers. This is important for design and lifetime estimation. A thermally coupled simulation (conjugate heat transfer) model was developed and validated using a combustion chamber experiment with rectangular cross-section and the propellant combination gaseous oxygen–methane. The simulation is based on a thermal finite element model of the structure, Reynolds-averaged Navier–Stokes simulations of nine cooling channel flows and a Reynolds-averaged Navier–Stokes simulation with flamelet extension of the hot-gas flow. A pseudo-transient, implicit Dirichlet–Neumann scheme is used for calculating the equilibrium of structure and fluids. A comparison with experiment shows good agreement with the axial, vertical and transverse temperature distribution in the structure, the transient behavior and the wall heat flux through the cooling channels. It is shown that wall functions in the coolant domains can efficiently decrease the computational effort.

COMPARISON OF ELECTROLYTES IN DIABETIC AND NON-DIABETIC PATIENTS

Introduction: Characterized by high blood glucose levels referred as hyperglycemia, diabetes mellitus (DM) is a metabolic disorder with changes in carbohydrates, protein and lipid metabolism which is caused due to disturbance in secretion of insulin or insulin action or both. There are several effects of diabetes, beginning with metabolic imbalances, degeneration of the walls of the blood vessels that can allow electrolyte concentrations to dilute and counteract the proportion of electrolytes. In several applications, electrolytes play an important part, such as acid base, body fluids, blood clots and muscle contractions are regulated. In preserving homeostasis in the body, and also in protecting cellular structure, tissue perfusion and acid base equilibrium, fluid and electrolyte equilibrium play important roles. The association with glucose in the blood and electrolytes are complex and electrolyte imbalances can influence the course and treatment of diabetes. We know that diabetes is a chronic disease and there are possible complications. For a long time people with extreme hyperglycemia may remain mostly asymptomatic. Consequently, many of them have some end-organ damage at the moment of diagnosis of diabetes. Pathophysiological factors like nutritional status, certain drugs, coexistence of acid-base imbalance, co-morbid conditions like renal disorder or acute illness play a key role in electrolyte imbalance, alone or in combination.&#x0D; Material &amp; Methods: Patients attending medicine OPD were selected for this study after obtaining their consent. Purposive sampling technique has been used to obtain sample. A total of 100 patients were included in this comparative study among which 50 were diabetic and 50 were non-diabetic patients. The demographic details of patients were noted. Blood samples were collected and investigated and analyzed for Magnesium, Sodium, Chloride and Potassium. RESULTS: In present study it has been observed that the levels of magnesium were 1.7 ± 0.4 in diabetic patients and 2.0 ± 0.2 in patients not suffering from diabetes. It was observed that the mean values of magnesium in diabetic patients were significantly lower compared to those of patients who did not suffer with diabetes. Sodium, chloride and potassium did not differ significantly among both groups.&#x0D; Conclusion: Importance of serum electrolytes is shown in this study. Diabetes mellitus patients are more likely to develop electrolytes. Most likely, imbalances are due to the complications they acquire and the medicines they take. Hypomagnesemia is more common in our sample than other electrolyte disorders in the diabetic population.&#x0D; Keywords: Electrolytes, Magnesium, Diabetes Mellitus

Multiple sulfur isotope fractionation in hydrothermal systems in the presence of radical ions and molecular sulfur

This study is aimed to evaluate the role played by the sulfur radical ions (S3− and S2−) and molecular sulfur (S0) on sulfur isotope fractionation and to investigate if these species may leave an isotope fingerprint in hydrothermal systems. For this purpose, we combined (i) experiments using a hydrothermal reactor with aqueous S3−(S2−)-S0-sulfate-sulfide fluids and pyrite across a wide range of temperatures (300–450 °C), pressures (300–800 bars), fluid acidity (4 < pH < 8) and with elevated total sulfur concentrations (0.1–1.0 mol/kg fluid) favorable for formation of those polymeric sulfur species, (ii) precise quadruple S isotope analyses of the different S-bearing aqueous species in sampled fluids and in-situ precipitated pyrite, and (iii) thermodynamic modeling of sulfur aqueous speciation and solubility. Our results quantitatively confirm both equilibrium and kinetic SO4-H2S and pyrite-H2S mass dependent fractionation (MDF) factors previously established using extensive experimental and natural data from more dilute fluids in which polymeric sulfur species are negligible. MDF signatures of S0 measured in the sampled fluids of this study reveal different S0-forming pathways such as (i) breakdown on cooling of S3− (and S2−) and other chain-like S0 polymers only stable at high temperature and being isotopically identical to H2S; (ii) cyclooctasulfur (S80, liquid or solid) precipitating by recombination of sulfate and sulfide and/or by exchange with polysulfide dianions (Sn2−) on cooling and being slightly 34S-enriched compared to H2S (by ∼2‰ of δ34S); and iii) a different type of S0 resulting from thiosulfate irreversible breakdown and being highly 34S-depleted (by ∼12‰) relative to H2S. Our data do not show any significant mass independent fractionation (MIF) of 33S and 36S, with Δ33S and Δ36S values of any S aqueous species and pyrite being within ±0.1‰ and ±1.0‰, respectively. Therefore, under the investigated experimental conditions, the radical S3− ion is unlikely to generate significant MIF in the hydrothermal fluid phase and in pyrite and native sulfur precipitated therefrom. Our study supports the existing interpretations of small Δ33S and Δ36S variations between sulfide/sulfate-bearing fluid and pyrite as MDF in terms of reaction kinetics, different reaction pathways, and mass conservation effects such as mixing of S reservoirs or Rayleigh distillation. Our data extend, across a wider range of sulfur concentration and chemical speciation, the existing multiple S isotopes models that exploit such variations as a complement to the traditional δ34S tracer to monitor the approach to equilibrium and evolution of hydrothermal fluids.