Entrapment Conditions Research Articles

Steady bubble rise and deformation in Newtonian and viscoplastic fluids and conditions for bubble entrapment

We examine the buoyancy-driven rise of a bubble in a Newtonian or a viscoplastic fluid assuming axial symmetry and steady flow. Bubble pressure and rise velocity are determined, respectively, by requiring that its volume remains constant and its centre of mass remains fixed at the centre of the coordinate system. The continuous constitutive model suggested by Papanastasiou is used to describe the viscoplastic behaviour of the material. The flow equations are solved numerically using the mixed finite-element/Galerkin method. The nodal points of the computational mesh are determined by solving a set of elliptic differential equations to follow the often large deformations of the bubble surface. The accuracy of solutions is ascertained by mesh refinement and predictions are in very good agreement with previous experimental and theoretical results for Newtonian fluids. We determine the bubble shape and velocity and the shape of the yield surfaces for a wide range of material properties, expressed in terms of the Bingham Bn=$\tau_y^{\ast}/\rho^{\ast}g^{\ast} R_b^{\ast}$ Bond Bo =$\rho^{\ast}g^{\ast} R_b^{\ast 2}/\gamma^{\ast}$ and Archimedes Ar=$\rho^{\ast2}g^{\ast} R_b^{\ast3}/\mu_o^{\ast2}$ numbers, where ρ* is the density, μ*o the viscosity, γ* the surface tension and τ*y the yield stress of the material, g* the gravitational acceleration and R*b the radius of a spherical bubble of the same volume. If the fluid is viscoplastic, the material will not be deforming outside a finite region around the bubble and, under certain conditions, it will not be deforming either behind it or around its equatorial plane in contact with the bubble. As Bn increases, the yield surfaces at the bubble equatorial plane and away from the bubble merge and the bubble becomes entrapped. When Bo is small and the bubble cannot deform from the spherical shape the critical Bn is 0.143, i.e. it is a factor of 3/2 higher than the critical Bn for the entrapment of a solid sphere in a Bingham fluid, in direct correspondence with the 3/2 higher terminal velocity of a bubble over that of a sphere under the same buoyancy force in Stokes flow. As Bo increases allowing the bubble to squeeze through the material more easily, the critical Bingham number increases as well, but eventually it reaches an asymptotic value. Ar affects the critical Bn value much less.

Entrapment of functionalized silica microspheres with photo-initiated acrylate-based polymers

The entrapment of silica-based microspheres, commonly used as stationary phases in chromatography, with an organic porous polymer based on poly(butyl acrylate- co-1,3-butanediol diacrylate) was explored. The spheres were immobilized by photopolymerization leading to entrapped beds within 75 μm i.d. fused silica capillaries, and were mechanically stable, resisting pressure drops of over 5600 psi (38.6 MPa) for only 1 cm of material. The morphology of the polymer formation around the spheres was investigated by SEM and corroborated with back pressure measurements, which indicated that the spheres were held together by encapsulating polymer. The entrapped material was extruded from the capillary in some cases to facilitate imaging. The entrapment conditions were explored, varying the polarity of the sphere surface, the solvent, and the monomers, revealing that polymer formation is based on partitioning of the monomers between the surface and solvent. The resulting polymer morphology is discussed with respect to the effects of confinement, supported by experiments with varying microsphere diameters. The columns described here have favourable properties for use in capillary chromatography and supported catalysis among other applications, and is suitable for lab-on-a-chip devices.

Fault–valve action and vein development during strike–slip faulting: An example from the Ribeira Shear Zone, Southeastern Brazil

Fluid inclusion microthermometry and structural data are presented for quartz vein systems of a major dextral transcurrent shear zone of Neoproterozoic–Cambrian age in the Ribeira River Valley area, southeastern Brazil. Geometric and microstructural constraints indicate that foliation–parallel and extensional veins were formed during dextral strike–slip faulting. Both vein systems are formed essentially by quartz and lesser contents of sulfides and carbonates, and were crystallized in the presence of CO 2–CH 4 and H 2O–CO 2–CH 4–NaCl immiscible fluids following unmixing from a homogeneous parental fluid. Contrasting fluid entrapment conditions indicate that the two vein systems were formed in different structural levels. Foliation–parallel veins were precipitated beneath the seismogenic zone under pressure fluctuating from moderately sublithostatic to moderately subhydrostatic values (319–397 °C and 47–215 MPa), which is compatible with predicted fluid pressure cycle curves derived from fault–valve action. Growth of extensional veins occurred in shallower structural levels, under pressure fluctuating from near hydrostatic to moderately subhydrostatic values (207–218 °C and 18–74 MPa), which indicate that precipitation occurred within the near surface hydrostatically pressured seismogenic zone. Fluid immiscibility and precipitation of quartz in foliation–parallel veins resulted from fluid pressure drop immediately after earthquake rupture. Fluid immiscibility following a local pressure drop during extensional veining occurred in pre-seismic stages in response to the development of fracture porosity in the dilatant zone. Late stages of fluid circulation within the fault zone are represented dominantly by low to high salinity (0.2 to 44 wt.% equivalent NaCl) H 2O–NaCl–CaCl 2 fluid inclusions trapped in healed fractures mainly in foliation–parallel veins, which also exhibit subordinate H 2O–NaCl–CaCl 2, CO 2–(CH 4) and H 2O–CO 2–(CH 4)–NaCl fluid inclusions trapped under subsolvus conditions in single healed microcracks. Recurrent circulation of aqueous–carbonic fluids and aqueous fluids of highly contrasting salinities during veining and post-veining stages suggests that fluids of different reservoirs were pumped to the ruptured fault zone during faulting episodes. A fluid evolution trending toward CH 4 depletion for CO 2–CH 4–bearing fluids and salinity depletion and dilution (approximation of the system H 2O–NaCl) for aqueous–saline fluids occurred concomitantly with decrease in temperature and pressure related to fluid entrapment in progressively shallower structural levels reflecting the shear zone exhumation history.

Photoinduced Polymerization for Entrapping of Octadecylsilane Microsphere Columns for Capillary Electrochromatography

A novel fritless capillary column for capillary electrochromatography (CEC) has been developed. The ODS microspheres were packed into a capillary and were then immobilized within an organic polymer prepared in situ through a photopolymerization process. The entrapment conditions were investigated to minimize the effect of the polymer matrix on the chromatographic properties of the packing material. The organic polymer matrix in the microsphere-packed column functions to link microspheres at specific sphere-sphere and sphere-capillary contact points. CEC separations of a PAH test mixture using entrapped columns with different UV illumination times were compared in terms of retention factor and separation efficiency. The optimized entrapped column demonstrated better chromatographic performance than similarly packed columns with conventional inlet and outlet frits. The electrochromatographic separations of hormones and peptides were also demonstrated on entrapped ODS columns.

Birefringence analysis of diamond utilising the MetriPol system

Birefringence has long been recognised in diamond as an anomalous optical property for a cubic mineral (Lang, 1967). Various causes have been postulated for this phenomenon but they all identify birefringence as being the result of the photoelastic effect (change of refractive index with stress) (Poindexter, 1955). Until now birefringence studies (a non-destructive analytical technique) has not been utilised because of the time-consuming and inaccurate nature of the analysis. The MetriPol is a new automated birefringence analysis system that can produce very accurate data in a matter of seconds (Glazer et al., 1996). The MetriPol system is being utilised in an experimental investigation to re-evaluate the photoelastic constants for diamond. These constants are fundamental in relating stress and strain to the resultant birefringence. Data generated from this birefringence analysis can easily be manipulated to calculate the stress and strain within a diamond. Optical studies of mineral inclusions have often reported the occurrence of strain birefringence in the surrounding diamond, and X-ray and Raman investigations of such inclusions have shown that some can remain under relatively high residual pressures after their transportation to the surface (e.g. Izraeli et al., 1999). We report quantitative birefringence analysis of such strain features and their implication concerning the P & T conditions of entrapment, assuming no subsequent strain release has occurred. This birefringence data is being compared with analyses using the above techniques, as well as finite element analysis modelling, to test the validity of the results.

Evaluation of contact conditions in hot forging of pure aluminum using ultrasonic examination

In isothermal upset forging of pure aluminum, the change in the contact condition and the lubricant behavior were evaluated by continuously measuring the ultrasonic reflection intensity from the contact interface between the tool (die) and workpiece. The relationships between ultrasonic reflection intensity, forging temperature, lubrication, forging pressure and workpiece surface during forging were examined. Depending on forging temperature, the conditions of the lubricant entrapment on the surface of the workpiece exhibited significant changes. The condition of lubricant pools and lubricant film was evaluated during warm and hot forging using the ultrasonic reflection intensity. The change in the contact condition and the lubricant behavior during warm and hot forging were measured with high sensitivity by the proposed ultrasonic measurement. The lubrication conditions can be optimized based on the in situ evaluation of the contact conditions.

A reassessment of models for hydrocarbon generation in the Khibiny nepheline syenite complex, Kola Peninsula, Russia

Although hydrocarbon-bearing fluids have been known from the alkaline igneous rocks of the Khibiny intrusion for many years, their origin remains enigmatic. A recently proposed model of post-magmatic hydrocarbon (HC) generation through Fischer-Tropsch (FT) type reactions suggests the hydration of Fe-bearing phases and release of H 2 which reacts with magmatically derived CO 2 to form CH 4 and higher HCs. However, new petrographic, microthermometric, laser Raman, bulk gas and isotope data are presented and discussed in the context of previously published work in order to reassess models of HC generation. The gas phase is dominated by CH 4 with only minor proportions of higher hydrocarbons. No remnants of the proposed primary CO 2-rich fluid are found in the complex. The majority of the fluid inclusions are of secondary nature and trapped in healed microfractures. This indicates a high fluid flux after magma crystallisation. Entrapment conditions for fluid inclusions are 450–550 °C at 2.8–4.5 kbar. These temperatures are too high for hydrocarbon gas generation through the FT reaction. Chemical analyses of rims of Fe-rich phases suggest that they are not the result of alteration but instead represent changes in magma composition during crystallisation. Furthermore, there is no clear relationship between the presence of Fe-rich minerals and the abundance of fluid inclusion planes (FIPs) as reported elsewhere. δ 13C values for methane range from − 22.4‰ to − 5.4‰, confirming a largely abiogenic origin for the gas. The presence of primary CH 4-dominated fluid inclusions and melt inclusions, which contain a methane-rich gas phase, indicates a magmatic origin of the HCs. An increase in methane content, together with a decrease in δ 13C isotope values towards the intrusion margin suggests that magmatically derived abiogenic hydrocarbons may have mixed with biogenic hydrocarbons derived from the surrounding country rocks.

Highly efficient immobilization of endo-1,3-β- d-glucanases (laminarinases) from marine mollusks in novel hybrid polysaccharide-silica nanocomposites with regulated composition

A novel immobilizing method developed previously by ourselves was successfully used to entrap endo-1,3-β- d-glucanases (laminarinases) separated from marine bivalvia Spisula sacchalinensis (glucanase L IV) and Chlamys albidus (glucanase L o) into hybrid polysaccharide-silica nanocomposite materials by means of the sol–gel processing. Its main advantage over the current immobilizing procedures is that the entrapment conditions are dictated by the enzymes, but not the processing. It was shown that both the 1,3-β- d-glucanases retained or even had sometimes an increased activity after the immobilization. At the same time, their characteristics (optimal pH, temperature and ionic strength) noticeably were not changed. They provided a depth of hydrolysis of laminaran comparable with that caused by free enzymes in solutions. Furthermore, glucanase L o retained its glucanosyl transferase activity, affording an enzymatic synthesis of biologically active 1,3;1,6-β- d-glucan, called translam, from the initially inactive laminaran. It was also demonstrated that the laminarinase entrapment into the hybrid nanocomposites led to a prominent increase of thermal and long-term stability that was particular striking in a case of such a labile enzyme as the glucanase L o. By varying the nanomaterial composition, its influence on the glucanase activity was found that differed for the studied enzymes.

Improved platinization conditions produce a 60-fold increase in sensitivity of amperometric biosensors using glucose oxidase immobilized in poly- o-phenylenediamine

Platinization has been used to increase electrode surface area and therefore electrode sensitivity. However there are few studies on platinization conditions and their effects on the reaction diffusion of enzyme biosensors. We report the fabrication of sensitive (192 ± 48 μA cm −2 mM −1) amperometric glucose sensors. The repeatability (precision) was at worst 2.32% ± 1.22% of the measured value, the limit of detection was 0.94 mM and the detection was linear up to at least 25 mM. Sensor-to-sensor variability was 24%. The half-life of the sensors at 21 °C was 12 days. Shelf life at 4 °C was at least one month without a decrease in sensitivity. Under continuous operation, sensors performed at least 120 determinations without a large decrease in sensitivity; however; fluctuations in current response indicate that frequent calibration is required. Sensors were used for the determination of glucose in apple juice and white wine. High sensitivity was achieved by improving the conditions of platinization and entrapment of glucose oxidase in poly- o-phenylenediamine. Potentiostatic platinization at −100 or −50 mV vs. Ag∣AgCl resulted in mechanically stable deposits unlike those formed at the commonly used −250 mV. Large concentrations of glucose oxidase did not inhibit the electropolymerization of o-phenylenediamine. H 2O 2 diffusion experiments using polished and platinized, bare and polymer-covered rotating disk electrodes suggest that H 2O 2 diffuses from the bulk of the solution through the polymer film to be oxidized at the platinized surface and the diffusion is apparently one-dimensional with platinization compensating for the coverage of catalytic sites by the polymer. Conversely, when, on a platinized electrode, glucose oxidase is immobilized in a thin poly- o-phenylenediamine film, substrate diffuses rapidly through the porous matrix and H 2O 2 is produced throughout the enzyme/polymer film. Under these conditions, diffusion is apparently multidirectional and platinization results in an effectively large increase in surface area that results in a high amperometric response. A mathematical model of the reaction–diffusion matrix of polished electrodes supports this interpretation of the increased response.

Thermodynamic modeling of post-entrapment crystallization in igneous phases

Inclusions of quenched silicate liquid in igneous phenocryst phases represent important windows into the pre-eruption chemistry of volcanic rocks. Melt inclusions are subject to a variety of potential modifications after entrapment, which obscure the connection between final inclusion composition, and entrapment conditions. We concentrate on the effects of post-entrapment crystallization (PEC) in the cooling inclusion. PEC is neither an isobaric nor an isochoric process. Pressure decreases between 2 and 27 bars per degree of cooling, depending on the chemistry of melt and host and on the degree of PEC. In the equilibrium case, between about 50% and 65% of this pressure effect is due to thermal expansivity of the liquid, 10–35% from thermal expansivity of the host, and 5–40% from mass transfer between the inclusion and host. This complicates the application of simple element-partitioning schemes for back-calculating the effects of post-entrapment crystallization except in the simplest cases. We present a thermodynamic algorithm for PEC correction. This method is based on the self-consistent thermodynamic model set used in the MELTS software package. The algorithm moves backward through the PEC process, incrementally adding equilibrium crystal composition to the liquid while accounting for consequent variations in pressure and oxygen fugacity. Entrapment conditions are assumed to have been reached when the instantaneous liquidus solid composition most closely matches that of the bulk host crystal. Besides giving information on the degree of PEC and initial inclusion composition, the proposed algorithm can provide constraints on the pressure, temperature and oxygen fugacity at the time of entrapment. Olivine- and orthopyroxene-hosted inclusions from Popocatépetl, Mexico help constrain pre-eruption conditions for mixed magmas from recent eruptive products. Feldspar-hosted inclusions from Satsuma-Iwojima, Japan suggest that these magmas were substantially undersaturated with respect to supercritical vapor phase at the time of entrapment and underwent on the order of 29% post-entrapment crystallization. Quartz-hosted inclusions can potentially be employed in more silicic compositions, but this will require refinement of existing thermodynamic models.

Effect of NAPL entrapment conditions on air sparging remediation efficiency

The effect of soil heterogeneity and the entrapment condition of NAPL source on the mass removal efficiency of air sparging coupled with soil vapour extraction (AS/SVE) was investigated using an intermediate scale two-dimensional laboratory soil tank. Four different NAPL entrapments were created by varying the height of the water table in heterogeneous soil models. Different mass removal efficiencies were achieved for different NAPL entrapment conditions, which were governed by soil heterogeneity and water table height before and during AS/SVE operation. Remobilization and redistribution of toluene and water improved the mass removal. Overall results suggested that it was difficult to achieve the complete remediation of NAPL source due to complex entrapment in heterogeneous soil system. In order to assess the potential contamination in the post-remediation stage, gas and dissolved concentrations of toluene were measured after the AS/SVE operation. The results showed that gas concentration close to remaining NAPL source zone increased rapidly and reached to steady state values, which were much smaller than the vapour pressure, whereas the aqueous phase concentrations increased continuously toward the solubility limit.

Is carpal tunnel syndrome surgery useful in patients with diabetes or autoimmune polyneuropathies?

In the neurological ‘out‐patient’ department, focused on neuropathies, we have to deal with two common diseases: diabetic neuropathy and autoimmune neuropathies. Carpal tunnel syndrome is the most frequent neurological syndrome. It is difficult to assess if, in a diffuse peripheral nerve involvement or in systemic condition that may involve nerves, as diabetes, an entrapment condition is a distinct entity, a co‐morbidity condition, or expression of a “locus minor resistentiae.” In clinical practice it is difficult to answer these questions: in autoimmune neuropathy patients and in diabetic patients, should we surgically treat nerve entrapment? Recently we provided evidence that a mechanical condition around the nerve, typical of the entrapment region, does not enhance autoimmune aggression in CIDP. Therefore, in CIDP patients a true entrapment, neurophysiologically demonstrated, could be a concomitant pathology and if a severe and persistent entrapment worsens functional deficit and symptoms, a surgical decompression could be useful. There is evidence that diabetic patients operated for carpal tunnel syndrome have the same post surgery evolution than non‐diabetic patients. In conclusion, in autoimmune neuropathies and diabetic patients, the physician should strongly consider the possibility of surgery.

Double crush syndrome.

Nerve entrapment conditions and peripheral neuropathies are sometimes related to injurious events, toxicosis, and repetitive microtrauma to soft tissue and nerve structures. An interesting theory concerning peripheral entrapment neuropathy has been discussed in the literature. This theory is called the double crush syndrome. This article briefly discusses the biologic/metabolic, structural, toxicogenic, and vasculopathic rationale for the pathogenesis of double crush syndrome.

Centrifuge Modeling of Nonaqueous Phase Liquid Movement and Entrapment in Unsaturated Layered Soils

Four geotechnical centrifuge tests with different soil layered systems were performed to investigate the movement and entrapment of water and of light nonaqueous phase liquids (LNAPLs) in unsaturated layered soil deposits. The tests were performed at 20 g and a vadose zone condition was created during the centrifuge tests by lowering the water table from the initially water saturated condition. During the water drainage stage, the water distribution within the models and the dynamic air-water capillary pressure saturation relationships of the three sands were obtained using tensiometers and resistivity probes. After achieving the unsaturated condition, a model LNAPL (Soltrol 220® or silicon oil) was injected near the soil surface and the movement and entrapment were monitored during the redistribution stage until the LNAPL reached the top of the water table. Complex LNAPL preferential flow and entrapment patterns were observed in the layered models with different textural interfaces due to the relative movement of all three phases [water, nonaqueous phase liquid (NAPL), and air]. The centrifuge tests data coupled with the numerical analyses show that NAPL properties, subsurface soil structures, initial water saturation, and NAPL infiltration rate affect the variation in entrapment conditions in heterogeneous unsaturated soil deposits.

Individual characterization of petroleum fluid inclusions (composition and P– T trapping conditions) by microthermometry and confocal laser scanning microscopy: inferences from applied thermodynamics of oils

This paper proposes a new method to characterize individual oil-bearing fluid inclusions. It uses both the homogenisation temperatures measured by microthermometry, and the degree of gas bubble filling measured by confocal laser scanning microscopy, in conjunction with thermodynamic modelling for describing liquid–gas phase transitions and the volumetric behaviour of hydrocarbon mixtures. It is associated with a two-parameter ( α, β) compositional model that describes the wide range of compositions of petroleums. We show that this method can give (1) useful estimations of the compositions and pressure–temperature entrapment conditions of oils in fluid inclusions, and (2) insights into the various processes that have affected these fluids either before entrapment (liquid–gas unmixing, gas leaching, mixing, etc.) or after (leakage, etc.).

Fluid inclusions and PVTX modelling: examples from the Garn Formation in well 6507/2-2, Haltenbanken, Mid-Norway

Fluid inclusions study and multi-techniques quantitative analyses have been coupled to reconstitute PVTX conditions of aqueous and petroleum fluid entrapment of a local Haltenbanken area (well 6507/2-2) from the Garn Formation. Unusual low temperature behaviour showing the liquid portion separating into two liquids has been described. This behaviour is typical of a gas condensate/volatile mixture with high methane content and heavy alkanes. The variable liquid–vapour ratio, compositions and morphologies of all petroleum inclusions can be interpreted as a result of a combination of heterogeneous trapping and necking down. Thus, all petroleum inclusions can be related to a single petroleum source. Three main episodes of fluid entrapment can be distinguished. The first one corresponds to the water trapped within detrital quartz microfractures, at around 50 °C and 50 bar; the second to the petroleum fluid arrival in the biphase field of a critical system around 100–120 °C and 190–230 bar. The third one to the main trapping of present-day petroleum inclusions during the recrystallisation of quartz cements (around 110–160 °C and 230–280 bar) within the last few million years of a short and relatively rapid burial.

Entrance meniscus in a pressurized optical fiber coating applicator

The present work describes experimental measurements relevant to the coating process of optical fibers in pressurized applicators. The focus was on the entrance geometry, which was simulated using micropipettes of different sizes allowing visualization of the free surface with apparatus operating off-line, using glycerol as the surrogate coating liquid. The meniscus shape and position were measured for different applicator pressures, fiber speeds and tube diameters, and conditions for air entrapment were identified.

FLUIDS ASSOCIATED WITH THE CAXIAS MESOTHERMAL GOLD MINERALIZATION, SÃO LUÍS CRATON, NORTHERN BRAZIL: A FLUID INCLUSION STUDY

The Caxias deposit is situated in the Gurupi Auriferous Province of the Paleoproterozoic São Luís Craton, northern Brazil. It is a lode-type gold mineralization associated with a narrow, steeply dipping, NE-trending, shear zone crosscutting a hydrothermalized microtonalite (northern sector) and schists (southern sector). Fluid inclusion studies on vein quartz crosscutting the microtonalite (northern sector) have identified early carbonic and aqueous-carbonic inclusions and late aqueous inclusions, unrelated to the mineralizing event. The CO 2 / H 2 O ratio and the other microthermometric properties show a wide range of values, which are interpreted as product of heterogeneous trapping of two (partially) immiscible fluids and to deformation-related post-formational processes. The resulting mineralizing fluid has XCO 2 : 6-45 mol %; XN 2 : < 2.5 mol %; XH 2 O: 55-95 mol %; mean salinity of 4.5 wt % NaCl equiv., and moderate density (0.7-1.0 g/cm3 ). Bulk isochores coupled with chlorite geothermometry constrained the P-T entrapment conditions between 262-307ºC and 1.6-3.7 kb. Log ¦O 2 for this P-T-X range was estimated between –29.8 and –34.2. Geological characteristics and fluid properties found in the northern sector of Caxias gold mineralization are similar to those described for metamorphic fluids of mesothermal gold deposits.

FLUIDS ASSOCIATED WITH THE CAXIAS MESOTHERMAL GOLD MINERALIZATION, SÃO LUÍS CRATON, NORTHERN BRAZIL: A FLUID INCLUSION STUDY

The Caxias deposit is situated in the Gurupi Auriferous Province of the Paleoproterozoic Sao Luis Craton, northern Brazil. It is a lode-type gold mineralization associated with a narrow, steeply dipping, NE-trending, shear zone crosscutting a hydrothermalized microtonalite (northern sector) and schists (southern sector). Fluid inclusion studies on vein quartz crosscutting the microtonalite (northern sector) have identified early carbonic and aqueous-carbonic inclusions and late aqueous inclusions, unrelated to the mineralizing event. The CO 2 / H 2 O ratio and the other microthermometric properties show a wide range of values, which are interpreted as product of heterogeneous trapping of two (partially) immiscible fluids and to deformation-related post-formational processes. The resulting mineralizing fluid has XCO 2 - 6-45 mol %; XN : < 2.5 mol %; XH 2 O: 55-95 mol %; mean salinity of 4.5 wt % NaCl equiv., and moderate density (0.7-1.0 g/cm 3 ). Bulk isochores coupled with chlorite geothermometry constrained the P-T entrapment conditions between 262-307°C and 1.6-3.7 kb. Log |O 2 for this P-T-X range was estimated between -29.8 and -34.2. Geological characteristics and fluid properties found in the northern sector of Caxias gold mineralization are similar to those described for metamorphic fluids of mesothermal gold deposits.

Survival of Bifidobacterium longum immobilized in calcium alginate beads in simulated gastric juices and bile salt solution.

Bifidobacterium longum KCTC 3128 and HLC 3742 were independently immobilized (entrapped) in calcium alginate beads containing 2, 3, and 4% sodium alginate. When the bifidobacteria entrapped in calcium alginate beads were exposed to simulated gastric juices and a bile salt solution, the death rate of the cells in the beads decreased proportionally with an increase in both the alginate gel concentration and bead size. The initial cell numbers in the beads affected the numbers of survivors after exposure to these solutions; however, the death rates of the viable cells were not affected. Accordingly, a mathematical model was formulated which expressed the influences of several parameters (gel concentration, bead size, and initial cell numbers) on the survival of entrapped bifidobacteria after sequential exposure to simulated gastric juices followed by a bile salt solution. The model proposed in this paper may be useful for estimating the survival of bifidobacteria in beads and establishing optimal entrapment conditions.