One-phase System Research Articles (Page 1)

Random positioning machines (RPM) are commonly used to simulate microgravity for plant growth and cell culturing experiments, but not properly in multi-phase flow studies, e.g., emulsions. The implications of fluid motion induced by RPM movement patterns have only been studied for one-phase system using computational fluid dynamics (CFD). This study investigates the impact of fluid motion of 5 different RPM motion modes (0 g, 0.4 g, clinostat of different frame rates) on dispersed droplets (d32 = 0.1-70 μm) applying scaling analysis. These computations are based on well-established fluid-dynamic laws and correlations, thereby giving microgravity researchers easier tool to evaluate potential deficiencies in their study design compared to CFD. We found that the clinostat modes (80 deg s-1; 100 deg s-1; 120 deg s-1) induce a transitional flow regime in the continuous phase, and considerate shear rates acting on the dispersed droplets. Under certain conditions, the shear rates might even impact the average particle size, representing a major corruption in study design, which must not be mistaken as an effect of simulated microgravity. On the other hand, the 0 g and 0.4 g motion modes lead to a laminar flow in the continuous phase, low shear forces, Stokes flow surrounding the dispersed droplets, little relative droplet movement, as well as neglectable forced convection and gravitational force, thus resembling a state similar to true microgravity (0 g motion mode) and partial gravity (0.4 g motion mode).

The article deals with the opportunity of using three-phase electric traction system which was operated from the end of XIX century to 1976. A comparison of the suggested system to one-phase electric traction system of alternating current has been conducted. During the research the ratio of the currents and the power losses in the traction networks of one-phase and three-phase systems has been determined. The calculations show that the losses of the electric power in the contact network of one-phase electric traction system is 3.35 times more than in the three-phase system. The influence of current on electro erosion, wear and tear of a contact wire and electric power collector of the runner of an electric rolling stock current-collector, and also, the influence of the intensiveness of the current-collection and the suspension zigzag of the contact wire on the gauge of the current-collector has been researched. The results of the experimental and calculated values of the coefficient of the wear and tear of the contact wire depending on the current of the current-collector have been presented. Three variants of the size of the runner for a small-sized current-collector of an electric locomotive of AC three-phase electric traction system have been suggested.

Simple and rapid ionic liquid-based one-, two-, three-phase transition microextraction for efficient extraction of trace organic pollutants and elimination of lipid co-extractives from fatty food matrices

The propagation velocities of shock waves with Mach numbers in the range 1.1--1.5 have been directly measured in liquid lead over a wide region of fluid states in the specific volume and pressure plane across the metal-nonmetal transition range. The measured values are compared with those obtained from a caloric equation of state (EOS) constructed using the results of dynamic experiments. The comparison shows that the measured values are in good agreement within the values calculated by the EOS. These results suggest that, for the entire region of the fluid states investigated here (where the fluid is a one-phase system) the shock waves are stable. The values of the critical pressure, critical volume, and critical enthalpy were determined using the EOS and compared with literature data. Thus, the EOS of liquid lead is presented, describing its thermodynamic properties with known accuracy in wide ranges of specific volume and pressure.

Rationally designing carriers to obtain efficient and stable immobilized enzymes for the production of food raw materials is always a challenge. In this work, hollow cube carbon (HMC) as a carrier of Candida rugosa lipase (CRL) was prepared to construct a Pickering interfacial biocatalysis system, which was applied to biphasic biocatalysis. For comparison, the nonporous carbon (HC) and porous MoS2 (HMoS2) were also designed. On these grounds, p-NPP and linolenic acid were selected as the representative substrates for hydrolysis and esterification reactions. Under the optimal conditions, the protein loading amount, specific activity, and expressed activity of CRL immobilized on HMC (HMC@CRL) were 167.2 mg g-1, 5.41 U mg-1, and 32.34 U/mg protein, respectively. In the "oil-water" biphase, the relative hydrolytic activity of HMC@CRL was higher than that of HC@CRL, HMoS2@CRL, and CRL by 50, 68, and 80%, respectively, as well as itself in one phase. Compared to other reports (1.13%), HMC@CRL demonstrated a satisfactory hydrolysis rate (3.02%) and was the fastest among all other biocatalysts in the biphase. Moreover, compared with the free CRL in one-phase system, the Pickering interfacial biphasic biocatalyst, HMC@CRL, exhibited a higher esterification rate (85%, 2.7-fold enhancement). Therefore, the HMC@CRL nanoreactors had more optimal performance in the field of biomanufacturing and food industry.

ObjectiveDietary phytase increases bioavailability of phytate-bound phosphorus (P) in pig nutrition affecting dietary calcium (Ca) to P ratio, intestinal uptake, and systemic utilization of both minerals, which may contribute to improper bone mineralization. We used phytase to assess long-term effects of two dietary available P (aP) levels using a one-phase feeding system on gene expression related to Ca and P homeostasis along the intestinal tract and in the kidney, short-chain fatty acids in stomach, cecum, and colon, serum, and bone parameters in growing gilts and barrows.MethodsGrowing pigs (37.9±6.2 kg) had either free access to a diet without (Con; 75 gilts and 69 barrows) or with phytase (650 phytase units; n = 72/diet) for 56 days. Samples of blood, duodenal, jejunal, ileal, cecal, and colonic mucosa and digesta, kidney, and metacarpal bones were collected from 24 pigs (6 gilts and 6 barrows per diet).ResultsPhytase decreased daily feed intake and average daily gain, whereas aP intake increased with phytase versus Con diet (p<0.05). Gilts had higher colonic expression of TRPV5, CDH1, CLDN4, ZO1, and OCLN and renal expression of TRPV5 and SLC34A3 compared to barrows (p<0.05). Phytase increased duodenal expression of TRPV5, TRPV6, CALB1, PMCA1b, CDH1, CLDN4, ZO1, and OCLN compared to Con diet (p<0.05). Furthermore, phytase increased expression of SCL34A2 in cecum and of FGF23 and CLDN4 in colon compared to Con diet (p<0.05). Alongside, phytase decreased gastric propionate, cecal valerate, and colonic caproate versus Con diet (p<0.05). Phytase reduced cortical wall thickness and index of metacarpal bones (p<0.05).ConclusionGene expression results suggested an intestinal adaptation to increased dietary aP amount by increasing duodenal trans- and paracellular Ca absorption to balance the systemically available Ca and P levels, whereas no adaption of relevant gene expression in kidney occurred. Greater average daily gain in barrows related to higher feed intake.

Modifications in surfactant-dependent phase behavior of colloidal nanoparticles under charge reversal

Extensive efforts have been devoted towards the development of methods for the direct conversion from methane (CH4), ethane (CH3CH3), or other abundant natural gasses into useful products, such as the corresponding alcohols, aldehydes, ketones, and carboxylic acids, as liquid fuels and precursors of chemical and pharmaceutical products. Selective aerobic oxygenation of CH4 into liquid products without the concomitant formation of CO2 and CO has served as an elusive target reaction. The one-step transformation of CH4 into methanol (CH3OH) is carried out in nature using methane monooxygenases. However, under chemical conditions, the selective oxygenation of CH4 to CH3OH with molecular oxygen (O2) has been unknown because the oxidation of oxygenated products, CH3OH and formic acid (HCOOH) is much easier than that of CH4, leading to over-oxidation products such as CO and CO2.Here we show that chlorine dioxide radical (ClO2 •) acts as an efficient oxidizing agent in the selective oxygenation of methane under photoirradiation. A fluorous solvent, perfluorohexane (PFH, n-CF3(CF2)4CF3) was chosen as an ideal solvent for CH4 oxygenation for the following reasons. First, PFH is more inert than CH4. It is only comprised of strong C–F bonds and does not contain any C–H bonds; therefore, PFH does not react with CH3 • and Cl• intermediates in the oxygenation of CH4. Notably, PFH can dissolve gaseous substrates such as CH4, CH3CH3, and O2 very well. Additionally, oxygenated products such as CH3OH and HCOOH, as well as water, are insoluble in PFH. Thus, if a two-phase PFH/water system was used for the oxygenation of CH4, the reaction would occur in the fluorous phase, and the products would be transferred into the aqueous phase without further oxygenation to CO and CO2. Towards that end, herein, we report the two-phase photooxygenation of CH4 by molecular oxygen (O2) with chlorine dioxide radical (ClO2 •) in PFH/H2O under ambient conditions to produce oxygenated products such as CH3OH and HCOOH.The oxygenation of CH4 (1.0 mM) with ClO2 • (1.0 mM) did not proceed in the dark. In contrast, the photochemical oxygenation of CH4 with O2 occurred to form CH3OH and HCOOH under photoirradiation with a xenon lamp (500 W) in an aqueous solution at 298 K and 1 atm for 2 h. The yields of CH3OH and HCOOH were 5% and 25%, respectively, as determined by 1H NMR and gas chromatography-mass (GC-MS) spectroscopies. The conversion of CH4 was determined to be 30% by 1H NMR. The selectivity of the formation of CH3OH and HCOOH was >99%, based on the consumption of CH4.2 Further improvement of the product yield by employing a two-phase system instead by one-phase aqueous system, a CH4-saturated solution of PFH (1.0 mL) was added to an oxygen-saturated aqueous solution containing ClO2 • (1.0 mM) to prepare a two-phase system; oxygenation of CH4 (1.0 mM) in an aqueous liquid-liquid two-phase solution (1:1 v/v) comprised of PFH and distilled water was carried out under the same conditions. CH4 dissolved in the aqueous and fluorous phases was completely consumed following photoirradiation for 15 min. The product yields of CH3OH and HCOOH were improved to 14% and 85%, respectively, as determined by the 1H NMR analyses of the aqueous phase. The selectivity of the CH3OH and HCOOH formation was >99%, based on the initial concentration of CH4. The formation of further oxygenated products such as CO and CO2, was not observed under the present reaction conditions. The quantum yield of the photo-driven CH4 oxygenation was130%, as determined by actinometric measurements using monochromatized light. When CH4 was replaced with ethane (CH3CH3), light-driven oxygenation also occurred to yield CH3CH2OH (19%) and CH3COOH (78%) under the otherwise same reaction conditions. The photochemical oxygenation of methane is initiated by generation of chlorine radical and singlet oxygen from photoexcited state of ClO2 •, leading to the final products by aerobic radical chain processes. Thus, the present study provides an environmentally benign approach towards the photooxidation of organic compounds. The photochemical oxygenation using ClO2 • reported herein could be generalized to provide novel chemical reactions, which may have significant implications in synthetic, pharmaceutical and polymer chemistry.3 Ohkubo, K.; Hirose, K.; Shibata, T.; Takamori, K.; Fukuzumi, S. Phys. Org. Chem. 2017, 30, e3619.Ohkubo, K.; Hirose, K. Chem. Int. Ed. 2018, 57, 2126-2129.Ohkubo, K.; Asahara, H.; Inoue, T. Chem. Commun. 2019, 55, 4723-4726.

The aim of this paper was to investigate whether a surface coating technique could be developed that can predict the phase behavior of amorphous solid dispersions (ASDs) coated on beads. ASDs of miconazole (MIC) and poly(vinylpyrrolidone-co-vinyl acetate) (PVP-VA) in methanol (MeOH) were studied as a model system. First, the low crystallization tendency of the model drug in MeOH was evaluated and confirmed. In a next step, a drug loading screening was performed on casted films and coated beads in order to define the highest possible MIC loading that still results in a one-phase amorphous system. These results indicate that film casting is not suitable for phase behavior predictions of ASDs coated on beads. Therefore, a setup for coating a solid surface was established inside the drying chamber of a spray dryer and it was found that this surface coating technique could predict the phase behavior of MIC-PVP-VA systems coated on beads, in case an intermittent spraying procedure is applied. Finally, spray drying was also evaluated for its ability to manufacture high drug-loaded ASDs. The highest possible drug loadings that still result in a one-phase amorphous system were obtained for bead coating and its predictive intermittent surface coating technique, followed by spray drying and finally by film casting and the continuous surface coating technique, thereby underlining the importance for further research into the underexplored bead coating process.

An Improved Sinusoidal Pulse Width Modulation (ISPWM) technique carried out to obtain pure sine waves for voltage and current signals in Quasi Z-Sourc Inverters (QZSIs) in the load side is given in this study. This switching method can be examined to two and multi-phase approaches simply through the addition of the same controller structure to per phase. This is the main advantage of the proposed converter to obtain higher voltage gains at the output ends of this inverter. The idea is to generate a positive rectified voltage at the output point of the QZSI and positive and negative rectified voltages at the output terminals of the QZSI in two-phase approaches to improve the quality of the output voltage of the F-Bridge Inverter (FBI). These rectified voltages are applied to the Full-Bridge Inverter (FBI) block and pure sine waves to obtain the load current and voltages. 1.34% of the Total Harmonic Distortion (THD) for the output voltage has been reported in the one-phase system while 0.88% of THD has been obtained in the two-phase approach. Besides, the reliability of the QZSI was tested through the Mean Time to Failure (MTTF) analysis with the values of the proposed components. The calculations show a very good result for the long-life of the converter. All experimental and simulations steps have been obtained for the same values of the components to support and confirm the accuracy and correctness of the proposed IMSPW. For the states of single-phase and two-phase converters, a 50 Hz sine-wave with 220 V and 440 V peak to peak amplitude has been acquired. Evaluations of the quality of the voltage and current waveforms related to different active (Resistive, P) and reactive (combination of Resistance and Inductance, QL) loads have been carried out. Experimental results show confirmation for all simulation and mathematical results.

The evolution of interactions in the bovine serum albumin (BSA) protein solution on addition of mono and multivalent (di, tri and tetra) counterions has been studied using small-angle neutron scattering (SANS), dynamic light scattering (DLS) and ζ-potential measurements. It is found that in the presence of mono and divalent counterions, protein behavior can be well explained by DLVO theory, combining the contributions of screened Coulomb repulsion with the van der Waals attraction. The addition of mono or divalent salts in protein solution reduces the repulsive barrier and hence the overall interaction becomes attractive, but the system remains in one-phase for the entire concentration range of the salts, added in the system. However, contrary to DLVO theory, the protein solution undergoes a reentrant phase transition from one-phase to a two-phase system and then back to the one-phase system in the presence of tri and tetravalent counterions. The results show that tri and tetravalent (unlike mono and divalent) counterions induce short-range attraction between the protein molecules, leading to the transformation from one-phase to two-phase system. The two-phase is characterized by the fractal structure of protein aggregates. The excess condensation of these higher-valent counterions in the double layer around the BSA causes the reversal of charge of the protein molecules resulting into reentrant of the one-phase, at higher salt concentrations. The complete phase behavior with mono and multivalent ions has been explained in terms of the interplay of electrostatic repulsion and ion-induced short-range attraction between the protein molecules.

TFASSIP-02 loop is a test facility that is used for research and development of safety technologies for future nuclear power plants based on natural law. This test facility is designed to study natural circulation phenomena caused by differences in fluid density due to temperature differences in the one-phase heat dissipation system during the simulation of heat removal from the reactor core when an accident occurs. FASSIP-02 loop consists of piping components, water heating tanks, water cooling tanks and expansion tanks. The purpose of this study was to understand the conditions of temperature change and pressure of water working fluid based on temperature changes in the heater section which were simulated on the loop geometry FASSIP-02. The research method was carried out in a simulation of Computational Fluid Dynamics using FLUENT 6.3 software. The working fluid in the FASSIP-02 loop uses water with a temperature of 27°C, the flow rate is varied 0.3 m/s and 0.45 m / s, while the temperature in the heating section is 70°C. CFD simulation results show that the increase in the working fluid temperature of the water with a flow rate of 0.3 m/s after passing through the heating section is 39°C, while the temperature increase of the working fluid of the water with a flow rate of 0.45 m/s is 36.6°C. Pressure drops at flow rates of 0.3 m/s and 0.45 m/s each occur in water working fluid before entering through WHT and after passing through the heating section.

A two-dimensional computational fluid dynamics model was utilized to test different kinetic models for the description of the anionic polymerization of octanol with ethylene oxide in a microreactor. The reaction was performed as a continuous reaction under elevated pressure and temperatures in a one-phase system. The kinetic parameters were determined with numerical methods by reducing the deviation to experimental data based on the Nelder–Mead method. Four different reaction models with one, two, three, and four different rates for the first propagation steps were tested. The best agreement with the experimental data was found for the four rate model, with a prediction accuracy close to the experimental error. The gathered data suggests an increasing reaction rate for the first four propagation steps, which is in agreement with the Weibull–Tornquist effect [Weibull and Tornquist. Berichte vom VI. Internationalen Kongress fur Grenzflachenaktive Stoffe, Zurich, vom 11. bis 15. September 1972; Carl Hanser V...

A minitablet formulation made from electrospun nanofibers

The influence of physical properties and the resulting limitations of heat and mass transport for the ethoxylation of octanol in a microstructured reactor were investigated by CFD simulations. The reaction was performed under supercritical conditions in a one-phase system at pressures between 90 and 100 bar and temperatures between 180 and 240 °C. A 2D CFD model was applied to determine the kinetic parameters by fitting the model to experimental data. Furthermore, the sensitivity of the simulations regarding different physical properties was determined. The influence of diffusion was studied in detail, and it was found that a low diffusion coefficient results in a radial gradient in viscosity which leads to segregated streamlines and a bending of the streamlines toward the center. This “bottleneck” effect causes a large increase of the velocity in the center of the pipe, with the risk of the breakthrough of ethylene oxide. This effect occurs only in the case of higher ethoxylation degrees.

This work has established the optimum reaction conditions in a biphasic system using microcrystalline cellulose as the raw material, an ionic liquid as the solvent, metal chloride as a catalyst, and an organic solvent as the extraction reagent. The optimum reaction conditions were microcrystalline cellulose:ionic liquid - 1:10 (mass ratio), chromium(III) chloride (CrCl3) - 6.8 mol% (based on the glucose unit of cellulose molecule), reaction time - 3 h, temperature - 130 °C, and mass ratio of 1-butyl-3-methyl-imidazolium chloride ([BMIM]Cl) to methylbenzene - 1:4.4]. Under these conditions, the yields of glucose and 5-(hydroxymethyl)furfural (5-HMF) were 27% and 55%, respectively. The solvent [BMIM]Cl could be reused twice. The first recovery rate of [BMIM]Cl was approximately 70.9%. The product 5-HMF was obtained in 64.7% yield, which decreased after the first [BMIM]Cl recycling. The second recovery rate of [BMIM]Cl was 45%. The yield of 5-HMF was 39.6%, which decreased after the second recycling of [BMIM]Cl. In this paper, the energy consumption, operation, reutilization of [BMIM]Cl, and product yields of a one-phase system and a biphasic system were compared. Experimental results demonstrated that the biphasic solvent system was suitable for the degradation of cellulose to glucose and 5-HMF.

The phase behavior of nanoparticle (silica)-polymer (polyethylene glycol) system without and with an electrolyte (NaCl) has been studied. It is observed that nanoparticle-polymer system behaves very differently in the presence of electrolyte. In the absence of electrolyte, the nanoparticle-polymer system remains in one-phase even at very high polymer concentrations. On the other hand, a re-entrant phase behavior is found in the presence of electrolyte, where one-phase (individual) system undergoes two-phase (nanoparticle aggregation) and then back to one-phase with increasing polymer concentration. The regime of two-phase system has been tuned by varying the electrolyte concentration. The polymer concentration range over which the two-phase system exists is significantly enhanced with the increase in the electrolyte concentration. These systems have been characterized by small-angle neutron scattering (SANS) experiments of contrast-marching the polymer to the solvent. The data are modeled using a two-Yukawa potential accounting for both attractive and repulsive parts of the interaction between nanoparticles. The phase behavior of nanoparticle-polymer system is explained by interplay of attractive (polymer-induced attractive depletion between nanoparticles) and repulsive (nanoparticle-nanoparticle electrostatic repulsion and polymer-polymer repulsion) interactions present in the system. In the absence of electrolyte, the strong electrostatic repulsion between nanoparticles dominates over the polymer-induced depletion attraction and the nanoparticle system remains in one-phase. With addition of electrolyte, depletion attraction overcomes electrostatic repulsion at some polymer concentration, resulting into nanoparticle aggregation and two-phase system. Further addition of polymer increases the polymer-polymer repulsion which eventually reduces the strength of depletion and hence re-entrant phase behavior. The effects of varying electrolyte concentration on the phase behavior of nanoparticle-polymer system are understood in terms of modifications in nanoparticle-nanoparticle and polymer-polymer interactions. The nanoparticle aggregates in two-phase systems are found to have surface fractal morphology.

The thermodynamic state function rigidity, defined simply as $$(\mathrm{d}p/\mathrm{d}\rho )_{T}$$ , where p is the pressure, $$\rho $$ is the density and T is the temperature, is the work required to reversibly increase the density of a fluid. Along any isotherm, rigidity $$(\omega )$$ decreases with density for a gas phase and increases with density for a liquid. Thermodynamics, therefore, can define a distinction between gas and liquid. For any one-phase system, rigidity is everywhere positive, in any two-phase region $$\omega =0$$ . For temperatures above critical coexistence, the rigidity has a constant value in the mesophase that separates the percolation loci, which bound the limits of existence of liquid and gas phases in the supercritical region. The law of rectilinear diameters extends in the supercritical region as a defining line of the colloid-like inversion between gas-in-liquid and liquid-in-gas. Every equilibrium state of gas phase has a corresponding isothermal state on the liquid phase with the same rigidity. We illustrate this symmetry between gas and liquid empirically using literature $$\rho (p,T)$$ equations-of-state for some real fluids, notably carbon dioxide, water and steam, and argon. At the molecular level, the symmetry can be explained by a correspondence between statistical properties of available holes in a liquid and sites of molecular clusters in the gas with equivalent number density fluctuations for complementary states of gas and liquid.

We report on the enhancement of turbulent convective heat transport due to vapour-bubble nucleation at the bottom plate of a cylindrical Rayleigh–Bénard sample (aspect ratio 1.00, diameter 8.8 cm) filled with liquid. Microcavities acted as nucleation sites, allowing for well-controlled bubble nucleation. Only the central part of the bottom plate with a triangular array of microcavities (etched over an area with diameter of 2.5 cm) was heated. We studied the influence of the cavity density and of the superheat $T_{b}-T_{on}$ ($T_{b}$ is the bottom-plate temperature and $T_{on}$ is the value of $T_{b}$ below which no nucleation occurred). The effective thermal conductivity, as expressed by the Nusselt number $\mathit{Nu}$, was measured as a function of the superheat by varying $T_{b}$ and keeping a fixed difference $T_{b}-T_{t}\simeq 16$ K ($T_{t}$ is the top-plate temperature). Initially $T_{b}$ was much larger than $T_{on}$ (large superheat), and the cavities vigorously nucleated vapour bubbles, resulting in two-phase flow. Reducing $T_{b}$ in steps until it was below $T_{on}$ resulted in cavity deactivation, i.e. in one-phase flow. Once all cavities were inactive, $T_{b}$ was increased again, but they did not reactivate. This led to one-phase flow for positive superheat. The heat transport of both one- and two-phase flow under nominally the same thermal forcing and degree of superheat was measured. The Nusselt number of the two-phase flow was enhanced relative to the one-phase system by an amount that increased with increasing $T_{b}$. Varying the cavity density (69, 32, 3.2, 1.2 and $0.3~\text{mm}^{-2}$) had only a small effect on the global $\mathit{Nu}$ enhancement; it was found that $\mathit{Nu}$ per active site decreased as the cavity density increased. The heat-flux enhancement of an isolated nucleating site was found to be limited by the rate at which the cavity could generate bubbles. Local bulk temperatures of one- and two-phase flows were measured at two positions along the vertical centreline. Bubbles increased the liquid temperature (compared to one-phase flow) as they rose. The increase was correlated with the heat-flux enhancement. The temperature fluctuations, as well as local thermal gradients, were reduced (relative to one-phase flow) by the vapour bubbles. Blocking the large-scale circulation around the nucleating area, as well as increasing the effective buoyancy of the two-phase flow by thermally isolating the liquid column above the heated area, increased the heat-flux enhancement.

In DNA dynamic nanotechnology, a toehold-mediated DNA strand-displacement reaction has demonstrated its capability in building complex autonomous system. In most cases, the reaction is performed in pure DNA solution that is essentially a one-phase system. In the present work, we systematically investigated the reaction in a heterogeneous media, in which the strand that implements a displacing action is conjugated on gold nanoparticles. By monitoring the kinetics of spherical nucleic acid (SNA) assembly driven by toehold-mediated strand displacement reaction, we observed significant differences, i.e., the abrupt jump in behavior of an "off/on switch", in the reaction rate when the invading toehold was extended to eight bases from seven bases. These phenomena are attributed to the effect of steric hindrance arising from the high density of invading strand conjugated to AuNPs. Based on these studies, an INHIBIT logic gate presenting good selectivity was developed.