Three-phase Curve Research Articles

Diagnosis of the venous duct in fetuses of the early period of human ontogeny

To carry out an analysis of data from the world literature regarding the role of Doppler assessment of blood flow in the venous duct of the fetus in chromosomal abnormalities in the first trimester of pregnancy, as a marker – the spectral form of wave blood flow and its pulsation, which is generated by changes in the pressure and volume of blood to the heart of the fetus. Prenatal diagnosis of venous blood flow makes it possible to assess the state of the fetal cardiovascular system. Blood flow in the ductus venosus is an integrative indicator that reflects the formation of blood circulation of both the uteroplacental and placental-fetal components of gestational hemodynamics during physiological and complicated pregnancy. The performance of this test is 63%, and in combination with the assessment of the thickness of the clavicle – 89.1%. When reverse values of blood flow in the ductus venosus are detected in the phase of contraction of the atrium and dilated cervical space, it is necessary to carry out karyotyping to rule out chromosomal abnormalities. Dopplerography allows us to objectively assess the functioning state of the fetus during physiological and complicated pregnancy based on the study of the state of blood flow in the vessels of the placenta, in the middle cerebral artery, thoracic aorta, renal arteries, inferior vena cava and venous duct. The spectrum of venous blood flow reflects changes in volume and pressure in the atria during the cardiac cycle. With normal fetal development, blood flow in the venous duct has a pulsating character in the form of a unidirectional three-phase curve that corresponds to different periods of the cardiac cycle. The spectrum of normal blood flow in the venous duct in a healthy newborn has a biphasic curve, with the direction from the portal sinus to the inferior vena cava. During three weeks of regular examinations in most babies, obliteration of the venous duct occurs, and the ductus turns into a venous connection. Two-dimensional echocardiogram, color and pulsed dopplerography allow recording the waveforms of blood flow in several structures of the heart. Doppler analysis of blood flow in the venous duct is important to perform in fetuses of the first trimester, as it increases the sensitivity of the combined test in assessing the risk of chromosomal disorders. Assessment of blood flow in the ductus venosus provides an understanding of physiological and pathological processes in the fetal body and identifies fetuses that are prone to or at risk of disease.

Morphology of seeds, seedlings, and young plants of Dimorphandra gardneriana Tul

Dimorphandra gardneriana Tul. is a legume, the fruits of which are used in routine extraction by the pharmaceutical industry. The objective was to study the morphological aspects of seeds, germination, seedlings, and young plants of Dimorphandra gardneriana Tul. The study was conducted at the Laboratory of Seed Analysis (LAS), Center of Agricultural Sciences, Federal University of Paraíba (CCA-UFPB), Areia - PB. The external morphological characteristics observed of the seeds were color, texture, and consistency of the teguments; seed shape; hilum and micropyle position; color and thickness of raphe and other structures present; besides internal embryo characteristics (cotyledons, hypocotyl-radicle axis, plumule, and central cylinder); and presence of the endosperm. The seed imbibition curve was determined by the weight of the seeds over a period of 90 h, evaluated every 6 h, with germination being considered as the protrusion of the primary root, or the moment when the primary root breaks the integument, and normal seedlings were evaluated on the 5th day after sowing. Most of the morphological characteristics identified in the plants and seedlings of D. gardneriana resembled those observed for other species of the same genus. The seeds of D. gardneriana Tul., were medium sized, with an average length of 11.95 mm, width of 5.33 mm, and thickness of 4.3 mm, unitegmic with a hard tegument, and impermeable to water. The process of imbibition of the seeds was initially slow and the three-phase curve of imbibition was not clear. The germination was epigeic and phanerocotiledonar and began on the 5th day after sowing.

Ion Association in Hydrothermal Sodium Sulfate Solutions Studied by Modulated FT-IR-Raman Spectroscopy and Molecular Dynamics

Saline aqueous solutions at elevated pressures and temperatures play an important role in processes such as supercritical water oxidation (SCWO) and supercritical water gasification (SCWG), as well as in natural geochemical processes in Earth and planetary interiors. Some solutions exhibit a negative temperature coefficient of solubility at high temperatures, thereby leading to salt precipitation with increasing temperature. Using modulated FT-IR Raman spectroscopy and classical molecular dynamics simulations (MD), we studied the solute speciation in solutions of 10 wt % Na2SO4, at conditions close to the saturation limit. Our experiments reveal that ion pairing and cluster formation are favored as solid saturation is approached, and ionic clusters form prior to the precipitation of solid sulfate. The proportion of such clusters increases as the phase boundary is approached either by decreasing pressure or by increasing temperature in the vicinity of the three-phase (vapor-liquid-solid) curve.

Adiabatic Processes in the Vapor–Liquid Two-Phase Region. 2. Binary Mixtures

The phase equilibrium conditions and entropy balance equations for multicomponent fluid mixtures are expressed with a density-based formalism (“isochoric thermodynamics”), and isentropes in the one- and two-phase region are computed from equations of state; here the Peng–Robinson equation is used as an example. Griffiths’ theorem—one- and two-phase isentropes meet at a maxcondenbar point (pressure maximum of an isopleth) with equal slopes—could be confirmed. For chemically similar compounds at subcritical conditions, the resulting isentrope patterns are similar to those of pure fluids. If one of the components is supercritical, it is possible that, along a part of a two-phase isentrope, the liquid phase has a higher molar entropy than the vapor phase (“entropic inversion”). The phenomenon not only poses a numerical problem, but is also relevant for the question whether a two-phase isentrope can run into the llg three-phase curve.

The effect of the freezing curve type on bull spermatozoa motility after thawing

The objective of this work was to determine the effect of selected freezing curves on spermatozoa survivability after thawing, defined by its motility. The ejaculates of nine selected sires of the same age, breed, and frequency of collecting, bred under the same breeding conditions including handling, stabling, feeding system and feeding ratio composition, were repeatedly collected and evaluated. Sperm samples of each sire were diluted using only one extender and divided into four parts. Selected four freezing curves – the standard, commercially recommended three-phase curve; a two-phase curve; a slow three-phase curve; and a fast three-phase curve, differing in the course of temperature vs time, were applied. The percentage rate of progressive motile spermatozoa above head was determined immediately after thawing, and after 30, 60, 90, and 120 min of the thermodynamic test (TDT). Moreover, average spermatozoa motility (AMOT) and spermatozoa motility decrease (MODE) throughout the entire TDT were evaluated. Insemination doses frozen using the simpler two-phase curve demonstrated the highest motility values (+2.97% to +10.37%;P< 0.05–0.01) immediately after thawing and during the entire TDT. Concurrently, the highest AMOT (+4.37% to +8.82%;P< 0.01) was determined. The highest spermatozoa motility values were detected after thawing doses frozen by the two-phase freezing curve in eight out of nine sires. Simultaneously, a significant effect of sire individuality was clearly confirmed. Inter-sire differences of spermatozoa motility during TDT as well as AMOT and MODE were significant (P< 0.01). The findings describing both factors of interaction indicate the necessity of individual cryopreservation of the ejaculate to increase its fertilization capability after thawing.

Counterpoint: The kinetics of oxygen uptake during muscular exercise do not manifest time-delayed phases

The existence of time-delayed phases ([1][1]) is not supported by oxygen uptake kinetics data. Despite many attempts for a number of years, no convincing physiological mechanism for such behavior has been proven to exist. The reason is that these time-delayed phases are a figment of the incorrect

High-Pressure Phase Behavior of the System Propane−Boltorn H3200

High-pressure phase equilibrium data have been measured for the system propane + Boltorn H3200 at temperatures of (300 to 470) K and at pressures up to 14 MPa. Boltorn H3200 is a hydroxyl-functional hyperbranched polyester whose OH-end groups are functionalized with a mixture of eicosanoic and docosanoic acid leading to C20/22 alkane chains as end groups. The phase equilibrium measurements were performed according to the synthetic method using the Cailletet apparatus. Besides two-phase fluid phase equilibria, a three-phase curve liquid−liquid−vapor, a three-phase curve solid polymer−liquid−liquid, and a three-phase curve solid polymer−liquid−vapor were measured also.

Phase behaviour of l-lactide in supercritical carbon dioxide at high pressures

The solid–fluid and the liquid–vapour equilibria for the binary system carbon dioxide + l-lactide were determined in the temperature range 275–355 K and in the pressure range 10–80 MPa. This system shows the type of phase behaviour characterized by two branches of the solid l-lactide + liquid + vapour curve ended with first and second critical endpoints. In this study only the high-temperature branch of the three-phase curve was determined. The second critical end point (solid l-lactide + liquid = vapour) was found at 323.0 K and 30.3 MPa. The liquid–vapour equilibria were modelled with the Peng–Robinson equation of state coupled with the classical mixing rules. For the calculations l-lactide critical temperature, critical pressure and acentric factor were estimated from the Joback–Lyndersen group contribution method.

High-Pressure Phase Behavior of the Binary Systems (Propane + Diamantane) and (Ethane + Diamantane)

(Solid + fluid) and (vapor + liquid) equilibria for the binary systems (propane + diamantane) and (ethane + diamantane) were determined according to the synthetic method in the temperature range 360−510 K and in the pressure ranges 0.3−14 and 0.3−200 MPa, respectively. Also, for both systems the high-temperature branch of the three-phase curve (solid diamantane + liquid + vapor) was determined. In both systems, this curve starts at the second critical endpoint where the three-phase curve intersects the vapor—liquid critical curve and runs to higher temperature with a negative slope dP/dT to the triple point of diamantane. Due to a solid—solid transition of pure diamantane, the three-phase curve (solid diamantane + liquid + vapor) of both systems shows an abrupt change in slope at the point where it intersects the solid—solid transition curve of diamantane. This quadruple point SISIILV is found for (propane + diamantane) at T = 442.64 K and P = 4.110 MPa and for (ethane + diamantane) at T = 445.49 K and P ...

Intravitreal steroids in the management of macular oedema

The use of intravitreal corticosteroids in the management of macular oedema has recently gained widespread acceptance. New long-acting steroid preparations and methods of delivery have facilitated the use of these new modalities. This review describes the various types of macular oedema for which this therapeutic option is used and the results.

On the phase behaviour of asymmetric systems: The three-phase curve solid–liquid–gas

In this paper, the phase behaviour of asymmetric systems is discussed, more in particular attention is paid to the possible shapes of the solid non-volatile component + liquid + vapour curve in the P, T-projection of binary systems of supercritical gases and non-volatile components.

Liquid–vapour and solid–fluid equilibria for the system methane + triacontane at high temperature and high pressure

In this work experimental vapour–liquid and solid–fluid equilibrium data are presented for 13 different compositions of the system methane + triacontane. This data cover the temperature range from 315 to 450 K, and pressures up to 200 MPa. The compositions studied range from almost pure methane to pure triacontane. On the basis of the primary experimental two-phase equilibrium results, the course of the three-phase curve (solid triacontane + liquid + vapour) was derived. The second critical endpoint of this curve, where solid triacontane is in equilibrium with a critical fluid phase ( s C30 + ( l = g)) was found at T = 340.73 ± 0.4 K, P = 128.55 ± 0.5 MPa and a mole fraction in the critical fluid phase of x C30 = 0.0275 ± 0.002.

High-pressure phase behaviour of the binary systems (propane + adamantane) and (ethane + adamantane)

(Solid+liquid) and (vapour+liquid) equilibria for the binary systems (propane+adamantane) and (ethane+adamantane) were determined according to the synthetic method in the temperature range 300–510K and in the pressure range 0.3–10 and 0.3–180MPa, respectively. For both systems also the three-phase curve (solid adamantane+liquid+vapour) was determined and some vapour–liquid critical points at low mole fractions of adamantane. In the case of (propane+adamantane) the three-phase curve (solid adamantane+liquid+vapour) is continuous and shows a pressure maximum at a temperature higher than the critical temperature of propane. In the case of (ethane+adamantane) the three-phase curve (solid adamantane+liquid+vapour) is split into a low-temperature branch which runs from low temperature with a positive slope dP/dT to higher temperature and ends at a first critical endpoint at T=309.55K and P=5.17MPa. The high temperature branch of this curve starts at the second critical endpoint T=432.65K and P=15.85MPa, runs to higher temperature with a negative slope dP/dT and ends at the triple point of adamantane.

Transitiometric determination of the three-phase curve in asymmetric binary systems

A new transitiometric method of investigation of the solid phase behaviour in asymmetric binary systems was described. Taking the (tetracosane + methane) binary system as a test example the three-phase curve (solid + liquid + vapour) has been determined. The coordinates of the minimum on this transition curve are: T=(317.8±0.2) K and p=(30±0.6) MPa. The extension of transitiometric measurements to higher pressures showed that the whole combined transition curve exhibits an inflection point whose coordinates { T=(322.5±0.2) K , p=(103.8±0.6) MPa} correspond to the coordinates of the second critical endpoint in this system. Heat flux curves for transitions investigated in ascending order of pressures demonstrated that both melting and the main crystallisation growth are homogeneous processes starting almost at the same equilibrium temperature, but the crystallisation itself starts with a slow homogeneous nucleation in a transient rotator phase a few kelvins above the melting temperature. If experiments are performed in descending order of pressure this transient phase is perturbed, the crystallisation starts from a supercooled state and the respective heat flux curves exhibit two peaks.

High-temperature defect structure of Cd- and Te-rich CdTe

Quasi-chemical formalism is used to evaluate high temperature (600/spl deg/C-1000/spl deg/C) in situ conductivity and Hall effect measurements and simultaneously tellurium atom fraction in CdTe along the three-phase curve. We show that the electric properties can be described only by two native defects-cadmium interstitial as the divalent donor and cadmium vacancy as the divalent acceptor. Close to Te saturation, another native defect must be involved in the model to allow the deviation from the stoichiometry irrespective of the low density of electrically charged defects. Deep divalent donor Te/sub Cd/ having both levels near or below the midgap best describes all the high-temperature experimental data.

High Pressure Phase Equilibria in the Systems Ammonia+Potassium Iodide, +Sodium Iodide, +Sodium Bromide, and +Sodium Thiocyanate: Solid–Liquid–Vapor and Liquid–Liquid–Vapor Equilibria

Solid salt liquid vapor equilibria and liquid liquid vapor equilibria were determined experimentally for the binary system NH 3 + KI in the temperature range 333 to 673 K and at pressures up to 80 MPa. It is found that the system NH 3 + KI belongs to Type V of fluid phase behavior according to the classification of van Konynenburg and Scott. The pressure of the three-phase curve solid salt liquid vapor is monotonically increasing in the temperature range investigated and reaches a value of 76 MPa at 670 K. The three-phase liquid liquid vapor curve starts in a lower critical end point at 407.3 K and 11.59 MPa and ends in an upper critical end point at 408.8 K and 11.92 MPa. For the systems NH 3 + NaI, NH 3 + NaBr, and NH 3 + NaSCN, Type V fluid phase behavior is also found, In the system NH 3 + NaI, the lower critical end point is found at 406.8 K and 11.52 MPa and the upper critical end point at 408.5 K and 11.86 MPa. For the system NH 3 + NaBr, these coordinates are 404.6 K. 11.03 MPa and 408.8 K, 11.90 MPa, respectively, and, for the system NH 3 + NaSCN, 409.2 K, 11.99 MPa and 409.6 K, 12.06 MPa.

High-Pressure Phase Behavior of the Binary System Isobutane + Diamantane

Solid−liquid and vapor−liquid equilibria for the binary system isobutane + diamantane were determined according to the synthetic method in the temperature range (320−530) K and the pressure range (0.3−10) MPa. Also, the three-phase curve solid diamantane−liquid−vapor was determined. The results show that the slope of this curve demonstrates a discontinuity, which can be explained by the existence of two solid modifications of diamantane. The two branches of this equilibrium intersect at the S1−S2 equilibrium line of diamantane. The influence of the occurrence of two modifications of diamantane on isobaric solid−liquid equilibria is less distinct.

A kinetical approach of texture changes of vegetables during blanching

The texture changes during the initial phase of blanching of potatoes, carrots and green peas at different blanching times (0–240 s) and temperatures (85 °C, 95 °C, 100 °C) were investigated. The breaking force (N) was determined by compression or Back extrusion tests with an Instron texture tester. Electronmicroscopic studies (SEM) were made to support the interpretation of the results.For each vegetable several sections of changes of the breaking force (lnF) were identified. For potatoes a three phase change of the breaking force by all temperatures (85 °C, 95 °C, 100 °C) was observed. In the first of the 3 different observed stages of potato blanching the breaking forces increased with time (0–40 s). In the second and third stage of the blanching process of potato a linear relationship was found between the logarithm of the breaking force and the blanching time. The second phase observed was faster (40–160 s) than the consecutive slower third phase (160–240 s).For green peas the change of the breaking force (lnF) can be described by two consecutive first rate reactions. A faster decreasing period between 0–25 s was followed by a slower decreasing one between 70–140 s. Between the first and second stage of the blanching process there was an initial lag period (25–70 s), which will not be described here. In the period after 140 s, there was not any change, this period is constant.For carrots the fastest change can be observed at 100 °C compared to the results at 85 and 95 °C. A three-phase curve was observed as well. An initial lag period (0–90 s) was followed by a faster (90–190 s) and a slower (190–240 s) decreasing one. In the second and third stage of the blanching process of carrots a linear relationship was found. For the changes of the breaking force (lnF) a kinetical approach was applied, reaction rate constants and apparent activation energies were calculated. The kinetical approach helps to compare and forecast changes at different process conditions.

Constant-volume heat capacity of H2O + Na2CO3 solutions near the critical point of pure water

The results of new isochoric heat capacity measurements of H2O + Na2CO3 solutions as a function of temperature along several isochores in the near-critical region of pure water are reported. The measurements cover temperatures from 331 to 661 K at Na2CO3 mole fraction 0.008869. The experiments were performed at seven densities between 245 and 875 kg-m−3. The measurements were made in a high-temperature, high-pressure, adiabatic, and nearly constant-volume calorimeter. Uncertainties of the isochoric heat capacity measurements are estimated to be 1–2% in the liquid phase, 2–3% in the vapor phase, and 4–5% near the critical point. Measurements were made in the two-phase (vapor–liquid, liquid–solid, vapor–solid) and three-phase (vapor–liquid–solid) regions. Two peaks in isochoric heat capacity have been found near the critical point of pure water. One of the peaks at TS1 occurs on the three-phase (L–V–S) curve and another peak at TS2 corresponds to a two-phase (L–S or V–S) curve. The experimental values of phase transition temperatures TS(ρ) on each isochore was determined. Uncertainty in the phase transition temperature measured was no greater than ±0.03 to 0.05 K.

The SiO2-H2O system along the lower three-phase curve and approximate values of critical end-point temperature

The SiO2-H2O system along the lower three-phase curve and approximate values of critical end-point temperature