Electric field effect on cholesterol-phospholipid complexes

Monolayer mixtures of dihydrocholesterol and phospholipids at the air-water interface are used to model membranes containing cholesterol and phospholipids. Specific, stoichiometric interactions between cholesterol and some but not all phospholipids have been proposed to lead to the formation of condensed complexes. It is reported here that an externally applied electric field of the appropriate sign can destabilize these complexes, resulting in their dissociation. This is demonstrated through the application of an electric field gradient that leads to phase separations in otherwise homogeneous monolayers. This is observed only when the monolayer composition is close to the stoichiometry of the complex. The electric field effect is analyzed with the same mean field thermodynamic model as that used previously to account for pairs of upper miscibility critical points in these mixtures. The concentrations of dihydrocholesterol, phospholipid, and complex vary strongly and sometimes discontinuously in the monolayer membrane in the field gradient. The model is an approximation to a two-dimensional liquid in which molecules freely exchange between free and complexed form so that the chemical potentials are constant throughout the membrane. The calculations are illustrated for a complex of about 15 molecules, composed of 5 cholesterol molecules and 10 phospholipid molecules.     

Investigation of phase transitions of lipids and lipid mixtures by sensitivity differential scanning calorimetry.

High sensitivity differential scanning calorimetry is applied to the study of the thermotropic behavior of mixtures of synthetic phospholipids in multilamellar aqueous suspensions. The systems dimyristoylphosphatidylcholine dipalmitoylphosphatidylcholine, and dimyristoylphosphatidylethanolamine-distearoylphosphatidylcholine, although definitely nonideal, exhibit essentially complete miscibility in both gel and liquid crystalline states, while the system dilauroylphosphatidylcholine-distearoylphosphatidylcholine is monotectic with lateral phase separation in the gel state. Comparison of the observed transition curves with theoretical curves calculated from the calorimetrically determined phase diagrams supports a literal interpretation of the phase diagrams.     

On the Miscibility of Nematic Liquid Crystals with Ionic Liquids and Joint Reaction for High Helical Twisting Power Product(s)

Mixtures of nematic liquid crystals (LCs) with chiral ionic liquids (CILs) may find application as active materials for electrically driven broadband mirrors. Five nematic liquid crystal hosts were mixed with twenty three ionic liquids, including chiral ones, and studied in terms of their miscibility within the nematic phase. Phase diagrams of the mixtures with CILs which exhibited twisted nematic phase were determined. Miscibility, at levels between 2 and 5 wt%, was found in six mixtures with cyanobiphenyl-based liquid crystal host—E7. On the other hand, the highest changes in the isotropization temperature was found in the mixtures with isothiocyanate-based liquid crystal host—1825. Occurrence of chemical reactions was found. A novel chiral binaphtyl-based organic salt [N₁₁₁₁₆][BNDP] was synthesized and, in reaction to the 1825 host, resulted in high helical twisting power product(s). Selectivity of the reaction with the isothiocyanate-based liquid crystal was found.     

Evidence for liquid-like and nonideal behavior of a mixture of organic aerosol components

The condensation, evaporation, and repartitioning of semivolatile organic compounds (SVOCs) in the atmosphere depends both on the phase of condensed material and the effective condensed phase vapor pressures of the SVOCs. Although direct measurements of vapor pressures of individual SVOCs exist, there are limited measurements of how the properties of a given compound changes in mixtures of multiple components that exist in the atmosphere. Here, the evaporation behavior of mixtures of dicarboxylic acids, which are common atmospheric aerosol constituents, is investigated. These measurements demonstrate that complex mixtures of the individually solid organic compounds take on liquid-like properties. Additionally, the vapor pressures of individual components show strong, identity-dependent deviations from ideality (i.e., Raoult's Law), with the vapor pressures of the smaller, more volatile compounds decreased significantly in the mixtures. The addition of an inorganic compound (NaNO₃) further influences the nonideal behavior, again in a compound-specific manner. These results suggest that nonideal behavior of particle-phase compounds influences the abundances of organic aerosol observed in the atmosphere and in the laboratory.     

Critical fluctuations in domain-forming lipid mixtures

Critical fluctuations are investigated in lipid membranes near miscibility critical points in bilayers composed of dioleoylphosphatidylcholine, chain perdeuterated dipalmitoylphosphatidylcholine, and cholesterol. Phase boundaries are mapped over the temperature range from 10 degrees C to 60 degrees C by deuterium NMR. Tie-lines and three-phase triangles are evaluated across two-phase and three-phase regions, respectively. In addition, a line of miscibility critical points is identified. NMR resonances are broadened in the vicinity of critical points, and broadening is attributed to increased transverse relaxation rates arising from modulation of chain order with correlation times on a microsecond time scale. We conclude that spectral broadening arises from composition fluctuations in the membrane plane with dimensions of <50 nm and speculate that similar fluctuations are commonly found in cholesterol-containing membranes.     

Evolution of the Study of Phase Diagram of Binary and Ternary Mixtures Involving Fatty Acid Esters

Interest in phase change materials keeps on rising as thermal energy storage grows in popularity in the scientific community as a promising complement for renewable energies in the future. Extending the possibilities beyond pure compounds, the use of mixtures (especially eutectics) widens the range of suitable phase change materials (PCM) available in the market. However, a precise knowledge of the mixtures’ phase behavior is required, making phase diagrams the most appropriate tools to follow. The aim of this work is to collect and analyze published literature concerning the phase diagrams of fatty acid esters mixtures, which constitute promising candidates as PCM due to their attractive properties, such as high latent heat, chemical stability and the possibility of extracting them from vegetable and animal oils. The topic appears as a still open scientific field, where further studies need to be performed to complete, complement and perfect the currently available information.     

Control of haemolymph protein synthesis and oocyte maturation by the corpora allata in female adults of locusta migratoria (Orthoptera): role of the blood-forming tissue

Oocyte growth in Locusta migratoria is divided into three major periods: previtellogenesis (oocyte length less than 0.8 mm; days 1–7 of adult life); subphase I of vitellogenesis (oocyte length between 0.8 and 2 mm; days 7–10 of adult life), and subphase II of vitellogenesis (oocyte length greater than 2 mm; day 10 of adult life till egg-laying). Subphase I of vitellogenesis is characterized by a marked increase in total hemolymph proteins.Both oocyte growth and hemolymph protein synthesis are known to be controlled by the corpora allata, the activity of which is very high only during subphase I of vitellogenesis. In addition, this subphase corresponds to a markedly increased activity of the hemocytopoietic tissue, resulting in a rise in the number of highly differentiated hemocytes in the blood.Selective X-irradiations of the hemocytopoietic tissue (pericardial region of the abdomen) affect both oocyte growth and hemolymph protein synthesis if they are performed during subphase I of vitellogenesis (time of highest activity of the corpora allata). The effects of these irradiations on both parameters are very similar to those of allatectomy. Sham-irradiations of other abdominal regions of equivalent surface affect neither oocyte growth nor hemolymph protein synthesis.It is therefore suggested that radiosensitive cells of the hemocytopoietic tissue elaborate one or several factors necessary for the transport and/or the mode of action of the corpora allata hormone.     

Equilibration rates in lipid monolayers

A theoretical analysis is given for the rate of change of domain sizes in lipid monolayers at the air–water interface. The calculation is applicable to liquid domains formed from binary mixtures of lipids that form two coexisting liquid phases. Under conditions where the two lipid molecules have approximately equal areas, the equilibration rate does not involve macroscopic hydrodynamic flow in the subphase but rather depends on the diffusion coefficient of the lipid molecules. The calculation shows that the equilibration rate in binary mixtures of cholesterol and phosphatidylcholine is remarkably slow, the radius of a typical 20-μm diameter domain changing by as little as a part in a million per second. Under these circumstances, equilibration times of the order of days or weeks are expected. Even with such long times, the final state reached by the monolayer will in general be a state of metastable equilibrium, rather than true equilibrium.     

Surfactant displaces particles toward the epithelium in airways and alveoli

This study was designed to investigate the early stages of particle deposition on airway and alveolar surfaces. To do this we used morphometric studies of aerosol deposition, in situ measurements of surface tension, and in vitro assays of particle displacement and mathematical modelling. We observed that latex particles, equal or less than 6 microns in diameter deposited in hamster lungs were submerged in the subphase of the alveolar lining layer and became completely coated with an osmiophilic film. Similar results were obtained for particles deposited in the conductive airways which were also covered with a surface active film, having a surface tension of 32 +/- 2 dyn.cm-1. In vitro experiments showed that pulmonary surfactant promotes the displacement of particles from air to the aqueous phase and that the extent of particle immersion depends on the surface tension of the surface active film. The lower the surface tension the greater is the immersion of the particles into the aqueous subphase. Mathematical analysis of the forces acting on a particle deposited on an air-fluid interface show that for small particles (less than 100 microns) the surface tension force is several orders of magnitude greater than forces related to gravity. Thus, even at the relatively high surface tension obtained in the airways (32 +/- 2 dyn.cm-1) particles will still be displaced into the aqueous subphase. Particles in peripheral airways and alveoli likely are below the surfactant film and submerged in the subphase. This may promote clearance by macrophages. In addition, particle displacement into the subphase is likely to increase the contact between the epithelial cell and particle. Toxic or allergenic particles would be available to interact with epithelial cells and this may be important in the pathophysiology of airway disease.     

Localization Properties of a Quasiperiodic Ladder under Physical Gain and Loss: Tuning of Critical Points,Mixed-Phase Zone and Mobility Edge

We explore the localization properties of a double-stranded ladder within a tight-binding framework where the site energies of different lattice sites are distributed in the cosine form following the Aubry–André–Harper (AAH) model. An imaginary site energy, which can be positive or negative, referred to as physical gain or loss, is included in each of these lattice sites which makes the system a non-Hermitian (NH) one. Depending on the distribution of imaginary site energies, we obtain balanced and imbalanced NH ladders of different types, and for all these cases, we critically investigate localization phenomena. Each ladder can be decoupled into two effective one-dimensional (1D) chains which exhibit two distinct critical points of transition from metallic to insulating (MI) phase. Because of the existence of two distinct critical points, a mixed-phase (MP) zone emerges which yields the possibility of getting a mobility edge (ME). The conducting behaviors of different energy eigenstates are investigated in terms of inverse participation ratio (IPR). The critical points and thus the MP window can be selectively controlled by tuning the strength of the imaginary site energies which brings a new insight into the localization aspect. A brief discussion on phase transition considering a multi-stranded ladder was also given as a general case, to make the present communication a self-contained one. Our theoretical analysis can be utilized to investigate the localization phenomena in different kinds of simple and complex quasicrystals in the presence of physical gain and/or loss.     

Anatomy of the interstitial tissue.

Aspects on composition and function of the interstitial tissue have been given. The glycosaminoglycans of the interstitum have at physiological pH a net negative charge and are osmotically active. They restrict free diffussion through the interstitium. The ground substance phase can be further subdivided into a colloid-rich subphase and a colloid-poor subphase. The latter seems to constitute the true tissue fluid phase of the interstitium. The functional importance of the interstitium on exchange processes between the vascular and the cellular compartments is discussed. Changes in aggregation and hydration of the ground substance change the physico-chemical properties and the functional characteristics of the interstitium.     

Clinical-instrumental relationships in post-phlebitic syndrome

981 lower limbs belonging to 829 subjects, 67.6% of which were females, have been examined. The average venous pressure at the tibial posterior vein was 101 +/- 12 mmHg and 102 +/- 13 mmHg on the internal saphenous vein. In 311 lower limbs with femoro-iliac thrombosis, venous pressures are slightly higher than in 670 lower limbs with calf veins occlusion. In the 44.4% of cases the phlebothrombosis was clearly dependent on traumas, deliveries, surgical operations or other conditions. The relationships between the supposed aetiopathogenesis of the affection and the pressure values have been examined. The 6.7% refers to phlebitis, which caused pulmonary embolism during their acute phase. The different objective and subjective symptoms have, furthermore, been taken into consideration. It has been noticed by the analysis of the diagrams of the pressure values in the time that the same values which are considerably high at the initial phase of the iliac postphlebitic syndrome, are always high in the following years. On the other hand, in postphlebitic syndrome of the leg those pressures whose value are not remarkably high in the initial phase, increase from the second to the fourth year after the arising of phlebitis and, finally become stable at fairly high values, but still lower than those of iliac syndrome. The venous orthostatic pressure of internal saphenous vein in the iliac postphlebitic syndrome was also found to exceed the deep pressures, likely because of the altered saphenous discharge at the cross level.     

Semipersistently Transmitted,Phloem Limited Plant Viruses Are Inoculated during the First Subphase of Intracellular Stylet Penetrations in Phloem Cells

The green peach aphid Myzus persicae Sulzer is the main vector of the semipersistently transmitted and phloem-limited Beet yellows virus (BYV, Closterovirus). Studies monitoring the M. persicae probing behavior by using the Electrical penetration graphs (EPG) technique revealed that inoculation of BYV occurs during unique brief intracellular punctures (phloem-pds) produced in companion and/or sieve element cells. Intracellular stylet punctures (or pds) are subdivided in three subphases (II-1, II-2 and II-3), which have been related to the delivery or uptake of non-phloem limited viruses transmitted in a non-persistent or semipersistent manner. As opposed to non-phloem limited viruses, the specific pd subphase(s) involved in the successful delivery of phloem limited viruses by aphids remain unknown. Therefore, we monitored the feeding process of BYV-carrying M. persicae individuals in sugar beet plants by the EPG technique and the feeding process was artificially terminated at each phloem-pd subphase. Results revealed that aphids that only performed the subphase II-1 of the phloem-pd transmitted BYV at similar efficiency than those allowed to perform subphase II-2 or the complete phloem-pd. This result suggests that BYV inoculation occurs during the first subphase of the phloem-pd. The specific transmission mechanisms involved in BYV delivery in phloem cells are discussed.     

Algorithm for Determining Time Series of Phase Transformations in the Solid State Using Long-Short-Term Memory Neural Network

In the numerical analysis of manufacturing processes of metal parts, many material properties depending on, for example, the temperature or stress state, must be taken into account. Often these data are dependent on the temperature changes over time. Strongly non-linear material property relationships are usually represented using diagrams. In numerical calculations, these diagrams are analyzed in order to take into account the coupling between the properties. An example of these types of material properties is the dependence of the kinetics of phase transformations in the solid state on the rate and history of temperature change. In literature, these data are visualized Continuous Heating Transformation (CHT) and Continuous Cooling Transformation (CCT) diagrams. Therefore, it can be concluded that time series analysis is important in numerical modeling. This analysis can also be performed using neural networks. This work presents a new approach to storing and analyzing the data contained in the discussed CCT diagrams. The application of Long-Short-Term Memory (LSTM) neural networks and their architecture to determine the correct values of phase fractions depending on the history of temperature change was analyzed. Moreover, an area of research was elements that determine what type of information should be stored by LSTM network coefficients, e.g., whether the network should store information about changes of single phase transformations, or whether it would be better to extract data from differences between several networks with similar architecture. The purpose of the studied network is strongly different from typical applications of artificial neural networks. The main goal of the network was to store information (even by overfitting the network) rather than some form of generalization that allows computation for unknown cases. Therefore, the authors primarily investigated in the ability of the layer-based LSTM network to store nonlinear time series data. The analyses presented in this paper are an extension of the issues presented in the paper entitled “Model of the Austenite Decomposition during Cooling of the Medium Carbon Steel Using LSTM Recurrent Neural Network”.     

Condensed complexes in vesicles containing cholesterol and phospholipids

Animal cell membranes pose conceptual problems related to the physical chemistry of liquids. An avenue to the solution of some of these problems has been opened by the discovery of liquid-liquid immiscibility in synthetic membranes composed of cholesterol and phospholipids. This discovery has led to the development of a thermodynamic model involving condensed complexes. In this model, the phospholipids with longer fatty-acid chains react reversibly with cholesterol to form complexes. The complexes themselves can have a repulsive interaction with other phospholipids, leading to immiscibility. A striking example of this effect is revealed in the phase diagrams of ternary mixtures of cholesterol, a saturated phosphatidylcholine (or sphingomyelin), and an unsaturated phosphatidylcholine. As found by a number of investigators, all binary pairs are miscible in bilayers, whereas the ternary mixture can form two liquid phases. The model of condensed complexes accounts for this effect. Condensed complexes also have a major effect on the chemical activity of cholesterol and on the ordering of phospholipid acyl chains both in the presence and absence of phase separations. Model calculations of phospholipid order parameters account for several features of the deuterium NMR spectra of labeled phospholipid molecules in bilayer mixtures with cholesterol.     

A manner of characterizing the development of countries

An attempt is made to characterize the socio-economic state and the temporal evolution of countries by the use of labor force distribution data on a multidimensional phase plot so that the development of a country is represented by an evolutionary track of a phase point. The evolutionary tracks of several countries are examined, and the phase points of many countries are compared. Snowflake diagrams, which make easy comparison of the socio-economic character of various countries, have also been developed.     

Solid?liquid critical behavior of water in nanopores

Nanoconfined liquid water can transform into low-dimensional ices whose crystalline structures are dissimilar to any bulk ices and whose melting point may significantly rise with reducing the pore size, as revealed by computer simulation and confirmed by experiment. One of the intriguing, and as yet unresolved, questions concerns the observation that the liquid water may transform into a low-dimensional ice either via a first-order phase change or without any discontinuity in thermodynamic and dynamic properties, which suggests the existence of solid−liquid critical points in this class of nanoconfined systems. Here we explore the phase behavior of a model of water in carbon nanotubes in the temperature−pressure−diameter space by molecular dynamics simulation and provide unambiguous evidence to support solid−liquid critical phenomena of nanoconfined water. Solid−liquid first-order phase boundaries are determined by tracing spontaneous phase separation at various temperatures. All of the boundaries eventually cease to exist at the critical points and there appear loci of response function maxima, or the Widom lines, extending to the supercritical region. The finite-size scaling analysis of the density distribution supports the presence of both first-order and continuous phase changes between solid and liquid. At around the Widom line, there are microscopic domains of two phases, and continuous solid−liquid phase changes occur in such a way that the domains of one phase grow and those of the other evanesce as the thermodynamic state departs from the Widom line.The possibility of the solid–liquid critical point has been reported by computer simulation studies of various systems in quasi-one, quasi-two, and three dimensions that exhibit both continuous and discontinuous changes in thermodynamic functions and other order parameters (1–7). However, the idea that a solid–liquid phase boundary never terminates at the critical point is still commonly accepted as a law of nature, largely because of the famous symmetry argument (8, 9) together with the lack of experimental observations. Furthermore, critical phenomena in quasi-1D systems are often considered impossible from a different point of view; that is, to begin with, there is no first-order phase transition in 1D systems as proved for solvable models (10) or shown by the phenomenological argument (9). Therefore, a thorough investigation is much needed to support or reject the possibility of the solid–liquid critical point. We examine the phase behavior of a model system of water confined in a quasi-1D nanopore (1, 11–15) and provide evidence to support the existence of first-order phase transitions and solid–liquid critical points.     

Alloy Design,Thermodynamics, and Electron Microscopy of Ternary Ti-Ag-Nb Alloy with Liquid Phase Separation

The Ti–Ag alloy system is an important constituent of dental casting materials and metallic biomaterials with antibacterial functions. The binary Ti–Ag alloy system is characterized by flat liquidus lines with metastable liquid miscibility gaps in the phase diagram. The ternary Ti–Ag-based alloys with liquid phase separation (LPS) were designed based on the mixing enthalpy parameters, thermodynamic calculations using FactSage and Scientific Group Thermodata Europe (SGTE) database, and the predicted ground state diagrams constructed by the Materials Project. The LPS behavior in the ternary Ti–Ag–Nb alloy was investigated using the solidification microstructure analysis in arc-melted ingots and rapidly solidified melt-spun ribbons via trans-scale observations, combined with optical microscopy (OM), scanning electron microscopy (SEM) including electron probe micro analysis (EPMA), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM). The solidification microstructures depended on the solidification processing in ternary Ti–Ag–Nb alloys; macroscopic phase-separated structures were observed in the arc-melted ingots, whereas fine Ag globules embedded in the Ti-based matrix were observed in the melt-spun ribbons.     

Central blood pressures: do we need them in the management of cardiovascular disease? Is it a feasible therapeutic target?

It is well established that in young and healthy individuals central (aortic or carotid) systolic and pulse pressures are different from peripheral (brachial) corresponding pressures as a consequence of progressive changes in arterial stiffness and pressure wave reflections along the arterial tree. There is evidence indicating that in interventions with pharmaceutical and non-pharmaceutical agents, central pressures are subjected to greater changes than peripheral pressures, and they are more closely related to the pathophysiology of end-organ damage or cardiovascular risk. Therefore central blood pressures may be of higher clinical importance than peripheral pressures. The present review aims to provide an insight into the (patho)physiology of central blood pressures, to present the most accurate techniques for their estimation, and to discuss the available experimental and epidemiological data that support the emerging need for the evaluation of central blood pressures in clinical practice.     

Comparative effects of ajmaline and lidocaine on hemodynamics in myocardial infarct

Haemodynamic changes after single intravenous injection of antiarhythmic doses of ajmaline (50 mg) and lidocain (100 mg) were measured comparatively in 10 patients with acute myocardial infarction, stable cardiac rhythm and without manifest left heart failure. The effects of ajmaline were characterized by a significant decrease of systolic arterial pressure (9%), of left ventricular stroke work index (15%) as well as by an increase of the mean pressure of the pulmonary artery (7%) in the early phase after application. No significant changes in cardiac index, stroke volume index, systemic vascular resistance, right and left ventricular filling pressures and heart rate occurred. The effects of lidocain on the cardiac circulation were comparatively small. The intravenous administration of lidocain did not result in significant changes of the cardiac index or left and right ventricular filling pressures. Diastolic arterial pressure increased significantly (5%), while the heart rate decreased (5%).