Double-phase System Research Articles

Lipschitz truncation method for parabolic double-phase systems and applications

We discuss a Lipschitz truncation technique for parabolic double-phase problems of p-Laplace type in order to prove energy estimates and uniqueness results for the Dirichlet problem. Moreover, we show existence for a non-homogeneous double-phase problem. The Lipschitz truncation method is based on a Whitney-type covering result and a related partition of unity in the intrinsic geometry for the double-phase problem.

Gradient higher integrability for singular parabolic double-phase systems

We prove a local higher integrability result for the gradient of a weak solution to parabolic double-phase systems of p-Laplace type when 2nn+2<p≤2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ frac{2n}{n+2}< p\\le 2$$\\end{document}. The result is based on a reverse Hölder inequality in intrinsic cylinders combining p-intrinsic and (p, q)-intrinsic geometries. A singular scaling deficits affects the range of q.

Spark plasma sintered TiB2-SiC UHTC derived from B4C and stoichiometric intermetallic phases from Ti-Si system

Previously conducted studies determined that the reactive sintering of B4C and stoichiometric additions of TiSi2 or Ti5Si3 intermetallics created a dense TiB2-SiC double-phase system that could be classified as ultra-high temperature ceramics (UHTC). In this work, a spark plasma sintering (SPS) technique was used to improve the sintering process and thus further reduce the obtaining temperature and improve the final microstructure and mechanical properties of the proposed, double-phase TiB2-SiC UHTC systems. To evaluate the effects of the experiment, a comprehensive study of phase composition, microstructure and mechanical properties was added. As a result, minimal sintering temperatures were further reduced from 1420 - 1650 ºC to a range of 1200–1400 ºC. Among the prepared composites those sintered at 1400 ºC achieved the best properties. The prepared composites maintained high hardness (up to 24.85 GPa), high tensile strength (up to 309 GPa), relatively high fracture toughness (up to 4.80 MPa∙m1/2) and relatively low density, all of which characterized TiB2-SiC UHTC systems.

Double phase systems with convex–concave nonlinearity on complete manifold

Double phase systems with convex–concave nonlinearity on complete manifold

Gradient Higher Integrability for Degenerate Parabolic Double-Phase Systems

We prove a local higher integrability result for the gradient of a weak solution to degenerate parabolic double-phase systems of p-Laplace type. This result comes with reverse Hölder type estimates. The proof is based on a careful phase analysis, estimates in the intrinsic geometries and stopping time arguments.

Tailoring the Random Lasing Properties by Controlled Phase Separation Process in PMMA:PVK Dye-Doped Polymeric Blends.

This article describes the random lasing (RL) phenomenon obtained in a dye-doped, polymeric double-phase system composed of PMMA and PVK polymers. It shows how relative concentrations between mentioned macromolecules can influence lasing parameters of the resulting blends, including obtained emission spectra and threshold conditions. We describe the influence of lasers’ composition on their morphologies and link them with particular RL properties. Our studies reveal that the disorder caused by phase separation can support the RL phenomenon both in the waveguiding and quasi-waveguiding regimes. Changing the relative concentration of polymers enables one to switch between both regimes, which significantly influences threshold conditions, spectral shift, number of lasing modes, and ability to support extended and/or localized modes. Finally, we show that a simple phase separation technique can be used to fabricate efficient materials for RL. Moreover, it enables the tailoring of lasing properties of materials in a relatively wide range at the stage of the laser material fabrication process in a simple way. Therefore, this technique can be seen as a fast, cheap, and easy to perform way of random lasers fabrication.

Singular double-phase systems with variable growth for the Baouendi-Grushin operator

<p style='text-indent:20px;'>In this paper we study a class of singular systems with double-phase energy. The main feature is that the associated Euler equation is driven by the Baouendi-Grushin operator with variable coefficient. In such a way, we continue the analysis introduced in [<xref ref-type="bibr" rid="b6">6</xref>] to the case of lack of compactness corresponding to the whole Euclidean space. After establishing a related compactness property, we establish the existence of solutions for the Baouendi-Grushin singular system.

FORMATION OF PLATINUM SILICIDE LAYERS DURING THE RAPID THERMAL PROCESSING OF THE SYSTEM PLATINUM-SILICON: STRUCTURAL-PHASE CHANGES

The paper presents the performed investigations of the structural-phase changes of the platinum-silicon system during rapid thermal processing (RTP) in the nitrogen medium within the temperature range from 200°C to 550°C with a step of 50 K and the time duration of 7 s. High effectiveness of the RTP process was demonstrated for formation of the thermally stable platinum silicides in the nanodimensional film (40 nm Pt)/(Si 111) substrate system. Within the temperature range of 200°C ≤ T ≤ 300°C during 7 s of the RTP process on the border of the → metallic film with the substrate there grows the Pt2Si layer at the expense of the Pt atoms diffusion into silicon through the layer of the growing silicide. It is peculiar for the temperature T = 300°C to use completely the film of Pt for 7 s in the process of the silicide formation of the single-phase system of Pt2Si. At 350°C ≤ T < 450°C formation is registered of the double-phase system of Pt2Si PtSi, starting from the interphase boundary of Si/Pt2Si predominantly at the expense of the oncoming diffusion of Si atoms into the layer of Pt2Si. The RTP temperature T = 450°C marks formation of the thermally stable structure of PtSi along the entire thickness of silicide, which is 50-100°C lower and substantially faster, than during the continuous furnace thermal treatment (FTT).

Molecular layering of phosphorus oxide structures on the surface of gamma alumina

Phosphorus oxide structures were synthesized on the surface of porous gamma alumina, with phosphorus oxychloride and water vapors used as reagents for successive and alternating (up to four times) treatment of a solid-phase matrix by the molecular layering method with in situ monitoring of the process. It was shown that this procedure yields a double-phase system constituted by a core (aluminum oxide) and shell (amorphous phosphorus oxide layer) with a prescribed chemical composition and structure with characteristics dependent on the number of molecular layering cycles. With increasing treatment rate (from 1 to 4) of the solid-phase matrix with halide and water vapors, the concentration of phosphorus in the samples steadily grows. In the process, the specific surface area, pore volume, and pore size in the double-phase system being formed become smaller. The results obtained in the study are of interest for development of catalytic, sorption, and other functional systems of the core–shell type.

Sistemas de cultivo in vitro e aclimatização de Aechmea setigera Mart. ex Schult. & Schult. f. (Bromeliaceae)

Aechmea setigera is an endemic bromeliad from Amazon with ornamental potential. Bromeliads have been propagated by tissue culture. The consistency of the culture medium in vitro multiplication influences the rate of propagation. In this sense, the objective of this study was to evaluate different culture systems with the use of 6-benzylaminopurine (BAP) on in vitro propagation and the effect of different substrates in acclimatization of plantlets Aechmea setigera . In vitro germinated seedlings were inoculated in MS medium in liquid stationary, semisolid, double-phase systems, plus 6-benzylaminopurine (BAP) in different concentrations (0, 2.2, 4.4, 8.8 and 17.7 μM). The ex vitro rooting and acclimatization were performed on substrate Plantmax Forest ®, vermiculite and sawdust eucalyptus. After three successive subcultures, the double-phase system showed a higher number of regenerated shoots in comparison to other systems. Acclimatization using the combination of commercial substrate Plantmax Forest ® and vermiculite favored the growth of micropropagated plants. The use of a culture medium double-phase without growth regulator, and the rooting in acclimatization are feasible strategy for the micropropagation of A. setigera .

Optimizing rooting and survival of oil palm (Elaeis guineensis) plantlets derived from somatic embryos

In species of the Arecaceae, initial conversion of somatic embryos to non-rooted plantlets (those with only shoot development and no roots) is common. A consistent methodology for improving rooting and survival of oil palm plantlets derived from somatic embryos was developed. Two experiments were carried out. In the first, non-rooted shoots regenerated via somatic embryogenesis were inoculated in nutrient medium supplemented with 0, 53.7, or 107.4 μM indole-3-butyric acid (IBA) or 1-naphthaleneacetic acid (NAA). In the second, the optimum treatment as determined in the first experiment was evaluated in three culture systems: semi-solid medium (SS), stationary liquid (SL), and double-phase system (DP), with and without the addition of activated charcoal. Next, the plantlets were acclimatized in a greenhouse, where the influence of the presence or absence of roots, the number of roots, the length of the main root, and the height of the shoot on survival were assessed. Supplementation with 53.7 μM IBA and the DP system without activated charcoal provided the highest percentage of rooted plantlets (92.9%) and number of roots (6.3) and improved the length of the aerial parts (11.0 cm) and the survival of the plantlets during the acclimatization (82.1%). The best survival of plantlets was obtained when they were acclimatized with at least one root and with a height greater than 7.5 cm.

In vitro multiplication and essential oil composition of Thymus moroderi Pau ex Martinez, an endemic Spanish plant

Thymus moroderi Pau ex Martinez (Lamiaceae) is a species endemic to South-eastern Spain valuable for its use in traditional medicine and in the production of a liqueur called cantueso. We describe a rapid and reliable in vitro propagation protocol for this species, starting from wild adult vegetative explants. Sterilization and establishment of in vitro culture were shown to be extremely difficult because of the high presence of contamination and the inability of non-contaminated explants to restore growth. In just two cases we were able to obtain non-contaminated explants with ability to grow: combining a fungicide dip with the presence of kanamycin in culture medium, and when mother plants were maintained for a week in a growth chamber with occasional fungicide spray. Once established in vitro, explants showed rapid and vigorous growth with spontaneous rooting. The presence of cytokinin alone or in combination with auxin gave worse results than untreated controls, thus revealing Thymus moroderi as a cytokinin-sensitive species. Better multiplication rates were however obtained when double phase system was included in the protocol. Fully acclimatized micropropagated plants were phenotypically indistinguishable from their wild relatives. Essential oils of micropropagated and wild plants were analyzed revealing a slightly different overall terpene profile. Micropropagated plants were abundant in monoterpene and sesquiterpene hydrocarbons but less in oxygenated sesquiterpenes with respect to wild plants. Major compounds were in both cases 1,8-cineole and camphor, although at different relative abundances. Despite these dissimilarities micropropagated plants produced a clearly recognizable and characteristic thyme odor.

SIMPLEX OPTIMIZATION FOR ALOE-EMODIN SEPARATION AND PURIFICATION USING AQUEOUS DOUBLE-PHASE EXTRACTION SYSTEM

We report a new method of aloe-emodin separation and purification that is based on the simplex optimization method of an acetone-ammonium sulfate aqueous double-phase system. We investigated the partitioning trends and conditions of this double-phase system and identified an optimized double-phase recipe for aloe-emodin separation and purification. With this recipe, aloe-emodin was extracted at a purity of 95.23%. The simplex method reported here only requires simple equipment, and mild experimental conditions. The operations are cheap and easy, and produce products with high purity and yield. Thus, the simplex optimization method is effective in optimizing aqueous double-phase systems for industrialized production.

Effect of Inclination Angles on Heat Transfer Characteristics of a Closed Loop Pulsating Heat Pipe (CLPHP)

Abstract At present Closed Loop Pulsating Heat Pipe (CLPHP) is a novel cooling strategy for successful thermal management though it is a complex heat transfer device having a strong thermo-hydrodynamic coupling to govern the thermal performance. This research is to study the effect of inclination angle and working fluid on the heat transfer characteristics and performance of CLPHP. The performance characterization has been done using two different working fluids of water and ethanol with inclination angle of 0˚ (vertical), 30˚, 45˚, 60˚, 75˚ and 90˚ (horizontal). The experiment is conducted on a CLPHP made of 148 cm long copper capillary tube of 3.0 mm outer diameter and 2.0 mm inner diameter creating a total of 13 turns. The total length of evaporator section is 39.5 cm and condenser section is 31.5 cm; while the rest is assumed to be adiabatic. The evaporator section is heated by electrical heat input, while the condenser section is cooled by atmospheric air flow. Since a PHP is recognized as a two phase heat transfer device, for comparative studies it is operated as a double-phase system by filling it 70% with the working fluid. The comparative study results in a better understanding of the underlying physics of the PHP operation. The experimental results indicate a strong influence of gravity and thermo physical properties of the working fluid on the performance of the CLPHP. The results demonstrate the effect of the input heat flux, inclination angle and physiochemical properties of the working fluid on the thermal performance of the device.

Towards a Model for Fresh Granular-Paste Systems Based on Discrete Element Method

Modelling the rheological behaviour of fresh granular-paste systems is the main aim of this study. The research approach is based on a conceptual idea where the paste-interaction system is explicitly modelled by an interactive two phase particle system. As a first approach the cohesive force-displacement interaction was measured for two ideally shaped glass particles bridged by water. Later on, the water was replaced by cement paste and the attraction force acting on the glass particles was measured for increasing inter-particle distances. The results gave a very good impression of the cohesive forces acting on a granular paste system employed by the cementations material in its fresh state. The Discrete Element Method (DEM) is one of the computational techniques that is applied to simulate the granular-paste system. With this method, the fresh granular-paste system is divided into two phases (aggregate/paste) and is modelled by a single-phase or a double-phase system of DEM elements. At the first step, the interaction forces of the particle-paste system are compared with the experimental results achieved from the particle-liquid measurements and expressed as an explicit function based on local geometrical and physical parameters. Modelling and experimental results show good agreement.

A Granular Inorganic Cation-Exchanger Selective to Cesium

The investigation results on the structure, sorptive-selective properties and exchange reversibility of the adsorbent selective to cesium cations are presented in this paper. A trade mark of this adsorbent is Termoxid-35. The composition of Termoxid-35 is the “mixed” nickel ferrocyanide distributed over zirconium hydroxide as an inorganic carrier. The structure of the cation-exchanger was studied by the infrared spectroscopy and the X-ray diffraction, differential-thermal and thermo-gravimetric analyses. The adsorbent is the double-phase system consisting of a highly-dispersed amorphous phase of zirconium hydroxide and a micro-crystalline phase of mixed nickel ferrocyanide. The isotherms of cesium cation adsorption in the pH region of 6.2 to 9.6 in the presence of 1 mol/l NaCl are presented. The distribution coefficient for cesium in the Henry region increases with the pH of the solution and reaches 6.5 x 105 cm3/g at pH = 9:6. The distribution coefficient for cesium is more than 1.0 x 104 cm3/g with the concentration of the cation in the solid phase of 0.1 mmol/g. The cesium cation sorption on the ion-exchanger is irreversible.

A Granular Inorganic Cation-Exchanger Selective to Cesium

The investigation results on the structure, sorptive-selective properties and exchange reversibility of the adsorbent selective to cesium cations are presented in this paper. A trade mark of this adsorbent is Termoxid-35. The composition of Termoxid-35 is the “mixed” nickel ferrocyanide distributed over zirconium hydroxide as an inorganic carrier. The structure of the cation-exchanger was studied by the infrared spectroscopy and the X-ray diffraction, differential-thermal and thermo-gravimetric analyses. The adsorbent is the double-phase system consisting of a highly-dispersed amorphous phase of zirconium hydroxide and a micro-crystalline phase of mixed nickel ferrocyanide. The isotherms of cesium cation adsorption in the pH region of 6.2 to 9.6 in the presence of 1 mol/l NaCl are presented. The distribution coefficient for cesium in the Henry region increases with the pH of the solution and reaches 6.5 x 105 cm3/g at pH = 9:6. The distribution coefficient for cesium is more than 1.0 x 104 cm3/g with the concentration of the cation in the solid phase of 0.1 mmol/g. The cesium cation sorption on the ion-exchanger is irreversible.

Biotransformation in double-phase systems: physiological responses of Pseudomonas putida DOT-T1E to a double phase made of aliphatic alcohols and biosynthesis of substituted catechols.

Pseudomonas putida strain DOT-T1E is highly tolerant to organic solvents, with a logP(ow) (the logarithm of the partition coefficient of a solvent in a two-phase water-octanol system of > or =2.5. Solvent tolerant microorganisms can be exploited to develop double-phase (organic solvent and water) biotransformation systems in which toxic substrates or products are kept in the organic phase. We tested P. putida DOT-T1E tolerance to different aliphatic alcohols with a logP(ow) value between 2 and 4, such as decanol, nonanol, and octanol, which are potentially useful in biotransformations in double-phase systems in which compounds with a logP(ow) around 1.5 are produced. P. putida DOT-T1E responds to aliphatic alcohols as the second phase through cis-to-trans isomerization of unsaturated cis fatty acids and through efflux of these aliphatic alcohols via a series of pumps that also extrude aromatic hydrocarbons. These defense mechanisms allow P. putida DOT-T1E to survive well in the presence of high concentrations of the aliphatic alcohols, and growth with nonanol or decanol occurred at a high rate, whereas in the presence of an octanol double-phase growth was compromised. Our results support that the logP(ow) of aliphatic alcohols correlates with their toxic effects, as octanol (logP(ow) = 2.9) has more negative effects in P. putida cells than 1-nonanol (logP(ow) = 3.4) or 1-decanol (logP(ow) = 4). A P. putida DOT-T1E derivative bearing plasmid pWW0-xylE::Km transforms m-xylene (logP(ow) = 3.2) into 3-methylcatechol (logP(ow) = 1.8). The amount of 3-methylcatechol produced in an aliphatic alcohol/water bioreactor was 10- to 20-fold higher than in an aqueous medium, demonstrating the usefulness of double-phase systems for this particular biotransformation.

RBa2Cu2FeO7 phases (R=Y, Eu): Synthesis, structure, and mössbauer spectra

The reaction of Y/Eu, Cu, Fe oxides and Ba carbonate in a ratio of 1:2:1:2 at 980°C in an oxygen current forms double-phase systems; in each system, the major phase is a 123 type orthorhombic three-layered structure, and the secondary phase, amounting to about one-third of the major phase, is a tetragonal, nearly pseudocubic 123 structure. Both phases in the yttrium and europium systems are characterized by formation of weak superstructures with doubled parameters of the ordinary three-layered cell. In each system, the two phases seem to differ in the content and distribution of iron. Based on the gamma resonance data, it is concluded that ∼2/3 of iron atoms occupy Cu(2) positions in the form of Fe3+ and are magnetically ordered at room temperature. The other Fe atoms occupy Cu(1) positions with different coordinations; some of the octahedrally coordinated Fe3+ ions in Cu(1) positions (major part in the case of the Eu system) are magnetically ordered, probably, under the influence of magnetic ordering in Cu(2) sublattices containing Fe3+ ions.

Quantitative nano-characterization of heterogeneous catalysts

Heterogeneous catalysts can be of varying complexity ranging from single or double phase systems to complicated mixtures of metals and oxides with additives to help promote chemical reactions, extend the life of the catalysts, prevent poisoning etc. Although catalysis occurs on the surface of most systems, detailed descriptions of the microstructure and chemistry of catalysts can be helpful for developing an understanding of the mechanism by which a catalyst facilitates a reaction. Recent years have seen continued development and improvement of various TEM, STEM and AEM techniques for yielding information on the structure and chemistry of catalysts on the nanometer scale. Here we review some quantitative approaches to catalyst characterization that have resulted from new developments in instrumentation.HREM has been used to examine structural features of catalysts often by employing profile imaging techniques to study atomic details on the surface. Digital recording techniques employing slow-scan CCD cameras have facilitated the use of low-dose imaging in zeolite structure analysis and electron crystallography. Fig. la shows a low-dose image from SSZ-33 zeolite revealing the presence of a stacking fault.