Structure Of Solid Phase Research Articles

THE STRUCTURES OF CEREBROSPINAL FLUID IN DIAGNOSTICS AND TREATMENT EFFICACY ASSESSMENT IN PATIENT WITH NEUROSYPHILIS

Background: In the last years, there has been an increase in cases of latent and late neurosyphilis. Due to the wide implementation of antibiotics, there is a significant reduction in sensitivity of serological and general clinical tests used for diagnosis of this disease. The situations are not uncommon when it is not possible to exclude or confirm the invasion of Treponema pallidum into the nervous system structures. Absence of objective diagnostic criteria for neurosyphilis hints the timely administration of an adequate treatment aimed at prevention of an irreversible derangement of the nervous system and to the patient death. Aim: To search for new diagnostic symptoms of an injury to the brain structures caused by Treponema pallidum in patients with previous syphilis, based on a new technology of assessment of solid phase structures of cerebrospinal fluid. Materials and methods: One hundred and thirty one patient that had been treated for various forms of syphilis were recruited to this study. In addition to generally accepted clinical and laboratory assessments, including various serological methods, all patients underwent clinical and serological assessment of cerebrospinal fluid (CSF). According to the results of this assessment, all patients were categorized into three groups. Group 1 (n=27) consisted of patients with early asymptomatic neurosyphilis, group 2 (n=46), with late meningovascular neurosyphilis, group 3 (n=58), those without diagnosed neurosyphilis but with strong positive serum tests, negative CSF serology and negative VDRL test. An innovative method of marginal dehydration of biological fluids was used. The method is included into the Lithos-system diagnostic technology and allows for evaluation of the structures of CSF systems “lipid – water”, “lipid – protein – water” after their transition from liquid crystal phase into a solid phase. These structures called anisomorphons are seen only at polarized microscopy. The control group comprised 24 patients from in-patient department of neurology and neurosurgery with serous meningitis (n=8), as well as with purulent meningitis and meningoencephalitis (n=16) of bacterial etiology. Results: The morphological sign of a destructive process in central nervous system of neurosyphilis patients was represented by amorphous ovals that were absent in normal CSF. In group 1 patients, the amorphous ovals were found in small numbers within basic anisomorphons – dendrites. In group 2 patients, multiple separated amorphous ovals were detected as spheres, as well as basic anisomorphons – dendrites, fully filled with spheres made of amorphous ovals. Based on these characteristics, in 2 patients from group 3, early asymptomatic neurosyphilis was diagnosed, and in 5 patients, late meningovascular syphilis. At follow-up of 22 patients from group 2, positive trend towards normalization of CSF anisomorphons were seen only after 6 months of additional specific treatment. Conclusion: Assessment of CSF anisomorphon contents in patients with neurosyphilis by means of marginal dehydratation may serve as an additional diagnostic criterion of an early or late phase of neurosyphilis, help decide on the sanitation of the central nervous system and assess the treatment efficacy.

The electrochemical hydrogen storage properties of Ti0.72Zr0.28Mn1.6V0.4 alloy synthesized by vacuum plasma spraying and vacuum copper boat induction melting: A comparative study

In this study, two different rapid solidification techniques; vacuum plasma spraying and vacuum copper boat induction melting, were performed to synthesize Ti0.72Zr0.28Mn1.6V0.4 hydrogen storage alloy. The structure and electrochemical properties of the produced samples were comparatively investigated. The chemical and phase compositions of the samples were characterized by XRD and SEM analysis. The electrochemical hydrogen storage characteristics including the cyclic stability, the maximum discharge capacity, the high rate dischargeability, and the electrochemical impedance spectra (EIS) were measured. Results indicated that both samples consisted of a hexagonal C14 Laves phase matrix and a body centered cubic (BCC) structure of V-based solid solution phase. The electrochemical results showed that in the alloy prepared by induction melting, the maximum discharge capacity was higher, while the cyclic stability of the vacuum plasma sprayed sample was much better. These results were attributed to the quantity and distribution of the presence phases and the anti-corrosion performance of the alloys. Moreover, the results from the electrochemical kinetic experiments showed that the vacuum plasma sprayed sample had superior kinetic parameters, including the hydrogen diffusion rate and charge-transfer resistance, than that for the vacuum induction melted sample. Thus, vacuum plasma spraying could be an efficient production method for preparation of hydrogen storage alloys with improved properties which could be used for Ni–MH secondary batteries as negative electrodes.

Melting point trends and solid phase behaviors of model salts with ion size asymmetry and distributed cation charge.

The melting point trends of model salts composed of coarse grain ions are examined using NPT molecular dynamics simulations. The model salts incorporate ion size asymmetry and distributed cation charge, which are two common features in ionic liquids. A series of single-phase and two-phase simulations are done at set temperatures with 50 K intervals for each salt, and the normal melting point is estimated within 50 K. The melting point trends are then established relative to a charge-centered, size symmetric salt with a normal melting point between 1250 K and 1300 K. We consider two sets of size asymmetric salts with size ratios up to 3:1; the melting point trends are different in each set. The lowest melting point we find is between 450 K and 500 K, which is a reduction of over 60% from the charge-centered, size symmetric case. In both sets, we find diversity in the solid phase structures. For all size ratios with small cation charge displacements, the salts crystallize with orientationally disordered cations. When the partial cation charge is far enough off-center in salts with ion size ratios near 1:1, the salts can become trapped in glassy states and have underlying crystal structures that are orientationally ordered. At ion size ratios near 3:1, the salts with large cation charge displacements show premelting transitions at temperatures as low as 300 K. After the premelting transition, these salts exist either as fast ion conductors, where the smaller anions move through a face centered cubic (fcc) cation lattice, or as plastic crystals, where ion pairs rotate on a fcc lattice.

Simple Method to Compute Pair Distribution Function from Molecular Dynamics Data

A new simple method to compute the pair distribution function from molecular dynamics data is proposed, which is applied to two examples to determine the crystal structure in the solid phase. It is found that the short-range order of a two-dimensional repulsive system is a triangular lattice, and the crystal structure of a three-dimensional finite-range potential (including both repulsive and attractive parts) system is a hexagonal-close-packed lattice.

From crab shells to smart systems: chitosan-alkylethoxy carboxylate complexes.

In this work, self-assembly of alkyl ethylene oxide carboxylates and the biopolymer chitosan into supramolecular structures with various shapes is presented. Our investigations were done at pH 4.0, where the chitosan is almost fully charged and the surfactants are partially deprotonated. By changing the alkyl chain length and the number of ethylenoxide units very different water-soluble complexes can be obtained, ranging from globular micelles incorporated in a chitosan network to formation of ordered multiwalled vesicles. The structural characteristics of these complexes can be finely controlled by the mixing ratio of chitosan and surfactant, i.e., simply by the solutions composition. For instance, the vesicle wall thickness can be varied between 5 and 50 nm just by varying the mixing ratio. Accordingly, we expect this system to be an outstanding carrier for hydrophilic compounds with tunable release time option. Moreover, an easy route for preparation of chitosan-based complexes in the solid state with controlled mesoscopic order is presented. This work opens the way to prepare biofriendly materials on the basis of chitosan and mild anionic surfactants which are rather versatile with respect to their structure and properties, allowing for preparation of complexes with highly variable structures in both aqueous and solid phase. Formation of such different structures can be exploited for preparation of carriers, which are able to transport hydrophilic as well as hydrophobic molecules. Furthermore, as chitosan is well known to exhibit antibacterial and anti-inflammatory properties, different applications of these complexes can be indicated, i.e., as drug delivery systems or as coatings for medical implants.

Structural Organization and Supramolecular Interactions of the Task-Specific Ionic Liquid 1-Methyl-3-carboxymethylimidazolium Chloride: Solid, Solution, and Gas Phase Structures

Using a set of different techniques, which included single crystal X-ray, NMR, UV–vis, conductivity measurements, SAXS (small angle X-rays), ESI-MS(/MS) (electrospray (tandem) mass spectrometry), and theoretical calculations, an ample study of the structural organization and supramolecular interaction of the task-specific ionic liquid 1-methyl-3-carboxymethylimidazolium chloride (named MAI.Cl) was conducted. All techniques allowed for comprehensive investigation in the solid state, solution, and gas-phase behavior of MAI.Cl. Most relevant interactions are demonstrated showing the importance of hydrogen bonding to supramolecular organization of MAI.Cl in different states and its tendency to aggregate in aqueous solutions.

Experimental study of the structural characteristics of Al melts on the basis of Fourier analysis of acoustic emission signals

This scientific work is devoted to the study of the genetic connection structures of solid and liquid phases. Fourier analysis of signals of acoustic emission (AE) accompanying the melting of high purity aluminum from the melting point up to t=860°C was performed. The experimental data allowed for following the dynamics of the range order of the disorder zones in the melt with increasing melt temperature until their complete destruction.

Structural ordering and glass forming of soft spherical particles with harmonic repulsions

We carry out dissipative particle dynamics simulations to investigate the dynamic process of phase transformation in the system with harmonic repulsion particles. Just below the melting point, the system undergoes liquid state, face-centered cubic crystallization, body-centered cubic crystallization, and reentrant melting phase transition upon compression, which is in good agreement with the phase diagram constructed previously via thermodynamic integration. However, when the temperature is decreased sufficiently, the system is trapped into an amorphous and frustrated glass state in the region of intermediate density, where the solid phase and crystal structure should be thermodynamically most stable.

Nanocrystalline Ni-30wt%Fe Supersaturated Solid Solution Synthesized by Mechanical Alloying

Ni-30wt%Fe elemental power mixture was mechanically milled under argon atmosphere for variuos times up to 25h.The evolution of Ni-Fe alloying during milling and the microstructure of the as-milled powders were characterized by XRD, EPMA (electron probe microanalysis), SEM and TEM, respectively. The results show that nanocrystalline Ni (Fe) supersaturated solid solution alloy powders with 30wt. % Fe in composition can be synthesized by mechanical milling of the elemental powder mixture. Both the content of Fe dissolved and the microstrain developed in the as-synthesized Ni (Fe) solid solution phase increase, while the crystallite size decreases, steadily with increasing milling time. In particular, the Ni-30wt%Fe alloy powders obtained by 25h milling consist of a single Ni (Fe) supersaturated solid solution phase with average crystallite size of about 15nm and accumulated microstrain as high as 1.12%. DSC tests show that the nanocrystalline Ni-30wt%Fe alloy powders have a lower melting temperature than the elemental powder mixture, attributed to the unique Ni (Fe) solid solution phase structure, the nanocrystallization, and the high strain energy.

A Three‐Dimensional Structure and Process Model for Integrated Hydro‐Geo‐Pedologic Analysis of a Constructed Hydrological Catchment

A structure model describes the boundary geometries and the three‐dimensional solid phase distributions of the catchment. In contrast to an established ecosystem, feedback relations can be assumed for an initial geosystem between the development of spatial structures and the water and element fluxes. The objective was to develop a hydrological catchment model as a three‐dimensional spatial database of the solid phase that allows an integrative analysis, a periodical mass balance, and the generation of distributed model parameters for the developing system. Data were from the constructed catchment “Chicken Creek.” The initial texture and bulk density distributions were generated by imitating sediment dumping, segregation, and compaction. Boundary geometries and changes in surface topography due to erosion and sedimentation processes were quantified on the basis of digital elevation models (DEMs) derived from aerial photographs. The catchment was visualized with the three‐dimensional software GoCad; the “emergence” of the water table and other structures (e.g., soil horizons, root zone) could be spatially assigned and quantified to identify regions with specific processes. A combination of three‐dimensional catchment with time‐dependent two‐dimensional surface models allowed generating the development of spatially distributed erosion–deposition patterns that formed new initial surfaces. The three‐dimensional distributed solid phase structure of the catchment allowed for a more direct comparison with observations using minimal invasive methods. The mass balance of the solids could be related with pedologic development and transfer to other geopedologic systems achieved by adapting sediment transport and deposition in the descriptions of the model. This model may help improve the integrative analysis of hydrological catchments.

Quantifying the effect of solid phase composition and structure on solid–liquid partitioning of siderophile and chalcophile elements in the iron–sulfur system

We report experimentally determined partition coefficients between solid and liquid phases for bulk compositions on either side of the Fe–FeS eutectic for a suite of siderophile, chalcophile, and lithophile elements. Experiments were performed at conditions of 1.5 and 2GPa in pressure (P), 1323K in temperature (T), and virtually identical eutectic sulfide liquid compositions in equilibrium with either solid face centered cubic Fe or solid FeS. This enabled isolation of the effect of solid phase composition and structure from pressure–temperature–melt composition effects. Solid phase–liquid metal partition coefficients (D values) for Ge, Re, Ni, Co, Cr, Mn, V, Sn, Pb, Re and W differ significantly if partitioning occurs between identical metallic liquids but different solid phases, whereas Zn, Cu and Mo are virtually unaffected. For all elements except Ge and Sn, measured solid Fe–liquid sulfide partition coefficients at 1.5 and 2GPa are inconsistent with model predictions based on atmospheric pressure experiments, indicating that such models may not be appropriate for modeling core crystallization processes at non-ambient pressure.The framework of a lattice strain-based model of solid–liquid metal partitioning (Stewart et al., 2009) enables us to quantify the effect of the solid phase. Changing the solid phase from Fe to FeS leads to systematic increases in r0 (from 1.54 to 1.65Å) and apparent Young's modulus E (from 112 to 178GPa). These systematic changes can be used to predict element partitioning in eutectic solid FeS-bearing systems from measurements in eutectic solid Fe-bearing systems. Although changing the solid phase from face centered cubic Fe to FeS is an end member example, our data suggest that changes with pressure in the structure (e.g., to hexagonally close packed at high pressure) and composition (e.g. to higher S content at high pressure) of solid iron could affect the partitioning of elements between Fe and liquid metal during the solidification of planetary cores.

A new perturbed-chain equation of state for square-well chains in fluid and solid phases

Considering the hard-chain system as reference, a perturbed-chain equation of state (EOS) is developed. The second-order thermodynamic perturbation theory EOS is applied to the reference system. Monte Carlo simulation data for average intra-molecular and inter-molecular segment-segment radial distribution function of hard-chain systems with a chain length of 3-10 in the range of packing fraction between 0.1 and 0.72, covering both fluid and solid phases, are reported. A disordered solid phase structure is considered in this work. These customized data are used to develop the perturbation term of square-well (SW) attractions. The performance of perturbed-chain EOS is tested against computer simulation data from the literature for compressibility factor and phase equilibrium in the systems of SW chains. Results within good accuracy are obtained for all the test cases. Global vapor-liquid-solid equilibrium diagrams for SW chain systems predicted by the new EOS are reported.

Thermodynamic description of Np(VI) solubility, hydrolysis, and redox behavior in dilute to concentrated alkaline NaCl solutions

The solubility of Np(VI) was investigated in carbonate-free NaCl solutions (0.1 M ≤ I ≤ 5.0 M) at T = 22 ± 2 °C to derive thermodynamic properties of aqueous species and solid compounds formed under alkaline conditions. The experimentally derived solubility curves can be divided into four main regions: (I) ~7 ≤ pHm ≤ ~9, showing a steep decrease in Np solubility with a slope (log [Np] vs. pHm) of –3 or –2 (depending on NaCl concentration); (II) ~9 ≤ pHm ≤ ~10.5, with a nearly pH-independent [Np]; (III) ~10.5 ≤ pHm ≤ ~13.5, showing an increase in the solubility with a well-defined slope of +1. A region (IV) with a slope ≥ +2 was only observed at I ≥ 1.0 M NaCl and pHm ≥ ~13.5. The solubility-controlling solid Np phases were characterized by X-ray diffraction (XRD), quantitative chemical analysis, thermogravimetric analysis and scanning electron microscopy-energy-dispersive spectrometry (SEM-EDS), confirming the presence of anhydrous Na2Np2O7(cr) in regions II and III. The same solid phase was identified in region I except for the system in 0.1 M NaCl, where a NpO2(OH)2·H2O(cr) phase predominates. XRD patterns of this solid phase show a very good agreement with that of metaschoepite (UO3·2H2O), highlighting the similarities between Np(VI) and U(VI) with respect to solid phase formation and structure. Based on the analysis of solubility data, solid phase characterization and chemical analogy with U(VI), the equilibrium reactions 0.5 Na2Np2O7(cr) + 1.5 H2O ⬄ Na+ + NpO2(OH)3 – and 0.5 Na2Np2O7(cr) + 2.5 H2O ⬄ Na+ + NpO2(OH)4 2– + H+ were identified as controlling Np(VI) solubility in regions II and III, respectively. The predominance of NpO2 + in the aqueous phase of region I (quantified by UV–vis/NIR) indicates the reductive dissolution of Np(VI) [either as Na2Np2O7(cr) or NpO2(OH)2·H2O(cr)] to Np(V)aq. Oxidation to Np(VII) can explain the experimental observations in region IV, although it is not included in the chemical and thermodynamic models derived. The conditional equilibrium constants determined from the solubility experiments at different ionic strengths were evaluated with both the specific ion interaction theory (SIT) and Pitzer approaches. Thermodynamic data for aqueous Np(VI) species [NpO2(OH)3 – and NpO2(OH)4 2–] and solid compounds [Na2Np2O7(cr) and NpO2(OH)2·H2O(cr)] that are relevant under alkaline conditions were derived. These data are not currently included in the Nuclear Energy Agency-Thermochemical Database (NEA-TDB) compilation.

Thermal behaviour and structural properties of surfactant—Picrate compounds: The effect of the ammonium headgroup number

Novel quaternary n-dodecyldimethylammonium picrates with two to four chains connected by an ethylene spacer at the ammonium headgroup level were synthesized. The effect of the headgroup number and the impact of picrate anion to their physicochemical properties was examined. A crystal structure of dimeric dipicrate is significantly different from bromide analogue. The dominant feature of this crystal packing is a layered structure with aromatic rings of picrate molecules, stacked via strong π···π interactions and connected to the alkylammonium molecules with their nitro groups by C–H···O hydrogen bonds. Weak NO2···HC hydrogen bonds further stabilize the structure. Higher degree of oligomerization leads to the less-ordered solid phase and amorphous picrate structure. These amorphous structures result from widespread and disordered hydrogen bonding and rupture of π–π stacking in samples with more than two headgroups. Unlike corresponding bromides, picrate compounds show reversible phase transitions without thermal decomposition. Temperature-dependent infrared spectroscopy in the liquid phase detected adiabatic phase transitions.

Microstructures and Properties of Nanocrystalline NiFe Alloy With and Without Particulate TiC Reinforcement by Mechanical Alloying

In the current study, Ni50Fe50 alloy powders were prepared using a high-energy planetary ball mill. The effects of TiC addition (0, 5, 10, 20, and 30 wt pct) and milling time on the sequence of alloy formation, the microstructure, and microhardness of the product were studied. The structure of solid solution phase, the lattice parameter, lattice strain, and grain size were identified by X-ray diffraction analysis. The correlation between the apparent densities and the milling time is explained by the morphologic evolution of the powder particles occurring during the high-energy milling process. The powder morphology was examined using scanning electron microscopy. It was found that FCC γ (Fe–Ni) solid solution was formed after 10 hours of milling, and this time was reduced to 7 hours when TiC was added. Therefore, brittle particles (TiC) accelerate the milling process by increasing crystal defects leading to a shorter diffusion path. Observations of polished cross section showed uniform distribution of the reinforcement particles. The apparent density increases with the increasing TiC content. It was also found that the higher TiC amount leads to larger lattice parameter, higher internal strain, and lower grain size of the alloy.

Characterization of CeO2-ZrO2 mixed oxides prepared by two different co-precipitation methods

A series of cerium zirconium mixed oxides were prepared by two co-precipitation methods using magnesium hydrogen carbonate (MHC) and mixed ammonia-ammonia hydrogen carbonate (AAHC) as precipitant respectively. The crystal structure, BET surface area and morphology of the produced cerium zirconium mixed oxides were characterized by X-ray diffraction (XRD), Brumauer-Emmett-Teller (BET) and scanning electron microscopy (SEM) techniques. The reduction-oxidation behavior and oxygen storage capacity (OSC) performance were also studied by temperature programmed reduction (TPR) and oxygen pulse chemical adsorption methods. The XRD results demonstrated that the cerium zirconium mixed oxides obtained by both methods possessed structure of cubic solid solution phase. The fresh surface area calcinated at 600 °C, aged surface area after 1000 °C and OSC at 500 °C of cerium zirconium mixed oxides were determined to be 89.337, 34.784 m2/g, and 567 μmol O2/g for MHC method and 122.010, 46.307 m2/g, and 665 μmol O2/g for AAHC method, respectively.

Materials characterization of the low temperature sensitive liposome (LTSL): effects of the lipid composition (lysolipid and DSPE–PEG2000) on the thermal transition and release of doxorubicin

This paper describes how we have used material science, physical chemistry, and some luck, to design a new thermal-sensitive liposome (the low temperature sensitive liposome (LTSL)) that responds at clinically attainable hyperthermic temperatures releasing its drug in a matter of seconds as it passes through the microvasculature of a warmed tumor. The LTSL is composed of a judicial combination of three component lipids, each with a specific function and each affecting specific material properties, including a sharp thermal transition and a rapid on-set of membrane permeability to small ions, drugs and small dextran polymers. Experimentally, the paper describes how bilayer-concentration changes involving the lysolipid and the presence or absence of DSPE-PEG2000 affect both the lipid transition temperature and the drug release. While the inclusion of 4 mol% DSPE-PEG2000 raises the transition temperature peak (T(m)) by about 1 degrees C, the inclusion of 5.0, 9.7, 12.7 and 18.0 mol% MSPC slightly lowered this peak back to 41.7 degrees C, while not further broadening the peak breadth. As for drug release, in the absence of MSPC, the encapsulated doxorubicin-citrate is hardly released at all. Increasing the composition of MSPC in the lipid mixture (5.0, 7.4, 8.5 and 9.3 mol% MSPC) shows faster and faster initial doxorubicin release rates, with 8.5 and 9.3 mol% MSPC formulations giving 80% of encapsulated drug released in 4 and 3 min, respectively. The Thermodox formulation (9.7 mol% MSPC) gives 60% released in the first 20 s. The presence of PEG-lipid is found to be essential in order for the lysolipid-induced permeability to reach these very fast times. From drug and dextran release experiments, and estimates of the molecular and pore size, the conclusions are that: in order to induce lasting nanopores in lipid bilayers -10 nm diameter, they initially require the presence (from the solid phase structure) of grain boundary defects at the DPPC transition and the permeabilizing component(s) can either be a pore forming lysolipid/surfactant plus a PEG-lipid, or can be generated by a PEG-surfactant incorporated at -4-5 mol%. The final discussion is centered around the postulated defect structures that result in membrane leakage and the permeability of doxorubicin and H+ ions.

セリア－ジルコニア－テルビア系固溶体の合成と分光特性評価

Ceria-zirconia-terbia solid solutions were synthesized by co-precipitation method. The powders were characterized by XRD, colorimetric assessment and UV-Vis diffuse reflectance. A solid solution phase structure was obtained for all of the samples heated at 900°C and belongs to cubic fluorite structure or distorted fluorite structure. It was found that the lattice size decreased with increasing Zr content in the range x = 0 to 0.8 in ZrxCe1-xO2 and ZrxCe0.99-xTb0.01O2-δ. Diffuse reflectance spectra of the ZrxCe1-xO2 solid solutions in the UV region showed the broad shoulder-type band at 320-350 nm, which was assigned to interband transitions in CeO2 and additionally broader band in higher wave length region in solid solution. It was observed that ZrxCe1-xO2 powder became deeper yellow depending on Zr content, and that the doping of Tb resulted in warm colour in CeO2-ZrO2 based solid solution. The powders in the system of ZrxCe1-xO2 and ZrxCe0.99-xTb0.01O2-δ were possible pigments with environmental friendly properties toward future ceramic application.

Phase behavior of mixed submonolayer films of krypton and xenon on graphite

Using the results of extensive Monte Carlo simulations in the canonical and grand canonical ensembles, we discuss the phase behavior of mixed submonolayer films of krypton and xenon adsorbed on the graphite basal plane. The calculations have been performed using two- and three-dimensional models of the systems studied. It has been demonstrated that out-of-plane motion does not affect the properties of the films as long as the total density is well below the monolayer completion and at moderate temperatures. For the total densities close to the monolayer completion, the promotion of particles to the second layer considerably affects the film properties. Our results are in a reasonable agreement with the available experimental data. The melting point of submonolayer films has been shown to exhibit non-monotonous changes with the film composition, and reaches minimum for the xenon concentration of about 50%. At the temperatures below the melting point, the structure of solid phases depends upon the film composition and the temperature; one can also distinguish commensurate and incommensurate phases. Two-dimensional calculations have demonstrated that for the xenon concentration between about 15% and 65% the adsorbed film exhibits the formation of a superstructure, in which each Xe atom is surrounded by six Kr atoms. This superstructure is stable only at very low temperatures and transforms into the mixed commensurate (√3×√3)R30° phase upon the increase of temperature. Such a superstructure does not appear when a three-dimensional model is used. Grand canonical ensemble calculations allowed us to show that for the xenon concentration of about 3% the phase diagram topology of monolayer films changes from the krypton-like (with incipient triple point) to the xenon-like (with ordinary triple point).

The model of structure place transformation for phase change from graphite to diamond through explosion

Graphite powder subjected high velocity impact, under high pressure and temperature can be changed from graphite to diamond according to solid phase structure, The cubic face-centred lattice of diamond is constituted of 18 carbon atoms, among which, there are 14 atoms which is formed 16 covelant bond pairs, so correspondingly, in four net plane layers of the ABCA type graphite, also have 16 proper atoms corresponding to each other. This paper has founded the model to illustrate that the 14 carbon atoms of diamond and graphite are how to correspondence, then may be to obtain the maximal shifting distance of atom in 16 covalent bond pairs x* and activated energy U, at last,may be to calculate the transformation rate under the pressure p and temperature T; it takes key effect to design explosive parameters