High Pressure Theoretical Studies of Actinide Dioxides

Actinide dioxides (ThO 2 , UO 2 , Pu 2 etc.) compounds have the CaF 2 -type structure at ambient pressure and temperature. Under high pressure, they exist in the PbCl 2 -type structure, belonging to space group Pnma [1]. We have studied crystal structures under high pressure in actinide dioxides by means of first-principles self-consistent total-energy calculations with the non-local Perdew, Burke and Ernzerhof (PBE) exchange correlation using the full-potential linear-muffin-tin-orbital (FPLMTO) method. The atomic equilibrium volume, bulk modulus and transition pressure for actinide dioxides were calculated, covering the full pressure range for which the mentioned experiments have been done [2].     

The use of the high pressure hydrothermal method for tailored synthesis of zeolites without structure directing agents. Instance: Synthesis of natural zeolites with 5-1 building units

Abstract

The synthetic counterparts of natural alumosilicate zeolites containing 5-1 structural building units have been synthesized by simulating the natural hydrothermal formation conditions. Synthetic glasses of the respective zeolite composition were used as starting materials, while distilled water under hydrothermal conditions was used as pressure and reaction medium. No structure directing agents, additional solutions or sol-gel material has been employed.

The experience of former investigations on the tailored synthesis of alumosilicate zeolites showed, that 220°C is the expected temperature of maximum gain. Synthesis time was always 60 d. Synthesis pressure for mazzite (MAZ), mordenite (MOR), fer-rierite (FER), epistilbite (EPI) and dachiardite PAC) was 1 kbar while bikitaite (BIK) could only be synthesized at 2 kbar pressure.

The results of the investigations on hand show, that this process can be applied for the tailored synthesis of zeolites with completely new properties (e.g., semiconducting frameworks).     

Development of a high pressure stirring cell up to 2 GPa: a new window for chemical reactions and material synthesis

ABSTRACT

A new method for stirring under high pressure conditions has been developed and tested. The key component is a Teflon cell assembly equipped with magnetic stirring function, which is capable to operate across a wide pressure range, up to at least 2?GPa, in a large volume press. The setup enables adjustable stirrer rotation rate and detection of stirring in a sample, e.g. to observe liquid–solid phase transitions at high pressure. The viscosity limit of stirring is ca. 500 times that of water at room temperature (i.e. ～500?mPas). Moreover, we show that zinc oxide nanoparticles hydrothermally synthesized at 0.5?GPa and 100°C under stirring conditions show an order of magnitude smaller size (100?nm) compared to those synthesized under non-stirring conditions (1?μm). The wide pressure range for stirring of viscous media opens interesting possibilities to produce novel materials via hydrothermal synthesis and chemical reactions.     

Solvothermal synthesis of nitrides

Abstract

III-V nitrides are large band-gap semiconductors. They are very promising materials for opto-electronic and microelectronic applications.

The present paper deals with a new process for preparing nitrides. Two nitrides, gallium nitride (GaN) and aluminium nitride (AlN), have been synthesiaed through a solvothermal route. This process uses ammonia in supercritical conditions as solvent and metals as source of gallium and aluminium. Moreover, an additive is used to improve the nitridation of the metals.

The resulting microcrystallites of nitrides have been charactensed by X-ray diffraction and the morphology has been observed by scanning Electron Microscopy.     

Solvothermal synthesis of AlN

Abstract

Aluminum nitride is an important material due to its physical properties (electronic, thermal conductivity…). Different processes have been used for preparing such a material. The solvothermal synthesis is characterised by the use of a solvent in supercritical conditions in order to improve the reactivity of the precursors and to control the size of the crystalhtes. Using finely divided aluminum particles as precursor, a new process for the preparation of AlN has been optimised versus the thermodynamical parameters: pressure and temperature and the nature of the additive used for improving the kinetics of nitridation.     

The Nuclear Quadrupole Interaction in High Temperature Superconductors

Abstract

Since their discovery in 1986 [11], the high temperature superconducting (HTS) copper oxides have presented a continuing challenge to both experiment and theory. The identification of the underlying mechanism (or mechanisms) responsible for their superconductivity remains an unanswered question. Numerous theories have been proposed ranging from phonon-mediated pairing of the charge carriers, similar to the Bardeen–Cooper–Schrieffer (BCS) [2] theory developed for conventional low-temperature superconductors, to novel concepts independent of phonons [3–-l0]. For conventional superconductors the variation of the transition temperature T_c , with isotopic mass M (from BCS theory T_c ～ M^?a ) was an important verification of the contribution of electron-phonon interactions to electron pairing. Measurements of this effect of HTS cuprates resulted in isotope shifts much smaller than predicted by theory [ll-14], raising doubts about the role of phonons. However, Barbee [15] argued that the size of the isotope shift is not a unique indicator of phonon-mediated pairing. Since the HTS materials contain Cu ions with partially filled 3d shells, many of the alternative theories of HTS have focused on magnetic interactions and associated spin fluctuations [3–10]. The reader is referred to Ref. 16 for the details of other theories that have been proposed and to the article by Schrieffer and Anderson [17) for an overview discussion of the theory of high temperature superconductivity.     

A Method for q-Calculus

Abstract

We present a notation for q-calculus, which leads to a new method for computations and classifications of q-special functions. With this notation many formulas of q-calculus become very natural, and the q-analogues of many orthogonal polynomials and functions assume a very pleasant form reminding directly of their classical counterparts.

The first main topic of the method is the tilde operator, which is an involution operating on the parameters in a q-hypergeometric series. The second topic is the q-addition, which consists of the Ward–AlSalam q-addition invented by Ward 1936 [102, p. 256] and Al-Salam 1959 [5, p. 240], and the Hahn q-addition.

In contrast to the the Ward–AlSalam q-addition, the Hahn q-addition, compare [57, p. 362] is neither commutative nor associative, but on the other hand, it can be written as a finite product.

We will use the generating function technique by Rainville [76] to prove recurrences for q-Laguerre polynomials, which are q-analogues of results in [76]. We will also find q-analogues of Carlitz’ [26] operator expression for Laguerre polynomials. The notation for Cigler’s [37] operational calculus will be used when needed. As an application, q-analogues of bilinear generating formulas for Laguerre polynomials of Chatterjea [33, p. 57], [32, p. 88] will be found.     

Biocompatibility of monoelementary carbon polymer prepared for the soft and hard tissue implantation

Abstract

Glassy-like carbon to be applicable in two amas of advanced technology:

1—as Source of sp³ organizad carbon orbitals in HP/HT diamond synthesis [1].

2—as chamically inert parts for implantation in surgery [2].

For first application the temporatwe of carbonization proam should be lower thau 1300 K, for the second one higher than 1300 K (the best ?1473 K). Usefafnercr of dense body for surgery prepared by us was analysed on: as heart valves and as parts for face-skull restoration. Biocompatibility was tested in soft tisrue of ratrr, pig8 and dogs. Positive results have shown that such a body may be applicable as biomaterial.     

High oxygen pressures and the stabilization of six-coordinated Ir(VI) in an oxygen lattice

Abstract

During these last twenty five years a great efforts have been made in the Laboratoire de Chimie du Solide du CNRS in order to develop high oxygen pressure for the stabilization of unusual oxidation state of transition elements.

The aims of such research works was to correlate the increase of the Mⁿ⁺-O bond covalency versus the increase of the oxidation state n+ to the physicochemical properties of resulting oxides [1].

Iridium was an interesting element due to its position (5d) in the Periodic Table. In 1980 Ir(V) (d⁴) was stabilized in La₂LiIrO₆ in the perovskite structure [2]. Such a study had underlined the strong value of the spin-orbit coupling associated to Ir(V) [3].

The stabilization of Ir(VI) is interesting from two points of view : (i) its isotropic electronic configuration (d³), (ii) such a high oxidation state could lead to the strongest M-O bond in an oxygen lattice.

Selecting, through a specific methodology, the most appropriate local structural and chemical factors and with the help of high oxygen pressure, Ir(V1) was stabilized in the perovskite Ba₂CaIrO₆. Structural, magnetic and Mössbauer studies have been carried out in order to characterize the physicochemical properties induced by this unusual oxidation state.     

Higher-Order Effects Induced Optical Solitons in Fiber

In this paper, we study the existence conditions of the soliton solutions induced by considering the higher-order effects such as the third-order dispersion (TOD), self-steepening (SS), and self-frequency shift arising from stimulated Raman scattering (SRS) simultaneously in optical soliton communication. Based on the Jacobian expansion method, we successfully obtain bright and dark solitons. The results shows that the resultant inclusion is in agreement with Mollenauer et al. [Physical Review Letters 45 (1980) 1095] when the SRS is not considered; while when the SRS is considered, the existence conditions of the higher-order effects induced bright and dark solitons are not only quite different from those of the group velocity dispersion (GVD)-induced and self-phase modulation (SPM)-induced solitons, but also different from those of the TOD- and SS-induced solitons discussed by Mollenauer et al. [Physical Review Letters 45 (1980) 1095].     

Decrease of free amino acids in high-pressure treated cheese

Abstract

High-pressure treatment of cheese has been studied with a view to preserving fresh cheese [1], and also of developing a method of accelerating its ripening [2-7]. While these objectives can be reached, other changes also occur in cheese when high pressure is applied. One of those changes is the decrease of free amino acids (FAA) in cheese treated in pressures over 200-300MPa. In this paper we will try to summarize the results obtained by different research groups, as well as our own. These results have been published separately, but not previously tied together and explained.     

On a Lie group of infinite order as a nontrivial coupling of an intrinsic and space-time symmetries II

A real Lie algebra of denumerable infinite order that contains as subalgebras the Poincaré algebraP and the algebraSU(3) is derived by the method introduced in [1]. A nontrivial mass formula is obtained.     

The numerical modelling of the stress-strained state of diamond anvil cell components

Abstract

The method of numerical modelling of the behaviour of main components (anvils and deformable gasket) in diamond anvil cells (DAC) in the process of pressure generation has been developed and realized in the form of programs packages. The optimization of the geometry and loading conditions for an anvil was conducted in line with the multilevel factor plan of major effects (MFPME). A combination of optimizing factors allowing to obtain the theoretically predicted pressure of 465 GPa has been found, the value that by 2.7 times higher than that obtained on anvils at an analogous external pressure distribution [1] and the same diamond strength.

FEM     

A note on q-Bernoulli numbers and polynomials

Abstract

Recently, B. A. Kupershmidt have constructed a reflection symmetries of q-Bernoulli polynomials (see [9]). In this paper we give another construction of a q-Bernoulli polynomials, which form Barnes’ multiple Bernoulli polynomials at q=1, cf. [1, 13, 14]. By using q-Volkenborn integration, we can also investigate the properties of the reflection symmetries of these’ q-Bernoulli polynomials.     

Molecular dynamics simulations of AlN deposition on GaN substrate

ABSTRACT

In this work, we investigated the deposition of AlN film on GaN substrate by using molecular dynamics (MD) simulations. The effects of GaN substrate surface, growth temperature, and injected N: Al flux ratio on the growth of AlN film were simulated and studied. Consequently, the deposited AlN film on the (0001) Ga-terminated GaN surface achieves better surface morphology and crystallinity than that on the (000-1) N-terminated GaN surface due to the different diffusion ability of Al and N adatoms on two GaN surfaces. Furthermore, with the increase of growth temperature, the surface morphology and crystallinity of AlN film were improved owing to the enhanced mobility of adatoms. At the optimised injected N: Al flux ratio of 1, comparatively good surface morphology and crystallinity of deposited AlN films were realised. This method lays a foundation for the follow-up real-time study of defects and stress evolution of AlN on GaN and can be applied to film growth of other materials.     

New packaging solutions for high pressure treatments of food

Abstract

High pressure is a promising technology for developing new processes in food treatment. In most cases, pre-packaged foods are used in high pressure treatments (HP). Consequently, the behavior of the package under treatment conditions is an important factor. The following work was devoted to the evaluation of different packages under high pressure conditions in the presence of different substances used as simulants. Three main characterizations were carried out after HP treatment: mechanical resistance, barrier properties and integrity.

The experimental results using multilayer plastic films (PA/PE) have led to the selection of several solutions which may be used as packages for high pressure treatments.     

A New Benzothiazin-functionalized Calix[4]arene-based Fluorescent Chemosensor for the Selective Detection of Co2+ Ion

Calixarenes, which have a great place in supramolecular chemistry, have become the most prominent macrocyclic compounds in synthetic organic chemistry due to their easy synthesis and functionalization. In this study, p-tert-butyl calix[4]arene dihydrazide derivative was synthesized and then reacted with 3-oxo-3,4-dihydro-2 H-benzo[b][1,4] thiazin-2-ylideneacetyl chloride to prepare new calixarene based chromophore compound 4. The structure of the synthesized compound was elucidated by spectroscopic methods such as ¹H NMR ¹³C NMR and FT-IR spectroscopy. Chromogenic and fluorescence properties of compound 4 were evaluated. It was observed from both studies that compound 4 was Co²⁺ selective and shows fluorescence Switched-off behavior. Stoichiometry, binding constant and the detection limit were calculated. The stoichiometry between compound 4 and Co²⁺ was found to be 1:1. The binding constant value (K) was calculated as 666.67 M^??1 using Benesi–Hildebrand equation, while the detection limit for Co²⁺ ion was calculated as 0.0465 µM.

     

A control method for congested traffic in the coupled map car-following model

Based on the pioneer work of Konishi et al, a new control method is presented to suppress the traffic congestion in the coupled map (CM) car-following model under an open boundary. A control signal concluding the velocity differences of the two vehicles in front is put forward. The condition under which the traffic jam can be contained is analyzed. The results are compared with that presented by Konishi et al [Phys. Rev. 1999 E 60 4000--4007]. The simulation results show that the temporal behavior obtained by our method is better than that by the Konishi's et al. method, although both the methods could suppress the traffic jam. The simulation results are consistent with the theoretical analysis.     

A novel determination of activation quantities and reaction order(s) for the hydrothermal destruction and its applications

Abstract

A novel determination method of activation quantities and reaction order(s) of hydro-thermal reactions was developed in order to achieve economically, easily and speedily research and development of new hydrothermal plants. This method is called the NIT method (abbreviation of ‘Nonisothemal method’) in the case of a batch reactor and the F-NIT method (abbreviation of ‘nonisothermal method for flow reactor’) in the case of a plugged flow reactor. The main merit of the NIT method (or the F-NIT method) is to give access to the determination of activation quantities and/or reaction orders by measuring the changes in amount of chemical species under nonisothermal conditions.

After summary of the recently published NIT method, the newly F-NIT method is described briefly. Then the two types of hydrothermal fluids (hydrothermal steam and supercritical/subcritical water) are applied to the destruction of phenol under nonisothermal conditions. The activation quantities can be obtained at once by use of these methods and are compared with the reported values in the scWO.     

GaN中Zn的均匀掺杂

在Ar-HCl-Ga-NH3气相外延生长GaN的过程中,分析了Zn在GaN中分布不均匀的原因,认为除生长出晶体完整性好的n-GaN提供均匀掺杂的必要条件外,Zn气流的合理分布是获得Zn均匀掺入的关键。我们通过设计新的Zn喷口,能在φ25mm的GaN:Zn样品上,得到了Zn的均匀分布,PL、CL、EL均为一种颜色,室温下测定了EL光谱,不同点的峰值偏差小于10Å。