Effect of Stretching on β-Phase Content of Isotactic Polypropylene Melt Containing β-Nucleating Agent

Pure isotactic polypropylene (iPP) and that containing 0.2 wt% of a β-nucleating agent (β-NA) were extruded through a slit die. Simultaneously, the extruded melt was stretched at the die exit with different stretching rates (SR). The change of β-phase content with different SR was investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The results indicate that, for pure iPP, the content of β-phase first increases with increasing SR till it reaches a maximum and then it gradually decreases. However, for the case of β-nucleated iPP, it decreases monotonously with increasing SR. The spatial confinement is considered as the best explanation for the suppression of β-phase in the nucleated iPP melt upon stretching.     

Spectrofluorimetric Study and Detection of Ketoconazole in the Presence of β-cyclodextrin

The formation of a complex between ketoconazole and β-cyclodextrin was followed by spectrofluorimety. The inclusion of ketoconazole in β-cyclodextrin cavity enhanced the native fluorescence of the drug. The stoichiometry of the complex was 1:1 β-cyclodextrin to ketoconazole and the stability constant of the complex (log K _f) was determined to be 4.3 ± 0.01 at pH = 7.9 and 3.7 ± 0.04 at pH = 2.6. A sensitive spectrofluorimetric method for the detection of ketoconazole is presented. At optimized experimental conditions, a linear relationship between the fluorescence intensity of the solution and concentration of ketoconazole is observed in the range of 0.01–10 μg ml⁻¹ (5 × 10⁻⁸ M–1.88 × 10⁻⁵ M). The method was applied to the detection of ketoconazole in pharmaceutical products and the results were satisfactory in comparison to the official method (relative error = 2.8% and standard deviation = 0.06 for tablets of ketoconazole). The recovery of ketoconazole from a blood serum sample, determined by the proposed method, was 97.1 ± 2.4%.     

MWCNTs Supported N,N′-Dicyclohexyl-1,5-diamino-2,6-naphthalenedicarboxamide: A Novel β-Nucleating Agent for Polypropylene

N,N′-Dicyclohexyl-1,5-diamino-2,6-naphthalenedicarboxamide (NA), a highly efficient and selective β-nucleating agent for isotactic polypropylene (iPP), was synthesized and chemically supported on the surface of multiwall carbon nanotubes (MWCNTs) via an amidation reaction. The β-nucleation ability of NA, itself, is superior to the commonly used, highly efficient, and selective β-nucleating agents, e.g., commercial rare earth WBG-and aryl amide derivative TMB-5, as proved by the results of wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The effect of MWCNTs supported NA (MWCNT-NA) on the crystallization and melting behavior of iPP was investigated by means of WAXD and DSC. The results show that the MWCNTs supported NA can effectively induce the formation of β-crystals in iPP/MWCNT-NA, although the grafting degree of NA onto the surface of MWCNTs could still to be improved.     

Distribution of iron atoms in Fe-Mn alloys with the structure of β-Mn

X-ray analysis and Mössbauer spectroscopy were used to study the distribution of iron atoms in Fe-Mn alloys isostructural to -Mn and to determine the iron concentrations in the positions 8(c) and 12(d) of the -Mn structure in alloys of different compositions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 86–89, March, 1981.     

C-13 NMR Investigation of Cellobiose in the Presence and Absence of β-Glucosidase

T1(C-13) NMR measurements of cellobiose in aqueous solutions at pH=5 in the presence and absence of enzyme β-glucosidase detected at T=276°K a fast interaction between cellobiose and the enzyme at C1′α level of the disaccharide molecule. T1(C-13) measurements of equal solutions of cellobiose in the presence and absence of EDTA at the same temperatures suggest also a competitive interaction of cellobiose, at C1′α level, with EDTA complexed with a metal ion. T1 data justify a nearly spherical shape of cellobiose in solution.     

A Spectrofluorimetric Sequential Injection Method for the Determination of Penicillamine Using Fluorescamine in the Presence of β-cyclodextrins

A simple, robust and sensitive sequential injection spectrofluorimetric method for the determination of penicillamine (PA) in pharmaceutical formulations is developed. The method is based on the formation of a highly fluorescent derivative when penicillamine is reacted with fluorescamine (FL) in borate buffer of pH 9.3. The derivative produced is monitored at an emission wavelength of 495 nm using an excitation wavelength of 355 nm. The optimum conditions for the determination of PA with FL were: 3 mM FL, pH 9.3, 5 mM methyl-β-cyclodextrin, sample volume of 75 μL and reagent volume of 75 μL. Furthermore, the effect of various media on the fluorescence intensity of the PA–FL derivative was studied and methyl-β-cyclodextrin was found to give the largest enhancement. A linear dynamic range for the determination of PA of 5–80 ppm was obtained with a sampling frequency of 50 h⁻¹ and a relative standard deviation of less than 2.5%. The method was applied to the determination of PA in pharmaceutical formulations with reasonable recoveries ranging from 101.0–103.1%, indicating that no interference is observed from concomitants usually present in dosage forms.     

Ambiguities of the Seiberg-Witten Map in the Presence of Matter Field

The ambiguities of the Seiberg-Witten map for gauge field coupled with fermionic matter are discussed.We find that only part of the ambiguities can be absorbed by gauge transformation and/or field redefinition and thus are negligible.The existence of matter field makes some other part of the ambiguities difficult to be absorbed by gauge transformation of field regefinition.     

Computer Modelling of Metal Dissolution in the Presence of Aqueous Electrolyte

The semi-empirical Hartree-Fock intermediate neglect of differential overlap (INDO) method was used to explore the potential energy surface of adsorbed water molecules and to speculate,using fairly simple chuster models,on the reaction path followed by metal ions leaving the surface.As an example,INDO calculations were used to calculate the potential energy curve for a metal atom leaving the surface and entering into a solvation cage composed of tetrahedral arranged water molecules.The effect of adding a NaCl ion pair to the system with the halide ion above the dissolving atom was also explored.     

Classical Electromagnetic Field Theory in the Presence of Magnetic Sources

Using two new well-defined four-dimensional potential vectors,we formulate the classical Maxwell field theory in a form which has manifest Lorentz covariance and SO(2) duality symmetry in the presence of magnetic sources.We set up a consistent Lagrangian for the theory.Then from the action principle we obtain both Maxwell‘s equation and the equation of motion of a dyon moving in the electromagnetic field.     

Propagation Control of Soliton Trains in Dispersion-Shifted Fibres in the Presence of Third-Order Dispersion

The evolution of soliton trains in dispersion-shifted fibres (DSFs) in the presence of third-order dispersion (TOD) is investigated. The results show that the collision of neighbouring solitons in the trains can be suppressed by means of a proper TOD, but the maximum transmission distance (or bandwidth) is limited by the increasing soliton separation that results from the TOD. It is also shown that the separation can be suppressed by adjusting the initial phase or amplitude difference between the solitons. These results are helpful to re-establish the potential application of the soliton-based optical-communication systems in DSFs.     

Stability of the Distribution in a Money Exchange Model

A nonlinear money exchange model is revised and a correct master equation is derived. The evolution of the distribution is studied from direct numerical and analytical calculations. The stability of the final steady state of the system is investigated. It is argued that the final distribution is valid for a group of conservative money exchange models.     

Velocity Distribution of the Powder Particles in Laser Cladding

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Transmission Probability of an Ultracold Atom in the Presence of Atomic Coherence

We investigate the transmission probability of an ultracold V-type three-level atom passing through a micromaser cavity,in the presence of atomic coherence which is established by a coherent driving field.We show that the transmissibility of this micromaser system with the atomic coherence is better than that of the ordinary micromaser system without atomic coherence.When the driving field is strong enough,for any cavity length the ultracold atom can pass through the micromaser cavity freely.     

Hierarchical Distribution of β-Phase in Compression- and Injection-Molded,Polypropylene-Based TPV

The distribution of the β-phase crystals of polypropylene (PP) in different zones of compression and injection moldings molded from PP-based dynamically vulcanized thermoplastic elastomer (TPV) in the presence of a β-nucleating agent (β-NA) was investigated. The influence of shear and cooling conditions and the addition of β-NA on the development of β-phase was examined and discussed based on the one-dimensional heat conduction behaviors with phase change. A hierarchical distribution of β-phase was observed in both compression- and injection-molded TPV/β-NA specimens. For the compression-molded TPV/β-NA specimens, the hierarchical distribution of β-phase induced by β-NA is dominated by the cooling conditions. For the injection-molded TPV/β-NA specimens, the occurrence of β-phase is also mainly induced by the addition of β-NA; the effect of shear on the relative content of β-phase can hardly be observed and the cooling conditions control the hierarchical distribution of β-phase. Both in compression and injection-molded TPV/β-NA specimens, the relative content of β-phase increases from the skin to the core zones, owing to the cooling rate decreasing from the skin to the core zones.     

Phase Transition in β-nucleated Isotactic Polypropylene Induced by Combination of Annealing and High Pressure

The effects of annealing and high pressure on the microstructure of β-nucleated isotactic polypropylene (iPP) were investigated. Annealing treatment was carried out at different temperatures from 90–170°C under different pressure conditions, that is, atmospheric pressure and high pressures of 150, 250, and 350 MPa, respectively. The microstructure of the specimens was comparatively investigated through using wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Different from the common annealing treatment under atmospheric pressure, which induces the single-phase transition from metastable β-iPP to the more stable α-iPP (β→α) depending on the annealing temperatures, the application of high pressure induces not only the phase transition of β→α but also the phase transition of β→γ. Furthermore, the thermostability of β-iPP was improved greatly under high pressure. The higher the pressure applied, the smaller was the degree of the transition from β-iPP to α-iPP and/or γ-iPP. This work reports, for the first time, a novel crystalline morphology composed of β-iPP and γ-iPP.     

Spin Filter Effect in Organic Polymers in the Presence of Local Magnetic Field

Using a nonadiabatic evolution method, we investigate the spin filter effect in organic polymers in the presence of a local magnetic field. Through a spin-dependent magnetic field, polarons （charge carrier） with different spins will feel repulsive or attractive force determined by their spins. Our simulations show that in a single-site magnetic field （affecting electrons at a single site）, for example V150 = 0.35 eV, or V150 = 0.45 eV, a spin-up polaron accelerated to saturated velocity by an electric field can pass through the field while the spin-down polaron is trapped. When the local field extends over several sites （Vn～ exp[-（n - nc）2/nw^2]）, similar behaviour is also found. Simultaneously we find that it is more likely to realize the spin filter effect in a comparatively large field since the polaron which feels attractive force is easily trapped by a local magnetic field.     

Dissipative Collapse in the Presence of Λ

We present the general junction conditions for the smooth matching of a spherically symmetric, shear-free spacetime to Vaidya’s outgoing metric across a four-dimensional time-like hypersurface in the presence of a cosmological constant. These results generalise earlier treatments by Santos and co-workers on radiating stellar models. We study the thermal evolution of a particular radiating model within the framework of extended irreversible thermodynamics.     

Binding Energies of Excitons in Square Quantum-Well Wires in the Presence of a Magnetic Field

The binding energies of the ground state of excitons in the GaAs/Ga1-xAlxAs square quantum-well wire in the presence of a magnetic field are investigated by using the variational method. It is assumed that the magnetic field is applied parallel to the axis of the wire. The calculations of the binding energy as a fimction of the wire size have been performed for infinite and finite confinement potentials. The contribution of the magnetic field makes the binding energy larger obviously, particularly for the wide wire, and the magnetic field is much more pronounced for the binding energy in a square quantum wire than that in a cylindrical quantum wire. The mismatch of effective masses between the well and the barrier is also considered in the calculation.     

Quantum Dynamics of Cooled Atoms in the Presence of Bose—Einstein Condensates

Under the Markov approximation,the quantum dynamics of cooled atoms in the presence of Bose-Einstein condensates is studied.A master equation governing the evolution of such a system is derved.Using this master equation,the distribution of the atoms in the excited states at finite temperature and the dynamics of the excited atom at zero temperature are given and discussed.     

The Role of Interfacial Interactions in the Toughening of Precipitated Calcium Carbonate–Polypropylene Nanocomposites

This paper investigates the effect of the interphase properties and the interfacial interactions between matrix and filler on mechanical properties of precipitated calcium carbonate (PCC)–polypropylene nanocomposites. PCC particles were coated with stearic acid (SA). The weight ratio of SA on the particles (w _SA) ranged from 0 to 0.135 g SA/g PCC. The introduction of PCC particles resulted in an increase in stiffness and yield stress compared with the pristine polymeric matrix and, at the same time, it increased the impact resistance. The maximum improvement in the impact behaviour was achieved for the composites with w _SA =0.045 corresponding to the theoretical monolayer ratio. A decrease in interfacial interactions between monolayer coated PCCs and the matrix with respect to the uncoated particles was observed by using a semi-empirical equation developed by Pukànszky. The low degree of interfacial interactions between particulate filler and matrix allows a matrix–particle debonding phenomenon, as shown by scanning electron microscopy analysis. Extensive plastic deformations were evident as well, promoting an improvement in toughness. The thickness of the interphase between particles and matrix was evaluated by using the Shen–Li model which is based on the hypothesis of a non-homogeneous interphase. It results that the thickness increased in the order uncoated < monolayer coated < 3% SA coated ? 13.5% SA coated particles. The thinner and stronger interphase found for the composite with uncoated particles can be explained with the high interaction between matrix and filler and the consequent low mobility of the polymeric chains.