Distributed Gaussian discrete variable representation

A discrete variable representation (DVR) made from distributed Gaussians g_n(x) = e, (n = ?∞, …, ∞) and its infinite grid limit is described. The infinite grid limit of the distributed Gaussian DVR (DGDVR) reduces to the sinc function DVR of Colbert and Miller in the limit c → 0. The numerical performance of both finite and infinite grid DGDVRs and the sinc function DVR is compared. If a small number of quadrature points are taken, the finite grid DGDVR performs much better than both infinite grid DGDVR and sinc function DVR. The infinite grid DVRs lose accuracy due to the truncation error. In contrast, the sinc function DVR is found to be superior to both finite and infinite grid DGDVRs if enough grid points are taken to eliminate the truncation error. In particular, the accuracy of DGDVRs does not get better than some limit when the distance between Gaussians d goes to zero with fixed c, whereas the accuracy of the sinc function DVR improves very quickly as d becomes smaller, and the results are exact in the limit d → 0. An analysis of the performance of distributed basis functions to represent a given function is presented in a recent publication. With this analysis, we explain why the sinc function DVR performs better than the infinite grid DGDVR. The analysis also traces the inability of Gaussians to yield exact results in the limit d → 0 to the incompleteness of this basis in this limit. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Synthesis of novel heterobimetallic complexes of platinum(II) bridged by the mixed phosphine-phosphine oxide ligands Ph2P(CH2)2P(O)Ph2

Summary The mixed phosphine-phosphine oxides Ph₂P(CH₂)_n-P(O)Ph₂ (n = 1 or 2) react with K₂PtCl₄ to give cis-{PtCl₂- ¹-Ph₂P(CH₂) _n P(O)Ph₂]₂}. Treatment of the latter (n = 2) with transition metal chlorides MCl₂·nH₂O, or with Me₂SnCl₂, SnCl₄·5H₂O, Th(NO₃)₄·xH₂O or UO₂(NO₃)₂· 6H₂O, gives novel heterobimetallic complexes identified as cis-{PtCl₂[-Ph₂P(CH₂)₂P(O)Ph₂]₂MX₂}·nH₂O. Attempts to prepare similar heterobimetallic complexes using the starting complexes {PtX₂[ ¹-Ph₂PCH₂P(O)-Ph₂]₂} (X = C1), cis- or CN, trans-] were unsuccessful. Possible reasons for this are discussed.     

Somehow emancipating Probabilistic Evolution Theory (PREVTH) from singularities via getting single monomial PREVTH

This paper deals with the combination of the evolver dynamics of a hydrogen-like quantum system with the conical PREVTH (Probabilistic Evolution Theory) and excessively with the single monomial PREVTH. The new original applications are degree escalations in each monomial of a set of Poisson Bracket equations with multinomial right hand side and arbitrary, optimisable, parameters insertion to the resulting single monomial via an approach based on commutativity relations amongst the system basis operators. What we have shown that the additions based on commutativities with the Constancy Adding Space Extension (CASE) operator which is in fact proportional to identity operator, does not contribute to the suppression of the norm square of the single monomial coefficient matrix. This is just an observation for a specific family of systems but may be signaling a more general reality. If so it needs rather a rigorous proof.     

Study of transients in the propagation of nonlinear waves in some reaction diffusion systems

We study the transient dynamics of single species reaction diffusion systems whose reaction terms f(u) vary nonlinearly near u ≈ 0, specifically as f(u) ≈ u² and f(u) ≈ u³. We consider three cases, calculate their traveling wave fronts and speeds analytically and solve the equations numerically with different initial conditions to study the approach to the asymptotic front shape and speed. Observed time evolution is found to be quite sensitive to initial conditions and to display in some cases nonmonotonic behavior, ascribable to the disparity in time scales between the evolution of the front interior and the front tail.     

Processing and physical property relationships in injection-molded isotactic polypropylene. 1. Mechanical properties

The aim of the research reported in these two articles was to explore the relationship between processing conditions and the physical properties of different grades of isotactic polypropylene injection moldings and propylene/ethylene copolymers. This first article describes the methods and processing conditions used for molding, together with mechanical test results. Both conventional and shear-controlled orientation injection molding (SCORIM) have been employed for the production of moldings. SCORIM is based on the application of specific macroscopic shears to a solidifying melt, which in turn, facilitates enhanced molecular alignment. SCORIM results in more pronounced molecular orientation than conventional injection molding, which is consistent with the substantial increase in Young's modulus of moldings produced by SCORIM. By controlling the processing parameters it is possible to control and enhance the stiffness without loss of tensile strength. An increase of up to four times in impact strength has been achieved with SCORIM as well as a substantial increase in Young's modulus. The conventional injection moldings containing pronounced molecular orientation exhibited impact resistance well below that for the SCORIM moldings. The mechanical tests carried out at 80°C showed that the high-temperature mechanical properties of all the materials, converted into moldings using SCORIM, exhibited substantial enhancement when compared with moldings of the same material converted by conventional injection molding. © 1997 John Wiley & Sons, Inc.     

Porous coordination polymer hybrid device with quartz oscillator: effect of crystal size on sorption kinetics

A new strategy to synthesize monodispersed porous coordination polymer (PCP) nanocrystals at room temperature was developed and utilized for the formation of PCP thin films on gold substrates with fine control over the crystal sizes using the coordination modulation method. Hybridization of these PCP thin films with an environment-controlled quartz crystal microbalance system allowed determining the adsorption properties for organic vapors (methanol and hexane). In the case of high sensitivity (at the low-concentration dosing of analytes), the sensor response depended on the crystal size but not on the type of analyte. In contrast, at the high-concentration dosing, a clear dependence of the sorption kinetics on the analyte was observed due to significant sorbate-sorbate interaction.     

Crystallization behavior in a highly driven marginal glass forming alloy

Al₉₀Sm₁₀, a marginal glass former, was rapidly solidified using Cu-block single roller melt spinning at wheel speeds of 30 and 40 m/s. The product phases of rapid solidification were identified and analyzed using high energy synchrotron X-ray diffraction (HEXRD), high resolution transmission electron microscopy, and atom probe tomography. The as-quenched structure consists of a saturated amorphous phase and nanocrystalline Al with typical length scale of about 5 nm. The appearance of a pre-peak on HEXRD diffraction patterns and a low activation energy for first crystallization as determined using the Kissinger and Ozawa methods indicate some local ordering in the amorphous phase. The devitrification phase transformation path was determined using in situ high energy synchrotron radiation. Three phases, MS1, H1, and Al₄Sm, were identified during decomposition of the amorphous phase. MS1, H1 and Al₄Sm are cubic, hexagonal and orthorhombic metastable phases, respectively.     

The effect of shear controlled orientation in injection moulding on the mechanical properties of an aliphatic polyketone

This article relates to an investigation of injection moulding a new commercial polymer, an aliphatic polyketone (PK). A terpolymer and a 30% glass-filled grade were used as study materials together with an isotactic polypropylene that was used as a basis for comparison. Both conventional injection moulding and shear-controlled orientation injection moulding (SCORIM) were employed in processing. Tensile testing was carried out at 80°C as well as at room temperature. Polarized light microscopy and wide-angle x-ray diffraction were used in the characterization of the mouldings. An increase of up to 30% in Young's modulus and 35% in ultimate tensile strength, and a 70–90% increase in strain at peak were gained for the terpolymer (PK) at room temperature, as a result of SCORIM processing. A substantial improvement at 80°C was also recorded for unfilled SCORIM PK mouldings, and is attributed to the pronounced molecular alignment that was induced in SCORIM mouldings, as shown by Debye patterns. It is notable that the SCORIM mouldings of PK exhibit a greater tensile strength at 80°C than the SCORIM mouldings of isotactic polypropylene at 23°C. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 415–430, 1997     

Interlocking shish‐kebab morphology in polybutene‐1

The aim of this research was to explore the effect of shear‐controlled orientation injection molding (SCORIM) on polybutene‐1 (PB‐1). This article describes the methods and processing conditions used for injection molding and discusses the properties of the moldings. Both conventional and SCORIM have been used for the production of moldings. SCORIM is based on the application of specific macroscopic shears to a solidifying melt that facilitates enhanced molecular alignment. The effect of the process was investigated by performing mechanical tests, X‐ray studies, differential scanning calorimetric studies, polarized light microscopy, and atomic force microscopy (AFM). Moldings exhibited an improved mechanical performance as compared with conventional moldings. Young's modulus was increased over twofold, and the impact energy was enhanced by 60%. The improvement in mechanical performance was combined with an increase in crystallinity and enhanced molecular orientation. The application of SCORIM also favored the formation of the stable Form I′ in PB‐1. The formation of interlocking shish‐kebab morphology following the application of SCORIM was observed in the AFM studies. Relationships between the mechanical properties of PB‐1 and the micromorphologies formed during processing are demonstrated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1828–1834, 2002     

Chromatography of Epoxy Resins

Abstract

This review covers the literature in the field of chromatographic analysis of epoxy resins and epoxy resin formulations from about 1970 to the present. Although exhaustive reviews of general chromatographic techniques have recently been published [1–9], and size exclusion chromatography has received additional coverage in journals and monographs on polymers [5–7], no reviews specifically devoted to the application of chromatographic techniques to epoxy resins have appeared.