Search results for "linear"

Molecular modifications—Mechanical behaviour relationships for gamma irradiated LLDPE/PA6 blends

1994

Abstract The molecular modifications, due to γ radiation under vacuum, of linear low density polyethylene/polyamide 6 blends are presented and related to their mechanical behaviour. Solubility and melt viscosity tests indicate that in blends the polyethylene component undergoes mainly crosslinking phenomena, whereas the main effect on polyamide is chain branching. According to these molecular modifications, the most relevant effect is the increase of the tensile modulus for the polyethylene rich blends and the increase of the impact strength for the polyamide rich blends.

Synthesis, crystal structures, and solid state quadratic nonlinear optical properties of a series of stilbazolium cations combined with gold cyanide …

2011

Three salts built up from (E)-4′-(dimethylamino)-stilbazolium (DMAS)H+, (E)-4′-(diethylamino)-stilbazolium (DEAS)H+, (E)-4′-{2-(methoxymethyl) pyrrolidinyl}-stilbazolium (MPS)H+, and gold cyanide as a counter-ion, are reported. The crystal structures have been solved for (DEAS)H+ Au(CN)2− (Cc space group), and for (MPS)H+ Au(CN)2− (P1 space group). The semi-empirical (ZINDO) calculated static hyperpolarizability (β0) of (MPS)H+ is equal to 147 × 10−30 cm5esu−1, in solid state, which is 25% higher than that of the cation of the well known (E)-4′-(dimethylamino)-methylstilbazolium tosylate (DAST). (MPS)H+ Au(CN)2− exhibits a unique crystal structure in which the cations are perfectly aligned.…

Transient birefringence of polymer melts in intermittent shear flow: Model analysis of the non-linear viscoelastic behaviour

1977

A non-linear viscoelastic model has been used to interpret transient flow birefringence in changing shear flow for a polymer melt. It is shown how the new model is consistent with the basic hypothesis of the linear stress-optical law. Stress growth in shear flow and relaxation after different amounts of shearing are compared with the predictions of the non-linear model. A good agreement between experimental data and theoretical predictions is found.

1986

The variation of the Huggins coefficient KH with the relative molecular mass M of the polymers was measured for solutions of polystyrene and of polyisobutylene and found to be most pronounced in the case of thermodynamically good solvents but vanishing at the theta-temperature, where the individual curves kH (T; M) intersect with each other. The experimental results are interpreted as a consequence of the rheological inequality of inter- and intra-molecular contacts between polymer segments. A model is presented according to which kH should be a linear function of M−(a−0,5), where a is the exponent of the intrinsic viscosity-relative molecular mass relationship (Kuhn-Mark-Houwink). The eval…

NonclassicalPschorr andSandmeyer Reactions in Pyrazole Series

2005

The diazonium salt derived from 4-amino-N,1,3-trimethyl-N-(3-methyl-1-phenyl-1H-pyrazol-5-yl)-1H-pyrazole-5-carboxamide (14) was reacted with a mixture of CuSO4 and NaCl, with ascorbic acid as an initiator to afford the planar derivative 4,6-dihydro-1,4,6,8-tetramethyl-3-phenyldipyrazolo[3,4-b:4′,3′-d]pyridin-5(3H)-one (16) and its unexpected isomer 4,6-dihydro-3,4,6,8-tetramethyl-1-phenyldipyrazolo[4,3-b:4′,3′-d]pyridin-5(1H)-one (17), as well as the epimers (3S,4S)- (or (3S,4R)-) and (3S,4R)- (or (3S,4S)-) 4-chloro-2,4-dihydro-1′,3′,5,5′-tetramethyl-2-phenylspiro[pyrazole-3,4′(1′H)-pyrrolo[3,4-c]pyrazol]-6′(5′H)-one (18a and b, respectively). Epimers 18a and b were converted under basic c…

Conjugated Oligomers with Terminal Donor–Acceptor Substitution

2005

Conjugated oligomers represent a prominent class of compounds from a viewpoint of their theory, synthesis, and applications in materials science. Push-pull substitution with an electron donor D at one end of the conjugation and an electron acceptor A at the other end results in them having outstanding optical and electronical properties. This Review highlights fundamental synthetic strategies for the preparation of such oligomers with n repeat units (n=1, 2, 3, 4, ..) and the rules that govern their linear and nonlinear optical properties (absorption, frequency doubling and tripling). The unification of chemical, physical, and theoretical aspects with an interdisciplinary image of this clas…

Theoretical characterization of the electronic structure of polymeric systems combining disilanylene and /spl pi/-conjugated units

1994

Summary form only given. Polymeric organosilicon systems are in the forefront of research, due to their intriguing properties (semiconducting behavior, photoconduction, non-linear optical properties, and thermo- and piezochromism). The fundamental skeletons of most of these polymers consist of a /spl sigma/-electron network formed by silicon-silicon bonds. Recently, polymeric organosilicon systems containing a regular alternation of a disilanylene unit and carbon /spl pi/-conjugated moiety as phenylene, ethynylene, or ethenylene have been synthesized. The purpose of this contribution is to perform a detailed study of the electronic structure of polymers containing alternated disilanylene an…

Investigation on the indentation behavior of sandwich beams using crushable and hyperelastic foam cores

2010

In this work the indentation behaviour of sandwich beams is studied adopting the classical approach representing the core material as a Winkler-type foundation. It is shown how most of the proposed theories can be derived from a general fourth order linear differential equation expressing the equilibrium of the indented beam skin. Different assumptions on the supporting boundary constraints and materials constitutive behaviour, lead to simplifications of the general equation and to the prediction of different indentation features. An extension of the Segment-Wise approach recently proposed in the literature is in particular presented with potential to better simulate foam cores with markedl…

Relationship between Metabolic Fluxes and Sequence-Derived Properties of Enzymes

2014

Metabolic fluxes are key parameters of metabolic pathways being closely related to the kinetic properties of enzymes, thereby could be dependent on. This study examines possible relationships between the metabolic fluxes and the physical-chemical/structural features of enzymes from the yeast Saccharomyces cerevisiae glycolysis pathway. Metabolic fluxes were quantified by the COPASI tool using the kinetic models of Hynne and Teusink at varied concentrations of external glucose. The enzyme sequences were taken from the UniProtKB and the average amino acid (AA) properties were computed using the set of Georgiev’s uncorrelated scales that satisfy the VARIMAX criterion and specific AA indices th…

Non-linear optical spectra of excitons in polydiacetylene

1992

Abstract Adding long-range Coulomb interactions to the Su-Schrieffer-Heeger model makes it possible to investigate excitonic states in conjugated polymers. Various characteristic features due to these states as well as due to the electron-hole continuum can be found in the calculated non-linear optical susceptibilities. In particular the electroabsorption spectrum and the third harmonic generation intensity and its dependence on the system size are examined. Using only moderate interaction strength, various experiments in polydiacetylene can be interpreted in a consistent way.