Proefschrift--Groningen--Rijksuniversiteit, 1995. / Textes en néerlandais, résumé en anglais. Bibliogr. p. 495-512.

Texte remanié de: Dissertation (Ph. D.)--Institut für Germanistik--Potsdam--Universität Potsdam, 2001. / Bibliogr. p. 217-228.

This research presents an experimental study of the formation of drops of suspensions consisting of a viscous liquid and spherical, neutrally buoyant, noncolloidal particles. Pendant drop formation and low Reynolds number jetting of suspensions are investigated, as is the transition between the two. Throughout, the particles utilized are on the order of 100 μm and the orifice from which the drops are formed is on the order of 1 mm. The presence of the particulate phase causes the structure at pinch-off in the pendant drop regime to change noticeably from that of pure liquids. Thick cone-like structures, termed "spindles" here, form at either end of the slender thread and are the result of particle motions during necking. These spindles become more pronounced with increasing particle concentration. Depending on particle concentration, the particles can have either a destabilizing effect (low concentration) on drop formation or a stabilizing one (high concentration). At low concentrations, the particles lead to earlier rupture of the thread and much shorter jet lengths, while at elevated concentrations the particles stabilize the thread after rupture and lead to fewer satellite drops as well as induce jetting at lower flower rates. A two-stage model has been proposed to describe the necking process for particle-laden suspensions in the pendant drop regime. The first stage occurs when the thread is thick relative to the particles and the effect of the particles can be attributed solely to a change in the effective viscosity of the mixture. The second stage occurs nearer pinch-off when the thread has thinned to only a few particle diameters. In this stage the individual particle motions within the thread determine the behavior and the thread ultimately ruptures over a region of the thread devoid of particles.

Articulated rigid-rod polymers asPBI were synthesized via polycondensation reaction. Using 2-sulfoterephthalic acid and 5-sulfoisophthalic acid in different ratios for copolycondensation reaction making the fully conjugated rigid-rod backbone became articulated. Both rigid-rod and articulated rigid-rod were further derivatized using alkane sulfonated pendants and became water-soluble rigid-rod and articulated rigid-rod polyelectrolytes. Lithium salt doped cast films of the polyelectrolytes showed a root-temperature DC conductivity parallel to film surface (

This study utilized polycondensation reaction to synthesize fully conjugated rod-like polymer dihydroxy-PBI. Chemical derivatizations were applied to attach pendants of propane sulfonic coil for dihydroxy-PBI-PS and to attach aromatic phenylene ring with Li ionic moiety for dihydroxy-PBI-AS. The attachment of pendants for dihydroxy-PBI-PS was 42.27 % and for dihydroxy-PBI-AS was only for 0.04 % causing by stereo hindrance of this molecule. These polymers seemed to have good thermal stability. Dihydroxy-PBI started to show degradation at 467.8 oC and retained 60.5 wt. % at 800 oC. Derivatized dihydroxy- PBI-PS and dihydroxy-PBI-AS lost their pendants at 295.3 oC and 314.4 oC, respectively. Dihydroxy-PBI was cast into thin film. Upon doping with lithium salt of LiClO at 2.02 wt. %, dihydroxy-PBI cast film showed the highest room-temperature dc conductivity parallel to the film (£m¡ü) of 1.71 x 10-4 S/cm and perpendicular to the film (£m¡æ) of 1.49 x 10-5 S/cm. For dihydroxy-PBI-PS cast film, the highest conductivity was at 0.49 wt. % of LiClO4 with £m¡ü of 1.05 x 10-3 S/cm and £m¡æ of 1.05 x 10-4 S/cm. For dihydroxy-PBI-AS cast film, the highest conductivity was at 2.02 wt. % of LiClO4 with £m¡ü of 1.32 x 10-3 S/cm and £m¡æ of 2.26 x 10-5 S/cm. From scanning electron microscopy and wide-angle x-ray scattering, it was learned that cast films of dihydroxy-PBI and dihydroxy-PBI-AS had anisotropic layered structure parallel to the film, and that of dihydroxy-PBI-PS showed less of this anisotropy.

No description available.

The intent of this thesis is to explore whether any patterns emerge among families or through graph operations regarding the appearance of Weierstrass vertices on graphs. Currently, patterns have been identified and proven on cycles, complete graphs, complete bipartite graphs, and the house and house-x graphs. A Python program developed as part of this thesis to perform the algorithms used in this analysis confirms these findings. This program also revealed a pattern: if v is a Weierstrass vertex, then the vertex v* added to the graph as a pendant vertex to v is also a Weierstrass vertex. The converse is also true: if v is not a Weierstrass vertex, v* will not be either.

In this thesis, I present my experimental work on the collective properties of frictionless, cohesive particles. Our main question is how lack of friction as well as a well-distributed, well-controlled cohesive interaction among the particles give rise to collective properties that might or might not differ from conventional granular materials with interparticle friction, and cohesion due to capillary bridges. This is a “sandwich” thesis, in which each project is presented as a standalone manuscript in a separate chapter. In Project 1, inspired by the pendant drop experiment, we extrude dense particle aggregates from an orifice. The aggregate breaks into clusters due to interparticle cohesion, much like a dripping faucet. We analyze the cluster volume while varying the cohesion, orifice size and particle size. Our results show that the volume is proportional to the orifice area multiplied by a characteristic length that balances cohesion and gravity, known as the granular capillary length. This finding indicates that the aggregate behaves more like a soft solid than a liquid, as the volume of a classic pendant drop is proportional to the orifice perimeter rather than the orifice area. In Project 2, we investigate how geometrical constraints influence the spreading of frictionless, cohesive particles. Conducting the spreading experiment in a cylinder, we unexpectedly observe the formation of a conical pile, as the angle of repose in conventional granular materials is attributed to interparticle friction. We vary the cohesive force, particle size, and cylinder size to examine how these factors affect the angle of repose. Our findings indicate that the angle of repose is proportional to the granular capillary length divided by the particle size, and remains independent of the cylinder size within the experimental range. These results underscore the significant role of cohesion and geometrical constraints in aggregate stability. / Dissertation / Doctor of Philosophy (PhD)

Title: Cross-bridged cyclams as manganese(II) chelators Autor: Bc. Luděk Míka Department: Department of Inorganic Chemistry, Faculty of Science Supervisor: doc. RNDr. Jan Kotek, Ph.D. Supervisor's e-mail address: modrej@natur.cuni.cz Abstract: The aim of this project was to synthesize a new kind of Mn(II) complexes with ligands derived from cross-bridged cyclam. These complexes may be potentially used as contrast agents in magnetic resonance imaging. Six macrobicyclic ligands with various pendant arm were synthesized, three complexes were sucesfully prepared. Electrochemical properties of prepared manganese(II) complexes with synthesized ligands were studied using cyclic voltammetry. Relaxivity of prepared complexes was determined by 1 H NMR spectroscopy. Keywords: cross-bridged cyclam, phosphonate, phosphinate, pendant arms, manganese

Polycondensation reaction was carried out for synthesizing rigid-rod polymer hPBI. Various molar ratios (50:1, 25:1, and 15:1) of 2-hydroterephthalic acid and 5-hydroisophthalic acid were also introduced in the synthesis for articulated rigid-rod polymer a-hPBI. The polymers were further derivatized with 1,3-propanesulton for pendants of lithium ionomer to become water soluble polyelectrolytes hPBI-PS(Li+) and a-hPBI-PS(Li+), respectively. Lithium salt doped cast film of the rigid-rod polyelectrolyte hPBI-PS(Li+) showed a room-temperature DC conductivity parallel to film surface as high as 4.02¡Ñ10-3 S/cm. Molecular weight of the rigid-rod polyelectrolyte was low indicating a small molecular aspect ratio. In cast film, the molecules were randomly distributed and highly isotropic facilitated Li cations mobility for a high film conductivity. The conductivity was also insensitive to the anion of lithium salt. No apparent layered structure was revealed by scanning electron microscope suggesting that the cast films had near three-dimensionally isotropic structure and conductivity.