Special Theory of Relativity in Electrodynamics

A method of teaching of one of the divisions of electrodynamics devoted to relativity theory is suggested. The presentation is based on the four-dimensional formalism, which allows a number of fundamental physical phenomena to be considered from a unified position. The content is in full conformity with the approved standard programs for students and postgraduates of radio physical and radio technical specialities of universities. The methods can be useful to the teachers, scientific workers, and engineers concerned with other directions and specialities.     

Sulfonated poly(aryl ether ketone)s containing naphthalene moieties obtained by direct copolymerization as novel polymers for proton exchange membranes

A series of sulfonated poly(aryl ether ketone)s (SPAEKs) were prepared by aromatic nucleophilic polycondensation of 2,6‐dihydroxynaphthalene with 5,5′‐carbonyl‐bis(2‐fluorobenzenesulfonate) and 4,4′‐difluorobenzophenone. The structure and degree of sulfonation (DS) of the SPAEKs were characterized using ¹H NMR spectroscopy. The experimentally observed DS values were close to the expected values derived from the starting material ratios. The thermal stabilities of the SPAEKs were characterized by thermogravimetric analysis, which showed that in acid and sodium salt forms they were thermally stable in air up to about 240 and 380 °C, respectively. Transparent membranes cast from the directly polymerized SPAEKs exhibited good mechanical properties in both dry and hydrated states. The dependence of water uptake and of membrane swelling on the DS at different temperatures was studied. SPAEK membranes with a DS from 0.72 to 1.60 maintained adequate mechanical properties after immersion in water at 80 °C for 24 h. The proton conductivity of SPAEK membranes with different degrees of sulfonation was measured as a function of temperature. The proton conductivity of the SPAEK films increased with increased DS, and the highest room temperature conductivity (4.2 × 10^?2 S/cm) was recorded for a SPAEK membrane with a DS of 1.60, which further increased to 1.1 × 10^?1 S/cm at 80 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2866–2876, 2004     

Photoinitiators with functional groups. VII. Covalently bonded camphorquinone—amines

Camphorquinone (CQ), a widely used photoinitiator (PI) in dental applications, was covalently bonded to aromatic amines to enhance the rate of electron and proton transfer effect due to the close vicinity of the diketone and the amine group. 10‐bromocamphorquinone and 10‐bromomethylcamphorquinone were selected as suitable precursors for esterification with the carboxyl group containing aromatic amines based on 4‐dimethylaminobenzoic acid. Properties of the new photoinitiating systems were investigated by UV spectroscopy and differential scanning photocalorimetry in lauryl acrylate. Compared to physical mixtures, in all cases similar or even better performance was obtained. Surprisingly, 10‐acetyl derivatives 7 – 9 and 18 especially, were found to be highly reactive. Compared to CQ/ethyl 4‐dimethylaminobenzoate, the rate of photopolymerization was increased by a factor of up to 2. Intramolecular reaction was confirmed by photo‐differential scanning calorimetry experiments with varying PI concentrations. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4948–4963, 2004     

Dendrimers as scaffolds for multifunctional reversible addition–fragmentation chain transfer agents: Syntheses and polymerization

The synthesis and characterization of novel first‐ and second‐generation true dendritic reversible addition–fragmentation chain transfer (RAFT) agents carrying 6 or 12 pendant 3‐benzylsulfanylthiocarbonylsulfanylpropionic acid RAFT end groups with Z‐group architecture based on 1,1,1‐hydroxyphenyl ethane and trimethylolpropane cores are described in detail. The multifunctional dendritic RAFT agents have been used to prepare star polymers of poly(butyl acrylate) (PBA) and polystyrene (PS) of narrow polydispersities (1.4 < polydispersity index < 1.1 for PBA and 1.5 < polydispersity index < 1.3 for PS) via bulk free‐radical polymerization at 60 °C. The novel dendrimer‐based multifunctional RAFT agents effect an efficient living polymerization process, as evidenced by the linear evolution of the number‐average molecular weight (M_n) with the monomer–polymer conversion, yielding star polymers with molecular weights of up to M_n = 160,000 g mol^?1 for PBA (based on a linear PBA calibration) and up to M_n = 70,000 g mol^?1 for PS (based on a linear PS calibration). A structural change in the chemical nature of the dendritic core (i.e., 1,1,1‐hydroxyphenyl ethane vs trimethylolpropane) has no influence on the observed molecular weight distributions. The star‐shaped structure of the generated polymers has been confirmed through the cleavage of the pendant arms off the core of the star‐shaped polymeric materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5877–5890, 2004     

Thermoplastic poly(ester‐imide)s derived from anhydride‐terminated polyester prepolymer and diisocyanate

The phase‐separation behavior of thermoplastic poly(ester‐imide) [P(E‐I)] multiblock copolymers, (A‐B)_n, was investigated by a stepwise variation of the imide content. All the multiblock copolymers were synthesized by solution polycondensation with dimethylformamide as a solvent. P(E‐I)s were prepared with anhydride‐terminated polyester prepolymer and diisocyanates. Polyester prepolymers were prepared by the reaction of pyromellitic dianhydride and two different polyols [poly(tetramethylene oxide glycol) (PTMG) and polycaprolactone diol (PCL)]. Structural determination was done with Fourier transform infrared spectroscopy and Fourier transform NMR, and the molecular weight was determined by gel permeation chromatography. The effect of the imide content on the thermal properties of the synthesized P(E‐I)s was investigated by thermogravimetric analysis and differential scanning calorimetry. The polymers were also characterized for static and dynamic mechanical properties. Thermal analysis data indicated that the polymers based on PTMG were stable up to 330 °C in nitrogen atmosphere and exhibited phase‐separated morphology. Polymers based on PCL showed multistage decomposition, and the films derived from them were too fragile to be characterized for static and dynamic mechanical properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 341–350, 2004     

Understanding the quality concept in health care

During the past three decades there has been an intense debate on the quality of health care. Errors in medicine, practice variations, competence of physicians, scarcity and lack of resources have all been reasons for discussing the quality of care. A clear definition of quality should explain the nature of the debate, improve uniformity of speech and facilitate meaningful actions such as quality assurance or quality improvement. However, in due course many different definitions have been proposed and principles of quality assurance in health care have been frequently questioned, because of their industrial nature. It raises questions on our understanding of quality in health care. In this paper, we (i) explore the nature of the quality concept, (ii) explain its meaning by Wittgenstein's theory on rule-following, and (iii) argue for understanding medical care as a reflexive practice, in order to integrate the meaning of quality in medical care.     

Synthesis,characterization, and curing kinetics of novel ladder‐like polysilsesquioxanes containing side‐chain maleimide groups

Two ladder‐like polysilsesquioxanes (LPS) containing side‐chain maleimide groups have been synthesized successfully by reacting N‐(4‐hydroxyphenyl)maleimide (HPM) with LPS containing 100 mol % of chloropropyl groups (Ladder A ) and 50 mol % of each methyl and chloropropyl group (Ladder B ). HPM was synthesized by reacting maleic anhydride with 4‐aminophenol, and the resulting amic acid was imidized using p‐toluenesulfonic acid as a catalyst (Scheme 1 ). The LPSs were characterized by Fourier transform infrared (FTIR), ¹H nuclear magnetic resonance (NMR), proton‐decoupled ¹³C NMR, ²⁹Si NMR, wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Characterization indicated that these polymers had ordered ladder‐like structures with possible defects. These polymers were soluble in common solvents at ambient temperature, which suggested that they were not crosslinked. Both the polymers and the HPM were cured, and their kinetics were followed by dynamic DSC. The Ozawa and Kissinger methods were used to calculate activation energies for curing. Curing increased the temperature at which both 5% weight loss and maximum rate of weight loss were observed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4036–4046, 2004     

Amphiphilic membranes crosslinked and reinforced by POSS

This article concerns the synthesis and characterization of novel tricomponent amphiphilic membranes consisting of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic polydimethylsiloxane (PDMS) segments cocrosslinked and reinforced by octasilane polyhedral oligomeric silsesquioxane (octasilane‐POSS) cages. Rapid and efficient network synthesis was effected by cocrosslinking diallyl‐telechelic PEG (A‐PEG‐A) and divinyl‐telechelic PDMS (V‐PDMS‐V) with pentamethylpentacyclosiloxane (D₅H), using Karstedt's catalyst in conjunction with Et₃N cocatalyst and water. Films were prepared by pouring charges in molds and crosslinking by heating at 60 °C for several hours. The films were characterized by sol fractions and equilibrium swelling both in hexane and water, extent of crosslinking, contact angle hysteresis, oxygen permeability, thermogravimetric analysis, and mechanical properties. The crosslinking of octasilane‐POSS achieved by the same catalyst system was studied in separate experiments. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4337–4352, 2004     

Metallo‐supramolecular block copolymer micelles: Improved preparation and characterization

Micelles prepared from amphiphilic block copolymers in which a poly(styrene) segment is connected to a poly(ethylene oxide) block via a bis‐(2,2′:6′,2″‐terpyridine‐ruthenium) complex have been intensely studied. In most cases, the micelle populations were found to be strongly heterogeneous in size because of massive micelle/micelle aggregation. In the study reported in this article we tried to improve the homogeneity of the micelle population. The variant preparation procedure developed, which is described here, was used to prepare two “protomer”‐type micelles: PS₂₀‐[Ru]‐PEO₇₀ and PS₂₀‐[Ru]‐PEO₃₇₅. The dropwise addition of water to a solution of the compounds in dimethylformamide was replaced by the controlled addition of water by a syringe pump. The resulting micelles were characterized by sedimentation velocity and sedimentation equilibrium analyses in an analytical ultracentrifuge and by transmission electron microscopy of negatively stained samples. Sedimentation analysis showed virtually unimodal size distributions, in contrast to the findings on micelles prepared previously. PS₂₀‐[Ru]‐PEO₇₀ micelles were found to have an average molar mass of 318,000 g/mol (corresponding to 53 protomers per micelle, which is distinctly less than after micelle preparation by the standard method) and an average hydrodynamic diameter (d_h) of 18 nm. For PS₂₀‐[Ru]‐PEO₃₇₅ micelles, the corresponding values were M = 603,000 g/mol (31 protomers per micelle) and d_h = 34 nm. The latter particles were found to be identical to the “equilibrium” micelles prepared in pure water. Both micelle types had a very narrow molar mass distribution but a much broader distribution of s values and thus of hydrodynamic diameters. This indicates a conformational heterogeneity that is stable on the time scale of sedimentation velocity analysis. The findings from electron microscopy were in disagreement with those from the sedimentation analysis both in average micelle diameter and in the width of the distributions, apparently because of imperfections in the staining procedure. The preparation procedure described also may be useful in micelle formation from other types of protomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4458–4465, 2004