Solvent induced crystallization of syndiotactic poly(methyl methacrylate) relation to the formation of polymer aggregates in solution

Polymer Bulletin - Solutions of syndiotactic (s) poly (methyl methacrylate) (PMMA) and samples of solid s-PMMA prepared from these solutions were studied by NMR and infrared (IR) spectroscopy and...     

Efficient Monte Carlo rendering with realistic lenses

In this paper we present a novel approach to simulate image formation for a wide range of real world lenses in the Monte Carlo ray tracing framework. Our approach sidesteps the overhead of tracing rays through a system of lenses and requires no tabulation. To this end we first improve the precision of polynomial optics to closely match ground‐truth ray tracing. Second, we show how the Jacobian of the optical system enables efficient importance sampling, which is crucial for difficult paths such as sampling the aperture which is hidden behind lenses on both sides. Our results show that this yields converged images significantly faster than previous methods and accurately renders complex lens systems with negligible overhead compared to simple models, e.g. the thin lens model. We demonstrate the practicality of our method by incorporating it into a bidirectional path tracing framework and show how it can provide information needed for sophisticated light transport algorithms.     

Scalable Realistic Rendering with Many‐Light Methods

Recent years have seen increasing attention and significant progress in many‐light rendering, a class of methods for efficient computation of global illumination. The many‐light formulation offers a unified mathematical framework for the problem reducing the full lighting transport simulation to the calculation of the direct illumination from many virtual light sources. These methods are unrivaled in their scalability: they are able to produce plausible images in a fraction of a second but also converge to the full solution over time. In this state‐of‐the‐art report, we give an easy‐to‐follow, introductory tutorial of the many‐light theory; provide a comprehensive, unified survey of the topic with a comparison of the main algorithms; discuss limitations regarding materials and light transport phenomena and present a vision to motivate and guide future research. We will cover both the fundamental concepts as well as improvements, extensions and applications of many‐light rendering.     

Tomorrow’s ethics and today’s response: An investigation into the ways information systems professionals perceive and address emerging ethical issues

This paper explores the question of how foresight and futures research can identify and address ethical issues in the field of Information Systems (IS). Starting from the premise that such IS are part of socio-technical systems, the interaction between technology and human actors raise ethical concerns. Early recognition of these concerns can address ethical issues and improve the use of the technology for a range of social and organisational goals. This paper discusses research conducted in two futures research projects. Both projects investigated emerging information and communication technologies (ICTs) and ethics. The first project established approaches for identifying future technologies and their related ethical concerns. This led to the identification of 11 emerging ICTs and their associated ethical concerns. The second project took these general ethical concerns and focused on their role in IS. Specifically, how IS professionals view future emerging technologies, their associated ethical concerns, and how they think these concerns could be addressed. The key findings are that IS professionals are primarily interested in the job at hand and less so in the ethical concerns that the job might bring; ethics is a concern that is best left for others to deal with. This paper considers the implications of research on ethics in emerging ICTs and draws general conclusions about the relevance of future technologies research in IS.     

From a theoretical model to a predictive simulation model of operator interaction with support systems: designing experiments to build the numerical simulation

In this paper, we will discuss a methodology developed and applied in the European ITERATE project with the objective of designing experiments that will provide data to seed the numerical model of operator behaviour in different surface transport modes: road vehicles, rail transport and ships. The experiments aim to investigate how new technologies support different types of operators in different contexts. A structured approach was adopted. Firstly, an initial selection of the systems to be investigated was made, describing the support they provide for operators. Hypotheses were formulated on the effects of operator parameters on the interaction with the systems. A final selection of systems for the experiments was made, focusing on systems providing support for collision avoidance and speed management. The operator parameters (culture, attitude and personality, experience, driver state (such as fatigue) and the demands of the task) were operationalised and piloted. The next step was the development of scenarios to be implemented in a driving simulator. In the last step, the final experiments were designed and detailed.     

QUANTITATIVE MEASUREMENT OF CHROMIUM'S ABILITY TO PROMOTE ADHESION

Using atomic force spectroscopy, we investigated the adhesion-promoting ability of chromium. An intermediate layer of chromium can overcome the low adhesion between metal films and silicon dioxide. For the first time, we quantitatively studied this experimentally well known fact. We compared the adhesion between chromium and different substrates such as gold, silver, mica, and silicon dioxide and, beyond that, the adhesion between silicon dioxide and the same substrates. To avoid additional effects due to water, we chose ethanol as a nonpolar solvent. Taking the interfacial energies of the surfaces with the liquid into account eliminates the direct influence of the fluid medium on the adhesion of the solid material. The results we obtained corroborate the experimental fact of higher adhesion of chromium with the chosen substrates, as well as substantiate the value of chromium as an adhesion promoter. The adhesion of chromium-coated probes on gold, silicon dioxide, and mica is higher than the adhesion of silicon dioxide probes on the same substrates.     

Stretching and deformation vibrations of CH2, C(CH3) and O(CH3) groups of poly(methyl methacrylate)

Infrared and Raman spectra of atactic PMMA and infrared spectra of stereoregular PMMA and of its four deuterated derivatives

, were measured. They were used to assign the bands of stretching and deformation vibrations of CH₂, CCH₃ and OCH₃ groups in the infrared and Raman spectra and to discuss the effect of stereoregularity on these bands in the infrared spectra.     

Enzymatic esterification of glycerol I. Lipase-catalyzed synthesis of regioisomerically pure 1,3-sn-diacylglycerols

Regioisomerically pure 1,3-sn-diacylglycerols are conveniently prepared in high yields (>80%) and in large quantities by enzymatic esterification of glycerol in the presence of various 1,3-selective lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) and a variety of different acyl donors like free fatty acids, fatty acid alkyl esters and vinyl esters. All reactions are carried out in aprotic organic solvents of low water content, namelyn-hexane, diethyl ether or tBuOMe. The creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol and the hydrophobic reaction media by the adsorption of glycerol onto a solid support prior to use was essential for the success of these transformations. The effects of reaction conditions and the regioselectivities of the lipases on the product yields are described in detail.     

C-13 Rotating frame relaxation of solid polymers

Summary ¹³c T₁ of some polymers has been measured at various temperatures. This relaxation is sensitive to other motions than those determining the proton relaxation. The T₁'s of polyethylene and poly(ethylene-vinylacetate) show minima which correspond to second moments of 108 s^–2 and 4·10⁸ s^–2, respectively, in contrary to the theoretical value of 4·10⁹ s^–2. The reason is a strongly restricted motion — e. g. torsional oscillation — which cannot average out completely the dipolar interaction. In poly(methylmethacrylate) and in poly(vinylacetate) a decrease of the restriction with increasing temperature has been observed.Presented at the 22nd Microsymposium, Characterization of Structure and Dynamics of Macromolecular Systems by NMR Methods, Prague, CSSR, July 20–23, 1981