Zehn weitere Briefe zwischen K.E. v. Baer und L.F. und R. Froriep aus den Jahren 1825–1851

Following the publication of 7 letters from Baer to the Frorieps by H.E. Müller-Dietz inNTM N.S. 1 (1993), 2 further letters from Baer and 8 from the Frorieps are published. A curious technical problem in the presentation of the journalNotizen published by Froriep in his Landes-industriecomptoir in Weimar is discussed at length. Froriep recommends his son Robert, to whom Baer sends several enquiries and commissions, which Robert deals with carefully (1831 in Jena, 1849 in Paris). Robert explains in great detail his intention to leave Jena for Berlin in 1831. After his father's death in 1847 he returns to take charge of the Landesindustriecomptoir and begins to cooperate with the newly founded Russian Geographic Society as publisher on behalf of the Society. But about 1850 the cooperation is discontinued by the Russians, and Froriep, who is in economic difficulties, asks Baer (who lives and works in St. Petersburg) urgently (but in vain) to help him with the Society.     

Context relevance assessment and exploitation in mobile recommender systems

In order to generate relevant recommendations, a context-aware recommender system (CARS) not only makes use of user preferences, but also exploits information about the specific contextual situation in which the recommended item will be consumed. For instance, when recommending a holiday destination, a CARS could take into account whether the trip will happen in summer or winter. It is unclear, however, which contextual factors are important and to which degree they influence user ratings. A large amount of data and complex context-aware predictive models must be exploited to understand these relationships. In this paper, we take a new approach for assessing and modeling the relationship between contextual factors and item ratings. Rather than using the traditional approach to data collection, where recommendations are rated with respect to real situations as participants go about their lives as normal, we simulate contextual situations to more easily capture data regarding how the context influences user ratings. To this end, we have designed a methodology whereby users are asked to judge whether a contextual factor (e.g., season) influences the rating given a certain contextual condition (e.g., season is summer). Based on the analyses of these data, we built a context-aware mobile recommender system that utilizes the contextual factors shown to be important. In a subsequent user evaluation, this system was preferred to a similar variant that did not exploit contextual information.     

Formation of compounds by high-flux nitrogen ion implantation in titanium

Polycrystalline titanium was implanted with nitrogen ions at energies from 30 to 60 keV and with doses from 1 × 10¹⁶ to 1.5 × 10¹⁸ N⁺-ions cm^–2 at room temperature. The implanted titanium layers were investigated by high-voltage electron microscopy and transmission high-energy electron diffraction. The formation of titanium nitride, titanium carbonitride and titanium carbide phases were considered in relation to their dependence on nitrogen ion implantation dose. In the dose range from 1 × 10¹⁶ up to 1.5 × 10¹⁸ N⁺-ions cm^–2 the cubic phase -TiN _x was formed. In the dose range between 1 to 2.5 × 10¹⁷ and 1.5 × 10¹⁸N⁺-ions cm^–2 the tetragonal phase -Ti₂N was found in addition to the -TiN _x phase. The lattice structure of these titanium nitride phases is a function of the nitrogen ion implantation dose. Additionally, the presence of titanium carbonitrido TiC _y O _x and titanium carbide TiC _y phases can be proved. The analysed titanium nitride, titanium carbUnitride and titanium carbide phases are represented in a state diagram as a function of implantation dose.     

The effect of reaction conditions on montmorillonite-catalysed peptide formation

Oligomerization of glycine (gly) and diglycine (gly₂) on montmorillonite was performed as cyclic, drying-wetting process at temperatures below 100°C, under varying reaction conditions. The influence of substrate/clay ratio, temperature and pH was found to be different for amino acid (AA) dimerization, cyclic anhydride (CA) formation and peptide chain elongation. High temperatures and neutral pH favour CA formation over diglycine production. An AA/catalyst ratio of 0.2 mmol/g leads to optimal yields. This supports the assumption that amino acid dimerization and CA formation take place at the edges of clay particles. Peptide chain elongation, starting from gly₂, produces higher yields at higher temperatures and neutral pH.     

Studies on miscibility in homopolymer/ random copolymer blends by equation of state theory

The miscibility of poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile random copolymers (SAN) blends was investigated on the basis of the Flory—Orwoll—Vrij equation of state theory. To obtain the equation of state parameters (P*, V*_sp, T*: characteristic parameters), the pressure—volume—temperature (PVT) behaviour was measured for PMMA and a series of SANs with various acrylonitrile contents. The exchange energy parameter X_ij was also calculated by fitting the theory to some phase diagrams of PMMA/SAN blends. The Flory—Huggins interaction parameter χ was separated into two contributions based on the equation of state theory for mixtures: the exchange energy term χ_inter and the free volume term χ_free. Both the temperature and copolymer composition dependences of χ_inter and χ_free were estimated by calculations using the equation of state parameters. There exists a region in which χ_inter is negative, leading to a miscibility window in PMMA/SAN blends. However, the immiscibility at high temperatures in the blends cannot be explained only by χ_inter; it is caused by the free volume contribution, χ_free. The miscibility window behaviour in PMMA/SAN blends may be explained within the framework of the equation of state theory.     

Untersuchung des einflusses molekularer parameter auf morphologie und eigenschaften von polyethylenen niedriger dichte

Based on the example of PE-LD grades and on model substances obtained by preparative fractionation (fractions in the molecular weight range M?_w = 1.2 ? 390·10⁴ g/mol), comprehensive investigations regarding the problems of structure/properties have been carried out. The correlations of M?_w with 15 physical and application technological perameters have been investigated taking into account the reaction mechanism during the manufacturing of PE-LD in the tubular and agitated autoclave reactor, resulting in the formation of so-called primary structure perameters M?_n, M?_w, molar mass distribution, short chain branching and long chain branching. For the interpretation of the results, among other factors, also the morphological conditions have been taken into consideration, which in connection with the molecular parameters reveal — for specific M?_w-ranges — strong changes and saturation ranges, resp., for the physical and application technological properties.     

A vibrational study of the activation sequence of C–H and C–C bonds of isobutene and 1-butene on Mo(110) and (4 × 4)-C/Mo(110) surfaces

The thermal decomposition pathways of isobutene and 1-butene on both Mo(110) and 4 × 4-C/Mo(110) surfaces have been studied using high-resolution electron energy loss spectroscopy (HREELS) in order to highlight the substantially different activities of these two surfaces towards the cleavage of C–H and C–C bonds. On clean Mo(110), the CH₂ group of isobutene decomposes upon heating to 150 K, producing either a /-bonded isobutenylidene [(CH₃)₂CCH] species or a 1,1-di-/-bonded isobutenyl [(CH₃)₂CC] species. Upon further heating, extensive C–H bond scission occurs to form hydrocarbon fragments which do not contain CH₃ or CH₂ groups, but appear to have largely intact carbon skeletons. By contrast, isobutene is molecularly adsorbed on the carbide-modified surface at 150 K. Further heating produces isobutylidyne [(CH₃)₂HCC] by 300 K, which subsequently decomposes via C–C bond scission to generate surface methyl groups. The different activation sequence of the C–H and C–C bonds of isobutene on clean and carbide-modified Mo(110) surfaces is also qualitatively confirmed by comparative studies of 1-butene on the two surfaces.     

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.