Synthesis, photophysical and photochemical properties of fluorescent poly(amidoamine) dendrimers

The study reports on the synthesis of four novel PAMAM dendrimers of generation 2, modified with 1,8-napthalimide. Their photophysical characteristics have been determined in organic solvents of different polarity (chloroform and N,N-dimethylformamide). The spectral assignments of the dendrimers are dependent on the nature of the substituent at C-4 position of the 1,8-naphthalimide structure. The low quantum yield of fluorescence of the novel materials reveals that a photo-induced electron transfer is proceeding from the core of the dendrimer molecule to the naphthalimide fluorophore located in its periphery. The PAMAM dendrimers thus modified exhibit good photo stability in N,N-dimethylformamide solution.     

Transition to Henry’s law in ultra-low concentration adsorption equilibrium for n-pentane on BPL activated carbon

Experimental data for n-pentane adsorbed on BPL activated carbon in a nitrogen environment are reported at ultra-low concentrations into the Henry’s law region. We introduce two methods to prepare pre-equilibrated samples at known loadings. The samples were analyzed by a purge and trap method. Adsorption data were measured at loadings from 1.0 to 0.0001 mol kg⁻¹ and pressures of 6 to 5 × 10⁻¹⁰ kPa. The transition into the Henry’s law region occurs over a range of loadings near 0.01 mol kg⁻¹ for all temperatures. The data are compared with the DR, Langmuir, and Toth equations. We discuss how the three equations transition into the Henry’s law region, and how well they describe the data. Since the DR equation does not have a proper Henry’s law region, we show where this equation no longer applies. The Toth equation describes the data better than the Langmuir equation.     

Binary potassium-silicate glass irradiated with electrons

Binary potassium-silicate glass of composition 15 mol% K₂O + 85 mol% SiO₂ was irradiated with 2.5 MeV. The thickness of glass was chosen so as electrons stopped near the back surface. After the high-energy irradiation both, back and top surfaces, were depleted from potassium; the back surface was depleted more than the top one. The decay curves were recorded on pristine glass, and on top and back surfaces of the glass pre-irradiated with high-energy electrons. The incubation times of the top surface increased while the incubation time of the back one decreased in comparison with the pristine glass. Observation of the volume changes induced by the following impaction of 50 keV revealed the top surface is closer to the pristine glass than the back one.     

The IsoMetrics usability inventory: an operationalization of ISO 9241-10 supporting summative and formative evaluation of software systems

Aiming at a user-oriented approach in software evaluation on the basis of ISO 9241 Part 10, we present a questionnaire (IsoMetrics) which collects usability data for summative and formative evaluation, and document its construction. The summative version of IsoMetrics shows a high reliability of its subscales and gathers valid information about differences in the usability of different software systems. Moreover, we show that the formative version of IsoMetrics is a powerful tool for supporting the identification of software weaknesses. Finally, we propose a procedure to categorize and prioritize weak points, which subsequently can be used as basic input to usability reviews.     

Ion-conducting lithium bis(oxalato)borate-based polymer electrolytes

Poly(2-ethoxyethyl methacrylate) polymer gel electrolytes containing immobilised lithium bis(oxalato)borate in aprotic carbonates: propylene carbonate (PC), propylene carbonate–ethylene carbonate (PC–EC 50:50 vol.%) and diethyl carbonate–ethylene carbonate (DEC–EC 50:50 vol.%) were prepared by a direct radical polymerisation. The electrolyte composition was optimised to achieve suitable ionic conductivity 0.5 and 2.4 mS cm⁻¹ at 25 and 70 °C respectively along with good mechanical properties. The electrochemical stability up to 5.1 V vs. Li/Li⁺ was determined on gold electrode by voltammetrical measurements. The polymer electrolytes with high-boiling solvents (PC and PC/EC) showed higher thermal stability (up to 110–120 °C) compared to the liquid electrolytes. The proposed area of application is in the lithium-ion batteries with cathodes operating at elevated temperatures of 70 °C, where higher electrochemical stability of the polymer electrolytes is employed.     

Forty Years of Designing Catalytic and Adsorptive Sites in FAU Type Zeolites at K.U. Leuven

An overview of scientific achievements at K.U. Leuven on the design and characterization of active sites in X and Y zeolites and on the development of adsorptive and catalytic processes in which these active sites are operated is provided. The historical development of this research area and the scientific progress are presented. Zeolite Y and ultrastabilized specimen present Brønsted and Lewis sites that can be operated in vapor and liquid phase hydrocarbon conversion processes, bifunctional catalysis, epoxidation and ring opening of epoxides. Examples of molecular shape selective catalysis with Y zeolites are presented. The redox chemistry of transition metal exchanged faujasites is understood in great detail and has been exploited in Wacker chemistry and water splitting in a photochemical-thermal cycle. Selective adsorbents were designed based on knowledge of cation siting in X and Y zeolites. The occlusion of coordination compounds in the faujasite supercages is a means of creating unique active sites. Catalytic oxidative properties of the enzymes can be mimicked by embedding zeozyme in a hydrophobic membrane.     

Sustainable development and global security

The sustainable development paradigm demands that we leave to future generations at least the same or better possibilities for development as they exist today. This requires a balanced development of economy, society and environment, and the absence of wars and terrorism. Wars and terror attacks are causing grave damage to the development, including loss of human lives, destruction of property, decrease in economic activity, threatened individual freedoms, and destruction of natural environment. It is therefore very important for sustainability to establish a secure global environment. This requires both protection against violence and elimination of its root causes, as well as active work of individuals, national states, non-governmental and international organisations toward peace.     

Computation of the I/V characteristic of a molecular switch

We report on the study of a molecular torsional switch made up of two distinct aromatic moieties bound by an acetynil group. The mechanism of operation is based on the action of a static electric field perpendicular to the ring–ring bond which modifies the torsional angle and, as a consequence, the inter-ring conjugation. The current is computed with a method based on the molecular Green’s function, in which the electrodes are taken into account in an effective way. The current/voltage profile at several dihedral angles shows that the current is maximum for the planar conformation and decreases by a factor ∼1000 for the orthogonal conformation, suggesting the potential applicability of the proposed switching function in devices at the molecular scale.