Homogeneous assay based on anti-Stokes' shift time-resolved fluorescence resonance energy-transfer measurement

We report here a novel, time-resolved, lanthanide-based energy-transfer assay utilizing nonoverlapping acceptor fluorophores, which have their absorption energetically at a higher level than the emittive transitions of the donor. The technique was studied by comparing a series of nonoverlapping acceptors in a homogeneous DNA model assay utilizing Eu3+ chelate as a donor. The assay provides strong energy-transfer enhanced acceptor emission and enables the anti-Stokes' shift FRET measurement, in which the induced acceptor emission is at shorter wavelength than the donor emission. This results in high sensitivity, and 0.8 pM detection limit was measured for the DNA target. The acceptor signal of the assay is characterized by exceptional lifetime properties and is not strictly following the Forster's theory. The mechanism of nonoverlapping energy transfer is considered, and we propose that when nonoverlapping acceptors are utilized, the energy transfer arises from the upper 5D2 and 5D1 excited states of europium. The assumption was studied using a simplified energy level scheme of the Eu3+ donor and the acceptors, and a correlation between the acceptor emission behavior and the energy level scheme was found.     

The long-term performance of Co/SiO2 catalysts in CO hydrogenation

The activity in terms of conversion of carbon monoxide was determined for Co/SiO₂ catalysts in CO hydrogenation over a reaction time of 120 h. The catalysts were prepared from nitrate (N) and carbonyl (CO) precursors. The conversion decreased rapidly during the first five hours, and thereafter moderately at a rate related to dispersion, i.e. the higher the dispersion the higher the rate of decrease. The active sites were blocked by wax and coke formed in the reaction, although some agglomeration of particles probably took place on the Co(CO)/SiO₂ catalysts. More carbon was accumulated on Co(CO)/SiO₂ than on Co(N)/SiO₂ during the reaction suggesting a need for frequent regeneration. The reduction-oxidation-reduction treatments indicated, however, that the regenerability of the Co(CO)/SiO₂ in terms of hydrogen uptake is poor, although the amounts adsorbed still remained higher than those for Co(N)/SiO₂.     

Preparation and characterization of Co/SiO2, Co-Mg/SiO2 and Mg-Co/SiO2 catalysts and their activity in CO hydrogenation

Co/SiO₂, Mg-Co/SiO₂ and Co-Mg/SiO2 catalysts were prepared from acetate, nitrate or carbonyl precursors. The catalysts were characterized by XRD, XPS, SIMS and TGA. The steady-state activity and product distribution of the catalysts were evaluated in synthesis gas reactions at 0.5 MPa and 235-290°C using 3 : 1 : 3 molar ratio of Ar : CO : H₂. The activity in CO hydrogenation decreased in the precursor order Co₂(CO)₈>Co(NO₃)₂> Co(CH₃COO)₂, and the probability of chain growth decreased in the precursor order Co(NO₃)₂>Co₂(CO)₈>Co(CH₃COO)₂. Alcohol yields were highest with Co₂(CO)₈, and lowest with Co(NO₃)₂, Magnesium promotion influenced the catalyst activity and decreased the CO₂ formation, but the promotion effects were less profound than those of the precursor. Surface studies on partially magnesium covered cobalt foil model catalysts suggested that magnesium promotes CO dissociation and chain growth, neither of which were, however, observed in the supported catalysts.     

Practical considerations in the use of polarized light microscopy in the analysis of the collagen network in articular cartilage

Polarized light microscopy is a traditional method for visualizing the collagen network architecture of articular cartilage. Articular cartilage repair and tissue engineering studies have raised new demands for techniques capable of quantitative characterization of the scar and repair tissues, including properties of the collagen network. Modern polarized light microscopy can be used to measure collagen fibril orientation, parallelism, and birefringence. New commercial instruments are computer controlled and the measurements are easy to perform. However, often the interpretation of results causes difficulties, even errors, because the theoretical aspects of the technique are demanding. The aim of this study was to describe the instrumentation and properties of a modern polarized light microscope, to point out some sources of error in the interpretation of the results, and to recall the theoretical background of the polarized light microscopy.     

PEM water electrolyzer model for a power-hardware-in-loop simulator

Power-electronics-based power-hardware-in-loop (PHIL) simulator for water electrolyzer emulation with a nominal current of 405 A is developed to study the electrolyzer as part of a smart grid and to analyze the characteristics of various electrolyzer power supply electronics. A simplified model of a proton exchange membrane (PEM) electrolyzer is implemented into the PHIL simulator to describe the voltage and current characteristics of the electrolyzer stack. The model is verified comparing the current and the estimated hydrogen production of the PHIL simulator with the measured values of the commercial PEM electrolyzer following the measured solar photovoltaic (PV) system output power.     

Ripening of cheese made from full concentrated milk retentate with and without peptidase addition

The aim of this study was to determine ripening of cheese made from full concentrated (FC) milk retentate with and without peptidase addition. No free amino acids (FAAs) were found in FC cheese at the end of ripening. However, added peptidase increased FAA formation. Protein and peptide profile analysis showed that FAA and small peptides increased during ripening and therefore some secondary proteolysis occurred. Added peptidase increased D‐lactic acid formation during ripening of cheeses. This kind of changes in lactose fermentation should be considered during developing the making cheese with different enzyme addition.     

Utilization of Pisat temperature-dependency in modelling adsorption on zeolites

In this study, the feasibility of utilizing pure component saturated vapour pressure P_i^sat in representing the temperature-dependency of physisorption of vapours on zeolites is examined. Adsorption data of water, alcohols and aromatic compounds both on hydrophilic on and hydrophobic zeolites has been collected from the literature and represented as a function of P/P_i^sat. It is found that the temperature-dependency of adsorption of a component can be described by the saturated vapour pressure, especially for water adsorption on zeolites. For systems where chemisorption also plays an important role, such as aromatics adsorption on zeolites, P_i^sat alone is not capable of predicting the temperature-dependency accurately enough. It is also observed that contrary to common practice, the maximum adsorption loading q_i^sat on zeolite should be considered independent of temperature. The proposed approach can be used in the modelling and design of industrial processes exploiting adsorption, such as in zeolite membrane systems, where separation is based on both adsorption and diffusion phenomena.     

The effects of changing water flow velocity on the formation of biofilms and water quality in pilot distribution system consisting of copper or polyethylene pipes

We studied the effects of flow velocity on the formation of biofilms and the concentration of bacteria in water in copper and plastic (polyethylene, PE) pipes. The formation of biofilms increased with the flow velocity of water. The increase in microbial numbers and contents of ATP was clearer in the PE pipes than in the copper pipes. This was also seen as increased consumption of microbial nutrients in the pipeline system. This indicates that the mass transfer of nutrients is in major role in the growth of biofilms. However, the increased biomass of biofilms did not affect microbial numbers in the water. Rapid changes in water flow rate resuspended biofilms and sediments which increased the concentrations of bacteria and copper in water. The disturbance caused by the changing water flow was also seen as an increase in the particle counts and water turbidity recorded with online instrumentation.     

Effects of speed limit variation on judged mean speed of a trip

Three experiments were set up to study how drivers estimate mean travel speeds on trips with different speed limits. To specify, participants judged mean speeds of trips with speed limits on different distances of the trip. Study 1 showed that the mean speed on a road with a temporary 30 km/h speed limit was overestimated if the speeds were greater than 80 km/h on the rest of the trip. Study 2 replicated and extended the results to problems with more speed combinations. In Study 3 the distances of the speed limits were varied and the results showed that a temporary 30 km/h speed restriction gave overestimations of the mean speeds of a trip for all combinations of original and temporary speed limits over all distances. Finally, some psychological issues and applied implications for speed regulation policies were discussed.     

Towards deeper co-understanding of software quality

The major problem in understanding quality concepts has been explained by the characteristic that people see it quite differently from different perspectives. In the present paper we borrow this explanation for our starting point and broaden the consideration of software quality from the implementation-oriented in the individual and organization-oriented directions. Our main hypothesis is that these ‘soft’ aspects give us a deeper co-understanding of software quality. We proceed with three hermeneutic cycles such that after an introduction to five perspectives we analyse them through Kolb's experiential learning theory and finally deepen the analysis through the team and organization-oriented theory of Nonaka and Takeuchi.