Reduction of convective heat transfer losses from flat surfaces

The study of reduction of convective heat transfer losses from flat surfaces by means of vertical perimenter wall has been presented. The optimum screening wall height has been theoretically calculated as: (H/D)_cr = 6.283/Ra^5/16. To determine the phenomenon of influence of plate screen on convective heat transfer, Nusselt-Rayleigh correlation has been given. The experimental data were in substantial agreement with the theoretical results.     

N‐(2‐biphenylenyl)‐4‐[2′‐phenylethynyl] phthalimide: 2. Detailed study of the monomer cure and properties of the resulting polymer

A detailed study is presented of the high‐temperature cure of the difunctional monomer N‐(2‐biphenylenyl)‐4‐[2′‐phenylethynyl]phthalimide (BPP) and the thermal properties of the resulting homopolymer. Although the phenylethynyl groups are consumed within 1 h at 370 °C, other reactions continue well after this, leading to a cured polymer whose glass transition temperature (T_g) is highly dependent on cure time and temperature. A T_g of 450 °C is achieved after a 16 h cure at 400 °C. Use of chemometrics to analyse the infrared spectra of curing BPP provides evidence for changes in the aromatic moieties during cure, perhaps indicative of co‐reaction between the biphenylene and phenylethynyl groups; however, other processes also contribute to the overall complex cure mechanism. Despite the high T_g values, BPP homopolymer exhibits unacceptably poor thermo‐oxidative stability at 370 °C, showing a weight loss of about 50 % after 100 h ageing. This is perhaps a result of formation of degradatively unstable crosslink structures during elevated‐temperature cure. Copyright © 2004 Society of Chemical Industry     

Frequency-domain lifetime measurements and sensing in highly scattering media

For clinical chemistry, or for non-invasive sensing through skin, it is often necessary to obtain quantitative information in highly scattering media. We describe two simple methods for fluorescence lifetime measurements in highly scattering media, and in particular in an intralipid suspension. Lifetimes can be measured using an intensity decay law that accounts for the time delays and pulse-broadening effects of multiple light-scattering events in the intralipid. Alternatively, the phase and modulation measurements can be performed relative to a reference fluorophore with a known lifetime. These approaches provide reliable lifetime data for a pH-sensitive fluorophore contained within a microcuvette 4 mm under the surface of the intralipid suspension. Fluorescence lifetime-based sensing is now recognized as a valuable methodology in clinical and analytical chemistry, and the possibility of lifetime-based sensing in turbid media has been demonstrated.     

Law of continuous damage parameter for non-ageing materials

The paper describes an experimental and theoretical study of continuous damage parameter. The results of tests of concrete elements are presented in this work. (The eight-ageing concrete may be treated as non-ageing material). The experimental results are used to formulate relation between continuous damage parameter and net stress. Proposed relation may be used for next study of damage material problems.     

Simulation of metal flow and heat transfer during hot rolling of bimetal plates

Coupled thermomechanical finite element model is applied to simulate metal flow and temperature distribution during hot rolling of bimetal plates. Calculations are carried out for various reductions and dimensions of the plates. Two possible versions of the boundary conditions are assumed. The first considers the case when special guides or tensions prevent bending of the sample before entering and after exit from the roll gap. The second allows free bending of the plate on both sides of the mill. Results of calculations include distributions of strain rates, strains, roll pressure, friction forces and temperatures during rolling. Calculated rolling force and torque are compared with the experimental data. Several conclusions regarding the metal flow and heat transfer in various rolling conditions are drawn.     

Crystallization characteristics of amorphous Fe-Si-B alloys

Crystallization of soft magnetic Fe-Si-B glasses was investigated by transmission electron microscopy and X-ray diffraction. Electron micrographs of the successive crystallization stages of some Fe-Si-B glasses were obtained and the morphology variations for different alloy compositions were determined. The compositional dependence of the crystallization mode exhibited by the Fe-Si-B glasses was analysed, and on this basis some suggestions about crystallization rules in these glasses are proposed. Two kinds of iron—silicon phases occurred, depending on the Fe-Si-B alloy composition: bcc Fe(Si) solid solution and an ordered solid solution on the structural basis of Fe₃Si iron suicide. It is suggested that the metastable Fe₃B phase (observed during crystallization of only few glasses) was not a simple consequence of boron content. Crystallization of the Fe₃B phase was related to the formation of the iron—silicon phase which was produced during the first crystallization stage.     

Depolarization of surface-enhanced fluorescence: an approach to fluorescence polarization assays

Localized surface plasmons of metallic particles of subwavelength sizes strongly modify the spectral properties of nearby fluorophores. The enhanced radiative decay rate leads to high fluorescence efficiencies and decreased fluorescence lifetimes. In this report we show that metal-enhanced fluorescence generated by the presence of the silver islands on the glass substrate displays high depolarization. Intensities, lifetimes, and emission anisotropies of several fluorophore protein conjugates have been studied in the absence and presence of metallic nanostructures. Despite highly decreased lifetimes of about 10-fold and immobilization of conjugates on the solid substrate, the observed emission anisotropies for all fluorophores on the metal-enhanced substrate decreased 300-500% compared to that in solution. This observation implies a new generation of fluorescence polarization immunoassays with broad applications because of no restrictions to the lifetime of the probe and the size of labeled biomolecules. The changes in polarization are due to binding that occur on the bioactive surface localized near the metal particles.     

Multiphase Biomineralization: Enigmatic Invasive Siliceous Diatoms Produce Crystalline Calcite

Diatoms are considered unicellular eukaryotic organisms exclusively depositing biogenic silica. Heretofore there has been no report of calcification by these algae. Here it is shown that calcium carbonate within the stalks of Didymosphenia geminata, a nuisance species that has prolifically colonized streams and rivers globally, is biogenic in origin and occurs as a network of calcite nanofibers. The nanofibrous framework in the mineralized polysaccharide matrix imparts mechanical support to the stalks, providing stability in variable flow conditions. The results demonstrate that D. geminata possesses cellular and periplasmic carbonic‐anhydrases that contribute to carbon fixation and biomineralization, respectively. The activity of external carbonic‐anhydrase was more than 50% of the total activity, which points to its role in anchoring this bioeroding diatom on hard surfaces. The first evidence of multiphase biomineralization by diatoms that deposit both biogenic silica and crystalline biogenic calcite which are imparting distinct functional advantage to the organism is provided.     

High-cycle fatigue bending strength of rapidly solidified and plastic consolidated RS442 aluminium alloy

Grain refinement in metallic materials down to submicro and nano scale results in improvement of mechanical properties. However, increase in strength under static load is not always accompanied by improved fatigue behaviour. In the current studies microstructure and mechanical properties of the submicrocrystalline RS442 aluminium alloy (chemical composition corresponds to conventional 442 cast alloy) were investigated. The alloy was subjected to rapid solidification followed by the extrusion process (variant 1) and additional annealing at 450 °C (variant 2). Rapidly solidified alloy was also consolidated with addition of graphite (variant 3). As the reference material conventionally cast and extruded alloy was also tested (variant 4). For all material variants strength properties were tested in static tensile test and high-cycle stress-controlled fatigue bending tests. It was found that rapid solidification and plastic consolidations led to increase of static mechanical properties of 442 alloy but reduced its fatigue strength.     

Physical and organizational provision for installation, regulatory requirements and implementation of a simultaneous hybrid PET/MR-imaging system in an integrated research and clinical setting

The implementation of hybrid imaging systems requires thorough and anticipatory planning at local and regional levels. For installation of combined positron emission and magnetic resonance imaging systems (PET/MRI), a number of physical and constructional provisions concerning shielding of electromagnetic fields (RF- and high-field) as well as handling of radionuclides have to be met, the latter of which includes shielding for the emitted 511 keV gamma rays. Based on our experiences with a SIEMENS Biograph mMR system, a step-by-step approach is required to allow a trouble-free installation. In this article, we present a proposal for a standardized step-by-step plan to accomplish the installation of a combined PET/MRI system. Moreover, guidelines for the smooth operation of combined PET/MRI in an integrated research and clinical setting will be proposed. Overall, the most important preconditions for the successful implementation of PET/MRI in an integrated research and clinical setting is the interdisciplinary target-oriented cooperation between nuclear medicine, radiology, and all referring and collaborating institutions at all levels of interaction (personnel, imaging protocols, reporting, selection of the data transfer and communication methods).