Structural analysis of tars from fluidized bed pyrolysis of coal:: 2. 1H n.m.r. and i.r. spectroscopy

¹H n.m.r. and i.r. spectroscopy of aromatic and polar fractions of two tars from the rapid pyrolysis of coal in a fluidized bed at 550 °C show that the nature of the products depends on the reactivity of the pyrolysis gas. In the presence of flue gas, there is more thermolysis leading to shorter and fewer alkyl side chains and generation of lower molecular mass material. Pyrolysis by means of char gasification gas results in much less thermolysis of the tar but leads to secondary reactions which can be interpreted by a radical mechanism involving the reactive constituents of the char gas.     

Least-squares adjustment of mathematical model of heat and mass transfer processes during solidification of binary alloys

Classical boundary and initial-boundary value problems in heat and mass transfer are generally formulated in a mathematically unique way. Boundary and initial conditions together with physical properties of the thermodynamic system are treated as exactly known. The influence of different kinds of mathematical model simplifications on the accuracy of solution and reliability of the model are not usually analyzed. The problems become more complicated when inverse ill-posed initial-boundary problems are considered. The widely used procedure of model validation is based on direct comparison of analytical or numerical solution, unique in a mathematical sense, with measurement results. The main feature of the method presented in this article is that all experimental results are included into the mathematical model. Thus, because of the inevitable errors of measurements, the system of model equations becomes internally contradicted as the number of unknown variables is less than the number of equations. In consequence, basic laws of energy and mass conservation are not satisfied. To adjust the experimental data to the mathematical model, an orthogonal least-squares method is proposed. Special attention has been paid to the coupling of experimental data with the nucleation and grain growth models formulated by Rappaz and co-workers. Theoretical considerations are illustrated with experimental data for an Al-Si alloy.     

Bioactive Nanofiber-Based Conduits in a Peripheral Nerve Gap Management—An Animal Model Study

The aim was to examine the efficiency of a scaffold made of poly (L-lactic acid)-co-poly(ϵ-caprolactone), collagen (COL), polyaniline (PANI), and enriched with adipose-derived stem cells (ASCs) as a nerve conduit in a rat model. P(LLA-CL)-COL-PANI scaffold was optimized and electrospun into a tubular-shaped structure. Adipose tissue from 10 Lewis rats was harvested for ASCs culture. A total of 28 inbred male Lewis rats underwent sciatic nerve transection and excision of a 10 mm nerve trunk fragment. In Group A, the nerve gap remained untouched; in Group B, an excised trunk was used as an autograft; in Group C, nerve stumps were secured with P(LLA-CL)-COL-PANI conduit; in Group D, P(LLA-CL)-COL-PANI conduit was enriched with ASCs. After 6 months of observation, rats were sacrificed. Gastrocnemius muscles and sciatic nerves were harvested for weight, histology analysis, and nerve fiber count analyses. Group A showed advanced atrophy of the muscle, and each intervention (B, C, D) prevented muscle mass decrease (p < 0.0001); however, ASCs addition decreased efficiency vs. autograft (p < 0.05). Nerve fiber count revealed a superior effect in the nerve fiber density observed in the groups with the use of conduit (D vs. B p < 0.0001, C vs. B p < 0.001). P(LLA-CL)-COL-PANI conduits with ASCs showed promising results in managing nerve gap by decreasing muscle atrophy.     

Application of Comparative Method for Estimating Microporosity of Porous Solids in Adsorption from Solutions

The concept of a comparative method in terms of the liquid adsorption on solids is presented. This method is based on comparison of the excess adsorption isotherm on a porous solid with that measured on a reference nonporous adsorbent. It is proved that proposed approach gives the possibility for separating a total excess adsorption isotherm into partial isotherms, proper for micro- and mesopores. Several experimental systems are analyzed to illustrate the usefulness of the comparative method for evaluating the surface phase capacity, which presents an important quantity in the study of adsorption from solution in the whole concentration region. The comparative method examined for adsorption systems of microporous active carbons seems to be useful for investigating other porous materials as silica gels, zeolites or metal oxides.     

Influence of the sintering conditions on the physical proprieties of the ceramic PFN multiferroics

An influence of compacting conditions on applied properties of the multiferroic PbFe_1/2Nb_1/2O₃ (PFN) ceramics synthesized by the columbite method and powder calcination technique is presented in this work. The obtained specimens were subjected to X-ray and chemical composition homogeneity analyses, magnetic tests, electric direct current conductivity and electromechanical tests. Differences in the degree of diffuseness, densities and a grain size were observed depending on the sintering method. The dielectric and magnetic parameters as a function of temperature were measured. The tests confirmed that PFN powder compacting by a hot uniaxial pressing method had an advantageous influence on the crystalline structure ordering and the ceramics microstructure, what improves the applied properties of the material.     

Ba4In2−x(CO3)1+xO6−2.5x and Ba4In0.8Cu1.6(CO3)0.6O6.2—new indium oxycarbonates closely related to n=3 Ruddlesden–Popper phases

Investigations of phase relations in the Ba-rich part of the In₂O₃–BaO(CO₂)–CuO pseudo-ternary system at 900 °C have revealed the existence of new indium–copper oxycarbonate – Ba₄In_0.8Cu_1.6(CO₃)_0.6O_6.2. Rietveld refinement of the X-ray powder diffraction data combined with infrared studies gives evidence that this phase is a oxycarbonate crystallising in the tetragonal structure (space group I4/mmm) with unit cell parameters: a=4.0349(1) Å and c=29.8408(15) Å. In the binary part of the In₂O₃–BaO(CO₂) system we have identified the occurrence of Ba₄In_2−x(CO₃)_1+xO_6−2.5x oxycarbonate solid solution showing a crystal structure also described by I4/mmm space group, but with the unit cell parameters: a=4.1669(1) Å and c=29.3841(11) Å for x=1. The existence range of this phase, −0.153<x<0.4, includes chemical compositions of earlier found phases: Ba₅In_2+xO_8+0.5x with 0≤x≤0.45 (known as the -solid solution), as well as the binary Ba₄In₂O₇ phase. The crystal structures of both new oxycarbonates are isomorphic and related to n=3 member of the Ruddlesden–Popper family.     

Navigation and discovery in 3D CAD repositories.

Due to increasing product design complexities and the ever-expanding variety of product parts, the amount of information that designers must catalog has exploded. Accordingly, capable CAD tools to help designers create engineering artifacts are now pervasive. The volume of such engineering artifacts generated has increased exponentially and enterprises spend huge resources to organize and archive them into repositories. In these large design repositories, traditional text-based searches prove unwieldy and impractical, and are thus insufficient for individuals seeking 3D content. The paper explains that while traditional text-based searches are impractical for users seeking 3D content in large repositories, existing 3D search systems present search results in a 1D list, which is hard to search. A new interaction paradigm lets users navigate results in 2D and 3D spaces and easily find 3D models that are similar overall or in a single orientation.     

Activity of Ni-Moly catalysts in tetralin or decalin dehydrogenation and in hydrogenation of coal-extract solution

The activity of several NiMoly catalysts in the processes of dehydrogenation of tetralin or decalin and hydrogenation of coal-extract solution has been determined. In both processes studied, the activities of the catalysts investigated have been found to follow rectilinear relations with quantity. It has also been shown that the activity of a NiMoly catalyst can be predicted in hydrogenation of coal-extract solution, from its activity in dehydrogenation of tetralin or decalin; the latter reaction is relatively simple to conduct in laboratory conditions. However, caution must be exercised when very narrow pores, making possible Knudsen diffusion of hydrogen at high pressure, exist in the catalyst.     

Ultraviolet surface plasmon-coupled emission using thin aluminum films

Surface plasmon-coupled emission (SPCE) is the directional radiation of light into a substrate due to excited fluorophores above a thin metal film. To date, SPCE has only been observed with visible wavelengths using silver or gold films. We now show that SPCE can be observed in the ultraviolet region of the spectrum using thin (20 nm) aluminum films. We observed directional emission in a quartz substrate from the DNA base analogue 2-aminopurine (2-AP). The SPCE radiation occurs within a narrow angle at 59 degrees from the normal to the hemicylindrical prism. The excitation conditions precluded the creation of surface plasmons by the incident light. The directional emission at 59 degrees is almost completely p-polarized, consistent with its origin from surface plasmons due to coupling of excited 2-AP with the aluminum. The emission spectra and lifetimes of the SPCE are those characteristic of 2-AP. Different emission wavelengths radiate at slightly different angles on the prism providing intrinsic spectral resolution from the aluminum film. These results indicate that SPCE can be used with numerous UV-absorbing fluorophores, suggesting biochemical applications with simultaneous surface plasmon resonance and SPCE binding assays.