Release of K,Cl, and S during combustion and co-combustion with wood of high-chlorine biomass in bench and pilot scale fuel beds

Studies of the release of critical ash-forming elements from combustion of biomass are typically conducted with small sample masses under well controlled conditions. In biomass combustion on a grate, secondary recapture and release reactions in the fuel-bed may affect the overall release and partitioning of these elements. Earlier work by the authors on the release of K, Cl, and S from a high-chlorine biomass (corn stover) in a lab-scale setup is, in the present work, supplemented with novel results from a bench-scale fixed bed reactor and a 100 kW moving grate pilot facility. The results from the bench-scale reactor indicate that S and K release are not significantly affected by secondary reactions, while Cl is partly recaptured by secondary reactions in the char. A linear increase in K-release was observed from 50% at 906 °C to almost 80 wt.% at 1234 °C when firing only corn stover. A similar release profile was observed for Cl, from 65% to nearly 100%. Complete release of S was achieved at 1234 °C with a linear increase from 70% at 906 °C. Co-combustion of corn stover with low-Cl wood chips served to increase the bed temperature, resulting in complete and close to complete release of Cl and S, respectively. An increase in the relative K-release was observed when increasing the wood chip fraction from 40% to 100% (energy basis). Pilot scale flue gas results indicate that the share of Cl released as HCl decreases towards 0% as the share of wood chips is increased towards 100%. Hence, co-combustion of corn stover with wood chips is expected to decrease the absolute release of KCl due to the lower feedstock quantity of Cl, however, increase the relative release of Cl as KCl.     

Reelin expression during embryonic development of the pig brain

Background  

Reelin is an extracellular glycoprotein of crucial importance in the developmental organisation of neurons in the mammalian cerebral cortex and other laminated brain regions. The pig possesses a gyrencephalic brain that bears resemblance to the human brain. In order to establish an animal model for neuronal migration disorders in the pig, we have studied the expression pattern and structure of Reelin during pig brain development.     

Geometry and transport in a model of two coupled quadratic nonlinear waveguides

This paper applies geometric methods developed to understand chaos and transport in Hamiltonian systems to the study of power distribution in nonlinear waveguide arrays. The specific case of two linearly coupled chi((2)) waveguides is modeled and analyzed in terms of transport and geometry in the phase space. This gives us a transport problem in the phase space resulting from the coupling of the two Hamiltonian systems for each waveguide. In particular, the effect of the presence of partial and complete barriers in the phase space on the transfer of intensity between the waveguides is studied, given a specific input and range of material properties. We show how these barriers break down as the coupling between the waveguides is increased and what the role of resonances in the phase space has in this. We also show how an increase in the coupling can lead to chaos and global transport and what effect this has on the intensity.     

Observation of hotspot in BSCCO thin film structure by fluorescent thermal imaging

Hotspot formation is observed in a structured thin superconducting film of Bi₂Sr₂CaCu₂O_x (BSCCO) using the fluorescent thermal imaging technique. The BSCCO film is deposited on SrTiO₃ (STO) and has a superconducting transition at 80 K. A film of rare-earth doped polymer film deposited directly on the superconductor is used as thermal sensor down to 4 K.     

Combustion in a horizontal channel partially filled with a porous media

Experiments were carried out to investigate the combustion propagation phenomenon in a horizontal channel partially filled with ceramic-oxide spherical beads. A 1.22 m long, 43 mm nominally thick layer of spherical beads is located at the ignition end of a 2.44 m long, 76 mm square channel. Tests were performed with 6.4 and 12.7 mm diameter beads. A flame is ignited at the bead end wall by an automotive spark ignition system. Flame propagation and pressure measurements are obtained via ionization probes and piezoelectric pressure transducers mounted on the top and bottom surfaces of the channel. High-speed schlieren video was used to visualize the structure of the explosion front. Experiments were performed with a 31% nitrogen diluted stoichiometric methane–oxygen mixture at room temperature and at an initial pressure in the range of 15–50 kPa. For initial pressures of 15 and 20 kPa the flame accelerates to a velocity close to the speed of sound in the combustion products. For initial pressure of 30 kPa and higher DDT occurs in the gap above the bead layer. An explosion front propagating at a velocity just under the CJ detonation velocity is detected in the bead layer even though the bead layer pore size is much smaller than the detonation cell size. It is demonstrated that flame propagation within the bead layer is the driving force behind the very rapid flame acceleration observed, however the DDT event occurring in the gap above the bead layer is not affected by the bead layer porosity. Schlieren video indicates that the structure of the explosion front varies across the channel height and with propagation distance down the channel.     

Rasterelektronenmikroskopische Kontrastuntersuchungen an Germanium-Einkristallfolien

Statements made after scanning electron microscope contrast investigations on the geometrical and physical properties of thin, foil-like crystal regions strongly depend on the utilized interaction between electron probe and specimen. At the example of germanium single crystal foils of a thickness of only a few hundred Å in thinned regions the image contrasts resulting from secondary, backscattered, and absorbed electrons within an accelerating voltage range of between 15 and 45 kV are discussed. This is done based on the present knowledge of the ejecting mechanisms of the three interactions. It is not yet determined whether by means of adequate calibration methods a technique for evaluation of the thickness of such specimens can be developed from this.     

Parallel sequential Monte Carlo samplers and estimation of the number of states in a Hidden Markov Model

The majority of modelling and inference regarding Hidden Markov Models (HMMs) assumes that the number of underlying states is known a priori. However, this is often not the case and thus determining the appropriate number of underlying states for a HMM is of considerable interest. This paper proposes the use of a parallel sequential Monte Carlo samplers framework to approximate the posterior distribution of the number of states. This requires no additional computational effort if approximating parameter posteriors conditioned on the number of states is also necessary. The proposed strategy is evaluated on a comprehensive set of simulated data and shown to outperform the state of the art in this area: although the approach is simple, it provides good performance by fully exploiting the particular structure of the problem. An application to business cycle analysis is also presented.     

Determination of primary aromatic amine in quality control of X-ray contrast media by flow-injection analysis

An automated flow-injection method for determination of primary aromatic amines based on the Bratton-Marshall reaction is described. This method is used for analysis quality control of three different X-ray contrast media (Omnipaque, Imagopaque and Visipaque) which are viscous solutions. In flow-injection analysis, such samples cause refractive index effects and low. broad peaks due to prolonged residence time, these interferences are minimized by the use of a carrier solution (7 w/v % NaCl in 1 M HCl) with same refractive index as the samples, careful pH adjustment, use of knotted coils, and a specially designed detector. Validation of the method in the concentration range 4-40 microg ml(-1) (injected samples) shows a repeatability (n = 6) and day-to-day reproducibility (n = 9) of 0.4-9.2 and 2.3-17.5% RSD respectively. The accuracy is 81(near the lower limit of detection)-101%, with a limit of detection of 1 microg ml(-1). Linearity was shown in the concentration range tested. The method is well suited for in-process analysis, release control and stability testing of both drug substance and drug product. The cost of analysis is reduced compared to the manual method.     

Die Sattelkonformation der hydroporphinoiden Nickel(II)-Komplexe: Struktur,Ursprung und stereochemische Konsequenzen

The Saddle Conformation of Hydroporphinoid Nickel(II) Complexes: Structure, Origin, and Stereochemical Consequences Thirteen crystal structures document the general phenomenon of coordination-hole contraction in hexahydro- and tetrahydroporphinoid ligands of complexes with small metal ions such as low-spin Ni(II). The contraction is characterized by a deformation of the ligand system towards a saddle-shaped, ruffled conformation of approximate S₄ symmetry. The central metal ion is coplanar with the four coordinating N-centers whereas the four C(meso)-atoms are situated alternately above and below this coordination plane. Increasing steepness of the saddle (parameter d_m) is associated with decreasing metal-N distances. For metal pyrrocorphinates, d_m increases in the order Cu(II) < (pyridine) Co(II) < Ni(II), for Ni(II) complexes it does so in the order porphyrin < chlorin < bacteriochlorin < isobacteriochlorin < pyrrocorphin. In the saddle conformation of hydroporphinoid Ni(II) complexes, the hydropyrrole rings assume half-chair conformations whereby the individual half-chairs are conformationally constrained in such a way that the inclination of their peripheral single bond parallels the inclination of the ligand saddle (W-conformation of the ensemble of 5-membered ring half-chairs). There are only two such conformations available for a given complex; they interrelate by saddle inversion with concomitant inversion of the ensemble of half-chairs. The coordination-hole contraction of hydroporphinoid ligands is expected and observed experimentally to exert control on the stereochemistry and reactivity of the ligand periphery as well as on the axial electrophilicity of the central metal ion. Tetracoordinate nickel(II) pyrrocorphinates are found to favor the tctct configuration of substituents at the ligand periphery, nickel(II) isobacteriochlorinates the tct configuration, whereas nickel(II) bacteriochlorinates are expected to favor the ttt configuration. Relative rates and regioselectivities of autoxidation of nickel(II) pyrrocorphinates to corresponding bacterio-and isobacteriochlorinates depend on the configuration and conformation of the ligand periphery. The residual axial electrophilicity of the metal ion in tetracoordinate Ni(II) complexes of the octaethyl series appears to increase in the order chlorin < isobacteriochlorin ? bacteriochlorin < pyrrocorphin. All hydroporphinoid metal complexes used in the X-ray structure studies were prepared as part of exploring the porphyrinogen → pyrrocorphin tautomerization, a novel structural transformation of porphyrinogens.