The roles of added chlorine and sulfur on ash deposition mechanisms during solid fuel combustion

The focus of this paper is on effects of chlorine and sulfur on coal ash deposition rates, under practically relevant but systematically controlled combustion conditions. This problem is important, not so much for coal, but to understand and predict deposition rates for biomass combustion where chlorine contents can be high. To this end, ash deposition rates on a controlled temperature surface were measured for controlled amounts of chlorine and sulfur added to a pulverized coal, doped with potassium and burned in a 100 kW rated combustion rig. Previous work with 35 tests on 11 coal, biomass and petroleum coke fuels burned under a range of operating conditions had strongly suggested that the deposition rate of the tightly bound inside deposits was independent of the ash aerosol composition, and depended only on PM₁ in the flue gas. The loosely bound outside deposition rate was dependent primarily on the total alkali content in the flue gas. The new results using chlorine added to the fuel (in the form of ammonium chloride) required these previous conclusions to be drastically revised. They showed that chlorine, not alkali alone, had large effects on the deposition rate of the inside deposits, which now were orders of magnitude higher than without chlorine addition, and did not fit previous (multi-fuel) correlations with PM₁. Sulfur addition, together with chlorine, did not affect deposition rates much, although it did lower the chlorine content of the deposit. These results are interpreted in terms of the ash aerosol size segregated composition, which was also measured, and potential sulfation reactions within the deposit.     

Editorial

On behalf of your students your colleagues, and your friends     

Chaos synchronization in networks of coupled maps with time-varying topologies

Complexity of dynamical networks can arise not only from the complexity of the topological structure but also from the time evolution of the topology. In this paper, we study the synchronous motion of coupled maps in time-varying complex networks both analytically and numerically. The temporal variation is rather general and formalized as being driven by a metric dynamical system. Four network models are discussed in detail in which the interconnections between vertices vary through time randomly. These models are: 1) i.i.d. sequences of random graphs with fixed wiring probability, 2) groups of graphs with random switches between the individual graphs, 3) graphs with temporary random failures of nodes, and 4) the meet-for-dinner model where the vertices are randomly grouped. We show that the temporal variation and randomness of the connection topology can enhance synchronizability in many cases; however, there are also instances where they reduce synchronizability. In analytical terms, the Hajnal diameter of the coupling matrix sequence is presented as a measure for the synchronizability of the graph topology. In topological terms, the decisive criterion for synchronization of coupled chaotic maps is that the union of the time-varying graphs contains a spanning tree.     

Search for weakly interacting sub-eV particles with the OSQAR laser-based experiment: results and perspectives

Recent Planck measurements show some CMB anomalies on large angular scales, which confirms the early observations by WMAP. We show that an inflationary model, in which before the slow-roll inflation the Universe is in a superinflationary phase, can generate a large-scale cutoff in the primordial power spectrum, which may account for not only the power suppression on large angular scales, but also a large dipole power asymmetry in the CMB. We discuss an implementation of our model in string theory.     

On the regularity of minimal surfaces with free boundaries in Riemannian manifolds

We show c^1,-regularity of minimal surfaces in Riemannian manifolds with a free boundary on C²-hypersurfaces with bounded second fundamental form and a uniform neighborhood on which the nearest point projection is uniquely defined and differentiable. The decisive step is the proof of continuity at the free boundary.partially supported by SFB 72 (Deutsche Forschungsgemeinschaft)     

5,6,7,8-Tetrahydro-4H-1,2,5-oxadiazocin-6-one durch Ringerweiterung nach Addition eines 3-Isoxazolidinons mit 3-Amino-2H-azirinen

5,6,7,8-Tetrahydro-4H-1,2,5-oxadiazocin-6-ones, Ring Enlargement Products from a 3-Isoxazolidinone and 3-Amino-2H-azirines 3-Dimethylamino-2H-azirines 1 and 4,4-dimethyl-3-isoxazolidinone ( 7 ) undergo already at room temperature a ring enlargement reaction to yield 5,6,7,8-tetrahydro-4H-1,2,5-oxadiazocines of type 8 . The structure of 8a has been confirmed by X-ray crystallography. The conformation of the eight-membered ring with a trans-amide group is of particular interest (Fig. 1 and 2).     

Desoxy-nitrozucker. 13. Mitteilung. Herstellung ungeschützter und partiell geschützter 1-Desoxy-1-nitro-D-aldosen sowie Röntgenstrukturanalysen einiger ihrer Vertreter

Preparation of Unprotected and Partially Protected 1-Deoxy-1-nitro-D -aldoses and Some Representative X-Ray Structure Analyses The unprotected and partially protected 1-deoxy-1-nitro derivatives of α-and β-D -glucopyranose (see 15 and 14 ), β-D -mannopyranose (see 16 ), N-acetyl-β-D -glucosamine (see 17 ), β-D -galactofuranose (see 19 ), β-D -ribofuranose (see 20 ), α-D -arabinofuranose (see 21 ), 4,6-O-benzylidene-β-D -glucose (see 40 ), N-acetyl-4,6-O-benzylidene-β-D -glucosamine (see 41 ), and 4,6-O-benzylidene-β-D -galactose (see 42 ) were prepared by ozonolysis of the corresponding nitrones which were obtained from the acid-catalyzed reaction of p-nitrobenzaldehyde with the hydroxylamine 4 , the unprotected oximes 3 and 5–9 and the 4,6-O-benzylidene oximes 35–37 , respectively (Schemes 1–3). The gluco- and manno-nitrones 10 and 12 were isolated, and their ring size and their anomeric and (E/Z) configurations were determined by NMR spectroscopy and by their transformation into their corresponding nitro derivatives. The structure of the deoxynitroaldoses were determined by NMR spectroscopy, polarimetry, and, in the case of 14 , 16 , and 17 , by formation of the 4,6-O-benzylidene ( 14 → 40 ) or 4,6-O-isopropylidene ( 16 → 43 , 17 → 23 ) derivatives (Scheme 3). Acetylation of the nitroglucopyranose 14 , the 2-acetamido-nitroglucopyranose 17 , and the nitrogalactofuranose 19 gave the crystalline peracetylated nitroaldoses 22 , 24 , and 45 , respectively (Scheme 4, Figs. 1 and 3); acetylation of the nitromannopyranose 16 gave the nitro-arabino-glycal 44 (Scheme 4). The structure of the peracetylated nitroglucopyranose 22 , the nitroglucosamine 25 , the nitrogalactofuranose 45 , and the nitroribofuranose 20 were confirmed by X-ray analysis (Figs. 1 4). In all cases, including the β-D -glucopyranose derivative 22 , considerably shortening of the (endocyclic) C(1)-O bond was observed. Base-catalyzed anomerization of the β-D -configurated nitroglucopyranose 14 , the nitromannopyranose 16 , the benzylidene acetal 40 of nitroglucose, and the 2,3,4,6-tetraacetylated glucosamine derivative 24 gave the corresponding nitro-α-D -aldoses 15 , 26 , 47 , and 25 , respectively (Scheme 4).     

Cyano-modified pre-coated plates — a medium polar modification for high performance thin-layer chromatography

Summary The introduction of a cyano-modified, pre-coated layer substantially widens the selectivity of stationary phases in thin-layer chromatography. This is a moderately polar sorbent based on silica gel 60, which can be used both in adsorption chromatography and in reversed-phase chromatography. This new pre-coated layer is particularly suitable for separation of steroids, alkaloids and derivatized amino acids. The possibility of separating habitforming drugs and preservatives in the presence of ionpair reagents is also discussed.     

Gas phase chromatography of halides of elements 104 and 105

On-line isothermal gas phase chromatography was used to study halides of²⁶¹104 (T_1/2=65 s) and^262,263105 (T_1/2=34 s and 27 s) produced an atom-at-a time via the reactions²⁴⁸Cm(¹⁸O, 5n) and²⁴⁹Bk(¹⁸O, 5n, 4n), respectively. Using HBr and HCl gas as halogenating agents, we were able to produce volatile bromides and chlorides of the above mentioned elements and study their behavior compared to their lighter homologs in Groups 4 or 5 of the periodic table. Element 104 formed more volatile bromide than its homolog Hf. In contrast, element 105 bromides were found to be less volatile than the bromides of the group 5 elements Nb and Ta. Both 104 and Hf chlorides were observed to be more volatile than their respective bromides.