Synthesis of Pyridazine Derivatives. XXIII. Synthesis of Isomeric Azolopyrido (3,2-d) - and Azolopyrido (2,3-d) pyridazines

The synthesis of six new parent azolopyridopyridazines (I-VI) is described. Electropnilic substitutions were studied on two isomeric imidazopyrd.dopyridazines and it was found that position 3 is attacked

Syntheses in the Pyridazine Series. XXXII. Some Investigations on Polynuclear Systems Containing a Pyridazine Ring

Some 5,6-dihydrobenzo[f]phthalazines have been aromatized to II and the structures of a number of nitro derivatives prepared from several polynuclear systems (III, IV, V) , have been established

Syntheses in the Pyridazine Series. XXXII. Some Investigations on Polynuclear Systems Containing a Pyridazine Ring

Some 5,6-dihydrobenzo[f]phthalazines have been aromatized to II and the structures of a number of nitro derivatives prepared from several polynuclear systems (III, IV, V) , have been established

The Crystal and Molecular Structure of 3-(Pyridyl-2\u27)- imidazo-[1,i-a] Pyridine

The crystal structure of 3:.(pyridyl-2\u27)-imidazo-[l,5-a] pyridine has been determined using three-dimensional MoK a diffractometer data. The crystal data at 293 (1) K are as follows: C12H0Na, Mr= = 195.23, orthorhombic, P212121 (No. 19), a = 0.5107(1), b = 1.3076(2}, c = 1.4343(3) nm, V = 0.9578 nm3, Dm = 1.37(5), Dx = 1.354 Mg · m-3, Z = 4. The structure has been solved with direct methods and refined by full-matrix least-squares techniques to R and Rw values of 0.085 and 0.080, respectively, for 641 contributing reflexions. The crystal structure consists of discrete molecules. Most of the bond lengths and angles are within normal ranges for aromatic heterocyclic systems. The dihedral angle between the pyridine and imidazo- pyridine parts of the molecule is 3.8°; thus the molecule is planar to within 7 pm owing to two weak C-H .. . N interactions

The Crystal and Molecular Structure of 3-(Pyridyl-2\u27)- imidazo-[1,i-a] Pyridine

The crystal structure of 3:.(pyridyl-2\u27)-imidazo-[l,5-a] pyridine has been determined using three-dimensional MoK a diffractometer data. The crystal data at 293 (1) K are as follows: C12H0Na, Mr= = 195.23, orthorhombic, P212121 (No. 19), a = 0.5107(1), b = 1.3076(2}, c = 1.4343(3) nm, V = 0.9578 nm3, Dm = 1.37(5), Dx = 1.354 Mg · m-3, Z = 4. The structure has been solved with direct methods and refined by full-matrix least-squares techniques to R and Rw values of 0.085 and 0.080, respectively, for 641 contributing reflexions. The crystal structure consists of discrete molecules. Most of the bond lengths and angles are within normal ranges for aromatic heterocyclic systems. The dihedral angle between the pyridine and imidazo- pyridine parts of the molecule is 3.8°; thus the molecule is planar to within 7 pm owing to two weak C-H .. . N interactions

Tests of a proximity focusing RICH with aerogel as radiator

Using aerogel as radiator and multianode PMTs for photon detection, a proximity focusing Cherenkov ring imaging detector has been constructed and tested in the KEK $\pi$2 beam. The aim is to experimentally study the basic parameters such as resolution of the single photon Cherenkov angle and number of detected photons per ring. The resolution obtained is well approximated by estimates of contributions from pixel size and emission point uncertainty. The number of detected photons per Cherenkov ring is in good agreement with estimates based on aerogel and detector characteristics. The values obtained turn out to be rather low, mainly due to Rayleigh scattering and to the relatively large dead space between the photocathodes. A light collection system or a higher fraction of the photomultiplier active area, together with better quality aerogels are expected to improve the situation. The reduction of Cherenkov yield, for charged particle impact in the vicinity of the aerogel tile side wall, has also been measured.Comment: 4 pages, 8 figure

The Mannich Reaction for 2,5-Dimercapto-1,3,4-thiadiazole

The formation of Mannich bases with 2,5-dimercapto-1,3,4- -thiadiazole (III) and some of its derivatives has been investigated. Depending on the amount of formaldehyde and a secondary amine used in the reaction, three different types of Mannich bases were prepared. With equimolecular amounts of both reagents a mono- Mannich base IV was obtained, but using formaldehyde in excess a mono-hydroxymethyl mono-M.annich base V was isolated. If both reagents were used in amounts corresponding to two equivalents, a bis-Mannich base VI was formed. Evidence- for the structures of all these products was presented on the basis of chemical transformatfons and spectroscopic data. The mono-Mannich base IV .was converted in its S-methyl derivative VIII which was prepared independently from IX in a Mannich reaction. Thus aminoalkylation proceeds first on the ring nitrogen and in a further reaction the exo-cyclic sulfur is substituted

The HERA-B Ring Imaging Cherenkov Counter

The HERA-B RICH uses a radiation path length of 2.8 m in C_4F_10 gas and a large 24 square meters spherical mirror for imaging Cherenkov rings. The photon detector consists of 2240 Hamamatsu multi-anode photomultipliers with about 27000 channels. A 2:1 reducing two-lens telescope in front of each PMT increases the sensitive area at the expense of increased pixel size, resulting in a contribution to the resolution which roughly matches that of dispersion. The counter was completed in January of 1999, and its performance has been steady and reliable over the years it has been in operation. The design performance of the RICH was fully reached: the average number of detected photons in the RICH for a beta=1 particle was found to be 33 with a single hit resolution of 0.7 mrad and 1 mrad in the fine and coarse granularity regions, respectively.Comment: 29 pages, 23 figure

Baryon polarization in low-energy unpolarized meson-baryon scattering

We compute the polarization of the final-state baryon, in its rest frame, in low-energy meson--baryon scattering with unpolarized initial state, in Unitarized BChPT. Free parameters are determined by fitting total and differential cross-section data (and spin-asymmetry or polarization data if available) for $pK^-$, $pK^+$ and $p\pi^+$ scattering. We also compare our results with those of leading-order BChPT