Poly[[tris­(μ-4,4′-bipyridine-κ2 N:N′)bis­(μ-l-lysinato-κ3 N 1,O 1:O 1′)dizinc(II)] tetra­nitrate 0.6-hydrate dimethyl­formamide disolvate]

In the title compound, {[Zn2(C6H14N2O2)2(C10H8N2)3](NO3)4·0.6H2O·2C3H7NO}n, the ZnII ion is six-coordinated with a distorted octa­hedral geometry by two carboxyl­ate O atoms and one amino N atom from two l-lysinate (l-lys) ligands, and three N atoms from three 4,4′-bipyridine (4,4′-bipy) ligands. The ZnII ions are connected by the carboxyl­ate groups of the l-lys ligands in the a-axis direction and the bridging 4,4′-bipy ligands in the b- and c-axis directions, forming a three-dimensional cationic framework with channels along [100]. The nitrate anions and solvent water and dimethyl­formamide (DMF) mol­ecules are located in the channels and linked to the cationic framework by N—H⋯O and O—H⋯O hydrogen bonds. The occupancy of the water mol­ecule was fixed at 0.6. One of the DMF mol­ecules is disordered over two sets of sites, with an occupancy ratio of 0.632:0.368 (11)

2-(4-tert-Butyl­phen­yl)-5-{3,4-dibutoxy-5-[5-(4-tert-butyl­phen­yl)-1,3,4-oxadiazol-2-yl]-2-thienyl}-1,3,4-oxadiazole

In the title compound, C36H44N4O4S, the dihedral angles between the central thio­phene ring and the pendent oxadiazole rings are 12.7 (2) and 13.7 (2)°, and the dihedral angles between the oxadiazole rings and their adjacent benzene rings are 6.1 (2) and 17.5 (2)°. An intra­molecular C—H⋯O inter­action may help to establish the conformation

On sumsets involving kkth power residues

In this paper, we study some topics concerning the additive decompostions of the set $D_k$ of all $k$th power residues modulo a prime $p$. For example, we prove that $$\lim_{x\rightarrow+\infty}\frac{B(x)}{\pi(x)}=0,$$ where $\pi(x)$ is the number of primes $\le x$ and $B(x)$ denotes the cardinality of the set $$\{p\le x: p\equiv1\pmod k; D_k\ \text{has a non-trivial 2-additive decomposition}\}.$

Effective Tag Set Selection in Chinese Word Segmentation via Conditional Random Field Modeling

PACLIC 20 / Wuhan, China / 1-3 November, 200

(4Z)-4-[(2-Chloro­anilino)(phen­yl)methyl­idene]-3-methyl-1-phenyl-1H-pyrazol-5(4H)-one

The title compound, C23H18ClN3O, exists in an enamine–keto form with the amino group involved in an intra­molecular N—H⋯O hydrogen bond. The five-membered ring is nearly planar, the largest deviation being 0.0004 (7) Å, and makes dihedral angles of 16.62 (6), 41.89 (5) and 71.27 (4)° with the phenyl rings. In the crystal, weak C—H⋯O hydrogen bonds link the mol­ecules into supra­molecular chains along the b axis