微囊藻毒素-LR的特征红外光谱

利用傅里叶变换红外(FTIR)光谱仪研究了微囊藻毒素-LR在扫描范围4 000～600 cm-1的红外吸收光谱图,微囊藻毒素-LR分子构成中的主要官能团,如带有单一取代基的苯环、胍基、γ-羧基等特征红外吸收带在谱图上均得到了确认。     

Structure and thermal decomposition of poly[[triaqua(μ4‐oxydiacetato)lanthanum(III)] nitrate]

In the title lanthanum complex, {[La(C₄H₄O₅)(H₂O)₃]NO₃}_n, the lanthanum cation is immersed in a nine‐coordinate environment provided by a tridentate oxydiacetate (oda) ligand (through two carboxylate and one ether O atoms), three carboxylate O atoms from neighbouring oda ligands and three aqua ligands. The LaO₉ polyhedra are interlinked into a tight three‐dimensional framework, which leaves holes where the nitrate anions lodge. The links to the polymeric framework are by an extensive hydrogen‐bonding scheme utilizing all the water H atoms. Thermogravimetric analysis shows that the three coordinated water molecules leave the structure in two well differentiated steps.     

Conic blocking sets in Desarguesian projective planes

Define a conic blocking set to be a set of lines in a Desarguesian projective plane such that all conics meet these lines. Conic blocking sets can be used in determining if a collection of planes in projective three-space forms a flock of a quadratic cone. We discuss trivial conic blocking sets and conic blocking sets in planes of small order. We provide a construction for conic blocking sets in planes of non-prime order, and we make additional comments about the structure of these conic blocking sets in certain planes of even order.     

Bilinear flocks

A flock in PG(3, q) is a set of q planes which do not contain the vertex of a cone and have the property that the intersections of the planes of the flock with the cone partition the points of the cone except for the vertex. In this paper, we examine flocks, called bilinear flocks, where the planes of the flock pass through at least one of two distinct lines, called supporting lines in PG(3, q). We classify and provide examples of cones that admit bilinear flocks whose supporting lines intersect in PG(3, q). We also examine bilinear flocks whose supporting lines are skew, providing an example and also showing that this situation can not occur under certain conditions.     

Omitting types and AF algebras

We prove that the classes of UHF algebras and AF algebras, while not axiomatizable, can be characterized as those C*-algebras that omit certain types in the logic of metric structures.     

Triaqua­manganese sulfite revisited

Ortho­rhom­bic Mn(SO₃)(H₂O)₃ has been reinvestigated by single‐crystal X‐ray diffraction in two possible space groups, viz. P2₁2₁2₁ (with all atoms in general positions) and Pnma (with the mol­ecule bisected by a mirror plane). The results confirm the lower symmetry assigned in a previous single‐crystal neutron diffraction study. However, the refinement of the P2₁2₁2₁ model requires the introduction of racemic twinning and soft positional and displacement restraints for the H atoms. The importance of a scrupulous report on symmetry absence violations as standard policy in crystallographic work is discussed.