Ab,stract—Concept learning and learning .strategies of pigeons were titanipnkited in a ntatching-to-sampie task. Groups of 4 pigeons responded either 0. 1. W. or 20 times to a sample stimulus, and then chose between a matching cotnparison stimulus and a ttonmatching comparison stimulus. Tests with unfamiliar arrangements of the three training stimuli .showed that learning n-as not hy if-then ru...

The structure of the title uric acid derivative, C(7)H(8)N(4)O(5), from human kidney stones, is characterized by the C and O atoms of one of the two hy-droxy-methyl groups being disordered nearly equally over three different sites. In the crystal, mol-ecules are connected by a three-dimensional hydrogen-bonding scheme though they look stacked in planes nearly parallel to ([Formula: see text]04).

In the title compound, C13H14O5, the furan ring is essentially planar [maximum deviation = 0.031 (3) Å] with a stereogenic center (R) at the sp (3) hybridized C atom. The C atom bearing the dihy-droxy ethyl group is S. The absolute configuration is based on the precursor in the synthesis. The two O-H groups are in an anti conformation with respect to each other. The mean plane of the furan-one ...

We present a novel method for determining the surface density of protoplanetary disks through consideration of disk ‘dust lines’ which indicate the observed disk radial scale at different observational wavelengths. This method relies on the assumption that the processes of particle growth and drift control the radial scale of the disk at late stages of disk evolution such that the lifetime of t...

In the title ferrocene derivative, [Fe(C5H5)(C9H8NO)], the dihedral angle between the ene-nitrile group and the substituted cyclo-penta-dienyl ring is 71.2 (1)°. The cyclopentadienyl rings of the ferrocene moiety are arranged in an eclipsed conformation. The hy-droxy group, and the corresponding methine H atom, are disordered over two sets of sites with site-occupancy factors of 0.744 (4) and 0...

The title compound, C4H6N2O, displays two predominant hydrogen-bonding inter-actions in the crystal structure. The first is between the unprotonated imidazole N atom of one mol-ecule and the hy-droxy H atom of an adjacent mol-ecule. The second is between the hy-droxy O atom of one mol-ecule and the imidazole N-H group of a corresponding mol-ecule. These inter-actions lead to the formation of a ...

Let X be a hyperkähler manifold. Trianalytic subvarieties of X are subvarieties which are complex analytic with respect to all complex structures induced by the hyperkähler structure. Given a K3 surface M , the Hilbert scheme classifying zero-dimensional subschemes of M admits a hy-perkähler structure. We show that for M generic, there are no trianalytic subvarieties of the Hilbert scheme. This...

In the crystal structure of the zinc(II) complex of bicine, [Zn(C(6)H(12)NO(4))(2)], the deprotonated amino acid O,N,O'-chelates to the metal atom through a carboxyl-ate O atom, a hy-droxy O atom and the N atom, the three atoms occupying fac positions of the distorted octa-hedron surrounding the metal atom. The metal atom lies on a center of inversion. The uncoordinated carboxyl-ate O atom is h...

2-Hydrazino-4-(5-nitro-2-furyl)thiazole , 2-(2 , 2-dimethyihy drazi no)-4-(5-nitro-2-furyl)thiazole, 2-hydrazino-4-(4-nitro phenyl)thiazole, and 2-hydrazino-4-(4-aminophenyl)thiazole were fed to female Sprague-Dawley rats, and all were found to be potent carcinogens. Each induced chiefly carcinomas of the mammary gland (32/35 , 30/3 1, 27/34, 34/35 , respec tively), as well as a lower incidence...

The title compound, C(20)H(26)O(2), was isolated from a chloro-form extract of Tetra-clinis articulata wood. The mol-ecule contains three fused rings which exhibit different conformations. The non-aromatic oxo-substituted ring has a screw-boat conformation, while the central ring has a half-chair conformation. In the crystal, mol-ecules are linked to each other by inter-molecular O-H⋯O hydrogen...