The nonlinear optical properties of the crystal (S)-3-methyl-5-nitro-N-(1-phenylethyl)-2-pyridinamine

The organic crystal (S)-3-methyl-5-nitro-N-(1 -phenylethyl)-2-pyridinamine has been previously identified by the powder technique as a promising nonlinear optical material. Large single crystals (3 x 3 x 2 cm(3)) of this material have been grown by temperature lowering of a seeded supersaturated solution in acetone, Refined refractive indices were obtained from the predicted angles of incidence of the phase-matched second harmonic signals. Second-order nonlinear optical coefficients, d(ij), as measured by the Maker fringe technique, are 11, 9, and 7 pm V-1 for d(14), d(25), and d(36). respectively. The results are compared with calculations based on the oriented gas model

Refractive indices of the optically nonlinear organic crystal (S)-3-methyl-5-nitro-N-(1-phenylethyl)-2-pyridinamine

The refractive indices of structurally well-characterized crystals of the new optically nonlinear organic crystal (S)-3-methyl-5-nitro-N-( I-phenylethyl)-2-pyridinamine have been measured from 480 to 660 nm and fitted to four-parameter Sellmeier equations with an accuracy of +/-3 x 10(-3) to +/-5 x 10(-3). The value of n(y) was accurately verified by the measurement of the external angle of incidence required, at the (101) plane, to observe type I phase matching with a fundamental wavelength of 1064 nm. The phase matching locus has been established and is of Hobden class eight. The values of the n(x), n(y), and n(z) refractive indices at 532 nm were found from the Sellmeier equations to be 1.690, 1.901, and 1.725, respectively, and their relative magnitudes are correlated with the molecular arrangement in the crystal lattice. This material is a member of a series of pyridinamines that can exhibit the phenomenon of frequency-dependent orientation of their dielectric axes. Since this compound crystallizes in an orthorhombic structure, rotation of the dielectric axes is precluded for symmetry reasons

Synthesis, characterisation and structure-property analysis of derivatives of the non-linear optical material 5-nitro-N-(1- phenylethyl)pyridin-2-amine

The effects of a series of small structural changes to (S)-5-nitro-N-(1-phenylethyl)pyridin-2-amine on its solid state non-linear optical properties, including the phenomenon of rotating dielectric axes, have been investigated. Installation of a methyl group in the 3-position of the heterocyclic ring or at the amino nitrogen atom gave the most promising materials, though neither of these materials showed rotating dielectric axes. Details of the crystal structure analyses of a family of these compounds illustrate the delicate interplay between molecular conformation and intermolecular interactions in determining the packing arrangements

Development of extrinsic innervation in the abdominal intestines of human embryos

Compared to the intrinsic enteric nervous system (ENS), development of the extrinsic ENS is poorly documented, even though its presence is easily detectable with histological techniques. We visualised its development in human embryos and foetuses of 4–9.5 weeks post-fertilisation using Amira 3D-reconstruction and Cinema 4D-remodelling software. The extrinsic ENS originated from small, basophilic neural crest cells (NCCs) that migrated to the para-aortic region and then continued ventrally to the pre-aortic region, where they formed autonomic pre-aortic plexuses. From here, nerve fibres extended along the ventral abdominal arteries and finally connected to the intrinsic system. Schwann cell precursors (SCPs), a subgroup of NCCs that migrate on nerve fibres, showed region-specific differences in differentiation. SCPs developed into scattered chromaffin cells of the adrenal medulla dorsolateral to the coeliac artery (CA) and into more tightly packed chromaffin cells of the para-aortic bodies ventrolateral to the inferior mesenteric artery (IMA), with reciprocal topographic gradients between both fates. The extrinsic ENS first extended along the CA and then along the superior mesenteric artery (SMA) and IMA 5 days later. Apart from the branch to the caecum, extrinsic nerves did not extend along SMA branches in the herniated parts of the midgut until the gut loops had returned in the abdominal cavity, suggesting a permissive role of the intraperitoneal environment. Accordingly, extrinsic innervation had not yet reached the distal (colonic) loop of the midgut at 9.5 weeks development. Based on intrinsic ENS-dependent architectural remodelling of the gut layers, extrinsic innervation followed intrinsic innervation 3–4 Carnegie stages later