Hydrogen bonding in 1-carb­oxy­propanaminium nitrate

There are two crystallographically independent cations and two anions in the asymmetric unit of the title compound, C4H5NO2 +·NO3 −. In the crystal, the 1-carb­oxy­propanaminium cations and nitrate anions are linked to each other through strong N—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional complex network. C—H⋯O inter­actions also occur

trans-Diaqua­bis­(dl-valinato-κ2 N,O)nickel(II)

In the title complex, [Ni(C5H9NO2)2(H2O)2], the NiII atom, located on a centre of inversion, is trans-coordinated by two O atoms and two N atoms from d-bidentate valine and l-bidentate valine ligands and two water O atoms in an octa­hedral geometry. In the crystal, the discrete mononuclear units are linked into a three-dimensional network via O—H⋯O and N—H⋯O hydrogen bonds. C—H⋯O inter­actions are also observed

Nonlinear Phenomena of Ultra-Wide-Band Radiation in a Photonic Crystal Fibre

We report the results of a numerical and experimental analysis of femtosecond pulse propagation in a highly nonlinear photonic crystal fibre (PCF). The propagation of ultrashort pulses in PCF is studied taking into account the effects of dispersion, self-phase modulation, stimulated Raman scattering, and self-steepening. The interaction between linear and nonlinear effects is investigated in order to better understand the interplay of these effects leading to the supercontinuum generation. The initial stage of an ultra-wide-band supercontinuum generation under femtosecond pumping is pointed out. Details about the expansion of the blue and red sides of the supercontinuum due to transfer of energy to dispersive waves are revealed and experimentally confirmed. Our experimental results are compared to numerical solution of the nonlinear Schrödinger equation. Good agreement is found

Ultrabroadband, Midinfrared Supercontinuum Generation in Dispersion Engineered As2Se3-Based Chalcogenide Photonic Crystal Fibers

Small core As2Se3-based photonic crystal fibers (PCFs) are accurately characterized for compact, high power, ultrabroadband, and coherent supercontinuum generation within few millimeters fiber length. Bandwidths of ~5.3 μm, 5 μm, and 3.2 μm were calculated for hole-to-hole spacings Λ= 3.5 μm, 4.5 μm, and 5.5 μm, respectively. The spectral broadening in the chalcogenide PCF is mainly caused by self-phase modulation and Raman-induced soliton self-frequency shift. The results show that small core As2Se3 PCFs are a promising candidate for mid-IR SCG up to ~8 μm

Full modal analysis of the Brillouin gain spectrum of an optical fiber

We present a numerical study of stimulated Brillouin scattering in optical fibers based on a full modal analysis of the acoustic and optical properties. The computation of each acoustic mode supported by the fiber structure allows us a deep and detailed investigation of the characteristics of the Brillouin gain spectrum. We focus our attention on optical fibers acting as acoustic antiwaveguides where the biggest contribution to the Brillouin response often comes from very high-order modes but it is sometimes overlooked because of computational issues. Our analysis clearly highlights their role and their dependence on the physical and geometrical structure of the fiber

A comparative study of two polymorphs of L-aspartic acid hydrochloride

International audienceTwo polymorphs of l-aspartic acid hydrochloride, C4H8NO4+center dot Cl-, were obtained from the same aqueous solution. Their crystal structures have been determined from single-crystal data collected at 100 K. The crystal structures revealed three-and two-dimensional hydrogen-bonding networks for the triclinic and orthorhombic polymorphs, respectively. The cations and anions are connected to one another via N-H center dot center dot center dot Cl and O-H center dot center dot center dot Cl interactions and form alternating cation-anion layer-like structures. The two polymorphs share common structural features; however, the conformations of the l-aspartate cations and the crystal packings are different. Furthermore, the molecular packing of the orthorhombic polymorph contains more interesting interactions which seems to be a favourable factor for more efficient charge transfer within the crystal