Guanine‐Stabilized Formamidinium Lead Iodide Perovskites

Formamidinium (FA) lead iodide perovskite materials feature promising photovoltaic performances and superior thermal stabilities. However, conversion of the perovskite α‐FAPbI₃ phase to the thermodynamically stable yet photovoltaically inactive δ‐FAPbI₃ phase compromises the photovoltaic performance. A strategy is presented to address this challenge by using low‐dimensional hybrid perovskite materials comprising guaninium (G) organic spacer layers that act as stabilizers of the three‐dimensional α‐FAPbI₃ phase. The underlying mode of interaction at the atomic level is unraveled by means of solid‐state nuclear magnetic resonance spectroscopy, X‐ray crystallography, transmission electron microscopy, molecular dynamics simulations, and DFT calculations. Low‐dimensional‐phase‐containing hybrid FAPbI₃ perovskite solar cells are obtained with improved performance and enhanced long‐term stability.     

Crystal and molecular structure of 1-(3,5-dimethyl-2-furyl)-3-(p-tolyl) -prop-2-en-1-one

The structure of 1-(3,5-dimethyl-2-furyl)-3-(p-tolyl)-prop-2-en-1-one, C₁₆H₁₆O₂ is determined by single-crystal x-ray diffractometry. Crystals are triclinic, , a=7.381(7), b=8.871(5), c=10.745(13) Å, =93.53(7), =102.25(8),=95.43(7)°, V=682(1) ų, Z=2, d_calc=1.170 g cm^–3, (Cu K)=1.54178 Å,=5.697 cm^–1, M=270.30, F(000)=256, R=0.077 for 1601 unique observed reflections. The trans-geometry of the C=C double bond, thes-cis-geometry of the C=C-C=O moiety, and thes-trans arrangement of the carbonyl and furane oxygen atoms are proved.     

Eine verbesserte Methode zur Bestimmung der Transaminase

Ohne Zusammenfassung     

Broad multiwavelength source with 50 GHz channel spacing for wavelength division multiplexing applications in the telecom C band

We present a multiwavelength source with a spectral width of 42 nm at -20 dB. The frequency comb is generated by spectrally broadening the output of an amplified 50 GHz Er:Yb:glass laser with a highly nonlinear photonic crystal fiber. After spectral flattening the comb covers 37 channels with 5.4 mW average power per channel, and locking only one central wavelength channel to the International Telecommunication Union grid results in a maximum frequency error of 0.24% for all channels.     

Bicovariant differential calculus on quantum groups and wave mechanics

The bicovariant differential calculus on quantum groups being defined by Woronowicz and later worked out explicitly by Carow-Watamura et at. and Juro for the real quantum groupsSU _q (N) andSO _q (N) through a systematic construction of the bicovariant bimodules of these quantum groups is reviewed forSU _q (2) andSO _q (N). The resulting vector fields build representations of the quantized universal enveloping algebras acting as covariant differential operators on the quantum groups and their associated quantum spaces. As an application a free particle stationary wave equation on quantum space is formulated and solved in terms of a complete set of energy eigenfunctions.Presented at the Colloquium on the Quantum Groups, Prague, 18–20 June 1992.     

The Witten deformation for even dimensional spaces with cone-like singularities and admissible Morse functions

In this Note we generalise the Witten deformation to even dimensional Riemannian manifolds with cone-like singularities X and certain functions f, which we call admissible Morse functions. As a corollary we get Morse inequalities for the L²-Betti numbers of X. The contribution of a singular point p of X to the Morse inequalities can be expressed in terms of the intersection cohomology of the local Morse datum of f at p. The definition of the class of functions which we study here is inspired by stratified Morse theory as developed by Goresky and MacPherson. However the setting here is different since the spaces considered here are manifolds with cone-like singularities instead of Whitney stratified spaces.