On the Dynamic Interaction of n‐Butane with Imidazolium‐Based Ionic Liquids

The impact of a reactant from the gas phase on the surface of a liquid and its transfer through this gas/liquid interface are crucial for various concepts applying ionic liquids (ILs) in catalysis. We investigated the first step of the adsorption dynamics of n‐butane on a series of 1‐alkyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide ILs ([C_nC₁Im][Tf₂N]; n=1, 2, 3, 8). Using a supersonic molecular beam in ultra‐high vacuum, the trapping of n‐butane on the frozen ILs was determined as a function of surface temperature, between 90 and 125 K. On the C₈‐ and C₃‐ILs, n‐butane adsorbs at 90 K with an initial trapping probability of ≈0.89. The adsorption energy increases with increasing length of the IL alkyl chain, whereas the ionic headgroups seem to interact only weakly with n‐butane. The absence of adsorption on the C₁‐ and C₂‐ILs is attributed to a too short residence time on the IL surface to form nuclei for condensation even at 90 K.     

High‐Performance Perovskite Light‐Emitting Diode with Enhanced Operational Stability Using Lithium Halide Passivation

Defect passivation has been demonstrated to be effective in improving the radiative recombination of charge carriers in perovskites, and consequently, the device performance of the resultant perovskite light‐emitting diodes (LEDs). State‐of‐the‐art useful passivation agents in perovskite LEDs are mostly organic chelating molecules that, however, simultaneously sacrifice the charge‐transport properties and thermal stability of the resultant perovskite emissive layers, thereby deteriorating performance, and especially the operational stability of the devices. We demonstrate that lithium halides can efficiently passivate the defects generated by halide vacancies and reduce trap state density, thereby suppressing ion migration in perovskite films. Efficient green perovskite LEDs based on all‐inorganic CsPbBr₃ perovskite with a peak external quantum efficiency of 16.2 %, as well as a high maximum brightness of 50 270 cd m^?2, are achieved. Moreover, the device shows decent stability even under a brightness of 10⁴ cd m^?2. We highlight the universal applicability of defect passivation using lithium halides, which enabled us to improve the efficiency of blue and red perovskite LEDs.     

A Simple and Highly Effective Ligand System for the Copper(I)‐Mediated Assembly of Rotaxanes

A [2]rotaxane was produced through the assembly of a picolinaldehyde, an amine, and a bipyridine macrocycle around a Cu^I template by imine bond formation in close‐to‐quantitative yield. An analogous [3]rotaxane is obtained in excellent yield by replacing the amine with a diamine, thus showing the suitability of the system for the construction of higher order interlocked structures. The rotaxanes are formed within a few minutes simply through mixing the components in solution at room temperature and they can be isolated through removal of the solvent or precipitation.     

A fluorescence lifetime-based binding assay for acetylpolyamine amidohydrolases from Pseudomonas aeruginosa using a [1,3]dioxolo[4,5-f][1,3]benzodioxole (DBD) ligand probe

High-throughput assays for drug screening applications have to fulfill particular specifications. Besides the capability to identify even compounds with low potency, one of the major issues is to minimize the number of false-positive hits in a screening campaign in order to reduce the logistic effort for the subsequent cherry picking and confirmation procedure. In this respect, fluorescence lifetime (FLT) appears as an ideal readout parameter that is supposed to be robust against autofluorescent and light-absorbing compounds, the most common source of systematic false positives. The extraordinary fluorescence features of the recently discovered [1,3]dioxolo[4,5-f][1,3] benzodioxole dyes were exploited to develop an FLT-based binding assay with exceptionally robust readout. The assay setup was comprehensively validated and shown to comply not only with all requirements for a powerful high-throughput screening assay but also to be suitable to determine accurate binding constants for inhibitors against enzymes of the histone deacetylase family. Using the described binding assay, the first inhibitors against three members of this enzyme family from Pseudomonas aeruginosa were identified. The compounds were characterized in terms of potency and selectivity profile. The novel ligand probe should also be applicable to other homologues of the histone deacetylase family that are inhibited by N-hydroxy-N′-phenyloctandiamide.

Evolving phylogenies of trait-dependent branching with mutation and competition,Part I: Existence

We propose a type-dependent branching model with mutation and competition for modelling phylogenies of a virus population. The competition kernel depends on the total mass, the types of the virus particles, and the genetic information available through the number of nucleotide substitutions separating the virus particles. We consider evolving phylogenies in the huge population, short reproduction time and frequent mutation regime, show tightness in the space of marked metric measure spaces and characterize the limit through a martingale problem. Due to heterogeneity in the branching rates, the phylogenies are not ultra-metric. We therefore develop new techniques for verifying compact containment.     

Coherent matter waves for ultrafast laser pulse characterization

A technique for the characterization of ultrashort laser pulses using coherent matter waves is demonstrated. We emphasize the analogy between matter wave packets and electromagnetic wave packets propagating in dispersive media. Due to quadratic dispersion the wave packets are stretched and their temporal structure eventually converges to their spectrum, thus providing a possibility for energy measurements in conjugate space. This is demonstrated theoretically and experimentally and is the basis for our laser pulse characterization technique. We use energy resolved interferometrically recorded photoelectron spectra generated by above-threshold ionization in an autocorrelation setup to characterize ultrashort laser pulses at 800 nm wavelength. This approach is potentially applicable to the XUV wavelength region.     

New studies of the plasma emission detector

Being an element-selective detector, the plasma emission detector was used to determine carbon in organic compounds. Experiments were carried out with the aid of osculating interference filters and lock-in amplifiers. The obtained signals were processed by a fast-Fourier-transform analyzer to study their frequency spectra. Results are given for the detection of carbon. Furthermore studies on the influence of angle-adjustment, microwave power, photomultiplier voltage and oscillation frequency on the determination of fluorine in organic compounds were carried out and results for detection limits and dynamic range of this method are presented.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Temperature measurements according to the International Temperature Scale of 1990 and its associated uncertainties

The measurement of temperatures accompanies almost every determination of physical quantities or material properties. This paper gives an outline of the concept of the traceability of temperature measurements according to the International Temperature Scale of 1990 (ITS-90) and the determination of measurement uncertainties. Furthermore, differences between ITS-90 and thermodynamic temperatures are discussed. Presented at the PTB Seminar “Conductivity and Salinity”, September 2007, Braunschweig, Germany.