How To Make Nitroaromatic Compounds Glow: Next‐Generation Large X‐Shaped,Centrosymmetric Diketopyrrolopyrroles

Red‐emissive π‐expanded diketopyrrolopyrroles (DPPs) with fluorescence reaching λ=750 nm can be easily synthesized by a three‐step strategy involving the preparation of diketopyrrolopyrrole followed by N‐arylation and subsequent intramolecular palladium‐catalyzed direct arylation. Comprehensive spectroscopic assays combined with first‐principles calculations corroborated that both N‐arylated and fused DPPs reach a locally excited (S₁) state after excitation, followed by internal conversion to states with solvent and structural relaxation, before eventually undergoing intersystem crossing. Only the structurally relaxed state is fluorescent, with lifetimes in the range of several nanoseconds and tens of picoseconds in nonpolar and polar solvents, respectively. The lifetimes correlate with the fluorescence quantum yields, which range from 6 % to 88 % in nonpolar solvents and from 0.4 % and 3.2 % in polar solvents. A very inefficient (T₁) population is responsible for fluorescence quantum yields as high as 88 % for the fully fused DPP in polar solvents.     

Metabolic Behavior and Enzymatic Aspects of Denitrifying EBPR Sludge in a Continuous-Flow Anaerobic–Anoxic System

The metabolic aspects of enhanced biological phosphorus removal (EBPR) were investigated for the first time in a continuous-flow anaerobic–anoxic plant fed with acetate, propionate, or substrates which are involved in the tricarboxylic acid and/or glyoxylate cycle, i.e., fumarate, malate, or oxaloacetate, as the sole carbon source. Although the polyphosphate-accumulating organisms (PAOs) population remained stable with any carbon source examined, no typical EBPR metabolism was observed during fumarate, malate, or oxaloacetate utilization. Specific enzymatic activities related to EBPR were determined in activated sludge homogenates and directly correlated with the nutrient metabolic rates. The experimental results indicated the direct involvement of alkaline phosphatase, pyrophosphatase, and exopolyphosphatase in the denitrifying EBPR process. Metabolic aspects of glyoxylate cycle enzymes are discussed with regard to the biomass anaerobic and anoxic activity. Process performance was highly influenced by the kind of substrate utilized, indicating that specific metabolic pathways should be followed to favor efficient EBPR.     

Measuring monotony in two-dimensional samples

This note introduces a monotony coefficient as a new measure of the monotone dependence in a two-dimensional sample. Some properties of this measure are derived. In particular, it is shown that the absolute value of the monotony coefficient for a two-dimensional sample is between |r| and 1, where r is the Pearson's correlation coefficient for the sample; that the monotony coefficient equals 1 for any monotone increasing sample and equals ?1 for any monotone decreasing sample. This article contains a few examples demonstrating that the monotony coefficient is a more accurate measure of the degree of monotone dependence for a non-linear relationship than the Pearson's, Spearman's and Kendall's correlation coefficients. The monotony coefficient is a tool that can be applied to samples in order to find dependencies between random variables; it is especially useful in finding couples of dependent variables in a big dataset of many variables. Undergraduate students in mathematics and science would benefit from learning and applying this measure of monotone dependence.     

A comparative study on the use of the extended-Cauchy dispersion equation for fitting refractive index data in crystals

This study attempts a comparative evaluation of chromatic dispersion equations in 61 crystalline solids. Based on previously published data, it is demonstrated that the extended-Cauchy equation (which in the past has been mainly used with glasses) outperforms Sellmeier models and other alternative approaches in the cases of 43 crystals, including BBO, BiBO, KTP, etc. Accumulated Cauchy coefficients for these 43 materials are presented. Performance characteristics of the extended-Cauchy model are related to specific experimental conditions, such as the number of available refractive index data, as well as the spectral location and bandwidth of measurement. The number of Cauchy coefficients required for reaching practically maximum fitting accuracy is determined. It is shown that typically, extended-Cauchy equations constructed by use of only five experimental data may be used for precise modeling of two-octave spanning spectral bandwidths.     

An efficient string sorting algorithm for weighing matrices of small weight

In this paper, we demonstrate that the search for weighing matrices of small weights constructed from two circulants can be viewed as a string sorting problem together with a linear time algorithm to locate common strings in two sorted arrays. We also introduce a sparse encoding of the periodic autocorrelation function vector, based on concepts from Algorithmic Information Theory, also known as Kolmogorov complexity, that allows us to speed up the algorithm considerably. Finally, we use these ideas to find new weighing matrices W(2 · n, 9) constructed from two circulants, for many values of n in the range 100 ≤  n ≤  300. These matrices are given here for the first time. We also discuss briefly a connection with Combinatorial Optimization.     

Extremal metrics for the first eigenvalue of the Laplacian in a conformal class

Let be a compact manifold. First, we give necessary and sufficient conditions for a Riemannian metric on to be extremal for with respect to conformal deformations of fixed volume. In particular, these conditions show that for any lattice of , the flat metric induced on from the standard metric of is extremal (in the previous sense). In the second part, we give, for any , an upper bound of on the conformal class of and exhibit a class of lattices for which the metric maximizes on its conformal class.

     

Lumina: an adaptive,automated and extensible prototype for exploring,enriching and visualizing data

Journal of Visualization - Given a tabular dataset which should be graphically represented, how could the current complex visualization pipeline be improved? Could we produce a more visually...     

Surfing π Clouds for Noncovalent Interactions: Arenes versus Alkenes

A comparative study of molecular balances by NMR spectroscopy indicates that noncovalent functional‐group interactions with an arene dominate over those with an alkene, and that a π‐facial intramolecular hydrogen bond from a hydroxy group to an arene is favored by approximately 1.2 kJ mol^?1. The strongest interaction observed in this study was with the cyano group. Analysis of the series of groups CH₂CH₃, CH?CH₂, C?CH, and C?N shows a correlation between conformational free‐energy differences and the calculated charge on the C^α atom of these substituents, which is indicative of the electrostatic nature of their π interactions. Changes in the free‐energy differences of conformers show a linear dependence on the solvent hydrogen bond acceptor parameter β.