Hetero-Diels–Alder reactions of hetaryl thiochalcones with acetylenic dienophiles

Hetaryl-substituted thiochalcones react with acetylenic mono- and diesters in the THF solution in the presence of LiClO₄ at 65°C to give, after 24?h, 4H-thiopyran carboxylates and dicarboxylates, respectively, in moderate to good yields. The same reactions were performed also in the THF solution without a catalyst under microwave irradiation. In that case, the reaction time was reduced to three minutes and, in most cases, an improvement in the yield of the [4+2]-cycloadduct was observed. The reactions with methyl propiolate occurred regioselectively and the 3-carboxylates were formed exclusively.     

Velocity Diagnostics for Gas Velocity Distributions in Cold Gas and Plasma Spraying Using Non-Resonant Laser Scattering

In cold spray and thermal spray applications, one of the primary factors affecting coating deposition is the location where particles are injected into the gas jet. Therefore, a detailed knowledge of the gas flow distribution at that location is required. Use of non-resonant laser scattering allows to spatially resolve the distribution of drift velocity and mass density within the flow, particularly, at locations close to the injector. Based on this technique, this article presents a new diagnostic to locally measure drift velocity and relative mass density distribution of a gas stream. Its application is mainly focused on cold gas flows, where velocity measurements in a supersonic nozzle, obtained by means of laser scattering correlate well with theoretical calculations and particle image velocimetry (PIV) experimental results.     

Processing Routes Toward Textured Polycrystals in Ferromagnetic Shape Memory Alloys

Ni–Mn–Ga single crystals can produce large strain in moderate magnetic fields. It is the scope of this article to demonstrate, that also polycrystalline materials can show strain in a magnetic field, so called MFIS (magnetic field‐induced strain). In order to design functional polycrystalline materials the interactions of twin boundaries and grain boundaries have to be understood. Therefore, different ways of introducing a texture into Ni–Mn–Ga polycrystals are presented. The different kinds of texture and the consequences for the corresponding materials are discussed. Moreover, thermal, magnetic, and/or mechanical training concepts are presented and their working principle is explained. Several possibilities of evaluating the MFIS capability of the resulting samples are displayed. Finally methods of increasing the strain further are discussed.     

Hybrid Cooling Towers in a Free‐Cooling Application: Modeling and Field Measurement Verification

The energy‐saving potential of free cooling in chilled‐water systems was investigated. As a preliminary study, simulation was used to quantify the performance of free cooling in a given reference system. To reduce the computational effort for the simulation of long time periods, simplified models for dry and evaporative cooling were developed. The simulation results indicate that free cooling reduces the electric energy demand for cold supply almost by half. In a follow‐up investigation, free cooling was implemented in the reference system. The actual energy savings showed good agreement with the simulation forecasts and confirmed the feasibility of the concept.     

openModeller: a generic approach to species’ potential distribution modelling

Species’ potential distribution modelling is the process of building a representation of the fundamental ecological requirements for a species and extrapolating these requirements into a geographical region. The importance of being able to predict the distribution of species is currently highlighted by issues like global climate change, public health problems caused by disease vectors, anthropogenic impacts that can lead to massive species extinction, among other challenges. There are several computational approaches that can be used to generate potential distribution models, each achieving optimal results under different conditions. However, the existing software packages available for this purpose typically implement a single algorithm, and each software package presents a new learning curve to the user. Whenever new software is developed for species’ potential distribution modelling, significant duplication of effort results because many feature requirements are shared between the different packages. Additionally, data preparation and comparison between algorithms becomes difficult when using separate software applications, since each application has different data input and output capabilities. This paper describes a generic approach for building a single computing framework capable of handling different data formats and multiple algorithms that can be used in potential distribution modelling. The ideas described in this paper have been implemented in a free and open source software package called openModeller. The main concepts of species’ potential distribution modelling are also explained and an example use case illustrates potential distribution maps generated by the framework.     

Molecular electronic spectroscopy: from often neglected fundamental principles to limitations of state‐of‐the‐art computational methods

The creation of the first synthetic dyes not only stimulated the hunt for new colorants but also drove the search for rules correlating the constitution of organic compounds with their colour. Dye chemistry additionally facilitated the development of molecular electronic spectroscopy as well as theories of molecular electronic structure and electronic transitions. Powerful quantum chemical computational tools are now available for the prediction of the electronic structure and spectroscopic characteristics of organic compounds. Such methods are thus useful in designing new functional colorants and aiding interpretation of their properties. However, without a deep appreciation of the principles and assumptions behind the calculations, one runs the risk of misunderstanding what can be achieved as well as becoming confused about how the outputted electronic and vibronic transition data correspond to observed absorption spectra. This review therefore aims to cover fundamentals of electronic spectroscopy that are often overlooked and enable the dye chemist using modern computational methods to comprehend the subtle differences in the types of transition energy value that such software can generate. In addition, the limitations of these methods in predicting absorption maxima and intensities of real‐world colorants will be discussed in the context of physical influences on absorption band position and shape, for example from the perspective of different forms of the Franck–Condon principle. In essence, the goal of this review is to clarify, in terms that practical dye chemists will understand, what computational methods can predict and how valid these predictions are compared with reality.     

Structural analysis of articular cartilage using multiphoton microscopy: input for biomechanical modeling

The 3-D morphology of chicken articular cartilage was quantified using multiphoton microscopy (MPM) for use in continuum-mechanical modeling. To motivate this morphological study we propose aspects of a new, 3-D finite strain constitutive model for articular cartilage focusing on the essential load-bearing morphology: an inhomogeneous, poro-(visco)elastic solid matrix reinforced by an anisotropic, (visco)elastic dispersed fiber fabric which is saturated by an incompressible fluid residing in strain-dependent pores. Samples of fresh chicken cartilage were sectioned in three orthogonal planes and imaged using MPM, specifically imaging the collagen fibers using second harmonic generation. Employing image analysis techniques based on Fourier analysis, we derived the principal directionality and dispersion of the collagen fiber fabric in the superficial layer. In the middle layer, objective thresholding techniques were used to extract the volume fraction occupied by extracellular collagen matrix. In conjunction with information available in the literature, or additional experimental testing, we show how this data can be used to derive a 3-D map of the initial solid volume fraction and Darcy permeability.