Polarized naphthalimide CH donors enhance Cl- binding within an aryl-triazole receptor

The dipolar character of 1,8-naphthalimide together with polarization of the C(4)-H and C(5)-H donors has been utilized in receptor 1 to effectively bind chloride alongside triazole and phenylene units. The Cl(-) binding strength of 1 shows that the naphthalimide provides greater anion stabilization than an unactivated phenylene, and DFT calculations show that its collinear donor array can be a "urea-like" analog for CH···anion interactions.     

Dielectric and impedance measurements on (1−x)Ba(Fe1/2Ta1/2)O3-xBa(Zn1/3Ta2/3)O3 ceramics

In this work, ((1−x)Ba(Fe_1/2Ta_1/2)O₃-xBa(Zn_1/3Ta_2/3)O₃), ((1−x)BFT-xBZT) ceramics with x = 0.00–0.12 were synthesized by the solid–state reaction method. X-ray diffraction data revealed that both the powders and ceramics were of a pure-phase cubic perovskite structure. All ceramics showed large dielectric constants. For the x = 0.12 sample, a very high dielectric constant (>20,600) was observed. A lowering in the dielectric loss compared to pure BFT ceramics was observed with the BZT addition. The impedance measurements indicated that BZT has a strong effect on the bulk grain and grain boundary resistance of BFT ceramics. These results are in agreement with the measured dielectric properties. Based on dielectric and impedance results, (1−x)BFT-xBZT ceramics could be of great interest for high performance dielectric materials applications due their giant dielectric constant behavior.     

Design,development and first experiments on the X‐ray imaging beamline at Indus‐2 synchrotron source RRCAT,India

A full‐field hard X‐ray imaging beamline (BL‐4) was designed, developed, installed and commissioned recently at the Indus‐2 synchrotron radiation source at RRCAT, Indore, India. The bending‐magnet beamline is operated in monochromatic and white beam mode. A variety of imaging techniques are implemented such as high‐resolution radiography, propagation‐ and analyzer‐based phase contrast imaging, real‐time imaging, absorption and phase contrast tomography etc. First experiments on propagation‐based phase contrast imaging and micro‐tomography are reported.     

Nanometer-sized reactor--a porphyrin-based model system for anion species

Although many cagelike molecules can create a catalytic environment for promoting chemical reactions, the construction of receptors that can host anionic species and sensitize their reaction is novel. Here we report the photochemically induced dimerization of the anion radicals of TCNQ (7,7,8,8-tetracyano-para-quinodimethane) in organic solvent under aerobic conditions when they are encapsulated inside a cationic photoactive receptor. There is clear evidence for a rate increase of over two orders of magnitude, photosensitization of the host, and demonstrated turnover of the catalyst.     

Aromatic and aliphatic CH hydrogen bonds fight for chloride while competing alongside ion pairing within triazolophanes

Triazolophanes are used as the venue to compete an aliphatic propylene CH hydrogen‐bond donor against an aromatic phenylene one. Longer aliphatic C? H ??? Cl^? hydrogen bonds were calculated from the location of the chloride within the propylene‐based triazolophane. The gas‐phase energetics of chloride binding (ΔG_bind, ΔH_bind, ΔS_bind) and the configurational entropy (ΔS_config) were computed by taking all low‐energy conformations into account. Comparison between the phenylene‐ and propylene‐based triazolophanes shows the computed gas‐phase free energy of binding decreased from ΔG_bind=?194 to ?182 kJ mol^?1, respectively, with a modest enthalpy–entropy compensation. These differences were investigated experimentally. An ¹H NMR spectroscopy study on the structure of the propylene triazolophane’s 1:1 chloride complex is consistent with a weaker propylene CH hydrogen bond. To quantify the affinity differences between the two triazolophanes in dichloromethane, it was critical to obtain an accurate binding model. Four equilibria were identified. In addition to 1:1 complexation and 2:1 sandwich formation, ion pairing of the tetrabutylammonium chloride salt (TBA⁺ ? Cl^?) and cation pairing of TBA⁺ with the 1:1 triazolophane–chloride complex were observed and quantified. Each complex was independently verified by ESI‐MS or diffusion NMR spectroscopy. With ion pairing deconvoluted from the chloride–receptor binding, equilibrium constants were determined by using ¹H NMR (500 μM ) and UV/Vis (50 μM ) spectroscopy titrations. The stabilities of the 1:1 complexes for the phenylene and propylene triazolophanes did not differ within experimental error, ΔG=(?38±2) and (?39±1) kJ mol^?1, respectively, as verified by an NMR spectroscopy competition experiment. Thus, the aliphatic CH donor only revealed its weaker character when competing with aromatic CH donors within the propylene‐based triazolophane.     

Morphogenesis of growing soft tissues

Recently, much attention has been given to a noteworthy property of some soft tissues: their ability to grow. Many attempts have been made to model this behavior in biology, chemistry, and physics. Using the theory of finite elasticity, Rodriguez has postulated a multiplicative decomposition of the geometric deformation gradient into a growth-induced part and an elastic one needed to ensure compatibility of the body. In order to fully explore the consequences of this hypothesis, the equations describing thin elastic objects under finite growth are derived. Under appropriate scaling assumptions for the growth rates, the proposed model is of the F?ppl-von Kármán type. As an illustration, the circumferential growth of a free hyperelastic disk is studied.     

Combination of Passive and Active Solar Heating with Thermal Energy Storage

This study investigated the impact of individual and combination of different sources of heating (passive solar heating, electric oil-heater, and solar air heater) in a pilot-scale building containing phase change material (PCM) for a potential reduction in energy consumption while maintaining thermal comfort. Unlike most of the recent simulations and modelling studies, this impact was tested experimentally using two identical control and test huts located at the University of Auckland. The control hut was equipped with standard gypsum boards while the test hut had gypsum boards containing PCM (PureTemp 20, PT20). The study found that combining both active and passive solar heating with a temperature-controlled electric oil heater demonstrated the ability to provide significant energy savings and maintain thermal comfort in the test hut, most notably overnight. The suggested combination was tested over different weather conditions and with different temperature constraints to maintain thermal comfort and achieve energy savings ranging from 33% to 87.5%.     

Extended Hamiltonian Hessenberg Matrices arise in Projection based Model Order Reduction

We show that extended Hamiltonian Hessenberg matrices arise naturally in projection-based model order reduction. Therefore we reduce a large dynamical system by projecting it on an extended Krylov subspace. The eigenvalues of the reduced order model can then be computed directly by applying the extended Hamiltonian QR algorithm. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Burning Graphite Faster than Carbon Black: A Case of Diffusion Control

External diffusion may be exploited as a tool to purify materials in a way thought to be inaccessible from a chemical reactivity point of view. A mixture of two carbonaceous materials, graphite and carbon black, are thermally oxidized in either i) outside total diffusion-limited regime or ii) total diffusion-limited regime. Depending on the treatment applied it is possible to purify either graphite, a trivial task, or carbon black, a task thought impossible. Introducing geometrical selectivity, controlled total diffusion-limited chemistry exceeds by far the field of carbon materials and can be used as an engineering tool for many materials purification, original synthesis, or to introduce asymmetry in a system. Several examples for direct applications of the findings are mentioned.