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Porphyrins with steric hindrance at the periphery are known to exhibit severely non-planar macrocycle conformations. Among other dodecasubstituted porphyrins, the title compound has been studied widely and shows a typical saddle-distorted macrocycle. The specific conformation of the porphyrin leads to the formation of distinct cavities on both sides of the macrocycle. Compared to planar porphyrins this should increase steric interactions between the macrocycle and axial ligands in five- and six-coordinated metal derivatives. In order to study the influence of different axial ligands on the conformation (or vice versa) a variety of five- and six-coordinated metal derivatives of 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetranitroporphyrin (oetnp) were prepared and their conformation investigated by X-ray crystallography. Structural data for Zn^II oetnp (L) where L is imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole and 3,5-lutidine clearly indicated that a mutual influence exists between axial ligands and non-planar porphyrins. An asymmetric macrocycle distortion and axial ligand orientation was found in the sterically hindered 2- and 4-methylimidazole derivatives. The presence of four electron-withdrawing nitro-groups led to the formation of the novel polymeric porphyrins (Zn^IIoetnp)_n and (Co^IIoetnp)_n where polymer formation was achieved via the utilization of nitro oxygen atoms as axial ligands to the metal centre of neighbouring porphyrins. The structure of the six-coordinated Ni^IIoetnp(pyr)₂ (where pyr is pyridine) yielded first structural data on neutral, non-planar, high-spin Ni(II) porphyrins. A comparison with the respective low-spin Ni^IIoetnp clearly showed that a change to the high-spin form leads to a less non-planar macrocycle conformation further proving that spin state changes can have a profound effect on the conformation in distorted porphyrins.

Exhaustive electro-oxidation of ZnOEP in the presence of pyridine and Et₄NPF₆ affords in high yield the new tetracationic porphyrin in which the four meso protons of ZnOEP are replaced by four pyridinium groups linked via their nitrogens: [Zn-5,10,15,20-tetrakis(N-pyridiniumyl)-2,3,7,8,12,13,17,18-octaethylporphyrin]⁴⁺, 1. The compound has been characterized by elemental analysis, ¹H NMR, and crystallography. The latter confirms the preparative electrosynthetic methodology and molecular structure of 1, and shows the porphyrin skeleton to adopt a severely nonplanar saddle conformation which minimizes steric crowding between the 12 peripheral substituents. As a consequence of the nonplanarity (and the high charge) of the complex, 1 exhibits significant red-shifts of the visible and Soret bands as well as a considerable broadening and loss of intensity of the latter. 1 first undergoes four one-electron reduction steps at the four pyridinium sites before the normal one-electron reduction of the porphyrin π-system.

We discuss the role that synchrotron light sources, such as SESAME, could play in improving the socioeconomic conditions in developing countries. After providing a brief description of a synchrotron light source, we discuss the important role that they played in the development of several economically emerging countries. Then we describe the state of synchrotron science in South Africa and that country’s leadership role in founding the African Light Source initiative. Next, we highlight a new initiative called Lightsources for Africa, the Americas & Middle East Project, which is a global initiative led by the International Union of Pure and Applied Physics and the International Union of Crystallography, with initial funding provided by the International Council for Science. Finally, we comment on a new technology called the multibend achromat that has launched a new paradigm for the design of synchrotron light sources that should be attractive for construction in developing countries.

The objective of this investigation is to compare the crystallographic characteristics of two different compositions of Fe–Mn–Si alloys forged with the newly designed and constructed High Energy Rate Forming (HERF) hammer with conventional hydraulic and mechanical presses. The degree of martensite formation may depend on metal forming conditions. For both of the alloys, one of the specimens was investigated in as "prepared form", the other specimen was investigated after air cooling with homogenization treatment and three specimens were deformed in different velocities after homogenization treatments. The changes which occurred in the transformation parameters of two FeMnSi alloys with different compositions due to the effects of thermal and mechanical procedures have been studied by using X-ray diffraction. In the alloy specimens cooled to different conditions from the high-temperature γ phase region, γ→ε and γ→ε→α′ martensitic transformations were observed. The lattice parameters (LP) of fcc γ and hcp ε structures were determined, and changes in forging speed on the LPs were found.

Finding a universal method of crystal structure solution and proving the Riemann hypothesis are two outstanding challenges in apparently unrelated fields. For centro-symmetric crystals however, a connection arises as the result of a statistical approach to the inverse phase problem. It is shown that parameters of the phase distribution are related to the non-trivial Riemann zeros by a Mellin transform.

This paper considers higher-dimensional generalizations of the classical one-dimensional two-automatic Thue–Morse sequence on ℕ. This is done by taking the same automaton-structure as in the one-dimensional case, but using binary number systems in ℤ^m instead of in ℕ. It is shown that the corresponding ±1-valued Thue–Morse sequences are either periodic or have a singular continuous spectrum, dependent on the binary number system. Specific results are given for dimensions up to six, with extensive illustrations for the one-, two- and three-dimensional case.

Titanium nitride (TiN) films were deposited on high-speed steel (HSS) using cathodic arc physical vapor deposition (CAPVD) technique. The effect of substrate bias on the crystallography, microstructure, deposition rate, coating thickness and composition, hardness, and adhesion strength of TiN films was investigated. The crystallography of the films was investigated using X-ray diffraction with glazing incidence angle technique. The coating microstructure and elemental composition analysis were carried out using field emission scanning electron microscopy (FE-SEM) together with energy-dispersive X-ray. Crystallography of the films revealed that the effect of substrate bias shows complex symmetry in crystal structure. The resputtering effect due to the high-energy ion bombardment on the film surface influenced the thickness as well as the color of deposited coatings. By increasing the substrate bias from 0 to - 150 V, the size and amount of macrodroplets decreased, whereas the micro-Vickers hardness decreased from 2530 HV_0.05 to 1500 HV_0.05. Scratch tester used to compare the critical loads for coatings and the adhesion achievable at substrate bias of - 50 V was demonstrated, with relevance to the various modes.

More to Structure than Meets the Eye.

Medical Technology Integration in Healthcare.

Investing in Healthcare in China.

Feeding Asia in the 21st Century: Building Urban-Rural Alliances at International Conference on Asian Food Security (ICAFS) 2011 in Singapore.

Life Sciences in Asia: Is The Tiger An Endangered Species?

Bridging the Scientific Gap; a Conversation with Ada E. Yonath.

A series of fully β-pyrrole brominated triarylcorrole metal complexes has been prepared for investigating the changes in visible spectra and redox potentials relative to the non-brominated derivatives, as well as for comparing the effect of bromination in corroles and porphyrins. The results reveal that bromination has a much larger effect on the electrochemistry of metallocorroles relative to metalloporphyrins, for both macrocycle- and metal-centered redox processes. The HOMO–LUMO gap energy of the triarylcorrole post-transition metal complexes decreases upon bromination because the effect on the LUMO is about twice as large of as on the HOMO; and both the HOMO and the LUMO are more affected in corroles than in porphyrins. Spectroscopic examinations of the transition metal complexes reveal that the synthetic access to divalent metallocorroles becomes feasible for the brominated derivatives.

The reactivity of two phenolic porphyrins bearing respectively catechol and gallol-derived meso substituents (5,10,15,20-tetrakis(3,4-dihydroxyphenyl)porphyrin and 5,10,15,20-tetrakis(3,4,5-trihydroxyphenyl)porphyrin) with trivalent metallic ions (Fe, Mn, In) was studied. Six supramolecular compounds were obtained and structurally characterized by single crystal X-ray diffraction. In each compound, the supramolecular assembly was based on the axial coordination of a phenolate function to the metallic ion lying in the porphyrinic core. A great diversity of supramolecular architectures was accessible through such simple arrangements, and objects ranging from dimers to one-dimensional polymers were isolated. Some of these assemblies were further investigated in solution by mass spectrometry and by UV-vis absorption spectroscopy. For the iron-based materials, the redox behavior was studied in solution through cyclic voltammetry experiments in inert conditions and under air.

The novel lead-free ferroelectric relaxor system $x$(Bi(${\text{Zn}}_{2/3}$${\text{Nb}}_{1/3})$${\text{O}}_3)$(1$-x)$BaTiO₃ ($x$BZN(1$-x)$BT) has received interest as a high-capacity relaxor dielectric material. Small quantities (< 10.0 mol.%) of BZN-based dopant had significant impacts on the structure of the BaTiO₃ host. This study evaluates the effect of BZN additions to the BaTiO₃ host up to $x$BZN = 10.0%. Initial additions of BZN were observed to stabilize tetragonal and orthorhombic coexistence at 295 K, alongside increasing dielectric constant. Peak dielectric constant and polarization were observed at $x$ < 4.0%, coinciding with maximum orthorhombic intensity and a local minima in tetragonal intensity. Compositions 0 < $x$ < 4.0% showed increasing polarization and a drop in $T_m$ and classical ferroelectric properties. No significant dielectric dispersion was observed for compositions $x$ < 4.0% over the frequency range 5–640 kHz. Compositions at $x$ > 4.0% showed the onset of dielectric relaxation alongside a drop in polarization coincident with a drop in the tetragonal $c_T$/$a_T$ ratio and the onset of the cubic phase at 295 K. Peak piezoelectric, dielectric and polarization values occurred over the range 3.8% < $x$ < 4.0%, alongside maximum orthorhombic intensity. Subsequent BZN additions showed a rapid onset of dielectric relaxation, alongside an increase in cubic intensity and a continuous drop in $T_m$ with a minima near $x$ = 7.0%. Tetragonal presence at 295 K also vanished to zero at $x$ = 7.0%. Polarization loops ceased showing ferroelectric characteristics at $x$ > 5.0%, showing a transition from lossy relaxor dielectric to low-loss relaxor dielectric at $x$ > 10.0%.

The paper has been designed to make a comprehensive review of a particular series of organic molecular assembly in the form of compendium. An overview of general description of fifteen quinoline derivatives has been given. The biological activity spectra of quinoline derivatives have been correlated on structure activity relationships base which provides the different P_a (possibility of activity) and P_i (possibility of inactivity) values. Expositions of the role of intermolecular interactions in the identified derivatives have been discussed with the standard distance and angle cut-off criteria criteria as proposed by Desiraju and Steiner (1999) in an International monogram on crystallography. Distance-angle scatter plots for intermolecular interactions are presented for a better understanding of the packing interactions which exist in quinoline derivatives.

The reactivity of two phenolic porphyrins bearing respectively catechol and gallol-derived meso substituents (5,10,15,20-tetrakis(3,4-dihydroxyphenyl)porphyrin and 5,10,15,20-tetrakis(3,4,5-trihydroxyphenyl)porphyrin) with trivalent metallic ions (Fe, Mn, In) was studied. Six supramolecular compounds were obtained and structurally characterized by single crystal X-ray diffraction. In each compound, the supramolecular assembly was based on the axial coordination of a phenolate function to the metallic ion lying in the porphyrinic core. A great diversity of supramolecular architectures was accessible through such simple arrangements, and objects ranging from dimers to one-dimensional polymers were isolated. Some of these assemblies were further investigated in solution by mass spectrometry and by UV-vis absorption spectroscopy. For the iron-based materials, the redox behavior was studied in solution through cyclic voltammetry experiments in inert conditions and under air.

Kyropoulos method has a temperature gradient, so the sapphire single crystal produced by it has generally stress. Three-step program annealing was proposed after researching the relation between vacuum degree and heat transfer as well as the temperature under different heating power. High quality sapphire single crystal without stress has been produced by using optimized annealing program, and light-emitting diode chip substrate grade sapphire rods with 4 inches in diameter has been processed from those crystal.