A GGA plus U approach to effective electronic correlations in thiolate-ligated iron-oxo (IV) porphyrin

High-valent oxo-metal complexes exhibit correlated electronic behavior on dense, low-lying electronic state manifolds, presenting challenging systems for electronic structure methods. Among these species, the iron-oxo (IV) porphyrin denoted Compound I occupies a privileged position, serving a broad spectrum of catalytic roles. The most reactive members of this family bear a thiolate axial ligand, exhibiting high activity toward molecular oxygen activation and substrate oxidation. The default approach to such systems has entailed the use of hybrid density functionals or multi-configurational/multireference methods to treat electronic correlation. An alternative approach is presented based on the GGA+U approximation to density functional theory, in which a generalized gradient approximation (GGA) functional is supplemented with a localization correction to treat on-site correlation as inspired by the Hubbard model. The electronic structure of thiolate-ligated iron-oxo (IV) porphyrin and corresponding Coulomb repulsion U are determined both empirically and self-consistently, yielding spin-distributions, state level splittings, and electronic densities of states consistent with prior hybrid functional calculations. Comparison of this detailed electronic structure with model Hamiltonian calculations suggests that the localized 3d iron moments induce correlation in the surrounding electron gas, strengthening local moment formation. This behavior is analogous to strongly correlated electronic systems such as Mott insulators, in which the GGA+U scheme serves as an effective single-particle representation for the full, correlated many-body problem

Synthesis, characterization and crystal structures of two new phenolic mannich bases

Two new Mannich bases, 5-methyl-2-((4-(pyridin-2-yl)piperazin-1-yl)methyl)phenol (1) and 5-methyl-2-((4-(4-nitrophenyl)piperazin-1-yl)methyl)phenol (2), were prepared and characterized structurally with elemental analysis, IR, UV and NMR spectroscopic techniques as well as single crystal X-ray diffraction. Compound I crystallizes in the monoclinic space group P21/c with unit cell dimensions a = 6.6726(2) Å, b =   17.0542(6)   Å, c = 13.3222(4) Å, β = 100.832(1)°, V = 1489.00 (8) Å3, Z = 4, R1 = 0.0408, wR2 = 0.1143. Compound II crystallizes in the monoclinic space P21 with unit cell dimensions a = 5.9519(2) Å, b = 17.3315(8) Å, c = 15.7237(7) Å, β = 90.348(2)°, V = 1621.95(12) Å3, Z = 4, R1 = 0.0353, wR2 = 0.0965. Both compounds have their structures stabilized by hydrogen bonding and π∙∙∙π interactions.               KEY WORDS: Mannich base, Piperazine, X-ray diffraction, Hydrogen bonds Bull. Chem. Soc. Ethiop. 2019, 33(2), 341-348.DOI: https://dx.doi.org/10.4314/bcse.v33i2.1

Synthesis, characterization and DPPH scavenging activity of some benzimidazole derivatives

A base-catalyzed conversion of aldehydes to benzimidazoles has been achieved. The compounds have been characterized by IR, NMR, micoranalysis, and GC-MS. The reaction for the formation of benzimidazoles has been monitored with 1H NMR and IR. The crystal structures of two derivatives, 2-(2-chlorophenyl)-1H-benzimidazole and 2-(1H-benzimidazol-2-yl)-4-nitrophenol, are presented. A study of the DPPH scavenging activity of these compounds showed that 2-(1H-benzimidazol-2-yl)phenol (2), 2-p-tolyl-1H-benzimidazole (3) and 2-(4-methoxyphenyl)-1H-benzimidazole (7) gave IC50 values 1974, 773 and 800 µM.               KEY WORDS: Benzimidazole, o-Phenylenediamine, Aldehydes, Base catalysis, DPPH scavenging activity Bull. Chem. Soc. Ethiop. 2018, 32(2), 271-284.DOI: https://dx.doi.org/10.4314/bcse.v32i2.

Vegetation Change from the Euro-American Settlement Era to the Present in Relation to Environment and Disturbance in Southwest Oregon

Faced with landscapes degraded by fire suppression, logging, and grazing, land managers in the interior western US are attempting to restore habitat structure and function. In southwest Oregon, landscape-scale fuels treatments are being implemented with goals including recreating historic vegetation structure, despite poor understanding of the nature of the landscape prior to widespread Euro-American influence, or the patterns and processes of vegetation change over time. We compared a General Land Office-based reconstruction of Euro-American settlement era (1850s) vegetation in southwest Oregon's interior valleys and foothills with modern vegetation interpreted from aerial orthoimages to determine patterns of vegetation distribution in both eras, trajectories of vegetation change, and environmental and disturbance factors related to these themes. We found that this landscape was primarily occupied by closed plant community types in both eras, with a comparatively minor proportion in open types; vegetation was distributed along a dominant environmental gradient that ran from prairies in xeric lowlands to conifer forests in steeper, cooler uplands. Temporal shifts from open to closed vegetation were consistent with expected effects of fire suppression in many cases, but in other cases, the long-term persistence of open vegetation in the absence of recorded fire indicated that other mechanisms were also in operation. Human encroachment into wildlands, particularly in valleys, has also been a major driver of landscape-level change in the past 150 yr. Our results suggest that conservation should focus on lowlands, particularly where uncommon vegetation types such as savanna, shrubland, and prairie still exist.Keywords: vegetation distribution, Klamath-Siskiyou region, General Land Office surveys, southwest Oregon, environmental gradient

(2E)-3-(6-Methoxynaphthalen-2-yl)-1-(pyridin-3-yl)prop-2-en-1-one and its cyclocondensation product with guanidine, (4RS)-2-amino-4-(6-methoxynaphthalen-2-yl)-6-(pyridin-3-yl)-3,4-dihydropyrimidine monohydrate: Two types of hydrogen-bonded sheet

The structures of a chalcone and of its cyclo­condensation product with guanidine are reported. In (2E)-3-(6-meth­oxy­naphthalen-2-yl)-1-(pyridin-3-yl)prop-2-en-1-one, C19H15NO2, (I), the planes of the pyridine and naphthalene units make dihedral angles with that of the central spacer unit of 23.61 (13) and 23.57 (15)°, respectively, and a dihedral angle of 47.24 (9)° with each other. The mol­ecules of (I) are linked into sheets by a combination of C-H...O and C-H...[pi](arene) hydrogen bonds. In the cyclo­condensation product (4RS)-2-amino-4-(6-meth­oxy­naphthalen-2-yl)-6-(pyri­din-3-yl)-3,4-dihydro­pyrimidine monohydrate, C20H18N4O·H2O, (II), the di­hydro­pyrimidine ring adopts a conformation best described as a shallow boat. The mol­ecular components are linked by two N-H...O hydrogen bonds, two O-H...N hydrogen bonds and one N-H...N hydrogen bond to form complex sheets, with the meth­oxy­naphthalene inter­digitated between inversion-related pairs of sheets

Different patterns of supramolecular assembly in constitutionally similar 6-arylimidazo2,1-b1,3,4thiadiazoles

Four imidazo2,1-b1,3,4thiadiazoles containing a simply-substituted 6-aryl group have been synthesized by reaction of 2-amino-1,3,4-thiadiazoles with bromoacetylarenes using microwave irradiation and brief reaction times. 6-(2-Chlorophenyl)imidazo2,1-b1,3,4thiadiazole, C10H6ClN3S, (I), 6-(2-chlorophenyl)-2-methylimidazo2,1-b1,3,4thiadiazole, C11H8ClN3S, (II), 6-(3,4-dichlorophenyl)imidazo2,1-b1,3,4thiadiazole, C10H5Cl2N3S, (III), and 6-(4-fluoro-3-methoxyphenyl)-2-methylimidazo2,1-b1,3,4thiadiazole, C12H10FN3OS, (IV), crystallize with Z� values of 2, 1, 1 and 2 respectively. The molecular skeletons are all nearly planar and the dihedral angles between the imidazole and aryl rings are 1.51(8) and 7.28(8)° in (I), 9.65(7)° in (II), 10.44(8)° in (III), and 1.05(8) and 7.21(8)° in (IV). The molecules in (I) are linked by three independent C - H�N hydrogen bonds to form ribbons containing alternating R 2 2 (8) and R 4 4 (18) rings, and these ribbons are linked into a three-dimensional array by three independent �-stacking interactions. Both (II) and (III) contain centrosymmetric dimers formed by �-stacking interactions but hydrogen bonds are absent, and the molecules of (IV) are linked into centrosymmetric R 2 2 (8) dimers by C - H�N hydrogen bonds. Comparisons are made with a number of related compounds

Quantum Optical Systems for the Implementation of Quantum Information Processing

We review the field of Quantum Optical Information from elementary considerations through to quantum computation schemes. We illustrate our discussion with descriptions of experimental demonstrations of key communication and processing tasks from the last decade and also look forward to the key results likely in the next decade. We examine both discrete (single photon) type processing as well as those which employ continuous variable manipulations. The mathematical formalism is kept to the minimum needed to understand the key theoretical and experimental results

Demonstration of quantum Zeno effect in a superconducting phase qubit

Quantum Zeno effect is a significant tool in quantum manipulating and computing. We propose its observation in superconducting phase qubit with two experimentally feasible measurement schemes. The conventional measurement method is used to achieve the proposed pulse and continuous readout of the qubit state, which are analyzed by projection assumption and Monte Carlo wave-function simulation, respectively. Our scheme gives a direct implementation of quantum Zeno effect in a superconducting phase qubit.Comment: 5 pages, 4 figure

ENIGMA and global neuroscience: A decade of large-scale studies of the brain in health and disease across more than 40 countries

This review summarizes the last decade of work by the ENIGMA (Enhancing NeuroImaging Genetics through Meta Analysis) Consortium, a global alliance of over 1400 scientists across 43 countries, studying the human brain in health and disease. Building on large-scale genetic studies that discovered the first robustly replicated genetic loci associated with brain metrics, ENIGMA has diversified into over 50 working groups (WGs), pooling worldwide data and expertise to answer fundamental questions in neuroscience, psychiatry, neurology, and genetics. Most ENIGMA WGs focus on specific psychiatric and neurological conditions, other WGs study normal variation due to sex and gender differences, or development and aging; still other WGs develop methodological pipelines and tools to facilitate harmonized analyses of "big data" (i.e., genetic and epigenetic data, multimodal MRI, and electroencephalography data). These international efforts have yielded the largest neuroimaging studies to date in schizophrenia, bipolar disorder, major depressive disorder, post-traumatic stress disorder, substance use disorders, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, autism spectrum disorders, epilepsy, and 22q11.2 deletion syndrome. More recent ENIGMA WGs have formed to study anxiety disorders, suicidal thoughts and behavior, sleep and insomnia, eating disorders, irritability, brain injury, antisocial personality and conduct disorder, and dissociative identity disorder. Here, we summarize the first decade of ENIGMA's activities and ongoing projects, and describe the successes and challenges encountered along the way. We highlight the advantages of collaborative large-scale coordinated data analyses for testing reproducibility and robustness of findings, offering the opportunity to identify brain systems involved in clinical syndromes across diverse samples and associated genetic, environmental, demographic, cognitive, and psychosocial factors

Geometric Spin Hall Effect of Light at Polarizing Interfaces

The geometric Spin Hall Effect of Light (geometric SHEL) amounts to a polarization-dependent positional shift when a light beam is observed from a reference frame tilted with respect to its direction of propagation. Motivated by this intriguing phenomenon, the energy density of the light beam is decomposed into its Cartesian components in the tilted reference frame. This illustrates the occurrence of the characteristic shift and the significance of the effective response function of the detector. We introduce the concept of a tilted polarizing interface and provide a scheme for its experimental implementation. A light beam passing through such an interface undergoes a shift resembling the original geometric SHEL in a tilted reference frame. This displacement is generated at the polarizer and its occurrence does not depend on the properties of the detection system. We give explicit results for this novel type of geometric SHEL and show that at grazing incidence this effect amounts to a displacement of multiple wavelengths, a shift larger than the one introduced by Goos-H\"anchen and Imbert-Fedorov effects.Comment: 6 pages, 4 figure