Structural studies of organic and organometallic compounds using x-ray and neutron techniques

This thesis is sub-divided into two parts. Part (i) is entitled 'Structure / Property Relationships in Non-linear Optical Materials' (chapters 1-8) whilst part (ii) is entitled 'Structural Studies of imido, (bis)imido and aryloxide group VA and VIA transition metal complexes' (chapters 9-10).Chapters 1, 2 and 3 provide an introduction to non-linear optics, X-ray and neutron experimental techniques used in this thesis and charge density studies respectively. Chapters 4 to 8 describe the investigations of the part (i) topic. These include bond length alternation studies on a series of tetracyanoquinodimethane derivatives and a charge density study of one of these compounds in chapter 4. Several other charge density studies are reported in chapters 5 and 6 which concentrate on methyl- nitropyridine and nitroaniline derivatives and the compound, 3-( 1,1 -dicyanoethenyl)-l-phenyl-4,5- dihydro-1 H-pyrazole (DCNP) respectively. Chapter 5 also deals with the effect of intermolecular interactions on the non-linear optical phenomenon whilst in chapter 6, a detailed analysis of the thermal motion present in DCNP is also given. Investigations on intermolecular interactions are also reported in chapters 7 and 8 which studies the compounds, N-methylurea and zinc(tris)thiourea sulphate respectively. In the former case, the neutron derived structure of N-methylurea is reported at two temperatures and it is revealed that disorder is present at the higher temperature. In the latter case, neutron results from an instrument presently in the testing stages of its development are reported and contrasted with those obtained using a well established instrument. Chapters 9 and 10 describe the investigations of the part (ii) topic. These concentrate on the structural features of two series of organometallic compounds which have potential use as polymerization catalysts. Relationships between structure and reactivity are reported

Auto-generated materials database of Curie and Néel temperatures via semi-supervised relationship extraction.

Large auto-generated databases of magnetic materials properties have the potential for great utility in materials science research. This article presents an auto-generated database of 39,822 records containing chemical compounds and their associated Curie and Néel magnetic phase transition temperatures. The database was produced using natural language processing and semi-supervised quaternary relationship extraction, applied to a corpus of 68,078 chemistry and physics articles. Evaluation of the database shows an estimated overall precision of 73%. Therein, records processed with the text-mining toolkit, ChemDataExtractor, were assisted by a modified Snowball algorithm, whose original binary relationship extraction capabilities were extended to quaternary relationship extraction. Consequently, its machine learning component can now train with ≤ 500 seeds, rather than the 4,000 originally used. Data processed with the modified Snowball algorithm affords 82% precision. Database records are available in MongoDB, CSV and JSON formats which can easily be read using Python, R, Java and MatLab. This makes the database easy to query for tackling big-data materials science initiatives and provides a basis for magnetic materials discovery

SOARING Towards Positive Transformation and Change

The SOAR strategic thinking and planning framework is a dynamic, modern, and innovative approach for framing strategic thinking, assessing individual and team performance, building strategy, and creating strategic plans. SOAR stands for strengths, opportunities, aspirations, and results. As a framework, SOAR focuses on the formulation and implementation of a positive strategy by identifying strengths, building creativity in the form of opportunities, encouraging individuals and teams to share aspirations, and determining measurable and meaningful results. This article presents the SOAR framework’s evolution from the fields of strategy, organization development and change, and Appreciative Inquiry (AI) to the discipline of positive organizational scholarship (POS)

Preferred Molecular Orientation of Coumarin 343 on TiO2 Surfaces: Application to Dye-Sensitized Solar Cells.

The dye···TiO2 interfacial structure in working electrodes of dye-sensitized solar cells (DSCs) is known to influence its photovoltaic device performance. Despite this, direct and quantitative reports of such structure remain sparse. This case study presents the application of X-ray reflectometry to determine the preferred structural orientation and molecular packing of the organic dye, Coumarin 343, adsorbed onto amorphous TiO2. Results show that the dye molecules are, on average, tilted by 61.1° relative to the TiO2 surface, and are separated from each other by 8.2 Å. These findings emulate the molecular packing arrangement of a monolayer of Coumarin 343 within its crystal structure. This suggests that the dye adsorbs onto TiO2 in one of its lowest energy configurations; that is, dye···TiO2 self-assembly is driven more by thermodynamic rather than kinetic means. Complementary DSC device tests illustrate that this interfacial structure compromises photovoltaic performance, unless a suitably sized coadsorbant is interdispersed between the Coumarin 343 chromophores on the TiO2 surface.J. M.-G. acknowledges ANSTO for a part-funded PhD studentship. J. M. C. is grateful to the 1851 Royal Commission for the 2014 Design Fellowship, and Argonne National Laboratory where work done was supported by DOE Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.This is the author accepted manuscript. The final version is available from ACS via http://dx.doi.org/10.1021/acsami.5b0357

The Role of Architecture and Tissue Properties in the Structural Integrity of Human Vertebral Cancellous Bone

Age-related disorders of bone metabolism like osteoporosis may compromise structural integrity of bone and result in fragility fractures, particularly at cancellous bone sites. Several factors contribute to cancellous bone strength, including bone density, architecture, and material properties. Clinical assessment of bone density using dual-energy X-ray absorptiometry (DXA), which is somewhat distorted by the fan-shaped X-ray beam, does not fully account for fracture incidence and only partially correlates with bone strength. Spatial variations in trabecular architecture captured by micro-computed tomography (microCT) have been related to structural behavior using microstructure-based models. However, the impact of material variations is not well understood and should be investigated. DXA fan-beam magnification was quantified by scanning aluminum rods at several distances above the X-ray source. Projected area and bone mineral content decreased by 1.6-1.8% per centimeter distance above the source, indicating that changes in girth over time would artificially reduce DXA measurements and obscure actual gains associated with growth or interventions. The ability of DXA to predict bone architecture and material properties was assessed in thoracolumbar specimens from 21 cadavers. T11-L4 was scanned using DXA, and cancellous bone cores drilled from the center of T12 and L2 were scanned at 17 microns using microCT and then compressed uniaxially to failure. DXA and microCT bone mass correlated similarly with cancellous bone stiffness and strength in females but not males. DXA could not account for variations in architecture detected by microCT, particularly in the thoracic spine, for either males or females. MicroCT scans may better assess bone strength in the thoracic spine and could replace DXA scans altogether if measurements could be made non-invasively, accurately, and affordably. Spatial variations in architecture and material properties were examined with architecture- and material-based finite element (FE) models developed from microCT scans. Homogeneous and heterogeneous material models were examined. FE models were improved by heterogeneity, whether between subjects using specimen-specific uniform properties or within subjects using spatially varying properties. Apparent stiffness was the same for specimen-specific models, regardless of variations in tissue modulus. The mean tissue modulus, rather than its distribution, appears to drive the overall mechanical behavior for vertebral cancellous bone

Nanooptomechanical Transduction in a Single Crystal with 100% Photoconversion.

Materials that exhibit nanooptomechanical transduction in their single-crystal form have prospective use in light-driven molecular machinery, nanotechnology, and quantum computing. Linkage photoisomerization is typically the source of such transduction in coordination complexes, although the isomers tend to undergo only partial photoconversion. We present a nanooptomechanical transducer, trans-[Ru(SO2)(NH3)4(3-bromopyridine)]tosylate2, whose S-bound η1-SO2 isomer fully converts into an O-bound η1-OSO photoisomer that is metastable while kept at 100 K. Its 100% photoconversion is confirmed structurally via photocrystallography, while single-crystal optical absorption and Raman spectroscopies reveal its metal-to-ligand charge-transfer and temperature-dependent characteristics. This perfect optical switching affords the material good prospects for nanooptomechanical transduction with single-photon control

Mechanical and Vascular Cues Synergistically Enhance Osteogenesis in Human Mesenchymal Stem Cells

Development and maintenance of a vascular network are critical for bone growth and homeostasis; strategies that promote vascular function are critical for clinical success of tissue-engineered bone constructs. Co-culture of endothelial cells (ECs) with mesenchymal stem cells (MSCs) and exposure to 10% cyclic tensile strain have both been shown to regulate osteogenesis in isolation, but potential synergistic effects have yet to be explored. The objective of this study was to expose an MSC-EC co-culture to 10% cyclic tensile strain to examine the role of this mechanical stimulus on MSC-EC behavior. We hypothesized that paracrine signaling from ECs would stimulate osteogenesis of MSCs, and exposure to 10% cyclic tensile strain would enhance this anabolic signal. Human umbilical vein ECs and human bone marrow-derived MSCs were either monocultured or co-cultured at a 1:1 ratio in a mixed osteo/angiogenic medium, exposed to 10% cyclic tensile strain at 1 Hz for 4 h/day for 2 weeks, and biochemically and histologically analyzed for endothelial and osteogenic markers. While neither 10% cyclic tensile strain nor co-culture alone had a significant effect on osteogenesis, the concurrent application of strain to an MSC-EC co-culture resulted in a significant increase in calcium accretion and mineral deposition, suggesting that co-culture and strain synergistically enhance osteogenesis. Neither co-culture, 10% cyclic tensile strain, nor a combination of these stimuli affected endothelial markers, indicating that the endothelial phenotype remained stable, but unresponsive to the stimuli evaluated in this study. This study is the first to investigate the role of cyclic tensile strain on the complex interplay between ECs and MSCs in co-culture. The results of this study provide key insights into the synergistic effects of 10% cyclic tensile strain and co-culture on osteogenesis. Understanding mechanobiological factors affecting MSC-EC crosstalk will help enhance strategies for creating vascularized tissues in tissue engineering and regenerative medicine