Energy Absorption Mechanisms in Layer-to-Layer 3D Woven Composites

3D woven composites provide improved out-of-plane performance over their two-dimensional counterparts. This sort of reinforced through thickness behaviour is desirable in crashworthiness applications where energy absorption can be increased by the composite material's resistance to delamination. The behaviour of these 3D materials in not well understood and fundamental data that can be used to validate and improve material models is not yet sufficiently comprehensive. Here we demonstrate that a modified layer-to-layer type 3D woven architecture can be effectively used in energy absorbing elements to produce repeatable and predictable progressive failure under axial crush conditions. Specific energy absorption (SEA) values in glass and carbon coupons of up to 62J/g and 95J/g respectively are achieved in the quasi-static regime; values up 93J/g to were achieved in the dynamic regime when carbon coupons are tested. Carbon specimens displayed uncharacteristic mixed mode failure with elements of ductile and brittle failure. The addition of a toughening agent showed mixed results in this study, providing quasi-static improvements (+8%) in SEA but significant diminishment in dynamic SEA (-22%). The failure modes present in all cases are explored in depth and the suitability of this material for industry crash applications is investigated

Conformal Robotic Stereolithography

Additive manufacturing by layerwise photopolymerization, commonly called stereolithography (SLA), is attractive due to its high resolution and diversity of materials chemistry. However, traditional SLA methods are restricted to planar substrates and planar layers that are perpendicular to a single-axis build direction. Here, we present a robotic system that is capable of maskless layerwise photopolymerization on curved surfaces, enabling production of large-area conformal patterns and the construction of conformal freeform objects. The system comprises an industrial six-axis robot and a custom-built maskless projector end effector. Use of the system involves creating a mesh representation of the freeform substrate, generation of a triangulated toolpath with curved layers that represents the target object to be printed, precision mounting of the substrate in the robot workspace, and robotic photopatterning of the target object by coordinated motion of the robot and substrate. We demonstrate printing of conformal photopatterns on spheres of various sizes, and construction of miniature three-dimensional objects on spheres without requiring support features. Improvement of the motion accuracy and development of freeform toolpaths would enable construction of polymer objects that surpass the size and support structure constraints imparted by traditional SLA systems.American Society for Engineering Education. National Defense Science and Engineering Graduate FellowshipNational Institute of Mental Health (U.S.) (University of Michigan Microfluidics in Biomedical Sciences Training Program. 5T32-EB005582)Singapore-MIT Alliance for Research and Technology (SMART

Health-related quality of life in patients with pulmonary arterial hypertension

BACKGROUND: Improved outcomes with expanding treatment options for patients with pulmonary arterial hypertension present the opportunity to consider additional end-points in approaching therapy, including factors that influence health-related quality of life. However, comparatively little is known about health-related quality of life and its determinants in patients with pulmonary arterial hypertension. METHODS: Health-related quality of life was evaluated in a cross sectional study of 155 outpatients with pulmonary arterial hypertension using generic and respiratory-disease specific measurement tools. Most patients had either World Health Organization functional Class II or III symptoms. Demographic, hemodynamic and treatment variables were assessed for association with health-related quality of life scores. RESULTS: Patients with pulmonary arterial hypertension suffered severe impairments in both physical and emotional domains of health-related quality of life. Patients with idiopathic ("primary") pulmonary arterial hypertension had the best, and those with systemic sclerosis the worst health-related quality of life. Greater six-minute walk distance correlated with better health-related quality of life scores, as did functional Class II versus Class III symptoms. Hemodynamic measurements, however, did not correlate with health-related quality of life scores. No differences in health-related quality of life were found between patients who were being treated with calcium channel antagonists, bosentan or continuously infused epoprostenol at the time of quality of life assessment. CONCLUSION: Health-related quality of life is severely impaired in patients with pulmonary arterial hypertension and is associated with measures of functional status. Specific associations with impaired health-related quality of life suggest potential areas for targeted intervention

Syntheses, characterization, density functional theory calculations, and activity of tridentate SNS zinc pincer complexes based on bis-imidazole or bis-triazole precursors

A series of tridentate pincer ligands, each possessing two sulfur- and one nitrogen-donor functionalities (SNS), based on bis-imidazole or bis-triazole salts were metallated with ZnCl2 to give new tridentate SNS pincer zinc(II) complexes [(SNS)ZnCl]+. The zinc complexes serve as models for the zinc active site in liver alcohol dehydrogenase (LADH) and were characterized with single crystal X-ray diffraction, 1H, 13C, and HSQC NMR spectroscopies, electrospray mass spectrometry, and elemental analysis. The zinc complexes feature SNS donor atoms and pseudotetrahedral geometry about the zinc center, as is seen for liver alcohol dehydrogenase. The bond lengths and bond angles of the zinc complexes correlate well to those in horse LADH. The SNS ligand precursors were characterized with 1H, 13C, and HSQC NMR spectroscopies, elemental analysis, and cyclic voltammetry, and were found to be redox active. Gaussian calculations were performed and agree with the experimentally observed oxidation potentials for the pincer ligand precursors. The zinc complexes were screened for the reduction of electron-poor aldehydes in the presence of a hydrogen donor, 1-benzyl-1,4-dihydronicotinamide (BNAH), and it was determined that they enhance the reduction of electron-poor aldehydes. The SNS zinc pincer complexes with bis-triazole ligand precursors exhibit higher activity for the reduction of 4-nitrobenzaldehyde than do SNS zinc pincer complexes with bis-imidazole ligand precursors. Quantitative stoichiometric conversion was seen for the reduction of pyridine-2-carboxaldehyde via SNS zinc pincer complexes with either bis-imidazole or bis-triazole ligand precursors

Synthesis, Characterization, Density Functional Theory Calculations, and Activity of a Thione-Containing NNN-Zinc Pincer Complex Based on a Bis-triazole Precursor

A novel ambidentate tridentate pincer ligand based on a bis-triazole precursor, was prepared, characterized, and metallated with ZnCl2 to give a new tridentate NNN-bound pincer zinc(II) pincer complex: dichloro(η3-N,N,N)-[2,6-bis(3-[N-butyl]triazol-5-thione-1-yl)]pyridinezinc(II), [(NNN)ZnCl2]. This compound has pseudo-trigonal bipyramidal geometry at the zinc(II) center and exhibits metal–ligand binding that contrasts with our previously reported SNS-bound systems despite the availability of these same donor atoms in the current ligand set. The zinc complex was characterized with single crystal X-ray diffraction, 1H, 13C, and HSQC NMR spectroscopies, and electrospray mass spectrometry. The ligand precursors were characterized with 1H, 13C, and HSQC NMR spectroscopies, and cyclic voltammetry, and were found to be redox active. Density functional calculations, which investigate and support the nature of the NNN binding suggest that the experimentally observed oxidation and reduction waves are not the result of a simple one-electron process. The zinc complex was screened for the reduction of electron-poor aldehydes in the presence of a hydrogen donor, 1-benzyl-1,4-dihydronicotinamide (BNAH), and it was determined that they enhance the reduction of 4-nitrobenzaldehyde. Quantitative stoichiometric conversion was seen for the reduction of pyridine-2-carboxaldehyde

Moyo Vol. III N 1

Boyden, John and Rich Vanderklok. Are You a $nob? . 2. Herman, James. River Phoenix: A Final Conversation . 4. Blake, Ben. Arbor Vitae Victories: Other Crafty Everyday Uses For Those Inconspicuous Little Trees . 9. Fischesser, S. Separate But Unequal: A View of Denison\u27s Black Orientation . 10. Gilmore, Seth. Evil Upheaval: The Reforming of Organized Religion... in Granville .; Boyden, John. “Reaching Out & Talking Dirty (When Touching Turns to Touch Tones)”. 20. Vanderklok, Rich. Gen-X Angst . 24. Driscoll, Julie. Bang! Thump (Getting A Taste For The Meat Processing Industry). 25. Stillman, Lisa. The Bare Facts: An Exposé on Public Nudity . 26. Endicott, Josh. Frames . 29. Emmons, Alex. Frames . 29. Emmons, Alex. Untitled. 11. Bussan, Dave. Bull Session With a Former Editor On Denison\u27s Sacred Cow . 30. Webb, Aaron. Color Blind: From Diversity Adversity to Racial Rapport . 33. Archer, Troy Color Blind: From Diversity Adversity to Racial Rapport . 33

Opportunity or dead end? Rethinking the study of entrepreneurial action without a concept of opportunity

This article has two objectives: to critique the dominant opportunity discovery and creation literatures and to propose a new, critical realist–inspired analytical framework to theorise the causes, processes and consequences of entrepreneurial action – one that needs no concept of opportunity. We offer three reasons to support our critique of opportunity studies. First, there are important absences, contradictions and inconsistencies in definitions of opportunity in theoretical and empirical work that mean the term cannot signal a clear direction for theorising or empirical research. Our central criticism is that the concept of opportunity cannot refer simultaneously, without contradiction, to a social context offering profit-making prospects, to particular practices and to agents’ subjective beliefs or imagined futures. Second, a new definition of opportunity would perpetuate the conceptual chaos. Third, useful concepts to capture important entrepreneurial processes are readily available, for instance, combining resources, creating new ventures and achieving product sales, which render a concept of opportunity superfluous. Instead, we conceptualise entrepreneurial action as investments in resources intended to create new goods and services for market exchange emergent from the interaction between agential, socialstructural and cultural causal powers