Plasticity in pentacene thin films

We have investigated the structure, defects and plasticity of thermally evaporated thin films of the organic molecular semiconductor pentacene using X-ray Diffraction (XRD), Optical microscopy (OM), Transmission Electron Microscopy (TEM), Electron Diffraction (ED), and High Resolution Electron Microscopy (HREM). Using XRD the degree of (001) texturing present in the as-grown films was characterized. The nature of pentacene plasticity and deformation-induced molecular alignment was investigated using rubbing and scratching techniques, as well as nanoindentation. Rubbing of the bulk powder produced thin oriented films, and a deformation length scale dependence was seen. Under stress pentacene crystals initially fail by cracking, until they reach a critical size of about one micron, when they tend to plastically deform into thin sheets. Alignment of thermally evaporated films was achieved under a controlled load scratch, and the degree of molecular orientation inside the scratched region was directly imaged using HREM. Finally, using nanoindentation we measured pentacene's plastic hardness to be 0.25 GPa at a loading rate 0.05 mN/s. A loading rate dependence of the hardness and stiffness was measured, with thin films behaving harder and stiffer at faster indentation rates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44778/1/10853_2004_Article_5277106.pd

Defect-mediated curvature and twisting in polymer crystals

Crystalline polymer solids almost inevitably exhibit defects due to chain ends, chain folding and the limited molecular mobility. The defects result in local (dislocations, grain boundaries) or global (bending, twisting) distortions of the molecular symmetry with pronounced implications on materials properties. Depending on the localization of the deformation, continuous molecular distortions or chain scission are expected, resulting in distinct differences for the mechanical (crack formation) and optoelectronic properties (charge transport and delocalization), which become especially important in the light of the recent extraordinary developments in molecular electronics. Further studies of defect structure and properties in polymers are expected to result in an increasingly sophisticated understanding of the microstructure and microstructural evolution during processing necessary to control and optimize the nano- and micrometerscale structure of organic materials. Copyright © 2000 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/35029/1/322_ftp.pd

Analytical High-Resolution Electron Microscopy Reveals Organ-Specific Nanoceria Bioprocessing

This is the first utilization of advanced analytical electron microscopy methods, including high-resolution transmission electron microscopy, high-angle annular dark field scanning transmission electron microscopy, electron energy loss spectroscopy, and energy-dispersive X-ray spectroscopy mapping to characterize the organ-specific bioprocessing of a relatively inert nanomaterial (nanoceria). Liver and spleen samples from rats given a single intravenous infusion of nanoceria were obtained after prolonged (90 days) in vivo exposure. These advanced analytical electron microscopy methods were applied to elucidate the organ-specific cellular and subcellular fate of nanoceria after its uptake. Nanoceria is bioprocessed differently in the spleen than in the liver

Military Medicine and Medical Research as a Source of Inspiration and Innovation to Solve National Security and Health Challenges in the 21st Century

The history of military medicine and research is rife with examples of novel treatments and new approaches to heal and cure soldiers and others impacted by war’s devastation. In the 21st century, new threats, like climate change, are combined with traditional threats, like geopolitical conflict, to create novel challenges for our strategic interests. Extreme and inaccessible environments provide heightened risks for warfighter exposure to dangerous bacteria, viruses, and fungi, as well as exposure to toxic substances and extremes of temperature, pressure, or both providing threats to performance and eroding resilience. Back home, caring for our veterans is also a healthcare priority, and the diseases of veterans increasingly overlap with the health needs of an aging society. These trends of climate change, politics, and demographics suggest performance evaluation and resilience planning and response are critical to assuring both warfighter performance and societal health. The Cleveland ecosystem, comprising several hospitals, a leading University, and one of the nation’s larger Veteran’s Health Administration systems, is ideal for incubating and understanding the response to these challenges. In this review, we explore the interconnections of collaborations between Defense agencies, particularly Air Force and Army and academic medical center-based investigators to drive responses to the national health security challenges facing the United States and the world.

ФОРМИРОВАНИЕ ПРОЕКТИВНОГО ПОКРЫТИЯ ГАЗОННОГО ТРАВОСТОЯ ПРИ ПРИМЕНЕНИИ МИНЕРАЛЬНЫХ И КРЕМНИЙСОДЕРЖАЩИХ УДОБРЕНИЙ

Silicon containing fertilizer “Siliplant” and mineral fertilizers are established to influence ornamental traits of lawn herbage. Increased projective covering of lawn herbage – meadow grass and red fes-cue – is marked with the preparation “Siliplant” and mineral fertilizers applied, particularly with their joint application. In the first and second years of research in dry and excessively humid vegetation periods the optimal results were obtained through the joint treatment with mineral fertilizers and the preparation “Siliplant”: the projective covering increased in the year of sowing by averaged 27.5 % in meadow grass and 25 % in red fescue versus the control, in the second year the covering went up by averaged 19.7 and 8.44 %, respectively. Mineral fertilizers applied increased the projective covering in the year of sowing on average by 22.5 % in meadow grass and by 20 % in red fescue, in the second year they did by 14.7 % and 6.25 %, respectively. The treatment with the silicon-containing preparation “Siliplant” increased the projective covering in the year of sowing by averaged 15 % in meadow grass and by 7.5 % in red fescue; in the second vegetation period the averaged effect of the treatment was by 6.58 and 1.51 % higher, respectively.Установлено влияние кремнийсодержащего удобрения «Силиплант» и минеральных удобрений на декоративные качества газонного травостоя. Отмечено увеличение проективного покрытия газонных травостоев мятлика лугового и овсяницы красной при применении препарата «Силиплант» и минеральных удобрений, особенно при их совместном использовании. В  первый и второй годы исследований при засушливом и избыточно влажном вегетационном периоде оптимальные результаты получены при применении минеральных удобрений совместно с препаратом «Силиплант»: проективное покрытие увеличивалось в год посева в среднем на 27,5% у мятлика лугового и на 25% у овсяницы красной по отношению к контролю, во второй год – на 19,7 и 8,44% соответственно. Применение минеральных удобрений увеличивало проективное покрытие в год посева в среднем на 22,5% у мятлика лугового и на 20% у овсяницы красной, во второй год на 14,7 и 6,25% соответственно. Применение кремнийсодержащего препарата «Силиплант» увеличивало проективное покрытие в год посева в среднем на 15% у мятлика лугового и на 7,5% у овсяницы красной; во втором вегетационном периоде на 6,58 и на 1,51% соответственно

A Prokaryotic Membrane Sculpting BAR Domain Protein

Bin/Amphiphysin/RVS (BAR) domain proteins belong to a superfamily of coiled-coil proteins influencing membrane curvature in eukaryotes and are associated with vesicle biogenesis, vesicle-mediated protein trafficking, and intracellular signaling. Here we report the first prokaryotic BAR domain protein, BdpA, from Shewanella oneidensis MR-1, known to produce redox-active membrane vesicles and micrometer-scale outer membrane extensions (OMEs). BdpA is required for uniform size distribution of membrane vesicles and scaffolding OMEs into a consistent diameter and curvature. Cryogenic transmission electron microscopy reveals a strain lacking BdpA produces lobed, disordered OMEs rather than membrane tubes produced by the wild type strain. Overexpression of BdpA promotes OME formation during conditions where they are less common. Heterologous expression results in OME production in Marinobacter atlanticus and Escherichia coli. Based on the ability of BdpA to alter membrane curvature in vivo, we propose that BdpA and its homologs comprise a newly identified class of prokaryotic BAR (P-BAR) domains

Crystal structure, defects and plasticity in pentacene thin films.

Pentacene is a crystalline organic molecular material currently under investigation for use as the active layer in all-organic flexible electronic devices. For pentacene and materials like it to be developed and integrated into useful devices, a greater understanding of their growth, crystal structure, defects and mechanical behavior in the thin film form must be obtained. Low-dose High Resolution Electron Microscopy (HREM) was used to image pentacene structure and defects with lattice resolution. A new technique, Low Voltage Electron Microscopy (LVEM), was used to characterize pentacene and other organic thin films with high contrast. Pentacene thin films were produced by vacuum sublimation onto various crystalline and amorphous substrates. The crystal structure and morphology of the films were characterized using microscopy and diffraction techniques, and a new orthorhombic crystal structure was found in very thin films. Although the bulk energy of this orthorhombic phase is higher than the pentacene triclinic phase, it is thermodynamically stable at low film thickness because of its low (001) surface energy. Single crystal growth of the triclinic phase was studied by complementing molecular mechanics simulations of surface energies with experimental images of pentacene films. Details of the structural relaxations near defects in pentacene thin films were investigated using HREM and Electron Diffraction (ED). Characteristic streaking in ED patterns gave evidence for anisotropic relaxations near molecular vacancies. Direct images of grain boundaries in the as-grown films gave insight into molecular reorganization under internal strain. Finally, the plasticity of pentacene was investigated by rubbing, scratching and nanoindentation. Alignment of the thermally evaporated films was achieved under a controlled load scratch. Evidence for single crystalline texturing inside the scratched region was seen using HREM, with the contact plane being {110} type. Nanoindentation was used to investigate the mechanical response of the films and to quantify the amount of plastic deformation at a given indentation load and loading rate. A pronounced loading rate effect was seen in the data, with the apparent hardness increasing from ∼0.1 GPa at a rate of 0.015 mN/s to ∼0.5 GPa at a rate of 0.7 mN/s.Ph.D.Applied SciencesMaterials scienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/123826/2/3106049.pd