Ab initio electronic structure calculations of solid, solution-processed metallotetrabenzoporphyrins

An ab initio study of the electronic structures of solid metallotetrabenzoporphyrins (MTBPs) utilized in organic transistors and photovoltaics is presented. Bandstructures, densities of states, and orbitals are calculated for H2, Cu, Ni, and Zn core substitutions of the unit cell of solid TBP, as deposited via soluble precursors that are thermally annealed to produce polycrystalline, semiconducting thin-films. While the unit cells of the studied MTBPs are nearly isomorphous, substitution of the core atoms alters the structure of the bands around the energy bandgap and the composition of the densities of states. Cu and Ni core substitutions introduce nearly-dispersionless energy bands near the valence and conduction band edges, respectively, that form acceptor or deep generation/recombination states.Comment: 7 pages, 3 figures, 4 table

Field-effect mobility of polycrystalline tetrabenzoporphyrin thin-film transistors

A possible relation between a thin-film microstructure and an organic thin-film field-effect transistor (OFET) behavior is discussed in terms of nonlinearity in the extraction of the device electrical parameters. Staggered source and drain electrode OFETs were fabricated using a soluble precursor form of the organic small molecule semiconductor tetrabenzoporphyrin, and characterized using linear and nonlinear best-fit methods. Linear best-fit models overestimated the field-effect mobility and accumulation threshold voltage when compared to a nonlinear best-fit model that accounts for dispersive charge-carrier transport. The deviation between the methods is found to be consistently less than that for polymer OFETs, as indicated by smaller nonlinearity factors of γ = 1.2γ=1.2 and 1.7 in the linear and saturation regimes, respectively. The nonlinear field-effect mobility exhibits a sublinear gate-bias dependence wherein the mobility increases at a slower rate in strong accumulation than near threshold. Furthermore, nonlinear curve fitting indicates lower trap characteristic temperatures as compared to polymer OFETs, and a relatively moderate density of grain-boundary trap states localized at the dielectric interface and in the bulk to be filled before accumulation-related conduction dominates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87400/2/014503_1.pd

Methanofullerene-coated tetrabenzoporphyrin organic field-effect transistors

Organic field-effect transistors (OFETs) using a solution-processable form of the organic semiconductor tetrabenzoporphyrin were fabricated with a top coating of a soluble nn-type organic semiconductor. The top coating was found to extend the lifetime of the device in that the field-effect mobility, subthreshold slope, and OFF-state current were maintained at or near their as-fabricated states. Oxygen doping by extended air exposure was effectively slowed by the electron-accepting coating layer. Coated devices also display a transfer characteristic indicative of a parasitic latch-up transistor formed at the back channel of the OFETs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87830/2/173506_1.pd

Solution-processed nickel tetrabenzoporphyrin thin-film transistors

We describe nickel tetrabenzoporphyrin (NiTBP) as a solution-processible organic semiconductor. Whereas porphyrins in an unmodified state are typically planar and insoluble, a precursor synthetic route (NiCP) was used to deposit thin films via solution. Amorphous, insulating thin films of NiCP were deposited, and thermally converted to polycrystalline, semiconducting NiTBP. Films were studied using optical absorption and microscopy, atomic force microscopy, and x-ray diffraction. Highly concentrated NiCP was shown to form large, needle-shaped crystals drop-cast from solution. NiTBP thin-film field-effect transistors fabricated from spun-cast films demonstrated charge-carrier field-effect mobilities on the order of 0.1 and 0.2 cm2/V s0.2cm2∕Vs and accumulation threshold voltages of −19−19 and −13−13, in the linear and saturation regimes, respectively.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87777/2/034502_1.pd

Comparison of Measured and Modeled Radiation, Heat, and Water Vapor Fluxes: Fife Pilot Study (CAMaC Progress Report 87-7)

Mémoire de fin d'étude du diplôme de conservateur d'Elydia Barret, promotion 22 portant sur les humanités numériques, publié par les Collections numériques de l’Enssib en janvier 2014 : http://www.enssib.fr/bibliotheque-numerique/notices/64711-quel-role-pour-les-bibliotheques-dans-les-humanites-numeriques Les humanités numériques sont nées au tournant du XXIe siècle avec l’arrivée de l’internet qui ouvre un nouveau chapitre dans l’histoire des rapports des technologies numériques et des scien..

Comparison of measured and modeled radiation, heat and water vapor fluxes: FIFE pilot study

The feasibility of using radio frequency receivers to collect data from automated weather stations to model fluxes of latent heat, sensible heat, and radiation using routine weather data collected by automated weather stations was tested and the estimated fluxes were compared with fluxes measured over wheat. The model Cupid was used to model the fluxes. Two or more automated weather stations, interrogated by radio frequency and other means, were utilized to examine some of the climatic variability of the First ISLSCP (International Satellite Land-Surface Climatology Project) Field Experiment (FIFE) site, to measure and model reflected and emitted radiation streams from various locations at the site and to compare modeled latent and sensible heat fluxes with measured values. Some bidirectional reflected and emitted radiation data were collected from 23 locations throughout the FIFE site. Analysis of these data along with analysis of the measured sensible and latent heat fluxes is just beginning

Inhaled Nanoparticles Accumulate at Sites of Vascular Disease

The development of engineered nanomaterials is growing exponentially, despite concerns over their potential similarities to environmental nanoparticles that are associated with significant cardiorespiratory morbidity and mortality. The mechanisms through which inhalation of nanoparticles could trigger acute cardiovascular events are emerging, but a fundamental unanswered question remains: Do inhaled nanoparticles translocate from the lung in man and directly contribute to the pathogenesis of cardiovascular disease? In complementary clinical and experimental studies, we used gold nanoparticles to evaluate particle translocation, permitting detection by high-resolution inductively coupled mass spectrometry and Raman microscopy. Healthy volunteers were exposed to nanoparticles by acute inhalation, followed by repeated sampling of blood and urine. Gold was detected in the blood and urine within 15 min to 24 h after exposure, and was still present 3 months after exposure. Levels were greater following inhalation of 5 nm (primary diameter) particles compared to 30 nm particles. Studies in mice demonstrated the accumulation in the blood and liver following pulmonary exposure to a broader size range of gold nanoparticles (2-200 nm primary diameter), with translocation markedly greater for particles <10 nm diameter. Gold nanoparticles preferentially accumulated in inflammation-rich vascular lesions of fat-fed apolipoproteinE-deficient mice. Furthermore, following inhalation, gold particles could be detected in surgical specimens of carotid artery disease from patients at risk of stroke. Translocation of inhaled nanoparticles into the systemic circulation and accumulation at sites of vascular inflammation provides a direct mechanism that can explain the link between environmental nanoparticles and cardiovascular disease and has major implications for risk management in the use of engineered nanomaterials

Experimental Evaluation of Inlet Distortion on an Ejector Powered Hybrid Wing Body at Take-off and Landing Conditions

As part of the NASA Environmentally Responsible Aircraft project, an ultra high bypass ratio engine integration on a hybrid wing body demonstration was planned. The goal was to include engine and airframe integration concepts that reduced fuel consumption by at least 50% while still reducing noise 42 db cumulative on the ground. Since the engines would be mounted on the upper surface of the aft body of the aircraft, the inlets may be susceptible to vortex ingestion from the wing leading edge at high angles of attack and sideslip, and separated wing/body flow. Consequently, experimental and computational studies were conducted to collect flow surveys useful for characterizing engine operability. The wind tunnel tests were conducted at two NASA facilities, the 14- by 22-foot at NASA Langley and the 40- by 80-foot at NASA Ames Research Center. The test results included in this paper show that the distortion and pressure recovery levels were acceptable for engine operability. The CFD studies conducted to compare to experimental data showed excellent agreement for the angle of attacks examined, although failed to match the low speed experimental data at high sideslip angles