560 research outputs found

    Fermi resonance-algebraic model for molecular vibrational spectra

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    A Fermi resonance-algebraic model is proposed for molecular vibrations, where a U(2) algebra is used for describing the vibrations of each bond, and Fermi resonances between stretching and bending modes are taken into account. The model for a bent molecule XY_2 and a molecule XY_3 is successfully applied to fit the recently observed vibrational spectrum of the water molecule and arsine (AsH_3), respectively, and results are compared with those of other models. Calculations show that algebraic approaches can be used as an effective method for describing molecular vibrations with small standard deviations

    New particle formation from sulfuric acid and amines : Comparison of monomethylamine, dimethylamine, and trimethylamine

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    Amines are bases that originate from both anthropogenic and natural sources, and they are recognized as candidates to participate in atmospheric aerosol particle formation together with sulfuric acid. Monomethylamine, dimethylamine, and trimethylamine (MMA, DMA, and TMA, respectively) have been shown to enhance sulfuric acid-driven particle formation more efficiently than ammonia, but both theory and laboratory experiments suggest that there are differences in their enhancing potentials. However, as quantitative concentrations and thermochemical properties of different amines remain relatively uncertain, and also for computational reasons, the compounds have been treated as a single surrogate amine species in large-scale modeling studies. In this work, the differences and similarities of MMA, DMA, and TMA are studied by simulations of molecular cluster formation from sulfuric acid, water, and each of the three amines. Quantum chemistry-based cluster evaporation rate constants are applied in a cluster population dynamics model to yield cluster concentrations and formation rates at boundary layer conditions. While there are differences, for instance, in the clustering mechanisms and cluster hygroscopicity for the three amines, DMA and TMA can be approximated as a lumped species. Formation of nanometer-sized particles and its dependence on ambient conditions is roughly similar for these two: both efficiently form clusters with sulfuric acid, and cluster formation is rather insensitive to changes in temperature and relative humidity. Particle formation from sulfuric acid and MMA is weaker and significantly more sensitive to ambient conditions. Therefore, merging MMA together with DMA and TMA introduces inaccuracies in sulfuric acid-amine particle formation schemes.Peer reviewe

    Infrared Excess in the Be Star Delta Scorpii

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    We present infrared photometric observations of the Be binary system delta Scorpii obtained in 2006. The J,H and K magnitudes are the same within the errors compared to observations taken 10 months earlier. We derive the infrared excess from the observation and compare this to the color excess predicted by a radiative equilibrium model of the primary star and its circumstellar disk. We use a non-LTE computational code to model the gaseous envelope concentrated in the star's equatorial plane and calculate the expected spectral energy distribution and Halpha emission profile of the star with its circumstellar disk. Using the observed infrared excess of delta Sco, as well as Halpha spectroscopy bracketing the IR observations in time, we place constraints on the radial density distribution in the circumstellar disk. Because the disk exhibits variability in its density distribution, this work will be helpful in understanding its dynamics.Comment: 12 pages, 14 figures, to be published in PASP May 200

    Persistent Currents in Small, Imperfect Hubbard Rings

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    We have done a study with small, imperfect Hubbard rings with exact diagonalization. The results for few-electron rings show, that the imperfection, whether localized or not, nearly always decrease, but can also \emph{increase} the persistent current, depending on the character of the imperfection and the on-site interaction. The calculations are generally in agreement with more specialized studies. In most cases the electron spin plays an important role.Comment: 6 pages, 4 figure

    A non-invasive method for hydration status measurement with a microwave sensor using skin phantoms

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    AbstractFluid balance is important for a healthy human being. In this paper, a method to measure hydration status was developed and tested towards non-invasive measurement from human skin. Measurement of hydration status was performed by a microwave sensor utilizing a complementary split ring resonator (CSRR). The sensor was modeled, manufactured and then characterized by measuring tailor made skin phantoms based on the realistic electrical properties of skin with different degrees of hydration status. Qualitative longer term (>24 h) evaluation of the sensor was also performed by measuring polyester tissue that was drying over the time. Hydration status, represented by dehydrated, normal and hydrated skin phantoms, based on polyurethane with carbon and ceramic additives, was measured successfully by monitoring the changes in resonance frequency around 5.52 GHz. All results were compared to the dielectric reference measurements done by a commercial laboratory instrument.Abstract Fluid balance is important for a healthy human being. In this paper, a method to measure hydration status was developed and tested towards non-invasive measurement from human skin. Measurement of hydration status was performed by a microwave sensor utilizing a complementary split ring resonator (CSRR). The sensor was modeled, manufactured and then characterized by measuring tailor made skin phantoms based on the realistic electrical properties of skin with different degrees of hydration status. Qualitative longer term (>24 h) evaluation of the sensor was also performed by measuring polyester tissue that was drying over the time. Hydration status, represented by dehydrated, normal and hydrated skin phantoms, based on polyurethane with carbon and ceramic additives, was measured successfully by monitoring the changes in resonance frequency around 5.52 GHz. All results were compared to the dielectric reference measurements done by a commercial laboratory instrument

    An agenda for rethinking mid-career master programs in public administration

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    The pace of societal change and the development of societal challenges have speeded up considerably during the last couple of decades, with substantial impact on different levels, i.e. ranging from global to local, or from business to government. When focusing on the public domain, these changes and challenges have had a major impact on public professionals, who face different and frequently changing questions. Mid-career programs in Public Administration (MPA) have the mission to support enrolled professionals in dealing with these changes and challenges. This article is about the development of such MPAs. Both substantive and didactic development is needed. To counter institutional inertia it seems vital to institutionalize a regular rethinking and adaptation of curricula and didactic strategies. This article identified some important points of attention and some options to deal with these in order to continuously improve the contribution of MPA programs to relevant and effective professional development and ongoing professional learning

    Using Routinely Collected Administrative Data in Public Health Research: Geocoding Alcohol Outlet Data

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    We describe our process of geocoding alcohol outlets to create a national longitudinal exposure dataset for Wales, United Kingdom from 2006 to 2011. We investigated variation in the availability of data items and the quality of alcohol outlet addresses held within unitary authorities. We used a standard geocoding method augmented with a manual matching procedure to achieve a fully spatially referenced dataset. We found higher quality addresses are held for outlets based in urban areas, resulting in the automatic geocoding of 68 % of urban outlets, compared to 48 % in rural areas. Missing postcodes and a lack of address structure contributed to a lower geocoding proportion. An urban rural bias was removed with the development of a manual matching procedure. Only one-half of the unitary authorities provided data on on/off sales and opening times, which are important availability factors. The resulting outlet dataset is suitable for contributing to the evidence-base of alcohol availability and alcohol-related harm. Local government should be encouraged to use standardised data fields, including addresses, to enable accurate geocoding of alcohol outlets and facilitate research that aims to prevent alcohol-related harm. Standardising data collection would enable efficient secondary data reuse using record linkage techniques, allowing the retrospective creation and evaluation of population-based natural experiments to provide evidence for policy and practice

    Identification of the Microsporidian Encephalitozoon cuniculi as a New Target of the IFNγ-Inducible IRG Resistance System

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    The IRG system of IFNγ-inducible GTPases constitutes a powerful resistance mechanism in mice against Toxoplasma gondii and two Chlamydia strains but not against many other bacteria and protozoa. Why only T. gondii and Chlamydia? We hypothesized that unusual features of the entry mechanisms and intracellular replicative niches of these two organisms, neither of which resembles a phagosome, might hint at a common principle. We examined another unicellular parasitic organism of mammals, member of an early-diverging group of Fungi, that bypasses the phagocytic mechanism when it enters the host cell: the microsporidian Encephalitozoon cuniculi. Consistent with the known susceptibility of IFNγ-deficient mice to E. cuniculi infection, we found that IFNγ treatment suppresses meront development and spore formation in mouse fibroblasts in vitro, and that this effect is mediated by IRG proteins. The process resembles that previously described in T. gondii and Chlamydia resistance. Effector (GKS subfamily) IRG proteins accumulate at the parasitophorous vacuole of E. cuniculi and the meronts are eliminated. The suppression of E. cuniculi growth by IFNγ is completely reversed in cells lacking regulatory (GMS subfamily) IRG proteins, cells that effectively lack all IRG function. In addition IFNγ-induced cells infected with E. cuniculi die by necrosis as previously shown for IFNγ-induced cells resisting T. gondii infection. Thus the IRG resistance system provides cell-autonomous immunity to specific parasites from three kingdoms of life: protozoa, bacteria and fungi. The phylogenetic divergence of the three organisms whose vacuoles are now known to be involved in IRG-mediated immunity and the non-phagosomal character of the vacuoles themselves strongly suggests that the IRG system is triggered not by the presence of specific parasite components but rather by absence of specific host components on the vacuolar membrane.Grants from the Deutsche Forschungsgemeinschaft: SFB635, 670, 680, SPP1399

    High-pressure autohydrolysis process of wheat straw for cellulose recovery and subsequent use in PBAT composites preparation

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    AbstractThe effect of autohydrolysis (AH) temperature (165 °C, 195 °C, 225 °C) on the structure, purity, and recovery yield of the cellulose residue isolated after additional alkaline and bleaching steps from wheat straw, was investigated. The processes were quantified for mass yields in the different steps and for antioxidants and sugars release during AH.AH at 195 °C allowed for the highest cellulose residue yield (83.5%) with purity (∼70%) and structure similar to the other residues. FTIR and XRD analyses showed straw cellulose (SC) with a type II polymorphism and crystallinity index increasing with AH temperature. SC obtained at the end of the entire fractionation process (SC-195 °C) starting from AH residue-195 °C was tested as a reinforcing agent in different percentage (0, 2 and 5% by weight) in poly(butylene adipate-co-terephthalate) (PBAT) films. The Young’s modulus of the films increased by ∼17% with 5 wt% cellulose, while tensile strength and elongation at break decreased.Abstract The effect of autohydrolysis (AH) temperature (165 °C, 195 °C, 225 °C) on the structure, purity, and recovery yield of the cellulose residue isolated after additional alkaline and bleaching steps from wheat straw, was investigated. The processes were quantified for mass yields in the different steps and for antioxidants and sugars release during AH. AH at 195 °C allowed for the highest cellulose residue yield (83.5%) with purity (∼70%) and structure similar to the other residues. FTIR and XRD analyses showed straw cellulose (SC) with a type II polymorphism and crystallinity index increasing with AH temperature. SC obtained at the end of the entire fractionation process (SC-195 °C) starting from AH residue-195 °C was tested as a reinforcing agent in different percentage (0, 2 and 5% by weight) in poly(butylene adipate-co-terephthalate) (PBAT) films. The Young’s modulus of the films increased by ∼17% with 5 wt% cellulose, while tensile strength and elongation at break decreased
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