Determination of the packing fraction in photonic glass using synchrotron radiation nanotomography

Photonic glass is a material class that can be used as photonic broadband reflectors, for example in the infrared regime as thermal barrier coating films. Photonic properties such as the reflectivity depend on the ordering and material packing fraction over the complete film thickness of up to 100 μm. Nanotomography allows acquiring these key parameters throughout the sample volume at the required resolution in a non-destructive way. By performing a nanotomography measurement at the PETRA III beamline P05 on a photonic glass film, the packing fraction throughout the complete sample thickness was analyzed. The results showed a packing fraction significantly smaller than the expected random close packing giving important information for improving the fabrication and processing methods of photonic glass material in the future

Photocatalytic oxidation of volatile organic compounds in indoor air

Two frequently occurring volatile organic compounds (VOCs), trichloroethylene (TCE) and acetaldehyde were oxidised in a heterogeneous flat bed flow reactor over a titanium dioxide (TiO₂) catalyst illuminated by near ultraviolet light. The kinetics of the photooxidation, the effect of mass transfer resistance and the photoefficiency were investigated. The effects of moisture content and residence time on the percentage of TCE oxidised to CO and CO₂ were studied. A maximum reaction rate of 19.1 μmol min^-1 g^-1 TiO₂ for TCE and 8.6 μmol min^-1 g^-1 TiO₂ for acetaldehyde was observed. For a residence time of less than 3 minutes, (330 ml min^-1 airflow), 100 ppm VOC, 2000 ppm H₂O, 2.0 mW cm^-2 light intensity and 0.6 g TiO₂, 98% of the TCE and 69% of the acetaldehyde were converted

In Our Own Words: Native Impressions—It Helped Us to Breathe

The pair of original prints is from the “In Our Own Words: Native Impressions” portfolio. Focused on individuals from the Tribal Nations of North Dakota, this collaborative project was intended to chronicle lives of contemporary Native American people through a series of original artworks. Four North Dakota tribal colleges hosted visits from two UND art professors, Kim Fink and Lucy Ganje, as well as Philadelphia artist Daniel Heyman and Leigh Jeanotte, a member of the Turtle Mountain Band of Chippewa and Director of UND\u27s American Indian Student Services. During these visits, they talked with twelve tribal members, while Heyman drew their portraits. Produced by Sundog Multiples at the University of North Dakota, the portfolio contains twelve reduction woodblock prints based on the portraits by Heyman, along with fourteen letterpress prints by Ganje that contain words taken from interviews. The production of the prints was overseen by Fink.https://commons.und.edu/lam-all/1170/thumbnail.jp

Cross-Linked Gold Nanoparticles on Polyethylene: Resistive Responses to Tensile Strain and Vapors

In this study, coatings of cross-linked gold nanoparticles (AuNPs) on flexible polyethylene (PE) substrates were prepared via layer-by-layer deposition and their application as strain gauges and chemiresistors was investigated. Special emphasis was placed on characterizing the influence of strain on the chemiresistive responses. The coatings were deposited using amine stabilized AuNPs (4 and 9 nm diameter) and 1,9-nonanedithiol (NDT) or pentaerythritol tetrakis­(3-mercaptopropionate) (PTM) as cross-linkers. To prepare films with homogeneous optical appearance, it was necessary to treat the substrates with oxygen plasma directly before film assembly. SEM images revealed film thicknesses between ∼60 and ∼90 nm and a porous nanoscale morphology. All films showed ohmic I-V characteristics with conductivities ranging from 1 × 10^–4 to 1 × 10^–2 Ω^–1 cm^–1, depending on the structure of the linker and the nanoparticle size. When up to 3% strain was induced their resistance increased linearly and reversibly (gauge factors: ∼20). A comparative SEM investigation indicated that the stress induced formation and extension of nanocracks are important components of the signal transduction mechanism. Further, all films responded with a reversible increase in resistance when dosed with toluene, 4-methyl-2-pentanone, 1-propanol or water vapor (concentrations: 50–10 000 ppm). Films deposited onto high density PE substrates showed much faster response-recovery dynamics than films deposited onto low density PE. The chemical selectivity of the coatings was controlled by the chemical nature of the cross-linkers, with the highest sensitivities (∼1 × 10^–5 ppm^–1) measured with analytes of matching solubility. The response isotherms of all film/vapor pairs could be fitted using a Langmuir–Henry model suggesting selective and bulk sorption. Under tensile stress (1% strain) all chemiresistors showed a reversible increase in their response amplitudes (∼30%), regardless of the analytes’ permittivity. Taking into consideration the thermally activated tunneling model for charge transport, this behavior was assigned to stress induced formation of nanocracks, which enhance the films’ ability to swell in lateral direction during analyte sorption

Elastic and Viscoelastic Properties of Cross-Linked Gold Nanoparticles Probed by AFM Bulge Tests

To enable applications of nanoparticle films in flexible electronics, actuators, and sensors, their mechanical properties are of critical concern. Here, we demonstrate that the elastic and viscoelastic properties of covalently cross-linked gold nanoparticles (GNPs) can be probed using AFM bulge tests. For this purpose 30–60 nm thick films consisting of 1,9-nonanedithiol (NDT) cross-linked GNPs (3.8 nm core diameter) were transferred onto substrates with ∼100 μm circular apertures. The resulting freestanding membranes were bulged by applying pressure differences of up to 10 kPa, and the deflection was measured by intermittent contact atomic force microscopy (AFM). Analyzing the pressure-deflection data using the spherical cap model, either by taking into account the peak deflection values or the measured arc profiles of the bulge, yielded 2.3 ± 0.3 and 2.7 ± 0.4 GPa for Young’s modulus, respectively. When cycling the stress–strain measurements at overpressures up to 2.4 kPa, hysteresis was observed and assigned to viscoelastic effects. Creep tests performed at a pressure of 2 kPa revealed both viscoelastic retardation (time constant: 3.3 × 10^–3 s^–1) and nonrecoverable relaxation (creep rate: 9.0 × 10^–8 s^–1). Several membranes resisted pressures up to 10 kPa without fracturing, indicating that the ultimate biaxial tensile strength of the films was above ∼30 MPa

Layout and first results of the nanotomography endstation at the P05 beamline at PETRA III

The Helmholtz-Zentrum Geesthacht operates the P05 Imaging Beamline at the DESY storage ring PETRA III. This beamline is dedicated to micro- and nanotomography with two endstations. This paper will present the nanotomography endstation layout and first results obtained from commissioning and test experiments.First tests have been performed with CRLs as X-ray objectives and newly developed rolled X-ray prism lenses as condenser optics. This setup allows a resolution of 100 nm half period with an effective detector pixel size of 15nm. A first tomograph of a photonic glass sample was measured in early 2014

Synthesis and thermal stability of zirconia and yttria-stabilized zirconia microspheres

Zirconia microparticles produced by sol-gel synthesis have great potential for photonic applications. To this end, identifying synthetic methods that yield reproducible control over size uniformity is mportant. Phase transformations during thermal cycling can disintegrate the particles. Therefore, understanding the parameters driving these transformations is essential for enabling high-temperature applications. Particle morphology is expected to influence particle processability and stability. Yttria-doping should improve the thermal stability of the particles, as it does in bulk zirconia

Pressure induced local phase transformation in nanocrystalline tetragonal zirconia microparticles

Mechanical properties and local martensitic phase transformation of individual nanocrystalline zirconia microspheres were assessed by complementary (in situ) electron microscopy techniques. Particles were deformed by compression in a SEM and the local structure was determined by ex situ SAED of a FIB prepared lamella. The local texture and amount of transformed grains can be explained by a continuum-like behavior modelled by FEM calculations: The phase transformation is found for grains which are preferentially oriented with respect to the deviatoric stresses and show the rotation of the maximum shear stress during the experiment

"Pulmonary Nocardiosis in Western Europe-Clinical evaluation of 43 patients and population-based estimates of hospitalization rates".

BACKGROUND Pulmonary nocardiosis (PN) is an uncommon but potentially life-threatening infection. Most of our knowledge is derived from case reports or smaller case series. Recently, increasing PN incidence rates have been reported. We aim to describe the clinical course of and risk factors for PN in four Western European countries and to estimate population-based annual hospitalization rates. METHODS Retrospective evaluation (1995 to 2011) of the clinical course of and risk factors for PN in patients from 11 hospitals in four European countries (Germany, Austria, Switzerland and The Netherlands). Calculation of population-based estimates of hospitalization rates of PN in Germany (2005 to 2011) using official German nationwide diagnosis-related groups (DRG) hospital statistics. RESULTS Forty-three patients fulfilled stringent criteria for proven (n=8) and probable (n=35) PN; seven with extrapulmonary dissemination. Within the 43 patients, major PN risk factors were immunocompromising (83.7%) and/or pulmonary (58.1%; in 27.9% as only comorbidity) comorbidities. Median duration of PN targeted therapy was 12 weeks. Distinguished patterns of resistance were observed (imipenem susceptibility: N. farcinica 33.3%; N. asteroides 66.7%). Overall mortality rate was 18.9%; in disseminated PN 50%. Over time, annual PN hospitalization rates remained unchanged at around 0.04/100'000 with the highest rate among men aged 75-84 years (0.24/100'000). CONCLUSION PN is rare, but potentially life-threatening, and mainly affects immunocompromised elder males. Overall annual hospitalization rates remained stable between 2005 and 2011