Search results for "Hafnia"
showing 10 items of 13 documents
Genetic Diversity of O-Antigens in Hafnia alvei and the Development of a Suspension Array for Serotype Detection.
2016
Hafnia alvei is a facultative and rod-shaped gram-negative bacterium that belongs to the Enterobacteriaceae family. Although it has been more than 50 years since the genus was identified, very little is known about variations among Hafnia species. Diversity in O-antigens (O-polysaccharide, OPS) is thought to be a major factor in bacterial adaptation to different hosts and situations and variability in the environment. Antigenic variation is also an important factor in pathogenicity that has been used to define clones within a number of species. The genes that are required to synthesize OPS are always clustered within the bacterial chromosome. A serotyping scheme including 39 O-serotypes has…
Niobium enhanced europium ion luminescence in hafnia nanocrystals
2018
This work was supported by the UL ISSP grant for Scientific Research Projects for Students and Young Researchers SJZ/2016/15 .
Local structural investigation of hafnia-zirconia polymorphs in powders and thin films by X-ray absorption spectroscopy
2019
Björn Matthey (Fraunhofer IKTS, Dresden) is acknowledged for providing HfO2 and ZrO2 powders on short notice after DESY’s renowned customs office punished us. Parts of this research were carried out at Petra III at DESY, a member of the Helmholtz Association (HGF). The experiments on single Si:HfO2 thin film samples were performed at the CLAESS beamline at ALBA Synchrotron with the collaboration of ALBA staff. We would like to thank Edmund Welter for assistance (in using beamline P65) and DESY for enabling this research for proposal no. 20160591 and for travel support. T.S. acknowledges the German Research Foundation (DFG) for funding this work in the frame of the project “Inferox” (project…
New functional ligands for ficolin-3 among lipopolysaccharides of Hafnia alvei.
2011
Ficolin-1 (M), ficolin-2 (L), ficolin-3 (H) and mannan-binding lectin (MBL) activate the complement system and have opsonic activity. The specificity of ficolin-3 is poorly characterized and currently limited to a few ligands only. We present new specific targets for human ficolin-3, identified among lipopolysaccharides (LPSs, endotoxin) of Hafnia alvei. The interaction was restricted to LPSs of four strains: 23, Polish Collection of Microorganisms (PCM) 1200, PCM 1203 and PCM 1205 and limited to their O-specific polysaccharides (O-specific PSs) composed of different numbers of oligosaccharide (OS) repeating units (RUs). Moreover, these LPS/ficolin-3 complexes activated the lectin pathway o…
Novel O-antigen of Hafnia alvei PCM 1195 lipopolysaccharide with a teichoic acid-like structure
2009
Abstract The lipopolysaccharide (LPS) of Hafnia alvei strain PCM 1195 was obtained by the hot phenol/water method. The O-specific polysaccharide was released by mild acidic hydrolysis and isolated by gel filtration. The structure of the O-specific polysaccharide was investigated by 1 H, 13 C, and 31 P NMR spectroscopy, MALDI-TOF MS, and GC–MS, accompanied by monosaccharide and methylation analysis. It was concluded that the O-specific polysaccharide is composed of a hexasaccharide repeating units interlinked with a phosphate group: {→4-α- d -Glc p -(1→3)-α- l - Fuc p NAc-(1→3)-[α- d -Glc p -(1→4)]-α- d -Glc p NAc-(1→3)-α- l - Fuc p NAc-(1→4)-α- d -Glc p -(1→P} n .
Formation of anodic films on sputtering-deposited Al–Hf alloys
2009
Abstract The growth of barrier-type anodic films at high efficiency on a range of sputtering-deposited Al–Hf alloys, containing from 1 to 95 at.% Hf, has been investigated in ammonium pentaborate electrolyte. The alloys encompassed nanocrystalline and amorphous structures, the latter being produced for alloys containing from 26 to 61 at.% Hf. Except at the highest hafnium content, the films were amorphous and contained units of HfO 2 and Al 2 O 3 distributed relatively uniformly through the film thickness. Boron species were confined to outer regions of the films. The boron distributions suggest that the cation transport number decreases progressively with increasing hafnium concentration i…
Structural Stability of Hafnia-Based Materials at Ultra-High Temperature
2018
This study assesses the structural stability at ultra-high temperature of the following selected compositions: 6.5 and 14 mol. % of RE2O3 (RE = Dy, Y, Er, Yb, and Lu) doped HfO2. Under thermal cycling and thermal shock, the structural stability was evaluated at 2400°C with water vapor flux using a specific test bench with a 3 kW CO2 laser. The cubic phase stability, which is theoretically important in the broad temperature range from 25 to 2800°C, was determined by a quantitative analysis of the X-ray diffractograms. Fully and partially stabilized HfO2, obtained respectively with 14 mol. % and 6.5 mol. % of dopants, showed different behaviors to thermal damage. Thermal expansion was measure…
Z-Scan theory for thin film measurements: Validation of a model beyond the standard approach using ITO and HfO2
2023
The Z-Scan technique is an easy and widespread approach to evaluate the nonlinear optical coefficient of materials. However, the evaluation of the same coefficients for thin films requires complex experimental setups that allow to remove the contributions of the substrate. Here, we propose a simple, yet effective, theoretical approach that allows to include the substrate contribution to the focusing effect when scanning along the propagation axis. The proposed method therefore removes the need of complex experimental setups and paves the way for a simpler retrieval of optical properties of complex nanostructures.
Oxide or carbide nanoparticles synthesized by laser ablation of a bulk Hf target in liquids and their structural, optical, and dielectric properties
2016
International audience; Laser ablation of a bulk Hf target in deionized (DI) water, ethanol, or toluene was carried out for the production of nanoparticles' colloidal solutions. Due to the interaction of the ablation plasma plume species with the species which are produced by the liquid decomposition at the plume-liquid interface, hafnia (HfO2) nanoparticles are synthesized in DI water, hafnium carbide (HfC) nanoparticles in toluene, and a mixture of these in ethanol. The hafnia nanoparticles are in the monoclinic low temperature phase and in the tetragonal and fcc high temperature phases. Their size distribution follows log-normal function with a median diameter in the range of 4.3–5.3 nm.…
Photocurrent spectroscopy study of passive films on hafnium and hafnium–tungsten sputtered alloys
2003
Abstract Anodic and air-formed films on sputtered Hf and W–Hf alloys of different composition have been investigated by Rutherford back scattering, photocurrent spectroscopy (PCS) and transmission electron microscopy (TEM) techniques. In alkaline solutions the PCS data suggest the formation on Hf metal of a duplex layer with anodic hafnia covered by an external layer of composition close to HfO(OH) 2 . This last compound is also present on Hf air-formed films. In acidic solutions the initial oxy-hydroxide film disappears at high anodising potentials ( V f >10 V). In the case of W–Hf alloys films of different composition and semiconducting behaviour are formed by air exposure or by anodising…