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Made available in DSpace on 2019-10-06T16:32:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-09-15 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Percutaneous medical devices are prone to bacterial contamination that causes dramatic clinical conditions. At the percutaneous level of dental implant systems, microbial pathogens induce biofilm formation that may result in bone resorption and dental implant loss. In view of peri-implantitis caused by bacterial inflammation at the percutaneous abutment region, we here establish a novel drug release system based on layer-by-layer (LbL)-deposited poly(acrylic acid) (PAA) and poly-L-lysine (PLL) coatings on titanium (Ti). Detailed multilayer coating characterization was performed by different microscopy and spectroscopy techniques to probe physical and chemical properties. Our data revealed a significant difference in roughness average between ten double layers coated (141 nm ±30) and uncoated Ti discs (115 nm ±40). Although roughness of the coatings increased significantly after immersion in water for 24 h at 37 °C, this physical property remained below 200 nm. Coating stability was confirmed under neutral and acidic pH, mimicking healthy and diseased/inflammatory environments, respectively. LbL coatings supported in vitro human keratinocytes growth, demonstrating absence of cytotoxic effects. Tetracycline (TC) showed an initial burst release under neutral and acidic conditions, which further demonstrated robust antibacterial efficacy against Porphyromonas gingivalis. However, a convenient pH-dependent 2-folds increase in TC release was observed for coatings incubated at pH = 4.5. Sustained TC release was observed from coatings up till 15 days of incubation in both pH conditions. These results demonstrate the potential application of this simple surface modification to leverage anti-bacterial efficacy at the percutaneous abutment region. Regenerative Biomaterials Radboudumc, Philips van Leydenlaan 25 Department of Dental Materials and Prosthodontics School of Dentistry at Araraquara Sao Paulo State University (Unesp), Humaita, Sao Paulo Department of Tumor Immunology Radboudumc and Radboud Institute for Molecular Life Sciences (RIMLS), Geert Grooteplein Zuid Department of Preventive Dentistry Academic Centre for Dentistry Amsterdam (ACTA) University of Amsterdam and Vrije Universiteit Amsterdam, Gustav Mahlerlaan Department of Organic Chemistry Radboud University, Heyendaalseweg 135 Faculty of Applied Sciences Delft University of Technology, Lorentzweg 1 Department of Dental Materials and Prosthodontics School of Dentistry at Araraquara Sao Paulo State University (Unesp), Humaita, Sao Paulo FAPESP: 2015/03567-7 FAPESP: 2016/19650-3

In-situ Neutron Diffraction and Small-Angle Neutron Scattering (SANS) are employed for the first time simultaneously in order to reveal the interaction between the austenite to ferrite phase transformation and the precipitation kinetics during isothermal annealing at 650 and at 700 °C in three steels with different vanadium (V) and carbon (C) concentrations. Austenite-to-ferrite phase transformation is observed in all three steels at both temperatures. The phase transformation is completed during a 10 h annealing treatment in all cases. The phase transformation is faster at 650 than at 700 °C for all alloys. Additions of vanadium and carbon to the steel composition cause a retardation of the phase transformation. The effect of each element is explained through its contribution to the Gibbs free energy dissipation. The austenite-to-ferrite phase transformation is found to initiate the vanadium carbide precipitation. Larger and fewer precipitates are detected at 700 than at 650 °C in all three steels, and a larger number density of precipitates is detected in the steel with higher concentrations of vanadium and carbon. After 10 h of annealing, the precipitated phase does not reach the equilibrium fraction as calculated by ThermoCalc. The external magnetic field applied during the experiments, necessary for the SANS measurements, causes a delay in the onset and time evolution of the austenite-to-ferrite phase transformation and consequently on the precipitation kinetics.

The precipitation kinetics of vanadium carbides and its interaction with the austenite-to-ferrite phase transformation is studied in two micro-alloyed steels that differ in vanadium and carbon concentrations by a factor of two, but have the same vanadium-to-carbon atomic ratio of 1:1. Dilatometry is used for heat-treating the specimens and studying the phase transformation kinetics during annealing at isothermal holding temperatures of 900, 750 and 650 °C for up to 10 h. Small-Angle Neutron Scattering (SANS) and Atom Probe Tomography (APT) measurements are performed to study the vanadium carbide precipitation kinetics. Vanadium carbide precipitation is not observed after annealing for 10 h at 900 and 750 °C, which is contrary to predictions from thermodynamic equilibrium calculations. Vanadium carbide precipitation is only observed during or after the austenite-to-ferrite phase transformation at 650 °C. The precipitate volume fraction and mean radius continuously increase as holding time increases, while the precipitate number density starts to decrease after 20 min, which corresponds to the time at which the austenite-to-ferrite phase transformation is finished. This indicates that nucleation and growth are dominant during the first 20 min, while later precipitate growth with soft impingement (overlapping diffusion fields) and coarsening take place. APT shows gradual changes in the precipitate chemical composition during annealing at 650 °C, which finally reaches a 1:1 atomic ratio of vanadium-to-carbon in the core of the precipitates after 10 h.

[Image: see text] Nanostructured metal hydrides are able to efficiently detect hydrogen in optical sensors. In the literature, two nanostructured systems based on metal hydrides have been proposed for this purpose each with its own detection principle: continuous sub-100 nm thin films read out via optical reflectance/transmittance changes and nanoparticle arrays for which the detection relies on localized surface plasmon resonance. Despite their apparent similarities, their optical and structural response to hydrogen has never been directly compared. In response, for the case of Pd(1–y)Au(y) (y = 0.15–0.30) alloys, we directly compare these two systems and establish that they are distinctively different. We show that the dissimilar optical response is not caused by the different optical readout principles but results from a fundamentally different structural response to hydrogen due to the different nanostructurings. The measurements empirically suggest that these differences cannot be fully accounted by surface effects but that the nature of the film–substrate interaction plays an important role and affects both the hydrogen solubility and the metal-to-metal hydride transition. In a broader perspective, our results establish that the specifics of nanoconfinement dictate the structural properties of metal hydrides, which in turn control the properties of nanostructured devices including the sensing characteristics of optical hydrogen sensors and hydride-based active plasmonic systems.

The fact that a neutron possesses a spin can be used to develop devices to manipulate the polarization of the neutron beam in such a way that much higher resolution (in energy and/or wave vector) can be obtained, without sacrificing intensity. An example of this application is the neutron-spin echo technique. It has been used for several decades for inelastic neutron scattering, where a resolution can be obtained down to the neV range (or times up to several tens of ns) [1]. Since the end of last century, a new application has matured, i.e., the use of spin-echo techniques to label small scattering angles, down to several microradians; see [2,3]. In the preceding paper [4], the application of the spin-echo technique in small-angle scattering is described for the Delft setup, where a monochromatic beam is used (SESANS). Here we will describe a technical solution for a polychromatic beam that will be used in the neutron reflectometer OffSpec for the second target-station at ISIS, which is planned to be oper...

Using precession devices with tilted interfaces with respect to the polarised neutron beam enables measurement of structures by scattering. The scattering techniques can be small-angle neutron scattering, neutron diffraction and both specular and non-specular neutron reflectivity. We describe in this article all these techniques in a real-space concept. In all the techniques this concept describes in which direction structural information is obtained. In some cases the concept shows directly how to interpret the measured data in real-space.

Nanostructuring is widely applied in both battery and hydrogen materials to improve the performance of these materials as energy carriers. Nanostructuring changes the diffusion length as well as the thermodynamics of materials. We studied the impact of nanostructuring on the hydrogenation in a model system consisting of a thin film of magnesium sandwiched between two titanium layers and capped with palladium. While we verified optically the coexistence of the metallic α-MgDx and the insulating β-MgD2–y phase, neutron reflectometry shows significant deviations from the thermodynamic solubility limits in bulk magnesium during the phase transformation. This suggests that the kinetics of the phase transformation in nanostructured battery and hydrogen storage systems is enhanced not only as a result of the reduced length scale but also due to the increased solubility in the parent phases.

The phase-object approximation for neutron scattering is applied to determine the real-space sample correlation function for a sphere for kinematic and dynamic scattering. The sample correlation function determined in this way corresponds to the kinematic and refraction limits.

The phase-object approximation for neutron scattering based on a one-dimensional dynamic forward scattering theory is discussed and used to calculate the differential cross section of an object. It is shown that this approximation is valid in ultra-small-angle neutron scattering (USANS) and spin-echo small-angle neutron scattering (SESANS) experiments on silicon gratings. In the weak scattering limit, the phase-object approximation reduces to the kinematic or first Born approximation. The spatial coherence function is used to describe instrumental resolution effects. Measurements on three different instruments are in good agreement with calculation results. In the experiment with a time-of-flight SESANS instrument, the effect ofPendellösungwith object size is observed.

Addition of TiO2 nanoparticles (25 nm) to lithium-diglyme causes only minor changes to the molecular vibrations of the diglyme species in the spectral region that is diagnostic of the diglyme conformation. In the low-frequency region, however, the spectrum of lithium diglyme without nanoparticles shows evidence of considerable dispersion, which is removed on addition of nanoparticles. It seems likely that nanoparticles improve the conductivity of polymer electrolytes via an interaction with the ions rather than with the polymer.

Intercalation of Li in TiO2 anatase results in a phase separation in a Li-poor and a Li-rich phase. The local lithium configuration in the coexisting crystallographic phases is resolved by detailed analysis of neutron diffraction data. In each of the phases, two distinct positions within the octahedral interstices are found, with a temperature-dependent occupancy. A combination of quasi-elastic neutron scattering and force field molecular dynamics simulations shows that Li is hopping on a picosecond time scale between the two sites in the octahedral interstices. The results also suggest a specific Li arrangement along the crystallographic a direction, albeit without long range order. It is likely that multiple discrete Li sites within a distorted oxygen octahedron occur not only in intercalated TiO2 anatase but also in other (transition metal) oxides.

We investigate the microscopic structure and density fluctuations of complex coacervates of flexible polyelectrolytes using scattering of neutrons, X-rays, and light. Poly(acrylic acid) and poly(N,N-dimethylaminoethyl methacrylate) offer a well-defined model system that allows for selective labeling and systematic variation of the strength of the attractive electrostatic interactions. Two neutron scattering experiments have been carried out: (i) we use deuterated polymeric tracers in a complex coacervate with an overall neutron scattering length density that is matched to that of the solvent, to probe the conformation of single polymer chains in the complex coacervates, and (ii) we measure complex coacervates in which all polymer chains of one type are deuterated, to probe their overall structure. The single chain static structure factors reveal that both polycations and polyanions have an ideal Gaussian chain conformation in the complex coacervates. At the same time, the overall structure is similar to that of a semidilute polymer solution, with polycations and polyanions strongly overlapping to form a network with a mesh size that is much smaller than the radius of gyration of the polymers. The mesh size decreases with decreasing salt concentration, following a scaling that is in good agreement with predictions from the corresponding salt–polymer phase diagram. These findings are confirmed by complementary X-ray scattering experiments. Finally, in all scattering experiments with light, X-rays, and neutrons, and for all polymer chain lengths and salt concentrations, we find a remarkable low-q excess scattering, following a power law with a slope close to -2. This points to the presence of equilibrium, large-scale density fluctuations in the complex coacervates. Dynamic light scattering experiments reveal two complementary diffusive modes in the complex coacervates, corresponding to fluctuations of the polymer mesh and diffusion of domains of varying density, respectively

Based on the application of coherence theory to neutron scattering a description is given of the propagation of neutrons or x-rays through a reflectometer. Important coherence effects at the sample position are discussed. Further, an outline is given how to determine the measured count rate in a detector on the basis of this method including neutron-polarization effects. It is shown in what way the Born approximation and distorted-wave Born approximation can be used within this theory. An outline is given of the phase-object approximation, describing the specular and diffuse scattering from a surface with large surface structure, extending over the existing capabilities of the distorted-wave Born approximation. The incorporation of neutron-polarization effects enables the detailed discussion of neutron spin-echo coding techniques applied to reflectometry.

The Goos-Hänchen effect is a spatial shift along an interface resulting from an interference effect that occurs for total internal reflection. This phenomenon was suggested by Sir Isaac Newton, but it was not until 1947 that the effect was experimentally observed by Goos and Hänchen. We provide the first direct, absolute, experimental determination of the Goos-Hänchen shift for a particle experiencing a potential well as required by quantum mechanics: namely, wave-particle duality. Here, the particle is a spin-polarized neutron reflecting from a film of magnetized material. We detect the effect through a subtle change in polarization of the neutron. Here, we demonstrate, through experiment and theory, that neutrons do exhibit the Goos-Hänchen effect and postulate that the associated time shift should also be observable.

A two-dimensional position-sensitive neutron detector (PSD) was constructed using a scintillator attached to a position-sensitive photo-multiplier with 100 mm diameter. Position determination is based on charge division. Spatial resolution, gamma sensitivity, linearity, temperature dependence and radiation shielding have been investigated. The shaping amplifiers used in the detection electronics were optimized. Two kinds of scintillators were examined: LiI(Eu) crystal and Li-glass. Concerning the gamma sensitivity and resolution, the best performance was obtained using the LiI. A spatial resolution with full width half maximum of 1.3(1) mm was measured. A good shielding against gamma radiation was found to consist out of three layers: 5 mm of boron rubber, 5 cm of lead and 5 mm of boron rubber. The influence of the temperature on the PSD signal output was measured and indicates that a stabilization is necessary. The PSD will be used in a time-of-flight neutron reflectometer.

Interuniversitair Reactor Instituut, 2629 JB, Delft, The Netherlands In addition to previously published neutron scattering experiments on liquid argon at 120 K and four pressures up to 400 bar, more data are obtained at 120 K and 19.5, 266.6 and 844 bar. The data at the two lower pressures have been used to check the consistency of the two sets of measurements. The data at 844 bar have been analyzed in terms of three extended hydrodynamic modes for wave numbers 4.2 ≤ k ≤ 22.2 nm-1. Within the experimental error no anomalous dispersion is visible. The sound propagation gap, previously found in liquid argon, neon and computer simulations at liquid densities, decreases with density and disappears completely close to solidification. This has been confirmed by a computer simulation of a Lennard-Jones liquid.

A description is given of a system of computer programs to calculate the dynamic structure factor from thermal neutron scattering time-of-flight measurements. A high degree of flexibility is obtained, in order to suit different demands of various experiments. Each program, as well as the data organisation, is described separately. The general applicability will be illustrated with two case histories: an experiment on liquid argon to obtain accurate data on the dynamic structure factor and an experiment on solid NH4MnCl3 to obtain information on the rotational motions of the NH4-group.

The properties of a filter consisting of a 3 m long parallel stacking of curved glass plates covered with 58Ni are calculated. It is demonstrated that for thermal and cold neutrons (λ > 0.15 nm) this filter is a considerable improvement on conventional materials such as beryllium, silicon, sapphire or pyrolytic graphite.

We report the results of measurements of the static structure factor S(\ensuremath{\kappa}) for gaseous $^{36}\mathrm{Ar}$ at 140 K and four (subcritical) low densities from which, for the first time, we derive the well of the isotropic pair potential directly by means of a simple Fourier transform inversion.

We argue that the narrowing at increasing densities of the light spectra obtained for Ar and Kr by An et al.(J. Chem. Phys., 1979, 70, 4626) using depolarized interaction-induced light scattering techniques is due to the slowing down of structural relaxation in dense fluids which is observed in neutron scattering experiments on He, Kr, Ar and Rb.