In some approaches, the experimental data are peptide molecular weights from the digestion of a protein by an enzyme. Still others combine mass data with amino acid sequence data.
We present results from a new computer program, Mascot, which integrates all three types of search. The scoring algorithm is probability based, which has a number of advantages: i A simple rule can be used to judge whether a result is significant or not. This is particularly useful in guarding against false positives. Volume 20 , Issue If you do not receive an email within 10 minutes, your email address may not be registered, and you may need to create a new Wiley Online Library account.
If the address matches an existing account you will receive an email with instructions to retrieve your username. David N. Darryl J. Pappin Corresponding Author E-mail address: d. David M. Creasy Matrix Science Ltd. A comprehensive summary of investigated alloys and cluster algorithm parameters is given. Moreover, the findings in AlMgSi alloys regarding clusters and changes upon different heat treatments are discussed, starting from early to the latest works. We investigate the effect of various spherical nanoparticles in a polymer matrix on dispersion, chain dimensions and entanglements for ionic nanocomposites at dilute and high nanoparticle loading by means of molecular dynamics simulations.
The nanoparticle dispersion can be achieved in oligomer matrices due to the presence of electrostatic interactions. We show that the overall configuration of ionic oligomer chains, as characterized by their radii of gyration, can be perturbed at dilute nanoparticle loading by the presence of charged nanoparticles. The charged nanoparticles are found to move by a hopping mechanism. There are various ways of immobilizing carbonic anhydrase CA on solid materials.
The immobilization method investigated allows a straightforward, stable, and quantifiable immobilization of bovine erythrocyte carbonic anhydrase BCA on silicate surfaces. In all three cases, the immobilized enzyme was highly active and stable when tested with p-nitrophenyl acetate as a model enzyme substrate at room temperature. The micropipettes and the glass fiber filters were applied as flow-through systems for continuous operation at room temperature.
In the case of the glass fiber filters, the filters were placed inside a homemade flow-through filter holder which allows flow-through runs with more than one filter connected in series. This offers the opportunity of increasing the substrate conversion by increasing the number of BCA-containing filters.
Using x-ray magnetic nanotomography the internal magnetization structure within extended samples can be determined with high spatial resolution and element specificity, without the need for assumptions or prior knowledge of the magnetic properties of a sample. Here we present the details of a new algorithm for the reconstruction of a three-dimensional magnetization vector field, discussing both the mathematical description of the problem, and details of the gradient-based iterative reconstruction routine.
To test the accuracy of the algorithm the method is demonstrated for a complex simulated magnetization configuration obtained from micromagnetic simulations. The reconstruction of the complex three-dimensional magnetic nanostructure, including the surroundings of magnetic singularities or Bloch points , exhibits an excellent qualitative and quantitative agreement with the simulated magnetic structure.
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This method provides a robust route for the reconstruction of internal three-dimensional magnetization structures obtained from x-ray magnetic tomographic datasets, which can be acquired with either hard or soft x-rays, and can be applied to a wide variety of three-dimensional magnetic systems.
Poly phenylene methylene s PPMs with high molar masses were isolated by polymerization of benzyl chloride catalyzed with tungsten II compounds and subsequent fractionation. Four different tungsten II catalysts were successfully exploited for the polymerization, for which a strict temperature profile was developed. The PPMs possessed roughly a trimodal molar mass distribution. The evolution of the trimodal distribution and the monomer conversion was monitored by gel permeation chromatography GPC and 1H NMR spectroscopy, respectively, over the course of the polymerization.
The results revealed that polymerization proceeded via a chain-growth mechanism. This study illustrates a new approach to synthesize PPM with hitherto unknown high molar masses which opens the possibility to explore new applications, e. Poly phenylene methylene PPM is a thermally stable, hydrophobic, fluorescent hydrocarbon polymer. PPM has been proposed earlier to be useful as a coating material but this polymer was isolated in relevant molar masses only recently, and in large quantities.
Accordingly, the preparation of coatings based on PPM and their behavior was explored in this study, with the example of the metal alloy AA as a common substrate for corrosion tests. Coatings free of bubbles and cracks were obtained by hot pressing and application of the following steps: Coating on AA with a layer of polybenzylsiloxane to improve the adhesion between PPM and the metal surface, the addition of polybenzylsiloxane to PPM in order to enhance the viscosity of the molten PPM, and the addition of benzyl butyl phthalate as a plasticizer.
Electrochemical corrosion tests showed good protection of the metal surface towards a NaCl solution, thanks to a passive-like behavior in a wide potential window and a very low current density. Remarkably, the PPM coating also exhibited self-healing towards localized attacks, which inhibits the propagation of corrosion. The vacancies produced in high energy collision cascades of irradiated tungsten can form vacancy clusters or prismatic vacancy dislocation loops. Moreover, vacancy loops can easily transform into planar vacancy clusters. We investigated the formation energies of these three types of vacancy defects as a function of the number of vacancies using three embedded-atom method tungsten potentials.
The most favorable defect type and vacancy loop stability was determined. For very small sizes the planar vacancy cluster is more favorable than a vacancy loop, which is unstable. The void is the most stable vacancy defect up to quite large size, after that vacancy dislocation loop is more favorable. We conclude that the vacancy dislocation loops are nevertheless hlmetastable at low temperatures as the transformation to voids would need high temperature, in contrast to previous works, which found planar vacancy clusters to have lower energy than vacancy dislocation loops.
The occurrence of the inverse or negative electrocaloric effect, where the isothermal application of an electric field leads to an increase in entropy and the removal of the field decreases the entropy of the system under consideration, is discussed and analyzed. Inverse electrocaloric effects have been reported to occur in several cases, for example, at transitions between ferroelectric phases with different polarization directions, in materials with certain polar defect configurations, and in antiferroelectrics. This counterintuitive relationship between entropy and applied field is intriguing and thus of general scientific interest.
The combined application of normal and inverse effects has also been suggested as a means to achieve larger temperature differences between hot and cold reservoirs in future cooling devices. A good general understanding and the possibility to engineer inverse caloric effects in terms of temperature spans, required fields, and operating temperatures are thus of fundamental as well as technological importance. Here, the known cases of inverse electrocaloric effects are reviewed, their physical origins are discussed, and the different cases are compared to identify common aspects as well as potential differences.
In all cases the inverse electrocaloric effect is related to the presence of competing phases or states that are close in energy and can easily be transformed with the applied field. Two-dimensional magnetic systems with continuous spin degrees of freedom exhibit a rich spectrum of thermal behaviour due to the strong competition between fluctuations and correlations. When such systems incorporate coupling via the anisotropic dipolar interaction, a discrete symmetry emerges, which can be spontaneously broken leading to a low-temperature ordered phase.
However, the experimental realisation of such two-dimensional spin systems in crystalline materials is difficult since the dipolar coupling is usually much weaker than the exchange interaction. Here we realise two-dimensional magnetostatically coupled XY spin systems with nanoscale thermally active magnetic discs placed on square lattices. Using low-energy muon-spin relaxation and soft X-ray scattering, we observe correlated dynamics at the critical temperature and the emergence of static long-range order at low temperatures, which is compatible with theoretical predictions for dipolar-coupled XY spin systems.
Furthermore, by modifying the sample design, we demonstrate the possibility to tune the collective magnetic behaviour in thermally active artificial spin systems with continuous degrees of freedom. Significantly, this approach is scalable ca. We investigate the zero-temperature limit of thermodynamic quantum master equations that govern the time evolution of density matrices for dissipative quantum systems.
We discuss some implications of that observation for dissipative quantum field theory. This study presents a unique Mg-based alloy composition in the Mg—Zn—Yb system which exhibits bulk metallic glass, metastable icosahedral quasicrystals iQCs , and crystalline approximant phases in the as-cast condition. Microscopy revealed a smooth gradual transition from glass to QC.
We also report the complete melting of a metastable eutectic phase mixture including a QC phase , generated via suppression of the metastable-to-stable phase transition at high heating rates using fast differential scanning calorimetry FDSC. The melting temperature and enthalpy of fusion of this phase mixture could be measured directly, which unambiguously proves its metastability in any temperature range.
The kinetic pathway from liquid state to stable solid state an approximant phase minimizes the free-energy barrier for nucleation through an intermediate state metastable QC phase because of its low solid—liquid interfacial energy. At high undercooling of the liquid, where diffusion is limited, another approximant phase with near-liquid composition forms just above the glass-transition temperature. These experimental results shed light on the competition between metastable and stable crystals, and on glass formation via system frustration associated with the presence of several free-energy minima.
Surface roughness affects many properties of colloids, from depletion and capillary interactions to their dispersibility and use as emulsion stabilizers. It also impacts particle—particle frictional contacts, which have recently emerged as being responsible for the discontinuous shear thickening DST of dense suspensions. Tribological properties of these contacts have been rarely experimentally accessed, especially for nonspherical particles. Here, we systematically tackle the effect of nanoscale surface roughness by producing a library of all-silica, raspberry-like colloids and linking their rheology to their tribology.
Rougher surfaces lead to a significant anticipation of DST onset, in terms of both shear rate and solid loading. Strikingly, they also eliminate continuous thickening. Direct measurements of particle—particle friction therefore highlight the value of an engineering-tribology approach to tuning the thickening of suspensions. This study investigates the crystallization and phase transition behavior of the amorphous metallic alloy Au70Cu5. This alloy has been recently shown to exhibit a transition of a metastable to a more stable crystalline state, occurring via metastable melting under strong non-equilibrium conditions.
Such behavior had so far not been observed in other metallic alloys. In this investigation fast differential scanning calorimetry FDSC is used to explore crystallization and the solid—liquid—solid transition upon linear heating and during isothermal annealing, as a function of the conditions under which the metastable phase is formed.
It is shown that the occurrence of the solid—liquid—solid transformation in FDSC depends on the initial conditions; this is explained by a history-dependent nucleation of the stable crystalline phase. The microstructure was investigated by scanning and transmission electron microscopy and x-ray diffraction. Chemical mapping was performed by energy dispersive x-ray spectrometry. The relationship between the microstructure and the phase transitions observed in FSDC is discussed with respect to the possible kinetic paths of the solid—liquid—solid transition, which is a typical phenomenon in monotropic polymorphism.
We report an electric-field poling study of the geometrically-driven improper ferroelectric h-ErMnO3. From a detailed dielectric analysis, we deduce the temperature and the frequency dependent range for which single-crystalline h-ErMnO3 exhibits purely intrinsic dielectric behaviour, i. Special emphasis is put on frequency dependent polarisation switching, which is explained in terms of domain-wall movement similar to proper ferroelectrics. Controlling the domain walls via electric fields brings us an important step closer to their utilization in domain-wall-based electronics.
The magnetic anisotropy and exchange coupling between spins localized at the positions of 3d transition metal atoms forming two-dimensional metal—organic coordination networks MOCNs grown on a Au metal surface are studied. We explain these observations using both a model Hamiltonian based on mean-field Weiss theory and density functional theory calculations that include spin—orbit coupling.
Our main conclusion is that the antiferromagnetic coupling between Mn spins and the in-plane magnetization of the Mn spins can be explained by neglecting effects due to the presence of the Au surface, while for Ni—TCNQ the metal surface plays a role in determining the absence of magnetic anisotropy in the system. We develop the basic ideas and equations for the BRST quantization of Yang-Mills theories in an explicit Hamiltonian approach, without any reference to the Lagrangian approach at any stage of the development.
We present a new representation of ghost fields that combines desirable self-adjointness properties with canonical anticommutation relations for ghost creation and annihilation operators, thus enabling us to characterize the physical states on a well-defined Fock space. The Hamiltonian is constructed by piecing together simple BRST invariant operators to obtain a minimal invariant extension of the free theory. It is verified that the evolution equations implied by the resulting minimal Hamiltonian provide a quantum version of the classical Yang-Mills equations.
The modifications and requirements for the inclusion of matter are discussed in detail. In this work, ultra-small europium-doped HfO2 nanoparticles were infiltrated into native wood and used as trackers for studying penetrability and diffusion pathways in the hierarchical wood structure. The high electron density, laser induced luminescence, and crystallinity of these particles allowed for a complementary detection of the particles in the cellular tissue.
Confocal Raman microscopy and high-resolution synchrotron scanning wide-angle X-ray scattering WAXS measurements were used to detect the infiltrated particles in the native wood cell walls. This approach allows for simultaneously obtaining chemical information of the probed biological tissue and the spatial distribution of the integrated particles. The in-depth information about particle distribution in the complex wood structure can be used for revealing transport pathways in plant tissues, but also for gaining better understanding of modification treatments of plant scaffolds aiming at novel functionalized materials.
The speed of writing of state-of-the-art ferromagnetic memories is physically limited by an intrinsic gigahertz threshold. Recently, realization of memory devices based on antiferromagnets, in which spin directions periodically alternate from one atomic lattice site to the next has moved research in an alternative direction.
We experimentally demonstrate at room temperature that the speed of reversible electrical writing in a memory device can be scaled up to terahertz using an antiferromagnet. A current-induced spin-torque mechanism is responsible for the switching in our memory devices throughout the order-of-magnitude range of writing speeds from hertz to terahertz.
Our work opens the path toward the development of memory-logic technology reaching the elusive terahertz band.
An investigation of the polymerisation of 2-hydroxyethyl methacrylate HEMA by means of surface-initiated atom transfer radical polymerisation SI-ATRP has been carried out in situ using a quartz crystal microbalance, with multiple reinitiations under continuous flow of the reaction mixture. Such experiments enabled the design of a polymerisation protocol that leads to a reasonably fast but well-controlled growth of poly HEMA brushes.
Furthermore, only a minor change in growth rate was observed when the polymerisation was stopped and reinitiated multiple times essential for block synthesis , demonstrating the living nature of the SI-ATRP reaction under such conditions. The clean switching of reaction mixtures in the flow-based QCM has been shown to be a powerful tool for real-time in situ studies of surface-initiated polymerisation reactions, and a promising approach for the precise fabrication of block-containing brush structures.
Multiferroism can originate from the breaking of inversion symmetry caused by magnetic-spiral order. The usual mechanism for stabilizing a magnetic spiral is competition between magnetic exchange interactions differing by their range and sign, such as nearest-neighbor and next-nearest-neighbor interactions. In insulating compounds, it is unusual for these interactions to be both comparable in magnitude and of a strength that can induce magnetic ordering at room temperature. Therefore, the onset temperatures for multiferroism through this mechanism are typically low.
By considering a realistic model for multiferroic YBaCuFeO5, we propose an alternative mechanism for magnetic-spiral order, and hence for multiferroism, that occurs at much higher temperatures. We show, using Monte Carlo simulations and electronic structure calculations based on density functional theory, that the Heisenberg model on a geometrically nonfrustrated lattice with only nearest-neighbor interactions can have a spiral phase up to high temperature when frustrating bonds are introduced randomly along a single crystallographic direction as caused, e.
This long-range correlated pattern of frustration avoids ferroelectrically inactive spin-glass order. Finally, we provide an intuitive explanation for this mechanism and discuss its generalization to other materials. Due to the low power density and the resulting high mass, size and thereby capital costs, the technology still requires improvements in materials, designs and performance to achieve widespread adoption. Despite recent improvements, the power density in current systems is limited by transport resistances in the AdHEX. Therefore, various transport rate enhancement approaches have been proposed in the literature.
However, most approaches so far have not focused on identifying and facilitating the limiting transport mechanism. Improving sorption rates requires the determination of the limiting transport phenomenon, which is usually difficult as mass and heat transport are strongly coupled by the sorption process.
This thesis focuses on the characterization and optimization of mass and heat transport in solid sorption heat pump technology. A novel experimental approach to discriminate between mass and heat transport in temperature-swing sorption processes is described. In this isochoric method, temperature swings are applied to an adsorbent while mass transport is captured by the loading transient and heat transport is quantified by the transient of the adsorbent temperature measured by an IR-camera.
The sorption equilibrium properties are measured prior to the kinetic measurement in the same setup. With both equilibrium and kinetic data, the respective equivalent driving temperatures for mass and heat transport are discriminated. Based on these driving temperatures, the time-averaged mass and heat transport impedances are determined.
The novel characterization method introduced here is termed Transport Impedance Analysis TIA and enables to identify transport limitations by quantitatively comparing heat and mass transport in-situ. In order to evaluate the performance of new structures, Ragone plots were introduced to compare the pareto-front, emerging from the trade-off between energy and power density of different adsorbent architectures.
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TIA was applied to commercial adsorbent architectures to determine the transport limitation in these systems. Different arrangements of silica beads and coatings consisting of zeolite microparticles and organic binder were examined using water as working fluid. While a monolayer silica bed configuration exhibits balanced heat and mass transport, we found that a bilayer and a thermally-enhanced configuration are limited by heat and mass transport, respectively.
Mass transport was found to be the main limiting factor in zeolite coatings despite the fact that most approaches reported in literature predominantly focus on improving heat transport. Based on these findings, this work focused next on facilitating the limiting mass transport by introducing directed porosity into the adsorbent coatings. With the help of TIA, a characteristic transport length CTL model was introduced that predicts the optimal ratio of heat to mass transport diffusion lengths in these hierarchical adsorbents.
The coatings with optimal pore architecture exhibit a higher power density than thinner non-structured coatings with the same amount of adsorbent mass per unit of heat exchanger area. Since these model structures cannot be easily fabricated at an industrial scale, an inexpensive route for the manufacturing of structured zeolite coatings based on the bottom-up assembly of colloids directed by magnetic and capillary forces was developed.
Such an assembly process relies on the chaining of oil droplets under an external magnetic field followed by the formation of a percolating network of bridged adsorbent particles upon drying. This results in vertical one-dimensional open channels and thermal bridges that co-enhance mass and heat transport across the zeolite coating. Since these one-dimensional channels can be placed close to each other while maintaining a low channel volume fraction, the one-dimensional channels produced by colloidal assembly exhibit a lower mass transport impedance compared to the two-dimensional channels.
Overall, this thesis provides a powerful toolset to characterize and optimize mass and heat transport in temperature-swing processes using a simple isochoric sorption test-rig. With this toolset, the transport rates in zeolite coatings were considerably improved, enabling a 3-fold increase in power density compared to non-structured coatings using an up-scalable manufacturing process. These improvements might be adaptable to other processes that require high mass and heat transport such as gas separation processes or to applications that requires high electrical conductivity and mass transport such as solid oxide fuel cells or batteries.
Enhanced light-matter interactions are the basis of surface-enhanced infrared absorption SEIRA spectroscopy, and con- ventionally rely on plasmonic materials and their capability to focus light to nanoscale spot sizes. Phonon polariton nanor- esonators made of polar crystals could represent an interesting alternative, since they exhibit large quality factors, which go far beyond those of their plasmonic counterparts.
The recent emergence of van der Waals crystals enables the fabrication of high- quality nanophotonic resonators based on phonon polaritons, as reported for the prototypical infrared-phononic material hex- agonal boron nitride h-BN. In this work we use, for the fi rst time, phonon-polariton-resonant h-BN ribbons for SEIRA spectro- scopy of small amounts of organic molecules in Fourier transform infrared spectroscopy. Strikingly, the interaction between phonon polaritons and molecular vibrations reaches experimentally the onset of the strong coupling regime, while numerical simulations predict that vibrational strong coupling can be fully achieved.
Phonon polariton nanoresonators thus could become a viable platform for sensing, local control of chemical reactivity and infrared quantum cavity optics experiments. The large plasticity observed in newly developed monolithic bulk metallic glasses under quasi-static compression raises a question about the contribution of atomic scale effects. Here, nanocrystals on the order of 1—1.
The accumulation of nanocrystals is linked to the presence of hard and soft zones, which is connected to the micro-scale hardness and elastic modulus confirmed by nanoindentation. Furthermore, we performed systematic simulations of HRTEM images at varying sample thicknesses, and established a theoretical model for the estimation of the shear transformation zone size. The findings suggest that the main mechanism behind the formation of softer regions are the homogenously dispersed nanocrystals, which are responsible for the start and stop mechanism of shear transformation zones and hence, play a key role in the enhancement of mechanical properties.
Hydrocarbon polymers belong to the basic structures in polymer architecture. Poly phenylene methylene PPM represents one of the simplest structured polymer of this category. Before this PhD thesis, however, poly phenylene methylene was not available with molar masses sufficiently high to attract interest in materials science, in spite of numerous attempts to synthesize this polymer. Yet, based on the attractive properties of related polymers such as polyethylene, poly para-phenylene , and pol para-xylylene , it has been expected that poly phenylene methylene possesses interesting properties, such as high hydrophobicity, excellent thermal stability, and good barrier properties.
This dissertation demonstrates the successful isolation of poly phenylene methylene s with broad range of molar masses by optimization of the catalytic polymerization of benzyl chloride with SnCl4, FeCl3, or organometallic tungsten II compounds, followed by fractionation. Low molar mass products were also obtained by quenching the reaction at moderate monomer conversions.
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The glass transition temperature Tg of these polymers with different molar masses follows the Flory-Fox equation. The analysis revealed that the signal group of the methylene unit in 13C NMR spectra are sensitive to the substitution pattern of the two adjacent phenylene rings, which is utilized to compare the substitution patterns of different PPM samples.
Moreover, it was demonstrated that poly phenylene methylene exhibits pronounced blue fluorescence in solutions as well as in the solid state despite its non-p-conjugated nature. Optical spectroscopy was used to explore the characteristics and the physical origin of its unexpected optical properties, namely absorption in the nm — nm and photoluminescence in the nm — nm spectral regions.
Instead there is sufficient evidence that PPM supports homoconjugation. Poly 2-methylphenylene methylene and poly 2,4,6- trimethylphenylene methylene — two derivatives of PPM — were synthesized and found to exhibit comparable spectroscopic properties, confirming the generality of the findings reported for PPM. Finally, the processability of fluorescent poly phenylene methylene has been investigated by employing various processing techniques. The fibers exhibited birefringence and the ability to guide light waves red light. Furthermore, a broad thickness range for films few nm to few mm was achieved with different approaches such as spin- coating, hot pressing, and die casting.
The films featured crack-free and very smooth surfaces. Additionally, freestanding foams of the polymer were obtained by foaming highly concentrated solutions and near quasi-monodisperse microspheres were prepared by a microfluidic high-throughput emulsification. The materials properties of these morphologies were investigated and discussed for implementation as potential products from plastic optical fibers and light emitting diodes, to protective coatings and packaging, to insulators and separation membranes.
Mineral-oxide particles exhibit an amphoteric nature in aqueous solution due to ionization of surface hydroxyl groups. The magnitude of ionization is a collective outcome of factors, such as the speciation of surface hydroxyl groups, composition and size of the particle, pH of the solution and electrolytes present in the solution. The charge distribution on and around the surface of a particle in solution affects the reactions taking place at this solid-liquid interface. The charged surface, together with the ions near the interface makes up the electrical double layer EDL.
Due to its direct implications on surface reactivity, the EDL is significant for investigations in catalysis, colloidal science, energy-storage devices, ion adsorption and toxicology. Despite the attention given to it, the exact structure of the EDL is still debatable. One of the reasons for this is the lack of a direct measurement of surface properties such as the surface potential and acid dissociation constant of the weak acidic surface hydroxyl groups.
This thesis uses a combination of experimental techniques and a modeling approach to understand the EDL for the silica nanoparticle np —electrolyte water interface. The abundance of the silica-water interface in the environment and the relatively simple surface reactions compared to other mineral oxides make silica an ideal choice for such EDL investigations.
Potentiometric titrations PT are the core of the experimentation along with electrokinetic EK measurements, in this thesis. Electrokinetic measurements, on the other hand, provide information on the charge cloud associated with the charged particle. Experimentally obtained charge density data is often used as input to carry out surface complexation modeling SCM to interpret the EDL at the silica np-electrolyte water interface. This modeling procedure is greatly simplified by using previously estimated Stern-layer capacitances as constraints in the modeling approach.
Here, the Stern layer capacitances used were calculated from surface-potential estimates that were recently measured by our group using liquid-jet X-ray photoelectron spectroscopy LJ-XPS. In this thesis, we see how a well-constrained SCM allows for the estimation of the electrolyte binding constant and the negative logarithm of the acid dissociation constant for the terminal silanol groups. A long-standing view in the colloid community is that the SCD of silica is directly influenced by the absolute concentration of electrolyte present in the solution.
While this is true, it must be remarked that detailed investigations presented in this thesis suggest that the SCD of colloidal silica is directly influenced by the ratio of counterions to the surface silanol groups and not solely on the absolute electrolyte concentration.
Gradient surfaces with a continuously changing surface parameter allow rapid, high-throughput investigations and systematic studies in tribology, adhesion and biology. Surface roughness is an important surface parameter on both micrometer and nanometer scales. Nanoparticle-density gradients were produced by a simple dip-coating process of a positively charged poly ethylene imine PEI -coated silicon wafer into a negatively charged silica-nanoparticle suspension. Gradients were coated with TiO2 to mimic the surface of bone implants.
A step-by-step in vivo like model that follows the natural processes occurring after implantation of an osseous implant was chosen to study the effect of nano-rough surfaces on protein adsorption, blood coagulation as well as cell behavior. TiO2-coated nanoparticle-density gradients were used for protein-adsorption studies. For gradients with and nm-diameter nanoparticles no influence of nano-features on the amount of adsorbed proteins could be found.
In contrast, for gradients with nm-diameter nanoparticles, fibrinogen in competition with albumin and fibronectin or serum, showed a higher adsorption at the high-particle-density end of the gradient. Blood-coagulation studies revealed that nanostructures involving nm-diameter nanoparticles seem to enhance blood coagulation. With an increase in 39 nm particle-density, faster fibrin-network formation was observed, while smaller 12 nm and bigger 72 nm nanoparticles did not influence the activation of platelets or the fibrin-network formation.
Human-bone-cell HBC experiments performed on nano-roughness gradients exhibited a gradual change in the cell behavior along the gradient with decreasing proliferation with decreasing inter-particle distance. Ten days post seeding, the number of HBCs on 39 nm particle-density gradients was six times higher at positions without particles compared to the high-density end of the gradient.
Since biological experiments require a large number of substrates, different replication techniques were used to create copies of master gradients. Injection molding from polymer inserts was shown to be a successful replication technique for the mass production of samples with 72 nm features. For smaller nanoparticle, a novel replication method called substrate conformal imprint lithography SCIL demonstrated the replication of nanofeatures down to a size of 12 nm and was proven to be able to replicate combined nano- and micro-featured structures.
Lastly, silver-particle gradients with changing particle size, height and density along the gradient were prepared by dewetting of gradients in silver thickness. Replication of the silver-particle gradients in PDMS and epoxy was shown to be a possible way to produce identical particle-size gradients and TiO2 coated epoxy replicas could be used for biological applications. If run under optimal conditions, the reaction yields oligomeric products which resemble the emeraldine salt form of polyaniline PANI-ES in its polaron state, known to be the only oxidation state of linear PANI which is electrically conductive.
For this complex, heterogeneous, vesicle-assisted, and enzyme-mediated reaction, in which dissolved dioxygen also takes part as a re-oxidant for TvL, small changes in the composition of the reaction mixture can have significant effects. Initial conditions may not only affect the kinetics of the reaction, but also the outcome, i. Dispatched in working days. Availability In Stock. Guaranteed service. International Shipping available. Other Books By Author. New Book Releases. Contact Us.
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