Towards hybrid silicon-organic molecular electronics: The stability of acetone on the Si(0 0 1) surface

We present the results of a combined study using scanning tunneling microscopy (STM) and density functional theory (DFT) of the interaction of acetone [(CH₃)₂CO] with the Si(0 0 1) surface. Three distinct adsorbate features were observed using atomic-resolution STM. One of the features appears as a bright protrusion located above a Si-Si dimer, while the other two are asymmetric about the dimer row and involve a second neighboring Si-Si dimer. One of the two asymmetric features has a protrusion located between the two dimers, while the other has a protrusion which is located at the site of a single dimer and exhibits a dimer sized depression on the adjacent dimer. DFT calculations have been performed for two structures; the four-membered ring structure and dissociation structure. Our calculations show that the bright single-dimer sized feature observed in the STM images could be attributed to either of these two calculated structures. However, neither of the two calculated structures can explain the appearance of the two-dimer wide asymmetric features observed in the experiment.     

Silica-titania sol-gel hybrid materials: synthesis, characterization and potential application in solid phase extraction

The biphenilaminepropylsilica and biphenilaminepropylsilicatitania were synthesized by sol-gel method, in two steps: (a) biphenylamine reacts with chloropropyltrimethoxysilane and (b) the product of reaction was polycondensed with tetraethylorthosilicate (TEOS) or TEOS and titanium isopropoxide. The sol-gel materials were characterized using infrared spectroscopy and N₂ adsorption-desorption isotherms and they were employed as sorbents for carcinogenic N-containing compound retention, in aqueous solution, using the SPE technique. The N-containing compounds adsorption was influenced by the titania presence and the sorption process seems to happen in the pores with higher organic density.     

Preparation of NiO decorated CNT/ZnO core-shell hybrid nanocomposites with the aid of ultrasonication for enhancing the performance of hybrid supercapacitors

Supercapacitor (SC) electrodes fabricated with the combination of carbon nanotubes (CNTs) and metal oxides are showing remarkable advancements in the electrochemical properties. Herein, NiO decorated CNT/ZnO core-shell hybrid nanocomposites (CNT/ZnO/NiO HNCs) are facilely synthesized by a two-step solution-based technique for the utilization in hybrid supercapacitors. Benefitting from the synergistic advantages of three materials, the CNT/ZnO/NiO HNCs based electrode has evinced superior areal capacity of ~67 µAh cm⁻² at a current density of 3 mA cm⁻² with an exceptional cycling stability of 112% even after 3000 cycles of continuous operation. Highly conductive CNTs and electrochemically active ZnO contribute to the performance enhancement. Moreover, the decoration of NiO on the surface of CNT/ZnO core-shell increases the electro active sites and stimulates the faster redox reactions which play a vital role in augmenting the electrochemical properties. Making the use of high areal capacity and ultra-long stability, a hybrid supercapacitor (HSC) was assembled with CNT/ZnO/NiO HNCs coated nickel foam (CNT/ZnO/NiO HNCs/NF) as positive electrode and CNTs coated NF as negative electrode. The fabricated HSC delivered an areal capacitance of 287 mF cm⁻² with high areal energy density (67 µWh cm⁻²) and power density (16.25 mW cm⁻²). The combination of battery type CNT/ZnO/NiO HNCs/NF and EDLC type CNT/NF helped in holding the capacity for a long period of time. Thus, the systematic assembly of CNTs and ZnO along with the NiO decoration enlarges the application window with its high rate electrochemical properties.     

Disjoint sparsity for signal separation and applications to hybrid inverse problems in medical imaging

The main focus of this work is the reconstruction of the signals f and $g_i$, $i=1,\dots ,N$, from the knowledge of their sums $h_i=f+g_i$, under the assumption that f and the $g_i$'s can be sparsely represented with respect to two different dictionaries $A_f$ and $A_g$. This generalizes the well-known “morphological component analysis” to a multi-measurement setting. The main result of the paper states that f and the $g_i$'s can be uniquely and stably reconstructed by finding sparse representations of $h_i$ for every i with respect to the concatenated dictionary $[A_f,A_g]$, provided that enough incoherent measurements $g_i$ are available. The incoherence is measured in terms of their mutual disjoint sparsity.This method finds applications in the reconstruction procedures of several hybrid imaging inverse problems, where internal data are measured. These measurements usually consist of the main unknown multiplied by other unknown quantities, and so the disjoint sparsity approach can be directly applied. As an example, we show how to apply the method to the reconstruction in quantitative photoacoustic tomography, also in the case when the Grüneisen parameter, the optical absorption and the diffusion coefficient are all unknown.     

Computation of periodic solutions in maximal monotone dynamical systems with guaranteed consistency

In this paper, we study a class of set-valued dynamical systems that satisfy maximal monotonicity properties. This class includes linear relay systems, linear complementarity systems, and linear mechanical systems with dry friction under some conditions. We discuss two numerical schemes based on time-stepping methods for the computation of the periodic solutions when these systems are periodically excited. We provide formal mathematical justifications for the numerical schemes in the sense of consistency, which means that the continuous-time interpolations of the numerical solutions converge to the continuous-time periodic solution when the discretization step vanishes. The two time-stepping methods are applied for the computation of the periodic solution exhibited by a power electronic converter and the corresponding methods are compared in terms of approximation accuracy and computation time.     

Functional polymer/inorganic hybrid nanoparticles for macrophage targeting delivery of oligodeoxynucleotides in cancer immunotherapy

To efficiently deliver CpG oligodeoxynucleotides (ODN) in cancer immunotherapy, a multifunctional macrophage targeting delivery system was designed and prepared. Mannosylated carboxymethyl chitosan/protamine sulfate/CaCO₃/ODN (MCMC/PS/CaCO₃/ODN) nanoparticles were prepared using a facile self-assembly method. The functional components, including MCMC to endow the nanoparticles with macrophage targeting ability, PS to improve the ODN loading capacity and enhance the cell uptake, and CaCO₃ to encapsulate ODN and induce the favorable pH sensitivity, were introduced to the delivery systems by self-assembly. Due to the mannose mediated endocytosis and the favorable effects of PS in overcoming delivery barriers, MCMC/PS/CaCO₃/ODN nanoparticles exhibit a much higher ODN delivery efficiency and a significantly enhanced immune stimulation capacity as compared with Lipofectamine 2000/ODN complexes. The regulation of NF-κB activity by our ODN delivery system results in dramatically increased production of proinflammatory cytokines including IL-12, IL-6, and TNF-α in RAW264.7 cells. The significantly increased CD80 expression after stimulation by the ODN delivery systems indicates the successful modulation of the macrophage polarity to the anti-tumor M1 phenotype. The multifunctional macrophage targeting delivery system developed has promising applications in delivery of CpG ODN in cancer immunotherapy.     

Bioactive peptides grafted silicone dressings: A simple and specific method

The need for bioactive dressings increases with the population aging and the prevalence of chronic diseases. In contrast, there are very few dressings on the market which are designed to display a chosen bioactivity. In this context, we investigated the surface-functionalization of silicone wound dressing with bioactive peptides. One of the challenges was to avoid multistep grafting reactions involving catalysts, solvents or toxic reagents, which are not suitable for the fabrication of medical devices at an industrial scale. In the other hand, a covalent bonding was necessary to avoid the loss of the biological effect by progressive removal of the peptide in biological fluids generated by the wound. To solve these limitations, we developed a strategy allowing an easy and direct functionalization of silicone. This strategy relies on hybrid silylated bioactive peptides, which chemoselectively react with plasma-activated silicone surfaces. We synthesized three hybrid peptides with wound healing properties, which were grafted on commercially available silicone dressings Cerederm^® and Mepitel^®. Grafted dressings were evaluated in vitro and enabled a quicker scare recovery and extracellular matrix deposition with human dermal fibroblasts. These results were confirmed by in vivo studies showing an enhanced wound-healing of the pig skin. By this simple method, we transformed inert dressing into bioactive dressing which showed properties of wound healing.     

Hybrid (numerical-experimental) modeling of complex structures with linear and nonlinear components

The present work investigates the performance of two systematic methodologies leading to hybrid modeling of complex mechanical systems. This is done by applying numerical methods in determining the equations of motion of some of the substructures of large order mechanical systems, while the dynamic characteristics of the remaining components are determined through the application of appropriate experimental procedures. In their simplest version, the models examined are assumed to possess linear characteristics. For such systems, it is possible to apply several hybrid methodologies. Here, the first of the methods selected is performed in the frequency domain, while the second method has its roots and foundation in time domain analysis. Originally, the accuracy and effectiveness of these methodologies is illustrated by numerical results obtained for two complex mechanical models, where the equations of motion of each substructure are first set up by applying the finite element method. Then, the equations of motion of the complete system are derived and their dimension is reduced substantially, so that the new model is sufficiently accurate up to a prespecified level of forcing frequencies. The formulation is developed in a general way, so that application of other methods, including experimental techniques, is equally valid. This is actually performed in the final part of this study, where experimental results are employed in conjunction with numerical results in order to predict the dynamic response of a mechanical structure possessing a linear substructure with high modal density, supported on four substructures with strongly nonlinear characteristics.     

Performance of propellant decomposition products as fuel in an airbreathing PDE

Decomposition products of a solid propellant are considered as a possible fuel in an airbreathing pulse detonation engine (PDE). However, these decomposition products contain not only gaseous species but also a significant amount of solid carbon particles. Whether performance can be improved by burning these particles is investigated numerically. Thermodynamic calculations allow predicting the quantity of additional air required for optimum performance. Gasdynamic numerical simulations indicate that particle burning has an effect on the pressure impulse on the thrust wall. The particle size determines the detonation structure, according to the model of hybrid detonations, thus governing the delay and rate of heat release from particle combustion behind the detonation front. In the situation investigated here, the particles are incompletely burnt inside a 0.6-m-long tube. As a result, smaller particles ( ≤ 5μm) contribute to an increase in the impulse, by up to 6%. However, larger particles either have a negligible effect on the pressure impulse, if around 10 μm, or result in a decrease, if around 20 μm. Overall, the calculations show that the best efficiency is obtained for this fuel by diluting the gaseous decomposition products with an additional quantity of air, allowing for incomplete particle combustion rather than letting them behave as if inert, absorbing part of the energy released by gaseous combustion.This paper was based on a work that was presented at the 20th International Colloquium on the Dynamics of Explosions and Reactive Systems, Montreal, Canada, July 31–August 5, 2005.