Studying the in vitro corrosion response of nanostructured TaN coatings in Hank's physiological solution

The goal of this research is to determine the effect of N₂ pressure to argon pressure on the microstructural analysis and corrosion behavior of nanostructured TaN deposited coatings using a reactive DC-magnetron sputtering (RDCMS) technique. The samples coated microstructure was studied by the X-ray diffraction (XRD) and scanning electron microscope (SEM), and elemental distribution was studied using energy-dispersive X-ray spectroscopy (EDS). To investigate the corrosion behavior of nanostructured TaN coatings, the potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests were performed in Hank's physiological solution. The results of different tests revealed that the coating with a content of 17.6% P_N2/P_Ar consisted of hexagonal and orthorhombic TaN phases and had denser microstructure and free pores. This coating showed superior corrosion behavior in comparison to the other ones. Also, the corrosion resistance of this coating raised by increasing the time of immersion from 48 to 168 h.     

Thermal effects on the enhanced ductility in non-monotonic uniaxial tension of DP780 steel sheet

To understand the material behavior during non-monotonic loading, uniaxial tension tests were conducted in three modes, namely, the monotonic loading, loading with periodic relaxation and periodic loading-unloadingreloading, at different strain rates (0.001/s to 0.01/s). In this study, the temperature gradient developing during each test and its contribution to increasing the apparent ductility of DP780 steel sheets were considered. In order to assess the influence of temperature, isothermal uniaxial tension tests were also performed at three temperatures (298 K, 313 K and 328 K (25 °C, 40 °C and 55 °C)). A digital image correlation system coupled with an infrared thermography was used in the experiments. The results show that the non-monotonic loading modes increased the apparent ductility of the specimens. It was observed that compared with the monotonic loading, the temperature gradient became more uniform when a non-monotonic loading was applied.     

Self-assembled targeted nanoparticles: evolution of technologies and bench to bedside translation

Nanoparticles (NPs) have become an important tool in many industries including healthcare. The use of NPs for drug delivery and imaging has introduced exciting opportunities for the improvement of disease diagnosis and treatment. Over the past two decades, several first-generation therapeutic NP products have entered the market. Despite the lack of controlled release and molecular targeting properties in these products, they improved the therapeutic benefit of clinically validated drugs by enhancing drug tolerability and/or efficacy. NP-based imaging agents have also improved the sensitivity and specificity of different diagnostic modalities. The introduction of controlled-release properties and targeting ligands toward the development of next-generation NPs should enable the development of safer and more effective therapeutic NPs and facilitate their application in theranostic nanomedicine. Targeted and controlled-release NPs can drastically alter the pharmacological characteristics of their payload, including their pharmacokinetic and, in some cases, their pharmacodynamic properties. As a result, these NPs can improve drug properties beyond what can be achieved through classic medicinal chemistry. Despite their enormous potential, the translation of targeted NPs into clinical development has faced considerable challenges. One significant problem has been the difficulty in developing targeted NPs with optimal biophysicochemical properties while using robust processes that facilitate scale-up and manufacturing. Recently, efforts have focused on developing NPs through self-assembly or high-throughput processes to facilitate the development and screening of NPs with these distinct properties and the subsequent scale-up of their manufacture. We have also undertaken parallel efforts to integrate additional functionality within therapeutic and imaging NPs, including the ability to carry more than one payload, to respond to environmental triggers, and to provide real-time feedback. In addition, novel targeting approaches are being developed to enhance the tissue-, cell-, or subcellular-specific delivery of NPs for a myriad of important diseases. These include the selection of internalizing ligands for enhanced receptor-mediated NP uptake and the development of extracellular targeting ligands for vascular tissue accumulation of NPs. In this Account, we primarily review the evolution of marketed NP technologies. We also recount our efforts in the design and optimization of NPs for medical applications, which formed the foundation for the clinical translation of the first-in-man targeted and controlled-release NPs (BIND-014) for cancer therapy.     

Airborne GNSS-Receiver Threat Detection in No-Fading Environments

Jamming and spoofing detection of global navigation satellite systems (GNSS) is of great importance. Civil and military aerial platforms use GNSS as main navigation systems and these systems are main target of threat attacks. In this paper a simple method based on different empirical probability density functions of successive received signal powers and goodness of fit technique is proposed for airborne platforms such as unmanned aerial vehicle (UAV), in no fading environment. The two different paths between UAV-satellite and UAV-threat, experience different empirical probability density functions which can be used to distinguish between authentic and threat signals. Simulation results including detection and false alarm probabilities show good performance of proposed method as well as low computational burden.     

Cellulose nanocrystal (CNC)-based nanocomposites for UV curable high-solid coating systems

Demand for durable clear wood coatings is on the rise. Cellulose nanocrystals (CNC) constitute an organic nanomaterial widely studied in polymer composites for its reinforcing effect. In this study, CNC was used to enhance the performance of a UV curable high-solid content coating system intended for indoor environments. The CNC surface was modified by a cationic surfactant since the coating system was hydrophobic resin-based requiring hydrophobic nanomaterial reinforcement. Modified CNC was mixed with the coating system using a high-speed mixer and the ultrasonication technique. Mechanical, thermal and morphological properties and curing behavior of the newly developed UV-curing coatings were assessed. Inclusion of CNC in the coating increased the mechanical properties (hardness and reduced modulus) of the coating system to a large extent. Thermal stability of the coating system was also improved by CNC addition. The CNC did not affect the curing behavior of the coating, in contrast to most inorganic nanomaterials. The CNC dispersed well in the matrix at 1% loading. Results of this study show that CNC can be used successfully with high-solid content coating systems.     

Determination of molecular weight and molecular radius of the polyamido carboxylic acid dendrimer using generation numbers

Using of a Molecular equation of a first dendrimer surface and its relation to dendrimer molecular radios, it is possible to suggest the number of generation. Whereas a relative molecular weight is affiliated to the number of molecule formed in structural cells and on the other hand, structural cells have definite and determined dimensions, so by a simple replacement, the dendrimer molecular weight was directly related to its generation number. Data analysis derived from specific equation was shown that the prediction of a dendrimer molecular weight may be applicable by a specific generation.Molecular weight of polyamido carboxylic acid dendrimer with specific number of generation could be theoretically estimated using the following eqs. (4) and (5).

y = log M_w

=2.0703 + 0.0844R_i (4)

=2.6339 + 0.4750G_n (5)

R_i and G_n are molecular radius and number of generation respectively.Such equations would result the molecular radius of the dendrimer. In this invented model there is no need to experiments and it can be key value to evaluate the experimental data.     

Novel fabrication route for porous silicon carbide ceramics through the combination of in situ polymerization and reaction bonding techniques

For the first time, an in situ polymerization technique was applied to produce mullite‐bonded porous SiC ceramics via a reaction bonding technique. In this study, SiC microsized particles and alumina nanopowders were successfully coated by polyethylene (PE), which was synthesized from the particle surface in a slurry phase reactor with a Ziegler–Natta catalyst system. The thermal studies of the resulting samples were performed with differential scanning calorimetry and thermogravimetric analysis. The morphology analysis obtained by transmission electron microscopy and scanning electron microscopy (SEM) confirmed that PE was successfully grafted onto the particle surface. Furthermore, the obtained porous ceramics were characterized in terms of their morphologies, phase composition, open porosity, pore size distribution, and mechanical strength. SEM observations and mercury porosimtery analysis revealed that the quality of the dispersion of nanosized alumina powder into the microsized SiC particles was strongly enhanced when the particles were coated by polymers with in situ polymerization. This resulted in a higher strength and porosity of the formed ceramic porous materials with respect to the traditional process. In addition, the X‐ray diffraction results reveal that the amount of mullite as the binder increased significantly for the samples fabricated by this novel method. The effects of the sintering temperature, forming pressure, and polymer content on the physical and mechanical properties of the final porous ceramic were also evaluated in this study. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40425.