The therapeutic effect of mesenchymal stem cells (MSCs) has been investigated in various clinical applications, in which their functional benefits are mainly attributed to the secretion of soluble factors. The enhancement of their therapeutic potential by physical and chemical properties of cell culture substrate is a safe and effective strategy, since they are highly sensitive to their microenvironment such as the elasticity and surface topography. In this study, we demonstrated that the geometry of polymeric substrate regulated the interleukin-6 (IL-6) secretion of human adipose derived MSCs. Polystyrene substrates comprising arrays of square-shaped (S50) or round-shaped (R50) microwells (side length or diameter of 50 μm and depth of 10 μm) were prepared by injection molding. Cellular apoptototic rate of MSCs was not affected by the microwell geometry, while the upregulated secretion of IL-6 and the enhancement of nuclear transcription factor STAT3 were detected in MSCs seeded on S50 substrate. The geometry-dependent modulatory effect was highly associated with ROCK signaling cascade. The inhibition of ROCK abolished the disparity in IL-6 secretion. These findings highlight the possibility to steer the secretion profile of stem cells via microwell geometry in combination with the manipulation of ROCK signaling pathway.

Silica aerogels are unique lightweight, nanostructured materials with extremely high porosity (usually above 90%), making them particularly attractive for thermal insulation, although their mechanical fragility still requires strategies of reinforcement that may compromise some of their most appealing properties. The use of silica aerogels still needs to be matured for a broad range of other high-performance applications, and even improved for insulation application. This can be achieved by intensely exploring their surface chemistry versatility, by relying on the enormous variety of silane precursors and chemical routes that can be used. In this work, we present two examples of using reactive moieties in the silane precursors for the preparation of silica aerogels for multipurpose application. In the first case, an acrylate containing silane (3-(trimethoxysilyl)propyl methacrylate) is used along with tetramethyl orthosilicate to produce an organically-modified silica network, which could be reinforced by adding 1,6-bis(trimethoxysilyl)hexane or 1,4-bis(triethoxysilyl)-benzene as spacers and tris[2-(acryloyloxy)ethyl] isocyanurate as cross-linker. These hybrid aerogels have shown an interesting combination of thermal insulation and mechanical properties. Moreover, they could be chemically doped with silica-functionalized magnetite nanoparticles imparting magnetic behaviour to the aerogels but also improving their thermal insulation performance and mechanical strength. Their magnetic feature can be useful for several applications including magnetic separation and drug delivery. As a second example, amine and thiol-functionalized aerogels were used as adsorbents to capture heavy metals from wastewater by complexation, and the preparation of these materials could be accomplished using a combination of silanes, including hydrophobic moieties for a compromise to ensure material stability and good adsorption capacities. Removal percentages of heavy metals reaching 90% were found for metal concentrations of environmental relevance. The amine functionality in aerogels is also useful for other purposes, for example to improve the rate capability of silica aerogels to remove carbon dioxide from gaseous streams or environments.

We perform molecular dynamics (MD) simulations to understand thermally triggered shape memory behavior of a thermoplastic polyurethane (TPU) elastomer with an enhanced coarse-grained (CG) model. Hard and soft phases of shape memory polymers (SMPs) are known as fixed and reversible phase, respectively. Fixity depends on the content of hard segments due to their restricted mobility. On the contrary, recovery depends on the dynamic motion of the soft segments as well the degree of cross-linking, which is also affected by the quantity of hard segment. Several CG models of the TPU are constructed varying the weight percentage of soft segments to observe their effects on shape recovery and fixity. All of the models are equilibrated at 300K (above glass transition, Tg: 200-250 K) and deformed under uniaxial loading with NPT (isothermal-isobaric) ensembles. The deformed state is cooled to 100K (below Tg) and further equilibrated to estimate the shape fixity. Shape recovery is predicted by heating and equilibrating the structures back to 300K. By the end of this study, we may answer how much the shape fixities and recoveries are changed for varying concentration of hard segments from thermomechanical cycles with CGMD simulations.

This paper presents the results of our studies on the deposition and characterization of multi wall carbon nanotube films in combination with polyurethane (PU) and N-methyl- 2-pyrrolidone (NMP). These studies mainly focused on the effect of ultra violet Ozone plasma treatment on the on the contact angle and wettability characteristics of the substrates, Silicon and Polyimide. Polyurethane/ multi-walled carbon nanotube elastomer composite films are synthesized on polyimide and glass substrates using spin coating methods. The effect of Ultraviolet-Ozone Plasma treatment (UVO) on the wettability of the substrate was studied after different exposure times, by making contact angle measurements on the chosen substrates. These measurements showed that the contact angle decreases with increasing exposure times, which indicated enhanced wettability after longer exposure to UVO plasma. The microstructure of these films are examined using optical and scanning electron microscopes. The conductivities of the films are examined using Van der Pauw method. The AC conductivity of 1wt%, 5wt% and 8wt% CNT loaded PU nanocomposite films were found to be 3.86, 5.90 and 5.38 S/m respectively which are few orders higher than the values reported in the literature. These values were confirmed with the Nyquist plot and equivalent circuit modelling. This shows the frequency independent conductive nature of the composite films. The quality of these films is analyzed using Laser Raman spectroscopy. The effect of substrate (Polyimide or Glass), UVO exposure (Ultraviolet-Ozone plasma treatment, carbon nanotube loading (1-8%) on the quality of the films are presented in detail in this paper.

A Zn/Al LDH with fluorescein intercalated as counterion with fluorescent properties was prepared. Fluorescein was prepared by the reaction between resorcinol and phthalic anhydride using the mixed oxide obtained after the thermal treatment of the LDH as catalyst. The material thus obtained, i.e. fluorescein adsorbed onto the mixed oxide from the calcined LDH, was treated with a mixture of water and pentanol in order to reconstitute the LDH and intercalate the fluorescein in the material. Three mixtures of water/pentanol with volume percent ratios of 100/0, 50/50, 20/80, were used to obtain the LDH with fluorescein intercalated. The best treatment could be determined according to the degree reconstruction and fluorescein intercalated into the LDH.

Key drivers for the application of thermal treatment processes include the reduced volume, improved passive safety, and superior long term stability of the vitrified wasteform products. These advantages have led to a renewed interest in thermally treating various UK ILW streams. To support the increased investment in thermal treatment technologies a fundamental understanding of the processes and the impact of waste inventory needs to be established. The research described in this report aims to provide the evidence necessary to support a major investment in thermal treatment of Plutonium Contaminated Materials (PCM). The report describes the use of laboratory scale waste simulants to develop an understanding of the waste and matrix interactions during thermal treatment of PCM waste. The report includes the thermal treatment process and characterization of the vitrified product.

Charge transport between nickel oxide nanoparticles and CdSe/ZnS alloyed core/shell nanocrystals is investigated. The crystal structure and composition of the nickel oxide nanoparticles are evaluated using X-ray diffraction, Raman and X-ray photoelectron spectroscopies. The nanoparticles are near-stoichiometric with very low defect densities. The optical properties of the materials are studied by measuring the absorbance and time resolved photoluminescence spectra. The band gap of the nickel oxide nanoparticles is around 4.42 eV. The CdSe/ZnS nanocrystals exhibit shorter average lifetimes when mixed with nickel oxide nanoparticle powder. The lifetime quenching can be attributed to the efficient charge transport from the CdSe/ZnS nanocrystals to nickel oxide nanoparticles due to the relative valence band alignment.

Polymer imprint thermal mapping (PITM) is a high-resolution thermal mapping technique that is especially valuable for nanoscale plasmonic devices. PITM leverages a ∼50 nm polymer film coating that crosslinks irreversibly with temperature, which records the peak temperature rise of the surface in the local, linear reduction of polymer film thickness. Using AFM to measure topography before and after heating, but not during operation, PITM sidesteps plasmonic artifacts seen in other near-field thermometries, where the probe tip disturbs and is heated directly by the near- and far-field radiation around the plasmonic device. This is notably troublesome for characterizing heat-assisted magnetic recording (HAMR) heads for next-generation hard disk drives. HAMR heads use near-field transducers (NFTs) to focus light on a magnetic media, heating a nanoscale region to its Curie temperature to enable magnetic writing. The PITM proof-of-concept was introduced at The Magnetic Recording Conference (TMRC) in 2015: here, we present a mature technique capable of benchmarking finite-element thermal simulations of nanoscale devices.

Forming-free bipolar resistive switching characteristics in a Vanadium oxide based sandwich structure is observed for the first time. The bottom conducting layer is the common ground electrode for all devices. The top conducting layer acts as an active element with an additional Cr/Al/Cr electrode patterned on its top for making contact. Different from the typical metal/transition metal oxide/metal sandwich structure based resistive memories, our device exhibits a low resistance state (LRS) in its virgin state, and can be switched to a high resistance state (HRS) when a positive bias of +2.5V is applied to the top electrode. Following this, the device can be reset to a LRS when a negative bias of approximately 2.5V is applied. A significant decrease of switching voltages is observed when the diameter of the top contact decreases, indicating an electric field enhanced switching mechanism. Simulation using TCAD confirms that electric field beneath the top metal contact increases due to fringing. The results suggest future applications in low power integrated non-volatile memories.

We investigate the feasibility of inert ion beam etch (IBE) for subtractive patterning of ReRAM-type structures. We report on the role of the angle-dependent ion beam etch rates in device area control and the minimization of sidewall re-deposition. The etch rates of key ReRAM materials are presented versus incidence angle and ion beam energy. As the ion beam voltage is increased, we demonstrate a significant enhancement in the relative etch rate at glancing incidence (for example, by a factor of 2 for HfO2). Since the feature sidewall is typically exposed to glancing incidence, this energy-dependence plays a role in optimization of the feature shape and in sidewall re-deposition removal.

We present results of SRIM simulations to estimate depth of ion-bombardment damage to the TMO sidewall. Damage is minimized by minimizing ion energy; its depth can be reduced by roughly a factor of 5 over typical IBE energy ranges. For example, ion energies of less than ∼250 eV are indicated to maintain damage below ∼1nm. Multi-angle and multi-energy etch schemes are proposed to maximize sidewall angle and minimize damage, while eliminating re-deposition across the TMO. We utilize 2-D geometry/3-D etch model to simulate IBE patterning of tight-pitched ReRAM features, and generate etched feature shapes.

Electric field-modulated photoluminescence (PL) of perovskite solar cells is investigated to gain deeper insight about the role of the mobile ions in organometal halide perovskites. The PL intensity of perovskite solar cells show significant dependence on the polarity of the external electric field and the voltage scanning direction. This phenomenon is discussed in the framework of an ion migration mechanism, which has been widely accounted for the current density-voltage (J-V) hysteresis in perovskite solar cells. The result suggests that the mobile ions not only change the internal electric field of perovskite solar cells, but also have an effect on the recombination of photogenerated charge carriers.

In this research, zinc chloride has been used as precursor and zinc oxide nanostructures have been synthesized by Sol-Gel process, using deionized water and 2-propanol as solvents in order to evaluate their influence on the final materials and their properties. Thin films of synthesized samples were deposited on glass substrates by the dipping method. The structure and morphology of crystals were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The electrical response of the samples to CO was investigated at different operating temperatures and sensitivity curves are presented for samples synthesized in water and 2-propanol (IsOH) solvents. The SEM analysis revealed that ZnO thin films have yielded to different morphologies depending on the solvent, and material was found on the non-immersed side of the substrate attributable to migration during the dip-coating process. XRD analysis shows that the samples present the ZnO wurtzite structure. In EDS analysis it was found the presence of chlorine on the sample, opening the possibility the presence of zinc oxychloride.

Phenylcoumarin glucoside (4-PC) is a compound extracted from the plant Hintona latiflora and was studied as inhibitor for AISI 1018 steel corrosion in 3% NaCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques, which may find application as eco-friendly corrosion inhibitors. The 4-PC provides inhibitor properties that protect AISI 1018 low carbon steel against corrosion at low concentrations (5 ppm) obtained by EIS. Polarization studies showed that the inhibitor was of mixed type. The inhibition efficiency by the two electrochemical techniques shows similar results. The inhibitor adsorption was demonstrated to be a combined process (physisorption and chemisorption) according to the Langmuir isotherm.

In this work, we present low temperature flash light based curing of spray coated high-k zirconium oxide (ZrOx) thin film to realize low voltage operated flexible and fully patterned organic thin film transistors (OTFTs). A simple sol-gel technique was followed to prepare ZrOx from a zirconium complex. By spraying the precursor solution onto substrate through shadow mask, a patterned film was obtained. On the other hand subsequent flash light curing of the coated film not only reduced processing time but also allowed us to fabricate device on polymeric flexible substrate. Spectroscopic analysis confirmed formation of ZrOx film from the solution of zirconium complex. Finally as prepared ZrOx was used as gate dielectric layer in OTFT structure to keep operating voltage as low as -3V. Flexible polyethylenetrephthalate (PET) sheet was used as flexible substrate and pentacene was used as organic active layer. Each and every layer was deposited through metal made shadow mask to develop fully patterned OTFT. Field effect mobility and ON/OFF ratio of as fabricated transistor was found to be as high as 1.2 cm2V-1S-1 and 105 respectively.

The Swedish spent nuclear fuel canister design KBS-3 consists of a cylindrical copper shell surrounding an iron insert that holds the spent fuel. Like in most other canister designs the mass of iron constitutes the majority of the canister weight. In order for groundwater to access the spent fuel in a future repository the copper shell must fail and iron corrosion occur. Spent nuclear fuel dissolution will therefor likely proceed under conditions of simultaneous anoxic iron corrosion. The iron corrosion can likely suppress the spent fuel release by creation of strongly reducing conditions from Fe(II) formation and the generation of large quantities of hydrogen. Redox sensitive radionuclides may either be reductively precipitated by dissolved Fe(II) or from interaction with iron corrosion products such a magnetite or green rusts. The generated hydrogen (up to several MPa) may also inhibit the spent nuclear fuel dissolution at the surface of the fuel via the so called hydrogen effect. In order to probe these effects an autoclave experiment was performed in which a basket with PWR spent nuclear fuel (burnup ∼43 MWd/kgU) was suspended in an autoclave containing a simplified groundwater (10 mM NaCl, 2 mM NaHCO3) with iron powder. The autoclave was sparged and pressurized with argon. Following an initial rise in radionuclide concentrations from dissolution of pre-oxidised phases the U concentration dropped to 3x10-9 M within 76 days, in-line with the solubility of amorphous UO2, expected to form under reducing conditions. Any Cs and Sr release also ceased within 223 days indicating complete transition from dissolution of pre-oxidized phases and instant release fractions to conditions with inhibition of the dissolution of the fuel matrix. Gas phase analysis and pressure monitoring showed a steady build-up of hydrogen at a rate higher than what could be attributed to radiolysis, reaching hydrogen partial pressures of several hundred kPa. The results indicate continuous corrosion of iron, with magnetite as the dominating iron corrosion product.

Catalytic chemical vapor deposition enables the synthesis and deposition of carbon nanotubes (CNT) directly on substrates, thereby immobilizing them and potentially preventing them from bundling after synthesis. In this work, we investigate the use of this strategy to prepare ceramic hybrids with unbundled CNTs on aluminum oxide (AO) powder and fabric substrates, which are commonly used in the fabrication of ceramic laminate composites. CNT –AO powder hybrids are produced in 250 g batches with up to about 3 wt% CNT content, which is a sufficient amount for sintering into composite plates for mechanical and ballistic characterization. CNT – AO fabric hybrids are produced and it is found that the polymer coating that comes on the as-purchased fabric aids with CNT deposition. Conformal nickel and nickel oxide films deposited by an atomic layer deposition process are found to be excellent catalysts for CNT deposition. These conformal metal films are being used to create better CNT – ceramic hybrids for processing into better composite materials.

Periodic array of metallic nanocylinder combined with the highly luminous dielectric layer is a good platform to control the intensity, spectral shape and directionality of photoluminescence (PL). In spite of its importance, the effect of cylinder height on the PL properties has not been verified experimentally. Here we investigate the effect of cylinder height on the PL properties both experimentally and numerically. The system consisted of a highly luminous layer made of Eu(III) complex and a series of periodic array of aluminum nanocylinders with different heights. The strongest directional PL was achieved when the height is similar to the diameter, i.e., the aspect ratio close to unity. Our finding is useful for designing the compact and efficient luminescence source with directional output.

The conservation of the architectural surfaces in the tablinum of the House of the Bicentenary at the ancient Roman site of Herculaneum is a collaborative project of the Getty Conservation Institute, the Herculaneum Conservation Project and the Soprintendenza Pompeii. The tablinum was selected as a case study given the significance, beauty, and severe deterioration of its decorated surfaces. A multi-disciplinary team with a wide range of expertise, comprised of conservators, chemists, geo-physicists, engineers, and conservation scientists, worked in partnership across a number of institutions with the objective to study the wall paintings in the tablinum. Scientists and conservators worked together to test the feasibility of portable techniques and in situ investigations to better understand Roman painting technology; identify previous restoration materials; determine the presence of alteration products; and characterize deterioration mechanisms commonly found on architectural surfaces at archaeological sites of the Vesuvian Region. The collection and interpretation of the instrumental data has been critical to the design and implementation of appropriate passive and remedial interventions to stabilize the architectural surfaces and mitigate deterioration. The paper will present the results of the investigations using portable instrumentation along with a discussion of the capabilities and limitations of each technique and the practical implications of their use for architectural surfaces on archaeological sites.