Multifunctional substrates of thin porous alumina for cell biosensors

We have fabricated anodic porous alumina from thin films (100/500 nm) of aluminium deposited on technological substrates of silicon/glass, and investigated the feasibility of this material as a surface for the development of analytical biosensors aiming to assess the status of living cells. To this goal, porous alumina surfaces with fixed pitch and variable pore size were analyzed for various functionalities. Gold coated (about 25 nm) alumina revealed surface enhanced Raman scattering increasing with the decrease in wall thickness, with factor up to values of approximately 10⁴ with respect to the flat gold surface. Bare porous alumina was employed for micro-patterning and observation via fluorescence images of dye molecules, which demonstrated the surface capability for a drug-loading device. NIH-3T3 fibroblast cells were cultured in vitro and examined after 2 days since seeding, and no significant (P > 0.05) differences in their proliferation were observed on porous and non-porous materials. The effect on cell cultures of pore size in the range of 50–130 nm—with pore pitch of about 250 nm—showed no significant differences in cell viability and similar levels in all cases as on a control substrate. Future work will address combination of all above capabilities into a single device.     

Influence of thermally induced,dehydroxylated nanoclay on polymer nanocomposites

This work reports a novel approach towards a chemical-free treatment of nanoclay through extensive thermal exposure. Dehydroxylation at high temperature was utilized to enhance the influence of nanoclay on the properties of polymer. The effect of this treatment of nanoclay, on the polymer properties, with reference to Polypropylene (PP) has been investigated. The FTIR spectra revealed the successful removal of water from the intergallery spacing of the nanoclay. The maintained structural configuration of the clay was confirmed using WAXD pattern. The uniform dispersion and exfoliation of thermally treated clay layers inside the polymer matrix was confirmed through enhanced mechanical properties. Improved crystallization properties, thermal stability and flame retardant characteristic were also noticed in the nanocomposites reinforced with thermally dehydroxylated clay. This study revealed that the dehydroxylation approach of modification of nanoclay may provide much enhanced properties of polymer, without involvement of any chemical for modification.     

Superhydrophobic surface decorated with vertical ZnO nanorods modified by stearic acid

Static and dynamic wettability of the ZnO nanorod surface prepared by a facile and inexpensive route is reported. The wettability of the ZnO surface was controlled and tuned by post hydrophobization using different stearic acid concentrations. The surface of the ZnO nanorods modified with 8 mM stearic acid showed a static water contact angle of 152° and sliding angle of 9°, which indicates superhydrophobicity. This suggests that the combination of the rough structures achieved by the ZnO nanorods and low surface energy provided by stearic acid modification results in superhydrophobicity and a very low sliding angle. The crystal structure, surface chemical elements, surface morphology, surface roughness, and static and dynamic water contact angles of the ZnO coatings were studied in detail. Further, the surface properties were assessed by calculating the surface free energies and work of adhesion for unmodified and stearic-acid-modified ZnO nanostructure surfaces. These coatings can find potential industrial applications in the electronic industry.     

Influence of compatibilizer on mechanical,morphological and rheological properties of PP/ABS blends

The objective of this work was to study the compatibilizer effect on polypropylene (PP) and acrylonitrile butadiene styrene (ABS) blends. The blends were coextruded and injection molded in various ratios of ABS with and without compatibilizers. Universal testing machine was employed to analyze the tensile properties of basic PP/ABS binary blends. From the mechanical testing, the impact and tensile properties of PP/ABS blend were optimized at 80/20 weight ratio. Various compatibilizers such as PP-g-MAH, SEBS-g-MAH and ethylene α-olefin copolymer were used and their comparative performance on binary blend was enumerated. Hybrid compatibilization effect was also studied and reported. However, the addition of compatibilizers showed the maximum increase in impact strength attributed to rubber toughening effect of ABS. The effect of compatibilizers on morphological properties was examined using scanning electron microscopy (SEM). SEM micrographs depicted the more efficient dispersion of ABS particles in PP matrix with the addition of compatibilizers. Further, interparticle distance analysis was carried out to evaluate the rubber toughening effect. The ABS droplet size in compatibilized PP/ABS blend was brought to minimum of 3.2 μm from 9.9 μm with the addition of compatibilizers. The melt rheology of PP/ABS blend systems was investigated through parallel plate arrangement in frequency sweep. Linear viscoelastic properties like storage (G′) and loss (G″) modulus and complex viscosity (η*) have been reported with reference to the virgin materials. It is understood that the combination of compatibilizers (hybrid compatibilizer) had a considerable effect on the overall blend properties.     

Load Induced Microstructure Evolution and Friction in an Organic Monolayer Self-assembled on a Silicon Substrate

In sliding of organic self-assembled monolayer against a probe the friction force is generally found to vary linearly with normal load. Here, lateral force microscopy is used to track the physical changes at the interface brought about when an octadecyltrichlorosilane monolayer, self-assembled on a silicon wafer, is slid against a Si₃N₄ tip in the 0–30 nN load range. Regarding a morphologically heterogeneous monolayer domain to be made up of tiles of characteristic friction forces, each tile is in a unique physical state; the variation of area fraction (in a scan area) of each tile is tracked as a function of normal load. The area averaged friction force at a load is obtained by summing the fractional forces of constituent friction tiles. The friction force obtained thus, is found to vary linearly with normal tip load. It is observed that this force is dominated by the low-friction crystalline tiles at low loads and by the high friction more amorphous tiles at high loads. This suggests that for a self- assembled monolayer the load governance of friction as implied by the Amontons Law may be attributed to the physical changes that are brought about at the interface by changing the normal load.     

Evolution of ZnS Nanoparticles via Facile CTAB Aqueous Micellar Solution Route: A Study on Controlling Parameters

Synthesis of semiconductor nanoparticles with new photophysical properties is an area of special interest. Here, we report synthesis of ZnS nanoparticles in aqueous micellar solution of Cetyltrimethylammonium bromide (CTAB). The size of ZnS nanodispersions in aqueous micellar solution has been calculated using UV-vis spectroscopy, XRD, SAXS, and TEM measurements. The nanoparticles are found to be polydispersed in the size range 6–15 nm. Surface passivation by surfactant molecules has been studied using FTIR and fluorescence spectroscopy. The nanoparticles have been better stabilized using CTAB concentration above 1 mM. Furthermore, room temperature absorption and fluorescence emission of powdered ZnS nanoparticles after redispersion in water have also been investigated and compared with that in aqueous micellar solution. Time-dependent absorption behavior reveals that the formation of ZnS nanoparticles depends on CTAB concentration and was complete within 25 min.     

A probabilistic approach to integrating dynamic data in reservoir models

Developing geostatistical reservoir models that are geologically realistic and correctly reflect production history is important for accurately assessing the uncertainty associated with production forecasts. Conditioning reservoir models to dynamic data is challenging due to the non-linear relationship between the measured flow response data and the model parameters (porosity, permeability, etc.). The focus of this paper is to present a methodology for efficiently integrating dynamic production data into reservoir models. In contrast to other methods for production data integration, the proposed methodology attempts to quantify the information in production data pertaining to reservoir heterogeneity in a probabilistic manner. The conditional probability representing the uncertainty in permeability at a location is iteratively updated to account for the additional information contained in the dynamic response data. It is demonstrated that the reservoir models obtained by integrating dynamic data exhibit accurate reservoir connectivity characteristics. A localized perturbation procedure is also presented to account for multiple flow regions within the reservoir. Such an improved scheme utilizes a set of locally varying deformation parameters to guide the iterative updating process in order to obtain a global history match. The proposed methodology is demonstrated on a realistic case example.     

One-shot learners using negative counterexamples and nearest positive examples

As some cognitive research suggests, in the process of learning languages, in addition to overt explicit negative evidence, a child often receives covert explicit evidence in form of corrected or rephrased sentences. In this paper, we suggest one approach to formalization of overt and covert evidence within the framework of one-shot learners via subset and membership queries to a teacher (oracle). We compare and explore general capabilities of our models, as well as complexity advantages of learnability models of one type over models of other types, where complexity is measured in terms of number of queries. In particular, we establish that “correcting” positive examples are sometimes more helpful to a learner than just negative (counter) examples and access to full positive data.