Synthesis and characterization of triazole rich polyether polyols using click chemistry for highly branched polyurethanes

The present work describes development of moisture cured polyurethane–urea coatings based on 1,2,3-triazole rich polyether polyols. In this paper, two polyether polyols were synthesized by using 1,3-dipolar azide–alkyne cycloaddition reaction and they were named as PL-1 and PL-2 where PL-1 is 9 terminal hydroxyl groups and PL-2 is 6 terminal hydroxyl groups. These polyols were reacted with 4, 4′-diisocyanatodicyclohexylmethane (H₁₂MDI) at OH:NCO ratio of 1:1.2 in order to obtain isocyanate terminated polyurethane prepolymers. The resulted prepolymers were casted on tin foil and cured under atmospheric moisture in order to get completely cured polyurethane–urea free films. The free films were characterized by using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) techniques. The TGA and DMTA results showed that these films have good thermal and mechanical stability. Anti-microbial studies proved that these polyurethane films show good resistance towards different bacterial and fungal attacks. These polymers were also coated on mild steel panels in order to evaluate corrosion resistance properties by using salt spray and electro chemical polarization studies.     

Choice modeling and the brain: A study on the Electroencephalogram (EEG) of preferences

Choice conjures the idea of a directed selection of a desirable action or object, motivated by internal likes and dislikes, or other such preferences. However, such internal processes are simply the domain of our human physiology. Understanding the physiological processes of decision making across a variety of contexts is a central aim in decision science as it has a great potential to further progress decision research. As a pilot study in this field, this paper explores the nature of decision making by examining the associated brain activity, Electroencephalogram (EEG), of people to understand how the brain responds while undertaking choices designed to elicit the subjects’ preferences. To facilitate such a study, the Tobii-Studio eye tracker system was utilized to capture the participants’ choice based preferences when they were observing seventy-two sets of objects. These choice sets were composed of three images offering potential personal computer backgrounds. Choice based preferences were identified by having the respondent click on their preferred one. In addition, a brain computer interface (BCI) represented by the commercial Emotiv EPOC wireless EEG headset with 14 channels was utilized to capture the associated brain activity during the period of the experiments. Principal Component Analysis (PCA) was utilized to preprocess the EEG data before analyzing it with the Fast Fourier Transform (FFT) to observe the changes in the main principal frequency bands, delta (0.5–4 Hz), theta (4–7 Hz), alpha (8–12 Hz), beta (13–30 Hz), and gamma (30–40 Hz). A mutual information (MI) measure was then used to study left-to-right hemisphere differences as well as front-to-back difference. Eighteen participants were recruited to perform the experiments with the average results showing clear and significant change in the spectral activity in the frontal (F3 and F4), parietal (P7 and P8) and occipital (O1 and O2) areas while the participants were indicating their preferences. The results show that, when considering the amount of information exchange between the left and right hemispheres, theta bands exhibited minimal redundancy and maximum relevance to the task at hand when extracted from symmetric frontal, parietal, and occipital regions while alpha dominated in the frontal and parietal regions and beta dominating mainly in the occipital and temporal regions.     

Toward improved control of prosthetic fingers using surface electromyogram (EMG) signals

A fundamental component of many modern prostheses is the myoelectric control system, which uses the electromyogram (EMG) signals from an individual’s muscles to control the prosthesis movements. Despite the extensive research focus on the myoelectric control of arm and gross hand movements, more dexterous individual and combined fingers control has not received the same attention. The main contribution of this paper is an investigation into accurately discriminating between individual and combined fingers movements using surface EMG signals, so that different finger postures of a prosthetic hand can be controlled in response. For this purpose, two EMG electrodes located on the human forearm are utilized to collect the EMG data from eight participants. Various feature sets are extracted and projected in a manner that ensures maximum separation between the finger movements and then fed to two different classifiers. The second contribution is the use of a Bayesian data fusion postprocessing approach to maximize the probability of correct classification of the EMG data belonging to different movements. Practical results and statistical significance tests prove the feasibility of the proposed approach with an average classification accuracy of ≈90% across different subjects proving the significance of the proposed fusion scheme in finger movement classification.     

Forecasting stock returns based on information transmission across global markets using support vector machines

This paper provides evidence that forecasts based on global stock returns transmission yield better returns in day trading, for both developed and emerging stock markets. The study investigates the performance of global stock market price transmission information in forecasting stock prices using support vector regression for six global markets—USA (Dow Jones, S&P500), UK (FTSE-100), India (NSE), Singapore (SGX), Hong Kong (Hang Seng) and China (Shanghai Stock Exchange) over the period 1999–2011. The empirical analysis shows that models with other global market price information outperform forecast models based merely on auto-regressive past lags and technical indicators. Shanghai stock index movement was predicted best by Hang Seng Index opening price (57.69), Hang Seng Index by previous day’s S&P500 closing price (54.34), FTSE by previous day’s S&P500 closing price (57.94), Straits Times Index by previous day’s Dow Jones closing price (54.44), Nifty by HSI opening price (60), S&P500 by STI closing price (55.31) and DJIA by HSI opening price (55.22), and Nifty was found to be the most predictable stock index. Trading using global cues-based forecast model generates greater returns than other models in all the markets. The study provides evidence that stock markets across the globe are integrated and the information on price transmission across markets, including emerging markets, can induce better returns in day trading.     

The Effect of Concurrent Straining on Phase Transformations in NiAl Bronze During the Friction Stir Processing Thermomechanical Cycle

Equivalent strains up to a value of ≈2.7 were determined by evaluation of the shape changes of the phases in a duplex α(fcc)/β(bcc) microstructure formed ahead of the pin tool extraction site during the friction stir processing (FSP) thermomechanical cycle in a cast NiAl bronze alloy. Correlation of the local strains with volume fractions of the various microstructure constituents in this alloy shows that the concurrent straining of FSP results in acceleration of the α + β → β reaction in the thermomechanically affected zone (TMAZ) ahead of the pin extraction site. The resulting volume fraction of β (as determined by the volume fraction of its transformation products formed during post-FSP cooling) corresponds closely to the volume fraction expected for the peak stir zone temperature measured separately by means of thermocouples embedded within the tool pin profile along the tool path. The stir zone (SZ) in this material exhibits near-equilibrium microstructures despite brief dwells near the peak temperature (T _peak ≈ 0.95T _melt), reflecting large local strains and strain rates associated with this process.     

Freeze dried cross linking free biodegradable composites with microstructures for tissue engineering and drug delivery application

Biodegradable laminated polymer composites of agarose (A), gelatin (G) and hydroxyapatite (HAp) having 3D network of interconnected pores (1–500 μm) were fabricated without using cross linking agents. The incorporation of HAp to A, G and AG had considerable influence on the swelling behaviour, drug release and haemolytic activity. A-HAp scaffolds demonstrated interconnected porosity with extended drug release. G-HAp scaffolds possessed enhanced mechanical property. AG-HAp scaffolds exhibited extended drug delivery, haemocompatibility and efficacy against Gram positive bacteria compared with G-HAp. Hence, AG-HAp composites could be used us a scaffold for tissue engineering and drug delivery system. This method provides non toxic, versatile and cost effective biodegradable scaffolds which could be used for various biomedical applications.     

Ion beam studies on reactive DC sputtered manganese doped indium tin oxide thin films

Indium based transparent conducting oxides doped with magnetic elements have been studied intensively in recent years with a view to develop novel ferromagnetic semiconductors for spin-based electronics. In the present work, we have grown manganese doped indium tin oxide (Mn:ITO) thin films, onto Si and Si/SiO₂ substrates by DC reactive sputtering of a composite target containing indium-tin alloy and manganese, in a gas mixture of oxygen and argon. Glancing angle X-ray diffraction (GXRD) studies reveal the polycrystalline nature of the films. Magnetic measurements carried out using vibrating sample magnetometer (VSM) suggest that the films are ferromagnetic at room temperature, with a saturation magnetization of ∼22.8 emu/cm³. The atomic percentages of In, Sn, Mn and O, as estimated using Rutherford backscattering spectrometry (RBS) are 37.0, 4.0, 1.6 and 57.4, respectively. RBS measurements reveal that the interface of the films with Si substrate has a ∼30 nm thick intermediate layer. This layer consists of oxygen, silicon, indium, tin and manganese, in the ratio 1:0.56:0.21:0.07:0.03, indicative of diffusion of elements across the interface. The films on Si/SiO₂, on the other hand, have a sharp interface.     

Hierarchically Ordered Nano‐Heterostructured PZT Thin Films with Enhanced Ferroelectric Properties

Realization of ferroelectric (FE) devices based on the polarization effects of Pb(Zr_0.52Ti_0.48)O₃ (PZT) has reinforced the investigation of this material in multiple dimensions and length scales. Multi‐level hierarchical nanostructure engineering in PZT thin films offer dual advantages of variable length‐scale and dimensionality. Here, the growth of hierarchically ordered PZT nano‐hetero­structures (Nhs) from PZT seed‐layer deposited on SrTiO₃:Nb (100) substrates, using a physical/chemical combined methodology involving pulsed laser deposition (PLD) and hydrothermal processes, is reported. Systematic SEM, TEM, and Raman spectroscopy studies reveal mixed hetero‐ and homo‐epitaxial growth mechanism. In the final stage, 3D Nh units cross‐link and form a dense network‐like Nh PZT thin‐film. FE polarizations are measured without using any polymer fill‐layer which otherwise introduces huge dielectric losses and lowers the polarization values for a FE device. In benefit, well saturated and symmetric FE hysteresis loops are observed with high degree of squareness and a high remnant polarization (54 μC cm^‐2 at a coercive field of 237 kV cm^‐1). This work provides a pathway towards preparing hierarchical PZT Nhs offering coherent design of high‐performance FE capacitors for data storage technologies in future.     

Relative performance of correlations to estimate hourly ambient air temperature and development of a general correlation

Correlations available in the literature to predict hourly ambient temperature are climate specific. Based on extensive meteorological database, correlations to predict hourly ambient temperature in terms of maximum and minimum temperatures of the day have been developed. The applicability of the present correlation has been examined for a wide range of locations, along with its comparison with other correlations developed earlier for a specific set of locations. The performance of the present correlation has been found to be superior to the performance of the existing correlations. Monthly average hourly ambient temperature values predicted with the present correlation agree with the data values within r.m.s differences of 0·26% when the ambient temperature is in K and the absolute error has been found to be 0·75. Copyright © 1999 John Wiley & Sons, Ltd.     

Thermopower and optical studies on undoped and manganese doped indium tin oxide films

Thermopower measurements in the range of 300-650 K along with room temperature optical absorption and electrical resistivity studies have been performed on indium tin oxide (ITO) and manganese doped indium tin oxide (Mn:ITO) thin films grown by reactive DC sputtering. The thermopower of the films measured in Ar ambient displayed irreversible changes attributable to oxygen loss. Thermopower, carrier concentration and resistivity of the films have been found to depend on oxygen vacancies and Mn concentration. The observations have been substantiated with optical absorption and room temperature electrical resistivity results. It has also been observed that band gap tuning in these films is possible by the introduction of Mn as well as oxygen vacancies.