Polymer-metal complexes of phenolic resin with Ln (III): thermal, catalytic and antimicrobial aspects

The polycondensation of 2-hydroxy-4-ethoxybenzophenone with 1, 3 butane diol was carried out in presence of polyphosphoric acid as a catalyst at 155 °C for 10 h to synthesize desired resin. The resin was used to synthesize polymer-metal complexes with 4f-block elements. The resin and its polymer-metal complexes were characterized on the basis of elemental analyses, electronic spectra, magnetic susceptibilities, FTIR, NMR and Thermogravimetric analyses. Morphology of resin and its polymer-metal complexes was studied by SEM. Catalytic activity of selected polymer-metal complexes in organic synthesis was examined. Antimicrobial activity of polymer-metal complexes against Escherichia coli, Bacillus subtilis, Staphylococcus aureus (bacteria) and Saccharomyces cerevisiae (yeast) were measured. It is observed that polymer-metal complexes are efficient and effective catalysts and antimicrobial agents.     

Centaurus: An Infrastructure for Service Management in Ubiquitous Computing Environments

In the near future, we will see dramatic changes in computing and networking hardware. A large number of devices (e.g., phones, PDAs, even small household appliances) will become computationally enabled. Micro/nano sensors will be widely embedded in most engineered artifacts, from the clothes we wear to the roads we drive on. All of these devices will be (wirelessly) networked using Bluetooth, IEEE 802.15 or IEEE 802.11 for short range connectivity creating pervasive environments. In this age where a large number of wirelessly networked appliances and devices are becoming commonplace, there is a necessity for providing a standard interface to them that is easily accessible by any user. This paper outlines the design of Centaurus, an infrastructure for presenting services to heterogeneous mobile clients in a physical space via some short range wireless links. The infrastructure is communication medium independent; we have implemented the system over Bluetooth, CDPD and Infrared, three well-known wireless technologies. All the components in our model use a language based on Extensible Markup Language (XML) for communication, giving the system a uniform and easily adaptable interface. Centaurus defines a uniform infrastructure for heterogeneous services, both hardware and software, to be made available to diverse mobile users within a confined space.     

PD/SOI SRAM performance in presence of gate-to-body tunneling current

This paper presents a detailed study on the effects of gate-to-body tunneling current on partially depleted silicon-on-insulator (PD/SOI) CMOS SRAM. It is shown that the presence of gate-to-body tunneling current changes the strength of individual cell transistor in the quiescent (standby) state, thus affecting subsequent write/read operations. The degradation in the "write" performance is shown to be more significant than the degradation in the "read" performance, and the effect is more pronounced at lowered temperature. For the beneficial side, the presence of the gate-to-body tunneling current reduces the initial cycle parasitic bipolar disturb from unselected cells on the same bitline during write/read operation.     

Effect of rapid thermal reoxidation on the electrical properties ofrapid thermally nitrided thin-gate oxides

The authors report a systematic study of the impact of post-nitridation rapid thermal anneals in oxygen and nitrogen on the electrical properties of MOS devices with thin gate oxides. A comparative study of the two annealing ambients has led to the formulation of qualitative models to describe the charge trapping properties of the respective gate dielectrics. Roles of the post-nitridation anneals in altering the radiation and hot-electron sensitivity of the MOS devices are investigated and explained on the basis of structural changes in the gate oxides during nitridation and subsequent annealing. The performance and reliability of MOSFETs with reoxidized nitrided gate oxides are investigated. Overall, the results indicate that reoxidized nitrided oxides show improved charge trapping properties, better resistance to radiation and hot-carrier stress, and improved high-field electron mobility in MOSFETs     

Effect of pressure stress work and viscous dissipation in some natural convection flows

A regular two-parameter perturbation analysis is presented here to study the effects of both viscous dissipation and pressure stress on natural convection flows. Four different vertical flows have been analyzed, those adjacent to an isothermal surface and uniform heat flux surface, a plane plume and flow generated from a horizontal line energy source on a vertical adiabatic surface, or wall-plume. For high gravity levels, stress work effects may be important for gases at very low temperatures, and for high Prandtl number liquids. Significant changes in heat transfer and flow quantities are observed even at moderate values of the perturbation parameters. For the entire range of Prandtl number values considered, the viscous dissipation term is seen to inhibit heat transfer from the surface for heated upward flows. The pressure term enhances heat transfer from the surface for lower Prandtl numbers. However, this effect is seen to reverse at Pr = 100, for both the isothermal and uniform flux surfaces. It is observed that viscous dissipation effects on heat transfer are much smaller than those due to the pressure stress, for many practical circumstances.     

Single-walled carbon nanotube incorporated novel three phase carbon/epoxy composite with enhanced properties

In the present work, single-walled carbon nanotubes were dispersed within the matrix of carbon fabric reinforced epoxy composites in order to develop novel three phase carbon/epoxy/single-walled carbon nanotube composites. A combination of ultrasonication and high speed mechanical stirring at 2000 rpm was used to uniformly disperse carbon nanotubes in the epoxy resin. The state of carbon nanotube dispersion in the epoxy resin and within the nanocomposites was characterized with the help of optical microscopy and atomic force microscopy. Pure carbon/epoxy and three phase composites were characterized for mechanical properties (tensile and compressive) as well as for thermal and electrical conductivity. Fracture surfaces of composites after tensile test were also studied in order to investigate the effect of dispersed carbon nanotubes on the failure behavior of composites. Dispersion of only 0.1 wt% nanotubes in the matrix led to improvements of 95% in Young's modulus, 31% in tensile strength, 76% in compressive modulus and 41% in compressive strength of carbon/epoxy composites. In addition to that, electrical and thermal conductivity also improved significantly with addition of carbon nanotubes.     

Growth and properties of transparent p-NiO/n-ITO (In2O3:Sn) p-n junction thin film diode

We have grown “all oxide” transparent p-n junction thin film nanostructure device by using chemical solution deposition and E-beam evaporation onto SiO₂ substrate. Combined grazing incidence X-ray diffraction and atomic force microscopy confirm phase pure, mono-disperse 30 nm NiO and 2 at. wt.% Sn doped In₂O₃ (ITO) nanocrystallites. Better than 70% optical transparency, at a wavelength of 600 nm, is achieved across 160 nm thick p-n junction. The optical band gap across the junction was found to decrease as compared to the intrinsic ITO and NiO. The current-voltage (I-V) characteristics show rectifying nature with dynamic transfer resistance ratio of the order of 10³ in the forward bias condition. Very small reverse leakage current with appreciable breakdown was observed under the reverse bias condition. The observed optical and electrical properties of oxide transparent diode are attributed to the heteroepitaxial nature and carrier diffusion at the junction interface.     

Implications of polarity of unipolar ionisers on reduction of effective dose attributable to thoron progeny

Negative ionisers have been proved to be effective in reducing indoor particulates in general and activity concentrations due to radon and thoron (220Rn) decay products in workplace environments in particular. However, in comparison, there exist few studies on the effect of positive ions for mitigation. In the present work, particle and activity concentration reduction has been compared for three experimental conditions (two for positive ions and one for negative) in an unoccupied room with elevated (220)Rn levels. The negative ioniser configuration provided a better concentration reduction factor of 4.59 with smallest characteristic depletion time. A theoretical estimate of the dose reduction factor is found to be 3.96 and 3.74, respectively, for positive and negative ioniser configuration.