Current conveyor based R- and C- multiplier circuits

One of the most limiting problems in the design of integrated circuits is related with the realization of resistance and capacitance values higher than those normally integrable. To meet the objectives of realizing resistance and capacitance values higher than those normally integrable three R- and C- multiplier circuits using IC AD844 configured as a second-generation current conveyor (CCII+) with a built-in buffer stage are described, analyzed and studied experimentally. The effects of AD844 non-idealities are also evaluated and discussed. The approach provides the designer with a new building block suitable for integrated and tunable filters. Computer simulations under PSpice environment are also reported.     

Investigation on the role of Joule heating on flash sintering using a combined experimental and modeling approach

Flash sintering is a novel technique of ultrafast densification. There is a continuous debate over the mechanisms that are responsible for such fast sintering. In this work, we have assessed the role of Joule heating and thermal runaway on densification using a combined experimental and modeling approach. First, flash sintering (FS) experiments have been carried out for three different oxides that have very different electrical and thermal conductivities, namely, 3- and 8-mol% yttria-stabilized zirconia and titania (TiO₂). Then, we modeled the densification during FS, for identical experimental conditions, using a novel combined finite element modeling and master sintering curve approach. The results obtained through experiment and modeling have been compared. Finally, our results show that ultrafast densification observed during FS cannot be replicated through Joule heating and thermal runaway alone at low current density (<100 mA/mm²), suggesting that a contribution from other mechanisms is likely essential to explain the observed ultrafast densification. However, Joule heating and thermal runaway can account for the ultrafast densification at higher than 100 mA/mm² current density.     

Synthesis and characterization of novel saponified guar‐graft‐poly(acrylonitrile)/silica nanocomposite materials

The combination of carbohydrates with silicon‐based ceramic materials offers attractive means of production for high performance materials. Present article describes the synthesis of novel nanocomposites out of SiO₂ and saponified guar‐graft‐poly(acrylonitrile) (SG). Tetraethoxysilane was used as the precursor for silica and growth of SiO₂ phase was allowed concurrently in the presence of SG. The material so obtained was thermally treated at 80°C, 160°C, 500°C, and 900°C to study the effect of thermal curing on its properties. During the curing process, silanol surface groups of silica globules reacted to create the reinforced SiO₂‐SG substance. It was observed that at 900°C, the SiO₂ phase crystallized out in tetragonal shape (similar to Cristobalite form of silica) in presence of SG. The chemical, structural and textural characteristics of the composites were determined by FTIR, XRD, TGA‐DTA, SEM and BET studies. The materials were also evaluated as efficient Zn²⁺ metal binder. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 536–544, 2007     

A Tryptophan-Deficient Diet Induces Gut Microbiota Dysbiosis and Increases Systemic Inflammation in Aged Mice

The gut microflora is a vital component of the gastrointestinal (GI) system that regulates local and systemic immunity, inflammatory response, the digestive system, and overall health. Older people commonly suffer from inadequate nutrition or poor diets, which could potentially alter the gut microbiota. The essential amino acid (AA) tryptophan (TRP) is a vital diet component that plays a critical role in physiological stress responses, neuropsychiatric health, oxidative systems, inflammatory responses, and GI health. The present study investigates the relationship between varied TRP diets, the gut microbiome, and inflammatory responses in an aged mouse model. We fed aged mice either a TRP-deficient (0.1%), TRP-recommended (0.2%), or high-TRP (1.25%) diet for eight weeks and observed changes in the gut bacterial environment and the inflammatory responses via cytokine analysis (IL-1a, IL-6, IL-17A, and IL-27). The mice on the TRP-deficient diets showed changes in their bacterial abundance of Coriobacteriia class, Acetatifactor genus, Lachnospiraceae family, Enterococcus faecalis species, Clostridium sp genus, and Oscillibacter genus. Further, these mice showed significant increases in IL-6, IL-17A, and IL-1a and decreased IL-27 levels. These data suggest a direct association between dietary TRP content, the gut microbiota microenvironment, and inflammatory responses in aged mice models.     

3D Modelling of Superconductor Enabled Magnetic Induction Transmitter and Relay Coil for Non-conventional Media Communication

The well established way of communication using radio frequency (RF) waves do not perform well in Non-Conventional (Non-Con) media viz. underground and underwater. Herein, the medium of soil or water is dynamic thus the use of RF technique is unusable. To establish a more effective communication in Non-Con media, researches showed that Magnetic Induction (MI) communication to be more suitable. In MI communication, parameters like number of turns, size and coil orientation have a significant effect on transceiver coil model. In this paper, a novel MI transmitter model using superconductor (SC) in one directional (1D) and in three directional (3D) is proposed. The model provides an enhanced magnetic field strength over a given distance. Further, SC based relay coils which collectively known as waveguide structure is also proposed to increase the MI communication range with intensified field strength. The performance evaluations are quantified in terms of communication range and received power for Non-Con medias. The frequency response for SC based transmitter model is given for maximum power transfer. Besides, the performance of traditional MI systems and waveguide are quantitatively compared with our improved SC based MI system and waveguide. The results show that the system has stronger magnetic field strength and greater communication range than the traditional ones.

     

Environmental Ageing of Adhesively-Bonded Joints. II. Mechanical Studies

The effects of exposure to moisture on the mechanical properties of a series of adhesively-bonded structures are reported. Changes observed in the maximum load, shear modulus, strain at maximum load, fracture energy, fracture toughness and stress are discussed and correlated with variation of the dielectric parameters. An initial increase in fracture toughness observed in the joints correlates well with the uptake of moisture having led to a lowering of the glass-rubber transition temperature. Differences in the ultimate strength and energy to failure for different surface pretreatments are observed. Loss in mechanical properties observed over the period of the study are paralleled by changes in the dielectric properties of the joints.     

Co,Fe, and Ti Implants in InGaAs and Co Implants in InP at 200° C

Elevated temperature (200° C) single- and multiple-energy Co implants inn-type InP, Co and Fe implants in n-type In_0.53Ga_0.47As, and Ti implants inp-type In_0.53Ga_0.47As were performed. For elevated temperature, single-energy Co and Fe implants, no satellite peaks at various locations like 0.8R _P, R_P + ΔR_P, and 2R _P R _P is the projected range and ΔR _P the straggle of the implant) are observed, in contrast to the case of room temperature implants. However, the outdiffusion of the implant is as severe as that in room temperature implantation for high temperature anneals. Indiffusion of the implant also occurs, but it is not as severe as the outdiffusion. High temperature annealing of Ti-implanted material results in a slight indiffusion of Ti, with minimal redistribution or outdiffusion. For all elevated temperature implants, the lattice quality of the annealed material is close to that of the virgin unimplanted material. For all ion species used in this study, resistivities close to the intrinsic limit are obtained in the implanted and annealed materials.