Different type of mechanisms of gas sensing, various factors that affect the mechanisms, ways to improve the gas sensitivity, state of the art of fabrication techniques and materials used are reviewed. The work also discusses a novel type of gas sensor derived based on the reviewed mechanisms and materials. The development of semiconductor-based gas sensors using tin oxide which is simple to implement, low cost and offering good stability and sensitivity is discussed.

All biological molecules and cell organelles are chemo mechanically controlled systems known to every biologist. The control signals governing them are electrical. The influence of an electric field in them makes a disturbance such that they behave as an electronic distributed network. It is an interdisciplinary art to activate them and work as an electronic device. Modeling the biological molecules as per the devices is by understanding their stability and work functions. Here a micro tubule (MT) molecule is modeled to function as a diode in electronic parameters, there by not disturbing its biological function. The MT is similar to its other cytoskeleton filament. In its two dimers alpha and beta, in the tunneling effect of the ions, can establish the diode characteristics in its conductivity of electric ionic current.

The proposed work discusses different parameters which are considered to improve the performance of a tin oxide-based thin film gas sensor. This includes analysing and deducing suitable catalytic additives to enhance the performance of the sensor in terms of selectivity and sensitivity. Chemical sensitization and electronic sensitization are performed to improve the rate of response of the sensor.

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Over the years there has been a natural evolution of frequency control devices. This has come about due to the various requirements, some being cost driven, others performance/reliability issues and others by the ever reducing design cycle times. The incumbent quartz based devices have long since been the standard by which most of the new invention devices are compared, at least from a marketing standpoint. This is due to the long (some 75 years) history of quartz as a very stable, high quality material. Frequency versus temperature response as well as aging, jitter and phase noise characteristics are well chronicled in the industry. However a concise technical correlation of such characteristics with the 'replacement' technology is rather elusive. This exercise seeks to apply standard measurement techniques under the same test conditions for all devices for direct comparison of performance and capability.All devices characterized in this paper were commercially purchased to ensure a random sampling of the technology. This data represents the technology that was commercially available at the time of the study. Frequency Temperature Test Conditions:All devices were tested at 0.2° C step size in the same test system at the same time. -40 -20