8 research outputs found
Design and Development of an RF Energy Harvesting Wireless Sensor Node (EH-WSN) for Aerospace Applications
AbstractNumerous applications of wireless sensor networks are constrained by the limited battery power of the sensors. The power consumption of processors and microcontrollers could be scaled down dramatically with the new advances in microelectronics. This reduction gives rise to the possibility of energy harvesting sources to power wireless sensor nodes. In this paper a summary is given of our ongoing research work on RF Energy Harvesting Wireless Sensor Node (EH-WSN) which can plug-in to the already developed Wireless Instrumentation System (WIS) for aerospace applications. Present WSN's which are powered from battery have limited operational lifetime. While energy harvesting has the potential to enable near-perpetual system operation, design of which is a complex trade-off due to the interaction of numerous factors such as the characteristics of the energy source, power supply requirements, power management futures, WSN application behaviour, chemistry and capacity of batteries used etc. In this work, we have identified a suitable power harvesting cum battery management scheme which harvests power consistently and deterministically from a secondary RF source which can be used even in harsh real-time applications. Using a RF power harvesting receiver IC and a compact power management cum storage circuit, we establish the test bed and conduct a series of experiments to verify the effectiveness of the proposed scheme. We have demonstrated continuous operation of the sensor node at an operating distance of 2 meters from the RF power source for a data rate of 240 sps. This is achieved by using special synchronized MAC protocol, low power techniques, usage of low leakage components and systematic coding of the micro controller firmware. This paper provides an insight into how various power reduction techniques can be used and orchestrated such that satisfactory performance can be achieved for a given energy budget
Antimicrobial effects of Citrus sinensis peel extracts against dental caries bacteria: an in vitro study
Background: Ethnomedicine is gaining admiration since years but still there is abundant medicinal flora which is
unrevealed through research. The study was conducted to assess the
in vitro
antimicrobial potential and also determine the minimum inhibitory concentration (MIC) of
Citrus sinensis peel
extracts with a view of searching a novel
extract as a remedy for dental caries pathogens.
Material and Methods: Aqueous and ethanol (cold and hot) extracts prepared from peel of
Citrus sinensis
were
screened for
in vitro
antimicrobial activity against
Streptococcus mutans
and
Lactobacillus acidophilus
, using agar
well diffusion method. The lowest concentration of every extract considered as the minimal inhibitory concentration (MIC) values were determined for both test organisms. One way ANOVA with Post Hoc Bonferroni test was
applied for statistical analysis. Confidence level and level of significance were set at 95% and 5% respectively.
Results: Dental caries pathogens were inhibited most by hot ethanolic extract of
Citrus sinensis
peel followed by
cold ethanolic extract. Aqueous extracts were effective at very high concentrations. Minimum inhibitory concentration of hot and cold ethanolic extracts of
Citrus sinensis peel
ranged between 12-15 mg/ml against both the dental
caries pathogens.
Conclusions:
Citrus sinensis peels
extract was found to be effective against dental caries pathogens and contain
compounds with therapeutic potential. Nevertheless, clinical trials on the effect of these plants are essential before
advocating large-scale therap
Data acquisition and processing at ocean bottom for a Tsunami warning system
The design and development of a Bottom Pressure Recorder for a Tsunami Early Warning System is described here. The special requirements that it should satisfy for the specific application of deployment at ocean bed and pressure monitoring of the water column above are dealt with. A high-resolution data digitization and low circuit power consumption are typical ones. The implementation details of the data sensing and acquisition part to meet these are also brought out. The data processing part typically encompasses a Tsunami detection algorithm that should detect an event of significance in the background of a variety of periodic and aperiodic noise signals. Such an algorithm and its simulation are presented. Further, the results of sea trials carried out on the system off the Chennai coast are presented. The high quality and fidelity of the data prove that the system design is robust despite its low cost and with suitable augmentations, is ready for a full-fledged deployment at ocean bed. (C) 2013 Elsevier Ltd. All rights reserved
Molecular Catch Bonds and the Anti-Hammond Effect in Polymer Mechanochemistry
While
the field of polymer mechanochemistry has traditionally focused
on the use of mechanical forces to accelerate chemical processes,
theoretical considerations predict an underexplored alternative: the
suppression of reactivity through mechanical perturbation. Here, we
use electronic structure calculations to analyze the mechanical reactivity
of six mechanophores, or chemical functionalities that respond to
mechanical stress in a controlled manner. Our computational results
indicate that appropriately directed tensile forces could attenuate
(as opposed to facilitate) mechanochemical phenomena. Accompanying
experimental studies supported the theoretical predictions and demonstrated
that relatively simple computational models may be used to design
new classes of mechanically responsive materials. In addition, our
computational studies and theoretical considerations revealed the
prevalence of the anti-Hammond (as opposed to Hammond) effect (i.e.,
the increased structural dissimilarity between the reactant and transition
state upon lowering of the reaction barrier) in the mechanical activation
of polyatomic molecules
Molecular Catch Bonds and the Anti-Hammond Effect in Polymer Mechanochemistry
While
the field of polymer mechanochemistry has traditionally focused
on the use of mechanical forces to accelerate chemical processes,
theoretical considerations predict an underexplored alternative: the
suppression of reactivity through mechanical perturbation. Here, we
use electronic structure calculations to analyze the mechanical reactivity
of six mechanophores, or chemical functionalities that respond to
mechanical stress in a controlled manner. Our computational results
indicate that appropriately directed tensile forces could attenuate
(as opposed to facilitate) mechanochemical phenomena. Accompanying
experimental studies supported the theoretical predictions and demonstrated
that relatively simple computational models may be used to design
new classes of mechanically responsive materials. In addition, our
computational studies and theoretical considerations revealed the
prevalence of the anti-Hammond (as opposed to Hammond) effect (i.e.,
the increased structural dissimilarity between the reactant and transition
state upon lowering of the reaction barrier) in the mechanical activation
of polyatomic molecules
Molecular Catch Bonds and the Anti-Hammond Effect in Polymer Mechanochemistry
While the field of polymer mechanochemistry has traditionally focused on the use of mechanical forces to accelerate chemical processes, theoretical considerations predict an underexplored alternative: the suppression of reactivity through mechanical perturbation. Here, we use electronic structure calculations to analyze the mechanical reactivity of six mechanophores, or chemical functionalities that respond to mechanical stress in a controlled manner. Our computational results indicate that appropriately directed tensile forces could attenuate (as opposed to facilitate) mechanochemical phenomena. Accompanying experimental studies supported the theoretical predictions and demonstrated that relatively simple computational models may be used to design new classes of mechanically responsive materials. In addition, our computational studies and theoretical considerations revealed the prevalence of the anti-Hammond (as opposed to Hammond) effect (i.e., the increased structural dissimilarity between the reactant and transition state upon lowering of the reaction barrier) in the mechanical activation of polyatomic molecules