The method employed to extract features from the sensor JQ1 molecular weight transients is based on the discrete wavelet transform [8, 12] and the pattern recognition makes use of simple support vector machine algorithms [13-16].2.?Experimental2.1. Set-upTo achieve a flow-modulation capable sniffer, a closed loop system was designed which was based on a PC-controlled peristaltic selleck chemicals Pazopanib Inhibitors,Modulators,Libraries pump and two three-way electro valves. Figure 1 shows the configuration devised. The stainless-steel sensor chamber housed three commercially-available Taguchi 8-series sensors (i.e. TGS-800,822 and 826). The Inhibitors,Modulators,Libraries system had two operating modes (cleaning phase and measurement phase). In the cleaning configuration, pure dry air enters the system through the first electro valve and cleans the peristaltic pump, the sensor chamber and the evaporation chamber.

Solid arrows in Figure 1 mark the flow of clean air in this mode. In the measurement mode, air re-circulates Inhibitors,Modulators,Libraries in the closed circuit indicated by dashed arrows in Inhibitors,Modulators,Libraries Figure 1. Initially, Inhibitors,Modulators,Libraries the flow is kept constant at 250 sccm and a calculated quantity of a given pollutant in the liquid phase is sprayed into the evaporation chamber using a chromatographic syringe (since temperature, Inhibitors,Modulators,Libraries pressure and system volume were known, the volume of liquid to be injected could be calculated with the ideal gas theory [11]). This allows for obtaining the steady-state response of the sensors. Then, a square-wave flow modulation at a given frequency is initiated, which allows for measuring the transient response of the sensors.

Inhibitors,Modulators,Libraries The system can generate other types of waveforms such as sinusoids or sawtooth functions, although they have not been used in this study.Figure 1.Experimental set-up during flow modulation Inhibitors,Modulators,Libraries experiments.A microcontroller commands Batimastat the speed of the peristaltic pump, which directly translates into different flow rates. A PC programmed with a in-house-written program communicates with the microcontroller so that the user can select the flow rate and the frequency and type of waveform that is applied to modulate the flow. Via this program, the PC commands the microcontroller to open or close the electro valves and to change the configuration of the system depending upon AV-951 the operating phase.

Moreover, the PC records the sensor response (i.e. sensor conductivity) at the rate of 2 samples per second.Figure selleck compound 2 shows that after a few modulation periods (e.

g. 2) the transient pattern of the sensors becomes highly selleck chemicals Tofacitinib reproducible. In practice, a measurement would take 2 periods of the modulation frequency to complete.Figure 2.Dynamic response of three sensors. The flow modulation is applied from 550 s onwards.Additionally, a temperature sensor was located inside the sensor chamber (placed perpendicular to the flow and between the chamber inlet and the gas sensors) so the effect of flow modulation in the temperature of the chamber (and hence in the operating temperature of the sensors) could be estimated.