Sensitivity water vapor effect

CO has no effect on sensitivity. On the other hand, high concentrations of oxygen in the ambient decrease hydrogen sensitivity. Water vapor has the same effect but only for T < 100°C. 

Since feedbacks may have a large potential for control of albedo and therefore temperature, it seems necessary to highlight them as targets for study and research. Besides the simple example above of cloud area or cloud extent, there are others that can be identified. High-altitude ice clouds, for example, (cirrus) have both an albedo effect and a greenhouse effect. Their occurrence is very sensitive to the amount of water vapor in the upper troposphere and to the thermal structure of the atmosphere. There may also be missing feedbacks. 

Grain boundaries have a significant effect upon the electrical properties of a polycrystalline solid, used to good effect in a number of devices, described below. In insulating materials, grain boundaries act so as to change the capacitance of the ceramic. This effect is often sensitive to water vapor or other gaseous components in the air because they can alter the capacitance when they are absorbed onto the ceramic. Measurement of the capacitance allows such materials to be used as a humidity or gas sensor. 

Laser-induced electronic fluorescence. Two devices reported recently look very promising for continuous atmospheric monitoring. Sensitivities of 0.6 ppb for nitrogen dioxide and ppb for formaldehyde are claimed. Careful attention to possible interference from other species is necessary. Detection of the hydroxyl radical in air ( 10 molecules/cm ) has been claimed for this technique, but it has been pointed out that this concentration seems much too high, especially because the air had been removed fix>m the sunlight 6 s before analysis spurious effects, such as photolysis of the ozone in the air by the laser beam and two-photon absorption by water vapor, might have been responsible for the hydroxyl radical that was observed. 

As stated, the capability of plasma deposits to reduce the access of water to corrosion-sensitive surfaces may be an important motivation for their application in corrosion protection. In order to study this property, Kapton polyimide film was selected as the substrate because of its high inherent permeability to water and its ability to resist elevated temperatures. The response of Kapton film overcoated by PPHMDSO to the permeation of water vapor is shown in Fig. 1. Clearly, the presence of the organo-silicone plasma film greatly reduces water permeation. The magnitude of the effect is much enhanced when plasma polymers are produced at high T and p. 

By controlling the structural and electronic properties of sNPS which are related to the nanocrystallite dimensions and porosity, their surface selectivity and sensitivity to different gases (nitrogen and carbon oxide, vapors of water and organic substances) can be adjusted. This approach for the effective detection of acetone, methanol and water vapor in air was described in [13-15].The minimal detectable acetone concentration was reported to be 12 pg/mL. Silicon sensors for detection of SO2 and some medicines such as penicillin were created [16-18]. sNPS were used for the development of a number of immune biosensors, particularly using the photoluminescence detection. Earlier we developed similar immune biosensors for the control of the myoglobin level in blood and for monitoring of bacterial proteins in air [19-23]. 

The effect of the presence of water vapor on hydrogen detection at room temperature for C-I-S capacitor sensors is seen in Figure 16. The data show that water vapor tends to reduce the sensitivity to... 

The effect of water vapor on the device hydrogen sensitivity however, is the same for both C-I-S diode and C-I-S capacitor structures that is, high concentrations of water vapor speed up the response but significantly reduce the sensitivities. 

The effect of temperature on the activity of the fresh catalysts was first studied. For the Hopcalite catalyst with feed A there was complete conversion above 300 °C. However, significant loss of activity was observed at lower temperatures, though activity could be restored by heating the catalyst above 300 °C. This is probably due to water vapor adsorption, given the known sensitivity of other Hopcalite formulations to water. There appears to be almost an on off switch for this material at 300 °C, but the long-term... 

Another significant environmental factor for vapor-phase applications is humidity. The ubiquitous nature of water vapor requires development of means to exclude or correct for interferences from water [92a,b]. Careful selection of coating materials, for example, can minimize the effect of water vapor on the sensor response. Alternatively, a coating with appropriate sensitivity to water can be used in the development of correction algorithms [93]. Other instrumental or system approaches, such as preconcentrators or sensor arrays with pattern recognition [94a-c], will be discussed in Section 5.5 and in Chapter 6. 

After the preliminary selection of 300 series stainless steel, these alloys were subjected to further tests to study the effect of stress in the presence of chloride, oxygen, and water vapor, the effect of sensitization, and the rate at which the alloying constituents are leached and transported under the influence of a temperature gradient. A molten salt loop has been in operation for nearly a year as a part of these tests. The... 

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