Sensor active

Sources of Error. pH electrodes are subject to fewer iaterfereaces and other types of error than most potentiometric ionic-activity sensors, ie, ion-selective electrodes (see Electro analytical techniques). However, pH electrodes must be used with an awareness of their particular response characteristics, as weU as the potential sources of error that may affect other components of the measurement system, especially the reference electrode. Several common causes of measurement problems are electrode iaterferences and/or fouling of the pH sensor, sample matrix effects, reference electrode iastabiHty, and improper caHbration of the measurement system (12). 

Dynamic explosion detectors use a piezoresistive pressure sensor installed behind the large-area, gas-tight, welded membrane. To ensure optimum pressure transference from the membrane to the active sensor element, the space between the membrane and the sensor is filled with a special, highly elastic oil. The construc tion is such that the dynamic explosion detec tor can withstand overpressures of 10 bar without any damage or effect on its setup characteristic. The operational range is adjustable between 0 and 5 bar abs. Dynamic explo-... 

Newman, R. H. and Zhang, J. (2008). Visualization of phosphatase activity in living cells with a FRET-based calcineurin activity sensor. Mol. Biosyst. 4, 496-501. 

Opitz N., Lubbers D.W., New fluorescence photometrical techniques for simultaneous and continuous measurements of ionic strength and hydrogen ion activities, Sensor Actuat. 1983 4 473. 

In [25], Megerian et al. introduce the exposure concept as the ability to observe a target moving in a sensor field. By expressing the sensibility of a sensor in a generic form, the field intensity is defined as the sum of the active sensor sensibilities. The exposure is then defined as the integral of the intensities (involving all sensors or just the closest one) on the points in a path in the sensor field. 

Several lipases AOT-isooctane p-Nitrophenyl ester hydrolysis as an activity sensor [19,20]... 

When it is important to control the water activity in a reactor, a water activity sensor is quite useful. The sensor should ideally measure the water activity in the liquid reaction medium. However, the sensors available are designed for gas phase measurements, and, provided there is effective enough equilibration between the liquid and gaseous phases, they can be used to control the water activity in the reactor. If the measured water activity is above the set point, drying is initiated, for example, by passing dry air through the reactor. On the other hand, if the water activity is too low, water can be added, either as liquid water or as humid air. Automatically controlled systems of this kind have been successfully used to monitor and control enzymatic reactions in organic media [13, 14]. 

Linear sweep or preset potential and current measurement providing instrument can be used with immunosensor and enzyme-free sensor. Potential measured instrument can be used with antioxidant activity sensor. 

PREVIOUS STUDIES OF THE FOREIGN BODY REACTION TO AN IMPLANTED SENSOR AND THE NECESSITY TO EVALUATE ACTIVE SENSORS IN SITU... 

In addition, the ability to optimize biosensor design is of central importance and initially depends on the determination of what aspects of the foreign body reaction and biosensor surface properties are critical to the success of the implanted biosensor. To accomplish this efficiently, it would be very beneficial if active sensors could be imaged in situ. Thus, sensor performance could be quantified relative to the manipulation of local tissue and microvascular conditions in response to various implant properties. Some important implant features include surface texture, porosity, and surface material composition. Surface texture of the implant has been observed to affect the extent of collagen formation. Smooth implant surfaces, which the local... 

Although at present their use has been restricted to redox-active sensors in solution, it should be possible to immobilise these receptors at an electrode, and we may then have a simple redox-active electrode whose behaviour in solution is modified by the presence of ions. The high sensitivity of electrochemical techniques would then give us a sensitive and selective method of anion detection. 

Analytical Methodologies Based on a Direct Interaction of the Analyte with the QD ("Active" Sensors)... 

Two different types of membrane-based osmosensors have been proposed for animal cells extracellular solute sensors and membrane stretch-activated sensors. The former sensors are conjectured to function by detecting changes in the concentration of specific ions, for instance, sodium ion, in the external fluids. There is some indirect evidence for sodium-specific sensors in animal cells, and sodium-gated cation channels have been proposed as candidates for this role. However, no direct evidence for their involvement as upstream osmoregulatory elements has yet been presented. 

Membrane stretch-activated sensors, membrane-localized proteins whose activities are modulated by mechanical forces generated in the membrane due to stress, appear to be more promising candidates for the role of... 

Stretch-activated proteins in animal cell membranes that are candidates for osmosensing activity include mechanosensitive ion channels and the membrane-localized enzyme phospholipase A2 (PLA2). The former proteins remain to be conclusively linked to osmosensing. Activity of PLA2 is sensitive to packing of the lipid bilayer of the cell and is responsive to osmotic changes, two attributes that mark it as a prime candidate for a stretch-activated sensor (Lehtonen and Kinnunen, 1995). 

Fig. 5.16. Different immobilization strategies for receptor attachment (Adapted from Ref. [4] with permission from John Wiley). Binding is achieved using (a) dextran (b) amino (c) carboxylate, and (d) biotin surfeces. Each cartoon represents from the initial activated sensor surface to the covalent bonding with the receptor.

Altarejos JY, Montminy M (2011) CREB and the CRTC co-activators sensors for hormonal and metabolic signals. Nat Rev Mol Cell Biol 12(3) 141-151. doi 10.1038/nrm3072... 

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