Absorbance sensors

Unfortunately, this novel technique is unsuitable for any UV absorbing sensor or mediator but could find a significant application in the realm of ISFET fabrication (3). 

Fluorescence intensity in the absence of the quencher Fluorescence intensity in the presence of quencher Imaginary component of the index related to the materials absorbance Sensor response... 

A concept of the fiber-optic-based absorbance sensor is shown in Figure 18-8. Again, the fiber is threaded in a standard catheter, thus allowing its insertion into tissue or body fluids. A piece of aluminium foil is attached to the end of the inner needle (which contains the optical fiber). Fluids can be drawn into the sample irradiation cavity by aspiration, the volume between foils and Hber being Hlled through the hole shown. Typical pathlengths (twice the distance from the Hber tip to the foil) are O.S-4.3 mm. 

Absorber Sensor Operating Electrical Measuring Response Ref. 

As a third example the development of an analytical micro probe by "down-scaling" of a macro evanescent field absorbance sensor" (EFAS) previously produced at KfK shall be demonstrated. 

Fig. 11. Evanescent field absorbance sensor operating in near infrared (NIR) region...

Current research is now directed towards realizing a miniaturized sensor by using integrated optics technology and planar waveguide structures. The construction of planar evanescent wave absorbance sensors offers some advantages compared to the existing fiber-optic sensor ... 

Fig. 12. Basic-set up of integrated-optical evanescent field absorbance sensor...

Reverse saturable absorption is an increase in the absorption coefficient of a material that is proportional to pump intensity. This phenomenon typically involves the population of a strongly absorbing excited state and is the basis of optical limiters or sensor protection elements. A variety of electronic and molecular reorientation processes can give rise to reverse saturable absorption many materials exhibit this phenomenon, including fuUerenes, phthalocyanine compounds (qv), and organometaUic complexes. 

Cadmium Telluride. Cadmium teUuride [1306-25-8] CdTe, is another promising thin film. CdTe is a well-known semiconductor often used in high performance infrared sensors. CdTe absorbs visible light very strongly, and very thin films (1—2 llm) are sufficient to absorb most sunlight. 

The majoiity of the various analyte measurements made in automated clinical chemistry analyzers involve optical techniques such as absorbance, reflectance, luminescence, and turbidimetric and nephelometric detection means. Some of these ate illustrated in Figure 3. The measurement of electrolytes such as sodium and potassium have generally been accomphshed by flame photometry or ion-selective electrode sensors (qv). However, the development of chromogenic ionophores permits these measurements to be done by absorbance photometry also. 

Carbonate ionophore I [ETH 6010] (heptyl 4-trifluoroacetylbenzoate) [129476-47-7] M 316.3, b 170°/0.02 Torr, d 0.909. Purified by flash chromatography (2g of reagent with 30g of Silica Gel 60) and eluted with EtOAc/hexane (1 19). The fractions that absorbed at 260nm were pooled, evapd and dried at room temp (10.3 Torr). The oily residue was distd in a bubbled-tube apparatus (170°/0.02 Torr). Its IR (CHCI3) had peaks at 1720, 1280, 940cm and its sol in tetrahydrofuran is 50mg/0.5mL. It is a lipophilic neutral ionophore selective for carbonate as well as being an optical humidity sensor. [Anal Chim Acta 233 41 1990.]... 

A steering tool sensor and electronic package is mounted in a housing in Figure 4-238 with a shock absorber and a spring to decrease the value of deceleration when engaging the mule shoe. 

The two other foam sensors mentioned above are ultrasound and rotating disks. The ultrasound sensor is a transmitter and receiver mounted opposite to each other and operating at 25—40 kHz. In the bioreactor, the waves are absorbed by the foam and the signal is generated. The rotational disk foam sensor is a mechanical foam breaker which is used by increasing the rotational resistance. 

Fig. 3a, b. Schematic representation of (a) conventional fluorescent sensor and (b) fluorescent sensor with signal amplification. Open rhombi indicate coordination sites and black rhombi indicate metal ions. The curved arrows represent quenching processes. In the case of a den-drimer, the absorbed photon excites a single fluorophore component, which is quenched by the metal ion regardless of its position... 

In addition to the four detectors used to detect backscattered radiation from the sample, there is a fifth detector to measure the transmission spectrum of the reference absorber (a- Fe, a- Fe203, Fc304 see Fig. 3.16). Sample and reference spectra are recorded simultaneously, and the known temperature dependence of the Mossbauer parameters of the reference absorber can be used to give a measurement of the average temperature inside the SH, providing a redundancy to measurements made with the internal temperature sensor (see Sect. 3.3.4). 

MIMOS II has three temperature sensors one on the electronics board and two on the SH. One temperature sensor in the SH is mounted near the internal reference absorber, and the measured temperature is associated with the reference absorber and the internal volume of the SH. The other sensor is mounted outside the SH at the contact ring assembly. It gives the approximate analysis temperature for the sample on the Martian surface. This temperature is used to route the Mossbauer data to the different temperature intervals (maximum of 13, with the temperature width software selectable) assigned in memory areas. Shown in Fig. 3.21 are the data of the three temperature sensors taken on Mars (rover Opportunity at Meridiani Planum) in January 2004 between 12 10 PM on Sol 10 (10 Martian days after landing) and 11 30 AM on Sol 11. The temperature of the electronics board inside the rover is much higher than the temperatures inside the SH and the contact plate sensor, which are nearly identical and at ambient Martian temperature. 

Fig. 3.21 Example of temperature variation as measured by MIMOS II temperature sensors on MER (i) inside the rover body at MIMOS electronics board (black curve), (ii) outside the rover, at the MIMOS II SH (green and red curves), which is at ambient Martian temperature (a) inside the sensor-head, at the reference absorber position (green), (b) outside the SH at the sample s contact plate (red). Temperatures at the two SH positions are nearly identical (difference less than 2 K). During data transmission between the rover and the Earth (or the relay satellite in Mars orbit) the instrument is switched off resulting in immediate small but noticeable temperature changes (see figure above)...

Mossbauer resonance of Zn to study the influence of the gravitational field on electromagnetic radiation. A Ga ZnO source (4.2 K) was used at a distance of 1 m from an enriched ZnO absorber (4.2 K). A red shift of the photons by about 5% of the width of the resonance line was observed. The corresponding shift with Fe as Mossbauer isotope would be only 0.01%. The result is in accordance with Einstein s equivalence principle. Further gravitational red shift experiments using the 93.3 keV Mossbauer resonance of Zn were performed later employing a superconducting quantum interference device-based displacement sensor to detect the tiny Doppler motion of the source [66, 67]. 

MIMOS II has three temperature sensors, one on the electronics board and two on the sensor head. One temperature sensor in the sensor head is mounted near the internal reference absorber, and the measured temperature is associated with the reference absorber and the internal volume of the sensor head. The other sensor is mounted outside the sensor head at the contact ring assembly. It gives the analysis temperature for the sample on the Martian surface. This temperature is used to route... 

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