Luminous sensitivity measurement

The data in Tables VII and VIII suggest that for emission measurements, the detection limits for the image dissector are lower than those for the silicon vidicon by a factor of about 24. The decrgase in the detection limit ratio at longer wavelengths (> uSOOOA) results from a decrease in the luminous sensitivity of the image dissector relative to the silicon vidicon. The effect is quite apparent in the case of potassium. 

In the test sheets of PMTs, the manufacturers occasionally specify the measured anode luminous sensitivity" instead of the cathode sensitivity. The anode sensitivity is the cathode sensitivity (including the electron transfer efficiency) multiplied by the gain of the tube. Because almost any gain can be obtained by increasing the supply voltage, the anode luminous sensitivity cannot be used to compare the photon counting performance of PMTs. 

Fig. 6.27 Measurement of the Cathode Luminous Sensitivity (Ze/f) and the Anode Luminous Sensitivity (right)...

The Anode Luminous Sensitivity" is measured in a similar setup as the Cathode Luminous Sensitivity. However, the PMT is operated in the normal way, i.e. by applying the specified voltage distribution to the dynode chain (Fig. 6.27, right). Of course, a calibrated filter has to be inserted in the light path to attenuate the light of the lamp to a level that does not overload the PMT. As mentioned before, the anode luminous sensitivity is not very useful in characterising a PMT for TCSPC. 

A microphysiometer is an instrument capable of very sensitive measurement of pH changes in a flow-through system, which avoids the use of strong buffers to maintain a constant pH environment. This reflects the conditions in the stomach in the postdigestive phase, in which there is little buffering of secreted acid, and gastric luminal pH falls to as low as 1.0. 

Luminous lu-m9-n9s adj [ME, fr. L luninosus, fi-. lumin-, lumen] (15c) (1) Adjective used to imply dependence on the spectral response characteristic of the Standard Observer defined in the CIE System. Thus, the luminous reflectance or the luminous transmittance is described by the Y tristimulus value in the CIE System. The adjective is applied to many measures of light, such as intensity, density, etc., and always indicates the measures are weighted for the relative luminous sensitivity of the human observer. (2) Material emitting or spearing to be emitting, visible radiant energy. 

Eor LEDs utilized in visible/display appHcations, the human eye serves as the detector of radiation. Thus a key measure of performance is luminous efficiency which is weighted to the eye sensitivity (CIE) curve. The relative eye sensitivity, V (L), peaks in the green at A 555 nm where it possesses a value of 1.0. It drops sharply as the wavelength is shifted to the red or blue, reaching a value of 0.5 at 510 and 610 nm. The luminous efficiency, in units of Im/W, of an LED is given by equaton 11 ... 

Increases in the levels of Ins 1,4,5-P3 can be measured in several ways (e.g. by radioimmunoassay), whilst intracellular levels of Ca2+ can be monitored by the inclusion into the neutrophil cytoplasm of suitable Ca2+ indicators. Some elegant work using the Ca2+-sensitive photoprotein obelin (obtained from the luminous jellyfish Obelia) has shown that increases in intracellular Ca2+ can be detected within seconds of activation of neutro-... 

Absorption evaluation from luminal disappearance of drugs has been widely employed as a simple and easy method. Although the appearance of drugs in the mesenteric blood can provide a more sensitive way that enables to detect lower levels of absorption, it is technically more complicated, especially due to the colon s anatomical and morphological configuration. Another alternative for absorption evaluation is to measure drugs that appear in the systemic circulation, although this method cannot provide a direct measure of membrane permeability. 

Baylor et. al. have provided recent in-vitro isotropic absorption spectrum for Rhodonine based on Macaca fascicularis143. The data was collected over five and one-half orders of intensityusing transverse illumination at near 37 Celsius. Baylor, et. al. also provide a review of other available measurements and perform a circuitous calculation to compare the isotropic spectrum to the human scotopic luminous efficiency function attributed to Carpenter rather than the C.I.E. Based on ten photoreceptors, the peak sensitivity was estimated to be 491 nm. This is lower than most other investigators. However, data points were only collected at 20 nm intervals using filters of 10 nm nominal half-widths. This sampling plan does not support three digit accuracy in their peak value. 

A more recent cell-based in vitro assay involves the use of the microphysiometer, a sensitive extracellular pH sensor, which has been used to measure luminal (or apical) secretion and basolateral release of OH- as well as liberation of acidic metabolites in rabbit gastric glands. Adenosine 3, 5 -cyclic monophosphate stimulation produced a biphasic change... 

The light is generated within a few seconds after the formation of NADH and disappears shortly afterwards. However, various problems may arise in this assay (non-specific binding, degradation of NAD+) and sensitive equipment for the measurement of bio-lumines-cence is needed. 

Luminous intensity-time curves and spectra of test samples stimulated thermally and photochemically were measured with a chemiluminescence spectrometer CLA-FSl. Colour photos of the photoluminescence of samples placed in a cell with a diameter of 50 mm were taken with the Cube-2DI, which is employing an ultra high sensitive colour CCD camera of Bitran Co., Japan. Both types of the apparatus are available from the Tohoku Electronic Industrial Co., Japan. The black light has power of 240 aW cm" and wavelength of 365 nm. In order to obtain a spectrum for steep decay photoluminescence curves, a sample was irradiated with the NUV light for 5 sec... 

To estimate water quality, bioluminescent biosensors have been devised and successfully used. They are characterized by rapidity and simplicity of use, high sensitivity, and accuracy. The Collection of Luminous Bacteria IBSO (http //www.bdt.org.brA3dt/msdn/ibso) is being used to develop bioassays for monitoring the environment, using lyophilized luminous bacteria and the luminescent system isolated from them. Bioluminescent assays have an advantage over other biological assays luminescence is easy to measure, the method is rapid, and the measurements can be automated. 

Bioluminescence serves as an excellent reporter system as a sensitive marker for microbial detection, as a real-time, non-invasive reporter for measuring gene expression and as a measure of intracellular biochemical function (cell viability). Most widely studied of the bioluminescence systems are those belonging to the luminous bacteria Vibrio sp.. Photobacterium sp. and Photorhabdus luminescens) and the firefly Photinus pyralis). While these systems have proved extremely versatile, there are caveats to their use limiting the array of applications they can be applied to. These caveats mainly surround the nature of the luciferase enzymes, and include temperature and pH stability. 

An accurate and convenient configuration for measuring luminous efficiency from OLEDs/PLEDs is shown in Fig. 4.5. Because the luminous efficiency strongly depends on the OLED/PLED emission spectrum (even for constant quantum efficiency), an eye-sensitivity filter is mounted directly onto the surface of the calibrated photodiode (see Fig. 4.4) [15],... 

Lumen - An empirical measure of the quantity of light. It is based upon the spectral sensitivity of the photosensors in the human eye under high (daytime) light levels. Photometrically it is the luminous flux emitted with a solid angle (1 steradian) by a point source having a uniform luminous intensity of 1 candela. 

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