Measurable transmission

Numerous texts and a wealth of literature exist that describe many approaches to X-ray CT imaging. Examples include Refs [2—4]. All approaches involve a large number of X-ray transmission measurements of the item being imaged. In addition to measuring transmission at different positions of the item, all these measurements are then repeated at a large number of different trajectory directions of the incident X-ray beams. 

Measurement of the transmittance and reflectance of a slab for light at near-normal incidence. The samples must be sufficiently transparent for measurable transmission in thin slabs, but not as transparent as required in method 1. 

Figure 11.10 Theoretical power loss ratio for a sphere in a waveguide (upper curves) compared with measured transmission spectra (lower curves). The curves on the right are enlargements of the two bands the effect of absorption on the lowest frequency band is shown in the upper right. From P. Affolter and B. Eliasson, IEEE Trans. Microwave Theory Tech., MTT-21 (1973), 573-578 1973 IEEE.

Treu (1976) measured transmission spectra (optical density) for indium films of the type used for immunological slides. His calculations based on Mie theory led him to the conclusion that this theory was not compatible with observations. In particular, calculations for spheres of diameter 1390 A showed a feature that was not observed in experiments. Although calculations for spheres half this size did not show this feature, the wavelength of maximum optical density was much shorter than that observed. 

There are some potential problems that should be taken into account when interpreting such spectra. A spectrophotometer measures transmission (and maybe also reflection) but not absorption. What is measured as absorption is a transmission measurement that is mathematically manipulated to convert it to absorption. Absorption is usually measured as absorbance. A, which by definition is given by... 

Many studies present optical absorption or transmission spectra of the resulting films. (A reminder that a spectrophotometer measures transmission, not ab-... 

Fig. 4. Measured transmission versus incident light intensity for solutions of cryptocyanine in glycerol and methanol at room temperature. Initial dye transmission T0 = 1%. Theoretical curves (—) according to Eq. (11a) were obtained from matching theory and experiment at points indicated by arrows. (From Ref. 12))...

Test Methods. There is no standard test method for measuring transmissibility or isolation efficiency of vibration isolation devices. The most common procedure is to measure the vibration transmitted to the supporting structure with the isolators in place and with the equipment supported on rigid blocking. From these measurements the insertion loss in dB is determined by the following where L, is the transmitted vibration with isolators in place and L,m is the transmitted vibration with rigid supports. 

The decrease in transmission in regions where the film is nonabsorbing allows the determination of the thickness of the film from the measured transmission usinglS. 

The vibrational spectrum of benzene around 1000 cnf has also been measured. IQ. Benzene was physisorbed on a cooled copper substrate in the vacuum chamber. Figure 19 shows the transmission for several thicknesses of benzene and a prism separation of 3 cm. The thickness was determined from the measured transmission in transparent regions using Eg. (7). The solid curves were calculated from Eqs. (5) and (6) using optical constants for benzene obtained from an ordinary transmission experiment.il The benzene film was assumed to be isotropic. Of the two absorption lines seen, one belongs to an in-plane vibrational mode, and one to an out-of-plane vibration. Since the electric field of the SEW is primarily perpendicular to the surface, the benzene molecules are clearly not all parallel or all perpendicular to the copper surface. Also it should be noted that the frequencies are the same (within the experimental resolution) as those of solid benzene22 and of nearly the same width. These features indicate that the benzene interacts only weakly with the copper surface, as would be expected for physisorbed molecules. 

The theory required to interpret the experimental absorption data is well established. The governing equation which links the measured transmissivity, Tv, at wavenumber V, to the absorbing species concentration and its absorption line parameters is the Bouguer-Lambert law of absorption... 

The FundaLux system, for instance, aspirates a liquid aliquot with a Teflon piston into an external glass cell, allows a (selectable) time (typically 2 min) to degas, measures transmission in comparison to an air blank, and releases the aliquot back to the reactor an interesting feature - specific to this instrument -is the repetitive cleaning of the optical window by the moving Teflon piston. Some problems with infections have been communicated with this device since the measuring cell is external to the bioreactor and the sensor is probably insufficiently sterilized in situ. 

Absorption of intense x-radiation from a synchrotron source interacting with a sample is studied, usually by measuring transmission intensity. Specifically, the variations in absorption around and above the absorption edge that display complex fine structure in a molecular or condensed phase are studied... 

For colored glass containers, not intended for parenteral preparations, the measured transmission must not exceed a maximum value of 10% at any wavelength between 290 and 450 nm, irrespective of the size or glass type. The limits for colored glass containers, used for parenteral preparations, depend on their intended fill volume. The respective limits for these containers are given in Table 1 (3,4). 

Table 12.1. Measured Transmission of 200 pm Core Diameter Optical Fiber" at Ar+ Wavelengths...

Figure 1. The measured transmission through a 1 nm thick single oystal platelet of PTS-polydiacetylene.

Measurement. Transmission and scanning electron photomicrographs were taken using two types of electron microscopes (model HU-11C manufactured by Hitachi Co. Ltd. and model JSM-U3 by JEOL In Japan). The detailed method for analyzing pore characteristics by applying stereology will be given elsewhere (13). 

Once the objective has been established, the sampling options are appraised. The field of view required for the application, the type of measurement (transmission or diffuse reflection), the type and intensity of the NIR source, requirements for depth of field and spatial resolution must also be established. 

Figure 6.7. Experimental set-up to measure transmission of liquid crystal cell against applied magnetic field. (Modified from DuPre, 1982.)...

Measurements, transmission, and signal processing are crucial elements for the design of computer-process interfaces. The reader will find Refs. 4 and 5 very useful in this respect, as well as the following paper ... 

Refractive indices for several polytypes of silicon carbide have been measured [8-12]. The 6H polytype of SiC has been measured in the most detail [8]. For the hexagonal form the c axis is assumed to be perpendicular to the surface. Thus, a normal incidence wave can be used to measure transmission and/or reflection. This normal incidence wave is often called the ordinary ray. A prism with its sides perpendicular to the c-axis is used to determine both n0 and ne in the normal way (n0 = ordinary ray, ne = extraordinary ray). A short summary of the data is presented here for additional information please refer to [8,9]. 

Mossbauer spectroscopy is based on the phenomenon of recoil-free resonant absorption of y rays by atomic nuclei, and the spectrum reflects the perturbation induced in the nuclear levels due to the interaction of the Mossbauer atom with its chemical environment. The Mossbauer elements, iron and tin, can be used conveniently as in situ probes in environmental and geochemical applications. Since Mossbauer spectroscopy has now become relatively familiar to chemists, I present here only a brief description of typical experimental techniques used in Mossbauer measurements. There are two types of Mossbauer measurements transmission method and scattering method. 

These are the oldest and most basic sampling techniques for IR spectroscopy and apply to both FTIR and dispersive IR systems. Transmission analysis can handle a wide range of sample types and can provide both qualitative and quantitative measurements. Transmission analysis provides maximum sensitivity and high sample throughput at relatively low cost. There is in some cases substantial sample preparation required. 

Rather than simply getting surface measurements, transmission measurements give content uniformity of the whole wafer. The spectra can then be used to monitor the variance within the blend for all components by measuring the standard deviation between samples taken from various points in the blend. 

Digest sample with acid mixtures remove method sulfide, nickel and cobalt add dithiozone and CCI4 measure transmission at 540 nm... 

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