Optical comparators

A measure of turbidity of suspended particles. The Jackson turbidity method compares optical obscurity against a series of standards. 

Filter measured volume of air through lead-acetate-impregenated filter paper tape compare optical density with unexposed impregnated spot of similar area. Lead-acetate-impregnated filter paper tape No data NR EPA 1978... 

Scheme 71).124 An intermediate 7t-allylpalladium species (60) is thought to effect this transformation and in this context it is significant that presynthesized bis[acetoxy(7,l, 2)- j-pinene)palladium(II)]12 5 reacts in a similar fashion, affording optically active 59 in comparable optical yield.124... 

These optical probes are the most universally applicable in situ devices for on-line biomass monitoring up to now [15,16]. Konstaninov et al. [17] tested several absorbance and scattering sensors for real-time biomass concentration monitoring in mammalian cell cultivation processes and Hatch and Veilleux [18] compared optical density probes with oxygen uptake rates, packed cell volume, and off-line cell mass monitoring in commercial fed-batch fermentations of Saccharomyces cerevisiae [19]. In order to minimize influencing effects, special chemometric data treatment is necessary [20]. 

Figure 1. Comparable optical (a) and acoustical (b) images of subsurface layers BHC-2M steel (a) 200x b) H20,/= 407 MHz, scale 28 pm /div., Z = -12 gm).

The comparative optical photo with the same magnification gives the image of a polished surface without revealing structure elements. Structure transformation has been observed after deformational and thermal influences. Acoustomicroscope method of V(Z) - curves essentially increases possibility of obtaining information about investigated materials [3]. It allows to get the specific curves, for given materials, which are connected with elastic - mechanical constant ones. The example of such dependence for carbonaceous steel is demonstrated in Fig. 2. 

The mode-locked pulse train is one of a range of ways of comparing optical frequencies. A second technique which we have been investigating is the use of a frequency modulated (FM) dye laser. This has similarities to the mode-locked laser in that we are using the precise nature of the mode spacing when intracavity modulation is applied. In the case of the FM laser phase modulation is applied and in the case of the mode-locked laser amplitude modulation is applied. 

This ideal FM spectrum can be Fourier transformed into the frequency domain to give a spectrum of equally spaced modes with a Bessel function amplitude distribution. These equally spaced modes can be used for comparing optical frequencies by heterodyning a reference laser, unknown laser and FM laser on a nonlinear detector. Three beats can be observed ie the beats between the reference laser and one of the modes of the FM laser, the beats between the unknown laser and one of the modes of the FM laser and the mode spacing of the FM laser. The separation between the reference and unknown laser can hence be deduced. 

The rapid progress in recent years in the spectroscopy of the hydrogen atom has renewed pressure for a much better optical frequency standard. This in itself would not be enough to solve the measurement problem. New techniques of comparing optical frequencies are needed. He have developed methods of modulating lasers which can be used for frequency differences in excess of 2THz. 

Long before such ultimate resolution is reached, new approaches for measuring and comparing optical frequencies are urgently needed. 

In this paper, we address two aspects of this general problem. First, we discuss the problem of frequency standards in the optical spectrum. (An analogue in the microwave region of the spectrum is the cesium beam frequency standard.) If one or a few of these reference frequencies can be accurately calibrated (perhaps by a frequency synthesis chain- -) then it may be possible to compare optical spectra to these standards. As an example of the precision that might be achieved, we discuss only optical standards based on stored ions. Second, we discuss the problem of frequency comparison of unknown frequencies to the standards. Here we primarily restrict discussion to generation of wideband frequency "combs". 

Effect of Polyhalogenated Additives. We (36) have also observed that the rate of bleaching of solid polysilane films upon irradiation is considerably slower than that observed for solutions at comparable optical densities. Although this result is consistent with the observed decrease in the quantum yields for scission, 4>(s), in going from solution to the solid state (24) (vide infra), this decreased sensitivity is inconvenient for imaging processes. For this reason, a search was made for compatible additives that might influence the bleaching rate of poly silane derivatives in the solid state. 

Later Mitsui et al.( ) reported the asymmetric syntheses of phenylglycine by the Hiskey type reaction and proposed a steric course for the asymmetric synthesis as shown in Scheme 2. If it is applicable to all of the Hiskey type reactions, the following may be expected (a) an increase in optical yield upon substitution of a-methylbenzylamine by a-ethylbenzylamine and (b) a comparable optical yield upon substitution of a-methylbenzylamine by a-(1-naphthyl)ethylamine. 0097-6156/82/0185-0169 05.00/0 1982 American Chemical Society... 

Two types of high electron mobility transistors (HEMTs) with 2D electron gas were made from AlGaN/GaN heterostructures grown by MOCVD on Si (111) substrates, and their electrical DC properties were compared. Optical study, namely photoluminescence, photoreflection and reflection spectroscopy of the structures was performed. The strain values in GaN layers (6.6 and 1.7 kBar) and electric field strength near the heterointerface (470 and 270kV/cm) were determined. A correlation between the HEMTs DC characteristics and the optical properties of GaN layers was demonstrated. 

The geometry of the measurement, incident and refleeted angle of spectrophotometer beams, reference beams and use of integrating spheres are important considerations of these measurements especially when comparing optical properties measured using different configurations or instmments. 

Table HI. Comparative optical and electrochemical properties of various polymers...

Also, the existence of the upper limit of the parameter K, which was explained in Chapter 1, solves one more problem. Namely, in Ref. [21], optical and acoustical frequencies were compared. Optical frequency is defined by Equation (27.27). The same procedure for linear wave. Equation (27.12), instead of for that nonlinear, Equation (27.13), would lead to a so-called acoustical frequency [21,31] ... 

The various general microscopy techniques are listed and compared in Tables 7.6 and 7.7. Table 7.6 compares optical, electron and scanning probe microscope techniques, with the magnification, resolution, field of view and imaging... 

When compared, optically pure and racemic polymers reveal some significant differences in their properties such as crystallization, solubility or crystalline structure. The way of racemiza-tion of a polymer could be realized either by intercrystallite compensation, as in the case of polymethylthiirane (56) or by formation of a racemic lattice, as observed for monomers with bulky substituents such as t-butylthiirane (57). The properties of the racemic polymer are then very different of those of the optically pure one, for example, the melting points could differ of more than 50 C. A similar behaviour was recently observed in the case of substituted 6 propiolactones (58-60). Therefore the preparation of pure optically active polymers remains of inte-... 

---