Optical turbidity

Turbidity Many studies have been focused on developing a sterUizablc probe to measure the turbidity of the culture broth, because the turbidity can be an index of cell concentration, which is one of the most important parameters in bioprocess operations. Sterihzable laser or optical turbidity probes are now available and are being used successfully [1]. However, the accuracy ofthe measurements is insufficient for industrial applications, because the outputs from the probes are affected by some factors including the absorbance of the broth and the bubbles caused by aeration. 

Similar dependencies on concentration are observed for the osmotic pressure or the electrical conductance of the solution. If we look at the optical turbidity of the solution the trend is opposite. At low concentration the solution is transparent. When the concentration reaches the CMC many solutions become opaque. In parallel, a property, which is of great practical relevance, changes the capacity to solubilize another hydrophobic substance. At concentrations below the CMC of the surfactant, hydrophobic substances are poorly dissolved. At the CMC they start being soluble in aqueous solution. This capability increases with increasing surfactant concentration. There may be small systematic differences in the concentration at which the specific property abruptly changes and the CMC determined by different methods may be different. However, the general trend and the dependency on external parameters such as temperature or salt concentration is always the same. 

Characterisation of vesicles was achieved using a combination of methods, including photon-correlation spectroscopy, video-enhanced and cryo-electron microscopy. Measurements of the cmc of the surfactants (in the absence of salt) were made using uv-visible spectrophotometry and electrical conductivity (k). For cmc measurements, there is a convenient change in the extinction coefficient of the benzene chromophore at 262 nm. The onset of vesicle formation, and hence the determination of the esc, can be measured by 90° scattering and 180° optical turbidity measurements at 300 nm. 

Optical turbidity measurements showed a LCST for aqueous solutions of P14 up to 17°C. On the other hand, solutions of copolymer with cyclohexyl P15 have a transition at 31°C, which is 4°C lower than that of pure NIPAAM polymer P16 (Table 3). The lower LCST for P15 compared to P16 is attributed to the hydrophobic effect [60], which is the decrease of the LCST with increasing numbers of hydrophobic side-chain groups. 

We are now going to calculate the attenuation of direct (directional) solar radiation through scattering and absorption in the atmosphere. The atmosphere is assumed to be cloudless for details on the complicated effect of clouds, [5.34] is suggested. We will consider a bundle of rays that goes through an optically turbid, namely absorbent and scattering medium, Fig. 5.42. The reduction dLx of its spectral... 

One example, which demonstrates the feasibility of this approach, is a time-resolved study on sarcoplasmic reticulum membranes during active transport this will be reviewed in some detail in the following paragraphs. Other important applications are the studies on the kinetics of lipid phase transitions, where only optical turbidity methods and certain spectroscopic relaxation techniques are able to provide useful information on the rates, however not on the actual structural processes and possible intermediates. 

Physical-chemical properties temperature salinity density dissolved gases (CO, O), chemical, or pollutants acoustic electromagnetic mechanical optical (turbidity) and corrosion effects... 

Clearly if the dilution rate exceeds [x j, [ ] rises to and x becomes 0 thus the population will wash out the vessel. Consequently any value of [x obtained in continuous culture in a chemostat is always less then [x j, determined in a corresponding batch culture. Furthermore the dilution rate at which washout occurs (the critical dilution rate, D ) is always less than that corresponding to (x. Continuous cultures at values of D approaching [x j may be achieved in a turbidostat where the biomass concentration as represented by optical turbidity is measured and used to control D [20]. 

The choice of detection device is also quite important since the resolution of size separation for a given column can be markedly affected by the signal characteristics of the detector. The most commonly employed detection is optical turbidity. As will be shown, for a given latex, the effect of detection wavelength can be critical. Thus the optimal set-up employs a variable wavelength UV-visible detector and a standard strip-chart output. 

The draft versions of ISO norms (1983) describe both simple techniques for on-the-spot turbidity measurement and optical turbidity meters. The diagram below illustrates the principle of a turbidity photometer for laboratory use (Dr, Lange, model LTP 3). 

The construction of calibration curves is recommended in nephelometric and turbidimetric determinations, since the relationship between the optical properties of the suspension and the concentration of the disperse phase is, at best, semi-empirical. If the cloudiness or turbidity is to be reproducible, the utmost care must be taken in its preparation. The precipitate must be very fine, so as not to settle rapidly. The intensity of the scattered light depends upon the number and the size of the particles in suspension, and provided that the average size of particles is fairly reproducible, analytical applications are possible. 

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

In practice, very few applications of FEWS sensors can be found outside laboratory applications and demonstration systems. In the near-IR, suitable fibres are readily available but usually there is no real necessity to use them. Possible transmission pathlengths are sufficiently large to allow using standard transmission probes, while turbid samples can be measured using transflection or diffuse reflection probes. In the mid-IR, high intrinsic losses, difficulties in fibres handling and limited chemical and mechanical stability limit the applicability of optical fibres as sensor elements. 

The turbidity level or more exactly the optical transmittance and reflectance provides a range of information about the washing and rinsing water in automatic washing and dishwashing machines. The most important parameters are soil and detergent concentration, both of which have an impact on turbidity. 

R. F. Bonner, R. Nossal, S. Havlin, and G. H. Weiss. Model for photon migration in turbid biological media. Journal of the Optical Society of America A, 4(3) 423-432, 1987. 

S. J. Madsen, B. C. Wilson, M. S. Patterson, Y. D. Park, S. L. Jacques, and Y. Hefetz. Experimental tests of a simple diffusion model for the estimation of scattering and absorption coefficients of turbid media from time-resolved diffuse reflectance measurements. Applied Optics, 31 3509-3517, 1992. 

Hence c(g/ml) is the concentration of colloidal suspension G90 is the reading on the LS photometer at 6 = 90°, 2 is the path length, which equals the cell diameter when using a cylindrical cell t is the turbidity obtained from measurements of optical density. Table 4 gives the results of calibrating a Sofica instrument with colloidal... 

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