Direct visual observation

Direct visual observation preliminary observation for final characterization, or preparative for other instrumentation... 

By direct visual observation we can watch the contents of these two bulbs approach the constancy of macroscopic properties (in this case,, color) that indicates equilibrium. In bulb A equilibrium was approached by the dissociation of > N2Qi, reaction (4) in bulb B it was approached by the opposite reaction, reaction (5). Here it is clear why the color of each bulb stopped changing at the particular hue characteristic of the equilibrium state at 25°C. The reaction between N02 and N204 can proceed in both directions ... 

Two methods were used to detect the onset of flocculation in the dispersions direct visual observation and turbidity/wavelength... 

Empirical analysis of wave motion, fluid velocities. and stress can be made to enable vessel size, configuration and baffle system to be optimized. Analysis of the data Is made by direct visual observation of the fluid motion In the vessel, and computer plotting of wave profiles, fluid velocities, etc. 

Figure 7.16 An illustration of the efficiency of back-pulsing in removing fouling materials from the surface of microfiltration membranes. Direct microscopic observations of Mores and Davis [9] of cellulose acetate membranes fouled with a 0.1 wt% yeast suspension. The membrane was backflushed with permeate solution at 3 psi for various times. Reprinted from J. Membr. Sci. 189, W.D. Mores and R.H. Davis, Direct Visual Observation of Yeast Deposition and Removal During Microfiltration, p. 217, Copyright 2001, with permission from Elsevier...

W.D. Mores and R.H. Davis, Direct Visual Observation of Yeast Deposition and Removal During Microfiltration, J. Membr. Sci. 189, 217 (2001). 

Index Entries Secondary membrane backflushing microfiltration ultrafiltration direct visual observation fouling. 

In the current work, we employed a modified approach, with predeposition of a secondary membrane of yeast (SMY) before starting the filtration of protein. Backflushing was employed periodically to remove the deposited secondary membrane to recover the flux, and a new secondary membrane was deposited subsequently with the start of each new cycle, prior to restarting the filtration of protein. Microfiltration experiments were performed with yeast as the secondary membrane and BSA-only solutions and yeast-BSA mixtures as the feed. Ultrafiltration experiments were performed with yeast as the secondary membrane deposition medium and cellulase enzyme solutions, used in the conversion of biomass into ethanol, as the feed. In this article, we also present direct visual observation images (19) of the formation of the secondary membrane and its subsequent removal. 

Fig. 2. Direct visual observation pictures of surface of membrane (A) during first cycle of deposition ofSMY,and (B) at end of several cycles ofyeast-BSA microfiltration with a secondary membrane, with the pictures taken just after backflushing portion at end of indicated cycle.

Results are assessed either by direct visual observation or spectrophotometrically. For the sake of completeness, it should be mentioned in this section that enzyme detection systems have been described which are monitored by alternative methods. These... 

In some cases r can be so short that experimental observation of the bilayer after its formation is possible only with a certain probability IV depending on the resolution time tr of the particular equipment used. In direct visual observation of bilayer rupture, for instance, tr 0.5 s, which is the reaction time of the eye. Since observation of the bilayer is possible only if the bilayer has ruptured during the time t=tr,W is merely equal to 1 - P(tr) so that, in view of Eqs. (3.120), it becomes [382]... 

The interparticle reaction between the Anti-HSA-IgG-spacer-latex and the HSA-spacer-latex was also examined by direct visual observation of latex particles using an ultramicroscope(2) The percent of monomeric latex particles in the visual field was determined with the lapse of time. At time=0, only monomeric particles of the anti-HSAIgG-spacer-AL-2 were found to be present in the visual field and by the addition of a small amount of HSA-spacer-AL-2 suspension into the observation cell, the number of monomeric particles decreased with time and almost levelled off (Figure 5). Although not shown in the figure, the number of dimeric particles in the visual field increased with time correspondingly to the decrease in the number of monomeric particles. 

The duration of the induction period seems to be independent of the method of observation, whether by direct visual observation, more sensitive optical means, or measurement of electrical conductance. In addition, the conductivity remains nearly constant during the induction period, indicating that during this period oifiy a small fraction of the solute exists as ion pairs or higher aggregates. 

The identified characteristics of secondary hydrocarbon migration can be verified with e.g. the location and physico-chemical characteristics of known hydrocarbon accumulations (e.g. England and Mackenzie, 1989) direct and indirect observations of oil and gas seeps (direct visual observations indirect observations, such as hydrocarbon-charged sediments, pock marks, clay diapirs) and gas leakages indicated by seismic chimneys. 

The disagreements about the location of a critical point might easily be settled if the monolayer phases could be viewed directly. Early attempts were made to observe the texture of monolayers by dark field microscopy, but the refractive index differences between the phases is small and only collapsed portions of the film are clearly discernible. It has only been recently that direct visual observations of Langmuir monolayers have been made. 

Direct visual observation of a moving pointer instrument is not recommended, since this leads to variable errors through the variable speed of response of the human eye. For the... 

Firstly, in this section, we consider those static methods in which the gas and liquid phases are analysed and there is no optical system whereby the contents of the cell can be observed. Secondly, we consider those static methods which have been used to study the one phase-two phase boundary using optical techniques. Usually in such methods, the appearance of the second phase is determined by direct visual observation of the resulting turbidity or meniscus. The optical method usually provides fewer experimental data than the analytical methods because the concentrations of co-existing phases are not usually determined. However, there are some workers who have sought to combine the advantages of both the analytical and optical methods by designing an optical cell with provision for analysis of both phases. 

At s.d.e. die determination of the time dependence of the t.d.c. is sufficient for the investigation of coalescence. In Refs 27 and 28 this was accomplished through direct visual observation. By using video-enhanced microscopy and computerized image analysis the determination of t.d.c. can be automated. Such automated determination of total droplet number in a dilute DCD-in-water emulsion at the s.d.e. can be recommended as a standard method for the characterization of the elementary act of coalescence. 

If we look at the simplified schematic diagram presented in Figiue 13.7, which presents the whole electromagnetic spectrum, we will notice that direct visual observable universe is very narrow. 

The method of direct visual observation can be used in conjunction with in-situ Raman spectra. X-ray absorption fine structure (XAFS) and X-ray diffraction measurements (Zotov and Keppler, 2000 Fulton et al., 2000 Schmidt and Rickers, 2003 Bassett etal., 2000 Mayanovic etal., 2003) to study salt solubility, metal ion hydration, complexation and oxidation state in aqueous solution in a wide range of temperatures and pressures, and with the hydrothermal scanning force microscopy technique (Higgins etal., 1998) for observation of the advance or retreat of atomic layers (steps) on a crystal surface during the processes of dissolution or crystal growth. 

The high pressure cylindrical cell (Figure 2.5) made in a nickel-steel alloy contains the sample, which extends from a synthetic sapphire window at the extreme of the cell to the front side of a movable piston. A platinum mirror is attached to the piston to allow the direct visual observation of the sample. The position of a movable piston, and hence the sample volume, can be determined with a magnetic device with an uncertainty close to 0.4—1% (Gehrig et al, 1986). 

The study of droplet rupture and coalescence by direct visual observation has been utilized in numerous essential studies [39-43]. Of principal importance are the experimental studies by Amelina et al. on the analysis of colloid stability in artificial blood substitutes [40-43]. These studies involved the use of various nonpolar phases, including perfluo-rinated systems, such as perfluorodecalin (PFD), perfluorotributylamine (PFTBA), per-fluoromethylcyclohexylpiperidine (PFMCHP), and conventional hydrocarbons, such as heptane. Stabilizing agents included Pluronic surfactants (ethylene oxide (EO)/propylene oxide (PO) block copolymers), as well-fluorinated surfactants, such as perfluorodiisononyl-ene with 20 mol of EO (( )-PEG). Tables 4.1 and 4.2 show some very characteristic results. 

Various amounts of water and surfactant were sealed in ampoules. A series of sample solutions were heated at about 1 °C/min in a thermostat. If necessary, the samples were kept at constant temperature to observe phase separation. The phase change was detected by direct visual observation with polarizers. The type of liquid crystals were determined by polarizing microscopy and small-angle X-ray scattering. 

Direct Visual Observation of Microfiltration Membrane Fouling and Cleaning... 

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