Escape phenomenon

Pig. 11. Typical sequential results that may be obtained for the scrum immunoglobulin concentrations in a patient with IgA-type myelomatosis. Note (a) the subsequent marked increase of the IgA, representing an escape phenomenon of the paraprotein, (b) the marked reduction of the senim IgG and IgM, and (c) the concentrations of the C-reactive protein (CRP), also heralding tliat treatment was no longer effective. This patient died 2 months after these results were obtained. 

In cases of severe liver disease or advanced cirrhosis, the occurrence of secondary aldosteronism must always be anticipated and initially rated as an epiphenomenon. Nevertheless, at a certain point, the activated RAAS can act as a signal for a boost to the renal retention of sodium and may intervene in the pathogenesis of ascites. The aldosterone value and the renal excretion of sodium are closely and inversely correlated. Yet a higher aldosterone value is not always accompanied by a reinforced retention of sodium. This is particularly the case if the feedback by means of sodium is ineffective (= escape phenomenon). The refilling of the plasma volume may well lead to normalization of the renin and aldosterone values, yet not to normalization of the sodium excretion. The reduction in increased aldosterone values is usually accompanied by reinforced natriuresis and diuresis - as has been observed after bilateral adrenalectomy. (s. p. 315) Cirrhosis patients with ascites thus usually show a reduced life expectancy if the renin-plasma value is increased, whereas the prognosis is clearly better if the renin value is normal, (for further reference, see 2, 4—6)... 

The biochemical response of patients with Paget s disease to other therapeutic agents is similar to that detailed for calcitonin except for the occurrence of the escape phenomenon, which has been observed only with calcitonin therapy. During mithramycin therapy, serum alkaline phosphatase declines more rapidly than during calcitonin therapy (L7)... 

Wolfi ChaikofF effect. Raben (1949) showed that this effect was dependent on the amount of iodine in the thyroid gland and not on the plasma concentration of iodine. The acute inhibitory effect of iodine overload is usually transient. Intrathyroidal iodine decreases within a few days despite a high plasma iodine concentration and thyroid hormone synthesis then returns to the previous level. This resumption of the organification of iodine is known as the escape phenomenon (Wolff, 1969), and it means that hypothyroidism will not develop in most individuals despite excessive iodine intake. 

For very fast reactions, the competition between geminate recombmation of a pair of initially fomied reactants and its escape from the connnon solvent cage is an important phenomenon in condensed-phase kinetics that has received considerable attention botli theoretically and experimentally. An extremely well studied example is the... 

What has become an even greater concern in recent years is the phenomenon known as multiple chemical sensitivity disorder triggered by exposures to many chemicals in the environment. Synthetic chemicals are all around us. They are in the products we use, in the clothes we wear, in the food we eat, in the air we breathe at work. Because chemicals are everywhere in the environment, it is not possible to escape exposure. For this reason many people have become sensitized to the chemicals around them. In fact, it is estimated that 15% of the population has become sensitized to common household and commercial products. For some people the sensitization is not too serious a problem. They may have what appears to be a minor allergy to one or more chemicals. Other people are much more seriously affected. They may feel tired all the time, and suffer from mental confusion, breathing problems, sore muscles, and a weakened immune system. Such people suffer from a condition known as Multiple Chemical Sensitivity (MCS). 

At any temperature, molecules can escape from the surface of a liquid (vaporizing or evaporating) to enter the gas phase as vapor. At the special temperature at which the vapor pressure just equals the atmospheric pressure, a new phenomenon occurs. There, bubbles of vapor can form anywhere within the liquid. At this temperature, the liquid boils. 

Permeation When a fluid contacts one side of an elastomer membrane, it can permeate right through the membrane, escaping on the far side. The process again combines adsorption and diffusion as above, but with the additional process eventually of evaporation—treated mathematically as negative adsorption. (Permeation could also be viewed as combining one-way absorption and evaporation.) Wherever these conditions for permeation exist the phenomenon occurs, whatever the shape of the elastomer barrier— but the associated mathematics becomes complex for irregular barrier shapes. 

C12-0057. A drop in temperature accompanies the escape of CO2 from a carbonated beverage. Explain this phenomenon in terms of intermolecular forces. 

Models available to explain the CHF phenomenon are the hydrodynamic instability model and the macrolayer dryout model. The former postulates that the increase in vapor generation from the heater surface causes a limit of the steady-state vapor escape flow when CHF occurs. The latter postulates that a liquid sublayer (macrolayer) formed on the heating surface (see Secs. 2.2.5.5 and 2.4.1.2)... 

Group C powders are of small particle size, cohesive by nature and hence, difficult to fluidize. Either the fluidized bed lifts as a solid plug of material or forms stable channels of air flow, which allows the fluidizing gas to escape. The latter phenomenon is referred to simply as channelling . It may be possible to fluidize such powders by mechanical agitation (e.g., stirring, vibration). 

The PAS phenomenon involves the selective absorption of modulated IR radiation by the sample. The selectively absorbed frequencies of IR radiation correspond to the fundamental vibrational frequencies of the sample of interest. Once absorbed, the IR radiation is converted to heat and subsequently escapes from the solid sample and heats a boundary layer of gas. Typically, this conversion from modulated IR radiation to heat involves a small temperature increase at the sample surface ( 10 6oC). Since the sample is placed into a closed cavity cell that is filled with a coupling gas (usually helium), the increase in temperature produces pressure changes in the surrounding gas (sound waves). Since the IR radiation is modulated, the pressure changes in the coupling gas occur at the frequency of the modulated light, and so does the acoustic wave. This acoustical wave is detected by a very sensitive microphone, and the subsequent electrical signal is Fourier processed and a spectrum produced. 

The baking process, particularly the batch variety, presents a number of serious disadvantages. Not only does the reaction produce solid urea decomposition products, but it also releases large amounts of ammonia and ammonium salts which escape by sublimation. The foam which is thus formed makes for a porous reaction mixture, which in turn even prevents heat conduction. Moreover, the reaction mixture tends to adhere to the surface of the reaction vessel and the stirring unit a phenomenon which adds to the complexity of the problem. 

Vibrational spectroscopy can help us escape from this predicament due to the exquisite sensitivity of vibrational frequencies, particularly of the OH stretch, to local molecular environments. Thus, very roughly, one can think of the infrared or Raman spectrum of liquid water as reflecting the distribution of vibrational frequencies sampled by the ensemble of molecules, which reflects the distribution of local molecular environments. This picture is oversimplified, in part as a result of the phenomenon of motional narrowing The vibrational frequencies fluctuate in time (as local molecular environments rearrange), which causes the line shape to be narrower than the distribution of frequencies [3]. Thus in principle, in addition to information about liquid structure, one can obtain information about molecular dynamics from vibrational line shapes. In practice, however, it is often hard to extract this information. Recent and important advances in ultrafast vibrational spectroscopy provide much more useful methods for probing dynamic frequency fluctuations, a process often referred to as spectral diffusion. Ultrafast vibrational spectroscopy of water has also been used to probe molecular rotation and vibrational energy relaxation. The latter process, while fundamental and important, will not be discussed in this chapter, but instead will be covered in a separate review [4],... 

In the hydrocracking process, this phenomenon is exploited to shift catalyst selectivity from the naphtha to the distillate products. Here the wide separation of sites is exploited to minimize the potential for secondary cracking in initial products and intermediates. This, along with the introduction of escape routes for the primary product tends to preserve the higher molecular weight hydrocarbons, thereby producing more dishllates [49, 61, 62]. 

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