Diffusion losses

Tritium has also been observed in meteorites and material recovered from sateUites (see also Extraterrestrial materials). The tritium activity in meteorites can be reasonably well explained by the interaction of cosmic-ray particles and meteoritic material. The tritium contents of recovered sateUite materials have not in general agreed with predictions based on cosmic-ray exposure. Eor observations higher than those predicted (Discoverer XVII and sateUites), a theory of exposure to incident tritium flux in solar flares has been proposed. Eor observations lower than predicted (Sputnik 4), the suggested explanation is a diffusive loss of tritium during heating up on reentry. 

Vaned diffuser ioss. Vaned diffuser losses are based on conical diffuser test results. They are a function of the impeller blade loading and the vaneless space radius ratio. They also take into account the blade incidence angle and skin friction from the vanes. 

Boyce, M.P., and Bale, Y.S., Diffusion Loss in a Mixed-Flow Compressor, Intersociety Energy conversion Engineering conference, San Diego, Paper No. 729061, September 1972. 

Blade loading or diffusion loss. This loss is due to the type of loading in an impeller. The inerease in momentum loss eomes from the rapid inerease in boundary-layer growth when the veloeity elose to the wall is redueed. This loss varies from around 7% at a high-flow setting to about 12% at a low-flow setting. 

One may ask why some experiments, for instance those done by microwave-afterglow technique 15,16 and the experiments by Canosa et al., 21,22 gave no indications of an anomalous decay. In part, the answer may be that small variations of the deionization coefficients are not easily detected in the presence of ambipolar diffusion. They were detected in the work of Adams et al. and of Smith and Spanel only because the diffusion losses were unusually slow in their large flow tube. 

Pipelines represent the primary option for the most efficient transportation mode in a hydrogen energy environment. Pipeline is the most economical option for transportation however, the embrittlement of steels and diffusion losses represents a technical challenge. Sensor technologies for continued integrity management of such a pipeline network will be critical in the development of the hydrogen economy. 

Even when using LDPE and PP, the diffusive losses of most nonpolar solvents may be unacceptably large for A designs that exceeded 1 cm . This is especially true at higher exposure temperatures because both solute diffusion and polymer free volume increase with temperature (Comyn, 1985). Even when solvent losses were not excessive, uptake of HOCs by membrane-enclosed solvents appeared to become curvilinear well before thermodynamic equilibrium was approached. This phenomenon is likely due to the outward flux of sampler solvent with elevated HOC levels (relative to water), which appears to facilitate residue... 

Diffusive losses into or through containers may occur. 

Fatty acid synthase in vertebrates consists of two identical peptide chains—i. e., it is a homodimer. Each of the two peptide chains, which are shown here as hemispheres, catalyzes all seven of the partial reactions required to synthesize palmitate. The spatial compression of several successive reactions into a single multifunctional enzyme has advantages in comparison with separate enzymes. Competing reactions are prevented, the individual reactions proceed in a coordinated way as if on a production line, and due to low diffusion losses they are particularly ef dent. 

Diffusive loss of Ar from a mineral, affecting age determination (closure temperature)... 

Therefore, to kineticists and informed geochronologists, the age obtain from an isochron equation or from Example 1-5 is an apparent age, and is called the closure age (Dodson, 1973) because it means the age since the closure of the mineral, not necessarily since the formation of the mineral. The closure age may differ from the true age or formation age because of diffusive loss (or exchange) of the daughter nuclide. For the closure age to be the same as the formation age, the mineral must have cooled down rapidly (for volcanic rocks) or formed at not-so-high a temperature (for metamorphic rocks) so that diffusive loss from the mineral is negligible. 

Estimation of diffusion distance or diffusion time is one of the most common applications of diffusion. For example, if the diffusion distance of a species (such as °Ar in hornblende or Pb in monazite) is negligible compared to the size of a crystal, it would mean that diffusive loss or gain of the species is negligible and the isotopic age of the crystal reflects the formation age. Otherwise, the calculated age from parent and daughter nuclide concentrations would be an apparent age, which is not the formation age, but is defined as the closure age. This has important implications in geochronology. Another example is to evaluate whether equilibrium between two mineral phases (or mineral and melt) is reached if the diffusion distances in the two phases are larger than the size of the respective phases, then equilibrium is likely reached. 

As introduced in Section 1.7.3 and Figure 1-20, because of diffusive loss of Ar, the "age" obtained from the K-Ar system is not necessarily the real age (formation age or peak temperature age), but is an apparent age (fa) as defined by Equation 1-114 ... 

Because the closure temperature (A) is low enough that diffusive loss below A is not major, the square of the diffusive distance Dgi must be smaller than a, where a is the half-thickness of a plane sheet, or the radius of a sphere or an infinitely long cylinder. That is. 

The second effect is on the diffusive loss of daughters of radioactive nuclides. For example, decays into many daughters and finally becomes AH the... 

The most commonly used radioactive-radiogenic system in thermochronology is the " °K-" °Ar system, often refined as the °Ar- Ar method. Recently, the U-Th-He method has been developed with applications to understand erosion. Below, the closure temperature relation is first derived using a simple method. Then, diffusive loss and radiogenic growth of °Ar are examined in more detail. 

The next section discusses diffusive loss and radiogenic growth in more detail. Because the full problem of diffusive loss and radiogenic growth is complicated, to build our understanding of the problem, we start from simple cases and move to more realistic cases. Readers who do not wish to go through the detailed mathematical analyses may jump to Section 5.2.3. 

S.2.2 Mathematical analyses of diffusive loss and radiogenic growth... 

Figure 5-14 Diffusive loss of Ar that was initially in hornblende during cooling after complete cooling down t=rx>) for asymptotic cooling history with (a) a fixed cooling timescale but varying the initial temperature and (b) a fixed initial temperature but varying the cooling rate.

On the other hand, at a lower temperature of 500 K, D in hornblende is 2.3 X lO " m /s (this value requires large extrapolation and, hence, is not expected to be accurate, but our interest is only an order of magnitude estimation). Because this diffusivity is a finite number, diffusive loss in infinite time would be complete. However, the age of the Earth is not infinite, and hornblende age cannot exceed that of the Earth. Even if hornblende has an age of 4.4 x 10 years (the age of the oldest zircon on the Earth), is only 5.7 nm. If a = 0.5 mm,... 

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