Exchange region

RESPIRABLE DUST That fraction of total inhalable dust which penetrates to the gas exchange region of the lung (usually considered to be in the range 0.5 /xm-7 /xm). 

In the intermediate exchange region, where Q2 A2, the signal is spread over the whole frequency range d> A, for details see Refs. 16-1S 27,43). 

RESPIRABLE DUST That fraction of total inhalable dust which penetrates to the gas exchange region of the lung. 

The conducting airways carry out two major functions. The first is to lead inspired air to the more distal gas-exchanging regions of the lungs. The second is to warm and humidify the inspired air as it flows through them. The alveoli are delicate structures and may be damaged by excessive exposure to cold, dry air. 

In the so-called intermediate exchange region, eqn (5.18) is not easily tractable and recourse is usually made to computer simulations. Qualitatively, however, it is clear that as the rate increases, the separate resonances of the slow exchange limit broaden, shift together, coalesce and then begin to sharpen into the single line of the fast exchange limit. 

Simulations spanning all three exchange regions are shown in Figures 5.3 and 5.4. 

The linewidth of the diamagnetic MnOT resonance, fV°, is broadened on the addition of the paramagnetic MnO ", but there is no shift in the signal position, which is proof that we are in the slow-exchange region. The broadened line width is a linear function of added MnOj"... 

We can obtain the exchange regions outlined previously by considering various terms in... 

The H nmr spectrum of Zr(Hf)(acac)4 in CHCIF2 shows two Me proton resonances of equal intensity in the slow exchange region only at lowered temperature ( —170°Ci). This observation is consistent with a square antiprism geometry 11. At — 145°C coalescence of the signals occurs arising from complicated intramolecular rearrangements. 

Some bacteria are able to take up DNA from their surroundings and exchange regions with their own DNA. This recombination is the basis of a primitive sexual process known as transformation. However, recombination with DNA from species other than the same as the bacterium is unlikely to be beneficial and it is likely that restriction enzymes have evolved to destroy such foreign DNA. 

Prom these approximate equations, it follows that exchange rate constants kex = 1/xm are easily obtained in region II and, if the chemical shift difference is large, in region III also. In the very fast exchange, region IV information on water exchange can also be obtained if the interaction between the... 

Coalescence studies on the equilibrium 114/115 by recording the NMR spectra at different temperatures revealed that the coalescence temperature for the NH protons was found to be 65°C, and 70°C for the CH3 protons. Based on these coalescence temperatures and the chemical shift differences of the two separate peaks in the slow exchange region (82MI2), the free energy of activation AG was calculated as 20.8 kcal/mol. 

We may wish reaction to occur in the center of the bed so that both ends can be used as heat exchange regions to heat up reactants. This can be done by matching the gas and solids flow rates however, this is inherently an unstable system and requires proper control. A second alternative, shown in Fig. 26.8c,... 

Fig. 3. Simulation of the lineshape of the aldehyde proton in furfural in the intermediate exchange region, and its constituents (lower lines). The lineshape consists of two components, each normal NMR lineshapes but distorted in position, phase, intensity by the dynamics.

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