Moderated diffusion

In one case report a 37-year-old male maintenance fitter was accidentally exposed to a large cloud of hot acetic acid while disconnecting a pressurized pump. The patient suffered first-degree burns on the hands and face and developed progressive dyspnea. At 3 months there were persistent extensive crackles in the basal area of the lungs, widespread bronchial inflammatory changes, and diffuse moderate interstitial pneumonitis that promptly improved after treatment with corticosteroids and bronchodilators. 

Male and female Fischer 344 rats and B6C3Fi mice were exposed to 0, 10,30,90 or 150 ppm [0, 45, 136, 409 or 681 mg/m ] technical grade 1,3-dichloropropene (cis, 48.6% trans, 42.3%) vapours for 6 h per day on five days per week for 13 weeks (Stott et al., 1988). At the end of the exposure, slight degeneration of the nasal olfactory epithelium and mild hyperplasia of the nasal respiratory epithelium were observed in rats exposed to 150 ppm 1,3-dichloropropene. All male and female Fischer 344 rats exposed to 90 or 150 ppm and two of the 10 rats exposed to 30 ppm 1,3-dichloropropene exhibited minimally detectable hyperplasia of the respiratory epithelium. Exposure to 90 or 150 ppm 1,3-dichloropropene also produced diffuse, moderate hyperplasia of the olfactory epithelium in female B6C3Fi mice. 

Fosfomycin has relatively low toxicity. Its penetration into tissues, including bones and joints, and into the cerebrospinal fluid is good. When given orally (2-3 g/day), it can produce gastrointestinal distress when injected intramuscularly, it can cause local pain. Fosfomycin is recommended in daily doses of 4-16 g intravenously for the treatment of severe infections resistant to other commonly used antibiotics. Fosfomycin diffuses moderately well into bone tissue (2). 

Vancomycin is particularly useful in infections caused by meticillin-resistant or penicillinase-producing staphylococci and diphtheroids, as well as in the prophylaxis of bacterial endocarditis and in the treatment of antibiotic-associated colitis. Sufficient fecal concentrations can be achieved with oral therapy. It is poorly absorbed from the gastrointestinal tract and painful when injected intramuscularly. It diffuses moderately well into bone tissue (6). 

The account of influence of diffusion moderation is connected first of all with the concentration factor and the influence of hydrogen chloride. As shown earlier [40], in the... 

Estimation of parameters of the given system on the basis of experimental data on kinetics of silica gel interaction with gas mixture of HCl and VOCI3 in conditions of avoiding the diffusion moderation [40], demonstrating adequacy of the proposed model, was performed. Influence of diffusion stages of heterogeneous process (5-7) equations (8) should be complemented by differential diffusion equations for gas components in pore space of silica grains ... 

Fig. 4. 2.29. Unenhanced CT scan of the liver shows diffuse moderate fat infiltration of the parenchyma, which is isodense to the vessels. Mean attenuation of the liver is 42 HU...

In most practical cases (and at moderate voltages) the high-field growth law can control film growth, say up to only a maximum of 10 nm, as at this thickness the field strength effects become even less important than film growth due to diffusion of vacancies or ions. 

Density functional theory calculations have shown promise in recent studies. Gradient-corrected or hybrid functionals must be used. Usually, it is necessary to employ a moderately large basis set with polarization and diffuse functions along with these functionals. 

Jet Aerators. Jet aerators are a cross between the diffused and mechanical aerators. Air and water are pumped separately under the water surface into a mixing chamber and ejected as a jet at the bottom of the tank or pond (Fig. 3f). Jet aerators are suited for deep tanks and have only moderate cost. Disadvantages include high operational costs, limitations caused by tank geometries, and nozzles that can clog. Additionally, they require blowers. 

Heat is used to darken amber, ivory, and jade to simulate age. Pieces of amber and tortoiseshell can be reconstmcted, ie, joined under heat and moderate pressure. By careful heating in oil, milky amber can be clarified when the gas and water within small bubbles diffuse out of the stone. If heating is rapid, the attractive sun-spangle cracking shown in Figure 1 results. 

Asfour-Dullien developed a relation for predicting alkane diffusivities at moderate concentrations that employs ... 

High mass-transfer rates in both vapor and hquid phases. Close approach to eqiiilihriiim. Adiabatic contact assures phase eqiiilihriiim, Only moderate mass-transfer rate in liquid phase, zero in sohd. Slow approach to equilibrium achieved in brief contact time. Included impurities cannot diffuse out of solid. Sohd phase must be remelted and refrozen to allow phase equilibrium. 

Titanium and most of its alloys readily absorb and evolve hydrogen due to high solubility and diffusion mobihty of hydrogen at moderate temperatures. 

The question of the compatibility of metals and alloys with carbon and carbonaceous gases has assumed considerable importance in connection with the development of the gas-cooled nuclear reactor in which graphite is used as a moderator and a constituent of the fuel element, and carbon dioxide as the coolant. Tests of up to 1 000 h on a series of metals and nickel-containing alloys under pressure contact with graphite at 1 010°C" showed that only copper was more resistant than nickel to diffusion of carbon and that the high-nickel alloys were superior to those of lower nickel content. The more complex nickel-chromium alloys containing titanium, niobium and aluminium were better than the basic nickel-chromium materials. 

If the circuit is broken after the e.m.f. has been applied, it will be observed that the reading on the voltmeter is at first fairly steady, and then decreases, more or less rapidly, to zero. The cell is now clearly behaving as a source of current, and is said to exert a back or counter or polarisation e.m.f., since the latter acts in a direction opposite to that of the applied e.m.f. This back e.m.f. arises from the accumulation of oxygen and hydrogen at the anode and cathode respectively two gas electrodes are consequently formed, and the potential difference between them opposes the applied e.m.f. When the primary current from the battery is shut off, the cell produces a moderately steady current until the gases at the electrodes are either used up or have diffused away the voltage then falls to zero. This back e.m.f. is present even when the current from the battery passes through the cell and accounts for the shape of the curve in Fig. 12.1. 

---