Desorption cycle

Abstract. A model of the conformational transitions of the nucleic acid molecule during the water adsorption-desorption cycle is proposed. The nucleic acid-water system is considered as an open system. The model describes the transitions between three main conformations of wet nucleic acid samples A-, B- and unordered forms. The analysis of kinetic equations shows the non-trivial bifurcation behaviour of the system which leads to the multistability. This fact allows one to explain the hysteresis phenomena observed experimentally in the nucleic acid-water system. The problem of self-organization in the nucleic acid-water system is of great importance for revealing physical mechanisms of the functioning of nucleic acids and for many specific practical fields. 

Rapid Adsorption-Desorption Cycles For rapid cycles with particle diffusion controlling, when the cycle time is much smaller than the time constant for intraparticle transport, the LDF approximation becomes inaccurate. The generalized expression... 

Fixed-bed adsorbers may be operated in either intermittent or semicon-tinuous mode. A typical removal system is a semicontinuously operated dnal-bed system one bed is in adsorption mode while the other is being re generated (Fig. 13.23). " The adsorption performance of the bed can he monitored by analyzing the outlet gas. Once organic vapors are detected in the gas stream, the incoming gas stream is routed to the parallel adsorber, and the exhausted bed is regenerated. The adsorption and desorption cycles can also be fixed. 

All AB, alloys are very brittle and are pulverized to fine particles in the hydrid-ing-dehydriding process (see Sec. 7.2.1). Thus electrodes must be designed to accommodate fine powders as the active material. There are several methods of electrode fabrication Sakai et al [35] pulverize the alloy by subjecting it to several hydrogen absorption-desorption cycles, before coating the resulting particles with Ni by chemical plating. The powder is mixed with a Teflon dispersion to obtain a paste which is finally roller-pressed to a sheet and then hot-pressed to an expanded nickel mesh. The fabrication of a simple paste electrode suitable for laboratory studies is reported by Petrov et al. [37],... 

Laboratory experiments have shown that reaction 15 occurs on ice in the absence of HCl (11-13) furthermore, the product HOCl appears on a time scale of minutes, in contrast to CI2 in reaction 13, which is produced on at most a millisecond time scale (11). Thus, in this mechanism HOCl serves as an intermediate if there is enough HQ on the ice, HOCl will react with HCl while still on the ice surface otherwise the HOCl will desorb, eventually finding an HCl molecule in the ice, perhaps after several adsorption-desorption cycles. 

Fig. 7.10 Ni Mossbauer spectra of LaNi5 samples after various treatments (a) no hydrogen exposure, (b) activated in hydrogen, (c) after 1,584 thermally induced absorption-desorption cycles, as described in the text. The solid lines are least-squares fits to a single Lorentzian in (a) and (b). (c) was fitted with a single Lorentzian (representing nonmagnetic nickel atoms) and a 12-line hyperfine spectrum (from [20])...

Figure 5. Top Adsorption isotherms of C02 for 1-en at the indicated temperatures. Bottom Adsorption-desorption cycling of C02 for 1-en showing reversible uptake from (a) simulated air (0.39 mbar C02 and 21% 02 balanced with N2) and from (b) simulated flue gas (0.15 bar C02 balanced with N2). (c) time-dependent C02 adsorption for porous materials (A = 1-en, B = mmen-Mg2(dobpdc), C = 1, D = Mg-MOF-74, E = Zeolite 13X, F = MOF-5). (d) C02 adsorption ratio of 1-en in flue gas (after 6 min exposure to 100% RH at 21 °C) to 1-en in flue gas (Adapted from [192]).

Figures. (A)VoltammogramsofPt(lI0)cooledinH2 + Arand0.1Af HCIO4. (B) Voltammogram of Pt( 110) cooled in H2 + Ar and 0.5M H2SO4, where the dotted curve was observed after the first oxygen adsorption-desorption cycle. The sweep rate was 50 mV s. (From Ref. 26.)...

Cycle life-time (absorption/desorption cycles) 500 1,000 1,500... 

D. Fdtay, T. Spassov, P. Delchev, G. Ribirik, A. Revesz, Microstmctural development in nanocrys-tadine MgH during H-absorption/desorption cycling, Int. J. Hyd. Ener. 32 (2007) 2914-2919. 

Details of the trap heater are also shown in Figure 2. The adsorption-desorption cycle may be accomplished conveniently with the use of a six port valve and a plumbing system constructed of materials that neither adsorb volatile organics nor outgas... 

After a sorption/desorption cycle on a control, the Tg is 2 C below the mean Tg of the untreated specimens. The a-peak intensity is unchanged. The sorption/desorption cycle does not appear to alter the mechanical properties or final network structure. The Tg at the 10,000 Mrad dose level increases approximately 10 C for the 80/20 and 73/27 samples after a sorption/desorption cycle (73/27 Tg=248°C,... 

The weight loss after the sorption/desorption cycle is 1.3% for the specimens irradiated to 10,000 Mrads. The low weight loss indicates limited degradation. The glass transition temperature should have returned to the value of the unirradiated epoxy (280°C) if degradation products are the only species plasticizing the network. 

In IR experiments it was confirmed that NO could adsorb as NO, NO and (NO)2- species on the Cu-zeolite, and the anionic species decreased with adsorption time to yield N2 and N2O in the gas phase whereas NO" " increased. After adsorption of NO for about 1 h, anionic species had almost disappeared and the intensity of NO species became approximately constant. These results indicate that all the Cu ions generated through pretieatment at elevated temperature were oxidized to Cu2 ions by oxygen produced in the NO decomposition at ambient temperature and the resulting CU2+ ions acted as adsorption sites for NO" " (Cu2+ + NO = Cu -NO ). This NO species could not be desorbed by evacuation at room temp ature. The IR spectra indicated the presoice of a large amount of NO and small amounts of NO2 and NO3 after the evacuation, i.e., weakly adsorbed or physisorbed NO molecules were absent from the zeolite under these condititHis. These phenomena were further confirmed by ESR experiments the adsorption-desorption cycles of NO resulted in a decrease-increase in the intensity of Cu2+ ESR signals. 

The Thermatrix, Inc., PADRE process is a commercial, off-gas treatment technology that purifies airstreams contaminated with volatile organic compounds (VOCs). The PADRE vapor treatment process traps VOCs using filter beds that contain a proprietary resin. This regenerative adsorption method involves an on-line treatment bed for infiuent air, while another bed undergoes a desorption cycle. PADRE often works in conjunction with soil vapor extraction or air stripping systems. The PADRE process can be applied at site remediation projects, industrial wastewater facilities, and industrial air processing sites. 

Fig. 3.18 Schematic drawing of the hysteresis of the absorption-desorption cycle at constant temperature.

The absorption-desorption cycle works below a hydrogen pressure of... 

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