CO2 production rates

Note in FIr. 3 a distinct break in CO2 production rate versus 6. We relate this break to the existence of two pathways to CO2 production ( ). Under most conditions (in this case for 0 > 0.03),... 

Off-gas analysis is widely used in many industrial fermentation plants to determine the cellular activity of growing cultures by monitoring respiration. One can measure oxygen uptake and CO2 production rates and thus measure metabolic activity/9 In addition, off-gas analysis is also used for monitoring other volatiles, the synthesis of which are strongly dependent on cultivation conditions 10 and product formation. 11 Off-gas estimation and control therefore serves as an indirect method for process analysis and control. 

In 1983, Stockwell and Calvert (fi) presented data which suggested that an alternate mechanism might be more appropriate for the description of the HO-SO reaction in air. In their experiments, they photolyzed HONO/NOx/CO mixtures in the presence and absence of SO . Data were collected on the CO2 production rate from the photooxidation of CO. This is directly related to the HO radical concentration in the reaction system. The data suggested that there was no significant change in the HO concentration upon the addition of SO2 to the reaction chamber. They interpreted their data with the following mechanism ... 

Fig. 40. (a) SFG spectra recorded during CO oxidation at temperatures between 300 and 700 K at a total pressure of 20mbar (CO 02 Ar = 1 2 7molar). CO surface coverage (b) and CO2 production rate (c) are shown as a function of the oxidation (substrate) temperature adapted from Pery et al. (314). Copyright (2002) The Combustion Institute. 

Roy, S. O., and Packard, T. T. (2001). CO2 production rate predicted from isocitrate dehydrogenase activity, intracellular substrate concentrations and kinetic constants in the marine bacterium Pseudomonas nautica. Mar. Biol. (Berl.) 138, 1251-1258. 

Fig. 4. Sustained oscillations that occur during the oxidation of CO over Pt(lOO) at 500 K, Poj = 5 X 10 Pa, Pco = 5 X lo Pa. The dashed vertical lines that coincide with the sudden decrease in the c(2 X 2) signal occur at the maximum work function (oxygen coverage), which also corresponds to the maximum production rate of CO2. The next vertical line corresponds to the maximum in the hex signal, and the simultaneous minima for the oxygen surface coverage and the CO2 production rate (after 82).

Fig. 11. Experimental setup for the in situ detection of chemisorbed CO during catalytic combustion of CO on Pt using optical infrared-visible sum frequency generation (SFG) and mass spectrometry. A mode-locked Nd YAG laser system is used to provide the visible laser beam (second harmonic 532 nm) and to pump an optical parametric system to generate infrared radiation (wir) tunable with a pulse duration of 25 ps. MC monochromator, PMT Photomultiplier, AES Auger Electron Spectrometer, LEED Low Energy Electron Diffraction Spectrometer, QMS Quadrupole Mass Spectrometers for CO Thermal Desorption (TD) and CO2 production rate measurements.

In the following, we will discuss DMC simulations on the CO oxidation on the Pt(lOO) surface, that were done in our laboratories. The simulations show oscillations in the CO2 production rate as well as several types of spatio-temporal pattern formation. In essence, it is an extension of the ZGB model with desorption and diffusion of A, finite reaction rates and surface reconstruction. We will discuss it to illustrate the complexity of the models with which DMC simulations can be done nowadays. For clarity, we will stick to the A and B2 notation employed in the previous section. Species A corresponds to CO and B2 corresponds to 02- Furthermore, we will speak in terms of reaction rates instead of relative reaction probabilities. This terminology is entirely justified in the DMC approach that we used. 

Figure 13 CO2 production rate (dotted), conversion (broken), and time-averaged conversion (drawn). Time zero represents steady state. Conditions as in Fig. 11.

Amarri S, Coward WA, Harding M, Weaver LT. Importance of measuring CO2-production rate when using C-breath tests to measure fat digestion. Br J Nutr 1998 79 541-5. 

The actual calculations were performed using balance, an earlier inverse mass balance modeling code that is now superseded by netpath and phreeqc. Chapelle and Lovley (1990) then calculated the time interval in these segments from flow velocities calculated by a numerical groundwater flow model and the length of the flow path. The total CO2 production rate from oxidation of organic matter is... 

Dimensionless CO2 production rate versus a single dimensionless gas-phase concentration. ... 

Figure 5.23 Dimensionless CO2 production rate versus dimension-Jess gas-phase CO and O2 concentrations.

Figure 5.24 Dimensionless CO2 production rate versus a single dimensionless gas-phase concentration while holding the other fixed at 1.0 slices through Figure 5,23,... 

O2 consumption rate or CO2 production rate differs from units indicated ... 

Source Spector, W.S., ed., Handbook of Biological Data, WADC Technical Report 56-273, Wright-Patterson Air Force Base, OH, 1956. CO2 production rate different from units indicated ... 

The respiration rate of fresh fruits and vegetables can be expressed as the rate of O2 consumption and CO2 production rate. The usual methods for determining the concentration of respiration are static or closed system, continuous flow system, and permeable system. The respiration rate is measured in permeable system, in other words, the product is within the dimensions and permeability of packaging film known (Beaudry, 1993 Joles et al., 1994 Lakakul, Beaudry, Hernandez, 1999 Lee, Song, Yam, 19% Piergiovanni, Fava, Ceriani, 1999 Smyth et al., 1998). The concentrations of O2 and CO2 are determined and stable mass balance is done on the system in order to estimate respiration rates. 

C indicates concentration. In the tissue compartment, the CO2 production rate from cellular metabolism, Vco, is balanc by net inflow versus outflow in the tissues i.e., Vco, = Q(f vco, co)-Noting that Ci co, 0 and combining the two equations, while converting concentrations to partial pressures, leads to the alveolar ventilation equation... 

Fig. 8.4 STM during CO oxidation on Pt(l 10) Upperpanel) Mass spectrometer signals of O2, CO, and CO2, measured directly from the reactor cell. Labels (a-h) correspond to the STM images in the lower panel. and Rhigh denote the low and high CO2 production rate branches of the metallic surface and the oxidized surface, respectively. Fa, indicates the threshold value of the CO pressure at which the rate switched from Flow to Fhigh and the surface changed from metallic to oxide. Lower panel) STM images of 210x210 nm from an STM movie of a Pt(llO) surface at 425 Kin a 3.0 ml/ min flow of mixtures of CO and/or O2 at 0.5 bar (65 s/image). The images were differentiated to enhance the contrast. From Ref. [27] (2002), by The American Physical Society...

Figure 4 Dynamic response of a continuous culture of 5. cerevisiae after a sudden increase of the dilution rate from 0.05 to 0.18 h". ( ) CO2 production rate (O) O2 consumption rate (A) ethanol vapor content (-) dissolved oxygen (+) heat flow rate, which gives the fastest response [24].

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