Mass-correlation acceleration

Ei before and after the time-delayed extraction pulse, (b) Implementation of the mass-correlated acceleration scheme on a miniaturized instrument. 

Figure 13.10 Schematic and picture of the 4-inch TOF mass spectrometer using the mass-correlated acceleration (MCA) technique.

Figure 13.11 Mass spectra of a peptide mixture using (a) time-delayed extraction and (b) mass-correlated acceleration.

Table 13.1 BSA (66 432.96 Da) tryptic digest comparison of peak widths using delayed extraction and mass-correlated acceleration (MCA).28...

Figure 10.7. (a) Positions of ions following delayed extraction showing normal mass dependence of space-velocity-correlated focusing, (b) Positions of ions after correction using mass-correlated acceleration. 

Kovtoun, S. V English, R. D. Cotter, R. J. Mass correlated acceleration in a reflectron MALDl TOF mass spectrometer An approach for enhanced resolution over a broad mass range. J. Am. Soc. Mass Spectrom. 2002, 13, 135-143. 

The science of mechanics provides objective criteria by which forces may be compared. Newton s laws relate force, mass, and acceleration. In a strict sense the mere formulation of the rule force = mass X acceleration is not helpful, since by it force cannot be defined except in terms of mass, nor mass except in terms of force. But the value of mechanics lies in the coherence of the system to which it leads. If masses are compared in terms of the accelerations imparted by a constant force, such as gravity at a given place (about which nothing need be postulated save its constancy), then the order found will in fact determine their relative behaviour under the infiuence of quite different forces. A very vast system of observed phenomena can be correlated in terms of the auxiliary quantities force and mass, even though a logician uninterested in calculations about the actual behaviour of matter may see little point in their introduction. 

Thiazole disulfides absorb at 235 and 258 nm (320-322) and characteristic infrared bands are reported in Ref. 320. The activities of 2-cyclo-hexyldithiomethylthiazoles as vulcanization accelerators have been correlated with their mass-spectral fragmentation patterns (322). 

For a better idea of the toxicity of VOCs, we can look more closely at some studies of TCE (Bogen et al., 1998). In vitro uptake of C-14-labeled trichloroethylene (TCE) from dilute (similar to 5-ppb) aqueous solutions into human surgical skirt was measured using accelerator mass spectrometry (AMS). The AMS data obtained positively correlate with (p approximate to 0) and vary significantly nonlinearly with (p = 0.0094) exposure duration. These data are inconsistent (p approximate to 0) with predictions made for TCE by a proposed EPA dermal exposure model, even when uncertainties in its recommended parameter values for TCE are considered but are consistent (p = 0.17) with a 1-compartment model for exposed skin-surface. This study illustrates the power of AMS to facilitate analyses of contaminant biodistribution and uptake kinetics at very low environmental concentrations. Eurther studies could correlate this with toxicity. 

Also, one classical question is whether dust formation initiates mass-loss or whether dust is formed as a result of mass-loss. It is to be noted that the latter process may be rather easy, once mass-loss occurs by another mechanism. This problem can be examined on the basis of recent observations of CO radio emission lines, by which stellar mass-loss rate has been determined with better accuracy than by any other method for a large sample of red giant stars, and terminal flow velocities have also been determined with high accuracy( e.g.,Knapp,Morris,1985). The result revealed that the momentum in the stellar wind and that in the stellar radiation do not necessarily show good correlation(e.g.,Zuckerman,Dyck,1986). Also, a necessary condition for the winds to be accelerated by radiation pressure on dust( Mv [Pg.160]

Fig. 5 shows how the discolouration developed in these semibatch experiments is correlated against conversion. At low conversion levels up to 50K, the reaction and mass transfer conditions do not affect the extent of discolouration achieved. Beyond 50K, there is some evidence that under severe conditions (ie. 3011 SO-) the degree of discolouration is accelerating. However for the purposes of initial assessment, the by-product colour can be represented by a parallel reaction where the sulphonation and discolouration reactions have similar activation energies. Brostrom s colour results are different, and shown in Fig. 5 for comparison (15). 

If the pressure drop in a pipeline is reasonable and the linear gas velosity is well below the speed of sound, the acceleration term in the equation of notion is usually neglected, and the pressure to mass flow correlation is described by eqn (4). 

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