Mass increase

As m increases, At becomes progressively smaller (compare the difference between the square roots of 1 and 2 (= 0.4) with the difference between 100 and 101 (= 0.05). Thus, the difference in arrival times of ions arriving at the detector become increasingly smaller and more difficult to differentiate as mass increases. This inherent problem is a severe restriction even without the second difficulty, which is that not all ions of any one given m/z value reach the same velocity after acceleration nor are they all formed at exactly the same point in the ion source. Therefore, even for any one m/z value, ions at each m/z reach the detector over an interval of time instead of all at one time. Clearly, where separation of flight times is very short, as with TOF instruments, the spread for individual ion m/z values means there will be overlap in arrival times between ions of closely similar m/z values. This effect (Figure 26.2) decreases available (theoretical) resolution, but it can be ameliorated by modifying the instrument to include a reflectron. 

Liquids that are sufficiently volatile to be treated as gases (as in GC) are usually not very polar and have little or no hydrogen bonding between molecules. As molecular mass increases and as polar and hydrogen-bonding forces increase, it becomes increasingly difficult to treat a sample as a liquid with inlet systems such as El and chemical ionization (Cl), which require the sample to be in vapor form. Therefore, there is a transition from volatile to nonvolatile liquids, and different inlet systems may be needed. At this point, LC begins to become important for sample preparation and connection to a mass spectrometer. 

Ammonium Phosphates. In the manufacture of ammonium phosphates, an atmosphere of ammonia may need to be maintained because the partial pressure of ammonia rises rapidly as either the temperature or the NH2/P20 mole ratio of the reaction mass increases. Phosphoric acid reacts quickly with ammonia vapor and is used in multistage reactor systems as a scmbber fluid to prevent NH emissions and recover ammonia values. For example, H PO scmbbing of coke-oven off-gases produces ammonium phosphates of relatively good purity. 

Fig. 4. Schematic of a multisequence biosensor in which the target glucose is first converted to glucose-6-phosphate, G6P, in the test solution by hexokinase. G6P then reacts selectively with glucose-6-phosphate dehydrogenase immobilized on the quartz crystal surface. Electrons released in the reaction then chemically reduce the Pmssian blue film (see Fig. 3), forcing an uptake of potassium ions. The resulting mass increase is manifested as a...

The addition of this small mass increases the radius of the droplet, r, to r - - dr, and the surface area by 8jrr dr. If the fluid density is p, then the... 

Exponential growth The phase of cell growth in which the number of cells or the cell mass increases exponentially. 

Purely physical laws mainly control the behaviour of very large particles. Further down the particle size range, however, specific surface area, i.e. surface area per unit mass, increases rapidly. Chemical effects then become important, as in the nucleation and growth of crystals. Thus, a study of particulate systems within this size range of interest has become very much within the ambit of chemical engineering, physical chemistry and materials science. 

The energy of a Is-electron in a hydrogen-like system (one nucleus and one electron) is —Z /2, and classically this is equal to minus the kinetic energy, 1/2 mv, due to the virial theorem E — —T = 1/2 V). In atomic units the classical velocity of a Is-electron is thus Z m= 1). The speed of light in these units is 137.036, and it is clear that relativistic effects cannot be neglected for the core electrons in heavy nuclei. For nuclei with large Z, the Is-electrons are relativistic and thus heavier, which has the effect that the 1 s-orbital shrinks in size, by the same factor by which the mass increases (eq. (8.2)). 

The quantitative proportion of the mesomorphous phase in PET fibers is strongly diversified and depends on the conditions of fiber manufacture. According to Lindner fl7], it is estimated to be in the range 0.21-0.36. For poorly stretched fibers (below 300% of draw ratio), the mesophase constitutes almost exclusively an ordered part of the polymer in the fiber. With an increase in the draw ratio of the fiber, the proportion of the mesophase in the whole fiber mass increases, mainly at the cost of the amorphous phase. It is assumed that the mesophase constitutes about 0.5 of the amorphous phase mass for poorly stretched fibers and about 1.2 of this mass for highly stretched fibers. 

Not all organic compounds that contain —OH groups are soluble in water (Table 10.1). As molar mass increases, the polar —OH group represents an increasingly smaller portion of the molecule. At the same time, the nonpolar hydrocarbon portion becomes larger. As a result, solubility decreases with increasing molar mass. Butanol, CH3CH2CH2CH2 OH, is... 

Recent ECQM work and X-ray diffraction have confirmed the conversion of the a/y cycle to the / // cycle up on electrochemical cycling in concentrated alkali. Earlier ECQM studies of a- Ni(OH)2 films had shown a mass inversion in the microgravi metric curve after prolonged cycling [64] there is a mass decrease in charge instead of a mass increase. More recent work has confirmed that this mass... 

Foam behavior and foam stability are strongly dependent on the water hardness. With a water hardness of 0 ppm the foam behavior and foam stability of LAS improves as the molecular mass increases. This behavior is exactly the opposite at a water hardness of 300 ppm. From 100 ppm the optimum for the Cn homologs is obtained. With the same molecular mass, the foam consistancy of the homologs is highest when the content of 2- and 3-phenylalkanes is highest [187]. In terms of stability in hard water a higher 2-phenylalkane content has a positive influence. An increase in molecular mass has the effect of reducing the hard water stability [189-191]. 

Thus, the energy per unit mass increases with radius r and is independent of depth In the absence of an agitator or mechanical means of rotation energy transfer will take place to equalise j/ between all elements of fluid. Thus the forced vortex tends to decay into a free vortex (where energy per unit mass is independent of radius). 

This is graphically illustrated in Fig. 4-10. Initially, the mass increases almost linearly with... 

The practical effect shown by this equation is that polymers become more difficult to process as their molar mass increases. For example, doubling the degree of polymerisation leads to an approximately ten-fold increase in melt viscosity. Fortunately, melt viscosity decreases with increasing temperature, so that in many cases the effect of high viscosity for higher molar masses can be overcome. However, there is an upper limit at which polymers can be processed without beginning to degrade so it follows that, at some point, a polymer cannot be processed from the melt at all. 

One major drawback of end group analysis is that it rapidly becomes inaccurate as relative molar mass increases. This arises because the percentage of the end groups becomes smaller and smaller, and hence more and more uncertainty attaches to the numerical values of end group content that may be obtained. To illustrate this point, let us consider a polyester with acid end groups being determined by titration. Results for such titrations are shown in Table 6.5. 

Hofner, R., Vazquez-Morena, L., Winter, K., Bohnert, H.J. Schmitt, J.M. (1987). Induction of Crassulacean acid metabolism in Mesembryanthemum crystallinum by high salinity mass increase and de novo synthesis of PEP-carboxylase. Plant Physiology, 83, 915-19. 

Diffusion rates for liquids in an elastomer are easily measured by absorption (immersion) testing, a simple process as indicated in Figure 23.6. An initially weighed immersed sheet sample of elastomer is removed from the liquid periodically, rapidly dabbed with tissue paper, reweighed, and replaced. A plot of mass increase versus root time is drawn (also see Figure 23.6), root time being chosen due to the form of appropriate solutions of Fick s laws. 

Table 4-2. Mass increases resulting from common posttranslationai modifications.

Fig. 1. Mass increases of anode electrodes with time by the contact with electrolytes.

C19-0097. Electrochemistry can be used to measure electrical current in a silver coulometer, in which a silver cathode is immersed in a solution containing Ag" " ions. The cathode is weighed before and after passage of current. A silver cathode initially has a mass of 10.77 g, and its mass increases to 12.89 g after current has flowed for 15.0 minutes. Compute the quantity of charge in coulombs and the current in amperes. 

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