Missing mass

Here we encountered a typical situation in the de novo sequencing—there is a part of the sequence that is not covered by any ion series. Not all bonds between amino acids are of equal strength, and some of them might be particularly resistant to collisions, which in turn results in the missing mass-shifts (and missing residues). 

In the reaction profile shown in Figure 1 (similar to that shown by Smith et al. (10)) the initial product was azoxybenzene. However this figure is deceptive firstly azoxybenzene may be produced by a non-catalyzed reaction between nitrosobenzene and phenyl hydroxylamine (10), secondly the figure does not show the mass balance. Indeed at 10 min when all nitrosobenzene has been removed from the solution the amount of azoxybenzene formed was 18.6 mmol, equivalent to 37.2 mmol of reacted nitrosobenzene. Therefore, 42.8 mmol of the original 80 mmol of nitrosobenzene (53.5 %) were unaccounted for. It is possible that the missing mass is in the form of phenyl hydroxylamine in solution, which continues to disproportionate to produce aniline and nitrosobenzene and subsequently azoxybenzene and azobenzene. However as we shall subsequently discover this interpretation is unsustainable. 

As we saw earlier, even these masses are not exactly whole numbers. Aston s instrument could measure masses very accurately, and he generally found around a 1 per cent deficit in mass relative to a whole number of hydrogen atoms. This missing mass is converted into the binding energy of the nucleus (see page 131). 

Because we are told that oxygen is also present in the sample, the "missing" mass must be due to oxygen, which can t be detected by combustion. We therefore need to find the number of moles of oxygen in the sample ... 

We must include electrons in this calculation because 4.0026 amu is the mass of the helium-4 atom, not the nucleus.) This missing mass corresponds to 0.0305 x 931.4 MeV = 28.4 MeV of energy. If we could put together a helium atom directly from two neutrons, two protons, and two electrons, then 28.4 MeV of energy would be given off for every atom formed ... 

In view of these problems, the fits to the compositions of the fine fractions are quite good. Only about 80% of the mass is explained, nearly all of it as regional sulfate, but this is typical for fits to fine fractions. The missing mass is probably condensed water and carbonaceous material, nitrates, etc. Potassium is seriously underpredicted, partly because we included no wood-smoke component. The latter would account for residual K, but little else. Several elements, including Cr, Co and Cd may have sources not included in the CMBs, or the components used may be deficient in these elements. 

Kanazawa et al. [20] and their calculations are valid for rigid films immersed in liquid. However, this work is not valid for non-rigid soft materials. For soft material layers it was even noticed that in applying Sauerbrey s equation the mass of the viscoelastic layer is underestimated and the result is a missing mass which was elucidated in calculations by Voinova et al. [21],... 

Voinova MV, Jonson M, Kasemo B (2002) Missing mass effect in biosensor s QCM applications. Biosens Bioelectron 17 835-841... 

This missing mass has come to be called dark matter. Since the... 

The present state of knowledge about invisible dark matter indicates that it represents the predominant part (about 90%) of the total mass of the universe. It includes the so-called missing mass. Dark matter is not discernible by any kind of electromagnetic radiation in the region from y rays to radiowaves, but its gravitational effects on other kinds of matter are observable. For example, the rotation of spiral galaxies such as the Milky Way can only be explained if 90% of the matter is invisible in the sense mentioned above. The question of the nature of the dark mass is still open. Various possibilities are discussed matter different from that on the earth (no protons, neutrons and electrons), remnants of the big bang, neutrinos. However, the actual mass of neutrinos is still uncertain. 

The mass spectral data for acetylene is given in the following table. The molecular formula can be deduced as follows. If the molecular ion is at m/z = 26, then the ratio of M -I- 1 to M is 2.2%, indicating 2 carbon atoms. Their total mass is 24 Da. The missing mass of 2 Da can only be two hydrogen atoms. Hence, the formula is C2H2. Note that the M -I- 2 peak is too small to indicate the presence of oxygen, and the even numbered m/z value... 

The idea of dark matter was first mooted to resolve Zwicky s paradox, which relates to different estimates of galactic mass, based on luminosity and rotational models respectively. Rotational analysis consistently predicts excess mass, compared to the total luminous mass within the assumed limiting size of a galaxy, as defined by its so-called Holmberg radius. The subsequent discovery of massive clouds of both atomic and molecular hydrogen around typical galaxies and clusters may well account for this missing mass. 

If Population III remnants are to provide the missing mass, one may need to give up the conventional cosmological nucleosynthesis picture anyway [.as.] the dark matter problem cannot be solved by black holes or low-mass stars of nonprimordial origin unless one modifies the conventional nucleosynthesis scenario". 

Reactions of this type also release a lot of energy. Where does the energy come from Well, if you make very accurate measurement of the masses of all the atoms and subatomic particles you start with and all the atoms and subatomic particles you end up with, and then compare the two, you find that there s some ""missing mass. Matter disappears during the nuclear reaction. This loss of matter is called the mass defect The missing matter is converted into energy. 

Fig. 2.2. CT of a typical, partially calcified cavernoma adjacent to the left ventricle. The missing mass effect (no compression of the ventricle, normal width of the external cerebrospinal-fluid space) is a striking argument against a true tumor (like oligodendroglioma)...

In the response spectrum method, the maximum response of each mode should be calculated by direct use of the design response spectrum. The maximum response in each principal direction should be determined by an appropriate combination of the modal maxima, such as the square root of the sum of the squares of each modal response, or by the complete quadratic combination procedure. For closely spaced modal frequencies, a conservative procedure should be applied by taking the sum of the absolute values of each closely spaced modal and rigid response. The missing mass as a function of the modelling detail, cut-off frequencies and modal participation factors used in the analysis should also be carefully assessed and documented. 

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