Further Observations

Two further observations can help us to predict stable nuclei  

These observations can be understood in terms of the shdl model of the nucleus, in which nucleons are described as residing in shells analogous to the shell structure for electrons in atoms. Just as certain numbers of electrons correspond to stable filled-shell electron configurations, so also the magic numbers of nucleons represent filled shells in nuclei. 

Among the elements shown here, how many have an even number of protons and fewer than three stable isotopes How many have an odd number of protons and more than two stable isotopes  

Evidence also suggests that pairs of protons and pairs of neutrons have a special stability, analogous to the pairs of electrons in molecules. This evidence accounts for the second observation noted earlier, that stable nuclei with an even number of protons and/or neutrons are far more numerous than those with odd numbers. The preference for even numbers of protons is illu.strated in A FIGURE 21.4, which shows the number of stable isotopes for aU elements up to Xe. Notice that once we move past nitrogen, the elements with an odd number of protons invariably have fewer stable isotopes than their neighbors with an even number of protons. 

What can you say about the number of neutrons in the stable isotopes of fluorine, sodium, aluminum, and phosphorus  

Each blue arrow represents decay by alpha emission 

Each red arrow represents decay by beta emission 

What else can we learn from studying the sequences There are many observations, but it seems rather hard to bring them into a system. We just choose several examples by om subjective taste to list here. 

Here is another example of an interesting observation. Imagine that you have a globular protein, and replace — not in an active center — one of the hydrophobic amino acid by another hydrophobic one, or hydrophilic by hydrophilic (see Section 5.7). Then, most likely, such a substitution will not cause much trouble the three dimensional structure of the globule will not be violated, and the protein will still be able to do its job. Here, most likely does not mean always , there are exceptions, some of them are unfortunate, for they have to do with inheritable diseases, but overall proteins have remarkable stability against mutations, as we already discussed in Section 10.6. 

Genetic code also seems to have some error correcting capabilities. One particular property was noticed by M.V. Volkenstein, and can hardly be accidental. To explain the point, let s imagine that we have a gene — DNA sequence coding for a certain protein. If one DNA nucleotide is accidentally replaced by another, there is a more than even chance (in fact, about 2/3) that this will lead to the safest, that is, hydrophobic-hydrophobic or hydrophilic-hydrophilic substitutions in the coded protein. 

---

The observation that certain kinds of parallel-computing architectures best support only certain kinds of problems seems to be general. The further observation that interprocessor communication can be the primary impediment to parallel performance is also general. As of this writing, any hope of a truly general purpose parallel computer seems to be remote. The best hope may He in software efforts that describe problems at higher levels of abstraction, which can then be ported and optimized for different parallel architectures (22). 

As motivation for the rest of the chapter, a few further observations can be made. Eirst, the calculation of full electrostatics is expensive. A typical molecular mechanics potential function is of the form... 

On the basis of these results they assigned formula (II) to ehelerythrine, and this was confirmed by the further observation that dihydrocheler -thrine, m.p. 166-7°, on treatment with phloroglucinol and sulphuric acid and subsequent methylation of the dihydric phenolic base so formed, yields tetramethoxy-A -methyldihydro-a-naphthaphenanthridine (VI), m.p. 182-3°, also obtainable from sanguinarine. ... 

The formation of the complex is expected to decrease the free energy of activation for the homolysis of the peroxide bond, and the decomposition of TBHP would occur at a lower temperature. It was further observed that at a higher concentration of mineral acid, the decomposition of TBHP occurs via an ionic pathway, as reported by Turner [27]. 

The bubble size at formation varied with particle characteristics. It was further observed that the bubble size decreased with increasing fluidization intensity (i.e., with increasing liquid velocity). The rate of coalescence likewise decreased with increasing fluidization intensity the net rate of coalescence had a positive value at distances from 1 to 2 ft above the orifice, whereas at larger distances from the orifice the rate approached zero. The bubble rise-velocity increased steadily with bubble size in a manner similar to that observed for viscous fluids, but different to that observed for water. An attempt was made to explain the dependence of the rate of coalescence on fluidization intensity in terms of a relatively high viscosity of the liquid fluidized bed. 

The catalytic activity of doped nickel oxide on the solid state decomposition of CsN3 decreased [714] in the sequence NiO(l% Li) > NiO > NiO(l% Cr) > uncatalyzed reaction. While these results are in qualitative accordance with the assumption that the additive provided electron traps, further observations, showing that ZnO (an rc-type semi-conductor) inhibited the reaction and that CdO (also an rc-type semi-conductor) catalyzed the reaction, were not consistent with this explanation. It was noted, however, that both NiO and CdO could be reduced by the product caesium metal, whereas ZnO is not, and that the reaction with NiO yielded caesium oxide, which is identified as the active catalyst. Detailed kinetic data for these rate processes are not available but the pattern of behaviour described clearly demonstrates that the interface reactions were more complicated than had been anticipated. 

A further observation is the fact that differences in rates of nitration between the reagents prepared at different temperatures tended to zero as the water concentration of the added nitric acid was decreased to zero73. It has been argued that, since the acid-catalysed hydrolysis of acetic anhydride must be very rapid at 25 °C and removes water which initially competes with acetic anhydride and acetyl nitrate for protons, this removal permits equilibria (30) and (31) to be displaced towards products. The more anhydrous the nitric acid, the less important is this initial hydrolysis of the acetic anhydride and so the difference in the nitrating power of the differently prepared mixtures becomes less. When reagents are mixed at low temperatures, the hydrolysis of the anhydride is very slow, but once this is accomplished, formation of the protonated acetyl nitrate and subsequent nitration is rapid as observed73. 

Deoxy-sugars. Part XI. Further Observations on the Dische Reaction of 2-Deoxypentoses, W. G. Overend, F. Shafizadeh, and M. Stacey,/. Chem. Soc., (1950) 1027-1029. 

Harding, S.E. Day, K. Dham, R. Lowe, P.M. 1997a. Further observations on the size, shape and hydration of kappa-carrageenan in dilute solution. Carbohydrate Polymers 32, 81-87. 

Combination of (41) with the foregoing allows us to establish (38). Before going further, observe that a solution to the problem... 

Several comments on these data were presented earlier (Section II). One might make two further observations here. First, there is a general trend to higher 1/2 values which is seen with progressive replacement of isocyanides by carbonyls. This means that these species are progressively less easy to oxidize. Second, a further oxidation for the complexes with 0, 1, and 2 carbonyls is observed. This oxidation was believed to be associated with the process MnLj + -> MnLj +. 

Hofer H.O. (1980b). Further observations on the occurrence of taste buds in the papilla palatina of primates. Morphol Jb 126, 110-117. 

These data show that bromine works better than chlorine in high pH waters such as the ocean. Similarly, most industrial water is quite alkaline and therefore, a practical form of bromine is also preferred. The technical attributes of bromine antimicrobials are of value in water treatment and are apparently also worth the cost to many aquatic plants. Further observations of natural microbial fouling control systems reveal that animals also preferentially manufacture, in situ, certain bromine-based antimicrobials. 

Runanine (17) was isolated from the roots of Stephania sinica, a species found in the Chinese provinces of Heibei, Gueizhou, and Yunnan (35). The H-NMR spectrum of runanine (17) (Table II) revealed the presence of two aromatic protons, C-5 methylene protons, one N-methyl, and four methoxyl groups. An NOE effect (10% enhancement) was observed between the protons of two methoxyl groups (53.79 and 3.80) and the aromatic protons (56.47 and 6.64), but the same phenomenon was not observed for the other methoxyl protons (53.61 and 4.05). Therefore, the former methoxyls should be situated on ring A. From the further observation of an NOE (22.6% enhancement) between the aromatic C-4 proton (56.64) and one (53.00) of the C-5 methylene protons, it was assumed that the two methoxyl groups (53.79 and 3.80) should be located at C-2 and C-3, respectively. The absence of signals for olefinic... 

Paglia DE, Valentine WN, Fink K. 1977. Lead poisoning Further observations on erythrocyte pyrimidine-nucleotidase deficiency and intracellular accumulation of pyrimidine nucleotides. J Clin Invest 60 1362-1366. 

Firstly, the analysis implicitly allows water reuse even in a situation where the source and sink processes are simultaneously active as observed in Fig. 12.6. According to Fig. 12.6, in concentration interval (20CMKX) ppm), 37.5 t and 25 t of water are available for reuse in the (0.5-1.0 h) and (1.0-1.5 h) time intervals, respectively. This semi-batch behaviour is further observed in the water network shown in Fig. 12.7. Some of the water from process 3 is reused in process 1, even though process 1 is 0.5 h from completion. This would not be possible for truly batch operations, since the reuse potential of water could only be realized after the completion, and not during the course of the process. 

Tanaka and Kakiuchi (6) proposed catalyst activation via a hydrogen donor such as an alcohol as a refinement to the mechanism discussed by Fischer (7) for anhydride cured epoxies in the presence of a tertiary amine. The basic catalyst eliminates esterification reactions (8). Shechter and Wynstra ( ) further observed that at reaction conditions BDMA does not produce a homopolymerization of oxiranes. 

Recently, Astruc et al. [189] reported novel amido-ferrocene dendrimers (e.g., 91) which were shown to act as supramolecular redox sensors for the recognition of small inorganic ions (Fig. 41). It was further observed that as the den-drimer generation number increased the sensitivity to the guest molecules also increased as observed by cyclic voltammetry experiments. 

Lee et al. utilized the self-assembled layer of thiol group-modified protein A for the oriented immobilization of antibodies [64], An increased binding capacity was further observed. As another illustrative instance, a protein A-based orientation-controlled immobilization strategy for antibodies was proposed for the fabrication of a QCM immunosensor using nanometer-sized gold particles and amine-terminated PPF [65], Moreover, in recent years, there has emerged another oriented immobilization... 

Sources of organoleads in the environment are being reduced or eliminated through environmental and occupational safety regulations. Even no, we need to further observe and control the decline of organolead levels in our environment. 

NH3 and H2O, also appeared as sharp peaks, but the maximum in the signals for these products occurred at 2.5 s. Changes in the experimental conditions did not alter the qualitative features of the responses. In all cases the peaks for N2 and N2O occurred simultaneously and preceded the peaks for NH3 and H2O. It was further observed that the reaction temperature, duration of NO exposure, and the H2 partial pressure during NO reduction affected the intensities of the product peaks and the time delay between the N2/N2O peaks and the NH3/H2O peaks. To a much lesser degree, the reaction conditions also affected the time at which the N2 and N2O signals reached a maximum. 

---