Expected trends

A semi-quantitative estimation was recently proposed by NIST [43] along the following orientations  

Ten-year horizon, considering the recent evolution in the development of measurement instruments, the CRM demand should grow about 5% per annum because their usage is growing from a smaller base, the needs for non-certified reference materials (e.g. for proficiency testing in support of laboratory accreditation) should increase by 10% per annum. 

Twenty-year horizon, the use of CRMs should continue to grow at a rate of 5% per annum. The needs in terms of the quality of routine measurements should yield to an increasing use of non-certified reference materials (linked to accreditation) at a rate of 15% per annum. 

Thirty-year horizon, the increasing sophistication of measurement instruments should enable the resolving of all difficulties inherent to validation and the use of CRMs should hence decrease it is likely that the needs will be directed towards the continued replacement of obsolete materials with new types of materials to address the challenges. Needs for materials linked to accreditation will likely slow to a still high rate of 5% per annum. 

Certification of Reference Materials — General and Statistical Principles, ISO Guide 35 (1985), International Organisation for Standardisation, Geneva. CH. 

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Table 10.2 shows expected trends in specifications for some major products. 

Mathematical Consistency Requirements. Theoretical equations provide a method by which a data set s internal consistency can be tested or missing data can be derived from known values of related properties. The abiUty of data to fit a proven model may also provide insight into whether that data behaves correctiy and follows expected trends. For example, poor fit of vapor pressure versus temperature data to a generally accepted correlating equation could indicate systematic data error or bias. A simple sermlogarithmic form, (eg, the Antoine equation, eq. 8), has been shown to apply to most organic Hquids, so substantial deviation from this model might indicate a problem. Many other simple thermodynamics relations can provide useful data tests (1—5,18,21). 

IR spectra of systems related to /3-lactams show the expected trends in the frequency of the carbonyl absorption, where present. For example, the presence of an exocyclic double bond at C-4 in an azetidin-2-one raises the value of vc=o considerably. Thus the 4-thioxoazetidin-2-one (62 Z=S) and the derived 4-alkylidene systems (62 Z = CR R ) exhibit /3-lactam carbonyl absorptions at 1835 and 1800-1810 cm respectively (80JOC1477, 80JOC1481), while the 4-iminoazetidin-2-ones (63) have vc=o at 1800-1825 cm (81CC41). Additional spectral data for these and similar systems may be found in the references in Table 5. 

IR spectra of 2-substituted 1-azetines show the expected trends in the frequency of the imine absorption thus 2-aryl-l-azetines generally show vq=n at ca. 1550-1580 cm while 2-ethylthio and 2-alkoxy-1-azetines show absorptions at ca. 1535 and 1620 cm respectively (79CB3914, 67JHC619, 69LA(725)124). The parent 1-azetine shows vc=n at 1570 cm ... 

Look for trend statements in the report and ask the toller to explain their expected trend if it is potentially relative to ABC Co. interests. 

BWR results, grouped by containment type, follow expected trends and indicate that, in general, Mark I containments are more likely to fail during a severe accident than th c II... 

In general, it was found that this process is strongly endothermic for sulfur diimides, approximately thermoneutral for selenium diimides and strongly exothermic for tellurium diimides, consistent with experimental observations. These differences can be attributed to the expected trend to lower r-bond energies for chalcogen-nitrogen (np-2p) r-bonds along the series S (n = 3), Se (n = 4) and Te (n = 5). 

Photoelectron spectra have confirmed the expected trends in the frontier orbitals.The tetrafiuoro derivative 12.12 (R = F) is prepared by treatment of C6F5SNSNSiMc3 with CsF in acetonitrile (Scheme 12.2). Several difiuoro- and trifiuoro-benzodithiadiazines have also been prepared by these methods.In contrast to 12.12 (R = H), which has an essentially planar structure in the solid state,the dithiadiazine ring in the tetrafiuoro derivative is somewhat twisted. In the gas phase, on the other hand, electron diffraction studies show that 12.12 (R = F) is planar whereas 12.12 (R = H) is non-planar. ... 

Many of the ionic fiuorides of M, M and M dissolve to give highly conducting solutions due to ready dissociation. Some typical values of the solubility of fiuorides in HF are in Table 17.11 the data show the expected trend towards greater solubility with increase in ionic radius within the alkali metals and alkaline earth metals, and the expected decrease in solubility with increase in ionic charge so that MF > MF2 > MF3. This is dramatically illustrated by AgF which is 155 times more soluble than AgF2 and TIF which is over 7000 times more soluble than TIF3. 

The aufbau principle must be obeyed when an electron is added to a neutral atom, so the electron goes into the most stable orbital available. Hence, we expect trends in electron affinity to parallel trends in orbital stability. However, electron-electron repulsion and screening are more important for negative ions than for neutral atoms, so there is no clear trend in electron affinities as ft increases. Thus, there is only one general pattern ... 

For nitromethane and aci-nitromethane, the optimized structures of the present calculations with the small basis set (4-31G) are very similar to the 3-21G and 6-31G McKee s optimized structures [1] the variation of bond lengths and bond angles with the level of theory follows the expected trends with an increase in the bond lengths when correlation effects are taken into account. The results of the present calculations for nitromethane are also in better agreement with the cristal structure [5. ... 

ESCA analysis showed a similar trend of incomplete surface coverage for the IK systems. Also, no domains were visible in any of the IK styrenic graft systems by TEM. There is an expected trend with respect to solubility parameter, p(t-butyl styrene) (6 s 8.1) has a solubility parameter much closer to that of polydimethylsiloxane (S a 7.3) than does p(p-methyl styrene) which is closer than p(styrene) (S s 9.1). 

The flatness of the computed curves in Fig. 6 shows that in the case of spheres in contact F is insensitive to rather large changes in V (or / ). Mason and Clark (M3) have measured the pendular bonding force as a function of the separation distance and bridge volume. Considering the experimental uncertainty involved, their results follow the expected trend quite satisfactorily. 

Mendez, D., Warner, K.E., Courant, P.N. Has smoking cessation ceased Expected trends in the prevalence of smoking in the United States. Am. J. Epidemiol. 148 249, 1998. 

The expected trends of CPA and PTA uptake for the three materials are seen in Figure 6.27. The high-PZC material, like alumina in Figure 6. 18a, should adsorb the most CPA and the low-PZC material should adsorb the least. Correspondingly, the low-PZC carbon should adsorb the most PTA, like silica in Figure 6.18b, and the high-PZC carbon the least. 

Association trends also reflect for the most part increasing solvation with decreasing size (Table 4). Tetraalkylammonium salts become less associated as the size of the alkyl group becomes larger, an expected trend for these relative-... 

Halide ion mobilities follow the expected trends (Fig. 9). Chloride ion, with the smallest crystallographic radius of the three halides considered, is the most mobile in solvents such as nitrobenzene and dimethylformamide, where anion solvation is expected to be small. In these solvents the Walden products are large. 

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