Necessary but not sufficient

Mechanical properties of mbber-modifted epoxy resins depend on the extent of mbber-phase separation and on the morphological features of the mbber phase. Dissolved mbber causes plastic deformation and necking at low strains, but does not result in impact toughening. The presence of mbber particles is a necessary but not sufficient condition for achieving impact resistance. Optimum properties are obtained with materials comprising both dissolved and phase-separated mbber (305). 

CUO2 layers appear in all cuprate superconductors and appear to be a necessary but not sufficient condition for high temperature superconduction. The La2SrCu20g 2 compound has CUO2 layers but does not superconduct. Experiments also indicate that T is proportional to the carrier density in the CUO2 layer but not to the volume carrier density, which is further evidence that the YBa2Cu202 is a two-dimensional superconductor. 

UHV is necessary but not sufficient to ensure an uncontaminated surface. Certainly, the surface will not be contaminated by atoms arriving from the vacuum space, but such contamination as it had before the vacuum was formed has to be removed by bombardment with argon ions. This damages the surface structurally, and that has to be healed by in situ heat treatment. That, however, allows dissolved impurities to diffuse to the surface and cause contamination from below. This problem has to be dealt with by many cycles of bombardment and annealing, until the internal contaminants are exhausted. This is a convincing example of Murphy s Law in action one of the many corollaries of the Law is that new systems generate new problems . 

An apparently universal truth is that intimate contact between adhesive and adherend is a necessary (but not sufficient) requirement for good adhesion. 

The important beneficial effects that substrate roughness can bring were firmly established in the late sixties and early seventies, principally as a result of work in two areas. The first was associated with the electroless deposition of metals onto plastics such as ABS and polypropylene. In the process the plastics must be etched in a way which produces pits on a micrometre scale. Such a topography had been shown to be a necessary, but not sufficient condition for adequate adhesion [40]. 

The analyst must remember that solubility of a polymer in the chosen eluant is a necessary, but not sufficient, requirement for ideal GPC separations. Once injected on the column, the polymer has a choice of partitioning onto the stationary phase or remaining in the solvent. It is imperative that the analyst choose solvent and column conditions such that the ideal, nonadsorptive, GPC mechanism can occur. 

Another important aspects of solubilization are the physical state of the dissolved polymer as well as the thermo-chemistry and kinetics of the dissolution reaction. It is known that a clear cellulose solution is a necessary, but not sufficient condition for the success of derivatization. The reason is that the polymer may be present as an aggregate, as will be discussed below. Additionally, dissolution of activated cellulose requires less time at low temperature, e.g., 2 h at 40 °C, and more than 8 h at 70 °C [106]. These aspects will be commented on below. 

Three-dimensional structures Three-dimensional structures are also quite interesting. A determinate structure must satisfy S = dN — 6. This is a result of 3 constraints needed for each node and the object as a whole can move in six degrees of freedom. As in the case of 2-d, this is a necessary but not sufficient condition. 

NeuA, has broad substrate specificity for aldoses while pyruvate was found to be irreplaceable. As a notable distinction, KdoA was also active on smaller acceptors such as glyceraldehyde. Preparative applications, for example, for the synthesis of KDO (enf-6) and its homologs or analogs (16)/(17), suffer from an unfavorable equilibrium constant of 13 in direction of synthesis [34]. The stereochemical course of aldol additions generally seems to adhere to a re-face attack on the aldehyde carbonyl, which is complementary to the stereoselectivity of NeuA. On the basis of the results published so far, it may be concluded that a (31 )-configuration is necessary (but not sufficient), and that stereochemical requirements at C-2 are less stringent [71]. 

It should be emphasized that it is necessary but not sufficient for Ef(Q) -Ej(Q) to be small over an appreciable range of geometries this only guarantees that the denominator in Eq. (13) is small. It is also necessary that Ef(Q) - E,(Q) decrease at a significant rate as the point of closest approach is reached this is why we say the surfaces must approach closely. Viewed another way, if Ef(Q)... 

Solution We suppose that a collision between an A and a B molecule is necessary but not sufficient for reaction to occur. Thus, we expect... 

As mentioned in the Introduction, it is necessary but not sufficient for isotopically discriminating reactions to occur if isofractionation is to be observed in any particular body component. Whether the isofractionation incurred in a particular reaction in the pathway leads to a measurable effect in a body pool component depends on the pattern or topology of the metabolic fluxes. Three basic cases are considered here for illustrative purposes. 

The data to be examined are correlated with eq. (24). Successful correlation with eq. (24) is a necessary but not sufficient condition for the existence of case (a). Strong evidence for case (a) is provided by a confidence level of Ij greater than or equal to 90.0. The confidence level of p is obtained by means of a student t test of. If is not significant, then this fact implies either the existence of cases (b), (c), or (d), or the use of an incorrect steric parameter. The data are now correlated with eq. (2). If the correlations with... 

The necessity of the statistical approach has to be stressed once more. Any statement in this topic has a definitely statistical character and is valid only with a certain probability and in certain range of validity, limited as to the structural conditions and as to the temperature region. In fact, all chemical conceptions can break dovra when the temperature is changed too much. The isokinetic relationship, when significantly proved, can help in defining the term reaction series it can be considered a necessary but not sufficient condition of a common reaction mechanism and in any case is a necessary presumption for any linear free energy relationship. Hence, it does not at all detract from kinetic measurements at different temperatures on the contrary, it gives them still more importance. 

Goldratt EM, Schragenheim E, Ptak CA. Necessary but not sufficient. North River Press, 2000. 

Evaluation of success is of primary importance. Loss of substrates is a necessary but not sufficient condition, in the light of the frequency of biotransformation reactions and the formation of terminal and possibly toxic metabolites. 

Charge condensation near the electrode (quite a typical feature, which is necessary but not sufficient for attaining C < 0) charging is accompanied by increased charge density near the electrode at the expense of some depletion in the tail regions of the ionic distribution. 

Hunt The MAP kinase is actually necessary but not sufficient for CSF arrest and, by implication, something else is made in that interval. Jim Mailer published some data (I don t think I d agree with them) that cyclin E/Cdk2 may be part of the contribution. There certainly is a cohort of proteins that are made in that interval, one of which may be the vital additional component for CSF. But no one knows what it is. 

Dauben et al. have investigated the scope of the photochemical type A rearrangement/60 They conclude that the rearrangement occurs only if the fourth carbon atom of the 2-cyclohexenone ring is fully alkyl-substituted. If this requirement is not met, photodimers are the major products. This substituent requirement is necessary but not sufficient to ensure rearrangement since the presence of other groups can inhibit the reaction. 

Since the main topic of this review is STM imaging, growth properties, surface morphology, and atomic structures of oxide nanosystems are the central themes. Oxide nanolayers on noble metal surfaces often display very complex structural arrangements, as illustrated in the following sections. The determination of the surface structure of a complex oxide nanophase by STM methods is, however, by no means trivial resolution at the atomic scale in STM is a necessary but not sufficient condition for elucidating the atomic structure of an oxide nanophase. The problem... 

Albert Tauber. I d like to give a reference that everyone knows. Sickle-cell is commonly evoked as a great reductionist victory. I treat many patients with sickle-cell anemia, and I can tell you that the genetic defect is not the disease, because the disease manifestation is highly variable. Some patients have an enormous number of pain-crises. Some patients have a lot of haemolysis that s red-cell destruction. Other patients have pulmonary hypertension. And it s obvious that the disease that we call sickle-cell anemia is an extraordinarily complex phenomenon interacting with many many different systems and many other genes. And the bottom line, from a clinical perspective, which is the phenomenon that we call sickle-cell anemia, is that the sickle-cell gene is necessary but not sufficient for the disease. 

This list includes BP, 7,12-dimethylbenz[a]anthracene, 3-methylchol-anthrene, dibenzo[a,i]pyrene and dibenzo[a,h]pyrene. These PAH can be activated both by one-electron oxidation and/or monooxygenation. There are a few PAH with low IP which are inactive (Table I), such as perylene, or weakly active, such as anthanthrene. This indicates that low IP is a necessary, but not sufficient factor for determining carcinogenic activity by one-electron oxidation. These inactive or weakly active PAH have the highest density of positive charge delocalized over several aromatic carbon atoms in their radical cations, whereas the active PAH with low IP have charge mainly localized on one or a few carbon atoms in their radical cations. 

Reaction mechanism a postulated sequence of elementary reactions that is consistent with the observed stoichiometry and rate law these are necessary but not sufficient conditions for the correctness of a mechanism, and are illustrated in Chapter 7. 

A necessary (but not sufficient) prerequisite for models of stereospecific catalytic systems is the stereoselectivity of each monomer insertion step. The possible origin of stereoselectivity for models of several kinds of catalytic systems has been investigated through molecular modeling. 

The reason for the double-edged nature of reliability is that reliability is a necessary but not sufficient criterion for validity. It is necessary to make consistent assessments to have a valid system. However, it is possible that these reliable assessments measure something that is largely irrelevant to what is actually of interest. The quest for increasing interrater reliability has resulted in disassembling disorders into only those components that can be reliably assessed. However, some have suggested that some of the more essential behaviors (i.e., valid indicators of the diagnostic entity) that are less reliably assessed have been excluded. 

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