Tentative explanation

LaCo03. In such a situation, tentative explanations on possible changes in the chemical environment of oxidic palladium species could be proposed with a subsequent stabilisation of oxidic Pd species in the perovskite matrix. The formation of well-dispersed Pd"1 entities could further inhibit the formation of sulphate generally observed on PdO at high temperature [113,115],... 

Under similar profiles of raising in temperature, it was shown that the selectivity favoring 1,2 Stevens rearrangement is exemplified under the action of microwaves. A tentative explanation can be to consider that, under the action of radiation, the more polar mechanism (1,2 ionic shift) is favored when compared to less polar one (2,3 radical shift). Maybe this result is indicative of a competition between ionic and radical pathways. 

The stability of these dispersions has been investigated. A strong dependence of critical flocculation conditions (temperature or volume fraction of added non-solvent) on particle concentration was found. Moreover, there seems to be little or no correlation between the critical flocculation conditions and the corresponding theta-conditions for the stabilising polymer chains, as proposed by Napper. Although a detailed explanation is difficult to give a tentative explanation for this unexpected behaviour is suggested in terms of the weak flocculation theory of Vincent et al. 

There are many published examples in which the coupling of two different materials leads to an increase in the photocatalytic activity. Many of them concern coupling and junctions between different nanopartides, considering also different topologies, like coupled and capped systems [72]. Tentative explanations based on possible heterojunction band profiles are given. However, in-depth analysis of the hetero junction band alignment, the physical structure of the junction, the role of (possible) interfadal traps and of spedfic catalytic properties of the material is still lacking. Some recently published models and concepts based on (nano)junction between different materials are briefly reviewed here. 

A tentative explanation for the importance of connected triple excitations for the inner-shell contribution to TAE can be found in the need to account for simultaneously correlating a valence orbital and relaxing an inner-shell orbital, or conversely, requiring a double and a single excitation simultaneously. 

Lipases generally show low hydrolytic activity when their ester substrates are dissolved in aqueous media and present in imimeric form. A pronounced increase in activity is observed when the substrate concentration reaches the solubiUty limit and a separate phase is formed. In the case of surfactants this impUes that a possible increase in activity can be expected above the CMC. Attempts to investigate how the hydrolysis is affected by micelUzation were made for the linear surfactant 1 of Fig. 4. The CMC of this surfactant is 10 mM, and a marked change in the activity of the MML is indeed observed when this concentration is exceeded, see Fig. 6. The initial reaction is faster (steeper slope) above the CMC. When CALB was used to catalyze the reaction, no increase of the reaction rate was observed above the CMC. It was also found that the rate, expressed in moles of surfactant consumed per minute, was independent of the start concentration (same slope). A tentative explanation to the fact that the MML but not the CALB-catalyzed hydrolysis is accelerated by the presence of micelles may be that MML but not CALB is able... 

After the period of almost constant reaction rate and at conversions higher than 60%, the decrease in reaction rate follows approximately first-order kinetics. A tentative explanation for this behavior of vinylidene chloride emulsion systems may be the following. Let us first assume that... 

Exposure to heated water or water vapor also might be somewhat erratic like the oxygen as determined by analysis of this coal. This suggestion, consequently, seems most attractive as a tentative explanation for oxygen anomalies. Possibly some of the unusual moisture determinations may be explained as an accompaniment of this process. 

Ballard and Bamford (43) also investigated the kinetics of the polymerisation of D,L-phenyl alanine NCA initiated by tributyl amine in nitrobenzene. This reaction does not ensue1 in pure tertiary amine (11), but it proceeds rapidly in polar solvents. (For a tentative explanation of this observation see p. 49.) However, the polarity does not appear to be a necessary condition for a rapid reaction since a fast polymerisation initiated by triethyl amine in benzene was observed by Blout (49). It seems, therefore, that the role of solvent in these reactions needs further and extensive examination (see also p. 48). In the tributylamine-initiated polymerisation, sarcosine NCA again proved to be inert (44) under conditions which led to a rapid polymerisation of the non-N-substituted NCA s. 

A recent instance225 of reaction 22 (X = NH) involves the reactions of some (het-eroarylchloromethyl)lithium (165) reagents with imines (166) to form 167 and to produce the heteroaryl aziridines (168) as depicted in Scheme 50. Aziridines (167) are obtained in the preferential (or exclusive) conformation E. A tentative explanation of this behaviour is the different steric compression in the transition states affording isomeric E or Z aziridines. 

How the experimental panorama is influenced by parameters still to be defined was demonstrated by Shibata et al. [86]. Here, preliminary results obtained in aqueous media using a specific brand of high-purity commercial copper cathode were positive with regards to hydrocarbons C3+, provided that no electropolishing was performed before the electrochemical process. If electropolishing preceded the C02 reduction, the cathodes behaved similarly to any other copper cathode, leading essentially (besides hydrogen) only to methane end ethylene. A tentative explanation of this behavior was proposed which referred to the polycrystalline matrix of this brand of copper, which made it particularly adaptable to be covered by oxide layers active in the formation of C3+. However, further experimental evidence on the surface structure, composition and modifications with electrolysis time will be required to substantiate this hypothesis. 

Hypothesis In a scientific investigation, a tentative explanation of observations in a laboratory or nature. Hypotheses are then tested with the scientific method to determine their validity. If a hypothesis is highly reliable at explaining and even predicting a phenomenon, it becomes a theory. 

The thermogram of this sample is shown in Figure 8. The ammonium nitrate peak and the first peak of ammonium sulfate match closely the positions of standard compounds. However, the peak at 270°C is noticeably shifted from the second ammonium sulfate peak, although the overall appearance of the doublet is similar to that of ammonium sulfate. A tentative explanation of this observation is that the sample does not contain pure ammonium sulfate, but rather that some of the ammonium ions are replaced by a charged organic nitrogen complex. This complex should produce the right chemical shift (relative to ammonium) in the ESCA spectrum, decompose at a lower temperature than ammonium bisulfate, and hydrolyze to ammonium in water solution. 

The origin of the various additive effects is still unknown. However, taking into account the wide variety of chiral additives that cause effects with considerable sensitivity, it can be assumed that unspecific rather than specific interactions between the additives and species involved in the reaction mechanism of the Soai reaction take place. These may cause small but directed chiral perturbations where advantage is taken of the extraordinarily strong autocatalytic amplification capacity of the system. As already demonstrated by Singleton and Vo [36], these perturbations can be extremely small without losing its enantiomeric direction. In fact, as we describe later, the assumption of interactions between these chiral additives and the Soai reaction product itself, i.e., the autocatalytic species, could provide a tentative explanation for such effects. 

If the question has not been answered, the scientist may prepare for an experiment by making a hypothesis. A hypothesis is a statement of a possible answer to the question. It is a tentative explanation for a set of facts and can be tested by experiments. Although hypotheses are usually based on observations, they may also be based on a sudden idea or intuition. 

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