Underlying Hypothesis

The original theory of diffusional coagulation of spherical aerosol particles was developed by von Smoluchowski (1916,1917). The underlying hypothesis in this theory is that every aerosol particle acts as a sink for the diffusing species. The concentration of the diffusing species at the surface of the aerosol particle is assumed to be zero. At some distance away, the concentration is the bulk concentration. 

Over the last years, a renewed interest on the antibiotic resistance phenotypes in municipal waste water treatment plants became apparent in the scientific literature. The underlying hypothesis of these smdies is that urban sewage treatment plants are potential reservoirs of antibiotic resistance, and, in general, it is aimed at contributing to assess the risks of dissemination, posed by the treated effluents discharged into natural water courses. As a general trend, these studies focus on human/animal commensal and environmental bacteria, frequently disseminated via faecal contamination, and which can survive in waters. The relevance of these bacteria, which may exhibit clinically relevant resistance phenotypes, as possible nosocomial agents seems also to be a motivation behind these smdies. 

These attempts may be called thermodynamic semi-theoretical approaches . They concern mostly the simplest kind of bonding, namely the metallic bond. The underlying hypothesis is that the contributions of different outer orbitals (7 s, 6 d, 5 f) in some chosen thermodynamic or structural property can be linearly combined, the coefficients of this linear combination being related to the degree of participation of the different orbitals in the bonding an approach clearly related to the molecular orbital approach of quantum chemistry and to the hybridization concept, and which had been previously employed in other transition metals and to the rare-earth metallic systems " (for a criticism of this approach, see Ref. 6). The chosen thermodynamic and structural properties are, therefore, bonding indicators , since they will reflect contributions introduced by the fact that the wavefunctions of bonding electrons have mixed orbital characters. 

Step 2. The second step consists in testing for equahty of intercepts among the batches. To derive the appropriate statistic for testing the underlying hypothesis, it is required to compute the following sum and cross products for the %LC and the sampling time. The hypothesis to be tested is... 

Retained substrate specificity (binding), changed chemistry A new enzyme evolves to supply substrate from an available precursor by evolution of enzyme using the substrate. The underlying hypothesis states that metabolic pathways evolve backwards A > 15 > C, 1 A >Pi is new, B >C is old enzyme ... 

Retained chemistry, changed substrate specificity (binding) Nature selects protein from a pool of enzymes whose mechanism provide a partial reaction or stabilization strategy for intermediates or transition states. Evolution decreases the proficiency of the reaction catalyzed by the progenitor. The underlying hypothesis states that chemical mechanism dominance starts with a low level of promiscuous activity and that once evolved it is beneficial for nature to utilize it over and over again. 

The underlying hypothesis of oxidative stress, antioxidants, and chronic diseases is illustrated in Figure 7. 

Fig. 4. Schematic model of the mechanisms of oestrogen control of cell proliferation. Three different mechanisms are illustrated. In (1) the interaction of oestrogen (E) with ER leads to increased transcription of genes whose products are directly involved in the control of cell replication. The mechanism illustrated in (2) postulates that oestrogens modulate the production of autocrine growth factors which in turn bind to growth factor receptors at the cell surface and mitogenesis occurs as a consequence of growth factor-activated metabolic pathways. The underlying hypothesis in (3) is that cells are under inhibitory (I) control by undefined molecules in the extracellular fluid and that oestrogens block the effects of these inhibitory molecules.

In the present paper, after a rapid presentation of the reptation model in its simplest version, in order to pinpoint the underlying hypothesis, we discuss the interest of complementary self diffusion and viscoelastic measurements, and present the currently available methods for measuring diffusion in entangled polymer systems. Then, results obtained on polydimethylsiloxane (PDMS), a model liquid polymer well above its glass temperature at room temperature will be described, and the consequences on the limits of the entangled regime as seen from diffusion measurements, compared to what is observed in rheometry, will be discussed. 

When reptation is used to develop a description of the linear viscoelasticity of polymer melts [5, 6], the same underlying hypothesis ismade, and the same phenomenological parameter Ng appears. Basically, to describe the relaxation after a step strain, for example, each chain is assumed to first reorganise inside its deformed tube, with a Rouse-like dynamics, and then to slowly return to isotropy, relaxing the deformed tube by reptation (see the paper by Montfort et al in this book). Along these lines, the plateau relaxation modulus, the steady state compliance and the zero shear viscosity should be respectively ... 

Under hypothesis (15) and under some smothness conditions on the (bounded) domain of the flow, and on the functions Aijki and, Renardy [41] proves the local existence and the uniqueness of a Hj fl solution of equations (3) and (14), provided that the initial data Vo and To are smooth, and satisfy a compatibility condition at time t = 0. 

Resolution of this ambiguity requires additional experiments. The processes and reactions hypothesized for a given model can suggest experiments to support or reject the underlying hypothesis. For example, the proposed formation of PtO is consistent with a... 

Vie extend an offer to Interested experimentalists to test the underlying hypothesis of our model and the correctness of Its predictions. A series of controlled studies using a mixture, either natural or synthetic, of a large known number of components with widely varying functional structure Is one possible procedure. Only experimental testing will reveal the degree of applicability and universality of our model and Its predictions. 

The underlying hypothesis is that because EC and primary OC often have the same sources, there is a representative ratio of OC/EC for the primary aerosol. If the measured ambient OC/EC ratio exceeds this expected value, then the additional OC can be considered to be secondary in origin. A weakness of that approach is that OC/EC emission rates vary by source and therefore the primary ratio will be influenced by meteorology, diurnal and seasonal fluctuations in emissions, and local sources. 

The philosophy underlying hypothesis testing is easy to understand. The term that appears in the denominator of Eq. (2.29) is an example of a standard error (in this case, of the average of the differences xa — xg). The estimate i is the deviation of the sample value relative to the population value corresponding to the null h3q)othesis, measured in standard error units. The larger this deviation, the less are the chances that the null hypothesis is true. Confidence intervals can always be transformed into hypothesis tests, for which the numerator is an estimate of the parameter of interest and the denominator is the corresponding standard error. For the difference between two averages, for example, the standard error is. 

In the 1980s and 1990s, considerable work was done at the National Institute of Standards and Technology (NIST) and the Southwest Research Institute (SwRI) to establish the extent to which the toxicity of a material s combustion products could be explained and predicted by the interaction of the major toxic gases. TTus work led to the development of the N-Gas models [4—6]. The underlying hypothesis is that the toxicity of smoke in a fire is due to a small number "N of constituent gases. 

In the sections which immediately follow (c and d) these functions are again derived in a more complete treatment which exhibits more clearly the underlying hypothesis (the general form of the distribution and frequency functions is shown in Fig. 2.4). The physical content of these probability functions is discussed in Sec. 2.3. 

These observations are obviously far away from reaching any statistical significance (due to the small sample size), but they illustrate the underlying hypothesis (lower dose/total drug body burden leads to less side effect and toxicity risks for a given project), which can be further elaborated by the following hypothetical example (Figure 2.6). 

In fact, it is difficult to establish a simple and easy to handle formula in the general case of X rays scattered by a mixed (monomer polymer) crystal. We shall thus follow a step by step approach and discuss the underlying hypothesis and simplifications,... 

It is useful to emphasize that the development of such an informational formalism should not wait for the verification of the above hypotheses for one thing, no existing informational formalism insisted on any underlying hypothesis about the informational structure of the universe. I believe, however, that in contrast to such practices, it is important to state up front an informational hypothesis which would clarify and inform the development of the corresponding informational formalism. 

In this review, we shall present the reptation ideas in their simple version, see how they apply to self-diffusion, viscoelasticity and more local processes, critically analyze the underlying hypothesis, and sketch the additional effects which have to be included to get a realistic description of the dynamic properties of entangled polymers. 

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