Casual models

Problem The Ag atoms in a silver crystal are arranged like spheres in the cubic closest packing. Students may pack spheres of the same diameter as densely as possible, thereby casually modeling the correct structure of the silver crystal. The structure is called the cubic close packing because a cubic packing of 14 spheres can be distinguished in the layered sphere structure - the basic cube can be regarded as a reflection of the entire structure. 

The focus of this chapter is Michael Strevens (2008) kairetic account of scientific explanation, which offers an interesting solution to the problem of explanatory idealization. In its most general terms, Strevens claims that the scientific explanation of events and regularities consists of a process of abstraction away from detailed, veridical causal models in order to generate causal models that contain only those factors that make a difference to the causal production of the explanatory target. Strevens approach to idealized explanatory casual models is simply to assert that while idealizations are literally false, they distort only non-difference-makers. Hence they do not misrepresent the explanatorily relevant causal factors that... 

Among the current (ca 1997) selection of software systems which together help to exemplify the promise of computer graphics. Advanced Visualization Systems (AVS), stands out as one of the more extensible and practical of them to use. The premise behind development of the system was to provide modelers with a toolkit of modules having sophisticated intrinsics that would enable even casual programmers to link together multiple simple functionahties into a complex constmct with which to accomplish exactly the types of visualization and manipulations that their work required. Researchers... 

A Structure-Selectivity Model. Nitrosamines are usually highly sensitive towards one or a few target organs some examples are listed in Table III. A casual examination of the structures... 

We chose the number of PCs in the PCR calibration model rather casually. It is, however, one of the most consequential decisions to be made during modelling. One should take great care not to overfit, i.e. using too many PCs. When all PCs are used one can fit exactly all measured X-contents in the calibration set. Perfect as it may look, it is disastrous for future prediction. All random errors in the calibration set and all interfering phenomena have been described exactly for the calibration set and have become part of the predictive model. However, all one needs is a description of the systematic variation in the calibration data, not the... 

The presentation is mainly on a fundamental and general level and yet the reader—student or professional—is gradually and almost casually introduced to all important natural and synthetic polymers. Complicated phenomena are explained with the aid of the simplest available examples and models in order to ensure complete understanding. However, the reader is also encouraged to think for himself and even to criticize the author s point of view. All of the chapters have been revised and enlarged from the German edition, and many of the sections are entirely new. 

Now that we have a simple model for the continuum spectrum of the stars based around the Planck curve, the temperature and the luminosity, we can make some observations and classifications of the stars. There are some constellations that dominate the night sky in both the northern and southern hemispheres and even a casual look should inspire wonder. Star hopping in the night sky should lead to the simplest observation not all stars have the same colour. A high-quality photograph of the constellation of Orion (see page 2 of the colour plate section) shows stars... 

The n.O.e. values have, in general, paralled the Tj values and provide little additional information. Increasing n.O.e. values reflect decreasing solvent interaction for the specific carbon atom position associated with the resonance studied. Interestingly, the largest n.O.e. values observed, vl.97 (near the theoretical maximum of 1.99 for this value) is associated with resonance 3 in the spectrum of dextran B-742 fraction S. This resonance 3 corresponds to the linked C-3 position of the branching backbone residue, and model building, or even a casual inspection of the drawn structure, indicates that this is an extremely hindered position. 

This model fits the self-reports of addicts and the common experience of people trying to give up bad habits generally. The model is certainly time-honored. However, close examination suggests that the dichotomies it rests on are only casual rules of thumb, which people use to decide how difficult certain experiences will be to control, rather than basic distinctions. I argue that modem behavioral research and simple logic demote this model from the explanatory to the merely descriptive. Let us look at the tenets of two-factor theory one by one ... 

Over the past four decades, RIS models for hundreds of polymer structures, and sometimes many different ones for one and the same macromolecule, have been developed and published. The casual user of RIS techniques, even one intimately familiar with the method and its foundation, is often faced with the task of finding RIS parameters from the literature for unfamiliar constitutions and configurations. It is this task that the present review is aimed at easing by providing a comprehensive overview of the published models available to date. While completeness cannot be claimed, care has been taken to find as many models as possible and to report them in as brief a space as practical. 

Medical expectations. Some ill-prepared subjects unconsciously impose a medical model on the experience. They look for symptoms, interpret each new sensation in terms of sickness/health, place the guide in a doctor-role, and, if anxiety develops, demand chemical rebirth - i.e., tranquilizers. Occasionally one hears of casual, ill-planned, non-guided sessions which end in the subject demanding to be hospitalized, etc. It is even more problem- provoking if the guide employs a medical model, watches for symptoms, and keeps hospitalization in mind to fall back on, as protection for himself. 

Although more complex models have been proposed to describe the process [57, 85, 86], involving the Ps bubble state and its shrinking upon reaction, the equations based on a reversible reaction with a forward and reverse reaction rate constants as in scheme (X) enables the fitting of the data perfectly, as shown by the solid line in Figure 4.9. The kinetic equations corresponding to such a scheme are tedious to derive, particularly as concerns the intensities (still more when a magnetic field is applied). However, they do not present insuperable mathematical difficulties and should be used instead of the approximate expressions that have appeared casually (e.g., "steady state" treatment of the reversible reaction). From scheme (X), it is not expected that the variation of X3 with C be linear, but the departure from linearity may be rather small, so that the shape of the X3 vs C plots may not be taken as a criterion to ascribe the nature of the reaction. 

The simple model for activation proposed by Whetten et al (2) was later questioned by Smalley and coworkers ".. one wonders how a simple electrostatic model can possibly explain the known sensitivity of H and Ng chemisorption to particular surface geometries, and to the presence of open d orbitals at the reactive site" and they continue by raising the question "Is the correspondence between I.P. and reactivity causal, or casual " (9). To answer this question Smalley et al studied the reactivity pattern of ionized clusters. It turned out that the positive clusters had a very similar reactivity pattern as the neutrals and sometimes reacted with even greater cross sections even though these clusters have a far less tendency to donate eletronic charge to the neutral adducts. This finding is consequently in conflict with the simple electrostatic model of Whetten et al. 

Casual reading of the literature may give the impression that secrets of stellar nucleosynthesis are revealed only by detailed quantitative analysis of a stellar spectrum involving model atmospheres and spectrum synthesis with perhaps attention to non-LTE and other effects. Exacting but not exciting work may be the verdict. Although there is important information in abundances that can come only from a detailed and precise analysis, there have been and surely remain startling results which can be unearthed from quite simple analyses and even from mere inspection of a spectrum. I discuss two such examples. 

---