2 descriptive concepts

For human beings, two different memory categories have been introduced. According to Schacter, imphcit (or unconscious/unaware) memory is revealed when previous experiences facilitate performance on a task that does not require conscious or intentional recollection of those experiences. Explicit memory, in turn, is revealed when the performance of a task requires conscious recollection of previous experiences. These are descriptive concepts that are primarily concerned with a person s psychological experience at the time of memory retrieval. Accordingly, the concepts of implicit and expUcit memory neither refer to nor imply the existence of two independent or separate memory systems (Schacter 1987). As these two memory categories cannot be easily appHed to the situation in animals, they will not be further considered in this chapter. 

Depth obtained in the above way is a purely descriptive concept. 

Depth obtained in the above way is a purely descriptive concept. It helps us summarize and relate our observations, but it will probably not allow us to predict things we have not yet observed. If, however, we view the effects and their changes as manifestations or alterations in the subsystems and structures that make up the d-SoC, depth becomes a scientific hypothesis. We should then be able to predict things other than those we have measured and test these predictions.[Ij... 

The primary goal in using perfusion based microfluidic cell culture chips is to achieve a high degree of control over the microenvironment that the cultured cells are exposed to, i.e. to create a microenvironment that resembles the one cells are exposed to in vivo. In order to illustrate the difference between traditional culture vessels and perfusion based microfluidic cell culture chips, an effective culture volume (ECV) has been proposed as a descriptive concept [4]. ECV is a combined function of the characteristic mode of mass transfer (convection or diffusion), the magnitude of the mass transfer in all directions (x, y, z) in space (Fig. 2) as well as the extent of protein adsorption to the surfaces in a system. In vivo systems, e.g. tissue as part of an organ, are characterized by a fluid volume that is comparable to the volume of the cells in the tissues as well as by diffusive mass transfer. Based on these features the ECV of in vivo systems is small. 

D. Reichert, G. Hempel, Receiver imperfections and CYCLOPS An alternative description, Concepts in Magnetic Resonance 14 (2002) 130. 

Table III. Descriptive Concepts for a Chemical Health and Safety Chapter.

Intuitions of this kind led some philosophers to require that facts about the world should be regarded as matters of objective causal relations in the world and not ideas that people have in their heads. In this context, the Kripke-Putnam causal theory of reference was born. It was now claimed that nouns that are meant to designate natural kind terms do not have their extension determined by descriptive concepts but by a causal chain beginning with the original baptism or naming of a sample object. In addition, the reference of the term is provided by whatever is dictated by the latest scientific research, hence the use of atomic number in the case of any particular element. This last feature led Kripke and Putnam to adopt Paneth s definition of elements in terms of atomic number, since this remains as the most up-to-date scientific definition of an element. 

While some concepts in chemistry that serve us well are non-numerical and will remain qualitative, others have been from the start numerical and quantitative, even if not uniquely defined. For example, molecular shape and molecular similarity are qualitative, descriptive concepts that may not be characterized uniquely by a single number, or even by a sequence of numbers. Shape at best will require numerous descriptors that may not even be easy to order, while similarity may depend to a great extent on descriptors selected for the representation of objects considered. Thus, molecules that may be similar in one aspect are not necessarily similar when some other structural or experimental feature is considered. 

The classical description of magnetic resonance suffices for understanding the most important concepts of magnetic resonance imaging. The description is based upon the Bloch equation, which, in the absence of relaxation, may be written as... 

The preceding sections were concerned with the description of molecular motion. An ambitious goal is to proceed further and influence molecular motion. This lofty goal has been at the centrepiece of quantum dynamics in the past decade and is still under intense investigation [182. 183. 184. 185. 186. 187. 188. 189. 190. 191. 192. 193 and 194]. Here we will only describe some general concepts and schemes. 

The concept of macroscopic kinetics avoids the difficulties of microscopic kinetics [46, 47] This method allows a very compact description of different non-thennal plasma chemical reactors working with continuous gas flows or closed reactor systems. The state of the plasma chemical reaction is investigated, not in the active plasma zone, but... 

Rutscher A and Wagner H - E 1993 Chemical quasi-equilibria a new concept in the description of reactive plasmas Plasma Sources Sc/. Technol 2 279-88... 

This review has covered many of the essential features of the physical chemistry of nanocrystals. Rather than provide a detailed description of the latest and most detailed results concerning this broad class of materials, we have instead outlined the fundamental concepts which serve as departure points for the most recent research. This necessarily limited us to a discussion of topics that have a long history in the community, leaving out some of the new and emerging areas, most notably nonlinear optical studies [152] and magnetic nanocrystals [227]. Also, the... 

This section describes briefly some of the basic concepts and methods of automatic 3D model builders. However, interested readers are referred to Chapter II, Section 7.1 in the Handbook, where a more detailed description of the approaches to automatic 3D structure generation and the developed program systems is given. 

The course instructors or professors have not tried to intentionally deceive their students. Most individuals cannot grasp the full depth and detail of any chemical concept the first time that it is presented to them. It has been found that most people learn complex subjects best when first given a basic description of the concepts and then left to develop a more detailed understanding over time. Despite the best elforts of educators, a few misconceptions are at times possibly introduced in the attempt to simplify complex material for freshmen students. The part of this process that perpetuates any confusion is the fact that texts and instructors alike often do not acknowledge the simplifications being presented. 

Thermodynamics is one of the most well-developed mathematical descriptions of chemistry. It is the held of thermodynamics that dehnes many of the concepts of energy, free energy and entropy. This is covered in physical chemistry text books. 

The degree of data spread around the mean value may be quantified using the concept of standard deviation. O. If the distribution of data points for a certain parameter has a Gaussian or normal distribution, the probabiUty of normally distributed data that is within Fa of the mean value becomes 0.6826 or 68.26%. There is a 68.26% probabiUty of getting a certain parameter within X F a, where X is the mean value. In other words, the standard deviation, O, represents a distance from the mean value, in both positive and negative directions, so that the number of data points between X — a and X -H <7 is 68.26% of the total data points. Detailed descriptions on the statistical analysis using the Gaussian distribution can be found in standard statistics reference books (11). 

Work on plasmas has roots extending back to the Greeks who found that amber mbbed with various materials tended to attract certain objects. The concept of plasma as the fourth state of matter can be traced to Sir William Crookes (2) in 1879. "So distinct are these phenomena from anything which occurs in air or gas at the ordinary tension, that we are led to assume that we are here brought face to face with Matter in a Fourth state or condition, a condition so far removed from the State of gas as a gas is from a Hquid." This description has been shown to be accurate over many years of experimentation and appHcation of plasmas. 

Transport Models. Many mechanistic and mathematical models have been proposed to describe reverse osmosis membranes. Some of these descriptions rely on relatively simple concepts others are far more complex and require sophisticated solution techniques. Models that adequately describe the performance of RO membranes are important to the design of RO processes. Models that predict separation characteristics also minimize the number of experiments that must be performed to describe a particular system. Excellent reviews of membrane transport models and mechanisms are available (9,14,25-29). 

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