Basic principle

The basic principle of the radioreceptor assay is that the amount of radioligand bound to a receptor site is a function of the amount of unlabeled ligand present in the incubation medium. Since there is a quantitative relationship between the quantity of radioligand bound versus the amount of unlabeled ligand, it is possible to determine the concentration of unlabeled ligand in the incubation medium by simply analyzing the potency of the sample to displace the radioligand. 

From the previous section it should be apparent that the sensitivity of such an assay is directly related to the affinity of the ligand for the receptor. The higher the affinity, the less unlabeled substance necessary to manifest a significant displacement. Once again, since the affinity of a ligand for a particular receptor may vary with incubation conditions, 

This tissue preparation contrasts with that used to prepare membranes for benzodiazepine receptor binding vide supra) wherein no detergent treatment was necessary nor did the tissue have to be frozen prior to assay. In most cases, tissue can be used for receptor binding assays over extended periods of time if stored frozen. However, some receptor binding procedures, such as that used to measure the serotonin2 site, require that the tissue be used within 24 hr of preparation. 

In any event, there is no standard tissue preparation that lends itself to use for all neurotransmitter and drug receptor binding assays. Each procedure is tailored to a particular receptor binding site in order to obtain the most robust assay, reliable and consistent kinetic constants, and receptor site specificity. 

One of the chief advantages of radioreceptor assays over most other analytical procedures is that, in many cases, very little or no extraction of the sample is necessary prior to analysis. Thus, to measure GABA in CSF, small portions of untreated spinal fluid are placed directly into the receptor binding assay tubes since other CSF substances do not appreciably 

There are several key safety principles that should be observed during withdrawal from psychiatric drugs, especially if the drug exposure exceeds a few weeks or months or if the individual has serious preexisting 

How to More Safely Stop Taking Psychiatric Drugs 

Drug withdrawal requires collaboration between the health care provider and the patient, in which a great deal of attention is paid to the patient s feelings about withdrawal and to the patient s reactions during withdrawal. 

Someone close to the individual should help in monitoring potentially dangerous mood changes. 

Supervision by an experienced health care provider can be lifesaving. 

The following section aims to provide a brief description of the principles of HPLC and its most important parameters in water analysis. 

In contrast with classical column chromatography, HPLC uses columns with considerably smaller internal diameters (2 to 3 mm) and considerably 

This results in a build-up of considerably higher back pressure (up to 400 bar) as. the solvent passes through the separation column. Today the method achieves separation efficiencies and detection limits which previously 

A pump (2) delivers a certain quantity of solvent through the system from a reservoir (1) at a very even rate (even against differing back pressure). (Fig. 39 b) 

Schematics of typical liquid chromatographic systems for organic and inorganic compounds 

STRUCTURAL STUDIES WITH SMALL ANGLE SCATTERING 3-1. Basic Principles 

Small angle scattering is a technique for measuring spatial correlations at large distance. The resolution is lost at the atomic and even at the monomer unit scale, typically we can not expect to have an accurate structural information for length smaller than 10 A. The experiment can be achieved either using light. X-ray or neutrons. 

In a scattering experiment, a betun of electromagnetic radiation (light. X-rays) or neutrons is directed onto a sanq le and the scattered intensity is measured as a function of 

At small scattering angles 6, inelastic contributions can be neglected and the quasi elastic scattering is dominant. The scattered intensity is mainly described by a process where the ma itude of the wavenumber remains constant ki = k = k and consequently the Bragg relation applies  

Type of radiation wavelength (A) q range (A f) Spatial resolution (A) 

1 Deformation, Breakup, and Coalescence Phenomena during Melt-Blending 7.7.7.7 Basic Principles 

Historically, Einstein was the first to derive an expression for the viscosity of hard spheres in a dilute suspension [4]. Later, Oldroyd [5] considered the case where the spheres are themselves liquid. Taylor extended the study to a system where the suspending medium, as well as the dispersed spheres, are Newtonian liquids [6,7]. It was observed that when the radius of the drop is great enough or the rate of distortion is high, the drop breaks up. Taylor derived the following two equations  

From the above equations it is possible to calculate the size of the largest drop that exists in a fluid undergoing distortion at any shear rate. In these equations, the governing parameters for droplet breakup are the viscosity ratio p (viscosity of the dispersed phase to that of the matrix) the type of flow (elongational, shear, combined, etc.) the capillary number Cfl, which is the ratio between the deforming stress (matrix viscosity x shear rate) imposed by the flow on the droplet and the interfacial forces a/R, where ais the interfacial 

Sinusoidal distortions on a polyamide 6 (PA6) thread, with diameter 54 pm, embedded in a polystyrene matrix. The measurement was performed at 230°C the times for subsequent photographs are 0 sec, 183 sec, 300 sec, 340 sec, 396 sec, 494 sec, and infinite. (From Y. Son, Polymer 42,1287-1291,2001. With permission.) 

Critical capillary number versus viscosity ratio in simple shear and plane hyperbolic (two-dimensional elonga-tional) flow. (From H. P. Grace, Chem. Eng. Commun. 14,225,1982. With permission.) 

Glass formation by mechanical alloying of elemental crystalline powders can be considered a special form of solid-state interdiifusion reaction. The basic principles of such a reaction [3.15] are described in Fig. 3.4. As is well known, the thermodynamic stable state of a system is determined by a minimum in the free enthalpy G. In metallic systems, the free enthalpy of the equilibrium crystalline state Gx is always lower than that of the amorphous state Ga below the melting temperature. The amorphous state is a metastable state, i.e., an energy barrier prevents the amorphous phase from spontaneous crystallization. To form an amorphous metal by a solid-state reaction, it is necessary to establish first a crystalline initial state with a high free enthalpy G0 (Fig. 3.4). Depending on the formation process, this initial state can be achieved, for example, by 

1) the system intermetallic phase (Zr3Rh) plus hydrogen gas [3.16], 

2) a layered system of two crystalline elemental metals [3.4, 3.17], if the alloy system has a negative free enthalpy of mixing, 

3) an increase in the free enthalpy of one intermetallic phase by introducing lattice defects [3.18-20], 

Starting from this initial state G0, the free enthalpy of the system can be reduced either by the formation of the metastable amorphous phase or by the formation 

An interferometer can be basically described as an instrument that measures the interference of an electromagnetic field. The advantage of interferometers over other instruments when measuring astronomical sources is the angular resolution achievable, providing means to address certain scientific questions not available to single aperture telescopes. In this Section the basic principles and characteristics of an ideal stellar interferometer are presented, as well as the interferometric observables and its synthesis (Born and Wolf 1999 Monnier 2003 Quirrenbach 2001). 

When using an interferometer one is measuring coherence functions (Haniff 2007). In this section the focus is on the spatial coherence function, which is the case associated with measuring the electric field from a source at two locations but at the same time. This is equivalent to the Young s two slit experiment. 

The first experiment for demonstrating the interference of light is due to Young (1804). In his experiment, light from a monochromatic point source S falls on two pinholes. Pi and P2 which are close together on a screen and equidistant Ifom S. The 

If instead of the Rayleigh criterion the full width at half maximum (FWHM) criterium is considered, the angular resolution is AOjei = 1.02A./T) X/D. For an interferometer, two equal brightness sources will be resolved when the fringe contrast goes to zero at the longest baseline b, this is 

However, if the radiation is not monochromatic one has to consider each frequency separately and add the resulting fringe patterns, which have different separation (A. /b) between maxima. In this situation, the visibility fringes wash out , limiting the field of view of the interferometer. If the bandwidth is AX, the field of view is given by 

To achieve a Total Safety Culture, we need to integrate behavior-based and person-based psychology and effect large-scale culture changes. The five chapters in Section 3 explain principles and proce-dures founded cm behavioral research which can be applied successfully to change behaviors and attitudes throughcmt organizations and communities. This chapter describes the primary characteristics of the behavior-based approach to the prevention and treatment of human problems and shows their special relevance to occupational safety. The three basic ways we learn are reviewed and related to the development of safe vs. at-risk behaviors and attitudes. 

Specific safety techniques can be viewed as possible routes to reach a destination, in our case, a Total Safety Culture. A particular route may be irrelevant or need to be modified substantially for a given work culture. The key is to begin with a complete and accurate map. In other words, it is most important to start with an understanding of the basic principles. 

In Chapter 1,1 justified a behavior-based approach to industrial health and safety by citing the research review article by Guastello (1993) that evaluated a variety of procedures. 

The two with the greatest impact on injury reduction, behavior-based and ergonomics, use principles and procedures from behavioral psychology. Actually, Guastello s review supports the power of behavior-based problem solving. Over the past 30 years, 1 have personally witnessed the large-scale effectiveness of this approach to 

Improve the teaching/leaming potential in elementary schools (Geller, 1992c) and universities (Geller, 1972 Geller and Easley, 1986). 

The mass analyser described in the preceding section is sometimes referred to as a linear quadrupole, since the electrodes consist of parallel rods. Another type of mass spectrometer based on the use of a quadrupolar electric field is the three-dimensional (3D) quadrupole ion trap, which is sometimes also known as a Paul trap. This is a device that has been in existence for several decades, but it is only in the past twenty years or so that it has moved from a small number of research laboratories out into the commercial domain. Ion traps are now popular devices for a whole range of mass spectrometry applications, their popularity being enhanced by their very compact size and the ease with which they can be used in MS experiments (see Section 3.5.3.2). Several PTR-MS instruments have been constructed with a quadrupole ion trap and so a description of the basic operating principles 

HPLC is a form of liquid chromatography, where separation (or partition) occurs between a mobile phase (the solvent) and a stationary phase (the column packing). It is the ability with which the sample constituents will distribute themselves between the two phases that will effect the separation. Depending on the nature of the stationary phase, the separation process can be of four different modes  

Adsorption chromatography is the most widely used and, in practice, we refer to two modes of action, depending on the polarity of the two phases  

Normal phase chromatography, where the stationary phase is polar in nature e.g., silica or alumina) and the mobile phase is non polar e.g., hexane). In this mode, polar samples are retained more strongly by the column therefore allowing elution of non polar compounds first. 

Reversed-phase chromatography, where the stationary phase is non-polar in nature (e.g., hydrocarbon) and the elution solvent (or mobile phase) is polar (e.g., water or methanol). This being the exact reverse of normal phase chromatography, non-polar compounds will be retained longer on the column [5]. 

To change the polarity of the mobile phase, a mixture of solvents can be used to elute the compounds. When composition of such a solvent mixture remains constant throughout the elution step, it is referred to as an isocratic elution. On the other hand, when the composition of the solvent mixture is varied during the course of the elution step, we are using a so-called gradient elution. 

Due to the quite different structures of industrial plants equipped with electrical installations, there are different probabilities for the existence of potentially explosive atmospheres formed by gas-air, vapour-air or dust-air mixtures. With respect to economical reasons, the types of explosion protection for electrical apparatus and systems will depend strongly on the explosion risk at the installation point. It is very unusual to construct and build all explosion protected electrical apparatus in such a manner that they can operate permanently in a surrounding hazardous atmosphere with combustible gases, vapours and dusts in air. The common way is to classify different areas in industrial plants according to the probability for the existence of a hazardous atmosphere and to establish adequate types of explosion protection. In other words, industrial plants with potentially explosive atmospheres are divided and classified into zones.  

Following the historical development of electrical engineering and explosion protection, zone classification was the objective of national standards and installation rules. Most of the leading industrial countries established an installation practice for chemical plants and the oil and gas industry with two or three zones for areas hazardous due to gas- or vapour-air mixtures and two zones for areas with hazardous dust-air mixtures. Apart from this philosophy, the coal mining industry in most countries tends to avoid an area classification and defines only one category of explosion protection ( firedamp-proof ). More recent standards or directives present a three-zone concept for areas endangered by combustible gas- (vapour-, mist-) air mixtures and dust-air mixtures in industrial plants (other than coal mines). 

As time passes, national standards for area classification have been superseded by international standards (IEC, International Electrotechnical Commission, Geneva/Switzerland, and EN, European Standard or European Norm, established by CENELEC, Comite Europeen de Normalisation Electrotechnique, Brussels/Belgium), which have been adopted as subsequent national standards. In the member countries of the European Community (EC), a joint area classification is defined by a directive (Directive 1999/92/EC of the European Parliament and of the Council, dated 1999-12-16). 

I Classification system with three zones for areas hazardous due to  

II Classification system with three zones for areas hazardous due to combustible gas, vapour or mist (Ha) or due to combustible dust (lib). 

A formal operability study is the systematic study of the design, vessel by vessel, and line by line, using guide words to help generate thought about the way deviations from the intended operating conditions can cause hazardous situations. 

The seven guide words recommended in the CIA booklet are given in Table 9.7. In addition to these words, the following words are also used in a special way, and have the precise meanings given below  

Intention the intention defines how the particular part of the process was intended to operate the intention of the designer. 

Deviations, these are departures from the designer s intention which are detected by the systematic application of the guide words. 

Causes reasons why, and how, the deviations could occur. Only if a deviation can be shown to have a realistic cause is it treated as meaningful. 

The infrared region of the electromagnetic spectrum lies between the wavelengths 1000 and 15000 nm (Kemp AVellacdo, 1980). Absorption of radiation in this region by organic compounds has been known since 1866, when Tyndall first conducted experiments on the interaction of radiation with compounds such as chloroform, methyl and ethyl iodides, benzene. 

The specific requirement for a vibration to give rise to an absorption in the infrared spectrum is that there should be a change in the dipole moment as that vibration occurs. In practice, this means that vibrations which are not centrosymmetric are the ones of interest, and since the symmetry properties of a molecule in the solid state may be different from those of the same molecule in solution, the presence of bands may depend on the physical state of the specimen. This may be an important phenomenon in applying infrared spectroscopy to the study of AB cements. 

Procedure. Prepare a standard solution of ascorbic acid (ca 10 3M) by dissolving about 0.18 g (accurately weighed) in a 1 L graduated flask using oxygen-free water. 

Prepare a buffer solution (pH 4.5) by dissolving 6 g acetic (ethanoic) acid and 13,6 g sodium acetate in 1 L of distilled water. Pipette 10 mL of a commercial sample of citrus fruit juice into a 1 L graduated flask and make up to the mark with oxygen-free water, 

The electrolysis current is not stopped, the stirrer switched off, and the cell allowed to stand for about 30 seconds to allow the solution to become quiescent. 

From the nature of the process described above it has been referred to as stripping polarography , but the term anodic stripping voltammetry is preferred. It is also possible to reverse the polarity of the two electrodes of the cell, thus leading to the technique of cathodic stripping voltammetry. 

In just the same way as differential pulse polarography represents a vast improvement over conventional polarography (see Section 16.10), the application of a pulsed procedure leads to the greatly improved technique of differential pulsed anodic (cathodic) stripping volammetry. A particular feature of this 

The sensor molecule probability of remaining in the excited state pm as a function 

FIGURE 2. Correlation between experimentally observed 0-0 bond lengths and MO bond order n r(n) = -0.245 + 1.681 A (R = 0.97) 

FIGURE 3. A synopsis of the most important groups and selected examples of acyclic peroxides (R = alkyl, aryl, alkoxycarbonyl R = H, NO2, R) 

In principle, the fundamental equation for the effect of high pressure on a reaction rate constant was deduced by Evans and Polanyi on the basis of transition state theory  

In general, formation of a bond, concentration of charge, and ionization during the transition state lead to a negative volume of activation, whereas 

Reactions in which molecularity decreases in the products e.g., cycloadditions, condensations. 

Reactions which proceed via cyclic transition states e.g., Claisen and Cope rearrangements. 

Crystallization from solution can occur only in supersaturated solution. Under lower supersaturation nucleation cannot occur spontaneously spontaneous nucleation 

It is generally considered that crystal-growth includes two steps (1) diffusion of the solute from the solution bulk towards the surface of the crystals, and (2) crystallizing reaction on the surface, the kinetics of which are represented, respectively, by 

In practice, the kinetics of crystallization is even more complex some different relationships were introduced in Ref. [ 1801. For the system to be investigated, since disodium phosphate has a very good crystallization nature, few complicated factors would be involved, and Eq. (12-4) should be valid. 

On the other hand, as an implication, the equation for the diffusion rate based on Pick s law includes the assumption of the solute concentration in the liquid bulk being completely uniform, which is actually difficult to realize and thus may yield a deviation from reality. The poorer the micromixing, the larger would be the deviation. Therefore the crystal-growth rate coefficients measured in different devices with different micromixing conditions may be different from each other. 

In order to avoid other complicated factors concealing the major problems being examined, the overall crystal-growth rate equation, Eq. (12.3), is assumed to be valid for the system under consideration and is used as the basis for the interpretation of data. 

An important concept in treating the adsorption of a component from one phase onto another is that of the adsorption isotherm. An adsorption isotherm is simply a means of representing the equilibrium distribution of a component 

Second, there are problems in using concentrations, because the true driving force for the adsorption reaction is chemical potential, which is related to activity. For the dissolved component this means that adsorption isotherms measured in one solution do not necessarily apply to other solutions a point commonly overlooked by geochemists, particularly with regard to organic compounds. Also, variation in solution composition can result in the introduction of other ions or compounds that have an affinity for the surface. These ions may severely alter the adsorption of the component of interest. 

A final area of difficulty is in the application of data analysis to specific models of adsorption isotherms. This difficulty results from the fact that different models for adsorption isotherms generate plots of surface versus dissolved concentration that have characteristic shapes. If a plot of observational data results in a curve with a shape similar to that generated by a model, this result is often taken as proof that the particular model applies. Unfortunately, this assumption has been made for situations where many of the basic requirements of the model are violated in the system under study. The Langmuir adsorption isotherm model has suffered considerable abuse by geochemists in this regard. It should be remembered that shapes of adsorption isotherms are far from proof that a specific model applies. 

Two other closely related concepts are connected with the idea of adsorption isotherms. These are the distribution coefficient (usually called Kd) which is the 

Chemisorption raises basic questions for the carbonate geochemist about the boundary between sorption and coprecipitation. If the adsorption reaction takes place in a solution that is also supersaturated with respect to the carbonate mineral substrate, then the adsorbed ions can be buried in the growing layers of the mineral and become coprecipitates. This mechanism can result in distribution coefficients that are dependent on growth rates. Also, when chemisorption is involved, an entirely new phase or a coprecipitate can form in the near-surface region of the carbonate (e.g., see Morse, 1986 Davis et al 1987). A classic example is apatite formation on calcite in dilute solutions (e.g., Stumm and Leckie, 1970). 

We present here a brief summary of quantitative aspects of centrifugation needed in this chapter fuller treatments can be found in Cantor and Schimmel (1980), Harding et al. (1992), van Holde et al. (1998) and Sheehan (2000). 

The gravitational force in a centrifuge is dependent on two quantities the speed of rotation and the distance from the centre of rotation. Equation 4.12 expresses the relative centrifugal force (RCF) (in units of g - the Earth s gravitational field) in terms of these two parameters. 

The term m( 1 - vp) represents the reduced mass of the particle, which is the actual mass of the partide (m) reduced by its buoyancy in solution. The centrifugal force causes particles to accelerate, generating an opposing frictional force that is proportional to the velocity of the sedimenting particle. 

After a short period equilibrium is established between these two forces Fsed=FR (4-15) 

In addition to these sedimentation properties, there is another operationally important parameter, the integral effect of the gravitational force on the partide, which determines the distance travelled by a particle over a given time interval. At a distance x from the centre of rotation the distance moved by particle in time t is given by the equation  

The photoemission process creates a final state that has a positive hole, that is, it is lacking one electron with respect to the initial state. Hence, in a more fundamental treatment, the binding energy of an orbital x will be the difference between the total energies of the final hole state (with N — 1 electrons) and of the initial state (with N electrons)  

Since solving the Schrodinger equation for systems investigated in XPS is not possible, several approximations have been applied to theoretically describe the photoelectric process and to calculate binding energies. It is far beyond the scope of this chapter to present these models instead the reader is referred to the corresponding literature [1, 2]. 

As in all spectroscopic techniques, EPR has its own jargon . This is not the place to go into any detail with regard to theory or experimental techniques. A number 

In actual practice the unpaired electron is not free. It is generally associated with one or more nuclei, which may have a nuclear spin magnetic moment. This moment generates a magnetic field at the location of the unpaired electron, due to the so-called contact or Fermi hyperfine interaction (the electron has a finite probability of penetrating to the atomic nucleus) and to the through-space dipolar interaction between nuclear and electronic magnetic spin moment, represented by 

Gyromagnetic ratio = ratio between magnetic moment due to orbital motion and intrinsic magnetic moment (spin) y = 1.7608 x 10 rad s G y/2ir = 2.8025 MHz G  

Magnetic spin vector = quantum mechanic operator 5 = (5)t, Sy, 5 ) 

Projection of S on magnetic field B = B z ms, magnetic quantum number 

Simple molecular photoionization is the interaction of electromagnetic radiation with a molecule (in its ground state) to generate an ion (in a variety of different possible energy, and symmetry states) and a free electron Equation (17.2). In this process, mass, momentum and energy are conserved, according to Equation (17.3). 

It has been found empirically that the band intensities in photoelectron spectra can vary dramatically with photon energy. Thus, bands due to ionization from halogen-based 

The modes of excitation which can provoke X-ray fluorescence are various photons or particles such fast electrons, protons, a radiation. Whatever the method chosen, the X-ray emission yields nevertheless an identical spectrum. 

The emission spectrum depends very slightly on the chemical combination or chemical state of the elements in the sample. For this reason, this non-destructive mode of analysis can be used for all elements starting from boron (Z = 5) to uranium (Z = 92) in solid or liquid homogeneous samples, without, theoretically, any fastidious preparation. 

Although semi-quantitative analysis does no present any major difficulty, quantitative analysis is not quite simple, because a significant part of the emitted radiation from the outer surface of the sample is re-absorbed before being able 

Chemical Analysis Second Edition Francis and Annick Rouessac 

In general. X-ray fluorescence spectrometers consist of a source of excitation radiation, a radiation detector to detect the stimulated radiation from the sample and a display of the spectral output. Since each element has a different and identifiable X-ray signature, the presence and concentration of the element(s) within the sample can be determined. 

When a beam of light or electromagnetic radiation impinges on a solid (Fig. 16.2), that radiation can be  

For a total incident flux of photons energy conservation requires 

In the following sections and throughout this chapter the relationship between the makeup of a solid and its optical properties is discussed. The optical properties of greatest interest here are the refractive index n. which for low-loss materials determines the reflectivity and transmissivity, and the various processes responsible for absorption and/or scattering. 

As noted, the major effect of the interaction of the incident and reradiated waves is to make the velocity of the transmitted light appear to have traveled through the solid (i soi) rnore slowly than through vacuum (t vac) which leads to perhaps the simplest definition of n. namely. 

The exact details of how this occurs are beyond the scope of this book but are excellently described in R. P. Feynman, R. B. Leighton, and M. Sands. The Feynman Lectures on Physics, vol. 1, Chap. 31. Addison-Wesley, Reading, Massachusetts. 1963. 

The accumulation of deposits on the surfaces of a heat exchanger increases the overall resistance to heat flow. Fig. 2.1 illustrates how the temperature distribution is affected by the presence of the individual fouling layers. 

FIGURE 2.1. Temperature distribution across fouled heat exchanger surfaces 

Thermal conductivities of some common foulant-like materials are given in Table 2.1 that also includes data for common construction materials. The effects of even thin layers of foulant may be readily appreciated. 

The resistance to heat flow across a solid surface is given as 

Referring to the diagram (Fig. 2.1) the resistances of the solids to heat flow are  

Breiter, Electrochemical Processes in Fuel Cells , Springer, Berlin, 1969, p. 39. 

Conway, M. Vukovic, and H. Angerstein-Koslowska, J. Appl. Electrochem., 

The past two decades have seen a number of advances in electrocatalysis, which include- 

In the following, only a brief outline to the above developments can be given. WilP used single-crystal Pt in an attempt to elucidate some aspects of chemisorption of H2. Apart from some sporadic subsequent attempts, 

Ultraviolet (UV) and visible spectra, also known as electronic spectra, involve transitions between different electronic states. The electronic transition is accompanied by the vibrational and rotational transitions so that what woidd otherwise be an absorption line becomes a broad peak containing vibrational and rotational fine structure. Furthermore, the molecular interaction between solute and solvent levels it to a smooth curve (envelope) for the absorption spectra in solutions. The accessible regions are 200-400nm for 

TABLE 7.1 Various spectroscopic methods used in biomacromolecular characterization 

Spectroscopy Principle Biopolymer Structural information and application 

Ultraviolet and visible Absorption of UV and visible radiation leading to electronic excitation N, P Ligand binding sites, side chain exposure, environment. Apphcable to proteins and nucleic acids but not glycans. Quantitative analysis. DNA conformation. Anneahng and hybridization studies of nucleic acids. 

Fluorescence mission of radiation when a molecule in an excited electronic state returns to the ground state N, P Environment, relative abundance and interactions of fluorophore. Quantitation of proteins and fluorophoric compounds. Ligand binding studies. 

Fuel cells are galvanic cells, in which the free energy of a chemical reaction is converted into electrical energy via an electrical current. The Gibbs free energy change of a chemical reaction is related to the cell voltage via Equation 9-28  

The anode reaction in fuel cells is either the direct oxidation of hydrogen or the oxidation of methanol. An indirect oxidation via a reforming step can also occur. The cathode reaction in fuel cells is oxygen reduction, in most cases from air. For the case of a hydrogen/oxygen fuel cell the overall reaction according to Equation 9-29 is  

Fuel cell catalysis occurs in two parts of the fuel cell system in the processing of the fuel before feeding it into the fuel cell stack and in the catalysts at the electrodes of the fuel cell. 

As mentioned before, reactions at the surface of catalysts in electrochmical cells have much in common with heterogeneous chemical reactions. In both cases a mass transfer of species to and from the surface of the catalyst occurs. If more than just one reaction step has to be catalyzed, two or more different catal5dic materials are required in the form of a bi- or multifunctional electrocatalyst. 

Using only small amounts of catalytic material, the current density, which represents the rate of reaction per square centimeter of electrode surface, has to be as high as possible. Hence, the catalyst has to be finely distributed, in most cases on a suitable support such as high surface area carbon or graphite. The role of adsorption and chemisorption of reactants and/or intermediates on the rate of the processes is very similar to that in heterogeneous catalysis. 

Reactions at Solid Surfaces. By Gerhard Ertl Copjoight 2009 John Wiley Sons, Inc. 

But there is another effect that may have utmost influence on the reactivity Small catalyst particles exhibit different crystal planes together with structural defects and chemisorbed foreign 

FIGURE 1.1. High-resolution electron micrograph from asmall Ruparticleona MgO support together with a sketch of its structure [1]. 

Most finely divided catalysts must have structures of great complexity. In order to simplify our theoretical consideration of reactions at surfaces, let us confine our attention to plane surfaces. If the principles in this case are well understood, it should then be possible to extend the theory to the case of porous bodies. In general, we should look upon the surface as consisting of a checkerboard. .. 

What Langmuir had in mind were clean, well-defined singlecrystal surfaces that can now be prepared and investigated through the introduction of ultrahigh vacuum techniques and the development of a whole arsenal of surface physical methods. 

The development of atomic spectroscopic techniques and their appHcation to fundamental studies fostered the concurrent development of atomic theory and quantum mechanics. In turn, the better understanding of atomic theory has led to the implementation of many beneficial techniques and instrumental features in atomic spectroscopy, particularly for the reduction or elimination of interferences and background. 

A first step toward the interpretation of atomic spectra was made in 1885, when Bahner found a formula describing the different emission lines of hydrogen in the visible region  

Handbook of Spectroscopy, Volume 1. Edited by Gunter Gauglitz and Tuan Vo-Dinh Copyright 2003 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-29782-0 

Ti and T2 are the Bohr energy levels. Considering systems with a single valence electron, the energy of this electron can be expressed as  

7 2 Atomic Absorption Spectrometry (AAS) and Atomic Emission Spectrometry (AES) 423 27tZ e fi 

The rotation of the plane of polarized light is measured as an optical rotation a. What is termed the specific optical rotation [a] in organic chemistry is a function of the mass fraction W2 of the solute, the density of the solution p, and the length / of the sample cell, as well as the optical rotation  

The effective molar rotation is also sometimes used. In this case, the refractive index is taken into account with a factor n + 2)/3  

Generally, the wavelength dependence can be adequately represented by one of the following empirical equations  

Generally, the Drude equation describes the optical activity of coil molecules the Moffit-Yang equation is more suitable for helices. 

The left-hand and right-hand rotating components of polarized light are absorbed to different extents by optically active compounds. The dependence of the difference in absorption of left- and right-hand rotating components of polarized light on wavelength is called circular dichroism (CD). 

It may be helpful to summarize the precautions applied in the period range and in the power range. Since most restarts will occur in the period range, high-speed withdrawal is necessary. Operation is mahnal and is under the supervision of the period meters as follows  

A 30--sec period trips latched withdrawal. Subsequent withdrawal requires constant operator attention. 

The top of the period range is guarded by the servo which levels the rise at or if the servo is turned off and the operator fails to level, all 

Short periods in the power range are both less probable and relatively harmless because of the proximity of the level safety setting and because of the corrective capacity of the servo. Therefore, of the period controls only the l-sec period scram is retained. In the region of full power, inadequate cooling of the reactor ranks equally with excessive power level and the two situations are treated in the same fashion in order of severity as follows  

Automatic continuous reduction of power level through servo control as long as the unsatisfactory coolant or power level situation exists or until the power level is reduced to 1% of. full power. 

If two closely spaced levels 1 and 2 are simultaneously excited from a common lower level i) at time r = 0 by a short laser pulse with the pulse width Af h/ E2 — El) (Fig. 7.9a), the wave function of the coherent superposition state 1 + 2) at f = 0 

If the detector measures the total fluorescence emitted from both levels /c), the time-dependent signal 5 (r) is 

Here C is a constant factor depending on the experimental arrangement, fi = e r is the dipole operator, and e gives the polarization direction of the emitted light. Inserting (7.25a) into (7.26) yields for equal decay constants yi = K2 = K of both levels 

This represents an exponential decay exp(-yt) superimposed by a modulation with the frequency u2i = Ei - Ei)/h, which depends on the energy separation A 2i of the two coherently excited levels (Fig. 7.9b). This modulation is called quantum beats, because it is caused by the interference of the time-dependent wave functions of the two coherently excited levels. 

The Fourier analysis of the time-dependent signal (7.27a-7.27b) yields a Doppler-free spectrum /( ), from which the energy spacing A as well as the width y of the two levels ) can be determined, even if A is smaller than the Doppler width of the detected fluorescence (Fig. 7.9c). Quantum-beat spectroscopy therefore allows Doppler-free resolution [868]. 

3 Assessing Risks Due to the Toxic Effects of Laboratory Chemicals 41 

Federal law requires that manufactures and distributors of chemicals provide users with Material Safety Data Sheets (MSDSs), which are designed to provide the information needed to protect users from any hazards that may be associated with the product. MSDSs have become the primary vehicle through which the potential hazards of materials obtained from commercial sources are communicated to the laboratory worker. Institutions are required by law to retain and make readily available to workws the MSDSs provided by chemical suppliers. 

As the first step in a risk assessment, laboratory workers should examine their plan for a proposed experiment and identify the chemicals whose toxicological properties they are not already familiar with from previous experience. The MSDS for each unfamiliar chemical should then be examined. Procedures for accessing MSDS files vary from institution to institution. In some cases, MSDS files may be present in each laboratory, while in many cases complete files of MSDSs are maintained only in a central location, such as the institution s environmental health and safety office. Some laboratories now have the capability to access MSDSs electronically, either from CD-ROM disks or via computer networks. As a last resort, the laboratory worker can always contact the chemical supplier directly and request that an MSDS be sent by mail. 

1- Name of supplier (with address and phone number) and date MSDS was prepared or revised. Toxicity data and exposure limits sometimes undo-go revision, and for this reason MSDSs should be reviewed periodically to check that they contain up-to-date information. Phone numbers are provided so that, if necessary, users can contact the suppher to obtain additional information on hazards and emergency procedures. 

Name of the chemical. For products that are mixtures, this section may include the identity of most but not every ingredient. Common synonyms are usually hsted. 

The simplest representation of the thermal circuit of an infrared detector is shown in Fig. 3.1. The detector is represented by a thermal mass H coupled via a conductance Gto a heat sink at a constant temperature T. In the absence of a radiation input the average temperature of the detector will also be T, although it will exhibit a fluctuation about this value. This fluctuation gives rise to a source of detector noise ( temperature noise ) which sets the ultimate limit to the minimum signal detected by a perfect thermal detector. When a radiation input is received by the detector, the rise in temperature is found by solving the equation  

I may be time independent but more generally will consist of a time independent component / , plus at least one component modulated at an angular frequency CO. Consideration of one modulated component only is sufficiently general for this discussion. 

Equation (3.4) shows that as co is increased, the term co H will eventually exceed G and then will fall inversely as co. A characteristic thermal response time for the detector can therefore be defined as 

For typical detector design falls within the range of milliseconds to seconds. This is much longer than the typical response time of a photon detector. For some applications this puts thermal detectors at a disadvantage with respect to photon detectors, but when all the systems tradeoffs are taken into account this disadvantage may not be as great as it would at first sight seem. 

The implication of making H as small as possible is that the thermal detector should be as small and of as light a construction as practicable. This is the reason for the fragile and delicate nature of many types of thermal detector. One of the reasons for the large amount of interest in the current developments of the pyroelectric detector is that (as we shall see in Sect. 3.5) it offers a way round this dilemma of achieving both sensitivity and robustness. 

According to the second law of thermodynamics, the Gibbs energy ( free energy ) G is related to the enthalpy H, the entropy S, and the thermodynamic temperature T by 

AG AA frequently holds for isobaric processes in condensed systems since the change in volume is often (but not always) negligibly small. 

The change of Gibbs energy of a system caused by the addition of 1 mol of component i to an infinite system is called the partial molar Gibbs energy GT, or the chemical potential pi  

Differentiation of the chemical potential of component / gives (see textbooks on chemical thermodynamics) 

VT is the partial molar volume of component / of relative activity a,. The complete differential form of G is 

Both longitudinal and transverse relaxation are stimulated by time-dependent perturbations acting on the nuclei, such as dipole-dipole coupling. Usually the time-dependence arises from molecular motion, and measurements of relaxation times are a powerful method of studying polymer motion in both solution and the solid state. Detailed discussions of such applications. 

The use of an inkjet-type printhead to deliver a liquid or colloidal binder material to layers of a powdered build material is involved in 3D printing (8). The printing technique involves applying a layer of a powdered build material to a surface typically using a roller. After the build material is applied to the surface, the printhead delivers the liquid binder to predetermined areas of the layer of material. 

The binder infiltrates the material and reacts with the powder, causing the layer to solidify in the printed areas by, for example, activating an adhesive in the powder. The binder also penetrates into the underlying layers, producing interlayer bonding. After the first cross-sectional portion is formed, the previous steps are repeated, building successive cross-sectional portions until the final object is formed. 

Apparatus for carrying out 3D printing typically move the print-heads over the print surface in raster fashion along orthogonal X and Y axes. In addition to the time spent printing, each printhead 

In design-related fields, 3D printing is used for visualization, demonstration and mechanical prototyping. It may also be useful for making patterns for molding processes. In addition, 3D printing is useful in the field of medicine (9). 

3D printing can be quicker and less expensive than conventional machining of prototype parts or production of cast or molded parts by conventional hard or soft tooling techniques (9). 

Relation between particle size and sieve aperture to cause clogging. 

Diagram of cumulative frequency of oversized particles for (a) feed, (b) ideal separation, and 

When the detector is in thermal equilibrium with the heat sink, the rms fluctuation in the power flowing through the thermal impedance into the detector is (Smith et al. [3.7]) 

Dendritic architectures are highly branched polymers with tree like branching having an overall spherical or ellipsoidal shape and are known as additives having peripheral functional groups. These macromolecules consist of three subsets namely dendrimers, dendrigraft polymers and hyperbranched polymers (Figrrre 1). 

FIGURE 3 Schematic representation of a hyperbranched polymer construction and its structural units include terminal (T), dendritic (D), and hnear (L) units. 

Properties Dendritic architectures Dendrimers Dendrigraft Hyperb ranched 

Terminal units Small Linear chains Small 

Molecular mass distribution Narrow Narrow Broad 

Before the scanning starts, the working electrode is usually held at a potential that does not cause any electrochemical reactions. After the start of the scanning, the potential goes higher (or lower), and when it becomes high (or low) enough to 

If the electrochemical reactions are thermodynamically reversible, the positions of the cathodic or anodic peaks do not change with the potential scan rate (u), and the peak height is proportional to the square root of the potential scan rate, u, according to the following equation (T = 25 °C)  

If the reactions are not completely reversible, the anodic peak potential becomes more positive and the cathodic peak potential becomes more negative. The separation of the two peaks becomes larger than in the reversible case. 

Reversibility is often a relative term because it is related to the potential scan rate. A reaction that is reversible at low scan rates may become quasi-reversible (or even irreversible) at high scan rates. When the quasi-reversible starts, the peak current will become smaller than that expressed by Equation 11.1, and the curve of ip versus u starts to bend down. 

A special case results when a monolayer or an ultra-thin layer of an electrochemically active species is confined to the electrode surface and the thickness of this layer is less than that of the diffusion layer within the experiment time scale. Mass transport resistance becomes negligible. Both the anodic and the cathodic peaks become symmetrical, and they look like mirror images of each 

Whereas amplification (oscillation) is obtained comparatively readily at these frequencies, which are of the order of 10 Hz, it is considerably more difficult to achieve a corresponding situation for optical waves with a frequency of 10 Hz. The reason is clear from (4.27). 

The first demonstration of X-ray lasing was made in 1985 for 3s-3p transitions at 20.6 and 21.0 nni in neon-like selenium (Se XXV) [8.20]. Population inversion was created in an elongated plasma created after the impinging of 0.5ns pulses (0.53 pm) from part of the NOVA Nd glass laser facility. Smce then much progress has been made [8.21-8.26], facilitated by the development of relatively compact, ultra-intense lasers. These aspects will be covered in Sects. 8.7.2 and 9.6. 

As a general principle, safety-related control systems such as interlocks should be well designed, be of simple construction, and be sufficiently robust for the application. Furthermore, it should not be possible easily to defeat interlocking devices, yet where appropriate it should be possible for authorised persons to override them for tests or other necessary purposes. 

The general provisions of the Health and Safety at Work etc. Act apply to the safety of control systems, both in terms of their supply and their use. Whereas the Act is goal-setting and non-prescriptive, there are Regulations that provide more specific legal requirements. 

In the context of safety-related control systems, the Essential Health and Safety Requirements of the Supply of Machinery (Safety) Regulations 1992 lay down generic requirements that must be considered by suppliers for the safety and reliability of control systems control devices starting and stopping devices mode selection failure of the power supply and the control circuit software and movable guards. 

Users of machinery and other work equipment need to be familiar with the 

The other relevant main A standard is BS EN 1050 Safety of machinery -Risk assessment, which provides advice on how to carry out a risk assessment on machinery. 

The electrons released in this reaction pass round the external circuit, reaching the cathode, where they react, forming new OH ions. 

The cell theory is predicated upon four fundamental assumptions. Two of these (that the guests are trapped within cavities that contain at most one guest, and that quantum effects can be ignored) are well justified and will not be considered further. The other two assumptions are more interesting. 

Using these assumptions in a very elegant statistical mechanical derivation, van der Waals and Platteeuw were able to calculate the conditions required for the clathrate hydrate to be thermodynamically stable. The central result of this theory shows that for a mixture of gases, the chemical potential of the water molecules is related to y Q - the fraction of cavities of type i (i.e. 12-, 14- or 16-hedra) occupied by a guest of species K - according to the equation 

Here i refers to the chemical potential of water in the phase a, with a = H being the hydrate at the appropriate composition and a = p being the hypothetical empty hydrate lattice. Other symbols in (1) are v- is the number of cavities of type i in the hydrate lattice, k is Boltzmann s constant, and T is the temperature. 

Equation (1) is readily recast in a form that is suitable for calculating the conditions for hydrate stability. Note that for a true three-phase equilibrium between water, hydrate and guest phases, the chemical potential of each individual species must be the same in all three phases. Thus must equal the chemical potential of water in its stable pure phased and we have that 

The cell theory also shows how is related to the guest-host interactions. This may be done in two steps. If the chemical potential of the guest in the hydrate and bulk guest phases may be equated (Le. three-phase equilibrium) then yiQ may be expressed in terms of the fugacity of the guest in its bulk phase, and the so-called Langmuir constants, Ki 

The term aging inhibitor is commonly used for the stabilization of elastomers. 

Optical brighteners are also referred to as fluorescent whitening agent or fluorescent brightening agent. 

The physical process of whitening of fluorescent additives follow a different mechanism. The incident UV light is absorbed by the additive and transformed into a blue light which is subsequently emitted. 

Several compounds are known that can achieve brightening. The selection of a particular substance should follow the following criteria  

The whitening effect depends on the nature of the polymeric substrate. 

The selection is also affected by its hue. In general, a neutral to blue hue is preferred. However, in Asia, sometimes a reddish hue is preferred. 

The principle of RBS is as follows. A beam of energetic He ions strikes a sample. Due to nuclear interactions (elastic collisions between the nuclei) the He are backscattered and collected by a nuclear particle detector (Fig. 3). Extensive de.scriptions of RBS can be found in the literature [13, 14]. Analy.sis of the 

Positioning the reference electrode (or Luggin probe [34]) close to the working electrode further helps to minimise the IR drop between the reference and working electrode due to the resistivity of the solution phase. Instrumental 

The liquid phase in an electrochemical experiment typically consists of a solvent containing the dissolved material to be studied and a supporting electrolyte salt to achieve the required conductivity and hence minimise the IR potential drop. With sufficient supporting electrolyte, the electrical double layer (see also Chap. I.l) at the working electrode occupies a distance of about 1 nm from the electrode surface (Fig. II.1.8). Note that the length scale in Fig. II.1.8 is not linear. This layer has been shown to consist of a compact or inner Helmholtz layer and the diffuse not diffusion layer) or Gouy-Chapman layer [41]. The extent to which the diffuse layer extends into the solution phase depends on the concentration of the electrolyte and the double layer may in some cases affect the kinetics of electrochemical processes. Experiments with low concentrations or no added supporting electrolyte can be desirable [42] but, since the double layer becomes more diffuse, they require careful data analysis. Furthermore, the IR drop is extended into the diffusion layer [43] (see also Chap. III.4.5). 

Under most experimental conditions, the size of the diffusion layer (see above) is several orders of magnitude larger than that of the diffuse layer (see Fig. II. 1.8). Initiated by a change in the electrode potential, a concentration perturbation travels away from the electrode surface into the solution phase and the 

With very fast scan rate cyclic voltammetry, an upper limit of the scan rate where standard theory prevails is given by the condition that the dijfusion layer becomes equal in size to the diffuse layer (see Fig. II. 1.8). It has been estimated that this limit occurs at a scan rate of 1 to 2 x 10 V s [45]. In the other extreme, at very slow scan rates, natural convection is known to affect the shape of experimental cyclic voltammograms. 

A series of conventional cyclic voltammograms obtained for a model system, the oxidation of 3.3 mM ferrocene in acetonitrile containing 0.1 M NBU4PF6 as supporting electrolyte at a 0.4 mm diameter platinum electrode, is shown in Fig. II. 1.9. The current scale has been normalised by dividing through the square root of scan rate in order to compare data obtained at different scan rates. Data obtained from these cyclic voltammograms are summarised in Table II. 1.1. 

What happens, though, as the control logic becomes more complicated For example, if the output X is dependent on inputs A, B and C, or even the inputs A, B and C and ff e present outputs W and Z, how is ffiis sort of operation best represented Storing the present state of the outputs obviously requires some form of sequential logic, and this must be implemented using a Process statement. It is already known that tfie Case statement generally creates a more efficient circuit than its If-Else equivalent. It is also a neat structure in which to construct the jfinite state machine that will usually be used to implement such control operations. 

The issues associated with using sequential logic are as important as ever here, but constructing a finite state machines requires tfiat wider issues are also considered. In particular the following should be taken into account. 

So are the two states 0 and M an accurate representation of die signals in a circuit How should the designer construct a design that accurately models in simulation the occurrence of a high impedance input signal yet still synthesizes the required two-state logic operation  

There are a number of physical circuit conditions that may give rise to signals with differing strengths and values  

From the designer s viewpoint this means ffiat it is not sufficient to believe that if X does not equal I it automatically equals 0. This will increase the complexity of a VHDL description, particularly affecting flie structure of conditional statements such as If and Case, most commonly used in control logic design. This aspect is discussed below. 

Adhesives can be applied as drops or beads, roll coated, sprayed or screen printed. The application equipment ranges from simple hand guns, bottles and tubes to highly sophisticated six-axis robots with automated parts handling. 

There are a number of factors that need to be considered before selecting a dispense system  

Single-part or two-part adhesive. Viscosity of the adhesive, 

Cycle time to achieve production, Cure method, 

The first suggestions to use electromagnetic radiation, namely, interferometers, to monitor the variation of relative distance between test masses were made in 1956 by Pirani and in 1962 by Gertsenshtein. The first tabletop prototype Michelson interferometer with an He-Ne laser and optical elements in vacuum was realized in 1970 by 

The first solution for folding the optical path is the Herriot delay line, with two concave mirrors having a radius of curvature such that the injected light exits from the entrance hole after N round-trips, which means after an optical path 2NL. The number of reflections is limited by the reflection losses, thus the mirrors should have high optical quality over the whole surface. During the N trips the laser spots move over a circle with radius Ncofj, where uo is the minimum laser beam width in typical working conditions, the mirrors should be 1 m in diameter, a number with a great impact on the scale and the cost of the vacuum system. 

The second solution is the use of Fabry-Perot cavities, where the laser spots from aU reflections coincide. A Fabry-Perot cavity consists of two plane mirrors at distance L. The power transmitted by the cavity is maximum at the resonance, when kL = nit, where is the wave vector. In this case, the power trapping in the cavity replaces the many round-trips of the laser beam. The phase of the light leaving from the cavity depends on the cavity length. If the cavity is working at resonance, the passage of a gravitational wave produces a phase shift near the resonance. The resonance characteristics of the Fabry-Perot cavity are described by the finesse F, which is related to the reflectivities ri, ri of the mirrors  

FIGURE 4 Sensitivity curve (thick solid line) for a 3-km baseline interferometer with 30-kg test masses. The sources of noise are outlined standard quantum limit (thin solid line) seismic noise (long dashed line) gravity gradient noise (dotted line) thermal noise (short dashed line) shot noise (dash-dot line). 

The variation of the optical path corresponds to a phase shift  

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The treatment of these issues will be discussed jointly with the health, safety and environment (HSE) departments within the company and with the process and facilities engineers, and their treatment should be designed in conjunction with an environmental impact assessment. Some of the important basic principles for waste management are to ... 

General hydrodynamic theory for liquid penetrant testing (PT) has been worked out in [1], Basic principles of the theory were described in details in [2,3], This theory enables, for example, to calculate the minimum crack s width that can be detected by prescribed product family (penetrant, excess penetrant remover and developer), when dry powder is used as the developer. One needs for that such characteristics as surface tension of penetrant a and some characteristics of developer s layer, thickness h, effective radius of pores and porosity TI. One more characteristic is the residual depth of defect s filling with penetrant before the application of a developer. The methods for experimental determination of these characteristics were worked out in [4]. 

Basic principles of URT are now well established for weakly varying media as biological structures [1]. 

In this paper, we have exposed a solution to improve the resolution in Low Frequency Ultrasonic Tomography. Since the basic principle of ultrasonic reflection tomography prohibits the inspection of objects with strong contrast and large extension, we turn down the frequency of the transducer, in order to increase the penetration length of the wave and the validity of the method. But this is done at the expense of resolution. 

D. H. Everett, ed., Basic Principles of Colloid Science, CRC Press, Boca Raton, FL,... 

The purpose of this chapter is to provide an introduction to tlie basic framework of quantum mechanics, with an emphasis on aspects that are most relevant for the study of atoms and molecules. After siumnarizing the basic principles of the subject that represent required knowledge for all students of physical chemistry, the independent-particle approximation so important in molecular quantum mechanics is introduced. A significant effort is made to describe this approach in detail and to coimnunicate how it is used as a foundation for qualitative understanding and as a basis for more accurate treatments. Following this, the basic teclmiques used in accurate calculations that go beyond the independent-particle picture (variational method and perturbation theory) are described, with some attention given to how they are actually used in practical calculations. 

An excellent treatment of molecular quantum mechanics, on a level comparable to that of Szabo and Ostiund. The scope of this book is quite different, however, as it focuses mainly on the basic principles of quantum mechanics and the theoretical treatment of spectroscopy. 

Because surface science employs a multitude of teclmiques, it is necessary that any worker in the field be acquainted with at least the basic principles underlying tlie most popular ones. These will be briefly described here. For a more detailed discussion of the physics underlymg the major surface analysis teclmiques, see the appropriate chapter m this encyclopedia, or [49]. 

Joy D C 1986 The basic principles of EELS Principles of Analytical Electron Microscopy ed D C Joy, A D Romig Jr and J I Goldstein (New York Plenum)... 

The principles of operation of quadnipole mass spectrometers were first described in the late 1950s by Wolfgang Paul who shared the 1989 Nobel Prize in Physics for this development. The equations governing the motion of an ion in a quadnipole field are quite complex and it is not the scope of the present article to provide the reader with a complete treatment. Rather, the basic principles of operation will be described, the reader being referred to several excellent sources for more complete infonnation [13, H and 15]. 

The basic principle behind TOP mass spectrometry [36] is tire equation for kinetic energy, ze V... 

NMR basic principles and progress specialised monograph giving detailed descriptions of specific areas of solid state NMR. 

Schwelger A 1991 Pulsed electron spin resonance spectroscopy basic principles, techniques, and examples of applications Angew. Chem. Int. Edn Engl. 30 265-92... 

Figure Bl.19.12. Basic principles of SECM. (a) With ultramicroelectrode (UME) far from substrate, diflfiision leads to a steady-state current, ij, (b) UME near an insulating substrate. Flindered diflhision leads to < ij, 3D. (c) UME near a conductive substrate. Positive feedback leads to go. (Taken from [62],...

Exchange in the solid state follows die same basic principles as in liquids. The classic Cope re-arrangement of bullvalene occurs in both the liquid and solid state [25], and the lineshapes in the spectra are similar. 

Limbach H H 1991 Dynamic NMR spectroscopy in the presence of kinetic hydrogen/deuterium isotope effects NMR Basic Principles and Progress vol 23, ed P Diehl, E Fluck, H Gunther, R Kosfeld and J Seelig (Berlin ... 

To become familiar with the application of the basic principles of the model building process by means of calculating log P and log 5 values... 

These few examples are of course a small and arbitrarily chosen set of methods for the calculation of log P values. Nevertheless, it is hoped that they demonstrate some basic principles in the prediction of a physicochemical property. 

Murray-Rust P and H Rzepa 1999. Chemical Markup, XML, and the Worldwide Web. 1. Basic Principles. Journal of Chemical Information and Computer Science 39 923-942. 

Ithough knowledge-based potentials are most popular, it is also possible to use other types potential function. Some of these are more firmly rooted in the fundamental physics of iteratomic interactions whereas others do not necessarily have any physical interpretation all but are able to discriminate the correct fold from decoy structures. These decoy ructures are generated so as to satisfy the basic principles of protein structure such as a ose-packed, hydrophobic core [Park and Levitt 1996]. The fold library is also clearly nportant in threading. For practical purposes the library should obviously not be too irge, but it should be as representative of the different protein folds as possible. To erive a fold database one would typically first use a relatively fast sequence comparison lethod in conjunction with cluster analysis to identify families of homologues, which are ssumed to have the same fold. A sequence identity threshold of about 30% is commonly... 

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