Introductory Remark

PURITY PROBLEMS, THE ROLE OF IMPURITIES 6.3.1 Introductory remarks 

Both in the preparation of intermetallics and in their handling, special problems are encountered due to impurities present in the materials involved or produced by unwanted side reactions, such as reactions with the atmosphere, the containers, etc. The purity control is especially important when working at high temperature. It is well-known that the fundamental law of high-temperature chemistry is that . .. everything reacts with everything  

These problems have of course different weights for the different metals. The high reactivity of the elements on the left-side of the Periodic Table is well-known. On this subject, relevant examples based on rare earth metals and their alloys and compounds are given in a paper by Gschneidner (1993) Metals, alloys and compounds high purities do make a difference The influence of impurity atoms, especially the interstitial elements, on some of the properties of pure rare earth metals and the stabilization of non-equilibrium structures of the metals are there discussed. The effects of impurities on intermetallic and non-metallic R compounds are also considered, including the composition and structure of line compounds, the nominal vs. true composition of a sample and/or of an intermediate phase, the stabilization of non-existent binary phases which correspond to real new ternary phases, etc. A few examples taken from the above-mentioned paper and reported here are especially relevant. They may be useful to highlight typical problems met in preparative intermetallic chemistry. 

Polymeric materials can absorb considerable amounts of gas, for example CO2 especially at elevated pressures (p) and temperatures (T) above the so-called glass transition temperature [5.19]. This often causes changes in size and volume of the polymer, which have to be taken into account in industrial processing situations, for example in gas separation processes using polymeric sorbent materials [5.20]. Sorption phenomena of swelling polymers cannot be measured adequately by either gravimetric or volumetric methods. 

In this section we first will describe the experimental device. Sect. 3.2, then provide formulas to calculate m and V of a polymer sample from measured data Sect 3.3, and finally present an example namely sorption of CO2 in (swelling) polycarbonate (Makrolon 2400), Sect 3.4. 

Combined oscillometric and gravimetric measurements provide a basis to determine simultaneously the mass and the volume of a swelling sorbent material like polymers or resins in a sorptive gas atmosphere. However measurements seem in practice to be restricted to determinations of sorption equilibria of these materials as the kinetics of mass uptake often is very slow. To give an example we mention that in case of sorption of CH4 on pellets of Makrolon 2400 at 35 °C, p = 2 MPa, it took more than 4 days till equilibrium was reached. 

Rotational Pendulum for combined oscillometric-gravimetric sorption measurements of gases in swelling (polymeric) materials. IFT University of Siegen, 1999. 

Also it should be mentioned that by adding a gas chromatograph or a mass spectrometer to the instrument. Fig. 5.9, cosorption equilibria of gas mixtures in swelling sorbents can be measured. The theory of measurements of this t)rpe is based on the theory of osdUometric-gravimetric sorption measurements of pure gases. Sect 3.3. In addition concentrations of the sorptive gas originally supplied to the system (y ) and those in sorption equilibrium (yi, i=l... N) have to be taken into account. 

It will be obvious from the content of Chapter 5 why such combinations are desired. First, only such functions can, in themselves, constitute acceptable solutions to the wave equation or be directly combined to form acceptable solutions, as shown in Section 5.1. Second, only when the symmetry properties of wave functions are defined explicitly, in the sense of their being bases for irreducible representations, can we employ the theorems of Section 5.2 in order to determine without numerical computations which integrals or matrix elements in the problem are identically zero. 

The kind of functions we need may be called symmetry-adapted linear combinations (SALCs). It is the purpose of this chapter to explain and illustrate the methods for constructing them in a general way. The details of adaptation to particular classes of problems will then be easy to explain as the needs arise. 

Host-guest interactions. The area of host-guest chemistry encompasses the complexation by organic hosts of a range of both organic and inorganic guests. 

2 Host-guest complexation involving crowns and related polyether 

Apart from complex formation involving metal ions (as discussed in Chapter 4), crown ethers have been shown to associate with a variety of both charged and uncharged guest molecules. Typical guests include ammonium salts, the guanidinium ion, diazonium salts, water, alcohols, amines, molecular halogens, substituted hydrazines, p-toluene sulfonic acid, phenols, thiols and nitriles. 

With simple crowns, complex formation may involve various degrees of inclusion of the guest into the cavity of the crown and a conformational rearrangement of the crown is almost always necessary for strong complexation to occur. This will normally involve a redirection of the donor electron pairs on complex formation so that their final orientations optimize a particular host-guest interaction. 

A large number of other host compounds have been designed to incorporate functional sites which are suitably placed for interaction with the binding sites of a guest. Molecular models suggested (Newcomb, Timko, Walba Cram, 1977) that the somewhat more rigid ring in the 

To formulate a model is to put together pieces of knowledge about a particular system into a consistent pattern that can form the basis for (1) interpretation of the past history of the system and (2) prediction of the future of the system. To be credible and useful, any model of a physical, chemical or biological system must rely on both scientific fundamentals and observations of the world around us. High-quality observational data are the basis upon which our understanding of the environment rests. However, observations themselves are not very useful unless the results can be interpreted in some kind of model. Thus observations and modeling go hand in hand. 

This chapter focuses on types of models used to describe the functioning of biogeochemical cycles, i.e., reservoir or box models. Certain fundamental concepts are introduced and some examples are given of applications to biogeochemical cycles. Further examples can be found in the chapters devoted to the various cycles. The chapter also contains a brief discussion of the nature and mathematical description of exchange and transport processes that occur in the oceans and in the atmosphere. This chapter assumes familiarity with the definitions and basic concepts listed in Section 1.5 of the introduction such as reservoir, flux, cycle, etc. 

Modeling biogeochemical cycles normally involves estimating the spatial and temporal averages for concentrations and fluxes in and out of reservoirs (i.e., reservoir modeling). The 

The advent of fast computers and the availability of detailed data on the occurrence of certain chemical species have made it possible to construct meaningful cycle models with a much smaller and faster spatial and temporal resolution. These spatial and time scales correspond to those in weather forecast models, i.e. down to 100 km and 1 h. Transport processes (e.g., for CO2 and sulfur compounds) in the oceans and atmosphere can be explicitly described in such models. These are often referred to as tracer transport models. This type of model will also be discussed briefly in this chapter. 

In Section 1.1 it was mentioned that Blomstrand (1869, 1875) first proposed the 

This historical development explains why some classes of compounds containing the group — N2 — are called diazo compounds (e. g., Ar — N2 — OH, Ar — N2 — CN, etc.), whereas others — also with the — N2— group — are called azo compounds (e. g., Ar — N2 —Ar, R-N2-R, etc.). 

Diazo Chemistry I Aromatic and Heteroaromatic Compounds. By Heinrich Zollinger Copyright 1994 VCH Verlagsgesellschaft mbH ISBN 3-527-29213-6 

In this chapter we discuss only the physical structure of arene- and heteroarene-diazonium ions and salts. The chemical reactions of diazonium ions and the chemical structures of the products will be the subject of later chapters. 

To replace the aforementioned acyl-main group and acyl-transition metal complexes, the natural course of events was to search for a stable and easy-to-handle acyl-metal complex that reacts as an unmasked acyl anion donor. Thus, the salient features of acylzirconocene chlorides as unmasked acyl anion donors remained to be explored. In the following, mostly carbon—carbon bond-forming reactions with carbon electrophiles using acylzirconocene chlorides as acyl group donors are described. 

the involvement of one of the following three possible mechanisms has been suggested (i) nucleophilic addition of the acylzirconocene chloride to the Lewis acid activated aldehyde, (ii) nucleophilic addition of the cationic species of the acylzirconocene chloride formed by an Ag(I) salt or a Lewis acid, or (iii) transmetalation of the acylzirconocene chloride with the Lewis acid and subsequent nucleophilic addition. 

Although the reactivity of acylzirconocene chlorides towards imine derivatives under Yb(OTf)3/TMSOTf (20 mol%, l l)-catalyzed conditions is not necessarily very high, the direct access to a-amino ketone derivatives indicates the usefulness of acylzirconocene chlorides as unmasked acyl anion donors. 

2 Bransted acid-catalyzed reactions with imines 

The reactions of acylzirconocene chlorides with imines also proceed under Bransted acid-catalyzed conditions, even with aqueous acids (Table 5.3) [23], 

A heterogeneous reaction of the type A + B = AB necessarily begins with the nucleation of AB. Nucleation and early growth are different from the later stages of reaction as long as the number of atomic particles in the boundary region is similar to the number of those in the bulk. This means that the chemical potential of the components and the growth kinetics depend explicitly on the size and form of the nuclei. 

Since the interface (surface) excess Gibbs energy is positive, ju,(/ ) /(r2) if the radius of nucleus rt r2 As a consequence, for the Gibbs energy, g(ri) g(r2) as well (where g = //, = Therefore, in order to nucleate a new phase, 

These g values are defined per unit volume. Let us now put in the interface energy previously left out. If V = 4/3-7rr3 is the volume of the nucleus, the net Gibbs energy change is (neglecting elastic misfit energies) 

The above thermodynamic considerations are fundamental to the kinetics of phase nucleation to be outlined in the next section. 

In this chapter we try to classify the more important types of reactions encountered in inorganic chemistry, and describe some of their mechanisms. The emphasis is placed upon the principles which determine the stability or instability, existence and nonexistence of inorganic substances from the viewpoint of the ease or otherwise of preparing a compound, and the tendency a compound - once prepared - may have to react spontaneously to give other products. Both thermodynamic and kinetic considerations are obviously involved here. The division of material between this chapter and the next has not been easy, and there is inevitably a good deal of overlap. Coupling reactions, which might have deserved a section in this chapter, are discussed in Sections 10.5 and 10.6. 

In general, results from investigations based on measurements may be falsified by three principal types of errors gross, systematic, and random errors. In most cases gross errors are easily detected and avoidable. Systematic errors (so-called determinate errors) affect the accuracy and therefore the proximity of an empirical (experimental) result to the true result, which difference is called bias. Random errors (so-called indeterminate errors) influence the precision of analytical results. Sometimes precision is used synonymously with reproducibility and repeatability. Note that these are different measures of precision, which, in turn, is not related to the true value. 

Remember that British Standard BS 5532 [CAULCUTT and BODDY, 1983] provides qualitative and quantitative definitions of both reproducibility and repeatability. The determination of repeatability and reproducibility for a standard test method by interlaboratory tests is given in [ISO 5725]. 

As a consequence the reliability of results, and hence decisions derived therefrom, is determined by both the accuracy and the precision of the measurements. 

Within the legal and forensic science context, in order to prove that an offence has been committed, it is necessary to prove that a drug is present, and, if required, to determine the amount of the drug and its relationship to other samples. It is essential for those working in this area to understand how such analyses are 

Reductive carbonylation of nitro compounds, especially nitroaromatic compounds according to eq. (1), has been the subject of thorough industrial research starting in 1962 and continuing until the beginning of the 1990s due to the demand for a new, phosgene-free method for the production of isocyanates [1] and the discussions on the chlorine cycle in industry. 

The purpose of this section is to summarize the results of this continuous development, focusing on the most interesting compounds isocyanates and urethanes. Analogous reactions of this type leading to different products will just be mentioned in passing [1, 5-7]. 

Permeation and separation data reported in the literature are difficult to compare directly. This is due to the variety of parameters which influence the absolute value of permeation and separation data and which are usually badly described and sometimes cannot even be adequately described. As is shown in the preceding sections the pressure conditions and the flow dynamics (aerodynamic conditions) play a very important role. These pressure conditions are not always adequately described and data describing the external flow conditions do not directly reflect flow conditions in the membrane (model design and/or membrane architecture playing a role). 

A membrane material with a high permeation which is valid only in a small pressure range and which saturates at low pressure is inferior compared with a membrane material with lower permeation which is valid in a wide pressure range. 

Data given in the form of permeability (mol m/ir s Pa) are usually meaningful only in symmetric membranes (single, homogeneous wall, non-supported). 

In asymmetric supported membranes the use of permeability data can give rise to much confusion and erroneous conclusions for several reasons. In most cases the layer thickness is not precisely known and usually it is not known whether this layer is homogeneous or has property gradients (e.g. a skin and a more porous part). In many cases the material of the layer penetrates the support to some extent and so it is not possible to separate properties of separation layer and support without giving account of the interface effect. Finally, even if all these complications can be avoided, a comparison based on separation layer properties expressed in terms of permeabilities can give a completely wrong impression of the practical possibilities (as done in e.g. Ref. [109]). This is illustrated by comparison of hydrogen permeabilities of ultra-thin silica layers (see Tables 9.14-9.16) with other materials such as zeolites and metals. The intrinsic material properties of these silica layers are not impressive  

9 — TRANSPORT AND SEPARATION PROPERTIES OF MEMBRANES WITH GASES AND VAPOURS 

In Chapter 2, we developed statistical thermodynamics as the central theory that enables ns in principle to calculate thermophysical properties of macroscopic confined flriids. A key feature of statistical thermodynamics is an enormous reduction of information that takes place as one goes from the microscopic world of electrons, photons, atoms, or molecules to the macroscopic world at which one performs measurements of thermophysical properties of interest. This information reduction is effected by statistical concepts such as the most probable distribution of quantum states (see Section 2.2.1). 

By introducing the notion of various statistical physical ensembles in Section 2.2.1, we saw that wc can make the quantum iiurhaitical treatment consistent with several constraints imposed at the macroscopic level of description. That way we obtain an understanding of a thermal system at the microscopic level that is, we can interpret thermodynamic properties in terms of the interaction between the micro.scopic constituents forming a macroscopic system. 

The notion of an on,scmble was first suggested by Gibbs in a remarkably insightful manner. In the preface of his book Elementary Principles in Statistical Mechanics Developed with Special Reference to the Rational Foundation of Thermodynamics Gibbs writes [29]  

In his writings Gibbs based statistical thermodynamics on entirely classical concepts when, for example, he writes about thermodynamics as pertaining to the department of rational mechanics (29]. Nevertheless he knew that classical physics was not entirely adequate. In fact, Gibbs expresses a deep understanding of the status of statistical mechanics of his era in writing  

However, regardle-ss of whether we base our trcatiiumt on classical or quantimi statistics, the development of statistical thermodynamics in Chapter 2 shows that the partition fmiction is a key ingredient of the theory. This is because we may deduce from it explicit expressions for the thermophysical properties of equilibrium systems that may be of interest. At its core (and irrespective of the specific ensemble employed), the partition function is determined by the Boltzmann factor exp [-U (r ) /A-bT], where the total configurational potential energy U (r ) tiuns out to be a horrendously complex function of the configuration on account of the interaction between the microscopic constituents. 

1 In this chapter we use amorphous state and metallic glasses synonymously. 

Much effort therefore was directed onto simple alloys like Mg70Zn30 with no d-states at EF. In r- as well as in Ac-space, the electronic influence on ionic structure has been observed [5.5], and quite recently an MDOS was found experimentally as well as theoretically [5.18,19]. Unfortunately, there is no change of Z by changing the composition because both elements are divalent. In order to have this control, we focused our research on vapour-quenched alloys between noble metals with d-states well below EF and polyvalent simple elements. Using Au and Sb, for example, Z changes from 1 e/a (Au) to 5e/a (Sb). Different alloys were systematically investigated during the last decade by Mizutani et al. [5.20] and by the author [5.10] and may now serve as model systems in this field. 

After presenting the sample preparation in Sect. 5.2, we give an introduction to the theoretical background in Sect. 5.3. In Sect. 5.4, we briefly review the electronic influence on structure and phase stability of crystalline Hume-Rothery phases. In Sect. 5.5, we discuss the properties of non-magnetic amorphous alloys of the type just mentioned. The electronic influence on structure (5.5.1) and consequences for the phase stability (5.5.2) are also discussed. Structural influences on the electronic density of states are shown in 5.5.3. Electronic transport properties versus composition indicate additionally the electron-structure interrelation (5.5.4), and those versus temperature, the influence of low-lying collective density excitations (5.5.5). An extension of the model of the electronic influence on structure and stability was proposed by Hdussler and Kay [5.21,22] whenever local moments are involved as, for example, in Fe-containing alloys. In Sect. 5.6, experimental indications for such an influence are presented, and additional consequences on phase stability and magnetic properties are briefly discussed. 

The amorphous state has many similarities to the liquid state and can in fact be considered an undercooled liquid. Physical properties such as the electronic and ionic structure as well as electronic transport properties are temperature dependent and can be extrapolated from one state to the other. In this paper close relationships between both are shown. 

The chemical and physical status of the Earth is characterized by transport and transformation processes, many of which are of a cyclical nature. The circulation of water between oceans, atmosphere, and continents is an example of such a cyclic process. The basic characteristics of a cycle of a particular element or compound are often described in terms of the content in the various reservoirs and the fluxes between them. In our example, the reservoirs could be the oceans , the water in the atmosphere , the ground water , etc. A fundamental question in the cycle approach is the determination of how the rates of transfer between the reservoirs depend on the content of the reservoirs and on other, external, factors. In many cases, the details of the distribution of the element within each of the reservoirs are disregarded. 

The cycle approach to describe the physiochemical environment on Earth has advantages as well as disadvantages. The advantages include the following. 

It provides an overview of fluxes, reservoir contents, and turnover times. 

It helps to estimate the relative magnitudes of anthropogenic and natural fluxes. 

It stimulates questions such as Where is the material coming from Where is it going next  

Early applications of IR spectroscopy in zeolite research go back to studies by Szymanski et al. [201],Bertsch and Habgood [202], Tsitsishvili [203], Watanabe andHabgood [204] and especially the pioneering works of Uytterhoeven,Christ-ner and Hall [205] and Cant and Hall [206] who, in particular, investigated the formation of OH groups on the external and internal surface of Y-type zeolites as, somewhat later. Ward [207] also did. Hall s group also studied the adsorption of small molecules such as ammonia [205] and ethylene [208-210] and employed pyridine as a probe to discriminate Bronsted and Lewis acid sites (cf. 

It is worthy to note that IR spectroscopy was also relatively early employed to identify and investigate framework vibrations (vide supra, cf. [112, 114] and Sect. 5.2). In these experiments, usually the so-called KBr-technique was used (cf. Sects. 2.5,4.2). Relationships between the vibration modes and, e.g., the nsi/n i ratio of the zeolite fi-amework were disclosed and discussed. 

Furthermore, with the advent of improved instriunentation and experimental techniques interesting in-situ investigations became possible which were related, for instance, to the synthesis of and heterogeneous catalysis on zeofites, catalyst deactivation, diffusion or solid-state ion exchange as well as other postsynthesis modifications. Combinations of IR spectroscopy with various characterization techniques such as, e.g., temperature-programmed desorption of probe molecules (TPD/IR, cf.[223,224]), electron spin resonance spectroscopy (ESR/IR, cf.[225,226]), UV-Vis spectroscopy [227,228], etc. were developed. 

Application of Raman spectroscopy to zeolite research was, for a long time, hampered by severe problems due to fluorescence phenomena. These could be overcome during the recent past (cf. Sect. 4.4 and [229]). Meanwhile, IR and Raman results of zeolite investigation, as reported in the literature are so muner-ous that an exhaustive overview would be beyond the frame of the present chapter [compare, therefore, also earlier reviews such as those by Yates [230], Ward [231], Baker et al. [232] (especially for Fourier transform far-infrared spectroscopy), Foerster [233] and Karge et al. [234]. However, in the following subsections many examples will be provided which are meant to demonstrate the high potential of IR, Raman spectroscopy and INS for the characterization of zeofites and related systems. 

Two important points discussed in detail in Section 1.3 should be remembered here the fact that CyDs and their complexes are highly dynamic systems and that 

CYclodextrins and Their Complexes. Edited by Helena Dodziuk Copyright 2006 WILEY-VCH Veriag GmbH Co. KGaA, Weinheim ISBN 3-527-31280-3 

In Comprehensive Supramolecular Chemistry Szejtli, J., Ed. Pergamon Oxford, 1996 Vol. 3, p 441. 

Szejtli, J. In Comprehensive Supramolecular Chemistry Szejtli, J., Ed. Pergamon Oxford, 1996 Vol. 3, p 5. SzENTE, L. In Comprehensive Supramolecular Chemistry Szejtli, J., Ed. Pergamon Oxford, 1996 Vol. 3, p 253. Mohanambe, L. Vasudevan, S. Inorg. Chem. 2005, 44, 2128-2130. 

PoNCHEL, A. Abramson, S. Quartararo, J. Bormann, D. Barbaux, Y. Monelier, E. Micro-porous and Nanoporous Mat. 2004, 75, 261-272. 

From a materials perspective, the field of semiconductor electrochemistry and photoelectrochemistry has evolved from the use of semiconductor single crystals to polycrystaUine thin films and, more recently, to nanocrystalline films. The latter have been variously termed membranes, nanoporous or nanophase films, meso-porous films, nanostructured films, and so on they are distinguished from their polycrystalhne electrode predecessors by the crystallite size (nm versus pm in the former) and hy their permeability to the electrolyte phase. These films are referred to as nanocrystalline in the following sections. These features render three-dimensional geometry to nanocrystalline films as opposed to the flat or two-dimensional (planar) nature of single crystal or polycrystalline counterparts. 

What are the virtues of these emerging photoelectrode materials The first is related to their enormous surface area. Consider that the 3D structure is built up of close-packed spheres of radius, r. Then ignoring the void space, the specific area. As (area/volume) is given by 3/r [205]. For r = 10 nm, Ag is on the order of 10 cm , and for a 1 cm film of 1 pm thickness, this value corresponds to an internal sxtrface area of 100 cm (i.e. a surface roughness factor of 100). Clearly, this becomes important if we want the electrolyte redox species to be adsorbed on the electrode surface (see following). Alternatively, a large amount of sensitization dye can be adsorbed onto the support semiconductor although this dye sensitization approach is not considered 

As we shall see later, electron transport in nanocrystalline films is necessarily accompanied by charge-compensating cations because the holes are rapidly injected into the flooded electrolyte phase. This provides opportunities for studying ion transport processes in mesoporous media that are coupled to electron motion. Ion insertion also has practical consequences as in energy storage device applications [206]. 

Surface state densities on the order of cm are commonplace for semiconductor electrodes of the sort considered in previous sections of this chapter. These translate to equivalent volrnne densities of cm for nanocrystalline 

In this section we analyze creep results reported in [50] for PLC + PP blends, where the PLC is the same PET/0.6PHB discussed above, while PP is the isotactic polypropylene. In particular, thermal effects on the short-term creep in a wide temperature range have been investigated, as well as long-term (more than 1 year) creep. On this basis we discuss further the time-temperature correspondence and possibilities of long-term creep prediction from short-term tests. 

Methodologies Based on Macroscopic Adsorption Data and Potentiometric Titrations as well as on Microelectrophoretic Mobility or Streaming Potential Measurements 

The determination of the extent of deposition of the TMIS at various pH values and constant ionic strengfh (adsorption edge) is a very useful methodology [1,4]. 

Diagnostic mctliodoiogies based on electrochemical techniques and adsorption experiments 

Application of spectroscopic techniques and/or q uant u tiMncchanical calculations 

Another method is based on the determination of pzc both in the absence and presence of the TMIS to he mounted [1, 4]. As already explained, the surface adsorbs protons upon adsorption of anionic TMIS through coordinative bonds. Thus, its proton charge increases. This takes place at all pH values and obviously at pzc, where the surface was neutral before adsorption. Therefore, in the presence of the so-adsorbed anionic TMIS we need more hydroxyls in the solution in order to deprotonate additional surface groups and restore a zero charge at the surface. Therefore, a shift of the pzc to a higher value is rather expected. The opposite shift should be expected upon adsorption of cationic TMIS. 

Numerous efforts have been made in the last decade to evaluate spatial correlations of fluctuations. The examination of specific models was given preference over the formulation of general models. Different approaches to stochastic modelling of reaction-diffusion systems will be shortly reviewed in this chapter. 

The Higgs mass, on the other hand, is completely arbitrary within the paradigm of the SM. In fact, there are arguments suggesting that the SM with fundamental Higgs fields cannot be the full story and that some new kind of physics must appear at a high energy scale. This is linked to the so-called hierarchy problem and will be briefly mentioned in the next section. 

This section, which covers the period 1985 through 1988, continues the treatment found in Boron Compounds 3rd Suppl. Vol. 1, 1987. For earlier presentations, see Boron Compounds 2nd Suppl. Vol. 1, 1983, and Boron Compounds 1st Suppl. Vol. 1, 1980. As in the recent past, the presentation does not rigorously adhere to the Gmelin classification principle of the last position, and for species containing two or more linked boron atoms, all types of derivatives, even those containing heavy metal atoms, are included here. 

The field of borane chemistry continues to expand as evidenced by the extent of published literature in the field during the past years borane lectures [1] included transition metal-promoted coupling of boranes and carboranes [2], the kinetics and mechanisms of the thermolysis and photolysis of binary boranes [3], organoboranes for synthesis [4], and a description of a career in organoborane chemistry [5]. 

The rearrangement of boranes has been studied by theoretical methods. The popular diamond-square-diamond (DSD) process has been studied by the tensor surface harmonic theory [37], and by topological [38, 39] and orbital symmetry analyses [39, 40]. Advances in the NMR technique as applied to boranes were reported [41] methods to predict B NMR 

Hard-coating materials range from ultra-hard materials such as diamond-like carbon through the refractory compounds to alloys. However, the transition-metal carbides and nitrides have achieved by far the highest level of commercial success. Perhaps, the most important property of this group of carbides and nitrides is their defect structure. Ideal stoichiometry is generally not found in these phases deviations from the stoichiometry are found to be far more common. The transition-metal carbides and nitrides are typically metallic in their electrical, magnetic and optical properties. 

The flow pattern and local turbulence structures largely determine the performance characteristics of metallurgical operations. The transport phenomena in these processes typically have the following basic features  

The variety of multiphase flows encountered in metallurgical processes [1-6] include gas-liquid, liquid-liquid, gas-soUd, solid-liquid, and gas-liquid-solid systems. This book focuses on gas-liquid two-phase flows, being the most popular and relevant to current metallurgical processes. Due to their complexity, the exact equations governing gas-liquid two-phase flows are not known except for very limited situations. A typical example is one in which dispersed bubbles in a liquid are spherical and uniformly distributed since the interface between the two phases is deformable and the gas phase is compressible. It is therefore imperative to develop a set of approximate or simplified governing equations to describe the flow field. 

The measurement of fluid flow characteristics in real processes is quite difficult due to the opacity and high temperature characteristics. In addition, model experiments using molten metals as in the real process are often cumbersome. The situation is further complicated when heat and mass transfer, and chemical reactions occur simultaneously. Under these severe and complex conditions, it is very difficult to carry out experimental investigations on the real processes in order to improve efficiency or to develop novel processes. 

The poor wettability at the metal/solid interface implies that the boundary conditions on solid walls immersed in molten metal-gas two-phase flows would be different from the relatively well-known conditions for wetted interface. The heat and mass transfer boundary conditions would be similarly different. In addition. 

Iguchi and O.J. Ilegbusi, Modeling Multiphase Materials Processes Gas-Liquid Systems, DOI 10.1007/978-1-4419-7479-2 l, 

Uosiali Willard Gibbs (1839-19U3), professor of mathematical physics at Yale University and one of the founding fathers of statistical mechanics and vector calculus. 

At time t, a volume (or a surface) F of a single unimpinged spherulite nucleated at time t, equals the volume (or the area) of a sphere (or a circle) having the radius r(T, t)  

When neighboring spherulites impinge, the boundary is formed. It can be noticed that for any two spherulites nucleated at Ti and T2, a difference between their radii, expressed by Equation (7.1a), remains constant during the further growth  

The locus of points sharing this property is a branch of a hyperboloid or a plane, the latter being the case when Ti = t2. After impingement on neighboring spherulites, the volume of each individual spherulite evolves in a complex way that depends on the nucleation (positions and times) of spherulites involved. All growing entities contribute to the conversion degree. The two best known approaches to the description of overaU crystallization kinetics in infinite samples are those of Avrami and Evans, both based on the isovolume assumptions, which enabled to assimilate volume and volume fraction terms. 

Simple transformation and integration leads to the well-known Avrami equation  

For nonisothermal crystallization, where G is a function of time t, E in Equation (7.5) can be expressed as 

In the first part (Chapter 1.2.1, p. 6) a general survey about masses and decay data is given. Their systematic behavior, i.e., their dependence on the proton number Z and nucleon number (mass number) A, is discussed. In Chapter 1.2.2 (p. 22) a quick overview on the decay data of the nuclides of the Pt group is given more detailed descriptions of nuclear and decay properties are compiled in Chapter 1.2.3, p. 29. The methods used for production and separation of short-lived isotopes from irradiated materials are summarized in Chapter 1.3, p. 126. 

The structure of nuclides as well as their decay properties are discussed in many books and monographs see, for instance, [1 to 14]. Brief descriptions are also found in many volumes of this handbook, see, e.g., [15, 16]. 

All Isotopes of the elements of the Pt group which are stable against radioactive decay were found in nature. In the case of Os and Pt even the two radioactive Isotopes Os and do occur in nature because they did not decay out due to their long half-life. The abundance in the natural elements of these two primordial nuclides as well as of 

The values listed were evaluated by Wapstra etal. [22] those marked by were obtained by them from systematic trends [24]. As an example for calculated data the results obtained by Liran and Zeldes [27] are also included. Those nuclei which 

Lanthanum, or virtually all rare earth cations, are important constituents of catalysts employed in cracking of vacuum distillates from petroleum [77]. Thus, it seemed interesting to explore the possibility of introducing La cations into 

Essentially the same results were obtained when a higher excess of La was applied. Table 7 presents the data for a ratio nLa/n i = 0.67. The only difference was that, after completion of the reaction, a higher amount of LaClj was found in the washing water, viz., the total excess was extracted by the washing water and again only an amount of La + corresponding to the Al content of the framework was irreversibly held. 

Further evidence for the solid-state ion exchange with La + was provided by IR [78]. An IR transmittent wafer made from a stoichiometric mixture of NH4-Y 

exchange experiments were carried out starting with NH4-Y materials with a degree of exchange of almost 100% which can be achieved by repeated exchange in aqueous ammonium salt solutions. When these starting materials were subjected to solid-state ion exchange, a 100% replacement of NH4 (or H+) by La was achieved in one step (cf. Sect. 5.2.8). 

In contrast to the above findings with the anunonium form of faujasite-type zeolites with a regular low ns/nAi ratio of 2.5, exchange experiments with H-ZSM-5 or NH4-ZSM-5 (nsi/nAi 15) and LaCl3 7H2O led to incomplete removal of the IR band at 3605 cm which indicates the acidic OH groups. Thus, the IR investigations confirmed the observations described in Sect. 5.2.2. 

The visible ablation of material during the etching process is effected by chemical interphase reactions. In addition to the chemical interphase reactions, physical interactions, e.g. diffusion, adsorption, streaming, impact, are also involved in the complex process of etching. In the sequence of the manifold influences the effect of the lowest speed is controlling the complete process [430], 

To the best of our knowledge, a bibliographical review of US patents devoted to photoalignment has never been published despite a number of review articles (see e.g. [7-11] in Chapter 1). Such a review is very important because (i) 70-90% of patent data is never published in other sources and (ii) web analysis of the patent documents is complicated, since a person of ordinary skills has to make a selection from the enormous amount of a weakly structured information. This chapter is a bibliography of US patents (December 2007 included) on materials and processes for the photoalignment of liquid crystals, liquid crystal displays, optical liquid crystal devices and anisotropic optical elements, and other nondisplay applications. We restricted our attention to US patents only, since the majority of European, Asian, or other world patents are duplicated in the USA. 

Photoalignment of Liquid Crystalline Materials Physics and Applications V. Chigrinov, V. Kozenkov and H.-S. Kwok 2008 John Wiley Sons, Ltd 

The bibliography has the following structure number of patent (family of patents), inventors, assignee, title of patent, international class and current US class, date of patent, and original abstract. 

Following the bibliography. Table 7.1 provides the numbers of patents in accordance with the classification described in our book. Table 7.2 includes the names of companies and institutes which are patent owners as well as the numbers of the corresponding patents. A conclusion briefly analyzes the patent data presented. 

1 Photosensitive structures based on photochemical active compounds in solid state 

Oscillations originating from any source propagate further in space. The propagating oscillations are referred to as waves. 

Mechanical waves can propagate only in an elastic media. If particle vibrations are agitated in a region of an elastic medium (soUd, liquid or gaseous), as a consequence of the 

The process is not instantaneous a wave propagates with a speed v, which depends on the properties of the medium. However, it must be noted that no transportation of the medium s particles take place, particles oscillate around their permanent equilibrium positions. 

In isotropic elastic media all waves propagate at the same speed. Therefore, if the source of waves is tightened down to a point the wavefront is spherical and the wave is also spherical. If the wave front is a plane, a plane wave is produced. If the initiating oscillation is harmonic, the wave produced in isotropic media is also harmonic. 

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The introductory remarks about unimolecular reactions apply equivalently to bunolecular reactions in condensed phase. An essential additional phenomenon is the effect the solvent has on the rate of approach of reactants and the lifetime of the collision complex. In a dense fluid the rate of approach evidently is detennined by the mutual difhision coefficient of reactants under the given physical conditions. Once reactants have met, they are temporarily trapped in a solvent cage until they either difhisively separate again or react. It is conmron to refer to the pair of reactants trapped in the solvent cage as an encounter complex. If the unimolecular reaction of this encounter complex is much faster than diffiisive separation i.e., if the effective reaction barrier is sufficiently small or negligible, tlie rate of the overall bimolecular reaction is difhision controlled. 

In our introductory remarks, we said that this section would be devoted to model systems. Nevertheless it is important to emphasize that although this case is treated within a group of model systems this model stands for the general case of a two-state sub-Hilbert space. Moreover, this is the only case for which we can show, analytically, for a nonmodel system, that the restrictions on the D matrix indeed lead to a quantization of the relevant non-adiabatic coupling term. 

Introductory Remarks- The Orbital, Configuration, and State Pietures of Eleetronie Strueture... 

We close these introductory remarks with a few comments on the methods which are actually used to study these models. They will for the most part be mentioned only very briefly. In the rest of this chapter, we shall focus mainly on computer simulations. Even those will not be explained in detail, for the simple reason that the models are too different and the simulation methods too many. Rather, we refer the reader to the available textbooks on simulation methods, e.g.. Ref. 32-35, and discuss only a few technical aspects here. In the case of atomistically realistic models, simulations are indeed the only possible way to approach these systems. Idealized microscopic models have usually been explored extensively by mean field methods. Even those can become quite involved for complex models, especially for chain models. One particularly popular and successful method to deal with chain molecules has been the self-consistent field theory. In a nutshell, it treats chains as random walks in a position-dependent chemical potential, which depends in turn on the conformational distributions of the chains in... 

Before discussing the correlation error, we will make some introductory remarks about the Hartree-Fock approximation based on the use of the Slater determinant (Eq. 11.38). We note that, if we... 

Introductory Remarks.—As a considerable amount of this material is likely to be known, we shall abridge the exposition, referring for details to the recent text of the author.6... 

Introductory Remarks.—As was mentioned in the introduction to this chapter, the quantitative part of the theory of Poincar6 was first applied in celestial mechanics.1 The two approaches the topological,2 and the analytical are unrelated in the original publications of Poincar6, and the connection between the two appeared nearly 50 years later when the theory of nonlinear oscillations was developed. 

Introductory Remarks.—In the following sections we apply some of the preceding theories to the investigation of a few very important types of nonlinear oscillatory phenomena. 

Introductory Remarks.—Up to this point in this chapter we have given a brief survey of the wide field of nearly linear phenomena. If the condition of the near linearity is waived, the theory of Poincar6 does not apply, and the preceding methods cease to hold. The most... 

The photolysis of carbonyl compounds is one of the most intensively studied areas of photochemistry. Since CIDNP studies have been concerned mostly with aldehydes and ketones we shall confine these brief introductory remarks to such compounds. More extensive reviews are available (e.g., Simons, 1971). 

Nelson DR. Introductory remarks on human CYPs. Drug Metab Rev 2002 34 1-5. 

It should be clear that the most likely or physical rate of first entropy production is neither minimal nor maximal these would correspond to values of the heat flux of oc. The conventional first entropy does not provide any variational principle for heat flow, or for nonequilibrium dynamics more generally. This is consistent with the introductory remarks about the second law of equilibrium thermodynamics, Eq. (1), namely, that this law and the first entropy that in invokes are independent of time. In the literature one finds claims for both extreme theorems some claim that the rate of entropy production is... 

Palingenius, Marcellus. The zodiac of life being twelve books concerning human existence, the pursuit of knowledge, and the institutes of ethical law, now for the first time rendered into English prose, with some introductory remarks on Hermetic poetry. London Privately printed, 1896. 299p. 

Introductory Remarks. In contrast with the popularity and usefulness of the polysiloxane chains, which constitute the structural backbone of silicones, the knowledge of polymers based on the silazane unit is still limited. In the sixties there was still some hope of the possibility of producing long chain polysilazane molecules and a number of laboratories were active in seeking convenient methods for their synthesis (e.g. see review by Aylett (12)). 

An appropriate starting point for any discussion of drug transport in the gastrointestinal (GI) tract at the cellular level requires some introductory remarks on the structure and function of GI tissue. As a class of tissue, epithelia demarcate body entry points (skin, eye, respiratory, urinary, and GI organ systems), predisposing a general barrier function with respect to solute entry and translocation. In addi-... 

Introductory Remarks on Coal Paleobotany, Geology and Geochemistry... 

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