959 resultados para dissociation constants


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Transparent SrLiB9O15 (SLBO) glasses were fabricated via the conventional melt-quenching technique. X-ray powder diffraction and differential thermal analysis carried out on the as-quenched samples confirmed their amorphous and glassy nature, respectively. The dielectric constants in the 100 Hz to 10 MHz frequency range for SLBO glasses were measured as a function of temperature (300–1023 K). The dielectric relaxation characteristics were rationalized using the electric modulus formalism. The electrode polarization effect was subtracted from the low-frequency dielectric constant to have an insight into the intrinsic dielectric behavior of SLBO glasses. The imaginary part of electric modulus spectra was modeled using an approximate solution of Kohlrausch–Williams–Watts relation. The dielectric constant for the as-quenched glass increased with increasing temperature and exhibited anomalies in the vicinity of the glass transition and crystallization temperatures.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Mixed ligand complexes of the type Ni(R-AB)(AC') and Ni(R-AC)(AB') where AB/AC denote N-bonded isonitroso- [3-ketoimino ligands, AB'/AC' denote the corresponding Obonded ligands and R = Me, Et, n-Pr are synthesised and characterised. The complexes are neutral with square planar geometry around nickel(II). The bonding isomerism of the isonitroso group is discussed on the basis of i.r. and 1H n.m.r. studies. The crystal structure of the title complex, Ni(n-Pr-IEAI)(IMAI') has been determined from diffractometer data by Patterson and Fourier methods and refined by least squares to R = 0.088 for 2209 observed reflections. Unit cell constants are: a = 11.945(2), b = 22.436(7), c = 13.248(5) ~, [3 = 95.13(2) ~ The space group is P2Jc with Z = 8. Niekel(II) has a square planar coordination of two imine nitrogens, an isonitroso-nitrogen (from n-Pr-IEAI) and another isonitrosooxygen (from IMAI').

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A method employing two liquid crystals of opposite diamagnetic anisotropies to determine chemical shift anisotropy without using any reference compound is described. It also provides individual values of the direct and the indirect spin-spin coupling constants between heteronuclei. The parameters for acetonitrile are reported.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The interactions of metallo derivatives of macrocyclic tetrapyrrole pigments, pheophytin a (pheo), phthalocyanin (phth), and tetraphenylporphyrin (TPP) with sym-trinitrobenzene (TNB) have been studied with use of spectroscopic methods. These macrocyles form 1:l molecular complexw with the acceptor. The association constants (K) for the interactions follow the decreasing order of binding as pheo > phth > TPP. The divalent metal ions influence the values of K for the various metallo TPP derivatives, and the relative order of stabilities decrease as Co > Cu = VO > Ni > Zn. The stereochemistry of M(TPP) and the electronic configuration of the metal ions are shown to contribute to the magnitudes of K. The acceptor strongly quenches the fluorescence of the metallo macrocycles, and the quenching constant decreases as pheo > phth > TPP. The formation of exciplexes is postulated on the basis of the rate of bimolecular quenching constants and solvent effects.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Bertrand Russell (1872 1970) introduced the English-speaking philosophical world to modern, mathematical logic and foundational study of mathematics. The present study concerns the conception of logic that underlies his early logicist philosophy of mathematics, formulated in The Principles of Mathematics (1903). In 1967, Jean van Heijenoort published a paper, Logic as Language and Logic as Calculus, in which he argued that the early development of modern logic (roughly the period 1879 1930) can be understood, when considered in the light of a distinction between two essentially different perspectives on logic. According to the view of logic as language, logic constitutes the general framework for all rational discourse, or meaningful use of language, whereas the conception of logic as calculus regards logic more as a symbolism which is subject to reinterpretation. The calculus-view paves the way for systematic metatheory, where logic itself becomes a subject of mathematical study (model-theory). Several scholars have interpreted Russell s views on logic with the help of the interpretative tool introduced by van Heijenoort,. They have commonly argued that Russell s is a clear-cut case of the view of logic as language. In the present study a detailed reconstruction of the view and its implications is provided, and it is argued that the interpretation is seriously misleading as to what he really thought about logic. I argue that Russell s conception is best understood by setting it in its proper philosophical context. This is constituted by Immanuel Kant s theory of mathematics. Kant had argued that purely conceptual thought basically, the logical forms recognised in Aristotelian logic cannot capture the content of mathematical judgments and reasonings. Mathematical cognition is not grounded in logic but in space and time as the pure forms of intuition. As against this view, Russell argued that once logic is developed into a proper tool which can be applied to mathematical theories, Kant s views turn out to be completely wrong. In the present work the view is defended that Russell s logicist philosophy of mathematics, or the view that mathematics is really only logic, is based on what I term the Bolzanian account of logic . According to this conception, (i) the distinction between form and content is not explanatory in logic; (ii) the propositions of logic have genuine content; (iii) this content is conferred upon them by special entities, logical constants . The Bolzanian account, it is argued, is both historically important and throws genuine light on Russell s conception of logic.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This dissertation explores the role of the German minister to Helsinki, Wipert von Blücher (1883-1963), within the German-Finnish relations of the late 1930s and the Second World War. Blücher was a key figure – and certainly one of the constants – within German Finland policy and the complex international diplomacy surrounding Finland. Despite representing Hitler’s Germany, he was not a National Socialist in the narrower sense of the term, but a conservative civil servant in the Wilhelmine tradition of the German foreign service. Along with a significant number of career diplomats, Blücher attempted to restrict National Socialist influence on the exercise of German foreign policy, whilst successfully negotiating a modus vivendi with the new regime. The study of his political biography in the Third Reich hence provides a highly representative example of how the traditional élites of Germany were caught in an cycle of conformity and, albeit tacit, opposition. Above all, however, the biographical study of Blücher and his behaviour offers an hitherto unexplored approach to the history of the German-Finnish relations. His unusually long tenure in Helsinki covered the period leading up to the so-called Winter War, which left Blücher severely distraught by Berlin’s effectively pro-Soviet neutrality and brought him close to resigning his post. It further extended to the German-Finnish rapprochement of 1940/41 and the military cooperation of both countries from mid-1941 to 1944. Throughout, Blücher developed a diverse and ambitious set of policy schemes, largely rooted in the tradition of Wilhelmine foreign policy. In their moderation and commonsensical realism, his designs – indeed his entire conception of foreign policy – clashed with the foreign political and ideological premises of the National Socialist regime. In its theoretical grounding, the analysis of Blücher’s political schemes is built on the concept of alternative policy and indebted to A.J.P. Taylor’s definition of dissent in foreign policy. It furthermore rests upon the assumption, introduced by Wolfgang Michalka, that National Socialist foreign policy was dominated by a plurality of rival conceptions, players, and institutions competing for Hitler’s favour (‘Konzeptionen-Pluralismus’). Although primarily a study in the history of international relations, my research has substantially benefited from more recent developments within cultural history, particularly research on nobility and élites, and the renewed focus on autobiography and conceptions of the self. On an abstract level, the thesis touches upon some of the basic components of German politics, political culture, and foreign policy in the first half of the 20th century: national belonging and conflicting loyalties, self-perception and representation, élites and their management of power, the modern history of German conservatism, the nature and practice of diplomacy, and, finally, the intricate relationship between the ethics of the professional civil service and absolute moral principles. Against this backdrop, the examination of Blücher’s role both within Finnish politics and the foreign policy of the Third Reich highlights the biographical dimension of the German-Finnish relationships, while fathoming the determinants of individual human agency in the process.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

1H and 13C NMR spectra are reported for several pyridylamides and thionamides. Complete analyses of the 13C spectra have yielded the chemical shifts and the direct and long range (13C, 1H) coupling constants. 13C chemical shifts show linear relationship with charge densities computed by the CNDO method. The variations in the chemical shifts are discussed.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

XPS studies of the interaction of carbon monoxide with surfaces of Fe, Co and Ni indicate that at 300 K, the disproportionation reaction is prominent up to exposures of 103 L giving rise to high surface concentrations of carbon. At higher exposures and higher temperatures, dissociation of carbon monoxide accompanied by the formation of surface oxide layers becomes more prominent. In the case of copper, disproportionation is prominent up to 104 L even at 500 K followed by dissociation at higher exposures. These results are also supported by Auger spectroscopic studies.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Oxovanadium(1V) porphyrins appended with crown ether (benzo-15-crown-5) at the 5 (mono), the 5 and 10115 (cis/trans bis), the 5, 10, and 15 (tris), and the 5, 10, 15, and 20 (tetrakis) positions have been synthesized. The cation complexation behavior of these cavity-bearing porphyrins has been studied by using optical aborption and ESR spectral methods. The cations K+, Cs+, NH4+, and Ba2+, which require two crown ether cavities for complexation, induce dimerization of the porphyrins. The cation-induced dimerization constants for a representative tetrasubstituted porphyrin vary as K+ > Ba2+ > Cs+ - NH4+, and the relative stabilities of the dimers are dependent on the type of the substitution, tetrakis > tris > cis bis. ESR spectra recorded at a sample temperature of 77 K have low-field components attributed to Ah& = f 2 transitions, providing further evidence for the existence of dimers in solutions. The eclipsed sandwich dimers have V-V distances in the range 4.70 A. The relative distributions of oxovanadium crown porphyrins in terms of monomeric and dimeric forms rest on the geometric dispositions of the crown ether appendages.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The free radical polymerization of acrylonitrile (AN) initiated by Cu(I1) 4-anilino 3-pentene 2-one [Cu(II) ANIPO] Cu(II), 4-p-toluedeno 3-pentene 2-one [Cu(II) TPO], and Cu(I1) 4-p-nitroanilino 3-pentene 2-one [Cu(II) NAPO] was studied in benzene at 50 and 60°C and in carbon tetrachloride (CCld), dimethyl sulfoxide (DMSO), and methanol (MeOH) at 60°C. Although the polymerization proceeded in a heterogeneous phase, it followed the kinetics of a homogeneous process. The monomer exponents were 22 at two different temperatures and in different solvents. The square-root dependence of R, on initiator concentration and higher monomer exponents accounted for a 1:2 complex formation between the chelate and monomer. The complex formatign was shown by ultraviolet (UV) study. The activation energies, kinetics, and chain transfer constants were also evaluated.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

We show that the large anomalous Hall constants of mixed-valence and Kondo-lattice systems can be understood in terms of a simple resonant-level Fermi-liquid model. Splitting of a narrow, orbitally unquenched, spin-orbit split, f resonance in a magnetic field leads to strong skew scattering of band electrons. We interpret both the anomalous signs and the strong temperature dependence of Hall mobilities in CeCu2Si2, SmB6, and CePd3 in terms of this theory.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Infrared spectra are recorded for S-methyl dithiocarbazate and its N-deuterated compound in two molecular conformations in the solid state and in solution between 4000 and 30 cm−1. The assignments have been supported from a complete normal coordinate analysis; the conformation sensitive bands of the –CSNHNH2 grouping are discussed. The assignments are compared with those of related molecules to check the internal consistency and to obtain the pattern of the characteristic bands of thiocarbazoyl (–CSNHNH2) group. The magnitudes of the C–N and S–CH3 torsional barriers are estimated from the force constants.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Le naturalisme finlandais. Une conception entropique du quotidien. Finnish Naturalism. An Entropic Conception of Everyday Life. Nineteenth century naturalism was a strikingly international literary movement. After emerging in France in the 1870s, it spread all over Europe including young, small nations with a relatively recent literary tradition, such as Finland. This thesis surveys the role and influence of French naturalism on the Finnish literature of the 1880s and 1890s. On the basis of a selection of works of six Finnish authors (Juhani Aho, Minna Canth, Kauppis-Heikki, Teuvo Pakkala, Ina Lange and Karl August Tavaststjerna), the study establishes a view of the main features of Finnish naturalism in comparison with that of French authors, such as Zola, Maupassant and Flaubert. The study s methodological framework is genre theory: even though naturalist writers insisted on a transparent description of reality, naturalist texts are firmly rooted in general generic categories with definable relations and constants on which European novels impose variations. By means of two key concepts, entropy and everyday life , this thesis establishes the parameters of the naturalist genre. At the heart of the naturalist novel is a movement in the direction of disintegration and confusion, from order to disorder, from illusion to disillusion. This entropic vision is merged into the representation of everyday life, focusing on socially mediocre characters and discovering their miseries in all their banality and daily grayness. By using Mikhail Bakhtin s idea of literary genres as a means of understanding experience, this thesis suggests that everyday life is an ideological core of naturalist literature that determines not only its thematic but also generic distinctions: with relation to other genres, such as to Balzac s realism, naturalism appears primarily to be a banalization of everyday life. In idyllic genres, everyday life can be represented by means of sublimation, but a naturalist novel establishes a distressing, negative everyday life and thus strives to take a critical view of the modern society. Beside the central themes, the study surveys the generic blends in naturalism. The thesis analyzes how the coalition of naturalism and the melodramatic mode in the work of Minna Canth serves naturalisms ambition to discover the unconscious instincts underlying daily realities, and how the symbolic mode in the work of Juhani Aho duplicates the semantic level of the apparently insignificant, everyday naturalist details. The study compares the naturalist novel to the ideological novel (roman à these) and surveys the central dilemma of naturalism, the confrontation between the optimistic belief in social reform and the pessimistic theory of determinism. The thesis proposes that the naturalist novel s contribution to social reform lies in its shock effect. By means of representing the unpleasant truth the entropy of everyday life it aims to scandalize the reader and make him aware of the harsh realities that might apply also to him.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

We have investigated the structure, magnetic and dielectric properties of the double perovskite oxides, R2NiMnO6 (R = Pr, Nd, Sm, Gd, Tb, Dy, Ho and Y). We could refine powder X-ray diffraction patterns of all the phases on the basis of monoclinic (P2(1)/n) double perovskite structure where Ni and Mn atoms are ordered at 2c and 2d sites, respectively. All the phases are ferromagnetic insulators exhibiting relatively low dielectric loss and dielectric constants in the range 15-25. The ferromagnetic ordering temperature of the R2NiMnO6 series seems to correlate better with the radius of R3+ atoms than with the average Ni-O-Mn angle (phi) in the double perovskite structure. These results are consistent with all samples having Mn4+ and Ni2+ With minimal antisite disorder.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A number of bile acid derived photoinduced electron transfer (PET) based sensors for metal ions are prepared. A general strategy for designing the sensor with a modular nature allows for making different molecules capable of sensing different metal ions by a change in the fluorophore and receptor unit. Keeping the basic molecular structure the same, different bile acid base fluoroionophores were prepared inorder to achieve the highest sensitivity toward the metal ions. Thesensors showed similar binding constants for the same metal ion, but the degree Of fluorescence enhancement upon addition of the metal salts were different. The sensitivities of the sensors towards a certain metal were determined from the observed fluorescence enhancement upon addition of the metal salt.