Mellum Island (southern North Sea): dynamic processes and sedimentary structures. I. Southern tidal flat, transition zone and high-surface.[p.72 (Blasensand) only][Translation from: Senckenbergiana Maritima 11, 59-113, 1979]

This partial translation of a longer article describes the phenomenon of ”Blasensand”. Blasensand is formed when sedimentation of dried out sand is suddenly flooded from above. A more detailed explanation of Blasensand is given in this translated part of the paper.

Study and comparison of four forest structures on Mt. Chortiatis (northern Greece)

EL proyecto estudia y analiza la estructura de cuatro bosques en el monte Chortiatis, Grecia.

Late Transition Metals Supported by Aryl Ethers and Phenoxides Bearing Pendant Phosphines: Mechanistic Insights Relevant to Ether C-O Bond Cleavage

Terphenyl diphosphines bearing pendant ethers were prepared to provide mechanistic insight into the mechanism of activation of aryl C–O bonds with Group 9 and Group 10 transition metals. Chapters 2 and 3 of this dissertation describe the reactivity of compounds supported by the model phosphine and extension of this chemistry to heterogenous C–O bond activation.

Chapter 2 describes the synthesis and reactivity of aryl-methyl and aryl-aryl model systems. The metallation of these compounds with Ni, Pd, Pt, Co, Rh, and Ir is described. Intramolecular bond activation pathways are described. In the case of the aryl-methyl ether, aryl C–O bond activation was observed only for Ni, Rh, and Ir.

Chapter 3 outlines the reactivity of heterogenous Rh and Ir catalysts for aryl ether C–O bond cleavage. Using Rh/C and an organometallic Ir precursor, aryl ethers were treated with H2 and heat to afford products of hydrogenolysis and hydrogenation. Conditions were modified to optimize the yield of hydrogenolysis product. Hydrogenation could not be fully suppressed in these systems.

Appendix A describes initial investigations of bisphenoxyiminoquinoline dichromium compounds for selective C2H4 oligomerization to afford α-olefins. The synthesis of monometallic and bimetallic Cr complexes is described. These compounds are compared to literature examples and found to be less active and non-selective for production of α-olefins.

Appendix B describes the coordination chemistry of terphenyl diphosphines, terphenyl bisphosphinophenols, and biphenyl phosphinophenols proligands with molybdenum, cobalt, and nickel. Since their synthesis, terphenyl diphosphine molybdenum compounds have been reported to be good catalysts for the dehydrogenation of ammonia borane. Biphenyl phosphinophenols are demonstrated provide both phosphine and arene donors to transition metals while maintaining a sterically accessible coordination sphere. Such ligands may be promising in the context of the activation of other small molecules.

Appendix C contains relevant NMR spectra for the compounds presented in the preceding sections.

The Design and Synthesis of Transition Metal Complexes Supported by Non-innocent Ligand Scaffolds for Small Molecule Activation

This dissertation focuses on the incorporation of non-innocent or multifunctional moieties into different ligand scaffolds to support one or multiple metal centers in close proximity. Chapter 2 focuses on the initial efforts to synthesize hetero- or homometallic tri- or dinuclear metal carbonyl complexes supported by para-terphenyl diphosphine ligands. A series of [M₂M’(CO)₄]-type clusters (M = Ni, Pd; M’ = Fe, Co) could be accessed and used to relate the metal composition to the properties of the complexes. During these studies it was also found that non-innocent behavior was observed in dinuclear Fe complexes that result from changes in oxidation state of the cluster. These studies led to efforts to rationally incorporate central arene moieties capable managing both protons and electrons during small molecule activation.

Chapter 3 discusses the synthesis of metal complexes supported by a novel para-terphenyl diphosphine ligand containing a non-innocent 1,4-hydroquinone moiety as the central arene. A Pd⁰-hydroquinone complex was found to mediate the activation of a variety of small molecules to form the corresponding Pd⁰-quinone complexes in a formal two proton ⁄ two electron transformation. Mechanistic investigations of dioxygen activation revealed a metal-first activation process followed by subsequent proton and electron transfer from the ligand. These studies revealed the capacity of the central arene substituent to serve as a reservoir for a formal equivalent of dihydrogen, although the stability of the M-quinone compounds prevented access to the PdII-quinone oxidation state, thus hindering of small molecule transformations requiring more than two electrons per equivalent of metal complex.

Chapter 4 discusses the synthesis of metal complexes supported by a ligand containing a 3,5-substituted pyridine moiety as the linker separating the phenylene phosphine donors. Nickel and palladium complexes supported by this ligand were found to tolerate a wide variety of pyridine nitrogen-coordinated electrophiles which were found to alter central pyridine electronics, and therefore metal-pyridine π-system interactions, substantially. Furthermore, nickel complexes supported by this ligand were found to activate H-B and H-Si bonds and formally hydroborate and hydrosilylate the central pyridine ring. These systems highlight the potential use of pyridine π-system-coordinated metal complexes to reversibly store reducing equivalents within the ligand framework in a manner akin to the previously discussed 1,4-hydroquinone diphosphine ligand scaffold.

Chapter 5 departs from the phosphine-based chemistry and instead focuses on the incorporation of hydrogen bonding networks into the secondary coordination sphere of [Fe₄(μ₄-O)]-type clusters supported by various pyrazolate ligands. The aim of this project is to stabilize reactive oxygenic species, such as oxos, to study their spectroscopy and reactivity in the context of complicated multimetallic clusters. Herein is reported this synthesis and electrochemical and Mössbauer characterization of a series of chloride clusters have been synthesized using parent pyrazolate and a 3-aminophenyl substituted pyrazolate ligand. Efforts to rationally access hydroxo and oxo clusters from these chloride precursors represents ongoing work that will continue in the group.

Appendix A discusses attempts to access [Fe₃Ni]-type clusters as models of the enzymatic active site of [NiFe] carbon monoxide dehydrogenase. Efforts to construct tetranuclear clusters with an interstitial sulfide proved unsuccessful, although a (μ₃-S) ligand could be installed through non-oxidative routes into triiron clusters. While [Fe₃Ni(μ₄-O)]-type clusters could be assembled, accessing an open heterobimetallic edge site proved challenging, thus prohibiting efforts to study chemical transformations, such as hydroxide attack onto carbon monoxide or carbon dioxide coordination, relevant to the native enzyme. Appendix B discusses the attempts to synthesize models of the full H-cluster of [FeFe]-hydrogenase using a bioinorganic approach. A synthetic peptide containing three cysteine donors was successfully synthesized and found to chelate a preformed synthetic [Fe₄S₄] cluster. However, efforts to incorporate the diiron subsite model complex proved challenging as the planned thioester exchange reaction was found to non-selectively acetylate the peptide backbone, thus preventing the construction of the full six-iron cluster.

I. Baryon-antibaryon phase transition at high temperature. II. Inclusive virtual photon-hadron reactions in the parton model

Part I

Present experimental data on nucleon-antinucleon scattering allow a study of the possibility of a phase transition in a nucleon-antinucleon gas at high temperature. Estimates can be made of the general behavior of the elastic phase shifts without resorting to theoretical derivation. A phase transition which separates nucleons from antinucleons is found at about 280 MeV in the approximation of the second virial coefficient to the free energy of the gas.

Part II

The parton model is used to derive scaling laws for the hadrons observed in deep inelastic electron-nucleon scattering which lie in the fragmentation region of the virtual photon. Scaling relations are obtained in the Bjorken and Regge regions. It is proposed that the distribution functions become independent of both q² and ν where the Bjorken and Regge regions overlap. The quark density functions are discussed in the limit x→1 for the nucleon octet and the pseudoscalar mesons. Under certain plausible assumptions it is found that only one or two quarks of the six types of quarks and antiquarks have an appreciable density function in the limit x→1. This has implications for the quark fragmentation functions near the large momentum boundary of their fragmentation region. These results are used to propose a method of measuring the proton and neutron quark density functions for all x by making measurements on inclusively produced hadrons in electroproduction only. Implications are also discussed for the hadrons produced in electron-positron annihilation.

Development of trophic state and phytoplankton in an oligo-mesotrophic reservoir (Kleine Kinzig) in Black Forest, Germany

Since 1989, intensive studies have been made on a relatively new (1983-84) oligotrophic reservoir and its pre-reservoir in the Black Forest. This paper briefly reports on the hydrochemistry, especially annual variations in phosphorus loadings, and the seasonal development of phytoplankton in 1989 and 1990.

1. Ultrasonic studies of binary liquid structure in the critical region. Theory and experiment for the 2,6-lutidine/water system. 2. Hartree-Fock calculations of electric polarizabilities of some simple atoms and molecules, and their practicality. 3. Calculation of vibrational transition probabilities in collinear atom-diatom and diatom-diatom collisions with Lennard-Jones interaction

Part 1. Many interesting visual and mechanical phenomena occur in the critical region of fluids, both for the gas-liquid and liquid-liquid transitions. The precise thermodynamic and transport behavior here has some broad consequences for the molecular theory of liquids. Previous studies in this laboratory on a liquid-liquid critical mixture via ultrasonics supported a basically classical analysis of fluid behavior by M. Fixman (e. g., the free energy is assumed analytic in intensive variables in the thermodynamics)--at least when the fluid is not too close to critical. A breakdown in classical concepts is evidenced close to critical, in some well-defined ways. We have studied herein a liquid-liquid critical system of complementary nature (possessing a lower critical mixing or consolute temperature) to all previous mixtures, to look for new qualitative critical behavior. We did not find such new behavior in the ultrasonic absorption ascribable to the critical fluctuations, but we did find extra absorption due to chemical processes (yet these are related to the mixing behavior generating the lower consolute point). We rederived, corrected, and extended Fixman's analysis to interpret our experimental results in these more complex circumstances. The entire account of theory and experiment is prefaced by an extensive introduction recounting the general status of liquid state theory. The introduction provides a context for our present work, and also points out problems deserving attention. Interest in these problems was stimulated by this work but also by work in Part 3.

Part 2. Among variational theories of electronic structure, the Hartree-Fock theory has proved particularly valuable for a practical understanding of such properties as chemical binding, electric multipole moments, and X-ray scattering intensity. It also provides the most tractable method of calculating first-order properties under external or internal one-electron perturbations, either developed explicitly in orders of perturbation theory or in the fully self-consistent method. The accuracy and consistency of first-order properties are poorer than those of zero-order properties, but this is most often due to the use of explicit approximations in solving the perturbed equations, or to inadequacy of the variational basis in size or composition. We have calculated the electric polarizabilities of H₂, He, Li, Be, LiH, and N₂ by Hartree-Fock theory, using exact perturbation theory or the fully self-consistent method, as dictated by convenience. By careful studies on total basis set composition, we obtained good approximations to limiting Hartree-Fock values of polarizabilities with bases of reasonable size. The values for all species, and for each direction in the molecular cases, are within 8% of experiment, or of best theoretical values in the absence of the former. Our results support the use of unadorned Hartree-Pock theory for static polarizabilities needed in interpreting electron-molecule scattering data, collision-induced light scattering experiments, and other phenomena involving experimentally inaccessible polarizabilities.

Part 3. Numerical integration of the close-coupled scattering equations has been carried out to obtain vibrational transition probabilities for some models of the electronically adiabatic H₂-H₂ collision. All the models use a Lennard-Jones interaction potential between nearest atoms in the collision partners. We have analyzed the results for some insight into the vibrational excitation process in its dependence on the energy of collision, the nature of the vibrational binding potential, and other factors. We conclude also that replacement of earlier, simpler models of the interaction potential by the Lennard-Jones form adds very little realism for all the complication it introduces. A brief introduction precedes the presentation of our work and places it in the context of attempts to understand the collisional activation process in chemical reactions as well as some other chemical dynamics.

Spectroscopic, and thermal studies of some new binuclear transition metal(II) complexes with hydrazone ligands containing acetoacetanilide and isoxazole

A new chelating ligand, 2-(2-(5-tert-butylisoxazol-3-yl)hydrazono)-N-(2,4-dimethylphenyl)-3-oxobutanamide (HL), and its four binuclear transition metal complexes, M-2(L)(2) (mu-OCH3)(2) [M = Ni(II), Co(II), Cu(II), Zn(II)], were synthesized using the procedure of diazotization, coupling and metallization. Their structures were postulated based on elemental analysis, H-1 NMR, MALDI-MS, FT-IR spectra and UV-vis electronic absorption spectra. Smooth films of these complexes on K9 glass substrates were prepared using the spin-coating method and their absorption properties were evaluated. The thermal properties of the metal(II) complexes were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC. Different thermodynamic and kinetic parameters namely activation energy (E

Study of crystal structure and phase transition studies in perovskite-type oxides using powder-diffraction techniques and symmetry-mode analysis.

251 p.

Investigation on nonradiative decay of the (Er3+I13/2)-I-4 -> I-4(15/2) transition in different tellurite glass matrix

Three kinds of Er3+-doped tellurite glasses with different hydroxyl groups are prepared by the conventional melt-quenching method. Infrared spectra are measured to estimate the exact content of OH- groups in samples. The maximum phonon energy in glasses are obtained by measuring the Raman scattering spectra. The strength parameters Omega(t) (t = 2, 4, 6) for all the samples are calculated and compared. The nonradiative decay rate of the Er3+ I-4(13/2) -> I-4(15/2) transition are calculated for the glass samples with different phonon energy and OH- group contents. Finally, the effect of OH- groups on fluorescence decay rate of Er3+ is analysed, the constant KOH-Er Of TWN, TZPL and TZL glasses are calculated to be 9.2 x 10(-19) cm(4)s(-1), 5.9 x 10(-19) cm(4)s(-1), and 3.5 x 10(-19) cm(4)s(-1), respectively.