Iron environment non-equivalence in both octahedral and tetrahedral sites in NiFe2O4 nanoparticles: study using Mössbauer spectroscopy with a high velocity resolution

Mössbauer spectrum of NiFe2O4 nanoparticles was measured at room temperature in 4096 channels. This spectrum was fitted using various models, consisting of different numbers of magnetic sextets from two to twelve. Non-equivalence of the 57Fe microenvironments due to various probabilities of different Ni2+ numbers surrounding the octahedral and tetrahedral sites was evaluated and at least 5 different microenvironments were shown for both sites. The fit of the Mössbauer spectrum of NiFe 2O4 nanoparticles using ten sextets showed some similarities in the histograms of relative areas of sextets and calculated probabilities of different Ni2+ numbers in local microenvironments. © 2012 American Institute of Physics

Studien zur Totalsynthese der Naturstoffe (-)-Englerin A und Crotogoudin

In the first part of the thesis four different approaches to the core structure of the novel guaiane sesquiterpene englerin A are described. The first approach features a Rh(II)-catalyzed generation of a cyclic carbonyl ylide from a diazoketone precursor which was trapped with allyl propiolate. The 1,3-dipolar cycloaddition led to the stereoselective formation of an oxygen-bridged polycyclic structure, however with opposite stereochemistry of the ether bridge compared to natural englerin. In further studies the core structure of the sesquiterpene was prepared by an oxy-Cope rearrangement/transannular epoxide opening sequence. Utilizing this strategy an analogue of the natural product without a glycolate at C-9 (9-deoxy-englerin) was synthesized. Studies on the cytotoxic activity of this analog proved the importance of the hydroxyl group and glycolic acid at C-9. The second part describes studies on the total synthesis of another terpene – crotogoudin. The key bicyclo[2.2.2]octane subunit was constructed by an early stage domino Michael reaction. Subsequent Stork reductive alkylation resulted in an opposite stereochemistry at C-10 in respect to the one in natural crotogoudin. Attempts to perform a late stage double Michael reaction were not successful, however the total synthesis of another diterpene – moluccanic acid, was achieved from the common intermediate.Im ersten Teil der Dissertation wurden vier verschiedene Zugänge zur Kernstruktur des neuen Guajan-Sesquiterpens Englerin A entwickelt. Die erste Methode beinhaltet eine Rh(II)- katalysierte Bildung eines cyclischen Carbonylylides aus einer Diazoketon-Vorstufe, welche mittels Allylpropiolat abgefangen wurde. Die 1,3-dipolare Cycloaddition führte zur stereoselektiven Bildung einer sauerstoffverbrückten polycyclischen Struktur, jedoch wies die Etherbrücke im Vergleich zu Englerin A die entgegengesetzte Stereochemie auf. In weiteren Studien konnte die Kernstruktur des Sesquiterpens über eine Oxy-Cope Umlagerung und anschließende transannulare Epoxidöffnung erhalten werden. Mittels dieser Synthesestrategie konnte ein Analogon des Naturstoffes, ohne Glykolat an C-9 synthetisiert werden. Studien zur cytotoxischen Aktivität des Analogons bewiesen die bedeutende Rolle der Hydroxygruppe und der Glykolsäure an C-9. Der zweite Teil der Dissertation befasst sich mit Studien zur Totalsynthese eines weiteren Terpens- Crotogoudin. Die Schlüsselverbindung ein Bicyclo[2.2.2]octan wurde über eine Domino Michael Reaktion in einem frühen Stadium der Synthese aufgebaut. Die anschließende Stork Alkylierung führte zur entgegengesetzten Stereochemie an C-10, verglichen mit dem Naturstoff Crotogoudin. Der Versuch einer doppelten Michaeladdition in einem späten Stadium der Synthese scheiterte, jedoch war die Totalsynthese eines anderen Diterpens erfolgreich - Moluccansäure, diese konnte aus dem gemeinsamen Intermediat synthetisiert werden

Design of Pre-Dumping Ring Spin Rotator with a Possibility of Helicity Switching for Polarized Positrons at the ILC

The use of polarized beams enhance the possibility of the precision measurements at the International Linear Collider (ILC). In order to preserve the degree of polarization during beam transport spin rotators are included in the current TDR ILC Lattice. In this report some advantages of using a combined spin rotator/spin flipper are discussed. A few possible lattice designs of spin flipper developed at DESY in 2012 are presented.Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS15), Whistler, Canada, 2-6 November 201

Orbitally induced hierarchy of exchange interactions in zigzag antiferromagnetic state of honeycomb silver delafossite Ag3Co2SbO6

We report the revised crystal structure, static and dynamic magnetic properties of quasi-two dimensional honeycomb-lattice silver delafossite Ag3Co2SbO6. The magnetic susceptibility and specific heat data are consistent with the onset of antiferromagnetic long range order at low temperatures with N\'eel temperature TN ~ 21.2 K. In addition, the magnetization curves revealed a field-induced (spin-flop type) transition below TN in moderate magnetic fields. The GGA+U calculations show the importance of the orbital degrees of freedom, which maintain a hierarchy of exchange interaction in the system. The strongest antiferromagnetic exchange coupling was found in the shortest Co-Co pairs and is due to direct and superexchange interactions between the half-filled xz+yz orbitals pointing directly to each other. The other four out of six nearest neighbor exchanges within the cobalt hexagon are suppressed, since for these bonds active half-filled orbitals turned out to be parallel and do not overlap. The electron spin resonance (ESR) spectra reveal a Gaussian shape line attributed to Co2+ ion in octahedral coordination with average effective g-factor g=2.3+/-0.1 at room temperature and shows strong divergence of ESR parameters below 120 K, which imply an extended region of short-range correlations. Based on the results of magnetic and thermodynamic studies in applied fields, we propose the magnetic phase diagram for the new honeycomb-lattice delafossite

Трансформация института конституционного контроля в политико-правовом пространстве России

Introduction. The article presents the author’s interpretation of the process of constitutional control institutionalization in Russia. The paper highlights the dominant factors and main vectors of the constitutional control transformation in the context of modernizing the political and legal systems of the Russian Federation. The authors pay a particular attention to the specifics of the Constitutional Court of the Russian Federation functioning in the current system of separation of powers and upholding the sovereignty of the Russian state in the context of contradictory modern processes of political globalization. Methodology and methods. The theoretical and methodological base of the work includes theses of Russian and foreign scientistsconstitutionalists A. Medushevskiy, V.E. Chirkin, L. Fridman, F. Luscher. The theories of political modernization and globalization (A.Yu. Melvil, S. Lantsov, S. Eisenstadt, S. Huntington, I. Wallerstein, Z. Bauman) were used to analyze the functional specificity of constitutional control institute activities in the conditions of forming a global and regional “risk society”, and a new Russian state after the Soviet Union collapse. The empirical base of the study was the following: the Constitution of the Russian Federation; Constitutional and Federal laws of the Russian Federation, other legal documents regulating the activities of state authorities and administration; periodical materials; research results of the leading sociological centers – Russian Public Opinion Research Center (VTsIOM), Levada-Center. Analysis. The stages of forming the constitutional control institution and its transformation should be considered in the context of modernizing the Russian state, its political and legal systems. At the same time, the inconsistency of the statist model of political modernization in Russia has a significant impact on modern institutional reinforcement and the practice of implementing the principle of separation of powers, including the political and legal status of the Constitutional Court of the Russian Federation. The escalation of internal and external risks and threats to the Russian society and state objectively defines a number of restrictions to the comprehensive disclosure of the constitutional justice political potential. Discussion. The main discussion dominants in analysing factors and directions of the constitutional control institute transformation in modern Russia are the following: the degree of rootedness of constitutionalism principles and constitutional values in the public consciousness of Russian citizens, and first of all among the ruling elite; the effectiveness of implementing constitutional control in comparison with other types of control – public, civil, parliamentary, etc.; the indicators of performance of the Constitutional Court of the Russian Federation to strengthen Russia as a legal, democratic state while ensuring stable and safe development of the national society. Results. The article highlights the main stages of the constitutional control institutionalization in the national history. The interrelation of modernization transformations of Russian society and the state with formation and functioning of the Constitutional Court of the Russian Federation is traced. The paper presents the dominant vectors of the constitutional control institute transformation in the Russian political and legal space, taking into account real and potential risks and threats in the personality-society-state system

Complex therapy of chronic pancreatitis complicated by anxio-depressive disorders in railroad workers

The authors have found out negative impact of anxio-depressive disorders on the course of chronic pancreatitis with the development of stable pain syndrome, gastro-intestinal disorders, resistance to the performed pharmacotherapy, and decrease of reaction rate to presented stimul

The Structure of Liquid and Amorphous Hafnia.

Understanding the atomic structure of amorphous solids is important in predicting and tuning their macroscopic behavior. Here, we use a combination of high-energy X-ray diffraction, neutron diffraction, and molecular dynamics simulations to benchmark the atomic interactions in the high temperature stable liquid and low-density amorphous solid states of hafnia. The diffraction results reveal an average Hf-O coordination number of ~7 exists in both the liquid and amorphous nanoparticle forms studied. The measured pair distribution functions are compared to those generated from several simulation models in the literature. We have also performed ab initio and classical molecular dynamics simulations that show density has a strong effect on the polyhedral connectivity. The liquid shows a broad distribution of Hf-Hf interactions, while the formation of low-density amorphous nanoclusters can reproduce the sharp split peak in the Hf-Hf partial pair distribution function observed in experiment. The agglomeration of amorphous nanoparticles condensed from the gas phase is associated with the formation of both edge-sharing and corner-sharing HfO6,7 polyhedra resembling that observed in the monoclinic phase

Novel electronic states close to Mott transition in low-dimensional and frustrated systems

Recent studies demonstrated that there may appear different novel states in correlated systems close to localized-itinerant crossover. Especially favourable conditions for that are met in low-dimensional and in frustrated systems. In this paper I discuss on concrete examples some of such novel states. In particular, for some spinels and triangular systems there appears a "partial Mott transition", in which first some finite clusters (dimers, trimes, tetramers, heptamers) go over to the itinerant regime, and the real bulk Mott transition occurs only later. Also some other specific possibilities in this crossover regime are shortly discussed, such as spin-Peierls-Peierls transition in TiOCl, spontaneous charge disproportionation in some cases, etc.Comment: To be published in Journal of Physics - Condensed Matter, conference serie

Characterization of structural changes in modern and archaeological burnt bone: Implications for differential preservation bias

Structural and thermodynamic factors which may influence burnt bone survivorship in archaeological contexts have not been fully described. A highly controlled experimental reference collection of fresh, modern bone burned in temperature increments 100–1200˚C is presented here to document the changes to bone tissue relevant to preservation using Fourier transform infrared spectroscopy and X-ray diffraction. Specific parameters investigated here include the rate of organic loss, amount of bone mineral recrystallization, and average growth in bone mineral crystallite size. An archaeological faunal assemblage ca. 30,000 years ago from Tolbor-17 (Mongolia) is additionally considered to confirm visibility of changes seen in the modern reference sample and to relate structural changes to commonly used zooarchaeological scales of burning intensity. The timing of our results indicates that the loss of organic components in both modern and archaeological bone burnt to temperatures up to 700˚C are not accompanied by growth changes in the average crystallite size of bone mineral bioapatite, leaving the small and reactive bioapatite crystals of charred and carbonized bone exposed to diagenetic agents in depositional contexts. For bones burnt to temperatures of 700˚C and above, two major increases in average crystallite size are noted which effectively decrease the available surface area of bone mineral crystals, decreasing reactivity and offering greater thermodynamic stability despite the mechanical fragility of calcined bone. We discuss the archaeological implications of these observations within the context of Tolbor-17 and the challenges of identifying anthropogenic fire