Rocky plateaus are globally threatened ecosystems and the lateritic plateaus in northern section of the Indian Western Ghats/Sri Lanka Biodiversity Hotspot (NWG) are notable landscape features. The NWG are geologically distinct from and biologically isolated from the other two sections of the Western Ghats. The NWG is known to possess elevated levels of endemic flora their biotic relationships remain poorly understood. We present here the first quantitative multi-taxa comparative study of plateau fauna in the northern Western Ghats. Ants, water beetles and amphibians were selected for the comparison as they use different ecological resources from each other and at various times of year therefore may provide a wider representation of plateau usage. Distribution and endemism were expected to reflect distribution and isolation by plateau and inter-plateau environment related to elevational, latitudinal, climatic and land-use clines. The study explored patterns of amphibian, water beetle, ant and fungal distribution and sampling seasonal pools and terrestrial surfaces of 13 representative plateaus in western Maharashtra, with sites ranging from 67-1179 m and across 2° of (sub) tropical latitude. Distribution of all taxonomic groups was spatially non-random at all levels of organisation and across all spatial scales. At the macroscale assemblages differed significantly with climate related to elevation, latitude but at a local scale land-use and microhabitat availably had an impact. Ants displayed a large seasonal assemblage variation, responding to seed availability. Water beetles the ants (combined survey data) were the best surrogates for all taxa data with amphibians the weakest representatives. Infection by the fungal pathogen, Batrachochytrium dendrobatidis, was extensive but less intense below the escarpment. We report the first records of infection in 13 endangered and data deficient amphibian species in the Western Ghats. The plateaus of western Maharashtra have recently been recognised as fragile and threatened ecosystems most still lack adequate statutory protection. In the absence of peer reviewed comparative data, the importance of individual sites is difficult to demonstrate hampering evidence-based conservation decisions.

Thesis (doctoral)--Freie Universität Berlin, 2003. / "April 2003"--P. [2] of cover. Lebenslauf. Includes bibliographical references. Also available via the World Wide Web.

The unique performance offerings of NiTi based shape memory alloys (SMAs), which includes the shape memory effect (SME), pseudoelasticity (PE) and biocompatibility have led to widespread acceptance of these alloys as valuable engineering materials. Over the past several decades the complex metallurgy behind the SME and PE properties has for the most part been uncovered and the design and engineering knowhow has been demonstrated; facilitating successful application of NiTi devices in numerous industries. Specifically, more mature applications in the medical industry including medical devices such as, catheters, guide wires, orthodontic arch wires, maxillofacial reconstruction implants, minimally invasive surgical tools, and arterial and gastrointestinal stents, have become common practice in modern medicine. Recently however, there has been a drive for more demanding functionality of SMAs for example to locally modify properties creating tuneable or gradient SME and PE performance. Unique processing protocols are therefore necessary to meet these demands and allow SMAs to reach their full potential in a wider range of applications. The current thesis successfully details the application of pulsed Nd:YAG laser processing along with post-processing techniques to locally tune both the SME and PE functional properties of monolithic binary NiTi wires and strip, while maintaining confidence in the retained corrosion performance and limited release of biologically harmful Ni ions. This extensive study contains three distinct parts which include: i) application of a laser induced vaporization protocol to locally embed multiple memories in a monolithic wire actuator; ii) uncovering the process, structure, and performance relationship of combined laser, cold working, and heat treatment processes; and iii) comprehensive characterization of surface characteristics and their relationship with corrosion performance and Ni ion release from laser processed material.

Este trabalho apresenta os resultados do estudo do relevo e dos solos da bacia do Rio Preto, região centro norte do Estado de Minas Gerais, abrangendo parte do município de São Gonçalo do Rio Preto. Também integra, o Parque Estadual do Rio Preto. O Rio Preto,importante afluente do Rio Araçuaí, faz parte da Bacia do Rio Jequitinhonha. A bacia do Rio Preto encontra-se inserida na Serra do Espinhaço Meridional, estrutura decorrente da tectônica compressiva com cavalgamento, no Mezoproterozóico, sobre rochas quartzíticas. A Carta Exploratória de Solos foi elaborada através de descrições de perfis de solo em campo, e da literatura desenvolvida pelos integrantes do projeto de pesquisa, do qual faz parte este trabalho, visando a espacialização das informações. A Carta Morfológica foi construída por meio da restituição de fotografias aéreas nas escalas de 1:40.000 e 1: 60.000. A predominância dos quartzitos faz com que a região apresente uma cobertura rígida, fraturada e cisalhada. Assim, dado o forte controle estrutural nesta região, neste trabalho foram realizadas analises de parâmetros morfométricos: analise morfométrica, analise da rede de drenagem, através de averiguação de padrões de drenagem, anomalias de drenagem, lineamentos de drenagem, parâmetros relacionados a assimetria da rede hidrográfica, densidade de textura de drenagem, com o intuito de verificar a influência tectônica na bacia do Rio Preto, além do já destacado controle estrutural. Portanto, a análise dos parâmetros morfométricos corroborou o forte controle estrutural e tectônico na bacia do Rio Preto. Portanto, a distribuição dos solos e das feições do relevo sofrem grande influência deste controle. Os solos da bacia foram incluídos em três sistemas de solos: Laterítico, Podzolizado e Lito-dependente, apresentam uma distribuição muito particular. No alto curso predominam os solos do sistema podzolizado e alguns litodependentes. No médio e baixo curso dominam os solos pertencentes ao sistema laterítico, com lito-dependentes nas declividades mais acentuadas. As feições do relevo, sofrem grande controle estrutural e tectônico, principalmente no alto curso. No médio e baixo curso dominam as feições de relevo ligadas a erosão e a estrutura. / his paper presents the results of the study of relief and soils of the basin of the Rio Preto, northcentral region of Minas Gerais state, located in the city of São Gonçalo do Rio Preto, part of the Parque Estadual do Rio Preto. Rio Preto is a important tributary of the Rio Araçuaí which is a tributary of Jequitinhonha. The Black River basin is inserted into the Meridional Espinhaço mountain range, due to the tectonic structure with compressive thrust in Mezoproterozic on quartzite rocks. The Charter Exploratory Soil was prepared through descriptions of soil profiles in the field, and literature developed by members of the research project, which is part of this work, the spatial order of the information. The Charter Morphologic was built by the restitution of aerial photographs on scales of 1:40.000 and 1: 60.000. The predominance of quartzite makes the region presents a rigid cover, fractured and sheared. Thus, given the strong structural control in this region, this work was performed analyzes of morphometric parameters: morphometric analysis, analysis of the drainage network, through investigation of drainage patterns, drainage anomalies, lineaments drainage, asymmetry parameters related to network hidrographic, drainage density of texture, in order to verify the tectonic influence on Rio Preto basin, beyond the already prominent structural control. The analysis of morphometric parameters allowed us to understand the evolution of the spatial distribution of soils and relief in the basin of the Rio Preto, because they present evidence on patterns of tectonic dissection of relief distribution and formation of pedological substrate.Therefore, the analysis of morphometric parameters confirmed a strong structural control and tectonic basin of the Black River. Therefore, the distribution of soil and relief features are greatly influenced by this control. The soils of the basin were included in three soil systems: laterite, podzolic and Litodependent, have a very particular distribution. In the upper course soils predominate system podzolic and some litho-dependent. In the middle and lower course dominate the laterite soils belonging to the system, with litho-dependent on slopes more pronounced. The relief features, suffer major structural and tectonic control, especially in the upper reaches. In the middle and lower course dominate the features of erosion and relief linked structure.

We present in this thesis a series of studies on the physical properties of some one dimensional systems. In particular we study the low energy properties of various spin chains and a junction of Luttinger wires. For spin chains we specifically look at the role of perturbations like frustrating interactions and dimerisation in a nearest neighbour chain and the formation of magnetisation plateaus in two kinds of models; one purely theoretical and the other motivated by experiments. In our second subject of interest we study using a renormalisation group analysis the effect of spin dependent scattering at a junction of Luttinger wires. We look at the physical effects caused by the interplay of electronic interactions in the wires and the scattering processes at the junction. The thesis begins with an introductory chapter which gives a brief glimpse of the ideas and techniques used in the specific problems that we have worked on. Our work on these problems is then described in detail in chapters 25. We now present a brief summary of each of those chapters. In the second chapter we look at the ground state phase diagram of the mixed-spin sawtooth chain, i.e a system where the spins along the baseline are allowed to be different from the spins on the vertices. The spins S1 along the baseline interact with a coupling strength J1(> 0). The coupling of the spins on the vertex (S2) to the baseline spins has a strength J2. We study the phase diagram as a function of J2/J1 [1]. The model exhibits a rich variety of phases which we study using spinwave theory, exact diagonalisation and a semi-numerical perturbation theory leading to an effective Hamiltonian. The spinwave theory predicts a transition from a spiral state to a ferrimagnetic state at J2S2/2J1S1 = 1 as J2/J1 is increased. The spectrum has two branches one of which is gapless and dispersionless (at the linear order) in the spiral phase. This arises because of the infinite degeneracy of classical ground states in that phase. Numerically, we study the system using exact diagonalisation of up to 12 unit cells and S1 = 1 and S2 =1/2. We look at the variation of ground state energy, gap to the lowest excitations, and the relevant spin correlation functions in the model. This unearths a richer phase diagram than the spinwave calculation. Apart from revealing a possibility of the presence of more than one kind of spiral phases, numerical results tell us about a very interesting phase for small J2. The spin correlation function (for the spin1/2s) in this region have a property that the nextnearest-neighbour correlations are much larger than the nearest neighbour correlations. We call this phase the NNNAFM (nextnearest neighbour antiferromagnet) phase and provide an understanding of this phase by deriving an effective Hamiltonian between the spin1/2s. We also show the existence of macroscopic magnetisation jumps in the model when one looks at the system close to saturation fields. The third chapter is concerned with the formation of magnetisation plateaus in two different spin models. We show how in one model the plateaus arise because of the competition between two coupling constants, and in the other because of purely geometrical effects. In the first problem we propose [2] a class of spin Hamiltonians which include as special cases several known systems. The class of models is defined on a bipartite lattice in arbitrary dimensions and for any spin. The simplest manifestation of such models in one dimension corresponds to a ladder system with diagonal couplings (which are of the same strength as the leg couplings). The physical properties of the model are determined by the combined effects of the competition between the ”rung” coupling (J’ )and the ”leg/diagonal” coupling (J ) and the magnetic field. We show that our model can be solved exactly in a substantial region of the parameter space (J’ > 2J ) and we demonstrate the existence of magnetisation plateaus in the solvable regime. Also, by making reasonable assumptions about the spectrum in the region where we cannot solve the model exactly, we prove the existence of first order phase transitions on a plateau where the sublattice magnetisations change abruptly. We numerically investigate the ladder system mentioned above (for spin1) to confirm all our analytical predictions and present a phase diagram in the J’/J - B plane, quite a few of whose features we expect to be generically valid for all higher spins. In the second problem concerning plateaus (also discussed in chapter 3) we study the properties of a compound synthesised experimentally [3]. The essential feature of the structure of this compound which gives rise to its physical properties is the presence of two kinds of spin1/2 objects alternating with each other on a helix. One kind has an axis of anisotropy at an inclination to the helical axis (which essentially makes it an Ising spin) whereas the other is an isotropic spin1/2 object. These two spin1/2 objects interact with each other but not with their own kind. Experimentally, it was observed that in a magnetic field this material exhibits magnetisation plateaus one of which is at 1/3rd of the saturation magnetisation value. These plateaus appear when the field is along the direction of the helical axis but disappear when the field is perpendicular to that axis. The model being used for the material prior to our work could not explain the existence of these plateaus. In our work we propose a simple modification in the model Hamiltonian which is able to qualitatively explain the presence of the plateaus. We show that the existence of the plateaus can be explained using a periodic variation of the angles of inclination of the easy axes of the anisotropic spins. The experimental temperature and the fields are much lower than the magnetic coupling strength. Because of this quite a lot of the properties of the system can be studied analytically using transfer matrix methods for an effective theory involving only the anisotropic spins. Apart from the plateaus we study using this modified model other physical quantities like the specific heat, susceptibility and the entropy. We demonstrate the existence of finite entropy per spin at low temperatures for some values of the magnetic field. In chapter 4 we investigate the longstanding problem of locating the gapless points of a dimerised spin chain as the strength of dimerisation is varied. It is known that generalising Haldane’s field theoretic analysis to dimerised spin chains correctly predicts the number of the gapless points but not the exact locations (which have determined numerically for a few low values of spins). We investigate the problem of locating those points using a dimerised spin chain Hamiltonian with a ”twisted” boundary condition [4]. For a periodic chain, this ”twist” consists simply of a local rotation about the zaxis which renders the xx and yy terms on one bond negative. Such a boundary condition has been used earlier for numerical work whereby one can find the gapless points by studying the crossing points of ground states of finite chains (with the above twist) in different parity sectors (parity sectors are defined by the reflection symmetry about the twisted bond). We study the twisted Hamiltonian using two analytical methods. The modified boundary condition reduces the degeneracy of classical ground states of the chain and we get only two N´eel states as classical ground states. We use this property to identify the gapless points as points where the tunneling amplitude between these two ground states goes to zero. While one of our calculations just reproduces the results of previous field theoretic treatments, our second analytical treatment gives a direct expression for the gapless points as roots of a polynomial equation in the dimerisation parameter. This approach is found to be more accurate. We compare the two methods with the numerical method mentioned above and present results for various spin values. In the final chapter we present a study of the physics of a junction of Luttinger wires (quantum wires) with both scalar and spin scattering at the junction ([5],[6]). Earlier studies have investigated special cases of this system. The systems studied were two wire junctions with either a fully transmitting scattering matrix or one corresponding to disconnected wires. We extend the study to a junction of N wires with an arbitrary scattering matrix and a spin impurity at the junction. We study the RG flows of the Kondo coupling of the impurity spin to the electrons treating the electronic interactions and the Kondo coupling perturbatively. We analyse the various fixed points for the specific case of three wires. We find a general tendency to flow towards strong coupling when all the matrix elements of the Kondo coupling are positive at small length scales. We analyse one of the strong coupling fixed points, namely that of the maximally transmitting scattering matrix, using a 1/J perturbation theory and we find at large length scales a fixed point of disconnected wires with a vanishing Kondo coupling. In this way we obtain a picture of the RG at both short and long length scales. Also, we analyse all the fixed points using lattice models to gain an understanding of the RG flows in terms of specific couplings on the lattice. Finally, we use to bosonisation to study one particular case of scattering (the disconnected wires) in the presence of strong interactions and find that sufficiently strong interactions can stabilise a multichannel fixed point which is unstable in the weak interaction limit.

Dans ce mémoire, il sera question des propriétés de deux composés appartenant à la famille avec la composition AkLn2O4 (où Ak sont des métaux alcalino-terreux et Ln des lanthanides). Certains membres de cette famille ont démontré des comportements associés à une chaîne monodimensionnelle zigzag incluant des interactions au deuxième plus proche voisin (ANNNI, acronyme de l’anglais anisotropic next-nearest neighbours Ising model). En particulier, une étude de diffusion neutronique en champ sur le SrHo2O4 a montré des plateaux dans l’intensité du pic (200). Si on identifie l’intensité avec l’aimantation au carré, ceci indiquerait la présence d’un plateau dans l’aimantation et peut-être la présence d’une phase magnétique. En conséquence, des mesures de chaleur spécifique et d’aimantation ont été prises pour chercher cette transition de phase. Les mesures de chaleur spécifique et d’aimantation en fonction du champ magnétique appliqué parallèle à l’axe b montrent qu’il y a des phases induites en champ dans ce composé. En particulier, l’aimantation montre la formation de plateaux suggérant une phase robuste à l’augmentation du champ magnétique pour un intervalle de température de T = 0:6 K à 1.3 K. Les champs critiques déterminés à partir des mesures de chaleur spécifique et d’aimantation sont comparés à l’aide d’un diagramme de phase. Les champs critiques des données de diffraction de neutrons précédemment obtenus par [1] sont aussi comparés. Cependant, ces résultats ne montrent pas encore avec certitude où se trouvent les limites de phase. Comme l’état fondamental magnétique dépend du niveau du champ cristallin électrique (CEF, acronyme de l’anglais crystalline electric field), changer l’ion Sr2+ pour un plus grand ion Ba2+ va changer la structure cristalline et donc le CEF. De plus, le moment magnétique J du Ce3+ est 5=2 qui est plus petit que celui du Ho3+ (J = 8) ou du Dy3+ (J = 15=2), deux ions qui ont beaucoup été étudiés dans les composés SrLn2O4 et BaLn2O4. Un moment magnétique plus petit devrait rendre le système plus quantique et ainsi obtenir une chaîne de iii spin quantique. Nous avons donc essayé de synthétiser le BaCe2O4 et d’étudier ses propriétés. L’étude de chaleur spécifique et de l’entropie à champ nul de l’aimant frustré BaCe2O4 est présentée. Ces mesures ont été faites sur des monocristaux synthétisés par la méthode de flux métallique. Les résultats de la chaleur spécifique ont démontré une transition de phase à un ordre magnétique à longue portée à la température de T = 0:43 K. L’entropie magnétique a été calculée à partir des résultats de la chaleur spécifique dans l’intervalle de température T = 0 K à 5 K. L’entropie magnétique dans cet intervalle de température a été trouvée à être en dessous de celle correspondant à l’état doublet des champs cristallins. Les résultats de la chaleur spécifique et de l’entropie indiquent la présence de frustration géométrique dans le composé BaCe2O4. / The focus of this master’s thesis is on the properties of two members of the family with the general composition AkLn2O4 (where Ak are alkaline earth metals and Ln are lanthanides). Some members of this family showed behaviours associated with a one-dimensional zigzag chain with next-nearest neighbors interactions (ANNNI model). In particular, an in-field neutron diffraction study of SrHo2O4 showed plateaus in the intensity of the peak (200). If we identify the intensity as the square of the magnetization, this would indicate the presence of a plateau in the magnetization and perhaps the presence of a magnetic phase which was not previously observed. Thus, specific heat and magnetization measurements were carried out to search for this phase transition. Measurements of the field dependent specific heat and magnetization with a field applied parallel to the b-axis showed the presence of field induced phase transitions in this compound. In particular, the magnetization shows the formation of plateaus suggesting a phase robust to the increase of the magnetic field for the temperature interval T = 0:6 K to 1.3 K. The critical fields determined from the specific heat and magnetization are compared using a phase diagram. The critical fields from neutron diffraction previously obtained by [1] are also compared. However, the results do not yet show clearly where the phase boundaries are. Since the magnetic ground state depends on the crystalline electric field (CEF), changing the Sr2+ ion for the bigger Ba2+ ion will change the crystal structure and thus the CEF levels. Furthermore, the magnetic moment J of Ce3+ is 5=2 which is smaller then that of Ho3+ (J = 8) or of Dy3+ (J = 15=2), two ions that have been extensively studied in the SrLn2O4 and the BaLn2O4 series. A smaller magnetic moment should result in a more quantum mechanical system and the hope is to obtain a quantum spin chain. We thus tried to synthesize BaCe2O4 and study its properties. To this end, a study of the heat capacity and entropy at zero field of the frustrated magnet BaCe2O4 will be presented. The measurements v were taken on single crystals grown from a metallic flux method. The results from the specific heat show a phase transition to a long range magnetic order at a temperature of T = 0:43 K. The magnetic entropy was calculated from the results of specific heat in the temperature range from T = 0 K to 5 K. In this range of temperature, the magnetic entropy was found to be below the value expected for a crystalline electric field doublet as the ground state. The results from the specific heat and the entropy indicate the presence of geometrical frustration in the compound BaCe2O4.

<p>This thesis concerns the development and validation of methods for characterization of multi-component preparative LC systems. Measurements of competitive adsorption isotherms are performed to gain detailed information about the interactions inside the chromatography column. This information increases our understanding of the separation process and makes it possible to perform computer simulations and numerical optimizations to find optimal operating conditions.</p><p>The methods under focus are called “the tracer-pulse method”, “the inverse method”, and “the inverse method on plateaus”. They are extensions of existing methods, with new experimental and numerical procedures to enable rapid and accurate multi-component adsorption isotherm determination. In the validation it was shown that they can produce results agreeing with traditional methods and that the acquired adsorption isotherm parameters can be used in simulations to accurately predict the outcome of preparative LC separations.</p><p>The methods were used to characterize several complex LC systems and two phenomena were discovered and theoretically treated: 1) The presence of invisible deformed peaks in single-component systems. 2) Peak deformations encountered with modern chiral stationary phases, caused by strongly adsorbed eluent additives. The latter type of deformation was highly tuneable and it was possible to adjust the enantiomer peak shapes so that the peaks tailed in opposite directions with the sharp sides in between, yielding baseline resolution at remarkably high sample loads.</p><p>In a final applied study both the LC-based perturbation peak method and a biosensor method based on surface plasmon resonance (SPR) were used for the first time for detailed characterization of chiral drug-protein interactions. The fundamental properties of the two very different methods were compared and it was found that the LC method is more suitable for multi-component analysis and that the SPR method is more suitable for stronger interactions.</p>

This thesis concerns the development and validation of methods for characterization of multi-component preparative LC systems. Measurements of competitive adsorption isotherms are performed to gain detailed information about the interactions inside the chromatography column. This information increases our understanding of the separation process and makes it possible to perform computer simulations and numerical optimizations to find optimal operating conditions. The methods under focus are called “the tracer-pulse method”, “the inverse method”, and “the inverse method on plateaus”. They are extensions of existing methods, with new experimental and numerical procedures to enable rapid and accurate multi-component adsorption isotherm determination. In the validation it was shown that they can produce results agreeing with traditional methods and that the acquired adsorption isotherm parameters can be used in simulations to accurately predict the outcome of preparative LC separations. The methods were used to characterize several complex LC systems and two phenomena were discovered and theoretically treated: 1) The presence of invisible deformed peaks in single-component systems. 2) Peak deformations encountered with modern chiral stationary phases, caused by strongly adsorbed eluent additives. The latter type of deformation was highly tuneable and it was possible to adjust the enantiomer peak shapes so that the peaks tailed in opposite directions with the sharp sides in between, yielding baseline resolution at remarkably high sample loads. In a final applied study both the LC-based perturbation peak method and a biosensor method based on surface plasmon resonance (SPR) were used for the first time for detailed characterization of chiral drug-protein interactions. The fundamental properties of the two very different methods were compared and it was found that the LC method is more suitable for multi-component analysis and that the SPR method is more suitable for stronger interactions.

No description available.

Made available in DSpace on 2016-06-02T20:15:29Z (GMT). No. of bitstreams: 1 5202.pdf: 3904832 bytes, checksum: c623a581c3cdb03d9cc81fc16ecef935 (MD5) Previous issue date: 2013-04-08 / Universidade Federal de Minas Gerais / This thesis presents a study of the magnetization plateau and the phenomenon of geometrical frustration in spin systems applied to lattices with triangular structure, as well as the results achieved by applying the differential operator technique of the Ising and Heisenberg models with external magnetic field applied to the easy magnetization axis z, their phase diagrams, behavior plateaus observed and analyzed according to the Haldane conjecture and appearance of plateaus presented by Oshikawa, Yamanaka and Affleck, and also to study the behavior of the magnetic susceptibility in order to verify the behavior of frustrated systems using the frustration factor f= &#952;WC/TN to verify frustration encountered at various stages of the study models / Este trabalho apresenta um estudo da magnetização de platô e do fenômeno de frustração geométrica em sistemas de spins, aplicados às redes com estrutura triangular, bem como os resultados alcançados aplicando-se a técnica do operador diferencial a modelos de Ising e Heisenberg com campo magnético externo aplicado sobre o eixo fácil de magnetização z, seus diagramas de fases e comportamento de platôs observados e analisados segundo a conjectura de Haldane e a condição de aparecimento de platôs apresentada por Oshikawa, Yamanaka e Affleck, e ainda, o estudo do comportamento da susceptibilidade magnética com o objetivo de verificar o comportamento dos sistemas frustrados utilizando-se o fator de frustração f= &#952;WC/TN para verificar a frustração nas diversas fases encontradas ao longo do estudo dos modelos.