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Structural Transformations (structural + transformation)
Kinds of Structural Transformations Selected AbstractsExport Processing Zones: Free Market Islands or Bridges to Structural Transformation?DEVELOPMENT POLICY REVIEW, Issue 2 2001Andrew Schrank Do export processing zones draw local manufacturers into world markets , and thereby engender broader market reform , by way of a ,demonstration effect'? The answer is likely (i) to be determined, not in the EPZ, but in the host country's national customs area, and (ii) to vary systematically with the size of the relevant market. While manufacturers from large economies are able to compete in world markets, and are therefore susceptible to the demonstration effect, their counterparts from small economies are unable to do so, and are therefore intractable. Thus, the nature of the EPZ life-cycle, like the legacy of import-substituting industrialisation, is in no small measure a function of market size. [source] A Dynamically Entangled Coordination Polymer: Synthesis, Structure, Luminescence, Single-Crystal-to-Single-Crystal Reversible Guest Inclusion and Structural TransformationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2010Arshad Aijaz Abstract A ZnII coordination polymer {[Zn2(cpa)2(bpy)]·3H2O}n (1) (cpa2, = 4-(methoxycarbonyl)benzoate and bpy = 4,4,-bipyridine) has been synthesized under solvothermal condition and structurally characterized. This coordination polymer has nanotubular threefold entangled (2D,3D) structure with embedded water molecules; the water molecules can be partially exchanged in reversible single-crystal-to-single-crystal (SC-SC) fashion by different solvent molecules like methanol, ethanol and acetone giving rise to {[Zn2(cpa)2(bpy)]·(0.5MeOH)·(2.5H2O)}n (2), {[Zn2(cpa)2(bpy)]·(0.5EtOH)·(0.5H2O)}n (3) and {[Zn2(cpa)2(bpy)]·(0.5Me2CO)·(H2O)}n (4). Inclusion of EtOH or MeOH leaves the size of the voids in the framework unaltered. Inclusion of acetone, however, is accompanied by shrinking of the voids in the framework. Heating of 1 at 100 °C under vacuum for 4 h affords the de-solvated compound, {Zn2(cpa)2(bpy)}n (1,). Single-crystal X-ray structure of 1, shows sliding of the individual nanotubular components expanding the overall framework. Thus, the coordination polymer exhibits dynamic motion of the molecular components in SC-SC fashion. All compounds were further characterized via IR spectroscopy, PXRD, elemental and TGA analysis. When 1 is placed in benzene at 100 °C for 2 days, compound {[Zn2(cpa)2(bpy)]·(2.5H2O)}n (5) is formed in a SC-SC fashion where coordination number of ZnII ion increases from four to five. Compound 1 also exhibits reversible guest-dependent photoluminescence properties. [source] Novel Cadmium(II) Adipate Coordination Polymers with Structural Transformation via Oxalate Ligand: Syntheses, Structures and Fluorescence PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2004Na Hao Abstract Two novel cadmium adipate coordination polymers [Cd{O2C(CH2)4CO2}{1,10-phen}]n (1) and [Cd2(C2O4){O2C(CH2)4CO2(OH2)2}{2,2,-bipy}]·H2O (2) [adipic acid = HO2C(CH2)4CO2H] have been hydrothermally synthesized and characterized by elemental analyses, IR spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. Crystallographic data for 1: monoclinic, C2/c, a = 16.186(3) Å, b = 15.487(3) Å, c = 14.052(3) Å, , = 112.73(3)°, Z = 8. Crystal data for 2: monoclinic, Cc, a = 23.448(5) Å, b = 11.826(2) Å, c = 8.3163(17) Å, , = 99.08(3)°, Z = 4. The structural analysis reveals that 1 forms a novel one-dimensional chain in which the binuclear Cd centers are linked by adipate anions. Compound 2 is the first example in which both a 2,2,-bipy ligand and an oxalate group are found in the {M/adipate} system. Compound 2 possesses one-dimensional sine- or cosine-type chains, which are alternately connected together by the oxalate group to form a three-dimensional framework. The structural determination reveals that the introduction of the oxalate ligand causes the dimensional transformation of the compounds. Compounds 1 and 2 show strong fluorescent properties at room temperature. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] ChemInform Abstract: Structural Transformation from Trinuclear Linear to Tetranuclear Cubane Heterobimetallic Selenium Compounds.CHEMINFORM, Issue 20 2009-WSe4)(CuCl)2]., Optical Linearities of [Et4N]2[(, Structure Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Structural Transformations during Formation of Quasi-Amorphous BaTiO3,ADVANCED FUNCTIONAL MATERIALS, Issue 7 2007D. Ehre Abstract A model of structural transformations of amorphous into quasi-amorphous BaTiO3 is suggested. The model is based on previously published data and on X-ray photoelectron spectroscopy data presented in the current report. Both amorphous and quasi-amorphous phases of BaTiO3 are made up of a network of slightly distorted TiO6 octahedra connected in three different ways: by apices (akin to perovskite), edges, and faces. Ba ions in these phases are located in the voids between the octahedra, which is a nonperovskite environment. These data also suggest that Ba ions compensate electrical-charge imbalance incurred by randomly connected octahedra and, thereby, stabilize the TiO6 network. Upon heating, the edge-to-edge and face-to-face connections between TiO6 octahedra are severed and then reconnected via apices. Severing the connections between TiO6 octahedra requires a volume increase, suppression of which keeps some of the edge-to-edge and face-to-face connections intact. Transformation of the amorphous thin films into the quasi-amorphous phase occurs during pulling through a steep temperature gradient. During this process, the volume increase is inhomogeneous and causes both highly anisotropic strain and a strain gradient. The strain gradient favors breaking those connections, which aligns the distorted TiO6 octahedra along the direction of the gradient. As a result, the structure becomes not only anisotropic and non-centrosymmetric, but also acquires macroscopic polarization. Other compounds may also form a quasi-amorphous phase, providing that they satisfy the set of conditions derived from the suggested model. [source] Single-Crystal to Single-Crystal Photochemical Structural Transformations of Interpenetrated 3,D Coordination Polymers by [2+2] Cycloaddition Reactions,ANGEWANDTE CHEMIE, Issue 2 2010Hedayetullah Mir, Mohammad Lichtempfindliche Säulen: Genau ausgerichtete CC-Bindungen von Paaren von trans- 1,2-Bis(4-pyridyl)ethen-Liganden in verzahnten 3D-Koordinationspolymeren gehen quantitative [2+2]-Photocycloadditionen ein. Diese Reationen werden von Einkristall-Einkristall(SCSC)-Übergängen begleitet (siehe Schema). [source] Structural transformations in organic crystals during photochemical reactionsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 10 2004Ilona Turowska-Tyrk Abstract In the 1980s and 1990s, x-ray studies of the photochemical reaction course in crystals dealt with the analysis of changes in cell constants or movements of atom groups inside molecules. This review presents the results of crystallographic studies on the monitoring of the behaviour of whole molecules in organic crystals during photochemical reactions. Papers on this subject started to appear only a few years ago. The studies showed quantitatively that reactant and product molecules do not take a fixed position in a crystal during the reaction. The product molecules move smoothly to a position assumed in the pure product crystal and the reactant molecules move from a position occupied in the pure reactant crystal. Moreover, with the reaction progress the adjacent reactant molecules gradually come closer and change their mutual orientation to resemble the product. The analysis of the photoreaction kinetics in crystals is also presented. Copyright © 2004 John Wiley & Sons, Ltd. [source] Effects of annealing on structural, electrical and optical properties of AgGa(Se0.5S0.5)2 thin films deposited by using sintered stoichometric powderCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2009H. Karaagac Abstract The structural, electrical and optical properties of AgGa(Se0.5S0.5 )2 thin films deposited by using the thermal evaporation method have been investigated as a function of annealing in the temperature range of 450,600 °C. X-ray diffraction (XRD) analysis showed that the structural transformation from amorphous to polycrystalline structure started at 450 oC with mixed binary phases of Ga2Se3, Ga2S3, ternary phase of AgGaS2 and single phase of S. The compositional analysis with the energy dispersive X-ray analysis (EDXA) revealed that the as-grown film has different elemental composition with the percentage values of Ag, Ga, Se and S being 5.58, 27.76, 13.84 and 52.82 % than the evaporation source powder, and the detailed information about the stoichometry and the segregation mechanisms of the constituent elements in the structure have been obtained. The optical band gap values as a function of annealing temperature were calculated as 2.68, 2.85, 2.82, 2.83, and 2.81 eV for as-grown, annealed at 450, 500, 550, and 600 °C samples, respectively. It was determined that these changes in the band gap are related with the structural changes with annealing. The temperature dependent conductivity measurements were carried out in the temperature range of 250-430 K for all samples. The room temperature resistivity value of as-grown film was found to be 0.7x108 (,-cm) and reduced to 0.9x107 (,-cm) following to the annealing. From the variation of electrical conductivity as a function of the ambient temperature, the activation energies at specific temperature intervals for each sample were evaluated. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Photoelectrical properties of crystalline titanium dioxide thin films after thermo-annealingCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2007R. Sathyamoorthy Abstract This paper reports the photoelectrical properties of sol gel derived titanium dioxide (TiO2) thin films annealed at different temperatures (425-900°C). The structure of the as-grown film was found to be amorphous and it transforms to crystalline upon annealing. The trap levels are studied by thermally stimulated current (TSC) measurements. A single trap level with activation energy of 1.5 eV was identified. The steady state and transient photocurrent was measured and the results are discussed on the basis of structural transformation. The photocurrent was found to be maximum for the films annealed at 425°C and further it decreases with annealing at higher temperatures. The photoconduction parameters such as carrier lifetime, lifetime decay constant and photosensitivity were calculated and the results are discussed as a function of annealing temperature. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reengineering Academic Teams Toward a Network Organizational Structure,DECISION SCIENCES JOURNAL OF INNOVATIVE EDUCATION, Issue 2 2007Emmanouil Kaldis ABSTRACT This article examines student teamwork in the academic field from a structural perspective. Student teams are often prearranged and then left to organize themselves and get on with their work, without any further structural support; this, however, can become a negative experience on teamwork. A varied contribution among team members often occurs and unavoidably leads to friction and reduced performance. The aim of this project is to explore the main problems in academic teamwork and investigate tools that provide relevant solutions. We present the concept of network organizational structure and discuss how this can improve collaboration and communication. The main tools to achieve a structural transformation from the more traditional form of team organization to the fairer network form, and their implications are discussed. [source] Spirocycle (SitBu3)6Si9Cl2: The First of Its Kind among Group 14 Elements,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2010Thomas M Klapötke Abstract Structural studies on (R*3Si4)2SiCl2, prepared by the reaction of tetrasilatetrahedranide KR*3Si4 with SiCl4, show that the tetrahedral moieties R*3Si4 undergo structural transformation. The molecule exhibits a spiro[4.4]nonasilane network that comprises two homonuclear tricyclo[2.1.0.02,5]pentasilane rings with a common "naked" silicon bridge. The compound shows structural similarities with R*6Si8, which consists of similar rings fused together along an Si,Si bridge. Comparison of valence angles, interplanar angles and bridgehead distances with respect to tricyclo[2.1.0.02,5]pentanes or similar ring systems with heteronuclear group homologues are reported to highlight the influence of bulky supersilyl R* groups in the structure. [source] Developing new measures of welfare state change and reformEUROPEAN JOURNAL OF POLITICAL RESEARCH, Issue 5 2002Francis G. Castles Since the publication of Gøsta Esping,Andersen's The Three Worlds of Welfare Capitalism (Esping,Andersen 1990), which built its typologies on a rich database of detailed programme characteristics, it has been generally accepted that measures of social expenditure are an inferior, and even a misleading, source of information concerning the character of welfare state development. The problem is, however, that the kinds of detailed programme data Esping,Andersen used are not routinely available, while the quality of social expenditure data has been improving rapidly, culminating in the Organisation for Economic Cooperation and Development's (OECD) now regularly updated and highly disaggregated Social Expenditure Database (SOCX). This article explores the possibility of using SOCX to devise measures of the extent, structure and trajectory of welfare state change and reform in 21 OECD countries over the period 1984 to 1997. On the basis of these measures, it suggests that there has been almost no sign of systematic welfare retrenchment in recent years and only limited evidence of major structural transformation or programmatic reorientation. [source] Bifurcated Mechanical Behavior of Deformed Periodic Porous SolidsADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Srikanth Singamaneni Abstract The transformation of periodic microporous structures fabricated by interference lithography followed by their freezing below glass transition is described. Periodic porous microstructures subjected to internal compressive stresses can undergo sudden structural transformation at a critical strain. The pattern transformation of collapsed pores is caused by the stresses originated during the polymerization of acrylic acid (rubbery component) inside of cylindrical pores and the subsequent solvent evaporation in the organized microporous structure. By confining the polymerization of acrylic acid to localized porous areas complex microscopic periodic structures can be obtained. The control over the mechanical instabilities in periodic porous solids at a sub-micron scale demonstrated here suggests the potential mechanical tunability of photonic, transport, adhesive, and phononic properties of such periodic porous solids. [source] Molten Salt Synthesis and Characterization of Potassium Polytitanate Ceramic Precursors with Varied TiO2/K2O Molar RatiosJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2008Tomas Sanchez-Monjaras Semi-crystalline potassium titanates, useful as precursors to produce composite materials and coatings, were synthesized by thermal treatment of powdered TiO2 in molten mixtures of KNO3 and KOH at 450°,550°C. The products obtained had similar structures of laminar crystals, aggregated in particles of about 3 ,m of n=TiO2/K2O molar ratio in the range 2.8,6.0. The value of n could be regulated by the temperature of synthesis, the weight ratio of [KOH]/[KNO3] in the molten salt mixture, and the number of water washing operations. The reduction of the TiO2/K2O molar ratio increased the contents of H2O in the composition of potassium polytitanate, from 5.3 to 11.4 and from 0.2 to 8.6 (wt%) in the adsorbed and structural forms. The thermal treatment of the potassium polytitanate precursors obtained resulted in dehydration and chemical interaction with unreacted TiO2 at 500°,750°C, amorphization at 750°,850°C, crystallization of K2Ti4O9 (in some cases K3Ti8O17) at 850°,1090°C, and crystallization of K2Ti6O13 at temperatures >1090°C. The mechanisms of the structural transformation and phase evolution were considered as a function of the TiO2/K2O molar ratio in the potassium polytitanate. [source] The Judicial Transformation of the State: The Case of U.S. Trade Policy, 1974,2004LAW & POLICY, Issue 1 2009NITSAN CHOREV The recent shift in state policies from Keynesianism to neoliberalism was accompanied by a transformation in state structures. The case of trade liberalization in the United States reveals that this structural transformation is of a judicial nature. In 1974, supporters of free trade successfully shifted authority over the management of protectionist claims from Congress to quasi-judicial bodies in the U.S. executive; in 1994, they successfully strengthened the dispute settlement mechanisms of the World Trade Organization. This judicial transformation indicates a shift from sites where decisions are made by way of political negotiations to sites where judges preside over legal disputes. In the article, I identify the political origins of these judicial transformations and discuss the factors that make judicial sites more favorable to neoliberal policies than political sites. [source] Beyond Therapy: Problem-Solving Courts and the Deliberative Democratic StateLAW & SOCIAL INQUIRY, Issue 4 2008Rekha Mirchandani Problem-solving courts (drug courts, community courts, domestic violence courts, and mental health courts), unlike traditional courts, attempt to get at the root of the individual and social problems that motivate criminal behavior. Theoretical understandings of problem-solving courts are mostly Foucauldian; proponents argue that these new institutions employ therapeutic techniques that encourage individuals to self-engineer in ways that subtly increase state power. The Foucauldian approach captures only some elements of problem-solving courts and does not fully theorize the revolution in justice that these courts present. Problem-solving courts, domestic violence courts in particular, orient not just around individual change but also around social change and cultural transformation. Combining the Foucauldian idea of a therapeutic state (as developed by James Nolan) with an understanding of the deliberative democratic mechanisms of larger-scale structural transformation (found in Habermas and others) leads to a more balanced and empirically open orientation to the actual motivations, goals, and achievements of problem-solving courts. [source] 23Na and 87Rb relaxation study of the structural phase transitions in the Tutton salts Na2Zn(SO4)2·6H2O and Rb2Zn(SO4)2·6H2O single crystalsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2010Ae Ran Lim Abstract The NMR spectrum, spin,lattice relaxation times, T1, and the spin,spin relaxation times, T2, for the 23Na and 87Rb nuclei in Tutton salts Na2Zn(SO4)2·6H2O and Rb2Zn(SO4)2·6H2O single crystals were determined by using an FT NMR spectrometer. The NMR spectrum and relaxation times for the 23Na and 87Rb nuclei in two crystals undergo significant changes near TC. These changes close to TC were the only detectable result of the structural transformation; the change is due to the fact that the electric field gradient value becomes 0. Especially, T1 and T2 for 87Rb in the Rb2Zn(SO4)2·6H2O crystals at high temperature have similar values on the order of milliseconds, which is indicative of a liquid-like system. The motion giving rise to this liquid-like behavior is probably related to superionic motion at high temperature. [source] Temperature-induced phase transition in simulated amorphous Al2O3PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2006Vo Van Hoang Abstract Our previous simulation studies indicated the existence of pressure-induced phase transition in liquid and amorphous Al2O3. In the current paper, we present the structural transformation of simulated amorphous Al2O3 from an octahedral to a tetrahedral network structure by heating from the high-density amorphous (hda) model at constant pressure P = 0 GPa. The structure of the models was analyzed through the partial radial distribution functions (PRDFs), coordination number distributions, bond-angle distributions and interatomic distances. Furthermore, significant differences in structural characteristics of low-density amorphous (lda) models obtained by heating from the hda one and by cooling from the low-density melt have been found and are presented. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Secondary structural formation of ,-synuclein amyloids as revealed by g -factor of solid-state circular dichroismBIOPOLYMERS, Issue 3 2006Xiao-Jing Lin Abstract ,-Synuclein (,-Syn) has been identified as a component of intracellular fibrillar deposits in Parkinson's disease. Though the real pathogenesis is still unknown, many investigations have revealed that conformational alteration and fibril formation of ,-Syn protein have an important role in causing the disease. In this work, we introduced the g -factor spectra of solid-state circular dichroism to estimate the secondary structure contents of ,-Syn fragments in amyloids. Fourier-transform infrared (FTIR) was also applied to confirm the structural formation. The results suggest that the central hydrophobic region is critical for ,-sheet formation and the conformational alteration is the foundation of protein abnormal aggregation. The research provides a practical approach to estimate the secondary structure contents of protein amyloids and further insight into the relevance of structural transformation and amyloidogenesis. © 2006 Wiley Periodicals, Inc. Biopolymers 83: 226,232, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Self-Assembly of a Two-Dimensional Bimetallic Coordination Framework and Dynamic Control of Reversible Conversions to Homo-Metallic Hydrogen-Bond ArraysCHEMPHYSCHEM, Issue 1 2010Ziliang Shi A novel 2D coordination bimetallic framework composed of Cu and Zn is obtained at a Au(111) surface by the supramolecular assembly of Cu and zinc-5,10,15,20-tetra(4-pyridyl)porphyrin molecules (see figure). Suppressing Cu concentration at high temperature transforms the 2D bimetallic frameworks into 2D homo-metallic hydrogen-bond arrays. Enriching the Cu concentration can reverse the structural transformation. [source] Development of the corneal stroma, and the collagen,proteoglycan associations that help define its structure and functionDEVELOPMENTAL DYNAMICS, Issue 10 2008Andrew J. Quantock Abstract The cornea of the eye is a unique, transparent connective tissue. It is comprised predominantly of collagen fibrils, remarkably uniform in diameter and regularly spaced, organized into an intricate lamellar array. Its establishment involves a precisely controlled sequence of developmental events in which the embryonic cornea undergoes major structural transformations that ultimately determine tissue form and function. In this article, we will review corneal developmental dynamics from a structural perspective, consider the roles and interrelationships of collagens and proteoglycans, and comment on contemporary concepts and current challenges pertinent to developmental processes that result in an optically clear, mature cornea. Developmental Dynamics 237:2607,2621, 2008. © 2008 Wiley-Liss, Inc. [source] Vertical (La,Sr)MnO3 Nanorods from Track-Etched Polymers Directly Buffering SubstratesADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Adrián Carretero-Genevrier Abstract A novel and general methodology for preparing vertical, complex-oxide nanostructures from a sol,gel-based polymer-precursor solutions is developed using track-etched polymers directly buffering substrates. This method is able to develop a nanostructure over the entire substrate, the dimensions and localization of the vertical nanostructures being preset by the polymeric nanotemplate. Thereby, nanostructures with lateral sizes in the range of 100 to 300,nm and up to 500,nm in height have been grown. Two examples are presented herein, the latter being the evolution of the initial, metastable nanostructure. Specifically, La0.7Sr0.3MnO3 polycrystalline rods are grown at mild temperatures (800,°C); upon strong thermal activation (1000,°C) they suffer a profound transformation into vertical, single-crystalline (La,Sr)xOy nanopyramids sitting on a La0.7Sr0.3MnO3 epitaxial wetting layer. The driving force for this outstanding nanostructural evolution is the minimization of the total energy of the system, which is reached by reducing the grain-boundary, total-surface, and strain-relaxation energies. Finally, advanced electron-microscopy techniques are used to highlight the complex phase separation and structural transformations occurring when the metastable state is overcome. [source] Experimental hearths and the thermal alteration of Caliche on the Southern High PlainsGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 7 2005Paul N. Backhouse Throughout the Holocene, caliche has been a ubiquitous technological resource for the people of the Southern High Plains. Archaeological sites on the Southern High Plains often contain thermal features that appear to utilize caliche nodules in various cultural processes. These processes usually involve some degree of thermal dynamic alteration to the caliche, identified in the archaeological record as fire-scorched or blackened nodules. Previous studies of the pyrodynamic properties of caliche have focused on quantification of color and fracture patterns within a laboratory setting, without direct involvement of cultural processes or problems associated with thermal features. Thermal alteration variables of caliche are examined from an actualistic perspective, utilizing previously excavated basin feature geometry and local caliche outcrops. Results indicate that sustained, intense heating of caliche (above 204°C) causes significant, but variable, structural transformations at the specimen level. The experimental use of shallow basin hearths demonstrates that hearth structures were easily capable of achieving and sustaining temperatures that would result in the physical alteration of individual caliche nodules, defined here as hearthstones. The broader implications of this study suggest that the interpretation of archaeological hearthstone assemblages should reflect variability, as observed during this experiment. © 2005 Wiley Periodicals, Inc. [source] Structural Transformations during Formation of Quasi-Amorphous BaTiO3,ADVANCED FUNCTIONAL MATERIALS, Issue 7 2007D. Ehre Abstract A model of structural transformations of amorphous into quasi-amorphous BaTiO3 is suggested. The model is based on previously published data and on X-ray photoelectron spectroscopy data presented in the current report. Both amorphous and quasi-amorphous phases of BaTiO3 are made up of a network of slightly distorted TiO6 octahedra connected in three different ways: by apices (akin to perovskite), edges, and faces. Ba ions in these phases are located in the voids between the octahedra, which is a nonperovskite environment. These data also suggest that Ba ions compensate electrical-charge imbalance incurred by randomly connected octahedra and, thereby, stabilize the TiO6 network. Upon heating, the edge-to-edge and face-to-face connections between TiO6 octahedra are severed and then reconnected via apices. Severing the connections between TiO6 octahedra requires a volume increase, suppression of which keeps some of the edge-to-edge and face-to-face connections intact. Transformation of the amorphous thin films into the quasi-amorphous phase occurs during pulling through a steep temperature gradient. During this process, the volume increase is inhomogeneous and causes both highly anisotropic strain and a strain gradient. The strain gradient favors breaking those connections, which aligns the distorted TiO6 octahedra along the direction of the gradient. As a result, the structure becomes not only anisotropic and non-centrosymmetric, but also acquires macroscopic polarization. Other compounds may also form a quasi-amorphous phase, providing that they satisfy the set of conditions derived from the suggested model. [source] Governance and poverty in sub-Saharan Africa: rethinking best practices in migration managementINTERNATIONAL SOCIAL SCIENCE JOURNAL, Issue 190 2006Thanh-Dam Truong This article explores the interface between migration and human trafficking in sub-Saharan Africa fromthe two angles of governance and poverty. A salient feature in the emerging frameworks of migration management is its implicit bifurcated vision of mobility. Trade-connected mobility is well protected by government rules whereas mobility to sustain livelihoods is subject to a punitive regime with a limited scope for resolving the discrepancy between the legal and social interpretations of human rights and well-being. The rise of migration by women, children and young people within and outside traditional practices under risky conditions may reflect deeper structural transformations than are commonly acknowledged by policy-makers. Reactions based on human rights concerns have contributed to new international, regional and national legislative frameworks for preventing abusive and exploitative practices in migration. The prevalence of glaring differences of interests in the variant policy approaches to all these issues , migration management, crime control, labour standards, poverty reduction and the particular needs of communities at risk , requires the concept of best practices to address the relationship between dominant forms of social knowledge and the policy field to situate and tackle issues of rights violation in different scales of governance and their interrelationships. [source] Supramolecular control of spin-crossover phenomena in lipophilic Fe(II)-1,2,4-triazole complexesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2006Keita Kuroiwa Abstract The spin-crossover properties of lipophilic, supramolecular Fe(II) complexes bridged by 4-(3-dodecyloxy)propyl-1,2,4-triazole [Fe(II)(1)3Cl2] were investigated in chloroform and cast films. A purple low-spin (LS) complex in a powdery form was transformed into pale yellow high-spin (HS) polymers by dissolution in chloroform. The formation of lipophilic molecular wires in chloroform was observed with transmission electron microscopy. The casting of chloroform solutions onto solid supports produced purple, transparent films (LS state). The cast films exhibited sluggish spin-crossover (LS , HS) behavior without thermal hysteresis. On the other hand, the cocasting of equimolar dodecanol or tetradecanol with Fe(II)(1)3Cl2 produced composite films in which alcohol molecules were bound to the complex by ionic hydrogen bonding (ROH···Cl,) and van der Waals interactions. At room temperature, the cast films exhibited regular lamellar structures before and after alcohol doping; this was confirmed by wide-angle X-ray diffraction measurements. Interestingly, the Fe(II)(1)3Cl2/CnOH (n = 12 or 14) ternary films showed a reversible abrupt spin crossover accompanied by thermal hysteresis. The observed bistability was related to dynamic structural transformations between lamellar and hexagonal structures. This study provides a novel supramolecular approach to designing spin-crossover polymer films with controlled thermal bistability. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5192,5202, 2006 [source] In situ Raman scattering studies of high-pressure stability and transformations in the matrix of a nanostructured glass,ceramic compositeJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2005Kristina E. Lipinska-Kalita Abstract High-pressure Raman scattering studies have been performed on a glass-based composite consisting of nanometer-sized gallium oxide aggregates embedded in a potassium-silicate host glass using the diamond anvil cell technique. The Raman spectra of this heterophase nanocomposite showed a range of pressure-induced structural transformations occurring in the glass matrix. Compression from ambient pressure up to 10.8 GPa indicated a progressive reduction in the width of the intertetrahedral SiOSi angle distribution, which was completely reversible on decompression to ambient pressure. At higher pressures, the Raman spectra demonstrated a breakdown of the intermediate-range order in the glass matrix of the nanocomposite. The enhancement of scattering intensity in the region of the D-defect band at 565 cm,1 together with the blue shift of the main SiOSi symmetric stretching wavenumber are evidence of a permanent reduction in SiO4 ring statistics toward smaller-than-six-ring configurations in the three-dimensional glass network. Starting from 13 GPa, the Raman spectra displayed a remarkable decrease in the scattering intensity of the SiOSi symmetric stretching that has been related to a coordination change of the silicon atom. The Raman spectrum of the composite quenched from 23 GPa to ambient conditions illustrated the pressure-driven, permanent reconstructive modification of the glass matrix in the nanocomposite. The pressure-induced evolution of the Raman peaks assigned to the gallium oxide phase indicated a progressive densification of the nanocrystalline phase, reversible on decompression to ambient pressure. Copyright © 2005 John Wiley & Sons, Ltd. [source] The Lost Leader: Sir Stafford Northcote and the Leadership of the Conservative Party, 1876,85*PARLIAMENTARY HISTORY, Issue 3 2008NIGEL THOMAS KEOHANE Sir Stafford Northcote has gone down in history as a man who fell short of the ultimate achievement of being prime minister largely because of personal weakness, and lack of political virility and drive. The picture painted by Northcote's political enemies , most notably the Fourth Party , has been accepted uncritically. Yet, political motives lay behind the actions of these supporters, and their harsh black and white portrait is not illustrative of the complexity of the situation in which Northcote found himself. Although individual characteristics undoubtedly played a part in his final political failure, underlying dynamics and structural transformations in politics and political life were more significant. It was more than simply the misfortune in succeeding the exceptionally charismatic Disraeli as leader. Northcote was faced with unparalleled disruption in parliament from Irish Nationalist MPs; the starkly polarised debate on the eastern question left him detached as a moderate. His temperament was better suited to constructive government rather than to opposition. However, following general election defeat in 1880, Northcote was denied this opportunity. Equally, his position in the lower House denied him the capacity to define a clear political critique of the Liberal government. Northcote's leadership of the party reflected the changing nature of British politics as radicals, tories, Irish Nationalists and Unionists increasingly contested the consensual style more appropriate to the political world of Palmerston and the 14th earl of Derby. [source] Observation and Characterization of Structural Phase Transitions by X-Ray Powder DiffractionPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 6 2005Wulf Depmeier Abstract Some of the basic properties of powder diffraction are summarized after a short introduction into the theory. Then it is described phenomenologically how various kinds of structural transformations affect the powder diffraction pattern. This is achieved on emphasizing that diffraction studies on powders are statistically more sound than those on single crystals, thus allowing the reliable determination of the generic properties of a given crystal structure. [source] Ternary magnetic semiconductors: recent developments in physics and technologyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2009V. Tsurkan Abstract Recent results in physics and technology of ternary magnetic oxide and chalcogenide spinels AB2X4 (A = Fe, Mn, Co, Cd, Zn, Hg; B = Cr, Co, Sc, Al; X = O, S, Se) are reviewed. Using magnetic susceptibility, specific heat, thermal expansion, electron-spin resonance, neutron diffraction, broad-band dielectric spectroscopy, and infrared optical spectroscopy, the spin, charge, orbital, and lattice correlations in these compounds were investigated. The novel magnetic ground states, e.g., spin liquid, spin,orbital liquid, and orbital glass, and in triguing effects, like colossal magnetocapacitive coupling, negative thermal expansion, and spin-driven Jahn,Teller structural transformations were revealed. In considering the origin of these phenomena, the concept of geometrical and bond frustration is explored. It relates the interplay of charge, spin, and orbital degrees of freedom with the inherent topological frustration and competing exchange interactions between the magnetic ions. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||||||||||||||